Preparation method of CO2-based degradable plastic catalyzed by organic alkoxide

Abstract

The invention discloses a preparation method of organic alkoxide catalyzed CO2-based degradable plastic, which comprises the following steps: by taking propylene oxide (PO) and CO2 as raw materials, carrying out copolymerization in the presence of organic alkali metal alkoxide (main catalyst), alkyl borane (cocatalyst) and quaternary ammonium salt (phase transfer catalyst), and synthesizing CO2-based degradable plastic polypropylene carbonate (PPC). According to the method for preparing the PPC, the phenomena that synthesis, addition, storage and transportation of an organic catalyst are troublesome, and the production cost of the PPC is increased are overcome, the concept of carbon neutralization is achieved, and the prepared PPC has high gas barrier property, solvent resistance and the like, has the characteristics of high strength, high elastic coefficient, no toxicity, no harm and the like, is biodegradable, and is suitable for industrial production. Wide market application prospects are realized.

Description

Technical Field

[0001] The present invention belongs to the field of production processes of degradable plastics, and particularly relates to a method for preparing a CO2-based degradable plastic catalyzed by an organic alcoholate. Background Art

[0002] Most of the plastic products on the market are currently made from petroleum, with high costs and being not easily degradable after use, polluting the environment. The "white pollution" caused by the random discarding of these plastic product wastes is particularly serious. The period required for them to be completely decomposed in nature is long. Taking polyethylene as an example, it takes about 30 - 50 years, and environmental pollution will be caused during decomposition. For this reason, the country has introduced 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 applied as a major technology in the industrial field in the future.

[0003] There are many varieties of degradable plastics, such as poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and copolymers of PHB and PHV (PHBV), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate / terephthalate (PBAT), polyglycolic acid (PGA), and poly(propylene carbonate) (PPC) or poly(propylene carbonate), etc.

[0004] Among these degradable plastics, only the PPC degradable plastic synthesized from propylene oxide and CO2 has the following advantages: (a) The only degradable plastic with the concept of "carbon neutrality"; (b) Good biocompatibility, relatively high gas barrier performance, solvent resistance, etc., with characteristics such as relatively high strength, elastic modulus, non-toxic and harmless; (c) Can be widely used in food packaging, medical materials, adhesives, and engineering plastics, etc. Therefore, the copolymerization of carbon dioxide as a raw material to prepare CO2-based biodegradable polymer materials has attracted extensive attention at home and abroad.

[0005] In the existing PPC synthesis technologies, organic zinc acids, ternary rare earth complex catalysts, bimetallic catalysts, etc. are mostly used as catalysts. For example, CN1306021A discloses a method for efficiently preparing high molecular weight aliphatic polycarbonate, using a rare earth complex as a catalyst to catalyze the copolymerization reaction of PO and CO2. CN101402726A discloses a combined catalyst for the copolymerization of carbon dioxide and epoxide and its preparation method, using a ternary rare earth catalyst plus zinc salt as a 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, its preparation method and application, using the complex of tertiary amine and zinc glutarate as a catalyst to catalyze the copolymerization reaction of PO and CO2. CN1116332C discloses a method for efficiently preparing high molecular weight aliphatic polycarbonate, using a rare earth complex to catalyze the copolymerization reaction of PO and CO2. CN1250603C discloses a ternary catalyst for preparing high molecular aliphatic polycarbonate, using metal salt and alkyl zinc as catalysts. CN102659850B discloses a preparation method of a tetradentate Schiff base metal complex, a metal porphyrin complex and a polycarbonate, using the tetradentate Schiff base metal complex and the metal porphyrin complex as catalysts to catalyze the copolymerization reaction of PO and CO2.

[0006] Although the molecular weight of PPC synthesized with metal-based multifunctional catalysts is relatively high, reaching above 100 kg / mol, enabling the preparation of high-performance polycarbonate materials with controllable molecular weight and alternating chemical / regio / stereoselectivity, most metal-based catalysts have problems such as complex ligands, high synthesis costs, and high environmental risks, and there is metal residue, seriously affecting their applications in fields such as microelectronics, food packaging, and biomedical materials. In sharp contrast, ring-opening polymerization catalyzed by organic catalysts is more environmentally friendly and economical, not only avoiding metal residues but also reducing the consumption of metal resources. Most of the reported non-metal catalysts are composites of alkyl boranes and organic amines. For example, in the article "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 triethyl borane (TEB) and triethylamine (TEA) was used as the 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 the catalyst, the maximum molecular weight Mn of the obtained PPC did not exceed 35.1 kg / mol. In the article "Precision copolymerization of CO2 and epoxides enabled by organoboron catalysts" by Guan-Wen Yang et al. (Nature Synthesis, 2022, 1, 892-901), 9 kinds of dinuclear organoboron-nitrogen catalysts were synthesized for catalyzing the copolymerization of PO and CO2, and the maximum molecular weight Mn of PPC was 62.8 kg / mol. However, in these reports, the requirements for the synthesis and addition of the catalyst are relatively harsh and need to be completed in a glove box, otherwise the catalyst will be deactivated. It can be seen that the molecular weight of PPC synthesized with composite non-metal catalysts of alkyl boranes and organic amines is usually relatively low, not as high as that of PPC synthesized with metal catalysts, which brings some difficulties to later processing applications; at the same time, the synthesis, addition, storage, and transportation of the catalyst are relatively troublesome, increasing the production cost of PPC. Summary of the Invention

