Development and application of high-performance first-stage dispersion hydroxypropyl emulsion

Author
: Chen Weilin, Sheng Guangjia, Jin Yaping, Yang Libin, Xia Jianfeng / BASF New Materials Co., Ltd.
water-based wood paint in China has been developing for more than 20 years, the most
can be traced back to 1996 German Dufang water-based wood paint and
Shandong Alemei two brands listed in China. For the first
, formulation engineers were basically in the original groping phase, constantly testing emulsions
raw material reserve formulations. Because of the relative advantage of price/performance ratio, the single-group system
(including acrylic acid, polyurethane acrylic PUA and polyurethane dispersion PUD),
in pine children's furniture, wooden doors, board furniture, wood toys and ornaments, such as
sub-sectors to stand out by 2010 After the application of technology basic
formed an "oil bottom surface" or "UV bottom water surface" mature process
genre, but the performance is still difficult to get close to solvent-based two-part polyurethane (2K
PU), can not achieve more breakthroughs in high-end applications . Water-based 2K PU's
technology exploration started about the second decade, technology has developed three generations of
polycyanate curing agent, performance of hydroxypropyl emulsion and even hydroxyl
PUD, physical properties can be comparable to solvent-based 2K PU, but high raw materials into
, complex raw material mixing and narrow construction adaptability, so that the application of water-based
2K PU to promote the "thunder rain point."
, the water-powered 2K PU has developed two systems, "low hydroxy low light" and "high
hydroxy highlight", as shown in Table 1 below. Due to good construction adaptation, not
easy to find paint film ills (dark bubbles, pinholes, tweezers, etc.), low-hydroxy system has been
mature application and promotion. On the other way, high hydroxyl system, although can achieve ultra-high light and not
wrong fullness, but the paint film drying slowly, poor stacking resistance, seriously affecting the production
efficiency, and paint film defects are very easy to find, repair rate is very high, rarely into
mature solutions, the overall cost is higher. These are applications of high
pain points, making formulation engineers easily afraid to try.
technical route for hydroxypropyl emulsion synthesis
analysis of the synthetic classification of hydroxypropyl emulsions for the requirements of high hydroxy systems,
will help us to understand more development ideas. Hydroxypropyl emulsions can be divided into
dispersions and secondary dispersions according to the process of synthesis. Figure 1 below
shows that the first dispersion is a one-step method to obtain the final product, the second-stage
dispersion needs to be polymerized by solvent polymerization to obtain the polymer, and then through the molecular chain
on the hydro-water-based group to regain stability dispersion to the water to obtain the product. Figure 1
shows that from the equipment, the secondary dispersion must be equipped with explosion-proof reactor,
investment costs, transfer to the product unit cost is higher, the price is naturally
high. From the microstructure of the polymer, the molecular weight of the secondary dispersal body
cloth is narrower, and the particle size and water phase matter of the dispersion are more controllable, the theory
, emulsion appearance permeability and chemical resistance should be better than the first dispersion
.
experimental

Joncryl® OH 8770ap, Hydropalat® WE 3221, FoamStar
® SI 2280, Rheovis® PU 1191, Dispex Ultra P X4575: Bar
New Materials Co., Ltd.; Target Product 1, Target Product 2: Other Foreign
-funded Companies; BDDE (BDG), DMEA, Ethanol: National Pharmaceuticals
Group Chemical Reagents Co., Ltd.; Tioxide R706:Chemours Co., Ltd.
test equipment
portable gloss instrument, swing bar hardness tester, wire rod -100 microns:
BYK Company; pencil hardness tester: Modern Environment Co., Ltd.
water-based paint preparation
water-based varnish preparation: A part according to Table 3 emulsion in the stirring 600rpm state
, in turn according to the formula slowly added to each raw material, all A-part raw materials added to
finished, and then evenly and fully stirred for 15 minutes.
water-based white paint preparation process is as follows: according to table 2 formula will be the various groups of grinding
scattered to 15 microns, white water-based white pulp. When making white paint, the table 3 varnish
and table 2 white paste according to the quality ratio of 5:1 mixed evenly, obtained the white
coating.
sample paint film preparation
paint film
: using black and white paper jam and glass plate, reference
GB/T9271-1988 preparation paint film test plate, using wire rod 100 microns
for coating film, paint film dry film thickness of 25-30 microns. After 7 days of room temperature
test the luster, hardness and stain resistance of the paint film.
test
the film gloss by GB/T9754-2007 and the hardness of the coated pencil by GB/T6379
2006. According to ISO-MAT-0066-R2 to determine the coating film
sterol stain performance.
measurement of scratch-resistant preservation rate:
scraped 100 micron wet film on TheLeneta paper jam, after 4 hours of drying at room temperature
, 50 degrees C dried for 16 hours, measuring the original gloss
(60 degrees); Underneath the weight is 3 M standard sandpaper (model 3M2 81Q
WETORDRY, diameter 3.5cm), friction back and forth 20 times, the gloss of the
after the scratch (60 degrees);
to calculate the preservation rate , the gloss after scraping / the original gloss.
high hydroxy emulsion formulation design and test results
for the water-based 2K PU application difficulties in the high hydroxy system, and then comparative analysis of the characteristics of the
two dispersions, it is not difficult to see the technical route of the first-stage dispersion
line is easier to obtain cost-effective solutions. BASF has developed and produced a new
-stage dispersion, Joncryl® OH 8770 ap, which we will analyze and compare from
to sex.
will be Joncryl® OH 8770 ap and two commonly used secondary dispersion
, choose with good compatible raw materials, with high-gloss varnish. In addition to
other instructions, the performance of the highlight varnish
is compared according to the test method of the national standard, and the
difference between Joncryl® OH 8770 ap and the target product is analyzed.
1) The clearness of the paint film
. By controlling the particle size of hydroxypropyl emulsion, the
can further improve the appearance of the emulsion and the moisture film permeability of the water-based paint, Figure 3 also fully confirms this, the average particle size of about 100 microns can be translucent effect. As for the permeability of the dry film, in addition to the average particle size of hydroxypropyl emulsion, there are also dry conditions, film-forming conditions, as well as water-based paint formula in the compatible of the various ingredients, can only be based on the actual results.
2) Double cross-link
. The formulation cost of water-based 2K PU mainly comes from hydroxypropyl
emulsion and curing agent, especially the curing agent price is more high, so the introduction of appropriate self-connecting monosome in hydroxypropyl, in the case of the same proportion of curing agent dosage, paint film crosslinking is higher, denser, chemical resistance will be better, as shown in Figure 4. Therefore, the introduction of more self-linking monosomes with the same cross-link density without affecting performance can reduce the amount of curing agent, thereby reducing the overall cost of water-based paint formulation, and also reducing the risk of bubble production during the reaction process, so that the coating episosis can be further improved.
In accordance with the varnish formula in Table 2 and the addition of 20%
titanium white slurry to the varnish formula, the chemical resistance of the dry film was tested and found that Joncryl® OH 8770 ap
also differs from the two secondary dispersions, as shown in Figures 5 to 6. In the
paint dry film alcohol resistance (1 hour) test, the same curing agent dosage,
to the standard product 2 ethanol resistance test process, the paint film breakage, Joncryl®
OH 8770 ap passed the test, and the standard product 2 must increase the curing agent
dosage to pass the test. In the stain resistance test of the paint, we selected
the most demanding test medium yellow mustard (1 hour), the same curing agent
dosage, after testing Joncryl® OH 8770 ap residue of yellow mustard significantly less than
.
3)
glassing temperature
. To increase the glassy temperature of hydroxypropyl emulsion, one side of the
side helps the emulsion itself to become faster and drier, effectively and quickly paint film hardness is established, and enhances the stack resistance of the paint film, but on the other hand, the rapid drying of the emulsion naturally makes the lacquer film leveling time shorter, gloss and plumpness will be worse, can only be balanced by adjusting the formula. By comparing the physical properties of three hydroxypropyl emulsions at different NCO/OH ratios, it is found that Joncryl® OH8770ap and the swing bar hardness of the benchmark product 2 can reach a higher level at an early stage, so both dryness and stack resistance can meet the actual requirements, and in the case of increased curing agent dosage, Joncryl® OH 8770 ap On the other hand, while the final hardness of Joncryl®OH 8770 ap is slightly less full, the initial gloss of Joncryl® OH 8770ap is high, as shown in Figure 7, mainly due to the monosome used and its dosing optimization.
from the above test results, you can see the advantages ® advantages and disadvantages of Joncryl's oh 8770 ap.
To compensate for the slight deficiency of Joncryl® OH 8770 ap plumpness, the actual
should be adjusted with a formula that blends slow-drying secondary dispersants, as in traditional
solvent-based two-part polyurethane coatings, 2-3 resins with 3-4 solid
agents, the effect will be better. The screening of curing agents is critical, mainly considering
compatible and performance of the two-way solution.
membrane additive screening should also be carefully examined, from our pre-screening
results, PnB will affect its transparency, DPnB will affect storage stability
qualitative, in addition to single-use diethylene glycol butyl ether, can also use DPM
with TPnB (4:1) combination is also appropriate. In addition, if
with other water-based resins, it is important to note whether they contain film-forming additives that do not match Joncryl®
OH 8770 ap.
Conclusion
With the collection of VOC consumption tax and the gradual strictness of environmental regulations, the market share of
solvent-based wood coatings in China will be replaced by UV coatings and water-based wood
coatings. Since the water-based single-part system is still unable to compete directly with solvent-based products in terms of performance
, the water-based 2K PU is the most
direction of development. The Joncryl® OH 8770 ap described in this article is a breakthrough product for
ultra-high-gloss coatings, with fast drying, fast hardness development
fast, stack-resistant features, and Cyanate curing agent demand
low, reduce the risk of dark bubbles can also reduce formulation costs, the product is very special
colors, excellent chemical resistance and ultra-high gloss performance is highly recommended formulator
master try.