BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a new polyacrylate derivative, and more particularly it relates to a quaternary ammonium salt of polyacrylic acid or polymethacrylic acid. 
     2. Description of the Prior Art 
     Among the known quaternary ammonium salt of high molecular weight compounds are quaternary ammonium salts of carboxymethylcellulose such as the dimethyllaurylcetylammonium salt (West German Pat. No. 1,103,336), trimethyloctadecylammonium salt (U.S. Pat. No. 2,881,074), dodecyldimethyl (3,4-dichlorobenzyl)ammonium salt [Deut. Apotheker-Ztg., 106,(35), 1206-8, (1966)], tetradecylpyridinium salt and cetyltrimethylammonium salt [Pham. Ind., 37,(2), 100, (1976)]. Nevertheless, nothing has heretofore been known about a quaternary ammonium salt of a polymer, such as a polyacrylate derivative as is described in to the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention provides a polyacrylate derivative represented by the formula: ##STR1## (where R is a hydrogen atom or methyl group; R 1  to R 4  are groups of which two are methyl groups, one is a benzyl group, and the remaining one is a tetradecyl group or p-1,1,3,3-tetramethylbutylphenoxyethoxyethyl group; and n is a numeral from 50 to 20,000.) 
     The compounds of the present invention are effective for preventing the accumulation or attachment of marine organisms (e.g., periphytons such as seaweeds or shellfishes) on ship&#39;s bottom, fishing nets or various marine structures. In addition, they show a very low degree of toxicity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 and FIG. 2 are infrared absorption spectra of tetradecyldimethylbenzylammonium salt of polyacrylic acid and benzethonium salt of polyacrylic acid, respectively, which are the compounds of the invention. FIG. 3 and FIG. 4 are  1  H-NMR spectra of tetradecyldimethylbenzylammonium salt of polyacrylic acid and benzethonium salt of polyacrylic acid, respectively. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The polyacrylate derivative of the present invention can be obtained by reacting an alkali metal salt (e.g., sodium salt) of polyacrylic acid (or polymethacrylic acid) and a corresponding quaternary ammonium halide in approximately equimolar amount in an aqueous solution. The preferred polyacrylic acid or polymethacrylic acid is one which has a degree of polymerization in the range of about 50 to 20,000 (measured by osmometry). In a case where the polyacrylate derivative is intended for use as an agent for preventing the accumulation or attachment of marine organisms such as periphyton, it is preferred to employ a polyacrylic acid or polymethacrylic acid raw material having a degree of polymerization in the range of about 100 to 1000, because one having an excessively high degree of polymerization shows an undesirably high viscosity. 
     The reaction gives a product sparingly soluble in water, which precipitates. The precipitate can be collected by filtration and if necessary is purified. The purification can be easily conducted by washing with water; or by dissolving in an organic solvent (e.g., a lower alkanol such as ethanol or isopropanol, a ketone such as methyl isobutyl ketone or a benzene anologue such as benzene, toluene or xylene) containing water (10% or less), followed by addition of water to re-precipitate. 
     When the polyacrylate derivative of the invention is used as an agent for preventing the accumulation or attachment of periphyton, it is conventionally formulated in the form of a paint. The paint is usually composed of an organic solvent (as mentioned above) and a solution of a conventional resin for painting such as acrylic resins. The concentration of the polyacrylate derivative in the paint is usually about 2-30% by weight. Such paint can be applied to the subject by dip coating or direct coating. 
     To further illustrate the invention, and not by way of limitation, the following examples are given. 
    
    
     EXAMPLE 1 
     In a 1-liter three-neck flask was placed 500 ml of water and then 18.8 g (0.2 mol) of sodium polyacrylate having a degree of polymerization of 300. Dissolution was effected by heating (at 40° C.) and stirring. An equivalent of each of the quaternary ammonium compounds shown in Table 1 was dissolved in 370 ml of water. The resulting aqueous solution was slowly added with stirring to the aqueous solution of sodium polyacrylate. Stirring was continued for 30 minutes. The resulting precipitate was filtered off and fully washed with water, followed by vacuum drying at normal temperature. Thus there were obtained two kinds of quaternary ammonium salts of polyacrylic acid. Their solubility in solvents and compatibility with resins are shown in Tables 1 and 2 below, respectively. 
     
