CA1140097A - Process for the treatment of halide titanium dioxide pigments to improve durability - Google Patents
Process for the treatment of halide titanium dioxide pigments to improve durabilityInfo
- Publication number
- CA1140097A CA1140097A CA000335974A CA335974A CA1140097A CA 1140097 A CA1140097 A CA 1140097A CA 000335974 A CA000335974 A CA 000335974A CA 335974 A CA335974 A CA 335974A CA 1140097 A CA1140097 A CA 1140097A
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- CA
- Canada
- Prior art keywords
- pigment
- steam
- fluid energy
- dry heat
- temperature
- 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
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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
- C09C1/36—Compounds of titanium
- C09C1/3692—Combinations of treatments provided for in groups C09C1/3615 - C09C1/3684
-
- 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
- C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
- C09C3/041—Grinding
-
- 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
- C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
- C09C3/043—Drying, calcination
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
Abstract
Case 380 ABSTRACT
"A PROCESS FOR THE TREATMENT OF HALIDE TITANIUM DIOXIDE
PIGMENTS TO IMPROVE DURABILITY"
A process for improving the durability of titanium dioxide pigment produced by the oxidation of a titanium tetrahalide when incorporated into a binding medium which is exposed to light comprising fluid energy milling particulate reactor discharge in the presence of steam and thereafter subjecting the milled discharge to dry heat at a temperature of at least 400°C.
"A PROCESS FOR THE TREATMENT OF HALIDE TITANIUM DIOXIDE
PIGMENTS TO IMPROVE DURABILITY"
A process for improving the durability of titanium dioxide pigment produced by the oxidation of a titanium tetrahalide when incorporated into a binding medium which is exposed to light comprising fluid energy milling particulate reactor discharge in the presence of steam and thereafter subjecting the milled discharge to dry heat at a temperature of at least 400°C.
Description
~4~
The present invention relates to a process for improving the durability of titanium dioxide pigments made by the halide process, particularly when incorporated into binding media which are then exposed to light.
It is known that titanium dioxide pigments, both when made by the so-called sulphate or halide processes, ultimately cause breakdown of the binding medium into which they are incorporated, or example to form pigmented surface coatings or in polymers etc. and it is desirable to produce titanium dioxide pigments which cause as little breakdown of binding medium as possible, i.e.
pigments which are of improved durability. One method of testiny such p'gments is to incorporate the pigment in the desired bindin~ medium and to expose the product (when applied to a suitable substrate in the case o surace coa~ings) either to natural sunlight or to artific-ially-produced radiation or a prolonged period of time before examining the product for evidence of breakdown of the binding medium. Where the product is exposed --~ 20 to artificially-produced radiation, this is commonly carried out in an apparatus known as a Marr Weather-O-Meter (which name is a Registered Trade Mark).
It is an object of this invention to provide a process whereby the durability of titanium dioxide pigment made by the halide process, and particularly that of pigment made by the so-called chloride process, may be improved.
An aspect of the invention is as follows:
A process for the treatment of reactor discharge - 30 from the oxidation of a titanium tetrahalide comprising :~ subjecting particulate reactor discharge to fluid energy milling in a fluid energy mill in presence of steam, removing the so treated reactor discharge from said fluid energy mill and then subjecting it external of said fluid energy mill to dry heat at a temperature ; of at least 400C.
0~97 The particulate reactor discharge is normally produced by the oxidation of titanium tetrachloride in the vapour phase by means of oxygen or an oxygen-containing gas, for example air or oxygen-enriched air.
- 5 The reactor discharge is then separated from its - reaction environment, for example by cooling of the reaction products and by filtration or by cyclone separa-tion, and is then subjected to fluid energy milling in the presence of steam.
Such fluid energy milling may be carried out in any suitable apparatus, for example in a "Microniser"
(which name is a Registered Trade Mark) or in a tube or pipe mill, for example of the type shown and described in U.K. Patent Specifications 1,019,833 and 1,019,834.
The steam is usually used as the milling medium and is injected in to the mill at super-atmospheric pressure and temperature.
It has been found that excellent results are obtained using steam at a temperature in the range 150C to 350C
and particularly at temperatures in the range 200C
; to 300C and, of course, at corresponding pressures, at least in mills of the type previously re~erred to.
