BACKGROUND ART Paints that are generally used nowadays include chemical paints having an excellent drying property, and natural paints having a poor drying property.

However, in the chemical paints that are most generally used nowadays, drying agents containing large amounts of heavy metals and volatile organic compounds (VOC), including benzene, toluene and xylene, harmful to the human body, are used in order to ensure the drying property. Thus, the chemical paints are advantageous in that they are quickly dried.

However, the chemical paints contain the harmful heavy metals and volatile organic compounds in large amounts so that poisonous substances, including lead and chrome, remain. Moreover, in a drying process of the chemical paints, the volatile organic compounds, such as aromatic hydrocarbons, halogenated hydrocarbons and sulfur-containing hydrocarbons, in addition to the poisonous substances, are continuously emitted to the outside, thereby causing serious environmental problems.

Furthermore, it is assumed that the chemical paints directly affect the human body so as to cause respiratory diseases, allergic diseases, general paralysis, cancers and the like in paint workers or a person exposed to the paints. Also, in persons moved into a house which was newly furnished with the chemical paints, several phenomena, including allergic diseases, eczema, diarrhea, coughing and headaches, frequently occur, and such phenomena are widely known as sick house syndrome.

Actually, according to researches conducted by Ministry of Environment, Republic of Korea, in April, 1996, it was reported that the volatile organic compounds (VOC) were the main cause of ozone generation and photochemical smog, and were poisonous substances which are fatal to the human body, including the occurrence of cancer. Also, it was reported that the use of chemical paints formed about 37% of the generation causes of these volatile organic compounds, which is the largest portion.

Meanwhile, according to one study conducted in the USA, it was reported that more than 80% of persons who had been poisoned by heavy metals or chemical substances were poisoned in a house or room. In view of this point, room contamination caused by the chemical paints is a serious problem. For this reason, in the USA and some advanced European countries, the use of paints containing the volatile organic compounds in excess of the permitted limit has been prohibited according to the law for a long time. Thus, studies for substituting chemical paints with natural paints are actively conducted.

On the other hand, in order to produce the natural paints, the alkyd resin synthesis is widely generalized, in which an alkyd resin is formed by esterification of a polybasic acid, such as phthalic acid, with a polyhydric alcohol, such as glycerin, and modified with oil. This

method was developed in order to solve the problems of environmental breakdown and heavy metals harmful to the human body, which are intrinsic to the chemical paints.

However, although the prior natural paints produced by this method were successful in that they are environment-friendly and harmless to the human body, they have serious shortcomings with respect to the drying time which is the most important physical property in paints. Namely, they exhibit a set-to-touch time of 10 hours and a dry-hard time of 24 to 48 hours.

In addition, they have problems of poor workability and formation of a poor paint film.

Accordingly, although the chemical paints that are most widely used nowadays are advantageous in terms of the drying time, they have disadvantages in that they are harmful to the human body and not environment- friendly. On the other hand, although the natural paints are advantageous in that they are environment-friendly and harmless to the human body, they are not widely used since the problems of long drying time, poor workability and formation of poor paint film are not yet solved.

The present inventors have conducted many studies in an attempt to solve such actual problems, and consequently developed unique natural paints which have excellent physical properties as compared to the existing German-made natural paints. Such developed natural paints are disclosed in Korean Patent

Application Nos. 1998-40664 and 1998-40665. The natural paints disclosed in these patent applications should be ones that were significantly improved in that they exhibit a reduced drying time. However, these natural paints need to be further improved in view of workability and paint film stability.

DISCLOSURE OF THE INVENTION It is therefore an object of the present invention to provide a new natural, oily resin composition which has an excellent drying property while exhibiting improved workability and paint film stability, and also to provide a method for producing the natural, oily resin composition, as well as natural paints containing the natural, oily resin composition as a main ingredient.

To accomplish the above object, the present invention is characterized in that vegetable oils which were selected in a more limited manner are polymerized at selected ratios and polymerization conditions.

The natural, oily resin composition according to the present invention allows elimination of the poisonous ingredients that are the serious shortcoming with the prior chemical paints, and also can solve the problems of delayed drying time, poor workability and poor paint film stability.

Also, another object of the present invention is to

provide natural paints produced by using the natural, oily resin composition as a main raw material, and other ingredients as minor raw materials.

This object can be achieved by mixing the natural, oily resin composition and vegetable oil as main ingredients with conventional minor raw materials, at selected mixing ratios and conditions.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The present invention provides a natural, oily resin composition used as a main raw material in producing natural paints, as well as a method for producing the natural, oily resin composition.

The present invention provides a natural, oily resin composition which is produced by stepwise polymerizing natural raw materials consisting of 25 to 40 parts by weight of tung oil, 25 to 40 parts by weight of boiled linseed oil and 20 to 50 parts of rosin ester, and then adding citrus-turpentine oil to the polymerization product at the amount of 40 to 80 parts by weight relative to the weight of the polymerization product.

The present invention provides a method for producing the natural, oily resin composition, which

comprises the steps of providing natural raw materials consisting of 25 to 40 parts by weight of tung oil, 25 to 40 parts of boiled linseed oil and 20 to 50 parts of rosin ester; weighing the natural raw materials, introducing them into a reaction kettle, and then subjecting them to a first polymerization, at a temperature of 200 to 300 °C for 7 to 12 hours under an atmosphere of inert gas such as nitrogen; subjecting a product from the first polymerization step to a second polymerization for 3 to 8 hours, in a state where a viscosity (#G) of the first polymerization product is V, until a viscosity of Z and an acid value of less than 10 are reached; and lowering the temperature within the reaction kettle to 90 °C and adding citrus-turpentine oil to the second polymerization product at the amount of 40 to 80 parts by weight relative to 100 parts by weight of the second polymerization product and then cooling the resulting mixture to room temperature.

The step of providing the natural raw material according to the present invention comprises selecting the natural raw materials from vegetable oils and weighing the selected raw materials according to a predetermined ratio.

It is preferred to use tung oil in a state where it was completely purified at its boiling point and thus present at a pure concentration. Tung oil is selected because it has covalent double bonds and thus has an

excellent drying property and high viscosity, although is has a relatively low iodine value. Moreover, tung oil has such properties in that it contains a-eleostearic acid as a main ingredient and has an excellent alkaline resistance. Also, it has such properties in that it is rapidly dried in oil and fat and forms a tough film.

This tung oil is used at the amount of about 25 to 40 parts by weight relative to a total weight of the natural raw materials used in the first step.

If tung oil is used at the amount of less than 25 parts by weight, it will have little or no effect on the drying property, whereas it is used at the amount of 40 parts by weight, a poor paint film will be caused. This tung oil has covalent double bonds. Thus, in the polymerization step, atmospheric oxygen acts on the covalent double bonds to produce peroxides and then to produce hydroxy groups and oxygen bridges, so that tung oil is polymerized.

Another vegetable oil used in the present invention is boiled linseed oil. Boiled linseed oil is obtained by heating linseed oil at a temperature of about 250 to 300 °C. This heating can further reduce the drying time of a final paint product.

Thus, the usage of boiled linseed oil is critical to the present invention. Boiled linseed oil is used at the amount of about 25 to 40 parts by weight relative to a total weight of the natural raw material used in the

first step. It is used at the amount of less than 25 parts by weight, insufficient workability and poor paint film formation phenomena will occur in the produced paint, whereas if is used at the amount of more than 40 parts by weight, delayed drying and poor paint film formation phenomena will occur in the paint.

At the polymerization step, methylene groups adjacent to double bonds in boiled linseed oil are oxidized to produce unstable hydroperoxides which are immediately dissociated into free radicals. Fatty acids act on the free radicals to produce peroxide bonds, ether bonds, C-C bonds and the like so that boiled linseed oil is cured.

Another vegetable oil used in the present invention is rosin ester which can be obtained by reaction of rosin with glycerin according to a conventional method.

Rosin ester is used at the amount of about 25 to 50 parts by weight relative to a total amount of the natural raw materials. If it is used at the amount of less than 20 parts by weight, elasticity of a paint film will be poor, whereas if it is used at the amount of more than 50 parts by weight, a paint film will have an overly strong elasticity and thus will be brittle.

