Method for mixing polyol formulations capable of reacting with isocyanates

Abstract

The invention discloses a mixing method of a polyol preparation capable of reacting with isocyanate, which comprises the following steps: adding premixed polyether polyol and an alkane physical foaming agent into a mixing kettle, and mixing in the mixing kettle in a high shear emulsification and mechanical stirring manner to obtain the polyol preparation, an emulsifier and a mechanical stirrer are arranged in the mixing kettle, at least one high-shear emulsification point is provided, and each high-shear emulsification point is positioned in a 0-60% depth area of the liquid level of the mixing kettle; at least one mechanical stirring point is provided, and the at least one mechanical stirring point is located in a 60-100% depth area of the liquid level of the mixing kettle; the rotating speed of the mechanical stirrer is less than 1000 revolutions per minute, and the rotating speed of the emulsifier is less than 20000 revolutions per minute. According to the invention, phase separation or escape loss of a physical foaming agent with a low boiling point or a physical foaming agent with poor compatibility can be effectively prevented, and a polyol preparation which has good performance and can react with isocyanate is obtained.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for mixing polyol formulations that can react with isocyanates. Background Technology

[0002] Polyol formulations capable of reacting with isocyanates are one of the key raw materials for preparing rigid polyurethane foam. They typically consist of polyether compounds and physical blowing agents, including polyether polyols, foam stabilizers, catalysts, physical blowing agents, and water, and are commonly referred to in the industry as "white material." Currently, white material is mostly mixed using mechanical stirring, where all components are added to a mixing tank at once, mixed thoroughly, and then transported to a white material tank in front of the high-pressure foaming machine for storage. However, due to the low boiling point and limited solubility of physical blowing agents in materials, they are prone to escaping from the material system during storage or intermittent use, leading to decreased dispersion uniformity and consequently affecting the performance of the final foam product.

[0003] To address the issue of low-boiling-point physical blowing agents escaping, CN112457461A proposes a polyurethane foaming system and method. This involves adding a portion of the easily escaping low-boiling-point blowing agent to the isocyanate black component tank, and then suppressing its volatilization loss by cooling. However, cooling is only applicable to the black component system, while a larger amount of blowing agent needs to be added to the white component. Due to the flowability requirements of the white component, a relatively high material temperature is usually maintained, therefore cooling cannot be used to prevent its volatilization.

[0004] Furthermore, CN223115681U discloses a premixing system for a foaming machine nozzle, which reduces the loss of foaming agent by installing a pressurization device on the material tank. However, for physical foaming agents with poor compatibility, pressurization alone is insufficient to solve the problem of uniform dispersion, and high pressurization levels pose safety hazards. Further, this solution also includes an external emulsification device, hoping to improve the uniform dispersion of the gas-liquid two phases and the stability of the emulsion through emulsification circulation. However, the increased material temperature during emulsification can further exacerbate the coalescence or escape of bubbles from the physical foaming agent.

[0005] In summary, providing a more reliable method to balance the uniformity of foaming agent dispersion and low leakage has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a mixing method applicable to both low-boiling-point physical foaming agents and poorly compatible physical foaming agents. This method can achieve uniform dispersion and low leakage of physical foaming agents in white materials under relatively mild process conditions.

[0007] The present invention adopts the following technical solution: A method for mixing a polyol formulation capable of reacting with isocyanates includes the following steps: adding a combined polyether and an alkane-based physical blowing agent to a mixing vessel, and mixing them in the mixing vessel by high-shear emulsification and mechanical stirring to obtain the polyol formulation; the mixing vessel is equipped with an emulsifier and a mechanical stirrer, the position where the emulsifier contacts the material is the high-shear emulsification point, and the position where the mechanical stirrer contacts the material is the mechanical stirring point; there is at least one high-shear emulsification point, each high-shear emulsification point is located in the 0-60% depth region of the liquid surface in the mixing vessel, excluding 0%; there is at least one mechanical stirring point, at least one of which is located in the 60-100% depth region of the liquid surface in the mixing vessel, excluding 60% and 100%; the rotation speed of the mechanical stirrer is <1000 rpm, and the rotation speed of the emulsifier is <20000 rpm; the alkane-based physical blowing agent is at least one selected from cyclopentane, n-pentane, isopentane, neopentane, n-butane, isobutane, and propane.

