Polyurethane hard thermal insulation material, preparation method thereof and refrigerator

Abstract

The invention discloses a polyurethane hard thermal insulation material, a preparation method thereof and a refrigerator, and belongs to the field of thermal insulation materials in the refrigerator industry. The polyurethane hard thermal insulation material is prepared from the following raw materials: a white material, a black material, a foaming agent and a nucleating agent. The white material comprises combined polyether, the black material is selected from polymerized MDI, the foaming agent is selected from LBA, and the nucleating agent comprises a gas nucleating agent composed of nitrogen or carbon dioxide and a fluorine-containing nucleating agent; the white material is mixed with nitrogen or carbon dioxide as a gas nucleating agent, and the black material is mixed with a fluorine-containing nucleating agent; the foam heat conductivity coefficient of the polyurethane hard thermal insulation material is selected from any one value in the range of 15.0-15.5 mW / mK, and the foam density is selected from any one value in the range of 31.5-32.5 kg / m < 3 >. The thermal insulation material is applied to the aspect of thermal insulation materials in the refrigerator industry, the problem that an existing polyurethane material is not suitable for the refrigerator shell face due to the high heat conductivity coefficient is solved, the heat conductivity coefficient can reach 15.0-15.5 mW / mK, and therefore the deterioration amplitude of energy consumption is reduced when a VIP plate is partially replaced, and the requirement of a high-energy-efficiency refrigerator can be better met.

Description

Technical Field

[0001] The invention belongs to the field of heat-insulating materials in the refrigerator industry, and in particular relates to a polyurethane hard heat-insulating material, a preparation method thereof and a refrigerator. Background Art

[0002] Polyurethane rigid foam plastics have excellent thermal insulation properties and high specific strength, and are widely used in the refrigeration industry. In order to achieve increasingly higher energy efficiency requirements, the current mainstream technology is to add VIP panels (vacuum insulation panels) to each outer shell surface of the refrigerator. However, VIP panels are expensive, and the industry uses ultra-low thermal conductivity polyurethane materials to partially replace VIP panels to reduce costs. Among them, the main polyurethane material used is a pure LBA system formula. However, partial replacement of VIP panels will inevitably deteriorate the energy efficiency of refrigerators, which requires further reducing the thermal conductivity of polyurethane materials and reducing the degree of deterioration of energy efficiency. At present, the number of LBA parts is about 30, which can reduce the thermal conductivity of polyurethane rigid foam to 16.5-17.0mw / mk, but the amount of LBA has reached a bottleneck. Continuing to increase the amount will reduce the stability of the foaming process, deteriorate other physical and chemical properties, and further increase costs. There is little room for further optimization of thermal conductivity.

[0003] Affected by the deterioration of foam performance, when it is inconvenient to continue to increase the proportion of LBA, in order to further increase the thermal conductivity, a technical solution of adding nucleating agents on the basis of the pure LBA system is generally adopted. Nucleating agents are mainly fluoroalkanes or fluoroolefins containing multiple fluorine atoms. Fluorine atoms can increase the nucleation rate of the foaming process, increase the number of pores, reduce the pore diameter, and reduce the radiation conductivity, thereby reducing the overall thermal conductivity. However, when the fluorine-containing nucleating agent is used in a low proportion, the effect of reducing the thermal conductivity is significant. Increasing the dosage will continue to reduce the effect until it is ineffective. Too high a proportion will also deteriorate other properties of the foam.

[0004] Chinese patent CN202010969928 discloses a technical solution using LBA as a foaming agent and MFT as a foaming aid, i.e., a nucleating agent. MFT is an isomer of perfluoroolefins, and fluorine atoms can promote nucleation, obtain finer pores, and reduce thermal conductivity. However, the amount of MFT additives used is limited, and excessive use will hardly reduce the thermal conductivity, and will also have an adverse effect on other properties. Patent CN201710112796 discloses a technical solution using pentane as a foaming agent and nitrogen or carbon dioxide as a nucleating agent, and introduces a foaming route in which a gas nucleating agent is added to a conventional foaming agent, so that the nucleating effect is exerted in the white material in advance, which can significantly reduce the thermal conductivity of the conventional foaming system. However, after using the foaming agent and the nucleating agent, the thermal conductivity of the above-mentioned patented technical solution is still greater than 19mW / mK, resulting in the prepared polyurethane foam material being unable to replace the VIP board, thus failing to meet the latest energy efficiency requirements. At the same time, if the amount of foaming agent is further increased or multiple nucleating agents are used to reduce the thermal conductivity, other properties of the polyurethane foam material will be affected. Summary of the invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to overcome the problem that the existing polyurethane materials cannot be applied to the outer surface of the refrigerator due to their high thermal conductivity, and to propose a polyurethane hard thermal insulation material, a preparation method thereof, and a refrigerator that can achieve a thermal conductivity of 15.0-15.5mW / mK and ensure that other properties of the material are not affected, thereby reducing the deterioration of energy consumption when partially replacing VIP panels, and better meeting the requirements of high-efficiency refrigerators.

