A method for preparing biodegradable material poly 3-hydroxybutyrate

Abstract

The present invention provides a method for preparing a biodegradable material poly 3-hydroxybutyrate, and belongs to the technical field of polymer material synthesis. The present invention uses 3-hydroxybutyrate as a monomer to obtain an oligomer through catalytic polymerization; then diisocyanate is added to the oligomer for reaction, and the reaction product is treated to obtain poly 3-hydroxybutyrate. The preparation method of the present invention can effectively increase the molecular weight of the poly 3-hydroxybutyrate product, and the raw material source of the present invention is wide and green and environmentally friendly, will not cause environmental pollution and affect health, and is easy to industrialize.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a method for preparing biodegradable material poly 3-hydroxybutyrate. Background Art

[0002] With the development of the plastics industry, the demand for plastic products in all walks of life is increasing, which makes the consumption of plastics increase year by year. The environmental problems caused by discarded plastics are becoming more and more serious. However, due to the durability and corrosion resistance required for plastic products in the past, it has become a difficult problem to eliminate "white pollution". Biodegradable plastics will gradually become the preferred alternative material.

[0003] Poly 3-hydroxybutyrate (PHB) is a simple structured, fully biodegradable polymer. The properties of PHB are similar to those of many commonly used synthetic plastics. At the same time, PHB also has excellent biocompatibility and is easily metabolized into carbon dioxide and water in the body without producing toxins. Therefore, PHB synthetic materials have excellent properties, and its products are an ideal substitute for synthetic plastics and a new type of environmentally friendly polymer material, which can be widely used in the production of engineering plastics, packaging materials, medical devices and supplies, and many other fields.

[0004] At present, PHB is mainly produced by biological fermentation. However, the biological production of PHB has the disadvantages of long cycle, complex process and high cost, which limits its promotion and application. The large-scale production of PHB by chemical method can reduce its production cost and has the potential for industrial application.

[0005] Foreign research institutions reported [J.Chem.Soc., Chem.Commun., 1992, 23, 1725; Macromolecules, 1993, 26, 5533.] that a new method for producing PHB by chemical route was developed by using β-butyrolactone produced by selective hydrogenation of diketene in industry as polymerization monomer and dialkyltin oxide as catalyst through ring-opening polymerization. However, relevant reports show that β-butyrolactone is a carcinogenic compound and does not conform to the concept of green environmental protection.

[0006] Chinese patent CN02100406.4 reports that acetaldehyde is used as a raw material to first condense into β-hydroxybutyraldehyde, and then selectively oxidized and esterified to generate 3-hydroxybutyric acid ethyl ester, and then under the catalysis of isopropyl titanate, reduced pressure polymerization is carried out at 150-170°C to synthesize a PHB polymer with a degree of polymerization >15 and a molecular weight >1,300 g / mol. Due to the instability of 3-hydroxybutyric acid ester itself, a dehydration reaction is easily caused at the polymerization temperature, which terminates the polymerization reaction and makes it difficult to obtain a high molecular weight PHB product.

[0007] Although PHB has attracted wide attention as a biodegradable material synthesized by microorganisms, PHB extracted by microorganisms is a material with high crystallinity, fast crystallization rate, brittleness and slow degradation rate, which limits the use of PHB. At the same time, PHB polyester materials synthesized by chemical homopolymerization also have disadvantages such as environmental pollution and low molecular weight. The development of a new method for copolymerizing 3-hydroxybutyrate with other compounds to produce polymers is a necessary process for achieving industrial production of PHB. Summary of the invention

[0008] In view of this, the present invention provides a method for preparing poly 3-hydroxybutyrate, a biodegradable material, wherein 3-hydroxybutyrate is used as a monomer and catalytically polymerized to obtain an oligomer; then diisocyanate is added to the oligomer for reaction, and the reaction product is treated to obtain poly 3-hydroxybutyrate. The method has a simple process route, mild reaction conditions, stable catalyst, easy recycling, high reaction yield, low cost of PHB products, and easy industrialization.

[0009] The preparation method of the biodegradable material poly 3-hydroxybutyrate of the present invention comprises the following steps:

[0010] (1) In a nitrogen flow, methyl 3-hydroxybutyrate monomer, diol and dibutyltin oxide catalyst are added to a three-necked round-bottom flask; the temperature is rapidly raised to 80° C. under normal pressure for reaction for 2 hours, and then the temperature is raised to 100° C. for reaction for 10 hours;

[0011] (2) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours to generate oligomers;

[0012] (3) In a nitrogen flow, the oligomer produced in step (2) is dissolved in dry dichloroethane, the temperature is rapidly raised to 80° C., diisocyanate is added dropwise, and the reaction is carried out for 6 hours; after the reaction is completed, dichloromethane is added to dissolve the product, and then the product is slowly poured into cold n-hexane to form a precipitate, and the precipitate is dried in a vacuum drying oven to constant weight to obtain the poly 3-hydroxybutyrate.

