US2915787A - Embossing - Google Patents

Description

DEC' 8, 1959 H. EwlNG Erm. 2,915,787

EMBossING 'Filed April e, 1955 United States Patent O EMBOSSING Henry Ewing and Joseph Rowland Wylde, Spondon, near Derby, England, assignors to British Celanese Limited,

a corporation of Great Britain Application April 6, 1955, Serial No. 499,710 Claims priority, application Great Britain April 12, '1954 4 Claims. (Cl. 18-56) This invention relates to embossing, and particularly to embossing thermoplastic fabrics and other fibrous webs.

In this specification the w'ord fibres includes continuous laments as Well as staple fibres.

According to the process of the invention, a fabric or other fibrous web, while travelling is embossed by pressing it in a condition in which it can readily be distorted, between a travelling belt of resilient material and an embossing surface travelling with said belt and suitably supported to resist the pressure of the belt, and the fibrous web while still travelling in close contact with the surface, is converted to a condition in which the pattern embossed upon it is retained after the brous web leaves the embossing surface.

In a fabric of thermoplastic material, the condition in which the fabric is readily distorted to take the pattern of the embossing surface may be obtained by the action of heat. The embossed surface, for instance, may be heated along one part of its path, so that along that part of the path the fabric is raised to a temperature at which it readily conforms with the pattern, and may be cooled along a further part of its path while still subject to the pressure applied by the pressing belt, so that on emerging from between the embossing surface and the pressing belt it is sufficiently set to retain the pattern irnparted. The action of dry heat,'however, is apt to damage some thermoplastic fabrics, and it is preferred, to employ heat in conjunction with a liquid or vapour that, at the temperature of embossing, has a softening action on the material. In this way, embossing can be carried out at lower temperatures and without damage to the material. For cellulose acetate, hot water, and especially steam, have such a softening effect. A very advantageous way of carrying out the process with such materials is to wet the fabric to be treated and then to subject it, whilebeing pressed against the embossing surface, to a temperature above the boiling point of water, e.g. a temperature of l60-220 C., and preferably l70-l90 C. At these high temperatures steam is quickly generated, and facilitates the distortion of the material to conform with the pattern. The process can be arranged so that the material, by the time it emerges from between the embossing surface and the pressing belt, is substantially dry and at a temperature at which the embossed effect is retained. Instead of or in addition to the effect of water, other agents which develop softening properties at elevated temperatures can be employed. Such agents include aqueous solutions of alcohols, and dilute aqueous solutions of solvents for cellulose acetate, as well as various liquids that develop solvent properties or near-solvent properties only at elevated temperatures. Particularly useful results have been obtained with esters and ethers of glycols, especially diethylene glycol diacetate in aqueous solution. Aromatic hydrocarbons such as benzene and toluene, and chlorinated aliphatic hydrocarbons that are not solvents for the cellulose acetate, can also be used, provided that due care is taken having regard to their toxic properties. We prefer to employ dilute aqueous solutions of solvents for the thermoplastic material of boiling point between 100 and about 280 C.

Preferably, therefore, the embossing is effected at an 2,915,787 Patented Dec. 8, 1959 elevated temperature and while the fabric contains a liquid having a softening effect at that temperature, so producing the readily distortable condition, and the conversion of the fabric to a condition in which the pattern is retained is effected by removal of said liquid.

Preferably also the embossing surface is a cylindrical surface rotating about its axis and heated from within, and the belt is an endless felted wool blanket driven in the same direction and at the same speed as said surface, said blanket being pressed along one part of its path towards said surface to effect the embossing of the fabric, and along the next part of its path running partly round said surface and serving to absorb softening liquid from the embossed fabric while holding said fabric in contact with the embossing surface, the return path of the blanket to the region in which it is pressed towards the embossing surface being out of proximity lto said surface, the pressing of the blanket towards the surface being effected by a pressing member the surface of which moves with the blanket, and the softening liquid absorbed by the blanket being continuously evaporated so that the blanket is substantially dry as it leaves the region lin which it is pressed against the embossing surface.

