10 Chlorinated Normal Paraffins as Polyvinyl Chloride Plasticizers D. H . ROTENBERG
Downloaded by GEORGETOWN UNIV on August 27, 2015 | http://pubs.acs.org Publication Date: January 1, 1965 | doi: 10.1021/ba-1965-0048.ch010
Chemicals Research Division, Esso Research & Engineering Co., Linden, N. J.
The
chlorination
of high
purity
molecular
- s i e v e d n o r m a l p a r a f f i n s y i e l d s p l a s t i c i z e r s for p o l y v i n y l c h l o r i d e ( P V C ) with b e t t e r p r o p e r t i e s t h a n c h l o r i n a t e d w a x e s . T h e c h l o r i n a t e d n- p a r a f f i n s are much l i g h t e r i n c o l o r t h a n c h l o r i n a t e d wax and are m o r e t h e r m a l l y s t a b l e in PVC
formulations.
plasticizer
They
also
have
better
efficiency a n d l o w temperature
p r o p e r t i e s i n P V C and h a v e l o w e r v i s c o s i t y . The l a t t e r three p r o p e r t y a d v a n t a g e s a r e d u e to the use o f l o w e r m o l e c u l a r w e i g h t p a r a f f i n s t h a n t h o s e a v a i l a b l e from wax. These p r o p e r t i e s are functions o f b o t h the c h l o r i n e c o n t e n t a n d c a r b o n c h a i n l e n g t h o f the n - p a r a f f i n s . The c o m p a t i b i l i t y a n d volatility p r o p e r t i e s o f t h e c h l o r i n a t e d n - p a r a f f i n s i n P V C are s i m i l a r t o t h o s e o f c h l o r i n a t e d wax and s e r v e t o s e t l o w e r limits on c h l o r i n e c o n t e n t a n d a v e r a g e molecular weight, respectively.
Chlorinated paraffinic hydrocarbons have been commercially available for at least 45 years (6). The literature on the chemistry and technology of chlorination processes of all types is rather extensive (7). However, the principal chlorinated paraffins or chloroalkanes of commerce today represent what can best be described as either low or high molecular weight products. This is essentially a reflection of the length of the carbon chain of the hydrocarbon used in the chlorination process. On one hand, there are the chlorinated derivatives of hydrocarbons ranging from methane to the pentanes; on the other, there are the chlorinated derivatives of petroleum wax. This wax usually consists of mixtures of paraffins with average molecular weights in the range C20 to C26. The uses for low molecular weight chloroparaffins are familar; they include solvents, cleaning agents, fire extinguishing agents, and chemical intermediates. Applications for the chlorinated waxes include plasticizers, cutting oils, additives 108 In Plasticization and Plasticizer Processes; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1965.
Downloaded by GEORGETOWN UNIV on August 27, 2015 | http://pubs.acs.org Publication Date: January 1, 1965 | doi: 10.1021/ba-1965-0048.ch010
10.
ROTENBERG
Chlorinated Normal
Paraffins
109
for paint, rubber, printing inks, plastics, mastics, adhesives, and textiles. Often their principal function is to reduce or eliminate flammability. An important reason for the lack of intermediate molecular weight products has been the unavailability of low cost paraffins with molecular structures suitable for these materials. Synthetic paraffins, prepared by the Fischer-Tropsch process and often known as Kogasin, have been available in this intermediate molecular weight range (10) and have been used in Europe to make chloroparaffins(P). However, these materials also are not completely satisfactory because of a combination of cost, purity, and molecular structure. The problem of availability of suitable paraffinic feedstocks of low cost, which represent a potentially wide range of molecular weight, will soon be rectified. Linear alkanes of high purity will be available from petroleum on a large scale, as is evident from recent announcements by both chemical and petroleum companies of plans to build normal paraffin extraction plants (£, 3, 8). The balance of this article consists of a discussion of the properties of chlorinated derivatives of these w-paraffins as plasticizers for polyvinyl chloride (PVC). This application of course, represents just one of many potential uses for these materials. Experimental All elemental and molecular weight analyses on both laboratory and commercial samples of chlorinated paraffins and the composition and purity determinations of the w-paraffins were carried out by the Analytical Research Division of Esso Research & Engineering Co. n-Paraffins. Single component w-paraffins, W - C 1 6 H 3 4 , W - C 1 8 H 3 8 , and w-C22H4e were obtained from Matheson, Coleman, and Bell Co. Gas chromatography showed that essentially only one component was present. The purity was not checked further, and they were used without further treatment. The w-paraffin mixture was used as produced by the Esso molecular seive process. Commercial Chlorinated Products. The commercial products reported herein are typical of chloroparaffins produced both in the U. S. and in Germany. They were used as received. All reported analyses and physical properties were determined in these laboratories. Chlorinations. Photochemical chlorinations were carried out both with and without solvent (CCI4) as is typified by the following example : A solution of 100 grams (0.39 mole) of Cis average w-paraffin and 150 grams of carbon tetrachloride was placed in a two-necked 500-ml. round-bottomed flask equipped with a condenser, thermometer, magnetic stirrer, and a gas inlet tube that did not extend below the surface of the liquid. The flask was partially immersed in a water bath at 25°C, and the system was swept with nitrogen. Chlorine was then introduced at a measured rate of 150 cc./minute as determined by a calibrated Brooks rotameter. A 150-watt unfrosted tungsten light bulb was placed against the flask. The temperature of the solution during the course of the reaction was 35°C. The effluent gas stream was checked for unreacted chlorine by passing it through an excess of IN potassium iodide solution for 0.5 hour, followed by titration with 2.00iV sodium thiosulfate. Approximately 5 cc./minute of chlorine was not reacting, so that the actual rate of absorption was 145 cc./minute. To obtain a product that has an average structure of C 1 8 H 3 3 C I 5 (molecular weight 427, 41.6% CI), 1.95 moles (approximately 48 liters at 25°C.) of chlorine are required. Thus, In Plasticization and Plasticizer Processes; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1965.
110
PLASTICIZATION A N D PLASTICIZER PROCESSES
the chlorination was run for 5.5 hours. The solution was then washed with aqueous sodium bicarbonate and water, followed by drying and heating to remove solvent at 0.05 mm. pressure and 100°C.
Downloaded by GEORGETOWN UNIV on August 27, 2015 | http://pubs.acs.org Publication Date: January 1, 1965 | doi: 10.1021/ba-1965-0048.ch010
The product was characterized as follows: Color, Gardner scale Viscosity, Brookfield, 25°C, cp. Analvsis, % C * H CI Empirical formula Molecular weight, Calculated Found (Osmometer)