[0006] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0007] On one hand, the present invention provides a polyurethane rigid thermal insulation material, wherein the raw materials for preparing the polyurethane rigid thermal insulation material include white material, black material, foaming agent and nucleating agent; the white material includes a combined polyether, the black material is selected from polymerized MDI, the foaming agent is selected from LBA, and the nucleating agent includes a gas nucleating agent composed of nitrogen or carbon dioxide, and a fluorine-containing nucleating agent; nitrogen or carbon dioxide is mixed in the white material as a gas nucleating agent, and a fluorine-containing nucleating agent is mixed in the black material; the foam thermal conductivity of the polyurethane rigid thermal insulation material is selected from any value in the range of 15.0-15.5 mW / mK, and the foam density is selected from 31.5-32.5 kg / m 3 Any value in .

[0008] Preferably, by mass, the amount of the white material is 100 parts, the amount of the black material is selected from any value between 123 and 171 parts, the amount of the LBA is selected from any value between 25 and 35 parts, the amount of the gas nucleating agent is selected from any value between 7.5 and 8.5 parts, and the amount of the fluorine-containing nucleating agent is selected from any value between 1 and 4 parts.

[0009] Preferably, the white material comprises 90-95 parts of combined polyether, 2-4 parts of surfactant, 1.5-3.5 parts of catalyst and 1.5-2.5 parts of water.

[0010] Preferably, the fluorine-containing nucleating agent is one or more of C5-18, PF-90, perfluorohexane, hexafluoropropylene, perfluorobutadiene, octafluorocyclopentene, and perfluorohexene.

[0011] Preferably, the polymeric MDI has a viscosity of 200-400 mPa·s at 25° C. and an isocyanate content of 30-32%.

[0012] Another aspect of the present invention provides a method for preparing the polyurethane rigid thermal insulation material described in any of the above technical solutions, comprising a white material 1 preparation step, a white material 2 preparation step, a black material preparation step, and a polyurethane foam preparation step.

[0013] Preferably, the preparation step of the mixed white material 1 includes: mixing the white material and the LBA at a temperature of 15-25°C and a pressure of 2-4 bar to obtain the mixed white material 1; the preparation step of the mixed white material 2 includes: mixing the mixed white material 1 and 0.5-1 part of nitrogen or carbon dioxide at a temperature of 15-25°C and a pressure of 20-30 bar, and then adding the mixture into a white material tank to obtain the mixed white material 2.

[0014] Preferably, the mixed black material preparation step comprises: mixing the polymeric MDI and the fluorine-containing nucleating agent and adding them into a black material tank at a temperature of 15-25°C and a pressure of 20-30 bar to obtain a mixed black material; the pressure difference between the black material tank and the white material tank is ≤2 bar.

[0015] Preferably, the polyurethane foam preparation step comprises: mixing the mixed white material 2, the mixed black material, and 7-7.5 parts of nitrogen or carbon dioxide at a mixing pressure of 120-150 bar in a high-pressure foaming machine at a temperature of 15-25°C, injecting into a refrigerator body, controlling the mold temperature to 35-50°C, and curing for 180-360s to obtain polyurethane foam.

[0016] The present invention also provides a refrigerator, wherein the refrigerator body is made of the polyurethane hard heat-insulating material described in any of the above technical solutions.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a polyurethane rigid heat-insulating material, which adopts two nucleating agents and limits the addition method of the nucleating agents, thereby avoiding the mutual influence between the nucleating agents and making full use of the nucleating principles of the two nucleating agents, combining different nucleating processes, and avoiding the disadvantage of limited use of a single nucleating agent, and can achieve a thermal conductivity of 15.0-15.5 mW / mK, thereby reducing the deterioration of energy consumption when partially replacing VIP panels, and better meeting the requirements of high-efficiency refrigerators;

[0019] The present invention provides a refrigerator which, based on a pure LBA system, achieves a further reduction in thermal conductivity without significant deterioration in performance such as compression strength, dimensional stability, and foam pressure tank deformation rate. When partially replacing a VIP panel, the refrigerator can meet higher energy efficiency standards and is more in line with emission reduction regulations. DETAILED DESCRIPTION

[0020] The technical scheme in the specific embodiment of the present invention is described in detail and completely below. Obviously, the described embodiment is only a part of the specific implementation of the overall technical scheme of the present invention, rather than all implementations. Based on the overall concept of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.

