Aqueous resin and method for producing same

Abstract

The present invention addresses the problem of providing an aqueous resin comprising vegetable oil as a raw material, wherein the aqueous resin can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, can be cured in a short time from the state of the liquid resin composition, and can form a coating film and a molded product having sufficient strength, and to provide a method for producing the aqueous resin. The problem is solved by an aqueous resin which contains a polymer of an unsaturated fatty acid having a carboxyl group and a basic salt of a carboxyl group, and can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition.

Description

Water-based resin and its manufacturing method

[0001] The present invention relates to a water-based resin useful as an aqueous binder and an aqueous paint, and in particular to a water-based resin made from vegetable oil.

[0002] Lipids such as fats and oils or fatty acids are naturally derived and have a low environmental impact. It is well known that lipids containing unsaturated fatty acids, i.e., drying oils, oxidize and harden. However, their reaction rate is slow, and it takes a long time for them to change from an amorphous state to a fixed shape, making them insufficiently useful as resin materials for binders, paints, and other applications.

[0003] Furthermore, these cured products have almost no solubility or thermoplasticity. Therefore, for example, cured products of such lipids cannot be used as raw materials for coating films and molded articles, and are insufficiently versatile as resin materials for binders, paints, etc.

[0004] An object of the present invention is to provide an aqueous resin made from vegetable oil, which can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, which can be cured from the liquid resin composition state in a short time, and which can form coating films and molded products with sufficient strength, and a method for producing the same.

[0005] The present invention provides means for solving the problems in the following aspects: [Aspect 1] A water-based resin that contains a product obtained by reacting a base reaction product of a solid resin made of a polymer of an unsaturated fatty acid or a derivative thereof with an acid to liberate a carboxyl group from a carboxylate of the base reaction product, and that can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition.

[0006] [Embodiment 2] The aqueous resin of embodiment 1, wherein the polymer of unsaturated fatty acid is made from an unsaturated fatty acid or a derivative thereof.

[0007] [Embodiment 3] The aqueous resin of embodiment 1 or 2, wherein the unsaturated fatty acid derivative comprises a drying oil.

[0008] [Embodiment 4] The aqueous resin of any one of embodiments 1 to 3, wherein the base is a substance containing an alkali metal or an alkaline earth metal.

[0009] [Embodiment 5] The aqueous resin of any one of embodiments 1 to 4, wherein the unsaturated fatty acid has 16 to 22, preferably 16 to 20, and more preferably 18 carbon atoms.

[0010] [Aspect 6] The aqueous resin of any one of Aspects 1 to 5, wherein the unsaturated fatty acid includes linoleic acid or linolenic acid, and the unsaturated fatty acid derivative includes linseed oil.

[0011] [Embodiment 7] A liquid resin composition comprising the aqueous resin of any one of embodiments 1 to 6 and a hydrophilic solvent.

[0012] [Embodiment 8] A coating film or a molded article comprising a cured product of the liquid resin composition of embodiment 7.

[0013] [Embodiment 9] An alkyd resin modified with the water-based resin of any one of embodiments 1 to 6.

[0014] [Embodiment 10] A coating film or a molded article comprising a cured product of the alkyd resin of embodiment 9.

[0015] [Embodiment 11] A method for producing an aqueous resin that can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, the method comprising the steps of: reacting a solid resin made of a polymer of an unsaturated fatty acid or a derivative thereof with a base; and reacting the obtained base reaction product with an acid to liberate a carboxyl group from the carboxylate of the base reaction product.

[0016] [Embodiment 12] The method for producing the aqueous resin of embodiment 11, wherein the unsaturated fatty acid derivative comprises a drying oil.

[0017] [Embodiment 13] A method for producing a coating film or a molded article, comprising: a step of applying the liquid resin composition of embodiment 7 to a substrate or molding the composition; and a step of drying the resulting coating film or molded article.

[0018] [Embodiment 14] A method for producing a coating film or a molded article, comprising: a step of applying the alkyd resin of embodiment 9 to a substrate or molding the substrate; and a step of drying the resulting coating film or molded article.

[0019] [Embodiment 15] A method for producing an aqueous resin that can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, comprising reacting a base reaction product of a solid resin made of a polymer of an unsaturated fatty acid or a derivative thereof with an acid to liberate a carboxyl group from the carboxylate of the base reaction product.

[0020] According to the present invention, there are provided an aqueous resin made from vegetable oil, which can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, which can be cured from the liquid resin composition state in a short time, and which can form coating films and molded products with sufficient strength, and a method for producing the same.

