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Office europeen des brevets (11) EP 0 763 61 6 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:ation: (51) int. CI.6: D04H 11/00 19.03.1997 Bulletin 1997/12

(21) Application number: 95306396.3

(22) Date of filing : 1 3.09.1 995

(84) Designated Contracting States: • Sumimoto, Kazushi AT BE CH FR GB IT LI NL Suita-shi, Osaka-fu (JP) • Taguchi, Junji (71 ) Applicant: DUSKIN COMPANY LIMITED Suita-shi, Osaka-fu (JP) Suita-shi, Osaka-fu (JP) (74) Representative: Senior, Alan Murray (72) Inventors: J.A. KEMP & CO., • Nagahama, Yuji 14 South Square, Suita-shi, Osaka-fu (JP) Gray's Inn London WC1 R 5LX (GB)

(54) Dust-control mat having excellent dimensional stability and method of producing the same

(57) A dust-control mat having excellent dimen- coupled to the base, wherein the floss-like nonwoven sional stability during the processing, good -erecting layer contains low-melting and is thermally property and excellent pattern expression, and a fixed after pile are implanted thereon. The inven- method of producing the same. The dust-control mat tion further provides a method of producing the dust- having excellent dimensional stability comprises a base control mat. in which a base fabric is composed of a or a nonwoven fabric and a floss-like nonwoven fiber layer

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Description fabric obtained by implanting piles on the base fabric is better long as much as possible from the standpoint of BACKGROUND OF THE INVENTION working efficiency, and a long starting fabric has been used in practice. Here, the long starting fabric must be (Field of the Invention) 5 rolled up or must be stacked being folded on a pallet. In this , however, the starting fabric is distorted or is The present invention relates to a dust-control mat permanently folded. and to a method of producing the same. More specifi- When the starting fabric is to be coated with latex, cally, the invention relates to a dust-control mat having in general, tension is given to the starting fabric in the excellent dimensional stability during the processing, 10 direction of width by using pin-like tenter, the starting favorable pile-erecting property and excellent pattern fabric is continuously coated with latex using a coating expression, and to a method of producing the same. In roll, followed by drying to diffuse the water in the latex. this specification, the dust-control mats refer to those In this case, however, the distortion of about 5 cm/m in mats that are laid in porches and entrances of shops, the direction of width could not be avoided due to exter- hotels, hospitals, offices and houses through where 15 nal force that is applied, small amounts of deviation in people go in and out, in order to remove dust and dirt the speed and tension on the right and left sides in the adhered to the bottoms of the shoes so that dust and direction of width, deviation in the starting fabric-starting dirt are prevented from entering into indoors. fabric junction, and error.

