A bio-based flame retardant and its use in polylactic acid and / or polyhydroxyalkanoate

Abstract

The application relates to the technical field of functional polymers, and discloses a bio-based flame retardant and application of the bio-based flame retardant in polylactic acid and / or polyhydroxyalkanoate, the structure of the bio-based flame retardant is as follows, the bio-based flame retardant combining hydroxy acid ester and ring phosphorus is used for retarding combustion of polylactic acid and / or polyhydroxyalkanoate, the bio-based flame retardant has ecological friendliness, small toxicity to human bodies, high efficient flame retarding effect, certain plasticizing effect on the base resin on the basis of keeping the bio-based characteristics and degradability of the base resin, also has the effect of slightly expanding the chain to realize the increase of the molecular weight of the material, so that the thermal stability and comprehensive mechanical properties and other properties of the base resin are improved, and the product is very excellent in various aspects.

Description

Technical Field

[0001] This invention relates to the field of functional polymer technology, specifically to a bio-based flame retardant and its application in polylactic acid and / or polyhydroxy fatty acid esters. Background Technology

[0002] To address environmental pollution, bioplastics (i.e., polymeric materials derived from renewable resources and possessing biodegradability) are being vigorously developed and applied to replace traditional petroleum-based plastics. Among them, polylactic acid (PLA) and polyhydroxyalkanoates (PHA) are currently the most promising bioplastics, already finding widespread use in packaging, disposable products, biomedicine, and textiles. However, the inherent flammability of PLA and PHA limits their application in many other fields, such as automotive, electronics, and construction. Therefore, the development and research of flame retardants for PLA and PHA is urgently needed.

[0003] Phosphazene compounds possess a skeletal structure with alternating phosphorus and nitrogen atoms, endowing them with excellent thermal stability and flame retardant properties. Simultaneously, phosphazene structures exhibit biocompatibility and low toxicity, with decomposition products being non-toxic and harmless phosphates and amines, making them ideal raw materials for green flame retardants. Hexachlorocyclotriphosphazene, due to its poor thermal stability and chlorine content, cannot be used directly as a flame retardant. However, thanks to the six reactive sites on the phosphorus atom, it offers high designability, and numerous flame-retardant compounds have been synthesized on the phosphazene ring and used for flame retardant PLA, such as DOPO, triazine, and compounds containing phenyl or furan rings.

[0004] For example, CN106928490A discloses an organic-inorganic hybrid nanocompound with synergistic chain extender-flame retardant effects and its preparation method. Hexachlorocyclotriphosphazene, which has inherent flame-retardant properties, is modified with KH550 to obtain a novel synergistic flame retardant integrating silicon, phosphorus, and nitrogen elements. This novel flame retardant is then reacted with KH560 and tetraethyl orthosilicate via a sol-gel reaction to finally obtain an organic-inorganic hybrid nanocompound with synergistic chain extender-flame retardant effects. This compound exhibits good thermal stability, high char formation rate, and good processability. Its application in the flame-retardant modification of polylactic acid (PLA) resin can simultaneously exert synergistic effects of flame retardancy and chain extender, not only significantly improving the flame-retardant properties of the material but also effectively mitigating the chain-breaking degradation phenomenon of PLA under heat, thereby effectively preventing PLA from dripping.

[0005] CN104558046A discloses a method for synthesizing hyperbranched ionic liquid flame retardants based on HCCP. This method utilizes the reaction of HCCP with trialkyl tertiary amines, trialkyl phosphorus, and N-alkyl imidazole to achieve ionization. Then, it uses salts containing different anions, such as sodium tetrafluoroborate, potassium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide, to perform ion exchange to obtain hyperbranched ionic liquid flame retardants with different anions, thereby achieving a synergistic flame retardant effect of HCCP and ionic liquid.

