阅读说明：本技术 一种拉膜熔体不间断输送方法及设备 (Continuous conveying method and equipment for film-drawing melt ) 是由 吴培服 邓十全 池卫 吴迪 于 2021-08-31 设计创作，主要内容包括：一种拉膜熔体不间断输送方法及设备,包括聚合物制备装置、熔体输送总泵、拉膜装置、切片装置以及流量分配阀,流量分配阀同步将熔体输送总泵输送的熔体的一部分通过管道输送至拉膜装置、将剩余部分的熔体通过管道输送至切片装置；流量分配阀和拉膜装置之间并联设置有两路管道,其中第一路管道中设置有补偿输送泵,第二路管道中设置有压力变送器；补偿输送泵的熔体流量由压力变送器的压力控制。本申请的拉膜熔体通过在两个方向都不间断输送的,因而两个方向的熔体可以相互调剂,当拉膜装置发生问题停机的时候,多余熔体可以输送给切片装置,以实现拉膜熔体不间断输送避免浪费的目的,而且还可以通过双向的调剂输送保证拉膜的品质。(A method and equipment for continuously conveying a film-drawing melt comprise a polymer preparation device, a melt conveying master pump, a film-drawing device, a slicing device and a flow distribution valve, wherein the flow distribution valve synchronously conveys one part of the melt conveyed by the melt conveying master pump to the film-drawing device through a pipeline and conveys the rest part of the melt to the slicing device through the pipeline; two pipelines are arranged in parallel between the flow distribution valve and the film drawing device, wherein a compensation delivery pump is arranged in the first pipeline, and a pressure transmitter is arranged in the second pipeline; the melt flow of the compensating delivery pump is controlled by the pressure of the pressure transmitter. The utility model provides a draw membrane fuse-element is through all incessant the transport in two directions, therefore the fuse-element of two directions can transfer the agent each other, when drawing the membrane device to take place the problem and shut down, and slice device can be carried to unnecessary fuse-element to the realization is drawn the incessant purpose of avoiding wasting of carrying of membrane fuse-element, but also can guarantee to draw the quality of membrane through two-way accent agent transport.)

1. The uninterrupted conveying equipment for the film-drawing melt comprises a polymer preparation device (400), a melt conveying master pump (100), a film-drawing device (200), a slicing device (300) and flow distribution valves (10), and is characterized in that the polymer preparation device (400) at least comprises a final polymerization tank (401) and a melt discharging tank (402), and the final polymerization tank (401) is provided with a functional material adding device (403); the melt discharge tank (402) is connected with the melt conveying master pump (100) through a pipeline, the flow distribution valve (10) synchronously conveys one part of the melt conveyed by the melt conveying master pump (100) to the film drawing device (200) through the pipeline and conveys the rest part of the melt to the slicing device (300) through the pipeline; two pipelines are arranged in parallel between the flow distribution valve (10) and the film drawing device (200), wherein a compensating delivery pump (21) for controlling the flow of the melt is arranged in the first pipeline (20), and a pressure transmitter (31) for detecting the pressure of the melt is arranged in the second pipeline (30); the melt flow of the compensation delivery pump (21) is controlled by the pressure of the pressure transmitter (31).

2. The equipment for continuously conveying the stretch film melt according to claim 1, wherein an inlet of the first pipeline (20) is arranged after the flow distribution valve (10) and before the pressure transmitter (31), and an outlet of the first pipeline (20) is arranged before the stretch film device (200) and after the flow distribution valve (10).

3. The equipment for the uninterrupted delivery of the stretch film melt according to claim 1, wherein a metering pump (32) for metering the melt flow is further arranged in the second pipeline (30), and the metering pump (32) is arranged at the downstream of the pressure transmitter (31); the inlet of the first pipeline (20) is arranged behind the flow distribution valve (10) and in front of the pressure transmitter (31), and the outlet of the first pipeline (20) is arranged in front of the film drawing device (200) and behind the metering pump (32).

