Process for treating textile substrates

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority to U.S. provisional patent application serial no. 60/241,262 filed Oct. 18, 2000, herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally a process for treating textile substrates, and more particularly to a process for treating a textile substrate in treatment bath having a transport material entrained therein, the transport material having a treatment material dissolved, dispersed or suspended therein. In a preferred embodiment, the process comprises treating a textile substrate in supercritical fluid carbon dioxide (SCF—CO

2

).

BACKGROUND ART

It will be appreciated by those having ordinary skill in the art that conventional aqueous dyeing processes for textile substrates generally provide for effective dyeing, but possess many economic and environmental drawbacks. Particularly, aqueous dye baths that include organic dyes and co-solvents must be disposed of according to arduous environmental standards. Compliance with environmental regulations and process heating requirements thus drive up the costs of aqueous textile dyeing to both industry and the consuming public alike. Accordingly, there is a substantial need in the art for an alternative dyeing process wherein such problems are avoided.

One alternative to aqueous dyeing that has been proposed in the art is the dyeing of textile substrates in a supercritical fluid. Particularly, textile dyeing processes using supercritical fluid carbon dioxide (SCF—CO

2

) have been explored.

However, those in the art who have attempted to treat textile substrates in SCF—CO

2

have encountered a variety of problems. These problems include, but are not limited to, “crocking” (i.e. tendency of a dye to smudge when a dyed article is touched) of a dye on a dyed textile article; unwanted deposition of the dye onto the article and/or onto the dyeing apparatus during process termination; difficulty in characterizing solubility of the dyes in SCF—CO

2

; insolubility of many dyes and other treatment materials in CO

2

; difficulty introducing the dyes into the SCF—CO

2

flow; difficulty in preparing the dyes for introduction into the dyeing process; high pressure and temperature requirements for solubility; and trimer (cyclic oligomer) extraction from polyester at high temperature. These problems are exacerbated when attempts to extrapolate from a laboratory process to a plant-suitable process are made.

Poulakis et al.,

Chemiefasern/Textilindustrie

, Vol. 43-93, February 1991, pages 142-147 discuss the phase dynamics of supercritical carbon dioxide. An experimental section describing an apparatus and process for dyeing polyester in supercritical carbon dioxide in a laboratory setting is also presented. Thus, this reference only generally describes the dyeing of polyester with supercritical carbon dioxide in the laboratory setting and is therefore believed to be limited in practical application.

U.S. Pat. No. 5,199,956 issued to Schlenker et al. on Apr. 6, 1993 describes a process for dyeing hydrophobic textile substrate with disperse dyes by heating the disperse dyes and textile substrate in SCF—CO

2

with an azo dye having a variety of chemical structures. The patent thus attempts to provide an improved SCF—CO

2

dyeing process by providing a variety of dyes for use in such a process.

U.S. Pat. No. 5,250,078 issued to Saus et al. on Oct. 5, 1993 describes a process for dyeing hydrophobic textile substrate with disperse dyes by heating the disperse dyes and textile substrate in SCF—CO

2

under a pressure of 73 to 400 bar at a temperature in the range from 80° C. to 300° C. Then the pressure and temperature are lowered to below the critical pressure and the critical temperature, wherein the pressure reduction is carried out in a plurality of steps.

U.S. Pat. No. 5,578,088 issued to Schrell et al. on Nov. 26, 1996 describes a process for dyeing cellulose fibers or a mixture of cellulose and polyester fibers, wherein the fiber material is first modified by reacting the fibers with one or more compounds containing amino groups, with a fiber-reactive disperse dyestuff in SCF—CO

2

at a temperature of 70-210° C. and a CO

2

pressure of 30-400 bar. Specific examples of the compounds containing amino groups are also disclosed. Thus, this patent attempts to provide level and deep dyeings by chemically altering the fibers prior to dyeing in SCF—CO

2

.

U.S. Pat. No. 5,298,032 issued to Schlenker et al. on Mar. 29, 1994 describes a process for dyeing cellulosic textile substrate, wherein the textile substrate is pretreated with an auxiliary composition that promotes dye uptake subsequent to dyeing, under pressure and at a temperature of at least 90° C. with a disperse dye from SCF—CO

2

. The auxiliary composition is described as being preferably polyethylene glycol. Thus, this patent attempts to provide improved SCF—CO

2

dyeing by pretreating the material to be dyed.

