GB2176787A - Process for preparing salts of ethylenediamine tetraacetic acid disodium salt and their hydrates - Google Patents
Process for preparing salts of ethylenediamine tetraacetic acid disodium salt and their hydrates Download PDFInfo
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- GB2176787A GB2176787A GB08615063A GB8615063A GB2176787A GB 2176787 A GB2176787 A GB 2176787A GB 08615063 A GB08615063 A GB 08615063A GB 8615063 A GB8615063 A GB 8615063A GB 2176787 A GB2176787 A GB 2176787A
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- edta
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- wet cake
- under vacuum
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C227/14—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof
- C07C227/16—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof by reactions not involving the amino or carboxyl groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C227/14—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof
- C07C227/18—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof by reactions involving amino or carboxyl groups, e.g. hydrolysis of esters or amides, by formation of halides, salts or esters
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C229/02—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton
- C07C229/04—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated
- C07C229/06—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton
- C07C229/10—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton the nitrogen atom of the amino group being further bound to acyclic carbon atoms or to carbon atoms of rings other than six-membered aromatic rings
- C07C229/16—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton the nitrogen atom of the amino group being further bound to acyclic carbon atoms or to carbon atoms of rings other than six-membered aromatic rings to carbon atoms of hydrocarbon radicals substituted by amino or carboxyl groups, e.g. ethylenediamine-tetra-acetic acid, iminodiacetic acids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C229/76—Metal complexes of amino carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
A process for preparing salts of ethylenediamine tetra-acetic acid of the formula <IMAGE> wherein n is 1 or 2 and M is Na, K, Li, Rb, Zn, Ca, Fe, Mn or Cu or in case one of the M is Na, K, Li or Rb the other M can also be H, is disclosed. The process comprises mixing under vacuum Na2.EDTA wet cake with an oxide, hydroxide or carbonate of the M component, in the presence of sufficient water to ensure ionisation, dissipating the resulting exotherm heat and collecting the product obtained.
Description
SPECIFICATION
Process for preparing salts of ethylenediamine tetraacetic acid disodium salt and their hydrates
This invention relates to a process for preparing salts of ethylenediamine tetraacetic acid disodium salt and the hydrates of such salts.
Ethylenediaminetetraacetic acid (EDTA) is the most widely used chelating and complexing agent. It is useful for controlling the concentration of metal ions in various media as well as for modifying, controlling and directing reactions mediated by such controlled metal ions; for example, EDTA and its soluble salts are important adjuncts in laundry compositions for controlling, by chelating, the unwanted calcium ions which form soap curds.
Preferred metal chelates of EDTA are also used in large quantities for agricultural applications as well as in drug and pharmaceutical uses.
The disodium zinc EDTA chelate is useful in agricultural service. The disodium calcium EDTA chelate is used as a preservative in pharmaceutical compositions and to prevent calcium depletion diuretics in the body.
This purified calcium chelate is also directly administered as a drug for chelating lead in cases of acute and chronic lead poisoning and heavy metal ingestion. Iron, copper and manganese chelates have also been used in agriculture, and in the oxidation and reduction of nitrogen oxides and in the sweetening of sour natural gases. The chelating activity of EDTA is used to selectively concentrate and isolate valuable heavy metals such as uranium, plutonium and thorium as well as the rare earths.
The preparation of these EDTA salts, until now, was according to the processes originally disclosed in U.S. Patents 2,407,645; 2,461,519, 2,855,428. This last is the basis for the present manufacture of EDTA and proceeds via cyanomethylation in acid solution to retard polymerization of HCN. This synthesis, via the hydrolysis of the nitrile, yields primarily EDTA tetrasodium salt (EDTA.Na4) which is then converted to the EDTA free acid (EDTA.AA). The desired salts until now had been prepared from the latter by neutralization. However due to the limited solubility of EDTA.AA, the reaction to form the salts proceeded slowly and yielded variable products requiring re-crystallization and repurification.
As the desired products are required in large quantity, such purification procedures are not economical or competitive.
