Degradable composite material for injection molding and method for preparing the same

Abstract

This invention relates to the field of biodegradable materials technology, specifically to a biodegradable composite material for injection molding and its preparation method. The biodegradable composite material is made from the following raw materials in parts by weight: 50-70 parts polylactic acid, 15-25 parts polycaprolactone, 30-40 parts starch, 3-8 parts composite degradable catalytic fiber, 5-10 parts sepiolite powder, 5-10 parts talc powder, 2-5 parts clay, and 1-3 parts plasticizer. In this invention, by introducing a specially formulated composite degradable catalytic fiber as an additive into the injection molding material, not only is the injection molding material highly biodegradable and capable of rapid complete degradation under light exposure, but the mechanical properties of the biodegradable composite material are also effectively improved, giving it high strength and better meeting application requirements.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, specifically to a biodegradable composite material for injection molding and its preparation method. Background Technology

[0002] Injection molding is a method of shaping industrial products. Products are typically made using rubber injection molding and plastic injection molding. Injection molding can also be divided into injection compression molding and die casting. An injection molding machine (or simply injection molding machine) is the main molding equipment used to create various shapes of plastic products from thermoplastic or thermosetting plastics using plastic molds. Injection molding is achieved through the injection molding machine and molds. The resulting shape is often the final product, requiring no further processing before installation or use as a finished product. Many details, such as protrusions, ribs, and threads, can be formed in a single injection molding operation.

[0003] Traditional plastics are widely used due to several key characteristics: good processability, high plasticity, simple preparation, and low price. The monomers and polymerization methods of traditional plastics are flexible and varied, making them applicable in almost every industry. However, due to their low price and non-biodegradability, especially single-use plastic products, they are often carelessly discarded after use, causing increasingly serious pollution. For example, invention patent CN112778733A discloses a fully biodegradable material and its injection molding process. The fully biodegradable material includes bamboo powder, cassava powder, bio-resin, PLA, PBS, and talc, which are mixed and then catalyzed by bio-enzymes. The injection molding process includes: preheating the fully biodegradable material to 50-70℃; heating the preheated material to 120-150℃ until it reaches a molten state; injecting the molten material into a mold cavity and holding it under pressure for a short time (T1); and allowing the mold to cool after injection molding. This process rapidly cools the mold cavity temperature from 140-160℃ during injection to 10-15℃ within a short time (T2), allowing for demolding and product acquisition. This injection molding material can completely degrade under composting conditions in approximately 180 days, with microbial digestion breaking it down into CO2 and H2O. While it can achieve complete degradation, the degradation rate is slow, often requiring about six months to fully degrade, easily leading to waste accumulation in the environment and increasing environmental burden. Furthermore, this injection molding material is formed from conventional raw materials, resulting in generally poor mechanical properties, limiting its applicability and making large-scale promotion and use difficult. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to provide a biodegradable composite material for injection molding and a method for preparing the same.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A biodegradable composite material for injection molding, said biodegradable composite material is made from the following raw materials in parts by weight: 50-70 parts polylactic acid, 15-25 parts polycaprolactone, 30-40 parts starch, 3-8 parts composite biodegradable catalytic fiber, 5-10 parts sepiolite powder, 5-10 parts talc powder, 2-5 parts clay, and 1-3 parts plasticizer.

[0007] As a further preferred embodiment of the present invention, the starch is composed of cassava starch, sweet potato starch and potato starch in a mass ratio of (2-3):(1-2):(1-2);

[0008] The plasticizer is at least one of tributyl citrate, triethyl citrate, and epoxidized soybean oil.

[0009] As a further preferred embodiment of the present invention, the method for preparing the composite degradation catalytic fiber is as follows:

[0010] 1) Place a titanium plate in a glycerol solution containing 0.5-0.8% ammonium fluoride by mass, with the titanium plate as the anode and a platinum sheet as the cathode. Set the distance between the two electrodes to 2-3 cm. At room temperature, pass a voltage of 20-25 V into the system for 2-3 hours. After the anodization is completed, rinse the obtained product repeatedly with deionized water and dry it. Transfer it to a tube furnace, heat it to 500-560℃ and calcine it for 2-5 hours to obtain titanium dioxide nanotubes.

