SPECIFICATIONTextile products comprising flocked fibres and their manufactureTextile products comprising flocked fibres, often called flocked products, comprise a layer of flocked fibres bonded to a substrate. They may be used in, for instance, upholstery, wallcoverings, carpets and garments. It is often required that the products should have discontinuous coloured areas, either of the same or different colours. Also it is often required that the flock should be deposited only in the discontinuous coloured areas, so that the flock is in register with the colour. At present it is difficult to produce many such products without adversely affecting other properties, such as the feel, of the product.
Thus, satisfactory colour effects can be obtained by printing the desired multicolour pattern onto a flocked product, for instance by gravure, screen, flexographic or transfer printing processes.
Gravure, screen, flexographic or other printing processes in which the print is deposited from a liquid system can be conducted using either pigment based inks containing a binder or conventional textile printing techniques using textile dyestuffs. When the liquid composition is of the type that is generally referred to as a pigment based ink the ink contains a binder and it may be, for instance, a dispersion of pigment in a vinyl plastisol. The binder is necessary to hold the pigment physically on the fibres but the presence of the binder tends to stick the fibres together and give the product a harsh handle. Also the pigment may only bond to the tips of the fibres, and so can be worn away.
The methods referred to as textile printing techniques avoid these disadvantages. They use an aqueous solution of a dye, optionally with a very small amount of binder, and the dye fixes onto the fibre optionally in the presence of a mordant. Unfortunately, it is necessary to wash the material after printing to remove excess dye and binder. After washing it is essential to dry the printed and flocked product but drying such products is an expensive operation and involves the use of, for instance, drying ovens.
When transfer printing processes are used paper carrying transferable dye in the desired pattern is laid against the flocked product and heat and pressure are applied to cause the dye to transfer to the fibres. The combination of heat and pressure may permanently flatten the flock and this is generally undesirable.
A particular problem arises when it is desired to make a product containing non contiguous areas of flock and in particular to make a multicoloured product because of the difficulty of achieving registration of the desired colour with the area of flock. Thus when a product containing non contiguous areas of flock in which more than one colour of flock is to be provided it has been necessary either to print the flock, with the already described disadvantages coupled with the difficulties of achieving accurate registration, or the product is made by applying the discrete areas of adhesive for part of the design, flocking with one appropriately coloured flock and curing the adhesive, and then repeating the operation until the complete multicoloured design has been made up.
In the invention a flocked product in which the fibres are dyed with one or more dyes that are substantive to the fibres is made by a method comprising depositing the or each dye onto a substrate, applying and bonding flock fibres onto the substrate in intimate contact with the or each dye, and causing the or each dye to migrate along the fibres and to become substantive to the fibres by heating the product.
The dye must be one that is substantive to the fibres and that can be converted from a form in which it is intimate contact with the outside of one end of the fibres to a form in which it is fixed in the fibres and imparts the desired colour along most at least of the length of the fibres. Thus, the dye must not only migrate along the fibres from their base to their tips but must also become substantive with the fibres, for instance moving into the interstices of individual fibres. This may be referred to as dissolution of the dye in the fibres. By saying that the dye is substantive to the fibres we mean that it is not readily removed by the physical environment to which the product will generally be subjected, for instance moderate physical abrasion at ambient temperatures or warm water washing.
Extreme conditions, for instance contact with steam or ironing at high temperatures may result in some loss of the dye but this is acceptable.
Best results are achieved by the use of dyes of the type that are designed for heat transfer printing, in which event the heat is generally conducted at temperatures typical of those used for effecting heat transfer printing, for instance 1 60 to 250"C. Although many dyes useful for heat transfer printing are often referred to as sublimable dyes we find that the migration and fixing of the dyes in the invention occurs at temperatures below those at which sublimation may occur. Accordingly the mechanism involved in the invention may be a liquid phase rather than a vapour phase mechanism. We believe that a liquid phase mechanism may be involved when many such dyes are used in conventional heat transfer methods.
