WO2013120719A1

WO2013120719A1 - Antistatic flooring composition

Info

Publication number: WO2013120719A1
Application number: PCT/EP2013/052136
Authority: WO
Inventors: Andrew Tasker
Original assignee: Construction Research & Technology Gmbh
Priority date: 2012-02-17
Filing date: 2013-02-04
Publication date: 2013-08-22

Abstract

The present invention suggests a new flooring composition obtainable by forming a mixture of a (wide variety of) curable resin composition and stainless steel fibers, and allowing the mixture to cure.

Description

Antistatic flooring composition

The present invention relates to an antistatic flooring composition and the use of stainless steel fibers for producing such antistatic flooring composition.

In the industrial environment, electrostatic discharge creates a significant hazard. It is responsible for fires and explosions due to the ignition of both dust and vapor. It is also responsible for destruction of delicate electronic equipment. Antistatic flooring to reduce this risk is thus highly desirable.

Concrete or cement floors have inherent anti-static properties but they do not provide many other desirable properties that are required in an industrial environment. Resin Flooring with aesthetically desirable, easy to clean and easy to decontaminate smooth surface, an overall seamless finish, easy maintenance, thermal, mechanical and chemical resistance is therefore widely applied to industrial floors in all industry sectors. In an unmodified format Resin Flooring does not provide Anti-Static properties.

It is therefore necessary to modify Resin Flooring when it is applied in areas where there is a risk due to static discharge in industrial environments such as chemical processing areas, pharmaceutical manufacturing facilities, food manufacturing areas where organic dust is present such as flour mills, electronics manufacturing facilities, and the like.

Such modified Resin Flooring should retain all the desirable properties associated with resin flooring but in addition must have anti-static properties.

It is well known that antistatic resin flooring systems can be created with epoxy, polyurethane, polyurea/polyurethane hybrid, cement modified polyurethane and other resin systems. The standard systems for antistatic properties have been created with the use of carbon fibers or carbon powder.

The properties of carbon fibers, such as high flexibility, high tensile strength, low weight, high resistance, high temperature tolerance and low thermal expansion, make them very popular in aerospace, civil engineering, military, and motorsports, along with other competition sports. However, they are relatively expensive when compared to similar fibers, such as glass fiber or plastic fibers. There are a number of weaknesses associated with the use of carbon fibers or carbon powder in these systems. These weaknesses become more apparent when the thickness of the finished Resin Floor increases because these systems with increased thickness often contain a higher ratio of mineral filler and may contain larger size mineral aggregate fillers to assist the required properties such as slip resistance.

Anti-static systems based on carbon fiber, in particular where there is a higher filler loading and/or large aggregate, suffer from a loss of conductivity performance with increasing mix times during manufacture.

Moreover, when carbon fiber breaks down a very dark pigment is formed. As a result all the products based on carbon fiber have a dark color when compared to the same product without carbon fiber. This is a major drawback with respect to products having light colors such as cream.

Additionally, the use of carbon fiber has a negative effect on the flow of materials and therefore limits the ability to formulate cost effective fluid materials.

Industrial resin flooring is often made up of more than one component that has to be mixed on site in order to create the finished material that is applied to the floor. If carbon fibers are to be used for the avoidance of electrostatic charges, this mixing has a strong negative effect on the conductivity making the product very sensitive to site conditions and application variables.

It was the object of the present invention to develop an antistatic flooring composition as an al- ternative to carbon fiber modified flooring compositions in order to eliminate these problems.

Flooring compositions are described in WO 2004/065109, JP2006-036994 A, US 5,736,603 and US 2009/0149574 A1 . WO 2004/065109 discloses a method for manufacturing an object with conductive properties from a plastic composition, wherein a suitable thermoplastic plastic composition is selected for the object, wherein metal fibers are added to the plastic composition, the metal fibers are distributed substantially homogeneously through the plastic composition, and this composition containing metal fibers is then subjected to a treatment in order to form the object. In this manner an object is obtained with conductive properties which are retained. JP2006-036994 A discloses an electroconductive resin composition containing stainless steel fibers having 80 to 150 μηη fiber length and 10 to 15 μηη fiber diameter, a sedimentation-preventing agent, a resin and a blended material. US 5,736,603 relates to electrically conductive thermoplastic composite materials which have specific volume resistances of less than 10⁹ ohm cm and comprise electrically conductive fibers, to a process for their preparation and to their use.

US 2009/0149574 A1 discloses a flooring composition relating to durable cementitious composi- tions suitable, for example, for the manufacture of industrial floorings, and the like. According to certain embodiments of the subject flooring composition, there are provided cementitious compositions which are the products obtained by mixing together and allowing to cure, hydraulic cement, water, iron aggregate filler, and resin forming components comprising a polyisocyanate and an isocyanate-reactive organic compound.

The present invention provides a flooring composition obtainable by forming a mixture of a curable resin composition and stainless steel fibers, and allowing the mixture to cure.

The flooring composition preferably includes stainless steel fibers in an amount of 0.01 - 5 % by weight.

