CN112500611B - Biodegradable plastic bag and preparation method thereof - Google Patents
Biodegradable plastic bag and preparation method thereof Download PDFInfo
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- CN112500611B CN112500611B CN202011193521.5A CN202011193521A CN112500611B CN 112500611 B CN112500611 B CN 112500611B CN 202011193521 A CN202011193521 A CN 202011193521A CN 112500611 B CN112500611 B CN 112500611B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
- C08L3/02—Starch; Degradation products thereof, e.g. dextrin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
- B65D65/38—Packaging materials of special type or form
- B65D65/46—Applications of disintegrable, dissolvable or edible materials
- B65D65/466—Bio- or photodegradable packaging materials
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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Abstract
The invention relates to the technical field of blow molding grade plastic bags, in particular to a biodegradable plastic bag and a preparation method thereof, wherein the biodegradable plastic bag comprises the following raw materials: modified polylactic acid, polybutylene adipate/terephthalate, corn starch, nano calcium carbonate, aluminate coupling agent, citric acid, citrate compounds and heat stabilizer. The biodegradable plastic bag improves the using amount of corn starch, reduces the using amounts of modified polylactic acid and poly adipic acid/butylene terephthalate, and saves the cost of raw materials; meanwhile, the polylactic acid is modified to obtain the modified polylactic acid, and the modified polylactic acid is combined with other raw materials, so that the overall tensile strength, the elongation at break, the puncture resistance and the water permeability resistance of the biodegradable plastic bag are improved together, and the market popularization is facilitated.
Description
Technical Field
The invention relates to the technical field of blow molding grade plastic bags, in particular to a biodegradable plastic bag and a preparation method thereof.
Background
Plastic bags are made of plastic as a main raw material through film blowing and bag making, are essential articles in daily life, and are often used for containing other articles. The plastic bag has the advantages of low price, extremely light weight, large capacity and convenient storage, but is prohibited from production and use by some countries due to the defects of extremely long degradation period and difficult processing of the plastic bag.
At present, degradable plastic bags exist in the market, but are difficult to popularize in the mass market due to high manufacturing cost and high price, and although scholars try to mix starch into PBAT plastic to reduce the cost, the higher the starch content is, the poorer the mechanical property of the degradable plastic bags is and the water seepage is easy to occur.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide the biodegradable plastic bag, the weight content of the corn starch is high, the use amounts of the modified polylactic acid and the poly adipic acid/butylene terephthalate are reduced, and the raw material cost is saved; meanwhile, polylactic acid is modified to obtain modified polylactic acid, and the modified polylactic acid is combined with poly (butylene adipate/terephthalate), corn starch, nano calcium carbonate, an aluminate coupling agent, citric acid, a citrate compound and a heat stabilizer, so that the overall tensile strength, the elongation at break, the puncture resistance and the water permeability resistance of the biodegradable plastic bag are improved, and the market popularization is facilitated.
The invention also aims to provide a preparation method of the biodegradable plastic bag, which has the advantages of simple operation, convenient control, high production efficiency and low production cost and can be used for large-scale production.
The purpose of the invention is realized by the following technical scheme: a biodegradable plastic bag comprises the following raw materials in parts by weight:
preferably, the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 1-3 parts of phthalic anhydride, 5-10 parts of 1, 4-butanediol and 1-3 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
Preferably, the weight average molecular weight of the polylactic acid is 1.0 × 105-3.0×105The screw rotating speed of the double-screw extruder is 100-200r/min, the length-diameter ratio of the screw of the double-screw extruder is 32-40: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 180 DEG, 210 DEG, 220 DEG, 230 DEG, 240 DEG, 235 DEG, 240 DEG, and 250 DEG, and a head temperature of 220 DEG and 230 deg.
Preferably, the melt flow rate of the polybutylene adipate/terephthalate is 2.7-5.0g/10min under the conditions that the temperature is 190 ℃ and the pressure load is 2.16 kg.
Preferably, the corn starch is dried at the temperature of 60 ℃ until the water content reaches 5-10 wt%.
Preferably, the particle size of the nano calcium carbonate is 50-80 nm.
