WO2002049960A2

WO2002049960A2 - Anti-corrosion agents

Info

Publication number: WO2002049960A2
Application number: PCT/EP2001/014605
Authority: WO
Inventors: Martin Müller
Original assignee: Ciba Specialty Chemicals Holding Inc.
Priority date: 2000-12-20
Filing date: 2001-12-12
Publication date: 2002-06-27
Also published as: WO2002049960A3; AU2002233244A1

Abstract

Tripolyphosphates of formula (I) MaHbP3O10 (I), wherein M is NR4, NR3H, NR2H2, NRH3, NH4, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C1-C8alkyl, C1-C8alkoxy, or phenyl unsubstituted or mono- to tri-substituted by C1-C8alkyl, C1-C4alkoxy or by halogen, and wherein a (valency of M) + B = 5, and a = 1, 2, 3, 4 or 5 and B = 0, 1, 2, 3 or 4, and mixtures thereof, further tripolyphosphates that have been after treated with one or more bases, processes for the preparation thereof, their use as anti-corrosion agents and as biocides (anti-microbial agents) and, where applicable, as encrustation-inhibiting agents.

Description

Anti-corrosion agents

The present invention relates to tripolyphosphates of formula I and to mixtures thereof, to mixtures according to the invention that have been aftertreated with a base, to processes for their preparation, and to their use as anti-corrosion agents and as anti-microbial and, where applicable, encrustation-inhibiting agents.

Phosphate-containing anti-corrosion agents are known. For example, JP 2 986 963 B2 describes mixtures of AIH₂P₃O₁₀ and bismuth- and ZnO-containing compounds, and

JP 6 346 258 A2 describes mixtures of FeH₂P₃O₁₀ and ZnO.

JP 06 287 009 A1 describes FeH₂P₃O₁₀ and the preparation thereof. SU 1 816 803 A1 discloses the corresponding calcium analogue Ca₂HP₃O₁₀ in admixture with further calcium phosphates. The single compound - Ca₂HP₃O₁₀ - is mentioned as a fertiliser in Ind. Eng.

Chem. 1947, page 1667 ff..

The synthesis and the use of Zn₂NaP₃O₁₀, Mn₅(P₃O₁₀)₂, Cu₅(P₃O_1Q)₂ and Sr₅(P₃O₁₀)₂ in corrosion-inhibiting compositions is described in US-A-4 511 404. Those anti-corrosion compounds are produced from an aqueous solution by reaction, for example, of appropriately soluble nitrates, chlorides etc. with Na₅P₃O₁₀.

A disadvantage of the above-mentioned anti-corrosion agents is that they lack suitability for use in film-forming media (e.g. surface-coatings, especially in the case of the mixtures from SU-A1 1 816 803) and they exhibit an excessive number and size of blisters as well as a too high degree of infiltration when such agents, with the customary additives, are tested for their use as anti-corrosion agents in accordance with DIN regulations, and also that they contain zinc compounds, since according to the EPA directive EPCRA (Emergency Planning and Community Right-To-Know, Section 313) zinc compounds in dust form are classified as toxic in the USA.

The object of the present invention was therefore to provide improved anti-corrosion agents that do not have the above-mentioned disadvantages. Furthermore, attention was to be paid to improved environmental protection measures during production and use, and the efficiency was likewise to be improved as compared with processes from the prior art, e.g. by the use of suitable raw materials. In addition, the known very good anti-corrosion properties of chromium-containing products, such as zinc chromate, were to be achieved using products that do not contain chromium. Moreover, anti-corrosion agents containing no zinc, or containing less zinc than customary zinc-containing anti-corrosion agents, were to be provided.

The above-mentioned aim has been achieved by tripolyphosphates of formula

M_aH_bP₃O₁₀ (I), wherein M is NR₄, NR₃H, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C_rC₈alkyl, CrCgalkoxy, or phenyl unsubstituted or mono- to tri-substituted by C₁-C₄alkyl, C_rC₄alkoxy or by halogen, and wherein a (valency of M) + b = 5, and a = 1 , 2, 3, 4 or 5 and b = 0, 1 , 2, 3 or 4, and also mixtures thereof and mixtures according to the invention that have been aftertreated with a base.

Especially preferred tripolyphosphates of formula I are Mn₂HP₃O₁₀, Mg₂HP₃O₁₀, Ca₂HP₃O₁₀, Sr₂HP₃O₁₀, Bι^'H₂P₃O₁₀ and Zn₂HP₃O₁₀, and also mixtures thereof with one another and/or with AIH₂P₃O₁₀ and/or FeH₂P₃O₁₀.

According to the invention, the above-mentioned formula (I) also includes any corresponding compounds containing water of crystallisation, special preference being given to the aluminium and iron dihydrogen tripolyphosphates that contain water of crystallisation AIH₂P₃O₁₀x(1-2)H₂O and FeH₂P₃O₁₀x(1-2)H₂O and to mixtures that contain those compounds together with Ca₂HP₃O₁₀, Sr₂HP₃O₁₀, BiH₂P₃O₁₀, Zn₂HP₃O₁₀ and/or Mn₂HP₃O₁₀.

The tripolyphosphates I according to the invention are usually prepared as follows:

(a) a mixture of

(A) water and

(B) M_e(H₂PO₄)_e, wherein e is the valency of M and may be 1 , 2, 3, 4 or 5, and M is NR₄, NHR₃, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C_rC₈alkyl, CrCgalkoxy, or phenyl unsubstituted or mono- to tri-substituted by C.,-C₄alkyl, C^Calkoxy or by halogen, either

(a1) is heated first to a temperature in the range from 120 to 250°C, preferably from 180 to 220°C, for from one to five hours, preferably from two to four hours, and then to a temperature in the range from 250 to 500°C, preferably from 280 to 350°C, for from one minute to ten hours, preferably from 15 minutes to five hours, or (a2) is heated directly to a temperature in the range from 250 to 500°C, preferably from

280 to 350°C, for from one minute to 20 hours, preferably from 30 minutes to ten hours, (b) then water is added at a temperature in the range from 20 to 150°C, preferably from 50 to 100°C, the ratio by weight of water to product from (a) being selected in the range from 1 : 1 to 20:1 , preferably from 2:1 to 10:1, and the treatment being carried out for from one to 20 hours, preferably from two to ten hours, and the reaction mixture from (b) is then filtered, washed with water and, if desired, dried.

The reaction time for the calcination in a temperature range of from 250 to 500°C is usually selected in the range of from one minute to ten hours (a1) or twenty hours (a2), the reaction time being chosen inter alia in dependence upon the desired dimensions of the end product. Especially for the preparation of materials having a small layer thickness, the reaction can be terminated after a very short time, for example within one minute.

In step (b) water can be added to the calcined product immediately after the calcination, the product thus also being cooled at the same time. It is also possible, however, to use steam to carry out the hydrolysis.

The d/hydrogen phosphates Ca(H₂PO₄)₂, AI(H₂PO₄)₃, Fe(H₂PO₄)₃ and M_e(H₂PO₄)_e are generally known or can be prepared by known methods, e.g. from corresponding metal oxides, hydroxides or carbonates (see e.g. Hollemann-Wiberg, Lehrbuch der Anorganischen Chemie, 81st-90th Edition, Walter de Gruyter, Berlin 1976, pages 449-458).

AINH₄HP₃O₁₀ and ZrNH₄HP₃O₁₀ can also be prepared by heating AlCI₃ and ZrCI₄, respectively, in the presence of NH₄H₂PO₄ to above the decomposition temperature or sublimation temperature. Especially preferred starting compounds M_β(H₂PO₄)_β are Mn(H₂PO₄)₂, Mg(H₂PO₄)₂, Ca(H₂PO₄)₂, Sr(H₂PO₄)₂, Bi(H₂PO₄)₃ and Zn(H₂PO₄)₂, and also mixtures thereof with one another and/or with AI(H₂PO₄)₃ or Fe(H₂PO₄)₃.

A further embodiment relates to mixtures comprising (a) a tripolyphosphate I and/or (b) AIH₂P₃O₁₀ and/or (c) FeH₂P₃O₁₀ and/or (d) Ca₂HP₃O₁₀.

