阅读说明：本技术 一种预溶胀连续挤出发泡聚乳酸材料及其制备方法与应用 (Pre-swelling continuous extrusion foaming polylactic acid material and preparation method and application thereof ) 是由 谢德明 郭胜利 赵睿 张志成 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种预溶胀连续挤出发泡聚乳酸材料及其制备方法与应用。本发明发泡聚乳酸材料以聚乳酸作为基体树脂材料,结合交联剂、偶联剂、成核剂、泡孔稳定剂,以及作为发泡剂的有机溶剂复合溶胀及挤出实现发泡。本发明方法所需设备可以采用通用型挤出设备,工艺简单,便于实现大规模生产。本发明可以在较低温度下实现对聚乳酸材料的发泡加工,可以显著节省能耗,降低成本,同时避免高温下聚乳酸材料的热降解。本发明可以实现聚乳酸材料的微孔发泡,平均泡孔直径小于50μm,平均孔密度可达到10～(9)/cm～(3),发泡聚乳酸材料的机械性能显著提高,适合于制备聚乳酸发泡片材和管材,满足多种市场应用需求,具有良好的应用前景。(The invention discloses a pre-swelling continuous extrusion foaming polylactic acid material and a preparation method and application thereof. The foaming polylactic acid material takes polylactic acid as a matrix resin material, and realizes foaming by combining a cross-linking agent, a coupling agent, a nucleating agent, a cell stabilizer and organic solvent serving as a foaming agent through composite swelling and extrusion. The equipment required by the method can adopt universal extrusion equipment, the process is simple, and the large-scale production is convenient to realize. The invention canThe foaming processing of the polylactic acid material is realized at a lower temperature, so that the energy consumption can be obviously saved, the cost is reduced, and the thermal degradation of the polylactic acid material at a high temperature is avoided. The invention can realize the microcellular foaming of the polylactic acid material, the average cell diameter is less than 50 mu m, and the average cell density can reach 10 9 /cm 3 The mechanical property of the foamed polylactic acid material is obviously improved, and the foamed polylactic acid material is suitable for preparing polylactic acid foamed sheets and pipes, meets various market application requirements, and has a good application prospect.)

1. A pre-swelling continuous extrusion foaming polylactic acid material is characterized in that:

(1) comprises the following basic units: PLA resin, with performance characteristics: a melt index of 4-20 g/10min under a load of 2.16kg, a particle size of 100-1000 meshes, a water content of 0-200 ppm, and a free lactic acid content of 0-100 ppm; wherein, PLA is the abbreviation of polylactic acid;

(2) also comprises the following compound constitutional units: crosslinking agent, coupling agent, cell stabilizer, nucleating agent and organic solvent;

(3) the paint is prepared from the following basic units and composition units in percentage by mass: PLA resin: 80.0-95.0%; 0.05-0.3% of a cross-linking agent; coupling agent: 0.5-5.0%; cell stabilizer: 0.5-5%; nucleating agent: 0.1-2.5%; organic solvent: 1.0 to 20.0 percent.

2. The pre-swollen continuous extrusion foamed polylactic acid material according to claim 1, wherein:

the PLA resin in the step (1) is selected from PLA resins of grades FY-801, FY-802, 3001D, 8052D, LX-175 and LX-530, or PLA resins obtained by adding a chain extender into the reclaimed materials of the PLA resins of the grades, wherein the chain extender comprises JoncrylADR series of BASF company, and the adding amount of the chain extender accounts for 0.1-0.5% of the mass of the PLA resin.

3. The pre-swollen continuous extrusion foamed polylactic acid material according to claim 1, wherein:

the cross-linking agent in the step (1) is one or a combination of more of di-tert-butylperoxy-diisopropylbenzene, di-isopropylbenzene peroxide, diacetyl peroxide, tert-butyl peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, diisobutyl peroxydicarbonate, 1-bis (tert-amyl peroxy) cyclohexane and 1, 1-bis (tert-amyl peroxy) -3,3, 5-trimethylcyclohexane.

4. The pre-swollen continuous extrusion foamed polylactic acid material according to claim 1, wherein:

the coupling agent in the step (1) is one or a combination of more of 1,2,3, 4-diepoxybutane, 1,2,5, 6-diepoxyhexane, 1, 6-di (2, 3-epoxypropyl) hexane, epoxidized soybean oil and ethylene glycol diglycidyl ester.

5. The pre-swollen continuous extrusion foamed polylactic acid material according to claim 1, wherein:

the nucleating agent in the step (1) is one or a plurality of white carbon black, talcum powder, montmorillonite and halloysite;

the foam stabilizer in the step (1) is one or more of glyceryl monostearate, propylene glycol monostearate, hydroxyl silicone oil acrylate and polyacrylamide.

6. The pre-swollen continuous extrusion foamed polylactic acid material according to claim 1, wherein:

the organic solvent in the step (3) is one or more of methanol, ethanol, propanol, n-butanol, isobutanol, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, cyclohexanone and dipropylene glycol dimethyl ether.

