Nordson Corporation

Walter H Cobbs, Jr

William R Rehman

Robert George Shong

Robert J Huddleston

Laurence B Saidman

Harry J Lader

Chan I Chung

Merle N Hirsh

Martin J Stewart

David H Chow

Robert A Guldner

Method and apparatus for charging powdered particles and delivering only these charged particles to a workpiece. A high voltage electric field is created between upper and lower surfaces. Powder is continuously delivered to the lower surface. The lower surface is vibrated to bounce the particles so that each repeatedly contacts the lower surface and picks up an electrostatic charge with each contact. When the charge from the particle is great enough to overcome gravity, the particle levitates and is thereafter transported to a workpiece, where it adheres by electrostatic attraction. Three important features of this method are: (1) No uncharged particles are levitated to the workpiece, thereby eliminating the need for recirculating uncharged powder. (2) The method is capable of producing high throughput of charged particles. (3) The method is capable of producing powder with a controlled charge level.

Method and apparatus for induction charging of powder by contact

Polymer materials having viscosities ranging from about 50,000 up to above 1,000,000 centipoises are mixed with a gaseous foaming agent to provide a polymer/gas solution under pressure such that when the polymer/gas solution is subsequently dispensed at atmospheric pressure the gas is released from the solution and becomes entrapped in the polymeric material to form a homogeneous polymer foam. Mixing is accomplished by force feeding the gas and polymeric material into and through a low energy input disk mixer with a low pressure drop across the mixer such that premature foaming or reaction of the polymeric material is avoided. The disk mixer includes a tubular housing, one or more driven shafts extending along the length of the housing, and a series of disks spaced along the shafts. The foaming gas enters into solution in the polymer in the compartments between the rotating disks. The process is characterized in that relatively high viscosity polymeric materials are mixed with gas and foamed with relatively low horsepower requirements, high throughput and low temperature rise of the polymer from conversion of the work of mixing to heat.

Method and apparatus for foaming high viscosity polymer materials

The method of screen printing with a hot melt foam composition includes providing a screen having the desired pattern to be transferred to a substrate, casting onto the screen a hot melt foam composition and forcing the foam composition through the screen to form the described pattern on the substrate. The method offers a number of advantages including the transfer of large amounts of hot melt inks through the screen, fast printing speeds, printing with highly viscous polymeric or thermosetting materials and control of processing temperatures, among other advantages.

Method of screen printing with hot melt foam compositions

Surface coating methods and compositions are disclosed which eliminate many of the disadvantages associated with known coating processes from pollution, equipment, materials, energy, labor and cost standpoints. According to techniques described, thermosetting liquid compositions containing film-forming solids are formulated, then conveyed in the foam state toward a surface, and upon foam disintegration, form a film of solids on the surface. The foamable thermosetting resin compositions contain a curable resin having a free hydroxyl or carboxyl group, a curing agent consisting of a lower (C.sub.1 -C.sub.4) alkoxylated amine for reaction with the resin hydroxyl or carboxyl group and a liquid blowing agent consisting of a C.sub.1 -C.sub.4 alkanol which is also a by-product of the thermosetting reaction.

Foamable thermosetting compositions and methods of coating therewith

A process for the recovery of solvent entrained in a water vapor laden exhaust gas stream exhausted from a spray painting system is disclosed. The process includes an oil absorption unit which absorbs and removes all but about 100 parts per million of the solvent from the exhaust gas stream while permitting air and water vapor to be vented from the system and a stripper which in turn removes all but about 0.001 mole fraction of any one solvent component trapped in the oil. The oil, which is substantially free of solvent, is returned to the absorption unit. The stripped solvent can then be condensed and reused by mixing it with the paint solids to be sprayed in the process; or, alternatively, it can be admitted as a vapor into the atmosphere surrounding a workpiece which is being coated in the spray painting system to raise the solvent humidity surrounding the workpiece to above about 70%. By raising the solvent humidity to above about 70% caking of paint on the interior surfaces of the spray booth, plugging of the paint spray nozzles, and rapid evaporation of solvent from the paint are reduced. The present process provides a means to recover and reuse even a complex mixture of solvents where the recovered solvent comprises a mixture of the same components in the same ratio as the solvent mixture originally used in the paint spray system. The system is described in relation to a continuous coater wherein parts to be coated move continuously through an enclosed paint spray area and are coated while the solvent laden atmosphere therein is exhausted from the coater for recovery of the solvent.

Continuous coater solvent recovery process

A process for providing a substrate such as a polyethylene terephthalate container with a gas barrier coating of a copolymer of vinylidene chloride is disclosed. The process includes locating the container to be coated in close proximity to one or more airless spray nozzles and impacting the outside surface of the container with a stream of a stabilized aqueous polymer dispersion such as an aqueous polyvinylidene chloride dispersion. The impacting force of the stable polyvinylidene chloride dispersion on the surface of the container is sufficient to cause selective destabilization of the dispersion at the surface interface to form a gel layer containing the polymer in the continuous phase. This gel layer serves as an adhesive layer for an overlying layer of the aqueous polymer dispersion as a continuous uniform coating. The resulting wet coating does not sag or run off. The coating on the container is then dried in a controlled atmosphere to complete the gel formation throughout its thickness whereupon it is further dried to remove the water from the coating and to collapse the gel to form a film without distorting the container. The dried coating is smooth, uniform and uniformly transparent. In operation, the overspray can be collected and returned to achieve greater than 95% material efficiency. The process can be carried out in a continuous manner to provide a continuously moving series of containers with a uniformly transparent, gas barrier polyvinylidene chloride coating at production rates suitable for commercial applications.

Process for coating substrates with aqueous polymer dispersions

A method of forming an adhesive bond comprising heating a thermoplastic, polymeric, thermotropic nematic liquid crystalline material until the material becomes fluid, and applying this material onto a substrate. Since the liquid crystalline material exhibits excellent tensile strength, the present method can be employed not only as an adhesive but also to strap articles and band a plurality of articles together.

Method for forming adhesive bond and a liquid crystal adhesive

A method and apparatus for dispensing liquid compositions. The apparatus includes a reservoir for containing the liquid at a low temperature, a metering device for transferring the liquid to a circulating loop at a higher temperature, a heater/mixer for coincidentally heating and mixing the liquid in the loop and means for dispensing the liquid from the loop. The invention is particularly useful for dispensing liquid adhesive and coating compositions, including thermosetting polymers, heat sensitive polymers or plastisols and other dispersed liquid systems. In addition, mixtures of polymeric liquids with other components such as gases, solvents or liquid blowing agents may be employed with uniformity of composition for dispensing foams or atomizable paints.

Method and apparatus for dispensing liquid compositions

A process for providing a substrate such as a polyethylene terephthalate container with a gas barrier coating of a copolymer of vinylidene chloride is disclosed. The process includes locating the container to be coated in close proximity to one or more airless spray nozzles and impacting the outside surface of the container with a stream of a stabilized aqueous polymer dispersion such as an aqueous polyvinylidene chloride dispersion. The impacting force of the stable polyvinylidene chloride dispersion on the surface of the container is sufficient to cause selective destabilization of the dispersion at the surface interface to form a gel layer containing the polymer in the continuous phase. This gel layer serves as an adhesive layer for an overlying layer of the aqueous polymer dispersion as a continuous uniform coating. The resulting wet coating does not sag or run off. The coating on the container is then dried in a controlled atmosphere to complete the gel formation throughout its thickness whereupon it is further dried to remove the water from the coating and to collapse the gel to form a film without distoring the container. The dried coating is smooth, uniform and uniformly transparent. In operation, the overspray can be collected and returned to achieve greater than 95% material efficiency. The process can be carried out in a continuous manner to provide a continuously moving series of containers with a uniformly transparent, gas barrier polyvinylidene chloride coating at production rates suitable for commercial applications.

High solids coating methods and apparatus are disclosed which eliminate many of the disadvantages associated with known coating processes. The techniques disclosed require only a minor amount of a volatile solvent to achieve atomization and application of a paint or other coating material. High solids coating compositions containing about 70-99% by weight solids are atomized and coated. This method also enables polymeric compositions having high molecular weight to be employed as coating materials. According to techniques described, liquid compositions containing film-forming solids are kept under pressure with a minor amount of a highly volatile solvent of from about 1 to 30% by weight, even as low as about 1-10% by weight, at a temperature above the normal boiling point of the solvent. Such a composition is then atomized by releasing the pressure upon a stream of the composition at a temperature above the normal boiling point of the solvent and below the minimum foam temperature at atmospheric pressure for the composition. The film-forming solids are thus conveyed with or without an external atomizing means.

Coating by atomization of high (i.e., about 70-99% by weight) solids

A method and apparatus for dispensing liquid compositions. The apparatus includes a reservoir for containing the liquid at a low temperature, transfer means to a circulating loop at a higher temperature, means for coincidentally heating and mixing the liquid in the loop and means for dispensing the liquid from the loop. The invention is particularly useful for dispensing liquid adhesive and coating compositions, including thermosetting polymers, heat sensitive polymers or plastisols and other dispersed liquid systems. In addition, mixtures of polymeric liquids with other components such as gases, solvents or liquid blowing agents may be employed with uniformity of composition for dispensing foams or atomizable paints.

Pressure vessels are disclosed for containing a foamable mixture of liquid and a blowing agent for incrementally or continuously dispensing a foam of constant foam-volume ratio. Liquid compositions having coating or polymeric solids are capable of being foamed and dispensed with the apparatus. The method and apparatus are especially advantageous in dispensing foamed coatings, paints or adhesives with superior control.

Apparatus and method for dispensing foamable compositions

Foamed hot melt adhesives are made and employed by methods which offer significant advantages and economies. The method employs surfactant stabilizers in making hot melt adhesive foams which are very useful in bonding substrates with efficiency and superior bond strengths. Continuous and reliable foaming operations are achieved with a uniform quality and output of foamed materials. Hot melt adhesives are also capable of being foamed with relatively simple mechanical apparatus and under conditions which provide considerable savings of energy. The number of hot melts which can be foamed employing the present technique in a controlled manner is unlimited. The method of stabilization is conducted at low or ambient pressures and resulting stabilized hot melt adhesive gas dispersions may then be pumped with pressurization and dispensed with immediate foaming.

Bonding with foamed hot melt adhesives

Surface coating methods and apparatus are disclosed which eliminate many of the disadvantages associated with known coating processes from pollution, equipment, materials, energy, labor and cost standpoints. According to techniques described, liquid compositions containing film-forming solids are formulated, then conveyed in the foam state towards a surface, and upon foam disintegration, form a film of solids on the surface. The techniques disclosed eliminate the need for solvents in paints or reduce volatile content to very minimal amounts. This method also enables polymeric compositions having high molecular weight to be employed as coating materials. Furthermore, the method has utility in nearly all coating processes where the film-forming solids are conveyed from a bulk state to a surface for coating.

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Amherst, OH, United States of America

Walter H Cobbs, Jr