Method for reducing yellowness of polyhydroxyalkanoate and use thereof

Abstract

The present invention relates to the technical field of bio-based polymer material processing. Particularly disclosed are a method for reducing the yellowness of a biopolymer material and the use thereof. The method for reducing the yellowness of a biopolymer material comprises the step of treating the biopolymer material by means of light irradiation. The present invention treats the biopolymer material by means of light source irradiation, such that influence caused by the color of the biopolymer material can be effectively reduced, especially the influence of the yellowness of polyamino acids, microbial polysaccharides and polyester polymer materials in the biopolymer material is reduced, and the aggregate colors of the types of the materials becomes light, the transparency is increased, and other properties are not changed.

Description

A method for reducing the yellowness of polyhydroxyalkanoate and its application

[0001] Citation of Related Applications

[0002] This application claims priority to and the benefits of Chinese Patent Application No. 2023107143700, filed on June 16, 2023, which is hereby incorporated by reference in its entirety into this application. Technical Field

[0003] The present invention relates to the technical field of biopolymer material processing, in particular to a method for reducing the yellowness of biopolymer materials and applications thereof, specifically to a method for reducing the yellowness of polyhydroxyalkanoate and applications thereof. Background Art

[0004] Biopolymers, particularly those synthesized by microorganisms, are a class of polymers produced by microorganisms through fermentation of various carbon sources. These primarily include microbial polyesters, microbial polysaccharides, and polyamino acids, such as polyhydroxyalkanoates (PHAs), hyaluronic acid, and polyglutamic acid. Currently, nearly 100 bacterial species are available for synthesizing microbial polymers. These biopolymers exhibit excellent biodegradability and thermoplasticity, making them easy to process and shape. They are widely used in high-value-added industries such as medicine and electronics.

[0005] Due to the diversity of raw material carbon sources, microorganisms, and fermentation extraction production during the production and extraction process, this type of biopolymer material synthesized by microorganisms often has the problem of impure color during the extraction of finished products. Adding conventional additives such as antioxidants and anti-yellowing agents will not only introduce excess materials, but may also affect the processing performance of the biopolymer, thus failing to effectively solve this problem.

[0006] Furthermore, in the pharmaceutical field, product color requirements are often high. For example, in cosmetics using materials such as hyaluronic acid and polyglutamic acid, and in the food industry, some biopolysaccharides are used. Darker colors and lower transparency often affect consumer choices. In the chemical materials processing field, darker raw materials, such as those with a high yellowness, can result in poor appearance and poor sales for daily products. Therefore, there is an urgent need to develop more effective methods for reducing the yellowness of biopolymer materials.

[0007] Summary of the Invention

[0008] One of the objects of the present invention is to provide a method for reducing the yellowness of biopolymer materials.

[0009] A second object of the present invention is to provide an application of a method for reducing the yellowness of biopolymer materials.

[0010] A third object of the present invention is to provide a molded body of polyhydroxyalkanoate.

[0011] A fourth object of the present invention is to provide a device for reducing the yellowness of biopolymer materials.

[0012] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0013] In a first aspect, the present invention provides a method for reducing the yellowness of a biopolymer material, comprising the step of treating the biopolymer material with light irradiation.

[0014] The light source for the light irradiation treatment is not particularly limited and can be a light source emitting light of a single frequency (or wavelength) or a light source emitting a mixture of different frequencies (or wavelengths). In other words, a light source emitting light of a single wavelength or a light source emitting light of a single wavelength band, or a combination thereof, can be selected.

[0015] There is no particular limitation on the light source, and it can be a light source of visible light with a wavelength of 380nm to 780nm, a light source of near-infrared light with a wavelength of 780nm to 2500nm, or a light source of near-infrared light with a wavelength of 2500nm to 1×10 6 In specific use, considering that the irradiation cost of light sources emitting infrared light with a longer wavelength is higher, the selection can be made based on the actual production cost, installation irradiation requirements, etc.

[0016] In some embodiments, the light source for the light irradiation treatment is selected from a light source that emits light with a wavelength of any one of 380 nm to 780 nm. Specifically, but not limited to, for example, the wavelength of the light emitted can be 380 nm, 400 nm, 410 nm, 415 nm, 420 nm, 425 nm, 430 nm, 435 nm, 440 nm, 450 nm, 455 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, m, 520nm, 530nm, 540nm, 550nm, 560nm, 570nm, 580nm, 590nm, 600nm, 610nm, 620nm, 630nm, 640nm, 650nm, 660nm, 670nm, 680nm, 690nm, 700nm, 710nm, 720nm, 730nm, 740nm, 750nm, 760nm, 770nm, 780nm, etc.

