Preparation method of ultrathin polyethylene microporous breathable film for paper diaper

Abstract

The invention discloses a preparation method of an ultrathin polyethylene microporous breathable film for paper diapers, the breathable film is composed of an inner layer, a secondary inner layer, a middle layer, a secondary outer layer and an outer layer, and the thickness ratio is 1: 1: 3-4: 1: 1; the inner layer, the secondary inner layer, the middle layer, the secondary outer layer and the outer layer are all formed by blending calcium carbonate master batch, polyethylene and a lubricant, wherein the calcium carbonate master batch contains traditional Chinese medicine extract modified antibacterial master batch; according to the preparation method, the five layers of raw materials are subjected to blow molding, air cooling and twelve-roller differential longitudinal stretching processes to prepare the composite material. Through a five-layer processing technology, the problems that calcium carbonate master batch is easy to separate out and uneven in mixing are solved, and the microporous breathable film which is low in gram weight, high in breathability, uniform in pore and good in antibacterial performance is prepared and can be used for paper diapers.

Description

Technical Field

[0001] The invention belongs to the technical field of polyethylene film production, and in particular relates to a method for preparing an ultra-thin polyethylene microporous breathable film for diapers. Background Art

[0002] The structure of the microporous breathable membrane is formed by adding incompatible inorganic microparticle porogens to the polymer and stretching it. There are many capillary-like micropores in its structure, which constitute a channel for the sequential passage of gas. However, since the diameter of the external liquid droplets is larger than the diameter of the micropores, they cannot pass through, thus having breathable and waterproof functional characteristics. Microporous breathable membranes are currently mainly used in the fields of personal hygiene care products and the medical field, such as sanitary napkins, panty liners, diapers, adult incontinence products, and medical or surgical disposables. However, from the current application point of view, most of them are produced by the cast film process, which generally has problems such as "easy to shrink, low resistance to hydrostatic pressure, and high gram weight", and the process needs to be further improved.

[0003] Chinese patent CN108623875A discloses a composite material for high-strength breathable membrane and its preparation method, which uses bimodal polyethylene as a substrate, blends metallocene polyethylene, high-density polyethylene, and inorganic calcium carbonate into granules, and forms a breathable membrane through cast molding, which has excellent waterproof and breathable functions and a strength of more than 2000g / m 2 / 24h water vapor transmission rate, used in diapers, sanitary napkins and other hygiene products.

[0004] Chinese patent CN107746499B discloses a biaxially stretched breathable film, which mainly uses 30kg of low-density polyethylene, 20kg of ultrafine calcium carbonate powder, 10kg of antibacterial masterbatch, 1kg of dimethyl silicone rheological agent, and 3kg of dodecylamine polyoxyethylene ether dispersant. After granulation by a twin-screw extruder, a single-screw film blowing molding is performed on a film blowing machine, wherein the screw aspect ratio is 30:1, the blowing ratio is 3:1, and the biaxial stretching technology of film blowing transverse stretching and then longitudinal stretching is adopted to form a microporous breathable film. However, it adopts single-screw single-layer film blowing molding, does not have a multi-layer interlayer design, and the film blowing biaxial stretching technology is ordinary traction stretching, without multi-roller MDO stretching annealing cooling.

[0005] Chinese patent CN111890767A discloses an ultra-thin polyethylene microporous breathable film and a preparation method thereof. The breathable film comprises an outer layer, a middle layer and an inner layer which are co-extruded by a film blowing machine. The material of the inner layer is blended by a weight ratio of 45-60 kg of calcium carbonate masterbatch, 25-30 kg of polyethylene, 18-25 kg of ethylene and octene copolymer polyethylene, and 1-3 kg of lubricant; the material of the middle layer is blended by a weight ratio of 60-70 kg of calcium carbonate masterbatch, 25-30 kg of polyethylene, and 1-3 kg of lubricant; the material of the outer layer is blended by a weight ratio of 45-60 kg of calcium carbonate masterbatch, 25-30 kg of polyethylene, 18-25 kg of ethylene and octene copolymer polyethylene, and 1-3 kg of lubricant. However, it adopts three-layer co-extrusion molding, the thickness of a single layer is relatively high, and the air permeability is average. In addition, due to the use of a relatively high content of calcium carbonate masterbatch, agglomeration is easy to occur during the mixing process, which leads to the precipitation of the calcium carbonate masterbatch after the film is prepared, affecting the air permeability and uniformity of micropore distribution. In addition, the precipitated calcium carbonate masterbatch is easy to cause allergies, which seriously limits its application in the field of personal hygiene care products and the medical field.

