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
• • 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
  • C09C1/3607—Titanium dioxide
  • C09C1/3653—Treatment with inorganic compounds
  • C09C1/3661—Coating
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
  • C01P2004/88—Thick layer coatings

Definitions

• the present invention relates to a titanium dioxide pigment having a surface treatment suitable for its use in paint compositions with high external resistance.
• Titanium dioxide is used for its pigmentary properties in paint compositions. Titanium dioxide pigments are generally treated with mineral compounds in order to improve their application properties such as their dispersibility, their whiteness or their covering power.
• the titanium dioxide pigment is known to absorb UV rays. It thus protects the organic matrix into which it is introduced (paint, plastic, ...) from degradation under the effect of this type of rays.
• titanium dioxide has photocatalytic properties so that it degrades the organic compounds in contact with it under the effect of these same UV rays. This degradation is characterized by chalking of the paint.
• Mineral treatments therefore also aims to avoid direct contact between titanium dioxide and the organic components of the matrix.
• it is known, for example, to use mineral treatments based on silica and / or alumina.
• surface treatments were insufficient when the pigment was used in paint compositions for exterior coatings highly exposed to the sun.
• An object of the present invention is to provide a titanium dioxide pigment, the mineral surface treatment of which gives the exterior paints good resistance over time and very particularly low chalking and good retention of the gloss.
• the invention relates to a titanium dioxide pigment, comprising a titanium dioxide core successively covered with a layer of hydroxide or zirconium oxyhydroxide, then a layer of titanium hydroxide or oxyhydroxide, then a layer of a phosphate and silica coprecipitate and finally a layer of alumina oxyhydroxide.
• the invention also relates to a process for the preparation of this pigment which consists in carrying out the following operations:
• a layer of zirconium hydroxide or oxyhydroxide is precipitated on the surface of the pigment
• a layer of a phosphate and silica coprecipitate is precipitated on the surface of the pigment
• a layer of alumina oxyhydroxide is precipitated on the surface of the pigment, - the pigment is recovered from the suspension.
• the invention relates to the use of this pigment in paints and plastics.
• the invention therefore relates, first of all, to a titanium dioxide pigment, comprising a titanium dioxide core successively covered with a layer of zirconium hydroxide or oxyhydroxide, then with a layer of hydroxide or titanium oxyhydroxide, then a layer of a phosphate and silica coprecipitate and finally a layer of alumina oxyhydroxide.
• the different layers which cover the titanium dioxide have a thickness generally between 50 and 100 ⁇ . These layers may be discontinuous, more or less regularly surrounding the titanium dioxide.
• the pigment according to the invention is covered with:
• zirconium hydroxide or oxyhydroxide expressed as ZrO 2
• silica 0.2 to 1.5% by weight of silica, expressed as SiO 2 ,
• the invention also relates to a method of surface treatment of this titanium dioxide pigment. This process includes the following steps:
• a layer of zirconium hydroxide or oxyhydroxide is precipitated on the surface of the pigment
• a layer of a phosphate and silica coprecipitate is precipitated on the surface of the pigment
• a layer of alumina oxyhydroxide is precipitated on the surface of the pigment, - the pigment is recovered from the suspension.
• the treatment therefore consists in producing a first layer of zirconium hydroxide or oxyhydroxide or oxyhydroxide directly on the surface of the pigment, then in a second layer of titanium hydroxide or oxyhydroxide, then a third layer which is a coprecipitate of phosphate and silica, and finally a last layer of alumina oxyhydroxide.
• an aqueous suspension of titanium dioxide pigments comprising titanium dioxide, preferably, predominantly in rutile form.
• This suspension can be formed by any means known to those skilled in the art such as, for example, by the sulphate or chlorine processes.
• the concentration of titanium dioxide pigments in this suspension usually varies between 100 and 500 g / l.
• This dispersion may optionally contain a dispersant in order to disperse and stabilize it. It can in particular be obtained by grinding a dispersion of titanium dioxide using said dispersant.
• the dispersant can be chosen from the following products: amino 2-methyl 2-propanol 1, potassium or sodium tetrapyrophosphate, potassium or sodium hexametaphosphate or alkaline salts of polyacrylic acid polymer or copolymer such as ammonium or sodium salts of polyacrylic acid.
• phosphate-based dispersants these are generally present in a concentration of the order of 0.1 to 0.5% by weight expressed as P 2 O 5 relative to the weight of the dioxide of titanium.
• the surface treatment process is generally carried out at a temperature above 60 ° C. This temperature is maintained throughout the treatment, but it is also possible to consider simply raising the temperature of the starting dispersion to a temperature above 80 ° C., then continuing the treatment without a heat source.
• the first stage of the treatment consists in depositing by precipitation a layer of zirconium hydroxide or oxyhydroxide on the surface of the pigment.
• a layer of zirconium hydroxide or oxyhydroxide is precipitated from a hydrolyzable zirconium compound chosen from zirconium sulfate, zirconium orthosulfate, zirconium chloride or l zirconium oxychloride.
• the amount of hydrolyzable zirconium compound introduced during this first step is generally between 0.5 and 1.5% by weight, expressed as ZrO, relative to the core of titanium dioxide to be treated, preferably, between 0.2 and 1.5%.
• the second stage of the treatment consists in depositing by precipitation a layer of titanium hydroxide or oxyhydroxide on the surface of the pigment.
• a layer of titanium hydroxide or oxyhydroxide is precipitated from a hydrolyzable titanium compound chosen from titanium chloride, titanium oxychloride or titanium sulfate.
• the quantity of hydrolyzable titanium compound introduced during the second step is generally between 0.05 and 1% by weight, expressed as TiO 2 , relative to the titanium dioxide core to be treated.
• the first two steps are carried out at a pH usually between 4 and 6, preferably 5.
• the pH can generally be controlled by adding an acid and / or a base such as sulfuric acid, hydrochloric acid or acetic acid, and soda or potash.
