CA2050612A1

CA2050612A1 - Addition of additives to polymeric materials

Info

Publication number: CA2050612A1
Application number: CA002050612A
Authority: CA
Inventors: Keith Gannon
Original assignee: Keith Gannon; Basf Corporation
Current assignee: BASF Corp
Priority date: 1990-09-21
Filing date: 1991-09-04
Publication date: 1992-03-22
Also published as: ES2097171T3; JPH0777751B2; US6149850A; EP0477634B1; AU641278B2; EP0477634A2; DE69124560D1; JPH05169515A; EP0477634A3; DE69124560T2; AU8467391A

Abstract

ADDITION OF ADDITIVES TO POLYMERIC MATERIALS
Abstract A process for introducing additives into a polymer melt comprising dispersing at least one additive in an at least partially volatile liquid vehicle with a dispersant and a stabilizer; feeding the resulting dispersion to a vented extruder which is extruding a polymer; and removing the fed volatiles through the extruder vent to achieve a substantially homogeneous system containing the polymer and at least one additive is disclosed.

Description

2~S06~1L2 ADDITION OF ADDITIVES TO POLYIUERIC MATERIALS
Backeround of the Invention This invention relates generally to the preparation of adl}~xtures from S thermoplastics. More specifically, the invention relates to the addition to a polymer melt of dispersed additives in a partially volatile liquid vehicle followed by removal of the vehicle.
It is known to modify tbe characteristics of thermoplastic materials by addition of additives. This addition normally occurs prior to the shaping step, that is, 10 prior to spinning or other extrusion, injection molding, etc. For example, colorants, stabilizers, delusterants, ~arne retardants, fillers, antimicrobial agents, antistatic agents, optical brightness, extenders, processing aids and other functional additives are used to impart preferred properties to the host polymer to which they are added. By way of illustration, the coloring of thermoplastic articles by incorporation of pigments 15 introduced as color concentrates is well known For the purposes of the present application, a concentrate contains the additive at a much higher loading than is desired in tbe final thermoplastic article. Typically, tbe coloring of fibrous materials through the use of color concentrates has presented unique challenges The reasons for this are many fold For instance, the amount of pigmentary particles dispersed in 20 the concentrate must be high enough to impart satisfactory color density and yct must not be so high as to interrupt the spinning process ;~0S06~2 When adding materials to nylon 6, moisture levels in the additive have formerly been kept as low as practical. The preseoce of excessive levels of water causes depolymerization and reduces the molecular weight and melt viscosity of nylon 6 to the point where bubbles will form in the extrudate or where fiber can no longer S be formed. As a consequence, it has been important to keep moishlre levels of concentrates low.
Pigment concentrate production may be performed by preparing a dispersion of the pigment in an aqueous medium. To achieve satisfactory dispersion, a watcr dispersible/soluble polymer may be used. It is normal in concentrate 10 production t~ flush the pigment from an aqueous dispersion to an organic phase in a separate step pAor to extrusion.
Another method of prepaAng pig nent concentrates involves the preparation of an aqueous color dispersion which is dried to remove the water. For instance, U. S. Patent No. 4,374,641 to Burlone describes the preparation of a color lS concentrate in an aqueous vehicle using a dispersant which is compatiblo with the thermoplastic mateAal with which the concentrate will be blended. The aqueous color concentratc ls filtered and dAed to remove residual water. Both of these methods require an extra step, like flushing or drying.
In the processing of plastics, ;t has been described that additives may be 20 Jntroduced into the plastic extruder, generally in a finely divided form, such as granules or powders, ~,vith devolatilization of the volatiles present within the polymer stream.

;~0S(~6~2 In the method of U. S. Patent No. 4,065,532 to Wild et al., the addilion of major amounts of compatible liquid additives is described as being preferably done after devolitalization of the polymer.
There remains a need for a process by which additives present in liquid S vehicles, which vehicles are not desirable in the final shaped polymer article, may be added to a polymer melt stream without interfering with the polymer's suitability for processing. Such a process is described hereinafter. As will be noted, this process, in some applications, employs dispersants to disperse the intended additive in the vehicle. These dispersants are often expensive. The invention disclosed herein results in decreased dispersant usage and also, in some cases, improved extrusion performance.

