Treatment method of polymer-containing waste

Abstract

The invention relates to the field of chemical waste treatment, and discloses a treatment method of polymer-containing waste. The treatment method comprises the following steps: S1, mixing the polymer-containing waste and alcohol for reaction; s2, separating a glycollate-containing product from the reaction product obtained in S1; wherein the polymer-containing waste comprises a first polymer which is generated by carrying out polymerization reaction on at least one of ethylene glycol, lactic acid and lactide and glycollic acid and / or glycolide; and / or the polymer-containing waste material comprises a second polymer generated by a polymerization reaction of glycollic acid and / or glycolide. According to the treatment method provided by the invention, the conversion of the polymer in the polymer-containing waste is realized, the glycolate component in the polymer-containing waste is recovered, meanwhile, no complex by-product is generated, the process is simplified, and the separation difficulty is reduced.

Description

Technical Field

[0001] The invention relates to the field of chemical waste treatment, and in particular to a method for treating polymer-containing waste. Background Art

[0002] Plastics, synthetic rubber and synthetic fibers are known as the three major modern polymer materials. Polyglycolide (PGA), also known as polyglycolic acid, is a highly crystalline, biodegradable aliphatic polymer with a fast degradation rate. It is mainly used in medical consumables, mulch films and other fields. There is no mature environmentally friendly MG production process in China. The industry still mainly uses chloroacetic acid hydrolysis and formaldehyde molecular carbonylation and re-esterification. This route is complex, long, costly, and has serious environmental pollution and low yield of target products. Dimethyl oxalate (DMO) is prepared from coal-to-syngas, and dimethyl oxalate is hydrogenated to prepare methyl glycolate (MG) and then produce polyglycolic acid (PGA). This route will generate a large amount of glycolate by-products during the production process. If these by-products can be fully recovered, it can bring considerable economic benefits.

[0003] Like most biodegradable resins, polyglycolic acid can be degraded quickly after use, but it still takes at least several months or even years for all polyglycolic acid to be completely decomposed into water and carbon dioxide. In addition, allowing polyglycolic acid to degrade into water and carbon dioxide is also a waste of resources from the perspective of material recycling.

[0004] Therefore, it is of great significance to develop a method for utilizing glycolic acid polymers to recover the effective components in glycolic acid polymers to obtain valuable glycolic acid esters and other substances. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that the prior art cannot utilize glycolic acid polymers to recover valuable components, and to provide a method for treating polymer-containing waste, which can recover glycolate products and the like in the polymer-containing waste without generating complex by-products.

[0006] In order to achieve the above object, the present invention provides a method for treating polymer-containing waste, the method comprising the following steps:

[0007] S1, mixing the polymer-containing waste and alcohol to react;

[0008] S2, separating a glycolate-containing component from the reaction product obtained in S1;

[0009] Wherein, the polymer-containing waste includes: a first polymer generated by a polymerization reaction of at least one of ethylene glycol, lactic acid, and lactide with glycolic acid and / or glycolide; and / or, the polymer-containing waste includes: a second polymer generated by a polymerization reaction of glycolic acid and / or glycolide.

[0010] Through the above technical solution, the beneficial effects of the present invention at least include:

[0011] The method provided by the present invention recovers the effective components in the polymer-containing waste, has simple process steps, is highly efficient and consumes less energy, has a fast reaction rate, does not generate complex by-products, does not affect the quality of subsequent products, is economical and practical, can fully utilize glycolate esters and by-products in the polymer-containing waste, reduces resource waste, and enhances the economic benefits of the enterprise.

