Dry wipe writing system and ink therefor

Abstract

This invention provides a dry-wipe writing system, particularly useful in the education field. The system comprises a writing surface formed from a polyfluorocarbon polymer laminated to a support, and a resin-bodied solvent ink on the writing surface in any desired configuration, the resin-bodied solvent ink comprising a volatile, organic solvent, a coloring material selected from the group consisting of dyestuffs and pigments, and a resin.

Description

This invention relates to a new dry-wipe writing system of particular application in education and in other fields where it is desired to write indicia, such as letters and figures, on a display sheet and to be able to rub off the indicia simply by dry-wiping e.g. with a dry duster or cloth. It also relates to an ink of particular utility in the new dry-wipe system.

It is an object of the invention to provide a new dry-wipe system on which indicia can readily be written and removed at will by dry-wiping.

According to the invention there is provided a dry-wipe system comprising a sheet of polymeric material which is a homopolymer or copolymer of at least one perfluorinated olefine and a support for the sheet, the sheet being capable of receiving a resin bodied solvent ink to form a dry-wipe image.

The invention is based on the observation that contrary to expectation it is possible to write on these fluorocarbon polymers using a resin bodied solvent ink without break up of the ink and furthermore that after the ink has dried it may readily be rubbed off.

The fluorocarbon polymer used for the sheet is preferably polytetrafluoroethylene (PTFE), fluoroethylene propylene (FEP) or, most preferably ethylene tetrafluoroethylene copolymer (EFTE).

The FEP is a thermoplastic copolymer of tetrafluoroethylene and hexafluoropropylene and is available from du Pont.

The EFTE is also a thermoplastic copolymer but of ethylene and tetrafluoroethylene, and again is available from du Pont.

The PTFE is preferably a type of smoothed PTFE supplied by Fluorplast Ltd., of Stoke-on-Trent, Staffordshire, England. PTFE, FEP AND EFTE are all generally translucent in appearance and will therefore show the colour of, or any designs or guide lines or indicia generally, with which the support may be provided. The writing surface of the material may be evenly embossed to cut down reflectance; this embossing also has the effect of masking skive marks and increasing scratch resistance. The support may be of any desired material which will allow one to write on the sheet and then to rub the writing off. Although a rigid support is preferred, supports with some flexibility may also be used. Preferred rigid supports include metal sheets, such as steel, which are preferably provided with a coloured coating by dipping, spraying or like process, the coating preferably being white in colour.

The sheet of polymeric material may be attached to the support in a semipermanent manner for example by use of springs or clips or a like mechanism or may be permanently bonded using an adhesive. A suitable adhesive is a high-tack adhesive. For ease of assembly the polymeric material can be provided with a layer of a high-tack adhesive which is covered with a release paper such as silicone coated paper, which may be removed before bonding.

The polymeric sheet can then be adhered to any desired support. However the polymeric sheet may be first applied to a flexible backing sheet, e.g. a polyvinyl chloride foil and the other side of the backing sheet can be coated with adhesive and, if desired, provided with a release paper. This assembly of the polymeric material and backing sheet can then be adhered to any desired support. The backing sheet may be translucent or opaque and can, if desired, be printed in any desired way.

The sheet of polymeric material can be formed on the backing sheet or support by spraying or otherwise applying the polymer to the backing sheet or support.

For permanent use the polymeric sheet and support is preferably applied to a sheet of blockboard, chipboard or like material, with the use of impact adhesive, and edged with a suitable trim. In this manner articles such as blackboards and display boards generally may be made.

The ink to be used should be a resin bodied solvent ink. This means that the ink comprises a solvent and dispersed or dissolved therein a colouring material which may either be a dyestuff or a pigment.

Clearly if such a simple ink were used the colouring material would simply tend to fall off the surface to which it had been applied. Thus the ink also must contain resin which causes the colouring material to adhere to the surface to which it has been applied when the solvent has evaporated. The term "resin bodied solvent ink" as used herein means an ink containing dyestuff and/or pigment dissolved or dispersed in a solvent and resin which causes the dyestuff or pigment to adhere to substrates to which it is applied.

Preferred inks which may be used according to the invention are resin bodied solvent inks, in which the solvent is a water miscible organic solvent, and the constitution of the ink is such that on application to a smooth, non-absorbent surface, such as PTFE, FEP or EFTE it dries to deposit an amorphous, non adherent, granular and brittle film which may be readily dusted off the surface.

According to an aspect of the invention there is provided a method of writing on a surface to give a dry-wipe image which comprises applying in any desired configuration a resin bodied solvent ink to a supported sheet of polymeric material which is a homopolymer or copolymer of at least one perfluorinated olefine.

