Water soluble resins and application thereof to paper coating

Abstract: A water soluble resin obtainable by reacting at least a polyamine and a urea compound, or at least a polyamine, a urea compound, a dibasic carboxylic acid compound and a lactam, followed by reacting the reaction product thus obtained with a cross-linking compound selected from epihalohydrins, α,γ-dihalo-β-hydrins, glycidyl compounds and isocyanates is provided. The water soluble resin may be used in a paper coating composition in admixture with a pigment and an aqueous binder. The paper coating composition does not generate formaldehyde and can give coated papers with various improved properties including excellent ink acceptability and water resistance.

Description: The present invention relates to a water soluble resin and a paper coating composition comprising the water soluble resin, particularly a paper coating composition comprising the resin and a pigment and an aqueous binder. More precisely, the present invention provides the water soluble resin and the paper coating composition not generating formaldehyde and capable of providing excellent printing aptitude as well as printing effects. As used herein, the term "paper" has a broad sense including paper and cardboard named in a narrow sense. Coated papers obtained by applying a coating composition mainly comprising a pigment and an aqueous binder onto a paper, followed by working up the paper by necessary treatments such as drying, calendering and so on have found wide applications in commercial pamphlets, magazines and books due to their characteristics such as excellent printing effects or the like. Because of increasing demands for higher quality and of increasing speed of printing, efforts for improving the quality of coated papers is currently continued. Particularly, in offset printing which is used for the majority of printed matters, improvements of ink acceptability under the influence of moistening water, water resistance such as wet pick-up and blister resistance during rotary press printing have become important problems in the art. For solving such problems, there have been known methods of addition of a melamine-formaldehyde resin, a urea-formaldehyde resin, a polyamidopolyurea-formaldehyde resin described in JP-B-44-11667, or a block glyoxal resin described in JP-A-63-120197 which corresponds to US-A-4 695 606, as a water resistance agent or an additive for binder. While these conventional water resistance agents and additives for binder had some effective merits, they also had important defects and insufficiency in effects in a part of their properties and therefore were not always satisfactory from the practical viewpoint. For example, resins so-called aminoplast resins such as melamine-formaldehyde resins and urea-formaldehyde resins had problems that they not only generated a large amount of formaldehyde during processing or from coated papers but also provided less improving effect on ink acceptability and blister resistance. They are also less effective in water resistance when the coating composition had a higher pH value. On the other hand, while block glyoxal resins, which are known as formaldehyde-free binder additives, could provide water resistance to moistening water to some extent, they had almost no effect on improvement of ink acceptability and blister resistance. One object of the present invention is to provide paper coating compositions which can give higher quality to coated papers, such as high level of ink acceptability and water resistance, in order to meet demands on quality of coated papers, and do not generate formaldehyde. Another object of the present invention is to provide a water soluble resin which is free of formaldehyde and the use of such paper coating composition. As the result of extensive studies for solving the above described problems, the present inventors have discovered that a paper coating composition containing a water soluble resin obtainable by reacting specific compounds can provide papers with good properties. The present inventors have further discovered that a combination of such a water soluble resin and a specific amide compound can provide papers with superior properties. Thus, the present invention has been completed. EP-A-0691432 discloses a paper coating composition which comprises: a pigment; an aqueous binder; and a mixture or a reaction product of a specified water-soluble resin and a specified amide compound or aminonitrile compound. EP-A-0634524 discloses a paper coating composition which comprises: a pigment; an aqueous binder; a specified water-soluble resin; and at least one amine, quaternary organic ammonium salt or polyamide compound. US-A-4091130 discloses a method for providing a cured coating on paper in which a coating formulation comprising a reactive polymer, a cross-linking agent, and a curing accelerator acid is applied to the paper, dried and calendered, controlled cure being obtained by encapsulating either or both the accelerator acid and cross-linking agent in microcapsules capable of rupture in the calendering step. The present invention provides a water soluble resin (A) obtainable by reacting at least a polyamine (a) selected from alkylene diamines and polyalkylene polyamines and a urea compound (b), followed by reacting the reaction product thus obtained with a cross-linking compound (c) selected from alkylene glycol diglycidyl ethers, polyoxyalkylene glycol diglycidyl ethers, aromatic diglycidyl ethers, trimethylol propane diglycidyl ether, trimethylol propane triglycidyl ether, sorbitol diglycidyl ether, sorbitol triglycidyl ether, sorbitol tetraglycidyl ether, sorbitol pentaglycidyl ether, sorbitol hexaglycidyl ether, pentaerythritol diglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether and isocyanates. In the reaction for producing the water soluble resin (A), other compounds, such as a dibasic carboxylic acid compound (d), an alicyclic compound (e) selected from alicyclic amines having at least one activated hydrogen and alicyclic epoxy compounds, and a compound (f) selected from epihalohydrins and α,γ-dihalo-β-hydrins, may further be added in addition to said polyamine (a), urea (b) and cross-linking compound (c). In the present specification, the term "amines having at least one activated hydrogen" means primary and secondary amines. The present invention also provides a water soluble resin (B) obtainable by reacting at least a polyamine (g) selected from alkylene diamines and polyalkylene polyamines, a urea compound (h), a dibasic carboxylic acid compound (i) and a lactam (j), followed by reacting the reaction product thus obtained with a cross-linking compound (k) selected from epihalohydrins, α,γ-dihalo-β-hydrins, glycidyl compounds and isocyanates. In the reaction for producing the water soluble resin (B), other compounds, such as an alicyclic compound (1) selected from alicyclic amines having at least one activated hydrogen and alicyclic epoxy compounds, may further be added in addition to said polyamine (g), urea (h), dibasic carboxylic acid (i), lactam (j) and cross-linking compound (k). The water soluble resin (A) and water soluble resin (B) obtainable in such manner are useful as an ingredient of a paper coating composition, which can provide the coated paper with good properties. Accordingly, the present invention further provides a paper coating composition comprising the water soluble resin (A) or water soluble resin (B) as an active ingredient. The water soluble resin (A) and water soluble resin (B) are particularly useful for a paper coating composition comprising a pigment and an aqueous binder. Accordingly, the present invention still further provides a paper coating composition comprising (I) a pigment, (II) an aqueous binder, and (III) the water soluble resin (A) or water soluble resin (B). When used for a paper coating composition, the water soluble resin (A) or water soluble resin (B) can be used in the form of a mixture or a reaction product with other resins. Example of the other resins include an amide compound (C) obtainable by reacting an α,γ-unsaturated carboxylic acid compound (x) with an amine (y) having a primary or secondary amino group. As mentioned above, the water soluble resin (A) can be obtained by reacting at least two members comprising a polyamine (a) selected from alkylene diamines and polyalkylene polyamines with a urea compound (b), followed by reacting a cross-linking compound (c) selected from glycidyl compounds and isocyanates. A water soluble resin (B) can be obtained by reacting at least four members comprising a polyamine (g) selected from alkylene diamines and polyalkylene polyamines, a urea compound (h), a dibasic carboxylic acid compound (i) and a lactam (j), followed by reacting the reaction product with a cross-linking compound (k) selected from epihalohydrins, α,γ-dihalo-β-hydrins, glycidyl compounds and isocyanates The polyamine (a) used in the production of the water soluble resin (A) and the polyamine (g) used in the production of the water soluble resin (B) are compounds having two primary amino groups, linked through an alkylene group which may be interrupted by a secondary amino group(s). Specific examples of the polyamine (a) and polyamine (g) include alkylene diamines, preferably containing 1 to 6 carbon atoms, such as ethylenediamine, 1,2-propanediamine, 1,3-propanediamine and hexamethylenediamine and polyalkylene polyamines, preferably containing 2 to 10 carbon atoms, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, iminobispropylamine, 3-azahexane-1,6-diamine and 4,7-diazadecane-1,10-diamine. Among them, diethylenetriamine, triethylenetetramine and tetraethylenepentamine are preferred as polyamine (a), and tetraethylenepentamine and pentaethylenehexamine are preferred as polyamine (g), from the industrial viewpoint. These polyamines (a) or polyamines (g) can be used independently or in combination of two or more. The urea compound (b) and urea compound (h) are urea or its derivative usually having a group represented by the formula: -NHC(=Q)NHR wherein Q is oxygen or sulfur and R is hydrogen or an alkyl group having about 1 - 4 carbon atoms. The urea compound (b) and urea compound (h) may, for example, be compounds of formula R 1 NHC(=Q)NHR wherein R 1 is hydrogen, an alkyl group having about 1-4 carbon atoms, or a guanyl group, and Q and R are as hereinbefore defined. Specific examples of the urea compound (b) and urea compound (h) include urea, thiourea, guanylurea, methylurea and dimethylurea. The urea compound (b) or urea compound (h) can also be used independently or in combination of two or more. From the industrial view point, urea is preferred. The urea compound (b) is used in an amount generally within a range of 0.3 - 1 time the molar quantity, preferably within a range of 0.4 - 1 time the molar quantity, of the total of primary and secondary amino groups in the polyamine (a). The urea compound (h) is used in an amount generally within a range of 0.3 - 1 time the molar quantity, preferably within a range of 0.5 - 1 time the molar quantity, of the total of primary and secondary amino groups in the polyamine (g). The dibasic carboxylic acid compounds (d) optionally used for the production of the water soluble resin (A) and dibasic carboxylic acid compounds (i) are compounds having two carboxylic groups per molecule or compounds derived therefrom. They may be, for example, a free acid, an ester or an acid anhydride. Also, they may be any of aliphatic, aromatic and alicyclic compounds. Examples of the free dibasic carboxylic acid compound include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid and fumaric acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; and alicyclic dicarboxylic acids such as tetrahydrophthtalic acid, hexahydrophthalic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cyclopentane dicarboxylic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-methylhexahydrophthalic acid and 4-methylhexahydrophthalic acid. When the alicyclic group has an unsaturated bond and position of said unsaturated bond is not specified, it is to be understood that the position of the unsaturated bond is optional and this is also applied hereinbelow. The dibasic carboxylic acid compounds (d) and dibasic carboxylic acid compounds (i) are not limited to these free acids. They may be an ester or acid anhydride. Examples of the ester include mono-esters or di-esters of the above described free acids with lower, e.g. C 1-6 , alcohols and polyesters of the above described free acids with glycols. Examples of the acid anhydride include succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, 4- methyltetrahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride. The reaction products of dibasic carboxylic acids with glycols, i.e. polyesters, are advantageously used as the dibasic carboxylic acid compounds (d) or dibasic carboxylic acid compounds (i). Among the polyesters, those having a free carboxylic group are preferred. Examples of the glycols used here include alkylene glycols such as ethylene glycol, propylene glycol and butanediol; cycloalkylene glycols such as cyclopentanediol and cyclohexanediol; alkenylene glycols such as butenediol and octenediol; polyalkylene glycols such as diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol and polytetramethylene glycol; and ethylene oxide adducts of bisphenol A. By using a dibasic carboxylic acid in molar excess in the reaction of the carboxylic acid with a glycol , a polyester having a free carboxylic acid at the end of molecule can be obtained. These dibasic carboxylic acid compound (d) and dibasic carboxylic acid compounds (i) can be used independently or in combination of two or more. The dibasic carboxylic acid compound (d) is used in an amount generally 1 mole or less and preferably 0.5 mole or less based on 1 mole of the polyamine (a). The dibasic carboxylic acid compound (i) is used in an amount generally within a range from 0.1 to 1 mole, preferably within a range from 0.2 to 0.8 mole, based on 1 mole of the polyamine (g). The lactam (j) is a cyclic compound having a group of -CONH- in the ring. The lactam (j) usually has 5-12 carbon atoms in the lactam ring. Lactam which has been industrially used, such as ∈-caprolactam and lauryllactam, is preferably used as the lactam (j). The lactam (j) is used in an amount generally within a range from 0.01 to 0.3 mole, preferably within a range from 0.03 to 0.2 mole, based on 1 mole of the polyamine (g). After reacting at least two members comprising a polyamine (a) with a urea compound (b), the reaction product is subjected to a reaction with a cross-linking compound (c) to produce a water soluble resin (A). After reacting at least four members comprising a polyamine (g) selected from alkylene diamines and polyalkylene polyamines, a urea compound (h), a dibasic carboxylic acid compound (i) and a lactam (j), the reaction product is subjected to a reaction with a cross-linking compound (k) to produce a water soluble resin (B). The cross-linking compound (c) is selected from glycidyl compounds and isocyanates. The cross-linking compound ( k) is selected from epihalohydrins, α,γ-dihalo-β-hydrins, glycidyl compounds and isocyanates. Among the cross-linking compound (c), the glycidyl compound has at least two glycidyl groups per molecule. Among the cross-linking compound (k), the glycidyl compound usually has at least two glycidyl groups per molecule. Specific examples of the glycidyl compound used as the cross-linking compound (c) and the cross-linking compound (k) include alkylene glycol diglycidyl ethers such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether and neopentyl glycol diglycidyl ether; polyoxyalkylene glycol diglycidyl ethers such as polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether; aromatic diglycidyl ethers such as resorcin diglycidyl ether and bisphenol A diglycidyl ether; trimethylol propane diglycidyl ether; trimethylol propane triglycidyl ether; sorbitol diglycidyl ether; sorbitol triglycidyl ether; sorbitol tetraglycidyl ether; sorbitol pentaglycidyl ether; sorbitol hexaglycidyl ether; pentaerythritol diglycidyl ether; pentaerythritol triglycidyl ether; and pentaerythritol tetraglycidyl ether. Among the cross-linking compound (c) and the cross-linking compound (k), the isocyanate usually has at least two isocyanato groups per molecule. Specific examples of the isocyanate include alicyclic isocyanates such as isophorone diisocyanate, 3-(2-isocyanatocyclohexyl)propyl isocyanate, bis(isocyanatomethyl)cyclohexane, isopropylidenebis(cyclohexyl isocyanate), transcyclohexane-1,4-diisocyanate and bicycloheptane triisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate, trimethylhexane-1,6-diisocyanate and methyl 2,6-diisocyanatohexanoate (also called lysine diisocyanate); and aromatic isocyanates such as tolylene diisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl)thiophosphate, phenylene diisocyanate, dianisidine diisocyanate and diphenyl ether diisocyanate. Among the cross-linking compound (k) or among the compound (f) optionally used for the production of the water soluble resin (A), the epihalohydrins are usually represented by the following general formula: wherein X is a halogen atom and w is 1, 2 or 3. Preferred examples of the epihalohydrins include epichlorohydrin and epibromohydrin. These epihalohydrins can be used independently or in combination of two or more. Among the cross-linking compound (k) or among the compound (f) optionally used for the production of the water soluble resin (A), the α, γ -dihalo- β -hydrins are usually represented by the following general formula: wherein Y and Z, which are the same or different, are each halogen atoms. Examples of the α,γ-dihalo-β-hydrins include 1,3-dichloro-2-propanol. The cross-linking compound (c) and the cross-linking compound (k) can also be used independently or in combination of two or more. Two or more kinds of cross-linking compounds belonging to different groups among epihalohydrins, α, γ-dihalo-β-hydrins, glycidyl compounds and isocyanates can also be used in combination. The cross-linking compound (c) is used in an amount generally within a range of 0.1 - 2 moles, preferably within a range of 0.2 - 1 mole, based on 1 mole of the polyamine (a). The cross-linking compound (k) is used in an amount generally within a range of 0.1 - 2 moles, preferably within a range of 0.2 - 1 mole, based on 1 mole of the polyamine (g). Among the alicyclic compound (e) optionally used for the production of the water soluble resin (A) or among the alicyclic compound (1) optionally used for the production of the water soluble resin (B), the alicyclic amine having at least one activated hydrogen generally has one alicyclic ring having about 5-8 ring carbon atoms, preferably a cyclohexane ring, or two alicyclic rings each having about 5-6 ring carbon atoms, preferably a cyclohexane ring, as well as at least one primary or secondary amino group. The two alicyclic rings may be directly linked or may be indirectly linked through an intervening linking group such as -O-, -S-, sulfo or alkylene having 1-6 carbon atoms. Said amino group may attach to the alicyclic ring either directly or indirectly through an intervening linking group such as alkylene, e.g. alkylene having 1-6 carbon atoms. Examples of the alicyclic amine having at least one activated hydrogen include cyclohexylamine, dicyclohexylamine, N-methylcyclohexylamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 4,4'-diamino-3,3'-dimethyldicyclohexyl methane, 4,4'-diamino-3,3'-dimethylbicyclohexyl ethane, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, 1,2-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, N-aminopropylcyclohexylamine, 1,5-bis(aminomethyl)octahydro-4,7-methanoindene, 2,6-bis(aminomethyl)octahydro-4,7-methanoindene, 2,2-bis(4-aminocyclohexyl)propane, bis(4-aminocyclohexyl)methane, 4,4'-oxybis(cyclohexylamine), 4,4'-sulfonebis(cyclohexylamine), 1,3,5-triaminocyclohexane, 2,4'-diamino-3,3',5,5'-tetramethyldicyclohexylmethane, 4,4'-diamino-3,3',5,5'-tetramethyldicyclohexylmethane, menthanediamine, N-methyl-1,3-diaminocyclohexane, N,N-dimethyl-1,3-diaminocyclohexane, 3-N-methylamino-3,5,5-trimethyl-cyclohexylamine and N,N-dimethylbis(4-aminocyclohexyl)methane. Among the alicyclic compound (e) optionally used for the production of the water soluble resin (A) or among the alicyclic compound (1) optionally used for the production of the water soluble resin (B), the alicyclic epoxy compound generally has an alicyclic ring having about 5 - 12 ring carbon atoms, preferably a cyclohexane ring, as well as an epoxy group. Said epoxy group may be formed either between intra-alicyclic adjacent carbon atoms or outside the alicyclic ring. The epoxy group formed outside the alicyclic ring may attach to the alicyclic ring either directly or indirectly, for example, in the form of glycidyl, glycidyloxy or glycidylcarbonyl group. Examples of the alicyclic epoxy compound include cyclohexeneoxide, vinylcyclohexenedioxide, bis(3,4-epoxycyclohexyl) adipate, 3,4-epoxycyclohexane-carboxylate, 