Transparent Combustible Material Suitable For Candle Bodies

Abstract

A transparent combustible candle body material formed by combining a straight chain aliphatic amide with light mineral oil and adding alcohol thereto.

Description

This invention relates to materials suitable for candle bodies, and refers more particularly to a transparent material for that purpose.

From time to time formulations have appeared which are said to provide candle body materials that are transparent, but no such formulation heretofore proposed has yielded a candle body material that was both truly transparent and satisfactory for use as a candle body. The materials of most such formulations that have possessed the necessary characteristics for candle bodies have been merely translucent rather than transparent.

When a candle burns, the heat of its flame melts a small pool of the candle body material around the base of the exposed portion of the wick, and this molten material is drawn up through the wick by capillary attraction, to fuel the flame. Thus the process that takes place in the burning of a candle imposes rather stringent functional requirements upon the candle body material.

The material of a candle body must be rigid enough to support itself and a relatively long wick filament, but it should not be excessively brittle at low room temperatures. Its melting point is critical, in that it should liquefy at temperatures to which it can be raised by radiant heat from the candle flame. If its 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 hazardous possibility that the surface of the pool will ignite when this happens. 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. When molten, moreover, the candle body material must have 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 these requirements the candle body material must burn with a flame that is both luminous and smokeless, and such odors as are produced by its combustion should not be unpleasant and should preferably be faint.

The functional requirements outlined above have of course been met by various candle body materials that are well known in the art, but heretofore no known material that meets these requirements has been transparent. However, the desire for a transparent candle body material has long persisted, as indicated by the above-mentioned prior formulations that were intended to provide such a material.

The present invention has as its object to provide a candle body material which possesses all of the necessary functional characteristics and which, moreover, is truly transparent.

It is also an object of this invention to provide a candle body material which has the transparency of glass, with no cloudiness or opacity whatsoever, and which can be colored if desired or can be left uncolored, so that it can be formed into candles having the clear, sparkling esthetic qualities of fine glassware.

Another object of this invention is to provide a transparent material which is in the gel phase and which is combustible with a luminous, smokeless flame and passes into a low viscosity liquid phase at temperatures on the order of those near the base of a flame produced by the combusting material.

From the fact that the material of this invention is in the gel phase it is at once apparent that it is basically very different from those heretofore used for candle bodies, which have generally been crystalline solids. As will also be apparent from the fact that it is in the gel phase, the material of this invention has a smooth, highly reflective surface and is readily molded and hence leads itself well to use for candle bodies.

It is also an object of this invention to provide an oil gel that has as its base a light mineral oil, an inexpensive nature oil, or a combination of such oils, and which oil gel has a nongreasy surface and feel and sufficient rigidity to be self-supporting at room temperatures.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description, which exemplifies the invention, it being understood that such changes may be made in the precise embodiments of the invention herein disclosed as come within the scope of the appended claims.

In general the composition of matter of this invention comprises light, clear mineral oil and/or a natural oil as the gel base, a polyamide resin as the gelling agent, and an 8-10-, or 12- carbon primary alcohol. Without the alcohol, the oil-polyamide gel system burns with an unsatisfactorily small flame and has a greasy appearance and feel. The inclusion of alcohol in the formulation overcomes these deficiencies. Preferably the material also includes in its composition small percentages of a methyl ester, a fatty acid and a reducing agent.

Natural oils that have been found satisfactory are: castor oil, peanut oil, safflower oil, corn oil and cod liver oil. All of them work well, either as the whole oil constituent of the composition or when combined with up to an equal amount of mineral oil. However, except in unusual circumstances, there appears to be no advantage in utilizing the natural oils, and light, clear mineral oil is preferred for the whole of the oil content inasmuch as it is generally cheaper than the natural oils and yields a composition which is at least as satisfactory in all respects as any containing a natural oil or natural oils. If a natural oil is to be used, it should have an iodine value in the range of 40 to 135 and a titre of 1.degree.- .degree. C. Castor oil is preferred.

The polyamide, which serves to get the oil, can be one of a number of long chain linear amide resin polymers derived from the reaction of dimerized linoleic acid with di- or polyamines. Polyamides are usually used as adhesives, for heat seals and in decorative coatings and sealants. The polyamides useful for formulating the composition of this invention are those having molecular weights in the range of 6,000 to 9,000. These polyamides are capable of producing a gel structure in oil when the solubility of the polyamide in the oil is exceeded; although without other additives the gel thus produced tends to be objectionably greasy or oily and burns with a poor flame in a candle system. The polyamide that is preferred is available commercially as a product of General Mills, sold under the trade name Versamide 940.

The proportion of polyamide in the composition determines its melting point. With Versamide 940, 7percent by weight appears to be the lower limit of concentration from an asthetic and functional standpoint, yielding a gel having a softening point of about 60.degree. C.; while 50 percent appears to be an upper limit of concentration, producing a gel with a softening point of about 100.degree. C. Most satisfactory candle body materials are obtained when the polyamide constitutes about 30 percent by weight of the total composition.

As mentioned above, the addition of an alcohol to the oil-polyamide gel serves to overcome the objectionable greasy or oily surface characteristics that the gel would otherwise have, without in any wise detracting from its appearance. Furthermore, the addition of the alcohol materially improves the combustion characteristics of the composition in a candle system. Alcohols of less than eight- carbon have been found to have too low a flash point for most candle bodies, in that the candle body material around the wick tends to catch fire from the candle flame; and such alcohols also tend to evaporate out of the body material during an extended period of storage. The preferred alcohols are 8-, 10-, or 12- carbon primary alcohols, or a combination of one or more of these with myrystyl alcohol. The percentage of alcohol by weight should be not less than about 7 percent nor more than about 30 percent of the total material, the preferred range being 10 percent to 20 percent.

