CN112029153A - A kind of environment-friendly starch-based foaming material and preparation method thereof - Google Patents

Abstract

The invention relates to an environment-friendly starch-based foaming material and a preparation method thereof, belonging to the technical field of biodegradable foaming materials. The starch-based foaming material is prepared from the following components in parts by weight: 100 parts of starch, 20-60 parts of glycerin, 0-10 parts of water, and 0-30 parts of ethylene-vinyl alcohol copolymer. The invention uses water as the foaming agent, and the prepared biodegradable foaming material is safe, non-toxic, light in weight, excellent in comprehensive mechanical properties and water resistance, and biodegradable. The preparation method is simple, easy to control and implement, has strong operability and low production cost, and can be applied to various fields of filling or buffering.

Description

A kind of environment-friendly starch-based foaming material and preparation method thereof

technical field

The invention belongs to the technical field of biodegradable foaming materials, and particularly relates to an environment-friendly starch-based foaming material and a preparation method thereof.

Background technique

Polymer foam materials have a huge market in the fields of packaging, transportation and heat preservation because of their good thermal insulation properties and buffering properties. Traditional foam materials are mostly made of general-purpose plastics such as polyolefins, but they are not degradable, which will cause serious pollution to the environment after they are discarded. Therefore, it is very important to prepare environmentally friendly foam materials from biodegradable materials. As a natural polymer material, starch has the advantages of low cost, recyclability and complete degradability. The preparation of foamed materials with starch can reduce the white pollution caused by general-purpose plastics, which is in line with the current concept of environmental protection and sustainability, and has attracted widespread attention. However, the current thermoplastic starch foaming materials have poor comprehensive performance and water resistance, which limits their large-scale market applications. Therefore, adding ethylene-vinyl alcohol copolymer (EVOH) with excellent barrier properties and water resistance to prepare starch-based foamed materials with excellent performance, low cost and good water resistance can significantly increase its application range.

In the prior art, the Chinese patent application "a starch foaming disposable tableware" with the application number of 201610971285.2 discloses a starch-based foaming material prepared by using modified corn starch, wood pulp fibers and modified rice husks, etc. Compared with the traditional disposable foaming material, it conforms to the strategy of environmental protection and sustainable development, but from the analysis of the formula, its overall water resistance is not ideal, and it is difficult to be promoted as a disposable tableware application, and the molding process is not suitable for starch. For base foaming, its stability is poor. The Chinese patent application "starch foaming product and its preparation method" with the application number of 201710015666.8 discloses a preparation method of starch or modified starch and a starch foaming material containing a nucleating agent, and the preparation process of the foaming material is a twin screw Extrusion foaming is easy to prepare, but the prepared starch foaming material has serious easy water absorption, which is not conducive to practical application. Chinese patent application No. 201710309478.6 "Completely biodegradable fiber-reinforced starch foaming tableware and preparation method thereof" and Chinese patent application No. 201610650903.3 "Starch foaming formula and foaming method" disclose The preparation method of blending and modifying thermoplastic starch with biodegradable polymer materials greatly increases the cost of raw materials, but the comprehensive properties such as compatibility, water resistance, cost performance and processing technology between the components of the composite materials need to be improved .

In China, the production of starch crops is huge, and the preparation of starch-based foaming materials with starch as the base material is an effective way to improve the non-edible value of starch, reduce costs and reduce environmental pollution. However, the field lacks a starch-based foaming material with excellent mechanical properties, good water resistance and simple preparation process. Therefore, there is an urgent need to seek a polymer material with excellent water resistance and good compatibility with starch, and to further improve the processing technology of starch-based foaming materials to improve its mechanical properties and water resistance, and improve the comprehensive performance of foamed materials. At the same time, the low cost is guaranteed.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide an environment-friendly starch-based foaming material.

Another object of the present invention is to provide a preparation method of an environmentally friendly starch-based foaming material.

The object of the present invention is achieved by the following solutions.

An environment-friendly starch-based foaming material comprises the following components by weight: 100 parts of starch, 20-60 parts of glycerin, 0-5 parts of water, and 0-20 parts of ethylene-vinyl alcohol copolymer.

Described a kind of preparation method of environment-friendly starch-based foaming material, comprises the following steps:

(1) Add the dried starch and glycerin into a high-speed mixer for uniform blending and plasticization, and then melt extrusion and granulation through a twin-screw extruder to obtain thermoplastic starch granules;

(2) Add ethylene-vinyl alcohol copolymer (EVOH) and glycerin into a beaker to blend evenly, then plasticize at high temperature, take out for cooling, pulverize and granulate, and seal for storage to obtain plasticized EVOH pellets;

(3) The thermoplastic starch granules obtained in step (1) and the plasticized EVOH granules obtained in step (2) were added to a high-speed mixer for uniform blending, and then melted and extruded through a twin-screw extruder for granulation. After humidity conditioning treatment, foamable starch-based pellets are obtained;

(4) adding the foamable starch-based granules obtained in step (3) into an injection molding machine for melting and injection, and then adjusting the humidity to obtain a starch-based foaming material.