[0021] 1 is a photograph showing the appearance of a gummy polymer obtained by reacting a base reaction product of a linseed oil polymer with an acid to liberate a carboxyl group from the carboxylate salt thereof, as prepared in Example 1. 2 is a 600x magnified photograph of an aqueous suspension of a linseed oil-derived fatty acid polymer prepared in Example 1. 3 is a graph showing the results of measuring the amount of formaldehyde generated when the aqueous resin prepared in the example is cured.

[0022] <Waterborne Resin> The waterborne resin of the present invention includes a polymer of unsaturated fatty acid. As described above, a polymer of unsaturated fatty acid has an internal structure in which unsaturated groups are bonded to each other and three-dimensionally crosslinked, and is known to be insoluble. For example, when an unsaturated fatty acid is thermally polymerized in the atmosphere, a particulate insoluble polymer (i.e., an insoluble resin mass) is produced, as shown in Example 1 described below. When this is brought into contact with a base and water, the unsaturated fatty acid polymer is dissolved in water by the addition of the base, as the appropriate molecular weight, the carboxyl groups derived from the unsaturated fatty acid, and a portion thereof are converted into salts. In other words, the unsaturated fatty acid polymer is saponified with a strong base to become water-soluble.

[0023] On the other hand, because this aqueous solution is a liquid soap, the dried product does not exhibit water resistance and cannot be used as a resin to form coatings or molded articles. However, when an acid was added to this solution to convert the carboxyl-derived salt into a carboxylic acid, thereby returning the resin to its original state, it was found that a viscous gum-like substance was produced without returning to the insoluble resin mass before saponification. It was also found that by dispersing or dissolving this in a hydrophilic solvent, a liquid resin composition could be obtained. Furthermore, it was found that when the resulting liquid resin composition was dried and the internal water evaporated, it hardened and became a solid with the same strength as the insoluble resin before saponification.

[0024] By adding an acid to a saponified solution of an unsaturated fatty acid polymer, the salts derived from the carboxyl groups are rapidly converted to carboxylic acids, which then aggregate to a certain size through hydrophobic interactions, surrounding the separated water. As a result, the interior of the aqueous resin of the present invention is filled with fine hydrophilic solvent channels. This increases the surface area accessible to hydrophilic solvents such as water and alcohol, allowing the resin to swell, disperse, or dissolve in these solvents. In this specification, "aqueous resin" refers to a resin that can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition. Hydrophilic solvents include water; water-soluble organic solvents such as ethanol, isopropanol, and acetone; aqueous solutions of water-soluble organic solvents; and aqueous solutions of water-soluble bases such as ammonia.

[0025] Furthermore, since cured resins made of polymeric compounds have poor solubility, they are difficult to separate into individual molecules, making it difficult to determine their internal structure using existing analytical methods. The aqueous resin of the present invention has an internal structure in which the polymers are three-dimensionally crosslinked, making it impossible to separate into independent polymers without destroying the molecules. In other words, with regard to the aqueous resin of the present invention, at the time of filing, there are circumstances in which it is impossible or almost impractical to directly identify the product by its internal structure or properties.

[0026] The aqueous resin of the present invention is produced using a composition containing unsaturated fatty acids or derivatives of unsaturated fatty acids as a raw material. Examples of unsaturated fatty acid derivatives include esters of unsaturated fatty acids and polyhydric alcohols, fats and oils of unsaturated fatty acids, and drying oils.

[0027] Unsaturated fatty acids and unsaturated fatty acid derivatives have double bonds and can be cured, for example, by polymerization in the presence of oxygen in the air.

[0028] As the unsaturated fatty acid, for example, a fatty acid having 16 or more carbon atoms, two or more double bonds, and a carboxyl group is used. By having two or more double bonds, the unsaturated fatty acid can form a crosslinked structure during the polymerization reaction, improving the chemical resistance, heat resistance, or strength of the resulting molded article. The number of double bonds in the unsaturated fatty acid is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 or 3. Furthermore, from the viewpoint of easy availability, the number of carbon atoms in the unsaturated fatty acid is preferably 16 to 22, more preferably 16 to 20, and even more preferably 18.

[0029] Specific examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. Among these, preferred unsaturated fatty acids are linoleic acid, linolenic acid, and arachidonic acid. From the viewpoint of reducing the environmental load, unsaturated fatty acids are preferably derived from plants, and more preferably linoleic acid, α-linolenic acid, and γ-linolenic acid. A single type of unsaturated fatty acid may be used, or multiple types may be used in combination.

