A smooth-textured non-woven, superabsorbent particle-impregnated fibrous structure is disclosed. The web exhibits an improved smooth surface texture. The structure contains from 50% to 80% of ion sensitive SAP having a particle size of less than 200 microns, wood pulp fibers and cellulose acetate fibers, each in preferred specified amounts indicated herein. The superabsorbent, ion sensitive polymer particle-impregnated fibrous structure is made from an aqueous, wet-lay process in which an aqueous furnish comprises solids of fibers and superabsorbent, ion sensitive polymer and dissolved salt, such as preferably, Na2SO4. The furnish is passed over a moving foraminous support, such as a Fourdrinier wire, and a wet web structure is formed, followed by drying.

This invention relates to a wet-laid nonwoven structure containing fibers and water insoluble, water-swellable, superabsorbent, ion sensitive polymer particles (SAP) and process for making an absorbent structure. The structure is intended for use in absorbent hygiene products such as diapers, incontinence pads, sanitary napkins and tampons and in wiping materials for mopping up spills of fluids. A wet-laid nonwoven fabric is a fabric comprising fibers which have been deposited from an aqueous suspension onto a moving foraminous support.
Fibrous, non-woven, superabsorbent, ion sensitive polymer-impregnated structures are known.
See generally, U.S. Pat. Nos. 5,167,764, 5,607,550, 5,516,585 and European Publication No. 437,816. Additionally, the following references disclose previously attempted methods of handling superabsorbent or hydrogel ion sensitive polymers to obtain superabsorbent structures. See U.S. Pat. No. 3,669,103; 4,610,678; 4,986,882; 5,049,235; 5,137,600; 5,160,789; 5,443,899; 5,531,728; and 5,547,745. See U.S. Pat. No. 5,516,585 teaching the well known binder polymers suggested for use with air laid nonwoven structures containing SAP.
EP-A-437816 discloses a nonwoven wet-laid superabsorbent material produced by the process of blending superabsorbent, ion sensitive polymer particles with a liquid to form a slurry, mixing particles with that slurry, filtering that slurry/fibre mixture to remove a portion of the liquid and drying the superabsorbent slurry/fiber mixture to form a nonwoven wet-laid superabsorbent material.
EP-A-359615 discloses a method for the manufacture of a superabsorbent fibrous structure in which a dry solid absorbent is applied directly to a wet-laid web of cellulosic fibers prior to drying the wet web.
EP-A-273075 discloses a high water-absorbency paper made by sheeting a mixture of wood pulp fiber, water-soluble resin and high water-absorbency resin.
A number of techniques for applying binders to webs of fibers are known. For example, U.S. Pat. No. 4,600,462 of Watt describes a process in which an adhesive binder is sprayed onto one or both surfaces of an air laid cellulose fiber web. Submersion of the web in the adhesive binder is another method disclosed in this patent of applying the binder. Individual binder coated fibers for mixing with other fibers are not produced by this process. A hydrophile solution is also all applied to the web. As another example, U.S. Pat. Nos. 4,425,126 and 4,129,132 of Butterworth, et al. describe a fiberous material formed by combining thermoplastic fibers and wood pulp, heat fusing the combined fibers, and thereafter depositing a binder on the heat fused web. Because the fibers are heat fused prior to adding the binder, individual binder coated fibers for mixing with other fibers are not produced by this process.
Absorbent products such as diapers which include particles of a superabsorbent ion sensitive polymer such as crosslinked sodium polyacrylate disposed between layers of wood pulp are known for example from EP-A-257951.
The use of fibers of water-swellable water-insoluble superabsorbent, ion sensitive polymer is disclosed in U.S. Pat. No. 5,607,550, wherein it is taught that incorporation of superabsorbent, ion sensitive polymers in particulate form in the fiber web has significant disadvantages in many respects. The prior art teaches that superabsorbent, ion sensitive polymer particles are less securely retained both during formation of the wet-laid nonwoven structure and when the structure is in further processed during incorporation into an absorbent product. Moreover the art indicates a relatively less uniform dispersion of superabsorbent, ion sensitive polymer particles in the web occurs as opposed to the dispersion of the SAP fiber in the web. It is also taught conventionally that with superabsorbent, ion sensitive polymer particle-impregnated structures, the particles become loosely attached to the fibrous structure of the nonwoven fabric.
In order to provide sufficient absorbency performance necessary for utilization in an absorbent article, it has been found that the loading of superabsorbent in a web must be at least about 50% by weight of the entire structure. However, significant loadings of particles in the fiber structure (such as above about 50% SAP particles on the total weight of the web) require sufficient strength of the wet web in the process
Whereas the cost associated with forming fibers of superabsorbent, ion sensitive polymer is inherently higher than that of the particulate SAP, it would be desirable to overcome the aforementioned drawbacks in the use of particles of SAP. Composite structures of fibers impregnated with superabsorbent, ion sensitive polymer particles could greatly reduce the manufacturing cost of end use products such as those aforementioned, however when forming such a structure with 50% or higher loadings of particles of SAP, the web thus formed has a rough texture which can be felt in a disposable article having a top sheet. The texture is telegraphed through the article and may provide undesirable comfort for the user.
Accordingly, there is an unmet need to develop improved superabsorbent, ion sensitive polymer particle-impregnated structures having improved texture for their intended uses. An improved superabsorbent, ion sensitive polymer particle-impregnated structure has been isolated and found to exhibit unexpected smooth texture and surprisingly good absorbency.
In accordance with the invention there is provided a non-woven, wet-laid, superabsorbent, ion sensitive polymer particle-impregnated fibrous structure having smooth surface texture and which is free of binder polymer. All percentages specified herein are weight percentages. Specifically, the structure comprises from 50% to 80% of ion sensitive SAP having a particle size of less than 250 microns, wood pulp fibers and cellulose acetate fibers, each in preferred specified amounts indicated below. The superabsorbent, ion sensitive polymer particle-impregnated fibrous structure is made from a aqueous, wet-lay process in which an aqueous furnish comprises )lids of fibers and superabsorbent, ion sensitive polymer. The aqueous furnish contains 0.2% to 5% or more dissolved salt, which is preferredly Na2SO4. The furnish is passed over a moving foraminous support, such as a Fourdrinier wire, and a wet web structure is formed. The wet web structure is conveyed to an in-line washing zone with a sufficient volume of water, preferably impinging the wet web in a continuous curtain flow, and the washed wet web structure is dried to form the non-woven, wet-laid, superabsorbent, ion sensitive polymer particle-impregnated structure (web).
The wet-laid, superabsorbent, ion sensitive polymer particle-impregnated structure, on a dry weight basis, comprises about 50% to about 80% water insoluble, water swellable ion sensitive polymer (SAP) and about 20% to about 50% fibers (fibrous portion). The fibrous portion of the web comprises 5% to 50% cellulose acetate fibers and 50% to 95% pulp fibers. Preferably the fibrous portion comprises 10% to 50% cellulose acetate fibers and 50% to 90% wood pulp fibers. More preferredly the fiberous portion comprises 10% to 40% cellulose acetate fibers and 60% to 90% wood pulp fibers. Most preferredly, the fibrous portion comprises 5% to 20% cellulose acetate fibers and 80% to 95% wood pulp fibers.
The wet-laid, superabsorbent, ion sensitive polymer particle-impregnated structure contains from 0% to 35% residual salt in the dried web, preferably from 5% to 35% such residual salt remains, and most preferably 10% to 16% residual salt. The level of residual salt on the total weight of the dried web has been found to correlate inversely with the AUL absorbency performance, described below. The minimum AUL absorbency of the wet-laid, superabsorbent, ion sensitive polymer particle-impregnated web which contains from 5% to 35% residual salt is greater than or equal to about 13 g/g. AUL on the basis of SAP polymer in the sheet is greater than or equal to 19 g/g within the range of 5% to 35% salt. The AUL on the basis of the SAP in the sheet is obtained by dividing the AUL of the web by the percent SAP in the web . Preferably at a lower residual salt content less or equal to about 20%, AUL absorbency per unit SAP in the web is greater than or equal to about 23 g/g. Most preferredly the AUL absorbency per unit of SAP in the web is greater than or equal to 30 g/g and the salt content in the web is between about 10% and 16% .
The SAP/fiber web is produced by the process referred to as wet lay processing. An exemplary apparatus known in the art is an inclined wire forming machine, which can be used to form the wet-laid, superabsorbent, ion sensitive polymer particle-impregnated web. The web is transferred from the inclined wire to a horizontal conveyor optionally equipped with vacuum suction ports to further remove processing water. A washing station typically a trough is mounted at a point along the conveyor to provide a receptacle for wash water applied to the wet web, thereby reducing the level of residual salt in the web. Means for reducing the salt content of the wet web include applying a continuous or discontinuous curtain of water, applying water in a spray pattern, submerging the web in a trough of water, flooding the web and the like, thereby retrieving some salt which has absorbed or adsorbed. After washing, the web is transferred into a means for substantial removal of water. Such means include one or more than one single means, for example, a rotary/thru air dryer, a heated drum dryer, an infrared heating source, hot air blowers, microwave emitting source, and the like, all which are known and used in web drying processes.
All processing waters except that which is driven off in the dryer exhaust, are captured and recycled to the process; these waters are collected in what is identified as the xe2x80x9cwhite waterxe2x80x9d tank. Web basis weight is controlled by regulating the concentration of superabsorbent ion sensitive polymer and fiber components in the feed or xe2x80x9cstockxe2x80x9d tank which is fed along with the xe2x80x9cwhite waterxe2x80x9d at prescribed solids content into the formation chamber (ie inclined wire machine). After exiting the dryer the web is edge trimmed and rolled onto cores. The water contains a salt. The salt can be sodium chloride, or a alkali (NA, K, Li) or alkaline (Ca, Mg, Ba) carbonate, or an alkali or alkaline sulfate. The preferred salt is sodium sulfate because chloride salts contribute to metal stress cracking, and carbonates have the effect of further neutralizing the SAP.
