CN109774034B - Cooling device for POF heat-shrinkable film and production process of POF heat-shrinkable film - Google Patents

Abstract

The invention discloses a cooling device for a multilayer co-extrusion polyolefin heat-shrinkable film and a production process thereof, wherein the cooling device comprises a frame and more than three cooling air rings arranged on the frame, and the cooling air rings are vertically and sequentially arranged; the cooling air ring at the uppermost side is arranged on the rack in a lifting manner; the air outlet of the cooling air ring at the uppermost side is obliquely arranged upwards, and a lifting device for driving the cooling air ring at the uppermost side to lift is arranged on the frame. The cooling device can effectively enhance the stability of the film bubble, reduce the thickness deviation and the natural shrinkage of the film, and the multilayer co-extrusion polyolefin heat shrinkage film prepared by combining the production process carried out by the device has higher transparency, glossiness, mechanical property and heat shrinkage.

Description

Cooling device for POF heat-shrinkable film and production process of POF heat-shrinkable film

Technical Field

The invention relates to the technical field of cooling devices in film production, in particular to a cooling device for a POF heat-shrinkable film and a production process of the POF heat-shrinkable film.

Background

Multilayer co-extruded polyolefin heat-shrinkable films (namely POF heat-shrinkable films) gradually replace PVC heat-shrinkable films in the global scope, and become the heat-shrinkable films with the fastest market demand and the widest application. Compared with PVC, PE, PVDC and other heat-shrinkable films, the POF film has the advantages of small density, smooth texture, good transparency and glossiness, high heat shrinkage (more than 50%), excellent tear resistance and heat sealing performance, outstanding antistatic property and cold resistance, environmental protection and no toxicity, is widely used in the fields of food, daily chemicals, medicine, electronics, toys, building materials and the like, and is favored by manufacturers and consumers.

The POF heat-shrinkable film is generally prepared from ternary polypropylene (PP) and Linear Low Density Polyethylene (LLDPE) serving as main raw materials by special processes such as multilayer coextrusion, film tube forming, film bubble inflation, cooling shaping and the like. The cooling and shaping process has extremely important influence on the comprehensive properties of the finally prepared POF heat-shrinkable film, such as dimensional stability, texture, gloss, transparency, heat shrinkage rate, mechanical properties and the like.

The air ring blowing cooling is a common mode in the cooling and shaping process of blown films, and by cooling and shaping the blown film bubble, the air ring structure and the cooling process have important influence on the quality and the production efficiency of the blown film product and have great difference due to different types of films.

In chinese patent document CN 204844842U, a cooling air ring is disclosed, which has an annular integral structure and is disposed concentrically with an annular die of a film blowing machine, the cooling air ring includes at least one air passage sequentially arranged along an axial direction thereof, the at least one air passage is each opened toward a bubble blown from a discharge port of the die, an opening of a lower air passage closest to the discharge port is located above the discharge port in the at least one air passage, the opening of the lower air passage is inclined upward with respect to a horizontal direction, and a distance from the center of the discharge port in a radial direction of the cooling air ring of the lower air passage is greater than or equal to a height from the discharge port in the axial direction of the cooling air ring. The cooling air ring disclosed in this patent document is applied to cooling in the film tube forming process, and is not used for cooling and shaping the blown film bubble.

The Chinese patent document with the authority of publication number CN 2494754Y discloses a manufacturing device of a POF heat-shrinkable film, which comprises a feeding melting device, a transmission device, a drying room air chamber combination device, a film blowing forming device and a material receiving device. The wind house device is characterized in that a wind wheel with a ventilation cavity is arranged below a drying room, and micropores are formed in the inner wall of the circumference of the wind wheel. Four wind wheels adopted in the wind house device are fixedly arranged below the drying room.

The cooling device is used for controlling the stability of the blown film bubble, particularly the bubble position (the bubble position with a shoulder-shaped blowing opening), usually depends on extrusion parameters and the air quantity and the air pressure of an air wheel to adjust, and in actual production, the bubble position easily vibrates up and down or swings left and right, the bubble stabilizing effect is not ideal, and the problems of uneven film thickness and width, scratch, tearing and the like are easily caused.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a cooling device for a multilayer co-extrusion polyolefin heat-shrinkable film and a production process of the multilayer co-extrusion polyolefin heat-shrinkable film, wherein the device can effectively enhance the stability of film bubbles, reduce the thickness deviation and the natural shrinkage rate of the film, and the multilayer co-extrusion polyolefin heat-shrinkable film prepared by combining the production process of the device has higher transparency, glossiness, mechanical property and heat shrinkage rate.

