Overview of the types and functions of common additives for spandex

Spandex production, polyether polyol spandex, MDI and PTMEG belong to the main raw materials, DMAC is recyclable solvent, strictly speaking, in addition to these three substances other materials are auxiliary materials, mainly including amines, alcohol-based chain extenders, and a variety of additives to improve the physical properties of fibers, spandex with a wide range of additives, this article will briefly introduce a few.

1. Anti-yellowing agent (HN-150)

As the spandex molecular chain contains a large number of reactive groups such as amino groups, it is easy to turn yellow during high temperature setting or storage and use, which affects the quality of finished products, especially fluorescent whitening fabrics or light-colored fabrics.

At the same time, in order to improve the spinning performance of spandex, silicone oil-based lubricants and other additives used in the weaving process will naturally degrade over time, causing the fiber to turn yellow.

Again, conventional dyes are not easy to make spandex colorful, so after fabric dyeing and reduction, the yellowing phenomenon will also occur if the reducing agent is not cleaned sufficiently.

2. Matting agent (titanium dioxide)

In general, spandex fibers (including other chemical fibers) have a strong luster on the surface, these luster sometimes rather affect the appearance of the fabric, improve the method is generally in the spinning before the matting agent into the spinning solution or melt, by spinning molding, so that the fiber scattered light and eliminate the luster, reduce transparency, increase whiteness (such as spandex this white silk), with light, matting, semi-matting, etc. are relatively speaking, according to process requirements, add the right amount of matting agent.

Matting agent is generally used titanium dioxide, the particle size range of most of the 1μm or less, matting agent concentration is mostly between 0.03-2%, the concentration of matting agent contained in elastic fiber can be as high as 4%.

Titanium dioxide matting agent content on the fiber polymer performance, the degree of wear and tear of equipment, the use of filter components cycle, spinning breakage rate, the physical and mechanical properties of the fiber have a certain degree of influence.

3. Antioxidants (antioxidant 1790, antioxidant 245, antioxidant GA-80, etc.)

Due to the characteristics of the molecular structure of spandex and the higher temperature requirements of the dry spinning production process, it is necessary to add stability additives for heat and oxygen aging in the production process to meet the requirements of users.

The addition of antioxidants can also overcome the spandex and its blends in the process, such as high temperature heat setting process due to exposure to a variety of heat sources in the fabric yellowing and fading of light-colored fabrics.

In the fabric storage and use process due to exposure to phenols and other chemical components and air ozone, nitrogen dioxide under the effect of yellowing phenomenon, antioxidants can also be inhibited to a certain extent.

4. Lubricant (magnesium stearate)

MG is mainly used as anti-caking agent, emulsifier, release agent, lubricant and stabilizer, etc. Adding MG in spandex production can reduce the surface friction of finished yarn and improve the rewinding performance of the cartridge yarn.

The content of magnesium stearate directly affects the surface friction performance of spandex yarn, relative to the finished yarn, each ton of finished products need to add MG 1.5-3kg, at the same time, the content of MG is related to the number of spider silk, experiments have shown that the original liquid MG content in the range of 0.2-0.5%, the number of spider silk and MG additive positive correlation, although reducing MG can reduce the incidence of spider silk Although reducing MG can reduce the incidence of spider silk, but also affects the operability of spinning, in general, its content in about 0.3% is more appropriate.

5. Metal chelating agent (diethylenetriamine)

Diethylenetriamine (DETA) is special in that it is not only used as an additive to improve the physical properties of spandex yarn, but also as a chain extender/crosslinker. The reason why it is included in the additive issue is that some spandex production processes explicitly require DETA to be used as an additive along with other auxiliaries, rather than added at the chain extender stage.

Some organic raw materials and auxiliaries used in the production of spandex (magnesium stearate, titanium dioxide, etc.) can contain small amounts of metal ions, in addition, the equipment and piping in the production process can also bring metal ions to the polymer. The presence of these metal ions can affect the normal reaction of the polymer, so metal chelators are needed to deal with the metal ions and thus improve the stability of the polymer.

Diethylenetriamine (DETA) contains an amino functional group, and the lone pair of electrons on the nitrogen atom has a certain chelating ability to metal ions, which can encapsulate metal ions inside the diethylenetriamine and turn it into a stable compound, thus preventing the metal ions from acting.

6. Other common additives

Spandex with a variety of additives is really more, space limitations, it is impossible to introduce one by one, like a certain alkyl amino alcohol and diisocyanate polymer DMAC solution, is a multi-functional spandex fiber additives, not only with spandex fibers have excellent compatibility with the anti-yellowing agent, but also can effectively improve the dyeing performance of spandex, spandex fiber dyeing fading has a significant inhibitory effect; there is a certain anionic succinate used to enhance the grip and adhesion between the spandex yarn; there are additives used to improve the chlorine resistance of spandex, etc.

7. Notes on the use of additives

Most additives have water absorption, storage and use process, to do a good job of drying, moisture-proof measures to avoid deterioration affect the quality of fibers, damage or moisture to stop using.

Additives in the use of full dispersion, grinding, the particle size to meet the process requirements, such as magnesium stearate and titanium dioxide are not soluble in DMAC, its dispersion is unstable, will sink after a long time, so the need for continuous stirring to ensure uniform distribution of the dispersion, this piece involves the additive process, we have the opportunity to talk again.

Due to the high processing temperature of spandex production process, it is required to add a variety of additives, especially antioxidants, anti-yellowing agents and other stabilizers must have good resistance to high temperature volatility and solvent extraction, to prevent its loss in the process of use because of heat volatilization or with DMAC from spandex yarn is extracted, resulting in reduced effectiveness.

In short, most of the spandex additives are used to improve the fiber such as anti-yellowing properties, anti-oxidation properties and other shortcomings of their own, generally have a variety of roles, in the production of general also used in conjunction with, and not a single use, according to the different process formulations, adjust the different additive ratio.