In the present invention, the respective natural raw materials described above are introduced in a reaction kettle, and subjected to the first polymeriza

tion step at a temperature of 200 to 300 °C for 3 to 8 hours.

The inert gas used in the first polymerization step is not reacted with the natural raw materials and includes nitrogen and helium. Nitrogen is preferably used as the inert gas in view of economical efficiency.

In the present invention, if the first polymerization step is carried out at 200 °C or below, polymerization does not occur well. On the other hand, if the first polymerization step is carried out at 300 °C or above, over-polymerization phenomenon occurs so that the natural raw materials tend to gel.

Generally, in the low temperature range, the natural raw materials should be polymerized for a relatively extended period for time, but in the high temperature range, they are polymerized in a relative short time.

In the present invention, the second polymerization step is carried out following the first polymerization step. In the second polymerization step, the product from the first polymerization step is further polymerized for 3 to 7 hours in a state where a viscosity (G#) of the first polymerization product is V.

The second polymerization step is carried out until a viscosity of Z and an acid value of less than 10 are reached. Since the first polymerization product is gradually changed from solid phase to liquid phase with

the passage of time, the point of time at which the viscosity and the acid value are changed is important.

If the solvent-adding step is carried out before the conditions as described above are reached, a paint film will have reduced adhesive strength and poor workability, and also an unstable resin state will occur. On the other hand, if the viscosity and the acid value exceed the conditions as above described, the natural raw materials will be gelled and over- polymerized so that a poor paint film phenomenon occurs.

In the present invention, after the second polymerization step is carried out, the step of adding the solvent is carried out. In the solvent-adding step, the heating is stopped to lower the temperature within the reaction kettle. When the temperature within the reaction kettle has reached about 90 °C, citrus- turpentine oil is added to the second polymerization product at the amount of 40 to 80 parts by weight relative to 100 parts by weight of the second polymerization product. The resulting mixture is cooled to room temperature, thereby terminating the reaction.

Citrus-turpentine oil used in the present invention serves as a natural solvent. This is preferably based on over-99%-pure D-lemonine, which is obtained by mixing orange oil with Eucalyptus-turpentine oil at a weight ratio of 3: 1 to 5 : 1 and then purifying by heating the

mixture at a temperature of 80 to 250 °C for more than 4 hours.

If the temperature within the reaction kettle is above 90 °C, citrus-turpentine oil is easily boiled and volatilized to be converted into a coagulated state. For this reason, the step of adding the citrus-turpentine oil is carried out at 90 °C or below, and preferably about 70 °C.

By conducting several steps as described above, the natural, oily resin composition of the present invention is produced.

It was found that the natural, oily resin composition of the present invention had physical properties as described below.

Namely, the natural, oily resin composition contains non-volatile ingredients at about 60 to 70E as measured by a KSM 5000 test method (2013). Also, it has a viscosity (G&num , 25 °C) of 0 to R as measured by a gastner viscometer. In addition, it has a specific gravity of 0.85 to 0.95 and is present as a millet jelly-like state when observed by the-naked eye.

The natural, oily resin composition according to the present invention is useful as a main ingredient for natural paints, enamels, primers, varnishes and the like.

Furthermore, the present invention provides a natural paint composition exhibiting excellent drying

property, workability and paint film forming properties, which contains the natural, oily resin composition as a main raw material.

The natural paint composition according to the present invention is characterized in that it comprises 30 to 50 parts by weight of the natural, oily resin as a main raw material, 8 to 20 parts by weight of vegetable oils, 0.1 to 2 parts by weight of lecithin, and the rest of assistant raw materials which are conventionally used in production of natural paints.

It is believed that the natural, oil resin as described above, when used in the paints, is polymerized with oxygen in air in an easy and rapid manner, so that its drying time is significantly reduced. However, it was found that if the natural, oily resin was used at the amount of less than 30 parts by weight, adhesive strength of the resulting paint was reduced, whereas if it was used at the amount of more than 50 parts by weight, drying of the resulting paint is delayed. In the natural paint composition according to the present invention, the above vegetable oils serve as a solvent and function to form a paint film by volatilization in air. As such vegetable oils, citrus-turpentine oil is preferably used.

Meanwhile, in the natural paint composition according to the present invention, lecithin, which is a natural additive, serves as a dispersing agent and used

at a small amount to perform a function as the dispersing agent. If lecithin is used at the amount of less than 0.1 parts by weight, its dispersing function is insufficient, whereas if it is used at the amount of more than 2 parts by weight, it is responsible for delayed drying.

The assistant raw materials used in the present invention indicate pigments, drying agents, fillers, that are conventionally used. They are selected depending on the use purpose of the natural paints according to the present invention.

The natural paint composition according to the present invention can be produced according to a conventional method. If the natural paint is of an oily nature, the natural, oily resin is mixed with vegetable oil, lecithin and pigment at a suitable ratio. The mixture is then milled three or four times with a roll mill until a particle size of less than 10 pTm is reached. Next, the drying agent and other assistant raw materials are added to the resulting particle, and the mixture is filled by filtration and packed, thereby producing a finished natural paint product.

The natural paint composition was found to have the following physical properties. Namely, it has a set-to- touch time of 2 hours, a dry-hard time of 10 hours, a non-volatile ingredient content of 68.0 2%, a viscosity

of 70 to 80 Ku, a specific gravity of 1.2 0.20 g/l, and a contrast ratio of 0.93 0.3.

Furthermore, three kinds of the natural, oily paint samples (white, red and green) according to the present invention were measured for their various physical properties in Korea Testing and Research Institute for Chemical Industry. Results are shown in Table 1 below.

TNnlT. STRTAT. APPT. TCARTT. TTY Therefore, since the natural, oily resin composition according to the present invention contains no drying agents comprising large amounts of heavy metals and volatile organic compounds as used in the prior chemical paints, there is no detection of the heavy metals and volatile organic compounds harmful to the environment and human body in the natural paint composition that is a final product. Thus, the natural, oily resin composition of the present invention is useful as a raw material for environment-friendly products.

Furthermore, the total solid contents in natural paints is in the range of 55 to 66% by the natural, oily resin of the present invention, so that the natural paints have a significantly improved workability and an excellent film-forming property.

Table 1: Results of measurement for physical properties of samples by Korea Testing and Research Institute for Chemical Industry

Test items Units Results Test methods Total solid content % 55-56 K SM-5701-96 Pigment content % 9-33 K SM-5701-96 Non-volatile extender content % 33-46 K SM-5701-96 Water content % 0.5-0.1 K SM-5701-96 (Karl Fischer method) Consistency K. U. 71-75 K SM-5701-96 Gloss (60°) % 94-96 K SM-5701-96 Softness N. S. 5 K SM-5701-96 Set-to-touchtime Hour 2-3 K SM-5701-96 Dry-hard time Hour 10 K SM-5701-96 Contrast ratio 0. 96-0.98 K SM-5701-96 Hg Ppm Not detected I. C. P. analysis As Ppm Not detected I. C. P. analysis Organic tin compound Ppm Not detected Notification No. 1997-390 by Korean Agency for Technology and Standards Sb Ppm 2-4 1. C. P. analysis Cr Ppm 0.5-3 I. C. P. analysis Pb Ppm 1-5 I. C. P. analysis Cd Ppm 0-0.02 I. C. P. analysis Co Ppm 0.0003-0.03 I. C. P. analysis I'b (in non-volatile content) % 0.0002-0.001 I. C. P. analysis Cd (in non-volatile content) % Not detected I. C. P. analysis Cr (in non-volatile content) % Not detected I. C. P. analysis Sb (in non-volatile content) % 0.0003-0.001 I. C. P. analysis Formaldehydes Ppm Not detected Notification No. 1997-390 by Korean Agency for Technology and Standards

In addition, where natural paints according to the present invention are used, they exhibit highly improved economical efficiency and workability, since they are far excellent in volumetric solid content and consistency properties as compared to the prior chemical paints.

Although the natural, oily resin composition, the method of producing the same, and the natural paint composition containing the same as a main ingredient, have been described above in detail, it is understood that they are only preferred embodiments of the present invention and not intended to limit the present invention thereto.

Also, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.