Multi-component fluorine-free low-GWP ultra-low thermal conductivity rigid polyurethane foam white material premixing process

Abstract

The invention belongs to the technical field of polyurethane, and provides a multi-component fluorine-free low-GWP ultralow-heat-conduction rigid polyurethane foam white material premixing process which comprises the following steps: firstly, preliminarily mixing an alkane foaming agent and premixed polyether through a static mixer, feeding the mixed material into a premixing intermediate tank, and primarily stirring; the materials subjected to primary stirring enter a jet mixer, then enter a static mixer to be mixed, then pass through a heat exchanger, return to a premixing intermediate tank to be stirred again, and then enter a premixing white material tank to be stirred for the third time; the materials are fed into the jet type mixer again, the materials subjected to jet mixing again are mixed through the static mixer, the constant temperature is kept through the heat exchanger, and finally the materials return to the premixed white material tank to obtain the premixed white material. According to the technical scheme, the fluorine-free foaming agent and the white material are kept in a micro-emulsion state for a long time after being premixed, the heat conductivity coefficient of foam prepared by mixing the premixed white material and isocyanate is improved, and foam defects are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane and relates to a multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process. Background Art

[0002] Refrigerators, freezers, electric water heaters and other fields have very high requirements for energy consumption. Polyurethane rigid foam plays a key role in product energy consumption with its excellent thermal insulation performance. Therefore, improving the thermal conductivity of foam is extremely important for these fields. At present, the thermal conductivity of polyurethane rigid foam is improved by using fluorinated foaming agents such as HFC, HFO and perfluorocarbons, or by adjusting the polyurethane white material formula to reduce the thermal conductivity of the foam. However, there are more and more restrictions on fluorinated foaming agents around the world, and the optimization of the polyurethane white material formula has made it difficult to make the thermal conductivity of the foam reach the same effect as using fluorinated foaming agents. Therefore, the energy consumption in these fields is greatly affected, and more expensive VIP materials have to be used to make up for it, resulting in an increase in product costs.

[0003] In order to overcome the above defects, the formula used now is fluorine-free foaming agent and special monomer polyether. The foaming agent currently used in the refrigerator industry is mixed with the combined polyether and stored in the storage tank, and then enters the foaming equipment for foaming. These components are easy to dissolve and not easy to stratify after mixing. It is only necessary to add ordinary stirring to the storage tank to prevent stratification. However, the fluorine-free foaming agent and special monomer polyether used now are not easy to dissolve and are easy to stratify compared with the previous formula. The fluorine-free foaming agent currently used in the industry is mainly alkane foaming agent, including pentane and butane. Alkane foaming agent has a high gas phase thermal conductivity and poor compatibility with white material. It will also cause many defects in premixed white material after foaming, such as many bubbles, low strength, high thermal conductivity, etc. At present, the home appliance industry uses static mixers and low-speed mixing kettles to premix white materials. Because the foaming agent with poor compatibility cannot be fully integrated into the white material or cannot be kept in a stable and uniform state, it is difficult to control defects such as high thermal conductivity of the foam.

[0004] Therefore, it is of great significance to develop a premixing process for polyurethane rigid foam white materials, which can keep the fluorine-free foaming agent and pure white materials in a micro-emulsified state for a long time after premixing, improve the thermal conductivity of the foam, and reduce foam defects. Summary of the invention

[0005] The present invention proposes a multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process, so that the fluorine-free foaming agent and the white material can maintain a micro-emulsified state for a long time after being premixed, thereby improving the thermal conductivity of the foam obtained after the premixed white material is mixed with isocyanate and reducing foam defects.

