Polyurethane rigid foam, preparation method thereof and refrigerator

Abstract

The invention discloses polyurethane rigid foam, a preparation method thereof and a refrigerator, and belongs to the field of cold product foaming thermal insulation materials. The raw materials comprise polyether polyol and a reaction catalyst; the polyether polyol is composed of bio-based polyether polyol and regenerated polyether polyol; the reaction catalyst comprises potassium isooctanoate. The polyurethane white material is applied to the aspect of foaming thermal insulation materials of refrigerators and freezers, and the problem that the environment-friendly low-carbon application of the polyurethane foam white material is hindered due to the fact that petroleum-based polyether polyol is indispensable in the existing white material for preparing the polyurethane foaming material is solved; not only can the performance use requirements of the polyurethane foam be met, but also the greenization and low carbonization of the polyurethane foam can be improved.

Description

Technical Field

[0001] The invention belongs to the field of foaming insulation materials for cold products, and in particular relates to a polyurethane rigid foam, a preparation method thereof and a refrigerator. Background Art

[0002] The polyurethane rigid foam material for refrigerators is generated by the reaction of black material and white material. The black material is composed of polymethylene polyphenyl diisocyanate (MDI) with different polymerization degrees, and the white material is mainly composed of various types of polyether polyols, foaming agents, catalysts, silicone oil surfactants, and water, of which polyether polyols account for more than 80%. At present, the polyol raw materials used in the industry mainly come from the cracking and fractionation of petrochemical energy. The products obtained through petrochemical cracking have uniform properties, excellent performance, and are stable and controllable, but the source is non-renewable and the process consumes a lot of energy. The raw materials produced by renewable means are limited by unstable sources, and the recycling process or pre-treatment process is complex and inefficient, so most of them remain in laboratory research. Affected by policies, renewable raw materials are bound to be further studied and expanded.

[0003] In polyurethane foam materials, the white material contains a variety of ingredients, and 80% of the content is 3-5 kinds of polyether polyols. Each polyol has different properties due to its different molecular structure. Some contribute significantly to the thermal insulation effect, some have a significant impact on the foam strength, and some have a low viscosity, which is conducive to industrial use. The green and low-carbon application of polyurethane foam white material is generally achieved through two ways: recycling and degrading waste polyurethane foam and using biomass polyol raw materials. However, due to the current types of bio-based polyethers, it is impossible to provide comprehensive performance requirements. Therefore, petroleum-based polyether polyols are often used in the preparation process of existing polyurethane foam materials. The principle of recycled polyether polyols is similar. Due to the molecular structure, some types of polyether polyols cannot be obtained by regeneration. Due to the limited types, they cannot be used alone and must be used in combination with petroleum-based polyether polyols. Summary of the invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is that petroleum-based polyether polyols are indispensable in the existing white materials for preparing polyurethane foam materials, which leads to the obstruction of the green and low-carbon application of polyurethane foam white materials. A polyurethane rigid foam, a preparation method and a refrigerator are proposed which use bio-based polyether polyols and waste recycled polyether polyols as polyurethane white material raw materials, which can not only meet the performance requirements of polyurethane foam, but also improve the green and low-carbonization of polyurethane foam.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0006] On one hand, the present invention provides a method for preparing polyurethane rigid foam, wherein the raw materials include polyether polyol and a reaction catalyst; the polyether polyol is composed of bio-based polyether polyol and recycled polyether polyol; the reaction catalyst includes potassium isooctanoate; the bio-based polyether polyol is prepared by the following method: the bio-based polyol is subjected to epoxidation reaction with an epoxidizing agent under the action of a catalyst to generate epoxidized bio-based polyol, the epoxidized bio-based polyol is subjected to ring-opening polymerization reaction to generate bio-based polyether polyol; the recycled polyether polyol is prepared by the following method: the polyurethane foam is ground to a particle size of ≤200 μm, ethylene glycol is used as a decomposition agent, alcoholysis is performed on the ground polyurethane foam, carbamate groups in the polyurethane foam are subjected to ester exchange reaction with ethylene glycol, the carbamate groups are replaced by short alcohol chains to obtain a decomposition liquid, and ethylenediamine is used to perform a hydrothermal aminolysis reaction on the decomposition liquid to obtain a regenerated polyether polyol.

