Polylactic acid composition capable of being printed at high speed and preparation method thereof

Abstract

The invention relates to the technical field of additive manufacturing, and particularly discloses a polylactic acid composition capable of being printed at a high speed and a preparation method thereof. The invention relates to a polylactic acid composition capable of being printed at a high speed. The polylactic acid composition is prepared from the following raw materials in parts by mass: polylactic acid, a compatilizer and a modified poly (terephthalic acid)-butylene adipate prepolymer, wherein a hydroxyl or carboxyl polar functional group is introduced into the modified poly (terephthalic acid)-butylene adipate prepolymer; the preparation method comprises the following steps: drying the poly (butylene adipate-co-terephthalate), weighing the dried poly (butylene adipate-co-terephthalate), putting the weighed poly (butylene adipate-co-terephthalate) into a heating reaction device, stirring, adding an initiator and glycollic acid, and continuously stirring; drying the polylactic acid; and weighing polylactic acid, the modified poly (butylene terephthalate)-adipate prepolymer and a compatilizer, and carrying out melt granulation to obtain the polylactic acid composition. The polylactic acid composition capable of being printed at high speed and the preparation method thereof have the advantage that the defect that the toughness of polylactic acid is still insufficient can be overcome.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and more specifically, to a high-speed printable polylactic acid composition and a preparation method thereof. Background Art

[0002] 3D printing, also known as additive manufacturing, is a new rapid prototyping technology that integrates digital modeling, material science, and mechatronics control. It is widely used in biomedicine, energy, aerospace, high-end jewelry, real estate and other fields. 3D printing consumables, as an important part of 3D printing technology, affect the molding speed, accuracy, and physical and chemical properties of the prototype, and directly affect the secondary application of the prototype and the user's choice of molding process equipment.

[0003] At present, the commonly used 3D printing consumables in the market are mainly polylactic acid, acrylonitrile-butadiene-styrene terpolymer, polyethylene terephthalate-1,4-cyclohexanedimethanol, etc., and polylactic acid is more popular and concerned because of its many advantages such as safety and non-toxicity, no 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, so its toughness is poor. In order to improve the toughness of polylactic acid without reducing sustainability, various petroleum-based and bio-based biodegradable materials have been widely used in blending research with polylactic acid. Common biodegradable materials used to toughen polylactic acid include polybutylene terephthalate-adipate. However, due to the large difference in the molecular structure of polybutylene terephthalate-adipate and polylactic acid, when polybutylene terephthalate-adipate and polylactic acid are blended, there may be poor compatibility, which affects the toughening effect of polylactic acid. Summary of the invention

[0005] In order to improve the defect that the toughness of polylactic acid is still insufficient, the present application provides a high-speed printable polylactic acid composition and a preparation method thereof.

[0006] In the first aspect, the present application provides a high-speed printable polylactic acid composition, which adopts the following technical solution: A high-speed printable polylactic acid composition comprises the following raw materials in parts by weight: 80-100 parts of polylactic acid, 0.1-0.3 parts of a compatibilizer and 5-15 parts of a modified poly(butylene terephthalate)-adipate prepolymer, wherein a hydroxyl or carboxyl polar functional group is introduced into the modified poly(butylene terephthalate)-adipate prepolymer.

[0007] Since polylactic acid is a bio-based material derived from renewable resources such as corn starch or sugarcane, lactic acid is produced through microbial fermentation and then formed through polymerization reaction. This allows polylactic acid to be biodegraded under industrial composting conditions after use, reducing the impact on the environment. The molecular chain of polylactic acid is mainly composed of repeating lactic acid units, forming a linear polyester structure with high crystallinity.

