High-molecular-weight CO2-based degradable plastic catalyzed by nonmetal catalyst and preparation method of high-molecular-weight CO2-based degradable plastic

Abstract

The invention discloses a high molecular weight CO2-based degradable plastic catalyzed by a non-metal catalyst and a preparation method thereof, the preparation method takes propylene oxide (PO) and CO2 as raw materials, in the presence of the non-metal catalyst, a molecular weight regulator and a branching agent, a copolymerization reaction is carried out, and the CO2-based degradable plastic polypropylene carbonate (PPC) is synthesized. The non-metal catalyst is composed of alkyl boron and quaternary ammonium salt, the molecular weight regulator is cyclic anhydride, and the branching agent is cyclic carboxylic acid dianhydride. The PPC prepared by the invention not only is high in molecular weight and good in processability, has the concept of carbon neutralization, relatively high gas barrier property, solvent resistance and the like, has the characteristics of relatively high strength, elastic coefficient, no toxicity, harmlessness and the like, is biodegradable, and has a wide market application prospect.

Description

Technical Field

[0001] The invention belongs to the field of biodegradable plastic production technology, and specifically relates to a high molecular weight CO2-based biodegradable plastic catalyzed by a non-metallic catalyst and a preparation method thereof. Background Art

[0002] At present, most plastic products on the market are made of petroleum as raw materials, which are expensive and difficult to degrade after use, polluting the environment. The "white pollution" caused by the random discarding of these plastic waste products is particularly serious. They take a long time to completely decompose in nature. Taking polyethylene as an example, it takes about 30-50 years, and it will cause environmental pollution during decomposition. For this reason, the country has issued a "plastic ban". With the implementation of the "plastic ban" at home and abroad, degradable materials will gradually replace traditional plastics, especially carbon dioxide-based polycarbonate degradable materials, which will surely be used as a major technology in the industrial field in the future.

[0003] There are many types of biodegradable plastics, such as poly 3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and copolymers of PHB and PHV (PHBV), polylactic acid (PLA), poly-ε-caprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate / terephthalate (PBAT), polyglycolic acid (PGA) and polymethyl ethylene carbonate (PPC) or polypropylene carbonate, etc.

[0004] Among these biodegradable plastics, only PPC biodegradable plastics synthesized from propylene oxide and CO2 have the following advantages: (a) the only biodegradable plastic with the concept of "carbon neutrality"; (b) good biocompatibility, high gas barrier properties and solvent resistance, high strength, elastic modulus and non-toxic and harmless; (c) can be widely used in food packaging, medical materials, adhesives and engineering plastics. Therefore, the preparation of CO2-based biodegradable polymer materials by copolymerization with carbon dioxide as raw material has attracted widespread attention at home and abroad.

[0005] In the existing PPC synthesis technology, most of them use organic acid zinc, ternary rare earth complex catalyst, bimetallic catalyst, etc. as catalysts. For example, CN1306021A discloses an efficient preparation method for high molecular weight aliphatic polycarbonate, using rare earth complex as catalyst to catalyze the copolymerization reaction of PO and CO2. CN101402726A discloses a combined catalyst and preparation method for the copolymerization of carbon dioxide and epoxide, using ternary rare earth catalyst plus zinc salt as catalyst to catalyze the copolymerization reaction of PO and CO2. CN102702501B discloses a composite catalyst for preparing a copolymer of carbon dioxide and propylene oxide, and its preparation method and application, using tertiary amine and zinc glutarate complex as catalyst to catalyze the copolymerization reaction of PO and CO2. CN1116332C discloses an efficient preparation method for high molecular weight aliphatic polycarbonate, using rare earth complex to catalyze the copolymerization reaction of PO and CO2. CN1250603C discloses a ternary catalyst for preparing high molecular weight aliphatic polycarbonate, using metal salt and alkyl zinc as catalyst. CN102659850B discloses a method for preparing a tetradentate Schiff base metal complex, a metal porphyrin complex and polycarbonate, wherein the tetradentate Schiff base metal complex and the metal porphyrin complex are used as catalysts to catalyze the copolymerization reaction of PO and CO2.

