Breathable bottom film for paper diaper as well as preparation method and application of breathable bottom film

Abstract

The invention relates to a breathable bottom film for a paper diaper as well as a preparation method and application of the breathable bottom film. The breathable bottom film comprises the following raw materials in parts by mass: 40-60 parts of polylactic acid, 15-30 parts of modified biological polysaccharide, 10-20 parts of an effervescing agent and 10-20 parts of modified composite fibers, wherein the modified biological polysaccharide comprises the following raw materials in parts by mass: 30-50 parts of biological polysaccharide, 10-15 parts of a water repellent agent and 1-3 parts of an emulsifier, the biological polysaccharide is chitosan, hemicellulose and gleditsia sinensis lam gum, and the water repellent agent is lacquer wax and / or trifluoropropyl methyl silicone oil. The breathable bottom film has good water resistance, barrier property, breathability and antibacterial property and has certain mechanical strength, the comfort, safety and use performance of the paper diaper are improved, and the requirements of adult paper diaper bottom films for multifunctionality and reliability can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of sanitary products, and in particular to a breathable bottom film for diapers, a preparation method thereof, and applications thereof. Background Art

[0002] The latest structure of adult diapers is mainly divided into a surface layer, an instantaneous absorption and distribution layer, an absorbent core layer, a backing film, and other functional components. The backing film of adult diapers is the main factor affecting their breathability, directly determining the breathability of the entire diaper and, in turn, affecting the comfort of adults when wearing it.

[0003] Based on daily usage, in breathable adult diapers currently sold on the market, after the absorbent core layer fully absorbs urine, urine may penetrate the backsheet and onto clothing, thereby staining the clothing. Therefore, a high-quality backsheet for adult diapers must not only have good breathability but also excellent waterproof performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a breathable bottom film for diapers and a preparation method and application thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a breathable backsheet for diapers, comprising the following raw materials, in parts by mass: 40-60 parts of polylactic acid, 15-30 parts of modified biopolysaccharide, 10-20 parts of effervescent agent, and 10-20 parts of modified composite fiber; wherein the modified biopolysaccharide comprises the following raw materials, in parts by mass: 30-50 parts of biopolysaccharide, 10-15 parts of hydrophobic agent, and 1-3 parts of emulsifier, and the biopolysaccharide is chitosan, hemicellulose, and saponin; the effervescent agent comprises the following raw materials, in parts by mass: 10-15 parts of acid source, 10-15 parts of alkali source, 40-60 parts of modified composite fiber, and 0.05-0.1 parts of surfactant;

[0007] The method for preparing the modified composite fiber comprises the following steps:

[0008] The composite fiber is subjected to pulping treatment, the composite fiber pulp is mixed with a silver sulfate solution, taken out and dried to obtain a modified composite fiber; wherein the composite fiber is kapok fiber and soybean fiber;

[0009] The method for preparing the breathable bottom film for diapers comprises the following steps:

[0010] Polylactic acid, modified biopolysaccharide and modified composite fiber are mixed, extruded and formed, stretched and cooled to obtain a base film, glue is sprayed on the surface of the base film, and then an effervescent agent is covered on the glue-sprayed surface of the base film. After drying, the breathable base film for diapers is obtained.

[0011] The breathable backsheet of this invention primarily consists of polylactic acid, modified biopolysaccharides, an effervescent agent, and modified composite fibers. Through the synergistic effect of raw material selection and process design, it achieves a multifunctional balance of water resistance, barrier properties, air permeability, antibacterial properties, and mechanical strength. The following is a detailed analysis of the mechanisms by which these functions are achieved from a material perspective:

[0012] Specifically, the present invention uses polylactic acid as the main material, which itself has a certain mechanical strength. At the same time, because its main chain contains ester bonds and has a certain hydrophobicity, polylactic acid can provide basic tensile strength, puncture resistance and waterproofness for the base film.

