A multilayer co-extruded cast film with one-way moisture conducting function and a preparation method thereof

Abstract

The application discloses a kind of multilayer co-extrusion casting film with one-way wet function and preparation method thereof, belong to layered film material technical field, its technical scheme main point is multilayer co-extrusion casting film, by outer layer hydrophilic layer, intermediate transition layer and inner layer hydrophobic layer is composed, the aperture from outer layer to inner layer decreases in turn, wherein, inner layer mixture is LDPE, LLDPE, modified calcium carbonate, nano calcium carbonate, processing aid;Intermediate layer mixture is HDPE, POE, modified calcium carbonate, outer layer mixture is mLLDPE, PP, PEG, modified calcium carbonate, opening agent, the above three kinds of mixture are sent into three different feed ports respectively, extrusion, stretching, cooling, post-processing or functionalization by extruder are obtained with one-way wet function multilayer co-extrusion casting film.By multilayer co-extrusion method, hydrophobic-hydrophilic wetting gradient and aperture gradient are constructed, process is simple, with excellent moisture transfer rate and durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of layered film materials, in particular to a multi-layer co-extrusion cast film with one-way moisture guiding function and a preparation method thereof. BACKGROUND

[0002] Waterproof and moisture-permeable film as a functional material made of high molecular polymer plays an important role in modern industry. It achieves the dual function of blocking liquid water penetration and permeating water vapor through the micro-porous structure or molecular chain segment characteristics. With the development of various industries, the demand for moisture management of materials is increasing, especially in the fields of medical and sports clothing, the demand for materials that can efficiently sweat is more urgent. One-way moisture guiding and breathable film as a new type of functional material has emerged as the times require, which is an improvement on the limitations of traditional textile and film materials in moisture management, and has great application potential and development prospects in related fields.

[0003] In the field of one-way moisture guiding materials, in order to realize the gradient of moisture and the gradient of pore size, traditional methods have adopted various means. For the realization of moisture gradient, usually the hydrophobic layer material and the hydrophilic layer material of different processes are secondarily compounded, or in-situ preparation is performed on one of the materials. For the control of the pore size gradient, different diameter fibers are used to control the pore size. In addition, the existing invention patent CN110141428B prepares a hydrophilic fiber layer and a hydrophobic fiber layer through an electrospinning device, and then constructs a one-way moisture guiding composite fiber film with mutually penetrating micro-nano level curved pore channels. These methods are all conventional means adopted under the existing technical conditions to solve the problem of one-way moisture guiding.

[0004] However, the existing one-way moisture guiding material preparation methods have obvious defects. The current method for realizing the moisture gradient is relatively cumbersome, which needs secondary compounding or in-situ preparation, which undoubtedly increases the production cost. The method of preparing a one-way moisture guiding composite fiber film through an electrospinning device is difficult to realize industrial production and cannot meet the large-scale market demand. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a multi-layer co-extrusion cast film with one-way moisture guiding function and a preparation method thereof. The present application constructs a pore size gradient structure by setting the particle size of modified calcium carbonate gradually increasing from inside to outside and the content gradually increasing, and realizes the effect of one-way moisture guiding.

[0006] The first aspect of the present application is to provide a multi-layer co-extrusion cast film with one-way moisture guiding function, which adopts the following technical scheme:

[0007] The application discloses a multilayer co-extrusion casting film with one-way moisture guiding function, which comprises an inner layer, an intermediate layer and an outer layer, wherein the outer layer is subjected to hydrophilic treatment, and the inner layer is subjected to hydrophobic treatment; the inner layer comprises the following raw materials in parts by weight: LDPE 34-45 parts, LLDPE 20-30 parts, modified calcium carbonate 15-25 parts, nano calcium carbonate 5-10 parts and processing aid 0.5-1.0 part; the average particle size of the modified calcium carbonate is 0.1-1 mu m.

[0008] The intermediate layer comprises the following raw materials in parts by weight: HDPE 40-45 parts, POE 10-15 parts, modified calcium carbonate 35-40 parts, PEG 3-5 parts and processing aid 0.5-1.2 part; the average particle size of the modified calcium carbonate is 1-5 mu m.