[0013] Preferably, the molar ratio of methyl 3-hydroxybutyrate, diol and dibutyltin oxide catalyst in step (1) is 100:10:1.

[0014] Preferably, the diol in step (1) is any one of 1,4-butanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol.

[0015] Preferably, the diisocyanate in step (3) is at least one of 1,6-hexamethyl diisocyanate (HDI) or diphenylmethane-4,4'-diisocyanate (MDI).

[0016] Preferably, the molar ratio of the diisocyanate in step (3) to the methyl 3-hydroxybutyrate in step (1) is 1:50.

[0017] Preferably, the preparation method of the methyl 3-hydroxybutyrate monomer in step (1) is:

[0018] Propylene oxide, methanol and a catalyst are put into a reaction kettle, and after nitrogen replacement, 1-8 MPa carbon monoxide is charged, and the temperature is rapidly raised to 40-100° C. for reaction, and maintained for 8-48 hours; after the reaction is completed, distillation is performed under the conditions of an absolute pressure of 100 Pa and a distillation head temperature of 35° C. to obtain 3-hydroxybutyric acid methyl ester monomer;

[0019] Preferably, the catalyst is a carbon-nitrogen doped supported nano-cobalt catalyst.

[0020] More preferably, the preparation method of the carbon-nitrogen doped supported nano-cobalt catalyst is:

[0021] Co(NO3)2·6H2O, trioxymethylene and melamine are mixed in a molar ratio of 1:1:4, added to methanol, and a transparent solution is formed under vigorous stirring. Then a ZrO2 carrier is added thereto, the temperature is rapidly raised to 70°C and maintained for 15 hours, the methanol solvent is rapidly evaporated under vacuum, and finally the generated solid is dried at 110°C overnight, and then calcined at 700°C in a nitrogen flow for 4 hours to obtain a carbon-nitrogen doped supported nano-cobalt catalyst; the volume mass ratio of the methanol to Co(NO3)2·6H2O is 90-110mL:4-5g; the mass ratio of the ZrO2 carrier to Co(NO3)2·6H2O is 4.5-5.5:4-5.

[0022] Preferably, the mass ratio of propylene oxide, methanol and catalyst is 5-50:100:5.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention provides a method for preparing poly 3-hydroxybutyrate, a biodegradable material. The method adopts a chemical method, uses non-toxic bulk chemical propylene oxide as a raw material, and prepares the biodegradable material poly 3-hydroxybutyrate through hydrogenation and polymerization reaction chemical methods. The catalyst preparation method used to prepare the 3-hydroxybutyrate monomer is simple, the structure and properties are stable, there is no loss of active center during the reaction, and separation and recovery are easy to achieve. Methyl 3-hydroxybutyrate is used as the polymerization body, and cheap commercial diols and diisocyanates are used as auxiliary reagents. The raw materials are easy to obtain and industrial production is easy to achieve; then, the two-step process of oligomerization and coupled polycondensation is used to generate poly 3-hydroxybutyrate, which can effectively increase the molecular weight of the polyester product, and the molecular weight of the blended polymer is controlled by adjusting the feed ratio of diols and diisocyanates. The present invention uses non-toxic chemicals that can be mass-produced in industry as raw materials, will not cause environmental pollution and affect health, can produce PHB products with high yield, and is easy to achieve industrial production. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments.

[0026] Example 1

[0027] A method for preparing a biodegradable material poly 3-hydroxybutyrate, comprising the following steps:

[0028] (1) 10 g of propylene oxide, 50 g of methanol and 2 g of catalyst were placed in a stainless steel batch reactor, which was sealed and replaced with 2 MPa nitrogen for 3 times, and then filled with 6 MPa of carbon monoxide, and the temperature was rapidly raised to 70° C. for reaction, which was maintained for 20 hours; after the reaction, the temperature was cooled in an ice bath, and distilled and purified under an absolute pressure of 100 Pa and a distillation head temperature of 35° C. to obtain 3-hydroxybutyric acid methyl ester monomer;