[0013] The chitosan in the modified biopolysaccharide provides hydrophilic groups and antimicrobial activity, hemicellulose creates continuous hydrophilic channels, and saponin optimizes pore distribution. While chitosan is hydrophilic before modification, the hydrophobic modification results in an alternating hydrophilic / hydrophobic structure that allows water vapor molecules to diffuse through hydrogen bond adsorption and desorption while also blocking liquid water. When the chitosan in the modified biopolysaccharide is compounded with a hydrophobic agent, its surface amino and hydroxyl groups may be replaced by hydrophobic groups, forming a micro-nanohydrophobic structure resembling the lotus leaf effect. The hemicellulose and saponin, combined with the emulsifier, form a uniformly dispersed hydrophobic network that fills the gaps between the polylactic acid (PLA) molecular chains, blocking capillary water absorption channels and reducing the hydrophilicity of the biopolysaccharide, further enhancing the base film's water resistance. Through chemical modification and physical blending, the modified biopolysaccharide forms a dynamic breathable network that allows water vapor to diffuse through hydrogen bond adsorption and desorption while blocking liquid water through micropores and interfacial hydrophobic regions, achieving a balance between breathability and water resistance.

[0014] The modified composite fiber is made by mixing composite fibers with a silver ion solution after pulping. The silver ions provide the composite fibers with antibacterial properties. The hollow structure of the kapok fiber and the natural pores of the soybean fiber provide a diffusion path for water vapor. The stretching process further expands the interfiber spaces, resulting in excellent breathability for the base film. The composite fiber, acting as a reinforcement, also further improves the tensile strength of the base film.

[0015] The effervescent agent uses modified composite fiber as a carrier. When the effervescent agent meets water, the acid source and the alkali source react to generate CO2 gas. The gas expands to form micron-level interconnected channels in the membrane, promoting the permeation of water vapor and achieving the effect of breathability and cooling.

[0016] The transparent base film of this invention achieves synergistic breathability, antibacterial properties, and enhanced performance through a single-layer structure, avoiding the process complexity and delamination risks associated with traditional multi-layer composites. The effervescent agent dynamically generates pores upon contact with water, achieving "on-demand breathability" and balancing barrier properties in a dry state with breathability requirements in a wet state.

[0017] Preferably, in the preparation method of the modified composite fiber, the amount of the silver sulfate solution added is 5-6 times the total mass of the composite fiber, the mass concentration of the silver sulfate solution is 40-60%; and the soaking time is 1-3 hours.

[0018] Preferably, the mass ratio of the kapok fiber to the soybean fiber is 1:(3-5).

[0019] Preferably, the mass ratio of chitosan, hemicellulose and saponin is (2-4):1:(0.5-1).

[0020] Preferably, the hydrophobic agent is lacquer wax and trifluoropropyl methyl silicone oil in a mass ratio of 1:(0.5-2); the emulsifier is glycerol monostearate. While the hydrophobic layer formed by lacquer wax on the surface of the biopolysaccharide blocks liquid water, the hydrophobic modification only affects the surface groups of the biopolysaccharide and does not disrupt its internal porous structure. The flexibility of trifluoropropyl methyl silicone oil helps maintain the softness of the base film and avoid the loss of air permeability caused by excessive densification.

[0021] Preferably, in the method for preparing the breathable bottom film for diapers, the extrusion molding temperature is 150-180°C.

[0022] Preferably, in the raw materials for preparing the effervescent agent, the acid source is citric acid, the alkali source is sodium bicarbonate, and the surfactant is sodium lauryl sulfate.

[0023] Specifically, the preparation method of the effervescent agent comprises the following steps:

[0024] (1) mixing the modified composite fiber, water, sodium bicarbonate and sodium lauryl sulfate, granulating the mixture, drying the mixture and sieving the mixture to obtain a powder with a size of 300-500 mesh;

[0025] (2) preparing citric acid into 300-500 mesh powder;

[0026] (3) mixing the powders obtained in step (1) and step (2) to obtain the effervescent agent.

[0027] Preferably, in step (1) of the method for preparing the effervescent agent, the amount of water added is 2-3 times that of the modified composite fiber; and the drying temperature is 60-80°C.

