CA1163037A - Inorganic pigments with fog-free gloss distributable in lacquer binders - Google Patents

Abstract

A TRACT OF THE DISCLOSURE

An inorganic pigment exhibiting improved gloss and distribution in lacquer binders, carrying a coating com-prising a-SiOH-containing organosilicon compound and an aklanolamine. Advantageously the alkanolamine comprises at least one of triethanolamine, triisopropanolamine, diethanolamine, diisopropanolamine and 2-amino-2-methyl-propanol-1, the organo-silicon compound is of the formula wherein n>3, R and R1 each independently is alkyl, cycloalkyl, aryl, alkenyl or a group of the formula

Description

~ 3 ~3037 Inorganic Pigments with improved gloss and good distribution in Lacauer ~inders The present invention relates to inorganic pi~ments having improved gloss and distribution in lacquer binders by means of treatment ~ith organic au.Yiliaries before or during final mieronization.
~og-free high gloss eoatings and good subtlivisr;on in lacquer binders are importan-t requirements of high quality pigments. In adclition to ccr-tain o-thF3r properties such as good resistanee to weathering and brightening capacity, they constitnte important eriteria for assessing quality.
~here has been no lacl{ of attempts in the past to achieve tlle above object. The charaeteristic procedure to achieve this object in many patents is that of rendering tlle organo-phobic surface of the pigment organ~pllilic by means of suitable substances sueh as organic auxiliaries which are added before or during the milling operation ~rhich concludes the procluetion process. This milling of the pigments is generally carried out in pin mills, ball mills or ring roll mills bu-t e.Yeeptionally high quality pigments are obtained by mieronizatiOn in fluid energy mills, e.g. using air ,jets or steam jets. Numerous organic compounds are l;nol~n as a,u~Yiliaries for modifying the sur-face of pigments.
Apart from polyols, alkene oYides, phello'ls~ long chain fatty alcohols and fatty acid esters, to name but a few of -tlle classes of compounds whieh may be usecl, it is also kno~n to use organosilicon compounds. ~he object o~ ~Ising these organosilicon compounds is to render the pigments or fillers hydrophobie and to malse them more readily dispersi-ble and capable of incorporation in syntlletic re~ins, In German Offenlegungsschrift No. 2 012 017, -for e~Yample, there is clescribed the treatmen-t of TiO2 ~v-ith sodium methyl siliconate to improve its dispersibility in polystyrene.
lt is also customary to rendf3r pigments hydrophobie by treating -them witll polysilo.Yanes, e.g. octamethylcyclotetra-silo.Yane (British Pa,tent No. 959 211) to iml)rove their incorporation in polyamicles, or to treat them ~ith silanes Le A 19 539 ~ ~ fi3037 such as trialko.Yysilanes :Eor example, as descr:ibecl in British Pa-tent No. 825 ~ 04. Such surface treatments are not however, capable of producing pigments with excellent fog-free gloss in lacquer bind~rs.
Organic treatment of pigments with alkanolamines is also known. The use of trialkanolamines antl, diisopropano-lamine, for example, have been described in US Patent No.
3 3~15 187 and ln German Patent No. 2 '~ 2 678, respectively.
In the process according to German OfIenlegungsschrift No.
1 792 022, tri.e~tllanolamine is brought into contact wi-th the pigment surface in the course of so-ca]:Led double ste&m jet milling. US Patent No. 2 737 ~160 is concerned wi-th the milling of pigments with trial~anolamines in the presence of ~ finely dividecl fillers such as Aerosil. It is also known 15 -to use salts ol a]kanolamines with organic acids such as lactic acid (German Patent No. 1 271 862) or benzoic acids (US Patent No. 3 172 772).
The procedures mentioned above are either e~pensive or technically complicated or else result in pigmen-ts 20 which, in spite of showing distinct improvements compared with titanium dioxides which have not been organically treated, do not satisfy the highest standards o:E quality demanded with regard to gloss and fineness of subdivision and dispersion. This applies partic~llar~ to pigments which 25 have been a~ter-treated with SiO2 or ~1~03.
It has now surprisingly been found that pigments with improved gloss and good distribution in lacquer binders can easily be obtained by treatment with organic auxiliaries before their final micronization if a combination of alkano-lamines with organic silicon compouncls containing SiOHgroups is used. The present invention provides inorganic pigments with improved gloss and subdivision in lacquer binders, having a coa-ting of organosilicon compounds con-taining SiOH groups and having more thall threc Si atoms in the mo]ecule and alkanolamines; and a l)rocess Lor the Le A 19 539 .

preparation thereof by coating the pigments with the above mentioned compounds before or during their final micronization. Pigments which are particularly suitable for this treatment are white pigments based on TiO2 or titanates, including also those which have been subjected to an inorganic after-treatment.
The new pigments are particularly suitable for pigmenting polymer materials and aqueous suspensions.
The pigments are brought into contact with about 0.1 to 4%, preferably about 0.3 to 1% of the organic auxiliaries. It has been found advantageous to use a proportion by weight of SiOH-containing organic silicon compounds to alkanolamine within the range of about 1:1 to 1:10 particularly of about 1:2 to 1:5. The preferred SiOH-containing organic silicon compounds are characterized by an OH:Si ratio within the range of about 1:1 to 1:20, preferably o:E about 1:2 to 1:10. Examples include linear and branched chain organic silicon compounds corresponding to the following formula R
HO - Si O - H

R' _ n wherein n ~ 3, and R' may be the same as or different from R. R may be an alkyl and/or a cycloalkyl and/or and aryl and/or an alkenyl group or a group corresponding to the following formula R
O Si O - - H
_ R' m where m > 1.
Specific fractions of the hydrolyzates of, for example, the following compounds are suitable: Dimethyldichlorosilane; dimethyldichlorosilane and methyl trichlorosilane; dimethyldichlorosilane and silicon tetrachloride; vinyl methyl dichlorosilane; vinyl methyl dichlorosilane and dimethyldichlorosilane, cyclohexylmethyldichlorosilane and ~ -3-.

~ :1 63037 climethyldichlorosilane; and the like. Condensat.ion products of diphenylsilane-diol are also suitable.
Particularly suitable compounds include, for example, linear poly-methylsiloxanes end-blocked with SiOH groups having an average molecular weight of about 490 and a viscosity of about 27 cP; also linear polyvinylmethylsiloxanes end-blocked with SiOH groups having a ~MeSiViO) content of about 5%, a (SiOH) content of about 18.2% and a viscosity of about 25.5 cP. Branched chain poly-methylsiloxanes end-blocked with SiOH groups, an average molar weight of about 545 and a viscosity of about 110 cP as well as branched chain polyvinylmethyl-siloxanes end-blocked with SiOH groups having a t~eSiViO) content of about 5% a ~SiOH) content of about 15.2% and a viscosity o~ about 96 cP are also suitable.
Common to all the above compounds is a certain ratio of OH groups to Si atoms which in the process according to the present invention should be within the range of from 1:1 to 1:20 if optimum pigment properties are to be obtained.
The alkanolamines used may be trialkanolamines, dialkanolamines and/or monoalkanolamines. The following are particularly suitable: Triethanol-amine~ diethanolamine, triisopropanolamine, diisopropanolamine, 2-amino-2-methyl-l-propanol, 2-amino-2-hydroxy-methyl-1,3-propanediol, 2-dimethylaminoethanol,

2-ethylaminoethanol and the like. The organic auxiliaries are brought into contact with the pigment in known manner, either before or during a final milling operation. I~ is immlaterial whether they are mixed with the moist filter cake obtained in the course of preparation of the pigment or with pastes or sludges of the pigment before drying, whether they are directly added to the dry substance in some suitable manner before the final milling, for example by spraying or else whether, for example in the case of steam jet milling, they are directly added to the steam before it is fed into the jet mill. The effectiveness of the compounds used according to the present invention does not -.. ~ -'1-, i ~ 6~3~

-5- ~
depend upon the sequence in which the components are added. ~egardLess of whether mi~t~ires oI a:Lkanolamines and organosilicon compounds are ac1ded or wh~t11er al~anol-amines are ~dded first, followed by organosilicon compounds, or vice-versa, the pigments obtained show considerable improvement in gloss, fogging and granu~arites after they have ~een micronized compared with products which have only been treated with alkanoJamines alone or with organo-silicon compounds alone.
. There is thus obviously a synergistic effect between thes~ two substances, as can be seen from Table l hereinai`ter.
The process of the present invention is suitable for all inorganic ~hite and colored pigments. Particularly 15 advantageous results are obtained with white pigments based on TiO2 or titanates or with iron o~ides. The pigments may also have u21t1ergone an inorganic after-treat1nent Pigmen-ts ~ith e~cellent gloss and good distribution are obtained by the process according to the present invention.
TiO2 pigments of both the rutile or anatase form obtaine~ by the sulphate process and thosc obtained by the TiCl~ combustion process may be treated according to -the prescnt invention. In the e~amples de-cri~ed in detail below, ~iO2 pigmen-ts which have been treatecl with inorganic 25 compounds are surface treated with the organic auæiliaries according to the present invention.
A furnace clinker, for e~ample is obtained after several preliminary stages, and this clin1~er is milled and graded. The line -fraction is subjected to an inorganic aftertreatment, which may consist of the precipitation of compounds such as Al(OH3), SiO2 or TiO2 011 the surface thereof and may be rarried out by vario~ls methods in sus-pension. The inorganically after-treated pigment slud~e is Ireed from wa-ter in a rotary filter and ~as11ed. The residue 021 this ~irst rotaIy filter may be mi~ed with water and Le A 19 359 `~ ~ B303~

trans~erred -to a second rotary filter. The residue (II) ~rom this seconcl filter is also washed, and then driecl on a drying belt or a sp-ray drier.
When the pigments have been dried, they are broken down either by milling in a jet mill, e.g. an air jet mill, or a steam jet mill~ or in a milling apparatus which has -a conlpacting e~fect, such as a l~aymond mil:L9 a ball mill or a pin mill. The organic auxiliaries acc,-rding to the l~resent invention may be brought into contact with the 10 pigment at various stages before or during micronization.
For e~ample, they may be added to the second filter residue (II) after it has been 1~ashed but before i-t is dried.
They may also be added to the dry pigmen-t substance, e g.
by spraying, immediately before it is micronized. Another 15 treatment method consists of adding the colllpounds used according to the present invention to the steam or air fed into the jet mill. The orgarlic au~iliaries according to the present invention may be added advantageously as mix-tures since this ensures the desired constant ratio of 20 alkanolamine to organosilicon compoullds.
According to another variation of the process of the present invention, the orgal1osilicon compound containing SiO~ groups is added to the filter residue (II) after it has been washed and before it is dried, and the alkanol-25 amine is added to the dry pigment by spraying before it ismilled, or else it is brought into contact 1~ith the pigment together with -the steam or air.
The above means that the co1nbination of organic auxiliaries may ~e added to the pigmcnt seI)arately at 30 various stages of the manufacturing process.
~ o test the pigment for gloss and distribution in lacquer binders, it is dispersed ~y a dissolver. ~his dis-persion is prodLIced in a highly viscous mi.Yture o~ binder solution of 60~ alkyd resin (ricinene-moc1ified alk~d resin, A 35 oil length 35; trac1e product Alkydal R 35 of ~AYER AG) in Le A 19 539 ~ 7--~ ~D~
.