[0006] However, the introduction of petroleum-based compounds such as DOPO can compromise the bio-based and environmentally friendly properties of bioplastics. Furthermore, most additive flame retardants often impair the mechanical properties of polymer materials due to poor compatibility. Currently, microencapsulation, the addition of compatibilizers, and surface treatment are common methods to improve the compatibility between flame retardants and matrix resins. However, starting from molecular design, selecting bio-based compounds, and directly synthesizing green flame retardants with good matrix compatibility through simple preparation methods has greater practical application value. Summary of the Invention

[0007] This invention addresses the problem that flame retardants based on hexachlorocyclotriphosphazene can easily damage the environmental characteristics and mechanical properties of bioplastics. It provides a bio-flame-retardant polylactic acid based on hydroxy acid esters and cyclotriphosphazene. The flame retardant used is eco-friendly, can maintain the bio-based characteristics and degradability of the matrix resin, and can also improve the thermal stability and comprehensive mechanical properties of the matrix resin.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The application of a bio-based flame retardant in polylactic acid and / or polyhydroxyalkanoates, wherein the structure of the bio-based flame retardant is as follows:

[0010]

[0011] Wherein, -R1- is selected from -R2 is selected from -CH3, -CH2CH3, -CH2CH2CH3 or -CH(CH3)2.

[0012] This invention utilizes a bio-based flame retardant combining small-molecule esters homologous to bioplastics such as polylactic acid (PLA) or polyhydroxyalkanoates (PHA). This bio-based flame retardant is eco-friendly, has low toxicity to humans, and exhibits highly efficient flame retardant effects on PLA or PHA, requiring only a small amount to achieve the desired flame retardant effect. Furthermore, due to its structural characteristics, it exhibits good compatibility with the matrix, maintaining the bio-based properties and biodegradability of the matrix resin while also providing plasticizing and micro-chain extension effects, increasing the molecular weight of the material and thus improving the thermal stability and overall mechanical properties of the matrix resin. In addition, it does not affect the transparency of the material at all, resulting in a product with excellent performance in all aspects.

[0013] Preferably, -R1- is selected from -R2 is selected from -CH2CH3 or -CH2CH2CH3. This flame retardant allows polylactic acid to achieve a UL-94V-0 rating while maintaining its mechanical properties with a smaller addition amount.

[0014] More preferably, when -R1- is selected from -R2 is selected from -CH2CH3 or -CH2CH2CH3.

[0015] When -R1- is selected -R2 is selected from -CH2CH2CH3. This flame retardant can provide more significant reinforcement and toughening effects while simultaneously retardant poly(3-hydroxybutyrate).

[0016] The preparation method of the bio-based flame retardant includes the following steps:

[0017] Step 1: Add hydroxy acid ester dropwise to a sodium or sodium hydride solution to react and generate sodium alkoxide;

[0018] Step 2: Continue to add hexachlorocyclotriphosphazene dropwise to the reaction solution from Step 1. After the reaction is complete, add an inorganic acid to adjust to neutral. After removing the solvent, wash and dry the product to obtain the bio-based flame retardant.

[0019] The hydroxy acid esters include one of methyl lactate, ethyl lactate, propyl lactate, isopropyl lactate, methyl 3-hydroxybutyrate, ethyl 3-hydroxybutyrate, propyl 3-hydroxybutyrate, isopropyl 3-hydroxybutyrate, methyl 4-hydroxybutyrate, ethyl 4-hydroxybutyrate, propyl 4-hydroxybutyrate, isopropyl 4-hydroxybutyrate, methyl 3-hydroxyvalerate, ethyl 3-hydroxyvalerate, propyl 3-hydroxyvalerate, isopropyl 3-hydroxyvalerate, methyl 4-hydroxyvalerate, ethyl 4-hydroxyvalerate, propyl 4-hydroxyvalerate, isopropyl 4-hydroxyvalerate, methyl 3-hydroxyhexanoate, ethyl 3-hydroxyhexanoate, propyl 3-hydroxyhexanoate, and isopropyl 3-hydroxyhexanoate.

[0020] Preferably, the hydroxy acid ester includes ethyl lactate, propyl lactate, and propyl 3-hydroxybutyrate.

