Overview of leather dyes
Overview of leather dyes
Song neili, senior engineer of Tianjin Shengda company
Abstract: This paper mainly discusses the basic concept of leather dyes, the classification of leather dyes, the description of economic leather dyes and high-grade environmental protection leather dyes, and the color matching in the application of leather dyes.
Key words: leather dyes, acid dyes, direct dyes, strong acid dyes, weak acid dyes, neutral dyes, acid complex dyes.
CLC classification No.: ts529.3 document identification code: a
Leather dyes overview
Song Neili
Abstract: This paper mainly discusses the basic concept of leather dyes, leather dyes classification, economy and environment protection type dye for leather leather and leather dyes applied in color.
Key words: leather dyes, acid dyes, direct dyes, acid dyes, weak acid dyes, neutral dyes, acid dyes.
CLC: TS529.3document code: A
1、 Basic concepts of leather dyes
Artificial use of appropriate methods to dye other fibrous substances into bright and firm organic compounds is called dyes. Dyes used for dyeing protein leather fibers are also called leather dyes. Leather dyes are easily soluble in water and adsorb with leather fibers under the action of acid medium; Fixation; The coloring process is called dyeing. Leather dyes should not only have bright colors, but also have good "affinity" for leather fibers and various fastness functions, such as light fastness; Washable; Resistance to dry and wet friction; Light resistance; Sweat resistance; Migration resistance and other professional indicators of leather dyeing.
2、 Classification of leather dyes
1. Economical leather dye
At present, the acid dyes and direct dyes in the domestic market are monoazo dyes with bright colors, but the dyeing fastness of leather is relatively poor and the price is low. The so-called acid black and direct black in the leather dye market are economic leather dyes.
Acid dye
Acid dyes are anionic dyes that dye leather fibers in an acid bath. According to their dyeing properties and application methods, they can be divided into strong acid dyes and weak acid dyes. Strong acid dyes have simple structure, small organic molecular structure and large proportion of sulfonic acid groups. In dyeing, the dye basically exists in ionic state. When dyeing, it needs to be well colored in strong acidic medium, so it can be used for leather fiber dyeing.
Properties of acid dyes:
<1> Acid dyes contain sulfonic acid (- SO3H) and very few contain hydroxyl acid (- COOH). Their commercial form is sodium salt. Therefore, they have good solubility in water and can also be dissolved in alcohol.
<2> Acid dyes will form color change when they meet metal ions such as calcium, magnesium, lead, copper and iron.
<3> The chemical structure of acid dyes mainly belongs to monoazo structure, accounting for 50%, and triarylmethane structure accounts for 20%. Most of the acid dyes with monoazo structure are yellow; Orange; Red. Such as acid orange II, acid scarlet 3R, acid golden yellow G, etc. The structure of Bisazo type is mostly blue; Brown; Black, etc. Such as acid black att; Acid black 10B, etc. The structural types of anthraquinone are mostly blue and green.
<4> Acid dyes have a strong "affinity" for protein leather fibers, which can be quickly absorbed by leather fibers, gradually spread to the interior of the fibers, and can be fixed on the leather fibers, which is called the "affinity" of dyes.
<5> When strong acid dyes are used in leather dyeing, they have fast penetration and bright color, but poor wet treatment fastness. Washable; The indexes of dry and wet friction resistance are relatively low. The production process is simple and the product price is low. It is a sunset product in the leather dye market.
Direct dye
Direct dyes do not need the help of mordants when dyeing cotton, hemp and viscose cellulose fibers. Direct dyes are called direct dyes. Some varieties of direct dyes can be directly used for leather dyeing in acid medium. Direct dyes have large molecular weight and slow penetration, such as direct frozen yellow G, direct red brown RN, direct yellow brown D3G, direct bright red 4BS, direct sun fast black G (referred to as direct black) and other varieties. The production process is more complex than monoazo acid dyes. The product price is low. The indexes such as wet fastness, water washing, light resistance and wet friction resistance are not ideal in leather fiber dyeing. It is also a product facing elimination in the leather dye market.
2. High grade environmental protection leather dyes
Weak acid dyes, leather acid complex dyes. This series of products have bright leather dyeing, fast penetration, good sun resistance, light resistance, water washing resistance, migration resistance and other indicators. The products do not contain aromatic amines and heavy metals, so they are green and environment-friendly. It is the main product in the leather dye market at home and abroad.
Weak acid dye
Weak acid dyes are a kind of acid dyes with relatively large molecules and long common system. It contains multiple water-soluble groups, which improves the "affinity" with leather fiber. For example: (- COOH)), (- SO3H), (- SO3Na), (CONH2) and other groups. The "affinity" for leather fiber is large. Leather has bright dyeing, complete chromatography, high color fastness, and general light fastness of Grade 5-6. It is the main variety in the high-end market of leather dyes at home and abroad. Such as weak acid orange GN; Weak acid brilliant red B; Weakly acidic yellow 49; Weak acid black 210#; Weak acid black 242#; Weak acid black 168# and other Brown varieties: weak acid brown 75#; Weakly acidic brown 348#; Weak acid brown 349# etc.
Leather acid complex dye
Leather acid complex dyes and neutral dyes are acid dyes containing ions. When dyeing leather fiber, it is suitable for leather dyeing in strong acid bath. Like weak acid dyes, it has strong affinity on leather fiber, but the color fastness is higher than that of weak acid dyes. With the help of metal ion complexation, the water washing fastness is greatly improved, and the light fastness is generally grade 6-7.
Properties of leather acid complex dyes, < I > the molecular structures of these dyes used for leather dyeing are bisazo or triazo metal complex structures, and the adjacent positions on both sides of the azo group contain hydroxyl groups, (- OH), and multiple sulfonic acid groups (SO3H). Dyes are easily soluble in water, leather dyeing penetration is fast and easy to penetrate. The parent dye forms a 1:1 complex with metal atoms, and the complexing agents are mainly copper and iron. This series of products have dark groups (- OH), (- NH2), (- NHR), etc., so there are many dark dyes used for leather dyeing. Such as acid brown 75#, acid brown 98#, acid brown 161#, acid brown 165# and other varieties.
3、 Color matching of leather dyes
1. Color scale of leather dyes
Name of leather dye "color": it refers to the color name obtained after dyeing with this dye on leather fiber.
Domestic unification: beige, light yellow, yellow, dark yellow, golden yellow, orange, bright red, red, peach, rose red, red purple, jujube, purple, Cuilan, lake blue, blue, brilliant blue, dark blue, brilliant green, fruit green, green, grass green, dark green, olive green, yellow brown, red brown, brown, dark brown, chestnut brown, olive brown, gray, black, etc.
2. Leather dye matching
Dyes can be divided into red, orange, yellow, green, green, blue, purple and continuous seven color spectra. Red, yellow and blue are called three primary colors, such as basic colors. The basic color matching is shown in figures (I) and (II).
(1).jpg)
Yellow, orange, red and are usually called light colors, while blue, green and green are called dark colors. Color matching is also called color matching. In short, it is to use the original color to spell a new color or change the color light of the original color. Two or more dyes are often mixed to achieve the desired ideal color.
The three primary colors are mixed to get black, yellow and red into orange, yellow and blue into green, and red and blue into purple. Two primary colors are mixed to form a complex color (also known as secondary color), so orange, green and purple are complex colors.
Further double color triangles < 2 >, you can know more color matching relationships in the color circle. Among them, yellow and purple are the lightest and darkest in the color circle, and the opposite color is combined into gray. If a certain proportion of light yellow and purple, or red and green, or blue and orange form gray, this complementary color on the dye is called gray or black, which is called complementary color.
The secondary hue can be mixed to obtain three colors, such as yellow gray (olive), red gray, (brown) and blue gray. In the process of dye mixing, it must be prevented from being too close to gray or black, otherwise; The resulting color is turbid, not beautiful and not full enough.
Color matching is not to mix dyes of various colors at will, but should have certain conditions: generally, the fewer types of pigments for color matching, the better, the type of dyes must be close, the performance of dyes must be close, and the dyeing speed must be close, otherwise the expected effect cannot be achieved.
Reference
1、Xiao Gang, Yang Xinwei and sun Chaohui, world dye varieties, Vol. 1, 2005.
2、Chemical products manual, Volume II of organic chemical raw materials, Institute of scientific and technological information, Ministry of chemical industry, 1985.
3、Yang Xinwei, Luo Yuyan, he Yanbin, chemical products manual, Fourth Edition, dyes, 2005.
4、Compilation of analytical methods for dye intermediates by Song Jie, 1992.
5、Indian dye production process compilation, 1997.
6、Korean leather dye production process compilation, 2001.
7、Collection of test methods for dyes in Tianjin, 1983