[0030] The above description of unsaturated fatty acids also applies to the unsaturated fatty acids constituting the unsaturated fatty acid derivatives.Specific examples of unsaturated fatty acid derivatives include linseed oil, tung oil, perilla oil, sesame oil, poppy seed oil, walnut oil, safflower oil, fish oil, dehydrated castor oil, rice oil, corn oil, grape seed oil, soybean oil, sunflower oil, peanut oil, rapeseed oil, cottonseed oil, tall oil, almond oil, jojoba oil, kukui nut oil, macadamia nut oil, and persic oil.

[0031] Polymerization of unsaturated fatty acids or derivatives thereof is carried out by oxidative polymerization of unsaturated groups in the presence of oxygen. The oxidative polymerization can be carried out, for example, by stirring the unsaturated fatty acids in air or by blowing air into the unsaturated fatty acids to bring them into contact with oxygen in the air. The polymerization can be carried out at room temperature.

[0032] To accelerate the oxidative polymerization reaction, heating or a catalyst may be used, if necessary. The oxidative polymerization reaction is preferably carried out until the polymer irreversibly gels and turns into powder, losing its thermoplasticity. This improves the strength or water resistance of coating films and molded articles formed from the aqueous resin.

[0033] When the oxidative polymerization reaction is carried out by heating, the reaction temperature is, for example, 100 to 500° C., preferably 200 to 450° C., and more preferably 300 to 400° C. If the heating temperature is less than 100° C., the oxidative polymerization reaction may not be sufficiently promoted, whereas if it exceeds 500° C., the amount of volatilization of the composition increases, which may reduce the yield of the aqueous resin.

[0034] The catalyst used in the oxidative polymerization reaction may be a conventionally known oxidation catalyst. Specific examples of the catalyst that can be used include metal powders of Co, Mn, Pb, Ca, Zn, Cu, Zr, Ce, Fe, Pd, Pt, Sn, Mo, W, Ti, V, Rh, Ni, Zr, Al, Ag, B, and Cr, which are used in drying oil driers, and oxides, hydroxides, sulfates, nitrates, chlorides, acetates, and naphthenates of these metals, as well as organic oxidizing agents such as anthracene, methyl ethyl ketone peroxide, and benzoyl peroxide.

[0035] The reaction time for the oxidation polymerization reaction varies depending on reaction conditions such as reaction temperature and type of catalyst, but is preferably adjusted appropriately between 3 and 48 hours, and more preferably between 6 and 10 hours.

[0036] The resulting polymer is then reacted with a base to saponify the polymer and convert the carboxyl groups derived from the unsaturated fatty acids into their salts. Specific examples of bases that can be used in the reaction include NaOH, KOH, Li(OH), and Ba(OH). ２ , Ca(OH) ２, NaHCO ３ , Na ２ CO ３ In a preferred embodiment, a strong base is used. Specific examples of preferred bases include NaOH and KOH.

[0037] The polymer of unsaturated fatty acid or its derivative may be the polymer electrolyte described in WO 2023 / 027057. The polymer electrolyte is a polymer electrolyte having a partial polymer of a fatty acid having 16 or more carbon atoms, two or more double bonds, and carboxyl groups, some of which have been neutralized with a basic substance to be converted to carboxylate anion groups.

[0038] In this polymer electrolyte, preferred examples of the fatty acid include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. Preferred examples of the basic substance include NaOH, KOH, and Ca(OH). ２ , K(OH), Li(OH), Mg(OH) ２ , Ba(OH) ２ , Zn(OH) ２ , ammonia, monoethanolamine, diethanolamine, triethanolamine, etc.

[0039] The polymer can be reacted with a base, for example, by mixing it with an aqueous base solution. The concentration of the base in the aqueous solution is adjusted to 0.1 to 18 N, preferably 1 to 10 N, and more preferably 3 to 6 N, from the viewpoint of improving the hydrophilicity of the aqueous resin. To promote the reaction, the reaction solution may be heated under pressure as necessary. The heating temperature of the reaction solution is adjusted to, for example, 50 to 200°C, preferably 80 to 180°C, and more preferably 100 to 150°C under pressure.

[0040] The reaction time for the reaction varies depending on reaction conditions such as the concentration of the base and the reaction temperature, but is preferably adjusted appropriately between 1 minute and 3 hours, preferably between 5 and 90 minutes, and more preferably between 10 and 60 minutes. Upon completion of the reaction, the base reactant of the polymer becomes a viscous fluid.