[0007] Preferably, the average number of functional groups of the bio-based polyether polyol is selected from 3-6, and the hydroxyl value is 300-600 mgKOH / g; the average number of functional groups of the recycled polyether polyol is 2-5, and the hydroxyl value is 200-600 mgKOH / g.

[0008] Preferably, the mass fraction of the bio-based polyether polyol in the polyether polyol is selected from any value between 10% and 90%, and the mass fraction of the recycled polyether polyol is selected from any value between 10% and 90%.

[0009] Preferably, the raw materials include: cyclopentane foaming agent, surfactant, polymeric MDI, the reaction catalyst, and the polyether polyol; the weight ratio of the polymeric MDI to the polyether polyol is selected from any value in the range of 1.25-1.30.

[0010] Preferably, the surfactant is selected from at least one of alkali metal salts of fatty acids, amine salts of fatty acids, castor oil, ricinoleic acid, and silicone polymers; the reaction catalyst includes a foaming catalyst, a gel catalyst, and a trimerization catalyst, and the trimerization catalyst includes potassium isooctanoate; the mass ratio of the foaming catalyst, the gel catalyst, and the trimerization catalyst is selected from any ratio of 2-4:3-8:1-3.

[0011] Preferably, the surfactant is selected from 1-3 of silicone oil L6863, silicone oil L6988, silicone oil AK8830, silicone oil B8525, silicone oil B8545L-6863, L-6869, L-6970, L-6900, B-8423, B-8404, B-8407, B-8465, and B-8444.

[0012] Preferably, the foaming catalyst is a mixture of one or more of pentamethyldiethylenetriamine, N-methyldicycloethylamine, tetramethylhexanediamine or bis-dimethylaminoethyl ether; the gelling catalyst is a mixture of one or more of dimethylbenzylamine, dimethylcyclohexane or triethylenediamine; the trimerization catalyst is potassium isooctanoate or a mixture of potassium isooctanoate and one or more of PC-41, anhydrous sodium acetate, potassium acetate, TMR / TMR2, TMR30.

[0013] Preferably, in parts by weight, the amount of the bio-based polyether polyol is selected from any value between 20 and 60 parts; the amount of the recycled polyether polyol is selected from any value between 15 and 45 parts; the amount of the cyclopentane foaming agent is selected from any value between 12 and 16 parts; the amount of the reaction catalyst is selected from any value between 1 and 4 parts; the amount of the surfactant is selected from any value between 1.5 and 3 parts; the amount of the polymeric MDI is selected from any value between 145 and 160 parts; and the raw materials also include 1 to 3 parts of water.

[0014] Another aspect of the present invention provides a polyurethane rigid foam, which is prepared by the method for preparing the polyurethane rigid foam described in any of the above technical solutions.

[0015] The present invention also provides a refrigerator, wherein the foamed heat-insulating material of the freezer of the refrigerator adopts the polyurethane rigid foam described in the above technical solution.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The invention provides a method for preparing polyurethane rigid foam, which uses bio-based polyether polyol and waste recycled polyether polyol as polyurethane white material raw materials, limits the bio-based polyether polyol and waste recycled polyether polyol, and simultaneously introduces a potassium isooctanoate trimerization catalyst to strengthen the molecular cross-linking structure and reduce the demolding expansion rate. The bio-based polyether polyol raw material and the chemically recycled polyether polyol raw material defined in the invention are used in combination to ensure that the foam has excellent overall performance, thereby avoiding the defects of the current green foaming material foam being easy to age and crack, having poor thermal insulation performance, and having poor weather resistance;

[0018] The present invention provides a polyurethane rigid foam which does not use petroleum-based polyether polyols and not only has the characteristics of being green and low-carbon, but also maintains the performance and use requirements of the polyurethane rigid foam;

[0019] The invention provides a refrigerator having the characteristics of good heat preservation performance, green and low carbon and good weather resistance. DETAILED DESCRIPTION

[0020] The technical scheme in the specific embodiment of the present invention is described in detail and completely below. Obviously, the described embodiment is only a part of the specific implementation of the overall technical scheme of the present invention, rather than all implementations. Based on the overall concept of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.

