Packaging Corporation of America reported first quarter 2018 net income of $140 million, or $1.48 per share and $1.55 per share excluding special items. First quarter net sales were $1.7 billion in 2018 and $1.5 billion in 2017.   “Demand in our Packaging segment remained strong with record first quarter sales volumes in both our containerboard mills and corrugated products plants as well as improved prices and mix compared to the first quarter of 2017,” Mark W. Kowlzan, chairman and CEO, said...