US 3731352 A
A method of manufacturing a fibrous sheet including an application of a locational cutting operation to one or more superimposed fibrous webby masses at a stage preceding the usual needle punching operation thereon and a fibrous sheet manufactured thereby having an internal configuration wherein numerous fine fibers are three-dimensionally entangled with each other. The known islands-in-a-sea type synthetic filaments are advantageously used in the formation of the fibrous webby masses with later elimination of the sea component.
Claims available in
Description (OCR text may contain errors)
ilnited States Patent 1 Okamoto et al.
[ 51 May8,1973
 METHOD OF MANUFACTURING A FIBROUS SHEET  Assignee: Toray Industries, Inc., Tokyo, Japan  Filed: June 15, 1970  Appl. No.: 46,410
 US. Cl ..28/72.2 R, 19/6 [51} Int. Cl. ..D04h 18/00  Field of Search ..28/72.2, 76 T; 161/80; 19/.6
 References Cited v UNITED STATES PATENTS 3,500,504 3/1970 Oguchi et al. ..19/.6 X
3,551,265 12/1970 Jackson ..28/72.2 R 3,401,467 9/1968 Koester ..28/76 T X 3,484,916 12/1969 Johnstone ..28/72.2 R
FOREIGN PATENTS OR APPLICATIONS 741,579 11/1943 Germany ..19/.6
Primary ExizminerLouis K. Rimrodt Attorney-Robert E. Burns and Emmanuel J. Lobato  ABSTRACT A method of manufacturing a fibrous sheet including an application of a locational cutting operation to one or more superimposed fibrous webby masses at a stage preceding the usual needle punching operation thereon and a fibrous sheet manufactured thereby having an internal configuration wherein numerous fine fibers are three-dimensionally entangled with each other The known islands-in-a-sea type synthetic filaments are advantageously used in the formation of the fibrous webby masses with later elimination of the sea component.
13 Claims, 13 Drawing Figures PATENTED MAY 81973 SHEET 1 [1F 2 METHOD OF MANUFACTURING AFIBROUS SHEET The present invention relates to an improved method for manufacturing a fibrous sheet and the resulting product, and more particularly relates to an improved method for manufacturing a fibrous sheet through employment of a locational cutting operation applied to one or moresuperimposed fibrous webby masses prior to the usual needle punching application and a fibrous sheet made thereby made up of numerous three-dimensionally entangled fine fibers.
'The conventional'fibrous sheets such as non-woven fabrics are roughly classified into two typical types. In one type of fibrous sheet, fibers are massedinto a sheet form and are bonded or fused to-each other. In this type, no application of a punching operation to the massed fibers is employed and therefore, fibers are not entangled with each other to an appreciable extent in the internal configuration of the fibroussheet. For convenience in the ensuingdescription, this type of fibrous sheet is herein named as non-entangled type." Another type of fibrous sheet is made up of mutually, randomly and three-dimensionally entangled numerous fine'fibers. This entanglement of the fibers is effectuated by the application of the needle punching operation to the'fibrous mass. This type of fibrous sheet will hereinafter be named'as entangled type.
In the case of the non-entangled type fibrous sheet, the sheet is made up of numerous fine fibers generally in the continuous filamentary form. So, the sheet is provided with a lesser number of fiber ends extending out of the surface thereof. This absence of fiber ends on the surface degrades the handling quality of the sheet, which handling quality is mostly dependent upon the presence of numerous very fine fiber endson the surface. Further, the fibers are not entangled with each other to an appreciable extent in the internal configuration of the sheet and the fibers composing the sheet are liable to be separated therefrom by application of, for example, an-external abrasive force. In addition, the internal configuration of the sheet of this type is essentially different from that of the entangled type sheet. The componental fibers are amalgamated together through mutual bonding or fusing but are not entangled together to an appreciableextent. lnother words, some bonding or fusing agent is necessary to effectuate this amalgamation.