~ ;~ 630~

,Yyl ene under the following conditions:
Volumetric concentration of pigment in m~terial to be groun~ (PVK): 37 6 %
Diam,ter of ~lissolver disc 3.5 cm - D
5 Diameter of container: 5.5 cm = 1.57 D
Distance of dissolver disc from bottom: 1.75 cm = 0.5 D
Height to which the container i~s filled with material to be ground 3 5 cm - D
Péripheral speecl of dissolver disc: 11 m/s 10 Dispersion time: 5 minutes.
Samples are removed after a dispersion time of 5 minutes and lacquered to a P~of 15~ with the alkyd resin ~~~ and a melamine resin (Maprenal~MF 800, trade product of Hoechst AG) so that the ratio of alkyd resin to melamine resin is 77:23. The degree of fineness of the dispersion is determined in the usual manner with a grindometer (DIN
53 203). The lacquers prepared in this way are then applied to glass plates to form films 120 ,um when wet, and are hardened at 120C for 30 minutes. TLte gloss is measure~
with a Gonio photomctcr at an angle oI 25 The height of the peak at the ref~ection ma~imum is a moasure of the gloss obtained ~hile the heig~t of the sca-tter curve 1 ne~t to the reflection ma~imum is a measure of the gloss fog values.
A high gloss lacquer is characterized by high gloss values and low gloss fog values.
The preparation of the pigments according to the present invention is described below by way of e~ample.

r~De ~,/C

Le A 19 539 ~ 1 631~37 A TiO2 pigmen-t having a ru-tile struc-ture and pre-pared ~y ~he sulphate process was after--treated inor-~anically with 3,~o~h SiO2 and 4% Ai2o3 and dried after the usual washing and filtra-tion. The pigment was sprayed with 0.1% by weight (based on dry pigment) of an a,~-polysiioxanediol mixture having an average molecular weight of 490 and a viscosity of 27cP and O, 3% of trietllanolamine and then micronized in a jet mill using superheated s-team. The dispersibili-ty, gloss and gloss-f'og vallles are shown in Table I
'Comparison Example A~
This comparison Example A shows that a pigment obtained wheli triethanolamine alone is used is qual-itatively consiclerably inferior.
The rutile pigment described in Example 1 issprayed with O.~L,~o triethanolamine a:Eter drying and is then micronized in a jet mill as described in Example 1.
The dispersing properties are shown in Table 1.
~ `
This comparison example shows that the use solely of an organic Si compound containing SiOH groups also results in a qualitatively inferior pigmen-t. The rutile pigment describecl in Example 1 is dried and then sprayed 25 with 0. 4% of an a,w polysiloxanediol mi~ture having an average molecular weight of 490 and a viscosity of 27 cP
and micronized. See ~able 1.

3 After drying, the rutile pigment as used in Example 1 is sprayed l~ith 0.17% of an a,w-po]ysiloxanediol mix-ture having an avera~e molecular weigh-t Or ~90 an~ a viscosity of 27 cP and 0.53% of triethanolamine and' milled in a steam jet mill; see ~able 1.

Le A 19 539 J ~ ~ ~3037 Example 3 The rutile pigment as used in Exampl.e l is dried and then sprayed with 0.12% Of an a,w-polysiloxane diol mixture having an average molecular weight o~ 1190 and 5 a viscosity Oï 27 CP and 0. 58% of trie-thanolamine and milled in a s-team jet mill; see Table I .

~.
The washed filter cake of the rutile pigment as used in Examp].e 1. is mixed, before drying, with 0.12,%
by weight (based on -the dry pigment) of a branched chain ~iOH-containing organosilicon compound having an average overall.formula of TD6 56 and containing 14% Of SiOH
gro-ups. .After the pigment has been dried, it is sprayed lS with 0.48% triethanolamine and mic~onized as described in the previous example; see Table l.

The rutile pig~ent as used in Example l is sprayed after drying with a mixture containing 0~12~o by weight (basecl on -the dry pigment) of a polysi].oxanediol mixture having an average molecular weight of 490 and a viscosity of 27 cP and O . 48% by weight (based on dry pigment) of 2-amino-2-methyl~l-propanol and then milled in a ste~m jet mill as described in Example l; see Tahle l.

Example 6 The rutile pigment as described in Example l does not receive an organic after-treatment.

