WO2006114599A1

WO2006114599A1 - Flooring and mat materials

Info

Publication number: WO2006114599A1
Application number: PCT/GB2006/001496
Authority: WO
Inventors: Mark Dalziel; Craig Rennolds
Original assignee: Dycem Limited
Priority date: 2005-04-26
Filing date: 2006-04-25
Publication date: 2006-11-02
Also published as: GB0508448D0

Abstract

A flooring material having a speckled or mottled surface effect and suitable for use in a clean room is made by a method comprising applying to a substrate absorbent backing sheet a mixture of polyvinyl chloride and plasticiser and a first colouring material, applying droplets of further polyvinyl chloride and plasticiser containing a second colouring material, curing the mixture applied to the sheet by heating, and rolling and cooling to form the final product.

Description

Flooring and Mat Materials

This invention relates to flooring and mat materials of the type comprising plasticised polyvinyl chloride for use in applying as a cover material to the floors of operating theatres, computer rooms or other "clean" rooms, the material presenting a surface which, between cleaning operations, causes dust or bacteria particles to adhere to the material and to prevent contamination of the room with such dust or bacteria. In this specification, such flooring and mat materials will be referred to as "materials of the type described". It is an object of the present invention to provide materials of the type described having a speckled or mottled surface effect.

Materials of the type described and methods for production thereof are disclosed in GB 1399191, GB 1475366, GB 2025319 A and GB 2144139 A. However, they all have a solid colour appearance. It would be desirable for such materials to exhibit a speckled or mottled surface effect. For such purposes, granules or grains of colouring materials which melt under the manufacturing conditions (which involve a heating stage to cure the plasticised polyvinyl chloride as applied to a backing web) have been added to the molten polyvinyl chloride, as is known in the art of conventional vinyl floorings, but it was found either that the granules or grains melted and dissolved in the plastics material, thereby losing their discrete colouring ability, or failed to melt sufficiently, resulting in surface bumps or undulations in the finished product. Such bumps or undulations are unacceptable; it is important for the surface of the material to be optically smooth, as it is understood in the art, to optimise the ability of the surface to remove dust and bacteria from the shoes of people walking on the material. In particular, it is important not only for the surface to be tacky, in order for it to have adhesive properties for dust and bacteria, but also for the material to be supple or resilient, whereby larger contaminating particles on shoes or wheels traversing the surface are pressed into the material, so that the surface is not occluded by the larger particles from being incident also to smaller particles, including sub-micron particles. The resilience of the material thus allows a dense packing of particles irrespective of particle size, so that the material remains effective even after multiple passage of shoes or wheels in the same area, until cleaning of the material takes place. It has been determined that one way of assessing the effectiveness of the surface in attracting particulate matter is to measure the tensile strength thereof, since the surface will gradually lose its effectiveness in use as microscopic damage is caused by particulate matter continually being impressed thereon, resulting in a loss of tensile strength. A tensile strength of 10 Newtons or above is generally regarded as being required for efficient particle attraction, preferably 12N or above, for example 15 to 2ON, especially for new or unused material.

In the light of the above criteria, any material of the type described which exhibits a speckled or mottled surface effect should also retain the uniformity or consistency of the previously-known solid-coloured materials in terms of their resilience and tensile strength, as well as optical smoothness as such , and it is an object of the present invention to provide a method of manufacture of a flooring material of the type described and which has a speckled or mottled surface effect while retaining the properties required for it, to maintain its optimum dust- and bacteria-retention ability. Especially where the material comprises a mat, it would be advantageous if the material forming the border of the mat could be bright in colour or otherwise contrast with the surface colour, to minimise the risk of tripping.

In one aspect, the present invention provides a method for the manufacture of a flooring material of the type described, the method comprising applying to a substrate absorbent backing sheet a mixture of polyvinyl chloride and plasticiser and a first colouring material, applying droplets of further polyvinyl chloride and plasticiser containing a second colouring material, curing the mixture applied to the sheet by heating, and rolling and cooling to form the final product.