It is of advantage to include in the softening liquid a small proportion e.g. l to 5% by weight, of a synthetic resin adapted to undergo hardening during the heat treatment. In this way the resistance of the embossed effects to washing and ironing can be increased. Suitable synthetic resins are found among the aminoplast class e.g. condensation products of formaldehyde with urea and with various urea derivatives especially melamine. Excellent results have been obtained with a modified melamine formaldehyde resin sold as Beetle 309 (registered trademark). Besides rendering the effects more resistant to washing the use of such resins appears to improve the sharpness of the effects. It is thought that this maybe due to the resin causing temporary adhesion between the fabric and the pattern, so helping to hold the 'two in close contact while the drying of the fabric is effected. A similar sharpening effect can be obtained by having present in the softening liquid a small proportion (e.g. 1 to 4%) of suitable size. Modified protein sizes, such, for example, as Hyalcol RA (registered trademark) have given very satisfactory results. Sizes based on methyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol and the sodium and ammonium salts of styrene-maleic acid copolymers can also be used. The size may be one that can be washed out of the embossed fabric, or if not used in quantity sufficient to stiffen the fabric unduly, may remain therein. The use of sizes and synthetic resins that produce temporary adhesion between the pattern and the fabric enables useful embossed effects to be obtained without a large angle of contact between the blanket and the fabric running on the drum.

The resins and sizes are preferably water-soluble and applied in solution in an aqueous liquid.

Av suitable form of apparatus for carrying out the process of the invention comprises an embossing surface adapted to move so that each part of it passes continuously along a closed path, heating means for said surface, a belt of resilient material incombination with guide members for constraining said belt to run for part of its path in close proximity to said surface, means for urging the belt towards said surface so that the fabric to be embossed, when fed between the surface of said belt and the embossing surface while one of said surfaces is being driven, is pressed into close Contact with the embossing surface and carried along, so transmitting the drive from the driven to the undriven surface, means for continuously drawing said fabric away from the embossing surface at the same linear speed as said surface.

Preferably, as indicated above, the embossing surface is that of a rotatable drum provided with internal heating means. The pattern on said surface may be obtained in various ways, for example by engraving, etching, or sand-blasting or by cementing patterning material to the surface. Very attractive effects can be obtained, for instance, from a pattern formed by cementing to the surface of the drum grains of sand or other hard nonthermoplastic material unaffected by the softening liquid.

It is of great advantage to be able to change the drum quickly and easily when it is desired to change the pattern. An arrangement which provides for easy changing of the drum, will now be described.

In the preferred arrangement, the drum is a hollow shell or endless cylinder which hangs from a roller and is prevented from swinging about said roller by rotatable guide members engaging its inner surface. This roller may with advantage constitute the driving member for the drum, which in turn, through the fabric to be embossed, drives the belt. With this arrangement the drum can be made very cheaply, for example of thin copper sheet, aluminum sheet or other sheet metal, and can in consequence be discarded when the pattern is no longer required. Thus, in forming the pattern surface of the drum, it is unnecessary to proceed in such a way that the pattern can ultimately be obliterated and replaced by another pattern. Hence, adhesives and cements can be used which could not be stripped from the drum without damaging it, whereas if the pattern is to be removed from the surface and replaced by a fresh pattern, the choice of suitable adhesives and cements is limited. The drum can be very easily and quickly removed and replaced by another.

The pressure may be applied to the blanket by an auxiliary belt of non-absorptive resilient material pressed against the blanket by a pressure roll. This auxiliary belt may with advantage be a thick belt of rubber or rubber-like material capable of withstanding the temperature resulting from heat transmission from the embossing drum through the pressing belt. Some of the synthetic rubbers7 e.g. polychloroprene, copolymers of butadiene with styrene7 such as GR-S, copolymers of butadiene with acrylonitrile, such as those sold under registered trademarks Hycar R15 and Hycar 0R25, and the butyl rubbers are more resistant than natural rubber to high temperatures, and the silicone rubbers will withstand much higher temperatures still. The rubber, whether natural or synthetic, is preferably formulated in such a way as to have relatively high heat conductivity. lt may, for instance, be loaded with a heat-conductive carbon, eg. graphite, To facilitate dissipation of heat by the auxiliary belt, cooling means may be provided for one or more of the rollers or guide rolls round which it runs; or cooling by direct Contact with cold water or cold air may be provided at a suitable point in the path of the belt. At temperatures up to about 185 or 190 C., e.g. 17() to 180 C., good service has been obtained with an auxiliary belt of sponge rubber. At higher temperatures it has been found better, with a view to obtaining increased thermal conductivity in the belt, to make it of solid rubber. A single pressing roller bearing on the inner surface of the auxiliary belt may serve to apply the necessary pressure to the pressing belt, but it is preferred to employ a plurality of pressing rollers. Excellent results have been obtained when the auxiliary belt is pressed towards the embossing drum by two rollers spaced slightly apart, carried in a frame that can be urged towards the drum by `means capable of adjustment to vary the pressure applied.

