A method for preparing polyurethane foams using recycled polyether polyols

Abstract

The application discloses a method for preparing polyurethane foam by using regenerated polyether polyol, and belongs to the technical field of recycling waste polyurethane products. The method uses waste rigid polyurethane foam as raw material, effectively reduces the content of aromatic amine and alcoholysis agent in the regenerated polyether polyol by means of one-step catalytic alcoholysis combined with the use of cyclic carbonate, reduces the residue of harmful substances, meets the environmental protection requirements, and realizes the resource utilization of waste at the same time. The prepared regenerated polyether polyol has suitable hydroxyl value, viscosity, water content and potassium and sodium ion concentration, these indexes ensure the good compatibility of the regenerated polyether polyol with various combined polyether, so that the prepared polyurethane foam has excellent physical performance and processing performance.

Description

Technical Field

[0001] The present invention relates to the field of recycling and reuse of waste polyurethane products, in particular to a method for preparing polyurethane foam by utilizing regenerated polyether polyol. Background Art

[0002] Polyurethane foam, an important polymer material, is widely used in construction, furniture, automotive, and other fields. With the widespread use of polyurethane foam, the disposal of waste rigid polyurethane foam has become an urgent environmental issue. Traditional methods of disposing of waste polyurethane foam, such as landfill and incineration, not only waste resources but also cause environmental pollution.

[0003] Currently, the primary method for preparing recycled polyether polyols is alcoholysis, but this traditional alcoholysis process has numerous drawbacks. For example, aromatic amine byproducts (such as 4,4'-diaminodiphenylmethane) are easily produced during the alcoholysis process and are difficult to effectively remove. This results in a high content of aromatic amines in the recycled polyether polyol, impacting the performance and environmental friendliness of subsequent polyurethane foams. Furthermore, the traditional process results in high levels of alcoholysis agent residues, a complex refining process, and high production costs. Furthermore, the resulting recycled polyether polyols face difficulties in precisely controlling key parameters such as hydroxyl value, viscosity, and moisture content, limiting their application in high-quality polyurethane foams.

[0004] Therefore, there is an urgent need for an efficient, environmentally friendly method for preparing high-performance recycled polyether polyols to achieve resource utilization of waste rigid polyurethane foam and improve the comprehensive performance of polyurethane foam. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing polyurethane foam using recycled polyether polyol to solve the problems in the background technology.

[0006] To achieve the above object, the present invention provides a method for preparing polyurethane foam using recycled polyether polyol, comprising the following steps:

[0007] S1. Using waste rigid polyurethane foam, alcoholysis agent and cyclic carbonate as raw materials, a one-step catalytic alcoholysis method is used to prepare regenerated polyether polyol;

[0008] S2. Add the recycled polyether polyol and the combined polyether into the reactor and mix them evenly, or add the recycled polyether polyol and new polyether polyol, catalyst, chain extender, foaming agent and defoamer into the reactor and mix them evenly;

[0009] Then add polyisocyanate and continue stirring until the mixture is uniform, quickly pour it into a preheated mold for foaming, and after completion, take out the foam to obtain polyurethane foam.

[0010] S11, mixing waste rigid polyurethane foam, an alcoholysis agent, and a catalyst in a mass ratio of (50-1500):(50-1000):(1-30), adding the mixture into a reactor, and heating the mixture to obtain an intermediate alcoholysis product;

[0011] S12, then adding cyclic carbonate to continue the reaction to obtain a polyether polyol with low aromatic amine and alcoholysis agent content;

[0012] S13. After the polyether polyol is cooled, a refining agent is added, and the target regenerated polyether polyol is obtained after neutralization, dehydration, and filtration.

[0013] Preferably, in S11, the reaction temperature is 150-220° C., and the reaction time is 1-6 h.

[0014] Preferably, in S11, the alcoholysis agent is one or more of ethylene glycol, propylene glycol, glycerol, polyethylene glycol 200, polyethylene glycol 400, and 1,4-butanediol, and the catalyst is one or more of sodium hydroxide, potassium hydroxide, potassium acetate, and diethanolamine.