The specific technical scheme is as follows:

The cooling device for the multilayer co-extrusion polyolefin heat shrinkage film comprises a frame and more than three cooling air rings arranged on the frame, wherein the cooling air rings are vertically and sequentially arranged;

the cooling air ring at the uppermost side is arranged on the rack in a lifting manner; the air outlet of the cooling air ring at the uppermost side is obliquely arranged upwards;

And a lifting device for driving the cooling air ring at the uppermost side to lift is arranged on the frame.

Because the film bubble near the inflation port has larger plasticity, the position of the cooling air ring at the uppermost side and the air outlet condition have larger influence on the stability of the film bubble. The cooling air ring capable of moving up and down can flexibly adjust the position of the air ring according to the formula of the POF film in actual production, the change of the cooling process and the change of the extrusion quantity of the die head, so that the film bubble is effectively stabilized and the cooling effect is improved. The air outlet is arranged obliquely upwards, so that the control of the cooling air ring on the bubble position and the stability of the film bubble can be further improved by utilizing the action component force of the air flow in the horizontal and vertical directions.

The lifting device can be a screw electric lifting device. Through this elevating gear, can control the cooling wind ring of the topside according to the production condition of film bubble and go up or down, cooperate fan amount of wind and wind pressure to stabilize the film bubble better.

The cooling air ring comprises a reversing air cavity, an air outlet communicated with the reversing air cavity, and a plurality of air inlets communicated with the reversing air cavity.

The air inlets are positioned at the outer side of the cooling air ring and uniformly distributed around the central axis of the cooling air ring. The multi-pipe tangential air inlet can be realized through a plurality of air inlets, and the number of the air inlets is generally designed to be 3-30, preferably 8-15, according to specific production conditions.

The air inlets are connected with the fan through the air pipes, and the joints are connected through rubber pipes, so that the tightness is ensured.

The air outlet is in a crack shape formed between the upper clamping plate and the lower clamping plate, and the upper clamping plate and the lower clamping plate are arranged in parallel and are fixed on the inner wall of the cooling air ring. The air outlet adopts a slit-shaped design, so that the venturi effect generated by the air flow passing through the slit can be effectively utilized to play a role in stabilizing the membrane bubble. Preferably, a triangular reinforcing rib is fixed between the lower part of the lower clamping plate and the inner wall of the cooling air ring; the reinforcing ribs are uniformly distributed along the circumferential direction of the cooling air ring, and the reinforcing ribs are additionally arranged to play a role in mechanical fixation, so that unstable air flow and uneven air outlet caused by deformation of the air inlet when the air pressure is high can be effectively prevented. Further preferably, the upper clamping plate and the lower clamping plate are further fixed through screws uniformly distributed along the annular clamping gaps, so that the gaps of the air outlet clamping gaps are ensured to be in a proper range.

Preferably, the ratio of the inner diameter to the outer diameter of the cooling air ring is 1/3 to 9/10, and more preferably 1/2 to 4/5.

The ratio of the thickness of the cooling air ring to the thickness of the slit-shaped air outlet gap is 10-80:1, and more preferably 20-50:1.

Preferably, the reversing air cavity is an S-shaped channel structure formed by surrounding annular baffles, a top plate and a bottom plate which are arranged in an up-down staggered mode in a radial extending mode. The annular baffle is at least two, and the S-shaped channel structure which is arranged in a radial extending way is designed to enable the reversing air cavity to continuously weaken tangential force of air inlet, strengthen radial force and ensure uniform air outlet.

The number of the cooling air rings adopted in the invention is at least three, and the cooling air rings can be named as a first cooling air ring, a second cooling air ring, … … and an Nth cooling air ring in sequence from bottom to top along the vertical direction.

Wherein, the cooling wind ring of the uppermost side (the Nth cooling wind ring) is installed on the frame in a lifting way, and the air outlet is kept to be upwards and obliquely arranged. Preferably, the included angle between the air outlet of the uppermost cooling air ring and the horizontal plane is 3-45 degrees, and more preferably 3-15 degrees.

