AQUEOUS DISPERSION OF BIODEGRADABLE RESIN COMPOSITION

Abstract: A thermally-decomposable, biodegradable resin composition is dispersed and stabilized in water optionally along with additives to give an aqueous dispersion of the resin composition. In the dispersion, the base polymer consists substantially of a water-insoluble starch-type, biodegradable resin. The dispersion is usable in various fields of papermaking, non-woven fabric production, film and sheet production and woven fabric production, in those of dispersed adhesive production, and in those of metal processing, plastic processing, wood processing and stone processing.

Description: The present invention relates to an aqueous dispersion of a biodegradable thermoplastic resin composition, which is prepared by dispersing and stabilizing in water an essential composition comprising a base polymer that consists substantially of a water-insoluble esterified starch-type, biodegradable resin, and optionally a plasticizer, a filler, an antioxidant, a stabilizer, a dispersant, an emulsifier, a thickener and a solvent, said resin being an esterified starch having a DS of > 1.0 and an ester moiety of 2 to 18 carbon atoms. It relates to an aqueous dispersion of a biodegradable resin composition with good handlability, which is thermoplastic and biodegradable and which is used in various fields of papermaking, non-woven fabric production, film and sheet production and woven fabric production, in those of dispersed adhesive production, and in those of metal processing, plastic processing, wood processing and stone processing. With various environmental problems being much discussed, materials good to the environment, such as typically various biodegradable plastics and processed paper, and applicable to the field where synthetic polymers have heretofore been used are being studied and developed. In particular, the applications of those materials to laminates and films are being much studied. Where such biodegradable plastics are used in producing laminates and films, extruders are used for extrusion lamination. In addition, used are techniques of melt spinning and injection molding of resins. In those techniques, resins are generally used as their hot melts. In other embodiments of using conventional synthetic resins including biodegradable resins, used are synthetic emulsions as prepared through emulsion polymerization, such as typically synthetic rubbers and polyvinyl acetate resins, and also hot melts of resin compositions as prepared by hot-melting resins, typically polyvinyl acetate resins along with paraffins. Where polyvinyl chloride resins and the like are used, they may be dispersed in plasticizers or organic solvents to give plastisols and organosols. In those conventional cases, resins are melted under heat, or emulsified during their production, or organic solvents (including plasticizers) are used. No one knows an aqueous dispersion consisting indispensably of a thermoplastic biodegradable resin, which is prepared by dispersing and stabilizing a powder of the resin itself in water, and even knows that the dispersion can be applied onto substrates or can be cast onto substrates for bonding those substrates through vaporization of water, or the dispersion can be used for processing substrates themselves or their surfaces, or the dispersion can be formed into films, sheets, plates and others through casting. The object of the present invention is to provide an aqueous dispersion of a biodegradable resin composition with biodegradability and thermal decomposability and with good handlability, which is prepared by dispersing and stabilizing in water a thermoplastic, biodegradable resin composition optionally along with additives, and which is used in various fields of papermaking, non-woven fabric production, film and sheet production and woven fabric production, in those of dispersed adhesive production, and in those of metal processing, plastic processing, wood processing and stone processing. U.S.