Stereo composite thermoplastic elastomer and preparation method thereof

Abstract

The invention discloses a steric composite thermoplastic elastomer and a preparation method thereof, and belongs to the field of high polymer materials. According to the invention, a stereocompounding strategy of polylactic acid is expanded to the field of thermoplastic elastomers, and two thermoplastic elastomers based on stereocompounding of polylactic acid are prepared by a solution blending method and a melt blending method, so that the water-oxygen barrier property, the thermal property and the mechanical property of the elastomer can be effectively improved, and the application range of the elastomer is widened.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a class of stereocomplex thermoplastic elastomers and a preparation method thereof. Background Art

[0002] Common thermoplastic elastomers on the market at present usually use aromatic polyesters such as polybutylene terephthalate (PBT) as hard segments. The melting point of PBT can reach above 220 °C, but after combining with soft segments, the material may still soften or the mechanical properties may decline at high temperatures, and the maximum service temperature generally does not exceed 200 °C.

[0003] Polylactic acid (PLA) is a green polymer that can be completely synthesized from renewable plant resources such as starch and can be degraded into carbon dioxide and water in nature. It has outstanding advantages such as good mechanical properties and easy processing, and can widely replace traditional polymers in fields such as automobiles, electronics, disposable products, and biomedicine. However, the properties of pure PLA also have some deficiencies, such as poor heat resistance and durability, which severely limit its application in the field of engineering plastics. The stereocomplex structure can not only significantly improve the thermal stability and upper limit of the temperature use of the material, but also enhance its mechanical strength, heat resistance, and creep resistance, thereby overcoming the problems of easy softening, deformation, or performance attenuation of existing thermoplastic elastomers in high-temperature applications and expanding their application potential in more demanding environments. Summary of the Invention

[0004] The present invention extends the stereocomplex strategy of polylactic acid to the field of thermoplastic elastomers, provides a class of stereocomplex thermoplastic elastomers and a preparation method thereof, aims to further improve the water and oxygen barrier properties, thermal stability, and mechanical properties of the material, broaden the application scope of such elastomers, and solve the performance limitations of existing materials in high-temperature environments.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A class of stereocomplex thermoplastic elastomers, and its preparation method includes the following steps: (1) Prepare two thermoplastic elastomers with the same soft segment structure, the same mass content of hard segments, similar molecular weights, and the hard segment structures being L-polylactic acid and D-polylactic acid respectively; (2) Treat the above two thermoplastic elastomers by solution blending method or melt blending method to obtain the stereocomplex thermoplastic elastomers.

[0006] Specifically, its possible reaction formula is:

[0007] Wherein, x is a real number from 1 to 10; y is a real number from 1 to 10; m is a non-zero natural number; n is a non-zero natural number.

[0008] Furthermore, in the solution blending method, two thermoplastic elastomers are dissolved in an organic solvent at a mass ratio of 1:1, and after stirring and mixing, the organic solvent is removed by vacuum distillation to obtain the stereocomplex thermoplastic elastomer.

[0009] Furthermore, the organic solution is one of dichloromethane, dichloroethane, tetrahydrofuran, toluene, and 1,4-dioxane; the rotation speed of the stirring and mixing is 100 - 500 r / min, the temperature is 0 - 35 °C, and the time is 2 - 12 h.

[0010] Furthermore, in the melt blending method, two thermoplastic elastomers are added to a twin-screw extruder at a mass ratio of 1:1, and after melt blending, the stereocomplex thermoplastic elastomer is obtained.

[0011] Furthermore, the rotation speed of the twin-screw extruder is 10 - 100 r / min; the temperature of the melt blending is 170 - 240 °C, and the time is 0.2 - 2 h.

[0012] Furthermore, the molecular weight of the obtained stereocomplex thermoplastic elastomer is 30.0 - 200.0 kg / mol, and the mass content of the hard segment is 20 - 80%.

[0013] The beneficial effects of the present invention are as follows: (1) The present invention introduces the stereocomplex strategy of polylactic acid into the field of thermoplastic elastomers, so that the obtained stereocomplex thermoplastic elastomer has more excellent heat resistance, mechanical properties, water vapor and oxygen barrier properties.

