CN112029153A - Environment-friendly starch-based foaming material and preparation method thereof - Google Patents

Environment-friendly starch-based foaming material and preparation method thereof Download PDF

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CN112029153A
CN112029153A CN201910480969.6A CN201910480969A CN112029153A CN 112029153 A CN112029153 A CN 112029153A CN 201910480969 A CN201910480969 A CN 201910480969A CN 112029153 A CN112029153 A CN 112029153A
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starch
foaming material
parts
preparation
foaming
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刘文勇
王志杰
曾翠
戴炳丰
刘家豪
胡时盛
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Hunan University of Technology
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Hunan University of Technology
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/125—Water, e.g. hydrated salts
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0014—Use of organic additives
    • C08J9/0023—Use of organic additives containing oxygen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/10—Water or water-releasing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2303/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2303/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/04—Homopolymers or copolymers of ethene
    • C08J2423/08—Copolymers of ethene

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 glycerol, 0-10 parts of water and 0-30 parts of ethylene-vinyl alcohol copolymer. The invention takes water as a foaming agent, and the prepared biodegradable foaming material is safe, nontoxic, light in weight, excellent in comprehensive mechanical property and water resistance and biodegradable. The preparation method is simple, easy to control and implement, strong in operability and low in production cost, and can be applied to various filling or buffering fields.

Description

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
The polymer foam material has great market in the fields of packaging, transportation and heat preservation due to good heat preservation performance and buffering performance. The traditional foaming material is mostly prepared from general plastics such as polyolefin and the like, but the traditional foaming material is not degradable, so that the environment can be seriously polluted after being discarded. Therefore, the preparation of the environment-friendly foaming material by using the biodegradable material is very important. The starch as a natural polymer material has the advantages of low cost, renewable utilization, complete degradability and the like. The preparation of the foaming material by using the starch can slow down white pollution caused by general plastic, accords with the current environmental protection and sustainable idea, and is widely concerned. However, the comprehensive performance and water resistance of the existing thermoplastic starch foaming material are poor, so that the large-scale market application of the thermoplastic starch foaming material is limited. Therefore, the starch-based foaming material with excellent barrier property and water resistance is prepared by adding the ethylene-vinyl alcohol copolymer (EVOH) with excellent barrier property and water resistance, and the application range of the starch-based foaming material can be remarkably improved.
In the prior art, the chinese patent application No. 201610971285.2, entitled "starch-foamed disposable tableware", discloses a method for preparing a starch-based foamed material by using modified corn starch, wood pulp fiber, modified chaff and the like, which conforms to the strategy of environmental protection and sustainable development compared with the traditional disposable foamed material, but the overall water resistance is not ideal from the formula analysis, and the disposable tableware is difficult to popularize as the disposable tableware application, and the molding process has poor stability for starch-based foaming. The Chinese patent application with the application number of 201710015666.8, namely 'starch foaming product and preparation method thereof', discloses a preparation method of starch or modified starch and a starch foaming material containing a nucleating agent, wherein the preparation process of the foaming material is twin-screw extrusion foaming, the preparation is simple and convenient, but the prepared starch foaming material has serious water absorbability and is not beneficial to practical application. The Chinese patent application with the application number of 201710309478.6, namely 'fully biodegradable fiber-reinforced starch foaming tableware and a preparation method thereof' and the Chinese patent application with the application number of 201610650903.3, namely 'starch foaming formula and a foaming method thereof', disclose two preparation methods for blending and modifying thermoplastic starch by using other biodegradable high polymer materials, so that the cost of raw materials is greatly increased, but the comprehensive properties such as compatibility, water resistance, cost performance, processing technology and the like among the components of the composite material need to be improved.
In China, the yield of starch crops is huge, and the preparation of the starch-based foaming material by taking starch as a base material is an effective way for improving the non-edible value of starch, reducing the cost and reducing the environmental pollution. However, the starch-based foaming material with excellent mechanical property, good water resistance and simple preparation process is lacked in the field. Therefore, a high polymer material with excellent water resistance and good starch compatibility is urgently needed to be found, the processing technology of the starch-based foaming material is further improved, the mechanical property and the water resistance of the foaming material are improved, and the comprehensive performance of the foaming material is improved while the cost is ensured to be low.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention mainly aims to provide an environment-friendly starch-based foaming material.
