Abstract:
A specially defined amount of hydrogen peroxide is used as a polymerization catalyzer; a specially defined amount and a specially defined kind of a polyvalent metal ion is used; and a specially defined amount of an alkaline substance is used, in order to polymerize a monomer component consisting essentially of only maleic acid, or a monomer component composed of maleic acid and another water-soluble ethylenically unsaturated monomer, in a specially defined proportion in water, whereby a maleic acid polymer salt, preferably a copolymer salt, of improved biodegradability is produced. The maleic acid polymer salt obtained is superior in biodegradability, has a low residual monomer content, and is useful as a detergent builder and as a scale inhibitor, etc.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a process for producing and use of maleic acid (co-)polymer salt improved in biodegradability. In detail, it relates to a process for producing a maleic acid (co-)polymer salt improved in biodegradability, which is very useful as a detergent building, a scale inhibitor, and various kinds of chelating agents etc., by using a specially defined polymerization catalyzer and a specially defined polymerization method, with high efficiency and cheap cost, and also, relates to the use as a detergent building and a scale inhibitor etc. 
     As a detergent building, a scale inhibitor, and a chelating agent etc., an additive based on phosphorus, such as a condensed phosphoric acid salt and a phosphoric acid salt, has so far been used. However, when run into the sea or lake through a river etc., these become an original substance for a red tide etc., so that their use is very limited. Thus, instead of a phosphorus additive, an additive in a series of polycarboxylic acid salts has practically been used in recent years in the forementioned field and in large quantity. However, the polycarboxylic acid salts additive which have so far been used are all poor in the biodegradability and, for example, in a case where it is used in large quantity as a detergent building or a scale inhibitor etc., there may take place such a greatly serious problem as the accumulation in circumstances. 
     For example, although there is proposed a maleic acid (co-)polymer (salt), which is obtained with polymerization in a mixed solvent of water and a primary alcohol or carbon number 1 4 or a ketone of carbon number 3 4 in Japanese Official Patent Provisional Publication, showa 62-91295, and Japanese Official Patent Provisional Publication, showa 62-91296, the maleic acid (co-)polymer (salt) thus published was low in the biodegradability and insufficient in properties useful as a scale inhibitor. Besides, in these arts, a maleic acid (co-)polymer (salt) of high polymerization percentage was not obtained. Also, although there are proposed maleic acid (co-)polymer salts obtained by a polymerization in water solvent in the presence of hydrogen peroxide, which were described in Japanese Official Patent Provisional Publications, showa 57-168906 (U.S. Pat. No. 4,519,920), showa 59-64615 (U.S. Pat. No. 4,668,735), showa 59-176312 (U.S. Pat. No. 4,589,995), showa 59-210913, showa 59-21374, showa 60-212410, showa 60-212411 (U.S. Pat. No. 4,709,091), showa 60-212412, showa 612-178097, showa 62-218407 (U.S. Pat. No. 4,659,793), showa 63-114986, showa 63-235313, and showa 63-236600, the maleic acid (co-)polymer salts thus published show very inferior biodegradability. There is no description about the biodegradability in all said literatures. 
     On the other hand, although there is described in &#34;YUKAGAKU, 35, 937 (1986)&#34; that sodium poly-β-DL-malic acid, which is formed with ring-opening polymerization of malolactons, shows high biodegradation percentage, properties of this polymer as a detergent building are unsufficient, and the synthesis of this polymer requires a complex process, so that the industrial utility is low. Also, there is described that a polymer of α-hydroxyacrylic acid shows biodegradability, but this polymer decomposes only with specially defined bacteria, and the synthesis and this polymer requires a complex process and, as a result, it becomes very expensive, so that the industrial utility is low. 
     Therefore, there has been greatly desired a process with which a polycarboxylioc acid salt which has useful biodegradability as a detergent builder, a scale inhibitor, and various kinds of chelating agents etc. is produced with cheap cost and in a high yield. 
     SUMMARY OF THE INVENTION 
     As a result of extensive studies, the present inventors improved the low biodegradability of a hitherto known polycarboxylic acid salt. Furthermore, they greatly raised the industrial utility by improving the insufficient properties of a hitherto known polycarboxylic acid salt as a detergent builder and a scale inhibitor. 
     That is, the first aspect of the present invention relates to a process for producing a maleic acid (co-)polymer salt improved process for producing a maleic acid (co-)polymer salt improved in biodegradability which, in a case where a monomer component composed of 75 100 weight % of maleic acid (A) and 25 0 weight % of another water-soluble ethylenically unsaturated monomer (B) (here, the total amount of (A) and (B) is 100 weight %) is polymerized in an aqueous solution, catalyzed by in 12.sup.˜ 150 g of hydrogen peroxide (against 1 mole of the monomer component) and the polymerization is carried out under a condition such that there exist 0.3 500 ppm (against weight of the monomer component) of at least a kind of polyvalent metal ion selected from a vanadium ion, an iron ion, and a copper ion as well as an alkaline substance which is required to neutralize up to 45 mole % of the whole acid group in the monomer component. 
     The second and the third aspects of the present invention, respectively, relates to the use of the products of the first aspect of this invention as a detergent builder and a scale inhibitor, both of which are characterized by being composed of a maleic acid (co-)polymer salt improved in biodegradabilty that is obtained from said first aspect of the present invention. 
     In this invention, it is necessary to surely use water as a polymerization media. When a hydrophobic solvent alone, such as an aromatic hydrocarbon, a hydrophilic solvent alone, such as alcohol and ketone, and a mixture of solvents, such as a mixture of water with these hydrophilic solvents, are used as a solvent in polymerization, the biodegradability of the product becomes very lower due to differences between a terminal end group or a main chain structure of the generated polymer and that of the maleic acid (co-)polymer salt of the present invention. That is, the biodegradability lowers by reason of either the terminal end of the polymer was an alcoholic or ketonic residue or because decarboxylation does not occur. 
     In the present invention, when the monomer component containing maleic acid is polymerized in an aqueous solution, it is essential that the polymerization is carried out under a condition of that there exist at least one polyvalent metal ion selected from a vanadium, an iron ion, and a copper ion in an amount in the range of 0.3 500 ppm, against the monomer component (standard weight of an acid form). Preferably, it is a range of 0.5 300 ppm and, more preferably, a range of 1 50 ppm. If the amount used is less than 0.3 ppm, the residual monomer increases unpreferably. If the amount used exceeds 500 ppm, the biodegradability lowers. Furthermore, the product purity decreases unpreferably. Also, in the case where an ion besides the vanadium ion, iron ion, and a copper ion is used, the amount of the residual monomer increases as in the case where metal ion is not used at all, and the biodegradability becomes low. 
     As a vanadium ion, an iron ion, and a copper ion being used in this invention, for example, there are cited V z+ , V 3+ , VO 2+ , VO 3   2-  Fe z+ , Cu z+ , and so on, but among those, are preferred VO z+ , Fe 3+ , Cu 2+ . In the case where increase in polymerization yield is desired, the VO z+  ion is most preferred. The polyvalent metal ion is not especially limited in the form being supplied into a polymerization system, and if it is capable of ionizing in a polymerization system, it can be fed as a polyvalent metal compound or as a simple substance. 