[0008] However, polybutylene terephthalate-adipate is a copolyester, which is formed by ester exchange reaction of three monomers: adipic acid, terephthalic acid and butanediol. Therefore, the molecular chain of polybutylene terephthalate-adipate contains not only ester bonds, but also flexible aliphatic segments and rigid aromatic segments. This makes the intermolecular interaction forces of polylactic acid and polybutylene terephthalate-adipate different, and it is not easy to form a stable interface when mixed, resulting in poor compatibility. The modified poly(butylene terephthalate)-adipate prepolymer used in the present application has introduced hydroxyl or carboxyl polar functional groups, so that the modified poly(butylene terephthalate)-adipate prepolymer has a certain polarity, which is beneficial to improving the interaction between poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer, reducing the interfacial tension, and allowing poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer to be better bonded during compounding, thereby having better compatibility.

[0009] Preferably, the modified polybutylene terephthalate-adipate prepolymer is introduced with a hydroxyl functional group.

[0010] Since the introduction of hydroxyl groups can increase the polarity of polybutylene terephthalate-adipate, and polylactic acid is also a polar polymer, the hydroxyl groups introduced into polybutylene terephthalate-adipate can form hydrogen bonds with the carboxyl groups or ester groups in polylactic acid, so that the hydroxyl functional groups can form a stronger interaction at the interface between polylactic acid and polybutylene terephthalate-adipate, reduce the interfacial tension, and thus improve the compatibility between polylactic acid and polybutylene terephthalate-adipate.

[0011] Preferably, the modified polybutylene terephthalate-adipate prepolymer is the glycolic acid grafted polybutylene terephthalate-adipate.

[0012] Since grafting refers to the reaction of combining appropriate side chains or functional side groups on the macromolecular chain through chemical bonds, the hydroxyl functional groups in glycolic acid can be introduced into the polybutylene terephthalate-adipate molecular chain at a specific point, and the grafted modified polybutylene terephthalate-adipate is blended with polylactic acid, which can reduce the phase separation phenomenon and thus improve the interaction between polybutylene terephthalate-adipate and polylactic acid.

[0013] Preferably, the modified polybutylene terephthalate-adipate prepolymer comprises the following raw materials: polybutylene terephthalate-adipate, an initiator and glycolic acid.

[0014] Since the initiator is a free radical initiator, during the modification process, the initiator is used to activate the polybutylene terephthalate-adipate molecular chain to generate free radicals, and these free radicals can undergo a grafting reaction with glycolic acid, so that the hydroxyl functional groups in the glycolic acid are introduced into the polybutylene terephthalate-adipate molecular chain.

[0015] Preferably, the modified polybutylene terephthalate-adipate prepolymer comprises the following raw materials in parts by weight: 46 parts to 54 parts of polybutylene terephthalate-adipate, 0.12 parts to 0.18 parts of initiator, and 0.31 parts to 0.35 parts of glycolic acid.

[0016] Preferably, the preparation method of the modified polybutylene terephthalate-adipate prepolymer is as follows: polybutylene terephthalate-adipate is placed in a vacuum drying oven at 75°C-85°C and dried for 10h-14h, 46-54 parts of the dried polybutylene terephthalate-adipate are weighed and placed in a heating reaction device at 155°C-165°C and stirred, then 0.12-0.18 parts of initiator and 0.31-0.35 parts of glycolic acid are added and stirring is continued for 8min-12min to obtain the modified polybutylene terephthalate-adipate prepolymer.

[0017] In a second aspect, the present application provides a method for preparing a high-speed printable polylactic acid composition, using the following technical solution: A method for preparing a high-speed printable polylactic acid composition comprises the following steps: S1: Put the polylactic acid into a vacuum drying oven at 115°C-125°C and dry it for 7h-9h; S2: Weigh 80-100 parts of polylactic acid, 5-15 parts of modified polybutylene terephthalate-adipate prepolymer and 0.1-0.3 parts of a compatibilizer, mix them evenly, and perform melt mixing and granulation through a melt extruder to obtain a polylactic acid composition.

