Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
2001-06-29
2004-05-25
Yoon, Tae H. (Department: 1714)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C264S173100, C264S175000, C057S002000, C057S310000, C523S351000, C523S353000, C428S365000, C428S395000
Reexamination Certificate
active
06740276
ABSTRACT:
The invention relates to a process for preparation of pigmented shaped articles (e.g., fibers).
Traditionally, fibers have been chemically dyed at the mills. Residual chemicals after the dyeing operations are costly to dispose of and chemical dyeing is expensive. Pigmented or producer colored fibers can be used to avoid the expense of chemically dyeing the fibers, and generally have better characteristics than dyed fibers, including color depth, resistance to fading and bleach resistance.
A number of techniques have been used for introducing color pigments into fibers. For instance, TiO
2
and color pigments may be added to a polyester manufacturing process. EP 1 016 692 and EP 1 016 741 (both incorporated herein by reference) describe use of East Bright (Eastman) and Hostaperm® pigment (Trademark of Hoechst Aktiengesellschaft), referring to Japanese Unexamined Patent Publication 5-262862, which corresponds to U.S. Pat. No. 5,340,909. U.S. Pat. No. 5,340,909 (incorporated herein by reference) describes preparing poly(1,3-propylene terephthalate) using Hostaperm pigments. These pigments are added before polycondensation and preferably with the initial terephthalic acid or lower dialkyl ester of terephthalic acid charge of raw materials. The resultant polyester is disclosed to be useful in making monofilaments. WO 00/26301 (incorporated herein by reference) teaches preparing a polyester resin composition comprising polytrimethylene terephthalate and TiO
2
. The composition is stated to be useful in spinning fibers. U.S. Pat. No. 5,872,204 (incorporated herein by reference) describes preparing polytrimethylene terephthalate flakes using pigment and spinning filament from the flakes. U.S. Pat. Nos. 3,350,871 and 3,671,379 and UK Patent Specification No. 1,075,689 (all incorporated herein by reference), Example 1, show preparation of polytrimethylene terephthalate using a catalyst prepared by dissolving 2.5 grams of sodium in 300 ml of n-butanol, adding 37 grams of tetrabutyl titanate, and diluting to 500 ml with n-butanol. Titanium dioxide is added as a delusterant. This polyester is disclosed to be useful in making bicomponent fibers.
To polymerize polymer with various color pigments is inflexible, impractical and uneconomical since typical polymer production is large scale and transition from one color to another would take days of lost production. Therefore, it is most advantageous to add color pigments into the fiber during the spinning process where color transition is short, and small lots color production is desirable and feasible.
Pigmented fibers offer no more chemical dyeing, high amount of color offerings, low cost colored fibers and most economic production. Thus, it is common for colorants to be added to a masterbatch, wherein all the pigments, dyes, or combinations thereof are added in a concentrated form to a polymer, and this polymer is mixed with the polymer to be colored. Usually masterbatches in pellet form are introduced to an extruder through a gravimetric feeder. Masterbatches have several disadvantages. It is difficult to adjust the color of the articles being extruded if the color is off aim without completely reformulating the masterbatch, and a separate masterbatch is required for each desired color.
U.S. Pat. No. 6,109,015, and its counterpart EP 0 949 363 (published Oct. 13, 1999) (both incorporated herein by reference), teach preparing polytrimethylene terephthalate yarn from chips, wherein the chips and any additives are added to a melt extrusion system wherein the input is melted, mixed, homogenized and extruded through a spinneret into filaments. Example 4 describes adding a carbon black dispersion and a titanium dioxide dispersion into the polytrimethylene terephthalate. Example 7 states that a white pigment was dispersed in a PA6 carrier to form a masterbatch concentrate and then was dispersed in the polytrimethylene terephthalate. Example 8 is directed to a bronze-colored solution-dyed yarn and states that “[t]he pigments in the formulated bronze color were predispersed in PA6 carrier prior to producing the compound for spinning.” Example 9 describes preparing a black-solution dyed yarn in a similar manner to Example 7 with pigments predispersed in PA6. Example 10 describes preparing a blue solution-dyed yarn with pigment predispersed in polytrimethylene terephthalate. Example 14 describes preparing an off-white formulated color concentrate with a polytrimethylene terephthalate carrier. Yarn and carpets were produced. The disclosed processes have the disadvantages described above.
Locke et al., in U.S. Pat. No. 5,756,020 (incorporated herein by reference), teach a process for introducing colorants (pigments and/or dyes) into thermoplastic polymers, such as nylon, polypropylene, polyester and copolymers and blend thereof, wherein colorants are fed from gravimetric feeders into an extruder containing the polymer. This patent discloses the advantage of having one colorant in each feeder so that color may be controlled by the rate each colorant is fed to the extruder. One major problem found is that typical polyester, polypropylene and polyamide producer colored fiber production requires the use of carefully selected pigments and associated carriers that can survive high remelt and transport temperatures without changing their desired properties due to thermal degradation. The pigments and carriers have a negative impact on the subsequent spinning process by significantly increasing the draw tension and draw tension variability, and causing breakouts and total breakdowns, thereby reducing productivity. Some polymers required for pigment processing are incompatible with the base polymer causing further reduced productivity and fiber performance. In addition, some color pigments required for certain critical colors in the high temperature processes are highly abrasive and can damage critical yam contact surfaces both on the spinning machine and in customers processing operations.
None of the processes described above present a satisfactory way of preparing a pigmented fiber. A satisfactory process of pigmenting fibers that enables use of more heat sensitive pigments, permits relatively easy control of color at the fiber manufacturing facility, and results in good pigment dispersion, enhanced spin performance (e.g., reduced fiber breaks and improved yields) and increased color offerings (e.g., use of a wider variety of pigments and control of color and uniformity) has been needed.
SUMMARY OF THE INVENTION
This invention is directed to a process of making a pigmented shaped article comprising: (a) providing polytrimethylene terephthalate chips and two or more colored pigmented chips each containing at least one different color pigment; (b) heating the polytrimethylene terephthalate chips and colored pigmented chips to a temperature of about 200-about 280° C. to melt the chips and form a polymer composition comprising the polytrimethylene terephthalate and at least one color pigment; and (c) forming a shaped article from the polymer composition.
The chips are preferably heated to about 245-about 270° C.
The spinning is preferably carried out using a spinneret at a polymer temperature of about 235-about 275° C.
The colored pigmented chips preferably comprise polytrimethylene terephthalate and at least one color pigment.
In one embodiment, preferably at least some of the polytrimethylene terephthalate chips contain TiO
2
. In that embodiment, or in another preferred embodiment, preferably at least some of the colored pigmented chips contain TiO
2
.
In another preferred embodiment, the colored pigmented chips do not contain TiO
2
.
In some embodiments, the color pigment is preferably a color pigment other than carbon black.
In a preferred embodiment, the polytrimethylene terephthalate chips and polytrimethylene terephthalate pigmented chips are fed to a remelter, melted and mixed in the remelter and formed into a shaped article through an extruder.
Preferably, the polytrimethylene terephthalate and the color pigment form a substantially uniform me
Agarwal Nirmal K.
Chang Jing C.
Dommel Richard Lee
Kurian Joseph V.
Longhi Raymond
E. I. du Pont de Nemours and Company
Kuller Mark D.
Yoon Tae H.
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