A method for preparing polylactic acid microporous injection foam material

Abstract

This application discloses a method for preparing polylactic acid microporous injection foam material, including step S1: adding PBS matrix, nucleating agent, foaming agent, zinc oxide and PDMS into a mixer for mixing and pelletizing to obtain GAC; step S2: adding chain extender, crosslinking agent, antioxidant and white oil to LX530, mixing and stirring to obtain a mixture, and extruding the mixture to obtain PLAAU; step S3: mixing PLAAU and GAC for injection molding to prepare injection molded parts. This method can also improve the preparation efficiency and can more efficiently prepare polylactic acid injection molded products of different shapes and sizes that meet environmental protection requirements. Moreover, this method can use traditional injection molding machines to prepare polylactic acid foamed products, and has broad application prospects.

Description

[0001] This invention relates to the field of polylactic acid foam materials technology, and in particular to a method for preparing polylactic acid microporous injection foam materials. Background Technology

[0002] Among biodegradable materials, polylactic acid (PLA) is a biodegradable plastic with physical and mechanical properties closest to polyolefins, and it can be manufactured on a large scale for commercial use. With increasing environmental awareness and the demand for sustainable development, PLA, as a biodegradable green polymer material, is increasingly widely used in packaging, medical, automotive, and home furnishing fields. Foaming technology can further reduce the density of PLA materials, improve their cushioning and thermal insulation properties, and meet more application needs. However, the high price and relatively high density of PLA products limit their application range. Furthermore, the low melt strength and slow crystallization rate of PLA limit its foaming performance. Therefore, when preparing PLA foam materials, PLA needs to be modified to improve its melt strength and crystallization properties. PLA foaming methods are generally divided into physical foaming and chemical foaming. Physical foaming uses supercritical CO2 or N2 as a foaming agent, employing a method of rapid pressure reduction and temperature increase to allow the gaseous foaming agent to nucleate and grow inside the PLA. Chemical foaming, on the other hand, uses a foaming agent to generate bubbles through a chemical reaction. Highly efficient injection molding methods allow for the production of polylactic acid (PLA) products of various sizes and shapes. While maintaining environmental friendliness and mechanical properties, this process achieves lightweighting and cost reduction, leading to a wide range of applications. PLA microporous injection-molded foam materials are characterized by their light weight, high strength, good thermal insulation, and excellent cushioning properties, making them promising for applications in packaging materials, automotive interiors, building insulation, and biomedicine. With continuous technological advancements and cost reductions, the application areas of PLA microporous injection-molded foam materials will continue to expand. Therefore, providing a method for preparing PLA microporous injection-molded foam materials that addresses the toughness defects of PLA while ensuring its excellent transparency is a pressing technical challenge. Summary of the Invention

[0003] To achieve the above objectives, this invention provides a method for preparing polylactic acid microporous injection foam material and the same method.

[0004] In a first aspect, the present invention provides a method for preparing a polylactic acid microporous injection foam material, comprising the following steps:

[0005] Step S1: Add PBS matrix, nucleating agent, foaming agent, zinc oxide and PDMS into a mixer and mix at a temperature of 100-105℃, a speed of 45-50 rpm and a time of 10-15 min. Then granulate to obtain GAC.

[0006] Step S2: Add chain extender, crosslinking agent, antioxidant, and white oil to LX530 and mix to obtain a mixture. Extrude and granulate using a twin-screw extruder with an aspect ratio of less than 35. The feed port temperature is 150-160℃, the melt zone temperature is 170-180℃, the homogenization zone temperature is 185-190℃, the die temperature is 180-185℃, the screw speed is 180-200 rpm, and the feed motor operating frequency is 6.5-8.5 Hz. After extrusion, place the mixture in a forced-air drying oven at 75℃ for 6 hours to obtain PLAAU.

[0007] Further, by weight, step S1 contains 3-6 parts PBS base, 4-7 parts foaming agent, 1-3 parts nucleating agent TMC-300, 0.3-0.5 parts PDMS and 0.02-0.06 parts zinc oxide.

[0008] Furthermore, by weight, 0.02-0.3 parts of chain extender, 0.01-0.4 parts of crosslinking agent, 0.01-0.04 parts of plasticizer and 0.01-0.04 parts of antioxidant are contained in step S2.