Further, it should be noted that the non-entangled type fibrous sheet contains less fibers running in the direction of the thickness thereof and this absence of the fiber causes paper-like handling of the end product. Poor entanglement of the componental fibers requires making the fibrous web rather compact in order to provide the product with enstrengthened binding. This results in undesirably hard touch of the end product especially when a thick construction is required.
On the other hand, in the case of the conventional entangled type fibrous sheets, the componental fibers are supplied in the form of short cut fibers. ln some instances, needle punching is exerted on a webby mass composed of fibers of non-continuous form. This is due firstly to a difficulty in the needle punching operation on a webby mass made up of continuous fibers. Such a needle punching operation is frequently accompanied with accidental breakage of the punching needles. Provided that long fibers are used in the formation of this entangled'type fibrous sheet, considerable difficulty in the punching operation practically results. This difficulty leads to the presence of fewer componental fibers running in the thickness direction of the sheet. So, even application of a buffing operation to the surface of the end product cannot assure raising of numerous fibers ends on the surface and the obtained end product lacks the suede like surface touch. In the needle punchingoperation, the webby mass of short fibers is pierced by a plurality of hooked punching needles so that the componental fibers are entangled with each other in a direction inclined or perpendicular to the surface of the mass. Therefore, the hooked punching needles tend to accidentally break through their hooking. of the fibers when the componental fibers are supplied in a continuous filamentary form. This frequent accidental needle breakage has formed a bar in the practical manufacture of the fibrous sheets such as non-woven fabrics using continuous filamentary fibers.
In order to overcome this difficulty, one of the conventional processes involves crimping the drawn filaments, cutting the crimped filaments after a pertinent oiling operation into a staple form, forming a webby fibrous mass by passing thus obtained staple fibers through cards, cross-lappers and random webbers and needle punching the thusly obtained webby fibrous mass or masses. However, this multiple staged process is accompained with an inevitable increase in the production cost of the obtained products. Further, when islands-in-a-sea type fibers are used, this type of process tends to cause undesirable exposure of the island components for example during the carding action and such exposure of the island component tends to form a bar in the smooth punching'operation. There have been no creative methods for attaining desirable modern techniques can assure success in cutting the filaments into short fibers of any desired fiber length while processing the filaments at high speeds in a range from 3,000 to 7,000 MPM.
A principal object of the present invention is to provide a simple method for manufacturing a fibrous sheet of a three-dimensionally entangled internal configuration directly from continuous filamentary fibers with lessened malfunctions such as punching needle breakage or damage.
Another object of the present invention is to provide a fibrous sheet durable against various types of external load applications and having an excellent dimensional stability even through long-time use under severe conditions.
In order to attain the above-recited objects, the method of the present invention is characterized by firstly forming a fibrous webby mass from a plurality of continuous filamentary fibers and secondly, applying a locational cutting operation to one or more superimposed fibrous webby masses so that the resultant fibrous sheet is provided with a three-dimensionally entangled internal configuration. Extremely fine fibers composing the resultant fibrous sheet can be obtained by using the islands-in-a-sea type fibers as the continuous filamentary fibers.
Further features and advantages of the present invention will be made more apparent from the following description including some examples, reference being made to the accompanying drawing, in which;
FIGS. 1A to U are fragmentary front views of the cutting blades used in the locational cutting operation in the method of the present invention,
FIG. 2 is a schematic representation of a transversal cross section of one embodiment of the islands-in-a-sea type fibers preferably used in the manufacturing of the fibrous sheet of the present invention,
FIG. 3 is a schematic side view of a device for measuring the loop strength of the fibers used in a particular case of the method of the present invention,
FIG. 4 is a graphical representation of the relationship between the punching density and the number of needle breakages during the needle punching operation.
