EP0028154A1

EP0028154A1 - Process of dyeing textile products

Info

Publication number: EP0028154A1
Application number: EP80303816A
Authority: EP
Inventors: John Patrick Anthony Kehoe; George Barry Hollinkrake; John Clifford Walmsley
Original assignee: Unilever NV
Current assignee: Unilever NV
Priority date: 1979-10-30
Filing date: 1980-10-28
Publication date: 1981-05-06
Also published as: AU6373480A

Abstract

A textile product is dyed by printing or otherwise applying a small amount of a liquid or powdered composition of a heat transfer dye to the product and then fixing all the dye, generally by dry heating. The composition is generally non-aqueous and may contain a small amount of binder. The dyed product does not need to be subjected to washing or drying.

Description

This invention relates to the application of dyes to textile products such as woven fabrics, knitted fabrics, non-woven fabrics and pile fabrics including flocked products. The textile products may be used as, for instance, garments but the invention is of particular value when applied to textile products that are to be used in upholstery, wall coverings, carpets and curtaining. Although for convenience we refer herein to "dyes" it should be understood that we include not only the materials conventionally referred to as dyes but also-those conventionally referred to as pigments, that is to say any organic or inorganic compound that can impart a chosen colour to the textile product. The entire class of dyes can alternatively be referred to as "dyestuffs".
Multicolour patterns can be produced by application of the dyes by various known techniques, such as gravure, screen, flexographic or transfer printing processes. Powder printing, for instance electrostatic powder printing, can also be used. These methods can also be adapted to give a.monocolour pattern or an overall monocolour. An overall monocolour can also be achieved by other methods such as dipping, impregnating and spread coating.
Most methods of applying dyes to textile products include the application of a liquid composition containing the dye direct onto the product.
When the liquid composition is of the type that is generally referred to as a pigment based ink the ink contains the pigment and a significant amount of a binder, such as an acrylic dispersion. The binder is necessary to bond the pigment permanently to the textile product. Unfortunately this means that the pigment can be worn away and the presence of the binder can adversely affect the handle of the product.
The application methods generally referred to as textile printing techniques minimise these disadvantages. They use a solution or dispersion, generally aqueous, of the chosen dye and containing a binder but instead of relying upon the binder to hold the dye on the surface of the textile product the dye is fixed into the textile product by a subsequent heating or steaming step.
It seems that the fixation of the dye into the product by the heating or steaming involves, to some extent at least, solution of the dye into the structure of the fibres of the textile product. It has been recognised that it is necessary when carrying out this method to ensure that the dye and the conditions are such that the dye does not volatilise during the heating or steaming since if volatilisation does occur there is loss of dye and reduced colour density.
The conditions and amounts used in textile printing are always such that, after the fixing step, there are significant amounts of binder and unfixed dye on the surface of the product. Unfixed dye will rub or wash off the product during use and the presence of binder in the amounts that are encountered results in the product having a poor handle. In practice the process therefore involves washing and drying the textile product after the fixing step. When fixing is by steaming then drying is necessary in any event, irrespective of whether the product is washed.
Having to dry a textile product is inconvenient and expensive. It requires the provision of heavy investment in large drying apparatus such as forced air ovens, and involves large energy consumption.
In recent years transfer printing techniques have been developed. In these a solution or dispersion of a transferable dye with a significant amount of binder is printed in the desired pattern on a transfer paper or other substrate, this is then laid against the textile product and heat and pressure are applied to cause the dye to transfer to the textile product. It is often said that this transfer is due to sublimation of the dyes and so the dyes are sometimes referred to as sublimable dyes. Irrespective of the precise mechanism, the result of the transfer is that some dye remains on the transfer paper while other dye is transferred to the textile product and enters the structure of the fibres of the product. This entry into the structure of the fibres can conveniently be referred to as dissolution of the dye in the fibres. It is necessary for the textile product, or at least a major component of it, to be receptive to the particular dyes that are transferred or to have been treated in known manner so as to make it receptive. Generally the textile product is formed of thermoplastic synthetic fibres, most preferably polyester.
Transfer printing does have some disadvantages. Thus it involves a two-stage process, the first one being the initial formation of the printed transfer paper. Much of the dye remains on the paper after transfer and so it involves a waste of a substantial amount of the dye. A particular disadvantage however is that with flocked or other pile fabrics the combination of heat and pressure may flatten or otherwise permanently damage the pile.
It would therefore be desirable to have a method of applying dyes to textile products that can be operated very simply without the need to conduct expensive drying techniques and without damaging the handle or appearance of the product and without the need to conduct an intermediate printing step onto transfer paper.
In the invention a textile fibrous product is dyed by a dye that is substantive to the product by a method comprising applying onto the product a powdered or liquid composition containing the dye, and thereby removably depositing the dye on the product, and then causing, in the absence of water, substantially all the applied dye to fix permanently to the product. The fixed product is dry and does not need washing.
The dye must be one that is substantive to the product and that can be converted from a form in which it removably rests on the. outside of the fibres of the product to a different physical form in which it is permanently fixed in the product and yields the desired colour. Generally the colour before fixing is a weaker colour than the desired final colour but sometimes it may be a different hue or tone as well. Before development the dye could be removed from the fibres but after development substantially all the dye is fixed permanently to the product. Thus before development the dye can be removed by, for instance, rubbing or washing but after development it is sufficiently firmly fixed that it is not removed by the physical environment to which the product will normally be subjected, for instance, moderate physical abrasion at ambient temperatures or warm water washing. Extreme conditions such as steam heating, ironing at high temperatures or prolonged bright sunlight may result in some loss of dye but this is acceptable.
The fixing involves migration of the dye into the structure of the product, for instance into the interstices within individual fibres, and may thus be referred to as dissolution of the dye into the fibres. Additionally the fixing generally involves migration of the dye along individual fibres within the product. Thus the dye may be applied to the tips only of the fibres but fixing results in the dyes dyeing most or all of the length of the fibres.
Best results are achieved by the use of dyes (which may be organic or inorganic) of the type that are.designed for heat transfer printing since development can then best be achieved merely by heating the product carrying the latent colour. Thus preferably the process is conducted by printing a dye that is capable of being heat transfer printed onto the product being printed. Although such dyes are often referred to as sublimable dyes we find that the fixing in the invention, and probably also the transfer that occurs during normal transfer printing, often occurs at a temperature below that at which sublimation may occur. Accordingly the mechanism of fixing may be a liquid phase rather than a vapour phase mechanism.
