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Publication numberUS20040167251 A1
Publication typeApplication
Application numberUS 10/787,567
Publication dateAug 26, 2004
Filing dateFeb 26, 2004
Priority dateFeb 9, 2000
Also published asDE10005685A1, DE50114820D1, EP1257604A2, EP1257604B1, US7776149, US20030159622, US20080268149, WO2001058809A2, WO2001058809A3
Publication number10787567, 787567, US 2004/0167251 A1, US 2004/167251 A1, US 20040167251 A1, US 20040167251A1, US 2004167251 A1, US 2004167251A1, US-A1-20040167251, US-A1-2004167251, US2004/0167251A1, US2004/167251A1, US20040167251 A1, US20040167251A1, US2004167251 A1, US2004167251A1
InventorsDjamschid Amirzadeh-Asl, Karl-Heinz Schwarz
Original AssigneeDjamschid Amirzadeh-Asl, Karl-Heinz Schwarz
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Barium sulfate, process for its preparation, and its use
US 20040167251 A1
Abstract
Barium sulfate particles having an average particle diameter d50 of from 0.1 to 10 μm which are produced by precipitation can be dispersed better if they are covered with at least one organic additive.
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Claims(11)
1. Barium sulfate having an average particle diameter d50 of from 0.1 to 10 μm, precipitated by mixing of barium- and of sulfate-containing solution, characterised in that the barium sulfate particles are covered with at least one organic additive, the organic additive being selected from one or more of the substances or groups of substances: carboxylic acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such as pentaerythritol, neopentyl glycol and trimethylolpropane; polyalcohols, such as polypropylene glycol and polyethylene glycol; organic esters, such as neopentyl glycol dibenzoate; silanes, siloxanes, silicone oils, organic sulfones corresponding to the formula RSO2R, organic ketones (R—(C═O)—R), organic nitrites (RCN), organic sulfoxides (R2—SO2), organic amides (R—(C═O)—NR′R or R—(S═O)—ONR′R).
2. Barium sulfate according to claim 1, characterised in that the content of organic additive, based on the content of barium sulfate, is 0.1 to 30 wt. %.
3. Barium sulfate according to claim 2, characterised in that the content of organic additive, based on the content of barium sulfate, is 0.1 to 10 wt. %.
4. Process for the preparation of barium sulfate having an average particle diameter d50 of from 0.1 to 10 μm and precipitated by mixing of barium- and of sulfate-containing solution, characterised in that the separated filter cake is processed to form a paste, the paste is homogeneously mixed with organic additive and then dried, the organic additive being selected from one or more of the substances or groups of substances: carboxylic acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such as pentaerythritol, neopentyl glycol and trimethylolpropane; polyalcohols, such as polypropylene glycol and polyethylene glycol; organic esters, such as neopentyl glycol dibenzoate; silanes, siloxanes, silicone oils, organic sulfones corresponding to the formula RSO2R, organic ketones (R—(C═O)—R), organic nitriles (RCN), organic sulfoxides (R2—SO2), organic amides (R—(C═O)—NR′R or R—(S═O)—ONR′R).
5. Process for the preparation of barium sulfate having an average particle diameter d50 of from 0.1 to 10 μm and precipitated by mixing of barium- and of sulfate-containing solution, characterised in that the separated filter cake is suspended in water, the suspension is mixed with organic additive and then dried, the organic additive being selected from one or more of the substances or groups of substances: carboxylic acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such as pentaerythritol, neopentyl glycol and trimethylolpropane; polyalcohols, such as polypropylene glycol and polyethylene glycol; organic esters, such as neopentyl glycol dibenzoate; silanes, siloxanes, silicone oils, organic sulfones corresponding to the formula RSO2R, organic ketones (R—(C═O)—R), organic nitriles (RCN), organic sulfoxides (R2—SO2), organic amides (R—(C═O)—NR′R or R—(S═O)—ONR′R).