The continuous filamentary fibers usable in the manufacturing method of the present invention can be supplied in the form of any of the conventionally known filaments such as filaments manufactured in the melt-spinning system, dry spinning system or wet spinning system. Further, the fibers can be supplied in 'the form of composite filaments, polymer blend type filaments, emulsion spinning type filaments, textured crimped filaments or islands-in-a-sea type filaments. In this connection, however, the process of the present invention is most desirably and advantageously employed in combination with the manufacturing process of the melt-spinning type filaments, polymenblend type filaments, composite filaments and islands-in-a-se a type filaments. This is because the extruded filaments in the melt spinning process can be taken up at speeds from 3000 to 8000 MPM with sufficient orientation effect and such a high speed processing of the filaments is well conformable to the relatively high speed manufacturing of the fibrous sheet of the present invention. Further, the configurationally modified filaments procured by the above-mentioned techniques well contribute to the enrichment of the bulkiness of the resultant fibrous sheet.
As to the mechanical nature of the continuous filamentary fibers, their breaking elongation should advantageously be l2 percent or larger, more particularly it should be 20 percent or larger in the condition before being cut into short fibers. In case the breaking elongation is smaller than 12 percent, the resultant fibrous sheet is provided with a very hard handling quality such as a board and further, wrinkles are liable to develop over its surface during use thereof.
The above-recitedmaterial filamentary fibers may advantageously be made up of such polyamides as nylon 6, nylon 66, nylon 6l0, nylon 7, nylon 8, nylon 9, nylon ll or nylon l2; such polyesters as polyethyleneterephthalate, polybutylene-terephthalate or polyoxyethylene-benzoate; such polyolefins as polyethylene or polypropylene; such polymers as polyvinyl-alcohol polyacrylonitrile, polystyrene or polyurethane; or the derivatives or copolymers of the above-recited polymers. Such additives as dyestufis,
extruded filaments, this distribution of the filaments is carried out using pneumatic flow and/or electro-static force. For a better formation of the webby mass, it is recommended to effect any pneumatic suction force from the underside of the collector belt. At this stage of the filaments distribution, it is also desirable to mix such substances as water, oiling agent, sizing bonding agent or filaments of low melting point to the webby mass so as to mitigate the undesirable scattering and flying of the distributed filamentary fibers outside the collector belt. In case the filaments are already provided with potential crimps, crimp development can be performed during or after this webby mass formation, thereby entanglement of the fibers composing the mass can be further increased. When required, the crimp development can be carried out in the'later stage of the fibrous sheet manufacturing.
It is further recommended to form this webby mass from several different kinds or types of fibers. This is also done by amalgamating two or more sets of webby masses of different kinds or types in a superimposed disposition. By the suitable introduction of the abovedescribed amalgamation of different kinds and/or types of fibers or webby masses, the resultant bending characteristics of the obtained fibrous sheet can be adjusted as desired.
After completion of the above-explained webby mass formation, the webby mass obtained is next subjected to a locational cutting operation. In this connection, two or more webby masses may be fed in a superimposed disposition. By this application of the locational cutting to the webby mass or masses, continuous filamentary fibers in the mass or. masses are cut into staple fibers so that the subsequent punching operation can be performed smoothly. This cutting is usually doneby using needles having blade-formed points or piercers having blade-formed points or saw-teethed points. Knife-edged cutters can be used, also. Piercing the above-described cutting device can be performed at random locations of the webby mass. When any particular esthetic effect is required on the surface of the resultant fibrous sheet, the cutting is done at purposelyselected locations. It is not always necessary that the cutting devices pierce through the webby mass perfectly. That is, in some instances, it is rather desirable for the resultant fibrous sheet to contain some extent of uncut continuous filamentary fibers. Presence of such survived continuous filamentary fibers within the resultant fibrous sheet contributes to the enrichment of the tensile strength of the obtained product.
