CN111471210A - Polyurethane composition of pentane co-foaming system and preparation method of polyurethane rigid foam - Google Patents

Abstract

The invention provides a polyurethane composition of a pentane co-foaming system and a preparation method of polyurethane rigid foam, wherein the polyurethane composition comprises a composite polyol, a nucleating agent, a foaming agent, a catalyst, a foam stabilizer, water and organic isocyanate; the composite polyol does not contain the o-tolylenediamine polyether polyol. By adopting the technical scheme of the invention, good heat conductivity coefficient, stronger compression strength, lower linear expansion rate and better dimensional stability can be realized under the condition of lower density, so that the material feeding amount can be relatively reduced, and the production cost can be reduced.

Description

Polyurethane composition of pentane co-foaming system and preparation method of polyurethane rigid foam

Technical Field

The invention belongs to the field of high polymer materials, and particularly relates to a polyurethane composition of a pentane co-foaming system and a preparation method of polyurethane rigid foam.

Background

With the continuous promotion of the replacement technology of the environment-friendly foaming agent, the pentane foaming agent is widely applied. Compared with a halogenated hydrocarbon foaming agent, the pentane foaming agent has no halogen atoms, zero ODP and approximately zero GWP, is environment-friendly, has relatively low price and is one of ideal alternative schemes of the foaming agent. However, pentane blowing agents have problems such as high boiling point, slow vaporization rate, poor compatibility with complex polyols, easy delamination, and plasticizing effect on foams, and these defects further affect the strength, dimensional stability, and the like of polyurethane foams.

In order to improve the physical properties of the pentane foaming system polyurethane foam, a mode of increasing the feeding density can be selected, but the increase of the density correspondingly increases the production cost; in order to improve the compatibility of the pentane foaming agent, a polyol with a special structure, such as o-tolylenediamine polyether polyol, can be selected and used, but the polyol is cured quickly at the later stage of foaming, the flowability of a foaming system is influenced, the raw material source is unstable, the application range is limited, and the popularization and the application of related technologies are finally influenced.

Therefore, the search for pentane foaming polyurethane compositions with excellent performance and low cost, and on the basis of the search, the development of polyurethane foams with lower cost and excellent performance is still the research focus in the field.

Disclosure of Invention

In order to solve the problems in the pentane foaming polyurethane composition, the application firstly provides a polyurethane composition of a pentane co-foaming system, and the polyurethane foam prepared by adopting the polyurethane composition has the advantages of low heat conductivity coefficient, good dimensional stability and low foam cost.

The specific technical scheme is as follows:

a polyurethane composition of a pentane co-foaming system comprises a complex polyol, a nucleating agent, a foaming agent, a catalyst, a foam stabilizer, water and organic isocyanate; the composite polyol does not contain the o-tolylenediamine polyether polyol.

After the nucleating agent is added, the surface tension of bubbles in a foaming system can be reduced, the formation of micro bubble nuclei is facilitated, meanwhile, the reduction of the surface tension is also beneficial to reducing the pressure difference among the bubbles, the stability of the bubbles is facilitated, and the bubbles have a finer and more uniform cell structure, so that the strength of a product is improved while the low density is ensured, and the size stability of the product is ensured.

Furthermore, the nucleating agent is a liquid substance with the surface tension less than or equal to 18 mN/m. Experiments show that when the surface tension is less than or equal to 18mN/m, the nucleating agent can generate better nucleating effect, and liquid substances are selected, so that uniform mixing is facilitated and the system stability is improved.

The production of foams requires the formation of a large number of cells formed by the gas produced by the thermal vaporization of the blowing agent. In the initial stage of the reaction, gas starts to be generated in the liquid phase material, and when the gas concentration in the material exceeds the equilibrium saturation concentration, fine bubbles start to be formed in the solution. In the application, after a liquid material with the surface tension less than or equal to 18mN/m is adopted as the nucleating agent, the solution has lower surface tension, so that a large number of fine bubbles can be quickly and continuously formed in the solution when the supersaturation degree of the gas is lower, the bubbles can be effectively prevented from being combined or broken, the compressive strength and the dimensional stability of the product can be reduced due to the broken bubbles or bubbles, the heat conductivity coefficient of the product can be improved, and the heat insulation performance of the product can be reduced.

