Development of VOC-free, high-T
g latex binders by a high-temperature water-extended latex technology |
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Authors: | Do I Lee Frank B Chen |
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Affiliation: | (1) Western Michigan University, Kalamazoo, MI 49008, USA;(2) Valspar, High Point, NC 27263, USA |
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Abstract: | The potentiometric titration of carboxylated methyl methacrylate latexes prepared with varying amounts of methacrylic acid
showed that only very small amounts of their total acids copolymerized were neutralized at room temperature until the acid
level was well above 10%. However, it was found that all the acids copolymerized were completely titrated either in a 50/50
water/ethanol mixture at room temperature or in water at high temperatures near their backbone polymer T
gs, regardless of their acid contents, as predicted from the existing theories on the alkali-swelling of carboxylated latexes.
It was also found that these high-temperature alkali-swollen latex particles remained in the swollen state even after they
were cooled down to room temperature and became film-forming at much lower temperatures. This discovery led to a new technology
coined as a high-temperature water-extended latex technology. This new technology enabled us to develop VOC-free water-extended
latexes of high-T
g polymers that would exhibit good film formation at ambient temperature and turn into hard and non-blocking latex films and
latex-bound pigmented coatings upon drying. Particularly, when fugitive bases were used for neutralization at high temperatures,
the resulting water-extended latexes became hard, non-blocking, and water-resistant binders upon drying. |
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Keywords: | High-temperature alkali-swelling Water-extended latexes Water plasticization Latex film formation VOC-free water-plasticized latexes |
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