CN113480836A

CN113480836A - Full-biodegradable packaging bag and preparation method thereof

Info

Publication number: CN113480836A
Application number: CN202110663036.8A
Authority: CN
Inventors: 李洋
Original assignee: Shanghai Leyi Plastic Products Co ltd
Current assignee: Shanghai Leyi Plastic Products Co ltd
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2021-10-08

Abstract

The application relates to a full-biodegradable packaging bag and a preparation method thereof. A full-biodegradable packaging bag comprises the following components in parts by weight: 100-150 parts of polylactic acid; 20-25 parts of polyethylene glycol; 5-10 parts of terpene resin; 3-5 parts of a plasticizer; 100 portions of modified starch and 125 portions; the preparation steps of the modified starch are as follows: a. first-stage modification: heating and mixing starch and the modified liquid under an alkaline condition to prepare a mixture A; the modified liquid consists of 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride; b. secondary modification: and then the mixture A is mixed with phosphate, acetic anhydride and plant fiber under the acidic condition by heating, thus obtaining the modified starch. The full-biodegradable packaging bag has the advantages of being green and environment-friendly and high in degradation rate.

Description

Full-biodegradable packaging bag and preparation method thereof

Technical Field

The application relates to the technical field of plastic films, in particular to a full-biodegradable packaging bag and a preparation method thereof.

Background

Plastic bags are essential articles for people in daily life and are often used for containing other articles. It is widely used because of its low price, extremely light weight, and easy to store. However, with the use of a large amount of plastic bags, the number of waste plastic bags is increased, and people develop various environment-friendly degradable plastic bags in order to improve the 'white pollution' caused by the difficulty in degrading the waste plastic bags to the environment.

In the related art, the environment-friendly plastic bags are mostly made of polylactic acid serving as a main raw material and starch or degradable fiber materials with the content of 15-30%. In the process of burying the plastic bag, starch or degradable fiber materials of the plastic bag are preferably degraded, so that more pores and cracks are formed on the surface of the plastic film, and then the plastic film is easily cracked into small fragments, the stability of the plastic film is reduced, and the plastic film is easily degraded in the natural environment.

However, the plastic bag prepared by the technology has low degradation rate under natural environmental conditions and can only be partially degraded, and the polyethylene material is only fragmented and superfine, but is not effectively decomposed, so that the damage caused by white pollution cannot be effectively reduced, and the potential risk is still possessed.

Disclosure of Invention

In order to improve the degradation rate of the packaging bag and reduce pollution and load brought to land, the application provides a full-biodegradation packaging bag and a preparation method thereof.

In a first aspect, the present application provides a full biodegradable packaging bag, which adopts the following technical scheme:

a full-biodegradable packaging bag comprises the following components in parts by weight:

100-150 parts of polylactic acid;

20-25 parts of polyethylene glycol;

5-10 parts of terpene resin;

3-5 parts of a plasticizer;

100 portions of modified starch and 125 portions;

the preparation steps of the modified starch are as follows:

a. first-stage modification: heating and mixing starch and the modified liquid under an alkaline condition to prepare a mixture A;

the modified liquid consists of 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride;

b. secondary modification: and then the mixture A is mixed with phosphate, acetic anhydride and plant fiber under the acidic condition by heating, thus obtaining the modified starch.

By adopting the technical scheme, when the starch and the modification liquid are heated and mixed, the 2-octenyl succinic anhydride, the dodecenyl succinic anhydride and the maleic anhydride can be gelatinized and esterified by the interaction among the three under the alkaline condition to generate the succinic starch salt with compact structure, the succinic starch salt is added by mixing phosphate, acetic anhydride and plant fiber under the acidic condition to further replace active groups on the starch to form the composite reticular copolymer taking the acetylated starch as a main body, the structure is complex and compact, the composite reticular copolymer can be cross-linked and filled with polylactic acid and terpene resin, and the environment-friendly plastic film is formed together.