[0017] In some embodiments, the light source for the light irradiation treatment is selected from a light source that emits light in any wavelength range of 380nm to 780nm. Specifically, but not limited to, for example, the wavelength range of the light emitted can be 380nm to 780nm, 400nm to 750nm, 410nm to 710nm, 430nm to 700nm, 450nm to 680nm, 460nm to 650nm, 480nm to 630nm, 500nm to 600nm, 510nm to 590nm. m, 520nm~580nm, 530nm~560nm, 540nm~550nm, 360nm~380nm, 390nm~420nm, 455nm~465nm, 455nm~475nm, 510nm~540nm, 560nm~575nm, 580nm~595nm, 605nm~615nm, 620nm~650nm, 655nm~665nm, 670nm~780nm, etc.

[0018] In some embodiments, the light source for the photoirradiation treatment is selected from a light source emitting light in the wavelength range of 380 to 780 nm, which can reduce the yellowness of the polymer material within this range. In some embodiments, the light source is selected from a light source emitting light at any wavelength between 405 nm and 750 nm, or a light source emitting light in the wavelength range of 405 nm to 750 nm, which can effectively reduce yellowness.

[0019] In some embodiments, the light source for the photoirradiation treatment includes one or more of the following lamp sources: a metal halide lamp, a tungsten lamp, a xenon lamp, and an LED lamp.

[0020] Metal halide lamp: A metal halide lamp that emits continuous or discontinuous light in the visible light range (380nm to 780nm).

[0021] Tungsten lamp: 320~2500nm, including incandescent lamp (the wavelength of the emitted light is 400~1050nm).

[0022] Xenon lamp: 190~1100nm, including long arc xenon lamp, short arc xenon lamp, pulse xenon lamp and other varieties. The main wavelength varies depending on the type of xenon lamp.

[0023] LED lights: Light-emitting diodes can also be divided into ordinary single-color LEDs, high-brightness LEDs, ultra-high-brightness LEDs, color-changing LEDs, flashing LEDs, voltage-controlled LEDs, infrared LEDs, and negative-resistance LEDs. The color of a single-color LED is related to its wavelength, which in turn depends on the semiconductor material used to manufacture the diode. The wavelength of light emitted by a red LED is generally 650-700nm, the wavelength of light emitted by an amber LED is generally 630-650nm, the wavelength of light emitted by an orange LED is generally around 610-630nm, the wavelength of light emitted by a yellow LED is generally around 585nm, and the wavelength of light emitted by a green LED is generally 555-570nm. The wavelengths of light emitted by LEDs can be specifically divided into: 390-420nm violet light; 455-465nm blue light; 455-475nm blue light; 510-540nm emerald green light; 560-575nm yellow-green light; 580-595nm yellow light; 605-615nm orange light; 620-650nm red light; 655-665nm red light; 880nm infrared light; 940nm infrared light.

[0024] The power of the light irradiation treatment is not particularly limited and can be 0.1W to 20,000W, preferably 100W to 6,000W. Specific non-limiting examples include 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W, 1000W, 1500W, 2000W, 2500W, 3000W, 3500W, 4000W, 4500W, 5000W, 5500W, 6000W, and the like. The power can be selected based on equipment limitations and energy consumption in actual production. Taking into account the effect of reducing yellowness and the impact on melt index stability, 300W to 4000W is more preferred.

[0025] There is no special restriction on the time of light irradiation treatment, which can be greater than or equal to 1 minute. The longer the irradiation treatment time, the greater the degree of yellowness reduction. In order to meet the needs of actual industrial production, it can be 1 minute to 1000 minutes. Combined with the actual energy consumption and yellowness index requirements, it is preferably 15 minutes to 120 minutes.

[0026] The distance of the light irradiation treatment, i.e., the vertical distance between the light source and the biopolymer material (e.g., PHA molded article), is not particularly limited and can be 1 cm to 100 cm, preferably 15 cm to 80 cm. Specific non-limiting examples include 5 cm, 10 cm, 15 cm, 25 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, etc. Generally, the closer the distance between the light source and the biopolymer material, the better the effect of reducing the yellowness of the biopolymer material. However, the problem of excessive temperature caused by the irradiation treatment with the light source must also be considered.

[0027] It should be noted that during light irradiation, the biopolymer material (e.g., pellets, etc.) is usually laid out for irradiation. Here, the vertical distance between the light source and the biopolymer material (e.g., PHA molded body) usually refers to the distance from the light source to the surface of the biopolymer material (e.g., PHA molded body).

[0028] According to the present invention, the form of the molded body is not particularly limited, and includes, for example, a sphere, a film, a sheet, a bottle, a straw, and the like.

[0029] Furthermore, prior to the light irradiation step, the biopolymer material can be subjected to a black box treatment. This study found that after the black box treatment, the transparency of some particle moldings (pellets) increased, and after the light irradiation treatment, the overall appearance quality of the pellets improved.

[0030] The black box treatment is to maintain a light-shielded dark environment. There is no special restriction on the method of black box treatment. It can be placed in a light-proof sealed cover, a light-proof black box, or a light-proof room.