3-(3,4-epoxycyclohexyl)-8,9-epoxy-2,4-dioxaspiro[5.5]undecane, diglycidylhexahydrophthalate and 2,2-bis(4-glycidyloxycyclohexyl)propane. These alicyclic compound (e) and alicyclic compound (1) can be used independently or in combination of two or more. The alicyclic amine and the alicyclic epoxy compound can be co-used as the alicyclic compound (e) or alicyclic compound (1). The alicyclic compound (e) is used in an amount generally 1 mole or less, preferably 0.5 mole or less, based on 1 mole of the polyamine (a). The alicyclic compound (1) is used in an amount generally 1 mole or less, preferably 0.5 mole or less, based on 1 mole of the polyamine (g) In the production of water soluble resin (A), the dibasic carboxylic acid compound (d) optionally used is generally used in the reaction of the polyamine (a) with the urea compound (b). The alicyclic compound (e) may be used in the reaction of the polyamine (a) with the urea compound (b) and/or in the reaction with the cross-linking compound (c). Further, the compound (f) is generally used in the reaction with the cross-linking compound (c). A preferred water soluble resin (A) can be obtained, for example, by condensing the polyamine (a) with the urea compound (b), followed by reacting the reaction product with the cross-linking compound (c). If desired, the alicyclic compound (e) can be added to the reaction in an optional reaction step. In the condensation reaction of the polyamine (a) and the urea compound (b), the urea compound (b) may either be charged in one portion (one-step manner), or a part of the urea compound (b) may be charged first for reacting with the polyamine (a), followed by adding the rest of the urea compound (b) to carried out further deammoniation (two-step manner). When the urea compound (b) is charged in one portion for reaction, the reaction is carried out at a temperature usually of about 80 - 180°C, preferably of 90 - 160°C, for about 1 - 15 hours, while removing generated ammonia outside the system. When the reaction of the polyamine (a) with the urea compound (b) is carried out according to the above-mentioned two-step manner, each of the first and second reaction steps is carried out at a temperature usually of about 80 - 180°C, preferably of 90 - 160°C, while removing generated ammonia outside the system. The reaction period in the two-step manner is suitably about 1 - 6 hours for the first step and about 1 - 15 hours for the second step. The product thus obtained is then subjected to the reaction with the cross-linking compound (c). The reaction with the cross-linking compound (c) is generally carried out in an aqueous solution having a reactant concentration of about 10 - 80% by weight at a temperature of about 50 - 100°C, preferably of 70 - 90°C, for about 1 - 10 hours, preferably 3 - 8 hours. When two or more kinds of the cross-linking compounds (c) are used, these may be reacted either concurrently or separately. When the compounds (c) are separately reacted, it is preferred that each of the reactions is carried out under the above described conditions. When the optional alicyclic compound (e) is added to the reaction, the reaction of alicyclic compound (e) may be carried out at any step. For example, the alicyclic compound (e) may be added during the condensation reaction of the polyamine (a) with the urea compound (b) so that the three members are reacted simultaneously. Alternatively, the alicyclic compound (e) may be added after completion of the condensation reaction of the polyamine (a) with the urea compound (b) and before the reaction with the cross-linking compound (c). Further, the alicyclic compound (e) may be added during the reaction of the cross-linking compound (c) with the condensate of the polyamine (a) and the urea compound (b). When the alicyclic compound (e) is an alicyclic amine, the alicyclic amine may be reacted with a part of the urea compound (b) to carry out a deammoniation and, then, the reaction product is further reacted with the polyamine (a) and the rest of the urea compound (b). The deammoniation condensation reaction of the urea compound (b) with the alicyclic amine is carried out at a temperature usually of about 80 - 180°C, preferably of 90 - 160°C, for about 1 - 15 hours while removing generated ammonia outside the reaction system. Another preferred water soluble resin (A) can be obtained by reacting the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d) in any desired order, followed by reacting the reaction product with the cross-linking compound (c). If desired, the alicyclic compound (e) can be added to the reaction in an optional step. The order of the reaction of the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d) is optional. Also in this reaction, the urea compound (b) may either be charged in one portion (one step manner), or a part of the urea compound (b) is first charged for deammoniation and, then, the rest of the urea compound (b) is added for further deammoniation (two step manner). For example, the reaction may be carried out: by reacting the polyamine (a) and the dibasic carboxylic acid (d) for carrying out a dehydration or dealcoholation, followed by reacting the reaction product with the urea compound (b) for carrying out a deammoniation; by reacting a part of the urea compound (b) and the polyamine (a) for carrying out a deammoniation and, then, reacting the reaction product with the dibasic carboxylic acid compound (d) for carrying out a dehydration or dealcoholation, followed by condensation reaction with the rest of the urea compound (b) for carrying out a deammoniation; by reacting the polyamine (a) and the dibasic carboxylic acid compound (d) in the presence of a part of the urea compound (b) for carrying out a dehydration or dealcoholation and deammoniation and, then, reacting the reaction product with the rest of the urea compound (b) for carrying out a deammoniation. The dehydration or dealcoholation is carried out usually at a temperature of about 120 - 250°C, preferably of 130 - 200°C, for about 2 - 12 hours, while removing generated water or alcohol outside the system. The deammoniation is carried out usually at a temperature of about 80 - 180°C, preferably of 90 - 160°C, for about 1 - 15 hours, while removing generated ammonia outside the system. When the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d) are reacted concurrently, the reaction is carried out usually at a temperature of about 80 - 200°C, preferably of 90 - 180°C, for about 2 - 15 hours, while removing generated water or alcohol and ammonia outside the system. The reaction of the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d) gives a polyamidopolyurea, which is then subjected to the reaction with the cross-linking compound (c). The reaction with the cross-linking compound (c) is generally carried out in an aqueous solution having a reactant concentration of about 10 - 80% by weight at a temperature of about 50 - 100°C, preferably of 70 - 90°C, for about 1 - 10 hours, preferably 3 - 8 hours. When two or more kinds of the cross-linking compounds (c) are used, these may be reacted either concurrently or separately. When the compounds are separately reacted, it is preferred that each of the reactions is carried out under the above described conditions. When the optional alicyclic compound (e) is added to the reaction, it can be reacted at any step. For example, the alicyclic compound (e) may be added in any step of the condensation reaction of three members: the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d), and subjected to a reaction with them. Alternatively, the alicyclic compound (e) may be added after the forming the polyamidopolyurea by the condensation reaction of the polyamine (a), the urea compound (b) and the dibasic carboxylic acid compound (d) and before the reaction of cross-linking compound (c). Further, the alicyclic compound (e) may be added during the reaction of the polyamidopolyurea with the cross-linking compound (c). When the alicyclic compound (e) is the alicyclic amine, the alicyclic amine may be condensed with a portion of the urea compound (b) and the reaction product may be reacted with the polyamine (a), the rest of the urea compound (b) and the dibasic carboxylic acid compound (d). Alternatively, when the alicyclic compound (e) is the alicyclic epoxy compound, the alicyclic epoxy compound may be firstly subjected to an addition reaction with the polyamine (a), and the reaction product may be subjected to the reaction with the dibasic carboxylic acid compound (d) and further with the urea compound (b). The addition reaction of the polyamine (a) with the alicyclic epoxy compound is carried out usually at a temperature of about 50 - 100°C, preferably of 70 - 90°C, for about 1 - 10 hours. When the compound (f) is used in any of the above reactions, part of the cross-linking compound (c) is replaced by the compound (f) and it is appropriate that the total amount of the both is within the range described above for the cross-linking compound (c), i.e. within a range of 0.1 - 2 moles, preferably within a range of 0.2 - 1 mole, based on 1 mole of the polyamine (a). In any of the above reactions, the reaction with the compound (f) is carried out usually after the reaction of the polyamine (a), the urea compound (b) and, if used, the dibasic carboxylic acid compound is terminated. The reaction of the compound (f) may be carried out immediately before the reaction of the cross-linking compound (c), simultaneously with the reaction of the cross-linking compound (c), or after completion of the reaction of the cross-linking compound (c). The reaction with the compound (f) is generally carried out in an aqueous solution having a solid concentration of about 10-80% by weight under weakly acidic to alkaline conditions, preferably at pH 5 or above, more preferably within a pH range of 7 - 12, and at a temperature of about 30 - 80°C, for about 1 - 10 hours. In the production of the water soluble resin (B), generally a polyamine (g), a urea compound (h), a dibasic carboxylic acid compound (i) and a lactam (j) reacted in any optional order and , then, the reaction products is reacted with the cross-linking compound (k). If desired, the alicyclic compound (l) can be added to the reaction in an optional reaction step. The order of the reaction of the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j) is optional. Also in this reaction, the urea compound (h) may either be charged in one portion (one step manner), or a part of the urea compound (h) is first charged for deammoniation and, then, the rest of the urea