CN105462196B - A preparation method of a high-strength polylactic acid composite film with barrier properties - Google Patents

Abstract

The invention relates to a preparation method of a high-strength polylactic acid composite film with barrier properties. The process is to dissolve polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, and maleic anhydride-isobutyl grafted POSS Obtain a transparent solution in dichloromethane solution, then move the solution into the tank as the bottom liquid, introduce electrospun nylon nanofibers into the solution, cast it in a polytetrafluoroethylene mold, dry and evaporate the solution after standing to obtain a composite membrane. The composite film has excellent strength and toughness, and good barrier property to oxygen, and can be applied in the field of environmental protection packaging film.

Description

A preparation method of a high-strength polylactic acid composite film with barrier properties

technical field

The invention relates to a polylactic acid composite film, in particular to a polylactic acid composite film with excellent strength, toughness and high barrier property and a preparation method thereof.

Background technique

Although plastic materials have excellent performance and wide applicability, they are derived from petroleum products and cannot be degraded. In today's resource crisis and environmental pollution are becoming more and more serious, looking for excellent performance and renewable alternative materials has become the current research field in the field of materials. top priority.

Among the current degradable materials, starch has been deeply studied due to its cheap price and wide range of sources, and a variety of daily and industrial products have been prepared through modification and compounding, such as starch-based films, starch tableware, etc. However, starch has its natural defects. Its mechanical properties are poor and its performance is unstable, so it can only be used in fields that require low mechanical properties. The emergence of polylactic acid has changed this situation. Polylactic acid (PLA) is an aliphatic polyester with lactic acid (2-hydroxypropionic acid) as its basic structural unit. PLA can be produced by fermenting natural raw materials such as corn, or by polycondensation of lactic acid. PLA and its end products can be naturally decomposed into _CO2 and water under composting conditions, which reduces solid waste emissions and is a green and environmentally friendly biological source material.

Although polylactic acid has good biodegradability, processability, and excellent mechanical properties, it is brittle and brittle, lacks elasticity and flexibility, which largely limits the application of polylactic acid, and, in the main film The application is the packaging application, and its barrier property is poor, so it cannot be used in the packaging field that requires better barrier property. For the strength modification of polylactic acid film, there has been some research. Different substances are added to polylactic acid by blending or chemical modification. For example, Sun Zhidan et al. (Sun Zhidan, Xu Yang, Chen Xiaolang, Zhang Zhibin; Polymer Materials Science and Engineering. 2013.2, 29(2): 54-57.) use polylactic acid-polyethylene glycol-polylactic acid block copolymer as the additive The toughness modifier is blended with polylactic acid to obtain a polylactic acid composite material with a 15% increase in the elongation at break at 80 °C, and the toughness is improved to a certain extent, but the preparation process is relatively complicated, and the relative energy and cost value increase; Zhang Wei et al. (Wei Zhang, Long Chen, Yu Zhang, Polymer.2009,50:1311-1315.) through the blending of polyamide elastomer and polylactic acid, the flexibility of polylactic acid was greatly improved, but it caused the composite A serious decline in the mechanical properties of the material. Chen Zhize et al. invented a method for preparing a transparent and high-toughness polylactic acid film (201310393192.2), which is formed by co-dissolving polylactic acid and methyl MQ silicone resin, which effectively improves the toughness of the film. The methods involving improving the barrier properties of polylactic acid include introducing layered nanoparticles such as nano-montmorillonite to achieve intercalation or blending other barrier substances, but the improvement of barrier properties is still limited and greatly depends on processing conditions.

Contents of the invention

The purpose of the present invention is to provide a preparation method of a polylactic acid film composite material with excellent toughness and strength in order to overcome the defects of high brittleness and poor barrier property of the polylactic acid film material.

