WO2002016282A1

WO2002016282A1 - Static-dissipative composition and panel manufactured therewith

Info

Publication number: WO2002016282A1
Application number: PCT/KR2000/001152
Authority: WO
Inventors: Sang Wook Ahn; Jae Hyun Hwang; Dong Cheol Park
Original assignee: Int Chem Co., Ltd
Priority date: 2000-08-21
Filing date: 2000-10-16
Publication date: 2002-02-28
Also published as: AU2001210584A1; KR20020026392A; KR100378074B1

Abstract

Disclosed is an electroconductive composition for dissipating electricity, which comprises a binder, a quick-curing, high strength admixture, an expansion agent, an electroconductive material, a chemical admixture, and a hardening accelerator, said electroconductive material being finely milled, pan- or pitch-type carbon fiber with a length from 100 to 1,000 νm and being used in the amount of 0.1 to 20 % by weight. In addition to being so excellent in scattering static electricity as to ensure uniform surface resistance, the electroconductive composition is very convenient to work with because of its high fluidity. Further, the composition is endowed with such a self-leveling property as to require no additional finishing processes. It can be formed into a layer as thin as 5 mm, which rsults in a significant reduction in material cost. With these advantages, the composition can find application in various fields. A panel prepared with the composition is also disclosed.

Description

STATIC-DISSIPATIVE COMPOSITION AND PANEL MANUFACTURED THEREWITH

TECHNICAL FIELD

The present invention relates to a static-dissipative electroconductive composition and a panel prepared therewith. More particularly, the present invention relates to an electroconductive composition which can so effectively absorb and discharge a variety of static electricity as to ensure the maintenance of the surface resistance within a certain range as well _.as exhibiting high strength and durability, and to a panel prepared therewit . " ^•'■ ' ^ „

PRIOR ART

In order to prevent the accumulation of static electricity on building floors, for instance, they are usually finished with organic coating agents or made with electroconductive floorings, such as electroconductive vinyl tiles, carpet tiles, rubber mats, etc. When such conventional materials are used, careful work is required: otherwise, such floorings are readily destroyed and deformed because of their poor strength and durability. Additionally, some of them, when being applied to pre-existing concrete bases, do not fully adhere to the bases, but easily become loose here and there. Further, upon being washed with water, separation and stripping of materials are not unusual, thereby requring large maintenance costs.

To avoid these problems, there have been suggested carbon fiber- reinforced mortar compositions, which are now under active study. Superior as they are in strength and durability, such mortar compositions have the disadvantage of providing the final products or floorings with non-uniform surface resistance, because the carbon fibers, used as electroconductive materials, are not uniformly distributed in the flooring. Furthermore, cracks are apt to occur in the flooring at places where the fibers are not evenly distributed, but massed, making the carbon fiber-reinforced mortar compositions almost useless for electroconductive floorings. An improvement to the carbon fiber-reinforced mortar compositions was proposed in the Korean Pat. Appln. No. 98-20949 which discloses an electroconductive composite in which 100 weight parts of a binder is combined with 5.5-107 weight parts of a mixture of particulate carbon having a particle size of 0.05-7.5 mm and fibrous carbon having a particle size of 2-40 mm in the proportions of 100:0.5-100:140. However, surface-finishing work of the composite is not easy, because it is poor in fluidity and fiber dispersion. Accordingly, the surface is so uneven as not to possess uniform surface resistance. Additionally, the surface is apt to crack easily or become stained, giving an unattractive appearance.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide an electroconductive composition which can provide the final product with uniform surface resistance, and sufficient strength and durability, good dissipation or dispersion of static electricity.

It is another object of the present invention to provide an electroconductive composition for dissipating or dispersing static electricity, which has high fluidity and a good self-leveling ability, and a panel manufactured therewith which does not require additional finishing work. In accordance with the present invention, the above objects could be achieved by providing an electroconductive composition for dissipating static electricity, which comprises milled type carbon fibers for the electroconductive material, and a panel prepared therewith. In addition to being excellent in electroconductivity, the electroconductive composition and panel according to the present invention exhibit high strength and durability.

