An articulation mechanism has a central part and a head part each made of a pair of shaped elements. The pairs of shaped elements form inner and outer shells. The inner shells are positioned inside the outer shells. The pairs of shaped elements are pivotable relative to one another and lockable relative to one another in several positions in one pivot direction. The outer shells have inwardly oriented projections and the inner shells have openings. A slide is moveably arranged inside the inner shells. The slide has locking members projecting through the openings of the inner shells and engaging intermediate spaces of the projections. A spring acts on the slide in an engagement direction of the locking members relative to the projections. The projections are shaped such that the locking members automatically reach a locking position in a first pivot direction of the head part.

1. Field of the Invention
The invention relates to an articulation mechanism having a center part and a head part, particularly for lounge chairs such as garden lounge chairs or camping beds.
2. Description of the Related Art
Lounge chair articulation mechanisms are provided in order to connect a head section with a lounge chair frame in a pivotable way and to foldably connect a leg part that serves as a support to the lounge chair frame. The head section is to be adjustable in several angular positions relative to the remaining lounge chair surface. In the case of known lounge chair articulation mechanisms, it is first required to fold out the leg part before pivoting of the head section relative to the remaining part of the lounge chair is carried out. However, this operational sequence is not always ensured and, when the articulation mechanism is accidentally mishandled, the head section must be folded back and the leg part must then be moved into its supporting position.
It is an object of the present invention to provide an articulation mechanism, particularly for lounge chairs, which is of a simple configuration but can still be safely and reliably handled.
In accordance with the present invention, this is achieved in that the articulation mechanism, particularly for lounge chairs, comprises a central part and a head part, wherein the head part and the central part are comprised of shaped elements interacting in pairs and having sockets formed thereon. One of the shaped element pairs is configured as inner shells and the other shaped element pair is configured as outer shells, wherein the shaped element pairs are pivotable relative to one another and are lockable relative to one another in one movement direction in several positions. The outer shells have inwardly oriented projections; between the inner shells a movable slide is arranged. Teeth are formed on the slide and act as locking members which project through openings in the inner shells and engage intermediate spaces of the projections of the outer shells. The slide is biased by a spring in the engagement direction of the locking members. The shape of the projections is such that the locking members automatically reach a locking position in one pivot direction of the head part.
The articulation mechanism according to the present invention is characterized, inter alia, in that it is comprised of a very small number of shaped elements that can be easily manufactured and easily mounted. Depending on the required force acting as torque on the slide, the teeth can be sized accordingly.
Instead of two locking members, additional locking members in the form of teeth neighboring the spring can be provided or the locking members themselves can be reinforced by providing for the slide a material with higher strength or by manufacturing the slide of a thicker material. The slide comprises a bent section so that the slide extends laterally adjacent to a rivet which forms a pivot axis of rotation of the shaped element pairs of the center part and the head part that are pivotable relative to one another.
In a preferred embodiment of the invention, on the outer shells several projections are arranged in a first group and the same number of projections of a second group are positioned diametrically opposite to the projections of the first group. Between the projections, intermediate spaces with identical contact surfaces and/or glide surfaces for the slide or its elements are formed. These groups with differently shaped projections and thus also different intermediate spaces. This makes it possible that one of the groups provides a locking action and enables in one direction a forward movement with catch action, while the projections of the other group provide only a locking action and thus a force transmission. The projections of the first group each have a slanted surface on which a leading edge of the slide glides upon pivoting of the head part in one pivot direction.
In order to lock the slide as needed such that it can be locked with regard to movement in its longitudinal direction upon certain pivot movements of the head part relative to the center part, measures can be provided by which the slide, i.e., its teeth neighboring the spring, is moved transversely to the longitudinal direction of the slide and engages behind a step of the corresponding opening of the inner shell. In addition, or as an alternative, the slide is provided on a lateral edge with an additional tooth which engages a guide slot in one of the inner shells, wherein the guide slot has a section on which a step is formed. Such a configuration of the additional tooth should be provided particularly in such arrangements in which only the leading end of the slide is provided with locking members. In order to lock the slide relative to its longitudinal movement in a certain angular position of the head part relative to the center part, or to release the locking action in a different angular or pivot position, additional projections are formed on the outer shells, wherein it is expedient that one of these additional projections is correlated with the first group of projections and the other additional projection is correlated with the other group of projections.
The spring is simply arranged in a socket formed by the shaped elements wherein the spring is supported on a spring stop which is formed as a unitary part of the shaped elements.
According to a preferred embodiment, the articulation mechanism according to the invention is provided with a leg part which is supported pivotably on the center part.
The leg part is comprised preferably of a hollow profiled section which has at its end two parallel wall parts with congruent bores for receiving a component serving as a pivot axis, wherein these wall parts serve for forming a hinge together with the shaped element pair that forms the center part. In a preferred embodiment, a first outer shell of a shaped element pair is provided with a shaped portion which cooperates with a wall part forming the hinge. This shaped portion is preferably essentially shaped like a circular segment and on the first wall part a concave gliding contour is formed having a curvature that is matched to the radius of the circular segment.
In order to ensure that the head part can not be folded out away from the center part before the leg part has been moved into the folded-out position, it is expedient that a second outer shell of a shaped element pair has a unitary projecting member which extends in the axial and radial direction and that the second wall part of the leg part has such a contour that, depending on the pivot angle of the leg part, the projection cooperates with the wall part or is released. Depending on the shape of this wall part, it may also be possible that the leg part is first pivoted open by a certain pivot angle and the remaining pivoting action is realized in a forced way simultaneously with the folding action of the head part away from the center part.
In an expedient configuration, the center part has correlated therewith the inner shells and the head part has correlated therewith the outer shells. Of course, it is also possible to reverse this arrangement, i.e., the outer shells are components of the center part. In order to prevent damage to the articulation mechanism by penetration of sand, dirt or the like, the inner hollow space containing the movable parts should be sealed off relative to the exterior. It is therefore expedient to provide the inner shells each with a rim oriented toward one another so that a contour closed off to the exterior is provided.

Articulation mechanism particularly for lounge chairs


A refrigerant system (10, 100, 200) is provided with a power control system (30, 130, 230). The power control system adjusts the speed of the motors driving the refrigerant system components such as a compressor, a fan or a pump via a variable speed device (75, 175, 275) or bypasses the variable speed device (75, 175, 275) for normal operating speeds. A single power control system may be provided for the entire refrigerant system or each component may be independently controlled.

1. Field of the Invention
This invention generally relates to machinery driven by variable speed drives and, more particularly, to systems for heating, ventilation, air-conditioning and refrigeration applications with variable speed components.
2. Description of the Related Art
In machinery that is driven by variable speed drives, there is approximately a five to ten percent penalty in power and efficiency due to losses associated with the operation of the variable speed drive. This efficiency loss or additional power draw is one of the drawbacks that has limited the application of variable speed drives in industrial or other installations. This limitation is especially significant where the need to slow down or speed up the machinery from its normal operating speed is infrequent.
Further, variable speed drive electronics generate heat and are frequently required to be cooled with an external source and/or by diverting a portion of refrigerant circulating through the refrigerant system. Therefore, additional efficiency and power draw penalties are paid to operate variable speed drives within the specified temperature limits. Also, variable speed drives often present a source of unreliability reducing overall system maintenance and uninterrupted service intervals.
Accordingly, there is a need for heating, ventilation, air-conditioning and refrigeration systems with the components driven at variable speeds (or incorporating variable speed drives) with enhanced efficiency of the operation and improved reliability. The method and apparatus of the present invention reduces losses associated with the operation of variable speed drives.
It is an object of the present invention to provide a system for heating, ventilation, air-conditioning and refrigeration applications with an enhanced operational efficiency and improved reliability.
It is a further object of the present invention to provide such a system with an increased service life and maintenance intervals for the components of the variable speed drive system.
It is yet a further object of the present invention to provide a configuration that allows for selective operation of the variable speed drive system.

Refrigerant system with variable speed drive


The present invention relates to a process for forming composite shaped articles used for athletic shoe soles, tubes, pipes, transmission belts and conveyor belts, comprising a vulcanized elastomer directly or autogenously bonded, that is, essentially in the absence of adhesive, to a thermoplastic elastomer comprising recurring polyamide-6 and polyether structural units, such as thermoplastic polyetheresteramide elastomers, are provided. The article is prepared by a process comprising placing a thermoplastic elastomer component into a vulcanization mold, overmolding onto at least a portion of the surface area of one face surface of the thermoplastic elastomer component with a vulcanizable elastomer component, and vulcanizing the vulcanizable elastomer component at a temperature below the melting point of the thermoplastic elastomer component but over a wide temperature range, which can be about 40xc2x0 C. or higher.