In order to mitigate the heterogeneity of the strength through the configuration of the obtained fibrous sheet, it is advantageous to effectuate this locational cutting operation in a direction inclined to the surface of the webby mass, in other words, in a direction not perpendicular to the surface of the webby mass. By this employment of the inclined directional cutting, cut points ofthe fibers can be randomly and rather uniformly distributed throughout the internal configuration of the webby mass. This inclined directional cutting is in general carried out in two ways. In the first method, the cutting devices obliquely pierce into the webby mass placed in a horizontal disposition whereas, in the second method, the cutting devices vertically pierce into the webby mass placed in an inclined disposition. In both cases, it is preferable to place the webby mass in a stationary disposition and move the cutting devices through a porous guide plate.
Several examples of the cutting blades used for this locational cutting operation are shown in FIGS. 1A to 11.
Subsequent to the locational cutting operation, the webby mass is processed to a usual needle punching stage, which needle punching is performed in a fashion conformable to the users requirement for the end product.
It should be understood that various modifications can be derived from the above-described principal method for manufacturing the fibrous sheet. For example, a needle punching of a moderate extent can be applied to the webby mass prior to the application of the locational cutting. By this application of moderate needle punching, the continuous filamentary fibers still in a non-entangled condition can be displaced rather freely in the configuration of the webby mass. This disordering of the componental fibers is helpful in enhancing the uniform distribution of the cut points of the fibers in the configuration of the mass after the application of the locational cutting operation. After the cutting operation, a final needle punching is performed. When required, this combination of needle punching and locational cutting can be repeated several times.
In another modification, the above-mentioned locational cutting can be attained by utilizing the usual needle punching operation itself. In this case, the material fiber should preferably have a loop strength of from 0.2 to l-.5 g/denier, or more preferably from 0.4 to 1.2 g/denier. When the loop strength exceeds this upper limit value, increased needle breakage will occur whereas, when the loop strength is smaller than this lower limit value, the obtained fibrous felt cannot be provided with sufficient strength.
In this connection, the loop strength of the used fiber is measured using the measuring device shown in FIG. 3, wherein a pair of looped fibers of 2.5 cm loop length are hooked with each other and the respective fiber loops and 11 are pulled in the opposite direction by the respective clamps l2 and 13. At the breakage of the fiber loops, the strength of the fiber per unit denier is recorded.
As is briefly mentioned in the foregoing description, the islands-in-a-sea type fibers are very desirably used as the filamentary fibers in the method of the present invention.
The term islands-in-a-sea type fibers as herein used is defined as follows in reference to the illustration shown in FIG. 2, wherein a perticular transversal cross section I of the fiber is composed of a continuous sea component 2 and a plurality of island components 3 distributed at random within the sea component 2. Some of the island components 3 are wholly embraced by the sea component 2 whereas some of the island components 3 may be only partly embraced by the sea component 2. The island components 3 are elongated along the lengthwise direction of the fiber in such a manner that the number of the island components within a particular transversal cross section is the same with that in other cross sections remotely away from that particular cross section by 5 meters or longer. The number of the island components should be 5 or more, desirably 10 or more and further desirably 15 or more. The transversal cross-sectional profile of the fiber may be round, square, polygonal, fiat square or elliptical.
As to the number of the island components within the particular transversal cross section of the fiber, it should be 5 or more as above-mentioned. When this number is fewer than 5, frequent needle breakage during the punching operation tends to result. Further, this causes relatively hard and rough handling quality of the fibrous sheet obtained.
The fineness of the island component should be in a range from 0.001 to 0.5 denier. Fineness of the island component exceeding 0.5 denier oftentimes causes frequent needle breakage in the punching operation and roughened surface touch with degraded handling quality of the resultant fibrous sheet.
The percent total weight content of the island component in the islands-in-a-sea type fiber should preferably be 55 percent or smaller, more desirably be 30 percent or smaller. In case the content exceeds 55 percent, it becomes difficult to spin the fiber continuously for a long time, frequent needle breakage results in the punching operation and the softness of the obtained fibrous sheet is oftentimes degraded.
