A step assembly comprising a pair of interengagable steps for use in climbing over a fence having T-shaped posts comprises a first step and a second step, the first step engaging the outer surface of the flat cross bar of the T-shaped post, the second step engaging the perpendicular leg of the T-shaped post wherein the first step is initially separate from the second step and is releasingly engageable thereto.

1. Field of the Invention
This invention relates to a step assembly for use by hunters and farmers who desire to climb over a fence having T-shaped posts. Usually, a fence having T-shaped posts has several strands of barbed wire spaced vertically along the outer surface of the flat cross bar of the T-shaped post each wire resting upon a protruding lug spaced along the outer surface of the flat cross bar. Climbing the T-shaped post cannot be accomplished as the lugs are too small to be engaged by a foot and crossing such a fence by trying to slide between the barbed wires often results in torn clothing and damage to the fence.
2. Prior Art Statement
It is known to provide a "hunter's step" which has a generally T-shaped cross section to both the step and the upright leg and further has belt loop holes in extensions of the crossbar of the upright T adapted to receive a belt therethrough for wrapping around a tree or wood post. For instance, see the U.S. Pat. No. 4,000,788 issued on Jan. 4, 1977, to Burgess, et al.
It is also known to provide a stile for placing alongside a post and securing it to the post with a pliable strap affixed to slot in the tube. The stile is substantially the same length as the post and has steps on either side for scaling the stile. For instance, see the U.S. Pat. No. 4,830,142 issued on May 16, 1989 to Bernard McManus.
It is further known to provide one piece step for use on building timbers making a ladder out of a 2.times.4. An open U is adapted to engage the timber from one edge with teeth biting into the face of the timber. The step is a substantially square extension of one leg of the U and may be made from reinforcing bar. For instance, see U.S. Pat. No. 5,407,025 issued on Apr. 18, 1995 to Donald Nickel.
Finally, it is known to provide a step or step assembly which has a body recess for engaging a post lug. The step is placed between two post lugs and slid downwardly to engage the lug. The step may be a solid mass but may have a telescoping leg. For instance, see the U.S. Pat. No. 5,857,542 issued on Jan. 22, 1999 to Robert Mason.

Step assembly for t-post, components therefor and methods of making the same


A low molecular weight, telechelic polymer containing polar internal functionality is produced by (a) treating a copolymer of a polar alpha olefin and a conjugated diene with ozone to degrade the copolymer and form polymer segments which have aldehyde or ketone groups on the chain ends, wherein the copolymer has a random distribution of predominantly 1,4-diene double bonds and the pendant functional groups of the polar alpha olefin are stable to ozone, and (b) further reacting the aldehyde or ketone end groups to provide terminal functionality. The terminal functionality which can be provided includes carboxylic acid groups, primary hydroxyl groups, and amide groups.

This invention relates to a process for producing telechelic functionalized polymers by ozonation degradation of diene polymers. More particularly, this invention relates to the synthesis of fully saturated mono-ol polymers and telechelic polymers containing reactive endgroups and polar midblocks.
Functionalized anionically polymerized polymers of conjugated dienes and other monomers wherein the functionalization is terminal and/or internal are known. Particularly, U.S. Pat. No. 5,393,843 describes polybutadiene polymers having terminal functional groups. One of the methods described for making such polymers involves anionic polymerization utilizing a dilithium initiator such as the adduct derived from the reaction of m-diisopropenylbenzene with two equivalents of s-BuLi. Monomer is added to the initiator in hydrocarbon solution and anionic living polymer chains grow outwardly from the ends of the dilithium initiator. These polymers are then capped to form functional end groups as described in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991. Of particular interest herein are terminal hydroxyl, carboxyl, sulfonate, and amine groups.
The aforementioned patent describes one method of making functionalized polymers. In order to get saturated functionalized polymers, a hydrogenation step is necessary. It would be advantageous to be able to produce such polymers without the necessity of the hydrogenation step. Also, it would be advantageous to be able to produce such polymers which contain polar functionality in the midblock or interior of the polymer. The present invention provides a method for accomplishing these desired results.
In one aspect of the present invention, a fully saturated monohydroxylated polyolefin polymer is produced by (a) treating an unsaturated polydiene polymer with ozone to degrade the polymer to polymer segments which have an aldehyde or ketonic group at the chain terminus; and (b) selectively reducing the aldehyde or ketone end group by treatment with hydrogen in the presence of a hydrogenation catalyst such as Raney nickel to form a polymer which has hydroxyl groups on the chain ends as shown in the following generic formula where R is hydrogen, methyl, or higher alkyl:
If Rxe2x95x90H, then both ends have a primary hydroxyl group. In a preferred embodiment, the unsaturated polydiene polymer is butyl rubber which is a copolymer of polyisobutylene and isoprene or polyisobutylene and butadiene.
In another aspect of the present invention, a low molecular weight, telechelic polymer containing polar internal functionality is produced by (a) treating a copolymer of a polar alpha olefin and a conjugated diene with ozone to degrade the copolymer and form polymer segments which have aldehyde or ketone groups at the chain ends, wherein the copolymer has a random distribution of predominantly 1,4-diene double bonds and the pendant functional groups of the polar alpha olefin are stable to ozone, and (b) further reacting the aldehyde or ketone end groups to provide terminal functionality. The terminal functionality which can be provided includes carboxylic acid groups, primary hydroxyl groups, and amide groups.
Polyolefin-co-polydiene polymers which are used as the starting polymer in the process of the present invention are well known. They can be produced by anionic polymerization of conjugated diene hydrocarbons with lithium initiators as described in U.S. Pat. Nos. 4,039,593 and Reissue 27,145 which are herein incorporated by reference. In this case, the resultant polymer must be partially hydrogenated. These polymers can also be produced by cationic polymerization using Lewis acid initiators. Anionic polymerization commences with a monolithium, dilithium, or polylithium initiator which builds a living polymer backbone at each lithium site.
Almost any polyolefin-co-polydiene polymer can be utilized in the present invention. The main requirement is that there be some Cxe2x80x94C double bonds in the backbone of the polymer which are subject to degradative attack by ozone. Such polymers may contain polar internal functionality as described below. Thus, polymers which can be used in the present invention include butyl rubber, which is a copolymer of polyisobutylene (PIB) and isoprene or butadiene, partially saturated polyisoprene, partially saturated polybutadiene, copolymers of these dienes, polymers of other conjugated dienes, copolymers of conjugated dienes with styrene and styrene derivatives, and copolymers of conjugated diene with acrylic monomers. In order to obtain a telechelic polymer containing polar internal (ofttimes referred to as midblock) functionality, the starting polymer must be a copolymer of a polar alpha olefin and a conjugated diene. The polar comonomer in this copolymer is preferably an acrylate or methacrylate polymer but may also be acrylamide or similar structure:
where Yxe2x95x90NR2, NRH, NH2, ester, or halide. For this copolymer, it is important that it contain a random distribution of predominantly 1,4-diene double bonds (where the degradation attack will take place), that the polar functional groups be pendant and inert to ozone, and that the molecular weight of the copolymer be high enough to afford an average functionality on the final polymer of at least 2.0. This means that the number average molecular weight of the precursor polymer should be at least 25,000, preferably 100,000. However, if polymers with lower functionality are desired, a lower number average molecular weight polymer can be used.
The starting polymers described above may be subjected to degradative ozonation through the use of a gas consisting wholly of ozone but more generally through the contacting of these polymers with gases such as air or oxygen containing up to 15 percent by weight of ozone. Mixtures of oxygen and ozone are preferred from a practical standpoint. The starting polymers are dissolved in a suitable solvent such as carbon tetrachloride, the straight or branched chain aliphatic hydrocarbons such as normal hexane, normal heptane, isohectane, isopentane, or any other non-reactive solvent for the polymer which is inert to ozone under the conditions of this invention. Generally, for convenience, the concentration of the polymer in the solvent will range from about a 1 percent to about 30 percent by volume, preferably about 10 percent to about 20 percent by volume. Into this solution, there is bubbled a stream of an ozone-containing gas while maintaining the temperature of between xe2x88x9280xc2x0 C. and 85xc2x0 C., preferably between xe2x88x9250xc2x0 C. and 50xc2x0 C., especially when the solvent is a hydrocarbon. Pressures of from atmospheric up to 500 psig, preferably from atmospheric up to 100 psig, may be employed. The higher pressure is used where the solvent would normally volatilize if temperatures in the upper range of those specified are employed. The time for carrying out the reaction may range from about 5 minutes to about 15 hours, preferably between 15 minutes to 2 hours is sufficient. U.S. Pat. No. 3,392,154, which is herein incorporated by reference, describes the ozonolysis of polymers of the type described herein. The conditions specified in the patent may generally be used in this invention.
The reaction conditions during ozonation are correlated so as to achieve, as far as possible, a polymeric ozonide which, on ozonolysis, will yield a polymer having the desired molecular weight and preferably a polymer in which each molecule has attached at each chain end a functional group. The primary decomposition of the ozonide of this type of polymer is believed to give rise to the formation of aldehyde or ketone functional groups at the chain ends.
The decomposition of the ozonides prepared as described above may be carried out in a number of ways. The ozonides, still in the solvent solution, may be subjected to small quantities of hydrogen, using a hydrogenation catalyst, or to an active hydrogen-containing compound such as water, tertiary amines such as pyridine and tributylamine, or to low molecular weight primary alcohol such as methanol, ethanol, etc.
The decomposition operation results in the formation of polymer chains having a lower molecular weight than those of the original polymer. Generally, the average theoretical molecular weight will be determined by             MW      n                  xe2x80x83            copolymer        Number              xe2x80x83            double              xe2x80x83            bonds              xe2x80x83            per              xe2x80x83            chain
There is at least one terminal radical per molecule and in most cases one at each end of the newly formed chains.
The new polymer of lower molecular weight can then further be oxidized by the use of conventional reagents such as air, oxygen, or by aqueous or non-aqueous solutions of oxidizing reagents, for example, peroxides such as hydrogen peroxide, sodium peroxide, solutions of hydrogen peroxide and aqueous sodium hydroxide or carbonate, peracids such as performic acid, peracetic acid, and perbenzoic acid, persulfates such as potassium persulfate, ceric salts such as ceric sulfate, potassium permanganate in mineral acid or alkalin solution, potassium ferocyanide, potassium dichromate, potassium bromate, and the like, such that the functional endgroups are substantially all converted to carboxyl groups. As a result, the starting polymer is converted to a degraded linear chain, low molecular weight compound having either hydroxyl endgroups on each chain or carboxyl groups on each chain or mixture of the two types of radicals.
The degraded polymer can also be reacted with amines to hydroaminate the polymer to form primary amide groups on the ends of the polymer. For example, the polymer may be treated with Raney nickel and an amine.
Since aldehyde or ketone groups are generally produced on each end of the polymer by ozonation, the polymers produced are telechelic polymers having aldehyde or ketone groups at each end. Depending on what polydiene is degraded, there can be two aldehyde groups (1,4 polybutadiene), two ketone groups, or one of each (polyisoprene). It is possible to produce a mono-ol polymer which has a primary hydroxyl group on one end of the polymer. Such polymers are advantageous because they can be used for a variety of applications as described in the aforementioned U.S. Pat. No. 5,393,843.
The PIB-co-isoprene or butadiene polymer which has been ozonated may be selectively reduced by using a Raney Nickel catalyst or other hydrogenation catalyst. This reduces the aldehyde endgroup to a primary hydroxyl group but leaves the ketone group on the other end of the chain intact. Ketones can be reduced but require more severe conditions than do aldehydes. Thus, this affords a way to make a saturated mono-ol polymer without the necessity of hydrogenating the entire polymer in the process. The Raney Nickel catalyst is successful in selectively reducing one endgroup of the polymer because the sterically-hindered ketone requires substantially more severe reaction conditions in order to hydrogenate. Other catalysts which could be used include palladium on carbon and ruthenium on carbon. The reduction reaction will generally be carried out at 70xc2x0 C. to 120xc2x0 C. for 10 to 300 minutes under pressures of 100 to 10,000 psi.

