Background Art Generally, a laundry detergent is required to have excellent detergency when applied to laundry and must not generate wastewater which pollutes the environment Accordingly, much effort has been made to develop a nonpolluting detergent. For example, a detergent made of a vegetable surfactant and a detergent made of waste oil have been developed. However, the vegetable surfactant is problematic in that since it is difficult to extract the surfactant from a plant, assurance of a sufficient amount of surfactant is not easy. Furthermore, the detergent employing the waste oil is problematic in that use of the detergent is inconvenient because it is difficult to provide the detergent in powder form. Therefore, some of the study of nonpolluting detergent has been directed toward reducing the content of the surfactant and maximizing the performance of a builder. Korean Pat. Laid-Open Publication No. 2001-0082782 discloses that cationic, anionic, and/or nonionic surfactants are used in an amount of about 10-45 % based on the total weight of detergent composition, and a builder, such as sodium tripolyphosphate as a phosphorus compound, aluminosilicate-based 4A zeolite, sodium nitrilotriacetate, sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, sodium sulfate, sodium silicate, layered silicate, Burkeite, and citrate, is used in an amount of about 35-75 % based on the total weight of the detergent composition.

Sodium sesquicarbonate and layered silicate are popular choices for the builder in current studies of nonpolluting detergent Sodium sesquicarbonate has some advantages such as having excellent detergency and being nonpolluting. Another advantage is that it has a weak alkaline pH, thereby minimizing damage to a fiber. Usually, layered silicate has a structure provided in two- dimensional sheets, that is to say, 8-sheet structure. Since various sizes of inorganic ions can be exchanged between the sheets and organic polymer materials can be inserted between the sheets, layered silicate is desirably capable of removing hardness components from water and has excellent sorptivity to contaminants during a washing process, and thus, it has physical properties suitable as a builder for detergent. Furthermore, since it has excellent capability to enable oil to be absorbed into a surfactant, the amount of surfactant used in a detergent may be reduced during a compounding of the detergent. Particularly, when layered silicate is used as the builder for detergent, disadvantages of aluminosilicate zeolite A, which was frequently used as the builder for detergent after the commercial use of sodium tripoly phosphate (STPP) was restricted, can be avoided, that is to say, there can be avoided the disadvantages that ions having a large hydrated radius, such as magnesium ions, are scarcely removed, even though the removal ability of calcium ions constituting hardness components from water is excellent, because a size of a cavity is constant ; and zeolite particles which cause alkalinity because they are insoluble in water are deposited in fiber gaps, thereby damaging the fiber and affecting humans, and deposited in operating parts of a washing machine, increasing abrasion in the washing machine. Accordingly, layered silicate is in the forefront as a substitute.

Furthermore, it is possible to produce a compact detergent according to the world-wide trend, and thus, it attracts considerable attention as an auxiliary substance for detergent capable of contributing to the protection of the environment The above components are known as an auxiliary substance for detergent of the next generation because of excellent detergency and nonpolluting characteristic, and are suggested as components constituting a detergent in many documents. U. S. Pat. No. 5,756, 445 discloses a granular detergent composition which contains 20-50 wt% of aluminosilicate (low bulk density component) and 10-50 wt% of mixture of layered silicate and sesquicarbonate (high bulk density

component). British Pat No. 2315762 describes a detergent composition which contains dicarboxylic acid in conjunction with sesquicarbonate and/or layered silicate as an alkaline source.

The Korean Pat. Laid-Open Publication No. 2001-0082782 discloses a detergent composition which includes sodium bicarbonate, anhydrous soda ash, water, synthetic surfactants, silica, sodium silicate, neutral salts, and powder containing a large amount of sesquicarbonate produced from a polymer dispersing agent.

