Vinylon
Vinylon is the trade name of polyvinyl acetal fiber, also called the abbreviation of vinylon, English Vinylon or Vinalon. Its performance is close to that of cotton, and it is known as “synthetic cotton”. It is the most hygroscopic variety among existing synthetic fibers. There are fewer pure fibers, and they are mostly blended or interwoven with other fibers.
The development of vinylon
Vinylon was made in Germany in the 1930s, but it is not resistant to hot water and is mainly used for surgical sutures. In 1939, the heat treatment and acetalization methods were successfully researched, making it a fiber with good resistance to hot water. The raw materials for producing vinylon are easily available, the manufacturing cost is low, and the fiber strength is good. In addition to being used in clothing, it also has a variety of industrial uses. However, due to its long industrial production process, the comprehensive fiber performance is not as good as polyester, nylon and acrylic fiber, and the annual output is small, ranking fifth among synthetic fiber varieties.
Production of vinylon
The main component of vinylon is polyvinyl alcohol, but vinyl alcohol is unstable and generally uses stable vinyl alcohol acetate (i.e. vinyl acetate) as the monomer. Polymerize, and then hydrolyze the generated polyvinyl acetate to obtain polyvinyl alcohol. After spinning, it is treated with formaldehyde to introduce a six-membered ring structure into the polymer chain to generate polyvinyl formal to enhance its strength. Only in this way can you get vinylon that is resistant to hot water.
Before decomposition, polyvinyl alcohol has no obvious molten state, so solution spinning is used, and wet spinning using water as the solvent is often used. Preparation of polyvinyl alcohol acetalized fiber The process includes the preparation of spinning solution, spinning and finishing
Preparation process
Preparation of spinning solution: Dissolve the washed and refined polyvinyl alcohol at 80~90℃ A spinning solution with a concentration of 15% to 16% is made in hot water.
Spinning: The spinning solution is pressed out from the spinneret and solidified into fibers in the coagulation bath. Coagulants commonly use ammonium sulfate and other electrolyte solutions with strong dehydration capabilities.
The shape and structure of vinylon
Longitudinal straight, with 1 to 2 grooves,
The cross-section is kidney-shaped and has an obvious skin-core structure.
Characteristics of vinylon
1) Hygroscopicity: good (WK=5%), good sweat-absorbing and moisture-permeable properties.
2) Warmth retention: better than cotton. Similar to wool, it is easy to wear as winter clothes.
3) Strength: The wear resistance is better than cotton. But less flexible.
4) Dyeability: poor, can only dye dark colors.
5) Acid and alkali resistance: Good chemical stability, no quality change occurs in acid, alkali, oil and other solutions.
6) The hot water resistance is not good enough, the elasticity is poor, and the dyeability is poor.
Identification
It is not easy to ignite. It melts and shrinks near the flame. There is a little flame at the top when burning. When the fibers are melted into a gel, the flame becomes larger, with thick black smoke and a bitter smell. , small black bead-like particles remain after burning, which can be crushed with your fingers.
Dyeing process of vinylon
It is difficult to dye dark colors with vinylon, and the dyeing color is darker and the phenomenon of “white core” is prone to occur. There are hydrophilic hydroxyl groups and hydrophobic acetal groups on the macromolecules of vinylon fiber, so it has varying degrees of affinity for most dyes. If the dyes can be screened during dyeing, and a variety of dyes can be dyed in one or two baths in the same bath, the white core phenomenon can be overcome and deep colors can be obtained.
The following is a brief introduction to the application of different dyes in vinylon dyeing.
①
Choose direct dyes with fewer sulfonic acid groups and more amino groups in their molecular structure. Because the former has high water solubility and low directivity, while the latter is just the opposite. Practice has proved that when dyeing vinylon with direct dyes, the dosage should generally be controlled at about 1% (owf). At this time, the color yield is higher than that of cotton.
② The color fastness of vat dyes is relatively high. When dyeing vinylon, it is advisable to use products with an indigo structure. The dye uptake rate of indanthrene with anthraquinone structure is more ideal to a certain extent.
The dyeing method is similar to dyeing cotton, but there are a few points to note:
The amount of sodium hydroxide used is reduced by 1/3 compared with dyeing cotton;
Dyeing The temperature can be appropriately higher, especially for method A and special method reduction dyeing;
The dyeing time should be extended to 30 to 40 minutes to ensure thorough dyeing;
After dyeing, 1 ~2
g/L hydrogen peroxide oxidizes, but the dye is alkaline. If too much hydrogen peroxide is used and the oxidation reaction is violent, it will be over-oxidized, causing the vinylon fiber to turn yellow, and even break the macromolecular chain of vinylon and reduce the strength of the fiber.
③
Dyeing vinylon with sulfurized and sulfurized vat dyes has more disadvantages than advantages. First of all, since sodium sulfide needs to be added during dyeing, the dye bath is too alkaline. If the dyeing temperature is high, the finished product will feel hard and the color will be reddish. If you add 2~3g/
L ammonium sulfate can moderate the alkalinity, improve dyeing strength, and reduce fiber damage; adding non-ionic surfactants, such as Pingping O, can also prevent the color from turning red.
Secondly, sulfur dye alone cannot dye deep colors. For example, when dyeing black, be sure to mix sulfide reduction black CLN (deserved element GLN), reduce sodium sulfide by 1/2, and add ammonia (alkali agent) and reducing agent (preferably thiourea dioxide) to the dye bath. ).
