Technology of watch production - part 92
Nitroglyptal primer No. 1 4 7 (TU MKhP 1 94 5 - 1 94 9 ). Brown color.
Glyptal base with added c olloidal xylene base and a plastifier. It is used
as a primer for less c ritical parts. Its properties are rougly the same
as those of primer No . 1 38 , with the exception that it is diluted by s ol vent
No . 6 4 6 or RDV. It is dried at 6 0 to 6 5°C fo r not more than 3 5 min .
Nitroglyptal primer N o . 1 4 8 ( T U MKhP 2032 - 4 9 ) . Black c olor. Used
for parts subjected to frequent contamination and dust . Made from a nitric
base with the addition of lacquer No . 1 54 . Soot is added to the primer as
a pigment. Primer 1 4 8 is similar in other respects to primer 1 4 7 .
F i
1 1
e r s are applied to the surface for smoothing purposes . F ill e r is
applied on the prime r and is sanded after it drie s . Its mechanical strength
is l ower than that of the primer, and it is accordingly applied in a thick
layer (25 - 3 0
fL
). The m ost widely used glyptal- base fillers are No . 1 7 5 and
No. 1 8 5 (TU MKhP 3 3 1 -48) . They are applied on the primer and s erve as
an undercoat for the cover paint. The filler is diluted by a c oal s ol vent
( 1 0 - 2 5 % by weight ) and is sprayed on at 18 to 2 0°C . It is dried for an hour
at 1 0 0 to 1 1 0°C . Filler is applied on No . 1 38 prim e r and differs from the
p rimer in its lower oil content and higher pigment content.
No . 1 7 5 is pink, and No . 1 8 5 is gray.
L a c q u e r e n a m e l s a n d l a c q u e r s . C oating paints, laquer enamels
among them , must have high c o v e r i n g p o w e r (cove ring power is the capac
ity to cover the metal or earlier coating s o that they are not visible through
the paint film ). Lacquer paints are suspensions of pigments in various resins ,
oils and lacquers , with solvents (and s om etimes als o plas tifiers ) added.
Pigm ents are insoluble mineral dyes introduced into the paint in a finely
divided form and which remain in a suspended state . E ve ry paint has a liquid
phase (sol vent), which evaporates during drying, and a solid phase which
consists of resins , oil s , dyes and plas ticize rs and forms the film in drying.
A film is called r e v e r s i b l e if it can be reconverted to the original paint
by dissolving it; and it is called i r r e v e r s i b
1
e if it p olymerizes in drying.
Lac quer paints form irreve rsible films . These films nevertheless grad
ually deteriorate with time, a process known as aging. The physicochemical
properties of the film dete riorate during aging under the influence of heat,
humidity, and especially sunlight, until the film is destroyed and peels off .
Oil-paint film s have many advantages over nitrofilm s : better adhesion
to the metal , greater elasticity (but lesser hardness ), better temperature
resis tance (can stand up to temperatures as high as 1 5 0°C ). Oil-paint film s
s well i n water, howeve r .
U r e a f o r m a l d e h y d e e n a m e l s (VTU MKhP 2 5 3 1 - 5 1 ) are mixtures
of pigments in urea formaldehyde resin with the addition of alkyd resin and
RKB - 1 sol vent. These enamels are being used of late for painting the cases
of alarm and other clocks , supplanting the nitroenam els , because of a
number of engineering and ope rational advantages . Enamels are applied by
spray guns at 1 8 to 2 0°C . They can also be applied by dipping. The parts
are dried at 80 to 90°C fo r 20 min and at 1 2 0°C for a further 40 min.
During this drying process, the butanol in the sol vent evaporates s lowly
from the film, leaving a smooth surface free of fine pits . The enamel film
is as hard as glass and is at the sam e time sufficiently elastic . Enamel can
be applied directly on the m etal in two layers, thus satisfactory adhesion is
achieved . Colored enamels are produced: black ( U - 4 1 7 , U - 4 1 8 ) , blue
(UZ- 1 6 ), apple- green (UE - 1 1 ), ivory (UE - 2 ) , green ( UE - 1 3 ) .
3 6 5