A kind of acetylated lactate flame retardant plasticizer containing phosphaphenanthrene group and its preparation method and application

Abstract

The present invention belongs to the field of polymer additives, and in particular to a kind of acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups and its preparation method and application. The method of the present invention is based on L-lactic acid, monobasic fatty acid, epichlorohydrin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, acetic anhydride as raw materials, through esterification, epoxidation, ring opening and acylation series of reactions, to obtain an acetylated lactate plasticizer containing phosphaphenanthrene groups. By giving lactate epoxy functional groups and then introducing DOPO structure, it not only has excellent plasticizing properties, but also has excellent flame retardant properties, and is conducive to improving the compatibility of plasticizer and polylactic acid resin.

Description

Technical Field

[0001] The invention belongs to the field of environmentally friendly bio-based flame retardant plasticizers, and specifically relates to an acetylated lactate flame retardant plasticizer containing a phosphaphenanthrene group, and a preparation method and application thereof. Background Art

[0002] Polylactic acid materials are widely used in food packaging, agricultural mulch, automotive interiors and other fields due to their good biocompatibility, biodegradability and good mechanical properties. However, their high brittleness, strong rigidity and flammability hinder their further development. In order to obtain ideal flexible and durable polylactic acid products, a large amount of plasticizers are usually added to polylactic acid. At present, the commonly used polylactic acid plasticizers on the market have the problems of poor compatibility and unobvious improvement in mechanical properties. It is still necessary to explore new plasticizers with better comprehensive performance, especially plasticized polylactic acid is extremely flammable, which seriously limits its application, especially in fields with high flame retardant requirements. In response to the above problems, in recent years, domestic and foreign countries have begun to develop low-toxic bio-based flame retardant plasticizers whose raw materials are derived from renewable resources.

[0003] Patent CN105541912A discloses a phosphorus-sulfur-halogen three-element synergistic flame retardant plasticizer compound and its preparation method. Although the flame retardant effect is good when the flame retardant contains phosphorus, sulfur and halogen triple flame retardant elements, harmful dioxins will be released during combustion and heating, and can exist in the environment for many years, or even accumulate in the organism for life, and cannot be discharged, which seriously threatens the health of the human body. Patent CN 113372550A discloses a flame retardant plasticizer and a flame retardant polymer-based composite material. By reacting phenylphosphonic dichloride with a reactive plasticizer, the Cl group of phenylphosphonic dichloride can be reacted with some hydroxyl groups of the reactive plasticizer. Although the toxic halogen can be removed, the raw materials used are all non-renewable resources, which does not conform to the concept of green environmental protection. Patent CN112480565A discloses a phosphorus-containing cardanol-based flame retardant plasticizer for modified polyvinyl chloride, and its preparation method and application. Cardanol phosphate is prepared by reacting cardanol and dichlorophosphate; then cardanol phosphate is reacted with DOPO to obtain phosphorus-containing cardanol flame retardant plasticizer, but the prepared flame retardant plasticizer has too large molecular weight, resulting in low plasticizing efficiency and poor compatibility with resin. Therefore, it is urgent to develop a bio-based flame retardant plasticizer that is derived from biological raw materials, has high plasticizing efficiency and excellent flame retardant properties.

[0004] L-lactic acid is a chemical raw material derived from biomass renewable resources such as starch, with good application performance, due to its left-handed characteristics, has good biocompatibility, and it exists naturally in the human body, will not produce toxic effects on the human body, meet the concept of health and environmental protection, can be used as an ideal plasticizer raw material. But existing lactic acid-based plasticizers (such as patent CN 112920394 A, patent CN 106278888A, patent CN 110951055 A), although the flexibility of PVC resin can be effectively improved, the plasticized PVC material is very easy to burn, which seriously limits its application in the flame retardant field. At present, there is no flame retardant plasticizer prepared for PLA, only some vegetable oil-based flame retardant plasticizers are used to plasticize PVC, but the molecular weight is too large, and the plasticizing efficiency is very low, and PLA cannot be plasticized. Therefore, by structural design, it is very necessary to prepare a plasticizer with excellent plasticizing efficiency and excellent flame retardant efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a non-toxic and highly effective acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups, which is synthesized by using L-lactic acid derived from renewable resources as raw material, and a preparation method and application thereof.

[0006] The acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups provided by the present invention has a general structural formula as shown in Formula I:

[0007]

[0008] Here, R is a saturated alkyl group having 4 to 9 carbon atoms.

[0009] The present invention also provides a method for preparing the above-mentioned acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups, and the specific steps are as follows:

[0010] (1) adding L-lactic acid and monobasic fatty acid into a reactor and mixing them evenly, adding catalyst A, heating to 110° C. to 140° C., reacting for 2 to 6 hours to obtain a crude product, and the reaction product is post-treated to obtain lactic acid fatty acid ester;

[0011] (2) adding the lactic acid fatty acid ester and epichlorohydrin obtained in step (1) into a reactor and mixing them evenly, adding catalyst B, heating to 100-130° C., and reacting for 1-4 hours; then cooling to 40-80° C., adding sodium hydroxide and calcium oxide respectively, and reacting for 1-4 hours to obtain a crude product; then filtering, washing, and vacuum rotary evaporating the crude product to obtain lactic acid fatty acid glycidyl ester;

[0012] (3) adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into a reactor, heating it to 140° C. to completely dissolve it, then adding the lactic acid fatty acid glycidyl ester obtained in step (2), heating it to 150-180° C., reacting for 2-6 hours to obtain a crude product, and then filtering, washing, and vacuum-evaporating the crude product to obtain a lactic acid fatty acid ester containing a phosphaphenanthrene group;

[0013] (4) Acylation reaction is carried out on the lactic acid fatty acid ester containing phosphaphenanthrene groups obtained in step (3) with acetic anhydride, and the temperature is raised to 120-160° C. and the reaction is carried out for 1-3 hours. The reaction product is post-treated to obtain an acetylated lactic acid ester flame retardant plasticizer containing phosphaphenanthrene groups having a structure as shown in Formula I.

