CA1064664A - Method of manufacturing a relief-textured decorative plastics web - Google Patents

Abstract

Abstract of the Disclosure In a method of manufacturing relief-textured plastics webs, the plastics web is embossed with a pattern at such a temperature that the embossing is made permanent but a latent state of tension is created in the embossed valleys. The valleys are then filled in with a suitable material, whereupon the web material is heated to a pre-determined temperature for release of the state of tension in the embossed valleys.

Description

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The invention relates to a method of manufacturing relief-textured decorative plastics webs.
Floor and wall coverings of plastics have been modified considerably in recent years, particularly with regard to their appearance. Earlier, the function of the material was a domina-ting factor, but at present there is a trend towards providing -products having figurative patterns and multi-colour charac- ;
ter, the object of which is to permit, in combination with furniture and textiles, creating an aesthetically pleasing interior environment. However, reauirements for satisfactory function have not been waived on that account, and for instance flooring materials shall, in addition to an aesthetical appea-rance, provide walking comfort and possess a high wearing 1 strength.
- A soft relief-textured flooring material substantialIy . .~ ,- .
- comprises three layers of different function, viz. a backing - -layer, a relief or pattern-forming intermediary layer and a wear layer. At the manufacture of such a flooring material the most difficult problems are those of co-ordinating the colour-.. .. .
printing and relief~forming operations. It has been tried tosolve these problems in different ways which will be brieflv discussed below.
, Colour embossing : , Compact or foamed thermoplastic webs are heated to the ~-~
plastic temperature range of the materlal and a pattern is ;

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pressed into the web bv means of an engraved pattern press roll ~embossing roll). In conjunction with the pattern pressing operation the elevated areas of the embossing roll are coated with suitable inks of the desired colour or colours which are transferred to the embossed valleys produced in the plastics web by said elevated areas. However, when this method is applied difficulties are encountered in connection with the drying of the inks. If the web is a foam plastics web it is heavily compressed in the valleys of the pattern, the foam texture being thereby obliterated. If the valleys occupy a large surface as compared with the total surface, the charac-teristics of resilience of the web are reduced when the web is utilized as a floor covering material.
Stencil printin~ method A foamable polymer composition in the orm of a plasti- ;
sol is applied to a bac1~ng layer. The layer is pregelled in a furnace at a temperature in which the plastisol is transformed into a thermoplastic, flexible mass. This temperature, however, is considerably lower than the decomposition temperature of the foaming agent. The semi-finished article thus produced ~;
is then supplied to a rotary stencil printing assembly in which colour-pigmented foamable plastisols are applied to the article in the form of printing patterns. If printing is carried out in ., ::
several stations a drying operation must be carried out bet- ~
ween said stations. Finally, a transparent plastisol is applied, ~ `
which constitutes the wear layer of the flooring material, whereupon the material is finally gelled and foamed. This will ~ . ~,,,~ .. .. . .. . . .

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expand the foamable layer first applied as well as the portions of the pattern whlch have been printed by means of the stencils.
A certain relief surfac~ is obtained since the foam thickness of the base material is added to that of the printed portions.
The pattern effects can be varied by utilizing foamable as well as normal plastisols to bring about the relief effects.
The colour design and relief areas can be caused to register.
This method is disadvantageous in that it is hardly possible to provide relief areas higher than 0.3 mm and that stencil printing as such is technically less advanced than the modern photogravure screen printing. Difficulties arise in reproducing fine lines, exact contours and halftones.
Chemical embossing (Inhibition method) A foamable plastisol or organosol is applied to a -backing layer and pregelled. This semi-finished article is then provided with a pattern by some conventional printing method, such as silkscreen, offset or photogravure. In addition to the customary ingredients, that is, colour pigment, binder, solvent and plastisizer, the ink also contains an inhibitor. Said inhibi-tor is conformed to the foaming agent of the foamable material ;~-:.
and usually is a multi-basic organic acid. After colour prin-.....
ting, a transparent upper layer is applied, ans~ the composition is finally gelled and foamed. At the locations which have been ~ .
printed with the ink containing the inhibitor, the acid migrates into the foamable sublayer and prevents foaming, whereby a ! relief texture is obtained. The colour design and relief areas can be caused to register. The lastmentioned method is disadvan~