[0018] In summary, this application has the following beneficial effects: 1. Since polylactic acid is a bio-based material derived from renewable resources such as corn starch or sugarcane, lactic acid is produced through microbial fermentation and then polymerized to form polylactic acid. This allows polylactic acid to be biodegraded under industrial composting conditions after use, reducing the impact on the environment. The molecular chain of polylactic acid is mainly composed of repeated lactic acid units, forming a linear polyester structure with high crystallinity.

[0019] However, polybutylene terephthalate-adipate is a copolyester, which is formed by ester exchange reaction of three monomers: adipic acid, terephthalic acid and butanediol. Therefore, the molecular chain of polybutylene terephthalate-adipate contains not only ester bonds, but also flexible aliphatic segments and rigid aromatic segments. This makes the intermolecular interaction forces of polylactic acid and polybutylene terephthalate-adipate different, and it is not easy to form a stable interface when mixed, resulting in poor compatibility. The modified poly(butylene terephthalate)-adipate prepolymer used in the present application has introduced hydroxyl or carboxyl polar functional groups, so that the modified poly(butylene terephthalate)-adipate prepolymer has a certain polarity, which is beneficial to improving the interaction between poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer, reducing the interfacial tension, and allowing poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer to be better bonded during compounding, thereby having better compatibility.

[0020] 2. Since the introduction of hydroxyl groups can increase the polarity of polybutylene terephthalate-adipate, and polylactic acid is also a polar polymer, the hydroxyl groups introduced into polybutylene terephthalate-adipate can form hydrogen bonds with the carboxyl groups or ester groups in polylactic acid, so that the hydroxyl functional groups can form a strong interaction at the interface between polylactic acid and polybutylene terephthalate-adipate, reduce the interfacial tension, and thus improve the compatibility between polylactic acid and polybutylene terephthalate-adipate.

[0021] 3. Since grafting refers to the reaction of combining appropriate side chains or functional side groups on the macromolecular chain through chemical bonds, the hydroxyl functional groups in glycolic acid can be introduced into the polybutylene terephthalate-adipate molecular chain at a fixed point, and the grafted modified polybutylene terephthalate-adipate is blended with polylactic acid, which can reduce the phase separation phenomenon and thus improve the interaction between polybutylene terephthalate-adipate and polylactic acid. DETAILED DESCRIPTION

[0022] The present application is further described in detail below in conjunction with Examples 1-6 and Comparative Examples 1-2.

[0023] raw material Polylactic acid Shanghai Yuanye Biotechnology Co., Ltd.; compatibilizer ADR4370S BASF, Germany; glycolic acid CAS: 79-14-1; polybutylene terephthalate-adipate CAS: 55231-08-8; initiator DCP Anhui Xiangyun Rubber & Plastic Co., Ltd.

[0024] Example Example 1 A high-speed printable polylactic acid composition comprises the following raw materials: 90 g of polylactic acid, 0.2 g of a compatibilizer ADR4370S, and 10 g of a modified polybutylene terephthalate-adipate prepolymer.

[0025] Specifically, the method for preparing a high-speed printable polylactic acid composition comprises the following steps: S1: Place polybutylene terephthalate-adipate in a vacuum drying oven at 80°C and dry for 12 hours; S2: Weigh 50g of dried polybutylene terephthalate-adipate and put it into a torque rheometer at 160°C. Set the speed to 20r / min. After adding 50g of polybutylene terephthalate-adipate, set the speed to 60r / min. After reacting for 1min, the pellets melt and the torque decreases. S3: Then, 0.15 g of initiator DCP and 0.33 g of glycolic acid were added, and after reacting for 10 min, the torque was stable and the rotor stopped, thereby obtaining a modified polybutylene terephthalate-adipate prepolymer; S4: placing the polylactic acid in a vacuum drying oven at 120° C. and drying for 8 h; S5: Weigh 90g of dried polylactic acid, 10g of modified poly(butylene terephthalate-adipate) prepolymer and 0.2g of compatibilizer ADR4370S, mix them evenly, put them into a micro-mixing rheometer at 200°C, and perform melt extrusion granulation through a twin-screw mixing system in the micro-mixing rheometer to obtain a polylactic acid composition.