     As a polyvalent metal compound or a simple substance like the above, for example, are cited water-soluble polyvalent metal salts such as vanadium oxytrichloride, vanadium trichloride, vanadyl oxalate, vanadyl sulfate, anhydrous vanadic acid, ammonium methavanadic acid, ammonium hypovanadous sulfate ((NH 4 )  z  SO 4  . VSO 4  .6 H 2  O), ammonium vanadous sulfate ((NH 4 ) VSO 4 .12 H 2  O), cupric acetate, cupric bromide, cupric acetyl acetate, ammonium cupric chloride, cupric carbonate, cupric chloride, cupric citrate, cupric formate, cupric hydroxylic acid, cupric nitrate, cupric naphthenic acid, cupric oleinic acid, cupric maleate acid, cupric phosphate, cupric sulfate, iron acetyl acetonate, ammonium iron citrate, ammonium ferric oxalate, ammonium ferrous sulfate, iron citrate, iron fumarate, iron maleate, ferrous lactate, ferric nitrate, iron pentacarbonyl, ferric phosphate, ferric pyrophosphate and so on; polyvalent metal oxides such as vanadium pentoxide, cupric oxide, ferrous oxide, ferric oxided, and so on; polyvalent metal sulfides such as cupric sulfide, ferric sulfide, ferrous sulfide, and so on; others such as copper powder, iron powder, and so on. 
     Furthermore, in order to adjust the ion concentration of the polyvalent metal ions, it is possible to use, in combination with the forementioned polyvalent metal ion, for example, a chelate-forming agent based on condensed phosphoric acids such as pyrophosphoric acid, hexamethaphosphoric acid, and tripolyphosphoric acid etc.; aminocarboxylic acids such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, and diethylenetriaminepentaacetic acid etc.; phosphonic acids such as 1-hydroxyethylydene-1,1-diphosphonic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid etc.; organic acids such as fumaric acid, malic acid, citric acid, itaconic acid, oxalic acid, and crotonic acid, etc.; and polycarboxylic acids such as polyacrylic acid etc. The polymerization temperature preferred is in a range of 85 180° C., because it fits with a purpose of short polymerization time and increase of biodegradability. The more preferable temperature is in a range of 100 150° C. If the temperature is less than 85° C., the polymerization process may be disturbed. During polymerization, a solid portion is performabe in a wide range, but the 30.sup.˜ 99 weight %, more preferably the range of 40.sup.˜ 95 weight % is recommended because of capability to reduce the amount of the residual monomer. 
     In the present invention, these should be used 12.sup.˜ 150 g (against 1 mole of a monomer component) of a polymerization initiator. Preferably 15.sup.˜ 100 g (against 1 mole of a monomer component) and more preferably 20.sup.˜ 70 g (against 1 mole of a monomer component) are used. In the case of an amount less than 12 g (against 1 mole of a monomer component), a maleic acid (co-)polymer salt which is superior in biodegradability can not be obtained. In the case of an amount exceeding 150 g (against 1 mole of a monomer component), although the biodegradability does not decrease, hydrogen peroxide is apt to remain in the obtained maleic acid (co-)polymer salt and the cost for production increases, so that an amount of 150 g or less is preferably used. Also, if the hydrogen peroxide is replaced with another water-soluble initiator, for example with a persulfate salt, such as ammonium persulfate, sodium persulfate, and potassium persulfate, etc.; a hydrophilic organic peroxide such as tertiary-butyl hydroperoxide, etc.; a water-soluble azo compound such as 2,2&#39;-azobis (2-aminozinopropane) hydrochloric acid salt, etc., a maleic acid (co-)polymer salt, which has superior biodegradability as that produced by this invention, can not be obtained. A method to supply the hydrogen peroxide into water is not especially limited and, for example, it is carried out by one time addition into the reaction system at an initial stage, continuous addition into the reaction system, or in a case, dividing followed by adding into the system. 
     In the present invention, the polymerization is required to be carried out under a condition that an alkaline substance, necessary for neutralizing up to 45 mole % of the whole acid group of the monomer component exists. A preferable range can be set as 5 to 40 mole %. A maleic acid (co-)polymer salt, which is obtained under a condition such that an alkaline substance exceeding 45 mole % exists, shows inferior biodegradability. 
     As described above, if the existing amount of the alkaline substance exceeds 45 mole % compared to the whole acid group, or if an especially defined amount of an especially defined polyvalent metal ion or an amount of 12 g or more of hydrogen peroxide is not used, the obtained maleic acid (co-)polymer salts show very inferior biodegradability. 
     Although there is no special limitation on the alkaline substance which can be used, there are cited the hydroxides or carbonates of alkali metals such a sodium, potassium, and lithium etc.; ammonia; the alkylamines, such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamined etc.; the alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, and dimethyethanolamine, etc.; pyridine and so on. Among those, the hydroxides and carbonates of alkali metals, since they are of cheap cost and most easily available from an industrial viewpoint, are especially preferred. 
     Also, the maleic acid (co-)polymer salt in this invention is required to be derived from a monomer component which contains 75 weight % or more of maleic acid (in the case where the water-soluble ethylenically unsaturated monomer B) is a monomer in the salt form, it is necessary that the amount used is 25% or less on a standard of the acid form). More preferably the amount can be 80 weight % or more. A maleic acid (co-)polymer salt, which results from polymerization of a monomer component that contains 75 weight % of maleic acid, shows very inferior biodegradability. 
     It should be remembered that the present invention is not to be confused with the conventional art of component conditions similar to the present invention. For example, the maleic acid (co-)polymer salt, which is published in said Japanese Official Patent Provisional Publication, showa 62-218407 (U.S. Pat. No. 4,659,793), show very inferior biodegradability because of any one of the undermentioned reasons, that is, because the amount of maleic acid used is less than that used in the case of the maleic acid (co-) polymer salt of the present invention, or because 12 g (against 1 mole of a monomer component) or more of hydrogen peroxide has not been used in an example of the publication, furthermore because the neutralization extent against the whole acid group is 50% or more. Besides, there is no description about the biodegradation in the literature. The present invention overcomes a significant lack of biodegradability of the maleic acid copolymer salt, which is published in said Japanese Official Patent Provisional Publication, showa 62-218407 (U.S. Pat. No. 4,659,793), as well as insufficiency in properties which a detergent builder and a scale inhibitor etc. should have. 
     It should be understood that maleic anhydride can of course replace maleic acid (A), because the maleic anhydride easily reacts with water converting it into maleic acid. 
     As long as the water-soluble ethylenically unsaturated monomer (B) of this invention is water-soluble and is a monomer capable of copolymerization with maleic acid, the monomer (B) can be used without any limitation. The polymer salts thus-derived from polymerization of maleic acid alone and from copolymerization with maleic acid show very high biodegradability compared with that of the conventional maleic acid (co-)polymer salt. 