Preferably, the type of the aluminate coupling agent is F-2, DL-411 or DL-411D; the citrate compound is tributyl citrate, trioctyl citrate, acetyl tributyl citrate or acetyl trioctyl citrate.
Preferably, the heat stabilizer is compounded by triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 5-8.
The other purpose of the invention is realized by the following technical scheme: the preparation method of the biodegradable plastic bag comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
Preferably, the stirring temperature of the high-speed stirrer is 40-60 ℃, the stirring speed is 1000-1500r/min, and the stirring time is 15-30 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 220 ℃ at 210-.
The invention has the beneficial effects that: according to the biodegradable plastic bag, the weight content of the corn starch reaches 48.8-58.5%, the use amounts of the modified polylactic acid and the poly adipic acid/butylene terephthalate are reduced, and the raw material cost is saved; meanwhile, polylactic acid is modified to obtain modified polylactic acid, and the modified polylactic acid is combined with poly (butylene adipate/terephthalate), corn starch, nano calcium carbonate, an aluminate coupling agent, citric acid, a citrate compound and a heat stabilizer, so that the overall tensile strength, the elongation at break, the puncture resistance and the water permeability resistance of the biodegradable plastic bag are improved, and the market popularization is facilitated.
The preparation method of the biodegradable plastic bag has the advantages of simple operation, convenient control, high production efficiency and low production cost, and can be used for large-scale production.
Detailed Description
The present invention will be further described with reference to the following examples for facilitating understanding of those skilled in the art, and the description of the embodiments is not intended to limit the present invention.
In an exemplary embodiment of the present application, there is provided a biodegradable plastic bag, comprising the following raw materials in parts by weight:
according to the biodegradable plastic bag, the weight content of the corn starch reaches 48.8-58.5%, the use amounts of the modified polylactic acid and the poly adipic acid/butylene terephthalate are reduced, and the raw material cost is saved; meanwhile, polylactic acid is modified to obtain modified polylactic acid, and the modified polylactic acid is combined with poly (butylene adipate/terephthalate), corn starch, nano calcium carbonate, an aluminate coupling agent, citric acid, a citrate compound and a heat stabilizer, so that the overall tensile strength, the elongation at break, the puncture resistance and the water permeability resistance of the biodegradable plastic bag are improved, and the market popularization is facilitated. The modified polylactic acid and the polybutylene adipate/terephthalate are used as main plastics, and the citric acid is added to reduce the interfacial tension between the modified polylactic acid and the polybutylene adipate/terephthalate, increase the interfacial bonding force, improve the overall mechanical compatibility and impact resistance of the system, supplement each other, and ensure that the overall good tensile strength, elongation at break, puncture resistance and water impermeability can be maintained after a large amount of corn starch is added; the added aluminate coupling agent enables the corn starch and the nano calcium carbonate to be uniformly dispersed in the system, the mechanical stability of the system is improved, the nano calcium carbonate has an obvious effect of toughening the impact strength, and the nano calcium carbonate and the modified polylactic acid together improve the overall puncture resistance.
In one embodiment, the poly (butylene adipate/terephthalate) is used in an amount of 12 to 15 parts by weight, preferably 12 to 14 parts by weight, more preferably 13 to 14 parts by weight. Controlling the weight ratio of the modified polylactic acid to the poly adipic acid/butylene terephthalate to be 30: 10-15, the two functions are exerted, the integral tensile strength and the elongation at break are improved, and the occurrence of holes and grooves in a system caused by excessive consumption of the poly (butylene adipate)/terephthalate is avoided.
In one embodiment, the corn starch is used in an amount of 60 to 65 parts by weight, preferably 60 to 63 parts by weight, more preferably 61 to 62 parts by weight.
In one embodiment, the nano calcium carbonate is used in an amount of 3 to 8 parts by weight, preferably 4 to 8 parts by weight, and more preferably 6 to 8 parts by weight.
In one embodiment, the biodegradable plastic bag further comprises 1-3 parts by weight of a pigment selected from at least one of pigment yellow, pigment orange, pigment red, pigment violet, pigment blue, pigment green, pigment brown, pigment black and pigment white, wherein the pigment is prepared according to the customer's requirements.
