Selection of rubber colorants

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Selection of Rubber Colorants Most rubber products are colored black, gray or white. These are all achromatic colors. In addition, there are colored colors including red, blue, yellow, green, brown, pink and other colors. Rubber products can be colored not only with various pigment mixtures, but also with specific pigments in non-mainstream colors such as orange-red, green and pink. This article will focus on pigment pigments and their matching techniques. Color Regarding the selection of pigments, the selection of appropriate color pigments depends on the processing requirements described previously and the end use of the product, with the latter being more important. The following factors must be considered: Resistance to fading (caused by factors such as sunlight, heat or natural aging) ； Bleed resistance ； and harmful effects on the aging properties of the base compound (avoid colors containing copper or manganese). In addition, because colored rubber products must participate in market competition, in order to reduce the color cost per pound of vulcanized rubber products, it is necessary to carefully select the most economical pigments to achieve the desired results. There are two types of pigment pigments available - inorganic pigments and organic pigments. Inorganic pigments iron oxides, lead pigments (such as chrome yellow), ultramarine blue, chromium oxide and cadmium pigments are commonly used types. Iron oxides include red, yellow, brown and tan, all of which produce dark light. It is recommended to use synthetic iron oxide. They all work as pretty good powders with specific gravity. Care must be taken when selecting iron oxide because some grades of iron oxide contain impurities, such as copper – which can accelerate the aging of the vulcanized rubber product. Ultramarine blue pigment produces a range of blue colors from greenish to reddish. These pigments have superior thermal stability and lightfastness. However, they are not resistant to acids, which would limit their use in many outdoor applications, as well as any indoor applications containing fruit juices, etc. The biggest use of ultramarine blue in rubber is to tint white rubber compounds, just as bluing is used to clean white undershirts. Bright colors are possible when using ultramarine blue, which produces a full color light. Chromium oxide green can provide a blue-cyan light that has good heat resistance and light fastness. Its proportion is huge. Lead pigments include numerous chromate yellow pigments and molybdate orange pigments. They all produce bright colors with good heat and light fastness, but they are lead compounds and the dust in them can flicker and burn. In compounds vulcanized with sulfur, any moisture may cause lead sulfide spotting. Now mostly replaced by organic pigments. Cadmium pigments are only used in professional applications where specific fastness properties are required. This pigment is often used as a basis for improving dispersion and hand. But they are heavy and expensive, and cadmium is also a heavy metal that should be avoided in rubber compounds. All inorganic pigments have weak coloring power. They are usually used in amounts of 2% to 5% by weight of the compound. Under normal circumstances, inorganic substances are easier to disperse and have less dust than organic substances, because their particle size is larger and their specific gravity is larger. Despite this, all color paints still contain dust, and precautions must be taken before production. Organic Pigments Organic pigments are used because they can form bright and attractive shades of color. The technical requirements for certain rubber products can be achieved by selecting the appropriate pigment or mixing pigments. From an aesthetic point of view, the use of organic pigments produces bright colors, as opposed to the dark colors produced by inorganic pigments. This reason has led to the extensive use of organic pigments in rubber compounds. However, most organic pigments are not as good as inorganic pigments in terms of heat resistance, light resistance and bleeding. In fact, their advantage lies in producing a more beautiful appearance of the product. Organic pigments are much more expensive per unit than inorganic pigments, but they are also more effective. Still, using organic pigments is naturally expensive. The attached table lists the types of organic pigments commonly used in rubber compounds by chemical type and color index value. The data show key technical properties including thermal stability, light stability, soap resistance and direct water vapor vulcanization capability. Organic Red Pigments Red is probably the most popular color. Because of the chemical properties of red organic pigments, it can also be the most troublesome color. When coloring rubber products, there are 8 types of organic pigments commonly used (see table). They are: Permanent Red 2B ； Pyrazoline red ； Sulfur red ； Quinacridine red ； Naphthol red ； Lisol ruby ​​red ； Lake Red C and Lisol Red. Permanent Red 2B is the most widely used and includes barium and calcium salts. Barium salts produce orange-red light, while calcium salts produce particulate blue-red light. Mixing the two salts can create a variety of shades, all of which are deep bright colors and have fairly good resistance to color bleed. They also have good thermal and light stability, in fact they start to fade above 176°C. Pyrazoline red can form a color between the two colors of barium salt and calcium salt. Different types of pyrazoline and red will produce different shades of light, but there is no obvious difference between these shades of light. Pyrazoline red is bright, clean and transparent, and is a purely organic pigment rather than a salt. Their thermal stability and light stability are roughly equivalent to 2B red. Pyrazoline red is an organic pigment that can be used in rubber products that come into contact with food. This is described in Section 177.2600 of the Federal Register, Chapter 1 of Title 21, "Reusable Rubber Products." It is much more expensive than 2B red, but it is necessary to use it when there are specific requirements for color light, better resistance to bleeding, or for medical purposes. Technically speaking, sulfur red is an expensive pigment with superior properties. It is mostly used in mixed pigments, and is only used to obtain a special color. The technical