Wax compositions comprising wax and oil

Details Wax compositions comprising wax and oil Wax compositions comprising wax and oil

2000-03-29

2003-03-18

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S275000

Reexamination Certificate

active

06534573

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to wax compositions comprising wax and oil.
BACKGROUND OF THE INVENTION
Fully refined petroleum waxes have numerous industrial applications including use in adhesives, candlemaking, food coatings, lubricants, paper coatings and waterproofing.
In a typical sequence of wax production, long residue is subjected to vacuum distillation, leading to spindle oil distillate, light machine oil distillate, medium machine oil distillate and distillation residue as typical products. Such products may be subjected to solvent refining and de-waxing to yield wax products such as spindle oil slack wax (SPO wax), light machine oil slack wax (LMO wax), medium machine oil slack wax (MMO wax) and bright stock slack wax (BSO) wax. These waxes may be treated by re-pulping processes, typically leading to waxes having >3% w/w oil content, or solvent de-oiling, typically leading to waxes having <1% w/w oil content.
The initial de-waxing stage removes a relatively small proportion of wax from a large proportion of oil. This operation is usually performed by ‘solvent de-waxing’ in which the waxy feed is mixed with a blend of solvents, chilled to crystallise the wax, and then filtered to remove the wax. At this stage SPO wax, LMO wax, MMO wax and BSO wax fractions usually contain between 10 to 35% w/w oil.
The presence of oil in a petroleum wax has a negative influence on its final properties. As the oil content increases, the tensile strength, hardness and resistance to scuffing are impaired. The oil content of such waxes may cause staining upon contact with paper.
In candlemaking, for example, the presence of excess oil can result in both the candles bending and dripping during use at ambient temperature and also tacking/sticking during storage at room temperature.
In order to mitigate the negative effects that oil impart on the wax, de-waxing is usually followed by an expensive de-oiling step to reduce the oil contents to typical levels of <1% w/w. This is usually achieved by a ‘solvent de-oiling’ process. Solvent de-oiling is essentially similar to solvent de-waxing but is designed to remove a relatively small amount of oil from a larger proportion of wax. The operation is controlled to produce a wax of the required oil content and melting point. An older ‘sweating’ process can be used to de-oil coarsely crystalline paraffin waxes. The sweating process results in a crude fractionation of the wax components wherein lower melting point waxes are removed along with the oil.
The Foots oil (approximately 12-20% w/w) that results from such de-oiling processes is normally sent to a catcracker. Hence solvent de-oiling is both a costly and wasteful process.
The tendency of a wax to ‘bleed’ or sweat oil can be evaluated by determining its bleeding number. Tests for assessing the bleeding number of petroleum waxes are known in the art and are described, for example, in
Petroleum Refiner
, 1948, Vol. 27, No. 8, pp429-431.
It is highly desirable to be able to produce waxes that do not ‘bleed’ or sweat oil, without having to employ the full de-oiling process.
SUMMARY OF THE INVENTION
The present invention provides a method for reducing the bleeding number of wax compositions comprising wax and oil, wherein said waxes are selected from petroleum and synthetic waxes and said oil is present in the range of 1 to 45 percent by weight (% w/w), by incorporating in the composition an effective amount of an oil retention agent in the form of an elastomeric polymer. The invention has particularly useful application to wax compositions used for wax candles. The invention further provides the use of elastomeric polymers for reducing bleeding number in wax compositions.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for reducing bleeding number in petroleum and synthetic wax compositions containing wax and oil, wherein an oil retention agent in the form of an elastomeric polymer is incorporated in the composition. The incorporation of elastomeric polymer makes it feasible to avoid having to fully de-oil the wax prior to use, depending upon the bleeding tendency required in the composition.
Examples of waxes that can be treated by the invention are paraffin waxes and paraffin wax blends, preferably SPO, LMO, MMO and BSO waxes.
The process can be equally applied to synthetic waxes, such as Fischer-Tropsch (FT) waxes. Said FT waxes are hydrocarbon waxes that are produced by the reaction of carbon monoxide and hydrogen in the presence of a catalyst.
Petroleum and synthetic waxes that may be conveniently treated by the present invention preferably have an oil content in the range of from 1 to 35% w/w and most preferably in the range of from 1.5 to 15% w/w.
Elastomeric polymers are generally associated with polymers of conjugated dienes, such as butadiene or isoprene, or with copolymers of conjugated dienes with another copolymerisable monomer for example a mono vinyl aromatic hydrocarbon, such as styrene. It is emphasised that the elastomeric polymer used in the present invention is not restricted to such polymers or copolymers and may include any polymer with elastomeric (i.e. rubbery) properties. Suitable elastomeric polymers include elastomeric polymers of olefins, diolefins and cyclic olefins amongst others those that have been produced using metallocene catalysts (metallocene polymers). However, the polymers of conjugated dienes, or copolymers of dienes are the preferred elastomeric polymers in respect of this invention. These polymers may be random and/or block copolymers.
The preferred elastomeric polymers in respect of this invention are block copolymers of at least one mono vinyl aromatic monomer and at least one conjugated diene. More preferably, the block copolymer contains at least one predominantly poly(mono vinyl aromatic) block and at least one predominantly poly(conjugated) diene block. Optionally, the poly(conjugated diene) block may be completely, partially or selectively hydrogenated.
With the term “predominantly” is meant that the main monomer of the respective individual blocks optionally may be mixed with minor amounts (e.g. amounts less than 50% mol/mol) of another comonomer and more in particular with minor amounts of the main monomer of other blocks.
Examples of the mono vinyl aromatic monomers may be selected from styrene, &agr;-methylstyrene, p-methylstyrene, m-methylstyrene, o-methylstyrene, p-tert-butylstyrene, dimethylstyrene, and various other alkyl-substituted styrenes, alkoxy-substituted styrenes vinylnaphthalene and vinyl xylene. The alkyl and alkoxy groups of the alkyl-substituted or alkoxy substituted styrenes respectively preferably contain from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms. The conjugated diene monomers are preferably conjugated dienes with from 4 to 8 carbon atoms per monomer, for example, butadiene, isoprene, 2-ethyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, 3-ethyl-1,3-pentadiene, and mixtures thereof.
Of these monomers styrene is the preferred vinyl aromatic monomer. Butadiene or isoprene or mixtures thereof are the preferred conjugated dienes. Block copolymers which contain only substantially pure poly(butadiene) or pure poly(isoprene) blocks are particularly preferred.
The apparent molecular weight of the elastomeric polymer may conveniently be in the range of from 20,000 to 750,000 and preferably in the range of from 40,000 to 730,000 and more preferably in the range of from 60,000 to 700,000.
With the term “apparent molecular weight” as used throughout the specification is meant the molecular weight of a polymer, as measured with gel permeation chromatography (GPC) using poly(styrene) calibration standards (according to ASTM D 3536).
The elastomeric block copolymers may be linear triblock or multiblock copolymers or multi-armed or star shaped symmetrical or unsymmetrical block copolymers. Diblock copolymers may also be used, as well as mixtures of block copolymers such as triblock copolymers containing diblock copolymers

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