A compound nucleating agent, PHA granules and a preparation method thereof
By combining phosphate ester nucleating agents with solid acids, the problems of thermal degradation and low crystallization efficiency of PHA were solved, achieving rapid crystallization and efficient granulation, thus improving the processing performance and stability of amorphous PHA.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING PHABUILDER BIOTECHNOLOGY CO LTD
- Filing Date
- 2025-01-21
- Publication Date
- 2026-07-21
AI Technical Summary
Existing nucleating agents cause thermal degradation and molecular weight reduction during PHA processing, making it difficult to achieve efficient crystallization and granulation, especially for amorphous PHA, where the crystallization efficiency is low and adhesion is severe.
A compound nucleating agent is formed by combining phosphate ester salt nucleating agents with solid acids. This promotes rapid crystallization of PHA in an acidic environment, avoids thermal degradation, and improves crystallization speed and thermal processing stability.
It achieves rapid crystallization and efficient granulation of PHA, protects the molecular weight from degradation, improves processing performance and yield, and is suitable for the production of amorphous PHA.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, and in particular to a compound nucleating agent, PHA granules, and their preparation method. Background Technology
[0002] Polyhydroxyalkanoates (PHAs), as a biosynthetic thermoplastic polymer, are characterized by a slow crystallization rate. Therefore, selecting a highly efficient nucleating agent will greatly benefit the improvement of PHA's crystallization performance, thereby enhancing its mechanical properties. However, some nucleating agents, while improving crystallization efficiency, suffer from reduced thermal stability during granulation due to the introduction of an alkaline environment during processing, resulting in a significant decrease in molecular weight.
[0003] Furthermore, random copolymers of PHA, especially highly copolymerized amorphous PHA, are almost impossible to cool and solidify during hot processing. Even after cooling for a long time (more than 24 hours), they still have a lot of viscosity. The pellets after pelleting are prone to sticking together, resulting in extremely low processing efficiency and making it difficult to granulate and process into finished products.
[0004] Current technologies generally use nucleating agents to promote the crystallization of PHA. However, the selected nucleating agents have low crystallization efficiency and are almost ineffective for amorphous PHA (such as random copolymer P34HB with a 4HB comonomer ratio ≥20%). Another technique involves coating the surface of the pelleted material with inorganic powders such as silica powder to prevent particle adhesion. However, this introduces powder onto the pellet surface and generates dust during the coating process. Some existing technologies use phosphate ester nucleating agents. Although these nucleating agents have high crystallization efficiency, they suffer from rapid thermal degradation during PHA thermal processing, which compromises product performance.
[0005] Therefore, effective improvement plans still need to be proposed. Summary of the Invention
[0006] To address the problems of slow crystallization rate and difficulty in efficient granulation production of PHA (especially amorphous PHA), this invention first provides a novel compound nucleating agent.
[0007] Specifically, the compound nucleating agent of the present invention includes a phosphate ester nucleating agent and a solid acid. The mass ratio of the phosphate ester nucleating agent to the solid acid is 1:1-5, preferably 1:1-3, and a more suitable ratio is 1:1, etc.
[0008] Although phosphate ester nucleating agents have been used in the processing of PHA materials, thermal degradation of PHA during hot processing leads to a significant decrease in molecular weight. This invention employs a phosphate ester nucleating agent combined with a solid acid (such as boric acid) that can react with hydroxyl groups. This creates an acidic environment in the combined nucleating agent, facilitating rapid crystallization of PHA. The crystallization is fast, the granules do not stick together, achieving high-speed production. Simultaneously, it effectively protects the molecular weight of PHA, preventing degradation during hot processing. This enables online granulation production, increases yield, and ensures product quality.
[0009] The phosphate ester nucleating agent described in this invention may be selected from one or more of alkyl / aryl phosphate esters, phosphate diesters, fatty alcohol / alkylphenol phosphates, alkylolamide phosphate esters, imidazoline phosphate esters, and siloxane phosphate esters.
[0010] Further, the alkyl / aryl phosphate salt is selected from one or more of sodium monododecyl phosphate and aluminum bis(4,6-di-tert-butylphenyl) phosphate; the phosphate diester salt is selected from one or more of magnesium saturated fatty alcohol polyoxyethylene ether phosphate; the fatty alcohol / alkylphenol phosphate is selected from sodium fatty alcohol polyoxyethylene ether phosphate; the alkylolamide phosphate salt is selected from potassium stearamide phosphate; the imidazoline phosphate salt is selected from sodium imidazoline phosphate; and the siloxane phosphate salt is selected from potassium polydimethylsiloxane phosphate.