[0021] On one hand, the present invention provides a method for preparing polyurethane rigid foam, wherein the raw materials include polyether polyol and a reaction catalyst; the polyether polyol is composed of bio-based polyether polyol and recycled polyether polyol; the reaction catalyst includes potassium isooctanoate; the bio-based polyether polyol is prepared by the following method: the bio-based polyol is subjected to epoxidation reaction with an epoxidizing agent under the action of a catalyst to generate epoxidized bio-based polyol, the epoxidized bio-based polyol is subjected to ring-opening polymerization reaction to generate bio-based polyether polyol; the recycled polyether polyol is prepared by the following method: the polyurethane foam is ground to a particle size of ≤200 μm, ethylene glycol is used as a decomposition agent, alcoholysis is performed on the ground polyurethane foam, carbamate groups in the polyurethane foam are subjected to ester exchange reaction with ethylene glycol, the carbamate groups are replaced by short alcohol chains to obtain a decomposition liquid, and ethylenediamine is used to perform a hydrothermal aminolysis reaction on the decomposition liquid to obtain a regenerated polyether polyol.

[0022] The preparation method of the above-mentioned polyurethane rigid foam adopts bio-based polyether polyols and waste recycled polyether polyols as polyurethane white material raw materials. By limiting the bio-based polyether polyols and waste recycled polyether polyols, a potassium isooctanoate trimerization catalyst is introduced to strengthen the molecular cross-linking structure and reduce the demolding expansion rate. The bio-based polyether polyol raw material and chemically recycled polyether polyol raw material composition defined by the present invention are used in combination to make the overall performance of the foam excellent, avoiding the defects of the current green foaming material such as easy aging and brittle cracking, poor thermal insulation performance, and poor weather resistance.

[0023] It should be noted that in polyurethane foaming materials, the reactants are divided into two categories: black materials and white materials. The white materials contain a variety of ingredients, and 80% of the content is 3-5 types of polyether polyols. Each polyol has different properties due to different molecular structures. Some contribute significantly to the thermal insulation effect, some have a significant impact on the foam strength, and some have a low viscosity, which is conducive to industrial use. Limited by the current types of bio-based polyethers, it is impossible to provide comprehensive performance requirements. Therefore, in the preparation process of existing polyurethane foaming materials, it is often necessary to use petroleum-based polyether polyols. The principle of recycled polyether polyols is similar to this. Due to the molecular structure, some types of polyether polyols cannot be obtained by regeneration. The types are limited, so they cannot be used alone and must be used with petroleum-based polyether polyols. The bio-based polyether polyols used in the above technical solution are sucrose-based, palm oil-based, castor oil-based and propylene oxide / ethylene oxide ring-opening polymerization to synthesize polyether polyols. The high-functionality bio-based enhances the degree of molecular cross-linking and provides foam strength. The recycled polyether polyol used in the above technical solution is obtained by dismantling waste refrigerators and freezers to obtain polyurethane foam. Specifically: the foam is crushed and ground into micron level, and then alkyl glycol is used as a decomposition agent to break the carbamate group in the polyurethane waste at 200°C, and the recycled polyether polyol is separated and purified by vacuum distillation. With the help of the amino groups formed by the above regeneration process and the polyamino groups formed by decomposition, the black material has a self-catalytic effect, the foam pore strength is high, the pore wall is thin, and the foam thermal insulation performance is improved. Due to the low activity of the recycled polyol, slow post-reaction, and poor demolding performance, the above technical solution also defines potassium isooctanoate as a trimerization catalyst to enhance the post-reaction speed, so that the black material molecules form trimers and form six-membered rings, enhance the foam strength, and reduce the foam expansion rate after demolding, so as to achieve the effect of fully using bio-based and petroleum-based polyether polyols.

[0024] The above technical scheme specifically defines the preparation method of bio-based polyether polyol and regenerated polyether polyol, realizes the complete replacement of petroleum-based polyether polyol as white material in polyurethane foam by the combination of bio-based polyether polyol and regenerated polyether polyol, and ensures the relevant performance of polyurethane foam material. Generally speaking, polyurethane foam regeneration only adopts alcoholysis method to break the carbamate group in polyurethane waste material and produce regenerated polyol. The advantage of this method is that the process is relatively simple, but the product reaction activity is low and the generated foam performance is poor. The present invention uses a two-step method to modify the regenerated polyether polyol: on the basis of alcoholysis method, an aminolysis reaction is added, and ethylenediamine is used as a decomposition agent. Ethylenediamine can react with the isocyanate part in the polyurethane foam to generate new amine end groups, increase the regenerated polyether functional group, and the amino group can react with the isocyanate, which is a key reaction in the formation process of polyurethane. In this reaction, the amino group and the isocyanate react to form urea (-NH-CO-NH-) connection, which is of great help to enhance the reactivity of the regenerated polyether polyol, improve the strength of the molecular chain, and enhance the strength of the foam microstructure.

