阅读说明：本技术 主链为Si-O-B-O结构的聚合物及用其增韧改性聚乳酸的方法 (Polymer with main chain of Si-O-B-O structure and method for toughening and modifying polylactic acid by using polymer ) 是由 陈明锋 吕娇娇 马志毅 罗文慧 林菽丰 章华桂 于 2021-09-01 设计创作，主要内容包括：本发明公开了一种用主链为Si-O-B-O结构的聚合物增韧改性聚乳酸的方法,属于聚乳酸改性技术领域,该方法通过将一定量的聚乳酸溶于1,2-二氯乙烷,再加入一定质量百分比的主链为Si-O-B-O结构的聚合物,一定温度下反应一段时间,烘干除去溶剂后,即可得到一种主链为Si-O-B-O结构的聚合物增韧改性聚乳酸。本发明利用主链为Si-O-B-O结构的聚合物结构中含有的环氧基团与聚乳酸结构中的羧基和羟基发生反应,进而实现对聚乳酸的扩链作用,利用聚合物结构中含有的硅、硼等元素、Si-O-B-O重复单元,可赋予改性聚乳酸优异的力学性能和热稳定性,拓宽聚乳酸的应用范围,具有良好的应用前景。(The invention discloses a method for toughening and modifying polylactic acid by using a polymer with a main chain of a Si-O-B-O structure, which belongs to the technical field of polylactic acid modification. According to the invention, the epoxy group contained in the polymer structure with the main chain of the Si-O-B-O structure reacts with the carboxyl and hydroxyl in the polylactic acid structure, so that the chain extension effect on the polylactic acid is realized, and the Si-O-B-O repeating unit and elements such as silicon and boron contained in the polymer structure can endow the modified polylactic acid with excellent mechanical property and thermal stability, widen the application range of the polylactic acid and have good application prospects.)

1. The polymer with the main chain of a Si-O-B-O structure is characterized in that the structural formula of the polymer is as follows:

2. the polymer with the main chain of Si-O-B-O structure according to claim 1, wherein the polymer is synthesized by the following steps: under the atmosphere of inert gas, adding phenylboronic acid and 1, 2-dichloroethane into a three-neck flask, stirring and dissolving, dropwise adding gamma-glycidoxypropyltrimethoxysilane dissolved in 1, 2-dichloroethane through a constant pressure dropping funnel, heating for reaction, performing suction filtration, and performing rotary evaporation to obtain the polymer with the main chain of Si-O-B-O structure.

3. The polymer with the main chain of Si-O-B-O structure as claimed in claim 2, wherein the reaction time of the temperature-raising reaction is 8-12h, and the reaction temperature is 70-90 ℃.

4. The polymer with the main chain of Si-O-B-O structure as claimed in claim 2, wherein the molar ratio of the phenylboronic acid to the gamma-glycidoxypropyltrimethoxysilane is 3: 2.

5. the method for toughening and modifying the polylactic acid by using the polymer with the main chain of the Si-O-B-O structure according to any one of claims 1 to 4, which is characterized by comprising the following steps: dissolving polylactic acid in 1, 2-dichloroethane, adding a polymer with a main chain of a Si-O-B-O structure for reaction, drying and removing the solvent to obtain the polymer toughening modified polylactic acid with the main chain of the Si-O-B-O structure.

6. The method for toughening and modifying polylactic acid by using the polymer with the main chain of the Si-O-B-O structure according to claim 5, wherein the mass ratio of the polylactic acid to the 1, 2-dichloroethane is 1: 5-30; the mass ratio of the polylactic acid to the polymer with the main chain of Si-O-B-O structure is 1: 0.01 to 0.2.

7. The method for toughening and modifying polylactic acid by using the polymer with the main chain of the Si-O-B-O structure according to claim 5, wherein the reaction temperature of the reaction is 40-90 ℃, and the reaction time is 2-5 h.

Technical Field

The invention belongs to the technical field of polylactic acid modification, and particularly relates to a polymer with a main chain of a Si-O-B-O structure and a method for toughening and modifying polylactic acid by using the polymer.

Background

With the development of modern society, plastics are widely applied to various industries, but most of the plastics are prepared by taking petroleum as a raw material, are nondegradable and difficult to recover, cause a great deal of waste on resources and generate huge burden on the environment. The biodegradable material is a high molecular material which can be chemically, biologically and physically degraded or enzymolyzed under the action of microorganisms, and is an effective substitute material for solving the problems encountered by the traditional plastics, wherein polylactic acid is an important biodegradable material and is polymerized by taking lactic acid as a raw material, the lactic acid is prepared from starch provided by renewable plant resources (sugar, starch and the like), and the polylactic acid has the excellent characteristics of easily available raw materials, biodegradability, easy processing, high strength, high modulus and the like, but the application of the traditional polylactic acid is severely limited due to poor toughness and thermal stability. The toughness and thermal stability of polylactic acid are improved by the synthetic lactic acid-polyamide-polyether block copolymer such as Higashi, but the amount of catalyst used is too large and the operation is complicated (CN 107857884A). Dawning et al disclose a method for toughening polylactic acid with polycarbodiimide, which is good in toughness, but dangerous in isocyanate (CN 112920412A). Therefore, the research and development of a modification method which is simple and convenient in preparation process and can simultaneously improve the toughness and the thermal stability of the polylactic acid has important application value.

Disclosure of Invention

In order to overcome the defects of the prior art, the technical problems to be solved by the invention are as follows: how to solve the problem of poor toughness and thermal stability of polylactic acid.

In order to solve the technical problems, the invention adopts the technical scheme that: a method for toughening and modifying polylactic acid by using a polymer with a main chain of a Si-O-B-O structure mainly comprises the synthesis of the polymer with the main chain of the Si-O-B-O structure and the preparation of the polymer toughening and modifying polylactic acid with the main chain of the Si-O-B-O structure.

The method specifically comprises the following steps:

(1) the synthesis method of the polymer with the main chain of Si-O-B-O structure comprises the following steps:

under the atmosphere of inert gas, adding phenylboronic acid and 1, 2-dichloroethane into a three-neck flask, and stirring for dissolving; adding gamma-glycidoxypropyltrimethoxysilane dissolved in 1, 2-dichloroethane dropwise through a constant pressure dropping funnel, heating to react for a certain time, and performing suction filtration and rotary evaporation to obtain a polymer with a main chain of a Si-O-B-O structure;

in particular: the molar ratio of the phenylboronic acid to the gamma-glycidoxypropyltrimethoxysilane is 3: 2, the reaction time is 8-12h, and the reaction temperature is 70-90 ℃.

The structural formula of the polymer with the main chain of the Si-O-B-O structure is as follows:

(2) the method for toughening and modifying the polylactic acid by the polymer with the main chain of the Si-O-B-O structure comprises the following steps:

dissolving a certain amount of polylactic acid in 1, 2-dichloroethane, adding a polymer with a main chain of Si-O-B-O structure in a certain mass percentage, reacting for a period of time at a certain temperature, and drying to remove the solvent to obtain the polymer toughening modified polylactic acid with the main chain of Si-O-B-O structure;

in particular: the mass ratio of polylactic acid to 1, 2-dichloroethane is 1: 5-30; the mass ratio of the polylactic acid to the polymer with the main chain of Si-O-B-O structure is 1: 0.01-0.2, the reaction temperature is 40-90 ℃, and the reaction time is 2-5 h.

The invention has the beneficial effects that: the invention provides a polymer with a main chain of a Si-O-B-O structure and a method for toughening and modifying polylactic acid by using the polymer.

Detailed Description

In order to explain the technical content, the objects and the effects of the present invention in detail, the following description will be given with reference to the embodiments.

Example 1:

the synthesis method of the polymer with the main chain of the Si-O-B-O structure comprises the following steps:

under the inert gas atmosphere, adding phenylboronic acid (15mmol) and 1, 2-dichloroethane into a three-neck flask, stirring and dissolving, then dropwise adding gamma-glycidoxypropyltrimethoxysilane (10mmol) dissolved in 1, 2-dichloroethane through a constant pressure dropping funnel, heating to 90 ℃ for reaction for 8 hours, and obtaining a polymer with a main chain of a Si-O-B-O structure through suction filtration and rotary evaporation, wherein the polymer structure is as follows:

FT-IR: epoxy group (906 cm)^-1)，Si-O(1088cm^-1)，B-O(1350cm^-1)，Ph(1600cm^-1)。

Example 2:

the synthesis method of the polymer with the main chain of the Si-O-B-O structure comprises the following steps:

under the inert gas atmosphere, adding phenylboronic acid (15mmol) and 1, 2-dichloroethane into a three-neck flask, stirring and dissolving, then dropwise adding gamma-glycidoxypropyltrimethoxysilane (10mmol) dissolved in 1, 2-dichloroethane through a constant pressure dropping funnel, heating to 70 ℃ for reaction for 12 hours, and carrying out suction filtration and rotary evaporation to obtain a polymer with a main chain of a Si-O-B-O structure, wherein the polymer structure is as follows:

FT-IR: epoxy group (904 cm)^-1)，Si-O(1080cm^-1)，B-O(1353cm^-1)，Ph(1606cm^-1)。

Example 3:

the synthesis method of the polymer with the main chain of the Si-O-B-O structure comprises the following steps:

under the inert gas atmosphere, adding phenylboronic acid (15mmol) and 1, 2-dichloroethane into a three-neck flask, stirring and dissolving, then dropwise adding gamma-glycidoxypropyltrimethoxysilane (10mmol) dissolved in 1, 2-dichloroethane through a constant pressure dropping funnel, heating to 80 ℃ for reaction for 10 hours, and obtaining a polymer with a main chain of a Si-O-B-O structure through suction filtration and rotary evaporation, wherein the polymer structure is as follows:

FT-IR: epoxy group (908 cm)^-1)，Si-O(1084cm^-1)，B-O(1349cm^-1)，Ph(1602cm^-1)。

Example 4:

the method for toughening and modifying the polylactic acid by using the polymer with the main chain of a Si-O-B-O structure comprises the following steps: 4.0g of polylactic acid is dissolved in 1, 2-dichloroethane (70mL), 1 percent (relative to the mass of the polylactic acid) of the polymer with the main chain of Si-O-B-O structure prepared in the example 1 is added, the mixture is stirred and reacted for 5 hours at the temperature of 40 ℃, and the polymer toughening modified polylactic acid with the main chain of Si-O-B-O structure can be obtained after drying and removing the solvent.

Example 5:

the method for toughening and modifying the polylactic acid by using the polymer with the main chain of a Si-O-B-O structure comprises the following steps: 4.0g of polylactic acid is dissolved in 1, 2-dichloroethane (70mL), 10 percent (relative to the mass of the polylactic acid) of the polymer with the main chain of Si-O-B-O structure prepared in the example 2 is added, the mixture is stirred and reacted for 3 hours at 70 ℃, and the polymer toughening modified polylactic acid with the main chain of Si-O-B-O structure can be obtained after drying and removing the solvent.

Example 6:

the method for toughening and modifying the polylactic acid by using the polymer with the main chain of a Si-O-B-O structure comprises the following steps: 4.0g of polylactic acid is dissolved in 1, 2-dichloroethane (70mL), 20 percent (relative to the mass of the polylactic acid) of the polymer with the main chain of Si-O-B-O structure prepared in the example 3 is added, the mixture is stirred and reacted for 2 hours at the temperature of 90 ℃, and the polymer toughening modified polylactic acid with the main chain of Si-O-B-O structure can be obtained after drying and removing the solvent.

The toughened and modified polylactic acids obtained in examples 4 to 6 were tested for molecular weight, mechanical properties, and thermal stability, and the test results are shown in table 1.

TABLE 1

As can be seen from Table 1, the number average molecular weight of the unmodified polylactic acid was 3.1X10⁴g/mol, tensile strength of 20.2MPa, elongation at break of 8 percent and maximum degradation temperature of 358 ℃. When the polymer with the main chain of Si-O-B-O structure is added, the molecular weight, the mechanical property and the thermal stability of the toughened and modified polylactic acid are improved to different degrees. For example, the toughened and modified polylactic acid obtained in example 4 has a number average molecular weight of 2.9 × 10⁵g/mol, elongation at break of 40%, 32% improvement, tensile strength of 21.4MPa, maximum degradation temperature of 362 ℃. The method shows that the chain extension reaction occurs between the epoxy group contained in the polymer with the main chain of Si-O-B-O structure and the carboxyl group and the hydroxyl group of the polylactic acid structure, so that the data molecular weight of the modified polylactic acid is obviously increased; meanwhile, the polymer contains elements such as silicon, boron and the like, and Si-O-B-O repeating units endow the modified polylactic acid with excellent mechanical property and thermal stability.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention in the specification or directly or indirectly applied to the related technical field are included in the scope of the present invention.