Clear compositions for use in solid transparent candles

The present invention relates to clear solid compositions that may be used as the base material of a transparent candle, to the transparent candles made therefrom, and to methods of making the same. The compositions of the present invention comprise one or more polyamide resins, which may be present in a total amount of about 40-70% by weight of the composition; and one or more 12-hydroxystearic acid ester solvents, which may be present in a total amount of about 10-70% by weight of the composition, having the following chemical structure: ##STR1## and wherein R may by selected from the group consisting of alkyl radicals, aryl radicals, and arylalkyl radicals.

FIELD OF INVENTION 
The present invention relates to clear solid compositions that are useful 
as the base material of a transparent candle, to the transparent candles 
made therefrom, and to methods of making the same. 
BACKGROUND OF THE INVENTION 
While the burning of a candle might appear to be simple and uninvolved, the 
process that takes place in the burning of a candle has been described, in 
fact, as a process that imposes rather stringent requirements upon the 
candle body material, U.S. Pat. Nos. 5,578,089, 3,819,342, 3,645,705 and 
3,615,289. This is illustrated, in particular, with respect to the actual 
burning of the candle when the heat of the candle's flame melts a small 
pool of the candle body material around the base of the exposed portion of 
the wick. This molten material is then drawn up through and along the wick 
by capillary action to fuel the flame. A candle's melting point is, 
therefore, important in that the candle material should liquefy at or 
below temperatures to which the candle's material can be raised by radiant 
heat from the candle flame. If the candle's melting temperature is too 
low, the candle will drip or, in an extreme case, the entire candle body 
will melt, dropping the wick into a pool of molten body material, with the 
potential that the surface of the pool could ignite. If too high a 
temperature is required to melt the body material, the flame will be 
starved because insufficient fuel will be drawn up through the wick, with 
the result that the flame will be too small to maintain itself. Moreover, 
when molten, the candle body material preferably has a relatively low 
viscosity to insure that it will be capable of being drawn up through the 
wick by capillary action. In addition to meeting the above requirements, 
it is preferred that the candle body material burn with a flame that is 
both luminous and smokeless, and that the odors produced by its combustion 
should not be unpleasant or intrusive. 
The desire to make candles that are transparent or clear places still 
further demands on these already stringent requirements. The terms "clear" 
and "transparent" are used interchangeably herein and connote a 
substantial absence of cloudiness or obscurity, so that the body of the 
candle features an ability to let light pass through in a substantially 
unobstructed manner, and an ability to have coloring agent added to the 
composition without causing cloudiness or reducing the candle's ability to 
let light pass through in a relatively unobstructed manner. Preferably, 
the composition has a degree of clarity comparable to window glass, clear 
glassware, or water. 
To add yet one more demand on transparent candle compositions, it would 
also be desirable if the transparent candles could be used as a fragrance 
carrier for dispersing selected fragrances, such as fragrances having a 
pleasant odor, or fragrances that repel insects. 
Transparent compositions used to make transparent candles typically have 
one or more undesirable characteristics. In particular, such compositions 
typically do not have enough rigidity to form a self-supporting candle, 
and require some type of container or external support. Such compositions 
also typically lack hardness, which may lead to an undesirable gelatinous 
feeling. In addition, such compositions may darken or smoke during 
burning, which is aesthetically undesirable. 
Known transparent candle compositions which are comprised of a 
thermoplastic polyamide resin and a flammable solvent for solubilizing the 
resin, such as described in U.S. Pat. Nos. 3,615,289 and 3,819,342 are 
vulnerable to auto-ignition, and tend to sweat, produce black smoke, and 
darken during burning. Sweating is the process whereby oils migrate out of 
the candle body to the surface, giving it an oily texture, and is most 
commonly caused by syneresis. Syneresis occurs whenever oil is physically 
squeezed out from the candle body because of excessive chemical cross 
linking. Sweating is not only an aesthetic drawback, but can be a 
performance or safety problem as well. If a candle sweats, the oil on the 
surface is available to ignite, which can result in an uncontrolled or 
torch-like situation rather than a candle. 
