A breathable film stretching device

Abstract

The present invention relates to a breathable film stretching device. The breathable film stretching device comprises an oven, a hot air blower and at least 4 groups of stretching rollers, wherein the two ends of the oven are respectively provided with a film inlet and a film outlet, and each side thereof is provided with a hot air outlet, and the top is provided with an air suction port; the air inlet of the hot air blower is fluidly connected to the air suction port, and the air outlet is fluidly connected to the hot air outlet; the stretching rollers are centrally arranged on the same horizontal plane in the oven and are evenly spaced apart, and each group of stretching rollers comprises an active roller and two pressure rollers symmetrically arranged on both sides of the active roller, and the rotation speed of the stretching rollers increases successively along the traveling direction of the film. The film is stretched by multiple steps, and the stretching rate of each step is small, which can not only realize full and uniform stretching of the film, uniform air permeability, but also less reduction in width, thereby improving product output; and since the film is evenly heated in the oven by heated air, the heating temperature of the film surface is more uniform compared to the existing heat transfer oil heating method, thereby making the stretching more uniform.

Description

Technical Field

[0001] The invention relates to the field of breathable film production devices, in particular to a breathable film stretching device. Background Art

[0002] The breathable membrane is mainly made of thermoplastic plastic as a carrier, and after adding inorganic mineral fillers, it is extruded by cold roll casting method, and then longitudinally stretched to give it a unique microporous structure. These special structure micropores distributed at a high density on the surface of the breathable membrane enable the breathable membrane to block the leakage of liquid water and allow gas molecules such as water vapor to pass through. At present, the main application areas of breathable membranes include personal hygiene care products, medical protective products (such as medical mattresses, protective clothing, surgical clothing, surgical sheets, hot compresses, medical pillowcases, etc.), personal protective equipment for special places, clothing linings, auxiliary materials for pharmaceutical packaging, construction industry, etc. Breathable membranes have been widely used in the above fields in many areas. Existing breathable membrane stretching devices (such as Figure 1 As shown in the figure, three groups of hollow stretching rollers 3 are used to stretch the film 100. The film 100 adopts an S-shaped film path and has a small number of stretching times, resulting in a large single stretching ratio and prone to unevenness. The roller surface is heated by heat transfer oil flowing through its inner cavity, and then the heat is transferred to the film. After long-term use, scaling will occur, resulting in uneven roller surface temperature, which will cause uneven heating temperature on the film surface, resulting in uneven stretching and large air permeability deviation between different parts of the final breathable film product, making it difficult to apply to fields requiring a small air permeability deviation. Summary of the invention

[0003] The purpose of the present invention is to provide a breathable film stretching device to solve the problem that the existing stretching device is prone to uneven stretching.

[0004] To achieve the above object, according to an embodiment of the present invention, a breathable film stretching device is provided, which may include:

[0005] An oven, wherein the two ends of the oven are respectively provided with a film inlet and a film outlet, hot air outlets are provided on each side, and an air suction outlet is provided on the top;

[0006] A hot air blower, wherein the air inlet of the hot air blower is fluidly connected to the air inlet, and the air outlet is fluidly connected to the hot air outlet,

[0007] and at least four groups of stretching rollers, which are centrally arranged on the same horizontal plane in the oven and evenly spaced apart, each group of stretching rollers comprising a driving roller and two pressing rollers symmetrically arranged on both sides of the driving roller, the film enters from the film inlet, is stretched by each group of stretching rollers in turn, and leaves from the film outlet, and the rotation speed of the stretching rollers increases successively along the traveling direction of the film.

[0008] Further, the number of the stretching rollers does not exceed 8 sets.

[0009] Further, the number of the stretching rollers is 5 groups, and the rotation speed ratios therebetween are 1.15, 1.17, 1.17 and 1.17 respectively.

[0010] Furthermore, the active roller is a stainless steel roller, and the pressure roller is a rubber roller; or vice versa.

[0011] Furthermore, the diameters of the driving roller and the pressure roller are 240 mm and 100 mm, respectively.

[0012] Furthermore, the distance between two adjacent active rollers is 400 mm.

[0013] Furthermore, a line connecting the centers of the active roller and the pressure rollers on both sides thereof forms an isosceles triangle with a base angle of 30 to 45 degrees.

[0014] Furthermore, an air suction hood is provided in the oven, and the air suction hood is located above the stretching roller and serves as the air suction port.

