在生产中为了提高白度，想通过增加增白剂用量来达到目的，结果不白反而织物泛黄，通过查资料和分析原因，经过多次实验，找到了泛黄点和解决方法。

In order to improve the whiteness of the production, we want to increase the amount of whitening agent to achieve the goal, but the result is not white but yellowing fabric, through checking the data and analyzing the reasons, after many experiments, we found the yellowing point and solution.

1、荧光增白剂的原理

1、 Principle of fluorescent whitening agent

荧光增白剂的品种甚多，各种纤维的增白都有一定牌号的增白剂，虽然各种增白剂的化学结构和性能不同，但对纤维或织物的增白原理都是一样的。其增白原理主要是由于增白剂的分子中含有共轭双键系统，具有良好的平面性，这种特殊的分子结构在日光照射下能吸收日光中紫外线（波长为 300~400nm)而发出蓝紫色光（波长为420~500nm)，蓝紫色光与纤维或织物上的黄光混合而变成白光，从而使纤维或织物明显变白。

There are varieties of fluorescent whitening agent, whitening of various fiber need different brand of whitening agent, although the chemical structure and properties of various whitening agent is different, but the whitening principle of fiber or fabric is the same. The principle of whitening is mainly due to the whitener molecules containing a total of conjugate double bond system, good flatness, the special molecular structure under the sunlight can absorb sunlight, ultraviolet light (wavelength of 300 ~ 400nm) and violet light (wavelength of 420 ~ 500nm), or violet light and fiber mixed with the yellow light on the fabric into a white light,Thus the fiber or fabric becomes noticeably white.

2、用量过多白度反而下降的原因

2 、 The reason why whiteness decreases

1.由于织物上黄光的强度是有限的，因此抵消该黄光（主波长在570nm左右）所需要的由荧光增白剂吸收紫外线而发射出的黄光的补色光——蓝紫色光也是有限的。

1.Since the intensity of yellow light on the fabric is limited, the complementary color light -- blue and purple light -- emitted by fluorescent whitening agent absorbing ultraviolet light is also limited to offset the yellow light (the main wavelength is about 570nm).

2.荧光增白剂的增白作用只是光学上的增亮补色，并不能代替化学漂白，为此不经漂白的织物直接用荧光增白剂来增白，其增白效果是不会理想的。

2.The whitening effect of fluorescent brightener is only optical brightening and complementing, and cannot replace chemical bleaching. Therefore, the whitening effect of fluorescent brightener is not ideal for the fabric without bleaching.

3.由荧光增白剂的原理可知，增白剂的增白效果主要取决于照射日光中紫外线的含量以及纤维或织物上荧光增白剂的浓度。当照射日光中紫外线的含量充足时，织物上荧光增白剂的浓度在一定范围内变化时，増白效果随织物上增白剂浓度的增加而增强，发射的蓝紫光强度也增加，从而抵消织物上的部分黄光，织物也随之越来越白。当增白剂的浓度提高到某一恰当浓度时，其发射出蓝紫光的强度恰好与织物上的黄光强度相等，彼此恰好抵消，其增白效果最佳，可获得最高的白度值。但若增白剂的用量超过最佳浓度，织物上吸收蓝紫色光强度大于抵消织物上黄光的强度时，增白剂所反射出的蓝紫光表现得极为明显，同时因増白剂的各种组成基团不同，所呈现的不同色调（如青光紫、红光蓝等）也较明显地表现出来，上述因素综合作用的结果，使织物的灰色调增加，其作用随之白度下降。

3.According to the principle of fluorescent whitening agent, the whitening effect of whitening agent mainly depends on the UV content in the sunlight and the concentration of fluorescent whitening agent on fiber or fabric.When the UV content is sufficient, the fluorescence whitening agent concentration on the fabric changes within a certain range, and the whitening effect increases with the increasing of the whitening agent concentration on the fabric, and the blue violet light intensity also increases, so as to offset some yellow light on the fabric, and the fabric becomes whiter and whiter.When the concentration of whitening agent increases to a certain proper concentration, the intensity of blue violet light emitted by it is exactly the same as the intensity of yellow light on the fabric, which exactly cancels each other, and the whitening effect is the best, and the whiteness value is the highest.But if increasing the dosage of white agent than optimal concentration, the fabric on the absorption of violet light intensity degrees more than offset the fabric on the strength of the yellow light, is an obvious whitening agent blue violet light reflected by, at the same time due to the raised all sorts of white agent group into different groups, different shades of the rendered (such as green light purple, red, blue, etc.) are clearly shown, a result of the combined action of the above factors, the increase of gray fabric, its whiteness subsequently decline.

4.漂白织物当存放的地方有酸或氯等气体时，含湿量又高，就高吸湿，由于溶解有酸性气体的水是液态的，它在附近纤维的亲水性基团的分子引力作用下，具有使布面回潮率趋向于平衡的动向，这就是织物泛黄和织物斑点由点扩大成块、面以及渗化到织物的上下各层的主要原因。

4.When there is acid or chlorine gas in storage places of the bleached fabric , the moisture content is high, it is easy to absorb water, due to the water is liquid, Under the molecular attraction of hydrophilic groups ,It has the tendency that the moisture regain of cloth cover tends to balance, this is the reason why fabric yellowing and expand into pieces, fabric spot by point and bleeding in the upper and lower layers of fabrics.

