Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-04-10
2002-03-26
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S493000, C106S496000, C106S504000, C106S505000
Reexamination Certificate
active
06361595
ABSTRACT:
The present invention relates to a process for the preparation of pigment compositions. It more particularly relates to such compositions which are stabilised, especially with respect to the two major sources of pigment instability—microbial contamination and loss of colour strength on storage.
All organic matter is decomposable by micro-organisms which use it as their source of energy. According to estimates, microbial decomposition destroys materials to the value of at least one hundred thousand million dollars several times every year. Organic pigments are widely used for the colouration of formulations (such as inks, paints, toiletries etc.), and are themselves known to be carriers of wide-spread microbial contamination. As to aqueous formulations of pigments it is common practice to add chemical biocides in order to prevent microbial spoilage. Examples of such biocides are commercial preparations based individually or in mixtures on the following molecular types:
1,2-Benzisothiazolin-3-one (BIT);
N-butylbenzisothiazolin-3-one;
5-Chloroisothiazolin-3-one (5-CIT);
Methylisothiazolin-3-one (MIT);
N-octylisothiazolin-3-one;
Pentane-1,5-dialdehyde;
1,3,5-Trishydroxyethyltriazine;
Tetrakishydroxymethylphosphonium sulphate.
These biocides are, however, ineffective at preventing microbial contamination of pigments in the dry state.
In addition, many pigments, in particular monoazo pigments, suffer from the serious disadvantage of loss of colour strength on storage. It is known that some pigment powders may undergo apparent crystallographic modification when stored at ambient temperatures (for example, opaque Pigment Yellow 74 powders on storage increase in opacity and result in colouristically weaker paint compositions). There have been a number of attempts to produce in particular, storage-stable Pigment Yellow 74, e.g. U.S. Pat. Nos. 4,457,783 and 5,271,769. Both of these approaches suffer from the problem that they are commercially non-viable due to the high cost of the patented treatments and are difficult to manufacture consistently to achieve the desired stability.
It is thus an object of the present invention to provide a process for the preparation of pigment compositions which are stable with respect to microbial contamination and loss of colour strength, particularly the composition should be simple, reproducible in manufacture, and highly cost-effective.
Accordingly, a process for the preparation of stabilised pigment compositions has been found.
It has been found, too, that water-miscible quaternary ammonium compounds can be used to effectively stabilize pigments with respect to microbial contamination. In addition, it has been found that certain water-immiscible organic solvents stabilize against loss of colour strength on storage. Further, a novel composition, and its use have been found, too.
The inventive process is characterised by mixing a water-miscible quaternary ammonium compound, a water-immiscible organic solvent and a pigment. Preferably, the addition is carried out after the pigment synthesis.
In a preferred embodiment an aqueous slurry of a pigment, for example obtained by re-dispersing (usually according to common methods) a previously formed pigment press-cake (separated from its reaction slurry) in water, is mixed with the water-miscible quaternary ammonium compound and the water-immiscible organic solvent.
In those cases where a pigment is prepared in an aqueous medium, the water-miscible quaternary compound and the water-immiscible organic solvent may be added to the reaction slurry without first separating the pigment from the reaction slurry.
The treated pigment aqueous dispersion is preferably heated to a temperature usually in the range of from 50 to 100° C., particularly from 80 to 100° C. In general, the heat treatment is carried out for 30 to 200 minutes.
The treated pigment can be separated from the aqueous medium by known methods in the art such as filtration. Preferably it is then washed, stored as a press-cake and finally dried.
After drying, pigment powder may be prepared by common grinding processes such as hammer milling, sifter milling or classifier milling. It is also possible to use dryers which give the pigment directly in the powder form.
As pigments all known inorganic or organic pigments can be used, preferred are the following organic pigments: azo-containing pigments, phthalocyanines, quinacridones, indanthrones, flavanthrones, pyranthrones, perylenes, thioindigos, dioxazines, perinones, isoindolines, isoindolinones, diketopyrrolopyrroles, basic dye complexes and metal complexes.
