Preparation method of aging-resistant polylactic acid material and aging-resistant polylactic acid material

Abstract

The invention discloses a method for preparing an aging-resistant polylactic acid material and the aging-resistant polylactic acid material comprises the following steps: S1: preparing a reactive anti-aging agent: mixing a hexamethylene diisocyanate trimer and a heterocyclic amine compound in an equal molar ratio, then heating, adding a catalyst when the reaction system reaches a uniform molten state, reacting under a nitrogen atmosphere, and preparing a reactive anti-aging agent; S2: preparing an aging-resistant polylactic acid material: mixing 98 to 99.5 parts of polylactic acid and 0.5 to 2 parts of the reactive anti-aging agent described in S1 uniformly by weight, heating and drying, melt blending in an extruder, extruding and granulating, and then heating and pressurizing in an injection molding machine to obtain an aging-resistant polylactic acid material. The invention has the advantages of simple preparation process, simple processing, good aging resistance, and good toughening effect of the prepared aging-resistant polylactic acid material.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a preparation method of an aging-resistant polylactic acid material and the aging-resistant polylactic acid material. Background Art

[0002] Lactic acid is a colorless and transparent liquid produced by modern biotechnology from corn full of starch. Lactic acid can then be used to generate granular polymer materials, namely polylactic acid (PLA) materials, through a special polymerization process. Polylactic acid (PLA), also known as polylactide, can be completely degraded by microorganisms in nature, eventually generating carbon dioxide and water. Polylactic acid has a high modulus, medium strength, good chemical inertness, easy processing, biocompatibility and environmental friendliness. It is considered to be one of the most competitive renewable biopolymers among many degradable materials and the most potential substitute for petroleum-based polymers. Polylactic acid has been widely used in packaging, medical, automotive, home, electronic appliances and other fields. However, polylactic acid also has some performance defects, such as poor toughness and aging resistance, which restricts its further application. Therefore, it is particularly important to improve the aging resistance of polylactic acid composite materials and extend their service life.

[0003] For example, Chinese patent CN112538241A discloses "an aging-resistant and hydrolysis-resistant biodegradable masterbatch and its preparation method and application", which is composed of 60-90 parts of biodegradable polyester, 6-8 parts of anti-hydrolysis agent, 4-8 parts of light stabilizer, 5-10 parts of ultraviolet absorber, 1-5 parts of antioxidant, 10-50 parts of pigment, and 1-10 parts of lubricant. Another example is Chinese patent CN114316544A discloses "a heat-resistant and aging-resistant polylactic acid composite material and its preparation method", which is prepared by the following weight percentage components: polylactic acid 20-80%, polybutylene adipate terephthalate 10% 50%, diethyl tartaric acid modified terpene resin grafted modified monomethoxy polyethylene glycol polylactic acid diblock copolymer 5% 20%, plasticizer 0.2% 5%, lubricant 0.2% 5%. For another example, Chinese patent CN116162337A discloses “aging-resistant polylactic acid material, preparation method thereof and tableware”, wherein the aging-resistant polylactic acid material comprises polylactic acid resin magnesium element, wherein the mass proportion of the magnesium element is 5ppm to 700ppm.

[0004] Although the above-mentioned preparation method of polylactic acid is helpful to improve the aging resistance of polylactic acid, it is common to directly add antioxidants, anti-aging agents, etc. into the masterbatch for preparing the composite material. The poor compatibility and insufficient dispersibility of the polylactic acid resin often lead to a decrease in the comprehensive performance of the prepared composite material, making the mechanical properties of the originally brittle polylactic acid even worse, seriously affecting the actual use effect of the polylactic acid. Therefore, in view of the shortcomings of the prior art, it is necessary to propose a preparation process that can simultaneously achieve aging resistance and toughening of polylactic acid. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method for preparing an aging-resistant polylactic acid material with good aging resistance and toughening effect and an aging-resistant polylactic acid material.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The preparation method of the aging-resistant polylactic acid material comprises the following steps:

[0008] S1: preparing a reactive antioxidant: mixing hexamethylene diisocyanate trimer and a heterocyclic amine compound in an equal molar ratio, then heating, and when the reaction system reaches a uniform molten state, adding a catalyst, reacting under a nitrogen atmosphere, to prepare a reactive antioxidant;

[0009] S2: Preparation of aging-resistant polylactic acid material: In parts by weight, 98-99.5 parts of polylactic acid and 0.5-2 parts of the reactive anti-aging agent described in S1 are mixed evenly, heated and dried, melt-blended and extruded into granules in an extruder, and then heated and pressurized by an injection molding machine to obtain the aging-resistant polylactic acid material.

