Introduction of The Warp Sizing Technology Part 3-Slurry

Slurry

Divided into two categories: main slurry and auxiliary slurry.

Main slurry: It is a polymer compound. Their molecular structure must have the same or similar functional groups as fibers, and they should have good adhesion to fibers, so they are also called adhesives. There must be a certain self-adhesive force between the macromolecules of the main slurry, and the solution can form a film with certain mechanical strength and elongation properties after drying. In addition, the main slurry should also contain a certain amount of hydrophilic groups in order to be prepared into a slurry. Commonly used main slurries include starch, animal glue, carboxymethyl cellulose, polyvinyl alcohol and acrylic acid copolymer, etc.

(1) Starch: It is one of the traditional main sizing materials. Commonly used starches include wheat, potato, sweet potato, indica rice, cassava, etc. Among them, wheat flour has better sizing performance and can be used for warp sizing of fine high-density cotton cloth. Non-edible starches such as oak kernel starch can also be used as sizing materials. Starch expands in water as the temperature increases, gelatinizes into slurry, and forms a gel when the temperature decreases. Starch slurry is suitable for sizing only after gelatinization and above the gel temperature. Starch slurry has poor fluidity, insufficient viscosity, and brittle and hard slurry film, which is easily corroded and corrupted by microorganisms. Therefore, auxiliary slurries such as softeners, surfactants, starch decomposers, and preservatives must be used. Starch also has a large amount of hydroxyl groups and has good adhesion to cotton, linen, viscose and other fibers. Starch slurry has good mechanical formation.

(2) Animal glue: Extracted from animal bones, tendons, skin or other connective tissues, it is a hard element protein and is composed of various amino acids. Two commonly used ones are bone glue and gelatin, which are used for sizing natural silk, viscose silk, etc. The animal glue slurry has poor permeability, the slurry film is brittle and hard, and is easily corruptible. It must be equipped with auxiliary slurries such as grease, surfactants and preservatives.

(3) Algin: widely found in various algae. Alginic acid obtained through chemical processing is insoluble in water, and its sodium (or ammonium) salt is soluble in water, which is called sodium alginate. Its aqueous solution has low concentration and high viscosity characteristics, and can be used alone as the main slurry for cotton yarn. Viscose yarn sizing.

(4) Cellulose derivatives: mainly water-soluble cellulose ethers, commonly used is CMC. CMC is made by etherification of alkali cellulose with monofluoroacetic acid. When the degree of substitution is greater than 0.4, it is water-soluble. Industrial CMC is generally the sodium salt of carboxymethyl cellulose, which is suitable for sizing cotton yarn and viscose yarn. CMC aqueous solution has low concentration, low viscosity characteristics, poor permeability, good hygroscopicity, strong flower power, and good miscibility with other main slurries. The crude product has high salt content, is highly corrosive to machine parts, and is not suitable for sizing. . Another commonly used cellulose derivative is carboxyethylcellulose HEC, which has similar sizing properties to CMC.

(5) Polyvinyl alcohol: a water-soluble polymer obtained by alcoholysis of polyvinyl acetate. Commonly used polyvinyl alcohol PVA can be divided into two types: high degree of

polymerization and low degree of polymerization according to different degrees of polymerization. The former is suitable for staple fiber yarns, and the latter is suitable for sizing synthetic fiber filaments. PVA can be divided into two types according to different alcoholysis degrees: complete alcoholysis type and partial alcoholysis type. The former is suitable for hydrophilic fibers, and the latter is suitable for sizing hydrophobic fibers. The PVA slurry film is both versatile and elastic, and is the best among the existing sizing materials. It can also be miscible with other main slurries in a wide range of mixing ratios to obtain good sizing effects. Its main disadvantages are: slurry foaming, skinning, and low adhesion to highly hydrophobic synthetic fibers.

(6) Acrylic copolymer: mainly refers to copolymers and polyacrylamide with acrylate as the main body. The components are complex and changeable and can be prepared according to the purpose. Most of them are sticky liquids with solid content between 10-40%. Polyacrylic acid and its salt sizing was initially used for sizing nylon yarn, and later was often mixed with starch for sizing synthetic fiber blended yarn.

Auxiliary pulp

Mainly include softeners, surfactants, starch decomposing agents, preservatives and waxes.

(1) Softener: It can increase the flexibility of the serosa film to withstand the dynamic load during weaving. Commonly used ones include beef tallow, mutton fat, cottonseed oil, etc., which are all glycerides of higher fatty acids. Among them, tallow is the most suitable for sizing.

(2) Surfactant: a substance that can significantly reduce the surface tension of a liquid. It is mainly suitable for anionic and nonionic surfactants, which can improve the permeability of slurry, and can also eliminate static electricity and emulsify.

(3) Starch decomposing agents: Acids, alkalis, oxidants and enzymes can all be used as decomposing agents to moderately hydrolyze starch macromolecules to improve the fluidity of the slurry. Sodium silicate is a commonly used alkaline decomposition agent, while acids and enzymes are less commonly used.

(4) Preservative: It can inhibit the reproduction of microorganisms in the slurry or on the gauze to prevent the slurry from deteriorating and the sizing or fabric from becoming moldy. Natural slurries such as starch, algin and animal glue often require preservatives. Commonly used preservatives include naphthol, which is a light reddish-brown scaly solid that can be dissolved in alkali solution. However, it cannot be added to the slurry at the same time as the oxidizing agent to avoid an effective addition reaction with naphthol and weaken the oxidative decomposition effect.

(5) Wax: Mainly used for sizing synthetic fibers. The wax used as auxiliary slurry should be able to melt at 50-60°C and solidify at room temperature. Wax generally needs to be emulsified and then applied to the surface of the sized yarn through post-waxing to improve its smoothness and reduce static electricity accumulation. There are three main types: paraffin wax, beeswax, and synthetic wax. Paraffin and beeswax should not be used on fabrics that require printing and dyeing.