[0006] The technical solution of the present invention is achieved in this way: A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process comprises the following steps: The alkane foaming agent and the combined polyether are first preliminarily mixed in a static mixer, and the mixed materials enter the premixing intermediate tank for initial stirring. The materials after the initial stirring enter the jet mixer, and the materials after jet mixing enter the static mixer for mixing again. Then, the raw materials are controlled at a constant temperature through a heat exchanger, and the materials after constant temperature treatment are returned to the premixing intermediate tank and stirred again. Then, the materials enter the premixing white material tank for the third stirring; The material coming out of the premixed white material tank is sent to the jet mixer again. After the second jet mixing, the material is mixed by the static mixer, kept at a constant temperature by the heat exchanger, and finally returned to the premixed white material tank to obtain the premixed white material.

[0007] Preferably, the mass ratio of the combined polyether to the alkane foaming agent is 100:15-25.

[0008] Preferably, the viscosity of the composite polyether is 4000-8000 cps.

[0009] Preferably, the heat exchanger controls the material to maintain a constant temperature, and the constant temperature range is 20±5°C.

[0010] Preferably, the processing capacity of the static mixer is 40-100 kg / min; the material flow rate entering the jet mixer is 35-45 L / min, and the material flow rate entering the premix white material tank is 35-45 L / min; Preferably, the stirring rates of the first stirring and the second stirring in the premixing intermediate tank are both 200-500 rpm; the stirring rate of the third stirring in the premixing white material tank is 100-300 rpm. Preferably, the jet mixer is built with multiple sets of nozzles, and the materials enter the mixing chamber through the nozzles. The nozzles generate a certain pressure and collide with each other in the mixing chamber. Preferably, the alkane foaming agent is selected from one or two of n-pentane, isopentane, cyclopentane, n-butane and isobutane.

[0011] Preferably, the composite polyether comprises 86-93 parts of polyether polyol, 3 parts of foam stabilizer, 2 parts of catalyst and 2 parts of water, calculated by weight.

[0012] Preferably, the preparation method of the composite polyether comprises: mixing polyether polyol, foam stabilizer, catalyst and water, and stirring to obtain the composite polyether.

[0013] Preferably, the polyether polyol is selected from one or more of polyether polyol A, polyether polyol B, polyether polyol C, polyether polyol D and polyether polyol E; The polyether polyol A is a polyether polyol produced by polymerization of propylene oxide with aromatic amine as an initiator, and has a hydroxyl value of 400±20 mgKOH / g; The polyether polyol B is a polyether polyol produced by polymerization of propylene oxide with sucrose / glycerol as an initiator, and has a hydroxyl value of 430±20 mgKOH / g; The polyether polyol C is a polyether polyol produced by polymerization of propylene oxide and ethylene oxide with sucrose / glycerol as initiators, and has a hydroxyl value of 430±20 mgKOH / g; The polyether polyol D is a polyether polyol produced by polymerization of propylene oxide and ethylene oxide using aromatic amine as an initiator, and has a hydroxyl value of 400±20 mgKOH / g; The polyether polyol E is a polyether polyol produced by polymerization of propylene oxide with glycerol as an initiator, and has a hydroxyl value of 330±20 mgKOH / g; The foam stabilizer is selected from one or two of AK8805, AK8830, AK88316, B8462, B84841, L6860, and L6863; The catalyst is selected from one or two of PC-5, PC-8, PC-41 and TMR-2.

[0014] The present invention also provides a polyurethane foam, the raw materials of which include a premixed white material and isocyanate in a mass ratio of 1:1.2, and the premixed white material is obtained by adopting the above-mentioned multi-component fluorine-free low GWP ultra-low thermal conductivity polyurethane rigid foam white material premixing process.

[0015] Preferably, the isocyanate is polymethylene polyphenyl polyisocyanate, and its NCO percentage is 30-32%; The preparation process of the polyurethane foam comprises: mixing the premixed white material with the isocyanate in the isocyanate storage tank through a foaming machine injection gun for foaming production to obtain the polyurethane foam, wherein the mixing pressure of the foaming injection gun head is 100-150 bar.

