WO2008022240A1

WO2008022240A1 - Exothermic polyphenylene sulfide compounds using carbon black

Info

Publication number: WO2008022240A1
Application number: PCT/US2007/076073
Authority: WO
Inventors: David Jarus; Roger W. Avakian
Original assignee: Polyone Corporation
Priority date: 2006-08-18
Filing date: 2007-08-16
Publication date: 2008-02-21

Abstract

Use of particles of carbon black as the only exothermic additive in a polyphenylene sulfide compound results in an extruded or molded thermoplastic article that is electrically conductive and exothermic when connected to a source of electrical energy. Electronic devices benefit from these articles, particularly where ink must be melted for imaging of commercial graphics on a substrate.

Description

EXOTHERMIC POLYPHENYLENE SULFIDE COMPOUNDS USING CARBON BLACK

CLAIM OF PRIORITY

[0001] This application claims priority from U.S. Provisional Patent

Application Serial Number 60/822,863 bearing Attorney Docket Number 12006016 and filed on August 18, 2006, which is incorporated by reference.

FIELD OF THE INVENTION

[0002J This invention concerns polyphenylene sulfide compositions useful for electronic devices.

BACKGROUND OF THE INVENTION

[0003J Electronic devices are concerned with power management, energy consumption, evacuation of heat from, and delivery of heat to, key electronic components. As electronic devices become more sophisticated, alternative materials are sought to reduce weight, cost, and other factors affecting both price and performance.

[0004] There are many examples of thermally conductive thermoplastic compounds which are designed to evacuate heat from electronic components that require certain operating temperatures to be productive and efficient. For example, Therma-Tech brand products from PolyOne Corporation are engineered to transport heat away from a key component, such as a microprocessor.

[00Θ5] However, there are some electronic devices that require the delivery of heat to key components. Examples of such electronic devices are certain electronic printing devices that require components to be of a certain temperature for delivery of colorants to the imaging media. U.S. Pat. No. 6,905,201 describes the use of heat to melt a solid ink into a liquid ink in commercial graphics printers. [0006] U.S. Pat. No. 6,086,791 (Miller) discloses coatings and films of a non-metallic electrically conductive coating composition effective in emitting heat without break-down when connected to a source of electricity, which comprises: (a) a binder; (b) electrically conductive flake carbon black of particle size between about 5 and 500 micrometers; (c) electrically conductive flake graphite of particle size between about 5 and 500 micrometers; (d) a volatile solvent; wherein the weight amount of (b) and (c) together ranges from between about 10 and 75 weight percent based on the non- volatile solids content of the coating composition. U.S. Pat. No. 6,818,156 (Miller) also discloses coating and films using carbon-based materials having particle sizes in the nanometric and micrometric range for emitting heat.

SUMMARY OF THE INVENTION

[0007] Unfortunately, films and coatings such as those disclosed by

Miller are present only at the surface of an article. Such films and coatings can chip, delaminate, or flake leaving the article untreated.

[0008] What the art needs is a compound that melts or degrades only at very high temperatures yet is exothermic throughout the bulk of the compound to deliver heat of a desired temperature to key components of an electronic device such as a commercial graphics printer. Because the compound is exothermic throughout its bulk, there is no possibility of loss of the thermally conductivity because of loss of a treatment on the surface of the component.

[ΘΘ09] The present invention solves that problem in the art by providing a polyphenylene sulfide compound that is exothermic throughout its bulk when connected to a source of electrical energy.

[00010] One aspect of the present invention is a high temperature exothermic composition, comprising a polyphenylene sulfide and an exothermic additive consisting essentially of particles of carbon black.

[00Θ11] Another aspect of the present invention is a thermoplastic article, comprising the polyphenylene sulfide composition described above, wherein the article is exothermic throughout the bulk of the article when the article is connected to a source of electrical energy.

|00012j Another aspect of the present invention is an electronic device having at least one component comprising a thermoplastic article described above.