[0031] The time for black box processing can be selected according to actual needs, including but not limited to short-term, such as 30 minutes to 120 minutes, and long-term, such as 1 day to 3 days.

[0032] The biopolymer materials described herein refer to polymer materials synthesized by microorganisms and are a class of polymer materials produced by microorganisms through fermentation of various carbon sources. These materials include, but are not limited to, polyamino acid biopolymers such as polyglutamic acid and polylysine; microbial polysaccharide biopolymers such as chitosan, Monascus polysaccharide, flavobacterium gum, pullulan, α-glucan, cyclodextrin, and hyaluronic acid; and polyester biopolymers such as polymalic acid, polyhydroxyalkanoates (PHAs), polylactic acid (PLA), polyglycolic acid (PGA), polycarbonate, polypropylene carbonate, polyurethane, and polyanhydrides. For example, polyhydroxyalkanoates, specifically polyhydroxyalkanoate shaped bodies, have a diameter D of 10 mm or less, or a thickness T of 10 mm or less; further, the diameter D of the shaped body can be 2-10 mm, or the thickness T can be 2-10 mm. Specifically, it includes but is not limited to polyhydroxyalkanoate granules (such as uniformly sized spheres with an approximate diameter of D), films (thickness of T), sheets (thickness of T), bottles (bottle body thickness of T), straws (straw wall thickness of T), etc.; considering that the actual online production of polyhydroxyalkanoates is mostly granules, polyhydroxyalkanoate granules with an approximate diameter D of 2-10 mm are preferred.

[0033] Wherein, the polyhydroxyalkanoate contains the structural unit represented by the following general formula I: [OCHR(CH2) m C(O)] General Formula I

[0034] Where R is C p H 2p+1 The alkyl group represented by the formula (a) is an integer from 1 to 15, preferably an integer from 1 to 10, and more preferably an integer from 1 to 8; R includes, for example, a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a hexyl group;

[0035] m is 1, 2 or 3.

[0036] When m = 1, Formula I represents a 3-hydroxyalkanoate structural unit; when m = 2, Formula I represents a 4-hydroxyalkanoate structural unit; and when m = 3, Formula I represents a 5-hydroxyalkanoate structural unit. Among these, 3-hydroxyalkanoate structural units and 4-hydroxyalkanoate structural units are more common, such as the 3-hydroxybutyrate structural unit (sometimes referred to as 3HB) and the 4-hydroxybutyrate structural unit (sometimes referred to as 4HB).

[0037] Preferably, the polyhydroxyalkanoate is a poly(3-hydroxyalkanoate). Further, the poly(3-hydroxyalkanoate) is a poly(3-hydroxybutyrate) homopolymer containing only 3-hydroxybutyrate structural units, or a poly(3-hydroxybutyrate) copolymer containing 3-hydroxybutyrate structural units and other hydroxyalkanoate structural units.

[0038] Specific examples of poly(3-hydroxyalkanoates) include poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH, hereinafter referred to as PHBH), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB).

[0039] Furthermore, the weight average molecular weight of the polyhydroxyalkanoate is 100,000 to 1,000,000; preferably 200,000 to 900,000; and more preferably 300,000 to 800,000.

[0040] The current status of PHA material industrialization faces problems such as odor and color caused by low product purity. As a microbial intracellular product, PHA has completed polymerization in the microbial cell and does not need to go through the process of first producing 3-hydroxybutyric acid monomer and then polymerizing in vitro. There is no particular limitation on the microorganisms with PHA production capacity. Microorganisms isolated from nature, microorganisms preserved in strain collection institutions (such as IFO, ATCC, etc.), or mutants and transformants prepared from these microorganisms can be used. For example, the genus Cupriavidus, the genus Alcaligenes, the genus Ralstonia, the genus Pseudomonas, the genus Bacillus, the genus Azotobacter, the genus Nocardia, and the genus Aeromonas can be cited. Particularly preferred are strains such as Alcaligenes lipolytica (A.lipolytica), Alcaligenes latus (A.latus), Aeromonas caviae (A.caviae), Aeromonas hydrophila (A.hydrophila), and C.necator. In addition, when the microorganism does not originally have the ability to produce polyhydroxyalkanoates, or when the production volume is low, a transformant obtained by introducing a synthase gene and / or a mutant thereof of the target polyhydroxyalkanoate into the microorganism can also be used. The synthase gene of the polyhydroxyalkanoate used in the production of such a transformant is not particularly limited, but is preferably a gene for the polyhydroxyalkanoate synthase from Aeromonas caviae.

[0041] According to the present invention, the method for preparing polyhydroxyalkanoates is not limited, as long as they are produced by microbial fermentation of a carbon source. Specifically, methods for preparing polyhydroxyalkanoates (PHA) can be referenced in Chinese patent application CN109504715A; methods for recovering high-purity polyhydroxyalkanoates from microbial cells can be referenced in Chinese patent CN100572544C.