The present inventors mixed and reacted aqueous solutions, in which sodium bicarbonate and sodium silicate are homogenized in water, with each other to produce slurry, dried the slurry to produce powder, and analyzed the powder using an XRD, resulting in the surprising finding that the powder consists of layered silicate and sodium sesquicarbonate. Particularly, SEM (scanning electron microscope) analysis of the powder confirmed that detected sodium sesquicarbonate has desirable qualities of crystalline structure, particle size and density even though a seed nucleus or an anionic surfactant is not employed. Thereby, the present inventory filed for a process of simultaneously producing sodium sesquicarbonate and layered silicate on January 23,2002 with the Korea Industrial Property Office, which is disclosed in pending Korean Pat Application No. 10- 2002-0003998.

Disclosure of the Invention Accordingly, an object of the present invention is to provide an environmentally friendly and nonpolluting laundry detergent composition, which employs only layered silicate and sodium sesquicarbonate as builders without employing other substances as builders, thereby minimizing surfactant content and assuring excellent detergency.

In order to accomplish the above object, the present invention provides a laundry detergent composition which includes 75-90 wt% (hereinafter, the total weight of the laundry detergent composition is set as the basis) of powder consisting of sodium sesquicarbonate and layered silicate

mixed with each other in a weight ratio of 65: 35-95 : 5,5-10 wt% of surfactant, and 0-20 wt% of additives that are typically applied to a laundry detergent.

Brief Description of the Drawings FIG. 1 is an XRD analysis graph of a powder sample produced according to the present invention; and FIG. 2 is an SEM picture of the powder sample produced according to the present invention.

Best Mode for Carrying Out the Invention Sodium sesquicarbonate and layered silicate applied to a laundry detergent composition of the present invention may be produced according to pending Korean Pat. Application No. 10-2002- 0003998 developed by the present inventors. Sodium bicarbonate and sodium silicate are used as a starting material in the course of producing sodium sesquicarbonate and layered silicate.

Typically, sodium carbonate (Na2CO3) is carbonated to produce sodium bicarbonate (R. N.

Shreve et al. , Chemical Process Industries, McGraw-Hill Book Co., 4i ed., 1977, p. 213). A commercial method of producing sodium bicarbonate includes dissolving soda ash (hydrated mineral matter mostly consisting ofNa2C03) in aqueous liquid, putting the resulting saturated solution of soda ash in a carbonation vessel to simultaneously cause the solution to come into contact with carbon dioxide gas and cool the solution. After aqueous slurry is recovered and filtered in the carbonation vessel, it is dried to produce sodium bicarbonate crystals. Additionally, sodium bicarbonate may be produced from a trona ore (coarse sodium sesquicarbonate) through a multi-stage purifying process.

Such aproduction is disclosed in U. S. Pat Nos. 2,346, 140,2, 639,217, 3,028, 215,3, 780,160, 6,207, 123, and 200/0001037, and Chinese Pat. No. 1270926.

Sodium silicate is produced by reacting a mixture of silica with soda ash or caustic soda at 1200 °C or above, consists of Si02 and Na2O, and forms various compounds according to the relative proportion of the above two components. It is usually classified into a crystal type and an amorphous type, and amorphous-type silicate is exemplified by sodium metasilicate, sodium orthosilicate, and sodium sesquisilicate, which respectively contain Si02 andNa2O mixed in a molar ratio of 1: 1, 1: 2, and 2: 3, and first to fourth liquid sodium silicates which contain from 30 % to 50 % water corresponding to a ratio of Si02 from 2 to 4. Commercial liquid sodium silicate contains Si02 and Na20 mixed in a ratio of about 2-4 : 1. Preferably, sodium silicate contains Si02 and Na2O mixed in a ratio of 2.1- 3.8 : 1.

In the middle of the process according to the present invention, an amount of water may be controlled to prevent formation of lumps which are considered an obstruction to the process, thereby increasing yield. According to a preferable aspect of the present invention, a ratio of solids to water is maintained at about 50-70 % in mixed liquid of sodium bicarbonate with sodium silicate. In this regard, since sodium silicate essentially contains water, the amount of water added in practice is less than 50-70 %. When the amount of water is small, a large amount of anhydrous soda ash may be generated. On the other hand, when the amount of water is large, the reaction of sodium silicate with sodium bicarbonate may be hindered. In other words, when separate reactions of sodium silicate and sodium bicarbonate occur, sodium silicate forms a transparent crystal and sodium bicarbonate is dissolved in water.