To be high in fluidity, the electroconductive composition for dispersing or scattering static electricity is further added with an emulsifiable liquid polymer or a re-emulsifiable powder polymer, a defoaming agent, a thickener, an accelerator, and a retarder. In addition to being highly electroconductive, the resulting electroconductive composition has excellent fluidity, so that it can form such a flat surface as to ensure the accomplishment of uniform surface resistance. With these advantages, the electroconductive composition can be formed into a layer as thin as 5 mm, which results in a significant reduction in material cost.

In accordance with the present invention, there is provided an electroconductive composition for scattering static electricity, which comprises 100 parts by weight of a formulation composed of 30-70 % by weight of a binder, 20-60 % by weight of a quick-curing, high strength mixing admixture, 1-20 % by weight of an expansion agent, 1-30 % by weight of an inorganic admixture, 0.1-20 % by weight of an electroconductive material, 0.1-5 % by weight of a chemical admixture, and 0.1-5 % by weight of a hardening accelerator, 50-300 parts by weight of aggregate, and 0.1-20 parts by weight of pigment.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 is a cross sectional view showing an electroconductive panel prepared in accordance with an embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Details will be given of electroconductive compositions for scattering static electricity and their effects herein below.

In accordance with an embodiment of the present invention, an electroconductive composition is provided for dissipating static electricity, which comprises a binder, a concrete admixture, an expansion agent, an electroconductive material, a chemical admixture, a hardening accelerator, and aggregate and pigment.

Examples of the binder useful in the present invention, but not by way of limitation, include Portland cement, white cement and mixed cement, and they are used at an amount of 30-70 % by weight based on the total weight of the composition. The concrete admixture is composed of a quick-curing, high strength material and an inorganic material, which are used in the amounts of 20-60 % by weight and 1-30 % by weight respectively.

With the aim of accelerating the coagulation and curing of the composition to prevent the shrinkage attributed to a long time period of drying and curing, as well as providing a high strength property for the composition, used are the quick-curing high strength materials which is preferably calcium sulfoaluminate-based minerals or alumina-based minerals. This quick-curing, high strength material can bring about an improvement in bending strength and compressive strength, thereby increasing the durability of the final product.

Serving to improve the filling property and reactivity, and thus strength of the composition, the inorganic material is preferably selected from the group consisting of fine silica powder, fine slag powder, fine calcium carbonate powder, fine flyash powder, fine clay powder and mixtures thereof. Preferable amounts of the expansion agent fall into the range of 1-20 % by weight. Examples of the expansion useful in the present invention include expansive calcium sulfoaluminate minerals, anhydrous gypsum, burnt lime, and mixtures thereof.

As an electroconductive material, finely milled, pan- or pitch-type carbon fiber is used in the present invention. Preferred is the pan- or pitch- type carbon fiber which ranges in length from 100 to 1,000 μm and in diameter from 1 to 10 μm. The electroconductive material is used at an amount of 0.1 to 20 % by weight.

For example, if the carbon fiber is longer than 1,000 μm, it cannot be dispersed well, negatively affecting the resistance and strength of the product.

Less than 0.1 % by weight of the carbon fiber results in a surface resistance of 109 Ω or greater, affording the composition no desired electroconductive properties. On the other hand, when the carbon fiber is used at an amount of 20 % by weight or greater, the composition has a surface resistance of 104 Ω or less, introducing the danger of causing a backward current. In addition, too much carbon fiber not only makes it difficult to mix the composition and thus to carry out construction work with the composition, but also lowers the strength of the composition. In contrast, the milled type carbon fiber of the present invention can be mixed well with other components, so that the composition has a uniform surface resistance and it can be easily controlled.

Used to improve the dispersion of components and the workability of the composition, the chemical admixture is selected from the group consisting of naphthalene-, melamine-. lignin- and polycarbonic acid-based plasticizers and mixtures thereof and is preferably added at an amount of 0.1-5 % by weight.