Preferred pigments, especially with regard to stabilization against loss of clour strength, are monoazo pigments, particularly preferred arylamide pigments of formula I
where Ar
1
and Ar
2
independently from each other denote an unsubstituted phenyl group or substituted by one or two substituents selected from the group consisting of C
1
-C
4
alkyl, such as methyl, ethyl, n-, i-propyl, n-, i-, sec.- or tert.-butyl, preferably methyl, halogen such as fluorine, chlorine, bromine or iodine, preferably chlorine, nitro and C
1
-C
4
alkoxy such as methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, preferably methoxy, or a pigment of formula II
Ar
1
—N═N—Ar
3
II
where Ar
3
denotes a 2-hydroxynaphthyl group which may be further substituted by a carboxylic acid group or by a group —CONHAr
2
. Such pigments include C.I. Pigment Yellow 1, Yellow 3, Yellow 4, Yellow 5, Yellow 73, Yellow 98, Yellow 111 and especially Yellow 74; C.I. Pigment Red 3 and Red 12 and C.I. Pigment Orange 5.
The water-miscible quaternary ammonium compound may be a compound (or mixture of compounds) of formula III
wherein R
1
, R
2
, R
3
and R
4
independently of each other stand for C
1
-C
22
alkyl, C
2
-C
22
alkenyl, benzyl, pyridyl, quinolyl, isoquinolyl or polyoxyalkylenyl, and X
n−
is an anion such as a halide like chloride or bromide, hydroxide, sulphate, hydrogen sulphate, phosphate, hydrogen phosphate, dihydrogen phosphate, nitrate, preferably chloride and hydroxide, most preferably chloride, and n is 1, if the anion is monovalent, 2, if the anion is di-, or 3, if the anion is trivalent.
Preferred as water-miscible quaternary ammonium compounds are those wherein R
2
is benzyl. More preferred are compounds wherein R
2
is benzyl and R
1
and R
3
are preferably C
1
-C
4
alkyl, particularly preferred methyl, and R
4
is C
12
-C
22
alkyl or C
12
-C
22
alkenyl. Also preferred are those wherein R
1
, and R
2
are 2-hydroxyethyl and R
3
is C
1
-C
4
alkyl, especially methyl.
C
1
-C
22
alkyl stands for e.g. linear or branched C
1
-C
22
alkyl such as methyl, ethyl, n-, i-propyl, n-, i-, sec.-, tert.-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexydecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-uneicosyl, n-doeicosyl, preferably for linear or branched C
12
-C
22
alkyl such as n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexydecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-uneicosyl, n-doeicosyl.
C
2
-C
22
alkenyl stands for e.g. linear or branched C
2
-C
22
alkenyl such as ethenyl, n-, i-propenyl, n-butenyl, n-pentenyl, n-hexenyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl, n-undecenyl, n-dodecenyl, n-tridecenyl, n-tetradecenyl, n-pentadecenyl, n-hexydecenyl, n-heptadecenyl, n-octadecenyl, n-nonadecenyl, n-eicosenyl, n-uneicosenyl, n-doeicosenyl, preferably for linear or branched C
12
-C
22
alkenyl such as n-dodecenyl, n-tridecenyl, n-tetradecenyl, n-pentadecenyl, n-hexydecenyl, n-heptadecenyl, n-octadecenyl, n-nonadecenyl, n-eicosenyl, n-uneicosenyl, n-doeicosenyl.
Particularly preferred as water-miscible quaternary ammonium compounds are those of the formula IV
where n is an integer from 12 to 18 and X is an anion, preferably chloride.
In general, the ratio by weight of pigment to water-miscible quaternary ammonium compound is chosen in the range from 50:50 to 99.5:0.5, preferably from 90:10 to 99.5:0.5, particularly preferred from 94:6 to 99:
Ciba Specialty Chemicals Corporation
Crichton David R.
Green Anthony
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