CN115612071B - Preparation method of antibacterial colored polylactic acid - Google Patents

Abstract

The invention belongs to the technical field of polymer preparation, and in particular relates to a preparation method of antibacterial colored polylactic acid. Under the protection of nitrogen, the complex catalyst and lactide undergo ring-opening polymerization to obtain antibacterial colored polylactic acid. In the present invention, lactide realizes the covalent bonding between guanidine compounds, antibacterial natural dyes and polylactic acid polymer chains in the catalytic polymerization process, simplifies the production steps of antibacterial colored polylactic acid, and synthesizes a polylactic acid with strong The colored polylactic acid with excellent antibacterial properties and durability improves the diversity and selectivity of antibacterial polylactic acid materials, and meets the requirements for preparing polylactic acid textiles with excellent antibacterial properties and color properties; the raw materials used are green and environmentally friendly , the product has good biocompatibility and has a very good market prospect.

Description

Preparation method of antibacterial colored polylactic acid

technical field

The invention belongs to the technical field of polymer preparation, and in particular relates to a preparation method of antibacterial colored polylactic acid.

Background technique

Polylactic acid is one of the most common degradable plastics. PLA (polylactic acid) is a polymer obtained by polymerizing lactic acid produced by biological fermentation as the main raw material. A single lactic acid molecule has a hydroxyl group and a carboxyl group. Multiple lactic acid molecules are combined, and the hydroxyl group dehydrates and condenses with the carboxyl groups of other molecules, and the carboxyl group dehydrates and condenses with the hydroxyl groups of other molecules to form polylactic acid. The sources of PLA raw materials are sufficient and renewable, the production process is pollution-free, and the product is biodegradable. After use, the PLA can be degraded into carbon dioxide and water by composting at a temperature higher than 55°C or under the action of oxygen-enriched and microorganisms. The material cycle will not have an impact on the environment, so it is an ideal green polymer material. PLA also has reliable biological safety, biodegradability, good mechanical properties and easy processing, and is widely used in packaging, textile industry, agricultural mulch film and biomedical polymers and other industries.

At present, the advent of antibacterial polylactic acid has also provided many conveniences for life, and can be used in the fields of environmental protection medical appliances, food and pharmaceutical packaging, etc. Its preparation methods mainly include blending, physical modification, and chemical grafting. However, the blending and physical modification methods cannot guarantee that the antibacterial substances will not fall off, and the antibacterial effect and safety cannot be guaranteed. The chemical grafting method has the disadvantages of cumbersome process, high requirements for equipment and solution preparation, and is not conducive to environmental protection.

Chinese patent CN111996794A discloses a preparation method of antibacterial polylactic acid nonwoven material, comprising the following steps:

Step 1, carrying out surface modification treatment on the polylactic acid nonwoven material in an atmospheric pressure dielectric barrier discharge (DBD) plasma device; step 2, carrying out chitosan grafting on the polylactic acid nonwoven material after the atmospheric pressure plasma treatment Finishing: step 3, dipping the polylactic acid nonwoven material after the above treatment into silver nitrate solution for antibacterial finishing. This patent uses atmospheric pressure argon DBD plasma to pretreat the polylactic acid nonwoven material, and uses the environmentally friendly natural polymer material chitosan to graft the polylactic acid on the surface to generate in situ on the surface of the polylactic acid nonwoven material Nano-silver makes the material have excellent antibacterial properties; however, the patented production process is cumbersome and requires high production conditions. It is difficult for nano-silver particles to be evenly distributed on the surface of polylactic acid, and it will produce sewage with heavy metal ions to pollute the environment.

In the existing antibacterial polylactic acid synthesis process, there are generally problems such as cumbersome process, difficult equipment cleaning, and environmental pollution. Facing the large gap in the market, it is urgent to provide an antibacterial colored polylactic acid with simple process and excellent antibacterial performance. method of preparation.