[0006] Therefore, it is necessary to develop a method for preparing a microporous breathable membrane to improve the air permeability and uniformity of raw material mixing. Summary of the invention

[0007] In view of the above technical problems, the present invention provides a method for preparing an ultra-thin polyethylene microporous breathable film for diapers.

[0008] In order to achieve the above-mentioned purpose, the present invention provides an ultra-thin polyethylene microporous breathable film for diapers, wherein the breathable film consists of an inner layer, a sub-inner layer, a middle layer, a sub-outer layer and an outer layer; the thickness ratio of the inner layer, the sub-inner layer, the middle layer, the sub-outer layer and the outer layer is 1:1:3-4:1:1; the gram weight of the breathable film is 10-15gsm.

[0009] Preferably, the inner layer is blended with calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:25-34:0.5-1.5; The secondary inner layer is formed by mixing calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:21-27:0.5-1.5; The middle layer is formed by mixing calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 60-70:25-30:1-3; The secondary outer layer is formed by blending calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:21-27:0.5-1.5; The outer layer is formed by blending calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:25-34:0.5-1.5.

[0010] Further preferably, the calcium carbonate masterbatch is formed by blending and granulating polyethylene, calcium carbonate, a modified antibacterial agent, a silane coupling agent, an antioxidant and a lubricant in a mass ratio of 18-22:60-75:4-6:2-3:0.3-1:0.3-1.

[0011] More preferably, the modified antibacterial agent is obtained by immersing and mixing the antibacterial masterbatch and the modifier, and then drying; the silane coupling agent is any one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3(phenylamino)propyltrimethoxysilane; the antioxidant is compounded by antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; the lubricant is any one of polyphthalamide, nonylphenol polyoxyethylene ether ammonium sulfate and polyhydroxyethyl acrylate-acrylamide.

[0012] More preferably, the modifier is a Chinese herbal extract consisting of Houttuynia cordata, Scutellaria baicalensis, Herba Phellodendri and Phellodendron amurense; and the antibacterial masterbatch is nanosilver, sodium titanate or ammonium molybdate.

[0013] Preferably, the mass ratio of Houttuynia cordata, Scutellaria baicalensis, Phellodendron chinense and Phellodendron amurense is 2:1:1:1.

[0014] Preferably, the modification method is to grind Houttuynia cordata, Scutellaria baicalensis, Herba Phellodendri and Phellodendron amurense and boil them for 25-35 minutes to obtain a Chinese medicine extract, soak the antibacterial masterbatch in the Chinese medicine extract, stir for 5-10 minutes, let it stand for 2-3 hours, remove and dry to obtain a modified antibacterial agent.

[0015] More preferably, the polyethylene has a melt index of 0.8-2.0 g / min and a density of 0.925-0.932 g / cm 3 ; The particle size of the calcium carbonate is 1.0-1.2μm.

[0016] The present invention also provides a method for preparing an ultra-thin polyethylene microporous breathable film for diapers, comprising the following steps: (1) Preparing calcium carbonate masterbatch: drying and dehumidifying calcium carbonate, antibacterial agent, silane coupling agent, antioxidant, and lubricant, mixing them evenly, and granulating them to obtain calcium carbonate masterbatch; (2) Preparation of five layers of raw materials: Inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the inner layer raw material; Second inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the second inner layer raw material; Middle layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the middle layer raw material; Second outer layer: raw material obtained by blending calcium carbonate masterbatch, polyethylene and lubricant; Outer layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the outer layer raw material; (3) Blow molding: blow molding a total of five layers including inner layer, sub-inner layer, middle layer, sub-outer layer and outer layer, and air cooling to obtain a polyethylene film; (4) MDO stretching: After the polyethylene film is cooled and flattened, a twelve-roller differential longitudinal stretching process is used to prepare a breathable film, which is then corona treated and rolled up to obtain an ultra-thin polyethylene microporous breathable film.

