Method for recycling rigid polyurethane foam by acidolysis method

Abstract

The invention discloses a method for recycling rigid polyurethane foam by using an acidolysis method, which comprises the following steps: (1) adding polyol and a catalyst into a reaction container, carrying out nitrogen replacement, and heating to a temperature at which acid / anhydride reacts with carbamate bonds and urea bonds of polyurethane; (2) adding part of rigid polyurethane foam particles, uniformly mixing, adding acid / acid anhydride, and continuously adding the rigid polyurethane foam particles until the rigid polyurethane foam particles are completely added after the rigid polyurethane foam is reacted and dissolved; and (3) finally, cooling, and continuously and completely reacting to obtain the rigid polyurethane foam regenerated polyol. Wherein the catalyst is an acidic molecular sieve. According to the method, rigid polyurethane foam is recycled through an acidolysis method, due to the fact that acidolysis products do not contain toxic aromatic amine and molecular sieves are used as catalysts in the acidolysis method, foam decomposition can be accelerated, the viscosity of the products is reduced, follow-up utilization of the products is facilitated, and meanwhile the molecular sieves can be recycled after being filtered.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane decomposition, recovery and reuse, and particularly relates to a method for recovering polyurethane rigid foam by using an acid hydrolysis method. Background Art

[0002] Polyurethane is a widely used polymer material, among which rigid polyurethane foam is widely used in refrigerators and construction fields due to its excellent thermal insulation and heat preservation properties. With the development of the rigid polyurethane industry, the impact of more and more rigid polyurethane waste on the environment has attracted increasing attention, and the treatment and effective recycling of its waste has become one of the key difficulties in the field of resource recycling.

[0003] The main methods of recycling waste polyurethane foam are physical recycling, thermal recycling and chemical recycling. The physical recycling method is easy to operate and low in cost, but there are limitations in both processing and products. Thermal recovery is also a common method, but the incineration process is very likely to produce toxic and harmful substances. A large number of studies have shown that chemical recycling is the most promising method for polyurethane recycling. According to different degradation processes, chemical recycling can be divided into thermal decomposition, hydrolysis, ammonia decomposition, alcoholysis, acidolysis, etc. At present, the more mature chemical recovery process is mainly alcoholysis, but it has the disadvantages of slightly higher energy consumption and longer reaction time. Summary of the invention

[0004] Objective of the invention: The first objective of the present invention is to provide a method for recovering rigid polyurethane foam by acid hydrolysis.

[0005] The method for recovering polyurethane rigid foam by acid hydrolysis of the present invention comprises the following steps:

[0006] (1) adding a polyol and a catalyst into a reaction vessel, replacing the atmosphere with nitrogen, and heating the vessel to a temperature at which the urethane bonds and urea bonds of the acid / anhydride and polyurethane react;

[0007] (2) adding some polyurethane rigid foam particles, mixing evenly, adding acid / acid anhydride, waiting for the polyurethane rigid foam to react and dissolve, and then continuing to add polyurethane rigid foam particles until all the polyurethane rigid foam particles are added;

[0008] (3) finally cooling down and continuing the reaction to complete, thereby obtaining polyurethane rigid foam regeneration polyol;

[0009] The catalyst is an acidic molecular sieve.

[0010] When using acidic molecular sieves as catalysts, there are acidic or alkaline sites in the pore structure of the molecules, which have the ability to interact with the reactants. This can not only accelerate the decomposition of the foam, but also reduce the viscosity of the product, which is beneficial to the subsequent use of the product. At the same time, the molecular sieve can be filtered and reused.

[0011] Preferably, the acidic molecular sieve is CanNa 12-2n [(AlO2) 12 (SiO2) 12 ]·xH2O, purchased from Shanghai Testing Reagent.

[0012] Preferably, the mass ratio of the polyol, acid / anhydride and polyurethane rigid foam is: 1.2-1.7:1:1-2.5.

[0013] Preferably, the added amount of the catalyst is 0.5% to 1% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles.

[0014] Preferably, in step (1), the reaction temperature is 160-200°C.

[0015] Preferably, the polyol in step (1) is at least one of ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol, which is advantageous for dissolution as a solvent and can make the product have a lower viscosity.

[0016] Preferably, in step (2), the acid / anhydride is one or a mixture of two or more of oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, succinic acid, and succinic anhydride.

[0017] Preferably, in step (2), the total reaction time is 3 to 5 hours.

[0018] In step (2), since the polyurethane rigid foam particles are relatively large and the reaction of the acid / anhydride with the carbamate bond and urea bond of the polyurethane will produce gas, the polyurethane rigid foam should be added in batches to prevent the addition of too much polyurethane rigid foam from causing insufficient reaction or excessive reaction gas production.

[0019] Step (3) is to cool the reaction to further complete the reaction of the residual acid (reactant). The purpose of cooling is to avoid side reactions, such as the hydroxyl groups generated during the reaction being consumed by the residual carboxyl groups to cause esterification.

[0020] Preferably, in step (3), the cooling temperature is 110-130°C.