[0021] On one hand, the present invention provides a polyurethane rigid thermal insulation material, wherein the raw materials for preparing the polyurethane rigid thermal insulation material include white material, black material, foaming agent and nucleating agent; the white material includes a combined polyether, the black material is selected from polymerized MDI, the foaming agent is selected from LBA, and the nucleating agent includes a gas nucleating agent composed of nitrogen or carbon dioxide, and a fluorine-containing nucleating agent; nitrogen or carbon dioxide is mixed in the white material as a gas nucleating agent, and a fluorine-containing nucleating agent is mixed in the black material; the foam thermal conductivity of the polyurethane rigid thermal insulation material is selected from any value in the range of 15.0-15.5 mW / mK, and the foam density is selected from 31.5-32.5 kg / m 3 Any value in .

[0022] The above-mentioned polyurethane rigid thermal insulation material adopts two nucleating agents, and by limiting the addition method of the nucleating agents, it not only avoids the mutual influence between the nucleating agents, but also makes full use of the nucleating principles of the two types of nucleating agents, combines different nucleating processes, and avoids the disadvantage of limited use of a single type of nucleating agent, so as to achieve a thermal conductivity of 15.0-15.5mW / mK, thereby reducing the deterioration of energy consumption when partially replacing VIP panels, and better meeting the requirements of high-efficiency refrigerators. Nitrogen, carbon dioxide nucleating agents and fluorine-containing nucleating agents are mixed in white materials and black materials respectively, and do not directly contact before the reaction, and do not affect each other. And when nitrogen, carbon dioxide nucleating agents and fluorine-containing nucleating agents are used at the same time, there is no obvious mutual influence problem when the dosage of the two is low (the gas nucleating agent does not exceed 8 parts, and the fluorine-containing nucleating agent does not exceed 4 parts), because the nucleating principles and nucleating processes of the two are not the same (nucleation is the generation of tiny bubble nuclei in the foaming material). Among them:

[0023] Nucleation principle of nitrogen or carbon dioxide nucleating agent: Nitrogen or carbon dioxide has a low boiling point (carbon dioxide is -78.5℃, nitrogen is -196℃), a high vapor pressure, and is easy to overflow. After being fully mixed in the white material under high pressure (12-15MPa), bubble nuclei can be generated in the white material under the influence of overflow tendency. Nucleation process: When mixed with the white material, bubble nuclei are generated in the white material. This process produces nucleation in advance before the foaming reaction.

[0024] Nucleation principle of fluorinated nucleating agents: The fluorine atoms in fluorinated additives can promote the generation of bubble nuclei during the foaming stage and play a nucleation role. Nucleation process: It plays a nucleation role during the foaming stage.

[0025] From the above, it can be seen that the nucleation principle and process of nitrogen or carbon dioxide are different from those of fluorine-containing nucleating agents, and they are mixed in white material and black material respectively, and they do not contact each other before foaming, and do not affect each other. After the foaming process begins, nitrogen or carbon dioxide has already played a nucleation role and will evaporate quickly, and will not have a significant effect on the nucleation effect of fluorine-containing additives.

[0026] Furthermore, the above technical solution also limits the addition of nitrogen or carbon dioxide to the white material, while the addition of the fluorine-containing nucleating agent to the black material is the best choice after fully considering the nucleating effect and avoiding mutual influence, for the following reasons:

[0027] (1) The best effect is achieved by mixing the two additives separately, because nitrogen or carbon dioxide and the fluorinated nucleating agent are mixed separately in the white material and the black material, and there is no direct contact before foaming, which can minimize the influence between them and give full play to their respective nucleating effects.

