Controlling chemical residues during the wrinkle-resistant finishing process for shirts is a key component in ensuring product safety. The key lies in comprehensive process control, from source screening and process optimization to end-of-line testing. Traditional wrinkle-resistant finishing relies on formaldehyde-containing resins, which enhance fabric stiffness by cross-linking with cellulose molecules. However, as a Class 1 carcinogen, formaldehyde residues can cause allergies, respiratory irritation, and even genetic mutations through skin contact. Therefore, modern processes are gradually shifting towards low-formaldehyde or formaldehyde-free finishing techniques. For example, polycarboxylic acids (such as butanetetracarboxylic acid) and sodium hypophosphite catalysis systems achieve wrinkle-resistant effects through esterification, thereby reducing formaldehyde introduction at the source. Furthermore, the selection of auxiliary reagents requires strict control, such as avoiding the use of catalysts containing heavy metals or surfactants containing APEOs (alkylphenol polyoxyethylene ethers) to prevent secondary contamination.
Precise control of process parameters is key to reducing chemical residues. Wrinkle-resistant finishing typically involves padding, drying, and baking, with baking temperature and duration directly affecting the completeness of the cross-linking reaction. If the temperature is insufficient or the treatment time is too short, the chemical reagents will not fully bond with the fibers, resulting in increased residual amounts. Conversely, over-baking may cause fiber degradation and release more free reagents. Therefore, optimal process conditions should be determined through laboratory tests based on the fabric type (e.g., pure cotton, blended) and the properties of the finishing agent. For example, when finishing a pure cotton shirt with a polycarboxylic acid, the baking temperature is generally controlled between 160-180°C and the treatment time is 90-120 seconds. This ensures wrinkle resistance while keeping residual amounts within a safe range. Furthermore, the pH value of the padding solution must be strictly controlled. Excessive acidity or alkalinity can affect the stability of the reagents and increase the risk of residual amounts.
Washing and post-treatment are crucial steps in removing chemical reagent residues. Finished shirts should be thoroughly washed to remove unreacted reagents through physical rinsing and chemical dissolution. The washing process should adhere to the "multiple small washes" principle, using multiple tanks (usually 3-5 tanks) with a moderate water volume in each tank to prevent the reagents from re-adsorbing onto the fabric surface. Chelating agents (such as EDTA) or oxidizing agents (such as hydrogen peroxide) can also be added to decompose or complex residual metal ions or organic reagents. For sensitive areas (such as collars and cuffs), additional scrubbing or ultrasonic treatment can be used to improve residue removal efficiency. After washing, the fabric's moisture content should be reduced by centrifugal dehydration or vacuum extraction to prevent residual reagents from concentrating during the drying process.
End-of-line testing is the last line of defense to ensure compliance with chemical reagent residue standards. Currently, the detection of formaldehyde residues in textiles is mostly done using acetylacetone spectrophotometry, a colorimetric quantitative analysis. Residues of formaldehyde-free reagents such as polycarboxylic acids require high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS) for precise qualitative and quantitative analysis. Testing standards must strictly adhere to international environmental standards. For example, the EU Oko-Tex Standard 100 stipulates that formaldehyde residues in shirts intended for direct skin contact must not exceed 75 ppm, while those in baby products must be below 20 ppm. Companies should establish internal quality control systems, conduct random inspections of each batch of products, and maintain test records for traceability. The development and application of alternative technologies offer new avenues for controlling chemical reagent residues. For example, bio-enzymatic finishing utilizes the catalytic action of cellulase or transglutaminase to achieve wrinkle-resistant effects by modifying the fiber structure. This process eliminates the need for chemical crosslinkers and eliminates the risk of residual chemicals at the root. Furthermore, nanotechnology is being used to develop environmentally friendly finishing agents. For example, nanosilica, through its physical filling effect, enhances fabric stiffness, combining wrinkle-resistant and antibacterial properties. While still in the promotional phase, these technologies represent future trends in wrinkle-resistant finishing.
Consumer perception and usage habits also influence the actual risk of chemical reagent residues. New shirts should be washed before wearing to remove some surface residual chemicals. Storage should be avoided in high-temperature and high-humidity environments to prevent hydrolysis or volatilization of residual chemicals. For those with sensitive skin, products labeled "formaldehyde-free" or "ecological textile" can reduce health risks.
Control of chemical reagent residues in the wrinkle-resistant finishing process for shirts must be implemented throughout the product's lifecycle. From the screening of alternative reagents, optimization of process parameters, strengthening of post-wash treatment, to rigorous end-of-line testing, every step must be guided by safety. With increasingly stringent environmental regulations and rising consumer health awareness, low-residue, high-performance wrinkle-resistant finishing technologies will become mainstream in the industry, driving the transformation of shirt products towards green and sustainable development.