In one embodiment, the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 1-3 parts of phthalic anhydride, 5-10 parts of 1, 4-butanediol and 1-3 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
By adopting the technical scheme, the phthalic anhydride, the 1, 4-butanediol and the 1, 4-butanediol isocyanate are used as modifiers to carry out melt modification on the polylactic acid together, so that the weight average molecular weight of the polylactic acid is increased, the crystallization temperature of the modified polylactic acid is effectively improved, the crystallinity is reduced, meanwhile, the interfacial bonding force between the modified polylactic acid and the poly adipic acid/butylene terephthalate is also obviously improved, the mechanical compatibility between the modified polylactic acid and the poly adipic acid/butylene terephthalate is improved, and the breaking elongation and the puncture resistance of the biodegradable plastic bag are increased.
In one embodiment, the polylactic acid has a weight average molecular weight of 1.0 × 105-3.0×105The screw rotating speed of the double-screw extruder is 100-200r/min, the length-diameter ratio of the screw of the double-screw extruder is 32-40: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 180 DEG, 210 DEG, 220 DEG, 230 DEG, 240 DEG, 235 DEG, 240 DEG, and 250 DEG, and a head temperature of 220 DEG and 230 deg.
By adopting the technical scheme, although the weight average molecular weight of the polylactic acid is further increased by modification on the basis of the polylactic acid with the weight average molecular weight, the mechanical property of the modified polylactic acid is more favorably improved, the following is found in the modification process: along with the continuous modification, the melting point of the modified polylactic acid is gradually increased and finally reaches the melting point of 220-230 ℃, so that the processing temperature of each section of the double-screw extruder is set, the smooth modification of the polylactic acid is facilitated, and the thermal degradation of the polylactic acid caused by overhigh processing temperature is avoided.
In one embodiment, the polybutylene adipate/terephthalate has a melt flow rate of 2.7 to 5.0g/10min at a temperature of 190 ℃ and a pressure load of 2.16 kg.
By adopting the technical scheme, the melt viscosity of the system is improved, which is beneficial to the realization of blow molding and tape casting processing processes and is convenient for blow molding of the system into a film and bag making. Preferably, the type of the polybutylene adipate/terephthalate is selected from the group consisting of basf C1200 or echoville FP-0615, and more preferably, the type of the polybutylene adipate/terephthalate is selected from the group consisting of C1200.
In one embodiment, the corn starch is dried at a temperature of 60 ℃ until the water content reaches 5 wt% to 10 wt%, preferably 6 wt% to 10 wt%, and more preferably 7 wt% to 9 wt%.
By adopting the technical scheme, the corn starch is sold on the market and has the water content of 13.5-14 wt%, the water content of the corn starch is reduced to 5-10 wt% at the temperature of 60 ℃, and the tensile strength of the produced biodegradable plastic bag is improved to a certain extent; meanwhile, the water content of the corn starch is controlled to be not less than 5 wt%, higher energy consumption is avoided, and the production cost is controlled.
In one embodiment, the nano calcium carbonate has a particle size of 50 to 80 nm.
By adopting the technical scheme, the particle size of the nano calcium carbonate is controlled to be 50-80nm, the toughening effect on impact strength is obvious, and the overall puncture resistance is improved together with the modified polylactic acid. If the particle size of the nano calcium carbonate is too large, the overall tensile strength is easily reduced, and stress concentration is easily formed at the defect part when a large tensile force is borne, so that the biodegradable plastic bag is easily broken; if the particle size of the nano calcium carbonate is too small, the impact performance is weakened.
In one embodiment, the aluminate coupling agent is of type F-2, DL-411 or DL-411D; the citrate compound is tributyl citrate, trioctyl citrate, acetyl tributyl citrate or acetyl trioctyl citrate.