[0007] The object of the present invention is to disclose a preparation method of a CO2-based degradable plastic catalyzed by an organic alcohol salt, so as to overcome the defects of the existing composite non-metal catalyst of alkyl borane and organic amine for synthesizing PPC technology, such as low molecular weight and difficulty in processing and application, and to overcome the phenomenon that the catalyst is troublesome in synthesis, addition, storage and transportation, increasing the production cost of PPC.

[0008] To achieve the above object, the technical solution adopted by the present invention includes the following steps: A preparation method of a CO2-based degradable plastic catalyzed by an organic alcohol salt, which comprises using propylene oxide (PO) and CO2 as raw materials, and carrying out a copolymerization reaction in the presence of an organic alkali metal alcohol salt (main catalyst), an alkyl borane (co-catalyst) and a quaternary ammonium salt (phase transfer catalyst) to synthesize the CO2-based degradable plastic poly(propylene carbonate) PPC, characterized in that: the organic alkali metal alcohol salt is one or more of those having the general formula C n H 2n+1 OM, the alkyl borane is one or more of those having the general formula R3B, and a combination of one or more of the quaternary ammonium salts having the general formula R’4NX.

[0009] Further, M in the organic alkali metal alcohol salt C n H 2n+1 OM is Li, Na, K, Rb, Cs; R in the alkyl borane R3B is an alkyl group or an aryl group, and R’ in the quaternary ammonium salt R’4NX is a hydrocarbon group, which may be the same or different; X is a halogen negative ion.

[0010] Further, in the organic alkali metal alcohol salt catalyst, the mass ratio of the organic alkali metal alcohol salt:alkyl borane:quaternary ammonium salt is 1:0.4~0.9:0.2~2.0.

[0011] Further, the mass ratio of the raw material PO to the organic alkali metal alcohol salt catalyst is 50:1~300:1.

[0012] Further, the copolymerization reaction temperature is 50~90 °C, the reaction time is 2~28 h, and the CO2 pressure is 0.5~5 MPa.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: simple operation, low catalyst cost, the molecular weight of PPC is significantly increased, reaching more than 30 kg / mol, the glass transition temperature is higher than 30 °C, and the tensile strength is as high as more than 30 MPa.

[0014] The following will further illustrate the present invention through examples, but these examples do not limit the protection scope of the present invention. Example 1

[0015] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 4 ml of triethylboron (TEB) (a 1 mol / L tetrahydrofuran solution), 0.3 g of potassium tert-butoxide, and 0.2 g of tetrabutylammonium bromide (TBAB) were added. The autoclave was filled with 2.0 MPa of CO2 and reacted at 60 °C for 5 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 33 kg / mol, the glass transition temperature was 31 °C, and the tensile strength was 31.2 MPa. Example 2

[0016] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 4 ml of tricyclohexylboron (TCB) (a 1 mol / L tetrahydrofuran solution), 0.4 g of rubidium tert-butoxide, and 0.3 g of hexadecyltrimethylammonium chloride (HTAC) were added. The autoclave was filled with 2.0 MPa of CO2 and reacted at 60 °C for 5 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 42 kg / mol, the glass transition temperature was 33 °C, and the tensile strength was 33.4 MPa. Example 3

[0017] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 4 ml of tripropylboron (TPB) (a 1 mol / L tetrahydrofuran solution), 0.5 g of potassium methoxide, and 0.4 g of methyltriethylammonium chloride (MTCl) were added. The autoclave was filled with 2.0 MPa of CO2 and reacted at 60 °C for 5 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 40 kg / mol, the glass transition temperature was 32.5 °C, and the tensile strength was 32.6 MPa. Example 4

[0018] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 4 ml of triphenylboron (a 1 mol / L tetrahydrofuran solution), 0.3 g of potassium ethoxide, and 0.2 g of tetrabutylammonium iodide (TBAB) were added. The autoclave was filled with 2.0 MPa of CO2 and reacted at 60 °C for 5 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 53 kg / mol, the glass transition temperature was 34 °C, and the tensile strength was 35.3 MPa. Example 5