Despite extensive research into SCF—CO

2

textile treatment processes, there remains room for improvement in the development of a process for treating a textile substrate with a textile treatment material. A process for treating a textile substrate would be particularly desirable in a plant-scale application of an SCF—CO

2

textile treatment process. Therefore, the development of such a process meets a long-felt and significant need in the art.

SUMMARY OF THE INVENTION

A process for treating a textile substrate is disclosed. The process comprises providing a textile substrate; providing a treatment bath; entraining a transport material in the treatment bath wherein the transport material further comprises a treatment material dissolved, dispersed or suspended therein and wherein the transport material is substantially immiscible with the treatment bath; and contacting the textile substrate with the transport material in the treatment bath to thereby treat the textile substrate with the treatment material in the transport material. In a preferred embodiment, the process comprises treating a textile substrate in supercritical fluid carbon dioxide (SCF—CO

2

).

Accordingly, it is an object of the present invention to provide a novel process for treating a textile substrate. This object is achieved in whole or in part by the present invention.

An object of the invention having been stated hereinabove, other objects will be evident as the description proceeds, when taken in connection with the accompanying Drawings and Laboratory Examples as best described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B

is a detailed schematic of a system suitable for use in the textile treatment process of the present invention;

FIG. 2

is a detailed perspective view of a system suitable for use in the textile treatment process of the present invention;

FIG. 3

is a schematic of an alternative embodiment of a system suitable for use in the textile treatment process of the present invention;

FIG. 4

is a schematic of another alternative embodiment of a system suitable for use in the textile treatment process of the present invention;

FIG. 5

is a schematic of a system for introducing textile treatment materials into a textile treatment system in accordance with a process of the present invention;

FIG. 6

is a schematic of a system for introducing textile treatment materials into a textile treatment system in accordance with a process of the present invention; and

FIG. 7

is a schematic of a textile treatment system suitable for use in a process of the present invention, wherein the system includes a treatment material preparation subsystem and a dyeing/treatment subsystem.

DETAILED DESCRIPTION OF THE INVENTION

A process for treating a textile substrate is disclosed. The process comprises providing a textile substrate; providing a treatment bath; entraining a transport material in the treatment bath wherein the transport material further comprises a treatment material dissolved, dispersed or suspended therein and wherein the transport material is substantially immiscible with the treatment bath; and contacting the textile substrate with the transport material in the treatment bath to thereby treat the textile substrate with the treatment material in the transport material.

The process of the present invention can further comprise an optional drying step. Optionally, the drying step can be accomplished using a conventional apparatus or system, such as dielectric drying (radio-frequency or microwave), a centrifugal system or other thermal or mechanical/thermal system. Preferably, however, drying is accomplished by a process step, such as by circulating fresh treatment bath (i.e. having substantially no transport material entrained therein) through the textile substrate to remove excess transport material (e.g. water) present in the textile substrate. Optionally, bath temperature can be increased to enhance the drying step.

In a preferred embodiment, the transport material comprises water and the treatment bath comprises near-critical liquid CO

2

or SCF—CO

2

. More preferably, the water is present in the near-critical liquid CO

2

or SCF—CO

2

treatment bath in a trace amount. Thus, a major advantage of a preferred embodiment of the present inventive process is that it eliminates virtually all water usage and attendant waste treatment required in conventional textile dyeing processes. The process also has great advantage in that the present inventive process can easily apply dyes of very low affinity, normally not suitable for batch/exhaust dyeing.

I. Process of the Present Invention

In the process of the present invention, the treatment bath can comprise any fluid that is (1) inert with respect to the dye, transport material and textile substrate and (2) has physical properties (density, viscosity, etc.) sufficient to entrain and transport finely distributed droplets or agglomerations of dye- or chemical-laden transport material. Near-critical liquid CO

2

or SCF—CO

2

represent preferred embodiments of such a fluid that is safe, economical and environmentally acceptable. Nitrogen, hexane and propane are additional examples. High-density fluids are preferred.