compound (h) is added for further deammoniation (two step manner). Examples of the order of the reaction of the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j) include following (i)-(iv): (i)After reacting the polyamine (g) and the dibasic carboxylic acid (i) for carrying out a dehydration or dealcoholation followed by reacting the reaction product with the lactam (j), or reacting the polyamine (g), dibasic carboxylic acid (i) and the lactam (j) simultaneously to produce a polyamide, the reaction product, i.e. the polyamide thus produced, is reacted with the urea compound (h) to carry out deammoniation. (ii) After reacting a part of the urea compound (h) and the polyamine (g) for carrying out a deammoniation, the reaction product is reacted with the dibasic carboxylic acid compound (i) and the lactam (j), in an optional order or simultaneously, for carrying out a dehydration or dealcoholation and a ring-opening addition, followed by condensation reaction with the rest of the urea compound (h) for carrying out a deammoniation. (iii) After completion of the reaction of the polyamine (g), the dibasic carboxylic acid compound (i) and the lactam (j) in the presence of a part of the urea compound (h) for carrying out a dehydration or dealcoholation, deammoniation and ring-opening addition, the reaction product is reacted with the rest of the urea compound (h) for carrying out a deammoniation. (iv) After completion of the reaction of the polyamine (g) and the dibasic carboxylic acid compound (i) in the presence of a part of the urea compound (h) for carrying out a dehydration or dealcoholation and deammoniation, the reaction product is reacted with the lactam (j) for carrying out a ring-opening addition, followed by the reaction of the rest of the urea compound (h) for carrying out a deammoniation. The dehydration or dealcoholation is carried out usually at a temperature of about 120 - 200°C, preferably of 130 - 180°C, for about 2 - 10 hours, while removing generated water or alcohol outside the system. The deammoniation is carried out usually at a temperature of about 80 - 180°C, preferably of 90 - 160°C, for about 1 - 18 hours, while removing generated ammonia outside the system. When the polyamine (g), the urea compound (h) and the dibasic carboxylic acid compound (i) are reacted concurrently, the reaction is carried out usually at a temperature of about 80 - 200°C, preferably of 90 - 160°C, for about 2 - 18 hours, while removing generated water or alcohol and ammonia outside the system. The reaction of lactam (j) with the reaction product of the other members is carried out usually at a temperature of about 120 - 200°C, preferably of 130 - 180°C, for about 1 - 15 hours, preferably for about 5 - 10 hours. The reaction of the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j) gives a polyamidopolyurea, which is then subjected to the reaction with the cross-linking compound (k). When epihalohydrins or α,γ-dihalo-β-hydrins is used as the cross-linking compound (k), the cross-linking reaction is generally carried out in an aqueous solution having a reactant concentration of about 10 - 80% by weight at a neutral or alkaline condition, for example, pH 7 or above, preferably pH 8-12, at a temperature of about 30 - 90°C for about 1 - 10 hours. When glycidyl compounds or isocyanates is used as the cross-linking compound (k), the cross-linking reaction is generally carried out in an aqueous solution having a reactant concentration of about 10 - 80% by weight at a temperature of about 30 - 100°C, preferably about 40 - 90°C for about 1 - 10 hours, preferably about 3 - 8 hours. When two or more kinds of the cross-linking compounds (k) are used, these may be reacted either concurrently or separately. When the compounds are separately reacted, it is preferred that each of the reactions is carried out under the above described conditions. When the optional alicyclic compound (1) is added to the reaction, it can be reacted at any reaction step. For example, the alicyclic compound (l) may be added in any step of the condensation reaction of the four members: the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j), and subjected to a reaction with them. Alternatively, the alicyclic compound (l) may be added after the forming the polyamidopolyurea by the condensation reaction of the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j), and before the reaction of cross-linking compound (k). Further, the alicyclic compound (l) may be added during the reaction of the polyamidopolyurea with the cross-linking compound (k). When the alicyclic compound (1) is the alicyclic amine, the alicyclic amine may be condensed with a part of the urea compound (h) and then the reaction product may first be reacted with the polyamine (g), the rest of the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j). The deammoniation condensation reaction of the urea compound (h) with the alicyclic amine compound is carried out usually at a temperature of about 80 - 180°C, preferably of 90 - 160°C, for about 2 - 18 hours, while removing the generated ammonia outside the reaction system. Alternatively, when the alicyclic compound (l) is the alicyclic epoxy compound, the alicyclic epoxy compound may be firstly subjected to an addition reaction with the polyamine (g), and then the reaction product may be subjected to a reaction with the dibasic carboxylic acid compound (i) and the lactam (j), and further with the urea compound (h). The addition reaction of the polyamine (g) with the alicyclic epoxy compound is carried out usually at a temperature of about 30 - 100°C, preferably of 40 - 90°C, for about 1 - 10 hours. The water soluble resin (A) and water soluble resin (B) obtained in this manner is useful for paper coating. The water soluble resin (A) and water soluble resin (B) can be used as it is, or can be used in the form of a mixture or a reaction product with an amide compound (C). The amide compound (C) can be obtained by reacting an α,β-unsaturated carboxylic acid compound (x) with an amine (y). The α,β-unsaturated carboxylic acid compound (x) may either be in the form of free acid or in the form of ester or acid anhydride. Specific examples of the α,β-unsaturated carboxylic acid compound (x) include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, itaconic acid, itaconic anhydride, crotonic acid and methyl crotonate. The amine (y) as the other starting material for the amide (C) has a primary or secondary amino group in the molecule. Those having 4 or more carbon atoms are preferred. Those having 4 or more carbon atoms as well as two amino groups in the molecule are particularly preferred. When the amine (y) has two amino groups, at least one of the amino groups is primary or secondary amino. The amino compound may have tertiary amino group(s). Specific example of the amine (y) include the compounds exemplified as the polyamine (a) and as the alicyclic amine in the alicyclic compound (e). The specific example of the amine (y) further include monoamines such as butylamine, pentylamine, hexylamine, heptylamine, 2-ethylhexylamine, octylamine, benzylamine, diisopropylamine and N-methyl-benzylamine; diamines such as N-ethyl-ethylenediamine, N,N-dimethyl-1,3-propanediamine, N-methyl-hexamethylenediamine, 2,4,4-trimethyl-hexamethylenediamine and xylylenediamine; and polyamines such as N-ethyl-iminobisethylamine, N-methyl-iminobispropylamine and N,N-dimethylaminoethylethylenediamine. The amide compound (C) can be obtained by reacting the α,β-unsaturated carboxylic acid compound (x) with the amine (y) usually at a temperature of about 100 - 250°C, preferably of 130 - 200°C, for about 2 - 20 hours, while removing generated water or alcohol and ammonia outside the system. Another preferred method is to carry out the reaction of the both compounds usually at a temperature of about 10 - 80°C for 1 - 5 hours, then heating to 100 - 250°C, followed by carrying out the reaction further at that temperature for about 2-15 hours while removing the distillate. In this reaction, an acid catalyst such as sulfuric acid or phosphoric acid may be used. Preferred amount of the α, β-unsaturated carboxylic acid compound (x) is within a range of 0.2 - 0.5 time the molar quantity of the total of primary and secondary amino groups in the amine (y). It is preferred that 70% by weight aqueous solution of the amide compound (C) has a viscosity of 1 - 1,000 P, particularly preferably of 5 - 500 P, at 25°C. When the amide compound (C) is converted to a reaction product with the water soluble resin (A) or with the water soluble resin (B), the reaction is carried out usually at a temperature of about 20 - 100°C for about 1 - 10 hours. When the compound (f) selected from epihalohydrins and α,γ-dihalo-β-hydrins is used in the production of water soluble resin (A) and the water soluble resin (A) is converted to a reaction product with the amide compound (C), the reaction of the compound (f) may be terminated before the reaction with the amide compound (C). Alternatively, the reaction of all or a part of the compound (f) may be carried out while the reaction with the amide compound (C) is carried out. That is, the water soluble resin (A) having the compound (f) as the component may be formed within the reaction system with the amide compound (C). In this case, the reaction may be carried out at least among the polyamine (a), the urea compound (b) and the cross-linking compound (c) without the compound (f) or with only part of the necessary amount thereof, and then the reaction may be continued in the reaction system supplied with the amide compound (C) and the rest of the compound (f). When epihalohydrins or α,γ-dihalo-β-hydrins are used as the cross-linking compound (k) in the production of water soluble resin (B) and the water soluble resin (B) is converted to a reaction product with the amide compound (C), the reaction of the epihalohydrins or α,γ-dihalo- β -hydrins may be terminated before the reaction with the amide compound (C). Alternatively, the reaction of all or a part of the epihalohydrins or α,γ-dihalo-β-hydrins may be carried out while the reaction with the amide compound (C) is carried out. That is, the water soluble resin (B) may be formed within the reaction system with the amide compound (C). In this case, the reaction may be carried out at least among the polyamine (g), the urea compound (h), the dibasic carboxylic acid compound (i) and the lactam (j) without the epihalohydrins or α,γ-dihalo-β-hydrins or with only a part of the necessary amount thereof, and then the reaction may be continued in