Polyurethane foam, preparation method thereof and refrigerator

Abstract

The invention discloses polyurethane foam, a preparation method thereof and a refrigerator, and belongs to the technical field of refrigerator production. The polyether composition includes a polyol, a blowing agent, water, a catalyst, and a foam stabilizer; the polyol is prepared by reacting an initiator and oxyalkylene, the oxyalkylene is selected from one or more of propylene oxide, ethylene oxide and butylene oxide, the initiator is selected from a compound containing reactive hydrogen, the functionality of the polyol is greater than 3, and the hydroxyl value of the polyol is greater than 450; the foaming agent is prepared from at least one of pentane, 1, 1, 1, 3, 3-pentafluoropropane and trans-1-chloro-3, 3, 3-trifluoropropene; the catalyst is prepared from potassium isooctanoate and 1, 2-dimethylimidazole. The low-boiling-point foaming agent is applied to refrigerators, the problems that an existing low-boiling-point foaming agent system is poor in environmental friendliness and still long in refrigerator demolding time are solved, demolding can be achieved within the pressure maintaining time of 60-100 s, the expansion rate of polyurethane foam is effectively reduced, the foam skin thickness is improved, and the low-boiling-point foaming agent has the low heat conductivity coefficient and high strength.

Description

Technical Field

[0001] This invention belongs to the field of refrigerator manufacturing technology, and particularly relates to a polyurethane foam, its preparation method, and a refrigerator. Background Technology

[0002] Polyurethane foam, as a highly efficient thermal insulation material, is widely used as an insulation layer in the production of refrigerators, freezers, and water heaters. Its physical properties and manufacturing process performance cannot be completely replaced by other materials in the future. Currently, the industry commonly uses low-boiling-point foaming agents (boiling point < 0℃) to increase the flowability of the foam and reduce its density, thereby reducing the amount of material injected and achieving cost reduction and efficiency improvement. Low-boiling-point foaming agents mainly include two categories: hydrofluorocarbon foaming agents, such as tetrafluoroethane and difluoroethane, and pure alkanes, such as n-butane and isobutane. Considering environmental friendliness, international regulations have already restricted the use of high GWP (Gross Content Power) chlorofluorocarbons, further increasing the usage rate of alkane-based low-boiling-point foaming agents. Currently, the demolding time for large refrigerators using alkane-based low-boiling-point foaming agents is mainly concentrated at 3-5 minutes, while for small refrigerators it is 2-3 minutes of pressure holding time (demolding time) to ensure the flatness of the refrigerated products, thus limiting production efficiency. In the refrigeration industry, where production efficiency is constantly improving, it is increasingly worthwhile to further study how to improve the demolding rate of refrigerators based on the foaming technology of low-boiling-point alkane systems.

[0003] Chinese patent CN107177028A discloses a hydrofluorocarbon low-boiling-point foaming agent system. The method for shortening the demolding time and improving the demolding efficiency is mainly achieved by using a high-functionality polyether and aromatic amine polyether polyol composition with high component content. The polyether composition mainly includes a polyol composition, a foaming agent composition, water, a catalyst composition, and silicone oil. The foaming process using the above-mentioned polyether composition as raw material is completed in a demolding time of 3 minutes. The refrigerator made with the above-mentioned foaming agent system is obtained in a demolding time of 150s-160s.

