A degradable polypropylene carbonate resin and preparation method thereof

Abstract

The present invention discloses a degradable polypropylene carbonate resin and a preparation method thereof. The resin is prepared by weight from 40-80 parts of modified polypropylene carbonate, 10-30 parts of modified ramie fiber, 10-30 parts of gelatinized starch masterbatch, and 0.5 parts of an auxiliary agent; wherein the polypropylene carbonate is modified with methacrylic acid; and the modified ramie fiber is modified with mercaptopropyltriethoxysilane. The terminal hydroxyl groups of the polypropylene carbonate are capped, an acrylate double bond is introduced, and the surface of the ramie fiber is functionalized by a mercapto-double bond click chemistry reaction. The ramie fiber is then cross-linked to the polypropylene carbonate resin molecules by chemical bonding, thereby improving the low interchain interaction force, low glass transition temperature, and poor thermal stability of the PPC molecular chain, thereby forming a modified material with good compatibility and excellent macroscopic performance.

Description

Technical Field

[0001] The invention relates to the technical field of polymer modified materials, in particular to a degradable polypropylene carbonate resin and a preparation method thereof. Background Art

[0002] Polypropylene carbonate, also known as poly(methyl ethylene carbonate) (PPC), is a fully biodegradable, environmentally friendly plastic synthesized from carbon dioxide and propylene oxide. Currently, PPC is widely used in fields such as food and medical packaging materials. However, the PPC chain is relatively flexible and amorphous, with relatively low interactions between the molecular chains and a low glass transition temperature. It also suffers from thermal sensitivity and high low-temperature brittleness, which severely limits the application and development of PPC. When a polypropylene carbonate polymer is heated and receives activation energy for thermal degradation, it can begin to degrade due to thermodynamic equilibrium. The thermal degradation mechanisms of polypropylene carbonate can be roughly divided into two categories: scissoring, in which any portion of the molecular ring breaks, and back-biting, in which a series of cyclic propylene carbonates are separated from the ends of the molecule.

[0003] Ramie is a perennial herbaceous plant belonging to the genus Ramie of the family Ramaceae. Also known as "Chinese grass," it is a unique hemp resource in China with a long history of cultivation. Ramie fiber develops from a single ramie cell. The fiber is slender, closed at both ends, and has a lumen. The thickness of the cell wall varies depending on the hemp variety and maturity. Ramie fiber is cylindrical or flat in its longitudinal appearance, without twists or turns. The outer surface of the fiber can be smooth or have distinct striations, with blunt ends. The cross-section of ramie fiber is elliptical, with an elliptical or oval-shaped central lumen. The cell wall thickness is uniform and has radial cracks. Summary of the Invention

[0004] The object of the present invention is to provide a degradable polypropylene carbonate resin and a preparation method thereof, so as to solve the problems of low interaction force between PPC molecular chains and low glass transition temperature in the prior art of degradable polypropylene carbonate resin proposed in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention discloses a biodegradable polypropylene carbonate resin, which is prepared by weight from 40-80 parts of modified polypropylene carbonate, 10-30 parts of modified ramie fiber, 10-30 parts of gelatinized starch masterbatch, and 0.5 parts of an additive. The polypropylene carbonate is modified with methacrylic acid, and the modified ramie fiber is modified with mercaptopropyltriethoxysilane. The gelatinized starch masterbatch serves as a biodegradable filler, reducing the cost of biodegradable plastics.

[0007] As a further embodiment of the present invention, the modification process of the modified polypropylene carbonate comprises the following steps:

[0008] Polypropylene carbonate is dissolved in chloroform, methacrylic acid is added thereto, and the mixture is heated under reflux with stirring, and cooled to obtain a first reaction solution. The heating temperature is 80-90°C, and the reflux stirring time is 4-6 hours. It should be noted that methacrylic acid acts as a capping agent, and its carboxyl group undergoes an esterification reaction with the hydroxyl group at the end of PPC.

