A polylactic acid composition printable at high speed and a method for preparing the same

Abstract

This application relates to the field of additive manufacturing technology, specifically disclosing a high-speed printable polylactic acid (PLA) composition and its preparation method. The high-speed printable PLA composition comprises the following raw materials in parts by weight: PLA, a compatibilizer, and a modified polybutylene terephthalate (PET) prepolymer, wherein the modified PET prepolymer incorporates hydroxyl or carboxyl polar functional groups. The preparation method involves: drying the PET; weighing the dried PET and placing it in a heating reaction apparatus for stirring; adding an initiator and glycolic acid and continuing stirring; drying the PLA; and weighing the PLA, the modified PET prepolymer, and the compatibilizer for melt granulation to obtain the PLA composition. This high-speed printable PLA composition and its preparation method have the advantage of improving upon the shortcomings of PLA's toughness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, more particularly, it relates to a polylactic acid composition capable of high-speed printing and a preparation method thereof. BACKGROUND

[0002] 3D printing, also known as additive manufacturing, is a new rapid prototyping technology integrating digital modeling, material science, and mechatronic control, and is widely used in the fields of biomedicine, energy, aerospace, high-end jewelry, real estate, and the like. As an important component of 3D printing technology, 3D printing consumables affect the forming speed, accuracy, and physical and chemical properties of the prototype, and directly affect the secondary application of the prototype and the selection of the user for the forming process equipment.

[0003] At present, the commonly used 3D printing consumables on the market mainly include polylactic acid, acrylonitrile-butadiene-styrene terpolymer, and polyethylene terephthalate-1,4-cyclohexane dimethanol, etc. Polylactic acid is more popular and concerned due to its safety, non-toxicity, non-pungent odor, low melting temperature, excellent biocompatibility, biodegradability, low shrinkage, transparency, and easy dyeing.

[0004] However, polylactic acid is a brittle polymer with low crack initiation energy and low crack propagation energy, and thus has poor toughness. In order to improve the toughness of polylactic acid without reducing sustainability, various petroleum-based and biobased biodegradable materials have been widely used in blending research with polylactic acid. Commonly used biodegradable materials for toughening polylactic acid include polybutylene terephthalate-adipate, but due to the large difference in molecular structure between polybutylene terephthalate-adipate and polylactic acid, there may be poor compatibility when they are blended, thereby affecting the toughening effect of polylactic acid. SUMMARY

[0005] In order to improve the toughness of polylactic acid, the present application provides a polylactic acid composition capable of high-speed printing and a preparation method thereof.

[0006] In a first aspect, the present application provides a polylactic acid composition capable of high-speed printing, which adopts the following technical solution:

[0007] A polylactic acid composition capable of high-speed printing comprises the following raw materials by mass: 80-100 parts of polylactic acid, 0.1-0.3 parts of a compatibilizer, and 5-15 parts of a modified polybutylene terephthalate-adipate pre-polymer, wherein the modified polybutylene terephthalate-adipate pre-polymer is introduced with a hydroxyl or carboxyl polar functional group.

[0008] Since polylactic acid is a bio-based material, derived from renewable resources such as corn starch or sugar cane, through microbial fermentation to produce lactic acid, and then through polymerization to form polylactic acid, which makes polylactic acid can be biodegraded under industrial composting conditions after use, reducing the impact on the environment, and the molecular chain of polylactic acid is mainly composed of repeated lactic acid units, forming a linear polyester structure with high crystallinity.

[0009] However, polybutylene adipate terephthalate is a copolyester formed by ester exchange reaction of adipic acid, terephthalic acid and butanediol three monomers, so the molecular chain of polybutylene adipate terephthalate not only contains ester bond, but also contains flexible aliphatic segment and rigid aromatic segment, which makes the intermolecular interaction force of polylactic acid and polybutylene adipate terephthalate different, not easy to form stable interface when mixed, resulting in poor compatibility. Since the modified polybutylene adipate terephthalate prepolymer used in the present application introduces hydroxyl or carboxyl polar functional groups, the modified polybutylene adipate terephthalate prepolymer has a certain polarity, which is beneficial to improve the interaction between polylactic acid and modified polybutylene adipate terephthalate prepolymer, reduce the interfacial tension, so that polylactic acid and modified polybutylene adipate terephthalate prepolymer can be better bonded when compounded, thereby having good compatibility.

