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Polyurethane water remover: molecular sieve activated powder
Many polyurethane components and raw materials contain water, pigments and fillers surface absorb water, in addition, pigments will adsorb water during storage. Usually, the lytic, polyols and other components used for the polyurethane reaction require drying.
If the solvent in the solvent-free two-component polyurethane does not remove water, it will produce carbon dioxide and cause bubbling. Water-containing polyols and pigments eventually lead to the formation of carbon dioxide bubbles in the cured film, which not only cause large bubbles and pinholes, but may also reduce the luster of the coating.
In the construction environment, the moisture can be imported into the polyurethane under construction, which is quite prominent when spraying the polyurethane elastomer. Usually the substrate itself may be damp, which will cause additional problems. For example, polyurethane maintenance coating is generally coated on the wet surface, the environment is wet and the hydroxyl component of the coating is not clean, which will lead to the production of carbon dioxide gas and the formation of bubble holes in the coating.
Therefore, the water needs to be removed in the polyurethane raw material. Physical method dehydration is a common process, generally the oligomer polyols in 100~120℃ of high vacuum pressure dehydration for 1~2h, can remove most of the water, to meet the requirements of use. The solvent can be added with molecular sieve drying and distillation to remove moisture, and the filler should be dried before use.
In some cases without conditions for dehydration using the above method or with a trace amount of water residue, water can be removed by adding water remover. Physical water removal agent has molecular sieve (molecular sieve), molecular sieve products supply abroad, is the molecular sieve fine powder dispersed in the plasticizer.
A molecular sieve is the removal of water from a crystalline synthetic zeolite (a special sodium aluminum silicate / potassium salt) structure, or "activated", from a microporous powder solid with a specific pore size. The molecular screens can adsorb mixtures of small molecules, including water molecules, so some molecular sieves are physical water remover (i. e., desiccant). French company ARKEMA Chemical sells industrial molecular screens produced by CECA with Si1ipoite and powder sizes of 2-4 μ. The water removal (water absorption and drying) agents that can be used in single-component and two-component polyurethane systems are mainly Siliporite NK 30 and Siliporite SA1720, and the brands SL-2033, SL-G2035 and SL-2034 can perfectly replace imported products. The parameter table is shown in the table below.
|
Term |
SA 1720 |
NK30 |
NK10 |
SL-2033 |
SL-G2035 |
SL-2034 |
|
product form |
powder |
powder |
powder |
powder |
powder |
powder |
|
Aperture A |
3 |
3 |
4 |
3 |
3 |
4 |
|
Water absorption capacity (RH 10%) |
23.5 |
24 |
26 |
24 |
25 |
25 |
|
Loss of burning (950℃),% |
1.2 |
1 |
2.5 |
1.5 |
2.0 |
2.0 |
|
Relative density |
0.7 |
0.7 |
0.6 |
0.6 |
0.6 |
0.6 |
In the two-component Polyurethane system, the molecular sieve can be added to the polyol / dressing mixture, but the influence of the molecular sieve on the pot life should be considered. SL-G2035 are water-absorbing agents specially developed for polyurethane system, which improves pot life of two-component polyurethane system. According to the different water in the system, adding 3%~5% is enough to remove the residual water.
Dalian Chuangge Technology Co., Ltd
Richard Han
Doris Zhou
Headquater: 9th Floor, Century Classic Building, No.10, Xinghai Square, Shahekou District, Dalian City, Liaoning Province
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