Preferably, the starch described in step (1) is tapioca starch, the temperature of drying starch is 50-100 ° C, the drying time is 5-72 h, and the mass ratio of the starch to glycerol is 100:30 to 100: 50.

Preferably, the starch plasticization in step (1) is plasticized in a drying oven at 10-50° C. for 12-72 h.

Preferably, the twin-screw extruder described in step (1) and step (3) is a co-rotating twin-screw extruder, the extrusion temperature is 130-180 ° C, the frequency of the main engine is 10 Hz, and the feeding frequency is 5 Hz.

Preferably, the content of glycerin for plasticizing EVOH described in step (2) is 5-40%.

Preferably, the high-temperature plasticization of EVOH described in step (2) is placed at a temperature of 150-200° C. and stirred for 1-5 h.

Preferably, the mass ratio of the plasticized starch to the plasticized EVOH described in step (3) is 100:5 to 100:20.

Preferably, the humidity conditioning treatment described in step (3) is placed under the conditions of a temperature of 25-60° C. and a relative humidity of 40-90% for 1-60 minutes, then sealed, and allowed to stand at room temperature for 5-48 hours. The purpose is to make the foaming agent water evenly dispersed in the pellets to obtain foamable pellets.

Preferably, the humidity conditioning treatment described in step (4) is placed under the conditions of a temperature of 25-60° C. and a relative humidity of 40-90% for 10-90 min, then sealed, and allowed to stand at room temperature for 5-48 h, The purpose is to make the water evenly dispersed in the starch-based foaming material to obtain starch-based foaming material with better performance.

The above-mentioned environmentally friendly starch-based foaming material is safe and non-toxic, has a simple preparation process, excellent mechanical properties, good water resistance and is biodegradable.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. In the starch-based foaming material prepared by the present invention, EVOH is uniformly dispersed in the thermoplastic starch, and the strengthening effect of EVOH on the thermoplastic starch is fully exerted, which is beneficial to improve the moisture resistance and mechanical properties of the starch-based foaming material.

2. The moisture-conditioning treatment of starch-based foaming materials can significantly improve the mechanical properties of starch-based foaming materials.

3. The main components in the material used in the present invention are starch and glycerol, which are environmentally friendly materials.

4. The starch-based foaming material of the present invention has the advantages of simple preparation method, easy control, strong operability, low production cost, high production efficiency, easy industrialized large-scale production, good economic benefit and broad application prospect.

Detailed ways

The present invention will be described in further detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

The reagents used in the following examples were all obtained from commercial sources and were dried before use.

Example 1

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) The thermoplastic starch granules obtained in (1) are placed under the conditions of a temperature of 50°C and a relative humidity of 80% for 12 minutes, and then sealed at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Example 2

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of plasticized EVOH pellets

Weigh 200 g of EVOH and 40 g of glycerol, add 40 g of glycerol to 200 g of EVOH in 4 times and mix evenly, stir and melt at 180 °C for 1 h, take out, cool, pulverize, granulate, and store in a sealed container to obtain plasticized EVOH pellets. material.

(3) Preparation of starch-based foaming materials

a) Weigh 1000 g of thermoplastic starch pellets obtained in (1) and 100 g of plasticized EVOH pellets obtained in (2) into a high-speed mixer, stir for 10 min, and then melt and extrude through a twin-screw extruder , the extruded strips were cooled and pelletized, and then placed under the conditions of a temperature of 50 °C and a relative humidity of 80% for 12 minutes of humidity treatment, and sealed at room temperature for 24 hours to obtain expandable starch-based pellets; among them, the twin-screw The output frequency of the main inverter of the extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feeding port to the head) is set between 130-180 °C;

b) Add the foamable starch-based granules obtained in a) into an injection molding machine for injection foaming, and then place it at 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the starch-based foaming material becomes soft, and then put it in an injection molding machine for foaming. After standing at room temperature for 24 h, starch-based foaming materials with excellent performance were obtained; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) was respectively set between 130-180 °C.

