Application technology and experience of hot melt adhesive in disposable hygiene products industry
Disposable hygiene products also known as absorbent disposable products include sanitary napkins, pads, diapers, diapers, mattresses, pet pads, etc.
The hot melt adhesives for disposable hygiene products are usually hot melt pressure sensitive adhesives. It is a kind of material based on thermoplastic polymer, which is coated in the molten state, wets the adherent, and can be quickly bonded by applying light pressure after cooling and hardening. The glue does not contain organic solvents, the coating speed is fast, safe and hygienic, so it is widely used in the disposable hygiene products industry.
Common substrates for disposable hygiene products include non-woven fabrics, plastic PE films, toilet paper, spandex (rubber), etc.
Non-woven fabrics for disposable hygiene products include hot-rolled non-woven fabrics, hot air non-woven fabrics, spun-bonded non-woven fabrics, spun-bonded-melt-blown-anti-bonded non-woven fabrics, and chemically bonded non-woven fabrics.
Hot-rolled non-woven fabrics, hot air non-woven fabrics, hydrophilic spun-bonded non-woven fabrics are usually used for surface layer or wrapping layer materials, coarse denier non-woven fabrics and chemically bonded non-woven fabrics are used for the deflector layer; hydrophobic Anti-sticking non-woven fabric is used for bottom film compounding, anti-sticking-melt-blown-anti-sticking non-woven fabric is used for leak-proof, edge-blocking and urine blocking. Non-woven fabric is a kind of porous material, especially for bottom film compounding. Sticky non-woven fabrics and perforated non-woven fabrics are easy to cause glue penetration due to too large amount of glue or compound pressure, and the outer surface of the product becomes sticky. Therefore, in the actual sizing process, the amount of glue, sizing method, and compound pressure must be strictly controlled Process parameters such as hot-rolled and hot-air non-woven fabrics that prevent sticking of staple fibers on the surface of the product while ensuring bonding strength. Hot-rolled non-woven fabrics are difficult to stick to hot air non-woven fabrics. This is because hot air non-woven fabrics are Fluffy fiber mesh structure, the fluffy structure is conducive to the wetting and penetration of hot melt adhesives, and the surface fibers of hot air nonwoven fabrics are more, which increases the interface bonding area. When bonding with other substrates, the surface fibers and the inner layer fibers Form a three-dimensional combination of space, greatly improve the bonding strength, and hot rolling The surface of the woven fabric is smooth and the fiber web is dense, which is not conducive to the infiltration and penetration of the hot melt adhesive. Therefore, it is difficult to stick to the hot air nonwoven fabric and the soft anti-sticking non-woven fabric is difficult to bond compared to the ordinary anti-sticking non-woven fabric. This is because The softening finishing agent is a mineral oil or surfactant containing a linear aliphatic hydrocarbon structure. When the softening agent is adsorbed on the surface of the fiber, the linear aliphatic hydrocarbon parts are neatly arranged outwards, and friction occurs easily Between sliding linear aliphatic hydrocarbon structures, at the same time, the softener will reduce the surface tension of the fiber, reduce the fiber's tendency to accumulate, and make the nonwoven fabric fluffy and jammed, resulting in a soft feel. The linear aliphatic hydrocarbon The structure reduces the friction coefficient of the fiber and reduces the surface tension of the fiber, which makes the wet ability of the hot melt adhesive to the fiber more difficult, so it is difficult to bond.
Plastic PE film
Plastic PE film is divided into air-permeable film and non-air-permeable film. The air-permeable film adds inorganic filler (such as calcium carbonate) to the raw material. During the stretching process, inorganic filler particles (1 ～ 10um) and the plastic film being shaped are basically The pores are separated from each other to form micropores. The size of these micropores is sub-nano level, that is, hundreds of millions of micropores can be distributed per unit area. These micropores form a passage that allows gas to pass through, so that the membrane is breathable and impermeable. Performance, breathable film for sanitary napkins, due to the multi-voids of the breathable base film and the effect of calcium carbonate filler, mineral oil, softeners, plasticizers and other small molecules in ordinary adhesives will penetrate into the breathable film and cause adhesive flow The property deteriorates and loses tack. Therefore, a special adhesive for breathable film must be used. The non-breathable film is formed by extruding and casting PE plastic particles. It has the advantages of high transparency and uniform thickness. The main function is to prevent the body fluids absorbed by the feminine products from seeping, and to maintain the overall condition of the sanitary products. Commonly used non-breathable films are low gram weight micro-embossed cast film (18-25g / m), high gram weight dotted micro-embossed imitation breathable cast film (25-30g / m) plastic PE film with surface tension of 31dyn / cm is a material with a low surface tension. In order to improve the color fastness of the PE film and the ink and the adhesion of the PE film, the film corona treatment is usually required. Corona can make the film surface polar. Molecules, make the surface tension of the film reach 36-38dyn / cm, promote the chemical bond between the surface of the material and the hot melt adhesive, improve the wettability of the hot melt adhesive to the substrate, and thus achieve better adhesion.
The toilet paper is processed by pulp board or wet pulp through defibration, beating, wet part web forming, drying, slitting and other processes. Toilet paper is mainly used to carry or wrap the absorbent core (wood pulp mixed polymer), to maintain the integrity of the absorbent core during production and use, to prevent the absorbent core from breaking and clumping, but also has a certain acceleration of body fluid absorption and Spreading function, disposable hygienic products mostly use high-strength wet-strength paper, which requires good absorption, diffusion performance and certain wet strength between wet-state toilet paper and I paper, and the bonding of toilet paper and non-woven fabric The effect is poor, because the paper fiber is a kind of polyhydroxy cellulose fiber, and its affinity for water is much greater than the affinity of the paper fiber and the hot melt adhesive. In the wet state, water will destroy the interface between the hot melt adhesive and the toilet paper , Resulting in a linear decline in adhesion. Therefore, the bonding of paper and toilet paper, toilet paper and non-woven fabric of the guide layer must use thick glue lines, or use high-humidity hot-melt adhesive, which can reduce the damage of urine or menstrual blood to the bonding interface.
Spandex yarn (rubber band) is used for the leg contraction members, the elastic members at the left and right ends of the leak-proof partition nonwoven fabric, and the leg circumference contraction members ensure that the diapers have a good fit with the human body; the elasticity of the free end of the leak-proof partition nonwoven fabric Components, so that the non-woven fabric with leak-proof side edges can be established to better fit the human body and limit the leakage of liquid from the side of the product. Spandex yarn is a polyurethane circular elastic fiber roll-shaped packaging material, commonly known as Spandex, rubber The rib is a flat elastic box-type packaging material of natural rubber / synthetic rubber. The narrow cross-linking structure of the rubber is a permanent sulfur bridge network structure, so it has a stronger ability to maintain the retractive force than the spandex wire, and the elastic energy loss The advantages are low rate and low oppression. Therefore, in order to improve the processing performance of spandex yarn and avoid the phenomenon of unwinding and broken yarn caused by the high tension of the material in the coil or the aging and stickiness, silicone, mineral oil and other lubricants are usually added before the spandex yarn is wound to improve the processing performance of the elastic. To avoid tangling of the materials in the box, usually adding 1.5% -2.5% of talc, talc, silicone, and mineral oil during the processing of the rubber band will affect the bonding effect of the hot melt adhesive.
Types of hot melt adhesives for disposable hygiene products
(1) Adhesive: The back layer of the sanitary napkin. Its function is to stick the sanitary napkin on the underwear so that it does not move.
(2) Structural adhesive: bonding non-woven fabric / perforated film and PE back film, bonding absorbent paper and non-woven fabric, PE or fluff pulp; bonding elastic waist and PE back film; bonding three-dimensional leak-proof molding; The bonding forms a firm all-round seal, so that the core material is stable and in close contact.
(3) Core glue: It contains a large amount of polymer to ensure the absorption of diapers. After absorbing water, the whole expands. The glue will be flat and will not be flat. It will still maintain its original shape after absorbing liquid.
(4) Elastic rubber: The function of the elastic material is fixed, so that the elastic material is better bonded to the non-woven fabric and the bottom film, and the sanitary products are provided with better personal comfort and better leakage resistance.
(5) Urine gel: Urine gel is a hot-melt adhesive containing PH color-developing agent. It changes from yellow to green when wet.
(6) Left and right waist stickers and front waist stickers: Adhere to the magic buckle without glue and the non-woven fabric of the bottom film, and the non-woven fabric with leak-proof side.
Each batch of Weihai Yingmu Medical Products Co., Ltd. will use a variety of testing equipment for performance inspection before shipment, so that both manufacturers and consumers can use and rest assured. We have accumulated more than ten years of experience, we continue to innovate, we The integrity and quality service of the company have been unanimously affirmed and praised by customers in various industries, and have won excellent business reputation for the enterprise.