[0014] Furthermore, in step (1), the monobasic fatty acid is one of n-butyric acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid or n-nonanoic acid.

[0015] Furthermore, in step (1), the preferred esterification reaction temperature is 120° C. to 130° C., more preferably 130° C.; the preferred esterification reaction time is 3 to 5 h, more preferably 4 h.

[0016] Furthermore, the preferred reaction temperature of the temperature-raising reaction in step (2) is 115° C. to 120° C., and more preferably 117° C.; the preferred reaction time of the temperature-raising reaction is 2 to 3 h, and more preferably 2 h.

[0017] Furthermore, the preferred reaction temperature for the cooling reaction in step (2) is 50°C to 70°C, more preferably 60°C; the preferred cooling reaction time is 2 to 3h, more preferably 3h.

[0018] Furthermore, in step (3), the preferred reaction temperature is 150° C. to 170° C., more preferably 160° C.; the preferred reaction time is 3 to 5 h, more preferably 4 h.

[0019] Furthermore, in step (4), the preferred reaction temperature is 130° C. to 150° C., more preferably 140° C.; the preferred reaction time is 2 to 3 h, more preferably 2 h.

[0020] The amount of the reaction raw materials used in the present invention is not strictly limited. Generally, the reaction is carried out according to the chemical reaction stoichiometric ratio. In order to increase the product yield, the monobasic fatty acid, epichlorohydrin, DOPO and acetic anhydride are all reacted in excess.

[0021] Furthermore, in step (1), the molar ratio of L-lactic acid to monobasic fatty acid is 1 to 2:1, preferably 1.2 to 1.5:1, and more preferably 1.5:1;

[0022] In step (2), the molar ratio of lactic acid fatty acid ester to epichlorohydrin is 1:5-15, preferably 1:5-10, and more preferably 1:10;

[0023] In step (3), the molar ratio of the epoxy bond in glycidyl lactate to the phosphorus-hydrogen bond of DOPO is 1:1 to 1.5, preferably 1:1.2 to 1.5, and more preferably 1:1.2;

[0024] In step (4), the molar ratio of glycidyl lactate containing phosphaphenanthrene group to acetic anhydride is 1:1-1.5, preferably 1:1.2-1.5, and more preferably 1:1.2.

[0025] The amount of the catalyst used in the present invention is not strictly limited and can be adjusted according to the amount of the reaction raw materials: the amount of the catalyst used is based on the ability to catalyze the reaction and to promote the reaction to the target product. Further, catalyst A is one or more of concentrated sulfuric acid, phosphoric acid, p-toluenesulfonic acid, zinc oxide, aluminum oxide, tin oxide, and stannous oxide; its addition amount is 0.1-1% of the mass of the reactants, and in order to save costs, the preferred mass fraction is 0.5-0.8%, and more preferably 0.8%;

[0026] Catalyst B is one or more of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, hexadecyltrimethylammonium chloride or hexadecyltrimethylammonium bromide; the addition amount of catalyst B is 0.5-1.5% of the mass of the reactants, and in order to save costs, the preferred mass fraction is 0.8-1.2%, and more preferably 1%.

[0027] The acetylated lactate plasticizer containing phosphaphenanthrene groups prepared by the present invention is a bio-based environmentally friendly flame retardant plasticizer, which is green, environmentally friendly and non-toxic, and can be used as a plastic plasticizer in fields such as food packaging, medical supplies, water supply pipes and children's toys.

[0028] The acetylated lactate plasticizer containing phosphaphenanthrene groups prepared by the present invention has good compatibility with polylactic acid and has good plasticizing and flame retardant effects, and can be used as a main plasticizer for polylactic acid.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention uses renewable resource L-lactic acid as the main raw material, avoiding dependence on petrochemical raw materials and improving the use of bio-based raw materials.

[0031] (2) The present invention utilizes the characteristics of L-lactic acid containing hydroxyl and carboxyl groups in its molecular structure, and the prepared product has a structure containing a polar functional biphenyl ring structure and a large number of polar ester groups of lactic acid ester, which is beneficial to improving the compatibility of the plasticizer and the polylactic acid resin.

[0032] (3) The present invention introduces a DOPO structure into lactic acid ester after imparting epoxy functional groups to lactic acid ester, thereby preparing polylactic acid products with excellent flame retardancy, wherein the limiting oxygen index thereof can reach 27 to 32%, and the flame retardancy grade is V-0. In view of the shortcomings of polylactic acid such as high brittleness and flammability, the lactic acid ester flame retardant plasticizer of the present invention can effectively improve its flame retardancy and flexibility, and has broad application prospects in products with high requirements for flame retardancy such as plastics, rubbers, textiles and various building materials.

[0033] (4) The acetylated lactic acid ester flame retardant plasticizers containing phosphaphenanthrene groups prepared by the present invention are all light yellow oily substances, and have good compatibility with polylactic acid resins. The corresponding polylactic acid products have the advantages of good mechanical properties, flame retardant properties, thermal stability and migration resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The infrared spectra of the raw materials and products of Example 1 of the present invention are as follows;

[0035] Figure 2 It is a thermogravimetric analysis TGA curve diagram of the product of Example 1 of the present invention and the plasticizer ATBC;

[0036] Figure 3 The tensile stress-strain curves of six polylactic acid samples in Application Example 1 are as follows; 1, sample 1; 2, sample 2; 3, sample 3; 4, sample 4; 5, sample 5; 6, sample 6;

[0037] Figure 4 These are TGA curves of pure polylactic acid, sample 1, comparative example 1, comparative example 2, comparative example 3, and comparative example 4. DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0039] In the present invention, the plasticizing method of the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups preferably includes thermoplastic blending.