[0016] The working principle and beneficial effects of the present invention are: 1. The premixing process of the multi-component fluorine-free low GWP ultra-low thermal conductivity polyurethane rigid foam white material provided by the present invention is first premixed, and then a set of small cycles are added through the premixing intermediate tank and the premixing white material tank respectively. The static mixer in the small cycle is combined with a jet mixer. The jet mixer is a dynamic collision mixing device with pressure, which is different from the traditional static mixing device in the industry. This setting makes the raw material mixing achieve an emulsification effect, more uniform, and less prone to decomposition, and realizes the high-efficiency mixing of fluorine-free foaming agent and white material. The premixing process provided by the present invention improves the K value of the thermal conductivity coefficient of the foam, which is 3~5% lower than the prior art, reduces the large air pores generated by foaming, and the number is reduced by more than 50%; improves the demoulding time, which is reduced by 10%; avoids the stratification of the fluorine-free foaming agent and the white material. The prior art is stratified within 3 days at 10°C, while the present invention will not be stratified within 3 days; improves the fluidity of the foam by more than 3%.

[0017] 2. The present invention also reduces the thermal conductivity of the foam by adjusting the polyurethane white material formula, wherein the hydroxyl values ​​of polyether polyols A, B, C, and D are relatively close, and when used in combination, the active points of the reaction system are evenly distributed to a certain extent. This helps to form a uniform polymer network structure and avoid structural inhomogeneity caused by excessive differences in local reaction activity, and a uniform structure is beneficial to reducing uneven channels for heat transfer and reducing thermal conductivity. At the same time, the combined polyether also uses a portion of polyether polyol E, which has a different hydroxyl value from other component polyether polyols. This difference can adjust the crosslinking density of the entire reaction system when used in combination, and can form a foam structure with a certain structural support and a relatively large gas holding space on the basis of the framework constructed by other polyether polyols. The gas filled in the larger gas holding space can play a good role in heat insulation and reduce thermal conductivity. If the combined polyether is not mixed uniformly with the alkane foaming agent, the thermal conductivity of the foam will be affected, resulting in foam defects. However, the combined polyether adopts the premixing process of the present invention to effectively avoid this defect and maximize the advantages of the combined polyether formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0020] Figure 2 It is a schematic diagram of the premixing process flow of the prior art.

[0021] In the figure, 1, ISO storage tank, 2, alkane foaming agent storage tank, 3, POL transport vehicle, 4, foaming agent intermediate tank, 5, POL intermediate tank, 6, static mixer, 7, premixing intermediate tank, 8, jet mixer, 9, static mixer, 10, heat exchanger, 11, premixing white material tank, 12, isocyanate tank, 13, foaming machine injection gun; A. Delivery pump, B. Control valve, C. Valve, D. Check valve, E. Dual-zone control regulating valve. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The materials in the following examples and comparative examples can all be purchased from commercial sources.

[0024] Among them, polyether polyol A is YD-402P, polyether polyol B is YD-4502, polyether polyol C is YD-8315E, polyether polyol D is YD-TS400, and polyether polyol E is YD-305; polyether polyols A, B, C, D, and E are all provided by Hebei Yadong Chemical Group Co., Ltd.

[0025] Foam stabilizers AK8805, AK8830, and AK88316 are provided by DeMeishic; foam stabilizers B8462 and B84841 are provided by Evonik; foam stabilizers L6860 and L6863 are provided by Momentive. Catalysts PC-5, PC-8, PC-41, and TMR-2 were provided by Evonik Industries.

[0026] Polymethylene polyphenyl polyisocyanate (PAPI), preferably with an NCO percentage of 30-32% in the present invention. The present invention uses M20S from BASF Chemical Co., Ltd., PM200 and PM400 from Wanhua Chemical Group.

[0027] like Figure 1 The POL transport vehicle 3 transports the combined polyether to the warehouse, and then stores it in the POL intermediate tank 5 through the delivery pump A, and the alkane foaming agent storage tank 2 stores the foaming agent in the foaming agent intermediate tank 4 through the delivery pump A.

