Related research and discussion on green flame-retardant finishing technology of cotton fabrics
With the improvement of finishing equipment and the increasing research strength, people have higher and higher requirements for the performance of fire retardant agents. Fire retardant agents are required to not only have good fire retardant properties, but also not release a large amount of formaldehyde during finishing and fabric use [3-5]. For this reason, making the finished fabric not only have good fire resistance, but also be green and environmentally friendly is a key issue in current research. Starch has good biodegradability and is widely used in fabrics, food, paper and other industries [6]. By modifying starch with phosphonate, it can be given fire-retardant properties; at the same time, it meets the requirements of green finishing of fabrics. This article mainly discusses the green fireproof finishing of cotton fabrics and determines the best process for green fireproof finishing.
1 Experiment
1.1 Materials and instruments
1.1.1 Fabric
29×29 S boiled and bleached pure cotton muslin.
1.1.2 Drugs
Fire retardant A, homemade; cross-linking agent polyurethane, softener CGF, are all industrial grade, provided by Shanghai Auxiliary Factory.
1.1.3 Instruments and Equipment
YG815 vertical fabric combustion performance tester (Ningbo Fabric Instrument Factory), YG065 electronic fabric strength tester (Wuxi Fabric Instrument Factory), DK-5E dryer (Wuxi Fabric Instrument Factory).
I． 2 Fireproof finishing process
Technology: fabric is dipped in one step, padded twice (padded rate 75-80%), dried (100°C, 2 min), baked (160°C, 3 min), soaped (soap powder 3 g/L, 60℃, 3 min) to dry.
1.3 Test
1.3.1 Fire prevention effect
According to the regulations of GB5455-97, the vertical combustion test method is used to measure the char length of the fabric (the largest length that is burnt) for all fabrics that have been treated with fireproofing, and measured on a vertical combustion tester.
1.3.2 Power
Tested according to GB/T 3923-97 “Test Conditions for Tensile Properties of Fabrics”.
1.3.3 Water resistance test
Clean the sample several times under the conditions of 4O℃, soda ash 2 g/L, and liquor ratio 1:10, then wash with water and dry.
1.3.4 Formaldehyde content
The formaldehyde content of fabrics is tested in accordance with the GB 184O1-2003 standard.
1.4 Preparation of fire retardant agent A
Add equal amounts of sodium hydrogen phosphate and water-soluble starch into the three-necked flask, then add water until the two are completely dissolved, turn on the stirrer, and gradually raise the temperature to about 80°C, react for about 5 hours, and the mixture in the flask That is the product. This experiment is based on phosphonate modification of water-soluble starch, and then using the cross-linking agent polyurethane under certain conditions to cross-link the fire retardant and cellulose to form a network structure, thereby giving the fabric fire-proof properties [ 7]．
2 Results and Discussion
2.1 Orthogonal test
The fire-proof finishing experiment of cotton fabrics adopts the orthogonal design analysis method and adopts the L9 (3rd power of 4) orthogonal table. The experimental factor levels, experimental arrangements and results are shown in Tables 1 and 2. Range analysis is shown in Table 3.
Range is the basis for inferring the primary and secondary relationships between factors affecting experimental results. A large range indicates that the factor is vivid and plays a greater role in the experiment, and its changes have a greater impact on the experimental results; a small range indicates that the factor is conservative and its role in the experiment is small. The change has little impact on the experimental results. It can be seen from the difference value R in Table 3 that the factors affecting the fire prevention effect in descending order are: mass concentration of cross-linking agent > mass concentration of fire retardant > temperature × time > mass concentration of softener. The factors that affect the breaking strength loss rate are in descending order: mass concentration of fire retardant > mass concentration of cross-linking agent > mass concentration of softener > temperature × time. Therefore, in the fireproof finishing of cotton fabrics, the cross-linking agent concentration plays a key role in the fireproofing effect, and the fireproofing agent concentration plays a key role in the fabric breaking strength
The loss plays a more important role. Because under normal conditions, it is difficult for fire retardant A to react directly with cellulose. Only through the cross-linking agent polyurethane can the fire retardant agent be cross-linked on the fabric. Therefore, the concentration of the cross-linking agent determines the amount of N and P elements on the fabric. The main factors, thus affecting the fire protection effect of fabrics. It can be seen from Table 3 that as the concentration of cross-linking agent increases, the carbon length becomes shorter and shorter. When the mass concentration of cross-linking agent is 90 g/L, the fire-proof effect of the fabric is good. If the mass concentration of cross-linking agent is continued to increase, the fire protection effect will be better. sexual decline. This is because the number of hydroxyl groups that can undergo cross-linking reactions on cellulose macromolecules is certain. When the concentration of the cross-linking agent is too high, too much cross-linking agent accumulates on the surface of the fabric, affecting the progress of the cross-linking reaction and resulting in the fire resistance of the fabric. decline. However, the loss of breaking strength shows an increasing trend as the mass concentration of cross-linking agent increases. Therefore, in order to ensure that the finished cotton fabric has sufficient strength and does not affect the wearing performance of the fabric, the mass concentration of the cross-linking agent is selected to be 90 g/L. As the mass concentration of the fire retardant increases, the shorter the carbon length, the better the fire retardant effect. However, as the mass concentration of the fire retardant increases, the breaking strength of the fabric decreases. Therefore, on the premise of ensuring the fire retardant performance of the fabric, the concentration of the fire retardant should be reduced as much as possible, and fire retardant is preferred. The mass concentration of the agent is 250 g/L. The use of softener can improve the feel of the fabric. When the mass concentration of the softener is 9 g/L, it can not only make the fabric have good fire protection effect, but also ensure the fabric’s wearing strength. Therefore.The selected softener mass concentration is 9 g/L.
It can be seen from Table 3 that when the baking temperature is 160°C and the time is 3 minutes, the fire resistance and strength of the fabric can meet the wearing requirements, so the temperature is 160°C and the time is 3 minutes. Therefore, the best process conditions are: fire retardant mass concentration 250 g/L, cross-linking agent mass concentration 90 g/L, softener mass concentration 9 g/L, temperature 160°C, time 3 minutes.
2.2 Fireproofing performance of cotton fabrics after optimal finishing process
Under optimal process conditions (fire retardant mass concentration 250 g/L, cross-linking agent mass concentration 90 g/L, softener mass concentration 9 g/L, temperature 160°C, time 3 minutes), cotton fabrics were processed After fireproofing, the char length of the fabric was measured to be 82 mm, and the breaking strength loss was 29%. Compared with the results in Table 2, the fireproof effect and breaking strength loss of cotton fabrics under this process condition are relatively ideal.
2.3 Water resistance and formaldehyde content of fabrics after optimal processing
After using the best process conditions to finish the samples, wash the samples 5, 10, 15, 20, and 25 times respectively. The fire resistance and formaldehyde content on the fabric are shown in Table 4. It can be seen from Table 4 that the fire-retardant properties of the fabrics have declined after cleaning. After 25 cleanings, the fabrics still have certain fire-retardant properties, indicating that the fabrics treated with this fire-retardant agent have better washability. According to GB 18401-2003 – National Basic Safety Technical Specifications for Fabric Products, the extraction method was adopted to test the formaldehyde content, and the result was 46 mg/kg. This result is much lower than the standard formaldehyde content limit for fabric products in direct contact with the skin (75 mg/kg). kg)．
3 Conclusion
(1) The optimal process conditions for green fireproof finishing of cotton fabrics are: fire retardant mass concentration 250 g/L, cross-linking agent mass concentration 9Og/L, softener mass concentration 9 g/L, temperature 160°C, time 3 mim.
(2) As a cross-linking agent, water-based polyurethane does not produce a large amount of free formaldehyde like other cross-linking agents; at the same time, it can introduce nitrogen elements and use the synergistic effect of P and N to improve the fire resistance of the fabric.
(3) Since the fire retardant is obtained by modifying starch, it can be biodegraded under certain conditions and meets the requirements for functional finishing and cleaning of fabrics.
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