A preferred embodiment thereof relates to mixtures comprising

(a) from 0.1 to 99.9 % by weight of a tripolyphosphate I, and

(b) from 99.9 to 0.1 % by weight of a second component, consisting of (b1) from 0 to 100 % by weight of AIH₂P₃O₁₀ and

(b2) from 0 to 100 % by weight of Ca₂HP₃O₁₀, (b1) and/or (b2) being present in an amount of at least 0.1 % by weight, and the sum of the percentages by weight both of (b1) and (b2) and of (a) and (b) being 100 % by weight.

The tripolyphosphate mixtures according to the invention are prepared in customary manner e.g. as follows: (a) a mixture of

(A) water,

(B) AI(H₂PO₄)₃ and/or Ca(H₂PO₄)₂ and/or Fe(H₂PO₄)₃, and

(C) M_e(H₂PO₄)_e, wherein e is the valency of M and may be 1 , 2, 3, 4 or 5, and M is NR₄, NHR₃, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C.|-C₈alkyl, C_rC₈alkoxy, or phenyl unsubstituted or mono- to tri-substituted by C,-C₄alkyl, C₁-C₄alkoxy or by halogen, either

(a1) is heated first to a temperature in the range from 120 to 250°C, preferably from 180 to 220°C, for from one to five hours, preferably from two to four hours, and then to a temperature in the range from 250 to 500°C, preferably from 280 to 350°C, for from one minute to ten hours, preferably from 15 minutes to five hours, or

(a2) is heated directly to a temperature in the range from 250 to 500°C, preferably from 280 to 350°C, for from one minute to 20 hours, preferably from 30 minutes to ten hours, (b) then water is added at a temperature in the range from 20 to 150°C, preferably from 50 to 100°C, the ratio by weight of water to product from (a) being selected in the range from 1 :1 to 20: 1 , preferably from 2: 1 to 10: 1 , and the treatment being carried out for from one to 20 hours, preferably from two to ten hours,

(c) and the reaction mixture from (b) is then filtered, washed with water and, if desired, dried.

Examples of ammonium phosphates are ammonium dihydrogen phosphate, diammonium hydrogen phosphate and tert-ammonium phosphate.

CrC₈Alkyl is methyl, ethyl, n-propyl, isopropyl, n-, sec-, iso- or tert-butyl, n-pentyl, n-hexyl, n- heptyl and n-octyl, especially C₁-C₄alkyl, such as methyl, ethyl, n-propyl, isopropyl and n-, sec-, iso- or tert-butyl.

Ci-CsAlkoxy is methoxy, ethoxy, n-propoxy, isopropoxy, n-, sec-, iso- or tert-butoxy, n-pentyl- oxy, n-hexyloxy, n-heptyloxy and n-octyloxy, especially C₁-C₄alkoxy, such as methoxy, ethoxy, n- or iso-propoxy and n-, sec-, iso- or tert-butoxy.

Halogen is fluorine, chlorine, bromine or iodine, preferably chlorine.

In a preferred embodiment, for the purpose of better hydrolysis and avoiding inclusions the aqueous reaction mixture obtained in (b) can be comminuted using customary wet grinding tools, such as a ball mill, a high-speed mixer or a heavy-duty stirring device, such as Ultra- turrax®, for a period of from three to 60 minutes, or grinding is carried out until a homogeneous suspension having particle sizes of preferably less than 100 μm has been formed.

A preferred embodiment of the present invention relates to a further process for the preparation of tripolyphosphates I according to the invention and mixtures thereof, in which process an oxide, hydroxide, carbonate, hydrogen carbonate, silicate, primary, secondary or tertiary phosphate, pyrophosphate, hydrogen pyrophosphate, di-, tri- or poly-phosphate, metaphosphate, metapolyphosphate, nitrite, nitrate, halide or sulfate, of a metal selected from the group consisting of Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni and Co and also calcium, aluminium and iron, or an ammonium hydroxide, carbonate, hydrogen carbonate, phosphate (the phosphate being primary, secondary or tertiary), pyrophosphate, hydrogen pyrophosphate, diphosphate, triphosphate, polyphosphate, metaphosphate, metapolyphosphate, nitrite, nitrate, halide or sulfate, is reacted with phosphoric acid or a phosphate-containing compound and the product is subsequently calcined, for example as described above under (a1) or (a2).

According to observations hitherto, it is not important to the success of the invention whether phosphoric acid or a suitable phosphate-containing compound is added to the components that are preferably present in water, or wee versa. It is preferable for the components that are present in water, for example in the form of a solution or suspension, to be added to the phosphoric acid. It is also possible, for the purpose of finely divided calcination, to carry out the reaction in a spray-dryer.

Furthermore, according to observations hitherto, it is not important to the success of the invention whether phosphoric acid or a suitable phosphate-containing compound is added to the components that are preferably in dry-premixed form, or Wee versa. It is preferable for the components that are in dry-premixed form to be added in portions or in a controlled manner continuously to the phosphoric acid or to the phosphate-containing compound. The process according to the invention can be carried out analogously to the process described in US-A-4 147 758 also in the form of an extrusion process having a mixing zone and a subsequent reaction zone (calcination).

The molar ratio of Ca compound (starting material) to Al compound (starting material), Ca compound (starting material) to Fe compound (starting material), or Al compound to Fe compound (starting materials) - insofar as at least two of those compounds are used - is selected generally in the range from 0.01 :1 to 100:1 , preferably from 0.1 :1 to 10:1.

The molar ratio of Ca compound (starting material) (or Al compound or Fe compound where a Ca compound is not being used) to M_e(H₂PO₄)_e (starting material) is selected generally in the range from 0.01 :1 to 100:1 , preferably from 0.1 :1 to 10:1.

The molar ratio of M_e(H₂PO₄)_e to phosphoric acid or phosphate-containing compound is selected generally in the range from 0.1 :1 to 10:1 , preferably from 0.5:1 to 2:1 , for the formation of primary phosphates.

It is customary to use phosphoric acid having a concentration in the range from 40 to 100 % by weight, preferably from 50 to 85 % by weight, more especially technical grade 85 % or 75 % by weight phosphoric acid.

Instead of phosphoric acid it is also possible to use corresponding amounts of P₂O_s or alkali metal dihydrogen phosphates, such as sodium or potassium dihydrogen phosphate or ammonium dihydrogen phosphate.

It is likewise possible to replace some or all of the Al, Ca, Fe, metal or ammonium component by secondary, tertiary or higher phosphates that are obtainable, for example, at a corresponding temperature in the range of, for example, from 270 to 500°C in an acidically digested form, e.g. using phosphoric acid.

The components are generally mixed together in known manner, for example by stirring.

The reaction temperature is generally selected in the range of from 20 to 160°C, preferably from 50 to 110°C.

The reaction time is generally selected in the range of from 3 to 240 minutes, preferably from 15 to 60 minutes. The reaction mixture so obtained is customarily worked up using methods known per se, without isolation of the resulting primary phosphates, by carrying out calcination as described above under points (a1) and (a2) at temperatures in the range of from 250 to 500°C.

A further preferred embodiment relates to mixtures comprising

(a) from 0 to 99.9 % by weight of a tripolyphosphate I according to claim 1 ,

(b) from 0 to 99.9 % by weight of AIH₂P₃O₁₀

(c) from 0 to 99.9 % by weight of Ca₂HP₃O₁₀

(d) from 0 to 99.9 % by weight of FeH₂P₃O₁₀

(e) from 0.1 to 99.9 % by weight of at least one base selected from the group consisting of oxides, hydroxides, carbonates, phosphates, silicates and metasilicates of alkali metals, alkaline earth metals and of iron, cobalt, nickel, zinc, aluminium, titanium, zirconium, yttrium, vanadium, cerium, lanthanum, manganese, bismuth, copper, silver and tin, and primary, secondary and tertiary amines, polyamines, and ammonium compounds, it being necessary for at least one of components (a) to (c) to be present in an amount greater than 0 % by weight, and the sum of the weights of the individual components being 100 % by weight, with the proviso that when a mixture of AIH₂P₃O₁₀ and M_aH_bP₃O₁₀, wherein M = Bi or Bi and Mn, is used or when FeH₂P₃O₁₀ is used, the base does not contain zinc.

According to the invention, the phrase "at least one base" generally includes from 1 to 5 bases, it being preferable to use one base or a mixture of two bases, for example Ca(OH)₂ and ZnO.

