US2153449A - Clarification of rayon spin baths - Google Patents
Clarification of rayon spin baths Download PDFInfo
- Publication number
- US2153449A US2153449A US152469A US15246937A US2153449A US 2153449 A US2153449 A US 2153449A US 152469 A US152469 A US 152469A US 15246937 A US15246937 A US 15246937A US 2153449 A US2153449 A US 2153449A
- Authority
- US
- United States
- Prior art keywords
- bath
- clarification
- flotation
- baths
- spin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229920000297 Rayon Polymers 0.000 title description 12
- 238000005352 clarification Methods 0.000 title description 9
- 239000002964 rayon Substances 0.000 title description 5
- 238000000034 method Methods 0.000 description 20
- 239000003153 chemical reaction reagent Substances 0.000 description 13
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 12
- 238000005188 flotation Methods 0.000 description 10
- 239000002253 acid Substances 0.000 description 9
- 239000011593 sulfur Substances 0.000 description 8
- 229910052717 sulfur Inorganic materials 0.000 description 8
- 239000012535 impurity Substances 0.000 description 7
- 238000011084 recovery Methods 0.000 description 7
- 229920002678 cellulose Polymers 0.000 description 6
- 239000001913 cellulose Substances 0.000 description 6
- 238000009291 froth flotation Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000005864 Sulphur Substances 0.000 description 4
- 239000012141 concentrate Substances 0.000 description 4
- 230000001172 regenerating effect Effects 0.000 description 4
- 230000008929 regeneration Effects 0.000 description 4
- 238000011069 regeneration method Methods 0.000 description 4
- 238000009987 spinning Methods 0.000 description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000003350 kerosene Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052938 sodium sulfate Inorganic materials 0.000 description 3
- 235000011152 sodium sulphate Nutrition 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- ZOOODBUHSVUZEM-UHFFFAOYSA-N ethoxymethanedithioic acid Chemical compound CCOC(S)=S ZOOODBUHSVUZEM-UHFFFAOYSA-N 0.000 description 2
- 239000008396 flotation agent Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000012991 xanthate Substances 0.000 description 2
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000002547 anomalous effect Effects 0.000 description 1
- 238000011001 backwashing Methods 0.000 description 1
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- -1 dithiophosphoric acid compound Chemical class 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 235000010265 sodium sulphite Nutrition 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 1
- 229960001763 zinc sulfate Drugs 0.000 description 1
- 229910000368 zinc sulfate Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/02—Froth-flotation processes
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F13/00—Recovery of starting material, waste material or solvents during the manufacture of artificial filaments or the like
- D01F13/02—Recovery of starting material, waste material or solvents during the manufacture of artificial filaments or the like of cellulose, cellulose derivatives or proteins
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
Definitions
- This invention relates to a process for the clarification of fouled spin baths used in the viscose rayon manufacture.
- the cellulose xanthate 5 viscose is extruded through fine openings in socalled spinnerettes into a bath which regenerates hydrated cellulose to form a filament which maythen be spun with others to form rayon yarn.
- These spin baths contain salts and acids for delo composing the strongly alkaline cellulose xanthate.
- Typical baths contain from 8-10% of sulfuric acid, glucose and various salts such as sodium sulfate, sodium sulfite and the like.
- the alkali in the viscose reacts to form 15 sodium sulfate and the decomposition of the xanthic acid radical results in setting free a considerable amount of sulfur which is present in a very finely divided and sometimes colloidal form.
- the bath soon fouls with decomposition products including sulfur and requires clarification before the bath can be reused.
- the volume of spin baths used is very large, one-half liter of spin bath per minute per spindle being a common amount in the rayon industry. With the large volume of bath required it is of course economically undesirable to discard the fouled solution as it contains too large a quantity of valuable chemicals.
- spin baths are clarified by froth flotation such as is used in the ore dressing art. It is found that the sulfur and other impurities can be floated off from the bath with a very slight loss of bath and with the production of an extraordinarily clear bath for reuse.
- the flotation process is in some respect unique in that it is apparently not dependent on the use of any particular definite flotation agent. It is possible to fioat with air alone without any reagents or with the addition of frothers or collectors. This is most unusual as the ordinary flotation processes are rather rigidly limited to the use of particular classes of collecting agents.
