General Status of Light Stabilizers
                       By Zhi Guo
The research and development of light  stabilizers  started
in the late 60's in China. In the  early  70's  there  was
small production of diphenyl  ketone,   benzotriazole  and
  triazine  varieties.   In  the  late  70's   organonickel
complexes and hindered amine varieties were developed. All
kinds of light stabilizers can now be produced in domestic
chemical enterprises, but the production  scale  is  small
and the process is outdated. Hindered amine varieties have
good effect and low price,  and  remarkable  progress  has
been made in their development in the recent 20 years.
Domestic diphenyl ketone varieties include UV-9 and UV-531.
Such light stabilizers absorb harmful ultraviolet ray  and
emit fluorescence, converting harmful optical energy  into
harmless thermal energy. They can be extensively  used  in
all kinds of polymers. China  has  7  -   8  producers  of
diphenyl ketone light stabilizers with a total capacity of
  800  t/a.   However,   these  producers  have   scattered
distribution, small production scale,   outdated  process,
low yield and high production cost. The  total  output  is
not more than 100 tons a year. Some products  have  to  be
imported. The total domestic  consumption  is  around  200
tons a year. UV-531 is mainly used to produce PVC  and  PE
anti-aging agricultural film, plastic  doors  and  windows
and some other engineering plastics. UV-9 is  mainly  used
to produce PVC agricultural film.
Domestic benzotriazole varieties include UV-326 and UV-327.
Such light stabilizers also absorb harmful ultraviolet ray
and emit harmless thermal energy. They have extensive uses
. Due to the small output and high price,  the  application
fields are not developed yet and the total consumption  is
only 20 - 30 tons a year.
Light stabilizer 2002 is the only nickel quenching agent in
China. It started production in the  early  70's  and  the
output has maintained at 20 - 40 tons a year. It was  once
one of major light stabilizers and  was  used  to  produce
agricultural film after being blended with GW-540. As  the
product is carcinogenic and causes heavy  metal  pollution
to farmlands, agricultural film producers no longer use it
in the recent  years  and  the  consumption  is  therefore
reduced by a big margin. As an effective light stabilizer,
  it  is  still  used  in  ordinary  plastic  products  for
prevention of light aging.
First domestic hindered amine  light  stabilizers  included
piperidine benzoate and PDS. Shanxi Research Institute  of
Chemical Industry took the lead in producing GW-540 in the
early 80's. The total output of hindered  amine  varieties
was 10 -  20  tons  a  year.   The  polyethylene  industry
developed fast and the output  increased  sharply  in  the
late 80's. The  expansion  in  the  use  of  polypropylene
agricultural film led to  a  rapid  increase  of  hindered
amine light stabilizers. The average annual growth rate in
the recent 10 years has reached more than 10%.  The  major
variety is GW-540. The product is also used in PP and  ABS
engineering plastics. The weakness of GW-540 is  induction
of accumulative hypersensitivity, causing harm to  workers
  in  chemical  production  and  plastic  processing.   The
existence of GW-540 would cause asthma, cough, rhinorrhea,
herpes and shock to sensitive  people.   Some  enterprises
have developed improved  varieties  and  some  enterprises
have used protective  masks,   but  the  results  are  not
satisfactory. As GW-540 has a low molecular weight, it  is
easily moved to the film surface with  antifogging  agents
and get lost. When the processing temperature is too high,
the consumption becomes big.
PDS is a  polymeric  light  stabilizer  with  the  earliest
application. Beijing  Research  Institute  of  Auxiliaries
also once produced similar varieties GW-560  and  GWF- 11.
The capacity of these varieties is only around 50  tons  a
year. They have a low  content  of  effective  groups  and
therefore the light stabilizing effect is not satisfactory.
Light stabilizer 622 is new generation polymeric variety in
China. It overcomes the weakness of GW-450  and  has  good
light stabilizing effect.  It  is  one  of  the  varieties
replacing GW-540 in the production of  agricultural  film.
China already has a 300 t/a unit. The output was around 60
tons in 1997 and will reach over 100 tons in 1998.  It  is
also used in PP woven bags and engineering  plastics  such
as polyformaldehyde and polyamide.
Light stabilizer 944 was developed in China  in  the  early
90's. However commercial production has  not  yet  started
due to problems in the yield of  piperidine  hexanediamine
synthesis. Beijing Research Institute  of  Auxiliaries  is
making efforts in its commercial production.  Satisfactory
results have been achieved in its use in agricultural film
. It is expected that the consumption in agricultural  film
will increase by a big margin and it will  become  another
variety to replace GW-450. Light  stabilizer  944  can  be
used in PP woven bags,  especially  big  bags  for  export
products, and also canopies and umbrellas for tourism.
Due attention has been paid to the development of  hindered
  amine  varieties  with  low  basicity.   Shan