A method for recycling and plasticizing PVC with polycaprolactone

Abstract

The present invention discloses a method for recycling and plasticizing PVC with polycaprolactone, belonging to the technical field of polycaprolactone depolymerization and PVC plasticization. The present invention uses an organic base catalyst, and in the presence of an alcohol compound, under relatively mild conditions, polycaprolactone is degraded into oligomers with corresponding molecular weights (1.0 - 3.0 kg / mol). This depolymerization product can be applied to the plasticization of PVC, showing excellent plasticization effects, thereby realizing the effective utilization of waste polycaprolactone. In addition, the operation of the present invention is simple, the process is green and environmentally friendly, truly realizing the circular reuse of polycaprolactone materials, and providing a new idea for the plasticization of PVC.

Description

Technical Field

[0001] The present invention relates to a method for recycling and plasticizing PVC with polycaprolactone, belonging to the technical field of polycaprolactone depolymerization and PVC plasticization. Background Art

[0002] In the past century, engineering plastics have gradually developed into an important part of many industrial production fields, and have gradually penetrated into the field of metal materials, and their usage is increasing at an annual growth rate of 5.09%. Polyvinyl chloride (PVC), as the second most widely used resin in plastic products globally, is widely used in building materials, wire and cable, food and medical packaging, and technology fields. As an essential additive for its production, the usage of plasticizers has also increased year by year. However, traditional phthalate plasticizers are prone to migrate out of products and have been proven to have potential carcinogenicity to the human body. Therefore, the development of new environmentally friendly and resource-saving plasticizers has gradually become a research hotspot. Polyester plasticizers have attracted the attention of scientists due to their biodegradable and biocompatible characteristics.

[0003] The prior art CN102731755B uses nylon acid as the main raw material and utilizes the good solubility of diol in nylon acid to prepare a polyester plasticizer with a low acid value at low cost through two reactions of esterification and polycondensation. The reaction conditions are relatively harsh and need to be carried out at a lower vacuum degree and a higher temperature; CN111253341B prepares a safe and environmentally friendly bio-plasticizer from cardanol, which combines the advantages of epoxy plasticizers and polyester plasticizers, but the preparation process requires steps such as esterification, capping, and epoxidation, and the preparation route is relatively cumbersome.

[0004] Meanwhile, with the increasing depletion of oil resources in recent years and the proposal of the dual-carbon strategy, the sustainable development of oil-based plastics has become particularly important. Poly(ε-caprolactone) (PCL) material is an oil-based polyester plastic, which has been widely used in packaging, 3D printing, and biomedical fields due to its good biocompatibility, biodegradability, high crystallinity, and low melting point. With the increase in the production of PCL materials in the past few decades, the recycling of PCL has also received extensive attention. Although PCL is biodegradable, it usually takes 2-4 years to achieve complete biodegradation and transformation in the natural environment. In addition, carbon dioxide (the main component of greenhouse gases) and water are the decomposition products of PCL plastics. During the biodegradation process, the value of PCL materials cannot be recovered. Therefore, the most sustainable solution is to recycle and reuse waste PCL through chemical recycling. Currently, the main chemical recycling methods for polymers include pyrolysis, hydrolysis, enzymatic hydrolysis, etc. However, pyrolysis and hydrolysis usually need to be carried out at relatively high temperatures, resulting in more energy loss and increased operating costs, and the products generated are mostly small molecular compounds that cannot be directly applied; enzymatic hydrolysis is specific and only depolymerizes certain specific polyester materials, which also has certain limitations, and only microorganisms can benefit from the whole process, wasting a large amount of energy and resources. Another chemical recycling method is the transesterification reaction involving alcohols. Under the catalysis of a transesterification catalyst, polyesters are alcoholyzed into organic small molecules (Chinese Patent Applications CN114797971A, CN114031600A). Although the alcoholysis products generated by this method can be effectively utilized as useful chemicals, their value needs to be further reflected through further reactions.

[0005] Therefore, it is urgent to achieve the efficient recycling and reuse of waste polycaprolactone materials and develop a green and non-toxic plasticizer. This is of great significance for environmental protection and sustainable development. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for recycling and plasticizing PVC with polycaprolactone.

