**2.5 Light fastnesses improvement**

104 Natural Dyes

Table 1 shows dyeing fastness of the flame retardant polyester fibers along with the contents

conent(wt%) Washing Rubbing Sublimation Light

Normal PET(0.3%) 3~4 4~5 4~5 5

Among dyeing fastnesses, rubbing and sublimation fastness showed similar trend with Normal PET, but washing fastness was better than Normal PET, light fastness was lower

It is assumed that washing fastness is related to chain mobility of polyester polymer caused by the difference of glass transition temperature. Flame retardant polyester fiber has lower glass transition temperature than normal PET. Therefore, it has better chain mobility than normal PET, and the uptake of the dyestuff at the same temperature is higher than that of

Decrease of light fastness is assumed that the influence of photocatalytic activity of titanium dioxide above mentioned. Under the same condition, light fastness using azo disperse dyestuff has 3~4 grade of level which is somewhat better than that using anthraquinone disperse dyestuff, but the dyeing fastness of the flame retardant polyester fiber shows still

We can see the dyeing fastnesses are almost same level of flame retardant polyester and

The effect of phosphorous content in the flame retardant polyester on Light fastness was conducted by varying the phosphorous contents in the polymer(deluster contents are same

(wt%) 0(Normal PET) 0.5% 0.65%

Light fastness 5 3~4 3

Light fastness of Flame retardant polyester fiber is inferior to that of normal PET. The difference is brought about by the content of phosphorous flame retardant, not by the content of titanium dioxide. For that reason, there is a necessity for flame retardant polyester

0% 4~5 4~5 4~5 3 0.3% 4~5 4~5 4~5 3 2.5% 4~5 4~5 4~5 3

**2.3 Dyeing fastnesses with deluster contents** 

Table 1. Dyeing fastnesses(grade) with deluster contents.

inferior property compared to normal PET.

Phosphorous content

**2.4 Light fastnesses with phosphorous contents** 

as 0.3% by weight), and the result is shown in Table 2.

Table 2. Light fastness with phosphorous contents.

normal polyester except for the light fastness as shown in Table 1.

of titanium dioxide used as Deluster.

Deluster

than Normal PET.

normal PET. 2)

To improve the light fastness of the flame retardant polyester fiber, following method was chosen and conducted ;

1. Increase of inorganic UV stabilizer(manganese acetate) in polymer

Manganese acetate is known to be incorporated into the polymer as UV stabilizers under polymerization of flame retardant polyester9). Flame retardant polyester fibers incorporated manganese acetate as the basis of 60, 120, 200, 300 ppm of manganese metal in polymer were polymerized. And the polymers were spun in a same method as above mentioned. The results of the light fastness were shown in Table 3.


Table 3. Light fastness with manganese contents.

Table 3 shows that the light fastness decreases with the content of manganese metal. Above all, the coagulation of the manganese acetate brought about the increase of filtration pressure in the polymerization and spinning process to conducting long period test. If the light fastness is improved, this method would be difficult to apply to commercial production of flame retardant polyester fiber.

2. Incorporation of organic UV stabilizer into polymer

To improve the light fastness of the flame retardant polyester fiber, some UV stabilizers were recommended by UV stabilizer maker. The basic properties of the UV stabilizers used in this test were shown in Table 4. The UV stabilizers were incorporated in polymerization reactor as in the state of ethylene glycol dope and the contents of the UV stabilizers were adjusted to 0.3 wt% based on the polyester polymer. The fibers are prepared as same method above mentioned.

Light fastnesses of all flame retardant polyester fibers incorporated various UV stabilizers how negligibly little difference as compared with that not containing the UV stabilizers.(same grade of light fastness of 3)

3. Using of UV absorber under dyeing

Benzotriazole type UV absorber as dyeing auxiliary was recommended form dyestuff maker and dyeing test was conducted. It is added to dyeing solution whose concentration is owf 1%, and the other conditions are same as the above dyeing method. The light fastnesses are increased to the grade over 4(at least 1 grade better that of not treated good).

To investigate the effect of benzotriazol UV absorber on the light fastness of polyester fibers, the UV absorption spectrum is shown in Figure 4.

