Chlorinated wax flux compositions

Disclosed is a wax-flux composition and a process for making a wax-flux composition comprising a normally solid chlorinated wax having a chlorine content below about 60 weight percent.

BACKGROUND OF THE INVENTION 
This invention relates to soldering and fluxes used in soldering processes. 
More particularly, this invention relates to soldering fluxes useful in 
high-temperature soldering processes. 
Soldering is one of the oldest methods of joining two or more metal 
articles. Soldering involves the joining of metallic surfaces by flowing 
between them by capillary attraction alloys of lower melting point than 
the metals to be joined. The metal surfaces remain unmelted, but are 
solidly united when the solder alloy or solder metal solidifies. 
Preparation of the joint surfaces is an important factor in soldering. With 
few exceptions, a flux composition is utilized. Fluxes are used to prevent 
the oxidation of the filler metal and of the surfaces of the metal being 
joined during the heating. The flux will also dissolve oxides which 
naturally exist on most surfaces as well as those that may form during the 
heating operation. Additionally, fluxes influence the surface-tension 
equilibrium in the direction of solder spreading. 
Fluxes are applied to the metal surfaces to be soldered by many methods, 
for example brushing, spraying, dipping, etc. However, utilization of a 
liquid vehicle for application of the flux has many disadvantages in many 
processes. For example, in the assembly of automotive radiators, the parts 
to be soldered are commonly dipped in a flux-containing bath. Dipping of 
the part has many disadvantages. First, it results in a large waste of 
material, since the entire part is coated with fluxing material rather 
than just the surface to be soldered; secondly, the solvent must be 
evaporated first before the soldering occurs, and this results in a loss 
of energy; thirdly, use of a solvent-or water-based flux creates air 
pollution problems due to emissions of volatile constituents into the 
atmosphere. 
The aforementioned problems can be overcome through utilization of a wax 
flux. Wax-flux compositions are known in the art and have been used in 
low-temperature soldering processes. See, for example, U.S. Pat. Nos. 
3,977,916; 3,960,614; 3,960,613; 3,975,216; and 3,954,494, which discloses 
wax-flux compositions containing sulfonic acids. Wax-flux compositions 
avoid some of the prior art problems encountered with liquid fluxes in 
that the flux can be readily applied only to the surface to be soldered, 
thus avoiding waste of flux. Furthermore, the wax quickly solidifies so 
that the parts can be easily stored for future soldering. However, 
wax-flux compositions have not been utilized in higher-temperature 
soldering for many reasons, but particularly because of the auto-ignition 
hazards caused by the wax component of the flux. 
The use of inorganic gases and liquid organic halogen-containing fluxes is 
known in the art. See, for example, pages 19-20 of Manko, Solders and 
Soldering, McGraw-Hill (1964). One problem with the organic 
halogen-containing fluxes is that of corrosion. The organic 
halogen-containing fluxes are extremely temperature-sensitive by virtue of 
the organic radical and the halogen and acids formed therefrom are 
extremely corrosive. Also, because of their hazardous nature, special 
equipment is required for safety reasons. Furthermore, any residual flux 
or flux residues must be removed from the part soldered to prevent future 
corrosion. 
SUMMARY OF THE INVENTION 
Disclosed is a normally solid chlorinated wax-flux having a chlorine 
content below 50 weight percent comprising a mixture of (a) a wax having a 
melting point between 40.degree. and 100.degree. C; and (b) a normally 
solid chlorinated wax having a chlorine content greater than 60%. The wax 
flux composition of the present invention increases the autoignition 
temperature of the wax, allowing use of the wax flux in higher-temperature 
soldering processes. The low chlorine content of the wax fluxes of the 
present invention are more stable, which reduces corrosion and special 
handling costs normally associated with liquid organic halogen-containing 
fluxes.

DETAILED DESCRIPTION OF THE INVENTION 
Wax-flux compositions for use in soldering processes, particularly 
high-temperature soldering processes, are provided comprising: a normally 
solid chlorinated wax flux having a chlorine content below 50 weight 
percent comprising a mixture of (a) a wax having a melting point between 
40.degree. and 100.degree. C; and (b) a normally solid chlorinated wax 
having a chlorine content greater than 60%. 
