WO2024060636A1 - Polyhydroxyalkanoate composition containing ester nucleating agent, polyhydroxyalkanoate molded body, and preparation method therefor - Google Patents

Abstract

Provided are a polyhydroxyalkanoate composition containing an ester nucleating agent, a polyhydroxyalkanoate molded body, and a preparation method therefor. The polyhydroxyalkanoate composition comprises polyhydroxyalkanoate and a nucleating agent. The nucleating agent is an ester compound, including fatty acid esters, especially one or more of fatty acid esters with the carbon atom number of more than 5. The nucleating agent in the polyhydroxyalkanoate composition has high nucleation efficiency, and the defects of a low crystallization speed, low processing efficiency and the like of polyhydroxyalkanoate in the process of preparing various molded bodies by means of thermoplastic processing can be overcome. The obtained polyhydroxyalkanoate molded body has the advantages of high transparency and low haze.

Description

Polyhydroxyalkanoate composition containing ester nucleating agent, polyhydroxyalkanoate molded body and preparation method thereof Technical Field

The present invention relates to the technical field of polyhydroxyalkanoate materials, and in particular to a polyhydroxyalkanoate composition containing an ester nucleating agent, a polyhydroxyalkanoate molded body and a preparation method thereof.

Background technique

Polyhydroxyalkanoates (PHAs or PHAs) are intracellular polyhydroxyalkanoates synthesized by many microorganisms and are natural polymer biomaterials. Most monomers of polyhydroxyalkanoates are 3-hydroxy fatty acids with a chain length of 3 to 14 carbon atoms, and their side chains are highly variable saturated or unsaturated, linear or branched, aliphatic or aromatic groups. The diversity of the composition structure brings about the diversity of performance, which gives it obvious advantages in application. At the same time, polyhydroxyalkanoates are a bio-based polymer that is biodegradable in the marine environment. They can solve the environmental problems caused by waste plastics and have excellent biocompatibility and mechanical properties. Therefore, they can be processed into various molded bodies, such as films, straws, tableware, etc.

Simple polyhydroxyalkanoates have shortcomings such as slow crystallization rate, low crystallinity, and low processing efficiency during thermoplastic processing to prepare various molded bodies. The existing technology often increases the crystallization rate of PHAs by adding nucleating agents and other additives.

In the prior art, nucleating agents are usually mainly inorganic substances or metal salts. Although they can improve the crystallization speed and crystallinity of molded bodies prepared by traditional polyhydroxyalkanoates to a certain extent, the degree of improvement is limited; more importantly, It will cause the molded body to be colored, reduce its transparency and affect its application.

In view of this, the present invention is proposed.

Contents of the invention

One of the objects of the present invention is to provide a polyhydroxyalkanoate composition containing an ester nucleating agent.

The second object of the present invention is to provide a polyhydroxyalkanoate molded body prepared from the above-mentioned polyhydroxyalkanoate composition.

The third object of the present invention is to provide a method for preparing the above-mentioned polyhydroxyalkanoate molded body.

In order to achieve the above objects of the present invention, the following technical solutions are adopted:

In a first aspect, the present invention provides a polyhydroxyalkanoate composition, comprising:

polyhydroxyalkanoates, and

A nucleating agent, wherein the nucleating agent includes at least one ester compound.

Exemplary components included in the polyhydroxyalkanoate composition will be described in detail below.

Polyhydroxyalkanoate

The polyhydroxyalkanoate may be a single polymer or a combination of two or more polymers. The polymerized monomers of each polymer may be one or more types (ie, the structural units in the polymer may be one or more types).

Specifically, any polymer contains structural units represented by the following general formula (1):

Among them, R ₁ is an alkyl group represented by C _p H _2p+1 , and p is an integer of 1 to 15, preferably an integer of 1 to 10, more preferably an integer of 1 to 8; examples of R ₁ include: Methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl and other linear or branched alkyl groups;

n is 1, 2 or 3.