Suitable dyes that are sold for use in transfer printing and that may be used in the invention are the Resiren (Trade Mark) dyestuffs sold by Bayer, the Teraprint (Trade Mark) dyestuffs sold by Ciba-Geigy and the Sublaprint (Trade Mark) dyestuffs sold by L.B.Holliday Limited. The dye must be selected so that it is substantive to the fibrous product, but combinations of dyes and fibres suitable for transfer printing are known. An advantage of the invention is that the dyes tend to be substantive to a wider range of fibres or to have improved substantive properties, compared to when the same dyes are applied in the traditional manner by transfer printing from a transfer sheet under heat and pressure.
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%. Additionally other products may be used provided they have been treated in known manner so as to make them receptive to the transfer dyes. For instance the product may first be treated by methods such as those described in British Patent Specifications Nos. 1,501,998 or 1,445,201.
The textile product is preferably a woven, knitted, non-woven or pile fabric. Suitable pile fabrics are tufted pile fabrics and flocked products comprising flocked fibres bonded to a substrate which may be a textile or may be a sheet of polymeric material. For instance it may be a sheet of vinyl chloride polymer reinforced by glass or other fibres.
The product may have been made by conventional methods. For instance flocked products may have been made by flocking fibres having a length of 0.5 to 6 mm and denier of 3 to 25 denier onto a suitable adhesive substrate. The product onto which the dye is to be applied may initially be coloured or uncoloured.
The dye may be applied as a powder, either as an overall application or in a monocolour or multicolour pattern, for instance by known powder printing techniques such as electrostatic printing.
Generally however the dye is applied as a liquid composition. The dye may be dissolved in the composition but generally is dispersed in it. The composition is generally substantially non-aqueous, for instance containing less than 10% and often less than 5% water, and most preferably is free of water other than amounts that may be introduced as a result of using industrial grade solvents. Preferably the liquid phase of the composition is more volatile than water, e.g. organic solvents that are volatile at temperatures below 150°C. Preferably at least 25% and generally at least 40% of the liquid phase of the composition is provided by a low boiling organic solvent, for instance one boiling at below 80°C. Suitable low boiling organic solvents may be selected from alcohols, such as methanol or ethanol, ketones such as acetone or methylethyl ketone or aliphatic hydrocarbons. The balance of the organic solvent is preferably an aromatic hydrocarbon having a boiling point below 150°C, for instance benzene or toluene. The proportions by weight may be from 2:1 to 1:2 but preferably are about 1:-l. Industrial methylated spirits may be used as the source of ethanol.
The dye-containing composition may contain a small amount of binder. The binder is present to prevent rub off of the dye before development and to adjust the printing characteristics of the composition. It may therefore be omitted if development occurs substantially immediately after the initial application, without any intervening handling step. For instance if development is effected by infra-red irradiation immediately after, for instance powder or an overall application it may be unnecessary to include any binder. Often however there is some intermediate handling or delay and therefore the composition preferably contains at least 0.5% binder. However since the binder only has to hold the dye in position before the development step and the handling and physical conditions to which it is exposed before development can be very mild the amount will always be very low, generally being below 10% and often below 5%. All percentages are by weight based on the weight of composition unless otherwise specified.
Some or all of the binder may serve as, for instance, a thickener or rheology adjuster so as to improve the printability of a liquid composition. However other additives may be included for such purposes although the total amount of additive, including binder, added to the dye and volatile organic solvent is generally always below 10% and preferably below 5%. Suitable additives that may be included as binders, thickeners'and so forth include synthetic polymers such as acrylic polymers and polyvinyl alcohol, proteinaceous additives and cellulosic compounds. Preferably the composition includes ethyl cellulose.
The amount of dye that is applied to the product must always be low and in particular must be such that substantially all the dye is fixed during the development stage. The amount that is applied is generally below 2g/m² (i.e. 2 grams per square metre of product on which dye is actually applied). Best results are achieved using dye 2 amounts of 0.05 to 1 g/m , preferably 0.1 to 0.7 g/m .
When the composition is applied as a powder it generally consists solely of the dye and so the amounts of composition applied will be these amounts. When the composition is applied as a liquid composition the amount of dye in the composition is generally from 1 to 10%, most preferably about 2 to 5%. The total application of liquid composition 2 2 is generally 3 to 25 g/m , preferably about 7 to 15 g/m². As a result the total amount of binder applied is generally from 0 to 1.5, preferably 0.2 to 1, g/m .
The liquid compositions may be made in conventional manner, by dispersing the dye in some or all of the liquid vehicle, generally using a high speed mixer so as to ensure that any powder agglomerates are broken down.
The application of the dye containing composition may be an overall application or as a pattern which may be printed either as a monocolour or multicolour pattern. Suitable printing techniques include flexographic printing, gravure printing and screen printing.
The printed product will generally have a weak colour printed onto it, which may or may not be the colour of the final fixed dye. The dye may then be fixed, generally simply by heating the product to a temperature which is the same as or similar to the temperature at which heat transfer can be achieved using the same dye. The heating is best conducted as dry heating, i.e. without applying steam or water to the atmosphere or product. This heating may be achieved by passing the product through an oven or subjecting it to infra-red heating, or both. The temperature is generally between 160 and 250°C, most preferably 180 to 220°C, the optimum temperature being selected having regard to the particular dye being used. The heating may be for 5 seconds to 5 or 10 minutes. When infra-red heating is used it is generally applied for 5 to 30 seconds while oven heating is generally applied for 2 to 5 minutes. Instead of developing solely by heat development may also be achieved by use of appropriate organic solvents. These may be applied after the dye has been applied to the product or, more usually, are incorporated into the initial dye composition.
During fixing the dye migrates along the fibres and enters the structure of them and develops a much stronger colour. As a result of this migration it is not essential for the dye initially to cover the entire surface area of the fibres and thus a pile fabric can be dyed merely by printing the dye initially onto the ends of the pile.
The fixed product is then ready for use without any further treatment. Thus it is unnecessary to subject it to further drying and it is unnecessary to wash it.
The invention is of special value when applied to the printing of a flocked product, for instance in the production of a printed floor covering comprising flock fibres bonded to a substrate comprising a sheet of vinyl chloride polymeric composition reinforced by a glass fibre scrim. These and other flocked products are capable of receiving a very clear print without damage to the flock and without the necessity to wash or dry.
The following are some examples:

Example 1

A woven cotton fabric of 180 g/m² is coated with an acrylic latex at 150 g/m² (dry weight) and then flocked electrostatically with 1.0 mm 3.3 decitex precision cut nylon 66 flock. The material is flocked to maximum density, which is about 120 g/m². The material is dried in an oven at 140°C. The product is then roto gravure printed in two colours using inks comprising 3% transferable dyestuff, 3% ethyl cellulose, 47% toluene and 47% industrial methylated spirit. The rate of application is 9.3g/m² and the amount of dye applied is 0.28 g/m . The printed fabric is heated in an oven for five minutes at 180°C to fix the dye and develop the colours. The product is suitable for use as an upholstery fabric.

Example 2

A product is prepared and printed as in Example 1, but the colour is developed by passing the material under a bank of infra-re.d heaters. The material may or may not be embossed during this process. The product is again suitable for use as an upholstery fabric.

Example 3

A non-woven glass web of 35 g/m² is encapsulated in plasticised PVC, which is then cured in the normal way. This material is then coated with a PVC plastisol adhesive at 400 g/m² and flocked electrostatically with 2.0 mm 22 decitex precision cut nylon 66 flock. The material is flocked to maximum density which is about 250 g/m². The material is heated in an oven at 180°C - 200°C to cure the adhesive. The product is then roto gravure or screen printed using inks comprising 10% transferable dyestuff 10% ethyl cellulose, 40% toluene and 40% industrial methylated spirit. The rate of application is9.3g/m² and the amount of dye applied is 0.93g/m² The printed material is heated at 140°C and passed immediately under a bank of infra-red heaters to fix the dye and develop the colour. The product is suitable for use as a floorcovering.

