AU2020101700A4

AU2020101700A4 - Method for preparing water-and-oil-resistant nanocellulose composite film

Info

Publication number: AU2020101700A4
Application number: AU2020101700A
Authority: AU
Inventors: Guodong Li; Wei Li; Wenxia Liu; Xi LU; Xinle Ren; Zhaoping SONG; Jiebin Tang; Huili Wang; Dehai Yu; Shuqian Zhao
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2020-08-06
Filing date: 2020-08-06
Publication date: 2020-09-17
Anticipated expiration: 2028-08-06

Abstract

This invention is disclosed a method for preparing a water-and-oil-resistant nanocellulose composite film comprises steps of: Si. filler modification: subjecting a coupling agent and a filler at a mass ratio of 0.5-15:100 to surface modification 5 treatment using a dry modification process to obtain a modified filler; S2. preparation of intermediates: mixing the modified filler and cellulose at a mass ratio of 1-20:100 thoroughly to obtain the intermediates; S3. preparation of products: preparing the intermediates as the composite film. The composite film of the invention has excellent characteristics of water-and-oil-resistance, and no toxic or harmful chemical solvent is 10 used during the synthesis process. The process is simple and has strong operability.

Description

METHOD FOR PREPARING WATER-AND-OIL-RESISTANT NANOCELLULOSE COMPOSITE FILM

Technical Field

The present invention relates to a method for preparing a water-and-oil-resistant

nanocellulose composite film.

Background Art

Cellulose exists widely in various plant resources. The development of plant

fiber-based materials can effectively relieve the non-renewability and environmental

pollution issues of petroleum-based derivatives that are currently widely used.

Nanocellulose extracted from plant fiber resources is a high-performance, renewable

green raw material with properties such as nontoxicity, biocompatibility, low density

and excellent mechanical strength. It can be used as a basic unit to construct a variety

of structural materials and functional composite materials with excellent performance.

A transparent film formed by intertwining nanocellulose has excellent mechanical

strength, low oxygen permeability, low thermal expansion coefficient and excellent

thermostability and can be applied to green packaging materials or as a transparent

substrate for flexible electronic components. However, a large number of hydrophilic

groups are exposed on the surface of nanocellulose, which tends to form a hydrated

layer and exhibits strong hydrophilicity. In a humid environment, water molecules can

be easily adsorbed on its surface, destroying the hydrogen bonding between

nanocellulose, drastically degrading the mechanical properties and insulation

properties of the nanocellulose film. The nanocellulose has poor water resistance, and

also the nanocellulose film has poor oil impermeability, which severely restricts the

application of its thin films as packaging materials of high impermeability.

Therefore, a water-and-oil-resistant nanocellulose film is desired to meet the demand

for novel packaging materials. Gousse (2002) modified the nanocellulose via

silanization to improve the hydrophobicity of the nanocellulose. Rodionova (2011) modified the surface of nanocellulose via esterification by acetic anhydride in a toluene solvent system. Shimizu (2014) adsorbed different kinds of alkyl quaternary ammonium salts on the carboxyl groups on the surface of the nanocellulose, and prepared a hydrophobic, flexible and transparent thin film by a means of casting. Hambardzumyan (2015) used Fenton reagents (H 2 0 2 and FeSO4) to graft lignin to the surface of nanocellulose crystals through covalent bonding to increase its hydrophobicity. Wang (2015) used the nanocellulose film to adsorb Cu 2+ and Fe 3 , so that it maintains excellent mechanical properties in a high humidity environment.

Although these methods improved the hydrophobicity of nanocellulose films to a certain extent, some of these methods require the use of a large amount of organic solvents or metal ions, which is not an environment-friendly technical process; some of them will cause damages to the properties of nanocellulose; and some processes are too complicated. Moreover, no prior art documents and patents has implemented beneficial exploration in improving the oil-and-water-resistant properties of nanocellulose films.

[1] Gousse C, Chanzy H, Excoffier G, et al. Stable suspensions of partially silylated cellulose whiskers dispersed in organic solvents[J]. Polymer, 2002, 43(9): 2645-2651.