When n=1, the general formula (1) represents a 3-hydroxyalkanoate structural unit; when n=2, the general formula (1) represents a 4-hydroxyalkanoate structural unit; when n=3, the general formula (1) represents a 5-hydroxyalkanoate structural unit. Among them, the 3-hydroxyalkanoate structural unit and the 4-hydroxyalkanoate structural unit are more common, such as the 3-hydroxybutyrate structural unit (hereinafter sometimes referred to as 3HB) and the 4-hydroxybutyrate structural unit (hereinafter sometimes referred to as 4HB).

Preferably, the polyhydroxyalkanoate includes at least one poly(3-hydroxyalkanoate).

Furthermore, 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.

Further, the other hydroxyalkanoate structural units include: 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxycaproate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3 -One or more of hydroxynonanoate, 3-hydroxydecanoate, 3-hydroxyundecanoate or 4-hydroxybutyrate; preferably 3-hydroxycaproate.

Briefly, specific examples of poly(3-hydroxyalkanoate) include poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxypropionate). , poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV, hereinafter referred to as PHBV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3 -hydroxycaproate) (hereinafter referred to as P3HB3HV3HH), poly(3-hydroxybutyrate-co-3-hydroxycaproate) (referred to as: P3HB3HH, hereinafter referred to as PHBH), poly(3-hydroxybutyrate-co- -3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (hereinafter referred to as PHBO), poly(3-hydroxybutyrate-co-3-hydroxynonanoate) ), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), poly(3-hydroxybutyrate) -co-4-hydroxybutyrate) (abbreviation: P3HB4HB, hereinafter referred to as P34HB), etc. special From the viewpoint of processability, mechanical properties, etc., poly(3-hydroxybutyrate-co-3-hydroxycaproate) is preferred.

The production method of the polyhydroxyalkanoate is not particularly limited, and may be a production method using chemical synthesis or a production method using microorganisms. The polyhydroxyalkanoate of the present invention is particularly preferably a polyhydroxyalkanoate produced by microorganisms. In the polyhydroxyalkanoate produced by microorganisms, all 3-hydroxyalkanoate structural units are (R) 3-hydroxyalkanoates. Contains in the form of acid ester structural units.

In some embodiments, in the copolymer of 3-hydroxybutyrate structural units and other hydroxyalkanoate structural units, the average content ratio of the 3-hydroxybutyrate structural units to other hydroxyalkanoate structural units is 50/50~99/1 (mol%/mol%); preferably 80/20~94/6 (mol%/mol%); when the polyhydroxyalkanoate raw material is a mixture of two or more polyhydroxyalkanoates In the case of , the average content ratio refers to the molar ratio of each monomer contained in the entire mixture.

In some embodiments, the weight average molecular weight of the polyhydroxyalkanoate is 100,000 to 1,000,000; preferably 200,000 to 900,000; further preferably 300,000 to 800,000. When the weight average molecular weight is less than 100,000, the mechanical properties of the obtained polyhydroxyalkanoate molded article tend to be reduced. On the other hand, when the weight average molecular weight exceeds 1 million, the load on machinery during melt processing tends to increase and productivity tends to decrease.

Nucleating agent

The nucleating agent of the present invention includes at least one ester compound.

Ester compounds are small molecule compounds with ester bonds in their molecules, that is, small molecule compounds that contain -C(=O)O- groups in their structures.

Preferably, the ester compound is a fatty acid ester compound, that is, in R-COO-R', R is a C5-C30 alkyl group (that is, R-COOH used to synthesize R-COO-R' is a fatty acid), and R' is a C1-C16 alkyl group.

Further, the nucleating agent is at least one fatty acid ester with a carbon number greater than 5; preferably, the nucleating agent is at least one fatty acid ester with a carbon number greater than 12; more preferably, the nucleating agent is The nucleating agent is at least one fatty acid ester with a carbon number greater than 18. The upper limit of the number of carbon atoms is not particularly limited, but may be, for example, 45 or less, 40 or less, or 35 or less.

