High-stability foaming composition for polyurethane and application thereof

Abstract

The invention relates to the field of foaming agents, and particularly discloses a high-stability foaming composition for polyurethane and application of the high-stability foaming composition, and the foaming composition comprises the following raw materials in percentage by mass: 58-72% of a solubilizer, 10-15% of a chlorine-free fluorine foaming agent, 1-3% of a catalyst, 2-4% of a flame retardant and the balance of water. The foaming composition does not contain harmful elements such as fluorine, chlorine and the like, is green and environment-friendly, greatly reduces pollution to the environment and harm to health of operators, reduces flammable and explosive risks through formula adjustment, and reduces the risks of fire disasters and explosions in the processes of production, transportation, storage and use.

Description

Technical Field

[0001] The present invention belongs to the field of foaming agents, and particularly relates to a highly stable foaming composition for polyurethane and its applications. Background Art

[0002] Foamed materials are materials that form a porous structure by gasifying inside a substance to generate gas, and have characteristics such as light weight, heat insulation, sound absorption, and insulation. According to the foaming principle, foamed materials can be divided into chemical foamed materials and physical foamed materials. Chemical foamed materials are formed by adding chemical foaming agents, which react with raw materials to generate gas (such as carbon dioxide or nitrogen), thereby forming pores. Physical foamed materials do not rely on chemical reactions, but form fine bubbles inside the material through physical means (such as reducing the liquid surface tension or heating), thereby generating a foam structure. Currently, the main types of foamed materials are plastic foamed materials, rubber foamed materials, metal foamed materials, and starch-based foamed materials. These materials are widely used in fields such as construction, packaging, transportation vehicles, and electronic devices.

[0003] For polyurethane-based foamed materials, the foaming agents used have undergone a series of changes. The first-generation foaming agent CFCs has been phased out due to its serious damage to the atmospheric ozone layer; currently, the second-generation chlorofluorocarbon foaming agent HCFC-141b (1,1-dichloro-1-fluoroethane) mainly used in industrial production in China has also been gradually restricted. In order to improve environmental protection, technicians have increased research on new foaming agents. Currently, there are two major mainstream directions for the research of new foaming systems in China. One is to adopt a mixed system of cyclopentane and HFC-245fa with more balanced cost performance; the other is to continue to develop a newer generation of environmentally friendly foaming agents. For example, Patent CN114805907B adopts a multi-component foaming agent formed by neopentane and other foaming agents and / or auxiliaries, and other foaming agents can be trans-1-chloro-3,3,3-trifluoropropene. Another example is that Patent Application CN112812354A discloses a polyurethane foaming agent, and the foaming agent A used has the molecular formula CF3CF=CHCl.

[0004] The foaming agents adopted in the above patents are new foaming agents represented by HFO-1233zd (trifluoropropene), which are non-volatile organic compounds with a short atmospheric lifetime and are more environmentally friendly. However, at the beginning of 2024, the Council of the European Union issued a legislative act document of the new F-GAS regulation in the EU legislation database (EUR-LEX). This new regulation has more stringent requirements for fluorine-containing substances. Therefore, there is an urgent need in the market for a fluorine-free foaming agent for polyurethane. Summary of the Invention

[0005] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a foaming composition that does not contain harmful elements such as fluorine and chlorine, greatly reducing environmental pollution and health hazards to operators, and reducing the risk of flammability and explosiveness through formulation adjustment, thereby reducing the risks of fire and explosion during production, transportation, storage, and use.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a highly stable foaming composition for polyurethane, which, based on 100% by mass percentage, comprises the following raw materials: 58 - 72% of a solubilizer, 10 - 15% of a chlorine- and fluorine-free foaming agent, 1 - 3% of a catalyst, 2 - 4% of a flame retardant, and the balance is water.

