Super detailed explanation of the characteristics and technology of hydrophilic non-woven fabrics

Polypropylene (pp) non-woven fabrics are widely used because of their excellent properties, simple processing methods and low prices. Especially in recent years, it has been widely used in medical care, clothing, packaging materials, wiping materials, agricultural covering materials, geotextiles, industrial filter materials and other fields, and has a tendency to replace its traditional materials. Because pp has a non-polar structure and basically does not contain hydrophilic groups, pp non-woven fabrics basically have no water absorption properties. Hydrophilic modification or hydrophilic finishing must be carried out to make hydrophilic pp nonwoven fabrics. I. Method for preparing hydrophilic non-woven fabrics In order to improve the hydrophilicity of pp non-woven fabrics, the surface wetting properties are usually improved, mainly by physical modification and chemical modification. Chemical modification mainly changes the molecular structure of PP and adds hydrophilic groups to the macromolecular chain to change its hygroscopicity. There are mainly copolymerization, grafting, cross-linking, chlorination and other methods. Physical modification mainly changes the higher structure of the molecule to improve the hydrophilic effect, mainly blending modification (i.e. before spinning) and surface modification (i.e. after spinning). two. Hybrid modification (spinning pre-modification) can be divided into master batch method, full granulation method and spin coating agent injection method according to the different adding time of the modified additives. (1) Ordinary masterbatch method This is an important method for hydrophilic non-woven fabrics produced by non-woven fabric manufacturers. First, the wood manufacturer will make jellyfish particles from ordinary hydrophilic additives, and then blend them with pp spinning to spin into cloth. Advantages: simple production, no need to add any equipment, suitable for small batch production of cattle, in addition to its strong hydrophilic durability. Disadvantages: slow hydrophilic effect, poor processing performance, often in woven fabrics. The cost is high, 2 to 3 times that of surface modification. The spinnability is poor and requires an adjustment process. Some customers waste 5 tons of fabric from two masterbatch factories without producing finished products. (2) Full granulation method: The modifier, pp chips and additives are uniformly mixed, granulated under the screw, and made into hydrophilic pp granules, which are then melted and spun into a cloth. Advantages: good processability, long-lasting effect, and the fabric can be used repeatedly. Disadvantages: Need to increase screw extruder equipment, high cost per ton, slow hydrophilic effect, only suitable for mass production. (3) Fangqian injection adds the hydrophilic agent, that is, the hydrophilic polymer directly to the main screw of the non-woven fabric, and mixes it with the pp melt for direct spinning. Advantages: The effect is long-lasting, and the fabric can be used repeatedly. Disadvantages: Due to the inability to mix uniformly, spinning is often difficult and the maneuverability is not strong. three. Surface hydrophilic finishing (after spinning treatment) Hydrophilic finishing is a simple, effective and low-cost method to produce hydrophilic non-woven fabrics. Most of our non-woven fabric manufacturers mainly use this method. The main process is as follows: On-line spunbond hot-rolled non-woven fabric-roll coating or water spraying hydrophilic agent-infrared or hot air advantages: non-woven problem, non-woven fabric has fast hydrophilic effect, high efficiency, low price, ordinary color 1/2-1/3 of the cost of masterbatch. Suitable for large-scale production; Disadvantages: Need to purchase separate post-processing equipment, which is expensive. After washing 3 times, the water penetration time increased by about 15 times. Can not meet the requirements of repeated use; mass production; the advantages and disadvantages of this method determine that it is mainly used for disposable products that require high water permeability and hydrophilicity, such as sanitary materials, diapers, sanitary napkins, etc. Fourth, use the complex hydrophilic parent particle PPS03 method. In view of the advantages and disadvantages of the (-) and (ii) methods, the composite hydrophilic parent particle PPS030 was developed. This jellyfish particle has the characteristics of a medium dose (similar to ordinary jellyfish particles). The effect is fast, the cloth effect is fast, the effect is good, the effect is long-lasting, and the washing resistance is good, but the cost is slightly higher (similar to ordinary jellyfish particles). Good spinnability, no need to adjust the production process. Suitable for small batch production and high washing resistance, reusable products, such as forestry cloth and agricultural cloth. The main evaluation indicators of hydrophilic PP non-woven fabrics include water absorption, contact angle and capillary effect. (1) Water absorption rate: refers to the amount of water absorbed per unit mass of hydrophilic nonwoven fabric in the standard time or within the time required to completely wet the material. The greater the water absorption, the better the effect. (2) Contact angle method: Put the hydrophilic pp non-woven fabric on a clean and smooth glass plate and place it flat on the oven to melt it. After melting, take out the glass plate and let it cool to room temperature naturally. Use the direct test method to measure the equilibrium contact angle. The smaller the contact angle, the better. (After reaching about 148°, there is no hydrophilic treatment of PP non-woven fabric).