[0006] Although the molecular weight of PPC synthesized by metal-based multifunctional catalysts is relatively high, reaching more than 100 kg / mol, achieving the preparation of high-performance polycarbonate materials with controllable molecular weight and alternating chemical / regional / stereoselectivity, most metal-based catalysts have problems such as complex ligands, high synthesis costs, high environmental risks, and metal residues, which seriously affect their application in microelectronics, food packaging, biomedical materials and other fields. In sharp contrast, non-metallic catalyzed ring-opening polymerization is more environmentally friendly and economical, not only avoiding metal residues, but also reducing the consumption of metal resources. Most of the non-metallic catalysts reported are composites of alkyl boron and organic amines. For example, in the paper Highly Selective and Productive Synthesis of a Carbon Dioxide Based Copolymer upon Zwitterionic Growth by Ying Wang et al. (Macromolecules 2021, 54, 2178-2186), a combination of triethylboron (TEB) and triethylamine (TEA) was used as a catalyst to catalyze the copolymerization of PO and CO2, and the maximum molecular weight Mn of the obtained PPC was 56.0 kg / mol; while when a combination of TEB and N,N,N',N'-tetraethylethylenediamine (TEED) was used as a catalyst, the maximum molecular weight Mn of the obtained PPC did not exceed 35.1 kg / mol. In the paper Precision copolymerization of CO2 and epoxides enabled by organoboron catalysts by Guan-Wen Yang et al. (Nature Synthesis, 2022, 1, 892-901), 9 binuclear organic boron nitrogen catalysts were synthesized to catalyze the copolymerization of PO and CO2, and the maximum molecular weight Mn of the PPC was 62.8 kg / mol. It can be seen that the molecular weight of PPC synthesized by the composite non-metallic catalyst of alkyl boron and organic amine is usually relatively low, and the molecular weight of PPC synthesized without metal catalyst is high, which brings some difficulties to the subsequent processing and application. Summary of the invention

[0007] The purpose of the present invention is to disclose a high molecular weight CO2-based biodegradable plastic catalyzed by a non-metallic catalyst and a preparation method thereof, so as to overcome the defects of the existing composite non-metallic catalyst synthesis technology of alkyl boron and organic amine PPC, such as low molecular weight and difficulty in processing and application.

[0008] To achieve the above object, the technical solution adopted by the present invention includes the following steps:

[0009] A method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst comprises the following steps: using propylene oxide (PO) and CO2 as raw materials, and carrying out a copolymerization reaction in the presence of a non-metallic catalyst, a molecular weight regulator and a branching agent to synthesize the CO2-based degradable plastic polypropylene carbonate (PPC); the non-metallic catalyst is a combination of one or more alkyl borons having the general formula R3B and one or more quaternary ammonium salts having the general formula R'4NX; the molecular weight regulator is a cyclic acid anhydride having the general formula A(CO)2O; the branching agent is a cyclic carboxylic dianhydride having the general formula (CO)2OD(CO)2O; in the general formula, A and D refer to the parts of the cyclic acid anhydride excluding the acid anhydride group, and are one of cycloalkyl groups or aromatic groups.

[0010] Furthermore, R in the alkyl boron R3B is an alkyl group or an aryl group, R' in the quaternary ammonium salt R'4NX is a hydrocarbon group, and N is a nitrogen atom; R and R' may be the same or different, or R' is triphenylphosphine; and X is a halogen anion.

[0011] Furthermore, the alkyl boron is one of triethyl boron, tricyclohexyl boron, tri-n-butyl boron, triphenyl boron, triisobutyl boron, tri-sec-butyl borane, trimethyl boron, etc.; the quaternary ammonium salt is one of methyltriethylammonium chloride, methyltriethylammonium bromide, tetramethylammonium iodide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, hexadecyltrimethylammonium chloride, etc.

[0012] Further, the cyclic anhydride A(CO)2O is one or more selected from cyclic anhydrides having the following structures:

[0013]

[0014] Further, the cyclic carboxylic acid dianhydride (CO)2OD(CO)2O is one or more selected from cyclic acid anhydrides having the following structures:

[0015]

[0016] Furthermore, the molar ratio of propylene oxide to the molecular weight regulator is 6:1 to 14:1, and the branching agent is 1 to 5 mol% of the molecular weight regulator.