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tageous since the valleys are formed by unfoamed material and therefore lack the desired springiness.
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Chemical embossincJ (Acceleratir~ method?
A foamable plastisol is applied to a backing layer. The recipe of said plastisol does not include an agent important to the foaming, viz. the accelerator, which comprises certain metal compounds, such as lead or zinc salts, and serves to accelerate the decomposition of the foaming agent. By adding the accelerator to the ink it is possible to provide a selec-tive foaming at the subsequent heating operation. The method ,, :.
now described suffers from the same disadvantage as the inhi-i bition method.
The main object of the present invention is to elimi-nate as far as possible the disadvantages of the methods hitherto used and to provide a new method of broader application for the production of relief-textured plastics webs. To this end, the method comprises embossing a plastics web with a pattern, preferably b~ means of an embossirlg roll, at a temperature ~.:
within the viscoelastic range of the web material, said embossing being made permanent at the subsequent temperature decrease, but with a latent state of tension in the embossed valleys formed; filling in the embossed valleys with a solid or liquid material which adheres to the web material, and again heating the web material to a temperature corresponding to the first mentioned temperature for release of the state of tension in the embossed valleys. -, , ~': --5 ~
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The method according to the inve~ltion is based on the followiny rheoloyical conditions: If a thermoplastic layer is subjected to mechanical deformation the material behaves in different ways depending upon load, temperature and time.
At a moderate deformation of a therrnoplastic material above the transformation point, the material will display a viscoelastic behaviour, provided that the temperature does not become to high. Elastic opposing forces and friction forces will arise at the same time. The elastic opposing forces tend ~;
to restore the material into the original form upon relief of load, while the friction forces (which are a function int.
al. of the viscosity of the polvmer~ counter-act the change of form of the material both at the deformation of the material and at its restoration into the original form.
The lower the temperature, the greater the friction forces. At high temperatures the mobility of the polymer :: ~
chains increases more and more and the materiaI will progressive~
ly display a purely viscous flow (polymer melt).
~; ~ If the material is now heated to a temperature well above the transformati.on point but below the temperature ~d where the material is converted into a pure melt (within~ the viscoelastic range, the term employed in the following de~
soription and the appended claims) and at this temperature is deformed by being placed under load and is then relieved of load, the material reverts to its original form by reason of the elastic forces counter-acting the viscous forces, provided -~
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relaxation of tension will take place.
~ owever, if the material is cooled after being deformed (but before being relieved of load), the fxiction forces will increase~ The lower the temperature, the longer time will the elastic forces require to restore the material into its ori-ginal form. ~t a sufficient cooling, the restoration takes place so slowly that the deformation can be considered per-manent and the elastic forces oan be considered to be frozen tensions. If the material is again heated the viscosity and consequently the friction forces decrease, and so the elastic forces restore the material into its original form.
The following approximate -temperature limits apply for plastisized polyvinylchloride:

Transformation point Tg 0 - 80C (depending upon the plastisizer'content),, Viscoelastic range Tg 150C ', Melt 170C and higher , The abovementioned plastics property is exploited in the ~ollowing manner. The plastics ]a,ver which mav be compact or ' foamed, is heated to a temperature within the intermediary tem-perature range, say 130C, and is embossed with a pattern by means of a cold embossing roll. The depressed embossed areas are then filled in with one or more organosols and plastisols of thermoplastics, dispersions of thermoplastics and elastomers, monomers, prepolymers, polymer melts, sinterable powders, decorative metal frits and organic and inorganic granules. At the subsequent gelling ~hich ta~es place at a higher temperature, ;,~
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say 175C, the embossed areas will revert to their initial posi tion, resulting in the Eormation of a relief pattern. It will readily be seen that the embossed valleys produced by means of the embossing roll will be highest in the finish product, because of the plastisol filled into said valleys and the subsequent elevation of the material in said valleys.
A floor covering produced in accordance with the present invention normally comprises three layers, viz. a backing layer, a relief-textured intermediaLy layer, and an upper wear layer. The backiny layer is of course selected in dependence on the contemplated use of the floor covering and can either re- ;
main as a part of the final product or be removed after coating has been realized. Suitable materials are asbestos felt, tex- -~
tile felt, glass fibre felt, fabrics of various kinds, paper (also release paper~, cork, thermoplastic and elastic polymer -~
; materials. During manufacture, the backing layer constitutes a base for the other layers which are mostly applied in lic~uid - ` form, and mechanically stabilizes the web during printing. A -~ ' ~ .~, -: ' favourable dimensional stability of the base is a prerec~uisite ~ -for obtaining the matching multicolour printing. If the backing layer is to be retained, it must display good adhesion, be relatively insensitive to moisture, have favourable aging pro-perties and contribute to the mechanical dimensional stability of -the product. In certain cases the backing layer also contri-butes to the springiness, step sound insulation etc. of the finished product.

