Overview of water-based color pastes, production process formulations, instruments and equipment and precautions detailed
Comprehensive overview of color paste
Water-based color paste refers to the organic or inorganic pigments under the wetting and dispersing effect of surfactants (water-soluble resin can also be added), forming a uniform, stable, liquid or thixotropic liquidity, strong coloring strength of concentrated pigment paste. There are two kinds of water-based color paste systems: one is a high pigment content resin-free system; the other is a low pigment content resin (general resin, other single resin) system. The former has high pigment concentration, strong coloring power, good color spreading performance, good compatibility, thixotropic fluidity, generally does not cause floating color and flowering, reasonable choice of additives, and is universal. The latter pigment concentration is relatively low, but has good coloring power, good color spreading, liquidity and viscosity is more stable, the system contains resin, compatibility needs to do test, otherwise it is easy to lead to paint floating color and flowering. The technical index of the color paste mainly consists of the following aspects:
The international pigment number of the color powder
The pigment number determines the light resistance (weather resistance) and chemical resistance (acid and alkaline resistance) of the color paste, and also determines the general hue of the color paste, because the production process of each color paste company is not the same, the hue of the color paste may have slight differences.
Coloring strength of the color paste (coloring power)
Coloring power refers to the number of grams of a certain color paste used when the white latex paint containing 100 grams of titanium dioxide is adjusted to 1/25 standard color depth, the less the amount of color paste, the stronger the coloring power. For the comparison of water-based color paste, coloring strength is an important indicator, which reflects the color concentration of the color paste, color performance and pigment dispersion flocculation. The stronger the coloring power of the color paste, the less the amount of color paste used in color mixing, the smaller the impact on the performance of the coating film, and the lower the cost of color mixing.
Color difference ΔE
The stability and color reproducibility of color paste are mainly reflected in two aspects: coloring power and color difference. The color difference of color paste includes the color difference between different production batches of the same color paste and the color difference between different packages of the same batch. The size of the color difference is expressed by ΔE, including color hue, lightness and darkness, saturation. Its calculation formula is as follows:
ΔE = (Δa2 + Δb2 + ΔL2)
1/2 The color difference of the color paste affects the accuracy of color mixing and the stability of the color mixing formula.
Light and weather resistance of color paste
The test of light and weather resistance of color paste is through outdoor exposure (such as Florida in the United States, China’s Turpan and other places have exposure field), but the actual outdoor exposure time is too long, and now most of the general color paste performance testing is through instruments and equipment and other simulation test. Light resistance test: Exposure under xenon light, measured by blue wool ruler, expressed as 1-8 level, level 8 is the best, level 1 is the worst. Weathering resistance test: use ATLAS aging instrument, regularly exposed to xenon light and sprayed with water, exposed to 500 hours, color difference is expressed by ISO gray scale 1-5, grade 5 is the best, grade 1 is the worst. The color paste for exterior wall needs to have the light resistance above grade 7 and weather resistance above grade 4 at the same time.
Pigment content of color paste
The pigment content is only for reference and cannot be used as an indicator to evaluate the performance of the color paste. The coloring power of the color paste is not simply proportional to the pigment content. The same pigment content, its fineness is different coloring power also has a great difference. In order to ensure the stability of the coloring power of the color paste, the pigment content of the color paste is within a certain range of variation values, the value provided on the color paste information is a typical reference value.
Fineness of color paste
Fineness is an intuitive indicator reflecting the coloring power dispersion effect and storage stability of the color paste. Generally, for the same pigment paste, the smaller the particle size, the larger the specific surface area, and thus the covering ability, the higher the coloring power; the smaller the fineness, the higher the gloss, the better the dispersion effect and storage stability. Of course, the fineness of the color paste is not the finer the better, because when the particles become smaller, its specific surface area increases, the absorbed light energy increases, the degree of damage also increases, resulting in its weather resistance is reduced; and the particle size is too small in the coating film drying, with the precipitation of water, the color paste together to the surface migration, easy to cause inaccurate color matching and wall color difference.