[0028] In a second aspect, the present invention provides use of a breathable backsheet for diapers in the preparation of adult diapers.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The modified composite fiber in the breathable base film of the present invention simultaneously undertakes the triple functions of reinforcement, effervescent agent carrier and antibacterial, avoiding multi-layer composite. After the modified composite fiber, polylactic acid and modified biopolysaccharide are extruded into a film, glue is applied on the surface of the base film, and then the effervescent agent is evenly covered, so that the effervescent agent (acid source + alkali source) remains stable in a dry state and does not release gas before encountering water, avoiding the risk of leakage caused by premature formation of pores in the membrane structure. The breathable base film of the present invention achieves breathability, antibacterial and enhanced synergy through a single-layer structure, avoiding the process complexity and stratification risk caused by traditional multi-layer composite. After the effervescent agent encounters water, air holes are dynamically generated to achieve "breathability on demand", balancing the barrier properties in a dry state with the breathability requirements in a wet state. The breathable base film of the present invention has good water resistance, barrier properties, air permeability, antibacterial properties, and a certain mechanical strength, which increases the comfort, safety and performance of diapers and can meet the needs of adult diaper base films for versatility and reliability. DETAILED DESCRIPTION

[0031] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0032] The raw materials used in the following examples and comparative examples are from:

[0033] Chitosan: The manufacturer is Qingdao Yunzhou Biotechnology Co., Ltd., and the model is chitosan for textile use;

[0034] Hemicellulose: manufacturer: Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., model number: DW3432;

[0035] Gleditsia gum: the manufacturer is Nanjing Songguan Biotechnology Co., Ltd.

[0036] Lacquer wax: Manufacturer: Keim-Additec, Germany, model: E-360;

[0037] Trifluoropropyl methyl silicone oil: manufacturer is Shenzhen Ruitongwei Technology Co., Ltd., model number is JP-401;

[0038] Polylactic acid: Manufacturer: Zhejiang Hisun Biomaterials Co., Ltd., model: REVODE110 / 190

[0039] Kapok fiber: The manufacturer is Dongguan Weixin Import and Export Co., Ltd., and the model is Haojin Kapok (Kapok 100%);

[0040] Soybean fiber: Manufacturer: Guangzhou Jinsheng Technology Co., Ltd., model A-09.

[0041] Unless otherwise specified, other materials, reagents, etc. used in the Examples and Comparative Examples can be obtained from commercial sources.

[0042] Example 1

[0043] A breathable backsheet for diapers, comprising the following raw materials, measured in parts by mass: 52 parts of polylactic acid, 17 parts of modified biopolysaccharide, 13 parts of effervescent agent, and 15 parts of modified composite fiber; wherein the modified biopolysaccharide comprises the following raw materials, measured in parts by mass: 32 parts of biopolysaccharide, 14 parts of hydrophobic agent, and 2 parts of emulsifier; the biopolysaccharide comprises chitosan, hemicellulose, and saponin gum in a mass ratio of 3:1:0.8; the hydrophobic agent comprises lacquer wax and trifluoropropyl methyl silicone oil in a mass ratio of 1:1; and the emulsifier is glyceryl monostearate;

[0044] The effervescent agent comprises the following raw materials in parts by mass: 12 parts of an acid source, 12 parts of an alkali source, 52 parts of a modified composite fiber, and 0.06 parts of a surfactant, wherein the acid source is citric acid, the alkali source is sodium bicarbonate, and the surfactant is sodium lauryl sulfate;

[0045] The method for preparing the modified composite fiber comprises the following steps:

[0046] The composite fiber is pulped, the composite fiber pulp is mixed with a silver sulfate solution, taken out and dried to obtain a modified composite fiber; wherein the composite fiber is kapok fiber and soybean fiber in a mass ratio of 1:4;

[0047] The preparation method of the effervescent agent comprises the following steps:

[0048] (1) The modified composite fiber, water, sodium bicarbonate and sodium lauryl sulfate were mixed and granulated, dried at 75° C., and sieved to obtain a 400-mesh powder; wherein the amount of water added was 3 times that of the modified composite fiber;

[0049] (2) preparing citric acid into 400-mesh powder;

[0050] (3) mixing the powders obtained in step (1) and step (2) to obtain the effervescent agent.

