Flame retardant process and modification method of polyester fiber
1 polyester fiber flame retardant process
For flame retardant polyester fibers, usually divided into two main process, first choose and develop good flame retardant performance, and then by physical or chemical method of adding flame retardant to the fiber spinning raw material, make the flame retardant achieve strong uniform distribution in the fiber, and the introduction of the flame retardant effect on the physical and mechanical properties of the fiber is not as much as possible.
2. Method of fiber modification
At present, there are four main methods to modify flame retardant fiber:
2.1 Copolymerization flame retardant modification
Containing flame retardant elements, mainly phosphorus, halogen (I, Br, Cl, F), sulfur and other small molecular flame retardant as a copolymer to participate in the polymerization process of fiber polymer, the flame retardant combined into the polymer macromolecular chain, to achieve a long-term flame retardant effect. The copolymerized flame retardant must be suitable for polymerization under high temperature conditions, with good stability, no decomposition, no side reactions, etc.
2.2 Blend flame retardant modification
Method of spinning flame retardant fibers by adding flame retardant to spinning melt or solution. Flame retardants have low molecular compounds, used in polymer or inorganic substances and their mixture, flame retardant can stand to the requirement and the melt blending melt spinning of high temperature and with the principal part of the compatibility of polymer is good, does not affect the spinning processing, the influence of the physical and mechanical properties of the fiber is not big, good flame retardant performance durability.
2.3 Grafting flame retardant modification
Fiber graft copolymerization is an effective and durable flame retardant modification method, such as the application of high energy radiation graft flame retardant modification.
2.4 Finish after flame retardant
A modified method of making fibers or fabrics with flame retardant properties by immerSING them in water or other solvents dissolved in flame retardant, and then by pressing, drying, etc.
3. Enumerate the production methods of flame retardant polyester filament
3.1 Section Drying
The melting point and maximum crystallization temperature of flame retardant polyester chip are lower than those of ordinary polyester chip, but the apparent viscosity is higher than that of ordinary polyester chip. If ordinary polyester slice drying process, flame retardant slice is prone to adhesion, agglomeration, yellowing, unable to normal production. Therefore, the drying process temperature of flame retardant slice should be controlled lower, longer and higher air volume. At the same time, the vibration intensity is increased, so that the flame retardant section has a good boiling effect on the boiling bed, in order to break up the adhesive particles. Actual process control: pre-crystallization temperature 148℃, drying temperature 155℃, air volume 8.5 m3/h, drying time more than 12 h, flame retardant section drying effect is good, viscosity of 0.621, water content of 1.8×10-5. In the production, attention should also be paid to: when the initial feed is fed, the precrystallization temperature should be controlled lower than 140℃, pay attention to observe the boiling situation of the pre-crystallization section, adjust the reasonable dosage, strictly control the heating rate, and reduce the section agglomerate.
3.2 Spinning temperature
The melting point of flame retardant chips is lower than that of ordinary polyester chips, so the spinning temperature control should be lower than that of PET chips. However, the flame retardant section is mixed with flame retardant, which weakens the activity of macromolecular chain and increases the apparent viscosity of melt, so the melt fluidity is poor. Too low spinning temperature easily causes the spinneret assembly to bear too high melt pressure, but too high temperature will cause the rapid thermal degradation of the flame retardant polyester with poor heat resistance.
3.3 Cooling forming
Compared with ordinary fiber, the crystallization rate of flame retardant fiber is obviously accelerated when flame retardant is added. Therefore, the cooling conditions should be appropriately strengthened, which is conducive to improving the mechanical properties of the flame retardant fiber, but the wind speed should not be too large, because too much will cause the wire to oscillate, which will increase the unevenness rate of the wire.
Four, the development trend of flame retardant polyester fiber
1. Functional integration
Functional COMPOUND IS A NEW DEVELOPMENT TREND OF FUNCTIONAL FIBER, which aims to broaden THE application field OF the original single functional fiber, increase the added value of the product, and enhance the market competitiveness of the product. Its varieties include: flame retardant + cation, flame retardant + antibacterial, flame retardant + hygroscopic and so on.
2. High technology
The FLAME RETARDANT POLYESTER/INORGANIC NANOCOMPOSITES CAN NOT ONLY REACH THE FLAME retardant level required by many applications, but also maintain or even improve the original excellent properties of polyester, which makes this compound flame retardant polyester and fiber have a broad and attractive development prospect.
3. The green
The greenization of flame retardant fiber means to reduce the toxic effect of the production process on the environment and operators, and to prevent the adverse effect of the fiber on the wearer. Because the flame retardant used in flame retardant fiber generally contains halogen, phosphorus, sulfur and other elements have greater toxicity. When a fire occurs, there will be no "secondary poisoning". At present, the production process of flame retardant fiber which is beneficial to environment and daily use includes: composite spinning method of skin and core, flame retardant microcapsule method.