[0017] Preferably, the drying method in step (1) is drying at 80-90° C. for 3-5 hours.

[0018] Preferably, the moisture content of the raw material after dehumidification in step (1) is ≤300 ppm.

[0019] Preferably, the blow ratio during blow molding in step (3) is 2.0-3.2:1.

[0020] Preferably, the twelve-roller differential longitudinal stretching process described in step (4) includes the temperature of the preheating roller 1 being 65-70°C; the temperature of the preheating roller 2 being 75-80°C; the temperature of the heating rollers 3 and 4 being 90-95, the temperature of the forging rollers 5 and 6 being 90-100°C, the temperature of the fixed rollers 7-10 being 95-102°C, the temperature of the cooling roller 11 being 45-55°C, and the temperature of the cooling roller 12 being 35-45°C.

[0021] Further preferably, the stretching speed during the longitudinal stretching is 40-50 m / min; the linear speed of the preheating roller, the heating roller and the forging roller 5 is 40-50 m / min; the linear speed of the forging roller 6 is 200-240 m / min; the linear speed of the fixed roller and the cooling roller is 200-230 m / min; and the stretching ratio is 3.3-4.5.

[0022] Preferably, the corona treatment condition in step (4) is 42-45 dynes.

[0023] The beneficial effects of the present invention are: 1. Change the microporous breathable membrane to a five-layer structure, and change the thickness of the middle layer to 3-4 times that of the other four layers. Seal the calcium carbonate masterbatch with a higher content in the middle layer to reduce the precipitation phenomenon caused by uneven mixing of the calcium carbonate masterbatch, avoid affecting the air permeability and micropore uniformity of the microporous breathable membrane, and also avoid allergies caused by the precipitation of calcium carbonate, so that the prepared microporous breathable membrane is more suitable for infant products, such as diapers.

[0024] 2. Changing the microporous breathable membrane to a five-layer structure makes it easier to mix the various raw materials, avoids the agglomeration of raw materials such as calcium carbonate, reduces the difficulty of mixing, improves the uniformity of the microporous breathable membrane, and effectively avoids the problem of calcium carbonate particles leaking during the stretching process.

[0025] 3. The antibacterial masterbatch is modified with Chinese herbal extracts to improve the antibacterial effect of the microporous breathable membrane and extend the antibacterial time. While effectively isolating external microorganisms, it reduces the growth of Staphylococcus aureus, Escherichia coli, etc., thereby reducing diaper rash, urinary tract infection and other problems caused by bacteria to a certain extent and improving safety.

[0026] 4. The twelve-roller differential longitudinal stretching process is used to prepare the microporous breathable film, which significantly improves the flatness, tensile strength and micropore uniformity of the microporous breathable film and reduces the shrinkage rate of the microporous breathable film. After flexographic printing, colorful patterns can be formed for use in infant diapers. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the membrane layer structure of the polyethylene microporous breathable membrane in the present invention, wherein 1 is the outer layer, 2 is the sub-outer layer, 3 is the middle layer, 4 is the sub-inner layer, 5 is the inner layer, and 6 is calcium carbonate particles. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be understood as limiting the present invention. The protection scope of the present invention shall be based on the contents recorded in the claims. Any modification or replacement made by those skilled in the art to the technical solution of the present invention without creative work shall fall within the protection scope of the present invention.