Sodium bicarbonate aqueous solution reacts with sodium silicate aqueous solution, and the resulting solution is dried to produce powder consisting of sodium sesquicarbonate and layered silicate applied to the detergent composition of the present invention (FIG. 1). Sodium sesquicarbonate is expressed as an experimental equation of NaCO3 NaHCO3 2H20, and is a crystal having an acicular structure in a powdery state. Layered silicate may be expressed as a Formula of NaMSix02+1'yH2O (wherein, M is sodium (Na) orhydrogen tH), xis 1.9-4, and y is 0-20).

In the process according to the present invention, when the sodium bicarbonate aqueous solution reacts with the sodium silicate aqueous solution, a reaction temperature is preferably about

100 °C or above. The reason for this is that when the reaction temperature is about 100 °C or below, the yield of layered silicate may be significantly reduced. On the other hand, when the temperature is about 150°C or above, layered silicate is generated but sodium sesquicarbonate may be decomposed.

Accordingly, it is preferable that the reaction temperatures of the sodium bicarbonate and sodium silicate aqueous solutions of the present invention be about 100-150°C. Reaction times of the sodium bicarbonate and sodium silicate aqueous solutions depend on temperature, and may be easily determined through repeated experimentation incurring no expenses to those skilled in the art According to a preferred aspect of the present invention, when the reaction is carried out at 125 C for 1 - 1. 5 hours, a high yield results. Slurry of sodium bicarbonate and sodium silicate mixed according to the present invention may be conveniently dried by heating. Alternatively, drying may be conducted in spray and belt manners, which are well known in the art and may be desirably applied to the present invention.

The reaction of sodium bicarbonate and sodium silicate by heating in an aqueous solution is achieved according to the following Reaction Equations. First, sodium bicarbonate reacts according to the following Reaction Equations 1 and 2.

Reaction Equation 1 NaHCO3-Na+ + HCO37 Reaction Equation 2 2HC03-- H20 + C02 The above reactions scarcely occur in aqueous solution at room temperature, but are actively carried out at 60 °C or above. C02 generated in Reaction Equations 1 and 2 reacts with sodium silicate as follows. At this time, C02 is a main component initiating a reaction of Reaction Equation 3.

Reaction Equation 3 Na2O# 2SiO2 + CO2 + 4H2O # Na2CO3 + 2Si (OH)4 wherein, Na2CO3 reacts with water to produce Na2CO3# H2O.

Reaction Equation 4 Na2COs+H20- Na2C03'H20 Na2CO3 H20 produced through Reaction Equation 3 reacts with NaHCO3 which is not decomposed by Reaction Equations 1 and 2 to produce products of Reaction Equation 5.

Reaction Equation 5 Na2CO3# H2O + NaHCO3 + H2O # Na2CO3 # NaHCO3# 2H2O Sodium sesquicarbonate is produced in Reaction Equation 5, and a combination of Reaction Equations 4 and 5 is as follows.

Reaction Equation 6 Na2CO3 + NAHCO3 + 2H2O # Na2CO3# NaHCO3# 2H2O Since Si (OH) 4 produced in Reaction Equation 3 is very unstable, it is combined with other Si (OH) 4 to form disilicic acid.

Reaction Equation 7 Disilicic acid of Reaction Equation 7 is combined with Na+ ions existing in an excessive amount in Reaction Equation 1 to produce layered silicate. In this regard, when the temperature is 100 °C or below, layered silicate is not produced. If anhydrous soda ash is applied to this reaction, the amount of soda ash is excessively increased in conjunction with soda ash generated from sodium silicate according to a reaction mechanism, and thus, a portion of anhydrous soda ash which does not participate in a sodium sesquicarbonate combination is generated in an excessive amount Additionally, a probability of a reverse reaction of Reaction Equation 3 increases.

