Patent Application
20060070192
The present invention relates to dyeing or coloring of fabrics and non-fabrics, more particularly to a dyeing process concerning the usage of a glue layer applied over a fabric or a non-fabric.
The dyeing of fabrics and non-fabrics of the prior art is not only for ornamental purposes, such as coloring, adding patterns and changing touch, but also for functional purposes, such as enhancing wear-resistance, water-resistance while maintaining reasonable permeability and ventilation.
The dyeing process of the prior art, such as that applied to non-fabric artificial leather, utilizes PU resin to mix a solvent, such as benzyl, DMF and MEK . . . etc., and a colorant and thereby form a colored film over a substrate material. However, this conventional process is disadvantageous in that color tones are difficult control and that the colorant is susceptible to the solvent and the high operational temperature, resulting in a departure of the dyeing material from the substrate material, therefore called “migration”.
Further, because of growing emphasis on environmental protection, the choice of substrate film materials for dyeing is restricted; for example, in developed countries adopting the EN71 Europe standards, products having PVC films are already banned. As a substitute, thermoplastic polyurethane (TPU) invented in 1937 has become popular due to its environmental friendliness and its superiorities over PVC. TPC film is wear-resistant, cold-resistant, aging-resistant, biocompatible, ventilating, permeable, water-resistant and oil-resistant; its permeability can be as high as 10000. The molecular structure of TPU consists of simple atoms such as carbon, hydrogen, oxygen and nitrogen, and therefore it won't produce hazardous pollutants when incinerated. TPU can be easily decomposed and recycled in 3 to 5 years when buried in the ground. As further advantage, TPU does not irritate allergic reactions in human body.
However, even the material for substrate film used in dyeing is improved, the production cost for dyeing is still high, because that the conventional dyeing process includes adding colorant into the substrate film material. If a change in dyeing color is required, the machine producing the substrate films has to be cleaned thoroughly the variation in colors is restricted. Therefore, in consideration of controlling cost, a minimum economic order quantity is need, and variation in colors is restricted.
To cut down the production cost and to increase the flexibility of selecting colors, printing machines is used to directly print desired colors on substrate materials. This method comprises the steps of laying a surface layer and an adhesive layer on a piece of insulating paper, pressing the paper on a fabric and striping the paper from the fabric; the method is suitable for soft layers. A solvent of resin (5000˜15000 mPa.s) of low viscosity is applied on an insulting paper, After being heated, the paper is applied with another layer of adhesive material so as to attach on a fabric.
However, the above two dyeing methods require solvents, and the colorants attached to the fabric products thereby produced is of lower adhesive force, lower water and sunlight resistance and therefore lower price. Since solvents are used in the coloring process, poisonous gases are produced at the same time, which needs a corresponding recycling device and therefore raises the production cost. There is always a risk of industrial hazards due to incomplete processing of the poisonous gaseous pollutants.
Also, the improvements of the prior art for dyeing usually emphasize on the glue materials or coloring materials. The improvement for the process is seldom. Accordingly, the present invention provides an innovative dyeing method.
The primary objective of the present invention is to provide a dyeing method utilizing a covalent bond between TPU and water soluble dyes, wherein the gluing process and the coloring process are independent, and whereby the goals of lowing cost and environmental protection can be achieved.
The method comprises the steps of laying a substrate film made of melted TPU on a surface of a substrate material (a fabric or a non-fabric), cooling the film, coloring the film with a water soluble dyes that are free of solvents, washing extra dyes off the film, and drying the substrate material.
Compared with the methods of the prior art, the present invention has the following advantages.
The dyeing method of the present invention comprises two independent steps: laying substrate film and coloring, whereby small amounts of coloring can be done without too much a production cost; therefore, a substantial economic order quantity is not needed. Further, the covalent bond between the water soluble dyes and the substrate film greatly enhance the adhesion of the dyes.
Since the water soluble dyes do not contain solvents, the product thereby produced is free from pollutant emission, which is environmentally friendly.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings.
Referring to
coating 10; laying a TPU film over a substrate material, which can be a fabric or a non-fabric;
cooling 20 cooling down the substrate material coated with the TPU film;
coloring 30; using water soluble dyes that are free of solvents to color the substrate material by a covalent bond between the dyes and the TPU film after the film thereon is cooled; and
washing and drying 40; washing extra dyes off the substrate material and drying the material so as to enhance adhesion of the dyes.
Further, to attain water and air permeability of various degrees, gluing wheel can be applied in the step of coating 10.
To produce stereo patterns on the substrate material, a pressing wheel can be used after the TPU film is cooled.
Further, it should be noted that, because of the TPU film structure of the present invention, the dyes completely cover the surface of a substrate material while leaving the pores on the surface unblocked, therefore maintaining the ventilation function of the original fabric/non-fabric. The coloring methods by press-printing or dry-adhesion will change the water and air permeability since some pores thereon are blocked.
It is also worth mentioning that the chemical substances used to assist coloring or fixing color tones in the conventional dyeing can also be used in the present invention.
Further, fixing chemicals can be used in this method to make the product more wash-resistant.
According to the above preferred embodiment, the present invention emphasizes the choice of dyes. A proper dye must be able to be attached onto a TPU film through a covalent bond and must be free from solvents which would induce pollutants hazardous to the environment. Also, since the coloring step is proceeded after the formation of the TPU film, the substrate material coated with the film can be handled independently.
In another preferred embodiment, a TPU film is adhered to a substrate material using a gluing substance, and then the step of coloring is applied. The difference of this preferred embodiment from the dry adhesion of the prior art is the TPU film is transparent when adhered to the substrate material. Therefore, the air and water permeability of the product can be controlled later in the colorings step. Also in the dry adhesion of the prior art, the residues of poisonous solvents cannot be removed from the product by washing.
The present invention is thus described, and it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
