CN111673999A

CN111673999A - Preparation method and preparation system of transparent film

Info

Publication number: CN111673999A
Application number: CN202010383446.2A
Authority: CN
Inventors: 王同心; 郝启军; 薛群山; 沈一春
Original assignee: Zhongtian Technology Advanced Materials Co ltd; Jiangsu Zhongtian Technology Co Ltd
Current assignee: Zhongtian Technology Advanced Materials Co ltd; Jiangsu Zhongtian Technology Co Ltd
Priority date: 2020-05-08
Filing date: 2020-05-08
Publication date: 2020-09-18

Abstract

The invention provides a preparation method and a preparation system of a transparent film. The preparation method of the transparent film comprises the following steps: plasticizing and extruding the material into a tube blank; introducing room temperature air for heat exchange treatment to obtain cold air with a preset temperature; and blowing the tube blank to form a film bubble, and simultaneously carrying out air-cooled rapid cooling on the film bubble by using the cold air to crystallize to obtain the transparent film. The method provided by the invention converts the air at room temperature into cold air, increases the temperature difference between the inflation molding film bubble and the environment, enables the film bubble to be rapidly cooled and crystallized into a film which is comparable to or even more excellent in performance with a transparent film produced by a tape casting method, has the characteristics of high production speed, low loss and low cost of the film blowing process, and improves the product yield by 3% compared with a product prepared by the tape casting method.

Description

Preparation method and preparation system of transparent film

Technical Field

The invention relates to the technical field of materials, in particular to a preparation method and a preparation system of a transparent film.

Background

The principle of effectively improving the transparency of a transparent film (such as a fluorine film) is to rapidly cool and crystallize the produced film, and the conventional methods for producing the fluorine film comprise a casting method and a film blowing method, wherein the casting method adopts a cooling roller cooling mode to realize rapid crystallization; on the contrary, the film blowing method can effectively solve the defects of the casting method, and has the advantages of high production speed, low loss and low cost, but the cooling mode is room temperature natural cooling, the product haze is 20-35%, the transparency is low, and the contact type rapid cooling method (such as water cooling and the like) is not suitable for the film blowing method, because the contact can influence the inflation molding, the volume of non-contact manufacturing equipment is larger, the cooling effect is limited, and in summary, no rapid cooling method in the film blowing molding exists at present, so that the produced product has poor transparency and high haze. Therefore, when a transparent fluorine film is produced using a blown film method, it is not possible to obtain a fluorine film having high transparency and low haze while securing high productivity.

Disclosure of Invention

In view of the above, there is a need for an improved method for preparing transparent films.

The technical scheme provided by the invention is as follows: a method for preparing a transparent film, comprising the steps of:

plasticizing and extruding the material into a tube blank;

introducing room temperature air for heat exchange treatment to obtain cold air with a preset temperature;

and blowing the tube blank to form a film bubble, and simultaneously carrying out air-cooled rapid cooling on the film bubble by using the cold air to crystallize to obtain the transparent film.

Further, in the step of introducing room temperature air to perform heat exchange treatment to obtain cold air at a preset temperature, the heat exchange treatment is performed by one of a plate exchanger, an air compressor and a refrigerator, or by a combination of the plate exchanger and at least one of the air compressor and the refrigerator.

Further, when the heat exchange treatment is performed by combining the plate exchanger with at least one of the air compressor and the refrigerator, the air compressor or/and the refrigerator firstly performs primary cooling on the air at room temperature, and the plate exchanger performs secondary cooling on the gas after the primary cooling.

Further, when the heat exchange treatment is performed by the plate exchange, the room temperature air and the cold water are continuously convected to two sides of the plate exchange sheet to perform heat exchange so that the room temperature air is changed into the cold air, and the cold water is changed into the hot water and then is discharged.

Further, after the hot water is discharged, the hot water is cooled by a cooling machine to become cold water for recycling.

Further, the preparation method of the transparent film comprises the following steps:

plasticizing and extruding the fluorine material into a tube blank;

introducing room temperature air for heat exchange treatment to obtain cold air with the temperature of 5-15 ℃;

and blowing the tube blank to form a fluorine film bubble, and simultaneously carrying out cold air type rapid cooling on the fluorine film bubble by using the cold air so as to crystallize and obtain the transparent fluorine film.

Furthermore, the haze of the fluorine film is 5-15%, and the transparency of the fluorine film is 91-93%.