[0009] Furthermore, the PBS matrix mentioned in step S1 is Shandong Xuke 118; the foaming agent is Hangzhou Greenbee HH74; and the PDMS is Hubei Yamaide 9006-65-9 with a viscosity of 750 CP.

[0010] Furthermore, the chain extender mentioned in step S2 is BASF ADR-4468 or BASF AS-K25, the crosslinking agent is Dongguan Haosheng UN3106, the antioxidant is BASF 1010 or BASF B225, and the plasticizer is Suzhou Hesen 10# white oil.

[0011] Furthermore, in step S1, the process settings for the mixer are 100°C, 50 rpm, and 10 min.

[0012] Furthermore, in step S2, the feed port temperature of the twin-screw extruder is 150℃, the melting zone temperature is 170℃-180℃, the homogenization zone temperature is 185℃, the die temperature is 180℃, and the screw speed is 180-200 rpm.

[0013] Furthermore, in step S2, the operating frequency of the feeding motor is 6.5-8.5Hz, and the extruded material in step S2 needs to be dried at 75℃ for 6 hours in a forced-air drying oven.

[0014] Furthermore, the weight ratio of PLAAU and GAC in step S3 is 100:3.

[0015] This invention relates to a method for preparing polylactic acid (PLA) microporous injection foam material. The PLA microporous injection foam material prepared has internal pore sizes of 50µm-75µm and a pore density of 1.5*10⁻⁶. 6 cells / cm 3 -4.5*10 6 cells / cm 3 .

[0016] The present invention discloses a method for preparing polylactic acid microporous injection foam material, as well as the method for preparation and its application, which has the following beneficial effects:

[0017] 1. Due to the low melt strength of polylactic acid (PLA), direct foaming processes can easily cause internal cell rupture in related products. This invention modifies PLA by blending a fixed amount of foaming agent masterbatch with the modified PLA into an unmodified injection molding machine. A lower injection pressure, a faster injection speed, and a higher holding pressure are used, with the injection temperature gradient from high to low from the feeding point to the nozzle. The injection speed is around 80%, the holding time is maintained at around 2 seconds, and the entire injection time is controlled at around 20 seconds. This allows for the efficient preparation of PLA microporous injection foam materials. Attached Figure Description

[0018] Figure 1 This is a SEM image of the liquid nitrogen brittle fracture surface of the dumbbell-shaped injection-molded specimen from Example 1. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component content, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. Unless otherwise specified, the experimental materials used in the following examples are all purchased from commercial channels.

[0021] The materials mentioned in this invention were sourced as follows: Cobian LX530 was purchased from Total Energy Cobian; TMC-300 was purchased from Shanxi Chemical Research Institute.

[0022] Unless otherwise specified, all reagents should be used as is without further purification.

[0023] In the preparation examples and embodiments of the present invention, unless otherwise specified, "parts" refers to parts by weight, and unless otherwise specified, "concentration percentage" refers to weight concentration.

[0024] Example 1

[0025] This embodiment provides a polylactic acid injection foam product, the preparation method of which specifically includes the following steps:

[0026] Step S1: Add 5.597 parts of PBS118, 1 part of TMC-300 from Shanxi Chemical Research Institute, 3 parts of HH74, 0.03 parts of zinc oxide and 0.4 parts of PDMS into a mixer. Set the process temperature to 100℃ and the rotation speed to 50 rpm. Mix for 10 min and then pelletize to obtain GAC.

[0027] Step S2: Add 0.2 parts AS-K25, 0.02 parts UN3106, 0.02 parts B225 and 0.03 parts white oil to 9.1 parts LX530 and mix to obtain a mixture. Take 10 parts of the mixture and put it into a high-speed mixer for mixing. Then put it into a twin-screw extruder with the feed port temperature at 150℃, the melting zone temperature at 175℃, the homogenization zone temperature at 185℃, the die temperature at 180℃, the screw speed at 200rpm, and the operating frequency of the feed motor at 8Hz. After extrusion, place it in a forced-air drying oven at 75℃ for 6 hours to obtain PLAAU1.

[0028] Step S3: Mix 100 parts PLAAU1 and 3 parts GAC and add them to the hopper of the injection molding machine to prepare the injection molded part. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0029] The liquid nitrogen embrittlement fracture surface of the injection molded part prepared in Example 1 was scanned by SEM. The results are shown in the figure. Figure 1 It can be seen that the bubbles are evenly distributed, uniformly mixed, and relatively consistent in size, indicating a good foaming effect. The dumbbell shape indicates that the cracks are hindered during the expansion process, and the stress is relatively strong.