Preferred bases are CaSiO₃, Ca(OH)₂, MgSiO₃, MgO, Mg(OH)₂, CaO, SrCO₃, SrSiO₃ and ZnO, special preference being given to CaSiO₃, Ca(OH)₂ and ZnO.

A further embodiment therefore relates also to a process for the preparation of the mixtures mentioned immediately above, wherein a tripolyphosphate I, AIH₂P₃O₁₀, Ca₂HP₃O₁₀ or FeH₂P₃O₁₀ or a mixture thereof is treated with at least one base selected from the group consisting of oxides, hydroxides, carbonates, phosphates, silicates and metasilicates of alkali metals, alkaline earth metals and of iron, cobalt, nickel, zinc, aluminium, titanium, zirconium, yttrium, vanadium, cerium, lanthanum, manganese, bismuth, copper, silver and tin, and primary, secondary and tertiary amines, polyamines, and ammonium compounds, preferably oxides, hydroxides, carbonates, phosphates and silicates of alkaline earth metals, with the proviso that when a mixture of AIH₂P₃O₁₀ and M_aH_bP₃O₁₀, wherein M = Bi or Bi and Mn, is used or when FeH₂P₃O₁₀ is used as the sole component, the base does not contain zinc.

The base treatment is preferably carried out by treating the product obtained in accordance with the above-described process in step (c) with at least one base, the molar ratio of base to product from (c) being selected in the range from 0.1:1 to 10:1 , preferably from 0.5:1 to 5:1 , wherein either

(d) if the product from (c) is in dry form, the bases are likewise added in dry form and, for example, intimately mixed with the product obtained in (c) by grinding in such a manner that a reaction (H / metal exchange) can be detected in the IR spectrum, the grinding generally being carried out in customary powder mills (e.g. ball mills etc.) at room temperature for from three to 60 minutes, or

(c2) the base treatment is carried out in an aqueous medium at a temperature in the range from 15 to 90°C, preferably from 30 to 80°C, in the course of from three to 60 minutes with an amount of water to pigment and base in the range from 5:1 to 20:1 (parts by weight), and the product so treated is then separated from the reaction mixture, preferably by filtration, then washed and then (e.g from 10 to 20 hours) dried, for example at a temperature in the range from 100 to 110°C, and (d) if required, grinding to the desired particle size is carried out using methods known per se.

A further preferred embodiment relates to mixtures that comprise from 0.1 to 99.9 % by weight of a tripolyphosphate I according to the invention and/or AIH₂P₃O₁₀ and/or Ca₂HP₃O₁₀ and/or FeH₂P₃O₁₀ and from 99.9 to 0.1 % by weight of at least one base, with the proviso that when a mixture of AIH₂P₃O₁₀ and M_aH_bP₃O₁₀, wherein M = Bi or Bi and Mn, is used or when FeH₂P₃O₁₀ is used as the sole component, the base does not contain zinc.

The composition of such mixtures is generally governed by the intended use. For example, for a film-forming medium, such as an alkyd surface-coating system, the following composition can be used: from 40 to 80 % by weight of a tripolyphosphate I according to the invention, AIH₂P₃O₁₀ or Ca₂HP₃O₁₀ or a mixture thereof, especially e.g. from 30 to 50 % by weight AIH₂P₃O₁₀x2H₂O and from 10 to 30 % by weight Ca₂HP₃O₁₀, and from 20 to 60 % by weight of at least one of the above-mentioned bases, such as Ca(OH)₂, ZnO (with the proviso that when a mixture of AIH₂P₃O₁₀ and M_aH_bP₃O₁₀ wherein M = Bi or Bi and Mn is used, the base does not contain zinc) or CaSiO₃.

For a so-called 2P-epoxy surface-coating system, the following composition, for example, can be used: from 10 to 60 % by weight of a tripolyphosphate I according to the invention, AIH₂P₃O₁₀ or

Ca₂HP₃O₁₀ or a mixture thereof, especially e.g. from 5 to 35 % by weight AIH₂P₃O₁₀ and from

5 to 25 % by weight Ca₂HP₃O₁₀ and from 40 to 90 % by weight of one, e.g. Ca(OH)₂, CaSiO₃ or ZnO, or more, e.g. Ca(OH)₂ and

ZnO, of the above-mentioned bases (with the proviso that when a mixture of AIH₂P₃O₁₀ and

M_aH_bP₃O₁₀ wherein M = Bi or Bi and Mn is used, the base does not contain zinc) or CaO.

Alkyd surface-coating systems comprising AIH₂P₃O₁₀/Ca₂HP₃O₁₀/Ca(OH)₂ and 2P-epoxy surface-coating systems comprising AIH₂P₃θ₁₀ Ca₂HP₃O₁₀/ZnO are used especially for iron substrates, and 2P-epoxy surface-coating systems comprising AIH₂P₃O₁₀/Ca₂HP₃O₁₀/ Ca(OH)₂/ZnO or comprising AIH₂P₃O₁₀/Ca₂HP₃O₁₀/CaSiO₃ are used especially for aluminium substrates.

The base-treated phosphate derivatives according to the invention can be used as anti- corrosion agents. An embodiment of the present invention therefore relates to the use as anti-corrosion agents of tripolyphosphates I according to the invention, mixtures thereof with AIH₂P₃O₁₀ and/or Ca₂HP₃O₁₀ and/or FeH₂P₃O₁₀, and tripolyphosphates I, AIH₂P₃O₁₀, FeH₂P₃O₁₀, Ca₂HP₃O₁₀ and tripolyphosphate mixtures thereof treated according to the invention with at least one base, as defined above.

A further embodiment relates to anti-corrosion agents, comprising a tripolyphosphate I according to the invention and AIH₂P₃O₁₀ and/or Ca₂HP₃O₁₀ and/or FeH₂P₃O₁₀, that have been treated according to the invention with at least one base, or a mixture according to the invention as defined above. The invention relates also to anti-corrosion agents comprising a mixture consisting of

(1) a tripolyphosphate mixture comprising

(1.1) from 0 to 100 % by weight of a component A, consisting of

(1.1.1) from 0 to 99.9 % by weight of AIH₂P₃O₁₀ and

(1.1.2) from 0.1 to 100 % by weight of Ca₂HP₃O₁₀, the sums of the percentages by weight of the components mentioned under (1.1.1) and (1.1.2) being 100 % by weight, and

(1.2) from 100 to 0 % by weight of a tripolyphosphate of formula I, the percentages by weight of the mixture components mentioned under (1.1) and (1.2) adding up to 100 % by weight, and it being possible for the components A and the tripolyphosphate of formula I to have been aftertreated according to the invention with a base in accordance with the process described above, and

(2) from 0 to 99.9 % by weight, based on the sum of the mixture components mentioned under (1) and (2), of a component B selected from the group consisting of anti-corrosion agents not mentioned under (1), bases and layered pigments.

Tripolyphosphates of formula (I) and mixtures thereof and also the above-mentioned mixtures comprising copper or silver are distinguished by an anti-microbial (biocidal) action or encrustation-inhibiting action, for example on ships.

The present invention accordingly relates also to the use of tripolyphosphates of formula (I) and mixtures thereof and also to the above-mentioned mixtures comprising copper or silver, especially copper- or silver-doped aluminium hydrogen tripolyphosphate, as anti-microbial agents (biocides) or encrustation-inhibiting agents.

Known anti-corrosion agents or corrosion inhibitors generally comprise aluminium, iron, magnesium, calcium, strontium or zinc phosphates, hydrogen phosphates, polyphosphates, metaphosphates, pyrophosphates, aluminium dihydrogen tripolyphosphate, and optionally a base.

The tripolyphosphate mixtures according to the invention mentioned under (1) can also be mixed with layered pigments, such as mica, calcium metasilicates, zeolites, ZnO, CaO, MgO, ZnSiO₃, CaSiO₃ and MgSiO₃ and also with intermediates for the preparation of known anti- corrosion agents, or with organic anti-corrosion additives, such as the commercially available products of the CibaOIRGACOR® range (such as N-ethylmorpholine complex with 4-methyl- γ-oxo-phenyl-butanoic acid, zirconium complex with 4-methyl-γ-oxo-phenyl-butanoic acid or (2-benzothiazolylthio)succinic acid) or Heucorin®.