7. The method for preparing a pre-swollen continuous extrusion foaming polylactic acid material according to any one of claims 1 to 6, which is characterized in that: the method comprises the following steps:

(1) uniformly mixing PLA resin with a cross-linking agent, a coupling agent, a nucleating agent and a foam stabilizer in a selected ratio, extruding and cutting into granules to obtain modified PLA resin granules;

(2) drying the modified PLA resin particles, crushing, and sieving to obtain modified PLA powder;

(3) mixing the modified PLA powder with an organic solvent in a selected proportion, and stirring to obtain modified PLA powder after swelling of the organic solvent;

(4) and extruding the swelled modified PLA powder again through an extruder to obtain the foamed PLA material.

8. The method of claim 7, wherein:

the extrusion in the step (1) is realized through a parallel co-rotating twin-screw extruder, the length-diameter ratio of the adopted screw is 40-48, the temperature of the screw is adjusted between 150-190 ℃, 10-13 temperature zones are arranged, and the temperature of the extruder head is adjusted between 155-185 ℃;

the number of the sieved screens in the step (2) is 100-1000;

the stirring condition in the step (3) is that the rotating speed is 10-15 rpm, and the time is 5-15 minutes;

the time for the sealed preservation in the step (3) is 1-2 h;

the extruder in the step (4) is realized through a single-screw extruder or a double-screw extruder, wherein the length-diameter ratio of a screw of the single-screw extruder is 30-36, the length-diameter ratio of a screw of the double-screw extruder is 36-48, the temperature of the screw is adjusted between 50-175 ℃, 8-13 temperature zones are arranged, and the temperature of a machine head of the extruder is adjusted between 120-165 ℃.

9. The method of claim 8, wherein:

in the step (1), the temperature of the screw is adjusted between 150 ℃ and 190 ℃, 10 temperature zones are arranged, the processing temperature is sequentially set to be 150, 175, 185, 180 and 175 from the feed inlet, the unit is that the temperature of each zone is adjusted within the range of +/-10 ℃ according to the PLA resin melting index value;

in the step (4), the temperature of the screw is adjusted between 50 ℃ and 175 ℃, 8 temperature zones are arranged, and the processing temperature is set to be 40-60 ℃, 120-160 ℃, 160-170, 160-175, 150-170, 130-170 in sequence from the feed inlet, wherein the unit is.

10. The use of the pre-swollen continuous extrusion foamed polylactic acid material according to any one of claims 1 to 6 in the fields of packaging, heat insulation and preservation or anti-cushioning.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a pre-swelling continuous extrusion foaming polylactic acid material and a preparation method and application thereof.

Background

Polylactic acid (PLA) is derived from starch and cellulose biological polysaccharide produced by photosynthesis of plants and microorganisms, lactic acid is obtained by further fermentation, and finally, a high molecular material is synthesized through polymerization reaction. Polylactic acid has complete regeneration, complete biodegradability, good processing and forming capability and excellent mechanical properties, and has been widely paid attention and paid attention as degradable plastics. In developed countries, polylactic acid polymer materials have been used as a new generation of renewable environment-friendly materials, and intensive research, development and utilization are carried out. Polylactic acid is widely used as a substitute material for a series of polymer materials derived from petroleum resources, such as Polyethylene (PE), polypropylene (PP), Polystyrene (PS), polyvinyl alcohol (PVC), polyethylene terephthalate (PET), Polyurethane (PU), acrylonitrile-styrene-butadiene copolymer (ABS), and the like, in the related fields of engineering plastics, daily necessities, packaging materials, medical materials, and the like.

However, PLA, as a thermoplastic polymer material, has relatively high glass transition temperature, high crystallinity and long crystallization time, and has the defects of high brittleness at low temperature or normal temperature, low thermal stability at high temperature, low thermal deformation temperature, easy hydrolysis, insufficient mechanical strength, narrow thermal processing window, and the like, so that it is difficult to apply to large-scale industrialization. Therefore, various modifications of polylactic acid to improve the comprehensive performance thereof have become bottlenecks that affect large-scale popularization and application of the material. In recent years, research on modification of polylactic acid is active, many results are obtained, and the application field of polylactic acid is effectively expanded.

Meanwhile, the PLA has complex production process and technology, long flow, high equipment requirement and great technical difficulty. These all result in high production cost and large investment scale, and finally directly result in high price enterprises of polylactic acid materials, the comprehensive cost of the polylactic acid materials exceeds more than 80 percent of the traditional petroleum-based plastics, the large-scale application space of the polylactic acid materials is limited, and the polylactic acid materials are difficult to accept by common consumers. Therefore, the cost of PLA materials and products is reduced, which is the first condition for large-scale popularization and application.