In order not only to accelerate the hardening of the composition, but also to retard the rapid coagulation of the composition in the early stage and thus to ensure the workability, there is used a coagulation-retardant, hardening accelerator, examples of which include silica fluoride salts, such as K₂SiF₆, MgSiF₆, and Na₂SiF₆. In accordance with the present invention, the amount of the hardening accelerator is in the range from 0.1 to 5 % by weight. As the aggregate, sand and/or silica may be used. When account is taken of an improvement in the dispersion of the carbon fiber so as to give a homogeneous mixture, and in the strength of the composition, the aggregate is preferably used at an amount of 50-300 parts by weight based on 100 parts by weight of the composition. Optionally, pigment may be added at an amount of 0.1-20 parts by weight based on 100 parts by weight of the composition. Its color may be selected from, for example, black, green, red, yellow, blue, etc., according to the use of the composition.

In accordance with another embodiment of the present invention, 1-20 parts by weight of an emulsifiable liquid polymer or a re-emulsifiable powder polymer, 0.05-5 parts by weight of a defoaming agent, 0.01-2 parts by weight of a thickener, 0.01-5 parts by weight of an accelerator, and 0.01-5 parts by weight of a retarder are further added to the electroconductive composition for scattering static electricity. In addition to being highly electroconductive, the resulting electroconductive composition has excellent fluidity, so that it can form a flat surface after being applied. With these advantages, the electroconductive composition can be formed into a layer as thin as 5 mm. The polymer useful in the present invention, in a form of emulsifiable liquid or re-emulsifiable powder, is based on acryl, ethylene vinyl acetate, or polyvinyl alcohol and used to reinforce the combined structure resulting from the hydration between the binder and the aggregate. When the polymer is used at an amount of 1-20 parts by weight based on 100 parts by weight of the electroconductive composition, the most preferable fluidity can be obtained.

Acting to eliminate or destroy foams with the aim of making the final surface attractive, the defoaming agent is required to be low in surface tension because it is so highly restrictive of foaming as to retard the dissolution of the composition in water. Suitable are silicon or alcohol defoaming agents.

As for the thickening agent, it is added to increase the viscosity of the paste with the aim of controlling its fluidity and providing a self-leveling property for the composition upon carrying out construction work therewith. The viscosity increase function of the thickening agent also brings about the effects of preventing the bleeding and dry shrinkage of the composition. Suitable for use in the present invention is the thickening agent which is selected from the group consisting of HPMC (hydroxypropylmethyl cellulose), HEC (hydroxyethyl cellulose), starch, polyacrylamide and mixtures thereof.

Preferably, the accelerator useful in the present invention is selected from the group consisting of potassium chloride, potassium hydroxide, sodium hydroxide, lithium carbonate and mixtures thereof while examples of useful retarders include citric acid, sodium gluconate, succinic acid, and mixtures thereof.

Being superior in electroconductivity and fluidity, the composition can be used to construct floorings which have even surfaces and uniform surface resistances.

In accordance with another embodiment of the present invention, there is provided a method for constructing an electroconductive panel with the electroconductive composition for dissipating static electricity. The electroconductive panel is constructed by mixing 100 parts by weight of the electroconductive composition with 10-30 parts by weight of compounding water, applying the mixture to a mold, subjecting the mixture to vibration molding, curing the molded object in air, under steam or by autoclaving, and polishing the surface of the cured product.

Upon constructing the electroconductive panel, steel wire meshes may be buried in the panel at depths of 1/3 and 2/3 of the total thickness, as shown in Fig. 1, with the aim of preventing drying shrinkage and improving durability such as bending strength. Additionally, when the panel is applied to floorings, the wire meshes may be used as grounding means.

When account is taken of an economic aspect, a panel may be comprised of ordinary cement mortar for the lower 2/3 of the total thickness, and a slurry of the electroconductive composition mixed with water for the remaining upper 1/3.

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

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLES 1 TO 4

An electroconductive material, a binder, an admixture, a chemical admixture, aggregate and other necessary ingredients were formulated, as shown in Table 1 below, followed by mixing the formulations with water, in accordance the "Method of physical test for cement" described by JIS R 5201.

TABLE 1

(Unit: wt. part)

The compositions thus obtained were separately molded in a mold of dimensions 4x4x16 cm , in accordance with JIS R 5201 and cured under constant temperature and humidity conditions. After 3, 7 and 28 days of the curing, the molded test pieces were measured for bending strength and compressive strength.

