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What should I pay attention to when dyeing polyester knitted fabrics?

Date:Jan 09, 2021

Blended fabric is a textile product made of chemical fiber mixed with other natural fibers such as cotton, silk, linen and other natural fibers. It has both the style of polyester and the advantages of cotton fabrics, such as polyester-cotton cloth and polyester-wool gabardine. Blending is divided into wool and viscose blending, sheep and rabbit hair quilting, TR fabrics, high-density NC fabrics, 3M waterproof mousse fabrics, TENCEL fabrics, soft silk, TNC fabrics, composite fabrics, etc.


For example, polyester-cotton blended fabrics are made of polyester as the main component, using 65%-67% polyester and 33%-35% cotton blended yarns. Polyester-cotton cloth is commonly known as cotton. This article briefly introduces the dyeing of synthetic fiber blended knitted fabrics



Picture The dyeing method and precautions of blended knitted fabric


1. Blended knitted fabric


That is, two or more different fibers are mixed and spun, and then the resulting knitted fabric is knitted.

1.1 Interwoven knitted fabric: a knitted fabric made of two kinds of yarns (different fibers) or two kinds of filaments.

1.2 Multicolor effect: In the dyeing of mixed yarn knitted fabrics, it is required to dye different colors.

1.3 White space effect: require one fiber to be dyed while another fiber to avoid dyeing.


2. Dyeing method of mixed yarn knitted fabric


2.1 One-step method in the same bath: that is, one or two dyes with different properties are simultaneously dyed in the same dye bath for different fibers.

2.2 Two-step method in the same bath: first dye one fiber with one dye, then add another dye in the bath, and use another process to over-dye another fiber. In this dyeing method, it is required that the residue from the first dyeing has no adverse effect on the second dyeing.

2.3 Two-bath two-step method: First prepare a dye bath for dyeing a fiber, then vent the remaining bath, and then prepare a second bath for the second fiber dyeing.

2.4 Which dyeing method to use depends on the composition, properties and blending ratio of the fibers in the blended fabric, as well as the types and properties of dyes, auxiliaries, dyeing depths and product quality requirements.


3. Precautions for dyeing blended and interwoven fabrics


3.1 The selection of dyes, the principle of selection is;

a. Whether the color effect of a dye in different fibers, the dyeing rate, the dyeing saturation, and the fastness are close.

b. If it is two types of dyes, the following points should be noted:

①Prevent precipitation, (cation and acid dyes, add anti-settling agent)

②Prevent contamination (for example, dyeing polyester and nitrile interlaced fabric, dyeing with one bath method)

③Similar fastness

3.2 Dyeing temperature: The dyes selected in the one-bath one-step dyeing process should preferably have similar heating and dyeing rate curves.

3.3 Dyeing pH

3.4 The influence of additives


Picture The dyeing process of synthetic fiber blended or interwoven knitted fabric


1. Dyeing of polyester-cotton interwoven knitted fabric


1.1 Disperse dyes, reactive dyes, and direct dyes are dyed in the same bath in one step, and a carrier is added to the dye bath to dye polyester with disperse dyes. This method has poor fastness.

1.2 Two-bath dyeing is mostly used in actual production. The two-bath method is to first dye polyester with high temperature and high pressure, then use reactive dyes to dye cotton in another bath. In order to make the color of the dyed product bright, it can be reduced and washed after the first bath to remove the disperse dye stained on the cotton fiber. However, the fixation of reactive dyes must be carried out in an alkaline bath, which often affects the shade or depth of disperse dyes.

 

2. Dyeing of polyester/acrylic blended yarn or interwoven knitted fabric


2.1 Disperse dyes cannot be used. One-step dyeing in the same bath, because the dye uptake rate is too different and color matching is more difficult.

2.2 Disperse dyes and cationic dyes are dyed in the same bath in one step, with wintergreen oil as the carrier. Disadvantages, acrylic fiber is easy to shrink, cationic dyes are easy to form precipitation with the diffusing agent in disperse dyes.

2.3 It is best to use the same bath two-step method or two-bath method for dyeing. The polyester should be dyed with high temperature and high pressure, and then over-dye acrylic with cationic dye in the second bath. Finally, it is softened. The polyester must be thoroughly reduced and cleaned after dyeing, otherwise the cationic dyes will affect the rubbing fastness.

2.4 Dyeing of polyester and nylon interwoven knitted fabrics. When dyeing the same hue, attention should be paid to the problem of disperse dyes, which may show different colors on different fibers.

2.5 Dyeing most products of acrylic/cotton blended yarn or interwoven knitted fabrics only requires dyeing acrylic fiber but not cotton fiber, that is, a blank product. At this time, disperse dyes can be used to dye light colors, cationic dyes can be used to dye dark colors, and cleaning can be strengthened for dyeing such as cotton quilts. Sometimes in order to improve the vividness of the product, the cotton can be bleached and then dyed. For double dyeing, dye cotton first and then acrylic.