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~; , Ac mentioned above, the intermediary layer to be sub-jected to relieE-texturing can consist of thermoplastic rnate-rials, preferably plastisized polyvinvlchloride or co-~olymeri-sates thereof. The material can also be cellular plastics with o~en or closed cells. It is essential that the mate-:~ .......
rial is viscoelastically deformable within some temperaturerange, and the deformation can be retained latently for some time and be caused to revert rapidly when the material is heated to a temperature preferably higher than the deformation temperature. Many alternative plastics materials are suited for this purpose. The intermediary layer is applied to the backing either by being coated with plastisols or by being laminated with a pre-calendered or pre-extruded film or sheeting. During the first heating the plastisols undergo a hardening process and are embossable from about 80C. The deformation characteristlc follows another pattern and does not conform to the characteristic of the material already gelled. It is worthwhile mentioning that this behaviour also ;~
can be exploited for the application of processes providing relief pat~erns. A particularly advantagèous material for ` - this purpose is soft, mechanically foamed PVC-cellular plas-tics with open cells. This material is easily applied by coating to the backing. The surface having the open pores is very smooth and displays a good colour printability almost comparable to that of paper. The material can be applied to -the backing with narrow thickness tolerances, contrary to those obtained with layers foamed by means oE chemical preparations.
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Excellent properties of springiness are obtained with the use of this material as a layer in a floor covering.
he polymer of vinylchloride is preferably emplo~ed as a wear layer. This material can either be a homopolymer or a co-pol~mer and mostly is in the form of a plastisol in which fine-grained polymeric material is dispersed in li~uid plasti-sizer. The application of the wear layer can be effected by means o~ doctor blade, roller or screen stencil, depending upon the patterning technique selected. If the embossed intermediary layer has been provided with colour print on the elevated areas the final coating is preferablv carried out with a transparent ~;
plastisol. This will fill in the valleys produced by the em-bossing operation and provide the elevated areas with a layer of the desired thickness. At the subsequent heat treatment the plastisol is gelled to a tough, wear-resistant mass and the `
valleys rise, forming relief areas. The wear layer can also be applied in the form of a pre-calendered film or sheeting. -In this case, the valleys must first be levelled by means of a doctor blade before the coating operation to prevent air from being trapped between the layers. ~elding can take place on a heated drum. -: . .
- The invention will be more fully described hereinbelow and with reference to some examples.
Exam~le l ~ , Manufacture of a soft floor covering. ~
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Backinq m.lterial Glass fibre fabric having a to-tal weight of 50-~0 g/m2 and with ~Irea resin as binder.
Relief donor Soft, whisked PVC foam having the following constituents:
Microsuspension-PVC100 parts by weight Straight-chain dioctylphthalate 60 Tin stabilizer (Irgastab 17 MOK) 2 ~
Colour pigrnent paste 5 "
Silicon emulsifier (DOW Corning 1250~ 5 "
Wear layer Suspension-PVC of paste auality (K value 70) 50 Emulsion-PVC (K-value 80) 50 "
Butylbenzylphthalate 40 "
Epoxy plastisizer 2 Stabilizer (e.g. Irgastab T9) 2 UV protective agent (e.g. Tinuv:in P ~ 0.5 "
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The paste shall have a viscosity not exceeding 10 000 cP.
The foam components of the relief donor were mixed in a propeller mixer and had a viscosity less than 10 000 cP. Re-gulation can be effected with viscosity loweriny agents, e.g.
low volatile hydrocarbon fractions. The plastisol was then whisked in a mixer (type Oakes or Euromatic) to the desired foam density, e.g. 500 g/l. The foam was spread on the backing by means of a doctor blade to a thickness of 1.0 mm. In a first `
furnace the foam was gelled at about 170C with a gel time of about 3 minutes. The foam web was cooled to a material temPera-~ 7~t. Ie ~ k 11 .1 '; ' :

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ture o about 140C and was embossed with a pattern by meansof a water-cooled embossing roll.
Then the non-embossed areas (the areas elevated in relief) were colour-printed in a photoyravure machine. Drying took place between the individual printing stations. The inks utilized were of the conventional type, comprising polymer solutions or dispersions with colour pigments ~organosols and plastisols~ respectively).
Example of organosol ink ~ -~
Mikrolite pigment (Ciba Geigy) 10 % by weight Vinylit VYNS (union Carbidel 6 "
Paraloid A lol 40 ~ lsg. in MEK (Rohm & Haas Co.) 4 Cellit BP (Bayer~ 0~.8 "
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;' Methylethylketone 41.2 "

Methylisobutylketone 38 "

After printing the transparent plastisol was applied .. . .
' with a doctor blade distance from the highest areas of about 0.3 mm, and the layer was gelled at about 170C.

Example 2 . . -~-A compact floor for e.g. moisture~proof rooms.

~; A backing layer which, simultaneously constituted a relief-forming layex was prepared from calendered soft PVC with .~:
1; a low content of filler and of the following composition~

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Suspension PVC (K-value 65)100 parts by weight Didecylphthalate 40 Epoxy plastisizer 5 "
Asbestos fibres 30 "
Ba-Cd-stearate 2 Lubricant (glycerin monooleate) 2 " - .
The web material was heated in a heat channel to a surface temperature of about 150C and was embossed with a pattern by means of a cooled embossing roll. The embossed areas were then levelled with coloured plastisol by means of a doctor blade. After gelling, an 0.3 mm thick pre-calendered sheeting was applied and laminated with the aid of a hot drum (type Auma). ~.
The lastmentioned step could also alternatively have been :
realized by plastisol coating. The process was concluded by ;~
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' elevation of depressed areas in relief in an infrared furnace - at a surface temperature of about 175C.

Exam~e 3 : . .
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-` Wall foam material.

.` Backing material Glass fibre fabric with a total weight of 50 g/m2 and a binder ~' , ~ , : comprising urea resin.
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Soft, whisked PVC foam with a density of 450 g~1. ;`~

The whisked foam was applied by means of a doctor blade ~

and gelled in the manner already described. After cooling o : ;

~ the foam layer, 0.3 mm coloured Plastisol was applied by means ;~ 13 , . .

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of a roll or cloctor blade. The web was Dre-gelled at 140C and embossed by means of a water-cooled roll. The valleys of the ~ , . embossment were filled in and levelled with a foamable plastisol of contrasting colour, using a heavy doctor blade pressure. At .. . .
a subsequent treatment in the furnace, the material in the valleys reverted to its orlginal shape and simultaneously the colour in the valleys was raised, forming relief. The material ;~ temperature in this operation was about 175C.

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Claims (6)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A method of manufacturing a relief-textured de-corative plastics web, comprising embossing a web of plastics material with a pattern, by means of an embossing roll, at a temperature within the viscoelastic range of the web material, said embossing being made permanent at a subse-quent decrease of temperature but retaining a latent state of tension in the embossed valleys formed; filling in the embossed valleys with a solid or liquid material which adheres to the web material; and again heating the web material to a tempera-ture corresponding to said firstmentioned temperature for relea-se of the state of tension in the embossed valleys

2. A method as claimed in claim 1, wherein the plastics web comprises polymers of vinylchloride and vinylace-tate or co-polymerisates thereof.

3. A method as claimed in claim 1, wherein the plastics web is made of cellular plastics with closed cells.

4. A method as claimed in claim 1, wherein the plastics web is made of cellular plastics with open cells.

5. A method as claimed in claims 1, 2 or 3, wherein the material with which the embossed valleys are filled in, is selected from one or more organosols or plastisols of thermo-plastics, dispersions of thermoplastics and elastomers, monomers, pre-polymers, polymer malts, sinterable powders, decorative metal frits, and organic and inorganic granules.

6 A method as claimed in claims 1, 2 or 3, wherein the raised portions realized by the embossing operation are colour printed.