[0029] The catalyst is a carbon-nitrogen doped supported nano-cobalt catalyst, and the preparation method is as follows:

[0030] 4.94 g Co(NO3)2·6H2O (17 mmol), 1.53 g trioxymethylene (17 mmol), 8.56 g melamine (68 mmol), and 100 mL methanol were added to a round-bottom flask to form a transparent solution under vigorous stirring, and then 5 g ZrO2 carrier was added thereto, and the temperature was rapidly raised to 70°C and maintained for 15 hours, and the methanol solvent was rapidly evaporated under vacuum, and finally the generated solid was dried at 110°C overnight, and then calcined at 700°C in a nitrogen gas stream for 4 hours to obtain a carbon-nitrogen doped supported nano-cobalt catalyst;

[0031] (2) In a nitrogen gas flow of 40 mL / min, 12 g of methyl 3-hydroxybutyrate monomer (100 mmol) prepared in step (1), 0.92 g of 1,4-butanediol (10 mmol) and 0.25 g of dibutyltin oxide (1 mmol) were added to a three-necked round-bottom flask; under normal pressure, the temperature was rapidly raised to 80° C. for reaction for 2 hours, and then the temperature was raised to 100° C. for reaction for 10 hours;

[0032] (3) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours to generate oligomers;

[0033] (4) After cooling to room temperature, the oligomer produced in step (2) was dissolved in 100 mL of dry dichloroethane in a nitrogen stream, and the temperature was rapidly raised to 80° C., and 0.34 g of 1,6-hexamethyl diisocyanate (2 mmol) was added dropwise, and the reaction was carried out for 6 hours. After the reaction was completed, 100 mL of dichloromethane was added to dissolve the product, and then the product was slowly poured into 100 mL of cold n-hexane to form a white precipitate. The precipitate was dried in a vacuum drying oven at 50° C. overnight to constant weight to obtain 9.3 g of poly 3-hydroxybutyrate. The polymerization process yield (based on the yield of methyl 3-hydroxybutyrate + diol + diisocyanate) was 93.6%, the mass average molecular weight was 301200, and the dispersion degree was 1.1.

[0034] Example 2

[0035] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as described in Example 1, except that the pressure of the carbon monoxide introduced in step (1) is 1 MPa.

[0036] Example 3

[0037] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as described in Example 1, except that the pressure of the carbon monoxide introduced in step (1) is 8 MPa.

[0038] Example 4

[0039] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as described in Example 1, the difference from Example 1 being that in step (1), the reaction temperature is 40° C. and the reaction time is 48 hours.

[0040] Example 5

[0041] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as described in Example 1, the difference from Example 1 being that in step (1), the reaction temperature is 100° C. and the reaction time is 8 hours.

[0042] Example 6

[0043] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as in Example 1, the difference from Example 1 being that the raw materials in step (1) are 2.5 g of propylene oxide, 50 g of methanol and 2.5 g of a catalyst, the reaction temperature is 100° C., the reaction time is 8 hours, the reaction in step (1) is repeated three times to meet the feeding requirements of step (3); and the amount of monomer added in step (3) is methyl 3-hydroxybutyrate prepared by three reactions in step (1).

[0044] Example 7

[0045] A method for preparing a biodegradable material poly 3-hydroxybutyrate, the specific steps of which are as described in Example 1, except that the raw materials in step (1) are 25 g of propylene oxide, 50 g of methanol and 5 g of a catalyst, the reaction temperature is 100° C., and the reaction time is 8 hours.

[0046] Comparative Example 1

[0047] A method for preparing a biodegradable material poly 3-hydroxybutyrate, wherein the specific steps are as in Example 1, and the difference from Example 1 is that the catalyst used in step (1) is dicobalt octacarbonyl. Finally, 9.3 g of a polymer product is obtained.

[0048] The polymerization method in Examples 2 to 7 and Comparative Example 1 is the same as that in Example 1, so the output, yield and molecular weight do not change.

[0049] Comparative Example 2

[0050] A method for preparing a biodegradable material poly 3-hydroxybutyrate, comprising the following steps:

[0051] (1) As in Example 1;

[0052] (2) In a nitrogen gas flow of 40 mL / min, 12 g of methyl 3-hydroxybutyrate monomer (100 mmol) prepared in step (1) and 0.25 g of dibutyltin oxide (1 mmol) were added to a three-necked round-bottom flask; under normal pressure, the mixture was stirred magnetically, and the temperature was rapidly raised to 80° C. for reaction for 2 hours, and then raised to 100° C. for reaction for 10 hours;

[0053] (3) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours;

[0054] (4) After the reaction, 100 mL of dichloromethane was added to dissolve the product, and then slowly poured into 100 mL of cold n-hexane to form a white precipitate. The precipitate was dried in a vacuum drying oven at 50° C. overnight to constant weight to obtain 7.4 g of poly (3-hydroxybutyrate), and the polymerization yield was 85.0%.

