Preparation method of polylactic acid microporous injection foaming material

Abstract

The invention discloses a preparation method of a polylactic acid microporous injection foaming material. The preparation method comprises the following steps: S1, putting a PBS matrix, a nucleating agent, a foaming agent, zinc oxide and PDMS into a mixing mill for mixing and pelletizing to obtain GAC; s2, adding a chain extender, a cross-linking agent, an antioxidant and white oil into LX530, mixing and stirring to obtain a mixture, and mixing and extruding to obtain PLAAU; s3, the PLAAU and the GAC are subjected to mixed injection molding to prepare injection molded parts, meanwhile, the preparation efficiency can be higher, polylactic acid injection molded products which meet the environmental protection requirement and have different boundary dimensions can be more efficiently prepared, a traditional injection molding machine can be adopted for preparing polylactic acid foaming products, and the application prospect is wide.

Description

[0001] The invention relates to the technical field of polylactic acid foaming materials, in particular to a method for preparing a polylactic acid microporous injection foaming material. Background Art

[0002] Among biodegradable materials, polylactic acid is a degradable plastic whose physical and mechanical properties are closest to those of polyolefins, and it can be manufactured commercially on a large scale. With the improvement of environmental awareness and the demand for sustainable development, polylactic acid, as a biodegradable green polymer material, is increasingly used in packaging, medical, automotive, home furnishing and other fields. Foaming technology can further reduce the density of polylactic acid materials, improve the buffering and thermal insulation properties of the materials, and meet more application requirements. However, the high price and high density of polylactic acid products limit their scope of use. In addition, the low melt strength and slow crystallization rate of polylactic acid limit its foaming properties. Therefore, when preparing polylactic acid foamed materials, polylactic acid needs to be modified to improve its melt strength and crystallization properties. The foaming methods of polylactic acid are generally divided into physical foaming and chemical foaming. Physical foaming uses supercritical CO 2 or N 2 As a foaming agent, the method of reducing pressure and raising temperature in a short time is adopted to make the gas foaming agent nucleate and grow inside the polylactic acid; chemical foaming is a method of using a foaming agent to react chemically to generate bubbles. Through the high-efficiency injection foaming method, polylactic acid products of various sizes and shapes can be prepared more efficiently, and lightweight can be achieved under the premise of certain environmental protection effects and mechanical properties, and costs can also be reduced. It has a wide range of application prospects. Polylactic acid microporous injection foaming materials have the characteristics of light weight, high strength, good thermal insulation performance, and excellent buffering performance. It has broad application prospects in packaging materials, automotive interiors, building insulation, biomedicine and other fields. With the continuous advancement of technology and the reduction of costs, the application field of polylactic acid microporous injection foaming materials will continue to expand. Therefore, it is a technical problem to provide a preparation method of polylactic acid microporous injection foaming materials to solve the toughness defects of polylactic acid while ensuring the excellent transparency of polylactic acid. Summary of the invention

[0003] To achieve the above purpose, the present invention provides a method for preparing a polylactic acid microporous injection foam material and a preparation method thereof.

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

[0005] Step S1: Put PBS matrix, nucleating agent, foaming agent, zinc oxide and PDMS into a mixer for mixing at a temperature of 100-105° C., a rotation speed of 45-50 rpm, and a time of 10-15 min, and pelletize to obtain GAC;

[0006] Step S2: Add chain extender, crosslinker, antioxidant and white oil to LX530, mix and stir 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°C, the melting section temperature is 170°C-180°C, the homogenization section temperature is 185-190°C, the die temperature is 180-185°C, the screw speed is 180-200rpm, the feeding motor operating frequency is 6.5-8.5Hz, and after extrusion, place in a blast oven at 75°C for 6h to obtain PLAAU

[0007] Furthermore, in step S1, by weight, 3-6 parts of PBS base, 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 are included.

[0008] Furthermore, the chain extender described in step S2 is 0.02-0.3 parts, the cross-linking agent is 0.01-0.4 parts, the plasticizer is 0.01-0.04 parts and the antioxidant is 0.01-0.04 parts by weight.

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

[0010] Furthermore, in step S2, the chain extender is BASF ADR-4468 or BASF AS-K25, the cross-linking 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 of the mixer are 100° C., the rotation speed is 50 rpm, and the mixing time is 10 min.

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

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

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

[0015] The invention relates to a method for preparing a polylactic acid microporous injection foam material. The prepared polylactic acid microporous injection foam material has a pore size of 50um-75um and a pore density of 1.5*10 6 cells / cm 3 -4.5*10 6 cells / cm 3 .

