Mercerizing Technology And Its Common Quality Problems And Solutions

Mercerization is the processing of cotton fabric in a certain tension state, which is treated by concentrated caustic liquor and maintained the required size to make the fabric get silk luster.

1, mercerizing process mechanism

When the mercerized cotton fibers are treated with strong caustic soda, because of the small volume of sodium ions, they can enter the amorphous zone and crystalline region of the fiber at the same time, and the water molecules surrounding the sodium ions form a hydration layer. When the sodium ions enter the fiber and bind with the fibers, the water molecules also bring in, resulting in the intense swelling of the fibers, forcing the diameter of the cotton fibers to increase, and the length to shorten. The longitudinal curl of the dimension almost disappeared, the fiber cross section changed from waist to nearly circular, and the entire fiber changed from a flat strip to a cylindrical shape. At this time, a certain tension was applied, the fiber was stretched after drawing, the uniformity increased, and the surface smoothness increased. The diffuse reflection of the light before the mercerized fiber changed into more directional reflection, which increased the intensity of the reflected light, so that the fabric displayed. The luster of cotton fibers was reduced to 50 to 60% by mercerizing crystallinity from 70% before mercerization. As a result of the decrease of fiber crystallinity, the dyeing properties were improved, and the dyeing properties of dead cotton were improved, and the quality of dyed products was improved. Improve fabric dimensional stability, eliminate fabric internal stress and remove wrinkles.

The main mercerizing agents include caustic soda, alkali permeating agent, acetic acid and so on.

The role of alkali permeating agent is to accelerate the wetting and penetration of mercerized lye, improve mercerizing effect, and improve dyeing depth, brightness, fullness and luster.

Mercerizing machine types: straight roller mercerizing machine, cloth mercerizing machine, straight roller cloth mercerizing machine, knitted fabric mercerizing machine, knitted fabric split width mercerizing machine, short process straight roll marking mercerizing machine, etc.

2, mercerizing process

1 the mercerization of woven fabrics: the following is the mercerization of the woven fabric: strong alkali to air, then to air, then to strong alkali, then to air to (preheat), then to cloth, to expand, to absorb and remove the alkali.

2 knitted fabric mercerization: flat width cloth > photoelectric straight weft device > straight roll groove two roller heavy rolling car five roll and big roller base rolling machine two roller heavy rolling car > cloth spreading expansion and suction alkali removing two roller heavy rolling car high efficiency rotary drum washing box > two roller light rolling car high efficiency rotary drum washing box two roller light rolling car efficient rotary drum washing box two roller light rolling car high efficiency rotary drum washing box two roller light rolling car high The rotary drum is used for washing the box, rolling the car in two rolls, washing the box in the high efficiency drum, rolling the two rollers to flat width.

3, mercerizing process conditions

The main technical parameters of mercerization include: caustic soda concentration, rolling rate, alkali action time, meridional tension, weft tension, drench alkali number, alkali removing temperature, falling width, falling cloth pH value and so on.

　　 4, mercerizing matters needing attention

1 the wet and dry degree of mercerized fabric must be uniform. When wet mercerizing, cotton and linen fabrics are rolled at 60% and 50% of polyester and cotton fabrics are made.

2 when the dry cloth is mercerized, the fabric must be cooled sufficiently through the ventilating frame before rolling the lye to maintain the stable temperature of the mercerized alkali liquor.

3 when facing mercerization, the warp and weft fabric must bear some tension. The greater the tension, the better the gloss of the fabric, the higher the dimension and temperature.

4 in the mercerizing process, the fabric must be kept flat to prevent curling and wrinkling. Once the test has to be reproduced, mercerizing is necessary.

5 the mercerizing process of knitted fabrics usually uses grey mercerization or mercerizing after mercerizing. Because of poor water absorption of fabrics, penetrant must be used to strengthen the permeability of concentrated caustic liquor and enhance mercerizing effect.

6 always use a wide range of indicators or test paper to detect the pH value of the mercerizing cloth. Keep the fabric as neutral as possible and neutralize it with acid during the washing process if necessary.

7 strong caustic soda (concentrated acid) has strong corrosion and burning effect on the skin of human body. The personnel contacting with strong lye (concentrated acid liquor) should equip with necessary protective articles. If the lye (or acid) is spattered to the skin or eyes, rinse with plenty of water before going to the doctor.

5, mercerizing effect evaluation.

1) gloss is one of the main indexes to measure the appearance effect of mercerized fabric, but there is no uniform ideal test method.

2) microscopic sections were used to observe the micromorphological changes.

3) adsorption properties

A barium method is a test method to measure the absorbability of cotton fibers. It is commonly used to test the absorbability of fabrics after mercerizing. Take the mercerized and mercerized cloth samples, wash them in hot water and cold water, and then dry them. 100~105 1H bake, remove the constant weight, weigh each 2 grams, cut them into small pieces, put them in 100 ml cone shaped bottles respectively, and draw 0.25mol/L barium hydroxide into the bottle, then cover them well and shake them from time to time. After 2 hours, 10Ml was taken, phenolphthalein as an indicator, and 0.1mol/L hydrochloric acid standard solution titrated to calculate the barium value.

B iodine contamination and dyeing method: different barium (100150) samples were treated with iodine iodine or direct blue 2B to make color cards. Then the iodine liquid of unknown samples was stained and stained with the known color cards in comparison with the dyeing depth, and the mercerizing barium value was quantitatively evaluated.

4) fabric dimensional stability: the fabric shrinkage test method is used to test the warp and weft length of fabric before and after mercerization. The smaller the shrinkage rate of fabric is, the better the mercerizing effect.

6, mercerizing common quality problems and Solutions

1) left right right chromatic aberration

The A pretreatment did not match the left and right sides, resulting in inconsistency of alkali content in each part of the fabric.

The alkali concentration in each part of B rolling tank is inconsistent.

C wear and cylinder inflexibility result in inconsistent liquid volume in the left, right and right parts of the fabric.

When the D expands, the ratio of alkali to right is not consistent with that of the left side.

E is not adequately washed.

2) the warp and weft shrinkage of fabrics is too large.

The concentration of A base is too high. (weft shrinkage of rarefied fabrics)

The expansion of B is insufficient (the tension is too high when entering the cloth), which results in the difficulty of zonal expansion.

The tension of the intermediate roller of the C two base roller is too small, so the fabric has a poor sizing effect through the mercerizing.

The alkali leaching effect of D is poor, and the alkali content of fabric is too large. The fabric shrinks when washing at high alkali and high temperature.

The tension of the E equipment is too large and the weft shrinkage of the fabric is large.

3) breaking edges and holes

A cloth is worn or not flexible.

The tension of B fabric is uneven, and the tension of the fabric is inconsistent.

C cloth outlet door width is too wide.

D enlargement is too large or too urgent.

E edge detection or expansion device is not flexible.

4) auxiliaries

In the process of boiling and bleaching, the residual surfactants on the fabric are destroyed by alkali, and the oil affinity groups gather and stain the fabric, causing the fabric to cause local dyeing to form shallow spots.