[0025] The preparation method of bio-based polyether polyol specifically includes: bio-based polyol is subjected to epoxidation reaction with an epoxidant (propylene oxide) under the action of a catalyst, sulfuric acid, at 150°C, anhydrous, nitrogen atmosphere, 2Mpa pressure, and reaction time of 5h to generate epoxidized bio-based polyol. Then, the epoxidized bio-based polyol is subjected to a ring-opening polymerization reaction to generate bio-polyether polyol.

[0026] The preparation method of the regenerated polyether polyol specifically comprises:

[0027] The first step is to add the polyurethane foam into the grinder for crushing and grinding. The grinding time is 1 hour. The particle size is required to be ≤200um. The finer the particle size, the more complete the reaction and the more significant the modification effect.

[0028] Step 2: Add twice the volume of ethylene glycol to the ground powder, stir and disperse the polyurethane powder, use the hydrothermal method, heat at 190℃ for 3h, and separate the unreacted ethylene glycol by distillation in a three-necked flask after the reaction. The basic principle is to use ethylene glycol as a decomposition agent to break the carbamate group in the polyurethane waste, that is, the carbamate group and ethylene glycol undergo an ester exchange reaction, and the carbamate group is replaced by a short alcohol chain.

[0029] Step 3: Add ethylenediamine in a weight ratio of 20:1 to the foam decomposition liquid after decomposition liquefaction and distillation, and heat it at 140°C for 2h by a hydrothermal method to obtain a modified regenerated polyether polyol.

[0030] In a preferred embodiment, the average number of functional groups of the bio-based polyether polyol is selected from 3-6, and the hydroxyl value is 300-600 mgKOH / g; the average number of functional groups of the recycled polyether polyol is 2-5, and the hydroxyl value is 200-600 mgKOH / g. The technical scheme further defines the structure of the bio-based polyether polyol and the recycled polyether polyol, because not all bio-based polyether polyols and recycled polyether polyols can be used as white materials in polyurethane foams and can maintain the performance requirements of polyurethane foams. In the white materials, whether it is bio-based polyether polyols or recycled polyether polyols in the prior art, they all need to be used in combination with petroleum-based polyether polyols to ensure the performance requirements of the obtained polyurethane foams. The present invention improves the raw material system, specifically, including the structural definition of bio-based polyether polyols and recycled polyether polyols and the use of catalysts, to achieve complete replacement of petroleum-based polyether polyols, while also ensuring the performance requirements of the obtained polyurethane foams.

[0031] In a preferred embodiment, the mass fraction of the bio-based polyether polyol in the polyether polyol is selected from any value between 10% and 90%, and the mass fraction of the recycled polyether polyol is selected from any value between 10% and 90%.

[0032] The present invention uses cyclopentane as a foaming agent to mix bio-based polyether polyol and recycled polyether polyol in the above ratio as a polyurethane rigid foam white material and a black material to generate a rigid polyurethane foam for use in the field of refrigerators and freezers. The mixing ratio of the above bio-based polyether polyol and recycled polyether polyol defined in the technical solution (the ratio of bio-based polyether polyol is in the range of (10%-90%) and recycled polyether polyol is in the range of (10%-90%), preferably 50% / 50%) can ensure that the foam performance is consistent with that of petroleum-based polyether polyol, and can also ensure that the foam is green and low-carbon.

[0033] Furthermore, the above-mentioned bio-based polyether polyols are palm oil polyols and castor oil polyols. Castor oil polyols are synthesized into polyether polyols by ring-opening polymerization of propylene oxide / ethylene oxide on hydroxyl groups using a bimetallic catalyst. Palm oil polyols have a high content of saturated fatty acids and are then esterified and modified and then combined with an epoxidation method to prepare polyols. The above-mentioned regenerated polyols are obtained by dismantling waste refrigerators and freezers to obtain polyurethane foams. After the foams are crushed and ground into micron levels, alkyl glycols are used as decomposition agents to break the carbamate groups in the polyurethane waste at 200°C, and the regenerated polyols are separated and purified by vacuum distillation. Since the regenerated polyols have low activity, slow post-reaction, and poor demolding performance, the potassium isooctanoate trimerization catalyst is introduced to enhance the post-reaction rate, so that the black material molecules form trimers and six-membered rings, thereby enhancing the foam strength and reducing the foam expansion rate after demolding.