When the plastic environment-friendly material film is subjected to landfill treatment, the composite reticular copolymer and the polylactic acid component of the plastic environment-friendly material film can be degraded preferentially, so that the surface structure and the property of the plastic film can be damaged rapidly, the degradation rate is higher, and the degradation rate is higher due to full biodegradation, so that the plastic environment-friendly material film has obvious environmental benefit.

Preferably, the modifying liquid is prepared by mixing 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride according to a weight ratio of 1: (0.5-0.8): (0.2-0.3).

By adopting the technical scheme, the 2-octenyl succinic anhydride, the dodecenyl succinic anhydride and the maleic anhydride in the proportion can generate a large amount of succinic starch salt with compact structure through mutual promotion among the three under the alkaline condition, and after the active groups on the succinic starch salt are activated by phosphate ions, the binding force is stronger, and the active groups can form a composite reticular copolymer with more complex structure with acetic anhydride and plant fibers, so that the various performances of the plastic bag are ensured, and the plastic bag can be efficiently degraded under the natural condition, thereby having great environmental protection benefit.

Preferably, the weight ratio of the starch to the modifying liquid in the step a is 1: (0.5-0.8) heating and mixing under the condition of pH 8-10.

By adopting the technical scheme, the starch is modified by the ratio modifying solution with good effect, the structure of the generated succinic starch salt is most compact, and a large amount of succinic starch salt can be obtained under the pH condition, so that the succinic starch salt is crosslinked and mixed with phosphate, acetic anhydride and plant fibers under the acidic condition when the subsequent secondary modification treatment is facilitated, and the plastic bag can be rapidly degraded under the natural condition while various performances are ensured.

Preferably, the mixture A is mixed with phosphate, acetic anhydride and plant fiber at the pH of 4-6 according to the weight ratio of 1 (0.2-0.3): (0.5-0.8): (0.3-0.5) heating and mixing.

Through adopting above-mentioned technical scheme, the combination of the mixture A of above-mentioned ratio and phosphate, acetic anhydride and plant fiber, modification effect are better, and acetic anhydride and plant fiber can form the compound netted copolymer that the structure is more complicated compact with succinic acid starch salt, and under this pH condition, when both combination efficiency are higher, stable in structure has ensured each item performance of plastic bag when using then, and the plastic bag has higher environmental benefit, can degrade fast under natural condition.

Preferably, the phosphate is one or more of monocalcium phosphate, sodium pyrophosphate and sodium hexametaphosphate.

By adopting the technical scheme, orthophosphate and metaphosphate are mixed for use, so that a compounding effect is achieved, the activity of phosphate groups is guaranteed, phosphate ions can be released when the phosphate groups react with the mixture A which is still partially alkaline, and then the succinic starch salt can be fully combined and modified with acetic anhydride and plant fibers, and the components are beneficial to degradation under natural conditions, and are green, environment-friendly, non-toxic and harmless.

Preferably, the plant fiber is one or more of straw fiber, lignin fiber and rice hull fiber.

By adopting the technical scheme, the plant fiber has good mutual filling effect among the components, is more fully combined with the composite reticular copolymer, and the straw fiber, the lignin fiber and the rice hull fiber are all green and environment-friendly materials, so that the resource is fully utilized while the property of the plastic bag is improved, and in the process of landfill degradation, the straw fiber, the lignin fiber and the rice hull fiber can provide certain nutrient substances and water for microorganisms after being degraded by the microorganisms, so that the degradation process is promoted.

Preferably, the plasticizer is composed of one or more of phthalate, tricresyl phosphate and epoxidized soybean oil.

By adopting the technical scheme, the plasticizer can be synchronously used among different components, so that the plastic bag has certain tensile strength and flexibility, the mobility and the dispersity of the polylactic acid are obviously improved, the polylactic acid can be fully combined with the composite reticular copolymer, and in the soil burying treatment process, the plastic bag can be rapidly cracked into small molecules through preferential degradation of the composite reticular copolymer, so that the aim of reducing the soil load is fulfilled.

