COMPONENTS ROLE IN MANUFACTURING PROCESS
Resins
Basic polymers generally used in the manufacturing of high
pressure plastic laminates are aminic resins such as urea
formaldehyde and melamine formaldehyde, as well as Phenolic resins such as phenol formaldehyde. The laminates physical and
chemical nature is provided by the resin used. Synthetic thermo fixed resins like animic and
Phenolic resins do not
generally form sheets. Their low molecular weight, 600-800, and
their amorphous molecular structure do not allow this. Through
impregnation on paper it is possible to reduce them to flat
sheets. Some modifiers are added to the resins for post forming in
order to provide them with a thermoplastic nature. Sugar,
toluensulfonamide and benzenesulfonamide are some examples of
modifiers or plasticizers.
Papers
Up to three different kinds of paper are used in the
manufacturing of high pressure decorative laminates: decorative
papers which go on the laminates surface and which can have
printed patterns (wood-like, marble-like and leather-like), and
solid papers (one color, also called plain). These papers weigh
between 70 to 120 g/m squared.
Cover paper (also known as overlay) with a 33 g/m squared weight.
This paper is placed on top of the decorative paper. Once
pressed, this paper is characterized by being completely
transparent and provides the laminate with high resistance to
staining and wear, that is, resistance to use.
Kraft paper, with a 170 g/m squared weight, is the decorative
paper support and the laminates body. Depending on the laminates
type and thickness 4 to 33 sheets of kraft paper can be
integrated.
Papers used in the manufacturing of plastic laminates must have
certain very specific properties, first of all, in order to
obtain a good saturation without affecting the celluosic fiber
lay, and, second, in order to obtain a good appearance in the
final pressing.
Paper is passed through resin in order to accomplish saturation.
The highest limit for resin pick up is between 100% to 200%, and
it is best to keep it controlled at 140% to 180%. Saturated paper
is then taken to a hot air dryer where it is dried at 120-180
degrees C by applying hot air. The volatile material contents in
the impregnated paper are controlled at 5% to 8%. At the same
time, the resin goes through condensation because of the heats
influence. Molecular weight of melamine resins changes from
300-400 to 600-800, which has to do with the formation to
triazine compounds (with about 4 to 6 reactive groups). At this
point the resin goes from a aqueous state to a solid insoluble
state. After drying, the resin is solid but it still melts and
flows under pressure and temperature (during the laminates
pressing the resin changes to an insoluble state).