The purpose of the present invention is achieved through the following technical solutions:

A preparation method of a high-strength polylactic acid composite film with barrier properties, the composite film is made of polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, maleic anhydride-isobutyl grafted POSS and electrospinning Nylon nanofibers are used as raw materials and prepared by solvent method;

Its preparation process is:

(1): Dry polylactic acid, polylactic acid grafted with maleic anhydride, polycaprolactone, and maleic anhydride-isobutyl grafted POSS in vacuum for 24 hours at 60 degrees, then put them into dichloromethane, and run at high speed at 70 degrees After stirring for 1-2h, the solution obtained a transparent solution, wherein the mass concentration of polylactic acid in the solution was 15-25wt%, the mass concentration of polycaprolactone was 5-15wt%, and the mass concentration of polylactic acid grafted maleic anhydride 3-6wt%, the mass concentration of maleic anhydride-isobutyl grafted POSS is 1-3wt%;

(2): The solution prepared in (1) was moved to the tank as the electrospinning base liquid, and nylon nanofibers were introduced into the solution by electrospinning, and left to stand for 4 hours, wherein the quality of the nylon nanofibers introduced into the solution was poly 20-40% of lactic acid;

(3): Move the solution obtained in (2) into a polytetrafluoroethylene mold, dry and evaporate the solution after standing to obtain a composite film.

Further, the polylactic acid is L-lactic acid, D-lactic acid, or L, D-lactic acid composition, the molecular weight of the polylactic acid is between 100,000-300,000, and optimally, the molecular weight is between 150,000-250,000 .

Further, the degree of grafting of the polylactic acid grafted with maleic anhydride is between 1.2% and 2%, and the molecular weight is between 120,000 and 240,000.

Further, the maleic anhydride-isobutyl grafting POSS involved in the present invention is a polyhedral oligomeric silsesquioxane (POSS) derivative, and POSS is a silicon-oxygen structure with an octahedral cage structure, and POSS is in a cage There are 8 modifiable groups R on the corners of the structure. Among the present invention, R group is an isobutyl group, and its molecular structural formula is as follows:

Further, the solvent used for the electrospinning of the nylon nanofibers is a mixed solution of dichloromethane/formic acid, the volume ratio of which is between 2:1-1:2, and the mass fraction of nylon in it is 20-35wt%.

Further, the conditions of the electrospinning are: the solution flow rate is between 0.7-1ml/h, the voltage is between 20-30kV, the spinning distance is set at 15-20cm, and the humidity is between 25%-35%. between.

Further, the diameter of the nylon nanofiber is between 20-200nm.

Further, the excellent effect of the present invention is that the addition of polylactic acid grafted maleic anhydride effectively makes the maleic anhydride-isobutyl grafted POSS well dispersed in the polylactic acid matrix, and closely connected with the polylactic acid matrix, thereby To improve the barrier property of the material, the addition of electrospun nylon greatly improves the mechanical properties of the material on the one hand, and on the other hand, the addition of nylon is also conducive to the improvement of the barrier property of the film.

detailed description

Exemplary implementation methods of the present invention will be described in detail below. However, these implementation methods are for exemplary purposes only, and the present invention is not limited thereto.

Example 1

A high-strength polylactic acid composite film with barrier properties, made of polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, maleic anhydride-isobutyl grafted POSS and electrospun nylon nanofibers as raw materials, Prepared by solvent method;

Its preparation process is:

Polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, and maleic anhydride-isobutyl grafted POSS were vacuum-dried at 60 degrees for 24 hours, and then dissolved in dichloromethane solution to obtain a transparent solution. Among them, polylactic acid was Concentration in the solution is 22wt%, and the concentration of polycaprolactone is 12wt%, and the concentration of polylactic acid grafted maleic anhydride is 4.5wt%, and the concentration of maleic anhydride-isobutyl grafted POSS is 1.3wt%; The solution was moved into the tank as the bottom liquid, and the nylon nanofibers were introduced into the solution by electrospinning, and then placed in a polytetrafluoroethylene mold, and after standing still, the solution was dried and evaporated to obtain a composite film. Wherein, the quality of the nylon nanofiber introduced into the solution is 25% of the polylactic acid.

The polylactic acid is L-lactic acid, and the molecular weight of the polylactic acid is between 150,000 and 200,000.

The degree of grafting of the polylactic acid grafted with maleic anhydride is 1.4%, and the molecular weight is between 140,000 and 200,000.

Further, the solvent used for the electrospinning of the nylon nanofibers is a mixed solution of dichloromethane/formic acid, the volume ratio of which is 2:1.5, and the mass fraction of nylon in it is 30wt%.

The electrospinning conditions are as follows: the solution flow rate is 0.8ml/h, the voltage is 25kV, the spinning distance is set at 18cm, and the humidity is 30%.

The diameter of the nylon nanofiber is between 50-100nm.