[0009] The first reaction solution is heated and concentrated under stirring, and the concentrated reaction solution is added dropwise to an excess of anhydrous methanol. The precipitate is collected, washed with anhydrous methanol, and dried to obtain modified polypropylene carbonate. As a further embodiment of the present invention, the modification treatment of the modified ramie fiber includes the following steps:

[0010] Under the condition of passing nitrogen, ramie fiber is put into anhydrous ethanol, to which mercaptopropyl triethoxysilane is added, and the mixture is heated under reflux and stirred, and a second reaction liquid is obtained after cooling; wherein, the heating temperature is 70-80°C, and the reflux and stirring time is 4-6 hours; wherein, anhydrous ethanol serves as a medium for the grafting reaction between ramie fiber and mercaptopropyl triethoxysilane.

[0011] The second reaction liquid is filtered, and the filter residue is collected, washed with anhydrous ethanol, and then dried to obtain modified ramie fiber.

[0012] As a further solution of the present invention, the mass ratio of polypropylene carbonate to methacrylic acid is 300:(3-5). This is an optimal ratio summarized from multiple experiments, which is a comprehensive reflection of chemical reaction kinetics and chemical reaction equilibrium.

[0013] As a further embodiment of the present invention, the melt index of the polypropylene carbonate is 8 g / 10 min at 170° C. and 2.16 kg.

[0014] As a further solution of the present invention, the mass ratio of the ramie fiber to mercaptopropyl triethoxysilane is 20:(1-3). This is an optimal ratio summarized from multiple experiments, which is a comprehensive reflection of chemical reaction kinetics and chemical reaction equilibrium.

[0015] As a further solution of the present invention: the auxiliary agent is composed of antioxidant 1076, antioxidant 168, and oleamide in a mass ratio of 1:2:2.

[0016] Another aspect of the present invention discloses a method for preparing a degradable polypropylene carbonate resin as described in any one of the above, comprising the following steps:

[0017] Modified polypropylene carbonate, modified ramie fiber, gelatinized starch masterbatch and additives are weighed according to weight parts, mixed, extruded and granulated to obtain degradable polypropylene carbonate resin.

[0018] As a further solution of the present invention: the extrusion and granulation adopt a twin-screw extruder, and the extrusion temperatures in each extrusion zone of the twin-screw extruder are 130-150℃, 140-160℃, 155-175℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, and 160-180℃, respectively.

[0019] As a further solution of the present invention: the mixing is carried out using a high-speed mixer, and the mixing time is 5-15 minutes.

[0020] Another object of the present invention is to provide a degradable polypropylene carbonate resin prepared by the above-mentioned preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] By capping the terminal hydroxyl groups of polypropylene carbonate, introducing double bonds of acrylate, and utilizing the thiol-double bond click chemistry reaction to functionalize the surface of ramie fiber, it is cross-linked to the polypropylene carbonate resin molecules through chemical bonding, thereby improving the low interaction force between PPC molecular chains, low glass transition temperature, and poor thermal stability, and forming a modified material with good compatibility and excellent macroscopic performance.

[0023] The polypropylene carbonate resin used in the present invention is a degradable resin material, and the ramie fiber is a natural fiber. Compared with general natural fibers, the ramie fiber has high rigidity, high heat resistance, and good processing resistance. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0027] Polypropylene carbonate, brand PPC-8801, manufactured by Jiangsu Zhongke Jinlong;

[0028] Methacrylic acid was purchased from Sigma-Aldrich;

[0029] Mercaptopropyltriethoxysilane was purchased from Sigma-Aldrich;

[0030] Ramie fiber was purchased from Shandong Jinyue Textile Co., Ltd.

[0031] Other raw materials not mentioned are commercially available conventional products and are not described in detail here.

[0032] In addition, "parts" described in the Examples and Comparative Examples refer to parts by weight unless otherwise specified.

