A dimensionally stable flash-spun nonwoven sheet

Abstract

The present application relates to a kind of size-stable flash nonwoven sheet, characterized in that, the flash nonwoven sheet is at 80±1 ℃, after constant temperature 240 hours, thermal shrinkage rate ≤5%;The root mean square roughness Rq of the flash nonwoven sheet is ≤8 microns;And the pendulum method tear strength of the flash nonwoven sheet is 3~8 N.The long-term high-temperature dimensional stability of the flash nonwoven sheet of the present application, ultra-low surface roughness and moderate tear strength, realize the high clean, high precision, long period, high reliability of packaging protection requirement.

Description

Technical Field

[0001] This invention relates to the field of textile production technology, and more specifically, to the field of flash spinning technology, and to dimensionally stable flash nonwoven sheets prepared by flash spinning. Background Technology

[0002] In the field of semiconductor wafer storage, transportation, and process protection, existing wafer packaging protective materials mostly use traditional materials such as ordinary non-woven fabrics, polyester films, and conventional fiber pads. However, these materials have significant shortcomings in overall performance and are difficult to adapt to the high-end protection requirements of high-precision wafers: First, traditional materials have poor heat resistance and dimensional stability. Under the long-term effects of storage, temperature zone switching, and short-term high-temperature environments, they are prone to significant thermal shrinkage and deformation. At the same time, the thermal shrinkage rate is generally high after long-term constant-temperature aging, which can easily cause the packaging pads to shift or misalign, thereby squeezing and pulling the wafer, causing wafer warping and orientation displacement, seriously affecting the product storage accuracy and safety. Second, conventional protective materials have a loose fiber structure and insufficient surface micro-smoothness, with high root mean square roughness values ​​and large surface undulations. This not only easily causes micro-scratches on the precision surface of the wafer during contact friction, but also easily generates fiber debris and micro-dust particles, causing wafer surface contamination and significantly reducing chip fabrication yield. Finally, traditional nonwoven packaging materials have weak fiber bonding strength and insufficient overall tear resistance. Their pendulum tear strength is low. During packaging, unpacking, material transfer, and repeated use, they are prone to cracking, breakage, and shedding due to stretching, corner squeezing, and friction. This leads to the failure of the protective structure's integrity, and the impurities generated by the breakage further exacerbate the risk of cleanroom contamination.

[0003] In summary, existing wafer packaging materials cannot simultaneously achieve the three core properties of long-term high-temperature dimensional stability, ultra-low surface roughness, and moderate and stable tear resistance. They can no longer meet the packaging protection requirements of high cleanliness, high precision, long cycle time, and high reliability for advanced process wafers. The industry urgently needs to optimize and develop protective sheets with better comprehensive performance, including dimensional stability, dense and flat surface, and suitable mechanical toughness. Summary of the Invention

[0004] In one aspect, this disclosure provides a dimensionally stable flash nonwoven sheet, characterized in that the flash nonwoven sheet has a heat shrinkage rate of ≤5% after being kept at 80±1 ℃ for 240 hours; the root mean square roughness Rq of the flash nonwoven sheet is ≤8 micrometers; and the pendulum tear strength of the flash nonwoven sheet is 3~8N.

[0005] In some embodiments, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being held at 80±1 °C for 240 hours is 0-1%. In some embodiments, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being held at 80±1 °C for 240 hours is 1%-2%. In some embodiments, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being held at 80±1 °C for 240 hours is 2%-3%. In other embodiments, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being held at 80±1 °C for 240 hours is 3%-4%. In some embodiments, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being held at 80±1 °C for 240 hours is 4%-5%.

[0006] In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 0-1 micrometer. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 1-2 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 2-3 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 3-4 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 4-5 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 5-6 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 6-7 micrometers. In some embodiments, the root mean square roughness Rq of the flash-evaporated nonwoven sheet is 7-8 micrometers.

[0007] In some embodiments, the pendulum tear strength of the flash-dried nonwoven sheet is 3-4.5 N. In some embodiments, the pendulum tear strength of the flash-dried nonwoven sheet is 4.5-6 N. In some embodiments, the pendulum tear strength of the flash-dried nonwoven sheet is 6-8 N.

[0008] Another aspect of this disclosure provides a method for preparing the dimensionally stable flash nonwoven sheet described herein, comprising: (1) Provide flash spinning solution; (2) Flash spinning is performed on the flash spinning solution to obtain flash fibers; (3) The flash-evaporated fibers are laid into a web to obtain a nascent nonwoven sheet; (4) Hot rolling the nascent nonwoven sheet; (5) Post-processing; and (6) Shaping; In step (4), the angle at which the nascent nonwoven sheet contacts the rollers of the hot rolling mill is called the wrap angle, and the wrap angle is 60°~90°.

[0009] In some embodiments, step (5) includes (5-1) a cooling operation; in some preferred embodiments, the cooling temperature is 5 ℃ to 20 ℃.

[0010] In some implementations, step (5) may optionally include (5-2) a winding operation.

[0011] In another aspect of this disclosure, a packaging material is provided, comprising the dimensionally stable flash material described in this disclosure, or comprising the dimensionally stable flash material prepared according to the method of this disclosure.

[0012] Another aspect of this disclosure provides the use of the dimensionally stable flash material of this disclosure or the dimensionally stable flash material prepared according to the method of this disclosure in packaging materials.

[0013] In some implementations, the packaging material includes wafer packaging material.

[0014] The technical advantages of this disclosure are as follows: The dimensionally stable flash-spun nonwoven sheet provided by this disclosure achieves a synergistic improvement in long-term high-temperature dimensional stability, ultra-low surface roughness, and moderate tear resistance by optimizing the flash spinning, hot rolling wrapping, and cooling temperature processes. This effectively solves the problems of traditional wafer protection materials, such as easy shrinkage and deformation, easy scratching of wafers, and easy tearing and shedding. The sheet of this disclosure shows no significant shrinkage, warping, or displacement after high-temperature aging, avoiding the squeezing and pulling of the wafer by misaligned pads, ensuring storage accuracy and usage safety. Simultaneously, the sheet of this disclosure has a dense and flat surface with minimal microscopic unevenness, preventing microscopic scratches during contact friction. The tightly bonded fibers are not prone to shedding, significantly reducing the risk of wafer contamination and improving chip yield. Furthermore, the sheet of this disclosure has moderate mechanical strength and matched toughness, making it less prone to cracking and damage during transportation, disassembly, and repeated handling, ensuring a complete and reliable protective structure. The method disclosed herein enables flash evaporation materials to achieve sufficient thermal bonding, full release of internal stress, and uniform surface shaping, thereby ensuring that the overall performance of the product meets the packaging and protection requirements of advanced process wafers for high cleanliness, high precision, long cycle time, and high reliability. Attached Figure Description

[0015] This disclosure can be more fully understood with reference to the following figures.

[0016] Figure 1 An SEM image of one side surface of the flash nonwoven sheet prepared in Example 2 is shown.

[0017] Figure 2 An SEM image of the other side surface of the flash nonwoven sheet prepared in Example 2 is shown. Detailed Implementation

[0018] The following description of this disclosure is merely intended to illustrate various embodiments of the disclosure. Therefore, the specific modifications discussed should not be construed as limiting the scope of this disclosure. It will be apparent to those skilled in the art that various equivalents, changes, and modifications can be made without departing from the scope of this disclosure, and it should be understood that these equivalent embodiments are included herein. All references cited herein, including publications, patents, and patent applications, are incorporated herein by reference in their entirety.

[0019] On the one hand, this disclosure provides a dimensionally stable flash nonwoven sheet, characterized in that the flash nonwoven sheet has a heat shrinkage rate of ≤5% after being kept at 80±1 ℃ for 240 hours; preferably, the root mean square roughness Rq of the flash nonwoven sheet is ≤8 micrometers; and the pendulum tear strength of the flash nonwoven sheet is 3~8 N.

[0020] The heat shrinkage rate of flash-frozen nonwoven sheets refers to the percentage shrinkage of their longitudinal (MD) and transverse (CD) dimensions after being heated at a specified temperature for a certain period of time, used to characterize the dimensional stability of the material under heat. In this disclosure, the test method for heat shrinkage rate is as follows: (1) Take three samples, each with a length of 120 mm. 120 mm; Measure the longitudinal direction L0 and transverse direction T0 of each sample separately; (2) Place the metal container containing the kaolin bed into an oven and set it to 80 ℃ until the temperature of the kaolin bed stabilizes; (3) The sample is laid flat on the kaolin bed and a thin layer of kaolin is lightly covered on the surface to prevent warping and sticking between the samples. The distance between the sample and the box wall is ≥50 mm. (4) Heating at a constant temperature of 80±1 ℃ for 240 hours; (5) After heating is complete, remove the sample and cool it under a standard environment of 23±1℃ for at least 60 min; (6) Measure the longitudinal and transverse mark lengths L and T again, accurate to 0.5 mm, and record them; (7) Calculate for each sample separately: Longitudinal shrinkage rate ΔL = [(L0-L) / L0] 100%; Lateral shrinkage rate ΔT = [(T0-T) / T0] 100%; Calculate the arithmetic mean of the longitudinal shrinkage rate and the arithmetic mean of the transverse shrinkage rate for the three samples respectively.

[0021] The shrinkage rate described in this application is the arithmetic mean of the longitudinal shrinkage rate or the arithmetic mean of the transverse shrinkage rate. According to embodiments of this disclosure, the arithmetic mean of the longitudinal shrinkage rate and the arithmetic mean of the transverse shrinkage rate are numerically equivalent.

[0022] According to this disclosure, the heat shrinkage rate of the flash-evaporated nonwoven sheet after being kept at 80±1 °C for 240 hours is ≤5%, preferably 1% to 4%. For example, the heat shrinkage rate includes, but is not limited to: 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.5%, 5%, or any combination of both or values ​​within a range. In some embodiments, the flash-evaporated nonwoven sheet of this disclosure exhibits a heat shrinkage rate of 0-1% after being kept at 80±1 °C for 240 hours. In some embodiments, the heat shrinkage rate is 1%-2% after being kept at 80±1 °C for 240 hours. In some embodiments, the heat shrinkage rate is 2%-3% after being kept at 80±1 °C for 240 hours. In some embodiments, the heat shrinkage rate is 3%-4% after being kept at 80±1 °C for 240 hours. In some embodiments, the heat shrinkage rate is 4%-5% after being kept at 80±1 °C for 240 hours.

[0023] In this invention, the root mean square roughness of the flash nonwoven sheet refers to the root mean square height (Rq) of the profile measured according to ISO 21920-2:2021 standard. When the Rq value is too high, the surface unevenness increases. Therefore, in this invention, the root mean square roughness Rq is defined as one of the key characteristic parameters of the flash nonwoven sheet to more accurately define the surface structure characteristics of the product of this invention and to more sensitively distinguish the microstructure differences between the products of this invention and those of the prior art. According to this disclosure, the root mean square roughness Rq of the flash nonwoven sheet is ≤ 8 micrometers, for example, including but not limited to: 8 micrometers, 7.5 micrometers, 7 micrometers, 6.5 micrometers, 6 micrometers, 5.5 micrometers, 5 micrometers, 4.5 micrometers, 4 micrometers, 3.5 micrometers, 3 micrometers, 2.5 micrometers, 2 micrometers, 1.5 micrometers, 1 micrometer, 0.8 micrometers, 0.5 micrometers, 0.2 micrometers, or any combination thereof or values ​​within a range. In some embodiments, the root mean square roughness (RMS) of the flash-evaporated nonwoven sheet of this disclosure is 0-1 micrometer. In some embodiments, the RMS roughness is 1-2 micrometers. In some embodiments, the RMS roughness is 2-3 micrometers. In some embodiments, the RMS roughness is 3-4 micrometers. In some embodiments, the RMS roughness is 4-5 micrometers. In some embodiments, the RMS roughness is 5-6 micrometers. In some embodiments, the RMS roughness is 6-7 micrometers. In some embodiments, the RMS roughness is 7-8 micrometers.

[0024] In this invention, the pendulum tear strength of flash-blown nonwoven sheets refers to the performance parameter measured according to the ASTM D1424-21 / 25 standard. Pendulum tear strength reflects the material's ability to resist the propagation of a pre-existing tear (cut) along the direction of force under instantaneous impact load. This parameter simulates the process of a sheet being punctured or hooked by a sharp object in actual use, and continues to tear under stress, characterizing the material's resistance to crack propagation. A higher tear strength value indicates that the sheet is less likely to experience large-area tear propagation due to localized damage. On the one hand, flash-blown nonwoven sheets may develop localized tears due to punctures, hooking, or stress concentration during use. The tear strength directly determines whether this tear will catastrophically propagate under external force. Sheets with high tear strength can effectively prevent the spread of localized damage, maintaining the overall protective barrier function and reliability of the product. On the other hand, during post-processing, flash-treated nonwoven sheets may be subjected to mechanical action, resulting in microscopic cuts or stress concentrations at these cuts. If the tear strength is insufficient, these initial tears during processing can easily expand into large-scale tears in subsequent stages such as conveying, winding, or lamination, leading to a decrease in yield or even process interruption. According to this disclosure, the pendulum tear strength of the flash-treated nonwoven sheet is 3-8 N, for example, including but not limited to: 3 N, 3.5 N, 4 N, 4.5 N, 5 N, 5.5 N, 6 N, 6.5 N, 7 N, 7.5 N, 8 N, or any combination thereof. In some embodiments, the pendulum tear strength of the flash-treated nonwoven sheet of this disclosure is 3-4.5 N. In some embodiments, the pendulum tear strength of the flash-treated nonwoven sheet of this disclosure is 4.5-6 N. In some embodiments, the pendulum tear strength of the flash-treated nonwoven sheet of this disclosure is 6-8 N.

[0025] On the other hand, this disclosure provides a method for processing dimensionally stable flash-evaporated nonwoven sheets, comprising the steps of: (1) Provide flash spinning solution; (2) Flash spinning is performed on the flash spinning solution to obtain flash fibers; (3) The flash-evaporated fibers are laid into a web to obtain a nascent nonwoven sheet; (4) Hot rolling the nascent nonwoven sheet; and (5) Post-processing; In step (4), the angle at which the nascent nonwoven sheet contacts the rollers of the hot rolling mill is called the wrap angle, and the wrap angle is 60°~90°.

[0026] In the hot rolling process of flash materials, if the wrap angle is too small and the residence time is too short, the material surface cannot be fully bonded during the thermal bonding process. This results in a loose material with low strength, incomplete release of internal stress, and increased susceptibility to deformation under dimensional stability testing. Furthermore, the surface becomes rough, ultimately affecting various aspects of the product's performance (e.g., increased Rq, low pendulum tear strength). Conversely, if the wrap angle is too large, the residence time is too long, leading to excessive thermal bonding. This results in poor material toughness, amplifies the uneven fiber distribution defects in the flash material, and reduces surface smoothness, similarly affecting various aspects of the product's performance (e.g., increased Rq, low pendulum tear strength).

[0027] In flash spinning, if the polymer mass fraction in the spinning solution is too low, continuous fibers cannot be formed during flash spinning; if it is too high, the viscosity is too high, resulting in loss of spinnability. Simultaneously, this mass fraction directly affects the microstructure, crystallinity, and orientation of the flash-spun fibers. Appropriately increasing the mass fraction is beneficial for increasing fiber diameter, improving crystallinity, and mechanical strength; however, exceeding the optimal range will lead to decreased structural uniformity and mechanical properties due to hindered solvent evaporation. In some non-limiting embodiments, in the preparation method of impact-resistant flash-spun materials, the flash spinning solution in step (1) can be formed by dissolving the polymer in the spinning solvent. In some non-limiting embodiments, the polymer includes, but is not limited to, polyethylene, polypropylene, similar polymers, or homologues thereof. In some non-limiting embodiments, the polymer mass fraction in the spinning solution is 8-12%, for example, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, or any two values ​​within a range.

[0028] In some non-limiting embodiments, the spinning solvent is selected from (e.g., benzene, toluene, etc.), halogenated hydrocarbons (e.g., dichloromethane, chloroform, carbon tetrachloride, chloroethane, trichlorofluoromethane, etc.), aliphatic hydrocarbons (e.g., butane, n-hexane, pentene, heptane, etc.), alicyclic hydrocarbons (e.g., cyclohexane, cyclopentane, unsaturated cyclic hydrocarbons, etc.), and mixtures of one or more of the above substances.

[0029] In some specific embodiments, step (5) includes (5-1) a cooling operation, and the cooling temperature is 5 ℃~20 ℃. When the cooling temperature is too high, the material surface is not cooled in time, the heat is not fully transferred after hot rolling, the internal stress is not fully released, and the surface is easily damaged during subsequent processing. At the same time, under the dimensional stability test, the fiber crystallizes and reconstructs after heating, and the internal stress is released, resulting in shrinkage, which ultimately affects the performance of the product (e.g., Rq increases). When the cooling temperature is too low, the material surface cools too quickly, which easily leads to dense shrinkage lines. At the same time, the material surface cools too quickly, the material crystallizes and reconstructs too quickly, the material becomes brittle, and the toughness deteriorates, which also affects the performance of the product (e.g., Rq increases, pendulum tear strength is low).

[0030] In some specific implementations, step (5) includes (5-2) the winding operation.

[0031] In another aspect, this disclosure provides a packaging material comprising the flash material described herein.

[0032] In another aspect, this disclosure provides a packaging material comprising the flash material prepared by the methods described in this disclosure.

[0033] On the other hand, this disclosure provides the use of the flash materials described herein or flash materials prepared by the methods described herein in packaging materials. Preferably, the packaging material is used for wafer packaging.

[0034] Example To enable those skilled in the art to better understand the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments.

[0035] Test method: The testing methods for the relevant parameters are detailed in the implementation details section.

[0036] Example 1 A method for processing dimensionally stable flash-evaporated nonwoven sheets includes the following steps: (1) Dissolve the polymer in a spinning solvent to obtain a flash spinning solution. The polymer is polyethylene; the spinning solvent is a mixture of dichloromethane, 1,2-dichloroethylene, and 2,3-dihydrodecafluoropentane in a mass ratio of 5:4:1; the polymer has a mass fraction of 9.2% in the spinning solution. (2) Flash spinning is performed on the flash spinning solution to obtain flash fibers; (3) The flash-evaporated fibers are laid into a web to obtain a nascent nonwoven sheet; (4) Hot rolling: The angle of contact between the nascent nonwoven sheet and the rollers of the hot rolling mill is the wrap angle, which is 60°. (5) After hot rolling, the product is cooled to a temperature of 5 ℃; (6) Finally, the flash nonwoven sheet is obtained by winding.

[0037] Example 2 Flash-spun nonwoven sheets were prepared according to the method of Example 1, except that the mass fraction of polymer in the spinning solution was adjusted to 9.4%; the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was 70°; and the cooling temperature was 10°C; the rest were the same as in Example 1.

[0038] Example 3 Flash-spun nonwoven sheets were prepared according to the method of Example 1, except that the mass fraction of polymer in the spinning solution was adjusted to 9.6%; the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was 80°; and the cooling temperature was 15°C; the rest were the same as in Example 1.

[0039] Example 4 Flash-spun nonwoven sheets were prepared according to the method of Example 1, wherein the only adjustments were made to the following: the mass fraction of the polymer in the spinning solution was adjusted to 9.8%; the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was 90°; and the cooling temperature was 20°C; the rest were the same as in Example 1.

[0040] Comparative Example 1 Flash-steamed nonwoven sheets were prepared using the method described in Example 3, except that the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was adjusted to 40°; the rest was the same as in Example 3.

[0041] Comparative Example 2 Flash-steamed nonwoven sheets were prepared using the method described in Example 3, except that the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was adjusted to 50°; the rest was the same as in Example 3.

[0042] Comparative Example 3 Flash-steamed nonwoven sheets were prepared using the method described in Example 3, except that the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was adjusted to 100°; the rest was the same as in Example 3.

[0043] Comparative Example 4 Flash-steamed nonwoven sheets were prepared using the method described in Example 3, except that the wrap angle between the nascent nonwoven sheet and the rollers of the hot rolling mill was adjusted to 110°; the rest was the same as in Example 3.

[0044] Comparative Example 5 Flash-evaporated nonwoven sheets were prepared using the method described in Example 3, except that the cooling temperature was adjusted to 2°C; the rest was the same as in Example 3.

[0045] Comparative Example 6 Flash-evaporated nonwoven sheets were prepared using the method described in Example 3, except that the cooling temperature was adjusted to 24 °C; the rest was the same as in Example 3.

[0046] The above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0047] Table 1.

[0048] SEM images of both sides of the flash-evaporated nonwoven sheet prepared in Example 2 are shown below. Figure 1 and Figure 2As shown in the figure, the flash nonwoven sheet prepared according to this disclosure has a dense and smooth surface microstructure with low unevenness, strong surface consistency on both sides, and roughness that meets the requirements of this disclosure, making it suitable for use as a wafer packaging material.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0050] By incorporating references The full contents of every patent and scientific document mentioned in this article are incorporated herein by reference for all purposes.

[0051] Equivalence This disclosure may be embodied in other specific ways without departing from its spirit or essential characteristics. Therefore, the above embodiments should be considered illustrative in all cases and not as limiting of the invention described herein. Consequently, the scope of this disclosure is defined by the appended claims rather than by the foregoing description and is intended to be encompassed therein by all variations within the equivalent meaning and scope of the claims.

Claims

1. A dimensionally stable flash-evaporated nonwoven sheet, characterized in that, The flash-evaporated nonwoven sheet exhibits a heat shrinkage rate of ≤5% after being kept at 80±1℃ for 240 hours. The root mean square roughness Rq of the flash nonwoven sheet is ≤ 8 micrometers; and The pendulum tear strength of the flash-steamed nonwoven sheet is 3~8 N.

2. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The flash-evaporated nonwoven sheet has a heat shrinkage rate of 1%~2% after being kept at 80±1℃ for 240 hours.

3. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The flash-evaporated nonwoven sheet has a heat shrinkage rate of 2%~3% after being kept at 80±1℃ for 240 hours.

4. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The flash-evaporated nonwoven sheet has a heat shrinkage rate of 3%~4% after being kept at 80±1℃ for 240 hours.

5. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 1~2 micrometers.

6. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 2-3 micrometers.

7. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 3-4 micrometers.

8. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 4-5 micrometers.

9. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 5-6 micrometers.

10. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The root mean square roughness Rq of the flash nonwoven sheet is 6-7 micrometers.

11. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The pendulum tear strength of the flash-spun nonwoven sheet is 3~4.5 N.

12. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The pendulum tear strength of the flash-spun nonwoven sheet is 4.5~6 N.

13. The flash-evaporated nonwoven sheet as described in claim 1, characterized in that, The pendulum tear strength of the flash-steamed nonwoven sheet is 6-8 N.

14. A method for preparing flash-evaporated nonwoven sheets as described in any one of claims 1-13, characterized in that, The method includes: (1) Provide flash spinning solution; (2) Flash spinning is performed on the flash spinning solution to obtain flash fibers; (3) The flash-evaporated fibers are laid into a web to obtain a nascent nonwoven sheet; (4) Hot rolling the nascent nonwoven sheet; and (5) Post-processing; In step (4), the angle at which the nascent nonwoven sheet contacts the rollers of the hot rolling mill is called the wrap angle, and the wrap angle is 60°~90°.

15. The method of claim 14, wherein, Step (5) includes (5-1) a cooling operation, wherein the cooling temperature is 5°C to 20°C; and / or Step (5) may optionally include (5-2) the winding operation.

16. A packaging material comprising a dimensionally stable flash sheet as described in any one of claims 1-13.

17. Use of the dimensionally stable flash sheet as described in any one of claims 1-13 in packaging materials.

18. The use as described in claim 17, wherein, The packaging material is a wafer packaging material.

Images