Calendering cost

Poly(vinyl chloride). To be converted into film, poly(viayl chloride) [9002-86-22] (PVC) must be modified with heat stabilizers and plasticizers, which increase costs. Plasticized PVC film is highly transparent and soft, with a very high gas-permeation rate. Water-vapor transmission rate is relatively low. At present, PVC film is produced by blown-film extmsion, although casting and calendering are employed for heavier gauges (see Vinyl POLYAffiRS). 

In the calendering method, a PVC compound which contains plasticizers (qv) (60—120 phr), pigments (qv) (0—10 phr), fillers (qv) (20—60 phr), stabilizers (10—30 phr), and other additives, is kneaded with calender roUs at 150—200°C, followed by extmsion between clearance-adjusted roUs for bonding onto the substrate. This method is employed for products with thick PVC layers, ie, of 0.05—0.75 mm thickness. The main plasticizer used is di-2-ethylhexyl phthalate (DOP). For filler to reduce cost, calcium carbonate is mainly used. A woven or knit fabric made of cotton, rayon, nylon, polyester, and their blend fiber is used as substrate. For foamed vinyl-coated fabrics, the bonded materials are heated in an oven to decompose the foam-blowing... 

The principal benefit of using red aim is its lower cost compared to virgin mbbers. Reclaim typicaUy seUs for 20—30% of the cost of its none-reclaimed counterparts. Reclaimed mbber also imparts some desirable improvements in processing it has much lower nerve than virgin polymers. As a result, compounds containing reclaim have much lower die sweU and extmsion rates. It also increases calender rates and improves flow and mold filling. 

Basically the calendering process is used in the production of plastic films and sheets. It converts plastic into a melt and then passes the pastelike mass through roll nips of a series of heated and rotating speed-controlled rolls into webs of specific thickness and width. The web may be polished or embossed, either rigid or flexible (9). One of its sheets major worldwide markets is in credit cards. At the low cost side these lines can start a million. A line, probably the largest in the world... 

Calenders are capable of higher production speeds. Thus, there are situations where they provide a favorable situation for long runs. For these long runs, cost advantages exist. Tolerancewise the calender is easier to produce products that can meet tighter... 

The current technology is very cost-effective. If applied correcfly in line with other processes, such as extrusion or calendering, it can produce substantial savings by the reduction in material or the tire component s weight. The reduction of overall thickness can be as much as 20%. ... 

Capital investment for a calender line may be about 5 million. Operating cost may be about 500 per hr. Calendering is a very highspeed method of producing plastic film and sheet, but high-speed economy must be balanced against quality of the finished product. 

New oilseed crops, currently studied as potential sources of specialty fatty acids, include Crambe abyssinica for erucic acid, Limnanthes alba for very long-chain fatty acids, Dimorphotheca pluvialis for dimor-phecolic acid, Lesquerella fendleri for les-querolic acid, Calendula officinalis for calendic acid, and Euphorbia lagascae and various Vernonia species for vernolic acid.194 The lowest cost sources (inedible fats and oils and palm oil fractions) are likely most likely to be exhausted first as world trade in industrial applications grows. Cornstarch is becoming a major feedstock for plastics production. This may compete with potential oil uses, but also will increase production of com oil. 

Films and sheets are produced in several ways, including extrusion, calendering, and casting. Method used involves the properties required of the basic plastics and finished products as well as cost usually based on quantity. The following classification can be helpful as a guide to film and sheet thicknesses (1) film is generally less than 0.010 in. (0.003 mm) and (2) sheet at 0.010 in. or more. In turn sheet can be classified as ... 

The complete equipment usually consists of a mixer such as a Banbury mixer followed by the heated rolls, chilled rolls, and finally a windup roll.3 The windup roll controls the tension on the film or sheeting as it moves through the calender rolls. Calenders are generally designed to meet the specific needs of the customer. Once installed and operating continuously, the cost per pound of film or sheet is lower than by any other process such as extrusion. 

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