High-strength polylactic acid material, preparation method therefor, and use thereof

Abstract

Disclosed in the present invention are a high-strength polylactic acid material, a preparation method therefor, and use thereof, belonging to the technical field of macromolecular materials. The high-strength polylactic acid material comprises the following components in parts by weight: 80-90 parts of polylactic acid, 10-20 parts of polybutylene adipate terephthalate, 1-5 parts of a nucleating agent, and 2-5 parts of a compatibilizing agent. The mesh number of the nucleating agent is 1500-2500 mesh; the compatibilizing agent is polycaprolactone, and the intrinsic viscosity thereof is 1.0-3.0 dL / g. The present invention lowers the melting temperature and shortens the melting time of PLA and PBAT, reduces the negative impact of polymer degradation and aging on mechanical properties, produces a heterogeneous nucleation effect, and performs the function of a crystallization nucleus in the cooling crystallization stage, improving crystallization speed and crystallinity, while causing the crystalline phase structure to tend toward a spherulitic state, improving the tensile strength of the polylactic acid material.

Description

A high-strength polylactic acid material and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more specifically, to a high-strength polylactic acid material and a preparation method and application thereof. Background Art

[0002] Polylactic acid (PLA) is a polymer material derived from lactic acid through chemical or biological synthesis. Its raw materials, primarily corn and potatoes, are inexpensive and, because they are made from natural crops, produce minimal carbon emissions. PLA also exhibits excellent transparency and biodegradability, making it an ideal green polymer material. Amidst the increasing demand for biodegradable materials and the increasingly limited availability of petroleum resources, PLA is attracting increasing attention as a biodegradable material that is not reliant on petroleum resources.

[0003] In addition to being biodegradable, products made from polylactic acid (PLA) exhibit biocompatibility, excellent gloss, and transparency, as well as certain antibacterial, flame retardant, and UV resistance. Consequently, they have a wide range of applications, including in the manufacture of baby bottles and transparent drinking cups, as well as in clothing, construction, and healthcare. However, PLA materials generally suffer from disadvantages such as poor processing properties, low elongation at break, and low tensile strength, which restrict their use, for example in thin films.

[0004] The prior art discloses a biodegradable breathable film and a preparation method thereof. The breathable film uses polylactic acid and polybutylene terephthalate-adipate (PBAT) as basic raw materials. The polylactic acid is modified using PBS and inorganic powder to form intermolecular gaps, thereby improving the processing performance and fracture growth rate of the polylactic acid, so that it can be prepared into a film product. However, the tensile strength of the product is still low, with a transverse tensile strength of about 9 to 10 MPa and a longitudinal tensile strength of 10 to 11 MPa. The resulting film product is easily deformed.

[0005] Summary of the Invention

[0006] In order to overcome the problem of low tensile strength of polylactic acid materials prepared by the prior art, the present invention provides a high-strength polylactic acid material. By adding polybutylene terephthalate-adipate (PBAT) to polylactic acid, and using specific nucleating agents and compatibilizers to lower the melting temperature of polylactic acid and PBAT, the crystallization rate and crystallinity are increased, the tensile strength of the polylactic acid material is improved, and its anti-aging performance is also improved.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned high-strength polylactic acid material.

[0008] Another object of the present invention is to provide a polylactic acid film.

[0009] Another object of the present invention is to provide a method for preparing a polylactic acid film.

[0010] Another object of the present invention is to provide an application of a polylactic acid film in the field of packaging materials.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] A high-strength polylactic acid material comprises the following components in parts by weight:

[0013] 80-90 parts of polylactic acid, 10-20 parts of polybutylene terephthalate-adipate, 1-5 parts of nucleating agent, 2-5 parts of compatibilizer;

[0014] The mesh number of the nucleating agent is 1500 to 2500 mesh;

[0015] The compatibilizer is polycaprolactone, and its melt index is 6-9 g / 10 min at a temperature of 100° C. and a pressure of 2.16 kg.