For testing the surface resistance, each of the electroconductive compositions of Examples 1 to 4 and Comparative Examples 1 to 4 was molded to a thickness of 2 cm on a cement base with a surface area of 120 x 120 cm . After being cured in the air for 7 and 28 days, the test pieces were measured for surface resistance in accordance with "Standard Test Method for electrical Resistance of Conductive Resilient Flooring" described by ASTM F 150.

Measurement results are given in Table 2 below. As apparent from the results, the test pieces of Comparative Examples 1 to 4 were generally poor in dissipation levels and had cracks formed on their surfaces while those of Examples 1 to 4 were found to show excellent dispersion levels and surface conditions. Also, they were measured to be lower in surface resistance and better in bending strength and compressive strength than those of Comparative Examples 1 to 4.

As shown in Table 2, all of the test pieces are increased in surface resistance, bending strength and compressive strength with increased curing time. The best results among the above examples and comparative examples are obtained from the test piece of Example 4.

TABLE 2

EXAMPLES 5 TO 8

To afford high fluidity to the electroconductive composition of Example 4, additives were used as shown in Table 3 below. Necessary materials were formulated, followed by mixing the formulation with water, in accordance with the "Method of physical test for cement" described by JIS R 5201.

TABLE 3

(Unit: wt. part)

The compositions thus obtained were separately molded in a mold of dimensions 4x4x16 cm³, in accordance with JIS R 5201 and cured under constant temperature and humidity conditions. 3, 7 and 28 days after the curing, the test pieces molded were measured for bending strength and compressive strength.

For testing the surface resistance, each of the electroconductive compositions of Examples 1 to 4 and Comparative Examples 1 to 4 was molded to a thickness on a cement base with a surface area of 120 x 120 cm². After being cured in air for 7 and 28 days, the test pieces were measured for surface resistance in accordance with "Standard Test Method for electrical Resistance of Conductive Resilient Flooring" described by ASTM F 150.

Measurement results are given in Table 4 below. As apparent from the results, the test pieces of Examples 5 to 8 were found to show excellent dispersion levels and surface conditions and be superior in surface resistance, fluidity, bending strength and compressive strength.

Their surface resistance, bending strength and compressive strength, as shown in Table 2, were observed to increase with curing time. Better results are obtained from the test pieces of Example 5 and 6.

TABLE 4

The most preferable electroconductive composition for scattering static electricity is described in Table 5 below. TABLE 5

(Unit: wt. part)

EXAMPLE 9

The electroconductive composition with high fluidity, prepared in Example 5, was mixed at a weight ratio of 100:20 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the steam curing thereof. EXAMPLE 10

The electroconductive composition with high fluidity, prepared in Example 8, was mixed at a weight ratio of 100:20 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the autoclave curing thereof.

EXAMPLE 11

The electroconductive composition with high fluidity, prepared in Example 8, was mixed at a weight ratio of 100:20 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the steam curing thereof.

COMPARATIVE EXAMPLE 9

The electroconductive composition, prepared in Comparative Example 5, was mixed at a weight ratio of 100:20 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the steam curing thereof.

COMPARATIVE EXAMPLE 10

The electroconductive composition, prepared in Comparative Example 8, was mixed at a weight ratio of 100:25 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the steam curing thereof.

COMPARATIVE EXAMPLE 11

The electroconductive composition, prepared in Comparative Example 8, was mixed at a weight ratio of 100:30 with compounding water, and the slurry was applied to a mold and subjected to vibration molding, followed by the steam curing thereof.

In the following Table 6 were summarized the preparation conditions of panels of Examples 9 to 11 and Comparative Examples 9 to 11.

TABLE 6

(Unit: wt. part)

The panels prepared in Examples 9 to 11 and Comparative Examples 9 to 11 were measured for surface resistance, squareness, flatness and tested for local compression and impact duration in accordance with KS F 4760. The measurement and test results are given in Table 7 below. As shown in Table 7, the panels prepared in Examples 9 to 11 are generally better in surface resistance, squareness and flatness and thus in electroconductivity than those prepared in Comparative Examples 9 to 11. In addition, the panels of Examples 9 to 11 were found to be superior in strength and durability as recognized from their high resistance to local compression and impact.

