Application of special structural polyurethane dispersions in water-based colorants

Foreword
Transparent color coating is one of the most common coating styles, because it can not only reveal the wood pattern through the bottom color, but also through the color difference between the background color and the face color to reflect the sense of hierarchy. In the protection of the wood at the same time, giving the wood a great aesthetic, to achieve excellent decorative effect. It is the main form of coating in the field of furniture, accounting for about 60% to 70% of the total amount of the whole field of furniture coating. At present, water-based wood coating in clean water coating, solid color coating, special effects coating can achieve better results, basically meet the general needs of furniture factory. However, in transparent color coating, there are still application bottlenecks, not suitable for large-scale production of furniture factories, hindering the large-scale application of water-based wood coatings market. The main problems are: dry film, wet film color difference is large, not suitable for furniture factory control color model production;
the above problems restrict the development of water-transparent color coating, so the development of a good water-like color repair agent is very necessary. After more than a year of research and testing, we have successfully developed a special structure polyurethane dispersion PU-5805 that can be used as a water-based color fixant.
PU-5805 is a solid content of 30%, the minimum film temperature of 45 degrees C, the appearance of translucent polyurethane dispersion, the product uses foreign imported raw materials, the amine synthesis to the polyurethane, with advanced process synthesis.
1 Experimental part
1.1 Experimental raw materials and instruments
styrene acrylic emulsion A, pure acrylic emulsion B, ordinary polyurethane dispersion C, special structure polyurethane dispersion PU-5805 D, water-soluble acrylic E, wetting agent, film-forming additive (DPnB), ethanol, water, red, yellow, black water oil two-use color essence and other
SZQ wet film preparationer, WGG60 E3 60 gloss gauge, JSF 400 mixing sander dispersion multi-use machine, 0-50um fine scraper, 202 AO table drying box, W-71 1.5mm caliber spray gun, JJ100 electronic scale.
1.2 experimental formulation and preparation process (for ease of operation, resin solid content is adjusted to 30%)
1.2.1 Table 1 experimental formulaRaw materials A B C DE 20-30 20-30 20-3 0 20-30 20-30humidifiers 0.5-1 0.5-1 0.5-1 0.5-1 0.5-1membrane additives

1-1.5 。 1-1.5 1-1.5 1-1.5 1-1.5Waterless Ethanol 60-60 70 60-70 60-70 60-7060-70desulbant 0 .1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.25-10 5-10 5-10 5-10 5-10 5-101-41-4 1-4 1-4 1-4Yellow Fine 1-4 1-4 1-4 1-4 1-4Black essence 1-4 1-4 1-4 1-4 1-4
1.2.2 preparation process
add resin to the container, mix well at low speed, add moisturizer, film-forming additives, waterless ethanol, desiccant, water, medium-speed dispersion of about 10min, Finally, add the color refinement of the target color and continue to disperse for 10 minutes. Before the material is made, scrape 100 micron wet film on the glass plate to see if there are shrink holes, if not, with 200 filter bags to filter out the material, that is, made of water-based wood paint finisher.
2 results and discussion
2.1 wet film and dry film color difference comparison
color, color is a major focus of the water-like wood paint repair process, but also difficult. Wet film opaque, dry film, wet film color difference, will increase the color chef's work difficulty, as well as paint master's accuracy of color.
table 2 the difference between the wet and dry film chroma of each resin (emulsion)
A 。 B C D E Resin (Emulsion) Appearance Milky White Milky White Blu-ray Translucent Blu-ray Translucent Blu-ray Full Transparent Dry, wet film color difference larger larger minor very slight None
from Table 2 can be seen that the resin itself the more transparent the appearance, the smaller the color difference of the wet film. C, D, E dry and wet membrane color difference is small.
2.2 Compared to waterless ethanol compatible
Drying speed is an important indicator of colorants, affecting the drying speed in addition to the resin itself, solvents also play a key role. Ethanol is the most common environmentally friendly fast-drying solvent.
Table 3 Comparing the compatibness of resins with a waterless ethanol
A 。 B C D E Waterless Ethanol (1:1) No Abnormality No Abnormality No Abnormality No Abnormality No Abnormality
From Table 3, it can be seen that A, B, D, E can be compatible with a waterless ethanol. C is a representative of the common water-based polyurethane species on the market, which have a characteristic: mixing directly with high-concentration ethanol thickens and becomes sticky. Even if the viscosity becomes thinner after increasing the amount of high-concentration ethanol, the spray will become a floc strip, which is not conducive to construction. Special structural polyurethane dispersions synthesized by special processes and materials can be mixed with aqueous ethanol in any proportion, and storage stability is good.
2.3 and chromosome compatible
more enterprises in the industry, each has a difference. There are too many factors, which is not conducive to comparing resins. Therefore, this experiment selected the industry to evaluate the better water and oil two-use color essence (Gongyao company).
table 4 the resins and the color refinement compatible comparison table
A 。 B C D E Blended Coloring (1:1:1) There is a small amount of slag no exceptions no anomalies no anomalies no anomalies
from Table 4 can be seen B, C, D, E are compatible with the color essence without abnormalities. Color essence is composed of alcohol ether solvent and dye powder, styrene acrylic emulsion cost is low, the use of raw materials is very likely not alcohol-resistant ether solvent, so the appearance of broken milk.
2.4 Water resistance comparison
the finished color is generally divided into bottom repair and face repair, whether it is bottom repair or face repair, after the finish of the finished color repair process to be sprayed on the finished layer of water-based paint, water-based paint accounted for 60-70%. Therefore, water-resistant wood paint has water resistance requirements for color repair agents. This experiment prepares a wet film with a thickness of 50 microns, drys 60min at room temperature, then drips water on top of the film, and keeps 15min on top of the film.
table 5 Water resistance comparison table for each resin
A 。 B C D E dry 60 min bubble water 15min no abnormal no abnormal blistering no abnormal blistering
from Table 5 can be seen A, B, D water resistance is better, C, E have foaming phenomenon. General polyurethane drying will be relatively slow, in the plasticization period is relatively easy to hydrophetize. Water-soluble acrylic resin contains amine neutralizers, at room temperature self-drying or in a short period of time, amine neutralizers are more difficult to volatile, so such resins will be less water resistant.
2.5 Adhesion Contrast
colorant as an intermediate coating, both to change the color to increase the beauty of the coating, but also to carry the role of the bridge. The color repair agent mainly relies on the resin in the system as the carrier to carry the color essence attached to the primer or wood. Therefore, the adhesion of resin is also an important indicator to consider color fixants.
table 6 resin adhesion comparison table
A 。 B C D E Adhesion (100-g method) 0 level 0 level 3 level 0 level 0 level
from Table 6 can be seen A, B, D, E adhesion no problem. C's adhesion is not good enough, mainly because it doesn't match the system.
2.6 color repair effect
from 2.2 experiment comparison, we ruled out C, because C is not good to do spray construction. Choose A, B, D, E resin, according to the reference formula ratio, the total amount of color essence is about 10% of the main agent of color repair agent, we try to do color contrast, spray 2 "crosses" under the same conditions.
table 7 each resin color repair effect comparison table
A 。 B D E color repair effect particles, spots uniform, slightly poor clarity uniform clarity home clarity
from Table 7 can be seen A because of poor compatible with color essence, particles appear;
a series of experiments, the special structure polyurethane dispersion PU-5805 color repair resin has great advantages.
3 Construction application notes
3.1 color and color addition
many master encountered to do a darker model, hope to be able to color soon, it is best to do only one color repair, so that "time-saving and labor-saving", but such a request often can not be desired. Because to do a dark repair, the total addition of color essence will be more than 15% or even 20%. Color essence contains a large number of high boiling point alcohol ether solvent, volatile is relatively slow, one-time thick spray, there will be bite bottom, flowering, seriously affecting the spraying effect of paint. In addition, the water-based wood finisher formulation of film-forming substances are polyurethane dispersion, generally accounted for 20% to 40% of the system, the formulation design should be as far as possible to reduce the amount of water-based resin, so that the effective film-forming substances in the system as little as possible, which is conducive to reducing the subsequent coating of film diseases, such as paint flatness, bite bottom and so on. Resin solid content is small, color essence is large, color essence can not be completely wrapped in resin, spraying the next paint, it is easy to appear flowering, corner blacking and other phenomena.
suggests that the total amount of color essence added during dark coating should be controlled to within 10%, and the color should be repaired in parts.
3.2 dilution
because the formulation design is relatively low viscosity, do not add any solvent or water dilution, can be used directly.
3.3 substrate requires the
substrate to be polished as carefully as possible, without visible sand marks, it is recommended to use 320 sandpaper before sanding with 600 sb paper light sand, in order to eliminate