CN113150520B

CN113150520B - Biodegradable plastic for disposable spoon

Info

Publication number: CN113150520B
Application number: CN202110456480.2A
Authority: CN
Inventors: 翁云宣; 张彩丽; 宋鑫宇
Original assignee: Beijing Technology and Business University
Current assignee: Beijing Technology and Business University
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2022-08-16
Anticipated expiration: 2041-04-26
Also published as: CN113150520A

Abstract

The invention discloses biodegradable plastic for a disposable spoon, and belongs to the field of bio-based high polymer materials. The invention adopts a one-step method to compound six components of polylactic acid, PBAT, bamboo powder, a chain extender, epoxidized soybean oil and sebacic acid to prepare the high-toughness biodegradable material. The method has the advantages that the conversion of the composite material from brittleness to toughness is realized by simply regulating and controlling the content of PBAT, the problems of poor compatibility, low impact strength, poor processing fluidity and the like of the polylactic acid/bamboo powder composite material are solved, and the high-impact polylactic acid/bamboo powder composite material can be prepared, and has the tensile strength of 20-38 MPa, the elongation at break of 2-20 percent and the impact strength of 10-20 KJ/m ² Compared with the unmodified polylactic acid/bamboo powder composite material, the impact strength is improved by 3 times after modification. In addition, due to the improvement of processing fluidity, the spoon formed by injection molding of the added formula does not have the defects of cavities, bubbles and the like.

Description

Biodegradable plastic for disposable spoon

Technical Field

The invention discloses a preparation method of biodegradable plastic for a disposable spoon, and belongs to the field of green biodegradable materials.

Background

Polylactic acid is a thermoplastic bio-based polymer material synthesized from renewable resources, has excellent biocompatibility and compost degradability, and is widely applied to packaging materials and biomedical materials. However, the problems of low heat distortion temperature, high brittleness, high cost and insufficient impact strength of polylactic acid limit the large-scale industrial application thereof. Research on high-performance and low-cost polylactic acid materials has received much attention. Polybutylene terephthalate-adipate (PBAT) has the characteristics of PBA and PBT, and has better ductility and elongation at break as well as better heat resistance and impact property; in addition, the biodegradable plastic has excellent biodegradability, and is one of the best degradable materials for the active research and market application of biodegradable plastics. The bamboo material belongs to fast growing wood, and the bamboo fiber powder film obtained from the bamboo material has the advantages of high strength, narrow included angle of superfine fibers, low cost and the like. Therefore, the bamboo powder can be used as the reinforcing fiber of the polylactic acid, so that the impact strength and the heat distortion temperature of the polylactic acid are improved, and the material cost is reduced to a certain extent. However, the bamboo powder contains a large amount of hydrophilic groups such as alcoholic hydroxyl and phenolic hydroxyl on the surface, so that the polarity and the hydrophilicity of the bamboo powder are high, and when the bamboo powder is compounded with non-polar polylactic acid, the bamboo powder is gathered together and is difficult to uniformly disperse in a polylactic acid matrix. In addition, the unmodified bamboo powder particles have large frictional resistance, so that the melt flowability is poor, and the processing and the forming are difficult. Therefore, the difficulty in developing a high-performance polylactic acid/bamboo powder composite material is to improve the interface compatibility between the polylactic acid matrix and the bamboo powder so as to obtain a product with excellent comprehensive performance.

Methods to improve interfacial compatibility include bamboo powder surface pretreatment (physical or chemical modification) and addition of compatibilizers (reactive and non-reactive). The surface pretreatment of the bamboo powder can change the surface morphology of the fiber and remove components (such as pectin, hemicellulose, lignin, parenchyma cells and the like) which have negative influence on the interface bonding strength. The addition of the compatibilizer can improve the interfacial bonding force among the components and improve the compatibility of the components. At present, the most common method for the surface pretreatment of bamboo powder is alkali treatment. Although the contact area between the blast furnace and the polylactic acid matrix can be effectively improved, more hydrophilic groups can be generated by alkaline hydrolysis, the operation process is time-consuming and complicated, and a large amount of waste liquid can be generated, so that certain pollution is caused to the environment. The addition of the compatibilizer (including reactive and non-reactive compatibilizers) can reduce the processing flow, and is simple and efficient. Therefore, the addition of proper types and dosage of the compatibilizer is the main research and development direction for improving the performance of the polylactic acid/bamboo powder composite material.

The vegetable oil is a green raw material with rich source and low price, the compatibility of the material obtained by directly blending the epoxidized soybean oil and the polylactic acid/bamboo powder is improved to a certain extent, but small molecules of the epoxidized soybean oil can migrate to the surface of the material along with the prolonging of time to cause the phenomena of stickiness and the like on the surface of a product, and the long-term use of the product is not facilitated. Sebacic acid is a long-chain fatty acid, is obtained by catalytically hydrolyzing castor oil, is a bio-based monomer derived from renewable resources, and is the same as epoxidized soybean oil. The epoxidized soybean oil, the sebacic acid and the polylactic acid are simultaneously added into an internal mixer for mixing, and the tensile property of the obtained polylactic acid material is greatly improved.

Disclosure of Invention

Based on the reasons, the invention adopts a one-step method to mix six components of PLA, PBAT, bamboo powder (BF), a chain extender (ADR), Epoxidized Soybean Oil (ESO) and Sebacic Acid (SA) to prepare the high-toughness biodegradable composite material. The method has the advantages that the conversion of the composite material from brittleness to toughness is realized by simply regulating and controlling the content of PBAT, so that the composite material suitable for injection molding of the disposable spoon can be obtained.

A fully-degradable composite material for a disposable spoon is composed of the following raw materials in percentage by weight:

polylactic acid: 40-80 parts;

bamboo powder: 10-50 parts;

PBAT: 10-40 parts;

chain extender: 0-2 parts of a solvent;

epoxidized soybean oil: 0-5 parts;

sebacic acid: 0 to 2 parts.

Wherein the sum of the weight of the polylactic acid, the bamboo powder and the PBAT is 100 parts.

The preparation process of the fully-degradable composite material for the disposable spoon comprises the following steps: firstly, adding polylactic acid (PLA), polybutylene terephthalate (PBAT), bamboo powder, a chain extender (ADR), epoxidized soybean oil and sebacic acid into a high-speed mixer, uniformly mixing at normal temperature, adding into a double-screw extruder, and performing melt extrusion, bracing, air cooling and granulation to obtain the fully biodegradable composite material.

The temperature of the double-screw extruder is controlled to be 180-190 ℃, and the rotating speed is controlled to be 80-150 rpm; the length-diameter ratio of the screw is 32: 1-45: 1.

The fully-degradable composite material for the disposable spoon has excellent mechanical property and processing property, and can be used in the field of food contact materials such as knife, fork and spoon due to the renewable and degradable raw materials and the characteristics of no toxicity and greenness.

Compared with the prior art, the fully-degradable composite material for the disposable spoon has the following outstanding advantages: all the raw materials used in the invention have biodegradability, have the characteristics of environmental protection and degradability after being discarded, and have positive promotion significance for sustainable development of environment and society. The epoxidized soybean oil-graft-sebacic acid oligomer formed by the epoxidized soybean oil and the sebacic acid in the double-screw extrusion process has the functions of a toughening agent, a compatilizer and an impact modifier, so that the compatibility of PLA and PBAT with bamboo powder is increased; the addition of the chain extender can effectively solve the compatibility of PLA and PBAT. The invention simply and efficiently solves the problems of poor compatibility between PLA and PBAT and between the PLA and PBAT and bamboo powder, low impact strength, poor processing fluidity and the like.

The material has the tensile strength of 20-38 MPa, the elongation at break of 2-20 percent and the impact strength of 10-20 KJ/m ² Compared with the unmodified polylactic acid/bamboo powder composite material, the impact strength is improved by 3 times after modification. In addition, due to the improvement of processing fluidity, the spoon formed by injection molding of the added formula does not have the defects of cavities, bubbles and the like.

Detailed Description

Comparative examples and preferred examples of the present invention will be described in detail below.

TABLE 1 proportions of the components of the present invention

Comparative example 1

Comparative example 1 is a polylactic acid/bamboo powder composite system without PBAT, epoxidized soybean oil, sebacic acid, and a chain extender. The preparation method comprises the following steps: adding polylactic acid and bamboo powder into a double-screw extruder according to the weight ratio of 70:30, carrying out melt extrusion, bracing, air cooling and granulation to obtain the polylactic acid/bamboo powder composite material, wherein the temperature of the double-screw extruder is controlled to be 180-190 ℃. Comparative example 1 had a tensile strength of 38.32MPa, an elongation at break of 1.65%, and an unnotched impact strength of 5.8KJ/m for a simply supported beam ² . It can be seen that the polylactic acid/bamboo powder composite material before modification has large brittleness and low impact strength, and is not suitable for production of injection molding parts.

The following examples are to improve the toughness and impact resistance of the polylactic acid/bamboo powder composite material by adding different components of PBAT, while adding 0.7 part of chain extender, 2.7 parts of epoxidized soybean oil and 0.3 part of sebacic acid as compatilizers.

Example 1

PLA, bamboo powder, PBAT, ADR, ESO and SA are mixed according to the weight ratio of 60:10:30:0.7:2.7:0.3, then double screws are added for melt extrusion, bracing, air cooling and granulation, and the fully degradable composite material is obtained, wherein the temperature of a double screw extruder is controlled to be 180-190 ℃. Example 1 had a modulus of 3746.4MPa, a tensile strength of 37.45MPa, an elongation at break of 9.83%, and an unnotched impact strength of 10.91KJ/m for a simply supported beam ² 。

Example 2

PLA, bamboo powder, PBAT, ADR, ESO and SA are mixed according to the weight ratio of 50:20:30:0.7:2.7:0.3, then double screws are added for melt extrusion, bracing, air cooling and granulation, and the fully degradable composite material is obtained, wherein the temperature of a double screw extruder is controlled to be 180-190 ℃. Example 2 had a modulus of 3012.6MPa, a tensile strength of 31.25MPa, an elongation at break of 13.62%, and an unnotched impact strength of 12.31KJ/m for a simply supported beam ² 。

Example 3

PLA, bamboo powder, PBAT, ADR, ESO and SA are mixed according to the weight ratio of 50:20:30:0.7:2.7:0.3, then double screws are added for melt extrusion, bracing, air cooling and granulation, and the fully degradable composite material is obtained, wherein the temperature of a double screw extruder is controlled to be 180-190 ℃. Example 3 had a modulus of 1940.8MPa, a tensile strength of 24.21MPa, an elongation at break of 19.06%, and an unnotched impact strength of 18.55KJ/m for a simply supported beam ² 。

All the mechanical property data of examples 1 to 3 are shown in table 2. From the results, it can be seen that as the content of PBAT increases, the tensile modulus and tensile strength of the composite gradually decrease, and the elongation at break and impact strength gradually increase. Table 2 shows the melt indexes of examples 1 to 3, wherein the higher the melt index is, the better the melt fluidity during injection molding is, and the processing fluidity does not change much with the increase of PBAT content in the examples, but the melt indexes of all the composite materials added with PBAT are larger than those of the composite materials not added with PBAT. The addition of the PBAT can ensure that injection molding parts can not have defects of cavities, bubbles and the like. Therefore, the addition of PBAT, epoxidized soybean oil, sebacic acid and a chain extender obviously improves the interfacial compatibility of the polylactic acid/bamboo powder system and simultaneously plays a role of a toughening agent, a compatilizer and an impact modifier.

TABLE 2 mechanical Properties of composites of different formulations

TABLE 3 melt index for composite materials of different formulations

Finally, it is noted that the above-mentioned preferred examples are merely intended to illustrate rather than to limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. The biodegradable plastic for the disposable spoon is characterized by comprising the following raw materials in percentage by weight:

polylactic acid: 40-60 parts;

bamboo powder: 30 parts of a binder;

PBAT: 10-30 parts;

chain extender: 0.7 part;

epoxidized soybean oil: 2.7 parts;

sebacic acid: 0.3 part;

the sum of the weight of the polylactic acid, the bamboo powder and the PBAT is 100 parts;

the preparation method of the biodegradable plastic for the disposable spoon comprises the following steps: firstly, completely adding polylactic acid, PBAT, bamboo powder, a chain extender, epoxidized soybean oil and sebacic acid into a high-speed mixer, uniformly mixing at normal temperature, adding into a double-screw extruder, carrying out melt extrusion, bracing, air cooling and granulation to obtain the biodegradable plastic for the disposable spoon;

controlling the temperature of the double-screw extruder to be 180-190 ℃ and controlling the rotating speed to be 80-150 rpm; the length-diameter ratio of the screw is 32: 1-45: 1.

2. Use of the biodegradable plastic of claim 1 in the preparation of a disposable spoon food contact material.