A multifunctional anhydride-type enhancer and its preparation method and application

Abstract

This invention discloses a multifunctional anhydride-type reinforcing agent, its preparation method, and its application. The multifunctional anhydride-type reinforcing agent uses a biphenyl fluorene derivative as its basic framework and is synthesized through a reaction. The anhydride molecule contains multiple functional groups, which can react with the hydroxyl groups of polylactic acid (PLA) molecules to increase the number-average molecular weight, thereby improving the melt strength of PLA. Simultaneously, the anhydride-type reinforcing agent of this invention contains ester groups, exhibiting certain compatibility. Adding a small amount can rapidly improve the melt strength of PLA, solving the problems of uneven cell structure and rough appearance caused by insufficient melt strength in existing PLA foams.

Description

Technical Field

[0001] This invention belongs to the field of polymer functional reagent technology, and more specifically, relates to a multifunctional anhydride-type reinforcing agent, its preparation method, and its application. Background Technology

[0002] Polylactic acid (PLA) exhibits good thermal stability, with a processing temperature range of 170–230°C. It also possesses good solvent resistance and can be processed in various ways, such as extrusion, spinning, biaxial stretching, and injection blow molding. In addition to being biodegradable, PLA products demonstrate good biocompatibility, gloss, transparency, feel, and heat resistance, making it a promising bio-based biodegradable material with broad application prospects.

[0003] In the application of sheet materials such as disposable lunch boxes and foamed packaging materials for cushioning, supercritical foaming and chemical foaming processes are generally used to reduce material costs. For foamed materials, the size and uniformity of the cells play a crucial role in the performance of the product. For low-magnification foamed sheets, small and uniform cells result in good toughness, high strength, and good surface quality. From the perspective of reducing the density of foamed sheets, only small and uniform cells offer the possibility of further density reduction; large and dispersed cells make further density reduction difficult. However, polylactic acid (PLA) melt strength is relatively poor, and during supercritical foaming, the pores are prone to collapse, resulting in low cell density, frequent cell coalescence, and a rough surface. To enhance the stability of the foamed pores, increasing the melt strength can effectively prevent gas loss, reduce cell coalescence, and improve the volume expansion rate of PLA foam. CN201910380087.2 discloses a high melt strength polylactic acid material and its preparation method, which comprises, by mass percentage, 95.7-99.7% polylactic acid (PLA), 0.1-5% 1,6-hexanediol diacrylate (HDDA), 0.01-0.4% dicumyl peroxide (DCP), and 0-2% processing aids. This invention uses dicumyl peroxide as an initiator and 1,6-hexanediol diacrylate as a grafting monomer, employing a melt extrusion grafting method in a twin-screw extruder to introduce a branched structure, thereby preparing high melt strength polylactic acid. Simultaneously, its crystallinity and toughness are also improved. Although grafting long branched structures onto the polylactic acid molecular chain alters the strain softening characteristics of ordinary polylactic acid and improves defects in the processing of polylactic acid, the grafting rate of this method is relatively low, limiting the efficiency of improving melt strength. Summary of the Invention

[0004] To overcome the problems of insufficient strength of existing polylactic acid melts leading to uneven cell structure and rough appearance during foaming, this invention provides a multifunctional anhydride-type reinforcing agent, its preparation method, and its application.

[0005] This invention is achieved through the following technical solution:

[0006] A multifunctional anhydride-type reinforcing agent, with the following structural formula:

[0007]

[0008] The multifunctional anhydride-type reinforcing agent utilizes the multiple anhydrides contained in its molecule to react with the hydroxyl groups of polylactic acid molecules, increasing the number-average molecular weight and thus improving the melt strength of polylactic acid. Simultaneously, the melt reinforcing agent molecule in this invention contains ester groups, exhibiting certain compatibility; adding a small amount can rapidly improve the melt strength of polylactic acid.

[0009] Furthermore, the preparation method of the multifunctional anhydride-type reinforcing agent includes the following steps:

[0010] S1. Dissolve the biphenyl fluorene derivative in an aprotic solvent, then add triethylamine, followed by trimellitic anhydride acyl chloride, and react.

[0011] S2. Filter and wash the product after the reaction in S1 to obtain a solid product. Then, put the solid product into acetic anhydride and crystallize it to obtain a multifunctional anhydride-type reinforcing agent.

[0012] Furthermore, the molar ratio of trimellitic anhydride acyl chloride to triethylamine in S1 is 1:1.

[0013] Further, the molar ratio of trimellitic anhydride acyl chloride to biphenyl fluorene derivative in S1 is 2-4:1. Preferably, the molar ratio of trimellitic anhydride acyl chloride to biphenyl fluorene derivative is 4:1.

[0014] Furthermore, the reaction temperature in S1 is -18℃, and the reaction time is 20h.