The invention also provides a dry-wipe writing system which comprises a sheet of polymeric material which is a homopolymer or copolymer of at least one perfluorinated olefine, the sheet being provided with a support and a resin bodied solvent ink which will, on application to the sheet, form a dry-wipe image.

The suitability of any particular ink for forming a dry-wipe image on EFTE, PTFE or FEP can be determined by a simple test, that is by application to a sheet of the polymer.

These resin bodied solvent inks may also be used for writing on smooth surfaces other than fluorocarbon polymers as specified such surfaces including for example, glass, porcelain, enamel and similar surfaces.

The water miscible organic solvent is preferably an alcohol or an alcohol-ether. Examples of water soluble alcohols include ethyl alcohol and industrial methylated spirits as well as glycols, such as ethylene glycol and glycol derivatives in particular ethers thereof such as the monoethyl ether of ethylene glycol (Cellosolve) and the monomethyl ether of ethylene glycol.

There are two major preferred classes of inks, one containing dyestuffs and the other containing pigments as the colouring materials.

The resin in the dyestuff-containing ink is preferably a phenol-formaldehyde Novolac resin. Suitable Novolac resins include, for example, Alvonol PN430 sold by the Albert Resin Co. (Reinhold-Albert GmbH) of Wiesbaden-Biebrich, Germany. Other resin materials which may be used include alkoxy-alkylated nylon such as Tresin 30.

The dye used in the ink is preferably of the metal complex type; particularly suitable are those of the copper of chromium complex type.

The dyestuff-containing ink preferably contains an inorganic salt which is soluble in the solvent used. Calcium chloride which is alcohol soluble is suitable. It is preferred that the salt, like CaCl.sub.2, be hygroscopic but this is not essential.

The ink according to the invention may contain water but only in a minor proportion (2 to 10%).

Preferred ratios of the components of the dyestuff-containing ink are as follows:

Percent (a) Water miscible organic solvent 85-97 (b) Novolac resin 2-6 (c) Dyestuff 1-4 (d) Inorganic salt 1-3 (e) Water 2-10 (f) Other ingredients 2-4 ______________________________________

A preferred type of pigment for use in the inks is one in which the pigment particles are already resin coated -- this means that addition of further resin to promote adherence is not always necessary. Such pigments are available under the "Hoesta" tradename from Farbwerke Hoescht. These pigments are already coated with a vinyl resin. The solvent used preferably has at least some solvent action on the vinyl resin. A particularly preferred mixture of solvents is of butyl acetate, ethyl acetate and methyl isobutyl ketone. In the inks containing pigments a barrier system is preferably used to prevent too strong an adherence of the pigment to the fluorocarbon polymers; such systems include mixtures of fatty acid alcohols and esters. Plasticisers are also preferably used.

The dry-wipe surface of the PTFE, FEP or EFTE and the ink combine to form a dry-wipe system of outstanding properties.

The invention is illustrated by the following Examples:

EXAMPLE 1

A dry-wipe system was made up as follows.

To a sheet of smoothed PTFE obtained from Fluorplast Ltd., there is applied a layer of high-tack adhesive.

If this material with an adhesive coating is to be stored before further processing there is applied to the adhesive a conventional silicone coated release paper. Otherwise the PTFE sheet is applied to a sheet of steel coated with a Colorcoat coating (Colorcoat is supplied by The British Steel Corporation) with the adhesive in contact to form the laminate which for final use is preferably adhered to a sheet of blockboard, chipboard, hardboard or like material with the use of impact adhesive and edged with a suitable trim. Any desired permanent markings may be printed on the coated steel before the PTFE is bonded to it.

The PTFE surface of the above material can readily be written upon using the inks referred to herein, representative inks being as follows:

EXAMPLE 2 (Dyestuff based)

"Alvonol PN 430" Resin (Albert Resin Co.) 4 gms. Calcium Chloride (CaCl.sub.2) 2 gms. Zapon Fiery Red B* 2 gms. 95% Industrial Methylated Spirits 100 mls. * Chromium complex dyestuff sold by B.A.S.F. (Badische Anilin & Sodafabrik), Ludwigshafen, Germany.

EXAMPLE 3 (Dyestuff based)

"Alvonol PN 430" Resin 4 gms. Crystalline Sodium Acetate (non-hygroscopic) 1 gm. Zapon Fast Blue FLE** 4 gms. 98% Industrial Methylated Spirits 100 mls. **Copper complex dyestuff sold by B.A.S.F. (Badische Anilin & Sodafabrik) Ludwigshafen, Germany.

EXAMPLE 4 (Pigment based)

Hoesta print Black L 5.5 gms. Paraplex G 53 1.0 gms. Barrier system* 5.5 gms. Ethyl acetate 6.7 mls. Butyl acetate 26.8 mls. Methyl isobutyl ketone 6.7 mls. *50:50 mixture of Alfoil 1216 and Estol 653.

EXAMPLE 5 (Pigment based)

Hoesta print Green GG 5.0 gms. Paraplex G 53 1.0 gms. Ethyl acetate 6.7 mls. Butyl acetate 26.8 mls. Methyl isobutyl ketone 6.7 mls.

EXAMPLE 6

A dry-wipe system was made up as follows.

To a sheet of FEP (du Pont) there is applied a layer of a high-tack adhesive.

If this material with an adhesive coating is to be stored before further processing there is applied to the adhesive a conventional silicone coated release paper. Otherwise the FEP sheet is applied to a sheet of steel coated with a Colorcoat coating with the adhesive in contact to form the laminate which for final use is preferably adhered to a sheet of blockboard, chipboard, hardboard or like material with the use of impact adhesive and edged with a suitable trim. Any desired permanent markings may be printed on the coated steel before the FEP is bonded to it.

The FEP surface of the above material can readily be written upon using the inks referred to in Examples 2 to 5.

EXAMPLE 7

A dry-wipe system was made up as follows.

To a sheet of EFTE (sold bu du Pont as "TEFZEL") there is applied a layer of a high-tack adhesive.

If this material with an adhesive coating is to be stored before further processing there is applied to the adhesive a conventional silicone coated release paper. Otherwise the TEFZEL sheet is applied to a sheet of steel coated with a Colorcoat coating with the adhesive in contact to form the laminate which for final use is preferably adhered to a sheet of blockboard, chipboard, hardboard or like material with the use of impact adhesive and edged with a suitable trim. Any desired permanent markings may be printed on the coated steel before the TEFZEL is bonded to it.

The TEFZEL surface of the above material can readily be written upon using the inks referred to in Examples 2 to 5.

In Examples 4 and 5 Paraplex G53 is a polyester plasticiser available from Messrs. Rohm and Haas; Estol 653 is glycerol monooleate and Alfoil 1216 is a mixture of higher fatty alcohols available from Messrs. Conoco.

Claims

What is claimed is:

1. A dry-wipe writing system comprising a writing surface which is a sheet of a polyfluorocarbon polymer selected from the group consisting of polytetrafluoroethylene, fluoroethylene propylene copolymer and ethylenetetrafluoroethylene copolymer; a support to which the said sheet is laminated; and a resin-bodied solvent ink on the said writing surface in any desired configuration, the resin-bodied solvent ink comprising a volatile, organic solvent, a coloring material which is selected from the group consisting of dyestuffs, in combination with an inorganic salt, and pigments, and a resin selected from the group consisting of phenol-formaldehyde novolacs, alkoxy-alkylated nylons and vinyl resins, which, together with the coloring material, forms, when dry, an amorphous, granular, brittle film wipably removably adherent to the writing surface.

2. The system of claim 1 wherein the said writing surface is a sheet of ethylenetetrafluoroethylene copolymer which is adhered to a rigid support by high tack adhesive.

3. The system of claim 2 wherein the said support is white in colour.

4. The system of claim 1 wherein the solvent is selected from the group consisting of alcohols, ethers, esters and ketones.

5. The system of claim 4 wherein the coloring material is a dyestuff of the metal complex type.

6. The dry-wipe writing system of claim 1 wherein the coloring material is a pigment.

7. A method of writing on a surface to give a dry-wipe image comprising applying to a writing surface which is a sheet of a polyfluorocarbon polymer selected from the group consisting of polytetrafluoroethylene, fluoroethylene propylene copolymer and ethylenetetrafluoroethylene copolymer which is laminated to a support, in any desired configuration a resin-bodied solvent ink comprising a volatile organic solvent, a coloring material which is selected from the group consisting of dyestuffs, in combination with an inorganic salt, and pigments, and a resin selected from the group consisting of phenol-formaldehyde novolacs, alkoxy-alkylated nylons and vinyl resins, which, together with the coloring material, forms, when dry, an amorphous, granular, brittle film wipably removably adherent to the writing surface.

8. The method of claim 7 wherein the sheet of polyfluorocarbon polymer is of ethylenetetrafluoroethylene copolymer.

9. The method of claim 7 wherein the said sheet has been adhered to a rigid support by a high tack adhesive.

10. The method of claim 9 wherein the said support is white in colour.

11. The method of claim 7 wherein the solvent is selected from the group consisting of alcohols, ethers, esters and ketones.

12. The system of claim 7 wherein the coloring material is a dyestuff of the metal complex type.

13. The method of claim 7 wherein the coloring material is a pigment.