[0008] This invention, by setting a high-shear emulsification point at a relatively high position and a mechanical stirring point at a relatively low position, allows the upper part of the material in the reactor to be sheared and emulsified, while the lower part is mechanically stirred. Simultaneously, the coordinated stirring and emulsification speeds ensure that the physical foaming agent is uniformly dispersed in the material while effectively preventing escape and loss. Furthermore, the simultaneous setup of high-shear emulsification and mechanical stirring in the reactor effectively solves the problem of material temperature rise caused by emulsification. The emulsion released from a specific emulsification point is promptly stirred and dispersed at that location, not only balancing the material temperature but also further stabilizing the dispersion uniformity of the physical foaming agent. The mechanical stirring speed is <1000 rpm, such as 100–950 rpm, to ensure sufficient uniform distribution of the physical foaming agent and prevent the formation of large bubbles. The high-shear emulsification speed is <20000 rpm, such as 2000–18000 rpm, to facilitate further mechanical dispersion.

[0009] Depending on the size of the mixing vessel volume, one or more high-shear emulsification points can be selected, such as 2 to 4. Based on the conventional mixing vessel volume sizes in the art, 1 to 2 high-shear emulsification points are preferred. The mechanical stirrer includes a drive motor and at least one set of stirring blades. When the number of mechanical stirring points is greater than one, the stirring points are distributed at different vertical heights.

[0010] Furthermore, based on the physical properties of the combined polyether and alkane-based physical foaming agents, the high-shear emulsification point is preferably located in the 25-60% depth region of the liquid surface in the mixing vessel. This facilitates the timely capture of the alkane-based physical foaming agent and the redispersion of the emulsified material.

[0011] Furthermore, in order to better coordinate with the location of the emulsification point, at least one of the mechanical stirring points is located in the region of 70-90% depth of the liquid surface in the mixing vessel.

[0012] Furthermore, to promote secondary dispersion of the emulsified material, prevent bubble coalescence, and ensure better uniform distribution, the mechanical stirring points are at least two. The specific number depends on the total height of the mixing vessel used, and can be 2 to 10 if the total height allows. Based on the conventional mixing vessel volume in the art, two points are preferred: a first mechanical stirring point B1 and a second mechanical stirring point B2. The first mechanical stirring point B1 is located in the 70-90% depth region of the liquid surface in the mixing vessel, and the second mechanical stirring point B2 is located in the 45-65% depth region of the liquid surface in the mixing vessel.

[0013] Furthermore, the first mechanical stirring point B1 and the second mechanical stirring point B2 are coaxially arranged, and the stirring diameter D1 of the first mechanical stirring point B1 is greater than the stirring diameter D2 of the second mechanical stirring point B2.

[0014] Furthermore, in order to form a composite flow field, improve mixing efficiency, and obtain more uniform bubble size, the stirring linear velocity V1 of the first mechanical stirring point B1 is the same as the stirring linear velocity V2 of the second mechanical stirring point B2. Here, the stirring linear velocity refers to the linear velocity of the stirring blades located at point B1 or B2.

[0015] Furthermore, the mixing method of the present invention can obtain a lower rigid foam density with a lower amount of alkane physical blowing agent, and prevent escape and foaming with a higher amount, thereby taking into account both low density and uniform distribution. Preferably, the mass ratio of the combined polyether to the alkane physical blowing agent is 100:(13-21).