The invention also aims to provide a preparation method of the environment-friendly starch-based foaming material.
The object of the present invention is achieved by the following means.
An environment-friendly starch-based foaming material comprises the following components in parts by weight: 100 parts of starch, 20-60 parts of glycerol, 0-5 parts of water and 0-20 parts of ethylene-vinyl alcohol copolymer.
The preparation method of the environment-friendly starch-based foaming material comprises the following steps:
(1) adding dried starch and glycerol into a high-speed mixer, uniformly blending and plasticizing, and performing melt extrusion granulation through a double-screw extruder to obtain thermoplastic starch granules;
(2) adding ethylene-vinyl alcohol copolymer (EVOH) and glycerol into a beaker, uniformly blending, plasticizing at high temperature, taking out, cooling, crushing, granulating, sealing and storing to obtain plasticized EVOH pellets;
(3) adding the thermoplastic starch granules obtained in the step (1) and the plasticized EVOH granules obtained in the step (2) into a high-speed mixer for uniform mixing, then carrying out melt extrusion granulation through a double-screw extruder, and carrying out humidity conditioning treatment to obtain foamable starch-based granules;
(4) and (4) adding the foamable starch-based granules obtained in the step (3) into an injection molding machine for melting and ejection, and then carrying out humidity conditioning treatment to obtain the starch-based foaming material.
Preferably, the starch in the step (1) is cassava starch, the temperature for drying the starch is 50-100 ℃, the drying time is 5-72 h, and the mass ratio of the starch to the glycerol is 100: 30-100: 50.
Preferably, the starch in the step (1) is plasticized in a drying oven at 10-50 ℃ for 12-72 hours.
Preferably, the twin-screw extruder in the step (1) and the step (3) is a co-rotating twin-screw extruder, the extrusion temperature is 130-180 ℃, the host frequency is 10 Hz, and the feeding frequency is 5 Hz.
Preferably, the glycerin content for plasticizing EVOH described in step (2) is 5-40%.
Preferably, the EVOH described in the step (2) is plasticized at high temperature by stirring at the temperature of 150 ℃ and 200 ℃ for 1-5 h.
Preferably, the mass ratio of the plasticized starch to the plasticized EVOH in the step (3) is 100:5 to 100: 20.
Preferably, the conditioning treatment in step (3) is carried out at a temperature of 25 to 60 ℃ and a relative humidity of 40 to 90% for 1 to 60 min, followed by sealing and standing at room temperature for 5 to 48 hours, in order to disperse the blowing agent water uniformly in the pellets and obtain expandable pellets.
Preferably, the humidity conditioning treatment in the step (4) is performed for 10-90 min at a temperature of 25-60 ℃ and a relative humidity of 40-90%, then sealing is performed, and standing is performed for 5-48 h at room temperature, so as to uniformly disperse water in the starch-based foaming material and obtain the starch-based foaming material with better performance.
The environment-friendly starch-based foaming material is safe and non-toxic, simple in preparation process, excellent in mechanical property, good in water resistance and biodegradable.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. according to the starch-based foaming material prepared by the invention, EVOH is uniformly dispersed in thermoplastic starch, the reinforcing effect of EVOH on thermoplastic starch is fully exerted, and the moisture resistance and mechanical property of the starch-based foaming material are improved.
2. The mechanical property of the starch-based foaming material can be obviously improved by humidifying the starch-based foaming material.
3. The main components of the material used in the invention are starch and glycerol, belonging to environment-friendly materials.
4. The preparation method of the starch-based foaming material is simple, easy to control, strong in operability, low in production cost, high in production efficiency, easy for industrial large-scale production, and good in economic benefit and wide in application prospect.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The reagents used in the following examples are commercially available and were dried before use.
