阅读说明：本技术 一种可降解淀粉塑料组合物及其制备方法和应用 (Degradable starch plastic composition and preparation method and application thereof ) 是由 徐德胜 于 2021-09-18 设计创作，主要内容包括：本申请涉及塑料技术领域,更具体地说,它涉及一种可降解淀粉塑料组合物及其制备方法和应用。一种可降解淀粉塑料组合物包括如下重量份数的组分：淀粉40-60份；纤维素纳米纤丝20-30份；水性聚氨酯乳液10-20份；增塑剂5-8份；偶联剂5-8份；其制备方法为：将淀粉干燥,加入占增塑剂总量为40-50%的增塑剂,搅拌混合,静置,加入纤维素纳米纤丝、水性聚氨酯乳液、偶联剂和剩余的增塑剂搅拌混合,得到混合物,将混合物挤出造粒,出料。本申请的可降解淀粉塑料组合物,其纤维素纳米纤维、水性聚氨酯乳液可提高淀粉体系的致密性和牢固性,提高最终制得的可降解淀粉塑料组合物的强度和疏水性能。(The application relates to the technical field of plastics, in particular to a degradable starch plastic composition and a preparation method and application thereof. The degradable starch plastic composition comprises the following components in parts by weight: 40-60 parts of starch; 20-30 parts of cellulose nano-filaments; 10-20 parts of aqueous polyurethane emulsion; 5-8 parts of a plasticizer; 5-8 parts of a coupling agent; the preparation method comprises the following steps: drying starch, adding plasticizer accounting for 40-50% of the total amount of the plasticizer, stirring and mixing, standing, adding cellulose nanofibrils, aqueous polyurethane emulsion, coupling agent and the rest plasticizer, stirring and mixing to obtain a mixture, extruding and granulating the mixture, and discharging. According to the degradable starch plastic composition, the cellulose nanofibers and the waterborne polyurethane emulsion can improve the compactness and the firmness of a starch system, and improve the strength and the hydrophobic property of the finally prepared degradable starch plastic composition.)

1. The degradable starch plastic composition is characterized by comprising the following components in parts by weight:

40-60 parts of starch;

20-30 parts of cellulose nano-filaments;

10-20 parts of aqueous polyurethane emulsion;

5-8 parts of a plasticizer;

5-8 parts of a coupling agent.

2. The degradable starch plastic composition of claim 1, which is characterized by comprising the following components in parts by weight:

44-52 parts of starch;

22-26 parts of cellulose nano-filaments;

12-16 parts of a water-based polyurethane emulsion;

5.6-6.8 parts of a plasticizer;

5.6-6.8 parts of a coupling agent.

3. The degradable starch plastic composition of claim 2 wherein the cellulose nanofibrils are prepared by:

grinding cellulose to obtain ground cellulose; adding the ground cellulose into formic acid, and soaking to obtain a cellulose formate mixed solution; centrifuging and precipitating the cellulose formate mixed solution, collecting the lower acidified cellulose layer, wherein the upper layer is formic acid solution and the lower layer is acidified cellulose; and adding deionized water into the acidified cellulose to obtain a cellulose mixed solution, and homogenizing the cellulose mixed solution to obtain the cellulose nanofibrils.

4. The degradable starch plastic composition as claimed in claim 3, wherein the cellulose is formed by mixing corn stalk fiber and wheat stalk fiber in a weight ratio of 1 (1.2-1.4) during the preparation process of the cellulose nano-fibrils.

5. The degradable starch plastic composition of claim 3, wherein the concentration of formic acid is 45-55% by mass percentage concentration during the preparation of the cellulose nanofibrils.

6. The degradable starch plastic composition of claim 3, wherein the weight ratio of the cellulose to the formic acid is 1 (6-8) and the weight ratio of the cellulose to the deionized water is 1 (1.2-1.4) in the preparation process of the cellulose nanofibrils.

7. The degradable starch plastic composition of claim 3, wherein in the preparation process of the cellulose nanofibrils, the ground cellulose is added into formic acid, the temperature of the formic acid is 70-90 ℃, and the soaking time in the formic acid is 0.2-0.4 h; the centrifugal rotating speed of the cellulose formate mixed solution is 2500-; the cellulose mixed solution has the homogenizing pressure of 130-150MPa, the homogenizing temperature of 90-100 ℃ and the rotating speed of 500-700 r/min.

8. The degradable starch plastic composition of claim 2, wherein the aqueous polyurethane emulsion is selected from any one of Eubang Bell 1650 and Wanhua Adwel 1633.

9. The method for preparing the degradable starch plastic composition of any one of claims 1 to 8, which is characterized by comprising the following steps: drying starch, adding plasticizer accounting for 40-50% of the total amount of the plasticizer, stirring and mixing, standing, adding cellulose nanofibrils, aqueous polyurethane emulsion, coupling agent and the rest plasticizer, stirring and mixing to obtain a mixture, extruding and granulating the mixture, and discharging.

10. Use of the degradable starch plastic composition of any one of claims 1 to 8 in degradable plastic bags and shells.

Technical Field

The application relates to the technical field of plastics, in particular to a degradable starch plastic composition and a preparation method and application thereof.

Background

Biodegradable plastic refers to plastic which is degraded by the action of microorganisms existing in nature under the conditions of nature, such as soil and/or sandy soil, and finally completely degraded into carbon dioxide and/or methane, water and mineralized inorganic salts of elements contained therein, and new biomass.

