50 years old paper sheets have been treated with different concentrations o
f PVAc/PV versatate copolymer dispersion. The effect of different dipping r
ime, of washing before treatment, of adding DOP to the copolymer dispersion
and of heat pressing after treatment were studied. The probes were aged at
80 degrees C and different humidities of 30 to 94%. Ageing at 80 degrees C
and 94%, was also done for several time intervals. As a result it can be s
aid that the polymer treatment is highly improving the mechanical propertie
s of the paper and its; ageing stability.