There is only a very minimal breakdown of stainless steel fibers which means that there is no sensitivity to mixing either in production when the materials are blended or on the building site when the finished material is mixed.

Since there is minimal fiber breakdown and the fibers do not have a strong pigmenting effect no darkening of the color is effected.

A curable resin is contained in the mixture according of this invention. Such curable resin for example can be represented by an epoxy resin, a polyurethane resin, an acrylic resin, polyam- ide resin, and the like.

There is only a very minimal breakdown of the fibers which means that it is possible to formulate materials with large aggregate that are not sensitive to mixing time and method. Materials can be formulated that are conductive in their bulk rather than on their surface. This means, that a material does not need a standard primer or conductive primer. As there is no fiber breakdown and no darkening of the color, light colors are clean and not affected.

Further preferred embodiments of the invention are defined hereinbelow.

In a preferred embodiment, the stainless steel fibers have a length from 1 mm - 25 mm, preferably from 3 mm to 6 mm, and have a diameter from 4 μηη - 200 μηη, preferably 6 - 8 μηη.

The mixture of the flooring composition preferably includes up to 95 % by weight, more prefera- bly up to 40 % by weight, of a mineral filler, preferably selected from silica, barium sulphate, calcium carbonate, and mixtures thereof.

It has been found to be particularly advantageous for the flooring composition that the mineral filler has a particle size within the range of 5 μηη to 5 mm.

In a preferred embodiment of the flooring composition the curable resin composition comprises a curable epoxy resin.

In particular the curable epoxy resin comprises at least one epoxide-containing polymer obtain- able from the reaction of epichlorohydrin with bisphenol-A or bisphenol-F, and an amine hardener selected from aromatic, aliphatic and/or cycloaliphatic amines or amine adducts.

In a further preferred embodiment of the invention the curable resin composition comprises a curable polyurethane resin.

In particular, the curable polyurethane resin comprises at least one polyol and at least one poly- isocyanate and/or polyisocyanate prepolymer.

In a further preferred embodiment the curable resin composition comprises a curable polyure- thane hybrid resin.

In particular, the curable polyurethane hybrid resin comprises at least one polyisocyanate and/or polyisocyanate prepolymer and at least one substance selected from Portland cement, hydrated lime, and an alkali silicate of the formula m Si02 * n M2O, wherein M is selected from Li, Na, K and NH4, and mixtures thereof, and the molar ratio of m : n is from 0.5 to 3,6, preferably 2.5, and mixtures thereof. In particular, the polyurea hybrid flooring composition is unfoamed.

In another preferred embodiment the curable resin composition comprises a free radical curable thermosetting polymer resin.

In particular, the free radical curable thermosetting polymer resin comprises at least one compound selected of unsaturated polyesters, acrylates and methacrylates. In a further preferred embodiment the curable resin composition comprises is a curable polyurea resin.

In particular, the flooring composition has a resistance to earth of less than 10⁹ ohm when measured in accordance to EN1081 :1998.

Moreover, the present invention provides for the use of stainless steel fibers for producing an antistatic flooring composition.

The present invention will now be illustrated in more detail with reference to the following exam- pies and the attached Figures. In the Figures:

Fig. 1 is a graphical representation of conductivity vs. mixing time,

Fig. 2 is a graphical representation of conductivity vs. mixing time,

Fig. 3 shows a sample formulated with stainless steel fibers,

Fig. 4 shows a sample formulated with carbon fibers.

EXAMPLES

Example 1 (Ucrete® TZ Flooring System) 1 18 g castor oil, 71 g of water, and 47 g butyl benzyl phthalate plasticizer were mixed, 286 g polymeric MDI (i.e. polymeric methylene diphenyl diisocyanate) was added under stirring, 372 g white cement, 25 g hydrated lime, 1 1 16 g dry washed silica sand (0.2-0.8 mm particle size), and 967 g calcined flint and granite aggregate (ca. 3.0 mm particle size) were added under stirring. Finally, 20 g inorganic yellow iron oxide pigment, 25 g castor oil, and 5 g of butyl benzyl phtha- late plasticizer were added under stirring.

Example 2 (Mixing with Carbon Fibers and Stainless Steel Fibers)

The powder components of Ucrete® TZ of Example 1 were mixed in a large plough shear mixer with varying mixing times after fiber addition. Carbon fibers (Grafil 34/700) or, respectively, stainless steel fibers (obtained from Koolon Corporation) were added at a level of 3.2 parts on 1000 parts of total formulation. The set of mixes was repeated with both 6 mm carbon fibers and 6 mm stainless steel fibers. These samples were then used to make samples of Ucrete® TZ AS (as detailed in Example 1 ) by adding the liquid components. The conductivity was tested after curing using the EN 1081 test method. The mixing times were each 0, 2 and 5 minutes. The results are shown in Fig. 1 , indicating that there was a considerable breakdown of carbon fibers after 5 minutes. The stainless steel fibers, however, did not show any breakdown.