1. Technical Field of the Invention
The present invention relates to composite shaped articles comprising a vulcanized elastomer directly or autogenously bonded, i.e., essentially in the absence of adhesive, to a thermoplastic elastomer comprising recurring polyamide-6 and polyether structural units, for example to thermoplastic polyetheresteramide elastomers.
2. Description of the Prior Art
EP-0,550,346 describes composite materials formed from a vulcanized elastomer in adhesive-free combination with a thermoplastic elastomer comprising polyamide sequences. These materials can exist in the form of a vulcanized elastomer sheet adhering to a sheet of the thermoplastic elastomer. By xe2x80x9cadhesive-free combinationxe2x80x9d is intended that the two elastomers adhere by themselves to one another and that, if an attempt is made to separate them, failure of one of the two elastomers occurs.
This is cohesive failure, in contrast to adhesive failure when the separation takes place at the interface of the two elastomers.
The composite material of the prior art can be produced by vulcanization of the elastomer in a mold, a part of which is occupied by the thermoplastic elastomer comprising polyamide sequences.
To date, it is necessary to carry out the vulcanization over a temperature range having a magnitude of at most 5xc2x0 C.
If this range is not observed, the risk exists of obtaining poor adhesion (adhesive failure), or difficulties in removing the composite material from the mold.
This prior art technique is useful for producing shoe soles, but it is difficult, in an industrial plant having many molds which are opened and closed frequently, to avoid temperature variations with a magnitude greater than 5xc2x0 C.
It has now unexpectedly been determined that composite shaped articles can be prepared from a thermoplastic elastomer comprising sequences based on polyamide-6 and polyether sequences, at vulcanization temperature varying over a temperature range, the magnitude of which can be as high as several tens of degrees and often more than 40xc2x0 C.
The composite materials thus produced are subject to cohesive failure, rather than adhesive failure, whatever the vulcanization temperature selected within this wide range. Thus, they are less subject to delamination.
Briefly, the present invention features a composite material comprising a vulcanized elastomer which is adhered, essentially without adhesive or autogenously bonded, to a thermoplastic elastomer comprising recurring structural units based on polyamide-6 and polyether sequences.
The present invention also features a process for the preparation of such composite material.
More particularly according to the present invention, the vulcanizable synthetic or natural elastomers which are suitable for the subject composites are well known to this art; the term xe2x80x9celastomerxe2x80x9d also includes mixtures of a number of elastomers.
These elastomers or elastomer mixtures exhibit a compression set (C.S.) at 100xc2x0 C. of less than 50%, generally ranging from 5% to 40% and preferably of less than 30%.
Exemplary of these are natural rubber, polyisoprene having a high degree of double bonds in the cis-orientation, a polymerized emulsion based on styrene/butadiene copolymer, a polybutadiene having a high degree of double bonds in the cis-orientation prepared via catalysis with nickel, cobalt, titanium or neodymium, a halogenated ethylene/propylene/diene terpolymer, a halogenated butyl rubber, a styrene/butadiene block copolymer, a styrene/isoprene block copolymer, the halogenated products of the above polymers, an acrylonitrile/butadiene copolymer, an acrylic elastomer, a fluorinated elastomer and chloroprene. Epichlorohydrin rubbers are also included.
In the event that the elastomers indicated above do not contain carboxylic acid functional groups or anhydrides thereof (which is the case in the majority of such instances), said functional groups will be introduced by grafting, in known manner, the elastomers indicated above or any mixtures of elastomers, for example with acrylic elastomers.
The selection will advantageously be made from among the elastomers indicated above, of the following: carboxylated nitrile elastomers, acrylic elastomers, carboxylated polybutadienes, grafted ethylene/propylene/diene terpolymers or mixtures of these polymers with the same elastomers, but ungrafted, such as nitrile rubbers, polybutadienes or ethylene/propylene/diene terpolymers, whether alone or in admixture.
The aforesaid vulcanizable elastomers preferably contain a degree by weight of carboxylic acid functional groups or dicarboxylic acid anhydride functional groups ranging from 0.3% to 10% with respect of said elastomers.
The vulcanization systems or initiators which are suitable for the present invention are well known to this art and the invention is consequently not limited to a specific type of system.
When the elastomer is based on an unsaturated monomer (butadiene, isoprene, vinylidene/norbornene, and the like), four types of vulcanization systems are exemplary:
(1) Sulfur systems comprising sulfur in combination with the usual accelerators such as metal salts of dithiocarbamates (zinc or tellurium dimethyldithiocarbamate, and the like), sulfuramides, and the like.
These systems can also contain zinc oxide in combination with stearic acid.
(2) Sulfur donor systems in which the majority of the sulfur employed for the bridgings emanates from sulfur-containing molecules such as the organosulfur compounds indicated above.
(3) Phenol resin systems comprising difunctional phenol/formaldehyde resins, which may be halogenated, in combination with accelerators such as stannous chloride or zinc oxide.
(4) Peroxide systems; all of the free radical donors can be used (dicumyl peroxides, and the like) in combination with zinc oxide and stearic acid.
When the elastomer is acrylic (poly(butyl acrylate) with acid or epoxy functional groups or any other reactive functional group which enables crosslinking), conventional crosslinking agents based on diamines ((ortho-tolyl)guanidine, diphenylguanidine, and the like), or on blocked diamines (hexamethylenediamine carbamate, and the like), are used.
The elastomeric compositions can be modified for certain specific properties (improvement in the mechanical properties, for example) by the addition of fillers such as carbon black, silica, kaolin, aluminum, clay, talc, chalk, and the like. These fillers can be surface-treated with silanes, poly(ethylene glycol)s or any other coupling molecule. In general, the amount of filler material in parts by weight ranges from 5 to 100 per 100 parts of elastomers.
In addition, the compositions can be rendered flexible by plasticizers such as mineral oils derived from petroleum, phthalic acid or sebacic acid esters, liquid polymer plasticizers such as optionally carboxylated low molecular polybutadiene and other plasticizers well known to this art.
The combinations of vulcanization agents used for carrying out the subject process are such that they must permit complete crosslinking of the elastomer according to kinetics providing good properties of resistance to separation, as indicated above, and in general to good rubber properties (measured by a compression set at 100xc2x0 C., tensile-test properties, and the like).
As regards the thermoplastic elastomers which comprise polyether sequences and recurring structural units based on polyamide-6, these can be distributed in a statistical or regular fashion. The polyamide units can be isolated or grouped in oligomers emanating from the condensation of caprolactam.
By xe2x80x9cbased on polyamide-6xe2x80x9d are intended that the polymers are homopolymers of caprolactam or copolymers with C6 diamines and diacids or lauryllacitam or any other structural unit, the polyamide units being comprised essentially of caprolactam residues.
The most typical elastomers are those comprising polyamide blocks and polyether blocks. The polyamide blocks can emanate from the condensation of caprolactam.
These polyamide blocks can be prepared in the presence of a diacid. Polyamide blocks having carboxylic acid endgroups are obtained. The {overscore (Mn)} of the polyamide blocks advantageously ranges from number-average molecular weight 600 to 5,000.
The polyethers include, for example, poly(ethylene glycol), polypropylene glycol) or poly(tetramethylene glycol) having a number-average molecular weight ranging from 250 to 6,000. A plurality of polyethers can be bonded together, for example, via diacid in the case of polyetherdiols.
It is also within the scope of the invention to employ other elastomers comprising polyamide blocks and polyether blocks. These can be prepared via reaction of lactam, diacid and polyetherdiol or polyetheramine. It is also possible to condense polyamide blocks containing amine endgroups with polyether diacids or to condense polyamide blocks comprising acid endgroups with polyetherdiamines.
Such elastomers are described in U.S. Pat. Nos. 4,331,786, 4,115,475, 4,195,015, 4,839,441 and 4,864,014.
Elastomers comprising polyamide-6 blocks having a number-average molecular weight ranging from 1,000 to 3,000 are advantageously employed.
Among these elastomers, preferred are those having polyether blocks originating from poly(tetramethylene glycol) (PTMG). The number average molecular weight of these PTMG preferably ranges from 300 to 2,000.
EP-550,346 mandates carrying out the vulcanization at a temperature close to the Vicat point of the thermoplastic elastomer, for example in the temperature range extending from the Vicat point to 5xc2x0 C. below the Vicat point.
The Vicat point or, alternatively, the softening point is a well known parameter for measuring the physical properties of a polymer. The Vicat point is the temperature at which a needle having a circular cross-section of 1 mm2 penetrates to a depth of 1 mm into the sample during a temperature increase of 50xc2x0 C. per hour according to ASTM Standard D1525. Thus, at this temperature, the polymer does not display plastic flow and is not in the molten state.
If this temperature range is not observed, a material having at best adhesive failure is obtained.
Thus, it has now surprisingly been determined that using thermoplastic elastomers comprising recurring structural units based on polyamide-6 and polyether sequences, the vulcanization could be carried out over a wider range than that of the prior art.
These thermoplastic elastomers have a melting point ranging from 170xc2x0 to 220xc2x0 C. and Vicat point ranging from 130xc2x0 to 180xc2x0 C.
Advantageously, the kinetics, measured by means of an oscillating rheometer, will be such that the characteristic time for vulcanization to 90%, t90, does not exceed 15 minutes and advantageously will range from 5 to 10 minutes.
Moreover, it was found that the time for initiation of vulcanization (or setting time) corresponding to an increase in torque of 0.2 N.m was a significant factor in obtaining materials having good performances. Thus, it is advantageous for the aforesaid increase in torque to be attained in a time greater than or equal to 4 minutes at the molding temperature and preferably ranging from 4 to 6 minutes.
Generally, the process entails forming the thermoplastic elastomer comprising polyamide structural units and polyether sequences and then depositing, by any appropriate means, the thermoplastic elastomer comprising polyamide structural units in a vulcanization mold, such that, preferably, it is affixed against one of the wall members of the mold. Thus, in the event that the elastomer is a film, the film is formed especially by extrusion. Its thickness will preferably range from 0.3 to 5 mm and advantageously is less than or equal to 1 mm. The width of the film is variable and it can be cut with a punch. The piece of film is then positioned against at least a part of the wall of the vulcanization mold for the elastomer, in known manner. The pieces of film can also be stored for any desired time.
In the event that the thermoplastic elastomer is formed from a component of defined shape, for example in the shape a cut section, the latter is preferably affixed to the base of the mold.
It is also possible to use a sequenced two-material injection mold. In this case, the mold is equipped with cavity covers for the elastomer portion, which are removed after injection of the thermoplastic to permit injection of the elastomer to be vulcanized.
The elastomeric composition containing the elastomer with the fillers, plasticizers and other adjuvants, but without the crosslinking system, is formulated in an appropriate reactor and is then introduced, optionally, into another mixer, at an appropriate temperature, with the vulcanization system.