The present invention has found that ester compounds, as nucleating agents, including fatty acid ester compounds, such as fatty acid esters with more than 5 carbon atoms, are used as nucleating agents in the preparation of polyhydroxyalkanoate molded bodies, which can significantly improve the performance of polyhydroxyalkanoates. The crystallization speed and crystallinity of the acid ester when preparing the molded body have the advantages of high nucleation efficiency and simpler processing. At the same time, the prepared polyhydroxyalkanoate molded body has the advantage of high transparency, so it has more A wide range of application scenarios.

From the perspective of saturation, the nucleating agent is preferably a saturated fatty acid ester.

Preferably, the nucleating agent is selected from the group consisting of butyl dodecanoate (also known as butyl dodecanoate and butyl laurate), ethyl pentadecanoate (also known as ethyl pentadecanoate), and hexadecanoic acid ethyl. Methyl hexadecanoate (also known as methyl hexadecanoate, methyl palmitate), ethyl hexadecanoate (Also known as ethyl hexadecanoate, ethyl palmitate), 2-ethylhexyl hexadecanoate (also known as 2-ethylhexyl palmitate, octyl palmitate), cetyl palmitate (or Called cetyl palmitate, palmityl palmitate, cetyl palmitate), methyl octadecanoate (or methyl stearate), methyl nonadecanate, methyl eicosate (or methyl octadecanoate) Methyl arachidate), ethyl behenate (or ethyl behenate), methyl behenate (or methyl behenate), ethyl behenate (or ethyl behenate) ), methyl lignocerate (or methyl lignocerate), ethyl lignocerate (or ethyl lignocerate), methyl triacontanoate (or methyl melisate, peak wax At least one of acid methyl ester).

Further preferably, the nucleating agent is selected from the group consisting of ethyl hexadecanoate, 2-ethylhexyl hexadecanoate, cetyl hexadecanoate, methyl nonadecanate, methyl eicosate, and eicosate. At least one of ethyl ester, methyl behenate, ethyl behenate, methyl behenate, ethyl behenate, and methyl triaconate.

In some embodiments, the added amount of the nucleating agent is 0.01%-20% of the mass of the polyhydroxyalkanoate; preferably 0.1%-5%; typically without limitation, it can be 0.1%, 1%, 2%, 2.5%, 3%, 4%, 5%.

Studies have shown that by controlling the addition ratio of the nucleating agent within this preferred range, the crystallization effect can be better, and the prepared molded body can have better processability.

The polyhydroxyalkanoate composition of the present invention can be prepared using conventional techniques and conventional equipment known in the art, and can be directly mixed in a mixing equipment to obtain a powder, for example, using a high-speed mixer to blend at room temperature.

In addition, without inhibiting the effect of the present invention, the polyhydroxyalkanoate composition of the present invention may also contain additives and other auxiliaries according to the production needs of the product. The additives may include plasticizers, cross-linking agents, chain extenders, lubricants and other organic or inorganic materials. Organic or inorganic materials may be used alone or in combination of two or more. Moreover, the addition amount of the additive can also be adjusted according to production needs, and the present invention has no particular limitation on this.

In a second aspect, the present invention also provides a polyhydroxyalkanoate molded body prepared from the polyhydroxyalkanoate composition according to the present invention.

The polyhydroxyalkanoate molded body obtained by the present invention has the advantages of high transparency and good mechanical properties, and therefore has a wider range of application scenarios.

The polyhydroxyalkanoate molded body of the present invention can include various forms, such as films, fibers, straws, plates, pellets, paper plastics, sheets, etc.

In a third aspect, the present invention also provides a method for preparing the polyhydroxyalkanoate molded body, which includes: molding with the polyhydroxyalkanoate composition according to the present invention.

The polyhydroxyalkanoate molded body of the present invention can be prepared by various thermal processing molding methods such as extrusion molding, injection molding, calendering molding, tape molding, blow molding, biaxial stretching molding, etc., or can also be prepared by solution pouring It is prepared by other non-thermal processing molding methods. Preferably it is produced by hot working forming methods.