The following test methods were used to determine the properties of the superabsorbent, ion sensitive polymers and the wet-laid, superabsorbent, ion sensitive polymer particle-impregnated structure where indicated.
Residual Sodium Sulfate salt in web is measurable with a Cole Parmer Sulfate Test Kit available from Cole Parmer as Product Code No. 05542-23. The procedure consists of extracting the sulfate with water and determining the sulfate content from the following procedure.
1. An approx. 2 in. diameter disc of the web sample is cut and weighed. The sample is placed in a beaker containing 150 mls. of deionized water for about three minutes. The supernatent is then poured off and retained for testing as follows:
2. The vial is rinsed with a small portion of the supernatent to be tested. The vial is filled with the supernatent to the lower scoreline (150 ml sample).
3. Phenolpthalein indicator is used to check and adjust to neutral pH, e.g. if the sample turns red, hydrochloric acid 10 N is added with swirling until the color is gone.
4. 1 (one) dipper (contained in the cap) of sulfate indicator powder is added to the vial and allowed to dissolve.
5. Isopropyl alcohol is added to raise the liquid to the upper scoreline followed by swirling.
6. Standard barium chloride solution provided in the kit is added counting dropwise (mixing after each drop) until the yellow color turns to dull red or orange. The number of drops added is recorded.
7. The number of drops of standard barium chloride consumed is multiplied by 25 to indicate the mg per liter (ppm) of sulfate present in the supernatent sample as the following calculation:             8.                    xe2x80x83                  grams                    xe2x80x83                  sodium                    xe2x80x83                  sulfate        =                            (                        drops                          xe2x80x83                        barium                          xe2x80x83                        sulfate        xc3x97                  xe2x80x83                        25                          xe2x80x83                        ppm                          /                        drop        xc3x97        150                          xe2x80x83                        ml                          )                    0.6763                  percent                    xe2x80x83                  sodium                    xe2x80x83                  sulfate        =                  grams                          xe2x80x83                        sodium                          xe2x80x83                        sulfate        xc3x97        100                    web                          xe2x80x83                        sample                          xe2x80x83                        weight
Absorbency Under Load (AUL) for particulate SAP
This test is designed to determine the absorbency under load of a particulate superabsorbent, ion sensitive polymer. This is a measure of the amount of saline (0.9% wt/% NaCl aqueous solution) absorbed by the ion sensitive polymer while a predetermined amount of weight is applied to the ion sensitive polymer gel and indicates the effectiveness of the ion sensitive polymer""s absorbency in relation to actual use conditions.
Absorbency under load is measured using a plastic petri dish with elevating rods and a 1.241xe2x80x3ODxc3x970.998xe2x80x3IDxc3x971.316xe2x80x3 long plexiglass tube with a wire net (100 mesh) at the bottom of the tube. The particle size of the test samples is between 30 to 50 mesh, (through 30 and retained on 50).
A test sample, 0.160xc2x10.01 g is weighed out and recorded as S1. The sample is placed in the plastic tube and is spread evenly over the wire net. A specified weight(e.g. a 100 g, 200 g or 300 g weight yielding 0.3 psi, 0.6 psi and 0.9 psi load, respectively) and a disc are placed on the sample. The assembly (polymer sample, tube, disc and weight) is weighed and recorded as W1. The assembly is then placed in a petri dish containing 40 ml 0.9% saline aqueous solution. After one hour of absorption, the assembly is removed from petri dish and excess saline blotted from the bottom. The assembly is weighed again and this value recorded as W2. Absorbency under load (AUL) is equal to (W2xe2x88x92W1)/S1 and is express in g/g.
Absorbency Under Load (AUL/(for web sample)
This test is designed to determine the absorbency under load of a web containing a mixture of superabsorbent polymer and fiberous materials. This is a measure of saline (0.9% wt/% NaCl aqueous) solution absorbed by the web while a predetermined amount of weight is applied to the web and indicates the effectiveness of the web""s absorbency in a diaper system under the weight of a baby. Absorbency under load is measured by cutting a 2 in. diameter circular sample with a die cutter. The sample is oven dried for 2 hours and then weighed to +/xe2x88x920.1 grams. Prior to testing the sample is cooled in a controlled environment (70xc2x0 C., 50% RH). The sample holder is then dried with a hand-held heating blow-dryer to complete dryness. The sample holder has small feet on the bottom to insure a clearance between the bottom of a saline liquid reservoir and the holder. The volume of saline solution to be added to the liquid reservoir is determined by adding a measured amount of saline solution to the reservoir until the liquid level rises to the top of the perforated plate(s) of the sample holder(s). This volume of saline solution is recorded as X. The volume of the saline to be added to the reservoir is X+120 mls. The circular web sample is placed top side down, inside the holder. The total weight of the sample in it""s holder is recorded as the dry weight. A weight (providing load of 0.5 psi) is placed on top of the web sample. The reservoir is filled with X+120 mls. of 0.9% saline solution at a temperature of 23+/xe2x88x921xc2x0 C. Simultaneously the sample holder(s) is placed into the solution. After ten minutes of swelling, the sample holder(s) are removed from the reservoir and allowed to drip approximately 60 seconds. The weight is removed. The weight of the wet sample is re-weighed in the sample holder (wet weight). Calculations:
absorbed weight=(total weight of wet sample and holder) minus (total weight of dry sample and holder)
AUL (g/g) absorbed weight divided by oven dried weight of sample
The fibers used may be filament or staple or a combination of a minor amount of filament and a major amount of staple, or staple fibers of varying lengths. The essential fibers in the web are cellulose acetate (CA) and wood pulp. Optional man-made fibers can be included but are not critical. Polyolefin fibers, polyester fibers and bicomponent fibers could be included. Preferably, all of the fibers used are CA and Pulp staple fibers, generally of length from 1 to 100 mm. In a preferred embodiment, a minor amount (about 20%-30% of the fibrous portion) is polyethylene fiber (type 103 sold under the TREVIRA(copyright) trademark), and from about 2 to 10% of the fibrous portion is made of bicomponent fibers sold under the type 105 Celbond(copyright) trademark of TREVIRA. The staple fibers are preferably of 0 to 50 mm in length. The greater the length, the greater the strength of the wet web structure up to a point where greater fiber length may adversely affect processing of the furnish, material cost, and web uniformity. Cellulose acetate staple is usually available in lengths of 2 to 50 mm. The more preferred lengths for cellulose acetate are from 0.25 to 0.75 inch (8 to 19 mm), and most preferred are lengths of about 0.5 in. (≅12 mm). Cellulose acetate staple is commercially available from Celanese Acetate, Charlotte, N.C. The denier per filament (dpf) for the cellulose acetate fiber is not critical. Preferably cellulose acetate having 1.8 dpf and 12 mm length (0.5 inch) is used. Longer lengths could be used but at small denier, fiber entanglement can lead to less uniformity in the web.
Wood pulp fluff of typical length of about 8 mm is used in the wet laid nonvoven industry and is also suitable in the practice of the process. Wood pulp fluff fibers can be obtained from well-known chemical processes such as the kraft and sulfite processes. Suitable starting materials for these processes include hardwood and softwood species, such a alder, pine, douglas fir, spruce and hemlock. Wood pulp fibers can also be obtained from mechanical processes, such as ground wood, refiner mechanical, thermomechanical, chemi-mechanical, and chemi-thermomechanical pulp processes. However, to the extent such processes produce fiber bundles as opposed to individually separated fibers or individual fibers, they are less preferred. However, treating fiber bundles is not within the scope of the present disclosure. Recycled or secondary wood pulp fibers and bleached and unbleached wood pulp fibers can also be used. Details of the production of wood pulp fibers are well-known to those-skilled in the art. These fibers are commercially available from sources including Weyerhaeuser Company, Buckeye Cellulose, and Rayonier.
Superabsorbent, ion sensitive polymer, as used herein, refers to particulate, water insoluble, but water swellable, materials which will pass through a fine mesh screen (U.S. seive). A fine mesh screen means a screen which allows particles of about 250 micron size or smaller to pass through. For example, particles passing through a 65 mesh screen correspond to particles having a particle size of less than 208 microns. Any metric or equivalent fine mesh screen may be used to give particles having this upper limit of particle size. A sizable portion of the particles used herein pass through a 100 mesh seive and are smaller than 150 microns. A minor portion of the particles will pass through even a 325 mesh seive which corresponds to 45 microns or less.
The superabsorbent-polymers in particulate form as specified above generally fall into three classes, namely, starch graft crosslinked copolymers, crosslinked carboxymethylcellulose derivatives, and hydrophilic polyacrylates. Examples of such absorbent polymers are hydrolyzed starch-acrylonitrile graft copolymer, a neutralized starch-acrylic acid graft copolymer, a saponified acrylic acid ester-vinyl acetate copolymer, a hydrolyzed acrylonitrilelcarboxylate copolymer or acrylamide copolymer, a partially neutralized self-crosslinking polyacrylic acid, a partially neutralized, lightly crosslinked polyacrylic acid polymer, carboxylated cellulose, a neutralized crosslinked isobutylene-maleic anhydride copolymer, and the like.
The superabsorbent polymer particles need not be but preferably have at least a portion of their surface which is crosslinked. Surface crosslinked poly acrylic acid polymers as taught in U.S. Pat. Nos. 4,507,438, 4,541,871, 4,666,983, 5,002,986, 5140,076, 5,164,459, 5,229,466, 5,322,896, 5,597,873, and EP 509,708 and falling under the following particle size limitations are suitable herein. The particles are typically isolated from the surface treatment of primary SAP particles which have been seived through a selected mesh size screen, e.g., a 65 mesh screen (U.S. seive). The fines represent attrited particle fragments, and it is expected that only a portion of the surface of these particles have surface crosslinking. The prevalent source of fine particle size ion sensitive SAP is from the sifting of the primary hydrogel process stream from the solution polymerization of partially neutralized polyacrylic acid SAP which has been dried, and chopped into granules. The fine particles are recovered from this mass. The fine particles may be recovered from a subsequent process in which primary seived material is treated with crosslinker and seived again. Thus the fine particles used herein may be a mixture of particles which have not been surface crosslinked along with particles which have been sifted from a mass of primary particles which have been treated with surface crosslinker. Commercially available ion sensitive SAP which passes through a 100 mesh screen are sold as SANWET(copyright) IM-3500F from Clariant Corp., ARIDALL(copyright) from Chemdal, Palatine, Ill. and J550 from Sumitomo Corporation of Japan.