[0017] Furthermore, in the non-metallic catalyst, the molar ratio of alkyl boron to quaternary ammonium salt is 2:1 to 4:1.

[0018] Furthermore, the molar ratio of the raw material PO to the quaternary ammonium salt is 2000:1 to 6000:1.

[0019] Furthermore, the copolymerization reaction temperature is 50-90°C, the reaction time is 2-28h, and the CO2 pressure is 0.5-5MPa.

[0020] The present invention also provides a high molecular weight CO2-based degradable plastic catalyzed by a non-metal catalyst, which is prepared by the preparation method described above.

[0021] The alkyl boron and quaternary ammonium salt combination catalyst can also be carried out efficiently at low concentrations. The active center concentration in the low-concentration catalytic system is low, and there are few chain transfer reactions, but more chain growth reactions, so a larger molecular weight will be produced. At the same time, using 1-5% mol of branching agent can connect multiple molecules together to form a network structure and increase the overall molecular weight.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the molecular weight of the CO2-based degradable plastic PPC catalytically synthesized by the present invention using a non-metallic catalyst combination of alkyl boron and quaternary ammonium salt is significantly increased to more than 100 kg / mol, the glass transition temperature is higher than 47°C, and the tensile strength is as high as more than 30 MPa. The conventional PPC directly synthesized from CO2 and PO has a glass transition temperature of 30 to 41°C and a tensile strength of about 30 MPa. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described by examples below, but these examples do not limit the protection scope of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0024] Example 1

[0025] A 200ml autoclave was placed in a glove box, and 0.648mol of dehydrated propylene oxide (PO) was added. Triethylboron (TEB) and methyltriethylammonium chloride (MTCl) were combined in a 2.6:1 (molar ratio) as catalysts. The molecular weight regulator was phthalic anhydride (PA), and the branching agent was pyromellitic anhydride (PMDA). The molar ratio of PO to PA, PMDA, TEB, and MTCl was 5000:500:5:2.6:1. 1.5MPa of CO2 was filled into the autoclave, and the reaction was carried out at 80°C for 6h. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC, and the number average molecular weight Mn was 119kg / mol, the glass transition temperature was 48°C, and the tensile strength was 33.2MPa.

[0026] Example 2

[0027] A 200ml autoclave was placed in a glove box, and 0.648mol of dehydrated propylene oxide (PO) was added. Tricyclohexyl boron (TCB) and quaternary ammonium salt hexadecyl trimethyl ammonium chloride (HTAC) were combined as catalysts at a molar ratio of 2.4:1. The molecular weight regulator was 1,2-cyclohexanedicarboxylic anhydride (HHPA), and the branching agent was 1,4,5,8-naphthalenetetracarboxylic anhydride (NTADA). The molar ratio of PO to HHPA, NTADA, TCB, and HTAC was 4000:400:4:2.4:1. 2.0MPa of CO2 was filled into the autoclave and reacted at 70°C for 8h. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC. The number average molecular weight Mn was 138kg / mol, the glass transition temperature was 50°C, and the tensile strength was 36.1MPa.

[0028] Example 3

[0029] Put a 200ml autoclave in a glove box, add 0.648mol of dehydrated propylene oxide (PO), combine triphenylboron (TPB) and tetraethylammonium bromide (TEAB) in a 3.0:1 (molar ratio) as a catalyst, the molecular weight regulator is maleic anhydride (MA), the branching agent is pyromellitic dianhydride (PMDA), and the molar ratio of PO to MA, PMDA, TPB, and TEAB is 5500:500:5:3.0:1. Fill the autoclave with 1.0MPa of CO2 and react at 80°C for 6h. After cooling, release CO2, take out the solid matter in the autoclave, precipitate the polymer in petroleum ether, and after vacuum drying, characterize the polymer by GPC. The number average molecular weight Mn is 127kg / mol, the glass transition temperature is 49°C, and the tensile strength is 33.6MPa.