-Patent No. 3,746,558 discloses stable colloidal suspensions of hydrophobic starch esters comprising 1-50% particles of hydrophobic starch esters having an average weight size of 0.1-1.0 µm. GB-A-2 075 537 relates to derivatized and thinned starches having a degree of substitution in the range of 0.05 to 0.4 and an intrinsic viscosity in the range of 0.12 to 0.28 dl/g. U.S.-Patent No. 4,301,017 discloses stable, aqueous polymeric dispersions comprising at least 25% solids of a thinned and derivatized starch and at least one vinyl monomer. U.S.-Patent No. 4,301,017 relates to stable, aqueous polymeric dispersions comprising graft copolymers of at least one vinyl monomer and a derivatized and thinned amylopectin starch. EP-A-0 276 770 discloses a glue agent for paper based on aqueous dispersions of co-polymerizates obtained from a monomer mixture of 20-65 wt.% (meth)acrynitrile, 35-80 wt.% of one or more arcylic acid esters of saturated C 3 -C 8 alcohols and 0-10 wt.% of another unsaturated copolymerizable monomer. U.S.-Patent No. 5,003,022 relates to stable, aqueous polymeric dispersions comprising a graft copolymer of thinned, gelatinized starch and one or more vinyl grafting monomers. U.S.-Patent No. 5,224,989 discloses a film-forming dispersion for the formation of protective coatings on shaped drug and food articles comprising 1-25 wt.% of acetylester of oxidized starch and 0.8-8 wt.% of triethylcitrate. DISCLOSURE OF THE INVENTION In order to attain the object, we, the present inventors have assiduously studied for obtaining and developing a starch-type, thermoplastic and biodegradable resin composition, and, as a result, have found an aqueous dispersion of a biodegradable resin composition with good handlability, which comprises the ingredients mentioned below, and its applications. We have further found that various products can be obtained by the use of the composition. The aqueous dispersion of a biodegradable resin composition of the invention basically comprises a biodegradable resin composition as dispersed and stabilized in water, in which the base polymer constituting the biodegradable resin composition substantially comprises a water-insoluble esterified starch-type, biodegradable resin. The biodegradable resin is selected from esterified starches having a high degree of ester substitution of larger than 1.0, and this is dispersed and stabilized in water along with additives such as plasticizer and others. The biodegradable resin may be combined with any other various polymers to form the base polymer. If desired, additives such as plasticizer, filler and dispersion stabilizer may be added to the base polymer. In the aqueous dispersion of a biodegradable resin composition said resin is present as water-insoluble solid particles as dispersed in water preferably having a mean grain size of not larger than 50 µm. The invention also relates to the use of the aqueous dispersion of said biodegradable resin composition, in which, concretely, the aqueous dispersion is used (1) in processing paper, non-woven fabrics, films, sheets and woven fabrics, (2) in adhesive compositions, or (3) in processing metals, plastics, wood, stone or (4) it is cast to give castings. BEST MODES OF CARRYING OUT THE INVENTION Now described in detail hereinunder are modes of carrying out the invention. A. The biodegradable resin composition to be in the aqueous dispersion of the invention comprises a base polymer, in which the base polymer substantially comprises a water-insoluble esterified starch-type, biodegradable resin. The esterified starch-type, biodegradable resin indicates a starch-derived polymer which is insoluble in water in its steady state and which is degraded by microbes into water and carbon dioxide. Preferred examples of the resin are mentioned below. The esterified starches of the present invention have a high degree of ester substitution: They are starch esters in which the ester moiety has from 2 to 18 carbon atoms and which have a degree of ester substitution of larger than 1.0. For these, used are any ordinary esterified starches having said high degree of ester substitution, which are produced using esterifying reagents of halides, anhydrides or vinyl esters of