[0040] The synthetic route of the present invention is as follows:

[0041]

[0042] Wherein R is a saturated alkyl group having 4 to 9 carbon atoms.

[0043] Example 1

[0044] The following is the screening of the reaction conditions of the present invention.

[0045] S1 reaction condition screening:

[0046] Add L-lactic acid and n-octanoic acid in a molar ratio of 1 to 2:1 to a round-bottom three-necked flask, then add p-toluenesulfonic acid monohydrate accounting for 0.1% to 1% of the total mass of the reactants, heat to 110 to 140°C, stir to react and reflux for 2 to 6 hours. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, vacuum rotary evaporation, washing, and filtration are performed to finally obtain lactic acid octanoate.

[0047] Table 1 S1 Condition Screening

[0048] S1 L-Lactic acid: Caprylic acid Catalyst dosage% Reaction conditions Yield % 1 1:1 0.8 130℃，4h 86.1 2 1.5:1 0.8 130℃，4h 96.2 3 2:1 0.8 130℃，4h 89.2 4 1.5:1 0.1 130℃，4h 76.3 5 1.5:1 1 130℃，4h 94.9 6 1.5:1 0.8 120℃，4h 85.9 7 1.5:1 0.8 140℃，4h 89.2 8 1.5:1 0.8 130℃，2h 91.4 9 1.5:1 0.8 130℃，6h 92.1

[0049] Conclusion: In the S1 reaction step, by changing the molar ratio of L-lactic acid: n-octanoic acid, the amount of catalyst, the reaction time and the reaction temperature, too high a reaction temperature and too long a reaction time will lead to side reactions and a decrease in yield; too low a reaction temperature and too short a reaction time will lead to incomplete reaction; therefore, based on the optimal yield, the following optimal reaction conditions can be selected: the molar ratio of L-lactic acid: n-octanoic acid is 1.5:1; the amount of catalyst is 0.8%; the reaction temperature is 130°C; and the reaction time is 4h.

[0050] S2 reaction condition screening

[0051] Lactic acid octanoate and epichlorohydrin are mixed in a ratio of 1:5-15 to obtain a reactant, and then 0.5%-1.5% of benzyltriethylammonium chloride accounting for the total mass of the reactant is added, the temperature is raised to 110-130° C., and the reaction is carried out for 1-4 hours; then the temperature is lowered to 40-80° C., and sodium hydroxide and calcium oxide are added in an amount twice the molar fraction of lactic acid octanoate, respectively, and the reaction is carried out for 1-4 hours to obtain a crude product; then after the reaction is completed, it is filtered, washed, and evaporated under reduced pressure to obtain lactic acid octanoate glycidyl ester.

[0052] Table 2 S2 condition screening

[0053] S2 S1 product: epichlorohydrin Catalyst dosage% Reaction conditions Cooling reaction Yield % 1 1:5 1％ 117℃，2h 60℃，3h 88.9 2 1:10 1％ 117℃，2h 60℃，3h 96.2 3 1:15 1％ 117℃，2h 60℃，3h 93.9 4 1:10 0.5％ 117℃，2h 60℃，3h 89.8 5 1:10 1.5％ 117℃，2h 60℃，3h 94.7 6 1:10 1％ 110℃，2h 60℃，3h 91.3 7 1:10 1％ 130℃，2h 60℃，3h 89.2 8 1:10 1％ 117℃，1h 60℃，3h 81.3 9 1:10 1％ 117℃，4h 60℃，3h 92.8 10 1:10 1％ 117℃，2h 40℃，3h 84.3 11 1:10 1％ 117℃，2h 80℃，3h 90.4 12 1:10 1％ 117℃，2h 60℃，1h 89.3 13 1:10 1％ 117℃，2h 60℃，4h 92.3

[0054] Conclusion: In the S2 reaction step, taking into account the raw material ratio, reaction temperature, reaction time, catalyst dosage and other factors, although too long a reaction time and too much catalyst dosage will lead to a slightly higher yield of the product, it will increase the preparation cost; while too short a reaction time and too low a catalyst dosage will lead to incomplete reaction of the raw materials and too low a yield. When screening the temperature, considering that the boiling point of epichlorohydrin is about 117-118°C, when the reaction temperature is 130°C, it may be due to the volatilization of a large amount of epichlorohydrin, resulting in a low yield. Therefore, the following optimal reaction conditions are selected: S1 product: raw material molar ratio is 1:10; catalyst dosage is 1%; reaction conditions are 117°C, 2h; cooling reaction conditions are 60°C, 3h.

[0055] S3 reaction condition screening

[0056] Add DOPO into the reactor, heat it to 140°C to completely dissolve it, then add S2 lactic acid octanoic acid glycidyl ester, wherein the molar ratio of epoxy bond in lactic acid octanoic acid glycidyl ester:phosphine-hydrogen bond of DOPO is 1:1-1.5, heat it to 150-180°C, react for 2-6h to obtain a crude product, filter, wash, and evaporate under reduced pressure to obtain lactic acid octanoate containing phosphorus phenanthroline groups.