[0015] Preferably, the alcoholysis agent is ethylene glycol and / or polyethylene glycol 200, more preferably ethylene glycol; and the catalyst is potassium hydroxide.

[0016] Preferably, in S12, the mass ratio of the cyclic carbonate to the polyurethane foam is (0.4-1.8):1, and the cyclic carbonate is one or more of ethylene carbonate and propylene carbonate.

[0017] Preferably, in S12, the reaction temperature is 150-220° C., the reaction time is 1-8 h, and the aromatic amine is 4,4′-diaminodiphenylmethane.

[0018] Preferably, in S13, the refining agent is a neutralizer, an adsorbent and an antioxidant, the neutralizer is one or more of acetic acid, phosphoric acid, oxalic acid and formic acid; the adsorbent is one or more of magnesium silicate, aluminum silicate, silica gel, diatomaceous earth and alumina; the antioxidant is one or more of phenolic antioxidants, auxiliary antioxidants and hindered amine light stabilizers.

[0019] Preferably, in S13, the neutralization reaction temperature is 40-90° C., and the reaction time is 0.8-1.2 h.

[0020] Preferably, in S1, the regenerated polyether polyol has an MDA content of ≤0.1%, an alcoholysis agent content of ≤1%, a hydroxyl value of 400-900 mg KOH / g, a viscosity of 2-2.5 Pa·s, a water content of ≤0.5%, and potassium and sodium ion concentrations of ≤50 mg / kg.

[0021] Preferably, in said S2, the apparent core density of the polyurethane foam prepared is 40-44 mg / m3 , the compression strength is 170~200kPa.

[0022] Preferably, the composite polyether in S2 is one of composite polyether for refrigerators / refrigeration equipment, composite polyether for filling, composite polyether for flame retardancy, composite polyether for pipe insulation, and composite polyether for spraying, and is selected according to actual application.

[0023] Preferably, the polyisocyanate in S2 is one of PM-200, Desmodur 44V20, and Lupranat M20S.

[0024] Preferably, in S2, the catalyst is one or more of bis(2-dimethylaminoethyl) ether, triethylenediamine, dimethylcyclohexylamine, stannous octoate, tetramethylhexanediamine, and pentamethyldiethylenetriamine; the chain extender is one of 1,4-butanediol, diethylene glycol, and diethyltoluenediamine; the foaming agent is one of water or cyclopentane; and the defoaming agent is silicone oil.

[0025] Therefore, the present invention provides a method for preparing polyurethane foam using recycled polyether polyol, which has the following beneficial effects:

[0026] (1) The present invention uses waste rigid polyurethane foam as raw material and effectively reduces the content of aromatic amines (such as 4,4'-diaminodiphenylmethane) and alcoholysis agents in the recycled polyether polyol through a one-step catalytic alcoholysis method combined with the use of cyclic carbonates. The MDA content of the recycled polyether polyol is ≤0.1%, and the alcoholysis agent content is ≤1%. This reduces the residual harmful substances, meets environmental protection requirements, and achieves resource utilization of waste, reducing dependence on petroleum-based raw materials.

[0027] (2) The regenerated polyether polyol prepared by the present invention has an appropriate hydroxyl value (400-900 mgKOH / g), viscosity (2-2.5 Pa·s) and water content (≤0.5%), and the potassium and sodium ion concentrations are ≤50 mg / kg. These indicators ensure its good compatibility with various combination polyethers, so that the prepared polyurethane foam has excellent physical properties and processing properties; and the prepared polyether polyol is lighter in color, light brown, and can be adapted to more application scenarios.

[0028] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further illustrated by the following examples.