[0055] A small amount of 3-hydroxybutyric acid methyl ester monomer prepared in step (1) of Examples 1 to 7 and Comparative Examples 1 to 2 was taken for qualitative and quantitative analysis by gas chromatography. A gas chromatograph equipped with an FID detector and an HP-5 capillary column Aglient 7890A was used to test the sample. The injector temperature was 260° C., the detector temperature was 280° C., and the internal standard method was used to calculate the conversion rate, selectivity and reaction yield. The results are shown in Table 1.

[0056] Table 1

[0057]

[0058] As can be seen from Table 1, under mild conditions, the carbon-nitrogen doped supported nano-cobalt catalyst exhibited excellent activity and product selectivity in the hydroesterification of propylene oxide to prepare methyl 3-hydroxybutyrate, which was superior to the commercial octacarbonyl dicobalt catalyst. Using 1,4-butanediol and 1,6-hexamethyl diisocyanate as copolymers, PHB products can be produced in high yield.

[0059] Example 8

[0060] A method for preparing a biodegradable material poly 3-hydroxybutyrate, comprising the following steps:

[0061] (1) In a nitrogen gas flow of 40 mL / min, 24.0 g of methyl 3-hydroxybutyrate monomer (200 mmol) prepared according to the steps of Example 1, 1.80 g of 1,4-butanediol (20 mmol) and 0.51 g of dibutyltin oxide (2 mmol) were added to a three-necked round-bottom flask; under normal pressure, the temperature was rapidly raised to 80° C. for reaction for 2 hours, and then the temperature was raised to 100° C. for reaction for 10 hours;

[0062] (2) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours to generate oligomers;

[0063] (3) After cooling to room temperature, the oligomer produced in step (2) was dissolved in 100 mL of dry dichloroethane in a nitrogen stream, and the temperature was rapidly raised to 80° C., and 0.67 g of 1,6-hexamethyl diisocyanate (4 mmol) was added dropwise, and the reaction was carried out for 6 hours. After the reaction was completed, 100 mL of dichloromethane was added to dissolve the product, and then the product was slowly poured into 100 mL of cold n-hexane to form a white precipitate. The precipitate was dried in a vacuum drying oven at 50° C. overnight to constant weight to obtain 18.6 g of poly 3-hydroxybutyrate.

[0064] Embodiments 9 to 16

[0065] A method for preparing a biodegradable material poly 3-hydroxybutyrate, wherein the specific steps are as in Example 8. The difference between Examples 9-16 and Example 8 is that different diols are added. The diols added in Examples 8 to 16 are as shown in Table 2:

[0066] Table 2

[0067]

[0068]

[0069] Comparative Example 3

[0070] A method for preparing a biodegradable material poly 3-hydroxybutyrate, comprising the following steps:

[0071] (1) In a nitrogen gas flow of 40 mL / min, 24.0 g of methyl 3-hydroxybutyrate monomer (200 mmol) prepared according to the steps of Example 1, 1.80 g of 1,4-butanediol (20 mmol) and 0.51 g of dibutyltin oxide (2 mmol) were added to a three-necked round-bottom flask; under normal pressure, the temperature was rapidly raised to 80° C. for reaction for 2 hours, and then the temperature was raised to 100° C. for reaction for 10 hours;

[0072] (2) Continue to heat to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours;

[0073] (3) After the reaction was completed, 100 mL of dichloromethane was added to dissolve the product, and then slowly poured into 100 mL of cold n-hexane to form a white precipitate. The precipitate was dried in a vacuum drying oven at 50° C. overnight to constant weight to obtain 13.1 g of poly (3-hydroxybutyrate).