The device has special design on the fixing mode of the cooling air ring close to the uppermost side of the inflation port and the structure of the air outlet, has no special requirements on the other first cooling air rings, … … and (N-1) th cooling air rings, and can be directly fixed on a frame or can be installed on the frame in a lifting manner; the air outlets of the first cooling air ring, … … and the (N-1) th cooling air ring are preferably arranged along the horizontal direction for processing convenience.

Preferably, the ratio of the outer diameter of the cooling air ring to the distance between two adjacent cooling air rings is 0.2-10:1, and more preferably 1-5:1.

The cooling air ring is made of cast iron, cast aluminum or stainless steel, and the specific materials and the specific dimensions can be flexibly adjusted according to actual production requirements.

The cooling device is vertical, and a plurality of film protecting bubble roller assemblies are arranged in sequence, and each film protecting bubble roller assembly comprises a plurality of film protecting bubble rollers which are arranged along the tangential direction of the same base circle.

The film protecting bubble roller comprises a vertical fixing shaft, a horizontal supporting rod and a sleeve roller. The film protecting bubble roller is installed on the frame through a vertical fixing shaft, and the fixing end of the transverse supporting rod is sleeved on the vertical fixing shaft and can rotate along the circumferential direction along the vertical fixing shaft so as to be suitable for producing film bubbles with different diameters. The sleeve roller is rotatably sleeved outside the transverse supporting rod.

The film protecting bubble roller is made of ceramic or metal, performs primary stabilization on the blown film bubble, and combines the primary stabilization with the Venturi effect of the cooling air ring to jointly protect the film and stabilize the film bubble.

Preferably, at least one film protecting bubble roller assembly is arranged between two adjacent cooling air rings so as to ensure a bubble stabilizing effect and ensure uniform thickness of the film bubble along the advancing direction.

Preferably, in each of the film protecting bubble roller assemblies, the plurality of film protecting bubble rollers are uniformly distributed around the circumference of the base circle. The plurality of film protecting bubble rollers which are uniformly distributed can ensure the uniformity of the thickness of the film bubble along the whole circumferential direction.

The invention also discloses a production process of the multilayer co-extrusion polyolefin heat-shrinkable film, which comprises multilayer co-extrusion, film tube forming, film bubble inflation and cooling shaping processes, wherein the cooling shaping process adopts the cooling device and specifically comprises the following steps:

(1) The blown film bubble passes through the uppermost cooling air ring and the uppermost film bubble protecting roller assembly from top to bottom through the traction device, and the film bubble is primarily stabilized through the uppermost film bubble protecting roller assembly, so that the film bubble is prevented from shaking; the upper and lower positions of the uppermost cooling air ring are adjusted through the lifting device, and the distance between the bubble position and the inflation port of the film bubble is adjusted by utilizing an inclined upward cooling medium blown out from the air outlet of the uppermost cooling air ring so as to keep the stability of the film bubble, and meanwhile, the primary cooling of the film bubble is realized;

(2) Continuously dragging the film bubble to sequentially pass through other cooling air rings and other film-protecting bubble roller assemblies, and ensuring that the film bubble keeps uniform thickness in the dragging process through the other film-protecting bubble roller assemblies; and through the adjustment of the air quantity of the other cooling air rings, the bubble position is stabilized, and after the film bubble is fully cooled, the subsequent process is continued.

The other cooling air rings are cooling air rings except the uppermost cooling air ring; the other film protecting bubble roller is a film protecting bubble roller component except the uppermost film protecting bubble roller component.

The subsequent process comprises a process of eliminating internal stress of the film through hot roller and cold roller treatment.

In the step (1), the distance between the bubble position and the inflation port of the film bubble is changed according to the formula and the width of the POF heat-shrinkable film to be prepared; the term "stable membrane bubble" specifically means that the membrane bubble neither vibrates up and down nor swings left and right.

In the cooling and shaping process, the air volumes of all cooling air rings are controlled independently, the air volumes of the fans are controlled by variable frequency speed regulation, the air volumes of the fans can be changed by changing the rotating speed of the fans so as to adapt to the requirements of the production process, the energy is saved, the efficiency is high, and the practicability and the controllability of the production operation are improved.