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0031] Example 1

[0032] In this Example 1, a polyurethane foam was prepared using commercially available new refrigerator-use composite polyether as raw material. The specific preparation steps are as follows:

[0033] S1. Using waste rigid polyurethane foam, alcoholysis agent and cyclic carbonate as raw materials, a one-step catalytic alcoholysis method is used to prepare regenerated polyether polyol, specifically:

[0034] In a 500mL four-necked flask, add 100g of glycerol and 2g of potassium hydroxide, then add 100g of waste polyurethane foam in batches for reaction, and heat to 170℃ for 5h;

[0035] Then add 120 g of ethylene carbonate to the four-necked flask and continue the reaction for 4 h;

[0036] The temperature was lowered to 60°C, and 4.3 g of phosphoric acid, 6 g of pure water, 0.15 g of antioxidant 1010, 0.5 g of antioxidant 168, and 1.5 g of magnesium silicate were added in sequence. After stirring and neutralizing for 1 hour, the temperature was raised to 115°C and dehydrated with nitrogen for 3 hours. The light brown polyether polyol was obtained by filtration. A nitrogen atmosphere was maintained throughout the reaction.

[0037] S2. Weigh 60 g of a new refrigerator composite polyether at room temperature (25°C) and stir for 6 seconds. Then add it and 30 g of the polyether polyol prepared in S1 into the reactor and stir at high speed for 10 seconds (speed 2000 r / min) at 25°C. After mixing evenly, add 110 g of PM-200 and continue stirring for 10 seconds until the mixture is evenly mixed. Pour the mixture quickly into an aluminum mold (size: 150 mm long, 150 mm wide, 50 mm thick) preheated to 60°C. Control the mold pressure at 0.08 MPa to foam the mixture. Then place it in an 80°C oven for aging. After 24 hours, remove the foam to obtain polyurethane foam.

[0038] Example 2

[0039] In Example 2, a polyurethane foam was prepared using commercially available composite polyether for filling as raw material. The specific preparation steps are as follows:

[0040] S1. Using waste rigid polyurethane foam and cyclic carbonate as raw materials, a one-step catalytic alcoholysis method is used to prepare regenerated polyether polyol, specifically:

[0041] In a 500 mL four-necked flask, 100 g of 1,4-butanediol and 2 g of potassium hydroxide were added, and 100 g of waste polyurethane foam was added in batches for reaction. The temperature was raised to 170°C and heated for 4 h.

[0042] Then add 110 g of propylene carbonate to the four-necked flask and continue the reaction for 5 h;

[0043] The temperature was lowered to 60°C, and 3.5 g of phosphoric acid, 6 g of pure water, 0.15 g of antioxidant 1010, 0.5 g of antioxidant 168, and 1.5 g of magnesium silicate were added in sequence. The mixture was stirred and reacted for 0.5 h, and then the temperature was raised to 115°C and dehydrated by nitrogen for 3 h. The light brown polyether polyol was obtained by filtration.

[0044] S2. Weigh 70 g of the composite polyether for filling at room temperature (25°C) and stir and mix for 5 seconds. Add the mixture and 20 g of the polyether polyol prepared in S1 into the reactor and stir at high speed for 10 seconds (2000 r / min) at 25°C until uniformly mixed. Then add 110 g of Desmodur 44V20 and continue stirring for 8 seconds until uniformly mixed. Pour the mixture into a mold (size: 150 mm long, 150 mm wide, 50 mm thick) preheated to 50°C. Control the mold pressure at 0.08 MPa to foam the mixture. During the foaming process, control the milky time to 70 seconds, the gel time to 2 minutes, and the demolding time to 20 minutes. Then place the mixture in an 80°C oven for aging. After 24 hours, remove the foam to obtain polyurethane foam.

[0045] Example 3

[0046] In Example 3, a polyurethane foam was prepared using commercially available flame-retardant composite polyether as raw material. The specific preparation steps are as follows:

[0047] S1. Using waste rigid polyurethane foam and cyclic carbonate as raw materials, a one-step catalytic alcoholysis method is used to prepare regenerated polyether polyol, specifically:

[0048] In a 500mL four-necked flask, add 100g of ethylene glycol and 2g of potassium hydroxide, then add 100g of waste polyurethane foam in batches for reaction, and heat to 170℃ for 6h;

[0049] Then add 130 g of ethylene carbonate to the four-necked flask and continue the reaction for 4 h;

[0050] The temperature was lowered to 60°C, and 3.5 g of phosphoric acid, 6 g of pure water, 0.15 g of antioxidant 1010, 0.5 g of antioxidant 168, and 1.5 g of magnesium silicate were added in sequence. After stirring and neutralizing for 1 hour, the temperature was raised to 115°C and dehydrated by nitrogen for 3 hours. The light brown polyether polyol was obtained by filtration.

[0051] S2. At room temperature (25°C), weigh 55 g of new polyether polyol 4110, 35 g of the polyether polyol prepared in S1, 2.5 g of silicone oil, 0.5 g of triethylenediamine, 3.4 g of deionized water, and 1.8 g of 1,4-butanediol, and stir and mix them for 0.5 h. After mixing evenly, stir and mix them with 110 g of PM200 in a stirrer (rotation speed 3000 rpm) for 7 seconds, and then quickly pour them into a mold (size: 150 mm long, 150 mm wide, 50 mm thick) preheated to 60°C to foam the mixture. Then, place it in an 80°C oven for aging. After 1 h, take out the foam to obtain polyurethane foam.

[0052] Comparative Example 1

[0053] Comparative Example 1 is to prepare polyether polyol by alcoholysis only. The specific steps are the same as those in Example 1, except that step S1 is modified as follows: 100 g of ethylene glycol and 2 g of potassium hydroxide are added to a 500 mL four-necked flask, and then 100 g of waste polyurethane foam is added in batches for reaction. The temperature is raised to 170 ° C and heated for 5 h, and a dark brown polyether polyol is obtained by filtration.

[0054] Comparative Example 2

[0055] Comparative Example 2: Polyether polyol was prepared by alcoholysis and purification using only an alcoholysis agent. The specific steps were the same as those in Example 1, except that step S1 was modified as follows: 100 g of ethylene glycol and 2 g of potassium hydroxide were added to a 500 mL four-necked flask, and 100 g of waste polyurethane foam was added in batches for reaction, and the temperature was raised to 170° C. and heated for 5 h.

[0056] Then the temperature was lowered to 60°C, and 4.3g of phosphoric acid, 6g of pure water, 0.15g of antioxidant 1010, 0.5g of antioxidant 168, and 1.5g of magnesium silicate were added in sequence. After stirring and neutralization reaction for 1h, the temperature was raised to 115°C and dehydrated with nitrogen for 3h. The light brown polyether polyol was obtained by filtration.

[0057] The intermediate products polyether polyol and polyurethane foam of Examples 1-3 and Comparative Examples 1-2 were characterized to obtain the following Tables 1 and 2.

[0058] Table 1 Analysis of polyether polyol indicators

[0059] ;

[0060] As can be seen from Table 1, compared with the polyether polyol obtained by alcoholysis by adding only an alcoholysis agent in Comparative Example 1, the polyether polyols obtained in Example 1 and Example 2 have lower hydroxyl values, lower MDA content, lower alcoholysis agent content, lower potassium ion concentration, and lighter color; compared with the polyether polyol prepared by alcoholysis and purification using only an alcoholysis agent in Comparative Example 2, the polyether polyols in Examples 1 and 2 have lower hydroxyl values, lower MDA content, and lower alcoholysis agent content.

[0061] Table 2 Analysis of polyurethane rigid foam indicators

[0062] ;

[0063] It can be seen from the results of the examples in Table 2 that the polyurethane rigid foam prepared by the regenerated polyether polyol obtained by the method of the present invention has the characteristics of high apparent core density and high compressive strength, and can meet the performance requirements of the reuse of rigid polyurethane foam.