By the term “high-density” (for the non-aqueous bath liquid) it is meant sufficient to entrain, propel and inhibit settling of the droplets of transport material. The required magnitude of the density of the bath liquid can depend on the velocity of the bath liquid; the viscosity of the bath liquid; the density of the entrained transport material droplets; the size of the entrained transport material droplets; the design of the treatment machine; and on combinations of any of these characteristics.

In a preferred embodiment, the process uses small amounts (trace amounts) of a transport material that is substantially immiscible in the treatment bath. By the term “substantially immiscible” it is meant that the transport material and the treatment bath do not mix to form a solution, i.e., they are substantially insoluble in each other and usually exist in separate phases when mixed. Representative combinations thus included hydrophobic and hydrophilic materials, polar and non-polar materials and/or aqueous and non-aqueous materials. For example, the transport material can comprise an aqueous material (e.g., water), while the treatment bath comprises a non-aqueous material (e.g., SCF—CO

2

).

Additionally, the term “transport material” is meant to refer to a material that (1) acts as a solvent, as a dispersing agent or as a suspending agent for the dye or other treatment materials; (2) is capable of wetting the textile substrate; and (3) is a liquid under the treatment conditions. Table 1 contrasts the action of conventional carriers that are used in conventional dyeing processes with that of a transport material of the present invention.

TABLE 1

Carrier vs. Transport Material

Feature

Carrier

Transport Material

Entrainment

Emulsion of oil-type material in

Entrained droplets of

water. Carriers are substantially

water-type material in

non-functional in SCF-CO

2

.

SCF-CO

2

. No emulsi-

Neither the carrier-active

fier is involved. The

material (e.g. 1,2,4

treatment bath is not

trichlorobenzene (TCB)), nor the

an emulsion; rather,

emulsifier systems (e.g.

the treatment

ethoxylated nonyl phenol)

bath comprises

are suitable for SCF-CO

2

use.

entrained droplets.

Dye interaction

Carriers do not dissolve non-

Treatment material

ionic dyes within the

(e.g. dye) is dissolved,

emulsified droplets.

dispersed or suspended

in the entrained drop-

lets; however, the

treatment material is

sparingly soluble in

the SCF-CO

2

.

Persistence

Carriers produce persistent

Once removed, the

effects in fibers. For example,

transport material (e.g.

polyester can be treated with

aqueous transport

carrier (1,2,4 TCB) then washed

material) preferably

thoroughly so that

has no permanent

no trace of the carrier

effect.

remains. Then the fiber can

be dyed and will respond

as if carrier were still

present in the bath.

Glass transition

Carriers reduce the glass

Cotton and wool have

of fibers

transition temperature of fibers,

no glass transition

and produce permanent

temperature. They

morphological changes.

decompose upon heat-

ing (or burns)-they

do not melt or undergo

a glass transition.

Therefore, carriers

would have no func-

tion with respect to

cotton, wool, silk

or similar fibers

Action

Carriers act in the fiber. A

The transport material

polyester fiber placed in a dye

acts in the bath to

bath containing fiber will absorb

deliver the treatment

essentially all of the carrier-

material to the

active material. The action of

textile substrate as

the carrier is done by the

entrainment of mater-

absorbed material in the fiber.

ial-laden droplets.

Continuous

The continuous phase is

The continuous phase

phase

aqueous, i.e. a conventional

is preferably non-

aqueous treatment (e.g.

aqueous.

dyeing) bath.

A preferred transport material comprises water or comprises an aqueous solution, an aqueous dispersion, an aqueous emulsification, and/or an aqueous suspension, such as: water/alcohol, water/reducing or oxidizing agent, water/buffer (for pH control), water/salt, or water/surfactant, wherein the surfactant is soluble in water and preferably not soluble in SCF—CO

2

. Though less preferred, other transport materials include, but are not limited to: alcohols, poly-alcohols, fluorocarbons, chlorocarbons, hydrocarbons, amines, esters and amides.

Any dyes, chemicals or other textile treatment materials can be used in the process of the present invention so long as the dyes or chemicals are (1) soluble in the transport material and (2) capable of dyeing or treating the textile substrate. An example is the use of direct dyes to dye cotton in SCF—CO

2

with water as the transport material. Another example is the dyeing of wool in SCF—CO

2

with acid dyes, using water as the transport material. The transport material can be conveniently introduced by using it to prewet the textile substrate, but can also be introduced by injection into the treatment bath, along with or separately from the dye or treatment chemical, at a preferred point in the process, i.e., with respect to location and time.