[0034] In a preferred embodiment, the raw materials include: cyclopentane foaming agent, surfactant, polymerized MDI, the reaction catalyst, and the polyether polyol; the weight ratio of the polymerized MDI to the polyether polyol is selected from any value between 1.25 and 1.30. The technical solution specifies that the foaming agent is cyclopentane foaming agent, because cyclopentane is one of the most environmentally friendly foaming agents currently, is suitable for low-carbon requirements, and has a boiling point of 49°C, which is suitable for the reaction rate of the catalyst system specified in the present invention.

[0035] In a preferred embodiment, the surfactant is selected from at least one of alkali metal salts of fatty acids, amine salts of fatty acids, castor oil, ricinoleic acid, and silicone polymers; the reaction catalyst includes a foaming catalyst, a gel catalyst, and a trimerization catalyst, and the trimerization catalyst includes potassium isooctanoate; the mass ratio of the foaming catalyst, the gel catalyst, and the trimerization catalyst is selected from any ratio of 2-4:3-8:1-3.

[0036] In a preferred embodiment, the surfactant is selected from 1-3 of silicone oil L6863, silicone oil L6988, silicone oil AK8830, silicone oil B8525, silicone oil B8545L-6863, L-6869, L-6970, L-6900, B-8423, B-8404, B-8407, B-8465, and B-8444.

[0037] In a preferred embodiment, the foaming catalyst is a mixture of one or more of pentamethyldiethylenetriamine, N-methyldicycloethylamine, tetramethylhexanediamine or bis-dimethylaminoethyl ether; the gel catalyst is a mixture of one or more of dimethylbenzylamine, dimethylcyclohexane or triethylenediamine; the trimerization catalyst is potassium isooctanoate or a mixture of potassium isooctanoate and one or more of PC-41, anhydrous sodium acetate, potassium acetate, TMR / TMR2, TMR30. 1-3 silicone oil catalysts are selected to match different types of bio-based polyether polyols and recycled polyether polyols, so that the overall compatibility is good and the uniformity of the foam cells is improved.

[0038] It should be noted that the above technical solution stipulates that the trimerization catalyst must contain potassium isooctanoate. The reason is that the regenerated polyol has low activity, slow post-reaction and poor demolding performance. By introducing potassium isooctanoate trimerization catalyst, the post-reaction speed can be enhanced, the black material molecules can form trimers and form a six-membered ring, thereby enhancing the foam strength and reducing the foam expansion rate after demolding.

[0039] In a preferred embodiment, the amount of the bio-based polyether polyol is selected from any value between 20 and 60 parts by weight; the amount of the recycled polyether polyol is selected from any value between 15 and 45 parts; the amount of the cyclopentane foaming agent is selected from any value between 12 and 16 parts; the amount of the reaction catalyst is selected from any value between 1 and 4 parts; the amount of the surfactant is selected from any value between 1.5 and 3 parts; the amount of the polymeric MDI is selected from any value between 145 and 160 parts; and the raw materials also include 1 to 3 parts of water.

[0040] On the other hand, the present invention provides a polyurethane rigid foam, which is prepared by the preparation method of the polyurethane rigid foam described in any of the above technical solutions. The polyurethane rigid foam uses bio-based polyether polyols and waste recycled polyether polyols as polyurethane white material raw materials, develops a formula, introduces a potassium isooctanoate trimerization catalyst to strengthen the molecular cross-linking structure, reduces the demolding expansion rate, meets the performance requirements, and improves the green and low-carbonization of polyurethane foam. The combination of bio-based polyether polyol raw materials and chemically recycled polyether polyol raw materials makes the foam have excellent overall performance, avoiding the defects of the current green foaming material foam being easy to age and crack, poor thermal insulation performance, and poor weather resistance.

[0041] The present invention also provides a refrigerator, wherein the foamed heat-insulating material of the refrigerator freezer adopts the polyurethane hard foam described in the above technical solution. The refrigerator has the characteristics of good heat-insulating performance, green and low-carbon, and good weather resistance.

[0042] In order to more clearly and in detail introduce a polyurethane rigid foam, a preparation method thereof and a refrigerator provided in the embodiments of the present invention, they will be described below in conjunction with specific embodiments.

[0043] Example 1

[0044] In parts by weight, the raw materials include: 100 parts of dry white material (including 50 parts of bio-based polyether polyol and 50 parts of recycled polyether polyol), 14 parts of cyclopentane cp, 3 parts of reaction catalyst, 2 parts of silicone oil surfactant, 2 parts of water, and 155 parts of polymerized MDI; the reaction catalyst includes potassium isooctanoate, PC-8\PC-41\TMR-2.

[0045] The preparation method of bio-based polyether polyol specifically includes: bio-based polyol is subjected to epoxidation reaction with an epoxidant (propylene oxide) under the action of a catalyst, sulfuric acid, at 150°C, anhydrous, nitrogen atmosphere, 2Mpa pressure, and reaction time of 5h to generate epoxidized bio-based polyol. Then, the epoxidized bio-based polyol is subjected to a ring-opening polymerization reaction to generate bio-polyether polyol.

[0046] The preparation method of the regenerated polyether polyol specifically comprises:

[0047] The first step is to add the polyurethane foam into the grinder for crushing and grinding. The grinding time is 1 hour. The particle size is required to be ≤200um. The finer the particle size, the more complete the reaction and the more significant the modification effect.

[0048] Step 2: Add twice the volume of ethylene glycol to the ground powder, stir and disperse the polyurethane powder, use the hydrothermal method, heat at 190℃ for 3h, and separate the unreacted ethylene glycol by distillation in a three-necked flask after the reaction. The basic principle is to use ethylene glycol as a decomposition agent to break the carbamate group in the polyurethane waste, that is, the carbamate group and ethylene glycol undergo an ester exchange reaction, and the carbamate group is replaced by a short alcohol chain.

[0049] Step 3: Add ethylenediamine in a weight ratio of 20:1 to the foam decomposition liquid after decomposition liquefaction and distillation, and heat it at 140°C for 2h by a hydrothermal method to obtain a modified regenerated polyether polyol.

[0050] Example 2

[0051] In parts by weight, the raw materials include: 100 parts of dry white material (20 parts of bio-based polyether polyol, 80 parts of recycled polyether polyol), 14 parts of cyclopentane cp, 3 parts of reaction catalyst, 2 parts of silicone oil surfactant, 2 parts of water, and 155 parts of polymerized MDI; the reaction catalyst includes potassium isooctanoate, PC-8\PC-41\TMR-2.

[0052] The preparation method of bio-based polyether polyol specifically includes: bio-based polyol is subjected to epoxidation reaction with an epoxidant (propylene oxide) under the action of a catalyst, sulfuric acid, at 150°C, anhydrous, nitrogen atmosphere, 2Mpa pressure, and reaction time of 5h to generate epoxidized bio-based polyol. Then, the epoxidized bio-based polyol is subjected to a ring-opening polymerization reaction to generate bio-polyether polyol.

[0053] The preparation method of the regenerated polyether polyol specifically comprises:

[0054] The first step is to add the polyurethane foam into the grinder for crushing and grinding. The grinding time is 1 hour. The particle size is required to be ≤200um. The finer the particle size, the more complete the reaction and the more significant the modification effect.

[0055] Step 2: Add twice the volume of ethylene glycol to the ground powder, stir and disperse the polyurethane powder, use the hydrothermal method, heat at 190℃ for 3h, and separate the unreacted ethylene glycol by distillation in a three-necked flask after the reaction. The basic principle is to use ethylene glycol as a decomposition agent to break the carbamate group in the polyurethane waste, that is, the carbamate group and ethylene glycol undergo an ester exchange reaction, and the carbamate group is replaced by a short alcohol chain.

[0056] Step 3: Add ethylenediamine in a weight ratio of 20:1 to the foam decomposition liquid after decomposition liquefaction and distillation, and heat it at 140°C for 2h by a hydrothermal method to obtain a modified regenerated polyether polyol.