[2] Rodionova G, Lenes M, Eriksen 0, et al. Surface chemical modification of microfibrillated cellulose: Improvement of barrier properties for packaging applications[J]. Cellulose, 2010, 18(1): 127-134.

[3] Shimizu M, Saito T, Fukuzumi H, et al. Hydrophobic, ductile, and transparent nanocellulose films with quaternary alkylammonium carboxylates on nanofibril surfaces[J]. Biomacromolecules, 2014, 15(11): 4320-4325.

[4] Wang B, Torresrendon J G, Yu J, et al. Aligned bioinspired cellulose nanocrystal-based nanocomposites with synergetic mechanical properties and improved hygromechanical performance[J]. Acs Appl Mater Interfaces, 2015, 7(8): 4595-4607.

Summary of the Invention

The invention provides a method for preparing a water-and-oil-resistant nanocellulose

composite film, which simplifies the synthesis steps, improves the overall properties

of the composite film, and solves the problems existing in the prior art.

The technical scheme adopted by the invention to solve the above technical problems

is as follows:

A method for preparing a water-and-oil-resistant nanocellulose composite film

comprises steps of: Si. filler modification: subjecting a coupling agent and a filler at a

mass ratio of 0.5-15:100 to surface modification treatment using a dry modification

process to obtain a modified filler;

S2. preparation of intermediates: mixing the modified filler and cellulose at a mass

ratio of 1-20:100 thoroughly to obtain the intermediates;

S3. preparation of products: preparing the intermediates as the composite film.

The filler obtained after modification by a coupling agent has a loose structure and a

uniform distribution, and improves the compatibility between the filler and the

nanocellulose. In Si, after the filler was subjected to surface modification treatment

via the coupling agent, the modified filler obtained therefrom has a good

water-and-oil-resistance; In S2, the modified filler and the cellulose were mixed, and

during the mixing process, the coupling agent will form a firm molecular bridge

between the filler and the cellulose at this time. Therefore the nanofiller and the

nanocellulose will be tightly bonded to obtain the intermediates, such that the

intermediates also have a good water-and-oil-resistance. The intermediates are then

prepared into the composite film, and the composite film prepared in such way also

has a good water-and-oil-resistance.

Preferred, the particle size of the filler is 50 nm-1.5 M in Si.

Preferred, in Si, the filler is one or a mixture of two or more selected from calcium carbonate, talc, clay, amorphous silicate, and titanium dioxide, wherein the two or more fillers are mixed in any proportion.

Preferred, the coupling agent is borate ester coupling agent.The borate ester coupling agent molecule contains an isopropyl group, which can be easily hydrolyzed and will generate alcohol after hydrolysis. It will condense with a hydroxyl group on the surface of the filler under the condition of heating, so that the long carbon chain structure in the coupling agent molecule is spreading on the surface of the filler or intertwining with each other to form a cross-linked network structure. Due to the introduction of the coupling agent, the polar hydroxyl groups on the surface of the filler condense with the coupling agent, so as to reduce the polarity of the surface of the filler, increasing the hydrophobicity of the surface of the modified filler, and also increasing the oleophobicity.

Preferred, the dry modification process comprises steps of placing the filler and the coupling agent in a container, heating to 50-95°C for 5-50min under a condition of continuous stirring, then stopping heating, and continuing stirring until a temperature drops to room temperature.

Preferred, in S2, the cellulose is cellulose suspension.

Preferred, in S2, the cellulose suspension is nanocellulose suspension, solvent in the nanocellulose suspension is water, and a concentration of the nanocellulose is 0.5-2%.The nanocellulose and the modified fller are mixed with stirring in an aqueous solution so as to make the nanocellulose and the filler mixed more uniformly, and make the coupling agent hydrolyzed fully with water as a solvent, and bonded more firmly with the filler and the nanocellulose.

Preferred,in S3, first, the solvent contained in the intermediates obtained in S2 is removed, and then hot-pressing treatment is performed to obtain the composite film.The solvent is removed in order to shorten the duration of subsequent hot-pressing and to prevent the excess solvent from adversely effecting under the hot-pressing temperature and therefore affecting the combination of the nanocellulose and the modified filler.