The biodegradable plastics are classified into biodegradable plastics based on the source of the raw material for degrading the plastics and degradable plastics based on petroleum, wherein the biodegradable plastics comprise polylactic acid, polyhydroxyalkanoates and the like, and the degradable plastics based on petroleum comprise polybutylene succinate, polycaprolactone and the like. Although polylactic acid, polyhydroxyalkanoate, polybutylene succinate and polycaprolactone have excellent degradability, polylactic acid, polyhydroxyalkanoate, polybutylene succinate and polycaprolactone are used as novel biodegradable materials, and the purchase cost is high, so that the application of biodegradable plastics is limited to a certain extent.

In the related literature, because starch has complete biodegradation property, and the starch raw material has rich sources and low price, the degradable starch plastic becomes an important direction for the research and development of biodegradation at home and abroad. However, because starch is a polyhydroxy polymer, intramolecular and intermolecular hydrogen bonds are easily formed, so that the finally prepared degradable starch plastic has strong water absorption, and the mechanical property of the degradable starch plastic is greatly reduced in a low-humidity environment, thereby limiting the application of the degradable starch plastic to a certain extent.

Disclosure of Invention

In order to improve the water resistance of the degradable starch plastic, the application provides a degradable starch plastic composition and a preparation method and application thereof.

In a first aspect, the present application provides a degradable starch plastic composition, which adopts the following technical scheme:

a degradable starch plastic composition is composed of the following components in parts by weight:

40-60 parts of starch;

20-30 parts of cellulose nano-filaments;

10-20 parts of aqueous polyurethane emulsion;

5-8 parts of a plasticizer;

5-8 parts of a coupling agent.

By adopting the technical scheme, after the raw materials are mixed, the coupling agent reduces the viscosity among the raw materials such as starch, cellulose nanofibrils, aqueous polyurethane emulsion and the like, improves the dispersibility among the raw materials, and is beneficial to preparing the degradable starch plastic bag in the subsequent processing process.

The plasticizer weakens the interaction between starch molecules by increasing the distance between the starch molecules; then, the polar part of the plasticizer is coupled with the polar group of the starch to destroy the original cross-linking point of the starch, thereby promoting the plasticization of the starch and obtaining the thermosetting starch. In the plasticizing process of thermosetting starch, the aqueous polyurethane emulsion, the cellulose nanofibrils and the starch are mixed, and a carbamate bond in the aqueous polyurethane emulsion can form a hydrogen bond with starch molecules, so that the starch can be promoted to be plasticized. Meanwhile, the aqueous polyurethane emulsion can also wrap the starch and the cellulose nano-fibrils, and bond the starch and the cellulose nano-fibrils to form a starch-cellulose nano-fibril-aqueous polyurethane emulsion mixed system. The hydrogen bond formed by the water-based polyurethane emulsion and the starch in the plasticizing process can also effectively inhibit the expansion of the mixed system and reduce the water absorption performance of the mixed system.

In the process of forming the mixed system, the cellulose nano-fibrils and the starch form a network structure, and the formed network can be combined and filled and adhered by the aqueous polyurethane emulsion, so that the compactness and firmness of the aqueous polyurethane emulsion, the cellulose nano-fibrils and the starch system are improved. Meanwhile, due to the pore structure on the surface of the cellulose nanofibrils, the aqueous polyurethane emulsion can be adsorbed on the surface of the cellulose nanofibrils, and an aqueous polyurethane emulsion layer is formed on the surface of the cellulose nanofibrils, so that the surface tension of a mixed system can be effectively reduced, and the strength and the hydrophobic property of the finally prepared degradable starch plastic bag are improved.

Preferably, the degradable starch plastic composition consists of the following components in parts by weight:

44-52 parts of starch;

22-26 parts of cellulose nano-filaments;

12-16 parts of a water-based polyurethane emulsion;

5.6-6.8 parts of a plasticizer;

5.6-6.8 parts of a coupling agent.

By adopting the technical scheme, the degradable starch plastic bag prepared by optimizing the weight parts of the components has the tensile strength of 43.0-43.3MPa, the elongation at break of 480-.

Preferably, the preparation process of the cellulose nanofibrils comprises the following steps: grinding cellulose to obtain ground cellulose; adding the ground cellulose into formic acid, and soaking to obtain a cellulose formate mixed solution; centrifuging and precipitating the cellulose formate mixed solution, collecting the lower acidified cellulose layer, wherein the upper layer is formic acid solution and the lower layer is acidified cellulose; and adding deionized water into the acidified cellulose to obtain a cellulose mixed solution, and homogenizing the cellulose mixed solution to obtain the cellulose nanofibrils.

By adopting the technical scheme, the cellulose is ground firstly, so that the size of the cellulose can be reduced preliminarily, and the subsequent operation on the cellulose is facilitated. After the ground cellulose is soaked in formic acid, the size of the ground cellulose is small, formic acid is accelerated to destroy hydrogen bond networks in the cellulose, and amorphous areas in the cellulose are removed, so that the rigid structure of the cellulose is softened, and crystal parts which are arranged tightly and orderly are left, and the cellulose nanofibrils with higher crystallinity and crystal form are obtained; and then, diluting the softened cellulose nanofibrils with water, homogenizing, repeatedly extracting the cellulose nanofibrils through repeated action of high pressure, and improving the crystallinity of the cellulose nanofibrils, so that the cellulose nanofibrils have good strength and hydrophobic property, and the strength of a mixed system can be better improved.