Preferably, the cooling medium used by the uppermost cooling wind ring and the other cooling wind rings is selected from natural wind and cooling wind; that is, natural wind is used as a cooling medium in all cooling wind rings, and cooling wind is used as a cooling medium in all cooling wind rings. Experiments show that compared with the POF film which is cooled by all cooling air rings by natural air or by all cooling air, the POF film finally prepared by the preferred cooling mode has better transmittance, glossiness and thermal shrinkage rate and higher tensile strength.

Preferably, the temperature of the cooling air is 5-15 ℃.

Preferably, the cooling shaping process is accompanied by biaxial stretching shaping of the film bubble, and the transverse stretching multiple and the longitudinal stretching multiple are independently selected from 4-7 times.

Compared with the prior art, the invention has the following advantages:

1. the cooling device disclosed by the invention has the characteristics of high production flexibility, convenience in assembly and maintenance and suitability for large-scale production;

2. The cooling device disclosed by the invention has sufficient and uniform air outlet, and can obtain ideal air quantity and air pressure required by the POF film;

3. The production process by using the specific cooling device realizes sectional gradual cooling, effectively controls the thermal behavior of the polyolefin material in the cooling process, reduces the wrinkling phenomenon of the film surface, ensures that the transverse and longitudinal stretching performances of the POF film reach ideal values, and improves the production efficiency; the most critical is that the stability of the film bubble can be ensured, the thickness and the precision of the film can be effectively controlled, the natural shrinkage rate can be reduced, the texture (smoothness), the glossiness and the transparency of the film can be improved, and the prepared POF can be ensured to have excellent thermal shrinkage rate and mechanical property.

Drawings

FIG. 1 is a schematic structural view of a cooling device for a multilayer coextruded polyolefin heat shrink film of the invention;

FIG. 2 is a schematic view of a cooling air ring;

FIG. 3 is a transverse cross-sectional view of a first cooling wind ring;

FIG. 4 is an enlarged view of part of B in FIG. 3;

FIG. 5 is a corner cross-sectional view of the first cooling wind ring along the direction A-A shown in FIG. 3;

FIG. 6 is an enlarged view of part of C in FIG. 5;

FIG. 7 is an axial cross-sectional view of a fourth cooling wind ring;

FIG. 8 is a top view of a single set of bubble roller assemblies;

In the figure: the device comprises a film bubble 1-a frame 2-a film bubble protecting roller 3-a first cooling air ring 4-a second cooling air ring 5-a third cooling air ring 6-a fourth cooling air ring 7-a big baking oven 8-a fan 9-and a wind pipe 10-respectively;

201-upper plate, 202-lower plate, 203-support column, 204-horizontal mounting plate;

301-a vertical fixed shaft, 302-a transverse supporting rod, 303-a sleeve roller and 304-a primitive;

401-a first air inlet, 402-a first top plate, 403-a first bottom plate, 404-a first lower annular baffle, 405-a first upper annular baffle, 406-a first air outlet, 407-a first upper clamping plate, 408-a first lower clamping plate, 409-a screw, 410-a reinforcing rib, 411-an outer wall, 412-an inner wall;

701-fourth air inlet, 702-fourth top plate, 703-fourth bottom plate, 704-fourth lower annular baffle, 705-fourth upper annular baffle, 706-fourth air outlet, 707-fourth upper clamping plate, 708-fourth lower clamping plate.

Detailed Description

The cooling device for the multilayer coextruded polyolefin heat shrink film of the present invention will be described in detail with reference to the accompanying drawings and specific examples.

Referring to fig. 1 to 8, the cooling device of the present invention includes a frame 2, four cooling air rings mounted on the frame 2, and three film-protecting bubble roller assemblies mounted on the frame 2. The four cooling air rings are sequentially arranged from bottom to top along the vertical direction and are respectively marked as a first cooling air ring 4, a second cooling air ring 5, a third cooling air ring 6 and a fourth cooling air ring 7. A film protecting bubble roller assembly is arranged between two adjacent cooling air rings.

The frame 2 is composed of an upper plate 201, a lower plate 202, a plurality of support posts 203 and a plurality of horizontal mounting plates 204.