6. Process for the preparation of barium sulfate having an average particle diameter d50 of from 0.1 to 10 μm and precipitated by mixing of barium- and of sulfate-containing solution, characterised in that the separated filter cake is dried and then homogeneously mixed with organic additive, the organic additive being selected from one or more of the substances or groups of substances: carboxylic acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such as pentaerythritol, neopentyl glycol and trimethylolpropane; polyalcohols, such as polypropylene glycol and polyethylene glycol; organic esters, such as neopentyl glycol dibenzoate; silanes, siloxanes, silicone oils, organic sulfones corresponding to the formula RSO2R, organic ketones (R—(C═O)—R), organic nitrites (RCN), organic sulfoxides (R2—SO2), organic amides (R—(C═O)—NR′R or R—(S═O)—ONR′R).
7. Process according to one of claims 4 to 6, characterised in that the dry barium sulfate covered with organic additive is subjected to a pulverisation, preferably by means of an impact mill or jet mill.
8. Process according to one of claims 4 to 7, characterised in that the drying is carried out in a spray dryer or mill dryer.
9. Process according to one of claims 4 to 8, characterised in that the barium sulfate is precipitated by mixing of BaCl2 solution or Ba(OH)2 solution with Na2SO4 solution or H2SO4.
10. Use of the barium sulfate according to one of claims 1 to 3 in the production of thermoplastics, thermosetting plastics and elastomers, in which the barium sulfate particles are dispersed.
11. Use of the barium sulfate according to one of claims 1 to 3 for dispersion in plastics compositions for the production of fibres, coating materials, adhesives, films, film supports and the like.
Description
  • [0001]
    This invention relates to barium sulfate having an average particle diameter d50 of from 0.1 to 10 μm and precipitated by mixing of barium- or of sulfate-containing solution, a process for its preparation and its use.
  • [0002]
    Such barium sulfate is used in particular in the production of photographic paper, paints and plastics as well as in medical diagnosis and in medical plastics. For use in the medical field, in addition to the high standards as regards purity, there are also legal requirements for pharmaceutical products which have to be complied with. Barium sulfate is a high-quality, pure white, inert, acid- and alkali-resistant filler which is completely weather-resistant.
  • [0003]
    Very finely-divided barium sulfate imparts colour stability and gloss to photographic paper. When used in paints, the very finely-divided barium sulfate produces resistance to flocculation in organic and inorganic pigments, so that segregation phenomena are largely prevented, depth of colour and purity of colour are increased and brightness and fogging are improved. Moreover, the mechanical properties of the plastics are improved as a result of the nucleating action of the barium sulfate powder.
  • [0004]
    In stretched films made from thermoplastics, in particular polymers containing incorporated very finely-divided barium sulfate, the latter acts as a white pigment, scattering light at the boundaries of the barium sulfate particles to the air, so that the films have an opaque colouring and a high gloss. A suitable thermoplastic is, in particular polyester, in which glycol suspension containing barium-sulfate has been incorporated, generally during the polycondensation. Here an adequate dispersion of the barium sulfate particles in the polyester is an essential precondition for opacity and high gloss in the stretched films. In the event of inadequate dispersion of the barium sulfate particles in the polymer, specks—these are agglomerates of barium sulfate particles—are formed after the stretching process and these can considerably impair the quality of the film surface.
  • [0005]
    DE-A 26 47 713 describes an opaque, simple thermoplastic film support made of a molecularly oriented film of a synthetic, linear polyester, in which 5 to 50 wt. %, based on the weight of the polyester, of barium sulfate particles having an average particle size of from 0.5 to 10 μm is dispersed, with the proviso that the actual particle size of 99.9% of the particles does not exceed 50 μm and that at least one light-sensitive image layer is disposed on at least one surface of the film support.
  • [0006]
    These film supports are highly impermeable to moisture and are therefore suitable for use as supports for photographic prints and copies for which it is possible to avoid a considerable part of the washing process which normally has to be carried out in the treatment of prints and copies on supports made of paper.