[0042] In a second aspect, the present invention also provides an application of a method for reducing the yellowness of a biopolymer material, such as a method for preparing a biopolymer material, the method comprising implementing the above-described method for reducing the yellowness of a biopolymer material downstream of the preparation of the biopolymer material.

[0043] In one embodiment, the method is a method for preparing a polyhydroxyalkanoate molded article, comprising performing the above-described method for reducing the yellowness of a biopolymer material after the polyhydroxyalkanoate is crystallized. Specifically, the method comprises performing the above-described method for reducing the yellowness of a biopolymer material downstream of crystallization of the polyhydroxyalkanoate molded article by various thermal processing methods such as extrusion molding, injection molding, calendering molding, tape casting, blow molding, and biaxial stretching molding. For example, an apparatus for reducing the yellowness of a polyhydroxyalkanoate molded article is manufactured and disposed downstream of crystallization of the polyhydroxyalkanoate molded article.

[0044] In one embodiment, the method includes: the crystallized polyhydroxyalkanoate molded body enters the interior of the device through a feeding device of a device for reducing the yellowness of the polyhydroxyalkanoate molded body, is irradiated with light, and after the treatment is completed, is output through the discharging device of the device.

[0045] The specific form and structure of the apparatus for reducing the yellowness of the polyhydroxyalkanoate molded body are not particularly limited, as long as the above process can be achieved.

[0046] As an embodiment, the device may include a box body and a light source, the box body includes an outer wall layer and an inner wall layer, the inner wall layer forms a receiving cavity for receiving a polyhydroxyalkanoate molded body, an interlayer is provided between the outer wall layer and the inner wall layer, and the light source is arranged in the interlayer for light irradiation treatment of the polyhydroxyalkanoate molded body placed in the receiving cavity.

[0047] Preferably, the outer wall layer is configured as a light-shielding structure; the inner wall layer is configured as a light-transmitting structure, which can be configured to be fully light-transmitting or partially light-transmitting, with the light-transmitting portion being made of a light-transmitting material.

[0048] Preferably, the device further comprises:

[0049] A drying device, located inside the housing, for drying the polyhydroxyalkanoate molded body; and / or

[0050] A material balancing device is provided in the accommodating cavity and is used for stirring the polyhydroxyalkanoate formed body.

[0051] Preferably, at least one group of light sources is arranged axially in the interlayer, and the vertical distance between each group of light sources and the inner wall layer is 1 cm to 100 cm.

[0052] The light emitted by the light source can be light of a single wavelength or light of mixed wavelengths, and the light source can be selected to emit one or more of the following light: visible light, near-infrared light and infrared light; for example, the light source can be selected from one or more of the following lamp sources: metal halide lamp, tungsten lamp, xenon lamp and LED lamp, etc.

[0053] In a third aspect, the present invention further provides a polyhydroxyalkanoate molded body, which is prepared by the method for preparing a polyhydroxyalkanoate molded body as described above, wherein the yellowness index of the polyhydroxyalkanoate molded body is lower than 51.7.

[0054] Specifically, when no yellowness-adjusting additive is used in the raw materials for preparing the polyhydroxyalkanoate molded body, the yellowness index (tested according to GB / T 39822-2021) of the molded body prepared by the above method can be effectively reduced to below 51.7, or even below 40. In addition, it is foreseeable that when a yellowness-adjusting additive is used in the raw materials for preparing the polyhydroxyalkanoate molded body, the yellowness index of the molded body prepared by the above method can be further reduced.

[0055] In a fourth aspect, the present invention also provides an apparatus for reducing the yellowness of biopolymer materials, which may exemplarily include a box body and a light source, wherein the box body includes an outer wall layer and an inner wall layer, the inner wall layer forms a holding cavity for holding the biopolymer material, and an interlayer is provided between the outer wall layer and the inner wall layer, and the light source is arranged in the interlayer for light irradiation treatment of the biopolymer material placed in the holding cavity of the inner wall layer.

[0056] Preferably, the outer wall layer is made of a light-shielding material, such as wood, metal (such as steel), etc.

[0057] Preferably, the inner wall layer is made of a light-transmitting material, such as tempered glass or other transparent, pressure-resistant and wear-resistant materials.

[0058] The inner wall layer can be set to be fully light-transmissive or partially light-transmissive (for example, only the side wall or part of the side wall is light-transmissive). Those skilled in the art can set it according to their needs. It is preferably set to be fully light-transmissive, that is, the entire inner wall layer is made of light-transmissive material.

[0059] The apparatus further includes a drying device located within the housing for drying the biopolymer material. The drying device may be a hot air device for delivering hot air into the housing, drying the biopolymer material from bottom to top. The hot air temperature may be 40-80°C, preferably 60-80°C.

[0060] Furthermore, the device also includes a constant temperature structure for maintaining a uniform temperature inside the box. For example, the outer wall layer of the box can be designed as a heat-insulating structure, such as an externally applied heat-insulating material.