It is an object of this invention to provide a method for the preparation of EDTA salts of the formula
wherein n is 1 or 2 and M is Na, K, Li, Rb, Zn, Ca, Fe, Mn or Cu or in case one of the M is Na,
K, Li or Rb the other M can also be H, which comprises mixing under vacuum 1 mole of the wet cake of the EDTA salt of the formula
a) with 1 or 2 mols of a compound of the formula (3) M3OH0 wherein Mo is NaO, KO, LiO or Rbo or
b) with 1 mol of a compound of the formula (4) 3-nM"OmX3-m0 wherein M is Li, Na, K, Rb, Ca, Mn, Fe, Cu or Zn, X is 0, OH or C03 and m and n each independently from one another are 1 or 2, in the presence of sufficient water to ensure ionisation, dissipating the resulting exothermic heat and the aqueous vapor generated and finally collecting the resulting product.
In the compounds of formula (4) X is O or CO3 if m is 1 and X is OH if m is 2.
The invention is based on the mixing of the commercially available dry or wet cake of ethylenediamine tetraacetic acid disodium salt with the oxide, carbonate or hydroxide of the M component in solid or moist state until the replacement of the hydrogen with the M component is completed and then recovering the resultant salt.
The commercially useful salts prepared according to the method of this invention and used in tonnage quantities for agriculture, pharmacy and the laundry and mining industries include Na EDTA, Na4-EDTA, Na2Mn-EDTA or Na2Ci-EDTA.
The oxides, hydroxides and carbonates of the M components useful in the reaction are e.g.
NaOH, Na2O, Na2CO3, ZnO, ZnCO3, Zn(OH)2, CuCO3, CuO, CaO, Ca(OH)2, CaCO3, MnO, MnCO3,
KOH, H2CO3 and FeCO3. While the sodium, zinc, calcium and manganese salts are at present commercially prepared in very large quantities other salts can be prepared by the process of this invention including the lithium, potassium and rubidium salts, the cadmium salts, the rare earth salts ("mischmetal"), heavy metal and uranium salts, iron, cobalt and nickel salts are usefully prepared in smaller amounts as either catalysts or as intermediates for isolation steps in mining or laboratory operations. The "dry" mix reaction of this invention is also economically useful for such operations.
As the reaction is essentially an ionically mediated reaction, it is promoted by the presence of some water. As the Na2EDTA wet cake contains about 15 % water, it is generally sufficient to initiate the reaction. However, as some of the oxide and hydroxide reactants require water of hydration to form ionic species, it is useful under such circumstances to add more water to the reaction vessel. The need for adding water is indicated where the combination of the Na2-EDTA with the M components shows an exotherm, but in the interest of manufacturing economy the stoichiometric amount need not be substantially exceeded. The water is either added in stoichiometric amount or in increments until no more exotherm reaction occurs.
The mixing of the Na2-EDTA wet cake with the MOH or MX component should take place in a vessel ensuring intimate mixing and contact of the solid reactants. Twin drum mixers, conical blenders and similar vessels which agitate, either by vessel rotation or equipped with internal agitation, are satisfactory. It is useful to have the vessels equipped with sources of heat in order to raise the temperature within the vessels so that reaction will be initiated and will proceed at an useful rate. Generally the initiating temperature should be above 15"C, but need not exceed this temperature as the exotherm and hydration heat will supply most of the heat necessary for the reaction.
As the reactions involved are ionic, and require some water, it is useful in order to provide a free-flowing final product to control the moisture of the reactive mixture when the reaction is completed and even during the reaction. This is easily achieved by exhausting the excess water vapor via a vacuum line from the interior of the reactor. As the temperature of the initiation rises due to the exotherm reaction to over 100 C it is useful to have between 600-720 mm Hg vacuum available. Moisture control reduces the crystal size formation in the final products, many of which are quite water-soluble. Large crystal formation is not desirable as it interferes with the free-flowing qualitites desired in the final product.
As mentioned above, agitation within the reaction vessel is useful to promote the reaction as well as to control particle size of the final product. Careful agitation, as well as control of the agitation rate during the latter stages of the reaction when much moisture may be present, will ensure a free-flowing powdered product. Proper agitation ensures heat transfer to remove the water vapor, and prevents low temperature crystallization and crystal growth beyond the desires size. It also helps keep the products and reactants below their melting points, as fusion within the mix also leads to particle sizes beyond those desired.
The completion of the reaction and the removal of the water vapor is achieved at a temperature ranging from 40 to 100"C and preferably 46 to 95"C.