  • [0007]
    DE-C 44 31 735 discloses the coating of barium sulfate particles with phosphorus pentoxide, aluminium oxide and silicon dioxide in order to achieve an excellent adhesion between the barium sulfate particles serving as filler and the polymer, so that the light scattering does not occur.
  • [0008]
    DE-A 22 46 818 provides a continuous process for the preparation of crystalline barium sulfate powder having an average particle size d50>2 μm to 20 μm by precipitating barium sulfate from barium chloride solution using sulfuric acid, wherein the barium sulfate particles having the intended particle size are deposited in the outlet of the precipitation vessel and the smaller barium sulfate particles remain in the upper region of the precipitation vessel.
  • [0009]
    DE-A 36 35 050 provides a process for the continuous preparation of barium sulfate having a defined particle-size range, wherein barium sulfate is precipitated in a first step by the reaction of barium ions with sulfate ions. The suspension containing barium sulfate is withdrawn and transferred to a single-stage or multistage wet-grinding step, in which the grinding to the required particle-size range is carried out. The barium sulfate and mother liquor are subsequently separated.
  • [0010]
    The barium sulfate powder chemically precipitated by the known methods has an undesirable tendency to form agglomerates which prevent a homogeneous dispersion of the barium sulfate particles as white pigment and/or filler in the thermoplastics.
  • [0011]
    The object of the present invention is to provide barium sulfate precipitated by mixing of barium- and of sulfate-containing solution and, having an average particle diameter d50 of from 0.1 to 10 μm; this barium sulphate is to show no tendency to form agglomerates and consequently is to have excellent properties as regards dispersibility and freedom from specks and is to produce an optimal film surface.
  • [0012]
    This object is achieved by covering the barium sulfate with at least one organic additive, the organic additive being selected from one or more of the substances or groups of substances: carboxylic acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such as pentaerythritol, neopentyl glycol and trimethylolpropane; polyalcohols, such as polypropylene glycol and polyethylene glycol; organic esters, such as neopentyl glycol dibenzoate; silanes, siloxanes, silicone oils, organic sulfones corresponding to the formula RSO2R, organic ketones (R—(C═O)—R), organic nitriles (RCN), organic sulfoxides (R2—SO2), organic amides (R—(C═O)—NR′R or R—(S═O)—ONR′R).
  • [0013]
    The organic additive content is given in claims 2 and 3.
  • [0014]
    The organic additives can be used in liquid or in solid form.
  • [0015]
    The barium sulfate particles can be covered with organic additive by a process described in claims 4 to 6. Further developments of this process are given in claims 7 to 9.
  • [0016]
    To achieve an optimal distribution of liquid organic additives on the surface of the barium sulfate particles, the solution containing organic additive is sprayed onto the barium sulfate particles with an even-speed mixer, or the solution is added to a suspension of BaSO4 and the mixture is homogenised by means of a dispersing apparatus.
  • [0017]
    When solid organic additives are used, first of all an aqueous or organic solution or suspension is prepared and is then sprayed onto the barium sulfate particles. In this way a very homogeneous distribution of the organic substances on the surfaces of the barium sulfate particles is achieved.
  • [0018]
    A particular advantage is that the barium sulfate particles aftertreated according to the invention render possible the preparation of masterbatches (pigment and filler concentrates) and compounds (mixtures) of thermoplastics in which the barium sulfate particles are so excellently dispersed that high-quality products can be made from them without special additional expense. The superior dispersibility in plastics of the barium sulfate particles aftertreated according to the invention is clearly shown by the fact that no specks arise in these plastics containing barium sulfate and the filter does not clog during a pressure filter test.
  • [0019]
    The barium sulfate particles according to the invention are suitable in particular for dispersion in plastics compositions, such as thermoplastics, thermosetting plastics and elastomers. The plastics thus treated are used in the production of fibres, coating materials, adhesives, films, film supports and the like.