(Description of the Prior Art) 20 SUMMARY OF THE INVENTION

The dust-control mats are mostly taffeting mats The object of the present invention therefore is to having a front surface made of a fibrous material and a provide a dust-control mat free from the above-men- back surface made of a rubber or a resin. tioned defects inherent in the conventional dust-control There has heretofore been employed a method of 25 mats, and having dimensional stability during the producing mats by implanting piles on a base fabric, processing, favorable pile-erecting property and excel- applying, as required, a latex onto the non-pile surface, lent pattern expression, as well as to provide a method and adhering a solid rubber to the non-pile surface by of producing the same. the application of heat and pressure. According to the present invention, there is pro- The base fabric may generally be either a woven 30 vided a dust-control mat having excellent dimensional fabric or a nonwoven fabric, which is used as . stability comprising a base fabric, piles implanted on The latex of any type can be used such as SBR, one surface of the base fabric, and an elastomer back- NBR or the like. However, it has been known that NBR ing applied to the non-pile surface of the base fabric, is particularly favorable from the standpoint of resist- wherein the base fabric comprises a base of a woven ance against oils and resistance against washing. 35 fabric or a nonwoven fabric and a floss-like nonwoven Piles are implanted by a customary method such as fiber layer bonded to the base, said floss-like nonwoven taffeting, hooking, etc. fiber layer contains low-melting fibers, and the floss-like The piles to be implanted may be of any type such nonwoven fiber layer after the pile yarns are implanted as filaments of , acryl, , , or is thermally fixed. vinylon, or may be of the spun type. 40 According to the present invention, furthermore, The solid rubber (unitary type) is often adhered there is provided a process for producing a dust-control depending upon the type of the mat; i.e., the solid rub- mat having excellent dimensional stability comprising; a ber is cut into a regular size, and the uncured solid rub- step for preparing a base fabric by bonding a floss-like ber is adhered to the non-pile surface under the nonwoven fiber layer comprising staple fibers or fila- application of heat and pressure to effect the curing. 45 ment fibers in which low-melting fibers uniformly dis- In producing the mats, so far, a problem arises in persed to a base of a woven fabric or a nonwoven fabric that when a rolled starting fabric obtained by implanting by such means as needle punching or dot-like heat piles on the base fabric is treated with latex, is cut, or is adhesion; a step for preparing a starting fabric by adhered with a solid rubber, the mat is distorted, bent, implanting piles onto the base fabric by taffeting or and is permanently folded due to the external force so hooking; a step for partly melt-adhering the piles and applied to the starting fabric. In the dust-control mats the base fabric, and the fibers in the base fabric by heat- that have characters or straight patterns, such a distor- treating the starting fabric so as to melt or soften the tion or deformation that remains deteriorates the low-melting fibers; and a step for forming an elastomer appearance and quality of the goods. The thus distorted backing on the non-pile surface of the starting fabric. mat produces force that works to assume the original 55 According to the present invention, a distinguished straight form after it is repetitively used, washed and feature resides in that the floss-like nonwoven layer of dried. As a result, the whole mat is undulated and is the staple type or the filament type in which low-melting warped, causing the life (rental life) to be shortened. fibers are uniformly dispersed is bonded to the base of This will be described in further detail. The starting a woven fabric or a nonwoven fabric, and the thermoset-

2 3 EP 0 763 616 A1 4 ting is effected after the piles are implanted, making it more, partly low-melting fibers exist at a low concentra- possible to greatly improve dimensional stability, pile- tion, and it is difficult to obtain an adhesive force which erecting property and pattern expression. is so large as to adhere the piles and the base fabric First, the floss-like nonwoven fiber layer formed on together. If it is attempted to increase the adhesive force the base does not at all impair the implantation of piles s by increasing the ratio of the melt-adhering compo- on the base fabric but rather works to improve the pile- nents, the life of the starting fabric tends to be short- erecting property of the piles that are implanted. After ened due to an increase in the rigidity of the base fabric. the piles are implanted onto the base fabric, the floss- As will be described later, however, the present inven- like nonwoven fiber layer is thermally fixed, so that the tion makes it possible to obtain excellent adhering force low-melting fibers contained in the floss-like nonwoven 10 despite the melt-adhering components are contained at fiber layer are melted or softened so as to be thermally a low concentration. adhered, whereby the implanted structure is fixed and is According to the present invention, the base fabric stabilized contributing to improving dimensional stabil- can be favorably used either when it is composed of a ity, pile-erecting property and pattern expression of the nonwoven fabric or when it is composed of a woven fab- mat irrespective of the subsequent processing. 