The invention also provides a preparation system of the transparent film, which comprises an extruder, a film blowing machine and a cooling unit, wherein the film blowing machine and the cooling unit are internally provided with an external cooling fan, the extruder extrudes materials into a tube blank, the film blowing machine pulls the tube blank and blows the tube blank through a die head of the film blowing machine to form a film bubble, and the cooling unit introduces room-temperature air to carry out heat exchange treatment to form cold air with preset temperature; the air outlet of the cooling unit is installed at the air inlet of the outer air cooling fan, cold air enters from the air inlet of the outer air cooling fan and is aligned with the film bubble to carry out cold air type quick cooling so as to crystallize and obtain the transparent film.

Further, the cooling unit includes one of a plate exchanger, an air compressor, and a refrigerator, or a combination of a plate exchanger and at least one of an air compressor and a refrigerator.

Further, the plate exchanger comprises an air inlet, an air outlet, a water inlet, a water outlet and a plate, wherein an airflow channel is formed on the air inlet, the air outlet and one side of the plate, a water flow channel is formed on the water inlet, the water outlet and the other side of the pole piece, room-temperature air and cold water are convected from the airflow channel and the water flow channel, heat exchange is carried out on the two sides of the plate, the room-temperature air is converted into the cold air, the cold water is converted into hot water, and the hot water is discharged from the water outlet.

Further, an air compressor and/or a refrigerator are installed at the front end of the plate exchanger, the air compressor or the refrigerator cools the room-temperature air for the first time, and the plate exchanger cools the gas after the first cooling for the second time.

Furthermore, the water outlet is also connected with a cooling machine, and the cooling machine cools the hot water into cold water which returns to the water inlet for recycling.

Compared with the prior art, the preparation method of the transparent film provided by the invention has the advantages that room-temperature air is converted into cold air, the temperature difference between the inflation molding bubble and the environment is increased, the bubble can be rapidly cooled and crystallized to form a high-transparency (91-93%) and low-haze (5-15%) film which is comparable to or even more excellent in performance than the transparent film produced by the tape casting method, the characteristics of high production speed, low loss and low cost of the film blowing process are realized, and the production yield of the product prepared by the tape casting method is improved by 3%.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram illustrating a heat exchange principle of plate exchange in an embodiment of the present invention.

FIG. 2 is a schematic view of a system for preparing a transparent film according to an embodiment of the present invention.

Description of the main element symbols:

board changer 10

Air inlet 1

Gas outlet 2

The water inlet 5

Water outlet 6

Sheet 0

Cooling machine 15

Cooling unit 100

Extruder 200

Film blowing machine 300

Die head 31

External cooling fan 35

Post-processing apparatus 400

Film winding device 500

The following detailed description further illustrates embodiments of the invention in conjunction with the above-described figures.

Detailed Description

So that the manner in which the above recited objects, features and advantages of embodiments of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. In addition, the features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth to provide a thorough understanding of embodiments of the invention, and the described embodiments are merely a subset of embodiments of the invention, rather than a complete embodiment. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the embodiments of the present invention.

Transparency herein is calculated as the light transmission of 400-1100 nm.

Herein, haze is an index for transparent materials, and high haze affects transmittance, resulting in low transmittance.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention.

The invention provides a preparation method of a transparent film, which comprises the following steps:

and step S1, plasticizing and extruding the material into a tube blank.

And step S2, introducing room temperature air to perform heat exchange treatment to obtain cold air with a preset temperature. In specific embodiments, the heat exchange process is performed by one of a plate exchanger, an air compressor, a refrigerator, or by a combination of a plate exchanger and at least one of an air compressor, a refrigerator. In some embodiments, when the heat exchange process is performed by a plate exchanger in combination with at least one of an air compressor and a refrigerator, the air compressor or/and refrigerator first cools room temperature air for the first time, and the plate exchanger secondarily cools the primarily cooled gas. In practical production, it is preferable to use plate exchange as the heat exchange method for applying the previous process step with cold air, because when the heat exchange treatment is performed by plate exchange, the room temperature air and cold water are continuously convected to both sides of the plate exchange plates to perform heat exchange so that the room temperature air is changed into the cold air, and the cold water is discharged after being changed into hot water (the principle is shown in fig. 1). In some embodiments, the hot water is discharged and then cooled to be cold water by a cooler for recycling.

And step S3, blowing the tube blank to form a film bubble, and simultaneously carrying out cold-air type rapid cooling on the film bubble by using the cold air to crystallize to obtain the transparent film.

