* Billionaire Hopp preparing sale of LTS Lohmann -sources
* Investment firm approaching prospective buyers -sources
* LTS was valued at 1.2 bln euros in 2014 deal
* Dievini says there is no sales process (Adds Dievini board member saying no sale process)
By Arno Schuetze, Ludwig Burger and Carl O'Donnell
FRANKFURT/NEW YORK, April 6 (Reuters) - German billionaire Dietmar Hopp is preparing to sell medical skin patch maker LTS Lohmann as part of a shake-up of his investment portfolio, four people close to the matter said.
Hopp's investment firm Dievini has begun approaching potential buyers to gauge their interest in LTS which employs 1,300 staff and generates more than 300 million euros in annual sales from nicotine and other medical patches to treat conditions such as Parkinson's and restless legs syndrome.
The co-founder of software group SAP shared ownership of LTS with Switzerland's Novartis and German investment firm BWK until 2014 when he bought them out in a deal valuing it at 1.2 billion euros ($1.3 billion), after failing to find a third-party buyer for the business.
Dievini board member Christof Hettich said on Thursday there was no sale process and no bank had been mandated.
LTS competes with groups such as Beiersdorf's Tesa Labtec unit, U.S. conglomerate 3M, Luye Pharma Group and unlisted AMW GmbH, and Hopp is expected to try to whet these groups' appetites, the sources said.
In 2014, German chemicals group Evonik was in exclusive talks to buy LTS, but it pulled out at the eleventh hour after a disagreement on price.
Hopp, one of Germany's largest investors in biotech firms, is seen as unlikely to be able to rekindle interest from Evonik, which has in the meantime focused more on acquisitions in speciality chemicals.
Private equity groups have started seeking advice from external legal and financial consultants on a possible bid for LTS Lohmann, people close to the matter said.
In 2014, Wendel of France and Sweden's Nordic Capital had bid for LTS. It was not clear whether one of these groups will come back with a new offer, the sources added.
Hopp had at the time hoped to sell LTS Lohmann at a valuation of 15 times its expected earnings before interest, tax, depreciation and amortisation (EBITDA) of about 90 million. LTS earnings figures for 2016 are not available. ($1 = 0.9384 euros) (Editing by Maria Sheahan and Alexander Smith)