Preferred,the hot-pressing treatment comprises steps of placing the intermediates into

a mould, then drying at 30-40°C followed by hot-pressing treatment. At this time, the

drying temperature should not be too high. If the temperature is too high, the

intermediate may produce bubbles or cracks, which will make the composite film

uneven and dense.

Preferred,the hot-pressing temperature is 90-100°C and the hot-pressing duration is

20-40s. Uniform and dense nanocellulose composite films were obtained at suitable

hot pressing temperature and time.The invention adopts the above-described process,

which has the following advantages. The resultant composite film has excellent

characteristics of water-and-oil-resistance, and no chemical solvent was used during

the synthesis process. Further, the process is simple and has strong operability.

Brief Description of the Drawings

Fig. 1 is a SEM image of the unmodified calcium carbonate;

Fig. 2 is a SEM image of the calcium carbonate modified by borate ester coupling

according to the invention;

Fig. 3 is a SEM image of the nanocellulose composite film (surface) according to the

invention;

Fig. 4 is a SEM image of the nanocellulose composite film (side surface) according to

the invention.

Detailed Description of the Invention

In order to clearly illustrate the technical features of the technical solution, the present

invention will be described in detail below with respect to implementations.

Example 1

Si. 50g of calcium carbonate powder (particle size 50nm-1.5 m) was taken and

placed in a 250ml flask. 0.5g of borate ester coupling agent was added. Stirring is

started simultaneously with heating. The temperature is kept constant when it rose to

75°C. Stirring is kept for 20min and then heating is stopped. Stirring was continued

until the temperature dropped to room temperature, and then the borate ester-modified

calcium carbonate was prepared.

S2. 2g of the above-mentioned borate ester-modified calcium carbonate was added

into 20g of nanocellulose suspension (the concentration ratio of the nanocellulose to

water was 0.5%) while stirring at the same time until it is uniformly stirred to obtain

the intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 30° C for

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 90° C and a hot-pressing time of 20s to obtain the nanocellulose

composite film.

Example 2

Sl. 5Og of clay powder (particle size 100nm-1.5 m) was taken and placed in a 250ml

flask. 1.Og of borate ester coupling agent was added. Stirring is started simultaneously

with heating. The temperature is kept constant when it rose to 85°C. Stirring is kept

for 15min and then heating is stopped. Stirring was continued until the temperature

dropped to room temperature, and then the borate ester-modified clay was prepared.

S2. 1.5g of the above-mentioned borate ester-modified clay was added into 20g of

nanocellulose suspension (the concentration ratio of the nanocellulose to water was

0.8%) while stirring at the same time until it is uniformly stirred to obtain the

intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 35 C for drying. After drying, hot-pressing treatment was performed at a hot-pressing temperature of 950 C and a hot-pressing time of 20s to obtain the nanocellulose composite film.

Example 3

Si. 50g of talc powder (particle size 500nm-1 m) was taken and placed in a 250ml

flask. 2.Og of borate ester coupling agent was added. Stirring is started simultaneously

with heating. The temperature is kept constant when it rose to 90°C. Stirring is kept

for 12 min and then heating is stopped. Stirring was continued until the temperature

dropped to room temperature, and then the borate ester-modified talc was prepared.

S2. 0.8g of the above-mentioned borate ester-modified talc was added into 20g of

1.5%) while stirring at the same time until it is uniformly stirred to obtain the

intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 40° C for

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 1000C and a hot-pressing time of 40s to obtain the nanocellulose

composite film.

Example 4

S. 20g of calcium carbonate powder (particle size 200nm-1.5 m) and 30g of talc

powder (particle size 200nm-1 m) were taken and placed in a 250ml flask. 0.4g of

borate ester coupling agent was added. Stirring is started simultaneously with heating.

The temperature is kept constant when it rose to 70°C. Stirring is kept for 30 min and

then heating is stopped. Stirring was continued until the temperature dropped to room

temperature, and then the borate ester-modified calcium carbonate was prepared.