[0011] 2) Immerse 2-5g of titanium dioxide nanotubes in 50-80mL of a mixture of equal volume water and ethanol containing 0.25-0.40g of silane coupling agent KH-570, stir at 80-90℃ for 1-3h, then wash the obtained product repeatedly with deionized water and dry it. Then, immerse the dried product in 50-80mL of silver nitrate solution at 60-65℃ for 1-3h, irradiate it under a xenon lamp for 1-3h, and dry the product obtained by photoreduction deposition to obtain composite titanium dioxide.

[0012] 3) In a tube furnace, urea is heated from room temperature to 550-600℃ and held at that temperature for 3-5 hours. After naturally cooling to room temperature, the resulting product is mixed with an equal mass of composite titanium dioxide and ball-milled to obtain a catalyst.

[0013] 4) Dissolve cationic dyeable polyester in hexafluoroisopropanol, stir thoroughly to dissolve, add catalyst, mix evenly to obtain spinning solution, electrospin the prepared spinning solution at room temperature, and dry the obtained fiber product to obtain the desired composite degradation catalytic fiber.

[0014] As a further preferred embodiment of the present invention, in step 1), the glycerol solution is composed of glycerol and deionized water in a volume ratio of (6-7):(3-4);

[0015] The heating rate in the tubular furnace is 3-5℃ / min.

[0016] As a further preferred embodiment of the present invention, in step 2), the concentration of the silver nitrate solution is 0.01-0.02 mol / L;

[0017] The power of the xenon lamp is 300-400W.

[0018] As a further preferred embodiment of the present invention, in step 3), the heating rate in the tubular furnace is 2-3℃ / min.

[0019] As a further preferred embodiment of the present invention, in step 4), the ratio of the amount of the cationic dyeable polyester, hexafluoroisopropanol and catalyst is (4-7)g:(20-50)mL:(0.5-0.8)g.

[0020] The parameters for electrospinning are as follows: voltage is 10-15kV, rotation speed is 3500-4000r / min, and distance from spinneret to receiver plate is 10-18cm.

[0021] A method for preparing a biodegradable composite material for injection molding specifically includes the following steps:

[0022] By weight, starch is pre-dried for 2-5 hours, then poured into a mixer, polylactic acid and polycaprolactone are added, the temperature is raised to 110-120℃, and stirred at 100-150 r / min for 3-8 minutes. Then the temperature is lowered to 80-86℃, composite degradable catalytic fiber, sepiolite powder, talc powder, clay and plasticizer are added, and stirring is continued for 10-15 minutes. Then it is added to a twin-screw extruder for melting and extrusion to obtain the desired degradable composite material.

[0023] As a further preferred embodiment of the present invention, the starch is pre-dried at a temperature of 50-56°C.

[0024] As a further preferred embodiment of the present invention, in the twin-screw extruder, the extrusion speed is 40-43 kg / hr and the screw speed is 320-360 rpm.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] In this invention, titanium dioxide nanotubes are prepared by anodizing using a titanium plate as a substrate. Under visible light, each titanium dioxide nanotube in soil moisture can be approximated as a small, short-circuited photoelectrochemical cell. Photogenerated electrons and holes generated by the photoelectric effect migrate to different positions on the surface of the titanium dioxide nanotube under the influence of an electric field. - They are easily captured by oxidizing substances such as dissolved oxygen in water, while cavitation h + This can oxidize the organic matter adsorbed on the surface of titanium dioxide nanotubes, or first remove the OH groups adsorbed on the surface of titanium dioxide nanotubes. - The hydroxyl radicals are oxidized by H2O molecules to form hydroxyl radicals, which have strong oxidizing power and can oxidize most organic and inorganic substances, mineralizing them into harmless substances such as inorganic small molecules, carbon dioxide, and water, thus enabling the material to degrade rapidly under light. Simultaneously, to further improve the photocatalytic activity of titanium dioxide nanotubes, metallic silver is used to modify the pretreated titanium dioxide nanotubes with silane coupling agents. This allows some silver ions to be incorporated into the titanium dioxide nanotubes and generate oxygen vacancies, effectively improving visible light utilization and thus accelerating the photocatalytic degradation rate. Furthermore, urea is used as a raw material, and graphitic nitriding is obtained through high-temperature calcination. Carbon is ball-milled and mixed with composite titanium dioxide to obtain a catalyst. The introduction of graphitic carbon nitride not only improves the defects of composite titanium dioxide such as narrow light absorption range and easy agglomeration, but also has the characteristic of absorbing visible light wavelengths, exhibiting excellent photocatalytic activity. This further enhances the photocatalytic performance of the formed catalyst. Moreover, by loading the catalyst onto fibers to form composite degradation catalytic fibers, the prepared biodegradable composite material not only has good degradation characteristics, but the network structure formed by their intertwining also helps to improve the mechanical properties of the biodegradable composite material, giving it high strength and better meeting the application requirements.