[0009] The outer layer comprises the following raw materials in parts by weight: mLLDPE 40-50 parts, PP 5-10 parts, modified calcium carbonate 40-45 parts, PEG 5-8 parts, opening agent 0.5-3 parts and processing aid 0.5-1.2 part; the average particle size of the modified calcium carbonate is 5-20 mu m.

[0010] By adopting the technical scheme, the inner layer is prepared from LDPE and LLDPE in a certain weight ratio, the LDPE has good flexibility and processability, the LLDPE has high tensile strength and tear resistance, and the combination of the two can make the inner layer have appropriate physical properties and help to realize the hydrophobic property of the inner layer; the intermediate layer is prepared from HDPE and POE, the HDPE has high hardness and rigidity, the POE has good elasticity and toughness, and the combination of the two can make the intermediate layer have appropriate structural support and certain elasticity and be beneficial to the transmission of water in the intermediate layer; the outer layer is prepared from mLLDPE, the mLLDPE has good tensile property and puncture resistance, the mLLPDE and PP in the outer layer can enhance the impact resistance of the film and help to ensure the strength and stability of the outer layer. The average particle size of the modified calcium carbonate in the inner layer is 0.1-1 mu m, and the content is 15-25 parts; the small particle size and appropriate content of the modified calcium carbonate can help to build the microstructure of the inner layer, enhance the hydrophobicity of the inner layer and promote the transmission of water to the intermediate layer; the average particle size of the modified calcium carbonate in the intermediate layer is 1-5 mu m, and the content is 35-40 parts; the increase of the particle size and the content can make the intermediate layer form appropriate pore structure and channels, and be beneficial to the rapid transmission of water; the average particle size of the modified calcium carbonate in the outer layer is 5-20 mu m, and the content is 40-45 parts; the large particle size and the high content can help to form high porosity and enhance the hydrophilicity of the outer layer, so that the one-way moisture guiding function of water from the inner layer to the intermediate layer and then to the outer layer is realized; therefore, the reasonable design of the formula of each layer in the application can not only build the one-way moisture guiding function of the material, but also balance the mechanical properties and softness of the material to some extent.

[0011] In addition, after adding PEG in the outer layer, the PEG migrates to the surface of the film or forms a hydrophilic microregion, thereby reducing the water contact angle and improving the one-way moisture transfer capability of the film.

[0012] Preferably, the average particle size of the nano calcium carbonate is 80-100 nm.

[0013] Preferably, the melt index of the LDPE is 5.0-7.5 g / 10 min, and the melt index of the LLDPE is 2.5-3.5 g / 10 min.

[0014] Preferably, the melt index of the HDPE is 6.5-8.0 g / 10 min, and the melt index of the POE is 9-20 g / 10 min.

[0015] Preferably, the melt index of the mLLDPE is 1.7-3.5 g / 10 min.

[0016] Preferably, the modified calcium carbonate in the inner layer, the intermediate layer and the outer layer is modified calcium carbonate treated by one or more of titanate coupling agent, silane coupling agent and fatty acid.

[0017] By adopting the above technical solution, when the melt indexes of the LDPE, the LLDPE, the HDPE, the mLLDPE and the POE are limited within the range, the layers have good fluidity and formability in the processing process, which helps to better composite the layers during the co-extrusion film forming, improves the integrity of the film, and further enhances the one-way moisture transfer performance of the multilayer co-extrusion cast film.

[0018] Preferably, the relative molecular weight of the PEG in the outer layer is 4000-20000.

[0019] Preferably, the relative molecular weight of the PEG in the intermediate layer is 10000-20000.

[0020] By adopting the above technical solution, when the molecular weight of the PEG in the outer layer is different from the molecular weight of the PEG in the intermediate layer, the one-way moisture transfer function of the multilayer co-extrusion cast film can be effectively realized, the directional transmission of water is realized, the air permeability is maintained, and the hydrophobic layer material and the hydrophilic layer material of different processes do not need to be secondarily compounded or prepared in situ, thereby reducing the production steps and costs.

[0021] The second aspect of the application is to provide a preparation method of the multilayer co-extrusion cast film with one-way moisture transfer function as described above, comprising the following steps:

[0022] S1, blending and granulating the raw materials in the inner layer, the intermediate layer and the outer layer, respectively;

[0023] S2, the three materials after granulation are respectively added into three double screw extruders for melt plasticization, co-extruded into a film through a composite die, stretched with a stretching ratio of 2.7-4.5, subjected to corona treatment, cooled and shaped, and cut and rolled to obtain a multilayer co-extruded casting film;

[0024] S3, the outer layer of the multilayer co-extruded casting film is subjected to hydrophilic treatment, and the inner layer is subjected to hydrophobic treatment.