S2. 2.4g of the above-mentioned borate ester-modified calcium carbonate was added

into 20g of nanocellulose suspension (the concentration ratio of the nanocellulose to water was 1.4%) while stirring at the same time until it is uniformly stirred to obtain the intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 35 C for

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 90 C and a hot-pressing time of 20s to obtain the nanocellulose

composite film.

Example 5

Si. lOg of talc powder (particle size 500nm-1 m), 20g of clay powder (particle size

500nm-1.24m) and 20g of amorphous silicate powder (particle size

800nm-1.5 m)were taken and placed in a 250ml flask. 1.5g of borate ester coupling

agent was added. Stirring is started simultaneously with heating. The temperature is

kept constant when it rose to 80°C. Stirring is kept for 20 min and then heating is

stopped. Stirring was continued until the temperature dropped to room temperature,

and then the borate ester-modified talc was prepared.

S2. 1.Og of the above-mentioned borate ester-modified talc was added into 20g of

1.2%) while stirring at the same time until it is uniformly stirred to obtain the

intermediates.

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 90° C and a hot-pressing time of 25s to obtain the nanocellulose

composite film.

Example 6

S. lOg of calcium carbonate powder (particle size 50nm-1.2[tm), 15g of titanium

dioxide powder (particle size 300nm-1.3 m),10g of clay powder (particle size

300nm-1.3 m) and 5g of talc powder (particle size 800nm-1.5 m)were taken and placed in a 250ml flask. 2.5g of borate ester coupling agent was added. Stirring is started simultaneously with heating. The temperature is kept constant when it rose to

90°C. Stirring is kept for 16 min and then heating is stopped. Stirring was continued

calcium carbonate was prepared.

S2. 0.4g of the above-mentioned borate ester-modified calcium carbonate was added

water was 0.6%) while stirring at the same time until it is uniformly stirred to obtain

the intermediates.

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 95° C and a hot-pressing time of 20s to obtain the nanocellulose

composite film.

Example 7

Sl. 1Og of clay powder (particle size 80nm-1.2[tm), 1Og of calcium carbonate powder

(particle size 50nm-1.5[tm),10g of titanium dioxide powder (particle size

300nm-1.5[tm),10g of amorphous silicate powder (particle size 500nm-1.2[tm) and

lOg of talc powder (particle size 100nm-1.5[tm)were taken and placed in a 250ml

flask. 0.25g of borate ester coupling agent was added. Stirring is started

simultaneously with heating. The temperature is kept constant when it rose to 5 0 °C.

Stirring is kept for 50 min and then heating is stopped. Stirring was continued until the

temperature dropped to room temperature, and then the borate ester-modified clay was

prepared.

S2. 0.2g of the above-mentioned borate ester-modified clay was added into 20g of

0.9%) while stirring at the same time until it is uniformly stirred to obtain the

intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 300 C for drying. After drying, hot-pressing treatment was performed at a hot-pressing temperature of 1000C and a hot-pressing time of 20s to obtain the nanocellulose composite film.

Example 8

Si. 50g of talc powder (particle size 60nm-1 m) was taken and placed in a 250ml flask. 7.5g of borate ester coupling agent was added. Stirring is started simultaneously with heating. The temperature is kept constant when it rose to 95°C. Stirring is kept for 40min and then heating is stopped. Stirring was continued until the temperature dropped to room temperature, and then the borate ester-modified talc was prepared.

S2. 4g of the above-mentioned borate ester-modified talc was added into 20g of nanocellulose suspension (the concentration ratio of the nanocellulose to water was 1.0%) while stirring at the same time until it is uniformly stirred to obtain the intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 40° C for drying. After drying, hot-pressing treatment was performed at a hot-pressing temperature of 90° C and a hot-pressing time of 20s to obtain the nanocellulose composite film.

Example 9

S. 50g of titanium dioxide powder (particle size 50nm-1.5 m) was taken and placed in a 250ml flask. 0.25g of borate ester coupling agent was added. Stirring is started simultaneously with heating. The temperature is kept constant when it rose to 70°C. Stirring is kept for 40min and then heating is stopped. Stirring was continued until the temperature dropped to room temperature, and then the borate ester-modified titanium dioxide was prepared.

