This application is a 371 of PCT/FI99/00180 filed Mar. 8, 1999.
The invention relates to methods for the preparation of N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine derivative, and to the products of the method, and to the uses of those products.
The general formula I of the compounds that can be prepared according to the invention is 
where R1 is:
an alkyl hydrocarbon chain containing 1-30-carbon atoms,
an alkyl hydrocarbon chain containing 1-30 carbon atoms as well as 1-10 carboxylic acid groups attached to said chain, or alkali or earth alkali metal salt thereof,
an alkyl hydrocarbon chain containing 1-30 carbon atoms and 1-10 carboxylic acid esters attached to said chain,
a polyethoxylated hydrocarbon chain containing 1-20 ethoxyl groups,
a carboxylic acid amide containing 1-30 carbon atoms, where Nxe2x80x94R1 bond is an amide bond, or
an N-alkyl-N-bis-[2-(1,2-dicarboxy-ethoxy-(ethyl]-amine containing 1-20 carbon atoms in the alkyl chain, or an alkali or earth alkali metal salt thereof,
and R2 and R3 are: hydrogen, an alkali metal ion or an earth alkali metal ion or an alkyl group containing 1-30 carbon atoms.
The compounds to be prepared find use especially as chelating agents.
Transition metal ions and earth-alkali metal ions are bound as water-soluble chelates, for example, in various washing processes. Chelates of metal ions are used in photography chemicals in the developing processes.
When oxygen or peroxide compounds are used in the total chlorine free (TCF) bleaching of pulp it is important to remove the transition metals from the fiber before bleaching, since transition metal ions catalyze the decomposition of peroxy compounds, thus forming radical compounds. In consequence of these reactions the strength properties of the fiber are deteriorated.
Peroxy compounds such as hydrogen peroxide and peroxy acids can also be used in the so-called ECF-bleaching (elemental-chlorine-free-bleaching). Also in sequences which use chlorine dioxide or a combination of chlorine dioxide and peroxy acids, as described in the application FI-974221, a chelating agent can advantageously be used. Traditionally chelating agents are used in the alkaline peroxide bleaching of mechanical pulps such as SGW (stone groundwood), TMP (thermomechanical pulp), PGW (pressure groundwood), CTMP (chemi-theromechanical pulp), etc. A chelating agent can be used directly in the bleaching or as a pretreatment before the bleaching proper. This is especially the case when a multistage peroxide bleaching is employed.
At present, the complexing agents most commonly used in the applications mentioned above are ethylenediaminetetraacetic acid (EDTA) and its salts and di-ethylenetriaminepentaacetic acid (DTPA) and its salts. These are excellent complexing agents, but their biodegradability is poor.
Patent applications FI-960758, FI-960757, FI-960756 and FI-960755 disclose the use of aspartic acid derivatives as chelators in the bleaching of pulp. Such chelators include ethylenediaminedisuccinic acid (EDDS) and its alkali and earth-alkali metal salts, as well as iminodisuccinic acid (ISA) and its alkali and earth-alkali metal salts. EDDS and ISA are effective chelators of transition metals. In addition, they are biodegradable.
EDDS-type aspartic acid derivatives with longer hydrocarbon chain than in EDDS, are known from JP patent applications 7 261 355 and 6 282 044. One such substance is N,Nxe2x80x2-(oxide-2,1-ethanediyl)-bis-L-aspartic acid.
In most cases the chelators are disposed to waste waters after their use. In order to minimize the nitrogen load in waste waters the nitrogen contents of the chelator should be as low as possible. Biodegradable chelators of the type EDDS, wherein some of the nitrogen atoms have been replaced with oxygen atoms, are disclosed in JP patent applications 7 120899 and 7 120894. The applications disclose the use of various isomers of N-[2-(1,2-dicarboxyethoxy)-ethyl]-aspartic acid (EDODS) in photographic chemicals. A method to prepare EDODS by La3+ -catalyzed O-alkylation of maleic acid salts has been described in the literature (J. van Vestrenen et al., Recd. Trav. Chem. Pays. Bas., vol. 109, 1990, p. 474-478).