[0016] Furthermore, the temperature inside the mixing vessel is preferably 15–28°C. The mixing method of this invention is less affected by temperature; it can be carried out at both higher and lower temperatures without affecting the flowability of the white material, exhibiting good process tolerance and suitability for application scenarios with different flowability requirements.

[0017] Furthermore, the pressure inside the mixing vessel is preferably 0 to 0.1 MPa (gauge pressure), meaning that the mixing method of the present invention can reduce the loss of physical foaming agent without applying pressure, and can further improve the dispersion uniformity of physical foaming agent when the pressure is increased.

[0018] Furthermore, in order to make full use of the internal space of the mixing vessel, the depth of the liquid level in the mixing vessel should preferably be 60-80% of the total height of the mixing vessel.

[0019] Overall, the beneficial effects of this invention are: by mixing the combined polyether and foaming agent in a mixing vessel using a combination of high-shear emulsification and mechanical stirring, phase separation or loss of low-boiling-point physical foaming agents or physical foaming agents with poor compatibility can be effectively prevented, and a high-performance polyol formulation capable of reacting with isocyanate can be obtained. In this way, rigid polyurethane foam with lower density and uniform distribution can be produced with equimolar amounts of physical foaming agent. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of mixing vessel I.

[0021] Figure 2 This is a schematic diagram of the structure of mixing vessel II.

[0022] The attached figures are labeled as follows: 1. High-shear emulsifier; 2. Mechanical agitator; 21. First agitator blade; 22. Second agitator blade. Detailed Implementation

[0023] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0024] The polyether composites used in this invention can be made from conventional raw materials in the art, and can be commercially available or prepared in-house. Typically, polyether composites contain polyether polyols, foam stabilizers, catalysts, and water; in-house preparation, only the components need to be mixed thoroughly. The polyether composite H5210 used in this embodiment was commercially available and purchased from Hongbaoli Group Co., Ltd.

[0025] The alkane-based physical blowing agents used in this invention are as follows: 1# Alkane-based physical foaming agent: a combination of cyclopentane, isopentane, and n-pentane in a mass ratio of 13:1:1; 2# Alkane-based physical foaming agent: a combination of cyclopentane, n-butane, and isobutane in a mass ratio of 19:1:1; 3# Alkane-based physical foaming agent: Pure cyclopentane; 4# Alkane-based physical foaming agent: a combination of cyclopentane, neopentane, and propane in a mass ratio of 16:1:1.

[0026] To achieve the synergistic effect of emulsification, dispersion, and mechanical stirring within the same reactor, the mixing reactor used in this embodiment of the invention is an improved version of existing equipment. This can be achieved by adding a high-shear emulsifier to a conventional 220L mixing reactor. The specific structure of the improved device is as follows: Figure 1 and Figure 2As shown. However, this does not mean that the present invention can only be achieved by this device. Any device that can meet the requirements of the high-shear emulsification point location, mechanical stirring point location, and rotation speed of the present invention can be used in the present invention.

[0027] This invention provides four different mixing vessels; like Figure 1 As shown, the mixing vessel I is equipped with a high-shear emulsifier 1 and a mechanical agitator 2. The position where the emulsification head of the high-shear emulsifier 1 contacts the material is the high-shear emulsification point. The lowest position of the high-shear emulsification point, i.e., the lowest position of the bottom of the emulsification head, is marked as A1. The mechanical agitator 2 has a set of stirring blades 21 on its central shaft. The position where the stirring blades 21 contact the material is the first mechanical stirring point. The lowest position of the first mechanical stirring point, i.e., the lowest position of the bottom of the stirring blades 21, is marked as B1.

[0028] like Figure 2 As shown, unlike mixing vessel I, mixing vessel II has two sets of stirring blades with different diameters on the central shaft of the mechanical stirrer 2, namely the second stirring blade 22 and the first stirring blade 21. The first stirring rod and the second stirring rod, which are connected to the first stirring blade 21 and the second stirring blade 22, are rotatably fitted together to achieve the same stirring linear speed. The position where the first stirring blade 21 contacts the material is the first mechanical stirring point, and the position where the second stirring blade 22 contacts the material is the second mechanical stirring point. The lowest position of the first mechanical stirring point, i.e., the lowest position of the bottom of the first stirring blade 21, is marked as B1, and the lowest position of the second mechanical stirring point, i.e., the lowest position of the bottom of the second stirring blade 22, is marked as B2.

[0029] The difference between mixing vessel III and mixing vessel II is that mixing vessel III is equipped with two high-shear emulsifiers 1, which are arranged symmetrically.

[0030] The difference between mixing vessel IV and mixing vessel I is that mixing vessel IV is equipped with two high-shear emulsifiers 1, which are arranged symmetrically.

[0031] When using the above-mentioned mixing vessel, the material is fed through the top inlet. The temperature inside the mixing vessel is controlled at 15-25℃ and the pressure at 0-0.1MPa. After the liquid level reaches 60-80% of the total height of the mixing vessel, the high-shear emulsifier 1 and the mechanical stirrer 2 are started to perform high-shear emulsification and mechanical stirring mixing of the raw materials. After the mixing is completed, the polyol formulation that can react with isocyanate flows out through the bottom outlet of the mixing vessel, and then enters the high-pressure foaming gun head to be mixed with the black material. It is then injected into the mold and, after curing, rigid polyurethane foam is obtained.

[0032] The black material used in this invention can be any material conventional in the art; the isocyanate used in the examples is Lupranate. ® Take the M20s (purchased from BASF) as an example.

[0033] This invention uses the core density and core density distribution uniformity of rigid polyurethane foam to evaluate the distribution and escape properties of the physical blowing agent in the polyol formulation that can react with isocyanate. Under the condition of the same molar amount of physical blowing agent, the lower the core density of the rigid polyurethane foam, the lower the escape loss of the physical blowing agent, and the better the core density distribution uniformity, the better the distribution uniformity of the physical blowing agent. Example 1

[0034] The combined polyether H5210 and alkane physical foaming agent #1 were added to mixing vessel I at a mass ratio of 100:15. The liquid level depth H0 of the mixing vessel reached 60% of the total height of the mixing vessel. The high-shear emulsification point A1 was located at 60% depth of the liquid level in the mixing vessel, and the highest position of the emulsification head was below the liquid level in the mixing vessel. The first mechanical stirring point B1 was located at 80% depth of the liquid level in the mixing vessel, and the highest position of the first stirring blade 21 was below 60% depth of the liquid level in the mixing vessel. The temperature inside the vessel was controlled at 28℃ and the pressure was 0 MPa (gauge pressure). The high-shear emulsifier 1 performed high-shear emulsification at a speed of 18,000 rpm, and the mechanical stirrer 2 performed mechanical stirring at a speed of 100 rpm. After thorough stirring until the pressure inside the mixing vessel was constant, a polyol formulation capable of reacting with isocyanate was obtained, denoted as B-1#.

[0035] The B-1# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 115:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-1#. Example 2

[0036] Polyether H5210 and alkane-based physical foaming agent #2 were added to mixing vessel II at a mass ratio of 100:21. The liquid level depth H0 of the mixing vessel reached 80% of the total height of the mixing vessel. The high-shear emulsification point A1 was located at 45% depth of the liquid level in the mixing vessel, and the highest position of the emulsification head was below the liquid level in the mixing vessel. The first mechanical stirring point B1 was located at 90% depth of the liquid level in the mixing vessel, and the second mechanical stirring point B2 was located at 65% depth of the liquid level in the mixing vessel. The highest position of the first stirring blade 21 was below 65% depth of the liquid level in the mixing vessel, and the highest position of the second stirring blade 22 was below 45% depth of the liquid level in the mixing vessel. The stirring diameter D1 of B1 was 28 cm, and the stirring diameter D2 of B2 was 12 cm. The temperature inside the mixing vessel was controlled at 20℃, and the pressure was 0.1 MPa (gauge pressure). The high-shear emulsifier 1 performed high-shear emulsification at a speed of 11,000 rpm. The rotation speed of the first stirring blade is set to 407 rpm, and the rotation speed of the second stirring blade is set to 950 rpm. That is, the stirring linear velocity V1 of B1 is the same as the stirring linear velocity V2 of B2. After stirring thoroughly until the pressure in the mixing vessel is constant, a polyol formulation that can react with isocyanate is obtained, denoted as B-2#.