The preferred nucleating agent in the invention is perfluoroolefin and/or fluorine-containing ether, wherein the perfluoroolefin can be at least one selected from perfluoro-1-butene, perfluoro-2-butene, perfluorobutadiene, perfluoro-2-methyl-2-pentene, perfluoro-4-methyl-2-pentene, octafluorocyclopentene, perfluoro-1-heptene, perfluorobutylethylene, perfluorocyclohexane, octafluorocyclobutane or perfluoro-1, 2-dimethylcyclohexane; the fluorine-containing ether may be selected from at least one selected from pentafluoropropylmethyl ether, hexafluoropropylmethyl ether, hexafluoroisopropylmethyl ether, nonafluorobutylmethyl ether, nonafluoroisobutylmethyl ether, nonafluorobutylethyl ether, nonafluoroisobutylethyl ether, difluoroethyltrifluoromethyl ether, difluoroethyltetrafluoroethyl ether, difluoromethyltrifluoroethyl ether, bis (trifluoroethyl) ether, tetrafluoroethylmethyl ether, tetrafluoroethylethyl ether, tetrafluoroethylpropyl ether, tetrafluoroethyldifluoromethyl difluoromethyl ether, tetrafluoroethylpropyl ether, octafluoropentyltetrafluoroethyl ether, heptafluoromethylpropyl ether, and trifluoromethyl trifluorovinyl ether.

The complex polyol comprises a polyester polyol and/or a polyether polyol. The polyester polyol is prepared by condensing low molecular weight alcohol and low molecular weight acid (anhydride), wherein the low molecular weight alcohol is one or more than two of ethylene glycol, diethylene glycol, propylene glycol, glycerol and trimethylolpropane; the low molecular weight acid (anhydride) is selected from one or more of maleic anhydride, adipic acid, phthalic anhydride, phthalic acid, and phthalic acid ester. The polyester polyol can improve the strength, heat resistance and the like of the material.

The polyether polyol is prepared by the reaction of an initiator and an alkylene oxide, wherein the alkylene oxide is selected from one or more of propylene oxide, ethylene oxide and butylene oxide, and the initiator is selected from one or more of active hydrogen-containing compounds such as sucrose, glycerol, vegetable oil, trimethylolpropane, pentaerythritol, sorbitol, xylitol, mannitol, methylglucoside, ethylenediamine, triethanolamine and the like. The high functionality, high hydroxyl number polyether polyols provide sufficient crosslinking and rigidity to the foam, and the low functionality, low hydroxyl number polyether polyols provide good flow properties to the foamed material. The invention does not use the o-tolylenediamine polyether polyol, so that the reaction is more stable, the fluidity of a reaction system can be improved, and the tolerance of a formula system is improved.

In a specific embodiment, the above polyols can be compounded according to actual needs to obtain better foam properties.

The catalyst is selected from two or more of pentamethyldiethylenetriamine, N-dimethylbenzylamine, dimethylcyclohexylamine, triethylenediamine, tetramethylethylenediamine, N-methylmorpholine, N-methyldicyclohexylamine, bis (dimethylaminoethyl) ether, N-dimethylaminoethanolamine, dimethylethanolamine, triethanolamine, 1,3, 5-tris (dimethylaminopropyl) -hexahydrotriazine, 2,4, 6-tris (dimethylaminomethyl) phenol, 2-hydroxypropyl trimethyl ammonium formate, 2-hydroxypropyl trimethyl ammonium acetate or 2-hydroxypropyl trimethyl ammonium caprylate.

The foam stabilizer may be selected from silicone surfactants such as L-6861, L-6863, L-6866, L-6912, L-6900, L-6920, etc., from the group of advanced materials of Michigan, AK8805, AK8806, AK8810, AK8811, AK8818, AK8863, etc., from the company of Maillard.

In particular embodiments, the reaction parameters may be controlled to achieve the desired process requirements for the reaction by selecting appropriate catalysts and foam stabilizers.