[0008] The foaming composition provided by the present invention has excellent foaming performance. When used, it can produce a uniform and fine foam structure when mixed with a polyurethane base material. These high-quality closed-cell foams not only have excellent heat insulation performance, but also can effectively prevent heat transfer when applied to the field of building insulation, reducing the energy consumption of buildings and achieving the goal of energy conservation and emission reduction, providing users with a more comfortable and energy-saving living and working environment. Moreover, they have good compressive strength and flexibility. When applied to the field of packaging materials, they can effectively protect products from damage such as collision, vibration, and extrusion during transportation and handling, ensuring the integrity and safety of products during transportation.

[0009] During the preparation process, the foaming composition has a low risk of combustion and explosion and does not involve key supervised hazardous chemical processes. The target product can be obtained through simple physical mixing, ensuring the reliability and safety during the production process. The obtained product has good chemical stability, is stable under normal temperature and pressure in a sealed condition, is not easily chemically reactive with other substances, and can be stored and used for a long time under different environmental conditions.

[0010] In some embodiments, the chlorine- and fluorine-free foaming agent comprises cyclopentane, isopentane, and diisopropyl azodicarboxylate.

[0011] The blowing agent provided by the present invention does not contain elements such as fluorine and chlorine, and is friendly to working conditions. Among them, cyclopentane vaporizes rapidly during the foaming process; the boiling point of isopentane is higher than that of cyclopentane. The combination of the two can not only control the foaming speed, but also endow the foam material with excellent heat insulation performance and improve the heat preservation effect. The present invention compensates for the defects of pentane blowing agents being flammable and explosive by adding diisopropyl azodicarboxylate. When diisopropyl azodicarboxylate decomposes by heating, it will release a large amount of nitrogen to dilute the combustible vapor formed by the volatilization of cyclopentane and isopentane in the system, reduce its local concentration, and thus significantly inhibit the risk of combustion or explosion; at the same time, the decomposition reaction of diisopropyl azodicarboxylate is an endothermic process, which can absorb the heat generated during the foaming process, slow down the rise of the system temperature, make the volatilization rate of low-boiling hydrocarbons such as cyclopentane and isopentane slow down, reduce the accumulation speed of combustible vapor in the air, and indirectly improve the process safety; and the decomposition products of diisopropyl azodicarboxylate are non-toxic and pollution-free in the range of 40-120 °C, which is suitable for the polyurethane foaming system.

[0012] In some embodiments, the mass ratio of cyclopentane, isopentane, and diisopropyl azodicarboxylate is 1:(0.6-0.9):(0.5-1.1).

[0013] The present invention controls the ratio of the three substances in the chlorine- and fluorine-free blowing agent, and while controlling the foaming speed, effectively plays the role of diisopropyl azodicarboxylate in compensating for the defects of pentane being flammable and explosive.

[0014] In some embodiments, the solubilizer comprises methyl tert-butyl ether and glycerol.

[0015] In some embodiments, the mass ratio of methyl tert-butyl ether and glycerol is 1:(0.06-0.18).

[0016] The chlorine- and fluorine-free blowing agent used in the present invention has a low solubility in polyether polyol, which will affect the foaming effect. Methyl tert-butyl ether in the solubilizer enhances the solubility of the three materials of the chlorine- and fluorine-free blowing agent in polyether polyol, and glycerol further improves the compatibility of the two pentanes with polyurethane raw materials. Moreover, glycerol acts as a plasticizer in polyurethane foam, making the foam softer and more elastic, and showing better flexibility and anti-deformation ability.

[0017] In some embodiments, the foaming composition further comprises 2-5% by mass of a foaming aid.

[0018] The above-mentioned chlorine-free and fluorine-free blowing agent is green and friendly, but its gas-phase thermal conductivity is higher than that of HFOs blowing agents, which easily leads to an increase in the overall thermal conductivity of polyurethane foaming materials, reducing the insulation effect of the materials. Moreover, the blowing agent with high gas-phase thermal conductivity also accelerates the thermal diffusion rate of the gas in the pores, thereby affecting the stability and uniformity of the pores. Uneven pore sizes or open-cell structures may occur, further affecting the foam density and compressive strength of the polyurethane foaming product.