[0061] Furthermore, the device further comprises a material balancing device for ensuring that the biopolymer material is evenly irradiated with light. For example, the material balancing device may be a stirring device.

[0062] According to one embodiment of the present invention, during the homogenization or stirring process, the homogenization device can make the biopolymer material adhere to the inner wall layer during the homogenization or stirring process, so that the light source can evenly irradiate and process the biopolymer material at an appropriate distance.

[0063] According to the present invention, the apparatus can be configured with a feed device and a discharge device as needed, each of which is in communication with the receiving chamber for receiving the biopolymer material. Those skilled in the art can configure these as needed to meet the requirements of light irradiation treatment of biopolymer materials.

[0064] The light source in the device can emit light of a single frequency (or wavelength), or a mixture of different frequencies (or wavelengths). A light source emitting light of a single wavelength can be selected, or a light source emitting light of a wavelength band can be selected, or a combination thereof. For example, the light emitted can be 380nm to 780nm visible light, 780nm to 1×10 6 The light source may be a light source of any wavelength or wavelength band of infrared light from 100 nm to 700 nm, preferably a light source of any wavelength or wavelength band of infrared light from 380 nm to 780 nm. For example, the light source may be one or more of the following: a metal halide lamp, a tungsten lamp, a xenon lamp, and an LED lamp.

[0065] The lamp power can range from 0.1W to 20,000W, preferably from 100W to 6,000W. The specific power can be selected based on equipment limitations and energy consumption in the actual production process. Taking into account the effect of reducing yellowness and the impact on melt index stability, 300W to 4,000W is more preferred.

[0066] At least one set of light sources can be arranged axially within the interlayer, with each set of light sources positioned vertically apart from the inner wall layer at a distance of 1 cm to 100 cm. Generally, the closer the light source is to the pellets, the better the yellowing effect on the biopolymer material will be. However, the issue of excess heat generated by the irradiation treatment with the light source must be considered.

[0067] The equipment can be used in the post-processing optimization stage of preparing biopolymer moldings.

[0068] The entire device can be loaded onto a production line for rotary irradiation, allowing for free design of the overall device size and processing time. A dry hot air source can also be added to the device (rotating and irradiating while drying). Beneficial effects

[0069] 1. This invention effectively reduces the color effects of biopolymer materials (e.g., reduced yellowness and increased transparency) by treating biopolymer materials with light sources, improving the quality and performance of biopolymer moldings and expanding the downstream application scenarios of biopolymer materials. This may be because this method effectively reduces the content of residual substances derived from microorganisms during the synthesis process in biopolymer materials, thereby lightening the color of the biopolymer materials.

[0070] 2. The present invention can lighten the color of the biopolymer material, reduce the yellowness, and increase the transparency without adding auxiliary agents to reduce the color. While reducing the introduction of auxiliary agents, the processability of the material itself is maintained unaffected, and the crystallization performance and melt mass flow rate (MFR) remain unchanged.

[0071] The present invention has been described in detail above, but the above embodiments are merely illustrative in nature and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the above prior art or invention summary or the following examples.

[0072] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] FIG1 shows a schematic structural diagram of an apparatus for reducing the yellowness of biopolymer materials according to an embodiment of the present invention;

[0074] Illustration: 10-box; 11-outer wall layer; 12-inner wall layer; 13-interlayer; 20-light source; 30-drying device; 40-material equalizing device.

[0075] FIG2 shows a graph showing the results of irradiating BP350 pellets with light of different wavelengths.

[0076] FIG3 shows a graph showing the results of irradiating BP350 pellets with light of different intensities.

[0077] FIG4 shows a graph showing the results of irradiating BP330 pellets with light of different intensities.

[0078] FIG5 shows the results of irradiation experiments in different light-proof test boxes and at different distances.

[0079] FIG6 shows the change in melt index of BP350 pellets before and after irradiation.

[0080] FIG7 shows the change in melt index of BP330 pellets before and after irradiation.

[0081] FIG8 shows the results of light irradiation of PHA pellets from different sources under the same lighting conditions. DETAILED DESCRIPTION

[0082] The present invention will be further described below with reference to the examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed in the present invention.

[0083] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, and methods in the art.

[0084] raw material:

[0085] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP330 pellets, Beijing Lanjing Microbiology Technology Co., Ltd., 3HB (3-hydroxybutyrate unit) content 94%, weight-average molecular weight ≥ 500,000.

[0086] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP350 pellets, Beijing Lanjing Microbiology Technology Co., Ltd., 3HB (3-hydroxybutyrate unit) content 89%, weight-average molecular weight ≥ 500,000.

[0087] Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), product number: Y1000P, Ningbo Tianan Biological Co., Ltd.

[0088] Poly(3-hydroxybutyrate) (PHB), product number: Y3000P, Ningbo Tianan Biological Co., Ltd.