[0057] Table 3 S3 condition screening

[0058] S3 S2 product:DOPO molar ratio Reaction conditions Yield % 1 1：1 160℃，4h 89.3 2 1：1.2 160℃，4h 93.3 3 1：1.5 160℃，4h 88.6 4 1：1.2 150℃，4h 83.9 5 1：1.2 180℃，4h 87.3 6 1：1.2 160℃，2h 86.6 7 1：1.2 160℃，6h 90.8

[0059] Conclusion: In the S3 reaction step, the raw material molar ratio, reaction temperature and reaction time were screened. The results showed that when the amount of DOPO was too much, the unreacted DOPO gradually precipitated as the temperature of the product dropped during the purification of the product. Therefore, it was difficult to separate the excessive DOPO from the product, and more DOPO was stuck to the product during purification, resulting in a decrease in yield. Excessive reaction temperature and long reaction time will lead to side reactions, resulting in a decrease in yield. Excessive use of DOPO, too low reaction temperature and too short reaction time will lead to incomplete reaction. The optimal reaction conditions were: raw material molar ratio of 1:1.2; reaction temperature of 160℃, reaction time of 4h.

[0060] S4 reaction condition screening

[0061] The S3 product is subjected to an acylation reaction with acetic anhydride, wherein the molar ratio of lactic acid octanoate containing phosphaphenanthrene groups to acetic anhydride is 1:1-1.5, the reaction temperature is 120-160°C, and the reaction time is 1-3h; the reaction product is washed and subjected to reduced pressure rotary evaporation to obtain an acetylated lactic acid octanoate flame retardant plasticizer containing phosphaphenanthrene groups.

[0062] Table 4 S4 condition screening

[0063]

[0064] Conclusion: In the S4 reaction step, the raw material molar ratio, reaction temperature and reaction time were screened, and it was found that when the amount of acetic anhydride was not excessive, the reaction yield was low and the reaction was not complete; when the amount of acetic anhydride was excessive, it had little effect on the product yield. Excessive use of acetic anhydride will increase the cost and make it difficult to purify the product; too high a reaction temperature and too long a reaction time will lead to side reactions and a decrease in yield; too low a reaction temperature and too short a reaction time will lead to incomplete reaction; therefore, considering the cost, energy consumption and yield, the optimal reaction conditions were obtained as follows: raw material molar ratio 1:1.2; reaction temperature of 140°C, reaction time of 2h, and the final molecular weight of the product was about 568.19.

[0065] Figure 1 The infrared spectra of the raw material lactic acid (curve 1), the intermediate product lactic acid octanoate (curve 2), the intermediate product lactic acid octanoate glycidyl ester (curve 3), the intermediate product lactic acid octanoate containing phosphaphenanthrene groups (curve 4) and the final product acetylated lactic acid octanoate flame retardant plasticizer containing phosphaphenanthrene groups (curve 5) in Example 1 are shown in FIG. 1 . All the curves are observed, and the peak at 1740 cm -1 The stretching vibration peak of the ester carbonyl C=O is at 3200-2500cm -1 It is the superposition peak of the absorption peak of the association between -OH in the carboxyl group and -OH in the hydroxyl group. In curve 2, at 1191 and 1049 cm -1 The asymmetric stretching vibration peak of COC in the ester bond appeared at 3200-2500cm -1 The characteristic absorption peaks of disappeared, proving the successful synthesis of the esterification reaction; on curve 3, at 910 and 853 cm -1 The characteristic absorption peak of the epoxy group appears, indicating that the lactic acid octanoate has undergone epoxidation. In the infrared spectrum of curve 4, it is found that the characteristic absorption peak of the epoxy group disappears, while the peaks at 1249 and 928 cm -1 The characteristic absorption peaks of P=O and POC appeared at 1667~1561cm -1 There are four sharp absorption bands between 3500 and 3400 cm -1 The characteristic absorption peak of -OH appeared at 3500~3400cm -1 There is no stretching vibration peak of -OH at 1740cm -1 The appearance of a stronger ester absorption peak than that of lactic acid octanoate containing phosphaphenanthrene groups indicates that the hydroxyl groups of lactic acid octanoate containing phosphaphenanthrene groups undergo an esterification reaction with acetic anhydride. The above proves that the flame retardant plasticizer of lactic acid octanoate containing phosphaphenanthrene groups has been successfully synthesized.

[0066] Figure 2 The TGA curve of the final product of Example 1, the acetylated lactic acid octanoate flame retardant plasticizer containing phosphaphenanthrene groups, and the commercially available plasticizer acetyl citrate tri-n-butyl ester plasticizer (ATBC). It can be seen from the figure that the thermal stability of the acetylated lactic acid octanoate flame retardant plasticizer containing phosphaphenanthrene groups is better than that of ATBC, indicating that the acetylated lactic acid ester flame retardant plasticizer containing phosphaphenanthrene groups has good thermal stability.

[0067] Example 2

[0068] Add L-lactic acid and n-butyric acid in a molar ratio of 1.5:1 and 0.8% p-toluenesulfonic acid monohydrate to a round-bottom three-necked flask, stir and reflux for 4 hours at a reaction temperature of 130°C. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, vacuum rotary evaporation, washing, and filtration are performed to finally obtain lactic acid butyrate with a yield of 93.2%.

[0069] Lactic acid butyrate: epichlorohydrin = 1:10 molar ratio to obtain a reactant, then add benzyltriethylammonium chloride accounting for 1% of the total mass of the reactant, heat to 117°C, and react for 2 hours; then cool to 60°C, add sodium hydroxide and calcium oxide twice the molar fraction of lactic acid butyrate, respectively, and react for 3 hours to obtain a crude product; then after the reaction is completed, filter, wash, and vacuum rotary evaporate to obtain lactic acid butyrate glycidyl ester, with a yield of 94.1%:

[0070] DOPO was added to the reactor, heated to 140°C to completely dissolve it, and then lactic acid butyrate glycidyl was added, wherein the molar ratio of lactic acid butyrate glycidyl: DOPO was 1:1.2, and the temperature was raised to 160°C, and the reaction was performed for 4 hours to obtain a crude product, which was filtered, washed, and vacuum rotary evaporated to obtain lactic acid butyrate containing phosphaphenanthrene groups, with a yield of 98.9%;

[0071] The lactic acid butyrate containing phosphaphenanthrene groups is acylated with acetic anhydride, wherein the molar ratio of the lactic acid butyrate containing phosphaphenanthrene groups to acetic anhydride is 1:1.2; the reaction product is washed and subjected to reduced pressure rotary evaporation to obtain an acetylated lactic acid butyrate flame retardant plasticizer containing phosphaphenanthrene groups, with a yield of 92.9% and a product molecular weight of about 512.32.

