Description

GLASS-FIBER REINFORCED PLASTIC PIPE HAVING CORE LAYER CONTAINING BOTTOM ASH

Technical Field

[1] The present invention relates to a glass-fiber reinforced plastic pipe, and, more particularly, to a glass-fiber reinforced plastic pipe having a core layer formed of a composition including bottom ash. Background Art

[2] Conventionally, steel pipes or cast-iron pipes are used as water supply pipes or water drainage pipes. However, they are disadvantageous in that they corrode very easily and are very heavy. In particular, cast-iron pipes are disadvantageous in that they are easily broken by impacts. When water supply pipes, buried under the ground, corrode or are cracked by impacts, enormous financial loss is incurred due to water leakage, and water quality is deteriorated by pollutants entering from outside into the water supply pipes or pollutants generated upon the corrosion of the inside thereof. In order to prevent pipes from corroding, steel pipes are coated with epoxy, and cast-iron pipes are coated with asphalt or concrete. Even in this case, since the epoxy, asphalt and concrete applied on the steel pipes or cast-iron pipes are easily damaged and peele d, there is some danger of corrosion of these steel pipes and cast-iron pipes. Further, since the steel pipes and cast-iron pipes are coated with epoxy, asphalt and concrete, the production cost thereof is increased, and thus it is difficult to apply them to general use. In particular, when these steel pipes and cast-iron pipes are used as water supply pipes or water drainage pipes, since they are buried under the ground, they are more problematic. Since the epoxy, asphalt and concrete are only coating agents for preventing corrosion, even when they are applied on steel pipes or cast-iron pipes, the thickness of the steel pipe or cast-iron pipe cannot be decreased. Therefore, such steel pipes or cast-iron pipes are as heavy as previous ones, and thus they also have poor workability and transportability.

[3] In order to solve the problem of corrosion, synthetic resin pipes may be used.

Synthetic resin pipes have high corrosion resistance, but have very low pressure resistance. This disadvantage becomes more serious when the diameter thereof is large. Middle and large sized synthetic resin pipes are typically buried under the ground. Therefore, if a synthetic resin pipe has low pressure resistance, the synthetic resin pipe must be fabricated to have a large thickness, so that the synthetic resin pipe becomes heavier, thereby increasing the production cost thereof. For this reason, synthetic resin pipes having a small diameter are frequently used.

[4] In order to solve the problem of the low pressure resistance of the synthetic resin pipe, Korean Patent Registration No. 0589012 discloses a fiber-metal composite pipe having high corrosion resistance and pressure resistance, in which a resin-impregnated fiber layer is axially formed on the inner surface of a metal pipe, a resin-impregnated fiber layer is axially formed on the outer surface of the metal pipe, and a plurality of resin-impregnated fiber layers is formed on the resin-impregnated fiber layer in a direction opposite to the axis. However, the fiber-metal composite pipe, disclosed in this patent document, is also problematic in that it is heavy and its production cost is high.

[5] Therefore, it is required to develop a composite pipe having the advantages both of a metal pipe and a synthetic resin pipe. As an example of the composite pipe, there is a glass-fiber reinforced plastic pipe. Here, the conventional glass-fiber reinforced plastic pipe is a pipe having a core layer made of mortar including resin and sand, and synthetic resin impregnated glass fiber layers formed on the inner and outer surfaces of the core layer. This glass-fiber reinforced plastic pipe has physical and chemical properties suitable for use as a water supply pipe, a water drainage pipe, a gas supply pipe, and the like.

[6] However, in this glass-fiber reinforced plastic pipe, since a core layer is formed of mortar including sand as a main component, the glass-fiber reinforced plastic pipe is problematic in that its weight is greatly increased due to sand, and in that there is a difficulty relating to the supply and demand of raw materials because the production of sand in Korea has already reached its limit due to the serious environmental destruction caused by sand collection. That is, almost no river sand has been observed since 1997, and there is almost no place for collecting cheap sea sand, and thus sand is imported from foreign countries, but the importation of sand is limited to the supply of sand and is uneconomical, with the result that the price of sand is increasing every year and thus the purchasing channels for sand are narrowing.

[7] Meanwhile, in order to stably handle waste, methods of incinerating it are chiefly used throughout the world. The methods of incinerating waste have various characteristics, but are problematic in that materials to be buried, such as fly ash, bottom ash, and the like, are discharged.

[8] Moreover, the number of thermoelectric power plants is increasing throughout the world. Korea is planning to construct 10 or more thermoelectric power plants by 2009, and it is predicted that the consumption of coal will be about 52,438,000 tons this year (based on data from Korea East- West Power Co., Ltd., 2007). Furthermore, it is predicted that the consumption of coal will be about 65,338,000 tons every year from 2010.