[0015] Furthermore, it also includes a preheating roller group and a shaping roller group, wherein the preheating roller group is arranged before the film inlet, and the shaping roller group is arranged after the film outlet.

[0016] Furthermore, a first guide roller is provided between the preheating roller group and the film inlet, and a second guide roller is provided between the film outlet and the shaping roller group, and the first guide roller and the second guide roller are arranged so that the film moves in a straight line in the oven.

[0017] Furthermore, the preheating roller group and the shaping roller group each include three hollow rollers and two pressing rollers, the three hollow rollers are arranged in an inverted isosceles triangle, and the two pressing rollers are pressed against the hollow rollers on both sides.

[0018] Furthermore, the diameter of the hollow roller is larger than the diameter of the pressing roller.

[0019] Furthermore, the first roller, the second roller and the hollow roller all have heat transfer oil flowing through their inner cavities.

[0020] The present invention adopts the above technical solution, and has the following beneficial effects:

[0021] 1) The film is stretched in multiple steps (more than three steps), and the stretching rate of each step is small, which not only enables the film to be fully and evenly stretched, and the air permeability is uniform, but also the width is reduced less, thereby increasing the product output;

[0022] 2) Use two pressing rollers to press the film from both sides, so that the film will not slip when stretched, which can improve the stretching rate of the product and make the pores more uniform;

[0023] 3) Since the film is evenly heated in the oven by heated air, the heating temperature of the film surface is more uniform compared to the existing thermal oil heating method, thereby making the stretching more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of an existing breathable film stretching device;

[0025] Figure 2 2 is a schematic front view of a breathable membrane stretching device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0027] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other cases, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0028] Unless the context requires otherwise, throughout the specification and claims, the word "comprise" and variations such as "include" and "have" should be construed in an open, inclusive sense, ie, should be interpreted as "including, but not limited to."

[0029] References throughout the specification to "one embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0030] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0031] In the following description, in order to clearly show the structure and working mode of the present invention, many directional words will be used for description, but the words "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", "down", etc. should be understood as convenient terms and should not be understood as restrictive terms.

[0032] It should be noted that in the claims and description of the present application, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0033] like Figure 2 As shown, the breathable film stretching device according to an embodiment of the present invention may include an oven 1, a hot air blower 2 and at least 4 groups of stretching rollers 3. The number of stretching rollers 3 is generally not more than 8 groups. The oven 1 is in the shape of a rectangular parallelepiped and is basically closed except for the film inlet 11 and the film outlet 12 arranged at both ends to prevent heat loss. Preferably, the outer surface of the oven 1 is covered with a heat-insulating layer to reduce heat loss and save energy consumption. Hot air outlets are provided on each side of the oven 1, and an air suction port is provided on the top. In the illustrated embodiment, the air suction port is in the form of an air suction hood 4. The air suction hood 4 is arranged in the oven 1 and is located above the stretching roller 3. The air inlet of the hot air blower 2 is fluidly connected to the air suction port, and the air outlet is fluidly connected to the hot air port. That is, the oven 1 realizes internal circulation through the hot air blower 2, which can ensure that the temperature in the oven 1 is basically at the required temperature (for example, 80°C) on the one hand, and greatly improve the energy efficiency on the other hand. Each group of stretching rollers 3 is centrally arranged on the same horizontal plane in the oven 1 and evenly spaced. The film enters the oven 1 from the film inlet 11, is stretched by each group of stretching rollers 3 in sequence, and leaves the oven 1 from the film outlet 12 to complete the stretching process. Since the film is evenly heated in the oven 1 by heated air, the surface temperature of the film is more uniform compared with the existing thermal oil heating method, so that the stretching is more uniform. The speed of the stretching roller 3 increases in sequence along the direction of the film. The speed increase ratio of two adjacent groups of stretching rollers 3 can be the same or different. In a specific embodiment, the number of stretching rollers is 5 groups, and the speed ratios between them are 1.15, 1.17, 1.17 and 1.17 respectively. In this case, the film can achieve 1.84 (1.15*1.17*1.17*1.17=1.84) times of stretching. Due to the use of multi-step (more than three steps) stretching, for the same stretching multiple, the stretching rate of each step is small, which can not only achieve full and uniform stretching of the film, uniform air permeability, but also less reduction in the width size of the product, thereby increasing the product output.