[0004] However, the low-boiling-point foaming agent system disclosed in the above patent has the problems of poor environmental friendliness and still long demolding time in refrigerators. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to overcome the problems of poor environmental friendliness and long demolding time in existing low-boiling-point foaming agent systems. The invention proposes an environmentally friendly polyurethane foam that can be demolded within a 60s-100s pressure holding time, effectively reduces the expansion rate of polyurethane foam, improves the foam skin thickness, has low thermal conductivity, and high strength, as well as its preparation method and a refrigerator.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a polyurethane foam comprising a polyether composition, wherein the polyether composition comprises a polyol, a blowing agent, water, a catalyst, and a foam stabilizer; the polyol is prepared by reacting an initiator with an oxidized olefin, wherein the oxidized olefin is selected from one or more of propylene oxide, ethylene oxide, and butene oxide; the initiator is selected from compounds containing active hydrogen; the polyol has a functionality >3 and a hydroxyl value >450; the blowing agent comprises at least one of pentane, 1,1,1,3,3-pentafluoropropane, and trans-1-chloro-3,3,3-trifluoropropene; and the catalyst comprises potassium isooctanoate and 1,2-dimethylimidazole.

[0008] Preferably, the pentane is cyclopentane, isopentane, or a mixture of cyclopentane and isopentane in a mass ratio of (7-10):(3-10).

[0009] Preferably, the foaming agent further includes a low-boiling-point foaming agent, which is a mixture of n-butane, isobutane, or n-butane and isobutane in a mass ratio of (0.8-1.2):(0.7-0.3).

[0010] Preferably, the catalyst comprises a foaming catalyst, a gel-type catalyst, and a polymerization catalyst; the foaming catalyst is selected from at least one of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, N-methyldicyclohexylamine, and tetramethylhexanediamine; the gel-type catalyst is selected from 1,2-dimethylimidazole, or a mixture of 1,2-dimethylimidazole with at least one of dimethylcyclohexylamine and dimethylbenzylamine; the polymerization catalyst is selected from isooctanoate, or a mixture of isooctanoate with at least one of potassium acetate, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine, (2-hydroxypropyl), trimethylammonium formate, ethyl quaternary ammonium salt, and octyl quaternary ammonium salt.

[0011] Preferably, the foam stabilizer is at least one of the following: alkali metal salt of fatty acid, amine salt of fatty acid, castor oil, ricinoleic acid, and siloxane polymer.

[0012] Preferably, the polyol comprises 100 parts by weight, the foaming agent comprises any value of 15-25 parts by weight, the water comprises any value of 1.6-2.3 parts by weight, the catalyst comprises any value of 1.5-5 parts by weight, the foam stabilizer comprises any value of 1.8-2.5 parts by weight; the potassium isooctanoate comprises any value of 0.5-2 parts by weight, the 1,2-dimethylimidazole comprises any value of 1.5-5 parts by weight, the pentane comprises any value of 10-13 parts by weight, the 1,1,1,3,3-pentafluoropropane comprises any value of 5-9 parts by weight, and the trans-1-chloro-3,3,3-trifluoropropene comprises any value of 4-8 parts by weight.

[0013] Preferably, the polyether composition is prepared by the following method:

[0014] The polyol, catalyst, water, and foam stabilizer are first mixed to obtain a first mixture; the first mixture is then mixed with the foaming agent to obtain a second mixture; the second mixture is then mixed with a low-boiling-point foaming agent at 0.4-1.0 MPa using a static premixing device to obtain a combined polyether.

[0015] Preferably, the first mixture is stirred for 0.5-1.5 h at a temperature of 25±5℃ and a pressure of 0.5-1.5 MPa; the second mixture further includes mixing the first mixture with pentane at 0.4-1.0 MPa for 0.5-1.5 h to obtain the second mixture.

[0016] Another aspect of the present invention provides a polyurethane foam according to any of the above technical solutions, comprising: mixing the polyether composition with an organic polyisocyanate and injecting it into a mold cavity through a high-pressure foaming machine at an overfill rate of 1.10-1.20 for foaming treatment to obtain the polyurethane foam.