[0029] Example 1 (1) Preparation of an antibacterial agent: dried Houttuynia cordata, Scutellaria baicalensis, Herba Phellodendri and Phellodendron amurense were crushed separately, then mixed in a mass ratio of 2:1:1:1, and three times the mass of water was added, and boiled for 30 minutes to obtain a Chinese medicine extract; nanosilver was soaked in the Chinese medicine extract, stirred for 10 minutes, and then allowed to stand for 3 hours to obtain an antibacterial agent; (2) Preparation of calcium carbonate masterbatch: polyethylene (melt index 0.8 g / min, density 0.925 g / cm 3 ), calcium carbonate particles, antibacterial agent, 3 (phenylamino) propyltrimethoxysilane, antioxidant and polyphthalamide are dried and dehumidified respectively and mixed evenly in a mass ratio of 20:70:5:3:1:1, and granulated by a twin-screw extruder and pelletized by water cooling at low temperature to obtain a calcium carbonate masterbatch; wherein the content of calcium carbonate in the calcium carbonate masterbatch is 70%; (3) Preparation of five layers of raw materials: Inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended in a mass ratio of 60:27:1 to obtain the inner layer raw material; Second inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended in a mass ratio of 60:21:1 to obtain the second inner layer raw material; Middle layer: calcium carbonate masterbatch, polyethylene, and lubricant are blended in a mass ratio of 68:28:2 to obtain a middle layer raw material; Second outer layer: calcium carbonate masterbatch, polyethylene and lubricant are blended in a mass ratio of 60:21:1 to obtain a raw material; Outer layer: calcium carbonate masterbatch, polyethylene and lubricant are blended in a mass ratio of 60:27:1 to obtain an outer layer raw material; The melt index of polyethylene is 1.0 g / min and the density is 0.925 g / cm 3 ; Lubricant is polyphthalamide (4) injecting the five layers of raw materials into a film blowing machine respectively, blow-molding at a blow-up ratio of 2.98, and air-cooling to obtain a polyethylene film; (5) MDO stretching: After the polyethylene film is cooled and flattened by the guide roller, it is stretched by a twelve-roll differential longitudinal stretching process to obtain a breathable film; wherein the temperature of the preheating roller 1 is 65°C and the line speed is 40m / min; the temperature of the preheating roller 2 is 75°C and the line speed is 41m / min; the temperature of the heating roller 3 is 90°C and the line speed is 42m / min; the temperature of the heating roller 4 is 95°C and the line speed is 43m / min; the temperature of the calcining roller 5 is 95°C and the line speed is 44m / min; the temperature of the calcining roller 6 is 95°C and the line speed is 230m / min; the temperature of the fixed rollers 7-10 is 95°C and the line speed is 228m / min; the temperature of the cooling roller 11 is 55°C and the line speed is 220m / min; the temperature of the cooling roller 12 is 45°C and the line speed is 215m / min; the extrusion speed is 40m / min, the stretching ratio is 4.1, and the stretching is to 10gsm; (6) After the outer layer of the breathable membrane is corona-charged to 42 dynes at a high voltage electrode, the membrane is trimmed, rolled flat, and rolled up to obtain an ultra-thin polyethylene microporous breathable membrane. The performance indicators are shown in Table 1.

[0030] Table 1 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0031] The antibacterial performance indicates the antibacterial rate against Escherichia coli; The precipitation test method of calcium carbonate masterbatch is as follows: cut 2000-mesh (simulating the surface roughness of ordinary aluminum guide rollers or steel rollers with a surface roughness of Ra1.6 level) sandpaper into 70mm*40mm; fix the cut fine sandpaper on the curved pipe of the rewinder so that the film can pass through its surface; start the rewinder with a line speed of 300m / min, stop the machine after rewinding 1000m, remove the fine sandpaper and store it separately; the weight of the 2000-mesh sandpaper after rewinding 1000m minus the weight of the just-cut 2000-mesh sandpaper (repeat 5 times for each group and take the average value), which is recorded as the powder loss weight, that is, the precipitation of calcium carbonate masterbatch.

[0032] Example 2 The method and steps are the same as those in Example 1, except that the melt index of polyethylene in step (3) is changed to 1.0 g / min and the density is changed to 0.920 g / cm 3 ; The stretching ratio in step (5) was changed to 3.8 to prepare an ultra-thin polyethylene microporous breathable film of 12 gsm. The performance parameters are shown in Table 2: Table 2 Performance indicators of 12gsm ultra-thin polyethylene microporous breathable film

[0033] Example 3 The method and steps are the same as those in Example 1, except that the melt index of the polyethylene in step (2) is changed to 1.3 g / min and the density is changed to 0.93 g / cm 3 ; The silane coupling agent was changed to glycidyl acrylate; Change the melt index of polyethylene in step (3) to 1.5 g / min and the density to 0.927 g / cm 3 ; The stretching ratio in step (5) was changed to 3.1, and a 14 gsm ultra-thin polyethylene microporous breathable film was prepared. The performance parameters are shown in Table 3: Table 3 Performance indicators of 14gsm ultra-thin polyethylene microporous breathable film