[0074] Comparative Example 4

[0075] (1) In a nitrogen gas flow of 40 mL / min, 24.0 g of methyl 3-hydroxybutyrate monomer (200 mmol) prepared according to the steps of Example 1 and 0.51 g of dibutyltin oxide (2 mmol) were added to a three-necked round-bottom flask; under normal pressure, the temperature was rapidly raised to 80° C. for reaction for 2 hours, and then raised to 100° C. for reaction for 10 hours;

[0076] (2) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours to generate oligomers;

[0077] (3) After cooling to room temperature, the oligomer produced in step (2) was dissolved in 100 mL of dry dichloroethane in a nitrogen stream, and the temperature was rapidly raised to 80° C., and 0.67 g of 1,6-hexamethyl diisocyanate (4 mmol) was added dropwise, and the reaction was carried out for 6 hours. After the reaction was completed, 100 mL of dichloromethane was added to dissolve the product, and then the product was slowly poured into 100 mL of cold n-hexane to form a white precipitate. The precipitate was dried in a vacuum drying oven at 50° C. overnight to constant weight to obtain 13.4 g of poly 3-hydroxybutyrate.

[0078] The yield of poly 3-hydroxybutyrate, polymerization process yield, mass average molecular weight (g / mol) and dispersion degree in Examples 8 to 16 and Comparative Examples 3 to 4 are shown in Table 3:

[0079] Table 3

[0080]

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable material poly 3-hydroxybutyrate, characterized in that: The following steps are involved: (1) In a nitrogen flow, methyl 3-hydroxybutyrate monomer, diol and dibutyltin oxide catalyst were added into a three-necked round-bottom flask; the temperature was rapidly raised to 80°C under normal pressure for 2 hours, and then raised to 100°C for 10 hours; (2) Continue to raise the temperature to 120°C, slowly evacuate to an absolute pressure of 100 Pa, and react for 4 hours to generate oligomers; (3) In a nitrogen gas stream, dissolving the oligomer produced in step (2) in dry dichloroethane, rapidly heating to 80° C., adding diisocyanate dropwise, and reacting for 6 hours; after the reaction, adding dichloromethane to dissolve the product, then slowly pouring it into cold n-hexane to form a precipitate, and drying the precipitate in a vacuum drying oven to constant weight to obtain the poly 3-hydroxybutyrate; The preparation method of the 3-hydroxybutyric acid methyl ester monomer in step (1) is: Propylene oxide, methanol and a catalyst are put into a reactor, and after nitrogen replacement, 1-8 MPa carbon monoxide is charged, and the temperature is rapidly raised to 40-100°C for reaction, and maintained for 8-48 hours; after the reaction is completed, distillation is performed under the conditions of an absolute pressure of 100 Pa and a distillation head temperature of 35°C to obtain 3-hydroxybutyric acid methyl ester monomer; The catalyst used in the preparation of 3-hydroxybutyric acid methyl ester monomer is a carbon-nitrogen doped supported nano-cobalt catalyst; The method for preparing the carbon-nitrogen doped supported nano-cobalt catalyst comprises the following steps: Co(NO3)2·6H2O, trioxymethylene and melamine are mixed in a molar ratio of 1:1:4, added to methanol, and a transparent solution is formed under vigorous stirring. Then a ZrO2 carrier is added thereto, the temperature is rapidly raised to 70°C and maintained for 15 hours, the methanol solvent is rapidly evaporated under vacuum, and finally the generated solid is dried at 110°C overnight, and then calcined at 700°C in a nitrogen flow for 4 hours to obtain a carbon-nitrogen doped supported nano-cobalt catalyst; the volume mass ratio of the methanol to Co(NO3)2·6H2O is 90~110mL:4~5g; the mass ratio of the ZrO2 carrier to Co(NO3)2·6H2O is 4.5~5.5:4~5.

2. The method for preparing the biodegradable material poly 3-hydroxybutyrate according to claim 1, characterized in that: In step (1), the molar ratio of methyl 3-hydroxybutyrate, diol and dibutyltin oxide catalyst is 100:10:

1.

3. The method for preparing the biodegradable material poly 3-hydroxybutyrate according to claim 1, characterized in that: The diol in step (1) is any one of 1,4-butanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol.

4. The method for preparing the biodegradable material poly 3-hydroxybutyrate according to claim 1, characterized in that: The diisocyanate in step (3) is at least one of 1,6-hexamethyl diisocyanate (HDI) or diphenylmethane-4,4'-diisocyanate (MDI).

5. The method for preparing the biodegradable material poly 3-hydroxybutyrate according to claim 1, characterized in that: The molar ratio of the diisocyanate in step (3) to the methyl 3-hydroxybutyrate in step (1) is 1:

50.

6. The method for preparing the biodegradable material poly 3-hydroxybutyrate according to claim 1, characterized in that: The mass ratio of propylene oxide, methanol and catalyst is 5-50:100:5.

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