In a specific embodiment, cold air is uniformly blown to a die head and a film bubble formed by blowing from the die head through an air ring surrounding the die head and the film bubble, the temperature of the die head for blowing is mostly set to be high (such as 170-180 ℃), room-temperature air at about 20 ℃ is influenced by the high temperature of the die head before being blown out through the air ring, the temperature can be rapidly increased, generally, the temperature reaches 60-70 ℃ or even higher, the temperature difference between the film bubble and air flow/environment is small, the process requirement of rapid cooling is difficult to achieve, the transmittance and haze of a product are high, and the transparency is not ideal; according to the invention, the room temperature air is processed into cold air of 5-15 ℃, and the temperature of the cold air can be controlled within the range of 10-25 ℃ before the cold air is blown out by the air ring, so that when the film bubble contacts the cold air blown by the air ring, the temperature difference between the film bubble and the air flow/environment is increased compared with the room temperature air blown by the air ring, thereby meeting the process conditions required by rapid cooling, and crystallizing the film bubble to obtain the film with high transparency and low haze. In some embodiments, for example, a shaped transparent fluorine film is prepared by the following specific steps:

step S1, plasticizing and extruding the fluorine material into a tube blank;

step S2, introducing room temperature air to perform heat exchange treatment to obtain cold air with the temperature of 5-15 ℃;

and step S3, blowing the tube blank to form a fluorine film bubble, and simultaneously carrying out cold-air type rapid cooling on the fluorine film bubble by using the cold air to crystallize to obtain the transparent fluorine film.

The temperature range of cold air for forming the fluorine film is set to be 5-15 ℃, the fluorine film can be a polytetrafluoroethylene film, a polyvinylidene fluoride film and other film materials containing fluorine elements, and when the temperature of the cold air is higher than or lower than a preset temperature, the preparation of the fluorine film is not facilitated; on one hand, when the temperature is higher than the preset temperature, the temperature difference is small, and the process requirement of rapid cooling is difficult to achieve; on the other hand, below the preset temperature, the super-cooled cold air is continuously blown to the die head, so that the actual temperature of the die head is lower than the set temperature, the requirement of the inflation molding process is difficult to meet, and finally, the transparency, the haze and other characteristics of the film are affected. In other embodiments, when the device is used for molding other films (such as polyethylene, polypropylene, etc.), the preset temperature of the cold air can be adjusted according to actual conditions, which is not described in detail herein.

The characteristics of the product formed by the method of the present invention are compared with those of a conventional product by taking a fluorine film as an example.

	Transmittance of light	Haze degree	Line speed	Yield of the product
					Cooling forming process	92％	8％	100m/min	97％
Non-cooling process	89％	20％	100m/min	97％
					Conventional tape casting method	92％	8％	40m/min	94％

In conclusion, the fluorine film prepared by the process has high yield of a film blowing method, and the defects of large loss and low yield of a casting method are avoided; meanwhile, the product prepared by the casting method has high transmittance and low haze, the product has excellent transparency, and the defects that the transparency of the product is influenced by low transmittance and high haze of the film blowing method are overcome. In other embodiments, the haze of the product formed by the method is 5-15% (actually, 8-10%), the transmittance is 91-93%, and compared with the haze of 20-35% of the room-temperature air-cooled product, the haze of the product is significantly reduced, and accordingly, the haze is low, the transmittance is high, and the transparency of the product is much higher than that of the conventional product.

Referring to fig. 2, the present invention further provides a system for preparing a transparent film, including an extruder 200, a cooling unit 100, a film blowing machine 300, a post-processing device 400, and a film winding device 500.

The extruder 200 is used for extruding the materials into a tube blank;

the cooling unit 100 introduces room temperature air to perform heat exchange treatment to obtain cold air at a preset temperature;

the film blowing machine 300 is internally provided with an external cooling fan 35, a die head 31 and a traction device (not shown), and the film blowing machine 300 draws the tube blank and blows the tube blank to form a film bubble through the die head 31;

the post-treatment device 400, such as a clamping plate, a corona treatment device, a water cooling device and the like, performs corresponding treatment on the prefabricated product; for example, the water cooling device can cool and shape the film;

the film winding device 500 is used for winding for standby.

The air outlet of the cooling unit 100 is installed at the air inlet of the outer air cooling fan 35, and cold air enters from the air inlet of the outer air cooling fan 35 and is directed at the film bubble to be cooled rapidly to obtain the transparent film through crystallization.

In specific embodiments, the cooling assembly 100 includes one of a plate exchanger 10, an air compressor, a chiller, or a combination of a plate exchanger and at least one of an air compressor and a chiller. In some embodiments, it is preferable that an air compressor and/or a refrigerator are installed at the front end of the plate exchanger, the air compressor or the refrigerator primarily cools the room temperature air, and the plate exchanger 10 secondarily cools the primarily cooled gas.