Meanwhile, as the cellulose nanofibrils are softened, the size of the cellulose nanofibrils can be effectively reduced, so that the cellulose nanofibrils are better dispersed in a starch-based system, the stability of a network structure formed by the cellulose nanofibrils and starch is improved, the water-based polyurethane emulsion can be adsorbed on the surface of the cellulose nanofibrils, the compactness of the whole network structure can be improved, the surface tension of the whole network structure can be reduced, and the strength and the hydrophobicity of the finally prepared degradable plastic bag are improved.

Preferably, in the preparation process of the cellulose nanofibrils, the cellulose is formed by mixing corn stalk fibers and wheat stalk fibers according to the weight ratio of 1 (1.2-1.4).

By adopting the technical scheme, the fiber prepared by compounding the corn stalk fiber and the wheat stalk fiber has good size and toughness, is beneficial to further processing the fiber subsequently, and improves the crystallinity and size of the finally prepared cellulose nanofibril. The cellulose nano-fibrils with good crystallinity and small size are added into a starch and aqueous polyurethane emulsion system, so that the compactness and crystallinity of a formed network structure can be improved, and the strength and hydrophobicity of the finally prepared degradable plastic bag are improved.

Preferably, the concentration of formic acid in the preparation process of the cellulose nanofibrils is 45-55% by mass percentage.

By adopting the technical scheme, the concentration of formic acid is in the range, the soaking effect on cellulose is the best, the cellulose nanofibrils with higher crystallinity and crystalline form can be obtained, and the strength and the hydrophobicity of the finally prepared degradable plastic bag are improved.

Preferably, in the preparation process of the cellulose nanofibrils, the weight ratio of the cellulose to the formic acid is 1 (6-8), and the weight ratio of the cellulose to the deionized water is 1 (1.2-1.4).

By adopting the technical scheme, the tensile strength of the finally prepared degradable plastic bag is 45.0-45.2MPa, the elongation at break is 495-plus-498 percent, the compost degradation rate is 100 percent after 3 months, and the contact angle is 132-plus-135 degrees.

Preferably, in the preparation process of the cellulose nanofibrils, the ground cellulose is added into formic acid, the temperature of the formic acid is 70-90 ℃, and the soaking time in the formic acid is 0.2-0.4 h; the centrifugal rotating speed of the cellulose formate mixed solution is 2500-; the cellulose mixed solution has the homogenizing pressure of 130-150MPa, the homogenizing temperature of 90-100 ℃ and the rotating speed of 500-700 r/min.

By adopting the technical scheme, the tensile strength of the degradable starch plastic bag prepared under the conditions is relatively improved by 0.66-0.88%, the elongation at break is relatively improved by 0.4-0.8%, and the contact angle is relatively improved by 4.44-5.93%. Therefore, the degradable starch plastic bags prepared in the examples 16 to 18 of the application have better degradation performance, tensile strength, extensibility and hydrophobic performance.

Preferably, the aqueous polyurethane emulsion is selected from the group consisting of the European Pont Bell 1650 and Wanhua1633.

In the examples of the present application, the aqueous polyurethane emulsion is used in the amount of only ten thousand flowers1633 by way of example, and not limitation, the Pont Bell 1650 or other implementations of Pont and Wanhua1633 the raw materials with the same function can be used as water-based polyurethane emulsion in preparing degradable starch plastic composition.

In a second aspect, the application provides a preparation method of a degradable starch plastic composition, which adopts the following technical scheme:

a preparation method of a degradable starch plastic composition comprises the following steps:

drying starch, adding plasticizer accounting for 40-50% of the total amount of the plasticizer, stirring and mixing, standing, adding cellulose nanofibrils, aqueous polyurethane emulsion, coupling agent and the rest plasticizer, stirring and mixing to obtain a mixture, extruding and granulating the mixture, and discharging.

By adopting the technical scheme, the method is simple to operate, has low requirements on production conditions, and is suitable for large-scale production. Meanwhile, the water-based polyurethane emulsion can promote starch plasticization, reduce the time of starch plasticization and improve the efficiency of the degradable starch plastic composition.

In a third aspect, the application provides an application of a degradable starch plastic composition, which adopts the following technical scheme: use of a degradable starch plastic composition in a degradable plastic bag.

By adopting the technical scheme, when the degradable starch plastic composition is used for preparing a degradable plastic bag or a degradable starch plastic shell, the degradable starch plastic composition has good strength and hydrophobic property.

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

1. in the plasticizing process of the thermosetting starch, the aqueous polyurethane emulsion, the cellulose nanofibrils and the starch are mixed, and the carbamate bonds in the aqueous polyurethane emulsion can form hydrogen bonds with starch molecules, so that the starch can be promoted to be plasticized, and the toughness of the finally plasticized starch is improved; the cellulose nano-fiber and the starch form a network structure, the water-based polyurethane emulsion can wrap the starch and the cellulose nano-fibrils, the compactness and the firmness of the water-based polyurethane emulsion, the cellulose nano-fiber and the starch system are improved, the water-based polyurethane emulsion can be adsorbed on the surface of the cellulose nano-fibrils, the surface tension of the cellulose nano-fibrils is reduced, and the strength and the hydrophobic property of the finally prepared degradable starch plastic are improved;

2. in the preparation process of the cellulose nano-fibrils, the grinding, the acidification and the homogenization are combined, so that the prepared cellulose nano-fibrils have good size and crystallinity, the adsorption of the water-based polyurethane emulsion and the formation of a network structure with starch in the thermoplastic process are facilitated, and the strength and the hydrophobic property of the finally prepared degradable starch plastic are improved.