By adopting the advanced technology, the light weight of the PLA product is realized, and the method is the best way for effectively reducing the product cost. The use amount of materials in the PLA product is reduced through a foaming technology, the production cost is obviously reduced on the premise of ensuring that the use performance of the product is not influenced, a novel material which is environment-friendly, low in price and excellent in performance is provided, the competitiveness is extremely high, and the market demand can be met. Meanwhile, equipment in the production process of the PLA foaming material is simplified, and the large-scale production of the PLA foaming material can be realized by simply modifying the polylactic acid material and utilizing general extrusion equipment. Once industrialization is realized, trillions of market scales can be formed, plastic pollution can be reduced to the maximum extent, huge social benefits are formed, the development of the whole bio-based material industry can be driven, and huge economic benefits are generated.

Since the 90 s of the last century, the American academy of technology in Massachusetts has reported research on PLA foaming technology. After the commercial production of polylactic acid is realized by NatureWorks LLC in 2005, the downstream development and application research of PLA is gradually increased along with the expansion of the productivity of PLA and the gradual reduction of the cost. In 2011, Li et al studied PLA in nitrogen and compressed CO by high pressure Differential Scanning Calorimetry (DSC)₂Non-isothermal crystallization behavior in the environment, CO₂Pure PLA is subjected to kettle pressure foaming as a foaming agent, the foaming temperature is between 90 and 105 ℃, and a PLA foamed sheet is prepared, wherein the porosity is about 67.9 to 91.4 percent, the foaming ratio is 15 to 30 times, and the average pore diameter distribution is wider and is between 80 and 270 mu m; 2012, Xiao Qian Zhen et al used supercritical CO₂As a foaming agent, the PLA microcellular foaming material is prepared by adopting a kettle pressure method, and the influence of process conditions including saturation temperature, pressure, time and foaming temperature on the foam material cell shape is researched. Of unmodified PLAThe melt strength is relatively low, the crystallization rate is slow, and the processing temperature is narrow, so that the preparation of a PLA foamed product with uniform foam holes is difficult by adopting foaming processes such as extrusion, injection molding and the like, so a great deal of research on PLA modification is performed in recent years, and the research mainly comprises methods such as toughening, blending, long-chain branching, nucleation modification and the like; corre et al (2011 years)]Modifying PLA by using Joncryl 4368-BASF as a Chain Extender (CE), and then using supercritical CO₂Pure PLA and modified PLA are subjected to kettle pressure foaming as a foaming agent, and the influence of the rheological property of the modified material and the foaming process condition on the foam morphology is researched; liu et al [2014]Pyromellitic dianhydride (PMDA), triglycidyl isocyanurate (TGIC) and DCP are taken as chain extenders, PLA is subjected to long-chain branching modification through melting and banburying, the pot pressure foaming process is adopted to compare the foaming performances of pure PLA, DCP modified PLA and LCB PLA, and the finding that pure PLA and DCP modified PLA can not obtain a foaming material with good cell morphology is that the foaming material prepared from LCB PLA has a good cell structure, cells are regular and uniformly distributed, and the average diameter is about 200-300 mu m; wang et al [2012]With CO₂As a foaming agent, three kinds of PLA with different structures, namely linear PLA, Short Chain Branched (SCB) PLA and LCB PLA are extruded and foamed by a double-stage continuous extrusion process, and the foaming effects of different PLA are compared; zhou et al [2015]A novel chain extender TMP6000 is selected for carrying out long-chain branching modification on PLA, and the influence of the novel chain extender on the crystallization property and rheological property of the modified PLA and the foam material cell shape is researched. Compared with pure PLA, the complex viscosity and the tensile viscosity of the modified PLA are greatly improved, and the cold crystallization behavior of the PLA is inhibited by the branched structure. When supercritical CO is used₂When the foaming agent is used for foaming, the viscoelasticity of the system is improved, so that the foaming material with regular shape, uniform distribution, small size and high density of foam cells can be prepared; xidedamine [2017 ]]The invention discloses technical invention patents (ZL 201110292129.0 and ZL 201510490024.4) which respectively realize a large-scale production technology for synchronously carrying out PLA modification and continuously extruding foaming sheets by using liquefied butane and supercritical carbon dioxide fluid as foaming agents and adopting a double-stage extruding machine set. Foaming rate of 10-25 times, diameter of foam hole of 50-2000 mu m and partial closed cell structureThe material is widely applied to food packaging and industrial buffer packaging, greatly reduces the comprehensive cost of the PLA material, and realizes industrialized production.

With the literature information in mind, PLA foaming research has focused primarily on batch (autoclave) foaming with CO₂As a blowing agent. Problems and disadvantages include low production efficiency, high cost, high equipment requirements, and undesirable expansion ratio and foam properties. The continuous extrusion foaming method disclosed at present has strict requirements on PLA modification, expensive cross-linking agents, branching agents and bridging agents are required to be adopted to react at high temperature so as to change the PLA molecular chain structure, extrusion foaming equipment has strict requirements on screw design, good mixing effect is required to be realized, and the foaming agent is promoted to be dispersed and dispersed uniformly at different parts.

