GB2032901A - Purifying and/or Bleaching Calcium Sulphate - Google Patents
Purifying and/or Bleaching Calcium Sulphate Download PDFInfo
- Publication number
- GB2032901A GB2032901A GB7934187A GB7934187A GB2032901A GB 2032901 A GB2032901 A GB 2032901A GB 7934187 A GB7934187 A GB 7934187A GB 7934187 A GB7934187 A GB 7934187A GB 2032901 A GB2032901 A GB 2032901A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bleaching
- calcium sulphate
- chlorine
- carried out
- per cent
- 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.)
- Granted
Links
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 title claims abstract description 49
- 239000001175 calcium sulphate Substances 0.000 title claims abstract description 24
- 235000011132 calcium sulphate Nutrition 0.000 title claims abstract description 24
- 238000004061 bleaching Methods 0.000 title claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000460 chlorine Substances 0.000 claims abstract description 13
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 13
- 239000002245 particle Substances 0.000 claims abstract description 13
- 239000002002 slurry Substances 0.000 claims abstract description 11
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000000049 pigment Substances 0.000 claims abstract description 10
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 7
- 239000000945 filler Substances 0.000 claims abstract description 5
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000007844 bleaching agent Substances 0.000 claims abstract description 4
- 238000005194 fractionation Methods 0.000 claims abstract description 4
- 238000009896 oxidative bleaching Methods 0.000 claims abstract description 3
- 150000002978 peroxides Chemical class 0.000 claims abstract description 3
- 239000000725 suspension Substances 0.000 claims abstract description 3
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract 4
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract 2
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract 2
- 238000000034 method Methods 0.000 claims description 28
- 150000001805 chlorine compounds Chemical class 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 2
- 238000009826 distribution Methods 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 4
- 238000004140 cleaning Methods 0.000 abstract description 2
- 229910052925 anhydrite Inorganic materials 0.000 abstract 1
- 239000010440 gypsum Substances 0.000 description 20
- 229910052602 gypsum Inorganic materials 0.000 description 20
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 10
- 239000011248 coating agent Substances 0.000 description 8
- 239000000123 paper Substances 0.000 description 7
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 6
- 239000002270 dispersing agent Substances 0.000 description 6
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 5
- 238000010009 beating Methods 0.000 description 5
- 239000001768 carboxy methyl cellulose Substances 0.000 description 5
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 5
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000008199 coating composition Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000004062 sedimentation Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 229920002472 Starch Polymers 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 239000011111 cardboard Substances 0.000 description 2
- 150000004683 dihydrates Chemical class 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 150000004676 glycans Chemical group 0.000 description 2
- 239000011368 organic material Substances 0.000 description 2
- 229920001282 polysaccharide Polymers 0.000 description 2
- 239000005017 polysaccharide Substances 0.000 description 2
- 239000008107 starch Substances 0.000 description 2
- 235000019698 starch Nutrition 0.000 description 2
- LNAZSHAWQACDHT-XIYTZBAFSA-N (2r,3r,4s,5r,6s)-4,5-dimethoxy-2-(methoxymethyl)-3-[(2s,3r,4s,5r,6r)-3,4,5-trimethoxy-6-(methoxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6r)-4,5,6-trimethoxy-2-(methoxymethyl)oxan-3-yl]oxyoxane Chemical compound CO[C@@H]1[C@@H](OC)[C@H](OC)[C@@H](COC)O[C@H]1O[C@H]1[C@H](OC)[C@@H](OC)[C@H](O[C@H]2[C@@H]([C@@H](OC)[C@H](OC)O[C@@H]2COC)OC)O[C@@H]1COC LNAZSHAWQACDHT-XIYTZBAFSA-N 0.000 description 1
- 239000005995 Aluminium silicate Substances 0.000 description 1
- 239000004131 EU approved raising agent Substances 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical group Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 229920001479 Hydroxyethyl methyl cellulose Polymers 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- YWIULWOWYIZJBX-UHFFFAOYSA-N [Cl].O1C=COC=C1 Chemical compound [Cl].O1C=COC=C1 YWIULWOWYIZJBX-UHFFFAOYSA-N 0.000 description 1