[0Θ013] "Exothermic additive" for purposes of this invention means the carbon black particles can be formulated into the polyphenylene sulfide to provide a specific temperature when the polyphenylene sulfide composition is formed into an article and is powered by electricity at a specific voltage. Stated another way, the formulation of the compounds of the present invention can be adjusted to accommodate specific voltages intended for electrical energy added to the compound, so as to generate a controlled and specific temperature. [00014] . Contrary to the requirement of employing a combination of particles of carbon black and graphite, in the manner as disclosed in U.S. Pat. No. 6,086,791 (Miller) or U.S. Pat. No. 6,818,156, dispersed throughout a polyphenylene sulfide compound, an article of the present invention formed from the compound can become electrically conductive effective to emit heat without break-down of the compound or the thermoplastic article into which it is formed and without the necessity of using graphite. Because the melting or other degradation point of polyphenylene sulfide is higher than the temperature desired for the components of the electronic device, it is possible to engineer any specific temperature of heat emitted from a thermoplastic article of the present invention,

[00015] Without being limited to a particular theory, it has been found for certain voltages to achieve certain temperatures in polyphenylene sulfide-based compounds that the contribution of graphite to the electrical and thermal properties of the compound is so negligible as to be non-existent. Use of formulations that are based on polyphenylene sulfide differs from those found in the Miller patents, in that the polyphenylene sulfide itself has a thermal conductivity multiply higher than that of conventional thermoplastics such as polyolefins and polyesters. Therefore, compounds of the present invention, as presently understood, utilize the polyphenylene sulfide with an exothermic additive consisting essentially of the carbon black particles to provide the balance of electrical conductivity needed to energize the bulk of an article made from the compound with thermal energy exothermically emitted from ingredients contained in the bulk of the article.

|ΘOO16] With that balance achieved, for a given formulation at a given voltage of electrical energy input, without undue experimentation, one of ordinary skill in the art will be able to adjust the relative weight percentages of the ingredients to provide a compound that receives electrical energy at a given voltage and emits thermal energy at a given temperature. Moreover, the thermal energy can be found to "plateau" or level off over time, based on the formulation and the voltage, such that when energized, relatively quickly, an article made from the compound of the present invention within 6 minutes achieves a temperature of more than 300⁰F (about 150⁰C) with as little as 70 volts of electrical energy.

[000! 7] Advantages of the invention are explained with reference to the following embodiments.

EMBODIMENTS OF THE INVENTION [00018] Polvphenylene Sulfides

[00019] Polyphenylene sulfides are polymers containing a phenyl moiety and one or more sulfides bonded thereto. Those skilled in the art will recognize the variety of commercially available polyphenylene sulfides are suitable for use in the present invention. Non-limiting examples of such commercially available polyphenylene sulfides ("PPS") include Ryton brand PPS powders in various grades from Chevron Phillips Chemical Co. of The Woodlands, Texas. Any of the patents in the literature known to those skilled in the art are appropriate for determining a suitable choice, without undue experimentation. [00020] Exothermic Additive [00021] The exothermic additive for the present invention is limited to particles of carbon black.

[00022] An acceptable commercially available carbon black is Printex

XE2 super conductive carbon black particles having a particle size of about 35 nm, from Degussa of Akron, Ohio, among other locations. Other types of carbon black particles include, without limitation, Corax^® and Purex^® brand carbon blacks, also from Degussa, Ketjenblack^® brand carbon blacks from Akzo

Nobel, Black Pearls^® brand carbon blacks from Cabot Corporation. Useful grades of carbon black as described in RUBBER TECHNOLOGY 59-85 (1995) range from NI lO to N990.

[00023] Therefore, average diameter particle size of the carbon black can be any size within the nanometric region, and more particularly from about 15 to about 900 nm, and preferably from about 20 to about 80nm. The aspect ratio of the carbon black can be any range customarily found, preferably ranging from about 1 :1 for spherical particles to about 5:1.

[00024] The cumulative amount of carbon black as the exothermic additive can range from about 1 to about 75 weight percent of the total thermoplastic compound, and desirably less than about 18 weight percent, preferably less than about 15 weight percent, and most preferably less than about 10 weight percent. Generally, the greater the concentration of carbon black, the more exothermic the thermoplastic compound at a given amount of applied electrical energy.

[00Θ25] Optional Other Polymers

[00026] The compound of the present invention can include additional polymer resins to alter the morphology or rheology of the compound. The other polymers can be compatible with PPS in order to form blends or incompatible with PPS in order to form a continuous/discontinuous two-phase polymeric system.