4. The apparatus for uninterrupted delivery of stretch film melt according to claim 1, wherein the slicing device (300) comprises an extruder (301), a slicer (302) and a dryer (303).

5. The equipment for continuously conveying the stretch film melt according to claim 1, wherein the stretch film device (200) comprises a feeding mechanism (201), an extruding mechanism (202), a longitudinal stretching mechanism (203), a transverse stretching mechanism (204) and a winding mechanism (205).

6. The continuous conveying method for the film-drawing melt comprises the following steps: directly conveying the melt produced by the polymer production device (400) to at least one flow distribution valve (10) by means of a melt conveying master cylinder (100); the flow distribution valve (10) synchronously conveys one part of the melt to the film drawing device (200) and conveys the rest part of the melt to the slicing device (300); the melt conveyed to the film drawing device (200) is conveyed through two pipelines connected in parallel, wherein the melt flow in the first pipeline (20) is controlled by the pressure in the second pipeline (30).

7. The method according to claim 6, characterized in that a compensating delivery pump (21) for melt flow control is arranged in the first pipeline (20), and a pressure transmitter (31) for detecting the melt pressure is arranged in the second pipeline (30); the melt flow of the compensation delivery pump (21) is controlled by the pressure of the pressure transmitter (31).

8. The method according to claim 7, characterized in that a metering pump (32) for metering the melt flow is also arranged in the second pipeline (30), the metering pump (32) being arranged downstream of the pressure transmitter (31).

9. Method according to claim 8, characterized in that the length Δ L of the conduit between the metering pump (32) and the pressure transmitter (31) and the difference Δ t between the start time of the flow change of the metering pump (32) and the pressure change of the pressure transmitter (31) are used as gradient values for controlling the opening change of the compensation delivery pump (21).

Technical Field

The application relates to a plastic film production technology in the field of chemical engineering, in particular to a method and equipment for continuously conveying a film-drawing melt in the production process of a plastic film.

Background

The plastic film is widely applied in the industrial and living fields. Common plastic films include various films prepared from thermoplastic high molecular compounds such as Polyethylene (PE), polyvinyl chloride (PVC), Polystyrene (PS), polyester film (PET), polypropylene (PP), nylon, and the like.

For example, CN 101550247A discloses a stretched film which is excellent in stretching uniformity, is formed of a resin composition, has a thickness of 10 to 100 μm, comprises components (A) and (B), and has a melt flow rate in the range of 0.1 to 100g/10 min and a density in the range of 898 to 960kg/m3, wherein: (A) 50-95 parts by weight of a polyethylene composition having a melt flow rate of 0.1-100 g/10 min and a density of 890-940 kg/m 3; (B) 5 to 50 parts by weight of a high-pressure low-density polyethylene having a melt flow rate of 0.1 to 100g/10 min and a density of 910 to 930kg/m3, wherein the total of the component (A) and the component (B) is 100 parts by weight. Two A, B materials are extruded to make pellets after preparing the resin composition which meets the requirement, and then are heated and stretched to prepare the film.

In the prior art, molten resin is prepared into pellets, various functional materials are added and re-melted during subsequent formal film drawing so as to adjust components, and meanwhile, the feeding can be stopped in time during production interruption so as to avoid waste and ensure the safety of equipment. The production mode has better reliability, but the re-melting component of the raw material can be changed, which causes the product quality to be poor, in addition, the production process is actually artificially divided into two steps of semi-finished product and re-melting film drawing, which not only increases the equipment cost, but also reduces the production efficiency, and the comprehensive economic benefit is not the optimal choice. In fact, the prior art has certain difficulties in obtaining films by uninterrupted formation of the molten resin prepared from the raw materials, on the one hand because the composition of the molten resin prepared from the raw materials is difficult to control, and the uninterrupted feeding from the melt is liable to result in relatively poor quality uniformity of the subsequent film products. On the other hand, the film drawing process is interrupted frequently due to various reasons, so that molten resin is solidified in equipment after being cut off to cause blockage, raw material waste is caused slightly, and equipment is damaged seriously.

