Electrodeposition of nickel
United States Patent 3884773
Bright nickel plating baths comprising aqueous nickel salt solution containing a sulfonated ester reaction product of maleic acid and acetylenic alcohol as a brightener.
US Patent References:
Electrodeposition of nickel
Brown - July 1957 - 2800440
Electrodeposition of nickel
Foulke et al. - October 1961 - 3002902
Sulfates of alkenoxylated butynediol
Mayhew et al. - May 1963 - 3089888
Electrodeposition of nickel
Kroll - April 1968 - 3378470
Electrodeposition of nickel
Brown - July 1957 - 2800440
Electrodeposition of nickel
Foulke et al. - October 1961 - 3002902
Sulfates of alkenoxylated butynediol
Mayhew et al. - May 1963 - 3089888
Electrodeposition of nickel
Kroll - April 1968 - 3378470
Inventors:
Merker, Reuven (Englewood Cliffs, NJ)
Lucca, Salvatore (Paramus, NJ)
Lucca, Salvatore (Paramus, NJ)
Application Number:
05/389379
Publication Date:
05/20/1975
Filing Date:
08/17/1973
View Patent Images:
Export Citation:
Assignee:
The Metalux Corporation (Paterson, NJ)
Primary Class:
Other Classes:
205/276
International Classes:
C25D3/16; C25D3/12; C23B5/08; C23B5/46
Field of Search:
204/49,43T,43N,43P 106/1 117/13E
Primary Examiner:
Kaplan G. L.
Claims:
What is claimed is
1. A bath for producing bright nickel electrodeposits comprising an aqueous acid solution of a nickel salt and at least 0.001 g./l. of a sulfonated ester reaction product of maleic acid and an acetylenic alcohol, said alcohol having the formula
2. The nickel plating bath of claim 1 containing between about 0.1 and 15 g./l. of at least one organic sulphur compound selected from the group consisting of aromatic and aliphatic unsaturated sulfonic acids, aromatic sulfonamides, and sulfonimides.
3. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with one mole of maleic acid.
4. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with two moles of maleic acid.
5. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-butynediol with two moles of maleic acid.
6. The bath of claim 1 containing between about 0.1 and 1.0 g./l. of said ester.
7. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of propargyl alcohol with one mole of maleic acid.
8. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-butynediol and with one mole of maleic acid.
9. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with one mole of maleic acid.
10. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-butynediol with 2 moles of maleic acid.
11. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with 2 moles of maleic acid.
12. The process of electrodepositing bright nickel which comprises electrolyzing an aqueous acidic solution comprising a nickel salt and at least about 0.001 g./l. of an ester sulfonated reaction product of maleic acid and an acetylenic alcohol having the formula
1. A bath for producing bright nickel electrodeposits comprising an aqueous acid solution of a nickel salt and at least 0.001 g./l. of a sulfonated ester reaction product of maleic acid and an acetylenic alcohol, said alcohol having the formula
2. The nickel plating bath of claim 1 containing between about 0.1 and 15 g./l. of at least one organic sulphur compound selected from the group consisting of aromatic and aliphatic unsaturated sulfonic acids, aromatic sulfonamides, and sulfonimides.
3. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with one mole of maleic acid.
4. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with two moles of maleic acid.
5. The bath of claim 2 containing the sulfonated ester reaction product of one mole of 1,4-butynediol with two moles of maleic acid.
6. The bath of claim 1 containing between about 0.1 and 1.0 g./l. of said ester.
7. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of propargyl alcohol with one mole of maleic acid.
8. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-butynediol and with one mole of maleic acid.
9. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with one mole of maleic acid.
10. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-butynediol with 2 moles of maleic acid.
11. The bath of claim 1 wherein said ester sulfonate is the sulfonated reaction product of one mole of 1,4-bis(hydroxyethoxy) butyne with 2 moles of maleic acid.
12. The process of electrodepositing bright nickel which comprises electrolyzing an aqueous acidic solution comprising a nickel salt and at least about 0.001 g./l. of an ester sulfonated reaction product of maleic acid and an acetylenic alcohol having the formula
Description:
This invention relates to compounds useful as additives to nickel electroplating baths and more particularly to the electrodeposition of smooth, lustrous deposits of nickel from baths containing these additives.