Dyes that can be used to carry out the present invention include, but are not limited to, acid, basic, azo (mono, di, poly), carbonyl, sulfur, methine, and triarylcarbonium dyes. The dyes can be anionic (acid including non-metallized acid, mordant, direct, reactive), cationic (brilliant color with good color fastness), direct (substantive character without mordants), dispersive (very low solubility in dyebath, substantive toward hydrophobics), and azoid (azo containing small molecule permeation followed by a reaction to form a larger substantive dye) dyes.

Materials that can be dyed by the process of the present invention include, but are not limited to, fiber, yarns and fabrics formed from polyester, nylon, acrylic fibers, acetate (particularly cellulose acetate), triacetate, silk, rayon, cotton and wool, including blends thereof such as cotton/polyester blends, as well as leather. In particular, textile substrates are treated by the process, and encompass a large number of materials. Such substrates are those formed from textile fibers and precursors and include, for example, fabrics, garments, upholstery, carpets, tents, canvas, leather, clean room suits, parachutes, yarns, fibers, threads, footwear, silks, and the other water sensitive fabrics. Articles (e.g., ties, dresses, blouses, shirts, and the like) formed of silk or acetate can also be treated via the process of the present invention.

In one embodiment, the process of the present invention pertains to the treatment of hydrophilic fibers, including natural fibers (e.g., cotton, wool and silk) in a non-aqueous fluid treatment bath (e.g., supercritical fluid carbon dioxide, SCF—CO

2

) with textile dyes and other textile treatment materials. The treatment is accomplished by entraining dye- or chemical-laden transport materials in an inert treatment bath in a manner that delivers the dye- or chemical-laden transport materials to the textile substrate to be dyed or treated.

The amount of transport material employed in the process of the present invention can vary in accordance with the textile substrate and the treatment conditions, among other variables. For example, the amount of transport material includes the amount that is sorbed by the textile substrate as well as the amount of transport material that is free to circulate and to form entrained droplets in the system. Different fibers and different forms of textile substrates (e.g. yarn package, fabric, etc) will sorb different amounts of water. Wool will absorb most, cotton a little less. Nylon and acrylic will absorb less than cotton and wool. And polyester will absorb almost none. Representative amounts of transport material (e.g. water) are disclosed in the Laboratory Examples presented below.

Thus, the term “trace amount” comprises an amount of transport material needed to result in enough entrainment to accomplish the treatment process plus any additional transport material needed directly in the treatment process. For example, some additional amount of transport material (e.g. water), beyond entrainment needs, can be employed to “swell” fibers such as cellulosics (e.g. cotton) so that they can be treated, but there would be no such need in the case of treating polyester. The amount of free transport material is preferably equal to or less than the weight of the textile substrate being dyed, but will also depend on the particular dye or other treatment material being applied.

The terms “supercritical fluid carbon dioxide” or “SCF—CO

2

” are meant to refer to CO

2

under conditions of pressure and temperature which are above the critical pressure (P

c

=about 73 atm) and temperature (T

c

=about 31° C.). In this state the CO

2

has approximately the viscosity of the corresponding gas and a density that is intermediate between the density of the liquid and gas states.

The terms “near-critical liquid carbon dioxide” or “NCL-CO

2

” are meant to refer to liquid CO

2

under conditions of pressure and temperature that are near the critical pressure (P

c

=about 73 atm) and temperature (T

c

=about 31° C.).

The term “textile treatment material” means any material that functions to change, modify, brighten, add color, remove color, or otherwise treat a textile substrate. Examples comprise UV inhibitors, lubricants, whitening agents, brightening agents and dyes. Representative fluorescent whitening agents are described in U.S. Pat. No. 5,269,815, herein incorporated by reference in its entirety. The treatment material is, of course, not restricted to those listed herein; rather, any textile treatment material compatible with the treatment process is provided in accordance with the present invention.