The heating may be achieved by passing the product through an oven or subjecting it to infrared heating, or both. The temperature of heating is preferably 180 to 220"C, the optimum temperature being selected having regard to the particular dye and fibres involved. Heating is generally conducted for from 5 seconds to 5 minutes, periods of 1 5 to 30 seconds generally being preferred when infrared heaters are used and 30 seconds to 5 minutes, generally 2 to 5 minutes, when heating is in an oven. The heating is best conducted dry, i.e. without applying steam or other moisture to the product.
Dyes suitable for use in transfer printing, and which will thus be suitable for use in the invention, are well known. They may sometimes be referred to as pigments and may be organic or inorganic. Typical examples are theResiren (trade mark) dyestuffs sold by Bayer and the Sublaprint (trade mark) dyestuffs sold by L.B. Holliday Ltd and the Teraprint (TradeMark) dyestuffs sold by Ciba-Geigy.
It is naturally necessary that the dyes should be substantive to the fibres being used but combinations of dyes and fibres suitable for transfer printing are known and are suitable in the invention. An advantage of the invention is that the dye stuffs tend to be substantive to a wider range of fibres or to have improved substantive properties compared to when the same dye stuffs are applied by traditional transfer printing to the same fibres.
Generally the fibres are thermoplastic, for instance nylon, acrylic or polyester fibres.
Other fibres, such as cotton, may be present as mixtures with these for instance in amounts up to 50%. Other fibres may be used provided they have been treated in known manner so as to make them receptive to the transfer dyes. For instance the fibres may first be treated by methods such as those described in British Patent Specification Nos. 1 501 889 or 1 445201.
The fibres may initially be uncoloured or they may be coloured. Generally their length will be from 0.5mm to 6mm and their denier from 3 to 25 denier.
It is necessary that the fibre along which a dye is to migrate should be in intimate contact with the dye before the heating, and that is generally best achieved by applying the dye as an adhesive ink and using the adhesive ink to bond the fibre to the substrate. A variety of adhesive inks may be used. They may be aqueous or non-aqueous. They may be based on, for instance, acrylic or polyurethane adhesives. PVC plastisol inks are often very suitable.
The process is of value for producing a variety of coloured flocked products. For instance a monocolour overall flock product may be made by depositing a single monocolor adhesive ink as an overall layer and flocking the fibres onto the whole area. The process is, however, of particular value for producing a product having a pattern of flock areas and this can be achieved by applying the adhesive ink or inks in discontiguous areas and bonding the fibres to the substrate in these discontiguous areas.This process can be used using a single colour ink but preferably the process is conducted so as to produce a multicoloured flocked product having a pattern of differently coloured discontiguous areas, in which event a plurality of differently coloured adhesives inks are applied in the desired pattern of discontiguous areas and the fibres are bonded to the substrate only in these discontiguous areas.
The ink or inks may be deposited by, for instance, flexographic printing, gravure printing or screen printing.
Any substrate suitable for use as the substrate of a flocked product may be used in the invention. Generally it is a sheet of vinyl chloride or other polymeric material, generally reinforced by glass or other fibres, or is a textile sheet.
The textile substrate may itself be a flocked product. Thus, for instance, the adhesive ink or inks containing the dye may be printed onto a flocked product, generally a flocked product having a monocolour overall layer.
This base layer of flocked fibres may itself be carried on convetional substrate and may have been coloured either by the method of the invention or by some other method, for instance the use of monocolour flocked fibres.
Substrates of polymeric material may be foamed or foamable. If the substrate is foamable it may be caused to foam either during the heating that causes migration of the dye into and along the fibres or before or subsequently. A pattern in relief as well as a pattern in colour can be obtained if at least one of the inks printed onto the substrate contains a reagent for altering the rate or temperature or effect of decomposition of the foarning agent, such that the subsequent foaming by heating results in the formation of a pattern in relief in register with those parts of the colour pattern containing the reagent.The reagent may act either directly upon the foaming agent to alter the temperature at which decomposition starts or upon other components in the polymeric composition, such as zinc oxide which is often present and which may serve as a "kicker' ',,to initiate in viscosity of the polymeric layer during foaming as a result of local crosslinking. Combinations of suitable reagents and foaming agents are known and are described, for example, in British Patent SpecificationsNo. 1,069,998 and 1,069,999. Fumaric acid and trimellitic anhydride are particularly preferred as suitable reagents, especially when the foaming agent is azodicarbonamide, whichis generally preferred.