The most preferred, but not essential embodiment of SAP, is recovered from the treatment of primary SAP particles with surface crosslinked from an aqueous crosslinker solution preferably comprising water, a diol selected from a C3to C6 diol and a crosslinking compound. The water and diol components of the crosslinker solution comprises from about 1.0 to about 6.0 percent by weight based upon the weight of the treated SAP polymer, preferably about 1.5 to about 5.5 percent. The crosslinker solution preferably has a surface tension of less than about 55 dynes per cm. The fine particles are recoverd from this treated mass which has been seived through a screen which retains the primary particles having greater than 65 mesh, U.S. seive.
The web structure is formed as a wet-laid nonwoven by any of the techniques known for wet-laying nonwoven fabrics, for example those described in xe2x80x9cManual of Nonwovensxe2x80x9d by R. Krcma (4th Edition 1974, Textile Trade Press, Manchester) at pages 222 to 226. In general, the fiber and particles are wet-laid in a process similar to a conventional papermaking process. The fiber and particles in the aqueous suspension are continuously deposited on the moving foraminous support. The wood pulp fibers may need to be refined, but this is not essential in the practice of the invention. It is preferred to mix the superabsorbent polymer particles into the slurry after refining has been completed.
The furnish can be poured at a controlled rate onto a substantially horizontal mesh screen, or the furnish may be deposited on an inclined mesh screen travelling upwards through the slurry. Alternatively, the furnish can be deposited on a mesh screen which is at the surface of a suction drum. The mesh size of the screen should be such as to allow easy drainage of water but to retain the solids; the most suitable mesh size will generally be in the range 0.2 to 1.5 mm. The mesh can be of metal wire or synthetic polymer, for example polyester filament. The basis weight of the resulting dried web having no more than 0.5% moisture content is preferably from 100 to 500 g/m2 (gsm), more preferably from 125 to 275 gsm, and most preferably webs of 150 and 250 gsm are both utilized in a two layered absorbent component for a disposable diaper.
The fiber/SAP/ solids content of the slurry referred to below, whereby salt is not included in reference to slurry solids, are deposited on the foraminous support (wire) is generally in the range 0.1 to 50 g/liter solids content, preferably 0.2 to 20 g/liter, and more preferably 0.2 to ≈5 g/liter. Depending on the feed rate of furnish on the wire and the speed of the line, a solids content in the area of 0.2 to 2 g/liter can be run and conditions adjusted so that a basis weight of from 100 to 500 gsm can be achieved on typical conventional wet-laying machinery. A portion of the water content of the slurry is drained from the deposited fiber/SAP layer while it is supported on the mesh screen, preferably without the aid of suction applied below the screen. Optional compression rolls can be used and may be desired when dryer capacity is limited and particulaly when making higher basis weight webs (350 gsm and above). The solids content of the wet-laid web as it is taken off the mesh screen is preferably at least 5% and most preferably at least 10% by weight, and it is generally not more than 30% and usually not more than 20% by weight prior to treatment with water.
The formed wet web is then passed under the means for reduction of salt, which is preferably a continuous flow of water in the form of a curtain of flowing water. The delivery rate of the water to the web is adjusted to be sufficient to reduce the residual salt content to the desired level in the web.
The extent of salt removal is directly proportional to the wash water flow per sq. area of web. Salt content in the web with no washing step is about 40% when the salt content in the white water is about 4%. Wash water flow rates between 0.5 and 5.0 gal./sq. ft. are preferred. More preferably, in the use of a water curtain, the water flow rate should be between 0.5 and 2 gal./sq ft. Most preferably the water flow rate should be between 0.75 and 1.25 gal./sq. ft. of web.
The wet web, after water treatment is brought to substantial dryness using any suitable techniques generally employed in papermaking including passage of the web around a heated drum, passage between a series of heated rolls, or on a flat bed, through air dryer.
The wet-laid nonwoven structure can optionally include dispersed particles such as silica, a zeolite or a mineral clay, such as kaolin or bentonite. Such particles, which preferably are not used at more than 10% by weight of the nonwoven fabric, can be added to the furnish as described in EP-A-437816 or incorporated in the superabsorbent particles as described in WO-A-92/19799.

Smooth textured wet-laid absorbent structure


The present invention relates to an apparatus for the simultaneous analysis of at least two samples by the field-flow fractionation method, where the apparatus has at least the following elements:

The present invention relates to an apparatus and a process for the simultaneous analysis of a plurality of samples containing colloidal particles by means of the field-flow fractionation method.
The field-flow fractionation method is a separation and measurement method which has already been known, for some time and goes back to J. C. Giddings and which is used in particular in the analysis of colloidal particles, for a number of polymers, for biological macromolecules and for a wide variety of polymer complexes [J. C. Giddings, Anal. Chem. 67 (1995), 592A]. The field-flow fractionation method is often referred to as xe2x80x9cone-phase chromatographyxe2x80x9d since the separation of the various particles to be separated takes place within a single phase. This phase is preferably a liquid phase.
The field-flow fractionation method profits from an essentially very simple analysis arrangement. The field-flow fractionation is preferably carried out within a narrow, shallow channel through which a constant stream of liquid is passed and maintained. A laminar flow profile is created here [Michel Martin, Advances in Chromatography (N.Y.), 1998, Vol. 39, 1-138]. As the second basic prerequisite for the performance of the field-flow fractionation method, a transverse force field or a transverse flow stream is superimposed on this flow profile. Through a combination of the laminar axial flow profile with the transversely superimposed force field or the transversely superimposed flow stream, samples containing different types of particle present in the carrier liquid can, utilizing the different effect of the resultant force field or flow stream on the different constituents of the samples, be divided spatially into precisely these different constituents. Fractionation takes place as a function of the hydrodynamic diameter (flow field-flow fractionation) or in other field-flow fractionation methods as a function of the chemical composition or density or charge, this usually being combined with the hydrodynamic diameter.
In general, a distinction can be made between four different techniques in the field-flow fractionation method, depending on the type of transversely applied force field. These are the following:
flow field-flow fractionation,
sedimentation field-flow fractionation,
thermal field-flow fractionation and
electrophoretic field-flow fractionation.
An example which may be mentioned is flow field-flow fractionation. In flow field-flow fractionation, a transverse flow stream of the carrier liquid takes on the role of the force field. With the aid of flow field-flow fractionation, the coefficient of friction of the particles to be analyzed, their hydrodynamic diameter and the diffusion coefficient can be determined directly from the following conditional equation chain:
Fflow stream=fU=3xcfx80xcex7dhU=(kT/D)U
where
f=coefficient of friction
U=transverse flow rate
xcex7=viscosity
dh=hydrodynamic diameter
k=Boltzmann constant
T=absolute temperature
D=diffusion coefficient.
Some measurement inaccuracy in flow field-flow fractionation is caused by uneven wall surfaces or compressible membranes serving as accumulation wall. This is preferably countered by appropriate calibration by means of a known diffusion coefficient or particularly preferably by coupling flow field-flow fractionation with one or more on-line detector(s).
Besides the parameters obtainable directly, further parameters, for example the molecular weight or gyration radii of polymers, can also be determined by means of appropriate models, assumptions or other prior knowledge regarding the particles to be analyzed.
Hitherto, when applying the field-flow fractionation method to the analysis of a sample, use has always been made of only a single separation channel, into which the sample was injected, transported through the channel by the carrier liquid and divided into individual zones, as explained above, during passage through the channel, depending on the choice of the specific field-flow fractionation method, these zones then ultimately allowing information to be provided on the individual particles present in the sample to be analyzed. Besides the separation channel, this required an extensive set of further peripherals, for example, inter alia, a pump for the carrier liquid, a further pump for the injection of the sample to be analyzed into the separation channel, depending on the analysis aim at least one detector or a further measurement or analysis unit coupled to the separation channel. Suitable detectors are, for example, all detectors from gel permeation chromatography (GPC), for example refractive index detectors (RI detectors), infra-red detectors (IR detectors), UV-VIS detectors, fluorescence detectors, light scattering detectors, Raman detectors, MALDI detectors and evaporation light scattering detectors. Furthermore, a storage container for the carrier liquid is provided. In addition, high quality demands are made of the separation channel, for example the requirement for an extremely pressure-stable construction so that the liquid streams remain stable in the narrow channels.