Detailed Description

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

The specifications of the various raw materials and information of manufacturers used in the examples or comparative examples of the present application are as follows:

starch, corn starch, CAS number 9005-25-8, purchased from Hubei Bolan chemical Co., Ltd;

corn fiber, purchased from bai-diligent fodder limited, jiro 384;

the wheat straw fiber is purchased from the Ministry of the Songyang pasture;

aqueous polyurethane emulsion1633 under the brand name of1633 procurement from Wanhua group；

Coupling agent Kh550 from English, CAS number 7-96-8, purchased from chemical technology Limited, English from Jinan province;

dimethyl phthalate, model cy-251680, purchased from Shandong Changyao New materials Co., Ltd;

thermoplastic starch, having a brand number of TPS, purchased from the chemical marketing department of the Shunddeli Hongjing of Foshan city;

the grinder is a high-speed universal grinder, has the model number of 60B and is purchased from Jiangsu Yuchang drying engineering Co., Ltd;

centrifuge, model LW450, purchased from sozhou military machinery manufacturing ltd;

a high pressure homogenizer model Gville-30, purchased from Suzhou micro-fluidic nanometer Biotechnology, Inc.;

the oven is a hot air circulation oven with the model of ct-c-IIA, purchased from Changzhou Nixiang drying equipment, Inc.;

an internal mixer, model BP-8172-B, available from precision instruments of Aquilaria sinensis, Inc.;

a twin screw extruder, model ZKJC-90, purchased from Cangzhou Zhenzi mechanical manufacturing, Inc.;

a film blowing machine which is purchased from Yonghong machinery Co Ltd of Ruian city and has the model number: TL-600.

The methods for detecting the tensile strength, the elongation at break, the compost degradation rate after 3 months and the contact angle of the degradable starch plastic bags prepared in the embodiments and the degradable corn starch plastic bags prepared in the comparative examples are as follows:

detecting the tensile strength and the elongation at break of the degradable starch plastic bag by referring to a method in GB/T1040.1-2018 'determination of plastic tensile property';

and (3) detecting the percent of degradation rate of the biological compost of the degradable starch plastic bag, and testing the percent of degradation rate of the compost of the degradable plastic after 3 months according to the GB/T16716.7-2012 standard.

And (3) detecting the contact angle of the degradable starch plastic bag, referring to the measurement of the contact angle of the GB/T30693-2014 plastic film and water.

Preparation examples of raw materials

Preparation example 1

A cellulose nanofibril, calculated on the basis of 1kg of total weight of cellulose nanofibril, having the components and their respective weights as shown in Table 1, and prepared by the following steps:

a1: adding 1kg of cellulose into a grinding machine, controlling the gap of a grinding disc to be 10 mu m, adjusting the rotating speed of the grinding disc to be 500r/min, and grinding for ten times, wherein each time is 2 min; and adjusting the gap of a grinding disc to-200 mu m, adjusting the rotating speed of the grinding disc to 2000r/min, and grinding for fifteen times, wherein each grinding time is 2min, so as to obtain the ground cellulose.

A2: adding the ground cellulose into 5kg of formic acid at 60 ℃, and soaking for 0.1h to obtain a cellulose formate mixed solution; and adding the cellulose formate mixed solution into a centrifuge, centrifuging for 3 times at the rotating speed of 2400r/min, layering, collecting the cellulose on the lower layer after acidification, wherein the upper layer is formic acid solution and the lower layer is acidified cellulose.

A3: and adding the acidified cellulose into a high-pressure homogenizer, adding 1.1kg of deionized water into the high-pressure homogenizer, adjusting the pressure of the high-pressure homogenizer to 120MPa, adjusting the temperature to 80 ℃, and homogenizing for 2 hours at the rotating speed of 400r/min to obtain the cellulose nanofibril.

Wherein the cellulose is formed by mixing corn stalk fiber and wheat stalk fiber according to the weight ratio of 1: 1;

the mass percentage concentration of the formic acid is 40 percent;

the weight ratio of the cellulose to the formic acid is 1: 5;

the weight ratio of cellulose to deionized water was 1: 1.1.

Preparation examples 2 to 4

A cellulose nanofibril differing from preparation example 1 in that each component and the corresponding weight thereof are shown in table 1.

TABLE 1 Components and weights (kg) thereof in preparation examples 1-4

Preparation example 5

A cellulose nanofibril which is different from that of production example 3 in that it is the same as that of production example 3 except that the concentration of formic acid is 45% by mass.

Preparation example 6

A cellulose nanofibril which is different from that of production example 3 in that it is the same as that of production example 3 except that the concentration of formic acid is 50% by mass.

Preparation example 7

A cellulose nanofibril which is different from that of production example 3 in that it is the same as that of production example 3 except that the concentration of formic acid is 55% by mass.

Preparation example 8

A cellulose nanofibril which is different from preparation example 6 in that when the total weight of cellulose is 1kg, it is the same as preparation 6 except that formic acid is 6kg and deionized water is 1.2 kg.

Preparation example 9

A cellulose nanofibril which is different from preparation example 6 in that when the total weight of cellulose is 1kg, it is the same as preparation 6 except that formic acid is 7kg and deionized water is 1.3 kg.

Preparation example 10

A cellulose nanofibril which is different from preparation example 6 in that when the total weight of cellulose is 1kg, it is the same as preparation 6 except that formic acid is 8kg and deionized water is 1.4 kg.

Preparation example 11

A difference between the cellulose nanofibril and the preparation example 9 is that in the preparation process A2 of the cellulose nanofibril, the temperature of adding ground cellulose into formic acid is 70 ℃, the soaking time is 0.2h, and the centrifugal rotating speed of the cellulose formate mixed solution is 2500 r/min; a3 the procedure was repeated except that the homogenization pressure was 130MPa, the homogenization temperature was 90 ℃ and the rotation speed was 500r/min, except that the procedure was as in preparation example 6.

Preparation example 12

A difference between the cellulose nanofibril and the preparation example 9 is that in the preparation process A2 of the cellulose nanofibril, the milled cellulose is added into formic acid, the temperature of the formic acid is 80 ℃, the soaking time is 0.3h, and the centrifugal rotating speed of the cellulose formate mixed solution is 2650 r/min; a3 the procedure was repeated except that the homogenization pressure was 140MPa, the homogenization temperature was 95 ℃ and the rotation speed was 600r/min, as in preparation example 6.

Preparation example 13

A difference between the cellulose nanofibril and the preparation example 9 is that in the preparation process A2 of the cellulose nanofibril, the milled cellulose is added into formic acid, the temperature of the formic acid is 90 ℃, the soaking time is 0.4h, and the centrifugal rotating speed of the cellulose formate mixed solution is 2800 r/min; a3 the procedure was repeated except that the homogenization pressure was 150MPa, the homogenization temperature was 100 ℃ and the rotation speed was 700r/min, except that the procedure was as in preparation example 6.

Example 1

A degradable starch plastic bag comprises the components and the corresponding weight shown in the table 1 and is prepared by the following steps:

s1: putting the starch into a dryer, and drying for 2 hours at 100 ℃ to obtain dried starch;

s2: adding the dried starch into an internal mixer, heating the internal mixer to 80 ℃, adding a plasticizer under the condition that the rotating speed is 500r/min, stirring and mixing for 15min, and standing for 2-3h under the condition of heat preservation;

s3: heating an internal mixer to 125 ℃, setting the rotating speed to 800r/min, then sequentially adding cellulose nanofibrils, aqueous polyurethane emulsion and a coupling agent into the internal mixer, and stirring and mixing for 1h to obtain a mixture;

s4: adding the mixture into a double-screw extruder, adjusting the temperature of the double-screw extruder to be 150-160 ℃, plasticizing at the screw rotating speed of 90rpm, extruding master batches by the double-screw extruder, putting the master batches into a film blowing machine, and performing blow molding to form a film under the conditions of 120 plus materials, 150 ℃, 200r/min and 40Hz to obtain the degradable starch plastic bag.

Wherein the starch is corn starch;

the plasticizer is dimethyl phthalate;

cellulose nanofibers prepared from preparation example 1;

the aqueous polyurethane emulsion is Wanhua1633；

Coupling agent is English Kh 550.

Examples 2 to 6

A degradable starch plastic bag is different from the degradable starch plastic bag in example 1 in that the components and the corresponding parts by weight are shown in Table 2.

TABLE 2 Components and weights (kg) thereof in examples 1-6

The degradable starch plastic bags obtained in examples 1 to 6 were subjected to the tests of tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle, and the test results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in examples 1-6 have tensile strength of 42.0-43.3MPa, elongation at break of 470-482%, compost degradation rate of 98% after 3 months, and contact angle of 102-112 deg. Therefore, the degradable starch plastic bags prepared in the embodiments 1 to 6 have good degradation performance, and have good tensile strength, extensibility and hydrophobic performance. The analysis of the method can be that the cellulose nano-fibrils, the aqueous polyurethane emulsion and the starch in the plasticizing process have a synergistic effect, so that the tensile strength, the extending capability and the hydrophobic property of the finally prepared degradable starch plastic bag can be improved.

In particular, the degradable starch plastic bags prepared in examples 2-4 have tensile strength of 43.0-43.3MPa, elongation at break of 480-482 ℃ and contact angle of 109-112 ℃. Therefore, in the total raw materials for preparing the degradable plastic bag, when the starch accounts for 44-52 parts, the cellulose nanofibrils account for 22-26 parts, the aqueous polyurethane emulsion accounts for 12-16 parts, the plasticizer accounts for 5.6-6.8 parts, and the coupling agent accounts for 5.6-6.8 parts, the finally prepared degradable starch plastic bag has better tensile strength, extensibility and hydrophobic property. In particular, the degradable starch plastic bag obtained from example 3 has the best properties compared to examples 2 and 4.

Example 7

A degradable starch plastic bag, which is different from example 3 in that, in the preparation process of cellulose nanofibrils, the cellulose is the same as example 3 except that the cellulose is formed by mixing corn fiber and wheat straw fiber in a weight ratio of 1:1.2, namely, the cellulose nanofibrils are prepared by the preparation example 2.

Example 8

A degradable starch plastic bag, which is different from example 3 in that, in the preparation process of cellulose nanofibrils, the cellulose is the same as example 3 except that the cellulose is formed by mixing corn fiber and wheat straw fiber in a weight ratio of 1:1.3, namely, the cellulose nanofibrils are prepared by the preparation example 3.