[0037] The B-2# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 121:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-2#. Example 3

[0038] The combined polyether H5210 and alkane-based physical foaming agent #3 were added to mixing vessel III at a mass ratio of 100:16. The liquid level depth H0 in the mixing vessel reached 80% of the total height of the mixing vessel. The two high-shear emulsification points A1 were identified. Both A1 and A2 are located at a depth of 25% of the liquid surface in the mixing vessel, and the highest point of both emulsifying heads is below the liquid surface in the mixing vessel. The first mechanical stirring point B1 is located at a depth of 80% of the liquid surface in the mixing vessel, and the second mechanical stirring point B2 is located at a depth of 45% of the liquid surface in the mixing vessel. The highest point of the first stirring blade 21 is below a depth of 60% of the liquid surface in the mixing vessel, and the highest point of the second stirring blade 22 is below a depth of 25% of the liquid surface in the mixing vessel. The stirring diameter D1 of B1 is 28cm, and the stirring diameter D2 of B2 is 12cm. The temperature inside the mixing vessel is controlled at 25℃, and the pressure is gauge pressure 0MPa. The high-shear emulsifier 1 performs high-shear emulsification at a speed of 2000 rpm. The speed of the first stirring blade is set to 200 rpm, and the speed of the second stirring blade is set to 467 rpm. That is, the stirring linear velocity V1 of B1 is the same as the stirring linear velocity V2 of B2. After stirring until the pressure inside the mixing vessel is constant, a polyol formulation that can react with isocyanate is obtained, denoted as B-3#.

[0039] The B-3# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 116:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-3#. Example 4

[0040] The combined polyether H5210 and alkane physical foaming agent #4 were added to mixing vessel IV at a mass ratio of 100:18. The liquid level depth H0 of the mixing vessel reached 70% of the total height of the mixing vessel. The two high-shear emulsification points A1 and A2 were located at a depth of 35% of the liquid level in the mixing vessel, and the highest position of both emulsification heads was below the liquid level in the mixing vessel. The first mechanical stirring point B1 was located at a depth of 70% of the liquid level in the mixing vessel, and the highest position of the first stirring blade 21 was below a depth of 60% of the liquid level in the mixing vessel. The temperature inside the mixing vessel was controlled at 15℃, and the pressure was 0 MPa (gauge pressure). High-shear emulsifier 1 performed high-shear emulsification at a speed of 7000 rpm, and mechanical stirrer 2 performed mechanical stirring at a speed of 800 rpm. After thorough stirring until the pressure inside the mixing vessel was constant, a polyol formulation capable of reacting with isocyanate was obtained, denoted as B-4#.

[0041] The B-4# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 118:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-4#.

[0042] Comparative Example 1 Unlike Example 2, high-shear emulsification was not performed. Instead, mechanical stirring was carried out under the same conditions at the first mechanical stirring point B1 (located at 90% depth of the liquid surface in the mixing vessel) and the second mechanical stirring point B2 (located at 65% depth of the liquid surface in the mixing vessel) which were set coaxially. After stirring until the pressure in the mixing vessel was constant, a polyol formulation that could react with isocyanate was obtained, denoted as B-D1#.

[0043] The B-D1# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black Lupranate® M20s at a mass ratio of 121:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D1#.