[0012] Waste materials from the production process of polyglycolic acid or a product production device using glycolic acid as one of the polymerization monomers are mainly used for incineration or waste treatment, and have low economic value. In the preferred embodiment of the present invention, solid waste materials, unqualified products, or recycled products from the production process of polyglycolic acid or a product production device using glycolic acid as one of the polymerization monomers are treated to achieve the conversion of the polymer therein, recover the glycolate component therein, simplify the process, reduce the difficulty of separation, and achieve the quality improvement and efficiency enhancement of glycolic acid production and polymerization waste. In addition, the present invention further improves the conversion rate of polymers in polymer-containing waste by introducing a material containing metal oxides, selecting the appropriate type and amount of the material containing metal oxides, the appropriate ratio of polymer-containing waste to alcohol, and the appropriate reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a flow chart of a method for treating polymer-containing waste in one embodiment of the present invention;

[0014] Figure 2 It is an XRD spectrum of the polymer-containing waste material in the present invention, in which the contents of the structural unit derived from glycolic acid and the structural unit derived from lactic acid are 70 wt % and 30 wt %, respectively. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The present invention provides a method for treating polymer-containing waste, the method comprising the following steps:

[0017] S1, mixing the polymer-containing waste and alcohol to react;

[0018] S2, separating a glycolate-containing component from the reaction product obtained in S1;

[0019] Wherein, the polymer-containing waste includes: a first polymer generated by a polymerization reaction of at least one of ethylene glycol, lactic acid, and lactide with glycolic acid and / or glycolide; and / or, the polymer-containing waste includes: a second polymer generated by a polymerization reaction of glycolic acid and / or glycolide.

[0020] The method provided by the present invention makes full use of polymer-containing waste, transforms the polymer in the polymer-containing waste, recovers glycolate and / or byproducts therein, and does not generate complex byproducts. The byproducts may include ethylene glycol, lactate and other substances.

[0021] In order to further accelerate the reaction rate, preferably, the reaction is carried out in the presence of a material containing a metal oxide.

[0022] Preferably, the material containing metal oxide is selected from a material containing zinc oxide and / or a material containing copper oxide, preferably a material containing zinc oxide.

[0023] According to the present invention, the polymer-containing waste can be solid waste, unqualified products, or recycled products in the production process of glycolic acid polymers. Preferably, the total content of the first polymer and the second polymer in the polymer-containing waste is greater than or equal to 80wt%, preferably 95-100wt%.

[0024] According to the present invention, preferably, the first polymer is a copolymer generated by polymerization reaction of glycolide and / or glycolic acid with lactic acid and / or lactide.

[0025] Wherein, in the copolymer, the weight ratio of the structural units derived from glycolide and / or glycolic acid to the structural units derived from lactic acid and / or lactide can be any value; preferably, in the copolymer, the content of the structural units derived from glycolide and / or glycolic acid is greater than or equal to 50wt%, more preferably 70-80wt%.

[0026] In the present invention, in addition to the first polymer and the second polymer, the polymer-containing waste material may further include various polymerization catalysts.

[0027] According to a preferred embodiment of the present invention, the copolymer is a copolymer generated by polymerization of glycolic acid and lactic acid. Accordingly, the glycolate-containing product recovered includes glycolate and lactate.

[0028] According to the present invention, preferably, the alcohol is selected from saturated monohydric alcohols, preferably selected from C1-C4 saturated monohydric alcohols, such as methanol and ethanol, etc. Methanol and ethanol react with the polymer in the polymer-containing waste, and the corresponding glycolic acid esters generated are methyl glycolate and ethyl glycolate, respectively.

[0029] Furthermore, the alcohol is methanol.

[0030] In the present invention, the alcohol may also include a small amount of low-boiling esters with a boiling point of 50-90°C, such as methyl acetate and ethyl acetate. Preferably, the content of low-boiling esters in the alcohol is less than or equal to 18wt%, more preferably less than or equal to 11wt%. When the alcohol does not contain impurity esters (low-boiling esters), the glycolate recovered has a higher yield and purity. If the alcohol contains impurity esters, the impurity esters may exchange with other substances in the polymer-containing waste to generate impurities. However, the inventors have found that when the total content of low-boiling esters in the alcohol meets the above range, the amount of impurities generated is small, and can be removed together in the subsequent separation, which has little effect on the yield and purity of the glycolate recovered. The purity requirements for alcohol (such as methanol) can be reduced, the difficulty and cost of its refining can be reduced, and the raw material range of alcohol can be widened.

[0031] In order to further accelerate the reaction rate, preferably, in S1, based on 100 g of the polymer-containing waste material, the amount of the material containing metal oxides is 0.1-100 g, more preferably 10-60 g.

[0032] According to the present invention, preferably, in S1, the polymer-containing waste and the alcohol are mixed in a weight ratio of 1:(0.5-50), preferably 1:(5-30).

[0033] According to the present invention, preferably, in S1, the reaction pressure is 0.1-8 MPa, preferably 3-7 MPa; the reaction temperature is not higher than the boiling point of the alcohol and its azeotrope under the same pressure conditions, preferably, the reaction temperature is 150-250°C, more preferably 180-220°C; the reaction time is 5 min-5 h, more preferably 15 min-3 h.

[0034] According to the present invention, preferably, the reaction is carried out in the presence of a protective gas, which may be, for example, at least one of an inert gas, nitrogen, carbon dioxide and hydrogen, wherein the inert gas may be, for example, helium and / or argon.

[0035] Furthermore, the protective gas is nitrogen.

[0036] According to the present invention, when the polymer-containing waste material includes a copolymer generated by a polymerization reaction of glycolic acid and lactic acid, the recovered glycolate-containing product includes glycolate and lactate. According to a preferred embodiment of the present invention, in S2, the light component with a boiling point lower than that of lactate is first separated out; then the lactate with a boiling point lower than that of glycolate is separated out; and then the glycolate is separated from the heavy component with a boiling point higher than that of glycolate, thereby recovering the glycolate-containing product including glycolate and lactate.

[0037] The present invention does not particularly limit the method for separating light components with a boiling point lower than that of lactic acid ester. For example, distillation, distillation concentration, adsorption and extraction methods can be used. In a preferred case, the light components are separated by distillation, which can be either atmospheric distillation or reduced pressure distillation. Preferably, the distillation is carried out at a temperature not higher than 160°C.

[0038] The present invention does not particularly limit the method for separating lactic acid esters. For example, atmospheric distillation, vacuum distillation, atmospheric distillation, vacuum distillation, pressurized distillation and the like can be used. Preferably, the vacuum distillation method is used to separate lactic acid esters, preferably, the vacuum distillation is carried out at a temperature not higher than 160°C.

[0039] The present invention does not particularly limit the method for separating glycolic acid esters. For example, atmospheric distillation, vacuum distillation, atmospheric distillation, vacuum distillation, pressurized distillation and the like can be used. Preferably, the glycolic acid esters are separated by vacuum distillation, preferably at a temperature not higher than 160°C.

[0040] According to a preferred embodiment of the present invention, in S2, the separation method comprises:

[0041] a. The reaction product obtained in S1 is subjected to a first distillation under the conditions of 101-141 kPa and 60-160° C., the number of plates of the first distillation is controlled to be 5-35, and the reflux ratio is controlled to be 0.1-7, to obtain a light component and undistilled materials of the first distillation;

[0042] Alternatively, the reaction product obtained in S1 is subjected to a first distillation under the conditions of 60-101 kPa and 50-150° C., the number of plates of the first distillation is controlled to be 5-35, and the reflux ratio is controlled to be 0.1-7, to obtain a light component and undistilled materials of the first distillation;

[0043] b. The undistilled material of the first distillation is subjected to a second distillation under the conditions of 5-101 kPa and 50-160 ° C, the number of plates of the second distillation is controlled to be 5-350, and the reflux ratio is 0.1-20, to obtain a lactic acid ester-containing material and an undistilled material of the second distillation;

[0044] c. The undistilled material of the second distillation is subjected to a third distillation under the conditions of 5-101 kPa and 50-160° C. The number of plates of the third distillation is controlled to be 5-350, and the reflux ratio is controlled to be 0.1-20, to obtain a glycolate-containing material and a heavy component.

[0045] According to the present invention, preferably, the treatment method further comprises: returning at least a portion of the remaining material after separating the glycolate-containing product to S1 to mix with alcohol.