In a second aspect, the application provides a preparation method of a full-biodegradable packaging bag, which adopts the following technical scheme:

a preparation method of a full-biodegradable packaging bag comprises the following steps:

s1, heating and mixing polylactic acid, polyethylene glycol and terpene resin according to the corresponding weight parts to prepare a first mixture;

s2, mixing the first mixture obtained in the step S1 with modified starch and a plasticizer according to corresponding parts by weight to obtain a second mixture, and performing extrusion granulation on the second mixture to obtain plastic particles;

s3, drying the plastic particles prepared in the S2, blowing the plastic particles into a film, cutting the film, and shaping the film to obtain the full-biodegradable packaging bag.

By adopting the technical scheme, the preparation method is simple, various parameter conditions are easy to achieve, and various raw materials are easy to obtain, so that the method is favorable for industrial production of the full-biodegradable packaging bag, and further, the economic benefit and the environmental benefit are guaranteed.

In summary, the present application has the following beneficial effects:

1. the composite reticular copolymer formed by the modified starch can be mutually cross-linked and filled with polylactic acid, polyethylene glycol and terpene resin to jointly form an environment-friendly plastic film, and the structure of the plastic film can be rapidly destroyed by preferential degradation of the composite reticular copolymer and the polylactic acid in the landfill degradation process of the plastic film, so that the degradation speed and the degradation rate of the plastic film are both improved, and the environment benefit is remarkable;

2. according to the method, the associativity among the components is enhanced by adding the plant fibers, and the straw fibers, the lignin fibers and the rice hull fibers are all green and environment-friendly materials, so that nutrients and moisture can be provided for microorganisms through self decomposition in the process of landfill degradation, and then the forward progress of the degradation process is promoted;

3. the preparation method is simple, various parameter conditions are met, and raw materials are easy to obtain, so that the preparation method is beneficial to large-scale industrial production, and the prepared full-biodegradable packaging bag is stable in performance and can be rapidly degraded in the landfill process.

Detailed Description

The present application will be described in further detail with reference to examples.

The raw materials used in the examples of the present application are commercially available, except for the following specific descriptions:

polylactic acid, a brand PLA fully degradable raw material, purchased from Jiajia plastic raw materials Co., Ltd, Dongguan city;

polyethylene glycol, CAS 25322-68-3, purchased from Haian petrochemical plants, Jiangsu province;

terpene resins, CAS 9003-74-1, available from yadeng lyon new materials science and technology ltd;

2-octenyl succinic anhydride, CAS 42482-06-4, available from Wuhan Carnox technologies, Inc.;

dodecenyl succinic anhydride, CAS 26544-38-7, available from Hubei Ferry chemical Co., Ltd;

maleic anhydride, CAS 108-31-6, available from Nantong Runfeng petrochemical Co., Ltd;

straw fiber, 200 mesh, purchased from asan panicum agro technologies ltd;

rice hull fiber, 200 mesh, purchased from asan panicum agri technologies ltd;

phthalate, CAS 131-11-3, available from Shandong Liang New Material science and technology Co., Ltd;

tricresyl phosphate, CAS 1330-78-5, available from Jiubei Jiujiu chemical Co., Ltd.;

epoxidized soybean oil, model ZH-epoxidized soybean oil, was purchased from Shandong Yuhe chemical Co., Ltd.

Preparation example

Preparation example 1

A modified starch is prepared by the following steps:

a. first-stage modification: mixing starch and a modifying solution according to a weight ratio of 1:0.3 heating to 60 ℃ under the condition that the pH value is 7.5, and stirring for 30min at the rotating speed of 500r/min to prepare a mixture A;

the modified liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride according to the weight ratio of 1:0.3: 0.1.

b. Secondary modification: mixing the mixture A with phosphate, acetic anhydride and plant fiber according to a weight ratio of 1: 0.1: 0.3: 0.2 heating to 100 ℃ under the condition that the pH value is 3.5, and stirring for 30min at the rotating speed of 150r/min to obtain modified starch; the phosphate is calcium dihydrogen phosphate;

the plant fiber is straw fiber.

