GB2048901A - Preparing Conductive Molding Compositions - Google Patents
Preparing Conductive Molding Compositions Download PDFInfo
- Publication number
- GB2048901A GB2048901A GB8013504A GB8013504A GB2048901A GB 2048901 A GB2048901 A GB 2048901A GB 8013504 A GB8013504 A GB 8013504A GB 8013504 A GB8013504 A GB 8013504A GB 2048901 A GB2048901 A GB 2048901A
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- United Kingdom
- Prior art keywords
- carbon black
- particles
- pvc
- resin
- added
- Prior art date
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- 239000000203 mixture Substances 0.000 title claims abstract description 49
- 238000000465 moulding Methods 0.000 title claims abstract description 28
- 239000006229 carbon black Substances 0.000 claims abstract description 61
- 239000002245 particle Substances 0.000 claims abstract description 56
- 239000011347 resin Substances 0.000 claims abstract description 42
- 229920005989 resin Polymers 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000006185 dispersion Substances 0.000 claims abstract description 10
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 22
- 229910052799 carbon Inorganic materials 0.000 claims description 18
- 229920002554 vinyl polymer Polymers 0.000 claims description 17
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 claims description 16
- 238000002156 mixing Methods 0.000 claims description 9
- 238000003801 milling Methods 0.000 claims 1
- 238000010924 continuous production Methods 0.000 abstract 1
- 235000019241 carbon black Nutrition 0.000 description 52
- 239000000654 additive Substances 0.000 description 16
- 239000000314 lubricant Substances 0.000 description 15
- 239000007788 liquid Substances 0.000 description 13
- 239000004615 ingredient Substances 0.000 description 11
- 239000007787 solid Substances 0.000 description 10
- 239000003381 stabilizer Substances 0.000 description 9
- 239000000126 substance Substances 0.000 description 9
- 239000004014 plasticizer Substances 0.000 description 8
- 238000005303 weighing Methods 0.000 description 8
- 239000006057 Non-nutritive feed additive Substances 0.000 description 7
- 239000003607 modifier Substances 0.000 description 6
- 239000011342 resin composition Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- HIZCTWCPHWUPFU-UHFFFAOYSA-N Glycerol tribenzoate Chemical compound C=1C=CC=CC=1C(=O)OCC(OC(=O)C=1C=CC=CC=1)COC(=O)C1=CC=CC=C1 HIZCTWCPHWUPFU-UHFFFAOYSA-N 0.000 description 3
- 238000007792 addition Methods 0.000 description 3
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 3
- 239000008116 calcium stearate Substances 0.000 description 3
- 235000013539 calcium stearate Nutrition 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 150000002148 esters Chemical class 0.000 description 3
- 239000012188 paraffin wax Substances 0.000 description 3
- 239000004800 polyvinyl chloride Substances 0.000 description 3
- 229920000915 polyvinyl chloride Polymers 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- ZBBLRPRYYSJUCZ-GRHBHMESSA-L (z)-but-2-enedioate;dibutyltin(2+) Chemical compound [O-]C(=O)\C=C/C([O-])=O.CCCC[Sn+2]CCCC ZBBLRPRYYSJUCZ-GRHBHMESSA-L 0.000 description 2
- QKUNKVYPGIOQNP-UHFFFAOYSA-N 4,8,11,14,17,21-hexachlorotetracosane Chemical compound CCCC(Cl)CCCC(Cl)CCC(Cl)CCC(Cl)CCC(Cl)CCCC(Cl)CCC QKUNKVYPGIOQNP-UHFFFAOYSA-N 0.000 description 2
- 241000156978 Erebia Species 0.000 description 2
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 2
- QQVHEQUEHCEAKS-UHFFFAOYSA-N diundecyl benzene-1,2-dicarboxylate Chemical compound CCCCCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCCCCC QQVHEQUEHCEAKS-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 235000019809 paraffin wax Nutrition 0.000 description 2
- 235000019271 petrolatum Nutrition 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 235000012424 soybean oil Nutrition 0.000 description 2
- 239000003549 soybean oil Substances 0.000 description 2
- 238000010186 staining Methods 0.000 description 2
- -1 vinyl chloride-polypropylene Chemical group 0.000 description 2