- the present invention is not limited to any particular type of flotation machine. Excellent results are obtained with highly efiicient machines of the mechanical type such as a Fagergren machine. However, the present invention represents a peculiar situation because simple pneumatic machines can be used without serious 1055 in flotation efficiency. This is not the case with most flotation processes where the highly developed mechanical machines with their superior agitation and aerating efliciency have relegated the pneumatic machines to a relatively minor position in the art.
- the possibility of using extremely simple pneumatic machines in the present process is of great importance because the spin baths are strongly acid and hence any metallic equipment has to be rendered acid proof, which is a difllcult matter with mechanical machines having rotating parts. Pneumatic machines can of course be made of completely acid proof construction without any materially increased cost.
- Example 1 A fouled spin bath having a composition typical of that used in bobbin spinning and containing when fresh 130 grams sulfuric acid per liter, 250 grams sodium sulfate per liter and 14 grams zinc sulfate per liter was treated in an acid proof mechanical flotation machine of the Fagergren type.
- the bath was clarified by three methods, first with the use of no reagents, then with a dicresyldithiophosphoric acid known in the trade as Aerofloat 15, then with an alcohol frother containing a mixture of higher alcohols and known in the trade as 13-48, and finally with kerosene. In every case, the bath was thoroughly clarified and a good recovery of sulfur was obtained.
- the details of the tests appear in the following table. The volumes and weight parts given in the table are in the same system:
- Example 3 A spin bath typical of the pot spinning process was floated in a pneumatic machine as described in Example 2. The results with no reagents were substantially the same as the corresponding results in Example 1 and in a second test, when the reagent was Aerofloat 15, a slightly better grade of concentrate was obtained with a larger output from a given size machine.
- baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution which comprises subjecting the bath to froth flotation and removing the froth which contains the bulk of the turbid impurities.
- a method of clarifying fouled regenerating baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution which comprises subjecting the bath to froth flotation in the absence of flotation reagents and removing the froth which contains the bulk of the turbid impurities.
- a method of clarifying fouled regenerating baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution which comprises subjecting the bath to froth flotation in the presence of a dithiophosphoric acid compound, and removing the froth which contains the bulk of the turbid impurities.
- Example 2 lose from viscose which bath contains sulphur
- a spin bathas described in Example 1 was treated in a pneumatic flotation machine provided with an acid proof air distributor in the bottom and of acid proof construction throughout. The results were substantially the same as in Example 1.
- deposited out of solution which comprises subjecting the bath to froth flotation in the presence of a saturated hydrocarbon collector and removing the froth which contains the bulk of the turbid impurities.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Degasification And Air Bubble Elimination (AREA)
Description
Patented Apr. 4, 1939 UNITED STATES PATENT FFECE CLARIFICATION OF RAYON SPIN BATES No Drawing. Application July 7, 1937,
Serial No. 152,469
4 Claims.
This invention relates to a process for the clarification of fouled spin baths used in the viscose rayon manufacture.
In the spinning of rayon the cellulose xanthate 5 viscose is extruded through fine openings in socalled spinnerettes into a bath which regenerates hydrated cellulose to form a filament which maythen be spun with others to form rayon yarn. These spin baths contain salts and acids for delo composing the strongly alkaline cellulose xanthate. Typical baths contain from 8-10% of sulfuric acid, glucose and various salts such as sodium sulfate, sodium sulfite and the like. During spinning the alkali in the viscose reacts to form 15 sodium sulfate and the decomposition of the xanthic acid radical results in setting free a considerable amount of sulfur which is present in a very finely divided and sometimes colloidal form. The bath soon fouls with decomposition products including sulfur and requires clarification before the bath can be reused. The volume of spin baths used is very large, one-half liter of spin bath per minute per spindle being a common amount in the rayon industry. With the large volume of bath required it is of course economically undesirable to discard the fouled solution as it contains too large a quantity of valuable chemicals.
Various methods of the clarification of the spin baths have therefore been proposed and some are in fairly extensive use. Most of the methods have depended on filtration using, for example, excelsior, wood, shavings, burlap, coarse woolen cloth and the like. A certain degree of clarification is achieved by these filters but they are only used where a high degree of clarity of bath is not required. In recent years some operators have required a bath of a higher degree of clarity and have installed sand filters which operate continuously. These filters, however, require periodic backwashing with water and considerable losses of bath occur. While it is possible to effect clarification by the prior filtering processes, they are expensive and the highest clarity is only obtained with special filters requiring very careful supervision and even with the best filters clarity is not as high as could be desired. The filtering processes also do not permit an economic recovery of the sulfur in a form in 60 which it is readily salable.
According to the present invention, spin baths are clarified by froth flotation such as is used in the ore dressing art. It is found that the sulfur and other impurities can be floated off from the bath with a very slight loss of bath and with the production of an extraordinarily clear bath for reuse.
The flotation process is in some respect unique in that it is apparently not dependent on the use of any particular definite flotation agent. It is possible to fioat with air alone without any reagents or with the addition of frothers or collectors. This is most unusual as the ordinary flotation processes are rather rigidly limited to the use of particular classes of collecting agents.
The great flexibility of the process of the present invention is one of its important advantages. While a good clarified concentrate with fairly good recovery is obtainable without any reagents, materially better sulfur recovery can be ob ained by the use of r. hydrocarbon collector such as kerosene, whereas substantially the same recovery as is obtained without reagents results when flotation agents of the dithiophosphate type are used. These reagents, however, give a purer concentrate.
The question of whether a reagent should be used is largely one of economics because, while the process without reagents gives good recovery and good clarification, this is obtained at the expense of lower flotation machine capacity. In every case, of course, the best economic compromise will be chosen between additional reagent cost and saving in equipment and power charges. The process of the present invention is also unique inanother respect; namely, that the same fiotation procedure removes a concentrate which contains sulfur to the extent of '70- 80% with the remaining material which is chemically totally unrelated to sulfur. Such a result is in marked contrast to the ordinary flotation processes which are highly selective and which depend for their action on the separation of materials of different types of chemical composition. The reason for the anomalous behavior of the present process is not as yet determined, and the invention is not limited to any set theory of operation.
The present invention is not limited to any particular type of flotation machine. Excellent results are obtained with highly efiicient machines of the mechanical type such as a Fagergren machine. However, the present invention represents a peculiar situation because simple pneumatic machines can be used without serious 1055 in flotation efficiency. This is not the case with most flotation processes where the highly developed mechanical machines with their superior agitation and aerating efliciency have relegated the pneumatic machines to a relatively minor position in the art. The possibility of using extremely simple pneumatic machines in the present process is of great importance because the spin baths are strongly acid and hence any metallic equipment has to be rendered acid proof, which is a difllcult matter with mechanical machines having rotating parts. Pneumatic machines can of course be made of completely acid proof construction without any materially increased cost.
The invention will be described in greater detail in conjuncticn with the following specific examples which set forth the clarification of typical spin baths using various reagent combinations. It should be understood that the invention is not limited to the particular details set forth in the examples.
Example 1 A fouled spin bath having a composition typical of that used in bobbin spinning and containing when fresh 130 grams sulfuric acid per liter, 250 grams sodium sulfate per liter and 14 grams zinc sulfate per liter was treated in an acid proof mechanical flotation machine of the Fagergren type. The bath was clarified by three methods, first with the use of no reagents, then with a dicresyldithiophosphoric acid known in the trade as Aerofloat 15, then with an alcohol frother containing a mixture of higher alcohols and known in the trade as 13-48, and finally with kerosene. In every case, the bath was thoroughly clarified and a good recovery of sulfur was obtained. The details of the tests appear in the following table. The volumes and weight parts given in the table are in the same system:
the results were substantially similar but with slightly lower recovery percent.
Example 3 A spin bath typical of the pot spinning process was floated in a pneumatic machine as described in Example 2. The results with no reagents were substantially the same as the corresponding results in Example 1 and in a second test, when the reagent was Aerofloat 15, a slightly better grade of concentrate was obtained with a larger output from a given size machine.
I claim:
1. A method of clarifying fouled regenerating,
baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution, which comprises subjecting the bath to froth flotation and removing the froth which contains the bulk of the turbid impurities.
2. A method of clarifying fouled regenerating baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution, which comprises subjecting the bath to froth flotation in the absence of flotation reagents and removing the froth which contains the bulk of the turbid impurities.
3. A method of clarifying fouled regenerating baths from the regeneration of hydrated cellulose from viscose which bath contains sulphur deposited out of solution, which comprises subjecting the bath to froth flotation in the presence of a dithiophosphoric acid compound, and removing the froth which contains the bulk of the turbid impurities.
4. A method of clarifying fouled regenerating baths from the regeneration of hydrated cellu- Reagent Spin bath Impurities removed Impurity Percent Type Lgblilgn w gs congeilif, P ts by 01 mm Parts lbty Recoverty, figigg par S y V 111116 V0 ume welg DGI'CBD bath treated weight treated percent None None 1, 669 1. 442 170 10.2 1.348 93.48 78.1 0. 105 2, 240 0. 484 230 10. 3 0. 450 02. 0s 79. 0 -4s 0. 11s 2, 230 o. 482 222 10. 0 0. 415 80. 7s. 0 Kerosene 0.172 1,900 0.410 204 10.7 0.402 98.05 74.0
Example 2 lose from viscose which bath contains sulphur A spin bathas described in Example 1 was treated in a pneumatic flotation machine provided with an acid proof air distributor in the bottom and of acid proof construction throughout. The results were substantially the same as in Example 1.
When cresylic acid was used in place of 3-48,
deposited out of solution, which comprises subjecting the bath to froth flotation in the presence of a saturated hydrocarbon collector and removing the froth which contains the bulk of the turbid impurities.
ROBERT IB. BOOTH.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US152469A US2153449A (en) | 1937-07-07 | 1937-07-07 | Clarification of rayon spin baths |
| GB37063/38A GB512111A (en) | 1937-07-07 | 1938-12-20 | Process for the clarification of fouled regenerating baths used in the manufacture of regenerated cellulose from viscose |
| NL91195A NL53876C (en) | 1937-07-07 | 1938-12-22 | |
| FR848075D FR848075A (en) | 1937-07-07 | 1938-12-27 | Viscose spinning bath clarification process |
| BE431956D BE431956A (en) | 1937-07-07 | 1939-01-02 | |
| CH209352D CH209352A (en) | 1937-07-07 | 1939-01-03 | Process for clarifying cloudy cellulose regeneration baths in hydrated form from viscose. |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US152469A US2153449A (en) | 1937-07-07 | 1937-07-07 | Clarification of rayon spin baths |
| GB37063/38A GB512111A (en) | 1937-07-07 | 1938-12-20 | Process for the clarification of fouled regenerating baths used in the manufacture of regenerated cellulose from viscose |
| NL91195A NL53876C (en) | 1937-07-07 | 1938-12-22 | |
| FR848075T | 1938-12-27 | ||
| BE431956T | 1939-01-02 | ||
| CH209352T | 1939-01-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2153449A true US2153449A (en) | 1939-04-04 |
Family
ID=10393448
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US152469A Expired - Lifetime US2153449A (en) | 1937-07-07 | 1937-07-07 | Clarification of rayon spin baths |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US2153449A (en) |
| BE (1) | BE431956A (en) |
| CH (1) | CH209352A (en) |
| FR (1) | FR848075A (en) |
| GB (1) | GB512111A (en) |
| NL (1) | NL53876C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2462948A (en) * | 1943-05-19 | 1949-03-01 | Woonsocket Rayon Inc | Flotation process of clarifying regenerating baths |
| US2578040A (en) * | 1942-09-03 | 1951-12-11 | American Cyanamid Co | Method of and circuit for material modification and coolant clarification |
| US2713420A (en) * | 1954-05-18 | 1955-07-19 | Southwestern Eng Co | Clarification process |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE743688C (en) * | 1941-05-03 | 1943-12-30 | Kurmaerkische Zellwolle | Process for cleaning the finishing agent used in the manufacture of rayon |
-
1937
- 1937-07-07 US US152469A patent/US2153449A/en not_active Expired - Lifetime
-
1938
- 1938-12-20 GB GB37063/38A patent/GB512111A/en not_active Expired
- 1938-12-22 NL NL91195A patent/NL53876C/xx active
- 1938-12-27 FR FR848075D patent/FR848075A/en not_active Expired
-
1939
- 1939-01-02 BE BE431956D patent/BE431956A/xx unknown
- 1939-01-03 CH CH209352D patent/CH209352A/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2578040A (en) * | 1942-09-03 | 1951-12-11 | American Cyanamid Co | Method of and circuit for material modification and coolant clarification |
| US2462948A (en) * | 1943-05-19 | 1949-03-01 | Woonsocket Rayon Inc | Flotation process of clarifying regenerating baths |
| US2713420A (en) * | 1954-05-18 | 1955-07-19 | Southwestern Eng Co | Clarification process |
Also Published As
| Publication number | Publication date |
|---|---|
| CH209352A (en) | 1940-04-15 |
| FR848075A (en) | 1939-10-23 |
| GB512111A (en) | 1939-08-29 |
| BE431956A (en) | 1939-02-28 |
| NL53876C (en) | 1943-02-15 |
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