The B. F. Goodrich Company

Dtm Corporation

Angelo J Magistro

Elmer D Dickens, Jr

Glenn A Taylor

Hendra Ng

Biing Lin Lee

Kevin P McAlea

Paul F Forderhase

William J Kroenke

Joseph A Cowfer

Frederic W Kunig

Richard Tobey Carroll

Eric Martin Weissman

Jamal S Eden

Richard G Parker

Dane E Jablonski

Ronald M Kovach

Douglas B Rahrig

Phillip S Neal

Timothy R Hradek

Mark E Ganninger

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 .mu.m, provided further that the number average ratio of particles smaller than 53 .mu.m is greater than 80%, the remaining larger particles being in the size range from 53 .mu.m to 180 .mu.m. A powder with slow recrystallization rates, as evidenced by non-overlapping or slightly overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10.degree. C. to 20.degree. C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

Sinterable semi-crystalline powder and near-fully dense article formed

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 .mu.m, provided further that the number average ratio of particles smaller than 53 .mu.m is greater than 80%, the remaining larger particles being in the size range from 53 .mu.m to 180 .mu.m. A powder with slow recrystallization rates, as evidenced by non-overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10.degree. C. to 20.degree. C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

A composite powder specially adapted for use in selective laser sintering is disclosed. The composite powder includes a polymer powder dry mixed with a reinforcement powder, where the polymer powder has a melting temperature substantially lower than that of the reinforcement powder. In the case where nearfully dense parts are to be formed, the first constituent powder is preferably a semi-crystalline powder, for example nylon 11, of a composition suitable for forming near-fully dense parts when used unblended in selective laser sintering; if porous parts are desired, the polymer powder is an amorphous powder, such as polycarbonate, polystyrene, acrylates, and styrene/acrylate copolymers. The reinforcement powder is preferably microspheres of glass, preferably coated to enhance wetting and adhesion with the polymer powder when selective laser sintering is performed. Besides improving the stiffness and heat resistance of the part produced, the composite powder widens the process window over that provided by unblended powder, provides improved dimensional accuracy in the part produced, and facilitates roughbreakout and smooth finishing of the part produced.

Selective laser sintering with composite plastic material

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering (SLS) machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, the powder has a two-tier distribution in which substantially no primary particles has an average diameter greater than 180.mu.m, provided further that the number average ratio of particles smaller than 53.mu.m is greater than 80%, the remaining larger particles being in the size range from 53.mu.m to 180.mu.m. When the powder is a semicrystalline synthetic resin having a number average molecular weight in the range from about 30,000 to 500,000; a molecular weight distribution M.sub.w /M.sub.n in the range from 1 to 5; and, provides a window of sinterability in the temperature range from near the powder's softening temperature T.sub.s to its caking temperature T.sub.c, it is sintered layer-upon layer to form a near-fully dense part of arbitrary shape.

This method teaches how to recover and reuse a powder of a thermally degradable material which is used in a selective laser sintering (SLS) process. To recycle such a laser-sinterable powder successfully in a SLS machine it is protected against degradation by cooling the hot bed while layer-upon-layer (layer-wise) of powder is being sintered, seriatim, to form successive slices fused together to form an article of arbitrary shape (part). The process requires maintaining the powder which has more than 80% of the number of particles &lt;53 .mu.m as a quiescent bed which is nevertheless porous enough to permit flowing a cooling gas downwardly through the bed without disrupting its surface. Since each slice is formed at the surface, and the part, as it is formed, is supported in a well-insulated bed, the powder adjacent the slice is at a much higher temperature than powder in the rest of the bed, which, but for the cooling gas, would get overheated. Overheated powder not only degrades but is fused to the surfaces of the hot part forming a 'growth' which makes the part unusable for its intended purpose. The process allows one to recycle the unused powder from the bed to extinction, economically. If the powder, when hot, is also sensitive to oxygen, an inert gas is used as the cooling gas.

Method of recovering recyclable unsintered powder from the part bed of a

Solid solution catalyst in particulate form consisting of attrition resistant .alpha.-Al.sub.2 0.sub.3 particles with 0.5 to 10% by weight, expressed as the oxide, of iron cations substituted for aluminum cations in said catalyst support stabilized with 0.5 to 10% by weight, expressed as the oxide, of lanthanum and modified with at least two, preferably three, metal cations selected from the metals consisting of chromium, cobalt, magnesium, manganese, and barium; wherein one of said metal cations is barium and said catalyst has X-ray diffraction pattern with peak positions different than that of the .alpha.-Al.sub.2 0.sub.3 structure. A process is disclosed which produces ethylene from ethane while producing reduced amounts of vinyl chloride from said ethane to ethylene process.

Catalyst composition and process for the preparation of ethylene from

Aromatic mono-, di-, or trihydroxy compounds are used alone or containing peel strength-improving additives, in association with a polyurethane adhesive, for adhering a polyurethane-coated nylon fabric to another polyurethane-coated nylon fabric to form a polyurethane-coated nylon composite, and for adhering a nylon fabric coated with an aluminum flake-containing polyurethane to a polyurethane-coated nylon fabric. Additionally, aromatic mono-, di-, or trihydroxy compounds are utilized in association with a polyurethane adhesive for forming a lamina composition comprising a polyurethane film adhered to a nylon fabric.

Composition for adhesion of polyurethane-coated nylon fabrics

Solid solution catalyst in particulate form consisting of attrition resistant .alpha.-Al.sub.2 O.sub.3 particles with 0.5 to 10% by weight, expressed as the oxide, of iron cations substituted for aluminum cations in said catalyst support stabilized with 0.5 to 10% by weight, expressed as the oxide, of lanthanum and modified with at least two, preferably three, metal cations selected from the metals consisting of chromium, cobalt, magnesium, manganese, and barium; wherein one of said metal cations is barium and said catalyst has X-ray diffraction pattern with peak positions different than that of the .alpha.-Al.sub.2 O.sub.3 structure. A process is disclosed which produces ethylene from ethane while producing reduced amounts of vinyl chloride from said ethane to ethylene process.

Catalyst composition for the preparation of ethylene from ethane

Ethylene is prepared in an oxydehydrogenation reaction of ethane by contacting a charge amount of ethane, an oxygen source, a chlorine source and water in the presence of a solid solution catalyst at an effective temperature. A low yield of vinyl chloride and a high yield of ethylene are obtained at a high ethane conversion.

Process for the preparation of ethylene and vinyl chloride from ethane

Alpha-alumina particles having a combination of low attrition, thermal stability and fluidizability are disclosed. The alpha-alumina particles are characterized by being devoid of crystalline grain boundaries. The particles are useful as support or carriers for a wide variety of catalysts, especially as catalyst carriers in high temperature catalystic processes.

Attrition resistant catalyst support

The invention is an improved catalyst and process for the manufacture of vinyl chloride from ethylene dichloride. Specifically, the invention is an improved catalyst for the catalyzed dehydrohalogenation of ethylene dichloride in the presence of oxygen. The catalyst comprises a rare earth metal chloride on a zeolite. The catalyst and process enables one to conduct the dehydrohalogenation (or cracking) operation at significantly lower temperatures than employed using a thermal process, without the coking problems observed in such cracking processes.

Catalytic dehydrohalogenation catalyst

At least three, and as many as eighteen, most preferably at least nine, crosslinking sites are provided through the alkoxy groups in multiple chains on a triazine ring (hence 'multisilane'), on a single molecule of the multisilane. The multisilane, useful as a coupling agent, is formed by reacting a triazine-containing compound with a suitable aminoalkyl-alkoxysilane, or, alkyl-aminoalkyl-alkoxysilane in either an anhydrous, or an aqueous liquid medium. A size containing the multisilane, enhances the reinforced properties of organic synthetic resinous materials in which the fibers are used, and most particularly those of rigid poly(vinyl chloride) (PVC) with which it provides cohesive bonding of glass fiber surfaces. Glass fibers coated with a basic film former and the multisilane are covalently bonded on the one hand through some of at least nine alkoxy groups on each of the multisilane molecules, to Si atoms of a glass surface, and on the other hand, through at least some of the amine groups on each of the molecules, to the vinyl chloride (VC) resin in a reaction which involves allylic chloride bonds in the VC resin. The multisilane is effective in adhesives for a wide variety of materials, and in protective coatings.

Triazine-containing multisilane coupling agents for coating glass

Vinyl chloride (VC) resins, particularly poly(vinyl chloride) (PVC) and chlorinated poly(vinyl chloride) (CPVC) are reinforced with glass fibers which have been sized with a particular aminosilane coupling agent and a particularly characterized basic film former. At the processing temperature of VC resin, containing a stabilizer against degradation during thermoforming, for example in an extruder, or on a mixing mill used to blend the resin with sized glass fibers, a reaction occurs between an aminosilane coupling agent and the VC resin which reaction involves C.dbd.C bonds in the homopolymer, provided the polymer film former in the size is more basic than poly(vinyl acetate) ('PVA'). The film former catalyzes the thermal dehydrohalogenation of the VC homopolymer at the fiber-resin interface so as to generate allylic Cl moieties in chains of the homopolymer, which moieties react with the amine groups of the aminosilane. The size is most conveniently coated on the fibers from a sizing solution, dispersion or emulsion containing the coupling agent and film former in which allylic Cl moieties in VC resin chains become covalently bonded to an aminosilane, so that even upon thorough extraction of a GFR VC composite with tetrahydrofuran (THF), sufficient bound VC resin remains so that X-ray photoelectron spectroscopic (XPS) examination indicates that the ratio of total chlorine to total carbon remaining on the surface of the glass fibers, i.e. the ratio of the areas of the 'Cl(2p)/C(1s)' peaks, is at least 0.91.

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Brecksville, OH, United States of America

Angelo J Magistro