Alternatively, sodium bicarbonate and sodium silicate may be separately produced in aqueous solution and then mixed with each other, or sodium bicarbonate and sodium silicate may be added into water to initiate the reaction before they are produced in separate aqueous solutions. However, these procedures are disadvantageous in that it is difficult to conduct the reaction and the yield may be reduced when they are produced in a great amount.

Sodium sesquicarbonate and layered silicate according to the present invention are used in an amount of 75-90 % based on the total weight of the detergent composition of the present invention.

At this time, a ratio of sodium sesquicarbonate and layered silicate is 65: 35-95: 5 based on the weight.

In the case of powder consisting of sodium sesquicarbonate and layered silicate produced according to the above procedure, a ratio of sodium sesquicarbonate and layered silicate is about 65: 35-95 : 5.

A surfactant available to the detergent composition according to the present invention is exemplified by a soap surfactant, an anionic surfactant and/or a nonionic surfactant An amount of the surfactant used is 5-10 % based on the total weight of the detergent composition. When the amount of the surfactant is 5 % or less, the influence of the surfactant is negligible, and thus, it is impossible to obtain desired detergency. The surfactant may be used in an amount of 10 % or more, but it is preferable that the amount be 10 % or less to provide environmentally friendly and nonpolluting properties. More preferably, the amount is 7 % or less. With respect to this, it is proved that it is possible to gain desirable detergency by employing sodium sesquicarbonate and layered silicate according to the present invention even though the surfactant is used in an amount of 10 % or less, and if the surfactant is used in an amount of 10 % or more, detergency is not significantly improved in comparison with the case of using the surfactant in an amount of 5-10 %.

Non-limiting, illustrative examples of the anionic surfactant are any one selected from the group consisting of a straight-chain type of alkyl sulfonate Cn-CH2-O-SO3Na n=12-16), alkane sulfonate (Rn-SO3-Na n--12-18), alpha-olefin sulfonate (Rnl-CH=CH-Rn2-S03Na), and a mixture thereof, and it is used in an amount of 1-10 % based on the total weight of the detergent composition.

Since most anionic surfactant contains a sulfur component, it causes denaturation of protein and is toxic, and thus, it is preferable to use the anionic surfactant in as small an amount as possible, for example in an amount of 3 % or less, so as to assure environmentally friendly and nontoxic proper ies.

Illustrative, but non-limiting examples of the nonionic surfactant include poly (oxyethylene) (POE) amine, POE fatty acid ester, polyethylene glycol, polyethylene glycol fatty acid ester, poly (oxyethylene) fatty acid alcohol ether, a condensate of poly (oxyethylene) and poly (oxypropylene), and sorbitan fatty acid ester. Its amount is 3-10 % based on the total weight of the detergent composition.

Preferably, the amount of the nonionic surfactant is more than that of the anionic surfactant.

The reason for this is that a predetermined amount of the anionic surfactant remains on clothes even after being washed, affecting humans, and in practice the nonionic surfactant has superior detergency compared to the anionic surfactant.

Non-limiting, illustrative examples of the soap surfactant include a fatty acid (RnCH2-C02Na n=8-18), whose content in the detergent composition is 2-5 % based on the total weight of the detergent composition. Since the soap surfactant is environmentally friendly because it employs a natural raw material but has poor detergency, it cannot be used in a large amount, but it is preferable to use it in conjunction with other surfactants.

The detergent composition of the present invention may further contain a bleaching agent, an enzyme, a dispersing agent (acryl-based), a perfume or the like in an amount of 5-20 wt%, and the amount of each component used is well known to those skilled in the art An oxidation bleaching agent which conducts the bleaching by use of oxidizing power is frequently used as the bleaching agent, and is exemplified by hydrogen peroxides (H202), such as sodium percarbonate (2Na2CO3* 3H202) and sodium perborate (NaBO2 H202 3H20). Sodium percarbonate is most often employed.

The enzyme is exemplified by neutral and alkaline protease, lipase, cutinase, esterase, amylase, pectinase, lactase, peroxidase, and cellulase. Protease functions to decompose contaminated protein in humans, and commercial protease may be used in the present invention. Examples of commercial protease include Primase (Novo Industries A/S), Maxapem (Gist-Brocades), and Optimase and Opticlean (Solvay Enzymes). An amount of protease used is about 0.0001-3 % based on the total weight of the detergent composition. Lipase serves to decompose human lipids, and may be obtained from fungi and bacillus, such as Humicola, Thermomyces, or Pseudomonas species.

Alternatively, commercial lipase may be used. Examples of commercial lipase include Lipolase (Novo Industry A/S). An amount of lipase used is about 0. 0001-2 % based on the total weight of the detergent composition. Amylase serves to decompose external contaminated starches. Illustrative, but non-limiting examples of amylase include commercial Rapidase (Gist-Brocades), and Termamyl and BAN (Novo Industries A/S). Finally, cellulase functions to decompose a fibroid material, thereby removing nuns from clothes made of natural cotton. Cellulase available to the present invention may be obtained from any bacillus or fungi type which has an optimum pH within a range of 5-9.5. U. S.

Pat. No. 4, 435, 307 discloses fungal cellulase from Humicola insolens or Humicola strain DSM 1800,

cellulase 212 generated from fungi belonging to the Aeromonas genus, and cellulase extracted from a hepapancreas of Dolabella Auricula Solander, that is, an oceanic mollusk, as cellulase available to the present invention. Furthermore, cellulase available to the present invention is disclosed in British Pat.

Nos. 2,075, 028 and 2,095, 275, and Germany OS 2,247, 832. All of the above cellulases may be applied to the detergent according to the present invention.

Non-limiting, illustrative examples of the dispersing agent include acryl polymers, which assure high water softening property, dispersibility, detergency, biodegradability, and heavy metal chelating property. An amount of the dispersing agent used is about 0. 0001-2 % based on the total weight of the detergent composition.

The detergent composition according to the present invention may be provided in various forms, such as powder, granule, tablet, bar, and liquid. The forms may be easily achieved by adopting technology typically used in the detergent field.

The liquid detergent composition may contain water and miscellaneous solvents, such as carriers. Primary alcohol or secondary alcohol having a low molecular weight (e. g. methanol, ethanol, propanol, and isopropanol) is suitable. Monohydric alcohol is proper for a soluble surfactant, but polyol having a carbon number of about 2-6 and about 2-6 hydroxyl groups (e. g. 1, 3-propandiol, ethylene glycol, glycerin and 1, 2-propandiol) may be used. The carrier may be used in an amount of 5 - 90 %, typically 10-50 % based on the composition. The detergent composition of the present invention is preferably formed as described above during a washing process employing water, and washing water has a pH of about 6.5-11, and preferably about 7.5-10. 5. Laundry generally has a pH of 9-11. A technology of controlling pH when they are used in a predetermined amount adopts the use of a buffer solution, alkaline acid and the like, which is known to those skilled in the art.

A better understanding of the present invention may be obtained through the following examples and experimental examples which are set forth to illustrate, but are not to be construed as the limit of the present invention.

Production of a raw material EXAMPLE 1 273 g of sodium bicarbonate was mixed with 150 mE of water to produce a homogeneous solution, 727 g of first liquid sodium silicate (SiO2Na20 = 2. 11 : 1) was mixed with 750 mt of water, and the resulting solutions reacted with each other in a reactor at 125-C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce white powder.

