Core-shell Patents (Class 525/902)
  • Patent number: 4398000
    Abstract: A solid type golf ball comprising a central core and an outer cover for the core and having an excellent flight performance and durability and acceptable "click" characteristics is presented. The main component of the outer cover of this golf ball is a polyetherester block copolymer containing the following X, Y and Z units:X: Butylene terephthalate unitY: Ester unit other than butylene terephthalateZ: Polyetherester unit derived from a dicarboxylic acid component containing terephthalic acid and poly(alkylene oxide) glycol having a number average molecular weight of 400 through 3000, wherein the X, Y and Z units are present in the following amounts:30% by weight .ltoreq.X.ltoreq.80% by weight0% by weight .ltoreq.Y.ltoreq.50% by weight20% by weight .ltoreq.Z.ltoreq.70% by weight.
    Type: Grant
    Filed: August 7, 1981
    Date of Patent: August 9, 1983
    Assignees: Bridgestone Tire Co., Ltd., Toray Industries, Inc.
    Inventors: Nobuyuki Kataoka, Tasuku Saito, Tsutomu Matsunaga, Chiaki Tanaka, Yoko Furuta, Nagayoshi Naito
  • Patent number: 4393169
    Abstract: A moldable resin composition comprising:(A) an aromatic vinyl-type polymer;(B) a polycarbonate; and(C) a three-stage polymerization product produced by three-stage emulsion polymerizations of an aromatic vinyl-type monomer, butadiene, alkyl methacrylate, etc.
    Type: Grant
    Filed: November 12, 1981
    Date of Patent: July 12, 1983
    Assignee: Daicel Chemical Industries, Ltd.
    Inventors: Takeshi Moriwaki, Shinji Tokuhara
  • Patent number: 4393172
    Abstract: A particulate graft polymer comprising (a) a core formed by a crosslinked homopolymer of a conjugated diene or a copolymer thereof with up to 10% by weight of styrene or acrylonitrile; (b) a first shell formed by a crosslinked homopolymer of an acrylic acid alkyl ester or a copolymer thereof with up to 30% by weight of vinyl monomers; (c) a second shell formed by a polymer of resin-forming monomers, a process for manufacturing these graft polymers by means of a multi-stage emulsion polymerization, and their application as molding compositions, optionally together with rigid thermoplastic resins.
    Type: Grant
    Filed: October 8, 1981
    Date of Patent: July 12, 1983
    Assignee: Bayer Aktiengesellschaft
    Inventors: Christian Lindner, Karl-Heinz Ott, Alfred Pischtschan
  • Patent number: 4391928
    Abstract: Opacifying and film-forming particles consisting of discrete capsules, each having a solid polymeric shell and a solid polymeric core and having a weight ratio of shell to capsule ranging from 0.25:1 to 0.5:1. The capsules are capable of providing a high degree of opacity and good film integrity in paint compositions in replacement for pigments in binding agents.
    Type: Grant
    Filed: September 4, 1981
    Date of Patent: July 5, 1983
    Assignee: NL Industries, Inc.
    Inventors: Daniel F. Herman, Uno Kruse
  • Patent number: 4391940
    Abstract: Fluoropolymer dispersions containing colloidal particles of a partially modified tetrafluoroethylene polymer, the fluoropolymer resin powder obtained therefrom by coagulation and a process for the preparation of the dispersions mentioned are described. The particles have a three-shell particle structure, the particle core and the other particle shell consisting of a tetrafluoroethylene polymer provided with a modifying fluoro-olefinic comonomer and the inner particle shell consisting of tetrafluoroethylene homopolymer. Fluoro-olefins, perfluoro-olefins, halogenofluoro-olefins and completely or partially fluorinated vinyl ethers are used as the modifying comonomers.The preparation is effected by the seed technique or intermediate letting down method, the modified core being formed in the first phase and the modifying comonomer being subsequently metered into the continuing tetrafluoroethylene polymerization in the second phase.