Optimum steam/pigment ratios can readily be determined by experiment and will depend to some extent on the type of fluid energy mill used. Generally, however, such ratios in the range 1.0 to 6.0 and particularly in the range 1.5 to 3.5, have ~een found to be very effective.
After subjecting the reactor to fluid energy milling in the presence of steam, the thus-treated pigment is su`bjectRd to dry heat at a tEmpera~ure of at least 400C. It is preferred to subject the pigment to dry heat at a temperature in the range 400C to ~COC and preferabl~ to one in the range ~00C to 600C.
By the term "dry heat" ismeant subjecting the pigment to the required temperature without the introduction into the treat~ent vessel of added steam. For exa~ple, the pi~ment m~y ke treated by exposure to a heated gas stream (not oontaIning added steam~ either by direct a~ltion of the pigment to the gas stream or in a fluidised bed of particulate solid heated and ~luidised by a suitable hot ga~
~uch as air or it may be heated (and preferably agitated, e.g.
by stirring or tu~bling) in a heated o~en or furnaoe .
Ihe cptimum duraticn of the exposure of the pig~ent to dry heat may readily be determined by trial and experi~ent and it is clearly commercially advantageous to carry out the pro oe ss for the shortest time which i5 consistent with cbtaining the desired improved durability of the pigment in order to redu oe unit costs and to obtain the maximum thLoughput. Additionally the opti~um duration of the pro oe ss may vary with the nature of the particulate titanium dioxide-to be treated. It is ~elieved, hc~ever, that exposure to dry hea~ as a~
agitated mass for a period of 1 to 60 minutes and particularly for a period of S to 30 minutes or exposure in a fluidised state for 0.2 to 60 seccnds and particularly for 1 to 10 seccnds, will normally give a pig~ent of high durability when co~pared with si~ilar pig~ent which has not } n treated by the prc~ess of the present m vention or ~ch has been subjected to either fluid energy milling in th~ presenoe of s~eam, ~L4~C~97 or to dry heat, alone.
It is believed that the process of the present invention gives titanium ~icxide pigment o high durability because the initial fluid energy milling in the presencP of steam hydrolyses or otherwise decc~poses impurities on the sur~ace of the reactor discharge and that the subsequent exposure to dry heat under the conditicns described modifies the hydrolysed surfaoe and/or removes those products of hydrolysis or other form of 2ecc~position from the surfaoe o~ the titanium diQxide particles.
m e following EXa~ples show the improve~ent in durabllity (expressed as the durability ratio) cbtained in reactor dischaLge treated by the pro oess of the present inventicn when compared with that of a similar starting material which has not been treated by the pro oess of the prese~t invention and also show the effect of varying the steam temperature during fluid energy milling~
., .
Example 1 Reactor discharge recovered frcm the vapour phase oxidation of titanium tetrachloride was divided into three separate portlans.
m e separate porticns were treated as follcws, (a) Portion untreated Ub) Portion subjected unstirYed to dry heat in an cven at 550 & for lS ~inutes (c) Portion subjected to treatment in the fluid energy pipemill shcwn in U.K. Specification 1,019,833 using steam at 2 C ~ut not further treated).
~l~40~7 Part of the product frcm (c) was then heated to a temperatu~e of 550C for a period of 15 minutes as described for sample (b) ~i.e.
this product - designated (d? - was made according to the process of the present inventicn. The durabilit~ ratio of each of the samples (a) to (d) was determined as set out belcw and the follcwing results were obtained:-Sample Durabi~it~ ratio (a) 0.62 Pb) 0.45 (c) 0.47 (d) 0.38 Example 2 ; ~he process descriked in Exa~ple l ~as repeated with a sa~ple of reactor discharge havlng a different durability ratio and the following results were cbtained:
- Sa~ple Durability ratio (a) 0,57 (b) 0~55 (c) 0~6 (d) 0~3 Examlple 3 Reactor discha~ge c~ta~ned as described in Example 1 was taken and divided into three portions~ The durability ratio of the untreated reactor discharge was dete~ined and eac~ of t~2 ~4~97 three portions was subjected to fluid energy milling in a pipemill of the type described in U.K. Patent Specificaticn l,019,833 in the presence of steam~ The temperature of the steam varied betwe~n 250C
and 350 C for the three sa~ples, as shown.