[0010] Preferably, the heterocyclic amine compound in step S1 is any one of 2-aminobenzimidazole, 2-aminooxazole, 2-aminobenzothiazole, and 2-aminobenzothiazole-6-carboxylic acid.

[0011] Preferably, the catalyst in step S1 is any one of bismuth decanoate, bismuth laurate, bismuth isooctanoate, bismuth cyclohexaneate, and bis(dimethylaminoethyl) ether.

[0012] Preferably, the heating temperature in step S1 is 60° C., the reaction temperature range in the nitrogen atmosphere in step S1 is 60-80° C., and the reaction time range in the nitrogen atmosphere in step S1 is 0.5-2 h.

[0013] Preferably, the heating and drying temperature in step S2 is 80° C., and the heating and drying time ranges from 4 to 8 hours.

[0014] Preferably, the temperature range of melt blending in step S2 is 170-190° C., the speed range of the extruder is 60-80 r / min, and the time range of melt blending is 5-10 min.

[0015] Preferably, in step S2, the heating temperature range of the injection molding machine is 180-190° C., and the pressurization pressure of the injection molding machine is 10 MPa.

[0016] The invention also discloses an aging-resistant polylactic acid material, which is prepared according to the preparation method of the aging-resistant polylactic acid material.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects:

[0018] The preparation method of the aging-resistant polylactic acid material provided by the present invention is to carry out addition polymerization reaction between two NCO groups in the structure of the reactive anti-aging agent and the terminal hydroxyl group and the terminal carboxyl group in the polylactic acid, so that the reactive anti-aging agent is grafted into the polylactic acid material in the form of a covalent bond, which plays a reaction volume expansion role, thereby simultaneously improving the mechanical properties and anti-aging properties of the aging-resistant polylactic acid material, and solving the problems of uneven dispersion of the anti-aging agent and reduced mechanical properties in the existing compounding process; at the same time, the preparation process of the aging-resistant polylactic acid material provided by the present invention is simple, the processing is simple, the aging-resistant property is good, the toughening effect is good, and the application field of the polylactic acid material can be broadened;

[0019] In summary, the present invention has the advantages of simple preparation process, simple processing, good aging resistance and toughening effect of the prepared aging-resistant polylactic acid material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic flow chart of the preparation method of the aging-resistant polylactic acid material of the present invention;

[0021] Figure 2 It is a comparison chart of the aging resistance of the aging-resistant polylactic acid materials prepared in Examples 2-5 of the present invention, the polylactic acid material of Comparative Example 1, and the aging-resistant polylactic acid material of Comparative Example 2. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0023] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0024] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0028] Those skilled in the art will recognize that the chemical reactions described herein can be used to appropriately prepare many other compounds of the invention, and other methods for preparing the compounds of the invention are considered to be within the scope of the invention. For example, the synthesis of non-exemplified compounds according to the invention can be successfully accomplished by those skilled in the art through modification methods, such as appropriate protection of interfering groups, by utilizing other known reagents in addition to those described herein, or by making some conventional modifications to the reaction conditions. In addition, the reactions disclosed herein or known reaction conditions are also recognized to be applicable to the preparation of other compounds of the invention.

[0029] The raw materials used in the present invention are all from conventional drugs on the market in the field. Among them, the weight average molecular weight of polylactic acid is 140,000 and the optical purity is 90%.

[0030] The index mechanical property test method involved in the present invention is: according to ISO 527 standard, the dumbbell-shaped specimen size is 170mm×10mm×4mm, and the tensile performance test is carried out using a universal mechanical testing machine, the tensile rate is 50mm / min, and 5 parallel samples are tested for each group of samples.

[0031] The aging resistance performance test method of the index involved in the present invention is: ageing dumbbell-shaped polylactic acid material specimens at 100°C for 24h, 48h, 72h, 96h, 120h and 144h respectively, testing the mechanical properties after thermal oxidation aging, and calculating the retention rate of tensile strength based on the tensile strength of the unaged specimens.