Telechelic polymers are produced by ozonation degradation of diene polymers


Improved system for delivering a controllable concentration of anesthetic gas to a patient by eluting with a carrier gas a solid polymeric adsorbent previously loaded with an anesthetic, the concentration being dependent only on the adsorbent temperature and the initial quantity of adsorbed anesthetic. Preferred embodiments utilize the polymeric adsorbent's capability of delivering a broad range of concentrations at low flow rates in a recycle delivery system.

This invention is concerned with a system for delivering anesthetics and analgesics. More particularly, the invention is concerned with a method for delivering anesthetic and analgesic inhalation gases. When used in a broad sense hereinafter and in the claims, "anesthetic" is intended to include the administration of inhalation gases which are both anesthetic and/or analgesic.
Present delivery systems for inhalation anesthetics utilize the principle that a volatile liquid maintains a constant vapor pressure in the gas phase above the liquid. Anesthesia machines are constructed so that a stream of carrier gas passes through a baffled mixing chamber containing a few hundred milliliters of the liquid anesthetic. This stream becomes saturated with anesthetic vapors and the concentration is determined exclusively by the temperature (the higher the temperature, the higher the anesthetic concentration in the saturated vapors). The saturated stream is then mixed with a controlled amount of oxygen and/or nitrous oxide to dilute the saturated stream to a known concentration which is then delivered to the patient. The anesthesiologist determines the concentration from the temperature and by adjustment of a complex series of valves and flow meters.
Since each anesthetic has a different vapor pressure, a recalibration or even replacement of the vaporizer is necessary each time the anesthetic is changed.
Anesthetic concentrations of 0.5 - 4% are generally employed. Recommended flow rates for proper functioning of the equipment are in the 2 - 4 liters/min range. However, flow rates of 1000 cc/min are more desirable since this is the rate of oxygen uptake by the patient. The reduction of flow rates from 2 - 4 liters/min to 200 - 400 cc/min is commonly accomplished by a pop-off valve usually located on a surge or breathing bag.
The present methods of delivering inhalation anesthetics possess a number of substantial drawbacks (some of them inherent) which although recognized by the large majority of anesthesiologists have heretofore not been resolved in a satisfactory manner. These disadvantages include the inability of present metering devices, particularly in recycling systems, to effectively provide desired concentrations of anesthetics at less than 2 liters/min. flow rates. As mentioned hereinbefore the decrease in flow rates is typically effected by a pop-off valve. Unfortunately pop-off valves commonlyrelease the anesthesia into the operating room itself, which is further disadvantageous since it may cause the operating surgeon to become drowsy at times when full concentration is absolutely essential. It is also suspected that prolonged exposure of operating personnel to anesthetics such as halogenated ethane may give rise to kidney and liver problems. Additionally, there has been alleged a relationship between exposure to inhalation of anesthetics and the high statistical rate of miscarriages experienced by operating room nurses. Venting inside and outside the operating room has been known to contaminate the closed circulatory air system of hospitals causing air pollution within the hospital. Regardless however of where the anesthesia is vented, excessive flow rates which require venting cause a considerable waste since up to 90% of the anesthetic gas delivered is unused.
A further difficulty arises when the exhaled gas is fed back via a closed recycling system eventually into the surge or breathing bag. The in-put of gas containing an unknown concentration of unused anesthetic obviously impairs the anesthesiologists's ability to establish the influent concentration of anesthesia that the patient inhales. Although the experienced anesthesiologist carefully determines the unconscious state of the patient during an operation by monitoring the patient's vital signs such as heart beat, etc., it would obviously be of great assistance for him to know exactly what amount of anesthetic the patient inhales at any given time and just as importantly for him to possess the ability to control precisely the amount of anesthetic supplied to the patient.
A further drawback of today's complicated anesthesia machines is their high maintenance cost. They are usually scheduled weekly for cleaning and "degumming" of the mixing chamber and ancillary equipment. Conscientious anesthesiologists frequently feel obligated to personally perform this function. A system which obviates the cleaning would therefore result in considerable savings of valuable time.
Inhalation anesthetics are sometimes used outside of hospital operating rooms, such as for example in dentists' offices. Dentists frequently use local analgesics by injection although they would prefer inhalation analgesics were it not for the cost of today's complex anesthesia machines and the mechanical difficulty of supplying dilute concentrations of gas to achieve a low analgesic state in the patient. Halogenated anesthetics such as trichloroethylene and methoxyflurane which are generally preferred cannot be used as analgesics with most present day equipment since the extremely dilute concentrations which are all that is necessary are not obtainable due to these anesthetics' great volatility in the liquid form. Delivery of analgesics or anesthetics by inhalation would however be preferred, if possible, as it allows the patients quick and total recovery without withdrawal symptoms commonly associated with narcotics delivered by injection. An increased number of patients have developed allergies to "local" analgesics and would therefore be benefited by thegreater range available in inhalation analgesics. Such analgesics would further establish better patient rapport particularly among children by eliminating the fears associated with needle injections.
It will be apparent, therefore, that some of the difficult problems confronting medical personnel in administering inhalation narcotics have been those of accurately and reliably delivering specific concentrations of gas without waste or danger to operating personnel. While various mechanical expedients have been developed for reducing flow rates, safely venting excess anesthetic gas and regulating or monitoring equipment, none has been entirely satisfactory or adequate under all operating conditions. Hence, those concerned with the development and use of inhalation narcotic systems have recognized the need for relatively simple, safe, reliable and accurate system which will be economical in price as well as use.
A relatively uncomplicated method and apparatus for delivering gaseous anesthetics in a closed system of anesthesia has been previously disclosed in Moyat U.S. Pat. No. 3,183,906, issued May 18, 1965. By one embodiment of that method essentially pure anesthetic is introduced into a carrier gas from a "reversible physical absorbing agent" (activated carbon is given as a preferred type adsorbent) and delivered together with the carrier gas to the patient. In another aspect, the Moyat method involves a closed anesthesia system in which a patient's exhaled gas is recycled through the adsorbing agent containing the anesthetic, with the carbon dioxide exhaled by the patient being removed and fresh oxygen added to make up for that which was consumed.
Unfortunately, the Moyat method which appears to offer great advantages in economy, safety and simplicity compared to existing systems for delivering anesthetics, has not gained widespread acceptance. At least in part, this lack of acceptance may be due to the unsuitability of activated carbon for sustained and controllable release of adsorbed anesthetics. Both the capacity for adsorption of anesthetics and the delivery characteristics of activated carbon vary appreciably from batch to batch. Frequently the initial delivery rate of anesthetic from activated charcoal is greater under ambient temperatures than desirable for anesthesia, necessitating complicated control means to reduce concentration. The friable nature of charcoal, leading to the production of a fine charcoal dust, may also lead to problems of containment and possibly blockage of sensitive control devices.
I have now discovered that a particular class of polymeric materials have outstanding properties for the adsorption and retention of common anesthetics, and are capable of uniform release of such anesthetics in controllable amounts and concentrations. Accordingly, these polymeric materials furnish an improved means for the practical implementation of the prior art methods of delivering anesthetics from a solid adsorbent material.
One of the principal disadvantages of the prior art activated carbon in anesthetic delivery is the wide difference in adsorption capacity and release, between different batches and different particle size carbon. This phenomenon is illustrated in the following table wherein w/w % means the weight of anesthetic divided by the weight of adsorbent plus anesthetic times 100.
TABLE I ______________________________________ Batch Variations on Delivery from NUCHAR WVH (33 w/w% Halothane adsorbed on Carbon) Sample Initial Halothane Delivery Carbon conc. at 30.degree. C. (in air) ______________________________________ 8 .times. 30 Mesh (No. 1) 0.30 % 8 .times. 3 Mesh (No. 2) 0.62 6 .times. 16 Mesh 0.22 ______________________________________
The large difference in delivery of anesthetic between Samples 1 and 2 in Table I is not unusual, nor is it surprising that different size particles yield different delivery rates. Further, the high initial anesthetic delivery of Sample 2, at relatively low temperature, makes this material of dubious value for anesthetic delivery which commonly employs sustained delivery concentrations of about 0.5% in air.
In contrast to the variations in delivery of anesthetics from activated carbon, the polymeric adsorbents useful by the method of the present invention are relatively uniform in delivery capability from batch to batch and can be routinely produced by chemical synthesis with uniform capabilities. Those polymers which are suitable include macroreticular homopolymers and copolymers which will adsorb at least 1.0 w/w % of an inhalation anesthetic from a gas stream at 25.degree. C and atmospheric pressure containing 0.5 v/v % inhalation anesthetic. Further, such polymeric adsorbents will deliver to an eluting gas stream under atmospheric pressure a concentration of 0.5 v/v % of anesthetic, at a temperature below that which will cause decomposition of the polymeric adsorbent or appreciable volatilization of extractables therefrom, when said adsorbent is initially loaded with at least 1.0 w/w % inhalation anesthetic.
The polymeric macroreticular resins suitable as adsorbents according to this invention include any of the well known prior art macroreticular resins useful for adsorption or ion exchange (see, e.g., U.S. Pat. No. 3,531,463 ). Among these are the crosslinked and uncrosslinked homopolymers and copolymers of styrene, vinyl toluene, vinyl benzyl chloride, ethyl vinyl benzene, acrylonitrile, vinyl pyridine, ethyl thioethyl acrylate, diacetone acrylamide, ethyl thioethyl methacrylate, butyl methacrylate, ethylacrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, dimethyl acrylamide, vinyl pyrrolidinone, 5-methyl-5-vinyl pyridine, 4-vinyl pyridine, and 2-vinyl pyridine.
Polyfunctional materials which are suitable for production of macroreticular polymeric adsorbents or which may serve as crosslinkers for the above monomers include divinyl benzene, trivinyl benzene, trimethylol propane trimethacrylate (X-980), trimethylol propane dimethyacrylate, penta eythritol tetramethacrylate, penta eythritol trimethacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, and butylene glycol dimethacrylate. The methods of producing macroreticular resins by suspension polymerization are illustrated in U.S. Pat. Nos. 3,843,566; 3,531,463 and 3,663,467.
The macroreticular resins may also be functionalized, i.e., converted to ion exchange resins without appreciably diminishing their capacity for adsorption of the anesthetic material. Suitable functional ion exchange groups that may even enhance the capacity of the polymeric adsorbents include sulfonic, carboxylic, amine oxide, sulfoxide, sulfone, ketone and amides.
The preferred macroreticular resins useful in accordance with the invention are those produced containing a large surface area, i.e., approximately 100 - 900 m.sup.2 /g, such as the styrene or ethyl vinylbenzene divinylbenzene (DVB) resins in which the DVB crosslinker is present in an amount between about 20 - 100%. This class of resins is marketed commercially by Rohm and Haas Company under its Amberlite trademark and designated as XAD-1, XAD-2 and XAD-4. Other preferred macroreticular polymers are acrylic ester-based materials marketed under the designations XAD-7, 8 and 12.