- 235000012211 aluminium silicate Nutrition 0.000 description 1
- 239000002518 antifoaming agent Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 229910001634 calcium fluoride Inorganic materials 0.000 description 1
- 239000005018 casein Substances 0.000 description 1
- BECPQYXYKAMYBN-UHFFFAOYSA-N casein, tech. Chemical compound NCCCCC(C(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(CC(C)C)N=C(O)C(CCC(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(C(C)O)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(COP(O)(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(N)CC1=CC=CC=C1 BECPQYXYKAMYBN-UHFFFAOYSA-N 0.000 description 1
- 235000021240 caseins Nutrition 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 235000019325 ethyl cellulose Nutrition 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000004088 foaming agent Substances 0.000 description 1
- 235000010855 food raising agent Nutrition 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 229920003087 methylethyl cellulose Polymers 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000005445 natural material Substances 0.000 description 1
- 238000009994 optical bleaching Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000011087 paperboard Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 239000002367 phosphate rock Substances 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920000193 polymethacrylate Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 239000003755 preservative agent Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 229940070527 tourmaline Drugs 0.000 description 1
- 229910052613 tourmaline Inorganic materials 0.000 description 1
- 239000011032 tourmaline Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/02—Compounds of alkaline earth metals or magnesium
- C09C1/025—Calcium sulfates
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/06—Treatment with inorganic compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Paper (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Detergent Compositions (AREA)
Abstract
Calcium sulphate to be used as pigment and/or filler agent is subjected to the effect of an oxidizing bleaching agent, e.g. chlorine, hypochlorite, hypochlorous acid, chlorine dioxide or peroxides. Preferably, the treatment is carried out with the CaSO4 being in the form of a suspension in water and the slurry also is subjected to a cleaning and fractionation for obtaining a definite particle size distribution.
Description
SPECIFICATION
Pigment Treatment Method
This invention relates to a method of treating pigment and/or filler agent, particularly calcium sulphate, primarily by purification and/or bleaching.
Calcium sulphate or gypsum is a natural material, which is found in several countries, for example in the Mediterranean countries. The usual form thereof is the dihydrate with the composition Ca S04.2 H20. Gypsum, however, exists, also as a waste product at the manufacture of phosphoric acid where it often is called "chemical gypsum". The term calcium sulphate in connection with the present invention is to be understood as calcium sulphate in all its forms, i.e. both the sulphate as such and its dihydrates and semihydrates.
It has been proposed previously to use gypsum as pigment in coating agents for paper. The reason why the proposal was not successfully realized in practice apparently has been that one had not understood the special prerequisites, which must prevail for obtaining a good result.
The present invention has the object of providing a method of pretreating calcium sulphate so as to render it suitable for use as pigment and/or filler agent. According to the invention, this is achieved in that the calcium sulphate is treated with an oxidizing bleaching agent.
According to an especially suitable embodiment, the treatment is carried out by bleaching with chlorine, hypochlorus acid, hypochlorite, chlorine dioxine and/or peroxides. It is then advantageous to carry out the bleaching with the calcium sulphate being in the form of a suspension in water. An especially good effect was obtained when the dry content in the slurry amount to at maximum 60 per cent by weight, preferably at maximum 50 per cent by weight.
When the bleaching is carried out with chlorine, hypochlorous acid or hypochlorite, it was found to be of essential importance that the pH value in the slurry is held at 1.5-6, preferably at 24. The bleaching can be carried out for a period of 5 minutes to 1 hour, preferably 20 to 30 minutes.
When treating with chlorine or chlorine compounds, it is important to add definite amounts for obtaining a maximum effect. It was found by experiments that the addition should amount to 0.11%, preferably 0.30.5% active chlorine, calculated on the amount of calcium sulphate.