[Θ0027] Non-limiting examples of other optional polymers include poiyoleflns, polyamides, polyesters, polyhalo-olefms, and polyurethanes. Presently preferred among these optional polymers are polyolefins such as polyethylenes, and more preferably high density polyethylenes (HDPE), in order to reduce brittleness of molded parts made from compounds of the present invention.

[00028] The cumulative amount of optional other polymers can range from 0 to about 25 weight percent of the total thermoplastic compound. [00029] Optional Additives

[00030] The compound of the present invention can include conventional plastics additives in an amount that is sufficient to obtain a desired processing or performance property for the compound. The amount should not be wasteful of the additive nor detrimental to the processing or performance of the compound. Those skilled in the art of thermoplastics compounding, without undue experimentation but with reference to such treatises as Plastics Additives Database (2004) from Plastics Design Library (www.williamandrew.com), can select from many different types of additives for inclusion into the compounds of the present invention.

[00031] In compounding PPS, other compounding ingredients are desirably incorporated into the PPS Io produce compounding formulas. Other compounding ingredients can include fillers, pigments and colorants if desired, processing lubricants, impact modifiers, uv-stabilizers, other processing aids, as well as other additives such as biocides or flame retardants. [00032] Fillers ordinarily are used to reduce cost and gloss and can include conventional calcium carbonates, clay, talc, mica, and diatomaceous earth fillers. Useful pigments and colorants can be organic, but preferably mineral such as titanium dioxide (which also serves as a uv- stabilizer). [00033] Impact modifiers are useful in PPS to increase toughness and can include chlorinated polyethylenes, ABS, acrylic polymers and copolymers, or methacrylic copolymers such as methylmethacrylate-butadiene-styrene (MBS). [00Θ34] Other processing aids for extruding PPS in complex profiles include acrylic or styrene-acrylonitrile copolymers to prevent edge tear in the extrusion of complex profiles or configurations.

[00035] Lubricants can be used to reduce sticking to hot processing metal surfaces and can include polyethylene, paraffin oils, and paraffin waxes in combination with metal stearates. Other lubricants include metal carboxylates, and carboxylic acids.

[00036] The cumulative amount of optional additives can range from 0 to about 40 weight percent of the total thermoplastic compound, depending on the type of additive and desired processing or performance property to be changed from the compound without such additive(s) therein. Without undue experimentation, one skilled in the art can determine the appropriate amounts using statistical techniques such as Design of Experiments. [00037J Processing

[Θ0038] The preparation of compounds of the present invention is uncomplicated to those skilled in the art of thermoplastic compounding. The compound of the present can be made in batch or continuous operations. [00039] Mixing in a continuous process typically occurs in an extruder that is elevated to a temperature that is sufficient to melt the polymer matrix with addition either at the head of the extruder or downstream in the extruder of the solid ingredient additives. Extruder speeds can range from about 50 to about 500 revolutions per minute (rpm), and preferably from about 100 to about 300 rpm. Typically, the output from the extruder is pelletized for later extrusion or molding into polymeric articles.

[00040] Prior to extruding at temperatures sufficient to melt the PPS, the ingredients are physically mixed together using a Henschel mixer. The processing of the present invention begins with mixing of carbon black with the PPS, This batch mixing improves dispersion of carbon black within and throughout the bulk of the extruded PPS article. [00041] Mixing in a batch process typically occurs in a Banbury mixer that is also elevated to a temperature that is sufficient to melt the polymer matrix to permit addition of the solid ingredient additives of any optional additive. The mixing speeds range from 60 to 1000 rpm and temperature of mixing can be ambient. Also, the output from the mixer is chopped into smaller sizes for later extrusion or molding into polymeric articles. [00042] Compounds can be formed into powder, cubes, or pellets for further extrusion or molding into polymeric electronic device components. [00043] Subsequent extrusion or molding techniques are well known to those skilled in the art of thermoplastics polymer engineering. Without undue experimentation but with such references as "Extrusion, The Definitive Processing Guide and Handbook"; "Handbook of Molded Part Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational Molding Technology"; and "Handbook of Mold, Tool and Die Repair Welding", all published by Plastics Design Library (www.williamandrew.com), one can make articles of any conceivable shape and appearance using compounds of the present invention.

USEFULNESS OF THE INVENTION

[00044] Compounds of the present invention can be made into articles which generate heat when connected to electrical energy. One can connect a source of electrical energy via electrodes to an article made from a compound of the present invention, to generate heat sufficient to raise the temperature of a component of the electronic device to a desired amount. The temperature can be controlled by a rheostat which controls the voltage of electrical energy introduced into the thermoplastic article.

[00045] If there is any concern about the amount of electrical energy that is being delivered to the article, one can also include any type of current arrestor, such as an inline fuse, to assure that no more than a specific amount of electrical energy is to be delivered to the exothermic thermoplastic article of the present invention. An inline fuse would forestall excessive electrical energy being delivered to the article that would otherwise generate such heat as to degrade or melt the polyphenylene sulfide in the article or harm any component of an electronic device in the vicinity of the thermoplastic article. [00046] Any form of electrode is suitable for connecting articles of the invention to the source of electrical energy. Ranging from alligator metal clips from a consumer retail outlet such as Radio Shack stores to pressure sensitive electrodes from a commercial wholesale outlet such as 3M Company, the goal of the electrode is to connect the article to the source of electrical energy without excessive loss of energy.

[00047] The amount and type of carbon black in the compound establishes the temperature at which an article remains, given the environment within which the article resides.

[00048] Contrasted with a coating or film as disclosed in the Miller patents, which might be susceptible to chipping or flaking from the exposed surface of the article, having the exothermic additive dispersed throughout the bulk of the thermoplastic polyphenylene sulfide compound assures continued performance even if the exposed surface of the article is scratched or marred. [00049] Depending on the geometry of the article, one may need to provide more than one set of electrodes to the article, perhaps providing the electrical energy to various sections of the article.

[0005Θ] Moreover, it is quite possible to engineer the article to have different sections made from different compounds having different concentrations of exothermic additive dispersed therein, thereby resulting in different temperatures in the different sections by design. [00051] Electronic devices that can benefit from compounds of the present invention are too numerous to exhaustively list. Non-limiting examples of electronic devices include those disclosed in U.S. Pat. Nos. 4,814,786; 5,123,961 ; 5,621,444; 6,860,591; and 6,905,201 and U.S. Published Patent Applications US 2004/01 14008 and US 2004/01 14010, especially the ink melter assembly disclosed in U.S. Pat. No. 6,905,201.

[0ΘΘ52] Two examples farther explain the invention.

EXAMPLES

[00053] Example 1

[00054] A compound of the present invention was compounded, extruded, and molded into test plaques. The compound was composed of 71 weight percent Ryton brand PPS, 9 weight percent Printex XE2 brand carbon black particles (CAS No. 1333-86-4) having an average particle size of about 35 nm, and 20 weight HDPE (Solvay No. R21-281).

[00055] The carbon black was dry-mixed in a Henschel mixer for about 3 minutes followed by addition of PPS and mixing for about 4 minutes, followed by addition of the HDPE and continued mixing for about 6 minutes. Then the dry-blend of the compound was introduced into a Century 30 extruder, with the settings and results shown in Table 1.

[00056] The extrudate was pelletized for later molding.

[00057] Using a 33 Cincinnati Millacron molding machine, the following settings were used to mold plaques and tensile test bars of the compound of the present invention.

[00058] To measure exothermic properties, two holes were drilled into a conventional tensile test bar at opposite ends approximately 6 inches apart in order to attach brass screws. Probes from a Variac voltage rheostat were then attached to the brass screws to create a voltage loop. An IR gun was affixed at approximately 4 inches above the tensile bar to measure surface temperature at the center of the bar.

[00059] Table 3 shows the results of measuring temperature, over time, for the compound with electrical energy added at 15, 30, 70, 100 volts (AC).

* Time to about 90% of temperature recorded at 14.75 mins. ** Approximately ambient temperature of the room.