EXAMPLE 2 345 g of sodium bicarbonate was mixed with 200 m# of water to produce a homogeneous solution, 655 g of first liquid sodium silicate (SiO2Na2O = 2.11 : 1) was mixed with 750 m of water, and the resulting solutions reacted with each other in a reactor at 125°C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXAMPLE 3 376 g of sodium bicarbonate was mixed with 300 m# of water to produce a homogeneous solution, 624 g of first liquid sodium silicate (Si02 : Na20 = 2.11 : 1) was mixed with 750 iut of water, and the resulting solutions reacted with each other in a reactor at 125°C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXAMPLE 4 429 g of sodium bicarbonate was mixed with 300 Int of water to produce a homogeneous solution, 571 g of first liquid sodium silicate (SiO2:Na2O = 2. 11: 1) was mixed with 600 m# of water,

and the resulting solutions reacted with each other in a reactor at 125°C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXAMPLE 5 385 g of sodium bicarbonate was mixed with 300 mt of water to produce a homogeneous solution, 615 g of second liquid sodium silicate (SiO2 : Na20 = 2.35 : 1) was mixed with 700 m of water, and the resulting solutions reacted with each other in a reactor at 125 °C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXAMPLE 6 357 g of sodium bicarbonate was mixed with 200 iii of water to produce a homogeneous solution, 643 g of third liquid sodium silicate (SiO2:Na2O = 3.21 : 1) was mixed with 700 mE of water, and the resulting solutions reacted with each other in a reactor at 125 °C for 1-2 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXAMPLE 7 332 g of sodium bicarbonate was mixed with 200 mA of water to produce a homogeneous solution, 668 g of fourth liquid sodium silicate (SiO2 : Na20 = 3.76 : 1) was mixed with 700 mt of water, and the resulting solutions reacted with each other in a reactor at 125°C for 1.5 hours to produce slurry containing 50-70 % of water. The slurry was dried to produce powder.

EXPERIMENTAL EXAMPLE 1 It was confirmed that powders produced according to examples 1 to 7 contained about 65- 95 % of sodium sesquicarbonate and about 5-35 % of layered silicate.

Production of a detergent composition Detergent compositions were produced using components as described in the following Table 1.

TABLE 1 Comparative example Example Detergent composition (wt%) 1 2 3 4 1 2 3 4 ied powder (1) - - - - 87. 4 80. 4 76. 5 85.9 Sodium carbonate 25 18 42 42 - Zeolite 25 10 30 30 STPP - 15 14 - - - - Sodium silicate 6. 7 Sodium alkylbenzene 14 24 - 5 sulfonate (2) Fatty acid salt (3) 3 - 5 5 - 2 2 2 Nonionic surfactant (4) 2 - 6 - 2 3 8 3 Sodium sulfate 30 18. 3 15 Miscellaneous additive (5) 1 8 3 3 2.6 14. 6 13.5 9. 1 '1) Powder consisting of sodium sesquicarbonate and layered silicate '2) The carbon number of the alkyl group is 12-16 ; 3) Fatty acid salt in which the carbon number of the alkyl group extracted from natural alcohol is 12 - 18 '4) Poly (oxyethylene) fatty acid ether extracted from natural fatty acid ;5) Bleaching agent, perfiume and dispersing agent

EXPERIMENTAL EXAMPLE2 Detergency of the detergent composition was evaluated using the following devices under the following conditions.

Washing device: Terg-o-tometer Washing temperature: 20 °C Washing water: hardness Ca2+ 80 ppm Me 20 ppm Bath ratio: 4.3 g/t (stained fabric/washing water) Stained fabric : CFT AS-9 (pigment/oil) Concentration of the detergent: 0.67 g/t Evaluation: converted with the proviso that a value of comparative example 1 is 100 Test results are described in the following Table 2.

TABLE 2 Comparative example Example 1 2 3 4 1 2 3 4 Detergency 100 109 105 109 107 108 114 109 Industrial Applicability As described above, the present invention provides an environmentally friendly and nonpolluting detergent composition, which includes powder consisting of sodium sesquicarbonate and layered silicate, and has detergency that is the same as or superior to a conventional detergent even though it contains a minimum amount of surfactant