Also possible is the use of the tripolyphosphates of formula (I) according to the invention or the tripolyphosphate mixtures according to the invention as carriers for inorganic/organic compounds, especially organic/inorganic pigments. For example, bismuth vanadate can be deposited onto a tripolyphosphate of formula (I) according to the invention or onto a tripolyphosphate mixture according to the invention, or organic pigments that carry one or more acid groups, especially sulfonic acid groups, can be deposited onto a tripolyphosphate of formula (I) according to the invention, or onto a tripolyphosphate mixture according to the invention, using the lake technique.

The present invention relates also to a coating composition comprising an organic film- forming binder and, as corrosion inhibitor, a tripolyphosphate I or one of the mixtures according to the invention.

A further preferred embodiment relates to a coating composition in which the coating composition is a coating material. An aqueous coating material is especially preferred.

Coating materials are, for example, lacquers, paints and varnishes. They always contain an organic film-forming binder alongside other, optional, components.

Preferred organic film-forming binders are epoxy resins, polyurethane resins, aminoplastic resins, acrylic resins, acrylic copolymer resins, polyvinyl resins, phenolic resins, styrene/- butadiene copolymer resins, vinyl/acrylic copolymer resins, polyester resins and alkyd resins or a mixture of two or more of those resins, or an aqueous basic or acidic dispersion of those resins or mixtures of those resins, or an aqueous emulsion of those resins or mixtures of those resins. Of particular interest are organic film-forming binders for aqueous coating compositions, such as alkyd resins, acrylic resins, 2-component epoxy resins, polyurethane resins, polyester resins, which are usually saturated, water-dilutable phenolic resins or dispersions derived therefrom, water-dilutable urea resins, resins based on vinyl/acrylic copolymers, and hybrid systems based on e.g. epoxy acrylates.

More specifically, the alkyd resins may be water-dilutable alkyd resin systems that are air- drying or can be used in the form of stoving systems, if desired in combination with water- dilutable melamine resins. They may also be oxidatively drying systems, air-drying systems or stoving systems which, if desired, may be used in combination with aqueous dispersions based on acrylic resins or copolymers thereof, with vinyl acetates etc..

The acrylic resins may be pure acrylic resins, epoxy acrylate hybrid systems, acrylic acid or acrylic acid ester copolymers, combinations with vinyl resins, or copolymers with vinyl monomers such as vinyl acetate, styrene or butadiene. Those systems may be air-drying systems or stoving systems.

Water-dilutable epoxy resins, in combination with suitable polyamine crosslinking agents, generally exhibit excellent mechanical and chemical stability. When liquid epoxy resins are used, it is usually possible to dispense with the addition of organic solvents to aqueous systems. The use of solid resins or solid resin dispersions generally requires the addition of very small amounts of solvent in order to improve the film formation.

Preferred epoxy resins are those based on aromatic polyols, especially based on bisphenols. The epoxy resins are preferably used in combination with crosslinking agents. The latter may include especially amino- or hydroxy-functional compounds, an acid, an acid anhydride or a Lewis acid. Examples thereof are polyamines, polyaminoamides, polysulfide-based polymers, polyphenols, boron fluorides and complex compounds thereof, polycarboxylic acids, 1 ,2-dicarboxylic anhydrides and pyromellitic dianhydride.

Polyurethane resins can usually be prepared from polyethers, polyesters or polybutadienes having terminal hydroxy groups on the one hand and aliphatic or aromatic polyisocyanates on the other hand. Suitable polyvinyl resins are, for example, polyvinyl butyral, polyvinyl acetate and copolymers thereof.

Suitable phenolic resins are generally synthetic resins which have been synthesised using phenols as main component, that is to say especially phenol-, cresol-, xylenol- and resorcinol-formaldehyde resins, alkylphenol resins and condensation products of phenols with acetaldehyde, furfural, acrolein or other aldehydes. Modified phenolic resins may also be of interest.

The coating compositions may additionally comprise one or more components from the group of pigments, dyes, fillers, flow-control agents, dispersants, thixotropic agents, adhesion promoters, antioxidants, light stabilisers and curing catalysts.

The coating compositions according to the invention may also comprise further known anti- corrosion agents, for example anti-corrosion pigments, such as phosphate- or borate- containing pigments, metal oxide pigments or other organic or inorganic corrosion inhibitors, e.g. salts of nitroisophthalic acid, phosphoric esters, amines or substituted benzotriazoles.

Anti-corrosion pigments are, for example, titanium dioxide, iron oxide, aluminium bronze and phthalocyanine blue.

Examples of fillers are talc, aluminium oxide, aluminium silicate, barytes, mica and silicon dioxide.

The corrosion inhibitors may also be applied to a carrier material. Powdered fillers or pigments, especially, can be used for that purpose.

Flow-control agents and thixotropic agents are known to the person skilled in the art; some are based, for example, on modified bentonites. Dispersants are known to the person skilled in the art; some are based, for example, on solutions of high molecular weight block copolymers with groups that have affinity for pigments (e.g. Disperbyk products from Byk).

Adhesion promoters are known to the person skilled in the art, e.g. modified silanes can be used.

The additional component or additional components can usually be used in amounts in the range from 0.1 to 50 % by weight, based on the total weight of the coating composition.

Furthermore, a special embodiment relates to the addition of basic fillers or pigments that, in certain binder systems, are able to bring about a synergistic effect on the inhibition of corrosion. Examples of such basic fillers and pigments are calcium or magnesium carbonate, zinc oxide, zinc carbonate, zinc phosphate, magnesium oxide, aluminium oxide and aluminium phosphate and mixtures thereof. Examples of basic organic pigments are those based on aminoanthraquinone.

The basic fillers or pigments are generally used in an amount in the range from 0.1 to 30 % by weight, based on the total weight of the coating composition.

The corrosion inhibitors can be added to the coating material during the preparation of the latter, for example during the distribution of the pigment by grinding, or the inhibitor is pre- dispersed in a solvent and the resulting dispersion is then added to the remainder of the coating composition.

Furthermore, when the organic film-forming binder is prepared by polymerisation or poly- condensation of monomers, the corrosion inhibitors can be mixed into the monomers prior to polymerisation, the corrosion inhibitors being either in solid form or in predispersed form.

The coating compositions according to the invention generally comprise the corrosion inhibitor in an amount in the range from 0.01 to 95 % by weight, preferably from 0.05 to 70 % by weight, more especially from 0.1 to 50 % by weight, based on the total weight of the coating composition. The coating materials can be applied to the substrate by customary methods, for example by spraying, dipping, coating or electrodeposition.

Several coats are usually applied. The corrosion inhibitors are generally added primarily to the primer, since they act chiefly at the metal/coating interface, but they may additionally be added to an intermediate coat or to the top coat.

According to whether the binder is a physically, chemically or oxidatively drying resin or a heat- or radiation-curable resin, the curing of the coating is usually carried out at room temperature or by heating (stoving) or by irradiation.

The coating material is preferably a primer for metal substrates, such as iron, steel, copper, zinc and aluminium and alloys thereof.

A further preferred embodiment of the present invention relates to the use of the corrosion inhibitors according to the invention in coating compositions for metal surfaces.

A further embodiment relates to a process for preparing a coating composition by mixing a corrosion inhibitor and a film-forming organic binder, wherein the corrosion inhibitor used is a corrosion inhibitor according to the invention.

A further embodiment of the present invention relates to a method of protecting a corrodible metal substrate by applying a coating composition that comprises a corrosion inhibitor, wherein the coating composition used is a coating composition according to the invention.

A further embodiment relates to a method of producing a corrosion-resistant surface-coating on a corrodible metal surface by treatment of that metal surface with a coating composition that comprises a corrosion inhibitor and subsequent drying or curing, wherein the coating composition used is a coating composition according to the invention.

A further embodiment relates to a method of pretreating metal surfaces, wherein an aqueous solution of a corrosion inhibitor according to the invention is applied to the metal surface and is then dried or allowed to dry. Compared with known chromium- and lead-free anti-corrosion agents, the anti-corrosion agents according to the invention exhibit an improvement in the number and size of blisters both on the surface and at a site of deliberate damage. In addition, infiltration is improved. The mixtures and anti-corrosion agents according to the invention therefore exhibit anti- corrosion properties comparable to those of chromium- and lead-containing compounds, in some cases exhibiting properties even better than those of the latter anti-corrosion agents. Furthermore, highly effective zinc-free anti-corrosion agents are also available. In addition, the anti-corrosion agents according to the invention can be used for upgrading known products and intermediates and, in combination with anti-corrosion additives, such as Ciba® IRGACOR®, for synergistically increasing the anti-corrosion properties. Finally, in addition to their good environmental compatibility, especially in the case of the zinc-free and reduced- zinc products, mention should also be made of their good economic efficiency. In addition to their anti-corrosive action, the hydrogen tripolyphosphates according to the invention, especially the base-treated compounds and mixtures, also have the advantage that they have a positive effect on adhesion between coating and metal, they have no adverse effects on the storage stability of the coating compositions according to the invention and they exhibit good compatibility with the binder.

Examples

Example 1: 200 g of aluminium hydroxide and 110 g of calcium hydroxide are suspended in 700 ml of water and dissolved completely using 1500 g of a commercially available concentrated phosphoric acid (85%). The reaction mixture is then calcined at a temperature of 300°C for four hours. The opaque intermediate is then hydrolysed by the addition of 2000 ml of water at a temperature of 70°C and then ground while wet. The resulting aluminium dihydrogen tripolyphosphate dihydrate / dicalcium hydrogen tripolyphosphate mixture is filtered off and washed twice using 1500 ml of water each time, and the filter cake obtained is dried at 110°C for 16 hours. Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ :

IR: v = 560, 582, 627, 701 , 760, 778, 930, 982, 1055, 1128, 1208, 1244 cm^"1 Spec, conductance (according to ISO 787/XIV 1973): 1500 μS/cm Spec, weight: 2.42 g/cm³ X-ray spectrum: 2Θ = 11.1 ° (main peak), otherwise not substantially different from added spectra of AIH₂P₃O₁₀x2H₂O and Ca₂HP₃O₁₀.

For aftertreatment with a base, 70 g of the resulting AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ are suspended in 1200 ml of water at a temperature of 65°C, and 40 g of Ca(OH)₂ are added.

The mixture is stirred at that temperature for about 10 min and filtered while still hot. After washing twice using 200 ml of water each time, the filter cake is dried at 110°C for 16 hours.

The product so dried is then ground to the desired particle size.

Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ after treatment with Ca(OH)₂:

IR: v = 560, 582, 627, 701 , 760, 778, 875, 930, 982, 1055, 1128, 1208, 1244 cm^"1

Spec, conductance (according to ISO 787/XIV 1973): 7100 μS/cm

Spec, weight: 2.51 g/cm³

X-ray spectrum: 2Θ = 11.1 ° (main peak), otherwise differing only slightly from the spectrum of

AIH₂P₃O₁₀x2H₂O as a result of the additional reflections of Ca₂HP₃O₁₀: 2Θ = 28.3°, a signal increase at 2Θ = 34° and an attenuation at 25.6°.

Example 2: 200 g of aluminium hydroxide and 100 g of manganese(ll) carbonate are suspended in 600 ml of water and slowly dissolved completely using 1500 g of a commercially available concentrated phosphoric acid (85%). The reaction mixture is then stirred at a temperature of 80°C for one hour until everything has been dissolved. The mixture is calcined for three hours at 300°C. The opaque intermediate is then hydrolysed by the addition of 1500 ml of water at a temperature of 70°C and then ground while wet. The resulting aluminium dihydrogen tripolyphosphate dihydrate / manganese hydrogen tripolyphosphate mixture is filtered off and washed three times using 600 ml of water each time, and the filter cake obtained is dried at 110°C for 16 hours. Physical data of AIH₂P₃O₁₀x2H₂O/Mn₂HP₃O₁₀ : IR: v = 508, 629, 713, 731 , 778, 985, 1055, 1127, 1209, 1243 cm^"1 X-ray spectrum: 2Θ = 11.1 ° (main peak AIH₂P₃O₁₀), 14.1°, 20.4°, 27.5° being very slightly different from the spectrum of AIH₂P₃O₁₀x2H₂O

Example 2a

For aftertreatment with a base, 70 g of the resulting AIH₂P₃O₁₀x2H₂O/Mn₂HP₃O₁₀ are thoroughly mixed with 40 g of Ca(OH)₂ and then ground to the desired particle size. Spec, conductance (according to ISO 787/XIV 1973): 7100 μS/cm

Example 3: With thorough stirring using a high-speed mixer, 100 g of calcium hydroxide are introduced, in portions, in the course of about 10 minutes into 330 g of a commercially available concentrated phosphoric acid (75%), the temperature of the mixture rising substantially. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 300°C for two hours. The opaque intermediate is then hydrolysed by the addition of 1000 ml of water at a temperature of 70°C and then ground while wet. The dicalcium hydrogen tripolyphosphate so obtained is filtered off and washed twice using

500 ml of water each time, and the filter cake obtained is dried at 110°C for 16 hours.

Physical data of Ca₂HP₃O₁₀:

IR: v = 560, 582, 701 , 760, 930, 970, 1047, 1128, 1196, 1256 cm^"1

Spec, conductance (according to ISO 787/XIV 1973): 1300 μS/cm

Spec, weight: 2.42 g/cm³

X-ray spectrum: identical to spectrum of Ca₂HP₃O₁₀ from: Ind.Eng.Chem. (1947), vol.39, no.12, 1667-1672.

Example 3a: For aftertreatment, 70 g of the Ca₂HP₃O₁₀ obtained according to Example 3 are suspended in 1000 ml of water at a temperature of 65°C, and 40 g of Ca(OH)₂ are added.

The mixture is stirred at that temperature for 5 min and filtered while still hot. After washing twice using 200 ml of water each time, the filter cake obtained is dried at 110°C for 16 hours.

The product so dried is then ground to the desired particle size (< 50 μm).

Physical data of Ca₂HP₃O₁₀ after treatment with Ca(OH)₂:

IR: v = 560, 582, 701 , 760, 875, 930, 970, 1047, 1128, 1196, 1256 cm^"1

Comparison Example 1 : The compound Ca₂HP₃O₁₀ obtained according to Example 3 is ground to the desired particle size (< 50 μm) after drying and, without further chemical after- treatment or addition of additives, subjected to an anti-corrosion test . The results (see Tables 1 to 3) show that the compound is not suitable for use in film-forming media (Tables 1 and 2).

Example 4: 275 g of aluminium hydroxide and 125 g of calcium hydroxide are premixed in the solid state and introduced in portions in the course of about 10 min, with vigorous stirring using a high-speed mixer, into 1700 g of a commercially available concentrated phosphoric acid (75%), the temperature of the mixture rising substantially. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 340°C for one hour. The opaque intermediate is then hydrolysed by the addition of 1000 ml of water at a temperature of 70°C and then ground while wet. The resulting mixed product of dicalcium hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 1500 ml of water each time, and the filter cake so obtained is dried at

110°C for 16 hours.

Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀:

IR: v = 560, 582, 627, 701 , 760, 778, 930, 982, 1055, 1128, 1208, 1244 cm^"1

Spec, conductance (according to ISO 787/XIV 1973): 1500 μS/cm

Spec, weight: 2.42 g/cm³

X-ray spectrum: 2Θ = 11.1 ° (main peak), otherwise not substantially different from added spectra of AIH₂P₃O₁₀x2H₂O and Ca₂HP₃O₁₀ or from the spectrum of Example 1.

For aftertreatment, 70 g of the AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ so obtained are suspended in

1200 ml of water at a temperature of 65°C, and 40 g of Ca(OH)₂ are added. The mixture is stirred at that temperature for about 10 min and filtered while still hot. After washing twice using 200 ml of water each time, the filter cake so obtained is dried at 110°C for 16 hours.

The product so dried is then ground to the desired particle size (< 50 μm).

Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ after coating e.g. with Ca(OH)₂:

Spec, conductance (according to ISO 787/XIV 1973): 7100 μS/cm

Spec, weight: 2.51 g/cm³

AIH₂P₃O₁₀x2H₂O as a result of the additional reflections of Ca₂HP₃O₁₀ : 2Θ = 24.8°, a signal increase at 2Θ = 34° and an attenuation at 25.6° (not perceptibly substantially different from the spectrum from Example 1).