By adopting the combined action of the aluminate coupling agent and the citric acid, the interface compatibility of the nano calcium carbonate, the corn starch and the modified polylactic acid is enhanced, the dispersion uniformity of the corn starch and the nano calcium carbonate in a system is improved, the processing performance of the biodegradable plastic bag added with the nano calcium carbonate can be improved, the physical and mechanical properties of the biodegradable plastic bag are obviously improved, the water absorption rate of the biodegradable plastic bag is reduced, and the water impermeability of the biodegradable plastic bag is improved. By adopting the citrate compounds, the crystallinity of the system is reduced, the plasticity of the system is increased, the ductility and the flexibility of the biodegradable plastic bag are increased, the processing performance is improved, and the tensile strength of the biodegradable plastic bag is improved; compared with the traditional phthalate ester compound, the citrate ester compound is more suitable for the biodegradable plastic bag, and is more environment-friendly and less in pollution.
In one embodiment, the heat stabilizer is compounded by triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 5-8.
Although the mechanical property of the modified polylactic acid is improved, the melting point of the modified polylactic acid is also improved to 230 ℃ at the same time, the processing temperature for preparing the biodegradable plastic bag is also greatly improved, the poly adipic acid/butylene terephthalate is easily overheated to degrade to generate oligomers in the processing process, and the tensile strength and the elongation at break are reduced; the specific heat stabilizer is compounded, so that the heat stability in the process of preparing the biodegradable plastic bag is improved, the added heat stabilizer is not easy to volatilize when being heated in the processing process, and the phenomenon that the polyadipic acid/butylene terephthalate is degraded to generate oligomers due to overheating caused by the fact that the heat stabilizer is volatilized by itself and the overall heat stability is reduced is avoided.
In another exemplary embodiment of the present application, there is provided a method for preparing a biodegradable plastic bag, comprising the steps of:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
The preparation method of the biodegradable plastic bag is simple to operate, and the biodegradable plastic bag can be prepared by preparing the biodegradable master batch and then adopting a conventional film blowing bag-making method. In the step (S2), the corn starch, the nano calcium carbonate and the aluminate coupling agent are pre-mixed so as to be uniformly dispersed and combined with the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound and the thermal stabilizer in the high-speed mixer in the step (S3).
In one embodiment, the stirring temperature of the high-speed stirrer is 40-60 ℃, the stirring speed is 1000-1500r/min, and the stirring time is 15-30 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 220 ℃ at 210-.
By adopting the technical scheme, the stirring temperature, the stirring speed and the stirring time of the high-speed stirrer are controlled, and the raw materials are promoted to be uniformly dispersed. The processing temperature of the extrusion equipment is controlled to be 210-250 ℃, the rotating speed of the screw is controlled to be 100-150r/min, and the length-diameter ratio of the screw is controlled to be 42-55:1, so that the raw materials are fully melted and blended, and the compatibility of the raw materials is improved, thereby facilitating the improvement of mechanical compatibility.
Example 1
A biodegradable plastic bag comprises the following raw materials in parts by weight:
the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 2 parts of phthalic anhydride, 7 parts of 1, 4-butanediol and 2 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
The weight average molecular weight of the polylactic acid is 2.0 multiplied by 105The screw rotating speed of the double-screw extruder is 150r/min, and the length-diameter ratio of the screws of the double-screw extruder is 35: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 185 deg.C, 215 deg.C, 225 deg.C, 235 deg.C, 238 deg.C, 245 deg.C, and a head temperature of 225 deg.C.
The melt flow rate of the polybutylene adipate/terephthalate under the conditions of the temperature of 190 ℃ and the pressure load of 2.16kg is 4.0g/10 min. The type of the poly (butylene adipate/terephthalate) is selected from basf C1200.
And drying the corn starch at the temperature of 60 ℃ until the water content reaches 8 wt%.
The particle size of the nano calcium carbonate is 60 nm.
The type of the aluminate coupling agent is F-2; the citrate compound is tributyl citrate.
The heat stabilizer is prepared by compounding triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 7.
The preparation method of the biodegradable plastic bag comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
The stirring temperature of the high-speed stirrer is 50 ℃, the stirring speed is 1300r/min, and the stirring time is 23 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 215 ℃, 225 ℃, 235 ℃, 238 ℃, 243 ℃, 245 ℃, the head temperature is 243 ℃, the rotating speed of a screw of the extrusion equipment is 120r/min, and the length-diameter ratio of the screw of the extrusion equipment is 50: 1.