[00060] Table 3 shows that a compound with 9 weight percent of carbon black particles in PPS can achieve a plateau temperature after 15 minutes between about 100⁰F and 33O⁰F (about 37°C to 165°C) when between 30 and 70 volts of electrical energy is introduced via electrodes into the test tensile bar. With this knowledge, one skilled in the art can adjust carbon black content or voltage, or both, to achieve any temperature between about 100⁰F and 400⁰F to provide an article formed from an exothermic compound of the present invention.

[00061] Table 4 shows additional details from the same experiment as reported as the data in Table 3. Specifically, for the 30 Volt and 70 Volt test, the temperatures were recorded at 15 second intervals. The rate of increase and percentage of final temperature are also computed. Certain cells are shaded for convenience of reading.

[Θ0062] The ability, using one formulation to establish a plateau temperature based on different voltages, allows one of ordinary skill in the art to achieve any temperature between the extremes of ambient temperature and as much as almost 170⁰C. As explained in Table 3, the times to 90% of plateau temperature are 3 minutes and 7 minutes, respectively.

[00063] It should also be noted that within two minutes of electrification at 70 volts (AC), one can exceed a temperature of the boiling point of water. Thus, a cycle of about two minutes "on" and two minutes "off", operating at 70 volts (AC) could be used in an article of the compound of the present invention to heat and maintain heat at any temperature above the boiling part of water, knowing that continuous heating of as much as 15 minutes would not exceed a temperature of about 17O⁰C. [00064] Example 2

[00065] A compound of the present invention was compounded, extruded, and molded into test plaques in the same manner as Example L The compound was composed of 70.2 weight percent Ryton brand PPS, 9.8 weight percent Printex XE2 brand carbon black particles (CAS No. 1333-86-4) having an average particle size of about 35 nm, and 20 weight HDPE (Solvay No. R21- 281). Thus, the amount of carbon black was increased 9% over Example 1 but remained below the preferred amount of about 10 weight percent. Table 5 shows the results for a test of 30 volts (AC). A 9% increase in carbon black concentration increased the plateau temperature 39%, from 38°C to 53⁰C.

[00066] One skilled in the art can readily see that adjustment of carbon black concentration from 9.0 to 9.8 weight percent, resulting in a plateau temperature increasing from 38°C to 53⁰C₅ demonstrates that without undue experimentation, that person could adjust carbon black concentration to adjust resulting plateau temperature, for a given input of electrical energy. Thus, it is possible by adjustment of formulation or electrical voltage to achieve almost any plateau temperature below the melting point of PPS. [00067] Table 5 also demonstrates that one can achieve more than 50⁰C of temperature in an article made from a compound of the present invention with electrical energy of only about 1.4 volt-amps.

[00068] The invention is not limited to the above embodiments. The claims follow.

Claims

What is claimed is:

1. A polyphenylene sulfide composition, comprising:

(a) a polyphenylene sulfide, and

(b) an exothermic additive consisting essentially of particles of carbon black,

2. The composition of Claim 1, wherein the particles of carbon black comprise from about 1 to about 75 weight percent of the composition.

3. The composition of Claims 1 or 2, wherein the particles of carbon black have an average diameter ranging from about 15 nm to about 500 nm.

4. The composition of any of the above Claims wherein the aspect ratio of the particles of carbon black can range from about 1 :1 to about 5: 1.

5. The composition of any of the above Claims further comprising an additional polymer to alter the morphology or rheology of the composition.

6. The composition of Claim 5, wherein the additional polymer is selected from the group consisting of poiyolefms, polyamides, polyesters, polyhalo- olefins, and polyurethanes.

7. The composition of Claims 5 or 6, wherein the additional polymer is high density polyethylene.

8. The composition of any of the above Claims, wherein the composition, upon electrification, becomes exothermic without the necessity of using graphite.

9. The composition of any of the above Claims, further comprising optional additives selected from the group consisting of fillers, colorants, processing lubricants, impact modifiers, uv-stabilizers, other processing aids, biocides, flame retardants, and combinations thereof.

10. A thermoplastic article, comprising the polyphenylene sulfide composition of any of Claims 1-9, wherein the article is exothermic throughout the bulk of the article when the article is connected to a source of electrical energy.

11. An electronic device, comprising a thermoplastic article of Claim 10.