Useful, commercially available, reactors for the "dry" or solid state blending and reacting according to this invention include e.g. the Day Mark II Mixer which is a jacketed conical vessel fitted with one or more interior screwtype agitators revolving parallel and in close clearance to the interior conical surface of the vessel and vented to a 720 mm Hg vaccum source, the
Patterson-Kelly jacketed mixer which is fitted with intensifier baffles and having hollow supporting axles connected to vacuum sources and the Stokes rotary vacuum dryer.
Such equipments or equivalents thereof permit the process of this invention to proceed economically even in large scale operations.
The invention will be more completely described in the following examples. Percentages are by weight.
Example 1: A jacketed conical Day Mark II mixer fitted with screw agitator was charged with 35.1 kg of Na2EDTA wet cake assaying 93 % purity. The vessel was heated by oil in the jacket, heating the material to 15"C, whereupon 7.8 kg of zinc oxide (99 %) were added. The exotherm heated the mix to about 40"C. 1.35 kg of water were sprayed on the mixing mass. The vessel was sealed and pumped down to about 635.0-711 mm Hg vacuum. The batch was then further heated to about 82-85"C by hot oil in the jacket. The vacuum pumping was continued during heating. Heating was discontinued and the batch temperature dropped to about 65"C. Dumping was continued for an additional hour and the product was then discharged. The free-flowing powder product was 45 kg of Na2.Zn-EDTA of 85.5 % purity.
Example 2: The procedure of Example 1 was followed but substituting 11.2 kg of zinc carbonate (ZnCO3) for the zinc oxide, yielding 45 kg of Na2.Zn-EDTA of 85-86 % purity.
Example 3: 45 kg Na3.EDTA was prepared by charging 39.9 kg Na2.EDTA (93 %) to the Day apparatus of Example 1 followed by 4.5 kg of NaOH flake (98 %) and 4.5 liter of water. After completion of exotherm reaction and heating to 65.5"C, vacuum drying and agitation was continued until a free-flowing powder could be discharged (about 2 hours) yielding 45 kg of
Na3.EDTA of 87 % purity.
Example 4: 39.9 kg of wet cake of Na2.EDTA was charged into the Day Mark II mixer. Over a half hour, 8.7 kg of a 50 % NaOH solution were uniformly sprayed under vacuum (711 mm Hg) to complete the reaction. After completion of exotherm reaction and heating to 65.5"C, vacuum drying and agitation was continued until a free-flowing powder could be discharged (about 2 hours) yielding 45 kg of Na3.EDTA of 87 % purity.
Example 5: The product Na3.EDTA was prepared by loading 75.6 kg of 93 % Na2.EDTA cake into a 0.028 m3 Patterson Kelly Twin Vacuum Blender. Into this charge were sprayed under 711 mm Hg vacuum 18.0 kg of NaOH (50 %). The exotherm reaction increased the temperature of the reaction mixture to 37.8 to 46"C. Heating and vacuum drying was continued for about an hour and the product, 92.7 kg of Na2.EDTA were recovered.
Example 6: The procedure of Example 4 was followed, substituting 23.6 kg of 50 % solution of Na3 CO3 for the 50 % solution of NaOH which were sprayed into the Day reactor under vacuum (711) mm Hg). After completion of the exotherm reaction the mixture was heated to dryness under vacuum and the product was discharged, yielding 85 % Na3.EDTA.
Example 7: The apparatus of Example 1 was charged with 43.5 kg of Na2.EDTA and the charge was sprayed with 18 kg of 50 % NaOH solution under vacuum (711 mm Hg). After completion of the exotherm reaction, the mixture was heated for about one hour. 45 kg of
Na4.EDTA of 91 % purity were obtained.
Example 8: To a Stokes-Pennwalt rotary vacuum dryer with double spiral agitator, heated by 172.25 kPa steam in the jacket and the agitator shaft, 1620 kg Na2.EDTA wet cake were charged and blended to break the lumps. 167.4 kg of NaOH beads (at 11 % excess) were charged. 9 kg of water were sprayed in to rinse off the material on the agitator. After blending for half an hour with the lid open the batch was dried to a 90.2 % Na3.EDTA assay. The pH of a 10 % solution of the product was 8.2 and the color 15 APHA.
Example 9: 1620 kg of Na2.EDTA wet cake were charged to the rotrary vacuum dryer of
Example 8, after unloading the previous batch. After blending to break the lumps, 72.3 kg of
NaOH beads and 54 kg water were charged and blended with the dryer cover open. The material was discharged after drying, using 172.25 kPa steam in the jacket to Na3EDTA of 92 % purity. The pH of a 10 % solution of the product was 8.2-8.3 and the color 15-25 APHA.