[0019] In some embodiments, the preparation steps of the blowing aid are as follows:

[0020] S1. Under nitrogen protection, react dehydrated polybutylene adipate with HDI at 70-90 °C for 3-5 h, then add anhydrous ethanol and react at 60-65 °C for 2-3 h, and perform vacuum distillation to obtain Reactant 1;

[0021] S2. Dissolve silane KH550 in an ethanol aqueous solution with a concentration of 40-70 wt%, adjust the pH value to 4-6 with acetic acid, let it stand for 40-60 min, then add Reactant 1, stir for 20-50 min, filter to collect the solid, wash, and dry to constant weight to obtain the blowing aid.

[0022] The present invention promotes foam nucleation and rapid crosslinking through the blowing aid, improving the quality of closed-cell foams. Reactant 1 obtained in Step S1 can reduce the gas diffusion rate, improve the porous structure of the foam, making it finer and more uniform. However, the applicant found that the simple addition of Reactant 1 would accelerate the curing time of polyurethane foam, that is, it would cure completely before the blowing agent was fully foamed, resulting in insufficient foaming. In Step S2 of the present invention, the chemical bonding between silane coupling agent KH550 and Reactant 1 introduces flame-retardant silicon elements into the blowing aid, improving the compatibility between the low-polarity blowing agent and the polyurethane system, contributing to the formation of a more uniform and delicate pore structure; it can also reduce the foam thermal conductivity and adjust the curing time, preventing over-expansion or structural collapse during the foaming process.

[0023] In this synthesis process, the present invention utilizes the fact that isocyanate and hydroxyl can react at room temperature, and the specifically selected symmetric diisocyanate HDI does not require a catalyst to selectively catalyze a specific reaction path, eliminating the presence of a catalyst and reducing the influence on the reaction with silane in Step S2.

[0024] In some embodiments, in Step S1, the molar ratio of the dehydrated polybutylene adipate to HDI is 1:(2.0-2.5).

[0025] In some embodiments, in Step S1, the molar ratio of HDI to anhydrous ethanol is 1:(0.3-0.7).

[0026] In some embodiments, in step S2, the mass ratio of the silane to reactant 1 is (0.01 - 0.04):1.

[0027] On the other hand, the present invention provides an application of the above-mentioned foaming composition, and the specific steps are as follows: Mix the polyol and the foaming composition evenly, then add MDI and stir evenly, and place it in a mold and let it stand to obtain a polyurethane foam material.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The process route of the foaming composition provided by the present invention is environmentally friendly, reducing the risk of flammability and explosiveness in the traditional process, reducing the risk of fire and explosion during production, transportation, storage and use, and greatly reducing environmental pollution and health hazards to operators.

[0030] 2. The blowing agent provided by the present invention does not contain elements such as fluorine and chlorine, is friendly to working conditions. By using cyclopentane / isopentane in combination, not only can the foaming speed be controlled, but also excellent heat insulation performance can be imparted to the foam material, improving the heat preservation effect. On this basis, the defect of flammability and explosiveness of pentane blowing agent is compensated by adding diisopropyl azodicarboxylate.

[0031] 3. The present invention strengthens the solubility of the chlorine-free and fluorine-free blowing agent in polyether polyol through a solubilizer to ensure the foaming effect.

[0032] 4. The present invention improves the problem of reduced heat preservation effect of polyurethane foam materials caused by the high gas-phase thermal conductivity of the chlorine-free and fluorine-free blowing agent; and the problem of uneven cell size or open-cell phenomenon that may be caused by the accelerated thermal diffusion rate of the gas in the cells; first, the reaction product of dehydrated polybutylene adipate and HDI is used to reduce the gas diffusion rate, improve the porous structure of the foam, and make it more delicate and uniform; then, the problem of incomplete foaming of the blowing agent caused by the former is adjusted by introducing the silane coupling agent KH550. Specific Embodiments

[0033] The present invention will be described below in conjunction with specific implementation examples. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not to limit the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0034] It should be noted that the raw materials used in the following preparation examples and examples, unless otherwise specified, are from any commercially available manufacturer: the model of dehydrated polybutylene adipate is PBA2000.

[0035] Preparation Example 1

[0036] The preparation steps of blowing aid A are as follows:

[0037] S1. Under nitrogen protection, 0.1 mol of dehydrated polybutylene adipate and 0.22 mol of HDI are reacted at 85 °C for 4 h, then 0.11 mol of absolute ethanol is added and reacted at 65 °C for 2.5 h, and then vacuum distillation is carried out to obtain reactant 1;

[0038] S2. 7 g of silane KH550 is dissolved in 100 g of an ethanol aqueous solution with a concentration of 60 wt%, acetic acid is added to adjust the pH value to 5, after standing for 50 min, 350 g of reactant 1 is added, stirred for 40 min, the solid is collected by filtration, washed with water, and dried at 40 °C to constant weight to obtain foaming aid A.

[0039] Preparation Example 2

[0040] The preparation steps of foaming aid B are as follows:

[0041] Under nitrogen protection, 0.1 mol of dehydrated polybutylene adipate and 0.22 mol of HDI are reacted at 85 °C for 4 h, then 0.11 mol of absolute ethanol is added and reacted at 65 °C for 2.5 h, and then vacuum distillation is carried out to obtain foaming aid B.

[0042] Preparation Example 3

[0043] The difference between the preparation steps of foaming aid C and Preparation Example 1 is that the amount of HDI used is 0.18 mol.

[0044] Preparation Example 4

[0045] The difference between the preparation steps of foaming aid D and Preparation Example 1 is that the amount of HDI used is 0.26 mol.

[0046] Preparation Example 5

[0047] The difference between the preparation steps of foaming aid E and Preparation Example 1 is that the amount of silane KH550 used is 2 g.

[0048] Preparation Example 6

[0049] The difference between the preparation steps of foaming aid F and Preparation Example 1 is that the amount of silane KH550 used is 15 g.

[0050] Example 1

[0051] A highly stable foaming composition for polyurethane, calculated by 100% by mass percentage, comprises the following raw materials: solubilizer 66%, chlorine-free fluorine foaming agent 13%, PT303 catalyst 2%, foaming aid A 4%, DMMP 3%, and the balance is water;

[0052] The chlorine-free fluorine-free blowing agent contains 5% cyclopentane, 3.7% isopentane, and 4.3% diisopropyl azodicarboxylate;

[0053] The solubilizer contains 59% methyl tert-butyl ether and 7% glycerol.

[0054] Example 2

[0055] A highly stable foaming composition for polyurethane, calculated by 100% by mass percentage, contains the following raw materials: 58% solubilizer, 10% chlorine-free fluorine-free blowing agent, 1% PT303 catalyst, 2% foaming aid A, 2% DMMP, and the balance is water;

[0056] The chlorine-free fluorine-free blowing agent contains 4.7% cyclopentane, 3% isopentane, and 2.3% diisopropyl azodicarboxylate;

[0057] The solubilizer contains 54% methyl tert-butyl ether and 4% glycerol.

[0058] Example 3

[0059] A highly stable foaming composition for polyurethane, calculated by 100% by mass percentage, contains the following raw materials: 72% solubilizer, 15% chlorine-free fluorine-free blowing agent, 3% PT303 catalyst, 5% foaming aid A, 4% DMMP, and the balance is water;

[0060] The chlorine-free fluorine-free blowing agent contains 5% cyclopentane, 4.5% isopentane, and 5.5% diisopropyl azodicarboxylate;

[0061] The solubilizer contains 61% methyl tert-butyl ether and 11% glycerol.

[0062] Example 4

[0063] This example provides a highly stable foaming composition for polyurethane. The specific implementation method is the same as that of Example 1, except that: the foaming aid A is replaced by an equal amount of foaming aid B.

[0064] Example 5

[0065] This example provides a highly stable foaming composition for polyurethane. The specific implementation method is the same as that of Example 1, except that: the foaming aid A is replaced by an equal amount of foaming aid C.

[0066] Example 6

[0067] This example provides a highly stable foaming composition for polyurethane. The specific implementation method is the same as that of Example 1, except that: the foaming aid A is replaced by an equal amount of foaming aid D.

[0068] Example 7

[0069] This embodiment provides a highly stable foaming composition for polyurethane. The specific implementation manner is the same as that of Embodiment 1, except that: the foaming aid A is replaced by an equal amount of foaming aid E.

[0070] Example 8

[0071] This embodiment provides a highly stable foaming composition for polyurethane. The specific implementation manner is the same as that of Embodiment 1, except that: the foaming aid A is replaced by an equal amount of foaming aid F.

[0072] Example 9

[0073] This embodiment provides a highly stable foaming composition for polyurethane. The specific implementation manner is the same as that of Embodiment 1, except that: the chlorine-free fluorine foaming agent contains 8.6% of cyclopentane and 6.4% of isopentane.

[0074] Example 10

[0075] This embodiment provides a highly stable foaming composition for polyurethane. The specific implementation manner is the same as that of Embodiment 1, except that: glycerol is replaced by an equal amount of methyl tert-butyl ether.

[0076] Example 11

[0077] A highly stable foaming composition for polyurethane, calculated by mass percentage of 100%, comprises the following raw materials: 66% of solubilizer, 13% of chlorine-free fluorine foaming agent, 2% of PT303 catalyst, 3% of DMMP, and the balance is water;

[0078] The chlorine-free fluorine foaming agent contains 5% of cyclopentane, 3.7% of isopentane, and 4.3% of diisopropyl azodicarboxylate;

[0079] The solubilizer contains 59% of methyl tert-butyl ether and 7% of glycerol.

[0080] Performance test:

[0081] The foaming compositions provided in Embodiments 1 to 11 are respectively stirred and mixed evenly with polyether polyol 4110 for 30 min, and then MDI is added and stirred for 1 min. The molar ratio of polyether polyol 4110 to MDI is 5:1, and the foaming composition accounts for 5 wt% of the total mass of polyether polyol 4110 and MDI. The mixed material is quickly and evenly poured into a mold and placed in an oven for foaming. After 20 min, it is taken out and cured at room temperature for 24 h to obtain a polyurethane foam material, and the following experiments are carried out:

[0082] 1. Foam density test: Cut the polyurethane foam material into cubes with dimensions of 1 cm × 1 cm × 1 cm. Use a micrometer to precisely measure the length, width, and height of the sample. Measure at multiple different positions and calculate the average value to obtain the volume of the polyurethane foam material. Then, precisely weigh the mass of the polyurethane foam material and take the average of three weighings as the final mass. Finally, calculate the density.

[0083] 2. Thermal conductivity test: Cut the polyurethane foam material into cubes with dimensions of 10 cm × 1 cm × 3 cm (length × width × height). Use the TC3000 universal thermal conductivity meter from Xi'an Xiaxi Electronic Technology to measure the thermal conductivity. The thermal conductivity is inversely proportional to the insulation effect.

[0084] 3. Compressive strength test: This test is carried out with reference to the literature "Compression Test Research on Polyurethane Foam Materials - Cao Jing".

[0085] The results are shown in Table 1.

[0086] Table 1

[0087] <![CDATA[Foam density (g / cm 3 )]]> Thermal Conductivity (w / m·k) Compressive Strength (MPa) Example 1 0.51 0.0304 12.55 Example 2 0.59 0.0375 11.91 Example 3 0.48 0.0332 11.48 Example 4 1.57 0.0794 11.10 Example 5 0.98 0.0541 10.96 Example 6 1.05 0.0616 10.72 Example 7 1.13 0.0672 10.68 Example 8 0.72 0.0473 10.11 Example 9 0.39 0.0289 8.64 Example 10 0.45 0.0408 9.28 Example 11 0.18 0.0833 6.88