[0046] According to a preferred embodiment of the present invention, Figure 1 A method for treating polymer-containing waste is described, comprising the following steps: in the presence of a material containing metal oxides, the polymer-containing waste and methanol are mixed and reacted in a reaction unit, and then the reaction product is introduced into a separation unit to obtain a light component, a lactate-containing material, a glycolate-containing material, and a heavy component, respectively. The glycolate-containing material and the lactate-containing material are drawn out of the separation unit as glycolate-containing products, and at least a portion of the light component and at least a portion of the heavy component are returned to the reaction unit to continue to participate in the reaction.

[0047] The present invention will be described in detail below through examples and comparative examples. In the following examples, unless otherwise specified, all methods are conventional methods; and the reagents and materials used, unless otherwise specified, can be obtained from commercial sources.

[0048] The composition of the components was determined by gas chromatography according to the normalization method.

[0049] In the following examples, unless otherwise specified, the composition of the polymer-containing waste material is a copolymer in which the content of the structural unit derived from glycolic acid and the structural unit derived from lactic acid are 70 wt % and 30 wt %, respectively.

[0050] Figure 2 is an XRD spectrum of the polymer-containing waste material in which the contents of the structural units derived from glycolic acid and the structural units derived from lactic acid are 70 wt % and 30 wt %, respectively, Figure 2 Clear characteristic peaks of polyglycolic acid unit structure can be seen.

[0051] Conversion rate of polymer % = (weight of polymer in polymer-containing waste - weight of polymer in reaction product) ÷ weight of polymer in reaction product × 100%;

[0052] Glycolate yield % = weight of glycolate in glycolate product ÷ weight of glycolate in reaction product × 100%;

[0053] Lactate yield % = weight of glycolate in lactate product ÷ weight of lactate in reaction product × 100%.

[0054] The following examples are provided to illustrate the treatment of polymer-containing waste materials.

[0055] Example 1

[0056] 50 g of polymer waste, 500 g of methanol and 25 g of zinc oxide-containing material (zinc catalyst, brici-zn-01, purchased from Beijing Institute of Chemical Industry) were added to a reactor, heated to 200 ° C under nitrogen protection, maintained at a system pressure of 5 MPa, and kept warm for 1 hour. After cooling, the reaction liquid was taken for chromatographic analysis, and the conversion rate of the polymer was 99.5%.

[0057] The reaction product is first separated into light components by a primary separation tower. The operating pressure of the primary separation tower is 60kPa, the number of plates is 25, and the reflux ratio is 5. A methanol-rich stream is obtained at the top of the tower, and the liquid phase in the bottom of the tower is sent to the product tower 1. The operating pressure of the product tower 1 is 15kPa, the number of plates is 25, and the reflux ratio is 5. The lactate product is obtained at the top of the tower, and the liquid phase in the bottom of the tower is sent to the product tower 2. The operating pressure of the product tower 2 is 15kPa, the number of plates is 25, and the reflux ratio is 5. The glycolate product is obtained at the top of the tower, and the heavy impurities are obtained in the bottom of the tower. 476g of methanol-rich stream, of which the purity of methanol is 99.61%; 53g of methyl glycolate product, purity of 98%, yield of 96.12%; 20g of lactate product, purity of 98%, yield of 90.83%.

[0058] Example 2

[0059] 50 g of polymer-containing waste, 600 g of methanol and 30 g of zinc oxide-containing material (the same as the zinc oxide-containing material in Example 1) were added to a reactor, heated to 180°C under nitrogen protection, the system pressure was maintained at 5 MPa, and the mixture was kept warm for 1 hour. After cooling, the reaction liquid was taken for chromatographic analysis, and the conversion rate of the polymer was 99.2%.

[0060] The reaction product was separated according to the separation method of Example 1 to obtain 577 g of methanol-rich stream, wherein the methanol purity was 99.52%, 52 g of methyl glycolate product, purity was 98%, and the yield was 94.59%, and 20 g of lactate product, purity was 98%, and the yield was 91.1%.