[0021] Preferably, the reaction time of step (3) is 0.5 to 1 hour.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) This method utilizes the acid hydrolysis method to recover polyurethane rigid foam. Since the acid hydrolysis product does not contain toxic aromatic amines, and the use of molecular sieves as catalysts can not only accelerate the decomposition of the foam, but also reduce the viscosity of the product, which is beneficial to the subsequent use of the product. At the same time, the molecular sieves can be filtered and reused; (2) In addition, the use of molecular sieves as catalysts will not introduce metal ions and will not affect the foaming performance. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments.

[0024] Example 1

[0025] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of diethylene glycol, adipic acid and polyurethane rigid foam particles is 1.5:1:1.5, and the molecular sieve CanNa 12-2n [(AlO2) 12 (SiO2) 12 ] xH2O (purchased from Shanghai Test Agent) is added in an amount of 0.5% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles; comprising the following steps:

[0026] (1) Add diethylene glycol and molecular sieves into a reaction vessel, replace with nitrogen three times, and heat to 200° C.;

[0027] (2) adding one tenth of the polyurethane rigid foam particles, stirring for 10 minutes, adding adipic acid and continuing to stir and react until the polyurethane rigid foam is dissolved, and continuing to add the polyurethane rigid foam particles in batches, adding the polyurethane rigid foam particles within 1.5 hours, and then reacting for 3 hours;

[0028] (3) Then the temperature was lowered to 120° C. and the reaction was continued for 1 hour to obtain the polyurethane rigid foam regeneration polyol S1.

[0029] Example 2

[0030] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of propylene glycol, sebacic acid and polyurethane rigid foam particles is 1.2:1:2.5, and the molecular sieve CanNa 12-2n [(AlO2) 12 (SiO2) 12 ] xH2O (purchased from Shanghai Test Agent) is added in an amount of 0.7% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles; comprising the following steps:

[0031] (1) Propylene glycol and molecular sieves were added to a reaction vessel, the atmosphere was replaced with nitrogen three times, and the temperature was raised to 160° C.;

[0032] (2) adding one tenth of the polyurethane rigid foam particles, stirring for 10 minutes, then adding sebacic acid and continuing to stir and react until the polyurethane rigid foam is dissolved, and continuing to add the polyurethane rigid foam particles in batches, adding the polyurethane rigid foam particles within 1.5 hours, and then reacting for 3.5 hours;

[0033] (3) Then the temperature is lowered to 110° C. and the reaction is continued for 1 hour to obtain the polyurethane rigid foam regenerated polyol S2.

[0034] Example 3

[0035] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of ethylene glycol, succinic acid and polyurethane rigid foam particles is 1.7:1:2, and the molecular sieve CanNa 12-2n [(AlO2) 12 (SiO2) 12 ] xH2O (purchased from Shanghai Test Agent) is added in an amount of 0.5% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles; comprising the following steps:

[0036] (1) Ethylene glycol and molecular sieves were added to a reaction vessel, the atmosphere was replaced with nitrogen three times, and the temperature was raised to 195° C.;

[0037] (2) adding one tenth of the polyurethane rigid foam particles, stirring for 10 minutes, adding succinic acid and continuing to stir and react until the polyurethane rigid foam is dissolved, and continuing to add the polyurethane rigid foam particles in batches, adding the polyurethane rigid foam particles within 1.5 hours, and then reacting for 3.5 hours;

[0038] (3) Then the temperature was lowered to 130° C. and the reaction was continued for 0.5 h to obtain the polyurethane rigid foam regeneration polyol S3.

[0039] Example 4

[0040] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of diethylene glycol and propylene glycol (4:1), succinic anhydride and polyurethane rigid foam particles is 1.4:1:1.8, and the molecular sieve CanNa 12-2n [(AlO2) 12 (SiO2) 12 ] xH2O (purchased from Shanghai Test Reagent) added in an amount of 1% of the total mass; comprising the following steps:

[0041] (1) Add diethylene glycol, propylene glycol and molecular sieves into a reaction vessel, replace with nitrogen three times, and heat to 200° C.;

[0042] (2) adding one tenth of the polyurethane rigid foam particles, stirring for 10 minutes, adding succinic anhydride acid and continuing to stir and react until the polyurethane rigid foam is dissolved, and continuing to add the polyurethane rigid foam particles in batches, adding the polyurethane rigid foam particles within 1 hour, and then reacting for 3 hours;

[0043] (3) Then the temperature was lowered to 115° C. and the reaction was continued for 1 hour to obtain the polyurethane rigid foam regenerated polyol S4.

[0044] Example 5

[0045] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of diethylene glycol, malonic acid and polyurethane rigid foam particles is 1.6:1:1.5, and the molecular sieve CanNa 12-2n [(AlO2) 12(SiO2) 12 ] xH2O (purchased from Shanghai Test Agent) is added in an amount of 0.5% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles; comprising the following steps:

[0046] (1) Add diethylene glycol and molecular sieves into a reaction vessel, replace with nitrogen three times, and heat to 195° C.;

[0047] (2) adding one tenth of the polyurethane rigid foam particles, stirring for 10 minutes, adding malonic acid and continuing to stir and react until the polyurethane rigid foam is dissolved, and continuing to add the polyurethane rigid foam particles in batches, adding the polyurethane rigid foam particles within 0.5 hours, and then reacting for 2.5 hours;

[0048] (3) Then the temperature was lowered to 125° C. and the reaction was continued for 1 hour to obtain the polyurethane rigid foam regeneration polyol S5.

