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Do you know how plastics match colors?

Issuing time:2022-03-23 14:43
To match a bright white product, the first choice is titanium dioxide with blue light in the background color (the chlorination process should be used to produce titanium dioxide with small particle size and uniform molecular weight distribution), because the preparation of white with titanium dioxide with blue light in the background color will give people a sense of freshness. On the contrary, if you choose titanium dioxide with large particle size and yellow light in the background color, no matter what method is used to adjust the color light, you can't achieve bright pure white.


1. How to prepare extra white plastic products

To match a bright white product, the first choice is titanium dioxide with blue light in the background color (the chlorination process should be used to produce titanium dioxide with small particle size and uniform molecular weight distribution), because the preparation of white with titanium dioxide with blue light in the background color will give people a sense of freshness. On the contrary, if you choose titanium dioxide with large particle size and yellow light in the background color, no matter what method is used to adjust the color light, you can't achieve bright pure white.

Because the whiteness of titanium dioxide is not enough, additives are often added to whiten when coloring plastics. A very small amount of blue and purple pigment or fluorescent brightener can be added for whitening. The whitening effect of titanium dioxide is as follows: the commonly used and simplest method is to carve white blocks with fresh green, and its whitening effect is called magnetic white on the market; Fluorescent whitening has the best effect, but its cost is the highest.

2. How to prepare extra black plastic products

When preparing special black products with carbon black, we should pay attention to the problem of carbon black light. Under the incident light, the carbon black with small particle size is usually more blue than the carbon black with large particle size, but it is brown under the transmitted light (transparent coloring) and gray. In order to get a bright black plastic product, choose low structure carbon black with small particle size. This is because when carbon black is colored, the blackness is mainly based on the absorption of light. Therefore, the smaller the particle size, the higher the degree of light absorption, the weaker the light reflection and the higher the blackness. The above carbon black varieties are selected. In order to obtain satisfactory coloring effect, special attention should be paid to the dispersion of carbon black. Only by solving the dispersion of carbon black can the highest coloring power of carbon black be achieved.

After the oxidation of carbon black, the introduction of polar groups such as - oh and - COOH will improve the dispersion of carbon black. Therefore, there is a volatile index in the performance index of carbon black. The higher its value, the higher the oxidation degree.

In any case, carbon black always has some yellow light, so blue can be used for color matching, and its dosage is 8% ~ 10%. In this way, the black blackness of the prepared black is greatly increased. The pigment blue 15 is generally used: if the blue colorant is used for color matching, and then purple or red is used for color matching, the black blackness of the prepared black may be darker.

3. How to prepare gray plastic products

When using carbon black to prepare gray, we should pay attention to the problem of carbon black light. The particle size of carbon black is small, and the gray with yellow tone appears when adding titanium dioxide; The particle size of carbon black is large. When titanium dioxide is added, it will be blue and gray. The particle size and particle size distribution of titanium dioxide also have a great relationship with the light of titanium dioxide. The large particle size of titanium dioxide has yellow light, and the small particle size has blue light. Therefore, when preparing gray, we should first understand the relationship between the particle size and tone of carbon black and titanium dioxide, otherwise the tone is wrong, and then adjust it with pigment, which will become more and more complex.

After determining carbon black and titanium dioxide, sometimes other colors need to be used for color matching of gray products to meet the requirements of users. Due to the small amount of pigment added, some varieties with low coloring power should be selected, such as iron oxide (pigment yellow 119, pigment red 101), metal oxide (pigment yellow 53, pigment Brown 24), which can make the color stability of the color matching system better.

4. How to prepare outdoor plastic products

(1) Dark outdoor plastic products.

Plastic products, such as stadium chairs, steel cable sheaths of bridges, building materials, advertising boxes, turnover boxes, plastic auto parts, etc. because they are used outdoors for a long time, they must have good light and weather resistance. Inorganic pigments generally have good light stability and can be used for color matching of outdoor plastic products, but they are limited due to their low coloring power.

When preparing outdoor products, we should first choose colorants with good light resistance and weather resistance, and then use less or no titanium dioxide in the products to make the pigment concentration as high as possible. In addition, there is enough antioxidant in the formulation to ensure that there is no discoloration in the resin. Plastic products for outdoor use shall be organic plastics.

(2) Light colored outdoor plastic products.

Light colored plastic products are prepared by adding a large amount of titanium dioxide and a small amount of pigment. Since the weather resistance and heat resistance of most organic pigments will decline in varying degrees after adding titanium dioxide, the impact of light colored varieties is greater due to the small amount of pigment added. Many varieties have a very bad impact due to poor weather resistance, resulting in fading of plastic products and customer complaints. In addition, due to the high coloring power of organic pigments, the amount of organic pigments added in light color varieties is small. Due to error transmission, there will be color difference in production and color deviation in use.

Light colored varieties should be prepared with inorganic pigments, mainly taking advantage of their good heat resistance and low coloring power. The optional inorganic pigments are pigment yellow 119 (iron oxide), pigment yellow 53 (metal oxide), pigment Brown 24 (metal oxide), pigment Brown 184 (bismuth vanadate), pigment red 01 (iron oxide), pigment blue 29 (ultramarine), pigment green 8 (cobalt blue) and pigment Brown 50 (cobalt green).

5. How to prepare transparent plastic products

Prepare light colored transparent products. Firstly, the resin itself is transparent and colorless, such as polypropylene and transparent styrene. Choose a colorant with good transparency and consistent color and light. Generally speaking, inorganic pigments have poor transparency and cannot be applied. The varieties with good transparency in organic pigments are: pigment yellow flower 139 (isoindolinone), pigment yellow 199 (anthraquinone), pigment red 149 (perylene system), Pigment Red 254 (diketone pyrrole pyrrole), pigment blue 15:1 (phthalocyanine), pigment green 36 (phthalocyanine) and pigment Brown 41 (condensed azo).

6. How to prepare pearlescent plastic products

The addition ratio of pearlescent pigment in plastic injection molding products is generally 1%; In extruded film products, it is 4% ~ 8%, and the specific situation depends on the thickness of plastic film; Similarly, during CO extrusion, the pearlescent content in the pearlescent layer should be increased accordingly. According to the thickness of the plastic pearlescent layer, the addition amount is 5% ~ 10%.

(1) Pay attention to the selection of pearlescent pigments and organic pigments. The following points should be paid attention to when using pearlescent pigment in plastic processing:

The transparency of the colored resin is better; Use pigments with good transparency (such as organic pigments) and solvent dyes as far as possible; It cannot be compatible with titanium dioxide. In order to achieve a certain hiding power, pearlescent pigments with small particle size can be used at the same time, and pigments with high hiding power should be avoided as far as possible; When pearlescent pigments are applied to outdoor plastic products, the weather resistance of pearlescent pigments should be considered.

(2) Pay attention to the processing and molding process of pearlescent pigment.

During injection molding, the back pressure is increased to improve the mixing performance of the screw, so as to improve the dispersion of pearlescent pigment. The processing temperature during injection molding is generally selected at the upper limit of the recommended service temperature range of the resin, which can ensure the dispersion of pearlescent powder. In the process of molding, the flow of melt drives the automatic orientation of pearlescent pigment flakes and achieves good pearlescent effect.

The finish of die surface is very important. The smoother the mold is, the more uniform direction arrangement and smooth pearlescent color can be obtained.

The design of mold gate is also very important. Choosing a single gate can reduce the outflow line of the die more than multiple gates. The gate should usually be located in a thick place away from the flow barrier, and the distance between the end of the gate and the runner system should be as small as possible, so as to reduce the uneven distribution and disordered arrangement of pearlescent pigments caused by the difference of fluid resistance.

Due to the existence of muguang pigment in flakes, the particle size of pigment will become smaller and the pearlescent effect will be reduced due to the influence of shear force in the process of plastic processing. The filter screen with large length diameter ratio and appropriate fineness is adopted to increase the pressure of the machine head and reduce the damage of shear force to pearlescent pigment during processing as much as possible.

Pearlescent pigments used in PMMA, PC and PA systems must be dried in advance.

In PVC plastics, when using gold and bronze pearlescent pigment series products, due to the presence of free iron ions, it will accelerate the decomposition of PVC resin, which must be paid attention to during use. Silver white pearlescent pigment will turn yellow in some pigment products. It is recommended to use anti yellowing series products.

7. How to prepare gold and silver plastic products

Silver powder is actually aluminum powder. Because the aluminum surface can strongly reflect the whole visible spectrum including blue light, aluminum pigment can produce very bright blue white specular reflection light.

There are different varieties of aluminum powder used in plastics. Average diameter of particles 5 μ m. Its coloring power and covering power are excellent; Average particle diameter 20 ~ 30 μ m. It can be used together with color pigments; Average particle diameter 330 μ m. It has extra thick flicker effect.

The melting point of aluminum powder is 660 ℃, but when it is in direct contact with air at high temperature, the surface is oxidized to gray white. Therefore, the surface treatment of aluminum powder and silicon oxide protective film can make it heat-resistant, weather resistant and acid resistant.

Gold powder is copper powder, which is easy to oxidize at high temperature. Its weather resistance is not good, and it will be dark outdoors for a long time. If the surface of copper powder is covered with silicon oxide protective film by treatment technology, its heat resistance, weather resistance and acid resistance can be greatly improved. Rsist brand gold powder provided by German Eckart company is treated with silicon oxide. The color masterbatch produced with its raw materials will not darken during injection molding at high temperature.

In order to prepare special metal effects, a small amount of organic pigments with good transparency and similar color and light can be appropriately added, but it should be noted that if too many substances such as titanium dioxide and pearl powder are added to the formula, the products will also be darkened.

Because both gold powder and silver powder are in flake structure, it is easy to produce mold flow outlet in injection molding with metal pigment and pearlescent pigment, which affects the appearance of plastic products. The following methods can be used to reduce or reduce the above situation: using large particle size metal pigment; Increase the amount of metal pigment; Select resin with high viscosity; Increase the injection aperture; Increase the injection speed.

8. How to prepare fluorescent plastic products

The fluorescent pigment used in plastics is made by dispersing the fluorescent dye in a specific polymer resin, so that the fluorescent pigment will not migrate. Since 1970, polyamide resin with complex system has been used to make the thermal stability of fluorescent pigment reach 305 ℃, and the recent development of fluorescent pigment with polyester as carrier has also been successful, and its thermal stability can also reach more than 285 ℃.

Fluorescent pigments are sensitive to ultraviolet light, so their light resistance is poor. The method to improve the light resistance of fluorescent products is to add non fluorescent colorants with the same tone.

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