The durability ratios of the sa~ples which were fluid energy milled in the presence of steam at the various steam temperatures were determined and the products of this milling were subjected to dry heat (at 550 C) for 15 minutes and the durability ratios were again determined.
The results were as shown below:~
Uhtreated discharge Pipemilled discharge Pipemi~led and heated discharge (DR) (DR) (550CC) (DR) 250 & 0.49 0.37 0.59 320 & 0.59 0,40 350C 0.64 0.55 Exam~ple 4 :
Ihe process described in Ex~ple 3 was reFeated with a different sample of reactor discharge and this was fluid energy milled in the presen oe of steam at differing temperatures in the range 200 C to 330C, as shcwn, prior to dry heat treatment (unstirred) at 550 C for 15 minutes.
Ihe results ~ere as shcwn below:-.
: 8 Uhtreated discharge PiFemllled discharge Pipemilled ~nd : heated (550 C) (DR) (DR) discharge (DR) 200C 0.44 0.35 0.66 250C 0.50 0.32 3C0C 0.53 0.38 : 330C 0.60 0.37 Example 5 . Four different sa~ples of reactor discharge frcm the vapour ;- phase oxidaticn of titanium tetrachloride were tahen and treated as described in Example 1. Ihe durability ratios were determined as set out below and the following results were Qbtained:-: Sample Durability Ratio (a) 0.64 0~62 0.49 0.47 (b) 0.51 0.50 0.39 0~44 (c) 0.61 0.57 0.53 0.49 (d) 0.44 0~45 0.34 0.38 . ~he measurement of the Durability Ratio is defined and carried out - a~. follc~s.
~ The prcperty measured is the mass loss (as defined in Eiperimental : and Theoretical Studies of the Durability of Paint Systems pigmented with Titanium Dioxide - Evans and Murl~y, VI FAIIPEC CCNGRESS, 1962) from a paint fi~m ccntain m g the experimental pig~ent~s) when ccmpared with a similar film ccntaining a standard pig~ent(s); the mass loss being . induced by accelerated weathering, using a weatherlng cycle generally ac oepted by the painttrade and as defined in British Sta~dard ~ OC~7 g 3900, Section F3.
Films of a paint(s) containing the test pigment(s) and Gther paint films containing cne or mo~e standard pigments are prepared under standard conditions by m corporatlng the pisment~ by bead milling into an air-d~y m g aIkyd resin solution, normally Uralac ta Registered Trade Mark)P470 which is a lcng oil linseed pentaerythritol alkyd resin, to pnDdu oe paint(s) which are spun onto a stainless steel substrate(s) to a dry film thickness of approximatel~ 35 These films, after drying, are exposed alongside each other~
i.e. under identical oonditions, in the twin-arc Marr Weather-C~
Meter.
; Ihe mass loss of the panel coated with the paintts) containing the test pigment(s) is compared with the mass loss o the panelts1 o~ntaining the standard pigment(s), after a series of exposure times.
A durability ratio (D.R.) expressed as experimental film l~ss/standard film loss of l.C0 indicates equivalent performanoe of the panel ooated with a paint contalning one of the standard pigmentts). A D.R. of less than 1.00 indicates performan oe superior to that of the standard(s).
Reactor discharge when treated by the process oS the present invention will usually be treated further, for example in the mann~r in which halide pigments are normally treated to improve their dispersion in organic media, their gloss and to further improve their durability.
The gloss of such pigments may be improved by additicnal milling, ~or example by additional fluid energy milling and/or mec~lanical milling and/or sand milling as an aqueous slurry. This prcperty may also be improved by ane or more classificaticn steps whexeby particles of less ~han optim~m size are removed or at least reduoed in prcportion.
V0~7 The properties of dispersion and of further l~prcvements in durability may for example ~e achieved by coating the pigment particles with one or more hydrous oxides of ele~ents such as siliccn, aluminium, cerium, zirconium or titanium ox wit~ a phosp~ate of Gne or more of these elem~nts, as is well kncw.n in t~e art~
Additionally or alte m atively, the pigment paxticles may be coated with one or more organic ccmpounds, for example with a polyhydroxy ccmpound such as pentaerythritol, trimethylol pxopa~e or an ethanolamine. Such organic ooatings are, again, well kncw.n in the art and are commo.nly applied to assist in imprcving further the dispexsion of the pigmentary particles in organic media.
A~ter coating titanium dioxide particles prepared ~y the process of the present inventlon it is normally advis~ble to subject the coated particles to more milling to break up aggregates which tend to form during the coating processes.
The final pigment may then be sold, for example either in the form of an aqueous slurry or as a dr~ed particulate solid~ It is of advantage, if the plgment is to be sold in t~e form of an aqueous slurry, to av~id the ne oe ssity for drying the pigment prior to red~spersing it in water to form the desired slurry and an~ milling w~i~h may be required in this case may be prcv~ded b~ sand milling or ~ mechanically milling an aqueous slurry~
The c~idation of the titanium tetrahalide, for example titanium tetrachloride, to produce the reactor discharge ~ ~ ch is to be treated by the process of the present invention will nor~ally be 1~4t)~7 , carried out under conditions which are well kncwn for such an oxidation to produce pigmentary titaniun dioxide. For exa~ple, the oxidation is carried out at an elevated tem~erature, for example at least 8CO & , and the titanium tatrahalide is ~intained in the vapour phase. m e oxidation c~mKnly takes plaoe in the presen oe of additives, for exampla in the presence of a minor pr3porticn of an alumini~n halide, normally the chloride, and, if desired, a minor proportion of a silicon .;
hali2e, normally the chlori2e. Minor proportions of water vapour and/or a souroe of an alkAl; metal ion, particularly potassium,are also c~monly added to the oxidation. Such additives, which as noted above~
are well kncwn in the prior art, ~nprove the ~uallty of the titani~n dioxide produced for pigmentary purposes.
Ihe temperature in the oxidation reactor is achieved by the introduction of heat into the reactlGn zone. m is may be provided directly b~ the combustion prGduc~s of a suitable gas, for example of c~rhon monQxide, or by the provision of a gas which has been heated by its passage through an electric arc. me gas in the latter pro oe ss may be an inert gas or it may be c~e of the reactants, for exa~ple o~ygen. ~lternatively, one or both of the reactants may be preheated indirectly, for example by means of a heat exchanger prior to its introducticn into the reacticn zcne. Where the reactants are preheated to reacticn temFerature they should, of course, be separately intr~duced into the reaction zone to prevent pn~nature reacticn. Normally, in such a process, one leactant, usually the o~ygen, is heated to a temperature in excess of the desired reacticn te~perature and the other neactant, the titanium tetrahalide, is heated to a te~perature sufficient to ` ~ 40~39~
, maintam it in the vapour phase; the temperature o~ the mixed gases :-~ being sufficient to produce the required temperature in the reacticn zcne.
;, ' . :
The present invention relates to a process for improving the durability of titanium dioxide pigments made by the halide process, particularly when incorporated into binding media which are then exposed to light.
It is known that titanium dioxide pigments, both when made by the so-called sulphate or halide processes, ultimately cause breakdown of the binding medium into which they are incorporated, or example to form pigmented surface coatings or in polymers etc. and it is desirable to produce titanium dioxide pigments which cause as little breakdown of binding medium as possible, i.e.
pigments which are of improved durability. One method of testiny such p'gments is to incorporate the pigment in the desired bindin~ medium and to expose the product (when applied to a suitable substrate in the case o surace coa~ings) either to natural sunlight or to artific-ially-produced radiation or a prolonged period of time before examining the product for evidence of breakdown of the binding medium. Where the product is exposed --~ 20 to artificially-produced radiation, this is commonly carried out in an apparatus known as a Marr Weather-O-Meter (which name is a Registered Trade Mark).
It is an object of this invention to provide a process whereby the durability of titanium dioxide pigment made by the halide process, and particularly that of pigment made by the so-called chloride process, may be improved.
An aspect of the invention is as follows:
A process for the treatment of reactor discharge - 30 from the oxidation of a titanium tetrahalide comprising :~ subjecting particulate reactor discharge to fluid energy milling in a fluid energy mill in presence of steam, removing the so treated reactor discharge from said fluid energy mill and then subjecting it external of said fluid energy mill to dry heat at a temperature ; of at least 400C.
0~97 The particulate reactor discharge is normally produced by the oxidation of titanium tetrachloride in the vapour phase by means of oxygen or an oxygen-containing gas, for example air or oxygen-enriched air.
- 5 The reactor discharge is then separated from its - reaction environment, for example by cooling of the reaction products and by filtration or by cyclone separa-tion, and is then subjected to fluid energy milling in the presence of steam.
Such fluid energy milling may be carried out in any suitable apparatus, for example in a "Microniser"
(which name is a Registered Trade Mark) or in a tube or pipe mill, for example of the type shown and described in U.K. Patent Specifications 1,019,833 and 1,019,834.
The steam is usually used as the milling medium and is injected in to the mill at super-atmospheric pressure and temperature.
It has been found that excellent results are obtained using steam at a temperature in the range 150C to 350C
and particularly at temperatures in the range 200C
; to 300C and, of course, at corresponding pressures, at least in mills of the type previously re~erred to.
Optimum steam/pigment ratios can readily be determined by experiment and will depend to some extent on the type of fluid energy mill used. Generally, however, such ratios in the range 1.0 to 6.0 and particularly in the range 1.5 to 3.5, have ~een found to be very effective.
After subjecting the reactor to fluid energy milling in the presence of steam, the thus-treated pigment is su`bjectRd to dry heat at a tEmpera~ure of at least 400C. It is preferred to subject the pigment to dry heat at a temperature in the range 400C to ~COC and preferabl~ to one in the range ~00C to 600C.
By the term "dry heat" ismeant subjecting the pigment to the required temperature without the introduction into the treat~ent vessel of added steam. For exa~ple, the pi~ment m~y ke treated by exposure to a heated gas stream (not oontaIning added steam~ either by direct a~ltion of the pigment to the gas stream or in a fluidised bed of particulate solid heated and ~luidised by a suitable hot ga~
~uch as air or it may be heated (and preferably agitated, e.g.
by stirring or tu~bling) in a heated o~en or furnaoe .
Ihe cptimum duraticn of the exposure of the pig~ent to dry heat may readily be determined by trial and experi~ent and it is clearly commercially advantageous to carry out the pro oe ss for the shortest time which i5 consistent with cbtaining the desired improved durability of the pigment in order to redu oe unit costs and to obtain the maximum thLoughput. Additionally the opti~um duration of the pro oe ss may vary with the nature of the particulate titanium dioxide-to be treated. It is ~elieved, hc~ever, that exposure to dry hea~ as a~
agitated mass for a period of 1 to 60 minutes and particularly for a period of S to 30 minutes or exposure in a fluidised state for 0.2 to 60 seccnds and particularly for 1 to 10 seccnds, will normally give a pig~ent of high durability when co~pared with si~ilar pig~ent which has not } n treated by the prc~ess of the present m vention or ~ch has been subjected to either fluid energy milling in th~ presenoe of s~eam, ~L4~C~97 or to dry heat, alone.
It is believed that the process of the present invention gives titanium ~icxide pigment o high durability because the initial fluid energy milling in the presencP of steam hydrolyses or otherwise decc~poses impurities on the sur~ace of the reactor discharge and that the subsequent exposure to dry heat under the conditicns described modifies the hydrolysed surfaoe and/or removes those products of hydrolysis or other form of 2ecc~position from the surfaoe o~ the titanium diQxide particles.
m e following EXa~ples show the improve~ent in durabllity (expressed as the durability ratio) cbtained in reactor dischaLge treated by the pro oess of the present inventicn when compared with that of a similar starting material which has not been treated by the pro oess of the prese~t invention and also show the effect of varying the steam temperature during fluid energy milling~
., .
Example 1 Reactor discharge recovered frcm the vapour phase oxidation of titanium tetrachloride was divided into three separate portlans.
m e separate porticns were treated as follcws, (a) Portion untreated Ub) Portion subjected unstirYed to dry heat in an cven at 550 & for lS ~inutes (c) Portion subjected to treatment in the fluid energy pipemill shcwn in U.K. Specification 1,019,833 using steam at 2 C ~ut not further treated).