[0011] In some preferred embodiments provided by the present invention, the phosphate ester nucleating agent is selected from potassium stearamide phosphate, sodium monododecyl phosphate, or magnesium fatty alcohol polyoxyethylene ether phosphate. The above-mentioned phosphate ester nucleating agents have the advantage of promoting the crystallization rate of PHA, which can greatly improve the crystallization rate of PHA, thereby making it easier to process and improving efficiency.
[0012] When the compound nucleating agent described in this invention is used for granulation of PHA raw materials, the amount of phosphate ester salt nucleating agent relative to PHA raw materials is preferably 0.01-0.5%, more preferably 0.1-0.5%, and more suitable amounts are such as 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, etc.
[0013] The phosphate ester nucleating agent selected in this invention can nucleate amorphous PHA well at low concentrations, with high nucleation efficiency and a very narrow half-peak width during cooling crystallization. However, when using such nucleating agents, because these nucleating agents are organometallic salts and are alkaline substances, PHA is very sensitive to alkaline environments during thermal processing and is particularly prone to thermal degradation, resulting in a rapid decrease in molecular weight. However, the addition of a slightly excessive amount of solid acidic substances can react with the hydroxyl groups of the nucleating agent and provide an acidic environment for the thermal processing of PHA.
[0014] The solid acid described in this invention is selected from one or more of the following: immobilized liquid acid, oxide, metal sulfide, metal phosphate, metal sulfate, zeolite molecular sieve, heteropoly acid, clay mineral, and acid anhydride.
[0015] Further, the supported liquid acid is selected from one or more of phosphoric acid / diatomaceous earth, HF / Al2O3, and BF3 / Al2O3; the oxide is selected from one or more of alumina, silicon dioxide, boric acid, lithium tetraborate, phosphorus pentoxide, and sulfur trioxide; the metal sulfide is selected from one or more of zinc sulfide and cadmium sulfide; the metal phosphate is selected from boron phosphate and / or aluminum phosphate; the metal sulfate is selected from one or more of zinc sulfate, ferric sulfate, and copper sulfate; the zeolite molecule is screened from one or more of zeolite X, zeolite Y, and zeolite B; and the heteropolyacid is selected from H3PW. 12 O 40 H4SiW 12 O 40 H3PMo 12 O 40 One or more of the following; the clay mineral is selected from one or more of glauconite, chlorite, bentonite, and montmorillonite; the acid anhydride is selected from one or more of maleic anhydride, succinic anhydride, and boron anhydride.
[0016] In some preferred embodiments provided by this invention, the solid acid is selected from boric acid, maleic anhydride, or boron phosphate. These solid acids have a strong proton-donating advantage, providing protons to the thermal processing environment of PHA, creating an acidic environment that neutralizes the alkalinity of the nucleating agent. Taking boric acid as an example, boric acid is a monoprotic very weak acid. Its acidity does not originate from its own proton donation. Because boron is an electron-deficient atom, it can combine with hydroxide ions from water molecules, releasing a proton. Utilizing this electron-deficient property, adding polyhydroxy compounds to form stable complexes can further enhance its acidity.
[0017] When the compound nucleating agent described in this invention is used for granulation of PHA raw materials, the amount of solid acid relative to the PHA raw materials is preferably 0.01-0.5%, more preferably 0.1-0.5%, and more suitable amounts are such as 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, etc.
[0018] In some specific embodiments of the present invention, selecting a suitable phosphate ester nucleating agent and combining it with a solid acid often yields better results. Specifically, the phosphate ester nucleating agent has a good nucleation effect on PHA, increasing the nucleation rate of PHA, while the solid acid can provide an acidic environment for the thermal processing of PHA, improving the thermal processing stability of PHA and preventing the reduction of PHA molecular weight. Suitable combinations include, but are not limited to, potassium stearamide phosphate and boric acid in a 1:1 mass ratio, aluminum bis(4,6-di-tert-butylphenyl) phosphate and maleic anhydride in a 1:1 mass ratio, magnesium fatty alcohol polyoxyethylene ether phosphate and silica in a 1:1 mass ratio, sodium fatty alcohol polyoxyethylene ether phosphate and diatomaceous earth in a 1:1 mass ratio, and sodium imidazoline phosphate and succinic anhydride in a 1:1 mass ratio. These combinations can better improve the crystallization speed and the thermal processing stability of PHA, protect the molecular weight from degradation, and thus ensure the processing performance of the material and the overall performance of the final product.