[0049] Example 6

[0050] The present invention utilizes an acid hydrolysis method to recover polyurethane rigid foam, wherein the weight ratio of dipropylene glycol, succinic acid and polyurethane rigid foam particles is 1.2:1:1, and the molecular sieve CanNa 12-2n [(AlO2) 12 (SiO2) 12 ] xH2O (purchased from Shanghai Test Agent) is added in an amount of 0.8% of the total mass of the polyol, acid / anhydride and polyurethane rigid foam particles; comprising the following steps:

[0051] (1) Add dipropylene glycol and molecular sieves into a reaction vessel, replace with nitrogen three times, and heat to 200° C.;

[0052] (2) Add one tenth of the polyurethane rigid foam particles, stir for 10 minutes, then add succinic acid and continue to stir and react until the polyurethane rigid foam is dissolved, continue to add the polyurethane rigid foam particles in batches, add the polyurethane rigid foam particles within 0.5 hours, and then react for 3 hours;

[0053] (3) Then the temperature was lowered to 130° C. and the reaction was continued for 1 hour to obtain the polyurethane rigid foam regeneration polyol S6.

[0054] Comparative Example 1

[0055] On the basis of Example 1, molecular sieves are not added, the reaction time needs to be extended to 8 hours, and the other conditions remain unchanged.

[0056] Comparative Example 2

[0057] On the basis of Example 1, the molecular sieve was replaced with zinc acetate, and the other conditions remained unchanged.

[0058] Performance Testing

[0059] The moisture content, viscosity, hydroxyl value and acid value of the regenerated polyols S1 to S6 prepared in Examples 1 to 6 were tested. The test results are shown in Table 1.

[0060] Table 1 Index data of the regenerated polyols prepared in Examples 1 to 6 and Comparative Examples 1 to 2

[0061]

[0062] As shown in Table 1, Examples 1 to 6 can better recycle hard foam into regenerated polyether polyols by acid hydrolysis, and the product indicators are also relatively excellent, and the viscosity and hydroxyl value are close to those of ordinary polyols, and can be used as a partial substitute in foaming formulas. This method uses molecular sieves as catalysts, which can not only accelerate the decomposition of foams, but also reduce the viscosity of the product, which is beneficial to the subsequent use of the product. At the same time, the molecular sieves can be filtered and reused.

[0063] In Comparative Example 1, the viscosity of the product increased from 5563 to 67840, and the reaction time was prolonged. This is because without the action of a catalyst, the foam dissolution rate slowed down, and the urethane bonds and urea bonds in the foam could not be completely broken, so the viscosity was high.

[0064] In Comparative Example 2, the viscosity of the product increased from 5563 to 9929, and the viscosity increased significantly. This is because the catalytic effect of zinc acetate is weaker than that of molecular sieves, and the polyurethane cannot be decomposed into short chains at the same temperature and time, so the viscosity is higher.

Claims

1. A method for recovering polyurethane rigid foam by acid hydrolysis, characterized in that: The following steps are involved: (1) adding a polyol and a catalyst into a reaction vessel, replacing the atmosphere with nitrogen, and heating the vessel to a temperature at which the urethane bonds and urea bonds of the acid / anhydride and polyurethane react; (2) adding some polyurethane rigid foam particles, mixing evenly, adding acid / acid anhydride, waiting for the polyurethane rigid foam to react and dissolve, and then continuing to add polyurethane rigid foam particles until all the polyurethane rigid foam particles are added; (3) finally cooling down and continuing the reaction to complete, thereby obtaining polyurethane rigid foam regenerated polyol; The catalyst is an acidic molecular sieve.

2. The method for recovering rigid polyurethane foam by acid hydrolysis according to claim 1, characterized in that: The molecular sieve is CanNa 12-2n [(AlO2) 12 (SiO2) 12 ]·xH2O.

3. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: In step (1), the reaction temperature is 160-200°C.

4. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: In step (3), the cooling temperature is 110-130°C.

5. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: The mass ratio of the polyol, acid / anhydride and polyurethane rigid foam is: 1.2～1.7﹕1﹕1～2.5。 6. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: The added amount of the catalyst is 0.5% to 1% of the total mass of the polyol, the acid / acid anhydride and the polyurethane rigid foam particles.

7. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: The polyol in step (1) is at least one of ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol.

8. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: In step (2), the acid / acid anhydride is one or a mixture of two or more of oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, succinic acid, and succinic anhydride.

9. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: In the step (2), the total reaction time is 3 to 5 hours.

10. The method for recovering polyurethane rigid foam by acid hydrolysis according to claim 1, characterized in that: The reaction time of step (3) is 0.5 to 1 hour.

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