Preparation method of spherical particle reinforced starch plastic

Abstract

The invention relates to a preparation method of spherical particle reinforced starch plastic, and belongs to the field of biodegradable plastic. The method comprises the following steps: firstly, uniformly mixing starch with lactic acid, maleic anhydride and succinic anhydride in a certain proportion, and then preparing the thermoplastic starch plastic by a reactive extrusion (single-screw or double-screw extruder) method. The spherical particle reinforced starch plastic can be obtained through the method, the tensile strength of the spherical particle reinforced starch plastic is improved by about 4-30 times, the spherical particle reinforced starch plastic shows high tensile strength and certain fracture toughness, and the spherical particle reinforced starch plastic further has complete biodegradability and is expected to be applied to the fields of disposable tableware, packaging, agricultural plastic mulching films, medical consumables and the like.

Description

Technical Field

[0001] The invention belongs to the field of biodegradable plastics and relates to a method for preparing spherical particle reinforced starch plastics. Background Art

[0002] In recent years, in order to solve the white pollution problem caused by the non-degradable petroleum-based plastics, the research and development of biodegradable plastics based on renewable resources has become a hot topic in the world today, in order to gradually replace petroleum-based plastics.

[0003] Starch is a polysaccharide bio-based polymer material widely distributed in nature. It has the advantages of environmental sustainability, low cost and biodegradability. It is widely present in the seeds and rhizomes of plants such as corn, wheat, and potatoes. It is mainly composed of two types of glucan polymers, such as amylose and amylopectin, and can be used as the best choice for biodegradable plastic raw materials. However, due to the effect of hydrogen bonds between natural starch macromolecules, it has a high degree of crystallinity and cannot be thermoplastic processed. For this reason, plasticizers are usually added to starch and the crystalline structure is destroyed under the action of high temperature and shear force, so that the starch macromolecules are transformed into an amorphous state, which can be thermoplastic processed, so it is called thermoplastic starch plastic. The mechanical properties of starch plastics prepared by traditional plasticizers (such as glycerol) are poor, which limits its application. For this reason, improving the mechanical properties of thermoplastic starch plastics has become the key to broadening its application.

[0004] Adding reinforcement to thermoplastic starch plastics is one of the effective ways to improve its mechanical properties. Patent No. CN109232998B discloses a chain SiO 2 Preparation method of reinforced thermoplastic starch plastic, using sol-gel method to prepare a chain SiO 2 The reinforcement, and then urea as plasticizer, starch and chain SiO 2 Thermoplastic starch plastics were obtained by extrusion and injection molding of reinforcements. The mechanical properties and hydrophobicity of the thermoplastic starch plastics obtained by this method were significantly improved. When 1% by weight of reinforcement was added, the tensile strength was the highest and the water surface contact angle was also improved to a certain extent. However, the disadvantage of this method is that the chain SiO 2 The preparation process of the reinforcement is cumbersome, and the toughness of urea-plasticized thermoplastic starch is poor, which is not conducive to application. Therefore, exploring particle-reinforced starch plastics with simple and easy preparation process is an important direction in this field.

[0005] At present, in addition to polyols and amines such as glycerol, ethylene glycol and urea, organic acids or anhydrides such as maleic anhydride are also used as plasticizers in thermoplastic starch plastics. In the process of exploring the use of organic acids or anhydrides to prepare starch plastics, the inventor unexpectedly discovered a method for preparing particle-reinforced starch plastics, namely: when lactic acid, maleic anhydride and succinic anhydride are used simultaneously to prepare starch plastics through reactive extrusion, spherical particles are formed inside the plastic, which can significantly improve the tensile strength of starch plastics while maintaining a certain fracture toughness. Based on the above findings, the present invention is completed.

[0006] Therefore, the present invention provides a method for preparing spherical particle reinforced starch plastic.

[0007] Specifically, the spherical particle reinforced starch plastic of the present invention is composed of the following components by weight:

[0008]

[0009] The specific method adopted by the present invention is:

[0010] 80 parts of starch, 10 parts of lactic acid, 4-12 parts of maleic anhydride and 8-16 parts of succinic anhydride are uniformly mixed in a container; extrusion granulation is carried out in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressing is carried out in a hot press at a temperature of 100°C to obtain spherical particle reinforced starch plastic.

[0011] The present invention has the advantages that:

[0012] 1) Starch, lactic acid, maleic anhydride and succinic anhydride are widely available, non-toxic and pollution-free, and have low cost;

[0013] 2) The tensile strength of starch plastics prepared with lactic acid, maleic anhydride and succinic anhydride is significantly improved while maintaining a certain fracture toughness;

[0014] 3) The starch plastic prepared from starch, lactic acid, maleic anhydride and succinic anhydride maintains complete biodegradability as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Scanning electron microscope image of a cross section of a spherical particle reinforced starch plastic DETAILED DESCRIPTION

[0016] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0017] In the following examples and comparative examples, the starch plastic film obtained by the hot press was cut into standard samples of 40×10×0.6 mm and measured using an E44.304 electronic universal testing machine produced by MTS Industrial Systems (China) Co., Ltd. at a tensile rate of 50 mm / min.

[0018] Embodiment 1:

[0019] 80 parts of starch, 10 parts of lactic acid, 12 parts of maleic anhydride and 8 parts of succinic anhydride are uniformly mixed in a container; extruded into granules in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressed in a hot press at a temperature of 100°C to obtain spherical particle reinforced starch plastic.

[0020] Embodiment 2:

[0021] 80 parts of starch, 10 parts of lactic acid, 8 parts of maleic anhydride and 12 parts of succinic anhydride are uniformly mixed in a container; extruded into granules in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressed in a hot press at a temperature of 100°C to obtain spherical particle reinforced starch plastic.

[0022] Embodiment 3:

[0023] 80 parts of starch, 10 parts of lactic acid, 4 parts of maleic anhydride and 16 parts of succinic anhydride are uniformly mixed in a container; extruded into granules in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressed in a hot press at a temperature of 100°C to obtain spherical particle reinforced starch plastic.

[0024] Comparative Example 1:

[0025] 80 parts of starch, 10 parts of lactic acid and 20 parts of maleic anhydride are uniformly mixed in a container; extruded into granules in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressed in a hot press at a temperature of 100°C to obtain thermoplastic starch plastic.

[0026] Table 1

[0027] Mechanical properties Example 1 Example 2 Example 3 Comparative Example 1 Tensile strength(MPa) 0.795 2.46 5.54 0.17 Elongation at break (%) 217 130 81.4 236

[0028] Table 1 shows the tensile strength and elongation at break of each embodiment and comparative example. The test data show that the tensile strength of the starch plastic prepared by using lactic acid, maleic anhydride and succinic anhydride at the same time is significantly better than that of the thermoplastic starch plastic prepared by using only lactic acid and maleic anhydride in comparative example 1, while maintaining a certain elongation at break; Figure 1This is a scanning electron microscope image of the fracture surface of the starch plastic, which further confirms that the mechanism of this method to enhance the starch plastic is the formation of spherical particles, and with the increase in the amount of succinic anhydride, the size of the spherical particles gradually increases, and the enhancement effect is significantly improved. Compared with the comparative example 1 without using succinic anhydride, the tensile strength can be increased by 4 to 30 times.

Claims

1. A method for preparing spherical particle reinforced starch plastic, characterized in that: Spherical particle reinforced starch plastic is obtained according to the following steps: 80 parts of starch, 10 parts of lactic acid, 4-12 parts of maleic anhydride and 8-16 parts of succinic anhydride are uniformly mixed in a container; extrusion granulation is carried out in a single-screw or twin-screw extruder, the temperature of each temperature zone of the extruder is 110°C, and the rotation speed is 25-35r / min; hot pressing is carried out in a hot press at a temperature of 100°C to obtain spherical particle reinforced starch plastic.

Images