15 ric. When the melt-adhering components are added to That is, according to the present invention, the the woven fabric, in particular, loose components in the floss-like nonwoven layer of the staple type or the fila- outer periphery of the base fabric (base fabric compo- ment type in which low-melting fibers (hereinafter often nents in parallel with the outer peripheral sides of the referred to as melt-adhering components) are uniformly base fabric) are melt-adhered, too, preventing the fray- dispersed, is bonded to the base of a woven fabric or a 20 ing even after the mat is washed repetitively. nonwoven fabric by such means as needle punching or Particular effects obtained by the present invention dot-like heat adhesion, so that the low-melting fibers are are as described below. In the dust-control mats uniformly dispersed and adhered on the surface of the expressing characters such as "WELCOME" and the base fabric. Then, piles are implanted on the base fabric like and in the multi-color pile mats expressing designs followed by the heat treatment, whereby the heat melt- 25 drawn by the customers themselves, pile-erecting prop- adhering components are melted and softened to effec- erties are distinctly improved and the pattern expression tively accomplish the adhesion between the piles and is very improved compared with those of the prior art. the base fabric and among the fibers in the base fabric. That is, in the mat of the present invention, piles of dif- At this moment, it is allowed to impart dimensional sta- ferent colors infiltrate little in the boundaries, and the bility to the base fabric and, particularly, to impart resist- 30 contours become very distinct. ance against the external force such as rolled In the conventional mat on which piles of different packaging or folding of the starting fabric. colors are implanted and, particularly, in the taffeted cut- Adhesion is also accomplished between the pile mat, piles frequently fell on the portions of different implanted piles and the base fabric making it possible to colors due to the external force in the subsequent step, increase resistance against taking out the piles and, 35 causing the appearance to become poor. The piles fell hence, to obtain a starting fabric in which the base fabric not only during the production but also during the wash- and the piles are melt-adhered together exhibiting flexi- ing and regeneration. bility and elasticity-recovering property. According to the present invention, the base is pro- The base fabric has a double structure consisting of vided with a floss-like nonwoven fiber layer, and the low- the base of a woven fabric or a nonwoven fabric and the 40 melting points component are melted and softened by floss-like nonwoven fiber layer. With the melt-adhering the step of heat melt-adhesion after the piles are components being dispersed in the floss-like nonwoven implanted to effect the fixing by the heat adhesion, fiber layer, it was learned that there is almost no differ- whereby pile-erecting property is produced and is stabi- ence in the flexibility of the starting fabric that is melt- lized. treated before and after the heating. 45 The detailed mechanism is as described below. This makes a fundamental difference from the con- That is, when the base fabric is provided with the floss- ventional non-woven fabrics in which heat melt-adher- like nonwoven fiber layer containing low-melting fibers ing components are mixed. In the nonwoven fabrics, the followed by the implantation of piles, the piles are melt-adhering components are uniformly distributed implanted on the base driving off the low-melting fibers. over the whole base fabric, and the starting fabric after so As a result, the concentration of the low-melting fibers melt-adhered has a large hardness. When the starting increases in the outer peripheral portions of the piles by fabric is used as a base fabric for dust-control mats, an amount that corresponds to a volume by which the therefore, stress is concentrated in the starting fabric piles are implanted. due to folding as a result of the repetition of washing Then, owing to the subsequent heat treatment, the and drying, resulting in the occurrence of breakage and 55 outer peripheral portions of the piles are firmly fixed to the like and causing the life to be shortened. The reinforce pile-erecting property. Even through the sub- present invention, however, is free from such defects. In sequent processing steps, the boundaries are not dis- the conventional nonwoven fabrics in which the melt- turbed and, as a result, there is obtained a dust-control adhering components are uniformly dispersed, further- mat having favorable pattern expression.