[0021] In step 1, the addition is carried out dropwise under an ice bath and inert gas protection; the hydroxy ester is first dissolved in the solvent before being added dropwise. The reaction time for step 1 is 0-2 hours.

[0022] The inert gas includes any one of nitrogen, argon, etc.

[0023] Step 2 is carried out dropwise in an ice bath, and after the dropwise addition is completed, the mixture is refluxed at 30-60℃ for 4-24 hours.

[0024] The inorganic acid includes any one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Solvent removal can be performed using any common treatment method such as rotary evaporation or centrifugation. Washing is carried out with deionized water or ethanol, and drying is performed at a temperature of 50-80℃.

[0025] The dropping rate in step 1 or step 2 is 1-5 s / drop;

[0026] The solvent used in step 1 or step 2 includes one or more of the following: tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, 1,4-dioxane, acetone, chloroform, dichloromethane, dichloroethane, petroleum ether, hexane, and cyclohexane.

[0027] Preferably, the solvent is tetrahydrofuran.

[0028] The molar ratio of the hydroxy acid ester, sodium or sodium hydride, and hexachlorocyclotriphosphazene is (6-12):(6-12):1.

[0029] The synthesis process of this bio-based flame retardant is simple, and it uses green and environmentally friendly renewable bio-based monomers, which is environmentally friendly. This ensures that the bio-environmental friendliness of the matrix is ​​not compromised when it is applied to biodegradable materials such as polylactic acid or polyhydroxyalkanoates.

[0030] The present invention also provides a bio-based flame retardant composite material, comprising a matrix and the bio-based flame retardant, wherein the bio-based flame retardant accounts for 3-20% of the total mass of the matrix and the bio-based flame retardant;

[0031] The matrix comprises polylactic acid and / or polyhydroxy fatty acid esters;

[0032] Preferably, the polyhydroxy fatty acid ester includes, but is not limited to, any one or more of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(4-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-3-hydroxyvalerate copolyester), poly(3-hydroxybutyrate-4-hydroxybutyrate copolyester), and poly(3-hydroxybutyrate-3-hydroxyhexanoate copolyester).

[0033] The bio-based flame retardant not only has a high flame retardant effect and can significantly improve the flame retardant performance of polylactic acid, but also has good compatibility with polylactic acid. During melt blending, it can react with polylactic acid to play a chain extension role, which can maintain or even improve the comprehensive mechanical properties of polylactic acid.

[0034] Preferably, the polylactic acid has a melting point of 145-170℃ and a melt index of 2-30g / 10min at 190℃ with a load of 2.16kg.

[0035] Preferably, the bio-based flame retardant composite material comprises, by mass percentage, 3% to 20% of bio-based flame retardant and 80% to 97% of matrix; the mechanical properties of the polylactic acid flame retardant composite material depend not only on the compatibility of polylactic acid with the hydroxy acid ester-based multifunctional flame retardant, but also on the degree of reaction between the hydroxy acid ester and the polylactic acid chain end groups.

[0036] More preferably, the bio-based flame-retardant composite material comprises 3% to 10% of a bio-based flame retardant and 90% to 97% of a matrix. More preferably, the bio-based flame-retardant composite material comprises 5% to 10% of a bio-based flame retardant and 90% to 95% of a matrix.

[0037] More preferably, the bio-based flame retardant composite material comprises 5% bio-based flame retardant and 95% matrix.

[0038] In some embodiments, the bio-based flame-retardant composite material further includes one or more common additives such as antioxidants. The amount of antioxidant used is 0.01-1 wt% of the matrix mass.

[0039] The bio-based flame-retardant composite material achieves a vertical combustion rating of V-2 or higher; a limiting oxygen index of 24% or higher; and while increasing elongation at break, it maintains or increases tensile strength and Young's modulus.

[0040] Preferably, the bio-based flame-retardant composite material achieves a vertical combustion rating of V-0 or higher and a limiting oxygen index of 25% or higher.

[0041] The present invention also provides a method for preparing the bio-based flame retardant composite material, wherein the raw materials including the matrix and the bio-based flame retardant are dried, mixed, melt-extruded, and granulated to obtain the bio-based flame retardant composite material.

[0042] Preferably, the matrix drying temperature is 90-110℃, the bio-based flame retardant drying temperature is 50-70℃, and the drying time is 5-10 hours. More preferably, the matrix drying temperature is 100℃, and the bio-based flame retardant drying temperature is 60℃.

[0043] The melt extrusion temperature is 170-190℃; the melt extrusion is performed using a twin-screw extruder with a screw length-to-diameter ratio of 35-45:1.

[0044] Furthermore, the present invention also provides a bio-based flame retardant of polylactic acid and / or polyhydroxyalkanoates, the structure of which is as follows:

[0045]

[0046] Wherein, -R1- is selected from -R2 is selected from -CH3, -CH2CH3, -CH2CH2CH3, or -CH(CH3)2; when -R1- is At that time, -R2 is not -CH2CH3.

[0047] The raw materials for preparing the bio-based flame retardant are all bio-based monomers and biodegradable inorganic substances, which have the advantages of being green, environmentally friendly, and having low toxicity. They can be used as flame retardants for biodegradable polymers such as polylactic acid and polyhydroxyalkanoates, and have excellent flame retardant effects. In addition, due to the similarity of the structure with the matrix material, it also has good compatibility and toughening and chain extension effects. The resulting composite material takes into account multiple properties such as mechanical properties, bio-environmental protection, flame retardancy, and transparency, and has excellent comprehensive performance.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The bio-based flame retardant prepared from cyclophosphonitrile and bio-based hydroxy acid esters in this invention exhibits highly efficient flame retardant effects when applied to polylactic acid or polyhydroxy fatty acid esters. Even at low addition levels, polylactic acid or polyhydroxy fatty acid esters can achieve a V-0 level during vertical combustion, and the oxygen index of the material is significantly improved. Simultaneously, this bio-based flame retardant has good compatibility with the matrix resin, maintains the transparency of the composite material, and reacts with the matrix resin during melt blending, playing a chain-extending role, thereby improving the thermal stability of the composite material and maintaining and enhancing its mechanical properties.

[0050] (2) The bio-based flame retardant of the present invention can plasticize the matrix resin to a certain extent, hinder its crystallization, reduce the glass transition temperature and melting temperature of the matrix resin, and keep the matrix transparent.

[0051] (3) The polylactic acid or polyhydroxy fatty acid ester flame retardant composite material prepared by the present invention has a certain promoting effect on the thermal stability and mechanical properties of the composite material due to the green and environmentally friendly nature of the flame retardant, the low addition amount, the good compatibility with the matrix resin, the existence of a certain chain extension reaction and plasticizing effect, and fully meets the requirements of green and sustainable application of polylactic acid or polyhydroxy fatty acid ester in the fields of electronics, automobiles, and construction. Attached Figure Description

[0052] Figure 1 The bio-based flame retardant prepared in Example 21 H NMR spectrum;

[0053] Figure 2 The bio-based flame retardant prepared in Example 2 31 P NMR spectrum;

[0054] Figure 3 The FT-IR spectrum of the bio-based flame retardant prepared in Example 2;

[0055] Figure 4 Thermogravimetric curves of the bio-based flame retardant prepared in Example 2, Application Example 3, and Comparative Example 1.

[0056] Figure 5 The transparency of the flame-retardant materials prepared in Comparative Example 1 and Application Example 4. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0058] All raw materials used in the following specific embodiments were purchased from the market. Among them, polylactic acid has a melt index of 16.0 g / 10 min (at 190°C, with a load of 2.16 kg) and a molecular weight of 126,000 g / mol; polyhydroxyalkanoate has a melt index of 15.9 g / 10 min (at 170°C, with a load of 5.0 kg) and a molecular weight of 130,000 g / mol.

[0059] Example 1

[0060] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of methyl lactate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed 3–5 times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (1).

[0061]

[0062] Example 2

[0063] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of ethyl lactate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (2).

[0064] Figure 1 The hydrogen NMR spectrum of the product of formula (2) is shown below. Figure 2 The phosphorus NMR spectrum of compound (2) is shown. Figure 3 The Fourier transform infrared spectrum of the compound of formula (2) is shown. It can be seen that the structure was successfully obtained. The structures in other embodiments were also characterized, proving that the target structure product was successfully obtained.

[0065]

[0066] Example 3

[0067] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution containing propyl lactate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution containing hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (3).

[0068]

[0069] Example 4:

[0070] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of isopropyl lactate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (4).

[0071]

[0072] Example 5:

[0073] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of methyl 3-hydroxybutyrate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (5).

[0074]

[0075] Example 6:

[0076] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of ethyl 3-hydroxybutyrate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40℃ and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (6).

[0077]

[0078] Example 7:

[0079] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution containing propyl 3-hydroxybutyrate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution containing hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40°C and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (7).

[0080]

[0081] Example 8:

[0082] Under an ice-water bath and nitrogen atmosphere, 1 mol of NaH was added to a 1L three-necked round-bottom flask equipped with a magnetic stirrer. After dissolving NaH in tetrahydrofuran, 1 mol of tetrahydrofuran solution of ethyl 4-hydroxybutyrate was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, 0.6 mol of tetrahydrofuran solution of hexachlorocyclotriphosphazene was slowly added dropwise to the flask using a constant-pressure dropping funnel at a rate of 1–3 s / drop. After the addition was complete, the temperature was raised to 40°C and the reaction was carried out for 12 h. After the reaction was completed, the mixture was neutralized to neutral with HCl solution, the solvent was removed by rotary evaporation, and the product was washed five times with deionized water and dried to obtain a yellow viscous liquid product with the structural formula shown in formula (8).

[0083]

[0084] Application Example 1

[0085] 96 kg of polylactic acid and 4 kg of the hydroxy ester multifunctional flame retardant of formula (2) in Example 2 were weighed. The polylactic acid and the flame retardant of formula (2) were dried at 100°C and 60°C for 8 hours, respectively. The raw materials were added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the polylactic acid flame retardant composite material was obtained.

[0086] Application Example 2

[0087] Weigh 95 kg of polylactic acid and 5 kg of the hydroxy acid ester multifunctional flame retardant of formula (2) in Example 2. Dry the polylactic acid and the flame retardant of formula (2) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0088] Application Example 3

[0089] 94 kg of polylactic acid and 6 kg of the hydroxy ester multifunctional flame retardant of formula (2) in Example 2 were weighed. The polylactic acid and the flame retardant of formula (2) were dried at 100°C and 60°C for 8 hours, respectively. They were then added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the polylactic acid flame retardant composite material was obtained.

[0090] Application Example 4

[0091] Weigh 90 kg of polylactic acid and 10 kg of the hydroxy ester multifunctional flame retardant of formula (2) in Example 2. Dry the polylactic acid and the flame retardant of formula (2) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0092] Application Example 5

[0093] Weigh 95 kg of polylactic acid and 5 kg of the hydroxy acid ester multifunctional flame retardant of formula (3) in Example 3. Dry the polylactic acid and the flame retardant of formula (3) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0094] Application Example 6

[0095] Weigh 90 kg of polylactic acid and 10 kg of the hydroxy ester multifunctional flame retardant of formula (3) in Example 3. Dry the polylactic acid and the flame retardant of formula (3) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0096] Application Example 7

[0097] Weigh 85 kg of polylactic acid and 15 kg of the hydroxy ester multifunctional flame retardant of formula (3) in Example 3. Dry the polylactic acid and the flame retardant of formula (3) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0098] Application Example 8

[0099] Weigh 80 kg of polylactic acid and 20 kg of the hydroxy acid ester multifunctional flame retardant of formula (3) in Example 3. Dry the polylactic acid and the flame retardant of formula (3) at 100°C and 60°C for 8 hours, respectively. Add them to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, obtain the polylactic acid flame retardant composite material.

[0100] Preparation of polyhydroxy fatty acid ester composite materials is shown in Application Examples 9-12.

[0101] Application Example 9

[0102] 94 kg of poly(3-hydroxybutyrate) and 6 kg of the hydroxy ester-based multifunctional flame retardant of formula (5) in Example 5 were weighed. The poly(3-hydroxybutyrate) and the flame retardant of formula (5) were dried at 100°C and 60°C for 8 hours, respectively. They were then added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the poly(3-hydroxybutyrate) flame-retardant composite material was obtained.

[0103] Application Example 10

[0104] 94 kg of poly(3-hydroxybutyrate) and 6 kg of the hydroxy ester-based multifunctional flame retardant of formula (6) in Example 6 were weighed. The poly(3-hydroxybutyrate) and the flame retardant of formula (6) were dried at 100°C and 60°C for 8 hours, respectively. They were then added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the poly(3-hydroxybutyrate) flame-retardant composite material was obtained.

[0105] Application Example 11

[0106] 94 kg of poly(3-hydroxybutyrate) and 6 kg of the hydroxy ester-based multifunctional flame retardant of formula (7) in Example 7 were weighed. The poly(3-hydroxybutyrate) and the flame retardant of formula (7) were dried at 100°C and 60°C for 8 hours, respectively. They were then added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the poly(3-hydroxybutyrate) flame-retardant composite material was obtained.

[0107] Application Example 12

[0108] 94 kg of poly(3-hydroxybutyrate) and 6 kg of the hydroxy ester-based multifunctional flame retardant of formula (8) in Example 8 were weighed. The poly(3-hydroxybutyrate) and the flame retardant of formula (8) were dried at 100°C and 60°C, respectively, for 8 hours. They were then added to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, the poly(3-hydroxybutyrate) flame-retardant composite material was obtained.

[0109] Comparative Example 1

[0110] Weigh 100 kg of polylactic acid and dry it at 100℃ for 8 hours. Add it to a twin-screw extruder for melt blending, with the screw temperature at 170℃~190℃. After cooling and granulation, polylactic acid particles are obtained.

[0111] Comparative Example 2

[0112] Weigh 100 kg of poly(3-hydroxybutyrate) and dry it at 100°C for 8 hours. Add it to a twin-screw extruder for melt blending at a screw temperature of 170°C to 190°C. After cooling and granulation, poly(3-hydroxybutyrate) particles are obtained.

[0113] The flame-retardant polylactic acid composite materials obtained from Application Examples 1-8 and Comparative Example 1 were injection molded into standard vertical burning (UL-94) specimens, limiting oxygen index (LOI) specimens, and tensile specimens. The injection temperature was 175℃–185℃, the injection pressure was 70–90 MPa, and the holding pressure was 45 MPa. Flammability and tensile properties were tested according to ASTM D3801, ASTM D2863-97, and GB / T 1040.1-20018. The test results are shown in Table 1, where NC indicates no grade. The molecular weight of each sample was also determined using high-temperature gel permeation chromatography (GPC), and the test results are shown in Table 1.

[0114] The flame-retardant polyhydroxyalkanoate composites obtained in Application Examples 9-12 and Comparative Example 2 were injection molded into standard vertical burning (UL-94) specimens, limiting oxygen index (LOI) specimens, and tensile specimens. The injection temperature was 175℃~185℃, the injection pressure was 70~90MPa, and the holding pressure was 45MPa. The flammability and tensile properties were tested according to ASTM D3801, ASTM D2863-97, and GB / T1040.1-20018. The test results are shown in Table 2, where NC indicates no rating.

[0115] Table 1. Properties of polylactic acid composites prepared in Application Examples 1-8 and Comparative Example 1

[0116]

[0117] Table 2 shows the properties of the polyhydroxyalkanoate composites prepared in Application Examples 9-12 and Comparative Example 2.

[0118]

[0119] Table 1 shows that the bio-based flame retardant containing hydroxy ester groups has a significant flame retardant effect on polylactic acid (PLA). When the addition amount reaches 5%, PLA can pass the UL-94V0 rating, and the oxygen index can reach a maximum of 28.2%, significantly improving the flame retardant performance of PLA. Simultaneously, with the addition of this hydroxy ester-based multifunctional flame retardant, the tensile strength of PLA shows a trend of first decreasing and then increasing, gradually becoming stronger than that of pure PLA; the elongation at break also increases with the increase of the amount of this multifunctional flame retardant added, indicating that the addition of this multifunctional flame retardant can improve the comprehensive mechanical properties of PLA.

[0120] from Figure 4The thermogravimetric curves of the flame retardant of formula (2) prepared in Comparative Example 1 and Example 2 and the composite material in Application Example 3 are given. By magnification, it can be seen that the maximum decomposition temperature of the material after adding the flame retardant is higher than that of pure polylactic acid. It can be seen that with the addition of this multifunctional flame retardant, the thermal stability of the flame-retardant polylactic acid composite material is improved.

[0121] Table 1 also shows that the molecular weight of the flame-retardant polylactic acid composite material increases with the addition of this multifunctional flame retardant, indicating that the flame retardant can react with the polylactic acid matrix and play a role in chain extension. Unlike conventional flame retardants, the addition of the bio-based flame retardant in this invention not only does not affect the mechanical properties of the matrix, but also improves its comprehensive properties such as tensile strength, Young's modulus and elongation at break.

[0122] As can be seen from Application Examples 5-8, the flame retardant in Example 3 also exhibits good flame retardant effect, can significantly improve the oxygen index of the material, and as the amount added increases, the molecular weight of the composite material gradually increases. After reaching 20%, the tensile properties gradually decrease, and further increasing the amount used will not bring better results.

[0123] Table 2 shows that the hydroxy ester-based multifunctional flame retardant also has a significant flame retardant effect on poly(3-hydroxybutyrate). When added at a concentration of 6%, it enables poly(3-hydroxybutyrate) to pass the UL-94V0 rating, while also improving the overall mechanical properties of poly(3-hydroxybutyrate). Furthermore, comparisons revealed that the chain length of the ester group in the hydroxy ester-based flame retardant has a relatively small impact on both flame retardant and mechanical properties.

[0124] The crystallization properties of Application Examples 1-3 and Comparative Example 1 are summarized in Table 3. Figure 5 Provide transparency diagrams for Comparative Example 1 and Application Example 4.

[0125] Table 3 shows the crystallinity of polylactic acid composite materials prepared in Application Examples 1-3 and Comparative Examples.

[0126]

[0127] As shown in Table 3, after adding the flame retardant formula (2) of Example 2, the glass transition temperature T of the polylactic acid composite material is reduced. g and cold crystallization temperature T cc The decrease indicates that the flame retardant has a certain plasticizing effect on polylactic acid. Based on the isothermal crystallization data, the half-crystallization time t in Examples 1-3 is [data missing]. 1 / 2 All were greater than Comparative Example 1. Although the crystallinity χ of Examples 1-3 was [not specified] c Compared to Comparative Example 1, the concentration decreased, but remained around 42%. This indicates that flame retardant formula (2) does not significantly affect the crystallinity of polylactic acid, but it does hinder polylactic acid crystallization to some extent, thus reducing its crystallization rate.

[0128] from Figure 5 As can be seen, the transparency of Application Example 4, which added 10% flame retardant (formula 2), is comparable to that of Comparative Example 1. This indicates that the addition of the flame retardant does not affect the transparency of the polylactic acid material.

[0129] The above embodiments are not intended to limit the present invention. The present invention is not limited to the above embodiments. Any embodiment that meets the requirements of the present invention is within the scope of protection of the present invention.

Claims

1. The application of a bio-based flame retardant in polylactic acid and / or polyhydroxyalkanoates, characterized in that, The structure of the bio-based flame retardant is as follows: Wherein, -R1- is selected from , , , , or -R2 is selected from -CH3, -CH2CH3, -CH2CH2CH3 or -CH(CH3)2.

2. The application of the bio-based flame retardant according to claim 1 in polylactic acid and / or polyhydroxyalkanoates, characterized in that, -R1- Selected from or -R2 is selected from -CH2CH3 or -CH2CH2CH3.

3. The application of the bio-based flame retardant according to claim 1 in polylactic acid and / or polyhydroxyalkanoate esters, characterized in that, The preparation method of the bio-based flame retardant includes the following steps: Step 1: Add hydroxy acid ester dropwise to a sodium or sodium hydride solution to react and generate sodium alkoxide; Step 2: Continue to add hexachlorocyclotriphosphazene dropwise to the reaction solution from Step 1. After the reaction is complete, add an inorganic acid to adjust to neutral. After removing the solvent, wash and dry the product to obtain the bio-based flame retardant. The hydroxy acid esters include one of methyl lactate, ethyl lactate, propyl lactate, isopropyl lactate, methyl 3-hydroxybutyrate, ethyl 3-hydroxybutyrate, propyl 3-hydroxybutyrate, isopropyl 3-hydroxybutyrate, methyl 4-hydroxybutyrate, ethyl 4-hydroxybutyrate, propyl 4-hydroxybutyrate, isopropyl 4-hydroxybutyrate, methyl 3-hydroxyvalerate, ethyl 3-hydroxyvalerate, propyl 3-hydroxyvalerate, isopropyl 3-hydroxyvalerate, methyl 4-hydroxyvalerate, ethyl 4-hydroxyvalerate, propyl 4-hydroxyvalerate, isopropyl 4-hydroxyvalerate, methyl 3-hydroxyhexanoate, ethyl 3-hydroxyhexanoate, propyl 3-hydroxyhexanoate, and isopropyl 3-hydroxyhexanoate.

4. The application of the bio-based flame retardant according to claim 3 in polylactic acid and / or polyhydroxyalkanoate esters, characterized in that, Step 1 is carried out dropwise under the protection of an ice bath and an inert gas. And / or, step 2 is carried out dropwise in an ice bath, and after the dropwise addition is completed, the mixture is refluxed at 30-60℃ for 4-24 hours; And / or, the inorganic acid includes any one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; And / or, the dropping rate in step 1 or step 2 is 1-5 s / drop; And / or, the solvent used in step 1 or step 2 includes one or more of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, 1,4-dioxane, acetone, chloroform, dichloromethane, dichloroethane, petroleum ether, hexane, and cyclohexane.

5. The application of the bio-based flame retardant according to claim 3 in polylactic acid and / or polyhydroxyalkanoates, characterized in that, The molar ratio of hydroxy acid ester, sodium or sodium hydride, and hexachlorocyclotriphosphazene is (6 ~ 12): (6 ~ 12):

1.

6. A bio-based flame-retardant composite material, characterized in that, The invention comprises a matrix and the bio-based flame retardant as described in claim 1, wherein the bio-based flame retardant accounts for 6-20% of the total mass of the matrix and the bio-based flame retardant; the matrix comprises polylactic acid and / or polyhydroxyalkanoates.

7. The bio-based flame-retardant composite material according to claim 6, characterized in that, It also includes antioxidants at 0.01-1 wt% of the matrix mass.

8. The method for preparing the bio-based flame-retardant composite material according to claim 6, characterized in that, The raw materials, including the matrix and bio-based flame retardant, are dried, mixed, melt-extruded, and granulated to obtain the bio-based flame retardant composite material.

9. The method for preparing the bio-based flame-retardant composite material according to claim 8, characterized in that, The melt extrusion temperature is 170-190℃; And / or, melt extrusion is performed using a twin-screw extruder with a screw length-to-diameter ratio of 35-45:

1.

10. A bio-based flame retardant of polylactic acid and / or polyhydroxyalkanoates, characterized in that, Its structure is as follows: Wherein, -R1- is selected from , , , , or -R2 is selected from -CH3, -CH2CH3, -CH2CH2CH3 or -CH(CH3)2; when -R1- is At that time, -R2 is not -CH2CH3.

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