Rigid polyurethane foam as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polyurethane materials, and provides rigid polyurethane foam and a preparation method and application thereof.The method comprises the steps that a first foaming component containing a foaming agent with the boiling point smaller than or equal to 0 DEG C is premixed with isocyanate, and an isocyanate premix is obtained; premixing a second foaming component containing a foaming agent with the boiling point being greater than 0 DEG C with premixed polyether to obtain a premixed polyether premix; respectively and independently shearing and emulsifying the isocyanate premix and the combined polyether premix until the particle size distribution of particles is less than 300nm, mixing, and reacting to obtain the rigid polyurethane foam. According to the invention, different foaming agents are respectively added into the combined polyether and the isocyanate according to different types, process conditions are optimized due to the change of the types of the foaming agents, and specific treatment is carried out on a premix through shear emulsification, so that the nanoscale rigid polyurethane foam with fine and stable foam holes is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane materials, and particularly relates to a rigid polyurethane foam, a preparation method thereof, and an application thereof. Background Art

[0002] Rigid polyurethane foams are mainly used in refrigerators and freezers, pipelines, and wall interlayers to play a role in heat preservation and energy conservation. With the increasingly strict requirements of global environmental protection regulations, using environmentally friendly blowing agents, such as HC blowing agents, HFC blowing agents, HFO blowing agents, etc., while ensuring the strength of rigid polyurethane foams, reducing the thermal conductivity of rigid polyurethane foams, and improving the heat preservation performance of polyurethane foams have become important indicators for the development of the industry technology. Summary of the Invention

[0003] The present invention provides a rigid polyurethane foam, a preparation method thereof, and an application thereof, so as to solve the defects in the prior art that when using environmentally friendly blowing agents, the usage amount and types of blowing agents are limited, and the improvement degrees of the mechanical properties and heat preservation performance of rigid polyurethane foams are insufficient.

[0004] Specifically, the present invention provides a preparation method of a rigid polyurethane foam, including:

[0005] Premixing a first blowing component containing a blowing agent with a boiling point less than or equal to 0°C with an isocyanate to obtain an isocyanate premix;

[0006] Premixing a second blowing component containing a blowing agent with a boiling point greater than 0°C with a polyol blend to obtain a polyol blend premix;

[0007] After subjecting the isocyanate premix and the polyol blend premix to shear emulsification treatment independently until the particle size distributions therein are both below 300 nm, mixing and reacting to obtain a rigid polyurethane foam.

[0008] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the first blowing component is premixed with an isocyanate at 25 - 32°C, and then cooled, pressurized, and left standing to obtain the isocyanate premix;

[0009] The conditions for the cooling, pressurization, and standing include: the temperature difference for cooling is 8 - 16°C, preferably 10 - 14°C, pressurized to more than 3 bar, and the standing time is more than 2 h.

[0010] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the first blowing component is mainly obtained by mixing a blowing agent with a boiling point less than or equal to 0°C and a blowing agent with a boiling point greater than 0°C;

[0011] Further preferably, based on 100 parts of the polyether, the content of the first foaming component in the isocyanate premix is within 15%, and the content of the blowing agent with a boiling point less than or equal to 0 °C is more than 3%.

[0012] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the second foaming component is premixed with a combined polyether having a temperature of 35 - 40 °C and an average functionality of 5 - 6 to obtain the combined polyether premix.

[0013] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the second foaming component is mainly obtained by mixing different blowing agents with a boiling point greater than 0 °C;

[0014] Preferably, based on 100 parts of the polyether, the content of the second foaming component in the combined polyether premix is 10 - 18%.

[0015] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the blowing agent with a boiling point less than or equal to 0 °C includes: one or more of n-butane (R600), isobutane (R600a), 1,3,3,3-tetrafluoropropene (HFO 1234ze) (also known as GBA), 2,3,3,3-tetrafluoropropene (HFO 1234yf), 1,1-difluoroethane (HFC 152a), 3,3,3-trifluoropropene, and hexafluoropropene;

[0016] And / or, the blowing agent with a boiling point greater than 0 °C includes: one or more of n-pentane (NP), isopentane (IP), cyclopentane (CP), 1-chloro-3,3,3-trifluoropropene (LBA), cis-1,1,1,4,4,4-hexafluoro-2-butene (FEA 1100), and perfluoro-4-methyl-2-pentene (Noah 218fa).

[0017] According to the preparation method of the rigid polyurethane foam as described above provided by the present invention, the rotor structure of the equipment used for the shear emulsification treatment is a three-blade impeller type, comb type, or turbine type, preferably the turbine type;

[0018] Preferably, during the shear emulsification treatment, the rotational speed of the equipment is 6000 rpm or more, preferably 8000 - 15000 rpm.