[0041] The base reactant of the polymer is then reacted with an acid, thereby liberating a carboxyl group from the carboxylate salt of the base reactant. Specific examples of acids that can be used in the reaction include sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and formic acid. In a preferred embodiment, a strong acid is used. Specific examples of preferred acids include sulfuric acid and hydrochloric acid.

[0042] The base reactant of the polymer can be reacted with an acid, for example, by mixing it with an acidic aqueous solution. The concentration of the acid in the aqueous solution is adjusted to 0.1 to 18 N, preferably 1 to 10 N, and more preferably 3 to 6 N, in order to efficiently generate carboxylic acid in the aqueous resin while preventing bumping due to excessive heat generation. To promote the reaction, the reaction solution may be heated under pressure as necessary. The heating temperature of the reaction solution is adjusted to, for example, 50 to 200°C, preferably 80 to 180°C, and more preferably 100 to 150°C under pressure.

[0043] The reaction time varies depending on reaction conditions such as the acid concentration and reaction temperature, but is preferably adjusted appropriately between 20 minutes and 10 hours, preferably 30 minutes to 5 hours, and more preferably 40 minutes to 2 hours. Upon completion of the reaction, the resulting acid reaction product becomes gum-like. By washing the acid reaction product with water, by-products such as salts and glycerol can be removed, and an aqueous resin can be obtained.

[0044] When the water content of this aqueous resin evaporates, it becomes a solid with strength comparable to that of the insoluble polymer before saponification. Furthermore, this aqueous resin exhibits high solubility in alcohol and other properties, making it easily soluble. When a suspension of the aqueous resin is observed under an optical microscope, numerous particles are observed, suggesting that an emulsion or suspension has been formed. In other words, the aqueous resin of the present invention includes an aqueous resin dispersed or dissolved in a solvent containing water.

[0045] <Liquid Resin Composition> The aqueous resin of the present invention can be mixed and suspended in an appropriate solvent to form a liquid resin composition including a solution, emulsion, or suspension thereof. From the viewpoint of solubility, suitable solvents include water-soluble organic solvents such as alcohols having 1 to 4 carbon atoms and acetone, aqueous solutions of water-soluble organic solvents, aqueous solutions of water-soluble bases such as ammonia, water such as distilled water, and mixtures thereof. Specific examples of such mixtures include aqueous ethanol solutions, aqueous ammonia solutions, and aqueous ethanol-ammonia solutions.

[0046] The aqueous resin of the present invention is expected to be in demand as a paint or an adhesive for wood boards. By applying the liquid resin composition of the present invention to a substrate and drying it, or by bonding members together via the liquid resin composition, it is possible to significantly speed up the drying of coating films and bonded products whose main components are drying oils or unsaturated fatty acids.

[0047] For example, when producing an oil-modified alkyd resin, by using the aqueous resin of the present invention instead of a modified oil such as a drying oil, it is possible to provide an ultra-fast-drying, low-formaldehyde modified alkyd resin. Furthermore, thick products made from unsaturated fatty acids such as the above-mentioned polymer electrolytes and linoleum, which have previously required a long time to harden, can now be completely hardened at the same time as molding, making them significantly easier to handle.

[0048] Demand for natural paints is increasing year by year, and while branding is currently being promoted primarily by overseas manufacturers, water-based resins made from vegetable oils are highly regarded for their low toxicity and natural origin. Substrates suitable for coatings containing the water-based resins and alkyd resins of the present invention include wood, cotton, paper, glass fiber, carbon fiber, metal materials (e.g., iron, copper, tin, aluminum, and titanium), glass, mortar, pulp, cellulose, cellulose nanofiber, hemp cotton, floss floss, wool, and rock wool. The Food Sanitation Act's positive list includes cases where vegetable oils and unsaturated fatty acids are used as monomer raw materials. By applying the water-based resins of the present invention to coating and bonding tableware, products that comply with the Food Sanitation Act can be produced with only a few basic tests.

[0049] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0050] Example 1 Preparation of Linseed Oil-Derived Fatty Acid Polymer 500 mL of linseed oil was poured into a 2 L beaker placed on a heater, and polymerization was carried out at 350°C for approximately 6 hours while stirring and thoroughly mixing with air. The liquid linseed oil became gel-like. Further mixing at 350°C caused it to disintegrate into powder, and polymerization was then continued for approximately 2 hours at the same temperature while mixing in air. Heating was stopped when the yellow powder turned black, and the mixture was cooled to room temperature.

[0051] To the obtained linseed oil polymer, 500 mL of a 5N aqueous solution of NaOH was added, and the mixture was pressurized and heated in an autoclave at 121°C for about 10 minutes. As a result, the linseed oil polymer became a black, starch-syrup-like dissolved product. It is believed that the linseed oil polymer was saponified, and the resulting carboxyl groups formed Na salts, thereby becoming water-soluble.

[0052] Here is H ２ SO ４ 500 mL of a 6N aqueous solution of the above was added and stirred at 100°C for approximately 1 hour to liberate the carboxylate group from the carboxylate salt (i.e., the Na salt of the carboxyl group) of the base reaction product. This resulted in a gum-like polymer containing approximately 50% (w / w) water inside. Figure 1 is a photograph showing the appearance of the resulting gum-like polymer.

[0053] If the mixture becomes more liquid-like and syrup-like at this point, the previous heat polymerization process is insufficient. Conversely, if the mixture contains a large amount of hard, sand-like particles, this indicates that carbonization is progressing due to an excessive reaction, and it is possible to determine whether the polymerization reaction was successful.

[0054] The resulting gum-like polymer was washed with plenty of running water while being kneaded to remove salt, glycerol, and other by-products, yielding a linseed oil-derived fatty acid polymer, which was then stored in a sealed container to prevent water from evaporating.

[0055] The linseed oil-derived fatty acid polymer was suspended in water and observed under an optical microscope. Figure 2 is a 600x magnification photograph of the aqueous suspension of the linseed oil-derived fatty acid polymer. Numerous particles are observed in the photograph of Figure 2, which suggests that the aqueous resin has been emulsified or suspended.

[0056] Example 2 Preparation of Linseed Oil-Derived Glyceride Polymer The same procedure as in Example 1 was repeated to polymerize linseed oil, add an aqueous NaOH solution, and ２ SO ４ By adding the aqueous solution, a gum-like polymer containing approximately 50% (w / w) water was produced. Heating was then continued until the lower aqueous layer disappeared. This resulted in a glossy, elastic rubber-like polymer. The glycerol, which had been hydrolyzed and transferred to the aqueous layer, was consumed in the esterification reaction. By carrying out the reaction in the presence of water, a certain amount of carboxyl groups remained.

[0057] The obtained rubbery polymer was washed with plenty of running water while being kneaded to remove salt, glycerol, and other by-products, thereby obtaining a linseed oil-derived glyceride polymer. The obtained linseed oil-derived glyceride polymer was stored in a sealed container to prevent evaporation of water.

[0058] Example 3 Preparation of Linoleic Acid-Derived Polymer 500 mL of linoleic acid was poured into a 2 L beaker placed on a heater and polymerized at 350°C for approximately 8 hours while stirring and thoroughly mixing with air. The liquid linoleic acid became gel-like. Further mixing at 350°C caused it to disintegrate into powder, and polymerization was then continued for approximately 2 hours at the same temperature while mixing with air. Heating was stopped when the powder became hard and black, and it was cooled to room temperature.

[0059] To the obtained linoleic acid polymer, 500 mL of a 5N aqueous solution of NaOH was added, and the mixture was pressurized and heated in an autoclave at 121°C for about 10 minutes. As a result, the linoleic acid polymer became a black, starch-syrup-like solution. It is believed that the carboxyl groups of the linoleic acid polymer formed Na salts, thereby making the polymer water-soluble.

[0060] Here is H ２ SO４ 500 mL of a 6N aqueous solution of the above was added and stirred at 100° C. for about 1 hour to liberate the carboxylate group from the carboxylate of the base reaction product, thereby obtaining a gum-like polymer containing about 50% (w / w) water inside.

[0061] The resulting gum-like polymer was washed with plenty of running water while being kneaded to remove salt and other by-products, and the resulting linoleic acid-derived polymer was stored in a sealed container to prevent evaporation of water.

[0062] Example 4 Preparation of Linseed Oil-Modified Alkyd Resin 9 g of glycerol, 4 g of phthalic anhydride, and 20 g (dry weight: 10 g) of a linseed oil-derived fatty acid polymer were added to a mortar and kneaded. A control sample was also prepared by adding 10 g of linseed oil as a monomer instead of the linseed oil-derived fatty acid polymer.

[0063] After heating and suspending them, 20 μL of concentrated sulfuric acid was added as a catalyst to proceed with the esterification reaction.

[0064] After heating and kneading for 1 hour, the mixture was washed with water and cooled to room temperature. The resulting gum-like linseed oil-modified alkyd resin was removed, sealed, and stored in ethanol at room temperature. A control sample was stored in a light-shielding bottle at 4°C.

[0065] Example 5 Solubility Test The linseed oil polymer and linseed oil-derived glyceride polymer of Example 2, and the linoleic acid polymer and linoleic acid-derived polymer of Example 3 were each added to distilled water, 28 wt % aqueous ammonia, ethanol, isopropanol, acetone, or an aqueous solution of 80 wt % ethanol and 0.5 wt % ammonia in an amount 10 times the dry weight thereof, and the mixture was shaken at 25° C. for 24 hours.

[0066] The mixture was centrifuged at 20,000 G for 15 minutes, and the supernatant was decanted. The residue was air-dried at 100°C for 24 hours and weighed to calculate the dissolved amount per added amount of polymer (% (w / w)). The results are shown in Table 1.

[0067]

[0068] The linseed oil polymer and the linoleic acid polymer were hardly soluble in the solvents, whereas the linseed oil-derived glyceride polymer and the linoleic acid-derived polymer were highly soluble in 28% aqueous ammonia, and were also soluble in organic solvents and ethanol-ammonia aqueous solutions.

[0069] The presence of ammonia in the solvent converts the carboxyl groups derived from the fatty acids of the polymer into ammonium salts, forming a polymer electrolyte and improving the hydrophilicity of the polymer, which allows the polymer to better conform to the surface of the slide glass and results in a coating with less unevenness compared to when ammonia is not added.

[0070] Example 6: Surface drying property test The aqueous resins prepared in Examples 1 to 4 and the following control samples were prepared as test subjects.

[0071] Commercially available woodworking oil (vegetable oil) paint A Commercially available woodworking oil (vegetable oil) paint B Commercially available oil-based urethane varnish Commercially available water-based urethane varnish

[0072] 500 μL of each saturated solution of the solubility test sample obtained in Example 5 at 25°C was dropped onto a slide glass (75 × 25 mm) and spread over the entire surface with the tip of a glass slide to form a coating film approximately 50 μm thick. All control reagents formed coating films approximately 100 μm thick.

[0073] The degree of drying of the coating film was evaluated by touch at regular intervals at room temperature of 25°C, with reference to JIS K 5600-1-1. The evaluation criteria are shown below. At the beginning of drying, a dry to the touch state (A) was observed, which then progressed to a semi-dry state (B), and the test for that coating film was terminated when it reached a hardened dry state (C). The evaluation results are shown in Table 2.

[0074] (A) Touch-dry: When the center of the coating surface is lightly touched with a fingertip, the fingertip does not get dirty. (B) Semi-dry: When the center of the coating surface is gently and lightly rubbed with a fingertip, no scratches are left. (C) Dry-dry: When the center of the coating surface is firmly pinched between the thumb and index finger, no fingerprint indentations are left on the surface, no movement of the coating film is felt, and when the center of the coating surface is rubbed rapidly and repeatedly with a fingertip, no scratches are left on the surface.

[0075]

[0076] Linoleic acid-derived polymers dry relatively quickly, probably due to their relatively high degree of polymerization. Linoleic acid does not form ester bonds like linseed oil, so the degree of oxidative polymerization required to form particles is high. Therefore, it is thought that at the time of particle formation, the degree of oxidative polymerization is uniform and high compared to linseed oil.

[0077] The polymer electrolyte, in which some of the carboxyl groups have been converted to ammonium salts, is amphiphilic and compatible with a variety of different materials, making it suitable for forming a uniform coating on a glass slide. Meanwhile, as the ammonia gradually evaporates, the carboxyl groups become non-electrolytes again, increasing water resistance after curing and drying. As a result, it was confirmed that both polymers dried to the touch much faster.

[0078] When 80% ethanol containing 0.5% ammonia was used, the linseed oil-derived polymer re-softened and became sticky after a certain period of time. Since the elastic modulus of fatty acid polymers increases when they become electrolytes, the volatilization of ammonia accelerates the non-electrolysis of the carboxyl groups, resulting in a decrease in the elastic modulus, which is thought to be the reason for the temporary re-softening. After that, the polymer hardens again as it dries.

[0079] Commercially available oil paints for woodworking maintained a certain level of viscosity throughout the test and did not completely dry. However, this viscosity is not considered to be a problem if the paint is intended to penetrate the wood. While existing oil paints require a very long drying time, the polymers produced using this technology all dried in a short time, demonstrating their potential for use as ultra-fast-drying oil paints. In particular, the linoleic acid-derived polymer dissolved in 80% ethanol containing 0.5% ammonia achieved a drying speed comparable to that of commercially available urethane varnish.

[0080] Example 7 Hardness Test The aqueous resins prepared in Examples 1 to 4 and the following control samples were prepared as test subjects.

[0081] Commercially available flaxseed oil Commercially available linoleic acid

[0082] 500 μL of each saturated solution of the solubility test sample obtained in Example 5 at 25°C was dropped onto a glass slide (75 × 25 mm) and spread over the entire surface with a tip to form a coating film approximately 50 μm thick. The coating film formed on the glass slide was cured by heating at a predetermined temperature for a predetermined time. All control reagents formed a coating film approximately 100 μm thick.

[0083] The hardness of the cured coating film (on a glass slide) was evaluated with reference to the old JIS K5400. Because the modified alkyd resin made from linseed oil-derived fatty acid polymers had only a small solubility in solvents, 500 mg of a gummy polymer mass softened in 95% ethanol was applied uniformly to a glass slide with a roller. Because the linseed oil-derived glyceride polymer showed a lower solubility in 0.5% ammonia water alone than the other samples, testing under these conditions was omitted.

[0084] As a control, a coating film was prepared by heating and polymerizing linseed oil and linoleic acid on a heater at 250°C. However, the film deformed significantly on the slide glass during heating, making it impossible to prepare a uniform coating film. Therefore, a location with relatively little unevenness was selected for testing. On the other hand, when each gum-like polymer was dissolved in a solvent, all of the polymers dried to a uniform strength within 30 minutes at room temperature (25°C) after application. From this point on, heating at 250°C yielded a glossy coating film with almost no deformation.

[0085] The tip of the pencil (3B to 6H) to be tested was placed perpendicularly against 400 grit abrasive paper and polished to a flat tip with sharp corners.

[0086] The sharpened lead was placed at an angle of 45° to the test surface and, while being pressed against the painted surface, was pushed forward for about 1 cm at a speed of 1 cm / s to scratch the painted surface.

[0087] The tip of the pencil lead was sharpened after each scratch, and the test was repeated five times for each pencil. The pencil hardness at which plastic deformation and cohesive failure occurred two or more times out of five tests was recorded. The test for that coating was terminated when cohesive failure occurred twice. The test results are shown in Table 3.

[0088]

[0089] Although both require a certain amount of time to reach sufficient hardness at room temperature, it was confirmed that a strong coating was ultimately formed. Furthermore, while it takes about four hours at 250°C to completely harden the monomers linseed oil and linoleic acid, this technology was shown to achieve the same level of hardness after just three minutes of heating.

[0090] Example 8 Water Resistance Test The cured coating film prepared in Example 7 was prepared as a test subject.

[0091] Water resistance was evaluated with reference to JIS K5600-6-2. 500 mL of distilled water was placed in a beaker and placed in a thermostatic oven at 40°C for 24 hours to degas the film to some extent. Each coating film on a slide glass was placed in the beaker and removed after 72 hours. The water was drained and the film was dried at 25°C for 24 hours.

[0092] The hardness and appearance of the coating film after drying were examined for any changes. The evaluation results are shown in Table 4.

[0093]

[0094] The reglyceride polymers and alkyd resins showed no visible changes, including in appearance, demonstrating their water resistance.On the other hand, the linseed oil-derived fatty acid polymers and linoleic acid-derived fatty acid polymers showed temporary peeling from the slide glass immediately after immersion in either solvent.

[0095] After drying, the coating film formed on the glass slide retains roughly its original strength, and this property may be utilized in practical applications such as transferring peeled coatings. Considering that no peeling was observed in the control coatings of linseed oil polymer and linoleic acid polymer prepared by heating the monomer, it is possible that the peeling and loss of hardness are caused by some of the carboxyl groups that came into contact with the alkali remaining in an electrolyte state.

[0096] Therefore, it is thought that strength, water resistance, and quick-drying properties can be achieved by re-esterifying the carboxyl groups through methods such as reglyceridation and alkyd resinification. In particular, reglyceridized resins form a high-strength, high-water-resistant coating film similar to existing oil-modified alkyd resins in a short time when heated, making them suitable for baked finishes and reactive hot melt adhesives.