Flame Retardancy and Dyeing Fastness of Flame Retardant Polyester Fibers 107

Benzotriazol UV absorber is thought to improve the light fastness of the polyester fiber by absorbing the light around 350nm wavelength which is mainly absorbed in polyester. Improving the light fastness using benzotriazol UV absorber can be adopted not only to

It would be the best way to find a suitable dyestuff to improve light fastness of the flame retardant polyester fiber if it is commercially available. The effect of the disperse dyestuff on light fastness of the flame retardant polyester fiber was compared using the dyestuff kind

From the standpoint of chemical structure, the disperse dyestuffs were categorized into nitrodiphenyl amine dyestuff, azo dyestuff and anthraquinone dyestuff. Among these

> Azo dyestuff (Red)

Azo dyestuff (Blue)

dyetuffs, the azo and anthraquinone dyestuffs are mainly used in commercial scale.

Light fastness 3 Above 4 4

In Table 5, there is a noticeable difference in light fastness dyed with between azo dyestuff and anthraquinone dyestuff. The light fastness dyed with anthraqunone dyestuff is much

dyestuff

Fig. 4. UV absorption spectrum of benzotrazole UV absorber

flame retardant polyester fibers but also to the normal PET fibers.

4. Comparison of the disperse dyestuff

according to their chemical structure.

Dyestuffs Anthraquinone

Table 5. Light fastness according to the dyestuff

inferior to that with azo dyestuff.


Table 4. UV stabilizers used in the test

weight

Melting Point (℃)

2286 115~150 Triazine

2261 108~123 Triazine

326 >48 Benzophenone

Remark

derivative

derivative

derivative

derivative

Absorber Chemical structure Molecular

HN <sup>N</sup> <sup>N</sup> NH

N

N

N N

C4H9 C4H9

N N

HN <sup>N</sup> <sup>N</sup> NH

N

N

N N

C4H9 C4H9

N N O O

> O OH

C N

H C

O

<sup>H</sup> 250~300 Benzoxazole

N

N

H R

H R

R R

R R

R :

R :

C8H17O

N

UV

Chimassorb 119FL

Flamestab NOR 116

Hostavin ARO 8P

Hostalux

KS <sup>O</sup>

Table 4. UV stabilizers used in the test

Fig. 4. UV absorption spectrum of benzotrazole UV absorber

Benzotriazol UV absorber is thought to improve the light fastness of the polyester fiber by absorbing the light around 350nm wavelength which is mainly absorbed in polyester. Improving the light fastness using benzotriazol UV absorber can be adopted not only to flame retardant polyester fibers but also to the normal PET fibers.

4. Comparison of the disperse dyestuff

It would be the best way to find a suitable dyestuff to improve light fastness of the flame retardant polyester fiber if it is commercially available. The effect of the disperse dyestuff on light fastness of the flame retardant polyester fiber was compared using the dyestuff kind according to their chemical structure.

From the standpoint of chemical structure, the disperse dyestuffs were categorized into nitrodiphenyl amine dyestuff, azo dyestuff and anthraquinone dyestuff. Among these dyetuffs, the azo and anthraquinone dyestuffs are mainly used in commercial scale.


Table 5. Light fastness according to the dyestuff

In Table 5, there is a noticeable difference in light fastness dyed with between azo dyestuff and anthraquinone dyestuff. The light fastness dyed with anthraqunone dyestuff is much inferior to that with azo dyestuff.

**Part 3** 

**Surface Modification** 

It is assumed that insoluble dyestuff is reduced to leuco compound by the high reductivity of the phenyl phosphinic acid in the phosphorous flame retardant 2, 6) as shown in Figure 5.

Fig. 5. The brief scheme of reduction state of anthraquinone dyestuff

#### **3. Conclusion**

In this chapter, the flame retardancies with deluster contents and dyeing fastnesses with phosphorous contents were investigated.

Whereas titanium dioxide as the deluster affects the flame retardancy of the polyester, it does not affect the dyeing fastness. Titanium dioxide is semi conductor material whose band gap is 3.2eV. Titanium compound in polyester fiber is activated by light, so polyester fibers containing titanium dioxide has color shading problem(yellowing) for outdoor usage. To minimize the yellowing of the polyester goods of polyester fiber with titanium dioxide, phosphorous stabilizer was used. So it could be thought that a part of phosphorous compound act as the stabilizer to reduce the activity of titanium dioxide and the remnant reveals the flame retardancy.

Low level of light fastness of phosphorous flame retardant polyester fiber is due to reductivity of the phosphorous compound. The phosphorous compound shows acidity by the nature of phenyl phosphinic acid to fade out the disperse dye. Light fastness of the phosphorous flame retardant polyester can be minimized by benzotriazole stabilizer5. In commercial scale, it is a proper way to improve of light fastness of Flame retardant polyester fiber.

#### **4. References**

[1] S.C.Yang; J.P.Kim(2007). *J. Appl. Polym. Sci*., Vol.106, No.5, pp.2870-2874