The thermal processing molding preparation method of the polyhydroxyalkanoate molded body provided by the invention includes the following steps: The clear polyhydroxyalkanoate composition is heated and melted at a temperature higher than the melting temperature of the polyhydroxyalkanoate; extended at a temperature between the glass transition temperature and the cold crystallization temperature of the polyhydroxyalkanoate; The polyhydroxyalkanoate is cooled and molded at a temperature between its glass transition temperature and melting temperature.

Furthermore, when the molded body is pellets, it can be made with granulation equipment: parallel co-rotating twin-screw extruders, parallel counter-rotating twin-screw extruders, and conical twin-screw extruders with different aspect ratios can be used. As well as extrusion granulation equipment commonly used in this field such as single-screw extruders; place the composition in the lower hopper of the twin-screw extruder or a weight loss scale; set the temperature of the extrusion granulation equipment within the range of 50°C to 180°C. The main engine speed is 50-500r/min, and the feeding amount or production capacity can be adjusted according to the actual production status; subsequent cutting can be performed such as air-cooled strand cutting, water bath strand cutting, grinding and cutting, water ring cutting and underwater pelletizing. The granulation method is carried out, and the water bath conditions of 25°C to 65°C are maintained during the production and processing; the prepared particles are dried in a blast drying oven to eliminate the impact of moisture on the properties of the particles, and at the same time, the particles are completely crystallized.

Further, when the molded body is a film, the preparation method includes the following steps: preparing the polyhydroxyalkanoate composition according to the present invention at a temperature 10°C to 60°C higher than the melting temperature of the polyhydroxyalkanoate ester (No. Heating and melting at one temperature); extending more than 150% at a temperature (second temperature) between the glass transition temperature of the polyhydroxyalkanoate and the cold crystallization temperature; at the glass transition temperature of the polyhydroxyalkanoate Cooling and molding at a temperature between the melting temperature and the melting temperature (third temperature).

During the processing of polyhydroxyalkanoate molded products, adhesion easily occurs, resulting in a decrease in the quality of the molded products. Therefore, in the prior art, it is well known to those skilled in the art that the adhesion of molded products can be reduced by extending the processing time, but this greatly reduces the processing efficiency.

The inventor found in the research that, taking into account the uniformity of mixing, when preparing the polyhydroxyalkanoate molded body, the first temperature is not particularly limited, and is preferably above the melting temperature of the polyhydroxyalkanoate, and more preferably It is 10°C or higher of the melting temperature of the polyhydroxyalkanoate, and more preferably 20°C or higher of the melting temperature of the polyhydroxyalkanoate. In addition, because the second temperature is too low or too high, the maximum stretch ratio of the polyhydroxyalkanoate molded body will be reduced and the transparency will be reduced. Therefore, preferably, when preparing the polyhydroxyalkanoate film molded body, cooling from the first temperature to the second temperature is a primary molding process, and secondary molding is performed by stretching at the second temperature. The second temperature is between the glass transition temperature and the cold crystallization temperature of the polyhydroxyalkanoate. Preferably, the second temperature is between 20°C and the cold crystallization temperature of the polyhydroxyalkanoate; further preferably, it is between 30°C and the polyhydroxyalkanoate cold crystallization temperature. ester cold crystallization temperature. During the research process, it was found that within the above preferred range, typically and without limitation, the second temperature may be, for example, 40°C, 45°C, 50°C, 53°C, 55°C, or 60°C. Finally, the crystallization is carried out at a third temperature, so that the polyhydroxyalkanoate molded body is better formed and has high stability and physical properties. Preferably, the third temperature is between the glass transition temperature and the melting temperature of the polyhydroxyalkanoate. Typically and without limitation, the third temperature may be, for example, 40°C, 45°C, 50°C, 55°C, or 60°C.