[0007] Technical Solution of the Present Invention:

[0008] One of the objectives of the present invention is to provide a method for recycling polycaprolactone, and the method is as follows:

[0009] Under the conditions of normal pressure, a certain temperature, and inert gas protection, in the presence of a catalyst and an organic solvent, an alcohol is used as an alcoholysis reagent to carry out alcoholysis on polycaprolactone to obtain oligomeric polyesters.

[0010] Further defined, the catalyst structure is as follows:

[0011]

[0012] Further defined, the addition amount of the catalyst is 0.2 to 50 mol% of the polycaprolactone.

[0013] Further defined, the number average molecular weight of the polycaprolactone is 10 4 ~10 7 g / mol.

[0014] Further defined, the organic solvent is one or a mixture of more than one of toluene, xylene, ethylbenzene, tetrahydrofuran, 2-methyl-tetrahydrofuran.

[0015] Further defined, the alcoholysis reagent is one or a mixture of more than one of methanol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-benzenedimethanol.

[0016] Further defined, the alcoholysis temperature is 30°C to 200°C.

[0017] Further defined, the molecular weight of the obtained oligomeric polyester is 1.0 to 3.0 kg / mol.

[0018] The second object of the present invention is the application of the oligomeric polyester prepared by the above polycaprolactone recovery method, specifically for plasticizing PVC resin.

[0019] Further defined, the oligomeric polyester is compounded and processed with the PVC resin material as a main plasticizer or an auxiliary plasticizer.

[0020] Further defined, the oligomeric polyester forms a PVC resin-based composite material with the PVC resin and additives.

[0021] Further defined, the additives are one or a mixture of more than one of stabilizers, light stabilizers, lubricants, anti-aging agents, antistatic agents, flame retardants.

[0022] The present invention uses an organic base catalyst, in the presence of an alcohol compound, under relatively mild conditions, to degrade polycaprolactone into oligomers with a corresponding molecular weight (1.0 to 3.0 kg / mol). This depolymerization product can be applied to the plasticization of PVC, showing excellent plasticization effects, thus realizing the effective utilization of waste polycaprolactone. Compared with the prior art, it has the following beneficial effects:

[0023] (1) The polycaprolactone recovery and degradation system provided by the present invention can be realized under relatively mild conditions. Oligomeric polyesters with a molecular weight in the range of 1.0 to 3.0 kg / mol are obtained, realizing the recycling of waste poly(ε-caprolactone), and reducing the plastic pollution caused by the large-scale use of polycaprolactone to a certain extent. In addition, the present invention can achieve the conversion of poly(ε-caprolactone) to oligomers using a non-metallic catalyst, without generating metal residues, which conforms to the principle of sustainable development.

[0024] (2) By changing the equivalent amount of the alcoholysis reagent, the present invention precisely cuts the polycaprolactone material to obtain oligomers with an expected molecular weight, and obtains oligomers with a specific molecular weight that have a good plasticizing effect. According to subsequent research, oligomers with a molecular weight in the range of 1.0 - 3.0 kg / mol have a good plasticizing effect. This is mainly because when the molecular weight of the oligopolyester is too low, there is not enough space volume to separate the PVC molecular chains, and it is easier to migrate from the PVC resin matrix to the surface and the external environment; when the molecular weight of the oligopolyester is too high, the molecular chains are prone to entanglement and aggregation, and form a mesoscopic-level blend with a "sea-island" structure with the PVC material, making it difficult to form a microscopic blend plasticization at the molecular level. Controlling the molecular weight of the oligomers obtained by depolymerization is of great significance for the recycling and reuse of materials.

[0025] (3) By changing the type of the alcoholysis reagent, the present invention regulates the plasticizing effect of the oligopolyester on the PVC material. Different alcoholysis reagents can effectively change the molecular structure of the oligopolyester material, provide alkyl groups or other groups with different carbon atom numbers. Increasing the alkyl carbon number of the alcoholysis reagent can effectively improve the flexibility of the oligopolyester molecule, and further improve the effect of the material in plasticizing PVC. And increasing the phenyl group can endow the oligopolyester with excellent heat resistance and improve the heat resistance of the plasticized PVC material.