If, for example, the flow field-flow fractionation method is considered for the determination of the size distribution of colloidal particles in a sample to be analyzed, the procedure adopted hitherto was to inject in each case one sample into a separation channel coupled to a corresponding set of peripherals. The separation channel corresponded to a shallow channel, typically with a length of from about 1 cm to 100 cm and a depth in the range from about 0.1 mm to 0.4 mm. At least one of the walls delimiting the channel was a semi-permeable membrane, which was permeable to the carrier liquid, but impermeable to the particles present in the sample. After injection of the sample into the separation channel, the sample was firstly focused on an area inside the separation channel. This is achieved, for example, by pumping the carrier liquid into the channel from both ends of the channel, i.e. both from the inlet and from the future outlet, immediately after injection of the sample, so that the sample is initially concentrated in an area within the channel. Due to the action of the transverse flow stream as employed in flow field-flow fractionation, the sample or the particles present therein is transported in the direction of the accumulation wall, which corresponds here to the semi-permeable wall, and is initially concentrated there. The diffusion motion of the particles then commences in the opposite direction to the transverse flow stream and to different degrees depending on the particle type and/or size. When an equilibrium has been reached between the transverse flow stream and the corresponding diffusion motion, the respective particles come to a xe2x80x9cstopxe2x80x9d at a certain point or in a certain, particle-dependent zone within the channel cross section; the particles have then reached their equilibrium position with respect to transverse motion. Depending on the position within the cross section, they are then transported through the channel at different speeds by the carrier liquid, which is pumped into the channel from the inlet side of the separation channel with a flow profile which is not uniform with respect to the channel cross section, i.e. the various particles have different residence times within the separation channel. The residence time as an actual parameter ultimately allows conclusions to be drawn on the respective forces acting on the particles within the channel, taking into account the known non-uniform flow profile of the carrier liquid, as explained above, and in turn, according to the abovementioned conditional equilibrium chain, allows information to be obtained on specific parameters, for example the hydrodynamic diameter. The duration of the measurement for particles of a single type is in the range from less than one minute to about 2 hours, depending on the sample type and on the structure of the separation channel.
A disadvantage here is that it has hitherto appeared impossible to measure quickly and accurately a plurality of samples to be compared with one another. For the analysis of a whole series of samples which were to be compared with one another, the field-flow fractionation method was consequently not suitable, since the procedure known hitherto was much too slow and consequently much too ineffective. In addition, it would have been necessary to create precisely the same analysis conditions for each new sample to be analyzed in order to be able to ensure any later meaningful comparison of the results of the individual samples. In addition, the requisite calibration procedures would have taken a considerable amount of time.
However, it is desirable in many analyses to test and compare a whole series of samples with one another as quickly as possible and nevertheless reliably. A xe2x80x9cscreeningxe2x80x9d of this type is essentially used in the optimization of certain selected parameters of one or more types of particle. One desired aim is, for example, to find an effective screening method for the optimization and monitoring of the size distribution, in particular of colloidal particles and/or of the particle type. The following particles may be mentioned here by way of example: solid particles, vesicles, gel particles, natural and synthetic polymers, protective colloids, associates, micelles, block and random copolymers, hybrid particles having a diameter of xe2x89xa610 xcexcm, for example micronizates, pigments, proteins, starches and sugars.
It is an object of the present invention to provide an apparatus and a process for the screening or parallel analysis of a plurality of particles to be investigated, in particular samples containing colloidal particles, with it being possible to obtain reliable and accurate information regarding the particles quickly.
We have found that this object is achieved by an apparatus as claimed in claim 1 and a process as claimed in claim 7. Preferred embodiments of the present invention are given in the sub-claims. The invention furthermore relates to the use of the apparatus according to the invention and of the process according to the invention for the optimization and/or monitoring of the size distribution of particles, in particular of colloidal particles and/or of the particle type.
The invention provides an apparatus for the simultaneous analysis of at least two samples by the field-flow fractionation method, where the apparatus has at least the following elements:
a) a source of a defined liquid stream, preferably a pump,
b) at least two separation channels, each with at least one inlet and each with at least one outlet for passing the at least two samples through in each case one of the at least two separation channels,
c) at least one controllable unit which is coupled to the at least two separation channels via their at least one outlet each in such a way that with their aid the at least two samples which can be passed through in each case one of the at least two separation channels can be passed on, separately from one another, to at least one unit downstream of the controllable unit.
The apparatus preferably comprises a whole series of identical separation channels. The number of separation channels is in the range from 2 to more than 1000.
The controllable unit is preferably one or more multi-port valves which are coupled to each separation channel. With the aid of the multi-port valve, it is possible, in accordance with a definable or controllable or adjustable time cycle, to connect in each case one separation channel to a unit downstream of the multi-port valve or to pass a sample which has been passed through this separation channel on to a unit downstream of the multi-port valve and thus to subject it to a further analysis. Owing to the use according to the invention of a multi-port valve, different samples passed simultaneously through different separation channels are prevented from coming into contact with one another and/or mixing with one another. It is not absolutely necessary for a dividing wall to be present between the individual separation channels since flow streams are generally laminar. Through the construction of the apparatus according to the invention, it is possible to provide only one set of peripherals in addition to the multiplicity of separation channels. The apparatus according to the invention preferably comprises only one pump for passing the carrier liquid through the various separation channels. In accordance with the invention, the pump here is preferably connected in each case to one of the multiplicity of separation channels via a regulation valve. The regulation valve is preferably time-controllable. Besides a considerable cost saving, this apparatus construction ensures that the requisite introduction and transport of the carrier liquid into and through the individual separation channels can always be carried out with the same pressure, which is a basic prerequisite for later comparison of the results obtained for the individual samples with one another. The advantage of the coupling of a plurality of separation channels to one another consists in an essentially higher sample throughput, at the same time lower costs and the comparability of samples which are unstable or changeable over time that this facilitates. This is necessary for a CMR (CMR=combinatorial materials research) capability, namely the balance between the parallel production of samples and the subsequent characterization by field-flow fractionation.
In a preferred embodiment of the apparatus according to the invention, the controllable unit with the aid of which the samples passed through the various separation channels can be passed on is followed by one or more detectors.
In a further preferred embodiment of the invention, other analysis units are provided in addition to detectors.
In a preferred embodiment, the analysis unit in the apparatus according to the invention, to which the samples divided after passage through the respective separation channels are fed, is a microscope, preferably a light microscope.
In another preferred embodiment, the apparatus according to the invention has devices for carrying out photon correlation measurements.
Furthermore, a further preferred embodiment of the apparatus according to the invention comprises devices for carrying out analytical methods, based on light scattering.
In another preferred embodiment of the apparatus according to the invention, the field-flow fractionation method is flow field-flow fractionation. To this end, a transverse flow stream is provided in addition to the axial flow of the carrier liquid. In a preferred embodiment of the invention, the transverse flow stream, after passing through the separation channels, is discharged via a multi-port valve to a flow meter, preferably to a flow meter with a small pressure drop. The outlet lines are preferably provided with a flow resistance in such a way that the pressure drop corresponds to that of the downstream flow meter. In a further preferred embodiment of the apparatus according to the invention, the discharge of the transverse flow stream does not take place via a multi-port valve, but instead by means of a piston pump operating a plurality of pistons in parallel.
In a further preferred embodiment of the apparatus according to the invention, the field-flow fractionation method is sedimentation field-flow fractionation or thermal field-flow fractionation or electrophoretic field-flow fractionation.
In a further preferred embodiment of the apparatus according to the invention, the at least two separation channels are arranged in a sandwich structure. This arrangement of the channels simplifies the requisite pressure-stable construction of the individual channels. In addition, this arrangement simplifies temperature control of the individual separation channels. The separations of the corresponding samples to be carried out within the individual separation channels are preferably carried out at temperatures above 25xc2x0 C., for example in the range from about 60xc2x0 C. to above 200xc2x0 C.
In a further preferred embodiment of the apparatus according to the invention, the at least two separation channels are connected in parallel. In this case, at least two separation channels are preferably covered by a large-area membrane. This particularly preferably has at least two inlets for the at least two samples to be passed through in each case one of the at least two separation channels. This likewise allows considerable cost savings to be made. The at least two separation channels are in this case separated from one another merely by the flow stream with the carrier liquid, i.e. the separation channels are not separated from one another by a physical separation device, for example a dividing wall. There are consequently no peripheral zones in the flow stream, which considerably improves the separation efficiency and ensures that the flow conditions are virtually identical in the various separation channels. The prerequisite for preventing the various samples from coming into contact with one another is merely that the particles present in the sample to be analyzed are not too small, so that they only exhibit very slight diffusion. Preference is given to the analysis of particles having a size of xe2x89xa710 nm.
The membrane used in accordance with the invention can be either an elastic membrane or a solid membrane, for example a ceramic membrane.
In a further preferred embodiment of the apparatus according to the invention, the separation channels have a reduced length, preferably a length reduced by a factor of 5. This enables the analysis time for a separation channel to be significantly reduced at the cost of a slight drop in separation efficiency which is acceptable for a screening apparatus.
The invention furthermore relates to a process for the simultaneous analysis of at least two samples containing colloidal particles, the process having at least the following steps:
a) introduction of the at least two samples into in each case at least one separation channel,
b) simultaneous exertion of a force acting perpendicular to the axial direction of the respective separation channel onto the at least two samples,
c) controllable, separate passing-on of the at least two samples from the respective at least one separation channel to at least one further unit.
The process is preferably one of the abovementioned different field-flow fractionation methods, i.e. either flow field-flow fractionation or sedimentation field-flow fractionation or thermal field-flow fractionation or electrophoretic field-flow fractionation.
The present invention furthermore relates to the use of the process according to the invention and/or of the apparatus according to the invention for the fractionation of particles, in particular of colloidal particles, in accordance with their diameter or in accordance with other properties, in particular in accordance with the chemical composition or the density or the charge, or in accordance with combinations thereof.
In accordance with the invention, all possible colloidal particles can be analyzed or fractionated. The term xe2x80x9ccolloidal particlesxe2x80x9d here covers particles having a diameter in the range from 1 to 5000 nm, preferably from 1 to 1000 nm, which are dispersed in a liquid or gaseous phase. Of these, particular mention may be made of the following:
synthetic or natural polymers which are branched, partially crosslinked or have a tertiary structure, for example proteins,
compact or hollowed dispersion particles, if desired comprising a protective colloid and/or an active ingredient;
spherical and aspherical associates of polymers, oligomers (micelles) and other colloidal particles;
spherical and aspherical particles, if desired comprising a protective colloid, of either organic, biological or inorganic origin.

Process and apparatus for the parallel analysis of colloidal particles using field-flow fractionation

Abstract: c) at least one controllable unit which is connected to the at least two separation channels via their at least one outlet each, and which can pass on the at least two samples, which can be passed through in each case one of the at least two separation channels, separately from one another to at least one unit downstream of the controllable unit.