Further, the polyurethane composition of the present invention further comprises a compatibilizer. The compatilizer is a compound capable of dissolving at least 300 parts of isopentane in 100 parts of the compatilizer, such as vegetable oil-based polyol, and can be selected from soybean oil-based polyol, rapeseed oil-based polyol, cashew oil-based polyol or castor oil-based polyol.

In order to improve the solubility of the complex polyol to the weak-polarity foaming agent, the invention also uses the compatilizer which can effectively reduce the early escape of the foaming agent, improve the relative content of the foaming agent in a system and be beneficial to reducing the foam density. Meanwhile, under the action of the compatilizer, the foaming agent can be relatively stably and uniformly distributed in the composite polyol system, so that a large number of fine bubble nuclei can be formed at the initial stage of foaming reaction, the nucleation speed and the fine degree of the bubbles are increased, the cell structure is optimized, and the foam performance is improved.

Further, the foaming agent comprises a first component group and a second component group, wherein the first component group comprises any one or at least two of cyclopentane, n-pentane and isopentane, and the second component group comprises any one or at least two of 1,1,1, 2-tetrafluoroethane, 1, 1-difluoroethane and butane.

The boiling points of the 1,1,1, 2-tetrafluoroethane, the 1, 1-difluoroethane and the butane are lower than those of the pentanes, so that the internal pressure of the foam can be increased, the foam fluidity during foaming can be improved, the dimensional stability of the foam can be improved, the density of the foam can be reduced, and the foam cost can be further reduced. Meanwhile, the plasticizing effect of the pentane foaming agent can be reduced by adopting the second component group part to replace the first component group.

Further, it is preferable that the ratio of the first component group to the second component group is 0.1 to 18, which is advantageous for the synergistic effect of the two components.

Furthermore, the functionality of the organic isocyanate is more than or equal to 2.7, which is beneficial to improving the system stability and the heat conductivity. Can be selected from at least one of M20S, M50, PM200, PM400 of Vanhua chemistry.

Further, the components in parts by weight are as follows:

100 parts of composite polyol, 0-10 parts of compatilizer, 0.01-2 parts of nucleating agent, 2-5 parts of catalyst, 10-28 parts of foaming agent, 1-4 parts of foam stabilizer, 1.5-2.8 parts of water and 110-200 parts of organic isocyanate.

The components are arranged, so that the reaction can be carried out stably in a balanced manner, and better foam performance is obtained. When the compatibilizer is 0 part, the polyurethane composition does not contain the compatibilizer.

More preferably, the weight parts of the components are as follows: 100 parts of composite polyol, 1-8 parts of compatilizer, 0.1-1.5 parts of nucleating agent, 2.5-4 parts of catalyst, 16-20 parts of foaming agent, 2-3.5 parts of foam stabilizer, 1.8-2.6 parts of water and 120-170 parts of organic isocyanate.

The invention also provides a preparation method of the polyurethane rigid foam, which adopts the components in the polyurethane composition and comprises the following specific steps:

(1) uniformly mixing composite polyol, a catalyst, a foam stabilizer and water to obtain a first mixture, then sequentially adding a nucleating agent, a compatilizer and a foaming agent into the first mixture, and uniformly mixing to obtain a second mixture;

(2) and mixing the second mixture with organic isocyanate, and performing foaming reaction, molding and curing to obtain the polyurethane rigid foam.

In the application, the first mixture is formed after mixing part of the conventional components, and then the nucleating agent is added into the first mixture, and the nucleating agent is a substance with low surface tension, so that the surface tension of the first mixture can be reduced after the nucleating agent is added, and the first mixture has higher stability. And then adding the compatilizer, wherein the first mixture has lower surface tension due to the action of the nucleating agent, the compatilizer can be rapidly dispersed into the first mixture after being added and can be linked with the composite polyol in the first mixture, and finally, the foaming agent is added, so that the foaming agent can be linked with the compatilizer added in advance, and the foaming agent, particularly the pentane foaming agent, can be stably kept in the mixed material to avoid overflow in advance. If the foaming agent overflows in advance, part of the foaming agent fails or the difference of foam pores in the product is large, and particularly, a large amount of foam merging or opening cells are caused, so that the strength of the product cannot be effectively improved.