Example 5: 590 g of aluminium hydroxide and 260 g of calcium hydroxide are premixed in the solid state and introduced in portions in the course of about 15 min, with vigorous stirring using a high-speed mixer, into 3250 g of a commercially available concentrated phosphoric acid (75%), the temperature of the mixture rising substantially. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 340°C for 1.5 hours. The opaque intermediate is then hydrolysed by the addition of 5000 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of dicalcium hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 3000 ml of water each time, and the filter cake so obtained is dried at

110°C for 16 hours.

Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀:

IR: v = 560, 582, 627, 701 , 760, 778, 930, 982, 1055, 1128, 1208, 1244 cm^"1

Spec, conductance (according to ISO 787/XIV 1973): 1000 μS/cm

Spec, weight: 2.42 g/cm³

X-ray spectrum: 2Θ = 11.1° (main peak), otherwise not substantially different from added spectra of AIH₂P₃O₁₀x2H₂O and Ca₂HP₃O₁₀ or from the spectrum of Example 1.

Example 6:

For the formulation of a zinc-free anti-corrosion agent for epoxy surface-coating systems applied to aluminium substrates, 600 g of the AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ obtained according to Example 5 are thoroughly mixed, in a mixer, with 500 g of calcium mefasilicate (Casiflux® A25) and 40 g of calcium hydroxide and then ground to the desired particle size (< 50 μm) in a pigment mill.

Example 7:

For the formulation of an anti-corrosion agent for epoxy surface-coating systems applied to iron and aluminium substrates and alloys, 600 g of the AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ obtained according to Example 5 are thoroughly mixed, in a mixer, with 500 g of zinc oxide and 40 g of calcium hydroxide and then ground to the desired particle size (< 50 μm) in a pigment mill.

Example 8: 675 g of aluminium hydroxide and 100 g of calcium hydroxide are premixed in the solid state and introduced in portions in the course of about 15 min, with vigorous stirring using a high-speed mixer, into 3250 g of a commercially available concentrated phosphoric acid (75%), the temperature of the mixture rising substantially. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 340°C for 1.5 hours. The opaque intermediate is then hydrolysed by the addition of 5000 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of dicalcium hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 3000 ml of water each time, and the filter cake so obtained is dried at

110°C for 16 hours.

Physical data of AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀:

IR: v = 560, 582, 627, 701 , 778, 982, 1055, 1128, 1208, 1244 cm^"1

Spec, conductance (according to ISO 787/XIV 1973): 1000 μS/cm

Spec, weight: 2.4 g/cm³

Example 9:

For the formulation of a zinc-free anti-corrosion agent for epoxy surface-coating systems applied to aluminium substrates, 600 g of the AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ obtained according to Example 8 are thoroughly mixed, in a mixer, with 500 g of calcium metasilicate (Casiflux® A25) and 40 g of calcium hydroxide and then ground to the desired particle size (< 50 μm) in a pigment mill.

Example 10:

For the formulation of an anti-corrosion agent for epoxy surface-coating systems applied to iron and aluminium substrates and alloys, 600 g of the AIH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ obtained according to Example 8 are thoroughly mixed, in a mixer, with 500 g of zinc oxide and 40 g of calcium hydroxide and then ground to the desired particle size (< 50 μm) in a pigment mill.

Example 11 : 500 g of aluminium hydroxide and 600 g of strontium carbonate are premixed in the solid state and introduced in portions in the course of about 25 min, with vigorous stirring using a high-speed mixer, into 3400 g of a commercially available concentrated phosphoric acid (75%), the temperature of the mixture rising substantially. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 340°C for 2 hours. The opaque intermediate is then hydrolysed by the addition of 5000 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of distrontium hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 3000 ml of water each time, and the filter cake so obtained is dried at 110°C for 16 hours.

Physical data of AIH₂P₃O₁₀x2H₂O/Sr₂HP₃O₁₀: IR: v = 513, 594, 630, 693, 707, 778, 982, 1057, 1125, 1208, 1242 cm^"1 X-ray spectrum: 2Θ = 11.1 ° (main peak AIH₂P₃O₁₀), 23.2°, 27.2°, 27.8°, 33.2° being only slightly different from the spectrum of AIH₂P₃O₁₀x2H₂O

Example 12:

A solution of 6 g of silver nitrate in 20 ml of water is stirred into 330 g of a commercially available concentrated phosphoric acid (75%) and, with vigorous stirring using a high-speed mixer, 65 g of aluminium hydroxide in the solid state are introduced in the course of about 10 min, the temperature of the mixture rising slightly. The resulting viscous, white doughy mass is homogenised and then calcined at a temperature of 340°C for 1.5 hours. The opaque intermediate is then hydrolysed by the addition of 700 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of silver hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 600 ml of water each time, and the filter cake so obtained is dried at 110°C for 16 hours and then ground to the desired particle size in a pigment mill. Physical data of AIH₂P₃O₁₀x2H₂O/Ag₃H₂P₃O₁₀:

IR: v = 532, 570, 596, 631 , 778, 985, 1041 , 1056, 1129, 1169, 1208, 1242 cm^"1 otherwise not substantially different from the spectrum of AIH₂P₃O₁₀x2H₂O

Example 13:

A mixture of 10 g of copper(ll) oxide and 50 g of aluminium hydroxide in the solid state is introduced in the course of about 10 minutes into 335 g of a commercially available concentrated phosphoric acid (75%) with vigorous stirring using a high-speed mixer, the temperature of the mixture rising slightly. The resulting viscous doughy mass is homogenised and then subjected to pre-calcination for two hours at a temperature of 200°C and to calcination for three quarters of an hour at 300°C. The opaque intermediate is then hydrolysed by the addition of 700 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of copper hydrogen tripolyphosphate and aluminium dihydrogen tripolyphosphate dihydrate is filtered off and washed twice using 600 ml of water each time, and the filter cake so obtained is dried at 110°C for 16 hours and then ground to the desired particle size in a pigment mill. Physical data of AIH₂P₃O₁₀x2H₂O/Cu₂HP₃O₁₀: IR: v = 510, 571 , 627, 727, 739, 780, 984, 1058, 1130, 1176, 1208, 1244 cm^"1 Example 14:

A mixture of 27 g of anhydrous aluminium trichloride and 69 g of ammonium dihydrogen phosphate in the solid state is mixed under protective gas and then calcined in a porcelain dish at a temperature of 350°C for two hours, ammonium chloride being deposited. The product is then hydrolysed by the addition of 700 ml of water at a temperature of 60°C and then ground while wet. The resulting mixed product of aluminium ammonium hydrogen tripolyphosphate is filtered off and washed twice using 600 ml of water each time, and the filter cake so obtained is dried at 110°C for 16 hours and then ground to the desired particle size.

Physical data of AINH₄HP₃O₁₀x2H₂O:

IR: v = 421 , 495, 617, 766, 976, 1078, 1185, 1249, 1420 cm^'1

X-ray spectrum: 2Θ = 11.5° (main peak AINH₄HP₃O₁₀) being different from the spectrum of

AIH₂P₃O₁₀x2H₂O

Example 15: 250 g of iron(lll) oxide and 110 g of calcium hydroxide are suspended in 700 ml of water and dissolved completely with 1500 g of a commercially available concentrated phosphoric acid (85%). The reaction mixture is then calcined at a temperature of 300°C for four hours. The opaque intermediate is then hydrolysed by the addition of 2000 ml of water at a temperature of 70°C, then ground while wet. The resulting iron hydrogen tripolyphosphate dihydrate / dicalcium hydrogen tripolyphosphate is filtered off and washed twice using 1500 ml of water each time, and the filter cake is dried at 110°C for 16 hours. Physical data of FeH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀: IR: v = 584, 599, 606, 701 , 720, 742, 760, 920, 993, 1013, 1066, 1112, 1154, 1189, 1212 cm^'

1

For aftertreatment, 70 g of the resulting FeH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ are suspended in

1200 ml of water at a temperature of 65°C, and 40 g of Ca(OH)₂ are added. The mixture is stirred at that temperature for about 10 min and filtered while still hot. After washing twice using 200 ml of water each time, the filter cake obtained is dried at 110°C for 16 hours. The product so dried is then ground to the desired particle size.

