Hydrolysis of poly(hydroxyalkanoate) in aqueous dispersion
By adjusting the pH value and controlling the reaction time in an aqueous dispersion to hydrolyze poly(hydroxyalkanoates), the problem of resin preparation for different applications has been solved, realizing the universal preparation and precise molecular weight control of poly(hydroxyalkanoate) resins, which are suitable for applications such as injection molding and water-based coatings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 丹尼米尔知识产权有限责任公司
- Filing Date
- 2024-04-18
- Publication Date
- 2026-08-04
AI Technical Summary
Existing technologies require the preparation of poly(hydroxyalkanoate) resins with different molecular weights for different end applications, resulting in the need for different microorganisms and fermentation conditions, and a lack of universal and modifiable preparation methods.
By adjusting the pH value with the addition of alkali or acid to the aqueous dispersion and controlling the reaction time, poly(hydroxyalkanoates) with high initial weight-average molecular weight are hydrolyzed to obtain the desired final weight-average molecular weight. The reaction is then terminated with a quencher, and the precipitated salt is filtered out to prepare poly(hydroxyalkanoates) with a narrow molecular weight distribution.
A general method is provided to prepare poly(hydroxyalkanoate) resins suitable for different end uses, achieving precise control of molecular weight and narrow molecular weight distribution, applicable to applications such as injection molding and waterborne coatings.
Smart Images
Figure CN121002101B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to biodegradable polymer compositions. More specifically, this invention relates to a method for preparing polyhydroxyalkanoates having desired molecular weights in an aqueous dispersion. Background Technology
[0002] Poly(hydroxyalkanoates) are a class of biodegradable and / or degradable polymers that can be used in a variety of applications. For example, poly(hydroxyalkanoates) can be used in injection molding or in water-based coatings. Poly(hydroxyalkanoates) are typically prepared by bio-fermentation methods, and the weight-average molecular weight of poly(hydroxyalkanoates) produced in this way can vary depending on the type of microorganism used in the fermentation, the choice of carbon source fed to the microorganisms, and so on.
[0003] High weight-average molecular weight poly(hydroxyalkanoates) are optimal for certain applications, such as injection molding. However, for other applications, such as waterborne coatings, poly(hydroxyalkanoates) with lower average molecular weights may be preferred. Therefore, different starting poly(hydroxyalkanoate) resins are typically required for different end applications, ensuring that the resin's average molecular weight is better suited to the final use. This necessitates the use of different microorganisms and / or different fermentation conditions to prepare different poly(hydroxyalkanoate) resins.
[0004] Conversely, it would be advantageous and desirable if a universal supply source of poly(hydroxyalkanoate) resins could be prepared using a set of fermentation conditions, and if such universal poly(hydroxyalkanoate) resins could then be modified and optimized for different end-use applications, such as injection molding and the preparation of waterborne coatings.
[0005] More specifically, it is desirable to provide a method for partially hydrolyzing a poly(hydroxyalkanoate) resin having a high initial weight-average molecular weight to rapidly provide a poly(hydroxyalkanoate) resin having a significantly reduced weight-average molecular weight, wherein the method allows for a high degree of control over the molecular weight and polydispersity of the final poly(hydroxyalkanoate) resin. Summary of the Invention
[0006] The method for preparing polyhydroxyalkanoates with the desired weight-average molecular weight according to the present invention satisfies the above and other requirements.
[0007] In a first aspect, the present invention provides a method for preparing a polyhydroxyalkanoate. According to one embodiment, the method includes an initial step of preparing a dispersion comprising about 10% to about 90% by weight of at least one polyhydroxyalkanoate and about 10% to 90% by weight of a solvent. The at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons. The solvent is selected from the group consisting of water, saturated and unsaturated alkyl alcohols having 1 to 10 carbon atoms, and mixtures thereof.
[0008] The method further includes the step of adding a base to the dispersion in an amount sufficient to provide a pH of about 12 to about 14 in the dispersion. A portion of the at least one polyhydroxyalkanoate is then hydrolyzed by reacting with the base for a reaction time interval. In this way, the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0009] The method also includes the steps of stopping the reaction by adding an amount of quenching acid sufficient to establish a pH of less than about 12.0 (preferably about 5.0 to about 7.5) in the dispersion and filtering the precipitated salt from the dispersion.
[0010] According to this method, all the above weight-average molecular weights were determined according to ASTM D5296.
[0011] According to the method of the present invention, at least one polyhydroxyalkanoate in the dispersion consists of particles with an average particle size of about 10 nanometers to about 50 micrometers, the particle size being determined by dynamic light scattering according to ISO 22412:2017.
[0012] In some embodiments, the initial weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 500,000 to about 5,000,000 Daltons, as determined by ASTM D5296. Furthermore, in some embodiments, the final weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 50,000 to 700,000 Daltons, more preferably from 250,000 to about 500,000 Daltons, and even more preferably from about 350,000 to about 400,000 Daltons, as determined by ASTM D5296.
