ORGANOCLAY CONCENTRATES AND THEIR USE

PRIORITY CLAIM

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

Application Serial Number 60/704,991 bearing Attorney Docket Number 12005002 and filed on August 3, 2005.

FIELD OF THE INVENTION

[0002] This invention relates to concentrates of organoclays in a polymer matrix and their use in making sheet molding compounds.

BACKGROUND OF THE INVENTION

[0003] Sheet molding compounds ("SMC") generally are composite structures of pre-mixed the resin, filler, fibrous reinforcement, and other additives which then can be formed into a desired shape and cured in a heated, matched metal dye. Very large and complicated plastic parts can be made from these materials and by this method for use in a variety of industries such as transportation, electronics, appliances, etc.

[0004] Organoclays are exciting additives for a variety of purposes.

Organoclays are nanoclays surface treated with organic surfactants for later intercalation or exfoliation with polymers into nanocomposites. Nanocomposites can be concentrates for dilution or "let down" into other plastics or can be compounds themselves with the addition of other desired ingredients. U.S. Pat. Nos. 6,906,127; 6,852,813; 6,828,370; 6,632,868; 6,596,803; 6,462,122; 6,461,423; 6,407,155; 6,399,690; 6,391,449; 6,387,996; 6,376,591; 6,251,980; 6,232,388; 6,225,394; 6,090,734; 6,050,509; 5,998,528; 5,844,032; and 5,837,763 disclose the manufacture and use of nanocomposites. All of these patents are incorporated by reference as if rewritten herein. Nanocor, Inc. is a significant commercial source of exfoliated or intercalated

nanoclays and has a web site: www.nanocor.com. Also PolyOne Corporation (www.polyone.com) is a source of Nanoblend™ organoclay concentrates for use in polyolefm compounds and in polyamide compounds. [0005] U.S. Pat. No. 6,887,931 (Twardowska) is a recent example of the efforts to bring organoclay additives to sheet molding compounds by making a thermosetting inorganic clay nanodispersion, for use in preparing thermosetting nanocomposite articles.

SUMMARY OF THE INVENTION

[0006] What the art needs is a convenient means for introducing organoclays into sheet molding compounds. The present invention solves that problem in the art by providing an organoclay concentrate increases the viscosity of the sheet molding compound to a level that is capable of use within continuous extruder equipment.

[0007] In general, compounding of additives into thermosetting resins uses a batch mixing process. For example, when making sheet molding compounds, it is common practice in production of sheet molding compound to have a low viscosity compound to permit the liquid compound to be easily transferred by pumping or otherwise, and also for other reasons of easier handling and efficiency.

[0008] Sheet molding compound is not prepared using extruding equipment because such equipment is designed to run at very high torque to account for the high viscosity of the thermoplastic medium. Extruders designed for processing thermoplastic resins, such as twin screw extruder from major companies such as Coperion, Berstoff, or Leistritz, are machines are designed to impart work on the material for distributive and dispersive mixing with a high viscosity medium.

[0009] Thus, sheet molding compounds are generally not viscous enough to be processed in extruder equipment, which is known to have an advantage over batch process mixing vessels, such as those currently used for

making sheet molding compounds, because the extruder equipment can be a continuous manufacturing process.

[00010] Organoclays are good viscosity enhancing materials, hi this invention, organoclays in the form of concentrates are used to raise the relatively low viscosity of the uncured thermoset resins to a level where the viscosity is high enough to impart work and dispersion in the extrusion equipment.

[00011] Typically, when using extruders, a processing parameter called

"specific energy consumption" ("SEC") is used to measure the amount of energy put into the material. This is a measure of the amount of work done on the material within the extruder as it mixes the ingredients and disperses the additives into the thermoplastic resin.