[0030] Comparative Example 1

[0031] Steps S1 and S3 are the same as in Example 1, except for step S2. In step S2, 0.02 parts of B225 and 0.03 parts of white oil are added to 9.95 parts of LX530 and mixed to obtain a mixture. 10 parts of the mixture are put into a high-speed mixer and then into a twin-screw extruder. The feed port temperature is 150°C, the melting zone temperature is 180°C, the homogenization zone temperature is 185°C, the die temperature is 180°C, the screw speed is 200 rpm, and the operating frequency of the feed motor is 8 Hz. After extrusion, the mixture is placed in a forced-air drying oven at 75°C for 6 hours to obtain DBL1.

[0032] The melt index, melt weight, and shear viscosity of Test Example 1 and Comparative Example 1 are shown in Table 1.

[0033] Table 1

[0034]

[0035] After testing and comparative analysis, it was found that the melt strength of PLAAU1 in Example 1 was significantly improved, and the melt index was within the processable range, meeting the requirements for injection molding.

[0036] Example 2

[0037] This embodiment provides a method for preparing polylactic acid microporous injection foam material, which specifically includes the following steps:

[0038] Step S1: Add 5.597 parts of PBS118, 1 part of TMC-300 from Shanxi Chemical Research Institute, 3 parts of HH74, 0.03 parts of zinc oxide and 0.4 parts of PDMS into a mixer. Set the process temperature to 100℃ and the rotation speed to 50 rpm. Mix for 10 min and then pelletize to obtain GAC.

[0039] Step S2: Add 0.02 parts ADR-4468, 0.02 parts UN3106, 0.02 parts antioxidant 1010 and 0.03 parts white oil to 9.91 parts LX530 and mix to obtain a mixture. Take 10 parts of the mixture and put it into a high-speed mixer for mixing. Then put it into a twin-screw extruder with the feed port temperature at 150℃, the melting zone temperature at 170℃, the homogenization zone temperature at 190℃, the die temperature at 185℃, the screw speed at 200rpm, and the operating frequency of the feed motor at 8Hz. After extrusion, place it in a forced-air drying oven at 75℃ for 6 hours to obtain PLAAU2.

[0040] Step S3: Mix 100 parts PLAAU2 and 3 parts GAC and add them to the hopper of the injection molding machine to prepare the injection molded part. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0041] Comparative Example 2

[0042] Steps S1 and S3 are the same as in Example 2, except for step S2: 0.02 parts of antioxidant 1010 and 0.03 parts of white oil are added to 9.93 parts of LX530 and mixed to obtain a mixture. 10 parts of the mixture are then fed into a high-speed mixer and fed into a twin-screw extruder. The feed port temperature is 150°C, the melting zone temperature is 180°C, the homogenization zone temperature is 190°C, the die temperature is 185°C, the screw speed is 200 rpm, and the feed motor operating frequency is 8 Hz. After extrusion, the mixture is placed in a forced-air drying oven at 75°C for 6 hours to obtain DBL2.

[0043] The melt index, melt weight, and shear viscosity of Test Example 2 and Comparative Example 2 are shown in Table 2.

[0044] Table 2

[0045]

[0046] Comparison of chain extender types: PLAAU1 changed from a multifunctional chain extender to an epoxy cyclic chain extender, which to some extent increased the compatibility of PLA and PBS, and the melt strength improvement effect was also more obvious.

[0047] Comparative Example 3

[0048] Steps S1 and S2 are the same as in Example 1, except for step S3: 100 parts PLAAU1 and 1 part GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0049] Comparative Example 4

[0050] Steps S1 and S2 are the same as in Example 1, except for step S3: 100 parts PLAAU1 and 5 parts GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0051] Comparative Example 5

[0052] Steps S1 and S2 are the same as in Example 1, except for step S3: 100 parts PLAAU1 and 7 parts GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0053] Comparative Example 6

[0054] Steps S1 and S2 are the same as in Example 2, except for step S3: 100 parts PLAAU2 and 1 part GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0055] Comparative Example 7

[0056] Steps S1 and S2 are the same as in Example 2, except for step S3: 100 parts PLAAU2 and 5 parts GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0057] Comparative Example 8

[0058] Steps S1 and S2 are the same as in Example 2, except for step S3: 100 parts PLAAU2 and 7 parts GAC are mixed and added to the hopper of the injection molding machine for injection molding to prepare injection molded parts. The injection temperature is 175°C, the injection pressure is 60 bar, the injection speed is 80%, the holding pressure is 80 bar, and the holding speed is 90%.