[0010] Preferably, the modified polybutylene adipate terephthalate prepolymer introduces a hydroxyl functional group.

[0011] Since the introduction of hydroxyl group can increase the polarity of polybutylene adipate terephthalate, and polylactic acid is also a polar polymer, the hydroxyl group introduced into polybutylene adipate terephthalate can form hydrogen bonds with the carboxyl or ester group in polylactic acid, so that the hydroxyl functional group can form a strong interaction at the interface between polylactic acid and polybutylene adipate terephthalate, reducing the interfacial tension, thereby improving the compatibility between polylactic acid and polybutylene adipate terephthalate.

[0012] Preferably, the modified polybutylene adipate terephthalate prepolymer is glycolic acid grafted polybutylene adipate terephthalate.

[0013] Since grafting refers to the reaction of macromolecular chain with appropriate branched chain or functional side group through chemical bond, the hydroxyl functional group in glycolic acid can be introduced into the molecular chain of polybutylene adipate terephthalate, and the grafted modified polybutylene adipate terephthalate can be blended with polylactic acid, which can reduce the phase separation phenomenon, thereby improving the interaction between polybutylene adipate terephthalate and polylactic acid.

[0014] Preferably, the modified polybutylene terephthalate-hexanedioic acid butanediol pre-polymer comprises the following raw materials: polybutylene terephthalate-hexanedioic acid butanediol, initiator and glycolic acid.

[0015] Since the initiator is a free radical initiator, during the modification process, the initiator is used to activate the molecular chain of polybutylene terephthalate-hexanedioic acid butanediol, so that free radicals are generated, which can react with glycolic acid to introduce the hydroxyl functional group in glycolic acid into the molecular chain of polybutylene terephthalate-hexanedioic acid butanediol.

[0016] Preferably, the modified polybutylene terephthalate-hexanedioic acid butanediol pre-polymer comprises the following raw materials: 46-54 parts of polybutylene terephthalate-hexanedioic acid butanediol, 0.12-0.18 parts of initiator and 0.31-0.35 parts of glycolic acid.

[0017] Preferably, the preparation method of the modified polybutylene terephthalate-hexanedioic acid butanediol pre-polymer comprises the following steps: drying polybutylene terephthalate-hexanedioic acid butanediol in a vacuum drying oven at 75-85°C for 10-14h, placing 46-54 parts of the dried polybutylene terephthalate-hexanedioic acid butanediol in a heating reaction device at 155-165°C and stirring, then adding 0.12-0.18 parts of initiator and 0.31-0.35 parts of glycolic acid and continuing to stir for 8-12min to obtain the modified polybutylene terephthalate-hexanedioic acid butanediol pre-polymer.

[0018] In a second aspect, the application provides a preparation method of a high-speed printable polylactic acid composition, which adopts the following technical scheme:

[0019] A preparation method of a high-speed printable polylactic acid composition, comprising the following steps:

[0020] S1: drying polylactic acid in a vacuum drying oven at 115-125°C for 7-9h;

[0021] S2: mixing 80-100 parts of polylactic acid, 5-15 parts of modified polybutylene terephthalate-hexanedioic acid butanediol pre-polymer and 0.1-0.3 parts of compatibilizer uniformly, and performing melt mixing and granulation through a melt extruder to obtain the polylactic acid composition.

[0022] In summary, the application has the following beneficial effects:

[0023] 1. Polylactic acid (PLA) is a bio-based material derived from renewable resources such as corn starch or sugarcane. It is produced by microbial fermentation to produce lactic acid, which is then polymerized to form PLA. This allows PLA to be biodegraded under industrial composting conditions after use, reducing its environmental impact. Furthermore, the molecular chain of PLA is mainly composed of repeating lactic acid units, forming a linear polyester structure with high crystallinity.

[0024] However, polybutylene terephthalate (PET) is a copolyester formed by the transesterification reaction of three monomers: adipic acid, terephthalic acid, and butanediol. Therefore, the molecular chain of PET not only contains ester bonds but also flexible aliphatic segments and rigid aromatic segments. This results in different intermolecular forces between polylactic acid (PLA) and PET, making it difficult to form a stable interface during mixing, leading to poor compatibility. The modified polybutylene terephthalate (PET) prepolymer used in this application incorporates hydroxyl or carboxyl polar functional groups, giving it a certain degree of polarity. This helps improve the interaction between polylactic acid (PLA) and the modified PET prepolymer, reduces interfacial tension, and allows for better bonding between PLA and the modified PET prepolymer during composite formation, thus exhibiting better compatibility.

[0025] 2. The introduction of hydroxyl groups increases the polarity of polybutylene terephthalate (PET), and polylactic acid (PLA) is also a polar polymer. This allows the hydroxyl groups introduced into PET to form hydrogen bonds with the carboxyl or ester groups in PLA. As a result, the hydroxyl functional groups can form a strong interaction at the interface between PLA and PET, reducing interfacial tension and thus improving the compatibility between PLA and PET.

[0026] 3. Since grafting refers to the reaction in which appropriate branches or functional side groups are attached to a macromolecular chain through chemical bonds, the hydroxyl functional groups in glycolic acid can be introduced onto the polybutylene terephthalate (PET) molecular chain. Blending the grafted PET with polylactic acid can reduce phase separation and thus improve the interaction between PET and polylactic acid. Detailed Implementation

[0027] The present application will be further described in detail below with reference to Examples 1-6 and Comparative Examples 1-2.

[0028] raw material

[0029] Polylactic acid (PLA) - Shanghai Yuanye Biotechnology Co., Ltd.; Compatibilizer ADR4370S - BASF GmbH, Germany; Glycolic acid CAS: 79-14-1; Polybutylene terephthalate (PET) CAS: 55231-08-8; Initiator DCP - Anhui Xiangyun Rubber & Plastics Co., Ltd.

[0030] Example

[0031] Example 1

[0032] A high-speed printable polylactic acid composition comprising the following raw materials: 90g polylactic acid, 0.2g compatibilizer ADR4370S, and 10g modified polybutylene terephthalate-adipate prepolymer.

[0033] Specifically, the method for preparing high-speed printable polylactic acid compositions includes the following steps:

[0034] S1: Place polybutylene terephthalate in a vacuum drying oven at 80℃ and dry for 12 hours;

[0035] S2: Weigh 50g of dried polybutylene terephthalate and place it in a torque rheometer at 160℃. First, set the rotation speed to 20r / min. After adding 50g of polybutylene terephthalate, set the rotation speed to 60r / min. After reacting for 1min, the granules melt and the torque decreases.

[0036] S3: Then add 0.15g of initiator DCP and 0.33g of glycolic acid. After reacting for 10 minutes, the torque stabilizes and the rotor stops, thus obtaining the modified polybutylene terephthalate-adipate prepolymer.

[0037] S4: Place polylactic acid in a vacuum drying oven at 120℃ and dry for 8 hours;

[0038] S5: Weigh 90g of dried polylactic acid, 10g of modified polybutylene terephthalate-adipate prepolymer and 0.2g of compatibilizer ADR4370S, mix them evenly, and put them into a micro-mixing rheometer at 200℃. Melt extrusion granulation is carried out through the twin-screw mixing system in the micro-mixing rheometer to obtain the polylactic acid composition.

[0039] Example 2-3

[0040] The difference between Examples 2-3 and Example 1 is that the amount of each component added to the high-speed printable polylactic acid composition is different, as shown in Table 1.

[0041] Table 1. Amounts (g) of each component added to the high-speed printable polylactic acid compositions in Examples 1-3.

[0042] Example 1 Example 2 Example 3 Polylactic acid 90 80 100 Compatibilizer ADR4370S 0.2 0.3 0.1 Modified polybutylene adipate terephthalate prepolymer 10 5 15

[0043] Example 4

[0044] The difference between Example 4 and Example 1 is that glycolic acid is replaced with an equal amount of 1,4-cyclohexanedicarboxylic acid.

[0045] Examples 5-6

[0046] The difference between Examples 5-6 and Example 1 is that the amount of each component added in the modified polybutylene terephthalate-adipate prepolymer is different, as shown in Table 2.

[0047] Table 2. Amounts (g) of each component added to the modified polybutylene terephthalate-adipate prepolymer in Examples 1 and 5-6.

[0048] Example 1 Example 5 Example 6 Polybutylene adipate terephthalate 50 54 46 Initiator DCP 0.15 0.18 0.12 Glycolic acid 0.33 0.31 0.35

[0049] Comparative Example

[0050] Comparative Example 1

[0051] The difference between Comparative Example 1 and Example 1 is that the modified polybutylene terephthalate prepolymer is no longer added.

[0052] Comparative Example 2

[0053] The difference between Comparative Example 2 and Example 1 is that the modified polybutylene terephthalate prepolymer was replaced with the same amount of polybutylene terephthalate.

[0054] Performance testing

[0055] Detection methods

[0056] I. Tensile property testing

[0057] Three samples were taken from Examples 1-6 and Comparative Examples 1-2 respectively, and tensile properties were tested in accordance with GB / T 1040.1-2006 "Determination of tensile properties of plastics - Part 1: General".

[0058] The test data is shown in Table 3.

[0059] Table 3 Tensile property test table for Examples 1-6 and Comparative Examples 1-2

[0060] Tensile strength (MPa) Elongation at break (%) Example 1 81.5 87 Example 2 80.6 83 Example 3 80.8 82 Example 4 78.1 79 Example 5 79.4 80 Example 6 79.2 81 Comparative Example 1 73.7 56 Comparative Example 2 76.9 60

[0061] As can be seen from Example 1 and Comparative Example 1 and Table 3, compared with Example 1, the tensile strength and elongation at break of Comparative Example 1 are significantly reduced. This shows that the addition of modified polybutylene terephthalate-adipate prepolymer can effectively improve the tensile strength and elongation at break of polylactic acid, thereby improving the toughness of polylactic acid.

[0062] The reason for this is that the modified polybutylene terephthalate (PET) prepolymer, with the help of glycolic acid, introduces hydroxyl polar functional groups, giving it a certain degree of polarity. Meanwhile, polylactic acid (PLA) is also a polar polymer, allowing the hydroxyl groups introduced into PET to form hydrogen bonds with the carboxyl or ester groups in PLA. This improves the interaction between PLA and the modified PET prepolymer, reduces interfacial tension, and enables better bonding between PLA and the modified PET prepolymer during composite formation, thus exhibiting better compatibility.

[0063] As can be seen from Example 1 and Comparative Example 2, and Table 3, compared with Example 1, the tensile strength and elongation at break of Comparative Example 2 are significantly reduced. This indicates that, compared with the addition of polybutylene terephthalate, the addition of modified polybutylene terephthalate prepolymer can effectively improve the tensile strength and elongation at break of polylactic acid, thereby improving the toughness of polylactic acid.

[0064] The reason for this is that polylactic acid (PLA) is a bio-based material derived from renewable resources such as corn starch or sugarcane. It is produced through microbial fermentation to generate lactic acid, which is then polymerized to form PLA. This allows PLA to be biodegraded under industrial composting conditions after use, reducing its environmental impact. Furthermore, the PLA molecular chain is mainly composed of repeating lactic acid units, forming a linear polyester structure with high crystallinity. However, polybutylene terephthalate (PET) is a copolyester formed by the transesterification of adipic acid, terephthalic acid, and butanediol monomers. Therefore, the PET molecular chain not only contains ester bonds but also flexible aliphatic segments and rigid aromatic segments. This results in different intermolecular forces between PLA and PET, making it difficult to form a stable interface during mixing, thus leading to poor compatibility.

[0065] Combining Examples 1 and 2-3 with Table 3, it can be seen that, compared with Example 1, the tensile strength and elongation at break of Example 2 are slightly lower than those of Example 1, and the tensile strength and elongation at break of Example 3 are also slightly lower than those of Example 1. This indicates that the amount of each component added to the polylactic acid composition also affects the tensile strength and elongation at break of polylactic acid, thereby affecting the toughness of polylactic acid.

[0066] Combining Examples 1 and 4 with Table 3, it can be seen that, compared with Example 1, the tensile strength and elongation at break of Example 4 are lower. This indicates that, compared with adding the same amount of 1,4-cyclohexanedicarboxylic acid, adding glycolic acid can more effectively improve the tensile strength and elongation at break of polylactic acid, thereby improving the toughness of polylactic acid.

[0067] The reason for this is that glycolic acid and polylactic acid (PLA) have more similar chemical structures. PLA is a polymer composed of lactic acid units linked by ester bonds, and glycolic acid is also a simple dicarboxylic acid with a structure similar to lactic acid. Therefore, polybutylene terephthalate (PET) modified with glycolic acid has a higher similarity in chemical structure to PLA. However, the carboxyl functional group is less reactive than the hydroxyl functional group, and may not easily react with PLA in the polymer due to steric hindrance. Furthermore, 1,4-cyclohexanedicarboxylic acid is a cyclic aliphatic dicarboxylic acid, so the polarity of 1,4-cyclohexanedicarboxylic acid may not be as strong as that of glycolic acid with a straight chain structure.

[0068] Combining Examples 1 and 5-6 with Table 3, it can be seen that, compared with Example 1, the tensile strength and elongation at break of Example 5 are lower than those of Example 1, and the tensile strength and elongation at break of Example 6 are also lower than those of Example 1. This indicates that the amount of each component added to the modified polybutylene terephthalate-adipate prepolymer also affects the tensile strength and elongation at break of polylactic acid, thereby affecting the toughness of polylactic acid.

[0069] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-speed printable polylactic acid composition, characterized in that, The product comprises the following raw materials in parts by weight: 80-100 parts polylactic acid, 0.1-0.3 parts compatibilizer, and 5-15 parts modified polybutylene terephthalate prepolymer, wherein the modified polybutylene terephthalate prepolymer is introduced with hydroxyl or carboxyl polar functional groups. The modified polybutylene terephthalate-adipate prepolymer is incorporating hydroxyl functional groups. The modified polybutylene terephthalate-adipate prepolymer is the glycolic acid-grafted polybutylene terephthalate-adipate.

2. The high-speed printable polylactic acid composition according to claim 1, characterized in that, The modified polybutylene terephthalate prepolymer comprises the following raw materials: polybutylene terephthalate, initiator, and glycolic acid.

3. The high-speed printable polylactic acid composition according to claim 2, characterized in that, The modified polybutylene terephthalate-adipate prepolymer comprises the following raw materials in parts by weight: 46-54 parts polybutylene terephthalate-adipate, 0.12-0.18 parts initiator, and 0.31-0.35 parts glycolic acid.

4. The high-speed printable polylactic acid composition according to claim 3, characterized in that, The preparation method of the modified polybutylene terephthalate prepolymer is as follows: Polybutylene terephthalate is dried in a vacuum drying oven at 75℃-85℃ for 10-14 hours. 46-54 parts of the dried polybutylene terephthalate are weighed and placed in a heating reaction apparatus at 155℃-165℃ and stirred. Then, 0.12-0.18 parts of initiator and 0.31-0.35 parts of glycolic acid are added, and stirring continues for 8-12 minutes to obtain the modified polybutylene terephthalate prepolymer.

5. A method for preparing a high-speed printable polylactic acid composition according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Place polylactic acid in a vacuum drying oven at 115℃-125℃ and dry for 7-9 hours; S2: Weigh 80-100 parts of polylactic acid, 5-15 parts of modified polybutylene terephthalate-adipate prepolymer and 0.1-0.3 parts of compatibilizer, mix them evenly, and then melt-mix and granulate them through a melt extruder to obtain a polylactic acid composition.