~l~40~7 Part of the product frcm (c) was then heated to a temperatu~e of 550C for a period of 15 minutes as described for sample (b) ~i.e.
this product - designated (d? - was made according to the process of the present inventicn. The durabilit~ ratio of each of the samples (a) to (d) was determined as set out belcw and the follcwing results were obtained:-Sample Durabi~it~ ratio (a) 0.62 Pb) 0.45 (c) 0.47 (d) 0.38 Example 2 ; ~he process descriked in Exa~ple l ~as repeated with a sa~ple of reactor discharge havlng a different durability ratio and the following results were cbtained:
- Sa~ple Durability ratio (a) 0,57 (b) 0~55 (c) 0~6 (d) 0~3 Examlple 3 Reactor discha~ge c~ta~ned as described in Example 1 was taken and divided into three portions~ The durability ratio of the untreated reactor discharge was dete~ined and eac~ of t~2 ~4~97 three portions was subjected to fluid energy milling in a pipemill of the type described in U.K. Patent Specificaticn l,019,833 in the presence of steam~ The temperature of the steam varied betwe~n 250C
and 350 C for the three sa~ples, as shown.
The durability ratios of the sa~ples which were fluid energy milled in the presence of steam at the various steam temperatures were determined and the products of this milling were subjected to dry heat (at 550 C) for 15 minutes and the durability ratios were again determined.
The results were as shown below:~
Uhtreated discharge Pipemilled discharge Pipemi~led and heated discharge (DR) (DR) (550CC) (DR) 250 & 0.49 0.37 0.59 320 & 0.59 0,40 350C 0.64 0.55 Exam~ple 4 :
Ihe process described in Ex~ple 3 was reFeated with a different sample of reactor discharge and this was fluid energy milled in the presen oe of steam at differing temperatures in the range 200 C to 330C, as shcwn, prior to dry heat treatment (unstirred) at 550 C for 15 minutes.
Ihe results ~ere as shcwn below:-.
: 8 Uhtreated discharge PiFemllled discharge Pipemilled ~nd : heated (550 C) (DR) (DR) discharge (DR) 200C 0.44 0.35 0.66 250C 0.50 0.32 3C0C 0.53 0.38 : 330C 0.60 0.37 Example 5 . Four different sa~ples of reactor discharge frcm the vapour ;- phase oxidaticn of titanium tetrachloride were tahen and treated as described in Example 1. Ihe durability ratios were determined as set out below and the following results were Qbtained:-: Sample Durability Ratio (a) 0.64 0~62 0.49 0.47 (b) 0.51 0.50 0.39 0~44 (c) 0.61 0.57 0.53 0.49 (d) 0.44 0~45 0.34 0.38 . ~he measurement of the Durability Ratio is defined and carried out - a~. follc~s.
~ The prcperty measured is the mass loss (as defined in Eiperimental : and Theoretical Studies of the Durability of Paint Systems pigmented with Titanium Dioxide - Evans and Murl~y, VI FAIIPEC CCNGRESS, 1962) from a paint fi~m ccntain m g the experimental pig~ent~s) when ccmpared with a similar film ccntaining a standard pig~ent(s); the mass loss being . induced by accelerated weathering, using a weatherlng cycle generally ac oepted by the painttrade and as defined in British Sta~dard ~ OC~7 g 3900, Section F3.
Films of a paint(s) containing the test pigment(s) and Gther paint films containing cne or mo~e standard pigments are prepared under standard conditions by m corporatlng the pisment~ by bead milling into an air-d~y m g aIkyd resin solution, normally Uralac ta Registered Trade Mark)P470 which is a lcng oil linseed pentaerythritol alkyd resin, to pnDdu oe paint(s) which are spun onto a stainless steel substrate(s) to a dry film thickness of approximatel~ 35 These films, after drying, are exposed alongside each other~
i.e. under identical oonditions, in the twin-arc Marr Weather-C~
Meter.
; Ihe mass loss of the panel coated with the paintts) containing the test pigment(s) is compared with the mass loss o the panelts1 o~ntaining the standard pigment(s), after a series of exposure times.
A durability ratio (D.R.) expressed as experimental film l~ss/standard film loss of l.C0 indicates equivalent performanoe of the panel ooated with a paint contalning one of the standard pigmentts). A D.R. of less than 1.00 indicates performan oe superior to that of the standard(s).
Reactor discharge when treated by the process oS the present invention will usually be treated further, for example in the mann~r in which halide pigments are normally treated to improve their dispersion in organic media, their gloss and to further improve their durability.
The gloss of such pigments may be improved by additicnal milling, ~or example by additional fluid energy milling and/or mec~lanical milling and/or sand milling as an aqueous slurry. This prcperty may also be improved by ane or more classificaticn steps whexeby particles of less ~han optim~m size are removed or at least reduoed in prcportion.
