Clariant Corp. makes a product called PV Fast Yellow HGR. They have
patented this product in the US. I am trying to determine when their
patent in the US expires for this product.

PV Fast Yellow HGR is an organic pigment which is used to color plastics.

Hello yss,

I have found the patent records for the pigment:

http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F5047517

It was made a bit more difficult to find as it was patented under the
assignee name of Hoechst Aktiengesellschaft, a German company which
used to own 45 percent of Clariant.

As for when the patent expires, new patent laws went into effect in
the US in 1995, so if a patent was filed by June 7, 1995 and issued
after June 7, 1978, the patent expires either 20 years from the filing
date or 17 years after the issue date, whichever is later.

The patent was issued on September 10, 1991 and filed on September 28, 1989. 

Since 20 years after the filing date is later than 17 years after the
issue date, the patent will expire on:

September 28, 2009

Sources:
on patent expiration
http://www.lectlaw.com/files/inp03.htm

Method of search:
Searched the US Patent Database for patents by Clariant and involving
yellow pigments.  Searched for "pigment 191" and found the patent
cited by another Clariant patent.

I hope that I have found exactly what you are looking for!  If you
need any additional help or clarification, let me know and I'd be glad
to help.

Cheers,
--keystroke-ga