Chlorinated waxes are old and well known in the art. However, depending 
upon the degree of chlorination, the wax can be either a solid or liquid 
at room temperature (25.degree. C). Generally, chlorinated waxes with a 
chlorine content below 60 weight percent are liquid at room temperature, 
while chlorinated waxes with greater than about 60 weight percent chlorine 
are solids at room temperature. The normally solid, high-chlorine-content 
waxes are not entirely suitable in the pure state for use as wax fluxes 
because at the elevated temperature utilized in soldering the wax 
dehydrochlorinates too rapidly, leading to severe corrosion and handling 
problems. Surprisingly, it has been found that one can form a 
low-chlorine-content wax which solidifies at room temperature by blending 
a portion of the normally solid, high-chlorine-content wax with a second, 
essentially chlorine-free wax (less than 0.1 weight percent) to form a 
low-chlorine-content wax which is solid at room temperature. The 
low-chlorine-content wax flux has the advantage of being solid at room 
temperature and the low chlorine content does not present the corrosion 
and special handling problems of the pure, high-chlorine-content waxes in 
the soldering process. 
The Wax 
Suitable waxes for blending with the chlorinated wax include any wax or wax 
blend which is solid at room temperature an has a melting point below the 
temperature at which the soldering process will be conducted. Preferably 
the waxes have a melting point of at least 40.degree. C and generally the 
waxes will have a melting point not greater than 100.degree. C. Preferably 
the waxes have a melting point between 50.degree. and 80.degree. C. 
Melting points as used herein are determined by ASTM D87-66. 
Suitable waxes include petroleum-derived waxes such as the well-known 
paraffin waxes, microcrystalline waxes, slack waxes, scale waxes, 
petrolatum, etc. These waxes are obtained from the processing of crude 
petroleum and are generally substantially saturated, substantially 
straight long-chain aliphatic hydrocarbons. Petroleum waxes suitable for 
use in this invention have melting points within the range specified 
above. Suitable wax blends for use in this invention include the hot-melt 
coatings which consist of blends of petroleum waxes and polymers, 
copolymers or resins. Suitable materials which may be blended with the 
petroleum waxes include polymers of low-molecular-weight olefins, such as 
polymers of ethylene, propylene, butylene, isobutylene, and the like. 
Suitable polymers will have molecular weights from about 1000 to about 
1,000,000, more usually from about 1000 to about 50,000. These are average 
molecular weights, and generally a major portion of the molecules of the 
polymer will have molecular weights close to the average. 
Suitable copolymers include copolymers of olefins. Suitable copolymers 
include copolymers of propene and butene. Typically such a copolymer will 
contain from about 15 to about 85 mol percent propene, more usually from 
about 25 to 75 mol percent propene. Typical copolymer molecular weights 
will range from about 1000 to about 1,000,000, more usually from about 
1000 to about 300,000. 
Suitable waxes for this invention also include waxes obtained from natural 
sources, such as animal, vegetable or insect sources. Suitable waxes 
include beeswax, carnuba wax, montan wax, wool wax, and the like. 
Another type of wax suitable for use in this invention includes the 
well-known Fischer-Tropsch waxes. Fischer-Tropsch waxes are waxes 
synthesized by the familiar Fischer-Tropsch process. By this process, coal 
is burned in the presence of oxygen and steam to produce hydrogen and 
carbon monoxide, which are then reacted in the presence of catalyst to 
make the desired hydrocarbon wax. Suitable Fischer-Tropsch waxes for this 
invention can be obtained under the trade name AFLINT. These particular 
Fischer-Tropsch waxes have a high molecular weight, on the average in the 
range of about 750 to 1000, and generally consist essentially of 
straight-chain hydrocarbons. 
A further type of wax suitable for this invention comprises the solid 
polyethers having a molecular weight in excess of about 1000. Suitable 
polyethers include polyethylene glycol, polypropylene glycol, polybutylene 
glycol and the like. Furthermore, one or both of the terminal hydroxy 
groups may be replaced by an alkoxy group (capped) such as methoxy, 
ethoxy, and the like. Polyether copolymers are also contemplated, for 
example a copolymer of ethylene glycol and propylene glycol. These 
copolymers may have a random or block structure, or mixtures thereof. The 
higher-molecular-weight polyethers are preferred, especially those of 4000 
or more molecular weight. Such compounds are commercially available. 
Although the above waxes have been mentioned individually, suitable waxes 
for this invention include mixtures of various proportions of the 
above-mentioned waxes. 
The Chlorinated Wax 
The normally solid chlorinated wax may be obtained from any of numerous 
commercial sources. The clorinated wax may be formed by bubbling chlorine 
through liquefied wax at an elevated temperature. Any of the 
above-described waxes can be utilized in making the chlorinated wax. The 
chlorine content of the wax can be as low as 60 weight percent, provided 
the chlorinated wax is solid at room temperature (25.degree. C). Generally 
the chlorinated wax will have a chlorine content greater than 60 weight 
percent, and preferably from 65 to 75 weight percent. 
The Chlorinated Wax-Flux Composition 
The chlorinated wax-flux compositions of this invention are prepared by 
melting and blending together the high-chlorine-content wax and a second, 
non-chlorinated wax. The mixture is stirred until homogeneity is obtained, 
and the composition is allowed to solidify. Surprisingly, when the mixture 
cools, it solidifies rather than remaining as a liquid, as one would 
expect with chlorinated waxes having a chlorine content in the range 25 to 
50 weight percent. 
The wax flux compositions of this invention will dehydrochlorinate 
thermally to cause fluxing at or below the soldering temperature of the 
piece to be soldered. The rate at which dehydrochlorination occurs can 
readily be determined by those skilled in the art by a few simple 
soldering tests to determine the minimum amount necessary. Excessive 
dehydrochlorination above that necessary to cause effective fluxing is 
generally undesirable, because it can cause corrosion of the soldered 
surfaces. In addition, the cost of the wax-flux composition is increased 
without additional benefits during the soldering process. 
The chlorinated wax-flux compositions of the present invention will 
generally have a chlorine content below 50 weight percent, and generally 
in the range of 5 to 30 weight percent, and preferably 10 to 20 weight 
percent. The desired chlorine level is simply obtained by blending the 
appropriate quantity of high-chlorine-content wax with the non-chlorinated 
wax. 
The fluxing compositions of the present invention can be utilized in any 
soldering process requiring a flux. The fluxing compositions of the 
present invention are particularly useful in high-temperature soldering 
processes wherein prior art wax fluxes would normally present a fire 
hazard. Such high-temperature soldering processes typically require 
soldering temperatures of 245.degree. to 375.degree. C, usually 
300.degree. to 375.degree. C. 
EXAMPLES 
The suitability of the wax-flux compositions of the present invention is 
illustrated by the following examples. The solderability tests were done 
using a General Electric meniscograph, which provides a continuous record 
of the wetting process by measuring the push-and-pull on a specimen as it 
is partially immersed in molten solder. When a test specimen first enters 
a solder bath, before wetting occurs, the specimen floats on the solder 
and resists being pushed into the bath. After wetting occurs, the solder 
climbs the surface of the specimen, pulling the specimen toward the 
solder. The push-and-pull on the specimen is measured by a transducer, 
which produces a direct-current signal that is recorded. The total time of 
the test is limited to 8 seconds. With the output initially set at zero, 
the time required to return to zero after being partially immersed is 
defined as the "wetting time". Generally, the shorter the wetting time, 
the hotter the flux composition. Wetting times of about 2.5 seconds show 
some fluxing effectiveness, but very good fluxing agents give wetting 
times of less than 1.5 seconds. 
Table I shows the wetting times of representative chlorine-containing 
organic compounds of this invention, as measured by the meniscograph. 
TABLE I 
______________________________________ 
Wax.sup.3 
Time 
Ex. Melting to wet 
No. Chlorine-containing compound, wt.% 
point,.degree. C 
(sec.) 
______________________________________ 
1 5% Chlorowax-70.sup.1 + 5% Armeen-2C.sup.2 
68-69 1.25 
2 5% Chlorowax-70.sup.1 + 5% stearic acid 
68-69 1.25 
3 10% Chlorowax-70.sup.1 + 5% 
dodecylbenzene 
sulfonic acid 68-69 1.0 
4 24% Chlorowax-70.sup.1 + 6% antimony 
oxide 
10% dodecylbenzenesufonic acid 
53.5-54.5 
0.8 
5 40% Chlorowax-70.sup.1 + 10% antimony 
oxide 
10% dodecylbenzene sulfonic acid 
53.5-54.5 
1.0 
______________________________________ 
.sup.1 A chlorinated petroleum wax having 70 weight percent chlorine 
.sup.2 A secondary amine from coconut oil 
.sup.3 A refined petroleum wax 
The following compositions having over 50% total chlorine were also tested 
by the same procedure: 
______________________________________ 
Composition Time to wet (sec) 
______________________________________ 
100% Chlorowax-70 Did not wet 
90% Chlorowax-70, 10% stearic acid 
5 
80% Chlorowax-70, 20% stearic acid 
Did not wet 
______________________________________