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As the melt-adhering components, there can be layer consists of a high molecular thermoplastic polyes- used any known heat melt-adhering components of the ter and, particularly, a thermoplastic copolyester com- type of polyester, polyolef in, polyamide, or posed chiefly of a terephthalate or an the like in such a structure as filaments, core-sheath ethylene terephthalate. structure, or the like. It is desired that the blending ratio 5 As the low-melting fibers included in the floss-like is from 1 to 80% by weight in the floss-like nonwoven nonwoven fiber layer, there can be used any known fiber layer (willowed cotton-like fiber layer). melt-adhering yarns of low-melting polyester, polyolefin, polyamide or polyurethane. The low-melting fibers have BRIEF DESCRIPTION OF THE DRAWINGS a melting point lower than those of other fibers and, 10 generally, have a melting point of from 60 °C to 200 °C. Fig. 1 is a sectional view illustrating a dust-control Low-melting melt-adhering fibers are, usually, mat according to the present invention; and obtained by incorporating a copolymerizable compo- Fig. 2 is a sectional view illustrating the sectional nent in the fiber-forming . A preferred example structure of a base fabric on an enlarged scale. of the low-melting fibers can be represented by a low- 15 melting copolymerized polyester and, particularly, a DETAILED DESCRIPTION OF THE INVENTION poly(ethylene terephthalate/isophthalate). Another pre- ferred example of the low-melting fibers can be repre- Referring to Fig. 1 illustrating a dust-contro 1 mat of sented by a low-melting copolymerized polyamide. the present invention, the mat comprises a base fabric The low-melting fibers may be composed of the 1 , mat piles 2 taffeted on the base fabric 1 , and a rubber 20 above-mentioned low-melting copolymer alone, or may backing 4 applied to a non-pile surface 3 of the base be composite fibers of the low-melting copolymer and fabric. other ordinary fiber-forming , such as compos- Referring to Fig. 2 illustrating the structure of the ite fibers of a core-shell structure or a bimetal (side-by- base fabric in cross section, the base 1 comprises a side) structure. composite of a base 1 of a woven fabric or a nonwoven 25 It is desired that the low-melting fibers are mixed in fabric and a floss-like nonwoven layer 6 containing fila- an amount of from 1 to 80% by weight and, particularly, ments of the filament type or the spun type, the floss- from 5 to 50% by weight in the floss-like nonwoven fiber like nonwoven layer 6 being needle-punched 7 through layer. That is, when the amount is smaller than the the base. In the floss-like nonwoven fiber layer 6 are uni- above-mentioned range, the effect for stabilizing the formly dispersed low-melting fiber, and fibers in the 30 dimension becomes poorer than when the amount lies floss-like nonwoven fiber layer, base fabric and piles 2 within the above-mentioned range. When the amount are heat-adhered together. exceeds the above-mentioned range, on the other The base may be any one of the woven fabric, non- hand, the low-melting fibers lose flexibility. woven fabric or , and the fibers constituting At least one layer of the web for forming the f loss- it may be any such as polyester fiber, 35 like nonwoven fiber layer is placed on at least the upper polyamide fiber, , or ultra-high molecular side (pile side) or both sides of the base composed of a polyolefin fiber. It is most desired that the fibers are woven fabric or a nonwoven fabric and the base and the composed chiefly of a high molecular thermoplastic pol- floss-like nonwoven layer are fastened together as a yester and, particularly, polyethylene terephthalate or unitary structure by the needle punching based upon an ethylene terephthalate. 40 widely known means. The web remains in a very bulky As the polyester fibers constituting the base woven state which is maintained even after the needle punch- fabric, there can be used film-like yarns obtained by ing. strongly drawing a polyester film to increase its tensile It is desired that the fibers constituting the floss-like strength and dividing it into a predetermined width. nonwoven layer have sizes of single yarns of, generally, In the case of the woven fabric, there is no particu- 45 from 0.1 to 50 deniers and, particularly, from 1 to 20 lar limitation in the woven structure and a plain deniers, and the single yarns may be so-called fila- is sufficient. As required, however, or any other ments or staple yarns. It is desired that the floss-like modified weaving may be employed. In the case of the nonwoven layer is a guarding web but may be a spun- nonwoven fabric, there may be employed a spun- bonded web. The weight of the floss-like nonwoven bonded nonwoven fabric, a melt-blown nonwoven fabric so layer is, usually, from 20 to 500 g/m2 and is desirably or a combination thereof. over a range of from 5 to 200% of the base. Desirably, It is desired that the weight of the base is, generally, the concentration of the needle punching is, usually, not from 50 to 500 g/square meter though it may vary smaller than 1000 punches/m2. depending upon the weight of the mat. The pile yarns to be driven into the base fabric will It is desired that the floss-like nonwoven layer con- 55 be spun yarns of one or two or more kinds of cotton sists of any synthetic fiber such as polyester fiber, polya- fiber, rayon fiber, polyvinyl alcohol fiber, acryl fiber, mide fiber, acrylic fiber, or ultra-high molecular nylon fiber or other synthetic fibers, or may be multi-fila- polyolefin fiber in the same manner as described above. ment yarns. It is desired that the length of the taffeted It is, however, most desired that the floss-like nonwoven pile is, usually, over a range of from 3 to 20 mm. The pile

