A highly transparent scPLA / PHA composite material and its preparation method

Abstract

This application belongs to the technical field of polymer composite materials, and discloses a highly transparent scPLA / PHA composite material and its preparation method. It is prepared from stereocomplex polylactic acid (scPLA) and polyhydroxyalkanoate (PHA) that are biodegradable. The tensile strength of the composite material is 30 - 100 MPa, the elongation at break is 30% - 120%, and the transparency is 80% - 100%. The composite material prepared by the present invention has the characteristics of high transparency, high quality, no generation of environmentally harmful substances during production and use, biodegradability, good toughness and elongation at break, simple manufacturing process, and low manufacturing cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer composites, and particularly relates to a highly transparent scPLA / PHA composite material and a preparation method thereof. Background Art

[0002] In recent decades, petroleum-based fibers have been widely used in fields such as textiles, biomedicine, and agriculture. However, petroleum-based synthetic materials are non-biodegradable and non-renewable, which has led to a series of environmental problems. Currently, petroleum resources are facing the problem of resource depletion caused by over-exploitation, which greatly limits the application of non-biodegradable petroleum-based synthetic materials. Therefore, biodegradable materials, as powerful substitutes for petroleum-based synthetic materials, will receive great attention from all sectors of society. Polylactic acid and polyhydroxyalkanoates have good biodegradability, biocompatibility, and regenerability, and are currently popular green environmental protection materials.

[0003] ScPLA prepared by compounding PDLA and PLLA in polylactic acid has better thermodynamic properties than ordinary polylactic acid, while polyhydroxyalkanoate (PHA) is an intracellular polyester synthesized by many bacteria and mainly exists as a storage substance for carbon and energy in living organisms. It has physical and chemical properties similar to synthetic plastics and many excellent properties such as biodegradability, biocompatibility, optical activity, piezoelectricity, and gas barrier properties that synthetic plastics do not have.

[0004] Therefore, compounding scPLA with PHA can obtain materials with better properties. Patent CN110358274A discloses a highly transparent PLA material, which is prepared by adding PHA, polyethylene terephthalate (PET), a toughening agent, and a stabilizer during the processing of PLA. Among them, PHA and polyethylene terephthalate (PET) are used to improve the heat resistance temperature, film-forming property, and toughness and transparency of the blend material. Other chemical substances are added during the material production process, which cannot be completely degraded, and the cost is relatively high. Moreover, the polylactic acid used is ordinary PLA, and its thermodynamic properties have not been improved.

[0005] The scPLA / PHA composite material prepared by the present invention using an scPLA electrospun membrane as a reinforcement and PHA as a matrix has high transparency, can be biodegradable, has good toughness and elongation at break, and is an effective multi-purpose composite material.

[0006] Chinese Patent CN202111245096.4 discloses a preparation method of a polylactic acid - polyhydroxyalkanoate melt - blown non - woven material, which relates to the technical field of new non - woven materials. By adding polyhydroxyalkanoate and blending it with polylactic acid, while increasing the melt index of the melt - blown non - woven material, the toughening effect in the melt - blown non - woven material is improved. Without much change in the tensile strength, the toughness of the melt - blown non - woven material is improved, and the elongation at break of the melt - blown non - woven material is increased. It not only has the properties of environmental friendliness and biodegradability, but also has good mechanical properties, providing the possibility for the subsequent development and wide application of the material. However, considering that Patent CN202111245096.4 belongs to the processing of non - woven fabrics, the target product of this application is a transparent plastic product, and the two products are different. Although both mention the toughening of PHA, this application also has changes in heat resistance and transparency in addition to toughness. Summary of the Invention

[0007] Technical problems to be solved:

[0008] In view of the deficiencies of the prior art, this application solves the technical problems that in the current material production process, other chemical substances are added, which cannot be completely degraded, have a high cost, and the polylactic acid used is ordinary PLA, and its thermodynamic properties have not been improved. This application provides a highly transparent scPLA / PHA composite material and its preparation method. The scPLA / PHA composite material prepared by this method can be completely biodegradable, highly transparent, has good toughness and elongation at break, has certain antibacterial functions, is easy to process, has a simple production process, and a low manufacturing cost, which is conducive to industrial production.

[0009] Technical solutions:

[0010] To achieve the above - mentioned purpose, this application is realized through the following technical solutions:

[0011] A preparation method of a highly transparent scPLA / PHA composite material, wherein the highly transparent scPLA / PHA composite material is composed of a reinforcing scPLA fiber membrane and a matrix polyhydroxyalkanoate PHA plate, and specifically includes the following steps:

[0012] The first step: Weigh 5 - 15 parts of scPLA fiber membrane and 85 - 95 parts of PHA plate according to the mass - fraction ratio, and conduct a drying treatment until the moisture content is less than 300 ppm;

[0013] The second step: Place the scPLA fiber membrane in the first step between two dried PHA plates to obtain a multi - layer structure;

[0014] Step 3: Place the multi-layer structure obtained in Step 2 into a hot press, hot press at 125 - 185 °C and 2 - 10 MPa for 1 - 10 minutes, rapidly cool at -10 °C - 20 °C, and trim to obtain a highly transparent scPLA / PHA composite material.

[0015] Furthermore, the scPLA fiber membrane is prepared by electrospinning.

[0016] Furthermore, the scPLA fiber membrane prepared by electrospinning is prepared by first dissolving equimolar PDLA and PLLA in a solvent to prepare a spinning solution, and then electrospinning under the conditions of a voltage of 13 - 20 KV, an injection speed of 1.0 - 2.5 ml / h, and a receiving distance of 10 - 15 cm.

[0017] Furthermore, the weight-average molecular weight of PLLA and PDLA is 150,000 - 250,000, and the mass fraction is 7 - 12%.

[0018] Furthermore, the solvent is chloroform, dichloromethane, dichloromethane or hexafluoroisopropanol.

[0019] Furthermore, the melting point of the scPLA fiber membrane is 220 - 230 °C, and the melting point of the PHA is 80 - 150 °C.

[0020] Furthermore, the thickness of the scPLA fiber membrane is 0.1 - 0.5 mm.

[0021] Furthermore, the drying treatment in the first step refers to placing the scPLA electrospun membrane and the PHA sheet in a vacuum drying oven at 70 °C for 0.5 - 5 hours.

[0022] Furthermore, in the second step, the scPLA electrospun membrane is placed between two dried PHA sheets, and the operation can be repeated until the desired thickness is reached.

[0023] This application also discloses a highly transparent scPLA / PHA composite material prepared by the above preparation method. The tensile strength of the composite material is 30 - 100 MPa, the elongation at break is 30% - 120%, and the transparency is 80% - 100%.

[0024] The principle of the above-mentioned highly transparent scPLA / PHA composite material and its preparation method is as follows: In this application, an electrospun sc-PLA nanofiber membrane is used as the reinforcement, and PHA is used as the matrix to prepare a highly transparent composite material. The melting temperatures of sc-PLA and PHA differ significantly. By utilizing the temperature difference between the two to process the composite material, the sc-PLA fiber network remains in a fibrous state, while the molten PHA serves as the matrix. The toughness of PHA can endow the composite material with excellent elongation at break; through quenching at -10°C to 20°C, the crystallization of PHA and sc-PLA is inhibited, endowing the composite material with excellent transparency.

[0025] Advantages:

[0026] This application provides a highly transparent scPLA / PHA composite material and its preparation method. Compared with the prior art, it has the following advantages:

[0027] 1. The prepared scPLA / PHA composite material has higher strength and better thermal properties than traditional polylactic acid, and also has better ductility and elongation at break of polyhydroxyalkanoates.

[0028] 2. The composite material of the present invention has the characteristics of high transparency, high quality, biodegradability, good toughness, etc., and is non-toxic and environmentally friendly.

[0029] 3. The manufacturing process is simple, the manufacturing cost is low, and it can be preferably applied in the field of environmental protection functional materials to meet the production needs of the polymer materials industry.

[0030] 4. The tensile strength of the scPLA / PHA composite material is 30 - 100 MPa, the elongation at break is 30% - 120%, and the transparency is 80% - 100%.

[0031] 5. The presence of sc-PLA makes the scPLA / PHA composite material have more excellent thermal stability, and the melting temperature is 220 - 230°C. Specific Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1:

[0034] A preparation method of a highly transparent scPLA / PHA composite material. First, weigh 7 wt% each of PDLA and PLLA with a weight average molecular weight of 250,000 and dissolve them in chloroform. Then, electrospinning is carried out within the range of a voltage of 13 KV, an injection speed of 1.0 ml / h, and a distance from the needle tip to the collection device of 15 cm to prepare a scPLA fiber membrane with a thickness of 0.1 mm. The PHA masterbatch is made into a PHA plate by a hot press at 80 °C under a pressure of 2 MPa. The specific steps are as follows:

[0035] Step 1: Weigh 5 parts of the corresponding mass of the scPLA electrospun membrane and 95 parts of the PHA plate and dry them in a vacuum drying oven at 70 °C for 0.5 hour.

[0036] Step 2: Place the scPLA electrospun membrane in Step 1 between two dried and treated PHA plates to obtain a multi-layer structure. The operation can be repeated until the desired thickness is reached.

[0037] Step 3: Put the multi-layer structure obtained in Step 2 into a hot press for heating. The hot pressing temperature is 185 °C, the time is 1 minute, and the pressure is 2 MPa. During the hot pressing process, the PHA melts and infiltrates into the gaps of the scPLA nanofibers. Immediately after molding, it is rapidly cooled with 20 °C and trimmed to obtain a highly transparent scPLA / PHA composite material.

[0038] Example 2:

[0039] A preparation method of a highly transparent scPLA / PHA composite material. First, weigh 12 wt% each of PDLA and PLLA with a weight average molecular weight of 150,000 and dissolve them in dichloromethane. Then, electrospinning is carried out within the range of a voltage of 20 KV, an injection speed of 2.5 ml / h, and a distance from the needle tip to the collection device of 10 cm to prepare a scPLA fiber membrane with a thickness of 0.1 mm. The PHA masterbatch is made into a PHA plate by a hot press at 150 °C under a pressure of 4 MPa. The specific steps are as follows:

[0040] Step 1: Weigh 15 parts of the corresponding mass of the scPLA electrospun membrane and 85 parts of the PHA plate and dry them in a vacuum drying oven at 70 °C for 2 hours.

[0041] Step 2: Place the scPLA electrospun membrane in Step 1 between two dried and treated PHA plates to obtain a multi-layer structure. The operation can be repeated until the desired thickness is reached.

[0042] Step 3: Place the multi-layer structure obtained in Step 2 into a hot press for heating. The hot pressing temperature is 125 °C, the time is 10 minutes, and the pressure is 10 MPa. During the compression process, PHA melts and infiltrates into the gaps of the filled scPLA nanofibers. Immediately after molding, it is rapidly cooled with 10 °C, trimmed, and a highly transparent scPLA / PHA composite material is obtained.

[0043] Example 3:

[0044] A method for preparing a highly transparent scPLA / PHA composite material. First, weigh 10 wt% of PDLA and PLLA with a weight average molecular weight of 200,000 and dissolve them in dichloromethane / hexafluoroisopropanol. Then, electrospinning is carried out within the range of a voltage of 15 KV, an injection speed of 2.5 ml / h, and a distance from the needle tip to the collection device of 13 cm to prepare a scPLA fiber membrane with a thickness of 0.25 mm. The PHA masterbatch is made into a PHA sheet by a hot press at 150 °C under a pressure of 3 MPa. The specific steps are as follows:

[0045] Step 1: Weigh 10 parts of the corresponding scPLA electrospun membrane and 90 parts of the PHA sheet and perform a drying treatment in a vacuum drying oven at 70 °C for 5 hours.

[0046] Step 2: Place the scPLA electrospun membrane in Step 1 between two dried PHA sheets to obtain a multi-layer structure. This operation can be repeated until the desired thickness is reached.

[0047] Step 3: Place the multi-layer structure obtained in Step 2 into a hot press for heating. The hot pressing temperature is 155 °C, the time is 5 minutes, and the pressure is 4 MPa. During the compression process, PHA melts and infiltrates into the gaps of the filled scPLA nanofibers. Immediately after molding, it is rapidly cooled with -10 °C, trimmed, and a highly transparent scPLA / PHA composite material is obtained.

[0048] Example 4:

[0049] A method for preparing a highly transparent scPLA / PHA composite material. First, weigh 9 wt% of PDLA and PLLA with a weight average molecular weight of 230,000 and dissolve them in dichloromethane / hexafluoroisopropanol. Then, electrospinning is carried out within the range of a voltage of 14 KV, an injection speed of 1.0 ml / h, and a distance from the needle tip to the collection device of 15 cm to prepare a scPLA fiber membrane with a thickness of 0.13 mm. The PHA masterbatch is made into a PHA sheet by a hot press at 150 °C under a pressure of 4 MPa. The specific steps are as follows:

[0050] Step 1: Weigh 5 parts of the corresponding scPLA electrospun membrane and 95 parts of the PHA sheet and perform a drying treatment in a vacuum drying oven at 70 °C for 3 hours.

[0051] Step 2: Place the scPLA electrospun membrane obtained in Step 1 between two dried PHA plates to obtain a multi-layer structure. This operation can be repeated until the desired thickness is achieved.

[0052] Step 3: Place the multi-layer structure obtained in Step 2 into a hot press for heating. The hot pressing temperature is 125 °C, the time is 6 minutes, and the pressure is 5 MPa. During the compression process, PHA melts and infiltrates into the gaps between scPLA nanofibers. Immediately after molding, it is rapidly cooled with 5 °C and trimmed to obtain an scPLA / PHA composite material with high transparency.

[0053] Example 5:

[0054] A preparation method of a high-transparency scPLA / PHA composite material. First, weigh 10 wt% of PDLA and PLLA with a weight-average molecular weight of 250,000 and dissolve them in chloroform. Then, electrospin within the range of a voltage of 13 KV, an injection speed of 2.5 ml / h, and a distance from the needle tip to the collection device of 12 cm to prepare an scPLA fiber membrane with a thickness of 0.3 mm. Use a hot press to obtain PHA plates from PHA masterbatch at 120 °C

[0055] under a pressure of 3 MPa. The specific steps are as follows:

[0056] Step 1: Weigh 10 parts of the corresponding scPLA electrospun membrane and 90 parts of PHA plates, and perform drying treatment in a 70 °C vacuum drying oven for 3 hours.

[0057] Step 2: Place the scPLA electrospun membrane obtained in Step 1 between two dried PHA plates to obtain a multi-layer structure. This operation can be repeated until the desired thickness is achieved.

[0058] Step 3: Place the multi-layer structure obtained in Step 2 into a hot press for heating. The hot pressing temperature is 175 °C, the time is 2 minutes, and the pressure is 3 MPa. During the compression process, PHA melts and infiltrates into the gaps between scPLA nanofibers. Immediately after molding, it is rapidly cooled with 0 °C and trimmed to obtain an scPLA / PHA composite material with high transparency.

[0059] Comparative Example 1:

[0060] Use a hot press to obtain PHA plates from PHA masterbatch at 80 °C under a pressure of 2 MPa. The prepared materials are compounded according to the following steps:

[0061] (1) Weigh 100 parts of the corresponding PHA plates and perform drying treatment in a 70 °C vacuum drying oven for 3 hours.

[0062] (2) Compose the PHA plates in step (1) to obtain a multi-layer structure. The operation can be repeated until the desired thickness is achieved.

[0063] (3) Place the multi-layer structure obtained in step (2) into a hot press for heating. The hot pressing temperature is 185 °C, the time is 1 minute, and the pressure is 2 MPa. During the hot pressing process, the PHA melts. Immediately after molding by pressing, it is rapidly cooled with 50 °C and trimmed to obtain the PHA material.

[0064] Comparative Example 2:

[0065] First, weigh 7 wt% of PLLA with a weight average molecular weight of 250,000 and dissolve it in chloroform. Then, electrospin to prepare a PLLA fiber membrane with a thickness of 0.1 mm within the range of a voltage of 13 KV, an injection speed of 1.0 ml / h, and a distance from the needle tip to the collection device of 15 cm. Prepare PHA plates from the PHA masterbatch using a hot press at 80 °C under a pressure of 2 MPa. Compose the prepared materials according to the following steps:

[0066] (1) Weigh 5 parts of the corresponding mass of the PLLA electrospun membrane and 95 parts of the PHA plates, and perform a drying treatment in a 70 °C vacuum drying oven for 0.5 hours.

[0067] (2) Place the PLLA electrospun membrane in step (1) between two dried PHA plates to obtain a multi-layer structure. The operation can be repeated until the desired thickness is achieved.

[0068] (3) Place the multi-layer structure obtained in step (2) into a hot press for heating. The hot pressing temperature is 185 °C, the time is 1 minute, and the pressure is 2 MPa. During the compression process, the PHA melts and infiltrates into the gaps between the PLLA nanofibers. Immediately after molding by pressing, it is rapidly cooled with 50 °C and trimmed to obtain the PLLA / PHA composite material.

[0069] Table 1 Performance of the samples in the examples and comparative examples

[0070] Sample Reinforcement state Tensile strength (MPa) Elongation at break (%) Transparency (%) Example 1 Fibrous state 43 114 95 Example 2 Fibrous state 90 56 82 Example 3 Fibrous state 82 78 87 Example 4 Fibrous state 30 120 100 Example 5 Fibrous state 100 35 90 Comparative example 1 None 24 118 59 Comparative example 2 Non-fibrous state 29 94 38

[0071] The above has made an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent replacement that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. Preparation method of a highly transparent scPLA / PHA composite material, characterized in that, the highly transparent scPLA / PHA composite material is composed of a reinforcing scPLA fiber membrane and a matrix polyhydroxyalkanoate PHA sheet, and specifically includes the following steps: First step: Weigh 5-15 parts of scPLA fiber membrane and 85-95 parts of PHA sheet according to the mass ratio, and perform drying treatment until the moisture content is less than 300 ppm; Second step: Place the scPLA fiber membrane in the first step between two dried PHA sheets to obtain a multi-layer structure; Third step: Put the multi-layer structure obtained in the second step into a hot press, hot press at 125-185 °C and 2-10 MPa for 1-10 minutes, and quickly cool at -10 °C - 20 °C, and then trim to obtain a highly transparent scPLA / PHA composite material; The scPLA fiber membrane is prepared by electrospinning. The scPLA fiber membrane prepared by electrospinning is to first dissolve equimolar PDLA and PLLA in a solvent to prepare a spinning solution, and then electrospin under the conditions of a voltage of 13-20 KV, an injection speed of 1.0-2.5 ml / h, and a receiving distance of 10-15 cm; The melting point of the scPLA fiber membrane is 220-230 °C, and the melting point of the PHA is 80-150 °C.

2. The preparation method of the highly transparent scPLA / PHA composite material according to claim 1, characterized in that: The weight-average molecular weight of the PLLA and PDLA is 150,000-250,000, and the mass fraction is 7-12%.

3. The preparation method of the highly transparent scPLA / PHA composite material according to claim 1, characterized in that: The solvent is chloroform, dichloromethane, dichloromethane or hexafluoroisopropanol.

4. The preparation method of the highly transparent scPLA / PHA composite material according to claim 1, characterized in that, The thickness of the scPLA fiber membrane is 0.1-0.5 mm.

5. The preparation method of the highly transparent scPLA / PHA composite material according to claim 1, characterized in that, The drying treatment in the first step means placing the scPLA electrospun membrane and the PHA sheet in a vacuum drying oven at 70 °C for 0.5-5 hours.

6. The preparation method of the highly transparent scPLA / PHA composite material according to claim 1, characterized in that, In the second step, the scPLA electrospun membrane is placed between two dried PHA sheets, and the operation is repeated until the ideal thickness is reached.

7. A highly transparent scPLA / PHA composite material prepared by any one of the preparation methods of claims 1-6, characterized in that, The tensile strength of the composite material is 30-100 MPa, the elongation at break is 30%-120%, and the transparency is 80% - 100%.