V0~7 The properties of dispersion and of further l~prcvements in durability may for example ~e achieved by coating the pigment particles with one or more hydrous oxides of ele~ents such as siliccn, aluminium, cerium, zirconium or titanium ox wit~ a phosp~ate of Gne or more of these elem~nts, as is well kncw.n in t~e art~
Additionally or alte m atively, the pigment paxticles may be coated with one or more organic ccmpounds, for example with a polyhydroxy ccmpound such as pentaerythritol, trimethylol pxopa~e or an ethanolamine. Such organic ooatings are, again, well kncw.n in the art and are commo.nly applied to assist in imprcving further the dispexsion of the pigmentary particles in organic media.
A~ter coating titanium dioxide particles prepared ~y the process of the present inventlon it is normally advis~ble to subject the coated particles to more milling to break up aggregates which tend to form during the coating processes.
The final pigment may then be sold, for example either in the form of an aqueous slurry or as a dr~ed particulate solid~ It is of advantage, if the plgment is to be sold in t~e form of an aqueous slurry, to av~id the ne oe ssity for drying the pigment prior to red~spersing it in water to form the desired slurry and an~ milling w~i~h may be required in this case may be prcv~ded b~ sand milling or ~ mechanically milling an aqueous slurry~
The c~idation of the titanium tetrahalide, for example titanium tetrachloride, to produce the reactor discharge ~ ~ ch is to be treated by the process of the present invention will nor~ally be 1~4t)~7 , carried out under conditions which are well kncwn for such an oxidation to produce pigmentary titaniun dioxide. For exa~ple, the oxidation is carried out at an elevated tem~erature, for example at least 8CO & , and the titanium tatrahalide is ~intained in the vapour phase. m e oxidation c~mKnly takes plaoe in the presen oe of additives, for exampla in the presence of a minor pr3porticn of an alumini~n halide, normally the chloride, and, if desired, a minor proportion of a silicon .;
hali2e, normally the chlori2e. Minor proportions of water vapour and/or a souroe of an alkAl; metal ion, particularly potassium,are also c~monly added to the oxidation. Such additives, which as noted above~
are well kncwn in the prior art, ~nprove the ~uallty of the titani~n dioxide produced for pigmentary purposes.
Ihe temperature in the oxidation reactor is achieved by the introduction of heat into the reactlGn zone. m is may be provided directly b~ the combustion prGduc~s of a suitable gas, for example of c~rhon monQxide, or by the provision of a gas which has been heated by its passage through an electric arc. me gas in the latter pro oe ss may be an inert gas or it may be c~e of the reactants, for exa~ple o~ygen. ~lternatively, one or both of the reactants may be preheated indirectly, for example by means of a heat exchanger prior to its introducticn into the reacticn zcne. Where the reactants are preheated to reacticn temFerature they should, of course, be separately intr~duced into the reaction zone to prevent pn~nature reacticn. Normally, in such a process, one leactant, usually the o~ygen, is heated to a temperature in excess of the desired reacticn te~perature and the other neactant, the titanium tetrahalide, is heated to a te~perature sufficient to ` ~ 40~39~
, maintam it in the vapour phase; the temperature o~ the mixed gases :-~ being sufficient to produce the required temperature in the reacticn zcne.
;, ' . :
Claims (12)
1. A process for the treatment of reactor discharge from the oxidation of a titanium tetrahalide comprising subjecting particulate reactor discharge to fluid energy milling in a fluid energy mill in presence of steam, removing the so treated reactor discharge from said fluid energy mill and then subjecting it external of said fluid energy mill to dry heat at a temperature of at least 400°C.
2. A process as claimed in claim 1 wherein the titanium tetrahalide is titanium tetrachloride.
3. A process as claimed in claim 1 wherein the fluid energy milling is carried out using steam at a temperature in the range 150°C to 350°C.
4. A process as claimed in claim 3 wherein the steam is at a temperature in the range 200°C to 300°C.
5. A process as claimed in claim 1 wherein the steam/pigment ratio during fluid energy milling is in the range 1 to 6.
6. A process as claimed in claim 5 wherein the steam/pigment ratio is in the range 1.5 to 3.5.
7. A process as claimed in claim 1 wherein the pigment is subjected to dry heat at a temperature in the range 400°C to 800°C.
8. A process as claimed in claim 7 wherein the pigment is subjected to dry heat at a temperature in the range 500°C to 600°C.