With regard to the anesthetics which may be useful in carrying out the invention, it should be understood that any liquid or gaseous anesthetic may be satisfactory. Specific anesthetics which have exhibited great utility have included chloroform, ether and vinyl ether, cyclopropane, halothane, methoxyflurane, enflurane and trichloroethylene. Preferred anesthetics are halothane, methoxyflurane and enflurane. Halothane, which is marketed broadly under the trademark Fluothane (trademark of Ayerst Laboratories, Inc.) is by far the most widely used anesthetic comprising an estimated 81% of the total inhalation anesthetic market.
In practicing the method of invention it will be necessary to use an apparatus for delivering the anesthetic fluid having an inlet and an outlet conduit connected to a chamber, said chamber containing a solid adsorbent bed which is capable when loaded with anesthetic of releasing a controllable, substantially constant concentration of anesthetic into an eluting fluid passed through the inlet, the bed, and then the outlet conduits. The solid adsorbent is herein further defined as one that will hold the anesthetic primarily in a two-dimensional phase as opposed to the liquid or gaseous state and as distinguished thereby from a support such as a wick which will hold an imbibed fluid largely in the liquid phase.
The carrier case which is used to elute the loaded adsorbent may be air, or any mixture of gases which includes oxygen. Preferred carrier gases are mixtures of oxygen and nitrous oxide. The concentration of the anesthetic in the carrier gas, depending upon the course of the patient and the degree of narcosis desired, will range from 0.01 to 20% by volume.
A preferred embodiment of the method of the invention comprises the use of a solid adsorbent in combination with a recycling or rebreathing system. It was surprisingly discovered that if unused portions of anesthetics, after having by-passed the patient, were led on to the solid adsorbent, the concentration of the effluent narcotic was in no way affected by this input. Instead such a secondary input merely prolongs the lifetime of the loaded solid adsorbent.
Recycling unused anesthetic and the gas mixtures exhaled by the patient involve avoiding three major possibilities of contamination. First, one must ensure that all expired carbon dioxide must be removed to avoid build-up to a dangerous level. Second, all expired water must be removed to avoid condensation. Third, sanitation must be achieved in surgical cases to preclude transfer of contagious diseases.
The preferred embodiment of the invention therefore utilizes a recycling chamber which additionally includes an agent to remove carbon dioxide and water. A further refinement would include a disinfectant in instances where sanitation is of major concern.
Known agents for the removal of carbon dioxide and water include calcium hydroxide and calcium chloride respectively. Naturally water removal may be accomplished by any deliquescent. Carbon dioxide may also be removed by a weak base resin in the free base form. A further refinement comprises a chamber containing adsorbent in combination with the weak base resin in the free base form to remove carbon dioxide and a strong acid resin in the hydrogen form to remove water. Optionally combined or admixed therewith may be a germicide functioning as a disinfectant.
A desirable embodiment of the invention would utilize a chamber of adsorbent with or without additional resins in the form of a disposable canister.
In view of the close proximity of the adsorbents to patients, particular care should be taken that none of the adsorbents release a detrimental amount of volatile extractants. In the case of polymeric adsorbents, this is of particular importance. Unless the adsorbents are specifically treated, there remains the possibility that extractants such as styrene, divinylbenzene, benzene, toluene, xylene, ethyl benzene, dimers and higher polymers or styrene and divinylbenzene may be present in the gas delivered to the patient.
Synthetic polymeric adsorbents may be modified to become relatively free of detrimental volatile extractants by various techniques. These techniques may include:
1. high temperature treatment under vacuum; PA0 2. high temperature treatment while subjected to a flow of inert gas; PA0 3. soxhlet extraction with ethylene dichloride; PA0 4. steam stripping.
For example, the use of technique No. 3 followed by technique No. 1 produces a product having less than one part per million volatile components at 170.degree. C. Technique No. 3 will produce a polymeric adsorbent having an even smaller amount of volatile components.
Steam stripping includes passing steam through the resin in slurried or dry form at flow rates of 1 to 10,000 bed volumes per hour and at temperatures of 100.degree. - 150.degree. C. Typically, the steam stripping will take from one-half to four hours. Care should be taken not to exceed the maximum temperature which is determined by the thermal stability of each resin. Generally, at temperatures approaching the glass transition temperature of the resins, usually at temperatures greater than 150.degree. C., the polymeric resins lose their structure.
Commonly used analytical techniques for determining the presence of volatile extractants include mass spectrometry and gas chromatography.
Further experiments are included to assist the skilled worker in the art and in no way are intended to be limiting to the broad concept of the invention.
A. Various possible adsorbents are evaluated by their capacity for holding narcotics. The experiments are performed utilizing 20 cc of adsorbent and loading thereon various well-known anesthetics under normal room temperature and atmospheric pressure. By weighing the adsorbent before and after, the capacity of the various adsorbents is determined, as shown in the following Table II.
B. To determine the relationship between the amount of initial loading of anesthetic and the elution concentration, various samples of adsorbent C and Pittsburgh Carbon were loaded with different amounts of three anesthetics. The following Table III shows that each narcotic has different elution characteristics with halothane being preferred.
TABLE II __________________________________________________________________________ Adsorbent Capacities for Inhalation Anesthetics Adsorbent Composition Surface area Character Halothane Enflurane Methoxyflurane __________________________________________________________________________ A Styrene-DVB polymer 100 m.sup.2 /g non-polar 6.25 w/w% 4.45 w/w% B Styrene-DVB polymer 300 m.sup.2 /g non-polar 17 23.6 w/w% C Styrene-DVB polymer 780 m.sup.2 /g non-polar 26 19 47 D Acrylic ester polymer 450 m.sup.2 /g slightly polar 21 23 27 E Acrylic ester polymer 140 m.sup.2 /g slightly polar 20 -- -- F Amine oxide polymer 22 m.sup.2 /g very polar 4.5 3.9 -- G Sulfonic acid polymer 571 m.sup.2 /g very polar 15 17 -- H Pittsburgh G W Active carbon 1000 m.sup.2 /g non-polar 28 25 30 __________________________________________________________________________ Adsorbents A through G are all available from the Rohm and Haas Company, Philadelphia.
Table III __________________________________________________________________________ Initial Anesthetic Elution Concentrations at Various Sample Concentrations of Adsorbent C and Pittsburgh Carbon Sample Concentration in Effluent Composition (Vol/Vol %) w/w% Halothane Enflurane Methoxyflurane Halothane on P. Carbon __________________________________________________________________________ 5 0.20% 0.16% 8 0.44 0.50 10 0.54 0.60 0 12 0.69 0.76 15 1.28 1.30 0.12% 20 1.96 2.6 0.18 0.01% 25 3.20 0.22 0.05 27 0.84 0.20 32 1.20 0.44 35 1.60 38 4.1 47 2.17 __________________________________________________________________________
To determine the effect of additional input concentration on the output concentration, two adsorbent C samples were loaded with 15% weight and 10% weight concentrations of halothane and subsequently subjected to additional halothane input to simulate a recycling system. The following Table IV shows the output being unaffected by subsequent input of anesthetic.
To determine the effective life of an adsorbent the output concentration of a halothane-loaded adsorbent C was monitored. The results are shown in Table V. It should be noted that this is an accelerated test since normal flow rates are not 25 bed volumes per minute but are in the range of 1 to 20 bed volumes per minutes. Normal beds are envisioned to be in the range of 0.1 to 1 liter in volume. It is interesting to note that any flow rates that are desirable may be used.
One embodiment, although not necessarily preferred, utilizes a mere replacement of vaporizer with an adsorbent in the present system. Such an embodiment would provide a constant concentration at flow rates of 2-4 liters/min. and continue to use a pop-off valve adsorbent bed. pg,18
Table IV ______________________________________ Initial Output Concentration of Halothane from Adsorbent C with Different Additional Input Concentrations of Halothane ______________________________________ Bed volume = 20 cc Flow rate = 25 BV/min O.sub.2 Temperature = 24.5.degree. C. Composition w/w % halo- thane on Adsorbent C input (%) output (%) ______________________________________ 15 0 1.5 1.0 1.5 1.5 1.5 13 1.5 10 0 1.0 1.5 1.0 13 1.0 ______________________________________
TABLE V ______________________________________ Elution Characteristics of Halothane on Adsorbent C (23.degree. C) Bed Volume (BV) = 20 cc Anesthetic Loading = 10 w/w% Flow = 25 BV min O.sub.2 BV v/v% Halothane in Effluent ______________________________________ 0 - 300 .18 325 .17 500 .15 700 .12 875 .11 1050 .08 1300 .06 ______________________________________
The ease with which the polymeric adsorbents may be utilized to maintain a constant output of halothane anesthetic is illustrated below in Tables VI (0.5 halothane) and VII (1.0 halothane). For comparison purposes a carbon control sample is included in each table. It is important to note that while Amberlite XAD-4 will release over half of its adsorbed anesthetic at a constant concentration of 0.5% (Table VI) when the temperature is increased only 9.5 C.degree., a .DELTA.T of opproximately 40 C.degree. is needed to obtain an equivalent utilization of anesthetic from activated carbon. Of equal significance, the carbon had an initial release temperature quite high and, accordingly, a rather high temperature was needed to achieve release of a high proportion of the anesthetic (Table VI). At a constant concentration of 1.0% halothane, the .DELTA.T required for release of anesthetic from carbon, when compared to Amberlite XAD-4, was again larger than might be desired (see Table VII).
Table VI ______________________________________ Temperature V. Utilization* to Maintain Constant 0.5% Halothane Output Trimethylolpropane NUCHAR WVH Styrene/DVB Copolymer trimethacrylate 8 .times. 30 (Amberlite XAD-4) (Amberlite XAD-7) ______________________________________ Utili- Temp. zation Temp. Utilization Temp. Utilization ______________________________________ 41.degree. C 1.4% 38.degree. C 2.4% 27.degree. C 1.5% 42 2.3 39 11.9 29 13.3 44 8.2 40 14.2 30 14.7 45.5 12.7 40.5 19.0 32 20.6 46 13.6 41 26.1 33 22.1 48.5 16.4 42.5 35.6 36 26.5 49 18.2 43.5 40.3 40 32.4 50.5 21.4 46.5 47.4 44 36.8 51 22.7 47.5 52.1 47 42.7 54 24.1 53 56.0 57 27.3 57 63.3 59 30.9 62 35.9 63.5 37.3 64 37.7 66 38.6 68 40.0 69 40.9 71.5 43.6 72 44.6 74 45.5 76 48.2 79 50.9 82 53.6 84 55.0 85.5 56.8 87.5 58.2 92 61.4 94 63.6 ______________________________________ *Utilization: The amount (weight) of halothane eluted divided by the tota amount loaded on the adsorbent multriplied by 100.
Table VII ______________________________________ Temperature V. Utilization to Maintain Constant 1.0% Halothane Output ______________________________________ Styrene/DVB Copolymer NUCHAR WVH 8.times.30 (Amberlate XAD-4) Temperature Utilization Temperature Utilization ______________________________________ 42.degree. C 1.7% 50.degree. C 5.1% 43 2.5 51 30.6 44 6.7 52 40.7 45 13.4 47 16.8 48 18.4 52 21.8 53 24.3 56 27.7 57 28.5 62 34.4 ______________________________________
The uniformity of polymeric adsorbents for adsorption of two popular anesthetics is illustrated below in Table VIII.
Table VIII ______________________________________ Batch Variations on Capacity * of Amberlite XAD-4 ______________________________________ Surface Halothane Enflurane Sample Area (m.sup.2 /g) Capacity .sup.a Capacity .sup.b ______________________________________ 1 748 32.4 w/w% 25.7 w/w% 2 717 33 24.2 3 740 32 27.9 ______________________________________ .sup.* Capacity data presented is w/w% anesthetic to adsorbent at breakthrough. .sup.a 13% halothane in O.sub.2 at 25.degree. C and atmospheric pressure influent. .sup.b Influent conc. 8.8 v/v% enflurane in O.sub.2 at 25.degree. C and atmospheric pressure.
Normally, the macroreticular polymeric adsorbent is contained in a canister which contains a heating device suitable for maintaining the temperature of the polymeric adsorbent. By this means the flow of anesthetic can be controlled or maintained at the desired concentration in the carrier gas passing through the canister. Care must, of course, be exercised in maintaining the temperature of the polymeric adsorbent below that which will cause any volatilization of extractables from the polymer or decomposition. With essentially all of the polymeric adsorbents of the invention, essentially complete release of adsorbed anesthetic (80+% is achieved at moderate temperatures, i.e, between 10.degree. C and 100.degree. C, well below the temperatures at which polymers liberate extractables or decompose (100.degree. C and .gtoreq. 150.degree. C, respectively).


A method for forming a trench in a semiconductor substrate includes configuring a mask on the substrate. The mask has a window in which a substrate surface is uncovered. The substrate is electrochemically etched proceeding from the substrate surface. A porous substrate is formed in a trench-shaped region proceeding from the substrate surface. The trench is formed by removing the porous substrate from the trench-shaped region.

The present invention relates to a method for producing a trench in a semiconductor substrate.
Semiconductor substrates are used to form electronic circuits and memories. By way of example, DRAMs (Dynamic Random Access Memory) are used as memories. These are dynamic random access memories. A DRAM chip contains an array of memory cells which are configured in the form of rows and columns and are driven by word lines and bit lines. A DRAM memory cell usually contains a transistor connected to a capacitor. Two basic concepts are customary for the capacitors, one concept provides a so-called stacked capacitor and the second concept provides a so-called trench capacitor. In order to form a trench capacitor with a large capacitance, it is necessary to form the trench capacitor with a large capacitor area. Since the substrate surface used by a memory cell decreases step-wise, one possibility for increasing the capacitance of the trench capacitor consists in forming a deeper trench (deep trench), in the substrate.
To date, trenches have been etched in a substrate such as silicon by performing reactive ion etching (RIE). First, a hard mask is formed on the substrate surface in order to cover the regions of the substrate surface which are not to be etched. The patterning of the hard mask is usually effected conventionally using a resist mask and subsequent lithography. As a result of the progressive miniaturization of circuits and the associated decrease in the trench diameters, the aspect ratio (ratio of trench depth to trench diameter) of a capacitor can increase while the capacitance remains the same. What is disadvantageous in this case is that reactive ion etching can only form trenches with limited aspect ratio.
As an example, V. Lehmann and H. Voll, xe2x80x9cFormation mechanism and properties of electrochemically etched trenches in n-type siliconxe2x80x9d J. Electrochemical Society 137 (1990) 653, describe a method in which trenches are formed by electrochemically etching a substrate in electrolytes containing hydrofluoric acid. Trenches having a larger aspect ratio are made possible by this method, but this method cannot be performed economically because of its low etching rate and its high current consumption.
It is accordingly an object of the invention to provide a method for forming a trench in a semiconductor substrate which overcomes the above-mentioned disadvantageous of the prior art methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for forming a trench in a semiconductor substrate that includes the following steps: providing a substrate having a substrate surface; providing a mask having a window and configuring the mask on the substrate to define an uncovered portion of the substrate surface that is within the window; electrochemically etching the substrate, proceeding from the uncovered portion of the substrate surface that is within the window; forming a porous substrate in a trench-shaped region proceeding from the substrate surface; and completely removing the porous substrate from the trench-shaped region.
The present method for forming trenches involves electrochemically etching only 20% to 80% of the substrate that is configured in the trench. This is in contrast to the method described by Lehmann in which all of the substrate that is configured in the trench is etched. This is made possible by suitable variation of the process parameters. Since only a fraction of the substrate is electrochemically etched from the region of the trench, the throughput rate can be increased to a multiple and the current consumption can be reduced to a fraction. A porous substrate remains within the electrochemically etched trench region. Once the desired trench depth is reached, the electrochemical etching process can be ended. Afterward, the porous network of the substrate in the trench region can be removed very rapidly and without further lithographic exposure steps. The trench is advantageously formed with a shape corresponding to the porous trench-shaped substrate region previously formed.
The process sequence specified describes a novel fabrication process for trenches in microelectronics.
In accordance with an added feature of the invention, the porous substrate has a density of between 20% and 80% of the original substrate. The lower the amount of the substrate that is electrochemically etched by the etching, correspondingly, the lower is the amount of the current that is consumed. Consequently, the etching process is ended more quickly, which means economic advantages.
In accordance with an additional feature of the invention, the porous substrate in the trench is etched using an alkaline etchant. The advantage of the alkaline etchant is that it is suitable for removing a porous substrate from a trench.
In accordance with a further feature of the invention, KOH is used as the etchant. KOH is advantageously suitable for etching silicon.
In accordance with a further added feature of the invention, the porous substrate is oxidized and porous substrate oxide is formed. The porous substrate is advantageously oxidized into porous substrate oxide thereby enabling the use of further etchants that are suitable for removing substrate oxide.
In accordance with a further additional feature of the invention, the etchant contains hydrofluoric acid.
In accordance with a concomitant feature of the invention, the substrate contains silicon.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for forming a trench in a semiconductor substrate, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Method for forming a trench in a semiconductor substrate


A liquid dish cleaning composition with desirable cleansing properties comprising at least one anionic surfactant, a magnesium containing inorganic salt, an improved preservative system, polyethylene glycol and water.

This invention relates to a liquid dish cleaning composition which is designed to have good foaming grease cutting, rinsing and mildness properties and an improved preservative system.
The present invention relates to novel light duty liquid detergent compositions with high foaming and good grease cutting properties and an improved preservative system.
The prior art is replete with light duty liquid detergent compositions containing nonionic surfactants in combination with anionic and/or betaine surfactants wherein the nonionic detergent is not the major active surfactant. In U.S. Pat. No. 3,658,985 an anionic based shampoo contains a minor amount of a fatty acid alkanolamide. U.S. Pat. No. 3,769,398 discloses a betaine-based shampoo containing minor amounts of nonionic surfactants. This patent states that the low foaming properties of nonionic detergents renders its use in shampoo compositions non-preferred. U.S. Pat. No. 4,329,335 also discloses a shampoo containing a betaine surfactant as the major ingredient and minor amounts of a nonionic surfactant and of a fatty acid mono- or di-ethanolamide. U.S. Pat. No. 4,259,204 discloses a shampoo comprising 0.8 to 20% by weight of an anionic phosphoric acid ester and one additional surfactant which may be either anionic, amphoteric, or nonionic. U.S. Pat. No. 4,329,334 discloses an anionic-amphoteric based shampoo containing a major amount of anionic surfactant and lesser amounts of a betaine and nonionic surfactants.
U.S. Pat. No. 3,935,129 discloses a liquid cleaning composition containing an alkali metal silicate, urea, glycerin, triethanolamine, an anionic detergent and a nonionic detergent. The silicate content determines the amount of anionic and/or nonionic detergent in the liquid cleaning composition. However, the foaming properties of these detergent compositions are not discussed therein.
U.S. Pat. No. 4,129,515 discloses a heavy duty liquid detergent for laundering fabrics comprising a mixture of substantially equal amounts of anionic and nonionic surfactants, alkanolamines and magnesium salts, and, optionally, zwitterionic surfactants as suds modifiers.
U.S. Pat. No. 4,224,195 discloses an aqueous detergent composition for laundering socks or stockings comprising a specific group of nonionic detergents, namely, an ethylene oxide of a secondary alcohol, a specific group of anionic detergents, namely, a sulfuric ester salt of an ethylene oxide adduct of a secondary alcohol, and an amphoteric surfactant which may be a betaine, wherein either the anionic or nonionic surfactant may be the major ingredient.
The prior art also discloses detergent compositions containing all nonionic surfactants as shown in U.S. Pat. Nos. 4,154,706 and 4,329,336 wherein the shampoo compositions contain a plurality of particular nonionic surfactants in order to affect desirable foaming and detersive properties despite the fact that nonionic surfactants are usually deficient in such properties.
U.S. Pat. No. 4,013,787 discloses a piperazine based polymer in conditioning and shampoo compositions which may contain all nonionic surfactant or all anionic surfactant.
U.S. Pat. No. 4,450,091 discloses high viscosity shampoo compositions containing a blend of an amphoteric betaine surfactant, a polyoxybutylenepolyoxyethylene nonionic detergent, an anionic surfactant, a fatty acid alkanolamide and a polyoxyalkylene glycol fatty ester. But, none of the exemplified compositions contain an active ingredient mixture wherein the nonionic detergent is present in major proportion which is probably due to the low foaming properties of the polyoxybutylene polyoxyethylene nonionic detergent.
U.S. Pat. No. 4,595,526 describes a composition comprising a nonionic surfactant, a betaine surfactant, an anionic surfactant and a C12-C14 fatty acid monoethanolamide foam stabilizer.
U.S. Pat. No. 6,147,039 teaches an antibacterial hand cleaning composition having a low surfactant content.
It has now been found that a liquid dish cleaning composition can be formulated with a magnesium containing inorganic salt, optionally, a sulfate anionic surfactant, at least one sulfonate anionic surfactant, polyethylene glycol, an improved preservative system consisting of a preservative and a preservative potentiator and water, wherein the composition has desirable cleaning and foaming properties and an excellent resistance to bacteria.
An object of this invention is to provide a liquid dish cleaning composition which comprises at least one anionic surfactant, a magnesium containing inorganic salt, polyethylene glycol and a preservative system consisting of a preservative and a preservative potentiator, wherein the composition does not contain any silicas,abrasives, acyl isoethionate, 2-hydroxy-4,2xe2x80x2,4xe2x80x2-trichloridiphenyl ether, monosuccinic acids and phosphoric acid and any salts thereof, ethylenediamine tetraacetic acid or any salt thereof, enzymes, zeolite, alkali metal silicates, phosphoric acid, boric acid, alkali metal carbonates, alkaline earth metal carbonates, alkyl glycine surfactant, cyclic imidinium surfactant, or more than 3 wt. % of a fatty acid or salt thereof.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
This invention relates to a liquid dish cleaning composition which comprises approximately by weight:
(a) 5% to 15% of at least one anionic surfactant selected from the group consisting of linear alkyl benzene sulfonates and paraffin sulfonates and mixtures thereof;
(b) 0 to 5%, more preferably 0.5% to 4% of a magnesium containing inorganic compound;
(c) 0 to 15%, more preferably 2% to 13% of a sodium salt of an ethoxylated alkyl ether sulfate;
(d) 0 to 5%, more preferably 0.1% to 4% of a polyethylene glycol;
(e) 0.0005% to 1%, more preferably 0.001% to 0.3% of a preservative selected from the group consisting of dimethylol dimethyl hydantoin, an isothiazolone mixture and 2-bromo-2-nitropropane-1,3-diol (Myacid BT) and mixtures thereof;
(f) 0.01% to 1.5%, more preferably 0.05% to 1% of a preservative potentiator which is preferably tetra sodium imino disuccinate or an optically pure isomer of trisodium S,S ethylenediamine N,Nxe2x80x2-disuccinate; and
(g) the balance being water.
This invention also relates to a liquid dish cleaning composition which comprises approximately by weight:
(a) 15% to 35% of at least one anionic sulfonated surfactant selected from the group consisting and linear alkyl benzene sulfonates and paraffin sulfonates and mixtures thereof;
(b) 0 to 5%, more preferably 0.5% to 4% of a magnesium containing inorganic compound;
(c) 0 to 12%, more preferably 0.1% to 10% of at least one ethoxylated nonionic surfactant;
(d) 0 to 5%, more preferably 0.1% to 4% of a polyethylene glycol;
(e) 0.0005% to 1%, more preferably 0.001% to 0.3% of a preservative which is selected from the group consisting of dimethylol dimethyl hydantoin, an isothiazoline mixture and 2-bromo-2-nitropropane-1,3-diol and mixtures thereof;
(f) 0.01% to 1.5%, more preferably 0.05% to 1.0% of a preservative potentiator which is preferably tetra sodium iminodisuccinate or an optically pure isomer of trisodium S,S ethylenediamine N,Nxe2x80x2-disuccinate;
(g) 0 to 15%, more preferably 2% to 13% of a sodium salt of an ethoxylated alkyl ether sulfate; and
(h) the balance being water.
The compositions of this invention have a pH of 4 to 8 and have a viscosity of 100 to 1,000 cps, more preferably 200 to 600 cps at 25xc2x0 C. as measured on a Brookfield RVTDV-II viscometer, wherein the compositions do not contain any grease release agents such as choline, chloride or a buffering system which is a nitrogenous buffer which is ammonium or alkaline earth carbonate, amine oxide surfactants, ethylene diamine tetraacetic acids or any salt thereof, guanidine derivates, alkoxylalkyl amines and alkyleneamines C3-C7 which do not contain a hydroxy group, boric acid, phosphoric acid, amino alkylene phosphonic acid and alkyl polyglucoside surfactants and the compositions are pourable and are not a gel.
The anionic sulfonate surfactants which may be used in the compositions of this invention are selected from the consisting of water soluble and include the sodium, potassium, ammonium, magnesium and ethanolammonium salts of linear C8-C16 alkyl benzene sulfonates and C10-C20 paraffin sulfonates.
The paraffin sulfonates may be monosulfonates or di-sulfonates and usually are mixtures thereof, obtained by sulfonating paraffins of 10 to 20 carbon atoms. Preferred paraffin sulfonates are those of C12-18 carbon atoms chains, and more preferably they are of C14-17 chains. Paraffin sulfonates that have the sulfonate group(s) distributed along the paraffin chain are described in U.S. Pat. Nos. 2,503,280; 2,507,088; 3,260,744; and 3,372,188; and also in German Pat. 735,096. Such compounds may be made to specifications and desirably the content of paraffin sulfonates outside theC14-17 range will be minor and will be minimized, as will be any contents of di- or poly-sulfonates.
Examples of suitable other sulfonated anionic detergents are the well known higher alkyl mononuclear aromatic sulfonates, such as the higher alkylbenzene sulfonates containing 9 to 18 or preferably 9 to 16 carbon atoms in the higher alkyl group in a straight or branched chain, or C8-15 alkyl toluene sulfonates. A preferred alkylbenzene sulfonate is a linear alkylbenzene sulfonate having a higher content of 3-phenyl (or higher) isomers and a correspondingly lower content (well below 50%) of 2-phenyl (or lower) isomers, such as those sulfonates wherein the benzene ring is attached mostly at the 3 or higher (for example 4, 5, 6 or 7) position of the alkyl group and the content of the isomers in which the benzene ring is attached in the 2 or 1 position is correspondingly low. Preferred materials are set forth in U.S. Pat. No. 3,320,174, especially those in which the alkyls are of 10 to 13 carbon atoms.
The C8-18 ethoxylated alkyl ether sulfate surfactants have the structure
Rxe2x80x94(OCHCH2)nOSO3M+