[0051] The method for preparing the breathable bottom film for diapers comprises the following steps:

[0052] Polylactic acid, modified biopolysaccharide and modified composite fiber are mixed, extruded and formed at 160°C, stretched and cooled to obtain a base film, glue is sprayed on the surface of the base film, and then an effervescent agent is covered on the glue-sprayed surface of the base film. After drying, the breathable base film for diapers is obtained.

[0053] Example 2

[0054] A breathable backsheet for diapers, comprising the following raw materials, measured in parts by mass: 40 parts of polylactic acid, 15 parts of modified biopolysaccharide, 10 parts of effervescent agent, and 10 parts of modified composite fiber; wherein the modified biopolysaccharide comprises the following raw materials, measured in parts by mass: 30 parts of biopolysaccharide, 10 parts of hydrophobic agent, and 1 part of emulsifier; the biopolysaccharide comprises chitosan, hemicellulose, and saponin gum in a mass ratio of 2:1:0.5; the hydrophobic agent comprises lacquer wax and trifluoropropyl methyl silicone oil in a mass ratio of 1:0.5; and the emulsifier is glyceryl monostearate;

[0055] The effervescent agent comprises the following raw materials in parts by mass: 10 parts of an acid source, 10 parts of an alkali source, 40 parts of a modified composite fiber, and 0.05 parts of a surfactant, wherein the acid source is citric acid, the alkali source is sodium bicarbonate, and the surfactant is sodium lauryl sulfate;

[0056] The preparation method of the effervescent agent comprises the following steps:

[0057] (1) The modified composite fiber, water, sodium bicarbonate and sodium lauryl sulfate were mixed and granulated, dried at 60° C., and sieved to obtain a 300-mesh powder; wherein the amount of water added was twice that of the modified composite fiber;

[0058] (2) preparing citric acid into 300-mesh powder;

[0059] (3) mixing the powders obtained in step (1) and step (2) to obtain the effervescent agent.

[0060] The method for preparing the modified composite fiber comprises the following steps:

[0061] The composite fiber is pulped, the composite fiber pulp is mixed with a silver sulfate solution, taken out and dried to obtain a modified composite fiber; wherein the composite fiber is kapok fiber and soybean fiber in a mass ratio of 1:3;

[0062] The method for preparing the breathable bottom film for diapers comprises the following steps:

[0063] Polylactic acid, modified biopolysaccharide and modified composite fiber are mixed, extruded and formed at 150°C, stretched and cooled to obtain a base film, glue is sprayed on the surface of the base film, and then an effervescent agent is covered on the glue-sprayed surface of the base film. After drying, the breathable base film for diapers is obtained.

[0064] Example 3

[0065] A breathable backsheet for diapers, comprising the following raw materials, measured in parts by mass: 60 parts of polylactic acid, 30 parts of modified biopolysaccharide, 20 parts of an effervescent agent, and 20 parts of modified composite fiber; wherein the modified biopolysaccharide comprises the following raw materials, measured in parts by mass: 50 parts of biopolysaccharide, 15 parts of a hydrophobic agent, and 3 parts of an emulsifier; the biopolysaccharide comprises chitosan, hemicellulose, and saponin gum in a mass ratio of 4:1:1; the hydrophobic agent comprises lacquer wax and trifluoropropyl methyl silicone oil in a mass ratio of 1:2; and the emulsifier is glyceryl monostearate;

[0066] The effervescent agent comprises the following raw materials in parts by mass: 15 parts of an acid source, 15 parts of an alkali source, 60 parts of a modified composite fiber, and 0.1 parts of a surfactant, wherein the acid source is citric acid, the alkali source is sodium bicarbonate, and the surfactant is sodium lauryl sulfate;

[0067] The method for preparing the modified composite fiber comprises the following steps:

[0068] The composite fiber is pulped, the composite fiber pulp is mixed with a silver sulfate solution, taken out and dried to obtain a modified composite fiber; wherein the composite fiber is kapok fiber and soybean fiber in a mass ratio of 1:5;

[0069] The preparation method of the effervescent agent comprises the following steps:

[0070] (1) The modified composite fiber, water, sodium bicarbonate and sodium lauryl sulfate are mixed and granulated, dried at 80° C., and sieved to obtain a 500-mesh powder; wherein the amount of water added is 3 times that of the modified composite fiber;

[0071] (2) preparing citric acid into 500-mesh powder;

[0072] (3) mixing the powders obtained in step (1) and step (2) to obtain the effervescent agent;

[0073] The method for preparing the breathable bottom film for diapers comprises the following steps:

[0074] Polylactic acid, modified biopolysaccharide and modified composite fiber are mixed, extruded and formed at 180°C, stretched and cooled to obtain a base film, glue is sprayed on the surface of the base film, and then an effervescent agent is covered on the glue-sprayed surface of the base film. After drying, the breathable base film for diapers is obtained.

[0075] Example 4

[0076] The difference between Example 4 and Example 1 is that the amount of the biopolysaccharide added remains unchanged, and the mass ratio of chitosan, hemicellulose and saponin is 1:3:0.8.

[0077] Example 5

[0078] The difference between Example 5 and Example 1 is that the amount of the biopolysaccharide added remains unchanged, and the mass ratio of chitosan, hemicellulose and saponin is 3:0.8:1.

[0079] Example 6

[0080] The difference between Example 6 and Example 1 is that the amount of the hydrophobic agent added remains unchanged, no lacquer wax is added, and an equal amount of trifluoropropylmethyl silicone oil is used to make up the missing amount.

[0081] Example 7

[0082] The difference between Example 7 and Example 1 is that the amount of the hydrophobic agent added remains unchanged, trifluoropropyl methyl silicone oil is not added, and an equal amount of lacquer wax is used to make up the missing amount.

[0083] Comparative Example 1

[0084] The difference between Comparative Example 1 and Example 1 is that the amount of the biopolysaccharide added remains unchanged, chitosan is not added, and hemicellulose and saponin in a mass ratio of 1:0.8 are used to make up for the missing amount.

[0085] Comparative Example 2

[0086] The difference between Comparative Example 2 and Example 1 is that the amount of the biopolysaccharide added remains unchanged, hemicellulose is not added, and chitosan and saponin with a mass ratio of 3:0.8 are used to make up for the missing amount.

[0087] Comparative Example 3

[0088] The difference between Comparative Example 3 and Example 1 is that the amount of the biopolysaccharide added remains unchanged, saponin gum is not added, and chitosan and hemicellulose are used in a mass ratio of 3:1.

[0089] Comparative Example 4

[0090] The difference between Comparative Example 4 and Example 1 is that no hydrophobic agent is added to the modified biopolysaccharide, and an equal amount of emulsifier is used to make up for the missing amount.

[0091] Comparative Example 5

[0092] The difference between Comparative Example 5 and Example 1 is that the modified composite fiber in the effervescent agent is replaced by PVP.

[0093] Comparative Example 6

[0094] The difference between Comparative Example 6 and Example 1 is that the method for preparing the breathable base film for diapers comprises the following steps: mixing polylactic acid, modified biopolysaccharide, modified composite fiber and effervescent agent, extruding and molding, stretching and cooling to obtain the breathable base film.

[0095] Performance Testing

[0096] The following tests were performed on the base film samples of Examples 1-7 and Comparative Examples 1-6:

[0097] 1. Waterproof test

[0098] The hydrostatic pressure values of the samples were tested according to GB / T 4744-2013, "Testing and evaluating the water resistance of textiles - Hydrostatic pressure method." The data are shown in Table 1. The higher the hydrostatic pressure value, the better the water resistance of the sample.

[0099] 2. Air permeability and moisture permeability test

[0100] Moisture permeability: measured according to GB / T 12704-2009 "Test method for moisture permeability of fabrics" - Moisture permeability cup method: Method A. The data are shown in Table 1.

[0101] Air permeability: Measured according to GB / T 5453-1997 "Determination of Air Permeability of Textile Fabrics". Data are shown in Table 1. The higher the moisture permeability and air permeability, the better the air and moisture permeability of the sample.