Example 1
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 12 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing for 24 h at normal temperature to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Example 2
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of plasticized EVOH pellets
Weighing 200 g of EVOH and 40 g of glycerol, adding 40 g of glycerol into 200 g of EVOH for 4 times, uniformly mixing, placing at 180 ℃, stirring and melting for 1 h, taking out, cooling, crushing, granulating, sealing and storing to obtain the plasticized EVOH pellets.
(3) Preparation of starch-based foamed material
a) Weighing 1000 g of the thermoplastic starch granules obtained in the step (1) and 100 g of the plasticized EVOH granules obtained in the step (2), adding into a high-speed mixer, stirring for 10 min, performing melt extrusion through a double-screw extruder, cooling and granulating extruded strips, performing humidity conditioning treatment for 12 min under the conditions of 50 ℃ and 80% relative humidity, and sealing at normal temperature for 24 h to obtain foamable starch-based granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is respectively set between 130 ℃ and 180 ℃;
b) adding the foamable starch-based granules obtained in the step a) into an injection molding machine for ejection foaming, then placing the injection molding machine at the temperature of 50 ℃ and the relative humidity of 80% for humidifying treatment until the surface of the starch-based foaming material becomes soft, and then standing the starch-based foaming material at room temperature for 24 hours to obtain the starch-based foaming material with excellent performance; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 1
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 8 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing at normal temperature for 24 h to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 2
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 16 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing at normal temperature for 24 h to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 3
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 60 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing for 24 h at normal temperature to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 4
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 350 g of glycerol into the high-speed mixer for mixing for 4 times, mixing for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 12 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing for 24 h at normal temperature to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 5
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 500 g of glycerol into the high-speed mixer for mixing for 4 times, mixing for 180 s each time, continuously stirring for 10 min, plasticizing at 30 ℃ for 24 h, performing melt extrusion by a double-screw extruder, cooling and granulating extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of thermoplastic starch foamed material
a) Humidifying the thermoplastic starch granules obtained in the step (1) for 12 min under the conditions of 50 ℃ and 80% of relative humidity, and sealing for 24 h at normal temperature to obtain foamable thermoplastic starch granules;
b) adding the foamable thermoplastic starch granules obtained in the step a) into an injection molding machine for injection foaming, then humidifying under the conditions of 50 ℃ and 80% of relative humidity until the surface of the foaming material becomes soft, and standing at room temperature for 24 hours to obtain a thermoplastic starch foaming material; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 6
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of plasticized EVOH pellets
Weighing 200 g of EVOH and 40 g of glycerol, adding 40 g of glycerol into 200 g of EVOH for 4 times, uniformly mixing, placing at 180 ℃, stirring and melting for 1 h, taking out, cooling, crushing, granulating, sealing and storing to obtain the plasticized EVOH pellets.
(3) Preparation of starch-based foamed material
a) Weighing 1000 g of the thermoplastic starch granules obtained in the step (1) and 50 g of the plasticized EVOH granules obtained in the step (2), adding into a high-speed mixer, stirring for 10 min, performing melt extrusion through a double-screw extruder, cooling and granulating extruded strips, performing humidity conditioning treatment for 12 min under the conditions of 50 ℃ and 80% relative humidity, and sealing at normal temperature for 24 h to obtain foamable starch-based granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is respectively set between 130 ℃ and 180 ℃;
b) adding the foamable starch-based granules obtained in the step a) into an injection molding machine for ejection foaming, then placing the injection molding machine at the temperature of 50 ℃ and the relative humidity of 80% for humidifying treatment until the surface of the starch-based foaming material becomes soft, and then standing the starch-based foaming material at room temperature for 24 hours to obtain the starch-based foaming material with excellent performance; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
Comparative example 7
(1) Preparation of thermoplastic starch
a) Drying the starch raw material in an electric heating forced air drying oven at 75 ℃ for 24 h, and sealing for storage to obtain dry starch;
b) putting 1000 g of dry starch into a high-speed mixer, adding 400 g of glycerol into the high-speed mixer for blending for 4 times, blending for 180 s each time, continuously stirring for 10 min, then plasticizing at 30 ℃ for 24 h, then performing melt extrusion by a double-screw extruder, cooling and granulating the extruded strips, and sealing and storing to obtain thermoplastic starch granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is set between 130 ℃ and 180 ℃.