[0072] Example 3

[0073] Add L-lactic acid and n-valeric acid in a molar ratio of 1.5:1 and 0.8% p-toluenesulfonic acid monohydrate to a round-bottom three-necked flask, stir and reflux for 4 hours at a reaction temperature of 130°C. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, vacuum rotary evaporation, washing, and filtration are performed to finally obtain lactic acid valeric acid ester with a yield of 94.6%;

[0074] The reactants were mixed in a molar ratio of valerate lactate:epichlorohydrin=1:10, and then 1% of the total mass of the reactants was added with benzyltriethylammonium chloride, and the temperature was raised to 117°C for reaction for 2 hours; then the temperature was lowered to 60°C, and sodium hydroxide and calcium oxide were added in an amount twice the molar fraction of valerate lactate, respectively, and the reaction was carried out for 3 hours to obtain a crude product; then after the reaction was completed, the product was filtered, washed, and evaporated under reduced pressure to obtain glycidyl valerate lactate, and the yield was 91.9%;

[0075] DOPO was added to the reactor, heated to 140°C to completely dissolve it, and then lactic acid valerate glycidyl ester was added, wherein the molar ratio of lactic acid valerate glycidyl ester to DOPO was 1:1.2, and the temperature was raised to 160°C, and the reaction was performed for 4 hours to obtain a crude product, which was filtered, washed, and vacuum evaporated to obtain lactic acid valerate ester containing phosphaphenanthrene groups, with a yield of 93.6%;

[0076] The phosphaphenanthrene-containing lactic acid valerate was acylated with acetic anhydride, wherein the molar ratio of the phosphaphenanthrene-containing lactic acid valerate to acetic anhydride was 1:1.2, the reaction temperature was 140°C, and the reaction time was 2h; the reaction product was washed and evaporated under reduced pressure to obtain an acetylated lactic acid valerate flame retardant plasticizer containing a phosphaphenanthrene group, with a yield of 91.8% and a product molecular weight of about 526.33.

[0077] Example 4

[0078] Add L-lactic acid and n-hexanoic acid in a molar ratio of 1.5:1 and 0.8% p-toluenesulfonic acid monohydrate to a round-bottom three-necked flask, stir and reflux for 4 hours at a reaction temperature of 130°C. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, vacuum rotary evaporation, washing, and filtration are performed to finally obtain lactic acid caproate with a yield of 96.9%;

[0079] The reactants were mixed in a molar ratio of lactic acid caproate: epichlorohydrin = 1:10, and then benzyltriethylammonium chloride accounting for 1% of the total mass of the reactants was added, the temperature was raised to 117°C, and the reaction was carried out for 2 hours; then the temperature was lowered to 60°C, and sodium hydroxide and calcium oxide were added in an amount twice the molar fraction of lactic acid caproate, respectively, and the reaction was carried out for 3 hours to obtain a crude product; then after the reaction was completed, it was filtered, washed, and vacuum rotary evaporated to obtain lactic acid caproic acid glycidyl ester, and the yield was 94.3%;

[0080] DOPO was added to the reactor, heated to 140°C to completely dissolve it, and then lactic acid caproic acid glycidyl ester was added, wherein the molar ratio of lactic acid caproic acid glycidyl ester to DOPO was 1:1.2, and the temperature was raised to 160°C, and the reaction was performed for 4 hours to obtain a crude product, which was filtered, washed, and vacuum evaporated to obtain lactic acid caproic acid ester containing phosphaphenanthrene groups, with a yield of 93.9%;

[0081] The lactic acid caproate containing phosphaphenanthrene groups is acylated with acetic anhydride, wherein the molar ratio of the lactic acid caproate containing phosphaphenanthrene groups to acetic anhydride is 1:1.2, the reaction temperature is 140°C, and the reaction time is 2h; the reaction product is washed and subjected to reduced pressure rotary evaporation to obtain an acetylated lactic acid caproate flame retardant plasticizer containing phosphaphenanthrene groups, with a yield of 91.6% and a product molecular weight of about 540.29.

[0082] Example 5

[0083] Add L-lactic acid and n-heptanoic acid in a molar ratio of 1.5:1 and 0.8% p-toluenesulfonic acid monohydrate to a round-bottom three-necked flask, stir and reflux for 4 hours at a reaction temperature of 130°C. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, heptanoic acid lactate is finally obtained by vacuum rotary evaporation, washing, and filtration, with a yield of 95.9%;

[0084] Lactate heptanoate: epichlorohydrin in a molar ratio of 1:10 are mixed to obtain a reactant, and then benzyltriethylammonium chloride accounting for 1% of the total mass of the reactant is added, the temperature is raised to 117° C., and the reaction is carried out for 2 hours; then the temperature is lowered to 60° C., and sodium hydroxide and calcium oxide are added in an amount twice the molar fraction of lactate heptanoate, respectively, and the reaction is carried out for 3 hours to obtain a crude product; then after the reaction is completed, the product is filtered, washed, and vacuum rotary evaporated to obtain lactate heptanoic acid glycidyl ester, and the yield is 94.6%;