     As the water-soluble ethylenically unsaturated monomer (B), for example, are cited monomers such as unsaturated monocarboxylic acids, such as acrylic acid, methacrylic acid, α-hydroxyacrylic acid, and crotonic acid etc.; unsaturated polycarboxylic acids such as fumaric acid, itaconic acid, citraconic acid, and aconite acid: 
     a monomers which are shown by the general formula (1) in the series of unsaturated alcohols ##STR1## (in the formula, R 1  and R 2  independently represent a hydrogen atom of a methyl group but are not both methyl group, R 3  represents a CH 2  --, --(CH 2 ) 2  --), or --C(CH 3 ) 2  -- group and the total number of the carbon atoms in the R 1 , R 2 , and R 3  groups is 3, Y represents an alkylene group of carbon number 2 to 3, and n is 0 or a integral number of 1 to 100) such as allyl alcohol and polyethyleneglycol monoallyl ether: a monomer which is shown by the general formula (2) in a series of unsaturated allyl ethers ##STR2## (in the formula, R 1  represents a hydrogen atom or a methyl group, a, b, d, and f independently represent 0 or a positive integral number and the total number of a, b, d, and f is 0 to 10, the --(OC 2  H 4 )-- and --(OC 3  H 6 )-units may be combined in any order, Z represents a hydroxyl, sulfonic acid, or phosphoric (or phosphorous) acid group when the sum of d and f is 0, and Z represents a hydroxyl group when the sum is a positive integral number of 1 to 100): a monomer containing an unsaturated sulfonic acid group such as vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, sulfoethylmaleimide, sulfopropyl (meth) acrylate, 2-hydroxysulfopropyl (meth) acrylate etc.: a monomer in a series of water-soluble mono- or diesters between an alcohol, which is formed by the addition of 0 to 100 moles of ethylene oxide and/or propylene oxide to an alkylalcohol of carbon number 1 to 50, and (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, or aconitic acid etc.: a monomer in a series of mono- or di esters containing a water-soluble hydroxyl group which are formed by the addition of 1 to 100 mole of ethylene oxide and/or propylene oxide to a monomer in a series of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crontonic acid, maleic acid, fumaric acid, itaconic acid, citranconic acid and aconitic acid etc.: a monomer in a series of unsaturated amides such as N-methylol (meth) acrylamids, (meth) acrylamide, tertiary-butyl (meth) acrylamide etc.: a monomer in a series of unsaturated phosphorus-containing compounds such as (meth) acrylamidomethanephosphonic acid, (meth) acrylamidomethanephosphoic acid methyl ester, and 2-(meth) acrylamido-2-methylpropanephosphonic acid etc.: and a monomer in a series of unsaturated aminoalkyl compounds such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide etc., and one or two or more kinds of monomers selected from these groups can be used. 
     In the case where a maleic acid (co-)polymer salt, obtained from a process for producing such, according to the present invention, is used as a detergent builder and a scale inhibitor, although there is no special limitation, the undermentioned unsaturated monomer is preferred as a water-soluble ethylenically unsaturated monomer (B). That is, these are preferred acrylic acid, methacrylic acid, a monomer in a series of unsaturated alcohols which is represented by the general formula (1), ##STR3## (but in the formula, R 1  and R 2  independently represent a hydrogen atom or a methyl group but both cannot be methyl groups at the same time, R 3  represents a --CH 2  --, --(CH 2 ) 2  --, or --C(CH 3 ) 2  -- group, the total of carbon number in the R 1 , R 2  and R 3  groups is 3, Y represents an alkylene group of carbon number 2 to 3, and n is 0 or a integral number of 1 to 100), for example, 3-methyl-3-buten-1-ol (isoprenol), 3-methyl-2-buten-1-ol (prenol), 2-methyl-3-buten-2-ol (isoprenealcohol) and a monomer which is formed with addition of 1 to 100 moles of ethylene oxide and/or propylene oxide to 1 mole of the forementioned unsaturated alcohol monomers (among them, isoprenol and polyethyleneglycol monoisoprenol ether are especially preferred.): and a monomer in a series of unsaturated allyl ethers, which is shown by the general formula (2), ##STR4## (but in the formula, R 1  represents a hydrogen atom or a methyl group, a, b, d, and f independently represent 0 or a positive integral number and the total of a, b, d, and f is 0 to 100, the units --(OC 2  H 4 )═ and --(OC 3  H 6 )-- may be combined in any order, Z is a hydroxyl, sulfonic acid, or phosphoric (or phosphorous) acid group when the sum of d and f is 0, and Z is a hydroxyl group when the sum of d and f is a positive integral number of 1 to 100.), for example, 3-(meth)allyloxy-2-hydroxypropanesulfonic acid, 3-(meth)allyoxy-2-hydroxypropanephosphorous acid, glycerol monoallyl ether, and a monomer which is formed with addition of 1 to 100 moles of ethylene oxide and/or propylene oxide to 1 mole of the forementioned allyl ether monomers (among them, 3-allyloxy-2-hydroxypropanesulfonic acid and glycerol monoallyl ether are especially preferred) and the like. In the case where these monomers are used, the dispersion ability of a detergent against a dirty component and the protective property of a scale inhibitor for attaching and so on are elevated, very preferably as a detergent builder and a scale inhibitor. 
     Besides, although in this invention a monomer in the salt form, which is neutralized with an alkaline substance, is possible for use as the maleic acid (A) and water-soluble ethylenically unsaturated monomer (B), in a case of that the monomer of a salt form is used, it is necessary to use an amount such that the neutralization extent for the whole acid group at the time of polymerization is up to 45 mole %. 
     Furthermore, a maleic acid (co-)polymer in the acid form, which is obtained without use of an alkaline substance, and a maleic acid (co-)polymer salt which is obtained from neutralization of the above polymer with an alkaline substance, even if the neutralization extent is 45 mole % or less, shows low biodegradability. 
     According to the process of this invention, a maleic acid (co-)polymer salt of 300 to 8,000 in molecular weight is usually obtained. 
     Why the maleic acid (co-)polymer salt obtained from the process described in this invention shows superior biodegradability is not yet clear, but it is guessed as follows. That is, decarbonylation takes place during polymerization and, as a result, a carbonyl group is formed in a main chain of the maleic acid (co-)polymer salt. Otherwise, an ether bond is formed in a main chain of the maleic acid (co-)polymer salt because a specially defined amount of a specially defined catalyzer for polymerization is used in a range of a specially defined neutralization extent and a specially defined polyvalent metal ion is used in a specially defined amount. Either one or both of the carbonyl structure and the ether bond is guessed to have a great effect on an increase of the biodegradability and an increase of properties as a detergent builder and a scale inhibitor and the like. 
     Accordingly, in the process for producing this invention, a maleic acid (co-)polymer salt, substantially improved in biodegradability, is obtained with high efficiency by using a definite amount in a range of hydrogen peroxide as a polymerization catalyzer under a condition of a specially defined neutralization extent and in the presence of a specially defined polyvalent metal ion, and that the (co-)polymer salt has superior properties as a detergent builder and a scale inhibitor etc. which could not have been predicted at all from the hitherto known conventional art. 
     The maleic acid (co-)polymer salt obtained from the process for producing this invention shows no toxicity and much improved biodegradability compared with that of the hiterto known polycarboxylic acid salts and, for example, in a case where it is used in large quantity as a detergent builder and a scale inhibitor, an important problem, such as accumlation in circumstances, can be greatly improved and, therefore, it is of very high utility in an industrial viewpoint. 
     DESCRIPTION OF THE INVENTION 
     Hereinafter, although the present invention is concretely explained with the examples, it is not limited to the examples. Besides, the % and part in the examples indicate the weight % and weight part, respectively. 