The first cooling air ring 4 is annular, and the ratio of the outer ring diameter D1 to the inner ring diameter D1 is 5:3. It includes a reversing air chamber, a first air outlet 406 communicated with the reversing air chamber, and ten first air inlets 401 communicated with the reversing air chamber. The first cooling air ring 4 is directly fixed on the frame.

The first air inlets 401 are located outside the outer wall 411 of the first cooling air ring 4 and uniformly distributed around the central axis of the first cooling air ring 4. Each air inlet is connected with the fan 9 through an air pipe 10, and the connection parts are connected by using rubber pipes, so that the tightness is ensured.

The reversing air cavity is an S-shaped channel structure surrounded by a first top plate 402, a first bottom plate 403, a first lower annular baffle 404 fixed with the first bottom plate 403 and a first upper annular baffle 405 fixed with the first top plate 402, and the S-shaped channel structure extends along the radial direction, so that the tangential force of air inlet can be weakened continuously, the radial force can be enhanced continuously, and the uniformity of air outlet can be ensured.

The first air outlet 406 is in a slit shape formed by a first upper clamping plate 407 and a first lower clamping plate 408, and the upper clamping plate and the lower clamping plate are both fixed on the inner wall 412 of the first cooling air ring 4 and are all arranged in parallel along the horizontal direction.

The ratio of the thickness of the first cooling air ring 4 to the gap thickness of the slit-shaped first air outlet 406 is 20:1. A plurality of triangular reinforcing ribs 410 (only one reinforcing rib is shown in the figure, and the rest are omitted) are fixed between the lower part of the first lower clamping plate 408 and the inner wall 412 of the first cooling air ring 4; the reinforcing ribs 410 are uniformly distributed along the circumferential direction of the cooling air ring, and the reinforcing ribs 410 are additionally arranged to play a role in mechanical fixation, so that unstable air flow and uneven air outlet caused by deformation of the air inlet when the air pressure is high can be effectively prevented. The first upper clamping plate 407 and the first lower clamping plate 408 are further fixed by screws 409 uniformly distributed along the slit-shaped air outlet, so as to ensure that the gap of the air outlet slit is fixed.

The second cooling air ring 5 and the third cooling air ring 6 have exactly the same structure and fixing manner as the first cooling air ring 4.

The fourth cooling air ring 7 is positioned at the uppermost part and is close to the inflation port of the membrane bubble. The fourth cooling air ring 7 is installed on the frame 2 in a liftable manner by a screw electric lifting device.

The four cooling air rings 7 have substantially the same structure as the first cooling air ring 4, and structurally still include a reversing air chamber, a fourth air outlet 706 in communication with the reversing air chamber, and ten fourth air inlets 701 in communication with the reversing air chamber. The diversion wind cavity is an S-shaped channel structure surrounded by a fourth top plate 702, a fourth bottom plate 703, a fourth lower annular baffle 704 fixed with the fourth bottom plate 703 and a fourth upper annular baffle 705 fixed with the fourth top plate 702.

The difference is that the fourth air outlet 706 is formed by a slit-like structure comprising a fourth upper clamping plate 707 and a fourth lower clamping plate 708, which are arranged in parallel but form an angle of 15 ° with the horizontal plane. The arrangement of the inclination angle can enable the air ring to more flexibly participate in the control of the bubble position, and the bubble stabilizing effect of the air ring is further improved by utilizing the action component force of the air flow in the horizontal and vertical directions.

The four cooling air rings all adopt the same size, and the distance ratio of the outer diameter D1 to the gap between the adjacent cooling air rings is 3.5:1.

The film protecting bubble roller assemblies are arranged vertically and sequentially, and each group of film protecting bubble roller assemblies comprises 8 film protecting bubble rollers 3 arranged along the tangential direction of the same base circle 304. The 8 film protecting bubble rollers 3 are uniformly distributed around the circumference of the base circle 304.

Each of the film bubble rollers 3 includes a vertical fixing shaft 301, a horizontal support bar 302, and a sleeve roller 303. The film protecting bubble roller 3 is arranged on the frame 2 through a vertical fixing shaft 301, and the fixing end of a transverse supporting rod 302 is sleeved on the vertical fixing shaft 301 and can rotate along the vertical fixing shaft 301 along the circumferential direction so as to adapt to producing film bubbles with different diameters. The sleeve roller 303 is rotatably sleeved outside the transverse supporting rod 302.