According to another embodiment, the calcium sulphate is purified by fractionation, preferably in a cyclone, prior or subsequent to the bleaching, in order to remove undesired particles.
After the bleaching the calcium sulphate must be washed with water, for example on a filter or in a column, in order to remove chlorine residue, chlorides and oxidizing compounds.
The invention is described in greater detail in the following by way of an example and with reference to the accompanying drawing, which is a block diagram of a way how to carry out the method.
Example
As raw material according to this invention waste gypsum from the manufacture of phosphoric acid was used. The material was suspended 1 in water to a dry content of about 1 5 per cent by weight, and the pH value for the slurry was adjusted to a value below 3. This value is a critical one, because at higher pH values discolouring impurities will adhere to the gypsum particles. Gypsum of the type here applied includes as impurities, besides organic material, heavily discoloured gypsum, calcium fluoride and silicates from previous processes. When the pH value exceeds 3, acidification preferably is carried out by means of sulphuric acid.
The resulting slurry then is fractionated in a hydrocyclone 2 whereby a fraction with a particle size of 25-1 00 y was recovered. The particle size must not be below 25 , because then the dewatering in a subsequent process step would be rendered substantially more difficult. The fraction containing particles with a size above 100 y consists partially of dark-coloured particles, which partially consist of tourmaline. The rock phosphate constituting the starting material for the manufacture of phosphoric acid exists, however, in many different qualities and the impurities, therefore, can be of varying kind.
The fractionation was carried out in two steps, 3 and, respectively, 4. In the first step the coarser, and in the second step the finer fraction were removed and carried away as waste from the process.
By carrying out the separation in this manner, one is independent of the operation conditions in the phosphoric acid factory, from which the gypsum is collected. The resulting slurry had a dry content of about 45 per cent by weight.
The recovered fraction then was bleached in a continuous bleaching plant 5 by the addition of chlorine water 6. The dry content dropped by this addition to about 20 per cent by weight. After the addition of the chlorine water the pH value was adjusted to 3, and the bleaching was carried out by stirring in two tanks connected in series in order to extend the stay-time. The amount of added chlorine was 0.5 per cent by weight calculated on dry gypsum. After the bleaching, the slurry was thickened in a sedimentation thickener to a dry content of about 35 per cent by weight.
In a subsequent step 7 the gypsum then was washed in order to remove foaming agents, chlorides, organic material and other impurities.
The washing was carried out continuously with water 8 flowing counter-current in vertical pipes, at the lower portion of which the gypsum is taken out by a screw. At the washing a thickening to about 45 per cent by weight dry content was obtained simultaneously.
The filtering of the slurry resulting from the washing step was then carried out on rotary vacuum filters 9, onto which water was sprayed simultaneously in order to primarily remove chlorides residue. From the filter a clean, bleached product with a dry content of about 75 per cent by weight was obtained. The effluents 10 and, respectively, 11 from the washing 7 and, respectively, filtering 9 can be led away together 22.
The main constituents in a coating composition, irrespective of whether it is to be used for coating paper and cardboard or as paint, are pigment, binding agent and liquid phase.
Generally it is necessary also to add a dispersing agent in order to obtain a good pigment distribution. It is thereby often possible to simultaneously also lower the viscosity of the composition, which implies the possibility of bringing about a higher dry content without deteriorating the coatability.
For coating paper, cardboard or the like, conventionally kaolin, titanium dioxide or chalk are used as pigment. It was, however, also proposed to use gypsum. The reason why gypsum has not been used in practice probably is, that gypsum was considered to require a much greater amount of dispersing agent.
Binding agents previously used for coating compositions consist, for example, of watersoluble substances such as starch and casein, or of dispersions of different polymers in water, for example polyacrylate, polymethacrylate and polyvinyl alcohol. It is per se known, however, to use certain cellulose derivatives, for example, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose and carboxymethyl cellulose.