While not necessary to a candle body material that is satisfactory for most purposes, the inclusion of up to about 15 percent by weight of a methyl ester has been found to improve the stiffness and hardness of the material and to limit the oiliness of its surface. Methyl ricinoleate and methyl oleate are preferred, in an amount of about 7 percent to 10 percent. Methyl palmitate and methyl caprylate have also been found satisfactory.

Up to about 5 percent of a fatty acid can be incorporated in the material to cheapen it, improve its stiffness and improve its burning characteristics. Stearic acid in an amount of about 2 percent to 5 percent is preferred. Satisfactory results have also been obtained with 12- hydroxy stearic.

To inhibit discoloration or the development of objectionable odor during storage, in the case of compositions subject to these disadvantages, up to about 1 percent of a reducing agent such as stearic hydrazide or butylated hydroxiditoluene can be advantageously incorporated in the material.

To inhibit discoloration at the base of the flame of a burning candle made of the body material of this invention, up to about 5 percent of a dimer or trimer acid can be added to the composition, the preferred amount being 1 percent to 2 percent, weight.

Specific dimer and trimer acids found to be useful are produced by the polymerization at midmolecule of two or more unsaturated monobasic acids of 18 carbon atom chain lengths. These are sold under the trade name "Empol" by Emory Industries. "Empol 1010" has been found very satisfactory in practice. The dimer or trimer acid may be substituted in whole or in part for the aforesaid reducing agent, inasmuch as it has the further advantage of inhibiting discoloration or the development of objectionable odor of the body material during storage.

The inclusion in the composition of certain alcohols that produce otherwise desirable properties may result in a material that burns with an acrid or pungent odor. In such cases a small amount of an odor masking agent can be incorporated in the composition. The material sold by Fritzsche, Dodge and Olcott as its No. 41984 has been found satisfactory when incorporated in the composition in amounts up to about 0.2 percent by weight. The odor-masking agent is desirable when less expensive alcohols are used and may be unnecessary if the alcohols are highly refined, but from the standpoint of cost, the use of the cheaper alcohols and an odor-masking is indicated and produces satisfactory results. If desired, a small amount of perfume can be added to the composition to complete the odor-masking effect.

A composition found to have very desirable properties as a candle body material is the following:

polyamide (Versamid 940 ) 30% Stearic acid 5% Methyl 12 -hydroxy stearate 5% 10 -carbon primary alcohol 5% (Continental Oil Co. Alfol. 10) Myrystyl (Shell Chemical Co. 10% Neodol 25) Empol 1010 2% Stearic hydrazide 0.1% Odor masking agent (Fritzsche, 0.2% Dodge & Olcott 41984 ) Light while mineral oil q.s. 100%

All of the materials except the polyamide are mixed at room temperature. This mixture is then heated gradually, with gradual addition of the polyamide, and with agitation beginning with commencement of the addition of the polyamide. In the proportion required, the polyamide does not become fully soluble until the mixture reaches a temperature of about 220.degree. F. A temperature on the order of 220.degree. F. to 230.degree. F. is maintained, with continuous agitation, until the polyamide is fully dissolved. Since higher temperatures promote solution of the polyamide, this temperature range can be slightly exceeded with some advantage, but care must be exercised in going to temperatures above this range because the alcohol tends to boil off the cause discoloration.

As soon as the polymide has dissolved completely, the mixture can be poured into molds, following the conventional practice in the manufacture of molded candles. As it cools, it of course hardens. As a rule no difficulty is experienced in freeing the candles from the molds, but, as with other gels, release of the product from a mold can be facilitated by briefly heating the mold to soften the surface of the material that is in contact with the mold. Irregularities in the surface of a molded candle can be corrected by the application of sufficient heat to soften the gel, or in the event of a complete molding failure the entire body can be reheated to flowable condition and remolded.

The material of this invention leads itself well to coloring by means of conventional dyes. If no color is added to it, it has the transparency of glass with a slightly yellow cast.

From the foregoing description it will be apparent that the invention provides a transparent combustible material that is in the gel phase and which is in all respects suitable for candle bodies.

Claims

The invention is defined by the following claims:

1. A transparent composition of matter suitable for a candle body, comprising:

A. from about 35 percent to about 85 percent by weight of an oil which is normally liquid at room temperature chosen from the group consisting of light mineral oil and natural oils having iodine values substantially within the range of 40-135;

B. from about 7 percent to about 40 percent by weight of a long chain polyamide having a molecular weight substantially within the range of 6,000--9,000 and a softening point substantially within a range of 185.degree. C. -48.degree. C.;

c. from about 7 percent to about 30 percent weight of alcohol selected from the group comprising 8- to 12carbon primary alcohols.

2. The transparent composition of matter of claim 1, further characterized by:

from about 1 percent to about 15 percent weight of a methyl ester.

3. The transparent composition of matter of claim 1, further characterized by:

up to about 5 percent by weight of a stearic fatty acid.

4. The transparent composition of matter of claim 1, further characterized by:

a small amount of an odor masking agent.

5. The transparent composition of matter of claim 1, further characterized by:

up to about 5 percent by weight of an oxidation inhibiting agent.

6. The transparent composition of matter of claim 1, further characterized by:

up to about 5 percent by weight of an acid from the class consisting of the dimer and trimer acids.