[9] In thermoelectric power plants in which coal is used, when coal is pulverized and

then introduced into a furnace together with air at high speed, the coal is instantaneously burnt at a temperature of 1300- 1700 ⁰ C. At this time, about 26 ~ 50% of anthracite coal and about 8 - 15% of bituminous coal are converted into coal ash. After the burning of the coal, the burnt coal adheres to a furnace wall, a superheater, reheater, and the like, and then falls to the bottom of a boiler due to its own weight and gravity, thus forming bottom ash having a particle length of about 1~ 2.5 mm. The bottom ash is porous particles, and belongs to the category of fine gravel. Among coal ash produced from a thermoelectric power plant, most bottom ash is buried, and fly ash is reused for brick, cement, tile, plywood adhesive, and the like. However, the reuse ratio of coal ash remains lower than 50%.

[10] Therefore, it is required that several thousands tons of waste, such as bottom ash, discharged every year in a thermoelectric power plant, be reused as a substitute material in various fields, thus contributing to the economy and improving the environment.

[11] Accordingly, novel light core layers, formed using no sand, having better physical and chemical properties than the conventional core layer formed of mortar, are required in the art. Disclosure of Invention Technical Problem

[12] The present applicant has made efforts to overcome the above problems. As a result, it was found that, when a core layer is formed using a new composition including bottom ash instead of mortar containing sand, a light glass-fiber reinforced plastic pipe having high strength can be obtained using the core layer. Base on these findings, the present invention was completed.

[13] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a glass-fiber reinforced plastic pipe that is lighter and stronger than conventional glass- fiber reinforced plastic pipes by forming a core layer composed of a new composition including bottom ash.

[14] Another object of the present invention is to provide a glass-fiber reinforced plastic pipe, the production cost of which is reduced because bottom ash, which is a waste material, is used as a raw material instead of sand.

[15] A further object of the present invention is to provide an environment- friendly glass-fiber reinforced plastic pipe which can protect the environment because no sand is collected and waste is reused. Technical Solution

[16] In order to accomplish the above objects, the present invention provides a glass-

fiber reinforced plastic pipe, including a core layer and synthetic resin impregnated glass fiber layers formed respectively on inner and outer surfaces of the core layer, wherein the core layer is formed of a composition including bottom ash. [17] The composition may include a resin, bottom ash and a reinforcing material such that the weight ratio of the resin, bottom ash and reinforcing material is

4-6:2-4.5:0.3-2.

[18] The bottom ash may have a size of 10 meshes or less.

[19] The reinforcing material may be a chop shaped general fiber or a chop shaped glass fiber.

[20] The chop shaped glass fiber may have a length of 1 - 100 mm.

[21] The composition may include a resin, bottom ash and a reinforcing material such that the weight ratio of the resin, bottom ash and reinforcing material is 5:4.5:0.5.

Advantageous Effects

[22] The present invention has the following advantages.

[23] The glass-fiber reinforced plastic pipe according to the present invention is advantageous in that it is lighter and stronger than conventional glass-fiber reinforced plastic pipes because a core layer is formed of a new composition including bottom ash instead of mortar.

[24] Further, the glass-fiber reinforced plastic pipe according to the present invention is advantageous in that the production cost thereof can be greatly reduced by using bottom ash, which is a waste material, as a raw material instead of sand.

[25] Further, the glass-fiber reinforced plastic pipe according to the present invention is advantageous in that the environment can be protected because no sand is collected and waste is reused. Brief Description of the Drawings

[26] FIGS. 1 to 3 are graphs showing the bending strengths of respective test pieces formed of a composition for forming a core layer according to an embodiment of the present invention;

[27] FIG 4 is a graph showing the bending strength of a test piece formed of mortar; and

[28] FIG. 5 is a bar graph showing the bending strengths of the test pieces of FIGS. 1 to

4. Best Mode for Carrying Out the Invention

[29] The present inventor received an order for an ash transfer pipe from Korea Midland

Power Co. Ltd., and will develop a pipe having high wear resistance soon. Further, while the present inventor has been interested in the general pipe business and has prepared to participate in the pipe business, he has taken great pains over the use of bottom ash due to the difficulty related to the supply and demand of raw materials. As

a result, a novel composition for forming a core layer, including bottom ash instead of mortar in conventional glass-fiber reinforced plastic pipes, was completed.

[30] Hereinafter, the present invention will be described in detail with reference to

Examples and the accompanying drawings.

[31] A glass-fiber reinforced plastic pipe of the present invention has a composition for forming a core layer different from that of a conventional glass-fiber reinforced plastic pipe, but is manufactured using a commonly-known filament winding method, that is, a method of manufacturing axially symmetric composite material structures, such as pipes, pressure containers, rocket motor cases, and the like, by winding a resin- impregnated continuous fiber around a core axis that rotates.

[32] First, the glass-fiber reinforced plastic pipe of the present invention includes a core layer, and synthetic resin impregnated glass fiber layers formed on inner and outer surfaces of the core layer, respectively. Here, the core layer is formed of a composition including bottom ash.

[33] In this case, it is preferred that the bottom ash included in the composition for forming the core layer have a size of 10 meshes or less. When the size of the bottom ash is above 10 meshes, there is a problem in that, in the formation of the core layer, pores are formed in the core layer by the impregnation of bottom ash and synthetic resin, or the binding force between bottom ash, synthetic resin and glass fiber is decreased, thus deteriorating the mechanical properties of the glass-fiber reinforced plastic pipe. Therefore, in order to be suitable for the features of the present invention, the bottom ash may have a size of 10 meshes or less.

[34] Further, it is preferred that the composition for forming the core layer include a resin, bottom ash and a reinforcing material such that the weight ratio of the resin, bottom ash and reinforcing material is 4-6:2-4.5:0.3-2.

[35] This weight ratio of the components has been determined through many tests in consideration of economic efficiency and the strength of a core layer. When the components are combined with each other below this weight ratio, the strength of the core layer is insufficient. In contrast, when the components are combined with each other above this weight ratio, economic efficiency is decreased.

[36] The resins used for the composition for forming the core layer according to the present invention are not limited as to the kind thereof, and may include all commonly- known resins, such as vinylester resin, unsaturated polyester resin, epoxy resin, phenol resin and the like. The resin may be the same as the synthetic resin impregnated into the glass fiber constituting the inner and outer layers of the pipe, and may also be different therefrom.

[37] Further, the reinforcing material used for the composition for forming the core layer according to the present invention, serving to reinforce the strength of the bottom ash,

may be a chop shaped general fiber and a chop shaped glass fiber. Here, in the case where the reinforcing material is the chop shaped glass fiber, the chop shaped glass fiber may have a length of 1 ~ 100 mm. When the length thereof is below 1 mm, the reinforcing effect is decreased. In contrast, when the length thereof is above 100 mm, economic efficiency is decreased. Further, the amount of the glass fiber may be changed depending on the length of the glass fiber. The reason for this is that, when the glass fiber is long, the core layer has high strength even if the amount of the glass fiber is small.

[38] Meanwhile, in the case where general fibers are used as the reinforcing material, commonly-known natural fibers, such as cotton, hemp, silk, wool, and the like, and commonly-known synthetic fibers, such as polyester, nylon, and the like, can be used. In this case, the length of the natural fiber or synthetic fiber ranges from 5 to 150 mm. The reason why the length of the natural fiber or synthetic fiber is longer than that of the glass fiber is to increase the strength of the core layer.

[39] Considering economic efficiency and strength, particularly, the composition may include a resin, bottom ash and a reinforcing material such that the weight ratio of the resin, bottom ash and reinforcing material is 5:4.5:0.5. Here, it is preferred that the reinforcing material be a long glass fiber, if possible.

[40] Example 1

[41] Vinylester resin, bottom ash and a chop-shaped glass fiber having a length of 3 mm were mixed each other at a mixing ratio of 6:2:2 to form a mixture. Thereafter, the mixture was cured at room temperature, and then further cured at a high temperature of 60 ~ 9O ⁰ C, particularly 7O ⁰ C, thereby obtaining a core layer test piece 1.

[42] Example 2

[43] A core layer test piece 2 was obtained using the same method as in Example 1, except that the length of the chop-shaped glass fiber was 12 mm. Example 3

[44] A core layer test piece 3 was obtained using the same method as in Example 1, except that the length of the chop-shaped glass fiber was 24 mm.

[45] Comparative Example

[46] A comparative core layer test piece 1 was obtained using the same method as in

Example 1, except that vinylester resin and sand were mixed with each other at a mixing ratio of 6:4.

[47] Experimental Example

[48] The bending strength of the test pieces, obtained from Examples 1 to 3 and

Comparative Example, were tested, and the results thereof are given in Table 1 (the bending tests were conducted two times, and the result values are average values). The respective results are shown in FIGS. 1 to 4, and FIG. 5 is a bar graph showing the bending strengths of test pieces of FIGS. 1 to 4.

[49] Table 1

[50] From Table 1 and FIG. 5, as the result of the bending test of the Comparative test piece 1, which is a mortar layer containing sand, the maximum load thereof was 23.5 kg . Therefore, it can be seen that the bending strengths of the core layer test pieces 1 to 3 are greater than that of the conventional mortar layer.

[51] In particular, the maximum load of the core layer test piece 2, in which a chop- shaped glass fiber having a length of 12 mm is mixed, was increased to two times that of the core layer test piece 1, in which a chop-shaped glass fiber having a length of 3 mm is mixed, and the maximum load of the core layer test piece 3, in which a chop- shaped glass fiber having a length of 24 mm, was 57.75 kg . Therefore, it can be seen that, as the length of a glass fiber is increased, the strength of a core layer is increased.

[52] As described above, since the glass-fiber reinforced plastic pipe according to the present invention has a core layer formed by mixing bottom ash having a sized of 10 meshes or less, a chop-shaped reinforcing material and a resin, it is lighter than a conventional glass-fiber reinforced plastic pipe in which a mortar layer is used as a core layer, the strength thereof can be greatly improved, and the production cost thereof can also be decreased. Industrial Applicability

[53] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, 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.