Status and development trends of additives for water-based coatings (3)

2.3.3 Polyurethane thickener and hydrophobic modified non-polyurethane thickener
Polyurethane thickener referred to as HEUR, is a hydrophobic group modified ethyl polyurethane water-soluble polymer, belongs to the non-ionized combined thickener.
HEUR is composed of hydrophobic group, hydrophobic chain and polyurethane group. Hydrophobic groups are the decision factors for thickening, usually oil-based, octane, xenane-based, pyriphenol-based, etc. Hydro-water chains provide chemical and viscosity stability and are commonly used in polyethers, such as polyoxyethylene and its derivatives. The HEUR molecular chain is expanded by polyurethane groups, which use IPDI, TDI and HMDI.
of the hydrate-type thickener is characterized by the hydrophobic base sealing end. However, some commercially available HEUR hydrophobic subsemissions at both ends are below 0.9, and the best is only 1.7.
conditions should be strictly controlled in order to obtain a narrow molecular weight distribution and stable performance of polyurethane thickeners. Most HEUR is legally synthesized by gradual polysynding, so commercially available HEUR is generally a mixture of wide molecular weights.
richey and other fluorescent tracer conceding thickeners (PAT, average molecular weight 30000, weight average molecular weight 60000) study found that at a concentration of 0.02% (weight), Acrysol RM-825 and PAT beam aggregation of about 6; The joint energy on the surface of the latex grain is approximately 25 KJ/mol, and the area of each PAT thickener molecule on the surface of the latex particle is approximately 13 nm
2
, about 14 times the area occupied by triton X-405 moisturizer 0.9 nm
2
.
polyurethane thickeners such as RM-2020NPR, DSX 1550, etc.
development of environmentally friendly connected polyurethane thickeners has received widespread attention, such as BYK-425 is a VOC- and APEO-free polyurethane thickener, Rheolate 210, Borchi Gel 0434, Tego ViscoPlus 3010, 3030 and 3060 are all non-VOC and APEO thickeners.
addition to the linearly concluded polyurethane thickener described above, there is also a comb-to-polyurethane thickener. The so-called comb-to-polyurethane thickener refers to each thickener molecule in the middle of the hanging hydrophobic base. Such thickeners such as SCT-200 and SCT-275.
hydrophobical modified aminoplast thickener-HEATturning specialty amino resins into a hydrophobic base that can be connected to four ends, but the activity of these four reaction points is different. In the normal hydrophobic base addition, there are only 2 on-end hydrophobic base, so that the synthetic hydrophobic modified amino thickener and HEUR are not much different, such as Optiflo H 500, see Figure 3. If more hydrophobic base is added, such as up to 8%, the reaction conditions can be adjusted to produce amino thickeners with multiple end hydrophobics. Of course, this is also a comb thickener. This hydrophobic modified amino thickener prevents a decrease in the viscosity of the coating due to the addition of a lot of surfactants and glycol solvents to the color scheme. The reason is that strong hydrophobic base can prevent desorption, and multi-hydrophobic base has strong co-operation. This thickener is like Optiflo TVS.performance of hydrophobic modified polyether thickeners (HMPE) hydrophobic polyether thickeners is similar to THATR, with Hercules Aquaflow NLS200, NLS210 and NHS 300.
modified polyphenyl thickener is a thickener
developed by BYK
, as shown in Figure 4. Its thickening process is not only the role of hydrogen bonds, but also the end-base of the contracting cooperation. Compared with the general thickener, its anti-sinking and anti-flow hanging properties are good. According to the different polarity of the end base, the modified polyxyl thickener can be divided into three kinds: low polar polyxyl thickener, medium polar polysaccharide thickener and high polar polysaccharide thickener. The first two are used for solvent-based coating thickening, while high-polar polysaccharide thickeners can be used in high-polar solvent-based coatings as well as water-based coating thickening. Products such as BYK-411, BYK-410 and BYK-420 are low-polar, neutral and high-polar polysaccharide thickeners, respectively.figure 4 Structural Schematic of modified polyurethane thickeners
2.4 membrane additives
Commonly used film-forming additives are Textanol, Lusolvan FBH, Coasol, DBE-IB, DPnB, DOWANOL PPh, alcohol esters 12, etc., while Textanol is often used as a benchmark.
most enterprises in China use Textanol and domestic alcohol esters 12.
Although film-forming additives have a great effect on latex paint film-forming, film-forming additives are organic solvents, which have an impact on the environment, so the direction of development is environmentally friendly effective film-forming additives.
is to reduce the odor. A mixture of Coasol, DBE-IB

, Optifilm Enhancer 300, TXIB, TXIB, and Textanol

reduce odors. Although TXIB is slightly less resistant to MFT and early wash, it can be improved in these areas by mixing with Textanol.
is to reduce volatile organic matter (VOC). In Europe, VOC refers to chemicals with boiling points equal to or below 250 degrees C. Substances with a boiling point of more than 250 degrees C do not fall into the VOC category, so membrane additives develop to a high boiling point. Examples such as Coasol, Lusolvan FBH, DBE-IB, Optifilm Enhancer 300, diopropyl alcohol
are
.
is low toxicity, safe and acceptable biodegradability. Table 1 is the toxicity of film-forming additives.
.