carboxylic acids having from 2 to 18 carbon atoms. (5) The base polymer may comprise other polymers apart from the esterified starch-type, biodegradable resins such as those mentioned hereinabove. As the additional polymers, preferred are one or more selected from ester-type and/or ether-type starch derivatives, biodegradable polyesters, cellulose derivatives, polyvinyl alcohols and polyvinyl esters. Also usable are polycondensates of, for example, polyamides, polycarbonates and polyurethanes; vinyl polymers other than polyvinyl esters; and polyolefins, polyalkylene oxides, biodegradable polyalkylene oxides, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, ABS resins, styrene-acrylonitrile copolymers, etc. Specific examples of those polymers are mentioned below. Biodegradable polyesters: Polycaprolactones, polylactic acids, polyadipates, polyhydroxybutyrates, polyhydroxybutyrate valerates, etc. Ester-type and ether-type starch derivatives: Hydroxyethylated starches, hydroxypropylated starches, cationic starches, maleic acid ester starches, sulfated starches, p-toluenesulfonated starches, octenylsuccinated starches, etc. Cellulose derivatives: Cellulose acetates, hydroxyethyl celluloses, hydroxypropyl celluloses, methyl celluloses, carboxyalkylated celluloses, etc. Polyvinyl esters: Polyvinyl acetates, polyacrylonitriles, polyvinyl carbazoles, polyacrylates, polymethacrylates, etc. Polyolefins : Polyethylenes, polyisobutylenes, polypropylenes, etc. Vinyl polymers (except polyvinyl esters): Polyvinyl chlorides, polystyrenes, etc. Polyalkylene oxides: Polyethylene oxides, polypropylene oxides, etc. B. If desired, additives such as plasticizers, fillers, dispersion stabilizers (emulsifiers, thickeners, dispersants), antioxidants and stabilizers etc. are optionally added to the base polymer to produce the biodegradable resin composition. These additives, if added to the base polymer, are to control the mechanical properties of the coated or shaped articles of the resin composition (for plasticizers, fillers), or to stabilize the liquid condition of the resin composition (for dispersion stabilizers, etc.), or to stabilize the properties of resins in water or to prevent the coated or shaped articles of the resin composition from being oxidized and deteriorated (for antioxidants, stabilizers, etc.). The amount of those additives to be added varies, depending on the applications of the aqueous dispersion of the biodegradable resin composition, and therefore could not be specifically defined. The additives are so selected that those added favorably realize their objects such as those mentioned above. The constitutions of those additives are described in more detail hereinunder. (1) Plasticizers: Mentioned are phthalates, aromatic carboxylates, esters of aliphatic dibasic acids, derivatives of esters of fatty acids, phosphates, polyester-type plasticizers, epoxy plasticizers, and polymer-type plasticizers, of which one or more are selected for use in the invention. Concretely mentioned are the following: Phthalates: Dimethyl, diethyl, dibutyl and dioctyl phthalates, ethylphthalylethyl glycolate, ethylphthalylbutyl glycolate, etc. Esters of aliphatic dibasic acids: Butyl oleate, glycerin monooleate, butyl adipate, n-hexyl adipate, etc. Aromatic carboxylates: Trioctyl trimellitate, diethylene glycol benzoate, octyl hydroxybenzoate, etc. Derivatives of esters of fatty acids: Sucrose octacetate, esters of diethylene glycol dibenzoate hydroxy acids, methyl acetylricinoleate, triethyl acetylcitrate, triacetin, tripropionin, diacetylglycerin, glycerin monostearate, etc. Phosphates: Tributyl phosphate, triphenyl phosphate, etc. Epoxy plasticizers: Epoxidated soybean oil, epoxidated castor oil, alkylepoxy stearates, etc. Polymer-type plasticizers: Various liquid rubbers, terpenes, linear polyesters, etc. (2) Fillers: Mentioned are inorganic fillers, organic fillers and synthetic fillers, of which one or more are selected for use in the invention. Concretely mentioned are the following: Inorganic fillers: Talc, titanium oxide, clay, chalk, limestone, calcium carbonate, mica, glass, diatomaceous