The molding of the elastomer, as well as the vulcanization thereof, is carried out in the mold, part of which is occupied by the elastomer piece comprising polyamide structural units as indicated above, according to one of the conventional processes of the rubber industry: simple compression, transfer compression, injection of transfer injection. In general, it is carried out in a steel compression mold, with a thickness of a few millimeters, placed between two heating plates of a press. The amount of elastomeric composition introduced into the mold can slightly exceed the volume of the cavity. Closing the press initiates plastic flow of the elastomer via the overflow channels. Thus, after a distribution of material, and taking account of the geometry of the mold, the pressure on the elastomeric composition is low (in the region of atmospheric pressure).
The melting point and Vicat point of the thermoplastic elastomers comprising polyamide recurring structural units of the invention are a function of the polyamide units and the polyether blocks.
The temperature range for vulcanization is also a function of the polyamide structural units and of the polyether blocks.
The advantage of the elastomers comprising polyamide structural units is that the vulcanization can be carried out well below its melting point.
The vulcanization temperature range is that wherein the material obtained exhibits an essentially cohesive failure. The lower limit is defined as being the lowest temperature which provides an adhesion of cohesive failure type. The upper limit is not in general established by the property of the material obtained, but is the maximum temperature which permits the material to be easily removed from the mold without plastic deformation or adhesion of the elastomer comprising polyamide structural units to the walls of the mold, or a sticking of the material to the walls of the mold.
For example, the thermoplastic elastomers comprising polyamide-6 blocks having a number average molecular weight of 1,300 and polyether blocks derived from PTMG and having a number average molecular weight of 650 permit a vulcanization range of 140xc2x0 to 180xc2x0 C. This comprises the usual vulcanization temperature of rubber, i.e., 155xc2x0 C.
It is also within the scope of this invention to apply a minor amount of the adhesive to the face surface of the elastomer comprising polyamide recurring structural units.
When vulcanization is complete, after a period of time of less than 15 minutes, advantageously from 5 to 10 minutes, determined beforehand by the t90 of the oscillating rheometer, the article is removed.
In the event that the thermoplastic elastomer comprising polyamide structural units is a film, an empirical formula which is well known to the art of vulcanization of elastomers is applied when the thickness is changed:       Vulcanization              xe2x80x83            time              xe2x80x83                  (      min      )        =            t      90        +          (                        E          2                -        2            )
in which E is the thickness in mm.
The resistance to separation is assessed by various standardized tests which will be selected according to the type of composite material under consideration.
If the polyether comprising polyamide blocks is in the form of a film, the resistance to separation will be measured by the peel test. The resistance to peeling will advantageously be greater than 5 daN/cm.
In the event, the most advantageous from an industrial standpoint, that the thermoplastic elastomer comprising polyamide structural units is a block or article having a defined shape, for example a reinforcing component partially embedded or inserted in the vulcanized elastomer, the tensile strength will be measured. The tensile strength will vary depending on the shape of the item.
The present invention is particularly applicable for the production of sporting goods which are at least in part comprised of a composite material as described above.
The invention is thus well suited for the production of soles for sports footwear, at least a part of which is made of a vulcanized elastomer containing one or more reinforcing components of a thermoplastic elastomer as described above.
In a specific embodiment of the present invention, the composite material successively comprises (axe2x80x2) a vulcanized elastomer, (bxe2x80x2) a thermoplastic elastomer comprising structural units based on polyamide-6 and polyether sequences and (cxe2x80x2) a mixture comprising polyamide-6 or polyamide-6,6 and, optionally, one or more polyolefins, the component (axe2x80x2) adhering essentially without adhesive to the component (bxe2x80x2) and with the proviso that component (cxe2x80x2) can only be PA-6 or PA-6,6.
By xe2x80x9cpolyolefinsxe2x80x9d are intended polymers comprising recurring olefin structural units such as, for example, ethylene, propylene or 1-butene units, and the like.
Exemplary of such polyolefins are:
(a) polyethylene, polypropylene, and copolymers of ethylene with xcex1-olefins, it being possible for these polymers to be grafted with anhydrides of unsaturated carboxylic acids such as maleic anhydride or unsaturated epoxides such as glycidyl methacrylate;
(b) copolymers of ethylene with at least one comonomer selected from among (i) unsaturated carboxylic acids, or salts or esters thereof, (ii) vinyl esters of saturated carboxylic acids, (iii) unsaturated dicarboxylic acids, or salts, esters, hemiesters or anhydrides thereof, or (iv) unsaturated epoxides, it being possible for these ethylene copolymers to be grafted with anhydrides of unsaturated dicarboxylic acids or unsaturated epoxides;
(c) styrene/(ethylene/butene)/styrene (SEBS) block copolymers, optionally comprising maleic functional groups.
Mixtures of two or more of these polyolefins can of course also be used.
The polyolefin is advantageously:
(1) polyethylene,
(2) copolymers of ethylene and an xcex1-olefin,
(3) copolymers of ethylene and an alkyl (meth)acrylate,
(4) copolymers of ethylene, an alkyl (meth)acrylate and maleic anhydride, the maleic anhydride being grafted or copolymerized,
(5) copolymers of ethylene, an alkyl (meth)acrylate and glycidyl methacrylate, the glycidyl methacrylate being grafted or copolymerized, and
(6) polypropylene.
It is advantageous, to facilitate mixing, and if the polyolefins have few or no functional groups which can facilitate compatibilization, to add a compatibilizer.
The compatibilizer is a material or agent per se for compatibilizing polyamides and polyolefins.
Exemplary of such compatibilizing agents are:
(a) polyethylene, polypropylene, ethylene/propylene copolymers or ethylene/butene copolymers, each of these polymers being grafted by maleic anhydride of glycidyl methacrylate;
(b) ethylene/alkyl (meth)acrylate/maleic anhydride copolymers, the maleic anhydride being grafted or copolymerized;
(c) ethylene/vinyl acetate/maleic anhydride copolymers, the maleic anhydride being grafted or copolymerized;
(d) the copolymers (b) and (c) in which the maleic anhydride is replaced by glycidyl methacrylate;
(e) ethylene/(meth)acrylic acid copolymers, and optionally, the salts thereof; and
(f) polyethylene, polypylene or ethylene/propylene copolymers, these polymers being grafted by a comonomer having a site which reacts with amines, these grafted copolymers then being condensed with polyamides or polyamide oligomers having a single amine endgroup.
These compatibilizing agents are described in FR-2,291,225 and EP-342,066, hereby expressly incorporated by reference.
The amount of polyamide constituting the matrix advantageously ranges from 55 to 95 parts per 5 to 45 parts of polyolefin.
The amount of compatibilizer is the amount sufficient for the polyolefin to disperse in the form of nodules in the polyamide matrix. It can constitute up to 20% of the weight of the polyolefin. These polymers are prepared by mixing the polyamide, the polyolefin and, optionally, the compatibilizer according to the usual techniques for mixing in the molten state (twin-screw, Buss or single-screw).
The mixture advantageously comprises polyamide-6 (PA-6) or polyamide-6,6 (PA-6,6) in which either nodules of a mixture of low density polyethylene and of a copolymer of ethylene, of alkyl (meth)acrylate and of maleic anhydride or of glycidyl methacrylate, or nodules of polypropylene, are dispersed.
Such mixtures are described in U.S. Pat. No. 5,070,145 and EP-564,338.
In the case of polypropylene, a compatibilizer is added which is advantageously an ethylene/propylene copolymer, principally propylene units in number, grafted by maleic anhydride and then condensed subsequently with monoamine oligomers of caprolactam.
These polyamide and polyolefin mixtures can be plasticized and can optionally include filler materials such as carbon black and the like.
Such polyamide and polyolefin mixtures are described in U.S. Pat. No. 5,342,886.
The material according to this specific embodiment of the invention is the above material, except that an additional layer (c) of a mixture comprising PA-6 or PA-6,6 and, optionally, one or more polyolefins has been added on the side of the thermoplastic elastomer comprising structural units based on polyamide-6 and polyether sequences.
This material comprising (axe2x80x2), (bxe2x80x2) and (cxe2x80x2) can be produced exactly as the material comprising (axe2x80x2) and (bxe2x80x2), by replacing (bxe2x80x2) with (bxe2x80x2) and (cxe2x80x2) in combination; (b) and (c) in combination can be prepared by coextrusion, laminating, etc.
It too is within the scope of this invention to deposit a coextrusion binder between the layers (bxe2x80x2) and (cxe2x80x2). These binders are materials per se known to this art.
Exemplary of such binders are
(1) polyethylene, polypropylene, copolymers of ethylene and at least one xcex1-olefin or mixtures of these polymers, each of these polymers being grafted by anhydrides of unsaturated carboxylic acids such as, for example, maleic anhydride (mixtures of these grafted polymers and of these ungrafted polymers can also be used), and
(2) copolymers of ethylene with at least one comonomer selected from among (i) unsaturated carboxylic acids, their salts or their esters, (ii) vinyl esters of saturated carboxylic acids, (iii) unsaturated dicarboxylic acids, their salts, their esters, their hemiesters or their anhydrides, or (iv) unsaturated epoxides, these copolymers optionally being grafted by anhydrides of unsaturated dicarboxylic acids, such as maleic anhydride, or unsaturated epoxides, such as glycidyl methacrylate.
It is also possible to add to one or to each of the layers a product which improves their adhesion without requiring use of a binder layer. This product can be the binder described above.
These materials can exist in various forms. They are, for example, pipes or tubes having an internal layer made of polyamide (c). They can be manufactured by coextrusion; for example, the layers (bxe2x80x2) and (cxe2x80x2) are coextruded and then sheathing is carried out with rubber, followed by vulcanization. In these pipes, the layer (bxe2x80x2) is in fact a binder.
In another embodiment, these are coextruded sheets or panels which are in the form of belts, such as transmission belts, which are mechanically strong. It is also possible, before depositing the rubber layer, to draw or stretch the material formed by the layers (bxe2x80x2) and (cxe2x80x2) in order to modify the mechanical properties thereof.
In yet another embodiment, they are conveyor belts.
The invention is thus advantageously well suited for the production of soles for sports footwear, at least a part of which is made of vulcanized elastomer containing one or more reinforcing components comprising the thermoplastic elastomer described above.
In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that same are intended only as illustrative and in nowise limitative.
In said examples to follow, the elastomeric composition, without the crosslinking system, was formulated in a 3.5-liter Repiquet K1 internal mixer, the rotors of which rotated at 60 rpm. The operation was carried out under semi-adiabatic conditions, with conversion of the mechanical energy into heat. An intimate mixture was obtained in less than 5 minutes and the temperature attained a value of 110xc2x0 C.
The elastomer thus formulated was then introduced into a mixing mill with rolls heated to 80xc2x0 C. and the vulcanization system was added thereto.
Overmolding onto the piece made of thermoplastic elastomer comprising polyamide sequences with the elastomeric composition was carried out in a steel compression mold placed between the two heating plates of a press.
The peel force w as measured at the end of 24 hours. Peeling was initiated by pulling an adhesion-free region inserted between the vulcanized elastomer and the polyether comprising polyamide blocks, i.e., an aluminum adhesive tape placed on the polyether comprising polyamide blocks before molding the elastomer.