[0044] Comparative Example 2 The emulsification and stirring operations were performed using the equipment disclosed in Example 1 of CN223115681U. The combined polyether H5210 and 2# alkane physical foaming agent were added to the second material tank (i.e., mixing vessel) at a mass ratio of 100:21. The temperature inside the second material tank was 20°C and the pressure was 0.1 MPa (gauge pressure). Mechanical stirring was performed after the liquid level in the mixing vessel reached 80% of the total height of the mixing vessel. At the same time, the circulation pump was turned on to perform emulsification circulation, so that the material could flow out from the second material tank and then enter the emulsification equipment for high-shear emulsification at a speed of 11,000 rpm. The emulsified material was then returned to the second material tank for stirring and dispersion. After sufficient circulation until the pressure inside the mixing vessel was constant, a polyol formulation capable of reacting with isocyanate was obtained, denoted as B-D2#.

[0045] The B-D2# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 121:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D2#.

[0046] Comparative Example 3 The difference from Comparative Example 2 is that 3# alkane physical blowing agent was used. The mass ratio of combined polyether H5210 and 3# alkane physical blowing agent was 100:18. After sufficient circulation until the pressure in the mixing vessel was constant, a polyol formulation that can react with isocyanate was obtained, denoted as B-D3#.

[0047] The B-D3# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 116:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D3#.

[0048] Comparative Example 4 Unlike Example 2, mechanical stirring was not performed. High-shear emulsification was only carried out at a speed of 11,000 rpm at the high-shear emulsification point A1 (located at a depth of 45% of the liquid surface in the mixing vessel). After stirring until the pressure in the mixing vessel was constant, a polyol formulation capable of reacting with isocyanate was obtained, denoted as B-D4#.

[0049] The B-D4# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 121:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D4#.

[0050] Comparative Example 5 The difference from Example 1 is that the high shear emulsification point A1 is located at 80% depth of the liquid surface in the mixing vessel, and the first mechanical stirring point B1 is located at 60% depth of the liquid surface in the mixing vessel. All other conditions are the same. After stirring thoroughly until the pressure in the mixing vessel is constant, a polyol formulation that can react with isocyanate is obtained, denoted as B-D5#.

[0051] The B-D5# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 115:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D5#.

[0052] Comparative Example 6 The difference from Example 4 is that the mechanical stirring speed is 1000 rpm, while all other conditions are the same. After stirring thoroughly until the pressure in the mixing vessel is constant, a polyol formulation that can react with isocyanate is obtained, denoted as B-D6#.

[0053] The B-D6# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 118:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D6#.

[0054] Comparative Example 7 The difference from Example 1 is that the high-shear emulsification speed is 20,000 rpm, while all other conditions are the same. After thorough stirring until the pressure in the mixing vessel is constant, a polyol formulation capable of reacting with isocyanate is obtained, denoted as B-D7#.

[0055] The B-D7# polyol formulation flows out through the bottom outlet of the mixing vessel, then enters the high-pressure foaming machine nozzle and is mixed with the black material Lupranate® M20s at a mass ratio of 115:136. The mixture is then injected into a mold at 40±2℃ and cured to obtain rigid polyurethane foam, denoted as P-D7#.

[0056] The rigid polyurethane foams prepared in Examples 1-4 were characterized for performance, and the results are shown in Table 1. The rigid polyurethane foams prepared in Comparative Examples 1-7 were characterized for performance, and the results are shown in Table 2. Apparent core density, dimensional stability, thermal conductivity, and compressive strength were all tested according to the methods in GB / T 26689. Density distribution uniformity was expressed by the core density range, which is the difference between the maximum and minimum core density measured at different sampling points on the same sample.