[0089] Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), Product No.: CJ PHACT, CJ BIO.

[0090] Granular material performance evaluation:

[0091] Yellowness index (Yellowness index, YI):

[0092] The test standard is GB / T 39822-2021, and the test equipment is a colorimeter, which measures the yellowness index (YI). A lower yellowness index indicates a lower degree of yellowness.

[0093] Weight average molecular weight:

[0094] The measurement was performed using a gel permeation chromatograph (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solution and in terms of polystyrene. As the column for the gel permeation chromatograph, any column suitable for measuring the weight average molecular weight may be used.

[0095] Melt flow rate (melt index):

[0096] The test standard is ISO1133-1:2011, and the test equipment is a melt flow rate tester. The melt flow rate of the pellets is measured under the conditions of 165°C and 5kg; the unit of melt flow rate is g / 10min.

[0097] Crystallization temperature (Tc) and crystallization enthalpy (ΔHc)

[0098] The measurement standard is GB / T 19466.3-2004. A differential scanning calorimeter (DSC25, manufactured by TA Instruments) is used. 2-10 mg of the polyhydroxyalkanoate molded product is measured and the temperature is raised from -50°C to 180°C at a heating rate of 10°C / min. The Tc and ΔHc are obtained from the DSC curve.

[0099] Experimental Example 1: Light irradiation experiment with different wavelengths

[0100] Experimental process: A constant temperature and humidity stainless steel light-proof test chamber was built, and BP350 pellets were spread on the bottom layer of the light-proof test chamber. A light source was set on the top of the test chamber. A diode (LED lamp) was used as the light source, and the wavelength was adjusted with a filter. Irradiation tests were carried out under different wavelengths (405nm, 510nm, 550nm, 610nm, 710nm, and 750nm). The vertical distance between the LED lamp and the BP350 pellets was 50cm, the irradiation power was 1000W, and the irradiation time was 2 hours. The yellowness of the pellets was tested before and after irradiation.

[0101] The results are shown in Figure 2. The dotted line represents the initial yellowness of the pellets, which is 51.7. As can be seen from the figure, at a light intensity of 1000W, the yellowness values ​​begin to decrease after short-term irradiation through different wavelength filters.

[0102] This embodiment also uses ultraviolet light of different wavelengths (UVA, UVB, UVC) for a certain period of time (15 minutes to 120 minutes). The yellowness of the pellets after irradiation is not significantly reduced. In contrast, when the pellets are irradiated with light of different wavelengths within the light source range outside the ultraviolet light band, the yellowness of the pellets has a significant downward trend.

[0103] Experimental Example 2: Light irradiation experiments with different intensities

[0104] Test process: BP350 pellets were spread on the bottom layer of a constant temperature and humidity stainless steel light-proof test box, and a light source was set on the top of the test box. Irradiation tests were carried out under the same LED light source (natural light, wavelength range 410-710nm) and different intensities (100W, 200W, 300W, 1000W, 2000W, 4000W, 6000W). The vertical distance between the LED lamp and the BP350 pellets was 50cm. The yellowness of the pellets was tested before irradiation and after different irradiation times.

[0105] The results are shown in Figure 3. As can be seen from the figure, at different irradiation intensities and for the same irradiation time, the yellowness of the BP350 pellets decreases with increasing irradiation intensity. Yellowness values ​​also show a decreasing trend with increasing irradiation time, with a 19.8% decrease at 1000W for 2 hours. The effects of 2000W, 4000W, and 6000W lamps on yellowness are essentially the same, with yellowness decreasing by approximately 25% within 120 minutes. This shows that irradiating pellets at different intensities, over the same time period, can effectively reduce yellowness.

[0106] Another PHA raw material, BP330 pellets, was irradiated using the same method at 1000W and 2000W intensities, with other conditions identical to those for BP350 pellets. The results are shown in Figure 4. As can be seen, the yellowness of BP330 pellets decreased with increasing irradiation time, with a decrease of approximately 28% within 120 minutes.

[0107] Experimental Example 3: Irradiation experiments in different light-proof test boxes and at different distances

[0108] A light-proof test box of different materials (wood, metal) was built, and BP350 pellets were spread on the bottom layer of the light-proof test box. A light source was set on the top of the test box. The light source used was an LED light source (natural light, wavelength range 410-710 nm). The vertical distances between the LED lamp and the BP350 pellets were 30 cm and 50 cm respectively. Irradiation tests were carried out at an intensity of 1000 W to test the yellowness of the pellets before irradiation and after different irradiation times.

[0109] The results are shown in Figure 5. As can be seen from the figure, the yellowness of BP350 pellets decreased with irradiation time in both the wooden and metal light-shielding test boxes. Under the same conditions, the decrease was lower in the wooden box, and under the same conditions, the closer the stainless steel box was, the better the yellowness reduction effect.