[0015] Furthermore, the aprotic solvent mentioned in S1 includes one or more of dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0016] Furthermore, the solid product in S2 is placed in acetic anhydride at a temperature maintained between -20 and -10°C for 20-30 hours.

[0017] Furthermore, the multifunctional anhydride-type reinforcing agent is applied to polylactic acid foam materials.

[0018] Furthermore, the polylactic acid foam material includes:

[0019] Polylactic acid 82-99 wt%

[0020] Multifunctional anhydride-type reinforcing agent 0.2–2 wt%

[0021] Antioxidant 0.1–1 wt%

[0022] Other processing aids: 0-15%.

[0023] Furthermore, the polylactic acid foam material contains L-polylactic acid, wherein the content of L-lactic acid is greater than 90%.

[0024] Furthermore, the antioxidant is antioxidant 168 or antioxidant 1010.

[0025] Further, the preparation steps of the polylactic acid foam material are as follows: polylactic acid, melt reinforcing agent and antioxidant are blended and then extruded and granulated at a temperature of 180-240°C to obtain polylactic acid granules, and then the polylactic acid granules are used to prepare polylactic acid foam sheets.

[0026] Compared with existing technologies, the beneficial effects are:

[0027] The multifunctional anhydride-type reinforcing agent of this invention uses biphenyl fluorene derivatives as its basic framework. The anhydride molecules synthesized through reaction contain multiple functional groups. These anhydride groups can react with the hydroxyl groups of polylactic acid (PLA) molecules, increasing the number-average molecular weight and thus improving the melt strength of PLA. Simultaneously, the anhydride-type reinforcing agent of this invention contains ester groups, exhibiting certain compatibility; adding a small amount can rapidly improve the melt strength of PLA. Detailed Implementation

[0028] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all commercially available.

[0029] In this implementation scheme, the selected polylactic acid is commercially available L-polylactic acid with a L-lactic acid content greater than 90%. Specifically, the trade name for Total Corbion is L175*, with a D-to-L-body mass ratio of 1 / 99; the trade name for Total Corbion is L175, with a D-to-L-body mass ratio of 4 / 96. The selected antioxidant is BASF antioxidant 1010.

[0030] Example 1

[0031] This embodiment provides a method for preparing a multifunctional anhydride-type reinforcing agent, the steps of which include:

[0032] S1. Dissolve 1 mol of 4-hydroxy biphenyl fluorene as shown in the figure in dimethylacetamide, then add 4 mol of triethylamine, and then slowly add 4 mol of trimellitic anhydride acyl chloride. React at -18℃ for 10 h.

[0033] S2. Filter the product from the reaction in S1, wash with anhydrous ethanol to remove triethylamine hydrochloride and solvent to obtain a solid product. Then, place the solid product in acetic anhydride and react at -18℃ for 24 hours to crystallize and obtain a multifunctional anhydride-type reinforcing agent. The reaction principle is as follows:

[0034]

[0035] Example 2

[0036] This embodiment provides a method for preparing a multifunctional anhydride-type reinforcing agent, the steps of which include:

[0037] S1. Dissolve 1 mol of 4-hydroxy biphenyl fluorene in dimethylacetamide, then add 3 mol of triethylamine, and then slowly add 3 mol of trimellitic anhydride acyl chloride. React at -18℃ for 10 h.

[0038] S2. Filter the product after the reaction in S1, wash it with anhydrous ethanol to remove triethylamine hydrochloride and solvent to obtain a solid product, then put the solid product into acetic anhydride, react it at -18℃ for 24 h to crystallize and obtain a multifunctional anhydride-type reinforcing agent.

[0039] Example 3

[0040] This embodiment provides a method for preparing a multifunctional anhydride-type reinforcing agent, the steps of which include:

[0041] S1. Dissolve 1 mol of 4-hydroxy biphenyl fluorene in dimethylacetamide, then add 2 mol of triethylamine, and then slowly add 2 mol of trimellitic anhydride acyl chloride. React at -18℃ for 10 h.

[0042] S2. Filter the product after the reaction in S1, wash it with anhydrous ethanol to remove triethylamine hydrochloride and solvent to obtain a solid product, then put the solid product into acetic anhydride, react it at -18℃ for 24 h to crystallize and obtain a multifunctional anhydride-type reinforcing agent.

