Bleaching and dyeing; fluid treatment and chemical modification – Nontextile – dyeing process or product – including inorganic... – Polymer from polyol and a polycarboxylic acid or derivative...
Reexamination Certificate
2001-12-21
2003-11-25
Einsmann, Margaret (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Nontextile, dyeing process or product, including inorganic...
Polymer from polyol and a polycarboxylic acid or derivative...
C008S444000, C008S506000, C008S522000, C008S576000, C008S922000
Reexamination Certificate
active
06652602
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to color dyeing of plastic films, and more particularly, to a dip dye coloring system employing a solution of dye in a carrier comprised at least in part of a high molecular weight polyol and employing ultrasonic application of the dye solution to the film
BACKGROUND OF THE INVENTION
Plastic films, such as polyethylene terephthalate (PET), are in extensive commercial use for a variety of purposes. For many applications, it is desirable to have the film colored. At present, PET films may be colored by a solution dyeing system wherein the dyes are mixed into the melt before the film is extruded; a printing technique wherein color is laid on to the film, then set by heat; and a dip dyeing technique wherein the film is dipped into a vat containing a heated dye solution and is then washed and dried.
Extrusion dyeing yields excellent results, but it is impractical for small quantities or small production runs of the film, and colors cannot easily be changed between runs. The printing technique usually results in having color on one side only of the film, and it is difficult to get truly uniform color, i.e., level dyeing. Colored films produced by the dip dyeing technique tend to change color and/or fade quickly and have a short life span in the original color and/or color intensity.
In conventional dip dyeing of PET film, a continuous web of the film is immersed in and passed through a dye bath that is charged with the dye, a dye carrier, one or more wetting agents, and various processing aids or additives, at a temperature of 140° C. to 180° C. The web is then passed through a washing bath that is charged with solvents to wash excess dye and additives off the web. After washing, the colored film is passed through a drying oven and dried at a temperature of about 180° C.
Dye carriers previously proposed include various ethylene glycols, propylene glycol, the methyl-ethyl-mono- and di-ethers of such glycols and the esters of such glycols; and also glycerol triacetate (triacetin).
U.S. Pat. Nos. 4,047,889, 4,055,054, and 4,115,054 disclose a process for the continuous and waterless dyeing of textile and plastic materials in which the dyestuff is dissolved, suspended or dispersed in a high boiling solvent, such as glycol or glycol ether, for carrying out the dyeing step per se, after which the dyed textile or plastic material is subjected to a washing with a low boiling liquid such as methanol or ethanol or a chlorinated hydrocarbon solvent, and subsequently dried. The entire series of operations is carried out under non-aqueous or substantially non-aqueous conditions with substantially complete recovery and recycling of the used dye stuff, the used high-boiling solvent, and the used low-boiling wash liquid. The entire operation is conducted in a substantially completely closed cyclic system with essentially complete recovery and reuse of the treating liquids.
U.S. Pat. Nos. 5,162,046 and 5,338,318 disclose a method of dyeing PET film wherein the film is submerged in a dye bath of solvent dyes dissolved in a carrier consisting of glycerol triacetate, the dye bath being heated so the film is raised to the glass transition temperature of the film, and the dye and carrier are absorbed into the film. Excess dye and carrier are removed from the surface of the film by a washing bath, and the film is then heated to remove the carrier absorbed in the film without depreciating the dye stuff or the film.
The glycols and glycol-ethers employed as dye carriers pursuant to the above practices, i.e., as described in the first group of patents, are of low molecular weight, e.g. a molecular weight in the order of about 100 or less, to facilitate penetration of the dye bath into the film. However, there is little if any chemical reaction or molecular bonding between the dyes, the carrier and the film, with the result that the low molecular weight carrier and dyes quickly migrate out of the film, causing the film to change color and fade.
The glycerol triacetate employed as the carrier in the second group of patents is of higher molecular weight, e.g., about 218, but diffusion into the film is slow and of low intensity. Also, the triacetate does not have any hydroxol group available for chemical reaction or molecular bonding, with the same result as above, i.e., the carrier and the dyes migrate out of the film, causing the film to change color and fade.
U.S. Pat. No. 4,419,160, entitled Ultrasonic Dyeing of Thermoplastic Non-woven Fabric, discloses a process of applying liquid dye to the ultrasonically bonded point bonds of non-woven fabrics before or at the same time that the crossing points are bonded by ultrasonic energy, such that the energy is used both to bond the points and to drive and fix the dye in the bond points.
Graduate studies at North Carolina State University, Department of Textile Engineering, Chemistry and Science, have explored the use of ultrasonics in the wet processing (dyeing) of textiles.
Despite the foregoing, there remains a significant need for improvement in the color dyeing of plastic films.
OBJECTS OF THE INVENTION
A prime object of the present invention is to provide color-fast dip dyed plastic films.
Another object of the invention is to provide a method of dip-dying plastic films wherein the dye or dyes and dye carrier are chemically, mechanically and/or molecularly bonded to one another and the film for long lasting color fastness.
Yet another object of the invention is to provide a method of dip-dyeing plastic films wherein the dye carrier includes at least one constituent having high molecular weight and at least one free hydroxyl group, capable of mechanically and chemically bonding the dye solution or bath into the molecular structure of the film.
A further object of the invention is to provide a method of dip-dyeing plastic films wherein thermal and ultrasonic energy are utilized to hasten the dyeing process and to enhance the bonding of the dye in the film.
A still further object of the invention is to provide a method of dip-dyeing plastic films that is convenient and economical to practice and that produces economical yet exceedingly high quality dyed films.
SUMMARY OF THE INVENTION
In accordance with the invention, dip dyeing of plastic films is performed utilizing (1) a high molecular weight polyol as the dye carrier or as a constituent of the carrier and (2) heat and ultrasonic energy as mutual forces to drive the dyes and the dye carrier into the film.
Use of a high molecular weight polyol in or as a dye carrier provides a dye system based on molecular interactions, such as hydrogen bonds, fusion and miscibility, by and between the dye or dyes, the carrier or carriers and the film. Thus, the dyed film is color-fast.
Heat in the range of the glass transition temperature and near the melting point of the film, i.e., 100-180° C., causes the film to expand and permits the dye bath to enter into the film structure. Ultrasonic energization and excitation of the bath speeds the rate and degree of penetration of the dye bath into the film, especially the penetration of the high molecular weight polyol into the film. Both energy sources also contribute to molecular bonding of the polyol, the dye or dyes and the film.
Thus, the method is performed rapidly and economically and the resulting film has the prescribed color intensity and color fastness over a prolonged period of time.
The foregoing and other objects and advantages of the invention will become apparent to persons of reasonable skill in the art from the following detailed description, as considered in conjunction with the accompanying drawing.
REFERENCES:
patent: 4047889 (1977-09-01), Hermes
patent: 4055971 (1977-11-01), Hermes
patent: 4115054 (1978-09-01), Hermes
patent: 4419160 (1983-12-01), Wang et al.
patent: 5162046 (1992-11-01), Mercado
patent: 5338318 (1994-08-01), Mercado
patent: 5466722 (1995-11-01), Stoffer et al.
patent: 5560751 (1996-10-01), Hoshiyama et al.
Turner Raymond B.
Yang Xiaoming
Einsmann Margaret
Greer Burns & Crain Ltd.
N.V. Bekaert S.A.
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