In the method according to the invention, the backing sheet may optionally be pre-heated to a temperature of at least 100⁰C to remove any moisture, for example by passing the sheet past or over pre-heating elements or over heated rollers. The sheet is then passed through a coating station for application of a mixture of polyvinyl chloride and plasticiser containing a first colouring material, preferably at a temperature in the range -10°C to 45⁰C, to coat the sheet with a layer of the mixture as a continuous base coat. The coated sheet is preferably then passed beneath one or more spray-heads to apply to the continuous phase a mixture containing a second colouring material, the temperature being such that the droplets thereof, while being compatible with the mixture already applied to the substrate, retain their integrity as discrete droplets within the continuous phase while being compatible therewith to form a physically homogeneous layer, whereby they form discrete areas or zones of a different colour to the continuous phase to create a speckled or mottled effect. After curing and rolling, the visual effect is retained but the surface of the resulting material is optically smooth and the resilience or suppleness thereof is uniform throughout the depth of the applied layer.

The one or more spray-heads may be machine-mounted and computer controlled so as to pass across the coated substrate at a pre-determined speed and/or in a pre-determined pattern, the mixture containing the second colouring material being held in a reservoir or tank which may be temperature-controlled.

Preferably, a first or base coat is applied to the backing sheet layer to reduce migration of the plasiciser to the backing sheet. The base coat has a reduced plasticiser content compared with the top coat and must be of a material which can be bonded to both the top coat and to the backing. Preferably, a mid coat is provided between the base and top coats, plasticised to a similar amount as the top coat. The plasticiser in the base coat may be the same or different as that in the upper coats. Although the base coat is fully compatible with the more highly-plasticised layer above it, it may be gradually penetrated by plasticiser from the highly-plasticised layer, especially when the material is exposed to hot environments.

The fibrous backing may be a knitted, woven, or non-woven sheet of synthetic or natural fibres, for example, cotton, nylon, polyester, or polyolefin, jute or hessian fibres or is formed from glass fibres. Particularly suitable materials are spun bonded or melded thermoplastic fibrous materials, a particular advantage of this construction being that the backing may be cut with a hot knife, and welded by fusion techniques. Preferably, the backing material comprises a polyester fabric. The pϊasticiser used in the plasticised PVC layer may be any substance conventionally used to plasticise PVC. These are normally considered to fall into two classes, high molecular weight or polymeric plasticisers (of molecular weight about 750 to 1250), and low molecular weight or monomelic plasticisers. Both types are usable, but high molecular weight polyester plasticisers, such as chain-stopped poly (propylene glycol adipate) or poly (1,3-butane diolazelate), are preferred, because of their lower volatility. The plasticised PVC preferably contains a modifier of rheological properties, (i.e. a material which makes the plastisol pseudoplastic and/or thixotropic), preferably finely divided silica such as the commercially-available product Aerosil (Trade Mark). Other possible types of rheological properties modifiers are, for example, those based on bentonite, china clay, hydrogenated castor oil, or aluminium or lithium stearate. When finely divided silica is used, the preferred range is 0.5 to 7 parts by weight, per 100 parts of plasticised PVC. The purpose of the rheological properties modifier is to prevent an unacceptable reduction in the viscosity of the plasticised PVC when this is heated during manufacture of the composite material.

The colouring material is preferably a pigment which is ground and dispersed in the mixture of polyvinyl chloride and plasticiser by methods known in the art. Two or more pigments may be used for particular effects. The pigment typically is present at between 1 and 10% by volume of the mixture, preferably from 2.5 to 7.5%, for example around 5%. The pigment may be initially dispersed in a relatively small amount of plasticiser to provide a millbase having a higher pigment volume concentration and, thereafter, let down with further mixture to the desired concentration for application to the absorbent backing sheet.

The mixture of polyvinyl chloride and plasticiser typically contains a preponderant amount by weight of plasticiser, for example 50 to 70% by weight, typically around 60%, with minor amounts of additives such as heat stabilisers, bactericides and the like. In the method of the invention, the mixture of polyvinyl chloride and plasticiser containing the first colouring material may be applied in more than one pass with each pass including a curing stage, the mixture containing the second colouring material being applied during the final pass.