S2. 0.2g of the above-mentioned borate ester-modified titanium dioxide was added into 20g of nanocellulose suspension (the concentration ratio of the nanocellulose to water was 0.8%) while stirring at the same time until it is uniformly stirred to obtain the intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 300 C for

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 950 C and a hot-pressing time of 40s to obtain the nanocellulose

composite film.

Example 10

S1. 30g of amorphous silicatepowder (particle size 400nm-1.24m) and 20g of calcium

carbonate powder (particle size 200nm-1.5[tm) were taken and placed in a 250ml

flask. 7.5g of borate ester coupling agent was added. Stirring is started simultaneously

with heating. The temperature is kept constant when it rose to 60°C. Stirring is kept

for 30 min and then heating is stopped. Stirring was continued until the temperature

dropped to room temperature, and then the borate ester-modified amorphous

silicatepowder was prepared.

S2. 4g of the above-mentioned borate ester-modified c amorphous silicatepowder was

added into 20g of nanocellulose suspension (the concentration ratio of the

nanocellulose to water was 0.5%) while stirring at the same time until it is uniformly

stirred to obtain the intermediates.

S3. The intermediates were poured into a mould and placed in an oven at 35° C for

drying. After drying, hot-pressing treatment was performed at a hot-pressing

temperature of 90° C and a hot-pressing time of 30s to obtain the nanocellulose

composite film.

Experimental Example 1

Comparing Fig. 1 with Fig. 2, it can be seen that the calcium carbonate modified by

borate ester coupling agent experienced obvious changes in the microstructure with respect to the unmodified calcium carbonate. The coupling agent-modified calcium carbonate obviously has a more uniform distribution and increased particle size, indicating that the borate ester coupling agent has chemical bonds with the surface of calcium carbonate.

As can be seen from Figs. 3 and 4, the nanocellulose and the filler in the prepared

nanocellulose composite film are mixed uniformly and integrated together. Its surface

is also even without defects such as cracks.

Experimental Example 2

The nanocellulose composite film was prepared by using the method of Example 1-10,

and its water resistance, oil resistance and tensile breaking strength were tested. The

results are shown in Table 2.

The tensile breaking strength was tested by using the strength tester Instron 2710-203

with a test method in accordance with GB 1040 in which: the film material was cut

into rectangular strips with a width of lcm and a length of 10cm, then fixed and

clamped, and the tensile test is initiated until the strips are broken, and data was

recorded. The water resistance was detected by measuring the contact angle of the

film. The oil-proof rating tested by the Kit method indicates the oil resistance property

of the nanofiber composite film. The higher the rating value, the better the oil

resistance property. The oil-proof rating was tested via the Kit method by the

following steps. The nanocellulose composite film was spread out with the test side

facing up, and a drop of test solution of a Kit number was dripped at a height of

25mm. After 15s, the remaining test solution on the nanocellulose composite film was

removed, and the film was immediately observed to determine whether the side

opposite the oil drop was penetrated and discolored. The test is repeated until the

paper surface opposite the test solution of a Kit number was not penetrated and

discolored. The oil resistance rating of the nanocellulose composite film is the value

of that Kit number. A part of standard reagents in the Kit test are shown in Table 1.

Table 1 Standard reagents in the Kit test

Kit No. castor oil (ml) toluene (ml) heptane (ml) surface tension (dyn/cm)

1 200 0 0 34.5 2 180 10 10 32.7

3 160 20 20 29.3 4 140 30 30 25.4

5 120 40 40 25.0

6 100 50 50 24.1

7 80 60 60 23.2 8 60 70 70 22.8

9 20 80 80 22.5 10 0 90 110 22.0 11 0 100 100 22.4

12 0 90 110 22.0

13 0 80 120 22.0

Table 2 The property tests of the nanocellulose composite film of the invention

Test item tensile breaking strength (MPa) contact angle (°) oil resistance rating