[0102] 3. Mechanical properties test

[0103] The tensile strength of the samples was tested according to GB / T3923.1-1997 "Determination of breaking strength and elongation at break of fabrics - Strip method", and the specific data are shown in Table 1. The greater the tensile strength, the higher the mechanical strength and durability of the base film.

[0104] Table 1 Test results of each group of samples

[0105] Group Hydrostatic pressure value / kPa <![CDATA[Water vapor permeability / g·m -2 , 24h]]> Air permeability / (mm / s) Tensile strength / N Example 1 40.70 9053 36.95 713 Example 2 40.38 8906 36.16 687 Example 3 40.65 8993 36.43 706 Example 4 36.15 8571 32.96 679 Example 5 36.08 8567 32.52 660 Example 6 32.06 7288 32.31 627 Example 7 31.78 7264 31.94 620 Comparative Example 1 28.80 6597 24.61 597 Comparative Example 2 28.96 6685 24.88 582 Comparative Example 3 28.74 6589 24.58 590 Comparative Example 4 25.74 9134 38.45 590 Comparative Example 5 31.45 7205 28.86 585 Comparative Example 6 31.17 6170 21.53 573

[0106] As shown in Table 1, combining the data of Examples 1 and 4-5, it can be seen that the waterproofness, air permeability, and mechanical strength of Examples 4-5 are all lower than those of Example 1. This may be because the mass ratio of the biopolysaccharide affects the hydrophobic modification effect, resulting in poor water resistance and easier water penetration. It may also cause the air permeable microporous structure to be destroyed or blocked, resulting in reduced air permeability. Therefore, when the mass ratio of the chitosan, hemicellulose, and saponin is (2-4):1:(0.5-1), the waterproofness, air permeability, and mechanical strength of the base film are at a relatively good level.

[0107] Combining the data of Example 1, Example 6-7 and Comparative Example 4, it can be seen that the addition of a hydrophobic agent and the specific type of hydrophobic agent are important parameters that affect the water resistance, air permeability and mechanical strength of the base film. Although the air permeability will be good without adding a hydrophobic agent, the water resistance and mechanical strength of the base film are greatly reduced. In addition, only one hydrophobic agent was added to Examples 6-7, and its performance was also worse than that of Example 1. This may be because the hydrophobic layer formed by the lacquer wax on the surface of the biopolysaccharide blocks liquid water, but the hydrophobic modification only acts on the surface groups of the biopolysaccharide and does not destroy its internal natural porous structure. The flexibility of trifluoropropyl methyl silicone oil helps to maintain the softness of the base film and avoid the decrease in air permeability caused by excessive densification. Therefore, the lacquer wax and trifluoropropyl methyl silicone oil synergistically improve the water resistance, air permeability and mechanical strength of the base film.

[0108] Combining the data from Example 1 and Comparative Examples 1-3, it can be seen that Comparative Examples 1-3 each lack one of the biopolysaccharides, resulting in incomplete barrier properties, hydrophobic modification, and tensile strength of the base film, and inferior water resistance and mechanical strength to Example 1. Furthermore, the lack of a complete range of biopolysaccharides affects the formation and distribution of the base film's breathable microporous structure, resulting in poor air permeability.

[0109] Combining the data from Example 1 and Comparative Example 5, we can see that the performance of the base film in Comparative Example 5, where PVP is the effervescent carrier, is lower than that of Example 1. This is likely because PVP's barrier properties and hydrophobicity are inferior to those of the modified composite fiber, resulting in reduced water resistance. PVP also has poor air permeability, which affects the overall air permeability of the base film. Furthermore, PVP's mechanical strength is lower than that of the modified composite fiber, resulting in reduced tensile strength. Therefore, the modified composite fiber used in the present invention simultaneously performs the triple functions of reinforcement, effervescent carrier, and antibacterial, avoiding multi-layer lamination while also improving the base film's water resistance, air permeability, and mechanical strength.