wherein n is about 1 to about 22 more preferably 1 to 3 and R is an alkyl group having about 8 to about 18 carbon atoms, more preferably 12 to 15 and natural cuts, for example, C12-14 or C12-16 and M is an ammonium cation or a metal cation, most preferably sodium. The ethoxylated alkyl ether sulfate is present in the composition at a concentration of about 2 to about 15 wt. %, more preferably about 3 to 12 wt. %.
The ethoxylated alkyl ether sulfate may be made by sulfating the condensation product of ethylene oxide and C8-10 alkanol, and neutralizing the resultant product. The ethoxylated alkyl ether sulfates differ from one another in the number of carbon atoms in the alcohols and in the number of moles of ethylene oxide reacted with one mole of such alcohol. Preferred ethoxylated alkyl ether polyethenoxy sulfates contain 12 to 15 carbon atoms in the alcohols and in the alkyl groups thereof.
Ethoxylated C8-18 alkylphenyl ether sulfates containing from 1 to 6 moles of ethylene oxide in the molecule are also suitable for use in the invention compositions. These detergents can be prepared by reacting an alkyl phenol with 1 to 6 moles of ethylene oxide and sulfating and neutralizing the resultant ethoxylated alkylphenol. The concentration of the ethoxylated alkyl ether sulfate surfactant is about 2 to about 15 wt. %.
The water soluble nonionic surfactants utilized in this invention are commercially well known and include the primary aliphatic alcohol ethoxylates, secondary aliphatic alcohol ethoxylates, alkylphenol ethoxylates and ethylene-oxide-propylene oxide condensates on primary alkanols, such a Plurafacs (BASF) and condensates of ethylene oxide with sorbitan fatty acid esters such as the Tweens (ICI). The nonionic synthetic organic detergents generally are the condensation products of an organic aliphatic or alkyl aromatic hydrophobic compound and hydrophilic ethylene oxide groups. Practically any hydrophobic compound having a carboxy, hydroxy, amido, or amino group with a free hydrogen attached to the nitrogen or the oxygen can be condensed with ethylene oxide or with the polyhydration product thereof, polyethylene glycol, to form a water-soluble nonionic detergent. Further, the length of the polyethenoxy chain can be adjusted to achieve the desired balance between the hydrophobic and hydrophilic elements.
The nonionic detergent class includes the condensation products of a higher alcohol (e.g., an alkanol containing 8 to 18 carbon atoms in a straight or branched chain configuration) condensed with 5 to 30 moles of ethylene oxide, for example, lauryl or myristyl alcohol condensed with 16 moles of ethylene oxide (EO), tridecanol condensed with 6 to moles of EO, myristyl alcohol condensed with about 10 moles of EO per mole of myristyl alcohol, the condensation product of EO with a cut of coconut fatty alcohol containing a mixture of fatty alcohols with alkyl chains varying from 10 to 14 carbon atoms in length and wherein the condensate contains either 6 moles of EO per mole of total alcohol or 9 moles of EO per mole of alcohol and tallow alcohol ethoxylates containing 6 EO to 11 EO per mole of alcohol.
A preferred group of the foregoing nonionic surfactants are the Neodol ethoxylates (Shell Co.), which are higher aliphatic, primary alcohols containing about 9-15 carbon atoms, such as C9-C11 alkanol condensed with 8 moles of ethylene oxide (Neodol 91-8), C12-13 alkanol condensed with 6.5 moles ethylene oxide (Neodol 23-6.5), C12-15 alkanol condensed with 12 moles ethylene oxide (Neodol 25-12), C14-15 alkanol condensed with 13 moles ethylene oxide (Neodol 45-13), and the like. Such ethoxamers have an HLB (hydrophobic lipophilic balance) value of 8-15 and give good emulsification, whereas ethoxamers with HLB values below 8 contain less than 5 ethyleneoxy groups and tend to be poor emulsifiers and poor detergents.
Additional satisfactory water soluble alcohol ethylene oxide condensates are the condensation products of a secondary aliphatic alcohol containing 8 to 18 carbon atoms in a straight or branched chain configuration condensed with 5 to 30 moles of ethylene oxide. Examples of commercially available nonionic detergents of the foregoing type are C11-C15 secondary alkanol condensed with either 9 EO (Tergitol 15-S-9) or 12 EO (Tergitol 15-S-12) marketed by Union Carbide.
Other suitable nonionic surfactants include the polyethylene oxide condensates of one mole of alkyl phenol containing from 8 to 18 carbon atoms in a straight- or branched chain alkyl group with 5 to 30 moles of ethylene oxide. Specific examples of alkyl phenol ethoxylates include nonyl condensed with 9.5 moles of EO per mole of nonyl phenol, dinonyl phenol condensed with 12 moles of EO per mole of phenol, dinonyl phenol condensed with 15 moles of EO per mole of phenol and di-isoctylphenol condensed with 15 moles of EO per mole of phenol. Commercially available nonionic surfactants of this type include Igepal CO-630 (nonyl phenol ethoxylate) marketed by GAF Corporation.
Also among the satisfactory nonionic surfactants are the water-soluble condensation products of a C8-C20 alkanol with a heteric mixture of ethylene oxide and propylene oxide wherein the weight ratio of ethylene oxide to propylene oxide is from 2.5:1 to 4:1, preferably 2.8:1-3.3:1, with the total of the ethylene oxide and propylene oxide (including the terminal ethanol or propanol group) being from 60-85%, preferably 70-80%, by weight. Such detergents are commercially available from BASF-Wyandotte and a particularly preferred detergent is a C10-C16 alkanol condensate with ethylene oxide and propylene oxide, the weight ratio of ethylene oxide to propylene oxide being 3:1 and the total alkoxy content being 75% by weight.
Other suitable water-soluble nonionic surfactants which are less preferred are marketed under the trade name xe2x80x9cPluronicsxe2x80x9d. The compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylene glycol. The molecular weight of the hydrophobic portion of the molecule is of the order of 950 to 4000 and preferably 200 to 2,500. The addition of polyoxyethylene radicals to the hydrophobic portion tends to increase the solubility of the molecule as a whole so as to make the surfactant water-soluble. The molecular weight of the block polymers varies from 1,000 to 15,000 and the polyethylene oxide content may comprise 20% to 80% by weight. Preferably, these surfactants will be in liquid form and satisfactory surfactants are available as grades L62 and L64.
The magnesium inorganic compound is a magnesium oxide, sulfate or chloride. The magnesium salt or oxide provides several benefits including improved cleaning performance in dilute usage, particularly in soft water areas. Magnesium sulfate, either anhydrous or hydrated (e.g., heptahydrate), is especially preferred as the magnesium salt. Good results also have been obtained with magnesium oxide, magnesium chloride, magnesium acetate, magnesium propionate and magnesium hydroxide. These magnesium salts can be used with formulations at neutral or acidic pH since magnesium hydroxide will not precipitate at these pH levels.
Polyethylene glycol which is used in the instant composition has a molecular weight of 200 to 1,000, wherein the polyethylene glycol has the structure
HO(CH2CH2O)nH
wherein n is 4 to 52. The concentration of the polyethylene glycol in the instant composition is 0 to 5 wt. %, more preferably 0.1 wt. % to 4 wt. %.
The preservative system used in the instant compositions is a mixture of a preservative and a preservative potentiator. The preservatives used in the instant composition are preferably selected from the group consisting of:
(i) 1,3-dimethylol-5,5-dimethylhydantoin having the structure of:
(ii) 2-bromo-2-nitropropane-1,3-diol having the structure:
(iii) a synergistic mixture of three different isothiazolones having the structure:
In the relative proportions of 2 to 2.5% for the 5-chloro-2-methyl-4-isothiazolin-3-one (R=CH3, X=Cl), 0.7 to 0.8% for the 2-methyl-4-isothiazolin-3-one (R=CH3, X=H) and 0.5 to 0.7% for the 2-n octyl-4-isothiazolin-3-one (R=n-C8H17, X=H).
The instant light duty liquid compositions can contain about 0 wt. % to about 10 wt. %, more preferably about 1 wt. % to about 8 wt. %, of at least one solubilizing agent selected from the group consisting of a C2-5 mono, dihydroxy or polyhydroxy alkanols such as ethanol, isopropanol, glycerol ethylene glycol, diethylene glycol, propylene glycol, and hexylene glycol and mixtures thereof and alkali metal cumene or xylene sulfonates such as sodium cumene sulfonate and sodium xylene sulfonate. The solubilizing agents are included in order to control low temperature cloud clear properties.
The instant formulas explicitly exclude alkali metal silicates and alkali metal builders such as alkali metal polyphosphates, alkali metal carbonates and alkali metal phosphonates because this material, if used in the instant composition, would cause the composition to have a high pH as well as leaving residue on the surface being cleaned.
The final essential ingredient in the inventive compositions having improved interfacial tension properties is water. The proportion of water in the compositions generally is in the range of 10% to 95%.
The liquid cleaning composition of this invention may, if desired, also contain other components either to provide additional effect or to make the product more attractive to the consumer. The following are mentioned by way of example: Colors or dyes or perfumes in amounts up to 1.0% by weight 2,6-di-tert.butyl-p-cresol, etc., in amounts up to 2% by weight for color improvement under stressed sun conditions and pH adjusting agents, such as citric acid or sodium hydroxide, as needed. Furthermore, if opaque compositions are desired, up to 4% by weight of an opacifier may be added.
In final form, the instant compositions exhibit stability at reduced and increased temperatures. More specifically, such compositions remain clear and stable in the range of 0xc2x0 C. to 50xc2x0 C., especially 5xc2x0 C. to 43xc2x0 C. Such compositions exhibit a pH of 4 to 8. The liquid compositions are readily pourable and exhibit a viscosity in the range of 100 to 1000 milliPascalxc2x7second (mPas.) as measured at 25xc2x0 C. with a Brookfield RVTDV-II Viscometer. Preferably, the viscosity is maintained in the range of 200 to 600 mPas.