Preparation example 2

The modified starch is different from the preparation example 1 in that the weight ratio of the starch to the modification liquid in the step a is 1: 0.5 was mixed with heating at pH 8.

Preparation example 3

A modified starch is different from the modified starch in preparation example 1 in that the starch and the modified liquid in the step a are heated and mixed at a pH of 8.5 according to a weight ratio of 1: 0.65.

Preparation example 4

A modified starch is different from the modified starch in preparation example 1 in that the starch and the modified liquid in the step a are heated and mixed at a pH of 9 according to a weight ratio of 1: 0.8.

Preparation example 5

A modified starch is different from the modified starch in preparation example 1 in that the starch and the modified liquid in the step a are heated and mixed at a pH of 9.5 according to a weight ratio of 1: 1.

Preparation example 6

A modified starch differing from preparation example 1 in that a modifying liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride in a weight ratio of 1: 0.5: 0.2.

Preparation example 7

A modified starch differing from preparation example 1 in that a modifying liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride in a weight ratio of 1: 0.65: 0.25.

Preparation example 8

A modified starch differing from preparation example 1 in that a modifying liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride in a weight ratio of 1: 0.8: 0.3.

Preparation example 9

A modified starch differing from preparation example 1 in that a modifying liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride in a weight ratio of 1:1: 0.4.

Preparation example 10

A modified starch was obtained as distinguished from preparation example 1 in that mixture A was mixed with phosphate, acetic anhydride and vegetable fibres in a weight ratio of 1:0.2:0.5:0.3 under heating at a pH of 4.

Preparation example 11

A modified starch, differing from preparation example 1 in that mixture a is mixed with phosphate, acetic anhydride and vegetable fibres in a weight ratio of 1: 0.25: 0.65: 0.4 was mixed with heating at pH 5.

Preparation example 12

A modified starch was obtained as distinguished from preparation example 1 in that mixture A was mixed with phosphate, acetic anhydride and vegetable fibres in a weight ratio of 1:0.3:0.8:0.5 under heating at a pH of 6.

Preparation example 13

A modified starch was obtained as distinguished from preparation example 1 in that mixture A was mixed with phosphate, acetic anhydride and vegetable fibres in a weight ratio of 1:0.4:1:0.6 under heating at a pH of 6.5.

Preparation example 14

A modified starch, differing from preparation example 1 in that the phosphate is sodium pyrophosphate.

Preparation example 15

A modified starch which is different from that of preparation example 1 in that the phosphate is sodium hexametaphosphate.

Preparation example 16

A modified starch which is different from preparation example 1 in that the phosphate is composed of monocalcium phosphate and sodium pyrophosphate in a weight ratio of 1: 1.

Preparation example 17

A modified starch was distinguished from preparation example 1 in that the phosphate salt consisted of monocalcium phosphate and sodium hexametaphosphate in a weight ratio of 1: 1.

Preparation example 18

A modified starch was distinguished from preparation example 1 in that the phosphate consisted of sodium pyrophosphate and sodium hexametaphosphate in a weight ratio of 1: 1.

Preparation example 19

A modified starch which is different from preparation example 1 in that the phosphate is composed of monocalcium phosphate, sodium pyrophosphate and sodium hexametaphosphate in a weight ratio of 1:1: 1.

Preparation example 20

A modified starch, which is different from preparation example 1 in that the plant fiber is lignin fiber.

Preparation example 21

A modified starch, which is different from preparation example 1 in that the plant fiber is rice hull fiber. Preparation example 22

A modified starch is different from the preparation example 1 in that plant fiber is composed of straw fiber and lignin fiber according to the weight ratio of 1: 1.