Example 2
A biodegradable plastic bag comprises the following raw materials in parts by weight:
the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 1 part of phthalic anhydride, 5 parts of 1, 4-butanediol and 1 part of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
The weight average molecular weight of the polylactic acid is 1.0 multiplied by 105The screw rotating speed of the double-screw extruder is 100r/min, and the length-diameter ratio of the screws of the double-screw extruder is 32: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 180 ℃, 210 ℃, 220 ℃, 230 ℃, 235 ℃, 240 ℃ and the temperature of a machine head is 220 ℃.
The melt flow rate of the polybutylene adipate/terephthalate under the conditions of the temperature of 190 ℃ and the pressure load of 2.16kg is 2.7g/10 min. The type of the poly (butylene adipate/terephthalate) is selected from basf C1200.
And drying the corn starch at the temperature of 60 ℃ until the water content reaches 5 wt%.
The particle size of the nano calcium carbonate is 50 nm.
The type of the aluminate coupling agent is DL-411; the citrate compound is trioctyl citrate.
The heat stabilizer is prepared by compounding triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 5.
The preparation method of the biodegradable plastic bag comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
The stirring temperature of the high-speed stirrer is 40 ℃, the stirring speed is 1000r/min, and the stirring time is 15 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 210 ℃, 220 ℃, 230 ℃, 235 ℃, 240 ℃ and 240 ℃, wherein the head temperature is 240 ℃, the screw rotating speed of the extrusion equipment is 100r/min, and the length-diameter ratio of the screw of the extrusion equipment is 42: 1.
Example 3
A biodegradable plastic bag comprises the following raw materials in parts by weight:
the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 3 parts of phthalic anhydride, 10 parts of 1, 4-butanediol and 3 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
The weight average molecular weight of the polylactic acid is 3.0 multiplied by 105The screw rotating speed of the double-screw extruder is 200r/min, and the length-diameter ratio of the screws of the double-screw extruder is 40: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 190 deg.C, 220 deg.C, 230 deg.C, 240 deg.C, 250 deg.C, and a head temperature of 230 deg.C.
The melt flow rate of the polybutylene adipate/terephthalate under the conditions of the temperature of 190 ℃ and the pressure load of 2.16kg is 5.0g/10 min. The type of the poly (butylene adipate/terephthalate) is selected from basf C1200.
And drying the corn starch at the temperature of 60 ℃ until the water content reaches 10 wt%.
The particle size of the nano calcium carbonate is 80 nm.
The type of the aluminate coupling agent is DL-411D; the citrate compound is acetyl trioctyl citrate.
The heat stabilizer is prepared by compounding triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 8.
The preparation method of the biodegradable plastic bag comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
The stirring temperature of the high-speed stirrer is 60 ℃, the stirring speed is 1500r/min, and the stirring time is 30 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 220 ℃, 230 ℃, 240 ℃, 245 ℃ and 250 ℃, the head temperature is 245 ℃, the screw rotating speed of the extrusion equipment is 150r/min, and the length-diameter ratio of the screw of the extrusion equipment is 55: 1.
Example 4
A biodegradable plastic bag comprises the following raw materials in parts by weight:
the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 1.5 parts of phthalic anhydride, 6 parts of 1, 4-butanediol and 1.8 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) and uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid.
The weight average molecular weight of the polylactic acid is 1.5 multiplied by 105The screw rotating speed of the double-screw extruder is 180r/min, and the length-diameter ratio of the screws of the double-screw extruder is 36: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 188 deg.C, 212 deg.C, 228 deg.C, 232 deg.C, 238 deg.C, 248 deg.C, and the head temperature is 225 deg.C.
The melt flow rate of the polybutylene adipate/terephthalate under the conditions of the temperature of 190 ℃ and the pressure load of 2.16kg is 3.0g/10 min. The type of the poly (butylene adipate/terephthalate) is selected from basf C1200.