Representative treatment materials also include but are not limited to antimicrobial agents (e.g., algaecides, bacteriocides, biocides, fungicides, germicides, mildewcides, preservatives); antimigrants (fixing agents for dyes); antioxidants; antistatic agents; bleaching agents; bleaching assistants (stabilizers and catalysts); catalysts; lubricants (coning and winding); crease-resisting finishing agents (anticreasing agents, durable press agents); desizing agents (enzymes); detergents; dye fixing agents; flame retardants; gas fading inhibitors (antifume agents, atmospheric protective agents); fumigants (insecticides and insect repellents); leveling agents; oil repellents; oxidizing agents; penetrating agents (rewetting agents, wetting agents); polymers (resins); reducing agents; retarding agents; scouring agents; soaps; softeners; soil release/stain resistant finishes; souring agents; stripping agents; surfactants; ultraviolet absorbers/light stabilizers; water repellents; waxes; whitening finishes; fluorescent finishes; and combinations of any of the foregoing.

Preferably, the process of the present invention is free of a surfactant that is soluble in the treatment bath, e.g., a surfactant that is soluble in SCF—CO

2

. Representative embodiments of such surfactants are disclosed in U.S. Pat. No. 6,010,542 issued to DeYoung et al. on Jan. 4, 2000. However, optionally, the transport material can further comprise a surfactant that is substantially insoluble in the treatment bath, but that is soluble in the transport material, e.g., a surfactant that is soluble in water but sparingly soluble in SCF—CO

2

.

The term “dye” is meant to refer to any material that imparts a color to a textile substrate. Preferred dyes comprise water-soluble and water-dispersible dyes, and many representative dyes are identified in the Colour Index, an art-recognized reference manual.

The term “hydrophilic textile fiber” is meant to refer to any textile fiber comprising a hydrophilic material. More particularly, it is meant to refer to natural and synthetic hydrophilic fibers that are suitable for use in textile substrates such as yarns, fabrics, or other textile substrate as would be appreciated by one having ordinary skill in the art. Preferred examples of hydrophilic materials include cellulosic materials (e.g. cotton, cellulose acetate), wool, silk, nylon and acrylic.

The term “hydrophobic textile fiber” is meant to refer to any textile fiber comprising a hydrophobic material. More particularly, it is meant to refer to hydrophobic polymers that are suitable for use in textile substrates such as yarns, fibers, fabrics, or other textile substrate as would be appreciated by one having ordinary skill in the art. Preferred examples of hydrophobic polymers include linear aromatic polyesters made from terephathalic acid and glycols; from polycarbonates; and/or from fibers based on polyvinyl chloride, polypropylene or polyamide. A most preferred example comprises 150 denier/34 filament type 56 trilobal texturized yarn (polyester fibers) such as that sold under the registered trademark DACRON® Type 54,64 (filaments) and 107W (spun/staple)(E.I. Du Pont De Nemours and Co.). Glass transition temperatures of preferred hydrophobic polymers, such as the listed polyesters, typically fall over a range of about 55° C. to about 65° C. in SCF—CO

2

.

The term “sparingly soluble”, when used in referring to a solute, means that the solute is not readily dissolved in a particular solvent at the temperature and pressure of the solvent. Thus, the solute tends to fail to dissolve in the solvent, or alternatively, to precipitate from the solvent, when the solute is “sparingly soluble” in the solvent at a particular temperature and pressure.

The term “crocking”, when used to describe a dyed article, means that the dye exhibits a transfer from dyed material to other surfaces when rubbed or contacted by the other surfaces.

Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

II. Representative Textile Treatment Systems

Any machine that has a suitable mechanical configuration can be used in the practice of the process of the present invention. For instance, in each of the Examples presented below, a package dyeing SCF—CO

2

system was employed. A representative embodiment of such a system is disclosed in U.S. Pat. No. 6,048,369, issued Apr. 11, 2000 to Smith, et al., herein incorporated by reference in its entirety. Other representative systems are disclosed in U.S. Pat. Nos. 5,298,032; 5,518,088; and 6,010,542; and the contents of each of these patents are incorporated herein by reference in their entirety.