Preparation example 23

A modified starch is different from the modified starch prepared in preparation example 1 in that plant fibers are composed of straw fibers and rice hull fibers according to the weight ratio of 1: 1.

Preparation example 24

A modified starch is different from the modified starch prepared in preparation example 1 in that plant fiber is composed of lignin fiber and rice hull fiber in a weight ratio of 1: 1.

Preparation example 25

A modified starch is different from the preparation example 1 in that plant fiber is composed of straw fiber, lignin fiber and rice hull fiber according to the weight ratio of 1:1: 1.

Examples

Example 1

A full-biodegradable packaging bag, the components and the corresponding weight thereof are shown in Table 1, and is prepared by the following steps:

s1, heating polylactic acid, polyethylene glycol, terpene resin and modified starch to 120 ℃ according to the corresponding weight, and mixing for 20min at the speed of 150r/min to obtain a first mixture;

s2, heating the mixture in the S1 and a plasticizer to 100 ℃ according to the corresponding weight, mixing at 75r/min for 30min to obtain a second mixture, and performing extrusion granulation on the second mixture to obtain plastic particles, wherein the extrusion temperature is 100 ℃, and the extrusion time is 2S;

s3, drying the plastic particles prepared in the S2, blowing the plastic particles into a film, cutting the film and shaping the film to obtain the full-biodegradable packaging bag;

the plasticizer is phthalate.

Examples 2 to 6

A fully biodegradable package, differing from example 1 in that the components and their respective weights are shown in table 1.

TABLE 1 Components and weights (kg) thereof in examples 1-6

Examples 7 to 30

A full biodegradable packaging bag is different from the one in example 1 in the using condition of the modified starch, and the specific corresponding relation is shown in Table 2.

Table 2 modified starch usage comparison table in examples 7-30

Example 31

A fully biodegradable package bag, which is different from that of example 1 in that the plasticizer is tricresyl phosphate.

Example 32

A fully biodegradable package, which differs from example 1 in that the plasticizer is epoxidized soybean oil.

Example 33

A fully biodegradable package, which is different from example 1 in that the plasticizer is a mixture of phthalate ester and tricresyl phosphate in a weight ratio of 1: 1.

Example 34

A fully biodegradable package, which differs from example 1 in that the plasticizer consists of phthalate ester and epoxidized soybean oil in the weight ratio of 1: 1.

Example 35

A fully biodegradable package, which is different from example 1 in that the plasticizer is a mixture of tricresyl phosphate and epoxidized soybean oil in a weight ratio of 1: 1.

Example 36

A fully biodegradable package, which is different from example 1 in that the plasticizer is a mixture of phthalate ester, tricresyl phosphate and epoxidized soybean oil in a weight ratio of 1:1: 1.

Comparative example

Comparative example 1

A fully biodegradable package, which differs from example 1 in that the starch is not modified.

Comparative example 2

A fully biodegradable packaging bag, which is different from the packaging bag in example 1 in that the modified solution does not contain 2-octenyl succinic anhydride.

Comparative example 3

A full biodegradable packaging bag is different from the one in example 1 in that the modifying liquid does not contain dodecenyl succinic anhydride.

Comparative example 4

A full-biodegradable packaging bag is different from the embodiment 1 in that maleic anhydride is not contained in the modified liquid.

Comparative example 5

A full-biodegradable packaging bag is different from the packaging bag in example 1 in that 2-octenyl succinic anhydride and dodecenyl succinic anhydride are not contained in the modified liquid.

Comparative example 6

A fully biodegradable packaging bag, which is different from that in example 1 in that the modified solution does not contain 2-octenyl succinic anhydride and maleic anhydride.

Comparative example 7

A fully biodegradable packaging bag, which is different from that in example 1 in that the modifying liquid does not contain dodecenyl succinic anhydride and maleic anhydride.

