Method and device for preparing synchronously-stretched polyphenylene sulfide film

Abstract

The embodiment of the invention discloses a method and a device for preparing a synchronously-stretched polyphenylene sulfide film. A specific embodiment of the method comprises the following steps: drying a polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material; carrying out melting treatment on the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt; carrying out tape casting operation on the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet; the polyphenylene sulfide sheet is subjected to preheating treatment, and the preheated polyphenylene sulfide sheet is obtained; the preheated polyphenylene sulfide sheet is conveyed to a stretching device, the stretched polyphenylene sulfide sheet is obtained, and the stretching device conducts transverse stretching and longitudinal stretching on the preheated polyphenylene sulfide sheet at the same time; carrying out heat setting treatment on the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film; and cooling the heat-set polyphenylene sulfide film to obtain the polyphenylene sulfide film. According to the embodiment, the thickness of the polyphenylene sulfide film is reduced, and the width of the film is increased.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of polyphenylene sulfide film preparation, and more particularly to a method and device for preparing a polyphenylene sulfide film by synchronous stretching. Background Art

[0002] Polyphenylene sulfide (PPS) is a high-performance semi-crystalline thermoplastic engineering plastic. Due to its excellent chemical resistance, high temperature stability, low water absorption, flame retardancy and excellent mechanical properties, it is widely used in the fields of automobile, aerospace, electronics and food engineering. At present, most of the preparation processes of polyphenylene sulfide films are to first stretch the polyphenylene sulfide sheet longitudinally and then stretch it transversely.

[0003] However, when the polyphenylene sulfide film is prepared in the above manner, the following technical problems often occur:

[0004] When the polyphenylene sulfide sheet is stretched longitudinally first and then transversely, problems such as uneven film thickness and inconsistent shrinkage rate may occur due to uneven stretching process, resulting in a lower film stretching width limit and a larger film thickness. Summary of the invention

[0005] The content of this disclosure is used to introduce concepts in a brief form, which will be described in detail in the detailed implementation section below. The content of this disclosure is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

[0006] Some embodiments of the present disclosure provide a method and apparatus for preparing a synchronously stretched polyphenylene sulfide film to solve one or more of the technical problems mentioned in the above background technology section.

[0007] In a first aspect, some embodiments of the present disclosure provide a method for preparing a synchronously stretched polyphenylene sulfide film, the method comprising: drying a polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material; melting the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt; casting the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet; preheating the polyphenylene sulfide sheet to obtain a preheated polyphenylene sulfide sheet; conveying the preheated polyphenylene sulfide sheet to a stretching device to obtain a stretched polyphenylene sulfide sheet, wherein the stretching device simultaneously stretches the preheated polyphenylene sulfide sheet in the transverse and longitudinal directions; heat-setting the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film; and cooling the heat-set polyphenylene sulfide film to obtain a polyphenylene sulfide film.

[0008] Optionally, the polyphenylene sulfide sheet is preheated to obtain a preheated polyphenylene sulfide sheet, including: passing the polyphenylene sulfide sheet through hot air for 4 to 8 seconds; raising the temperature of the polyphenylene sulfide sheet to 80 to 110°C to obtain a preliminarily preheated polyphenylene sulfide sheet; continuing to pass the preliminarily preheated polyphenylene sulfide sheet through hot air for 3 to 4 seconds; raising the temperature of the preliminarily preheated polyphenylene sulfide sheet to 90 to 120°C to obtain a preheated polyphenylene sulfide sheet.

[0009] Optionally, the preheated polyphenylene sulfide sheet is conveyed to a stretching device to obtain a stretched polyphenylene sulfide sheet, comprising: stretching the preheated polyphenylene sulfide sheet in both longitudinal and transverse directions by a synchronous biaxial stretching machine at a stretching ratio of 1:4 to 1:3 to obtain the stretched polyphenylene sulfide sheet.

[0010] Optionally, the stretched polyphenylene sulfide sheet is subjected to heat setting treatment to obtain a heat-set polyphenylene sulfide film, including: heating the stretched polyphenylene sulfide sheet with hot air at 120-200° C. for 1-3 seconds, and making the longitudinal stretching ratio between 1:0.95 and 1:0.88.

[0011] Optionally, the thermal shrinkage of the polyphenylene sulfide film is less than 2%.

[0012] Optionally, the heat-set polyphenylene sulfide film is cooled to obtain the polyphenylene sulfide film, including: cooling the heat-set polyphenylene sulfide film by a cooling roller and a cooling medium, wherein the surface temperature of the cooling roller is 30-50°C, and the temperature of the cooling medium is 15-25°C.

[0013] Optionally, the method further includes: pulling the polyphenylene sulfide film by a pulling device; detecting the thickness of the polyphenylene sulfide film in real time by a thickness gauge to obtain a measurement result of the thickness of the polyphenylene sulfide film; in response to the measurement result not reaching a preset thickness standard, the thickness gauge sending the measurement result to a control system; the control system generating an adjustment parameter according to the measurement result; the control system adjusting the pulling speed of the pulling device and the winding speed of the winder according to the adjustment parameter; in response to the measurement result reaching a preset thickness standard, winding the polyphenylene sulfide film reaching the preset thickness standard onto a winding roller by the winder; in response to the winding roller collecting a preset area of ​​the polyphenylene sulfide film, stopping the winder and replacing a new winding roller with the winder.

[0014] Optionally, the traction speed of the traction device is 10-60 m / min, and the traction tension of the traction device is 50-200 N.

[0015] Optionally, the winding speed of the above-mentioned winding machine matches the above-mentioned traction device and is 10-60m / min; the winding tension of the above-mentioned winding machine is 20-100N.