Liquid dish cleaning compositions having improved preservative system


A pharmaceutical composition comprising lactitol and one or more amphetamine salts in a rapid release formulation.

This invention relates to oral dosage forms with physicochemical stability and rapid drug release and the process to prepare them.
Factors controlling the processing of drug formulations include 1) processability, i.e., adequate flow properties and satisfactory compression characteristics; 2) product attributes, i.e., appearance, tablet hardness, friability, color uniformity, content uniformity, and dissolution; and 3) stability, i.e., performance of the formulation over time. In order to realize an adequate stability profile for a particular dosage, the product must first overcome the first two hurdles.
Rapid immediate release pharmaceutical compositions typically contain carriers comprised of reducing-sugar based excipients, for example, lactose, dextrose, maltose, and fructose. The discoloration of dosage forms often occurs when these excipients are used with a drug having an amino functional group (Castello R A and Mattocks A M, J Pharm Sci 51(2): 106-108 (1962)). The Maillard reaction (xe2x80x9cbrowningxe2x80x9d reaction) is the reaction of amino groups of amino acids, peptides, proteins or other chemicals with the glycosidic hydroxyl group of sugars which results in the formation of brown pigments. This leads to degradation and discoloration of formulations and leads to failure to meet the stability requirement of the dosage form.
As alternatives to the reducing sugar based excipients, less water soluble excipients, such as dicalcium phosphate and microcrystalline cellulose, have been used to avoid the Maillard reaction. However, for certain dosage forms, such as tablets, these excipients are not able to provide the desired processing properties (such as compressibility) and product attributes (such as rapid release).
In particular, it would be desirable to possess a pharmaceutical composition which avoids the occurrence of the Maillard reaction for compositions containing active agents with amino functional groups which composition will have chemical and physical stability. It further would be desirable to maintain the rapid release properties of a pharmaceutical formulation in a compressed tablet formulation.
It is an object of the present invention to provide a rapid release pharmaceutical composition having chemical and physical stability in a tablet formulation.
The present invention relates to a pharmaceutical composition comprising (1) at least one amphetamine as a pharmaceutically active agent, and (2) lactitol. The applicants have found that the use of lactitol, a polyol, in formulations containing active agents having functional amine moieties provides a pharmaceutical formulation with the processability, product attribute and stability characteristics required for the administration of the dosage form. The use of polyols with amine containing active compounds will not trigger the Maillard reaction. The polyol is present in the formulation in an amount effective to provide the desired solubility and hydration properties required for an immediate release formulation.
In a preferred embodiment, the formulation is a compressed tablet. It has been discovered that the use of lactitol in the pharmaceutical composition of the present invention advantageously facilitates the compression of the composition into a tablet. The direct compression method is a preferred method because it is less costly, less time-consuming, and has improved stability. However, wet granulation is also suitable.
Lactitol (4-O-(-D-Galactopyranosyl-D-glucitol monohydrate) is a non-hygroscopic, disaccharide sugar alcohol derived from lactose which heretofore has been used in food products, for example, as a sweetener. Lactitol provides chemical and physical stability to dosage forms with amine containing actives.
Incorporation of lactitol into the pharmaceutical composition advantageously facilitates the compression of the composition into a tablet and facilitates fast dissolution of the tablet matrix, due to its high water solubility.
In a preferred embodiment, lactitol is used as a carrier for a tablet formulation wherein the active comprises a mixture of amphetamine salts, i.e., d-amphetamine sulfate, d,l-amphetamine aspartate, d-amphetamine saccharate, d,1-amphetamine sulfate. In a particularly preferred embodiment, the mixture of amphetamine salts is present in a 1:1:1:1 ratio.
Accordingly, an embodiment of the present invention provides a rapid release pharmaceutical composition comprising a mixture of amphetamine salts and lactitol in tablet form. In a preferred embodiment lactitol is used in combination with at least one or more other direct compression excipients. In a particularly preferred embodiment lactitol is used in combination with microcrystalline cellulose.
Pharmaceutical actives which may be employed in the practice of the invention are those containing an amine functional group, which for example include, but are not limited to, amphetamines, phenylpropanolamine and its salts, carbidopa and levodopa.
In one embodiment of the invention the pharmaceutical actives are amphetamines including amphetamine base, all chemical and chiral derivatives and salts thereof. In a preferred embodiment of this invention a mixture of amphetamine salts is employed, i.e., d-amphetamine sulfate, d,l-amphetamine aspartate, d-amphetamine saccharate, d,1-amphetamine sulfate. In a particularly preferred embodiment, the mixture of amphetamine salts is present in a 1:1:1:1 ratio.
The pharmaceutical composition of the invention may further comprise bulking agents, disintegrating agents, antiadherants, glidants, lubricants, colorants and binding agents.
The bulking agents employed herein can be microcrystalline cellulose, for example, AVICEL(copyright) (FMC Corp.) or EMCOCEL(copyright) (Mendell Inc.); dicalcium phosphate, for example, EMCOMPRESS(copyright) (Mendell Inc.); calcium sulfate, for example, COMPACTROL(copyright) (Mendell Inc.); and starches, for example, STARCH 1500.
As disintegrating agents there may be employed herein microcrystalline cellulose, starches, crospovidone, for example, POLYPLASDONE XL(copyright) (International Specialty Products); sodium starch glycolate, for example, EXPLOTAB(copyright) (Mendell Inc.); and croscarmellose sodium, for example, AC-DI-SOL(copyright) (FMC Corp.).
Antiadherants and glidants employed herein can include talc, corn starch, silicon dioxide, sodium lauryl sulfate, and metallic stearates.
Lubricants employed herein can be magnesium stearate, calcium stearate, sodium stearate, stearic acid, sodium stearyl fumarate, sterotex, talc, colloidal silica dioxide, waxes and the like.
Binding agents employed herein can include but are not limited to polyvinyl pyrollidone, starch, methyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose, and the like.
The present invention is preferably in tablet form. The pharmaceutical composition of the present invention can also be produced as tablets in the form of hard gelatin capsules or packaged into sachets. Tablets prepared using lactitol may be used as chewable tablets, due to lactitol""s clean taste, sweetness, and non-cariogenic property.
The present invention is preferably formulated into a tablet prepared using methods known in the art including a wet granulation method and a direct compression method. In a preferred embodiment the tablets are prepared using the direct compression method.
The direct compression method offers a number of potential advantages over a wet granulation method, particularly with respect to the relative ease of manufacture. Factors limiting the use of a direct compression method are 1) processability, i.e., adequate flow properties and satisfactory compression characteristics; and 2) product attributes, i.e., appearance, tablet hardness, friability, color uniformity, content uniformity, and dissolution. In order to realize an adequate stability profile via a direct compression method, the product must first overcome these two hurdles.
In dissolution testing, 100% dissolution of amphetamine salts from tablets containing lactitol can be easily achieved in less than 15 minutes. This is advantageous over previously known methods of preparing formulations of compressed tablets which utilize water-insoluble excipients alone as a tablet matrix material. These tablet do not dissolve rapidly in water because the low porosity of the compressed tablets hinders water penetration into the matrix.
Accordingly, in one aspect of the invention, lactitol is used in combination with one or more other direct compression excipients. In a preferred embodiment lactitol is used in combination with microcrystalline cellulose, for example, AVICEL(copyright) (FMC Corp.). In a preferred embodiment lactitol and microcrystalline cellulose are present in an amount of from about 2 to about 5 (lactitol) and from about 0.25 to about 1.75 for microcrystalline cellulose. The most preferred range is Lactitol from 3 to 4, and microcrystalline cellulose from 0.5 to 1.5. These numbers represent the amount in the pharmaceutical product composition of weight ratios or percent.
It has been found that other binary or ternary mixtures of direct compression excipients including starches, various grades of microcrystalline cellulose and polyols other than lactitol, such as mannitol and sorbitol, did not provide the required formulation processing characteristics for amphetamine tablets. For example, in general, soft tablets (tablet hardness less than target 4 kp) were produced even at high compression forces. For example, the mixture of Starch 1500: Mannitol 2080LF exhibited poor flow properties and sticking problems, which hinder the compression process. The mixture of Starch 1500: Lactitol also showed irregular flow properties. The ternary mixture of Starch 1500: Lactitol: Avicel PH 302 showed comparable successful performance characteristics to those of the Avicel/lactitol formulation.
Other problems such as tablet capping, color non-uniformity, and punch sticking, were observed. Surprisingly, after trying numerous mixtures of direct compression excipients, the formula containing the mixture of Avicel: Lactitol was identified as a meeting the required processability and product performance characteristics for amphetamine tablets.

Rapid immediate release oral dosage form


An arrangement in screening apparatuses of the pulp and paper industry, including a conduit for removing reject formed in a screening process. The circulation of material is arranged between the reject removal conduit and the interior of the screening apparatus from the removal conduit into the interior of the screening apparatus via a conduit external to the screening apparatus. When such a by-pass flow is arranged for pulp via external circulation, heavy particles in the layer being diluted are allowed to be separated onto the bottom of the reject removal conduit and therethrough e.g. into a separate junk trap.

The present invention relates to an arrangement in connection with reject removal from screening apparatuses of the pulp and paper industry. A screening apparatus comprises at least an outer housing, conduits therein for pulp to be fed in, for accept and for reject. The invention is especially applicable for screening apparatuses, in which heavy reject fraction is removed from the fibrous pulp being treated, such as recycled pulp. This kind of reject removal conduit is often provided with a junk trap.
A reject removal technique has been developed from the screening apparatus and thus enhance the operation thereof in pulp cleaning. A problem in reject removal may on one hand be the passing of high quality fibrous material into the reject and on the other hand the disturbance caused by reject particles for the passing of the accept through the screening surface.
The concept of external circulation, in the present context, refers to a flow external in view of the main apparatus, the screening apparatus, in this case a flow passing outside the body of the screening apparatus, but without essentially changing the total pulp flow into and out of the screening apparatus and without having any direct contact with another process or process stage. The main apparatus is thus the actual screening apparatus, wherefrom a conduit leads to the external circulation and back therefrom. A device refers to this actual external circulation and possible mixing liquid pipes in connection therewith, such as a water pipe, and the flow taking place in the circulation.
The pulp flow through the device is increased such that the collection capability thereof for collecting reject particles, such as so-called junk, is intensified. If no flow-through via an external circulation is provided, non-pulp particles are in practice not allowed to pass through the static pulp layer into a junk trap or corresponding. When a by-pass flow is provided for the pulp via an external circulation so that the pulp is simultaneously preferably diluted, heavy particles in the layer being diluted are allowed to be separated onto the bottom of the reject removal conduit and therethrough into a separate junk trap, in case it is separately provided in the conduit. The arrangement has no effect on the operation of the junk trap known per se, but the operation of the junk trap is similar to that of known screening apparatuses with dilutions. Only the emptying interval of the junk trap may need to be changed to correspond to the amount of accumulating junk.
A typical screening apparatus comprises a vertical cylindrical screen rotating inside a housing. The outer surface of the screen and the inner surface of the housing of the screening apparatus define a pulp feed chamber, wherefrom the pulp flows into an accept chamber located inside the screen drum. The screening apparatus also comprises conduits connected to the housing for pulp, accept and reject flows. The inner surface of the housing may typically be provided with at least one so-called outer foil. For effecting the external material circulation, the outlet flow from the external circulation conduit is led in the feed chamber, preferably via the outer foil, to a zone with a low static pressure and the inlet flow into the external circulation is led to a zone having a static pressure slightly higher than in the other surroundings. The increase of the static pressure is due to the decelerating of the flow prior to the outer foil and, correspondingly, the decrease of the static pressure is due to the accelerating of the flow between the outer foil and the screen drum. The pressure difference provides for the required and essential flow in the external circulation. The outer foil may also be replaced by some other corresponding arrangement allowing to decrease the static pressure at that point of the screening apparatus.
Because the amount of water used for mixing is to be kept as small as possible, and on the other hand, the disturbance caused by the external circulation device to the main apparatus should be as insignificant as possible, the entering water must have a high velocity in order to provide good mixing.
The inlet of the external circulation is positioned in respect of the bottom of the body in such a way that it is only partly open, i.e. the inlet is lower than the bottom level. Thus, a step is formed, which prevents separated junk from getting back to the inside of the main apparatus. The rinsing water entering the junk trap further dilutes the entering pulp and thus washes off the remaining fibers from the junk. By means of valves the junk trap is purged into reject intermittently, and the junk trap in principle contains only low-fiber water and the junk to be removed.
FIG. 1 illustrates part of the outer housing 1 of a screening apparatus, to which outer housing a reject removal conduit 2 with a junk trap 3 and the associated valves (details not illustrated) is connected. A device for the external circulation comprises an initial part 4 of the reject removal conduit and a pipe elbow 5 associated therewith. The inlet of the device for the external circulation is marked with 4a and the outlet with 5a. The inlet 4, 4a is sloping downwards from the horizontal direction. The lower edge 4b of the inlet is positioned in a distance below the bottom level 8 of the body 1 of the screening apparatus, whereby a step (9, FIG. 3) is formed therein, which step contributes to preventing heavy undesired particles from flowing back into the screening apparatus.
Mixing liquid, such as water, is introduced into the circulation via conduit 6. The junk trap receives dilution liquid in a way known per se via conduit 7.
FIG. 2 illustrates the arrangement of FIG. 1 seen from the above. A typical screening apparatus may comprise a vertical rotating cylindrical screen 11. A pulp feed chamber 12 is defined by the outer surface of the screen drum and the inner surface of the housing of the screening apparatus, from which feed chamber the pulp flows into an accept chamber 13 located inside the screen drum. A so-called outer foil 10 is typically located on the inner surface of the housing. For providing the external material circulation, the outflow from the external circulation conduit 5a is led through the outer foil 10 in between the screen drum and the outer foil.
The model has been subjected to a flow-technical study. The rotation of the screen drum and the influence of the outer foil on the passing of the flows both in the apparatus and in the screen have been taken into account in the model. The consistency of the pulp in the model is 3%, i.e. mainly the viscosity and the density have been changed to correspond to a 3% pulp viscosity and density.
FIG. 3 illustrates a cut-away view of the inlet pipe 4a, 4 in the elevation direction. It may be noted in the vector diagrams that the mixing water 6 causes a longitudinal vortex in the inlet pipe so that at the start of the outlet pipe 5 the jet stream passes on the bottom of the inlet pipe 4, i.e. as far as possible in view of the passing of the junk under the suction effect of the outlet pipe 5. On the other hand, because of the hindrance caused by the suction and the mixing water jet from the inlet pipe, a vortex is formed in the initial part of the outlet pipe 5 directed in its axial direction, which contributes to the passing of heavy particles into the junk trap.
FIG. 4 illustrates a principal scheme of a screening apparatus, wherein a device 4,5 for external circulation has been adapted. The same reference numerals have been used in FIG. 4 as in FIGS. 1-3. The pulp being treated is fed via conduit 14 into feed chamber 12, wherefrom pulp particles flow through openings in the screen drum into accept chamber 13. The accept is removed from the screening apparatus via conduit 15. Reject is removed at the top of the housing via conduit 16. Heavy reject is removed via a conduit having a junk trap 3. The external circulation 4, 5 according to the invention is arranged in connection with heavy reject removal.
Thus, external circulation is utilized, whereby the pulp flow volume going through the device increases and thus improves the junk-separation capability of the device. The location and design of the piping are realized in such a way that the reject particles do not pass together with the flow back into the circulation but remain in the area of calm flow and sink onto the bottom of the device.
The invention is not limited to the illustrated and described embodiments, but many modifications associated thereto are conceivable in the scope defined by the claims. The use and application of the invention is not limited to the screening apparatus construction illustrated in the figures.

Arrangement in connection with screening apparatuses


A counterflow cooling tower (10) is provided having specially designed inlets (14, 16) which minimize turbulence and air flow disruption at the inlet region of the tower (10), thereby increasing cooling efficiency. The tower (10) preferably includes a casing (12) presenting sidewalls (28, 30) each having a lower edge (14a, 16a) which defines the upper margins of the inlets (14, 16). The tower fill structure (20) presents, adjacent each inlet (14, 16) a relieved air entrance face (44, 46) which extends at an angle both downwardly and inwardly from the adjacent casing wall edge (14a, 16a); in addition, the fill structure (20) includes a generally horizontal bottom surface (48) inboard of and below the edges (14a, 16a). A substantially unrestricted, fill-free air flow zone (51) extends between the inlets (14, 16) and between the fill bottom surface (48) and the tower cold water collection basin (22). Comparative tests demonstrate that the inlet arrangement of the invention lowers turbulence and air flow disruption inboard of the inlets (14, 16).

1. Field of the Invention
The present invention is broadly concerned with an improved counterflow water cooling tower construction characterized by an eased inlet structure serving to minimize undesirable air turbulence at the air inlets of the tower, thereby increasing the overall cooling efficiency thereof. More particularly, it is concerned with such a counterflow tower wherein the fill structure (preferably cross-corrugated film-type) presents a lower side marginal air entrance surface which extends below and inwardly at an oblique angle from the edge of the upper inlet-defining wall surface of the tower casing, with the bottom of the fill structure being generally horizontal. In this way, the velocity of entering air is maximized, and even air flow is facilitated within the substantially unrestricted air flow zone between the underside of the fill and the lowermost cold water collection basin of the tower.
2. Description of the Prior Art
Counterflow water cooling towers broadly comprise an upright casing supporting an elevated water distribution system, an underlying water-dispersing fill, means such as powered fan(s) for drawing ambient-derived cooling air currents into the casing through appropriate inlets and upwardly through the tower casing and fill, and an underlying cold water collection basin. The distribution system serves to receive initially hot water and to distribute the same for gravitation through the underlying fill structure. The latter can be of the splash or film variety, but in all cases serves to effect a thermal interchange relationship between the initially hot water descending through the fill and the countercurrently upwardly flowing air currents.
A persistent problem with counterflow towers stems from the tendency of such towers to suffer from substantial air flow disruption and turbulence at the region of the lower air inlets thereof. This in turn creates uneven and/or deprived air flow through the fill structure, particularly at the outboard regions thereof immediately adjacent the tower casing. Such an air flow pattern detracts from the cooling efficiency of the tower, which is maximized where the air flow is substantially uniform.
A variety of counterflow air inlet designs have been proposed in the past, but all suffer from poor inlet flow distribution to a greater or lesser degree. For example, it is known to provide fill structure within the tower which extends to a point essentially flush with the upper defining edges of opposed air inlets, and is also known to provide outwardly extending fins or air entrance guides above the inlets. U.S. Pat. No. 4,873,028 describes an inlet/fill arrangement wherein the fill structure includes a plurality of side-by-side trapezoidal-shaped fill sheets which cooperatively present an oblique, non-horizontal air entrance face. The fill structure in this instance extends essentially the full height of the tower down to the collection basin. Similarly, U.S. Pat. No. 3,983,190 provides full-height fill structure presenting an oblique air entrance face, but here again the fill extends down to the collection basin and effectively blocks lateral air flow through the tower.
There is therefore a decided need in the art for an improved counterflow tower design which ameliorates the problems associated with air flow disruption at the inlets thereof and thereby enhances overall cooling efficiency.

Relieved inlet structure for counterflow water cooling tower