- SIXWIUJQBBANGK-UHFFFAOYSA-N 4-(4-fluorophenyl)-1h-pyrazol-5-amine Chemical compound N1N=CC(C=2C=CC(F)=CC=2)=C1N SIXWIUJQBBANGK-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- VOWAEIGWURALJQ-UHFFFAOYSA-N Dicyclohexyl phthalate Chemical compound C=1C=CC=C(C(=O)OC2CCCCC2)C=1C(=O)OC1CCCCC1 VOWAEIGWURALJQ-UHFFFAOYSA-N 0.000 description 1
- 101000837626 Homo sapiens Thyroid hormone receptor alpha Proteins 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 102100028702 Thyroid hormone receptor alpha Human genes 0.000 description 1
- UYXTWWCETRIEDR-UHFFFAOYSA-N Tributyrin Chemical compound CCCC(=O)OCC(OC(=O)CCC)COC(=O)CCC UYXTWWCETRIEDR-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- GWOWVOYJLHSRJJ-UHFFFAOYSA-L cadmium stearate Chemical class [Cd+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O GWOWVOYJLHSRJJ-UHFFFAOYSA-L 0.000 description 1
- TZFWDZFKRBELIQ-UHFFFAOYSA-N chlorzoxazone Chemical compound ClC1=CC=C2OC(O)=NC2=C1 TZFWDZFKRBELIQ-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229960002380 dibutyl phthalate Drugs 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000012170 montan wax Substances 0.000 description 1
- RKISUIUJZGSLEV-UHFFFAOYSA-N n-[2-(octadecanoylamino)ethyl]octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(=O)NCCNC(=O)CCCCCCCCCCCCCCCCC RKISUIUJZGSLEV-UHFFFAOYSA-N 0.000 description 1
- LYRFLYHAGKPMFH-UHFFFAOYSA-N octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(N)=O LYRFLYHAGKPMFH-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 235000019198 oils Nutrition 0.000 description 1
- FATBGEAMYMYZAF-KTKRTIGZSA-N oleamide Chemical compound CCCCCCCC\C=C/CCCCCCCC(N)=O FATBGEAMYMYZAF-KTKRTIGZSA-N 0.000 description 1
- FATBGEAMYMYZAF-UHFFFAOYSA-N oleicacidamide-heptaglycolether Natural products CCCCCCCCC=CCCCCCCCC(N)=O FATBGEAMYMYZAF-UHFFFAOYSA-N 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920005606 polypropylene copolymer Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000010076 replication Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000004671 saturated fatty acids Chemical class 0.000 description 1
- 235000003441 saturated fatty acids Nutrition 0.000 description 1
- 238000006748 scratching Methods 0.000 description 1
- 230000002393 scratching effect Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- WCLDITPGPXSPGV-UHFFFAOYSA-N tricamba Chemical compound COC1=C(Cl)C=C(Cl)C(Cl)=C1C(O)=O WCLDITPGPXSPGV-UHFFFAOYSA-N 0.000 description 1
- 239000003039 volatile agent Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B7/00—Mixing; Kneading
- B29B7/74—Mixing; Kneading using other mixers or combinations of mixers, e.g. of dissimilar mixers ; Plant
- B29B7/7476—Systems, i.e. flow charts or diagrams; Plants
- B29B7/748—Plants
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/20—Compounding polymers with additives, e.g. colouring
- C08J3/203—Solid polymers with solid and/or liquid additives
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing chlorine atoms
- C08J2327/06—Homopolymers or copolymers of vinyl chloride
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
To produce dimensionally stable molding compositions at elevated temperatures without undue stiffness, on a commercial scale, low density conductive carbon black agglomerated particles are finely divided to a particle size below 0.044 millimeter, e.g. by bombardment in a mill 16 containing rotating intermeshing pins. The reduced size particles are then added in a portionwise manner to a PVC resin in a closed system e.g. including a high intensity vortex mixer 22, in a continuous process. The process ensures more uniform dispersion of the carbon black into the PVC resin and uniform bulk and surface properties of articles molded from the resultant resin. <IMAGE>
Description
SPECIFICATION
Preparing Conductive Molding Compositions
This invention relates to a process for making a
conductive molding composition. More
particularly, this invention relates to a process for
making conductive polyvinylchloride-based
molding compositions with improved dispersion
of the conductive material.
Conductive poiyvinylchloride (PVC)-based
molding compositions suitable for compression
molding of video discs have been disclosed in
German Patent Application No. P 2810367.5
(U.K. Appln. No. 10824/77) (Serial 1574595).
The molding composition contains sufficient
amounts of conductive carbon black particles to
impart a maximum resistivity of 500 ohm-cm at
900 MHz. Various molding compositions
disclosed contain from about 1 5 to about 35
percent by weight of the molding composition of
conductive carbon black. Because of the high
solids content, the molding compositions were
stiff and difficult to mold.
These highly conductive PVC molding
compositions were modified by Khanna as
disclosed in United States Patent No. 4,151,132, issued April 24, 1979. Large amounts of a variety
of lubricants, processing aids and modifiers were
added to a mixture of PVC resins to improve the
processability. However, these compositions have
less than the desired dimensional stability at
elevated temperatures.
Martin et al, in copending US application Serial No. 003,363, (UK Appln. 8000477), (Serial No.
2039933) disclose further improvements to the
molding compositions whereby video discs with
improved dimensional stability at temperatures
up to 1 300F (54.40C) and excellent processability
can be molded. These compositions have a lesser
total amount of additives than the compositions
of Khanna, and also limit the amount of liquid
additives that can be present. These molding
compositions comprise a PVC based resin;
conductive carbon black in amounts necessary to
obtain the required resistivity; from about 1.5 to 4
percent by weight of stabilizers; from about 1-3 percent by weight of at least 2 lubricants; and up
to 10 percent by weight of additional modifiers,
with the proviso that not more than 5 percent by
weight of liquid additives are present.
For molding compositions containing large
quantities of additives, the materials must be
blended in a high intensity mixer such as a
Henschel, Welex or Papenmeier type mixer. This
type mixer is bowl shaped and has a high speed
agitator projecting from the bottom whereby the
ingredients are pulled into a vortex in the center of
the agitator and whirled around to the walls of the
bowl. These mixers develop a great deal of shear,
raising the temperature so that a uniform
dispersion of the ingredients is achieved. The
resin and solid additives are generally mixed to a
temperature of at least about 1200F (48.90C),
liquid ingredients are added, and mixing
continued to a temperature of 1 600F (71.1 0C) or higher.After cooling down to about 80-1 200F (26.7-48.90C), the blended mixture is plasticated in a Banbury type mixer or an extruder where the mixture is subjected to high temperatures of about 300-5000F (148.9- 2600C) with high shear to form a dough-like mass which can be formed into tubing or solid strands which are cut into pellets for storage.
Excellent video discs can be made from the above compositions which are dimensionally and environmentally stable. No staining is apparent on the discs, replication of the minute information pattern is excellent and playback is of high quality.
However, difficuities were encountered when the above process was scaled up to commercial quantities. Because of the low bulk density of the preferred carbon black, it is very difficult to mix in with the PVC resin-and some of it is lost. Also because of the low bulk density of the carbon black, it is difficult to weigh the carbon black accurately and batch to batch variations in the amount of carbon in the molding composition were noted. In addition, the dispersion of the carbon black varied from batch to batch. On investigation it was found that the preferred carbon black has a wide particle size distribution; although the innate particle size of the carbon black is very small, the carbon particles agglomerate into larger particles which do not break up in a high intensity mixer.This large particle size leads to non-uniformity in playback performance of the video discs, to defects in the disc surface and even to scratching of the stampers during molding.
Thus, a process to improve the uniformity of the above molding composition and to improve the dispersion of large amounts of carbon black particles in a PVC resin was sought.
The present process proposes finely dividing the carbon black particles to a particle size of about 0.044 millimeters or less, and adding the finely divided carbon black to PVC resin particles in a stepwise manner. These steps ensure a uniform dispersion of the carbon black into the
PVC resin and uniform bulk and surface properties of video discs molded from the resultant molding composition.