BACKGROUND OF THE INVENTION
Brighteners are added to nickel plating baths, including the commonly used Watts-type acid bath, to increase the leveling characteristics and to produce bright nickel electrodeposits. The use of unsaturated molecules containing alkyne groups has been suggested. While compounds such as 1,4-butyne-diol and 1,4-bis(hydroxyethoxy) butyne produce some degree of improvement in the plating bath, uniform results are difficult to achieve. These deficiencies are readily evident in plating baths operated at temperatures above 50°C. Many commercial products have complex shapes which dictate that the nickel be deposited in certain areas of low current density. Accordingly, there exists a need for nickel plating baths in which irregularly shaped objects may be nickel electroplated with a uniform lustrous and bright nickel deposit. Such desirable electrodeposits must be made in the recesses of the object as well as in the elevated areas.
As stated above, acetylenic compounds tend to produce a cloudy haze on the deposited nickel surface, especially in high concentrations under the above-mentioned bath temperatures. This is stated clearly in U.S. Pat. No. 3,378,470 (col. 1, lines 30ff.) where it can be read that "acetylenic alcoholic brighteners produce a cloudy haze on the nickel deposit which is most evident in those areas at which nickel is deposited under conditions of low current density." Furthermore, acetylenic compounds have the tendency to "skip plate" and to impair ductility as clearly stated in U.S. Pat. No. 3,133,006 and in U.S. Pat. No. 3,305,461. Also, the acetylenic compounds mentioned in these patents, when present in a nickel plating solution, render it very sensitive to metallic contamination by impurities such as zinc, copper and iron. The acetylenic-olefinic esters disclosed in U.S. Pat. No. 3,378,470, while appearing superior to other prior art additive compounds, nevertheless are quite sensitive to metallic contamination and, furthermore, suffer the disadvantage of becoming quite unsatisfactory when utilized in amounts exceeding their optimum concentrations.
It is therefore an object of the present invention to overcome cloudy deposits, haze, "skip plating," metallic contamination and limitations in concentration, by providing a novel heretofore unknown group of plating additives, as more fully described hereinbelow.
DETAILED DESCRIPTION OF THE INVENTION
This invention, accordingly, provides acetylenic-olefinic ester sulfonates prepared by the condensation of acetylenic alcohols and maleic acid followed by sulfonation, which are particularly suitable as additives in aqueous acidic nickel electroplating baths to produce superior lustrous nickel electrodeposits. Nickel may be electrodeposited from such bath over a wide range of current densities, including regions of low current density now considered too low to obtain desirable electrodeposits. There is also a marked improvement in brightness and ductility, which is uniform throughout the nickel electrodeposit.
The desired acetylenic-olefinic ester sulfonates are prepared by first reacting maleic acid with acetylenic alcohols and diols, as fully described in U.S. Pat. No. 3,378,470, and having the formula
RC.tbd.CC(H 2 )(OCH 2 CH 2 ) n OH
where R is hydrogen, H 3 C--or HO(CH 2 CH 2 O) n CH 2 --and n is 0, 1, or 2; and n must be O when R is hydrogen methyl. Illustrative of these acetylenic alcohols and diols are propargyl alcohol; 1-hydroxy-butyne-2,3; 1,4-butynediol; and bis(hydroxyethoxy) 1,4-butyne and higher ethylene oxide adducts of 1,4-butynediol. The olefinic dicarboxylic acid reactant in the preparation of the acetylenic-olefinic esters is maleic acid or such equivalent olefinic acid compounds as maleic anhydride, and the alpha, beta-olefinic dicarboxylic acids containing up to about 8 carbon atoms in the chain. Subsequently, the reaction product is sulfonated in accordance with well known sulfonation techniques, known to any person skilled in the art. Typically, the radical SO 3 Na is introduced in the broken carbon double bond.