[0097] Example 9 Formaldehyde Emission Test 15 g (dry weight 8 g) of the linseed oil-modified alkyd resin prepared in Example 4 was placed in the center of a 380 x 330 mm paper towel (product name "Kimtowel" manufactured by Nippon Paper Crecia Co., Ltd.) and spread over the entire paper towel with a roller. As a control, 8 g of an oil-modified alkyd resin made from monomeric linseed oil was applied to the entire paper towel with a brush.

[0098] Similarly, 15 mL of ethanol solutions containing 0.5 g of the linseed oil-derived glyceride polymer prepared in Example 2 and the linoleic acid-derived polymer prepared in Example 3 were also applied to the entire paper towel. As a control, 0.5 g of linseed oil and linoleic acid were each suspended in 15 mL of ethanol, and this suspension was applied to the entire paper towel. Note that, because formaldehyde reacts with ammonia, the test using aqueous ammonia as a solvent was omitted.

[0099] The coated paper towel was placed in a polypropylene bag ("AUTO CLEAVE BAGS" (trade name) manufactured by intellim Japan Co., Ltd.) measuring 0.05 x 360 x 660 mm, and then sealed.

[0100] Vinyl tape was applied to one spot on the outside of the bag, a 3 mm slit was made at that spot with scissors, a 3 mm diameter silicone tube was pushed in about 3 cm, and the other end was connected to a pump (Millipore's "Masterflex Easy Load Peristaltic Pump" (trade name)).

[0101] After pumping 3 L of air, the tube was removed and the hole was sealed with vinyl tape. The bag was floated on a tray of water in a draft chamber to prevent ignition.

[0102] After 48 hours, a 3 mm cut was made in the vinyl tape again with scissors, a detector tube (Gastec Corporation, "30193 Formaldehyde" (trade name)) was inserted 3 cm, a gas sampler (Gastec Corporation, "GV-100S" (trade name)) was connected, and measurements were taken five times each, and the average amount of formaldehyde emitted was calculated. The results are shown in Figure 3.

[0103] It was confirmed that for all water-based resins, the amount of formaldehyde emitted was reduced to about one-fourth of that when a monomer was used.

Claims

1. A water-based resin that includes a base reactant of a solid resin consisting of a polymer of an unsaturated fatty acid or its derivative, which is reacted with an acid to liberate a carboxyl group from the carboxylate of the base reactant, and which can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition.

2. The aqueous resin according to claim 1, wherein the polymer of the unsaturated fatty acid is made from an unsaturated fatty acid or a derivative thereof.

3. The water-based resin according to claim 1 or 2, wherein the unsaturated fatty acid derivative comprises a drying oil.

4. The aqueous resin according to any one of claims 1 to 3, wherein the base is a substance containing an alkali metal or an alkaline earth metal.

5. The aqueous resin according to any one of claims 1 to 4, wherein the unsaturated fatty acid has 16 to 22 carbon atoms.

6. The aqueous resin according to any one of claims 1 to 5, wherein the unsaturated fatty acid comprises linoleic acid or linolenic acid, and the unsaturated fatty acid derivative comprises linseed oil.

7. A liquid resin composition comprising the aqueous resin according to any one of claims 1 to 6 and a hydrophilic solvent.

8. A coating film or a molded article comprising a cured product of the liquid resin composition according to claim 7.

9. An alkyd resin modified with the water-based resin according to any one of claims 1 to 6.

10. A coating film or a molded article comprising a cured product of the alkyd resin according to claim 9.

11. A method for producing an aqueous resin which can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition, comprising the steps of: reacting a solid resin composed of a polymer of an unsaturated fatty acid or a derivative thereof with a base; and reacting the obtained base reactant with an acid to liberate a carboxyl group from the carboxylate of the base reactant.

12. The method for producing a water-based resin according to claim 11, wherein the unsaturated fatty acid derivative comprises a drying oil.

13. A method for producing a coating film or a molded product, comprising the steps of: applying the liquid resin composition according to claim 7 to a substrate or molding it; and drying the resulting coating film or molded product.

14. A method for producing a coating film or a molded article, comprising the steps of: applying the alkyd resin according to claim 9 to a substrate or molding it; and drying the resulting coating film or molded article.

15. A method for producing an aqueous resin, which comprises reacting a base reactant of a solid resin consisting of a polymer of an unsaturated fatty acid or its derivative with an acid to liberate a carboxyl group from the carboxylate of the base reactant, and which can be dispersed or dissolved in a hydrophilic solvent to form a liquid resin composition.

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