[0061] Example 3

[0062] 50 g of polymer-containing waste, 500 g of solvent (92 wt % methanol, 8 wt % methyl acetate), and 25 g of zinc oxide-containing material (the same as the zinc oxide-containing material in Example 1) were added to a reactor, and the temperature was raised to 200° C. under nitrogen protection, the system pressure was maintained at 5 MPa, and the temperature was kept for 1 hour. After cooling, the reaction liquid was taken for chromatographic analysis, and the conversion rate of the polymer was 99%.

[0063] The reaction product was separated according to the separation method of Example 1 to obtain 476 g of a methanol-rich stream, wherein the methanol purity was 91.24%, 52 g of a methyl glycolate product, with a purity of 98% and a yield of 94.78%, and 20 g of a lactate product, with a purity of 98% and a yield of 91.28%.

[0064] Example 4

[0065] The polymer was treated according to the method of Example 1, except that no material containing zinc oxide was added. After the reaction product was cooled, the reaction solution was taken and analyzed by chromatography, and the conversion rate of the polymer was 82.1%.

[0066] The reaction product was separated according to the separation method of Example 1 to obtain 480 g of a methanol-rich stream, wherein the methanol purity was 99.72%, 41 g of a methyl glycolate product, with a purity of 98% and a yield of 90.11%, and 15 g of a lactate product, with a purity of 98% and a yield of 82.56%.

[0067] Example 5

[0068] The polymer was treated according to the method of Example 1, except that "raising the temperature to 140° C." was used instead of "raising the temperature to 200° C.". After the reaction product was cooled, the reaction liquid was taken and analyzed by chromatography, and the conversion rate of the polymer was 88.2%.

[0069] The reaction product was separated according to the separation method of Example 1 to obtain 479 g of a methanol-rich stream, wherein the methanol purity was 99.6%, 45 g of a methyl glycolate product, with a purity of 98% and a yield of 92.06%, and 17 g of a lactate product, with a purity of 98% and a yield of 87.1%.

[0070] Example 6

[0071] The polymer was treated in the same manner as in Example 1, except that 100 g of methanol was used instead of 500 g of methanol. After the reaction product was cooled, the reaction solution was analyzed by chromatography, and the conversion rate of the polymer was 84.3%.

[0072] The reaction product was separated according to the separation method of Example 1 to obtain 80 g of a methanol-rich stream, wherein the methanol purity was 97.63%, 43 g of a methyl glycolate product, with a purity of 98% and a yield of 92.04%, and 16 g of a lactate product, with a purity of 98% and a yield of 85.76%.

[0073] Example 7

[0074] The polymer was treated according to the method of Example 1, except that "ethanol" was used instead of "methanol". After the reaction product was cooled, the reaction liquid was taken and analyzed by chromatography, and the conversion rate of the polymer was 69.1%.

[0075] The reaction product was separated according to the separation method of Example 1 to obtain 485 g of ethanol-rich stream, of which ethanol purity was 99.39%, 35 g of ethyl glycolate product, purity was 98%, and yield was 91.4%, and 12 g of lactate product, purity was 98%, and yield was 78.47%.

[0076] Example 8

[0077] The polymer was treated in the same manner as in Example 1, except that the copolymer containing 70 wt % of structural units derived from glycolic acid and 30 wt % of structural units derived from lactic acid was replaced by the copolymer containing 40 wt % of structural units derived from glycolic acid and 60 wt % of structural units derived from lactic acid. After the reaction product was cooled, the reaction solution was analyzed by chromatography, and the conversion rate of the polymer was 83.7%.

[0078] The reaction product was separated according to the separation method of Example 1 to obtain 482 g of a methanol-rich stream, wherein the methanol purity was 99.35%, 23 g of a methyl glycolate product, with a purity of 98% and a yield of 86.77%, and 33 g of a lactate product, with a purity of 98% and a yield of 89.08%.

[0079] It can be seen from the results of the various embodiments that embodiments 1-3 use the method provided by the present invention to treat polymer-containing waste, and the polymer can be effectively converted into glycolate and lactate products with a high conversion rate. Embodiment 3 uses a mixed solvent of methanol and methyl acetate, which well meets the conversion requirements, while reducing the purity requirements of the solvent and broadening the solvent source.