[0028] (2) There are two ways of separate mixing: ① Nitrogen and carbon dioxide are used for white material, and fluorine-containing nucleating agent is used for black material; ② Fluorine-containing nucleating agent is used for white material, and nitrogen and carbon dioxide are used for black material. In the above two methods, nitrogen or carbon dioxide has the same effect when mixed in white material or black material due to its principle of early nucleation. However, the compatibility of fluorine-containing nucleating agent in white material in method ②, that is, the mixing effect is poor, it is easy to precipitate, and the fluorine-containing nucleating agent will react with the catalyst contained in the white material, which is not conducive to long-term storage. In method ①, the mixing effect of fluorine-containing nucleating agent in black material is better, and the black material does not contain foaming agent. Therefore, choosing method ①, nitrogen and carbon dioxide are used for white material, and fluorine-containing nucleating agent is used for black material, can avoid adverse effects to the greatest extent and give full play to the nucleation effect.

[0029] After the above white material is mixed with the black material, a reaction occurs and heat is released. The chemical foaming agent water reacts with the black material to release carbon dioxide, and the physical foaming agent is heated and vaporized. In the early stage of the reaction, a large number of tiny bubble nuclei are generated inside the foaming material, which is the nucleation process. The more and finer the bubble nuclei produced in the foaming material, the better the performance of the foam. The gas thermal conductivity of LBA (HFO-1233zd) itself is low, and the molecule contains multiple fluorine atoms, which can promote nucleation in the early stage of the reaction. A high fraction of LBA can achieve an ultra-low thermal conductivity (below 17mW / mK). The purpose of adding each nucleating agent is to play a nucleating role, enhance the nucleation effect, and further reduce the thermal conductivity on the basis of a high fraction of LBA system. In order to avoid the problem of limited dosage and effect of a single type of nucleating agent, two nucleating agents with nucleating principles are used to improve the nucleation effect at different stages, which is better than using a single type of nucleating agent. Specifically, nitrogen or carbon dioxide is used for white materials to play a nucleation role before the reaction starts; fluorine-containing nucleating agents are used for black materials. On the basis of pre-nucleation, they work together with LBA to enhance the nucleation process in the early stage of the reaction, playing a relay and amplification role. Throughout the process, the two types of nucleating agents and LBA play a synergistic role, which improves the nucleation before and during the reaction, maximizing the nucleation effect of the entire link, and the effect is far better than using a single foaming agent or nucleating agent.

[0030] In a preferred embodiment, the amount of the white material is 100 parts by mass, the amount of the black material is selected from any value between 123 and 171 parts, the amount of the LBA is selected from any value between 25 and 35 parts, the amount of the gas nucleating agent is selected from any value between 7.5 and 8.5 parts, and the amount of the fluorine-containing nucleating agent is selected from any value between 1 and 4 parts. The technical solution specifically defines the dosage of each component. It is understandable that the dosage of black material can also be 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, 150 parts, 155 parts, 160 parts, 165 parts, 170 parts and any point value within the range, the dosage of LBA can also be 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts and any point value within the range, the dosage of gas nucleating agent is preferably 8 parts, and the dosage of fluorine-containing nucleating agent can also be 2 parts, 3 parts and any point value within the range. The technical solution defines the dosage of gas nucleating agent to be less than 8 parts and the dosage of fluorine-containing nucleating agent to be less than 4 parts, avoiding the possible mutual influence between the two nucleating agents. At the same time, by limiting the addition method of the nucleating agent, the thermal conductivity of the foam material is effectively reduced when the dosage of LBA is not significantly increased compared with the prior art, while ensuring that other properties of the foam material are not affected.

[0031] In a preferred embodiment, the white material includes 90-95 parts of combined polyether, 2-4 parts of surfactant, 1.5-3.5 parts of catalyst, and 1.5-2.5 parts of water. It is understandable that the amount of combined polyether can also be 91 parts, 92 parts, 93 parts, 94 parts and any value within the range, the amount of surfactant can also be 3 parts and any value within the range, the amount of catalyst can also be 2.0 parts, 2.5 parts, 3.0 parts and any value within the range, and the amount of water can also be 2.0 parts and any value within the range.

[0032] In a preferred embodiment, the fluorine-containing nucleating agent is one or more of C5-18, PF-90, perfluorohexane, hexafluoropropylene, perfluorobutadiene, octafluorocyclopentene, and perfluorohexene.

[0033] In a preferred embodiment, the polymeric MDI has a viscosity of 200-400 mPa·s at 25° C. and an isocyanate content of 30-32%.

[0034] Another aspect of the present invention provides a method for preparing the polyurethane rigid thermal insulation material described in any of the above technical solutions, comprising a white material 1 preparation step, a white material 2 preparation step, a black material preparation step, and a polyurethane foam preparation step.