Physical data of FeH₂P₃O₁₀x2H₂O/Ca₂HP₃O₁₀ after treatment with Ca(OH)₂:

IR: v = 584, 599, 606, 701 , 720, 742, 760, 875, 920, 993, 1013, 1066, 1112, 1154, 1189,

1212 cm^'1. Example 16: A so-called "short-oil-alkyd" system, consisting of

16.3 g of a short-chain alkyd resin (URALAC®AK 424 x-60 from DSM Resins), 3.0 g of an iron oxide yellow pigment (BAYFERROX®3910 from Bayer),

3.0 g of TiO₂ (Kronos 2160 from Kronos),

3.6 g of a magnesium silicate (Micro Talc AT Extra from Norwegian Talc),

5.4 g of a barium sulfate (Blanc Fix from Sachtleben),

40.4 g of an aromatic hydrocarbon (xylene).

In order to maintain the volumetric concentration of pigment at the same level, X g of an anti- corrosion pigment from Tables 1 and 2 are dispersed (using a Scandex dispersing apparatus) with 100 g of glass beads (3 mm diameter) to give a particle size of all particles of <20 μm (about Vi h). In the case of zinc chromate, X= 8.6 g; in the case of ZAPP^®, X= 6.5 g; in the case of K-White 105^®, X= 7.2 g, and in the case of each of Examples 1 , 3a, 4 and 15 and Comparison Example 1 , X = 5.75 g.

Then, 1.0 g of a hardener (Servosyn WEB Co 8% from Servo Delden b.v.) and 1.0 g of an anti-skinning agent (Exkin 2 from Hϋls) are added to the dispersion and mixing is continued for about a further 10 min.

The "short-oil-alkyd" system so prepared is applied to bright steel plates and dried at a temperature of 20°C for seven days, the thickness of the dry layer being 50-60 μm. Before weathering begins, a cutting device is used to damage the surface-coating films in a defined manner, the damage taking the form of a parallel cut (that is to say parallel to the longest edge of the sheet). The edges of the sheet and the reverse side are protected by attaching edge-protection means.

The test plates so prepared are subjected to a corrosion test in a salt-spray chamber in accordance with DIN 50021 and a humidity test according to DIN 50017, the tests being evaluated in accordance with DIN 53 209 (number of blisters m/blister size q) and DIN 53 210 (degree of rust according to DIN). The results are given in Tables 1 and 2. Table 1 : Salt-sprav test 600 hours (DIN 50 021 .

Example

Blistering Degree Appearance Blistering* Infiltration*

( /g) of rust (m/g) (mm) Ri

ZnCrO₄ 0/0 Ri1 5 4/4 1.1-1.5

ZAPP® 1/2 Ri1 5 4/3 1.1-1.5

(Heubach)

K-White®105 0/0 Ri1 5 3/5 0.6-1.0

(Teikoku Kako)

Example 1 0/0 RiO 6 3/2 0.6-1.0

Comparison 4/3 Ri2 4 5/3 1.6-2.0

Example 1

Example 3a 0/0 RiO 6 4/2 0

Example 4 0/0 RiO 6 4/2 0

Example 15 0/0 RiO 6 4/3 0

Example 2a 010 RiO 6 3/3 0.1-0.5

Table 2: Humidity test 600 hours (DIN 50 017)

Example

Blistering Rust Appearance Blistering* Infiltration

(m/g) Ri (m/g) (mm)

ZnCrO₄ 1/2 RiO 6 0/0 0

ZAPP® 3/2 Ri1 5 2/3 0.6-1.0

(Heubach)

K-White®105 0/0 RiO 6 2/3 0.6-1.0

(Teikoku Kako)

Example 1 0/0 RiO 6 3/2 0.6-1.0

Comparison 4/3 Ri1 4 5/3 1.1-1.5

Example 1

Example 3a 0/0 RiO 6 0/0 0

Example 4 0/0 RiO 6 0/0 0

Example 15 0/0 RiO 6 0/0 0

Example 2a 0/0 RiO 6 0/0 0.1-0.5

* Measured after damage has been caused artificially using a scratching tool according to DIN, that is to say when the exposure in the salt-spray test and humidity test is complete, the infiltration of rust and the number and size of blisters at the damage site are determined, m denotes the number of blisters and g denotes the size of the blisters in accordance with comparison tables (DIN 53209). Ri denotes the degree of rust according to DIN 53210, the appearance being divided subjectively into six categories, six being the best value. The infiltration indicates the extent, in millimetres, of the damage to the substrate (under the surface-coating layer), measured from a site of deliberate damage (scratch).

Example 17: 70 g of AIH₂P₃O₁₀x2H₂O-/Ca₂HP₃O₁₀ (preliminary product from Example 4) are suspended in 1000 ml of water at a temperature of 65°C, and 70 g of calcium silicate (Riedel- deHaen) are added. The mixture is stirred at that temperature for about 10 min and filtered while still hot. After washing twice using 200 ml of water each time, the filter cake obtained is dried at 110°C for 16 hours. The product so dried is then ground to the desired particle size. Example 18: "Two-component (2K) epoxy/polyamidoamine system"

Component I:

12.9 g of epoxy resin Araldite GT 7071 (Ciba Spezialitatenchemie),

7.15 g of solvent isobutanol,

5.56 g of solvent cyclohexanone

8.41 g of solvent xylene

0.05 g of thixotropic agent Thixatrol ST (Rheox)

0.25 g of anti-settling agent/thickener Aerosil R972 (Degussa)

0.05 g of iron oxide yellow pigment Bayferrox 3910 (Bayer)

11.00 g of titanium dioxide TiO₂ (Kronos 2160, Kronos)

5.50 g of magnesium silicate Micro Talc AT extra (Ernstorm group)

4.50 g of barium sulfate Blanc Fix

X g of anti-corrosion pigment

Component II:

4.00 g of polyamidoamine hardener HY-815-2 (Ciba Spezialitatenchemie)

1.20 g of propylene glycol methyl ether Dowanol PM (Dow Corning)

3.6 g of solvent xylene

6.20 g of solvent isobutanol

Preparation of the anti-corrosion surface-coating:

The above component I, comprising X g of anti-corrosion pigment, and 70 ml of glass beads (3 mm diameter) are introduced into a 200 ml glass container. Then, using a coating shaking device (Scandex), dispersion is carried out for about 30 min until all particles have a particle size of < 20 μm. Component II is then added and the surface-coating mixture is dispersed for a further 5 min using the coating shaking device.

In order to maintain the volumetric concentration of anti-corrosion pigment at the same level, there are used in the case of zinc chromate, X= 5.85 g; in the case of CAPP^®, X= 4.55 g; in the case of K-White 105^®, X= 4.88 g and in the case of the anti-corrosion pigment obtained according to Example 17, X= 3.9 g. In order to adjust to the desired spraying viscosity, the surface-coating is diluted with solvent. The "2K-epoxy" system prepared above is applied to bright steel plates (19 x 10.5 cm) of the Bonder type (cold-rolled, degreased steel; manufacturer: Chemetall, Frankfurt am Main/Germany) in a layer thickness, after drying, of 50 to 60 μm and dried at a temperature of 20°C for seven days.

Before weathering begins, a cutting device is used to damage the surface-coating films in a defined manner, the damage taking the form of a parallel cut (that is to say parallel to the longest edge of the sheet). The edges of the sheet are protected by attaching edge- protection means. The prepared test plates are subjected to a corrosion test in a salt-spray chamber in accordance with DIN 50021 , the tests being evaluated in accordance with DIN 53 209 (number of blisters m/blister size g) and DIN 53 210 (degree of rust according to DIN). The results are given in Table 3.

Table 3: Salt-sprav test 800 hours (DIN 50 021)

Example

Blistering Degree Appearance Blistering* Infiltration

(m/g) of rust (m/g) (mm) Ri

ZnCrO₄ 0/0 RiO 6 3/4 0.6-1.0

K-White®105 0/0 RiO 6 4/3 0.6-1.0

CAPP® 0/0 RiO 6 4/3 0.6-1.0

Example 17 0/0 RiO 6 3/2 0.1-0.5

Example 7 0/0 RiO 6 3/3 0.1-0.5

Example 8 -/- Ri- - -/- —

* For explanation see Table 2

The above-prepared "2K-epoxy" system is applied to bright aluminium plates (102 x 152 mm) of the Mill Finish 3105 H24 type (manufacturer: Q-Panel, Cleveland/USA) in a layer thickness, after drying, of 50 to 60 μm and dried at a temperature of 20°C for seven days.