The working process is as follows:

the film bubble 1 is preheated and heated to a certain temperature by each area of the large baking furnace 8 and then enters the cooling device of the invention, and is inflated and inflated by the bubble blowing system to carry out preliminary shaping of the film bubble 1.

The air flow of each cooling air ring system is conveyed to the air inlets of each cooling air ring from the fan 9 through the air pipe 10, the air flow enters the air inlets along the circumferential tangent line of the cooling air ring, and after passing through the S-shaped channel structure which is surrounded by the top plate, the bottom plate and the upper and lower annular baffles and is arranged in a radial extending way, the tangential force of the air inlet is continuously weakened, and the radial force is enhanced so as to ensure the uniformity of the air outlet.

The positions of the film protecting bubble roller assemblies are adjusted, so that each film protecting bubble roller in each film protecting bubble roller assembly is uniformly arranged along the periphery of each film bubble, and the passing film bubble is subjected to preliminary bubble stabilization, so that the film bubble is prevented from shaking greatly. Then adjusting the bubble position (the position of a-a dotted line in fig. 1 is the bubble position), controlling the height of the blowing opening from the bubble position to be in a proper range, ensuring that the bubble position does not vibrate up and down or swing left and right, specifically adjusting the fourth cooling air ring 7 to move up and down by using a screw electric lifting device, and assisting in adjusting the air quantity of the fourth air ring so as to adapt to the formula of the POF film, the cooling process and the change of the extrusion quantity of a die head, thereby achieving the purposes of effectively stabilizing the film bubble and improving the cooling effect; the air outlet 706 of the fourth cooling air ring 7 is arranged obliquely upwards, so that the control of the air ring on the bubble position and the stabilization of the film bubble can be further improved by utilizing the action component force of the air flow in the horizontal and vertical directions. Meanwhile, the temperature of each area of the baking furnace and the air quantity of the first, second and third air rings are regulated in an auxiliary mode, so that the bubble position is stable, and the transparency and the strength of the film reach ideal values. The fully cooled bubble then enters the subsequent process flow.

Example 1

By adopting the cooling device, a POF film with the thickness of 19 micrometers and the width of 3.2 meters is prepared by five-layer coextrusion according to the formula of a commercial Jinwei film, a film tube is subjected to five-layer coextrusion, preheating (250-300 ℃), heating (280-360 ℃) and blowing to form bubbles (200-100), four cooling air rings and three bubble protection roller assemblies which are sequentially arranged at intervals are pulled from top to bottom, the bubble protection rollers are uniformly arranged along the periphery of the film bubble, primary bubble stabilization is carried out on the passing film bubble, the film bubble is prevented from shaking greatly, the upper and lower positions of the fourth cooling air ring are regulated by a screw electric lifting device, and the distance between the bubble position and a blowing port of the film bubble is controlled to be 20-30 cm by utilizing an upward-inclined cooling medium blown out from an air outlet of the fourth cooling air ring.

The continuous traction film bubble sequentially passes through a third cooling air ring, a second cooling air ring, a first cooling air ring, a film protection bubble roller assembly respectively positioned between the third cooling air ring and the second cooling air ring, and a film protection bubble roller assembly positioned between the second cooling air ring and the first cooling air ring. The thickness uniformity of the film bubble in the traction process is ensured by other film bubble protecting roller components; through the adjustment of the air quantity of other cooling air rings, the bubble position is stable, and after the film bubble is fully cooled, the subsequent process is continued.

The cooling process is accompanied with the biaxial stretching shaping of the film bubble, and the transverse stretching and longitudinal stretching multiplying power are respectively 6 times and 5.6 times. The air quantity of a fan in the cooling process is controlled by variable frequency speed regulation, wherein the fourth cooling air ring, the third cooling air ring and the second cooling air ring are cooled by natural air, and the first cooling air ring is cooled by cooling air. The product was then treated with a 65℃hot roll and a 20℃cold roll to eliminate internal stress of the film, and a POF film was produced, and the performance parameters of the POF film produced in this example are shown in Table 1 below.

Comparative example 1

The same apparatus and the same process as in example 1 were used, except that the four cooling air rings were cooled by cooling air.