[0035] In a preferred embodiment, the preparation step of the mixed white material 1 includes: mixing the white material and the LBA at a temperature of 15-25°C and a pressure of 2-4 bar to obtain the mixed white material 1; the preparation step of the mixed white material 2 includes: mixing the mixed white material 1 and 0.5-1 parts of nitrogen or carbon dioxide at a temperature of 15-25°C and a pressure of 20-30 bar, and then adding the mixture into a white material tank to obtain the mixed white material 2.

[0036] It should be noted that in the preparation step of mixed white material 2, only 0.5-1 parts of nitrogen or carbon dioxide (the total amount of gas nucleating agent is 7.5-8.5 parts) are added to the white material. The reason is that when the gas nucleating agent is mixed in the white material, if the amount is large, the mixing process and storage need to be carried out under very high pressure (120-150bar), which is much higher than the operating pressure of conventional foaming agents / additives, and the requirements for equipment are high, the control difficulty is large, and the cost is high. The scheme of the present invention is limited to mixing only a small amount of nitrogen or carbon dioxide (0.5-1 parts) in the white material in advance under a pressure of 20-30bar, and the remaining majority of the parts (7-7.5 parts) are mixed with the white material and the black material separately at the gun head, avoiding the ultra-high pressure environment required when a high number of nitrogen or carbon dioxide is mixed and stored in the white material, reducing the difficulty of operation and the requirements for equipment. At the same time, it can also give full play to the nucleation effect of nitrogen or carbon dioxide at different stages. Mixing fluorine-containing additives in black material avoids the disadvantage of poor compatibility of fluorine-containing additives in white material, has a longer storage time, and can exert the effect of fluorine-containing additives to a greater extent. Regarding the role of the nucleating agent of the present invention: a small amount of nitrogen or carbon dioxide is mixed with white material as a nucleating agent to produce nucleation in advance; black material is mixed with a fluorine-containing nucleating agent, and the nucleation principle and process different from nitrogen and carbon dioxide can give full play to the role of different types of nucleating agents to achieve the maximum nucleation effect, greatly reduce the thermal conductivity, and avoid the disadvantage of poor compatibility of fluorine-containing additives in white material; a large amount of nitrogen or carbon dioxide is then mixed with white material and black material independently at the gun tip to increase the amount of gas nucleating agent and enhance the overall nucleation effect.

[0037] In a preferred embodiment, the mixed black material preparation step includes: mixing the polymerized MDI and the fluorine-containing nucleating agent and adding them to a black material tank at a temperature of 15-25°C and a pressure of 20-30 bar to obtain a mixed black material; the pressure difference between the black material tank and the white material tank is ≤2 bar.

[0038] In a preferred embodiment, the polyurethane foam preparation step includes: at a temperature of 15-25°C, the mixed white material 2, the mixed black material, and 7-7.5 parts of nitrogen or carbon dioxide are mixed under a mixing pressure of 120-150 bar in a high-pressure foaming machine, and then injected into a refrigerator body, the mold temperature is controlled to be 35-50°C, and after curing for 180-360s, the polyurethane foam is obtained. In this process, the white material and the black material begin to react after mixing, water and isocyanate react to release heat, and the physical foaming agent is heated and vaporized, and a large number of tiny bubble nuclei are formed in the initial stage of the reaction, which is the nucleation process. During the reaction, the foaming agent gas diffuses into the bubble nucleus, causing the pores to grow and the foam to expand. The gaseous foaming agent is wrapped by the foaming material to form a large number of uniform pores. After the reaction is completed and the foam is cured, the pores are fixed. In order to promote nucleation, nitrogen or carbon dioxide is mixed into the white material as a nucleating agent. After the nitrogen or carbon dioxide is evenly dissolved, a large number of tiny bubbles can be formed in the white material in advance, which plays a pre-nucleation role before the reaction starts, and can increase the number of bubble nuclei and reduce the pore size of the foam, thereby reducing the thermal conductivity and improving the thermal insulation performance of the foam. Fluorine-containing nucleating agents are added to the black material. On the basis of pre-nucleation, fluorine atoms continue to play a nucleating role in the initial stage of the reaction, forming more bubble nuclei and further reducing the thermal conductivity.