[0017] The present invention also provides a refrigerator comprising the polyurethane foam described in any of the above technical solutions.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention provides a polyurethane foam by optimizing the polyol, foaming agent, and catalyst, particularly by using potassium isooctanoate (K15) and 1,2-dimethylimidazole (DMI) as part of the catalyst. This optimizes the foaming reaction time, shortens the curing time, and accelerates the post-curing speed of the foam, ensuring a low demolding expansion rate and adhesion after rapid demolding. Specifically, by adding K15 and DMI catalysts to the polyol and foaming agent specified in this invention, the reaction speed of the black and white materials can be accelerated, greatly improving the foam molding speed and demolding efficiency of refrigerated products. K15 can accelerate the foaming trimerization reaction, improve the expansion rate of the polyurethane foam after demolding, and reduce the deformation of the polyurethane foam and the refrigerator products using it. DMI can accelerate the foaming gelation reaction, thereby improving the foam curing effect. This results in a thinner skin on the foam surface, a uniform and fine cell structure, and increased foam adhesion. After demolding, the polyurethane foam exhibits characteristics such as reduced density, high strength, and low thermal conductivity, which can greatly improve the demolding efficiency of the foaming process for refrigerated products. Detailed Implementation

[0020] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0021] This invention provides a polyurethane foam comprising a polyether composition, wherein the polyether composition includes a polyol, a blowing agent, water, a catalyst, and a foam stabilizer; the polyol is prepared by reacting an initiator with an oxidized olefin, wherein the oxidized olefin is selected from one or more of propylene oxide, ethylene oxide, and butene oxide; the initiator is selected from compounds containing active hydrogen; the polyol has a functionality >3 and a hydroxyl value >450; the blowing agent includes at least one of pentane, 1,1,1,3,3-pentafluoropropane, and trans-1-chloro-3,3,3-trifluoropropene; the catalyst includes potassium isooctanoate and 1,2-dimethylimidazole. This polyurethane foam optimizes the polyol, blowing agent, and catalyst, particularly by using potassium isooctanoate (K15) and 1,2-dimethylimidazole (DMI) as part of the catalyst, thereby optimizing the foaming reaction time, shortening the curing time, accelerating the post-curing speed of the foam, and ensuring a low demolding expansion rate and adhesion after rapid demolding. Specifically, by adding two catalysts, K15 and DMI, to the polyol and foaming agent specified in this invention, the reaction speed of black and white materials can be accelerated, greatly improving the foam molding speed and demolding efficiency of refrigerated products. K15 can accelerate the foaming trimerization reaction, improve the expansion rate of polyurethane foam after demolding, and reduce the deformation of polyurethane foam and refrigerator products using it. DMI can accelerate the foaming gelation reaction, thereby improving the foam curing effect, resulting in a thinner skin on the foam surface, a uniform and delicate cell structure, and increased foam adhesion. After demolding, the polyurethane foam has characteristics such as reduced density, high strength, and low thermal conductivity, which can greatly improve the demolding efficiency of the foaming process of refrigerated products.

[0022] The polyurethane foam prepared by the above-mentioned technical solution using a low-boiling-point composite foaming system has the characteristics of low density, good thermal insulation performance, zero ozone potential (ODP), low GWP value and good environmental performance. Moreover, the smaller amount of foaming material used is more conducive to rapid demolding. This polyurethane foam has good mechanical properties, low expansion rate, rapid demolding (demolding time can be less than 100s), high production efficiency and strong economic applicability, which has great economic benefits in the refrigerator industry. It should be noted that this invention solves the problems of long demolding time and poor demolding efficiency in multi-component mixed foaming technology (CP+LBA / 245FA+R600+R600a) that uses alkane-based low-boiling-point foaming agents. It uses a novel low-boiling-point combined polyether foaming material containing multiple physical foaming agents. The low-boiling-point foaming agents are alkane-based and halogen-free. The specific foaming agent composition is CP+LBA / 245FA+R600+R600a. Furthermore, K-15 and DMI catalysts are added to accelerate the reaction of black and white materials. The speed of foam molding is greatly improved, enhancing the demolding efficiency of refrigerated products. Specifically, the K15 catalyst improves the expansion rate of polyurethane foam after demolding, reducing deformation of the foam and refrigerators using it. The DMI catalyst improves foam maturation within a shorter reaction time, resulting in a thinner skin on the foam surface, a more uniform and delicate cell structure, and increased foam adhesion. After demolding, the polyurethane foam exhibits reduced density, high strength, and low thermal conductivity. Refrigerators made using this foam material after rapid demolding maintain the same quality level as those made with ordinary foam material after longer demolding times. Regarding the combined use of DMI and K15 catalysts, the DMI catalyst primarily acts in the gelation reaction stage of the black and white materials, accelerating the reaction between hydroxyl and isocyanate groups. Since the gelation reaction is exothermic, this catalyst accelerates the exothermic process, releasing a large amount of heat in a short time. The K15 catalyst primarily acts on the polymerization reaction of isocyanate, accelerating this reaction, which requires higher temperatures. The rapid heat release during gelation provides the necessary high-temperature conditions for polymerization, accelerating the polymerization rate.