However, in working tests performed by the applicants, EDODS did not prove to be a sufficiently effective chelator in pulp and paper applications. One possible explanation for the poor chelation result is the length of the carbon chain between the dicarboxyl ethoxy ethyl groups. If the carbon chain is not sufficiently long, strains are produced in the molecule during complexing and the metal complex will not be sufficiently stable.
In a previous application WO97/45396 by the present applicant there were disclosed compounds according to the formula II. 
These compounds include N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine (BCEEA), N-tris-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine (TCEEA) and N-bis-[2-(1,2-di-carboxy-ethoxy)-ethyl]-aspartic acid (BCEEAA), as well as the alkali metal and earth alkali metal salts of the said compounds, preferably Na+, K+, Ca2+ and Mg2+ salts.
In the molecular structure of said compounds, the central atom is a secondary or tertiary nitrogen atom and additionally, the molecule contains four or six carboxylic acid groups, which coordinate effectively with transition metal ions. The carbon chains are sufficiently long in terms of the formation of advantageous bond angles.
The object of the present invention is to provide methods for the preparation of effective chelating agents which would be biodegradable and contain a minimum amount of nitrogen.
According to the invention compounds of the formula (I) can be prepared according to the method where an alkali or earth alkali metal salt of maleic acid is brought to a reaction with an N-substituted diethanolamine with a substituent group R1, to react with the two ethanol groups of said diethanolamine while the substituent group R1 bound to the N atom is essentially unreactive with said maleic acid salt and thus preserved in the derivative obtained as a product, and optionally further reacting the product with a substitution agent, for example 2-bromoacetic acid or 2-chloroacetic acid to obtain a second product. With the exception of the compound referred to as BCEEAA in the above the compounds of the formula (1) are new compounds.
The invention thus comprises preparation of amine compounds according to the formula (I) by using alkali metal or earth-alkali metal salts of maleic acid and N-substituted diethanolamines as starting material in the presence of a lanthanide or earth alkali metal catalyst, in accordance with the following reaction. 
where R1 has a meaning as defined above in connection with the formula (I)
and R2 and R3 alkyl, alkali or earth alkali metal ions.
The preferred meanings of R1 are alkyl and (CH2)nCOOR, where n=1-20 and R=alkyl, alkali or earth alkali metal.
The maleic acid salt which is the intermediate stage in the synthesis can be prepared in an aqueous solution by preferably using, available initial substances such as maleic anhydride and alkali metal or earth alkali metal compounds. Alkali metal compounds suitable for the reaction include lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and lithium carbonate. Earth alkali metal compounds suitable for the reaction include magnesium hydroxide, magnesium oxide, magnesium carbonate, calcium oxide, calcium hydroxide, and calcium carbonate.
The formation of maleate is an exothermal reaction. When maleic anhydride is added to water, maleic acid is formed. When an alkali is added to this solution at a suitable rate, the temperature of the reaction mixture will increase to 80-90xc2x0 C., which is a temperature preferable for the performing of the alkylation reaction.
The amino alcohol, which is a diethanol amine derivative, and the lanthanum compound used as the catalyst can thereafter be added rapidly to the alkaline reaction mixture.
Alternatively, the amino alcohol can be added to the reaction mixture at pH 7 and the pH is adjusted alkaline thereafter.
Rare earth metal ions or their mixtures can be used as the catalyst. Rare earth metal compounds containing organic ligands, achiral or chiral, can be used as catalyst. Likewise, suitable catalysts for O-alkylation include earth-alkali metal compounds such as calcium oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide and magnesium carbonate. Furthermore, nickel compounds can be used as the catalyst.
Rare earth metal catalyzed O-alkylation of maleic acid salt with amino alcohols is a useful reaction, since the synthesis is a one-pot synthesis and the catalyst can be recycled. The catalyst can be separated from the reaction mixture after the reaction by rendering the reaction mixture acidic by means of mineral acids or organic acids followed by addition of oxalic acid to the reaction mixture. The rare earth metal oxalate precipitate formed can be separated from the reaction mixture by filtration. The catalyst can also be precipitated from the reaction mixture by addition of a molar excess of oxalic acid. Furthermore, the catalyst can be precipitated from the reaction mixture by addition of sodium carbonate. The rare earth metal carbonate formed can be separated from the reaction mixture by filtration.