The composition of the acetylenic-olefinic esters is dependent upon the specific acetylenic compound and acid utilized and the relative proportions of each, and also is influenced by the reaction conditions. The products of the final sulfonation reaction may be mixtures of ester sulfonates as will be apparent.
The products of the reaction of maleic acid and an acetylenic mono-alcohol will be a monomeric ester which may be (a) a monoester formed esterification of only one of the acid groups of the maleic acid by one molecule of the alcohol, or, (b) a diester formed by esterification of both of the acid groups of the maleic acid by two molecules of the alcohol. Reaction of an acetylenic diol and the dicarboxylic acid may result in a variety of reaction products of a monomeric and polymeric nature. The reaction products may be mixtures of several of these polyesters. The reaction conditions utilized vary somewhat dependent upon the acetylenic alcohol reactant. Where it is a liquid and used in excess, it is often useful to dissolve the maleic acid in the alcohol and heat to temperatures up to about 150°C., where such temperature is not above the temperature at which the reactants volatilize under the reaction conditions. It is often desirable to carry the reaction out in a solvent which is inert to the reactants and reaction products. Such reactions are preferably carried out under reflex conditions. Maleic anhydride is often the preferred acid reactant instead of maleic acid. When used herein, it is understood that terms are used alternatively referring to these compounds which are equivalents for purposes of this invention. The following compounds are illustrative of the acetylenic-olefinic ester sulfonates of the invention: Compound no: ##SPC1##
The acetylenic-olefinic ester sulfonates, if containing terminal acid or hydroxy groups may be used in the form of the corresponding salt with such cations as nickel, sodium, potassium, lithium, or magnesium.
The brighteners in accordance with this invention are useful in acid nickel baths which usually contain nickel sulfate and/or nickel chloride. The Watts-type acid baths are most commonly employed. Generally, the ph range of these acid baths is between 2.5 to 5.0, and the temperature range is between about 35°C and 70°C. The concentration of the acetylenic-olefinic ester sulfonates in the bath, usually between 0.001 and 1.0 gram/liter (g./l.), for economic reasons, ned not be limited to these amounts, but may be employed in any excess desired. This is one of the most important advantages of the compounds of this invention, namely, the elimination of harmful effects regardless of the concentration of ester sulfonate employed.
The acetylenic-olefinic ester sulfonates may be used with auxiliary brighteners such as the aromatic and aliphatic unsaturated sulfonic acids, sulfonamides, and sulfonimides. They may, however, be employed as a brightening additive in electroplating baths which do not contain other additives. In addition to the baths discussed hereinbefore which contain nickel sulfate and/or nickel chloride, these sulfonate compounds may also be employed in nickel plating baths containing the sulfamate anion.
The acetylenic-olefinic ester sulfonates are most commonly used in conjunction with the following sulfonimides and sulfonamides: benezene sulfonamide; ortho-toluene sulfonamide; para-toluene sulfonamide; Saccharin, sodium salt; metabenzene disulfonamide; allylsulfonamide; and vinyl benzenesulfonamide. Other sulphur compounds which may be incorporated in the baths are benzenesulfonic acid; allyl sulfonic acid; para-vinylbenzene sulfonic acid; 1,5-naphthalene sulfonic acid; and 1,3,6-naphthalene sulfonic acid. These compounds may be added as the specified compound per se and used in amounts between about 0.1 and 15 g./l. Those compounds containing salt-forming groups may be added in the form of their nickel, sodium, potassium, or magnesium salt.
The following are specific examples of aqueous acidic nickel electro-plating baths containing the acetylenic-olefinic ester sulfonates of the invention. Bright, lustrous nickel electrodeposits were obtained over a wide current density range from these baths regardless of compound concentration. The acetylenic-olefinic ester sulfonates are identified by the compound No. specified hereinbefore.