[0027] In this invention, by introducing specially made composite degradable catalytic fibers as additives into injection molding materials, not only are the injection molding materials highly degradable and capable of rapid full degradation under light irradiation, but the mechanical properties of the injection molding materials are also effectively improved, giving them high strength characteristics and better meeting usage requirements. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this embodiment of the invention, the starch is composed of cassava starch, sweet potato starch, and potato starch in a mass ratio of 2:1:1;

[0030] The plasticizer is epoxidized soybean oil.

[0031] Example 1

[0032] A biodegradable composite material for injection molding, comprising the following parts by weight of raw materials: 50-70 parts polylactic acid, 15 parts polycaprolactone, 30 parts starch, 3 parts composite biodegradable catalytic fiber, 5 parts sepiolite powder, 5 parts talc powder, 2 parts clay, and 1 part plasticizer.

[0033] The preparation method of this biodegradable composite material is as follows:

[0034] By weight, starch is pre-dried at 50°C for 2 hours, then poured into a mixer, polylactic acid and polycaprolactone are added, the temperature is raised to 110°C, and stirred at 100 rpm for 3 minutes. Then the temperature is lowered to 80°C, and composite degradable catalytic fiber, sepiolite powder, talc powder, clay and plasticizer are added. Stirring is continued for 10 minutes, and then the mixture is added to a twin-screw extruder. It is melted and extruded at an extrusion speed of 40 kg / hr and a screw speed of 320 rpm to obtain the desired degradable composite material.

[0035] The preparation method of the composite degradation catalytic fiber is as follows:

[0036] 1) A titanium plate was placed in a glycerol solution containing 0.5% ammonium fluoride by mass, wherein the glycerol solution was composed of glycerol and deionized water in a volume ratio of 6:4. The titanium plate was used as the anode and the platinum sheet was used as the cathode. The distance between the two electrodes was set to 2 cm. At room temperature, a voltage of 20 V was applied to the system for 2 h. After the anodizing was completed, the product was repeatedly rinsed with deionized water and dried. It was then transferred to a tube furnace and heated to 500 °C at 3 °C / min and calcined for 2 h to obtain titanium dioxide nanotubes.

[0037] 2) Immerse 2g of titanium dioxide nanotubes in 50mL of a mixture of equal volume of water and ethanol containing 0.25g of silane coupling agent KH-570. Stir at 80℃ for 1h. Then, wash the obtained product repeatedly with deionized water and dry it. Then, immerse the dried product in 50mL of 0.01mol / L silver nitrate solution at 60℃ for 1h. Irradiate it under a 300W xenon lamp for 1h. After drying the product obtained by photoreduction deposition, composite titanium dioxide is obtained.

[0038] 3) Urea was heated from room temperature to 550°C in a tube furnace at a rate of 2°C / min, held at that temperature for 3 hours, and then naturally cooled to room temperature. The resulting product was mixed with an equal mass of composite titanium dioxide and ball-milled to obtain a catalyst.