5.水质不纯，硬度高或含有重金属离子，影响增白效果。

5.Impure water quality, high hardness of water or heavy metalions may affect the whitening effect.

3、增白剂的泛黄点

3、 The yellow spots of the whitening agent

增白剂的最佳浓度称为增白剂的泛黄点。各种荧光增白剂的泛黄点是不同的。例如荧光增白剂DT(用于涤纶)泛黄点为0.8%,即涤纶增白时，用DT增白剂用量超过0.8%时，其白度值随用量增加而降低；荧光增白剂VBL (用于纯棉织物）泛黄点为0.5%;荧光增白剂DCB(用于腈纶增白）泛黄点为0.8%; 荧光增白剂CH(用于腈纶膨体纱）泛黄点为3.3%. BlankophorBBU (液状,Bayer公司产品，用于纯棉织物）泛黄点为1.26%; Uvite ERN—P(CGY公司产品，用于涤纶织物)泛黄点为0.8%; Uvite EBF 250%C浆状MCGY公司产品，用于涤纶织物)泛黄点为3%。

The optimum concentration of whitening agent is called the yellowing point of whitening agent.The yellowing spots of various fluorescent brighteners are different.For example, the yellowing point of fluorescent whitening agent DT(used for polyester) is 0.8%, that is, when the amount of DT whitening agent exceeds 0.8%, its whiteness value decreases with the increase of the amount.The yellowing point of fluorescent whitening agent VBL (used for pure cotton fabric) was 0.5 %.The yellowing spot of fluorescent whitening agent DCB(used for whitening acrylic fiber) was 0.8%.The yellowing point of fluorescent whitening agent CH(used for acrylic bulked yarn) is 3.3 %. BlankophorBBU (liquid,Bayer products, for pure cotton fabrics) had a yellowing point of 1.26%; Uvite ERN -- P(a product of CGY company used in polyester fabric) has a yellowing point of 0.8%; Uvite EBF 250 %C pulp MCGY products, used in polyester fabrics) yellowing point of 3 %.

4、解决方法

4、 Solutions

1.在生产过程中应采取一系列相应措施，如在煮漂过程中，酸洗后的水洗一定要充分；皂洗要尽量减少皂质的残留；加白时应使用软水及控制pH 值偏碱性(pH8~9);选用的荧光增白剂应选耐酸性较好的产品，如Uvitex RT、CF、BT(汽巴-嘉基公司）；Tinopal2B、SP (汽巴-嘉基公司），Leucophor B (山德士公司）；BlankophorBBU(拜耳公司）等。

1.A series of corresponding measures should be taken in the production process, such as in the process of boiling and bleaching, the wash after pickling must be sufficient;Soaping to minimize the residue of soap; Soft water should be used to whiten and the pH value should be alkaline (pH8~9).The fluorescent whitening agent should choose products with good acid resistance, such as Uvitex RT, CF, BT(ciba -jiagi company);Tinopal2B, SP (ciba -jiaggi), Leucophor B (sandex); BlankophorBBU (Bayer, inc.), and so on.

2.传统工艺流程是：练漂—热水洗—过酸—脱氧—水洗。在排液热水洗后过冰醋酸。冰醋酸是挥发性酸，渗透能力差，只能中和纤维表面的烧碱,难以渗透到纤维内部。尤其是厚重织物，往往在纤维内部残留烧碱。因此改用中和酸，中和酸不仅可以中和纤维表面的烧碱，也能中和纤维内部的烧碱，可以达到完全中和的效果。同时过酸的时间和温度也要严格控制，以便中和彻底，因此将过酸时 间由15 min改为30 min。这对质量在190 g/m2以上的厚重织物的漂白尤其重要。

2.The traditional process is: scouring and bleaching - hot water washing - acid - deoxidation - water washing.Glacial acetic acid was washed after hot water.Glacial acetic acid is Volatile acid, poor permeability, can only neutralize the caustic soda on fiber surface, it is difficult to penetrate into the fiber interior.Especially thick fabrics, often leave residual caustic soda in the internal fiber .Therefore, neutralizing acid can not only neutralize caustic soda on the surface of the fiber, but also neutralize caustic soda inside the fiber, so that the effect of complete neutralization can be achieved. Meanwhile, the time and temperature of over-acidity should be strictly controlled so as to completely neutralize. Therefore, the time of over-acidity should be changed from 15 min to 30 min.This is especially important for bleaching heavy fabrics with a mass of 190 g/m2 or more.

3.阳离子柔软剂、弱阳离子柔软剂及普通硅油手感柔软，都会引起白色织物不同程度的黄变。阴离子柔软剂一般不会引起黄变，是白色织物的首选。

3.Cationic softener, weak cationic softener and ordinary silicone oil can cause different degrees of yellowing of white fabrics.Anion softener generally does not cause yellowing and is preferred for white fabrics.

4.织物应避免与酸或氯等气体接触。

4.The fabric should avoid contact with acid or gases such as chlorine .

5.应使用软水。水质硬度高，增白效果会下降。水中如含酸、游离氯及铜、铁等重金属离子会显著影响增白效果。

5.Soft water should be used.High water hardness will decline whitening effect. Acid, free chlorine and heavy metal ions such as copper and iron in water can significantly affect the whitening effect.

6.控制荧光增白剂用量。

6.Control the dosage of fluorescent whitening agent.