[0034] Example 4 The method and steps are the same as those in Example 1, except that the nanosilver in step (1) is replaced by sodium titanate; the silane coupling agent is changed to γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the lubricant is changed to nonylphenol polyoxyethylene ether ammonium sulfate; The melt index of polyethylene in step (2) and step (5) was changed to 0.63 g / min and the density was changed to 0.962 g / cm 3 ; The mass ratio of calcium carbonate masterbatch, polyethylene and lubricant in the inner layer and the outer layer in step (3) was changed to 22:26.5:1 to prepare an ultra-thin polyethylene microporous breathable film of 10 gsm. The performance parameters are shown in Table 4: Table 4 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0035] Example 5 The method and steps are the same as those in Example 1, except that the melt index of polyethylene in step (2) is changed to 1.52 g / min and the density is changed to 0.98 g / cm 3; Replace nanosilver with sodium titanate, and replace lubricant with nonylphenol polyoxyethylene ether ammonium sulfate; The stretching ratio in step (5) was changed to 3.3 to prepare an ultra-thin polyethylene microporous breathable film of 14 gsm. Its performance indicators are shown in Table 5: Table 5 Performance indicators of 14gsm ultra-thin polyethylene microporous breathable film

[0036] Example 6 The method and steps are the same as those in Example 1, except that the melt index of polyethylene in step (2) is changed to 1.26 g / min and the density is changed to 0.954 g / cm 3 ; Replace nanosilver with sodium titanate, and replace lubricant with nonylphenol polyoxyethylene ether ammonium sulfate; Change the melt index of polyethylene in step (3) to 1.26 g / min and the density to 0.954 g / cm 3 ; An ultra-thin polyethylene microporous breathable film of 10gsm was prepared, and its performance indicators are shown in Table 6: Table 6 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0037] Example 7 The method and steps are the same as those in Example 1, except that the inflation ratio in step (4) is changed to 2.8:1; The temperature and line speed of the twelve rollers in step (5) are modified as follows: the temperature of the preheating roller 1 is 70°C and the line speed is 48.5 m / min; the temperature of the preheating roller 2 is 80°C and the line speed is 49 m / min; the temperature of the heating roller 3 is 95°C and the line speed is 49.5 m / min; the temperature of the heating roller 4 is 95°C and the line speed is 50 m / min; the temperature of the calcining roller 5 is 95°C and the line speed is 50.5 m / min; the temperature of the calcining roller 6 is 95°C and the line speed is 220 m / min; the temperature of the fixed rollers 7-10 is 99°C and the line speeds are 214 m / min, 208 m / min, 204 m / min and 201 m / min; the temperature of the cooling roller 11 is 50°C and the line speed is 200 m / min; the temperature of the cooling roller 12 is 35°C and the line speed is 200 m / min; the extrusion speed is 45 m / min and the stretching ratio is 3.989; The ultra-thin polyethylene microporous breathable film of 12 gsm was prepared, and its performance indicators are shown in Table 7: Table 7 Performance indicators of 12gsm ultra-thin polyethylene microporous breathable film