[0039] 4) Dissolve 4g of cationic dyeable polyester in 20mL of hexafluoroisopropanol. After stirring and dissolving thoroughly, add 0.5g of catalyst and mix evenly to obtain a spinning solution. Perform electrospinning at room temperature with a voltage of 10kV, a rotation speed of 3500r / min, and a distance of 10cm between the spinneret and the receiving plate. After drying the obtained fiber product, the desired composite degradation catalytic fiber can be obtained.

[0040] Example 2

[0041] A biodegradable composite material for injection molding, the biodegradable composite material being made from the following raw materials in parts by weight: 60 parts polylactic acid, 20 parts polycaprolactone, 35 parts starch, 5 parts composite biodegradable catalytic fiber, 7 parts sepiolite powder, 7 parts talc powder, 3 parts clay, and 2 parts plasticizer.

[0042] The preparation method of this biodegradable composite material is as follows:

[0043] By weight, starch is pre-dried at 52°C for 3 hours, then poured into a mixer, polylactic acid and polycaprolactone are added, the temperature is raised to 115°C, and stirred at 130 r / min for 5 minutes. Then the temperature is lowered to 82°C, composite degradable catalytic fiber, sepiolite powder, talc powder, clay and plasticizer are added, and stirring is continued for 12 minutes. Then it is added to a twin-screw extruder and melted and extruded at an extrusion speed of 42 kg / hr and a screw speed of 350 rpm to obtain the desired degradable composite material.

[0044] The preparation method of the composite degradation catalytic fiber is as follows:

[0045] 1) A titanium plate was placed in a glycerol solution containing 0.7% ammonium fluoride by mass, wherein the glycerol solution was composed of glycerol and deionized water in a volume ratio of 7:3. The titanium plate was used as the anode and the platinum sheet was used as the cathode. The distance between the two electrodes was set to 3 cm. At room temperature, a voltage of 23 V was applied to the system for 2.5 h. After the anodizing was completed, the product was repeatedly rinsed with deionized water and dried. It was then transferred to a tube furnace and heated to 530 °C at 4 °C / min and calcined for 3 h to obtain titanium dioxide nanotubes.

[0046] 2) Immerse 3g of titanium dioxide nanotubes in 70mL of a mixture of equal volume of water and ethanol containing 0.35g of silane coupling agent KH-570. Stir at 85℃ for 2h. Then, wash the obtained product repeatedly with deionized water and dry it. Then, immerse the dried product in 70mL of 0.02mol / L silver nitrate solution at 62℃ for 2h. Irradiate it under a 350W xenon lamp for 2h. After drying the product obtained by photoreduction deposition, composite titanium dioxide is obtained.

[0047] 3) Urea was heated from room temperature to 570°C in a tube furnace at a rate of 3°C / min, held at that temperature for 4 hours, and then naturally cooled to room temperature. The resulting product was mixed with an equal mass of composite titanium dioxide and ball-milled to obtain a catalyst.

[0048] 4) Dissolve 5g of cationic dyeable polyester in 40mL of hexafluoroisopropanol. After stirring and dissolving thoroughly, add 0.7g of catalyst and mix evenly to obtain a spinning solution. Perform electrospinning at room temperature with a voltage of 13kV, a rotation speed of 3600r / min, and a distance of 15cm between the spinneret and the receiving plate. After drying the obtained fiber product, the desired composite degradation catalytic fiber can be obtained.

[0049] Example 3

[0050] A biodegradable composite material for injection molding, the biodegradable composite material being made from the following raw materials in parts by weight: 70 parts polylactic acid, 25 parts polycaprolactone, 40 parts starch, 8 parts composite biodegradable catalytic fiber, 10 parts sepiolite powder, 10 parts talc powder, 5 parts clay, and 3 parts plasticizer.

[0051] The preparation method of this biodegradable composite material is as follows:

[0052] By weight, starch is pre-dried at 56°C for 5 hours, then poured into a mixer, polylactic acid and polycaprolactone are added, the temperature is raised to 120°C, and stirred at 150 rpm for 8 minutes. Then the temperature is lowered to 86°C, and composite degradable catalytic fiber, sepiolite powder, talc powder, clay and plasticizer are added. Stirring is continued for 15 minutes, and then the mixture is added to a twin-screw extruder. It is melted and extruded at an extrusion speed of 43 kg / hr and a screw speed of 360 rpm to obtain the desired degradable composite material.