[0032] Example 1

[0033] In this embodiment, a preparation method of an aging-resistant polylactic acid material and an aging-resistant polylactic acid material are proposed, which solves the problems of uneven dispersion of anti-aging agents and reduced mechanical properties in the existing compounding process, and can simultaneously improve the mechanical properties and anti-aging properties of the aging-resistant polylactic acid material. Moreover, the overall preparation process is simple, and the aging resistance and toughening effect are good.

[0034] like Figure 1 As shown, in one embodiment of the present invention, the method for preparing the aging-resistant polylactic acid material of the present invention comprises the following steps:

[0035] S1: preparing a reactive antioxidant: mixing hexamethylene diisocyanate trimer and a heterocyclic amine compound in an equal molar ratio, then heating, and when the reaction system reaches a uniform molten state, adding a catalyst, reacting under a nitrogen atmosphere, to prepare a reactive antioxidant;

[0036] S2: Preparation of aging-resistant polylactic acid material: In parts by weight, 98 to 99.5 parts of polylactic acid and 0.5 to 2 parts of the reactive anti-aging agent described in S1 are mixed evenly, heated and dried, melt-blended and extruded into granules in an extruder, and then heated and pressurized by an injection molding machine to obtain the aging-resistant polylactic acid material. It can be understood that the extruder is a micro extruder and the injection molding machine is a micro injection molding machine. It can be understood that in parts by weight, the range of the number of polylactic acid parts is 98 to 99.5 parts, and the range of the number of reactive anti-aging agents described in S1 is 0.5 to 2 parts.

[0037] Specifically, the heterocyclic amine compound in step S1 is any one or more of 2-aminobenzimidazole, 2-aminooxazole, 2-aminobenzothiazole, and 2-aminobenzothiazole-6-carboxylic acid, the catalyst in S1 is any one or more of bismuth decanoate, bismuth laurate, bismuth isooctanoate, bismuth cyclohexaneate, and bisdimethylaminoethyl ether, the heating temperature in step S1 is 60° C., the reaction temperature range in step S1 under a nitrogen atmosphere is 60 to 80° C., and the reaction time range in step S1 under a nitrogen atmosphere is 0.5 to 2 h.

[0038] The heating and drying temperature in step S2 is 80°C, the heating and drying time range is 4 to 8 hours, the melt blending temperature range in step S2 is 170 to 190°C, the extruder speed range is 60 to 80 r / min, the melt blending time range is 5 to 10 min, the heating temperature range of the injection molding machine in step S2 is 180 to 190°C, and the pressurization pressure of the injection molding machine is 10 MPa.

[0039] The present invention also discloses an aging-resistant polylactic acid material, which is prepared according to the above-mentioned preparation method of the aging-resistant polylactic acid material. Any aging-resistant polylactic acid material prepared according to the above-mentioned steps or simple deformation should be covered within the protection scope of the present invention.

[0040] The following Examples 2-5 will prepare the aging-resistant polylactic acid material of the present invention according to different ratios and conditions, and the present invention will also propose Comparative Examples 1 and 2. Comparative Examples 1 and 2 are existing polylactic acid materials or aging-resistant polylactic acid materials prepared according to prior art and existing materials, among which Examples 2-5 are aging-resistant polylactic acid materials prepared according to the method of the present invention, Comparative Example 1 is a polylactic acid material prepared according to prior art, and Comparative Example 2 is an aging-resistant polylactic acid material prepared according to prior art.

[0041] Example 2

[0042] This embodiment is to prepare an aging-resistant polylactic acid material according to the method in Example 1. Specifically, this embodiment provides a method for preparing an aging-resistant polylactic acid material, comprising the following steps:

[0043] S1: preparing a reactive antioxidant: mixing 0.5 mol of hexamethylene diisocyanate trimer and 0.5 mol of 2-aminooxazole, heating to 60°C, adding 0.1 g of bismuth laurate when the reaction system reaches a uniform molten state, reacting at 80°C for 0.5 h under a nitrogen atmosphere, and preparing a reactive antioxidant;

[0044] S2: Preparation of aging-resistant polylactic acid material: 99 parts of polylactic acid and 1 part of reactive antioxidant are mixed evenly by weight, heated and dried at 80°C for 4 hours, melt-blended in a micro extruder (wherein, the melt-blending temperature is 170°C, the micro-extruder speed is 80r / min, and the melt-blending time is 8min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine is 180°C, and the pressurization pressure of the injection molding machine is 10MPa) to obtain the aging-resistant polylactic acid material.