[0057]

[0058]

[0059] As shown in Tables 1 and 2, the polyol formulations that can react with isocyanates, prepared using the mixing method of this invention, exhibit good uniformity of blowing agent distribution and minimal loss of blowing agent during the mixing process. This allows for the production of rigid polyurethane foam with lower core density and more uniform cell distribution at equimolar amounts of physical blowing agent. Furthermore, the mixing method of this invention facilitates the formation of uniform and fine cells, thereby optimizing cell shape, reducing the thermal conductivity of the rigid polyurethane foam, and achieving superior thermal insulation properties. Comparative Example 1, which used separate mechanical stirring, resulted in significant loss of foaming agent. Comparative Examples 2 and 3, which used external emulsification equipment, improved the uniformity of foaming agent distribution to some extent, but the loss problem, especially the loss of physical foaming agents with slightly poor compatibility at high boiling points, was difficult to effectively solve. Comparative Example 4, which only used emulsification, resulted in poor material flowability, leading to higher core density and density distribution uniformity. Although Comparative Examples 5-7 used a combination of mechanical stirring and emulsification dispersion within the same mixing vessel, the differences in parameters such as the location of high-shear emulsification points, the location of mechanical stirring points, stirring speed, and emulsification speed resulted in unsatisfactory improvements in density distribution uniformity and cell refinement.

Claims

1. A method for mixing polyol formulations capable of reacting with isocyanates, characterized in that, The process includes the following steps: adding a combination of polyethers and alkane-based physical foaming agents into a mixing vessel, and mixing them in the mixing vessel by high-shear emulsification and mechanical stirring to obtain the polyol formulation; The mixing vessel is equipped with an emulsifier and a mechanical stirrer. The position where the emulsifier contacts the material is the high-shear emulsification point, and the position where the mechanical stirrer contacts the material is the mechanical stirring point. There is at least one high-shear emulsification point, and each high-shear emulsification point is located in the 0-60% depth region of the liquid surface in the mixing vessel, excluding 0%. There is at least one mechanical stirring point, and at least one mechanical stirring point is located in the 60-100% depth region of the liquid surface in the mixing vessel, excluding 60% and 100%. The rotation speed of the mechanical stirrer is <1000 rpm, and the rotation speed of the emulsifier is <20000 rpm. The alkane physical foaming agent is at least one selected from cyclopentane, n-pentane, isopentane, neopentane, n-butane, isobutane, and propane.

2. The mixing method according to claim 1, characterized in that, The high-shear emulsification point is located in the region of 25-60% depth of the liquid surface in the mixing vessel.

3. The mixing method according to claim 1, characterized in that, At least one of the mechanical stirring points is located in the region of 70-90% depth of the liquid surface in the mixing vessel.

4. The mixing method according to claim 1, characterized in that, There are two mechanical stirring points, namely a first mechanical stirring point and a second mechanical stirring point. The first mechanical stirring point is located in the region of 70-90% depth of the liquid surface in the mixing vessel, and the second mechanical stirring point is located in the region of 45-65% depth of the liquid surface in the mixing vessel.

5. The material mixing method according to claim 4, characterized in that, The first mechanical stirring point and the second mechanical stirring point are arranged on the same axis, and the stirring diameter D1 of the first mechanical stirring point is greater than the stirring diameter D2 of the second mechanical stirring point.

6. The mixing method according to claim 5, characterized in that, The stirring linear velocity V1 at the first mechanical stirring point is the same as the stirring linear velocity V2 at the second mechanical stirring point.

7. The mixing method according to claims 1 to 6, characterized in that, The mass ratio of the combined polyether to the alkane-based physical foaming agent is 100:(13-21).

8. The mixing method according to any one of claims 1 to 6, wherein the mixing temperature of the combined polyether and the alkane-based physical foaming agent is 15 to 28°C.

9. The mixing method according to any one of claims 1 to 6, characterized in that, The pressure inside the mixing vessel is gauge pressure 0-0.1 MPa.

10. The mixing method according to any one of claims 1 to 6, characterized in that, The depth of the liquid level in the mixing vessel is 60-80% of the total height of the mixing vessel.

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