[0033] Example 1

[0034] S1: 300 g of polypropylene carbonate was dissolved in 200 ml of chloroform, 3 g of methacrylic acid was added thereto, and the mixture was refluxed and stirred at 80-90° C. for 5 h. After cooling to room temperature, a first reaction solution was obtained;

[0035] S2: Concentrating the first reaction solution by rotary evaporation under stirring, while adding anhydrous methanol dropwise, collecting the precipitate, washing and drying to obtain modified polypropylene carbonate;

[0036] S3: Under nitrogen, 20 g of ramie fiber was dissolved in 200 ml of anhydrous ethanol, 2 g of mercaptopropyltriethoxysilane was added thereto, and the mixture was heated under reflux at 70-80° C. with stirring for 5 h. After cooling to room temperature, a second reaction solution was obtained;

[0037] S4: filtering the second reaction liquid, collecting the filter residue, washing it with anhydrous ethanol, and drying it at 60° C. for 7 h to obtain modified ramie fiber;

[0038] S5: 40 parts of modified polypropylene carbonate, 30 parts of modified ramie fiber, 30 parts of gelatinized starch masterbatch, and 0.5 parts of an additive were weighed in parts by weight, and the mixture was added to a high-speed mixer and mixed for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder, mixed, extruded, cooled, and pelletized to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures of the extrusion zones of the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0039] Example 2

[0040] S1: 300 g of polypropylene carbonate was dissolved in 200 ml of chloroform, 4 g of methacrylic acid was added thereto, and the mixture was refluxed and stirred at 80-90° C. for 5 h, and then cooled to room temperature to obtain a first reaction solution;

[0041] S2: Concentrating the first reaction solution by rotary evaporation under stirring, while adding anhydrous methanol dropwise, collecting the precipitate, washing and drying to obtain modified polypropylene carbonate;

[0042] S3: Under nitrogen flow, 20 g of ramie fiber was dissolved in 200 ml of anhydrous ethanol, 1 g of mercaptopropyltriethoxysilane was added thereto, and the mixture was heated under reflux at 70-80° C. with stirring for 5 h. After cooling to room temperature, a second reaction solution was obtained;

[0043] S4: filtering the second reaction liquid, collecting the filter residue, washing it with anhydrous ethanol, and drying it at 60° C. for 7 h to obtain modified ramie fiber;

[0044] S5: 60 parts of modified polypropylene carbonate, 20 parts of modified ramie fiber, 20 parts of gelatinized starch masterbatch, and 0.5 parts of an additive were weighed in parts by weight, and the mixture was added to a high-speed mixer and mixed for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder, mixed, extruded, cooled, and pelletized to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures in each extrusion zone of the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0045] Example 3

[0046] S1: 300 g of polypropylene carbonate was dissolved in 200 ml of chloroform, 5 g of methacrylic acid was added thereto, and the mixture was refluxed and stirred at 80-90° C. for 5 h, and then cooled to room temperature to obtain a first reaction solution;

[0047] S2: Concentrating the first reaction solution by rotary evaporation under stirring, while adding anhydrous methanol dropwise, collecting the precipitate, washing and drying to obtain modified polypropylene carbonate;

[0048] S3: Under nitrogen, 20 g of ramie fiber was dissolved in 200 ml of anhydrous ethanol, 3 g of mercaptopropyltriethoxysilane was added thereto, and the mixture was heated under reflux at 70-80° C. with stirring for 5 h. After cooling to room temperature, a second reaction solution was obtained;

[0049] S4: filtering the second reaction liquid, collecting the filter residue, washing it with anhydrous ethanol, and drying it at 60° C. for 7 h to obtain modified ramie fiber;

[0050] S5: 80 parts of modified polypropylene carbonate, 10 parts of modified ramie fiber, 10 parts of gelatinized starch masterbatch, and 0.5 parts of an additive were weighed in parts by weight, and the mixture was added to a high-speed mixer and mixed for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder, mixed, extruded, cooled, and pelletized to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures of the extrusion zones in the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0051] Comparative Example 1