A great number of agents are available for use as dispersing agents. Most commonly used, beyond all comparison, are different types of phosphates, especially sodium hexametaphosphate. This dispersing agent, however, like several others, has certain disadvantages. For example, the binding force of the binding agent used often is reduced.
Furthermore, these dispersir.g agents when being used for the coating of paper to be printed in offset print, in certain cases can give rise to emulsification of the ink in the offset water, from which an undesired toning of the print may result.
In view of the aforesaid, at the method according to the present invention substantially a dispersing agent is used which itself acts as binding agent, viz. a polysaccharide substituted with carboxyl groups.
It was in this connection found entirely decisive that the gypsum is beaten in the presence of a polysaccharide substituted with carboxyl groups.
According to an especially advantageous method the beating is carried out in the presence of water.
At different experiments carried out in connection with the development of the present invention, it was found that particularly good results were obtained when beating with carboxymethyl cellulose, usually called CMC, and when the material had a mean molecular weight of 10,000-500,000, preferably 20,000- 150,000. When using CMC, this is added in an amount of 0.5-3 per cent by weight, calculated on the amount of dry calcium sulphate.
In this connection the particle size of the calcium sulphate is essential. When, for example, a coating composition for yielding a mat paper is to be prepared, the gypsum must have such a particle size distribution that 30 per cent has a size smaller than 2 ,u. For coating compositions intended to yield a glazed paper, 95 per cent of the material must have a particle size smaller than 2y. When pigment for filler agent is concerned, the particle size of the calcium sulphate must be such, that 50 per cent by weight of the material have a size smaller than 5,u.
The particle size distribution according to above was determined by means of a sedimentation apparatus according to Andreasen which in Sweden is marketed by the enterprise
Kebo Grave under the reference number
111.904. The test sample is prepared by weighing about 10 g gypsum slip, to which 2 ml of a 1-% CMC solution is added, whereafter the slip is mixed and stirred with about 40 ml water.
The sample is transferred to the sedimentation apparatus, and amounts to 10 ml are taken out with the pipette according to the scheme as follows.
1 st sample Sample 2nd sample after 60 minutes
3rd sample after 120 minutes
4th sample after 1080 minutes
5th sample after 1 560 minutes
According to a special embodiment a binding agent, for example latex or starch, is added. Such addition preferably should be made after the beating.
As mentioned above, a high dry content is of great importance for an effective and economic coating agent. With the binding agent/dispersing agent selected and the method used, dry contents as high as 60-80 per cent by weight for the coating agent to yield a mat paper can be obtained. For coating agents to yield a glazed paper, dry contents of 55-80 per cent by weight were obtained.
According to a special embodiment, the beating is carried out at increased temperature, preferably at a temperature below 1 300 C. The coating agent concretely can be manufactured as follows, with reference to the drawing.
The product resulting from the example was supplied to a dispersion equipment 12 while simultaneously 1.6 per cent by weight of carboxymethyl cellulose (CMC), calculated on dry gypsum, was added 13 in the form of a 1.4% solution. Thereafter, the pH value was raised to 1 2 by addition of sodium hydroxide, because as in the present case gypsum includes smail amounts of phosphoric acid which is set free at the subsequent beating. Also conventional glaze raising agents, antifoaming agents, optical bleaching agents, colouring substances and preservatives can be added to the mixture, according to desire. The different components are supplied to the mixing vessel continuously for obtaining a flow of about 4 m3/h. The dispersing effect is brought about by means of a rapidly rotating stirrer.
From the dispersing step 12 the material is transferred continuously to a vacuum deaerator 14 in order to remove enclosed air.
After the deaeration the dispersion was beaten in a pearl beater 1 5 at a temperature of about 500C in a single step, then was cooled 1 6 and screened in a seif-cleaning screen 1 7. As final product 18 a storage-durable slurry with a dry content of 71% was obtained. The product can be pumped and be delivered filled in tanks or barrels.
The invention is not restricted to the embodiments described, but can be varied within the scope of the invention idea.
Claims (17)
1. A method of purifying and/or bleaching impure calcium sulphate to be used as pigment and/or filler agent, which method comprises treating the calcium sulphate with an oxidizing bleaching agent.
2. A method as claimed in claim 1 wherein the treatment is carried out by bleaching with chlorine, hypochlorous acid, hypochlorite, chlorine dioxide and/or a peroxide.
3. A method as claimed in claim 1 or claim 2 wherein the bleaching is carried out with the calcium sulphate being in the form of a suspension in water.
4. A method as claimed in claim 3 wherein the dry content in the slurry amounts at maximum to 60 per cent by weight.
5. A method as claimed in claim 4 wherein the dry content in the slurry amounts to a maximum 50 per cent by weight.
6. A method as claimed in claim 2 wherein the bleaching with chlorine, hypochlorous acid or hypochlorite is carried out at a pH of from 1.5 to 6.
7. A method as claimed in claim 6 wherein the pH is from 2 to 4.
8. A method as claimed in claim 7 wherein the pH is 3.
9. A method as claimed in any one of the preceding claims wherein the bleaching is carried out for a period of from 5 minutes to 1 hour.
10. A method as claimed in claim 9 wherein the bleaching is carried out for a period of from 20 to 30 minutes.
11. A method as claimed in claim 2 wherein chlorine or the chlorine compound is added in an amount of from 0.1 to 1% active chlorine, based on the amount of calcium sulphate.
12. A method as claimed in claim 11 wherein the amount is from 0.3 to 0.5%, based on the amount of calcium sulphate.
13. A method as claimed in any one of the preceding claims wherein the calcium sulphate is purified by fractionation prior or subsequent to the bleaching to remove undesired particles.
14. A method as claimed in claim 13 wherein the calcium sulphate is purified in a cyclone.
1 5. A method as claimed in any one of the preceding claims wherein the calcium sulphate after the bleaching is washed with water to remove residual chlorine, chlorides or oxidized compounds.
1 6. A method as claimed in claim 1 5 wherein a filter or a column is utilised in the washing of the calcium sulphate.
17. A method as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7811216A SE417104B (en) | 1978-10-30 | 1978-10-30 | SET TO CLEAN RESPECTIVE PINK POLLUTANED CALCIUM SULPHATE INTENDED TO BE USED AS PIGMENT AND / OR FILLER |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2032901A true GB2032901A (en) | 1980-05-14 |
| GB2032901B GB2032901B (en) | 1982-11-03 |
Family
ID=20336216
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7934187A Expired GB2032901B (en) | 1978-10-30 | 1979-10-02 | Purifying and/or bleaching calcium sulphate |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5835937B2 (en) |
| CA (1) | CA1125456A (en) |
| DE (1) | DE2943205A1 (en) |
| ES (1) | ES8102059A1 (en) |
| FI (1) | FI66416B (en) |
| FR (1) | FR2440386A1 (en) |
| GB (1) | GB2032901B (en) |
| IT (1) | IT1128747B (en) |
| NL (1) | NL7907976A (en) |
| SE (1) | SE417104B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4310360A (en) | 1978-10-30 | 1982-01-12 | Supra Aktiebolag | Method for producing pigment for use in sizing compositions |
| US4344925A (en) * | 1979-01-12 | 1982-08-17 | Societe Chimique Des Charbonnages | Ozone whitening of synthetic gypsum |
| WO1993002963A1 (en) * | 1991-08-02 | 1993-02-18 | Prayon-Rupel Technologies | Method for preparing an aqueous calcium sulphate-based suspension |