                       TABLE 1______________________________________Quaternary ammoniumcompound used  Solvent         Solubility______________________________________Tetradecyldimethylbenzyl-          Water           Insolubleammoniumchloride          Methanol        Soluble          Isopropanol (IPA)                          Insoluble          Water/IPA (5/95)                          Soluble          Methyl isobutyl ketone                          Insoluble          (MIBK)          Water/MIBK (5/95)                          Soluble          Xylene          Insoluble          Xylene/IPA/water                          Soluble          (45/45/10)Benzethonium chloride          Water           Insoluble          Methanol        Insoluble          IPA             Insoluble          Water/IPA (5/95)                          Soluble          MIBK            Insoluble          Water/MIBK (5/95)                          Insoluble          Xylene          Insoluble          Xylene/IPA (50/50)                          Soluble______________________________________ 
    
     
                       TABLE 2______________________________________Quaternary ammonium          Trade namecompound used  of resin   Film appearance______________________________________tetradecyldimethylbenzyl-          LR-117     Clear film with slightammoniumchloride          tackiness          A-800      Clear film          EVAC-1000  Clear filmBenzethonium chloride          LA-117     Clear film with slight                     tackiness          A-800      Clear film          EVAC-1000  Clear film______________________________________ Remarks: Film appearance was evaluated by using a film prepared from a solution in which the quaternary ammonium salt of polyacrylic acid and resin are dissolved in the ratio of 35/65 in a suitable solvent. 
    
     
         Trade Name     Resin Name     Manufacturer______________________________________LR-117    Acrylic polymer                    Mitsubishi Rayon Co.,     (N.V. 40%)     Ltd., JapanA-800     Polyvinyl acetate                    Daicel Chemical     (N.V. 50%)     Industries, Ltd.,                    JapanEVAC-1000 Ethylene-vinyl acetate                    Kuraray Co., Ltd.,     copolymer (N.V. 50%)                    Japan______________________________________ 
    
     The thus obtained tetradecyldimethylbenzylammonium salt of polyacrylic acid and benzethonium polyacrylic acid were examined by elemental analysis, infrared absorption spectrometry, and  1  H-NMR spectrometry. The results are shown below. (Refer to FIGS. 1 to 4). 
     
         ______________________________________(1) Tetradecyldimethylbenzylammonium salt of polyacrylic acidResults of Elemental Analysis               Corrected value forElement  Calculated value               7% water content                             Found value______________________________________C      77.4%        72.0%         72.0%H      11.2%        11.2%         11.2%N      3.5%         3.3%          3.2%______________________________________ IR (KBr): 3400, 2860˜2930, 1570, 1450, 1400, 730, and 707 .sup.1 HNMR (ppm): 0.9 (g), 1.3 (f), 1.85 (e), 2.2˜2.7 (d), 3.1˜3.35 (c), 4.6 (b), 4.95 (H.sub.2 O), and 7.5˜7.6 (a). 
    
     
         (2) Benzethonium salt of polyacrylic acidResults of Elemental Analysis               Corrected value forElement  Calculated value               4.4% water content                             Found value______________________________________C      74.5%        71.2%         71.2%H      9.3%         9.4%          9.6%N      2.9%         2.8%          2.8%______________________________________ IR (KBr): 3400, 2860˜3010, 1570˜1585, 1418, 1415˜1460, 1395˜1410, 1365, 1245, 1190, 1128, 985, 902, 832, 770, and 720 cm.sup.-1 .sup.1 HNMR (ppm): 0.68 (m), 1.3 (l), 1.7 (k), 2.5 (j), 3.1 (i), 3.3 solv (methanol/H.sub.2 O), 3.65 (h), 3.9 (g), 4.1 (f), 4.65 (e), 4.9 (H.sub.2 O), and 6.8 (d). 
    
     Test Example 1 
     An antifouling paint was prepared from 30 g of tetradecyldimethylbenzylammonium salt of polyacrylic acid obtained in Example 1, 175 g of acrylate paint (containing 70 g of acrylic resin LR-117 made by Mitsubishi Rayon Co., Ltd.), and 560 g of isobutanol. The paint was applied to a polyethylene fishing net by dipping. After drying for two days at normal temperature, the fishing net was immersed in seawater for two months. The accumulation or attachment of marine organisms on the fishing net was examined. The results are shown in Table 3. 
     
                       TABLE 3______________________________________Weight increase of             Accumulation                        Accumulationfishing net after or attachment                        or attachmentapplication (%)   of shellfishes                        of seaweeds______________________________________The control   None          Great many Great manyfishing netThe fishing   5.1           Very few   Some greennet applied                      laverthe paint______________________________________
Disclosed herein are polyacrylate derivatives such as tetradecyldimethylbenzylammonium salt of polyacrylic acid and benzethonium salt of polyacrylic acid, which are effective as a paint ingredient to prevent the accumulation or attachment of marine organisms such as periphytons to ship's bottom. The polyacrylate derivatives have a very low degree of toxicity.