[0053] The preparation method of the composite degradation catalytic fiber is as follows:

[0054] 1) A titanium plate was placed in a glycerol solution containing 0.8% ammonium fluoride by mass, wherein the glycerol solution was composed of glycerol and deionized water in a volume ratio of 7:3. The titanium plate was used as the anode and the platinum sheet was used as the cathode. The distance between the two electrodes was set to 3 cm. At room temperature, a voltage of 25 V was applied to the system for 3 h. After the anodizing was completed, the product was repeatedly rinsed with deionized water and dried. It was then transferred to a tube furnace and heated to 560 °C at 5 °C / min and calcined for 5 h to obtain titanium dioxide nanotubes.

[0055] 2) Immerse 5g of titanium dioxide nanotubes in 80mL of a mixture of equal volume of water and ethanol containing 0.40g of silane coupling agent KH-570. Stir at 90℃ for 3h. Then, wash the obtained product repeatedly with deionized water and dry it. Then, immerse the dried product in 80mL of 0.02mol / L silver nitrate solution at 65℃ for 3h. Irradiate it under a 400W xenon lamp for 3h. After drying the product obtained by photoreduction deposition, composite titanium dioxide is obtained.

[0056] 3) Urea was heated from room temperature to 600°C in a tube furnace at a rate of 3°C / min, held at that temperature for 5 hours, and then naturally cooled to room temperature. The resulting product was mixed with an equal mass of composite titanium dioxide and ball-milled to obtain a catalyst.

[0057] 4) Dissolve 7g of cationic dyeable polyester in 50mL of hexafluoroisopropanol. After stirring and dissolving thoroughly, add 0.8g of catalyst and mix evenly to obtain a spinning solution. Perform electrospinning at room temperature with a voltage of 15kV, a rotation speed of 4000r / min, and a distance of 18cm between the spinneret and the receiving plate. After drying the obtained fiber product, the desired composite degradation catalytic fiber can be obtained.

[0058] Comparative Example 1: This comparative example is basically the same as Example 1, except that it does not contain composite degradation catalytic fibers.

[0059] Comparative Example 2: This comparative example is basically the same as Example 1, except that titanium dioxide nanotubes are used instead of composite degradation catalytic fibers.

[0060] Comparative Example 3: This comparative example is basically the same as Example 1, except that composite titanium dioxide is used instead of composite degradation catalytic fiber.

[0061] Comparative Example 4: This comparative example is basically the same as Example 1, except that a catalyst is used instead of the composite degradation catalytic fiber.

[0062] Comparative Example 5: This comparative example is basically the same as Example 1, except that step 3 is omitted in the preparation of the composite degradation catalytic fiber.

[0063] Test experiment:

[0064] Degradable composite material samples were prepared according to the methods in Examples 1-3 and Comparative Examples 1-5, respectively. Then, the tensile strength of each sample was tested according to the standard GB / T1040.3-2006. After that, each sample was placed in the soil under natural light and the residual rate was observed after 3 months. The results are shown in Table 1.

[0065] Table 1

[0066] Example 1 Example 2 Example 3 Comparative Example 1 Tensile strength (MPa) 29.3 30.2 29.8 18.7 Residual rate % 0 0 0 53.8 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Tensile strength (MPa) 19.0 19.2 19.3 25.3 Residual rate % 20.7 17.6 14.3 10.5

[0067] As shown in Table 1, the biodegradable composite material of this invention can achieve rapid full degradation under light irradiation and also has high strength.

