Research progress on durable flame retardant finishing of cotton fabrics
Classification:
flame retardant fabric
At present, the durable flame-retardant finishing of pure cottonFlame-retardant fabric mainly includes the British Proban process using tetrahydroxymethylphosphorus chloride (THPC) as the flame retardant and the Ciba-Geigy Switzerland’s process uses N-hydroxymethyl-3-(-methoxyphosphoryl)propionamide as the flame retardant (PyrovatexCP). Both have formaldehyde problems during the finishing and taking process.
With the implementation of regulations in various countries to limit the content of free formaldehyde in production sites and textiles, people have invested a lot of energy in the research of low-formaldehyde and formaldehyde-free flame retardants and cross-linking agents, and some results in this area have been reported in recent years.
1 CottonFlame-retardant fabricResearch progress on flame-retardant
Initial research in this area mainly focused on modifying 2D by replacing or blocking the N-hydroxymethyl group of 2D resin, but this method has not been widely accepted because the substitution or blocking is at the expense of reducing the activity of 2D. . In recent years, reports on the research results of formaldehyde-free or low-formaldehyde flame retardant systems have mainly focused on two aspects, namely, the replacement of formaldehyde-containing flame retardants or cross-linking agents in flame retardant systems. Since the development of polycarboxylic acid technology, promising progress has been made in research on flame retardant systems that use polybasic acids or other formaldehyde-free chemicals to replace the current nitrogen-containing hydroxymethyl compounds, and therefore low-formaldehyde flame retardant systems and formaldehyde-free systems have been proposed. Flame retardant system.
1.1 Low formaldehyde phosphorus flame retardant system
The main results reported on low formaldehydeflame retardant systems are mainly Jeffery K
Stowell et al. [2] and Professor Zhu Ping of Qingdao University [3] respectively used formaldehyde-free flame retardants and formaldehyde-free cross-linking agents to reduce the formaldehyde content of flame retardant systems.
Jeffery K
Stowell et al. used hydroxyl-containing phosphate oligomers to replace the conventionally used formaldehyde flame retardants (CP and THPC). However, since this flame retardant cannot form cross-links with cellulose, it does not react with the nitrogen hydroxymethyl group. Cross-linking agents (melamine resin or 2D resin) are used in combination. This type of cross-linking agent can not only cross-link with the hydroxyl groups of cellulose, but also react with the hydroxyl groups of the flame retardant so that the flame retardant can be fixed on the fiber. Withstand multiple washes.
The flame retardant used in the system is a hydroxyl-containing organic phosphate oligomer, and its structural formula can be expressed as:
Using this flame retardant system, you can directly use the DP finishing equipment of pure cottonFlame retardant cloth without increasing the equipment cost, and reducing the time and consumption during the processing of flame retardant cloth. The formaldehyde content in the process is also reported in the data. At the same time, there will be adverse effects of resin finishing: the flame retardant cloth has a higher strength reduction. The finishing process is as follows:
Two dips and two rollings (rolling residue rate 80%)-drying (60℃, 3min)-baking (160℃, 3min)-40℃ water washing
Formaldehyde-free flame retardants are used in combination with DMDHEU or melamine formaldehyde (MF) cross-linked resins. Three flame retardant systems are studied in the literature: flame retardant/DMDHEU, flame retardant/MF, and flame retardant/MF.
DMDHEU), and studied the stability of the flame retardant and DMDHE system, and found that the flame retardant/DMDHEU finishing fluid can be stably blended 24h, ensuring production use. The flame retardant system based on DMDHEU has lower formaldehyde content and good water washing resistance, while the MF system can give the flame retardant fabric higher initial flame retardant performance and less strength loss. The flame retardant system can be adjusted according to the characteristics of the two cross-linking agents to obtain the desired effect. WeidongWu[4] et al. used a two-factor experimental design method to study formaldehyde-free flame retardant/(MF
DMDHEU), it was found that as the content of DMDHEU in the system increases, the washing resistance of the flame retardantFlame retardant cloth increases, and the strength decreases more seriously, while with the increase of MF As the content increases, the flame retardancy of the flame retardant fabric increases, and the strength decreases slightly. The reason is that [5] there are two N-hemiacetal structures in the DMDHEU molecule, which can react with the hydroxyl groups on the cellulose and the flame retardant, thereby causing cross-linking between the cellulose and the flame retardant. After finishing Flame retardant cloth has better durability. MF contains -NH2 and N-CH2OH, which can cross-link each other. According to the data, in the flame retardant/MF system, most of the MF reacts with the hydroxyl group of the flame retardant or undergoes a white cross-linking reaction. Both DMDHEU and MF can act synergistically with the phosphorus element in flame retardants as nitrogen sources, but in comparison, MF is a better nitrogen source, so the synergistic effect of the flame retardant/MF system is more obvious, and the flame retardant Better results. Pyrovatex developed by Ciba-Geigy, Switzerland
CP flame retardant is a reactive flame retardant used in cellulose fiber Flame retardant cloth. It promotes cross-linking and enhances flame retardant durability during the finishing process. It is necessary to use N-hydroxymethyl cross-linking agent. After flame retardant finishing, it has high durability and reduces the risk of fire.However, both flame retardants and cross-linking agents will produce formaldehyde problems during the finishing and taking processes. In order to solve the formaldehyde problem in this flame retardant system, Professor Zhu Ping of Qingdao University used polycarboxylic acids as cross-linking agents instead. Conventional N-hydroxymethyl cross-linking agent. It is then baked at high temperatures in the presence of a catalyst to form covalent cross-links to achieve durable flame retardancy. The finishing process used in this system is: padding (two dips and two rollings, the padding rate is 100%) – drying (100℃, 3min) – baking (180℃, 3min) – water washing (cold water rinse), using this This method is introduced in the data [3]. This flame retardant system has good flame retardant effect and can meet the flame retardant requirements of textiles. The free formaldehyde content of flame retardant fabrics has been reduced from 1200mg/kg to 200mg/kg, and the flame retardant and The dosage of cross-linking agent is low, which can save costs. These two methods reduce the formaldehyde content caused by the original flame retardant system, but still cannot avoid the formaldehyde problem. The first system uses a formaldehyde-containing cross-linking agent, while the flame retardant used in the second flame retardant system is still Contains formaldehyde, so it does not completely solve the formaldehyde problem of Flame Retardant.
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