(2) Preparation of plasticized EVOH pellets
Weighing 200 g of EVOH and 40 g of glycerol, adding 40 g of glycerol into 200 g of EVOH for 4 times, uniformly mixing, placing at 180 ℃, stirring and melting for 1 h, taking out, cooling, crushing, granulating, sealing and storing to obtain the plasticized EVOH pellets.
(3) Preparation of starch-based foamed material
a) Weighing 1000 g of the thermoplastic starch granules obtained in the step (1) and 200 g of the plasticized EVOH granules obtained in the step (2), adding into a high-speed mixer, stirring for 10 min, performing melt extrusion through a double-screw extruder, cooling and granulating extruded strips, performing humidity conditioning treatment for 12 min under the conditions of 50 ℃ and 80% relative humidity, and sealing for 24 h at normal temperature to obtain foamable starch-based granules; wherein, the output frequency of a frequency converter of a main machine of the double-screw extruder is 10 Hz, the feeding frequency is 5 Hz, and the temperature of an extrusion area (from a feeding hole to a machine head) is respectively set between 130 ℃ and 180 ℃;
b) adding the foamable starch-based granules obtained in the step a) into an injection molding machine for ejection foaming, then placing the injection molding machine at the temperature of 50 ℃ and the relative humidity of 80% for humidifying treatment until the surface of the starch-based foaming material becomes soft, and then standing the starch-based foaming material at room temperature for 24 hours to obtain the starch-based foaming material with excellent performance; wherein the temperature of the extrusion region (from the feed port to the injection port) is respectively set between 130 ℃ and 180 ℃.
The starch-based foaming materials obtained in examples 1-2 and comparative examples 1-7 were cut to prepare mechanical property test specimens.
And (3) testing tensile property: according to the standard of GB 6344-1986, the determination of tensile strength and elongation at break of flexible foam polymers, a microcomputer-controlled electronic universal tester is adopted to carry out tensile property test at room temperature, and the tensile rate is 20 mm/min. At least five sample strips are selected for each group of samples to be tested, and the average value is taken. The test results are shown in table 1.
And (3) testing the compression performance: the test was performed according to GB/T1041-. At room temperature, a microcomputer controlled electronic universal tester is used for testing the tensile property and the compression speedThe rate was 2 mm/min. Compressive strength sigmam(KPa) is calculated using the following formula:
Figure 857080DEST_PATH_IMAGE001
Figure 826173DEST_PATH_IMAGE001
（1）
in the formula: fmMaximum compressive force (KN); s0Is the initial area (mm) of the cross section of the sample2). At least five sample strips are selected for each group of samples to be tested, and the average value is taken. The test results are shown in table 1.
Water absorption test: the samples were first dried at 40 ℃ for 24 h, sealed and cooled for 24 h, and weighed. They were then placed in distilled water at room temperature. After a specific immersion period, the samples were removed from the water, drained with a dry cloth or lightly wiped to remove water from the sample surface and weighed. The water absorption was calculated using equation (2).
Figure 246790DEST_PATH_IMAGE002
Figure 125884DEST_PATH_IMAGE002
（2）
In the formula: m0Mass (g) before water absorption; mtThe mass (g) after water absorption.