[0038] Example 8 The method and steps are the same as those in Example 1, except that the inflation ratio in step (4) is changed to 3.2:1; The temperature and line speed of the twelve rollers in step (5) are modified as follows: the temperature of the preheating roller 1 is 70°C and the line speed is 40 m / min; the temperature of the preheating roller 2 is 75°C and the line speed is 40 m / min; the temperature of the heating roller 3 is 90°C and the line speed is 50 m / min; the temperature of the heating roller 4 is 95°C and the line speed is 50 m / min; the temperature of the calcining roller 5 is 95°C and the line speed is 50 m / min; the temperature of the calcining roller 6 is 95°C and the line speed is 240 m / min; the temperature of the fixed rollers 7-10 is 96°C and the line speed is 210 m / min; the temperature of the cooling roller 11 is 55°C and the line speed is 210 m / min; the temperature of the cooling roller 12 is 35°C and the line speed is 210 m / min; the extrusion speed is 50 m / min and the stretching ratio is 4.5; The ultra-thin polyethylene microporous breathable film of 10 gsm was prepared, and its performance indicators are shown in Table 8: Table 8 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0039] Comparative Example 1 The method and steps are the same as those in Example 1, except that step (1) is omitted. In step (2), nanosilver is directly used as an antibacterial agent to prepare an ultra-thin polyethylene microporous breathable membrane of 10 gsm. The properties thereof are shown in Table 9: Table 9 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0040] Comparative Example 2 The method and steps are the same as those in Example 1, except that the twelve-roll differential longitudinal stretching process in step (5) is changed to an eight-roll differential longitudinal stretching process, specifically as follows: the polyethylene film is cooled and flattened by a guide roller, and then stretched by an eight-roll differential longitudinal stretching process to obtain a breathable film; wherein the temperature of the preheating roller 1 is 55°C, the temperature of the preheating roller 2 is 80°C, the temperature of the forging roller 1 is 95°C, the temperature of the forging roller 2 is 95°C, the temperature of the stabilizing roller 1 is 97°C, the temperature of the stabilizing roller 2 is 97°C, the temperature of the annealing roller 1 is 60°C, the temperature of the annealing roller 2 is 50°C, the stretching ratio is 4.1, and the film is stretched to 10 gsm. The properties are shown in Table 10: Table 10 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film

[0041] Comparative Example 3 The method and steps are the same as those in Example 1, except that the five-layer structure in step (2) is changed to a three-layer structure, as follows: Inner layer: calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 62:30:2; Middle layer: calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 65:30:2; Outer layer: Calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 62:30:2; The ultra-thin polyethylene microporous breathable film of 10 gsm was prepared by blow molding, and its properties are shown in Table 11: Table 1110gsm ultra-thin polyethylene microporous breathable film performance indicators

[0042] Comparative Example 4 (1) The melt index is 0.8g / min and the density is 0.925g / cm 3 20kg of bimodal molecular weight distribution polyethylene, 70kg of 1.0μm calcium carbonate particles, 5kg of nanosilver, 3kg of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 1kg of antioxidant, and 1kg of polyphthalamide are mixed evenly after drying and dehumidification (water content ≤ 300ppm), granulated by a twin-screw extruder, and pelletized by water cooling and low-temperature dicing to prepare as 70% calcium carbonate masterbatch; (2) Preparation of three layers of raw materials: Inner layer: calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 50:48:2; Middle layer: calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 70:28:2; Outer layer: calcium carbonate masterbatch, polyethylene and lubricant are mixed in a mass ratio of 50:48:2; The melt index of polyethylene is 1.0 g / min and the density is 0.925 g / cm 3 ; The lubricant is polyphthalamide; (4) injecting the three layers of raw materials into a film blowing machine respectively, and blowing and air-cooling the film at a blowing ratio of 2.0:1 to obtain a polyethylene film; (5) MDO stretching: After the polyethylene film is cooled and flattened by a guide roller, it is stretched by an eight-roller differential longitudinal stretching process to obtain a breathable film; wherein the temperature of the preheating roller 1 is 50°C, the temperature of the preheating roller 2 is 75°C, the temperature of the forging roller 1 is 95°C, the temperature of the forging roller 2 is 95°C, the temperature of the stabilizing roller 1 is 97°C, the temperature of the stabilizing roller 2 is 97°C, the temperature of the annealing roller 1 is 60°C, the temperature of the annealing roller 2 is 50°C, the stretching ratio is 4.3, and the stretching is to 10 gsm; (6) After the outer layer of the breathable film is corona-charged to 42 dynes by an online high-voltage electrode, the film is trimmed, flattened, and rolled to obtain an ultra-thin polyethylene microporous breathable film. The performance indicators are shown in Table 12: Table 12 Performance indicators of 10gsm ultra-thin polyethylene microporous breathable film .

Claims

1. An ultra-thin polyethylene microporous breathable film for diapers, characterized in that: The breathable film consists of an inner layer, a sub-inner layer, a middle layer, a sub-outer layer and an outer layer; the thickness ratio of the inner layer, the sub-inner layer, the middle layer, the sub-outer layer and the outer layer is 1:1:3-4:1:1; the gram weight of the breathable film is 10-15gsm.