Compatibility of color paste and paint (finger research method)
Take 100 grams of white paint, add 2-3 grams of color paste to be tested, stir well, spread on the surface of the object to be coated, when it is about to condense, grind the surface part of the coating film with fingers, after the paint film dries, observe whether there is a color difference between the place that has been rubbed and not rubbed with fingers, such as a large difference, the compatibility of the color paste and the tested paint is not good, the paint mixed with this color paste is easy to produce the phenomenon of floating color. If the color is the same, generally will not produce the phenomenon of floating color. When choosing the color paste should focus on the above factors, other conditions of each brand of color paste can basically reach and not much difference.
2 Application examples
Take BF-409 water-based color paste (black) as an example
Formulation:
Production quantity: 160Kg
Serial number
Name of raw material
Specification
Actual quantity Kg
1
Deionized water
Industrial
58
2
F-19 anti-freeze leveling agent
Industrial
8
3
H-28 Preservative
Industrial
1.1
4
H-9 defoamer
Industrial
1.6
5
J-11 pigment black
Industrial
40
6
H-21 Neutralizer
Industrial
Moderate amount
7
Other
Product index
Test items
Indicator
Test method
Condition in the container
No hard lumps and uniform state after stirring and mixing
Visual inspection
Solid content
≥30%
GB1725
Fineness, μm
≤30μm
GB1724
Weather resistance1/25ISD
4-5
GB/T 9755
Process:
1, put (1) into the pulling cylinder, start stirring, under low speed stirring, add 2, 3, 4, 5 in turn, stir evenly add (7), adjust PH = between 7~9, disperse evenly on the blue sand mill, until fineness ≤ 30μm can be;
2、After the fineness is qualified, notify the analysis to measure the solid content, and after meeting the index, filter, discharge and package.
3 Water-based color paste production and testing of the main equipment
Production equipment
1、High-speed disperser, 1 set, FL22, Jiangyin Fine Chemical Machinery Co.
2、Laboratory basket type sand mill, 1 set, Millennium Micromill EEX, Oliver+batlle company, Spain
3、Basket sand mill, 1 set, HCP-5, Oliver+batlle, Spain
4, pulling cylinder (with jacket), 1 each of 100L and 200L
Testing equipment
1, scraper fineness meter, 100um, 50um each 1 set, Tianjin Jingke material testing machine factory
2、Electronic balance, XP2002S, METTLER TOLEDO
3、Electric blast dryer, GHG-9076A, Shanghai Junzhu Instrument Manufacturing Co.
4、Artificial aging instrument (xenon lamp tester), Xe-3HS, USA
4 Other notes on the production of water-based color paste
Requirements for technical personnel
Due to the differences between different batches of pigments and other raw materials, it is necessary to make timely adjustments to the production formula to ensure the stability of the color paste production. Therefore, technicians are required to have a wealth of relevant expertise in the production of color pastes.
Stability of color paste
Different varieties or different batches of color paste production, because of the quality of raw materials and production process there are certain differences, so may cause the color paste in the process of storage thickening, water separation, back to coarse and other phenomena, need to re-grind the color paste dispersion qualified before use.
High price of raw materials, avoid waste
In order to ensure the quality of color paste, some pigments, dispersants and other imported products, the price of raw materials is very high, so in the production to eliminate waste, otherwise it will cause the cost of color paste growth.
Grinding equipment
As it is more difficult to disperse and stabilize pigments in color paste production, basket sand mill with high grinding efficiency is used.
In addition, imported equipment is much better than domestic manufacturers in terms of grinding efficiency, stability and service life, so imported equipment is used. Overseas production of the equipment companies mainly include: 1. Singapore Nissei company 2. Spain O + B company 3. Germany NETZSCH company. Spain O+B company’s products through the Changzhou coating research and design institute bidding after selection proved that its efficiency and wear resistance, are obvious other imported and domestic equipment, so we also choose Spain O+B company’s products.