One form of apparatus according to the invention is shown by way of example in the'accompanying diagrammatic drawing, which shows the apparatus in end elevation.

In the drawing, the web to be embossed (a pre-wetted thermoplastic fabric 10) is shown being drawn from a supply roll 11, embossed, dried and wound up on a takeup roll 28. The web fltl is continuously drawn from the supply roll 11 round the guide roll 11a into contact with the pressing belt `12 and then through the pass between the belt and the embossing surface 13 of the embossing drum 14. The embossing drum is a hollow endless cylinder of copper about 1/s thick, to the outer surface of which sand grains are bonded by means of a thermosetting synthetic resin which is then hardened by baking.

This drum hangs from the driving roll 15 having at each end a shoulder (not shown) to prevent endwise movement of the drum, and is prevented from swinging about that roll by four rotatable guide rolls 16 each mounted on a stub axle (not shown) and projecting into the drum two from each side. The embossing drum is heated internaily by radiant heaters 17. The machine frame (not shown) is designed for easy removal of the drum endwise.

The pressing belt 12 is a felted circular-woven endless wool blanket of weight about 6 ozs. per square yard. This blanket is pressed against the embossing surface (with the fabric between the two) by the auxiliary pressing belt 18. This belt is of soft sponge rubber and of thickness 1%". It runs partly round two pressure rolls 19 and 2% and a fixed idle roll 21. The pressure rolls are journalled in a frame (not shown) which is urged downwards by the lever 22 fulcrumed at 23, connected with said frame and carrying a weight 24 the distance of which from the fulcrum 23 can be varied. In this way pressure is exerted by the rollers 19 and 20 against the inside of the auxiliary pressing belt l1S, which in turn presses on the pressing belt 12. The thick resilient auxiliary belt 18, interposed between the pressing rollers and the pressing belt 12, when compressed by the pressing rolls has a large surface of contact with the pressing belt and this is an important advantage. The pressing belt 12 runs in contact with the auxiliary belt 18 through the nip between that belt and the embossing surface, thence partly round the embossing drum and thence round the guide rolls 25, 26 and 27. A suction hood 29 connected by suction-pipe 36 to exhaust means (not shown) draws off vapours of the softening liquid evaporated from the blanket. An adjustable tensioning pulley 31 enables the belt 12 to be tensioned so as to lift it away from the drum when required. The following examples illustrate the invention.

Example l The apparatus was as shown in the drawing.

The patterned surface was obtained by coating the drum evenly with a thermosetting synthetic resin, projecting on to it, while it was being rotated, sand of substantially uniform grain size, and baking the resin to convert it to the thermoset condition.

The fabric to be embossed was a cellulose acetate fabric warp-knitted from 55-denier yarn on a 2-bar, ZS-gauge machine, and having a weight of 3.71 pounds per yard of 48 width.

To render the fabric more readily deformable during the embossing operation, it was padded with water so as to retain about of its own weight thereof. In this condition it was drawn at the rate of one yard per minute into the nip between the pressing belt and the heated surface of the rotating embossing drum, was carried round between this surface and the pressing belt, and, in the course of this travel, embossed and dried, and was continuously drawn away from between the embossing surface and the pressing belt, and wound up on the takeup roll.

The temperature of the embossing drum was maintained at about C. throughout.

This treatment imparted to the fabric a pleasant pebble effect and improved its dimensional stability.