[0039] The above technical solution of the present invention adds 0.5-1 parts of gas nucleating agent (the nucleating agent is nitrogen or carbon dioxide) to the white material on the basis of the thermal conductivity of the pure LBA system of 16.5-17.0mw / mk, and after sufficient and uniform mixing, a large number of tiny bubble nuclei are formed in the white material in advance. 1-4 parts of fluorine-containing nucleating agent are added to the black material. Then 7-7.5 parts of gas nucleating agent are independently mixed with the white material and the black material at the foaming gun head. The effect of the gas nucleating agent can be fully exerted before foaming and in the early stage of foaming, and more tiny and uniform bubble nuclei are generated inside the foaming material to the greatest extent, thereby reducing the internal pore size of the polyurethane rigid foam, thereby further reducing its thermal conductivity, and having little effect on other properties of the foam. Specifically, in the above technical solution, in order to promote nucleation, 0.5-1 parts of nitrogen or carbon dioxide is mixed into the white material as a nucleating agent. After uniform dissolution, a large number of tiny bubbles can be formed in the white material in advance, which plays a role of pre-nucleation before the reaction begins; adding 7-7.5 parts as a nucleating agent at the beginning of the reaction can increase the number of bubble nuclei and reduce the pore size of the pores, thereby reducing the thermal conductivity and improving the thermal insulation performance of the foam. Adding a fluorine-containing nucleating agent into the black material, on the basis of pre-nucleation, fluorine atoms continue to play a nucleating role in the initial stage of the reaction, forming more bubble nuclei, and further reducing the thermal conductivity.

[0040] The present invention also provides a refrigerator, wherein the refrigerator body is made of the polyurethane hard insulation material described in any of the above technical solutions. The insulation material used in the refrigerator achieves a further reduction in thermal conductivity on the basis of the pure LBA system, and does not show significant deterioration in performance such as compression strength, dimensional stability, and foam pressure tank deformation rate. When partially replacing VIP panels, it can meet higher energy efficiency standards and is more in line with emission reduction regulations.

[0041] In order to more clearly and in detail introduce the polyurethane rigid thermal insulation material, the preparation method thereof and the refrigerator provided in the embodiments of the present invention, a description will be given below in conjunction with specific embodiments.

[0042] Example 1

[0043] A polyurethane rigid thermal insulation material with ultra-low thermal conductivity, comprising by weight:

[0044] 100 parts dry white material

[0045] LBA 30 copies

[0046] Gas nucleating agent 1 0.5 parts

[0047] Gas nucleating agent 2 7.5 parts

[0048] 4 parts of fluorinated nucleating agent

[0049] 146 pieces of black material

[0050] The foam preparation process is as follows:

[0051] Step 1: Under the conditions of temperature 15-25°C and pressure 2-4 bar, white material and LBA in proportion by mass are mixed through a binary mixer and added into white material tank 1 to obtain mixed white material 1;

[0052] Step 2: Under the conditions of temperature 15-25° C. and pressure 20-30 bar, the mixed white material 1 and the gas nucleating agent 1 in proportion by mass are mixed through a mixer and added into the white material tank 2 to obtain the mixed white material 2;

[0053] Step 3: Under the conditions of temperature 15-25°C and pressure 20-30 bar, mix the isocyanate and the fluorinated nucleating agent in proportion by mass and add them into the black material tank to obtain a mixed black material, and the pressure difference between the black material tank and the white material tank 2 is ≤2 bar;

[0054] Step 4: Under the condition of material temperature of 15-25°C, the mixed white material 2, the mixed black material and the gas nucleating agent 2 are mixed according to the proportion under the mixing pressure of 120-150 bar in the high-pressure foaming machine, and then injected into the refrigerator body; the mold temperature is controlled at 35-50°C, and after curing for 180-360s, the polyurethane foam is obtained.

[0055] Example 2

[0056] A polyurethane rigid thermal insulation material with ultra-low thermal conductivity, comprising by weight:

[0057] 100 parts dry white material

[0058] LBA 30 copies

[0059] Gas nucleating agent 1 1 part

[0060] Gas nucleating agent 2 7 parts

[0061] 4 parts of fluorinated nucleating agent

[0062] 146 pieces of black material

[0063] The foam preparation process and testing standards are the same as those in Example 1 and will not be described in detail.

[0064] Example 3

[0065] A polyurethane rigid thermal insulation material with ultra-low thermal conductivity, comprising by weight:

[0066] 100 parts dry white material

[0067] LBA 30 copies

[0068] Gas nucleating agent 1 1 part

[0069] Gas nucleating agent 2 7 parts

[0070] 1 part of fluorinated nucleating agent

[0071] 146 pieces of black material

[0072] The foam preparation process and testing standards are the same as those in Example 1 and will not be described in detail.