[0016] In the second aspect, some embodiments of the present disclosure provide a polyphenylene sulfide film preparation device, which includes a dryer, an extruder, a casting device, a hot air device, a synchronous stretching device, a heat setting device, a cooling device, a pulling device and a winding device. The polyphenylene sulfide film preparation device is configured to be able to implement any one of the methods described in the first aspect above.

[0017] Through the synchronously stretched polyphenylene sulfide film preparation method of some embodiments of the present disclosure, the thickness of the polyphenylene sulfide film is further reduced and the width of the polyphenylene sulfide film is further increased. Specifically, the reason why most polyphenylene sulfide film preparation methods have high thickness and low width is that most polyphenylene sulfide film method processes use the method of first longitudinally stretching and then transversely stretching the polyphenylene sulfide sheet, which is prone to uneven film thickness and inconsistent shrinkage due to uneven stretching process, resulting in a low film stretching width limit and a large film thickness. Based on this, some embodiments of the present disclosure provide a method for preparing a synchronously stretched polyphenylene sulfide film, the method comprising: drying a polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material; melting the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt; casting the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet; preheating the polyphenylene sulfide sheet to obtain a preheated polyphenylene sulfide sheet; conveying the preheated polyphenylene sulfide sheet to a stretching device to obtain a stretched polyphenylene sulfide sheet, wherein the stretching device simultaneously stretches the preheated polyphenylene sulfide sheet in the transverse and longitudinal directions; heat-setting the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film; and cooling the heat-set polyphenylene sulfide film to obtain a polyphenylene sulfide film. The synchronously stretched polyphenylene sulfide film preparation method makes the film stress distribution more uniform by simultaneously stretching in the transverse direction and the longitudinal direction, thereby making the film surface smoother and shrinking more consistent, thereby further reducing the thickness of the polyphenylene sulfide film and further increasing the width of the polyphenylene sulfide film. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that components and elements are not necessarily drawn to scale.

[0019] Figure 1 is a flow chart of some embodiments of the method for preparing a synchronously stretched polyphenylene sulfide film according to the present disclosure;

[0020] Figure 2 It is a schematic structural diagram of a polyphenylene sulfide film preparation device according to the present disclosure. DETAILED DESCRIPTION

[0021] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0022] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

[0023] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0024] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0025] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0026] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0027] Figure 1 is a flow chart 100 of some embodiments of a method for preparing a synchronously stretched polyphenylene sulfide film according to the present disclosure.

[0028] Step 101, drying the polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material.

[0029] In some embodiments, the polyphenylene sulfide raw material can be dried to obtain a dried polyphenylene sulfide raw material. The drying equipment can be a continuous hot air circulation dryer, and some parameters of the drying equipment (such as drying temperature and wind speed, the temperature range can be set between 100°C and 300°C, and the wind speed can be set between 0.5m / s and 5m / s, are not specifically limited). In practice, hot air can be used as a drying medium, and the hot air can be circulated in the dryer by a fan. Driven by a conveying device (such as a conveyor belt, chain conveyor, etc.), the raw material slowly passes through the hot air area inside the dryer, and the hot air is fully in contact with the raw material, and heat is transferred to the raw material by convection, so that the moisture in the raw material is vaporized and discharged with the hot air, thereby achieving drying to obtain a dried polyphenylene sulfide raw material.

[0030] Step 102, melting the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt.

[0031] In some embodiments, the dried polyphenylene sulfide raw material can be melt-treated to obtain a polyphenylene sulfide melt. In practice, the screw plasticizing system of an extruder or an injection molding machine can be used to complete the melt treatment. Taking an extruder as an example, the dried polyphenylene sulfide raw material enters the barrel of the extruder from the hopper, and a heating device, such as an electric heating ring or a heating rod, is usually provided on the outside of the barrel. The screw rotates in the barrel, on the one hand, conveying the raw material forward along the barrel, and on the other hand, applying shear force to the raw material. Under the combined action of the heat provided by the heating device and the shear heat generated by the rotation of the screw, the dried polyphenylene sulfide raw material gradually softens and melts, thereby obtaining a polyphenylene sulfide melt. Among them, since the melting point of polyphenylene sulfide is relatively high, generally around 280 to 300°C, the barrel temperature is usually set at 300 to 350°C to ensure that the raw material is fully melted.

[0032] Optionally, the above method further includes:

[0033] In the first step, the impurity detection equipment is used to detect impurities in the polyphenylene sulfide melt to obtain an impurity detection result. The impurity detection equipment may include but is not limited to: atomic absorption spectrometer (AAS) or inductively coupled plasma mass spectrometer (ICP-MS). The impurity detection result may be a list of components in which impurities are detected. For example, metal ion impurities (1%), acidic ion impurities (0.2%), etc.

[0034] In the second step, according to the above impurity detection results, the polyphenylene sulfide melt is subjected to the following treatment:

[0035] In the first sub-step, in response to the above impurity detection result indicating the presence of metal ion impurities, a metal impurity removal agent of a preset ratio is added to the above polyphenylene sulfide melt through a metering pump to obtain a polyphenylene sulfide melt with some metal ions removed and a type of precipitate. The specific value of the above preset ratio can be adjusted according to the actual situation. For example, when the impurity content is low (such as the test result shows that the mass fraction of metal ion impurities is between 0.01% and 0.1%), the above preset ratio (the mass ratio of metal impurity removal agent to polyphenylene sulfide melt) can be between 0.01% and 0.1%. When the impurity content is high (such as when the mass fraction of metal ion impurities is detected to be 0.1%-1% or even higher), the above preset ratio can be increased to 0.1%-1%. Metal impurity removal agents usually contain components that can react chemically with metal ions. For example, some complexing agents can form insoluble complex precipitates with metal ions, that is, the above-mentioned type of precipitates. In practice, these precipitates can be separated from the melt to reduce the content of metal ions in the melt and improve the purity of the melt.