4 7 EP 0 763 616 A1 8 may be a cut pile, a loop pile, and may further be edges of the base fabric. crimped or non-crimped. Besides, the pile length may The adhesion by curing is better carried out at a be constant or different and may, for example, be a high temperature of from 1 00 to 200 °C under a pressure of cut-low loop, etc. The total thickness of the pile can be from 0.1 to 20 kg/mm2. greatly changed over a range of from 300 to 10000 5 The present invention can be applied to not only the denier. The piles can be driven under the known condi- mat obtained by adhering the rubber sheet to the start- tions, and the number of gauges may be from 3 to 20 ing fabric as a unitary structure but also to the mat of the and the number of stitches may be from 3 to 20 over an so-called separate type in which the mat is used being inch. placed on a separate rubber sheet base. The starting fabric obtained by implanting piles on 10 In this case, the latex of the elastomer may be the base fabric is then subjected to the heat fixing (heat applied onto the non-pile surface of the starting fabric treatment). The heat treatment is to melt the low-melting followed by curing. It is desired that the amount (solid fibers and is effected by heating the starting fabric at a component) of the latex is from 50 to 3000 g/m2. temperature higher than the melting point of the low- The pile yarns of the mat of the present invention melting fibers. The starting fabric is heat-treated such 15 work to adsorb and hold dust and dirt adhered to the that no distortion remains in the subsequent treatment. bottoms of the shoes. To further enhance this action, It is therefore important that the starting fabric is heat- the pile yarns may be coated or impregnated with a treated in a free state so that no locking force acts upon dust-adsorbing oil. As the dust-adsorbing liquid, there the starting fabric. It is desired that the heating is carried can be used mineral oils such asfluidized paraffin, spin- out using the hot-air circulation furnace, infrared-ray 20 dle oil, alkyl benzene oil, diester oil and castor oil, or heating or steam heating. The copolymerized polya- synthetic oils or plant oils, or aqueous dust-adsorbing mide and the copolymerized polyester have wet melting agents disclosed in Japanese Patent Publications Nos. points which are lower than their dry melting points. 1019/1978 and 37471/1978. In general, the adsorbing Therefore, the steam heating serves as an effective agent is applied in an amount of from 0.01 to 200 g/m2. heat-treating means. 25 As the rubber sheet that serves as a backing, there EXAMPLES can be used a variety of elastomer polymers such as nitrile-butadiene rubber (NBR), styrene-butadiene rub- The invention will now be concretely described by ber (SBR), chloroprene rubber (CR), polybutadiene way of the following Examples. (BR), polyisoprene (MB), butyl rubber, natural rubber, 30 ethylene-propylene rubber (EPR), ethylene-propylene- (Example 1) diene rubber (EPDM), polyurethane, chlorinated poly- ethylene, chlorinated , soft vinyl chloride Piles: BCF nylon resin, etc. It is, however, desired to use the nitrile-buta- 6 stitches/inch, gauge 5/32 diene rubber (NBR) from the standpoint of resistance 35 pile length 9 mm, weight 880 g/m2, cut piles against oils and weatherability. Latex: NBR latex 300 g/cm2 (solid content 46%) The rubber sheet that is formed may be blended with known blending agents such as sulfur or organic By using the following base fabrics A and B, sam- curing agent, cure promoting agent, softening agent, ples were prepared and were regarded to be anti-aging agent, , dispersant, plasticizer, coloring 40 agent and the like agents in known amounts. Examples 1-A and 1-B. In forming a mat as a unitary structure, the above- mentioned rubber composition is kneaded using a roll, The base fabrics A and B were taffeted with the Bumbury's mixer or the like. The composition is then above-mentioned pile constitution, and Example 1-B molded into a sheet and on which is then placed a taf- 45 was continuously heat-treated at 1 80 °C for 5 minutes. feted mat. The laminate is then heated and pressurized The above-mentioned starting fabric was coated in a pressurizing mold to effect the adhesion and curing with the latex, dried at 175 °C for 15 minutes, cut into a simultaneously. piece of 70 x 85 cm, and was heated and cured with the To increase the adhesion between the rubber sheet application of pressure together with an uncured rubber and the base fabric, the non-pile surface of the base so sheet having a thickness of 1 .8 mm at a temperature of fabric may be coated with a rubber latex of the same 170 °C for 15 minutes under a pressure of 10 kg/cm2. kind as the rubber sheet. Or, an adhesive agent such as an ethylene acetate/vinyl copolymer or an adhesion Base fabric A: polyester plain woven fabric 200 g/m2 promoting agent may be applied thereto in advance. Base fabric B: polyester plain woven fabric 1 50 g/m2 It is desired that the weight of the rubber sheet lies 55 *polyester cotton 100 g/m2 (weight within a range of from 500 to 4000 g/m2, and the rubber ratio of low-melting floss-like fiber, sheet and the base fabric are adhered together as a uni- 25%) tary structure in such a manner that the edges of the rubber sheet slightly protrude outwardly beyond the The polyester cotton was punch-worked with a nee-