[0026] Example 2-3 The difference between Example 2-3 and Example 1 is that the addition amount of each component of the high-speed printable polylactic acid composition is different, as shown in Table 1.

[0027] Table 1 Addition amount of each component of the high-speed printable polylactic acid composition in Examples 1-3 (g) Example 1 Example 2 Example 3 Polylactic acid 90 80 100 Compatibilizer ADR4370S 0.2 0.3 0.1 Modified polybutylene terephthalate-adipate prepolymer 10 5 15 Example 4 The difference between Example 4 and Example 1 is that glycolic acid is replaced by an equal amount of 1,4-cyclohexanedicarboxylic acid.

[0028] Embodiment 5-6 The difference between Example 5-6 and Example 1 is that the addition amount of each component in the modified polybutylene terephthalate-adipate prepolymer is different, as shown in Table 2.

[0029] Table 2 Addition amount of each component in the modified polybutylene terephthalate-adipate prepolymer in Example 1 and Examples 5-6 (g) Example 1 Example 5 Example 6 Polybutylene terephthalate-adipate 50 54 46 Initiator DCP 0.15 0.18 0.12 Glycolic acid 0.33 0.31 0.35 Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no modified polybutylene terephthalate-adipate prepolymer is added.

[0030] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the modified polybutylene terephthalate-adipate prepolymer is replaced by the same added amount of polybutylene terephthalate-adipate.

[0031] Performance testing Detection Methods 1. Tensile performance test Three samples were taken from Examples 1-6 and Comparative Examples 1-2, respectively, and tensile properties were tested according to GB / T 1040.1-2006 "Determination of tensile properties of plastics - Part 1: General principles".

[0032] The test data is shown in Table 3.

[0033] Table 3 Tensile performance test table of Examples 1-6 and Comparative Examples 1-2 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 Combining Example 1 and Comparative Example 1 and Table 3, it can be seen that relative to Example 1, the tensile strength and elongation at break of Comparative Example 1 are greatly reduced, which shows that the addition of modified poly(butylene terephthalate-adipate) prepolymer can effectively improve the tensile strength and elongation at break of polylactic acid, thereby improving the toughness of polylactic acid.

[0034] The reason is that, with the help of glycolic acid, hydroxyl polar functional groups are introduced into the modified poly(butylene terephthalate)-adipate prepolymer, so that the modified poly(butylene terephthalate)-adipate prepolymer has a certain polarity. At the same time, poly(lactic acid) is also a polar polymer, so the hydroxyl group introduced into poly(butylene terephthalate)-adipate can form hydrogen bonds with the carboxyl group or ester group in poly(lactic acid), which is beneficial to improve the interaction between poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer, reduce the interfacial tension, and enable poly(lactic acid) and the modified poly(butylene terephthalate)-adipate prepolymer to bond better during compounding, thereby having better compatibility.

[0035] Combining Example 1 and Comparative Example 2 and Table 3, it can be seen that compared with Example 1, the tensile strength and elongation at break of Comparative Example 2 are greatly reduced, which shows that compared with the addition of polybutylene terephthalate-adipate, 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.

[0036] The reason is that polylactic acid is a bio-based material derived from renewable resources such as corn starch or sugarcane. Lactic acid is produced through microbial fermentation and then polymerized to form polylactic acid. This allows polylactic acid to be biodegraded under industrial composting conditions after use, reducing the impact on the environment. The molecular chain of polylactic acid is mainly composed of repeating lactic acid units, forming a linear polyester structure with high crystallinity. However, polybutylene terephthalate-adipate is a copolyester formed by ester exchange reaction of three monomers: adipic acid, terephthalic acid and butanediol. Therefore, the molecular chain of polybutylene terephthalate-adipate contains not only ester bonds, but also flexible aliphatic segments and rigid aromatic segments. This makes the intermolecular interaction forces of polylactic acid and polybutylene terephthalate different, making it difficult to form a stable interface when mixed, resulting in poor compatibility.