[0073] Example 4

[0074] A polyurethane rigid thermal insulation material with ultra-low thermal conductivity, comprising by weight:

[0075] 100 parts dry white material

[0076] LBA 30 copies

[0077] Gas nucleating agent 1 1 part

[0078] Gas nucleating agent 2 7 parts

[0079] 2.5 parts of fluorinated nucleating agent

[0080] 146 pieces of black material

[0081] The foam preparation process and testing standards are the same as those in Example 1 and will not be described in detail.

[0082] Comparative Example 1

[0083] 100 parts dry white material

[0084] Foaming agent LBA 30 parts

[0085] Polymeric MDI 158 parts

[0086] The foam preparation process is as follows:

[0087] Step 1: Under the conditions of a temperature of 15-20°C and a pressure of 2-6 bar, white material and a foaming agent in a certain proportion by mass are mixed and added into a white material tank to obtain a mixed white material;

[0088] Step 2: Control the temperature of the white material tank and the black material tank at 15-25℃, the pressure at 6-10bar, and the pressure difference between the two tanks is less than 0.5bar.

[0089] Step 3: Mix the black material and the mixed white material according to the ratio under the mixing pressure of 120-150 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the mold temperature is controlled at 40-50°C, and after curing for 180-360s, the polyurethane foam is obtained.

[0090] Comparative Example 2

[0091] 100 parts dry white material

[0092] Foaming agent LBA 30 parts

[0093] Foaming agent MFT 4 parts

[0094] Polymeric MDI 158 parts

[0095] The foam preparation process is as follows:

[0096] Step 1: under the conditions of a temperature of 15-20° C. and a pressure of 2-6 bar, white material and a foaming agent in a certain proportion by mass are mixed and added into a premixing tank 1 to obtain a mixed white material 1;

[0097] Step 2: Control the temperature to 10-15°C and the pressure to 6-10 bar, mix the mixed white material 1 and the foaming aid according to the proportion, and add them into the premixing tank 2 to obtain the mixed white material 2.

[0098] Step 3: Control the temperature of premix tank 2 and black material tank at 15-25°C, pressure at 6-10 bar, and the pressure difference between the two tanks is less than 0.5 bar.

[0099] Step 4: Mix the black material and the mixed white material 2 according to the ratio under the mixing pressure of 120-150 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the mold temperature is controlled at 40-50°C, and after curing for 180-360s, the polyurethane foam is obtained.

[0100] Comparative Example 3

[0101] 100 parts dry white material

[0102] 8 parts of cyclopentane

[0103] 5 parts of isopentane

[0104] 8 parts of foaming agent (carbon dioxide or nitrogen)

[0105] Polymeric MDI 136 parts

[0106] The foam preparation process is as follows:

[0107] Step 1: at a temperature of 15-25° C. and a pressure of 2-4 bar, white material, cyclopentane and isopentane in a certain proportion by mass are mixed through a ternary mixer and added into a white material tank 1 to obtain a mixed white material 1;

[0108] Step 2: Under the conditions of temperature of 15-25° C. and pressure of 120-150 bar, the mixed white material 1 and nitrogen or carbon dioxide in proportion by mass are mixed through a mixer and added into the white material tank 2 to obtain the mixed white material 2;

[0109] Step 3: Stir the isocyanate evenly in the black material tank at a temperature of 15-25°C to obtain a mixed black material, control the pressure of the black material tank to 120-150 bar, and the pressure difference between the black material tank and the white material tank 2 is ≤10 bar;

[0110] Step 4: When the material temperature is 15-25°C, mix the white material 2 and the black material according to the ratio under the mixing pressure of 120-150 bar in the high-pressure foaming machine, and inject them into the refrigerator body; the mold temperature is controlled at 35-50°C, and after curing for 180-360s, the polyurethane foam is obtained.

[0111] Performance Testing

[0112] The performance of the polyurethane foams obtained in the above examples and comparative examples was tested, and the test results are shown in Table 1.