[0064] Compared to Comparative Examples 1 and 2, in Examples 1 and 2, waste polyurethane foam undergoes an ester exchange reaction catalyzed by ethylene glycol and a base, decomposing it into low-molecular-weight polyols and amines. Ethylene carbonate undergoes an ester exchange reaction with ethylene glycol in the alcoholysis product, reducing the alcoholysis agent content. A nucleophilic ring-opening reaction with amine groups converts free amines into stable carbamate structures, reducing the aromatic amine content. This "cyclic carbonate modification" process simplifies the process and reduces energy consumption, while achieving high-purity control of the regenerated polyether polyol (low MDA and low alcoholysis agent residues). Furthermore, through formulation optimization, the overall performance of the polyurethane foam is enhanced.

[0065] Comparative Example 3

[0066] This comparative example 3 is another preparation method, which is as follows:

[0067] S1. Crush waste rigid polyurethane foam into particles less than 5 mm in diameter. Add 300 g of dipropylene glycol, 1 g of potassium hydroxide, and 300 g of foam particles to a 2 L reactor to prepare an alcoholysis solution. Heat to 180°C for 8 hours, then lower the reactor temperature to 80°C. Filter to obtain a wine-red alcoholysis product.

[0068] 300 g of alcoholysis product was added to another 2 L reactor, and 1.2 g of potassium hydroxide was added as a catalyst, and the temperature was raised to 110° C. and vacuum dehydration was performed for 1 h.

[0069] Then, add 150g of liquid propylene oxide at a feed rate of 2.5g / min, allowing the reaction to proceed simultaneously. The temperature was maintained at 110°C for 2 hours. The temperature was lowered to 60°C, and 0.06g of iminotris(dimethylamino)phosphorane was added. After stirring evenly, the temperature was raised to 110°C. Then, 300g of liquid propylene oxide was added to the reactor at a feed rate of 2.5g / min. The temperature was maintained at 110°C for 3 hours, with the gauge pressure maintained at no more than 0.4MPa.

[0070] The temperature was lowered to 60°C, and 1.5 g of phosphoric acid, 6 g of pure water, and 0.75 g of aluminum silicate were added in sequence. After stirring and reacting for 1 hour, the temperature was raised to 110°C for vacuum dehydration for 3 hours. The mixture was filtered at high temperature to obtain a yellow-brown regenerated polyether polyol. A nitrogen atmosphere was maintained in the reactor during the reaction.

[0071] S2. At room temperature (25°C), weigh 80g of recycled polyether, 2.4g of triethylenediamine, and 8g of deionized water. Stir and mix for 0.5h until uniformly mixed. Then, mix the mixture with 120g of PM-200 in a stirrer (3000rpm) for 6 seconds. The mixture is then quickly poured into an open aluminum mold (300mm long, 300mm wide, 50mm thick) preheated to 60°C and allowed to foam. After 7 minutes, remove the foam to obtain polyurethane foam.

[0072] After testing, the color of the product in Comparative Example 3 is dark brown, which is darker than the color of the product in Example 3.

[0073] Comparing the preparation steps of Example 3 with Comparative Example 3, the total reaction time of Example 3 was shortened by 35.7% compared to Comparative Example 3. In Example 3, ethylene carbonate was directly added to the reaction, eliminating the need to add propylene oxide in batches and control the pressure (gauge pressure ≤ 0.4 MPa) as in Comparative Example 3. This avoids the complex operation of high-pressure polymerization and improves safety.

[0074] The performance of the polyurethane foams prepared in Example 3 and Comparative Example 3 was tested, and the results are shown in Table 3.

[0075] Table 3 Polyurethane foam performance indicators

[0076] ;

[0077] By comparison, it can be seen that the polyurethane foam prepared in Example 3 exhibits increased strength, decreased density, a finer foam, and improved aging resistance and stability compared to Comparative Example 3. During the preparation of the polyurethane foam, the foaming system of Example 3 incorporates new polyether polyol 4110, compounded with recycled polyether. This leverages the stability of the new polyether (e.g., low viscosity and regular structure) to mitigate the defects of the recycled polyether (e.g., impurities and broad molecular weight distribution), resulting in improved cell uniformity and dimensional stability. Comparative Example 3, which utilizes only recycled polyether, exhibits fluctuating foam properties due to insufficient purity of the recycled material, resulting in lower performance than in Example 3.