earth, wollastonite, various silica salts, magnesium salts, manganese salts, glass fiber, various ceramic powders, etc. Organic fillers: Cellulose fiber and powder (including their derivatives), wood powder, pecan fiber, cotton powder, husks, cotton linters, wood fiber, baggasse, etc. Synthetic fillers: Urea resin filler, etc. (3) Dispersion stabilizers (dispersants, thickeners, emulsifiers): The dispersion stabilizers as referred to herein include dispersants for suspensions, emulsifiers for emulsions, and even thickeners and the like. The dispersion stabilizers are not always indispensable when the aqueous dispersion of the invention is such a colloidal dispersion that the dispersed phase therein, which will be referred to in detail hereinunder, is not larger than about 1 µm in size, but they are indispensable for dispersions of crude grains that are larger than about 1 µm. For the dispersion stabilizers, usable are one or more selected from salts of fatty acids having from 4 to 18 carbon atoms, anionic surfactants, nonionic surfactants, cationic or anionic, water-soluble polymers, condensed phosphates, cationic starch derivatives, cellulose derivatives, vegetable gum and its derivatives, animal polymers, microbial polymers, and aqueous, emulsified synthetic polymers. For those, concretely mentioned are the following: Salts of fatty acids having from 4 to 18 carbon atoms: Sodium butanoate, potassium octanoate, sodium stearate, etc. Nonionic surfactants: Alkyl polyalkylene oxides, sucrose esters of fatty acids, sorbitan esters of fatty acids, dimethylpolysiloxanes, etc. Anionic surfactants: Sodium alkylsulfates, sodium alkylsulfonates, etc. Water-soluble polymers: Cationic polyacrylamide, PVA, sodium polyacrylate, polyethyleneimine, condensed naphthalenesulfonic acid, etc. Condensed phosphates: Sodium hexametaphosphate, sodium tripolyphosphate, etc. Cationic starch derivatives: Corn starch base, tapioca starch base, potato starch base, etc. Cellulose derivatives: Carboxymethyl cellulose, carboxyethyl cellulose, hydroxypropyl cellulose, cationated celluloses, etc. Vegetable gum and its derivatives: Arabic gum, guar gum, xanthane gum, etc. Animal polymers: Casein, chitosan, chitin, etc. Microbial polymers: Xanthane gum, polydextrose, pullulan, etc. Aqueous, emulsified synthetic polymers: Synthetic rubber latex, polyvinyl acetate emulsion, etc. C. The aqueous dispersion of the invention basically comprises the biodegradable resin composition such as that mentioned herein above, as dispersed and stabilized in water. (1) The method of dispersing and stabilizing the resin composition in water is not specifically defined. For example, employable is any of a method of dispersing the biodegradable resin composition with stirring it in water, using a ball mill or the like; or a method of emulsifying and dispersing the biodegradable resin composition at a high temperature and under pressure followed by cooling it to give an aqueous dispersion of the biodegradable resin composition. Specifically, when the resin is soft and has a low softening point, it can be easily melted and dispersed (that is, emulsified and dispersed) in water at a high temperature and under high pressure, using a disperser or the like, and the resulting dispersion may be cooled with further stirring it. On the other hand, when the resin is hard and has a low softening point, it is pre-dispersed in water to give a slurry, then the slurry is wet-milled using a ball mill or the like, and additives such as plasticizers and others are added thereto. (2) The grain size of the dispersed phase (biodegradable resin composition) has some influences on the handlability of the resin composition in various processing steps and even on the properties of the processed products. For example, in producing processed paper, the degree of covering of the paper surface with the resin composition is influenced by the particle size of the dispersed phase. Therefore, it is desirable that the dispersed phase of the resin composition has a mean particle size of not larger than about 50 µm, more preferably not larger than about 10 µm. The resin composition having a mean particle size of larger than 50 µm could be used in the field of producing adhesives. However, if used in the filed of surface processing of articles, the resin composition having such a large mean particle size often produces various troubles that uneven coating still remains after the final finish of the surfaces coated therewith, or the coated surfaces have pin holes. If used in printing, it may produce mottles on the surfaces as printed therewith along with pigments. Therefore, for the present esterified starches having a high degree of ester substitution, of larger than 1.0 and in all their applications, it is preferable that the biodegradable resin composition has a mean particle size of not larger than about 50 µm, more preferably not larger than about 10 µm. However, where the composition is used in casting under limited conditions, its largest mean particle size may be up to 1mm. D. The aqueous dispersion of the biodegradable resin composition of the invention can be applied onto paper without using extruders or the like but using any ordinary coaters, and the thus-coated paper may be finished to be waterproof processed paper, which has good surface luster like laminated paper. This coating technique also applies not only to the processing of tabular substrates such as non-woven fabrics, films, sheets, fabrics and the like, as so mentioned hereinabove, for which the aqueous dispersion may be applied onto those substrates and cured thereon, or may be previously added to the materials from which those substrates are made, but also to the production of adhesives. In the latter, produced are biodegradable adhesives. Controlling its concentration or adding thereto suitable additives, the aqueous dispersion of the biodegradable resin composition of the invention can be cast to give various castings, such as cast films or cast articles. <Examples> The following Examples, Reference Examples and Comparative Examples are to concretely demonstrate the advantages of the invention, which, however, are not intended to restrict the scope of the invention. Unless otherwise specifically indicated, "parts" as referred to hereinunder to indicate the amount of ingredients are by weight. [Example 1] 6kg of highly-acetylated starch (DS = 2.5) was dispersed in 28kg of water, and milled, using a wet mill, to obtain a dispersion having a solid content of 18% and a mean particle size of 5µm. To 22kg of this dispersion, added was a plasticizer emulsion as previously emulsified with a colloid mill (its composition is shown in Table 1). This was further milled and dispersed, using a wet mill, to obtain an aqueous dispersion of the biodegradable resin. The properties of this aqueous dispersion are shown in Table 3. Reference [Example 2] 25g of plasticizer, triethyl acetylcitrate was added to 100g of acetylated, vinyl acetate-grafted polymer starch (degree of acetylation = 2.1; percentage by weight of grafting = 18%; homopolymer of polyvinyl acetate = 23%), which was then dissolved in 100g of ethanol. The resulting ethanol solution was gradually added to and finely dispersed in 500g of water, while being milled with a colloid mill, to give a dispersion having a mean particle size of 4.5 µm. Ethanol was removed under reduced pressure from this dispersion, and dispersant, thickener and emulsifier were added to the dispersion, using a colloid mill, as in Table 2. The properties of the aqueous dispersion thus obtained herein are shown in Table 3. Reference [Example 3] 30g of plasticizer, triacetin was added to 100g of acetylated, caprolactone-grafted polymer starch (degree of terminal hydroxyl blocking = 70%; percentage by weight of grafting = 45%), and milled using a plast mill. The resulting mixture was put into a hot-pressure emulsifying machine along with water, methyl cellulose and sodium dodecylsulfate, and emulsified under heat at 160°C, and thereafter cooled to room temperature, 25 °C to obtain a dispersion having a mean particle size of 3.1 µm. Its composition is shown in Table 2. The properties of the aqueous dispersion