[0014] (2) The present invention discloses two methods suitable for the stereocomplex of thermoplastic elastomers, namely the solution blending method and the melt blending method. These two methods have the characteristics of simple operation and are suitable for industrial scale-up. Specific Embodiments

[0015] A kind of stereocomplex thermoplastic elastomer, the preparation method of which is to first prepare two thermoplastic elastomers with the same soft segment structure, the same hard segment mass content, similar molecular weights, and the hard segment structures being L-polylactic acid and D-polylactic acid respectively, and then dissolve the two thermoplastic elastomers in an organic solvent at a mass ratio of 1:1 to obtain a mixed solution with a total concentration of 0.05 - 0.2 g / mL, mix for 2 - 12 h under the conditions of 0 - 35 °C and a stirring speed of 100 - 500 r / min, and then remove the organic solvent by vacuum distillation to obtain the stereocomplex thermoplastic elastomer.

[0016] Alternatively, two thermoplastic elastomers with the same soft segment structure, the same hard segment mass content, similar molecular weights, and the hard segment structures being L-polylactic acid and D-polylactic acid respectively are prepared separately. Then, the two thermoplastic elastomers are added to a twin-screw extruder at a mass ratio of 1:1 and melt-blended at 170 - 240 °C and a rotation speed of 10 - 100 r / min for 0.2 - 2 h to obtain the stereocomplex thermoplastic elastomer.

[0017] Among them, the organic solution is one of dichloromethane, dichloroethane, tetrahydrofuran, toluene, and 1,4-dioxane; its stirring speed is 100 - 500 r / min; the temperature for stirring and mixing is 0 - 35 °C, the time is 2 - 12 h, and the stirring speed is 100 - 500 r / min.

[0018] The technical solutions of the present invention are further described below through examples.

[0019] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art unless otherwise specified.

[0020] In the following examples, various processes and methods not described in detail are conventional methods well known in the art. At the same time, due to the diverse polymer structure ratios, not all preparation methods are described in detail. Typical examples are taken to illustrate the specific process steps of the present invention.

[0021] Example 1 Two thermoplastic elastomers (TPEE-L-1 and TPEE-D-1) with the hard segment structures being L-polylactic acid and D-polylactic acid respectively (the specific structures are as follows, and their preparation refers to Patent CN 116836353A) are used, and their hard segment mass contents are both 60%, and the molecular weights are 192.8 kg / mol and 198.5 kg / mol respectively.

[0022] 。

[0023] In a 100 mL three-necked flask equipped with a magnetic stirrer, under nitrogen protection, 2 g of each of the above two thermoplastic elastomers are added to the three-necked flask, and 80 mL of anhydrous tetrahydrofuran is added to dissolve them into a solution with a concentration of 0.05 g / mL. The reaction temperature is set at 35 °C, and the mixture is stirred at a rotation speed of 100 r / min for 8 h. Then, tetrahydrofuran is removed by vacuum distillation to obtain the stereocomplex thermoplastic elastomer (TPEE-SC-1).

[0024] Comparative Example 1-1 In a 100 mL three-necked flask equipped with a magnetic stir bar, under nitrogen protection, 4 g of TPEE-L-1 was added to the three-necked flask, and 80 mL of anhydrous tetrahydrofuran was added to dissolve it into a solution with a concentration of 0.05 g / mL. The reaction temperature was set at 35 °C, and the mixture was stirred at a speed of 100 r / min for 8 h. Then, tetrahydrofuran was removed by vacuum distillation to obtain TPEE-L-SC-1.

[0025] Comparative Example 1-2 In a 100 mL three-necked flask equipped with a magnetic stir bar, under nitrogen protection, 4 g of TPEE-D-1 was added to the three-necked flask, and 80 mL of anhydrous tetrahydrofuran was added to dissolve it into a solution with a concentration of 0.05 g / mL. The reaction temperature was set at 35 °C, and the mixture was stirred at a speed of 100 r / min for 8 h. Then, tetrahydrofuran was removed by vacuum distillation to obtain TPEE-D-SC-1.

[0026] Comparative Example 1-3 In a 100 mL three-necked flask equipped with a magnetic stir bar, under nitrogen protection, 2 g of each of L-polylactic acid PLLA-1 (molecular weight 198.0 kg / mol) and D-polylactic acid PDLA-1 (molecular weight 202.5 kg / mol) were added to the three-necked flask, and 80 mL of anhydrous tetrahydrofuran was added to dissolve it into a solution with a concentration of 0.05 g / mL. The reaction temperature was set at 35 °C, and the mixture was stirred at a speed of 100 r / min for 8 h. Then, tetrahydrofuran was removed by vacuum distillation to obtain PLA-SC-1.

[0027] Comparative Example 1-4 In a 100 mL three-necked flask equipped with a magnetic stir bar, under nitrogen protection, 4 g of L-polylactic acid PLLA-1 (molecular weight 198.0 kg / mol) was added to the three-necked flask, and 80 mL of anhydrous tetrahydrofuran was added to dissolve it into a solution with a concentration of 0.05 g / mL. The reaction temperature was set at 35 °C, and the mixture was stirred at a speed of 100 r / min for 8 h. Then, tetrahydrofuran was removed by vacuum distillation to obtain PLLA-SC-1.

[0028] The elastomers obtained in Example 1 and Comparative Examples 1-1 to 1-4 were prepared into dumbbell-shaped specimens and membranes with the same size for testing mechanical properties, water vapor and oxygen barrier properties; at the same time, thermal properties were tested, and the results are shown in Table 1.

[0029] Table 1 Performance Characterization of Samples Obtained in Example 1 and Comparative Examples 1-1 to 1-4

[0030] As can be seen from the results in Table 1, compared with the thermoplastic elastomers TPEE-L-SC-1 and TPEE-D-SC-1 prepared from single polylactic acid, the stereocomplex thermoplastic elastomer prepared in Example 1 has significantly improved thermal properties (melting point and 5% decomposition temperature) and gas barrier properties (water vapor, oxygen), and the yield strength and fracture strength are also significantly increased, while the ductility (elongation at break) is decreased. Therefore, such stereocomplex thermoplastic elastomers are more suitable for fields with requirements such as high strength, high heat resistance, high barrier, and low elongation at break.

[0031] Example 2 The two hard segment structures used are thermoplastic elastomers (TPEE-L-2 and TPEE-D-2) of L-polylactic acid and D-polylactic acid respectively. The specific structures are as follows, and their preparation refers to Patent CN 116836353A. The mass content of the hard segment is 80% for both, and the molecular weights are 83.1 kg / mol and 89.7 kg / mol respectively.

[0032] 。

[0033] Take 2 g of each of the above two dried thermoplastic elastomers and add them to a twin-screw extruder. Under the conditions of 240 °C and a stirring speed of 100 r / min, melt-blend the two thermoplastic elastomers for 0.2 h to obtain a stereocomplex thermoplastic elastomer (TPEE-SC-2).

[0034] Comparative Example 2-1 Take 4 g of dried TPEE-L-2 and add it to a twin-screw extruder. Stir for 0.2 h under the conditions of 240 °C and a stirring speed of 100 r / min to obtain TPEE-L-SC-2.

[0035] Comparative Example 2-2 Take 4 g of dried TPEE-D-2 and add it to a twin-screw extruder. Stir for 0.2 h under the conditions of 240 °C and a stirring speed of 100 r / min to obtain TPEE-D-SC-2.

[0036] Comparative Example 2-3 Take 2 g each of L-polylactic acid PLLA-2 (molecular weight 85.0 kg / mol) and D-polylactic acid PDLA-2 (molecular weight 89.7 kg / mol) and add them to a twin-screw extruder. Under the conditions of 240 °C and a stirring speed of 100 r / min, melt-blend the two materials for 0.2 h to obtain a stereocomplex polylactic acid (PLA-SC-2).

[0037] Comparative Example 2-4 4 g of left-handed polylactic acid PLLA-2 was added into a twin-screw extruder and stirred for 0.2 h at 240 °C and a stirring speed of 100 r / min to obtain PLLA-SC-2.

[0038] The elastomers obtained in Example 2 and Comparative Examples 2-1 to 2-4 were prepared into dumbbell-shaped specimens and films of the same size for testing of mechanical properties and water vapor and oxygen barrier properties; thermal properties were also tested, and the results are shown in Table 2.

[0039] Table 2 Performance characteristics of samples obtained from Example 2 and Comparative Examples 2-1 to 2-4

[0040] It can be seen from the results in Table 2 that, compared with TPEE-L-SC-2 and TPEE-D-SC-2, the stereocomposite thermoplastic elastomer prepared in Example 2 has significantly improved thermal properties (melting point and 5% decomposition temperature) and gas barrier properties (water vapor, oxygen), and the yield strength and fracture strength are also significantly improved, while the ductility (elongation at break) is reduced. Therefore, this type of stereocomposite thermoplastic elastomer is more suitable for fields with requirements such as high strength, high heat resistance, high barrier and low elongation at break.

[0041] Example 3 The two hard segment structures used are thermoplastic elastomers of left-handed polylactic acid and right-handed polylactic acid (TPEE-L-3 and TPEE-D-3, the specific structures are as follows, and their preparation refers to CN 116355188A), with a hard segment mass content of 20% and molecular weights of 31.9 kg / mol and 33.6 kg / mol, respectively.

[0042] .

[0043] In a 100 mL three-necked flask equipped with a magnet, under nitrogen protection, 2 g of each of the two thermoplastic elastomers mentioned above were added to the three-necked flask, and 20 mL of anhydrous dichloromethane was added to dissolve into a 0.2 g / mL solution. The reaction temperature was set to 0 °C, and mixed at a speed of 500 r / min for 12 h. After that, dichloromethane was removed by reduced pressure distillation to obtain a three-dimensional composite thermoplastic elastomer (TPEE-SC-3).

[0044] Comparative Example 3-1 In a 100 mL three-necked flask equipped with a magnet, under nitrogen protection, 4 g of TPEE-L-3 was added to the three-necked flask, and 20 mL of anhydrous dichloromethane was added to dissolve it into a 0.2 g / mL solution. The reaction temperature was set to 0 °C, and the mixture was mixed at a speed of 500 r / min for 12 h. Then, the dichloromethane was removed by reduced pressure distillation to obtain TPEE-L-SC-3.

[0045] Comparative Example 3-2 In a 100 mL three-necked flask equipped with a magnet, under nitrogen protection, 4 g of TPEE-D-3 was added to the three-necked flask, and 20 mL of anhydrous dichloromethane was added to dissolve it into a 0.2 g / mL solution. The reaction temperature was set to 0 °C, and the mixture was mixed at a speed of 500 r / min for 12 h. Then, the dichloromethane was removed by reduced pressure distillation to obtain TPEE-D-SC-3.

[0046] Comparative Example 3-3 In a 100 mL three-necked flask equipped with a magnet, under nitrogen protection, 2 g each of left-handed polylactic acid PLLA-3 (molecular weight 33.0 kg / mol) and right-handed polylactic acid PDLA-3 (molecular weight 35.2 kg / mol) were added to the three-necked flask, and 20 mL of anhydrous dichloromethane was added to dissolve into a 0.2 g / mL solution. The reaction temperature was set to 0 °C, and mixed at a speed of 500 r / min for 12 h. After that, dichloromethane was removed by reduced pressure distillation to obtain stereocomposite polylactic acid PLA-SC-3.

[0047] Comparative Examples 3-4 In a 100 mL three-necked flask equipped with a magnet, under nitrogen protection, 4 g of left-lactic acid PLLA-3 (molecular weight 33.0 kg / mol) was added to the three-necked flask, and 20 mL of anhydrous dichloromethane was added to dissolve it into a 0.2 g / mL solution. The reaction temperature was set to 0 ℃, and mixed at a speed of 500 r / min for 12 h. Then, dichloromethane was removed by reduced pressure distillation to obtain PLLA-SC-3.

[0048] The elastomers obtained in Example 3 and Comparative Examples 3-1 to 3-4 were prepared into dumbbell-shaped specimens and films of the same size for testing of mechanical properties and water vapor and oxygen barrier properties; thermal properties were also tested, and the results are shown in Table 3.

[0049] Table 3 Performance characteristics of samples obtained from Example 3 and Comparative Examples 3-1 to 3-4

[0050] It can be seen from the results in Table 3 that, compared with TPEE-L-SC-3 and TPEE-D-SC-3, the stereocomposite thermoplastic elastomer prepared in Example 3 has significantly improved thermal properties (melting point and 5% decomposition temperature) and gas barrier properties (water vapor, oxygen), and the yield strength and fracture strength are also significantly improved, while the ductility (elongation at break) is reduced. Therefore, this type of stereocomposite thermoplastic elastomer is more suitable for fields with requirements such as high strength, high heat resistance, high barrier and low elongation at break.

[0051] Example 4 The two hard segment structures used are thermoplastic elastomers of L - polylactic acid and D - polylactic acid (TPEE - L - 4 and TPEE - D - 4, the specific structures are as follows, and their preparation refers to CN 116355188A). The mass content of their hard segments is 30% for both, and the molecular weights are 113.4 kg / mol and 126.7 kg / mol respectively.

[0052] 。

[0053] Take 2 g of each of the above - mentioned two dried thermoplastic elastomers and add them to a twin - screw extruder. Under the conditions of 200 °C and a stirring speed of 50 r / min, melt - blend the two thermoplastic elastomers for 2 h to obtain stereocomplex thermoplastic elastomer (TPEE - SC - 4). Comparative Example 4 - 1 Take 4 g of dried TPEE - L - 4 and add it to a twin - screw extruder. Under the conditions of 200 °C and a stirring speed of 100 r / min, melt - blend it for 2 h to obtain TPEE - L - SC - 4.

[0054] Comparative Example 4 - 2 Take 4 g of dried TPEE - D - 4 and add it to a twin - screw extruder. Under the conditions of 200 °C and a stirring speed of 100 r / min, melt - blend it for 2 h to obtain TPEE - D - SC - 4.

[0055] Comparative Example 4 - 3 Take 2 g of each of L - polylactic acid PLLA - 4 (molecular weight 120.5 kg / mol) and D - polylactic acid PDLA - 4 (molecular weight 119.0 kg / mol) and add them to a twin - screw extruder. Under the conditions of 200 °C and a stirring speed of 100 r / min, melt - blend them for 2 h to obtain PLA - SC - 4.

[0056] Comparative Example 4 - 4 Take 4 g of L - polylactic acid PLLA - 4 and add it to a twin - screw extruder. Under the conditions of 200 °C and a stirring speed of 100 r / min, melt - blend it for 2 h to obtain PLLA - SC - 4.

[0057] Prepare dumbbell - shaped specimens and membranes with the same size from the elastomers obtained in Example 4 and Comparative Examples 4 - 1 to 4 - 4 for mechanical property, water vapor, and oxygen barrier property tests; at the same time, conduct thermal property tests, and the results are shown in Table 4.

[0058] Table 4 Performance Characterization of Samples Obtained in Example 4 and Comparative Examples 4 - 1 to 4 - 4

[0059] As can be seen from the results in Table 4, compared with TPEE-L-SC-4 and TPEE-D-SC-4, the stereocomplex thermoplastic elastomer prepared in Example 4 has significantly improved thermal properties (melting point and 5% decomposition temperature) and gas barrier properties (water vapor, oxygen), and the yield strength and fracture strength are also significantly increased, while the ductility (elongation at break) is decreased. Therefore, such stereocomplex thermoplastic elastomers are more suitable for fields with requirements such as high strength, high heat resistance, high barrier, and low elongation at break.

[0060] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a stereocomposite thermoplastic elastomer, characterized in that: The steps include: (1) preparing two thermoplastic elastomers with the same soft segment structure, the same hard segment mass content, and similar molecular weight, wherein the hard segment structures are L-polylactic acid and D-polylactic acid respectively; (2) The two thermoplastic elastomers are processed by solution blending or melt blending to obtain the stereocomposite thermoplastic elastomer.

2. The method for preparing a stereocomplex thermoplastic elastomer according to claim 1, characterized in that: The structural formula of the prepared L-polylactic acid thermoplastic elastomer is or ; The structural formula of right-handed polylactic acid thermoplastic elastomer is or ; Among them, x is a real number from 1 to 10; y is a real number from 1 to 10; m is a non-zero natural number; n is a non-zero natural number.

3. The method for preparing a stereocomplex thermoplastic elastomer according to claim 1, characterized in that: The solution blending method is to dissolve two thermoplastic elastomers in an organic solvent at a mass ratio of 1:1, and then remove the organic solvent by reduced pressure distillation after stirring and mixing to obtain the stereocomposite thermoplastic elastomer.

4. The method for preparing a stereocomplex thermoplastic elastomer according to claim 3, characterized in that: The organic solution is one of dichloromethane, dichloroethane, tetrahydrofuran, toluene, and 1,4-dioxane; the stirring and mixing speed is 100-500 r / min, the temperature is 0-35°C, and the time is 2-12 h.

5. The method for preparing a stereocomplex thermoplastic elastomer according to claim 1, characterized in that: The melt blending method is to add two thermoplastic elastomers in a mass ratio of 1:1 into a twin-screw extruder, and obtain the stereocomposite thermoplastic elastomer through melt blending.

6. The method for preparing a stereocomplex thermoplastic elastomer according to claim 5, characterized in that: The speed of the twin-screw extruder is 10~100 r / min; the temperature of melt blending is 170~240 ℃, and the time is 0.2~2 h.

7. A stereocomplex thermoplastic elastomer prepared by the method of claim 1, characterized in that: The molecular weight of the stereocomposite thermoplastic elastomer is 30.0-200.0 kg / mol, wherein the mass content of the hard segment is 20-80%.

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