Disclosure of Invention

The invention aims to provide a pre-swelling continuous extrusion foaming polylactic acid material according to the problems of complex process formula, high equipment requirement, low foaming ratio, large diameter and small density of cells, non-ideal performance of the foaming material, large energy consumption in the production process, high comprehensive cost and the like in the existing polylactic acid foaming material production technology. The polylactic acid foaming material is completely degradable, simple in production process, low in price and excellent in performance.

Another object of the present invention is to provide a method for preparing the above foamed polylactic acid material.

The invention also aims to provide application of the foamed polylactic acid material.

The purpose of the invention is realized by the following technical scheme:

a pre-swelling continuous extrusion foaming polylactic acid material,

(1) comprises the following basic units: PLA resin, with performance characteristics: a melt index of 4 to 20g/10min (2.16kg), a particle size of 100 to 1000 mesh, a water content of 0 to 200ppm (not 0), and a free lactic acid content of 0 to 100ppm (not 0);

(2) also comprises the following compound constitutional units: crosslinking agent, coupling agent, cell stabilizer, nucleating agent and organic solvent;

(3) the paint is prepared from the following basic units and composition units in percentage by mass: PLA resin: 80.0-95.0%; 0.05-0.3% of a cross-linking agent; coupling agent: 0.5-5.0%; cell stabilizer: 0.5-5%; nucleating agent: 0.1-2.5%; organic solvent: 1.0 to 20.0 percent.

Further, the PLA resin in the step (1) is selected from PLA resins of grades such as FY-801, FY-802, 3001D, 8052D, LX-175, LX-530 and the like, and can also be selected from PLA resins obtained by adding a chain extender into the reclaimed PLA resin of the grade, wherein the chain extender comprises Joncryl ADR series of BASF company, and the adding amount of the chain extender is 0.1-0.5 percent of the mass of the PLA resin.

Further, the crosslinking agent in the step (1) is one or a combination of several of organic peroxides such as di-tert-butylperoxydiisopropylbenzene, diisopropylbenzene peroxide, diacetyl peroxide, tert-butyl peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, diisobutyl peroxydicarbonate, 1-bis (tert-amyl peroxy) cyclohexane, 1-bis (tert-amyl peroxy) -3,3, 5-trimethylcyclohexane, and the like.

Further, the coupling agent in the step (1) is one or a combination of more of 1,2,3, 4-diepoxybutane, 1,2,5, 6-diepoxyhexane, 1, 6-di (2, 3-epoxypropyl) hexane, epoxidized soybean oil and ethylene glycol diglycidyl ester.

Further, the nucleating agent in the step (1) is one or a mixture of more of white carbon black, talcum powder, montmorillonite and halloysite.

Further, the cell stabilizer in the step (1) is one or more of glyceryl monostearate, propylene glycol monostearate, hydroxyl silicone oil acrylate and polyacrylamide.

Further, the organic solvent in the step (3) is one or more of methanol, ethanol, propanol, n-butanol, isobutanol, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, cyclohexanone and dipropylene glycol dimethyl ether.

The preparation method of the pre-swelling continuous extrusion foaming polylactic acid material comprises the following steps:

(1) uniformly mixing PLA resin with a cross-linking agent, a coupling agent, a nucleating agent and a foam stabilizer in a selected ratio, extruding and cutting into granules to obtain modified PLA resin granules;

(2) drying the modified PLA resin particles, crushing, and sieving to obtain modified PLA powder; the process can ensure that the organic solvent fully permeates into the modified PLA powder and is uniformly diffused;

(3) mixing the modified PLA powder with an organic solvent in a selected proportion, stirring, and hermetically storing to obtain modified PLA powder after swelling of the organic solvent;

(4) and extruding the swelled modified PLA powder again to obtain the foamed PLA material. The process can melt the PLA resin and fully and uniformly mix the PLA resin with the organic solvent, nucleates the organic solvent in the PLA melt at high temperature and high pressure to form micro bubbles, and finally, the micro bubbles are extruded and foamed through an extruder die head.

Further, the extrusion in the step (1) is realized by a double-screw extruder, and further realized by a parallel co-rotating double-screw extruder, the length-diameter ratio of the adopted screw is more than or equal to 40 (preferably 40-48), the temperature of the screw can be adjusted between 150 ℃ and 190 ℃, at least 10 temperature zones (preferably 10-13) are arranged, and the temperature of the extruder head can be adjusted between 155 ℃ and 185 ℃ according to actual conditions.

When 10 temperature zones were set, the processing temperatures were set in the order of 150, 175, 185, 180, 175 from the feed port, and the temperatures of the respective zones were adjusted within a range of ± 10 ℃ depending on the PLA resin quality (melt index value).

Further, the mixing condition in the step (1) is that the rotating speed is 40-60 rpm, and the time is 5-15 minutes.

Further, the mesh number of the sieved screen in the step (2) is 100-1000.

Further, the stirring condition in the step (3) is that the rotating speed is 10-15 rpm, and the time is 5-15 minutes.

