In-line ultrasonic check for detecting the partial vulcanization of a rubber mixture in the in situ silanization of bright fillers

A method for checking the silanization of pale-colored fillers, comprising:

• irradiating a rubber mixture comprising at least one silanized pale-colored filler and at least one rubber with ultrasound waves in a frequency range of 4 to 10 MHz, wherein the rubber mixture is produced at a temperature of above 160° C., and
• determining the signal strength of the ultrasound waves after transmission through the rubber mixture, where a relative attenuation coefficient αrel of the rubber mixture in the frequency range of the ultrasound waves is determined, a standard deviation σ of the relative attenuation coefficient αrel is determined, and αrel and σ are used for detection of incipient crosslinking of the rubber mixture,
• wherein the incipient crosslinking of the rubber mixture is detected in that the standard deviation σ of the relative attenuation coefficient αrel of the incipiently crosslinked rubber mixture is above 0.5 (1/m) and the relative attenuation coefficient αrel of the incipiently crosslinked rubber mixture is below 0 (1/m).