[0068] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A biodegradable composite material for injection molding, characterized in that, The biodegradable composite material is made from the following raw materials in parts by weight: 50-70 parts polylactic acid, 15-25 parts polycaprolactone, 30-40 parts starch, 3-8 parts composite biodegradable catalytic fiber, 5-10 parts sepiolite powder, 5-10 parts talc powder, 2-5 parts clay, and 1-3 parts plasticizer. The preparation method of the composite degradation catalytic fiber is as follows: 1) Place a titanium plate in a glycerol solution containing 0.5-0.8% ammonium fluoride by mass, with the titanium plate as the anode and a platinum sheet as the cathode. Set the distance between the two electrodes to 2-3 cm. At room temperature, pass a voltage of 20-25 V into the system for 2-3 hours. After the anodization is completed, rinse the obtained product repeatedly with deionized water and dry it. Transfer it to a tube furnace, heat it to 500-560℃ and calcine it for 2-5 hours to obtain titanium dioxide nanotubes. 2) Immerse 2-5g of titanium dioxide nanotubes in 50-80mL of a mixture of equal volume water and ethanol containing 0.25-0.40g of silane coupling agent KH-570, stir at 80-90℃ for 1-3h, then wash the obtained product repeatedly with deionized water and dry it. Then, immerse the dried product in 50-80mL of silver nitrate solution at 60-65℃ for 1-3h, irradiate it under a xenon lamp for 1-3h, and dry the product obtained by photoreduction deposition to obtain composite titanium dioxide. 3) In a tube furnace, urea is heated from room temperature to 550-600℃ and held at that temperature for 3-5 hours. After naturally cooling to room temperature, the resulting product is mixed with an equal mass of composite titanium dioxide and ball-milled to obtain a catalyst. 4) Dissolve cationic dyeable polyester in hexafluoroisopropanol, stir thoroughly to dissolve, add catalyst, mix evenly to obtain spinning solution, electrospin the prepared spinning solution at room temperature, and dry the obtained fiber product to obtain the desired composite degradation catalytic fiber.

2. The biodegradable composite material for injection molding according to claim 1, characterized in that, The starch is composed of cassava starch, sweet potato starch, and potato starch in a mass ratio of (2-3):(1-2):(1-2); The plasticizer is at least one of tributyl citrate, triethyl citrate, and epoxidized soybean oil.

3. The biodegradable composite material for injection molding according to claim 1, characterized in that, In step 1), the glycerol solution is composed of glycerol and deionized water in a volume ratio of (6-7):(3-4); The heating rate in the tubular furnace is 3-5℃ / min.

4. The biodegradable composite material for injection molding according to claim 1, characterized in that, In step 2), the concentration of the silver nitrate solution is 0.01-0.02 mol / L; The power of the xenon lamp is 300-400W.

5. The biodegradable composite material for injection molding according to claim 1, characterized in that, In step 3), the heating rate in the tubular furnace is 2-3℃ / min.

6. The biodegradable composite material for injection molding according to claim 1, characterized in that, In step 4), the ratio of the cationic dyeable polyester, hexafluoroisopropanol, and catalyst is (4-7) g: (20-50) mL: (0.5-0.8) g; The parameters for electrospinning are as follows: voltage is 10-15kV, rotation speed is 3500-4000r / min, and distance from spinneret to receiver plate is 10-18cm.

7. A method for preparing a biodegradable composite material for injection molding according to any one of claims 1-6, characterized in that, Specifically, the steps include the following: By weight, starch is pre-dried for 2-5 hours, then poured into a mixer, polylactic acid and polycaprolactone are added, the temperature is raised to 110-120℃, and stirred at 100-150 r / min for 3-8 minutes. Then the temperature is lowered to 80-86℃, composite degradable catalytic fiber, sepiolite powder, talc powder, clay and plasticizer are added, and stirring is continued for 10-15 minutes. Then it is added to a twin-screw extruder for melting and extrusion to obtain the desired degradable composite material.

8. A method for preparing a biodegradable composite material for injection molding according to claim 7, characterized in that, The starch is pre-dried at a temperature of 50-56℃.

9. A method for preparing a biodegradable composite material for injection molding according to claim 7, characterized in that, In the twin-screw extruder, the extrusion speed is 40-43 kg / hr and the screw speed is 320-360 rpm.