This study found that the smaller the crystallization enthalpy, the better the processability of the molded body at the second temperature (elongation molding). Good, it is more conducive to secondary molding, that is, the elongation at the second temperature can be higher. Considering the ease of processing and molding at the second temperature (elongation molding), the crystallization enthalpy is easier to process when it is 12.5 J/g or less, further 7.5 J/g or less, and further 3.5 J/g or less, it is easier to process. . Considering that the smaller the half-peak width data of secondary heating cold crystallization is, the molded body will be easier to crystallize and harden during the processing process, which is more conducive to processing and molding. Considering the improvement of processing efficiency, for the cold crystallization half-peak width, it is easier to improve the processing efficiency when it is below 15°C. It is easier to improve the processing efficiency when it is further selected to be below 10°C, and further below 8°C.

The transparency of the polyhydroxyalkanoate shaped bodies prepared from the polyhydroxyalkanoate composition according to the invention is greatly improved. In this field, the greater the light transmittance and the smaller the haze, the better the transparency of the film sample. The light transmittance of the molded article obtained by the present invention is 80% or more and the haze is 50% or less. In particular, in the examples, a fully biodegradable resin film product with a light transmittance of 90% or more and a haze of 40% or less and a total light transmittance of 90% or more and a haze of 30% or less was obtained.

beneficial effects

1. The nucleating agent for polyhydroxyalkanoate provided by the present invention has high nucleation efficiency, and can improve the shortcomings of polyhydroxyalkanoate in the process of preparing various molded bodies by thermoplastic processing, such as slow crystallization speed and low processing efficiency.

2. Compared with other existing nucleating agents, various types of polyhydroxyalkanoate molded bodies prepared using the nucleating agent provided by the present invention have higher transparency and will not affect the color of various types of molded bodies.

3. The molded body provided by the present invention is subjected to secondary processing and molding at a second temperature lower than the melting temperature, and still maintains good transparency after the secondary processing and molding.

The present invention has been described in detail above, but the above-mentioned embodiments are only illustrative in nature and are not intended to limit the present invention. Furthermore, there is no intention to be bound by any theory presented in the preceding prior art or summary of the invention or described in the following examples.

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values 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. These values The scope shall be deemed to be specifically disclosed herein.

Detailed ways

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 by the present invention.

Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are all conventional raw materials, reagents, and methods in this field.

All raw materials used in the following examples and comparative examples are commercially available unless otherwise specified.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP330, Beijing Blue Crystal Microbial Technology Co., Ltd., the content of 3HB (3-hydroxybutyrate unit) is 94%, The weight average molecular weight is about 600,000-800,000.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP350, Beijing Blue Crystal Microbial Technology Co., Ltd., the content of 3HB (3-hydroxybutyrate unit) is 89%, The weight average molecular weight is about 600,000-800,000.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Beijing Blue Crystal Microbial Technology Co., Ltd., has a weight average molecular weight of about 600,000-800,000.

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), Beijing Blue Crystal Microbial Technology Co., Ltd., weight average molecular weight is about 600,000-800,000.

Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHBO), Beijing Blue Crystal Microbial Technology Co., Ltd., with a weight average molecular weight of about 600,000-800,000.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate (P3HB3HV3HH), Beijing Blue Crystal Microbiology Technology Co., Ltd., with a weight average molecular weight of about 600,000-800,000.

Preparation of particle moldings in Examples 1 to 15 and Comparative Examples 1 to 4

Preparation of particle moldings: Use the compositions provided in Examples 1-15 and Comparative Examples 1-4 in Tables 1 to 3 respectively, and extrusion and granulate them with a twin-screw extruder.

The specific steps are:

Step 1. Mixing: Place polyhydroxyalkanoate powder and nucleating agent in a high-speed mixer, mix at room temperature, mixing speed is 200r/min, mixing time is 5min; after mixing, mix Place it in the lower hopper of the twin-screw extruder (Nanjing Mianya Machinery JSH-65);

Step 2. Extrusion: Set the conditions of the extrusion granulation equipment. The host speed is 50-500r/min. The feeding amount or production capacity is adjusted according to the actual production status; when the melt temperature is about 165°C (first temperature) Under the conditions, extrusion is carried out;

Step 3. Granulation and cooling: Granulation is carried out by stretching and cutting in a water bath. The water bath temperature (granulation temperature) of each embodiment is shown in the table.