Referring now to

FIGS. 1A

,

1

B and

2

, a system suitable for use in the practice of the process of the present invention is referred to generally as

10

. In the following detailed description, the parts of system

10

that are primarily involved in the process of the present invention are described. Additionally, a legend describing other parts of system

10

is provided in Table 2 below. For convenience, system

10

is referred to as an SCF—CO

2

dyeing system; however, system

10

can be adapted for use with any treatment material and any treatment bath.

TABLE 2

LEGEND FOR

FIGS. 1A

, 1B AND 2

Item No.

Name

 10

Supercritical CO

2

Treatment System

 12

CO

2

Supply Cylinder

 14

Line Section

 16

Pressure Regulating Valve

 18

Pressure Indicator

 20

Pressure Alarm

 22

Pressure Relief Valve

 24

Needle Valve

 26

Condenser (Shell-in-Tube Heat Exchanger)

 28

Chiller

 30

Turbine Flow Meter

 32

Temperature Element (Indicator)

 34

System Pressurization Pump (Positive Displacement)

 36

Pressure Control Valve

 38

Static Mixer

 40

Electric Preheater

 42

Temperature Alarm

 44

Over-Temperature Switch

 46

Needle Valve

 50

Co-Solvent Pump (Positive Displacement)

 52

Needle Valve

 54

Needle Valve

 56

Check Valve

 58

Rupture Disk

 60

Temperature Element (Indicator)

 62

Temperature Controller

 64

Needle Valve

 66

Needle Valve

 68

Check Valve

 70

Dye-Add Vessel

 71

Dye-Add Vessel Jacket

 72

Temperature Element (Indicator)

 74

Temperature Alarm

 76

Temperature Controller

 78

Control Valve (Temperature-Controlled)

 80

Control Valve (Temperature-Controlled)

 82

Control Valve (Temperature-Controlled)

 84

Control Valve (Temperature-Controlled)

 86

Rupture Disk

 88

Pressure Indicator

 90

Pressure Alarm

 91

Line Section

 92

Ball Valve (2-Way)

 93

Ball Valve

 94

Ball Valve (2-Way)

 96

Sight Glass

 98

Circulation Pump (Centrifugal)

100

Rupture Disk

102

Ball Valve (2-Way)

104

Ball Valve (2-Way)

106

Dyeing Vessel

107

Dyeing Vessel Jacket

108

Line Section

109

Needle Valve

110

Pressure Indicator

114

Ball Valve (2-Way)

116

Ball Valve (2-Way)

118

Coriolis Flow Meter

120

Ball Valve (3-Way)

122

Temperature Element (Indicator)

124

Temperature Alarm

126

Temperature Controller

128

Pressure Indicator

130

Pressure Alarm

132

Control Valve (Temperature-Controlled)

134

Control Valve (Temperature-Controlled)

136

Control Valve (Temperature-Controlled)

138

Control Valve (Temperature-Controlled)

140

Rupture Disk

142

Needle Valve

144

Needle Valve

146

Line Section

148

Needle Valve

150

Temperature Element (Indicator)

152

Needle Valve

154

Pressure Control Valve

156

Separator Vessel

158

Pressure Indicator

160

Pressure Alarm

162

Temperature Element (Indicator)

164

Rupture Disk

166

Pressure Control Valve

168

Needle Valve

170

Needle Valve

172

Filter

174

Filter

176

Pressure Relief Valve

178

Check Valve

180

Line Section

182

Check Valve

184

Line Section

Referring particularly to

FIGS. 1A

,

1

B and

2

, operation and control of the SCF—CO

2

dyeing system

10

optionally encompasses three distinct equipment subsystems. The subsystems include filling and pressurization subsystem A, dyeing subsystem B, and venting subsystem C. Carbon dioxide is introduced into system

10

via CO

2

supply cylinder

12

. Preferably, supply cylinder

12

contains liquid carbon dioxide. Thus, liquid CO

2

enters the filling and pressurization subsystem A from the supply cylinder

12

through line section

14

and regulating valve

16

and is cooled in condenser

26

by a water/glycol solution supplied by chiller

28

. The CO

2

is cooled to assure that it remains in a liquid state and at a pressure sufficiently low to prevent cavitation of system pressurization pump

34

.