[0043] Example 4

[0044] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0045] S1. Take 3000g of L-polylactic acid 175*, 6g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0046] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0047] S3. Prepare standard specimens of the modified polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0048] Example 5

[0049] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0050] S1. Take 1500g of L-polylactic acid 175*, 1500g of L-polylactic acid 175, 15g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0051] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0052] S3. Prepare standard specimens of the modified polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0053] Example 6

[0054] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0055] S1. Take 3000g of L-polylactic acid 175*, 25g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0056] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0057] S3. Prepare standard specimens of the modified polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0058] Example 7

[0059] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0060] S1. Take 3000g of L-polylactic acid 175*, 30g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0061] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0062] S3. Prepare standard specimens of the modified polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0063] Example 8

[0064] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0065] S1. Take 3000g of L-polylactic acid 175*, 45g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0066] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0067] S3. Prepare standard specimens of the modified polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0068] Example 9

[0069] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0070] S1. Take 3000g of L-polylactic acid 175*, 60g of multifunctional anhydride reinforcing agent and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0071] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0072] S3. The modified polylactic acid was used to prepare standard specimens, wherein the nozzle temperature was 220℃, the mold temperature was 80-90℃, and the holding pressure was 10-20s.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a polylactic acid (PLA) foam material, the raw materials of which include PLA and an antioxidant. Specific preparation steps include:

[0075] S1. Take 3000g of L-polylactic acid 175* and 15g of BASF antioxidant 1010 and add them to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0076] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0077] S3. Prepare standard specimens of the obtained polylactic acid, wherein the nozzle temperature is 220℃, the mold temperature is 80-90℃, and the holding pressure is 10-20s.

[0078] Example 10

[0079] This embodiment provides a method for preparing polylactic acid foam material, the raw materials of which include polylactic acid, the multifunctional anhydride reinforcing agent and antioxidant prepared in Example 1, and the specific preparation steps include:

[0080] S1. Add polylactic acid, multifunctional anhydride reinforcing agent, and antioxidant to a high-speed mixer and stir for 10 minutes to obtain a mixture.

[0081] S2. The mixture is granulated in a twin-screw extruder at a melting temperature of 180-230℃ and a screw length-to-diameter ratio greater than 30. After melting and plasticizing, the mixture is extruded, granulated, and dried to obtain modified polylactic acid.

[0082] S3. Add foaming agent, foaming aid, cell stabilizer and release agent to the modified polylactic acid and mix them. Then, mold the mixture in a mold to produce foamed material.

[0083] Uniaxial tensile rheological tests were performed on the polylactic acid materials prepared in Examples 4-9 and Comparative Example 1, respectively. The tensile rheological properties were tested using the tensile testing module of a Gottfert Rheograph 25 rheometer. The melt strength of the samples was characterized by the maximum tensile force at 175°C. The test results are shown in Table 1 below:

[0084] Table 1

[0085]

[0086] Table 1 shows that, compared to the polylactic acid (PLA) material without melt reinforcing agent in Comparative Example 1, the tensile strength and elongation at break of the PLA material with added multifunctional anhydride reinforcing agent did not change significantly. However, the addition of multifunctional anhydride reinforcing agent had a significant impact on the melt strength and impact strength of PLA. Within the range of 0.2–2 wt% of multifunctional anhydride reinforcing agent, the PLA melt strength increased with increasing multifunctional anhydride reinforcing agent content. The impact strength of PLA showed a trend of first increasing and then decreasing within this range, reaching a better effect when the multifunctional anhydride reinforcing agent content was 1 wt%. Furthermore, the PLA foam material prepared by this invention exhibited uniform cell size, no cell collapse, and a smooth surface.

[0087] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A multifunctional anhydride-type reinforcing agent, characterized in that, Its structural formula is: 。 2. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 1, characterized in that step... include: S1. Dissolve 4-hydroxy biphenyl fluorene in an aprotic solvent, then add triethylamine, followed by trimellitic anhydride acyl chloride, and react. S2. Filter and wash the product after the reaction in S1 to obtain a solid product. Then, put the solid product into acetic anhydride and crystallize it to obtain a multifunctional anhydride-type reinforcing agent.

3. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 2, characterized in that, The molar ratio of trimellitic anhydride chloride to triethylamine is 1:

1.

4. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 2, characterized in that, The molar ratio of trimellitic anhydride acyl chloride to biphenyl fluorene derivative is 2-4:

1.

5. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 2, characterized in that, The reaction temperature in S1 is -18℃, and the reaction time is 20h.

6. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 2, characterized in that, The aprotic solvent mentioned in S1 is one or more of dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

7. The method for preparing the multifunctional anhydride-type reinforcing agent according to claim 2, characterized in that, The solid product in S2 is placed in acetic anhydride at a temperature maintained between -20 and -10°C for 20-30 hours.

8. The multifunctional anhydride-type reinforcing agent according to claim 1 is applied to polylactic acid foam materials.

9. The application of the multifunctional anhydride-type reinforcing agent according to claim 8, characterized in that, The polylactic acid foam material includes 0.2-2 wt% of a multifunctional anhydride-type reinforcing agent.

10. The application of the multifunctional anhydride-type reinforcing agent according to claim 8, characterized in that, The polylactic acid foam material contains L-polylactic acid, with a L-lactic acid content greater than 90%.

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