Practice has proven that this is better than using sodium sulfide alone. Finally, sulfur dyes are not easily oxidized on vinylon. If they are to be fully oxidized,, it is necessary to add acetic acid and sodium or potassium dichromate, but there will be environmental problems. Therefore, in fact, sulfur dyes are rarely used to dye vinylon.
④
Reactive dyes dye vinylon with better color brightness, but the color yield of any reactive dye on vinylon is lower than that on cotton. This is mainly because vinylon has fewer groups that can react with reactive dyes than cotton. In order to further improve the brightness of reactive dyes such as pink, snow blue, sky blue and other colors, 0.2% to 0.3% can be added
The whitening agent VBL enhances the brightness.
⑤ It is very common to dye vinylon with neutral dyes (1:2 metal complex dyes). Commonly used foreign dyes include Lanasyn, Irgalan, Cibalan, Vialon,
Capracyl, Isolan, etc.; domestically produced ones include dark yellow GL, GRL, dark brown BRL, gray 2BL, purple BL, jujube GRI, peach red RL, etc. When dyeing vinylon with neutral dyes, except for slightly poor heat and washing fastness, the light fastness and other color fastness are ideal.
When starting dyeing, it should be carried out in a neutral or weakly alkaline medium, as color flowers will not easily appear. The maximum dyeing temperature should be controlled at 90°C. Generally, 1 should be added after 40 minutes of heat preservation dyeing.
mL/L acetic acid to make the dye bath slightly acidic; continue dyeing for 15 to 20
min to allow the dye to be fully absorbed. It must be pointed out that the metal ions contained in metal complex dyes, such as Cr, Cu, Ni, Co, etc., are restricted in use to varying degrees due to environmental regulations. Therefore, they should be used as little or as little as possible in practice. . If it must be used, the dye uptake rate should also reach more than 93%. Especially after dyeing small or medium samples of export products, it is necessary to first check whether the metal ions exceed the standard. In particular, chromium ions must be strictly controlled to less than 1
mg/kg.
In addition, neutral dyes with the word “Brilliant” in their names, such as brilliant blue GL, are not metal complex dyes. They are selected from acid dyes for wool and are only used for color matching and brightening, so their application performance is slightly different from metal complex dyes.
⑥ Disperse dyes are hydrophobic dyes and are easy to dye vinylon. The most suitable ones are monoazo low- and medium-temperature dyes, which can be dyed at 95°C and do not need to add carriers to promote dyeing.
⑦
Basic dyes (positively charged) can form salt bonds with the terminal carboxyl groups in vinylon. Practice has proved that when dyeing vinylon with alkaline dyes, the color is not only bright, but also free of “white core” phenomenon. It can be used for color matching or mixed with other dyes.
Applications of vinylon
Vinylon is soft and warm. Its relative density is smaller than cotton, so more clothing can be woven with the same weight of vinylon as cotton. It has low thermal conductivity and therefore good warmth retention. The abrasion resistance and strength of vinylon are also better than cotton, so vinylon can be blended with cotton in many ways to save cotton. Vinylon is mainly used to make knitted fabrics such as outerwear, cotton sweaters, sweatshirts, etc. It can also be used in canvas, fishing nets, surgical sutures, bicycle tire cords, filter materials, etc.
The main varieties of vinylon fabrics are
1) Vitamin/Viscose Gabardine
Also known as Vitamin/Viscose Dongfeng, it is made of 50% vinylon and 50% Wool type viscose fiber blended yarn. Woven by a 2/2 twill weave, it has the same front and back sides. The texture is thick and tight, tough, durable and similar to wool gabardine but has a better luster than wool. It is suitable for making coats
2) Dimensions/ Viscose Veridin
Using vinylon and wool-type viscose for plain weaving, the resulting Veridin-style fabric is usually woven with a vinylon/artificial wool ratio of 70/30 or 50/50, and has a thick fabric It is characterized by durability or tightness and thinness, but its disadvantages are large shrinkage and poor heat resistance. Mostly used as mid-to-low-end summer clothing.
Vinyl cement cable pipe
As a new generation of high-tech pipes, vinylon cement cable pipe is not used in many fields, but it is highly adaptable and its typical application areas are mainly There are five categories: (1) Urban power grid construction and renovation projects. (2) Urban municipal reconstruction projects. (3) Civil aviation airport project construction. (4) Industrial park and community project construction. (5) Traffic road and bridge engineering construction.
Vinyl cement cable pipe has become the leader in the laying of some national-level buildings. Vinyl cement cable pipe has eliminated the traditional cement protective pipe and added more protective vinylon. After the integration of these two Can make the protection of cables better
Water-soluble vinylon filament is widely favored
Vinyl fiber is a valuable functional differentiated fiber, and water-soluble vinylon fiber It is a special variety of vinylon, divided into two categories: filament and short fiber. Among them, water-soluble vinyl filament is the ideal water-soluble fiber. Water-soluble dimensional filament not only has an ideal water-soluble temperature and strong elongation, which can range from 0 to 100°C, but also has good acid and alkali resistance and dry heat resistance. When dissolved in water, it is odorless and non-toxic, and the aqueous solution is non-toxic. The color is transparent and can be naturally biodegraded in a short period of time