[0078] Therefore, the present invention provides a method for preparing polyurethane foam using recycled polyether polyol. The method uses waste rigid polyurethane foam as raw material and uses a one-step catalytic alcoholysis method combined with the use of cyclic carbonate to effectively reduce the content of aromatic amine and alcoholysis agent in the recycled polyether polyol, reduce the residual harmful substances, meet environmental protection requirements, and realize the resource utilization of waste. The prepared recycled polyether polyol has a suitable hydroxyl value, viscosity and water content, and the potassium and sodium ion concentrations are ≤50 mg / kg. These indicators ensure its good compatibility with the combined polyether, so that the prepared polyurethane foam has excellent physical properties and processing properties.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing polyurethane foam using recycled polyether polyol, characterized in that: The following steps are involved: S1. Using waste rigid polyurethane foam, alcoholysis agent and cyclic carbonate as raw materials, a one-step catalytic alcoholysis method is used to prepare regenerated polyether polyol; the specific steps are as follows: S11, mixing waste rigid polyurethane foam, an alcoholysis agent, and a catalyst in a mass ratio of (50-1500):(50-1000):(1-30), adding the mixture into a reactor, and heating the mixture to obtain an intermediate alcoholysis product; S12, then adding cyclic carbonate to continue the reaction to obtain a polyether polyol with low aromatic amine and alcoholysis agent content; the mass ratio of cyclic carbonate to polyurethane foam is (0.4-1.8):1, the cyclic carbonate is one or more of ethylene carbonate and propylene carbonate; the reaction temperature is 150-220°C, the reaction time is 1-8 hours; the aromatic amine is 4,4'-diaminodiphenylmethane; S13. After the polyether polyol is cooled, a refining agent is added, and the target regenerated polyether polyol is obtained after neutralization, dehydration, and filtration; the regenerated polyether polyol has an MDA content of ≤0.1%, an alcoholysis agent content of ≤1%, a hydroxyl value of 400-900 mgKOH / g, a viscosity of 2-2.5 Pa·s, a water content of ≤0.5%, and potassium and sodium ion concentrations of ≤50 mg / kg; S2. Adding the recycled polyether polyol and the combined polyether into a reactor and mixing them evenly, or adding the recycled polyether polyol and new polyether polyol, a catalyst, a chain extender, a foaming agent, and silicone oil into a reactor and mixing them evenly; the combined polyether is one of a combined polyether for refrigeration equipment, a combined polyether for filling, a combined polyether for flame retardancy, a combined polyether for pipe insulation, and a combined polyether for spraying; Then add polyisocyanate and continue stirring until the mixture is evenly mixed. Quickly pour it into a preheated mold to foam. After completion, take out the foam to obtain polyurethane foam.

2. The method for preparing polyurethane foam using recycled polyether polyol according to claim 1, wherein: In the step S11, the reaction temperature is 150-220° C., and the reaction time is 1-6 h.

3. The method for preparing polyurethane foam using recycled polyether polyol according to claim 1, wherein: In S11, the alcoholysis agent is one or more of ethylene glycol, propylene glycol, glycerol, polyethylene glycol 200, polyethylene glycol 400, and 1,4-butanediol, and the catalyst is one or more of sodium hydroxide, potassium hydroxide, potassium acetate, and diethanolamine.

4. The method for preparing polyurethane foam using recycled polyether polyol according to claim 1, wherein: In S13, the refining agent is a neutralizer, an adsorbent and an antioxidant, the neutralizer is one or more of acetic acid, phosphoric acid, oxalic acid and formic acid; the adsorbent is one or more of magnesium silicate, aluminum silicate, silica gel, diatomaceous earth and alumina; the antioxidant is one or more of phenolic antioxidants, auxiliary antioxidants and hindered amine light stabilizers.

5. The method for preparing polyurethane foam using recycled polyether polyol according to claim 1, wherein: In S13, the neutralization reaction temperature is 40-90° C., and the reaction time is 0.8-1.2 h.