An Anti-Parallel (AP)-Pinned SV sensor having a free layer separated from an AP-pinned layer by a conducting spacer. The AP-pinned layer includes a first, second and third pinned layers where the first pinned layer is separated from the second and third pinned layers by an anti-parallel coupling layer. An antiferromagnetic (AFM) layer is used to pin the AP-pinned layer magnetizations directions. The first pinned layer is formed over and in contact with the AFM layer. The first and second pinned layers are made of highly resistive material such as NiFeCr and the third pinned layer is made of low resistive material such as cobalt. The use of a highly resistive first and second pinned layers reduces the amount of sense current flowing in the AP-pinned layer as well as eliminating interdifussion at the AFM/first pinned layer interface resulting in larger GMR coefficient, well controlled net moment, highly stable sensor, and reduced read signal asymmetry.

1. Field of the Invention
This invention relates generally to spin valve magnetic transducers for reading information signals from a magnetic medium and, in particular, to an improved antiparallel-pinned spin valve sensor, and to magnetic recording systems which incorporate such sensors.
2. Description of Related Art
Computer systems generally utilize auxiliary memory storage devices having media on which data can be written and from which data can be read for later use. A direct access storage device (disk drive) incorporating rotating magnetic disks is commonly used for storing data in magnetic form on the disk surfaces. Data is recorded on concentric, radially spaced tracks on the disk surfaces. Magnetic heads including read sensors are then used to read data from the tracks on the disk surfaces.
In high capacity disk drives, magnetoresistive read sensors, commonly referred to as MR heads, are the prevailing read sensors because of their capability to read data from a surface of a disk at greater linear densities than thin film inductive heads. An MR sensor detects a magnetic field through the change in the resistance of its MR sensing layer (also referred to as an "MR element") as a function of the strength and direction of the magnetic flux being sensed by the MR layer.
The conventional MR sensor operates on the basis of the anisotropic magnetoresistive (AMR) effect in which an MR element resistance varies as the square of the cosine of the angle between the magnetization in the MR element and the direction of sense current flowing through the MR element. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded magnetic medium (the signal field) causes a change in the direction of magnetization in the MR element, which in turn causes a change in resistance in the MR element and a corresponding change in the sensed current or voltage.
Another type of MR sensor is the giant magnetoresistance (GMR) sensor manifesting the GMR effect. In GMR sensors, the resistance of the MR sensing layer varies as a function of the spin-dependent transmission of the conduction electrons between magnetic layers separated by a non-magnetic layer (spacer) and the accompanying spin-dependent scattering which takes place at the interface of the magnetic and non-magnetic layers and within the magnetic layers.
GMR sensors using only two layers of ferromagnetic material separated by a layer of non-magnetic electrically conductive material are generally referred to as spin valve (SV) sensors manifesting the GMR effect (SV effect). In an SV sensor, one of the ferromagnetic layers, referred to as the pinned layer, has its magnetization typically pinned by exchange coupling with an antiferromagnetic (e.g., NiO or Fe--Mn) layer. The magnetization of the other ferromagnetic layer, referred to as the free layer, however, is not fixed and is free to rotate in response to the field from the recorded magnetic medium (the signal field). In SV sensors, the SV effect varies as the cosine of the angle between the magnetization of the pinned layer and the magnetization of the free layer. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded magnetic medium (the signal field) causes a change in the direction of magnetization in the free layer, which in turn causes a change in resistance of the SV sensor and a corresponding change in the sensed current or voltage. It should be noted that the AMR effect is also present in the SV sensor free layer and it tends to reduce the overall GMR effect.
FIG. 1 shows a typical SV sensor 100 comprising end regions 104 and 106 separated by a central region 102. The central region 102 has defined edges and the end regions are contiguous with and abut the edges of the central region. A free layer (free ferromagnetic layer) 110 is separated from a pinned layer (pinned ferromagnetic layer) 120 by a non-magnetic, electrically conducting spacer 115. The magnetization of the pinned layer 120 is fixed through exchange coupling with an antiferromagnetic (AFM) layer 121. Free layer 110, spacer 115, pinned layer 120 and the AFM layer 121 are all formed in the central region 102. Hard bias layers 130 and 135 formed in the end regions 104 and 106, respectively, provide longitudinal bias for the free layer 110. Leads 140 and 145 formed over hard bias layers 130 and 135, respectively, provide electrical connections for the flow of the sensing current I.sub.s from a current source 160 to the MR sensor 100. Sensing means 170 connected to leads 140 and 145 sense the change in the resistance due to changes induced in the free layer 110 by the external magnetic field (e.g., field generated by a data bit stored on a disk).
IBM's U.S. Pat. No. 5,206,590 granted to Dieny et al. and incorporated herein by reference, discloses an MR sensor operating on the basis of the SV effect.
Another type of spin valve sensor currently under development is an antiparallel (AP)-pinned spin valve sensor. FIGS. 2A-2B show an AP-Pinned SV sensor 200 which has been a subject of experiment and modeling by the present inventor. SV sensor 200 has end regions 202 and 204 separated from each other by a central region 206. AP-pinned SV sensor 200 further comprises a Ni--Fe free layer 225 separated from a laminated AP-pinned layer 210 by a copper spacer layer 220. The magnetization of the laminated AP-pinned layer 210 is fixed by an AFM layer 208 which is made of NiO. The laminated AP-pinned layer 210 includes a first ferromagnetic layer 212 (PF1) of cobalt and a second ferromagnetic layer 216 (PF2) of cobalt separated from each other by a ruthenium antiparallel coupling layer 214. The AMF layer 208, AP-pinned layer 210, copper spacer 220, free layer 225 and a cap layer 230 are all formed sequentially in the central region 206. Hard bias layers 235 and 240, formed in end regions 202 and 204, provides longitudinal biasing for the free layer 225. Electrical leads 245 and 250 are also formed in end regions 202 and 204, respectively, to provide electrical current from a current source (not shown) to the SV sensor 200. The magnetization direction 265 of the free layer 225 is set to be parallel to the ABS in the absence of an external field. The magnetizations directions 255 and 260 of the pinned layers 212 and 216, respectively, are anti-parallel with each other and are set to be perpendicular to the ABS.
A key advantage of the AP-pinned SV sensor of FIG. 2A is the improvement of the exchange coupling field strength between the AFM layer 208 and AP-pinned layer 210. This improved exchange coupling increases the stability of the AP-pinned SV sensor 200 at high temperatures which allows the use of corrosion resistant antiferromagnetic materials such as NiO for the AFM layer 208.
Despite of its key advantage, there are two major problems associated with the AP-pinned SV sensor of FIG. 2A. First, the exchange coupling field between the AFM layer 208 and the AP-pinned layer 210 is inversely proportional to the magnetic moment difference (net magnetic moment) between the two AP-pinned ferromagnetic layers 212 and 216. However, it is very difficult to control the net moment of the AP-pinned layer 210 (Co/Ru/Co) because of interfacial diffusion and oxidation that takes place at the interface between the NiO AFM layer 208 and the first pinned layer 212 of Co. This interaction between the NiO AFM layer 208 and the Co first pinned layer 212 creates magnetic dead layer at the NiO/Co interface. The interfacial diffusion and oxidation that take place at the aforementioned interface causes a change in the moment of the first pinned Co layer 212 even after the AP-pinned SV sensor of FIG. 2A has been completely built. The change in the moment of the first pinned layer 212 causes the change in the net moment of the AP-pinned layer 210 by factors of 2 to 3 from one wafer to another. Such large variations in the net moment of the AP-pinned layer 210 result in large variations in pinning fields which compromises the stability of the SV sensor 200 as well as the size and symmetry of the signals detected (read) by the sensor.
Second, substantial amount of the sense current flows in the AP-pinned layer 210 due to the fact that cobalt has a low electrical resistivity of about 12 .mu..OMEGA.Cm. TABLE I summarizes the result of a modeling simulation on the SV sensor 200.
TABLE I ______________________________________ AP-PINNED SV SENSOR OF FIGS. 2A-2B Sheet Resistance Sense Current Material Thickness (.ANG.) .mu..OMEGA. cm Shunting (%) ______________________________________ NiO layer 208 400 insulator -- CO layer 212 29 11.6 15 Ru layer 214 6 20 1.25 CO layer 216 24 11.6 12 Cu layer 220 22 2.7 47 NiFe layer 225 72 25 24 TA layer 230 50 200 2 ______________________________________
According to the results summarized in TABLE I, about 28.25% of the sense current flows in the AP-pinned layer 210. Furthermore, about 15% of the sense current flows in the cobalt layer 212 which does not contribute to reading signals from a magnetic disk. Such a large current flow in the cobalt layers and inability to control the net moment of the cobalt layers contributes to smaller GMR coefficient and read signal asymmetry. Smaller GMR coefficient is due to the fact that a sizeable portion of the sense current flows in a layer that does not contribute to the GMR coefficient. Read signal asymmetry is due to the fact that the current field (H.sub.I), demag field (H.sub.Demag) and the ferromagnetic coupling field (H.sub.FC) effects (all in the same direction) on the free layer magnetization (FIG. 2B) are larger than the effect of the AMR on the free layer magnetization direction 265.
Therefore, there is a need for an AP-pinned SV sensor where the amount of current flow in the AP-pinned layer is minimized and the AP-pinned layer has a well controlled net moment.

Anti-parallel-pinned spin valve sensor with minimal pinned layer shunting

International Business Machines Corporation


A cleansing article having a substrate capable of absorbing and retaining a fluid therein, the substrate being impregnated with a cleaning composition containing a linear and/or branched alcohol polyglycol ether.

The invention is in the field of cleaners for hard surfaces and relates to wet wipes which are impregnated with a special species of a nonionic surfactant.