Before weathering begins, a cutting device is used to damage the surface-coating films in a defined manner, the damage taking the form of a parallel cut (that is to say parallel to the longest edge of the sheet). The edges of the sheet are protected by -attaching edge- protection means. The prepared test plates are exposed to hydrochloric acid vapour in accordance with DIN EN 3665 and then to air, and, thus prepared, are subjected to a corrosion test (filiform test) in a test chamber (humidity chamber), the tests also being evaluated in accordance with DIN 53 209 (number of blisters m/blister size g). The results are given in Table 4.

Table 4: Filiform test 800 hours (DIN EN 3665)

Example

Blistering Degree Appearance Blistering* Infiltration^*

(m/g) Ri (m/g) (mm)

SrCrO₄ 5/1 Ri1 4 5/2 0.6-1.0

K-White®G105 0/0 RiO 6 5/2 0.1-0.5

Example 6 0/0 RiO 6 5/1 0.1-0.5

Example 7 0/0 RiO 6 3/1 0.1-0.5

Example 9 -/- Ri- - -/- —

Example 10 -/- Ri- - -/- —

Blistering or filiform corrosion, thread-like defects

Claims

What is claimed is:

1. A tripolyphosphate of formula I

M_aH_bP₃O₁₀ I, wherein M is NR₄, NR₃H, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is Cr jalkyl, C_rC₈alkoxy, or phenyl unsubstituted or mono- to tri-substituted by C C₄alkyl, C.,-C₄alkoxy or by halogen, and wherein a (valency of M) + b = 5, and a = 1 , 2, 3, 4 or 5 and b = 0, 1 , 2, 3 or 4, or a mixture of such compounds.

2. A mixture, comprising

(a) a tripolyphosphate I according to claim 1 and/or

(b) AIH₂P₃O₁₀ and/or Ca₂HP₃O₁₀ and/or FeH₂P₃O₁₀.

3. A mixture according to claim 2, comprising

(a) from 0.1 to 99.9 % by weight of a tripolyphosphate I according to claim 1 , and

(b2) from 0 to 100 % by weight of Ca₂HP₃O₁₀, (b1) and/or (b2) being present in an amount of at least 0.1 % by weight, and the sum of the percentages by weight of both (b1) and (b2) and (a) and (b) being 100 % by weight.

4. A mixture, comprising

(a) from 0 to 99.9 % by weight of a tripolyphosphate I according to claim 1 ,

(b) from 0 to 99.9 % by weight of AIH₂P₃O₁₀

(c) from 0 to 99.9 % by weight of Ca₂HP₃O₁₀

(d) from 0 to 99.9 % by weight of FeH₂P₃O₁₀

5. A process for the preparation of a tripolyphosphate according to claim 1 , wherein

(a) a mixture of

(A) water and

(B) M_e(H₂PO₄)_e, wherein e is the valency of M and may be 1 , 2, 3, 4 or 5, and M is NR₄, NHR₃, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C C₈alkyl, C C₈alkoxy, or phenyl unsubstituted or mono- to tri-substituted by C₁-C₄alkyl, C C^lkoxy or by halogen, either (a1) is heated first to a temperature in the range from 120 to 250°C for from one to five hours and then to a temperature in the range from 250 to 500°C for from one minute to ten hours, or

(a2) is heated directly to a temperature in the range from 250 to 500°C for from one minute to 20 hours,

(b) then water is added at a temperature in the range from 20 to 150°C, the ratio by weight of water to product from (a) being selected in the range from 1 :1 to 20:1 , and the treatment being carried out for from one to 20 hours,

6. A process for the preparation of a mixture according to claim 2, wherein (a) a mixture of

(A) water,

(B) AI(H₂PO₄)₃ and/or Ca(H₂PO₄)₂ and/or Fe(H₂PO₄)₃, and

(C) M_e(H₂PO₄)_e, wherein e is the valency of M and may be 1 , 2, 3, 4 or 5, and M is NR₄, NHR₃, NR₂H₂, NRH₃, NH₄, Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni or Co, and R is C C₈alkyl, C^-Csalkoxy, or phenyl unsubstituted or mono- to tri-substituted by C_rC₄alkyl, C₁-C₄alkoxy or by halogen, either

(a1) is heated first to a temperature in the range from 120 to 250°C for from one to five hours and then to a temperature in the range from 250 to 500°C for from one minute to ten hours, or (a2) is heated directly to a temperature in the range from 250 to 500°C for from one minute to 20 hours,

7. A process for the preparation of a mixture according to claim 2, wherein an oxide, hydroxide, carbonate, hydrogen carbonate, silicate, primary, secondary or tertiary phosphate, pyrophosphate, hydrogen pyrophosphate, di-, tri- or poly-phosphate, metaphosphate, metapolyphosphate, nitrite, nitrate, halide or sulfate, of a metal selected from the group consisting of Li, Na, K, Mg, Sr, Mn, Zr, Sn, Cu, Ag, Ce, Y, La, Zn, Ti, V, Bi, Ni and Co and also calcium, aluminium and iron, or an ammonium hydroxide, carbonate, hydrogen carbonate, phosphate, pyrophosphate, hydrogen pyrophosphate, diphosphate, triphosphate, polyphosphate, metaphosphate, metapolyphosphate, nitrite, nitrate, halide or sulfate, is reacted with phosphoric acid or a phosphate-containing compound and the product is subsequently calcined.

8. A process for the preparation of a mixture according to claim 4, wherein a tripolyphosphate I, AIH₂P₃O₁₀, Ca₂HP₃O₁₀ or FeH₂P₃O₁₀ or a mixture thereof is treated with at least one base selected from the group consisting of oxides, hydroxides, carbonates, phosphates, silicates and metasilicates of alkali metals, alkaline earth metals and of iron, cobalt, nickel, zinc, aluminium, titanium, zirconium, yttrium, vanadium, cerium, lanthanum, manganese, bismuth, copper, silver and tin, and primary, secondary and tertiary amines, polyamines, and ammonium compounds, with the proviso that when a mixture of AIH₂P₃O₁₀ and M_aH_bP₃O₁₀, wherein M = Bi or Bi and Mn, is used or when FeH₂P₃O₁₀ is used as the sole component, the base does not contain zinc.

9. Use of a tripolyphosphate according to claim 1 or of a mixture according to claim 2, 3 or 4 as an anti-corrosion agent.

10. An anti-corrosion agent, comprising a tripolyphosphate I according to claim 1 , or AIH₂P₃O₁₀ and/or Ca₂HP₃O₁₀ and/or FeH₂P₃O₁₀ that have been treated with at least one base according to claim 8, or a mixture according to claim 2, 3 or 4.

11. An anti-corrosion agent, comprising a mixture consisting of

(1) a tripolyphosphate mixture comprising

(1.1) from 0 to 100 % by weight of a component A, consisting of

(1.1.1) from 0 to 99.9 % by weight of AIH₂P₃O₁₀ and

(1.2) from 100 to 0 % by weight of a tripolyphosphate of formula (I) according to claim 1 , the percentages by weight of the mixture components mentioned under (1.1) and (1.2) adding up to 100 % by weight, and it being possible for the components A and the tripolyphosphate of formula I to have been aftertreated with one or more bases in accordance with the process described in claim 8, and

12. A coating composition, comprising an organic film-forming binder and, as corrosion inhibitor, a tripolyphosphate I according to claim 1 or a mixture according to claim 2, 3 or 4.

13. A method of protecting a corrodible metal substrate by applying a coating composition that comprises a corrosion inhibitor, wherein the coating composition used is a coating composition according to claim 12.

14. A method of pretreating metal surfaces, wherein an aqueous solution of a tripolyphosphate of formula (I) according to claim 1 or of a mixture according to claim 2, 3 or 4 is applied as corrosion inhibitor to the metal surface and is then dried or allowed to dry.

15. Use of a tripolyphosphate of formula (I) according to claim 1 or of a mixture according to claim 2, 3 or 4 as an anti-microbial agent or encrustation-inhibiting agent.