Example 9

A degradable starch plastic bag is different from that in example 3 in that in the preparation process of cellulose nanofibrils, the preparation process is the same as that in example 3 except that the cellulose is prepared by mixing corn fiber and wheat straw fiber according to the weight ratio of 1:1.4, namely the cellulose nanofibrils are prepared by the preparation example 4.

The degradable starch plastic bags obtained in examples 7 to 9 were subjected to the tests of tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle, and the test results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in the examples 7-9 have tensile strength of 44.0-44.2MPa, elongation at break of 486-488%, compost degradation rate of 98% after 3 months, and contact angle of 120-123 deg..

Compared with the degradable plastic bags prepared in example 3, the degradable starch plastic bags prepared in examples 7-9 have the advantages that the tensile strength is relatively improved by 1.62-2.08%, the elongation at break is relatively improved by 0.62-1.24%, and the contact angle is relatively improved by 7.14-9.84%. Therefore, the degradable starch plastic bags prepared in the embodiments 7 to 9 have good degradation performance, and have better tensile strength, extensibility and hydrophobic performance. In particular, the degradable starch plastic bag obtained from example 8 showed the best performance compared to examples 7 and 9.

The reason for the analysis is that in the preparation process of the cellulose nanofibrils, when the cellulose is formed by mixing the corn stalk fibers and the wheat stalk fibers according to the weight ratio of 1 (1.2-1.4), the finally prepared cellulose nanofibrils have the best performance, and are beneficial to generating the synergistic compounding effect with the starch and the aqueous polyurethane emulsion in the plasticizing process, so that the tensile strength, the extension capacity and the hydrophobic performance of the finally prepared degradable starch plastic bag are improved.

Example 10

A degradable starch plastic bag, which is different from example 8 in that the cellulose nanofibrils are prepared in the same manner as example 8 except that the mass percentage concentration of formic acid is 45%, that is, the cellulose nanofibrils are prepared according to preparation example 5.

Example 11

A plastic bag of degradable starch, which is different from example 8 in that cellulose nanofibrils are prepared in the same manner as example 8 except that the mass percentage concentration of formic acid is 50%, that is, cellulose nanofibrils are prepared according to preparation example 6.

Example 12

A plastic bag of degradable starch, which is different from example 8 in that cellulose nanofibrils were prepared in the same manner as in example 8, except that the concentration of formic acid was 55% by mass, that is, cellulose nanofibrils were prepared according to preparation example 7.

The degradable starch plastic bags obtained in examples 10 to 12 were subjected to the tests of tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle, and the test results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in the examples 10-12 have tensile strength of 44.5-44.6MPa, elongation at break of 490-492%, compost degradation rate of 99% after 3 months, and contact angle of 126-127 deg.

Compared with the degradable plastic bags prepared in the embodiment 8, the degradable starch plastic bags prepared in the embodiments 10 to 12 have the advantages that the tensile strength is relatively improved by 0.68 to 1.36 percent, the elongation at break is relatively improved by 0.41 to 0.82 percent, the compost degradation rate is relatively improved by 1.02 percent after 3 months, and the contact angle is relatively improved by 2.44 to 4.07 percent. Therefore, the degradable starch plastic bags prepared in the examples 10 to 12 have good degradation performance, tensile strength, extensibility and hydrophobic property. In particular, the degradable starch plastic bags obtained in example 11 showed the best performances compared to those of examples 10 and 12.

The reason for the analysis is that in the preparation process of the cellulose nanofibrils, when the concentration of formic acid is 45-55% by mass percent, the soaking capacity of the cellulose is the best, so that the subsequent homogenization operation of the cellulose is facilitated, the performance of the finally prepared cellulose nanofibrils is improved, and the synergistic compounding effect of the cellulose nanofibrils and starch and aqueous polyurethane emulsion in the plasticizing process is facilitated, so that the degradation performance, the tensile strength, the extension capacity and the hydrophobic performance of the finally prepared degradable starch plastic bag are improved.

Example 13

A plastic bag of degradable starch, which is different from example 11 in that the cellulose nanofibrils were prepared in the same manner as in example 11 except that the weight of formic acid was 6kg and the weight of deionized water was 1.2kg, that is, the cellulose nanofibrils were prepared according to preparation example 8.

Example 14

A plastic bag of degradable starch, which is different from example 11 in that the cellulose nanofibrils were prepared in the same manner as in example 11 except that the weight of formic acid was 7kg and the weight of deionized water was 1.3kg, that is, the cellulose nanofibrils were prepared according to preparation example 9.

Example 15

A plastic bag of degradable starch, which is different from example 11 in that the cellulose nanofibrils were prepared in the same manner as in example 11, except that the weight of formic acid was 8kg and the weight of deionized water was 1.4kg, i.e., the cellulose nanofibrils were prepared according to preparation example 10.

The degradable starch plastic bags obtained in examples 13 to 15 were subjected to the tests of tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle, and the test results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in examples 13-15 have tensile strength of 45.0-45.2MPa, elongation at break of 495-498%, compost degradation rate of 100% after 3 months, and contact angle of 132-135 deg.

Compared with the degradable plastic bags prepared in the embodiment 11, the degradable starch plastic bags prepared in the embodiments 13 to 15 have the advantages that the tensile strength is relatively improved by 0.82 to 1.36 percent, the elongation at break is relatively improved by 0.6 to 1.22 percent, the compost degradation rate is relatively improved by 1.01 percent after 3 months, and the contact angle is relatively improved by 3.13 to 4.69 percent. Therefore, the degradable starch plastic bags prepared in the examples 13 to 15 have better degradation performance, tensile strength, extensibility and hydrophobic performance. In particular, the degradable starch plastic bags prepared in example 14 have the best performances compared with those of examples 13 and 15.