The POF film performance parameters prepared in this comparative example are listed in table 1 below.

Comparative example 2

The same apparatus and the same process as in example 1 were used, except that the four cooling air rings were cooled by natural air.

The POF film performance parameters prepared in this comparative example are listed in table 1 below.

TABLE 1

The above examples illustrate the construction and implementation of the apparatus of the present invention and are intended to aid in the understanding of the method and key points of the invention. The present disclosure should not be construed as limiting the invention to all other embodiments that may be made by those of ordinary skill in the art without inventive faculty.

Claims (5)

1. The cooling device for the POF heat-shrinkable film comprises a frame and more than three cooling air rings arranged on the frame, wherein the cooling air rings are vertically and sequentially arranged;

the method is characterized in that:

the cooling air ring at the uppermost side is arranged on the rack in a lifting manner; the air outlet of the cooling air ring at the uppermost side is obliquely arranged upwards;

The lifting device for driving the cooling air ring at the uppermost side to lift is arranged on the frame;

the cooling air ring comprises a reversing air cavity, an air outlet communicated with the reversing air cavity, and a plurality of air inlets communicated with the reversing air cavity;

the reversing air cavity is an S-shaped channel structure formed by surrounding annular baffles, a top plate and a bottom plate which are arranged in an up-down staggered mode in a radial extending mode;

The air outlet is in a crack shape formed between an upper clamping plate and a lower clamping plate, and the upper clamping plate and the lower clamping plate are arranged in parallel and are fixed on the inner wall of the cooling air ring;

The plurality of air inlets are positioned on the outer side of the cooling air ring where the air inlets are positioned, and are uniformly distributed around the central axis of the cooling air ring where the air inlets are positioned;

The cooling device for the POF heat shrink film is vertically provided with a plurality of film protecting bubble roller assemblies in sequence, and each film protecting bubble roller assembly comprises a plurality of film protecting bubble rollers which are arranged along the tangential direction of the same base circle;

the film-protecting bubble roller comprises a vertical fixing shaft, a horizontal supporting rod and a sleeve roller;

the vertical fixed shaft is arranged on the frame;

the fixed end of the transverse supporting rod is rotatably sleeved on the vertical fixed shaft;

the sleeve roller is rotatably sleeved outside the transverse supporting rod.

2. The cooling device for a POF heat-shrinkable film according to claim 1, wherein:

At least one film protecting bubble roller assembly is arranged between two adjacent cooling air rings;

in each film protecting bubble roller assembly, the plurality of film protecting bubble rollers are uniformly distributed around the circumference of the base circle.

3. The cooling device for a POF heat-shrinkable film according to claim 1, wherein:

The cooling air ring positioned at the lower side of the uppermost cooling air ring is fixed on the rack;

The air outlets of the cooling air rings positioned below the uppermost cooling air ring are arranged along the horizontal direction.

4. A process for producing a POF heat-shrinkable film, comprising multilayer coextrusion, film tube forming, film bubble inflation and cooling shaping, wherein the cooling shaping process adopts the cooling device as defined in any one of claims 1 to 3, and specifically comprises:

(1) The blown film bubble passes through the uppermost cooling air ring and the uppermost film bubble protecting roller assembly from top to bottom through the traction device, and the film bubble is primarily stabilized through the uppermost film bubble protecting roller assembly, so that the film bubble is prevented from shaking; the upper and lower positions of the uppermost cooling air ring are adjusted through the lifting device, and the distance between the bubble position and the inflation port of the film bubble is adjusted by utilizing an inclined upward cooling medium blown out from the air outlet of the uppermost cooling air ring so as to keep the stability of the film bubble, and meanwhile, the primary cooling of the film bubble is realized;

(2) Continuously dragging the film bubble to sequentially pass through other cooling air rings and other film-protecting bubble roller assemblies, and ensuring that the film bubble keeps uniform thickness in the dragging process through the other film-protecting bubble roller assemblies; and through the adjustment of the air quantity of the other cooling air rings, the bubble position is stabilized, and after the film bubble is fully cooled, the subsequent process is continued.

5. The process for producing a POF heat-shrinkable film according to claim 4, wherein in the step (1), the cooling medium used for the uppermost cooling air ring and the other cooling air rings is selected from natural wind and cooling wind.