Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to metal complexes. More
specifically, this invention relates to metal complexes which
may be used to confer a greatPr degree of structure to systems
containing protective organic colloids, for example, substan-
tially aqueous emulsion paints, solvent based foundry paints,
paint strippers and drilling muds.
Additives have been proposed, especially for use in
aqueous polymer systems containing organic colloids, which can
vary thestructure of the systems from a creamy consistency to
an immobile gel which liquefies under the shearing action of
a brush or roller. British patent specification No. 922,456
describes the use of water soluble titanium chelates as ad- '
ditives to impart thixotropy to emulsion compositions having a
water-soluble, hydroxyl group-containing organic colloid.
British patent specification No. 1,101,427 describes the use
of water solub7e zirconium or aluminum chelates in similar
systems. ,
An objéct of this invention is to provide improved
' metal complexes which can be used to impart thix,otropy to
aqueous or solvent based systems containing protective organic
colloids.
Accordingly, the present invention provides a metal
complex prepared by reacting less than 1 mole of an alkanol-
amine with at least 1 mole of a mixture of alkoxides of two or
more metals, with the remaining reactive sites on the metal
complex being occupied by groups derived from a pol~hydric
alcohol.
In another aspect of the invention there is provided
a thixotropic composition containing a flow-forming polymer
and an organic colloid, gelled with a metal complex of the
invention.
The invention also provides a method of preparing
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the metal complex which comprises reacting less than 1 mole of ~ ;
an alkanolamine with at least 1 mole of a mixture of alkoxides,
of two or more metals, and subsequently adding an excess of a
polyhydric alcohol. Any remaining monohydric alcohol co-
produced by the reaction is removed by distillation to
ensure none remains in equilibrium. ;
~ he invention further provides an alternative method
of preparin~ the metal complex which comprises adding to a mix-
ture of alkoxides of two or more metals, an excess of a poly-
hydric alcohol, heating the resulting mixture to remove by
distillation the liberated alcohol, and subse~uently adding an ~; ;
alkanolamine. The alkanolamine is introduced after the first
reaction between the polyhydric alcohol and the metal alkoxide
has been completed, preferably below 100C. as the product is
cooling down to about room temperature. The amount of poly-
hydric alcohol required to give the required excess of alcohol
is at least 2 moles of the alcohol per mole of metal present.
When dihydric alcohols are used, at least 3 moles of alcohol ~ -
are required per mole of metal present. In practice, the com- ;;
plex of the present invention is not isolated but is maintained
dissolved in a polyhydric alcohol for use as a gelling agent.
Usually the alcohol is that utilized in the preparation of the
complex.
The metal alkoxides used in the present invention are
derived from lawer aliphatic alcohols containing up to four
carbon atoms, such as methanol, ethanol, n-propanol, isopro-
panol, n-butanol and sec.butanol. The preferred metals are
titanium, aluminum and zirconium. In the invention a rnixture
of alXoxides of two or more metals is used in the
the process oE manufacture of the complexes. Typical metal
alkoxides are the iso-propoxides and butoxides of aluminum,
titanium and zirconium.
The al~anolamine used for preparing the metal com-
plexes may be a monoalkanolamine, a dialkanolamine or a tri-
alkanolamine derived from the lower primary alcohols having up
to about six carbon atoms, with the trialkanolamines being
preferred. In the preparation of the metal complex the
proportion of alkanolamine to metal alkoxide is preferably
from 0.25 to 0.9 moles alkanolamine to 1 mole o the metal
alkoxide.
Examples of polyhydric alcohols include the mono
and polyethylene glycols, 1,3,-butylene glycol, trimethylene
glycol and glycerol. For single metal complexes, polyethylene
glycols having average molecular weights of from about 200 to
about 400 andglycerol are preferred. Whereas, for mixed metal
complexes, diethylene glycol is a preferred alcohol.
When added to organic colloid solutions, the ~etal
complexes according to this invention show improved gelling
characteristics over gelling agents previously used. This
is attributable to the additional stabilizing effect of the
polyhydric alcohols. Although the polyhydric alcohols are
weak complexing agents, they are sufficiently strong to
delay hydrolysis sufficiently to allow the formation of
stronger links with the colloid itself.
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I ~Metal c,mplexes containing similar molar ratios Of metsl alkoxide ¦2 ¦to alkanolamine to those of the present invention but diluted by
3 ¦the presence of monhydric alcohol ~y-product, give cloudy lnferior
~els when added to or~anic colloid solutions. .
5 l ,,
6 ¦ The organic colloids which are gelled by the complexes
7 of the present invention may be ionic or non-ionic. Anionic col-
8 ¦loids are more reactive and consequently the metal must be more
9 stron~ly complexed in order to provide satisfactory stability.
