Candle composition

Details Candle composition Candle composition

2001-09-11

2003-06-24

Medley, Margaret (Department: 1714)

Fuel and related compositions

Candle composition

C044S268000, C431S288000, C431S289000, C431S291000

Reexamination Certificate

active

06582484

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a clear candle containing a gelled or solidified hydrocarbon oil.
Candles of gelled hydrocarbon oils are well known, for example, as described in International Patent Publication Nos. WO 96/34077 and WO 97/08282. However, these gelled, clear candles have the potential to catch fire, since the difference between the pool temperature and flashpoint is smaller than in conventional wax candles. If the candle then ignites, flames as high as 30 cm can occur with black smoke emanating. This is a potential health hazard and, indeed, is a reason why there have been a number of product recalls.
In addition it is important that the gelled candles do not flow when the candle holder is tipped on its side (e.g., as may occur during transportation or accidental spillage). Once the wick is buried in the gelled candle material, the product is spoiled. In other words, such a candle material must be firm (i.e., not flow) and have a large difference between the pool temperature and the flash point.
In the past it has been found that if, for example, the difference between the pool temperature and flash point is an acceptable amount, then there is too much flow, or vice versa. It has proved to be very difficult, if not impossible, to obtain an acceptable difference between pool temperature and flash point and, at the same time, produce a candle having desirable flow.
It is also well known in the art to use such gelled hydrocarbon oils for uses other than candles. For example, European Patent No.0 224 389 discloses styrene-dyene block copolymer compositions. However, none of these compositions would have suitable characteristics for forming candles.
International Patent Application No. WO97/31623 discloses gelled compositions suitable for a wide range of uses, but not suitable for use in candles. This is particularly because the hydrocarbon used in the compositions disclosed in this international application are volatile and thus would be likely to present a severe fire hazard if used in candles. In addition, the material forming the candle would simply disappear with time, due to evaporation of the hydrocarbon.
BRIEF SUMMARY OF THE INVENTION
To alleviate these problems, there is provided a gelled hydrocarbon composition, suitable for use as a candle body, comprising a hydrocarbon oil gelled with a low molecular weight and a medium molecular weight triblock polymer.
It has been found that through careful selection of the low molecular weight and medium molecular weight triblock polymer, a candle having improved safety results. In other words, through this careful selection, a candle may be formed in which the flash point and the pool temperature have acceptable values, and the difference between the pool temperature and the flash point is also large enough. Further, the resultant candle does not flow when the candle holder is tipped on its side.
DETAILED DESCRIPTION OF THE INVENTION
By low molecular weight triblock polymer is preferably meant a triblock polymer of molecular weight (either Mw or Mn) from 20,000 to 82,000, more preferably 50,000 to 82,000. Most preferably, Mw is about 78,000 and Mn is about 73,000, expressed as “polystyrene equivalent” molecular weights. An example of such a low molecular weight polymer is KRATON® G1652.
By medium molecular weight triblock polymer is preferably meant a triblock polymer of molecular weight (either Mw or Mn) of from 82,000 to 150,000, more preferably 85,000 to 120,000. Most preferably, Mw is about 95,000 and Mn is about 89,600, expressed as “polystyrene equivalent” molecular weights. An example of such a medium molecular weight polymer is KRATON® G1650.
Preferably, the molecular weight is measured by a technique known as “Comparison of the molecular weight distributions of ethylene-butylene-styrene copolymers using Gel Permeation Chromatography”, the process of which is as follows:
The determination of triblock polymers having low and medium molecular weight is expressed as the polystyrene equivalents. The samples are analyzed using gel permeation techniques with tetrahydrofuran as the solvent and columns appropriate to low/medium molecular weight polymers.
A single solution of the sample is prepared by adding 10 ml of solvent to 20 mg of the sample and leaving for a minimum of four hours to dissolve. A small amount of 1,2-dichlorobenzene in the solvent is added as an internal marker, and the solutions are mixed thoroughly. The solutions are filtered through a 0.2 micron polyamide membrane into sample vials, which are placed in an autosampler.
Chromatographic conditions are as follows:
Columns: Pl gel 2X mixed bed D 30 cm, 5 microns
Flow rate: 1.0 ml/min
Temperature: 30° C.
Data acquisition and handling are carried out using Viscotek “Trisec 3.0” software. The GPC system was calibrated with polystyrene, and the results are expressed as “polystyrene equivalent” molecular weight.
The term “triblock polymer” is one well known in the art, and suitable triblock polymers are styrene-ethylene/butylene-styrene block copolymers, such as are sold under the trade name KRATON® G by Shell. These copolymers are hydrogenated and are thus thermally stable. That is to say, decomposition is not likely to occur during the blending of the copolymer with the hydrocarbon oil. The KRATON® G copolymers are indicated as being compatible with paraffinic and napthenic oils and are reported as taking up more than 20 times their weight in oil to make a gelled product. Such co-polymers are described in WO 96/34077 and WO 97/08282, the contents of which are incorporated herein by reference.
The triblock is often substantially pure triblock and may also include up to 5% diblock copolymer. Alternatively, the triblock copolymers may contain blends with radial block copolymer or multiblock copolymer. Such copolymers and blends are described in WO 97/08282 and WO 97131623.
Desirable blends of low molecular weight and high molecular weight are in the ratios of 1:20 up to 20:1. Preferably, the blends are in the ratio of 1:10 up to 10:1, more preferably 1:5 up to 5:1.
Both the low and medium molecular weight polymers are tri-block co-polymers of the form a-b-a, where b is an oil soluble residue (e.g., ethylene or butylene) and a is an insoluble styrene residue. An example of this type of polymer is from the KRATON® G series of thermoplastic rubber polymers.
These polymers are a linear block styrene-ethylene-butylene-styrenes (SEBS) which have been hydrogenated to impart thermal stability during processing. These tri-block polymers are supplied as >99% pure systems with either low, medium or high molecular weights. These products can then be blended in the laboratory to change the rheological properties of the final hydrocarbon-oil gel as desired.
The hydrocarbon oil used is desirably a natural or synthetic hydrocarbon oil of C
16
to C
50
, desirably as disclosed in WO 96/34077 or WO 97/08282. The oil may, for example, be a paraffinic oil, a naphthenic oil or a natural mineral oil. The hydrocarbon oil can, for example, be a natural or synthetic cosmetic grade hydrocarbon oil. The hydrocarbon oil desirably is in liquid form at temperatures from 0° C. to 200° C. Preferred hydrocarbon oils are selected from paraffinic oils naphthenic oils or natural mineral oils, more preferably a white oil.
Advantageously, the vapour pressure of the hydrocarbon oil is very low, typically negligible at 20° C. Preferably, hydrocarbon oil comprises a carbon chain of 18 to 30 carbons.
The resistance to flow of the gelled compositions can be improved further by the addition of 0.01-3 wt % of a fatty acid, e.g., a compound of formula I or formula II:
HO—(CH
2
)
u
—COOH  (I)
CH
3
—(CH
2
)
p
—CH(OH)—(CH
2
)
q
—COOH  (II)
in which u is 8 to 24; p is 0 to 16, preferably 1 to 8, more preferably 3 to 5; and q is 8 to 24, preferably 8 to 16, more preferably 8 to 10. Desirably p plus q is from 8 to 24, preferably 12 to 20, more preferably 14 to 18.
A preferred fatty acid is a stearic acid containing one or more hydroxy groups. A particularly prefe

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