[0030] Example 4

[0031] A 200 ml autoclave was placed in a glove box, and 0.648 mol of dehydrated propylene oxide (PO) was added. Alkyl boron (of which triphenyl boron (TPB) and tri-n-butyl boron (TNBB) each accounted for 50% mol) and quaternary ammonium salt (of which tetraethylammonium bromide (TEAB) and tetramethylammonium iodide (TMAI) accounted for 60% and 40% mol, respectively) were combined in a molar ratio of 2.8:1 as a catalyst. The molecular weight regulator was methylsuccinic anhydride (MSA), and the branching agent was pyromellitic dianhydride (PMDA). The molar ratio of PO to MSA, PMDA, alkyl boron combination, and quaternary ammonium salt combination was 6000:600:8:2.8:1. 2.0 MPa of CO2 was charged, and the reaction was carried out at 65°C for 10 hours. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC. The number average molecular weight Mn was 141 kg / mol, the glass transition temperature was 49.5°C, and the tensile strength was 36.5 MPa.

[0032] Example 5

[0033] A 200 ml autoclave was placed in a glove box, 0.648 mol of dehydrated propylene oxide (PO) was added, triethylboron (TEB) and quaternary ammonium salt methyltriethylammonium chloride (MTCl) were combined in a 3.0:1 (molar ratio) as a catalyst, the molecular weight regulator was a combination of methylsuccinic anhydride (MSA) and phthalic anhydride (PA), MSA:PA=0.5:0.5 (mol), the branching agent was pyromellitic dianhydride (PMDA), wherein the molar ratio of PO to the molecular weight regulator, PMDA, TEB, and MTCl was 4100:500:7:3.0:1, 1.0 MPa of CO2 was charged, and the reaction was carried out at 80°C for 6 hours. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC. The number average molecular weight Mn was 130 kg / mol, the glass transition temperature was 49.3°C, and the tensile strength was 33.8 MPa.

[0034] Example 6

[0035] A 200 ml autoclave was placed in a glove box, 0.648 mol of dehydrated propylene oxide (PO) was added, triethylboron (TEB) and quaternary ammonium salt methyltriethylammonium chloride (MTCl) were combined in a 2.6:1 (molar ratio) as a catalyst, the molecular weight regulator was a combination of methylsuccinic anhydride (MSA) and phthalic anhydride (PA), MSA:PA=0.5:0.5 (mol), the branching agent was pyromellitic dianhydride (PMDA), wherein the molar ratio of PO to the molecular weight regulator, PMDA, TEB, and MTCl was 4100:520:7:2.6:1, 1.5 MPa of CO2 was charged, and the reaction was carried out at 80°C for 10 hours. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC. The number average molecular weight Mn was 133 kg / mol, the glass transition temperature was 49.4°C, and the tensile strength was 33.9 MPa.

[0036] Example 7

[0037] A 200 ml autoclave was placed in a glove box, 0.648 mol of dehydrated propylene oxide (PO) was added, tricyclohexylborane (TCB) and quaternary ammonium salt methyl triethyl ammonium chloride (MTCl) were combined in a 2.6:1 (molar ratio) as catalysts, the molecular weight regulator was phthalic anhydride (PA), and the branching agent was a combination of pyromellitic dianhydride (PMDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTADA), PMDA:NTADA=0.5:0.5 (mol). The molar ratio of PO to PA, branching agent, TEB, and MTCl was 4100:580:6:2.6:1, 1.5 MPa of CO2 was charged, and the reaction was carried out at 80°C for 6 hours. After cooling, CO2 was released, the solid material in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC. The number average molecular weight Mn was 129 kg / mol, the glass transition temperature was 49.1°C, and the tensile strength was 33.7 MPa.

[0038] Example 8

[0039] A 200ml autoclave was placed in a glove box, and 0.648mol of dehydrated propylene oxide (PO) was added. Tricyclohexylborane (TCB) and tetraethylammonium bromide (TEAB) were combined in a 2.8:1 (molar ratio) as catalysts, phthalic anhydride (PA) as molecular weight regulator, and 3,3',4,4'-benzophenone carboxylic acid dianhydride (BTDA) as branching agent. The molar ratio of PO to PA, BTDA, TCB, and TEAB was 4600:460:9:2.8:1, and 1.5MPa of CO2 was charged, and the reaction was carried out at 80°C for 6h. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC, and the number average molecular weight Mn was 151kg / mol, the glass transition temperature was 51°C, and the tensile strength was 38.2MPa.