[0019] In the second aspect, the present invention also provides a rigid polyurethane foam prepared by the preparation method of the rigid polyurethane foam as described above; the pore size distribution of the rigid polyurethane foam is 50 - 150 μm;

[0020] Preferably, the thermal conductivity of the rigid polyurethane foam is less than or equal to 18.43 mW / m.K, and the compressive strength is greater than or equal to 156 KPa.

[0021] In a third aspect, the present invention also provides the application of the rigid polyurethane foam as described above in refrigerators, freezers, pipelines or wall interlayers.

[0022] A nano-scale rigid polyurethane foam provided by the present invention, its preparation method and application. Different blowing agents are respectively added into the polyether polyol blend and isocyanate according to different categories. Among them, preferably, the low-boiling blowing agent is mixed with the isocyanate. At the same time, it is not limited to increasing the compatibility by premixing the HC type or HFO type (room temperature blowing agent) with the low-boiling blowing agent in advance to form an isocyanate premix; the high-boiling blowing agent or room temperature blowing agent is mixed with raw materials such as polyether polyol blend to form a polyether polyol blend premix. Due to the change in the type of blowing agent, the process conditions (such as the control of the material temperature) are optimized, and the premix is subjected to specific treatment by shear emulsification so that the particle size distribution of the particles is all below 300 nm. Finally, the two undergo a chemical reaction to obtain a nano-scale rigid polyurethane foam with delicate and stable cell structure. Detailed Embodiments

[0023] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0024] The main raw materials of traditional rigid polyurethane foam include the white material composed of polyether polyol blend, additives and blowing agent, and the black material composed of isocyanate.

[0025] With the increasing requirements for environmental protection and heat insulation performance, the compound use of various blowing agents such as HC type blowing agent, HFC type blowing agent, HFO type blowing agent, etc. is becoming more and more important, and the addition amount of the blowing agent is also gradually increasing. The defects of the polyether polyol blend premixed blowing agent process are becoming more and more obvious. For example, the low-boiling blowing agent (the blowing agent with a boiling point less than or equal to 0 °C) has poor stability in the polyether polyol blend, and the formed gas suspends at the upper end of the premixing tank, which can neither form foam according to the preset ratio nor easily cause surface defects of the foam, resulting in insufficient mechanical properties and heat insulation performance.

[0026] To overcome the above defects, premixing the low-boiling blowing agent in the white material is a feasible solution. However, it is still found in practice that on this basis, the premixing process of the blowing agent has a significant impact on the mechanical properties and heat insulation performance of the rigid polyurethane foam.

[0027] In some embodiments of the present invention, a method for preparing a rigid polyurethane foam is provided, including:

[0028] Premix a first foaming component containing a foaming agent with a boiling point less than or equal to 0 °C with an isocyanate to obtain an isocyanate premix;

[0029] Premix a second foaming component containing a foaming agent with a boiling point greater than 0 °C with a polyether polyol blend to obtain a polyether polyol blend premix;

[0030] After subjecting the isocyanate premix and the polyether polyol blend premix to shear emulsification treatment independently until the particle size distribution therein is below 300 nm, mix them and react to obtain a rigid polyurethane foam.

[0031] In the present invention, the first foaming component with a lower boiling point is added from the isocyanate system, while the second foaming component with a higher boiling point is added from the polyether polyol blend system. First, the problems of foaming agent dispersibility and stability are avoided, enabling the rigid polyurethane foam of the present invention to achieve its dissolution at a higher content of the foaming agent. Moreover, by subjecting them to shear emulsification treatment independently, the stability of the foaming agent is further increased, which significantly improves the reaction rate between the isocyanate and the polyether polyol without causing structural defects in the foam.

[0032] Specifically, the high-shear emulsification treatment of the present invention can shear-emulsify the premix to form nanoscale particles. When the isocyanate premix and the polyether polyol blend premix are both shear-emulsified to form nanoscale particles and then reacted, the reaction rate is increased and the resulting rigid polyurethane foam has a higher compressive strength at a lower density. Therefore, the foam is delicate, uniform, rich, and has a lower thermal conductivity.

[0033] In some embodiments of the present invention, the first foaming component is premixed with an isocyanate at 25 - 32 °C, and then cooled, pressurized, and left standing to obtain the isocyanate premix;

[0034] The conditions for cooling, pressurizing, and leaving standing include: the temperature difference for cooling is 8 - 16 °C, preferably 10 - 14 °C, pressurize to above 3 bar, and the standing time is 2 h or more.

