High tensile ductility polylactic acid and method for preparing the same

Abstract

The application discloses a kind of high tensile ductility polylactic acid, it is the grafting polymer of polylactic acid and hydrogenated epoxidized thermoplastic elastomer, with high tensile ductility polylactic acid quality 100 parts, hydrogenated epoxidized butadiene-styrene transparent impact resin is 20-40 parts, polylactic acid is 60-80 parts;Hydrogenated epoxidized butadiene-styrene transparent impact resin is 10-40% of the molar percentage of epoxidation degree, hydrogenation degree is not less than 90%;Hydrogenated epoxidized butadiene-styrene transparent impact resin is the hydrogenation product of epoxidized butadiene-styrene transparent impact resin, epoxidized butadiene-styrene transparent impact resin is the epoxidation product of butadiene-styrene transparent impact resin, butadiene-styrene transparent impact resin is the styrene-butadiene multi-block copolymer obtained by polymerization of styrene, butadiene monomer.The high tensile ductility polylactic acid prepared by the application has higher tensile strength and tensile modulus, and has good anti-aging, heat-resistant oxygen stability;Equipment process is simple, efficient and easy to operate, and has low production cost, and has high popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification technology, specifically relating to a method for preparing polylactic acid with high tensile toughness by toughening polylactic acid with hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin. Background Technology

[0002] Polylactic acid (PLA) is a commercially available thermoplastic material with renewable raw material sources. It exhibits good biocompatibility and biodegradability, gradually degrading in the human body and natural environment, ultimately breaking down into carbon dioxide and water. PLA is considered one of the most promising biomaterials to replace traditional petroleum-based polymers and has wide applications in medicine, pharmaceuticals, agriculture, and packaging. While PLA possesses high strength and modulus, its relatively poor toughness limits its use in applications requiring a certain degree of flexibility.

[0003] To improve the toughness of general-purpose polylactic acid (PLA) and thus broaden its application range, research on PLA toughening modification has been booming in recent years. Compared with synthesizing new biodegradable materials to obtain superior performance, the method of toughening PLA through intensive mixing, blending, and grafting is more economical and convenient. During the blending process, although the toughness of PLA is significantly improved by incorporating a toughening material with lower strength into the PLA resin, its strength and modulus decrease significantly. This presents a problem of unbalanced toughness, strength, chemical stability, and corrosion resistance. How to achieve a balanced improvement in the comprehensive mechanical properties, chemical stability, and corrosion resistance of impact-resistant PLA resins after blending is the technical problem this application aims to solve. Summary of the Invention

[0004] The purpose of this invention is to provide a type of high tensile toughness polylactic acid and its preparation method, so as to solve the problem of coordinating and unifying the comprehensive mechanical properties, chemical stability, and corrosion resistance of impact-resistant polylactic acid resin after blending. The invention mainly uses hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin to toughen and modify polylactic acid through a method of intensive mixing, blending and grafting. The high tensile toughness polylactic acid is a graft polymer of polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin.

[0005] The technical solution of this invention is as follows: a type of high tensile toughness polylactic acid, wherein the high tensile toughness polylactic acid is a graft polymer of polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin. Based on 100 parts by weight of the high tensile toughness polylactic acid, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin comprises 20-40 parts, and the polylactic acid comprises 60-80 parts; the epoxidation degree molar percentage of the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is 10-40%, and the hydrogenation degree is not less than 90%.

[0006] Preferably, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is a hydrogenation product of epoxidized styrene-butadiene transparent impact-resistant resin, the epoxidized styrene-butadiene transparent impact-resistant resin is an epoxidation product of styrene-butadiene transparent impact-resistant resin, and the styrene-butadiene transparent impact-resistant resin is a styrene-butadiene multiblock copolymer obtained by polymerization of styrene and butadiene as monomers.

[0007] Preferably, the polybutadiene block content in the styrene-butadiene transparent impact-resistant resin is 15-45 wt%.

[0008] Preferably, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is selected from hydrogenated epoxidized styrene-butadiene multiblock copolymer.

[0009] Preferably, the polybutadiene block content in the styrene-butadiene transparent impact-resistant resin is 20-30 wt%.

[0010] Preferably, based on 100 parts by weight of high tensile toughness polylactic acid, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin comprises 15-35 parts, and the polylactic acid comprises 65-85 parts.

[0011] Preferably, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has an epoxidation degree molar percentage of 20-30% and a hydrogenation degree of not less than 95%.

[0012] Preferably, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has a linear or branched structure.

[0013] Preferably, the polylactic acid has a number-average molecular weight of 50,000 to 500,000, and the hydrogenated epoxidized thermoplastic elastomer has a number-average molecular weight of 100,000 to 500,000.

[0014] Preferably, the polylactic acid is selected from L-polylactic acid; polylactic acid is a homopolymer or copolymer, and can be one of a linear structure, a star structure or a branched structure.

[0015] Preferably, the polylactic acid has a number-average molecular weight of 100,000 to 300,000; and the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has a number-average molecular weight of 200,000 to 250,000.

[0016] Secondly, this invention discloses a method for preparing high tensile toughness polylactic acid, specifically: polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin are placed in a mixer for a mixing time of 5-20 minutes, a mixing temperature of 170-200℃, and a torque of 40-80 rpm to obtain high tensile toughness polylactic acid.

[0017] Preferably, the input amounts of polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin are as follows: based on 100 parts of high tensile toughness polylactic acid, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is 20-40 parts and the polylactic acid is 60-80 parts.

[0018] Beneficial effects:

[0019] Polylactic acid (PLA) exhibits significantly improved elongation at break. By grafting PLA with hydrogenated epoxidized styrene-butadiene transparent impact resin, the high tensile toughness PLA demonstrates marked ductile fracture, while maintaining its biodegradable properties. Compared to PLA toughened with epoxidized thermoplastic elastomers, PLA toughened with hydrogenated epoxidized styrene-butadiene transparent impact resin exhibits higher tensile strength and tensile modulus, along with better anti-aging and heat-oxidation stability. The internal mixing grafting toughening method is simple, efficient, and cost-effective, making it highly valuable for widespread application. Detailed Implementation

[0020] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0022] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0023] In this embodiment, the epoxidized styrene-butadiene transparent impact-resistant resin was prepared using the classic formic acid / hydrogen peroxide in-situ peroxyformic acid method. For the epoxidation method of the styrene-butadiene transparent impact-resistant resin and the epoxidation degree test method of the epoxidized styrene-butadiene transparent impact-resistant resin, please refer to the literature: Zhang Hongxia, Research on star-shaped comb-like highly branched polymers of butadiene / isoprene / styrene, Doctoral Dissertation of Dalian University of Technology (2009).

[0024] Hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is a hydride of epoxidized styrene-butadiene transparent impact-resistant resin. For specific preparation processes and hydrogenation degree testing methods, please refer to: Li Wei, Preparation and Application of Hydrogenated Conjugated Diene Polymers, Doctoral Dissertation, Dalian University of Technology (2012). Researchers can select appropriate hydrogenation catalytic systems or adjust the preparation process of hydrogenated epoxidized rubber depending on the type of styrene-butadiene transparent impact-resistant resin.

[0025] Mechanical property testing:

[0026] Izod notched impact strength: Tested using an instrumented impact tester according to ASTM-D256 standard, with a test temperature of 23℃ and a pendulum weight of 5.5J. The impact strength of the sample was recorded.

[0027] Tensile properties: Tested according to ISO 527-1 standard using a universal testing machine at a tensile rate of 10 mm / min and a test temperature of 23℃. The tensile strength, tensile modulus and elongation at break of the samples were recorded.

[0028] Each sample was repeated at least 5 times.

[0029] Example 1

[0030] Take 80 parts of linear L-polylactic acid and 20 parts of hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin SBC. Mix the polylactic acid and hydrogenated epoxidized SBC together in a mixer for 5 minutes at a mixing temperature of 170℃ and a torque of 60 rpm to obtain polylactic acid with high tensile toughness, an elongation at break of 349%, a tensile strength of 61 MPa, a tensile modulus of 1.48 GPa, and a degree of hydrogenation of 99%.

[0031] The number-average molecular weight of the above-mentioned L-polylactic acid is 150,000; the number-average molecular weight of the above-mentioned hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin SBC is 130,000, wherein the butadiene content is 25wt% and the epoxidation degree molar percentage is 30%.

[0032] Example 2 (The epoxidation degree of the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is 5%, 10%, 20%, 25%, 30%, 40%, and 50%, respectively; other aspects are the same as in Example 1)

[0033] 5％ 102 60 1.47 10％ 198 61 1.47 20％ 309 61 1.47 25％ 327 61 1.48 30％ 349 61 1.48 40％ 321 62 1.48 50％ 288 61 1.48

[0034] Example 3 (Hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin ratios were 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%, with other parameters the same as in Example 1)

[0035]

[0036]

[0037] Example 4 (hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin with hydrogenation degrees of 90%, 95%, and 99%, respectively; other aspects are the same as in Example 1).

[0038] 99％ 349 61 1.48 95％ 346 60 1.46 90％ 334 58 1.43 80％ 277 54 1.32

[0039] Example 5 (The butadiene content in the styrene-butadiene transparent impact-resistant resin was adjusted to 10%, 15%, 20%, 30%, 40%, 45%, and 50%; other aspects were the same as in Example 1)

[0040]

[0041]

[0042] Comparative Example 1

[0043] Take 70 parts of L-polylactic acid and 30 parts of epoxidized styrene-butadiene transparent impact-resistant resin SBC. Mix the polylactic acid and epoxidized SBC together in a mixer for 15 minutes at a mixing temperature of 180℃ and a torque of 70 rpm to obtain polylactic acid with high tensile toughness, an elongation at break of 305%, a tensile strength of 56 MPa, and a tensile modulus of 1.25 GPa.

[0044] The number-average molecular weight of the L-polylactic acid is 120,000; the number-average molecular weight of the epoxidized styrene-butadiene transparent impact-resistant resin SBC is 100,000, wherein the butadiene content is 23 wt% and the epoxidation degree molar percentage is 29%.

[0045] Comparative Example 2

[0046] Take 70 parts of L-polylactic acid and 30 parts of hydrogenated styrene-butadiene transparent impact-resistant resin SBC. Mix the polylactic acid and hydrogenated SBC together in a mixer for 15 minutes at a mixing temperature of 180℃ and a torque of 80 rpm to obtain polylactic acid with high tensile toughness, an elongation at break of 20%, a tensile strength of 58 MPa, and a tensile modulus of 1.35 GPa.

[0047] The number-average molecular weight of the L-polylactic acid is 120,000; the number-average molecular weight of the epoxidized styrene-butadiene transparent impact-resistant resin SBC is 100,000, wherein the butadiene content is 32 wt% and the degree of hydrogenation is 99%.

[0048] Analysis revealed that to achieve optimal overall mechanical properties of polylactic acid (PLA) materials and a balance between strength and toughness, several key parameters synergistically interact when using hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin. These parameters include: epoxy degree, hydrogenation degree, amount of hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin added, type of hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin, and number-average molecular weight (HbA2 / PLA2). Based on extensive experimentation, the inventors developed a superior technical solution for toughening PLA with hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin. The resulting toughened PLA exhibits approximately 20% improvement in overall mechanical properties and excellent anti-aging properties.

[0049] Theoretically, after hydrogen epoxidation, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin contains a small amount of crystalline structure. This increases the strength of the resin itself to some extent, minimizing strength loss when used to toughen polylactic acid (PLA). Furthermore, the crystalline structure in the resin reduces material deformation or breakage under tension, not only inducing and effectively terminating crazes and shear bands, thus resulting in better toughening. Reducing double bonds and improving chemical stability also enhances the anti-aging properties of PLA to some extent.

[0050] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A class of high tensile strength polylactic acid, characterized in that, The high tensile toughness polylactic acid is a graft polymer of polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin. Based on 100 parts by weight of high tensile toughness polylactic acid, the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is 20-35 parts and polylactic acid is 65-80 parts. The hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has an epoxidation degree molar percentage of 20-40% and a hydrogenation degree of not less than 90%. The hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is a hydrogenation product of epoxidized styrene-butadiene transparent impact-resistant resin, and the epoxidized styrene-butadiene transparent impact-resistant resin is an epoxidation product of styrene-butadiene transparent impact-resistant resin. The styrene-butadiene transparent impact-resistant resin is a styrene-butadiene multiblock copolymer obtained by polymerization of styrene and butadiene as monomers. The content of polybutadiene blocks in the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is 20-30 wt%. The polylactic acid has a number-average molecular weight of 50,000 to 500,000, and the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has a number-average molecular weight of 100,000 to 500,000.

2. The high tensile strength polylactic acid according to claim 1, characterized in that, The hydrogenation degree of hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin is not less than 95%.

3. The high tensile strength polylactic acid according to claim 1, characterized in that, The polylactic acid has a number-average molecular weight of 100,000 to 300,000; the hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has a number-average molecular weight of 200,000 to 250,000.

4. The high tensile strength polylactic acid according to any one of claims 1-3, characterized in that, The hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin has a linear or branched structure.

5. A method for preparing high tensile toughness polylactic acid as described in any one of claims 1-3, characterized in that, Polylactic acid and hydrogenated epoxidized styrene-butadiene transparent impact-resistant resin are placed in an internal mixer for 5-20 minutes, at a temperature of 170-200℃ and a torque of 40-80 rpm to obtain polylactic acid with high tensile toughness.

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