[0036] In the second sub-step, in response to the above impurity detection result indicating the presence of small molecule organic impurities, the polyphenylene sulfide melt from which some metal ions have been removed is treated with activated carbon that has been ground to a suitable particle size to obtain a polyphenylene sulfide melt from which some small molecule organic impurities have been removed. The above small molecule organic impurities may include, but are not limited to: unreacted monomers (such as raw materials such as p-dichlorobenzene and sodium sulfide that may still have a small amount of residue after the reaction), oligomers, solvent and additive residues (such as solvents (such as N-methylpyrrolidone, etc.) used in the synthesis process and additives (such as antioxidants, lubricants, etc.) If the substances are not completely removed in the subsequent treatment, and degradation products (such as aldehydes, ketones, acids, esters, etc. organic compounds). The above suitable particle size can be determined based on the properties of the melt and the properties of the activated carbon itself, and is not specifically limited here. For example, the particle size can be set between 20 and 200 meshes. In practice, the above small molecule organic impurities can be adsorbed by the pores of the activated carbon and thus removed from the melt.

[0037] In the third sub-step, in response to the impurity detection result indicating the presence of acidic ion impurities, the polyphenylene sulfide melt from which some small molecular organic impurities have been removed is treated with an alkaline impurity removal agent to obtain a polyphenylene sulfide melt from which some acidic ion impurities have been removed. The acidic ion impurities may be halogen ions (such as chloride ions (Cl - ), bromide ion (Br - ) etc.), sulfate ions (SO 2- 4) etc. In practice, the alkaline components in alkaline impurity removal agents (such as sodium hydroxide solution) can be used to neutralize acidic ions and convert acidic ions into salts or other neutral substances, thereby reducing the acidity of the melt and reducing the adverse effects of acidic ions on product performance.

[0038] The fourth sub-step is to add a neutralizing agent to the polyphenylene sulfide melt from which some acidic ion impurities have been removed, so as to obtain a neutralized first polyphenylene sulfide melt and two types of precipitates. The neutralizing agent may be a reagent having properties opposite to those of the ionic impurities removed. For example, if an alkaline solution is used in the previous step to remove acidic ions, the neutralizing agent may be an acidic solution (such as a hydrochloric acid solution), and vice versa. The two types of precipitates may include, but are not limited to, silver halide precipitates, barium sulfate precipitates, and calcium phosphate precipitates. In practice, the alkaline component in the alkaline impurity removal agent may react with the acidic ions to convert the acidic ions into salts or other neutral substances, thereby reducing the acidity of the melt and reducing the adverse effects of the acidic ions on product performance.

[0039] In a fifth sub-step, in response to the impurity detection result indicating the presence of alkaline ion impurities, the polyphenylene sulfide melt from which some small molecular organic impurities have been removed or the first polyphenylene sulfide melt is treated with an acidic impurity removal agent to obtain a polyphenylene sulfide melt from which some alkaline ion impurities have been removed. The acidic impurity removal agent may be an acidic solution such as hydrochloric acid.

[0040] The sixth sub-step is to add a neutralizing agent to the polyphenylene sulfide melt from which some alkaline ion impurities have been removed, to obtain a neutralized second polyphenylene sulfide melt and three types of precipitates, wherein the three types of precipitates may include but are not limited to calcium carbonate precipitates and silicate precipitates.

[0041] The third step is to use a separation device to separate the first type of precipitate, the second type of precipitate and the third type of precipitate generated by the polyphenylene sulfide melt after the above treatment to obtain a polyphenylene sulfide melt with preliminary impurities removed. The above separation device can be a filter.

[0042] The fourth step is to homogenize the polyphenylene sulfide melt that has been preliminarily decontaminated to obtain a homogenized polyphenylene sulfide melt. The homogenization treatment can be carried out by stirring, mixing, etc., so that the various components in the melt are evenly distributed, ensuring that the physical and chemical properties of the melt are consistent throughout the system, and improving the stability of product quality. In practice, the preliminarily decontaminated polyphenylene sulfide melt can be placed in a container with a stirring device by means of a stirrer, a turbine stirrer, etc., and a suitable stirring speed and stirring time can be set. For example, for a paddle stirrer, the stirring speed is generally controlled at tens of revolutions per minute to hundreds of revolutions per minute, and the stirring time depends on the amount of the melt and the initial unevenness, and may vary from a few minutes to tens of minutes. During the stirring process, attention should be paid to controlling the stirring temperature to avoid excessive temperature causing melt degradation or other quality problems.

[0043] The fifth step is to perform vacuum degassing on the homogenized polyphenylene sulfide melt to obtain a decontaminated polyphenylene sulfide melt. The vacuum degassing can be achieved by a vacuum degassing tank. The vacuum degassing tank can be composed of a tank body, a stirring device, a heating device, a vacuum interface and the like. The tank body can be used to contain the polyphenylene sulfide melt. In practice, the stirring device can fully mix the melt and promote the escape of gas, the heating device can be used to maintain the temperature of the melt to ensure that it has good fluidity, and the vacuum interface is connected to a vacuum pump and can be used for vacuuming.