Example 3 (Loss Of Conductivity With On Site Mixing)

5 kg of the Ucrete® TZ system of Example 1 was mixed with a Hobart M50 planetary laboratory mixer. The fibers were added analogously to Example 2 so that there was no influence from mixing during manufacture. Samples were made with variable mixing times of from 1 to 7 minutes for both the 6 mm carbon fibers and the 6 mm stainless steel fibers. The cured samples were then tested for conductivity using the EN 1081 test method. The results are shown in Fig. 2, indicating a tremendous breakdown of carbon fibers after 2 to 3 minutes. With other words, carbon fibers are out of specification after only 3 minutes while stainless steel fibers hold up nicely even after 7 minutes. Example 4 (Ucrete® B6 Flooring System)

126 g castor oil, 76 g of water, and 50 g butyl benzyl phthalate plasticizer were mixed, 286 g polymeric MDI (i.e. polymeric methylene diphenyl diisocyanate) was added under stirring, 320 g white cement, 32 g hydrated lime, 720 g dry washed silica sand (0.2-0.8 mm particle size), and 528 g dry washed silica sand (1 -2 mm particle size) were added under stirring. Finally, 20 g inorganic pigment, 25 g castor oil, and 5 g of butyl benzyl phthalate plasticizer were added under stirring. Example 5 (Effect of Fiber on Material Flow)

Samples of the Ucrete® B6 basecoat system of Example 4 were made with varying levels of fiber addition, the samples were made with both the 6 mm carbon fibers and the 6 mm stainless steel fibers. The static flow was measured using a 40 mm flow ring on each of the samples as was the conductivity in accordance with EN 1081.

Table 1

Table 1 shows that with carbon fibers the flow of Ucrete® B6 Basecoat is reduced by at least 39% to achieve a conductivity of 0.02 ΜΩ. With the stainless steel fibers the reduction is only about 1 1 %. This means that the use of Carbon fibers has a negative effect on the flow of materials and therefore limits the ability to formulate cost effective fluid materials. Example 6 (Coloring Effect)

Samples of the Ucrete® TZ system of Example 1 (cream color) were manufacture based on the 6 mm carbon fibers or, respectively, the 6 mm stainless steel fibers. The effect on color can be seen in Fig. 3 (stainless steel fibers) and Fig. 4 (carbon fibers), indicating that carbon fibers exhibit a pronounced darkening effect.

Claims

Flooring composition obtainable by forming a mixture of a curable resin composition and stainless steel fibers, and allowing the mixture to cure.

Flooring composition of claim 1 , wherein the stainless steel fibers are present in an amount of 0.01 - 5 % by weight.

Flooring composition of claim 1 or 2, wherein the stainless steel fibers have a length from 1 mm - 25 mm, preferably from 3 mm to 6 mm, and have a diameter from 4 μηη - 200 μηη, preferably 6 - 8 μηη.

Flooring composition of claims 1 - 3, wherein the mixture additionally includes up to 95 % by weight, preferably up to 40 % by weight, of a mineral filler, preferably selected from silica, barium sulphate, calcium carbonate, and mixtures thereof.

Flooring composition of claim 4, wherein the mineral filler has a particle size within the range of 5 μηη to 5 mm.

Flooring composition of claims 1 - 5, wherein the curable resin composition comprises a curable epoxy resin.

Flooring composition of claim 6, wherein the curable epoxy resin comprises at least one epoxide-containing polymer obtainable from the reaction of epichlorohydrin with bi- sphenol-A or bisphenol-F, and an amine hardener selected from aromatic, aliphatic and/or cycloaliphatic amines or amine adducts.

Flooring composition of claims 1 - 5, wherein the curable resin composition comprises a curable polyurethane resin.

Flooring composition of claim 8, wherein the curable polyurethane resin comprises at least one polyol and at least one polyisocyanate and/or polyisocyanate prepolymer.

Flooring composition of claims 1 - 5, wherein the curable resin composition comprises a curable polyurethane hybrid resin.

1 1 . Flooring composition of claim 10, wherein the curable polyurethane hybrid resin comprises at least one polyisocyanate and/or polyisocyanate prepolymer and at least one substance selected from Portland cement, hydrated lime, and an alkali silicate of the formula m Si02 * n M2O, wherein M is selected from Li, Na, K and NH4, and mixtures thereof, and the molar ratio of m : n is from 0.5 to 3,6, preferably 2.5, and mixtures thereof.

12. Flooring composition of claim 1 1 , wherein the flooring composition is unfoamed.

13. Flooring composition of claim 1 - 5, wherein the curable resin composition comprises a free radical curable thermosetting polymer resin.

14. Flooring composition of claim 13, wherein the free radical curable thermosetting polymer resin comprises at least one compound selected of unsaturated polyesters, acrylates and methacrylates.

15. Flooring composition of claims 1 - 5, wherein the curable resin composition comprises a curable polyurea resin.

16. Flooring composition of claims 1 -15, having a resistance to earth of less than 10⁹ ohms when measured in accordance to EN 1081 : 1998.

17. Use of stainless steel fibers for producing an antistatic flooring composition as defined in claim 16.