Continuing with

FIGS. 1A

,

1

B and

2

, turbine flow meter

30

measures the amount of liquid CO

2

charged to dyeing system

10

. Pump

34

increases the pressure of the liquid CO

2

to a value above the critical pressure of CO

2

but less than the operating pressure for the dyeing system, typically ranging from about 1000 psig to greater that about 4000 psig, depending of the particular textile substrate being dyed or otherwise treated. A side-stream of water/glycol solution from chiller

28

provides cooling for pump

34

. Control valve

36

allows pump

34

to run continuously by opening to bypass liquid CO

2

back to the suction side of pump

34

once the system pressure set point has been reached. This valve closes if the system pressure falls below the set point that causes additional liquid CO

2

to enter the dyeing subsystem B. Optionally, the transport material can be injected into the liquid CO

2

stream by pump

50

at the discharge of pump

34

and mixed in by static mixer

38

.

Continuing with

FIGS. 1 and 2

, liquid CO

2

leaving mixer

38

enters electrical pre-heater

40

where its temperature is increased. Heated and pressurized CO

2

can enter the dyeing subsystem B through needle valve

66

and into dye-add vessel

70

; through needle valve

64

and into dyeing vessel

106

; or through both of these paths. Typically, dyeing subsystem B is filled and pressurized simultaneously through both the dye-add and dyeing vessels

70

and

106

, respectively.

Once a sufficient quantity of liquid CO

2

has been charged to dyeing subsystem B to achieve the operating density, typically a value in the range of 0 to about 0.75 g/cm

3

, preferably about 0.2 to about 0.7 g/cm

3

, more preferably to about 0.25 to 0.50 g/cm

3

, circulation pump

98

is activated. Optionally, system

10

is configured so that circulation pump

98

first drives the flow of liquid CO

2

through the dyeing vessel

106

, which contains a textile substrate that has been wetted out with transport material. Contacting of the liquid CO

2

flow with the textile substrate that has been wetted out with transport material entrains the transport material into the liquid CO

2

flow.

Once circulation is started, heating of subsystem B is initiated by opening control valves

78

and

84

to supply steam to and remove condensate, respectively, from the heating/cooling jacket

71

on dye-add vessel

70

. Similarly, control valves

132

and

136

are opened to supply steam to and remove condensate from, respectively, the heating/cooling jacket

107

on dyeing vessel

106

. Commercial practice would utilize a heat exchanger in the circulation loop to provide for heating of the CO

2

rather than relying on heating through the vessel jackets

71

and

107

. Heating is continued until the system passes the critical temperature of CO

2

and reaches the operating, or dyeing, temperature, typically ranging from about ambient (e.g., 22° C.-25° C.) to about 130° C., preferably ranging from about 25° C. to about 100° C., more preferably ranging from about 40° C. to about 95° C.

Continuing with FIGS,

1

A,

1

B and

2

, SCF—CO

2

leaving circulation pump

98

passes through sight glass

96

and is diverted, by closing ball valve

94

and opening ball valve

93

, through dye-add vessel

70

where dye is dissolved and/or suspended in the transport material. Transport material-laden SCF—CO

2

passes out of the dye-add vessel

70

through ball valve

92

and flow meter

118

to ball valve

120

. Ball valve

120

is a three-way valve that diverts the SCF—CO

2

flow to the inside or outside of the package loaded in dyeing vessel

106

depending on the direction in which it is set. If ball valve

120

is set to divert flow in the direction of ball valve

104

, and ball valve

104

is open and ball valve

102

is closed, then all of the SCF—CO

2

flow proceeds to the inside of the dye spindle (not shown in

FIGS. 1A

,

1

B and

2

). The flow continues from the inside to the outside of the dye spindle, from the inside to the outside of the dye tube (not shown in

FIGS. 1A

,

1

B and

2

) on which the textile yarn package is wound and out through the textile yarn package to the interior of dyeing vessel

106

. The SCF—CO

2

flow passes out of dyeing vessel

106

, through open ball valves

114

and

116

to the suction of pump

98

, completing a circuit for inside-to-outside dyeing of the yarn package.