Preparation of film moldings in Examples 16 to 23 and Comparative Examples 5 to 8

In Examples 16-23, it is preferred that the molded bodies of some of the examples in Examples 1-15 are subjected to secondary processing to prepare films. Of course, it should be noted here that it is also possible to directly prepare films using the compositions of Examples 1-15, which should be within the protection scope of the present invention.

In Comparative Examples 5-7, the molded bodies of Comparative Examples 1-3 were respectively used for secondary processing to prepare films, and for Comparative Example 8, Example 7 was used for secondary processing to prepare films.

The specific steps are: use a molding machine (produced by Jiangsu Tianyuan Company) to mold the particle molded bodies of the Examples and Comparative Examples. Molding is carried out at one temperature (melt temperature) to prepare a molded product with a thickness of 200 μm, and then placed in water at a second temperature (extension temperature) by holding both ends of the molded film to extend at a certain rate, and finally placed at a third temperature (heating temperature) in an oven to prepare a film sample. The specific process parameters are shown in Table 4.

The preparation method of this film is the same as the core process of biaxially oriented film, so it can be compared to the biaxially oriented process.

In order to achieve an elongation >150%, considering the ease of processing and molding at the second temperature, resins with crystallization enthalpy below 12.5J/g can be selected, and resins below 7.5J/g can be selected, and further options can be selected. Resin at 3.5J/g and below. Taking into account improving processing efficiency, for cold crystallization half-peak width, resins below 15°C can be selected, resins below 10°C can be selected, and resins below 8°C can be selected.

<Performance evaluation of polyhydroxyalkanoate molded articles>

Thermoplastic processing difficulty:

○: Can be processed continuously and stably, and the granulation is stable;

△: Basically stable during thermoplastic processing, and the pelletizing state is average.

×: The extruder is unstable during extrusion and cannot be continuously pelletized.

Crystallinity:

Using a differential scanning calorimeter (model DSC25 manufactured by TA Instruments), measure 2-10 mg of the polyhydroxyalkanoate molded body, and obtain a DSC curve when the temperature rises from -50°C to 180°C at a temperature rise rate of 10°C/min. Further data such as glass transition temperature, melting temperature, melting peak area, and cold crystallization peak area in the DSC curve of the polyhydroxyalkanoate composition were obtained.

Crystallinity (%) = 100% × melting enthalpy/100% crystallization melting enthalpy;

Where, the 100% crystalline melting enthalpy is the theoretical enthalpy of 100% crystalline material. The greater the crystallinity, the higher the crystallinity of the molded body, which is more conducive to subsequent processing and molding.

Cooling crystallization enthalpy:

Using a differential scanning calorimeter (model DSC25 manufactured by TA Instruments), measure 2-10 mg of the polyhydroxyalkanoate molded body, and heat it from -50°C to 180°C at a temperature rise rate of 10°C/min. The cooling rate of min is from 180℃ to -50℃, a cooling curve is obtained, and the crystallization enthalpy is obtained from the cooling curve.

The smaller the crystallization enthalpy, the better the processability of the molded body at the second temperature, which is more conducive to secondary molding, that is, the higher the elongation at the secondary temperature can be.

Half-peak width of cold crystallization with secondary heating:

Using a differential scanning calorimeter (model DSC25 manufactured by TA Instrument), measure 2-10 mg of the polyhydroxyalkanoate molded body, raise the temperature from -50°C to 180°C at a temperature rise rate of 10°C/min, and maintain the temperature at 180°C. 3min, at 10℃/min The cooling rate is from 180°C to -50°C, and the temperature rise rate is 10°C/min from -50°C to 180°C for a second time to obtain the DSC curve of the second heating. When the DSC curve of the secondary temperature rise has a cold crystallization peak, the cold crystallization half-peak width is obtained from the secondary temperature rise curve.