The specific performance is shown in Table 1.

Example 2

A high-strength polylactic acid composite film with barrier properties, made of polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, maleic anhydride-isobutyl grafted POSS and electrospun nylon nanofibers as raw materials, Prepared by solvent method; polylactic acid, polylactic acid grafted with maleic anhydride, polycaprolactone, and maleic anhydride-isobutyl grafted POSS are vacuum-dried at 60 degrees for 24 hours, then dissolved in dichloromethane solution to obtain a transparent solution , wherein, the concentration of polylactic acid in the solution is 20wt%, the concentration of polycaprolactone is 10wt%, the concentration of polylactic acid grafted maleic anhydride is 4wt%, the concentration of maleic anhydride-isobutyl grafted POSS is 2wt%; move the solution in the tank as the bottom liquid, introduce electrospun nylon nanofibers into the solution, place it in a polytetrafluoroethylene mold, dry and evaporate the solution after standing to obtain a composite film, wherein, the nylon nanofiber introduced into the solution The mass of nanofibers is 30% of that of polylactic acid.

The polylactic acid is D-lactic acid, and the molecular weight of the polylactic acid is between 150,000 and 200,000.

The degree of grafting of the polylactic acid grafted with maleic anhydride is 1.8%, and the molecular weight is between 160,000 and 200,000.

Further, the solvent for the electrospinning of nylon nanofibers is a mixed solution of dichloromethane/formic acid, the volume ratio of the two is 1:1, and the mass fraction of nylon in it is 25wt%.

The conditions of the electrospinning are: the solution flow rate is 0.9ml/h, the voltage is 25kV, the spinning distance is set at 16cm, and the humidity is 30%.

The diameter of the nylon nanofiber is between 50-150nm.

The specific performance is shown in Table 1.

The performance of composite membrane in table 1 embodiment 1,2

Composite properties Example 1 Example 2 Elongation at break (%) 94±10 102±10 Breaking strength (Mpa) 86.4±3.21 88.7±2.45 25±4 30±5

Claims (5)

1. A preparation method of a high-strength polylactic acid composite film with barrier properties, the composite film is based on polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, maleic anhydride-isobutyl grafted POSS and electrostatic Spun nylon nanofibers are used as raw materials and prepared by solvent method; the preparation process is as follows: (1): After drying polylactic acid, polylactic acid grafted maleic anhydride, polycaprolactone, and maleic anhydride-isobutyl grafted POSS in vacuum at 60 degrees Celsius for 24 hours, they were put into dichloromethane and heated at high speed at 70 degrees Celsius. After stirring for 1-2h, a transparent solution was obtained, wherein the mass concentration of polylactic acid in the solution was 15-25wt%, the mass concentration of polycaprolactone was 5-15wt%, and the mass concentration of polylactic acid grafted maleic anhydride was 3-6wt%, the mass concentration of maleic anhydride-isobutyl grafted POSS is 1-3wt%; (2): The solution prepared in (1) is moved in the tank as the electrospinning base solution, and nylon nanofibers are introduced in the solution by electrospinning, and left to stand for 4 hours, wherein the quality of the nylon nanofibers introduced into the solution is 20-40% of polylactic acid; (3): Move the solution obtained in (2) into a polytetrafluoroethylene mold, dry and evaporate the solution after standing to obtain a composite film. 2. the preparation method of a kind of high-strength polylactic acid composite film with barrier property as claimed in claim 1, is characterized in that, the used solvent of described electrospinning nylon nanofiber is dichloromethane/formic acid mixed solution, two The volume ratio of methyl chloride and formic acid is between 2:1-1:2, and the mass fraction of nylon in it is 20-35wt%. 3. A method for preparing a high-strength polylactic acid composite membrane with barrier properties as claimed in claim 1, wherein the electrospinning conditions are: the solution flow rate is between 0.7-1ml/h, the voltage Between 20-30kV, the spinning distance is set at 15-20cm, and the humidity is between 25%-35%. 4. A method for preparing a high-strength polylactic acid composite membrane with barrier properties as claimed in claim 1, wherein the nylon nanofibers have a diameter between 20-200nm. 5. A method for preparing a high-strength polylactic acid composite film with barrier properties as claimed in claim 1, wherein the degree of grafting of the polylactic acid grafted with maleic anhydride is between 1.2%-2%. between.