Contents of the invention

The purpose of the present invention is to provide a preparation method of antibacterial colored polylactic acid, which combines guanidine antibacterial compounds, natural dyes with antibacterial properties and complex catalysts for lactide ring-opening polymerization to prepare a new type of lactide open polylactic acid. A complex catalyst for ring polymerization, so as to simultaneously realize the synthesis of lactide ring-opening polymerization and antibacterial colored polylactic acid.

The preparation method of the antibacterial colored polylactic acid of the present invention is that under the protection of nitrogen, the complex catalyst and lactide undergo ring-opening polymerization reaction to obtain the antibacterial colored polylactic acid.

The structural formula of described complex catalyst is as follows:

Among them, M is a metal, Guanidine is a guanidine antibacterial compound ligand, and Dye is an antibacterial natural dye molecule containing a hydroxyl group. The above structural formula represents that M is connected with Guanidine and Dye respectively.

Said M is aluminum.

The structural formula of described Guanidine is as follows:

Wherein, R is -(CH ₂ ) _n CH ₃ , where 3≤n≤21, and n is an integer;

R ₁ is one of -H, -CH ₃ or -(CH ₂ )nCH ₃ , wherein 1≤n≤3, and n is an integer.

The structural formula of described Guanidine is one of following structural formulas:

The structural formula of the Dye is one of the following structural formulas:

The preparation method of described complex catalyst comprises the steps:

(1) Under nitrogen protection, Guanidine reacts with alkyl metal in a solvent to obtain a solution of alkyl metal complex;

(2) Under nitrogen protection, Dye is added to the solution of the alkyl metal complex for reaction to obtain the complex catalyst.

The metal alkyl described in step (1) is trimethylaluminum.

The solvent described in step (1) is one or more of benzene, toluene, tetrahydrofuran or dichloromethane.

The molar ratio of Guanidine described in step (1) to metal alkyl is 2-2.5:1.

The mass ratio of solvent and Guanidine described in step (1) is 20-200:1.

The reaction time in the step (1) is 3-12 hours; the reaction is a staged heating reaction, wherein the reaction temperature in the first stage is -78-25°C, and the reaction temperature in the second stage is 25-125°C.

The molar ratio of Dye to metal alkyl described in step (2) is 1-1.5:1.

The reaction temperature described in step (2) is 25-135°C, and the reaction time is 3-18h.

The molar ratio of the complex catalyst to lactide is 1:50-10000.

The temperature of the ring-opening polymerization reaction is 100-180° C., and the reaction time of the ring-opening polymerization is 2-24 hours.

Reaction equation of the present invention is as follows:

The structural formula of described complex catalyst is as follows:

Guanidine is a natural guanidine antibacterial compound with a good planar structure, which shortens the distance between the coordination atoms N and is more conducive to the coordination reaction with the metal center. When Guanidine has a coordination reaction with the metal center, due to the steric hindrance of the Guanidine guanidine antibacterial compound ligand, it is difficult to connect the third Guanidine after the metal center is connected to two Guanidines; and Dye contains hydroxyl Antibacterial natural dye molecules are more conducive to the hydroxyl group approaching the active methyl group and reacting due to its relatively small steric hindrance.

The reaction mechanism of synthesizing antibacterial colored polylactic acid in the present invention is that lactide coordinates with the metal center, resulting in electrophilic activation of lactide, and then undergoes nucleophilic attack by the metal center to form an intermediate, and an antibacterial natural dye containing hydroxyl The molecule attacks the activated monomer. The chemical bond with higher energy in the intermediate is broken to realize ring opening, forming a long chain of lactide monomer connected with Guanidine guanidine antibacterial compound ligand and Dye antibacterial natural dye molecule, and the chain growth is accompanied by the metal of lactide Coordination, nucleophilic reaction, bond breaking and ring opening, until the coordination bond is cleaved to terminate the reaction.

The beneficial effects of the present invention are as follows:

In the present invention, lactide realizes the covalent bonding between guanidine compounds, antibacterial natural dyes and polylactic acid polymer chains in the catalytic polymerization process, simplifies the production steps of antibacterial colored polylactic acid, and synthesizes a polylactic acid with strong The colored polylactic acid with excellent antibacterial properties and durability improves the diversity and selectivity of antibacterial polylactic acid materials, and meets the requirements for preparing polylactic acid textiles with excellent antibacterial properties and color properties; the raw materials used are green and environmentally friendly , the product has good biocompatibility and has a very good market prospect.

The invention can significantly improve the uniformity and stability of the antibacterial colored polylactic acid material, enhance the antibacterial performance of the polylactic acid, simplify the production process, reduce industrial costs, and have great significance for energy saving, emission reduction, and green development of the textile industry.

Description of drawings

Fig. 1 is the nuclear magnetic spectrogram of the yellow complex catalyst that embodiment 1 makes.

Fig. 2 is the nuclear magnetic spectrum of the yellow polylactic acid that embodiment 1 makes.

Detailed ways

The present invention is further described below in conjunction with embodiment.

Example 1

Under the protection of nitrogen, 0.292g G1 was dissolved in 30mL toluene, and placed at -78°C to react with 1mL 1mol/L trimethylaluminum solution for 6h, the mixture was slowly warmed to room temperature, heated to reflux for 1h, and then poured 0.49g of R4 was added to the mixture, and reacted at 110°C for 7 hours. The solvent was removed by distillation under reduced pressure. The product was washed with n-hexane and dried in vacuo to obtain 0.72g of a yellow complex catalyst. The nuclear magnetic spectrum of the complex catalyst is shown in Figure 1. The structural formula of the catalyst is as follows:

Under the protection of nitrogen, add 14.4g lactide and 0.0765g yellow complex catalyst in the Schlenk bottle, then add the ethanol solution that the volume fraction is 10% hydrochloric acid therein after polymerizing reaction at 100 ℃ for 8h to terminate the reaction, the reaction liquid Pour into n-hexane and let the precipitate settle, filter, dissolve the precipitate with dichloromethane, add an appropriate amount of n-hexane to precipitate a solid, and repeat this three times, filter and dry, and vacuum-dry to obtain yellow polylactic acid. The NMR spectrum of yellow polylactic acid is shown in figure 2.

After testing, the antibacterial rate of yellow polylactic acid to E. coli can reach 99.6%, and the antibacterial rate to Staphylococcus aureus can reach 98.5%. After soaping for 10 times, the antibacterial rate of yellow polylactic acid to E. coli remains the same. Reached 99.0%, the antibacterial rate to Staphylococcus aureus still reached 98.0%. The washing fastness of yellow polylactic acid reaches grade 5, and the rubbing fastness reaches grade 4-5.

Example 2

Under the protection of nitrogen, dissolve 0.333g G1 in 30mL tetrahydrofuran, and place it at -78°C to react with 1mL 1mol/L trimethylaluminum solution for 5h. Add 0.345g of R3 to the mixture, and place it under the condition of 125°C for 6h, distill off the solvent under reduced pressure, wash with n-hexane, and dry in vacuum to obtain 0.52g of purple complex catalyst. The structural formula of the complex catalyst is as follows:

Under the protection of nitrogen, add 25g lactide and 0.0592g purple complex catalyst in the Schlenk bottle, then polymerize at 120°C for 6h, then add ethanol solution of hydrochloric acid with a volume fraction of 10% to terminate the reaction, pour the reaction solution Put the precipitate in n-hexane and let it stand, filter, dissolve the precipitate with dichloromethane, add an appropriate amount of n-hexane to precipitate the solid, and repeat this three times, filter and dry, and dry in vacuo to obtain purple polylactic acid.

After testing, the antibacterial rate of purple polylactic acid on Escherichia coli can reach 99.5%, and the antibacterial rate on Staphylococcus aureus can reach 98.6%. After soaping for 10 times, the antibacterial rate of purple polylactic acid on Escherichia coli remains the same. Reached 99.1%, the antibacterial rate to Staphylococcus aureus still reached 98.3%. The washing fastness of purple polylactic acid reaches grade 5, and the rubbing fastness reaches grade 5.

Example 3

Under the protection of nitrogen, dissolve 0.352g of G2 in 30mL of dichloromethane, and place it at 0°C to react with 1mL of 1mol/L trimethylaluminum solution for 4h. Add 0.535g of R4 to the system, and place it under reflux conditions to react for 10h, distill off the solvent under reduced pressure, wash with n-hexane, and dry in vacuum to obtain 0.70g of a yellow complex catalyst. The structural formula of the complex catalyst is as follows:

Under the protection of nitrogen, add 20g of lactide and 0.0778g of yellow complex catalyst in the Schlenk bottle, then polymerize at 125°C for 5h, then add ethanol solution of hydrochloric acid with a volume fraction of 10% to terminate the reaction, pour the reaction solution Put the precipitate in n-hexane to stand still, filter, dissolve the precipitate with dichloromethane, add an appropriate amount of n-hexane to precipitate a solid, and repeat this three times, filter and dry, and vacuum dry to obtain yellow polylactic acid.

After testing, the antibacterial rate of yellow polylactic acid on E. coli can reach 99.5%, and the antibacterial rate on Staphylococcus aureus can reach 98.4%. After soaping 10 times, the antibacterial rate of yellow polylactic acid on E. coli remains the same. Reached 98.9%, the antibacterial rate to staphylococcus aureus still reached 98.1%. The washing fastness of yellow polylactic acid reaches grade 5, and the rubbing fastness reaches grade 5.

Claims (8)

1. The preparation method of the antibacterial colored polylactic acid is characterized in that under the protection of nitrogen, a complex catalyst and lactide carry out ring-opening polymerization reaction to obtain the antibacterial colored polylactic acid;

the structural formula of the complex catalyst is as follows:

wherein M is aluminum, guanidine is Guanidine antibacterial compound ligand, and Dye is antibacterial natural Dye molecule containing hydroxyl; the structural formula of the Guanidine is as follows:

wherein R is- (CH) ₂ ) _n CH ₃ Wherein n is more than or equal to 3 and less than or equal to 21, and n is an integer;

R ₁ is-H, -CH ₃ Or- (CH) ₂ )nCH ₃ Wherein n is greater than or equal to 1 and less than or equal to 3, and n is an integer.

2. The method for preparing antibacterial colored polylactic acid according to claim 1, wherein the structural formula of Guanidine is one of the following structural formulas:

3. the method for preparing antibacterial colored polylactic acid according to claim 1, wherein the Dye has one of the following structural formulas:

4. the method for preparing the antibacterial colored polylactic acid according to claim 1, which is characterized in that the method for preparing the complex catalyst comprises the following steps:

(1) Under the protection of nitrogen, guanidine reacts with aluminum alkyl in a solvent to obtain an aluminum alkyl complex solution;

(2) And adding Dye into the solution of the aluminum alkyl complex under the protection of nitrogen to react to obtain the complex catalyst.

5. The method for preparing antibacterial colored polylactic acid according to claim 4, wherein the alkyl aluminum in the step (1) is trimethylaluminum, the solvent is one or more of benzene, toluene, tetrahydrofuran or methylene dichloride, the molar ratio of Guanidine to alkyl aluminum is 2-2.5:1, the mass ratio of solvent to Guanidine is 20-200:1, and the reaction time is 3-12h; the reaction is a stage heating reaction, wherein the reaction temperature of the first stage is between-78 and 25 ℃, and the reaction temperature of the second stage is between 25 and 125 ℃.

6. The method for preparing antibacterial colored polylactic acid according to claim 4, wherein the molar ratio of Dye to aluminum alkyl in the step (2) is 1-1.5:1, the reaction temperature is 25-135 ℃, and the reaction time is 3-18h.

7. The method for preparing antibacterial colored polylactic acid according to claim 1, wherein the molar ratio of the complex catalyst to lactide is 1:50-10000.

8. The method for preparing antibacterial colored polylactic acid according to claim 1, wherein the ring-opening polymerization reaction temperature is 100-180 ℃ and the ring-opening polymerization reaction time is 2-24h.