The smaller the half-peak width data of secondary heating cold crystallization, the easier it is for the molded body to crystallize and harden during processing, which is more conducive to processing and molding.

Transmittance and Haze:

Use a Japanese SUGA haze meter HZ-V3 and D65 as the light source to measure the haze and light transmittance of a 5cm×5cm sample.

The greater the light transmittance and the smaller the haze, the better the transparency of the film sample.

The results are provided in Tables 1 to 4 below.

Table 1

Table 2


Note: - indicates no test results.

table 3

It can be seen from the above results that compared with the comparative example, the crystallinity of the particle molded body of this example is greater and the half-peak width data of the secondary heating cold crystallization is smaller, indicating that it is more conducive to processing and molding; that is, the nucleating agent provided by the invention is used The thermoplastic processing difficulty of the obtained particle molded body is relatively low, and it can be processed continuously and stably.

Add different contents of fatty acid ester nucleating agents, as in Examples 1 to 4; add different types of fatty acid esters, as in Examples 5 to 6; use a single PHA, such as BP350 in Examples 1 to 6, and BP350 in Example 13. BP330; or mixed PHA, as in Examples 7 to 12, 14 to 15; using a single fatty acid ester, as in Examples 1 to 6; or mixed fatty acid esters, as in Examples 7 to 15, to obtain the overall particle molded body The surface has high crystallinity and can be processed continuously and stably. Compared with the surface without adding nucleating agent, Proportion 1, and Comparative Examples 2, 3, and 4 in which existing nucleating agents such as calcium eicosate, boron nitride, and behenamide were added respectively. The overall nucleating effect of the fatty acid ester nucleating agent used in the present invention is better. It can be found that the crystallinity in Example 13 is the highest, and the half-peak width of the secondary heating cold crystallization cannot be measured. This may be related to the material itself. The raw material of Example 13 only contains PHBH-BP330, which itself is easy to crystallize, but its The crystallization enthalpy is large, which shows that the molded body has poor processability at the second temperature, which is not conducive to secondary molding.

Considering that it is easy to process and shape at the second temperature (stretching molding), when further preparing a thin film molding, a particle molding with a crystallization enthalpy below 12.5 J/g is used; further, a particle molding with a crystallization enthalpy below 7.5 J/g is used, and further, a particle molding with a crystallization enthalpy below 3.5 J/g is used.

Considering that the smaller the half-peak width data of secondary heating cold crystallization is, the molded body will be easier to crystallize and harden during the processing process, which is more conducive to processing and molding. Therefore, when further preparing a film molded body, in order to further improve the processing efficiency, a cold crystallized particle molded body with a half-peak width of 15°C or less can be used. Furthermore, a particle molded body having a cold crystallization half-peak width of 10° C. or less can be used. Furthermore, a cold crystallized particle molded product having a half-peak width of 8°C or less can be used.

Based on this, the present invention further selects the particle moldings in Examples 1, 2, 4, 6, and 11 to further prepare film moldings, and in order to expand the scope of application, the particle molding in Example 13 is selected. In order to further explore the relationship between the stretching ratios, Example 7 is also selected as Comparative Example 8 without stretching, and Comparative Examples 1, 2, and 3 are respectively selected as Comparative Examples 5, 6, and 7. The specific parameters of the film moldings are shown in Table 4.

Table 4

It can be seen from the above results that the thermoplastic processing difficulty of the molded film prepared by using the composition of the nucleating agent and polyhydroxyalkanoate of the present invention is relatively low, can be continuously and stably processed into the film, and the quality of the molded body is particularly transparent. Sex is better. That is, compared with existing nucleating agents, the fatty acid ester can obtain a molded body with high light transmittance, low haze, and good transparency. The light transmittance of the molded body obtained by the present invention is more than 80%, and the haze is less than 50%. In particular, the total light transmittance is more than 90%, the haze is less than 40%, and the total light transmittance is 90%. Above, fully biodegradable resin film products with a haze of less than 30%.

Using different process parameters, such as Examples 16-18, and different raw materials, such as Examples 19-23, the properties of the molded film are different, but the overall transparency is good. In addition, Comparative Example 8 uses the raw materials of Example 7 to prepare a film at an elongation of 100%, that is, without stretching. The transparency of the film is significantly lower than that of Examples 16-23, and the haze is higher than that of Examples 16-23; in addition Examples 16-18 adopt different elongations. It can be seen that when the molded body is a film, it is preferable to conduct more than 150% at a temperature (second temperature) between the glass transition temperature and the cold crystallization temperature of the polyhydroxyalkanoate. elongation, and the higher the elongation, the greater the transparency of the prepared shaped body.

The above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that the technical solutions described in the foregoing embodiments can be modified without departing from the spirit and essence of the present invention. Modifications, or equivalent substitutions of some or all of the technical features; and these modifications or substitutions are still within the scope of the present invention.

Claims (10)

1. A polyhydroxyalkanoate composition containing an ester nucleating agent, characterized in that it comprises:

   polyhydroxyalkanoates, and

   A nucleating agent, wherein the nucleating agent includes at least one ester compound.
2. The polyhydroxyalkanoate composition according to claim 1, wherein the nucleating agent is added in an amount of 0.1% to 5% of the mass of the polyhydroxyalkanoate.
3. The polyhydroxyalkanoate composition according to claim 2, wherein the nucleating agent is at least one saturated fatty acid ester with a carbon number greater than 5.
4. The polyhydroxyalkanoate composition according to claim 3, wherein the nucleating agent is selected from the group consisting of butyl dodecanoate, ethyl pentadecanoate, methyl hexadecanoate, and ethyl hexadecanoate. , 2-ethylhexyl hexadecanoate, hexadecanoic acid methyl ester, octadecanoic acid methyl ester, eicosanoic acid methyl ester, eicosanoic acid ethyl ester, behenic acid methyl ester, At least one of ethyl dodecanoate, methyl tetracosate, ethyl tetracosate, and methyl triacontate.
5. The polyhydroxyalkanoate composition according to any one of claims 1 to 4, wherein the polyhydroxyalkanoate contains a structural unit represented by the following general formula (1):
   

   Wherein, R ₁ is an alkyl group represented by C _p H _2p+1 , and p is an integer of 1 to 15;

   n is 1, 2 or 3.
6. The polyhydroxyalkanoate composition according to claim 5, wherein the polyhydroxyalkanoate is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co- 3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxy caproate), poly(3-hydroxybutyrate-co-3-hydroxycaproate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate) ester-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), At least one of poly(3-hydroxybutyrate-co-3-hydroxyundecanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).
7. A polyhydroxyalkanoate molded body is characterized in that it is prepared from the polyhydroxyalkanoate composition according to any one of claims 1 to 6.
8. A method for preparing a polyhydroxyalkanoate molded body, characterized in that it includes the following steps:

   The polyhydroxyalkanoate composition according to any one of claims 1 to 6 is heated at a temperature higher than the melting temperature of the polyhydroxyalkanoate. Heating and melting at 10000 °C;

   Extension at a temperature between the glass transition temperature and the cold crystallization temperature of the polyhydroxyalkanoate;

   The molding is performed by cooling at a temperature between the glass transition temperature and the melting temperature of the polyhydroxyalkanoate.
9. The method according to claim 8, characterized in that:

   Heating and melting at a temperature 10°C to 60°C higher than the melting temperature of polyhydroxyalkanoate;

   Elongation of more than 150% is performed at a temperature between the glass transition temperature and the cold crystallization temperature of the polyhydroxyalkanoate.
10. The method according to claim 9, characterized in that the crystallization enthalpy of the polyhydroxyalkanoate molded body is below 12.5 J/g, and/or the cold crystallization half-peak width is below 15°C.