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PCE
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DIFF Subgroup
D21C 3/06

sulfur dioxide; sulfurous acid; bisulfites

Introduced: September 1968

Full Title

Full titles differ between systems:

IPC:

Pulping cellulose-containing materials > with acids, acid salts, or acid anhydrides > sulfur dioxide; sulfurous acid; bisulfites

CPC:

Pulping cellulose-containing materials (digesters D21C7/00) > with acids, acid salts or acid anhydrides > sulfur dioxide; sulfurous acid; bisulfites

IPC and CPC are identically structured here. All 4 subcodes exist in both systems.

Child Classifications

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  • D21C 3/08 calcium bisulfite IPC+CPC Available in IPC and CPC
  • D21C 3/10 magnesium bisulfite IPC+CPC Available in IPC and CPC
  • D21C 3/12 sodium bisulfite IPC+CPC Available in IPC and CPC
  • D21C 3/14 ammonium bisulfite IPC+CPC Available in IPC and CPC

Top Applicants

Top Applicants (IPC)

Class D21,2013–2023, worldwide · Source: EPO PATSTAT

  1. VOITH PATENT DE 1,809
  2. STORA ENSO FI 1,467
  3. KEMIRA FI 1,086
  4. KIMBERLY-CLARK CORPORATION US 935
  5. VALMET TECHNOLOGIES FI 924
  6. VALMET SE 904
  7. P&G (PROCTER & GAMBLE COMPANY) US 862
  8. OJI HOLDINGS CORPORATION 696
  9. OMYA INTERNATIONAL CH 584
  10. SOUTH CHINA UNIVERSITY OF TECHNOLOGY 571

Top Applicants (CPC)

Class D21,2013–2023, worldwide · Source: EPO PATSTAT

  1. VOITH PATENT DE 1,857
  2. STORA ENSO FI 1,552
  3. KEMIRA FI 1,173
  4. KIMBERLY-CLARK CORPORATION US 1,107
  5. VALMET TECHNOLOGIES FI 965
  6. VALMET SE 943
  7. P&G (PROCTER & GAMBLE COMPANY) US 941
  8. OMYA INTERNATIONAL CH 821
  9. UPM-KYMMENE CORPORATION FI 512
  10. SEIKO EPSON CORPORATION JP 501