Process for producing pure material differential fiber crepe sheet

Abstract

The application discloses a production process of pure material differential fiber wrinkle sheet and belongs to the technical field of wrinkle sheets. The application solves the problems of the following aspects: the difference between the geometric permeability of the outer layer deep wrinkle and the middle layer shallow wrinkle causes the outer layer to be fully shaped by rapid condensation and heat absorption during steam shaping, the steam penetration of the middle layer is blocked, the heat history is insufficient, the residual stress is high, the interlayer heat transfer efficiency is poor, the abnormal quality inspection cannot be identified, and the middle layer relaxes and gradually shrinks first after long-term wearing and washing. In the spinning stage, the middle layer is stretched by weak hot air to make the fiber thicker and the pore larger, the air permeability of the middle layer is improved, and the heat shortage is reduced; the high setting temperature is taken and the speed is slowed down to make the middle layer fully set, and the step is slowly cooled to stabilize the shape; the thermal shrinkage rate is measured periodically, the setting uniformity is monitored by the difference between the interlayer shrinkage rates, the fiber thickness or the process parameters are adjusted when the limit is exceeded, and the interlayer unevenness of the middle layer that shrinks first after long-term washing is controlled within the range that does not affect the warmth and the resilience life.

Description

Technical Field

[0001] This invention relates to the field of pleated fabric technology, and in particular to a production process for pure fiber pleated fabric. Background Technology

[0002] The processing of pleated thermal insulation nonwoven fabric involves two continuous processes: substrate spinning and pleating. First, polyester raw materials are melted using meltblown equipment, and then laid out at a controlled temperature and speed to create a thin nonwoven base material, which is then rolled up for later use. Multiple layers of the base material are stacked and fed into a pleating machine, where patterned rollers and medium-temperature processing create layered pleats. Different pleat depths are set for the outer and middle layers to increase overall air retention. The shaped fabric is then heat-set with high-temperature steam to solidify the pleat shape, followed by low-temperature roller cooling to lock in the texture structure, and finally rolled up to obtain the finished fabric. The processed fabric has a durable and stable pleated structure, is not easily deformed after multiple washes, has inherent weft stretch, and is lightweight, breathable, and compression-resistant, making it suitable as a thermal insulation filling material for clothing. During garment processing, the fabric can be fixed at quilting points to prevent displacement.

[0003] In the continuous production of multi-layer gradient pleated polyester nonwoven fabric, due to the inherent geometric permeability difference between the outer deep pleats and the middle shallow pleats, the outer layer rapidly condenses and absorbs heat during steam setting due to its fluffy structure, while the middle layer, due to its tight structure, suffers from insufficient effective thermal process and high residual internal stress. This difference in interlayer heat transfer efficiency, which is not due to process parameter deviation, cannot be identified in conventional whole-piece material inspection. However, after long-term wear and washing of the garment, it will cause the middle layer to experience stress relaxation and gradual pleating shrinkage first, ultimately resulting in a differentiated decrease in the fluffiness of the material from the inside out and a compression recovery life lower than expected.

[0004] Therefore, a production process for pure material inferior fiber pleated sheets is proposed to solve or alleviate the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a production process for pure fiber pleated sheets.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A process for producing pure, low-grade fiber pleated sheets includes the following steps: Step S1, Differentiated spinning and web making: Using the same pure polyethylene terephthalate chips as the sole raw material, and at the same melt temperature, by reducing the hot air stretching intensity applied to the intermediate layer substrate, fine fiber outer substrate and coarse fiber middle layer substrate are spun separately, so that the average fiber diameter of the middle layer substrate is larger than that of the outer layer substrate and the air permeability of the middle layer substrate is greater than that of the outer layer substrate; Step S2, three-layer lamination: two outer substrate layers and one intermediate substrate layer are laminationd in the order of outer layer, intermediate layer, outer layer, and the intermediate substrate layer is centered. During the lamination process, the thickness reduction of the intermediate substrate layer does not exceed a set value. Step S3, mechanical pleating: Mechanically pleat the stacked multilayer substrates to form a gradient pleated structure in which the pleat depth of the outer layer is greater than that of the middle layer, and the air permeability of the middle layer substrate is still greater than that of the outer layer substrate after pleating; Step S4, steam setting: Saturated steam is used to perform single-zone heat setting on the pleated multilayer substrate. The setting steam temperature does not exceed the upper limit temperature that would cause over-setting of the outer substrate. The setting linear speed is equal to the pleating linear speed in step S3. Step S5, stepped slow cooling and fixing: The multilayer substrate that has been shaped is cooled to below the glass transition temperature by multiple cooling rollers with the temperature decreasing sequentially along the material running direction, and then wound up to obtain the finished product; Step S6, offline layer detection and feedback control: Sample the finished product and peel it into outer layer and middle layer. Measure the heat shrinkage rate of each layer. Subtract the heat shrinkage rate of the outer layer from the heat shrinkage rate of the middle layer to obtain the interlayer shaping difference index. When the interlayer shaping difference index is greater than the preset safety limit, feedback is provided to increase the average fiber diameter and air permeability of the middle layer substrate in step S1, and / or increase the shaping steam temperature and decrease the shaping linear speed in step S4, until the interlayer shaping difference index is not greater than the safety limit.