The pH of the reaction mixture before the precipitation of the catalyst can be adjusted by using hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid or oxalic acid, most preferably hydrochloric acid, formic acid, acetic acid or oxalic acid.
It is preferable to use as the catalyst lanthanum(III) compounds, such as lanthanum maleate, lanthanum(III) nitrate, lanthanum(III) chloride, lanthanum oxide or lanthanum octanoate. Likewise, lanthanum compounds which contain organic ligands, chiral ligands or achiral ligands, can be used as a catalyst in the reaction. Also other metal salts belonging to the lanthanum group can advantageously be used, especially such as praseodymium and neodymium salts depending on the availability and price of the compounds.
The lanthanum(III) ion used as a catalyst can be separated from the oxalate precipitate by treating the precipitate with nitric acid or hydrochloric acid. After the treatment the catalyst can be reused. Moreover, the lanthanum ions can be recovered to lanthanum oxide (La2O3), lanthanum hydroxide or lanthanum carbonate by treating the precipitate at elevated temperatures (400-1000xc2x0 C.).
When the lanthanum catalyst is precipitated from the reaction mixture as lanthanum carbonate, it can be either reused as is or converted to lanthanum oxide (La2O3) or lanthanum hydroxide by treating the precipitate at elevated temperatures (400-1000xc2x0 C.).
The invention further comprises a modification of the above described process in which an alkali metal or earth-alkali metal salt of maleic acid and diethanolamine are used as starting materials in the presence of a lanthanide or earth alkali metal catalyst. The synthesis starts with the following reaction: 
where R2 and R3=alkyl, alkali or earth alkali metal ions.
N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-aspartic acid (BCEEAA) as obtained can be converted to N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine by stirring the acidic reaction product containing N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-aspartic acid BCEEAA at elevated temperature for 1-2 hours. The cyclic amide A formed in this reaction can be further converted to N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine BCEEA in basic conditions. These reactions are as follows: 
At the last stage of the process the N-bis[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine as obtained is N-substituted by using a substitution agent replacing the hydrogen bound to the N atom with an organic group. The N-bis[2-(1,2-dicarboxyethoxy)-ethyl]-amine can thus be N-substituted by using a carboxylic acid halide, a carboxylic acid anhydride, a methoxylalcoxyl halide or an alkyl halide. 2-chloroacetic acid and 2-bromoacetic acid may be cited as examples. If for instance an organic chloride is used as the substitution agent the reaction is as follows: 
R1 may have the meanings as defined before.
The invention specifically comprises the novel compounds according to formula (I) wherein R1 is a group selected from alkyl groups and groups comprising an alkyl chain with a single carboxylic acid group, and R2 and R3 represent hydrogen or alkali or earth alkali metal ions. N-methyl-N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine or its alkali or earth alkali metal salt and N-carboxymethyl-N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]-amine or its alkali or earth alkali metal salt are specific examples of the novel compounds.
The compounds obtained according to the invention are especially well suited for use in alkaline aqueous solutions, such as detergents and cleaning agents. Furthermore, the compounds are suited for use in photography chemicals.
The compounds as obtained are useful chelators in, for example, alkaline aqueous solutions of hydrogen peroxide or in alkaline or acidic solutions of peroxy compounds such as peracetic acid. The compounds are particularly useful as chelators of transition metals in a pretreatment before the bleaching of cellulose with ozone, hydrogen peroxide or peroxy acids such as performic, peracetic, perpropionic or Caro""s acid and combinations of the same.
The compounds are usable chelators of earth alkali metals from alkaline water solutions. This ability makes them useful in detergent applications.
Since the compounds as obtained do not contain phosphorus and contain very little nitrogen, they load the environment considerably less than do the chelators currently used.
Specific uses covered by the invention are defined in claims 14-18.
The invention is described below with the help of examples. However, these examples do not limit the invention.