Characteristics And Process Analysis Of Knitted Fabric Pigment Printing

< p > generally speaking, the equipment used for knitted fabric printing is flat screen printing, rotary screen printing, roller printing and manual platen printing.

The printing process is mainly printing and reactive dyestuff printing, and a small amount of pfer printing is used.

This paper mainly describes the practice of coating < a href= "http://www.91se91.com/news/index_c.asp" > printing process < /a > over the past eight years.

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< p > coating is used for < a href= "http://www.91se91.com/news/" > knitted fabric printing > /a >. The key problem is that it is necessary to choose the components of printing paste (including adhesive, pigment paste and paste) reasonably, so as to maximize the balance between touch and fastness.

In the past 97 years, we have used the super soft TYS - 1 printing paste, which is made of imported raw materials and some domestic coatings. Since, we have used direct printing printing / reactive printing, special printing (including stereoscopic foaming printing, gold and silver powder printing, pearlescent printing, scintillating printing) and recent discharge discharge printing on the rotary screen printing machine.

Up to now, more than 2000 tons of knitted printed fabrics have been produced, and some practical experience of printing with circular screen paints has been accumulated.

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< p > 2 pretreatment of knitted fabric < /p >

Before the printing of knitted fabric P < 2.1, it is necessary to carry out pretreatment, such as impurity removal and bleaching, to improve the wearability and appearance quality of the knitted fabric, and prepare for the printing process. Good pre-processing is the foundation for the circular screen printing of knitted fabrics.

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< p > because of the structure, quality requirements and processing equipment of the grey cloth, different pretreatment processes can be produced, and its technological process is generally < < /p >.

< p > blank > a href= "http://www.91se91.com/news/" > cloth < /a > (alkali) (Si Guang); then scouring and bleaching (chlorine bleaching or bleaching) to whitening softening treatment to dehydration, drying to calendering (double faced fabric without alkali shrinkage) < /p >

< p > the pretreatment of knitted fabrics is mainly made up of three parts: alkali shrinkage (Si Guang), scouring and bleaching (Zeng Bai).

Alkali shrinkage is a process of cotton knitted fabric stacking under the condition of flat width (Yuan Tong) and tension free, leaching and caustic soda solution, and then washing alkali.

Through alkali shrinkage, fabric shrinkage, increase density, elasticity and gloss, enhance the smooth handle, reduce shrinkage and improve the dimensional stability of finished products.

In recent years, the use of mercerizing technology has gradually increased, and the quality of silk products is much higher than that of alkali shrinkage products.

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< p > the function and principle of scouring and bleaching of knitted fabrics are the same as those of woven fabrics, but because of their loose organization, the processing conditions (mainly the concentration of working fluids) are lower than those of woven fabrics.

The processing methods of scouring and bleaching are intermittent and continuous. Batch type is usually used in boiling cloth pot or in overflow dyeing machine. Continuous type usually adopts "Ding" box or crawler box.

Bleaching of semi finished products for knitting printing is often carried out by chlorine bleaching, oxygen bleaching, chlorine dioxide bleaching and bleaching.

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< p > > a href= "http://www.91se91.com/news/" > knitted printing > /a > semi finished products require uniform boiling, white consistency, good wool effect, small weft and weight requirements.

The quality problems caused by improper pre-processing are the same as those of woven fabrics, such as unevenness, unevenness of bleaching and lack of whiteness. Printing process often results in poor color matching, poor color difference or darker shade. At the same time, some special quality problems will also occur.

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< p > 2.2 square Mick heavy problem < /p >

< p > the weight of finished knitted fabric is one of the important indicators of customer quality requirements. It must be guaranteed. If it exceeds too much, it will lead to an increase in production costs. Therefore, it is very important to control the weight of the blanks on the premise of ensuring the weight of the finished products.

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< p > in pre processing and printing process, factors such as weight loss, such as impurity removal during pre processing, elongation at a certain tension during printing, and factors that increase weight gain, such as shrinkage of fabric during pretreatment, and amount of coating and auxiliaries added to fabric during printing, are also increased.

However, due to the different tension of the processing equipment, the area of the pattern printing is different, and the weight changes vary. The weight of the finished product fluctuates on the basis of the blank weight.

In order to avoid the problem that the weight of the finished product after printing is not up to date, unless the experience of multiple production is required, the pioneer sample should be generally required to formulate and correct the weight index of the wool fabric in the production of large goods after the same process route with the production of large goods and the change of the weight of knitted fabric after processing equipment.

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< p > 2.3 capillary effect problem < /p >

< p > bad wool effect, resulting in uneven printing block surface, serious will have a "bottom" phenomenon, or depth can not be improved, do darker large face pattern should pay special attention to.

In addition to the usual "insufficient scouring practice", the special "soft processing" process for knitted fabric pretreatment is also an important reason for the poor performance of the knitted fabric before treatment.

Improper selection of softeners or excessive dosage will result in water repellency of the finished fabrics. Therefore, it is also necessary to pay attention to the pretreatment of printing fabrics in "soft treatment". They should not simply apply the finishing process of bleach and dyed knitted fabric. The softeners should be carefully selected and their dosage should be reasonably formulated. Otherwise, the printing fastness will be affected. When improving the < a href= "http://www.91se91.com/news/" > fabric > /a > handle, the wool effect of the knitted semi-finished products should be taken into account and the printing process will be carried out smoothly.

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< p > 2.4 weft problem < /p >

< p > the pretreatment of knitted fabrics is mostly rope shaped, loosely woven, and the problem of weft deviation is more serious than that of woven fabrics.

If the flower pattern is broken, the problem of weft deviation can also be relaxed. If the lattice type pattern is used, the weft deviation is higher.

Measures to control and improve weft deviation: check the slanting direction before the opening of the slitting seam, make it consistent, and correct it when trimming the head. The automatic shaping device should be equipped with the stereotyping machine before printing. The pre press shaping should set the door width enough to reduce the amplitude of the printing after drawing, so as to reduce the cambered flower slanting.

The quality requirements of knitted grey fabrics, such as gate width, shrinkage, unit area weight (square Mick weight), strength, coil length and density, should meet national standards or customer requirements.

The intrinsic quality of grey cloth is related to the gate width, the square Mick weight and the shrinkage rate.

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< p > 3 knitted fabric < a href= "http://www.91se91.com" > circular screen printing < /a > /p >

< p > the process flow of knitted fabric circular screen printing is generally < < /p >.

< p > full coating: semi-finished products to cut width, sewing head to stereotype, printing to baking, then shaping to volume < /p >

< p > coating / activity: semi-finished products to cut width, sewing head to stereotype, printing to baking, water washing, drying, shaping, and finished product < /p >

< p > 3.1 selection of new pigment printing auxiliaries < /p >

< p > new pigment printing auxiliaries are composed of the following four pillars: < /p >

< p > (1) excellent coating dispersing system (Dystar coating, etc.); < /p >

< p > (2) excellent self crosslinking adhesive system (German, American large and self-made varieties); < /p >

< p > (3) excellent printing paste system (German, American large and self-made varieties); < /p >

< p > (4) excellent hand fastness adjustment assistant system.

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< p > the effect of pigment printing is mainly determined by these auxiliaries.

Traditional printing and printing products are of poor quality, usually using chemical knitted fabrics which do not meet the new printing standard. Because they are different from ordinary woven fabrics, there are many practical problems that are different from woven fabrics when printing. Now, the key problems are as follows: < /p >

< p > auxiliaries and unreasonable < a href= "http://www.91se91.com" > printing process < /a >: < /p >

< p > (1) paint dispersing system < /p >

< p > the conclusion of the study is that: the pigment is grinded to the size of 0.25 to 1.5 microns by the high-power heterogeneous sand mill, and it will cause the decrease of shading and color intensity at 0.25 microns.

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< p > practical printing, the choice of coatings focuses on price, color intensity, brightness and fastness.

After years of research, we believe that from the point of view of environmental protection or irreplaceable point of view, it is appropriate to choose the printing and bleaching (1mperon) system of Dystar company as the first choice. The bulk of the coatings produced in Shanghai can be selected.

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< p > (2) adhesive system < /p >

< p > new self crosslinking adhesives, most of which are PA series, and a few are PU series.

No matter what kind of adhesive is used, the first thing to consider is how to solve the problem of consistency between hand feeling and fastness.

Next is the pparency of the film, which directly relates to the brilliance of printed products.

There are many specific descriptions of components and types of adhesives and their effects on membranes.

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< p > through research, we believe that the important condition for adhesives must be achieved by achieving a good balance between adhesion and cohesion. The adhesive film is consistent with the adhesive force of the fabric and the good cohesion of the adhesive. This requirement should be improved as much as possible.

If the adhesive force is weak, or if it is weaker than cohesion, it will cause the fabric's surface rubbing fastness to drop and even fade. If the cohesion is weak, the particles of the coating will be easily rubbed off.

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< p > pigment printing binder should be carried out under acidic conditions (pH value 4) when heating reaction.

Dry hot air is the best fixing medium.

Wet steam or superheated steam are not suitable for fixing media.

Because it can only get about 60 - 80% fixation effect (as a result of hydrolysis, high temperature steam contains 100% water vapor), resulting in various color fastness index decline.

Generally, the thickness of pigment printing binder is about 5 - 10 microns, so it is difficult to observe the naked eye.

The coating is codeposited in the membrane, so the adhesive force of the adhesive will affect the adhesion of the film on the fiber.

This process is mainly due to physical adsorption and enhanced by hydrogen bonding. Some kinds of adhesives, under certain conditions, can even form a real chemical bond to the fibers, which is due to the special reaction groups in the polymer film forming agent.

In the synthesis or selection of adhesives, we pay special attention to vitrification temperature, minimum film forming temperature, particle size and its distribution, surface tension and electrolyte resistance.

In a sense, it is more strictly defined whether it is an excellent adhesive for knitted fabric printing. The choice of PA or PU adhesives should be based on the different requirements of different fabrics.

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