Composite shaped articles comprising vulcanized elastomers autogenously bonded to polyamide/polyether thermoplastic elastomers


A chirped pulse amplification system includes one or more polarization compensator configured to compensate for polarization altering elements with the chirped pulse amplification system. The polarization compensator is responsive to a sensor configured to provide feedback to the polarization compensator. In some embodiments, the chirped pulse amplification system further includes a controller configured to automatically adjust the polarization compensator responsive to the sensor. The sensor is optionally a power sensor.

1. Field of the Invention
The application is in the field of pulsed laser systems, and more specifically in the field of chirped pulse amplification systems.
2. Related Art
Chirped pulse amplification (CPA) is very useful for producing ultrashort-duration high-intensity pulses for use in high peak power ultrashort pulse laser systems. CPA increases the energy of an ultrashort laser pulse while avoiding optical amplifier damage. In this technique, the duration of the pulse is increased by first dispersing the ultrashort laser pulse temporally as a function of wavelength (a process called "chirping") to produce a chirped pulse, amplifying the chirped pulse, and then recompressing the chirped pulse to significantly shorten its duration. Lengthening the pulse in time reduces the peak power of the pulse and, thus, allows energy to be added to the pulse without reaching a damage threshold of the pulse amplifier and other optical components.
Some elements in a CPA system are polarization sensitive. For example, the performance of a pulse compressor that uses gratings to compress a laser pulse is highly polarization sensitive. Some elements in a CPA system alter polarizing in ways that are not precisely predictable. For example, passage of a pulse through a non polarization-maintaining (PM) fiber optic may alter the polarization of the pulse somewhat. This alteration can include a transformation of the polarization state into linear, circular or elliptical polarization.
The degree to which polarization is altered may be temperature or pulse power dependent, and may, therefore, be time dependent. This is a problem when subsequent elements within the CPA system are polarization sensitive, because their performance may be dependent on, for example, the temperature of polarization altering elements.
There is, therefore, a need for improved methods of managing polarization in CPA systems.


A fire retardant building material composed of a mixture of water and cellulose fibers, both of which can be comprised of readily available materials at the job site, such as the available water supply or natural water and scrap shredded paper, including newspaper or other discarded paper or cardboard materials. The water and cellulose fiber is mixed to form a slurry and calcium hydroxide, alumina, salt and ammonia are added. Pigments and aggregates may be added for appearance.