    
    
     EXAMPLE 1 
     Into a 1 l four-neck flask equipped with a therometer, a stirrer, and a reflux condenser were placed 196 parts of maleic anhydride (232 parts as maleic acid), 75.1 part of deionized water, 0.0138 parts of vanadyl sulfate dihydrate (as VO 2  +, 20 ppm against the weight of the monomer component), and 66.7 parts of a 48% aqueous sodium hydroxide solution (20 mole % against the whole acid group of the monomer component) and, with stirring, the aqueous solution was brought to boiling temperature under ordinary pressure. Next, 113.4 parts of a 60% hydrogen peroxide solution (34 g against 1 mole of the monomer component) was added dropwise continuously during 3 hours and a polymerization reaction was carried out. After completion of the additions, the reaction mixture was stirred for a further 1 hour at the boiling point of the mixture to complete the polymerization reaction, whereby a maleic acid polymer salt (1) of a 53% solid component was obtained, which was analyzed by gel permeation chromatography for determination of the amount of the residual monomer and the molecular weight of the produced polymer: 
     Besides, the biodegradation percentage (%) of the maleic acid polymer salt (1) obtained is determined by the following equation. ##EQU1## X: Biodegradation percentage (%) during 5 days A: Amount of oxygen biologically required by a maleic acid (co-)polymer (salt) during 5 days (BOD5) (*1) 
     B: Amount of oxygen biologically required by a residual monomer during 5 days (*2) 
     C: Amount of oxygen theoretically required by a maleic acid (co-)polymer (salt) (*3) 
     D: Amount of oxygen theoretically required by a residual monomer 
     (*1) It was determined with the undermentioned method which is in turn due to the Japanese Industrial Standard; JIS K0102. 
     At first, to 1 l of distilled water, wherein the water temperature was adjusted to about 20° C. and dissolving oxygen was saturated, were added 1 ml of a buffer solution of pH 7.2 containing 21.75 g/l of dipotassium hydrogenphosphate (potassium hydrogen phosphate), 8.5 g/l of potassium dihydrogenphosphate, 44.6 g/l of disodium hydrogenphosphate 12-hydrate (sodium hydrogenphosphate 12-hydrate), and 1.7 g/l 12-hydrate), and 1.7 g/l of ammonium chloride, respectively, 1 ml of an aqueous magnesium sulfate solution containing 22.5 g/l of magnesium sulfate 70hydrate, 1 ml of an aqueous calcium chloride solution containing 27.5 g/l of anhydrous calcium chloride, and 1 ml of an aqueous ferric chloride solution containing 0.25 g/l of ferric chloride 6-hydrate, whereby a diluted aqueous solution of pH 7.2 was prepared. Besides, this diluted aqueous solution was filled in the undermentioned bottle for cultivation and allowed to stand for 5 days in a thermostate of 20° C., thereby it was confirmed that difference in the amounts of dissolved oxygen between the initial time and after 5 days is 0.2 mg ∘/l or less. 
     Next, a diluted solution for innoculating was prepared by that a solution for innoculating composed of a supernatant fluid of a drain, a river water, a soil-extracting solution and the like was added to said diluted aqueous solution. 
     Next, using a siphon and giving attention to that a bubbie does not enter in, said diluted aqueous solution or the diluted solution for innoculating was filled up to about a half of 1 l messcylinder of a common stoper (in a case of that the undermentioned bottle for cultivation is 200 ml or more, a 2 l messcylinder of a common stopper is used). To this messcylinder was added a sample of proper amount and, to this, said diluted aqueous solution or the diluted solution for innoculating was added up to a 1 l symbol line (a 2 l symbol line in a case of that the messcylinder of a common stopper is 2 l), stopped, and quietly mixed. Four or five kinds of diluted samples in which the dilution magnification differs stepwise were prepared by that a similar procedure was repeated with changing the amount of the sample or diluting a diluted sample again. 
     For each one kind of the diluted samples thus-prepared, respectively, 2˜4 pieces of 100˜300 ml bottles for cultivation, whose volumes are exactly known, made of a glass and equipped with a thin common stopper, whose top is cut obliquely, were arranged and, using a siphon, said diluted samples were transferred into the bottles to fill with overflow and tightly stoppered. 
     Said diluted samples were allowed to stand for 15 minutes after being prepared, and an amount of dissolved oxygen was determined with a dissolved oxygen meter (D/O meter). 
     Said diluted samples were cultivated for 5 days in a thermostat or in a water bath of constant temperature whose temperature was adjusted at 20°±1° C. and then, an amount of dissolved oxygen was determined as carried out above. 
     With the following equation, the BOD5 (mg∘/l) was calculated of the sample from the dissolved oxygen amounts at before and after caltivation. ##EQU2## Here, BOD5: an amount of oxygen consumed in a sense of biological chemistry when being cultivated for 5 days (mg∘/l). 
     D 1  : an amount of oxygen dissolved in a diluted sample at 15 minutes later since it is prepared (mg∘/l). 
     D 2  : an amount of oxygen dissolved in a diluted sample after cultivation (mg∘/l). 
     P: proportion of a sample in a diluted sample (a ratio of a sample to a diluted sample). 
     B 1  : an amount of oxygen dissolved in a diluted solution for innoculating before cultivation when BOD5 of the solution for innoculating is determined (mg∘/l). 
     B 2  : an amount of oxygen dissolved in a diluted solution for innoculating after cultivation when BOD5 of the solution for innoculating is determined (mg∘/l). ##EQU3## x: a solution for innoculating in a diluted sample when BOD5 of a sample is determined (%). 
     y: a solution for innoculating in a diluted solution for innoculating when BOD5 of a solution for innoculating is determined (%). 
     (*2) The residual monomer amount is quantitatively analyzed with a gel permeation chromatography. The amount of oxygen in each monomer component biologically required is determined according to the same method as in the case of the maleic acid (co-)polymer (salt) and the amount of oxygen in the whole residual monomer biologically required is obtained by calculation. 
     (*3) The amount of oxygen necessary for complete oxydation was determined from the elementary analysis data of each maleic acid (co-)polymer (salt). 
     These results are shown in Table 1. 
     EXAMPLE 2 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salt (2) except that the amount of 48% aqueous sodium hydroxide solution in the example 1 was changed to 117 parts (35 mole % against the whole acid group of a monomer component). The maleic acid polymer salt (2) obtained was analyzed in the same way as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLE 3 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salt (3) except that the amount of the 60% hydrogen peroxide solution in the example 1 was changed to 50 parts (15 g against 1 mole of a monomer component) and 0.0412 parts of ammonium ferric sulfate 12-hydrate (as Fe 3+ , 20 ppm against the weight of a monomer component) was used in place of vanadyl sulfate. The maleic acid polymer salt (3) obtained was analyzed in the same way as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLES 4˜6 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salts (4)˜(6) except that ammonium ferric sulfate 12-hydrate was used in an amount shown in Table 1 instead of vanadyl sulfate and the amounts for use of a 48% aqueous sodium hydroxide solution and the hydrogen peroxide were such as indicated in Table 1. The maleic acid polymer salts (4)˜() were analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLE 7 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salt (7) except that 0.0335 part of ammonium ferrous sulfate 6-hydrate (as Fe 2+ , 20 ppm against the weight of a monomer component) was used instead of vanadyl sulfate. The maleic acid polymer salt (7) obtained was analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLE 8 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salt (8) except that cupric sulfate was used in the amount shown in Table 1 instead of vanadyl sulfate and a 10% aqueous sodium carbonate solution was used in the amount shown in Table 1 instead of the 48% aqueous sodium hydroxide solution. The maleic acid polymer salt (8) obtained was analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLE 9 
     In a vessel for polymerization as used in the example 1 were placed 232 parts of maleic acid, 39.1 parts of water, 0.0506 parts of ammonium ferric sulfate 12-hydrate (as Fe 3+ , 20 ppm against the weight of a monomer component), and 66.7 parts of a 48% aqueous sodium hydroxide solution (20 mole % against the whole acid group of a monomer component) and, with stirring, the aqueous solution was warmed up to the boiling point under ordinary pressure. Then, with stirring, a mixture of 151.6 parts of 60% hydrogen peroxide (34 g against 1 mole of a monomer component) and, as the other water-soluble unsaturated monomer (B), 58 parts of 3-methyl-3-buten-1-ol (isoprenol) (a weight ratio between maleic acid and the water-soluble unsaturated monomer (B) was 80 to 20) was continuously added dropwise during 3 hours to carry out polymerization reaction. After the addition finished, the reaction mixture was further stirred for 1 hour at the boiling temperature to complete polymerization reaction, whereby the maleic acid copolymer salt (9) was obtained. The maleic acid copolymer salt (9) obtained was analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLES 10˜15 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salts (10)˜(15) except that the kind and amount for use of the polyvalent metal ion, the amount for use of the 48% aqueous sodium hydroxide solution, and the amount for use of the 60% hydrogen peroxide in the example 9 were as shown in Table 1. The maleic acid copolymer salts (10)˜(15) obtained were analyzed as carried out in the example 1, and the results obtained in Table 1. 