[0026] (4) The oligopolyester product obtained by recycling and degrading polycaprolactone in the present invention is used to plasticize PVC. While effectively utilizing the waste polycaprolactone, it effectively reduces the glass transition temperature and elastic modulus of the PVC resin material, thereby reducing the material processing temperature and improving the processing performance of the material. After processing and forming, the hardness of the PVC composite material decreases significantly, effectively improving the softness of the material and expanding the application scenarios of the material. This is mainly because the oligopolyester after the depolymerization of polycaprolactone itself contains a large number of polar ester groups, which have good compatibility with the polar PVC molecular chains, and thus "shield" the interaction between the PVC molecular chains, promoting the chain mobility of the PVC molecular chains. At the same time, the oligopolyester contains some alkyl chains, and the flexibility of the alkyl chains can play a "lubricating" role to further increase the mobility of the PVC molecular chains. The enhanced mobility of the PVC molecular chains can effectively improve the plastic deformation of the material, which macroscopically shows a lower elastic modulus and hardness, effectively increasing the processing performance, service temperature range and softness of the PVC material.

[0027] (5) The method provided by the present invention is simple to operate and environmentally friendly, truly realizing the circular recycling of the polycaprolactone material, and providing a new idea for the plasticization of PVC. Description of the Drawings

[0028] Figure 1 is the nuclear magnetic spectrum of the depolymerization product of poly(ε-caprolactone) in Example 6. Detailed Embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and those skilled in the art can obtain them through commercial channels.

[0031] Example 1:

[0032] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0033]

[0034] The experimental process includes the following steps:

[0035] Take a 5 mL Schlenk flask, evacuate, bake and replace with argon, then in the glove box, add 1.14 g of poly(ε-caprolactone) (Mn = 10.7 kg / mol, PDI = 1.59), then add 13.9 mg of TBD catalyst and 5 mL of toluene solvent. Outside the glove box, add 40 μL of methanol and stir the reaction at 80 °C. After 2 h of reaction, the molecular weight was measured by gel permeation chromatography. The molecular weight of the oligomer was 1.05 kg / mol and PDI = 2.436.

[0036] Example 2:

[0037] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0038]

[0039] The experimental process includes the following steps:

[0040] Take a 5 mL Schlenk flask, evacuate, bake and replace with argon, then in the glove box, add 1.14 g of poly(ε-caprolactone) (M n = 34.6 kg / mol, PDI = 2.25), then add 13.9 mg of TBD catalyst and 5 mL of ethylbenzene solvent. Outside the glove box, add 56 μL of ethylene glycol and stir the reaction at 80 °C. After 2 h of reaction, the molecular weight was measured by gel permeation chromatography. The molecular weight of the oligomer was 1.20 kg / mol and PDI = 2.181.

[0041] Example 3:

[0042] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0043]

[0044] The experimental process includes the following steps:

[0045] Take a 5 mL Schlenk flask, evacuate, bake, and displace with argon. Then, in a glove box, add 1.14 g of poly(ε-caprolactone) (M n = 43.2 kg / mol, PDI = 1.72), then add 276 mg of TBD catalyst and 5 mL of tetrahydrofuran solvent. Outside the glove box, add 36 μL of 1,3-propanediol and stir the reaction at 30 °C for 72 h. After the reaction, measure the molecular weight by gel permeation chromatography. The molecular weight of the oligomer is 2.59 kg / mol and PDI = 2.235.

[0046] Example 4:

[0047] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0048]

[0049] The experimental process includes the following steps:

[0050] Take a 5 mL Schlenk flask, evacuate, bake, and displace with argon. Then, in a glove box, add 1.14 g of poly(ε-caprolactone) (M n = 10.7 kg / mol, PDI = 1.59), then add 13.9 mg of TBD catalyst and 5 mL of xylene solvent. Outside the glove box, add 87 μL of 1,4-butanediol and stir the reaction at 200 °C for 10 min. After the reaction, measure the molecular weight by gel permeation chromatography. The molecular weight of the oligomer is 1.41 kg / mol and PDI = 2.24.