In the specific embodiment shown in fig. 1, the plate exchanger 10 includes an air inlet 1, an air outlet 2, a water inlet 5, a water outlet 6, and a plate 0, wherein an airflow channel is formed on one side of the air inlet 1, the air outlet 2, and the plate 0, and a water flow channel is formed on the other side of the water inlet 5, the water outlet 6, and the pole piece 0, room temperature air and cold water are convected from the airflow channel and the water flow channel, and heat exchange is performed on the two sides of the plate 0, the room temperature air is changed into the cold air, the cold water is changed into hot water, and the hot water is discharged from the water outlet 6. In other embodiments, as shown in fig. 1, a cooling machine 15 is further connected to the water outlet 6, and the cooling machine 15 cools the hot water into cold water, and returns the cold water to the water inlet 5 for recycling. In other embodiments, only one refrigerant and one compressor are needed to be provided, and heat exchange may also be achieved, for example, the refrigerant and the heating medium which are arranged at intervals flow oppositely to achieve large-area heat exchange, and the like, and further description of other conventional alternatives is omitted here.

In conclusion, the method and the preparation system can realize equivalent or better rapid cooling compared with a casting method, the prepared film has the characteristics of low haze and high transparency, the product yield is further improved, and the method and the preparation system have the advantages of rapid production speed, small loss and low cost of a film blowing method.

Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the embodiments of the present invention.

Claims

1. A method for preparing a transparent film is characterized by comprising the following steps:

plasticizing and extruding the material into a tube blank;

2. The method for producing a transparent film according to claim 1, wherein: in the step of introducing room temperature air to perform heat exchange treatment into cold air at a preset temperature, the heat exchange treatment is performed by one of a plate exchanger, an air compressor and a refrigerator, or by the combination of the plate exchanger and at least one of the air compressor and the refrigerator.

3. The method for producing a transparent film according to claim 2, wherein: when the heat exchange treatment is carried out by combining the plate exchanger with at least one of the air compressor and the refrigerator, the air compressor or/and the refrigerator firstly carries out primary cooling on the air at room temperature, and the plate exchanger carries out secondary cooling on the gas after primary cooling.

4. The method for producing a transparent film according to claim 2, wherein: when the heat exchange treatment is carried out through the plate exchange, the room-temperature air and the cold water are continuously convected to two sides of the plate exchange sheet to carry out heat exchange so that the room-temperature air is changed into the cold air, and the cold water is changed into hot water and then is discharged.

5. The method for producing a transparent film according to claim 4, wherein: and after the hot water is discharged, the hot water is cooled into cold water by a cooler so as to be recycled.

6. The method for producing a transparent film according to claim 1, comprising the steps of:

plasticizing and extruding the fluorine material into a tube blank;

introducing room temperature air to perform heat exchange treatment to obtain cold air with the temperature of 5-15 ℃;

7. The method for producing a transparent film according to claim 6, wherein: the haze of the fluorine film is 5-15%, and the transparency of the fluorine film is 91-93%.

8. A system for preparing a transparent film, comprising: the device comprises an extruder, a film blowing machine and a cooling unit, wherein an external cooling fan is arranged in the film blowing machine, the extruder extrudes materials into a tube blank, the film blowing machine pulls the tube blank and blows and expands the tube blank to form a film bubble through a die head of the blow molding machine, and the cooling unit introduces room-temperature air to perform heat exchange treatment to obtain cold air with a preset temperature; and the air outlet of the cooling unit is arranged at the air inlet of the outer cooling fan, and cold air enters from the air inlet of the outer cooling fan and is aligned with the foam to carry out air-cooled rapid cooling so as to crystallize to obtain the transparent film.

9. The system for preparing a transparent film according to claim 8, wherein: the cooling unit comprises one of a plate exchanger, an air compressor and a refrigerator, or a combination of the plate exchanger and at least one of the air compressor and the refrigerator.

10. The system for preparing a transparent film according to claim 9, wherein: the plate exchanger comprises an air inlet, an air outlet, a water inlet, a water outlet and a plate piece, wherein an airflow channel is formed on the air inlet, the air outlet and one side of the plate piece, a water flow channel is formed on the water inlet, the water outlet and the other side of the pole piece, room-temperature air and cold water are convected from the airflow channel and the water flow channel, heat exchange is carried out on the two sides of the plate piece, the room-temperature air is converted into cold air, the cold water is converted into hot water, and the hot water is discharged from the water outlet.

11. The system for preparing a transparent film according to claim 9, wherein: the front end of the plate exchanger is provided with an air compressor and/or a refrigerator, the air compressor or the refrigerator is used for carrying out primary cooling on room-temperature air, and the plate exchanger is used for carrying out secondary cooling on gas subjected to primary cooling.

12. The system for preparing a transparent film according to claim 10, wherein: the water outlet is also connected with a cooling machine, and the cooling machine cools the hot water into cold water which returns to the water inlet for recycling.