And drying the corn starch at the temperature of 60 ℃ until the water content reaches 8 wt%.
The particle size of the nano calcium carbonate is 70 nm.
The type of the aluminate coupling agent is F-2; the citrate compound is acetyl tributyl citrate.
The heat stabilizer is prepared by compounding triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 6.
The preparation method of the biodegradable plastic bag comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
The stirring temperature of the high-speed stirrer is 45 ℃, the stirring speed is 1200r/min, and the stirring time is 20 min; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 213 ℃, 227 ℃, 233 ℃, 238 ℃, 243 ℃, 248 ℃, 242 ℃ of head temperature, 120r/min of screw rotation speed of the extrusion equipment, and 52:1 of length-diameter ratio of the screw of the extrusion equipment.
Example 5
This example differs from example 3 in that: the type of the poly (butylene adipate/terephthalate) is selected from echoville FP-0615.
Comparative example 1
This comparative example differs from example 1 in that: the modified polylactic acid is replaced by the modified polylactic acid with the weight-average molecular weight of 2.0 multiplied by 105The polylactic acid of (1).
Comparative example 2
This comparative example differs from example 1 in that: the weight portion of the poly-adipic acid/butylene terephthalate is 30 portions.
Comparative example 3
This comparative example differs from example 1 in that: the aluminate coupling agent is replaced by a silane coupling agent KH 560.
Comparative example 4
This comparative example differs from example 1 in that: the biodegradable plastic bag is free of citric acid.
Comparative example 5
This comparative example differs from example 1 in that: the citrate compound is replaced by butylene phthalate.
Comparative example 6
This comparative example differs from example 1 in that: the corn starch is not dried.
Comparative example 7
This comparative example differs from example 1 in that: the heat stabilizer is calcium stearate.
Comparative example 8
This comparative example differs from example 1 in that: the heat stabilizer is triethyl phosphate.
Example 6
The biodegradable plastic bags of examples 1 to 5 and comparative examples 1 to 8 were tested for their degradation properties, tensile strength, elongation at break, puncture resistance, water permeation resistance and heat seal strength by the following test methods:
and (3) degradation performance test: according to appendix D in GB/T18006.2-1999 test method for degradation performance of disposable degradable tableware: a method for testing the compostability of biodegradable materials, the biodegradation rate R is measured and calculated, and the unit is%.
Tensile strength test: the tensile strength was measured in MPa according to GB/T1040.1-2018 determination of tensile Properties of plastics.
Elongation at break test: the tensile strain at break was measured and calculated in% according to GB/T1040.1-2018 determination of tensile Properties of plastics.
Puncture resistance test: the puncture strength was tested in N according to the general rules of composite films and bags for packaging in GB/T _21302 and 2007.
And (3) water impermeability test: according to the 5.6.2 leakage resistance test of GB T24984-.
Testing the heat seal strength: the heat seal strength was measured in N/15mm in accordance with QB-T2358-1998 test method for heat seal strength of plastic film packaging bags.
The test results are shown in table 1 below:
TABLE 1
As can be seen from table 1 above, the modified polylactic acid obtained by modifying polylactic acid of the present invention is combined with poly (butylene adipate/terephthalate), corn starch, nano calcium carbonate, an aluminate coupling agent, citric acid, a citrate compound, and a heat stabilizer, so as to jointly improve the overall tensile strength, elongation at break, puncture resistance, and water permeation resistance of the biodegradable plastic bag, and retain the biodegradability, thereby being more beneficial to market promotion. Compared with comparative example 1, the tensile strength, elongation at break, puncture resistance, water permeability resistance and heat seal strength of example 1 are better, which shows that the polylactic acid modified by the invention improves the overall mechanical property and water permeability resistance. Comparative example 2 has a reduced tensile strength, elongation at break and puncture resistance compared to example 1, indicating that the mechanical properties of biodegradable plastic bags are adversely affected by the addition of too much polybutylene adipate/terephthalate. The mechanical properties of example 1 were slightly reduced compared to comparative example 3, indicating that the use of an aluminate coupling agent produces a more accelerating effect than that of a silane coupling agent. Compared with comparative example 4, the mechanical properties of example 1 were significantly enhanced and the water permeation resistance was better, indicating that citric acid plays an important role in the biodegradable plastic bag of the present invention. Compared with the comparative example 5, the elongation at break of the example 1 is better, which shows that the citrate compound adopted by the invention has a remarkable effect of promoting the elongation at break of the system. Compared with the comparative example 6, the tensile strength of the example 1 is better, and the fact that the moisture content of the corn starch is reduced by drying treatment of the corn starch is significant. Compared with comparative examples 7 and 8, the plastic bags obtained by compounding the heat stabilizer of example 1 according to the specific type have better performances of tensile strength and elongation at break.