the reaction system supplied with the amide compound (C) and the rest of the epihalohydrins or α,γ-dihalo-β-hydrins. The water soluble resin (A) or water soluble resin (B) is usually mixed with a pigment and an aqueous binder to make a paper coating composition. The pigment as a component of the paper coating composition may be one conventionally used for general paper coating. Examples of the pigment include white inorganic pigments and white organic pigments. Examples of the white inorganic pigments include kaolin, talc, calcium carbonate (heavy or light), aluminum hydroxide, satin white and titanium oxide. Examples of the white organic pigment include polystyrene, melamine-formaldehyde resin and urea-formaldehyde resin. These pigments can be used independently or in combination of two or more. Further, color pigments can also be used singly or together with the above pigment. The aqueous binder may also be one conventionally used for general paper coating. Examples of the aqueous binder include water soluble binders and aqueous emulsion binders. Examples of the water soluble binders include unmodified or modified starches such as oxidized starch and starch phosphate, polyvinyl alcohol, water soluble proteins such as casein and gelatin and modified cellulose such as carboxymethyl cellulose. Examples of the aqueous emulsion binders include styrene-butadiene resin, vinyl acetate resin, ethylene-vinyl acetate resin and methyl methacrylate resin. The aqueous binders can be used independently or in combination of two or more. In the preparation of the paper coating composition, although the ratio of the pigment and the aqueous binder depends on the ultimate utility and object, it is not particularly different from the ratio generally adopted in the art. In an example of the composition, the amount of the aqueous binder is preferably about 5 - 200 parts by weight, more preferably about 10 - 50 parts by weight, based on 100 parts by weight of the pigment. The amount of a resin component consisting of the water soluble resin (A) alone or as a mixture or reaction product of the water soluble resin (A) and any other compound(s), such as the amide compound (C) is preferably about 0.05 - 5 parts by weight, more preferably about 0.1 - 2 parts by weight in solid basis based on 100 parts by weight of the pigment. Preferred amount of the amide compound (C) in the mixture or reaction product of the water soluble resin (A) and the amide compound (C) as the resin component is within a range of about 1 - 90% by weight, particularly of about 3 - 80% by weight, based on the weight of the resin component in solid basis. The amount of a resin component consisting of the water soluble resin (B) alone or as a mixture or reaction product of the water soluble resin (B) and any other compound(s), such as the amide compound (C) is preferably about 0.05 - 5 parts by weight, more preferably about 0.1 - 2 parts by weight in solid basis based on 100 parts by weight of the pigment. Preferred amount of the amide compound (C) in the mixture or reaction product of the water soluble resin (B) and the amide compound (C) as the resin component is within a range of about 1 - 90% by weight, particularly of about 3 - 80% by weight, based on the weight of the resin component in solid basis. In the preparation of the paper coating composition, the order of adding and mixing the pigment, the aqueous binder and the resin component is not critical and is not particularly limited. In an example, when the resin component consists of the water soluble resin (A) alone or consists of the water soluble resin (B) alone, the water soluble resin may be added and mixed to a mixture of the pigment and the aqueous binder, or the water soluble resin may be added and mixed beforehand to a slurry of the pigment or the aqueous binder and then the rest of component be combined. When the resin component is a mixture of the water soluble resin (A) or water soluble resin (B) and the amide compound (C), the water soluble resin and the amide compound (C) may be mixed beforehand and then the pigment and the aqueous binder be combined, or the water soluble resin (A) or water soluble resin (B) and the amide compound (C) may be added and mixed independently to a mixture of the pigment and the aqueous binder. Alternatively, one or both of the water soluble resin (A) or water soluble resin (B) and the amide compound (C) may be added and mixed to the pigment or the aqueous binder and the rest of component is mixed in a step of preparing paper coating composition. Further, when the resin component is a reaction product of the water soluble resin (A) or water soluble resin (B) and the amide compound (C), the reaction product may be added and mixed to a mixture of the pigment and the aqueous binder, or the reaction product may be added and mixed beforehand to a slurry of the pigment or the aqueous binder and then the rest of component be combined. The paper coating composition of the present invention may further contain other components such as dispersant, viscosity/flowability modifier, antifoamer, preservative, lubricant, water retention agent or colorant, e.g. dye, or color pigment. The paper coating composition of the present invention may be applied on a paper by conventional means including methods using various known coaters such as blade coater, air knife coater, bar coater, size press coater gate roll coater and cast coater. Thereafter, the paper is subjected to the necessary drying step and, if necessary, smoothing step using a supercalender or the like to finish a coated paper. The water soluble resin according to the present invention is useful for paper coating and, because it does not contain formaldehyde, does not generate formaldehyde when used for paper coating operation and from the coated paper. Further, the paper coating composition prepared using this water soluble resin can give coated papers with various improved properties including excellent ink acceptability and water resistance. In addition, by using this water soluble resin in combination with the specific amide compound, coated papers with more improved properties can be obtained. EXAMPLES The present invention will now be described in more detail by means of Examples, which should not be construed as a limitation upon the scope of the present invention. In Examples, % and part used for indicating content or amount are of weight basis unless otherwise specified. Viscosity and pH were measured at 25°C. Synthetic Example 1 In to a four-necked flask equipped with a thermometer, a reflux condenser and a stirrer were charged 103.2 g (1 mole) of diethylenetriamine and 73.1 g (0.5 mole) of adipic acid and they were heated to an inner temperature of 140 - 160°C for 5 hours to effect dehydrating amidation reaction. Then, the inner temperature was lowered to 80°C and 96.1 g (1.6 mole) of urea was charged therto. The mixture was diluted by addition of 63.6 g of water to adjust the nonvolatile matter content to 80% and then heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 44.4 g (0.2 mole) of resorcin diglycidyl ether and 117 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours for carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 472.5 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 290 cP. Synthetic Example 2 After carrying out the dehydrating amidation reaction and deammoniation reaction according to manners similar to those in Synthetic Example 1, the inner temperature was lowered to 40°C, 35.5 g (0.16 mole) of resorcin diglycidyl ether and 111.5 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours for carrying out the reaction. Then, keeping the inner temperature at 70°C, 3.7 g (0.04 mole) of epichlorohydrin and 2.5 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours for carrying out the reaction. After the reaction was completed, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 466.3 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 230 cP. Synthetic Example 3 Into a vessel similar to that used in Synthetic Example 1, 82.5 g (0.8 mole) of diethylene triamine and 29.2 g (0.2 mole) of triethylenetetramine were charged and further 67 g of water was added. Then, after heating the mixture to an inner temperature of 80°C, 156.2 g (2.6 mole) of urea was charged and the mixture was kept at an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 40°C, 9.3 g (0.1 mole) of epichlorohydrin, 43.3 g (0.2 mole) of neopentyl glycol diglycidyl ether and 117.1 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours for carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 485.4 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.1 and a viscosity of 180 cP. Synthetic Example 4 Into a vessel similar to that used in Synthetic Example 1, 146.2 g (1 mole) of triethylenetetramine and 52.8 g (0.4 mole) of glutaric acid were charged and they were heated to an inner temperature of 140 - 160°C for 3 hours to effect dehydrating amidation reaction. Then, the inner temperature was lowered to 80°C and-144.2 g (2.4 mole) of urea was charged. The mixture was diluted by addition of 82.2 g of water to adjust the nonvolatile matter content to 80% and heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 70°C, 67.3 g (0.4 mole) of hexamethylene diisocyanate and 154.6 g of water were charged and the mixture was heated to an inner temperature of 70°C for 8 hours for carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 618.9 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.2 and a viscosity of 580 cP. Synthetic Example 5 Into a vessel similar to that used in Synthetic Example 1, 113.6 g (0.6 mole) of tetraethylenepentamine and 12.0 g (0.2 mole) of urea were charged and they were heated to an inner temperature of 90 - 150°C for 5 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 80°C and 108.1 g (1.8 mole) of urea was charged. The mixture was diluted by addition of 56.7 g of water to adjust the nonvolatile matter content to 80% and heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 70°C, 72.0 g (0.2 mole) of pentaerythritol tetraglycidyl ether and 159.9 g of water were charged and the mixture was heated to an inner temperature of 70°C for 8 hours for carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 469.4 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 6.9 and a viscosity of 330 cP. Synthetic Example 6 Into a vessel similar to that used in Synthetic Example 1, 65.6 g (0.5 mole) of iminobispropylamine and 5.0 g (0.05 mole) of cyclohexylamine were charged and further 14.8 g (0.1 mole) of phthalic anhydride was added thereto. They were heated to an inner temperature of 150 - 170°C for 5 hours to effect dehydrating amidation reaction. Then, the inner temperature was lowered to 80°C and 63.1 g (1.05 mole) of urea was charged. The mixture was diluted by addition of 36.7 g of water to adjust the nonvolatile matter content to 80% and heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 40°C, 2.8 g (0.03 mole) of epichlorohydrin, 41.8 g (0.24 mole) of ethylene glycol diglycidyl ether and 78.9 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours for carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 301.3 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 190 cP. Synthetic Example 7 Into a vessel similar to that used in Synthetic Example 1, 105.0 g (0.8 mole) of iminobispropylamine, 5.3 g (0.04 mole) of glutaric acid and 46.8 g (0.32 mole) of adipic acid were charged, and they were heated to an inner temperature of 150 - 170°C for 5 hours to effect dehydrating amidation reaction. Then, the inner temperature was lowered to 80°C and 61.3 g (1.02 mole) of urea was charged. The mixture was diluted by addition of 51.4 g of water to adjust the nonvolatile matter content to 80% and heated to an inner temperature of 90 - 110 °C for 12 hours to effect deammoniation reaction. Then, the inner temperature was lowered to 70°C, 2.0 g (0.02 mole) of cyclohexene oxide and 75.5 g of water were charged and the mixture was heated to an inner temperature of 80 - 90°C for 6 hours for carrying out the reaction. After lowering the inner temperature to 30°C, 111.5g (0.64 mole) of ethylene glycol diglycidyl ether and 74.3 g of water were charged and the mixture was heated to an inner temperature of 70 - 90°C for 4 hours for carrying out the reaction. After the reaction was completed, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 531.1 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 170 cP. Synthetic Example 8 In to a four-necked flask equipped with a thermometer, a reflux condenser and a stirrer were charged 232.4 g (1 mole) of pentaethylenehexamine and 73.1 g (0.5 mole) of adipic acid and they were heated to an inner temperature of 140 - 160°C for 5 hours to effect dehydrating amidation reaction while removing the generated water outside the system. Then, the inner temperature was lowered to 120°C and 6.8 g (0.06 mole) of e-caprolactam was charged and the mixture was heated to an inner temperature of 140 - 160 °C for 5 hours to effect a ring-opening addition reaction. Then, 264.3 g (4.4 mole) of urea and 139.6 g of water were charged and then the mixture was heated to an inner temperature of 90 - 110 °C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 27.8 g (0.3 mole) of epichlorohydrin and 201.4 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours to carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 861.9 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 250 cP. Synthetic Example 9 Into a vessel similar to that used in Synthetic Example 8, 92.9 g (0.4 mole) of pentaethylenehexamine and 43.8 g (0.3 mole) of adipic acid were charged. Keeping the inner temperature at 140 - 160°C, the dehydrating amidation reaction was carried out for 5 hours while removing the generated water outside the system. Then, the inner temperature was lowered to 120°C and 5.7 g (0.05 mole) of ε-caprolactam was charged and the mixture was heated to an inner temperature of 140 - 160 °C for 5 hours to effect a ring-opening addition reaction. Then, 78.1 g (1.3 mole) of urea and 52.4 g of water were charged and then the mixture was heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 27.8 g (0.3 mole) of epichlorohydrin, 44.4 g (0.2 mole) of resorcin diglycidyl ether and 120.8 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours to carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 452.4 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 760 cP. Synthetic Example 10 Into a vessel similar to that used in Synthetic Example 8, 139.4 g (0.6 mole) of pentaethylenehexamine and 43.8 g (0.3 mole) of adipic acid were charged. Keeping the inner temperature at 140 - 160°C , the dehydrating amidation reaction was carried out for 5 hours while removing the generated water outside the system. Then, the inner temperature was lowered to 120°C and 4.1 g (0.036 mole) of ε-caprolactam was charged and the mixture was heated to an inner temperature of 140 - 160 °C for 5 hours to effect a ring-opening addition reaction. Then, 144.2 g (2.4 mole) of urea and 80.2 g of water were charged and then the mixture was heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 66.7 g (0.3 mole) of resorcin diglycidyl ether and 150.8 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours to carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 599.1 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 340 cP. Synthetic Example 11 Into a vessel similar to that used in Synthetic Example 8, 75.7 g (0.4 mole) of tetraethylenepentamine, 9.9 g (0.1 mole) of cyclohexylamine and 41.5 g (0.25 mole) of isophthalic acid were charged. Keeping the inner temperature at 140 - 160°C, the dehydrating amidation reaction was carried out for 5 hours while removing the generated water outside the system. Then, the inner temperature was lowered to 80°C and 5.7 g (0.05 mole) of ε-caprolactam and 6 g (0.1 mole) of urea were charged at the same time and the mixture was heated to an inner temperature of 140 - 160 °C for 5 hours to effect a ring-opening addition reaction and deammoniation reaction concurrently. Then, 66.1 g (1.1 mole) of urea and 49.0 g of water were charged and then the mixture was heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 26.1 g (0.15 mole) of ethyleneglycol diglycidyl ether and 84.3 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours to carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 355.3 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 580 cP. Synthetic Example 12 Into a vessel similar to that used in Synthetic Example 8, 117 g (0.8 mole) of triethylenetetramine and44.4 g (0.3 mole) of phthalic anhydride were charged. Keeping the inner temperature at 140 - 160°C, the dehydrating amidation reaction was carried out for 5 hours while removing the generated water outside the system. Then, the inner temperature was lowered to 120°C and 7.9 g (0.04 mole) of lauryllactam was charged and the mixture was heated to an inner temperature of 140 - 160 °C for 5 hours to effect a ring-opening addition reaction. Then, 120.1 g (2 mole) of urea and 71 g of water were charged and then the mixture was heated to an inner temperature of 90 - 110°C for 12 hours to effect deammoniation reaction. Thereafter, the inner temperature was lowered to 40°C, 50.5 g (0.3 mole) of hexamethylenediisocyanate and 129.3 g of water were charged and the mixture was heated to an inner temperature of 70°C for 4 hours to carrying out the reaction. Thereafter, pH and concentration of the mixture were adjusted with sulfuric acid and water to give 355.3 g of an aqueous solution of a water soluble resin having a concentration of 60%, pH of 7.0 and a viscosity of 490 cP. Next, Examples of syntheses of the amide compound (C) are shown. Synthetic Example 13 In to a four-necked flask equipped with a thermometer, a Liebig's condenser, a dropping funnel and a stirrer was charged 232 g (2 moles) of hexamethylenediamine. Keeping the inner temperature at 40 - 50°C, 150 g (1.5 mole) of methyl methacrylate was added dropwise over an hour and the mixture was heated to 60 - 70°C for an hour. Then, the inner temperature was elevated to 120 - 150°C and the reaction was continued for 5 hours at that temperature while distilling out methanol. After the reaction was completed, water was added to give 477.1 g of an aqueous solution of an amide compound having a concentration of 70% and viscosity of 74 P. Synthetic Example 14 Into a vessel similar to that used in Synthetic Example 13, 204 g (2 moles) of N,N-dimethyl-1,3-propanediamine was charged and further 86 g (1 mole) of methyl acrylate was charged. Keeping the inner temperature at 100 - 130°C, the reaction was effected for 5 hours while distilling out methanol. After the reaction was completed, water was added to give 368.5 g of an aqueous solution of an amide compound having a concentration of 70% and viscosity of 7.3 P. Synthetic Example 15 Into a vessel similar to that used in Synthetic Example 13 was charged 170.3 g (1 mole) of isophoronediamine. Keeping the temperature in the system at 60 - 80°C, 45.0 g (0.5 mole) of 80% aqueous solution of acrylic acid was added dropwise and the mixture was kept at 60 - 80°C for an additional hour. Then, the mixture was heated to an inner temperature of 140 - 160°C for 5 hours to effect dehydrating amidating reaction. After the reaction was completed, water was added to give 281.9 g of an aqueous solution of an amide compound having a concentration of 70% and viscosity of 54.3 P. Synthetic Example 16 Into a vessel similar to that used in Synthetic Example 13 was charged 198.36 g (2 moles) of cyclohexylamine. Keeping the inner temperature at 60 - 80°C, 86.09 g (1 mole) of methyl acrylate was added dropwise and the mixture was kept at 60 - 80°C for an hour. Keeping the inner temperature at 140 - 160°C, the reaction was effected for 5 hours at that temperature while distilling out methanol. After the reaction was completed, water was added to give 360.6 g of a suspension of an amide composition having a concentration of 70%. Synthetic Example 17 Into a vessel similar to that used in Synthetic Example 13 was charged 60.1 g (1 mole) of ethylenediamine. Keeping the temperature in the system at 60 - 80°C, 45.0 g (0.5 mole) of 80% aqueous solution of acrylic acid was added dropwise and the mixture was kept at 60 - 80°C for an additional hour. Then, the mixture was heated to an inner temperature of 140 - 160°C for 5 hours to effect reaction while distilling out water. After the reaction was completed, water was added to give 124.4 g of an aqueous solution of an amide compound having a concentration of 70% and viscosity of 5.1 P. Synthetic Example 18 Into a vessel similar to that used in Synthetic Example 13 was charged 172.3 g (1 mole) of 1,10-diaminodecane. Keeping the inner temperature at 60 - 80°C, 45.0 g (0.5 mole) of 80% aqueous solution of acrylic acid was added dropwise and the mixture was kept at 60 - 80°C for an additional hour. Then, the mixture was heated to an inner temperature of 140 - 160°C for 5 hours to effect reaction while distilling out water. After the reaction was completed, water was added to give 284.7 g of an aqueous solution of an amide compound having a concentration of 70% and viscosity of 50.5 P. Further, Examples of syntheses of the reaction products of the water soluble resins (A) or (B) with the amide compound (C) are shown. Synthetic Example 19 In to a four-necked flask equipped with a thermometer, a reflux condenser and a stirrer were charged 236.3 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 1 but before the pH adjustment, 21.6 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 15 and 3.6 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 6.9 and a viscosity of 340 cP. Synthetic Example 20 Into a vessel similar to that used in Synthetic Example 19 were charged 236.3 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example but before the pH adjustment, 21.6 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 15, 6.4 g of epichlorohydrin and 7.9 g of water were charged. They were reacted at 60 - 70°C for 4 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 400 cP. Synthetic Example 21 Into a vessel similar to that used in Synthetic Example 19 were charged 185.7 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 4 but before the pH adjustment, 16.9 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 17 and 2.7 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.1 and a viscosity of 670 cP. Synthetic Example 22 Into a vessel similar to that used in Synthetic Example 19 were charged 241 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 6 but before the pH adjustment, 22.0 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 14 and 3.7 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 240 cP. Synthetic Example 23 In to a four-necked flask equipped with a thermometer, a reflux condenser and a stirrer were charged 170.5 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 8 but before the pH adjustment, 16.2 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 15 and 2.8 g of water. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 300 cP. Synthetic Example 24 Into a vessel similar to that used in Synthetic Example 23 were charged 170.5 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 8 but before the pH adjustment, 36.5 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 15 and 6.2 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 6.9 and a viscosity of 340 cP. Synthetic Example 25 Into a vessel similar to that used in Synthetic Example 23 were charged 170.5 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 8 but before the pH adjustment, 16.2 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 15, 1.9 g of epichlorohydrin and 4.1 g of water were charged. They were reacted at 60 - 70°C for 4 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 380 cP. Synthetic Example 26 Into a vessel similar to that used in Synthetic Example 23 were charged 192.5 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 10 but before the pH adjustment, 18.3 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 13 and 3.0 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 400 cP. Synthetic Example 27 Into a vessel similar to that used in Synthetic Example 23 were charged 144.4 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 10 but before the pH adjustment, 13.8 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 18 and 2.1 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 410 cP. Synthetic Example 28 Into a vessel similar to that used in Synthetic Example 23 were charged 125.2 g of a resin solution having a concentration of about 60% and prepared in a manner similar to that in Synthetic Example 12 but before the pH adjustment, 11.9 g of 70% aqueous solution of the amide compound obtained in Synthetic Example 14 and 1.9 g of water were charged. They were reacted at 60 - 70°C for 2 hours. Then, pH and concentration of the mixture were adjusted with sulfuric acid and water to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 540 cP. Paper coating compositions were prepared using the compounds or resins obtained in Synthetic Examples described above and evaluated in the following Examples, in which master colors having compositions shown in Table 1 were used. Composition of Master Colors Ingredient Product Ratio Pigment Ultrawhite 90 70 parts Carbital 90 30 parts Dispersant Sumirez resin DS-10 0.2 part Aqueous SN-307 12 parts Binder OJI ACE A 4 parts Application Examples 1 - 12 To the master color shown in Table 1 were added the aqueous solutions of water soluble resin obtained in Synthetic Example 1 - 12, respectively, such that the solid content is 0.5 part per 100 parts of the pigment in said master color. The resulting compositions were respectively adjusted with water and 10% aqueous sodium hydroxide to total solid content of 60% and pH of about 9 to give coating compositions. The obtained coating compositions were evaluated in physical properties according to the methods described below and results are shown in Table 2 and Table 3. (1) pH: Using a glass electrode hydrogen ion concentration meter (manufactured by Toa Dempa Kogyo K.K.), pH of the coating compositions was measured at 25°C immediately after the preparation. (2) Viscosity: Using a type B viscometer (model BL, manufactured by K.K. Tokyo Keiki), viscosity of the coating compositions was measured at 60 rpm and 25°C immediately after the preparation. The coating compositions was applied respectively on one side of fine papers having a basis weight of 80 g/cm 2 with a wire rod to a coating weight of 14 g/cm 2 . Immediately after the coating, the papers were dried in a hot air at 120°C for 30 seconds, subjected to moisture conditioning at a temperature of 20°C and relative humidity of 65% for 16 hours and subjected twice to super calender treatment under conditions of a temperature of 60°C and of a linear pressure of 60 kg/cm to give coated papers. The obtained coated papers were evaluated in water resistance and ink acceptability according to methods described below. The results are shown in Table 2 and Table 3. (3) Water Resistance: Wetpick process (WP process) Using an RI testing machine (manufactured by AKIRA Seisakusho), the coated side was printed after moistening with a water supplying roll and extent of peeling off was evaluated by visual observation. Scoring system and criteria for evaluation were as follows: Water resistance: (poor) 1 - 5 (excellent) (4) Ink Acceptability: (4-1) Process A Using an RI testing machine, the coated side was printed after moistening with a water supplying roll and ink acceptability was evaluated by visual observation. Scoring system and criteria for evaluation were as follows: Ink acceptability: (poor) 1 - 5 (excellent) (4-2) Process B Using an RI testing machine, the side was printed while kneading the ink with water and ink acceptability was evaluated by visual observation. Scoring system and criteria for evaluation were as follows: Ink acceptability: (poor) 1 - 5 (excellent) Test Results in Application Examples 1 - 7 Application Example 1 2 3 4 5 6 7 No. of Synthetic Example for Resin 1 2 3 4 5 6 7 Properties of Coating Composition pH 9.1 9.1 9.1 9.0 9.0 9.1 9.1 Viscosity (cP) 1330 1300 1280 1480 1350 1280 1270 Properties of Coated Paper Water Resistance: WP Process 3.1 3.0 2.7 2.6 2.8 2.3 2.4 Ink Acceptability: Process A 3.0 2.9 2.5 2.7 2.6 2.4 2.4 Ink Acceptability: Process B 3.1 3.1 2.4 2.8 2.6 2.5 2.4 Test Results in Application Examples 8 - 12 Application Example 8 9 10 11 12 No. of Synthetic Example for Resin 8 9 10 11 12 Properties of Coating Composition pH 9.0 9.1 9.0 9.0 9.0 Viscosity (cP) 1320 1460 1350 1410 1390 Properties of Coated Paper Water Resistance: WP Process 2.9 3.1 3.0 2.8 2.6 Ink Acceptability: Process A 2.8 2.6 3.0 2.5 2.4 Ink Acceptability: Process B 2.7 2.6 3.0 2.5 2.5 Application Example 13 The 60% aqueous solution of water soluble resin obtained in Synthetic Example 1 and the 70% aqueous solution of amide compound obtained in Synthetic Example 15 were mixed such that the content of the amide compound converted into solid content is 10% and then the mixture was subjected to pH and concentration adjustment with water and sulfuric acid to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 320 cP. The aqueous solution of resin component was added to the master color having a composition shown in Table 1 such that the solid content in the aqueous solution of resin component is 0.5 part per 100 parts of the pigment in said master color. Application Example 14 The 60% aqueous solution of water soluble resin obtained in Synthetic Example 8 and the 70% aqueous solution of amide compound obtained in Synthetic Example 13 were mixed such that the content of the amide compound converted into solid content is 10% and then the mixture was subjected to pH and concentration adjustment with water and sulfuric acid to give an aqueous solution of resin component having a concentration of 60%, pH of 7.0 and a viscosity of 280 cP. The aqueous solution of resin component was added to the master color having a composition shown in Table 1 such that the solid content in the aqueous solution of resin component is 0.5 part per 100 parts of the pigment in said master color. Application Examples 15 - 47 Aqueous solutions of resin component having properties shown in table 4 - 7 were prepared in a manner similar to that in Application Example 13 except that kinds and amounts of water soluble resins and amide compounds were changed as shown in Table 4 - 7, respectively. These solutions were added to the master color in the same ratio as that in Application Example 13. The compositions obtained in Application Examples 13 - 47 were subjected to pH and total solid concentration adjustment according to a manner similar to that in Application Examples 1 - 12. Respective coating compositions were applied to papers and the coated papers were tested according to the same manner. The results are shown in Table 4 - 7. In Table 4 - 7, the amounts of the amide compounds are weight ratios of the respective amide compounds based on the total solid in the aqueous solutions of resin component which are mixtures of the water soluble resins and the amide compounds. Said ratios are calculated by the following equation: Amount of Amide Compound = Weight of Amide Compound ÷ (Weight of Water Soluble Resin + Weight of Amide Compound) x 100 (%) Test Results in Application Examples 13 and 15 - 22 (using mixtures of water soluble resins and amide compounds) Application Example 13 15 16 17 18 19 20 21 22 No. of Synthetic Example for Water Soluble Resin 1 1 1 1 2 2 2 3 3 No. of Synthetic Example for