CN 101481827B discloses a control method and system for polyester melt conveying pressure, the control of polyester melt pressure is divided into five control links of polyester melt discharge pump flow control, final melt filter back pressure control, melt discharge pump speed control, granulator flow control and granulator speed control, the polyester melt discharge pump flow control, final melt filter back pressure control and granulator flow control form a cascade control loop by a main ring and an auxiliary ring, the melt discharge pump speed control is respectively controlled by a melt discharge pump speed PID control module, and the granulator speed control is respectively controlled by a granulator speed PID control module.

The prior art mentioned above proposes a method for controlling the melt pressure in the process of preparing filaments by direct polyester spinning, and the method only stays in the stage of simply controlling the melt flow in cascade by pressure feedback. However, since the viscosity of the plastic melt is much greater than that of other fluids, there is a problem in that the melt flow rate is delayed with respect to the pressure feedback. That is, when the measured melt pressure exceeds (or falls below) the threshold value, measures are taken to control the flow rate, and the amount of melt actually conveyed in the conveying pipe has already exceeded (or fallen below) the threshold value. On the other hand, if the position of the pressure transmitter is adjusted to be as close to the melt distribution valve as possible, the melt distribution valve needs to be immediately adjusted when the pressure is instantaneously changed, the abrupt instantaneous adjustment easily causes control signal divergence to cause control failure, and the abrupt instantaneous change of the flow rate also causes strong conveying pulse to destroy the conveying stability.

Disclosure of Invention

The technical problem to be solved by the present application is to provide a method and apparatus for continuously conveying a film-drawing melt, so as to reduce or avoid the aforementioned problems.

In order to solve the technical problem, the application provides continuous conveying equipment for film-drawing melt, which comprises a polymer preparation device, a melt conveying master pump, a film-drawing device, a slicing device and a flow distribution valve, wherein the polymer preparation device at least comprises a final polymerization tank and a melt discharging tank, and the final polymerization tank is provided with a functional material adding device; the melt discharge tank is connected with a melt conveying master pump through a pipeline, and the flow distribution valve synchronously conveys one part of the melt conveyed by the melt conveying master pump to the film drawing device through the pipeline and conveys the rest part of the melt to the slicing device through the pipeline; two pipelines are connected in parallel between the flow distribution valve and the film drawing device, wherein a compensation delivery pump for controlling the flow of the melt is arranged in the first pipeline, and a pressure transmitter for detecting the pressure of the melt is arranged in the second pipeline; the melt flow of the compensation delivery pump is controlled by the pressure of the pressure transmitter.

Preferably, the inlet of the first pipeline is arranged after the flow distribution valve and before the pressure transmitter, and the outlet of the first pipeline is arranged before the film drawing device and after the flow distribution valve.

Preferably, a metering pump for metering the melt flow is further arranged in the second pipeline, and the metering pump is arranged at the downstream of the pressure transmitter; the inlet of the first pipeline is arranged behind the flow distribution valve and in front of the pressure transmitter, and the outlet of the first pipeline is arranged in front of the film drawing device and behind the metering pump.

Preferably, the slicing apparatus includes an extruder, a slicer, and a dryer.

Preferably, the film drawing device comprises a feeding mechanism, an extruding mechanism, a longitudinal stretching mechanism, a transverse stretching mechanism and a winding mechanism.

In addition, the application also provides a method for continuously conveying the film-drawing melt, which comprises the following steps: directly conveying the melt prepared by the polymer preparation device to at least one flow distribution valve through a melt conveying main pump; the flow distribution valve synchronously conveys one part of the melt to the film drawing device and conveys the rest part of the melt to the slicing device; and conveying the melt conveyed to the film drawing device through two pipelines connected in parallel, wherein the melt flow in the first pipeline is controlled by the pressure in the second pipeline.

Preferably, a compensation delivery pump for melt flow control is arranged in the first pipeline, and a pressure transmitter for detecting melt pressure is arranged in the second pipeline; the melt flow of the compensation delivery pump is controlled by the pressure of the pressure transmitter.

Preferably, a metering pump for metering the melt flow is further arranged in the second pipeline, and the metering pump is arranged at the downstream of the pressure transmitter.

Preferably, the length Δ L of the pipeline between the metering pump and the pressure transmitter, and the starting time difference Δ t of the flow change of the metering pump and the pressure change of the pressure transmitter, and the ratio Δ L/Δ t between the two are used as gradient values for controlling and compensating the opening change of the delivery pump.

The utility model provides a draw membrane fuse-element is through all incessant the transport in two directions, therefore the fuse-element of two directions can transfer the agent each other, when drawing the membrane device to take place the problem and shut down, and slice device can be carried to unnecessary fuse-element to the realization is drawn the incessant purpose of avoiding wasting of carrying of membrane fuse-element, but also can guarantee to draw the quality of membrane through two-way accent agent transport.

Drawings

The drawings are only for purposes of illustrating and explaining the present application and are not to be construed as limiting the scope of the present application. Wherein the content of the first and second substances,

fig. 1 is a schematic structural view showing an uninterrupted conveying apparatus for a film-drawing melt according to an embodiment of the present application.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present application, embodiments of the present application will now be described with reference to the accompanying drawings. Wherein like parts are given like reference numerals.

The application provides a continuous conveying device for a film drawing melt as shown in figure 1, which can be used for continuously conveying melts of various polymers to a film drawing device to prepare various plastic films, wherein the polymers include but are not limited to thermoplastic high molecular compounds such as polyethylene, polyvinyl chloride, polystyrene, polyester films, polypropylene, nylon and the like.

As shown in the figure, the continuous conveying equipment for the film-drawing melt provided by the application comprises a polymer preparation device 400, a melt conveying master pump 100, a film-drawing device 200, a slicing device 300 and a flow distribution valve 10, wherein the polymer preparation device 400 at least comprises a final polymerization tank 401 and a melt discharge tank 402, and the final polymerization tank 401 is provided with a functional material adding device 403; the melt discharge tank 402 is connected with the melt delivery master pump 100 through a pipeline, and the flow distribution valve 10 synchronously conveys one part of the melt delivered by the melt delivery master pump 100 to the film drawing device 200 through the pipeline and conveys the rest part of the melt to the slicing device 300 through the pipeline.

The present application sets out the scenario of an uninterrupted transfer from the prepared polymer melt to a film drawing device for the purpose of drawing a film directly from the polymer, which firstly overcomes the problem of the stabilization of the melt composition. In order to solve the problem, the polymer preparation device at least comprises a final polymerization tank, and functional materials are added into the final polymerization tank through a functional material adding device, so that the melt required by the final polymerization tank is obtained through adjustment. Of course, the functional material added to the final polymerization tank needs to be spherical material, granular material, flaky material or the like purchased in advance or prepared, and in addition, the required amount of the functional material or the like can be added in real time according to the change of the melt composition in the final polymerization tank.

In addition, in the prior art, the slicing device is usually used as a backup of the film pulling device, the melt conveying master pump conveys all melts to the film pulling device, and when the film pulling device is out of order and stops, the melt is conveyed to the slicing device, so that the purpose of continuously conveying the film pulling melt and avoiding waste is achieved. However, this method cannot solve the problem that the melt flow rate in the film drawing direction is too low to cause the thickness of the film drawn later to be reduced and unqualified. In order to solve the problem, in the uninterrupted conveying scheme of the film-drawing melt, the melt is synchronously conveyed towards two directions, and when the melt flow in the film-drawing direction fluctuates, the melt flow in the slicing direction can be increased or decreased. That is to say, draw membrane fuse-element in this application all incessant the transport in two directions, therefore the fuse-element of two directions can transfer the agent each other, when drawing the membrane device to take place the problem and shut down, slice device can be carried to unnecessary fuse-element to the realization is drawn the incessant purpose of avoiding wasting of carrying of membrane fuse-element, but also can guarantee to draw the quality of membrane through two-way accent agent transport. It should also be noted that the melt slicing process is relatively simple and the requirements for the grain size are relatively wide, so that the reliability of the slicing apparatus in the prior art is generally high and the problem of production interruption generally does not occur. In contrast, the film drawing process is complex, has high requirements on quality, and has a high possibility of production interruption. The uninterrupted transport is therefore set mainly to prevent interruptions in production in the direction of film draw.

