Causes and solutions of fluorescence whitening agent yellowing

趙云瑞（新疆碟王針織有限責任公司，新疆烏魯木齊830002)

Zhao Yunrui (Xinjiang diewang knitting co., LTD., urumqi 830002, China)

關鍵詞：熒光增白劑；泛黃點；解決方法

中圖分類號:TS192.24文獻標識碼:B 文章編號：1005-9350(2008)10-0051-02

Key words: fluorescent whitening agent;Yellow point;The solution

Chinese library classification number: TS192.24 Document code: B Article number: 1005-9350(2008)10-0051-02

在生產(chǎn)中為了提高白度，想通過增加增白劑用量來達到目的，結(jié)果不白反而織物泛黃，通過查資料和分析原因，經(jīng)過多次實驗，找到了泛黃點和解決方法

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熒光增白劑的原理

1 Principle of fluorescent whitening agent

熒光增白劑的品種甚多，各種纖維的增白都有一定牌號的增白劑，雖然各種增白劑的化學結(jié)構和性能不同，但對纖維或織物的增白原理都是一樣的。其增白原理主要是由于增白劑的分子中含有共軛雙鍵系統(tǒng)，具有良好的平面性，這種特殊的分子結(jié)構在日光照射下能吸收日光中紫外線（波長為 300~400nm)而發(fā)出藍紫色光（波長為420~500nm)，藍紫色光與纖維或織物上的黃光混合而變成白光，從而使纖維或織物明顯變白。

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用量過多白度反而下降的原因

2  The reason why whiteness decreases

（1）由于織物上黃光的強度是有限的，因此抵消該黃光（主波長在570nm左右）所需要的由熒光增白劑吸收紫外線而發(fā)射出的黃光的補色光——藍紫色光也是有限的。

（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）熒光增白劑的增白作用只是光學上的增亮補色，并不能代替化學漂白，為此不經(jīng)漂白的織物直接用熒光增白劑來增白，其增白效果是不會理想的。

（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）由熒光增白劑的原理可知，增白劑的增白效果主要取決于照射日光中紫外線的含量以及纖維或織物上熒光增白劑的濃度。當照射日光中紫外線的含量充足時，織物上熒光增白劑的濃度在一定范圍內(nèi)變化時，増白效果隨織物上增白劑濃度的增加而增強，發(fā)射的藍紫光強度也增加，從而抵消織物上的部分黃光，織物也隨之越來越白。當增白劑的濃度提高到某一恰當濃度時，其發(fā)射出藍紫光的強度恰好與織物上的黃光強度相等，彼此恰好抵消，其增白效果最佳，可獲得最高的白度值。但若增白劑的用量超過最佳濃度，織物上吸收藍紫色光強度大于抵消織物上黃光的強度時，增白劑所反射出的藍紫光表現(xiàn)得極為明顯，同時因増白劑的各種組成基團不同，所呈現(xiàn)的不同色調(diào)（如青光紫、紅光藍等）也較明顯地表現(xiàn)出來，上述因素綜合作用的結(jié)果，使織物的灰色調(diào)增加，其作用隨之白度下降。

（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)漂白織物當存放的地方有酸或氯等氣體時，含濕量又高，就高吸濕，由于溶解有酸性氣體的水是液態(tài)的，它在附近纖維的親水性基團的分子引力作用下，具有使布面回潮率趨向于平衡的動向，這就是織物泛黃和織物斑點由點擴大成塊、面以及滲化到織物的上下各層的主要原因。

（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）水質(zhì)不純，硬度高或含有重金屬離子，影響增白效果。

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

3增白劑的泛黃點

3 The yellow spots of the whitening agent

增白劑的最佳濃度稱為增白劑的泛黃點。各種熒光增白劑的泛黃點是不同的。例如熒光增白劑DT(用于滌綸)泛黃點為0.8%,即滌綸增白時，用DT增白劑用量超過0.8%時，其白度值隨用量增加而降低；熒光增白劑VBL (用于純棉織物）泛黃點為0.5%;熒光增白劑DCB(用于腈綸增白）泛黃點為0.8%; 熒光增白劑CH(用于腈綸膨體紗）泛黃點為3.3%. BlankophorBBU (液狀,Bayer公司產(chǎn)品，用于純棉織物）泛黃點為1.26%; Uvite ERN—P(CGY公司產(chǎn)品，用于滌綸織物)泛黃點為0.8%; Uvite EBF 250%C漿狀MCGY公司產(chǎn)品，用于滌綸織物)泛黃點為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解決方法

4 Solutions

（1）在生產(chǎn)過程中應采取一系列相應措施，如在煮漂過程中，酸洗后的水洗一定要充分；皂洗要盡量減少皂質(zhì)的殘留；加白時應使用軟水及控制pH 值偏堿性(pH8~9);選用的熒光增白劑應選耐酸性較好的產(chǎn)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)傳統(tǒng)工藝流程是：練漂—熱水洗—過酸—脫氧—水洗。在排液熱水洗后過冰醋酸。冰醋酸是揮發(fā)性酸，滲透能力差，只能中和纖維表面的燒堿,難以滲透到纖維內(nèi)部。尤其是厚重織物，往往在纖維內(nèi)部殘留燒堿。因此改用中和酸，中和酸不僅可以中和纖維表面的燒堿，也能中和纖維內(nèi)部的燒堿，可以達到完全中和的效果。同時過酸的時間和溫度也要嚴格控制，以便中和徹底，因此將過酸時 間由15 min改為30 min。這對質(zhì)量在190 g/m2以上的厚重織物的漂白尤其重要。

（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）陽離子柔軟劑、弱陽離子柔軟劑及普通硅油手感柔軟，都會引起白色織物不同程度的黃變。陰離子柔軟劑一般不會引起黃變，是白色織物的首選。

（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）織物應避免與酸或氯等氣體接觸。

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

（5）應使用軟水。水質(zhì)硬度高，增白效果會下降。水中如含酸、游離氯及銅、鐵等重金屬離子會顯著影響增白效果。

（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）控制熒光增白劑用量。

（6）Control the dosage of fluorescent whitening agent