[0035] Before the shear emulsification treatment, the first foaming component and the isocyanate of the present invention need to be premixed, which helps the shear emulsification treatment. During the premixing process, controlling the temperature of the isocyanate is very beneficial to improving the solubility of the first foaming component. After cooling, the foaming agent will not escape, taking into account both energy consumption and ingredient stability.

[0036] The isocyanate premix and the polyether polyol blend premix of the present invention can both be premixed in a static mixer.

[0037] In some embodiments of the present invention, the first foaming component is mainly obtained by mixing a foaming agent with a boiling point less than or equal to 0 °C and a foaming agent with a boiling point greater than 0 °C;

[0038] Further preferably, based on 100 parts of the polyether, the content of the first foaming component in the isocyanate premix is within 15%, and the content of the blowing agent with a boiling point less than or equal to 0 °C is more than 3%.

[0039] The stabilities of blowing agents with different boiling points are different. It was found in the experiment that premixing a blowing agent with a higher boiling point with a blowing agent with a boiling point less than or equal to 0 °C and then adding it to the isocyanate helps to improve the compatibility between the first foaming component and the isocyanate.

[0040] In some embodiments of the present invention, the second foaming component is premixed with a combined polyether having a temperature of 35 - 40 °C and an average functionality of 5 - 6 to obtain the combined polyether premix.

[0041] In the related art, the combined polyether is the main raw material for dissolving the blowing agent. Therefore, the average functionality of the combined polyether is generally 3 - 4. By using the method of the present invention, adding the second foaming component to the combined polyether avoids low - boiling - point blowing agents. Thus, by simultaneously increasing the temperature of the feed liquid and raising the average functionality of the combined polyether to 5 - 6, an increase in the viscosity of the raw materials can be avoided, and finally the overall performance of the obtained polyurethane foam can be improved. During batching, the temperature of the feed tank is also increased simultaneously.

[0042] In some embodiments of the present invention, the second foaming component is mainly obtained by mixing different blowing agents with boiling points greater than 0 °C;

[0043] Preferably, based on 100 parts of the polyether, the content of the second foaming component in the combined polyether premix is 10 - 18%.

[0044] In some embodiments of the present invention, the blowing agent with a boiling point less than or equal to 0 °C includes one or more of: n - butane (R600), isobutane (R600a), 1,3,3,3 - tetrafluoropropene (HFO 1234ze) (also known as GBA), 2,3,3,3 - tetrafluoropropene (HFO1234yf), 1,1 - difluoroethane (HFC 152a), 3,3,3, - trifluoropropene, and hexafluoropropene;

[0045] And / or, the blowing agent with a boiling point greater than 0 °C includes one or more of: n - pentane (NP), isopentane (IP), cyclopentane (CP), 1 - chloro - 3,3,3, - trifluoropropene (LBA), cis - 1,1,1,4,4,4 - hexafluoro - 2 - butene (FEA 1100), and perfluoro - 4 - methyl - 2 - pentene (Noah 218fa).

[0046] In some embodiments of the present invention, the rotor structure of the equipment used for the shear emulsification treatment is a three - blade impeller type, comb type, or turbine type, preferably the turbine type;

[0047] Preferably, during the shear emulsification treatment, the rotation speed of the equipment is above 6000 rpm, preferably 8000 - 15000 rpm.

[0048] According to the above description, in some embodiments of the present invention, the following process flow can be adopted to prepare the rigid polyurethane foam:

[0049] Premix the first foaming component containing a blowing agent with a boiling point less than or equal to 0°C and isocyanate through a static mixer to obtain an isocyanate premix; after step - by - step transportation, it reaches the on - site intermediate tank or working tank.

[0050] Premix the second foaming component containing a blowing agent with a boiling point greater than 0°C and the polyol blend through a static mixer to obtain a polyol blend premix; after step - by - step transportation, it reaches the on - site intermediate tank or working tank.

[0051] After independently subjecting the isocyanate premix and the polyol blend premix to shear emulsification treatment until the particle size distribution therein is all below 300 nm, mix them and react to obtain the rigid polyurethane foam.

[0052] When the isocyanate premix and the polyol blend premix reach the on - site intermediate tank, add a set of high - shear emulsification equipment for each, and continue to perform shear emulsification on the isocyanate premix and the polyol blend premix to make the raw materials reach the required nano - scale particles. In order to ensure continuous automated production, a high - shear emulsification equipment is set near the operation platform.

[0053] Then, react the two materials that have completed shear emulsification through a high - pressure mixing nozzle to obtain the nano - scale rigid polyurethane foam.

[0054] On the premise of meeting production supply, mix as much as needed as much as possible. If production is not carried out for a long time, the amount of pretreated raw materials must be controlled and the product status should be confirmed after starting work.

[0055] Second, in some embodiments of the present invention, there is also provided the rigid polyurethane foam prepared by the preparation method of the rigid polyurethane foam as described above; the pore size distribution of the rigid polyurethane foam is 50 - 150 μm;

[0056] Preferably, the thermal conductivity of the rigid polyurethane foam is less than or equal to 18.43 mW / m·K, and the compressive strength is greater than or equal to 156 KPa.

[0057] Third, in some embodiments of the present invention, there is provided the application of the rigid polyurethane foam as described above in refrigerators and freezers, pipelines or wall interlayers.

[0058] In the embodiments of the present invention, the isocyanate used is crude MDI, also known as polymethylene polyphenyl isocyanate, purchased from Wanhua Chemical Co., Ltd., with the brand name PM-200; the polyether blend used in the embodiments of the present invention includes polyether polyol and an additive mixture, specifically including polyether polyols with different functionalities, catalysts, water, surfactants, etc., purchased from Nanjing Hongbaoli Co., Ltd., with the brand name H8761.37, and its average functionality is 4.5-5.0.

[0059] Examples 1-3

[0060] A method for preparing rigid polyurethane foam, the steps are as follows:

[0061] (1) Prepare materials:

[0062]

[0063]

[0064] (2) Mix the raw materials in the first component above to form the first foaming component;

[0065] Add the first foaming component to PM200 at 30°C, premix, then cool down, pressurize, and stand for more than 2 hours to form an isocyanate premix; among them, the temperature difference for cooling is 10°C, and the pressure is increased to 3 bar.

[0066] Use a turbine shear emulsification device to perform shear emulsification treatment on the isocyanate premix at 8000 rpm so that the particle size distribution is below 300 nm.

[0067] (3) Mix the raw materials in the second component above to form the second foaming component;

[0068] Add the second foaming component to the polyether blend at 38°C to form a polyether blend premix;

[0069] Use a turbine shear emulsification device to perform shear emulsification treatment on the polyether blend premix at 9000 rpm so that the particle size distribution is below 300 nm.

[0070] (4) Infuse, mix, and react the emulsions obtained in steps (2) and (3) to obtain rigid polyurethane foam.

[0071] Comparative Example 1

[0072] It is basically the same as Example 1, the difference is that: the formulation of Comparative Example 1 is as follows:

[0073]

[0074]

[0075] Comparative Example 2

[0076] It is basically the same as Example 1, except that: the formulation of Comparative Example 2 is as follows, and the turbine shear emulsification equipment in steps (2) and (3) is replaced with an electric stirrer, and the electric stirrer cannot make the particle size of the premix reach below 300 nm.

[0077]

[0078] Comparative Example 3

[0079] It is basically the same as Example 2, except that: in step (2), an electric stirrer is used to mix the combined polyether premix, and it cannot emulsify the premix to a particle size below 300 nm.

[0080] Comparative Example 4

[0081] It is basically the same as Example 2, except that: in step (3), an electric stirrer is used to mix the isocyanate premix, and it cannot emulsify the premix to a particle size below 300 nm.

[0082] Comparative Example 5

[0083] It is basically the same as Example 2, except that: the turbine shear emulsification equipment in steps (2) and (3) is replaced with an electric stirrer, and the electric stirrer cannot make the particle size of the premix reach below 300 nm.

[0084] The preparation process parameters and performance parameters of the rigid polyurethane foam in the examples were monitored, and the results are as follows:

[0085] Technical indicators Unit Example 1 Example 2 Example 3 Opalescence time s 5 4 4 Drawing time s 40 38 39 Free foam density at the gun tip <![CDATA[kg / m 3 > 19.44 18.36 18.17 Just filled g 428 410 407 Molding density (OP20%) <![CDATA[kg / m 3 > 27.56 26.43 26.27 Compressive strength (min) KPa 173 194 185 Thermal conductivity (10°C) mW / m.K 17.86 16.68 16.54 Coefficient of expansion (3 min) ％ 1.98 1.59 1.54

[0086] The preparation process parameters and performance parameters of the rigid polyurethane foam in the comparative examples were monitored, and the results are as follows:

[0087] Technical indicators Unit Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Opalescence time s 6 5 5 5 5 Drawing time s 43 42 40 40 39 Free foam density at the gun tip <![CDATA[kg / m 3 > 20.04 19.68 18.58 18.62 18.70 Just filled g 452 440 415 417 420 Molding density (OP20%) <![CDATA[kg / m 3 > 28.98 28.65 26.35 26.48 26.98 Compressive strength (min) kpa 135 145 156 148 146 Thermal conductivity (10°C) mW / m.K 18.64 18.38 18.34 18.29 18.42 Coefficient of expansion (3 min) ％ 2.98 2.64 2.21 2.14 2.36

[0088] It can be seen from Example 1 and Comparative Example 1 that adding a blowing agent with a boiling point less than or equal to 0 °C to the combined polyether is difficult to improve the performance of the rigid foam.

[0089] Taking Example 2 as a reference, compared with Comparative Example 1, when the filling amount decreased by 9.29%, the compressive strength still increased by 28%. At the same time, the feature of the present invention is that more blowing agents with low thermal conductivity are incorporated, and within the limited cost range, the thermal conductivity reaches 16.54 mW / m·K, which belongs to a leading level in the industry.

[0090] Moreover, it can be seen from Comparative Examples 3 to 5 that high-shear emulsification of the isocyanate premix and the combined polyether premix simultaneously can achieve synergistic effects, further increasing the compressive strength of the rigid foam and reducing the thermal conductivity.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing rigid polyurethane foam, characterized in that, Comprising: Pre - mixing a first foaming component containing a blowing agent with a boiling point less than or equal to 0 °C and an isocyanate to obtain an isocyanate premix; Pre - mixing a second foaming component containing a blowing agent with a boiling point greater than 0 °C and a polyether polyol blend to obtain a polyether polyol blend premix; After subjecting the isocyanate premix and the polyether polyol blend premix independently to shear emulsification treatment until the particle size distribution therein is below 300 nm, mixing and reacting to obtain a rigid polyurethane foam.

2. The preparation method of the rigid polyurethane foam according to claim 1, characterized in that, The first foaming component is pre - mixed with an isocyanate at 25 - 32 °C, then cooled, pressurized and left standing to obtain the isocyanate premix; The conditions for cooling, pressurizing and leaving standing include: the temperature difference for cooling is 8 - 16 °C, pressurizing to above 3 bar, and the standing time is 2 h or more.

3. The preparation method of the rigid polyurethane foam according to claim 1, characterized in that, The first foaming component is mainly obtained by mixing a blowing agent with a boiling point less than or equal to 0 °C and a blowing agent with a boiling point greater than 0 °C; Further preferably, based on 100 parts of polyether polyol, the content of the first foaming component in the isocyanate premix is within 15%, and the content of the blowing agent with a boiling point less than or equal to 0 °C is 3% or more.

4. The method for preparing rigid polyurethane foam according to claim 1, characterized in that, The second foaming component is pre - mixed with a polyether polyol blend at a temperature of 35 - 40 °C and an average functionality of 5 - 6 to obtain the polyether polyol blend premix.

5. The preparation method of the rigid polyurethane foam according to claim 1, characterized in that, The second foaming component is mainly obtained by mixing different blowing agents with a boiling point greater than 0 °C.

6. The method for preparing the rigid polyurethane foam according to claim 5, characterized in that, Based on 100 parts of polyether polyol, the content of the second foaming component in the polyether polyol blend premix is 10 - 18%.

7. The method for preparing a rigid polyurethane foam according to claim 1, characterized in that, The blowing agent with a boiling point less than or equal to 0 °C includes one or more of n - butane, isobutane, 1,3,3,3 - tetrafluoropropene, 2,3,3,3 - tetrafluoropropene, 1,1 - difluoroethane, 3,3,3 - trifluoropropene and hexafluoropropene; And / or, the blowing agent with a boiling point greater than 0 °C includes one or more of n - pentane, isopentane, cyclopentane, 1 - chloro - 3,3,3 - trifluoropropene, cis - 1,1,1,4,4,4 - hexafluoro - 2 - butene and perfluoro - 4 - methyl - 2 - pentene.

8. The production method of the rigid polyurethane foam according to any one of claims 1 to 7, characterized in that, The rotor structure of the equipment used for the shear emulsification treatment is a three - blade paddle type, comb type or turbine type, preferably the turbine type; Preferably, during the shear emulsification treatment, the rotational speed of the equipment is 6000 rpm or more, preferably 8000 - 15000 rpm.

9. A rigid polyurethane foam prepared by the method for preparing a rigid polyurethane foam according to any one of claims 1 - 8; the pore size distribution of the rigid polyurethane foam is 50 - 150 μm; Preferably, the thermal conductivity of the rigid polyurethane foam is less than or equal to 18.43 mW / m·K, and the compressive strength is greater than or equal to 156 KPa.

10. Use of the rigid polyurethane foam according to claim 9 in a refrigerator, freezer, pipeline or wall sandwich.

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