Flooring materials produced by the method of the invention may be used either as such, for the covering of large areas of floor, or may be used to produce mats by being laminated on a suitable backing or base material with a surrounding border. A suitable backing or base material comprises a polymeric material such as a thermoplastic elastomer or a nitrile rubber, especially a food-grade nitrile rubber, to which the substrate material may be bonded by application of heat and pressure via a heated platen. Nitrile rubber is useful as a backing for a mat because it enhances the lay-flat property of the mat. Typically, the thickness of the backing material is up to 5 mm, for example from 2 to 3 mm, especially where the backing material comprises vinyl rubber. However, for providing a border having a bright colour, a thermoplastic elastomeric material may be used, or a material available from the present application/assignee and comprising plasticised polyvinyl chloride, such material being known as Dycem non-slip material. Such material withstands the Helmke Drum Test without exhibiting any tendency to loss of integrity and resulting granulation or formation of particulates.

The invention also includes, in another aspect, a flooring or mat material comprising highly plasticised polyvinyl chloride applied as a continuous phase to a substrate absorbent backing sheet, the material having dispersed therein droplets of polyvinyl chloride and plasticiser containing a colouring material having a colour different from that of the continuous phase, the surface being optically smooth and the continuous phase containing the droplets having a substantially uniform resilience.

Preferably, the tensile strength of the surface of materials according to the invention is at least ION, preferably greater than 12N and more preferably in the range 15 to 2ON.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which

Figure 1 is a schematic drawing of the manufacturing apparatus, and Figure 2 shows a cross section through a mat produced using the apparatus.

Referring to Figure 1, a continuous web 1 of, for example, a polyester fabric, which is to form the backing, is continuously unwound from a supply roller 2. This passes around a series of idler rollers 3 until it reaches a coating station 4 where a polymeric material in paste or plastisol form which is to form the intermediate layer is applied to it. This material is smoothed out to the desired thickness by a doctor blade 5 acting against a supporting plate 6 or the roller 7. The cotton fabric with the layer of polymeric material is then passed through an oven 8. During its passage through the oven the web is supported by a series of support rollers 9 which are so arranged that the web follows a slightly convex path. This is to prevent creasing of the polymeric material as curing progresses. The oven is heated by gas burners 15 located beneath the web. This is important as the turbulence caused by any burners above the web would tend to disturb the layer of highly-fluid hot polymeric material. The polymeric material is cured in the oven and sets. The curing temperature is arranged to suit the polymeric material being applied and may for example be 190-200⁰C for a polyvinyl chloride-based material. After emerging from the oven, the edges of the strip are trimmed, or the strip is cut to width, by blades 14. The web then passes around a driven water-fed cooling roller 10, and is finally taken up on roller 11. A web of release material, to prevent adjacent turns of the coated web from sticking together, is interleaved with the coated web from a supply roller 12. The take-up roller 11 is frictionally driven by the cooling roller 10 and rests against it on an inclined plane 13. It gradually rises up the inclined plane as it fills up and its diameter increases. When it is full it is replaced by an empty take-up roller. The only driven roller in the apparatus is the cooling roller 10, all the other rollers are idlers.

The coated web passes through the same machine (or a similar machine) at least once more in order to apply the highly-plasticised PVC containing a colouring pigment, the number of times depending on the desired thickness of the highly-plasticised PVC layer. During the final pass, droplets of plasticised PVC containing a colouring material different from that of the first coating are applied from a spray-head 15 mounted on a travelling arm 16 disposed laterally over the web material. Two or more spray-heads connected respectively to separate reservoir tanks may be used, whereby two or more different colours, each different from the first colouring pigment, may be used. For example, the first colouring pigment (and hence the background colour of the material) may be blue, and a speckled or mottled effect may be provided by spraying droplets of respective white and black colours.

Referring to Figure 2, that mat is shown generally at 20 and has a semi-rigid polyvinyl chloride edging strip 21 to act as a border and to receive the raw edges of the backing material and layers applied thereto. The backing polyester 22, having a thickness of 0.6 mm, has applied thereto a base coat 23, thickness 0.5 mm, a mid coat 24, thickness 0.5 mm, and a top coat 25, thickness 0.5 mm, as shown more clearly in the enlarged fragmentary view. The mid and top coats contain the maximum amount of plasticiser and the top coat contains blue, white and black (for example) pigmentation, applied through different spray-heads connected to respective reservoir tanks. The backing polyester may be bonded to a sheet of food-grade vinyl rubber, of thickness 2.5 mm, to provide a non-slip engagement with a floor or other surface on which, in use, the mat is placed.

Claims

1. A method for the manufacture of a flooring or mat material for a clean room environment, the method comprising applying to a substrate absorbent backing sheet a mixture of polyvinyl chloride and plasticiser and a first colouring material, applying droplets of further polyvinyl chloride and plasticiser containing a second colouring material, curing the mixture applied to the sheet by heating, and rolling and cooling to form a flooring product material having a top coat exhibiting a speckled or mottled surface effect.

2. A method according to claim 1, in which the pasticiser is present as a major component of the mixture.

3. A method according to claim 1 or claim 2, in which the backing sheet is pre-heated to a temperature of at least 100⁰C.

4. A method according to any preceding claim, in which the sheet is passed through a coating station for application of a mixture of polyvinyl chloride and plasticiser containing a first colouring material at a temperature in the range -1O⁰C to 45⁰C, to coat the sheet with a layer of the mixture as a continuous phase.

5. A method according to claim 4, in which the coated sheet is passed beneath one or more spray-heads to apply to the continuous phase a mixture containing a second colouring material at a temperature at which the droplets of the second material retain their integrity as discrete droplets within the continuous phase while being compatible therewith to form a physically homogeneous layer.

6. A method according to any preceding claim, in which a first or base coat is applied to the backing sheet layer to reduce migration of the plasiciser to the backing sheet.

7. A method according to claim 6, in which a mid coat is provided between the base and top coats, the mid coat containing plasticiser in a similar amount as the top coat.

8. A method according to any preceding claim, in which the fibrous backing comprises a spun bonded or melded thermoplastic fibrous material, preferably a polyester fabric.

9. A method according to any preceding claim, in which the pasticiser comprises a high molecular weight polyester plasticiser such as chain-stopped poly (propylene glycol adipate) or poly (1,3-butane diolazelate).

10. A method according to any preceding claim, in which the plasticised polyvinyl chloride contains a modifier of rheological properties.

11. A method according to any preceding claim, in which the modifier comprises finely divided silica at an amount in the range 0.5 to 7 parts by weight, per 100 parts of plasticised polyvinyl chloride

12. A method according to any preceding claim, in which the colouring material comprises a pigment present at between 1 and 10% by volume of the mixture of polyvinyl chloride and plasticiser.

13. A method according to any preceding claim, in which the product material is applied to a backing material.

14. A method according to claim 13, in which the backing material comprises nitrile rubber.

15. A flooring material comprising plasticised polyvinyl chloride applied as a continuous phase to a substrate absorbent backing sheet, the material having dispersed therein droplets of polyvinyl chloride and plasticiser containing a colouring material having a colour different from that of the continuous phase to provide a speckled or mottled effect, the surface being optically smooth and the continuous phase containing the droplets having a substantially uniform resilience.

16. A material according to claim 15, in which the surface of the material has a tensile strength of from 10 to 2ON.

17. A material according to claim 15 or claim 16 in the form of a mat, the material being applied to a backing material.

18. A material according to claim 17, in which the backing material has a bright or contrasting colour compared with the colour of the continuous phase.

19. A material according to claim 17, in which the backing material comprises nitrile rubber.

20. A flooring or mat material produced by a method as defined in any of claims 1 to 14.