[0044] The above-mentioned first step to the fifth step and their related contents serve as an inventive point of an embodiment of the present disclosure, and solve the technical problem that "most polyphenylene sulfide film preparation processes lack impurity removal steps or have a single impurity removal process for the polyphenylene sulfide melt". The factors that lead to the lack of impurity removal steps or a single impurity removal process for the polyphenylene sulfide melt in most polyphenylene sulfide film preparation processes are as follows: Most polyphenylene sulfide film preparation processes directly start the sheet making process after melting the polyphenylene sulfide raw material, lacking further impurity removal of the raw material. If there are impurities in the raw material, it will affect the subsequent film preparation and reduce the quality of the generated polyphenylene sulfide film. If the above factors are solved, the quality of the generated polyphenylene sulfide film can be improved. In order to achieve this effect, the present disclosure further adds an impurity removal process, that is, by allowing an impurity inspection instrument to detect and inspect the impurity components in the polyphenylene sulfide melt, and then using physical and chemical methods to comprehensively remove impurities from the melt, the purity of the polyphenylene sulfide melt is improved, so as to further improve the treatment of the generated polyphenylene sulfide film. As a result, the impurity detection and removal process of polyphenylene sulfide melt was increased, and the quality of polyphenylene sulfide film was further improved.

[0045] Step 103 , performing a casting operation on the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet.

[0046] In some embodiments, the polyphenylene sulfide melt may be subjected to a casting operation to obtain a polyphenylene sulfide sheet. In practice, the casting operation may be completed by an air knife under the die head of the extruder. The air knife may be used to blow out a uniform airflow so that the melt extruded from the die head is closely attached to the cooling roller.

[0047] Step 104 , preheating the polyphenylene sulfide sheet to obtain a preheated polyphenylene sulfide sheet.

[0048] In some embodiments, the polyphenylene sulfide sheet can be preheated to obtain a preheated polyphenylene sulfide sheet. In practice, the polyphenylene sulfide melt can be transported from a melting device (such as an extruder) to a feed port of a casting device through a connecting pipe. During the transportation process, it is necessary to ensure that the temperature and pressure of the melt are stable to prevent the melt from cooling in the pipe or pressure fluctuations from affecting the subsequent casting quality. The melt enters the casting die from the feed port, and a common casting die is a slit die. The polyphenylene sulfide melt can be extruded from the slit of the die under pressure (for example, the extrusion speed can generally be 1 to 10 m / min) to form a material flow with a certain width and thickness, which is evenly cast onto the cooling roller or moving cooling belt below. The surface temperature of the cooling roller (for example, the cooling roller temperature can be set at 20 to 60°C) or the cooling belt is low. After contacting the high-temperature melt, the melt is quickly cooled and solidified to form a solid polyphenylene sulfide sheet. Among them, the electrostatic effect can be used to make the material in a molten state adhere to a specific casting device or carrier to form a preliminary sheet structure. The effect of static electricity can make the melt adhere and spread better, laying the foundation for subsequent molding operations. The electrostatic effect can be achieved by using an electrostatic generator. Usually the output voltage range of the above-mentioned electrostatic generator is 0 to 15kV. For the electrostatic attachment casting of polyphenylene sulfide sheets, if the material has good conductivity and the melt has high fluidity, a relatively high voltage is required to generate sufficient electrostatic adsorption force, which can be 10 to 15kV. If the material has average conductivity and good melt stability, it can be 5 to 10kV.

[0049] Optionally, the preheating of the polyphenylene sulfide sheet to obtain the preheated polyphenylene sulfide sheet comprises:

[0050] The first step is to pass the polyphenylene sulfide sheet through hot air for 4 to 8 seconds. The hot air can be achieved through a hot air circulation oven. The heat generated by the heating system of the hot air circulation oven can heat up the air in the box. The hot air circulation system drives the hot air to circulate continuously in the box, fully contacting the polyphenylene sulfide sheet, and transfers the heat to the sheet through convection heat exchange, so that the temperature of the sheet gradually increases to achieve the preheating purpose. The preheating time of hot air is greater than 4 seconds, which can prevent the polyphenylene sulfide sheet from absorbing insufficient heat due to too short a preheating time. The preheating time of hot air is less than 8 seconds, which can prevent the local overheating of the sheet due to too long a preheating time.

[0051] In the second step, the temperature of the polyphenylene sulfide sheet is raised to 80-110°C to obtain a preliminarily preheated polyphenylene sulfide sheet. Among them, raising the temperature of the sheet to 80-110°C can enable the polyphenylene sulfide molecular chain to obtain a certain amount of energy, begin to become more active, and enhance its plasticity and flexibility. The above-mentioned temperature range of 80-110°C is an important stage in the entire preheating process, which lays the foundation for further heating to a temperature more suitable for processing. If the temperature is lower than 80°C, the activity of the molecular chain is insufficient, and it may be difficult to meet the molding requirements in subsequent processing. If the temperature is higher than 110°C, it may cause unnecessary changes in the properties of the sheet, increase energy consumption and production risks. This temperature range helps the sheet to deform more easily during subsequent stretching and other processing, without problems such as cracking due to being too hard or too brittle. In practice, as the hot air continues to transfer heat to the sheet in the first step above, the heat absorbed by the sheet continues to accumulate, and the thermal motion of the molecules intensifies, which is manifested as a temperature increase. When the temperature reaches 80-110°C, the interaction force between the molecular chains of polyphenylene sulfide weakens, and the molecular chains can move and rearrange relatively easily.

[0052] The third step is to continue to pass the preheated polyphenylene sulfide sheet through hot air for 3 to 4 seconds. Among them, the sheet has undergone preliminary preheating and the temperature is relatively high. At this time, shortening the time to continue heating is, on the one hand, to further reduce the temperature gradient inside the sheet and make the temperature more uniform. On the other hand, at this stage, the molecular chains of the sheet have begun to become active. A shorter heating time can make the molecular chains further adjust and adapt on the basis of the existing activity, in preparation for reaching the final preheating temperature. If the time is too long, it may cause local overheating of the sheet and affect the quality, so 3 to 4 seconds is more appropriate.

[0053] The fourth step is to raise the temperature of the pre-heated polyphenylene sulfide sheet to 90-120°C to obtain a pre-heated polyphenylene sulfide sheet. After the preheating in the previous steps, the sheet absorbs enough heat under the continuous hot air, and the thermal motion of the molecular chain is further intensified, and the temperature rises to 90-120°C. At this time, the activity of the molecular chain is sufficient to make it orderly arranged along the stretching direction under the action of the stretching force to form a stable structure.

[0054] Step 105 , conveying the preheated polyphenylene sulfide sheet to a stretching device to obtain a stretched polyphenylene sulfide sheet.

[0055] In some embodiments, the preheated polyphenylene sulfide sheet can be transported to a stretching device to obtain a stretched polyphenylene sulfide sheet, wherein the stretching device stretches the preheated polyphenylene sulfide sheet in both the transverse and longitudinal directions at the same time. The stretching device can be a synchronous biaxial stretching machine. The stretching device can be composed of a preheating zone, a stretching zone, a heat setting zone, and a cooling zone. In the preheating zone, the polyphenylene sulfide sheet is heated to a suitable stretching temperature. The stretching zone is equipped with a special stretching mechanism that can apply transverse and longitudinal tension to the sheet at the same time. The heat setting zone is used to heat treat the sheet after stretching to fix the orientation of the molecular chains. The cooling zone allows the sheet to cool rapidly to stabilize its performance.

[0056] Optionally, the preheated polyphenylene sulfide sheet can be stretched in the longitudinal and transverse directions at a stretching ratio of 1:4 to 1:3 by a synchronous biaxial stretching machine to obtain the stretched polyphenylene sulfide sheet. Among them, the stretching ratio is controlled between 1:4 and 1:3, so that the molecular chains of the polyphenylene sulfide sheet can reach a suitable degree of orientation during the stretching process. When the stretching ratio is within this range, the molecular chains can be fully arranged along the stretching direction, thereby significantly improving the mechanical properties of the sheet in the longitudinal and transverse directions, such as tensile strength, modulus, etc. At the same time, the appropriate stretching ratio can also improve the optical properties of the sheet, making it more transparent and smooth. In practice, the preheated polyphenylene sulfide sheet can be fed into the stretching area of ​​the stretching device. The stretching device can clamp the edge of the sheet by a chain clamp or other mechanical device, and then apply tension in the longitudinal and transverse directions at the same time according to the preset stretching ratio.

[0057] Step 106 , performing heat setting treatment on the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film.

[0058] In some embodiments, the stretched polyphenylene sulfide sheet can be subjected to a heat setting treatment to obtain a heat-set polyphenylene sulfide film. The heat setting treatment is based on the thermal properties of the polymer material and the motion characteristics of the molecular chain. At the heat setting temperature, the polyphenylene sulfide molecular chain has sufficient energy to move and rearrange. The molecular chain is heated to a certain activity and then maintained at this temperature for a period of time to allow the molecular chain to have enough time to adjust to a more stable arrangement state. Subsequently, the molecular chain is fixed on this stable arrangement structure by cooling, thereby achieving the fixation of the molecular orientation, the elimination of internal stress and the improvement of crystallinity. In practice, the heat setting treatment can include a heating stage and a heat preservation stage.

[0059] Heating stage: The stretched polyphenylene sulfide sheet is sent to the heat setting equipment (such as heat setting oven or heat setting roller) to heat the sheet to the heat setting temperature at a certain heating rate. The heat setting temperature is usually higher than the glass transition temperature of polyphenylene sulfide, but lower than its melting point. The specific temperature is determined according to factors such as the stretching ratio, thickness and product requirements of the sheet.

[0060] Insulation stage: When the sheet reaches the heat setting temperature, it is kept for a period of time to allow the molecular chains to fully adjust and rearrange. The insulation time can range from tens of seconds to several minutes, which also depends on the characteristics of the sheet and the performance of the heat setting equipment. During the insulation process, it is necessary to ensure that the temperature of each part of the sheet is uniform to ensure the consistency of the heat setting effect.

[0061] Optionally, the stretched polyphenylene sulfide sheet can be heated and fixed by hot air at 120-200°C for 1-3s, and the longitudinal stretch ratio can be changed to between 1:0.95 and 1:0.88. Among them, when the temperature is lower than 120°C, the activity of the molecular chain is insufficient, and it is difficult to effectively eliminate the internal stress and adjust the orientation. When the temperature is higher than 200°C, polyphenylene sulfide may be thermally degraded, resulting in poor material performance. Therefore, controlling the temperature between 120 and 200°C can ensure that the performance of the material is not damaged while ensuring the heat setting effect. The heating time of 1 to 3 seconds can complete the heat setting process in a shorter time, thereby improving production efficiency. At the same time, this time range can also meet the needs of molecular chain adjustment and fixed orientation, so that the sheet can achieve a better heat setting effect. Adjusting the longitudinal stretch ratio to this range can make the sheet have a moderate retraction in the longitudinal direction and optimize the arrangement structure of the molecular chain. When the stretch ratio is greater than 1:0.95, the degree of retraction is insufficient, and it may not be possible to fully eliminate the internal stress and improve the performance. When the stretch ratio is less than 1:0.88, the shrinkage is excessive, which may affect the dimensional accuracy and mechanical properties of the sheet. In practice, during the heat setting process, the sheet will shrink to a certain extent in the longitudinal direction due to the shrinkage of the molecular chain. The longitudinal stretch ratio can be changed to between 1:0.95 and 1:0.88 by controlling the heating temperature and time. For example, the longitudinal stretch ratio can be precisely controlled by adjusting parameters such as the temperature and flow rate of the hot air and the conveying speed of the sheet.