In the Drawings:- Fig. 1 is a block diagram showing the passage of the carbon black from the initial feed to the final mixer.
Fig. 2 is a graph showing variations of shear stress at a shear rate of 4.42 (sex~1) for various
PVC resin composition samples.
Referring to Fig. 1, the resin mixing system 10 comprises a feed hopper 11 for conductive carbon particles which contains a weighing unit 12. A suitable weighing unit 12 includes a hopper for storing excess carbon black and an auger or screw conveyor to convey the carbon black to a basket which is preset to accept a predetermined quantity of material. A pneumatic load cell and a digital display on a remote control panel complete the weighing unit 12.
When the desired amount of carbon black is collected in the weighing unit 12, on demand the carbon black passes through a butterfly valve 14 and-is pneurriatically conveyed to a mill 16 which breaks up agglomerates of the carbon particles to the desired particle size. We have found a mill of the Centrimil type, manufactured by Entoleter Inc.
of New Haven, Connecticut to be suitable. This mill comprises a series of sets of rotatable pins wherein each set intermesh between top and bottom and rotate at very high speeds. Carbon particles which pass through the Centrimil are knocked against these pins. The carbon particles are reduced to a uniform size by a bombarding action, with no shear or attrition forces generated.
The final particle size of the carbon black can be varied by varying the number of sets of pins traversed by the carbon black particles through the mill, and by varying the speed of rotation of the pins. We have-found that by using 5 sets of steel pins and rotating them at 6000 rpm, over 99 percent by weight of the carbon black particles will pass through a 325 mesh screen (U.S. Sieve
Series), corresponding to a particle size of about 0.044 millimeters, and about 94-96 percent will pass through a 400 mesh screen, corresponding to a particle size of 0.038 millimeters. It takes about 40 seconds to grind about 7 pounds
(3,175.2 grams) of carbon black.During this step the bulk density of the carbon black changes from
about 140160 grams per liter for the starting
material to about 45-55 grams per liter for the
milled particles.
The now finely divided carbon black particles from the mill 1 6 are conveyed to a cyclone
separator 1 8 where the carbon particles are
deaerated and held in a carbon black collector
hopper 20 which connects to a high intensity
mixer 22.
The air from the cyclone separator 1 8 is then
conveyed through a vacuum line 23 to a carbon
black dust collector 24 wherein any airborne
carbon black particles are separated from the air,
dropped onto the bottom of the dust collector 24
and are conveyed through a rotary valve 25 back
to the collector hopper 20. This closed system
ensures against loss of carbon black and against
inadvertent discharge of carbon black into the
atmosphere. The purified air from the dust
collector 24 is pumped away through vacuum
pump 26.
A suitable high intensity mixer 22 is
manufactured by Welex Inc. of Blue Bell,
Pennsylvania. This mixer brings the ingredients to
be mixed down into a vortex, through a mixing
blade, up along the side walls of the mixer and
down into the vortex again. This type of mixing
generates high shear and high speeds of inter
particle friction and promotes a uniform
dispersion of the ingredients.
The PVC resin is weighed in a vinyl weigh
hopper 28 and the solid additives, including
stabilizers, lubricants and modifiers, weighed in a
solid additive hopper 30. The PVC resin and solid
additives are charged to the mixer 22 through a
conveyor system and the mixer 22 is turned on for a few seconds to mix the resin and the additives.
The mixer 22 is shut off, a first batch of carbon black from the carbon black collector hopper 20 is added through a knife gate valve 32 and the mixer 22 turned on again for about 30--45 seconds at low speed to mix the carbon black with the resin.
Conveniently about 1/4 of the total carbon black is added at a time; however this is not critical.
The knife gate valve 32 is closed automatically about 60 seconds after the collecter hopper 20 is emptied. This action turns on the mill 16 and the vacuum pump 26. The butterfly valve 14 opens and the next portion of carbon black is discharged from the weighing unit 12, passed through the mill 1 6 and on to the cyclone separator 1 8 where it is deaerated and discharged into the collector hopper 20. When all of the carbon black has been discharged from the weighing unit 12, the butterfly valve 14 closes. Forty (40) seconds later, the mill 1 6 and vacuum pump 26 are shut off. The next portion of carbon black is then weighed into the weighing unit 12.
After the first portion of carbon black is mixed as above, additional portion of carbon black are added to the mixer and mixed at low speeds until about half of the carbon black has been added.
During these additions, the carbon black is primarily filling up voids in the vinyl particles, which are initially very irregularly shaped and porous. When. additional amounts of carbon black are added however, the temperature of the resin must be increased enough so that the resin particles begin to adsorb additional carbon particles within the resin structure. The temperature required is a function of the glass transition temperature, hereinafter Tg, and melting point of the particular vinyl polymer used; lower
Tg resins will adsorb carbon particles at lower temperatures than higher Tg resins for example.
Thus additional portions of carbon black are mixed using both low amd high speed mixing to increase the temperature of the resin, thereby softening its surface and allowing increased adsorption of carbon black into the resin. The final temperature of the resin will be determined by the amount of carbon black to be added and the physical properties of the PVC resin.
After all of the carbon black has been added and mixed, the liquid additives are conveyed from the liquid additive feed 33 into the mixer 22 and blended at low speeds. When the liquid has been dispersed, a final high speed mixing is carried out to ensure a completely uniform dispersion of all of the ingredients. During this mixing period, the bulk density of the vinyl powder, which may originally be about 500-600 grams per liter, will decrease, generally to about 300-350 grams per liter, due to the expansion of the vinyl particles on heating. The vinyl particles then adsorb carbon black particles, solid additives and liquid additives, which in turn raises the bulk density to about 450 grams per liter.
The resin blend is then discharged to a cooler 34 where it is cooled to about 80-1 000F -(26.7-37.80C). During the cooling period the vinyl particles contract, and some additional adsorption may occur, so that the cooled molding composition may have a bulk density of about 500-550 grams per liter, similar to the starting vinyl resin.
Polyvinylchloride resins suitable for use herein include polymers and copolymers of vinyl chloride and mixtures thereof. In order to produce a desired characteristic in the molded articles, the
PVC resin should have a comparatively high heat distortion temperature, preferably 1400 F (600C) or higher for the unfilled resin. Suitable polymers include homopolymers of vinyl chloride such as a
PVC resin available from the B. F. Goodrich
Company which has a weight average molecular weight of 84,400 and number average molecular weight of 38,140 and a Tg of 880C; or a vinyl chloride-polypropylene copolymer commercially available as AP-480 from Air Products 8 Chemicals inc. which has a Tg of 760C. Other PVC homopolymers such as Great American Chemical
Company's 550 Resin and Air Products' 2160
Resin and the like can also be employed.
Conductive carbon particles suitable for use in the molding compositions include highly electrically conductive carbon blacks, preferably which have a low bulk density to reduce loading requirements. Presently preferred is a product of the Akzo Chemie Nederland, Ketjenblack EC, which has an apparent bulk density of about 140-160 grams per liter and an average primary particle size of about 300 angstroms. These carbon black particles have a high surface area and a high proportion of voids within the particles, as measured by dibutylphthalate absorption. This enables current to flow between the conductive particles in a non-conductive polymer matrix in a highly efficient manner. Other carbon blacks can also be employed, in whole or in part, provided they meet the electrical requirements.Denser particles of carbon will usually require higher weight loading, e.g., up to about 35-40 percent by weight, for an equivalent electrical conductivity. The particle size is not critical but it must be small enough so that a grainy surface in the piastic matrix is avoided. An amount of from about 12-20 percent by weight of a carbon black such as Ketjenblack EC is preferred.