[0019] The compound nucleating agent provided by this invention has a simple composition. During preparation, it is only necessary to directly mix the two components or directly add them to the granules for mixing. The specific operation is mastered by those skilled in the art, and this invention does not impose any particular limitations on it.
[0020] This invention also provides the application of the above-mentioned compound nucleating agent in the granulation or processing of PHA products, wherein the PHA is particularly preferably amorphous PHA, and the products include, but are not limited to, injection-molded cutlery, straws, film bags and coffee capsules, etc. Based on the positive effect of the compound nucleating agent on the granulation process, the performance of the resulting products is also effectively guaranteed.
[0021] The present invention also provides a PHA granule, wherein the raw material of the PHA granule contains 0.5%-5% by mass of the above-mentioned compound nucleating agent, preferably 1%-3%, and suitable dosages such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.
[0022] The PHA is preferably amorphous PHA, especially amorphous PHA with high comonomer content, such as amorphous PHA with a comonomer 4HB content ≥ 20%.
[0023] Since amorphous PHA is more difficult to crystallize, the above-mentioned compound nucleating agent can achieve particularly significant technical effects when used for amorphous PHA.
[0024] The PHA mentioned in this invention refers to polyhydroxy fatty acid esters, which can be classified into homopolymers and copolymers based on their monomer composition. Based on the number of carbon atoms in the monomer, the PHAs of this invention include, but are not limited to, short-chain PHAs (i.e., monomers of C3-C5 hydroxy fatty acids) and medium- to long-chain PHAs (i.e., monomers of C6-C16 hydroxy fatty acids).
[0025] In some embodiments of the present invention, PHA can be a homopolymer, including but not limited to polyhydroxypropionate, polyhydroxybutyrate, polyhydroxyvalerate, etc., such as poly-3-hydroxybutyrate (P3HB), poly-4-hydroxybutyrate (P4HB), poly-3-hydroxypropionate (P3HP) or poly-3-hydroxyvalerate (P3HV), etc.
[0026] In some embodiments of the present invention, PHA may be, but is not limited to, copolymers such as dimers and trimers. For example, the copolymer may be a copolymer of hydroxypropionate and hydroxybutyrate; a copolymer of hydroxypropionate and hydroxyvalerate; a copolymer of hydroxybutyrate and hydroxyvalerate; or a copolymer of hydroxypropionate, hydroxybutyrate, and hydroxyvalerate.
[0027] More specifically, in some embodiments of the present invention, PHA can be poly(3-hydroxybutyrate-4-hydroxybutyrate) copolyester (P3HB4HB), poly(3-hydroxybutyrate-3-hydroxyvalerate) copolyester (P3HB3HV), or poly(3-hydroxybutyrate-4-hydroxybutyrate-3-hydroxyvalerate) copolyester (P34HB3HV), or combinations thereof, especially those with a 4HB comonomer ratio ≥ 20%, such as P34HB-20%4HB.
[0028] The present invention also provides a processing method for the above-mentioned PHA granules, wherein the raw materials are mixed evenly and then fed into a twin-screw extruder for co-extrusion.
[0029] Preferably, the method includes: Step 1: Weigh each material according to the formula and add it to the high-speed mixer. Mix at a speed of 500-1000 rpm for 3-5 minutes. After mixing evenly, discharge the material for later use. Step 2: Add the material from Step 1 into the hopper of the preheated twin-screw extruder. Set the temperature of each section of the twin-screw extruder to 100-145℃, the main machine speed to 100-150rpm, the feeding speed to 6-8Hz, and use air-cooled strip cutting and pelletizing. Add a hot air blower above the conveyor belt and control the air temperature to 26-60℃. Perform extrusion granulation under these conditions.
[0030] The present invention also provides PHA granules prepared by the above method.
[0031] This invention is the first to propose a compound nucleating agent prepared by combining a phosphate ester nucleating agent with a solid acid. This compound nucleating agent can better promote the crystallization of PHA (especially amorphous PHA), resulting in faster crystallization and improved material processing performance. Simultaneously, the solid acid enhances the thermal stability of PHA, protecting its molecular weight from degradation and thus ensuring the performance of the final product. Furthermore, the production processes for both the compound nucleating agent and PHA granules provided by this invention are simple, feasible, and low-cost, showing broad application prospects. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be described below.