The above-described embodiments are preferred implementations of the present invention, and the present invention may be implemented in other ways without departing from the spirit of the present invention.
Claims (6)
1. A biodegradable plastic bag, which is characterized in that: the feed comprises the following raw materials in parts by weight:
the preparation method of each part of the modified polylactic acid comprises the following steps:
(A1) taking 100 parts of polylactic acid, 1-3 parts of phthalic anhydride, 5-10 parts of 1, 4-butanediol and 1-3 parts of 1, 4-butanediol isocyanate according to parts by weight for later use;
(A2) uniformly mixing polylactic acid, phthalic anhydride, 1, 4-butanediol and 1, 4-butanediol isocyanate, extruding by a double-screw extruder, and granulating to obtain the modified polylactic acid;
the weight average molecular weight of the polylactic acid is 1.0 multiplied by 105-3.0×105The screw rotating speed of the double-screw extruder is 100-The length-diameter ratio of the screw of the double-screw extruder is 32-40: 1; the processing temperature of each section of the double-screw extruder from the feeding section is respectively as follows: 180-190 ℃, 210-220 ℃, 220-230 ℃, 230-240 ℃, 235-240 ℃ and 240-250 ℃, and the head temperature is 220-230 ℃;
drying the corn starch at the temperature of 60 ℃ until the water content reaches 5-10 wt%;
the heat stabilizer is prepared by compounding triethyl phosphate and bis (2, 4-dicumylphenyl) pentaerythritol diphosphite according to the weight ratio of 2: 5-8.
2. A biodegradable plastic bag according to claim 1, characterized in that: the melt flow rate of the poly (butylene adipate/terephthalate) under the conditions of the temperature of 190 ℃ and the pressure load of 2.16kg is 2.7-5.0g/10 min.
3. A biodegradable plastic bag according to claim 1, characterized in that: the particle size of the nano calcium carbonate is 50-80 nm.
4. A biodegradable plastic bag according to claim 1, characterized in that: the type of the aluminate coupling agent is F-2, DL-411 or DL-411D; the citrate compound is tributyl citrate, trioctyl citrate, acetyl tributyl citrate or acetyl trioctyl citrate.
5. A method for preparing a biodegradable plastic bag according to any one of claims 1-4, characterized in that it comprises the following steps:
(S1) weighing the modified polylactic acid, the poly (butylene adipate/terephthalate), the corn starch, the nano calcium carbonate, the aluminate coupling agent, the citric acid, the citrate compound and the heat stabilizer in parts by weight for later use;
(S2), uniformly mixing the corn starch, the nano calcium carbonate and the aluminate coupling agent to obtain a premix;
(S3) adding the modified polylactic acid, the polybutylene adipate/terephthalate, the citric acid, the citrate compound, the heat stabilizer and the premix obtained in the step (S2) into a high-speed stirrer, uniformly stirring, extruding by an extruding device, and granulating to obtain biodegradable master batches;
(S4) carrying out film blowing and bag making on the biodegradable master batch obtained in the step (S3) to obtain the biodegradable plastic bag.
6. The method for preparing biodegradable plastic bag according to claim 5, wherein: the stirring temperature of the high-speed stirrer is 40-60 ℃, the stirring speed is 1000-; the extrusion equipment is a double-screw extruder, and the processing temperature of each section of the extrusion equipment from the charging section is respectively as follows: 220 ℃ at 210-.
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