That is, in the present application, the melt amount delivered by the melt delivery pump 100 is greater than the required amount of the film drawing device 200, so that the opening degree of the flow distribution valve 10 can be flexibly controlled according to the requirement of the film drawing device 200, so that the melt amount delivered to the slicing device 300 is changed to meet the requirement of the film drawing direction. Since the slicing apparatus 300 obtains a semi-finished product of polymer, the melt flow rate in the slicing direction does not need to be precisely controlled, and the film drawing apparatus 200 obtains a finished product of plastic film, the melt flow rate in the direction is precisely controlled to obtain a high-quality plastic film.

In addition, as shown in the figure, two pipelines are arranged in parallel between the flow distribution valve 10 and the film drawing device 200, wherein a compensation delivery pump 21 for melt flow control is arranged in the first pipeline 20, and a pressure transmitter 31 for detecting melt pressure is arranged in the second pipeline 30; the melt flow of the compensating feed pump 21 is controlled by the pressure of the pressure transmitter 31. In a specific embodiment, the inlet of the first pipeline 20 is disposed after the flow distribution valve 10 and before the pressure transmitter 31, and the outlet of the first pipeline 20 is disposed before the membrane drawing device 200 and after the pressure transmitter 31.

The film drawing device is provided with two pipelines connected in parallel, wherein the first pipeline 20 is used as a compensation pipeline, the second pipeline 30 is used as a main conveying pipeline, and the total flow of the first pipeline 20 and the second pipeline 30 is equal to the required flow of the film drawing device 200. Normally, the second pipeline 30 is used as the main conveying pipeline to convey most of the required melt, for example, 80% of the required amount, and once the pressure in the second pipeline 30 becomes higher as measured by the pressure transmitter 31, it means that the conveying amount in the film drawing direction needs to be reduced, for example, the melt distribution amount of the flow distribution valve 10 is controlled by the melt pressure detected by the pressure transmitter, so that more melt is conveyed in the slicing direction. However, in this case, a part of the excess melt is already accumulated in the second line 30 from the flow distributing valve 10 to the pressure transmitter 31, and this part of the excess melt is only allowed to be transported downstream in the prior art. The present application, by providing the first conduit 20, while conveying the excess, for example 20%, of the demand, is responsible for controlling the downstream flow fluctuations of the melt, for example, by pumping away a portion of the excess melt that has been accumulated by the compensating pump 21, so that the excess melt is distributed in a buffer over a relatively long downstream conveying distance over a period of time. Similarly, when the pressure in the second conduit 30 becomes lower as measured by the pressure transmitter 31, the melt distribution amount of the flow distribution valve 10 is controlled by the melt pressure detected by the pressure transmitter, and the melt transportation in the slicing direction is reduced. At the same time, the delivery capacity of the compensation delivery pump 21 in the first pipeline 20 is reduced, so that the part of the flow rate lacking in the second pipeline 30 can be partially supplemented in a period of time, and the melt flow rate reduction amplitude in the downstream direction can be reduced. The two pipelines are connected in parallel, melt conveying fluctuation cannot be removed absolutely, but fluctuation can be balanced as far as possible, and therefore the quality of subsequent film drawing can be improved.

In addition, a metering pump 32 for metering the melt flow rate may be further provided in the second branch pipe 30, and the metering pump 32 is provided downstream of the pressure transmitter 31. At this time, the inlet of the first pipeline 20 is disposed after the flow distributing valve 10 and before the pressure transmitter 31, and the outlet of the first pipeline 20 is disposed before the film drawing device 200 and after the metering pump 32.