TABLE 7

INDUSTRIAL APPLICABILITY

As described hereinbefore, the electroconductive compositions of the present invention and panels prepared therewith so effectively scatter static electricity as to secure uniform surface resistance in addition to being superior in strength and durability. With these advantages, the composition and panels are suitable for use in floorings.

Further, the electroconductive compositions of the present invention are very convenient to work with by virtue of their high fluidity. Moreover, the compositions are endowed with such a self-leveling property as to require no additional finishing processes. Thus, after construction work, the compositions thus form flat surfaces throughout with uniform resistances. Another advantage of the compositions of the present invention is that they can be formed into layers as thin as 5 mm, which results in a significant reduction in material cost. Consequently, the electroconductive compositions for dissipating static electricity of the present invention and panels prepared therewith can find applications in various fields, for example, where precise electronic parts or equipments are equipped, e.g., electronic part manufacturing plants, computer centers, laboratories; where ignitable or explosive materials are handled, e.g., chemical plants, gasoline stations, LPG repositories, armories; where volatile gas is used, e.g., operating rooms, etc.

The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

1. An electroconductive composition for dissipating static electricity, comprising a binder, a quick-curing, high strength admixture, an expansion agent, an electroconductive material, a chemical admixture, and a hardening accelerator, said electroconductive material being finely milled, pan- or pitch-

5 type carbon fiber with a length from 100 to 1,000 μm and being used in the amount of 0.1 to 20 % by weight.

2. The electroconductive composition as claimed in claim 1, further comprising aggregate in the amount of 5-300 parts by weight and pigment in the amount of 0.1-20 parts by weight based on 100 parts by weight of said 0 composition.

3. The electroconductive composition as claimed in claim 2, further comprising an emulsifiable liquid polymer or a re-emulsifiable powder polymer in the amount 1-20 parts by weight, an anti-foaming agent in the amount of 0.05-5 parts by weight, a thickening agent in the amount of 0.01-2 parts by 5 weight, an accelerator in the amount of 0.01-5 parts by weight, and a retarder in the amount of 0.01-5 parts by weight, based on 100 parts by weight of said composition.

4. The electroconductive composition as claimed in claim 1, wherein said quick-curing, high strength admixture is a calcium sulfoaluminate- or o alumina-based mineral and is used in the amount of 20-60 % by weight.

5. The electroconductive composition as claimed in claim 1, wherein the chemical admixture is selected from the group consisting of naphthalene-, melamine-, lignin- and polycarbonic acid-based plasticizers and mixtures thereof and is preferably added in the amount of 0.1-5 % by weight.

6. The electroconductive composition as claimed in claim 1, wherein the hardening accelerator is a silica fluoride salt and is used in the amount of 0.1 to 5 % by weight.

7. The electroconductive composition as claimed in claim 1, wherein the thickening agent is selected from the group consisting of hydroxypropylmethyl cellulose, hydroxyethyl cellulose, starch, polyacrylamide and mixtures thereof.

9. The electroconductive composition as claimed in claim 1, wherein the expansion agent is used in the amount of 1-20 % by weight and selected from the group consisting of expansive calcium sulfoaluminate minerals, anhydrous gypsum, burnt lime, and mixtures thereof.

10. The electroconductive composition as claimed in claim 3, wherein the retarder is selected from the group consisting of citric acid, sodium gluconate, succinic acid and mixtures thereof.

11. The electronic conductive composition as claimed in claim 3, wherein the accelerator is selected from the group consisting of potassium chloride, potassium hydroxide, sodium hydroxide, lithium carbonate, and mixtures thereof.

12. An electroconductive panel for dissipating static electricity, prepared by mixing the electroconductive composition of claim 2 or 3 at a weight ratio of 100:1 -30 with compounding water, applying the mixture to a mold, subjecting the mixture to vibration molding, curing the molded object in the air, under steam or by autoclaving, and polishing the surface of the cured product.