Comparative example 8

A fully biodegradable package, which differs from example 1 in that b does not contain phosphate.

Comparative example 9

A full biodegradable packaging bag, which is different from the embodiment 1 in that b does not contain plant fiber.

Performance test

The full-biodegradation packaging bags prepared in the examples 1-36 and the comparative examples 1-9 are respectively weighed as test objects and buried in soil for degradation test, the specific detection steps and the detection standards are carried out according to the standard of GB/T20197-.

TABLE 3 degradation test results

Combining examples 1-6, comparative example 1 and table 3, it can be seen that the weight loss rate of examples 1-6 is higher than 12% already at 30d of landfill, wherein example 3 is the most preferred example, and the weight loss rate can reach up to 80.0% after 90d of landfill, so that when the addition amount of the modified starch is 110kg, the overall degradation speed of the plastic film is faster and the degradation rate is higher.

In comparative example 1, because modified starch is not adopted, the weight loss rate is only 6.8% when the modified starch is buried for 30 days, the highest weight loss rate is only 37.2% when the modified starch is buried for 90 days, and the degradation rate is lower while the overall degradation speed is lower.

Therefore, the addition of the modified starch can be seen, so that when the packaging bag is buried and degraded, the structure and the performance of the plastic film are quickly damaged through the preferential degradation of the composite reticular copolymer, the degradation speed and the degradation rate of the packaging bag are greatly improved, and the environment benefit is obvious.

By combining example 1, examples 7-10 and table 3, it can be seen that the weight loss rates of examples 7-10 are all higher than 12% at 30d of landfill, wherein example 8 is the most preferred example, i.e. the pH and the blending ratio in preparation example 2 are the best conditions, and the weight loss rate can reach up to 82.2% at 90d of landfill.

Therefore, the modified starch prepared under the conditions of pH and proportion has the most compact structure of the succinic acid starch salt formed in the step a and the most complex structure of the composite reticular copolymer formed by crosslinking with acetic anhydride and plant fibers, so that in the degradation process, after the composite reticular copolymer is preferentially degraded, the structure and the performance of the plastic film can be rapidly damaged, the degradation speed is higher, and the degradation rate is higher.

Combining example 1, examples 11-14, comparative examples 2-7 and combining table 3, it can be seen that the weight loss rate of examples 11-14 is higher than 13% already at 30d of landfill, wherein example 12 is the most preferred example, i.e. preparation example 7 is the most preferred pH and proportioning condition, and the weight loss rate can reach 79.6% at the maximum after 90d of landfill.

In comparative examples 2-7, because three components are not added simultaneously, the weight loss rate is lower than 10% when the landfill is carried out for 30 days, the weight loss rate is only 52.1% at the highest when the landfill is carried out for 90 days, and the degradation rate is lower while the overall degradation speed is lower.

Therefore, the modified solution in the proportion has stronger active group bonding force under the alkaline condition through the synergistic effect of the three components, and simultaneously, the structure of the composite reticular copolymer formed by the modified solution and the starch, the acetic anhydride and the plant fiber is more complex and compact, so that various performances of the plastic bag are ensured, and the plastic bag can be degraded at a high rate and more thoroughly under the natural condition.

By combining example 1, examples 15-18 and table 3, it can be seen that the weight loss rate of examples 15-18 is higher than 13% already at 30d of landfill, wherein example 16 is the most preferred example, i.e. the optimal ratio and pH are in preparation example 11, and the weight loss rate can reach 81.5% at most after 90d of landfill.

Therefore, the mixture A under the pH and proportion has the best combination and modification effects with phosphate, acetic anhydride and plant fiber, and the composite reticular copolymer formed by crosslinking is the most compact and complex, so that the plastic bag can be quickly and fully degraded under natural conditions, and has higher environmental benefit.