If ball valve

120

is set to divert flow in the direction of ball valve

114

, and ball valve

114

is open and ball valve

116

is closed, then all of the SCF—CO

2

flow proceeds to the interior of dyeing vessel

106

and the outside of the textile yarn package. The flow passes through the textile yarn package, continues from the outside to the inside of the dye tube on which the yarn is wound and then passes from the outside to the inside of the dye spindle. The SCF—CO

2

flow exits the interior of the dye spindle and passes through open ball valves

104

and

102

to the suction of pump

98

, which completes a circuit for outside-to-inside dyeing of the textile yarn package.

The SCF—CO

2

flow having treatment material-laden transport material entrained therein is held at values ranging from values of 1 gallon per minute (GPM)/lb of textile or less, to values greater than 15 GPM/lb of textile. The treatment bath flow is periodically switched between the inside-to-outside(I-O) circuit and the outside-to-inside (O-I) circuit to promote uniformity of dyeing of the textile yarn; e.g., 6 min./2 min. I-O/O-I, 6 min./4 min. I-O/O-I, 5 min./5 min. I-O/O-I, etc. This dyeing process is continued with system

10

held at the dyeing temperature, usually about ambient temperature to about 130° C., and preferably about 40° C. to 95° C., until the treatment material in the transport material is exhausted onto the textile substrate to produce an even distribution, typically around 30 minutes.

Continuing with reference to

FIGS. 1A

,

1

B and

2

, venting is initiated by opening needle valve

109

to provide a flow path from the dyeing vessel

106

to control valve

154

. Control valve

154

is opened to set the pressure in dyeing subsystem B and control valve

166

is opened to set the pressure in separator vessel

156

. By adjusting control valves

154

and

166

appropriately, the pressure in the dyeing vessel

106

is reduced at a controlled rate. Dye-add vessel

70

is isolated during venting to prevent any additional dye remaining in dye-add vessel

70

from going into solution in the transport material that is entrained in the SCF—CO

2

. Isolation of dye-add vessel

70

is accomplished by closing ball valves

92

and

93

while opening ball valve

94

to maintain a circulation loop for the dyeing vessel.

During venting SCF—CO

2

flows from dyeing subsystem B through control valve

154

and into separator vessel

156

of venting subsystem C. In separator vessel

156

the pressure is sufficiently low so that the CO

2

is in the gaseous phase and any contaminants, and the treatment material solids collect in separator vessel

156

and gaseous CO

2

exits through control valve

166

. Once the gaseous CO

2

passes through control valve

156

it can be vented to atmosphere by opening needle valve

168

. The gaseous CO

2

can also be recycled to filling and pressurization subsystem A by keeping needle valve

168

closed so that the gaseous CO

2

passes through filters

172

and

174

. Filters

172

and

174

collect any minute amounts of solids that can have escaped separator vessel

156

with the gaseous CO

2

flow. The gaseous CO

2

exiting filters

172

and

174

passes through check valve

178

and enters filling and pressurization subsystem A for re-use in system

10

.

Referring now to

FIG. 3

, an alternative system

10

′ for use in the SCF—CO

2

dyeing process of the present invention is depicted schematically. Generally, however, system

10

′ works in a similar manner as system

10

described above and as depicted in

FIGS. 1 and 2

. System

10

′ includes a CO

2

cylinder

12

′, from which CO

2

flows through check valve

16

′ to a cooling unit

26

′. CO

2

is cooled and pressurized within cooler

26

′ and then is pumped, using positive displacement pump

34

′, into dye injection vessel

70

′. Prior to introduction of CO

2

into vessel

70

′, a dyestuff is placed within vessel

70

′. In dye injection vessel

70

′, the treatment material, i.e., the dyestuff, is dissolved and/or suspended into the transport material, which is preferably water or an aqueous solution. Thus, when CO

2

is introduced into vessel

70

′ the dye-laden transport material is entrained within the SCF—CO

2

flow.

Continuing with

FIG. 3

, the action of pump

34

′ drives the SCF—CO

2

that has dye-laden transport material entrained therein out of dye injection vessel

70

′ through a hand valve

64

′ and a check valve

182

′ into a dyeing vessel

106

′ that contains the textile substrate to be dyed. Dyeing vessel

106

′ is pressurized and heated to SCF dyeing conditions prior to the introduction of the SCF—CO

2

that has dye-laden transport material entrained therein. Steam and/or cooling water are introduced to jacket

107

′ of dyeing vessel

106

′ via valves

132

′ and