[0113] Table 1 Polyurethane foam performance test results

[0114]

[0115] From the foam test results in Table 1, comparative example 1 is a pure LBA system with a thermal conductivity of 16.43mw / mk; comparative example 2 is an LBA plus fluorine-containing nucleating agent system with a thermal conductivity of 15.82mw / mk; comparative example 3 is a CP plus gas nucleating agent system with a thermal conductivity of 19.53mw / mk. The present invention adds a gas nucleating agent and a fluorine-containing nucleating agent at the same time. Compared with the comparative example, the white material of Example 2 adds 1 part of gas nucleating agent, the black material adds 4 parts of fluorine-containing nucleating agent, and the gun head separately mixes 7 parts of gas nucleating agent, and the thermal conductivity is further reduced to 15.15mw / mk. It decreases by 1.28mw / mk relative to comparative example 1; decreases by 0.70mw / mk relative to comparative example 2; decreases by 4.41mw / mk relative to comparative example 3; the embodiments have obvious advantages, and the pressure tank deformation rate, compression strength, dimensional stability and other aspects of performance are comparable.

Claims

1. A polyurethane rigid thermal insulation material, characterized in that: The raw materials for preparing the polyurethane rigid thermal insulation material include white material, black material, foaming agent and nucleating agent; the white material includes combined polyether, the black material is selected from polymerized MDI, the foaming agent is selected from LBA, and the nucleating agent includes a gas nucleating agent composed of nitrogen or carbon dioxide, and a fluorine-containing nucleating agent; The white material is mixed with nitrogen or carbon dioxide as a gas nucleating agent, and the black material is mixed with a fluorine-containing nucleating agent; The foam thermal conductivity of the polyurethane rigid thermal insulation material is selected from any value between 15.0 and 15.5 mW / mK, and the foam density is selected from 31.5 to 32.5 kg / m 3 Any value in .

2. The polyurethane rigid thermal insulation material according to claim 1, characterized in that: In parts by mass, the amount of the white material is 100 parts, the amount of the black material is selected from any value between 123 and 171 parts, the amount of the LBA is selected from any value between 25 and 35 parts, the amount of the gas nucleating agent is selected from any value between 7.5 and 8.5 parts, and the amount of the fluorine-containing nucleating agent is selected from any value between 1 and 4 parts.

3. The polyurethane rigid thermal insulation material according to claim 2, characterized in that: The white material comprises 90-95 parts of combined polyether, 2-4 parts of surfactant, 1.5-3.5 parts of catalyst and 1.5-2.5 parts of water.

4. The polyurethane rigid thermal insulation material according to claim 1, characterized in that: The fluorine-containing nucleating agent is one or more of C5-18, PF-90, perfluorohexane, hexafluoropropylene, perfluorobutadiene, octafluorocyclopentene, and perfluorohexene.

5. The polyurethane rigid thermal insulation material according to claim 1, characterized in that: The polymeric MDI has a viscosity of 200-400 mPa·s at 25° C. and an isocyanate content of 30-32%.

6. The method for preparing the polyurethane rigid thermal insulation material according to any one of claims 1 to 5, characterized in that: The method comprises the steps of mixing white material 1, mixing white material 2, mixing black material and preparing polyurethane foam.

7. The method for preparing the polyurethane rigid thermal insulation material according to claim 6, characterized in that: The preparation step of the mixed white material 1 comprises: mixing the white material and the LBA at a temperature of 15-25° C. and a pressure of 2-4 bar to obtain the mixed white material 1; The preparation steps of the mixed white material 2 include: under the conditions of a temperature of 15-25° C. and a pressure of 20-30 bar, mixing the mixed white material 1 and 0.5-1 part of nitrogen or carbon dioxide, and then adding the mixture into a white material tank to obtain the mixed white material 2.

8. The method for preparing the polyurethane rigid thermal insulation material according to claim 7, characterized in that: The mixed black material preparation step comprises: mixing the polymeric MDI and the fluorine-containing nucleating agent and adding them into a black material tank at a temperature of 15-25° C. and a pressure of 20-30 bar to obtain a mixed black material; the pressure difference between the black material tank and the white material tank is ≤2 bar.

9. The method for preparing the polyurethane rigid thermal insulation material according to claim 7, characterized in that: The polyurethane foam preparation step comprises: mixing the mixed white material 2, the mixed black material, and 7-7.5 parts of nitrogen or carbon dioxide in a high-pressure foaming machine at a mixing pressure of 120-150 bar at a temperature of 15-25° C., injecting into a refrigerator box, controlling the mold temperature to 35-50° C., and curing for 180-360 seconds to obtain the polyurethane foam.

10. A refrigerator, characterized in that: The body of the refrigerator is made of the polyurethane hard insulation material according to any one of claims 1 to 5.

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