[0085] DOPO was added to the reactor, heated to 140°C to completely dissolve it, and then glycidyl lactate was added, wherein the molar ratio of glycidyl lactate to DOPO was 1:1.2, and the temperature was raised to 160°C. The reaction was performed for 4 hours to obtain a crude product, which was filtered, washed, and vacuum evaporated to obtain lactate heptanoate containing a phosphaphenanthrene group, with a yield of 93.2%;

[0086] The lactic acid heptanoate containing phosphaphenanthrene groups was acylated with acetic anhydride, wherein the molar ratio of the lactic acid heptanoate containing phosphaphenanthrene groups to acetic anhydride was 1:1.2, the reaction temperature was 140°C, and the reaction time was 2h; the reaction product was washed and subjected to reduced pressure rotary evaporation to obtain the acetylated lactic acid heptanoate flame retardant plasticizer containing phosphaphenanthrene groups, with a yield of 92.8% and a product molecular weight of about 554.12.

[0087] Example 6

[0088] Add L-lactic acid and nonanoic acid in a molar ratio of 1.5:1 and 0.8% p-toluenesulfonic acid monohydrate to a round-bottom three-necked flask, stir and reflux for 4 hours at a reaction temperature of 130°C. Connect a water separator to the round-bottom flask to receive the water generated during the reaction. After the reaction is completed, vacuum rotary evaporation, washing, and filtration are performed to finally obtain lactic acid nonanoic acid ester with a yield of 94.3%;

[0089] The reactants were mixed in a molar ratio of 1:10 for lactic acid nonanoate and epichlorohydrin, and then 1% of the total mass of the reactants was added with benzyltriethylammonium chloride, and the temperature was raised to 117°C for reaction for 2 hours; then the temperature was lowered to 60°C, and sodium hydroxide and calcium oxide were added in an amount twice the molar fraction of lactic acid nonanoate, respectively, and the reaction was carried out for 3 hours to obtain a crude product; then after the reaction was completed, the product was filtered, washed, and evaporated under reduced pressure to obtain lactic acid nonanoic acid glycidyl ester, and the yield was 93.6%;

[0090] DOPO was added to the reactor, heated to 140°C to completely dissolve it, and then lactic acid nonanoic acid glycidyl ester was added, wherein the molar ratio of lactic acid nonanoic acid glycidyl ester to DOPO was 1:1.2, and the temperature was raised to 160°C, and the reaction was performed for 4 hours to obtain a crude product, which was filtered, washed, and vacuum evaporated to obtain lactic acid nonanoic acid ester containing phosphaphenanthrene groups, with a yield of 90.9%;

[0091] The phosphaphenanthrene-containing lactic acid nonanoate was acylated with acetic anhydride, wherein the molar ratio of the phosphaphenanthrene-containing lactic acid nonanoate to acetic anhydride was 1:1.2, the reaction temperature was 140°C, and the reaction time was 2h; the reaction product was washed and evaporated under reduced pressure to obtain the phosphaphenanthrene-containing acetylated lactic acid nonanoate flame retardant plasticizer, with a yield of 90.4% and a product molecular weight of about 582.40.

[0092] Application Example 1

[0093] The above-mentioned acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups for modifying polylactic acid is used in the preparation of polylactic acid materials. 10 to 60 parts of lactate flame retardant plasticizer containing phosphaphenanthrene groups are thermoplastically blended with 100 parts of polylactic acid. The thermoplastic temperature is 150 to 180°C, the rotation speed is 50 to 100 rpm, and the processing time is 6 minutes. The polylactic acid material modified by lactate flame retardant plasticizer containing phosphaphenanthrene groups is obtained. Then, a dumbbell-shaped sample for tensile test, oxygen index test and vertical burning strip sample are prepared by injection molding machine. The tensile test is carried out according to ASTM D638-2003, the oxygen index is carried out according to ASTMD2863 standard, and the UL-94 vertical burning performance is carried out according to ASTM D 3801 standard. The experimental results show that when the amount of plasticizer in Examples 1 to 6 exceeds 50 parts, the miscibility of the polylactic acid matrix will be poor; when the amount is less than 30 parts, the mechanical properties of the polylactic acid products are not significantly improved; here only the experimental data of the mechanical properties and flame retardant properties of the samples prepared by thermoplastic blending of 40 parts of the plasticizer in Examples 1 to 6 and 100 parts of polylactic acid are provided, and the prepared samples are Sample 1, Sample 2, Sample 3, Sample 4, Sample 5, and Sample 6, respectively, and the results are shown in Table 1.

[0094] Application Comparative Example 1

[0095] According to the method of replacing L-lactic acid with ricinoleate, an acetylated ricinoleate flame retardant plasticizer containing phosphaphenanthrene groups was synthesized. Its structural formula is shown in Formula II, the molecular weight is 757, and the yield is 84.3%. The application of acetylated ricinoleate flame retardant plasticizer containing phosphaphenanthrene groups for modifying polylactic acid in the preparation of polylactic acid materials is to thermoplastically blend 100 parts of PLA resin with 40 parts of plasticizer; the thermoplastic temperature is 150-180°C, the rotation speed is 50-100rpm, the processing time is 6min, and the modified polylactic acid material is obtained by discharging. Then, a dumbbell-shaped sample for tensile test, an oxygen index test and a strip sample for vertical combustion are prepared by an injection molding machine. The tensile test is carried out according to ASTM D638-2003, the oxygen index is carried out according to ASTM D2863 standard, and the UL-94 vertical combustion performance is carried out according to ASTM D 3801 standard. The results are shown in Table 1.