[0052] S1: Under nitrogen, 20 g of ramie fiber was dissolved in 200 ml of anhydrous ethanol, 1 g of mercaptopropyltriethoxysilane was added thereto, and the mixture was heated under reflux at 70-80°C with stirring for 5 h. After cooling to room temperature, a reaction solution was obtained;

[0053] S2: filtering the reaction solution in S1, collecting the filter residue, washing it with anhydrous ethanol, and drying it at 60° C. for 7 h to obtain modified ramie fiber;

[0054] S3: 60 parts of polypropylene carbonate, 20 parts of modified ramie fiber, 20 parts of gelatinized starch masterbatch, and 0.5 parts of an additive were weighed in parts by weight, and the mixture was added to a high-speed mixer and mixed for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder, mixed, extruded, cooled, and pelletized to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures in each extrusion zone of the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0055] Comparative Example 2

[0056] S1: 300 g of polypropylene carbonate was dissolved in 200 ml of chloroform, 4 g of methacrylic acid was added thereto, and the mixture was refluxed and stirred at 80-90° C. for 5 h, and then cooled to room temperature to obtain a reaction solution;

[0057] S2: Concentrating the reaction solution in S1 by rotary evaporation under stirring, while adding anhydrous methanol dropwise, collecting the precipitate, washing and drying to obtain modified polypropylene carbonate;

[0058] S3: 60 parts of modified polypropylene carbonate, 20 parts of ramie fiber, 20 parts of gelatinized starch masterbatch, and 0.5 parts of an additive were weighed by weight and added to a high-speed mixer for mixing for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder for mixing, extrusion, cooling, and pelletizing to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures in each extrusion zone of the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0059] Comparative Example 3

[0060] S1: 300 g of polypropylene carbonate was dissolved in 200 ml of chloroform, 4 g of methacrylic acid was added thereto, and the mixture was refluxed and stirred at 80-90° C. for 5 h, and then cooled to room temperature to obtain a first reaction solution;

[0061] S2: Concentrating the first reaction solution by rotary evaporation under stirring, while adding anhydrous methanol dropwise, collecting the precipitate, washing and drying to obtain modified polypropylene carbonate;

[0062] S3: Under nitrogen flow, 20 g of ramie fiber was dissolved in 200 ml of anhydrous ethanol, 1 g of mercaptopropyltriethoxysilane was added thereto, and the mixture was heated under reflux at 70-80° C. with stirring for 5 h. After cooling to room temperature, a second reaction solution was obtained;

[0063] S4: filtering the second reaction liquid, collecting the filter residue, washing it with anhydrous ethanol, and drying it at 60° C. for 7 h to obtain modified ramie fiber;

[0064] S5: 60 parts of modified polypropylene carbonate, 20 parts of modified ramie fiber, 20 parts of raw starch, and 0.5 parts of an additive were weighed by weight and mixed in a high-speed mixer for 10 minutes to obtain a mixture. The mixture was added to a twin-screw extruder, mixed, extruded, cooled, and pelletized to obtain a biodegradable polypropylene carbonate resin. The extrusion temperatures in each extrusion zone of the twin-screw extruder were 140°C, 150°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 170°C, respectively.

[0065] The properties of the degradable polypropylene carbonate resins prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The test items and test standards are shown in Table 1, and the test results are shown in Table 2.

[0066] Table 1 Test items and standards

[0067] Test items / units Test standards Melt index / g / 10min ISO 1133 Tensile strength / Mpa ISO 527 Flexural modulus / Mpa ISO 178 <![CDATA[Density / g / cm 3 > ISO 1183 3000h compost mass loss rate / % GB / T 19277.2

[0068] Note: Further test conditions and test specimen dimensions are as follows:

[0069] Melt index conditions: 170℃, 2.16kg;

[0070] Tensile strength test: using 1A type molded specimens, tensile speed 50mm / min;

[0071] Flexural modulus: sample size 100 mm*10 mm*4 mm, test speed 2 mm / min.

