Steve - I always thought they were going to Union Carbide - on the Pt Reading Secondary... But for sure, you would see them parked in that small yard in Bound Brook.
Back in the days when you could publicly trace shipments on Conrail, I remember these cars were destined for UP in Texas City, TX...
My recollections are from a few years ago, I have not checked out much down there in recent years,
Lou