| US5188814A (en) * | 1990-10-29 | 1993-02-23 | Eka Nobel Ab | Method of bleaching |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE432675C (en) * | 1924-12-25 | 1926-08-07 | Hansa Phosphat U Mineral Muehl | Process for cleaning and bleaching barite |
| DE485007C (en) * | 1926-04-04 | 1929-10-25 | Ludwig Kaiser | Process for the production of pure white and finely divided barium or calcium sulfate |
| DE491350C (en) * | 1926-12-11 | 1930-02-08 | Ludwig Kaiser | Process for the production of pure, white and finely divided barium or calcium sulfate |
| DE537392C (en) * | 1928-02-10 | 1931-11-02 | Sachtleben Akt Ges Fuer Bergba | Process for the production of a white, transparent, pure barite |
| DE586007C (en) * | 1928-06-14 | 1933-10-14 | Peter Spence & Sons Ltd | Process for the production of finely divided and anhydrous calcium sulphate as paint |
| GB339797A (en) * | 1928-12-18 | 1930-12-18 | Rene Perdu | |
| US2197003A (en) * | 1937-11-18 | 1940-04-16 | Glidden Co | Process for making pigments |
| US2522971A (en) * | 1947-04-19 | 1950-09-19 | C K William & Co | Method of bleaching barytes |
| DE1467470C2 (en) * | 1963-10-28 | 1974-06-12 | Pluess-Staufer Ag, Oftringen, Aargau (Schweiz) | Improvement of the whiteness of chalk, calcite or dolomite |
| GB1394910A (en) * | 1972-10-23 | 1975-05-21 | Pluss Stauffer Ag | Process for the optical brightening of minerals |
| JPS5147598A (en) * | 1974-10-23 | 1976-04-23 | Denki Kagaku Kogyo Kk | Tansankarushiumuno hakushokudokairyoho |
-
1978
- 1978-10-30 SE SE7811216A patent/SE417104B/en not_active IP Right Cessation
-
1979
- 1979-10-02 GB GB7934187A patent/GB2032901B/en not_active Expired
- 1979-10-10 IT IT50519/79A patent/IT1128747B/en active
- 1979-10-11 FI FI793163A patent/FI66416B/en not_active Application Discontinuation
- 1979-10-23 JP JP54136960A patent/JPS5835937B2/en not_active Expired
- 1979-10-25 DE DE19792943205 patent/DE2943205A1/en not_active Ceased
- 1979-10-29 CA CA338,625A patent/CA1125456A/en not_active Expired
- 1979-10-29 ES ES485483A patent/ES8102059A1/en not_active Expired
- 1979-10-29 FR FR7926726A patent/FR2440386A1/en active Granted
- 1979-10-30 NL NL7907976A patent/NL7907976A/en not_active Application Discontinuation
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4310360A (en) | 1978-10-30 | 1982-01-12 | Supra Aktiebolag | Method for producing pigment for use in sizing compositions |
| US4344925A (en) * | 1979-01-12 | 1982-08-17 | Societe Chimique Des Charbonnages | Ozone whitening of synthetic gypsum |
| US5188814A (en) * | 1990-10-29 | 1993-02-23 | Eka Nobel Ab | Method of bleaching |
| WO1993002963A1 (en) * | 1991-08-02 | 1993-02-18 | Prayon-Rupel Technologies | Method for preparing an aqueous calcium sulphate-based suspension |
| BE1005164A3 (en) * | 1991-08-02 | 1993-05-11 | Prayon Rupel Technologies | Method for preparing a suspension aqueous calcium sulphate base. |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2440386A1 (en) | 1980-05-30 |
| FR2440386B1 (en) | 1983-07-08 |
| SE417104B (en) | 1981-02-23 |
| ES485483A0 (en) | 1980-12-16 |
| SE7811216L (en) | 1980-05-01 |
| GB2032901B (en) | 1982-11-03 |
| IT7950519A0 (en) | 1979-10-10 |
| DE2943205A1 (en) | 1980-05-08 |
| IT1128747B (en) | 1986-06-04 |
| NL7907976A (en) | 1980-05-02 |
| FI66416B (en) | 1984-06-29 |
| FI793163A (en) | 1980-05-01 |
| CA1125456A (en) | 1982-06-15 |
| JPS5560024A (en) | 1980-05-06 |
| JPS5835937B2 (en) | 1983-08-05 |
| ES8102059A1 (en) | 1980-12-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |