WO1995010564A1 - Dioxyde de silicium fume destructure utilise comme additif haute transparence - Google Patents

Dioxyde de silicium fume destructure utilise comme additif haute transparence Download PDF

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Publication number
WO1995010564A1
WO1995010564A1 PCT/US1994/011415 US9411415W WO9510564A1 WO 1995010564 A1 WO1995010564 A1 WO 1995010564A1 US 9411415 W US9411415 W US 9411415W WO 9510564 A1 WO9510564 A1 WO 9510564A1
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Prior art keywords
fumed silica
composition according
lbs
dispersion
bulk density
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PCT/US1994/011415
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English (en)
Inventor
Joginder N. Anand
Gregory W. Leman
Matthew Neville
Michael A. Lucarelli
Denis G. Miller
Robert S. Whitehouse
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Cabot Corporation
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Priority to AU80139/94A priority Critical patent/AU8013994A/en
Publication of WO1995010564A1 publication Critical patent/WO1995010564A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
    • C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
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    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
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    • C09C1/30—Silicic acid
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    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/28—Compounds of silicon
    • C09C1/30—Silicic acid
    • C09C1/309—Combinations of treatments provided for in groups C09C1/3009 - C09C1/3081
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/08—Treatment with low-molecular-weight non-polymer organic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/10—Treatment with macromolecular organic compounds
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    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/12—Treatment with organosilicon compounds
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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Definitions

  • the present invention relates to fumed silica and, more particularly, to fumed silica for use as a nucleating and clarifying additive in thermoplastic compositions.
  • Polyolefin resins are widely used in the production of packaging for sundries, containers, industrial parts and the like by virtue of their excellent mechanical and chemical properties, as well as their hygienic safety.
  • polyolefin resins are particularly suited for mass production because they can be molded easily. It is commonly known to add nucleating agents to certain polyolefins materials, such as polypropylene, to increase the rate of production, enhance physical properties, and improve the optical qualities of the polymer by modifying crystallization behavior.
  • Clarity is important in such items as household containers or housewares, household cleaners, personal care items, syringes, test tubes and other medical devices and the like.
  • clarity is not an inherent property of polyolefin plastics, most of which are more or less opaque due principally to their partially amorphous or crystalline nature.
  • polyolefins of good and enhanced clarity should possess crystal sizes at or smaller than the wavelength of visible light to prevent light scattering and thus, opacity.
  • the performance of a nucleating agent is, to a certain extent, dependent upon its degree of dispersion in a particular polymer melt. As a result, it is desirable that the nucleating agents be in as fine a form as possible.
  • Mechanical delumping, and other conventional size reduction devices are typically used to achieve a 1 to 10 micron powder. For an overview of size reduction technology, please see Kukla, "Understand Your Size-Reduction Options," Chemical Engineering Progress, pp. 23-
  • nucleators or nucleating agents are known to promote crystallization. See, for example, U.S. Patent Nos. 5,135,975 and 5,049,605 to Rekers, et al., and U.S. Patent No. 4,314,039 to Kawai et al., and U.S. Patent No. 4,016, 118 to Hamada. Also known as a sub-type of nucleating agents are clarifying agents which, in addition to improving processibility, substantially enhance the clarity of the polyolefin. See, for example, U.S. Patent No. 5,198,484 to Mannion, U.S. Patent No. 4,808,650 to Titus et al., U.S. Patent No. 4,483,952 to Uchiyama and U.S. Patent No. 4,371,645 to Mahaffey.
  • nucleators have therefore been added to accelerate the crystallization of thermoplastic compositions, as well as enhancing the impact resistance, rigidity, tensile strength and transparency is such compositions.
  • nucleators have been grouped into inorganic types, e.g. calcium carbonate, zinc fluoride, cadmium fluoride, talc, alumina and silica, and organic types, such as stearates, adipic acid, sebacates, aliphatic acid salts, benzoic acid salts, phenylsulfonic acid and the like.
  • inorganic types e.g. calcium carbonate, zinc fluoride, cadmium fluoride, talc, alumina and silica
  • organic types such as stearates, adipic acid, sebacates, aliphatic acid salts, benzoic acid salts, phenylsulfonic acid and the like.
  • Patent Nos. 4,321,357 and 4,321,357, fumed silicas and zinc oxide were found to have no effect in injection moldable amide-imide polymers and were useless as nucleating agents.
  • sodium benzoate and substituted sorbitols are the most common types of nucleating agents.
  • Sodium benzoate is the salt of benzoic acid and is frequently used as a nucleating agent in polyolefin compositions such as polypropylene. It has been found successful in the injection molding of polypropylene to improve processing (by reducing fabrication time) and enhance some of the performance characteristics. However, sodium benzoate is not an efficient clarifying agent.
  • substituted sorbitols provide improved processibility while increasing the aesthetic value by increasing clarity, i.e. reducing the amount of haze.
  • sorbitols like sodium benzoate, in plastics has resulted in several deficiencies, such as the transfer of unacceptable taste and odor to a contained material, plate-out in the mold at high processing temperatures, narrow molding temperature window, yellowing and inconsistent performance with different grades of material due to the presence of residual catalysts.
  • Prior art nucleating agents have resulted in polyolefin compositions having improved clarity, resistance to shrinkage and heat resistance, and improved physical and mechanical properties. There is, however, a need for further improvements and alternatives, particularly with respect to aesthetic features such as odor and yellowing, and processibility, such as broadening the molding temperature range and reducing plate-out. It is therefore an object of the present invention to produce a cost- effective, clarifying and nucleating agent which overcomes the problems associated with existing nucleating and clarifying agents.
  • the present invention is directed to a fumed silica having an average aggregate size of less than 0.09 micron, and in a preferred embodiment, an average aggregate size ranging from 0.01 to 0.05 micron.
  • the fumed silica is further characterized as having an increased bulk density and its destructured nature.
  • the fumed silica is particularly adapted for use an as effective nucleating and clarifying agent in thermoplastic compositions.