[0016] The present invention provides a method for preparing a polylactic acid microporous injection foam material, and a preparation method and application thereof, which have the following beneficial effects:

[0017] 1. Since the melt strength of polylactic acid is low, the direct foaming process for preparing related products will cause the internal bubbles to be easily broken. The present invention modifies the polylactic acid, blends a quantitative amount of foaming agent masterbatch and the modified polylactic acid into an injection molding machine that has not been specially modified, uses a lower injection pressure and a faster injection speed to match a higher holding pressure, and the injection temperature is adjusted from a high to a low gradient from a feeding part to a nozzle, the injection speed is about 80%, the holding time is maintained at about 2s, and the entire injection molding time is controlled at about 20s, thereby efficiently preparing a polylactic acid microporous injection foam material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM electron microscope photograph of the liquid nitrogen brittle fracture surface of the dumbbell-shaped injection molded specimen of Example 1. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 tests with the same components, component contents, preparation steps and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0021] The sources of the materials mentioned in the present invention are as follows: Corbijn LX530 was purchased from Total Energy Corbijn; TMC-300 was purchased from Shanxi Chemical Research Institute.

[0022] Unless otherwise stated, all reagents were used as received without further purification.

[0023] In the preparation examples and embodiments of the present invention, the “parts” are parts by weight unless otherwise specified, and the concentration percentages are concentrations by weight unless otherwise specified.

[0024] Example 1

[0025] This embodiment provides a polylactic acid injection foam product, and the preparation method thereof specifically comprises the following steps:

[0026] Step S1: 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 were put into a mixer, the process was set at 100°C and the speed was 50 rpm, and after mixing for 10 minutes, pelletization was performed to obtain GAC;

[0027] Step S2: Add 0.2 parts of AS-K25, 0.02 parts of UN3106, 0.02 parts of B225 and 0.03 parts of white oil to 9.1 parts of LX530, mix and stir to obtain a mixture, take 10 parts of the mixture and put it into a high-speed mixer for mixing, and then put it into a twin-screw extruder, the feed port temperature is 150°C, the melting section temperature is 175°C, the homogenization section temperature is 185°C, the die temperature is 180°C, the screw speed is 200rpm, the feeding motor operating frequency is 8Hz, and after extrusion, it is placed in a blast oven at 75°C for drying for 6 hours to obtain PLAAU1.

[0028] Step S3: 100 parts of PLAAU1 and 3 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare injection molded parts. The injection molding 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 brittle fracture surface of the injection molded part prepared in Example 1 was scanned by SEM electron microscope, and the results are shown in Figure 1 It can be seen that the pores are evenly distributed, mixed evenly, and of relatively consistent size, and the foaming effect is good. The dumbbell shape indicates that the cracks are hindered in the process of expansion and the stress is strong.

[0030] Comparative Example 1

[0031] Steps S1 and S3 are consistent with Example 1, except that in step S2, 0.02 parts of B225 and 0.03 parts of white oil are added to 9.95 parts of LX530, mixed and stirred to obtain a mixture, 10 parts of the mixture are put into a high mixer for mixing, and then put into a twin-screw extruder, the feed port temperature is 150° C., the melting section temperature is 180° C., the homogenization section temperature is 185° C., the die temperature is 180° C., the screw speed is 200 rpm, the operating frequency of the feeding motor is 8 Hz, and after extrusion, it is placed in a blast oven at 75° C. for drying for 6 h 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] Through testing and comparative analysis, it is found that the melt strength of PLAAU1 in Example 1 is significantly improved, and the melt index is within the processable range, meeting the requirements for injection molding.

[0036] Example 2

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

[0038] Step S1: 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 were put into a mixer, the process was set at 100°C and the speed was 50 rpm, and after mixing for 10 minutes, pelletization was performed to obtain GAC;

[0039] Step S2: Add 0.02 parts of ADR-4468, 0.02 parts of UN3106, 0.02 parts of antioxidant 1010 and 0.03 parts of white oil to 9.91 parts of LX530, mix and stir to obtain a mixture, take 10 parts of the mixture and put it into a high-speed mixer for mixing, put it into a twin-screw extruder, the feed port temperature is 150°C, the melting section temperature is 170°C, the homogenization section temperature is 190°C, the die temperature is 185°C, the screw speed is 200rpm, the feeding motor operating frequency is 8Hz, and after extrusion, it is placed in a blast oven at 75°C for drying for 6 hours to obtain PLAAU2.