In the method, the nucleating agent, the compatilizer and the foaming agent are sequentially added into the first mixture in sequence to prepare a second mixture, the mixing of the raw materials is completed, and the second mixture has stable performance so as to improve the controllability of the foaming process.

The temperature and pressure conditions in the processes of foaming, molding and curing can be controlled according to the actual requirements of production and use places, so as to obtain polyurethane foam products with better performance.

Further, in the step (1), the mixing temperature is 15-23 ℃, and the pressure is normal pressure; in the step (2), the mixing temperature is 15-23 ℃, and the pressure is normal pressure-20 MPa. The temperature is adopted to facilitate the stable dispersion of the foaming agent in the composition system. Meanwhile, the mixing pressure is controlled, so that the mixing device can adapt to various mixing requirements, and the application range is widened.

The invention has the following beneficial effects on the whole:

(1) the invention overcomes the defects of poor compatibility, low nucleation efficiency, poor dimensional stability and the like in a pentane foaming system;

(2) the polyurethane foam obtained by the invention achieves the lowest stable density, namely: dimensional stability can be ensured while at the same time having the lowest density. The raw material consumption is saved, and the production cost is reduced.

(3) The polyurethane foam obtained by the invention also has the advantages of low thermal conductivity, zero ODP, environmental protection and the like.

Detailed Description

The density, the thermal conductivity coefficient, the compressive strength, the expansion rate and the high-low temperature dimensional change rate of the foam are respectively measured according to national standards GB/T6343-.

The preparation of examples and comparative examples was carried out according to the raw material components in tables 1 to 2.

TABLE 1 raw Material Components of examples 1 to 5 and comparative examples 1 to 2

Example 1

The composite polyol, the catalyst, the foam stabilizer, the water, the nucleating agent and the foaming agent are sequentially added according to the formulation components No. 1 in the table 1, the first mixing is carried out at 15 ℃, then the second mixing is carried out with the organic isocyanate at 20 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at 20MPa and high pressure, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 2

The composite polyol, the catalyst, the foam stabilizer, the water, the nucleating agent and the foaming agent are sequentially added according to the formulation components No. 2 in the table 1, the first mixing is carried out at the temperature of 18 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 18 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the high pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 3

The composite polyol, the catalyst, the foam stabilizer, the water, the nucleating agent and the foaming agent are sequentially added according to the formulation components No. 3 in the table 1, the first mixing is carried out at the temperature of 19 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 19 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 4

The preparation method comprises the following steps of sequentially adding the composite polyol, the catalyst, the foam stabilizer, the water, the nucleating agent and the foaming agent according to the formula 4# in the table 1, mixing for the first time at 20 ℃, then mixing with the organic isocyanate for the second time at 20 ℃, and respectively carrying out free foaming and mold foaming, wherein the free foaming is carried out at normal pressure, the mold foaming is carried out at 20MPa and high pressure, the mold temperature is 45 ℃, and the demolding time is 5 min.

Example 5

The composite polyol, the catalyst, the foam stabilizer, the water, the nucleating agent and the foaming agent are sequentially added according to the 5# formula components in the table 1, the first mixing is carried out at 21 ℃, then the second mixing is carried out with the organic isocyanate at 21 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at 20MPa and high pressure, the die temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 1

The composite polyol, the catalyst, the foam stabilizer, the water and the foaming agent are sequentially added according to the formula components of the comparison No. 1 in the table 1, the mixture is mixed for the first time at 18 ℃, then the mixture is mixed with the organic isocyanate for the second time at 18 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out under normal pressure, the die foaming is carried out under high pressure and 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 2

According to the formula components of the comparison No. 2 in the table 1, composite polyol, a catalyst, a foam stabilizer, water and a foaming agent are sequentially added, first mixing is carried out at the temperature of 18 ℃, then, second mixing is carried out with organic isocyanate at the temperature of 18 ℃, free foaming and mold foaming are respectively carried out, the free foaming is carried out at normal pressure, the mold foaming is carried out at the high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