  • Another aspect of the invention are masterbatch compositions and dispersions for use in further polymer compounding which incorporate the fumed silica described above. Still another aspect are thermoplastic compositions incorporating such fumed silicas.
  • FIGURE 1 is a transmission electron micrograph (100,000X magnification) showing the structure of a typically commercially available fumed silica treated with polydimethylsiloxane oil.
  • FIGURE 2 is a transmission electron micrograph (100,000X magnification) showing the destructured fumed silica of the present invention treated with polydimethylsiloxane oil.
  • FIGURE 3 is a transmission electron micrograph (100,000X magnification) showing the structure of a commercially available fumed silica having a BET surface area of 200 +/- m 2 /g.
  • FIGURE 4 is a transmission electron micrograph (100,000X magnification) showing the fumed silica of Example 3 which has been destructured in accordance with the present invention.
  • FIGURE 5 is a histogram showing the aggregate size distribution of the fumed silica shown in Figure 3.
  • FIGURE 6 is a histogram showing the aggregate size distribution of the fumed silica shown in Figure 4.
  • FIGURE 7 is a plot of crystallite diameter on the x-axis versus the percentage of light transmitted on the y-axis.
  • FIGURE 8 is a plot of silica size on the x-axis versus crystallite size on the y-axis.
  • fumed silica is a well-documented process which involves the hydrolysis of silicon tetrachloride vapor in a flame of hydrogen and oxygen.
  • Molten particles of roughly spherical shapes are formed in the combustion process, the diameters of which are varied through process parameters.
  • These molten spheres of fumed silica typically referred to as primary particles, fuse with one another by undergoing ballistic collisions at their contact points to form branched, three dimensional chain-like aggregates.
  • the force necessary to break aggregates is considerable and often considered irreversible.
  • the aggregates undergo further collision that may result in some mechanical entanglement to form agglomerates.
  • Agglomerates are thought to be loosely held together by Van der Waals forces and can be reversed, i.e. de-agglomerated, by proper dispersion in suitable media.
  • the diameters of the silica sphere particles typically range from about 0.07 to 0.3 micron, it is useful to point out that such particles can not be individually obtained from currently available technology and commercially available fumed silica has an average aggregate size ranging from 0.09 to 0.13 micron, as illustrated in Figures 1 and 3.
  • the fumed silica of the present invention has an average aggregate size of less than 0.09 micron and preferably, less than 0.07 micron and is characterized by its destructured nature and high bulk density.
  • Average is defined to be the number mean equivalent spherical particle diameter and is sometimes referred to as DCircle.
  • destructured it is meant that the fumed silica aggregates are physically fractured or broken as illustrated in Figures 2 and 4.
  • Figure 1 shows a high magnification TEM of the same fumed silica as that in Figure 2. Note that the fumed silica of Figure 1 possesses the branched chain-like aggregate structure of fused spherical primary particles.
  • the fused branched chain aggregate structure of fumed silica is clearly segmented into much smaller aggregate sizes. Similar comparisons can be made between Figures 3 and 4.
  • the fumed silica is as destructured as possible in order to reduce the aggregate size and enhance its effectiveness as a nucleating agent in thermoplastic compositions.
  • the destructured fumed silica of the present invention can further be characterized by its aggregate size distribution as illustrated in Figures 5-6.
  • Figures 5-6 The destructured fumed silica of the present invention
  • FIG. 5 is a log normal distribution of the commercially available fumed silica having an average or mean aggregate size of approximately 129.4 nm.
  • Figure 6 shows the fumed silica of Figure 5, except that it has been destructured in accordance with the present invention.
  • the average aggregate size of the destructured fumed silica of Figure 6 is reduced to 90.5 nm.
  • particle and aggregate size measurements are not an exact science, it can be easily seen that, upon comparison of the two distributions in Figures 5 and 6, that the aggregate distribution is shifted significantly to the lower aggregate size.
  • the fractions of smaller sized aggregates is increased while the fractions of larger aggregates is reduced.
  • not only is the average aggregate size less than 0.07 micron, but the maximum size of any individual fumed silica aggregate is small as possible, and preferably less than 0.4 micron.
  • the aggregate size distribution of the present invention was chiefly determined by transmission electron microscopy (TEM).
  • TEM transmission electron microscopy
  • a fumed silica sample is dispersed in a liquid medium until the fumed silica agglomerates have been reversed to aggregates. Its concentration is then adjusted until discrete aggregates are shown on the TEM grid.