Example 4

A woven polyester fabric of 180 g/m is printed in five colours by roto gravure using inks comprising 5% transferable dyestuff, 10%.ethyl cellulose, 43% toluene and 42% industrial methylated spirit. The rate of application is9.3g/m²and the amount of dye applied is0.47g/m² The printed fabric is heated in an oven for 2½ minutes at 190°C to fix the dye and develop the colours. The product is suitable for use as a curtain or upholstery fabric.

Example 5

A woven 67% polyester/33% cotton fabric of 180 g/m²is treated as in Example 4 and again the product is suitable for use as a curtain or upholstery fabric.

Example 6

A woven nylon fabric of about 85 g/m²is printed in four colours by roto gravure using inks as in Example 4. The printed fabric is heated in an oven for four minutes at 180°C to fix the dye and develop the colours. The product is suitable for use as a curtain or upholstery fabric.

Example 7

A woven 67% polyester/33% cotton fabric of about 130 g/m²is coated with a foamed polyvinyldene chloride latex applied at 120 gsm (dry weight). The coated fabric is then printed on the fabric side as in Example 4. The material is heated in an oven for 2½ minutes at 180°C and passed under a bank of infra-red heaters to fix the dye and develop the colours. The product is an upholstery fabric which has a degree of flame retardancy.

Example 8

A woven cotton fabric of 200 gsm is coated with an acrylic latex at 160 gsm and then flocked electrostatically with 100 gsm of 1 mm 3 denier precision cut nylon flock. The product is then gravure printed in two colours using inks comprising 5% transferable dyestuff, 10% ethyl cellulose and 85% industrial methylated spirit. The printed fabric is heated in an oven for four minutes to 180°C to fix the dye. The product is suitable for use as an upholstery fabric.

Example 9

A non-woven glass fibre substrate is coated with a plastisol adhesive at 200 gsm and is then flocked with 2 mm 14 denier precision cut nylon,flock. It is printed and heated as in Example 8 and produces material suitable for use as a floorcovering.

Example 10

A woven nylon fabric of about 50g/m² is printed in four colours by flexographic printing using inks similar to those described in Example 8. The fabric is then heated for 4 minutes at 180°C. The product is suitable for use for garments or as a soft furnishing fabric.

Claims

1. A process of dyeing a textile product with a dyestuff that is substantive to the product and which comprises applying onto the product a powdered or liquid composition containing the dyestuff and thereby removably depositing the dyestuff on the product, and then fixing the dyestuff to the product characterised in that the fixing is conducted in the absence of water and the fixing causes substantially all the applied dyestuff to become fixed permanently to the product.

2. A process according to claim 1 characterised in that the dyestuff is a dyestuff that is capable of being heat transfer printed onto the product and the fixing is effected by dry heating the product at a temperature at which the said heat transfer printing can occur and which is preferably between 160 and 250°C.

3. A process according to any preceding claim characterised in that the amount of dyestuff applied to the product is from 0.05 to 1.0 g/m², preferably 0.1 to 0.7 g/m².

4. A process according to any preceding claim characterised in that the composition is a liquid composition comprising the dyestuff as a dispersion in a substantially non-aqueous organic solvent.

5. A process according to claim 4 characterised in that the composition contains 0 to 10% by weight binder and 1 to 10% by weight of the dyestuff, preferably 1 to 5% by weight binder and 1 to 5% by weight dyestuff.

6. A process according to claim 4 or claim 5 characterised in that the composition is applied at a rate 2 2 of 3 to 25 g/m , preferably 7 to 15 g/m .

7. A process according to claim 1 characterised in that the textile product is a flocked product comprising flock fibres bonded to a substrate that is selected from textiles and fibre reinforced plastics sheets and in which the dyestuff is a heat transferable dyestuff and is applied by printing onto the flock fibres a liquid composition consisting of 1 to 5% by weight dispersed dyestuff, 1 to 5% by weight binder and the remainder being substantially non-aqueous organic solvent, and the fixing is effected by dry heating the printed product at 160 to 250°C for 5 seconds to 5 minutes, and in which the amount of liquid composition that is printed is below 25 g/m² and the amount of dyestuff that is printed is 0.1 to 0.7 g/m².

8. A process according to any of claims 4.to 7 characterised in that 25 to 100% of the solvent by weight is a solvent boiling at below 80°C and 0 to 75% by weight is a solvent boiling at 80°C to 150°C, the solvent preferably being a mixture of ethanol and toluene in proportions by weight from 2:1 to 1:2.

9. A process according to any preceding claim characterised in that the composition containing the dyestuff is applied by printing, preferably gravure printing.

10. A process according to any preceding claim characterised in that the textile product is a flocked product.