Stabilizers are also added to PVC compositions, primarily to neutralize volatiles formed as decomposition products of the polyvinylchloride resin, particularly hydrogen chloride. Generally from about 1.5 to 4 percent by weight of stabilizers are added to the chosen PVC composition. Suitable stabilizers include organo tin compounds such as dibutyltin-P- mercaptopropionate, commercially available as T35 from M s T Chemical Company, Inc. and dibutyltin maleate, commercially available as
Mark 275 from Argus Chemical Company. Other metallic compounds derived from metals such as lead, zinc, barium and cadmium stearates, commercially available as Mark Q-232B from
Argus Chemical Company can also be used.If too much stabilizer is added to the resin it will not be absorbed, resulting in bleed-out or staining of the surface. Thus it is preferred to employ small amounts of more than one stabilizer in a particular molding composition.
Lubricants are also added to PVC compositions to prevent high shear heating during processing and to provide good release of the molded disc or other article from the mold. Generally from about 1-3 percent by weight of the molding composition of lubricants will be employed.
Suitable lubricants for PVC resins include calcium stearate; a room temperature solid esterified montan wax commercially available as Wax E of
Hoechst Company; a monofatty acid ester of varying molecular weight alcohols and acids commercially available as Loxiol G-30 from
Henkel International GmbH; polyfunctional complex esters of saturated fatty acids commercially available as Loxiol G-70, also available from Henkel International; low molecular weight paraffin oils such as Olio di
Vasilina from Carlo ERBA, a division of Chemica
Industrialle, Milan; and materials such as fatty acid amides including stearic amide, oleamide, ethylene bis stearamide and the like. At least two lubricants should be employed, again, to prevent bleed-out of the lubricant during the molding process.
Additional modifiers including plasticizers and processing aids in amounts up-to 10 percent by weight of the resin composition can also be added. The addition of primary plasticizers lowers the Tg of the resin composition and the heat distortion temperature. These materials are compatible with PVC resins. Liquid primary plasticizers have the greatest effect on the Tg and the heat distortion temperature. Suitable liquid plasticizers include epoxidized soybean oils having molecular weights of about 1000, commercially available as Paraflex G-62 from
Rohm 8 Haas Company; primary phthalate type plasticizers such as diisooctylphthalate and
Santicizer 711 from Monsanto Company; and polymeric ester plasticizers such as Kodaflex NP10 available from Eastman Chemical Products.
The-addition of solid plasticizers and processing aids have a small effect, if any, on the
Tg of the resin composition and the heat distortion temperature, and are added to improve the processing and molding characteristics of the resin composition. Suitable solid plasticizers include chlorinated paraffin waxes such as
Unichlor 70AX from Neville Chemical Company; glyceryl tribenzoate commercially available as
Benzoflex S-404 from Velsicol Chemical
Corporation; and dicyclohexylphthalate.
Suitable processing aids include low molecular weight acrylic resins, such as polymethylmethacrylate resins commercially available as Acryloid K-147 and Acryloid K-1 75 from Rohm and Haas Company.
The above process produces a composition containing large amounts of carbon black particles uniformly dispersed in a vinyl resin with a minimum of batch to batch variations. Although the exact reasons for the success of the present process is unknown, it is believed that by finely dividing the carbon black particle agglomerates so that they are substantiaily smaller than the vinyl particles, they are easier to mix and disperse and they are able to be absorbed into the voids present in the vinyl particles. By increasing the temperature of the vinyl as more carbon black is added, more adsorption of the carbon black onto the surface of the vinyl particles also takes place.
The closed system described prevents losses of carbon, allows exact weighing of low density carbon particles and minimizes batch to batch variations. Video discs of high quality and reproducibility can be molded from the compositions made by the above process.
The invention will be further illustrated by the following Examples which are not meant to limit the invention. In the Examples, parts are by percent.
Example 1
Using a system illustrated in Fig. 1,74.75 parts of vinyl resin, 1.50-parts of T-35 stabilizer, 2.00 parts of Acryloid K-147 processing aid, 0.75 part of Acryloid K-1 75 processing aid, 0.75 part of G30 lubricant, 0.25 part of G-70 lubricant and 0.50 part af calcium stearate lubricant were added at room temperature to a Welex mixer which was preheated to 1 650F (73.90C). The ingredients were mixed for 30 seconds at low speed (400 rpm) when the temperature was about 108 1 090F (41 .7-42.20C). A first portion of conductive carbon black, Ketjenblack EC which had been processed through a Centrimil so that the milled black had an apparent bulk density of about 50 grams per liter and wherein less than 1 percent of the milled particles were retained on a 325 screen (U.S. Sieve Series), 3.75 parts, was added and stirred at low speeds for 30 seconds when the temperature reached 125-1 270F (51.7--52.80C).The mixer was shut off for 1 minute to allow the next portion of milled carbon to reach the collector hopper and the second 3.75 part portion of carbon was added, stirred at low speed when the temperature reached 136 1 380F (57.8-58.90C). The third 3.75 portion of milled carbon was then added in similar manner, but mixed first at low speed for 30 seconds (the temperature was now 154-1 600 F) (67.8- 71.1 0C) and then at high speed (800 rpm) for about 60 seconds or until the temperature reached at least 1 500F (65.60C), whichever was last.Typically the temperature was now about 156-1 590F (68.9-70.60C). The fourth 3.75 part portion of milled carbon was then added, mixed for 30 seconds at low speed when the temperature was 1 65-1 700F (73.9-76.70C) and then at high speed to a temperature of 1 650F (73.90C) or for 60 seconds. The liquid additives were then added; 1.00 part of Mark 275, 3.0 parts of Santicizer 711 and 0.30 part of Olio di
Vasilina.The liquids were stirred in at low speed until the temperature reached 171-1750F (77.2-78.90C) (2-3 minutes) and then the
mixture was stirred at high speed until the temperature reached 235"F (1 12.5"C) (about 8.5-9.5 minutes). The blend was cooled, fed to a plasticating extruder and pelletized.
Excellent video discs were compression molded from the above composition.
Control
A molding composition was prepared by charging the following ingredients at room temperature in a Welex mixer preheated to 1 650F (73.90C): 74.05 parts of a vinyl chloridepolypropylene copolymer AP-480 of Air Products s Chemicals, Inc. which has a Tg of 760C;15.00 parts of conductive carbon black Ketjenblack EC which had an apparent bulk density of 1 57 grams per liter and wherein 1 8 percent of the carbon black remained on a size 1 8 screen (U.S.Sieve
Series); 0.50 part of Loxiol G-30 lubricant and 0.25 part of Loxiol G-70 lubricant; 0.30 part of calcium stearate lubricant; 2.00 parts of Acryloid
K-175 processing aid; 1.50 parts of the stabilizer
T-35; 0.40 part of Wax E lubricant; 1.00 part of
Benzoflex S-404 modifier and 2.00 parts of chlorinated paraffin wax Unichlor 70AX modifier.
The ingredients were mixed for 30 seconds at low speed, when the temperature was 104 1 060F (40.0-41.1 OC) and then at high speed until the temperature reached 1 650F (73.90C).
The liquid additives were then poured in; 1.00 part of dibutyltin maleate Mark 275 and 1.00 part of epoxidized soybean oil Paraplex G-62. The liquid additives were stirred in at low speed until the temperature reached 1 700F (76.70C) and then mixed at high speed until the temperature reached 1 900F (87.80C) which took about 2.53 minutes. The mixture was cooled, fed to a plasticating extruder and pelletized.
Twelve batches were mixed as above, pelletized and stored in twelve drums. The melt viscosity of a sample of each drum was measured using shear stress data at a shear rate of 4.42 (sec.-1). The measured shear stress data for each drum was plotted as shown in Fig. 2.
Example 2
Two lots of 10-12 drums each, designated lot 1 and lot 2, of a composition containing the same ingredients as the Control were mixed in accordance with the procedure described hereinabove in Example 1 using the system as in Fig. 1, except that the final temperature was 1 900F (87.00C) instead of 2350F. These lots were cooled, fed to a plasticating extruder and pelletized.
The melt viscosity from each of the drums of lots 1 and 2 was measured using shear stress data at a shear rate of 4.42 (sex.~1). The measured shear stress data was plotted in Fig. 2.
Drums 1597-1608 were compositions of the
Control; drums 1610--1621 were compositions of Example 2 lot 1; and drums 1622-1631 were compositions of Example 2 lot 2. The desired viscosity is within the range 12.5-1 6.5. It is apparent that the sample to sample variation for the compositions made according to the present process is less than that for the prior art method of the Control, indicating a more uniform dispersion of ingredients was achieved using the present disclosed process.