  • Multiple fields on the grid were then imaged using an image analysis system manufactured by Kontron and stored on a video tape until greater than 1000 aggregates were imaged and stored.
  • the stored images were in turn fed into an image analysis computer with a frame-grabber board for further processing, i.e. cleaning up aberrations, adjusting background and normalizing the image.
  • Individual particles in the binary field are finally measured for a number of primary particle sizes and aggregate size and shape parameters were calculated. Measurements may be recalled individually or in the form of statistical or histogram distributions.
  • the fumed silica of the present invention can be hydrophilic or hydrophobic, untreated or treated.
  • Hydrophobic silica can be produced by treating a fumed silica, which by its nature is hydrophilic, with a suitable treating agent which will vary depending on the desired degree of hydrophobicity and other characteristics. It is also recognized by those skilled in the art that hydrophilic fumed silicas may also be treated with the appropriate agents. Whether rendering the fumed silica either hydrophilic or hydrophobic, the treating agent is any suitable structure that is compatible with the thermoplastic composition to be nucleated.
  • typically treating agents include straight chain and branched hydrocarbons, amines, alcohols, glycols, carboxylic acids, esters, and/or amides, nitriles, ethers, silanes, siloxanes and polymers derived therefrom.
  • compatible is meant that the agent treated silica can be readily and uniformly dispersed into the thermoplastic composition and then act as an effective nucleation site upon cooling from the melt during production.
  • the treated fumed silica should serve to compatibilize the dispersant with the thermoplastic composition.
  • the fumed silica of the present invention can be destructured by subjecting it to extreme/severe mechanical forces/stresses such that fumed silica aggregates are fractured into sub-micron pieces.
  • mills such as tube mills, cone mills, cylinder mills and ball mills may be used to impart the necessary stress on the fumed silica. It is preferred that stress be of sufficient force to substantially decrease the aggregate size to less than 0.09 micron and preferably to less than 0.07 micron.
  • the bulk density of the fumed silica is significantly increased from its commercially available density of between 2.5 and 3.0 lbs/ft 3 to greater than 10 lbs/ft 3 , and preferable to greater than 20 lbs/ft 3 .
  • the time it takes to destructure the fumed silica in accordance with the present invention will vary depending on the type of mill, size of mill, and velocity of the mill. As a result, milling should continue until the desired average aggregate size and bulk density is achieved. Similarly, over- milling of the fumed silica should be avoided to prevent agglomeration of the fumed silica which tends to make the fumed silica difficult to disperse under normal shear conditions.
  • the fumed silica of the present invention can be produced directly in a dilute flame of hydrogen and oxygen during the hydrolysis of the silicon tetrachloride vapor. It has been found that the size of the fumed silica primary particles and aggregates are governed by the inter-relationship between the concentration of the precursor, temperature and time histories. By controlling the concentration of different diluents while maintaining a uniform temperature profile for the particles to grow, i.e. growth region, the size of the primary particles and aggregates can be controlled. Further growth of the particles can be prohibited by rapidly cooling the particles with a high velocity quench of air. It should be noted that the fumed silica, when produced in the flame, will typically have a bulk density lower than 2.5 lbs/ft 3 and will often range from about 0.8 lbs/ft 3 to about 2.5 lbs/ft 3 .
  • the fumed silica of the present invention is particularly useful as a nucleating and clarifying agent in thermoplastic systems, particularly polyolefin compositions.
  • the polyolefin polymers of the present invention may include aliphatic polyolefins and copolymers made from at least one aliphatic olefin and one or more ethylenically unsaturated comonomers.
  • the comonomers if present, will be provided in a minor amount, e.g., about 10% less or even about 5% or less, based upon the weight of the polyolefin.
  • a typical polypropylene copolymer will contain about 3& ethylene.
  • Such comonomers may serve to assist in clarity improvement of the polyolefin, or they may function to improve other properties of the polymer, such as fabrication characteristics, impact strength and/or other physical properties.
  • the polyolefin compositions contain from about 2 to about 6 carbon atoms and have an average molecular weight of from about 10,000 to about 2,000,000, preferably from about 30,000 to about 300,000.
  • examples of such polyolefin compositions include polyethylene, linear low density polyethylene, polypropylene, crystalline ethylene/propylene copolymer (random or block), poly(l-butene) and polymethylpentene.
  • the polyolefins of the present invention may be further described as semi-crystalline, basically linear, regular polymers which may optionally contain side chains, such as are found in conventional low density polyethylene.