[00012] Low viscosity materials, such as a conventional sheet molding compound, do not create enough torque and therefore have a very low SEC, less than about 0.01 kW hr/kg. By comparison, a typical SEC number for a thermoplastic compound undergoing extrusion processing can range from about 0.08 to about 0.4 kW hr/kg. Therefore, low molecular weight themoset resins typically used in making sheet molding compounds would not provide enough viscosity to reach these levels of SEC in an extruder. [00013] The present invention begins with the proposition for specific energy consumption that at least about 0.04 kW hr/kg would be required to achieve any level of mixing of a sheet molding compound in an extruder. Each incremental hundredth higher than 0.04 kW hr/kg, without listing each number for sake of space, is more desirable up to a practical limit of about 0.4 kW hr/kg that thermoplastics have as an SEC number. Preferably, the specific energy consumption can range from about 0.1 to about 0.25 kW hr/kg. [00014] Therefore, the present invention concerns the use of an organoclay that achieves a high level of interaction with the polymer resin(s) in the extruder to achieve higher viscosity of the sheet molding compound being worked in the extruder equipment.

[00015] It is unexpected that one would choose to use an additive that increases viscosity because traditional additives for thermoset resins that adversely increase viscosity are avoided to minimize problems with resin transport through normal batch mixing equipment suitable for thermoset resins, such as pumps and pipes.

EMBODIMENTS OF THE INVENTION

[00016] Organoclavs

[00017] Organoclays suitable for use in the present invention are those organoclays with higher organic contents to maximize interaction of the clay with the resin. Suitable surfactants to achieve this could be quaternary ammonium surfactants.

[00018] U.S. Pat. No. 6,462,122 (Qian et al.) and U.S. Pat. No. 6,583,209

(Mehta et al.), both incorporated by reference herein, disclose a variety of organoclays that employ quaternary ammonium surfactants which are suitable for the present invention. Organoclays containing dimethyl, dihydrogenated tallow quaternary ammonium surfactants or octadecyl amine quaternary ammonium surfactants are more preferred that those surfactants that have less than about 14 carbon atoms because higher molecular weight surfactants generally increase the SEC value of a nanocomposite being processed in an extruder.

[00019] Moreover, the amount of surfactant present in the organoclay can influence the interaction of the organoclay with the polymer resin(s) in the extruder, which causes increased viscosity. The amount of surfactant present in the organoclay can range from about 30 weight percent to about 50 weight percent, and preferably from about 35 weight percent to about 50 weight percent.

[00020] Without being limited to a particular theory, the amount of surfactant present in the organoclay is a determinator for how much melt dispersion is possible to increase viscosity of the compound being worked in the

extruder, whereas the identity or type of surfactant may change based on choice of thermoset resin to be made in to sheet molding compound or the carrier resin(s) for introducing the organoclay as a concentrate into that sheet molding compound.

[00021] Methods to treat inorganic nanoclay with surfactant are disclosed in the collection of patents identified in the Background of the Invention of this application and incorporated herein.

[00022] Moreover, commercially quantities of organoclays are available from Nanocor, Inc., Southern Clay, and Sued Chemie. Of these suppliers of organoclays, it is known that Southern Clay's Cloisite 1OA and 15A brand organoclays are treated with tallow-based surfactants that would satisfy the goal of interacting with the polymer resin(s) in the extruder and increase SEC and viscosity to a level acceptable for compounding sheet molding compound in an extruder.

[00023] Polymer Resinfs)

[00024] The polymer resin(s) to serve as a carrier for the organoclay in the concentrate can be any polymer that is compatible with any thermosettable polymer(s) that are to be used to make a sheet molding compound. [00025] One skilled in the art, without undue experimentation, can identify and use thermoplastic polymer(s) as carrier resin(s) for the organoclay in an analogous manner to the selection of carrier resin(s) for other additives employed in a batch processing of sheet molding compound. For example, U.S. Pat. No. 3,959,209 (Koppers), incorporated by reference herein, lists polymeric thermoplastics which reduce the shrinkage of thermosetting resin formulations as they are cured and thus effectively produce articles having smooth, high quality cosmetic surfaces. Listed in U.S. Pat. No. 3,959,209 are homopolymers of ethylene, styrene, vinyl toluene, alkyl methacrylates, alkyl acrylates, various copolymers of vinyl chloride and vinyl acetate, styrene and acrylonitrile, methyl methacrylate and alkyl esters of acrylic acid, methyl methacrylate and styrene, methyl methacrylate, and acrylamide. From this information, it is known that

these polymer resins are candidates for carrier resin(s) for concentrates of the present invention.

[00026] Moreover, one skilled in the art, can consult with industry leaders in thermosettable sheet molding compounds, such as Ashland Specialty Chemical Division of Ashland, Inc., to determine which carrier resin(s) are particularly suitable for use with such compounds from that company. [00027] The amount of organoclay in the concentrate can range from about 20 to about 80 weight percent. Conversely, the amount of carrier resin(s) can range from about 80 to about 20 weight percent.

[00028] It is optional to include other ingredients in the concentrate if the ingredients are desired as additives in the sheet molding compound and are otherwise compatible with the organoclays and the carrier resin(s). Non- limiting examples of optional additives include fillers, antioxidants, stabilizers, lubricants, pigments, biocides, and the like. Each of these additives is commercially available from well-known sources known to those skilled in the art.

[00029] Method of Making Concentrate

[00030] Compounding the concentrate of the present invention can take any number of routes according to preferences of those familiar with the compounding of thermoplastic materials. In one route, each ingredient is mixed into a large vessel, hi another route, batches of ingredients are first formed and then the batches are combined.

[00031] As preferred in the present invention, the following well-known steps can be employed in the following sequence: blenders containing ingredients feeding a hopper upstream from an extruder, usually twin-screw, co- rotating. The ingredients are thoroughly mixed under sufficient heat to melt the carrier resin(s).

[00032] Preferably, the mixing equipment is a co-rotating twin-screw extruder commercially available from Coperion/Werner-Pfleiderer. The extruder should be capable of screw speeds ranging from about 50 to about

2,000 rpm. The temperature profile from the barrel number two to the die should range from the melting temperature of the carrier resin to about 270°C. The composite can be pelletized for later use in the formation of articles as described below.

[00033] Method of Using the Concentrate

[00034] Any type of extruder equipment that achieves sufficient mixing of ingredients can be used to mix the concentrate into the ingredients of the sheet molding compound, either pre-mixed or introduced individually. The same or similar extruder equipment as used to make the concentrate can also be used in the processing of the thermosettable sheet molding compound, hi addition to the concentrate, one can add the thermosettable resin(s), the reinforcing ingredients, the stabilizers, and other conventional materials common in formulations of sheet molding compound. Without undue experimentation, one skilled in the art can adapt a formulation for a thermosettable sheet molding compound made in a batch process mixing vessel into a formulation for a thermosettable sheet molding compound to be made in an extruder.

[00035] Because of the possibilities of extruding thermosettable sheet molding compound in a continuous process, it is also possible to place in modular arrangement a molding machine in relative close proximity to the extruder, such that continuous flow of thermosettable sheet molding compound can be directed to one or more molding machines for automated or nearly automated compounding and molding operations into a final molded product. An example of that modular arrangement is shown in U.S. Pat. No. 6,852,268 (Valyi et al.).

USEFULNESS OF THE INVENTION

[00036] Organoclay concentrates of the present invention not only increase viscosity of thermosettable sheet molding compounds to a level

sufficient to use extruding equipment for compounding, but also the organoclays provide performance benefits for the ultimate molded product. [00037] Typically, molded articles have reinforcing additives and other materials to improve impact resistance. Replacement, at least in part, of these reinforcing additives with organoclays can reduce weight while maintaining strength and durability of the molded article. Alternatively, addition of these organoclays can increase strength and durability of the molded articles beyond that currently known.

[00038] Organoclays in compounds result in lighter weight, stiffer, and tougher molded plastic articles than compounds without such organoclays in them. For example, it is known from Nanoblend™ LST thermoplastic compounds that Izod Impact and Tensile Modulus are higher than the same thermoplastic compounds without organoclay present. [00039] Articles made from concentrates of the present invention are more valuable because organoclays provide increased lightness and stiffness while retaining toughness. Such articles can be made into any number of shapes,- among them, automobile and truck parts, large appliance parts, and the like.

[00040] The amount of organoclay in the final sheet molding compound can range from about 3 to about 15 weight percent, with appropriate dilution or "let-down" in a thermosettable sheet molding compound formulation. [00041] The invention is not limited to these embodiments. The claims follow.