Example 10: 1350 kg of Na2.EDTA wet cake were charged to a clean rotary vacuum dryer.
After blending to break the lumps, 45 kg sodium sulfate and 264.6 kg NaOH beads were charged and blended for about half an hour with the manhole cover open. The batch was dried under vacuum to Na4.EDTA of 87.8 % purity and discharged. The powder was screened and any lumps were ground to an uniform size.
Example 11: 1350 kg of Na2.EDTA wet cake were charged to a clean rotary vacuum dryer.
After blending to break lumps, 238.5 kg CuO were charged. Thereupon 108 kg water were charged, and the reaction mass was heated to about 90-100 C with 172.25 kPa steam in the jacket and the agitator. After about 2 hours, blending at approximately 90"C, the batch was tested for excess Na2.EDTA. 58.5 kg CuS04 5H20 and 39.1 kg NaHCO3 were added to the reaction mass and blended for an hour to reduce the free Na2.EDTA to low levels. The batch was then dried under vacuum, by steam in the jacket and agitation, to about 10 % moisture content. After drying 900 kg of Na2.Cu.EDTA were discharged.
Example 12: 1350 kg Na2.EDTA wet cake and 217 kg zinc oxide were charged to a clean rotary vacuum dryer and blended for half an hour. About 108 1 water were added to obtain 30-35 % moisture content in the reaction mass, and heated to 90-95"C with steam in the jacket and shaft. After 2 hours reaction time, the paste was tested for free Na2.EDTA and adjusted with 4.5 kg NaHCO3 and dried under vacuum. 90.75 kg of Na2.Zn.EDTA were obtained.
The product was screened and ground to an uniform size.
Example 13: After unloading the previous batch, 900 kg of Na2.EDTA wet cake were charged followed by 217 kg of ZnO. After blending for 15-30 minutes 108 1 water were sprayed in and the dryer heated to 90 to 950C. The batch was blended for 2 hours and tested for free
Na2.EDTA. 4.0 kg of ZnSO4.7 H20 and 6.3 kg of NaHCO3 were added to reduce the excess
Na2.EDTA and to adjust the pH. After adjustments the batch was dried under vacuum to a 63 % sample (EDTA basis) and discharged. 725.8 kg Na2.Zn.EDTA were recovered.
Example 14: To 1350 kg of Na2.EDTA charged and blended in a clean rotary vacuum dryer, were charged 202 kg of fine MnO followed by about 108 kg water. The batch was heated to 90-95"C under agitation, until the reaction mass becomes a flowable thin slurry. After two hours of blending at 90-95"C, a sample was tested for free Na2.EDTA. (The balance adjustments were made as follows: Too high a free Na2.EDTA is adjusted unsing MnSO4.H20 and
NaHCO3. Excess MnO is corrected using Na2.EDTA. Adjustments in product pH are made using
NaHCO3 or dilute H2SO4). After necessary adjustments (using 55.3 kg Na2.EDTA wet cake, 7.2 kg MnSO4.H20 and 21.1 kg NaHCO3) the batch was dried, and 729 kg of product were discharged and subsequently ground to a uniform size.
Claims (13)
1. A process for the preparation of salts of ethylendiamine tetra-acetic acid of the formula
wherein n is 1 or 2 and M is Na, K, Li, Rb, Ca, Fe, Mn or Cu or in case one of the M is Na, K,
Li or Rb the other M can also be H, which comprises mixing under vacuum 1 mole of the wet cake of the EDTA salt of the formula
a) with 1 or 2 mole of a compound of the formula M2ZOH0 wherein M is NaO, KO, Li" or RbO or
b) with 1 mol of a compound of the formula 3-nM""mX3-m0 wherein M is Li, Na, K, Rb, Ca, Mn, Fe, Cu or Zn, X is 0, OH or CO3 and m and n each independently from one another are 1 ar 2, in the presence of sufficient water to ensure ionisation, dissipating the resulting exothermic heat and the aqueous vapor generated and finally collecting the resulting product.
2. The process according to claim 1 for the preparation of
Na3.EDTA which comprises the step of mixing under vacuum Na2.EDTA, wet cake, with one mole of NaOH as compound MOH.
