A high transmittance-to-reflectance ratio flash evaporation material

Abstract

This invention relates to a flash material with high permeability-to-weight ratio, characterized in that the raw material of the flash material contains polyethylene; the Fraser permeability of the flash material is 0.45–0.85 μm. 3 / (min·m 2 The permeability-to-reflectance ratio of flash evaporation materials is 2–7 m. 3 / (min·m 2 Transparency-to-reflectance ratio = (Fraser air permeability · reflectivity) / thickness. This application addresses some performance pain points of existing technologies by comprehensively controlling and balancing four core parameters: solvent ratio, spinning parameters, web forming speed, and hot rolling process, in order to achieve a more suitable transmission-to-reflectance ratio design requirement.

Description

Technical Field

[0001] This invention relates to the field of textile production technology, specifically to a flash evaporation material with high permeability. Background Technology

[0002] Agricultural mulch film is a core supporting technology for modern agriculture in terms of warming, moisture retention, weed control, and yield increase. It is widely used in the greenhouse cultivation and open-field planting of crops such as vegetables (tomatoes, cucumbers), fruits (strawberries, watermelons), and grains (wheat, corn). As agricultural planting upgrades towards precision, lightweight, and green practices, the performance shortcomings of traditional mulch films (such as ordinary polyethylene mulch film and traditional biodegradable mulch film) are becoming increasingly prominent. The industry urgently needs new types of mulch films with strong functional synergy and excellent environmental adaptability.

[0003] Flash-spun materials (using polyethylene as the core raw material) have become an ideal choice for overcoming the bottlenecks of traditional mulch film technology due to their characteristics of being lightweight and thin (thickness as low as 0.01mm), weather-resistant (resistant to UV aging), and having controllable structure (adjustable porosity and reflectivity). In agricultural mulch film applications, the transmittance-to-reflectance ratio (transmittance-to-reflectance ratio = Fraser permeability × reflectivity / thickness) is a key indicator for measuring the core function of mulch film.

[0004] The air permeability determines the balance between moisture retention and root rot prevention: moderate air permeability can avoid high temperature and humidity inside the film (reducing gray mold and root rot in crops) while maintaining soil moisture;

[0005] Reflectivity determines the effects of temperature control and weed suppression: high reflectivity can reflect visible light (suppressing weed photosynthesis) and regulate soil temperature (cooling down by 3-5℃ in summer and keeping warm by 2-3℃ in winter).

[0006] Thickness determines lightweighting and cost: thin mulch film (<0.3mm) can save more than 30% of raw materials and is 100% recyclable, which is in line with the trend of green agriculture.

[0007] Therefore, high permeability-to-transparency ratio means that the mulch film can simultaneously achieve precise temperature control and strong weed suppression while remaining thin and lightweight, representing a core technological direction for addressing the current pain points of agricultural mulch films. However, existing flash evaporation mulch film processes generally have low permeability-to-transparency ratios due to parameter design not being adapted to the needs of agricultural scenarios, making it difficult to meet the high-end functional requirements of modern planting mulch films. This provides technical and market opportunities for this project. Furthermore, in certain heat-insulating packaging fields, there is an urgent need for high heat insulation and high air permeability, and flash evaporation materials with high permeability-to-transparency ratios also have broad market prospects and potential. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flash evaporation material with high permeability-to-inverse ratio.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A high permeability flash material, the raw material of which includes polyethylene; the Fraser permeability of the flash material is 0.45–0.85 μm. 3 / (min·m 2 );

[0011] The permeability-to-reflectance ratio of flash evaporation materials is 2–7 m. 3 / (min·m 2 ·mm)

[0012] Transparency = (Fraser air permeability · reflectivity) / thickness

[0013] The test standard for Fraser's air permeability is ASTM D737-18;

[0014] The reflectance is the reflectance with a wavelength of 380-780nm, and the test standard is ISO9050:2003.

[0015] The permeability-to-reflectance ratio of the flash evaporation material is 2–2.5 m. 3 / (min·m 2 ·mm).