For the cleaning of hard surfaces, liquids of greater or lesser viscosity are usually used, which are applied directly, run off from the surface to be cleaned and in so doing carry along the majority of the soiling. Another application form which is enjoying increased importance are wet wipes, which are textile fabrics or else tissue papers which are impregnated with a cleaning liquid. Thus, for example, international patent application WO 95/35411 (Procter and Gamble) proposes wet wipes albeit predominantly for cosmetic applications, which comprise, in addition to mineral oil, fatty acid esters, fatty alcohol ethoxylates and fatty alcohols.
The disadvantage of the use of these wet wipes is that the surfactants used leave behind a residue in the form of smearing, which makes the treated surface less shiny or even makes it appear soiled. A further problem arises in the production of the wet wipes. In order to impregnate the fabric or tissue paper with the cleaning solution, it is either sprayed therewith or immersed therein where, in both cases, it is possible for the output in production to be reduced as a result of foam formation or insufficient wetting. A first object of the present invention was therefore to provide wet wipes using special surfactants which are free from the problems described above.
For logistical reasons, the use of concentrates for the preparation of impregnation solutions for the wet wipes is advantageous. It is disadvantageous that the concentrates often show a tendency toward foam formation upon dilution. Furthermore, gel phases may form, which leads to increased time expenditure in the preparation of the impregnation solutions. In both cases, the production output is reduced. A further object of the invention was therefore to provide surfactants with which concentrates can be prepared which, by virtue of their viscosity, storage stability, lack of foam upon dilution and rapid dilutability, permits a technically simple and therefore cost-effective production of the wet wipes.
The invention provides wet wipes which are characterized in that they are impregnated with linear and/or branched alcohol polyglycol ethers.
Surprisingly, it has been found that nonionic surfactants of the linear and/or branched alcohol polyglycol ether type, preferably in combination with alkyl oligoglucosides, satisfy the complex object in an excellent manner. Impregnating agents based on alcohol polyglycol ethers have proven in the application to be low-viscosity and virtually foam-free, and in application the wet wipes impregnated therewith do not leave behind any streaks and do not impair the shine. Concentrates based on alcohol polyglycol ethers are low-viscosity and, upon dilution to the application concentration, particularly low-foaming.
Alcohol Polyglycol Ethers
Alcohol polyglycol ethers are known nonionic surfactants which are usually obtained by adding ethylene oxide and/or propylene oxide, blockwise or in random distribution, onto suitable primary alcohols or polyols. The polyglycol ethers usually conform to the formula (I),
in which R1 is a linear and/or branched alkyl and/or alkenyl radical having 6 to 22, preferably 8 to 18 and in particular 10 to 12, carbon atoms, an ethylene glycol or glycerol radical, x and z, independently of one another, are 0 or numbers from 1 to 40 and y is numbers from 1 to 40; the polyglycol ethers thus obligatorily contain at least one propylene oxide unit. Typical examples are the addition products of, on average, 1 to 40, preferably 5 to 30 and in particular 8 to 15, mol of ethylene oxide and/or 1 to 10, preferably 2 to 5, mol of propylene oxide onto fatty alcohols, oxo alcohols or alfols, such as, for example, caproic alcohol, caprylic alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, elaeostearyl alcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol and brassidyl alcohol, and technical-grade mixtures thereof, and also ethylene glycol or glycerol. The amount of alcohol polyglycol ethers used can, based on the wet wipes, be 0.05 to 2% by weight and preferably 0.1 to 0.5% by weight and, based on the concentrates, 10 to 50% by weight, preferably 15 to 25% by weight.
Cosurfactants
In a preferred embodiment of the present invention, the mixed ethers are used together with further anionic, nonionic, cationic and/or amphoteric or zwitterionic surfactants.
Typical examples of anionic surfactants are soaps, alkylbenzenesulfonates, alkanesulfonates, olefin-sulfonates, alkyl ether sulfonates, glycerol ether sulfonates, xcex1-methyl ester sulfonates, sulfo fatty acids, alkyl sulfates, fatty alcohol ether sulfates, glycerol ether sulfates, hydroxy mixed ether sulfates, monoglyceride (ether) sulfates, fatty acid amide (ether) sulfates, mono- and dialkyl sulfosuccinates, mono- and dialkyl sulfosuccinamates, sulfo-triglycerides, amide soaps, ether carboxylic acids and salts thereof, fatty acid isethionates, fatty acid sarcosinates, fatty acid taurides, N-acylamino acids, such as, for example, acyl lactylates, acyl tartrates, acyl glutamates and acyl aspartates, alkyl oligo-glucoside sulfates, protein fatty acid condensates (in particular wheat-based vegetable products) and alkyl (ether) phosphates. If the anionic surfactants contain polyglycol ether chains, these may have a conventional homolog distribution, but preferably have a narrowed homolog distribution.
Typical examples of nonionic surfactants are alkylphenol polyglycol ethers, fatty acid polyglycol esters, fatty acid amide polyglycol ethers, fatty amine polyglycol ethers, alkoxylated triglycerides, mixed ethers, hydroxy mixed ethers, unoxidized or partially oxidized alk(en)yl oligoglycosides or glucuronic acid derivatives, fatty acid N-alkylglucamides, protein hydrolysates (in particular wheat-based vegetable products), polyol fatty acid esters, sugar esters, sorbitan esters, polysorbates and amine oxides. If the nonionic surfactants contain polyglycol ether chains, these may have a conventional homolog distribution, but preferably have a narrowed homolog distribution.
Typical examples of cationic surfactants are quaternary ammonium compounds such as, for example, dimethyl distearyl ammonium chloride, and ester quats, in particular quaternized fatty acid trialkanolamine ester salts. Typical examples of amphoteric or zwittionic surfactants are alkylbetaines, alkylamidobetaines, aminopropionates, aminoglycinates, imidazoliniumbetaines and sulfobetaines. Said surfactants are exclusively known compounds. With regard to structure and preparation of these substances, reference may be made to relevant review works, for example J. Falbe (ed.), xe2x80x9cSurfactants in Consumer Productsxe2x80x9d, Springer Verlag, Berlin, 1987, pp. 54-124 or J. Falbe (ed.), xe2x80x9cKatalysatoren, Tenside und Mineralxc3x6ladditivexe2x80x9d, Thieme Verlag, Stuttgart, 1978, pp. 123-217.
Typical examples of particularly suitable surfactants are fatty alcohol polyglycol ether sulfates, monoglyceride sulfates, mono- and/or dialkyl sulfosuccinates, fatty acid isethionates, fatty acid sarcosinates, fatty acid taurides, fatty acid glutamates, xcex1-olefinsulfonates, ether carboxylic acids, fatty acid glucamides, alkylamidobetaines, amphoacetals and/or protein fatty acid condensates, the latter preferably based on wheat proteins.
Alkyl and/or Alkenyl Oligoglycosides
Performance investigations demonstrate that mixtures of mixed ethers and alkyl and/or alkenyl oligoglycosides are particularly advantageous. The latter are known nonionic surfactants which conform to the formula (II),
R2O-[G]p xe2x80x83xe2x80x83(II)
in which R2 is an alkyl and/or alkenyl radical having 4 to 22 carbon atoms, G is a sugar radical having 5 or 6 carbon atoms and p is a number from 1 to 10. They can be obtained by the relevant processes of preparative organic chemistry. By way of representation for the extensive literature, reference may be made here to the specifications EP-A1 0301298 and WO 90/03977.
The alkyl and/or alkenyl oligoglycosides can be derived from aldoses or ketoses having 5 or 6 carbon atoms, preferably from glucose. The preferred alkyl and/or alkenyl oligoglycosides are thus alkyl and/or alkenyl oligoglucosides. The index number p in the general formula (II) gives the degree of oligomerization (DP), i.e. the distribution of mono- and oligoglycosides, and is a number between 1 and 10. While p in a given compound must always be an integer and can here primarily assume the values p=1 to 6, the value p for a certain alkyl oligoglycoside is an analytically determined calculated parameter which in most cases is a fraction. Preference is given to using alkyl and/or alkenyl oligoglycosides with an average degree of oligomerization p of from 1.1 to 3.0. From a performance viewpoint, preference is given to those alkyl and/or alkenyl oligoglycosides whose degree of oligomerization is less than 1.7 and is in particular between 1.2 and 1.4.
The alkyl or alkenyl radical R2 can be derived from primary alcohols having 4 to 11, preferably 8 to 10, carbon atoms. Typical examples are butanol, caproic alcohol, caprylic alcohol, capric alcohol and undecyl alcohol, and technical-grade mixtures thereof, as are obtained, for example, in the hydrogenation of technical-grade fatty acid methyl esters or in the course of the hydrogenation of aldehydes from the Roelen oxo synthesis. Preference is given to alkyl oligoglucosides of chain length C8-C10 (DP=1 to 3) which are produced as for runnings during the distillative separation of technical-grade C8-C18-coconut fatty alcohol and may be contaminated with a content of less than 6% by weight of C12-alcohol, and also alkyl oligoglucosides based on technical-grade C9/11-oxo alcohols (DP=1 to 3). The alkyl or alkenyl radical R2 can also be derived from primary alcohols having 12 to 22, preferably 12 to 14, carbon atoms. Typical examples are lauryl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol, brassidyl alcohol, and technical-grade mixtures thereof, which can be obtained as described above. Preference is given to alkyl oligoglucosides based on hydrogenated C12/14-coconut alcohol with a DP of from 1 to 3. The alkyl and/or alkenyl oligoglycosides can, based on the wet wipes, be used in amounts of 0.05 to 2% by weight and preferably 0.5 to 1% by weight and, based on the concentrates, in amounts of from 10 to 50% by weight, preferably 25 to 25% by weight, where the weight ratio of mixed ethers to glycoside may be in the range from 10:90 to 90:10, preferably 25:75 to 75:25 and in particular 40:60 to 60:40.
Tissue Papers and Tissue Fabrics for Moistened Papers
Tissue papers to which the present invention refers can be single-ply or multi-ply. The papers generally have a weight per square meter of from 10 to 65 g, preferably 15 to 30 g, and a density of 0.6 g/cm3 and below. Examples of tissue papers to which the invention may extend are, in addition to household wipes, naturally also toilet papers, pocket tissues, face-cleansing wipes, make-up removal wipes, refreshing wipes and the like. In addition to the paper-based tissues, corresponding tissue fabrics which are prepared from fiber or fleece material are also suitable.
Industrial Applicability
Finally, the invention provides for the use of linear and/or branched alcohol polyglycol ethers as impregnating agents for the production of wet wipes, in which they can be used in amounts of from 0.01 to 2% by weight, preferably 0.5 to 1% by weight, based on the wipes.
Auxiliaries and Additives
In a further embodiment of the invention, the wet wipes can comprise further customary auxiliaries and additives, in particular complexing agents, such as, for example, citric acid, HEDP or EDTA, which serve both for the stabilization of the ingredients and also for improving the cleaning performance in the case of salt-containing soilings (e.g. water hardness), antibacterial active ingredients such as, for example, hydrogen peroxide and cationic surfactants, preferably ester quats, and skin care agents. Suitable skin care agents are primarily refatting agents, oil components and emulsifiers, as are typically used in cosmetic products.
Oily Bodies
Suitable oily bodies are, for example, Guerbet alcohols based on fatty alcohols having 6 to 18, preferably 8 to 10, carbon atoms, esters of linear C6-C22-fatty acids with linear or branched C6-C22-fatty alcohols or esters of branched C6-C13-carboxylic acids with linear or branched C6-C22-fatty alcohols, such as, for example, myristyl myristate, mynstyl palmitate, myristyl stearate, myristyl isostearate. myristyl oleate, mynstyl behenate, myristyl erucate, cetyl myristate, cetyl palmitate, cetyl stearate, cetyl isostearate, cetyl oleate, cetyl behenate, cetyl erucate, stearyl myristate, stearyl palmitate, stearyl stearate, stearyl isostearate, stearyl oleate, stearyl behenate, stearyl erucate, isostearyl myristate, isostearyl palmitate, isostearyl stearate, isostearyl isostearate, isostearyl oleate, isostearyl behenate, isostearyl oleate, oleyl myristate, oleyl palmitate, oleyl stearate, oleyl isostearate, oleyl oleate, oleyl behenate, oleyl erucate, behenyl myristate, behenyl palmitate, behenyl stearate, behenyl isostearate, behenyl oleate, behenyl behenate, behenyl erucate, erucyl myristate, erucyl palmitate, erucyl stearate, erucyl isostearate, erucyl oleate, erucyl behenate and erucyl erucate. Also suitable are esters of linear C6-C22-fatty acids with branched alcohols, in particular 2-ethylhexanol, esters of C18-C38-alkylhydroxycarboxylic acids with linear or branched C6-C22-fatty alcohols (cf. DE 19756377 A1), in particular dioctyl malate, esters of linear and/or branched fatty acids with polyhydric alcohols (such as, for example, propylene glycol, dimerdiol or trimertriol) and/or Guerbet alcohols, triglycerides based on C6-C10-fatty acids, liquid mono-/di-/triglyceride mixtures based on C6-C18-fatty acids, esters of C6-C22-fatty alcohols and/or Guerbet alcohols with aromatic carboxylic acids, in particular benzoic acid, esters of C2-C12-dicarboxylic acids with linear or branched alcohols having 1 to 22 carbon atoms or polyols having 2 to 10 carbon atoms and 2 to 6 hydroxyl groups, vegetable oils, branched primary alcohols, substituted cyclohexanes, linear and branched C6-C22-fatty alcohol carbonates such as, for example, dicaprylyl carbonate (Cetiol(copyright) CC), Guerbet carbonates based on fatty alcohols having 6 to 18, preferably 8 to 10, carbon atoms, esters of benzoic acid with linear and/or branched C8-C22-alcohols (e.g. Finsolv(copyright) TN), linear or branched, symmetrical or asymmetrical dialkyl ethers having 6 to 22 carbon atoms per alkyl group, such as, for example, dicaprylyl ether (Cetiol(copyright) QE), ring-opening products of epoxidized fatty acid esters with polyols, silicone oils (cyclomethicones, silicon methicone grades, etc.) and/or aliphatic or naphthenic hydrocarbons such as, for example, squalane, squalene or dialkylcyclohexanes.
Emulsifiers
Suitable emulsifiers are, for example, nonionogenic surfactants from at least one of the following groups:
addition products of from 2 to 30 mol of ethylene oxide and/or 0 to 5 mol of propylene oxide onto onto fatty acids having 12 to 22 carbon atoms, onto alkyl phenols having 8 to 15 carbon atoms in the alkyl group, and alkylamines having 8 to 22 carbon atoms in the alkyl radical;
addition products of from 1 to 15 mol of ethylene oxide onto castor oil and/or hydrogenated castor oil;
addition products of from 15 to 60 mol of ethylene oxide onto castor oil and/or hydrogenated castor oil;
partial esters of glycerol and/or sorbitan with unsaturated, linear or saturated, branched fatty acids having 12 to 22 carbon atoms and/or hydoxycarboxylic acids having 3 to 18 carbon atoms, and adducts thereof with 1 to 30 mol of ethylene oxide;
partial esters of polyglycerol (average degree of self-condensation 2 to 8), polyethylene glycol (molecular weight 400 to 5000), trimethylolpropane, pentaerythritol, sugar alcohols (e.g. sorbitol), alkyl glucosides (e.g. methyl glucoside, butyl glucoside, lauryl glucoside), and polyglucosides (e.g. cellulose) with saturated and/or unsaturated, linear or branched fatty acids having 12 to 22 carbon atoms and/or hydroxycarboxylic acids having 3 to 18 carbon atoms, and adducts thereof with 1 to 30 mol of ethylene oxide;
mixed esters of pentaerythritol, fatty acids, citric acid and fatty alcohol as in German Patent 1165574 and/or mixed esters of fatty acids having 6 to 22 carbon atoms, methyl glucose and polyols, preferably glycerol or polyglycerol.
mono-, di- and trialkyl phosphates, and also mono-, di- and/or tri-PEG alkyl phosphates and salts thereof;
wool wax alcohols;
polysiloxane-polyalkyl-polyether copolymers and corresponding derivatives;
block copolymers, e.g. polyethylene glycol-30 dipolyhydroxystearate;
polymer emulsifiers, e.g. Pemulen grades (TR-1, TR-2) from Goodrich;
polyalkylene glycols and
glycerol carbonate.
The addition products of ethylene oxide and/or propylene oxide onto fatty acids, alkyl phenols or onto castor oil are known, commercially available products. These are homolog mixtures whose average degree of alkoxylation corresponds to the ratio of the quantitative amounts of ethylene oxide and/or propylene oxide and substrate with which the addition reaction is carried out. C12/18-fatty acid mono- and diesters of addition products of ethylene oxide onto glycerol are known from German Patent DE 2024051 as refatting agents for cosmetic preparations.
Typical examples of suitable partial glycerides are hydroxystearic acid monoglyceride, hydroxystearic acid diglyceride, isostearic acid monoglyceride, isostearic acid diglyceride, oleic acid monoglyceride, oleic acid diglyceride, ricinoleic acid monoglyceride, ricinoleic acid diglyceride, linoleic acid monoglyceride, linoleic acid diglyceride, linolenic acid monoglyceride, linolenic acid diglyceride, erucic acid monoglyceride, erucic acid diglycende, tartaric acid monoglyceride, tartaric acid diglyceride, citric acid monoglyceride, citric acid diglycende, malic acid monoglyceride, malic acid diglyceride and technical-grade mixtures thereof which may also contain small amounts of triglyceride as byproducts from the preparation process. Likewise suitable are addition products of from 1 to 30 mol, preferably 5 to 10 mol, of ethylene oxide onto said partial glycerides.
Suitable sorbitan esters are sorbitan monoisostearate, sorbitan sesquilsostearate, sorbitan disostearate, sorbitan triisostearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan dioleate, sorbitan trioleate, sorbitan monoerucate, sorbitan sesquierucate, sorbitan dierucate, sorbitan trierucate, sorbitan monoricinoleate, sorbitan sesquiricinoleate, sorbitan diricinoleate, sorbitan triricinoleate, sorbitan monohydroxystearate, sorbitan sesquihydroxystearate, sorbitan dihydroxystearate, sorbitantiihydroxy-stearate, sorbitan monotartrate, sorbitan sesquitartrate, sorbitan ditartrate, sorbitantritartrate, sorbitan monocitrate, sorbitan sesquicitrate, sorbitan dicitrate, sorbitan tricitrate, sorbitan monomaleate, sorbitan sesquimaleate, sorbitan dimaleate, sorbitan trimaleate and technical-grade mixtures thereof. Also suitable are addition products of from 1 to 30 mol, preferably 5 to 10 mol, of ethylene oxide onto said sorbitan esters.
Typical examples of suitable polyglyceryl esters are polyglyceryl-2 dipolyhydroxystearate (Dehymuls(copyright) PGPH), polyglycerol-3 diisostearate (Lameform(copyright) TGI), polyglyceryl-4 isostearate (Isolan(copyright) GI 34), polyglyceryl-3 oleate, diisostearoyl polyglyceryl-3 diisostearate (Isolan(copyright) PDI), polyglyceryl-3 methylglucose distearate (Tego Care(copyright) 450), polyglyceryl-3 beeswax (Cera Bellina(copyright)), polyglyceryl-4 caprate (polyglycerol caprate T2010/90), polyglyceryl-3 cetyl ether (Chimexane(copyright) NL), polyglyceryl-3 distearate (Cremophor(copyright) GS 32) and polyglyceryl polyricinoleate (Admul(copyright) WOL 1403) polyglyceryl dimerate isosteararate, and mixtures thereof. Examples of further suitable polyol esters are the mono-, di- and triesters of trimethylolpropane or pentaerythritol with lauric acid, coconut fatty acid, tallow fatty acid, palmitic acid, stearic acid, oleic acid, behenic acid and the like, which are optionally reacted with 1 to 30 mol of ethylene oxide.