The experimental data of comparative examples 1-2 show that the foaming effect is greatly improved after the addition of EVOH, the foaming ratio of example 2 is improved by about 481.8% compared with example 1, analysis on mechanical properties shows that after the addition of EVOH, the strength parameter of the foamed material is obviously reduced, the toughness parameter is obviously increased, analysis on water resistance shows that after the addition of EVOH, the water resistance is obviously improved, the sample of example 1 is pasty and cannot be weighed after being taken out after being placed in water for 10 min, and the sample of example 2 is taken out, weighed and calculated after being placed in water for 10 min, so that the water absorption of the sample is 39.8%. The experimental data comparing example 1 with comparative examples 1 to 3 show that the conditioning time of the pellets, i.e., the water content of the foaming agent, has a large influence on the foaming effect. Compared with comparative examples 1-3, the foaming effect of example 1 is obviously improved, the humidity control time is long, the foaming ratio is low on the contrary because the foaming agent has too high water content and is collapsed in the injection foaming process, and the humidity control effect of 12 min under the conditions of 50 ℃ and 80% of relative humidity is the best. Compared with comparative examples 4-5, the foaming effect of example 1 is obviously improved, which shows that the influence of the glycerol content on the foaming effect is larger under the same humidity control time, and when the glycerol content is too high, because the melt fluidity is too high, the collapse phenomenon is easy to occur in the injection foaming process, so that some mechanical properties are higher than those of example 1, wherein when the glycerol content is 40%, the foaming effect is optimal. The expansion ratios of example 2 were increased by about 92.2% and 137.8% as compared with those of comparative examples 6 to 7, respectively, indicating that the best expansion effect was obtained when the EVOH content was 10%. From the analysis of mechanical properties, when 10% of EVOH is added, compared with comparative examples 6-7, the strength parameter is similar, and the toughness parameter is higher.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
TABLE 1
Figure 239334DEST_PATH_IMAGE003

Claims (2)

1. The environment-friendly starch-based foaming material is characterized by comprising the following components in parts by weight: 100 parts of starch, 20-60 parts of glycerol, 0-10 parts of water and 0-30 parts of ethylene-vinyl alcohol copolymer.
2. The method for preparing the environment-friendly starch-based foaming material of claim 1, comprising the following steps of:
(1) adding dried starch and glycerol into a high-speed mixer, uniformly blending and plasticizing, and performing melt extrusion granulation through a double-screw extruder to obtain thermoplastic starch granules;
(2) adding ethylene-vinyl alcohol copolymer (EVOH) and glycerol into a beaker, uniformly blending, plasticizing at high temperature, taking out, cooling, crushing, granulating, sealing and storing to obtain plasticized EVOH pellets;
(3) adding the thermoplastic starch granules obtained in the step (1) and the plasticized EVOH granules obtained in the step (2) into a high-speed mixer for uniform mixing, then carrying out melt extrusion granulation through a double-screw extruder, and carrying out humidity conditioning treatment to obtain foamable starch-based granules;
(4) and (4) adding the foamable starch-based granules obtained in the step (3) into an injection molding machine for melting and ejection, and then carrying out humidity conditioning treatment to obtain the starch-based foaming material.
CN201910480969.6A 2019-06-04 2019-06-04 Environment-friendly starch-based foaming material and preparation method thereof Pending CN112029153A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1049671A (en) * 1989-08-03 1991-03-06 蝴蝶有限公司 Expanded articles of biodegradable plastics materials and manufacture method thereof
US5308879A (en) * 1992-09-07 1994-05-03 Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha Process for preparing biodegradable resin foam
CN1112143A (en) * 1994-02-09 1995-11-22 诺瓦蒙特股份公司 Expanded articles of biodegradable plastic material and a process for the preparation thereof
CN105885103A (en) * 2015-01-16 2016-08-24 宁波高新区金杉新能源科技有限公司 Starch-base foam material and preparing method thereof
CN106800674A (en) * 2017-01-10 2017-06-06 广州绿发材料科技有限公司 Starch foaming product and preparation method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1049671A (en) * 1989-08-03 1991-03-06 蝴蝶有限公司 Expanded articles of biodegradable plastics materials and manufacture method thereof
US5308879A (en) * 1992-09-07 1994-05-03 Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha Process for preparing biodegradable resin foam
CN1112143A (en) * 1994-02-09 1995-11-22 诺瓦蒙特股份公司 Expanded articles of biodegradable plastic material and a process for the preparation thereof
CN105885103A (en) * 2015-01-16 2016-08-24 宁波高新区金杉新能源科技有限公司 Starch-base foam material and preparing method thereof
CN106800674A (en) * 2017-01-10 2017-06-06 广州绿发材料科技有限公司 Starch foaming product and preparation method thereof

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