[0045] Example 3

[0046] This embodiment is to prepare an aging-resistant polylactic acid material according to the method in Example 1. Specifically, this embodiment provides a method for preparing an aging-resistant polylactic acid material, comprising the following steps:

[0047] S1: Preparation of reactive antioxidant: 0.5 mol of hexamethylene diisocyanate trimer and 0.5 mol of 2-aminobenzothiazole were mixed, and the temperature was raised to 60°C. When the reaction system reached a uniform molten state, 0.25 g of bis(dimethylaminoethyl)ether was added, and the mixture was reacted at 60°C for 2 h under a nitrogen atmosphere to prepare a reactive antioxidant;

[0048] S2: Preparation of aging-resistant polylactic acid material: In parts by weight, 98.5 parts of polylactic acid and 1.5 parts of reactive antioxidant are mixed evenly, heated and dried at 80°C for 6 hours, melt-blended in a micro extruder (wherein, the melt-blending temperature is 190°C, the micro-extruder speed is 60r / min, and the melt-blending time is 5min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine is 190°C, and the pressurization pressure of the injection molding machine is 10MPa) to obtain the aging-resistant polylactic acid material.

[0049] Example 4

[0050] This embodiment is to prepare an aging-resistant polylactic acid material according to the method in Example 1. Specifically, this embodiment provides a method for preparing an aging-resistant polylactic acid material, comprising the following steps:

[0051] S1: Preparation of reactive antioxidant: 0.5 mol of hexamethylene diisocyanate trimer and 0.5 mol of 2-aminobenzimidazole were mixed, and the temperature was raised to 60°C. When the reaction system reached a uniform molten state, 0.15 g of bismuth isooctanoate was added, and the mixture was reacted at 70°C for 1.5 h under a nitrogen atmosphere to prepare a reactive antioxidant;

[0052] S2: Preparation of aging-resistant polylactic acid material: In parts by weight, 99.5 parts of polylactic acid and 0.5 parts of reactive antioxidant are mixed evenly, heated and dried at 80°C for 8 hours, melt-blended in a micro extruder (melt blending temperature 185°C, micro extruder speed 70r / min, melt blending time 10min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine is 185°C, and the pressurization pressure of the injection molding machine is 10MPa) to obtain the aging-resistant polylactic acid material.

[0053] Example 5

[0054] This embodiment is to prepare an aging-resistant polylactic acid material according to the method in Example 1. Specifically, this embodiment provides a method for preparing an aging-resistant polylactic acid material, comprising the following steps:

[0055] This embodiment provides a method for preparing an aging-resistant polylactic acid material, and the steps are as follows:

[0056] S1: Preparation of reactive antioxidant: 0.5 mol of hexamethylene diisocyanate trimer and 0.5 mol of 2-aminobenzothiazole-6-carboxylic acid were mixed, and the temperature was raised to 60°C. When the reaction system reached a uniform molten state, 0.1 g of bismuth cyclohexaneate was added, and the mixture was reacted at 75°C for 1 h under a nitrogen atmosphere to prepare a reactive antioxidant;

[0057] S2: Preparation of aging-resistant polylactic acid material: 98 parts of polylactic acid and 2 parts of reactive antioxidant are mixed evenly by weight, heated and dried at 80°C for 5 hours, melt-blended in a micro extruder (melt blending temperature 180°C, micro extruder speed 80r / min, melt blending time 7min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine is 180°C, and the pressurization pressure of the injection molding machine is 10MPa) to obtain the aging-resistant polylactic acid material.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a polylactic acid material in the prior art, and the steps are as follows:

[0060] In parts by weight, 100 parts of polylactic acid were heated and dried at 80°C for 5 hours, melt-blended in a micro extruder (melt-blending temperature of 180°C, micro-extruder speed of 80r / min, melt-blending time of 7min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine was 180°C, and the pressurization pressure of the injection molding machine was 10MPa) to obtain the polylactic acid material.