Claims (8)
1. In a process for mixing a conductive PVC based molding composition containing sufficient amounts of conductive carbon black particles so that the resultant composition has a resistivity below about 500 ohm-cm at 900 MHz, the improvement which comprises dividing the carbon black particles to a particle size of 0.044 millimeter or less and adding the carbon black particles in a portionwise manner to the PVC resin so that a uniform dispersion is obtained.
2. The process according to claim 1 wherein the carbon black has an initial bulk density of 140--160 grams per liter.
3. The process according to claim 2 wherein the carbon black is divided by milling and the milled carbon black has a bulk density of about 45-55 grams per liter.
4. The process according to claim 1 wherein the carbon black is finely divided and added to the
PVC resin in a closed system.
5. The process according to claim 1 wherein the carbon particles are added while increasing the temperature of the vinyl resin particles.
6. The process of claim 5 wherein the carbon black is absorbed and adsorbed onto the vinyl resin particles so that no free carbon black is present.
7. A process for mixing a conductive PVC based molding composition substantially as hereinbefore described with particular reference to the Figs. of the accompanying drawings.
8. A PVC-based molding composition when mixed using the process of any of Claims 1-7.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US4174779A | 1979-05-23 | 1979-05-23 |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2048901A true GB2048901A (en) | 1980-12-17 |
GB2048901B GB2048901B (en) | 1983-03-16 |
Family
ID=21918117
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8013504A Expired GB2048901B (en) | 1979-05-23 | 1980-04-24 | Preparing conductive moulding compositions |
Country Status (7)
Country | Link |
---|---|
JP (1) | JPS55158919A (en) |
AT (1) | AT372794B (en) |
DE (1) | DE3018233A1 (en) |
FR (1) | FR2457170A1 (en) |
GB (1) | GB2048901B (en) |
IT (1) | IT1141580B (en) |
NL (1) | NL8002983A (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4472336A (en) * | 1981-04-17 | 1984-09-18 | Matsushita Electric Industrial Co., Ltd. | Method of manufacturing video disc |
JPS59171052A (en) * | 1983-03-18 | 1984-09-27 | Victor Co Of Japan Ltd | Recording medium of high density information signal |
JPS59194818A (en) * | 1983-04-20 | 1984-11-05 | Victor Co Of Japan Ltd | Preparation of high density information signal recording medium |
JPS60115036A (en) * | 1983-11-26 | 1985-06-21 | Victor Co Of Japan Ltd | Electrostatic capacity type recording medium |
CN105000358B (en) * | 2015-08-03 | 2017-08-18 | 江苏锐升新材料有限公司 | Mixing device |
-
1980
- 1980-04-24 GB GB8013504A patent/GB2048901B/en not_active Expired
- 1980-04-28 IT IT21683/80A patent/IT1141580B/en active
- 1980-05-13 DE DE19803018233 patent/DE3018233A1/en not_active Withdrawn
- 1980-05-21 JP JP6840280A patent/JPS55158919A/en active Pending
- 1980-05-21 AT AT0271480A patent/AT372794B/en not_active IP Right Cessation
- 1980-05-22 FR FR8011454A patent/FR2457170A1/en active Granted
- 1980-05-22 NL NL8002983A patent/NL8002983A/en not_active Application Discontinuation
Also Published As
Publication number | Publication date |
---|---|
IT8021683A0 (en) | 1980-04-28 |
IT1141580B (en) | 1986-10-01 |
DE3018233A1 (en) | 1980-12-04 |
JPS55158919A (en) | 1980-12-10 |
NL8002983A (en) | 1980-11-25 |
FR2457170B1 (en) | 1984-01-27 |
GB2048901B (en) | 1983-03-16 |
ATA271480A (en) | 1983-03-15 |
AT372794B (en) | 1983-11-10 |
FR2457170A1 (en) | 1980-12-19 |
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PCNP | Patent ceased through non-payment of renewal fee |