     EXAMPLE 16 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salt (16) except that 153 parts of a 50% aqueous sodium acrylate solution (as acrylic acid, 58 parts) was used instead of 3-methyl-3-buten-1-ol and the amounts for use of the 48% aqueous sodium hydroxide solution and 60% hydrogen perioxide were as shown in Table 1. The maleic acid copolymer salt (16) obtained was analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLES 17˜25 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salts (17)˜(25) except that the other water-soluble unsaturated monomers (B) as shown in Table 1 were used in the amounts described in Table 1 instead of 3-methyl-3-buten-1-ol and the kind and amount for use of the polyvalent metal ion and the amounts for use of the 48% aqueous sodium hydroxide solution and 60% hydrogen peroxide were as shown in Table 1. The maleic acid copolymer salts (17)˜(25) were analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLES 26˜28 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salts (26)˜(28) except that the other water-soluble unsaturated monomers (B) as shown in Table 1 were used in the amounts described in Table 1 instead of 3-methyl-3buten-1-ol and a 10% aqueous sodium carbonate solution was used in an amount shown in Table 1 instead of the 48% aqueous sodium hydroxide solution and the amount for use of 60% of hydrogen peroxide was as shown in Table 1. The maleic acid copolymer salts (26)˜(28) obtained were analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLE 29 
     In a vessel for polymerization same as used in the example 1 were placed 232 parts of maleic acid, 10 parts of water, 0.0412 parts of ammonium ferric sulfate 12-hydrate (as Fe 3+ , 20 ppm against the weight of a monomer component), and 66.7 parts of a 48% aqueous sodium hydroxide solution (20 mole % against the whole acid group of a monomer component) and then, the procedure of example 1 was repeated to obtain the maleic acid polymer salt (29). The maleic acid polymer salt (29) was analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     EXAMPLES 30 AND 31 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salts (30) and (31) except that the other water-soluble unsaturated monomers (B) as shown in Table 1 were used in the amounts shown in Table 1 instead of 3-methyl-3-buten-1-ol and the amounts for use of the 48% aqueous sodium hydroxide solution and the 60% hydrogen peroxide were as shown in Table 1. The maleic acid copolymer salts (30)˜(31) obtained were analyzed as carried out in the example 1, and the results obtained are shown in Table 1. 
     Examples for Comparison 1˜3 
     The procedure of example 1 was repeated to obtain the maleic acid polymer salts for comparison (1)˜(3) except that the kind and amount for use of the polyvalent metal ion, the amount for use of the 48% aqueous sodium hydroxide solution, and the amount for use of the 60% of hydrogen peroxide solution were as shown in Table 2. The maleic acid polymer salts for comparison (1)˜(3) obtained were analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Examples for Comparison 4˜14 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salts for comparison (4)˜(14) except that the other water-soluble unsaturated monomers (B) as shown in Table 2 were used in the amounts described in Table 2, the kind and amount for use of the polyvalent metal ion, and the amounts for use of the 48% aqueous sodium hydroxide solution and 60% hydrogen peroxide solution were as shown in Table 2. The maleic acid copolymer salts for comparison (4)˜(14) were analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Example for Comparison 15 
     In an apparatus similar to that used in the example 1 were placed 196 parts of maleic anhydride, 131 parts of monochlorobenzene, and 65.4 parts of xylene and the mixture obtained was warmed up to 140° C. To this mixture a solution for dropping 1 composed of 65.4 parts of ditertiary-butyl peroxide, 41 parts of xylene, and 65.4 parts of monomchlorobenzene, and another solution for dropping 2 composed of 26 parts of acrylic acid were added dropwise during 3 hours and then, the reaction was completed by treating under reflux for 3 hours. After the solvent was distilled off, a hydrolysis reaction was carried out with addition of 197 parts of pure water, whereby the maleic acid copolymer for comparison (15) was obtained. This maleic acid copolymer for comparison (15) was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Example for Comparison 16 
     In a vessel for polymerization which was the same as that used in the example 1 were placed 196 parts of maleic anhydride and 300 parts of water (232 parts as maleic acid) and the mixture obtained was warmed up to 60° C. with stirring. The warming was stopped, and 138 parts of a 30% aqueous sodium hydroxide solution and then 140 parts of isopropanol were added. The, temperature of the reaction mixture was raised to the refluxing temperature and, after 0.25 parts of a 4.98% aqueous solution of ferrous sulfate (FeSO 4  .7H 2  O) (1% as FE 2+ ) was added, 40 parts of a 60% hydrogen peroxide solution were added dropwise during 6 hours. After the addition finished, further warming was carried out for 2 hours, whereby the maleic acid copolymer salt for comparison (16) was obtained, which was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Examples for Comparison 17 
     In a vessel for polymerization, which was the same as used in example 1, were placed 12.9 parts of 1-allyloxy-2-,3-dihydroxypropane (glycerol monoallyl ether), 116 parts of maleic acid, 166.6 parts of a 48% aqueous sodium hydroxide solution, and 157.4 parts of water and the aqueous solution thus-formed was warmed up to the boiling point. To this solution, 100 parts of a 10% aqueous ammonium persulfate solution were added dropwise from a dropping funnel during 2 hours and, during the addition, the temperature of polymerization was always controlled at the boiling point of this reaction system. Next, the polymerization was completed by maintaining the system at the temperature for 30 minutes, whereby the maleic acid copolymer salt for comparison (17) was obtained, which was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Example for Comparison 18 
     The procedure of example 1 was repeated to obtain the maleic acid polymer for comparison (18) except that the 48% aqueous sodium hydroxide solution was not used at all. This maleic acid polymer for comparison (18) was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Example for Comparison 19 
     The maleic acid polymer salt for comparison (19) was obtained by that the maleic acid polymer for comparison (18) obtained from the example for comparison 18 was neutralized with 66.7 parts of a 48% aqueous hydroxide solution. This maleic acid polymer salt for comparison (19) was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Example for Comparison 20 
     The procedure of example 9 was repeated to obtain the maleic acid copolymer salt for comparison (20) except that the other water-soluble unsaturated monomer (B) as shown in Table 2 was used in the amount described in Table 2 and the kind and amount for use of the polyvalent metal ion and the amounts for use of the 48% aqueous sodium hydroxide solution and the 60% hydrogen peroxide were as shown in Table 2. The maleic acid copolymer salt for comparison (20) was analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     Examples for Comparison 21 and 22 
     In a vessel for polymerization which was the same as used in example 1 were placed 232 parts of maleic acid, 200 parts of water, 0.0412 parts of ammonium ferric sulfate 12 hydrate (as Fe 3+ , 20 ppm against the weight of a monomer component), and 66.7 parts of a 48% aqueous sodium hydroxide solution (20 mole % against the whole acid group of a monomer component). The, the procedure of example 9 was repeated to obtain the maleic acid copolymer salts for comparison (21) and (22) except that the other water-soluble unsaturated monomers (B) as shown in Table 2 were used in the amounts described in Table 2. The maleic acid copolymer salts for comparison (21) and (22) were analyzed as carried out in the example 1, and the results obtained are shown in Table 2. 
     
                                           TABLE 1__________________________________________________________________________        (polyvalent) metal           alkaline substance maleic acid        ion (ppm against                  other water-soluble                             weight ratio                                     (mole % against (co-)polymer        weight of monomer                  unsaturated monomer                             between maleic                                     whole acid group ofExample salt   component)                  (B)        acid and (B)                                     monomer component)__________________________________________________________________________ 1     (1)   VO.sup.2+ --         100/0   20        (20)                         (sodium hydroxide) 2     (2)   VO.sup.2+ --         100/0   35        (20)                         (sodium hydroxide) 3     (3)   Fe.sup.3+ --         100/0   20        (20)                         (sodium hydroxide) 4     (4)   Fe.sup.3+ --         100/0   20        (20)                         (sodium hydroxide) 5     (5)   Fe.sup.3+ --         100/0   20         (2)                         (sodium hydroxide) 6     (6)   Fe.sup.3+ --         100/0   20        (300)                        (sodium hydroxide) 7     (7)   Fe.sup.2+ --         100/0   20        (20)                         (sodium hydroxide) 8     (8)   Cu.sup.2+ --         100/0    5        (20)                         (sodium hydroxide) 9     (9)   Fe.sup.3+ isoprenol  80/20   20        (20)                         (sodium hydroxide)10    (10)   Fe.sup.3+ isoprenol  80/20   40        (20)                         (sodium hydroxide)11    (11)   Fe.sup.3+ isoprenol  80/20   20        (20)                         (sodium hydroxide)12    (12)   VO.sup.2+ isoprenol  80/20   20         (2)                         (sodium hydroxide)13    (13)   Fe.sup.2+ isoprenol  80/20   20        (20)                         (sodium hydroxide)14    (14)   Fe.sup.3+ isoprenol  80/20   20        (300)                        (sodium hydroxide)15    (15)   Cu.sup.2+ isoprenol  80/20   20        (20)                         (sodium hydroxide)16    (16)   Fe.sup.3+ acrylic acid                             80/20   20        (20)                         (sodium hydroxide)17    (17)   Fe.sup.3+ acrylic acid                             75/25   20        (20)                         (sodium hydroxide)18    (18)   Fe.sup.3+ isoprenol 5 EO                             80/20   20        (20)      addition compound  (sodium hydroxide)19    (19)   Fe.sup.3+ 3-allyloxy-2-hydroxy                             80/20   20        (20)      propanesulfonic acid                                     (sodium hydroxide)20    (20)   Fe.sup.3+ glycerol monoallyl                             80/20   20        (20)      ether              (sodium hydroxide)21    (21)   VO.sup.2+ monomethyl maleate                             80/20   20        (20)                         (sodium hydroxide)22    (22)   VO.sup.2+ glycerol monoallyl                             80/20   20        (20)      ether EO 5 moles   (sodium hydroxide)                  addition compound23    (23)   VO.sup.2+ allyl alcohol EO 5                             80/20   20        (20)      moles addition     (sodium hydroxide)                  compound24    (24)   VO.sup.2+ 2-acrylamido-2-                             80/20   20        (20)      methylpropane-     (sodium hydroxide)                  sulfonic acid25    (25)   VO.sup.2+ methacrylic acid                             75/25   20        (20)                         (sodium hydroxide)26    (26)   Fe.sup.3+ fumaric acid                             80/20   20        (20)      monosodium salt    (sodium carbonate)27    (27)   Fe.sup.3+ itaconic acid                             80/20   20        (20)                         (sodium carbonate)28    (28)   Fe.sup.3+ polyethyleneglycol                             80/20   20        (20)      monoisoprenol ether                                     (sodium carbonate)29    (29)   Fe.sup.3+ --         100/0   20        (20)                         (sodium hydroxide)30    (30)   Fe.sup.3+ 2-acrylamido-2-                             80/20   20        (20)      methylpropane-     (sodium hydroxide)                  sulfonic acid31    (31)   Fe.sup.3+ acrylic acid                             80/20   20        (20)                         (sodium hydroxide)__________________________________________________________________________              hydrogen peroxide                         amount of                                  biodegradation              (g against 1 mole of                         residual monomer                                  percentage                                          molecular        Example              monomer component)                         (%)      (%)     weight__________________________________________________________________________         1    34         0.3      34       980         2    34         0.6      27      1200         3    15         3        20      1500         4    100        0.3      37       550         5    34         3        25       980          6   34         1        25      1800         7    34         0.5      31      1010         8    34         5        26       720         9    34         0.2      32      2500        10    34         0.5      28      3600        11    15         1        19      3700        12    34         0.9      22      3000        13    34         0.7      25      3100        14    34         3        31      4100        15    34         3        29      2600        16    34         0.2      26      3200        17    20         1        20      5500        18    34         0.4      30      2400        19    34         0.3      29      2800        20    34         0.5      30      2700        21    34         0.4      31       140        22    34         0.4      29      2500        23    34         0.3      28      2700        24    34         0.3      26      2900        25    20         3        20      4200        26    34         2        30      1500        27    34         2        29      1600        28    34         2        31      3000        29    34         1        36      2000        30    34         0.8      28      2900        31    34         0.3      26      3300__________________________________________________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________ maleic acid        (polyvalent) metal           sodium hydroxideExample (co-)polymer        ion (ppm against                  other water-soluble                             weight ratio                                     (mole % againstfor com- (salt) for        weight of monomer                  unsaturated monomer                             between maleic                                     whole acid group ofparison comparison        component)                  (B)        acid and (B)                                     monomer component)__________________________________________________________________________ 1     (1)   VO.sup.2+ --         100/0   50        (20) 2     (2)   VO.sup.2+ --         100/0   20        (20) 3     (3)   absence   --         100/0   20 4     (4)   Fe.sup.3+ isoprenol  80/20   50        (20) 5     (5)   Fe.sup.3+ isoprenol  80/20   20        (20) 6     (6)   absence   isoprenol  80/20   20 7     (7)   Mn.sup.2+ isoprenol  80/20   20        (20) 8     (8)   Co.sup.2+ isoprenol  80/20   20        (20) 9     (9)   Mg.sup.2+ isoprenol  80/20   20        (20)10    (10)   Ni.sup.2+ isoprenol  80/20   20        (20)11    (11)   Zn.sup.2+ isoprenol  80/20   20        (20)12    (12)   Fe.sup.3+ 2-acrylamido-2-                             50/50   20        (20)      methylpropane-                  sulfonic acid13    (13)   Fe.sup.3+ acrylic acid                             50/50   20        (20)14    (14)   Fe.sup.3+ acrylic acid                             80/20   20        (2000)15    (15)   absence   acrylic acid                             90/10    016    (16)   Fe.sup.2+ acrylic acid                             90/10     23.7        (9.7)17    (17)   absence   glycerol monoallyl                             90/10   100                  ether18    (18)   VO.sup.2+ --         100/0    0        (20)19    (19)   VO.sup.2+ --         100/0   20        (20)                         (added after                                     polymerization).20    (20)   Fe.sup.2+ acrylic acid                             40/60   50        (20)21    (21)   Fe.sup.3+ acrylic acid                             50/50   20        (20)22    (22)   Fe.sup.3+ 2-acrylamido-2-                             50/50   20        (20)      methylpropane-                  sulfonic acid__________________________________________________________________________        Example              hydrogen peroxide                         amount of                                  biodegradation        for com-              (g against 1 mole of                         residual monomer                                  percentage                                          molecular        parison              monomer component)                         (%)      (%)     weight__________________________________________________________________________         1    34          2       3       2100         2    10         19       8       2200         3    34         45       8       1050         4    34          2       2       2800         5    10         16       8       2600         6    34         35       7       2400         7    34         29       8       2500         8    34         30       7       2700         9    34         27       6       2700        10    34         28       8       2500        11    34         31       7       2600        12    34          5       8       5500        13    34          3       8        580        14    34          7       8       5200        15    di-t-butyl peroxide                         20       3       1800              (27.7)        16    hydrogen peroxide                         25       3       1000              (10.2)        17    ammonium persulfate                         12       3       1800               (9.1)        18    hydrogen peroxide                           0.3    14      1200              (34)        19    34           0.3    15      1200        20       2.19      0.3    1       6000        21    34          6       9       2800        22    34          8       9       2500__________________________________________________________________________ 
    
     As seen in Tables 1 and 2, the maleic acid (co-) polymer salt relating to the examples, compared with the maleic acid (co-)polymer (salt) relating to the examples for comparison, is less in amount of the residual monomer and superior in biodegradability. Also, when the results in Tables 1 and 2 are examined, comparing in detail, from a standpoint of difference in the reaction conditions between the examples and the examples for comparison, the undermentioned 1˜5 are seen. 
     1) With increasing the content of maleic acid, the biodegradability increases (from comparison between the examples 29 and 30 and the example for comparison 12, and between the examples 29 and 31 and the example for comparison 13). 
     2) If the amount of the polyvalent metal ion is too large or small, the biodegradability lowers (from comparison between the examples 5, 6, and 29 and the example for comparison 3, between the examples 9 and 14 and the example for comparison 6, and between the example 16 and the example for comparison 14). 
     3) When a metal ion other than a vanadium ion, iron ion, and copper ion is used, the amount of the residual monomer increases and the biodegradability lowers (from comparison between the examples 9 and 15 and the examples for comparison 7˜11). 
     4) If the neutralization extent for the whole acid group in the monomer component is 0 mole % or exceeds 45 mole %, the biodegradability lowers (from comparison between the examples 1 and 2 and the examples for comparison 1, 18, and 19, and between the examples 9 and 10 and the example for comparison 4). 
     5) If the amount of hydrogen peroxide is too small, the biodegradability lowers (from comparison between the examples 3, 4, and 29 and the example for comparison 2, and between the examples 9 and 11 and the example for comparison 5). 
     EXAMPLES 32˜62 
     To evaluate the properties of maleic acid (co-)polymer salts obtained from the examples 1˜31, as a scale inhibitor, the undermentioned examinations were carried out. With 170 g of water placed in a glass bottle of 225 ml volume, 10 g of a 1.56% aqueous calcium chloride 2-hydrate solution and 3 g of a 0.02% aqueous solution of the maleic acid (co-)polymer salts (1)˜(31) (3 ppm against an over saturated aqueous solution obtained) were mixed and, with further additions of 10 g of a 3% aqueous sodium hydrogencarbonate solution and 7 g of water, the total amount was adjusted to 200 g. The over saturated aqueous solution thus-obtained containing 530 ppm of sodium carbonate was tightly stoppered and treated with heating at 70° C. for 3 hours. Then, after cooling the precipitate is taken off with filtration using a membrane filter of 0.1 μ and the filtrate was analyzed. 
     According to the undermentioned chelate-titrating method, which is in true due to Japanese Industrial Standard: JIS K0101, the calcium concentration in the filtrate was determined. 
     In a beaker was placed a proper amount of a filtrate (which contained 5 mg or less as Ca) and the volume was adjusted to about 50 ml with addition of water. To this was added r ml of a 500 g/l aqueous potassium hydroxide solution and the solution obtained was well mixed and stood for 5 minutes, to which 0.5 ml of a 100 g/l aqueous potassium cyanide solution and 0.5 ml of a 100 g/l aqueous hydroxyl ammonium chloride (hydroxylamine hydrochloride) solution were added. Well mixing of the solution obtained gave a sample for titrating. 
     To a sample for titrating thus-obtained were added 5˜6 drops of an aqueous solution (a NANA solution) containing 5 g/l of both 2-hydroxy-1-(2&#39;-hydroxy-4&#39;-sulfo-1&#39;-naphthalenylazo)-3-naphthalenecarboxylic acid and hydroxylammonium chloride, and the solution obtained was titrated until the color becomes from reddish violet to blue with a 1/100 mole/˜ aqueous disodium ethylenediamine-tetraacetate solution (a EDTA solution in which 1 m˜ corresponds to 0.4 mg of calcium). Besides the EDTA solution used for titration was prepared by that disodium ethylenediaminetetraacetate 20hydrate was dried at 80° C. for 5 hours and stood for cooling in a desiccator, then 3.722 g of it was placed in a 1 ˜ flask and dissolved into water which was added up to a mark line of the flask. 
     With the following equation, the calcium concentration (mgCa/˜) in the filtrate was calculated. ##EQU4## Here, C: calcium concentration (mgCa/˜) a: amount of a EDTA solution required for titration (m˜) 
     V: amount of a filtrate used for titration (m˜) 
     0.4: amount of calcium which corresponds to 1 m˜ of the EDTA solution (mg) 
     According to the following equation, the scale inhibition percentage % for calcium carbonate was determined. The results obtained are shown in Table 3. ##EQU5## A: calcium concentration dissolving in a solution before examination. B: calcium concentration in a filtrate without addition of a scale inhibitor. 
     C: calcium concentration in a filtrate after examination 
     Examples for Comparison 23˜44 
     In the same way as carried out for the examples 32˜62, the properties as a scale inhibitor of the maleic acid (co-)polymers (salts) for comparison (1)˜(22) obtained from the examples for comparison 1˜22 were evaluated. The results obtained are shown in Table 4. 