3. The process according to claim 1 for the preparation of Na4. EDTA which comprises the step of mixing under vacuum, Na2.EDTA, wet cake, with two mole of
NaOH as compound MOH.
4. The process according to claim 1 for the preparation of
Na2.Zn.EDTA which comprises the step of mixing under vacuum, Na2.EDTA, wet cake, with one mole of ZnO as the compound MX.
5. The process according to claim 1 for the preparation of
Na4.EDTA which comprises the step of mixing under vacuum, Na2.EDTA, wet cake, with one mole of
Na2CO3 as the compound MX.
6. The process according to claim 1 for the preparation of
Na2.Mn.EDTA which comprises the step of mixing under vacuum, Na2.EDTA, wet cake, with one mole of MnO as the compound MX.
7. The process according to claim 1 for the preparation of Na2.Cu.EDTA which comprises the step of mixing under vacuum, Na2.EDTA, wet cake, with one mole of Cu(OH)2 as the compound MX.
8. The process according to claims 2 and 3, wherein the NaOH is added as caustic flakes or pellets.
9. The process according to claims 2 and 3, wherein the NaOH is added as a 50 % aqueous solution of NaOH.
10. The process according to claims 2 and 3 wherein Na2CO3 is used instead of NaOH.
11. The process according to claim 1 wherein the heating, to ensure reaction completion and water vapor removal, is to a temperature between 40 and 100"C.
12. Process for the preparation of salts of ethylenediamine tetraacetic acid according to claim 1, substantially as described with reference to any of the Examples.
13. Salts of ethylenediamine tetra-acetic acid when prepared by a process claimed in any of the preceding claims.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US74809585A | 1985-06-24 | 1985-06-24 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8615063D0 GB8615063D0 (en) | 1986-07-23 |
| GB2176787A true GB2176787A (en) | 1987-01-07 |
| GB2176787B GB2176787B (en) | 1989-04-12 |
Family
ID=25007995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8615063A Expired GB2176787B (en) | 1985-06-24 | 1986-06-20 | Process for preparing salts of ethylenediamine tetraacetic acid disodium salt and their hydrates |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS62451A (en) |
| CH (1) | CH668256A5 (en) |
| DE (1) | DE3620629A1 (en) |
| FR (1) | FR2583748A1 (en) |
| GB (1) | GB2176787B (en) |
| IT (1) | IT1191961B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6325654A (en) * | 1986-07-18 | 1988-02-03 | Fuji Photo Film Co Ltd | Color photographic developing solution composition and method for processing silver halide color photographic sensitive material |
| TW363075B (en) * | 1994-11-01 | 1999-07-01 | Daikin Ind Ltd | Fluoride polymer compound painting and coating method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2407645A (en) * | 1943-06-21 | 1946-09-17 | Martin Dennis Company | Aliphatic polycarboxylic amino acids and process of making them |
| US2461519A (en) * | 1948-03-17 | 1949-02-15 | Frederick C Bersworth | Method of producing carboxylic substituted aliphatic amines and metallic salts thereof |
| US4224310A (en) * | 1979-09-04 | 1980-09-23 | Richardson-Merrell, Inc. | Dentifrice compositions |
| US4322361A (en) * | 1980-03-03 | 1982-03-30 | The Dow Chemical Company | Method of preparing a manganese chelate having improved properties |
-
1986
- 1986-06-17 CH CH2435/86A patent/CH668256A5/en not_active IP Right Cessation
- 1986-06-20 GB GB8615063A patent/GB2176787B/en not_active Expired
- 1986-06-20 DE DE19863620629 patent/DE3620629A1/en not_active Withdrawn
- 1986-06-20 IT IT48161/86A patent/IT1191961B/en active
- 1986-06-20 FR FR8608971A patent/FR2583748A1/en not_active Withdrawn
- 1986-06-24 JP JP61146276A patent/JPS62451A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62451A (en) | 1987-01-06 |
| DE3620629A1 (en) | 1987-01-02 |
| IT8648161A0 (en) | 1986-06-20 |
| FR2583748A1 (en) | 1986-12-26 |
| CH668256A5 (en) | 1988-12-15 |
| GB8615063D0 (en) | 1986-07-23 |
| GB2176787B (en) | 1989-04-12 |
| IT1191961B (en) | 1988-03-31 |
| IT8648161A1 (en) | 1987-12-20 |
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| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |