WO2000005293A1

WO2000005293A1 - Polymeric color concentrates

Info

Publication number: WO2000005293A1
Application number: PCT/US1999/015933
Authority: WO
Inventors: Ram T. Khanna; Nirmal K. Agarwal; Henry L. Jakubauskas
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1998-07-23
Filing date: 1999-07-14
Publication date: 2000-02-03

Abstract

A process for making a polymeric color concentrate for use in coloring thermoplastic materials used in making molded plastic articles or fibers comprising the following steps: (a) adding a thermoplastic polymer, preferably a polyester or a polyamide, to an extruder having vents for the removal of vapors and melting the thermoplastic polymer, adding a pigment dispersion comprising at least one pigment, a polymeric dispersing resin and a non aqueous liquid carrier directly to the melted thermoplastic polymer; (b) blending the pigment dispersion and the thermoplastic polymer in the extruder to form the polymeric color concentrate having a uniform color throughout and removing substantially all of the non-aqueous liquid carrier from the resulting color concentrate via the vents of the extruder; and (c) extruding, cooling and pelletizing the color concentrate; in a preferred embodiment of this invention, the color of the color concentrate is continuously measured and the feed rate of pigment dispersion and thermoplastic polymer is adjusted and small amounts of other pigment dispersions are added to adjust the color to a predetermined color standard.

Description

TITLE

POLYMERIC COLOR CONCENTRATES

BACKGROUND OF THE INVENTION Field of the Invention

This invention is directed to polymeric color concentrates which are blended with thermoplastic polymers that are used to make colored fibers and colored molded plastic parts. Description of the Prior Art Processes for the formation of color concentrates that are then used to manufacture fibers are shown in Khanna U.S. Patent 3,905,937 issued Sept. 16, 1975 and in Khanna U.S. Patent 4,001,171 issued Jan. 4, 1977. These processes require that the polymer used to form the color concentrate is soluble in conventional solvents at ambient temperatures and these processes cannot be used for high molecular weight crystalline polymers such as nylon, polyethylene terephthalate and polybutylene terephthalate.

Jones U.S. Patent 5,236,645 issued Aug. 17, 1993 shows a process that uses aqueous solutions to form color concentrates. The aqueous solution used to form the color concentrate is harmful to many types of material such as polyester and is undesirable in materials such as nylon. Also, processes using aqueous solution must adjust the chemistry of the starting materials, and/or adjust the operating temperatures of extruders to volatilize the water which adds cost to the process^

A process is needed to form a polymeric color concentrate that does not use an aqueous solution or require that the thermoplastic polymer used be predissolved in a solvent. The process of this invention thoroughly blends pigment and other additives into a carrier polymer to form a polymeric color concentrate which can be added to polymers that are molded into parts or to polymers that are spun into fibers.

SUMMARY OF THE INVENTION A process for making a polymeric color concentrate used for coloring thermoplastic materials that are made into fibers and molded parts comprises the following steps: (a) adding thermoplastic polymer, preferably a polyesters or a polyamide, to an extruder having vents for the removal of vapors and melting the thermoplastic polymer, adding a pigment dispersion comprising at least one pigment, a polymeric dispersing resin and a non aqueous liquid carrier directly to the melted thermoplastic polymer in the extruder,

(b) melt blending the pigment dispersion and the thermoplastic polymer in the extruder to form the polymeric color concentrate having a uniform color throughout and removing substantially all of the non-aqueous liquid carrier from the resulting color concentrate via the vents of the extruder; and

(c) extruding, cooling and pelletizing the color concentrate; in a preferred embodiment of this invention, the color of the color concentrate is continuously measured and the feed rate of pigment dispersion and thermoplastic polymer is adjusted and small amounts of other pigment dispersions are added to adjust the color to a predetermined color standard; polymeric color concentrates made according to this process are also part of this invention.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a diagram showing one embodiment of the process of this invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention can be generalized by stating that a way has now been found to disperse pigment and optionally additives by adding them directly to a thermoplastic polymer and mixing them with the polymer, via melt mixing, before the polymer is extruded. The pigments and optional additives are added in the form of a non-aqueous dispersion which comprises the pigment and optional additive, dispersing agent and non-aqueous carrier. A thermoplastic polymer is continuously added to an extruder having vents to remove solvent and melt mixed in the extruder. A stream of the non-aqueous dispersion is added to the melted thermoplastic polymer in the extruder and via melt mixing the pigments and additives are homogeneously distributed throughout the thermoplastic polymer and are thoroughly mixed with the thermoplastic polymer to form the polymeric color concentrate. The non-aqueous carrier present is removed through the extruder vents under a vacuum and optionally recycled. The color concentrate is then extruded, cooled and pelletized and charged into a shipping containers.

The process of this invention has advantages over prior art process such as shown in U.S. Patent 4,001,171 and U.S. Patent 5,236,645. In reference to the '171 patent, the process of that patent requires the thermoplastic polymer to be predissolved in a solvent and pigments are dispersed therein and solvent is evaporated to form the color concentrate. With such a process, only polymers can be used that dissolve in solvents at ambient temperatures and high molecular weight crystalline polymers such as polyamides and terephthalic or isophthalate acid ester polymers can not be used since these polymers are not soluble in conventional solvents at ambient temperatures. The process of the invention does not require the thermoplastic polymer of the color concentrate to be predissolved in solvent but pigment dispersion is added directly to the melted thermoplastic polymer. With the process of the invention, all types of thermoplastic polymers can be used such as polyamides and polyesters such as polymers of terephthalic or isophthalic acid esters, and the like.

In reference to the '645 patent, an aqueous pigment dispersion is added to the thermoplastic polymer and water must be removed in the extrusion process. Water is harmful to certain polymers such as polyesters and undesirable to have present in other polymers such as polyamides. Also, excessive heat is required to drive off the water which may be harmful to certain polymers.

In another well known process, pigments and thermoplastic polymer are dry blended together and then charged into an extruder and melt blended to form the color concentrate. The process of this invention in comparison to this prior art process provides for a more uniform dispersion of the pigment in the thermoplastic polymer, superior color reproducibility and color control, and allows for the use of a wider variety of thermoplastic polymers. The process of this invention allows for the use of a wide spectrum of thermoplastic polymers in the color concentrate such as high Tg (glass transition temperature), low Tg polymers, high melting and low melting polymers, solvent soluble or solvent insoluble polymers, crystalline or amorphous polymers, homo or copolymers or blends thereof. Also, very high molecular weight polymers can be used that are not soluble under ambient temperature conditions in conventional process solvents such as toluene and xylene.

Figure 1 shows one embodiment of the invention. Thermoplastic polymer 3 is passed from storage bin 11 into an extruder 4 and melted. The extruder 4 typically is a twin screw either co or counter rotating extruder. Pigment dispersion 1 containing non-aqueous solvent, pigment and a pigment dispersant is pumped via metering pump 2, typically a positive displacement reciprocating diaphragm pump, and injected into a stream of melted thermoplastic polymer 3 in the extruder 4. Preferably, the pigment dispersion is injected into the extruder immediately after the thermoplastic polymer is melted. The pigment dispersion and thermoplastic polymer are thoroughly mixed together in the extruder and solvent is removed via vents 5 in the extruder. The solvent can be recycled using a conventional solvent recovery process. After thorough melt mixing of the pigment dispersion and the thermoplastic polymer and removal of any solvents present, the resulting polymeric color concentrate is extruded and cooled either by cooling at ambient temperatures or by quenching in a water bath and cooling below the Tg of the thermoplastic polymer used to form the concentrate. The extrudate is passed into a pelletizer 6, typically a strand pelletizer or the extrudate can be melt cut in an under water pelletizer and pelletized and then dried in drier 7, typically a Centrifugal Gala Drier. The pellets are classified in classifier 8, typically a vibrating screen type classifier and passed into an intermediate storage hopper 9 and via a filling machine and filled into a container 10.

The pigment dispersion used to form the polymeric color concentrate contains 1 -75% by weight pigment, 1 -80% by weight of a polymeric dispersing resin and 35-98% by weight of non-aqueous liquid carrier. Preferably, the pigment dispersion used to form the polymeric color concentrate contains 25-75% by weight pigment, 5-15% by weight of a polymeric dispersing resin and 20-70% by weight of non-aqueous carrier. Typical pigments that can be used are titanium dioxide, carbon black, zinc oxide, antimony oxide, various iron oxides, silicates, titanates, cobalt aluminate, phthalocyanines, quinacridones, isoindolenes, perylenes and various mixtures thereof. Soluble or insoluble dyes can be used such as dihydroxy bis arylamino anthraquinones and cyanobenzene-azo anilines and mixtures thereof. Additives that can be incorporated into the pigment dispersion in addition to the pigment or, in place of the pigment, are antioxidants, lubricants, UN-stabilizers, heat stabilizers optional brightness.

The non-aqueous liquid carrier used to form the pigment dispersion must not degrade the thermoplastic polymer of the color concentrate and form a pigment dispersion. Typical carriers that can be used are toluene, xylene, esters, ketones such as methyl ethyl ketone, methyl isobutyl ketone, alcohols such as methanol, ethanol, propanol, isopropanol and ethers.

The polymeric dispersing resin must be compatible with the thermoplastic polymer used to form the polymeric color concentrate and with the polymer to which the concentrate is added. Typically useful polymeric dispersing resins are shown in Khanna U.S. Patent 4,001,171 which is hereby incorporated by reference, particularly useful resins are shown on col. 6 line 59 - col. 7 line 12, col. 9 line 12 - col. 11, line 53.

One preferred dispersing resin is of a hydroxy terminated polycaprolactone having a weight average molecular weight of 1 ,000 - 50,000, that is reacted with a polyisocyanate such as "Desmodur" Ν, the trimer of hexamethylene diisocyanate and capped with ΝH₃ or an amine. Typical amines that can be used for capping the dispersing resin are dimethylaminopropyl amine and the like.

The pigment dispersion is formed by conventional techniques such as ball milling, sand grinding, author grinding and the like. The thermoplastic polymer used to form the color concentrate must be compatible with the polymer to which it will be added such as a molding polymer or a polymer for spinning fibers. Typically useful polymers are as follows: Polyamides such as Nylon 6/6 (hexamethylene adipamide), Nylon 6 (polycaprolactam having a number average molecular of 1,000-50,000); polyamide copolymers such as copolymers of Nylon 6, Nylon6/6 and Nylon 6/10, copolyamides such as"Elvamide"8063, "Elvamide 8061 or their analogs made with Nylon 6/6, Nylon 6/10 or Nylon 6/12; polyethylene terephthalate, polyethylene isophthalate, copolymers of polyethylene terephthalate and polyethylene isophthalate, polytrimethylene glycol terephthalate, polybutylene terephthalate, polycaprolactone polypropylene, polyethylene and copolymers thereof, polyolefins such as polyethylene, polypropylene and copolymers thereof. The resulting polymeric color concentrate contains 1-75% by weight of uniformly dispersed pigment, 1-50% by weight of a polymeric dispersant and 25-98% by weight of the thermoplastic polymer. Polymeric color concentrates of high quality of crystalline thermoplastic polyamides and polyesters have not been made by prior art processes.

For continuous operation of the process, the color of polymeric concentrate as it exits the extruder is continuously measured with a colorimeter and the color of the concentrate is compared to a color standard that has been determined for the polymeric color concentrate. These values are fed into a computer containing a program which automatically adjusts the feed of pigment dispersion and thermoplastic polymer to the extruder to maintain the color of the concentrate at it standard value. A typical continuous color matching process is shown in Campo et al U.S. Patent 5,559, 173 issued September 24, 1996. Polymers used for spinning fibers and formation of molded articles to which the color concentrates of this invention are added can be any of the above thermoplastic polymers used to form the color concentrate provided that the polymers and dispersants used in the color concentrate are compatible with the polymer used to form fibers or molded articles. The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated. All molecular weights are determined by gel chromatography using polystyrene as the standard. EXAMPLE

Eleven polymeric color concentrates were prepared using the process set forth in Fig. 1. A co-rotating 13 barrel twin screw extruder was used having vents, shown as "Ports 1,2,3, and 4" in the following Table, and each vent operated under different vacuum shown in "Hg in the Table for the removal of solvent. Each of the 13 barrels of the extruder (shown as BBL on the Table) are operated under the temperature as shown in the Table.

The pigment dispersion used to make the color concentrate is shown in the table and % solids of the dispersion, % pigment in the dispersion (solids) and % binder (dispersant solids) are shown for each of the dispersions are shown in the table as is each pigment that was used in the dispersion.

The polymeric dispersing resin (dispersant) used in the pigment dispersion is a hydroxy terminated polycaprolactone having a weight average molecular weight of 3,000 - 5,000 and is capped with "Desmodur" N which is the trimer of hexamethylene diisocyanate and is ammoniated. The non-aqueous solvent used in the pigment dispersion is toluene.

The rate the pigment dispersion is fed into the extruder is shown on the Table in pounds per hour abbreviated as phr.

The following thermoplastic polymers were used to form the color concentrates and are shown in the Table as "Polymer 1 " and "Polymer 2": Nylon 6 (polycaprolactam), Nylon 6,6 each having a number average molecular weight of 20,000 - 50,000, 3GT Polyester (polytrimethylene glycol terephthalate having a inherent viscosity of 0.7), Nylon Copolymer (copolymer of Nylon 6, Nylon 616, Nylon 6/10); PET (polyethylene terephthalate) and PET/I Copolymer ( copolymer of polyethylene terephthalate and polyethylene isophthalate 83/17 ratio).

The rate at which the thermoplastic polymer was fed into the extruder in pounds per hour (phr) is shown in the Table as "DRY FEED" "POLYMER 1 " and "POLYMER".

In the formation of each of the polymeric color concentrates, the constituents were thoroughly melt blended in the extruder and solvent removed, the extrudate was cooled below the Tg of the thermoplastic polymer used to form the concentrate and the resulting polymeric color concentrate was pelletized and dried and classified. Each of the color concentrates were added to a respective polymer which is compatible with the polymeric color concentrate and the resulting mixture was spun into a fiber. The fibers had acceptable physical properties and had a uniform color. Table

Table

Claims

1. A process for making a polymeric color concentrate for use in coloring thermoplastic materials comprising: (a) adding a thermoplastic polymer to an extruder having vents for the removal of vapors and melting the thermoplastic polymer, adding a pigment dispersion comprising at least one pigment, a polymeric dispersing resin and a non aqueous liquid carrier directly to the melted thermoplastic polymer in the extruder,

(b) melt blending the pigment dispersion and the thermoplastic polymer in the extruder to form the polymeric color concentrate having a uniform color throughout and removing substantially all of the non-aqueous liquid carrier from the resulting color concentrate via the vents of the extruder;

(c) extruding, cooling and pelletizing the color concentrate.

2. The process of claim 1 wherein the pigment dispersion comprise 1-80% by weight pigment, 35-98% by weight non-aqueous carrier and 1-15% by weight polymeric dispersing resin.

3. The process of claim 2 wherein an additive is incorporated into the pigment dispersion prior to adding the dispersion to said extruder.

4. The process of claim 2 further comprising: continuously measuring the color of the color concentrate and comparing said color to a color standard determined for the color concentrate and automatically adjusting the color of said color concentrate by adjusting the feed rate of pigment dispersion and thermoplastic polymer and adding small amounts of other pigment dispersion such that the color of said color concentrate is the same as the color standard.

5. The process of claim 2 wherein the thermoplastic polymer is selected from the group consisting of polyesters, polyamides, blends of polyesters and blends of polyamides, polypropylene and polyethylene.

6. The process of claim 5 in which the thermoplastic polymer is polycaprolactam having a number average molecular weight of 1,000-50,000 determined by gel permeation chromatography using polystyrene as the standard.

7. The process of claim 2 in which the polymeric dispersing resin is the reaction product of a hydroxy terminated polycaprolactone reacted with an organic polyisocyanate and capped with ammonia or an amine.

8. The process of claim 2 in which the non- aqueous liquid is an organic solvent and a solvent recovery system is attached to the extruder to recover solvent being removed through from the vents of the extruder under a vacuum.

9. The process of claim 2 in which the pigment dispersion and the thermoplastic resin are continuously fed into the extruder by a metering means.

10. The process of claim 1 wherein the pigment dispersion comprise 25^:75% by weight pigment, 20-70% by weight non-aqueous carrier and 5-15% by weight polymeric dispersing resin and the dispersion is injected into the thermoplastic polymer in the extruder; the thermoplastic polymer is selected from the group consisting of polyesters, polyamides, blends of polyesters, blends of polyamides, polypropylene and polyethylene, the non-aqueous liquid carrier is an organic solvent and a solvent recovery system is attached to the extruder to recover solvent being emitted from the vents of the extruder; the pigment dispersion and the thermoplastic resin are continuously fed into the extruder by a metering means; and the process further comprises continuously measuring the color of the color concentrate and comparing said color to a color standard determined for the color concentrate and automatically adjusting the color of said color concentrate by adjusting the feed rate of pigment dispersion and thermoplastic polymer and adding small amounts of other pigment dispersions such that the color of said color concentrate is the same as the color standard.

1 1. A polymeric color concentrate consisting essentially of 1-

75% by weight of uniformly dispersed pigment, 1-50% by weight of a polymeric dispersant and 25-98% by weight of a high melting crystalline thermoplastic polymer of a polyamide or a polyester.

12. The polymeric color concentrate of claim 11 in which the thermoplastic polymer is a polycaprolactam or copolymers thereof.

13. The polymeric concentrate of claim 11 in which the thermoplastic polymer is polyethylene terephthalate, polyethylene isophthalate, copolymers thereof or polyethylene isophthalate.

14. The polymeric concentrate of claim 11 in which the polymeric dispersant resin is the reaction product of a hydroxy terminated polycaprolactone reacted with an organic polyisocyanate and capped with ammonia or an amine.