[0059] Surface and compression tests were performed on Examples 3-8 and Comparative Examples 3-8. The surface of the material was observed using a microscope. The samples were placed on a testing device such as a universal tensile tester and compression tests were performed according to the set parameters. The compression deformation of a single compression test was set to 90%, and the compression rate was set to 2 mm / min. The compression strain of the cyclic compression test was set to 60%, the compression rate was 2 mm / min, and the recovery rate was 20 mm / min. The results are shown in Table 3.

[0060] Table 3

[0061]

[0062]

[0063] As shown in Table 3, when the amount of foaming agent added is too large, the gas cannot be fully dissolved and diffused, the formation of cells is not restricted, and the mechanical properties of the product are greatly affected. From the weight loss data of the DBL samples, it can be seen that the weight loss of Example 1 is smaller than that of Comparative Examples 3-5, and the weight loss of Example 2 is smaller than that of Comparative Examples 6-8.

[0064] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A method for preparing polylactic acid microporous injection foam material, characterized in that, Includes the following steps: Step S1: Add PBS matrix, nucleating agent, foaming agent, zinc oxide and PDMS into a mixer and mix at a temperature of 100-105℃, a speed of 45-50 rpm and a time of 10-15 min. Then granulate to obtain GAC. Step S2: Add chain extender, crosslinking agent, antioxidant and white oil to LX530 and mix to obtain a mixture. Extrude and granulate using a twin-screw extruder with an aspect ratio of less than 35. The feed port temperature is 150-160℃, the melting zone temperature is 170℃-180℃, the homogenization zone temperature is 185-190℃, the die temperature is 180-185℃, the screw speed is 180-200rpm, and the operating frequency of the feed motor is 6.5-8.5Hz. After extrusion, place in a forced-air drying oven at 75℃ for 6 hours to obtain PLAAU. Step S3: Mix PLAAU and GAC by mass ratio and then injection mold to prepare injection molded parts; In step S1, by weight, there are 3-6 parts of PBS matrix, 4-7 parts of foaming agent, 1-3 parts of nucleating agent TMC-300, 0.3-0.5 parts of PDMS, and 0.02-0.06 parts of zinc oxide. In step S2, by weight, there are 9-9.8 parts of LX530, 0.02-0.3 parts of chain extender, 0.01-0.04 parts of crosslinking agent, 0.01-0.04 parts of plasticizer, and 0.01-0.04 parts of antioxidant. The weight ratio of PLAAU and GAC in step S3 is 100:

3.

2. The method for preparing polylactic acid microporous injection foam material according to claim 1, characterized in that, The PBS matrix mentioned in step S1 is Shandong Xuke 118; the foaming agent is Hangzhou Greenbay HH74; and the PDMS is Hubei Yamaide 9006-65-9 with a viscosity of 750 cP.

3. The method for preparing polylactic acid microporous injection foam material according to claim 1, characterized in that, The chain extender mentioned in step S2 is BASF ADR-4468 or BASF AS-K25, the crosslinking agent is Dongguan Haosheng UN3106, the antioxidant is BASF1010 or BASF B225, and the plasticizer is Suzhou Hesen 10# white oil.

4. The method for preparing polylactic acid microporous injection foam material according to claim 1, characterized in that, In step S1, the process settings for the mixer are 100-105℃, 45-50rpm, and 10-15min.

5. The method for preparing polylactic acid microporous injection foam material according to claim 1, characterized in that, In step S2, the feed port temperature of the twin-screw extruder is 150-160℃, the melting zone temperature is 170-180℃-180℃, the homogenization zone temperature is 185-190℃, the die temperature is 180-185℃, and the screw speed is 180-200rpm.

6. The method for preparing polylactic acid microporous injection foam material according to claim 1, characterized in that, In step S2, the operating frequency of the feeding motor is 6.5-8.5Hz, and the extruded material in step S2 needs to be dried in a forced-air drying oven at 75-80℃ for 6-8 hours.

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