[0057] Example 3

[0058] In parts by weight, the raw materials include: 100 parts of dry white material (80 parts of bio-based polyether polyol, 20 parts of recycled polyether polyol), 14 parts of cyclopentane cp, 3 parts of reaction catalyst, 2 parts of silicone oil surfactant, 2 parts of water, and 155 parts of polymerized MDI; the reaction catalyst includes potassium isooctanoate, PC-8\PC-41\TMR-2.

[0059] The preparation method of bio-based polyether polyol specifically includes: bio-based polyol is subjected to epoxidation reaction with an epoxidant (propylene oxide) under the action of a catalyst, sulfuric acid, at 150°C, anhydrous, nitrogen atmosphere, 2Mpa pressure, and reaction time of 5h to generate epoxidized bio-based polyol. Then, the epoxidized bio-based polyol is subjected to a ring-opening polymerization reaction to generate bio-polyether polyol.

[0060] The preparation method of the regenerated polyether polyol specifically comprises:

[0061] The first step is to add the polyurethane foam into the grinder for crushing and grinding. The grinding time is 1 hour. The particle size is required to be ≤200um. The finer the particle size, the more complete the reaction and the more significant the modification effect.

[0062] Step 2: Add twice the volume of ethylene glycol to the ground powder, stir and disperse the polyurethane powder, use the hydrothermal method, heat at 190℃ for 3h, and separate the unreacted ethylene glycol by distillation in a three-necked flask after the reaction. The basic principle is to use ethylene glycol as a decomposition agent to break the carbamate group in the polyurethane waste, that is, the carbamate group and ethylene glycol undergo an ester exchange reaction, and the carbamate group is replaced by a short alcohol chain.

[0063] Step 3: Add ethylenediamine in a weight ratio of 20:1 to the foam decomposition liquid after decomposition liquefaction and distillation, and heat it at 140°C for 2h by a hydrothermal method to obtain a modified regenerated polyether polyol.

[0064] Comparative Example 1

[0065] By weight, the raw materials include: 100 parts of dry white material (non-green low-carbon polyol), 15 parts of cyclopentane cp, 3 parts of reaction catalyst, 2 parts of silicone oil surfactant, 2 parts of water, and 155 parts of polymerized MDI;

[0066] Among them, non-green low-carbon polyols are O-TDA and sorbitol; the reaction catalysts are PC-8\PC-41\TMR-2.

[0067] Comparative Example 2

[0068] The raw material composition is the same as that of Example 1, except that the bio-based polyol is a sugar polyol; and the regenerated polyether polyol is prepared only by alcoholysis.

[0069] Comparative Example 3

[0070] The raw material composition is the same as that in Example 1, except that the reaction catalyst is PC-8\PC-41\TMR-2.

[0071] Performance Testing

[0072] The polyurethane foams obtained in the above examples and comparative examples were tested for relevant properties, and the results are shown in Table 1.

[0073] Table 1 Performance test results

[0074]

[0075]

[0076] From the foam test results in Table 1, the performance of green and low-carbon foam is greatly affected by the content of recycled polyether, because the activity of recycled polyether decreases significantly after secondary processing, and the foam performance decreases with the increase of content. Examples 1-3 are white materials with different proportions of bio-based / recycled polyether. With the increase of recycled polyether polyols, the foam performance decreases, and the overall density of the foam is higher than that of the comparative example. The overall performance of Example 1 is close to that of Comparative Example 1, and they can be used as substitutes. It can be seen that the polyether polyols of the white material of the present invention are all composed of bio-based polyols and recycled polyols. Due to the use of the two, the thermal insulation and demolding properties do not meet the use requirements. Therefore, the present invention further adjusts the matching ratio of the two and introduces a potassium isooctanoate trimerization catalyst to solve the above problems.

[0077] Comparative Example 2 uses sugar polyether polyols, which have high viscosity and poor mixing and fluidity, resulting in coarse foam cells, high density, and high thermal conductivity. In addition, the recycled polyether polyol has not been modified by aminolysis, and the low reaction activity of the recycled polyether polyol also leads to high thermal conductivity and poor density distribution.

[0078] In Comparative Example 3, potassium isooctanoate was not added, the trimerization reaction was not complete, the residue was large, the density was high, the fluidity was poor, and the thermal conductivity was increased.

