United States Patent Office 3,361,652

Patented Jan. 2, 1968

2
3,361,652 3-furylacrylic acid-CHO-CH=CH-COOH
ELECTRODEPOSTION OF BRIGHT TN
Joachim Korpiun, Friedrich Sedlacek, and Joachin Steeg,
Benzylideneacetone-CH-CH=CH-CO-CH3
Curcumin
Geislingen an der Steige, Germany, assignors to Dr. Ing.
Max Schlotter, Geislingen an der Steige, Germany, a
firm
CH3(OH) (OCH)-CH=CH-CO2:CH2
No Drawing. Filed Aug. 24, 1964, Ser. No. 391,790 4-(2-furyl)-3-butene-2-one
Claims priority, application Germany, Aug. 28, 1963, CHO-CH=CH-CO-CH
Sch. 33,772; Aug. 5, 1964, Sch 35,588 4-p-sulfophenyl-3-butene-2-one
16 Claims. (CI. 204-54)
10 CH(SOH)-CH=CH-CO-CH3
ABSTRACT OF THE DISCLOSURE
1,5-di-p-sulfophenyl-1,4-pentadiene-3-one
Semi-bright or bright tin electrodeposits are formed CH(SOH)-CH=CH):CO
in otherwise conventional acid tin baths in the presence 2-pentyl-3-phenyl-propenal
of a dissolved primary brightener of the formula CH-CH=CH-(CH2)5-CHO
X-CHRCH-Y 4-hydroxy-3-methoxy-benzylideneacetone
in which X is phenyl, furfuryl, or pyridyl and Y may CH3(OH) (OCH3)-CH=CH-CO-CH
be hydrogen, formyl, carboxyl, alkyl, hydroxyalkyl, for 20 4-(pyridyl-2)-3-butene-2-one
mylalkyl, or the acyl radical of a carboxylic acid. Form C5H4N-CHFCH-CO-CH
aldehyde and certain imidazoline derivatives act as sec As is evident from the examples listed above, the length
ondary brighteners, particularly when employed with of carbon chains attached to the ethylene core of the
nonionic wetting agents.
brightening agent does not interfere with the brighten
-mmamm ing effect as long as adequate solubility is maintained,
This invention relates to a method of electrodeposit tance nor are substituents in the radicals X and Y of impor
ing bright tin, and to an acid solution suitable as an brightener as long as they do not affect the stability of the
aqueous electrolyte for performing the method. in a harmful manner.
30
Commercially used bright acid tin plating solutions Index, 7th ed., brighteners
The primary are listed in part in the Merck
contain as brighteners tar and tar fractions obtained in compounds not listed in themethods
with their of preparation. The
Index may be prepared ac
the destructive distillation of wood. Such electrolytes are
difficult to control, and it is not readily possible to pro cording to the following publications:
o-Methoxycinnamic acid: J. Chem. Soc. (London) 31,
duce bright tin plates of consistent quality from them 414 (Perkin);
over extended periods of time. 4-(2-furyl)-3-butene-2-one; Ber. 14, 1459 (Schmidt);
We have found a group of primary brighteners for 4-phenyl-3-butene-2-one-1-sulfonic acid and 1,5-di
acid tin plating electrolytes which perform reliably over phenyl-1,4-pentadiene-4-one-2,4-disulfonic acid: Zentral
extended periods of operation, and yield semi-bright or
fully bright deposits in a reproducible manner. The pri blatt 1954, p. 1927; -
2-pentyl-3-phenyl - propenal: Comptes Rendus 237
mary brighteners of the invention cooperate with sec (1953) 1012 (Durr);
ondary brighteners which improve brightness and/or
widen the cathode current density range in which the Soc.4-hydroxy-3-methoxy-benzylideneacetone:
(London) 1938, p. 1568 (Nisbet); and
J. Chem.
deposits have the desired brightness. 4-(pyridyl-2)-3-butene-2-one: Zentralblass, 1962, page
Wetting agents are employed in the acid tin plating 45 13728.
solutions of the invention. Non-ionic wetting agents are The concentrations of tin and free acid may be varied
preferred, and the water soluble ether of polyglycols
which are readily available are both effective and stable generally within the limits conventional in this art. A
tin content of 10 to 100 grams per liter, and a free
under the normal operating conditions of the electro 50 acid
lyte. They may have from ten to thirty ethyleneoxy radi cal ofconcentrationthe sulfate,
of 20 to 200 grams per liter are typi
fluoborate, and aromatic sulfonate
cals per molecule, the molecular weight being mainly lim Solutions, known in themselves, which may be provided
ited by considerations of solubility.