Example 2 'Ihe process was carried out as in Example 1, except that the fabric was impregnated before embossing with 70 to 90% of its weight of a 4% (by weight) aqueous solution of diethylene glycol diacetate. The drum was kept at a temperature of 165-170 and the fabric was run through the machine at the rate of 2 yards per minute. The effect was similar tothat obtained in EX- ample l but more resistant to washing and ironing. Useful results have been obtained with aqueous solutions of diethylene glycol diacetate ranging from 110% by weight.

Example 3 The process was carried out as in Example 2, except that: there was included in the softening liquid 2% by Weight of Beetle 309 (registered trademark) a modified melamine-formaldehyde synthetic resin; and the patterned surface of the embossing drum was provided by cementing a sheet of emery cloth round the drum (carefully scarting the join), and metal-spraying the surface so obtained.

The treatment gave the fabric an attractive pebble effect which was substantially unaffected after 20 consecutive cycles of washing and ironing.

Example 4 The process was carried out as in Example 3 but on a fabric of similar construction to that specified in Example 1 except that the cellulose acetate was of acetyl value 62%, and the temperature of the drum was kept at 190 C. The embossed effect was highly resistant to Washing and ironing.

Y Example 5 The process was carried out as in Example 2 but substituting for the diethylene glycol diacetate 4% by weight of the size Hyalcol RA (registered trademark) referred to above.

No undue stiffening of the fabrics occurred in treatment according to any of these examples.

Various embossing surfaces other than those described above can be employed. Thus, for example, the embossing surface may be provided by a wire gauze sleeve cemented on to the drum. Instead of wire gauze, other non-thermoplastic fabrics (or fabrics of thermoplastic material that does not soften at the embossing temperature) can be used to provide the pattern. Such materials include glass libre, asbestos, cotton or other form of natural cellulose, regenerated cellulose, as well as polyacrylonitrile` and non-thermoplastic acrylonitrile copolymers. Woven, knitted, netted, or even felted fabrics can be used to form the pattern. Lace fabrics provide particularly attractive patterns. In forming the embossing surface from a strip of fabric, care must of course be taken to avoid an unsightly joint that might disgure the pattern produced. ,By employing fabric in the form of va sleeve, made, for instance, by circular knitting or circular weaving, and slipping the fabric sleeve over the adhesive-coatedembossing drum, an embossing surface without a joint can be provided. Instead of fabrics, stiff papers perforated to produce the pattern can be used. Patterns can also be formed by sticking on to the surface of --the drum cut portions of fabric, paper, cardboard, metal foil, rubber or other` suitable material. When a relatively soft material such as fabric or paper is used to form the pattern, this may be reinforced by cementing a thin layer of ductile metal foil'on -to the pattern and causing it to conform thereto under the pressure applied by the pressing belt when the embossing drum is rotated with the lfoil in position before the cement has set. With a porous patterning material, a sheet of foil can be run through the machine between the pattern andV the pressing belt, immediately after applying the fabric or paper pattern to the cement-coated drum and before the cement is dry, so causing the foil to conform to the pattern and be bonded thereto by cement passing through the fabric or paper pattern. Other 4methods are available for reinforcing the pattern, e.g. spraying with metal, or with a dispersion of a non-thermoplastic, heatresistant polymer, e.g. polytetrauoroethylene, or with a thermosetting synthetic resin. Stencilling methods may also be used to form the pattern on the embossing surface.

Although excellent embossing can be obtained With the apparatus described above, in which the whole of the pressure required is applied mechanically, the invention includes a process and apparatus in which the pressure mechanically applied is supplemented by fluid pressure applied, for instance, to the pressing belt after it has passed out of contact with the auxiliary pressing belt. Thus, for example, in the apparatus described, the run of the pressing belt between the region in which it contacts the auxiliary pressing belt and that in which it passes out of contact with the fabric can be enclosed, and supplied with suitable iluid pressure means, e.g. air under pressure. Alternatively, internal suction means may be provided to operate through the pattern and the fabric upon the pressing belt over the region in which the fabric is in contact with the embossing surface. Naturally, if uid pressure is to act on the pressing belt, this belt must be of less permeable construction than that of the woolen blanket hitherto described. The pressing belt may, for example, be of rubber.

