Man's cotton spandex fabric production process and control

Man's cotton spandex fabric production process and control
In many high-end products, elastic spandex fibers not only show good elasticity, but also have high strength, high elastic modulus, and good recovery. In recent years, they have become popular all over the world. The fabric weaved by it is soft and elastic, and can significantly improve wearing comfort and added value. If the spandex bare yarn is mixed with rayon fiber blended high-grade knitted fabrics, the performance of the two fibers can be fully utilized to complement each other and icing on the cake. The garments made from this fabric have many characteristics such as high elasticity, softness, comfort, moisture absorption, breathability, smoothness, easy care, etc., and are high-tech products suitable for the human body that are developed for human body type and skin characteristics, and their performance is ordinary fabrics. Unmatched, the added value of the product is quite high, and it has been popular for many years.
However, rayon has loose structure, low crystallinity, low degree of orientation, amorphous area, and absorption capacity for dyes; and wet strength is half of dry strength, and there are phenomena such as easy dyeing and easy breakage during dyeing. The knitted fabrics with spandex involved in weaving also have difficulties in controlling dimensional stability, grammage, and dyeing width.
Therefore, how to balance the characteristics of the two fibers in the dyeing and finishing process, reasonably formulate and control the process, and solve the problems in the printing and dyeing process are the problems that this article focuses on.
1 production process

At present, the production process of the man-cotton spandex fabric is: weaving → slitting the volume → unwinding → pre-setting → seam edge → boil-dye → dyeing → dehydration → widening → complex setting → cloth inspection.
This type of elastic knitted jersey, which is interwoven with common rayon and spandex, is often susceptible to severe straight prints, fine wrinkles, chicken scratches, and colored flowers (such as dyeing green and blue) during the dyeing and finishing process. The appearance of cyan blue flowers, etc.) is affected by the flaws, and the potential stress and shrinkage force caused by the raw materials and their processing, the weight of the door fabric is very unstable, and the dimensional stability of the finished products is also very high. It is easy to make changes. Therefore, many dyeing and finishing plants are daunted when they produce and develop such products.
However, in order to solve the above problems and make the cotton spandex jerseys have good elasticity, dimensional stability, fabric flatness, color diversity and to achieve the required style, we must carefully and strictly control the various processes, from the weaving process , Weaving equipment, dyeing and finishing process, dyeing and finishing equipment and the actual operation of the various aspects of the process to pay attention to matters such as analysis and discussion.

1.1 Dyeing and finishing process
The process of dyeing and finishing of man's cotton spandex fabrics: pre-formed → edging → boiled → dyeing → soaping → dehydration → widening → complex setting → cloth inspection. Several major process flows are discussed as follows:
1.1.1 Preform of Grey Fabric
Preformation is one of the key processes. In the yarn ratio of spandex-containing elastic fabrics (people cotton spandex, cotton ammonia, polyester ammonia, etc.), the spandex content accounts for only a small amount, but during the weaving process, due to the strong effect, the spandex exists inside the fabric. Large residual stress, easy to produce tensile deformation. Therefore, the styling technology of the human cotton spandex fabric is quite difficult, and the arrangement of the stereotyped production process will have a great influence on the size and specification of the fabric.

The purpose of the pre-set type: On the one hand is to eliminate the internal stress of the fabric, so that the fabric door width, weight and other specifications of the square meter easy to control; make the fabric coil smooth, shiny bright cloth, soft to the touch. On the other hand, the finished product has good thermal dimensional stability (shrinkage rate), corrects distortion, wrinkles, eliminates uneven internal stress of the fabric in the weaving process, ensures that the fabric surface is smooth during dyeing, and prevents the dyeing process from occurring. Produce bars, creases, chicken marks, etc.

From Table 1, it can be seen that the styling process of the man-cotton spandex is generally based on the pre-dry type.