[0023] In a preferred embodiment, the pentane is cyclopentane, isopentane, or a mixture of cyclopentane and isopentane in a mass ratio of (7-10):(3-10). Further, the blowing agent also includes a low-boiling-point blowing agent, which is a mixture of n-butane, isobutane, or n-butane and isobutane in a mass ratio of (0.8-1.2):(0.7-0.3).

[0024] In a preferred embodiment, the catalyst comprises a foaming catalyst, a gel-type catalyst, and a polymerization catalyst; the foaming catalyst is selected from at least one of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, N-methyldicyclohexylamine, and tetramethylhexanediamine; the gel-type catalyst is selected from 1,2-dimethylimidazole, or a mixture of 1,2-dimethylimidazole with at least one of dimethylcyclohexylamine and dimethylbenzylamine; the polymerization catalyst is selected from isooctanoate, or a mixture of isooctanoate with at least one of potassium acetate, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine, (2-hydroxypropyl), ammonium trimethylformate, ethyl quaternary ammonium salt, and octyl quaternary ammonium salt.

[0025] In a preferred embodiment, the foam stabilizer is at least one of an alkali metal salt of fatty acid, an amine salt of fatty acid, castor oil, ricinoleic acid, and a siloxane polymer. More preferably, it is at least one of silicone oils L6863, L6988, L-6952, AK8830, B8525, B8545, AK8812 from Mester, and AK8809 from Mester.

[0026] In a preferred embodiment, the polyol comprises 100 parts by weight, the foaming agent comprises any value of 15-25 parts by weight, the water comprises any value of 1.6-2.3 parts by weight, the catalyst comprises any value of 1.5-5 parts by weight, the foam stabilizer comprises any value of 1.8-2.5 parts by weight, the potassium isooctanoate comprises any value of 0.5-2 parts by weight, the 1,2-dimethylimidazole comprises any value of 1.5-5 parts by weight, the pentane comprises any value of 10-13 parts by weight, the 1,1,1,3,3-pentafluoropropane comprises any value of 5-9 parts by weight, and the trans-1-chloro-3,3,3-trifluoropropene comprises any value of 4-8 parts by weight.