  • Other polymers which may benefit from the destructured fumed silica of the present invention include polyethylene terephthalate, glycol modified polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyamides, polyimides and liquid crystal polymers, typically referred to as LCD's. Clarifying properties are conferred when the destructured fumed silica of the present invention is formulated into the polyolefin composition in a quantity within the range of 0.1 to 1.0 % by weight.
  • a preferred range of 0.15 to 0.35 % by weight has been found effective to decrease haze, thereby increasing clarity. It should be noted that the use of a destructed fumed silica is anticipated to reduce clarity in thermoplastic systems because of its refractive index and aggregate size distribution. Therefore, the use of the fumed silica in accordance with the present invention as an effective nucleating and clarifying agent is truly unexpected.
  • additives may also be used in the composition of the present invention, provided that they do not interfere with the primary benefits of the invention. It may even be advantageous to premix these additives with the nucleating agent in order to enhance dispersion and distribution during melt processing.
  • additives are well known in the art and include for example, plasticizers, anti-static materials, lubricants such as waxes, calcium stearate, stearic acid, glycol monostearate, catalyst neutralizers, antioxidants, fillers, light stabilizers, colorants, other nucleating agents and the like.
  • Some of these additives may further provide beneficial physical characteristics such as improved aesthetics, easier processing, and improved stability in processing or end use condition.
  • the polypropylene crystallites will scatter the incident light, the amount of scattering being dependent on the size of the crystallites, the number of crystallites, and the delta in the refractive indices of the crystalline and amorphous phases.
  • the end result is a molded polypropylene part having a reduction in the amount of light transmitted and thereby being more opaque.
  • the amount of light transmitted through a known thickness is a measure of the clarity.
  • Figure 7 illustrates the fraction of light transmitted versus the volume average crystallite size.
  • the calculations were performed for polypropylene assuming an estimated delta of 0.0025 in the refractive indices, a typical wavelength for white light of 550 nm, and a plaque thickness of 1/8 inch.
  • the degree of crystallinity for the computations was 40% and was assumed to be constant.
  • Figure 7 clearly indicates that the percent light transmitted increases with decreasing crystallite diameter. The increase is proportionately significant in the lower crystallite size range.
  • Figure 8 a plot of crystallite diameter versus fumed silica aggregate size in polypropylene, can be used to calculate the size of the crystallites that would result if each one of the fumed silica aggregates would nucleate a site for a crystallite to grow on. The calculations were performed assuming 40% degree of crystallinity, a polypropylene density of 0.91 g/cc, and a fumed silica density of 2.2 g/cc. The plots of Figure 8 are shown at silica loadings of 0.01, 0.1 and 1.0 % by weight.
  • the size of the nucleating and clarifying agent is critical and is preferably less than 0.09 micron to achieve a crystallite size of about
  • nucleating and clarifying agent is a size of less that 0.05 micron.
  • nucleating and clarifying agent must be able to be uniformly dispersed in the particular thermoplastic composition. By uniformly dispersed is meant that the agent is isolated and well, i. e. uniformly, distributed throughout the composition.
  • suitable treating agents may be used to provide compatibility in the system and aid dispersing.
  • the agent must possess as little structure as possible meaning that is has reduced branching or enhanced linearity.
  • polypropylene and fumed silica have been used for illustrative purposes, it will be appreciated by those skilled in the are that similar plots may be prepared for varying nucleating agents and polymer systems.
  • any material having, in combination, the above criteria, namely, small size, low structure and is capable of being uniformly dispersed, will be particularly adapted for use as an effective nucleating and clarifying agent.
  • Such materials include, but is not limited to certain silica sols, precipitated silicas, titanium dioxide, zirconium dioxide and alumina.
  • organically modified silica sols prepared by the precipitation sol gel process will be useful as an effective nucleating and clarifying agents.
  • sols of monodispersed spheres with an aggregate size diameter of 0.05 microns or less are desirable when used with the appropriate organic modifier and dispersing aid to ensure compatibility with the thermoplastic system.
  • Such sols are commercially available under the name HIGHLINK ® OG sols (Highlink is a registered trademark of Hoechst AG, Frankfurt, Germany).
  • Non-limiting illustrations of the destructured fumed silica of the present invention follows.
  • the destructured fumed silica of the present invention was prepared by charging 125 grams of CAB-O-SIL ® TS-720 fumed silica (CAB-O-SIL is a registered trademark of Cabot Corporation) to a one gallon porcelain mill jar (available from U. S Stoneware Corp., East furniture, Ohio) containing approximately 480 - 3/4 inch (19 mm) ceramic balls (available from Fisher-Scientific Corporation, St. Louis, MO). Two grams of acetone were added to the mill jar as an anti-static agent. The mill jars were operated for varying lengths of time depending on the desired degree of destructuring.
  • CAB-O-SIL is a registered trademark of Cabot Corporation
  • molten spheres of fumed silica fuse with one another to form branched, three dimensional chain ⁇ like aggregates.
  • the configuration of these aggregates differ from one to another.
  • the structure of these aggregates is one measure of the degree of branching of the configuration of the primary particles in the fumed silica aggregates.
  • the structure, as defined herein, is the ratio of the convex perimeter to the perimeter of the two dimensional image of an aggregate as viewed in a TEM.
  • the convex perimeter is the smaller of the two perimeters and is the length of an imaginary line transcribed tightly around the two dimensional image of the aggregate. This line does not go into any of the valleys and/or crevices of the aggregate.
  • the perimeter is the actual outside length of the imaginary line as transcribed around the aggregate's image.
  • the ratio of the two has been termed the structure parameter.
  • the structure parameter will vary inversely with the branching or the actual structure/morphology of the aggregate. The closer the structure parameter is to zero, the higher the actual structure. The closer the structure is to one, the lower the recorded structure/morphology of the aggregate, i.e. the more destructured the aggregate will be.
  • the average aggregate size is significantly reduced during the ball milling process while the amount of destructuring is increased, as indicated by the structure parameter and bulk density measurements.
  • Example 2 Same procedure as Example 1 except 100 grams of destructured Cab-O-Sil ® M-5 fumed silica was charged to the one gallon porcelain mill jar. The BET surface area for determining nitrogen adsorbed was also calculated using a Gemini 2375 Instrument (available from Micromeritics, Inc., Norcross, GA).
  • Examples 3 to 6 are directed to making a masterbatch or concentrate of the destructured fumed silica of the present invention for further blending or compounding into various thermoplastic systems.
  • Example 7 is directed to a dispersion of the destructured fumed silica for further blending or compounding into various thermoplastic systems.
  • the destructured fumed silica of Example 2 was used to make a masterbatch in polypropylene by using a twin screw extruder having 85 cc capacity preparation mixer (Brabender Plasticorder ® extruder available from C. W. Brabender, Hakensack, NJ). The mixer was preheated to 200°C and the drive was set to run at 5 RPMs. Approximately 49.5 grams of base Quantum Petrothene ® 8310 GO polypropylene was added to the mixer and brought to a melt in approximately 10 minutes. Approximately 2.8 grams of calcium stearate was then as an internal lubricant. A total of about 2.8 grams of the destructured fumed silica was added in approximately 1 gram increments. Total incorporation time and maximum developed torque were recorded.
  • Example 3 Similar to Example 3 except 11.0 grams of destructured fumed silica and calcium stearate was used, thus yielding a final concentration of approximately of 20% by weight.
  • Example 2 Approximately 140 grams of the destructured fumed silica of Example 2 was mixed in 560 grams of Drakeol mineral oil at low speed with a bench scale mixer which has been fitted with Cowles blades (Chemineer Inc., Dayton, OH). The fumed silica and oil mixture was then charged to a 0.4 liter capacity Eiger Mill (Eiger Machinery, Inc., Mundelein, IL). The first portion of the material was discarded and the remaining material was passed through the mill three more times. The material was then dearated under full vacuum (30 in of mercury) using a Drais mixer (Drais
  • Example 6 The masterbatch of Example 6 was further blended with the same base polymer to yield a final concentration of 0.25% by weight fumed silica.
  • Test plaques having a size of 147 x 63.5 x 2.7 mm, were injection molded using a
  • Table III shows that the percent light transmission increased from 31.7% to 40.9% when the fumed silica of the present invention was incorporated into polypropylene, thus yielding an improvement in clarity.
  • the transmission was increased when compared to commonly used nucleating agents.
  • an increase from 112.6°C to 116.9°C in peak crystallization temperature is realized when the fumed silica of the present invention was incorporated into polypropylene, thus allowing for increased cycle time.
  • the fumed silica of the present invention has been found particularly useful as an effective nucleating and clarifying agent in thermoplastic compositions. Such compositions have improved clarity and can be achieved with low percentages of fumed silica. In addition, processing is improved, e.g. more consistent product performance, reduced mold times and the like, while achieving desirable aesthetic characteristics.