     
                       TABLE 3______________________________________Ex-am-  maleic acid (co-)polymer salt                   scale inhibitor percentageple  used               for calcium carbonate (%)______________________________________32   maleic acid polymer salt (1)                   8833   maleic acid polymer salt (2)                   8234   maleic acid polymer salt (3)                   7735   maleic acid polymer salt (4)                   8736   maleic acid polymer salt (5)                   8037   maleic acid polymer salt (6)                   8038   maleic acid polymer salt (7)                   8539   maleic acid polymer salt (8)                   8240   maleic acid copolymer salt (9)                   8941   maleic acid copolymer salt (10)                   8842   maleic acid copolymer salt (11)                   7743   maleic acid copolymer salt (12)                   8044   maleic acid copolymer salt (13)                   8645   maleic acid copolymer salt (14)                   8046   maleic acid copolymer salt (15)                   8047   maleic acid copolymer salt (16)                   8748   maleic acid copolymer salt (17)                   8249   maleic acid copolymer salt (18)                   8850   maleic acid copolymer salt (19)                   8651   maleic acid copolymer salt (20)                   8552   maleic acid copolymer salt (21)                   7453   maleic acid copolymer salt (22)                   8654   maleic acid copolymer salt (23)                   7355   maleic acid copolymer salt (24)                   7256   maleic acid copolymer salt (25)                   8457   maleic acid copolymer salt (26)                   7558   maleic acid copolymer salt (27)                   7359   maleic acid copolymer salt (28)                   7360   maleic acid polymer salt (29)                   8561   maleic acid copolymer salt (30)                   8062   maleic acid copolymer salt (31)                   81______________________________________ 
    
     
                                           TABLE 4__________________________________________________________________________Examplefor com-                    scale inhibitor percentageparisonmaleic acid (co-)polymer (salt) used                       for calcium carbonate (%)__________________________________________________________________________23   maleic acid polymer salt for comparison (1)                       5424   maleic acid polymer salt for comparison (2)                       6325   maleic acid polymer salt for comparison (3)                       4826   maleic acid copolymer salt for comparison (4)                       5227   maleic acid copolymer salt for comparison (5)                       6528   maleic acid copolymer salt for comparison (6)                       5129   maleic acid copolymer salt for comparison (7)                       5330   maleic acid copolymer salt for comparison (8)                       5231   maleic acid copolymer salt for comparison (9)                       5332   maleic acid copolymer salt for comparison (10)                       5533   maleic acid copolymer salt for comparison (11)                       5134   maleic acid copolymer salt for comparison (12)                       4835   maleic acid copolymer salt for comparison (13)                       4936   maleic acid copolymer salt for comparison (14)                       4537   maleic acid copolymer for comparison (15)                       5338   maleic acid copolymer salt for comparison (16)                       5839   maleic acid copolymer salt for comparison (17)                       7040   maleic acid polymer for comparison (18)                       8341   maleic acid polymer salt for comparison (19)                       8142   maleic acid copolymer salt for comparison (20)                       5143   maleic acid copolymer salt for comparison (21)                       4944   maleic acid copolymer salt for comparison (22)                       49__________________________________________________________________________ 
    
     EXAMPLES 63˜93 
     To evaluate the properties of the maleic acid (co-)polymer salts (1)˜(31) obtained from the examples 1˜31, as a detergent builder, the undermentioned examinations were carried out. Into 50 m˜ of a 10 -3  mol/˜ aqueous calcium chloride solution were added 10 mg (calculated on a basis of the solid portion) of the maleic acid (co-)polymer salts (1)˜(31), obtained from the examples 1˜31, and using an ion analyzer (MODEL 701) made by Orion Co., Ltd. and a calcium ion electrode, the amounts of calcium ion blocked by the maleic acid (co-)polymer salts (1)˜(31) were determined and the chelating ability of each of the maleic acid (co-)polymer salts were measured with the following equation, and the results obtained are shown in Table 5. ##EQU6## 
     Examples for Comparison 45˜66 
     In the same way as carried out for the examples 63˜93, maleic acid (co-)polymers (salts) for comparison (1)˜(22) obtained from the examples for comparison 1˜22 were evaluated in the properties when used as a detergent builder, and the results obtained are shown in Table 6. 
     
                       TABLE 5______________________________________   maleic acid (co-)polymer salt                      chelating abilityExample used               (mgCaCO.sub.3 /g)______________________________________63      maleic acid polymer salt (1)                      28064      maleic acid polymer salt (2)                      33065      maleic acid polymer salt (3)                      25066      maleic acid polymer salt (4)                      27567      maleic acid polymer salt (5)                      24568      maleic acid polymer salt (6)                      25569      maleic acid polymer salt (7)                      26070      maleic acid polymer salt (8)                      25071      maleic acid copolymer salt (9)                      24072      maleic acid copolymer salt (10)                      30573      maleic acid copolymer salt (11)                      23574      maleic acid copolymer salt (12)                      24075      maleic acid copolymer salt (13)                      24076      maleic acid copolymer salt (14)                      25077      maleic acid copolymer salt (15)                      24078      maleic acid copolymer salt (16)                      25579      maleic acid copolymer salt (17)                      26580      maleic acid copolymer salt (18)                      24081      maleic acid copolymer salt (19)                      25082      maleic acid copolymer salt (20)                      25083      maleic acid copolymer salt (21)                      21084      maleic acid copolymer salt (22)                      25085      maleic acid copolymer salt (23)                      21586      maleic acid copolymer salt (24)                      20587      maleic acid copolymer salt (25)                      26588      maleic acid copolymer salt (26)                      21589      maleic acid copolymer salt (27)                      21090      maleic acid copolymer salt (28)                      22091      maleic acid polymer salt (29)                      28292      maleic acid copolymer salt (30)                      26093      maleic acid copolymer salt (31)                      265______________________________________ 
    
     
                                           TABLE 6__________________________________________________________________________Examplefor com-                     chelating abilityparison maleic acid (co-)polymer (salt) used                        (mgCaCO.sub.3 /g)__________________________________________________________________________45    maleic acid polymer salt for comparison (1)                        18046    maleic acid polymer salt for comparison (2)                        17747    maleic acid polymer salt for comparison (3)                        11048    maleic acid copolymer salt for comparison (4)                        18649    maleic acid copolymer salt for comparison (5)                        17050    maleic acid copolymer salt for comparison (6)                        10551    maleic acid copolymer salt for comparison (7)                        18352    maleic acid copolymer salt for comparison (8)                        18053    maleic acid copolymer salt for comparison (9)                        11854    maleic acid copolymer salt for comparison (10)                        12055    maleic acid copolymer salt for comparison (11)                        12356    maleic acid copolymer salt for comparison (12)                        16557    maleic acid copolymer salt for comparison (13)                        16858    maleic acid copolymer salt for comparison (14)                        16059    maleic acid copolymer for comparison (15)                        13560    maleic acid copolymer salt for comparison (16)                        16461    maleic acid copolymer salt for comparison (17)                        18562    maleic acid polymer for comparison (18)                        24863    maleic acid polymer salt for comparison (19)                        24364    maleic acid copolymer salt for comparison (20)                        17065    maleic acid copolymer salt for comparison (21)                        15566    maleic acid copolymer salt for comparison (22)                        158__________________________________________________________________________ 
    
     As seen in Tables 3˜6, it is understood that a superior scale scale inhibitor and a detergent builder led from the maleic acid (co-)polymer salt in the examples are much superior to those led from the maleic acid (co-)polymer (salt) in the examples for comparison.