Zwitterionic surfactants can also be used as emulsifiers. Zwittionic surfactants is the term used to describe those surface-active compounds which contain at least one quaternary ammonium group and at least one carboxylate and one sulfonate group in the molecule. Particularly suitable zwitterionic surfactants are the so-called betaines, such as the N-alkyl-N,N-dimethylammonium glycinates, for example cocoalkyldimethylammonium glycinate, N-acylaminopropyl-N,N-dimethylammonium glycinates, for example cocoacylaminopropyldimethylammonium glycinate, and 2-alkyl-3-carboxymethyl-3-hydroxyethylimidazoline having in each case 8 to 18 carbon atoms in the alkyl or acyl group, and cocoacylaminoethyl hydroxyethylcarboxy-methylglycinate. Particular preference is given to the fatty acid amide derivative known under the CTFA name Cocamidopropyl Betaine. Likewise suitable emulsifiers are ampholytic surfactants. Ampholytic surfactants are to be understood as meaning those surface-active compounds which, apart from a C8/18-alkyl- or -acyl group, contain at least one free amino group and at least one xe2x80x94COOH or xe2x80x94SO3H group in the molecule and are capable of forming internal salts. Examples of suitable ampholytic surfactants are N-alkylglycines, N-alkylpropionic acids, N-alkylaminobutyric acids, N-alkylaminodipropionic acids, N-hydroxyethyl-N-alkylamidopropylglycines, N-alkyltaurines, N-alkylsarcosines, 2-alkylaminopropionic acids and alkylaminoacetic acids having in each case about 8 to 18 carbon atoms in the alkyl group. Particularly preferred ampholytic surfactants are N-cocoalkylaminopropionate, cocoacyl-aminoethylaminopropionate and C12/18-acylsarcosine. Finally, suitable emulsifiers are also cationic surfactants which are particularly preferably those of the ester quat type, preferably methyl-quaternized difatty acid triethanolamine ester salts.
These preparations are preferably emulsions, preferably microemulsions or PIT emulsions.


A latch handle for doors and drawers for latching construction elements such as windows and doors. The latch handle may be located on the upper front edge portion of a drawer or the midportion of a door and may be manually opened by reaching under the front edge portion or trim member of the handle and pressing upwards on an actuator bar located inside the frame of the handle. The handle provides an aesthetic advantage in that the latch mechanism is concealed behind the front panel of the drawer or behind the door. The latching mechanism is made up of an actuator bar, a connecting link, and a hook. The hook is configured to engage with a keeper. At least one spring is fixedly attached to the frame for urging the actuator downwards and for carrying the hook into a reliable and secure engagement with the actuator.

1. Field of the Invention
The present invention relates generally to locks and more particularly to latch mechanisms adapted to regulate the locking of doors and drawers.
2. Description of the Related Art
Numerous apparatuses have been devised for providing enhanced locking mechanisms for various construction elements such as windows, doors, and drawers. Over the years, some of the most significant advances have involved the development of latch fasteners which are configured to cooperate with a fixedly secured striker member for selectively locking and unlocking a door or drawer. However, none of the references described hereinbelow provides a concealed latch mechanism which allows a user to easily open a door or drawer with one hand, while reliably and securely fastening the door or drawer when in closed position. For example, U.S. Pat. No. 5,403,139, issued to Slivon et al., presents a latch mechanism which includes a drawer pull at the front of the drawer. Under the top flange of the drawer pull is located a channel in which a latch bar is slidably movable from side to side. One end of the latch bar carries a hook which is spring loaded in the latched position. When it is desired to open the drawer, the user places his fingertips beneath the pull and against the latch bar and moves the slide bar to its unlatched position.
U.S. Pat. No. 3,239,298, issued to McCarthy, discusses a combination drawer pull and latch mechanism adapted to regulate the locking structure provided to secure a file drawer, or the like, within its associated cabinet structure. And U.S. Pat. No. 3,252,746, issued to Kafferlin, presents a filing cabinet and latching mechanism comprising a handle that incorporates a finger actuated latch mechanism by which the operator may release the drawer for withdrawal from a closed or confined configuration.
U.S. Pat. No. 4,302,037, issued to Nunez, relates to a latch fastener for construction elements such as windows, doors or the like, which includes a base member and a movable member, having a latching hook configured to cooperate with a fixedly secured striker plate for selectively locking and unlocking the window or door. The members have positioned therebetween several bearing balls which facilitate movement of the movable member and a latching hook relative to the base member between at least two positions corresponding to the locked and unlocked positions of the window or door.
U.S. Pat. No. 5,165,737, issued to Riegelman, discloses a housing with a top wall, upstanding posts between the upstanding parallel walls, and two upstanding posts between the upstanding walls on a line parallel with the walls. Each post extends through an elongated opening in a first bolt which is mounted slidingly in the housing for reciprocation toward first and second ends of the housing. The bolt is extendible beyond the second ends of the housing for engaging a window jamb when the housing is mounted on a sash of a tilt window that is fully seated in the jamb. The bolt is urged toward the second end by a spring in one of the elongated openings, bearing on the bolt and the post in the opening.
U.S. Pat. No. 5,292,191, issued to Slivon, relates to a latch mechanism including a trim member secured to a drawer pull at the front of the drawer. An actuator plate is located under the drawer pull and is disposed in a slot of a trim member on the drawer pull. A keeper is located on a side wall of the cabinet adjacent the hook. A hook is attached to one end of the actuator plate and is arranged to engage the keeper when the drawer is closed. The hook is releasable from the keeper by pivoting the actuator plate toward the drawer pull to open the drawer.
U.S. Pat. No. 5,603,535, issued to Antonucci et al., discusses a slam latch for securing a slidable window or door to a corresponding frame consisting of a housing including a base plate, a catch, and a keeper, wherein the catch is spring biased downward against the housing so as to become operatively engaged with the keeper when the door or window is moved to a closed position, causing the catch and keeper to become in juxtaposition to one another.
U.S. Pat. No. 5,775,140, issued to Hallsten, relates to a lock for cassettes for the construction of drawer cabinets, including a frame structure which carries a locking bar passing through an opening in a frontal part of the drawer, the bar being turnable and projecting from the inside of the frontal part. A handle connected to the bar is also included. At least one fixed projection is connected to the frame structure. The projection extends from the back side of the frontal part, the locking bar being, by turning the handle, movable between a locking turned-up position in which the bar engages behind an upper vertical flange of the frontal frame of the cassette and a liberating turned-down position in which the bar is located below the upper side of the projection.
U.S. Pat. No. 3,003,202, issued to Mendelsohn, discloses a window sash construction having a side member and a cross member interengaged by a lock to form a corner of the sash, the side member having a cross sectional configuration comprising a channel. The cross member ha s a cross sectional configuration comprising a third channel normal to two other channels, including a cross web and bottom wall forming opposite sides of the third channel and an outer wall interconnecting the sides.
Canadian Patent (CA 568,243), granted to Anthony, discloses a drawer for a filing cabinet or the like having a drawer body and a front plate, characterized in that a portion of the front plate is depressed to define a recessed handle formation. The depressed portion has an open side and a latch mechanism for the door mounted in spaced relation to the depressed portion and presenting a finger contact surface along the open side. And finally, British Patent (BR 866,109) granted to Jeeves, illustrates improvements in or relating to sliding drawers, shelves, or other sliding structures for cases, cabinets, or the like.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a handle for doors and drawers solving the aforementioned problems is desired.
The latch handle for doors and drawers according to the invention is directed to an apparatus for latching construction elements such as windows and doors. In the preferred embodiment of the invention, the latch handle is fixedly disposed on the upper front edge portion of each drawer of a cabinet and is manually actuated by reaching under the front edge portion of the handle and pressing upwards on an actuator bar located inside the frame of the handle. When a user presses upwardly on the actuator bar, at least one hook, which is fixedly attached thereon, is caused to be upwardly displaced from engagement with a keeper.
The invention provides an aesthetic advantage in that the latch mechanism is concealed behind the front panel of the drawer so that, when the drawer is viewed from the front, the viewer sees only the front portion of the handle and the front panel with the rectangular opening in which the handle sits. And because the latching mechanism is hidden, almost any kind of keeper may be used. The latching mechanism is made up principally of three operative parts including the actuator bar, a connecting link, and the hook. The elongated actuator bar is preferably L-shaped in cross-section and dimensioned to be received in the frame. The actuator bar also has an upper and lower leg, the upper leg having an upper surface for supporting at least one spring thereon.
In the preferred embodiment of the invention, the outer frame of the handle is generally C-shaped and elongated and includes an upper wall, a lower wall, and a back. The upper wall has an inner surface and defines a lip or trim member which extends substantially downwardly and inwardly to create a space within the frame for nesting the spring securely therein. The spring has an inner diameter, a top portion, and a bottom portion, the inner diameter being greater at the top portion than at the bottom portion, a shape which helps to insure the spring is stable and remains in place under the trim member. The spring is fixedly attached to the inner surface of the upper wall by a fastener.
The lower wall of the frame includes at least one aperture for receiving a bolt and for mounting the frame to a support structure. The back of the frame includes at least one elongated oval slot for receiving a bolt therethrough for interconnecting the hook to the actuator bar to allow the hook to slide along the length of the slot. The hook is configured to frictionally engage with the keeper. The spring acts to urge the actuator downwards, reversibly holding the hook in engagement with the keeper.
Accordingly, it is a principal object of the invention to provide a latch mechanism for doors and drawers which requires only one hand to use.
It is another object of the invention to provide a latch mechanism for doors and drawers which is substantially concealed.
It is a further object of the invention to provide a latch mechanism for doors and drawers which is reliable and secure.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.