1. Field of Invention
The subject invention is generally related to asbestos-free, cellulose-based insulating materials and is specifically directed to an insulating material that can be cured to form a structural building material or an insulating layer on site at room temperature.
2. Description of the Prior Art
In the building industry in particular, the structural elements used, such as for example ceilings, walls, partitions, girders and columns and the like, must have adequate fire resistance. To this end, there are legal provisions in many local and national codes that stipulate the period for which the structural elements have to withstand a fire. The walls, installed materials and even sealed openings in such structural elements (for cables and slots for tubes or joints) have to show the same fire resistance as the structural elements in which they are situated. Accordingly, a number of fireproofing compounds are used, for example, to coat the structural elements to make them fireproof or to increase the fire resistance of the sealing systems for the openings.
The sheaths and insulations of electrical cables and plastic pipes consist of inflammable materials which, after ignition, can spread the fire very quickly and which, in addition, conceal the danger of filling workshops and escape routes with smoke and, at the same time, of forming corrosive or toxic combustion products. These risks can generally be minimized by fireproof coatings.
DE-PS 20 65 117 describes a fireproofing compound which contains chlorinated hydrocarbons, antimony trioxide and asbestos fibers in addition to other substances in an aqueous polymer emulsion. This compound is used as a protective coating for electrical cables. In the event of fire, however, the chlorine-containing compound gives off not only chlorine compounds, but also hydrogen chloride gas that is both toxic and highly corrosive. In addition, the fireproofing compound described in DE-OS 20 65 117 contains antimony trioxide which is regarded as a carcinogenic substance and also asbestos fibers which are now known to have a health-damaging effect.
DE-PS 20 39 969 also describes a fireproofing compound containing chlorinated hydrocarbons. The compound in question may also contain asbestos and antimony compounds as further components. Accordingly, the fireproofing compound according to DE-PS 20 39 969 also has the unfavorable properties mentioned above and shows adverse health-damaging effects.
Although the fireproofing compound disclosed in DE-OS 27 24 604 avoids the use of asbestos fibers, it still contains chlorinated hydrocarbons and antimony trioxide. Accordingly, the fireproofing compound according to this document also shows unfavorable health-damaging effects.
The use of a fire-retarding compound for coating electrical cables and lining cable runways is described in DE-PS 28 44 693. The problem addressed by the invention to which this document relates was to modify the fireproofing compound described in DE-PS 20 39 969 in such a way that asbestos need no longer be used. However, the compound used in accordance with DE-PS 28 44 693 still contains an organic halogen compound and, optionally, antimony compound which leads to the disadvantages already described.
Halogen-free fireproofing compounds are also known from the prior art, but contain large quantities of health-damaging antimony compounds, such as antimony trioxide for example. Despite a high content of antimony compounds, these known fireproofing compounds show poor fireproofing properties. For example, cables with a halogen-free sheath and a halogen-free insulation, such as telephone cables with PE sheaths and insulations, cannot be protected with a commercially available product of this type in such a way that the requirements of DIN 4102, Part 1 (Class B1 Building Materialsxe2x80x94Flame-Resistant Building Materials) are satisfied.
Because of the risks associated with fires involving PVC cables (heavy smoke generation, evolution of toxic and corrosive gases), numerous attempts have also been made to replace PVC by polyolefins or by halogen-free elastomers. However, the fire risks attending these new types of cables are often no less than those attending PVC cables and can even be greater.
The search for an insulating and fireproofing compound that is less hazardous to the environment and to human health than known fireproofing compounds has resulted in numerous new technologies. It is required that the dangers associated with the insulating material be minimized while the same time maintaining an effective structural, insulating and fireproofing integrity.
One example of a cellulose based material is shown and described in U.S. Pat. No. 5,496,881, entitled: xe2x80x9cComposition for Forming Fireproof Coatings and Caulking and a Method of Usexe2x80x9d, issued to Annemaier, et al on Mar. 3, 1996. This patent teaches an aqueous composition for forming fireproof coatings and caulking. The composition is halogen, asbestos and antimony-free. The composition contains 5-20% by weight of a binder resin; 10-60% by weight of a particulate flame proofing agent; 0.2 to 27.5% by weight of non-asbestos inorganic fibers with an average length of 300 micron; 0.1 to 10% by weight of a plasticizer; and water.
Other materials, such as board stock and structural materials have also been developed using a cellulose mixture. U.S. Pat. No. 5,611,882, entitled: xe2x80x9cBoard Stock and Method of Manufacture from Recycled Paperxe2x80x9d, issued to Riebel, et al, on Mar. 18, 1997, discloses a cellulose mixture including a protein based adhesive binder and colorant. The mixture can be compression molded or extruded and upon curing in the presence of microwave or radio frequency energy or in thermally controlled appliance, produces board or shape formed stock. The produced stock exhibits colorations and a grain pattern comparable to natural stone. Unlike stone, the material exhibits a lightweight, low density, structural rigidity and ready machinability. A preferred method includes admixing separate, colorized batches of feedstock, each feedstock includes shredded waste newsprint, soybean flour, water and a colorant; reducing the moisture content of each feedstock or a proportioned admixture of several feedstocks, such as by air drying or compressing or performing the admixture in the presence of heat; compacting the admixture to final shape; and curing the shaped material. Final forming and finishing apparatus complete the process.
In addition the need for inexpensive, useful and versatile structural materials continues to plague the building industry, particularly where costs of materials and unavailability of a transportation infrastructure or lack of skilled labor make building of new structures and repair of older structures both difficult and expensive. Moreover, these conditions generally exists in areas where costs is a significant issue to the inhabitants. As an example, while of superior durability, face brick, cut stone and/or floor tile, manufactured of materials which are permanent and non-deteriorating such as fired clay or concrete or natural stone, are often rejected in such regions even though such materials are universally accepted. Reasons for such acceptance include proven longevity, reasonable and permanent closure and resistance to the elements of weather, incombustibility and general appreciation of the styles and colors available which enhance the individual structures on which the face brick, cut stone and/or floor tile is installed. However, the weight, necessity of skilled labor for installation and cost of the installed face brick, cut stone and/or floor tile system have been primary reasons for not using or even considering usage of brick, cut stone and/or floor tile except those regions where usage is presumed as normal or preferred, or where style and visual effect have been primary considerations.
Often face brick, cut stone and/or floor tile cannot be installed on an existing interior wall or floor without significant structural modifications because of the weight of the product. Still another barrier to use is that only professional masons are capable of proper installation of the material.
Over the years the industry has tried to overcome these objections and numerous ideas have been published to overcome these weight and cost issues. The problems associated with weight have been addressed modifying the design of the products and constructing the products with new, lighter-weight materials.
Specifically, the industry has concentrated on decreasing the volume of material used in the manufacturing of each individual brick, stone or tile thereby reducing the attendant weight. The method of extruding holes parallel with respect to the face of the brick is universally known as prior art. The minimum weight achieved by this means, while maintaining sufficient strengths, has remained virtually constant for centuries. This has not lessened issues where a wall-facing product is too heavy for many uses. Teachings include that by Gerald T. Francis in U.S. Pat. No. 4,407,104 (1983), which has, as the primary focus, thin bricks adhesively attached to an extruded polystyrene foam backing panel and each panel joined to the wall with clips which protrude through the joints in the foam panel to provide mechanical attachment to the brick joint mortar subsequently applied. The problem common with adhesives is still extant with this teaching. In addition, in order to achieve a finished wall surface, the mortar joints must be filled manually.
Another teaching is disclosed in U.S. Pat. No. 5,526,630 issued to Steven R. Francis, et al (1996) wherein a formed panel incorporates channels for accepting preformed thin brick tiles frictionally inserted into said channels. There is an additional device, which protrudes from the outer surface of the panel into a space between the individual brick tiles for providing a mechanical attachment of the panel to the wall and for forming a positive attachment to joint mortar that is subsequently applied. This teaches a frictional fit of the individual thin brick tiles to the underlying panel which overcomes the adhesive problem, but introduces another problem by depending primarily on the thin mortar joints for stability of the wall facing.
Still another teaching is contained in U.S. Pat. No. 4,349,588 issued to Henry Schiffer (1982) where a monolific layer of modified cementious mortar is troweled onto an existing surface, subsequently scored, sealed and grouted to appear like brick or cut stone. The disadvantage of this teaching is that it is very labor intensive, requires a multitude of separate steps to accomplish, does not resist cracking because of the monolific coating, requires someone skilled in the art to install and would be difficult to approach a visual replica of the material that it attempts to emulate.
Various materials or combinations of materials have been utilized to achieve a lighter weight brick or cut stone. A common method has been taught by G. L. Bachner in U.S. Pat. No. 3,518,799 (1970) and S. C. Volent in U.S. Pat. Nos. 3,555,757 and 3,949,037 (1967 and 1976 respectively) where a brick, simulated or real, is either cut, pressed or extruded to a thickness of about one-half inch (xc2xdxe2x80x3) or less and then attaching it to the structure by utilizing adhesives. This has not been successful, especially on exterior surfaces because the adhesives are not good enough to provide permanent attachment and because the underlying surfaces must be absolutely sound, planar and without any presence of moisture behind or in them.
A variation of this concept is taught by James D. O""Leary in U.S. Pat. No. 3,740,911 (1973) where the thin bricks are adhesively bonded using a xe2x80x9cresin adhesivexe2x80x9d to a substrate, which is subsequently attached mechanically to the wall. A further variation of these attempts is taught by Chromic, et al in U.S. Pat. No. 4,963,305 where a lightweight, insulating facing brick is provided with a first outer layer formed from conventional bricking clay and a second insulating layer formed from a combination of clay and expanded vermiculite.
Although these approaches do indeed result in a lightweight or lighter weight wall facing material, other conceptual and actual problems arise in their usage. For instance, the current state of the art in the plastics industry does not allow for a material that is not attacked by Ultra-Violet (UV) rays from the sun in the long term, thereby obviating any possibility of true permanence as a wall facing product when compared to concrete or clay face brick, cut stone and/or floor tile. Additionally, plastics are expensive and do not present a visual equality to the natural materials which they seek to emulatexe2x80x94they look xe2x80x9cplasticxe2x80x9d. The dual composite teaching must still utilize expensive and increasingly difficult to find skilled masons to accomplish installation. In the concrete brick industry, various attempts have been made to utilize lighter weight materials, such as expanded shale or clay, to replace some of the normal graded sand as aggregate in the concrete mix. The resulting brick weighs less (about two-thirds the weight) than a normal aggregate mix, but is not as strong and is more absorbent, thereby making it more difficult to use.
The second primary issue is that of costs relating to initial manufacturing, transportation and installation. Initial costs of concrete brick, cut stone and/or floor tile are competitive. However, the costs of re-bracing an existing structure compel many to reject the use of brick, tile and/or stone to re-face the walls or floors (interior or exterior). Also, masons required to lay common brick, floor tile and/or cut stone who are skilled workers who demand high wages. The capital costs to install a manufacturing facility for the extrusion or molding of concrete face brick, floor tile and/or cut stone are considerable. A significant portion of the cost is in the purchase of the forms on which the brick, tile or stone are extruded. Additionally, if more than one size of brick, tile or stone is desired to be produced, the additional forms on which to extrude that size must be purchased. Variations in thickness or any other dimension are impossible because of the shape imposed, in major part, by the forms and by thicknesses necessary to achieve adequate installed strengths. The weight of the finished product limits the effective reasonable shipping radius, limiting the market area to about a 200-mile radius from the manufacturing facility.
The subject invention is directed to a new material composition that can be made on site, largely from available materials, without special tools or processes. The material cures through natural evaporation, without the application of artificial heat. The cured material has been tested to withstand a direct flame in excess of 1500xc2x0 C. and is durable as most lightweight aggregate materials of similar thickness when formed into a structural panel or product. The material may be diluted by water as it is mixed and is suitable for spray application. The material has been successfully used as an exterior wall coating or a roof coating and has shown very desirable increase in xe2x80x9cRxe2x80x9d factor insulation ratings as well as providing a good fire retardant layer.
In the preferred embodiment, the compound material of the subject invention is a mixture of water and cellulose fibers, both of which can be comprised of readily available materials at the job site, such as the available water supply or natural water and scrap shredded paper, including newspaper or other discarded paper or cardboard materials. The water and cellulose fiber is mixed to form a slurry. No specific ratio of water to fiber is required and this is primarily dependent on the application. If the material is to be spray applied then the slurry must be thinner. Where structural material is being created a thicker slurry is desirable primarily because it will lessen the cure period. The mixture may be made to a wet cement-type consistency as well and may be troweled onto a surface.
The water/cellulose slurry is well mixed to assure that the cellulose fibers are saturated with water. Typically, suitable mixing can be achieved in five to ten liter quantities using a hand mixer such as the blade of a shovel or hoe. Once the slurry is thoroughly mixed, the chemicals are added to provide the structural and fire retardant properties. In the preferred embodiment, the basic mixture comprises the following dry components:
6 kilograms of cellulose fibers
1 liter of ammonia (NH4)
1 liter of alumina
1 liter of salt (NaCl)
25 kilograms of calcium hydroxide(CaOH)
180 liters of water.
The cellulose is mixed with the water and the other components are then added in no particular order. Once mixed, the material is ready to use in its wet form as a troweled product, rolled product or sprayed product. It can also be placed in molds or forms to cure to a finished structural product such as a brick or a wall panel. When placed in a sealed container in the wet state, the product has a substantial, although undetermined, shelf life.
Where a more durable product is desired, for example as a replacement for stucco on the exterior of a building, an aggregate may be added. In the above formula, up to 18 liters of aggregate has been added with desirable results. A sand aggregate may also be added to create a desired texturized appearance. Three to four liters have been added with desirable results being achieved.
It is, therefore, and object and feature of the invention to provide a method for making a lightweight, inexpensive fire retardant coating that is non-toxic.
It is an additional object and feature of the invention to provide a method for making fire-resistant material that may be made on site without special tools.
It is another object and feature of the subject invention to provide a method for making a structural material that is non-toxic and may be molded or formed on site.
It is also an object and feature of the invention to provide a method for making a construction material that may be used as a coating by troweling or spreading, rolling, or spraying the material on in a wet form and allowing it to dry at ambient temperature.
It is a further object and feature of the subject invention to provide a method for making a coating material that may be stored in liquid form for long periods and may be diluted with water at room ambient temperatures.
Other objects and features of the invention will be readily apparent from the following detailed description of the invention.

Method of manufacture of structural insulating building materials


A nickel/rhenium catalyst composition for the reductive amination of lower aliphatic alkane derivatives is described. The catalyst includes from about 2 to about 75 weight percent nickel and has a nickel to rhenium weight percent ratio of from about 1:1 to about 200:1. The nickel and rhenium are supported on an alumina-silica support which contains from about 5 to about 65 weight percent silica and has a BET surface area of from about 30 to about 450 m2/g. A process for the reductive amination of lower aliphatic alkane derivatives using such a catalyst composition is also provided.

The present invention relates to a catalyst for the reductive amination of lower aliphatic alkane derivatives. The catalyst comprises rhenium, nickel and, optionally, boron, supported on an alumina-silica support, wherein the alumina-silica support contains from about 5 to about 65 weight percent silica and has a BET surface area of from about 30 to about 450 m2/g. The catalyst provided by the invention has increased activity as well as selectivity to a specified mix of polyamine products.
The reductive amination of lower aliphatic alkane derivatives, i.e., diols such as ethylene glycol and alkanolamines such as monoethanolamine, is a commercially important family of processes. A variety of catalyst compositions for this purpose are found in the literature and are used commercially. Many are based on nickel/rhenium mixtures deposited on a support material. For example, U.S. Pat. No. 4,795,733 to DeThomas relates to nickel/rhenium catalyst compositions also containing a Group VIII metal having an atomic number greater than 43. The catalyst composition is supported on a material such as carbon, magnesium silicate, bentonite, zeolite, metal alloys, silica-alumina, and magnesium oxide-silicon oxide mixtures. Preferred as a support material is gamma-alumina.
PCT Application No. WO 96/38226 discloses catalyst compositions comprising rhenium, nickel, cobalt, boron and copper and/or ruthenium deposited on a support material. Disclosed support materials are silica, aluminum, and/or titanium, preferably silica or alumina, particularly alpha-alumina, silica, silica-alumina, kieselguhrs, diatomaceous earths, or silica-titania, most preferably silica. Surface areas of 10 to 500 m2/g, more preferably from 40 to 200, m2/g are disclosed.
U.S. Pat. No. 5,202,491 to Burgess et al. discloses a continuously generated alkyleneamines composition that may be produced using a variety of nickel-containing catalyst compositions. The patent also discloses that the catalysts may be supported using a number of support materials, including silica-alumina.
Finally, U.S. Pat. Nos. 4,111,840 and 4,123,462 to Best disclose catalyst compositions comprising nickel and rhenium impregnated on a support material selected from alpha-aluminas, silica, silica-alumina, kieselguhrs, diatomaceous earths, and silica-titania, wherein the mole ratio of nickel to rhenium ranges from about 2:1 to about 30:1 and the catalyst is activated by reduction in the presence of hydrogen at elevated temperature.
The Best patents teach that not all support materials are equivalent and that higher surface area supports lead to more active Ni/Re catalyst compositions. However, the data provided in these patents do not support this conclusion. In particular, the data provided in Example 4 of the Best patents show that neither support surface area nor metal loading provides a statistically significant effect on catalyst activity, while the data provided in Example 5 in both references show that increasing the surface area of the support reduces the activity of the catalyst.
It is not clear why a rate effect is seen with respect to Example 5 and no such effect is shown in Example 4, particularly since the catalyst compositions and the reaction conditions are so similar. These inconsistent teachings lead to the conclusion that, at best, increasing the surface area of the support reduces the activity of the catalyst only under some circumstances.
Table 1 of the ""840 patent discloses several examples of commercially available, useful support materials, including the following containing both silica and alumina:
Reductive amination produces a variety of products, some of which have greater economic value than others, depending on current market requirements. For example, the reductive amination of monoethanolamine (MEA) produces lower molecular weight linear polyamine products, such as ethylenediamine (EDA), aminoethylethanolamine (AEEA), and diethylenetriamine (DETA). EDA is a highly commercially valuable product at present, and market demand also exists for AEEA and DETA. Higher molecular weight linear polyamines, such as diamine and triamine, and/or cyclic polyamine products, such as piperazine (PIP), hydroxyethylpiperazine (HEP), aminoethylpyrazine (AEP) and heavy polyamine oligomers, are also formed. Although these products tend to be less valuable than the lower molecular weight polyamine products, there is often an economic incentive for their production. Accordingly, for maximum economic benefit the catalyst compositions used in commercial reductive amination processes must be selective to the desired mixture of polyamine products, in addition to being highly active.
The prior art has not appreciated how to control catalyst composition and preparation variables in a manner that provides a catalyst which has a specified activity and which is selective for a particular mix of products. For example, a statistical analysis of the data presented in Example 4 of the Best ""840 patent leads to the conclusion that support surface area has no statistically significant effect on the EDAIPIP ratio. This is also the case with the data presented in Example 5 of the Best ""462 patent. In fact, if any effect is shown in this data, it is that increasing the surface area of the support decreases the EDA/PIP ratio. Examples I and F of U.S. Pat. No. 5,600,000 suggest that under some circumstances and in the presence of certain promoters, metal loading can have an effect on catalyst activity; however, the effects of surface area and other important catalyst preparation variables were not considered.
It has now been discovered that nickel/rhenium catalyst compositions supported on alumina-silica containing from about 5 to about 65 weight percent silica and having a BET surface area of from about 30 to about 450 m2/g (as measured by the method of Brunauer, Emmitt and Teller) are especially advantageous for the production of polyamine products. By appropriately selecting the composition of these catalysts and controlling certain catalyst preparation variables, it is possible to provide catalysts which have a desired activity and which are capable of providing a specified mix of polyamine products.
Accordingly, the catalysts taught by the invention can be used to provide a mix of polyamine products characterized by very favorable ratios of lower molecular weight polyamines, such as EDA, AEEA and DETA, to less favorable higher molecular weight linear and cyclic products such as diamine, triamine, PIP, and HEP. However, should market demands change, the catalyst composition can be appropriately adjusted and the conditions for preparing the catalyst controlled in a manner such that the catalyst is relatively more selective for the higher molecular weight linear and cyclic polyamine products.
The present invention provides a catalyst composition for the reductive amination of a lower aliphatic alkane derivative. The catalyst composition comprises nickel and rhenium as active metals. More particularly, the catalyst comprises from about 2 to about 75 weight percent nickel and has a nickel to rhenium weight percent ratio of from about 1:1 to about 200:1. The catalyst is supported on an alumina-silica support which contains from about 5 to about 65 weight percent silica and has a BET surface area of from about 30 to about 450m2/g. The catalyst optionally comprises boron and has a boron to nickel weight percent ratio less than or equal to about 1. The nickel content of the catalyst, the nickel to rhenium and boron to nickel weight percent ratios, the support surface area, and the silica content of the support are selected to provide the catalyst composition with a specified activity, and to provide a particular mix of polyamine products when the lower aliphatic alkane derivative is reductively aminated in the presence of the catalyst composition.
In a second aspect, the invention provides a process for the reductive amination of a lower aliphatic alkane derivative to produce a specified mix of polyamine products. The process comprises contacting the lower aliphatic alkane derivative with ammonia or an amine under reducing conditions in the presence of the catalyst composition described above to produce a particular mix of products.
As noted above, the catalyst composition contains nickel and rhenium as the active metals. In general, the amount of nickel in the catalyst composition is from about 2 to about 75 weight percent, based on the total weight of the composition. Depending on the lower aliphatic alkane derivative being aminated, the amount of nickel may vary. For the reductive amination of diols, for example, ethylene glycol and propylene glycol, the preferred amount of nickel in the catalyst composition is generally higher and ranges from about 10 to about 75 weight percent, more preferably from about 10 to about 50 weight percent. For the reductive amination of other lower aliphatic alkane derivatives such as monoethanolamine or ethylenediamine, the preferred amount of nickel in the catalyst composition varies from about 2 to about 30 weight percent, more preferably from about 5 to about 15 weight percent, based on the total weight of the composition.
The weight percent ratio of nickel to rhenium in the catalyst composition is preferably in the range of from about 1:1 to about 200:1, more preferably from about 1:1 to about 100:1, most preferably from about 2:1 to about 50:1.
The catalyst may optionally comprise boron as well. In those embodiments where boron is added to the composition, boron to nickel weight percent ratios are selected to range up to about 1, and preferably up to about 0.5. It is known in the art to use boron as a promoter to obtain high EDA selectivities in nickel/rhenium catalyst compositions. However, the use of boron has disadvantages, such as the suppression of catalytic activity, more complicated and expensive catalyst preparation and contamination of the polyamine products by leached boron. It is therefore preferable to use little or no boron in the catalyst compositions of the invention. Unexpectedly, good activities and selectivities to linear polyamine products can be achieved without adding boron to the catalyst composition by appropriate adjustment of the remaining catalyst variables.
The catalyst composition is supported on an alumina-silica support containing from about 5 to about 65 weight percent silica. The remainder of the support is alumina. The BET surface area of the alumina-silica ranges from about 30 to about 450 m2/g. The use of alumina-silica having these properties is critical to achieving the high activities and selectivities of the present invention. The alumina-silica preferably contains from about 10 to about 50 weight percent silica. A particularly preferred catalyst composition is made with a support material containing about 20 weight percent silica and about 80 weight percent alumina. In the most preferred embodiment of the invention, the alumina phase of the alumina-silica support material substantially comprises theta-alumina and the silica phase is largely amorphous. Preferably, the BET surface area of the alumina-silica is from about 35 to about 300 m2/g, more preferably from about 50 to about 200 m2/g. It has been found that where enhanced EDA production is desired, the preferred surface area of the alumina-silica varies somewhat depending on whether or not the catalyst composition comprises boron. The preferred BET surface area is typically higher in boron-free catalyst compositions. For instance, the most preferred BET surface areas for boron-containing catalyst compositions range from about 60 to about 150 m2/g, while the most preferred BET surface areas for boron-free catalyst compositions vary from about 100 to about 400 m2/g.
The pore volume of the alumina-silica may be varied within a wide range, so long as the surface area requirements are met. Generally, the pore volume of the alumina-silica may range from about 0.2 to 1.5 cc/g, preferably from about 0.5 to 1.0 cc/g.
Alumina-silicas having an appropriate combination of the above properties are not generally commercially available. However, preparation of such materials is well within the abilities of one skilled in the art of support material manufacture. The support material may be provided in any form commonly employed in the art, including tablets, extrudates, spheres, powders, and other forms well-known to those skilled in the art.
The particular method of incorporating the alumina-silica supports with nickel and rhenium is not critical; however, impregnated catalyst compositions generally perform better than precipitated catalyst compositions, unless very high metal loadings are being used. The amount of metals provided on the alumina-silica support can affect or vary the catalytic activity or selectivity.
One technique for impregnating the nickel and rhenium onto the support is by an incipient wetness techniques using aqueous solutions of salts of the metals. Various organic and inorganic salts may be used in the impregnation solutions. Examples of suitable nickel-containing salts for impregnation are nickel nitrate hexahydrate, nickel formate, nickel acetate tetrahydrate, nickel acetate, nickel chloride, nickel carbonate and the like. Typical rhenium salts employed include ammonium perrhenate, perrhenic acid, rhenium heptoxide and other salts typically used by those skilled in the art. Boron compounds include orthoboric acid, ammonium hydrogen tetraborate, ammonium tetraborate and other compounds known in the art.
In preparing the impregnation solutions, the total amount of metal desired to be impregnated on a specific quantity of support and the relative weight ratio of nickel to rhenium should be considered. Both factors have been found to affect the final properties of the catalyst compositions. As noted above, for the reductive amination of lower aliphatic alkane derivatives such as monoethanolamine or ethylenediamine, the total nickel content is preferably in the range of from about 2 to about 30 weight percent based on the total weight of the catalyst composition, more preferably from about 5 to about 15 weight percent. For the reductive amination of diols such as ethylene glycol, the total nickel content is preferably in the range of from about 10 to about 50 weight percent, more preferably from about 10 to about 25 weight percent. As also noted above, the weight percent ratio of nickel to rhenium in the catalyst composition is preferably in the range of from about 1:1 to about 200:1, more preferably about 1:1 to about 100:1, and most preferably from about 2:1 to about 50:1.
It may also be advantageous to pre-dry the alumina-silica support prior to impregnation in order to ensure that the support will take up as much of the solution as possible. Pre-drying also enables the metal to permeate more deeply into the support during impregnation. Penetration of the metal into the support may be further increased by techniques known to those skilled in the art such as increasing the time the support is in contact with the solution. Other impregnation techniques are well known in the art and may be utilized.
Where relatively large amounts of metal are to be impregnated on the support, a single impregnation step may not be sufficient. Although an impregnation solution may be prepared with the minimum amount of solvent required to dissolve the metal salts, the total amount of the impregnation solution may be greater than that which the support can absorb. In such cases, a portion of the impregnation solution approximately equal to the absorption volume of the support is initially contacted with the support. After contacting, the support is dried and then contacted with an additional amount of impregnation solution. Drying may be accomplished by any technique which sufficiently evaporates the volatile constituents of the impregnation solution. The sequential steps of contacting the support with the solution and then drying are continued until all of the impregnation solution is used. A typical drying step can comprise heating the impregnated support at an elevated temperature, e.g., 100-120xc2x0 C. for several hours. Evacuation drying may also be used where the support is cooled and reduced under pressure. Additionally, drying may by accomplished in an inert atmosphere such as nitrogen or under reduced pressure.
Prior to reduction, the catalyst composition may be optionally calcined. Preferably, the impregnated support is calcined at a temperature ranging from about 200 to about 700xc2x0 C., more preferably from about 300 to about 500xc2x0 C., for one minute or less, to about 3 hours or more. It is preferred, but not essential, that calcining be carried out in air. The drying step referred to above may be replaced by calcining or by reducing as described below.
The catalyst composition may then be reduced by contacting the composition with hydrogen at a temperature of from about 200xc2x0 C. to about 700xc2x0 C., preferably from about 300 to about 500xc2x0 C., for about 30 minutes to about 24 hours or more. The reduced catalyst composition is best handled in the absence of air in order to maintain optimal performance and prevent pyrophoric behavior. The catalyst composition may be stabilized by gentle oxidation, carbon dioxide treatment, or other conventional techniques for stabilizing pyrophoric catalyst compositions, and may then be safely handled in air prior to its utilization. Before it is used, the stabilized catalyst composition is activated in hydrogen, typically at a temperature between about 150-250xc2x0 C. Catalyst reduction or the activation of a reduced and stabilized catalyst composition may be accomplished in a separate step or in situ. The specific conditions for reduction are dependent on the particular catalyst composition being activated, as is known in the art, and on the desired activity and selectivity of the catalyst.
The amount of catalyst composition used in the reductive amination process of the invention depends on many variables including the relative proportions of the reactants, the reaction conditions, and the degree of conversion and selectivity desired. Moreover, the amount of catalyst composition will depend also on the nature of the catalyst composition itself, e.g., its metal loading, support composition and surface area, and the activity and age of the catalyst composition. The catalyst composition must be present in the reaction zone in sufficient catalytic amount to enable the desired reaction to occur.
The selectivity of the catalyst composition may be enhanced by the use of promoters. As used herein, a promoter is defined as any metal (or oxide) which when incorporated into the catalyst composition gives enhanced productivity and/or a higher selectivity to the preferred linear, low molecular weight products. In addition to boron, preferred metals or oxides for use as promoters are compounds containing elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group VIA, Group VIIA, Group VIIIA, Group IB, Group IIB and Group IVB of the Periodic Table (IUPAC format). The preferred metals include, for example, copper, cobalt, chromium, rhodium, iridium, ruthenium, zinc, palladium, platinum, sodium, calcium, magnesium, strontium, lithium, potassium, barium, cesium, lanthanum, tungsten, iron, silver, titanium, manganese, niobium, aluminum, tin and mixtures of these metals. Especially preferred metals are magnesium, zinc, niobium, chromium, ruthenium, cobalt, copper, tin and mixtures thereof.
Promoters may be added to the catalyst composition either by co-impregnation with nickel and rhenium or they may be added to the support either before or after incorporation of the nickel and rhenium salts. It should also be understood that the nickel and rhenium need not be added simultaneously with each other or with the promoter; the promoter, nickel and rhenium combination may be added in any sequence. Promoters are added to the catalyst composition at preferred levels which are generally no higher than the nickel present in the catalyst composition on a weight percent basis. On a weight percent basis, a promoter/nickel ratio of 0 to about 0.5 is preferred.
The lower aliphatic alkane derivatives that may be aminated in accordance with the present invention are those that are well-known to those skilled in the art. These derivatives include those having one or more functional groups such as hydroxy, amino, imino, and carbonyl groups and combinations. Preferred lower aliphatic alkane derivatives include those containing one to six carbons. The functional groups present may be on the primary, secondary or tertiary carbon atoms. Examples of preferred lower aliphatic alkane derivatives include ethanol, ethylene glycol, monoethanolamine, dimethylethanolamine, diethylethanolamine, methylethanolamine, ethylenediamine, diethylenetriamine and higher polyamines, ethyleneimine, propanols, propanolamines, propanediols, acetone, butanols, butanediols, aminobutanols, pentanols, pentanediols, aminopentanols, hexanols, hexanediols, aminohexanols, hydroxyhexanals, hydroxycaproic acids, acetaldehyde, glyoxal, and glycolaldehyde. The lower aliphatic alkane derivatives also include compounds from which the aforementioned may be derived. Preferably, at least one of the functional groups in the lower aliphatic alkane derivative is a hydroxy group or amino group.
The particular lower aliphatic alkane derivative to be used depends, of course, upon the particular polyamine product or products desired. Often, the desired polyamine product differs from the lower aliphatic alkane derivative by the addition of an amino group, which replaces a non-amino functional group or adds a further amino group to a lower aliphatic alkane derivative. For example, ethylene glycol or monoethanolamine may be used as one of the lower aliphatic alkane derivatives in the production of ethylenediamine.
In one particularly useful amination process as taught by the invention, ethylenediamine is reacted with itself to produce diethylenetriamine. In this case, the lower aliphatic alkane derivative is ethylenediamine, which is reacted with an amine, also ethylenediamine. It has been discovered that the present catalyst composition has an especially high selectivity to diethylenetriamine in the reductive amination of ethylenediamine.
The amination process may be run using an excess of ammonia or amine to suppress reactions giving polyamine products. The ammonia or amine employed in the reaction may be anhydrous or may contain small amounts of water. With some catalytic systems a large excess of ammonia or amine must be present. In the present process, the ammonia or amine should be present in an amount at least equivalent to the stoichiometric amount required by the lower aliphatic alkane derivative. The ammonia or amine should preferably be present in an amount between 2 and 30 times the stoichiometric amount required. For example, in the production of ethylenediamine from ethylene glycol, monoethanolamine, or mixtures thereof, ammonia is preferably present in an amount such that the mole ratio of ammonia to ethylene glycol and/or monoethanolamine is in the range 4:1 to 25:1. Higher ratios are typically commercially unattractive.
Equipment and reaction conditions for reductive amination are well known in the art, and any such equipment and reaction conditions may be used. Generally, reaction temperatures within the range of about 125xc2x0 to 350xc2x0 C. are suitable, while a preferred range is 130xc2x0 to 225xc2x0 C. A relatively high pressure for the reaction is also preferred. Normally, the increased pressure is obtained by the amount of ammonia or amine and hydrogen already present in the reaction vessel, which is then heated to the reaction temperature. The reaction pressure should normally be about 400 to about 5,000 psig, preferably from 500 to about 3000 psig.
Hydrogen gas is generally present during the reductive amination reaction. Usually, the addition of hydrogen in an amount sufficient to bring the reaction mixture to the desired reaction pressure is sufficient.
Where selectivity is of primary concern in the amination process, it is preferred not to run the process to a high conversion. It has been found that selectivity to the preferred, linear polyamine products decreases as conversion increases. This is because higher molecular weight, more substituted polyamine products are produced as a result of a chain of consecutive reactions. That is, lower molecular weight polyamine products react among themselves to form higher molecular weight polyamine products and/or cyclize. However, where the catalyst composition is sufficiently selective for a particular polyamine product, it is possible to increase the rate of conversion while still maintaining a commercially acceptable level of selectivity. The ability to provide both high conversion rates and acceptable selectivity is an important economic advantage provided by the catalysts taught by the present invention.
The amination process of the present invention may be carried out in any conventional high pressure equipment having mixing and heating means. The process may be carried out in continuous or batch mode. The reactor design is also not narrowly critical and may consist of a stirred-tank, fixed-bed, slurry, fluid-bed or other designs well known in the art, using liquid-phase, gas-phase, multi-phase or super-critical conditions. The feed thereto may be upflowing or downflowing, and design features in the reactor that optimize plug flow may be employed.
The process is not limited to a confining set of conditions. The feed stream may be liquid, supercritical fluid, or gaseous, and the product stream taken from the reaction zone may be liquid, supercritical fluid, or gaseous. It is not necessary that the feed stream and the product stream be in the same physical state.
The reactants may be fed as a stream, typically continuously, to the reaction zone, a bed of the catalyst composition. The catalyst composition is usually in the form of solid particles (pellets, tablets, extrudates, spheres, etc.). Effluent from the reaction zone is also a stream comprising the unreacted components of the feed stream and the reaction products.
Reductive amination using the present catalyst composition advantageously provides polyamine product mixes containing higher amounts of low molecular weight, linear polyamines as compared to catalysts of the prior art at similar MEA conversions. More specifically, use of the catalyst composition provides an increased weight ratio of low molecular weight, linear polyamines to higher molecular weight and/or cyclic polyamines in the product stream. The catalyst composition is therefore highly advantageous for converting monoethanolamine into EDA at high selectivities with relatively less PIP and higher polyamines in the product mix. The catalyst composition is also highly effective for the reductive amination of ethylenediamine to diethylenetriamine, again with relatively lower amounts of PIP and higher polyamines formed.
The following examples further illustrate the invention. However, before turning to the examples in detail, it should be understood that the examples are included for illustrative purposes only and that the scope of the invention is in no way limited to the use of the particular Ni/Re and Ni/Re/B catalyst compositions set forth in the examples or to the use of MEA and ethylene glycol as the lower aliphatic alkane derivative being aminated. Similar results can be achieved using other catalyst compositions and derivatives consistent with the scope of the invention as disclosed herein.
Unless otherwise noted, all catalyst compositions were prepared using the following generalized procedure. Precursor salts of the nickel, rhenium and optionally boron were dissolved in 70-80xc2x0 C. water to form an impregnation solution. The final volume of the impregnation solution was adjusted to equal three times the adsorption volume of the support to be impregnated, and the quantities of the precursor salts were those calculated to give the metal compositions provided in the Examples. In each case, the support was impregnated to incipient wetness by the addition of one-third of the hot impregnation solution and gently agitated until all the liquid had been adsorbed. The sample was then placed in a muffle furnace and calcined in air for one hour at 340xc2x0 C., or as otherwise specified in the Examples. When the support had cooled, the impregnation and calcination steps were repeated two additional times. The impregnation solution was maintained at 70-80xc2x0 C. throughout, and the final calcination time was increased from one to three hours. Those skilled in the art will appreciate that impregnation with the impregnation solution may optionally be done in one, two, four or more incipient wetness applications, as dictated by the solubility of the precursor salts, the porosity of the support to be impregnated, and the required weight loading of the metal.
Prior to use, the catalyst compositions were reduced in hydrogen by ramping the temperature at 3xc2x0 C./min to 230xc2x0 C., holding at this temperature for one hour, and then ramping at 3xc2x0 C./min to 340xc2x0 C., and holding for 3 hours, or as otherwise specified in the Examples. The catalyst compositions were allowed to cool under hydrogen to near room temperature. They were then stabilized by subjecting to a flowing stream of 10% air in nitrogen until the exotherm ceased. At no time was the exotherm allowed to exceed about 60xc2x0 C.
The catalyst compositions were tested as powders using a microreactor system for the reductive amination of ethylene glycol, or as intact pellets in a small tubular reactor for the reductive amination of monoethanolamine (MEA) as described below.
Micro-reactor
A micro-reactor consisting of a 316-stainless steel tube that was 0.57 cm in diameter and 23 cm in length was used for the reductive amination of ethylene glycol with ammonia. Typically, 1-2 grams of 60/100 mesh catalyst (0.15-0.25 mm) was sandwiched between plugs of glass wool in the reactor tubes.
Prior to use, the catalyst compositions were treated (i.e., reduced or activated) in a reconfigured gas chromatograph unit. Catalyst compositions used immediately after calcination were reduced, while those that were reduced and stabilized were activated before use.
During catalyst reduction, the unit was ramped up in hydrogen flowing at 1.5 slph from 30xc2x0 C. to 250-375xc2x0 C. at 10xc2x0 C./min and held at the final temperature for 3 hours. When reduction was complete, the catalyst compositions were purged with nitrogen flowing at 1.5 slph for 15 minutes and then cooled to ambient temperature. When reduced and stabilized catalysts were used they were first activated by heating at 180-200xc2x0 C. for 15-24 hours under one atmosphere of flowing hydrogen. All gas flow rates were determined by calibrated rotameters. At ambient temperature, the micro-reactor was sealed without exposure to air and then inserted into a main reactor system.
Once the micro-reactor tubes were inserted into a temperature controlled oven, the reactor system was brought to reaction temperature and pressure with 3 slph of hydrogen flowing through the system. Ammonia and ethylene glycol were sequentially introduced into the hydrogen stream. Both the ammonia and hydrogen flow rates were regulated by mass-flow controllers. The flow rates of ammonia and ethylene glycol were adjusted so that the ammonia to glycol feed ratio was about 10:1. The ethylene glycol was pumped into the system so that space velocities ranging from 0.097 to 0.152 gmole/g catalyst/hr were obtained during reaction.
The reaction mixture was preheated before passing through the catalyst bed in a downflow mode. The back pressure on the system was controlled with back pressure regulators. The reactor effluent from the unit was decreased to normal pressures and the ammonia and hydrogen flashed in a tank, and then was passed through a scrubber. Liquid product was then collected and subsequently analyzed by capillary gas chromatography.
Tubular Reactor
A tubular reactor consisting of a 316-stainless steel tube having an inside diameter of 1.75 cm and an overall length of about 76 cm was used for the reductive amination of MEA with ammonia. Typically, 50 g of catalyst composition were packed into the central portion of the tube using 60 mesh (about 0.25 mm) glass beads to fill the void spaces between the catalyst pellets. Glass wool plugs held the catalyst bed in place.
In each case, the reduced and stabilized catalyst composition was activated by passing approximately 45 slph of hydrogen through the bed for 18 hours at 180xc2x0 C. and atmospheric pressure. The reactor system was then brought to the temperature and pressure denoted in each specific example while still under hydrogen. A motor valve at the outlet of the reactor was used to control the system pressure.
When at the designated conditions, a solution of anhydrous ammonia and MEA (10:1 to 12:1 NH3/MEA molar ratio) was pumped into the reactor at a MEA space velocity of about 10-12 gmole/kg cat/hr. Just prior to a preheater, hydrogen was introduced to the ammonia/MEA feed stream at a flow rate of about 15 slph. After passing through the preheater, which was maintained at reactor temperature, the mixture was passed into the reactor and over the catalyst bed composition via downward flow. Downstream of the pressure-control valve, the reaction mixture was passed into a receiver where the product was collected in a semi-batch fashion. The liquid product was condensed in the receiver at ambient temperature, allowing the ammonia and hydrogen to flash off. The condensed sample, which contained some unreacted ammonia, unreacted MEA and the products of reaction, was then analyzed for water by a Karl-Fisher procedure and for organic amines by capillary gas chromatography.
Each catalyst composition was typically tested at three to seven different temperatures, over the range of 145 to 175xc2x0 C., to determine the effects of conversion on selectivity. The conversion and selectivity data thus obtained were subjected to curve fitting, and the resultant equation used to calculate selectivities at 30% MEA conversion. These 30% conversion values are used in Examples 1-6 for purposes of catalyst selectivity comparisons. Catalyst activities were compared by comparing MEA conversions obtained at a catalyst temperature of 160xc2x0 C. Pressure and the MEA, NH3 and hydrogen feed rates were held constant throughout.

Nickel-rhenium catalyst for use in reductive amination processes

Union Carbide Chemicals and Plastics Technology Corporation