Further, the time of the sealed preservation in the step (3) is 1-2 h.

Further, the extruder in the step (4) is realized by a single-screw extruder or a double-screw extruder, wherein the length-diameter ratio of a screw of the single-screw extruder is greater than or equal to 30 (preferably 30-36), the length-diameter ratio of a screw of the double-screw extruder is greater than or equal to 36 (preferably 36-48), the temperature of the screw can be adjusted between 50 ℃ and 175 ℃, at least 8 temperature zones (preferably 8-13) are arranged, and the temperature of a head of the extruder can be adjusted between 120 ℃ and 165 ℃ according to actual conditions.

When 8 temperature zones are set, the processing temperature is set to be 40-60, 120-160, 160-170, 160-175, 150-170 and 130-170 from the feed inlet, and the unit is ℃. The temperature of each zone was adjusted within + -10 deg.C depending on the PLA resin quality (melt index value).

Further, the extrusion in the step (4) can be performed by adjusting the type of the head of the extruder, so as to obtain a foamed PLA sheet, a foamed PLA pipe or a foamed PLA sheet; preferably, the PLA foamed sheet is obtained by extruding through an annular die head, cooling and shaping through a shaping drum and cutting, or the PLA foamed sheet is obtained by extruding through a tubular die head and cooling and shaping through a water tank under the traction condition.

The pre-swelling continuous extrusion foaming polylactic acid material is applied to the fields of packaging, heat insulation and preservation or anti-buffering.

Compared with the prior art, the invention has the following beneficial effects:

(1) based on the PLA foaming material and the dilemma faced by the technical field, the invention aims to realize the reduction of the cost and the improvement of the competitiveness from the technical aspect, and realizes the light weight in the production process of the plastic product through the composite swelling and the extrusion foaming of the PLA material and the organic solvent, namely the pre-swelling foaming technology, and other public reports are not seen yet;

(2) the invention relates to a 'polylactic acid material extruded and foamed based on a pre-swelling method' which is a novel environment-friendly material, wherein more than 80% of components are derived from renewable animal and plant resources, and the material can be completely degraded when placed in a field environment;

(3) the equipment used in the invention belongs to universal extrusion equipment, special equipment is not needed, the process is simple, and large-scale production is convenient to realize;

(4) the PLA foaming technology used in the invention can be realized at a lower temperature which is far lower than the existing PLA foaming processing temperature, the modification temperature is lower than 190 ℃, the foaming temperature is lower than 170 ℃, the modification and foaming temperature is averagely reduced by 20 ℃ compared with the modification and foaming temperature of the prior art which is higher than 210 ℃, the low-temperature foaming can obviously save energy consumption and reduce cost, simultaneously avoid thermal cracking of PLA materials at a high temperature, reduce the quality standard requirements on PLA raw materials, and can also be suitable for the recovered and processed PLA raw materials;

(5) the invention can realize microcellular foaming of PLA material, the average cell diameter is less than 50 μm, and the average cell density can reach 10⁹/cm³The mechanical property of the foaming PLA material is obviously improved;

(6) according to the invention, the organic solvent is added as the foaming agent, a conventional mixing technology can be adopted, special equipment for high-pressure metering and conveying the special foaming agent adopted in the prior art is not needed, the organic solvent used as the foaming agent can be accurately metered, the large-range adjustment of the foaming multiplying power can be realized, and the highest foaming multiplying power can reach 50 times; according to the invention, the organic solvent is adopted to swell the polylactic acid material, so that the organic solvent can be guaranteed to be highly dispersed in the polylactic acid material in a molecular state, and the defect that the foaming effect in the existing foaming technology is highly dependent on the dispersion degree of the foaming agent in a plastic melt, and the foaming agent needs to be dispersed by forced means such as high temperature, high shear, special screw design and the like is overcome; the mixing time of the organic solvent and the PLA powder is not more than 2h, the time is short, and the efficiency is high; the organic solvent can be recycled, so that the cost is further reduced;

(7) the invention is suitable for preparing PLA foaming sheets and pipes, meets the application requirements of various markets, and comprises small-caliber thin-wall foaming pipes, microporous foaming sheets and plastic uptake processing products thereof, such as various beverage straws, food packaging containers, integrated circuit packaging materials, cosmetic packaging materials, medicine packaging materials and the like;

(8) the thermal deformation temperature of the microporous foamed polylactic acid material prepared by the invention can reach more than 90 ℃, the tensile strength is more than 50MPa, the bending strength reaches 90MPa, the bending modulus reaches 2.0GPa, the compression strength reaches 30MPa, and the Izod notch impact strength is 15J/m.

Drawings

FIG. 1 is a scanning electron microscope photograph of the foamed PLA prepared in example 7.

Fig. 2 is a scanning electron microscope image of the foamed PLA prepared in example 8.

Fig. 3 is a scanning electron microscope photograph of the foamed PLA prepared in example 10.

FIG. 4 is a scanning electron microscope image of the foamed PLA prepared in comparative examples 1-4; wherein, A is comparative example 1, B is comparative example 2, C is comparative example 3, and D is comparative example 4.