[0072] Table 2 Test results

[0073]

[0074] From Table 2, it can be seen that by modifying the end groups of the polypropylene carbonate resin, the melt index, mechanical properties and degradability of the degradable polypropylene carbonate resins in Examples 1-3 are better than those in Comparative Examples 1-3; among them, by comparing the test results of Example 2 and Comparative Example 1, it can be seen that the mechanical properties of the resin material obtained by using unmodified polypropylene carbonate in the preparation method are very poor, especially the flexural modulus, indicating that the chain decomposition reaction of the polypropylene carbonate is optimized after modification; by comparing Example 2 and Comparative Example 2, it can be seen that the addition of surface-treated ramie fiber improves its compatibility with polypropylene carbonate; by comparing Example 2 and Comparative Example 3, it can be seen that the use of ungelatinized starch will cause severe carbonization of the resin material during processing, resulting in a decrease in the melt index and mechanical properties, and the degradation performance is also greatly affected.

[0075] Although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0076] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent modifications made according to the scope of the claims of the present application are within the scope of protection of the claims of the present application.

Claims

1. A degradable polypropylene carbonate resin, characterized in that: The invention relates to a novel nanostructured carbonic acid cellulose ester composite material, which is prepared by weight from 40-80 parts of modified polypropylene carbonate, 10-30 parts of modified ramie fiber, 10-30 parts of gelatinized starch masterbatch and 0.5 parts of an auxiliary agent; wherein the modified polypropylene carbonate is polypropylene carbonate modified with methacrylic acid; and the modified ramie fiber is ramie fiber modified with mercaptopropyl triethoxysilane. The processing method of the modified polypropylene carbonate comprises the following steps: Dissolve polypropylene carbonate in chloroform, add methacrylic acid, heat under reflux with stirring, and cool to obtain a first reaction solution; wherein the heating temperature is 80-90°C and the reflux stirring time is 4-6 hours; The first reaction solution is heated and concentrated under stirring, and the concentrated reaction solution is added dropwise into an excess of anhydrous methanol, and the precipitate is collected, washed with anhydrous methanol, and dried to obtain modified polypropylene carbonate; The mass ratio of the polypropylene carbonate to methacrylic acid is 300:(3-5); The mass ratio of the ramie fiber to mercaptopropyl triethoxysilane is 20:(1-3).

2. A degradable polypropylene carbonate resin according to claim 1, characterized in that: The method for treating the modified ramie fiber comprises the following steps: Under nitrogen flow, ramie fiber is added to anhydrous ethanol, mercaptopropyl triethoxysilane is added thereto, heated under reflux and stirring, and cooled to obtain a second reaction solution; wherein the heating temperature is 70-80° C., and the reflux and stirring time is 4-6 hours; The second reaction liquid is filtered, and the filter residue is collected, washed with anhydrous ethanol, and then dried to obtain modified ramie fiber.

3. A degradable polypropylene carbonate resin according to claim 2, characterized in that: The melt index of the polypropylene carbonate is 8 g / 10 min at 170° C. and 2.16 kg.

4. The degradable polypropylene carbonate resin according to claim 1, characterized in that: The auxiliary agent is composed of antioxidant 1076, antioxidant 168, and oleamide in a mass ratio of 1:2:

2.

5. The method for preparing a degradable polypropylene carbonate resin according to claims 1-4, characterized in that: The following steps are involved: Modified polypropylene carbonate, modified ramie fiber, gelatinized starch masterbatch and additives are weighed according to weight parts, mixed, extruded and granulated to obtain degradable polypropylene carbonate resin.

6. The preparation method according to claim 5, characterized in that The extrusion and granulation adopt a twin-screw extruder, and the extrusion temperature of each extrusion zone in the twin-screw extruder is 130-150℃, 140-160℃, 155-175℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, 160-180℃, and 160-180℃ respectively.

7. The preparation method according to claim 5, characterized in that The mixing is carried out using a high-speed mixer with a mixing time of 5-15 minutes.

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