TABLE 2 raw Material Components of examples 6 to 10 and comparative examples 3 to 6

Example 6

The composite polyol, the catalyst, the foam stabilizer, the water, the compatilizer, the nucleating agent and the foaming agent are sequentially added according to the No. 6 formula components in the table 2, the first mixing is carried out at the temperature of 17 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 17 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the high pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 7

The preparation method comprises the following steps of sequentially adding composite polyol, a catalyst, a foam stabilizer, water, a compatilizer, a nucleating agent and a foaming agent according to the formula 7# in the table 2, mixing for the first time at 23 ℃, then mixing with organic isocyanate for the second time at 23 ℃, and respectively carrying out free foaming and mold foaming, wherein the free foaming is carried out at normal pressure, the mold foaming is carried out at high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

Example 8

The composite polyol, the catalyst, the foam stabilizer, the water, the compatilizer, the nucleating agent and the foaming agent are sequentially added according to the formulation components No. 8 in the table 2, the first mixing is carried out at the temperature of 19 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 19 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the high pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 9

The composite polyol, the catalyst, the foam stabilizer, the water, the compatilizer, the nucleating agent and the foaming agent are sequentially added according to the formulation components No. 9 in the table 2, the first mixing is carried out at the temperature of 15 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 18 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the high pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Example 10

The composite polyol, the catalyst, the foam stabilizer, the water, the compatilizer, the nucleating agent and the foaming agent are sequentially added according to the 10# formula components in the table 2, the first mixing is carried out at the temperature of 20 ℃, then the second mixing is carried out with the organic isocyanate at the temperature of 20 ℃, the free foaming and the die foaming are respectively carried out, the free foaming is carried out at normal pressure, the die foaming is carried out at the high pressure of 20MPa, the die temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 3

According to the formula components of the comparison No. 3 in the table 2, composite polyol, a catalyst, a foam stabilizer, water and a foaming agent are sequentially added, first mixing is carried out at the temperature of 19 ℃, then, second mixing is carried out with organic isocyanate at the temperature of 19 ℃, free foaming and mold foaming are respectively carried out, the free foaming is carried out at normal pressure, the mold foaming is carried out at the high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 4

According to the formula components of the comparison No. 4 in the table 2, composite polyol, a catalyst, a foam stabilizer, water and a foaming agent are sequentially added, first mixing is carried out at the temperature of 19 ℃, then, second mixing is carried out with organic isocyanate at the temperature of 19 ℃, free foaming and mold foaming are respectively carried out, the free foaming is carried out at normal pressure, the mold foaming is carried out at the high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 5

According to the formula components of the comparison No. 5 in the table 2, composite polyol, a catalyst, a foam stabilizer, water, a nucleating agent and a foaming agent are sequentially added, first mixing is carried out at 19 ℃, then second mixing is carried out with organic isocyanate at 19 ℃, free foaming and mold foaming are respectively carried out, the free foaming is carried out at normal pressure, the mold foaming is carried out at high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

Comparative example 6

According to the formula components of the comparison No. 6 in the table 2, composite polyol, a catalyst, a foam stabilizer, water, a compatilizer and a foaming agent are sequentially added, first mixing is carried out at the temperature of 19 ℃, then, second mixing is carried out with organic isocyanate at the temperature of 19 ℃, free foaming and mold foaming are respectively carried out, the free foaming is carried out at normal pressure, the mold foaming is carried out at the high pressure of 20MPa, the mold temperature is 45 ℃, and the demolding time is 5 min.

The polyurethane foam samples prepared in examples 1 to 10 and comparative examples 1 to 6 were subjected to performance tests, and the results are shown in tables 3 and 4.

TABLE 3 test results of Properties of polyurethane foam samples of examples 1 to 5 and comparative examples 1 to 2

As can be seen from the data in Table 3, the polyurethane foam core prepared by the present invention has a density of 27 to 29kg/m³Can realize better physical and chemical properties within the range, and has the advantages of low density, low thermal conductivity and good dimensional stability, compared with the core density of No. 1, the core density is 32.2kg/m³And the feeding amount is reduced and the production cost is reduced in each embodiment.