[0025] Preferably, the outer layer is subjected to hydrophilic treatment and the inner layer is subjected to hydrophobic treatment by spraying or roller coating one side of the casting film and then solidifying to obtain; the hydrophilic treatment uses a hydrophilic finishing agent which is a polymer solution of one or more of PVA, PVP, polyacrylic acid and polyethylene glycol; and the hydrophobic treatment uses a hydrophobic finishing agent which is a polymer solution of one or more of fluorocarbon compounds, silicone oil, wax emulsion and polydimethylsiloxane.

[0026] In summary, the present application has the following beneficial effects: by introducing the multilayer co-extrusion technology, the particle size of the modified calcium carbonate particles in different layers is set and the one-way or two-way stretching process is set to construct the pore size gradient structure, and then the surface modification treatment is combined to form the asymmetric wettability, so as to guide the directional transmission of water, have the functions of moisture guiding, quick drying, preventing liquid reverse osmosis, accelerating the rapid discharge of human sweat, and preventing the external moisture from entering. The method can be formed at one time, the process is simple, has excellent water transmission rate and durability, the material selection and pore size structure are easy to design, is beneficial to large-scale production, and has a wide application prospect in the fields of medical protective clothing, sportswear, packaging materials and the like. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in combination with examples. All reagents not specified by the manufacturer are conventional reagent products which can be obtained by purchase in the market.

[0028] The amount used in the present application is commercially available, specifically:

[0029] The melt index of the LDPE is 5.0-7.5 g / 10 min, and the density is 0.917-0.922 g / cm 3 ;

[0030] The melt index of the LLDPE is 2.5-3.5 g / 10 min, and the density is 0.918-0.935 g / cm 3 ;

[0031] The melt index of the HDPE is 6.5-8.0 g / 10 min, and the density is 0.941-0.960 g / cm 3 ;

[0032] The melt index of the mLLDPE is 1.7-3.5 g / 10 min, and the density is 0.918-0.925 g / cm3 ;

[0033] The melt index of the POE is 9-20 g / 10 min;

[0034] The modified calcium carbonate used in the inner layer, the intermediate layer and the outer layer of the present application is modified calcium carbonate treated by one of titanate coupling agent, silane coupling agent and fatty acid. Since the effects of the titanate coupling agent, the silane coupling agent and the fatty acid on the modification of the calcium carbonate are basically the same, the modified calcium carbonate used in the examples of the present application is the calcium carbonate treated by the silane coupling agent. The modification method is to add the silane coupling agent after hydrolysis to the calcium carbonate, react at 60℃ for 2h and then dry to obtain the modified calcium carbonate.

[0035] In the three-layer raw material of the present application, the processing aid is one or several of lubricant, dispersant and coupling agent, and preferably the lubricant, the dispersant and the coupling agent in a weight ratio of 1:1:1.

[0036] Example 1

[0037] A multi-layer co-extrusion cast film with one-way wetting function, comprising an inner layer, an intermediate layer and an outer layer, wherein:

[0038] The inner layer comprises the following raw materials: LDPE 34 kg, LLDPE 30 kg, modified calcium carbonate 25 kg, nano calcium carbonate 10 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 0.1 μm, and the average particle size of the nano calcium carbonate is 80 nm;

[0039] The intermediate layer comprises the following raw materials: HDPE 40 kg, POE 13.8 kg, modified calcium carbonate 40 kg, PEG 5 kg, processing aid 1.2 kg, the average particle size of the modified calcium carbonate is 1 μm, and the relative molecular weight of the PEG is 10000-20000;

[0040] The outer layer comprises the following raw materials: mLLDPE 40 kg, copolymerized PP 10 kg, modified calcium carbonate 44 kg, PEG 5 kg, opening agent 0.5 kg, processing aid 0.5 kg, the average particle size of the modified calcium carbonate is 5 μm, and the relative molecular weight of the PEG is 4000-20000;

[0041] The preparation method thereof comprises the following steps:

[0042] S1, the raw materials in the inner layer, the intermediate layer and the outer layer are respectively blended and granulated, and the granulation temperature is 160-200℃;