    Type: Grant
    Filed: March 16, 1982
    Date of Patent: July 5, 1983
    Assignee: Hoechst Aktiengesellschaft
    Inventors: Jurgen Kuhls, Franz Mayer, Herbert Fitz
  • Patent number: 4387138
    Abstract: A four composition acrylate particle optimizes four sequence formulations: (1) beginning with a cross-linked elastomer core upon which (2) a successive layer of a principal quantity of cross-linked elastomer, which includes a graft-linking component, is polymerized, which in turn is (3) protectively encapsulated by a successively polymerized shell, which also includes a graft-linking component, and in turn is coated by (4) a final transition coating. The particle is chemically bonded into a unit and provides a radially graduated transition between the significantly different properties of the principal elastomer in the particle and the transition coating which is adapted in composition to a matrix system with which the particles may be blended.
    Type: Grant
    Filed: April 2, 1982
    Date of Patent: June 7, 1983
    Assignee: Plaskolite, Inc.
    Inventor: Warren H. Gift
  • Patent number: 4385152
    Abstract: Aqueous acrylic polymer emulsions containing as a first polymeric component a core-shell polymer having a core formed from one or more monomers selected from styrene, vinyl acetate, vinyl toluene and acrylic or methacrylic acid esters of alcohols of 1 to 4 carbon atoms and a shell formed of the above monomers in conjunction with one or more monomers selected from acrylic acid or methacrylic acid esters of alcohols of 1 to 8 carbon atoms and a minor amount of acrylic or methacrylic acid and as a second polymeric component a polymer composed of a major amount of one or more monomers selected from styrene, vinyl acetate, vinyl toluene and acrylic or methacrylic acid esters of alcohols of 1 to 4 carbon atoms and a minor portion of one or more acrylic acid esters of alcohols of 1 to 8 carbon atoms with acrylic and/or methacrylic acid.
    Type: Grant
    Filed: October 13, 1981
    Date of Patent: May 24, 1983
    Inventors: Robert M. Boyack, Perry J. Cooke, Bruce C. Henshaw
  • Patent number: 4381365
    Abstract: A process for preparing a copolymer latex by polymerization of at least one aliphatic conjugated diene monomer, at least one ethylenically unsaturated carboxylic acid monomer and at least one monoolefinic monomer copolymerizable with them in a weight proportion of 19.5-80:0.5-10:10-80, characterized in that (a) a mixture of the whole amount of the aliphatic conjugated diene monomer, the whole amount of the ethylenically unsaturated carboxylic acid monomer and a portion of the monoolefinic monomer, the combined amount of them being from 45 to 99% by weight on the basis of the total amount of the starting monomers, is subjected to emulsion polymerization, and (b) after or while the remainder of the monoolefinic monomer in an amount of from 1 to 55% by weight on the basis of the total amount of the starting monomers is added to the reaction mixture, the further emulsion polymerization is carried out.
    Type: Grant
    Filed: October 29, 1981
    Date of Patent: April 26, 1983
    Assignee: Sumitomo Naugatuck Co., Ltd.
    Inventors: Saburo Mishiba, Junkoh Hyoda, Akira Uchida, Hisao Usami, Akira Watanabe
  • Patent number: 4375497
    Abstract: There is disclosed a process for the production of tack-free, pourable, filler containing elastomer powder which comprises(a) dispersing a carbon black filler in water;(b) mixing the thus dispersed carbon black filler with an elastomer latex;(c) coagulating the thus produced mixture of elastomer latex and carbon black with an acid/alum solution;(d) partitioning the thus coagulated suspension with a coating resin; and(e) filtering, washing and drying of the resultant powder, the improvement comprising using as a coating resin a mixture of a styrene/butadiene resin and a styrene/.alpha.-methylstyrene or a polystyrene resin wherein the weight ratio of the styrene/butadiene resin to the styrene/.alpha.
    Type: Grant
    Filed: August 27, 1981
    Date of Patent: March 1, 1983
    Assignee: The Goodyear Tire & Rubber Company
    Inventor: Paul H. Sandstrom
  • Patent number: 4362845
    Abstract: A composition with high impact resistance and little fish eyes content, comprising 97 to 60 parts by weight of a polyvinyl chloride-base resin and 3 to 40 parts by weight of a graft copolymer obtained by the three-stage graft-polymerization of 65 to 25 parts by weight of a monomer combination (B) comprising 12 to 57% by weight of methyl methacrylate, 1 to 24% by weight of at least one of alkyl acrylates having a C.sub.
    Type: Grant
    Filed: December 9, 1981
    Date of Patent: December 7, 1982
    Assignee: Mitsubishi Rayon Co., Ltd.
    Inventors: Kazumasa Kamata, Kazuo Kishida, Kazuo Ueda, Norihisa Osaka
  • Patent number: 4360636
    Abstract: Blends of a sulfone polymer, such as polysulfone, polyethersulfone, or polyphenylsulfone, and an impact resistant interpolymer comprising crosslinked acrylic or methacrylic rubber, crosslinked styrene-acrylonitrile, and uncrosslinked styrene-acrylonitrile polymer components are disclosed.
    Type: Grant
    Filed: July 27, 1981
    Date of Patent: November 23, 1982
    Assignee: Stauffer Chemical Company
    Inventor: Joseph Silberberg
  • Patent number: 4355131
    Abstract: An aqueous alkaline dispersion of a rubbery graft or over polymerized copolymer of a diene and a vinyl pyridine on a polyacrylate seed (core or substrate), said acrylate polymer having a Tg of not above about -20.degree. C., desirably also containing a polybutadiene, and a water soluble, heat reactable phenolic resin, in certain amounts is useful in forming an adhesive for bonding glass fiber reinforcing elements or cords to rubber compounds or stocks. After dipping the glass fiber cord in the one-step adhesive dip, the coated cord is heated to dry it and heat cure or heat set the adhesive on the cord. Thereafter, the adhesive containing glass fiber cord is combined or laminated (calendered) with a curable rubber compound and the resulting assembly is cured to form a composite in which the glass fiber cord is bonded to the rubber by means of said adhesive.
    Type: Grant
    Filed: December 17, 1981
    Date of Patent: October 19, 1982
    Assignee: The General Tire & Rubber Company
    Inventor: Richard M. Wise
  • Patent number: 4352910
    Abstract: As an impact modifier copolymer to be blended with a vinyl chloride resin, a multilayer copolymer comprising a hard core polymer containing a relatively small quantity of a conjugated diene, a rubbery inner layer polymer containing a relatively large quantity of a conjugated diene, and an outer layer polymer comprising, for example, a copolymer of styrene and methyl methacrylate which is compatible with a vinyl chloride resin is used, whereby a vinyl chloride resin composition well balanced between impact strength and anti-stress-whitening property can be obtained.
    Type: Grant
    Filed: October 20, 1981
    Date of Patent: October 5, 1982
    Assignee: Kureha Kagaku Kogyo Kabushiki Kaisha
    Inventors: Takayuki Katto, Zenya Shiiki
  • Patent number: 4342676
    Abstract: A method for producing latices of copolymers of butyl acrylate and 1-methyacrylate-1-tert-butyl peroxy ethane resides in the emulsion copolymerization of butyl acrylate and 1-methacrylate-1-tert-butyl peroxy ethane carried out by prepolymerizing of butyl acrylate up to a conversion degree of 90-100% followed by introducing 1-methacrylate-1-tert-butyl peroxy ethane into the reaction mass. For a redox system, use is made of potassium persulfate and sodium metabisulfate.
    Type: Grant
    Filed: November 10, 1980
    Date of Patent: August 3, 1982
    Inventors: Sergei S. Ivanchev, Valery N. Pavljuchenko, Zinaida M. Pessina, Elena D. Vasilieva
  • Patent number: 4341883
    Abstract: A four composition particulate additive for blending with a moldable acrylic matrix resin is described. The particulate additive optimizes four sequenced formulations: (1) beginning with a cross-linked elastomer core upon which (2) a successive layer of the principal quantity of cross-linked elastomer, which includes a graft-linking component, is polymerized, which in turn is (3) protectively encapsulated by a successively polymerized thermoplastic shell, which also includes a graft-linking component, and in turn is coated by (4) a final thermoplastic transition coating which is compatible with the matrix resin. The particle is chemically bonded into a unit and provides a graduated transition between the significantly different properties of the principal elastomer in the particle and the matrix resin with which the particles are blended. The blends produced are particularly useful in glazing and the production of sanitary-ware and other products in which impact resistance is a desired quality.
    Type: Grant
    Filed: October 29, 1980
    Date of Patent: July 27, 1982
    Assignee: Plaskolite, Inc.
    Inventor: Warren H. Gift
  • Patent number: 4336177
    Abstract: A process is described for making sterically stabilized non-aqueous dispersions of composite polymer microparticles, in which (1) monomers including at least one crosslinking monomer are polymerized in an aqueous medium at a temperature at least 10.degree. higher than the glass transition temperature of the polymer to be formed, in the presence of a block or graft copolymer stabilizing agent, under conditions such that there is at no time present a separate monomer phase, (2) further monomers, not including any crosslinking monomer, are polymerized in the dispersion thus obtained, the presence of a separate monomer phase again being avoided, and (3) the microparticles are transferred from the resulting dispersion into a non-aqueous medium which is a solvent for the non-crosslinked polymer generated in (2). The microparticles are of value for incorporation into coating compositions the main film-forming constituent of which is compatible with the non-crosslinked component of the particles.
    Type: Grant
    Filed: December 4, 1980
    Date of Patent: June 22, 1982
    Assignee: Imperial Chemical Industries Limited
    Inventors: Alan J. Backhouse, Charles Bromley, Morice W. Thompson
  • Patent number: 4331784
    Abstract: Polymer particles composed of particles of a polymer (I) consisting of 96 to 100% by weight of at least one ethylenically unsaturated monomer and 4 to 0% by weight of at least one .alpha.,.beta.-ethylenically unsaturated carboxylic acid, and a (co-)polymer (II) comprising 100 to 10% by weight of a conjugated diolefin which is localized on the surface layer of the particles of the polymer (I) at a (I)/(II) weight ratio of 100/5-100/90. The localized polymer part of the polymer particles is very active, and the polymer particles are easy to modify with a monomer having any functional group, and hence are elemental materials having a high function and being utilizable for various purposes.
    Type: Grant
    Filed: October 8, 1980
    Date of Patent: May 25, 1982
    Assignee: Japan Synthetic Rubber Co., Ltd.
    Inventors: Yoshiyuki Ishibashi, Eijiro Tagami, Teruo Hiraharu, Shiro Yasukawa
  • Patent number: 4326046
    Abstract: A modified polytetrafluoroethylene is produced by polymerizing tetrafluoroethylene in an aqueous medium containing a dispersing agent with a polymerization initiator source and then, copolymerizing tetrafluoroethylene and a fluorinated monomer having an acid type functional group as a copolymerizable modifier in the presence of the resulting polytetrafluoroethylene to obtain a modified polytetrafluoroethylene having the modifier component of 0.001 to 10 mol %.
    Type: Grant
    Filed: November 3, 1980
    Date of Patent: April 20, 1982
    Assignee: Asahi Glass Company, Ltd.
    Inventors: Haruhisa Miyaka, Masami Yamashita, Tatsuro Asawa
  • Patent number: 4315085
    Abstract: Aqueous dispersions of soft polymers, and particularly butadiene-styrene copolymers, containing high amounts of carboxylic acid units are prepared by a core-shell polymerization technique in which there is first polymerized around the soft polymer an inner shell layer of methylmethacrylate, thereby completely encasing the soft polymer particles. Then an outer layer of methylmethacrylate and methacrylic acid monomers is polymerized around the encased particles. The product contains up to about 40 mole percent of methacrylic acid units in the shell.
    Type: Grant
    Filed: July 25, 1980
    Date of Patent: February 9, 1982
    Assignee: GAF Corporation
    Inventors: Yehuda Ozari, Eugene S. Barabas
  • Patent number: 4308335
    Abstract: A mordant layer for a color diffusion transfer photographic element containing a cationic polymer latex obtained by emulsion-polymerizing a monomer represented by formula (I) ##STR1## wherein R.sub.1 and R.sub.2 each represents hydrogen or an alkyl group having from 1 to 6 carbon atoms; R.sub.3, R.sub.4, and R.sub.5 each can represent an alkyl group having from 1 to 20 carbon atoms, or an aralkyl group having from 7 to 10 carbon atoms, or any two or R.sub.3, R.sub.4, and R.sub.5 together can form a ring; and X.sup..crclbar. represents an anion; as a shell component for a core component of dispersed particles of a polymer latex obtained by emulsion-polymerizing a water-insoluble monomer or monomers other than the monomer of formula (I).
    Type: Grant
    Filed: July 21, 1980
    Date of Patent: December 29, 1981
    Assignee: Fuji Photo Film Co., Ltd.
    Inventors: Tatsuya Yamamoto, Kazunobu Katoh
  • Patent number: 4307006
    Abstract: A latex of vinylidene chloride copolymer particle which has a three-layered structure comprising 20 to 70 parts by weight of a core layer of vinylidene chloride copolymer containing 85 to 94% by weight of vinylidene chloride, 3 to 15 parts by weight of an intermediate layer of vinylidene chloride copolymer containing more than 94% by weight of vinylidene chloride and 20 to 70 parts by weight of an outer layer of vinylidene chloride copolymer containing 85 to 94% by weight of vinylidene chloride, the three layers amounting to 100 parts by weight.
    Type: Grant
    Filed: September 19, 1980
    Date of Patent: December 22, 1981
    Assignee: Kureha Kagaku Kogyo Kabushiki Kaisha
    Inventors: Masayasu Suzuki, Masaki Kobori
  • Patent number: 4293476
    Abstract: Cross-linked, synthetic polymer compositions comprising an aqueous polymer dispersion of (1) heterogeneous polymer particles having a high concentration of reactive groups such as an activated halogen on their surface and (2) a water-soluble coreactive component bearing a plurality of reactive groups coreactive with the reactive groups of the heterogeneous polymer particle, e.g., ##STR1## are useful for preparing strong films or coatings. For example, a polymer composition consisting of an aqueous colloidal dispersion of heterogeneous polymer particles having a shell layer derived from a reactive monomer such as vinylbenzyl chloride and a coreactive component of triethylenetetraamine can be applied to a suitable substrate and cross-linked to form a strong, water-resistant film.
    Type: Grant
    Filed: August 2, 1979
    Date of Patent: October 6, 1981
    Assignee: The Dow Chemical Company
    Inventors: Carl Moore, Robert A. Kirchoff
  • Patent number: 4289823
    Abstract: There is disclosed a calenderable, soft, three-stage acrylic heteropolymer having a calculated T.sub.g of about (-) 40.degree. to (=) 20.degree. C. which is suitable for producing films and sheets useful to coat textile materials and other substrates to form composites. The heteropolymer can be coagulated and then introduced into a calendering apparatus to produce films and sheets at substantially lower temperatures than are required for calendering vinyl halide polymers.
    Type: Grant
    Filed: September 30, 1980
    Date of Patent: September 15, 1981
    Assignee: Rohm and Haas Company
    Inventor: Charles T. Arkens
  • Patent number: 4288511
    Abstract: A photographic element comprises a support having thereon a layer containing a hydrophilic vehicle having dispersed therein a particulate polymeric material encapsulated with a chelating or already chelated polymer, said element, when the polymer is not already chelated, comprising a source of metal ions. The elements are useful in diffusion transfer processes, and particularly useful with chelating acid dyes or dye-forming materials to provide a metallized dye image.
    Type: Grant
    Filed: April 29, 1980
    Date of Patent: September 8, 1981
    Assignee: Eastman Kodak Company
    Inventors: Drewfus Y. Myers, Jr., George H. Hawks, III
  • Patent number: 4278572
    Abstract: Olefin polymers are described having methylol phenolic groups grafted thereto which modified polymers are useful for preparing improved polymer blends.
    Type: Grant
    Filed: January 4, 1980
    Date of Patent: July 14, 1981
    Assignee: Monsanto Company
    Inventors: Aubert Y. Coran, Raman Patel
  • Patent number: 4277384
    Abstract: Tear resistance and flexibility of resin-treated textiles are improved while retaining good low temperature properties by using as the resin an acrylic emulsion polymer wherein the latex particles have a core-shell structure. The monomers forming the core are selected to provide a Tg in the core of -20.degree. C. or lower and the monomer composition forming the shell is selected to provide a Tg in the shell of about 60.degree. C. to about -10.degree. C. The core monomer composition contains 4-10 wt. % of a latent crosslinker together with 0-0.03 wt. % of an active crosslinker or a graftlinker, and the shell monomer composition contains 2-10 wt. % of a latent crosslinker.