Le A 19 539 Table 1 -10-Example Organic Treatmerlt Gloss Fog Grind- Heg-(%) (%) ometer man value value (,u ) 1O. 1% Si-org.cpd. 8726 16 6.7 and o . 3% triethanol-amine Compar-0.4,o triethanol- 7737 20 6.4 ison E~- amine ample A
" B0.4% Si-org.cpd. 701l0 16 6~7 2 O.17% Si-org,cpd. 8524 16 6.7 and O . 53% triethanol-amine 3 0 .12% Si-org.cpd. 8721~ 16 6.7 and 0.580,h triethanol-amine

4 0 .12% branch 8823 14 6.9 chained Si_org.cpd.
and 0.48% triethanol-amine 0.12,h Si-org.cpd. 8625 14 6.9 and O . 48% 2-amino-2-methyl-l-propanol 6 None 1~9~100 38 40 Le A 13 539 ~ :1 6303'`I

It will be appreciated that the instant speci-fication and examples are set forth by way of illustra tion and not limitatlon, and that various modifications and changes may be made without departing from the spi-rit and scope of the present invention.

Le A 19 539

Claims (10)

Claims:

1. An inorganic pigment with improved gloss and dis-tribution in a lacquer binder having a coating of a SiOH-con-taining organosilicon compound with more than three Si atoms and an alkanolamine.

2. An inorganic pigment according to claim 1, wherein the quantity of SiOH-containing organosilicon compound and of alkanolamine is from about 0.1% to 3% based on the weight of the pigment, and the ratio by weight of SiOH-containing organosilicon compound to alkanolamine is from about 1:1 to 1:10.

3. An inorganic pigment according to claim 1, com-prising TiO2 or a titanate.

4. An inorganic pigment according to claim 1, wherein the organosilicon compound is of the formula wherein n?3, R and R1 each independently is an alkyl, cycloalkyl, aryl, alkenyl or a group of the formula wherein m>1, the organosilicon compound having an OH:Si ratio within the range of about 1:1 to 1:20.
Le A 19 539-?S

5. An inorganic pigment according to claim 1, wherein organosilicon compound is of the formula wherein n>3, R and R1 each independently is methyl, ethyl, phenyl or a group of the formula wherein m>1, the SiOH-containing organosilicon compound having an OH:Si ratio within the range of about 1:1 to 1:20.

6. An inorganic pigment according to claim 1, wherein the alkanolamine comprises at least one of triethanolamine, diethanolamine, triisopropanolamine, diisopropanolamine and 2-amino-2-methyl-propanol.

7. An inorganic pigment according to claim 6, wherein-the organosilicon compound is of the formula wherein n>3, R and R1 each independently is methyl, ethyl, phenyl or a group of the formula wherein m>1, the SiOH-containing organosilicon compound having Le A 19 539-?S

an OH:Si ratio within the range of about 1:2 to 1:10, and the pigment comprises TiO2 or a titanate carrying an inorganic coating, the organosilicon compound plus alkanolamine ranging from about 0.3 to 1% by weight of the pigment and the ratio by weight of the organosilicon compound to alkanolamine ranging from about 1:2 to 1:5.

8. In the preparation of an inorganic pigment where-in the pigment is produced by chemical reaction and is thereafter micronized, the improvement which comprises mixing with the pigment before or during micronization an SiOH-containing organo-silicon compound with more than three Si atoms and an alkanol amine.

9. A process according to claim 8, wherein the alkanol-amine comprises at least one of triethanolamine, diethanolamine, triisopropanolamine, diisopropanolamine and 2-amino-2-methyl-propanol, the organosilicon compound is of the formula wherein n>3, R and R1 each independently is methyl, ethyl, phenyl or a group of the formula wherein m>1, the SiOH-containing organosilicon compound having Le A 19 539-?S

an OH:Si ratio within the range of about 1:2 to 1:10, and the pigment comprises TiO2 or a titanate carrying an inorganic coating, the organosilicon compound plus alkanolamine ranging from about 0.3 to 1% by weight of the pigment and the ratio by weight of the organosilicon compound to alkanolamine ranging from about 1:2 to 1:5.

10. A polymeric material pigmented with a pigment according to claim 1.

Le A 19 539-US