[0016] It should be noted that:

[0017] Adding a certain amount of polybutylene terephthalate adipate (PBAT) to polylactic acid (PLA) improves the toughness of PLA. Excessive PBAT usage should not be excessive, as it will reduce tensile strength, tear strength, and puncture resistance.

[0018] The addition of nucleating agent and compatibilizer polycaprolactone (PCL), on the one hand, can prompt PLA and PBAT to quickly enter the crystal phase transition during the melt plasticization stage, reduce the initial melting temperature of the two, and shorten the melting time of the two, which can reduce the degradation of the polymer during the processing and reshaping process. When plasticization and cross-linking are met, the lower the melting temperature, the shorter the processing time, the smaller the shear force, the smaller the impact on the physical properties of the material, and the reduction of the effects of polymerization degradation and aging, which is more conducive to improving the mechanical properties of polylactic acid materials, especially tensile strength. On the other hand, the addition of nucleating agent and polycaprolactone (PCL) can form a heterogeneous nucleation effect, which acts as a crystallization nucleus during the cooling crystallization stage, increases the crystallization rate and crystallinity, and makes the crystal phase structure tend to spherulites, thereby improving the tensile strength of polylactic acid materials.

[0019] The compatibilizer polycaprolactone of the present invention also has the function of a plasticizer.

[0020] Among them, the mesh number of the nucleating agent needs to be controlled between 1500 and 2500 meshes. If the mesh number is too large, it is easy to aggregate, affecting the dispersion uniformity and fluidity of the nucleating agent in the overall system, which is not conducive to the improvement of the final tensile strength. If the mesh number is too small, not only can it not be fully contacted, affecting the final effect, but it will also affect the appearance of the film-forming product, and it is easy to have bark patterns, wrinkles or other appearance defects.

[0021] The nucleating agent of the present invention may be a common nucleating agent in the art, such as heavy calcium carbonate.

[0022] In a specific embodiment, in order to further improve processing fluidity and enhance production efficiency, the intrinsic viscosity of the polylactic acid may preferably be 2.0 to 4.0 dL / g.

[0023] The intrinsic viscosity of polylactic acid is measured using an Ubbelohde viscometer.

[0024] In a specific embodiment, in order to be more suitable for the production of cast film, the melt index of polybutylene terephthalate-adipate is preferably close to the melt index of polylactic acid. Specifically, the melt index of polybutylene terephthalate-adipate at a temperature of 190° C. and a pressure of 2.16 kg is preferably 3.0 to 5.0 g / 10 min.

[0025] More preferably, the mesh size of the nucleating agent is 1800-2000 mesh.

[0026] In a specific embodiment, according to specific processing and production requirements, 0.5 to 1.0 parts by weight of lubricant and 0 to 5 parts by weight of masterbatch are further added to the high-strength polylactic acid material of the present invention.

[0027] In a specific embodiment, the lubricant of the present invention may be N,N'-ethylene bisstearamide (EBS) or the like.

[0028] In a specific embodiment, the high-strength polylactic acid material can be specifically composed as follows:

[0029] It comprises the following components in parts by weight:

[0030] 85 parts of polylactic acid, 15 parts of polybutylene terephthalate-adipate, 3 parts of nucleating agent, 5 parts of compatibilizer, 1.0 part of lubricant, and 4 parts of masterbatch.

[0031] The present invention specifically protects a method for preparing the above-mentioned high-strength polylactic acid material, comprising the following steps:

[0032] Polylactic acid and polybutylene terephthalate-adipate are first mixed, dried, and then other components are added for mixing, and then extruded to obtain a high-strength polylactic acid material; wherein the extrusion temperature is 185-210°C.

[0033] In the preparation method of the present invention, preferably, PLA and PBAT are first dried and dehumidified to a moisture content of ≤500 mg / kg.

[0034] The high-strength polylactic acid material of the present invention is a degradable material and is sensitive to water. Controlling the moisture content of the mixture of polylactic acid and polybutylene terephthalate-adipate to below 500 mg / kg helps to control the influence of moisture, avoid moisture accelerating the degradation of the polymer, and ultimately affect the tensile strength of the material.

[0035] Specifically, the mixing and drying conditions of the PLA and PBAT are: stirring and drying at 50-60° C. for 1-2 hours.

[0036] Specifically, during the extrusion process, the extruder barrel temperature is 185-210° C., the die head temperature is 200-210° C., and the screw aspect ratio is 27:1.

[0037] The present invention particularly protects a polylactic acid film, the raw material of which is the polylactic acid material mentioned above.

[0038] The polylactic acid material obtained by the invention can be used to prepare a film. The obtained film has good air permeability, high tensile strength, slow degradation rate and aging resistance.

[0039] Specifically, the thickness of the polylactic acid film is 0.05 to 0.1 mm.

[0040] The present invention also provides a method for preparing the polylactic acid film, comprising the following steps:

[0041] The high-strength polylactic acid material is cast, stretched, cooled, cut and rolled up to obtain a polylactic acid film.

[0042] In a specific embodiment, in order to further improve the appearance quality of the polylactic acid film and to control the film thickness, the casting roller pressure is preferably 0.5 to 1.0 MPa.

[0043] In a specific embodiment, in order to control the crystallinity of the polylactic acid film, it is also necessary to simultaneously control the radial stretch ratio of the stretching, which is preferably 1.05 to 1.15. A radial stretch ratio that is too large can easily lead to film perforation.

[0044] Among them, it should be noted that:

[0045] The radial direction of the present invention is the casting direction, and the radial stretching ratio of the present invention is the ratio of the winding linear speed of the winding roller to the linear speed of the casting roller.

[0046] In a specific embodiment, in order to further improve the crystallinity and reduce the thermal shrinkage, the temperature of the cooling roller during the cooling process is preferably 25-30°C.

[0047] The present invention protects application of the polylactic acid film in the field of packaging materials.

[0048] The polylactic acid film obtained by the present invention has the advantages of high tensile strength, aging resistance and degradation resistance, and is particularly suitable for the field of packaging materials, such as disposable shopping bags and packaging bags for disposable items.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The high-strength polylactic acid material of the present invention is prepared by adding a nucleating agent with a specific mesh size and a compatibilizer polycaprolactone with a specific intrinsic viscosity to a polylactic acid and polybutylene terephthalate adipate system, thereby lowering the melting temperature and shortening the melting time of PLA and PBAT, reducing the negative impact of polymer degradation and aging on mechanical properties, forming a heterogeneous nucleation effect, and acting as a crystallization nucleus in the cooling crystallization stage, thereby increasing the crystallization rate and crystallinity, and making the crystal phase structure tend to spherulites, thereby improving the tensile strength of the polylactic acid material. DETAILED DESCRIPTION

[0051] The raw materials used in the specific examples and comparative examples of the present invention are described as follows:

[0052] Polylactic acid: PLLA, intrinsic viscosity 4.0 dL / g, Hisun Bio REVODE201;

[0053] PBAT: melt index 4.0g / 10min, Blonde FLex-262;

[0054] Nucleating agent 1: heavy calcium carbonate, 2500 mesh, TECO calcium powder GX2500M;

[0055] Nucleating agent 2: heavy calcium carbonate, 2000 mesh, TECO calcium powder GX2000;

[0056] Nucleating agent 3: heavy calcium carbonate, 1000 mesh, TECO calcium powder GX1000;

[0057] Nucleating agent 4: heavy calcium carbonate, 3000 mesh, TECO calcium powder GX3000;

[0058] Compatibilizer 1: polycaprolactone, melt index 6-9g / 10min, Shenzhen Guanghua Weiye Esun600C;

[0059] Compatibilizer 2: polycaprolactone, melt index 9-11g / 10min, Shenzhen Guanghua Weiye Esun500C;

[0060] Compatibilizer 3: Polycaprolactone, melt index 1-4g / 10min, Shenzhen Guanghua Weiye Esun800C

[0061] Lubricant: N,N'-ethylenebisstearamide (EBS), commercially available, all parallel experiments were of the same type;

[0062] Masterbatch was commercially available and all parallel experiments were of the same type.

[0063] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise stated, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0064] Examples 1-2

[0065] A high-strength polylactic acid material includes the components listed in Table 1 below in parts by weight.

[0066] Table 1. Formula of high-strength polylactic acid material of Examples 1 to 2 (by weight)

[0067] The preparation method of the high-strength polylactic acid material of the above-mentioned embodiments 1 to 4 comprises the following steps:

[0068] Polylactic acid and PBAT were added to a mixing tank in batches, stirred and dried at 60°C for 2 hours until the moisture content of the pellets was less than 500 mg / kg. The mixed pellets were pumped into a hopper through a vacuum pumping device, and then the pellets were added to a twin-screw extruder. Nucleating agent, compatibilizer, lubricant and masterbatch were added to the extruder feeding section through a side hopper, and then extruded to obtain high-strength polylactic acid material; wherein, the extruder barrel temperature is 180°C, the die head temperature is 210°C, and the screw aspect ratio is 27:1.

[0069] Example 5

[0070] A polylactic acid film, the preparation method comprises the following steps:

[0071] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Example 1 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0072] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0073] Example 6

[0074] A polylactic acid film, the preparation method comprises the following steps:

[0075] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Example 2 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0076] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0077] Example 7

[0078] A polylactic acid film, the preparation method comprises the following steps:

[0079] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Example 3 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0080] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0081] Example 8

[0082] A polylactic acid film, the preparation method comprises the following steps:

[0083] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Example 4 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0084] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0085] Example 9

[0086] A polylactic acid film, the preparation method comprises the following steps:

[0087] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Example 1 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0088] The casting roller pressure was 1.0 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.105.

[0089] Comparative Example 1

[0090] A polylactic acid material comprising the following components in parts by weight:

[0091] Polylactic acid: 85 parts, PBAT: 15 parts, lubricant: 1.0 parts, masterbatch: 4 parts.

[0092] The preparation method of the polylactic acid material of Comparative Example 1 is the same as that of Example 1.

[0093] A polylactic acid film, the preparation method comprises the following steps:

[0094] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Comparative Example 1 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0095] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0096] Comparative Example 2

[0097] A polylactic acid material comprising the following components in parts by weight:

[0098] Polylactic acid: 85 parts, PBAT: 15 parts, lubricant: 1.0 parts, masterbatch: 4 parts, nucleating agent 8 parts.

[0099] The preparation method of the polylactic acid material of Comparative Example 2 is the same as that of Example 1.

[0100] A polylactic acid film, the preparation method comprises the following steps:

[0101] The high-strength polylactic acid material sheet with a thickness of 1 mm prepared in Comparative Example 2 was cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain a polylactic acid film with a thickness of 0.05 mm.

[0102] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0103] Comparative Examples 3 to 7

[0104] A high-strength polylactic acid material includes the components listed in Table 1 below in parts by weight.

[0105] Table 2. Formulas of high-strength polylactic acid materials of comparative examples 3 to 7 (by weight)

[0106] The preparation method of the high-strength polylactic acid material of Comparative Examples 3 to 7 comprises the following steps:

[0107] Polylactic acid and PBAT were added to a mixing tank in batches, stirred and dried at 60°C for 2 hours until the moisture content of the pellets was less than 500 mg / kg. The mixed pellets were pumped into a hopper through a vacuum pumping device, and then the pellets were added to a twin-screw extruder. Nucleating agent, compatibilizer, lubricant and masterbatch were added to the extruder feeding section through a side hopper, and then extruded to obtain high-strength polylactic acid material; wherein, the extruder barrel temperature is 180°C, the die head temperature is 210°C, and the screw aspect ratio is 27:1.

[0108] A polylactic acid film, the preparation method comprises the following steps:

[0109] The high-strength polylactic acid material sheets with a thickness of 1 mm prepared in Comparative Examples 3 to 7 were cast, cooled, and calendered to a thickness of 0.2 mm, and then cut and rolled to obtain polylactic acid films with a thickness of 0.05 mm.

[0110] The casting roller pressure was 0.5 MPa, the cooling roller temperature was 25° C., and the radial stretching ratio during the casting and cooling process was 1.1.

[0111] Result detection

[0112] The methods for detecting various parameters of the polylactic acid films prepared in the examples and comparative examples of the present invention are as follows:

[0113] Film thickness measurement: measured according to national standard GB / T 6672-2001;

[0114] Transverse and longitudinal tensile strength test: measured according to standard GB / T 1040-2018;

[0115] Elongation at break test: measured according to standard GB / T 1040-2018.

[0116] The specific test results are shown in Table 3.

[0117] Among them, the tensile strength and elongation at break of the polylactic acid films of Examples 7 to 8 are slightly greater than those of Examples 5 and 6.

[0118] The tensile strength and elongation at break of the polylactic acid film of Example 9 are substantially equivalent to those of Example 1.

[0119] From the data in Table 2 above, it can be seen that the high-strength polylactic acid material of the present invention reduces the effects of polymerization degradation and aging by adding a specific nucleating agent and a compatibilizer polycaprolactone (PCL), which is more conducive to improving the mechanical properties of the polylactic acid material, especially the tensile strength performance. The addition of the nucleating agent and polycaprolactone (PCL) can form a heterogeneous nucleation effect, which plays the role of a crystallization nucleus in the cooling crystallization stage, thereby increasing the crystallization rate and crystallinity, and at the same time making the crystal phase structure tend to spherulites, thereby improving the tensile strength of the polylactic acid material.

[0120] However, in Comparative Examples 1 and 2, the corresponding nucleating agent and compatibilizer are missing, and the transverse tensile strength and transverse tensile strength of the polylactic acid film cannot reach the effect of the present invention.

[0121] Comparative Examples 3 and 4 are nucleating agents with mesh sizes that are too large or too small, which are not within the protection range and have a significant impact on the tensile strength of the polylactic acid film, and cannot achieve the effect of the present invention.

[0122] Comparative Examples 5 and 6 use compatibilizers not protected by the present invention, and the synergistic effect of the overall system cannot be achieved.

[0123] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A high-strength polylactic acid material, characterized in that: The composition comprises the following components by weight: 80-90 parts of polylactic acid, 10-20 parts of polybutylene terephthalate-adipate, 1-5 parts of nucleating agent, 2-5 parts of compatibilizer; The mesh size of the nucleating agent is 1500 to 2500 mesh; The compatibilizer is polycaprolactone, and the melt index is 6-9 g / 10 min at a temperature of 100° C. and a pressure of 2.16 kg.

2. The high-strength polylactic acid material according to claim 1, characterized in that: The intrinsic viscosity of the polylactic acid is 2.0 to 4.0 dL / g.

3. The high-strength polylactic acid material according to claim 1, characterized in that: The polybutylene terephthalate-adipate has a melting index of 3.0 to 5.0 g / 10 min at a temperature of 190° C. and a pressure of 2.16 kg.

4. The high-strength polylactic acid material according to claim 1, characterized in that: The mesh number of the nucleating agent is 1800-2000 meshes.

5. A method for preparing the high-strength polylactic acid material according to any one of claims 1 to 4, characterized in that: The steps include: Polylactic acid and polybutylene terephthalate-adipate are first mixed, and after drying, other components are added to mix, and then extruded to obtain a high-strength polylactic acid material at an extrusion temperature of 185-210°C.

6. A polylactic acid film, characterized in that: The raw material of the polylactic acid film includes the high-strength polylactic acid material according to any one of claims 1 to 4.

7. A method for preparing the polylactic acid film according to claim 6, characterized in that: The steps include: The high-strength polylactic acid material is cast, stretched, cooled, cut and rolled up to obtain a polylactic acid film.

8. The method for preparing a polylactic acid film according to claim 7, characterized in that: The casting roller pressure is 0.5-1.0 MPa.

9. The method for preparing a polylactic acid film according to claim 7, characterized in that: The radial stretching ratio of the stretching is 1.05 to 1.

15.

10. Use of the polylactic acid film according to claim 6 in the field of packaging materials.

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