The reason for the analysis is that in the preparation process of the cellulose nanofibrils, when the weight ratio of the cellulose to the formic acid is 1 (6-8) and the weight ratio of the cellulose to the deionized water is 1 (1.2-1.4), the formic acid can be accelerated to destroy hydrogen bond networks in the cellulose and remove amorphous areas in the cellulose, so that the rigid structure of the cellulose is softened, the crystallinity of the prepared cellulose nanofiber is improved, the cellulose nanofiber is favorable for the synergistic compounding effect with starch and aqueous polyurethane emulsion in the plasticizing process, and the degradation performance, the tensile strength, the extension capacity and the hydrophobic performance of the finally prepared degradable starch plastic bag are improved.

Example 16

A degradable starch plastic bag, which is different from the plastic bag in example 14 in that in the preparation process of cellulose nanofibrils, except the preparation process A2, the ground cellulose is added into formic acid, the temperature of the formic acid is 70 ℃, the soaking time is 0.2h, and the centrifugal rotation speed of a cellulose formate mixed solution is 2500 r/min; a3 was repeated in the same manner as in example 14, except that the cellulose nanofibrils were produced according to preparation example 11 at a homogenization pressure of 130MPa, a homogenization temperature of 90 ℃ and a rotation speed of 500 r/min.

Example 17

A degradable starch plastic bag, which is different from the plastic bag in the embodiment 14 in that in the preparation process of cellulose nanofibrils, except the preparation process A2, the ground cellulose is added into formic acid, the temperature of the formic acid is 80 ℃, the soaking time is 0.3h, and the centrifugal speed of the cellulose formate mixed solution is 2650 r/min; a3 was repeated in the same manner as in example 14 except that the cellulose nanofibrils were produced according to preparation example 12 at a homogenization pressure of 140MPa, a homogenization temperature of 95 ℃ and a rotation speed of 600 r/min.

Example 18

A degradable starch plastic bag, which is different from the plastic bag in the embodiment 14 in that in the preparation process of cellulose nanofibrils, except the preparation process A2, the milled cellulose is added into formic acid, the temperature of the formic acid is 90 ℃, the soaking time is 0.4h, and the centrifugal rotation speed of the cellulose formate mixed solution is 2800 r/min; a3 was repeated in the same manner as in example 14 except that the cellulose nanofibrils were produced according to preparation example 13 at a homogenization pressure of 150MPa, a homogenization temperature of 100 ℃ and a rotation speed of 700 r/min.

The degradable starch plastic bags obtained in examples 16 to 18 were subjected to the tests of tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle, and the test results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in the examples 16-18 have the tensile strength of 45.5-45.6MPa, the elongation at break of 500-502%, the compost degradation rate after 3 months of 100% and the contact angle of 139-143 deg.

Compared with the degradable plastic bags prepared in the example 14, the degradable starch plastic bags prepared in the examples 16 to 18 have the advantages that the tensile strength is relatively improved by 0.66 to 0.88 percent, the elongation at break is relatively improved by 0.4 to 0.8 percent, and the contact angle is relatively improved by 4.44 to 5.93 percent. Therefore, the degradable starch plastic bags prepared in the examples 16 to 18 of the application have better degradation performance, tensile strength, extensibility and hydrophobic performance. In particular, the degradable starch plastic bag prepared in example 17 has the best performance compared with those of examples 16 and 18.

The reason for the analysis is that in the preparation process A2 of the cellulose nanofibrils, the temperature of adding the ground cellulose into formic acid is 70-90 ℃, and the soaking time is 0.2-0.4 h; the centrifugal rotating speed of the cellulose formate mixed solution is 2500-; in the preparation process A3, when the homogenization pressure of the cellulose mixed solution is 130-100 MPa, the homogenization temperature is 90-100 ℃, and the rotation speed is 500-700r/min, formic acid can be accelerated to destroy hydrogen bond networks in cellulose, the size of cellulose nano fibrils can be reduced, the crystallinity of the prepared cellulose nano fibers can be improved, the cellulose mixed solution is favorable for generating a synergistic compounding effect with starch and aqueous polyurethane emulsion in the plasticizing process, and thus the degradation performance, tensile strength, extension capability and hydrophobic performance of the finally prepared degradable starch plastic bag are improved.

Comparative example

Comparative example 1

A degradable corn starch plastic bag, model A7936, is purchased from Misojou tableware (Foshan) Co.

The degradable corn starch plastic bags obtained in comparative example 1 were subjected to tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle measurements, and the results of the measurements are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

From the analysis of the data in the above table, it can be seen that the degradable corn starch plastic bag of comparative example 1 is commercially available, the tensile strength is 40.0MPa, the elongation at break is 450%, the compost degradation rate after 3 months is 98%, and the contact angle is 92 °.

Compared with the degradable plastic bag prepared in example 17, the degradable starch plastic bag prepared in comparative example 1 has the advantages that the tensile strength is relatively reduced by 12.28%, the elongation at break is relatively reduced by 10.36%, the compost degradation rate is relatively reduced by 2.00% after 3 months, and the contact angle is relatively reduced by 35.66%. Therefore, the degradable starch plastic bag prepared in the embodiment 17 of the application has better degradation performance, tensile strength, extensibility and hydrophobic performance compared with the commercially available degradable corn starch plastic bag.

