CN106832834A - A kind of biaxial tension biodegradable high-strength membrane and its preparation technology - Google Patents

Abstract

The invention relates to a biaxially stretched biodegradable high-strength film and a preparation process. The high-strength film is composed of main materials and auxiliary materials and is biaxially stretched to form a film by melt extrusion. The main material includes (lactic acid-trimethylene carbonate) copolymer, (ε-caprolactone-trimethylene carbonate) copolymer, hydroxybutyric acid valeric acid copolyester, carboxyl-terminated hyperbranched polyester, acetic acid Esterified nano cellulose, the auxiliary materials include a small amount of transesterification catalyst, composite processing aid, antioxidant and fluorescent whitening agent. The composite film has excellent strength, toughness, and transverse and longitudinal tensile properties, and the prepared packaging bag can bear a relatively large weight, and the materials used are environmentally friendly, and can be widely used in the packaging field.

Description

A biaxially stretched biodegradable high-strength film and its preparation process

technical field

The invention relates to a method for preparing a film, in particular to a method for preparing a biomass degradable and environmentally friendly composite film with excellent strength and excellent barrier properties.

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.

At present, the amount of packaging film is increasing, and widely used plastic films such as PE film, PP film, PET film, etc. have good mechanical properties and are easy to prepare, but cannot be degraded, resulting in serious white pollution. Among the degradable materials, starch has been deeply researched 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 biomass polyester has made it possible to prepare materials with excellent mechanical properties. Biodegradable polyester can be degraded into carbon dioxide and water under certain conditions, and it is a kind of green environmental protection material. Generally, according to its synthesis method, it can be divided into two types: biosynthetic polyester and chemically synthesized polyester. The former includes PHA (polyhydroxyalkanoate), and the latter includes PRS (polybutylene succinate), PGA (polyglycolic acid), PLA (polylactic acid) and PCL (polyε-caprolactone), etc. . Biodegradable polyester has become the most promising biodegradable material due to its own biodegradability, tissue compatibility, good mechanical properties and process properties compared with other biodegradable materials (such as starch, fiber, etc.). materials, and have been widely used in the fields of packaging, textiles, tissue engineering and drug sustained release. However, in order to make it a new generation of materials to replace traditional plastics, the development of biodegradable polyester faces problems that must be solved. First of all, although biodegradable polyester has considerable advantages compared with other biodegradable materials, the wide range of applications of polymer materials poses challenges to the performance of biodegradable polyester. Biodegradable polyesters synthesized by biological methods are generally very brittle, and it is difficult to directly meet the general use requirements; while aliphatic polyesters prepared by chemical synthesis are mostly relatively low in molecular weight, and it is difficult to use them as plastic products alone. It can be seen that the performance of biodegradable polyester has become the primary factor restricting its development. Therefore, various modification methods have been used in the modification research of biomass polyester, such as chemical copolymerization method, physical blending method, etc. The modified products have basically met the practical requirements of fibers and plates, and have been There are more related products available. As for membrane materials, polylactic acid membranes are still the most researched polyester membrane materials. Due to the brittleness of polylactic acid itself, its membranes are very easy to break after being stressed, and various modifications are also carried out on this basis. , as disclosed in CN103467941B a kind of transparent high-toughness polylactic acid film and its preparation method, CN105199348A discloses a kind of preparation method of high-strength high-toughness heat-resistant polylactic acid base film material etc., all are to adopt the blending of different materials so as to improve single Membrane performance. However, there are still few researches on degradable membrane materials prepared from other biomass polyesters. With the help of the performance matching and modification of different biomass polyesters, the processability and melt strength of the materials can be comprehensively adjusted, and the structural design can be used to realize the biodegradable membrane materials. The control of material crystallization and amorphous regions to achieve film materials with good transverse and longitudinal tensile and tear properties is a new research field for film material preparation.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a biaxially stretched biomass polyester film with excellent tensile and tear strength for the defects of poor biomass film strength and low tear strength.

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

A biaxially stretched biodegradable high-strength film is compounded from main materials and auxiliary materials and biaxially stretched into a film by melt extrusion.

The main materials include (lactic acid-trimethylene carbonate) copolymer, (ε-caprolactone-trimethylene carbonate) copolymer, hydroxybutyric acid valeric acid copolyester (PHBV), carboxyl-terminated hyperbranched poly Esters and acetate nanocellulose, the auxiliary materials include transesterification catalysts, composite processing aids, antioxidants, and fluorescent whitening agents.