The metering pump 32 is designed as a complement to the pressure transmitter 31 for measuring the actual melt flow in the second pipe 30. As mentioned above, the continuous conveying device for stretch film melt is not limited to conveying one melt, and in some cases, melt materials with different compositions can be conveyed. The viscosity of different melts is different, and the parameters for controlling the melt flow in the first pipeline 20 through the pressure in the second pipeline 30 are also changed. Therefore, in the above embodiment of the present application, the metering pump 32 is further disposed in the second pipeline 30, and the pipeline length Δ L between the metering pump 32 and the pressure transmitter 31, and the start time difference Δ t between the flow rate change of the metering pump 32 and the pressure change of the pressure transmitter 31 obtained by measurement are used, so that the ratio Δ L/Δ t between the two is used as a gradient value for controlling the opening change of the compensation delivery pump 21, thereby perfectly solving the control problem of the compensation delivery pump 21 under different melt conditions, and improving the universality of the device.

For example, when the flow rate of the downstream metering pump 32 changes, the pressure change does not reach the upstream pressure transmitter 31, the time difference Δ t between the two changes represents the time of the melt property transfer change, and the melt property transfer change speed can be calculated by the ratio of the pipe length Δ L to the time difference Δ t, and can be used for controlling the gradient value for compensating the opening change of the delivery pump 21 gradually reaching the control value. For example, the pressure change in the second pipeline 30 is measured by the pressure transmitter 31, and the delivery amount of the compensating delivery pump 21 needs to be controlled to reach a certain control value, at this time, the opening degree of the compensating delivery pump 21 is not adjusted to a required size at a time, but the opening degree of the compensating delivery pump 21 is gradually adjusted to the required size from zero by taking the value of Δ L/Δ t as a gradient value for adjusting the opening degree, so that the technical effect of buffer distribution to a relatively long downstream delivery distance can be obtained within a period of time.

The continuous conveying method for the stretch film melt of the present application is further described below with reference to the accompanying drawings. Of course, the method for the continuous transport of a film-drawing melt according to the present application has in fact been described in the above-mentioned introduction with regard to the apparatus, with the following summary being supplemented by the summary of the present application.

As shown in the figure, the method for continuously conveying the film-drawing melt comprises the following steps: the melt produced by the polymer production plant 400 is fed directly via the melt feed pump 100 to at least one flow distribution valve 10; the flow distribution valve 10 synchronously conveys one part of the melt to the film drawing device 200 and conveys the rest part of the melt to the slicing device 300; the melt to be delivered to the film drawing device 200 is delivered through two parallel pipelines, wherein the melt flow in the first pipeline 20 is controlled by the pressure in the second pipeline 30. In one embodiment, a plurality of flow distribution valves 10 may be provided for delivering the melt delivered by the melt delivery pump 100 to a plurality of film drawing devices 200 and a plurality of slicing devices 300, respectively, depending on the problem of matching the melt throughput with the consumption of the film drawing devices. For example, assuming that the melt capacity is 50 tons per day and the consumption of one stretch film line is 20 tons per day, it may be necessary to provide two stretch film lines and 1 to 2 dicing lines.

Further, as shown, the sectioning device 300 of the present application may be any of the existing sectioning devices suitable for sectioning polymer melts, which may include, for example, an extruder 301, a slicer 302, and a dryer 303, among others.

Further, as shown in the drawings, the film drawing device 200 of the present application may be any one of existing film drawing devices suitable for polymer melt drawing of a film, and for example, it may include a feeding mechanism 201, an extruding mechanism 202, a longitudinal stretching mechanism 203, a transverse stretching mechanism 204, a winding mechanism 205, and the like.

It should be appreciated by those skilled in the art that while the present application is described in terms of several embodiments, not every embodiment includes only a single embodiment. The description is thus given for clearness of understanding only, and it is to be understood that all matters in the embodiments are to be interpreted as including all technical equivalents which are encompassed by the claims and are to be interpreted as combined with each other in a different embodiment so as to cover the scope of the present application.

The above description is only illustrative of the present invention and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations that may be made by those skilled in the art without departing from the spirit and principles of this application shall fall within the scope of this application.