Example 1 60.1 105.5 12

Example 2 62.5 117.5 12

Example 3 65.8 111.5 12

Example 4 68.9 109 12

Example 5 61.4 114 12

Example 6 60.6 107.5 12

Example 7 63.0 110.2 12

Example 8 67.1 108.6 12

Example 9 64.3 111.2 12

Example 10 60.7 103.9 12

As can be seen from the data in Table 2, the contact angles of the nanocellulose

composite film prepared by the method of the present invention are all greater than

90, indicating that the nanocellulose composite film of the present invention has a

good water resistance. Oil resistance ratings were tested by the Kit method, and the

results indicated that the nanocellulose composite film of the present invention has a

oil resistance rating of grade 12, which means a good oil resistance. The nanocellulose

composite film of the present invention has good water resistance and oil resistance

due to the introduction of the modified fillers. The filler is modified by the coupling

agents so that the compatibility between the filler and the nanocellulose is better, and

the filler can be mixed with the nanocellulose more uniformly. Moreover, the filler

has good water resistance. Then the modified filler and the nanocellulose are mixed

uniformly to prepare the composite nanocellulose film. As the dense structure of the

nanocellulose film has a certain ability of resisting the penetration of oil droplets, after

preparing the composite film with the modified filler, the composite nanocellulose

film has both good water resistance and oil resistance. In addition, the test of the

tensile breaking strength indicates that the tensile breaking strength of the

nanocellulose composite film of the present invention is also relatively high without

significant reduction. The reason is that the nanoscale filler is hydrophobically

modified by using the coupling agents and then mixed with the nanocellulose. The

resulting composite nanocellulose film has hydrophobicity, and water molecules can

not easily be adsorbed on the surface of the nanocellulose. Thus the hydrogen bonding

between the nanocellulose will not be destroyed, so that the mechanical properties of

the nanocellulose film can be maintained.

The above-mentioned specific implementations should not be regarded as limiting the

scope of the present invention. As understood by one skilled in the art, any

substitutions, improvements or changes made to embodiments of the present invention

all fall within the scope of the present invention.

Anything not described in detail in the present invention is well-known techniques for

those skilled in the art.

Claims

1. A method for preparing a water-and-oil-resistant nanocellulose composite film,

characterized by comprising steps of:

S. filler modification: subjecting a coupling agent and a filler at a mass ratio of

0.5-15:100 to surface modification treatment using a dry modification process to

obtain a modified filler;

ratio of 1-20:100 thoroughly to obtain the intermediates;

S3. preparation of products: preparing the intermediates as the composite film.

2. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 1, characterized in that in S1, the filler has a particle size of 50

nm-1.5 m.

3. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 1, characterized in that in S, the filler is one or a mixture of two

or more selected from calcium carbonate, talc, clay, amorphous silicate, and titanium

dioxide, wherein the two or more fillers are mixed in any proportion.

4. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 1, characterized in that the coupling agent is borate ester coupling

agent.

5. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 1, characterized in that the dry modification process comprises

steps of placing the filler and the coupling agent in a container, heating to 50-95°C for

-50min under a condition of continuous stirring, then stopping heating, and

continuing stirring until a temperature drops to room temperature.

6. The method for preparing a water-and-oil-resistant nanocellulose composite film according to claim 1, characterized in that in S2, the cellulose is cellulose suspension.

7. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 6, characterized in that in S2, the cellulose suspension is

nanocellulose suspension, solvent in the nanocellulose suspension is water, and a

concentration of the nanocellulose is 0.5-2%.

8. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 7, characterized in that in S3, first, the solvent contained in the

intermediates obtained in S2 is removed, and then hot-pressing treatment is performed

to obtain the composite film.

9. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 8, characterized in that the hot-pressing treatment comprises steps

of placing the intermediates into a mould, then drying at 30-40°C followed by

hot-pressing treatment.

10. The method for preparing a water-and-oil-resistant nanocellulose composite film

according to claim 9, characterized in that the hot-pressing temperature is 90-100°C

and the hot-pressing duration is 20-40s.