Further, in the main material, the mass fraction of (lactic acid-trimethylene carbonate) copolymer is between 20-40 parts, and the mass fraction of (ε-caprolactone-trimethylene carbonate) copolymer is between Between 30-55 parts, the mass fraction of hydroxybutyrate valeric acid copolyester is between 25-40 fractions, the mass fraction of carboxyl-terminated hyperbranched polyester is between 5-10 fractions, acetate The mass fraction of the nanocellulose is between 3-6. Among the auxiliary materials, the mass fraction of the transesterification catalyst is between 0.8-1.6 parts, the mass fraction of the composite processing aid is between 3-6 fractions, and the mass fraction of the antioxidant is between 1-3 fractions Between, the mass fraction of fluorescent whitening agent is between 0.6-1.2.

Further, the (lactic acid-trimethylene carbonate) copolymer, also known as polylactic acid-polytrimethylene carbonate copolymer, has a molecular weight between 200,000-400,000, and preferably, the one with a molecular weight between 200,000-300,000 product.

Further, the (lactic acid-trimethylene carbonate) copolymer, wherein the molar ratio of lactic acid groups and trimethylene carbonate is between 70:30-55:45, its structural formula is as follows:

Among them, as a crystalline polymer, polylactic acid has good strength and hardness, but as the main component of the film, the film itself has high hardness, poor flexibility and low tear strength, especially the longitudinal tear strength. A certain amount of trimethylene carbonate can improve the flexibility and toughness on the basis of ensuring the hardness and strength of the film, and also help to adjust the crystallinity to balance the mechanical properties.

Further, the (lactic acid-trimethylene carbonate) copolymer can be purchased as a commercially available product, and can also be polymerized using organotin such as stannous octoate as a catalyst and lactide and trimethylene carbonate as monomers. made.

Further, the (ε-caprolactone-trimethylene carbonate) copolymer has a molecular weight between 150,000-300,000, preferably a product with a molecular weight between 200,000-300,000.

Further, the molar ratio of ε-caprolactone and trimethylene carbonate in the (ε-caprolactone-trimethylene carbonate) copolymer is between 40:60-60:40, and its structural formula is as follows:

Among them, ε-caprolactone has a large number of methylene groups, strong hydrophobicity, and certain crystallinity, while trimethylene carbonate has less crystallinity and greater flexibility. The copolymer of the two can effectively improve the polyε-caprolactone. The flexibility, tearability and tensile resilience of lactones are relatively flexible components in the formula.

Further, the molecular weight of the hydroxybutyrate valeric acid copolyester is between 80,000-150,000. Due to the existence of branched chains, the hydroxybutyrate valeric acid copolyester is beneficial to the improvement of the two-way tear strength of the material.

Further, the carboxyl-terminated hyperbranched polyester is a long-chain aromatic polyester, the number of carboxyl groups is between 10-50/mol, the hydroxyl value is less than 15, the acid value is between 200-350, and the molecular weight is between 4000 Between -10000, the molecular weight distribution is between 1.8-2.5. The carboxyl hyperbranched polyester has more carboxyl groups, which can be used as the core to effectively connect various components in the material, which is beneficial to the overall dispersion of each component and the local crystallization of the material. At the same time, the long-chain aromatic polyester itself has good flexibility and does not affect the overall flexibility of the film.

Further, the acetic acidified nanocellulose is a surface esterified modified product of nanocellulose crystallites, its degree of substitution with acetic acid is between 2-3, its length is between 50-200nm, and its aspect ratio is between Between 10-100. The surface modification of nanocellulose can adopt the esterification method. The introduction of surface acetate groups can increase the dispersion of nanocellulose in the material, improve its connection with the matrix, and improve its processability.

Further, the transesterification catalyst is one or more of tetrabutyl titanate, stannous octoate and dibutyltin dilaurate in any proportion. The transesterification catalyst can catalyze the transesterification reaction between polyester groups in a molten state to further improve the compatibility between components.

Further, the compound processing aid is a compound of cyclic butylene terephthalate and butyl stearate, and the mass ratio of the two is between 2:1-3:1. Among them, cyclic butylene terephthalate is a large molecular weight processing flow modifier, and butyl stearate is a small molecular processing flow modifier. The combined use of large molecular weight and small molecule flow modifiers is beneficial to improve the comprehensive fluidity of polymers, rigid substances and small molecules, and has the best processing improvement effect.

Among them, the structural formula of cyclic butylene terephthalate (CBT) is as follows:

This oligomer has a macrocyclic oligoester structure. After heating to an appropriate temperature, the viscosity is very low and has good fluidity. It can also improve the rheological properties of composite materials at lower temperatures, thereby improving blending and extrusion. time processing performance. In the presence of a catalyst, CBT can directly open the ring and react quickly to form polybutylene terephthalate (PBT) at a certain temperature (220°C-230°C). PBT itself has good toughness and is also conducive to the improvement of film toughness. improve. In the present invention, the best choice for cyclic butylene terephthalate is a masterbatch with a tin catalyst, such as the CBT®160 masterbatch of Cyclics.

Further, the preparation process of the biaxially stretched biodegradable high-strength film is:

1. All raw materials were vacuum-dried at 50°C for 24 hours and set aside;

2. After blending all raw materials at 50°C for 10 minutes at high speed, melt extrude and pelletize to obtain masterbatch A. The melt extrusion temperature is 220-240°C, the screw speed is 150-200rad/min, and the residence time is 2 -3 minutes;

3. Put the masterbatch A into the biaxially stretched film production line to form a film. The conditions are: extrusion temperature 220-250°C, casting temperature 30-50°C, longitudinal stretching temperature 100-120°C, stretch ratio between Between 3.4-4.2, the transverse stretching temperature is 55-80°C, the stretching ratio is between 3.0-3.5, and the heat treatment temperature is 210-230°C.

Further, the biaxially stretched biodegradable high-strength film is characterized in that: the transesterification catalyst is one or more of tetrabutyl titanate, stannous octoate, and dibutyltin dilaurate. Proportional mix.

Further, the antioxidant is one or more of antioxidant 264, BHT, 168,1010.

Further, the beneficial effect of the invention lies in: the preparation of the membrane takes three kinds of biomass copolymers as main components, (lactic acid-trimethylene carbonate) copolymer and (ε-caprolactone-trimethylene carbonate) The copolymer has better flexibility and tear strength than pure polylactic acid and polyε-caprolactone, among which (lactic acid-trimethylene carbonate) copolymer has better hardness and strength, (ε-caprolactone -trimethylene carbonate) copolymer has better flexibility, hydroxybutyrate valeric acid copolyester is used to adjust the tearing performance of the film, and the best comprehensive performance can be obtained after compounding the ratio of the three. In particular, the similar macromolecular structure of the three and the addition of carboxyl-terminated hyperbranched polyesters can effectively improve the overall compatibility of the material, and the carboxyl-terminated hyperbranched polyesters can also play a role in dispersing crystallization nuclei to improve the overall uniformity of the film. Performance and strength, acetate nanocellulose plays a further strengthening role, and the occurrence of transesterification reaction also further improves the uniformity of the material during processing. Finally, biaxial stretching leads to the orientation of biomass chains during processing, resulting in a degradable film with excellent strength, transverse and longitudinal tear strength.

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 biaxially stretched biodegradable high-strength film is compounded from main materials and auxiliary materials and biaxially stretched into a film by melt extrusion.

The main ingredients include (lactic acid-trimethylene carbonate) copolymer, (ε-caprolactone-trimethylene carbonate) copolymer, hydroxybutyric acid valeric acid copolyester, carboxyl-terminated hyperbranched polyester, acetic acid Esterified nano cellulose, the auxiliary materials include a transesterification catalyst, an antioxidant, a fluorescent agent and a whitening agent.

In the main material, the mass fraction of (lactic acid-trimethylene carbonate) copolymer is 25 parts, the mass fraction of (ε-caprolactone-trimethylene carbonate) copolymer is 40 parts, and the mass fraction of hydroxybutyrate pentamethylene The mass fraction of the acid copolyester is 32 parts, the mass fraction of the carboxyl-terminated hyperbranched polyester is 6.5 parts, and the mass fraction of the acetate nanocellulose is 4.5 parts. Among the auxiliary materials, the mass fraction of the transesterification catalyst is 1.5 parts, the mass fraction of the composite processing aid is 5 fractions, the mass fraction of the antioxidant is 1.5 fractions; the mass fraction of the fluorescent whitening agent is 1.2 fractions.

The molecular weight of the (lactic acid-trimethylene carbonate) copolymer is between 200,000-300,000, wherein the molar ratio of lactic acid groups and trimethylene carbonate is 65:35.

The molecular weight of the (ε-caprolactone-trimethylene carbonate) copolymer is between 200000-300000, wherein the molar ratio of ε-caprolactone and trimethylene carbonate is 50:50.

The molecular weight of the hydroxybutyrate valeric acid copolyester is between 100,000-150,000.

The carboxyl-terminated hyperbranched polyester is a long-chain aromatic polyester with a carboxyl number of 48/mol, a hydroxyl value of 12, an acid value of 230, a molecular weight of 9500, and a molecular weight distribution of 2.2.

The acetate nanocellulose is a surface modified product of nanocellulose microcrystals, its degree of substitution with acetic acid is 2.4, its length is between 50-200nm, and its aspect ratio is between 10-50.

The transesterification catalyst is stannous octoate.

The compound processing aid is a compound of cyclic butylene terephthalate and butyl stearate, and the mass ratio of the two is 2.5:1.

The preparation technology of described a kind of film is:

(1) Vacuum-dry all raw materials at 50°C for 24 hours and set aside;

(2) After blending all raw materials at 50°C for 10 minutes at high speed, melt extrude and pelletize to obtain masterbatch A. The melt extrusion temperature is 220-240°C, the screw speed is 150-200rad/min, and the residence time is 2-3 minutes;

(3) Put the masterbatch A into the biaxially stretched film production line to form a film. The conditions are: extrusion temperature 225-245°C, casting temperature 30-40°C, longitudinal stretching temperature 110°C, stretch ratio 3.8, transverse stretching temperature The stretching temperature is 65°C, the stretching ratio is 3.2, and the heat treatment temperature is 220°C.

The performance of its environmental protection film is shown in Table 1 below:

Example 2

A biaxially stretched biodegradable high-strength film is compounded from main materials and auxiliary materials and biaxially stretched into a film by melt extrusion.

The main ingredients include (lactic acid-trimethylene carbonate) copolymer, (ε-caprolactone-trimethylene carbonate) copolymer, hydroxybutyric acid valeric acid copolyester, carboxyl-terminated hyperbranched polyester, acetic acid Esterified nano cellulose, the auxiliary materials include a transesterification catalyst, an antioxidant, a fluorescent agent and a whitening agent.

In the main material, the mass fraction of (lactic acid-trimethylene carbonate) copolymer is 30 parts, the mass fraction of (ε-caprolactone-trimethylene carbonate) copolymer is 35 parts, and the mass fraction of hydroxybutyrate pentyl The mass fraction of the acid copolyester is 35 parts, the mass fraction of the carboxyl-terminated hyperbranched polyester is 8 mass fractions, and the mass fraction of the acetate nanocellulose is 5 fractions. Among the auxiliary materials, the mass fraction of the transesterification catalyst is 1 part, the mass fraction of the composite processing aid is 5 fractions, the mass fraction of the antioxidant is 2 fractions; the mass fraction of the fluorescent whitening agent is 1.2 fractions.

The molecular weight of the (lactic acid-trimethylene carbonate) copolymer is between 200,000-300,000, wherein the molar ratio of lactic acid groups and trimethylene carbonate is 70:30.

The molecular weight of the (ε-caprolactone-trimethylene carbonate) copolymer is between 200000-300000, wherein the molar ratio of ε-caprolactone and trimethylene carbonate is 50:50.

The molecular weight of the hydroxybutyrate valeric acid copolyester is between 80,000-150,000.

The carboxyl-terminated hyperbranched polyester is a long-chain aromatic polyester with a carboxyl number of 24/mol, a hydroxyl value of 12, an acid value of 240, a molecular weight of 5800, and a molecular weight distribution of 2.3.

The acetate nanocellulose is a surface modified product of nanocellulose microcrystals, its acetic acid substitution degree is 2.7, its length is between 50-200nm, and its aspect ratio is between 10-50.

The transesterification catalyst is a mass 1:1 mixture of stannous octoate and tetrabutyl titanate.

The compound processing aid is a compound of cyclic butylene terephthalate and butyl stearate, and the mass ratio of the two is 2.2:1.

The preparation technology of described a kind of film is:

(1) Vacuum-dry all raw materials at 50°C for 24 hours and set aside;

(2) After blending all raw materials at 50°C for 10 minutes at high speed, melt extrude and pelletize to obtain masterbatch A. The melt extrusion temperature is 220-240°C, the screw speed is 150-200rad/min, and the residence time is 2-3 minutes;

(3) Put the master batch A into the biaxially stretched film production line to form a film. The conditions are: extrusion temperature 235-245°C, casting temperature 40°C, longitudinal stretching temperature 110°C, stretching ratio 3.8, transverse stretching The temperature is 70°C, the draw ratio is 3.3, and the heat treatment temperature is 220°C.

The performance of its environmental protection film is shown in Table 1 below:

Table 1: Membrane properties of Examples 1 and 2

Composite properties Example 1 Example 2 Elongation at break (%) 123±4.2 98.6±5.1 Tensile strength (Mpa) 51.7±3.41 53.7±3.15 Transverse tear strength (kN/m) 246.5±7.3 264±10 Longitudinal tear strength (kN/m) 172.5±4.5 165.5±5.5

Claims (4)

1. a kind of biaxial tension biodegradable high-strength membrane, by major ingredient and auxiliary material compounding by melting extrusion biaxial tension into Film.It is characterized in that：The major ingredient includes（Lactic acid-trimethylene carbonate）Copolymer,（6-caprolactone-trimethylene carbonic acid Ester）Copolymer, hydroxybutyric acid valeric acid copolyesters, end carboxyl super branched polyester, acetic acid esterified nano-cellulose, the auxiliary material include A small amount of ester exchange catalyst, composite auxiliary for processing, antioxidant, fluorescent whitening agent；In major ingredient,（Lactic acid-trimethylene carbonate） The mass fraction of copolymer between 20-40 parts,（6-caprolactone-trimethylene carbonate）The mass fraction of copolymer between Between 30-55 parts, the mass fraction of hydroxybutyric acid valeric acid copolyesters between 25-40 parts, the matter of end carboxyl super branched polyester Between 5-10 parts, the mass fraction of acetic acid esterified nano-cellulose is between 3-6 parts for amount number；In auxiliary material, ester exchange The mass fraction of catalyst between 0.8-1.6 parts, the mass fraction of composite auxiliary for processing between 3-6 parts, antioxygen Between 1-3 parts, the mass fraction of fluorescent whitening agent is between 0.6-1.2 parts for the mass fraction of agent；

It is further characterized in that：It is described（Lactic acid-trimethylene carbonate）The molecular weight of copolymer between 200000-400000 it Between, wherein the molar ratio of lactic acid group and trimethylene carbonate is between 70：30-55：Between 45；It is described（6-caprolactone-three Carbonate）The molecular weight of copolymer between 150000-300000, middle 6-caprolactone and trimethylene carbonate Molar ratio is between 40：60-60:Between 40；The end carboxyl super branched polyester be long-Chain aromatic adoption ester, its carboxyl number between Between 10-50/mol, hydroxyl value be less than 15, acid number between 200-350, molecular weight between 4000-10000, molecular weight Distribution is between 1.8-2.5.

2. a kind of biaxial tension biodegradable high-strength membrane as claimed in claim 1, it is characterised in that：The acetic acid esterified Nano-cellulose is the surface esterification modifier of nano-cellulose crystallite, and its acetic acid substitution value between 2-3, receive by acetic acid esterified Between 50-200nm, draw ratio is between 10-100 for rice fiber length.

3. a kind of biaxial tension biodegradable high-strength membrane as claimed in claim 1, it is characterised in that：The Compound Machining Auxiliary agent is the compound of both cyclic butylene terephthalate, butyl stearate, and both mass ratioes are between 2：1-3：1 it Between.

4. a kind of biaxial tension biodegradable high-strength membrane as claimed in claim 1, it is characterised in that its preparation technology For：

（1）It is standby by all raw materials in being vacuum dried 24 hours at 50 DEG C；

（2）By all raw materials after 10min is blended at a high speed at 50 DEG C, melting extrusion, pelletizing obtains masterbatch A, its melting extrusion temperature It is 220-240 DEG C to spend, and screw speed is 150-200rad/min, and the residence time is 2-3 minutes；

（3）It is by film forming in masterbatch A input Biaxial Oriented Plastic Film Lines, its condition：220-250 DEG C of extrusion temperature, curtain coating temperature Degree 30-50 DEG C, 100-120 DEG C of longitudinal drawing temperature, draw ratio between 3.4-4.2,55-80 DEG C of transverse drawing temperature, draw Stretch than between 3.0-3.5,210-230 DEG C of heat treatment temperature.