2. The ultra-thin polyethylene microporous breathable film for diapers according to claim 1, characterized in that: The inner layer is formed by mixing calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:25-34:0.5-1.5; The secondary inner layer is formed by blending calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:21-27:0.5-1.5; The middle layer is formed by mixing calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 60-70:25-30:1-3; The secondary outer layer is formed by blending calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:21-27:0.5-1.5; The outer layer is formed by blending calcium carbonate masterbatch, polyethylene and lubricant in a mass ratio of 55-65:25-34:0.5-1.

5.

3. The ultra-thin polyethylene microporous breathable film for diapers according to claim 2, characterized in that: The calcium carbonate masterbatch is prepared by blending and granulating polyethylene, calcium carbonate, a modified antibacterial agent, a silane coupling agent, an antioxidant and a lubricant in a mass ratio of 18-22:60-75:4-6:2-3:0.3-1:0.3-1.

4. The ultra-thin polyethylene microporous breathable film for diapers according to claim 3, characterized in that: The modified antibacterial agent is obtained by immersing and mixing the antibacterial masterbatch and the modifier, and then drying; the silane coupling agent is any one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3(phenylamino)propyltrimethoxysilane; the antioxidant is a compound of antioxidant 1010 and antioxidant 168; the lubricant is any one of polyphthalamide, nonylphenol polyoxyethylene ether ammonium sulfate and polyhydroxyethyl acrylate-acrylamide.

5. The ultra-thin polyethylene microporous breathable film for diapers according to claim 4, characterized in that: The modifier is a Chinese medicinal extract composed of houttuynia cordata, scutellaria baicalensis, physalis and phellodendron chinense; and the antibacterial masterbatch is nano silver, sodium titanate or ammonium molybdate.

6. A method for preparing the ultra-thin polyethylene microporous breathable film for diapers according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparing calcium carbonate masterbatch: drying and dehumidifying calcium carbonate, antibacterial agent, silane coupling agent, antioxidant, and lubricant, mixing them evenly, and granulating them to obtain calcium carbonate masterbatch; (2) Preparation of five layers of raw materials: Inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the inner layer raw material; Second inner layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the second inner layer raw material; Middle layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the middle layer raw material; Second outer layer: raw material obtained by blending calcium carbonate masterbatch, polyethylene and lubricant; Outer layer: calcium carbonate masterbatch, polyethylene and lubricant are blended to obtain the outer layer raw material; (3) Blow molding: blow molding a total of five layers including inner layer, sub-inner layer, middle layer, sub-outer layer and outer layer, and air cooling to obtain a polyethylene film; (4) MDO stretching: After the polyethylene film is cooled and flattened, a twelve-roller differential longitudinal stretching process is used to prepare a breathable film, which is then corona treated and rolled up to obtain an ultra-thin polyethylene microporous breathable film.

7. The preparation method according to claim 6, characterized in that: The blow ratio during blow molding in step (3) is 2.0-3.2:

1.

8. The preparation method according to claim 6, characterized in that: The twelve-roller differential longitudinal stretching process described in step (4) includes the temperature of the preheating roller 1 being 65-70°C; the temperature of the preheating roller 2 being 75-80°C; the temperature of the heating rollers 3 and 4 being 90-95, the temperature of the forging rollers 5 and 6 being 90-100°C, the temperature of the fixed rollers 7-10 being 95-102°C, the temperature of the cooling roller 11 being 45-55°C, and the temperature of the cooling roller 12 being 35-45°C.

9. The preparation method according to claim 8, characterized in that: The stretching speed during the longitudinal stretching is 40-50m / min; the linear speed of the preheating roller, the heating roller and the forging roller 5 is 40-50m / min; the linear speed of the forging roller 6 is 200-240m / min; the linear speed of the fixed roller and the cooling roller is 200-230m / min; and the stretching ratio is 3.3-4.

5.

10. The preparation method according to claim 6, characterized in that: The corona treatment conditions in step (4) are 42-45 dynes.

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