  • [0020]
    The subject matter of the invention is explained in more detail by the following Examples.
  • [0021]
    First of all, a BaSO4 suspension was prepared. For this purpose, an aqueous solution of Na2SO4 and an aqueous solution of BaCl2 in a molar ratio of 1:0.98 were simultaneously introduced into a precipitation apparatus. The precipitation conditions were established as in the prior art, in such a way that the precipitated BaSO4 in the aqueous solution had an average particle size d50=0.52 μm. The precipitated BaSO4 was then filtered and washed several times with deionised water. The filter cake obtained was dispersed in water. The suspension of barium sulfate had a solids content of approximately 250 g/l and was further processed in the following manner.
  • COMPARATIVE EXAMPLE A
  • [0022]
    A portion of the suspension was dried in a spray dryer. The BaSO4 powder obtained had a d50 of 0.52 μm and was used as a control (sample A).
  • EXAMPLE 1
  • [0023]
    1 wt. % (based on BaSO4) of neopentyl glycol was added to a portion of the suspension, which was then dried as described in Comparison Example A. The white BaSO4 powder obtained had a d50 of 0.51 μm (sample 1) and a carbon content of 0.1 wt. %.
  • EXAMPLE 2
  • [0024]
    1 wt. % (based on BaSO4) of 2,2-dihydroxymethyl-1-butanol was added to a portion of the suspension, which was then dried as described in Comparative Example A. The barium sulfate powder had a d50 of 0.51 μm (sample 2) and a carbon content of 0.17 wt. %.
  • EXAMPLE 3
  • [0025]
    1 wt. % (based on BaSO4) of polyethylene glycol 2000 was added to a portion of the suspension, which was then dried as described in Comparison Example A. The barium sulfate powder had a d50 of 0.50 μm (sample 3) and a carbon content of 0.48 wt. %.
  • EXAMPLE 4
  • [0026]
    5 wt. % (based on BaSO4) of polyethylene glycol 2000 was added to a portion of the suspension, which was then dried as described in Comparative Example A. The barium sulfate powder had a d50 of 4.9 μm (sample 4) and a carbon content of 2.5 wt. %.
  • EXAMPLE 5 Preparation of Polyester Masterbatches, and Their Properties
  • [0027]
    Samples A and 1 to 4 were extruded in a twin-screw extruder, with PETP (polyethylene terephthalate) in a mass ratio of 30:70 (BaSO4:PETP) at a temperature of approximately 270° C. A 30% masterbatch was prepared in each case.
  • [0028]
    These masterbatches were subjected to a pressure filter test. During the filtration of the polymer melts through a screen pack (consisting of nozzle, seal, perforated plate, 14 μm screen with support screen), any pigment agglomerates and/or impurities which may be present bring about a build-up of pressure in front of the filter. This increase in pressure is a measure of the quality of the polymer melt. The lower the increase in pressure, the better is the pigment dispersed in the polymer.
  • [0029]
    The results of the pressure filter test are shown in Table 1.
    TABLE 1
    Sample
    A 1 2 3 4
    Pressure filter value 15.47 1.74 2.53 5.89 0.27
    (bar × cm3/g), on a
    14 μm screen after
    60 min
  • [0030]
    It can be seen from the Table that a BaSO4 untreated with an organic substance (Comparison Example A) exhibits a very high pressure filter value. A comparison of untreated BaSO4 with BaSO4 treated according to the invention (samples 1 to 4) shows that the treated BaSO4 can be dispersed significantly better and consequently contains little material (agglomerates) which adheres to filters and would result in a blockage of the filter.
  • EXAMPLE 6 Production of 18% Polyethylene Terephthalate Films (PETP Films)
  • [0031]
    The 30% masterbatch control A and the 30% masterbatch sample 1 (containing neopentyl glycol) according to the invention were diluted to a solids content of 18% and directly extruded to form films.
