NEW COMPLEX-DRIER FOR COATINGS

GAO GE

FUZHOU GAODA RARE EARTH MATERIAL CO., LTD.

Abstract: The complex-drier is produced with good 2-ethylhexanoic acid, rare earths and other metals. Singly using such a complex-drier can match the total effect of the traditional driers such as Co, Mn, Pb, Zn, Ca etc. It has advantages of using singly and operating easily, small dosage with lower cost and without Co & Pb, light color and good quality, resisting the environment of low temperature and high wetness.

Keywords: complex-drier, coating, rare earth

Foreword 
Driers are the main auxiliary agents in coating industry. There are many problems in kinds of traditional driers such as Co, Mn, Pb, Zn and Ca etc. Some are costly, some are deep-color and some are poisonous. The rare earth drier exploited recently solved some of these problems, but they can not completely replace expensive Co drier. It is an urgent desire in coating industry to develop a new drier that can completely replace Co drier.

The complex-drier developed and produced by Gaoda Rare Earth Material Factory of Gushan Fuzhou has achieved the goal successfully. It is made from organic acids, rare earths and other metals. It can be used singly due to its characteristics of the complex reaction, its cooperative function, and its coherence between “dry to touch” and “dry through” in coatings.

2 The advantages of complex-drier

2.1 Used singly and operated easily

The design of the complex-drier has taken the best effect of the coating drying into account. Singly using such a complex-drier can match the same total effect as using several traditional driers that included Co, Mn, Pb, Zn, Ca etc. It is really an all-round drier for coatings. It makes the operation more convenient, simplified and avoids many easy-made mistakes.

2.2 Small dosage with lower cost and without Co & Pb

A multivalent metal has been selected to the production of the complex-drier. Its synergic function with organic acid is several times better than that of Co metal. So it can save quantity but get an excellent result. In alkyd varnish & white alkyd enamels, its using quantity in coatings is only one-tenth of the traditional driers. It dose not contain Pb, so it can be used to paint edible tins, toys and eliminates the environmental pollution.

As show in table 1,there is a comparison between the using quantity of Gaoda complex-drier and traditional driers. The using resin of applied coating is an oleinic acid modified alkyd resin. The solid content is about 57.5%.

Table 1. Comparison between the using quantity of Gaoda complex-drier and traditional driers

2.3 Light colour and good quality, resisting the environment of low temperature and high wetness

When the multivalent metal ion in complex-drier plays a part in the coatings, it is oxygenated to be a high valence ion. This metal ion only appears to be light yellow, which is lighter than the colour of the resins and the purple of the Co drier. Therefore, it can be used in varnish or light colour paint to get a good colour notation. It has formed the steady chelate of 5 or 6 member of ring, so it can stored below 0℃ for a long time without precipitation. After storing in coating for a year, its technological indexes do no change except that its viscidity increases slightly. Using the coating with this complex-drier, it is able to paint even at the rainy and cold days.

3 The effect of application

Since its putting into production in 1995, the complex-drier has received many users. Its effect is far better than expected. With little quantity, the effect of the complex-drier used in coating can match the traditional driers.

Table 2 shows some dry indexes of the selected coating when using 0.30% of the complex-drier which is one-eleventh of the quantity of the original driers at the standard of ZBG.

Table 2. The Example of Application of Coating Plant

Applied coating and standard	ZBG51035-87 white alkyd enamel
Using quantity of complex-drier	G-06 0.3 %(of total coating）
Using quantity of original driers	Co(2.0%) 1.4 % RE(4.0%) 2.0 %
technology index	original driers	complex-drier	one year later
viscosity (＞60s)	85	95	122
drying time (h) surface dry (≤5h)	4.5	4	5
through dry (≤15h）	15	15	15
hardness (≥0.25)	0.32	0.32	0.32
flexibility (1mm)	1	1	1
impact resistance (50kg.cm)	50	50	50
adhesion (≤2 stage)	2	2	2
water resistance (6h)	eligible	eligible	eligible
oil resistance (6h)	eligible	eligible	eligible

Generally, the using quantity is about 0.20% to 0.60%(account for the total quantity of coating). For example, in the alkyd varnish or white alkyd enamel of the medium oil, the using quantity of the complex-drier only needs 0.20-0.40% of its total coating quantity. For some coloured-paints such as blue & green is 0.45% or so. The black paint is 0.50% because of the physical adsorption of carbon black pigment. The red paint is 0.60% because of the complexation reaction between metal and pigment such as scarlet & toluidine red. As to new coatings, it is convenient to find out the best suitable quantity by selecting three points of using quantity of the complex-drier at 0.05-0.10% interval in expecting value to test.

Many users prefer to use the complex-drier for its convenience, excellent results, light colour and lower cost.

Since the complex-drier has the property of resistance to low temperature and high wetness, the coatings with the complex-drier can be used normally without changing its dry indexes in the bad weather.

4 Cost and benefit

As shown above the complex-drier is so superior in its effect to the traditional one. The cost of the complex-drier is reduced by 20% to 40% compared with Co, Mn, Pb driers or Co, RE driers.

In summary, as a drier for coatings the benefit of using the complex-drier is obvious. Since there is no purple colour influenced by Co, it is satisfied to choose the complex-drier to get good quality of light coloured painting films. The unit price will surely be good. Even more dispels the Pb pollution of environment. Coatings with complex-drier can be used normally whether it is in low temperature or high wetness that will of course sell well and occupy the market. Moreover, because of using single drier without other driers, it is operated conveniently and decreased many errors. Since using of small quantity, it can cut down ten times of transportation cost and storehouse area.

5 Discussion

5.1 Choice of organic auxiliary agents

The organic acids that used most often in the production of coating driers are naphthnenoic acid, C 7-9 carboxylic acid and 2-ethylhexanoic acid (or iso-octanoic acid). Considering their colour, solubility, dryness and smell, 2-ethylhexanoic acid is the best one, with C 7-9 carboxylic acid and naphthnenoic acid have deep colour and horrible. In addition to its colourless and without bad smell, the acid value of 2-ethylhexanoic acid can reach 385mgKOH/g that is twice of naphthnenoic acids’. It is necessary to choose 2-ethylhexanoic acid of good quality as raw material in order to produce driers of the best quality. By the way, 8-hydroxyquinoline, o-phenanthroline and bipyridine can be used as intensifiers.

5.2 Choice of RE elements

It is generally believed that Ce is the first choice for RE driers. Actually, that is not the case. The function of Ce on coating surface drying (dry to touch) is obvious, but this depends on whether it has been reducing to the low valent during the production of the coating driers. Its contribution to the "dry to touch" of coating is little compare to Co, and La on the " dry through ". Hence, it is difficult to replace Co drier completely with single Ce. However, it is welcome in using of La with multivalent metal at complex-drier to realize the total drying for coatings.

5.3 The best combination of "surface dry" and "through dry"

ASTM and ISO consider that the process of drying of the paint films has 8 and 3 stages respectively, and China state standard takes it is simply as a procession 2 stages, i.e., "surface dry" and "through dry". This is the two phases of the unity of opposites. If the first stage "surface dry" goes too fast, it is easily to make the coating covered and the film will be wrinkled or crusted. That will surely affect the second stage “through dry”. It is shown neither the simple pileup of the drying elements nor the higher the better of the multivalent metal content can produce the best drying outcome. The design of the complex-drier has considered the best coordination of the “surface dry” and “through dry”. To make the coating appear to be in the best quality, a proper proportion is needed among the elements to satisfy the demand of the coating during the whole drying process.

6 Prospect

The production and the application of the complex-drier are bound to give an impetus to the development of the drying theory of coating and bring forth new ideas. The developing product of the coating is forging ahead and bringing about changes day after day. That will be advantageous to the exploitation of series of the products of the complex-driers. Let the traditional driers go into history and let us use the complex-drier to start the new achievement.

Reference

（１）Xu GuangXian, Rare Earth (part two), metallurgy industry publish house, 1995

（２）Qian FengLin, Tu Liao Zhu Ji, chemistry industry publish house, 1992

（３）International Standard (ISO) 4619, Driers for paints and varnishes, 1980-08-15

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