[0037] Combining Example 1 and Examples 2-3 and Table 3, it can be seen that, relative to 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 shows that the addition amount of each component of the polylactic acid composition also affects the tensile strength and elongation at break of the polylactic acid, thereby affecting the toughness of the polylactic acid.

[0038] Combining Example 1 and Example 4 and Table 3, it can be seen that, relative to Example 1, the tensile strength and elongation at break of Example 4 are lower than those of Example 1, which 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.

[0039] The reason is that the chemical structures of glycolic acid and polylactic acid are more similar. Polylactic acid is a polymer formed by lactic acid units connected by ester bonds, and glycolic acid is also a simple dicarboxylic acid with a structure similar to that of lactic acid. Therefore, polybutylene terephthalate adipate modified with glycolic acid has a higher similarity with polylactic acid in chemical structure. The reactivity of the carboxyl functional group is lower than that of the hydroxyl functional group. It may not react easily with polylactic acid in the polymer due to the steric hindrance effect. In addition, 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.

[0040] Combining Example 1 and Examples 5-6 and Table 3, it can be seen that, relative to 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 shows that the addition amount of each component of 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.

[0041] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A high-speed printable polylactic acid composition, characterized in that: The invention comprises the following raw materials in parts by weight: 80-100 parts of polylactic acid, 0.1-0.3 parts of a compatibilizer and 5-15 parts of a modified poly(butylene terephthalate)-adipate prepolymer, wherein a hydroxyl group or a carboxyl group polar functional group is introduced into the modified poly(butylene terephthalate)-adipate prepolymer.

2. A high-speed printable polylactic acid composition according to claim 1, characterized in that: The modified polybutylene terephthalate-adipate prepolymer has hydroxyl functional groups introduced therein.

3. A high-speed printable polylactic acid composition according to claim 2, characterized in that: The modified polybutylene terephthalate-adipate prepolymer is the glycolic acid grafted polybutylene terephthalate-adipate.

4. A high-speed printable polylactic acid composition according to claim 3, characterized in that: The modified polybutylene terephthalate-adipate prepolymer comprises the following raw materials: polybutylene terephthalate-adipate, an initiator and glycolic acid.

5. A high-speed printable polylactic acid composition according to claim 4, characterized in that: The modified polybutylene terephthalate-adipate prepolymer comprises the following raw materials in parts by weight: 46 parts to 54 parts of polybutylene terephthalate-adipate, 0.12 parts to 0.18 parts of an initiator, and 0.31 parts to 0.35 parts of glycolic acid.

6. A high-speed printable polylactic acid composition according to claim 5, characterized in that: The preparation method of the modified polybutylene terephthalate-adipate prepolymer comprises the following steps: placing polybutylene terephthalate-adipate in a vacuum drying oven at 75°C-85°C and drying for 10h-14h, weighing 46-54 parts of the dried polybutylene terephthalate-adipate and placing them in a heating reaction device at 155°C-165°C and stirring them, then adding 0.12-0.18 parts of an initiator and 0.31-0.35 parts of glycolic acid and continuing stirring for 8min-12min to obtain the modified polybutylene terephthalate-adipate prepolymer.

7. A method for preparing a high-speed printable polylactic acid composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Place the polylactic acid in a vacuum drying oven at 115°C-125°C and dry for 7h-9h; S2: Weigh 80-100 parts of polylactic acid, 5-15 parts of modified polybutylene terephthalate-adipate prepolymer and 0.1-0.3 parts of a compatibilizer, mix them evenly, and perform melt mixing and granulation through a melt extruder to obtain a polylactic acid composition.