A transparent reinforced polylactic acid composition and its preparation method and application

Abstract

The present invention discloses a transparent enhanced polylactic acid composition, its preparation method, and application, belonging to the field of polymer material technology. The transparent enhanced polylactic acid composition comprises the following components in parts by weight: 40-60 parts of polylactic acid, 20-40 parts of polymethyl methacrylate, 0.1-1 part of a chain extender, 10-30 parts of glass fiber, 0.1-1 part of an antioxidant, and 0.1-1 part of a lubricant. The chain extender comprises at least one of a polyhydroxy alcohol, a polyhydroxy acrylate, and a polyisocyanate. The present invention adds an appropriate amount of polymethyl methacrylate and a chain extender to the composite system of polylactic acid and glass fiber, significantly improving the rigidity and impact resistance of the composite system while ensuring the transparency of the composition.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a transparent enhanced polylactic acid composition and a preparation method and application thereof. Background Art

[0002] Polylactic acid (PLA) is a bio-based, renewable, biodegradable material made from starch derived from renewable plant resources. It exhibits excellent biodegradability and can be completely degraded by natural microorganisms under specific conditions, ultimately producing carbon dioxide and water, without polluting the environment. This is highly beneficial for environmental protection and has made it a recognized environmentally friendly material. As a bio-based, renewable, biodegradable material, PLA exists in two forms: semi-crystalline and amorphous. Amorphous PLA not only exhibits excellent biocompatibility, good rigidity and strength, but also good transparency. It has found widespread application in industries such as healthcare, clothing, and tableware. However, as a linear polymer, amorphous PLA suffers from significant drawbacks such as high brittleness, poor impact resistance, and a low heat distortion temperature, which severely restrict the application of this environmentally friendly material. To overcome these inherent drawbacks, a commonly used method is blending modification: melt blending, adding toughening agents to the PLA matrix, alloying with resins with excellent impact resistance, or reinforcing with fibers to enhance PLA's impact resistance. Although this type of method can improve the impact resistance of PLA materials, it is difficult to ensure that the transparency of PLA materials is not sacrificed while achieving improved rigidity and toughness. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a transparent reinforced polylactic acid composition and its preparation method and application. The present invention adds an appropriate amount of polymethyl methacrylate and a chain extender to the composite system of polylactic acid and glass fiber, which greatly improves the rigidity and impact resistance of the composite system while ensuring the transparency of the composition.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] In a first aspect, the present invention provides a transparent reinforced polylactic acid composition comprising the following components in parts by weight: 40 to 60 parts of polylactic acid, 20 to 40 parts of polymethyl methacrylate, 0.1 to 1 part of a chain extender, 10 to 30 parts of glass fiber, 0.1 to 1 part of an antioxidant, and 0.1 to 1 part of a lubricant, wherein the chain extender comprises at least one of a polyhydroxy alcohol, a polyhydroxy acrylate, and a polyisocyanate, and the polylactic acid is amorphous polylactic acid.

[0006] The present invention incorporates polymethyl methacrylate (PMMA) into the formulation of a polylactic acid composition, utilizing it as a compatibilizer. The PMMA also adjusts the refractive index of the composition, ensuring excellent transparency even after mixing with glass fiber and pelletizing. The present invention also incorporates a small amount of a chain extender into the formulation, significantly enhancing the impact strength of the polylactic acid composition while maintaining high transparency without the addition of a toughening agent.

[0007] The present invention adds an appropriate amount of polymethyl methacrylate and a chain extender to a composite system of polylactic acid and glass fiber. Through a simple process, the impact resistance of the polylactic acid composition can be increased while ensuring the transparency of the polylactic acid composition, and the polylactic acid composition can be given higher rigidity and strength.

[0008] As a preferred embodiment of the present invention, the weight average molecular weight of the polylactic acid is 45,000 to 210,000.

[0009] Furthermore, the weight average molecular weight of the polylactic acid is 50,000 to 150,000.

[0010] The weight average molecular weight is tested by gel permeation chromatography.

[0011] As a preferred embodiment of the present invention, the polymethyl methacrylate has a melt index of 2 to 20 g / 10 min, more preferably 4 to 14 g / 10 min, under the test conditions of 238° C. and 3.8 kg according to ISO 1133-1:2022.

[0012] As a preferred embodiment of the present invention, the refractive index of the glass fiber is 1.43 to 1.47, more preferably 1.45 to 1.47. The refractive index is obtained by refractometer testing.

[0013] As a preferred embodiment of the present invention, the antioxidant includes at least one of hindered phenol antioxidants, phosphite antioxidants, metal alkylthiophosphoric acid antioxidants, carbamic acid antioxidants, and organic sulfur antioxidants.

[0014] Furthermore, the antioxidant is a phosphite antioxidant.

[0015] As a preferred embodiment of the present invention, the lubricant includes at least one of amide lubricants, polysiloxane lubricants, stearate lubricants, polyethylene wax, and polypropylene wax.

[0016] Furthermore, the lubricant is a polysiloxane ester lubricant.

[0017] As a preferred embodiment of the present invention, the chain extender is a polyisocyanate, preferably triallyl isocyanurate.

[0018] The present invention preferably uses triallyl isocyanurate as a chain extender. Compared with other chain extenders, triallyl isocyanurate enables the polylactic acid composition system to have excellent rigidity and toughness, and can also effectively improve the transparency of the system.

[0019] As a preferred embodiment of the present invention, the transparent reinforced polylactic acid composition comprises the following components by weight: 48-54 parts polylactic acid, 27-36 parts polymethyl methacrylate, 0.2-0.5 parts chain extender, 15-24 parts glass fiber, 0.4-0.8 parts antioxidant, and 0.4-0.8 parts lubricant. When the addition amounts of each component meet the above conditions, the polylactic acid composition has improved light transmittance, rigidity, and toughness.

[0020] In a second aspect, the present invention provides a method for preparing the transparent reinforced polylactic acid composition as described in the first aspect, comprising the following steps:

[0021] Polylactic acid, polymethyl methacrylate, chain extender, glass fiber, antioxidant and lubricant are mixed evenly and then fed into an extruder for extrusion and granulation to obtain a transparent reinforced polylactic acid composition.

[0022] As a preferred embodiment of the present invention, the extruder is a twin-screw extruder, and the extrusion temperature of the extruder is 120-230°C.

[0023] Furthermore, the extrusion temperature of the extruder is: zone 1 temperature 120-140°C, zone 2 temperature 190-210°C, zone 3 temperature 190-220°C, zone 4 temperature 190-220°C, zone 5 temperature 190-220°C, zone 6 temperature 190-220°C, zone 7 temperature 190-220°C, zone 8 temperature 200-220°C, zone 9 temperature 200-220°C, zone 10 temperature 220-230°C.

[0024] In a third aspect, the present invention provides a use of the transparent reinforced polylactic acid composition as described in the first aspect in the preparation of transparent plastic products.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention adds an appropriate amount of polymethyl methacrylate and a chain extender to a composite system of polylactic acid and glass fiber, thereby significantly improving the rigidity and impact resistance of the composite system while ensuring the transparency of the composition. The notched impact strength of the system is above 7.0 MPa, the flexural strength is above 6600 MPa, the light transmittance is above 70%, and the haze does not exceed 20%. The system can meet the requirements of transparent plastic products in the perspective window, lighting, diffuser and other industries for transparency, rigidity and impact resistance. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] The materials used in the examples and comparative examples are as follows:

[0029] Polylactic acid 1: amorphous polylactic acid, weight average molecular weight of 45,000 as measured by gel permeation chromatography, obtained from Zhuhai Wantong.

[0030] Polylactic acid 2: amorphous polylactic acid, weight average molecular weight of 50,000 as measured by gel permeation chromatography, obtained from Zhuhai Wantong.

[0031] Polylactic acid 3: amorphous polylactic acid, weight average molecular weight of 150,000 as measured by gel permeation chromatography, obtained from Zhuhai Wantong.

[0032] Polylactic acid 4: amorphous polylactic acid, weight average molecular weight of 210,000 as measured by gel permeation chromatography, obtained from Zhuhai Wantong.

[0033] Polylactic acid 5: crystalline polylactic acid, with a weight-average molecular weight of 50,000 as measured by gel permeation chromatography, from Zhuhai Wantong.

[0034] Polymethyl methacrylate 1: CM-205, tested according to ISO 1133-1:2022 at 238°C, 3.8 kg, MI = 2 g / 10 min, Chi Mei Chemical Co., Ltd.

[0035] Polymethyl methacrylate 2:8N, ISO 1133-1:2022, 238°C, 3.8 kg test conditions, MI = 4 g / 10 min, Evonik Chemicals;

[0036] Polymethyl methacrylate 3: CM-211, ISO 1133-1:2022 standard, 238°C, 3.8 kg test conditions, MI = 14 g / 10 min, Chi Mei Chemical Co., Ltd.