[0040] Step S3: 100 parts of PLAAU2 and 3 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part. The injection molding 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 consistent with Example 2, except that in step S2: 0.02 parts of antioxidant 1010 and 0.03 parts of white oil are added to 9.93 parts of LX530, mixed and stirred to obtain a mixture, 10 parts of the mixture are put into a high-speed mixer for mixing, and then put into a twin-screw extruder, the feed port temperature is 150°C, the melting section temperature is 180°C, the homogenization section temperature is 190°C, the die temperature is 185°C, the screw speed is 200rpm, the feeding motor operating frequency is 8Hz, and after extrusion, it is placed in a blast oven at 75°C for drying for 6h 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 has changed from a multi-functional chain extender to an epoxy ring chain extender, which has increased the compatibility of PLA and PBS to a certain extent, and the effect of improving the melt strength is also more obvious.

[0047] Comparative Example 3

[0048] Steps S1 and S2 are consistent with Example 1, except that in step S3: 100 parts of PLAAU1 and 1 part of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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 consistent with Example 1, except that step S3: 100 parts of PLAAU1 and 5 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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 consistent with Example 1, except that step S3: 100 parts of PLAAU1 and 7 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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 consistent with Example 2, except that in step S3: 100 parts of PLAAU2 and 1 part of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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 consistent with Example 2, except that step S3: 100 parts of PLAAU2 and 5 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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 consistent with Example 2, except that step S3: 100 parts of PLAAU2 and 7 parts of GAC are mixed and added into the hopper of an injection molding machine for injection molding to prepare an injection molded part, the injection molding 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] The examples and comparative examples 3-8 were subjected to surface and compression tests. The surface of the material was observed using a microscope. The samples were placed on a testing device such as a universal tensile machine, and compression tests were performed according to the set parameters. The compression deformation of the 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 return to original position rate was 20 mm / min. The results are shown in Table 3.

[0060] Table 3

[0061]

[0062]

[0063] As can be seen from Table 3, when the amount of foaming agent added is too much, the gas cannot be fully dissolved and diffused, the formation of bubbles is not restricted, and the mechanical properties of the product are also greatly affected. It can be seen from the weight loss data compared with the DBL spline 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 are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modification and substitution of the present invention is also within the scope of the present invention. Therefore, the equivalent changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a polylactic acid microporous injection foam material, characterized in that: The steps include: Step S1: Put PBS matrix, nucleating agent, foaming agent, zinc oxide and PDMS into a mixer for mixing at a temperature of 100-105° C., a rotation speed of 45-50 rpm, and a time of 10-15 min, and pelletize to obtain GAC; Step S2: adding a chain extender, a cross-linking agent, an antioxidant and white oil to LX530, mixing and stirring to obtain a mixture, extruding and granulating the mixture using a twin-screw extruder with an aspect ratio of less than 35, with a feed port temperature of 150-160° C., a melting section temperature of 170° C.-180° C., a homogenization section temperature of 185-190° C., a die temperature of 180-185° C., a screw speed of 180-200 rpm, and a feeding motor operating frequency of 6.5-8.5 Hz. After extrusion, the mixture is placed in a blast oven at 75° C. for drying for 6 hours to obtain PLAAU; Step S3: PLAAU and GAC are mixed in a certain mass ratio and then injection molded to prepare an injection molded part.

2. The method for preparing the polylactic acid microporous injection foam material according to claim 1, characterized in that: In step S1, by weight, 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 are included.

3. The method for preparing the polylactic acid microporous injection foam material according to claim 1, characterized in that: In step S2, the components are 9-9.8 parts of LX530, 0.02-0.3 parts of chain extender, 0.01-0.04 parts of cross-linking agent, 0.01-0.04 parts of plasticizer and 0.01-0.04 parts of antioxidant, by weight.

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

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

6. The method for preparing the polylactic acid microporous injection foam material according to claim 1, characterized in that: In step S1, the process settings of the mixer are 100-105° C., the rotation speed is 45-50 rpm, and the mixing time is 10-15 min.

7. The method for preparing the 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°C, the melting section temperature is 170-180°C-180°C, the homogenization section temperature is 185-190°C, the die temperature is 180-185°C, and the screw speed is 180-200rpm.

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

9. The method for preparing a polylactic acid microporous injection foam material according to claim 1, characterized in that: The weight ratio of PLAAU to GAC in step S3 is 100:3.

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