The primary brighteners of the invention are soluble with the brighteners of the invention. Sulfuric, fluoboric,
and aromatic sulfonic acids may be present simultane
ethylene derivatives of the formula X-CH=CH-Y ously in the electrolytes in a manner not novel in itself.
wherein X is phenyl, furfuryl or pyridyl, and Y may be 55
The secondary brighteners which are employed in con
hydrogen, formyl, carboxyl, alkyl, hydroxyalkyl, formyl junction with the olefinic primary brighteners in the tin
alkyl, or the acyl radical of a carboxylic acid, the na plating solutions of the invention include formaldehyde
ture of the substituents being limited mainly by the re and certain imidazoline derivatives which may be em
quirement that the brightener be soluble in the electrolyte ployed singly or in combination with each other. The
in effective amounts. 60
The following examples are representative of com the imidazoline derivatives which have been found to widen
pounds which are adequately soluble in the acid electro the formula bright and semi-bright current density range are of
lytes of the invention:
Styrene-CH-CH=CH2 65
Cinnamyl alcohol-CH-CH=CH-CHOH N /
R3-OOC-CH-N-CH-CH-O-R
Cinnamic acid-CH-CH=CH-COOH ÖH
Cinnamaldehyde-C6H5-CH=CH-CHO
o-Methoxycinnamic acid
70 wherein R1 is an alkyl radical with at least 5 carbon atoms,
CHO-CH-CH=CH-COOH R2 is hydrogen or the radical -CH-COOH, and R3 is
hydrogen or a monovalent metal, particularly an alkali
 3,361,652 4.
3 Furfurylideneacetone or 4-(2-furyl)-3-butene
metal. It will be appreciated that the metal may be re (III)
placed by hydrogen in the acid electrolyte, and other 2-one
brighteners of the invention containing carboxyl groups (IV) o-Methoxycinnamic acid
or sulfo radicals may thus be incorporated in the electro (V) 2-furylacrylic acid
lyte in the form of their salts. 5 (VI) Benzylideneacetone
Although the imidazoline derivatives described herein (VII) 2-pentyl-3-phenylpropenal
above are surface active because of the presence of rela (VIII) Pyridylideneacetone or 4-(pyridyl-2)-3-butene
tively long alkyl chains together with hydrophilic groups, 2-one
it is perferred to employ them in conjunction with other The plating solution I was originally somewhat turbid,
non-ionic wetting agents. The imidazoline derivatives, O but became clear after about one day.
however, may replace a portion or all of the formaldehyde Example 2
which would otherwise be necessary for producing a de
sired brightening effect. Similar results were obtained with fluoborate bath of
The amounts of primary and secondary brighteners to the following composition: Grams/liter
be employed vary greatly according to the nature of the 5
substituents present in the primary brightener, and such Tin (as fluoborate) --------------------------- 45
process variables as the configuration of the object which Fluoboric acid ------------------------------- 90
is made the cathode during the plating process, the de Ether of polyglycol --------------------------- 2
sired rate of depositions, and the like. Guidance for the Formalin ------------------------------------ 1.
use of the brighteners will be found hereinbelow in the 20 Cinnamaldehyde ----------------------------- 0.5
specific examples of embodiments of this invention. The ether of polyglycol employed contained approxi
Among the secondary brighteners, the imidazole deriva mately 11 CHO radicals per molecule. The solution
tives are effective in concentrations as low as 0.01 gram gave brightest deposits at temperatures between 20 and
per liter, and their beneficial effects increase with concen 35° C., and at cathode current densities of 1 to 4 amps.
tration up to approximately 0.05 to 2.0 grams per liter, the 25 per square decimeter. When the cinnamaldehyde was re
limit varying from compound to compound. At higher placed in the plating solution by 0.2 gram/liter benzyl
concentrations, no further significant improvement is ob ideneacetone bright tin deposits were formed under other
served, nor are there harmful effects up to the limit of wise identical conditions.
solubility. Example 3
Pyrocatechol which is a known antioxidant in acid tin 30
plating solutions, has a beneficial effect when employed A plating bath was prepared from the following ma
in the tin plating solutions of the invention in small terials:
amounts. Grams/liter
The temperature of the plating Solution is preferably Stannous Sulfate ----------------------------- 60.
held below 35° C. for best stability, but the maintenance 35 Cresolsulfonic acid --------------------------- 260
of a specific operating temperature in the tin electrolytes Formalin ----------------------------------- 2
is not critical for the production of bright coatings. Ether of polyglycol --------------------------- 2.
The following examples are further illustrative of the Benzylideneacetone --------------------------- 0.4
present invention, and it will be understood that the in 40 Bright deposits were obtained at 20 to 30° C. over a
vention is not limited thereto:
current density range from 1 to 4 amps. per sq. decimeter.
Example 1 The ether of polyglycol employed as a nonionic wetting
Eight plating solutions were prepared from stannous agent was the same as in Example 2.
Sulfate, sulfuric acid, formalin (aqueous formaldehyde 45 Example 4
solution of approximately 37% HCHO content), a poly A tin plating solution that gave a very bright tin elec
ethyleneglycol wetting agent, and an olefinic brightener
as indicated in Table I. The preferred temperature and trodeposit at 15° to 30° C. when operated at 1 to 3.5
cathode current density ranges in which smooth, bright amps./sq. decimeter has the following composition:
tin plates were electrodeposited from the several acid plat 50 Tin as fluoborate ----------------------------- Grams/liter
ing solutions are also listed in the table. 40
The wetting agents employed were ether of polyethoxy Fluoboric acid ------------------------------- 80
ethanols which contained approximately 11, C2H4O radi Wetting agent ------------------------------- 2
cais in solutions III, IV, and VI, approximately 15 CHO Formalin Pyridylideneacetone --------------------------- 0.3
radicals in solutions V, VII, and VIII, 25 CHO radicals 5 5 Pyrocatechol ------------------------------------ 1.
in solution II, and 30 C2H4O radicals in solution I. --------------------------------- 1.5
TABLE I

Piating Solution No.

Composition, grams/liter
II III W W WI W WII

Stannous Sulfate----------------------- 60 60 80 80 60 70 60 80
Sulfuric acid--------------------------- 100 00 80 120 80 160 120 00
Formalin.------ - I 1.5 0.8 .. 6 0.8 5 0, 8 1.
Wetting agent 2 6 5 6 6 6 4.
Brightener.--- - 0.35 0.65 1.3 0.35 0.32 0.4
Temperature, ---20-30 20-30 15-30 20-30 8-30 18-30 20-30 15-30
Current density, amps.fsq. decimeter. 1-2.5 1-2.5 0.8-4 1-2.5 0.7-3.5 0.7-3.5 1-2.5 1-3.5

The following eight brighteners were used in these Less bright, but still very smooth deposits were ob
eight solutions: tained when the pyrocatechol was omitted from the bath
(I) Styrene - composition. The ether of polyglycol was the same as in
(II) Cinnamyl alcohol 75 Example 2.
 5
3,361,652
Example 5 6
fonic acids as conductivity increasing and ionization re
A bright tin plating solution was prepared from the pressing agents. Fully bright tin electrodeposits were ob
following materials: tained from a solution of the following composition under
Grams/liter the operating conditions indicated:
Tin as divalent Sulfate ------------------------ 35 Tin, as sulfate ------------------grams/liter.-- 30
Sulfuric acid -------------------------------- 150 Phenolsulfonic acid -------------------do---- 250
Wetting agent -------------------------------- 6 Formalin ----------------------------do---- 1.
Formalin ----------------------------------- 1. Benzylideneacetone -------------------do---- 0.48
Benzylideneacetone --------------------------- 0.3 Wetting agent ------------------------do---- 5
Pyrocatechol -------------------------------- 0.8 Brightener B ------------------------------- 0.8
At a bath temperature of 20 to 35 C., the bright Temperature -------------------------- C 20-35
cathode current density range extended from 1 to 4 Current density ---------------amps./sq. dm-- 1-3.5
amps./sq. decimeter. The wetting agent employed was a The wetting agent used was an ether of polyethylene
ether of polyethyleneglycol containing approximately 15 5 golycol having approximately 15 CHO radicals. The
CHO radicals per molecule. Omission of the pyrocatechol brightener B was an imidazoline derivative of the formula
from the bath resulted in smooth, but less bright deposits. shown in Example 6 in which R1 was CH5, R2 was
Example 6 CH-COONa, R was sodium. Omission of brightener B
Four electroplating solutions were prepared from stan from the composition reduced the bright plating range,
nous sulfate, sulfuric acid, a polyethylene glycol wetting 20 and particularly the semi-bright plating range.
agent, an olefinic brightener and a secondary brightener Example 8
which was an imidazolidine derivative. Pyrocatechol and A stock solution was prepared to the following com
formalin were used in some of these brighteners. Their position:
compositions, preferred operating temperatures, and the 25 Grams/liter
bright plating ranges at these temperatures as listed in Tin (as stannous Sulfate) ---------------------- 30
Table II. Free sulfuric acid ----------------------------- 10
TABLE Ether of polyglycol (abt. 15 C2H4O groups) ------- 6
Benzylideneacetone --------------------------- 0.26
Composition, grams/liter Plating Solution No. 30 Three batches of this solution were mixed with the follow
ing secondary brighteners respectively:
IX X XI XII
Grams/liter
Tin (as Sulfate).------------------------- 30 40 35 35 (a) Formalin -------------------------------- 1.5
Sulfuric acid (free).
Wetting agent---
00
6
30
7
100
6
150
6 35
(b) Imidazoline derivative --------------------- 0.5
Formalln------- 1.5 0.8 ------------- Formalin -------------------------------- 0.8
Pyrocatechol---------------------------------------------------
Brightener All- 0.25 0.4 2
0.8
0.3
(c) Imidazoline derivative ---------------------- 1.0
Brightener B---
Temperature, C----
0.05
----20-30
0.6 .. O
8-30 20-30 20-35
.0 The imidazoline derivative employed was the same as in
Current density amps. per sq. decimeter. -4. 0.8-3.5 1-4 1-4 Example 6, DX. The three plating solutions were used at
40 temperatures between 20 and 30° C. and gave at least
The wetting agents in solutions IX to XII had approxi semi-bright, Smooth deposits at cathode current densities
mately 10-15, 30, 25, 15 CHO radicals per molecule from 0.5 to 4 amps. per square decimeter (about 4.5 to 36
respectively. The olefinic brighteners A were benzylidene amps./sq. ft.). The fully bright range, however, was
acetone (IX and XII), furfurylideneacetone (X), and 2 broadened significantly as the formalin of batch (a) was
furylacrylic acid (XI). The imidazolidine derivatives em 45
gradually replaced by the imidazoline derivative.
ployed as brighteners B may be prepared by the method While the invention has been described with particular
of U.S. Patents 2,528,378, 2,773,068 and 2,781,354, and reference to specific embodiments it is to be understood
were of the formula that it is not limited thereto but is to be construed broadly
and restricted solely by the scope of the appended claims.
What we claim is:
R1-C
N-H,
CH
50 1. An aqueous acid bright tin electroplating solution
N / including a tin salt, free acid, and as a primary brightener,
R3-O O C-CH-N-CH-CH-O-R, an effective amount of a compound of the formula
OH X-CH=CH-Y, wherein X is phenyl, furfuryl, or
in which the substituents were as follows: pyridyl, and Y is a member of the group consisting of
55 hydrogen, formyl, carboxyl, alkyl, hydroxyalkyl, formyl
alkyl, and acyl radicals of carboxylic acids, said compound
X X XI XII being dissolved in said aqueous plating solution.
R!------- CH23---------- CH:0 CH23 C11H23
2. A solution as set forth in claim 1, further including,
R2------- CH-COOH H CH-COOH CH-COOH as a secondary brightener, an effective amount of at least
R3------- H Na H. H 60 one member of the group consisting of formaldehyde and
imidazoline derivatives of the formula
A substantial broadening of the bright plating range was N-CH
achieved by the addition of the imidazoline derivatives as
compared to otherwise identical solutions not containing
an imidazoline derivative. This effect was noticeable not
only in the range of fully bright deposits, but also in the
semi-bright range. The use of formaldehyde is not abso
65
R-ooc-city CH-CH-O-R,
N
OH

lutely necessary when imidazoline derivatives are employed wherein R1 is an alkyl radical having at least five carbon
as secondary brighteners. 70 atoms, R2 is a member of the group consisting of hydrogen
Example 7 and -CH-COOH, and R3 is a member of the group
The imidazolidine derivatives of the invention are equal consisting of hydrogen and monovalent metal, said sec
ly effective as secondary brighteners in tin plating solu ondary brightener being dissolved in said solution.
tions which contain sulfuric, fluoboric, and aromatic sul 75
3. A solution
a wetting agent. as set forth in claim 2, further including
 3,361,652 8
- 7
4. A solution as set forth in claim 3, wherein said consisting of formaldehyde and imidazoline derivatives of
the formula
wetting agent is nonionic.
5. A solution as set forth in claim 3, wherein said
wetting agent is a water-soluble ether of polyglycol. R1-C
N-H,
CH
6. A solution as set forth in claim 3, wherein X is N /
phenyl. R3-OO C-CH-N-CH-CH-O-R,
OH
7. A solution as set forth in claim 3, wherein X is
methoxyphenyl. wherein R1 is an alkyl radical having at least five carbon
8. A solution as set forth in claim 3, wherein X is atoms, R2 is a member of the group consisting of hydrogen
furfuryl. - 0. and -CH-COOH, and R is a member of the group
9. A solution as set forth in claim 3, wherein X is consisting of hydrogen and monovalent metal, said Sec
pyridyl. ondary brightener being dissolved in said solution.
10. A solution as set forth in claim 3, wherein Y is 14. A method as set forth in claim 13, wherein said
the acyl radical of a carboxylic acid. Wetting agent is a water soluble ether of polyglycol.
11. A Solution as set forth in claim 5, wherein X is 5 15. A method as set forth in claim 13, wherein said
sulfophenyl. free acid is selected from the group consisting of sulfuric
12. A solution as set forth in claim 5, further including acid, fluoboric acid, and phenolsulfonic acids.
pyrocatechol as an antioxidant. 16. A method as set forth in claim 13, wherein said
13. A method of electrodepositing bright tin on an solution is at a temperature not substantially higher
article which comprises making said article the cathode 20 than 35 C.
in an aqueous solution including a soluble tin salt, free References Cited
acid, a nonionic wetting agent, and effective amounts of UNITED STATES PATENTS
primary and secondary brighteners, said primary bright
ener being a compound of the formula X-CH=CH-Y, 2,598,486 5/1952 Andrews ------------ 204-54
wherein X is phenyl, furfuryl, or pyridyl, and Y is a 25 3,082,157 3/1963. Francisco et al. ------- 204-54
member of the group consisting of hydrogen, formyl,
carboxyl, alkyl, hydroxyalkyl, formylalkyl, and acyl radi ROBERT K. MIHALEK, Primary Examiner.
cals of carboxylic acids, said compound being dissolved JOHN H. MACK, Examiner.
in said aqueous plating solution, and said secondary G. KAPLAN, Assistant Examiner.
brightener including at least one member of the group 30