¦Non-ioni,c colloids a~e less reactive towards the metal complexes
11 ¦and there~ore can be used ~ith a less strongly bound metal. Ex-
12 amples of or~anic colloids which are gelled on addition of the
13 ¦met~l oomplexes are cellulose derivatives such as sodium carboxy- ~ ~-
14 ¦methyl cellulose~ hydroxyethyl celluLose, hydroxypropylm~thyl ; '~
~S ¦cellulo~e and methyl cellulose; natural starches and gums and
16 ¦alkali metal and ammoniu~ salts of acrylic acid polymers.
17 "" ~ '
18 ¦ The final loading of themetal complex to the system con- ;;
19 ¦taining the protective colloid is determined by the degree o ~,
¦structure re~uired in the product. Generally additions of from
21 ¦about 0,25 to 5% by weight of the metal complex to an aqueous
22 ¦emulsion o~ a film-f,ormin~ polymer are suitable and particularly
23 suitable are addi,tions o~ from 0,25 to 2% by weight o~ the metal
24 ¦complex ba,sed on the weight o~ the emulsion. This range of addi-
¦tions o~ the metal complex is also typical for the other systems
26 ¦mentioned herein.
27 I
28 ¦ B~ way of example the ~nvention is further described by
29 reference to aqueous ilm-~orming compositions containing protec-
tive collo~ds, particularly emulsion paints. To be useful as ad-
31 ditives to emulsion paints to impaxt thixotropy and having the ap-
32 propXiate rheological properties, complexes must have the combina-
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1 tion of essential properties such as stability in aqueous systems
2 over a reasonably wide pH range, e.g. pH 5-ll, sta~ility against
3 compe~in~ paint ingredients and sufficient residual reac~ivity to
4 combins with the colloids to give the desired thixotropic gel.
S .
6 The reactivity o~ the final complex i~ dependent upon
7 the relative stren~th of the particular complexing agent selected.
8 ~ parti~l co~plex based on a strong complexing agent only occupy-
9 in~ some o~ the coordination sites on the metal still leaves sites
~vailable ~or reaction with the colloids in ~he paint. Weaker
11 complexing agents can be used in excess o the theoretical amount
12 because the bonds ~ormed with the colloid are stronger than those
13 in the original complex.
14
EmulsiOn paints conventionally contain, in addition to
16 f ilm-~orming polymer5 or co-polymers, other ingredients such as
17 extenders ~r fillers, ~or example barytes, blanc fixe, china clay,
18 mica, talc and whiting; plasticisers and dispersing aids such as
19 sodium hexametaphosphate~
2~
21 In ~ystems containin~ sodium hexametaphosphate and/or
22 calcium i~ns~ e.g.~ derived from whiting, the pre~erred metal com-
23 plexes are those containing titanium as the major or only metal
24 ingredient Titanium complexes show better stability against com-
petition from both sodiu~ hexametaphosphate and calcium ions than
26 the an~lo~ous aluminum and zirconium complexes which may prefer-
27 entiall~ ~eact with phosphate in some systems and precipitate or
28 form unsuitable complexes with calcium. It ls therefore preferred
29 to use aluminu~ or zirconium complexes in systems containing very
little or no phosphate or calcium salts.
31
32 However, I have found that complexes prepared containing
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the mixed metals of titanium and aluminum show synergism over
the single rnetal complexes. For paints containing sodium hexa-
metaphosphate, titanium is the main metal ingredient but I have
further found that the presence of aluminum up to a molar ratio
of 0.25Al/0.75Ti shows improved gelling characteristics over
the titanium complex alone. For sodium hexametaphosphate-free
paints, molar ratios of 0.95-0.7Al/0.05-0.30Ti have shown
improved gelling characteristics as illustrated in the follow~
ing Example 1.
EXAMPLE ~
:.
Mixed aluminum/titanium complexes containing a total
of 1 mole metal, 0.3 moles of triethanolamine and ~ moles of
diethylene glycol, were added at equal total metal loadings
to a 1% solution of the acrylic colloid Texicryl 13 301*.
The viscosity of the resulting colloids was measured and the
results obtained are recorded in Table I below. ~-
TABLE I
Moles Al1-.000.9S0.90 0.85 0.80 0.75 0.70
Moles Ti0.000.050.10 0.15 0.20 0.25 0.30
Viscosity60 78 87 125 130 125 85
(poises)
The ratio of alkanolamine to metal in the complexes
is mainly determined by the ionic nature of the colloid. As
mentioned in the foregoing, anionic colloids are more reactive
and consequently stronger complexes will be required than in ~ ;
the case of non-ionic colloids. The presence of an alkanol-
amine gives a metal comple~ of increased strength which is ~;
required to provide satisfactory solubility in aqueous systems.