[0027] In the above technical solution, the polyether polyol is prepared by reacting an initiator with an oxidized olefin. The oxidized olefin is selected from one or more of propylene oxide, ethylene oxide, and butene oxide. The initiator is selected from one or more compounds containing active hydrogen, such as o-toluene diamine, sucrose, glycerol, vegetable oil, trimethylolpropane, pentaerythritol, sorbitol, xylitol, mannitol, methyl glucoside, ethylenediamine, and triethanolamine. High-functionality, high-hydroxyl-value polyether polyols can provide sufficient crosslinking and rigidity for the foam, while low-functionality, low-hydroxyl-value polyether polyols can provide good flowability for the foaming material. Phthalic anhydride polyester polyols can also be selected as one of the composite polyols. Furthermore, according to actual needs, the above polyols can be compounded to achieve a functionality >3 and a hydroxyl value >450, thereby obtaining better foam performance. Preferably, the hydroxyl value of sorbitol polyether polyol is 400-500 mg KOH / g, and the viscosity is 8000-15000 mPa·s; the hydroxyl value of o-toluene diamine polyether polyol is 360-460 mg KOH / g, and the viscosity is 6000-9000 mPa·s; the hydroxyl value of sucrose polyether polyol is 380-480 mg KOH / g, and the viscosity is 5000-12000 mPa·s; the hydroxyl value of glycerol polyether polyol is 160-260 mg KOH / g, and the viscosity is 300-600 mPa·s; and the hydroxyl value of phthalic anhydride polyester polyol is 390-490 mg KOH / g, and the viscosity is 3000-5000 mPa·s.

[0028] In a preferred embodiment, the polyether composition is prepared by the following method: first mixing the polyol, catalyst, water, and foam stabilizer to obtain a first mixture; second mixing the first mixture with the blowing agent to obtain a second mixture; and third mixing the second mixture with a low-boiling-point blowing agent at 0.4-1.0 MPa using a static premixing device to obtain a combined polyether. In a preferred embodiment, the first mixing is completed by stirring for 0.5-1.5 h at a temperature of 25±5℃ and a pressure of 0.5-1.5 MPa; the second mixing further includes: mixing the first mixture with pentane at 0.4-1.0 MPa for 0.5-1.5 h to obtain the second mixture.

[0029] Another aspect of the present invention provides a polyurethane foam according to any of the above technical solutions, comprising: mixing the polyether composition with an organic polyisocyanate and injecting it into a mold cavity through a high-pressure foaming machine at an overfill rate of 1.10-1.20 for foaming treatment to obtain the polyurethane foam.

[0030] This invention also provides a refrigerator comprising the polyurethane foam described in any of the above technical solutions. This refrigerator uses less foam, has good environmental performance, and can ensure the flatness of the product after demolding in a short time. Compared with existing cabinet foam compositions, the rapid demolding foam composition of this invention achieves a demolding time of less than 100 seconds, and even less than 60 seconds, when applied to cabinet foaming; the thermal conductivity at an average temperature of 10°C is 18.5-18.9 mw / mK.

[0031] To provide a clearer and more detailed description of the polyurethane foam, its preparation method, and the refrigerator provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0032] In this invention, unless otherwise specified, the various terms used are defined as follows:

[0033] Just-in-fill weight (MFW): The minimum weight required to fully fill the mold, in grams;

[0034] Molded core density: The effective density of foam, that is, the core density of foam after removing the skin;

[0035] Fill rate: Injected weight * 100 / MFW, in %;

[0036] Fiber time: The time from the start of mixing to when the stick placed in the foam stretches out the fibers upon removal;

[0037] Free foam density: The density of foam prepared by foaming in a free state (without a mold);

[0038] Demolding time: The time from foam injection to mold opening;

[0039] Thermal conductivity λ: Measured using a TAFOX-200 thermal conductivity meter at an average temperature of 10℃ (2℃ for the upper plate and 18℃ for the lower plate) according to ISO 12939-01 / DIN 52612. Foam samples were cut from the center of the molded portion 24 hours after foam preparation, and the measurements were taken immediately after cutting. The unit is mW / m·K.

[0040] Foam compressive strength: Measured according to DIN 53421-06-84, unit: kPa;

[0041] Dimensional stability: The dimensional change of foam after 24 hours at -30℃ is measured, and the value is expressed as a percentage.

[0042] Expansion rate: Foam expansion rate is a method for detecting the curing level of foam; the expansion rate calculation formula is as follows, with units of %. In this invention, the expansion rate of foam material produced by H-Mould mold is measured.

[0043] Expansion rate = (maximum foam thickness after demolding - mold thickness) / mold thickness × 100%.

[0044] Adhesion level: Represents the level of foam maturation within a certain demolding time; divided into three levels: A, B, and C. A means the foam does not stick to the mold at all, indicating good maturation; B means the foam sticks slightly, indicating average maturation; and C means the foam sticks severely, indicating poor maturation.

[0045] Example 1

[0046] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 1 part of DMI, 0.5 parts of K15, 1.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0047] Preparation method of polyether composition: A first mixture is formed by mixing a polyol, a catalyst, water, and a foam stabilizer to obtain a first mixture; the first mixture is then mixed with a blowing agent to obtain a second mixture; the second mixture is then mixed with a low-boiling-point blowing agent at 0.4-1.0 MPa using a static premixing device to obtain a combined polyether. The first mixing is completed by stirring for 0.5-1.5 h at a temperature of 25±5℃ and a pressure of 0.5-1.5 MPa; the second mixing further includes mixing the first mixture with pentane at 0.4-1.0 MPa for 0.5-1.5 h to obtain the second mixture.

[0048] Example 2

[0049] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 1 part of DMI, 1 part of K15, 1.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0050] The polyether composition was prepared using the same method as in Example 1.

[0051] Example 3

[0052] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 1.5 parts of DMI, 1 part of K15, 1 part of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0053] The polyether composition was prepared using the same method as in Example 1.

[0054] Example 4

[0055] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 2 parts of DMI, 1 part of K15, 0.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0056] The polyether composition was prepared using the same method as in Example 1.

[0057] Example 5

[0058] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.2 parts of low-boiling-point blowing agent R600, 0.4 parts of low-boiling-point blowing agent R600 a, 2 parts of DMI, 1 part of K15, 0.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0059] The polyether composition was prepared using the same method as in Example 1.

[0060] Example 6

[0061] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 1.5 parts of DMI, 1.5 parts of K15, 0.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0062] The polyether composition was prepared using the same method as in Example 1.

[0063] Example 7

[0064] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 0 parts of DMI, 1 part of K15, 2.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0065] The polyether composition was prepared using the same method as in Example 1.

[0066] Example 8

[0067] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 1.6 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600 A, 1.5 parts of DMI, 0 parts of K15, 2 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 156 parts of polymeric MDI.

[0068] The polyether composition was prepared using the same method as in Example 1.

[0069] Comparative Example 1

[0070] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 0 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600a, 0 parts of DMI, 0 parts of K15, 3.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 155 parts of polymeric MDI.

[0071] The polyether composition was prepared using the same method as in Example 1.

[0072] Comparative Example 2

[0073] Polyether composition formulation: 100 parts of combined polyether polyol, 14 parts of cyclopentane CP, 7.5 parts of LBA or 245fa, 0 parts of low-boiling-point blowing agent R600, 0 parts of low-boiling-point blowing agent R600a, 0 parts of DMI, 0 parts of K15, 2.5 parts of other catalysts, 2 parts of silicone oil surfactant, 2.1 parts of water, and 155 parts of polymeric MDI.

[0074] The polyether composition was prepared using the same method as in Example 1.

[0075] The combined polyethers prepared in Examples 1-8 and Comparative Examples 1-2 were respectively mixed with organic polyisocyanate (PM-200) at a weight ratio of 1:1.20. The mixture was injected into a Laneige mold cavity under a pressure of 130±10 bar through the high-pressure mixing head of a foaming machine. (The mold dimensions are 2000×400×50mm (length×width×height), with vent holes at the top to allow timely discharge of gas generated inside the mold during foaming.) After curing for 300 seconds, the mold was opened to obtain polyurethane foam.

[0076] (I) The foam produced in Laneige molds can be used to measure thermal conductivity, compressive strength, and core density;

[0077] (II) Using the same method, the combined polyether and organic polyisocyanate were injected into an H-Mould mold with dimensions of 700×500×100mm. The obtained foam was used to test the demolding properties and expansion rate of the foam. The mold temperature was about 50℃.

[0078] The test results are shown in Table 1 below.

[0079] Table 1. Foam Performance Test Results

[0080]

[0081]

[0082] As can be seen from Examples 3-6 and Example 8 in Table 1 above, polyurethane foam with good demolding curing degree and non-stickiness after demolding can be obtained by using DMI catalyst polyol composition.

[0083] As can be seen from Examples 1-7 in Table 1 above, polyurethane foam with low demolding expansion rate and good dimensional stability can be obtained by using K15 catalyst polyol composition.

[0084] As can be seen from the examples, the polyol composition using DMI+K15 catalyst can produce polyurethane foam with good demolding curing degree, low expansion rate, high strength, and good dimensional stability within a demolding time of 100s. Furthermore, a comparison between Examples 1 and 2 shows that appropriately increasing the K15 catalyst is beneficial to further reduce the demolding expansion rate. A comparison between Examples 1 and 3 shows that appropriately increasing the DMI catalyst can further improve the demolding curing degree of polyurethane foam.

[0085] As can be seen from Table 1 and Comparative Example 1 above, Comparative Example 1, which does not contain DMI+K15 catalyst, shows a significant increase in foam expansion rate and thermal conductivity, a decrease in dimensional stability, and a worse degree of maturation. As can be seen from the comparative example, with a decrease in the total amount of catalyst, it is demolded at a demolding time of 150s, and the overall expansion rate and degree of maturation are poor.

[0086] The polyurethane foam prepared in Examples 1-3 and Comparative Example 1 was used as insulation material in refrigerators, and the performance of the refrigerators was tested. Specifically, two identical refrigerator models were made in Examples 1-3 and Comparative Example 1. The demolding time was 100s for the 336L refrigerator and 60s for the 136L refrigerator. The normal demolding time for both models of refrigerators was 150s.

[0087] The properties of the produced foam are detailed in Table 2. After the refrigerator is demolded, the thickness of the left and right sides of the cabinet at the top, middle and bottom is measured to be the difference between the thickness of the corresponding positions of the foamed cabinet, that is, the deformation of the cabinet before and after demolding (in mm). The average value is taken at each point, and the maximum and minimum difference at each point should be less than 2 mm.

[0088] Cabinet high and low temperature test: alternating ambient temperature changes of -30℃ for 24 hours and 50℃ for 24 hours constitute one cycle, with a total of 4 cycles. The main test is to determine whether the polyurethane foam delaminates from the refrigerator liner and outer shell under extreme high and low temperature environmental impact, thus assessing the degree of foam curing.

[0089] Table 2 Comparison of Refrigerator Foam Performance between Examples 1-3 and Comparative Example 1 Table 2 Comparison of Refrigerator Foam Performance in Examples 1-3 and Comparative Example 1

[0090]

[0091]

[0092]

[0093] As shown in Table 2, the refrigerator bodies produced using the DMI+K15 foaming agent polyol composition as insulation material in Examples 1-6 meet the product performance requirements. The comparative examples, prepared with cyclopentane and 245fa and R600 polyol formulations without DMI+K15 foaming agent, had a normal demolding time of 150s. After demolding for 100s, the refrigerator exhibited significant deformation (greater than 2mm), but passed high and low temperature tests, indicating good foam curing. Compared to Comparative Examples 3-4, the deformation was greater, and the high and low temperature tests failed, with the polyurethane foam detaching from the outer shell. Examples 1-6 showed smaller deformation and better curing. Refrigerator bodies of the same model were also produced. Therefore, it is evident that K15 foaming agent + DMI foaming agent is necessary in this invention; the low-boiling-point foaming agent promotes rapid curing of the foaming system and shortens the demolding time.

Claims

1. A polyurethane foam, characterized in that The invention comprises a polyether composition, which comprises a polyol, a foaming agent, water, a catalyst, and a foam stabilizer; the polyol is prepared by reacting an initiator and an olefin oxide, the olefin oxide is selected from one or more of propylene oxide, ethylene oxide, and butylene oxide, the initiator is selected from compounds containing active hydrogen, the functionality of the polyol is greater than 3, and the hydroxyl value is greater than 450; the foaming agent comprises at least one of pentane, 1,1,1,3,3-pentafluoropropane and trans-1-chloro-3,3,3-trifluoropropene; the catalyst comprises potassium isooctanoate and 1,2-dimethylimidazole.

2. The polyurethane foam according to claim 1, characterized in that The pentane is cyclopentane, isopentane, or a mixture of cyclopentane and isopentane in a mass ratio of (7-10):(3-10).

3. The polyurethane foam according to claim 1, characterized in that The foaming agent also includes a low boiling point foaming agent, which is n-butane, isobutane, or a mixture of n-butane and isobutane in a mass ratio of (0.8-1.2):(0.7-0.3).

4. The polyurethane foam according to claim 1, characterized in that The catalyst includes a foaming catalyst, a gel catalyst and a polymerization catalyst; the foaming catalyst is selected from at least one of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, N-methyldicyclohexylamine and tetramethylhexanediamine; the gel catalyst is selected from 1,2-dimethylimidazole, or a mixture of 1,2-dimethylimidazole and at least one of dimethylcyclohexylamine and dimethylbenzylamine; the polymerization catalyst is selected from isooctanoic acid ester, or a mixture of isooctanoic acid ester and at least one of potassium acetate, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine, (2-hydroxypropyl), trimethylammonium formate, ethyl quaternary ammonium salt and octyl quaternary ammonium salt.

5. The polyurethane foam according to claim 1, characterized in that The foam stabilizer is at least one of alkali metal salts of fatty acids, amine salts of fatty acids, castor oil, ricinoleic acid, and silicone polymers.

6. The polyurethane foam according to claim 1, characterized in that The weight portion of the polyol is 100 parts, the weight portion of the blowing agent is any value in the range of 15-25 parts, the weight portion of the water is any value in the range of 1.6-2.3 parts, the weight portion of the catalyst is any value in the range of 1.5-5 parts, and the weight portion of the foam stabilizer is any value in the range of 1.8-2.5 parts; the weight portion of the potassium isooctanoate is any value in the range of 0.5-2 parts, the weight portion of the 1,2-dimethylimidazole is any value in the range of 1.5-5 parts, the weight portion of the pentane is any value in the range of 10-13 parts, the weight portion of the 1,1,1,3,3-pentafluoropropane is any value in the range of 5-9 parts, and the weight portion of the trans-1-chloro-3,3,3-trifluoropropene is any value in the range of 4-8 parts.

7. The polyurethane foam according to claim 1, characterized in that The polyether composition is prepared by the following method: The polyol, catalyst, water and foam stabilizer are first mixed to obtain a first mixture; the first mixture is second mixed with the foaming agent to obtain a second mixture; the second mixture is third mixed with a low boiling point foaming agent at 0.4-1.0 MPa by a static premixing device to obtain a combined polyether.

8. The polyurethane foam according to claim 7, characterized in that The first mixing is completed by stirring for 0.5-1.5h at a temperature of 25±5°C and a pressure of 0.5-1.5MPa; The second mixing further comprises: mixing the first mixture with pentane at 0.4-1.0 MPa for 0.5-1.5 hours to obtain the second mixture.

9. The polyurethane foam according to any one of claims 1 to 8, characterized in that include: The polyether composition is mixed with an organic polyisocyanate and injected into a mold cavity through a high-pressure foaming machine at an overfilling rate of 1.10-1.20 for foaming treatment to obtain the polyurethane foam.

10. A refrigerator, characterized in that: The refrigerator comprises the polyurethane foam according to any one of claims 1 to 8.

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