Dispersion of pigments

Details Dispersion of pigments Dispersion of pigments

2000-10-20

2003-06-24

Lovering, Richard D. (Department: 1712)

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

C106S447000, C106S460000, C106S476000, C516S078000, C516S920000, C524S088000

Reexamination Certificate

active

06582505

ABSTRACT:

This invention relates to dispersions and in particular to aqueous dispersions of pigments, their production and use in paint and surface coating formulations.
Surfactants are frequently used to help in dispersing pigments used in the manufacture of paint and surface coating formulations. Alkyl phenol alkoxylates, especially ethoxylates (APE's), are commonly used for this purpose. Although they are effective surfactants, APE's are increasingly coming under scrutiny for alleged adverse environmental effects. Accordingly replacements for these surfactants have been sought for some time.
The present invention is based on our finding that certain classes of alcohol alkoxylates, particularly ethoxylates, can give aqueous pigment dispersions and paints and surface coating formulations including such dispersions with properties comparable with APE dispersants.
Accordingly, the present invention provides an aqueous dispersion of a pigment which includes as a dispersant at least one branched primary alcohol alkoxylate of the formula (I):
[CH
3
.(CH
2
)
n
][CH
3
.(CH
2
)
m
].CH.[(CH
2
)
p
.O.(AO)
q
.H]  (I)
where
n and m are each independently from 1 to 13; and p is 1 or 2;
such that n+m+p is from 5 to 19, particularly from 7 to 17;
AO is an alkylene oxide residue having from 2 to 4 carbon atoms and is particularly an ethylene oxide residue, a propylene oxide residue or a mixture of ethylene oxide and propylene oxide residues; and
q is from 5 to 40.
In compounds of the formula (I), n and m are desirably each independently at least 2 and not more than 12, p is desirably 1 and the total number of carbon atoms in the branched alkyl residue is desirably from 10 to 20, particularly 12 to 18 (corresponding to n+m+p from 7 to 17, particularly 9 to 15).
The alkylene oxide groups are desirably all ethylene oxide residues although mixtures of ethylene oxide and propylene oxide residues, particularly having a molar ratio of ethylene oxide residues to propylene oxide residues of from 1:5 to 10:1, can be used even though they will be less hydrophilic than polyethoxylates. When the alkylene oxide residues are mixed ethylene oxide and propylene oxide residues, the polyalkyleneoxy chain can be a random or block copolymeric chain. Within the range 5 to 40, q is desirably 5 to 25. More specific ranges depend on the nature of the pigment being dispersed (see below). The relative size of the hydrophile and hydrophobe will affect the HLB of the dispersing agent and these relative sizes may be chosen to provide specific properties in this respect depending on the circumstances of use. The number of units in the polyoxyalkylene chain, ‘q’, is an average value and may be non-integral.
The alkoxylate compounds of the formula (I) used in this invention can be made by alkoxylation of the corresponding ranched primary alcohols under conventional alkoxylation conditions, typically under alkali catalysis, particularly alkoxide catalysis e.g. using NaOH or KOH to form alkoxide in situ). The branched primary alcohols can be substantially wholly branched alcohols as can be made by the guerbet process e.g. 2-butyloctanol, 2-butyldecanol, 2-butyldodectanol, 2-hexyloctanol, 2-hexyldecanol, 2-hexyldodectanol and 2-octyldecanol; or they can be mixtures of the above branched primary alcohols with linear primary alcohols (or analogous alcohols containing methyl branches), containing similar numbers of carbon atoms, such as can be made by the oxo process starting with internal olefins under conditions where the double bond can migrate. Of course, mixtures can be made by mixing the corresponding compounds, but this is likely to be economically unattractive. Commercially available branched primary alcohols can be substantially pure or can include up to about 50% of substantially linear alcohols. In such mixed materials the proportion of branches material having branches at least two carbon atoms long is usually at least about 30%, more usually about 40% and the proportion of branched material having branches at least three carbon atoms long is usually at least about 20%, more usually about 30%. On alkoxylation, such materials give mixtures of linear and methyl branched alcohol alkoxylates and compounds of the formula (I).
The dispersing agent used in making the pigment dispersion of this invention may include other surface active agents. In particular, such other surfactants are other alcohol alkoxylates, particular ethoxylates. Typically such other ethoxylates are linear or substantially linear materials (see above). The proportion of branched primary alkyl compounds of the formula (I) (having branches at least two carbon atoms long in the alkyl chain) used in practical dispersing agents is desirably at least about 30% and more usually at least about 40%. Desirably, the proportion of branched material having branches at least three carbon atoms long is at least about 30%, more usually at about least 30%. Overall the proportion of branched material (including methyl branching) is typically at least about 40% and more usually at least about 50%. The specific proportion of branched alcohol ethoxylate used may depend on the nature of the pigment being dispersed (see further below).
This invention is applicable to the manufacture of aqueous dispersions of a wide range of pigments especially for ultimate use in paints or other surface coatings. The specific pigments referred to below by Colour Index references are sometimes shortened to the colour and the number i.e. omitting the phrase “C.I. Pigment” from the full reference. Suitable pigments include inorganic pigments such as titanium dioxide, pigmentary iron oxide (Fe
2
O
3
) and organic pigments such as phthalocyanine blue and green pigments, for example various forms of Blue 15, such as Heliogen blue L 7080 from BASF (Blue 15:3), Monastral blue FGX from Zeneca (Blue 15:4), Phthalocyanine blue from Minerva (Blue 15) and Heliogen blue L 6920 from BASF (Blue 15:1) and Green 7 such as Monastral green GNX-C from Zeneca and Heliogen green L 8730 from BASF; butanamide pigments for example Yellow 74, such as Hansa Bright yellow 2GX70 from Hoechst; naphthcarboxamide pigments for example Red 112 and Red 170, such as Sico Echtrot L 3855 from BASF (Red 112) and Novoperm red 3RK70 from Hoechst (Red 170); indolodioxazine pigments for example Violet 23, such as Monolite violet RN from Zeneca; benzimadazole pigments for example Orange 36, such as Novoperm orange HL70 from Hoechst; azo pigments for example Yellow 155, such as Sandorin Jaune 5GD from Clariant: and diazo pigments for example Red 214 such as Sandorin Rouge BN-P from Clariant; and carbon black, and similar materials.
Among the organic pigments, a division by specific surface area (e.g. as measured by the BET method) can be noted. Generally there are two groups of pigments a first group with a relatively low BET surface area e.g. from 10 to 40 m
2
.g
−1
, particularly the red, orange and yellow pigments, and a second group with a relatively high BET surface area e.g. from 40 to 80 m
2
.g
−1
(or possibly higher), particularly blue and green, phthalocyanine pigments, and violet pigments. For pigments with a relatively low BET surface area e.g. up to about 40 m
2
.g
−1
, particularly from 10 to 40 m
2
.g
−1
, particularly from 10 to 30 m
2
.g
−1
, more particularly those which are red, orange and yellow pigments it is advantageous to use a dispersing agent with a high proportion of branched chain alkyl moieties so that it is thus desirable that the proportion of branched alkyl compounds of the formula (I) in the dispersing agent used is at least 75%, more usually at least 85% and will usually be at least 95% e.g. about 100%. For pigments with a relatively high BET surface area e.g. at least 40 m
2
.g
−1
, particularly from 40 to 80 m
2
.g
−1
, more particularly at least about 60 m
2
.g
−1
, particularly those which are blue, green and violet pigments, the proportion of branched chain alkyl moieties is less important, b

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