• the third stage of the treatment consists in depositing by precipitation a layer of a phosphate and silica coprecipitate on the surface of the pigment.
• a layer of a phosphate and silica coprecipitate is precipitated from hydrolyzable phosphorus and silicon compounds chosen from: phosphoric acid, phosphates such as potassium or sodium tetrapyrophosphate, potassium or sodium hexametaphosphate, potassium or sodium tripolyphosphate, sodium dihydrogen phosphate,
• the amount of hydrolyzable phosphorus compound introduced during this step is generally between 0.2 and 1.5% by weight, expressed as P 2 O 5 relative to the titanium dioxide core to be treated.
• the hydrolyzable silicon compound it is generally between 0.2 to 1.5% by weight, expressed as SiO 2 , relative to the titanium dioxide core to be treated.
• this step is usually carried out at a pH between 6 and 9.
• the pH can be controlled by adding phosphoric acid and / or another acid such as than sulfuric acid or hydrochloric acid.
• the pH can also be controlled by the simultaneous and / or alternative introduction of the phosphorus-based compound and the silicon compound which will form the coprecipitate. This is the case, for example, when phosphoric acid and sodium silicate are used during this coprecipitation.
• the quantities of phosphorus and silicon compounds introduced are modulated so as to precipitate a coprecipitate layer having a P / Si atomic ratio of between 0.3 and 3, preferably between 0.6 and 1, 2.
• the amount of phosphate provided by the dispersant is subtracted from the amount of phosphate introduced during the third precipitation step.
• the phosphorus compound and then the silicon compound are successively introduced into the aqueous suspension of titanium dioxide pigment.
• the fourth step is to deposit a layer of alumina.
• alumina layer is understood here and throughout the description to be a precipitate of aluminum oxyhydroxide.
• this last layer is precipitated from a hydrolyzable aluminum compound such as basic hydroxylated salts.
• a hydrolyzable aluminum compound such as basic hydroxylated salts.
• the sodium aluminate the basic aluminum chloride, the aluminum hydroxide diacetate.
• Alumina sulfate can also be used.
• the amount of hydrolyzable aluminum compound introduced during this step is usually between 1 and 5% expressed by weight of AI 2 O 3 relative to the weight of the titanium dioxide core to be treated, preferably between 2% and 4%.
• This precipitation takes place at the pH necessary for the precipitation of the alumina layer.
• This pH can be between 3 and 10.
• this pH is between 5 and 10.
• the regulation can be carried out by adding sulfuric acid.
• ripening stages can be carried out.
• the latter consist in stirring the reaction mixture following the introduction of the hydrolysable compounds allowing precipitation.
• the ripening time is of the order of 5 to 30 minutes at each stage.
• the pigments are separated from the liquid phase of the suspension by any known means, for example by filtration. Then the pigment is generally washed with water, dried and micronized.
• the pigments according to the invention can also be treated with organic compounds in order to give them properties specific to their use, such as gloss, dispersibility, wetting, stabilization.
• organic compounds can be chosen from liquid or solid polyols such as low molecular weight polyglycols ethoxylated or not, trimethylolpropane (TMP), trimethylolethane (TME), ethoxylated trimethylolpropane, liquid polyphosphates, hydroxyamines such as triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP) or silicone products.
• TMP trimethylolpropane
• TME trimethylolethane
• ethoxylated trimethylolpropane liquid polyphosphates
• hydroxyamines such as triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP) or silicone products.
• This organic treatment can be carried out in the aqueous phase after the fourth precipitation step, or after the pigments have
• the invention finally relates to the use of pigments according to the invention in coating compositions, in particular paint, as well as in plastic compositions for which the pigment according to the invention avoids blueing over time.
• the pigments according to the invention can also be used in laminates of paper.
• the following examples illustrate the invention without, however, limiting its scope.
• the starting point is a suspension of titanium dioxide with a concentration of 900 g / l. It was ground in the presence of 0.2% by weight of aminomethylpropanol (AMP90) relative to the weight of titanium dioxide, then diluted to 350 g / l.
• AMP90 aminomethylpropanol
• the pH of the dispersion is adjusted to 5 by the addition of sulfuric acid.
• TiO 2 0.15% by weight of TiO 2 , relative to the weight of titanium dioxide to be treated, is added to the preceding reaction medium, in the form of a solution of titanium oxychloride.
• SiO 2 - 0.7% by weight of SiO 2 , relative to the weight of titanium dioxide to be treated, in the form of a sodium silicate solution.
• the pH is adjusted to 9.5 with sodium hydroxide.
• the dispersion is then filtered.
• the titanium dioxide pigments obtained are washed with water at 45 ° C, dried at 150 ° C for 15 hours.
• comparative pigment 1 titanium dioxide pigment covered with a surface treatment based on 2.8% by weight of I 2 O 3 and 0.8% by weight of ZrO 2 ,
• comparative pigment 2 titanium dioxide pigment coated with a surface treatment based on 3.5% by weight of AI 2 O 3 , 0.6% by weight of ZrO 2 and 0.6% by weight of P 2 O 5 ,
• comparative pigment 3 titanium dioxide pigment covered with a surface treatment based on 2.2% by weight of AI O 3 and 5% by weight of SiO 2 .
• the paint is based on an alkyd binder and a melamine in a 70/30 ratio by weight.
• the pigment rate is around 37% by weight.
• paints are applied on an aluminum support, for chalking measurements, or on a glass support, for gloss measurements, over a thickness between 40 and 90 ⁇ m. They are pre-dried for 30 min, then baked at 130 ° C for 30 min.
• Accelerated aging The aluminum supports coated with paint are introduced into an accelerated aging device QUVB.
• the aging cycle is as follows:
• the chalking of the paint reaches a saturation value of 80%:
• the gloss of the paint is: - 66 for the pigment according to the invention.
• the specific formulation of the mineral treatment according to the invention provides the paint with a slower appearance of chalking and a gloss retention at least as high as for the comparative treatments.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Paints Or Removers (AREA)
• Paper (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9502985

Family Applications (1)

Country Status (19)

Families Citing this family (42)

Family Cites Families (11)

• 1997
  • 1997-01-27 FR FR9700821A patent/FR2758826B1/fr not_active Expired - Fee Related
• 1998
  • 1998-01-20 TR TR1999/01753T patent/TR199901753T2/xx unknown
  • 1998-01-20 US US09/355,259 patent/US6200375B1/en not_active Expired - Lifetime
  • 1998-01-20 BR BR9808891A patent/BR9808891A/pt unknown
  • 1998-01-20 IL IL13087898A patent/IL130878A0/xx unknown
  • 1998-01-20 HU HU0002832A patent/HUP0002832A2/hu unknown
  • 1998-01-20 EP EP98903097A patent/EP0961814A1/de not_active Withdrawn
  • 1998-01-20 KR KR1019997006733A patent/KR20000070489A/ko not_active Ceased
  • 1998-01-20 NZ NZ33686698A patent/NZ336866A/xx unknown
  • 1998-01-20 JP JP53166798A patent/JP2000513763A/ja active Pending
  • 1998-01-20 AU AU59939/98A patent/AU5993998A/en not_active Abandoned
  • 1998-01-20 CN CN98802090A patent/CN1244888A/zh active Pending
  • 1998-01-20 PL PL33483798A patent/PL334837A1/xx unknown
  • 1998-01-20 ID ID990758A patent/ID22792A/id unknown
  • 1998-01-20 SK SK995-99A patent/SK99599A3/sk unknown
  • 1998-01-20 CA CA 2277058 patent/CA2277058A1/en not_active Abandoned
  • 1998-01-20 WO PCT/FR1998/000103 patent/WO1998032803A1/fr not_active Ceased
• 1999
  • 1999-07-09 BG BG103568A patent/BG103568A/bg unknown
  • 1999-07-26 NO NO993619A patent/NO993619L/no not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events