[0043] S2, the three materials after granulation are respectively added into three double screw extruders for melt plasticization, co-extrusion into film through a composite die, the extrusion temperature is 170-230℃, after stretching, the stretching ratio is 2.7, the stretching temperature is 80℃, the film is treated by corona, cooled and shaped, and after edge cutting and winding, a multilayer co-extrusion casting film is obtained;

[0044] S3, the outer layer of the multilayer co-extrusion casting film is hydrophilic treated, and the inner layer is hydrophobic treated, wherein the hydrophilic treatment is that 5wt% PVA aqueous solution is roll-coated on the outer layer of the co-extrusion film and dried, and glycerol with 10% of the mass of PVA is added in the PVA aqueous solution; the inner layer hydrophobic treatment is that 1wt% hexadecyl trimethoxysilane ethanol solution is roll-coated on the inner layer of the co-extrusion film, and then dried.

[0045] Example 2

[0046] A multilayer co-extrusion casting film with one-way wetting function, comprising an inner layer, an intermediate layer and an outer layer, wherein:

[0047] The inner layer comprises the following raw materials: LDPE 40kg, LLDPE 29kg, modified calcium carbonate 20kg, nano calcium carbonate 10kg, and processing aid 1kg, the average particle size of the modified calcium carbonate is 0.1μm, and the average particle size of the nano calcium carbonate is 80nm;

[0048] The intermediate layer comprises the following raw materials: HDPE 45kg, POE 15kg, modified calcium carbonate 35kg, PEG 4.5kg, and processing aid 0.5kg, the average particle size of the modified calcium carbonate is 1μm, and the relative molecular weight of the PEG is 10000-20000;

[0049] The outer layer comprises the following raw materials by weight kg: mLLDPE 48kg, copolymerized PP 5kg, modified calcium carbonate 40kg, PEG 5kg, opening agent 1kg, and processing aid 1kg, the average particle size of the modified calcium carbonate is 5μm, and the relative molecular weight of the PEG is 4000-20000;

[0050] A preparation method thereof, comprising the following steps:

[0051] S1, the raw materials in the inner layer, the intermediate layer and the outer layer are respectively blended and granulated, and the granulation temperature is 160-200℃;

[0052] S2, the three materials after granulation are respectively added into three double screw extruders for melt plasticization, co-extrusion into film through a composite die, the extrusion temperature is 170-230℃, after stretching, the stretching ratio is 2.7, the stretching temperature is 80℃, the film is treated by corona, cooled and shaped, and after edge cutting and winding, a multilayer co-extrusion casting film is obtained;

[0053] S3, the outer layer of the multilayer co-extrusion casting film is hydrophilic treated, and the inner layer is hydrophobic treated, wherein the hydrophilic treatment is that 8wt% PVA water solution is roll coated on the outer layer of the co-extrusion film and dried; the PVA water solution further contains 10% glycerol by weight of PVA; the inner layer hydrophobic treatment is that 3wt% hexadecyl trimethoxysilane ethanol solution is roll coated on the inner layer of the co-extrusion film, and then dried.

[0054] Example 3

[0055] A multilayer co-extrusion casting film with one-way wet guiding function, comprising an inner layer, an intermediate layer and an outer layer, wherein:

[0056] The inner layer comprises the following raw materials: LDPE 45kg, LLDPE 30kg, modified calcium carbonate 19.5kg, nano calcium carbonate 5kg, processing aid 0.5kg, the average particle size of the modified calcium carbonate is 0.1μm, and the average particle size of the nano calcium carbonate is 80nm;

[0057] The intermediate layer comprises the following raw materials: HDPE 45kg, POE 10kg, modified calcium carbonate 40kg, PEG 4kg, processing aid 1kg, the average particle size of the modified calcium carbonate is 1μm, and the relative molecular weight of the PEG is 10000-20000;

[0058] The outer layer comprises the following raw materials: mLLDPE 42.8kg, copolymerized PP 5kg, modified calcium carbonate 40kg, PEG 8kg, opening agent 3kg, processing aid 1.2kg, the average particle size of the modified calcium carbonate is 5μm, and the relative molecular weight of the PEG is 4000-20000;

[0059] A preparation method thereof, comprising the following steps:

[0060] S1, the raw materials in the inner layer, the intermediate layer and the outer layer are respectively blended and granulated, and the granulation temperature is 160-200℃;

[0061] S2, the three kinds of materials after granulation are respectively added into three double screw extruders for melt plasticization, co-extruded into a film through a composite die, the extrusion temperature is 170-230℃, stretched with a stretching ratio of 2.7 at a stretching temperature of 100℃, subjected to corona treatment, cooled and shaped, and then cut, rolled and obtained as a multilayer co-extrusion casting film;

[0062] S3, the outer layer of the multilayer co-extrusion casting film is hydrophilic treated, and the inner layer is hydrophobic treated, wherein the hydrophilic treatment is that 8wt% PVA water solution is roll coated on the outer layer of the co-extrusion film and dried; the PVA water solution further contains 10% glycerol by weight of PVA; the inner layer hydrophobic treatment is that 3wt% hexadecyl trimethoxysilane ethanol solution is roll coated on the inner layer of the co-extrusion film, and then dried.

[0063] Example 4

[0064] A multi-layer co-extrusion cast film with one-way wetting function, comprising an inner layer, a middle layer and an outer layer, wherein:

[0065] The inner layer comprises the following raw materials: LDPE 45 kg, LLDPE 29 kg, modified calcium carbonate 15 kg, nano calcium carbonate 10 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 0.1 μm, and the average particle size of the nano calcium carbonate is 80 nm;

[0066] The middle layer comprises the following raw materials: HDPE 45 kg, POE 13 kg, modified calcium carbonate 38 kg, PEG 3 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 1 μm, and the relative molecular weight of the PEG is 10000-20000;

[0067] The outer layer comprises the following raw materials: mLLDPE 40 kg, copolymerized PP 8 kg, modified calcium carbonate 40 kg, PEG 8 kg, opening agent 3 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 5 μm, and the relative molecular weight of the PEG is 4000-20000; the preparation method is the same as that of Example 1.

[0068] Example 5

[0069] A multi-layer co-extrusion cast film with one-way wetting function, comprising an inner layer, a middle layer and an outer layer, wherein:

[0070] The inner layer comprises the following raw materials: LDPE 45 kg, LLDPE 20 kg, modified calcium carbonate 24 kg, nano calcium carbonate 10 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 0.1 μm, and the average particle size of the nano calcium carbonate is 80 nm;

[0071] The middle layer comprises the following raw materials: HDPE 43 kg, POE 15 kg, modified calcium carbonate 37 kg, PEG 4 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 1 μm, and the relative molecular weight of the PEG is 10000-20000;

[0072] The outer layer comprises the following raw materials: mLLDPE 40 kg, copolymerized PP 8 kg, modified calcium carbonate 45 kg, PEG 5 kg, opening agent 1 kg, processing aid 1 kg, the average particle size of the modified calcium carbonate is 5 μm, and the relative molecular weight of the PEG is 4000-20000; the preparation method is the same as that of Example 1.

[0073] Example 6

[0074] A multi-layer co-extrusion cast film with one-way wetting function, which is different from example 1 in that the average particle size of modified calcium carbonate in the inner layer raw material is 0.6pm, and the average particle size of nano calcium carbonate is 90nm; the average particle size of modified calcium carbonate in the middle layer raw material is 3pm; the average particle size of modified calcium carbonate in the outer layer raw material is 15pm, and the others are the same as example 1.

[0075] Example 7

[0076] A multi-layer co-extrusion cast film with one-way wetting function, which is different from example 1 in that the average particle size of modified calcium carbonate in the inner layer raw material is 1pm, and the average particle size of nano calcium carbonate is 100nm; the average particle size of modified calcium carbonate in the middle layer raw material is 5pm; the average particle size of modified calcium carbonate in the outer layer raw material is 20pm, and the others are the same as example 1.

[0077] Example 8

[0078] A multi-layer co-extrusion cast film with one-way wetting function, which is different from example 1 in that the stretching ratio in the preparation method is 4.5, and the others are the same as example 1.

[0079] Comparative example 1

[0080] A multi-layer co-extrusion cast film, which is different from example 1 in that the amount of modified calcium carbonate in the three layers is the same, which is 45kg, and the average particle size of modified calcium carbonate is 1pm, so the amount of other raw materials in each layer is as follows:

[0081] The inner layer includes the following raw materials: LDPE 29kg, LLDPE 20kg, modified calcium carbonate 45kg, processing aid 1kg;

[0082] The middle layer includes the following raw materials: HDPE 40kg, POE 10kg, modified calcium carbonate 45kg, PEG 4kg, processing aid 1kg, and the relative molecular weight of PEG is 10000-20000;

[0083] The outer layer includes the following raw materials: mLLDPE 40kg, copolymerized PP 9kg, modified calcium carbonate 45kg, PEG 5kg, opening agent 0.5kg, processing aid 0.5kg, and the relative molecular weight of PEG is 4000-20000; the others are the same as example 1.

[0084] Comparative example 2

[0085] A multi-layer co-extrusion cast film, which is different from example 1 in that the outer layer is not subjected to surface hydrophilic treatment in the preparation method, and the other steps are the same as example 1.

[0086] Comparative example 3

[0087] A multi-layer co-extrusion cast film, which is different from example 1 in that the outer layer is not subjected to surface hydrophilic treatment and the inner layer is not subjected to surface hydrophobic treatment in the preparation method, and other steps are the same as example 1.

[0088] Performance detection

[0089] The multi-layer co-extrusion cast films obtained in the above examples and comparative examples were detected for contact angle, hydrostatic pressure and penetration time, and the detection results are shown in Table 1.

[0090] The hydrostatic pressure test was carried out according to the relevant provisions in GB / T 4744-2013, and the pressure increasing rate was 60 cmH20 / min;

[0091] The penetration time test was carried out according to the relevant provisions in GB / T 21655-2008, and the droplet size was 35 μL. The penetration and diffusion time of the inner layer refers to the diffusion time of the liquid droplet from the inner layer to the outer layer. The shorter the time, the faster the liquid can penetrate from the inside to the outside. The outer layer penetration / diffusion time refers to the diffusion time of the liquid droplet from the outer layer to the inner layer. The longer the time, the more difficult it is for the liquid to penetrate from the outside to the inside.

[0092] Table 1 Performance detection results of multi-layer co-extrusion cast film

[0093]

[0094] In combination with Table 1:

[0095] The three-layer co-extrusion cast films obtained in examples 1-5 all have good waterproof performance, and the penetration and diffusion time of the inner layer is all within 55 s, which indicates that the modified calcium carbonate in the three layers forms a gradient pore size and a surface wetting modification treatment, thereby realizing the function of one-way wet guiding.

[0096] Compared with example 1, the penetration and diffusion time of the inner layer decreases with the increase of the particle size of the modified calcium carbonate in examples 6-7, which indicates that the porosity of the co-extrusion film gradually increases with the increase of the pore size, making the one-way wet guiding performance more significant. However, the hydrostatic pressure of the outer layer and the inner layer of the co-extrusion film decreases with the increase of the particle size of the modified calcium carbonate, especially the decrease of the hydrostatic pressure in example 7 is more significant, which indicates that the ability to prevent liquid water is reduced. Therefore, it can be seen that when the particle size of the modified calcium carbonate is limited within this range, the ability to prevent liquid water of the co-extrusion film can be ensured, and the one-way wet guiding effect can also be realized.

[0097] Compared with example 1, the penetration time of the inner layer decreases after increasing the stretching ratio in example 8, and the hydrostatic pressure of the inner layer and the outer layer also decreases, which shows that when the stretching ratio is controlled within this range, the ability to prevent liquid water of the co-extrusion film can be ensured, and the one-way wet guiding effect can also be realized.

[0098] Comparative Example 1 and Example 1, when the amount of the three layers of modified calcium carbonate is the same, and the particle size of the modified calcium carbonate is also the same, the penetration time of the inner layer to the outer layer of the co-extruded film obtained by Comparative Example 1 is 112.3s, and the penetration time of the outer layer to the inner layer is 152.3s, which indicates that when the amount and particle size of the modified calcium carbonate in the three layers are the same, the pore size gradient cannot be constructed, and under the condition of retaining the wet treatment, water is difficult and slow to diffuse out from the inner layer, and easy and fast to come from the outer layer, and the surface pore size gradient is a necessary condition for the performance of the membrane directing and wetting.

