Abstract:
The present invention relates to environmentally safe low corrosive de-icers and the manufacturing method thereof, and more particularly, to environmentally safe low corrosive de-icers and the manufacturing method thereof, wherein said de-icers comprise calcium chloride (CaCl 2 .2H 2 O) as an active ingredient, along with a food stabilizer and a vegetable calcium as additives for anti-corrosion and a soil property improver as an ice-melting promoter thus having a much improved anti-corrosion property for metal such as steel structure as compared to conventional low de-icers, enabling to eliminate the danger of environmental contamination by using ingredients environmentally safe to plants and soils, and also enabling to mix the ingredients of the composition more uniformly during manufacture while retaining the essential property of fast solubility as a de-icer by introducing a system which can optimize temperature, mixing ratio, mixing speed and duration of mixing.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to environmentally safe and low corrosive de-icers and a method of manufacturing same. According to the present invention, the de-icers comprise calcium chloride (CaCl 2 .2H 2 O) as an active ingredient, a stabilizer (such as those used in foods) and a vegetable calcium preparation as additives for anti-corrosion, and a soil property improver as an ice-melting accelerator. Therefore, the present invention provides the de-icers having much improved anti-corrosion properties for metals such as steel structures as compared to conventional low corrosive de-icers, enabling to eliminate harmful damage to environment by using ingredients known as environmentally safe to plants and soils, and also enabling to mix the ingredients of the compositions more uniformly during manufacturing process, while still retaining the essential property of fast dissolution as a de-icer by introducing a system to optimize conditions such as temperature, mixing ratio, mixing speed and duration of mixing.  
         BACKGROUND OF THE INVENTION  
         [0002]    Calcium chloride and salt (rock salt) are most commonly used as de-icers during the winter season. They have advantages in that they are inexpensive, exhibit superior initial ice-melt activity due to the heat generated during their dissolution, and also prevent them from being refrozen by lowering their freezing point, however, they also have a disadvantage that they can corrode metal parts of a bridge due to their highly corrosive nature as described in the following table 1.  
                                               TABLE 1                           Most frequently used De-icers            De-icer   Advantages   Disadvantages                    Absorbent salt   Calcium   Excellent Reduction   More expensive           chloride   of Freezing point   than rock salt           Magnesium       Occurrence of           chloride       skidding       Chemical   Calcium   Environment-   Insufficient Deicing       Fertilizer   chloride   friendly   Effect           Urea   Plant Protection       Rock salt       Cheap   Harmful to plants                   when used in excess                   Insufficient Deicing                   effect       Antiskid agent   Sand       Insoluble           Ash       Inappropriate ice           Diatom       penetration for                   antiskid                  
 
           [0003]    Therefore, studies have been focused on developing organic salts of non-chlorine type de-icers but they do not appear to be applicable because they are rather expensive and also not sufficient with respect to the initial ice-melt activity. Korea Pat. No. 99-219190 discloses a low corrosive ice-melting composition comprising salt or calcium chloride as an active ingredient and many similar U.S. patent applications have been filed since 1994.  
           [0004]    The following table 2 shows registered patents which employ the addition of an anticorrosive agent or an ice-melt accelerator to the conventional de-icers which contain salt or calcium chloride as an active ingredient. The anticorrosive agents used in the patents of the following table 2 are shown to inhibit the corrosion of metals by protecting their surface via adsorption while ice-melt accelerator are used along with de-icers to expedite the deicing speed by activating the interface of ice by using a heat generating compound or a de-icer. However, the conventional low corrosive de-icers contain excessive amount of additives to prevent corrosion and thus there exists a great danger that they may damage the environment and it is noted that there is also a patent that uses phosphate type salt which is prohibited to use in several states of U.S.  