There may be employed, instead of a rotating embossing drum, a travelling embossing belt. This may, for example, be of metal or of resilient sheet material, e.g. rubber, a synthetic rubber, or a rubber-like polymer such as plasticised polyvinyl chloride, or of textile material. Suitable supporting means must, of course, be provided for the belt, to prevent distortion in the embossing region owing to the pressure of the pressure belt. It may, for example, be provided that the embossing occurs in a region in which the embossing belt is passing round a rotating drum. As when employing an embossing drum, so with the embossing belt, the mechanical pressure provided by one or more pressing rolls operating through auxiliary pressing belts may be supplemented by iluid pressure means.

Although it is preferable, as described above, for the pattern to be fixed to the drum or embossing belt, the invention includes a process and apparatus in which the pattern is provided by a web, e.g. of wire gauze or other non-thermoplastic material, which is drawn continuously between a rotating drum or travelling belt and the pressing belt so as to move with said drum or belt throughout the region in which the fabric to be embossed is in contact with the pressing belt. In this method the fabric is pressed between the pressing belt and the patterned web, which is preferably heated immediately before coming in contact with the pressing belt.

The process of the invention has beendescribed with particular reference to embossing knitted thermoplastic fabrics. Such fabrics are particularly suitable for use f' in the process of the invention, since they are inherently more readily distortable than Woven fabrics of the same material. Woven fabrics can, however, ibe embossed in the same. way provided that they are rendered sufficiently soft, e.g. in the case of cellulose acetate fabrics, by the action of water and/or of an organic softening agent such as those referred to above, at the temperature at which embossing is effected. The process of the present invention may be employed on other organic thermoplastic fabrics and on mixed fabrics, e.g. fabrics containing libres of cellulose acetate yarn or other organic thermoplastic yarn (either of continuous filaments or of staple libre) in admixture .with breslof other materials, e.g. of cotton, linen or regenerated cellulose. The fab- 7 rics may be composed of or contain continuous-filament and/or staple-fibre yarns. Mats of thermoplastic fibre may also be embossed by the process of the invention.

Cellulose acetate has been instanced above as the thermoplastic material. The cellulose acetate ordinarily used in the textile industry is completely soluble in acetone and has an acetyl value (expressed as percentage of combined acetic acid) between 52 and 54% The fabrics referred to in Examples l to 3 were composed of a cellulose acetate of this kind. Fabrics can also be made, however, from cellulose acetates of higher acetyl values, e.g. between 54 and 56%, between 56 and 58% or between 58 and 62.5% of combined acetic acid, the process of the invention includes embossing fabrics made of or containing such cellulose acetates and the embossing of a fabric of cellulose acetate of high acetyl value is described in Example 4. Other organic thermoplastic materials also may constitute the fibre-forming material of the fabric to be emossed, or may be employed as coatings on a non-thermoplastic fabric. Such other thermoplastic materials include other organic esters of cellulose, e.g. cellulose proponate, cellulose aceto-propionate and cellulose acetate-butyrate, and thermoplastic fibre-forming vinyl compounds such as polyvinyl chloride-acetate. We have also obtained useful results on knitted fabrics of polyethylene terephthalate with the embossing drum at 200 C.

The embossing may be effected without substantial stiffening of the fabrics. For some purposes, however, stiffening of the fabric is not disadvantageous, and the invention includes carrying out the embossing in such a way that a stiffened fabric results. In general, high temperatures and the presence of plasticisers (especially solvent plastic'isers) contribute towards the stiffening of the materials. Plasticisers may, for instance, be introduced in a softening liquid with which the fabric is impregnated before embossing. Stiffening can also be effected by impregnating the materials, before the embossing, with a thermosetting synthetic resin or the components thereof, or a cross-linking agent for the material of the fabric, and effecting the condensation or cross-linking necessary to give the required stiffness during, or immediately after, the embossing step7 and while the fabric is still pressed by the pressing belt against the embossing surface. With restricted quantities of suitable thermosetting synthetic resins or cross-linking agents, the permanence of the embossed effects may be increased, together with the resilience of the fabric, without undue stiffening.

