Extrusion of Thermo sets

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Paper is one of the highest consumed natural materials - consumed for commercial as well as domestic use, for a large spectrum of applications. Which means that paper is the greatest culprit for problems of ecology and enviornment, because the woods are destroyed for the production of most of the paper produced.

With a view to preserve the forests, development of synthetic paper has been on for almost four decades. A first major break-through was production of thin gauge partially oriented HM-HDPE film, around 1966 in India. Still, this was not very close to natural paper in many important properties.
The synthetic paper that is now developed and commerically getting a substantial penetration in the paper domain is based on HDPE and PP by blown and cast Processes, using a specially developed paper masterbatch.
The paper master-batch for HDPE / PP is offered by Schulman, represented by Reifenhauser Marketing in India.
The trials were taken on Kolsite 3-Layer blown film line and Colines CPP Film line using HDPE and PP with the Masterbatch and the results were encouraging. The results with HDPE on a Blown Film Line with a little orientation were excellent.

Salient properties

	The synthetic paper contains no fibres and is not coated and is therefore ideal for those applications where contact with water and moisture is likely.
	The paper is tough with outstanding tear resistance, folding strength, tensile strength and shock resistance.
	This paper has excellent resistance to chemicals.
	It has outstanding smoothness, which ensures high print quality and the finest finish by coating and Lamination.
	It is absolutely safe for enviornment and is fully recyclable.
	The paper thus produced has all the properties very close to that of natural paper - it can be printed by all the known methods; can be written on by ball pen, Computer printouts with dotmatrix as well as laser are possible.It can be folded, creased, stuck with adhesive.
	It is very ideally suited as a packing paper for applications such as laminated soap wrappers, twist-wrap as well with great advantage for advertisement billboards, machine catalogues, annual reports, documents required to be preserved, calendars, tourist maps, cards for educational equipments, book covers, book pages, etc.
	One great advantage is that it can be recycled like any plastics film.
	The synthetic paper has dimensional stability, waterproofness, resistance to chemicals, smoothness, whiteness and can be washed for cleaning. These properties have replaced paper in applications such as copy papers,second originals, thermal papers for clean room, bar code label and video printer, computer forms, drawing papers,plotter papers, etc.
	The market is importing its requirements mainly from Japan, but no special efforts have been made to develop the market.

Printing

The paper can be printed on a regular offset printing machine commonly used for printing paper. For best results, the top and bottom sheet which have been kept in contact with the cardboard packing sheet of each pack, should be discarded. The paper should be brought into the printing room at least a day before printing, in order to condition it to the room temperature and prevent moisture condensation. The relative humidity at the machine should be maintained at not less than 50% to minimize electrostatic problem.

Printing conditions

	Feeder Unwrapped sheets should be fanned before stacking to ensure smooth feeding. Folding is prohibited. The stacking should not be loaded more than 5,000 sheets at one time.
	Abrasions and Marks To avoid sucker marks, minimize the suction pressure and/or cover the rubber part of the sucker with cloth tape to avoid wheels and brushes marks, move them away from the image area or cover them with either PP tape or cloth tape.
	Plates Pre-sensitized (PS) Plates are the most recommended.
	Press setting Printing pressure should be maintained as high as possible. The blanket will sometimes show whitening which comes from the inorganic fillers and normally has no effect on print quality.
	Dampening water As paper is not absorbent, it is important to keep the amount of the dampening water to a minimum so as to avoid poor ink adhesion, longer drying times, set-off and washed out printed images.

Packing

Spray powder should be used and it should be of the hydrophilic type (i.e. having an affinity for water, but not soluble). Soluble or water-repellent powders are not suitable.

It is suggested that:

	sheets should be stacked in piles of 500-1000 sheets.
	air-pressure and jogging should be reduced to a minimum.
	sheets should not be subjected to impacts or shocks.
	humidity at delivery should be kept over 50% at least to avoid static problem.

Drying

This paper is not absorbent, and therefore, drying will take longer than with paper. Typical drying time :
1 colour 4-6 hours, 2 colour 5-8 hours, 4 colour 6-10 hours.

Inks

Inks must be specially formulated for synthetic papers and consist of 100% solids, contain less than 3% mineral oil and dry by oxidation.

Applications

Some of the very common applications in Japan as per one of the very large manufacturers like YUPO (Japan) include the following:-

	General graphics: Outdoor posters, sign boards, catalogues, pamphlets, calendars,menus.
	Publication: Book pages, children books, maps.
	Packaging: Mould-in labels, overwraps, blister packs, labels of all kinds including self-adhesive labels.
	Bags : Shopping bags, envelopes, courier bags, x-ray envelopes, preservation bags.
	Special applications: Ballot papers, golf score cards, ski tickets, various manuals, business cards, battery insulation paper.

The market potential appears extremely good, particularly because it can be produced on Indian equipments, with Indian Polymers and with comparatively small investments.

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