[0028] First, the POL intermediate tank 5 and the foaming agent intermediate tank 4 are connected to the inlet of the static mixer 6 respectively, and the combined polyether and the alkane foaming agent are respectively pumped into the static mixer 6 for preliminary mixing (if multiple foaming agents and the combined polyether are to be premixed, multiple foaming agent intermediate tanks 4 are provided, and the multiple foaming agents are respectively pumped into the static mixer 6 for preliminary mixing with the combined polyether), and the outlet of the static mixer 6 is connected to the premixing intermediate tank 7 with an agitator; wherein the premixing intermediate tank 7 is provided with an external circulation system, and the external circulation system includes a delivery pump A, a jet mixer 8, a static mixer 9 and a heat exchanger 10 connected in sequence, the inlet of the delivery pump A is connected to the circulating liquid outlet of the premixing intermediate tank 7, and the outlet of the heat exchanger 10 is connected to the inlet of the premixing intermediate tank 7; wherein the heat exchanger 10 is connected to the one-way valve D, the valve C, and the inlet of the premixing intermediate tank 7 in sequence.

[0029] The outlet of the premixing intermediate tank 7 is connected to the premixing white material tank 11 with an agitator, and the material in the premixing white material tank 11 is the premixed white material; the premixing white material tank 11 is provided with an external circulation system, and the external circulation system includes a conveying pump A, a jet mixer 8, a static mixer 9 and a heat exchanger 10 which are connected in sequence, the inlet of the conveying pump A is connected to the circulating liquid outlet of the premixing white material tank 11, and the outlet of the heat exchanger 10 is connected to the inlet of the premixing white material tank 11; the heat exchanger 10 is connected to the one-way valve D, the valve C and the inlet of the premixing white material tank 11 in sequence.

[0030] The pressure of the foaming agent intermediate tank 4 is 2 bar, the pressure of the POL intermediate tank 5 is 4 bar, and the pressure of the premixing intermediate tank 7 is 4 bar. The pressure balance of the POL intermediate tank 5 and the premixing intermediate tank 7 can be controlled by the dual-zone control regulating valve E. Control valves B are set at the inlet and outlet of the foaming agent intermediate tank 4 and the POL intermediate tank 5 to adjust the flow and pressure; control valve B is also set at the inlet of the jet mixer 8, and a delivery pump A, two control valves B, a one-way valve D, and a valve C are set between the premixing intermediate tank 7 and the premixing white material tank 11 in sequence.

[0031] The premixed white material tank 11 directly injects the premixed white material into the foaming machine injection gun 13 through the delivery pump A, or controls the premixed white material at a constant temperature through the heat exchanger 10 before injecting it into the foaming machine injection gun 13. The ISO storage tank 1 injects ISO into the isocyanate tank 12 through the delivery pump A. The isocyanate tank 12 directly injects isocyanate into the foaming machine injection gun 13 through the delivery pump A, or controls the isocyanate at a constant temperature through the heat exchanger 10 before injecting it into the foaming machine injection gun 13. The premixed white material and isocyanate are mixed and foamed in the foaming machine injection gun 13 at a pressure of 100-150 bar.

[0032] The present invention provides a multi-component fluorine-free low GWP ultra-low thermal conductivity polyurethane rigid foam white material premixing process, comprising the following steps: The alkane foaming agent and the combined polyether are first preliminarily mixed by a static mixer 6, and the mixed materials enter the premixing intermediate tank 7 for initial stirring. The materials after the initial stirring enter the jet mixer 8, and the materials after jet mixing enter the static mixer 9 for mixing again. Then, the raw materials are controlled at a constant temperature by a heat exchanger, and the materials after the constant temperature treatment are returned to the premixing intermediate tank 7 and stirred again. Then, the materials enter the premixing white material tank 11 for the third stirring; The material coming out of the premixed white material tank 11 is sent to the jet mixer 8 again, and the material after the second jet mixing is mixed through the static mixer 9, kept at a constant temperature through a heat exchanger, and finally returned to the premixed white material tank 11 to obtain the premixed white material.