[0062] Step 107 , cooling the heat-set polyphenylene sulfide film to obtain a polyphenylene sulfide film.

[0063] In some embodiments, the heat-set polyphenylene sulfide film can be cooled to obtain a polyphenylene sulfide film. In practice, after the heat preservation stage, an appropriate cooling method (such as air cooling, water cooling, etc., wherein the cooling rate of air cooling can be controlled at 10-50°C / min) can be used to quickly cool the sheet to room temperature. The cooling rate also has a certain influence on the performance of the film. Too fast a cooling rate may cause new internal stress to be generated inside the film, while too slow a cooling rate may cause the molecular chain to relax again, affecting the heat setting effect.

[0064] Optionally, the heat-set polyphenylene sulfide film can be cooled by a cooling roller and a cooling medium, wherein the surface temperature of the cooling roller can be 30-50° C., and the temperature of the cooling medium can be 15-25° C. The above 30-50° C. and 15-25° C. are both temperature ranges that take into account material properties and equipment costs.

[0065] Optionally, the thermal shrinkage rate of the above-mentioned polyphenylene sulfide film can be less than 2%. Among them, the above-mentioned thermal shrinkage rate can be the ratio of the shrinkage of the size (usually length or width) of the polyphenylene sulfide film after being subjected to a certain temperature. Temperature fluctuations are inevitable during the production and processing process. If the thermal shrinkage rate of the film is too large, a thermal shrinkage rate of less than 2% can effectively reduce the quality problems caused by thermal shrinkage differences and ensure the overall quality and performance consistency of the product. In practice, the film sample can be placed in a specific temperature environment for a certain period of time, and the dimensional change before and after shrinkage can be measured. Among them, it can be calculated according to the formula "thermal shrinkage rate = (size before shrinkage - size after shrinkage) ÷ size before shrinkage × 100%". The "direction" here can be longitudinal (film production direction), transverse (perpendicular to the production direction) or both directions are considered.

[0066] Optionally, the above method may further include:

[0067] In the first step, the polyphenylene sulfide film is pulled by a pulling device. The pulling device may be a device composed of a plurality of pulling rollers, and the pulling rollers may be driven to rotate by a motor. In practice, in a polyphenylene sulfide film production line, the pulling rollers may clamp the film and drive it to move forward. The pulling rollers may rotate at a stable speed to ensure that the film runs smoothly on the production line.

[0068] In the second step, the thickness of the polyphenylene sulfide film is detected in real time by a thickness gauge to obtain the measurement result of the thickness of the polyphenylene sulfide film. Among them, the thickness gauge can be a device specially used to measure the thickness of the film. The types of thickness gauges can include but are not limited to: thickness gauges include X-ray thickness gauges, ultrasonic thickness gauges, etc. The thickness gauge can obtain the thickness data of the film in the production process in real time and accurately. By continuously monitoring the thickness, the change of thickness can be discovered in time, providing a basis for subsequent thickness adjustment. In practice, for example, the thickness gauge can measure the thickness by using the change in intensity when the rays penetrate the film. On the film production line, the thickness gauge is installed at a specific position to continuously detect the passing film and display the measured thickness data in real time.

[0069] In the third step, in response to the measurement result not meeting the preset thickness standard, the thickness gauge sends the measurement result to the control system. The preset thickness standard is a film thickness range preset according to the quality requirements of the product. For example, the preset thickness standard may be 50±2 microns. In practice, for example, when the thickness gauge detects that the thickness of a certain part of the film is 55 microns, it means that the measurement result does not meet the preset standard, and the thickness gauge may send the measurement result of 55 microns to the control system via a data line or wireless transmission.

[0070] In the fourth step, the control system generates adjustment parameters based on the measurement results. In practice, after receiving the measurement results from the thickness gauge, the control system will analyze the deviation between the measurement results and the preset standard according to the preset algorithm and logic (such as proportional-integral-differential (PID) control algorithm or fuzzy control algorithm, etc.), and generate corresponding adjustment parameters. The adjustment parameters can be used to adjust related equipment in the production process to correct the deviation of the film thickness. For example, the control system can generate adjustment parameters based on the deviation between the measurement result of 55 microns and the preset standard of 50 microns, through calculation and analysis by the preset algorithm, such as generating instructions to increase the traction speed by 5% and reduce the winding speed by 3%.

[0071] In the fifth step, the control system adjusts the traction speed of the traction device and the winding speed of the winder according to the adjustment parameters. The traction speed refers to the speed at which the traction device pulls the polyphenylene sulfide film forward, and the unit is meter per minute (m / min). It determines the speed of the film moving on the production line, and directly affects the production efficiency and quality indicators such as the thickness and tensile properties of the film. In practice, for example, the control system increases the rotation speed of the traction roller by 5% by sending a signal to the motor controller of the traction device, thereby speeding up the forward speed of the film on the production line. At the same time, a signal is sent to the motor controller of the winder to reduce the rotation speed of the winding roller by 3%, thereby slowing down the winding speed of the film. In this way, the tension and stretching degree of the film on the production line change, and the thickness will be adjusted accordingly.

[0072] Step 6: In response to the measurement result reaching the preset thickness standard, the polyphenylene sulfide film reaching the preset thickness standard is rolled up onto a winding roller by a winding machine. In practice, the winding roller can roll up the polyphenylene sulfide film by self-rotation.

[0073] In the seventh step, in response to the winding roller collecting the polyphenylene sulfide film of the preset area, the winding machine is stopped and a new winding roller is replaced on the winding machine. The preset area is the film winding amount preset according to production requirements and packaging specifications. For example, the preset winding area can be 1,000 square meters. In practice, for example, when the counter on the winding machine records that the area of ​​the wound film reaches 1,000 square meters, the winding machine automatically stops rotating. At this time, the winding roller full of film can be removed from the winding machine, replaced with a new empty winding roller, and then the winding machine is restarted to continue the film winding work.

[0074] Optionally, the traction speed of the traction device is 10 to 60 m / min, and the traction tension of the traction device is 50 to 200 N. The traction tension may refer to the magnitude of the pulling force applied by the traction device to the film during the pulling process, in Newton (N). It can affect the stretching degree and internal stress distribution of the film during the pulling process, and thus affect the physical properties and dimensional stability of the film. The lower limit of the tension is set to 50 N to ensure that the film can be effectively pulled and stretched to a certain extent, so that the molecular chains are oriented and arranged, and the mechanical properties of the film are improved. If the tension is too small, the film may not be pulled normally, or the stretching degree is insufficient, resulting in low strength and modulus of the film. The upper limit of the tension is set to 200 N to prevent the film from breaking or over-stretching deformation due to excessive tension. Excessive tension will cause excessive internal stress in the film, exceeding the tolerance limit of the film, resulting in problems such as breakage and thinning, affecting the quality and yield of the film. In practice, the low speed condition (close to 10 m / min) can be applied to situations where the film quality requirements are extremely high and fine processing is required. At this time, the film has enough time to cool, crystallize and other processes, which is conducive to forming a uniform structure, but the production efficiency is low. For example, the production of polyphenylene sulfide films for some high-end electronic devices has strict requirements on thickness accuracy and surface quality, and a lower traction speed may be used. High speed (close to 60m / min) can be used to greatly improve production efficiency while ensuring that the film quality basically meets the requirements. However, more precise equipment control and process parameter adjustment are required to ensure the stability of film quality. For example, in the large-scale production of polyphenylene sulfide films for ordinary packaging, in order to increase production, the traction speed will be appropriately increased.

[0075] Optionally, the winding speed of the above-mentioned winder matches the above-mentioned traction device, which is 10 to 60 m / min, and the winding tension of the above-mentioned winder is 20 to 100 N. Among them, the matching of the winding speed and the traction device means that the linear speed of the winder winding the film needs to be consistent with the speed at which the traction device pulls the film forward. If the speeds of the two do not match, it will cause problems of film accumulation or excessive stretching on the production line. For example, if the winding speed is greater than the traction speed, the film will accumulate between the traction device and the winder, causing wrinkles and uneven thickness of the film; if the winding speed is less than the traction speed, the film will be over-stretched and may break, become thinner, etc., affecting the quality of the film.

[0076] Through the synchronously stretched polyphenylene sulfide film preparation method of some embodiments of the present disclosure, the thickness of the polyphenylene sulfide film is further reduced and the width of the polyphenylene sulfide film is further increased. Specifically, the reason why most polyphenylene sulfide film preparation methods have high thickness and low width is that most polyphenylene sulfide film method processes use the method of first longitudinally stretching and then transversely stretching the polyphenylene sulfide sheet, which is prone to uneven film thickness and inconsistent shrinkage due to uneven stretching process, resulting in a low film stretching width limit and a large film thickness. Based on this, some embodiments of the present disclosure provide a method for preparing a synchronously stretched polyphenylene sulfide film, the method comprising: drying a polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material; melting the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt; casting the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet; preheating the polyphenylene sulfide sheet to obtain a preheated polyphenylene sulfide sheet; conveying the preheated polyphenylene sulfide sheet to a stretching device to obtain a stretched polyphenylene sulfide sheet, wherein the stretching device simultaneously stretches the preheated polyphenylene sulfide sheet in the transverse and longitudinal directions; heat-setting the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film; and cooling the heat-set polyphenylene sulfide film to obtain a polyphenylene sulfide film. The synchronously stretched polyphenylene sulfide film preparation method makes the film stress distribution more uniform by simultaneously stretching in the transverse direction and the longitudinal direction, thereby making the film surface smoother and shrinking more consistent, thereby further reducing the thickness of the polyphenylene sulfide film and further increasing the width of the polyphenylene sulfide film.

[0077] Figure 2 It is a structural diagram of a polyphenylene sulfide film preparation device according to the present disclosure. Figure 2 The invention comprises a drying machine 1, an extruder 2, a casting device 3, a hot air device 4, a synchronous stretching device 5, a heat setting device 6, a cooling device 7, a pulling device 8 and a winding device 9.

[0078] In some embodiments, the polyphenylene sulfide film preparation device may include: Figure 2The dryer 1, extruder 2, casting device 3, hot air device 4, synchronous stretching device 5, heat setting device 6, cooling device 7, traction device 8 and winding device 9 are shown. Among them, the dryer 1 can be the continuous hot air circulation dryer. The extruder 2 can be a twin-screw extruder. The casting device 3 can be an air knife under the head of the extruder 2. The hot air device 4 can be the hot air circulation oven. The synchronous stretching device 5 can be the synchronous biaxial stretching machine. The heat setting device 6 can be the heat setting oven or the heat setting roller. The cooling device 7 can be a cooling roller and a cooling medium. The traction device 8 can be a traction roller. The winding device 9 can be the winding machine. The dryer 1 is connected to the extruder 2. The extruder 2 is connected to the casting device 3. The casting device 3 is connected to the hot air device 4. The hot air device 4, the synchronous stretching device 5 and the heat setting device 6 are connected. The heat setting device 6 is connected to the cooling device 7. The cooling device 7 is connected to the traction device 8. The traction device 8 is connected to the winding device 9.

[0079] The above-mentioned embodiments of the present disclosure have the following beneficial effects: through the polyphenylene sulfide film preparation device of some embodiments of the present disclosure, the polyphenylene sulfide sheet can be stretched longitudinally and transversely at the same time by cooperating with the synchronous stretching device, so as to further increase the width of the polyphenylene sulfide film and further reduce the thickness of the polyphenylene sulfide film. Specifically, the reason why the polyphenylene sulfide film produced by most polyphenylene sulfide film preparation devices is thick and small in width is that most polyphenylene sulfide film preparation devices usually divide the longitudinal stretching and transverse stretching into two steps when preparing the polyphenylene sulfide film, which will make the stress distribution of the polyphenylene sulfide not uniform enough, resulting in a smaller tensile limit. Based on this, the polyphenylene sulfide film preparation device of the embodiment of the present disclosure integrates the synchronous stretching device on the one hand, further improving the tensile limit and width limit of the polyphenylene sulfide film. On the other hand, the polyphenylene sulfide film preparation device of the embodiment of the present disclosure also integrates the heat setting device, the cooling device, the traction device and the winding device, so as to better collect the generated polyphenylene sulfide film and maintain its morphological stability. Therefore, a polyphenylene sulfide film preparation device integrating a synchronous stretching device and a related winding device is provided, which can further increase the width of the polyphenylene sulfide film and further reduce the thickness of the polyphenylene sulfide film.

[0080] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A method for preparing a synchronously stretched polyphenylene sulfide film, comprising: Drying the polyphenylene sulfide raw material to obtain a dried polyphenylene sulfide raw material; Melting the dried polyphenylene sulfide raw material to obtain a polyphenylene sulfide melt; Performing a casting operation on the polyphenylene sulfide melt to obtain a polyphenylene sulfide sheet; Preheating the polyphenylene sulfide sheet to obtain a preheated polyphenylene sulfide sheet; The preheated polyphenylene sulfide sheet is conveyed to a stretching device to obtain a stretched polyphenylene sulfide sheet, wherein the stretching device stretches the preheated polyphenylene sulfide sheet in the transverse and longitudinal directions simultaneously; performing heat setting treatment on the stretched polyphenylene sulfide sheet to obtain a heat-set polyphenylene sulfide film; The heat-set polyphenylene sulfide film is cooled to obtain a polyphenylene sulfide film.

2. The method according to claim 1, wherein: The preheating of the polyphenylene sulfide sheet to obtain the preheated polyphenylene sulfide sheet comprises: Passing the polyphenylene sulfide sheet through hot air for 4 to 8 seconds; Raising the temperature of the polyphenylene sulfide sheet to 80-110° C. to obtain a preliminarily preheated polyphenylene sulfide sheet; The preliminarily preheated polyphenylene sulfide sheet continues to pass through the hot air for 3 to 4 seconds; The temperature of the preliminarily preheated polyphenylene sulfide sheet is raised to 90-120° C. to obtain a preheated polyphenylene sulfide sheet.

3. The method according to claim 1, wherein: The method of conveying the preheated polyphenylene sulfide sheet to a stretching device to obtain a stretched polyphenylene sulfide sheet comprises: The preheated polyphenylene sulfide sheet is stretched in the longitudinal and transverse directions simultaneously by a synchronous biaxial stretching machine at a stretching ratio of 1:4 to 1:3 times to obtain the stretched polyphenylene sulfide sheet.

4. The method according to claim 1, wherein: The step of subjecting the stretched polyphenylene sulfide sheet to heat setting treatment to obtain a heat-set polyphenylene sulfide film comprises: The stretched polyphenylene sulfide sheet is heated and shaped by hot air at 120 to 200° C. for 1 to 3 seconds, and the longitudinal stretching ratio is changed to be between 1:0.95 and 1:0.

88.

5. The method according to claim 1, wherein: The thermal shrinkage rate of the polyphenylene sulfide film is less than 2%.

6. The method according to claim 1, wherein: The step of cooling the heat-set polyphenylene sulfide film to obtain the polyphenylene sulfide film comprises: The heat-set polyphenylene sulfide film is cooled by a cooling roller and a cooling medium, wherein the surface temperature of the cooling roller is 30-50°C, and the temperature of the cooling medium is 15-25°C.

7. The method according to claim 1, wherein: The method further comprises: Pulling the polyphenylene sulfide film by a pulling device; The thickness of the polyphenylene sulfide film is measured by a thickness gauge in real time to obtain a measurement result of the thickness of the polyphenylene sulfide film; In response to the measurement result not meeting a preset thickness standard, the thickness gauge sending the measurement result to a control system; The control system generates adjustment parameters according to the measurement results; The control system adjusts the traction speed of the traction device and the winding speed of the winding machine according to the adjustment parameters; In response to the measurement result reaching a preset thickness standard, the polyphenylene sulfide film reaching the preset thickness standard is rolled up onto a winding roller by a winding machine; In response to the winding roller collecting a preset area of ​​the polyphenylene sulfide film, the winding machine is stopped and a new winding roller is replaced on the winding machine.

8. The method according to claim 7, wherein: The traction speed of the traction device is 10-60 m / min, and the traction tension of the traction device is 50-200 N.

9. The method according to claim 7, wherein: The winding speed of the winding machine matches the traction device and is 10-60 m / min. The winding tension of the winding machine is 20-100 N.

10. A polyphenylene sulfide film preparation device, comprising a dryer, an extruder, a casting device, a hot air device, a synchronous stretching device, a heat setting device, a cooling device, a traction device and a winding device, and the polyphenylene sulfide film preparation device is configured to be able to implement the method as described in any one of claims 1 to 9.

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