[0013] According to some embodiments, the final weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 10% to about 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296. More preferably, the final weight-average molecular weight is from about 35% to about 70% of the initial weight-average molecular weight.
[0014] According to certain embodiments, the solvent is preferably selected from the group consisting of free water, methanol, ethanol, isopropanol, and mixtures thereof. In some cases, the solvent is composed of ethanol, and the reaction time interval is about 2 to about 60 minutes, more preferably about 5 to about 30 minutes. In other cases, the solvent is composed of water, and the reaction time interval is about 1 to about 48 hours.
[0015] According to certain implementation schemes, the preferred alkali is PK. b A strong base with a strength less than 1. In some embodiments, the base may be selected, for example, from alkali metal hydroxides, alkaline earth metal hydroxides, and mixtures thereof. More preferably, the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and mixtures thereof.
[0016] In other embodiments, the alkali is preferably PK. b It is a weak base with a strength of about 1 to about 5. In some embodiments, for example, the base may be selected from the group consisting of ammonium hydroxide, aniline, ammonia, and mixtures thereof.
[0017] According to some embodiments, the solid content of the dispersion is preferably about 5% to about 20%, more preferably about 10% to about 15%, before the addition of alkali.
[0018] In some cases, the quenching acid is preferably selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid, chloric acid, acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid, and mixtures thereof.
[0019] In some embodiments, hydrolysis is preferably carried out at a temperature of about 20°C to about 60°C.
[0020] In some embodiments, the dispersion is preferably composed of at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof.
[0021] According to some implementation schemes, dispersions are prepared using ultrasonic treatment, low-shear mixing, and / or ultra-high-shear mixing.
[0022] Furthermore, in some embodiments, the method preferably includes an additional step of synthesizing at least one poly(hydroxyalkanoate) prior to the preparation of the dispersion. This synthesis is carried out by: (1) mixing biomass containing bacteria with a carbon source, (2) fermenting the biomass and carbon such that the bacteria in the biomass consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) having an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons, and (3) isolating at least one poly(hydroxyalkanoate) from the biomass.
[0023] In some cases, when measured by gel permeation chromatography according to ASTM D5296, the polydispersity index (PDI) of the polyhydroxyalkanoate produced according to the method of the present invention is from about 1.0 to about 5.0, preferably from about 2.0 to about 4.0.
[0024] In a second aspect, the present invention provides another method for preparing polyhydroxyalkanoates. According to one embodiment, the method includes an initial step of preparing a dispersion comprising about 10 wt% to about 90 wt% of at least one polyhydroxyalkanoate and about 10 wt% to 90 wt% of a solvent. The at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons. The solvent is selected from the group consisting of water, saturated and unsaturated alkyl alcohols having 1 to 10 carbon atoms, and mixtures thereof.
[0025] The method further includes the step of adding an acid to the dispersion in an amount sufficient to provide a pH of about 1 to about 3 in the dispersion. A portion of the at least one polyhydroxyalkanoate is then hydrolyzed by reacting with the acid for a reaction time interval. In this way, the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0026] The method also includes the steps of stopping the reaction by adding an amount of quenching base sufficient to establish a pH of about 5.0 to about 7.5 in the dispersion and filtering the precipitated salt from the dispersion.
[0027] According to this method, all the above weight-average molecular weights were determined according to ASTM D5296.
[0028] According to the method of the present invention, at least one polyhydroxyalkanoate in the dispersion consists of particles with an average particle size of about 10 nanometers to about 50 micrometers, the average particle size being determined using dynamic light scattering according to ISO 22412:2017.
[0029] In some embodiments, the initial weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 500,000 to about 5,000,000 Daltons, as determined by ASTM D5296. Furthermore, in some embodiments, the final weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 300,000 to about 500,000 Daltons, as determined by ASTM D5296.
[0030] According to some embodiments, the final weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 10% to about 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296. More preferably, the final weight-average molecular weight is preferably from about 35% to about 70% of the initial weight-average molecular weight.
[0031] According to certain embodiments, the solvent is preferably selected from the group consisting of free water, methanol, ethanol, isopropanol, and mixtures thereof. In some cases, the solvent is composed of ethanol, and the reaction time interval is from about 2 minutes to about 60 minutes, more preferably from about 5 minutes to about 30 minutes. In other cases, the solvent is composed of water, and the reaction time interval is from about 1 hour to about 48 hours.
[0032] According to certain implementation schemes, the acid is preferably PK. a A strong acid with a strength less than 0. In some embodiments, the acid may be selected, for example, from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid, chloric acid, and mixtures thereof.