[0016] The permeability-to-reflectance ratio of the flash evaporation material is 2.5–3 m. 3 / (min·m 2 ·mm).

[0017] The permeability-to-reflection ratio of flash evaporation materials is 3-4m. 3 / (min·m 2 ·mm).

[0018] The permeability-to-reflection ratio of flash evaporation materials is 4-5m. 3 / (min·m 2 ·mm).

[0019] The permeability-to-reflection ratio of flash evaporation materials is 5-6m. 3 / (min·m 2 ·mm).

[0020] The permeability-to-reflection ratio of the flash evaporation material is 6–6.5 m. 3 / (min·m 2 ·mm).

[0021] The permeability-to-reflectance ratio of the flash evaporation material is 6.5–7 m. 3 / (min·m 2 ·mm).

[0022] The Fraser permeability of the flash evaporation material is 0.55–0.6 μm. 3 / (min·m 2 ).

[0023] The Fraser permeability of the flash evaporation material is 0.6–0.65 μm.3 / (min·m 2 ).

[0024] The Fraser permeability of the flash evaporation material is 0.65–0.70 m³. 3 / (min·m 2 ).

[0025] The Fraser permeability of the flash evaporation material is 0.70–0.75 m. 3 / (min·m 2 ).

[0026] The Fraser permeability of the flash evaporation material is 0.75–0.80 m³. 3 / (min·m 2 ).

[0027] The visible light reflectance of the flash material is greater than 0.8.

[0028] The trapezoidal tear strength (MD) of the flash material is greater than 10N; the trapezoidal tear strength (CD) of the flash material is greater than 11N; the test standard for trapezoidal tear strength is ISO9073-2021.

[0029] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0030] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0031] The spinning raw material includes polyethylene;

[0032] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.75:0.2 to 0.85:0.2;

[0033] The mass fraction of the spinning raw material in the spinning solution is 7-14%;

[0034] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 190-230℃ and a spinning pressure of 12-18MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 100-130m / min. Third, after web laying, the nascent flash material is hot rolled on a hot roller at a temperature of 130-145℃ and a pressure of 1-2MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency.

[0035] Compared with the prior art, the positive effects of the present invention are:

[0036] This application addresses some performance pain points of existing technologies by comprehensively controlling and balancing four core parameters: solvent ratio, spinning parameters, web forming speed, and hot rolling process, in order to achieve a more suitable design requirement for the transparency-to-inflection ratio.

[0037] The solvent used in this application is dichloromethane-cyclopentane with a mass ratio controlled at 0.75:0.22 to 0.85:0.22. Based on the dissolution kinetics of polyethylene (PE) in a mixed solvent, this method achieves complete dissolution of PE and uniform stability of the spinning solution system. This ensures uniform fiber formation during flash spinning, with no protruding impurities on the surface. This uniform fiber morphology guarantees material performance in two ways: firstly, improved fiber surface smoothness reduces clogging of the fiber web pores, allowing for unobstructed gas flow and maintaining a stable Fraser permeability of 0.45–0.85 m³ / (min・m²); secondly, a smooth fiber surface reduces diffuse reflection loss of light.

[0038] The web-forming stage of this application operates at a speed of 100–130 m / min, which allows the fibers to be evenly stacked on the web-forming curtain. This avoids pore compression caused by excessively high local surface density or structural loosening caused by excessively low local surface density, ensuring that the fiber web pores remain open and uniform, thus providing structural assurance for stable air permeability.

[0039] The hot rolling process of this application combines the crystallization and melting characteristics of PE with a temperature of 130-145℃ and a pressure of 1-2MPa. This avoids pore blockage caused by excessive hot rolling, while also solving the risk of disintegration of the fiber web structure caused by insufficient bonding due to insufficient hot rolling. Detailed Implementation

[0040] The following provides a specific embodiment of a flash evaporation material with high permeability ratio according to the present invention.

[0041] Example 1

[0042] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0043] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0044] The spinning raw material includes polyethylene;

[0045] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.75:0.2.

[0046] The mass fraction of the spinning raw material in the spinning solution is 9%;

[0047] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 205°C and a spinning pressure of 12 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 100 m / min. Third, after the initial flash material is laid, it enters the hot roller for hot rolling at a temperature of 130°C and a pressure of 1 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency.

[0048] High-permeability flash material, with a Fraser permeability of 0.55m. 3 / (min·m 2 );

[0049] The transflection ratio of the flash material is 2.36m. 3 / (min·m 2 ·mm).

[0050] The visible light reflectance of the flash material is 0.96.

[0051] The trapezoidal tear strength (MD) of the flash material is 12 N; the trapezoidal tear strength (CD) of the flash material is 13 N. The test standard for trapezoidal tear strength is ISO 9073-2021.

[0052] Example 2

[0053] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0054] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0055] The spinning raw material includes polyethylene;

[0056] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.80:0.2;

[0057] The mass fraction of the spinning raw material in the spinning solution is 10%;

[0058] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 220°C and a spinning pressure of 15 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 120 m / min. Third, after the initial flash material is laid, it enters the hot roller for hot rolling at a temperature of 140°C and a pressure of 1.5 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency ratio.

[0059] High-permeability flash material, with a Fraser permeability of 0.61m. 3 / (min·m 2 );

[0060] The transflection ratio of the flash material is 3.82m. 3 / (min·m 2 ·mm).

[0061] The visible light reflectance of the flash material is 0.94.

[0062] The trapezoidal tear strength (MD) of the flash material is 13N; the trapezoidal tear strength (CD) of the flash material is 14N.

[0063] Example 3

[0064] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0065] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0066] The spinning raw material includes polyethylene;

[0067] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.85:0.2;

[0068] The mass fraction of the spinning raw material in the spinning solution is 11%;

[0069] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 230°C and a pressure of 18 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 130 m / min. Third, after web laying, the nascent flash material is hot rolled on a hot roller at a temperature of 145°C and a pressure of 2 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency.

[0070] High-permeability flash material, with a Fraser permeability of 0.73m. 3 / (min·m 2 );

[0071] The permeability-to-reflectance ratio of the flash material is 5.54m. 3 / (min·m 2 ·mm).

[0072] The visible light reflectance of the flash material is 0.91.

[0073] The trapezoidal tear strength (MD) of the flash material is 15 N; the trapezoidal tear strength (CD) of the flash material is 17 N.

[0074] Comparative Example 1

[0075] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0076] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0077] The spinning raw material includes polyethylene;

[0078] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.6:0.2;

[0079] The mass fraction of the spinning raw material in the spinning solution is 10%;

[0080] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 220°C and a spinning pressure of 15 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 120 m / min. Third, after the initial flash material is laid, it enters the hot roller for hot rolling at a temperature of 140°C and a pressure of 1.5 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency ratio.

[0081] High-permeability flash material, with a Fraser permeability of 0.41m. 3 / (min·m 2 );

[0082] The transflection ratio of the flash evaporation material is 1.8m. 3 / (min·m 2 ·mm).

[0083] The visible light reflectance of the flash material is 0.83.

[0084] The trapezoidal tear strength (MD) of the flash material is 7N; the trapezoidal tear strength (CD) of the flash material is 8N.

[0085] The key solvent ratio in Comparative Example 1 was inappropriate; the mass ratio of dichloromethane to cyclopentane used was 0.6:2. While dichloromethane is a good solvent for polyethylene (PE), an excessively low ratio results in PE not dissolving sufficiently in the spinning solution, leaving undissolved PE particles. During flash spinning, this unevenly dissolved solution makes it difficult to form fibers of uniform thickness and smooth surface. The resulting fibers not only have large variations in thickness but also have protruding particles on their surface, significantly increasing roughness. These rough fibers directly block the air passages in the fiber web, increasing gas resistance and thus significantly reducing Fraser permeability. Simultaneously, the rough fiber surface exacerbates diffuse reflection, leading to a decrease in visible light reflectivity.

[0086] Comparative Example 2

[0087] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0088] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0089] The spinning raw material includes polyethylene;

[0090] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.80:0.2;

[0091] The mass fraction of the spinning raw material in the spinning solution is 10%;

[0092] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 220°C and a spinning pressure of 15 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 90 m / min. Third, after the initial flash material is laid, it enters the hot roller for hot rolling at a temperature of 140°C and a pressure of 1.5 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency ratio.

[0093] High-permeability flash material with a Fraser permeability of 0.42m. 3 / (min·m 2 );

[0094] The transflection ratio of the flash evaporation material is 1.9m. 3 / (min·m 2 ·mm).

[0095] The visible light reflectance of the flash material is 0.77.

[0096] The trapezoidal tear strength (MD) of the flash material is 8 N; the trapezoidal tear strength (CD) of the flash material is 9 N.

[0097] The key issue in Comparative Example 2 is the excessively slow web-forming speed, which is controlled at 90 m / min. The web-forming speed directly determines the fiber web's packing density: the slower the speed, the more fibers are adsorbed onto the web-forming curtain per unit time, resulting in an overly dense web and severely compressed pores between fibers. This dense web structure significantly increases resistance to gas passage, leading to a decrease in Fraser permeability. Excessive web packing also causes fibers to squeeze and entangle each other, forming an uneven surface, further exacerbating diffuse reflection and significantly reducing visible light reflectivity.

[0098] Comparative Example 3

[0099] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0100] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0101] The spinning raw material includes polyethylene;

[0102] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.80:0.2;

[0103] The mass fraction of the spinning raw material in the spinning solution is 10%;

[0104] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 220°C and a spinning pressure of 15 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 140 m / min. Third, after web laying, the nascent flash material is put into the hot roller for hot rolling at a temperature of 140°C and a pressure of 1.5 MPa. Finally, the hot-rolled flash material is then wound up to obtain a flash material with high transparency ratio.

[0105] High-permeability flash material, with a Fraser permeability of 0.88 μm. 3 / (min·m 2 );

[0106] The flash evaporation material has a permeability-to-reflectance ratio of 5.6m. 3 / (min·m 2 ·mm).

[0107] The visible light reflectance of the flash material is 0.70.

[0108] The trapezoidal tear strength (MD) of the flash material is 5N; the trapezoidal tear strength (CD) of the flash material is 6N.

[0109] The key issue with Comparative Example 3 is that the web-forming speed is too fast, controlled at 140m / min. Insufficient fiber accumulation leads to low areal density and an overly loose web structure. Although the air permeability increases to 0.88m³ / (min・m²) due to excessively open pores, the sparse fiber distribution results in a significant decrease in visible light reflectivity. The loose structure also leads to a decrease in overall trapezoidal tearing. Due to the severe deficiency in trapezoidal tearing and low emissivity, the product cannot be used normally.

[0110] Comparative Example 4

[0111] A method for preparing a flash evaporation material with high permeability-to-inverse ratio, comprising the following specific steps:

[0112] (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution;

[0113] The spinning raw material includes polyethylene;

[0114] The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.80:0.2;

[0115] The mass fraction of the spinning raw material in the spinning solution is 10%;

[0116] (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 220°C and a spinning pressure of 10 MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed should be controlled at 90 m / min. Third, after the initial flash material is laid, it enters the hot roller for hot rolling at a temperature of 125°C and a pressure of 0.5 MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency ratio.

[0117] High-permeability flash material, with a Fraser permeability of 0.32m. 3 / (min·m 2 );

[0118] The transflection ratio of the flash evaporation material is 1.6m. 3 / (min·m 2 ·mm).

[0119] The visible light reflectance of the flash material is 0.80.

[0120] The trapezoidal tear strength (MD) of the flash material is 6 N; the trapezoidal tear strength (CD) of the flash material is 7.5 N.

[0121] Comparative Example 4 shows that multiple process control parameters were below the set values. Among them, insufficient spinning pressure could not fully stretch the fibers, resulting in short, coarse fibers that were easy to break. The short fibers would further block the pores of the fiber web. The web forming speed was too slow, which led to dense accumulation of the fiber web and continuous compression of the pores. Insufficient hot rolling strength prevented the fiber web from being fully compacted as a whole, resulting in a loose structure and poor pore connectivity. This led to the triple effect of short fiber blockage, pore compression, and channel blockage, which resulted in the largest decrease in Fraser air permeability.

[0122] 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.

Claims

1. A flash evaporation material with high permeability and inverse ratio, characterized in that, The raw material for flash evaporation materials includes polyethylene; the Fraser permeability of flash evaporation materials is 0.45–0.85 m³. 3 / (min·m 2 ); The permeability-to-reflectance ratio of flash evaporation materials is 2–7 m. 3 / (min·m 2 (·mm); Transparency / Reflectance Ratio = (Fraser Air Permeability · Reflectivity) / Thickness; The test standard for Fraser air permeability is ASTM D737-18; The reflectance is the reflectance with a wavelength of 380–780 nm, and the test standard is ISO 9050:2003; The specific steps included in the preparation method of the high-transmittance flash evaporation material are as follows: (1) Dissolve the spinning raw material in the spinning solvent to form a spinning solution; The spinning raw material includes polyethylene; The spinning solvent is dichloromethane and cyclopentane, with a mass ratio of 0.75:0.2 to 0.85:0.2; The mass fraction of the spinning raw material in the spinning solution is 7-14%; (2) First, the spinning solution prepared in step (1) is subjected to flash spinning at a temperature of 190-230℃ and a spinning pressure of 12-18MPa. Second, in the flash fiber adsorption web laying system of flash spinning, the web forming speed is controlled at 100-130m / min. Third, after web laying, the nascent flash material is hot rolled on a hot roller at a temperature of 130-145℃ and a pressure of 1-2MPa. Finally, the hot-rolled flash material is wound up to obtain a flash material with high transparency.

2. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflectance ratio of the flash evaporation material is 2–2.5 m. 3 / (min·m 2 ·mm).

3. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflectance ratio of the flash evaporation material is 2.5–3 m. 3 / (min·m 2 ·mm).

4. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflection ratio of flash evaporation materials is 3-4m. 3 / (min·m 2 ·mm).

5. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflection ratio of flash evaporation materials is 4-5m. 3 / (min·m 2 ·mm).

6. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflection ratio of flash evaporation materials is 5-6m. 3 / (min·m 2 ·mm).

7. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflection ratio of the flash evaporation material is 6–6.5 m. 3 / (min·m 2 ·mm).

8. The high-permeability flash evaporation material as described in claim 1, characterized in that, The permeability-to-reflectance ratio of the flash evaporation material is 6.5–7 m. 3 / (min·m 2 ·mm).

9. The high-permeability flash evaporation material as described in claim 1, characterized in that, The Fraser permeability of the flash evaporation material is 0.55–0.6 μm. 3 / (min·m 2 ).

10. The high-transmittance flash evaporation material as described in claim 1, characterized in that, The Fraser permeability of the flash evaporation material is 0.6–0.65 μm. 3 / (min·m 2 ).

11. The high-transmittance flash evaporation material as described in claim 1, characterized in that, The Fraser permeability of the flash evaporation material is 0.65–0.70 m³. 3 / (min·m 2 ).

12. The high-transmittance flash evaporation material as described in claim 1, characterized in that, The Fraser permeability of the flash evaporation material is 0.70–0.75 m. 3 / (min·m 2 ).

13. The high-permeability flash evaporation material as described in claim 1, characterized in that, The Fraser permeability of the flash evaporation material is 0.75–0.80 m³. 3 / (min·m 2 ).