[0033] The jet mixer 8 has two sets of nozzles built in it. The materials enter the mixing chamber through the nozzles. The materials generate a certain pressure through the nozzles and collide in the mixing chamber to fully mix the raw materials. Specifically, the jet mixer on the market can be purchased, or the equipment described in the method and equipment for mixing chemical components for manufacturing polyurethane applied by Runying Polymer Industry Co., Ltd. can be used. The jet mixer 8 used in the following embodiment is the collision mixer 9406-MX-003 purchased from Runying Polymer Industry Co., Ltd., in which the nozzles are fixed nozzles D3 and D5 (diameter 5mm and diameter 3mm). The jet mixer 8 is also called a collision mixer, and the premixed white material tank is also called a foaming machine white material tank.

[0034] The static mixers 6 and 9 may be commercially available, or may be Fluitec of Switzerland, model: CSE-X, 42-1 Series L.

[0035] at the same time, Figure 1 It also embodies a preparation process of polyurethane foam, including: mixing the premixed white material in the above-mentioned premixed white material tank 11 and the isocyanate in the isocyanate storage tank through a foaming injection gun head for foaming production to obtain polyurethane foam, wherein the raw materials include the premixed white material and isocyanate in a mass ratio of 1:1.2, and the mixing pressure of the foaming injection gun head is 100-150 bar.

[0036] Among them, the mass ratio of the combined polyether and alkane foaming agent is 100:15-25, the processing capacity of the static mixer 6 in the preliminary mixing stage is 40-100 kg / min, and the processing capacity of the premixing intermediate tank 7 is 40-100 kg / min; the flow rate of the material entering the jet mixer 8 after the initial stirring is 35-45L / min, and the flow rate of the material entering the premixing white material tank 11 is 35-45L / min; the premixing intermediate tank 7 and the premixing white material tank 11 are stirred using a variable frequency stirring motor with a stirring rate of 200-1000 rpm, and the stirring speed is automatically adjusted according to different liquid levels, so as to achieve a more uniform mixing effect; specifically, the stirring rates of the premixing intermediate tank 7 for the first stirring and the second stirring are both 200-500 rpm, and the stirring rate of the premixing white material tank 11 for the third stirring is 100-300 rpm.

[0037] The specific gravity of the combined polyether is 1g / cm 3 , viscosity 4000-8000 cPs, flow range 300 g / s, accuracy ±1%. The preparation method of the combined polyether comprises: mixing polyether polyol, foam stabilizer, catalyst and water, stirring to obtain the combined polyether.

[0038] The specific gravity of alkane foaming agent is 0.75g / cm 3 , viscosity 0.4cPs, flow range 54g / s, accuracy ±1g / sec. The heat exchange area of ​​the heat exchanger can be 0.7-2 square meters.

[0039] like Figure 2 The existing process does not have a premixing intermediate tank 7, and the premixing intermediate tank 7 and the premixing white material tank 11 do not have an external circulation, that is, there is no jet mixing + static mixing + constant temperature control, but direct stirring to prevent stratification.