U.S. Pat. No. 5,578,089 describes a heterophase thermally reversible 
mineral oil gel formed by a system of physically crosslinked block 
copolymers which purportedly overcome the problem of sweating and 
syneresis by adjusting the ratio of diblock and triblock polymers so as to 
ensure that all the oil remains entrained within a system of physically 
crosslinked copolymers. The thermoplastic rubber type polymers of U.S. 
Pat. No. 5,578,029 consist of block segments of styrene monomer units and 
rubber monomer units, wherein each block segment may consist of 100 
monomer units or more (col. 7, lines 4-20). While such compositions are 
alleged to provide an improvement over the prior art transparent candle 
compositions, styrene/rubber-based candle compositions are susceptible to 
surface ignition, which may produce black smoke, and also have limited 
fragrance throw. 
It would be desirable to have transparent and odorless compositions that 
could be used to prepare self-supporting transparent candles that do not 
have a gelatinous feeling. It would also be desirable to have compositions 
that can be used to make self-supporting transparent candles that have an 
aesthetically attractive appearance and that can burn safely and cleanly. 
It would also be desirable if fragrances could be readily dissolved in the 
composition without causing cloudiness or hazing. 
The present invention is directed toward self-supporting transparent candle 
compositions that provide these advantages while not being handicapped 
with the above-noted disadvantages. 
SUMMARY OF THE INVENTION 
The present invention is directed to clear solid compositions that are 
useful as the base material for transparent candle compositions that bum 
safely and cleanly and which may be used for dispensing fragrances. 
More specifically, the present invention relate to a composition for use in 
a clear solid candle, comprising: one or more gellants, and one or more 
12-hydroxystearic acid ester solvents, where a 12-hydroxystearic acid 
ester solvent has the following chemical structure: 
##STR2## 
and where R may by selected from the group consisting of alkyl radicals, 
aryl radicals, and arylalkyl radicals. 
As a representative embodiment, the present invention is directed to a 
clear composition for use in a clear solid candle, that contains 
octylhydroxystearate, a 12-hydroxystearic acid ester solvent, in an amount 
of about 10% to about 70%, wherein octylhydroxystearate has the following 
chemical structure: 
##STR3## 
Preferably, the composition has a high degree of clarity, with little or no 
haze or cloudiness, and more preferably the composition is crystal clear, 
even when fragrances or coloring agents have been added. Preferably, the 
composition does not darken or smoke when a candle made of the composition 
is burning. Preferably, candles made of the composition do not crack or 
split during burning, nor suffer from syneresis. Preferably, candles made 
of the composition have a wide pool, which provides greater fragrance 
throw and helps avoid tunneling. Preferably, the composition is rigid 
enough to form a self-supporting candle, and avoids an undesirable 
gelatinous feel. Preferably, the composition is thermoreversible, such 
that the pool solidifies after the candle is extinguished, without 
significant change to the properties of the composition. Preferably, a 
candle made of the composition retains structural integrity while burning, 
and the sides of the candle do not bulge out. Preferably, the composition 
does not superheat, and the surface of candles made of the composition 
remains cool to the touch while the candle is burning. Preferably, candles 
made of the composition have a burn rate of about 3-4 grams per minute. 
The present invention is also directed to combinations of additional 
components that can be included in the composition to produce candles 
having enhanced or additional aesthetic and functional improvements. In 
particular, the additional materials that may be included in the 
transparent candle compositions include coupling agents, solubilizers, 
clarifiers, emulsifiers, and plasticizers. Also, a clear coating material 
may be applied to the candle to enhance hardness and mar resistance. 
The present invention is also directed toward transparent candles made from 
the clear solid compositions disclosed herein, and methods of making such 
candles. 
The transparent candles of the present invention are, in particular, 
characterized by being formed of a clear solid composition that is capable 
of burning with a smoke-free flame, and does not darken while the candle 
is burning. Moreover, the transparent candles formed of the clear solid 
composition are self-supporting, and do not require a container or 
external support, unlike clear gel candles. The transparent candles of the 
present invention also have other desirable aesthetic features, such as a 
waxy feel. 
Further objectives and advantages of the subject invention will be apparent 
to those skilled in the art from the detailed description of the disclosed 
invention.

DETAILED DESCRIPTION 
The subject invention will now be described in detail for specific 
preferred embodiments of the invention, it being understood that these 
embodiments are intended only as illustrative examples and the invention 
is not to be limited thereto. 
As used herein, "composition" refers to a base material from which solid 
transparent candles can be made. The composition of the present invention 
includes a gellant and a solvent, mixed together. The gellant should be 
soluble in the solvent at elevated temperatures, and at room temperature 
after cooling. The composition should be liquid at elevated temperatures 
but solid at room temperature. The gellant provides structure to the 
candle, although the quality of that structure may be affected by many 
factors, such as the type and amount of solvent used, and the type and 
amount of other additives. The solvent binds to the gellant, and has a 
large effect on the burning characteristics of the candles, such as 
whether the candle smokes while burning, whether the pool darkens during 
burning, and the heat of the flame. Other factors, such as the type and 
size of the wick, and other components included in the base material, can 
also contribute to the burning characteristics. 
The composition of the present invention includes one or more gellants, 
preferably totaling about 40-70% by weight of the composition, and more 
preferably about 50-60% by weight. Candles having the preferred range of 
gellants are more likely to have a larger pool size, and less likely to 
have internal or external cracking, or syneresis, although these problems 
can be addressed by the addition of other components rather than by 
adjusting the amount of gellant. Two classes of polyamides are typically 
soluble in solvents of interest, and are preferred gellants for the 
present invention: (1) polyamides based on terpolymers of simple nylons 
(such as DuPont ELVAMIDE.RTM. 8061, which is a terpolymer of nylon 6, 
nylon 66, and nylon 610); and (2) polyamides based on complex fatty acids, 
such as the VERSAMID.RTM. series of Henkel Corp. or the UNIREZ.RTM. series 
of Union Camp Corp. U.S. Pat. No. 5,500,209, which is incorporated herein 
by reference, provides a more detailed description of these polyamides. 
Preferably, the gellant is selected from the group consisting of polyamide 
resins and derivatives thereof. More preferably, the gellant is the 
polyamide resin VERSAMID.RTM. 1655, available from the Henkel Corporation 
located in Ambler, Pa. 
The composition of the present invention also includes one or more 
solvents, preferably totaling about 10-70% by weight of the composition at 
least about 10% by weight, more preferably about 20-70% by weight at least 
20% by weight, and more preferably about 35-45% by weight. Solvents 
suitable for use in the present invention include esters of 
12-hydroxystearic acid with a monohydric or polyhydric alcohol, i.e., 
octylhydroxystearate and derivatives thereof. This class of solvents is 
referred to herein as "12-hydroxystearic acid esters," and has a chemical 
structure represented by the formula: 
##STR4## 
where R is selected from the group consisting of alkyl radicals, aryl 
radicals, and arylalkyl radicals. Preferably, R is selected from the group 
consisting of: 
##STR5## 
More preferably, the solvent is octylhydroxystearate, which has a chemical 
structure represented by the formula: 
##STR6## 
Octylhydroxystearate is available commercially as WICKENOL.RTM. 171 from 
Alzo, Inc., located in Matawan, N.J., or as CRODAMOL.RTM. OHS from Croda, 
Inc., located in Parsippany, N.J. 
The solvent is a "reactive" solvent in the sense that the gellant binds 
with hydroxy group(s) on the solvent when the two components are mixed. 
For example, the VERSAMID.RTM. 1655 polyamide resin binds to the hydroxy 
group on the octylhydroxystearate when the two are mixed. 
Clear candles may be made from a composition using VERSAMID.RTM. 1655 as 
the gellant and octylhydroxystearate as the solvent, along with other 
components as described below. It has been demonstrated that such a 
composition allows for the manufacture of a solid clear candle having 
several advantages. Such candles are hard to the touch and capable of 
self-support, and do not require a container. Also, such a candle does not 
significantly darken or smoke during burning. 
Such a clear candle also has a desirable bum rate of 3-4 grams per hour, 
similar to a wax candle, and in contrast to styrene/rubber clear candles, 
which have a significantly slower burn rate on the order of 2 grams per 
hour. While not intending to be limited by any theory of how the present 
invention works, it is believed that the three oxygen atoms present in a 
single molecule of octylhydroxystearate lead to good oxygenation of the 
flame for a hotter burn and a faster burn rate. 
The inventors analysis shows that the other solvents disclosed as suitable 
for use in the present invention, i.e., 12-hydroxystearic acid esters 
other than octylhydroxystearate, would have properties similar to those 
exhibited by octylhydroxystearate. 
As used herein, "additional solvents" refers to solvents suitable for use 
in a candle, other than 12-hydroxystearic acid esters. Additional solvents 
include castor oil, oleic acid, or other conventional solvents known to 
the art, such as solvents disclosed in U.S. Pat. No. 3,819,342, which is 
incorporated herein by reference. These additional solvents may be used in 
conjunction with the solvents of the present invention. If the amount of 
additional solvent is kept low, the resultant composition would most 
likely have many of the desirable characteristics of the present 
invention. However, as the amount of these known solvents is increased, it 
is likely that undesirable properties of these known solvents would become 
manifest, such as darkening during burning. It is therefore preferable 
that substantially all of the solvents are selected from the group 
consisting of 12-hydroxystearic acid esters. 
While a candle made of a composition having only a gellant and a solvent 
would be functional, such a candle is likely to suffer from several 
problems. For example, such a candle may exhibit tunneling, which may 
occur when the pool is significantly smaller than the candle diameter. The 
clarity of such a candle may be decreased by the addition of a fragrance 
or coloring agent, due to poor solubility of the fragrance or coloring 
agent in the solvent/gel composition. Other potential problems include 
syneresis, cracking and splitting due to thermal differentials when the 
candle is burning, and haziness. For example, compositions containing only 
VERSAMID.RTM. 1655 and octylhydroxystearate were shown to make functional 
candles that were just slightly hazy. Other components can be added to the 
composition to address these problems. 
One or more solubilizers may be added to the composition of the present 
invention in a total amount of about 0-15% by weight, and preferably in an 
amount of about 7-12% by weight. Solubilizers improve the solubility of 
the gellant in the solvent, and thereby improve the clarity of the 
gellant/solvent blend. Solubilizers suitable for use with the present 
invention include isostearic acid, and branched chain fatty alcohols, such 
as isostearyl alcohol. Preferably, isostearyl alcohol is used as a 
solubilizer, because it is compatible with many other components that 
might be added to the composition. Solubilizers may also function as a 
coupling agent, which couple other components into the solution. 
One or more emulsifiers may be added to the composition of the present 
invention in a total amount of about 0-7% by weight, preferably about 0-5% 
by weight, and more preferably in an amount of about 1-2% by weight. 
Emulsifiers improve the solubility of multi-component fragrance oils in 
the composition of the present invention, thereby improving clarity when 
fragrance molecules are present. Preferably, a nonionic emulsifier is 
used, because nonionic emulsifiers have good compatibility with 
compositions of the present invention. Preferably, the emulsifier is 
non-ethoxylated, i.e., does not have any ethoxyl groups, to avoid hazing. 
Preferably, the emulsifier is a sorbitan derivative. More preferably, the 
emulsifier is selected from the group consisting of sorbitan laurate, 
sorbitan palmitate, sorbitan stearate, sorbitan tristearate, sorbitan 
oleate, sorbitan trioleate, sorbitan sesquioleate. These sorbitan 
derivatives are commercially available from ICI Americas, and are sold 
under the trademarks SPAN.RTM. and ARLACEL.RTM., with various alphanumeric 
designations for the different derivatives. More preferably, the 
emulsifier is selected from the group consisting of sorbitan laurate and 
sorbitan oleate. Most preferably, the emulsifier is sorbitan laurate. 
One or more plasticizers may be added to the composition of the present 
invention in a total amount of about 0-10% by weight, preferably in an 
amount of about 0-5% by weight, and more preferably in an amount of about 
1-2% by weight. Plasticizers increase the structural flexibility of 
compositions of the present invention, thereby allowing the compositions 
to deform slightly instead of cracking or splitting when subjected to the 
thermal stresses associated with burning a candle. Depending on the 
amounts of the other components, and in particular the amount of gellant, 
a plasticizer may not be needed to prevent cracking and splitting. 
Plasticizers suitable for use with the present invention include stearic 
acid; isopropyl palmitate; isopropyl myristate; linalool; 
.alpha.-terpineol; aldehyde C-14; dioctyl adipate; 1,2 benzenedicarboxylic 
acid, di-C6-8, branched alkyl ester (available commercially as 
JAYFLEX.RTM. 77 from Exxon Chemical Americas, located in Houston, Tex.); 
1,2 benzenedicarboxylic acid, di-C8-10, branched alkyl ester (available 
commercially as JAYFLEX.RTM.DINP from Exxon Chemical Americas); 
pentaerythrityl tetracaprylate/tetracaprate (available commercially as 
CRODAMOL.RTM.PTC from Croda, Inc., located in Parsippany, N.J.); and 
pentaerythrityl tetraisostearate (available commercially as 
CRODAMOL.RTM.PTIS from Croda, Inc.). Some plasticizers may not be 
compatible with particular fragrance systems, which can cause hazing. 1,2 
benzenedicarboxylic acid, di-C6-8, br alkyl ester (JAYFLEX.RTM.77) is a 
preferred plasticizer, because it exhibits compatibility with a wide 
variety of fragrance systems. 
The choice of wicking material is also important in making an aesthetically 
acceptable transparent candle. Wicks containing a paper core have been 
observed to provide the most desired combination of burn characteristics, 
especially with respect to attributes such as smoke, bloom, fragrance 
throw and burn rate. Suitable wicks are commercially available from 
Atkins-Pearce of Covington, Ky. 
The transparent candle compositions of the present invention may also 
contain a fragrance, for example, Citronella, AN114351 Sweet Peach, AN 
114349 Mountain Berry, AN114350 Country Garden, AN114462 Lavender Meadows, 
AN114463 Strawberries 'N Cream and AN114215 Vanilla from Noville Corp., 
South Hackensack, N.J. Such fragrances are typically added in an amount of 
about 0% to 5% by weight, and preferably in an amount of about 2.5%, with 
the level being selected so as to achieve the desired throwing power. 
The transparent candle compositions of the present invention may also 
contain a coloring agent, which produces a desired color appearance. A 
composition having a coloring agent would preferably be transparent, much 
like a clear colored gemstone such as a ruby or emerald. 
After a candle has been fabricated from a composition of the present 
invention, a clear coating may be added to the outside of the candle. When 
taken out of the mold, the candle may have a surface comparable in 
hardness to that of a wax candle that might be marred, for example by a 
fingerprint. Suitable coatings have a hard surface that is not easily 
marred, and preferably adhere well to the candle. Such a coating may be 
applied by dipping the candle in a material that dries to form a hard, 
adherent coating. Suitable coating materials may be selected from the 
group consisting of acrylic acid polymers and polyamide resins, such as 
VERSAMID.RTM. 1655. Depending on its thickness, the coating may reinforce 
the candle sides, 1655 although the composition of the candle should be 
hard enough that such reinforcement is not necessary. Depending on the 
thickness and material of the coating, a thin walled coating shell may be 
left as the candle burns. 
This invention will now be described in detail with respect to showing how 
certain specific representative embodiments thereof will be made, the 
materials, apparatus and process steps being understood as examples that 
are intended to be illustrative only. In particular, the invention is not 
intended to be limited to the methods, materials, conditions, process 
parameters, apparatus and the like specifically recited herein. 
EXAMPLES OF THE INVENTION 
Transparent candles representative of the present invention were prepared 
as follows: 
(1) Octylhydroxystearate was added to a suitably sized container, which was 
agitated and heated to a temperature of 80.degree. C. 
(2) The gellant VERSAMID.RTM. 1655 was added, a little at a time, while the 
contents of the container were heated to 94-96.degree. C and agitated. 
Heating and agitation were continued until a phase change was observed, 
indicating that substantially all of the hydroxy groups on the 
octylhydroxystearate had bound to the gellant. 
(3) The composition was poured into a mold, and a wick was added while the 
composition was liquid. The composition was allowed to cool to room 
temperature and solidify. 
The amount of gellant was varied between about 10% and 100%, with the 
amount of octylhydroxystearate correspondingly being varied between about 
90% and 0%. For amounts of gellant above about 70%, tunneling was observed 
in the resultant candles. For amounts of gellant below about 40%, hazing, 
cracking, and syneresis were observed in the resultant candles. While the 
candles were transparent and functional, there was some small degree of 
haziness in all of the candles made of a composition of only 
octylhydroxystearate and VERSAMID.RTM. 1655. 
Further transparent candles representative of the present invention were 
prepared as follows: 
(1) The solvent was added to a suitably sized container, which was agitated 
and heated to a temperature of 80.degree. C. 
(2) The gellant was added, a little at a time, while the contents of the 
container were heated to 94-96 .degree. C. and agitated. No other 
components were added until a phase change was observed, indicating that 
the gellant had bound completely with the hydroxy group on the solvent. 
(3) The other components were added, one at a time, stirring between each 
component. The components were added in an order determined by the amount 
of the component, from largest to smallest. Fragrance was added last. 
While a coloring agent was not used in the examples, any coloring agent 
would have been added after the other components. While this largest to 
smallest order, with the fragrance and coloring agent last, is preferred, 
the components other than the solvent and gellant may be added in any 
order. 
(4) The composition was poured into a mold, and a wick was added while the 
composition was liquid. The composition was allowed to cool to room 
temperature and solidify. 
While not intending to be limited by any theory of how the present 
invention works, it is believed that hydroxy groups on the solvent bind to 
the gellant, and that the best clarity is achieved when substantially all 
of the hydroxy groups on the solvent bind to the gellant. Because the 
solubilizer and other components may also have hydroxy groups that may 
bind to available sites on the gellant, it is believed that such 
components should not be added until after the gellant and solvent have 
been mixed for a time sufficient to allow substantially all of the hydroxy 
groups on the solvent to bind to the gellant, such that hydroxy groups on 
such components do not compete with the hydroxy groups on the solvent for 
binding sites on the gellant. 
Using the above-noted procedure, the compositions listed in Table 1 were 
prepared: 
TABLE 1 
__________________________________________________________________________ 
Composition 
1 2 3 4 5 6 7 8 9 
__________________________________________________________________________ 
Solvent 37.5 
39.5 
31.0 
48.0 
17.0 
31.0 
36.0 
41.0 
24.0 
Gellant 50.0 
50.0 
55.0 
45.0 
60.0 
55.0 
50.0 
50.0 
67.0 
Isostearyl alcohol 
8.0 8.0 10.0 
5.0 10.0 
5.0 5.0 4.0 3.0 
Fragrance 
2.5 2.5 3.0 2.0 3.0 3.0 3.0 3.0 5.0 
Isostearic acid 
0.0 0.0 1.0 0.0 10.0 
5.0 5.0 0.0 0.0 
Plasticizer 
1.0 0.0 0.0 0.0 0.0 1.0 1.0 2.0 1.0 
Emulsifier 
1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
__________________________________________________________________________ 
For each of the compositions of Table 1, the solvent was 
octylhydroxystearate and the gellant was VERSAMID.RTM. 1655. Isostearyl 
alcohol and isostearic acid were both used as solubilizers, either 
individually or in a mixture. The plasticizer was 1,2 benzene dicarboxylic 
acid, di-C-6-8, branched alkyl ester (JAYFLEX.RTM. 77) in composition 1, 
and stearic acid in compositions 6-9. The emulsifier was sorbitan laurate 
(SPAN.RTM.20) in composition 1. 
Candles made from each of the compositions of Table 1 were transparent and 
functional, although some of the compositions did not have as high a 
degree of clarity as others. Composition 1 is the preferred composition, 
because it shows the most desirable combination of properties, including a 
very high degree of clarity, and no cracking, syneresis, or darkening 
during burning.