[0037] Polymethyl methacrylate 4: brand SX303, ISO 1133-1:2022 standard, 238°C, 3.8 kg test conditions, MI = 20 g / 10 min, Shuangxiang Optical Materials Co., Ltd.

[0038] Chain extender 1: triallyl isocyanurate, Hefei Anbang Chemical;

[0039] Chain extender 2: trimethylolpropane diallyl ether, Hefei Anbang Chemical;

[0040] Chain extender 3: trimethylolpropane trimethacrylate, Hefei Anbang Chemical;

[0041] Glass fiber 1: ECS11-4.5-1.46, refractive index measured by refractometer is 1.45, Nanjing Glass Fiber Research Institute;

[0042] Glass fiber 2: ECS11-4.5-1.56, refractive index measured by refractometer is 1.43, Nanjing Glass Fiber Research Institute;

[0043] Glass fiber 3: ECS11-4.5-1.41, refractive index measured by refractometer is 1.47, Nanjing Glass Fiber Research Institute;

[0044] Antioxidant: phosphite antioxidant, commercially available;

[0045] Lubricant: polysiloxane ester lubricant, commercially available.

[0046] Example 1

[0047] An embodiment of the transparent enhanced polylactic acid composition of the present invention, the formula of the transparent enhanced polylactic acid composition of this embodiment is shown in Table 1, and the preparation method is as follows:

[0048] Polylactic acid, polymethyl methacrylate, chain extender, glass fiber, antioxidant and lubricant are mixed uniformly in proportion and then fed into a twin-screw extruder for melt extrusion and granulation to obtain a transparent reinforced polylactic acid composition; the temperature of the twin-screw extruder is as follows: zone 1 temperature is 120-140°C, zone 2 temperature is 190-210°C, zone 3 temperature is 190-220°C, zone 4 temperature is 190-220°C, zone 5 temperature is 190-220°C, zone 6 temperature is 190-220°C, zone 7 temperature is 190-220°C, zone 8 temperature is 200-220°C, zone 9 temperature is 200-220°C, and zone 10 temperature is 220-230°C.

[0049] Examples 2 to 15

[0050] The embodiments of the transparent reinforced polylactic acid composition of the present invention, the formulas of Examples 2 to 15 are shown in Table 1, and the preparation method is the same as that of Example 1.

[0051] Table 1 (parts by weight)

[0052]

[0053]

[0054] Comparative Example 1

[0055] This comparative example provides a reinforced polylactic acid composition. The only difference between this comparative example and Example 1 is that polymethyl methacrylate is not added to the formula of this comparative example.

[0056] Comparative Example 2

[0057] This comparative example provides a reinforced polylactic acid composition. The only difference between this comparative example and Example 1 is that no chain extender is added to the formula of this comparative example.

[0058] Comparative Example 3

[0059] This comparative example provides a reinforced polylactic acid composition. The only difference between this comparative example and Example 1 is that glass fiber is not added to the formula of this comparative example.

[0060] Comparative Examples 4-5

[0061] Comparative Examples 4 and 5 respectively provide a reinforced polylactic acid composition, which differs from Example 1 only in that the weight portion of the chain extender in the formula of Comparative Example 4 is 2 parts, and the weight portion of the chain extender in the formula of Comparative Example 5 is 0.05 parts.

[0062] Comparative Example 6

[0063] This comparative example provides a reinforced polylactic acid composition, which is different from Example 1 in that the polylactic acid used in this comparative example is polylactic acid 5.

[0064] The products of Examples 1 to 15 and Comparative Examples 1 to 6 were tested. The test results are shown in Table 2. The test method is as follows:

[0065] (1) Transmittance and haze: According to GB2140-2008, each product was injection molded into a 2.0 mm thick, 100 mm long, and 60 mm wide sample, and then tested using a transmittance-haze tester;

[0066] (2) Notched impact strength: According to ISO 180-2000, each product was injection molded into a 100 mm × 10 mm × 4 mm A-type notched impact specimen and subjected to the Izod notched impact strength test with an impact energy of 4 J.

[0067] (3) Flexural strength: Each product was injection molded into a 100 mm × 10 mm × 4 mm standard specimen for testing according to ISO 178-2019.

[0068] Table 2

[0069]

[0070] It can be seen from Examples 1 to 5 that the polylactic acid compositions of Examples 1 to 3 have good light transmittance, rigidity and toughness, and their comprehensive performance is significantly better than that of Examples 4 to 5. Obviously, when the corresponding components exceed a certain range, the light transmittance of the material will be significantly affected and drop significantly. This is mainly because the addition ratio of the corresponding components changes, and the refractive index balance between the components of the system is broken, resulting in a significant impact on the transparency of the material.

[0071] From Example 2, Examples 6 to 11, and Comparative Example 6, it can be seen that the polylactic acid compositions prepared in Examples 2, 7, and 10 have better transparency. This is mainly because, compared with other Examples and Comparative Examples 6 to 7, the viscosity matching difference between the polylactic acid and polymethyl methacrylate selected in Examples 2, 7, and 10 is smaller, which makes the microscopic phase change of the system smaller, thereby avoiding affecting the refractive index of the polylactic acid composition and making the material more transparent. Therefore, the polylactic acid of the present invention is preferably amorphous polylactic acid, the weight average molecular weight of the polylactic acid is preferably 50,000 to 150,000, and the MI of the polymethyl methacrylate under the test conditions of 238°C and 3.8 kg is preferably 4 to 14 g / 10 min.

[0072] It can be seen from Examples 2 and 12 to 13 that different chain extenders have a significant impact on the transparency of the material. Compared with other chain extenders, using triallyl isocyanurate as a chain extender allows the polylactic acid composition to have excellent rigidity and toughness while also having better transparency.

[0073] It can be seen from Comparative Example 1 and Example 1 that, compared with Example 1, in Comparative Example 1, PMMA is not added, and the light transmittance of the polylactic acid composition is extremely low, and the transparency is almost lost.

[0074] It can be seen from Comparative Example 2 and Example 1 that without adding a chain extender, the transparency of the material will be greatly reduced.

[0075] It can be seen from Comparative Example 3 and Example 1 that Comparative Example 3 does not add glass fiber. Although the transparency of the polylactic acid composition can be guaranteed, the toughness and rigidity of the polylactic acid composition are very poor, with the toughness being less than 25% of the polylactic acid composition of Example 1 and the rigidity being less than 50% of the polylactic acid composition of Example 1.

[0076] It can be seen from Example 1 and Comparative Examples 4-5 that although a chain extender was added in Comparative Examples 4 and 5, the amount of the chain extender added was inappropriate, which affected the refractive index of the polylactic acid composition, thereby greatly reducing the transparency of the entire system.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A transparent reinforced polylactic acid composition, characterized in that: The invention comprises the following components in parts by weight: 40-60 parts of polylactic acid, 20-40 parts of polymethyl methacrylate, 0.1-1 part of a chain extender, 10-30 parts of glass fiber, 0.1-1 part of an antioxidant, and 0.1-1 part of a lubricant, wherein the chain extender is at least one of polyhydroxy alcohol, polyhydroxy acrylate, and polyisocyanate; the polylactic acid is amorphous polylactic acid; and the melt index of the polymethyl methacrylate under the test conditions of 238° C. and 3.8 kg is 2-20 g / 10 min.

2. The transparent reinforced polylactic acid composition according to claim 1, characterized in that The weight average molecular weight of the polylactic acid is 45,000-210,000.

3. The transparent reinforced polylactic acid composition according to claim 1, wherein The refractive index of the glass fiber is 1.43-1.

47.

4. The transparent reinforced polylactic acid composition according to claim 1, wherein The antioxidant includes at least one of hindered phenol antioxidants, phosphite antioxidants, metal alkylthiophosphoric acid antioxidants, carbamic acid antioxidants, and organic sulfur antioxidants.

5. The transparent reinforced polylactic acid composition according to claim 1, wherein The lubricant includes at least one of amide lubricants, polysiloxane lubricants, stearate lubricants, polyethylene wax, and polypropylene wax.

6. The transparent reinforced polylactic acid composition according to claim 1, wherein The chain extender is polyisocyanate.

7. The transparent reinforced polylactic acid composition according to claim 1, wherein The polyisocyanate is triallyl isocyanurate.

8. A method for preparing a transparent reinforced polylactic acid composition according to any one of claims 1 to 7, characterized in that: The steps include: Polylactic acid, polymethyl methacrylate, chain extender, glass fiber, antioxidant and lubricant are mixed and sent into an extruder for extrusion and granulation to obtain a transparent reinforced polylactic acid composition.

9. The method for preparing the transparent reinforced polylactic acid composition according to claim 8, wherein: The extruder is a twin-screw extruder, and the extrusion temperature of the extruder is 120-230°C.

10. Use of the transparent reinforced polylactic acid composition according to any one of claims 1 to 7 in the preparation of transparent plastic products.

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