9. A process as claimed in claim 1 wherein the pigment is subjected to dry heat for a period of 1 to 60 minutes.
10. A process as claimed in claim 9 wherein the pigment is subjected to dry heat for a period of 5 to 30 minutes.
11. A process as claimed in claim 1 wherein the pigment is subjected to dry heat, when in the fluidised state, for a period of 0.2 to 60 seconds.
12. A process as claimed in claim 11 wherein the pigment is subjected to dry heat for a period of 1 to 10 seconds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB43810/78 | 1978-11-09 | ||
| GB7843810 | 1978-11-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1140097A true CA1140097A (en) | 1983-01-25 |
Family
ID=10500908
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000335974A Expired CA1140097A (en) | 1978-11-09 | 1979-09-19 | Process for the treatment of halide titanium dioxide pigments to improve durability |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5571630A (en) |
| AU (1) | AU519446B2 (en) |
| CA (1) | CA1140097A (en) |
| DE (1) | DE2944791A1 (en) |
| FR (1) | FR2440976A1 (en) |
| GB (1) | GB2035978B (en) |
| ZA (1) | ZA794869B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS591014U (en) * | 1982-06-25 | 1984-01-06 | オリエント時計株式会社 | optical fiber connector |
| JPS59104117U (en) * | 1982-12-28 | 1984-07-13 | 株式会社ニフコ | Optical fiber end fixing device |
| JPS59134117U (en) * | 1983-02-28 | 1984-09-07 | 松下電工株式会社 | Optical fiber relay connection equipment |
| JPS60143406U (en) * | 1984-03-02 | 1985-09-24 | 東北電力株式会社 | Optical cable connection device |
| JPS6181605U (en) * | 1984-10-31 | 1986-05-30 | ||
| JPS6181610U (en) * | 1984-10-31 | 1986-05-30 | ||
| JPH0423215Y2 (en) * | 1984-12-07 | 1992-05-29 | ||
| ES2050667T3 (en) * | 1986-10-31 | 1994-06-01 | American Telephone & Telegraph | PHOTOSTABLE COMPOSITION CONTAINING TITANIUM DIOXIDE PIGMENT. |
| US5037476A (en) * | 1987-01-20 | 1991-08-06 | At&T Bell Laboratories | Process for improving photostability of titanium dioxide pigments in binder compositions without decreasing reflectivity |
| US6193795B1 (en) * | 1993-08-02 | 2001-02-27 | Degussa Corporation | Low structure pyrogenic hydrophilic and hydrophobic metallic oxides, production and use |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3317145A (en) * | 1964-01-02 | 1967-05-02 | Fluid Energy Proc & Equipment | Method and means for pulverizing and drying solids |
| FR1431239A (en) * | 1965-03-13 | 1966-03-11 | Du Pont | Method and apparatus for finely grinding too coarse particles and pigments |
| US3531310A (en) * | 1967-05-29 | 1970-09-29 | Ppg Industries Inc | Production of improved metal oxide pigment |
| US4083946A (en) * | 1977-03-23 | 1978-04-11 | E. I. Du Pont De Nemours And Company | Process for removing chloride impurities from TiO2 |
-
1979
- 1979-08-30 GB GB7930026A patent/GB2035978B/en not_active Expired
- 1979-09-13 ZA ZA00794869A patent/ZA794869B/en unknown
- 1979-09-13 AU AU50829/79A patent/AU519446B2/en not_active Expired
- 1979-09-19 CA CA000335974A patent/CA1140097A/en not_active Expired
- 1979-11-06 DE DE19792944791 patent/DE2944791A1/en not_active Withdrawn
- 1979-11-06 FR FR7927363A patent/FR2440976A1/en active Granted
- 1979-11-08 JP JP14492579A patent/JPS5571630A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2440976A1 (en) | 1980-06-06 |
| GB2035978B (en) | 1982-10-20 |
| ZA794869B (en) | 1980-08-27 |
| JPS5571630A (en) | 1980-05-29 |
| AU519446B2 (en) | 1981-12-03 |
| JPS5757409B2 (en) | 1982-12-04 |
| DE2944791A1 (en) | 1980-05-22 |
| AU5082979A (en) | 1980-05-15 |
| FR2440976B1 (en) | 1984-02-17 |
| GB2035978A (en) | 1980-06-25 |
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