Pre-setting process:
Device door Fuji setting machine
Temperature 195°C
Speed ​​16m/min
Overfeed 30%-40%

Table 1 The difference between the wet and dry preset types

Cause Analysis
After the fabric has been pad-rolled, the fabric is in a wet state before it enters the shaping zone, and the elasticity of the elasticity of the elastic fabric is poor.
The whole process is dry, and the elasticity of the elastic fabric in the dry state is better.
1.1.2 Edge seams
Before the dyeing of the predetermined type, the cloth should be re-stitched into a tube. This is because the man-cotton spandex knitted fabric has a certain degree of shrinkage. If it is not seamed, the fabric may be easily curled under hot and humid conditions when scouring and dyeing. , resulting in the left and right sides of the fabric color defects, so the seam edge into a cylindrical shape is more favorable.
Be careful when sewing: 1. If there is a needle break or breakage, you must tie the end of the break, or tie it with a needle, to prevent breakage at the end of the line or the end of the dyeing to cause discoloration . 2. Sewing thread should be selected with less knots, better strength lines, bleaching or dyeing light colors, the sewing thread can only use white lines, color lines can not be used to prevent color.

1.1.3 Dyeing
The content of spandex in the man's cotton spandex is generally between 3% and 5%. Generally, only the dyed cotton is needed for dyeing, and the spandex need not be considered. However, when the spandex content is high, the dyeing of spandex yarn should be considered. The following dyeing process conditions, analysis of dyeing process (as shown in Figure 1).

Dyeing process: Permeation (80°C15min) → Cooling to 40°C Drainage → Washing → Dyeing (60°C 30min 30min) → Washing → Pickling (45°C 15min) → Soaping (70°C 15min) → Pickling → Fixation ( 40 °C15min) → cooling wash

60°C 30min30min, coloring (dark color, high temperature)
Process conditions: Dyeing equipment: High-temperature overflow dyeing machine (Hong Kong Ericsson), bath ratio: 1:15 Figure 1 Dyeing process temperature curve
The company selected a high-temperature and high-pressure jet overflow dyeing machine. The pressure of the nozzle should be matched with the speed of the lifting roller to prevent the mechanical friction from fluffing the fabric surface. At the same time, attention should be paid to the smoothness of the dyeing machine walls to prevent the occurrence of wire drawing, and if necessary, adding a smoothing agent. At the same time control the heating and cooling, 1 °C / min is appropriate, so as to avoid wrinkles, abrasions, chicken scratches and other rickets. In addition, when the alkali is added, the speed is slow, so as to prevent the fabric from producing color flowers.

The purpose of soaping is to remove the floating color on the surface of the fabric, improve the rubbing fastness of the fabric, and make the fastness of the fabric surface meet the requirements of the national standard and the customer. Different shades of color, the temperature is also different, generally light color is 50 °C -70 °C, medium color is 80 °C -90 °C, dark color is about 98 °C.

1.1.4 Dehydration

Centrifugal dewatering machine is a commonly used dewatering machine for knitwear. When dewatering, the knitwear is put into a porous rotating cage, so that the moisture in the fabric is removed under the effect of centrifugal force under high-speed rotation conditions.

1.1.5 Spreading

Before the fabric is shaped, it must first be expanded by a swing machine and the seam line must be torn off at the same time. In order to achieve the fabric width and stability of the role of the door.

1.1.6 Finished Shape
The purpose of setting is mainly to eliminate the wrinkles produced during the dyeing process, to keep the fabric surface flat, and to make the fabric dimensionally stable and have good shrinkage properties. Therefore, the setting temperature, speed, and overfeeding should all be controlled to ensure the stability of fabric size, shrinkage, and good elasticity and strength without damage. Selecting the right amount of softener can improve the hand feel and prevent pin holes (except for the print blank).

Styling process:
Device door Fuji setting machine
Temperature 160°C-170°C
Speed ​​20m/min
Overfeed 70%-80%
Softener 3%
The width is slightly larger than the finished 1-2CM
2 Factors Affecting the Dimensional Stability of Fabrics Analysis and Solutions
Broadly speaking, the dimensional stability of a knitted fabric is the ability of the index fabric to maintain its original geometric dimensions after being washed, cleaned, and dried under specified conditions during normal use. The relationship between fabric processing and fabric dimensional stability. Raw material specifications and composition ratio, weaving process, blank set, dyeing and other technical factors will affect the size of the cotton spandex jersey, mainly reflected in three areas: different widths, unbalanced weight, shrinkage rate. This article focuses on the factors affecting the dimensional stability of fabrics from the point of view of the production and processing technology of cotton spandex fabrics.
2.1 Influence Factors and Analysis
2.1.1 Spandex Specification and Content
a. spandex woven fabric blank weaving, spandex yarn specifications are different. Spandex commonly used D: 20D, 30D, 40D, 70D, 140D. The thicker the spandex filaments, the greater the elasticity, and the greater the shrinkage of the grey fabric's door width.
b. The content of spandex varies. There are many varieties of cotton spandex that are supplied on the market. The higher the spandex content, the greater the elasticity, and the more the width of the fabric retracts, resulting in different widths.
2.1.2 Weaving process
The cotton fabric spandex jersey fabric rough structure parameters and machine selection process inappropriate. The coil is the basic structural unit of the man-cotton spandex. The geometry of the coil and the connection of the coil in the relaxed state directly affect the appearance of the fabric, and also the thickness, elasticity, elongation, dimensional stability, etc. of the fabric. To the important role.

2.1.3 Placement of Grey Fabric
The degree of natural shrinkage of the grey fabric is directly related to the time of placement, stacking conditions, temperature and humidity. Different conditions for placing can also cause different blanks, affecting the width of finished products, weight and shrinkage of square meters.

2.1.4 stereotypes operating process

In the prefabricated type of grey cloth and the complex type of the finished product, if the temperature, speed, and process are not properly handled, for example, parking, peeling, overfeeding, etc. are unreasonable, the fabrics will have different weights, and the width and width of the fabric will be narrow. , Shrinkage rate instability phenomenon.

2.1.5 Measurement error when measuring weight
There will also be an error in the measurement. Therefore, the grammage measurement should be performed on the left, right, and right sides of the entire width of the door (especially when the rear vehicle is heavily clothed. The left and right grammage will be slightly lower than the middle grammage. In severe cases, there will be 10 -15 grams of weight difference).

2.1.6 fabric moisture regain
The full resurgence of the fabric led to a rise in grammage (any fabric is present, but only with the difference in moisture regain of the fabric fibers themselves, the degree of grammage increase is different).
2.2 Solutions
2.2.1 Reasonable choice of spandex filament size and content
According to the different specifications of the fabric, the specifications and proportions of the spandex yarn are selected, a reasonable prescription of the weaving process is formulated, the orderliness of the coil arrangement is maintained, and the process parameters are controlled.

2.2.2 increase the level of stereotyped process operation
Table 2 Relationship between setting machine door width, weight and finished product weight

Spandex filaments are thermoplastic fibers and act as a skeleton inside the fabric. The reproducibility of all of the above factors is due to poor reproducibility of elastic stress or elasticity damage of spandex filaments. Therefore, the operating level is improved and the reproducibility of the process conditions is guaranteed. If you get out of the edge, you must act fast. Reduce the speed of the vehicle by no less than 10 meters and reduce the probability of parking.

2.2.3 Guaranteed Knife and Gage Accuracy
When the gram weight under the knife is accurate, the diameter of the cloth disc is 11.28 CM, so when measuring the gram weight, be careful not to stretch the cloth, otherwise the gram weight diameter (horizontal or longitudinal) will be less than 11.28 CM. The final finished product weight is higher than the stereotyped machine weight measurement. This should also be noted, otherwise such measurement errors can give people an illusion.

2.2.4 Edge seam
Weft knitted fabrics have a poor consistency of the width of the door, so when the seams are hem, the overlapping of the two layers of cloth must be narrower in the width of the door, and wider in the next. In this way, we can truly meet the requirements of “flat, straight, secure, and homogeneous” and eliminate defects such as camouflage, curling and wrinkling.

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