[0019] In a 200 ml autoclave, add 100 ml of dehydrated propylene oxide (PO), 4 ml of triethylboron (TEB) (a 1 mol / L tetrahydrofuran solution), 0.3 g of sodium methoxide, and 0.2 g of tetraethylammonium bromide (TEAB). Fill the autoclave with 2.0 MPa of CO2 and react at 60 °C for 5 h. After cooling, release the CO2, take out the solid substance in the autoclave, precipitate the polymer in petroleum ether, and after vacuum drying, conduct GPC characterization on the polymer. The number-average molecular weight Mn is 46 kg / mol, the glass transition temperature is 33.6 °C, and the tensile strength is 34.5 MPa. Example 6

[0020] In a 200 ml autoclave, add 100 ml of dehydrated propylene oxide (PO), 4 ml of tributylboron (TNBB) (a 1 mol / L tetrahydrofuran solution), 0.3 g of sodium tert-butoxide, and 0.3 g of tetraethylammonium bromide (TEAB). Fill the autoclave with 2.0 MPa of CO2 and react at 60 °C for 5 h. After cooling, release the CO2, take out the solid substance in the autoclave, precipitate the polymer in petroleum ether, and after vacuum drying, conduct GPC characterization on the polymer. The number-average molecular weight Mn is 38 kg / mol, the glass transition temperature is 32.8 °C, and the tensile strength is 32.7 MPa. Example 7

[0021] In a 200 ml autoclave, add 100 ml of dehydrated propylene oxide (PO), 5 ml of triethylboron (TEB) (a 1 mol / L tetrahydrofuran solution), 0.5 g of lithium tert-butoxide, and 0.4 g of tetrabutylammonium bromide (TBAB). Fill the autoclave with 2.0 MPa of CO2 and react at 60 °C for 5 h. After cooling, release the CO2, take out the solid substance in the autoclave, precipitate the polymer in petroleum ether, and after vacuum drying, conduct GPC characterization on the polymer. The number-average molecular weight Mn is 46 kg / mol, the glass transition temperature is 34.1 °C, and the tensile strength is 35.3 MPa. Example 8

[0022] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 6 ml of triethylboron (TEB) (a 1 mol / L tetrahydrofuran solution), 0.4 g of cesium tert-butoxide, and 0.3 g of tetrapropylammonium chloride (TPAC). 3.0 MPa of CO2 was charged into the autoclave and the reaction was carried out at 60 °C for 6 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 52 kg / mol, the glass transition temperature was 35.1 °C, and the tensile strength was 36.3 MPa. Example 9

[0023] In a 200 ml autoclave, 100 ml of dehydrated propylene oxide (PO) was added, 4 ml of triethylboron (TEB) (a 1 mol / L tetrahydrofuran solution), 0.4 g of potassium isopropoxide, and 0.3 g of tetrabutylammonium bromide (TBAB). 2.0 MPa of CO2 was charged into the autoclave and the reaction was carried out at 60 °C for 5 h. After cooling, the CO2 was released, the solid substance in the autoclave was taken out, the polymer was precipitated in petroleum ether, and after vacuum drying, the polymer was characterized by GPC. The number-average molecular weight Mn was 39 kg / mol, the glass transition temperature was 32.6 °C, and the tensile strength was 32.9 MPa.

[0024] As described above, only some specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A preparation method of an organoalcoholate-catalyzed CO2-based degradable plastic, which comprises using propylene oxide (PO) and CO2 as raw materials to carry out a copolymerization reaction in the presence of an organic alkali metal alcoholate (main catalyst), an alkyl borane (co-catalyst), and a quaternary ammonium salt (phase transfer catalyst) to synthesize the CO2-based degradable plastic poly(propylene carbonate) PPC, and is characterized in that: The organic alkali metal alkoxide is one or more of those having the general formula C n H 2n+1 OM, the alkyl borane is one or more of those having the general formula R3B, and a combination of one or more of the quaternary ammonium salts having the general formula R’4NX.

2. The method according to claim 1, wherein: The described organic alkali metal alkoxide C n H 2n+1 In OM, M is Li, Na, K, Rb, or Cs; in the alkyl borane R3B, R is an alkyl group or an aryl group; in the quaternary ammonium salt R’4NX, R’ is a hydrocarbon group, which may be the same or different; X is a halogen anion.

3. The method according to claim 1, characterized in that: In the described organoalkali metal alkoxide catalyst, the mass ratio of organoalkali metal alkoxide: alkyl borane: quaternary ammonium salt is 1: 0.4 - 0.9: 0.2 - 2.

0.

4. The method according to claim 1, characterized in that: In the described preparation method, the mass ratio of raw material PO to the organoalkali metal alkoxide catalyst is 50:1 - 300:

1.

5. The method according to claim 1, characterized in that: The copolymerization reaction temperature is 50 - 90 °C, the reaction time is 2 - 28 h, and the CO2 pressure is 0.5 - 5 MPa.