[0096]

[0097] Application Comparative Example 2

[0098] In this comparative example, the lactic acid octanoic acid glycidyl ester synthesized in Example 1 is compounded with DOPO, wherein the molar ratio of the epoxy bond in lactic acid octanoic acid glycidyl ester to the phosphorus-hydrogen bond of DOPO is 1:1.2, and the structural formula of lactic acid octanoic acid glycidyl ester is shown in Formula III; 100 parts of PLA resin and 40 parts of compounded plasticizer are thermoplastically blended, the thermoplastic temperature is 150-180°C, the rotation speed is 50-100rpm, the processing time is 6min, and the modified polylactic acid material is obtained by discharging. Then, a dumbbell-shaped sample for tensile test, an oxygen index test and a strip sample for vertical combustion are prepared by an injection molding machine. The tensile test is carried out according to ASTM D638-2003, the oxygen index is carried out according to ASTM D2863 standard, and the UL-94 vertical combustion performance is carried out according to ASTM D 3801 standard. The results are shown in Table 1.

[0099]

[0100] Application Comparative Example 3

[0101] In this comparative example, the lactic acid octanoate glycidyl ester synthesized in Example 1 is used for modified polylactic acid, and 100 parts of PLA resins are thermoplastically blended with 40 parts of compound plasticizers, the thermoplastic temperature is 150-180°C, the rotating speed is 50-100rpm, the processing time is 6min, and the modified polylactic acid material is obtained by discharging. Then, an injection molding machine is used to prepare dumbbell-shaped samples for tensile testing, strip samples for oxygen index testing and vertical combustion, the tensile test is carried out with reference to ASTM D638-2003, the oxygen index is carried out according to ASTM D2863 standard, and the UL-94 vertical combustion performance is carried out according to ASTM D 3801 standard, and the results are shown in Table 1.

[0102] Application Comparative Example 4

[0103] The application of the existing commercial tri-n-butyl p-acetyl citrate plasticizer (ATBC) in modifying polylactic acid was investigated. 40 parts of ATBC was thermoplastically blended with 100 parts of polylactic acid; the thermoplastic temperature was 150-180°C, the rotation speed was 50-100 rpm, the processing time was 6 minutes, and the modified polylactic acid material was obtained. Then, a dumbbell-shaped sample for tensile test, oxygen index test and vertical burning strip sample were prepared by injection molding machine. The tensile test was carried out according to ASTM D638-2003, the oxygen index was carried out according to ASTM D2863 standard, and the UL-94 vertical burning performance was carried out according to ASTM D 3801 standard. The results are shown in Table 1.

[0104] Table 1 Properties of modified polylactic acid products

[0105] name Tensile strength(MPa) Elongation at break (%) Elastic modulus (MPa) Oxygen index (%) UL-94 Pure polylactic acid 50.68 3.7 1859 20 NR Sample 1 42.38 330 861 32 V-0 Sample 2 39.97 372 810 33 V-0 Sample 3 39.11 366 820 32.5 V-0 Sample 4 40.63 356 844 32 V-0 Sample 5 35.33 388 799 32 V-0 Sample 6 44.33 311 901 33.5 V-0 Comparative Example 1 35.69 3.2 566 31.5 V-0 Comparative Example 2 16.90 1.9 69 32 V-0 Comparative Example 3 15.32 401 456 18.5 NR Comparative Example 4 12.30 472 431 18.5 NR

[0106] From Table 1 and Figure 3 It can be seen that the polylactic acid products modified by the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups in Examples 1 to 6 prepared by the present invention all have good plasticizing properties and flame retardant properties, the oxygen index is above 30, and the flame retardant grade is V-0. At the same time, as the length of the plasticizer alkyl chain increases, the elongation at break decreases, while the tensile strength and elastic modulus are improved. Therefore, the order of plasticizing efficiency of the six flame retardant plasticizers prepared in the embodiment is: acetylated lactic acid butyrate flame retardant plasticizer containing phosphaphenanthrene groups> acetylated lactic acid valerate flame retardant plasticizer containing phosphaphenanthrene groups> acetylated lactic acid hexanoate flame retardant plasticizer containing phosphaphenanthrene groups> acetylated lactic acid heptanoate flame retardant plasticizer containing phosphaphenanthrene groups> acetylated lactic acid octanoate flame retardant plasticizer containing phosphaphenanthrene groups> acetylated lactic acid nonanoate flame retardant plasticizer containing phosphaphenanthrene groups. Comprehensive comparison shows that the flame retardant plasticizer prepared in the present application has both flame retardant and plasticizing effects. The acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups can be used as a flame retardant plasticizer for polylactic acid to obtain polylactic acid products with excellent mechanical properties and flame retardant properties.

[0107] Compared with the comparative example, the polylactic acid product modified by the acetylated lactate flame retardant plasticizer containing phosphorus heterophenanthrene group provided by the present invention has excellent plasticizing performance and flame retardant performance at the same time, wherein the polylactic acid product modified by the acetylated castor oil ester flame retardant plasticizer of comparative example 1 and the composite plasticizer of comparative example 2 improves the flame retardant performance of the polylactic acid product, but greatly reduces the mechanical properties of the polylactic acid, and does not play a plasticizing effect. The elongation at break of the polylactic acid product modified by the lactic acid caprylic acid glycidyl ester of comparative example 3 and the commercially available plasticizer ATBC of comparative example 4 is higher, but the tensile strength and elastic modulus decrease more seriously, and in the flame retardant test, the oxygen index is 18.5, and the UL-94 test grade is NR, which shows that the modified polylactic acid product is very easy to burn. It can be seen that the plasticizing effect of the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups prepared by the present invention is not greatly reduced due to the introduction of DOPO, and the advantages in tensile strength and elastic modulus are very obvious; in addition, since the flame retardant plasticizer contains a rigid skeleton of phosphaphenanthrene groups, a large number of polar lactate groups and ester bonds, it gives polylactic acid excellent strength.