[0088] From the data in Table 1, it can be seen that the polyurethane foam materials in Examples 1 - 3 have appropriate density, low thermal conductivity, and good compressive strength. Compared with Example 1, the blowing aid B used in Example 4 lacks the introduction of silane, which increases the foam density. The possible reason is that the foaming agent completes curing before sufficient foaming. Although it has little impact on the compressive strength, the insulation effect significantly decreases. In Examples 5 - 6, the amount of HDI is changed during the synthesis of the blowing aid, which may affect the subsequent introduction of silane, resulting in a relatively high foam density, and thus a certain decrease in the insulation effect and compressive effect. In Examples 7 - 8, the amount of silane KH550 is changed. From the data in the table, it can be seen that a decrease in the amount of silane KH550 is not conducive to forming a uniform and fine cell structure, leading to an increase in foam density. However, from the compressive strength, the cell structure is relatively firm; while an increase in the amount of silane KH550 has little impact on the density and insulation effect of the foam material.

[0089] Compared with Example 1, the non-chlorofluorocarbon blowing agent in Example 9 lacks diisopropyl azodicarboxylate, resulting in faster volatilization of pentane without the restriction of diisopropyl azodicarboxylate, accelerating the foaming speed and reducing the foam density. Although it improves the insulation effect, it affects the compressive strength of the material. Compared with Example 1, the solubilizer in Example 10 does not contain glycerol, reducing the compressive strength of the polyurethane foam. Example 11 does not add a blowing aid. In this state, the blowing agent will accelerate the thermal diffusion rate of the gas in the cells, thereby affecting the stability and uniformity of the cells, significantly reducing the foam density, and thus affecting the heat insulation effect and compressive strength.

[0090] The above-described embodiments and comparative examples do not impose any formal limitations on the present invention. Although the present invention has been disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, may make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A high stability foaming composition for polyurethane, characterized in that: The composition comprises the following raw materials by mass percentage: 58-72% of a solubilizer, 10-15% of a chlorine-free and fluorine-free foaming agent, 1-3% of a catalyst, 2-4% of a flame retardant, and the balance is water.

2. The high stability foaming composition for polyurethane according to claim 1, characterized in that: The chlorine-free and fluorine-free foaming agent comprises cyclopentane, isopentane and diisopropyl azodicarboxylate.

3. The high stability foaming composition for polyurethane according to claim 2, characterized in that: The mass ratio of cyclopentane, isopentane and diisopropyl azodicarboxylate is 1:(0.6-0.9):(0.5-1.1).

4. The high stability foaming composition for polyurethane according to claim 1, characterized in that: The solubilizing agent comprises methyl tert-butyl ether and glycerol.

5. The high stability foaming composition for polyurethane according to claim 4, characterized in that: The mass ratio of the methyl tert-butyl ether to glycerol is 1:(0.06-0.18).

6. The high stability foaming composition for polyurethane according to claim 1, characterized in that: The foaming composition further comprises 2-5% by mass of a foaming aid.

7. The high stability foaming composition for polyurethane according to claim 6, characterized in that: The preparation steps of the foaming aid are as follows: S1. Under nitrogen protection, dehydrated polybutylene adipate and HDI are reacted at 70-90° C. for 3-5 h, then anhydrous ethanol is added and reacted at 60-65° C. for 2-3 h, and distilled under reduced pressure to obtain reactant 1; S2. Dissolve silane KH550 in 40-70 wt% ethanol aqueous solution, add acetic acid to adjust the pH value to 4-6, let stand for 40-60 min, then add reactant 1, stir for 20-50 min, collect the solid by filtration, wash, and dry to constant weight to obtain a foaming aid.

8. The high stability foaming composition for polyurethane according to claim 7, characterized in that: In step S1, the molar ratio of the dehydrated polybutylene adipate to HDI is 1:(2.0-2.5).

9. The high-stability foaming composition for polyurethane according to claim 7, characterized in that: In step S2, the mass ratio of the silane to the reactant 1 is (0.01-0.04):

1.

10. Use of the high-stability foaming composition for polyurethane according to any one of claims 1 to 9, characterized in that: The specific steps are as follows: the polyol and the foaming composition are mixed evenly, then MDI is added and stirred evenly, and the mixture is placed in a mold and allowed to stand to obtain a polyurethane foam material.