[0051] Example 5:

[0052] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0053]

[0054] The experimental process includes the following steps:

[0055] Take a 5 mL Schlenk flask, evacuate, bake, and displace with argon. Then, in a glove box, add 1.14 g of poly(ε-caprolactone) (M n = 10.7 kg / mol, PDI = 1.59), then add 13.9 mg of TBD catalyst and 5 mL of 2-methyl-tetrahydrofuran solvent. Outside the glove box, add 6.9 mg of 1,4-benzenedimethanol and stir the reaction at 80 °C for 2 h. After the reaction, measure the molecular weight by gel permeation chromatography. The molecular weight of the oligomer is 2.89 kg / mol and PDI = 2.16.

[0056] Example 6:

[0057] The reaction process of polycaprolactone depolymerization in this example is as follows:

[0058]

[0059] The experimental process includes the following steps:

[0060] Take a 250 mL round-bottom flask, bake and displace argon, then in the glove box, add 45.6 g of poly(ε-caprolactone) (M n = 10.7 kg / mol, PDI = 1.59), then add 556 mg of TBD catalyst and 200 mL of toluene solvent. Outside the glove box, add 1.6 mL of methanol and stir and react at 80 °C. After reacting for 2 h, test the molecular weight by gel permeation chromatography. The molecular weight of the oligomer is 1.46 kg / mol and PDI = 2.12. The NMR spectrum of the obtained oligomer is as Figure 1 shown.

[0061] Example 7:

[0062] This example provides an application of an oligoester plasticizer in PVC resin.

[0063] By weight, the raw materials of the polyvinyl chloride plastic include 100 parts of PVC resin, 50 parts of oligoester plasticizer, and 4 parts of heat stabilizer (mercapto tin methyl).

[0064] Specifically, the PVC resin is purchased from Qilu Petrochemical with the grade of SG5; the oligoester plasticizer is obtained by the method of depolymerizing poly(ε-caprolactone) in Example 1; mercapto tin methyl is purchased from Jinan Yuan Su Chemical Co., Ltd.

[0065] This example provides a preparation method of an oligoester plasticized PVC resin material. The specific steps are as follows:

[0066] Mix the oligoester plasticizer, PVC resin, and heat stabilizer, and mix them for 40 minutes at 60 °C using a high-speed mixer. Then use a two-roll mill to knead the mixture evenly at a temperature of 155 °C and then take out the sheet and cool it. Then put the obtained cold sheet into a flat vulcanizer with a molding temperature of 165 °C and a press gauge pressure of 10 MPa, press for 15 min, then take it off and keep it under pressure and cool in a cold press. The press gauge pressure is 10 MPa. After cooling to 30 °C, sample the sheet to obtain the PVC plasticized material.

[0067] Example 8:

[0068] This example provides an application of an oligoester plasticizer in PVC resin.

[0069] By weight, the raw materials of the polyvinyl chloride plastic include 100 parts of PVC resin, 50 parts of oligomeric polyester plasticizer, and 4 parts of heat stabilizer (mercapto tin)

[0070] Specifically, the PVC resin is purchased from Qilu Petrochemical, with the grade of SG5; the oligomeric polyester plasticizer is obtained by the method of depolymerizing poly(ε-caprolactone) in Example 2; mercapto tin is purchased from Jinan Yuan Su Chemical Co., Ltd.;

[0071] This example provides a preparation method of an oligomeric polyester plasticized PVC resin material, and the specific steps are as follows:

[0072] Mix the oligomeric polyester plasticizer, PVC resin, and heat stabilizer, and use a high-speed mixer to mix for 40 minutes at a temperature of 60°C. Then use a two-roll mill to knead the mixture evenly at a temperature of 155°C and then take out the sheet and cool it. Then put the obtained cold sheet into a flat vulcanizer with a molding temperature of 165°C and a press gauge pressure of 10 MPa, press for 15 minutes, then take it out and keep it under pressure and cool it in a cold press, with a press gauge pressure of 10 MPa. After cooling to 30°C, take a sample sheet to obtain the PVC plasticized material.

[0073] Example 9:

[0074] This example provides an application of an oligomeric polyester plasticizer in PVC resin.

[0075] By weight, the raw materials of the polyvinyl chloride plastic include 100 parts of PVC resin, 50 parts of oligomeric polyester plasticizer, and 4 parts of heat stabilizer (mercapto tin)

[0076] Specifically, the PVC resin is purchased from Qilu Petrochemical, with the grade of SG5; the oligomeric polyester plasticizer is obtained by the method of depolymerizing poly(ε-caprolactone) in Example 3; mercapto tin is purchased from Jinan Yuan Su Chemical Co., Ltd.;

[0077] This example provides a preparation method of an oligomeric polyester plasticized PVC resin material, and the specific steps are as follows:

[0078] Mix the oligomeric polyester plasticizer, PVC resin, and heat stabilizer, and use a high-speed mixer to mix for 40 minutes at a temperature of 60°C. Then use a two-roll mill to knead the mixture evenly at a temperature of 155°C and then take out the sheet and cool it. Then put the obtained cold sheet into a flat vulcanizer with a molding temperature of 165°C and a press gauge pressure of 10 MPa, press for 15 minutes, then take it out and keep it under pressure and cool it in a cold press, with a press gauge pressure of 10 MPa. After cooling to 30°C, take a sample sheet to obtain the PVC plasticized material.

[0079] Example 10:

[0080] This example provides an application of an oligomeric polyester plasticizer in PVC resin.

[0081] By weight, the raw materials of the polyvinyl chloride plastic include 100 parts of PVC resin, 50 parts of oligomeric polyester plasticizer, and 4 parts of heat stabilizer (mercapto tin methyl)

[0082] Specifically, the PVC resin is purchased from Qilu Petrochemical with the grade of SG5; the oligomeric polyester plasticizer is obtained by the method of depolymerizing poly(ε-caprolactone) in Example 4; the mercapto tin methyl is purchased from Jinan Yuan Su Chemical Co., Ltd.;

[0083] This example provides a preparation method of an oligomeric polyester plasticized PVC resin material, and the specific steps are as follows:

[0084] Mix the oligomeric polyester plasticizer, PVC resin, and heat stabilizer, and use a high-speed mixer to mix for 40 minutes at a temperature of 60°C. Then use a two-roll mill to knead the mixture evenly at a temperature of 155°C and then take out the sheet and cool it. Then put the obtained cold sheet into a flat vulcanizer with a molding temperature of 165°C and a press gauge pressure of 10 MPa, press for 15 minutes, then take it out and keep it under pressure and cool in a cold press, with a press gauge pressure of 10 MPa. After cooling to 30°C, sample the sheet to obtain the PVC plasticized material.

[0085] Example 11:

[0086] This example provides an application of an oligomeric polyester plasticizer in PVC resin.

[0087] By weight, the raw materials of the polyvinyl chloride plastic include 100 parts of PVC resin, 50 parts of oligomeric polyester plasticizer, and 4 parts of heat stabilizer (mercapto tin methyl)

[0088] Specifically, the PVC resin is purchased from Qilu Petrochemical with the grade of SG5; the oligomeric polyester plasticizer is obtained by the method of depolymerizing poly(ε-caprolactone) in Example 5; the mercapto tin methyl is purchased from Jinan Yuan Su Chemical Co., Ltd.;

[0089] This example provides a preparation method of an oligomeric polyester plasticized PVC resin material, and the specific steps are as follows:

[0090] Mix the oligomeric polyester plasticizer, PVC resin, and heat stabilizer, and use a high-speed mixer to mix for 40 minutes at a temperature of 60°C. Then use a two-roll mill to knead the mixture evenly at a temperature of 155°C and then take out the sheet and cool it. Then put the obtained cold sheet into a flat vulcanizer with a molding temperature of 165°C and a press gauge pressure of 10 MPa, press for 15 minutes, then take it out and keep it under pressure and cool in a cold press, with a press gauge pressure of 10 MPa. After cooling to 30°C, sample the sheet to obtain the PVC plasticized material.

[0091] Comparative Example 1:

[0092] This comparative example provides an application of DOP plasticizer in PVC resin. The specific implementation manner is the same as that of Example 7; the difference is that the oligomeric polyester plasticizer is replaced with DOP (dioctyl phthalate).

[0093] Comparative Example 2:

[0094] This comparative example provides an application of DOTP plasticizer in PVC resin. The specific implementation manner is the same as that of Example 7; the difference is that the oligomeric polyester plasticizer is replaced with DOTP (dioctyl terephthalate).

[0095] Comparative Example 3:

[0096] This comparative example provides an application of ATBC plasticizer in PVC resin. The specific implementation manner is the same as that of Example 7; the difference is that the oligomeric polyester plasticizer is replaced with ATBC (tributyl acetylcitrate).

[0097] Effect Example:

[0098] For the PVC plasticized materials prepared in Examples 7 - 11 and Comparative Examples 1 - 3, specimens were cut with a cutter of standard size using a sample preparation machine, and the performance of the specimens was tested. The test results are shown in Table 1 below.

[0099] 1. Hardness test: Specimens were prepared and tested according to the standard of GB / T531 - 2008 "Indentation Hardness Test Method, Shore Hardness Tester Method". For each group of specimens, 3 points were selected, and each point was measured once, and the median value was taken.

[0100] 2. Elastic modulus: According to GB / T1040–2006 "Plastics - Determination of Tensile Properties", the tensile speed was 50 mm / min and the temperature was 25°C.

[0101] 3. Glass transition temperature: The glass transition temperature was tested by a dynamic mechanical analyzer (DMA). The PVC test piece was cut into a rectangular specimen of 30 mm × 6 mm, and a tensile fixture was used during the test. Test conditions: The test temperature range was -40 - 60°C, the heating rate was 3°C / min, and the vibration frequency was 1 Hz.

[0102] 4. Volatility test: The plasticized PVC resins prepared in Examples 7 - 11 and Comparative Examples 1 - 3 were tested according to HG / T 4458–2012 "Determination of Plasticizer Loss in Plastics - Activated Carbon Method". The test temperature was 70°C and the test time was 24 h. The results were recorded in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Although the present invention has been disclosed above in preferred embodiments, it is not intended to limit the present invention. Anyone skilled in this technology can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for recycling polycaprolactone, characterized in that, Under atmospheric pressure, at a certain temperature, under the protection of an inert gas, in the presence of a catalyst and an organic solvent, an alcohol is used as an alcoholysis reagent to carry out alcoholysis on polycaprolactone to obtain an oligomeric polyester; The structure of the catalyst is as follows: The addition amount of the catalyst is 0.2 to 50 mol% of polycaprolactone; The alcohol is one or a mixture of ethylene glycol, 1,3-propanediol, 1,4-butanediol or 1,4-benzenedimethanol; The molecular weight of the obtained oligomeric polyester is 1.0 to 3.0 kg / mol; The obtained oligomeric polyester is used as a primary plasticizer or a secondary plasticizer for plasticizing PVC resin.

2. The polycaprolactone recovery method according to claim 1, wherein, The number-average molecular weight of polycaprolactone is 10 4 ~10 7 g / mol.

3. The polycaprolactone recycling method according to claim 1, wherein The organic solvent is one or a mixture of toluene, xylene, ethylbenzene, tetrahydrofuran, 2-methyl-tetrahydrofuran.

4. The polycaprolactone recovery method according to claim 1, wherein, The alcoholysis temperature is 30°C to 200°C.

5. Use of the oligomeric polyester obtained by the method according to claim 1, characterized in that, For plasticizing PVC resin.

6. Use of the oligomeric polyester according to claim 5, characterized in that, The oligomeric polyester is compounded and processed with the PVC resin material as a primary plasticizer or a secondary plasticizer.

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