[0033] Figure 1 The following is a comparison chart of the DSC crystallization curves of Example 6, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Source information for some materials is as follows: P34HB-20%4HB: Beijing Microstructure Factory Biotechnology Co., Ltd.
[0036] Example 1 This embodiment provides a compound nucleating agent, which, by weight, is composed of potassium stearamide phosphate and boric acid in a 1:1 ratio.
[0037] Example 2 This embodiment provides a compound nucleating agent, which, by weight, is composed of aluminum bis(4,6-di-tert-butylphenyl) phosphate and maleic anhydride in a 1:1 ratio.
[0038] Example 3 This embodiment provides a compound nucleating agent, which, by weight, is composed of a 1:1 ratio of fatty alcohol polyoxyethylene ether phosphate magnesium salt and silicon dioxide.
[0039] Example 4 This embodiment provides a compound nucleating agent, which, by weight, is composed of sodium salt of fatty alcohol polyoxyethylene ether phosphate and diatomaceous earth in a 1:1 ratio.
[0040] Example 5 This embodiment provides a compound nucleating agent, which, by weight, is composed of sodium imidazoline phosphate and succinic anhydride in a 1:1 ratio.
[0041] Example 6 This embodiment provides a PHA granule with the following raw material composition: random copolymer P34HB-20% 4HB content 99%, stearamide phosphate potassium salt content 0.5%, boric acid content 0.5% (i.e., the compound nucleating agent described in Example 1).
[0042] This embodiment also provides a method for preparing the above-mentioned granules, including: Step 1: Weigh each material according to the formula and add it to the high-speed mixer. Mix at 1000 rpm for 4 minutes. After mixing evenly, discharge the material for later use. Step 2: Add the material from Step 1 into the hopper of the preheated twin-screw extruder. Set the temperature of each section of the extruder to 100-140℃, the main machine speed to 120rpm, use air-cooled strip cutting, add a hot air blower above the conveyor belt, and control the air temperature to 26℃. Under these conditions, extrusion granulation is carried out.
[0043] The properties of the granules obtained in this embodiment are shown in Table 1.
[0044] Example 7 This embodiment provides a PHA granule, the only difference between its raw material composition and that of Example 6 is that the compound nucleating agent used in it is replaced with the compound nucleating agent in Example 2.
[0045] This embodiment also provides a method for preparing the above-mentioned granules, which is the same as in Example 6.
[0046] The properties of the granules obtained in this embodiment are shown in Table 1.
[0047] Example 8 This embodiment provides a PHA granule, the only difference between its raw material composition and that of Example 6 is that the compound nucleating agent used in it is replaced with the compound nucleating agent in Example 3.
[0048] This embodiment also provides a method for preparing the above-mentioned granules, which is the same as in Example 6.
[0049] The properties of the granules obtained in this embodiment are shown in Table 1.
[0050] Example 9 This embodiment provides a PHA granule, the only difference between its raw material composition and that of Example 6 is that the compound nucleating agent used in it is replaced with the compound nucleating agent in Example 4.
[0051] This embodiment also provides a method for preparing the above-mentioned granules, which is the same as in Example 6.
[0052] The properties of the granules obtained in this embodiment are shown in Table 1.
[0053] Example 10 This embodiment provides a PHA granule, the only difference between its raw material composition and that of Example 6 is that the compound nucleating agent used in it is replaced with the compound nucleating agent in Example 5.
[0054] This embodiment also provides a method for preparing the above-mentioned granules, which is the same as in Example 6.
[0055] The properties of the granules obtained in this embodiment are shown in Table 1.
[0056] Table 1
[0057] Data comparison shows that the compound nucleating agent formulation system has a significant nucleation effect on P34HB-20%, which can be granulated online and transformed from an amorphous state to a semi-crystalline state. During cooling crystallization, a narrow crystallization peak appears, and the melt index and molecular weight do not change much.
[0058] Comparative Example 1 Comparative Example 1 uses 100% random copolymer P34HB-20%4HB as raw material and granulates it according to the method described in Example 1. The properties of the resulting material are shown in Table 2.
[0059] Table 2
[0060] Based on the data comparison, PHA powder cannot be thermally processed and granulated without the addition of any additives. Because PHA has no cooling crystallization peak and is in an amorphous state, it cannot be granulated for production.