properties of quinacridine are quite superior. In fact, they cost roughly $20+ per pound. This pigment can be used in rubber products that come into contact with food. This is described in Section 1772600 of the Federal Register, Chapter 1 of Title 21, "Reusable Rubber Products." Different salts of chromophen red can form different colors of light, such as orange red, blue red, etc. Similar to Permanent Red 2B, it is an expensive pigment. Lisol red, golden red C and Lisol red are all?span href=" tag.php ?name=%CF%B5%CD%B3" class="t_tag">The system is difficult to kill the mirror. It is difficult to kill 9 kinds of pigments. In fact, their technical properties are relatively poor. As people increasingly emphasize the quality and service life of rubber products, these three pigments are used less and less. Manufacturers of extruded, molded and calendered colored rubber products prefer the form of rubber color master mixes. In most cases, these master mixes are produced at approximately 50% color pigment content in a polymer binder. Their dosage is approximately 1% to 3% of the total weight of the compound. Pyrazoline Synchronous Red and Permanent Red 2B pigments are difficult to disperse, so the use of rubber color master blends of these two pigments is highly recommended. Organic Orange Pigments There are 2 main types of organic orange pigments: Dianisidine and Benzidine Orange. Dianisidine produces a clean, reddish shade, while Benzidine Orange produces a yellowish shade. They all have good color fastness, among which benzidine orange has better light fastness. Their relevant data are in the table. These two pigments are easier to disperse than the red pigment discussed before, but the use of rubber color master mixtures is more common. Its concentration and usage are the same as the red matrix mix. Benzidine Yellow These pigments create a bright, clean yellow shade. There are four main grades depending on the degree of substitution of the molecule. they are: AAA, AAOT, AAMX and AAOA. They are arranged in order from low to high colorfastness, as shown in the table. These pigments are considered the most easily dispersed of the organic color pigments. In fact, the master mix method is widely used and its properties are the same as those of the colors mentioned before. Phthalocyanine blue is the preferred pigment for blue rubber products. There are many kinds of light, among which red light (RS) is the most used in rubber. At the same time, its thermal stability is also the worst, so the vulcanization temperature must be considered when using this phthalocyanine blue. The amorphous grade has a less obvious red color, but has better thermal stability. Green photophthalocyanine blue is quite weak in intensity, but has good thermal stability and is more expensive than other grades. Phthalocyanine blue pigments are difficult to disperse and should be used in rubber color master mix form or color paste form. The properties of its rubber color master mix are similar to those of other colors. Phthalocyanine green is a pigment that can produce several colors of light, including slightly yellowish green light and slightly bluish green light. Although many green rubber products are made from a mixture of yellow, blue or green, phthalocyanine green is the most widely used single color pigment in green products. All shades of Phthalocyanine Green have good technical properties and are difficult to disperse. Likewise, it is recommended to use the master mix method, whose properties are similar to those of other colors. Color Matching In fact, very few rubber products are made from a single pigment, whether inorganic or organic. The final color of a rubber product is matched to a specific color approved by the buyer or seller of the product. Therefore, color matching becomes a major requirement in successful rubber product production. Moreover, colored products are related to fashion, and merchants or buyers are always asking for new colors. For color mixing, there will be inorganic pigments and organic pigments in the mix. The effectiveness of the match must be evaluated under both artificial and daylight sources. The new technology can even offer several different types of artificial light. This matching is performed by a skilled laboratory worker who uses his eyes and knowledge to achieve the best possible match. Today, color computers have been developed to the point where the color of a rubber compound can be determined graphically. In fact, with the right program, a color computer can even assist colorists in selecting the right pigments and the amount to use. In fact, at least in the author's experience, the final decision is still made visually. In cases where a rubber product has to match an entirely different item, it is possible to get some kind of match, which is characterized by: Perfect appearance under one light source ； Under another light source, it looks completely different. Whether such a match is acceptable depends on the light source used in the application and, in particular, the specific test procedures used by the customer. When a match is technically impossible, the colorist must adjust the work and raw materials to achieve the match as closely as possible under different test conditions. This usually requires 3 or more pigments and the composition of the mixture must be carefully adjusted. It is important to adjust the type and amount of titanium dioxide. Conclusion and Summary: In short, to summarize what has been said above: Inorganic pigments can provide rubber compounds with good heat resistance, light resistance and bleed resistance at low cost. These colorants are mostly used as powder pigments, and the dosage is 2% to 5% of the total weight of the compound. The resulting shade is less bright and clean. For brighter, cleaner colors, organic pigments are necessary. They have greater coloring power and are more expensive per unit. The thermal stability, light resistance and bleeding resistance of organic pigments are not as good as those of inorganic pigments, and they are more expensive to use. Generally speaking, organic pigments are difficult to disperse in rubber compounds and are dusty when applied. In fact, they are usually used as rubber color master mixtures. This early dispersion eliminates dust issues, greatly improves color uniformity in the final product, and makes colorant weighing and handling easier. This post was last edited by wivern on 2009-3-22 08:08 ]