Views: 1 Author: Site Editor Publish Time: 2024-08-06 Origin: Site
Softness is for fibers. The surfactants can form the reverse adsorption of hydrophobic groups on the fiber surface, reduce the dynamic and static friction factor of the fiber material, and obtain a smooth and soft hand feel. Usually, surfactants and oils are mixed together. Surfactants can effectively reduce the static friction factor of fiber materials, and oils can reduce the dynamic friction factor of fiber materials. The effect of soft lubrication can be expressed by the difference between the static friction factor and the dynamic friction factor, and the smaller the difference, the stronger the soft lubrication.
Different types of softeners are suitable for different types of fiber surfaces. The surface of the paper fiber is negatively charged, and the effect of cationic or zwitterionic surfactants is much better. In addition to surfactants, the formulation of softeners and smoothing agents is generally added to silicone polymers or lipids such as lanolin to fully reduce the surface energy of the fiber.
Silicone surfactants and silicone polymers have the best effect in softeners, but the price of raw materials is high, and they are often combined with other soft components to reduce costs.
Action mechanism of softener
Paper fiber molecular chain contains a number of hydroxyl groups, and is a straight chain type macromolecule, the chain has a strong intermolecular force and hydrogen bond association, has a high degree of crystallinity, belongs to the rigid chain. Through mechanical action such as beating and the addition of various chemicals, the fiber molecules can be dispersed, degraded and reduced in crystallinity, which can play a certain softening role. However, this is far from meeting the soft requirements of paper, so in recent years, both at home and abroad have attached great importance to the research and application of softener.
To make the paper soft, the interaction force between the fiber molecules should be reduced, so that the chain segment and the molecular chain can move, and the role of the softener is to form a non-polar isolation film between the fibers, so that the molecular chain is easy to slip and move each other under stress. Most of the paper softeners are surfactants containing hydrophobic groups above Cl6. Under the appropriate process conditions, attached to the surface of the fiber, can form a hydrophobic film wrapped in fiber, so that the softness of the fiber is improved, such as sulfate in anionic surfactants, sulfonated castor oil and non-ionic surfactants in polyethylene glycol ester, when attached to the surface of the fiber will show its soft effect.
The cationic group in the cationic surfactant can be directly combined with the negatively charged fiber, the hydrophobic group forms a low-energy surface on the outside of the fiber, and its soft effect is particularly good, such as the ze1an(trade name) manufactured by the DuPont chemical Company in the United States is a cationic surfactant, easy to dissolve in warm water, form a transparent foam solution, and can form ether bond with cellulose fibers. The molecular formula is [C17H35CON - HCH2CH2NHR2]+C1-. Ve1an(trade name), manufactured by the British ICI company, is also a surfactant of this kind. Amphoteric surfactants have a wide range of adaptation, and the cation group can act on the fiber, and the anionic group can be combined with the fiber through the polyelectrolyte or aluminum ions in the pulp, and the hydrophobic group can also be arranged outward, so that the surface energy is greatly reduced. In addition, cationic and amphoteric surfactants have antibacterial and bactericidal ability, which can effectively prevent the mold of paper.
The soft mechanism of organosilicon polymer is that the polar silicon oxygen chain forms a hydrogen bond with the fiber, and the hydrophobic group is arranged outward to form a low-energy film, which greatly reduces the intermolecular force of the fiber, so organosilicon polymer is the best kind of paper softener. Polyethylene wax, oxidized polyethylene wax, paraffin wax and stearate ester, stearate bisamide, lanolin, etc., mainly penetrate into the fiber, play a role in isolation and lubrication, so that the fiber molecules are easy to move.
Softener types and main varieties
(1) Cationic surfactants such as fatty acid bisamide epichlohydrin are mainly used for paper with high softness requirements, such as toilet paper, wrinkle paper, sanitary napkins, handkerchief paper, napkins and other paper products. This softener can be electrostatic combined with cellulose fibers, and can be used with cationic or non-ionic active agents, and has good miscibility.
(2) amphoteric ionic surfactants amphoteric imidazoline and betaine surfactants can be used as paper softeners. 1-(β-aminoethyl) -2-heptadecyl imidazoline carboxylic acid derivatives have been used in the paper industry.
(3) organosilicon surfactants Organosilicon surfactants belong to special surfactants, which are mainly cationic organosilicon quaternary ammonium salts used as softeners. In 967, the United States Dokang Company was the first to publish a patent, developed a silicone quaternary ammonium salt, the product name DC-5700, the structural formula is as follows: (CH3O)3Si(CH2)3N(CH3)2C18H37C1-
The compound contains both quaternary ammonium salts and three methoxyl silanes. This silicone surfactant with three easily hydrolyzed methoxy groups, hydrolyzed to easily cross-linked silicon hydroxyl, can firmly adhere to the surface of the fiber, play a soft role. At the same time, it has strong bactericidal and bacteriostatic ability, which can penetrate the cell wall of human bacteria and coagulate the protein of the cell wall, so as to achieve the purpose of bactericidal and bacteriostatic. Since the 1980s, China has also developed silicone quaternary ammonium salt surfactants similar in structure and performance to DC-5700, such as hydrogen-containing silicone oil and glycidyl allyl ether reaction to produce silicone oil with epoxy group, and then react with dimethylamine to produce organic silylamine, and then react with chloromethane under pressure to produce organic silicon quaternary ammonium salt.
(4) Other softeners
① Polyoxyethylene stearate, also known as softener SME-4, is a non-ionic softener. The appearance is beige paste, soluble in water ethanol, ether and toluene, etc., can be mixed with various surfactants, the pH value of the aqueous solution is neutral, the saponification value is 80 ~ 90, and the HLB value is l0.0.
Oxidized polyethylene Oxidized polyethylene emulsion can be made of low molecular weight polyethylene by oxidation and emulsification. The appearance is white emulsion; Solid content 20% : pH value is close to 7; Dispersed phase size ≤ 0.5μμm; It can be stable for more than l years. It is mainly used as paper softener and anti-sticking agent for highlighter paper.
(3) Lanolin is generally not used alone, because it is an oil-soluble surfactant, the main component is high carbonic acid and high carbon alcohol ester, cholesterol, etc., has excellent lubrication properties, and can be combined with wax and other hydrophilic surfactants to obtain emulsion softener. This kind of softener has been widely used abroad. The hydrophilicity and other properties of lanolin can be improved by polyoxyethylene reaction, making it more suitable for use as paper softener.
④ Emulsified wax can be divided into non-ionic, cationic and anionic types. As a paper softener, cationic products are mainly used. A stable wax emulsion was obtained by adding cationic and non-ionic surfactants to the wax. In order to modify, organic silicone oil and liquid paraffin can be added. The addition of emulsified wax can not only improve the softness, but also improve the smoothness, reduce the friction between the paper and the paper or other substrates, and enhance the water resistance and wet wear resistance of the paper.
Wax latex is a softening agent. Its main composition is non-ionic wax, because it is made of emulsification and dispersion with various surfactants, so the mechanism of action is the same as the above-mentioned, there are anion, cationic, non-ionic, amphotic activity and other softeners.
The production of wax latex can use many kinds of paraffin wax and animal and vegetable oils, according to the preparation of the situation, there are mainly soft, smooth, gloss, or with waterproof, hydrophobic and so on. In addition, there is a low relative molecular weight of oxidized polyethylene wax, and the relative molecular weight of more than 10000 polymer polyethylene, its relative molecular weight is generally about 1500-3000, at the end of the different acid values. It is initially saponified under pressure at high temperature and then emulsified in water with anionic surfactant, cationic surfactant or non-ionic surfactant to make wax emulsion. The ionic properties of this polyethylene wax emulsion depend on the ionic properties of the emulsifier.
Polyethylene wax emulsion softener is characterized by smooth, soft and good luster effect, and has good compatibility with other mixed resins. It can be used as a resin plasticizer and has the effect of preventing the strength of resin processing. In particular, the melting point and hardness of high-density polyethylene wax are higher than that of ordinary waxes, and it is also effective in improving the gloss of paper. Recently, it has been used as a smoothing agent instead of calcium stearate.