FIG. 5 is a scanning electron microscope photograph of the foamed PLA prepared in comparative example 5; wherein A is the surface of the foaming material, and B is the section of the foaming material.

Detailed Description

The present invention is further explained with reference to the following examples, which are not intended to limit the present invention in any way.

The parts described in the following examples are all parts by mass.

Example 1

(1) Weighing 80 parts of PLA granules with the brand number of FY-801 (Anhui Fengyilai company), 0.2 part of di-tert-butylperoxydiisopropylbenzene (BIPB), 1.5 parts of epoxidized soybean oil, 5 parts of propylene glycol monostearate, 5 parts of talcum powder (3000 meshes) and 8.3 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer (the rotating speed is 60rpm, the time is 15min) to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 180, 190, 185, 180, 175, 170 and 180 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 100-mesh sieve to obtain modified PLA powder;

(4) weighing 95 parts of modified PLA powder, adding 5 parts of absolute ethyl alcohol, stirring and mixing uniformly at a low speed (rotating speed of 15rpm for 15min) at room temperature, and continuously preserving for 1h in a closed manner at room temperature to obtain ethanol swelling PLA powder;

(5) adding the ethanol swelling PLA powder into an SJ-45 type single screw extruder (length-diameter ratio of 30, 8 temperature zones), setting the temperature gradient of the screws to be 50, 150, 170, 165, 170, 160 and 150 (unit ℃), extruding by adopting an annular die head, setting the temperature of the die head to be 150 ℃, cooling and shaping the shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 85kg/m³The calculated expansion ratio was 14.5 times, the average cell diameter was 250 μm, and the average cell density was 7.8X 10⁶/cm³。

Example 2

(1) Weighing 90 parts of PLA granular material with the brand number of FY-802 (Anhui Fengyitai company), 1 part of cyclohexanone peroxide, 1 part of 1,2,3, 4-diepoxybutane, 3 parts of glycerin monostearate, 3 parts of talcum powder (5000 meshes) and 2 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 180, 190, 185, 180, 175, 170 and 180 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 10 parts of acetone, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 0.5h in a closed manner at room temperature to obtain acetone-swollen PLA powder;

(5) adding the acetone swelling PLA powder into an SJ-45 type single screw extruder (length-diameter ratio of 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 160, 165, 160, 150 and 150 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 120 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 42kg/m³The average expansion ratio was calculated to be 30 timesThe cell diameter was 150 μm and the average cell density was 2.1X 10⁷/cm³。

Example 3

(1) Weighing 95 parts of PLA granules with the brand number of Ingeo 3001D (Nature works company in America), 0.5 part of 1, 1-bis (tert-amyl peroxy) cyclohexane, 0.2 part of 1,2,5, 6-di-epoxy hexane, 0.3 part of ethylene glycol diglycidyl ester, 1 part of hydroxyl silicone oil acrylate, 1.5 parts of talcum powder (5000 meshes) and 1.5 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 180, 185, 180, 175, 170 and 175 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 800-mesh sieve to obtain modified PLA powder;

(4) weighing 85 parts of modified PLA powder, adding 15 parts of ethyl acetate, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 1.5 hours in a closed manner at room temperature to obtain ethyl acetate swelling PLA powder;

(5) adding the acetone swelling PLA powder into an SJ-45 type single screw extruder (length-diameter ratio of 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 160, 150 and 150 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 125 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 31kg/m³The calculated expansion ratio was 40 times, the average cell diameter was 750 μm, and the average cell density was 8.1X 10⁶/cm³。

Example 4

(1) Weighing 90 parts of PLA granular material with the brand number of LX-175(Total-Corbion Thailand), 1 part of 1, 1-bis (tert-amyl peroxy) -3,3, 5-trimethylcyclohexane, 1 part of ethylene glycol diglycidyl ester, 4 parts of polyacrylamide, 1.5 parts of montmorillonite (5000 meshes) and 2.5 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 180, 190, 185, 175 and 185 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 200-mesh sieve to obtain modified PLA powder;

(4) weighing 97 parts of modified PLA powder, adding 3 parts of diethylene glycol dimethyl ether, stirring and mixing uniformly at low speed at room temperature, and keeping for 2 hours at room temperature in a closed manner to obtain diethylene glycol dimethyl ether swelling PLA powder;

(5) adding diethylene glycol dimethyl ether swelling PLA powder into an SJ-45 type single screw extruder (length-diameter ratio of 30, 8 temperature zones), setting the screw temperature gradient to be 50, 160, 170 and 170 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 165 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 96kg/m³The calculated expansion ratio was 13 times, the average cell diameter was 85 μm, and the average cell density was 8.65X 10⁷/cm³。

Example 5

(1) Weighing 94 parts of PLA granular material with the brand number of LX-530(Total-Corbion Thailand), 0.1 part of di-tert-butylperoxydiisopropylbenzene, 1.5 parts of ethylene glycol diglycidyl ester, 1.5 parts of glyceryl monostearate, 0.5 part of halloysite (2500 meshes) and 2.4 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 180, 190, 185, 180 and 185 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 8 parts of methanol and 2 parts of n-butyl alcohol, stirring and mixing uniformly at a low speed at room temperature, and keeping for 2 hours at room temperature in a closed manner to obtain PLA powder swelled by methanol and n-butyl alcohol;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradients to be 50, 160, 150 and 130 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 130 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 46kg/m³The calculated expansion ratio was 27 times, the average cell diameter was 175 μm, and the average cell density was 3.1X 10⁷/cm³。

Example 6

(1) Weighing 90 parts of PLA granules with the brand number of Ingeo 8052D (Nature works company, USA), 0.5 part of diisopropyl peroxydicarbonate, 0.5 part of 1, 6-di (2, 3-epoxypropyl) hexane, 5 parts of glyceryl monostearate, 2 parts of propylene glycol monostearate, 0.5 part of white carbon black (3000 meshes) and 1.5 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 170, 185, 190, 185, 180, 175 and 170 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 5 parts of ethanol and 5 parts of dipropylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 2 hours in a closed manner at room temperature to obtain PLA powder swelled by ethanol and dipropylene glycol dimethyl ether;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 165 and 160 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 160 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Measurement of PLA foamed sheet Density 28kg/m³Counting deviceThe cell magnification was 44 times, the average cell diameter was 65 μm, and the average cell density was 1.1X 10⁸/cm³The surface of the sheet is smooth and flat, the foam holes are fine and dense and are uniformly distributed when the sheet is observed by light, and the foamed sheet has good toughness.

Example 7 (best mode for foamed sheet)

(1) Weighing 92 parts of PLA granular material with the brand number of Ingeo 8052D (Nature works company in America), 0.15 part of di-tert-butylperoxydiisopropyl benzene, 0.5 part of ethylene glycol diglycidyl ether, 4 parts of glyceryl monostearate, 1 part of propylene glycol monostearate, 0.5 part of talcum powder (10000 meshes) and 1.85 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 170, 185, 190, 185, 180, 175 and 170 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 4 parts of ethanol, 4 parts of diethylene glycol dimethyl ether and 2 parts of dipropylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 2 hours in a closed manner at room temperature to obtain PLA powder after swelling of the composite solvent;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 175, 170 and 165 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 158 ℃, cooling and shaping a shaping drum, and cutting to obtain the PLA foamed sheet.

(6) Fig. 1 is a scanning electron microscope image of the prepared PLA foamed sheet. Measurement of PLA foamed sheet Density 25kg/m³The calculated expansion ratio was 50 times, the average cell diameter was 15 μm, and the average cell density was 5.84X 10⁸/cm³The surface of the sheet is smooth and flat, and the foam holes are fine, dense and uniformly distributed. The foamed sheet has tensile strength of 50.7MPa, bending modulus of 2000MPa and compression strength of 31.2MPa, Izod notched impact strength of 15J/m.

Example 8

(1) Weighing 92 parts of PLA granular material with the brand number of Ingeo 8052D (Nature works company in America), 0.15 part of di-tert-butylperoxydiisopropyl benzene, 0.5 part of ethylene glycol diglycidyl ether, 4 parts of glyceryl monostearate, 1 part of propylene glycol monostearate, 0.5 part of talcum powder (10000 meshes) and 1.85 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 170, 185, 190, 185, 180, 175 and 170 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 4 parts of ethanol, 4 parts of diethylene glycol dimethyl ether and 2 parts of dipropylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 2 hours in a closed manner at room temperature to obtain PLA powder after swelling of the composite solvent;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 175, 170 and 165 (unit ℃), extruding by adopting a tubular die head with the inner diameter of 15mm, setting the die head temperature to be 158 ℃, and cooling and shaping by a water tank under the traction condition to obtain the foamed PLA pipe.

(6) Fig. 2 is a scanning electron microscope image of the prepared PLA foamed sheet. The obtained pipe has an inner diameter of 11mm, a wall thickness of 1.5mm and a pipe density of 50kg/m³An expansion ratio of 25 times, an average cell diameter of about 50 μm, and an average cell density of about 3.8X 10⁷/cm³。

Example 9

(1) Weighing 92 parts of PLA granular material with the brand number of LX-530(Total-Corbion Thailand), 0.2 part of diisobutyl peroxydicarbonate, 0.5 part of ethylene glycol diglycidyl ether, 2.5 parts of glyceryl monostearate, 2.5 parts of propylene glycol monostearate, 0.5 part of organic montmorillonite (10000 meshes) and 1.3 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 170, 185, 190, 185, 180, 175 and 170 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 90 parts of modified PLA powder, adding 2 parts of acetone, 5 parts of diethylene glycol dimethyl ether and 3 parts of dipropylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 2 hours in a closed manner at room temperature to obtain the PLA powder after swelling of the composite solvent;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 175, 170 and 165 (unit ℃), extruding by adopting a tubular die head with the inner diameter of 15mm, setting the die head temperature to be 165 ℃, and cooling and shaping by a water tank under the traction condition to obtain the foamed PLA pipe.

(6) The obtained pipe has the inner diameter of 8mm, the wall thickness of 0.5mm and the density of 75kg/m³The expansion ratio was 16.5 times, the average cell diameter was about 35 μm, and the average cell density was about 5.5X 10⁷/cm³。

Example 10 (best mode for foamed pipe)

(1) Weighing 95 parts of PLA granular material with the brand number of LX-530(Total-Corbion Thailand), 0.1 part of di-tert-butylperoxydiisopropyl benzene, 1 part of ethylene glycol diglycidyl ether, 1.5 parts of glyceryl monostearate, 0.5 part of propylene glycol monostearate, 0.5 part of halloysite (5000 meshes) and 1.4 parts of ethylene bis stearamide, and uniformly mixing by adopting a high-speed mixer to obtain a raw material mixture;

(2) adding the raw material mixture into a MYSJ-65B type double-screw extruder (length-diameter ratio 48), setting the temperature gradient of screws to be 150, 170, 185, 190, 185, 180, 175 and 170 (unit ℃), performing reaction extrusion, and performing air cooling and granulating to obtain modified PLA granules;

(3) crushing the modified PLA granules by using a crusher, and sieving the crushed modified PLA granules by using a 1000-mesh sieve to obtain modified PLA powder;

(4) weighing 95 parts of modified PLA powder, adding 2 parts of ethanol and 3 parts of diethylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 1 hour in a closed manner at room temperature to obtain PLA powder after swelling of the composite solvent;

(5) adding the swelled PLA powder into an SJ-45 type single screw extruder (the length-diameter ratio is 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 175, 170 and 165 (unit ℃), extruding by adopting a tubular die head with the inner diameter of 15mm, setting the die head temperature to be 165 ℃, and cooling and shaping by a water tank under the traction condition to obtain the foamed PLA pipe.

(6) Fig. 3 is a scanning electron microscope image of the prepared PLA foamed sheet. The obtained pipe has the inner diameter of 5mm, the wall thickness of 0.3mm and the density of 90kg/m³The expansion ratio was 13.7 times, the average cell diameter was about 30 μm, and the average cell density was about 7.5X 10⁷/cm³。

The pipe in the forming process has the advantages of good tensile property, high toughness, uniform pipe wall, smooth and complete surface layer, high hardness and slight elasticity after cooling, and is suitable for being used as a beverage straw.

Comparative example 1

The preparation process is referred to example 7, except that the organic solvent added in step (4) is dichloromethane. The scanning electron micrograph of the foamed material is shown in FIG. 4A.

Comparative example 2

The preparation method is referred to example 7, which is different only in that the organic solvent added in step (4) is diethyl ether. The scanning electron micrograph of the foamed material is shown in FIG. 4B.

Comparative example 3

The preparation method is referred to example 7, which is different only in that the organic solvent added in step (4) is dimethylformamide. The scanning electron micrograph of the foamed material is shown in FIG. 4C.

Comparative example 4

The preparation method is referred to example 7, except that the organic solvent added in step (4) is hexafluoroisopropanol. The scanning electron micrograph of the foam is shown in FIG. 4D.

Comparative example 5 (unmodified)

(1) Weighing 100 parts of PLA granules with the brand number Ingeo 8052D (NatureWorks company in America);

(2) crushing the PLA granules by using a crusher, and sieving the crushed PLA granules by using a 1000-mesh sieve to obtain unmodified PLA powder;

(3) weighing 90 parts of unmodified PLA powder, adding 4 parts of ethanol, 4 parts of diethylene glycol dimethyl ether and 2 parts of dipropylene glycol dimethyl ether, stirring and mixing uniformly at a low speed at room temperature, and continuously preserving for 2 hours in a closed manner at room temperature to obtain the PLA powder after swelling of the composite solvent;

(4) adding the swelled PLA powder without modification into an SJ-45 type single screw extruder (length-diameter ratio of 30, 8 temperature zones), setting the screw temperature gradient to be 50, 150, 170, 175, 170 and 165 (unit ℃), extruding by adopting an annular die head, setting the die head temperature to be 158 ℃, cooling and shaping by using a shaping drum, and cutting to obtain the PLA foamed sheet. The scanning electron micrograph of the foam material is shown in figure 5 (wherein A is the surface and B is the cross section).

As can be seen from the scanning electron microscope image shown in FIG. 4, the four samples prepared in comparative examples 1 to 4 have irregular shapes of blast holes, large differences in diameter of the blast holes, small cell densities, extremely low foaming ratios, and poor foaming effects, and have no practical application value.

As can be seen from the scanning electron micrograph shown in FIG. 5, the polylactic acid material of comparative example 5, which is not modified, is directly foamed, and the effect is also poor.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.