[0110] Experimental Example 4: Pellet Performance Test Before and After Irradiation

[0111] 1. Crystallization properties (Tc and ΔHc) experiments before and after irradiation

[0112] The BP350 pellets were spread on the bottom layer of a constant temperature and humidity stainless steel light-proof test box. A light source was set on the top of the test box. The irradiation test was carried out under an LED light source (natural light, wavelength range 410-710 nm) with an intensity of 1000 W. The vertical distance between the LED lamp and the BP350 pellets was 50 cm. The crystallization properties of the pellets were tested before irradiation and after different irradiation times.

[0113] The results are shown in Table 1.

[0114] Table 1

[0115] It can be seen that when the BP350 pellets are irradiated at a light intensity of 1000 W, the crystallization properties of the BP350 pellets remain basically unchanged as the irradiation time increases.

[0116] 2. Melt index test before and after irradiation

[0117] BP350 pellets were spread on the bottom layer of a constant temperature and humidity stainless steel light-proof test box. A light source was set on the top of the test box. Irradiation tests were carried out under LED light source (natural light, wavelength range 410-710 nm) at different intensities (100W, 200W, 300W, 1000W, 2000W, 4000W). The vertical distance between the LED lamp and the BP350 pellets was 50 cm. The melt index of the pellets was tested before irradiation and after different irradiation times.

[0118] The results are shown in Figure 6. As can be seen, the melt index of the pellets remained essentially unchanged after exposure to different irradiation intensities, ranging from 100W to 2000W, for varying durations. The overall melt index variation remained within a range of ±0.5 with increasing irradiation time. Although the melt index of pellets exposed to 300W and 4000W fluctuated significantly, after 120 minutes of irradiation, it remained within ±0.5 relative to zero. Therefore, it can be concluded that the melt index of the pellets treated with light remains essentially unchanged.

[0119] BP330 pellets were spread on the bottom layer of a constant temperature and humidity stainless steel light-proof test box. A light source was set on the top of the test box. A diode (LED lamp) was used as the light source. The wavelength was adjusted with a filter. Irradiation tests were carried out under non-irradiation, full irradiation, and different wavelengths (405nm, 510nm, 550nm, 610nm, 710nm, 750nm). The vertical distance between the LED lamp and the BP330 pellets was 50cm, the irradiation power was 1000W, and the irradiation time was 2 hours. The melt index of the pellets before and after irradiation was tested.

[0120] The results are shown in FIG7 . It can be seen from the figure that the melt index of BP330 pellets remains basically unchanged after irradiation treatment with 1000W light intensity and different wavelengths.

[0121] It can be seen that the other properties of the pellets after light irradiation remain unchanged, but the yellowness is reduced and the transparency is increased. This method can effectively reduce the yellowness of the pellets and expand the application scenarios of the pellets.

[0122] Experimental Example 5: Light irradiation experiment of PHA from different sources

[0123] Light irradiation experiments were carried out on PHB (Y3000P, Ningbo Tianan Biological Co., Ltd.), PHBV (Y1000P, Ningbo Tianan Biological Co., Ltd.), and P34HB (CJ PHACT, CJ BIO) pellets. The irradiation tests were carried out under the same lighting conditions. The vertical distance between the LED lamp and the PHB, PHBV, and P34HB pellets was 50 cm, the irradiation power was 1000 W, and the irradiation time was 2 hours. The yellowness of the pellets before and after irradiation was tested at intervals of 15 minutes.

[0124] Specific experimental results are shown in Figure 8. After 120 minutes of irradiation, the yellowness values ​​of PHB, PHBV, and P34HB pellets all decreased significantly, indicating that the yellowness values ​​of PHAs from different sources decreased after irradiation.

[0125] Example

[0126] 1. Manufacture of equipment for reducing the yellowness of biopolymer materials:

[0127] A device for reducing the yellowness of a polyhydroxyalkanoate molded body, as shown in FIG1 , includes a housing 10 and a light source 20. The housing 10 is cylindrical and includes an outer wall layer 11 and an inner wall layer 12. The inner wall layer 12 forms a receiving cavity for receiving the polyhydroxyalkanoate molded body. An interlayer 13 is provided between the outer wall layer 11 and the inner wall layer 12. The light source 20 is disposed within the interlayer 13 for light irradiation treatment of the polyhydroxyalkanoate molded body placed in the receiving cavity. The device is also equipped with a feeding device and a discharging device, each of which is in communication with the receiving cavity.

[0128] The device further comprises: a drying device 30 (hot air device) located inside the box body, used to dry the polyhydroxyalkanoate molded body; and a material distribution device 40 (stirring device) provided in the accommodating cavity, used to stir the polyhydroxyalkanoate molded body;

[0129] In this example, the outer wall layer is set to a fully light-shielding structure, using a stainless steel outer wall; the inner wall layer is set to a fully light-transmitting structure, using a glass inner wall;

[0130] In this example, the light source is 5 groups of LED lights, each group has 4 LED bulbs, and each group of bulbs is arranged in parallel along the axial direction in the interlayer. The vertical distance between each group of light sources and the inner wall layer is 50 cm.