[0110] Combining the data from Example 1 and Comparative Example 6 reveals that in Comparative Example 6, the effervescent agent is directly extruded. High temperatures may affect the stability of the effervescent agent, thereby affecting the performance of the base film. Therefore, the dry lamination process and targeted spraying of the effervescent agent in this invention are crucial for performance uniformity; directly mixing the effervescent agent can lead to performance fluctuations.

[0111] In summary, the breathable bottom film of the present invention has good water resistance, barrier properties, air permeability, antibacterial properties, and certain mechanical strength, which increases the comfort, safety and performance of diapers and can meet the requirements of adult diaper bottom films for versatility and reliability.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A breathable bottom film for diapers, characterized in that: The invention comprises the following raw materials in parts by mass: 40-60 parts of polylactic acid, 15-30 parts of modified biopolysaccharide, 10-20 parts of effervescent agent and 10-20 parts of modified composite fiber; wherein the modified biopolysaccharide comprises the following raw materials in parts by mass: 30-50 parts of biopolysaccharide, 10-15 parts of hydrophobic agent and 1-3 parts of emulsifier, wherein the biopolysaccharide is chitosan, hemicellulose and saponin gum, and the hydrophobic agent is lacquer wax and / or trifluoropropylmethyl silicone oil; and the effervescent agent comprises the following raw materials in parts by mass: 10-15 parts of acid source, 10-15 parts of alkali source, 40-60 parts of modified composite fiber and 0.05-0.1 parts of surfactant; The method for preparing the modified composite fiber comprises the following steps: The composite fiber is subjected to pulping treatment, the composite fiber pulp is mixed with a silver sulfate solution, taken out and dried to obtain a modified composite fiber; wherein the composite fiber is kapok fiber and soybean fiber; The method for preparing the breathable bottom film for diapers comprises the following steps: Polylactic acid, modified biopolysaccharide and modified composite fiber are mixed, extruded and formed, stretched and cooled to obtain a base film, glue is sprayed on the surface of the base film, and then an effervescent agent is covered on the glue-sprayed surface of the base film. After drying, the breathable base film for diapers is obtained.

2. The method for preparing a breathable bottom film for diapers according to claim 1, wherein: In the preparation method of the modified composite fiber, the amount of the silver sulfate solution added is 5-6 times the total mass of the composite fiber, the mass concentration of the silver sulfate solution is 40-60%, and the soaking time is 1-3 hours.

3. The method for preparing a breathable bottom film for diapers according to claim 1, wherein: The mass ratio of the kapok fiber to the soybean fiber is 1:(3-5).

4. The method for preparing a breathable bottom film for diapers according to claim 1, wherein: The mass ratio of the chitosan, hemicellulose and saponin is (2-4):1:(0.5-1).

5. The method for preparing a breathable bottom film for diapers according to claim 1, wherein: The hydrophobic agent is lacquer wax and trifluoropropyl methyl silicone oil in a mass ratio of 1: (0.5-2); and the emulsifier is glyceryl monostearate.

6. The breathable bottom film for diapers according to claim 1, wherein: In the method for preparing the breathable bottom film for diapers, the extrusion molding temperature is 150-180°C.

7. The method for preparing a breathable bottom film for diapers according to claim 1, wherein: The raw materials for preparing the effervescent agent are selected from at least one of (I)-(III): (1) The acid source is citric acid; (II) the alkaline source is sodium bicarbonate; (III) The surfactant is sodium lauryl sulfate.

8. The breathable bottom film for diapers according to claim 7, wherein: The preparation method of the effervescent agent comprises the following steps: (1) mixing the modified composite fiber, water, sodium bicarbonate and sodium lauryl sulfate, granulating the mixture, drying the mixture and sieving the mixture to obtain a powder with a size of 300-500 mesh; (2) preparing citric acid into 300-500 mesh powder; (3) mixing the powders obtained in step (1) and step (2) to obtain the effervescent agent.

9. The breathable bottom film for diapers according to claim 8, wherein: In step (1) of the preparation method of the effervescent agent, the amount of water added is 2-3 times that of the modified composite fiber; and the drying temperature is 60-80°C.

10. Use of the breathable backsheet for diapers according to any one of claims 1 to 9 in the preparation of adult diapers.