5 9 EP 0 763 616 A1 10 die. stability comprising a base fabric, piles implanted The above-mentioned mat was cut and was meas- on one surface of the base fabric, and an elastomer ured for its deformation degree in the stitch and gauge backing applied to the non-pile surface of the base directions concerning 50 samples (Table 1). fabric, wherein the base fabric comprises a base of The above mat was placed on a place through 5 a woven fabric or a nonwoven fabric and a floss-like where 2000 people walk a day for three days and was nonwoven fiber layer bonded to the base, said then washed. This was repeated 40 times. After 10 floss-like nonwoven fiber layer contains low-melting times, a change in the pattern was measured relying fibers, and the floss-like nonwoven fiber layer after upon the number of piles that are infiltrating (Table 2). the pile yarns are implanted is thermally fixed. 10 2. A mat according to claim 1 , wherein the floss-like Table 1 nonwoven fiber layer contains the low-melting fibers Deformation A B in an amount of from 5 to 50% by weight. degree mm 15 3. A mat according to claim 1 or 2, wherein the low- Stitchina direction 3 0 mm mm melting fibers comprise low-melting copolymerized Gauae direction 34 mm 0.5 mm polyester fibers, low-melting copolymerized polya- mide fibers, or copolymerized polyolefin fibers.

20 4. A mat according to claim 1 , 2 or 3 wherein the floss- like nonwoven fiber layer is a fiber layer of the staple type or the filament type, and is coupled to the base Table 2 by the needle punching. A B A mat according to claim 1, 2, 3 or 4 wherein the After 1 time 55 piles 5 piles base has a weight of from 30 to 300 g/m2, and the After 10 times 83 piles 4 piles floss-like nonwoven fiber layer has a weight of from 50 to 90% of the base.

30 6. A process for producing a dust-control mat having A change in the pattern was measured based upon excellent dimensional stability comprising; a step the number of black piles that have infiltrated into white for preparing a base fabric by bonding a floss-like piles. nonwoven fiber layer comprising staple fibers or fil- ament fibers in which low-melting fibers uniformly (Results) 35 dispersed to a base of a woven fabric or a nonwo- ven fabric by such means as needle punching or From Table 1 , effect is obviously recognized in the dot-like heat adhesion; a step for preparing a start- deformation degree of the pattern of the starting fabric. ing fabric by implanting piles onto the base fabric by From Table 2, difference is obviously recognized in the taffeting or hooking; a step for partly melt-adhering number of piles that have infiltrated. Even after used 40 40 the piles and the base fabric, and the fibers in the times, no undulation or breakage is observed in the mat base fabric by heat-treating the starting fabric so as B. to melt or soften the low-melting fibers; and a step In the mat A, undulation of about 2 mm to 5 mm is for forming an elastomer backing on the non-pile observed at about three places on a side. In the mat B surface of the starting fabric. as described above, the pattern of the starting fabric is 45 not deformed, good pile-erecting property is main- tained, and undulation does not take place. According to the present invention, a floss-like non- woven layer of the staple type or the filament type in which low-melting fibers are uniformly dispersed, is 50 bonded to a base of a woven fabric or a nonwoven fabric and is, then, thermally fixed after the piles are implanted, making it possible to strikingly improve dimensional stability of the mat, pile-erecting property and pattern expression. 55

Claims

1. A dust-control mat having excellent dimensional

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European Patent EUROPEAN SEARCH REPORT APP'iCa,i0n office EP 95 30 6396

DOCUMENTS CONSIDERED TO BE RELEVANT Category Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE of relevant passages to claim APPLICATION (Int.CI.6) EP-A-0 466 308 (DUSKIN COMPANY LIMITED) 15 1,3,4,6 D04H11/00 January 1992 * whole document *

EP-A-0 604 897 (HOECHST CELANESE CORP) 6 1,3,4,6 July 1994 * column 3, line 30 - column 5, line 19 *

US-A-4 069 361 (KUMAR VI JAYENDRA) 17 January 1978 * whole document *

TECHNICAL FIELDS SEARCHED (Int.CI.6) D04H

The present search report has been drawn up for all claims Place of search Date of completion of the search THE HAGUE 20 March 1996 V Beurden-Hopkins, S CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document

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