By combining example 1, examples 19-24, comparative example 8 and table 3, it can be seen that the weight loss rate of examples 19-24 is higher than 12.5% at the time of burying for 30d, wherein example 24 is the most preferred example, namely preparation example 19 is the most preferred example, and the weight loss rate can reach 80.3% at the maximum after burying for 90 d.

In comparative example 8, due to the addition of phosphate, the weight loss rate is only 8.7% when the landfill is buried for 30 days, the highest weight loss rate is only 49.5% when the landfill is buried for 90 days, and the degradation rate is lower while the overall degradation speed is lower.

Therefore, the three phosphates are mixed for use, a good compounding effect is achieved, the activity of the phosphate group is high, the succinic acid starch salt can be fully combined and modified with acetic anhydride and plant fibers, then, in the degradation process, after the composite reticular copolymer is degraded, the plastic bag can be quickly cracked into small fragments and degraded, the degradation speed is high, and meanwhile, the degradation rate is high.

By combining example 1, examples 25-30, comparative example 9 and table 3, it can be seen that the weight loss rate of examples 25-30 is higher than 12.5% already at 30d, wherein example 24 is the most preferred example, i.e. preparation example 25 is the most preferred example, and the weight loss rate can reach 79.8% at most after 90d landfill.

In comparative example 9, due to the addition of the plant fiber, the weight loss rate is only 9.5% when the landfill is buried for 30 days, the highest weight loss rate is only 52.5% when the landfill is buried for 90 days, and the degradation rate is lower while the overall degradation speed is lower.

Therefore, the plant fiber has good mutual filling effect among the components, can provide certain nutrient substances and water for microorganisms through self degradation, further promotes the degradation process, is green and environment-friendly, and has high economic benefit and environmental benefit.

By combining example 1, examples 31-36 and table 3, it can be seen that the weight loss rate of examples 31-36 is higher than 12.5% already at 30d, wherein example 30 is the most preferred example, and the weight loss rate can reach 73.1% at most after 90d landfill.

Therefore, the plasticizer in the proportion can obviously improve the fluidity and the dispersibility of the polylactic acid, so that the polylactic acid and the composite reticular copolymer are fully combined and are more uniformly dispersed, the surface structure of the plastic bag is damaged through the preferential degradation of the composite reticular copolymer in the soil burying treatment process, the purpose of rapid degradation is realized, and the load of the soil is effectively reduced.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The full-biodegradable packaging bag is characterized by comprising the following components in parts by weight:

100-150 parts of polylactic acid;

20-25 parts of polyethylene glycol;

5-10 parts of terpene resin;

3-5 parts of a plasticizer;

100 portions of modified starch and 125 portions;

the preparation steps of the modified starch are as follows:

2. The fully biodegradable packaging bag according to claim 1, wherein the modified liquid is prepared from 2-octenyl succinic anhydride, dodecenyl succinic anhydride and maleic anhydride according to a weight ratio of 1: (0.5-0.8): (0.2-0.3).

3. The fully biodegradable packaging bag according to claim 1, wherein the weight ratio of the starch in the component a to the modified liquid is 1: (0.5-0.8) heating and mixing under the condition of pH 8-10.

4. The full-biodegradable packaging bag according to claim 1, wherein the mixture A is mixed with phosphate, acetic anhydride and plant fiber at a pH of 4-6 according to a weight ratio of 1 (0.2-0.3): (0.5-0.8): (0.3-0.5) heating and mixing.

5. The fully biodegradable package of claim 1, wherein the phosphate is one or more of monocalcium phosphate, sodium pyrophosphate, and sodium hexametaphosphate.

6. The full biodegradation packaging bag according to claim 1, wherein the plant fiber is one or more of straw fiber, lignin fiber and rice hull fiber.

7. The fully biodegradable package of claim 1, wherein the plasticizer is comprised of one or more of phthalate, tricresyl phosphate and epoxidized soybean oil.

8. The method for preparing a full biodegradable package bag according to any one of claims 1 to 7, comprising the steps of: