Active brilliant blue discharge printing technology

Introduction

Discharge printing, also known as engraving, is a printing process that uses chemical methods to partially destroy and decolor the background dye on dyed fabrics, thereby reprinting patterns. In this printing process, the printed The white pattern obtained is called whitening, the printed colored pattern is called color discharge, and the chemical agent that destroys the background dye and makes it decolorized is called dye discharge agent.

Conventional reactive dye discharge printing process uses the strong reducibility of ivory powder to destroy the chromogenic groups of the background color, and the color is reduced by a reducing agent. For dyes, Degurin is also used as a discharge agent and is used with paint that is resistant to reducing agents. The reactive dye discharge printing process is generally divided into neutral discharge and alkaline discharge. The difference between the two lies in whether to add an alkali agent. The choice of alkali agent can be caustic soda (36°Be), soda ash or potassium carbonate; in terms of dye selection Generally, vinyl sulfone-type dyes can be whitened under neutral or alkaline reducing conditions, while dyes with anthraquinone as the parent are more difficult to remove, such as Brilliant Blue KN-R (No. 19 Brilliant Blue), because of its The anthraquinone matrix is ​​highly resistant to reduction, and the areas where it is released are black and gray, making it impossible to obtain a satisfactory release effect.

Brilliant blue is one of the more important colors in printing and dyeing. Various gorgeous patterns are printed on the brilliant blue background, sometimes becoming a fashion designer. The more preferred style requires our printing and dyeing workers to find a solution. There is information on using triethanolamine as a release agent to draw out brilliant blue, but the test results are poor. Based on long-term research experience in release printing, the author introduces three process methods to achieve this style.

1. Alkaline discharge printing process

Reactive No. 19 Brilliant Blue is a vinyl sulfone-type reactive dye. Based on the vinyl sulfone reactive group’s non-alkali resistance, Shanghai Dongmei Chemical Co., Ltd. has developed an alkaline discharge printing process. The highly alkaline monochloro-s-triazine reactive dye (hereinafter referred to as P-type dye) is used as the color-incorporating dye, and a release printing paste EMVATEX DK-TN is developed, which is combined with the release aid CLEANTEX D-TN. Under high temperature conditions, the covalent bond between the fiber and the dye is destroyed, and the No. 19 brilliant blue has a better discharge printing effect. The specific process is as follows:

Dyeing of background color → printing → drying → steaming → baking → washing → soaping → washing → drying

1. Preparation of color paste

(1) Original paste Preparation

DK-TN has the reducing properties of a dye discharge agent and the functionality of a slurry. Because urea absorbs heat when dissolving, when preparing the original paste, urea must be added to warm water first, and the water temperature is about 80°C. Then, while stirring, add DK-TN to the urea solution. Stir thoroughly to fully dissolve DK-TN and form a semi-solid paste. Leave the transparent paste for 1-2 hours to fully swell and set aside. The slurry has a high pH value. The amount of urea should be adjusted according to the steaming conditions. If the humidity is high, the amount of urea can be appropriately reduced to ensure the fineness of the flower pattern.

(2) Preparation of discharge printing paste

Discharge printing paste

Matching pull-out resistant P type Reactive dyes include: bright yellow P-6G (yellow 95), golden P-2RN (yellow 181 or orange 12), orange P-2R (orange 13), red P-4BN (red 3:1), red P-6B ( Red 218), Brilliant Blue P-3R (Blue 49), Emerald Blue P-GR (Blue 72), Navy P-N3G (Black 39), Black P-GR (Black 39MIX).

2. Steamingn=””>Add water to

100%.

The discharge printing paste is prepared according to the following formula, and the monochloro-s-triazine reactive dye is based on demand Adjust, if it is not added, it will be whitening, and if it is added, it will be color extraction. Sodium sulfite is used as a release agent, and the amount of reactive dyes for the background color increases according to the above to ensure that the background color is fully extracted. Baking soda and urea increase as the dosage of monochloro-s-triazine reactive dye increases.

Among them, the first drying step must ensure that it does not exceed 80 degrees Dry to ensure that the background dye is not fixed or has less color fixation as possible. There is no such requirement for the second drying.

The principle of this process is derived from reactive anti-reactive printing. Of course, fabrics with bright blue background and colorful patterns can also be printed using anti-dye printing, but the wet Due to the wet process, the fineness of the pattern is still lacking compared to the discharge printing, and the background color is printed all over the ground, and the front and back cannot obtain consistent color. Using this anti-pull-out process, the effect of discharge printing can be obtained.

The key points of the process and solutions to common problems are as follows:

1. The background color-fixing alkali agent has a greater impact on the anti-pull-out effect. Sodium trichloroacetate, which is weakly acidic at room temperature, is preferred. Weakly alkaline baking soda can also achieve better results. Good effect, prevent the background color from solidifying in advance;

2. The drying temperature after padding the dyeing solution is also a more important parameter, in order to ensure that the dye is as It has little color fixation and the drying temperature should not exceed 80 degrees. Once the dye is fixed and covalently bonded to the fiber, sodium sulfite can no longer separate the dye from the fiber. Its main function is to preferentially bind the dye before it reacts. react to prevent it from reacting with the fiber;

3. Appropriately increase the amount of anti-dyeing salt S in the base dye solution to prevent reducing gases during steaming Destroying the background color ensures that the color of the background color is stable, and can also prevent the occurrence of white circles at the release point to a certain extent. In addition, the amount of sodium sulfite needs to be increased or decreased according to the depth of the brilliant blue background color to avoid excessive white circles.

4. This process can also be replaced by the principle of acidic anti-reactivity of coatings. The reactive brilliant blue background color adopts a slightly less reactive monochloro-s-triazine structure. No. 49 blue, anti-printing additives use ammonium sulfate or citric acid, the paint is colored, and the alkali agent in the background color is neutralized by acidic conditions to destroy its color-fixing conditions, which can also achieve better results.

3. Imitation brilliant blue printing:

In addition to studying the discharge printing process, we can also select dyes that can imitate bright blue from the conventional reducing agent pull-out background colors for color matching. From these, we choose those with brighter colors. Blue BB (Blue 220) and Blu-ray Red F3B (Red 180) are dithered. The ratio is roughly 9:1. When the color is closest to Brilliant Blue No. 19, the brightness is slightly lacking. For some situations where the color requirements are not very high. ,can use.

In summary, the active anthraquinone structure brilliant blue uses conventional reducing agents Discharge printing cannot achieve better results. The three methods described in this article can all achieve better results. Each factory can choose the appropriate process for production according to its own equipment conditions.

References:

Wang Yongwu and Bai Mingxu reactive dye discharge printing technology. Printing and Dyeing, 2003, Issue 7, Pages 23-25

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