[0080] In addition, in Example 4, no material containing zinc oxide is added, in Example 5, the reaction temperature is lowered, in Example 6, the amount of methanol used is reduced, in Example 7, methanol is replaced by ethanol, and in Example 8, the polymer composition of the polymer-containing waste treated is different. Compared with Example 1, the conversion rate of the polymer in Examples 4-8 is reduced, and the amount and yield of glycolate and lactate products are reduced. This shows that when the material containing metal oxide is added to the reaction, as well as the reaction conditions, the type and amount of alcohol, and the polymer composition of the polymer waste meet the preferred conditions, the utilization rate of the polymer in the polymer-containing waste can be further improved, thereby more effectively utilizing the polymer-containing waste to recover effective products.

[0081] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for treating polymer-containing waste, characterized in that: The processing method comprises the following steps: S1, mixing the polymer-containing waste and alcohol to react; S2, separating a glycolate-containing product from the reaction product obtained in S1; Wherein, the polymer-containing waste includes: a first polymer generated by a polymerization reaction of at least one of ethylene glycol, lactic acid, and lactide with glycolic acid and / or glycolide; and / or, the polymer-containing waste includes: a second polymer generated by a polymerization reaction of glycolic acid and / or glycolide.

2. The processing method according to claim 1, characterized in that: The reaction is carried out in the presence of a material containing a metal oxide.

3. The treatment method according to claim 2, wherein the material containing metal oxide is selected from a material containing zinc oxide and / or a material containing copper oxide, preferably a material containing zinc oxide.

4. The processing method according to any one of claims 1 to 3, characterized in that: The total content of the first polymer and the second polymer in the polymer-containing waste is greater than or equal to 80wt%, preferably 95-100wt%; Preferably, the first polymer is a copolymer formed by polymerization of glycolide and / or glycolic acid and lactic acid and / or lactide; Preferably, in the copolymer, the content of structural units derived from glycolide and / or glycolic acid is greater than or equal to 50wt%, preferably 70-80wt%; Preferably, the copolymer is a copolymer generated by polymerization reaction of glycolic acid and lactic acid.

5. The processing method according to any one of claims 1 to 4, characterized in that: The alcohol is selected from saturated monohydric alcohols, preferably from C1-C4 saturated monohydric alcohols, and more preferably methanol.

6. The processing method according to any one of claims 2 to 5, characterized in that: In S1, based on 100 g of the polymer-containing waste, the amount of the material containing metal oxides is 0.1-100 g, more preferably 10-60 g.

7. The processing method according to any one of claims 1 to 6, characterized in that: In S1, the polymer-containing waste and the alcohol are mixed in a weight ratio of 1:(0.5-50), preferably 1:(5-30).

8. The processing method according to any one of claims 1 to 7, characterized in that: In S1, the reaction conditions include: pressure of 0.1-8 MPa, preferably 3-7 MPa; temperature of 150-250° C., preferably 180-220° C.; time of 5 min-5 h, preferably 15 min-3 h; Preferably, the reaction is carried out in the presence of a protective gas.

9. The processing method according to any one of claims 1 to 8, characterized in that: In S2, the separation method comprises: a. The reaction product obtained in S1 is subjected to a first distillation under the conditions of 101-141 kPa and 60-160° C. to obtain a light component and undistilled material from the first distillation; Alternatively, the reaction product obtained in S1 is subjected to a first distillation under the conditions of 60-101 kPa and 50-150° C. to obtain a light component and undistilled material from the first distillation; b. subjecting the undistilled material from the first distillation to a second distillation at 5-101 kPa and 50-160° C. to obtain a lactic acid ester-containing material and an undistilled material from the second distillation; c. The undistilled material from the second distillation is distilled for the third time under the conditions of 5-101 kPa and 50-160° C. to obtain a glycolate-containing material and a heavy component.

10. The processing method according to any one of claims 1 to 9, characterized in that: The treatment method further comprises: returning at least a portion of the remaining material after separating the glycolate-containing product to S1 to be mixed with alcohol.

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