[0040] Example 9

[0041] A 200ml autoclave was placed in a glove box, and 0.648mol of dehydrated propylene oxide (PO) was added. Tricyclohexylborane (TCB) and tetraethylammonium bromide (TEAB) were combined in a 2.8:1 (molar ratio) as catalysts, phthalic anhydride (PA) as molecular weight regulator, and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BETDA) as branching agent. The molar ratio of PO to PA, BETDA, TCB, and TEAB was 4600:460:8:2.8:1, 1.5MPa of CO2 was charged, and the reaction was carried out at 80°C for 8h. After cooling, CO2 was released, the solid matter in the autoclave was taken out, and the polymer was precipitated in petroleum ether. After vacuum drying, the polymer was characterized by GPC, and the number average molecular weight Mn was 149kg / mol, the glass transition temperature was 50.2°C, and the tensile strength was 37.4MPa.

[0042] The above description is only part of the specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst, characterized in that: Propylene oxide (PO) and CO2 are used as raw materials, and copolymerization reaction is carried out in the presence of a non-metallic catalyst, a molecular weight regulator and a branching agent to synthesize a CO2-based biodegradable plastic polypropylene carbonate PPC. The non-metallic catalyst is a combination of one or more alkyl borons with the general formula R3B and one or more quaternary ammonium salts with the general formula R'4NX; the molecular weight regulator is a cyclic acid anhydride with the general formula A(CO)2O; the branching agent is a cyclic carboxylic acid dianhydride with the general formula (CO)2OD(CO)2O; in the general formula, A and D refer to the parts of the cyclic acid anhydride except the anhydride group, which are one of cycloalkyl or aryl groups.

2. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: The R in the alkyl boron R3B is an alkyl group or an aryl group, the R' in the quaternary ammonium salt R'4NX is a hydrocarbon group or R' is triphenylphosphine; and X is a halogen anion.

3. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 2, characterized in that: The alkyl boron is one of triethyl boron, tricyclohexyl boron, tri-n-butyl boron, triphenyl boron, triisobutyl boron, tri-sec-butyl borane and trimethyl boron; the quaternary ammonium salt is one of methyltriethylammonium chloride, methyltriethylammonium bromide, tetramethylammonium iodide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride and hexadecyltrimethylammonium chloride.

4. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: The cyclic anhydride A(CO)2O is selected from one or more of the following cyclic anhydrides: succinic anhydride, maleic anhydride, methylsuccinic anhydride, itaconic anhydride, 1,2-cyclohexanedicarboxylic anhydride, dimethylmaleic anhydride, phthalic anhydride, and 1,8-naphthalene dicarboxylic anhydride.

5. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: The cyclic carboxylic acid dianhydride (CO)2OD(CO)2O is selected from one or more of the following cyclic carboxylic acid dianhydrides: pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-dibenzophenonetetracarboxylic dianhydride (BTDA), 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-butanetetracarboxylic dianhydride (BuDA), and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BETDA).

6. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: The molar ratio of propylene oxide to the molecular weight regulator is 6:1 to 14:1, and the branching agent is 1 to 5% (mol) of the molecular weight regulator.

7. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: In the non-metallic catalyst, the molar ratio of alkyl boron to quaternary ammonium salt is 2:1 to 4:

1.

8. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: In the preparation method, the molar ratio of the raw material PO to the quaternary ammonium salt is 2000:1 to 6000:

1.

9. The method for preparing a high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst as claimed in claim 1, characterized in that: The reaction temperature is 50-90°C, the reaction time is 2-28h, and the CO2 pressure is 0.5-5MPa.

10. A high molecular weight CO2-based degradable plastic catalyzed by a non-metallic catalyst, characterized in that: The method is prepared according to any one of claims 1 to 9.

Images