           [0005]    U.S. Pat. Nos. 5,482,639 and 5,683,619 disclose additives used in manufacturing low corrosive de-icers and the process of manufacturing the same. Most of the patents shown in the following table 2 are concerned with the additives which are used to reduce the corrosiveness of the conventional de-icers. However, it should be noted that the process of manufacturing a low corrosive de-icer plays a crucial role in retaining and maintaining the essential properties of a de-icer required during the addition and mixing of additives.  
                                                             TABLE 2                           Patents related to Low corrosive De-icers            Pat. No.   Subject Matter   Additives               *6,039,890   Increase of melt speed by   Cation/anion and non-ionic           the addition of surfactant   surfactants       *5,935,487   Calcium chloride with a   Diethanolamide           corrosion inhibitor       **10-0219190   Calcium chloride with a   calcium nitrite with a nitrite           corrosion inhibitor   formates               heterocyclic or aromatic ring,               etc.               sodium chloride, calcium               chloride, potassium chloride,               ammonium chloride,               magnesium chloride, sodium               sulfate, magnesium sulfate,               ammonium sulfate,               ammonium acetate, calcium               acetate, potassium acetate,               sodium acetate, magnesium               acetate, etc.               phosphates such as sodium               phosphate, ammonium               phosphate, calcium phosphate;               and nitrites such as sodium               nitrite, ammonium nitrite,               calcium nitrite, etc.               silicates such as sodium               silicate and potassium silicate               chromates such as potassium               dichromate and sodium               dichromate               organic carboxylates               water-soluble organic amines               surfactants: anionic or               non-ionic               heterocyclic compounds:               pyrrole, imidazole, indazole,               1H-indazole, benzofuran,               benzotriazole, quinoline,               quinazoline, etc.               water-soluble polymers: non-               ionic, cationic, anionic, and               amphoteric               graphite powder               dyes and pigments: cobalt               blue, cobalt violet,               phenolphthalein,               p-nitrophenol, methyl violet,               thymolphthalein, natramine,               etc.               methanol, ethanol,               n-propanol, isopropylalcohol,               etc.               low aliphatic monovalent               alcohol or ethylene glycol,               diethylene glycol, propylene               glycol, etc.               low aliphatic divalent alcohol,               etc.       *5,851,418   Oxygen scavenger,   Sodium nitrate           De-icer with corrosion   Sodium borate           inhibitor   Ammonium phosphate       *5,840,207   Calcium chloride with   Diethanolamide           a corrosion inhibitor   Phthalic anhydride       *5,683,619   Vegetation-friendly   Urea           ice-melting composition           added with a chemical           fertilizer and method           the making the same            *5,645,755   Alkaline, non-   Thiourea,   Sulfur-           phosphate, ice-melter   aromatic and   containing           composition   alkyl amines,   compounds,               quarternaries,   acelyenic               fatty acid   alcohol               epoxylates and   derivatives,               the derivatives   hetero                   aromatic                   compounds                   and their                   mis-                   cellaneous                   compounds            *5,482,639   De-icer with corrosion   α-methyl glucoside           inhibitor and its   Urea           manufacturing method       *5,275,752   De-icer with a corrosion   Ammonium caramate           inhibitor       *5,366,650   De-icer with a corrosion   2 butene-1,4-diol           inhibitor (pH &lt; 7)                          
 
           [0006]    The de-icers shown in the above table 2 can be divided into two different groups of inventions; inventions which include the use of all the compounds that prevent corrosion and inventions which reduce the corrosion by using the intrinsic properties of selected compounds. However, compounds that prevent corrosion have been described in numerous reports and many of them are compounds that are prohibited to be used in most states of U.S. because of their harmfulness to the environment. Therefore, it is in urgent need to develop a de-icer and its manufacturing method which has an excellent anti-corrosion activity as well as an excellent ice-melt activity while not being harmful to plants or soils.  
         SUMMARY OF THE INVENTION  
         [0007]    To resolve the above-mentioned problems, the inventors of the present invention conducted their studies on the development of de-icers which are much less corrosive to metals than the conventional ones by using compounds of harmless food additives; are colored for easier identification of the amount of sprayed de-icers as well as their presence, and have fast rate of dissolution during ice-melt. For these purposes, anticorrosive compounds selected from the group consisting of known harmless food additives, calcium preparations for fruit trees, soil property improvers, and calcareous fertilizers were introduced to reduce corrosive properties of de-icers; colors were introduced by using the color change indicators based on the acid/base property as compared to the conventional white de-icers. Further, considering the importance of the mixing conditions of additives and color formers, which can result in change in shapes of de-icers and affect the melting activity, the inventors of the present invention set up mixing conditions optimal for manufacturing de-icers and finally completed the present invention.  
           [0008]    Therefore, the object of the present invention is to provide excellent de-icers which are environment-friendly as well as low corrosive thus enabling to secure the safety of steel structures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a schematic view showing the structure of a mixer used in manufacturing low corrosive de-icers according to the present invention.  
         [0010]    [0010]FIG. 2 is a picture showing the level of corrosion of a steel nail dipped in a conventional de-icer solution.  
         [0011]    [0011]FIG. 3 is a picture showing the level of corrosion of a steel nail dipped in an environment-friendly low corrosive de-icer solution manufactured according to the present invention.  
         [0012]    [0012]FIG. 4 is a graph showing the result of electrochemical test of corrosion of steel performed in various kinds of decier solutions.  
         [0013]    [0013]FIG. 5 is a graph showing the relative corrosion rate of steel performed in various kinds of decier solutions. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    The present invention relates to de-icing composition comprising calcium chloride as an active ingredient and potassium formate, a color change indicator and other additives as non-active ingredients characterized in that said deicing composition is an environmentally safe low corrosive deicing composition comprising 92-99.5 wt % of calcium chloride (CaCl 2 .2H 2 O), 0.5-5 wt % of sodium benzoate, 0.01-2 wt % of potassium formate, 0.01-1 wt % of calcium hydroxide and 0.0001-0.0003 wt % of a color change indicator. The present invention is also characterized in that the ingredients of the above de-icer composition are mixed in a mixer by using a revolving screw kept at 60-90° C.  
         [0015]    The present invention is described in detail as described hereunder.  
         [0016]    The present invention is added with various additives; i) additives sodium which are harmless to environment such as benzoate (food stabilizer) and calcium formate (calcium for a fruit tree) are used to reduce the corrosive property of the conventional de-icers; ii) soil property improvers or calcium hydroxide calcareous fertilizers are used to improve functionality and melt speed of de-icers, and iii) color change indicators are used to identify the amount as well as the presence of de-icers already sprayed. Further, the present invention also employs the adjustment of temperature and mixing speed to improve the functionality of the de-icers being manufactured.  
         [0017]    The invention is explained in more detail according to the ingredients of the de-icers as set forth hereunder.  
         [0018]    The de-icers of the present invention contain 92-99.5 wt % of calcium chloride as an active ingredient, the most well-known conventional de-icer component. In addition, the present invention also contains sodium benzoate, calcium formate and calcium hydroxide as non-active ingredients within the range of 0.5-8 wt %.  
         [0019]    The above sodium benzoate is a preservative for food and therefore the use of sodium benzoate in excess will not be harmful to environment (the standard use for food is less than 0.6 g/kg), however, it can lead to increase in chemical oxygen demand (COD) and thus it is preferred to be used in the range of 0.5-5 wt %.  
         [0020]    The above calcium formate is used as a calcium preparation for fruit trees; in fact, it is better for a given plant to have more amount of calcium for the calcium formate.  
         [0021]    The above calcium hydroxide is usually used as a soil property improver or a calcareous fertilizer and thus use of great amount of calcium hydroxide will be beneficiary from the environmental point of view, however, it can raise a problem in decolorization of a color change indicator and thus preferred to use in the range of 0.01-1 wt %. This color change indicator gives a color to de-icers. Examples of color change indicators are phenolphthalein tymol blue and the like, and 0.0001-0.0003 wt % of phenolphthalein is used in the present invention. Phenolphthalein performs the functions of ice-melt acceleration and anti-corrosion, and it takes on a reddish color in alkaline solution while it dos not form any color in acidic solution. The de-icer compositions of the present invention are basic prior to dissolution because they contain small amount of calcium hydroxide and thus take on a reddish color by phenolphthalein. Therefore, the presence and the amount of the de-icer can be easily identified when sprayed during snowfall. The de-icers of the present invention do not generate any color because they become acidic during the melting period of snow and thus remaining de -icers will not raise any color problem.  
         [0022]    Other additional ingredients of the de-icer compositions of the present invention include water and methanol which are used in uniform mixing and coloration but they are evaporated during manufacturing process and there will be only trace amount left eventually. The preferred mixing ratio between water and methanol is 1:1-3:1 (v/v).  
         [0023]    After adding solid ingredients and liquid ingredients to calcium chloride in the present invention, the mixture is then uniformly mixed by using a thermal exchange type mixer with a revolving screw as shown in FIG. 1 and the temperature and the amount of liquid play crucial roles in determining the final shapes of de-icers.  
         [0024]    The above mixer comprises an inlet  1  for calcium chloride and non-active solid ingredients; an inlet  2  for a mixture of water, methanol and a color change indicator; a boiler  3  that maintains the temperature of a mixer at 60-90° C.; a pipe  4  to transfer warm water from the boiler  3  to the external surface of the mixer; a pipe  5  that connects the cooled water from the external surface of the mixer to the boiler  3 ; a double-jacketed circulating system  6  for warm water; a sprayer  7  that helps to well mix between additives and calcium chloride; a revolving screw  8  that helps to well mix between additives and calcium chloride; a shaft  9  that transmits driving force from an electric motor  10  to the revolving screw  8 ; an electric motor  10  that rotates the revolving screw  8  of the mixer; an outlet  11  for a mixture between calcium chloride and non-active ingredients; and a temperature sensor and temperature control device  12 .  
         [0025]    For the uniform mixing of solid ingredients such as sodium benzoate, calcium formate and slaked lime and the liquid ingredients such as water, methanol and a color change indicator as well as for the maintenance of uniform shape of calcium chloride, the mixer should be kept at 60-90° C. so that liquid ingredients can be evaporated before the solid calcium chloride is melted and at the same time they should be uniformly mixed by the revolution of the screw  8  and the screw shaft  9 . The purpose of keeping the internal temperature of a mixer at a high temperature is to remove water content in the de-icer and this is ascribed to the fact that initial snow-melt effect is reduced by the presence of water in the de-icers.  
         [0026]    The speed of revolution of the revolving screw is preferred to be 25-30 rpm and the above liquid ingredients are added 3-5 parts by wt per 100 parts by wt of the above solid ingredients. The mixture is preferred to spray by using a sprayer at the rate of 0.2 1 parts by wt/min.  
         [0027]    Thus manufactured environment-friendly low corrosive de-icer compositions of the present invention are more advantageous as compared to those of conventional de-icer compositions in that they can substantially reduce the rate of steel corrosion by 5 times, minimize the level of corrosion, their initial snow-melt effect is equivalent to or better than those of conventional ones, and can reinforce the strength of a given cement concrete due to the presence of calcium in the composition, and this is because the elution of calcium ions are prevented by so-called ‘common ion effect’.  
         [0028]    The invention is explained in more detail based on the following examples by means of its preferred form with a certain degree of particularity, however, it is appreciated by those skilled in the art that the present disclosure of the preferred form has been made only by way of examples and that numerous changes in the details of the construction, combination, and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.  
       EXAMPLE  
       [0029]    To the inlet  1  of a mixer were added with 300 kg of calcium chloride (CaCl 2 .2H 2 O), and solid ingredients of 6 kg of sodium benzoate, 3 kg of calcium formate, and 0.3 kg of calcium hydroxide and then uniformly mixed by the revolution of the screw  8  and the screw shaft  9  driven by an electric motor  10 . The internal temperature of a mixer was kept at 80° C. by using a boiler system ( 3 ,  4 ,  5  and  6 ) and then the mixture containing water and methanol (1:1) (v/v) and about 10 ppm of a color change indicator was sprayed by using a sprayer  7  to uniformly mix the calcium chloride and the non-active ingredients. Ten liters of the mixture was sprayed by the rate of 2 L/min and was mixed for 1.5 hr at 80° C. by using the temperature control device  12  until the mixture was formed into granules.  
       EXPERIMENTAL EXAMPLE  
       [0030]    (1) Dipping Method  
         [0031]    Steel nails were dipped into each 5 wt % solution of the conventional calcium chloride de-icer and the de-icer of the present invention (example) for 7 days, respectively, and then photographed (FIGS. 2 and 3). The result revealed that the steel nail dipped in the de-icer solution of the present invention (FIG. 3) did not show the presence of oxidized iron around the steel nail while the steel nail (FIG. 2) of the conventional dipped in the conventional de-icer solution showed the heavy presence of oxidized iron around the steel nail.  
         [0032]    (2) Electrochemical Test Method of Corrosion  
         [0033]    The process of corrosion is an electrochemical phenomenon and thus the electrochemical test of corrosion is the most fundamental and important step in studying corrosion. In the present invention, the corrosion currents at corrosion potential were measured by using the steel nails for concrete as specimens and their corrosion rates were compared. The result showed that the corrosion rate of the de-icers of the present invention were greatly reduced as compared to those of conventional de-icers.  
         [0034]    [0034]FIG. 4 is a graph that shows the result of electrochemical measurements of corrosion of steels performed at various de-icer solutions. Here, (a) represents a low corrosive de-icer (ALCAO, KSRI Co., Ltd., Korea); (b) represents a conventional calcium chloride de-icer; (c) represents the de-icer of the rpesent invention; and (d) represents a non-chlorine low corrosive de-icer (Korea Highway Corporation). The corrosion current at each corrosion potential was measured as the result of the oxidation reaction of steels and the level of corrosion current is used in estimating the corrosion rate of steels.  
         [0035]    [0035]FIG. 5 is a graph that shows relative corrosion rates according to different corrosion currents measured in FIG. 4. The result shows that the low corrosive de-icers, as compared to the convention chlorine de-icer (b), had remarkably lower corrosion rates. The corrosion rate of steels measured in the solution (c) of example was lower than the solution in the conventional chlorine de-icer (b) by 5 times, whereas the corrosion rate of steels measured in the solution (a) of de-icer containing slaked lime was lower than the solution in the conventional non-chlorine de-icer (d) by 10 times.  
         [0036]    The conventional low corrosive de-icers are largely grouped into non-chlorine type and alkaline type de-icers, and the above (d) belongs to the non-chlorine type while the above (a) belongs to alkaline type de-icer.  
         [0037]    Non-chlorine type de-icers contain calcium formate as an active ingredient and they are not advantageous in that their initial ice-melt effect is not only insufficient but also very expensive. Moreover, alkaline type de-icers contain organic compounds and thus require high biological oxygen demand (BOD) as well as high chemical oxygen demand (COD). The above (a) contains oxidized calcium as an active ingredient and it can cause a drain problem in a rainy season because the above (a) sprayed during snowfall melts snow and is converted into calcium hydroxide which remains on roads undissolved thereby clogging the drain passage.  
         [0038]    As described in the above, the de-icer compositions of the present invention have many advantages in that they can greatly reduce the corrosive properties of the conventional de-icers thus securing the safety of steel structures; they are environment-friendly products by using additives such as food preservatives, calcium preparations for fruit trees, soil property improvers, calcareous fertilizers, and the like, which are also beneficiary to plants, and are therefore expected to contribute to greatly increase the safety of steel structures of highways, steel bridges, and the like.