[0108] From the thermogravimetric curve, it can be seen that Figure 4 ), the polylactic acid products modified with acetylated lactate flame retardant plasticizers containing phosphaphenanthrene groups have better thermal stability than those modified with acetylated castor oil ester flame retardant plasticizers containing phosphaphenanthrene groups, compound plasticizers, polylactic acid products modified with lactic acid octanoate glycidyl ester and commercially available plasticizer ATBC modified polylactic acid products, indicating that the polylactic acid samples plasticized by acetylated lactate flame retardant plasticizers containing phosphaphenanthrene groups show good thermal stability.

[0109] From the above application examples and comparative examples, it can be seen that the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups provided by the present invention has both excellent plasticization and flame retardancy. In addition, the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups provided by the present invention does not contain toxic substances, and the plasticization effect can effectively replace ATBC.

[0110] The above are only several preferred embodiments of the present invention. Any modifications or changes made by technicians familiar with this field according to the spirit and scope of the present invention should be included in the scope of the technical solution of the present invention.

[0111] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An acetylated lactate flame retardant plasticizer containing a phosphaphenanthrene group, characterized in that: Its general structural formula is shown in Formula I: ， Formula I Wherein R is a saturated alkyl group having 4 to 9 carbon atoms; The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups is characterized by comprising the following steps: (1) Add L-lactic acid and monobasic fatty acid into a reactor and mix them evenly, add catalyst A, raise the temperature to 110°C~140°C, react for 2~6 hours to obtain a crude product, and the reaction product is post-treated to obtain lactic acid fatty acid ester; (2) Add the lactic acid fatty acid ester and epichlorohydrin obtained in step (1) into a reactor and mix them evenly, add catalyst B, raise the temperature to 100-130°C, and react for 1-4 hours; then cool to 40-80°C, add sodium hydroxide and calcium oxide respectively, and react for 1-4 hours to obtain a crude product; then filter, wash, and vacuum evaporate the crude product to obtain lactic acid fatty acid glycidyl ester; (3) adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into a reactor, heating it to 140°C to completely dissolve it, then adding the lactic acid fatty acid glycidyl ester obtained in step (2), heating it to 150-180°C, reacting for 2-6 hours to obtain a crude product, and then filtering, washing, and vacuum rotary evaporating the crude product to obtain a lactic acid fatty acid ester containing a phosphaphenanthrene group; (4) Acylation reaction is carried out on the lactic acid fatty acid ester containing phosphaphenanthrene groups obtained in step (3) with acetic anhydride, and the temperature is raised to 120-160° C. and the reaction is carried out for 1-3 hours. The reaction product is post-treated to obtain an acetylated lactic acid ester flame retardant plasticizer containing phosphaphenanthrene groups.

2. A method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups as claimed in claim 1, characterized in that: The following steps are involved: (1) Add L-lactic acid and monobasic fatty acid into a reactor and mix them evenly, add catalyst A, raise the temperature to 110°C~140°C, react for 2~6 hours to obtain a crude product, and the reaction product is post-treated to obtain lactic acid fatty acid ester; (2) Add the lactic acid fatty acid ester and epichlorohydrin obtained in step (1) into a reactor and mix them evenly, add catalyst B, raise the temperature to 100-130°C, and react for 1-4 hours; then cool to 40-80°C, add sodium hydroxide and calcium oxide respectively, and react for 1-4 hours to obtain a crude product; then filter, wash, and vacuum evaporate the crude product to obtain lactic acid fatty acid glycidyl ester; (3) adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into a reactor, heating it to 140°C to completely dissolve it, then adding the lactic acid fatty acid glycidyl ester obtained in step (2), heating it to 150-180°C, reacting for 2-6 hours to obtain a crude product, and then filtering, washing, and vacuum rotary evaporating the crude product to obtain a lactic acid fatty acid ester containing a phosphaphenanthrene group; (4) Acylation reaction is carried out on the lactic acid fatty acid ester containing phosphaphenanthrene groups obtained in step (3) with acetic anhydride, and the temperature is raised to 120-160° C. and the reaction is carried out for 1-3 hours. The reaction product is post-treated to obtain an acetylated lactic acid ester flame retardant plasticizer containing phosphaphenanthrene groups.

3. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (1), the molar ratio of L-lactic acid to monobasic fatty acid is 1-2:

1.

4. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (2), the molar ratio of lactic acid fatty acid ester to epichlorohydrin is 1:5-15.

5. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (3), the molar ratio of the epoxy bond in the lactic acid fatty acid glycidyl ester to the phosphorus-hydrogen bond in the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1-1.

5.

6. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (4), the molar ratio of lactic acid fatty acid ester to acetic anhydride is 1:1-1.

5.

7. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (1), the monobasic fatty acid is one of n-butyric acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid or n-nonanoic acid.

8. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the step (1), the catalyst A is one or more of concentrated sulfuric acid, phosphoric acid, p-toluenesulfonic acid, zinc oxide, aluminum oxide, tin oxide, and stannous oxide. The amount of catalyst A added is 0.1 to 1% of the mass of the reaction raw materials.

9. The method for preparing the acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups according to claim 2, characterized in that: In the selected step (2), the catalyst B is one or more of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide, and the amount of catalyst B added is 0.5-1.5% of the mass of the reaction raw materials.

10. The use of the acetylated lactic acid ester flame retardant plasticizer containing phosphaphenanthrene groups according to claim 1, characterized in that: The acetylated lactate flame retardant plasticizer containing phosphaphenanthrene groups is used as a main plasticizer in the field of plastics.

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