    Type: Grant
    Filed: September 25, 1978
    Date of Patent: July 7, 1981
    Assignee: Rohm and Haas Company
    Inventor: Charles T. Arkens
  • Patent number: 4267094
    Abstract: Aqueous polymer mixture, process for its preparation and its use as substrate anchoring, blocking resistant one-coat sealing lacquer on sheet products.An aqueous polymer mixture containing at least two polymeric components A and B, A being present in form of an aqueous dispersion and consisting of micronuclear shell structures comprising as nuclear portion a copolymer of methyl acrylate, ethyl acrylate, acrylic acid, methacrylic acid -n-butyl ester and/or methyl methacrylate and vinylidene halide and as shell portion a copolymer of methyl acrylate, ethyl acrylate, ethyl methacrylate ethyl hexyl acrylate, n-butyl (meth)acrylate and/or itacaconic acid and vinylidene halide; and B being present in form of an aqueous alkaline solution and consists of a (co)polymer of unsaturated carboxylic acid amide -N-methylol derivatives and optionally unsaturated carboxylic acids and/or amides of said acids.
    Type: Grant
    Filed: February 14, 1980
    Date of Patent: May 12, 1981
    Assignee: Bayer Aktiengesellschaft
    Inventors: Helmut Huhn, Werner Karstens
  • Patent number: 4265939
    Abstract: A process is described for the production of particulate rubber wherein a synthetic rubber in latex form is coagulated to yield small particles and the particles are then coated with a rubbery-resinous or resinous polymer, the mixing conditions for each of the coagulation and coating being within certain limits of Reynolds Number and residence time. Such particulate rubber may be used for the manufacture of articles such as tire components or hoses and gaskets.
    Type: Grant
    Filed: December 5, 1979
    Date of Patent: May 5, 1981
    Assignee: Polysar Limited
    Inventors: Klaas Tebbens, Erhardt Fischer, Jhy-Dou R. Lo
  • Patent number: 4264678
    Abstract: Disclosed are improved core-shell polymer compositions and an improved process for applying patterns to textiles by screen printing employing these polymer compositions as binders. The polymer comprises a core of styrene-butadiene copolymer which is at least partially encased by an integral shell of a copolymer of butyl methacrylate and methyl acrylate. When used as a binder in a screen printing process, this composition produces textiles which exhibit a surprisingly desirable combination of the properties of crock fastness, cyclic aging and hand.
    Type: Grant
    Filed: May 29, 1979
    Date of Patent: April 28, 1981
    Assignee: GAF Corporation
    Inventors: Suzanne Nelsen, Edward Wotier, Dru Alwani, Yehuda Ozari
  • Patent number: 4199486
    Abstract: A storage-stable plastisol is disclosed comprising an organic plasticizer and particles of a methyl methacrylate copolymer, said particles comprising a core portion of a polymer compatible with said plasticizer and a surrounding shell portion of a polymer incompatible with the plasticizer.
    Type: Grant
    Filed: May 11, 1978
    Date of Patent: April 22, 1980
    Assignee: Rohm GmbH
    Inventors: Hans Boessler, Peter Quis, Joachim Buechse, Hubert Rauch
  • Patent number: 4195134
    Abstract: Polyester compositions comprising a blend of poly (C.sub.2 -C.sub.4 alkylene terephthalate) with a diepoxy compound and a multiphase composite polymer are disclosed. The multiphase polymer has a first elastomeric phase polymerized from a monomer system including C.sub.1 -C.sub.6 alkyl acrylate as well as crosslinking and graft-linking monomers and a final rigid thermoplastic phase polymerized in the presence of the elastomeric phase.
    Type: Grant
    Filed: December 21, 1978
    Date of Patent: March 25, 1980
    Assignee: GAF Corporation
    Inventor: Ernest A. Coleman
  • Patent number: 4167505
    Abstract: Disclosed is a method for preparing an impact-resistant, high melt flow polycarbonamide comprising the steps of:(a) preparing an impact modifier concentrate comprising a mixture of (i) 70-90 parts by weight of an acrylic impact modifier and (ii) 10-30 parts by weight of at least one high molecular weight aliphatic polycarbonamide; and(b) mixing 10-30 parts by weight of the impact modifier concentrate from (a) above with 70-90 parts by weight of at least one low molecular weight aliphatic polycarbonamide.The resulting polycarbonamide blends are characterized by high impact resistance and a melt flow which is essentially the same as that of the blend of the acrylic impact modifier and the low molecular weight nylon alone.
    Type: Grant
    Filed: January 12, 1978
    Date of Patent: September 11, 1979
    Assignee: Rohm and Haas Company
    Inventor: David L. Dunkelberger