Polyethylene waxes are manufactured by one of three methods: 1- Direct polymerization of ethylene (may include co -monomers such as alpha olefins, vinyl acetate, acrylic acid…); 2- Thermal degradation of high molecular weight polyethylene resin; 3- Refining of Low Polymer Wax (low molecular weight fractions) from high molecular weight polyethylene resin production.

Each production technique generates products with unique and different properties. Key properties of low molecular weight polyethylene waxes are viscosity, density and melt point. The term ‘wax’ generally implies a hard, somewhat brittle material with a relatively discrete melting point. Molecular weights can range from ~1,000 to about 20,000. Above this range of molecular weight the polymer begins to take on the properties of polyethylene polymer resins.

The stream of material that is recovered from high density polyethylene resin plants and is use as a feed-stock for refining operations is generally called Low Polymer Wax. Low Polymer Wax requires the removal of corrosive and potentially hazardous  oligimers and catalyst especially when being used in applications requiring FDA or other regulatory certification. In addition to residual catalysts, residual solvent and oligomers, Low Polymer Wax often contains significant quantities of water and other non-wax contaminants that must be removed. In particular the volatile compounds in Low Polymer Wax can cause fire and safety concerns in end use applications. Polyethylene wax manufactured by recovery of Low Polymer Wax and subsequent removal of volatile components and residual catalyst are called Refined Polyethylene Waxes. Refined Polyethylene Waxes are usually fractionated into grades based on the requirements of the end use application. Polyethylene waxes manufactured by this method should be stripped of low molecular weight fractions to yield a flash point > 500°F(> 260°C) in order to be used in a safe manner.

Analysis of the Low Polymer Wax received from various sources is shown in the Table 1 below. As can be seen the product properties can vary widely especially as related to flash point. The below does not reflect the level of contaminants such as water and catalyst that must be removed for safe use as a refined polyethylene wax.

TABLE 1	AVERAGE PROPERTIES OF LOW POLYMER WAX AS RECEIVED FROM DIFFERENT SUPPLIERS
SAMPLE	Source A (Flakes)	Source B (Lumps)	Source C (White)	Source D (Grey)	Source E (Range)	Source F (S America)	Source G (Africa )	Source H (Middle East)	Source I
VISCOSITY (cps)	15 – 200	50 – 200	16 – 35	20 – 60	5 – 40	15 – 40	25 – 60	40 – 70	15 – 70
FLASH POINT (⁰C)	165	165	170	170	175	145	145	145	160
MELTING POINT (⁰C)	93	95	95	95	65	90	95	96	90
DROP MELTING POINT (⁰C)	100	105	105	105	84 – 88	100	105	108	100
PENETRATION (dmm)	5.0	5.0	3.5	2.5 – 3	20	15 – 20	15 – 20	15 – 20	7 – 10
Acid No. (mgms KOH/gm)	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil	Nil
Whiteness Index	75	70	65	45	75	73	75	70	60
pH	6.5	6.5	7.0	7.0	6.0	7.5	7.0	8.0	6.5

Loses from Low Polymer Wax can be significant as shown in the table below. Additionally if catalyst is not properly removed through refining the Low Polymer Wax can begin to degrade over time as shown by color body generation. Volatile content can be determined by placing samples in ovens at 250C while residual catalyst can be determined by ash content testing (ASTM D5630) and should be well below 0.1% to insure safety of the Refined Polyethylene Wax.

TABLE 2	UNREFINED LOW POLYMER WAX VOLATILE LOSS AND STABILITY BY SOURCE
RAW MATERIAL FROM	WEIGHT LOSS AFTER 24HRS. RETAINTION AT 210⁰C	LOSS IN %	WEIGHT LOSS AFTER 24HRS. RETAINTION AT 250⁰C	LOSS IN %	OBSERVATIONS
HPL	12.49gm of 100gm	12.49%	15.46gms of 100gm	15.46%	Yellowing started after 12hrs.
GAIL	14.41gm of 100gm	14.41%	18.86gm of 100gm	18.86%	Yellowing started after 10hrs.
OPAL	9.87gm of 100gm	9.87%	12.69%gm of 100gm	12.69%	Yellowing started after 5hrs.
IOCL	19.52gm of 100gm	19.52%	24.73gm of 100gm	24.73	Yellowing started after 1hr.

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Direct polymerization of ethylene to produce polyethylene wax is by either either high or low pressure polymerization. Each production process yields polyethylene waxes with different molecular configuration (chain linearity, cross-linking, modality (mono or bi) polarity and any associated functional group(s) incorporated into the polymer either during polymerization or post polymerization. Adding functional groups to polyethylene wax post polymerization is usually via oxidation or maleation.

Polyethylene produced via polymerization of ethylene monomer usually in combination with one or more co-monomer. Polymerization can be classified into either high or low pressure polymerization with the following characteristics:
• High Pressure Polymerization -Produces Low Density Polyethylene (LDPE); Reaction is carried out at 1000 to 3000 barg. At about 80 to 300 deg. C. Peroxides are used as catalysts.
• Low Pressure Polymerization. Produces High Density Polyethylene (HDPE) / Linear Low Density Polyethylene (LLDPE); Uses co-monomer such as Butene 1, Hexene 1 or Octene 1; Reaction is carried out at 10 to 80 barg. At temperature of 70 to 300 deg.C. Using catalyst such as:
o Ziegler Natta
o Cr. /Mo Oxides
o Metallocene