A pattern in relief effect can also be obtained if one or more polymer based inks (e.g.
vinyl plastisol) containing a blowing agent aredeposited on the substrate. Normally theseinks will contain transferable dye, in which event there will be a pattern in colour in register with a pattern in relief.
The invention results in the production of a flocked product which can have a multicolour pattern in precise register with the original printed pattern, in which the colours are fast to light, to wet and dry running and abrasion, and which can have flock properties not adversely affected by the multicolour effect. Also it can have a pattern in colour in precise register with a pattern in relief. The product can have a multicolour pattern in any number of colours in any design.
The following are examples of the invention.
Example 1A vinyl coated paper or other substrate is printed over part of its area in a multicolour design by flexographic printing. The inks are based on PVC plastisol and contain migratory dyestuffs of the type described above. Each ink is formed of about 15% by weight dye and 85% by weight plastisol and in the areas where it is applied it is applied at about 80 g/m2. Uncoloured nylon flock is deposited into the printed area by electrostatic flocking.
The material is then passed through an oven for a period of four minutes at a temperature of 1 90 C, whereupon the inks are fused, and the flock in different areas becomes coloured according to the colour of the particular ink.
Example 2A suitable substrate, such as fabric or paper, is coated with a foamable plastisol containing azodicarbonamide as blowing agent and zinc oxide as kicker. The coating is gelled but not blown, at a temperature of 140"C-150"C. The surface of the coating is next printed in a multicolour design using plastisol inks. Suitable printing techniques include surface printing and flexographic printing. The inks are coloured with the types of dyestuffs used in making transfer printing inks, for instance of the type described above.
Some of the inks also contain an inhibitor for the blowing reaction, such as trimellitic anhydride or fumaric acid. While the plastisol inks are still wet, a layer of flock is deposited by electrostatic or other means, the plastisol inks acting as flock adhesives. The material is finally heated to a temperature of 1 90 C for a period of five minutes. During this final heating process the plastisol inks fuse, the areas of the foamable plastisol printed with inks free of inhibitor expand significantly while the areas printed with inks containing inhibitor expand not at all or to a lesser extent, and the dyes in the inks migrate up the flock fibres and colour them strongly. The final product is a flocked product having a multicolour design in which parts of the design are embossed in precise register with particular colours.
Example 3A vinyl coated paper is printed over part of its area in a multicolour design by flexographic printing. The inks are based on PVC plastisol and contain migratory dyestuffs of the type described above and at least one of them contains azodicarbonamide as a blowing agent and zinc oxide as a kicker. Uncoloured nylon flock is deposited into the adhesive by electrostatic flocking. The material is then passed through an oven for a period of five minutes at 1 90 C. During this period the plastisol inks fuse, the ink(s) containing the blowing agent expand and the dyes migrate up the flock fibres. The final product is a flocked product having a multicolour design in which parts of the design have an embossed effect in precise register with particular colours.
Example 4A woven cotton fabric is coated over its entire surface with a layer of acrylic latex adhesive. The adhesive contains migratory dyestuffs of the type described above. Uncoloured precision cut nylon flock of length 1 mm and gauge 3.3 dtex is deposited into the adhesive by electrostatic flocking and the adhesive is then dried at a temperature of 1 20 C. In this way, a plain flocked fabric is obtained. This material is then printed on the flock surface, in selected areas, with PVC plastisol adhesives containing migratory dyestuffs of the type described above. In a second pass through the flocking line, uncoloured 1 mm 3.3 dtex flock is deposited into the plastisol adhesives. The material is then passed through an oven for a period of four minutes at 1 90 C, whereupon the inks are fused and the flock in both the ground and printed areas becomes coloured according to the colour of the adhesive. The product is a simulated moquette suitable for upholstery applications.