  • [0032]
    The PETP film produced using untreated BaSO4 (sample A) contained clearly visible non-dispersible particles, which were present as agglomerates (so-called specks). In contrast, the PETP film produced using treated BaSO4 (sample 1) contained scarcely any such specks, which is to be attributed to the considerably better dispersibility of the BaSO4 treated according to the invention.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1915748 *Apr 22, 1931Jun 27, 1933Sachtleben Ag Fur Bergbau UndProcess for manufacturing barium sulphate of definite granule size
US2358050 *Dec 6, 1941Sep 12, 1944Eastman Kodak CoMethod and apparatus for manufacturing and controlling the grain size of barium sulphate
US2685499 *Dec 21, 1950Aug 3, 1954Eastman Kodak CoMethod of proeparing blanc fixe
US3669896 *Dec 2, 1969Jun 13, 1972Ciba Geigy AgInorganic white pigments containing optical brighteners and process for their manufacture
US3803065 *Nov 13, 1972Apr 9, 1974Mitsubishi Petrochemical CoResin composition
US3844810 *Nov 28, 1972Oct 29, 1974Plastic Molders Supply CoPigment dispersion
US4053537 *Nov 6, 1975Oct 11, 1977Bayer AktiengesellschaftProcess for the production of elastic composites
US4310483 *Aug 3, 1979Jan 12, 1982Ciba-Geigy CorporationThermal tumbling granulation
US4894093 *May 27, 1988Jan 16, 1990Metallgesellschaft AktiengesellschaftProcess for producing barium sulfate with reactive surface
US5149732 *Mar 6, 1990Sep 22, 1992The Yokohama Rubber Co., Ltd.Rubber composition for polymer-metal bonding and method of hose-metal fitting attachment
US5908498 *Mar 31, 1998Jun 1, 1999Kerr-Mcgee Chemical LlcProcess for preparing an improved low-dusting, free-flowing pigment
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7846409 *Dec 1, 2004Dec 7, 2010Solvay Infra Bad Hoenningen GmbhDeagglomerated barium sulfate
US8119716 *Jun 2, 2006Feb 21, 2012Solvay Infra Bad Hoenningen GmbhMethod of generating a dispersion of deagglomerated barium sulphate in plastics or plastics precursors
US8420215Jul 14, 2008Apr 16, 2013Sued-Chemie Ip Gmbh & Co. KgCyclic process for the preparation of barium sulphate and lithium metal phosphate compounds
US20070140938 *Dec 1, 2004Jun 21, 2007Solvay Infra Bad HoenningenDeagglomerated barium sulfate
US20080312362 *Jun 2, 2006Dec 18, 2008Solvay Infra Bad Hoenningen GmbhMethod of Generating a Dispersion of Deagglomerated Barium Sulphate in Plastics or Plastics Precursors
US20090318594 *Aug 27, 2007Dec 24, 2009Sachtleben Chemie GmbhBarium sulfate-containing composite
US20090326114 *Aug 27, 2007Dec 31, 2009Sonja GrotheBarium sulfate-containing composite
US20100255308 *Jul 14, 2008Oct 7, 2010Christian VoglerCyclic process for the preparation of barium sulphate and lithium metal phosphate compounds
WO2009010263A2 *Jul 14, 2008Jan 22, 2009Süd-Chemie AGProcess for the production of barium sulfate
WO2009010263A3 *Jul 14, 2008Mar 12, 2009Sued Chemie AgProcess for the production of barium sulfate
Classifications
U.S. Classification523/200, 106/471
International ClassificationC08K9/04, C08L101/00, C09C1/02, C01F11/46
Cooperative ClassificationC01P2004/84, C01P2004/62, C01F11/462, Y10T428/2991, Y10T428/2998, C01P2004/61, C09C1/027
European ClassificationC01F11/46B, C09C1/02F