Comparative Example 1

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) Place the thermoplastic starch granules obtained in (1) under the conditions of a temperature of 50°C and a relative humidity of 80% for 8 minutes, and then seal them at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Comparative Example 2

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) The thermoplastic starch granules obtained in (1) are placed under the conditions of a temperature of 50°C and a relative humidity of 80% for 16 minutes, and then sealed at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Comparative Example 3

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) Place the thermoplastic starch granules obtained in (1) under the conditions of a temperature of 50°C and a relative humidity of 80% for 60 minutes, and then seal at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Comparative Example 4

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and add 350 g of glycerol to the high-speed mixer for blending in 4 times, each time for 180 s, and continue to stir for 10 min, and then put it at 30 °C for plasticization 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) The thermoplastic starch granules obtained in (1) are placed under the conditions of a temperature of 50°C and a relative humidity of 80% for 12 minutes, and then sealed at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Comparative Example 5

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, add 500 g of glycerin into the high-speed mixer in 4 times for blending, each blending for 180 s, continue stirring for 10 min, and then put it at 30 °C for plasticization 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of thermoplastic starch foaming material

a) The thermoplastic starch granules obtained in (1) are placed under the conditions of a temperature of 50°C and a relative humidity of 80% for 12 minutes, and then sealed at room temperature for 24 hours to obtain expandable thermoplastic starch granules;

b) Add the foamable thermoplastic starch granules obtained in a) into an injection molding machine for injection foaming, and then place it under the conditions of a temperature of 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the foamed material becomes soft, and then put it at room temperature. Let stand for 24 h to obtain a thermoplastic starch foaming material; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) is respectively set between 130-180 °C.

Comparative Example 6

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of plasticized EVOH pellets

Weigh 200 g of EVOH and 40 g of glycerol, add 40 g of glycerol to 200 g of EVOH in 4 times and mix evenly, stir and melt at 180 °C for 1 h, take out, cool, pulverize, granulate, and store in a sealed container to obtain plasticized EVOH pellets. material.

(3) Preparation of starch-based foaming materials

a) Weigh 1000 g of thermoplastic starch pellets obtained in (1) and 50 g of plasticized EVOH pellets obtained in (2) into a high-speed mixer, stir for 10 min, and then melt and extrude through a twin-screw extruder , the extruded strips were cooled and pelletized, and then placed under the conditions of a temperature of 50 °C and a relative humidity of 80% for 12 minutes of humidity treatment, and sealed at room temperature for 24 hours to obtain expandable starch-based pellets; among them, the twin-screw The output frequency of the main inverter of the extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feeding port to the head) is set between 130-180 °C;

b) Add the foamable starch-based granules obtained in a) into an injection molding machine for injection foaming, and then place it at 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the starch-based foaming material becomes soft, and then put it in an injection molding machine for foaming. After standing at room temperature for 24 h, starch-based foaming materials with excellent performance were obtained; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) was respectively set between 130-180 °C.

Comparative Example 7

(1) Preparation of thermoplastic starch

a) The starch raw material was dried in an electric blast drying oven at 75°C for 24 hours and then sealed and stored to obtain dry starch;

b) Put 1000 g of dry starch into the high-speed mixer, and 400 g of glycerin are added to the high-speed mixer for blending in 4 times, each blending for 180 s, and stirring for 10 min, and then plasticizing at 30 °C 24 h, and then melted and extruded through a twin-screw extruder, and the extruded strips were cooled and pelletized, and then sealed and stored to obtain thermoplastic starch pellets; among them, the output frequency of the host inverter of the twin-screw extruder was 10. Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feed port to the head) is set between 130-180 °C.

(2) Preparation of plasticized EVOH pellets

Weigh 200 g of EVOH and 40 g of glycerol, add 40 g of glycerol to 200 g of EVOH in 4 times and mix evenly, stir and melt at 180 °C for 1 h, take out, cool, pulverize, granulate, and store in a sealed container to obtain plasticized EVOH pellets. material.

(3) Preparation of starch-based foaming materials

a) Weigh 1000 g of thermoplastic starch pellets obtained in (1) and 200 g of plasticized EVOH pellets obtained in (2) into a high-speed mixer, stir for 10 min, and then melt and extrude through a twin-screw extruder , the extruded strips were cooled and pelletized, and then placed under the conditions of a temperature of 50 °C and a relative humidity of 80% for 12 minutes of humidity treatment, and sealed at room temperature for 24 hours to obtain expandable starch-based pellets; among them, the twin-screw The output frequency of the main inverter of the extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of the extrusion area (from the feeding port to the head) is set between 130-180 °C;

b) Add the foamable starch-based granules obtained in a) into an injection molding machine for injection foaming, and then place it at 50 °C and a relative humidity of 80% to adjust the humidity until the surface of the starch-based foaming material becomes soft, and then put it in an injection molding machine for foaming. After standing at room temperature for 24 h, starch-based foaming materials with excellent performance were obtained; wherein, the temperature of the extrusion zone (from the feeding port to the injection port) was respectively set between 130-180 °C.