[0040] Example 1 A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process comprises the following steps: The alkane foaming agent and the combined polyether (material temperature 20°C) are first preliminarily mixed by a static mixer 6 (processing capacity 80 kg / min), and the mixed materials enter the premixing intermediate tank 7 (processing capacity 80 kg / min) for initial stirring (300 rpm), and the materials after the initial stirring enter the jet mixer 8 (flow rate 40 L / min), and the materials after jet mixing enter the static mixer 9 for mixing again, and then the raw materials are controlled at a constant temperature of 20°C through a heat exchanger, and the materials after constant temperature treatment are returned to the premixing intermediate tank 7, stirred again (300 rpm), and then the materials enter the premixing white material tank 11 for a third stirring (300 rpm); The material coming out of the premixed white material tank 11 is sent to the jet mixer 8 again, and the material after the second jet mixing is mixed by the static mixer 9, kept at a constant temperature of 20°C by the heat exchanger, and finally returned to the premixed white material tank 11 to obtain the premixed white material. Among them, the processing capacity of the static mixer 6 is 80 kg / min; the flow rate of the material entering the jet mixer 8 after the initial stirring is 40L / min, and the flow rate of the material entering the premixed white material tank 11 is 40L / min; the stirring rate of the initial stirring and the second stirring of the premixed intermediate tank 7 is 300 rpm, and the stirring rate of the third stirring of the premixed white material tank 11 is 300 rpm.

[0041] The preparation process of polyurethane foam comprises: mixing the premixed white material in the premixed white material tank 11 and the isocyanate in the isocyanate storage tank through a foaming injection gun head for foaming production to obtain polyurethane foam, wherein the raw materials include the premixed white material and PM200 in a mass ratio of 1:1.2, and the mixing pressure of the foaming injection gun head is 120 bar.

[0042] The formula of the premixed white material is as follows: Existing process comparison example 1 Compared with Example 1, the raw material formula is the same, the difference is only in the process. Figure 2 The existing process does not have a premixing intermediate tank 7, and the premixing white material tank 11 does not have an external circulation, that is, there is no spray mixing + static mixing + constant temperature control, but direct stirring to prevent stratification, and the stirring rate is 300 rpm. The effects of the prepared polyurethane foam are compared as shown in Table 2.

[0043] Example 2 A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process, same as Example 1.

[0044] The preparation process of polyurethane foam comprises: mixing the premixed white material in the premixed white material tank 11 and the isocyanate in the isocyanate storage tank through a foaming injection gun head for foaming production to obtain polyurethane foam, wherein the raw materials include the premixed white material and PM400 in a mass ratio of 1:1.2, and the mixing pressure of the foaming injection gun head is 100 bar.

[0045] The formula of the premixed white material is as shown in Table 3: Existing process comparison example 2 Compared with Example 2, the raw material formula is the same, the difference is only in the process, such as Figure 2The existing process does not have a premixing intermediate tank 7, and the premixing white material tank 11 does not have an external circulation, that is, there is no spray mixing + static mixing + constant temperature control, but direct stirring to prevent stratification, and the stirring rate is 300 rpm. The effects of the prepared polyurethane foam are compared as shown in Table 4.

[0046] Example 3 A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process is the same as Example 1, except that the material temperature is 16°C.

[0047] The preparation process of polyurethane foam comprises: mixing the premixed white material in the premixed white material tank 11 and the isocyanate in the isocyanate storage tank through a foaming injection gun head for foaming production to obtain polyurethane foam, wherein the raw materials include the premixed white material and M20S in a mass ratio of 1:1.2, and the mixing pressure of the foaming injection gun head is 150 bar.

[0048] The formula of the premixed white material is as shown in Table 5: Existing process comparison example 3 Compared with Example 3, the raw material formula is the same, the difference is only in the process, such as Figure 2 The existing process does not have a premixing intermediate tank 7, and the premixing white material tank 11 does not have an external circulation, that is, there is no spray mixing + static mixing + constant temperature control, but direct stirring to prevent stratification, and the stirring rate is 300 rpm. The effects of the prepared polyurethane foam are compared as shown in Table 6 below.