Comparative examples 2 to 7

A degradable starch plastic bag is different from the degradable starch plastic bag in example 17 in that the degradable starch plastic bag is the same as the degradable starch plastic bag in example 17 except that the weight of starch, cellulose nanofibrils and aqueous polyurethane emulsion is different, and the components and the corresponding weight are shown in the following table.

The degradable starch plastic bags prepared in comparative examples 2-7 were subjected to tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle measurements, and the results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in comparative examples 2-7 have tensile strength of 25-32MPa, elongation at break of 355-405%, compost degradation rate of 82-88% after 3 months, and contact angle of 40-51 deg.

The degradable starch plastic bags prepared in comparative examples 2 to 7 are different from the degradable starch plastic bag prepared in example 17 in that the weights of starch, cellulose nanofibrils and aqueous polyurethane emulsion are different in the total raw material process for preparing the degradable starch plastic bag, and compared with the degradable starch plastic bag prepared in example 17, the tensile strength is relatively reduced by 40.63 to 80 percent, the elongation at break is relatively reduced by 23.95 to 41.41 percent, the compost degradation rate is relatively reduced by 13.64 to 21.95 percent after 3 months, and the contact angle is relatively reduced by 180.39 to 257.50 percent. Therefore, the starch, the cellulose nano-fibrils and the aqueous polyurethane emulsion have a synergistic effect, and the degradation performance, the tensile strength, the extension capacity and the hydrophobic performance of the finally prepared degradable starch plastic bag can be improved.

Comparative example 8

A plastic bag of degradable starch, which is different from example 17 in that it is the same as example 17 except that cellulose is not ground in the process of preparing cellulose nanofibrils. The cellulose nanofibrils are prepared as follows:

a1: adding 1kg of cellulose into 6kg of formic acid with the mass percentage concentration of 50% at the temperature of 80 ℃, and soaking for 0.3h to obtain cellulose formate mixed solution; adding the cellulose formate mixed solution into a centrifuge, centrifuging for 3 times at the rotating speed of 2650r/min, layering, collecting the cellulose on the lower layer after acidification, wherein the upper layer is formic acid solution and the lower layer is acidified cellulose;

a2: and adding the acidified cellulose into a high-pressure homogenizer, adjusting the pressure of the high-pressure homogenizer to 140MPa and the temperature to 95 ℃, and homogenizing for 2 hours at the rotating speed of 600r/min to obtain the cellulose nanofibril.

Comparative example 9

A plastic bag of degradable starch, which is different from example 17 in that cellulose is the same as example 17 except that formic acid treatment is not performed on cellulose during the preparation of cellulose nanofibrils. The cellulose nanofibrils are prepared as follows:

a1: adding 1kg of cellulose into a grinding machine, controlling the gap of a grinding disc to be 10 mu m, adjusting the rotating speed of the grinding disc to be 500r/min, and grinding for ten times; adjusting the gap of a grinding disc to-200 mu m, adjusting the rotating speed of the grinding disc to 2000r/min, and grinding for fifteen times to obtain ground cellulose;

a2: and adding the ground cellulose into a high-pressure homogenizer, adjusting the pressure of the high-pressure homogenizer to 140MPa and the temperature to 95 ℃, and homogenizing for 2 hours at the rotating speed of 600r/min to obtain the cellulose nanofibril.

The degradable starch plastic bags prepared in comparative examples 8-9 were subjected to tensile strength, elongation at break, compost degradation rate after 3 months, and contact angle measurements, and the results are shown in the following table.

And (4) surface note: contact angles less than 90 ° represent partial wetting or wetting, contact angles greater than 90 ° represent no wetting, and the larger the contact angle, the better the hydrophobic properties.

As can be seen from the analysis of the data in the above table, the degradable starch plastic bags prepared in the comparative examples 8-9 have the tensile strength of 38-39MPa, the elongation at break of 410-450%, the compost degradation rate after 3 months of 85% and the contact angle of 55-56 deg.

The degradable starch plastic bag manufactured in comparative example 8 is different from the degradable plastic bag manufactured in example 17 in that cellulose is not ground in the manufacturing process for preparing cellulose nanofibrils. Compared with the degradable plastic bag prepared in example 17, the degradable starch plastic bag prepared according to comparative example 8 has the advantages that the tensile strength is relatively reduced by 18.42%, the elongation at break is relatively reduced by 22.44%, the compost degradation rate after 3 months is relatively reduced by 17.65%, and the contact angle is relatively reduced by 160%.

The degradable starch plastic bag manufactured in comparative example 9 is different from the degradable plastic bag manufactured in example 17 in that cellulose is not subjected to formic acid soaking treatment in the manufacturing process for manufacturing cellulose nanofibrils. Compared with the degradable plastic bag prepared in example 17, the degradable starch plastic bag prepared in comparative example 9 has the advantages that the tensile strength is relatively reduced by 15.38%, the elongation at break is relatively reduced by 20.96%, the compost degradation rate after 3 months is relatively reduced by 17.65%, and the contact angle is relatively reduced by 155.36%.

Therefore, in the preparation process of the degradable starch plastic bag, the degradable starch plastic bag finally prepared from the cellulose nanofibrils prepared through grinding, formic acid soaking and homogenizing treatment has better degradation performance, tensile strength, extensibility and hydrophobic performance.

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.