[0033] In other embodiments, the acid is preferably PK. a It is a weak acid with a strength of about 14 to about 0. In some embodiments, for example, the acid may be selected from the group consisting of acetic acid, citric acid, nitrous acid, phosphoric acid, glycolic acid, sulfurous acid, oxalic acid, benzoic acid, formic acid, and mixtures thereof.
[0034] According to some embodiments, the dispersion preferably has a solids content of about 5% to about 20%, more preferably about 10% to about 15%, before the acid is added.
[0035] In some cases, the quenching base is preferably selected from the group consisting of ammonium hydroxide, aniline, ammonia, and mixtures thereof.
[0036] In some embodiments, hydrolysis is preferably carried out at a temperature of about 20°C to about 60°C.
[0037] In some embodiments, the dispersion is preferably composed of at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof.
[0038] According to some implementation schemes, dispersions are prepared using ultrasonic treatment, low-shear mixing, and / or ultra-high-shear mixing.
[0039] Furthermore, in some embodiments, the method preferably includes an additional step of synthesizing at least one poly(hydroxyalkanoate) prior to the preparation of the dispersion. This synthesis is carried out by: (1) mixing biomass containing bacteria with a carbon source, (2) fermenting the biomass and carbon such that the bacteria in the biomass consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) having an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons, and (3) isolating at least one poly(hydroxyalkanoate) from the biomass.
[0040] In some cases, when measured by gel permeation chromatography according to ASTM D5296, the polydispersity index (PDI) of the polyhydroxyalkanoate produced according to the method of the present invention is from about 1.0 to about 5.0, preferably from about 2.0 to about 4.0. Attached Figure Description
[0041] Other advantages of the invention will become apparent when considered in conjunction with the accompanying drawings and with reference to the detailed description, wherein:
[0042] Figure 1 This is a graph illustrating the hydrolysis rate of poly(hydroxyalkanoate) according to one embodiment of the present invention. Detailed Implementation Plan
[0043] This invention provides a method for preparing poly(hydroxyalkanoate) resins with a target weight-average molecular weight. According to this method, a universal supply source of poly(hydroxyalkanoate) resins can be prepared, and then modified and optimized for different end uses requiring poly(hydroxyalkanoates) with different weight-average molecular weights.
[0044] Typically, the method of the present invention includes the step of preparing a dispersion of at least one polyhydroxyalkanoate having an initial weight-average molecular weight in a solvent. A portion of the at least one polyhydroxyalkanoate is then hydrolyzed for a specific reaction time interval. In this way, the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight. After the specific reaction time interval, the hydrolysis reaction is quenched to provide a final polyhydroxyalkanoate having the desired weight-average molecular weight.
[0045] Unless otherwise stated, all weight-average molecular weights mentioned herein are determined according to ASTM D5296.
[0046] The initial weight-average molecular weight (before hydrolysis) of at least one polyhydroxyalkanoate is typically from about 500,000 Daltons to about 5,000,000 Daltons. More preferably, the initial weight-average molecular weight of at least one polyhydroxyalkanoate is from about 1,000,000 to about 2,000,000 Daltons.
[0047] After hydrolysis, the final weight-average molecular weight of at least one polyhydroxyalkanoate is typically from about 50,000 to 700,000 Daltons, more preferably from about 250,000 to about 500,000 Daltons, and even more preferably from about 350,000 to about 400,000 Daltons.
[0048] In some cases, the final weight-average molecular weight of at least one polyhydroxyalkanoate is preferably from about 10% to about 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296. More preferably, the final weight-average molecular weight is from about 35% to about 70% of the initial weight-average molecular weight.
[0049] In some cases, the method further includes an initial step of synthesizing at least one poly(hydroxyalkanoate) prior to the preparation of any dispersion. This synthesis is carried out in a fermentation bioreactor and includes (1) mixing biomass containing bacteria with a carbon source, (2) fermenting the biomass and carbon such that the bacteria in the biomass consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) having an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons, and (3) isolating at least one poly(hydroxyalkanoate) from the biomass.
[0050] Suitable bacteria that can be included in biomass include *Pseudomonas* sp., *Ralstonia* sp., *Bacillus* sp., and *Cupriavidus* sp. Suitable carbon sources that can be supplied to the bacteria during fermentation include vegetable oils, such as, but not limited to, rapeseed oil, canola oil, soybean oil, and palm oil, and carbohydrate sources such as sugars and / or glycerol.
[0051] As described above, the method of the present invention includes the step of preparing a dispersion of at least one polyhydroxyalkanoate having an initial weight-average molecular weight in a solvent. More specifically, the dispersion comprises about 10% to about 90% by weight of at least one polyhydroxyalkanoate and about 10% to 90% by weight of solvent. More preferably, the dispersion comprises 10% to about 60% by weight of at least one polyhydroxyalkanoate and about 40% to 90% by weight of solvent.
[0052] Various polyhydroxyalkanoates can be used in the preparation of dispersions. In some cases, the dispersion may contain a polyhydroxyalkanoate homopolymer, such as polyhydroxybutyrate. In other cases, the dispersion may contain a polyhydroxyalkanoate copolymer, such as poly(hydroxybutyrate-co-hydroxyhexanoate) or polyhydroxyalkanoate terpolymer. The dispersion may also include mixtures of polyhydroxyalkanoate homopolymers, copolymers, and / or terpolymers.
[0053] As described above, at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons.
[0054] Typically, the solvent for the dispersion is selected from the group consisting of water, saturated and unsaturated alkyl alcohols having 1 to 10 carbon atoms, and mixtures thereof. In some embodiments, the solvent is preferably selected from the group consisting of water, methanol, ethanol, isopropanol, and mixtures thereof. Particularly preferred solvents include water, ethanol, and mixtures thereof.
[0055] According to some embodiments, the dispersion preferably also comprises at least one surfactant. The surfactant may be selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof. Particularly preferred surfactants include polysorbates and polyether siloxanes.
[0056] When present, the amount of surfactant in the dispersion is typically from about 0.01% to about 1.0%.
[0057] When preparing a dispersion, the dispersion generally preferably has a solids content of about 5% to about 20%, more preferably about 10% to about 15%, before the addition of the alkali.
[0058] In preparing the dispersion, the above components are thoroughly mixed to ensure that the polyhydroxyalkanoate solids are stably and uniformly dispersed in the solvent. Preferably, the dispersion is mixed using ultrasonic treatment, low-shear mixing (e.g., using a paddle mixer) and / or ultra-high-shear mixing (e.g., using a Cowles blade mixer or a rotor-stator mixer).
[0059] When the dispersion is prepared in this manner, at least one polyhydroxyalkanoate in the dispersion preferably comprises particles with an average particle size of about 10 nanometers to about 50 micrometers, which are determined by dynamic light scattering according to ISO 22412:2017.
[0060] Unbound by theory, it is believed that the relatively small average particle size of polyhydroxyalkanoates in the dispersion promotes rapid and uniform hydrolysis of polyhydroxyalkanoates, as discussed in more detail below.
[0061] Similarly, once the dispersion is prepared, the method includes the step of hydrolyzing a portion of at least one polyhydroxyalkanoate within a specific reaction time interval. This reduces the weight-average molecular weight of at least one polyhydroxyalkanoate to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0062] In some embodiments, this hydrolysis is base-catalyzed. Therefore, the method includes the step of adding a base to the dispersion in an amount sufficient to provide a pH of about 12 to about 14. A portion of the at least one polyhydroxyalkanoate is then hydrolyzed by reacting with the base for a reaction time interval.
[0063] Various bases can be used to catalyze hydrolysis reactions. For example, in some embodiments, the base is preferably PK. b A strong base with a concentration less than 1. This strong base may be selected, for example, from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and mixtures thereof. More preferably, the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and mixtures thereof.
[0064] However, in other embodiments, the alkali is preferably PK.b It is a weak base with a strength of about 1 to about 5. In some embodiments, for example, the base may be selected from the group consisting of ammonium hydroxide, aniline, ammonia, and mixtures thereof.
[0065] Typically, the alkaline-catalyzed hydrolysis is preferably carried out at a temperature of about 20°C to about 60°C. More preferably, the reaction is carried out at a temperature of about 30°C to about 50°C.
[0066] The hydrolysis reaction is allowed to proceed at specific time intervals, such that a portion (but not all) of at least one polyhydroxyalkanoate is hydrolyzed to provide a final polyhydroxyalkanoate having a desired final weight-average molecular weight, which is less than the initial weight-average molecular weight.
[0067] It has been found that the length of the reaction time interval varies depending on the solvent used to prepare the dispersion. For example, in some cases, the solvent is composed of ethanol, and the reaction time interval is from about 2 minutes to about 60 minutes, more preferably from about 5 minutes to about 30 minutes. In other cases, the solvent is composed of water, and the reaction time interval is from about 1 hour to about 48 hours.
[0068] Once the specific reaction time interval has elapsed, the method further includes the step of stopping the reaction by adding a quenching acid in an amount sufficient to establish a pH of less than about 12.0 (preferably about 5.0 to about 7.5) in the dispersion. For this reaction quenching step, a suitable quenching acid may preferably be selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid, chloric acid, acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid, and mixtures thereof.
[0069] In this way, the hydrolysis reaction is quenched to provide the final polyhydroxyalkanoate with the desired weight-average molecular weight.
[0070] In an alternative embodiment, the hydrolysis reaction may be acid-catalyzed. In such an embodiment, the method includes the step of adding an acid to the dispersion in an amount sufficient to provide a pH of about 1 to about 3 in the dispersion. A portion of the at least one polyhydroxyalkanoate is then hydrolyzed by reacting with the acid for a reaction time interval. In this way, the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0071] In some implementations, acid-catalyzed hydrolysis is preferably carried out using a strong acid, such as PK. a Acids with a concentration less than 0. For example, in some embodiments, the acid may be selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid, or chloric acid and mixtures thereof.
[0072] In other embodiments, a weak acid is preferably used to catalyze the hydrolysis. For example, the acid could be PK.a It is a weak acid with a strength of about 14 to about 0. In some embodiments, for example, the acid may be selected from the group consisting of acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid, and mixtures thereof.
[0073] Similar to base-catalyzed reactions, this acid-catalyzed hydrolysis is preferably carried out at a temperature of about 20°C to about 60°C. More preferably, the reaction is carried out at a temperature of about 30°C to about 50°C.
[0074] The hydrolysis reaction is allowed to proceed at specific time intervals, such that a portion (but not all) of at least one polyhydroxyalkanoate is hydrolyzed to provide a final polyhydroxyalkanoate having a desired final weight-average molecular weight, which is less than the initial weight-average molecular weight.
[0075] The method then includes the step of stopping the reaction by adding a quenching base in an amount sufficient to establish a pH of about 5.0 to about 7.5 in the dispersion. In some embodiments, the quenching base is preferably selected from the group consisting of ammonium hydroxide, aniline, ammonia, and mixtures thereof.
[0076] After the reaction catalyst is quenched (whether it is an acid-quenched base catalyst or an acid-quenched base catalyst), a certain amount of salt is formed and usually precipitates from the dispersion. Therefore, after quenching, the method of the present invention further includes the step of filtering the precipitated salt from the dispersion. For example, the precipitated salt can be filtered using a plate and frame filter press.
[0077] Advantageously, according to the method of this disclosure, a universal supply source of poly(hydroxyalkanoate) resin with a high initial weight-average molecular weight can be prepared, and then a portion of this universal poly(hydroxyalkanoate) resin can be optimized for different end applications by hydrolyzing a portion of the resin to reduce the weight-average molecular weight. For example, from the universal supply source of high molecular weight poly(hydroxyalkanoate) resin, a first portion of the resin can be hydrolyzed to provide a dispersion with a relatively low weight-average molecular weight suitable for waterborne coatings, while a second portion of the resin can retain a substantially higher weight-average molecular weight suitable for injection molding.
[0078] Furthermore, the final poly(hydroxyalkanoate) resin prepared according to the method of the present invention advantageously exhibits a relatively narrow molecular weight distribution, characterized in that, when measured by gel permeation chromatography according to ASTM D5296, the polydispersity index (PDI) is from about 1.0 to about 5.0, preferably from about 2.0 to about 4.0. The low PDI value demonstrates the precise control of this method when the poly(hydroxyalkanoate) is degraded.
[0079] Implementation Plan
[0080] This disclosure is further illustrated by the following implementation scheme:
[0081] Implementation Scheme 1. A method for preparing polyhydroxyalkanoates, comprising the following steps:
[0082] A dispersion comprising about 10% to about 90% by weight of at least one polyhydroxyalkanoate and about 10% to 90% by weight of a solvent, wherein the at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons, and wherein the solvent is selected from the group consisting of water, saturated and unsaturated alkyl alcohols having 1 to 10 carbon atoms and mixtures thereof;
[0083] An alkali is added to the dispersion in an amount sufficient to provide a pH of about 12 to about 14 in the dispersion;
[0084] A portion of the at least one polyhydroxyalkanoate is hydrolyzed by reacting with an alkali for a reaction time interval, wherein the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0085] The reaction is stopped by adding a quenching acid in an amount sufficient to establish a pH of less than 12.0 (preferably about 5.0 to about 7.5) in the dispersion; and
[0086] The precipitated salt is filtered from the dispersion.
[0087] All weight-average molecular weights were determined according to ASTM D5296, and
[0088] At least one polyhydroxyalkanoate in the dispersion comprises particles with an average particle size of about 10 nanometers to about 50 micrometers, the average particle size being determined using dynamic light scattering according to ISO 22412:2017.
[0089] Implementation Scheme 2. The method according to Implementation Scheme 1, wherein the initial weight-average molecular weight, as determined by ASTM D5296, is about 500,000 to about 5,000,000 Daltons.
[0090] Implementation Scheme 3. The method according to Implementation Scheme 1 or 2, wherein the final weight-average molecular weight, as determined by ASTM D5296, is about 50,000 to 700,000 Daltons, more preferably about 250,000 to about 500,000 Daltons, and even more preferably 350,000 to about 500,000 Daltons.
[0091] Implementation Scheme 4. The method according to any one of the preceding implementation schemes, wherein the final weight-average molecular weight is about 10% to about 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296.
[0092] Implementation Scheme 5. The method according to any one of the preceding implementation schemes, wherein the final weight-average molecular weight is about 35% to about 70% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296.
[0093] Implementation Scheme 6. The method according to any one of the preceding implementation schemes, wherein the solvent is selected from the group consisting of water, methanol, ethanol, isopropanol and mixtures thereof.
[0094] Implementation Scheme 7. The method according to any one of the foregoing embodiments, wherein the solvent comprises ethanol, and the reaction time interval is from about 2 minutes to about 60 minutes, more preferably from about 5 minutes to about 30 minutes.
[0095] Implementation Scheme 8. The method according to any one of the foregoing embodiments, wherein the solvent comprises water, and the reaction time interval is from about 1 hour to about 48 hours.
[0096] Implementation Scheme 9. The method according to any one of the foregoing implementation schemes, wherein the base has a pK value of less than 1. b .
[0097] Implementation Scheme 10. The method according to Implementation Scheme 9, wherein the alkali is selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and mixtures thereof.
[0098] Implementation Scheme 11. The method according to any one of Implementation Schemes 1-8, wherein the base has a pK ratio of about 1 to about 5. b .
[0099] Implementation Scheme 12. The method according to Implementation Scheme 11, wherein the base is selected from the group consisting of ammonium hydroxide, aniline, ammonia and mixtures thereof.
[0100] Implementation Scheme 13. The method according to any one of the foregoing embodiments, wherein the dispersion has a solid content of about 5% to about 20% before the addition of the alkali.
[0101] Implementation Scheme 14. The method according to any of the foregoing implementation schemes, wherein the quenching acid is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid or chloric acid, acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid and mixtures thereof.
[0102] Implementation Scheme 15. The method of any of the foregoing implementation schemes, wherein the hydrolysis is carried out at a temperature of about 20°C to about 60°C.
[0103] Implementation Scheme 16. The method according to any one of the preceding embodiments, wherein the dispersion further comprises at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof.
[0104] Implementation Scheme 17. The method according to any of the foregoing implementation schemes, wherein the dispersion is prepared by ultrasonic treatment, low-shear mixing and / or ultra-high-shear mixing.
[0105] Implementation Scheme 18. The method according to any one of the foregoing embodiments, further comprising the step of synthesizing the at least one polyhydroxyalkanoate by means of the following steps prior to preparing the dispersion:
[0106] Mix biomass containing bacteria with a carbon source.
[0107] Fermentation of biomass and carbon causes bacteria in the biomass to consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) with an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons.
[0108] The at least one poly(hydroxyalkanoate) is isolated from the biomass.
[0109] Implementation Scheme 19. The method according to any one of the preceding embodiments, wherein the polydispersity index (PDI) of the polyhydroxyalkanoate prepared by the method is about 1.0 to about 5.0, preferably about 2.0 to about 4.0, when measured by gel permeation chromatography according to ASTM D5296.
[0110] Implementation Scheme 20. A method for preparing polyhydroxyalkanoates, comprising the following steps:
[0111] A dispersion comprising about 10% to about 90% by weight of at least one polyhydroxyalkanoate and about 10% to 90% by weight of a solvent, wherein the at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 500,000 to about 5,000,000 Daltons, and wherein the solvent is selected from the group consisting of water, saturated and unsaturated alkyl alcohols having 1 to 10 carbon atoms and mixtures thereof;
[0112] An acid is added to the dispersion in an amount that provides a pH of about 1 to about 3 in the dispersion.
[0113] A portion of the at least one polyhydroxyalkanoate is hydrolyzed by reacting with the acid for a reaction time interval, wherein the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight.
[0114] The reaction was stopped by adding a quenching base in an amount sufficient to establish a pH of about 5.0 to about 7.5 in the dispersion; and
[0115] The precipitated salt is filtered from the dispersion.
[0116] All weight-average molecular weights were determined according to ASTM D5296, and
[0117] At least one polyhydroxyalkanoate in the dispersion comprises particles with an average particle size of about 10 nanometers to about 50 micrometers as determined by dynamic light scattering according to ISO 22412:2017.
[0118] Implementation Scheme 21. The method according to Implementation Scheme 20, wherein the initial weight-average molecular weight, as determined by ASTM D5296, is about 500,000 to about 5,000,000 Daltons.
[0119] Implementation Scheme 22. The method according to Implementation Scheme 20 or 21, wherein the final weight-average molecular weight, as determined by ASTM D5296, is about 50,000 to 700,000 Daltons, more preferably about 250,000 to about 500,000 Daltons, and even more preferably 350,000 to about 500,000 Daltons.
[0120] Implementation Scheme 23. The method according to any one of Implementation Schemes 20-22, wherein the final weight-average molecular weight is about 10% to about 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296.
[0121] Implementation Scheme 24. The method according to any one of Implementation Schemes 20-22, wherein the final weight-average molecular weight is about 35% to about 70% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296.
[0122] Implementation Scheme 25. The method according to any one of Implementation Schemes 20-23, wherein the solvent is selected from the group consisting of water, methanol, ethanol, isopropanol and mixtures thereof.
[0123] Implementation Scheme 26. The method according to any one of Implementation Schemes 20-24, wherein the solvent comprises ethanol, and the reaction time interval is from about 2 minutes to about 60 minutes, more preferably from about 5 minutes to about 30 minutes.
[0124] Implementation Scheme 27. The method according to any one of Implementation Schemes 20-24, wherein the solvent comprises water, and the reaction time interval is from about 1 hour to about 48 hours.
[0125] Implementation Scheme 28. The method according to any one of Implementation Schemes 20-27, wherein the acid has a pK value of less than 0. a .
[0126] Implementation Scheme 29. The method according to Implementation Scheme 28, wherein the acid is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid or chloric acid and mixtures thereof.
[0127] Implementation Scheme 30. The method according to any one of Implementation Schemes 20-27, wherein the acid has a pK value of less than 14 but greater than 0. a .
[0128] Implementation Scheme 31. The method according to Implementation Scheme 30, wherein the acid is selected from the group consisting of acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid and mixtures thereof.
[0129] Implementation Scheme 32. The method according to any one of Implementation Schemes 20-30, wherein the solid content of the dispersion is about 5% to about 20% before the acid is added.
[0130] Implementation Scheme 33. The method according to any one of Implementation Schemes 29-31, wherein the quenching alkali is selected from the group consisting of ammonium hydroxide, aniline, ammonia and mixtures thereof.
[0131] Implementation Scheme 34. The method according to any one of Implementation Schemes 20-33, wherein the hydrolysis is carried out at a temperature of about 20°C to about 60°C.
[0132] Implementation Scheme 35. The method according to any one of Implementation Schemes 20-34, wherein the dispersion further comprises a surfactant selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof.
[0133] Implementation Scheme 36. The method according to any one of Implementation Schemes 20-35, wherein the dispersion is prepared using ultrasonic treatment, low-shear mixing and / or ultra-high-shear mixing.
[0134] Implementation Scheme 37. The method according to any one of Implementation Schemes 20-36 further comprises, prior to preparing the dispersion, a step of synthesizing the at least one polyhydroxyalkanoate by means of the following steps:
[0135] Mix biomass containing bacteria with a carbon source.
[0136] Fermentation of biomass and carbon causes bacteria in the biomass to consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) with an initial weight-average molecular weight of about 500,000 Daltons to about 5,000,000 Daltons.
[0137] The at least one poly(hydroxyalkanoate) is isolated from the biomass.
[0138] Implementation Scheme 38. The method according to any one of Implementation Schemes 20-37, wherein the polydispersity index (PDI) of the polyhydroxyalkanoate prepared by the method is about 1.0 to about 5.0, preferably about 2.0 to about 4.0, when measured by gel permeation chromatography according to ASTM D5296.
[0139] Example
[0140] The following non-limiting examples illustrate various other aspects of the invention. Unless otherwise stated, temperatures are in degrees Celsius, percentages are based on weight percentages of the dry weight of the formulation, and weight-average molecular weight values are determined according to ASTM D5296.
[0141] Example 1. An ethanol slurry of a PHA copolymer consisting of 88% butyrate monomer and 12% hexanoate monomer was prepared in 20 wt% PHA solids and 80 wt% ethanol. The weight-average molecular weight of the PHA was 822 kDa. Sodium hydroxide (NaOH) was introduced into the slurry at different concentrations from about 5,000 ppm to about 11,000 ppm under stirring. Each concentration of NaOH resulted in a pH > 13.5 in the slurry. Samples were taken at different time intervals over 1 hour and quenched with citric acid, and the weight-average molecular weight and polydispersity index of each sample were measured. The results are shown in Tables 1 and 2 below, and are also as follows. Figure 1 As shown in Table 1 and Figure 1 The hydrolysis diagram shown indicates that higher concentrations of NaOH degrade PHA faster than lower concentrations of NaOH.
[0142] Table 1
[0143]
[0144] Table 2
[0145]
[0146] Example 2. An ethanol slurry of a PHA copolymer consisting of 91% butyrate monomer and 9% hexanoate monomer was prepared in 20 wt% PHA solids and 80 wt% ethanol. The weight-average molecular weight of the PHA was 1,060 kDa. Sodium hydroxide (NaOH) was introduced into the slurry at concentrations ranging from about 1,000 ppm to about 8,000 ppm under stirring. Each concentration of NaOH resulted in a pH > 13.5 in the slurry. Samples were taken after 15 minutes and quenched with citric acid, and the weight-average molecular weight and polydispersity index of each sample were measured. The obtained degradation data are shown in Table 3.