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Abstract

Dioxyde de silicium fumé se caractérisant par une grosseur moyenne d'agrégat inférieure à 0,09 νm, une masse volumique apparente supérieure à 2,5 livres/pied3 et une nature destructurée; et composition polyoléfinique très transparente contenant une quantité efficace de dioxyde de silicium fumé produit selon le procédé de cette invention.
PCT/US1994/011415 1993-10-15 1994-10-07 Dioxyde de silicium fume destructure utilise comme additif haute transparence WO1995010564A1 (fr)

Priority Applications (1)

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AU80139/94A AU8013994A (en) 1993-10-15 1994-10-07 Destructured fumed silica for use as a high clarity additive

Applications Claiming Priority (2)

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US13752593A 1993-10-15 1993-10-15
US08/137,525 1993-10-15

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318167A2 (fr) * 2001-12-07 2003-06-11 MERCK PATENT GmbH Matériau à base de polymère contenant des particules de silice
US20090286888A1 (en) * 2004-05-04 2009-11-19 Cabot Corporation Method of preparing an aggregate metal oxide particle dispersion having a desired aggregate particle diameter
EP1565400B1 (fr) * 2002-11-26 2019-04-10 Cabot Corporation Particules d'oxyde metallique sublime et procede de production correspondant

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4405729A (en) * 1982-06-17 1983-09-20 E. I. Du Pont De Nemours And Company Pigment grind with fumed silica
WO1986002088A1 (fr) * 1984-09-28 1986-04-10 Battelle Development Corporation Elastomeres optiquement transparents
US4699734A (en) * 1985-11-06 1987-10-13 A. Schulman, Inc. Flame-retardant polyolefin compositions containing exudation inhibitor and process for producing same
US4722952A (en) * 1986-05-09 1988-02-02 Elkem A/S Resin compositions

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4405729A (en) * 1982-06-17 1983-09-20 E. I. Du Pont De Nemours And Company Pigment grind with fumed silica
WO1986002088A1 (fr) * 1984-09-28 1986-04-10 Battelle Development Corporation Elastomeres optiquement transparents
US4699734A (en) * 1985-11-06 1987-10-13 A. Schulman, Inc. Flame-retardant polyolefin compositions containing exudation inhibitor and process for producing same
US4722952A (en) * 1986-05-09 1988-02-02 Elkem A/S Resin compositions

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
R¯MPP CHEMIE LEXIKON, "Aerosil", vol. 1, 9th edition, issued 1989, Georg Thieme Verlag- -Stuttgart-New York, page 65. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318167A2 (fr) * 2001-12-07 2003-06-11 MERCK PATENT GmbH Matériau à base de polymère contenant des particules de silice
EP1318167A3 (fr) * 2001-12-07 2005-02-09 Biomet Deutschland GmbH Matériau à base de polymère contenant des particules de silice
EP1565400B1 (fr) * 2002-11-26 2019-04-10 Cabot Corporation Particules d'oxyde metallique sublime et procede de production correspondant
US20090286888A1 (en) * 2004-05-04 2009-11-19 Cabot Corporation Method of preparing an aggregate metal oxide particle dispersion having a desired aggregate particle diameter

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