[0131] 2. Use the above equipment to process the polyhydroxyalkanoate molded body:

[0132] Polyhydroxyalkanoate pellets are used as the material to be treated, an LED lamp is installed in the interlayer, and the distance from the inner wall is adjusted. When in use, the crystallized polyhydroxyalkanoate pellets are fed into the containing cavity through the feeding device, the light source, hot air and stirring are turned on, and the pellets are dried while being rotated and irradiated (the pellets will stick to the wall at this time). After irradiation for 30 minutes, the pellets are output through the discharging device of the equipment. The yellowness of the pellets after output is reduced and they can be used further.

[0133] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced with equivalents, without departing from the spirit and substance of the present invention; and such modifications or replacements remain within the scope of the present invention.

Claims

1. A method for reducing the yellowness of polyhydroxyalkanoates, wherein the polyhydroxyalkanoates are synthesized by microorganisms, It is characterized in that The method comprises the step of treating the polyhydroxyalkanoate by light irradiation.

2. The method according to claim 1, It is characterized in that The light source for the light irradiation treatment is a light source that emits light of a single wavelength or mixed wavelengths; wherein the light source is selected from a light source that emits light of one or more of the following: visible light with a wavelength of 380nm to 780nm, near infrared light with a wavelength of 780nm to 2500nm, and near infrared light with a wavelength of 2500nm to 1×10 6 nm infrared light.

3. The method according to claim 1, It is characterized in that The power of the light irradiation treatment is 0.1W to 20000W; and / or The light irradiation treatment time is 1 min to 1000 min; and / or The vertical distance between the light source and the polyhydroxyalkanoate during the light irradiation treatment is 1 cm to 100 cm.

4. The method according to claim 2, It is characterized in that The light source for the light irradiation treatment is a light source that emits visible light, and the light source is specifically selected from: a light source that emits light of any wavelength between 380nm and 780nm, or a light source that emits light of any wavelength band between 380nm and 780nm.

5. The method according to claim 3, It is characterized in that The power of the light irradiation treatment is 100W to 6000W; and / or The light irradiation treatment time is 15min to 120min; and / or The vertical distance between the light source and the polyhydroxyalkanoate during the light irradiation treatment is 15 cm to 80 cm.

6. A method for preparing a shaped body of polyhydroxyalkanoate, It is characterized in that The method comprises the step of implementing the method for reducing the yellowness of polyhydroxyalkanoate according to any one of claims 1 to 5 after the polyhydroxyalkanoate is crystallized.

7. A molded body of a polyhydroxyalkanoate, It is characterized in that The polyhydroxyalkanoate molded body is prepared by the method for preparing a polyhydroxyalkanoate molded body according to claim 6, wherein the yellowness index of the polyhydroxyalkanoate molded body is lower than 51.

7.

8. A device for reducing the yellowness of polyhydroxyalkanoates, It is characterized in that The device includes a box body and a light source. The box body includes an outer wall layer and an inner wall layer. The inner wall layer forms a containing cavity for containing polyhydroxyalkanoates. An interlayer is provided between the outer wall layer and the inner wall layer. The light source is arranged in the interlayer for light irradiation treatment of the polyhydroxyalkanoates placed in the containing cavity.

9. The device according to claim 8, It is characterized in that The device also includes: A drying device, the drying device is located inside the housing and is used to dry polyhydroxyalkanoates; and / or A material balancing device is arranged in the containing chamber and is used for stirring the polyhydroxyalkanoate.

10. The device according to claim 8, It is characterized in that The outer wall layer is configured as a light-shielding structure; and the inner wall layer is configured as a light-transmitting structure.

11. The device according to claim 10, It is characterized in that The inner wall layer is configured to be completely light-transmissive, or configured to be partially light-transmissive, and the light-transmissive portion is made of a light-transmissive material.

12. The device according to any one of claims 8 to 11, It is characterized in that At least one group of light sources is arranged in the interlayer along the axial direction, and the vertical distance between each group of light sources and the inner wall layer is 1 cm to 100 cm.

13. The device according to claim 12, It is characterized in that The light source is a light source that emits light of a single wavelength or mixed wavelengths; wherein the light source is selected from a light source that emits light of one or more of the following: visible light with a wavelength of 380nm to 780nm, near-infrared light with a wavelength of 780nm to 2500nm, and near-infrared light with a wavelength of 2500nm to 1×10 6 nm infrared light.

14. The device according to claim 13, It is characterized in that The light source includes one or more of the following lamp sources: metal halide lamp, tungsten lamp, xenon lamp and LED lamp.

15. The device according to claim 14, It is characterized in that The power of the light source is 0.1W-20000W.

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