Claims

1. A method for preparing a polyurethane rigid foam, characterized in that: The raw materials include polyether polyol and a reaction catalyst; the polyether polyol is composed of bio-based polyether polyol and recycled polyether polyol; the reaction catalyst includes potassium isooctanoate; The bio-based polyether polyol is prepared by the following method: the bio-based polyol is subjected to an epoxidation reaction with an epoxidant under the action of a catalyst to generate an epoxidized bio-based polyol, and the epoxidized bio-based polyol is subjected to a ring-opening polymerization reaction to generate a bio-based polyether polyol; The regenerated polyether polyol is prepared by the following method: grinding polyurethane foam to a particle size of ≤200um, using ethylene glycol as a decomposition agent to perform alcoholysis on the ground polyurethane foam, performing an ester exchange reaction between the carbamate groups in the polyurethane foam and ethylene glycol, replacing the carbamate groups with short alcohol chains to obtain a decomposition liquid, and performing a hydrothermal aminolysis reaction on the decomposition liquid using ethylenediamine to obtain the regenerated polyether polyol.

2. The method for preparing a polyurethane rigid foam according to claim 1, characterized in that: The average functional group number of the bio-based polyether polyol is selected from 3-6, and the hydroxyl value is 300-600 mgKOH / g; the average functional group number of the recycled polyether polyol is 2-5, and the hydroxyl value is 200-600 mgKOH / g.

3. The method for preparing a polyurethane rigid foam according to claim 1, characterized in that: The mass fraction of the bio-based polyether polyol in the polyether polyol is selected from any value between 10% and 90%, and the mass fraction of the recycled polyether polyol is selected from any value between 10% and 90%.

4. The method for preparing a polyurethane rigid foam according to claim 1, characterized in that: The raw materials include: cyclopentane foaming agent, surfactant, polymeric MDI, the reaction catalyst, and the polyether polyol; the weight ratio of the polymeric MDI to the polyether polyol is selected from any value between 1.25 and 1.

30.

5. The method for preparing a polyurethane rigid foam according to claim 4, characterized in that: The surfactant is selected from at least one of alkali metal salts of fatty acids, amine salts of fatty acids, castor oil, ricinoleic acid, and silicone polymers; the reaction catalyst includes a foaming catalyst, a gel catalyst, and a trimerization catalyst, and the trimerization catalyst includes potassium isooctanoate; the mass ratio of the foaming catalyst, the gel catalyst, and the trimerization catalyst is selected from any ratio of 2-4:3-8:1-3.

6. The method for preparing a polyurethane rigid foam according to claim 4, characterized in that: The surfactant is selected from 1 to 3 of silicone oil L6863, silicone oil L6988, silicone oil AK8830, silicone oil B8525, silicone oil B8545 L-6863, L-6869, L-6970, L-6900, B-8423, B-8404, B-8407, B-8465, and B-8444.

7. The method for preparing a polyurethane rigid foam according to claim 5, characterized in that: The foaming catalyst is a mixture of one or more of pentamethyldiethylenetriamine, N-methyldicycloethylamine, tetramethylhexanediamine or bis-dimethylaminoethyl ether; the gelling catalyst is a mixture of one or more of dimethylbenzylamine, dimethylcyclohexane or triethylenediamine; the trimerization catalyst is potassium isooctanoate or a mixture of potassium isooctanoate and one or more of PC-41, anhydrous sodium acetate, potassium acetate, TMR / TMR2, TMR30.

8. The method for preparing a polyurethane rigid foam according to claim 4, characterized in that: In parts by weight, the amount of the bio-based polyether polyol is selected from any value between 20 and 60 parts; the amount of the recycled polyether polyol is selected from any value between 15 and 45 parts; the amount of the cyclopentane foaming agent is selected from any value between 12 and 16 parts; the amount of the reaction catalyst is selected from any value between 1 and 4 parts; the amount of the surfactant is selected from any value between 1.5 and 3 parts; the amount of the polymeric MDI is selected from any value between 145 and 160 parts; and the raw materials also include 1 to 3 parts of water.

9. A polyurethane rigid foam, characterized in that: The polyurethane rigid foam is prepared by the preparation method of any one of claims 1 to 8.

10. A refrigerator, characterized in that: The foamed heat-insulating material of the refrigerator freezer is the polyurethane rigid foam described in claim 9.

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