______________________________________ Examples 1-3: G./l. NiSO 4 6H 2 O 300 NiCl 2 6H 2 O 45 Boric Acid 45 Saccharin 1 Bromobenzene sulfonic acid 1 Compd. No. 3, respectively: 0.08, 0.32, 0.8 Sodium lauryl oxyethyl sulfate 1.0 Temperature, °C. 60 pH, 4.0 Examples 4-6: NiSO 4 6H 2 O 200 NiCl 2 6H 2 O 100 Boric Acid 45 Naphthalene trisulfonic acid 5 Compd. No. 8, respectively: 0.1, 0.3, 0.9 Temperature, °C. 60 pH, 4.0 Examples 7-9: NiSO 4 6H 2 O 300 NiCl 2 6H 2 O 45 Boric acid 45 Saccharin 1 Toluenesulfonamide 0.5 Compd. No. 2, respectively: 0.05, 0.2, 0.5 Sodium lauryl sulfate 9.50 Temperature, °C. 50-55 pH, 3.5-4.5. Examples 10-12: NiSO 4 6H 2 O 250 NiCl 2 6H 2 O 75 Saccharin 1.0 Vinyl benezenesulfonic acid 1.0 Compd. No. 5, respectively: 0.05, 0.2, 0.4 Sodium octyl sulfate 0.5 Temperature, °C. 45 pH, 4.0 Examples 13-15: NiSO 4 6H 2 O 25 NiCl 2 6H 2 O 250 Boric acid 45 Saccharin 1.0 Benzene disulfonate 10.0 Compd. No. 1, respectively: 0.08, 0.32, 0.8 Temperature, °C. 45 pH, 4.0 ______________________________________
The aqueous acidic nickel electroplating baths containing the acetylenic-olefinic ester sulfonates exhibit the unique property of producing nickel electrodeposits of high and uniform luster in areas of both high and low current density regardless of concentration, contrary to non-sulfonated esters. This is attributed to the effects of these sulfonates as additives. These additives were found to be more effective in this respect than the acetylenic alcohols or diols or the esters from which they are derived.
______________________________________ Examples 16-18 (bath same as examples 13-15): Compd. CH 3 C.tbd.CCH 2 OC(O)CH=CH(O)OH 1 a. Concentration 0.08 0.08 Result good good b. Concentration 0.16 0.16 Result good haze c. Concentration 0.32 0.32 Result good spots, skips ______________________________________
Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.
BACKGROUND OF THE INVENTION
Brighteners are added to nickel plating baths, including the commonly used Watts-type acid bath, to increase the leveling characteristics and to produce bright nickel electrodeposits. The use of unsaturated molecules containing alkyne groups has been suggested. While compounds such as 1,4-butyne-diol and 1,4-bis(hydroxyethoxy) butyne produce some degree of improvement in the plating bath, uniform results are difficult to achieve. These deficiencies are readily evident in plating baths operated at temperatures above 50°C. Many commercial products have complex shapes which dictate that the nickel be deposited in certain areas of low current density. Accordingly, there exists a need for nickel plating baths in which irregularly shaped objects may be nickel electroplated with a uniform lustrous and bright nickel deposit. Such desirable electrodeposits must be made in the recesses of the object as well as in the elevated areas.
As stated above, acetylenic compounds tend to produce a cloudy haze on the deposited nickel surface, especially in high concentrations under the above-mentioned bath temperatures. This is stated clearly in U.S. Pat. No. 3,378,470 (col. 1, lines 30ff.) where it can be read that "acetylenic alcoholic brighteners produce a cloudy haze on the nickel deposit which is most evident in those areas at which nickel is deposited under conditions of low current density." Furthermore, acetylenic compounds have the tendency to "skip plate" and to impair ductility as clearly stated in U.S. Pat. No. 3,133,006 and in U.S. Pat. No. 3,305,461. Also, the acetylenic compounds mentioned in these patents, when present in a nickel plating solution, render it very sensitive to metallic contamination by impurities such as zinc, copper and iron. The acetylenic-olefinic esters disclosed in U.S. Pat. No. 3,378,470, while appearing superior to other prior art additive compounds, nevertheless are quite sensitive to metallic contamination and, furthermore, suffer the disadvantage of becoming quite unsatisfactory when utilized in amounts exceeding their optimum concentrations.
It is therefore an object of the present invention to overcome cloudy deposits, haze, "skip plating," metallic contamination and limitations in concentration, by providing a novel heretofore unknown group of plating additives, as more fully described hereinbelow.
DETAILED DESCRIPTION OF THE INVENTION
This invention, accordingly, provides acetylenic-olefinic ester sulfonates prepared by the condensation of acetylenic alcohols and maleic acid followed by sulfonation, which are particularly suitable as additives in aqueous acidic nickel electroplating baths to produce superior lustrous nickel electrodeposits. Nickel may be electrodeposited from such bath over a wide range of current densities, including regions of low current density now considered too low to obtain desirable electrodeposits. There is also a marked improvement in brightness and ductility, which is uniform throughout the nickel electrodeposit.
The desired acetylenic-olefinic ester sulfonates are prepared by first reacting maleic acid with acetylenic alcohols and diols, as fully described in U.S. Pat. No. 3,378,470, and having the formula
RC.tbd.CC(H 2 )(OCH 2 CH 2 ) n OH
where R is hydrogen, H 3 C--or HO(CH 2 CH 2 O) n CH 2 --and n is 0, 1, or 2; and n must be O when R is hydrogen methyl. Illustrative of these acetylenic alcohols and diols are propargyl alcohol; 1-hydroxy-butyne-2,3; 1,4-butynediol; and bis(hydroxyethoxy) 1,4-butyne and higher ethylene oxide adducts of 1,4-butynediol. The olefinic dicarboxylic acid reactant in the preparation of the acetylenic-olefinic esters is maleic acid or such equivalent olefinic acid compounds as maleic anhydride, and the alpha, beta-olefinic dicarboxylic acids containing up to about 8 carbon atoms in the chain. Subsequently, the reaction product is sulfonated in accordance with well known sulfonation techniques, known to any person skilled in the art. Typically, the radical SO 3 Na is introduced in the broken carbon double bond.
The composition of the acetylenic-olefinic esters is dependent upon the specific acetylenic compound and acid utilized and the relative proportions of each, and also is influenced by the reaction conditions. The products of the final sulfonation reaction may be mixtures of ester sulfonates as will be apparent.
The products of the reaction of maleic acid and an acetylenic mono-alcohol will be a monomeric ester which may be (a) a monoester formed esterification of only one of the acid groups of the maleic acid by one molecule of the alcohol, or, (b) a diester formed by esterification of both of the acid groups of the maleic acid by two molecules of the alcohol. Reaction of an acetylenic diol and the dicarboxylic acid may result in a variety of reaction products of a monomeric and polymeric nature. The reaction products may be mixtures of several of these polyesters. The reaction conditions utilized vary somewhat dependent upon the acetylenic alcohol reactant. Where it is a liquid and used in excess, it is often useful to dissolve the maleic acid in the alcohol and heat to temperatures up to about 150°C., where such temperature is not above the temperature at which the reactants volatilize under the reaction conditions. It is often desirable to carry the reaction out in a solvent which is inert to the reactants and reaction products. Such reactions are preferably carried out under reflex conditions. Maleic anhydride is often the preferred acid reactant instead of maleic acid. When used herein, it is understood that terms are used alternatively referring to these compounds which are equivalents for purposes of this invention. The following compounds are illustrative of the acetylenic-olefinic ester sulfonates of the invention: Compound no: ##SPC1##
The acetylenic-olefinic ester sulfonates, if containing terminal acid or hydroxy groups may be used in the form of the corresponding salt with such cations as nickel, sodium, potassium, lithium, or magnesium.
The brighteners in accordance with this invention are useful in acid nickel baths which usually contain nickel sulfate and/or nickel chloride. The Watts-type acid baths are most commonly employed. Generally, the ph range of these acid baths is between 2.5 to 5.0, and the temperature range is between about 35°C and 70°C. The concentration of the acetylenic-olefinic ester sulfonates in the bath, usually between 0.001 and 1.0 gram/liter (g./l.), for economic reasons, ned not be limited to these amounts, but may be employed in any excess desired. This is one of the most important advantages of the compounds of this invention, namely, the elimination of harmful effects regardless of the concentration of ester sulfonate employed.
The acetylenic-olefinic ester sulfonates may be used with auxiliary brighteners such as the aromatic and aliphatic unsaturated sulfonic acids, sulfonamides, and sulfonimides. They may, however, be employed as a brightening additive in electroplating baths which do not contain other additives. In addition to the baths discussed hereinbefore which contain nickel sulfate and/or nickel chloride, these sulfonate compounds may also be employed in nickel plating baths containing the sulfamate anion.
The acetylenic-olefinic ester sulfonates are most commonly used in conjunction with the following sulfonimides and sulfonamides: benezene sulfonamide; ortho-toluene sulfonamide; para-toluene sulfonamide; Saccharin, sodium salt; metabenzene disulfonamide; allylsulfonamide; and vinyl benzenesulfonamide. Other sulphur compounds which may be incorporated in the baths are benzenesulfonic acid; allyl sulfonic acid; para-vinylbenzene sulfonic acid; 1,5-naphthalene sulfonic acid; and 1,3,6-naphthalene sulfonic acid. These compounds may be added as the specified compound per se and used in amounts between about 0.1 and 15 g./l. Those compounds containing salt-forming groups may be added in the form of their nickel, sodium, potassium, or magnesium salt.
The following are specific examples of aqueous acidic nickel electro-plating baths containing the acetylenic-olefinic ester sulfonates of the invention. Bright, lustrous nickel electrodeposits were obtained over a wide current density range from these baths regardless of compound concentration. The acetylenic-olefinic ester sulfonates are identified by the compound No. specified hereinbefore.
______________________________________ Examples 1-3: G./l. NiSO 4 6H 2 O 300 NiCl 2 6H 2 O 45 Boric Acid 45 Saccharin 1 Bromobenzene sulfonic acid 1 Compd. No. 3, respectively: 0.08, 0.32, 0.8 Sodium lauryl oxyethyl sulfate 1.0 Temperature, °C. 60 pH, 4.0 Examples 4-6: NiSO 4 6H 2 O 200 NiCl 2 6H 2 O 100 Boric Acid 45 Naphthalene trisulfonic acid 5 Compd. No. 8, respectively: 0.1, 0.3, 0.9 Temperature, °C. 60 pH, 4.0 Examples 7-9: NiSO 4 6H 2 O 300 NiCl 2 6H 2 O 45 Boric acid 45 Saccharin 1 Toluenesulfonamide 0.5 Compd. No. 2, respectively: 0.05, 0.2, 0.5 Sodium lauryl sulfate 9.50 Temperature, °C. 50-55 pH, 3.5-4.5. Examples 10-12: NiSO 4 6H 2 O 250 NiCl 2 6H 2 O 75 Saccharin 1.0 Vinyl benezenesulfonic acid 1.0 Compd. No. 5, respectively: 0.05, 0.2, 0.4 Sodium octyl sulfate 0.5 Temperature, °C. 45 pH, 4.0 Examples 13-15: NiSO 4 6H 2 O 25 NiCl 2 6H 2 O 250 Boric acid 45 Saccharin 1.0 Benzene disulfonate 10.0 Compd. No. 1, respectively: 0.08, 0.32, 0.8 Temperature, °C. 45 pH, 4.0 ______________________________________
The aqueous acidic nickel electroplating baths containing the acetylenic-olefinic ester sulfonates exhibit the unique property of producing nickel electrodeposits of high and uniform luster in areas of both high and low current density regardless of concentration, contrary to non-sulfonated esters. This is attributed to the effects of these sulfonates as additives. These additives were found to be more effective in this respect than the acetylenic alcohols or diols or the esters from which they are derived.
______________________________________ Examples 16-18 (bath same as examples 13-15): Compd. CH 3 C.tbd.CCH 2 OC(O)CH=CH(O)OH 1 a. Concentration 0.08 0.08 Result good good b. Concentration 0.16 0.16 Result good haze c. Concentration 0.32 0.32 Result good spots, skips ______________________________________
Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.