The starch-based foamed materials obtained in Examples 1-2 and Comparative Examples 1-7 were cut to prepare mechanical property test specimens.

Tensile property test: According to GB 6344-1986 "Determination of Tensile Strength and Elongation at Break of Flexible Foamed Polymers", the tensile property test was carried out at room temperature using a computer-controlled electronic universal testing machine, and the tensile rate was 20 mm/min. At least five splines are selected for each group of samples for testing, and the average value is obtained. The test results are shown in Table 1.

Compression performance test: Test according to GB/T 1041-1992 standard. The tensile properties were tested with a computer-controlled electronic universal testing machine at room temperature with a compression rate of 2 mm/min. The compressive strength σ _m (KPa) is calculated by the following formula:

（1）

(1)

In the formula: F _m is the maximum compressive force (KN); S ₀ is the initial area of the sample cross-section (mm ² ). At least five splines are selected for each group of samples for testing, and the average value is obtained. The test results are shown in Table 1.

Water absorption test: The samples were first dried at 40 °C for 24 h, sealed and cooled for 24 h, and weighed. They were then placed in distilled water at room temperature. After a specified immersion period, the samples are removed from the water, hydrated with a dry cloth or lightly wiped to remove water from the sample surface and weighed. The water absorption was calculated using equation (2).

（2）

(2)

In the formula: M ₀ is the mass before water absorption (g); M _t is the mass after water absorption (g).

Comparing the experimental data of Examples 1-2, it shows that the foaming effect is greatly improved after adding EVOH, and the foaming ratio of Example 2 is increased by about 481.8% compared with Example 1. After EVOH, the strength parameters of the foamed material decreased significantly, while the toughness parameters increased significantly. From the analysis of water resistance, the water resistance was significantly improved after EVOH was added. The sample of Example 1 was placed in water for 10 minutes and turned into a paste. However, it could not be weighed. The sample of Example 2 was placed in water for 10 min, taken out, weighed, and calculated. The water absorption rate of the sample was 39.8%. Comparing the experimental data of Example 1 and Comparative Examples 1-3, it is shown that the humidity adjustment time of the pellets, that is, the content of the foaming agent water, has a great influence on its foaming effect. Compared with Comparative Examples 1-3, the foaming effect of Example 1 is obviously improved, but the humidity adjustment time is long and the foaming ratio is low. Among them, the temperature of 50 °C and the relative humidity of 80% under the conditions of humidity treatment for 12 min had the best effect. Compared with Comparative Examples 4-5, the foaming effect of Example 1 is significantly improved, indicating that under the same humidity control time, the glycerin content has a greater impact on its foaming effect. When the glycerin content is too high, due to The melt fluidity is too high, and the collapse phenomenon is easy to occur during the injection foaming process, which leads to some mechanical properties higher than that of Example 1. When the glycerin content is 40%, the foaming effect is the best. Compared with Comparative Examples 6-7, the foaming ratio of Example 2 is increased by about 92.2% and 137.8%, respectively, indicating that the foaming effect is the best when the EVOH content is 10%. From the analysis of mechanical properties, when 10% EVOH is added, compared with Comparative Examples 6-7, the strength parameters are similar and the toughness parameters are higher.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Table 1

Claims (2)

1. an environmentally friendly starch-based foaming material, is characterized in that, this foaming material comprises the component of following parts by weight: 100 parts of starch, 20-60 parts of glycerin, 0-10 parts of water, ethylene-vinyl alcohol copolymer 0-30 servings. 2. the method for preparing a kind of environment-friendly starch-based foaming material according to claim 1, comprises the following steps: (1) Add the dried starch and glycerin into a high-speed mixer for uniform blending and plasticization, and then melt extrusion and granulation through a twin-screw extruder to obtain thermoplastic starch granules; (2) Add ethylene-vinyl alcohol copolymer (EVOH) and glycerin into a beaker to blend evenly, then plasticize at high temperature, take out for cooling, pulverize and granulate, and seal for storage to obtain plasticized EVOH pellets; (3) The thermoplastic starch granules obtained in step (1) and the plasticized EVOH granules obtained in step (2) were added to a high-speed mixer for uniform blending, and then melted and extruded through a twin-screw extruder for granulation. After humidity conditioning treatment, foamable starch-based pellets are obtained; (4) adding the foamable starch-based granules obtained in step (3) into an injection molding machine for melting and injection, and then adjusting the humidity to obtain a starch-based foaming material.