[0034] Each set of stretching rollers 3 includes an active roller 31 and two pressure rollers 32 symmetrically arranged on both sides thereof. That is, the line connecting the centers of the active roller 31 and the two pressure rollers 32 forms an isosceles triangle. The base angle of the isosceles triangle is usually between 30 and 45 degrees. Among them, the active roller 31 is a stainless steel roller, and the pressure roller 32 is a rubber roller; and vice versa. This can avoid rigid contact between the active roller and the pressure roller. The diameters of the active roller 31 and the pressure roller 32 can be the same or different. In the illustrated embodiment, the diameter of the active roller 31 is larger than the diameter of the pressure roller 32. In a specific embodiment, the diameters of the active roller 31 and the pressure roller 32 are 240 mm and 100 mm, respectively; the distance between two adjacent active rollers 31 is 400 mm; and the base angle of the isosceles triangle formed by the line connecting the centers of the active roller 31 and the two pressure rollers 32 is 36 degrees. Two pressing rollers 32 are used to press the film 100 from both sides, so that the film 100 will not slip when stretched, which can improve the stretching rate of the product and make the pores more uniform, that is, the air permeability is more uniform.

[0035] In the illustrated embodiment, the breathable film stretching device of the present invention may further include a preheating roller group 5 and a shaping roller group 6, wherein the preheating roller group 5 is arranged before the film inlet 11 of the oven 1, and is used to preheat the film, for example, to about 50°C. The preheating roller group 5 includes three hollow rollers 51 and two pressing rollers 52, wherein the three hollow rollers 51 are arranged in an inverted isosceles triangle, and the two pressing rollers 52 are pressed against the hollow rollers 51 on both sides. Heat transfer oil is passed through the hollow rollers 51, that is, the heat transfer oil is used for heating. The diameter of the hollow roller 51 is generally larger than the diameter of the pressing roller 52. The shaping roller group 6 is arranged after the film outlet 12 of the oven 1. The structure of the shaping roller group 6 is the same as that of the preheating roller group 5, and is used to shape the stretched film. The film passes through the preheating roller group 5 and the shaping roller group 6 in an S-shaped film path.

[0036] Preferably, a first guide roller 7 is provided between the preheating roller group 5 and the film inlet 11, and a second guide roller 8 is provided between the film outlet 12 and the shaping roller group 6. Specifically, the first guide roller 7 and the second guide roller 8 are respectively provided outside the oven 1 near the film inlet 11 and the film outlet 12. The first guide roller 7 and the second guide roller 8 are arranged with the stretching roller 3 so that the film therebetween is substantially on the same horizontal plane, so as to ensure that the film is substantially straight in the oven 1. In the illustrated embodiment, in order to avoid the oven 1, a third guide roller 9 is further provided between the second guide roller 8 and the shaping roller group 6, and the third guide roller 9 is located below the left side of the second guide roller 8 and above the left side of the shaping roller group 6. The first guide roller 7 and the second guide roller 8 are also heated by thermal oil.

[0037] The following comparative experiments are used to illustrate the beneficial effects of the breathable film stretching device of the present invention. The experimental materials are breathable films stretched by the conventional breathable film stretching device and the breathable film stretching device of the present invention. The width of the breathable film is about 1.6 meters, and a sample is taken every 300 mm. There are 5 groups of samples in total, which are represented by serial numbers 1-5 respectively.

[0038] Experiment 1

[0039] Measure weight (unit: g / m 2 ), the experimental results are shown in Table 1.

[0040] Table 1 Weight comparison

[0041] Sample No. 1 2 3 4 5 Breathable membrane obtained by using traditional breathable membrane stretching device 43.6 44.2 45.2 44.8 43.9 Breathable film obtained by using the breathable film stretching device of the present invention 43.7 44.1 44.7 44.3 44.0

[0042] It can be seen from Table 1 that the average gram weight of the breathable film obtained by using the traditional breathable film stretching device is 44.34, the maximum gram weight is 45.2, the minimum gram weight is 43.6, and the difference is 1.6. The average gram weight of the breathable film obtained by using the breathable film stretching device of the present invention is 44.16, the maximum gram weight is 44.6, the minimum gram weight is 43.7, and the difference is 1.0. It can be seen that the breathable film obtained by using the breathable film stretching device of the present invention has better uniformity.

[0043] Experiment 2

[0044] The air passage time (unit: seconds) was measured using a sphygmomanometer. The experimental results are shown in Table 2.

[0045] Table 2 Comparison of ventilation duration

[0046] Sample No. 1 2 3 4 5 Breathable membrane obtained by using traditional breathable membrane stretching device 52 40 39 46 60 Breathable film obtained by using the breathable film stretching device of the present invention 51 50 50 49 51

[0047] It can be seen from Table 2 that the breathable film obtained by using the breathable film stretching device of the present invention has better uniformity.

[0048] Experiment 3

[0049] The air permeability (unit: second) was measured using a Wang Yan-type air permeability meter. The data measured by the Wang Yan-type air permeability meter is the time it takes for each cubic meter of air to pass through 1 square meter of breathable membrane. The experimental results are shown in Table 3.

[0050] Table 3 Comparison of air permeability

[0051] Sample No. 1 2 3 4 5 Breathable membrane obtained by using traditional breathable membrane stretching device 20325 20119 13550 16539 24971 Breathable film obtained by using the breathable film stretching device of the present invention 17119 16852 16573 17052 17223

[0052] It can be seen from Table 3 that the air permeability of the breathable film obtained by the conventional breathable film stretching device is uneven: the maximum value reaches 20325, while the minimum value is only 13550, and the difference between the two is 6775. The maximum value 17223 and the minimum value 16573 of the breathable film obtained by the breathable film stretching device of the present invention only differ by 650. It can be seen that the breathable film obtained by the breathable film of the present invention has better uniformity.

[0053] Experiment 4

[0054] The moisture permeability (unit: g / m 2 ), the experimental results are shown in Table 4.

[0055] Table 3 Comparison of moisture permeability

[0056] Sample No. 1 2 3 4 5 Breathable membrane obtained by using traditional breathable membrane stretching device 541 529 969 819 1231 Breathable film obtained by using the breathable film stretching device of the present invention 601 593 572 608 587

[0057] It can be seen from Table 4 that the moisture permeability of the breathable film obtained by the conventional breathable film stretching device is uneven: the maximum value reaches 1231, while the minimum value is only 529, and the difference between the two is 702. The maximum value 608 and the minimum value 572 of the breathable film obtained by the breathable film stretching device of the present invention only differ by 36. It can be seen that the breathable film obtained by the breathable film stretching device of the present invention has better uniformity.

[0058] The preferred embodiments of the present invention have been described in detail above, but it should be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A breathable film stretching device, It is characterized in that include: An oven, wherein the two ends of the oven are respectively provided with a film inlet and a film outlet, hot air outlets are provided on each side, and an air suction outlet is provided on the top; A hot air blower, wherein the air inlet of the hot air blower is fluidly connected to the air inlet, and the air outlet is fluidly connected to the hot air outlet, and 5 groups of stretching rollers, which are centrally arranged on the same horizontal plane in the oven and are evenly spaced apart, each group of stretching rollers comprises a driving roller and two pressing rollers symmetrically arranged on both sides of the driving roller, the film enters from the film inlet, is stretched by the stretching rollers in sequence, and leaves from the film outlet, and the rotation speed of the stretching rollers increases in sequence along the film travel direction; as well as A preheating roller group and a shaping roller group, wherein the preheating roller group is arranged before the film inlet, and the shaping roller group is arranged after the film outlet, a first guide roller is provided between the preheating roller group and the film inlet, and a second guide roller is provided between the film outlet and the shaping roller group, and the first guide roller and the second guide roller are arranged so that the film moves in a straight line in the oven; The rotation speed ratios between the groups of stretching rollers are 1.15, 1.17, 1.17 and 1.17 respectively.

2. The breathable film stretching device according to claim 1, It is characterized in that The driving roller is a steel roller, and the pressure roller is a rubber roller; or the driving roller is a rubber roller, and the pressure roller is a steel roller.

3. The breathable film stretching device according to claim 2, It is characterized in that The diameters of the active roller and the pressure roller are 240 mm and 100 mm respectively.

4. The breathable film stretching device according to claim 3, It is characterized in that The distance between two adjacent active rollers is 400 mm.

5. The breathable film stretching device according to claim 3, It is characterized in that The connecting line of the centers of the active roller and the pressure rollers on both sides thereof forms an isosceles triangle with a base angle of 30 to 45 degrees.

6. The breathable film stretching device according to claim 1, It is characterized in that An air suction hood is provided in the oven, and the air suction hood is located above the stretching roller and serves as the air suction port.

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