[0061] Comparative Example 2

[0062] This comparative example provides a method for preparing an aging-resistant polylactic acid material in the prior art, and the steps are as follows:

[0063] In parts by weight, 98 parts of polylactic acid and 2 parts of commercially available anti-aging agent 2,6-di-tert-butyl-p-cresol are mixed evenly, heated and dried at 80°C for 5 hours, melt-blended in a micro extruder (melt blending temperature 180°C, micro extruder speed 80r / min, melt blending time 7min), extruded into granules, and then heated and pressurized by a micro injection molding machine (the heating temperature of the injection molding machine is 180°C, and the pressurization pressure of the injection molding machine is 10MPa) to obtain an aging-resistant polylactic acid material.

[0064] The aging-resistant polylactic acid materials or polylactic acid materials of Examples 2-5 and Comparative Examples 1-2 were subjected to mechanical property tests, and the results are shown in the following table.

[0065]

[0066]

[0067] It can be seen from the above table that the mechanical properties of the aging-resistant polylactic acid material prepared by the present invention are better than those of comparative examples 1-2, indicating that the reactive antioxidant has a good toughening effect.

[0068] The aging-resistant polylactic acid materials or polylactic acid materials prepared in Examples 2-5 and Comparative Examples 1-2 were subjected to thermal oxidation aging treatment at 100°C, and then subjected to mechanical property tests to observe the changes in the tensile strength of the polylactic acid materials before and after aging. Figure 2 As shown, the tensile strength retention rate of pure polylactic acid without adding an antioxidant after 144 hours of thermal oxidation aging is only 36%, while the tensile strength retention rate of Comparative Example 2 with 2% of commercial antioxidant added is 75%. The tensile strength retention rates of the aging-resistant polylactic acid material prepared by the present invention after 144 hours of thermal oxidation aging are 74%, 70%, 63% and 79% respectively, wherein the amount of reactive antioxidant added in Example 5 is 2%, which has better aging resistance than the commercial antioxidant added in the same amount in Comparative Example 2, and can effectively delay the aging of polylactic acid during use. Therefore, the preparation method of the aging-resistant polylactic acid material provided by the present invention is a new technology worthy of being widely promoted and applied.

[0069] This embodiment does not impose any formal limitation on the shape, material, structure, etc. of the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing an aging-resistant polylactic acid material, characterized in that , including the following steps: S1: preparing a reactive antioxidant: mixing hexamethylene diisocyanate trimer and a heterocyclic amine compound in an equal molar ratio, then heating, and when the reaction system reaches a uniform molten state, adding a catalyst, reacting under a nitrogen atmosphere, to prepare a reactive antioxidant; S2: preparing an aging-resistant polylactic acid material: by weight, 98-99.5 parts of polylactic acid and 0.5-2 parts of the reactive anti-aging agent described in S1 are mixed uniformly, heated and dried, melt-blended in an extruder, extruded and granulated, and then heated and pressurized by an injection molding machine to obtain an aging-resistant polylactic acid material; The heterocyclic amine compound in step S1 is any one of 2-aminobenzimidazole, 2-aminooxazole, and 2-aminobenzothiazole-6-carboxylic acid.

2. The method for preparing the aging-resistant polylactic acid material according to claim 1, characterized in that: The catalyst in step S1 is any one of bismuth decanoate, bismuth laurate, bismuth isooctanoate, bismuth cyclohexaneate, and bis(dimethylaminoethyl) ether.

3. The method for preparing the aging-resistant polylactic acid material according to claim 1, characterized in that: The heating temperature in step S1 is 60° C., the reaction temperature range in the nitrogen atmosphere in step S1 is 60-80° C., and the reaction time range in the nitrogen atmosphere in step S1 is 0.5-2 h.

4. The method for preparing the aging-resistant polylactic acid material according to claim 1, characterized in that: The heating and drying temperature in step S2 is 80° C., and the heating and drying time ranges from 4 to 8 hours.

5. The method for preparing the aging-resistant polylactic acid material according to claim 1, characterized in that: The temperature range of melt blending in step S2 is 170-190° C., the speed range of the extruder is 60-80 r / min, and the time range of melt blending is 5-10 min.

6. The method for preparing the aging-resistant polylactic acid material according to claim 1, characterized in that: In step S2, the heating temperature range of the injection molding machine is 180-190° C., and the pressurization pressure of the injection molding machine is 10 MPa.

7. Aging-resistant polylactic acid material, characterized by: It is obtained according to the preparation method of the aging-resistant polylactic acid material according to any one of claims 1 to 6.

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