Fabrics of non-thermoplastic material, e.g. fabrics of cellulose and other hydrophobe fibres, especially knitted fabrics and felt fabrics, may be embossed by the method of the invention, and the embossed effect may be fixed by effecting the hardening of a thermosetting synthetic resin in the fibre, or acting thereon with a cross-linking agent, during or immediately after the embossing operation, and while the fabric is still held by the pressing belt in contact with the embossed surface. Softening agents such as glycerol and polyglycols may be used to assist in the distortion of the fabric.

Having described our invention, what we desire to secure by Letters Patent is:

l. Process for embossing a fabric of thermoplastic material which comprises, as a continuous operation applied to the travelling fabric, pressing a knitted cellulose acetate fabric, while wet with an aqueous liquid that develops softening properties for the material of the fabric only at elevated temperatures, between a water absorbent belt of resilient textile material and an embossing surface, both travelling in the same direction at the same speed, the belt being yieldably pressed along a short part of its path against a part of said surface that is at a temperature of 170 to 190 C. by a travelling pressing surface to effect the desired embossing, and said belt along the next part of its path remaining in contact with said surface and absorbing liquid from the fabric while holding it in contact with said surface until the embossing thereon is fixed, and the liquid absorbed by the belt being evaporated in the further course of its travel, and stripping the embossed fabric from the embossing surface.

2. Process for embossing a fabric of thermoplastic material which comprises, as a continuous operation applied to the travelling fabric, pressing a knitted cellulose acetate fabric, while wet with water, between a water absorbent belt of resilient textile material and an embossing surface, both travelling in the same direction at the same speed, the belt being yieldably pressed along a short part of its path against a part of said surface that is at a temperature of to 190 C. by a travelling pressing surface to effect the desired embossing, and said belt along the next part of its path remaining in contact with said surface and absorbing liquid from the fabric while holding it in contact with said surface until the embossing thereon is fixed, and the liquid absorbed by the belt being evaporated in the further course of its travel, and stripping the embossed fabric from the embossing surface.

3. Process for embossing a fabric of thermoplastic material which comprises, as a continuous operation applied to the travelling fabric, pressing a knitted cellulose acetate fabric, while wet with a 2 to 5% aqueous Solution of diethylene glycol diacetate, between a belt of thick felted wool fibre and an embossing surface, both travelling in the same direction at the same speed, the `belt being yieldably pressed along a short part of its path against a part of said surface that is at a temperature of 170 to 190 C. by a travelling pressing surface to effect the desired embossing, and said belt along the next part of its path remaining in contact with said surface and absorbing liquid from the fabric while holding it in contact with said surface until the embossing thereon is fixed, and the liquid absorbed by the belt being evaporated in the further course of its travel, and stripping the embossed fabric from the embossing surface.

4. Process for embossing a fabric of thermoplastic material which comprises, as a continuous operation applied to the travelling fabric, pressing a knitted cellulose acetate fabric, While wet with an aqueous solution of 2 to 5% of diethylene glycol diacetate and 1 to 5% of a thermosetting condensation product of melamine and formaldehyde, between a belt of thick felted wool fibre and an embossing surface, both travelling in the same direction at the same speed, the belt being yieldably pressed along a short part of its path against a part of said surface that is ata temperature of 170 to 190 C. by a travelling pressing Surface to effect the desired embossing, and Said belt along the next part of its path remaining in contact with said surface and absorbing liquid from the fabric while holding it in Contact with said surface until the embossing thereon is fixed, and the liquid absorbed by the belt being evaporated in the further course of its travel, and strlpping the embossed fabric from the embossing surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,964,724 Dreyfus July 3, 1934 2,047,230 Schneider Iuly 14, 1936 2,077,508 Bierer Apr. 20, 1937 2,296,804 Winnek Sept. 22, 1942 2,442,598 Harrison et al. June 1, 1948 2,446,771 Knowland Aug. 10, 1948 2,526,318 Battin Oct. 17, 1950 2,562,078 Winnek July 24, 1951 2,669,527 Horwich Feb. 16, 1954 2,776,452 Chavannes Ian. 8, 1957 FOREIGN PATENTS 552,093 Great Britain Mar. 23, 1943

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