[0061] Comparative Example 2 Comparative Example 1 used P34HB-20%4HB at a dosage of 99.5% and stearamide phosphate potassium salt at a dosage of 0.5% as raw materials, and granulated them according to the method described in Example 6. The properties of the resulting material are shown in Table 3.
[0062] Table 3
[0063] Data comparison shows that PHA can be granulated well with only the addition of a nucleating agent. However, because the nucleating agent is alkaline, PHA is severely degraded after thermal processing and granulation, resulting in a significant increase in melt index and a substantial decrease in molecular weight, down to 38.5% of the blank sample.
[0064] The DSC crystallization curves of Example 6, Comparative Example 1, and Comparative Example 2 were compared, and the results are shown in the figure. Figure 1 From the DSC curve, it can be seen that when the blank sample is not mixed with nucleating agent, there is no crystallization peak when it is cooled and it is in an amorphous state. After adding nucleating agent, a very narrow crystallization peak appears, which can then be cooled and shaped, and can be granulated for production.
[0065] Comparative Example 3 This comparative example provides a method for preparing PHA granules. The only difference from Example 6 is the formulation of the added compound nucleating agent, which is composed of potassium stearamide phosphate and boric acid in a 2:1 ratio. The total content of the two in the PHA granules is the same as in Example 6. Granulation is carried out according to the method described in Example 6, and the properties of the resulting material are shown in Table 4.
[0066] Table 4
[0067] Data comparison shows that when the addition of compound additives was not within the appropriate ratio range, the granulation of PHA showed some adhesion. However, because the nucleating agent itself is alkaline and the proportion of compound additives was too high, PHA degraded after thermal processing and granulation, the melt index increased to 3.33 times that of the blank sample, and the molecular weight decreased to 58.5% of the blank sample.
[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions all fall within the protection scope of the present invention.
Claims
1. A compound nucleating agent, the raw materials of which include phosphate ester salt nucleating agents, characterized in that, It also includes a solid acid, wherein the mass ratio of the phosphate ester nucleating agent to the solid acid is 1:1-5.
2. The compound nucleating agent according to claim 1, characterized in that, The mass ratio of the phosphate ester nucleating agent to the solid acid is 1:1-3.
3. The compound nucleating agent according to claim 1 or 2, characterized in that, The phosphate ester nucleating agent is selected from one or more of alkyl / aryl phosphate esters, phosphate diesters, fatty alcohol / alkylphenol phosphates, alkylolamide phosphate esters, imidazoline phosphate esters, and siloxane phosphate esters.
4. The compound nucleating agent according to claim 1 or 2, characterized in that, The solid acid is selected from one or more of the following: immobilized liquid acid, oxide, metal sulfide, metal phosphate, metal sulfate, zeolite molecular sieve, heteropoly acid, clay mineral, and acid anhydride.
5. The compound nucleating agent according to claim 1, characterized in that, The compound nucleating agent is selected from the following in a mass ratio of 1:1: potassium stearamide phosphate and boric acid, 1:1: aluminum bis(4,6-di-tert-butylphenyl) phosphate and maleic anhydride, 1:1: magnesium salt of fatty alcohol polyoxyethylene ether phosphate and silica, 1:1: sodium salt of fatty alcohol polyoxyethylene ether phosphate and diatomaceous earth, or 1:1: sodium salt of imidazoline phosphate and succinic anhydride.
6. The application of the compound nucleating agent according to any one of claims 1-5 in the granulation or processing of PHA into PHA products.
7. A PHA granule, characterized in that: The raw materials of the PHA granules contain 0.5%-5% by mass of the compound nucleating agent as described in any one of claims 1-5.
8. The PHA granules according to claim 7, characterized in that, The PHA is preferably amorphous PHA, more preferably amorphous PHA with high comonomer content, and even more preferably amorphous PHA with a comonomer content of ≥20% 4HB.
9. The method for preparing PHA granules according to claim 7 or 8, characterized in that, The raw materials for PHA granules are mixed evenly and then fed into a twin-screw extruder for co-extrusion.
10. The method for preparing PHA granules according to claim 9, characterized in that, The temperature settings for each zone of the twin-screw extruder are 100-145℃, the main machine speed is 100-150rpm, and the feeding speed is 6-8Hz. Preferably, the temperature of each zone of the twin-screw extruder is set to 100-145℃, the main machine speed is 100-150rpm, the feeding speed is 6-8Hz, the extrusion is carried out by air-cooled strip cutting, and a hot air blower is added above the conveyor belt to blow air at a temperature of 26-60℃ for extrusion granulation.