[0049] The performance data of the polyurethane foams prepared by the above-mentioned embodiment process and the existing process are obtained according to GB / T 26689-2011 Test method for rigid polyurethane foam plastics for refrigerators and freezers.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process, characterized in that: The method comprises the following steps: the alkane foaming agent and the combined polyether are firstly mixed in a static mixer, the mixed materials enter a premixing intermediate tank for initial stirring, the materials after initial stirring enter a jet mixer, the materials after jet mixing enter a static mixer for mixing again, and then the raw materials are controlled at a constant temperature through a heat exchanger, the materials after constant temperature treatment are returned to the premixing intermediate tank, stirred again, and then the materials enter a premixing white material tank for a third stirring; The material coming out of the premixed white material tank is sent to the jet mixer again. After the second jet mixing, the material is mixed by the static mixer, kept at a constant temperature by the heat exchanger, and finally returned to the premixed white material tank to obtain the premixed white material.

2. A multi-component fluorine-free, low GWP, ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The mass ratio of the combined polyether to the alkane foaming agent is 100:15-25, and the viscosity of the combined polyether is 4000-8000 cps.

3. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The processing capacity of the static mixer is 40-100 kg / min; the material flow rate entering the jet mixer is 35-45 L / min, and the material flow rate entering the premixed white material tank is 35-45 L / min; The stirring rates of the first stirring and the second stirring in the premixing intermediate tank are both 200-500 rpm; the stirring rate of the third stirring in the premixing white material tank is 100-300 rpm.

4. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The heat exchanger controls the material to be kept at a constant temperature, and the constant temperature range is 20±5°C.

5. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The jet mixer has multiple sets of nozzles built in. Materials enter the mixing chamber through the nozzles. The nozzles generate a certain pressure and collide in the mixing chamber.

6. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The alkane foaming agent is selected from one or two of n-pentane, isopentane, cyclopentane, n-butane and isobutane.

7. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 1, characterized in that: The composite polyether comprises, by weight, 86-93 parts of polyether polyol, 3 parts of foam stabilizer, 2 parts of catalyst and 2 parts of water; The preparation method of the combined polyether comprises: mixing polyether polyol, foam stabilizer, catalyst and water, and stirring to obtain the combined polyether.

8. A multi-component fluorine-free, low GWP and ultra-low thermal conductivity polyurethane rigid foam white material premixing process according to claim 7, characterized in that: The polyether polyol is selected from one or more of polyether polyol A, polyether polyol B, polyether polyol C, polyether polyol D and polyether polyol E; The polyether polyol A is a polyether polyol produced by polymerization of propylene oxide with aromatic amine as an initiator, and has a hydroxyl value of 400±20 mgKOH / g; The polyether polyol B is a polyether polyol produced by polymerization of propylene oxide with sucrose / glycerol as an initiator, and has a hydroxyl value of 430±20 mgKOH / g; The polyether polyol C is a polyether polyol produced by polymerization of propylene oxide and ethylene oxide with sucrose / glycerol as initiators, and has a hydroxyl value of 430±20 mgKOH / g; The polyether polyol D is a polyether polyol produced by polymerization of propylene oxide and ethylene oxide using aromatic amine as an initiator, and has a hydroxyl value of 400±20 mgKOH / g; The polyether polyol E is a polyether polyol produced by polymerization of propylene oxide with glycerol as an initiator, and has a hydroxyl value of 330±20 mgKOH / g; The foam stabilizer is selected from one or two of AK8805, AK8830, AK88316, B8462, B84841, L6860, and L6863; The catalyst is selected from one or two of PC-5, PC-8, PC-41 and TMR-2.

9. A polyurethane foam, characterized in that: The raw materials include premixed white material and isocyanate in a mass ratio of 1:1.2, and the premixed white material is obtained by adopting the multi-component fluorine-free low GWP ultra-low thermal conductivity polyurethane rigid foam white material premixing process as described in any one of claims 1 to 8.

10. The polyurethane foam according to claim 9, characterized in that: The isocyanate is polymethylene polyphenyl polyisocyanate, and its NCO percentage is 30-32%; The preparation process of the polyurethane foam comprises: mixing the premixed white material with the isocyanate in the isocyanate storage tank through a foaming injection gun head for foaming production to obtain the polyurethane foam, wherein the mixing pressure of the foaming injection gun head is 100-150 bar.

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