*trademark
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The optimum amount of alkanolamine required for maximum
gelation varies depending on the paint system~ The following
Example 2 illustrates the variation in gelling characteristics
with the amount of alkanolamine used. ;~
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B
1~2~5~ ~
1 Example 2
2 Metal complexes were prepared comprisin~ 002 moles Ti,
3 0.8 ~oles Al~ 3.5 moles o~ diethylene ~lycol and 0.1-0.4 moles of :
4 triethanolamine. The resulting metal complexes were added to an
e~ulsion paint formulation ~ree of sodium hexametaphosphate and
6 the ViscositieS were measured. The results are recorded in
7 Table II below.
Ta~le II
~oles triethanolamine0.10 0,15 0.20 0.250.30 0.35 0.40
11 Viscosity (poises)423444 523 477563 482470
l2
13 The mixed complexes oX the present invention are prefer-
14 ably manufactured by mixing the alkoxides of the metals in the ap-
l~ ~opri~te molar pro~ortions, adding an excess of polyhydric alco-
l6 hol ~3 herein defined~ and heating, with or without vacuum, at a
17 temperature sufficient to remove the liberated alcohol by distilla-
1~ tion. The aesired amount o~ alkanolamine is added after the lib-
19 erated alcohol has been re~oved.
21 Alternatively~ single metal complexes may be mixed in
22 the desired proportions to ~orm suitable mixed metal complexes.
23
24 The following e~ples illustrate the preparation o the
metal complexes o~ the inyention,
26
27 Example 3 `
28 A reaction vessel was loaded with 204 ~rams of molten
29 aluminum iso~ropox~de. 112 ~rams of triethanolamine were added
o the yessel with stirrin~ and the vessel was heated sufficiently
31 to maintain a steady reflux o~ liberated isopropyl alcohol. 400
32 ~rams of polyethylene ~lycol of av. MW 300 were then added and the
_7
654 ~ ~
I ;refluxing was continued for a further 30 minutes.
3 ¦ Heating was reduced and all the liberated isopropyl al-
4 ¦cohol w~s removed by distillation under reduced pressure.
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6 ¦ A ~urther 200 ~r~s of polyethylene glycol were added
7 ¦to the product to provide a metal complex which was easily and
8 ¦homogeneously dispersible in aqueous systems.
9 ¦
¦ On ~ddition of the metal complex to a system containing ¦
II Ia watex~s~luble, polyacr~lic colloid, a strong stable gel was
I2 ¦obtained,
13
14 ¦ ExaInple 4
IS ¦ The procedure of Example 3 was repeated except that 126
16 ¦inste~d o~ 112 gra~s of txiethanolam:ine were used.
17
I8 ¦ On the addition o~ the metal complex product to an
19 ¦aqueous system containin~ sodium carboxymethyl cellulose a strong,
20 ¦stable gel was obtained~ ~ -
21 l
22 ¦ Example 5
23 I The ~rocedure o~ Example 3 was repeated except that 120
24 ¦grams instead o~ 112 g~ams ~f triethanolamine were used.
26 I On addition o~ the complex to aqueous systems containing
27 la polyacxylic coll~id or sodium carhoxymethyl cellulose and al-
28 ¦coholic systems co~tainin~ ~n acrylic colloid, strong stable gels
29 were o~t~ined in each case~
31 Exam~le 6
32 The procedure o~ Example 3 was repeated except tha-t 52.5
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6~4
1 ¦grams of diethanolamine were employed instead of the 117 grams of
2 ¦triethanolamine.
4 ¦ The metal complex product was suitable for the gelation
¦of ~ueous and ~lcoholic solutions o~ non-ionic colloids.
7 Example 7
8 A reaction vessel was loaded with 327 grams of zirconium
isop~opoxide. 112 g~ams ~f triethanolamine were introduced into
the vessel with stirrin~ and the vessel was heated until a steady
1l reflux of isopropyl alcohol was maint~inedO 400 grams o~ poly-
12 ethylene glycol of av. MW 300 were added and the refluxing was
3 ¦ continued for a further 30 minutes. Heating was reduced and all
th~ liberated isopropyl alcohol w~s removed by distillation unde~
1S ¦~educed pressure.
l6
17 ¦ A further 200 grams o~ polyethylene glycol were added
18 ¦to the product to provide a metal complex which was easily and
19 ¦homogene~usly dispersible in aqueous systems.
21 I Example 8
22 ¦ 41 ~s o~ aluminum isopropoxide and 179 grams of ti-
23 ¦taniu~ isopropoxide ~ere mixed together in a reaction vessel.
24 424 gra~s o~ diethylene glycol were added with stirring and the
¦yessel w~s heated to re~ove ~11 the libe~ated isopropyl alcohol
26 ¦~Y aistillation.
27 l
28 ¦ The product was allowed to cool and during the colling
29 cycle 50 grams of triethanolamine were added with stirring,
31 ¦ The metal compleY. produced was suitable for rendering
32 thixotropic emulsion paints containing phosphates and/or
_g_
l~lZô54
I calcium s~lts~ ~ ;
~,~
3 Similar results are obtained wi~h other alkanolamines
such as ethanol~mine, isopropanolamine, di-isopropanolamine,
butanola~ine~ and the like~
7 Various chan~es ~nd modifications of the invention can
8 be made! and, to the extent that such variations incorporate the
9 spirit o~ tiliS inVention, they are intended to be included within
SO the sc~pe of the appended claims.
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27
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