[0007] Preferably, step S1, differentiated spinning and web making, specifically includes the following steps: S1.1, Raw material pretreatment: Drying the pure polyethylene terephthalate chips, which are the only raw material and do not contain solid fillers or chemical additives; S1.2, Outer substrate spinning: The treated chips are melted and extruded at a set melt temperature and formed into a web with a first tensile strength to obtain a fine fiber outer substrate; S1.3, intermediate layer substrate spinning: the same type of chips are melted and extruded at the same melt temperature, and web is formed with a second draw strength less than the first draw strength. The distance from the spinneret to the web forming curtain is increased to obtain a coarse fiber intermediate layer substrate with an average fiber diameter greater than that of the outer layer substrate and a higher air permeability. S1.4, Online monitoring: The average fiber diameter, basis weight and thickness of each substrate are monitored online and recorded as roll data. The roll data is then transmitted to steps S2 and S6.

[0008] Preferably, step S2, the three-layer stacking, specifically includes the following steps: S2.1, Upper winding and fabric threading: The two outer layers of substrate and the one middle layer of substrate are threaded together from the independent unwinding station in the order of outer layer, middle layer, outer layer, so that the middle layer of substrate is centered; S2.2, Differential tension, applies closed-loop tension control to each unwinding station, and ensures that the unwinding tension of the intermediate layer substrate is lower than that of the outer layer substrate; S2.3, No compaction fixing, no full hot rolling of the fabric body or application of adhesive during the lamination process; S2.4, Thickness monitoring: Monitor the total thickness of the laminate online to ensure that the reduction in thickness of the intermediate layer substrate after lamination does not exceed the set ratio of its thickness before lamination, and transmit the total thickness of the laminate as roll-to-roll data to step S3.

[0009] Preferably, step S3, mechanical pleating, specifically includes the following steps: S3.1, Pattern roller configuration: A pair of pattern rollers with an upper pattern roller tooth height greater than the lower pattern roller tooth height are used; S3.2, Roller gap setting: The roller gap is set according to the total thickness of the composite body transmitted in step S2; S3.3, Gradient pleating: Pleating the multi-layered substrate after lamination to form deep pleats in the outer substrate and shallow pleats in the middle substrate; S3.4, Air permeability verification: After pleating, measure the air permeability of the outer substrate and the middle substrate to ensure that the air permeability of the middle substrate is still greater than that of the outer substrate. If this condition is not met, increase the average fiber diameter of the middle substrate in step S1 or decrease the roller gap in step S3.

[0010] Preferably, step S4, steam setting, specifically includes the following steps: S4.1, Steam preparation: Prepare saturated steam with a set dryness. S4.2, Temperature control: The temperature of the setting steam is controlled to not exceed the upper limit temperature that would cause over-setting of the outer substrate; S4.3, Synchronize the linear speed, making the shaping linear speed equal to the pleating linear speed in step S3; S4.4, Continuous shaping, allows the pleated multi-layer substrate to continuously pass through a single-zone shaping box in saturated steam at a shaping linear velocity.

[0011] Preferably, step S5, stepped slow cooling and fixing, specifically includes the following steps: S5.1, stepped cooling, uses multiple series cooling rollers with successively decreasing temperatures along the material's running direction to cool the shaped multilayer substrate to below its glass transition temperature; S5.2, Uniform cooling, ensuring that the multilayer substrate is uniformly cooled by being in contact with each cooling roller at a sufficient wrap angle; S5.3, Controlled winding: Under controlled tension, the cooled multilayer substrate is wound into a finished product and transferred to step S6.

[0012] Preferably, step S6, offline hierarchical detection and feedback control, specifically includes the following steps: S6.1 Sampling: Samples are taken from the finished product according to a set cycle; S6.2, Layering test: The sample is peeled into an outer layer and an intermediate layer, and the thermal shrinkage rate of each layer is measured separately; S6.3, Index Calculation: The interlayer shaping difference index is obtained by subtracting the outer layer's thermal shrinkage rate from the intermediate layer's thermal shrinkage rate; S6.4, Feedback Control: When the interlayer shaping difference index is greater than the preset safety limit, gradually increase the average fiber diameter and air permeability of the intermediate layer substrate in step S1 in the direction of reducing the interlayer shaping difference index, and / or gradually increase the shaping steam temperature and reduce the shaping linear speed in step S4. After each adjustment, resample and measure until the interlayer shaping difference index is not greater than the safety limit.

[0013] The present invention has the following beneficial effects: This invention employs a weaker hot air stretching technique on the intermediate layer during the spinning stage, resulting in fibers that are coarser and have larger pores than the outer layer. Even when the intermediate layer is compressed into shallow pleats during subsequent pleating, its air permeability remains close to that of the outer layer. This allows steam to enter the intermediate layer more smoothly during setting, reducing the likelihood of insufficient heating due to the intermediate layer's compactness. Furthermore, the steam setting temperature is set at a slightly higher value that does not damage the outer layer, and the machine speed is appropriately slowed down, allowing the already improved heating conditions of the intermediate layer to achieve more thorough setting. Finally, a stepped, slow cooling process is used to further... Once the layer morphology stabilizes without generating new internal stress, the finished product is sampled periodically and the heat shrinkage rate of each layer is measured. The difference in shrinkage rate between the middle layer and the outer layer is used to measure whether the interlayer shaping is uniform. Once the difference exceeds the allowable range determined by the wash resistance test, the coarseness of the middle layer fiber is appropriately increased or the shaping temperature is increased and the speed is slowed down to correct it. In this way, the interlayer unevenness, which cannot be detected in the whole roll inspection but will cause the middle layer to shrink first after long-term wear and washing, is controlled within a range that does not affect the warmth and resilience life. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart of the present invention; Figure 2 This is a comparison table of the experimental group, the baseline group, and the control group in this invention; Figure 3This is a diagram showing the fiber diameters of the experimental group, the baseline group, and the control group in this invention; Figure 4 This is a diagram showing the air permeability of the experimental group, the baseline group, and the control group in this invention; Figure 5 This is a thickness retention diagram of the experimental group, the reference group, and the control group in this invention; Figure 6 These are the pleating and air permeability diagrams for the experimental group, the baseline group, and the control group in this invention; Figure 7 This is a diagram showing the degree of heating of the experimental group, the baseline group, and the control group in this invention; Figure 8 These are heat shrinkage diagrams of the experimental group, the baseline group, and the control group in this invention; Figure 9 These are water washing retention images of the experimental group, the baseline group, and the control group in this invention; Figure 10 This is a comprehensive performance diagram of the experimental group, the benchmark group, and the control group in this invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0018] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0019] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0021] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] A process for producing pure, low-fiber pleated sheets, such as Figure 1 As shown, it includes the following steps: Step S1, Differentiated spinning and web making: Using the same pure polyethylene terephthalate chips as the sole raw material, and at the same melt temperature, by reducing the hot air stretching intensity applied to the intermediate layer substrate, fine fiber outer substrate and coarse fiber middle layer substrate are spun separately, so that the average fiber diameter of the middle layer substrate is larger than that of the outer layer substrate and the air permeability of the middle layer substrate is greater than that of the outer layer substrate; S1.1, Raw material pretreatment: Pure polyethylene terephthalate chips with an intrinsic viscosity of 0.64 to 0.68 dL / g and free of any solid fillers and chemical additives are crystallized and dried until the moisture content is no more than 30 ppm; S1.2, Outer substrate spinning: The chips treated in S1.1 are fed into the extrusion and spinning system. Melt extrusion is performed under the following conditions: extrusion temperature, spinning box temperature, and spinneret temperature are all 280±2℃, metering pump flow rate is 120 cc / rev, and metering pump pressure is 18 MPa. The fibers are then formed into a web at a speed of 15 m / min at a distance of 200 mm from the spinneret to the web-forming curtain, under a first draw strength of 300℃, 0.12 MPa, and 20 m / s. This produces a fine fiber outer substrate with an average fiber diameter of 10±2 μm and a basis weight of 12 g / m². S1.3, intermediate layer substrate spinning: The same chips treated in S1.1 are fed into the same extrusion and spinning system, and melt-extruded under the same extrusion temperature, spinning box temperature, spinneret temperature, metering pump flow rate, and metering pump pressure as in S1.2. However, the drawing conditions are changed to a second drawing strength with a drawing air temperature of 300℃, a drawing air pressure of 0.07 to 0.09 MPa, and a drawing air velocity of 12 to 15 m / s. The distance from the spinneret to the web forming curtain is increased to 250 mm, and the web is formed at a web forming curtain speed of 15 m / min. This produces a coarse fiber intermediate layer substrate with an average fiber diameter of 16 to 22 μm, a basis weight of 15 g / m², and a thickness and air permeability greater than that of the outer layer substrate. S1.4, Online monitoring and recording: During the spinning process of S1.2 and S1.3, each substrate is monitored in real time by online fiber diameter measurement, online basis weight measurement and online thickness measurement. When the average fiber diameter deviates from the target value, the corresponding drafting air pressure is adjusted by no more than 0.01 MPa each time. The average fiber diameter, basis weight and thickness are recorded as roll data for use in the lamination control of step S2 and the detection and feedback of step S6. Step S2, three-layer lamination: two outer substrate layers and one intermediate substrate layer are laminationd in the order of outer layer, intermediate layer, outer layer, and the intermediate substrate layer is centered. During the lamination process, the thickness reduction of the intermediate substrate layer does not exceed a set value. S2.1, Unwinding and Fabric Threading: The two outer layers and one middle layer of substrate obtained in step S1 are installed in three independent unwinding stations, and the fabric is threaded into the pleating machine inlet along the path from bottom to top: outer layer, middle layer, and upper outer layer, so that the middle layer of substrate is centered. S2.2, Differentiated tension setting: Apply closed-loop tension control to each unwinding station, setting the unwinding tension of the outer substrate to 8 N, and setting the unwinding tension of the middle substrate to 10 N lower than that of the outer substrate, with a tension control accuracy of ±0.5 N; S2.3, Centering and Correction: An automatic centering and correction device aligns the edges of the two outer substrate layers with the one middle substrate layer, with an edge alignment error of no more than 2 mm. The edge alignment provides a positional reference for sampling at the left, center, and right positions along the width direction in step S6. S2.4, No compaction fixing: During the lamination process, the main body of the fabric is not fully hot-rolled or adhesive is applied. When interlayer anti-slip is required, it is only fixed at the edges of the fabric in an intermittent point manner. S2.5, Thickness monitoring: The total thickness of the laminate is monitored online to ensure that the thickness reduction of the intermediate layer substrate after lamination does not exceed 10% of its thickness before lamination. When the thickness reduction exceeds this proportion, the unwinding tension of the intermediate layer substrate in S2.2 is checked and reduced. The total thickness of the laminate is transmitted to step S3 as the roll-on data. Step S3, mechanical pleating: Mechanically pleat the stacked multilayer substrates to form a gradient pleated structure in which the pleat depth of the outer layer is greater than that of the middle layer, and the air permeability of the middle layer substrate is still greater than that of the outer layer substrate after pleating; S3.1, Pattern Roller Configuration: A pair of steel pattern rolls with an upper pattern roll tooth height of 4.5 mm and a lower pattern roll tooth height of 2.5 mm are used. The temperature of the upper pattern roll is set to 110℃ and the temperature of the lower pattern roll is set to 115℃. S3.2, Roller gap setting: The roller gap of the patterned rollers is set according to the total thickness of the composite body transmitted in step S2, i.e., S2.5; S3.3, Gradient pleating: Mechanical pleating is performed on the stacked multilayer substrate at a pleating linear speed of 16 m / min, so that the outer substrate forms deep pleats of 2 to 6 mm and the middle substrate forms shallow pleats of 0.5 to 4.5 mm; S3.4, Air permeability verification and adjustment: After pleating, measure the air permeability of the outer substrate and the middle substrate respectively. When the air permeability of the middle substrate after pleating is not greater than that of the outer substrate, increase the average fiber diameter of the middle substrate in step S1 (i.e., S1.3) or decrease the roller gap in step S3 until the air permeability of the middle substrate after pleating is greater than that of the outer substrate. Step S4, steam setting: Saturated steam is used to perform single-zone heat setting on the pleated multilayer substrate. The setting steam temperature does not exceed the upper limit temperature that would cause over-setting of the outer substrate. The setting linear speed is equal to the pleating linear speed in step S3. S4.1, Steam preparation: Prepare saturated steam with a dryness of not less than 95%; S4.2, Shaping temperature control, controlling the temperature of saturated steam between 155 and 158°C and not exceeding 158°C; S4.3, Synchronize linear velocity: Set the shaping linear velocity to 16 m / min and make it equal to the pleating linear velocity in step S3, i.e., S3.3; S4.4, Continuous shaping, which allows the pleated multilayer substrate to continuously pass through a single-zone shaping box in saturated steam at a shaping linear velocity. The effective shaping time is determined by the length of the single-zone shaping box and the shaping linear velocity. S4.5, Outlet monitoring: Infrared monitoring of the fabric temperature distribution at the outlet of the shaping box. When a longitudinal low-temperature stripe indicating insufficient heating of the intermediate layer substrate appears, an early warning is issued, and the dryness and flow rate of the saturated steam and the air permeability of the intermediate layer substrate obtained in step S1 are checked. Step S5, stepped slow cooling and fixing: The multilayer substrate that has been shaped is cooled to below the glass transition temperature by multiple cooling rollers with the temperature decreasing sequentially along the material running direction, and then wound up to obtain the finished product; S5.1, Cooling roller configuration: six steel cooling rollers, each 400 mm in diameter, arranged in an S-shape; S5.2, stepped temperature setting: the temperature of the first cooling roller is set to 83℃, and the temperature of each subsequent cooling roller decreases sequentially along the material running direction at a ratio of 0.82, so that the fabric surface temperature gradually drops below the glass transition temperature; S5.3, Uniform cooling, ensuring that the wrapped angle between the shaped multilayer substrate and each cooling roller is greater than 200° and that it is cooled in a double-sided alternating contact manner; S5.4, Tapered tension winding: After the fabric temperature drops below the glass transition temperature, winding is carried out with an initial tension of 15N and a taper coefficient of 20%, so that the winding tension decreases linearly as the roll diameter increases, and the finished product is transferred to step S6. Step S6, offline layer detection and feedback control: Sample the finished product and peel it into outer layer and middle layer. Measure the heat shrinkage rate of each layer. Subtract the heat shrinkage rate of the outer layer from the heat shrinkage rate of the middle layer to obtain the interlayer shaping difference index. When the interlayer shaping difference index is greater than the preset safety limit, feedback is given to increase the average fiber diameter and air permeability of the middle layer substrate in step S1, and / or increase the shaping steam temperature and decrease the shaping linear speed in step S4, until the interlayer shaping difference index is not greater than the safety limit. S6.1 Periodic sampling: Samples are taken from three positions (left, center, and right) along the width of the finished product every four hours or every ten rolls, and each sample is numbered. S6.2, Equilibration and Standing: The sample is placed in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours to equilibrate and stand. S6.3, Layering test: The balanced sample is peeled into two outer layers and one middle layer. The length of each layer is measured before and after free shrinkage in dry hot air at 150°C for 30 minutes, and the thermal shrinkage rate of each layer is calculated. S6.4, Calculation of the difference index: The interlayer shaping difference index is obtained by subtracting the average heat shrinkage rate of the two outer layers from the heat shrinkage rate of the middle layer. At the same time, the overall elastic recovery rate E and the bulkiness retention rate B are measured by taking an unpeeled sample. S6.5, Safety Upper Limit Calibration: At least three groups of finished products with different interlayer shrinkage differences are pre-selected, with no fewer than ten samples in each group. After 50 cycles of washing and drying in warm water at 40°C containing 0.1% neutral detergent, the interlayer shrinkage rate difference of each group is measured. A linear fit is performed between the interlayer shrinkage rate difference and the interlayer shrinkage difference index to obtain a corresponding relationship. Based on the maximum allowable interlayer shrinkage rate difference of the product, the safety upper limit of the interlayer shrinkage difference index is calculated from this corresponding relationship. S6.6, Acceptance Judgment and Feedback: When the interlayer shaping difference index is not greater than the safety upper limit and the elastic recovery rate E and the bulkiness retention rate B are not lower than their respective set lower limits, it is judged as qualified. When the interlayer shaping difference index is greater than the safety upper limit, sampling is intensified, and the average fiber diameter and air permeability corresponding to the drawing wind pressure of the intermediate layer substrate in step S1 (i.e., S1.3) are gradually increased in the direction of reducing the interlayer shaping difference index, and / or the shaping steam temperature in step S4 (i.e., S4.2) is gradually increased and the shaping linear speed in S4.3 is decreased. Sampling and measurement are repeated after each adjustment until the interlayer shaping difference index is not greater than the safety upper limit.

[0023] To verify the two modifications in this process—high porosity of the intermediate layer coarse fibers and sufficient overall shaping—an experimental group G8 and seven control groups G1 to G7 were set up, as detailed below. Figure 2 As shown, all other processes and testing methods are the same, all using pure polyester without additives. G1 is the baseline group, with the middle layer and outer layer made of the same material and stretched at the same time, and the setting temperature is relatively low. G2 to G4 reduce the stretch of the middle layer step by step, G5 to G7 increase the setting temperature step by step, and G8 optimizes both aspects simultaneously.

[0024] Multiple indicators were measured at each stage of the process: at the spinning end, the diameter and air permeability of the intermediate layer were measured; at the folding and pleating end, the thickness retention rate of the intermediate layer and the air permeability after pleating were measured; at the setting end, the relative heat exposure and heat shrinkage rate of the intermediate layer were measured; at the finished product end, the difference in setting between layers, the overall fluffiness and resilience were measured; and at the durability end, the difference in the retention rate of wrinkles between layers after 50 washes was measured. At least ten pieces were sampled in each group and the average value was taken to examine the improvement of the entire process from the source to the service life.

[0025] Test results are as follows Figure 3 As shown, the horizontal axis represents the drafting pressure during the spinning of the intermediate layer, and the vertical axis represents the average diameter of the resulting fibers. The line connecting the dots shows that the lower the drafting pressure, the coarser the fibers, and the two have a clear inverse relationship. The experimental group marked by the square was taken in the low-pressure area and obtained fibers that were significantly coarser than those of the outer layer. This proves that this process can stably produce coarse fibers in the intermediate layer by simply adjusting the drafting strength, without any additives.

[0026] like Figure 4 As shown, the horizontal axis represents the diameter of the intermediate layer fibers, the vertical axis represents the air permeability of the intermediate layer, and the dashed line represents the air permeability level of the outer layer. The dotted line shows that the thicker the fiber, the higher the air permeability. Except for the finest reference point, the air permeability of each group of intermediate layers is significantly higher than that of the outer layer dashed line. This indicates that after the intermediate layer is made thicker, it is more permeable than the outer layer, laying the foundation for the smooth entry of subsequent steam into the intermediate layer. This is the first step of this process to reduce the interlayer difference from the source.

[0027] like Figure 5As shown, the vertical axis represents the thickness retention rate of the intermediate layer after lamination relative to that before lamination, and the dashed line represents the lower limit of the acceptable level. Under the lamination method of low tension and incomplete hot rolling, the thickness retention rate of the intermediate layer in each group is stable above the acceptable level, indicating that the intermediate layer is not compacted in the lamination process. This step preserves the high porosity made in the spinning stage and ensures that the previous improvements are not lost in the lamination process.

[0028] like Figure 6 As shown, the solid dot represents the air permeability of the middle layer after pleating, and the dashed triangle represents the outer layer. In the baseline group and the groups that only increased the temperature, the air permeability of the middle layer after being pleated into shallow pleats is lower than that of the outer layer. However, in the groups where the middle layer is made coarser and the experimental group, even when pleated into shallow pleats, the air permeability of the middle layer is still higher than that of the outer layer. This proves that this process ensures the key condition that the middle layer is still more permeable than the outer layer after being pleated into shallow pleats, so that steam can reach the middle layer during the setting process.

[0029] like Figure 7 As shown, the vertical axis represents the degree of heating of the middle layer relative to the outer layer. The solid dot represents the path to improve air permeability, and the dashed triangle represents the path to increase temperature. Both lines rise as improvement in air permeability intensifies, but the slope of the air permeability improvement is steeper and the effect is stronger, while the temperature increase path is faster and then slows down. The square experimental group superimposed the two paths, and the degree of heating was the highest and closest to the outer layer. This indicates that improving air permeability is the main means, and appropriate temperature increase is a beneficial supplement. The combination of the two is optimal.