[0147] Table 3
[0148]
[0149] Example 3. An ethanol slurry of a PHA copolymer consisting of 88% butyrate monomer and 12% hexanoate monomer was prepared in 20 wt% PHA solids and 80 wt% ethanol. The weight-average molecular weight of the PHA was 630 kDa. Sodium hydroxide (NaOH) was introduced into the slurry at concentrations ranging from approximately 3,215 ppm to approximately 12,000 ppm under stirring. Each alkali concentration resulted in a pH > 13.5 in the slurry. Samples were taken after 15 minutes and quenched with citric acid, and the weight-average molecular weight and polydispersity index of each sample were measured. The obtained degradation data are shown in Table 4.
[0150] Table 4
[0151]
[0152] For purposes of illustration and description, the above description of preferred embodiments of the invention has been given. These are not exhaustive, nor do they limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in accordance with the foregoing teachings. These embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application, thereby enabling those skilled in the art to utilize the invention in various embodiments and make various modifications to suit a particular intended use. All such modifications and variations are within the scope of the invention as defined by the appended claims when interpreted according to the breadth to which they are fairly, legally, and impartially authorized.
Claims
1. A method for preparing polyhydroxyalkanoates, comprising the following steps: A dispersion comprising 10% to 90% by weight of at least one polyhydroxyalkanoate and 10% to 90% by weight of a solvent, wherein the at least one polyhydroxyalkanoate has an initial weight-average molecular weight of 500,000 Daltons to 5,000,000 Daltons, and wherein the solvent is selected from the group consisting of water, saturated alkyl alcohols having 1 to 10 carbon atoms and unsaturated alkyl alcohols having 1 to 10 carbon atoms and mixtures thereof; An alkali is added to the dispersion in an amount sufficient to provide a pH of 12 to 14 in the dispersion; A portion of the at least one polyhydroxyalkanoate is hydrolyzed by reacting with an alkali for a reaction time interval, wherein the weight-average molecular weight of the at least one polyhydroxyalkanoate is reduced to a final weight-average molecular weight less than the initial weight-average molecular weight. The reaction was stopped by adding an amount of quenching acid sufficient to establish a pH less than 12.0 in the dispersion; and The precipitated salt is filtered from the dispersion. All weight-average molecular weights were determined according to ASTM D5296. Furthermore, the at least one polyhydroxyalkanoate in the dispersion comprises particles with an average particle size of 10 nanometers to 50 micrometers, the average particle size being determined using dynamic light scattering according to ISO 22412:2017.
2. The method according to claim 1, wherein, The initial weight-average molecular weight, as determined by ASTM D5296, is between 500,000 and 5,000,000 Daltons.
3. The method according to claim 1, wherein, The final weight-average molecular weight, as determined by ASTM D5296, is between 50,000 and 700,000 Daltons.
4. The method according to claim 1, wherein, The final weight-average molecular weight is 10% to 95% of the initial weight-average molecular weight, wherein both weight-average molecular weights are determined according to ASTM D5296.
5. The method according to claim 1, wherein, The solvent is selected from the group consisting of water, methanol, ethanol, isopropanol and mixtures thereof.
6. The method according to claim 1, wherein, The solvent includes ethanol, and the reaction time interval is from 2 minutes to 60 minutes.
7. The method according to claim 1, wherein, The solvent includes water, and the reaction time interval is from 1 hour to 48 hours.
8. The method according to claim 1, wherein, The base has a pK value of less than 1. b .
9. The method according to claim 8, wherein, The alkali is selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and mixtures thereof.
10. The method according to claim 1, wherein, The base has a pC of 1 to 5. b .
11. The method according to claim 10, wherein, The alkali is selected from the group consisting of ammonium hydroxide, aniline, ammonia, and mixtures thereof.
12. The method according to claim 1, wherein, Before the addition of the alkali, the dispersion has a solids content of 5% to 20%.
13. The method according to claim 1, wherein, The quenching acid is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, perchloric acid or chloric acid, acetic acid, citric acid, phosphoric acid, glycolic acid, nitrous acid, sulfurous acid, oxalic acid, benzoic acid, formic acid and mixtures thereof.
14. The method according to claim 1, wherein, The hydrolysis is carried out at a temperature between 20°C and 60°C.
15. The method according to claim 1, wherein, The dispersion further comprises at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and mixtures thereof.
16. The method according to claim 1, wherein, The dispersion was prepared using ultrasonic treatment, low-shear mixing, and / or ultra-high-shear mixing.
17. The method according to claim 1, wherein, The method further includes a step of synthesizing the at least one polyhydroxyalkanoate by means of the following steps prior to preparing the dispersion: Mix biomass containing bacteria with a carbon source. Fermentation of biomass and carbon, causing bacteria of the biomass to consume at least a portion of the carbon source and synthesize at least one poly(hydroxyalkanoate) having an initial weight-average molecular weight of 500,000 Daltons to 5,000,000 Daltons, and The at least one poly(hydroxyalkanoate) is isolated from the biomass.