The formula of the comparison-1 # and the formula of the comparison-2 # are basically the same as the formula of the comparison-2 # and the nucleating agent is added into the formula of the comparison-2 # so that more micro-bubble nuclei can be formed and the formed cell structure is finer and more uniform, therefore, the product produced by the formula of the comparison-2 # still has better compressive strength, thermal conductivity and stability even under the condition of lower core density. It can be seen in particular from the product produced by the comparative-1 # formulation that, even with a higher core density, the specifications of the product produced by the comparative-1 # formulation do not meet the specifications of the examples to which the nucleating agent was added. Therefore, in the absence of the nucleating agent, the compression strength of the product can be improved only by adopting a larger feeding amount and increasing the core density, but the linear expansion rate and the dimensional stability of the product cannot be effectively improved.

TABLE 4 test results of the Properties of polyurethane foam samples of examples 6 to 10 and comparative examples 3 to 6

As can be seen from the data in Table 4, the polyurethane foam core prepared by the present invention has a density of 27 to 29kg/m³Can realize better physical and chemical properties within the range, and has the advantages of low density, low thermal conductivity and good dimensional stability, compared with the core density of 33.8kg/m of No. 3³And the feeding amount is reduced and the production cost is reduced in each embodiment. And compared with No. 4, the polyurethane foam lacks of the coordination effect of the nucleating agent and the compatilizer, and the thermal conductivity, the dimensional stability, the linear expansion rate and the like of the obtained polyurethane foam are not ideal under the condition of lower density. Comparative-5 # and comparative-6 # phasesThe compatilizer and the nucleating agent are used independently, so that the foam performance is improved, the heat conductivity coefficient can be reduced, the physical and mechanical properties of the foam are improved, and the effect is still not ideal.

In conclusion, the technical scheme of the invention can realize good heat conductivity coefficient, stronger compression strength, lower linear expansion rate and better dimensional stability under the condition of lower density, thereby relatively reducing the feeding amount and lowering the production cost.

Claims (9)

1. A polyurethane composition of a pentane co-foaming system is characterized in that the components of the polyurethane composition comprise a complex polyol, a nucleating agent, a foaming agent, a catalyst, a foam stabilizer, water and organic isocyanate; the composite polyol does not contain the o-tolylenediamine polyether polyol.

2. The polyurethane composition of claim 1, wherein the components of the polyurethane composition further comprise a compatibilizer.

3. The polyurethane composition as claimed in claim 2, wherein the nucleating agent is a liquid substance having a surface tension of 18mN/m or less.

4. The polyurethane composition of claim 2, wherein the blowing agent comprises a first component group comprising any one or at least two of cyclopentane, n-pentane, and isopentane, and a second component group comprising any one or at least two of 1,1,1, 2-tetrafluoroethane, 1, 1-difluoroethane, and butane.

5. The polyurethane composition according to claim 4, wherein the mass ratio of the first component group to the second component group is 0.1 to 18.

6. Polyurethane composition according to claim 2, characterized in that the organic isocyanate has a functionality of 2.7 or more.

7. The polyurethane composition according to any one of claims 2 to 6, wherein the components are, in parts by mass:

100 parts of composite polyol, 0-10 parts of compatilizer, 0.01-2 parts of nucleating agent, 2-5 parts of catalyst, 10-28 parts of foaming agent, 1-4 parts of foam stabilizer, 1.5-2.8 parts of water and 110-200 parts of organic isocyanate.

8. A method for preparing rigid polyurethane foam, which is characterized by adopting the components of any one of claims 2 to 7 and comprising the following steps:

(1) uniformly mixing composite polyol, a catalyst, a foam stabilizer and water to obtain a first mixture, sequentially adding a nucleating agent, a compatilizer and a foaming agent into the first mixture, and uniformly mixing to obtain a second mixture;

(2) and mixing the second mixture with organic isocyanate, and performing foaming reaction, molding and curing to obtain the polyurethane rigid foam.

9. The method according to claim 8,

in the step (1), the mixing temperature is 15-23 ℃; in the step (2), the mixing temperature is 15-23 ℃, and the mixing pressure is normal pressure-20 MPa.