[0099] Comparative Example 2 and Example 1, only the inner layer is hydrophobic treated, and the outer layer is not hydrophilic, since PP itself has hydrophobic properties, water cannot be well directed from the inner layer to the outer layer at this time, but water can be blocked from entering the inner layer from the outer layer.

[0100] Comparative Example 3 and Example 1, neither hydrophilic treatment nor hydrophobic treatment is performed, only the pore size gradient is constructed, and there is no surface wetting treatment, water can diffuse from the inner layer to the outer layer, but water cannot be blocked from entering from the outer layer, and the same effect of one-way wetting cannot be achieved.

[0101] The embodiments of the specific implementation are preferred embodiments of the present application, and are not limited to the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A multilayer coextruded cast film having a one-way moisture conducting function comprising an inner layer, a middle layer and an outer layer, characterized in that: The outer layer is hydrophilic treated, and the inner layer is hydrophobic treated; The inner layer comprises the following raw materials in parts by weight: LDPE 34-45 parts, LLDPE 20-30 parts, modified calcium carbonate 15-25 parts, nano calcium carbonate 5-10 parts, and processing aid 0.5-1.0 parts, wherein the average particle size of the modified calcium carbonate is 0.1-1 μm; The middle layer comprises the following raw materials in parts by weight: HDPE 40-45 parts, POE 10-15 parts, modified calcium carbonate 35-40 parts, PEG 3-5 parts, and processing aid 0.5-1.2 parts, wherein the average particle size of the modified calcium carbonate is 1-5 μm; The outer layer comprises the following raw materials in parts by weight: mLLDPE 40-50 parts, PP 5-10 parts, modified calcium carbonate 40-45 parts, PEG 5-8 parts, opening agent 0.5-3 parts, and processing aid 0.5-1.2 parts, wherein the average particle size of the modified calcium carbonate is 5-20 μm.

2. The multi-layer co-extruded cast film with one-way wetting function according to claim 1, characterized in that: The average particle size of the nano calcium carbonate is 80-100 nm.

3. The multi-layer co-extruded cast film with one-way wetting function according to claim 1, characterized in that: The melt index of the LDPE is 5.0-7.5 g / 10 min, and the melt index of the LLDPE is 2.5-3.5 g / 10 min.

4. The multi-layer co-extruded cast film with one-way wetting function according to claim 1, characterized in that: The melt index of the HDPE is 6.5-8.0 g / 10 min, and the melt index of the POE is 9-20 g / 10 min.

5. The multi-layer co-extruded cast film with one-way wetting function according to claim 1, characterized in that: The melt index of the mLLDPE is 1.7-3.5 g / 10 min.

6. The multi-layer co-extruded cast film with one-way wetting function according to claim 1, characterized in that: The modified calcium carbonate in the inner layer, the middle layer and the outer layer is modified calcium carbonate modified by one or more of titanate coupling agent, silane coupling agent and fatty acid.

7. The multi-layer co-extruded cast film with one-way wet direction function according to claim 1, characterized in that: The relative molecular weight of the PEG in the outer layer is 4000-20000.

8. The multi-layer co-extrusion casting film with one-way wet guiding function according to claim 1, characterized in that: The relative molecular weight of the PEG in the middle layer is 10000-20000.

9. A process for the production of a multilayer co-extruded cast film with unidirectional liquid management function according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1, blending and granulating the raw materials in the inner layer, the middle layer and the outer layer respectively; S2, adding the three kinds of materials after granulation into three double-screw extruders respectively for melt plasticization, co-extruding into a film through a composite die, stretching with a stretching ratio of 2.7-4.5, performing corona treatment, cooling and setting, cutting edges and winding to obtain a multi-layer co-extrusion casting film; S3, performing hydrophilic treatment on the outer layer of the multi-layer co-extrusion casting film, and performing hydrophobic treatment on the inner layer.

10. The method for preparing a multilayer co-extruded cast film with unidirectional moisture-wicking function according to claim 9, characterized in that: The hydrophilic treatment and the hydrophobic treatment of the outer layer and the inner layer are obtained by spraying or roller coating one side of the casting film and then solidifying; The hydrophilic finishing agent used in the hydrophilic treatment is one or more of PVA, PVP, polyacrylic acid and polyethylene glycol polymer solution; The hydrophobic finishing agent used in the hydrophobic treatment is one or more of fluorocarbon compound, silicone oil, wax emulsion and polydimethylsiloxane polymer solution.

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