Summary of the Invention Accordlngly, the present invention is a process for introducing additives lS into a po!ymer melt comprising dispersing at least one additive in an at least partially volatile liquid vehicle with a dispersant and a stabilizer; feeding the resulting dispersion to a ventcd extruder which is extruding a polymer; and removing the fed volatiles through the extruder vent to achieve a substantially homogeneous system containing lhe polymer and at least one additive.
It is an object of the present invention to provide an improved process for preparing modified thermoplastics.

~1~15O~ ~lZ
Related objects and advantages will be apparent to one ordinarily skilled in the relevant art after re~iewing the following description.

Descri~tiQ~ of ~fm~nts To promoee an understanding of the principles of the present invention, descriptions of specific embodiments of the invention follow and specific language describes the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and that such alterations and further modifications, and such further applications of the principles of ~he invention as discussed are contemplated as would normally occur to one ordinarily skilled in the art to which the invention pertains.
The present invention concerns a process for introducing soluble or insoluble additives into a polymer melt in an extruder where the additive as a dispersion in a vehicle having volatile constituents and shaping the admixed polyrner without interference from the volatile vehicle constituents. Shaping may be by spinning into fibers, extrusion into tubes, injection molding or nearly any method known to form a polymer melt into a useful final article. In general, this process is the subject of copending U. S. Patent Application Serial No. . The present invention is directed to the dispersion and methods for improving the performance of processes wherein it is used. As an illustration, the process described is useful in coloring any melt spinnable polyamide such as nylon 6, nylon 6,6, nylon 10, nylon 11, nylon 12 and 2~506~L2 co-polyrners of these. Other thermoplastic polyrners, such as polyesters, may improve also from use of the process. It is ~urther contemplated that the process may be useful for introducing to polymeric melt processes other additives which are present in at least partially volatile vehicles. Examples of other additives w~2ich may ~e introduced S are colorants, stabilizers, delusterants, flarne retardants, ~llers, antirnicrobial agents, antistatic agents, optical brighteners, extenders, processing aids and other functional additives. It should be recognized that nearly any additive present in a partially undesirable volatile vehicle could be potentially successfully added to the polyrner melt by the present process. Furthermore, it is not necessary that the polymer product 10 resulting from the process is an adrnhl~ture. However, for purpose of illustration only, the following discussion concerns the preparation of pigrnented therrnoplastic materials.
The principles described below are readily adaptable to suit a particular application as will be apparent to one ordinarily skilled in the art.
The additive regardless of solubility is dispersed in a vehicle which is at 15 least partlally volatile under the conditions. For the present purposes, dispersed and dispersion refer to the presence of dispersants in the vehicle and do not indicate the solubillty of the additive. When the addithe is a pigrnent and the vehicle is aqueous, this dispersion may be prepared using the water soluble/dispersible polyrners of U. S.
Patent No. 3,846,507 as a dispersant. This patent is hereby incorporated by reference 20 for the water soluble/dispersible polyrners taught therein. One particularly useful dispersarlt Jn this class is a copolyrner of caprolactarn/hexarnethylenediarn~ne/isophthalic .210506~L2 acld/the sodium salt of sulfoisophthaUc acid (hereinafter referred to as C-68 and manufactured by BASF Corporation.) Other related water soluble/dispersible polymers are useful in the present invention. These include, but are not limited to, other water soluble/dispersible polyanudes and copolymers thereof, water soluble/dispersible5 polyesters and copolymers thereof, water soluble/dispersible vinyl polymers and co-polymers thereof, water soluble/dispersible alkylene oxide polymers and co-polymers thereof and water soluble/dispersible polyolefins and co-polymers thereof, as well as mixtures of these. But, of course, other dispersants, like monomeric dispersalnts, may be sùitable for use with the present invention.
The dispersant is preferably present in the dispersion at a concentration of between abo~lt 0.075% and about 7.5% by total dispersion weight. As is apparent, the level of dispersant needed to most efficiently achieve the desired results wili depend upon the particular pigment (or other additive) which is used and the target color density (or function). The upper limit of dispersant is related to the maximurn 1S total dispersant and pigment to polymet ratio which can bc succcssfully extruded.
The addition of a stabilizer has been surprisingiy discovered to disproportionately reduce the amount of the polymeric dispersant necessary for a suitable dispersion to be prepared. The stabilizer is preferably present at between abut 0.75% and 7.5% by total dispersion weight. Furthermore, in some instances, the 20 use of the stabiiizer causes additional decreases in the poly ner melt Pressure Index.
Thc production of some black pigment concentrates is exemplary of a process 205~)6~

improved by addition of the stabilizer. Stabilizers suitable for this purpose include many standard nonionic species and likely include many anionic species. Among these are polyethoxylates, polypropoxylates, block copolyrneric polyetbers, long chain alcohols, polya1cohols, alkyl-sulfates, alkyl-sulfonates, alkyl-benzenesulfonates, allyl-phosphates, S alkyl-phosphonates, alkyl-napthalene sulfonates, carboxylic acids and perfluoronates.
One stabilizer that is presently preferred is a polyethoxylated alkyl phenol (Tliton X-100 (l~C100)). 17~100 yields Pressure Indices (as determined by the method described below) less than about 5 in the about 6 to about 50 wt.% range based on the weight of pigrnent in conjunction with C-68 concentrations as low as about 0.5%
(based on pigmentary weight). In this aspect, about 20% TX100 with about 0.1 to 10% C-68 is presentb preferred. Specifically, 20% IX100 with 0.5% C-68 yields a Pressure Index of about 0.7. This is in contrast to a Pressure Index of about 0.9 when about 100% C-68 (based on pig nent weight) is used alone.
The disperslon may be prepared according to standard methods by, for lS e~tample, mixing a pigrnent press cakc with dispersant and stabillzer containing water until all of the components of the dispersion are appropriately dissolved and/or dispersed. The pigment concentration of the dispersion is preferably between about 15% and about 50% by total dispersion weight. As with dispersant concentration, the most preferable pigment concentration will depend on color density and processibility 20 of the extrudate. The dispersion may be subjected to mechanical ener~y to be certain that the dispersion particles are of sufficiently small and uniforrn size. This may be .20S06 IL2 accomplished, for example, by milling through a Chicago Boiler Company Model KDL
Pilot Dyno Mill or other suitable mill. ~e reduction in dispersion particle size may be monitored by measuring the Pressure Index.
The Pressure Index (psi pressure increase/gram pigment) is obtained by S mLxing the desired concentrate with the polymer to be modif;ed to give (in the case of pigment addition) a pigment concentration of 5~o. The 5~o concentrate and polyrner blend is extruded at 275 C through a 35mm 165x1400 mesh fillter screen (nominal 10 micron). The extrudate rate is adjusted so that the pressure drop across the filter screen is about 2000 psi. The test is run for two hours or until the pressure reaches about 3000 psi, whichever comes first. The pressure rise above 2000 psi and the calculated grams of pigment through the filter are used to calculate the Pressure Index.
The dispersion (or additive present in the volatile vehicle) may be added to a polymer stream to make a concentrate, which is then cooled and cut into chips 1S or added in thc molten phase directly to a primary melt stream. Thc dispersion may also be added directly to the primary melt stream being extruded through a twin screw vented extruder without first preparing a concentrate. When the goal is concentrate preparation, the dispersion is preferably thoroughly mixed with a compatible polymer, preferably of the same type in which the concentrate will finally be used. When the 20 goal is direct production of a shaped article from a dispersion and a polymer melt strearn, the dispersion and the polymer are preferably mixed in the cxtruder. In either 506~L2 case, the intimate n~ixing occurs preferably by adding the dispersion to a twln screw vented extruder such as those available from Werner & Pfleiderer or Arnerican Leistritz. To be sure of int;mate mixing, the screw speed and zone temperatures should be monitored and set as appropriate for the particular pigment and S thermoplastic material being extruded. The extrusion rate should be monitored, also.
The dispersion is preferably metered into the appropriate zone of the extruder to give a specific predeterrnined extruder output. Metering may be accomplished by a meshed gear pump, a piston pump, a diaphragm pump or other suitable metering means.
At the appropriate zone, the vehicle is preferably removed by using a LEMA S0 Type 20605 water sealed vacuum pump. The final extrudate, in the case of a pigment concentrate, preferably has a concentration of about 25% of pigment, about 0.25% to 2.5% dispersant, about 5% stabilizer, and about 65% to 70%
thermoplastic polymer by weight based on total weight of the concentrate.
lS When a concentrate is prepared, the concentrate may then be cooled, cut into chips and dried as desired. The fresh concentrate composition or concentrate chip may be used directly in the production of a thermoplastic polymer having a desired color density. Where the concentrate is used in ~lber spinning, the concentrate is preferably added to the polymer so that the final pigment concentration in the fiber 20 is about 1%. Spinning performance of the extruded thermoplastic material may be measured by spin pack pressure rise or estimated by the Pressure Index. In general - 2(~5~6~2 acceptablc spinning performance results in a Pressure Index of abou~ 10 or less, more preferably about S or less. It has been discovered that the Pressure Index achieved with the present invention is easily maintained below 10 and is surprisingly much better than the Pressure Index obtained with presently available commercial pigment 5 concentrates and may su~prisingly, in some cases, be better than when the dispersant is used alone.
The invention will now be described by referring to the following detailed examples. These examples are set forth by way of illustration and are not intended to be limiting in scope 10Bxamvle 1 Piement Dispersion Throu~h Usc of a Stabilizer A dispersion containing, per weight of the dispersion, 15% Raven Black 1200, 0.75 % of the water dispersible polyamide of U. S. Patent No. 4,098,741 (C-68) (5% based on pigrnent weight), 3% Triton X-100 (20% based on pigment weight), and 1581.3% H20 is prepared in the following maMer:
45 gms of C-68 and 180 gms of TX100 is added sequentially to 4875 g ns of H~0 that is being stirred at 1500 rpms with a Cowles Mixer. 900 gms of Raven Black 1200 Is added in increments to give a final sample weight of 6 kg and the mixture is stirrcd for 1 hr. The dispersion is passed three dmes through a laboratory scale beadmill such as that available from Chicago Boiler Company as Model KDL
Pilot Dyno Mill. The concentrate is prepared on a Werner & Pfleiderer co-rotating ~506~
twin screw vented extruder. The screw speed is 75-100 rpms and the zone temperatures are set at 275C. The nylon 6 is metered into the throat of the extruder at 15 gms/min. The dispersion is metered into zone 2 of the extruder at 33.6 gms/min.
The water is removed at zone 4 using a water aspirator vacuum source. Tbe S concentrate composition is 25% pigment, 1.15% C-68, 5~o IX100, and 68.75~o Nylon 6, calculated.
Nine hundred (900) gms of the concentrate chips are dried for 24 hours in a vacuum oven and then mixed with 3600 gms of dry nylon 6 chip. The mixture is then fed through a 10 ~m spin-pack at approximately 25 gms/min. The pressure required to maintain a constant polyrner feed through the spin pack is recorded on a chart recorder and converted to a Pressure Index.
The Pressure Index recorded for this sample is 0.0 after approximately 3 hrs of testing. A control sample that contained 100~b C-68 (based on pigment weight) and 0% TX100 has a Pressure Index of 0.9 after 3 hrs. Table 1 provides alS listlng of pressure indices for samples of various C-68/TX100 compositions.
~k~
Wt%~ TX100 Wt% C-68 ~r~S~
o.o 100 0-9 0.0 83 1.0 20.0 O.S 0.7 20.0 1.0 0.1 2:~5~2 20.0 5-0 20.0 10.0 0.0 20.0 15.0 0.8 all concentrations are based on pigment weight.

Claims

1. A process for introducing additives into a polymer melt comprising:
a) dispersing at least one additive in an at least partially volatile liquid vehicle with a dispersant and a stabilizer;
b) feeding the resulting dispersion to a vented extruder which is extruding a polymer; and c) removing the fed volatiles through the extruder vent to achieve a substantially homogeneous system containing the polymer and at least one additive.

2. The process of claim 1 wherein the additive is at least one or more pigment, stabilizer, delusterant, antimicrobial agent, antistatic agent, optical brightener, extender, filler, flame retardant, processing aid, nonpigment colorant, or a mixture thereof.

3. The process of claim 1 wherein the extruder is a twin screw vented extruder.

4. The process of claim 1 wherein the dispersant is selected from:
water dispersible/soluble polyamides or copolymers;
water dispersible/soluble polyesters or copolymers;
water dispersible/soluble vinyl polymers or copolymers;

water dispersible/soluble alkaline oxide polymers or copolymers;
water dispersible/soluble polyolefines or copolymers; and mixtures thereof.

5. The process of claim 4 wherein the dispersant is a water dispersible/soluble copolymer of caprolactam/hexamethylenediamine/isophthalic acid/
sulphonated isophthalic acid or a salt thereof,

6. The process of claim 5 wherein the stabilizer is one or more of:
polyethoxylates;
polypropoxylates;
block copolymeric polyethers;
long chain alcohols;
polyalcohols;
alkyl-sulfates;
alkyl-sulfonates;
alkyl-benzenesulfonates;
alkyl-phosphates;
alkyl-phosphonates;
alkyl-naphthalenesulfonates;
carboxylic acids; and perfluoronates.

7. The process of claim 6 wherein the dispersion contains between about 0.075% and about 7.5% dispersant by total dispersion weight and between about 0.75% and about 7.5% of stabilizer by total dispersion weight.

8. The process of claim 1 wherein the polymer melt is nylon 6.

9. The process of claim 1 wherein said feeding is through at least one injection port and is of more than one dispersion.

10. The process of claim 9 wherein the additives are fed through the same injection port.

11. A process for preparing modified thermoplastics comprising:
a) preparing in an at least partially volatile vehicle a dispersion of a modifying additive, a dispersant and a stabilizer;
b) adding the prepared dispersant to a twin screw vented extruder which is extruding a molten thermoplastic; and c) removing volatiles present in the thermoplastic from the addition of the dispersion.

12. The process of claim 11 wherein the dispersant is selected from:
water dispersible/soluble polyamides or copolymers;
water dispersible/soluble polyesters or copolymers;
water dispersible/soluble vinyl polymers or copolymers;
water dispersible/soluble alkylene oxide polymers or copolymers;
water dispersible/soluble polyolefines or copolymers; and mixtures thereof.

13. The process of claim 11 wherein the stabilizer is selected from:
polyethoxylates;
polypropoxylates;
block copolymeric polyethers;
long chain alcohols;
polyalcohols;
alkyl-sulfates;
alkyl-sulfonates;
alkyl-benzenesulfonates;
alkyl-phosphates;
alkyl-phosphonates;
alkyl-naphthalenesulfonates;

carboxylic acids; and perfluoronates.

14. The process of claim 11 wherein the modifying additive is selected from at least one or more pigment, stabilizer, delusterant, antimicrobial agent antistatic agent, optical brightener, extender, filler, flame retardant, processing aid, nonpigment colorant, or a mixture thereof.

15. The process of claim 11 wherein the dispersion contains between about 0.075% and about 7.5% dispersant by total dispersion weight and between about 0.75% and about 7.5% of stabilizer by total dispersion weight.