CA1112654A

CA1112654A - Metal complexes prepared by reacting an alkanolamine, a mixture of metal alkoxides and a polyhydric alcohol

Info

Publication number: CA1112654A
Application number: CA296,587A
Authority: CA
Inventors: Peter Womersley
Original assignee: Manchem Ltd
Current assignee: Manchem Ltd
Priority date: 1977-02-08
Filing date: 1978-02-07
Publication date: 1981-11-17
Also published as: SE7801418L; DE2804355C2; FR2379589B1; NL184627C; GB1588521A; NL184627B; DE2804355A1; FR2379589A1; NL7801191A

Abstract

ABSTRACT OF THE DISCLOSURE

Metal complexes prepared by the reaction of less than one mole of an alkanolamine with at least one mole of a metal al-koxide and a polyhydric alcohol. The complexes are useful imparting thixotropy to systems containing protective organic colloids.

Description

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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 -- 1 -- , ~ , 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.

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-Il.
~ L

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.

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~
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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.

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 '~3

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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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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.

24 The following e~ples illustrate the preparation o the metal complexes o~ the inyention, 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.
S I :'' 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, 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.

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 _~_ 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~ ~ ;
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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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Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows-

1. A metal complex prepared by reacting less than 1 mole of an alkanolamine with at least 1 mole of a mixture of alkoxides of two or more metals, with the remaining active sites on the metal complex being occupied by groups derived from a polyhydric alcohol.

2. A metal complex according to claim 1, wherein the metal is one or more of titanium, aluminum and zirconium.

3. A metal complex according to claim 1, wherein the molar proportion of the alkanolamine to the mixture of alkox-ides is within the range 0.25:1 to 0.9:1.

4. A metal complex according to claim 1, wherein the alkoxides are derived from aliphatic alcohols containing up to 4 carbon atoms.

5. A metal complex according to claim 1, wherein the polyhydric alcohol is glycerol.

6. A metal complex according to claim 1, in which said alkanolamine is derived from a lower primary alcohol having up to about six carbon atoms.

7. A metal complex according to claim 1, 3 or 4, wherein said alkanolamine is reacted with at least 1 mole of a mixture of an aluminum alkoxide and a titanium alkoxide.

8. A metal complex according to claim 5, wherein said alkanolamine is reacted with at least 1 mole of a mixture of an aluminum alkoxide and a titanium alkoxide.

9. A metal complex according to claim 1, wherein said mixture is a mixture of an aluminium alkoxide and a titanium alkoxide comprising aluminium and titanium in a molar ratio of 0.95 to 0.7Al/0.05 to 0.30Ti.

10. A metal complex according to claim 1, wherein said mixture is a mixture of an aluminium alkoxide and a titanium alkoxide comprising aluminium and titanium in a molar ratio of up to 0.25Al/0.75Ti.

11. A process for the preparation of a metal complex according to claim 1 which comprises reacting a mixture of alkoxides of two or more metals with (i) an excess of a polyhydric alcohol and (ii) an alkanolamine, wherein the reactions (i) and (ii) may be carried out in any order.

12. A process for the preparation of a metal complex according to claim 1, 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 and removing the monohydric alcohol by-product by distillation.

13. A process for the preparation of a metal complex according to claim 1, which comprises adding to a mixture of alkoxides of two or more metals, an excess of a polyhydric alcohol, heating the resulting mixture to remove by distil-lation the liberated alcohol and subsequently adding an alkanolamine.

14. A process according to claim 13, wherein the alkanol-amine is added after completion of the reaction between the polyhydric alcohol and the mixture of alkoxides as the product is cooling at a temperature below 100°C.

15. A process according to claim 13, which comprises mixing together alkoxides of two or more metals, adding an excess of the polyhydric alcohol, heating to remove by distillation the liberated alcohol and subsequently adding the alkanolamine.

16. A process according to claim 11 or 12, wherein said mixture is a mixture of an aluminum alkoxide and a titanium alkoxide.

17. A process according to claim 12 or 13, wherein said mixture is a mixture of an aluminum alkoxide and a titanium alkoxide.

18. A process according to claim 15, which comprises mixing an aluminium alkoxide and a titanium alkoxide.

19. A thixotropic composition containing a film-forming polymer and an organic colloid gelled with at least one metal complex according to claim 1.

20. A thixotropic composition according to claim 19, comprising from 0.25 to 5% by weight of the metal complex based on the film-forming polymer.

21. A thixotropic composition according to claim 19, wherein said mixture is a mixture of an aluminium alkoxide and a titanium alkoxide.

22. A thixotropic composition according to claim 20, wherein said mixture is a mixture of an aluminium alkoxide and a titanium alkoxide.

23. A thixotropic composition according to claim 21 or 22, wherein the molar ratio of said aluminium to said titanium in said metal complex is up to 0.25Al/0.75Ti, said composition also containing at least one of sodium hexa-metaphosphate and calcium ions.

24. A thixotropic composition according to claim 19, which contains at least one of sodium hexametaphosphate and calcium ions and wherein the metal complex comprises titanium as the major metal ingredient.

25. A thixotropic composition according to claim 19 or 20, which is free from sodium hexametaphosphate and wherein the metal complex comprises aluminum and titanium in a molar ratio of 0.95-0.7Al/0.05-0.30Ti.

26. A thixotropic composition according to claim 19 or 20, which is an emulsion paint.

27. A thixotropic composition according to claim 24, which comprises 0.25 to 5% by weight of the metal complex based on the film-forming polymer.