Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Primarily organic continuous liquid phase
Reexamination Certificate
2000-08-24
2003-04-22
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Primarily organic continuous liquid phase
C106S031860, C106S476000, C106S499000, C510S356000, C516S076000, C516S078000, C516S079000, C516S920000, C526S911000, C568S607000, C568S608000
Reexamination Certificate
active
06552091
ABSTRACT:
RELATED APPLICATIONS
This application claims priority to German application 199 40 797.5, filed Aug. 27, 1999, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to block-copolymeric polyalkylene oxides containing styrene oxide, obtained by alkoxylation, and their use as low-foam pigment wetting agents in aqueous pigment pastes with or without cosolvent and in aqueous and low-solvent coating materials and printing inks.
2. Description of the Related Art
For the dispersion of fillers and pigments in liquid media it is common to make use of dispersants in order to reduce the mechanical shear forces required for effective dispersing of the solids and at the same time to obtain very high degrees of filling. The dispersants assist in the disruption of agglomerates, wet and/or cover, as surface-active materials, the surface of the particles to be dispersed, and stabilize the particles against unwanted reagglomeration.
In the production of inks and paints, wetting agents and dispersants facilitate the incorporation of pigments and fillers, which are important formulation constituents that determine significantly the visual appearance and the physicochemical properties of coatings. Optimum utilization requires firstly that the solids are distributed uniformly in paints and inks and secondly that the state of distribution, once attained, is stabilized. In many cases, the stabilizing effect is perceived on binder components as well. This is particularly the case with acidic (styrene) acrylates, which are used, in particular, in the preparation of printing inks. In these cases, pigment wetting agents are used, whose action consists in wetting very rapidly the pigment surface, which displace the air from the surface of the pigments, and replace it by the liquid of the millbase. Especially when solids with a nonpolar surface are used in aqueous coating materials, the wetting must be assisted by wetting agents. This permits favorable development of color strength and thus virtally ideal utilization of the energy introduced.
Moreover, especially in the architectural paints industry, use is made of aqueous pigment pastes, with or without cosolvent, which are used universally for tinting in aqueous emulsion paints on an all-acrylate, styrene acrylate or silicate basis and in nonpolar decorating paints based on long-oil alkyds.
Particularly suitable for this purpose are alkylphenol ethoxylates or fatty alcohol alkoxylates, which also contribute to steric stabilization of dispersed pigment states. The high-performance alkylphenol ethoxylates have come under criticism on ecotoxicological grounds, and their use in laundry detergents and cleaning products is already banned in many countries. Similar bans may be expected for the paint and printing inks industry. Fatty alcohol ethoxylates in many cases fail to achieve the good properties of the alkylphenol-ethoxylates. Since they lack groups capable of adsorption, the pigment wetting properties are less pronounced. Moreover, the nonadsorbed portion of this product group, in particular, has the undesirable effect of stabilizing the foam, which can be suppressed only with the aid of substances having a strong defoaming action, which, in turn, induce other adverse phenomena, such as unwanted surface defects. The use of numerous dispersing additives also has a negative impact on the water resistance or light stability of coatings.
It is known to use of polyethylene glycol ethers as foam suppressant additives in low-foam aqueous cleaning products (EP-A-0 303 928, DE-A42 25 236), for papermaking (DE-A-22 25 318), or to use mixed polyglycol derivatives—containing oxyethylene and oxypropylene—as wetting agents in inks for inkjet printers (EP-A-0 447 896), and as foam suppressant additives in dishwashing compositions (U.S. Pat. No. 4,836,951).
However, applications of block copolymers containing styrene oxide in the coatings and printing inks industry are largely unknown. One exception (DE-A-198 06 964) is constituted by polystyrene oxide-block(b)-polyalkylene oxide copolymers which are reacted starting from a monofunctional starter alcohol by sequential addition reaction of at least 2 mol of styrene oxide and an alkylene oxide and subsequent phosphorylation to give the corresponding phosphoric esters.
Therefore, there is a high demand for highly adsorptive pigment wetting agents which, in particular, have a minimal foam stabilizing effect.
In particular, there should also be a positive effect on other coatings properties, such as, for example, the water resistance of coatings produced, or optical properties such as gloss and haze.
OBJECTS OF THE INVENTION
It is an object of the present invention to meet the above-mentioned requirements, in the context of which a high pigment affinity ought to go hand in hand with a low tendency toward foam stabilization, without adverse effects on other, essential coatings properties.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention, in a first embodiment, by means of block-copolymeric polyalkylene oxides of the general formula I:
R
1
O(SO)
a
(EO)
b
(PO)
c
(BO)
d
R
2
, (I)
where
R
1
is a straight-chain or branched or cycloaliphatic radical, preferably having 8 to 13 carbon atoms,
R
2
is hydrogen, an acyl radical, alkyl radical or carboxylic acid radical, preferably having in each case 1 to 8 carbon atoms,
SO is styrene oxide,
EO is ethylene oxide,
PO is propylene oxide,
BO is butylene oxide, and
a is from about 1 to about 1.9,
b is from about 3 to about 50,
c is from 0 to about; 3, and
d is from 0 to about 3,
a, c or d being other than 0, and b being>=a+c+d.
DETAILED DESCRIPTION OF THE INVENTION
An important factor in obtaining the properties of the compounds are the numerical values of the indices a, b, c and d. Indice a indicates the number of styrene oxide groups, which, especially in the case of hydrophobic pigment surfaces, provides for high adsorption a here has a value of from about 1 to about 1.9. Indice b defines the number of ethylene oxide groups. It being possible for b to adopt values of from about 3 to about 50, preferably from 10 to 30. Indice c defines the number of propylene oxide groups and has a value of from 0 to about 3, preferably from about 1 to about 3. Indice d determines the number of butylene oxide groups and likewise has a value of from 0 to about 3, preferably 1. The skilled worker is well aware that the compounds are present in the form of a mixture having a distribution governed essentially by laws of statistics. It is the case that mixed alkoxylates are intended for use in accordance with the invention. By means of the different alkylene oxide monomers and their fraction in the overall polymer it is possible to exert specific control over the hydrophobic/hydrophilic balance such that it is possible to tailor any steric requirements of the pigment surface, and, in particular, to tailor the compatibility in the respective coating system. The alkylene oxide groups may be arranged at random or in blocks. Particular preference is given to block arrangements with fairly hydrophobic terminal groups such as propylene oxide or, in particular, butylene oxide. The ratio of the molar amounts of the ethylene oxide groups to the other hydrophobic alkylene oxide groups is as follows: b>=a+c+d. It has been found that the structures of the polymers are of critical importance to the advantages achieved in accordance with the invention.
Another important factor is the structures of the straight-chain or branched or cycloaliphatic radicals R
1
, which can be used to control the space requirement of the surfactants at interfaces. For many applications, branched aliphatic radicals R
1
are advantageous for foam suppression. Especially preferred are branched C
9
alcohols as starting agents for the alkoxylation. Particular preference is given to 3,5,5-trimethylhexan-1-yl and 2,6-dimethylheptan-4-yl radicals; the skilled worker is well aware that the alcohols on which these
Boinowitz Tammo
Reuter Ellen
Silber Stefan
Venzmer Joachim
Frommer & Lawrence & Haug LLP
Goldschmidt AG
Lovering Richard D.
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