[0030] like Figure 8 As shown, the solid dot represents the thermal shrinkage rate of the intermediate layer, and the dashed triangle represents the outer layer. A high shrinkage rate indicates insufficient shaping and high residual stress. In the benchmark group, the shrinkage rate of the intermediate layer is significantly higher than that of the outer layer, and the two lines are far apart. As the intermediate layer becomes thicker or the temperature increases, the intermediate layer line gradually approaches the outer layer. In the experimental group, the intermediate layer line almost overlaps with the outer layer line, which directly shows that this process has basically eliminated the problem of insufficient shaping of the intermediate layer.

[0031] like Figure 9 As shown, the thick lines represent the baseline group and the thin lines represent the experimental group. The solid lines represent the outer layer and the dashed lines represent the middle layer. In the baseline group, the thick solid lines and thick dashed lines gradually separate as the water is washed. The middle layer descends much faster than the outer layer, which is a manifestation of the middle layer shrinking first and differentiating from the inside out. In the experimental group, the two thin lines remain close together and descend very slowly. This proves that after the interlayer is uniformly shaped, the durability of each layer is consistent under long-term water washing, and the differentiation is eliminated.

[0032] like Figure 10 As shown, solid dots represent interlayer differences, with lower being better; dashed triangles represent loft retention rate; and dotted squares represent compression rebound rate. The three lines converge in the experimental group, where the differences are lowest and the two properties are highest. The control group, with any single modification, cannot achieve this combination. This indicates that by reducing interlayer differences, the insulation support and rebound life of the finished product are improved simultaneously, verifying the overall effectiveness of this process.

[0033] The working principle is as follows: The reason why pleated fabrics shrink first in the middle layer and lose bulk from the inside out after long-term wear and washing is that the outer layer has deep and fluffy pleats while the middle layer has shallow and tight pleats. During steam setting, steam can easily enter the outer layer but has difficulty entering the middle layer, resulting in insufficient heating time, inadequate setting, and high internal residual stress in the middle layer. This difference in heating between layers cannot be seen in the routine inspection of the whole piece of fabric, so the hidden danger is carried over to the garment use stage. Therefore, this process does not remedy the problem in the setting stage, but rather starts to reduce this difference in heating from the fiber forming stage.

[0034] Therefore, in the differentiated spinning and web-making step, the outer and middle layers use the same polyester chips without any fillers or auxiliaries. The only difference is that the middle layer uses weaker hot air stretching and increases the distance between the spinneret and the web-forming curtain, making the fibers in the middle layer thicker and the gaps between the fibers larger than those in the outer layer. This results in a middle layer fabric that is more breathable than the outer layer, which lays the foundation for easier steam to enter the middle layer later. Since no foreign substances are added throughout the process, the fabric is still pure polyester and will not shed powder or precipitate during washing due to the addition of substances, thus preserving its washability and non-shedding properties.

[0035] When it comes to the three-layer lamination step, the key is not to compress the middle layer. Therefore, the middle layer is unwound with a slightly lower tension than the outer layer, and no full hot-pressing or gluing is done. Only necessary fixation is done at the fabric edge. The effect of doing this is to preserve the high breathability structure of the middle layer that was painstakingly created in the previous step, so that it is not flattened during lamination and all previous efforts are wasted.

[0036] In the mechanical pleating step, although the product requirements are still met by pressing out gradient pleats with a deeper outer layer and a shallower middle layer, thus preserving the original appearance and structural characteristics of the product, the middle layer uses coarser and looser fibers. Even when pressed into shallow pleats, its air permeability is still higher than that of shallow pleats made with ordinary fibers. The effect is that steam can reach the middle layer more smoothly than before during the subsequent setting process, thereby reducing the difference in heat between the outer layer and the middle layer from the root.

[0037] In this step, due to the requirements of the product itself, it is necessary to press out a gradient pleat with a deep outer layer and a shallow middle layer. It is this gradient that makes the middle layer dense and difficult for steam to enter, which constitutes the geometric root cause of insufficient heating of the middle layer. In other words, as long as the gradient of the pleating process is retained, the inherent disadvantage of poor permeability of the middle layer cannot be avoided. This process does not modify the pleating or smooth out the gradient, but instead entrusts the task of resolving this contradiction to the differentiated spinning web making at the front. During spinning, a weaker stretch is used on the middle layer to make its fibers thicker and the gaps between fibers larger. In this way, even if the middle layer is pressed into shallow pleats in the pleating process, its overall air permeability can still be close to or even higher than that of the outer layer. Thus, the geometric compactness created by the pleating end is offset by the material looseness created by the spinning end, the gradient is retained and the heating disadvantage is weakened.

[0038] In the steam setting step, since the middle layer has become relatively easy to heat, setting the steam temperature to the higher end that will not damage the feel of the outer layer, and appropriately slowing down the machine speed, will allow more of the extra heat supplied to actually fall on the middle layer, enabling the middle layer to be set more fully this time and reducing the internal residual stress. Keeping the setting temperature at the upper limit also prevents the outer layer from hardening and losing its elasticity due to overheating. Maintaining the same machine speed as the pleating process avoids the pleats being deformed due to mismatched front and rear tension.

[0039] In the steam setting step, to ensure the slower-heating intermediate layer is fully set, it's natural to tend to increase the overall steam temperature and slow down the machine speed. However, the outer layer has good permeability and heats up quickly. If the overall heating is intensified, the outer layer will be overheated first, hardening and losing its elasticity, damaging the product's feel and selling points. Increasing the temperature to take care of the intermediate layer damages the outer layer. In this process, on the one hand, a temperature limit is set at the setting end to prevent the outer layer from being over-set, limiting the overall heating to a range that the outer layer can withstand. On the other hand, the intermediate layer, which has already been pressed into shallow pleats at the pleating end, is still more breathable than the outer layer. This allows more of the extra heat supplied within the limited overall heating range to actually reach the intermediate layer. Thus, the intermediate layer receives sufficient heat without damaging the outer layer. This contradiction is resolved by the combined efforts of these two steps.

[0040] In the step of stepped slow cooling and fixing, multiple cooling rollers with progressively decreasing temperatures are used to slowly and evenly cool the fabric below the glass transition temperature. The purpose of this step is to stably fix the relatively consistent shape of each layer that has just been shaped, and to prevent the generation of new internal stress due to different cooling rates of each layer caused by sudden cooling. This is equivalent to maintaining the uniform shaping effect already achieved. When winding, the tension is reduced as the roll diameter increases in order to prevent the pleats from slowly loosening and shrinking during storage due to the rolling pressure.

[0041] In the offline layer detection and feedback control step, samples are taken from the finished product regularly, and the outer and middle layers are carefully separated to measure their shrinkage rate at high temperatures. The difference between the shrinkage rates of the middle and outer layers is used to measure whether the interlayer setting is uniform. A large difference indicates that the middle layer setting is still insufficient. Furthermore, the correlation between this difference and the degree of shrinkage after long-term use is found through repeated water washing tests in advance, and an allowable upper limit is determined accordingly. The effect is to turn the interlayer hidden dangers that could not be detected in the whole roll inspection into a visible and comparable value. Once the upper limit is exceeded, we go back and make the middle layer fibers thicker or increase the setting temperature and slow down the speed to correct it. This will prevent the middle layer from shrinking first and the insulation and resilience life from being reduced due to uneven interlayer heating. This is continuously controlled within a range that does not affect the use of the product.

[0042] Furthermore, in actual production, the insulation and support strength of the entire material and its resilience after repeated compression are inherently low, and the variations between different batches are unpredictable and difficult to control. The problem lies in the insufficient shaping of the interlayer. As the load-bearing framework sandwiched in the middle, if the interlayer loosens and shrinks first during use, the thickness support of the entire material collapses from the inside, and both bulkiness and resilience decrease. Moreover, the proper heating of the interlayer varies with raw materials and operating conditions, resulting in unstable batch performance. However, through this process... Figure 9 and Figure 10 As shown, from the baseline group to the control groups and then to the experimental group, the lower the difference between layers, the higher the two lines for bulk retention rate and compression rebound rate. The experimental group reached the highest in both aspects. The retention rates of each layer in the experimental group were always close and decreased slowly, indicating that the durability and rebound of the entire material were steadily improved. It was later found that this process can make the middle layer inherently breathable at the spinning end, retain this breathability at the lamination end, make it breathable even after being pressed into shallow pleats at the pleating end, make the middle layer breathable at the shaping end without damaging the outer layer, stabilize the uniform shape at the slow cooling end, and quantify the remaining deviation at the detection end and feed it back to the spinning and shaping to correct it. It is by raising the shaping level of the middle layer and maintaining its stability that the supporting skeleton of the entire material no longer collapses from the inside. The overall warmth and rebound are improved and become more consistent between batches.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A manufacturing process for pure raw material inferior fiber pleated sheets, characterized in that, Includes the following steps: Step S1, Differentiated spinning and web making: Using the same pure polyethylene terephthalate chips as the sole raw material, and at the same melt temperature, by reducing the hot air stretching intensity applied to the intermediate layer substrate, fine fiber outer substrate and coarse fiber middle layer substrate are spun separately, so that the average fiber diameter of the middle layer substrate is larger than that of the outer layer substrate and the air permeability of the middle layer substrate is greater than that of the outer layer substrate; Step S2, three-layer lamination: two outer substrate layers and one intermediate substrate layer are laminationd in the order of outer layer, intermediate layer, outer layer, and the intermediate substrate layer is centered. During the lamination process, the thickness reduction of the intermediate substrate layer does not exceed a set value. Step S3, mechanical pleating: Mechanically pleat the stacked multilayer substrates to form a gradient pleated structure in which the pleat depth of the outer layer is greater than that of the middle layer, and the air permeability of the middle layer substrate is still greater than that of the outer layer substrate after pleating; Step S4, steam setting: Saturated steam is used to perform single-zone heat setting on the pleated multilayer substrate. The setting steam temperature does not exceed the upper limit temperature that would cause over-setting of the outer substrate. The setting linear speed is equal to the pleating linear speed in step S3. Step S5, stepped slow cooling and fixing: The multilayer substrate that has been shaped is cooled to below the glass transition temperature by multiple cooling rollers with the temperature decreasing sequentially along the material running direction, and then wound up to obtain the finished product; Step S6, offline layer detection and feedback control: Sample the finished product and peel it into outer layer and middle layer. Measure the heat shrinkage rate of each layer. Subtract the heat shrinkage rate of the outer layer from the heat shrinkage rate of the middle layer to obtain the interlayer shaping difference index. When the interlayer shaping difference index is greater than the preset safety limit, feedback is provided to increase the average fiber diameter and air permeability of the middle layer substrate in step S1, and / or increase the shaping steam temperature and decrease the shaping linear speed in step S4, until the interlayer shaping difference index is not greater than the safety limit.

2. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S1, differentiated spinning and web making, specifically includes the following steps: S1.1, Raw material pretreatment: Drying the pure polyethylene terephthalate chips, which are the only raw material and do not contain solid fillers or chemical additives; S1.2, Outer substrate spinning: The treated chips are melted and extruded at a set melt temperature and formed into a web with a first tensile strength to obtain a fine fiber outer substrate; S1.3, intermediate layer substrate spinning: the same type of chips are melted and extruded at the same melt temperature, and web is formed with a second draw strength less than the first draw strength. The distance from the spinneret to the web forming curtain is increased to obtain a coarse fiber intermediate layer substrate with an average fiber diameter greater than that of the outer layer substrate and a higher air permeability. S1.4, Online monitoring: The average fiber diameter, basis weight and thickness of each substrate are monitored online and recorded as roll data. The roll data is then transmitted to steps S2 and S6.

3. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S2, the three-layer stacking, specifically includes the following steps: S2.1, Upper winding and fabric threading: The two outer layers of substrate and the one middle layer of substrate are threaded together from the independent unwinding station in the order of outer layer, middle layer, outer layer, so that the middle layer of substrate is centered; S2.2, Differential tension, applies closed-loop tension control to each unwinding station, and ensures that the unwinding tension of the intermediate layer substrate is lower than that of the outer layer substrate; S2.3, No compaction fixing, no full hot rolling of the fabric body or application of adhesive during the lamination process; S2.4, Thickness monitoring: Monitor the total thickness of the laminate online to ensure that the reduction in thickness of the intermediate layer substrate after lamination does not exceed the set ratio of its thickness before lamination, and transmit the total thickness of the laminate as roll-to-roll data to step S3.

4. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S3, mechanical pleating, specifically includes the following steps: S3.1, Pattern roller configuration: A pair of pattern rollers with an upper pattern roller tooth height greater than the lower pattern roller tooth height are used; S3.2, Roller gap setting: The roller gap is set according to the total thickness of the composite body transmitted in step S2; S3.3, Gradient pleating: Pleating the multi-layered substrate after lamination to form deep pleats in the outer substrate and shallow pleats in the middle substrate; S3.4, Air permeability verification: After pleating, measure the air permeability of the outer substrate and the middle substrate to ensure that the air permeability of the middle substrate is still greater than that of the outer substrate. If this condition is not met, increase the average fiber diameter of the middle substrate in step S1 or decrease the roller gap in step S3.

5. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S4, steam setting, specifically includes the following steps: S4.1, Steam preparation: Prepare saturated steam with a set dryness. S4.2, Temperature control: The temperature of the setting steam is controlled to not exceed the upper limit temperature that would cause over-setting of the outer substrate; S4.3, Synchronize the linear speed, making the shaping linear speed equal to the pleating linear speed in step S3; S4.4, Continuous shaping, allows the pleated multi-layer substrate to continuously pass through a single-zone shaping box in saturated steam at a shaping linear velocity.

6. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S5, stepped slow cooling and fixing, specifically includes the following steps: S5.1, stepped cooling, uses multiple series cooling rollers with successively decreasing temperatures along the material's running direction to cool the shaped multilayer substrate to below its glass transition temperature; S5.2, Uniform cooling, ensuring that the multilayer substrate is uniformly cooled by being in contact with each cooling roller at a sufficient wrap angle; S5.3, Controlled winding: Under controlled tension, the cooled multilayer substrate is wound into a finished product and transferred to step S6.

7. The production process of pure raw material inferior fiber pleated sheet according to claim 1, characterized in that, Step S6, offline hierarchical detection and feedback control, specifically includes the following steps: S6.1 Sampling: Samples are taken from the finished product according to a set cycle; S6.2, Layering test: The sample is peeled into an outer layer and an intermediate layer, and the thermal shrinkage rate of each layer is measured separately; S6.3, Index Calculation: The interlayer shaping difference index is obtained by subtracting the outer layer's thermal shrinkage rate from the intermediate layer's thermal shrinkage rate; S6.4, Feedback Control: When the interlayer shaping difference index is greater than the preset safety limit, gradually increase the average fiber diameter and air permeability of the intermediate layer substrate in step S1 in the direction of reducing the interlayer shaping difference index, and / or gradually increase the shaping steam temperature and reduce the shaping linear speed in step S4. After each adjustment, resample and measure until the interlayer shaping difference index is not greater than the safety limit.

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