thus obtained herein are shown in Table 3. [Example 4] The aqueous dispersion obtained in Example 1 was cast onto a glass sheet, using a film applicator as defined in JIS K5400, and processed in a hot air circulating drier at 90 C for 15 minutes to obtain a biodegradable resin film. Its glass transition temperature (Tg) and softening temperature were measured, according to JIS K7121 and JIS K7196, to be 24.93 °C and 38.33 °C, respectively. [Application Example 1] The aqueous dispersion obtained in Example 1 was applied onto woodfree paper (weight: 105 g/m 2 ), using a film applicator and a bar coater as defined in JIS K5400, and dried in a hot air circulating drier to form a film thereon. Thus was obtained biodegradable resin-coated paper. A part of this was surface-processed, using a heat pressure roll (roll surface temperature: 85 °C ). The amount of the dispersion applied onto the woodfree paper, the temperature at which the coated paper was dried, and the properties of the coated paper are shown in Tables 4and 5. [Reference Application Example 2] The aqueous dispersion obtained in Reference Example 2 was applied onto a corrugating medium (weight: 120 g/m 2 ), using a film applicator and a bar coater as defined in JIS K5400, and dried in a hot air circulating drier to form a film thereon. Thus was obtained biodegradable resin-coated paper. The amount of the dispersion applied onto the medium, the temperature at which the coated paper was dried, and the properties of the coated paper are shown in Table 6. [Application Example 3, Comparative Application Example 3] The aqueous dispersion obtained in Example 1 was added to 0.3% pulp slurry, which had been beaten at a beating degree of CSF 450, along with cationic starch, the ratio of the dispersion (in terms of its solid content) to pulp being 1%. This was sheeted and then heated under pressure at 105°C for 3 minutes to obtain biodegradable resin-containing, waterproof paper (weight: 65.0 g/m 2 ; L/N = 80/20; amount of calcium carbonate added: 15% relative to pulp) (Application Example 3). In the same manner as above except that liquid polyacrylamide (commercially-available, non-biodegradable resin, "POLYSTRON 117" manufactured by Arakawa Chemical Co.) was used in place of the aqueous dispersion of Example 1, the amount of the resin added being the same as in Application Example 3. Thus was obtained waterproof paper of Comparative Application Example 3. The wet tensile strength of those paper samples was 3.8 kgf (in Application Example 3) and 4.1 kgf (in Comparative Application Example 3). The data indicate that the aqueous dispersion of the biodegradable resin composition of the invention produces a high wet adhesion strength, which is comparable to that produced by synthetic resin. [Application Example 4, Comparative Application Example 4] The aqueous dispersion obtained in Example 1 was applied onto non-bleached kraft paper (weight: 77 g/m 2 ), using a film applicator and a bar coater as defined in JIS K5400, and dried in a hot air circulating drier to form a film thereon. Thus was obtained biodegradable resin-coated paper, in which the resin base coated was 27 g/m 2 (Application Example 4). In the same manner as above except that low-density polyethylene (SUMIKASEN L211, manufactured by Sumitomo Chemical Co.) was laminated on non-bleached kraft paper of the same type, in place of using the aqueous dispersion of Example 1. In this, the amount of the polymer laminated was 20 g/m 2 in terms of the resin base. Thus was obtained coated paper of Comparative Application Example 4. The hot-sealing strength of each paper sample is shown in Table 7. [Reference Application Example 5] The aqueous dispersion obtained in Reference Example 3 was applied onto aluminium foil having a thickness of 0.5mm, the amount of the resin base coated being 60 g/m 2 . Then, this was dried and heated, using a hot roll, whereby a protective film was formed on the foil. This protective film can be easily peeled off from the aluminium foil, and is surely practicable. [Application Example 6, Comparative Application Example 6] As in Table 8, a pigment-coating composition for paper was prepared, which comprised the aqueous dispersion obtained in Example 1 and an adhesive component, sodium carboxymethyl cellulose (Cellogen, manufactured by Dai-ichi Kogyo Seiyaku Co.). This was applied onto one surface of woodfree paper (weight: 64 g/m 2 ), then dried in a hot air circulating drier at 130 °C for 5 minutes, and thereafter calendered three times, using a super calender, at 55 °C and under a pressure of 100 kg/cm 2 . Thus was obtained pigment-coated paper (Application Example 6). In the same manner as above except that styrenebutadiene copolymer resin latex (SN-307, manufactured by Sumitomo Dow Co.) and oxidized starch (SK-200, manufactured by Japan Corn Starch Co.) were used as adhesive components and that polyamide resin (SUMIREZ RESIN 633, manufactured by Sumitomo Chemical Co.) was used as a water repellent, a pigment-coating composition for paper was prepared as in Table 8 (Comparative Application Example 6). Using this, produced was pigment-coated paper in the same manner as in Application Example 6. The properties of the pigment-coating compositions prepared herein, and those of the coated paper samples are shown in Table 9. The data in Table 9 indicate that the pigment-coated paper sample as produced using the aqueous dispersion of the biodegradable resin composition of the invention is comparable to that as produced using the conventional, non-biodegradable resin (latex). Components Amount(wt.pts.) Water 100 Plasticizer (EPEG) 100 Dispersion Stabilizer Sodium dodecylsulfate 0.5 Xanthane gum 0.25 Silicone emulsion 0.1 Components Reference Example 2 Reference Example 3 Dispersion medium 250 300 Base polymer Acetylated, vinyl acetate-grafted polymer starch 100 - Acetylated, caprolactone-grafted polymer starch - 100 Plasticizer Triethyl acetylcitrate 25 Triacetin - 30 Dispersion Stabilizer Sodium laurate 0.8 - Hydroxyethyl cellulose 7.2 - Sodium dodecylsulfate - 0.5 Methyl cellulose - 5.5 Example 1 Reference Example 2 Reference Example 3 Test Method Solid content (%) 23.6 28.2 28.2 105°C, constant weight pH 6.1 6.5 6.5 Glass electrode pH meter B-type viscosity B-type viscometer (rotor No. 3) 6 rpm 5480 4950 4950 60 rpm 1370 1060 1060 Sample No. Amount Coated Drying Temperature Surface Treatment 1 27.2 75 No 2 29.0 75 Yes 3 27.5 90 No 4 28.0 90 Yes 5 28.0 120 No 6 28.5 120 Yes 7 47.8 75 No 8 45.4 75 Yes 9 44.3 90 No 10 49.3 90 Yes 11 46.4 120 No 12 46.7 120 Yes Non-coated paper - - - Amount coated: g/m 2 , in terms of the resin base. Drying temperature: °C. Sample No. Surface Luster Water Absorption Moisture Permeation Oil Repellency 1 4.0 14.5 2870 <1 2 85.9 1.6 1880 16 3 8.0 3.4 2040 16 4 86.5 0.9 1780 16 5 17.1 3.6 1810 16 6 85.3 2.5 1960 16 7 6.6 2.5 1490 16 8 86.8 1.5 1420 16 9 5.8 3.0 1410 16 10 86.0 1.7 1370 16 11 18.6 2.5 1450 16 12 86.2 1.0 1240 16 Non-coated paper 6.2 20.7 7670 <1 <Test Methods> Surface luster: JIS P8142 (%) Water absorption: JIS P8140, for 1 minute (g/m 2 ) Moisture permeation: JIS Z0208 (g/m 2 ·24 hrs) Oil repellency: TAPPI-RC-338 Sample No. Amount Coated Drying Temperature Water Absorption Moisture Permeation Oil Repellency 1 50.6 90 13.1 1490 16 2 56.6 120 11.9 1360 16 3 99.1 90 6.8 860 16 Non-coated paper - - 105.0 7260 <1 Sample No. Hot-sealing Temperature(°C) Hot-sealing Strength (gf/1.5 cm) Application Example 4 Comparative Application Example 4 1 60 142 0 2 80 383 0 3 100 407 95 4 120 410 104 Absolute Amount Added (wt.pts.) Application Example 6 Comparative Application Example 6 Clay 70 70 Precipitated calcium carbonate 30 30 Sodium polyacrylate 0.2 0.2 Composition of Example 1 25 - Sodium carboxymethyl cellulose 0.5 - Styrene-butadiene latex - 12 Oxidized starch - 6 Polyamide resin - 0.8 Calcium stearate 0.5 0.5 Solid content (%) 50 60 Application Example 6 Comparative Application Example 6 Viscosity (cp)( ) 870 920 Amount coated (g/m 2 ) 11.2 10.9 Whiteness (%)( ) 80.5 80.8 Surface smoothness (sec)( ) 2900 2800 Surface luster 73.4 72.8 Dry pick( ) 8 9 Wet pick( ) 10 8

Claims: An aqueous dispersion of a biodegradable thermoplastic resin composition dispersed and optionally stabilized in water, wherein the biodegradable resin composition comprises a base polymer consisting substantially of a water-insoluble esterified starch-type biodegradable resin, wherein said starch-type biodegradable resin is an esterified starch having a degree of ester substitution of larger than 1.0 and wherein the ester moiety of said esterified starch has from 2 to 18 carbon atoms. The aqueous dispersion of a biodegradable resin composition as claimed in claim 1, wherein said starch ester is produced using a vinyl ester as the esterifying reagent. The aqueous dispersion of a biodegradable resin composition as claimed in claim 1 or 2, wherein the base polymer is comprised of said starch-type, biodegradable resin and one or more polymers selected from ester-type and/or ether-type starch derivatives, polyolefinic polymers, polyvinylic polymers, polyester-type polymers, polyamide-type polymers, polyalkoxide-type polymers and cellulose derivatives. The aqueous dispersion of a biodegradable resin composition as claimed in any one of claims 1 to 3, wherein said biodegradable resin composition optionally contains a plasticizer and wherein one or more are selected from phthalates, aromatic carboxylates, esters of aliphatic dibasic acids, derivatives of esters of fatty acids, phosphates, polyester-type plasticizers, epoxy plasticizers and polymer-type plasticizers as said plasticizer. The aqueous dispersion of a biodegradable resin composition as claimed in any one of claims 1 to 4, wherein said biodegradable resin composition optionally contains a filler and wherein one or more are selected from natural inorganic fillers, natural organic fillers and synthetic fillers as said filler. The aqueous dispersion of a biodegradable resin composition as claimed in any one of claims 1 to 5, wherein said biodegradable resin composition optionally contains a dispersion stabilizer comprising a dispersant, a thickener and/or an emulsifier and wherein one or more are selected from metal salts of fatty acids, anionic surfactants, nonionic surfactants, cationic surfactants, cationic or anionic water-soluble polymers, condensed phosphates, cationic starch derivatives, cellulose derivatives, vegetable gum and its derivatives, animal polymers, microbial polymers and synthetic polymer emulsions as the dispersion stabilizer. The aqueous dispersion of a biodegradable resin composition as claimed in any one of claims 1 to 6, wherein the resin that constitutes the base polymer has, in water, a mean particle size of not larger than 50 µm. A tabular product as produced by applying the aqueous dispersion of a biodegradable resin composition of any one of claims 1 to 7 onto a tabular substrate, such as paper, non-woven fabric, film, sheet and woven fabric, followed by curing it thereon. A tabular product as produced by adding the aqueous dispersion of a biodegradable resin composition of any one of claims 1 to 7 to materials for said product during its production. An adhesive composition indispensably comprising the aqueous dispersion of a biodegradable resin composition of any one of claims 1 to 7. A method for forming a protective film, which comprises applying the aqueous dispersion of a biodegradable resin composition of any one of claims 1 to 7 onto the surface of a hard substrate selected from metal sheet, metal film, plastic, wood or stone followed by curing it to form a protective film thereon. A casting as produced by casting the aqueous dispersion of a biodegradable resin composition of any one of claims 1 to 7.

Inventors: HOSOKAWA NOBUHIRO, SUGIURA NOBUYUKI, TAKAHARA MASATO, TANAKA HIDEYUKI, HOSOKAWA, NOBUHIRO;, SUGIURA, NOBUYUKI;, TAKAHARA, MASATO;, TANAKA, HIDEYUKI;, HOSOKAWA, Nobuhiro; Japan Corn Starch Co., Ltd., SUGIURA, Nobuyuki; Japan Corn Starch Co., Ltd., TAKAHARA, Masato; Japan Corn Starch Co., Ltd., TANAKA, Hideyuki; Japan Corn Starch Co., Ltd.
Applicants: JAPAN CORN STARCH CO LTD, JAPAN CORN STARCH CO., LTD.
Application year: 1996
Main classification: C08L3
IPC codes: C08F251, B05D5, B29C41, C08L101, B05D7, C09D103, C08L23, C08L3, C09J103, C08L77, C08J3, B29K1