Amide Compound 15 16 17 17 13 14 18 14 15 Amount 10 % 10 % 5 % 20 % 10 % 10 % 30 % 5 % 10 % Properties of Aqueous Solution of Resin Component pH 7.0 7.0 7.1 6.9 7.0 7.0 7.0 7.0 7.1 Viscosity (cP) 320 320 300 340 270 240 320 190 200 Properties of Coating Composition pH 9.1 9.1 9.1 9.1 9.0 9.1 9.0 9.0 9.0 Viscosity (cP) 1350 1350 1340 1400 1320 1310 1420 1400 1290 Properties of Coated Paper Water Resistance: WP Process 4.5 4.0 3.4 3.8 4.1 3.5 4.3 2.9 3.2 Ink Acceptability: Process A 4.2 3.9 3.5 3.8 3.9 3.7 4.4 2.9 3.3 Process B 4.3 3.8 3.4 3.9 3.9 3.6 4.5 2.9 3.2 Test Results in Application Examples 23 - 31 (using a mixture of a water soluble resin and an amide compound) Application Example 23 24 25 26 27 28 29 30 31 No. of Synthetic Example for Water Soluble Resin 4 4 4 5 5 6 6 7 7 No. of Synthetic Example for Amide Compound 13 15 16 14 16 17 18 13 17 Amount 10 % 10 % 20 % 5 % 10 % 40 % 10 % 10 % 10 % Properties of Aqueous Solution of Resin Component pH 7.1 7.1 6.9 7.0 7.0 6.9 7.0 7.0 7.0 Viscosity (cP) 600 590 620 340 350 280 210 200 180 Properties of Coating Composition pH 9.1 9.0 9.1 9.1 9.0 9.0 9.1 9.1 9.0 Viscosity (cP) 1490 1480 1500 1460 1360 1440 1290 1290 1280 Properties of Coated Paper Water Resistance: WP Process 3.4 3.6 3.0 2.9 3.0 3.5 2.9 2.9 2.6 Ink Acceptability: Process A 3.2 3.5 3.4 2.7 2.9 3.6 2.8 2.7 2.7 Process B 3.3 3.6 3.5 2.8 3.0 3.4 3.0 2.7 2.6 Test Results in Application Examples 14 and 32 - 39 (using mixtures of water soluble resins and amide compounds) Application Example 14 32 33 34 35 36 37 38 39 No. of Synthetic Example for Water Soluble Resin 8 8 8 8 8 9 9 9 9 No. of Synthetic Example for Amide Compound 13 15 15 17 18 14 15 16 18 Amount 10 % 10 % 20 % 10 % 10 % 5 % 10 % 5 % 10 % Properties of Aqueous Solution of Resin Component pH 7.0 7.0 6.9 7.0 7.0 6.9 7.0 6.9 6.9 Viscosity (cP) 280 270 340 250 270 730 780 750 780 Properties of Coating Composition pH 9.1 9.0 9.0 9.1 9.1 9.0 9.0 9.1 9.0 Viscosity (cP) 1330 1330 1350 1320 1330 1570 1470 1450 1470 Properties of Coated Paper Water Resistance: WP Process 4.0 4.1 4.2 3.9 4.1 3.7 4.2 3.7 4.2 Ink Acceptability: Process A 3.9 4.0 4.2 3.7 4.0 3.6 3.8 3.5 3.8 Process B 3.8 4.1 4.2 3.7 4.0 3.6 3.7 3.5 3.8 Test Results in Application Examples 40 - 47 (using a mixture of a water soluble resin and an amide compound) Application Example 40 41 42 43 44 45 46 47 No. of Synthetic Example for Water Soluble Resin 10 10 10 11 11 12 12 12 No. of Synthetic Example for Amide Compound 13 15 17 14 16 13 13 18 Amount 30% 5% 20% 40% 10% 5% 10% 20% Properties of Aqueous Solution of Resin Component pH 6.9 7.0 7.0 6.8 7.0 7.0 7.0 7.0 Viscosity (cP) 440 350 300 500 600 500 520 550 Properties of Coating Composition pH 9.0 9.0 9.0 9.1 9.0 9.0 9.0 9.0 Viscosity (cP) 1370 1350 1330 1710 1410 1390 1390 1400 Properties of Coated Paper Water Resistance: WP Process 4.4 4.0 4.3 4.0 3.9 3.6 3.9 4.2 Ink Acceptability: Process A 4.5 3.9 4.3 4.6 3.3 3.1 3.3 3.6 Process B 4.4 4.0 4.3 4.6 3.2 3.1 3.3 3.5 Application Examples 48 - 51 To the master color shown in Table 1 were added the aqueous solutions of water soluble resin obtained in Synthetic Example 19 - 22, respectively, such that the solid content is 0.5 part per 100 parts of the pigment in said master color. The resulting compositions were subjected to solid concentration and pH adjustment in a manner similar to that in Application Examples 1 - 7. Respective coating compositions were applied to papers and the coated papers were tested in the same manner. The results are shown in Table 8. Test Results in Application Examples 48 - 51 Application Example 48 49 50 51 No. of Synthetic Example for Reaction Product 19 20 21 22 Properties of Coating Composition pH 9.0 9.0 9.1 9.0 Viscosity (cP) 1440 1510 1680 1390 Properties of Coated Paper Water Resistance: WP Process 4.4 4.5 3.0 2.8 Ink Acceptability: Process A 4.2 4.4 3.1 2.8 Process B 4.2 4.4 3.2 2.9 Application Examples 52 - 57 To the master color shown in Table 1 were added the aqueous solutions of water soluble resin obtained in Synthetic Example 23- 28, respectively, such that the solid content is 0.5 part per 100 parts of the pigment in said master color. The resulting compositions were subjected to solid concentration and pH adjustment in a manner similar to that in Application Examples 8 - 12. Respective coating compositions were applied to papers and the coated papers were tested in the same manner. The results are shown in Table 9. Test Results in Application Examples 52 - 57 Application Example 52 53 54 55 56 57 No. of Synthetic Example for Reaction Product 23 24 25 26 27 28 Properties of Coating Composition pH 9.1 9.0 9.0 9.0 9.0 9.0 Viscosity (cP) 1400 1480 1520 1440 1440 1660 Properties of Coated Paper Water Resistance: WP Process 4.2 4.3 4.3 4.3 4.4 3.9 Ink Acceptability: Process A 4.1 4.4 4.1 4.1 4.2 3.7 Process B 4.2 4.3 4.1 4.1 4.1 3.6 Comparative Synthetic Example 1 In to a four-necked flask equipped with a thermometer, a reflux condenser and a stirrer was charged 435 g (3 moles of glyoxal) of 40% aqueous glyoxal solution and, keeping it at 16°C with stirring, 60 g (1 mole) of urea was added. The mixture was gradually heated up to 45°C over 1 hour or more. Then, the mixture was kept at that temperature for 4.5 hours, and after confirming the fact that pH became constant, it was cooled to 20°C. Then, 0.85 g of 50% aqueous sodium hydroxide solution and 3.5 g of water were added to the mixture to give an aqueous solution of block glyoxal resin having a solid content of 46.9% and pH of 6.9. Comparative Synthetic Example 2 Into a vessel similar to that used in Comparative Synthetic Example 1 was charged 406 g (2.8 moles of glyoxal) of 40% aqueous glyoxal solution and, keeping it at 15°C with stirring, 60 g (1 mole) of urea was added. The mixture was gradually heated up to 46°C over 1 hour. Then the mixture was kept at that temperature for 4 hours, and it was cooled to 20°C. Then, 4 g of 10% aqueous sodium hydroxide solution was added to the mixture to give an aqueous solution of block glyoxal resin having a solid content of 47.3% and pH of 6.0. Comparative Synthetic Example 3 Into a vessel similar to that used in Comparative Synthetic Example 1 was charged 464 g (3.2 moles of glyoxal) of 40% aqueous glyoxal solution and, keeping it at 12°C with stirring, 60 g (1 mole) of urea was added. The mixture was gradually heated up to 44°C over 1 hour. Then, the mixture was kept at that temperature for 4 hours, and cooled to 20°C. Then, 4 g of 10% aqueous sodium hydroxide solution was added to the mixture to give an aqueous solution of block glyoxal resin having a solid content of 46.5% and pH of 6.0. Comparative Application Examples 1 - 4 To the master color shown in Table 1 were added the aqueous solutions of resin obtained in Comparative Synthetic Example 1 - 3, respectively, such that the solid content is 0.5 part per 100 parts of the pigment in said master color to give compositions for Comparative Application Examples 1 - 3. For Comparative Application Example 4, the master color shown in Table 1 was used as it is without adding an aqueous solution of resin. The compositions were subjected to solid concentration and pH adjustment in a manner similar to that in Application Examples. Respective coating compositions were applied to papers and the coated papers were tested in the same manner. The results are shown in Table 10. Results in Comparative Application Examples 1 - 4 Comparative Application Example 1 2 3 4 No. of Comparative Synthetic Example for Resin 1 2 3 - Properties of Coating Composition pH 9.1 9.1 9.1 9.1 Viscosity (cP) 1550 1500 1590 1200 Properties of Coated Paper Water Resistance: WP Process 2.0 1.7 2.2 1.5 Ink Acceptability: Process A 1.8 1.6 2.0 1.5 Process B 1.7 1.7 2.0 1.5

Claims: A water soluble resin obtainable by reacting at least a polyamine (a) selected from alkylene diamines and polyalkylene polyamines and a urea compound (b), followed by reacting the reaction product thus obtained with a cross-linking compound (c) selected from alkylene glycol diglycidyl ethers, polyoxyalkylene glycol diglycidyl ethers, aromatic diglycidyl ethers, trimethylol propane diglycidyl ether, trimethylol propane triglycidyl ether, sorbitol diglycidyl ether, sorbitol triglycidyl ether, sorbitol tetraglycidyl ether, sorbitol pentaglycidyl ether, sorbitol hexaglycidyl ether, pentaerythritol diglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether and isocyanates. A water soluble resin according to claim 1, wherein a dibasic carboxylic acid compound (d) is added in the reaction of the polyamine (a) and the urea compound (b). A water soluble resin according to claim 1 or 2, wherein an alicyclic compound (e) selected from alicyclic amines having at least one activated hydrogen and alicyclic epoxy compounds is added in the reaction. A water soluble resin according to any one of claims 1 to 3, wherein a compound (f) selected from epihalohydrins and α,γ-dihalo-β-hydrins is added in the reaction. A water soluble resin obtainable by reacting at least a polyamine (g) selected from alkylene diamines and polyalkylene polyamines, a urea compound (h), a dibasic carboxylic acid compound (i) and a lactam (j), followed by reacting the reaction product thus obtained with a cross-linking compound (k) selected from epihalohydrins, α,γ-dihalo-β-hydrins,glycidyl compounds and isocyanates. A water soluble resin according to claim 5, wherein an alicyclic compound (1) selected from alicyclic amines having at least one activated hydrogen and alicyclic epoxy compounds is added in the reaction. A water soluble resin obtainable by reacting a water soluble resin according to any one of claims 1 to 6 with an amide compound (C) obtainable by reacting an α,β-unsaturated carboxylic acid compound (x) with an amine (y) having a primary or secondary amino group. A composition comprising a water soluble resin according to any one of claims 1 to 6 and an amide compound (C) obtainable by reacting an α,β-unsaturated carboxylic acid compound (x) with an amine (y) having a primary or secondary amino group. A paper coating composition comprising: (I) a pigment, (II) an aqueous binder, and (III) a water soluble resin according to claim 1, 3, 5, 6 or 7 or a composition according to claim 8. Paper coated with a composition according to claim 9.

Inventors: HASEGAWA TOSHIYUKI, KAWAMURA AKIRA, SATO SONOE, TANIKAWA AKIRA, HASEGAWA, TOSHIYUKI, KAWAMURA, AKIRA, SATO, SONOE, TANIKAWA, AKIRA
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY LIMITED
Application year: 1997
Main classification: C08G71
IPC codes: C08G71, D21H19, C08G73, C08G18