Combustion – Candle – e.g. – taper – etc.
Reexamination Certificate
2001-09-28
2003-01-07
Zitomer, Fred (Department: 1713)
Combustion
Candle, e.g., taper, etc.
C528S332000, C528S335000, C528S339000, C528S339300
Reexamination Certificate
active
06503077
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to gelled articles, and in particular to articles that are flammable, such as a candle, and/or contain and emit an active ingredient, such as fragrance, where the article may include an exterior coating.
2. Description of the Related Art
A common type of candle that sees widespread use consists of a wick embedded in a block of paraffin wax, where the wax provides the fuel for the burning candle. Paraffin has many properties that make it suitable for use in a candle. Paraffin as used in candles is typically highly refined and, at room temperature, is in a crystalline state. Crystalline paraffin is naturally white, and white paraffin candles are commonplace. Colorants may be added to these paraffin-based candles, to thereby achieve essentially any desired coloration. Paraffin-based candles are also rigid, and can be formed into a free-standing pillar structure. Such pillar candles, whether white or colored, can be placed atop candlesticks and the like, and are a popular consumer item. Paraffin is an inexpensive raw material, which makes it an economically-attractive ingredient for a candle. Perhaps unappreciated by consumers is that paraffin is also a good material from which to prepare a candle because it meets the rather stringent burning requirements for a candle, as discussed in more detail herein.
Paraffin-based candles have a significant drawback, however. Paraffin-based candles are neither transparent nor translucent, and in fact are opaque. Candle manufacturers have recognized an unmet need for transparent candles, and particularly transparent candles which can adopt the pillar form, i.e., are rigid and self-supporting. Thus, the literature describes numerous attempts to prepare a satisfactory transparent pillar candle.
One approach has been to combine a thermoplastic polyamide resin with a solvent, where the polyamide resin is formed from dimer acid and acts as a gellant. Examples of this approach are found in, for example, U.S. Pat. Nos. 3,615,289; 3,645,705; 3,819,342 and 4,449,987. Candles made by this approach, which may be referred to as polyamide gel candles, have significant shortcomings which have limited their commercial acceptance. For example, such compositions are often not very transparent or even translucent, and may require the addition of a “clarifying agent” to achieve even a semi-transparent state (see, e.g., U.S. Pat. No. 3,819,342). In addition, such compositions are often not as hard as desired, and may require additives that increase stiffness and hardness in order to achieve even a short pillar form (see, e.g., U.S. Pat. No. 3,645,705), or are simply recommended for use in containers (see, e.g., U.S. Pat. No. 3,819,342).
Another significant problem with candles prepared with polyamide gellants is that they typically exhibit syneresis, where this term refers to the formation of liquid on the surface of a gel or colloidal suspension. In other words, droplets of solvent or other candle additive often form on the surfaces of a polyamide gel candle. Syneresis is a highly undesirable property in a candle because, among other reasons, 1) consumers don't want to touch a wet, oily candle; 2) the candle becomes more brittle, as oil escapes; and 3) the droplets of liquid solvent/additives tend to burn quite quickly once the candle is lit, giving the candle a torch-like quality.
Syneresis is particularly pronounced when the candle incorporates fragrance: he fragrance is frequently observed to exude from the candle and exacerbate the flaring problem (as discussed in, e.g., U.S. Pat. No. 3,615,289). Thus, for example, U.S. Pat. No. 3,645,805 suggests using only a small amount of fragrance in a polyamide gel candle, while U.S. 3,615,289 recommends up to about 2 percent fragrance.
Basically, the phenomena of syneresis and blooming reflect the fact that the components of a polyamide gel candle are not sufficiently compatible with one another to maintain a homogeneous state. The prior art has both recognized this problem and attempted to solve it by various means. Two such approaches are the judicious choice of solvent (see, e.g., U.S. Pat. No. 3,819,342), and/or including additives in the candle composition, such as “anti-flaring” compounds (see, e.g., U.S. Pat. No. 3,615,289). These approaches have not been very successful in providing a candle that is desired by the public.
There are several other problems associated with the gel candles prepared with prior art polyamide gellants. One such problem is the failure of the candle to have and/or retain a completely colorless clear appearance. More specifically, it is observed that these gel candles will typically develop an undesirable yellow hue over time and/or with burning. Another problem is that when a colorant has been added to a polyamide gel candle, the initial color of the candle can fade, possibly due to a reaction between the organic components of the candle and the colorant. Also, polyamide gel candles are often observed to form an irreversibly crosslinked structure, which is undesirable because once the molten composition is poured into the form of a candle, it cannot be remelted and repoured in instances where the original candle contained a structural defect. In general, gel candles made with polyamides of the prior art have serious shortcomings, and have not received wide commercial acceptance.
Accordingly, research has been directed to developing non-polyamide gelling agents. Two such examples are the ester-terminated polyamide resins described in U.S. Pat. Nos. 5,783,657 and 5,998,570, and their incorporation into products including candles as described in U.S. Pat. No. 6,111,055. A second approach is to use block copolymers. See, e.g., U.S. Pat. No. 5,578,089 and PCT International Application No. PCT/US96/13993.
The present invention provides another approach to preparing gel-based candles, where the present invention is based on the very surprising discovery that a properly prepared polyamide resin may be used as a suitable gellant for low polarity liquids. These and other related advantages of the present invention are disclosed below.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a candle, where the candle includes a wick and a gel phase. The gel phase includes a gellant and a liquid that is gelled by the gellant. The gellant includes a tertiary amide-terminated polyamide (ATPA) resin of the formula (1):
wherein, n designates a number of repeating units such that terminal amide groups constitute from 10% to 50% of the total amide groups; R
1
at each occurrence is independently selected from a C
1-22
hydrocarbon group; R
2
at each occurrence is independently selected from a C
2-42
hydrocarbon group; R
3
at each occurrence is independently selected from an organic group containing at least two carbon atoms in addition to hydrogen atoms, and optionally containing one or more oxygen and nitrogen atoms; and R
3a
at each occurrence is independently selected from hydrogen, C
1-10
alkyl and a direct bond to R
3
or another R
3a
such that the N atom to which R
3
and R
3a
are both bonded is part of a heterocyclic structure defined in part by R
3a
—N—R
3
.
In various aspects of the candle: terminal amide groups of the formula C(═O)N(R
1
)(R
1
) constitute from 20% to 35% of the total of the amide groups; and/or n is an integer from 1 to 5; and/or R
2
is a C
30-42
hydrocarbon group having the structure of polymerized fatty acid with the carboxylic acid groups removed; and/or between 1% and 50% of the R
2
groups are a C
4-19
hydrocarbon group; and/or R
3
is a C
2-36
hydrocarbon group and R
3a
is hydrogen; and/or at least 1% of the —N(R
3a
)—N
3
—N(R
3a
)-groups are independently selected from polyalkylene amine,
and
wherein R
c
is a C
1-3
alkyl group; and/or the candle further contains diamide having formula (1) wherein n=0, such that the ratio of terminal amide groups to the total of the amide groups in the resin is from 0.1 to 0.7; and/or the liquid being gelled by the
MacQueen Richard C.
Orth Stephen D.
Pavlin Mark S.
Arizona Chemical Company
Seed Intellectual Property Law Group PLLC
Zitomer Fred
LandOfFree
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