In addition to the already recited polymeric substances, the island component may be made up of such fiber formable polymeric substances as polyvinyl acetate, cellulose and its derivative, polyether, polycarbonate or polyalkyl substituted phenyleneoxide.
As to the mechanical property of the sea component, it is desirable that the loop strength is 1.5 g/denier or smaller for a filament of l to 6 denier fineness and made up of the polymeric substance composing the sea component. If a polymeric substance of larger loop strength is used, it results in frequent needle breakage and damage during the punching operation.
The kind and type of polymeric substance composing the sea component should preferably be so selected posed of threedimensionally entangled numerous bundles of extremely fine fibers converted from the island components. Removal of the sea component can be done by using solvents such as, for example, formic acid, sulfuric acid, benzene, xylene, toluene, dimethyl forrnamide, dimethyl sulfoxide, acetone, water, alcohol or alkaline solution.
in a modified embodiment of the method of the present invention, the fibrous sheet made up of the islands-in-a-sea type fibers is impregnated with a polymeric substance of a water soluble nature after the completion of the cutting and the needle punching operations. Next, the sea component is removed from the fibrous sheet by the solvent application.
Further, the fibrous sheet is impregnated with polymeric substance of elastic nature. Upon or after the solidification of the elastic polymeric substance, the water-soluble polymeric substance is removed from the fibrous sheet. I
The merit and advantage ascertained through the employment of the method of the present invention is as hereinafter described in detail.
In the first place, because the cutting operation is applied to the webby mass prior to the needle punching operation, the subsequent needle punching can be carried out smoothly with lessened operational troubles such as needle breakage or damage. Further, by suitably changing the manner of cutting, the functional property of the resultant fibrous sheet can be adjusted in conformity to the requirements of the end use thereof. Owing to the smoothness in the operation, a sufficient needle punching effect can be expected and the undesirable partial separation of the fibrous sheet during the actual use can be effectively obviated.
Next, owing to the sequentially continuous manufacturing process of the present invention, the work required for manufacturing the fibrous sheet can be remarkably reduced and simplified.
Thirdly, use of the islands-in-a-sea type fibers in the manufacturing of the fibrous sheet introduces further advantages. At the stage of the webby mass formation, fibers are supplied in the form of continuous filaments and this considerably contributes to the lessening of the unevenness in thickness of the obtained webby mass. At the needle punching stage the sea component is not yet removed from the webby mass and the individual islands-in-a-sea type fiber still retains its relatively large fineness. This assures an effective punching effect and the fibers are well entangled with each other. After the removal of the sea component, the fibrous sheet is composed of three-dimensionally entangled numerous bundles of extremely fine fibers converted from the island components. This particular internal configuration of the fibrous sheet has excellent mechanical properties with enhanced handling quality and surface touch. Further, the use of the islands-in-a-sea type fibers in the present invention is far more advantageous over the use of the known blend fibers. In the case of the blend fibers, removal of the sea component merely results in disintegration of the entire fiber configuration whereas, in case the island components are removed therefrom, no extremely fine fibers such as that ob tained in the present invention can be acquired.
The fibrous sheet of the present invention is suited for such uses as floor coverings, interior decoration, artificial leathers, felts for paper making, warmth retainers, shock absorbers, belts or bags.
The following examples are illustrative ofthe process of the present invention but are not to be construed as limiting the same.
EXAMPLE 1 A copolymer of styrene with acrylonitrile was used as the sea component forming material whereas nylon 6 was used as the island components forming material. Sixty parts by weight of the former was amalgamated with 40 parts by weight of the latter. Both material chips were molten at 285C in respective melters of the spinning devices and both molten material were introduced, via gear pumps, to a common spinning terminal having a nozzle particularly designed for this purpose. The amalgamated materials were extruded through the nozzle in the form of islands in-a-sea type filaments, each filament containing 16 island components in its transversal cross section. The extruded filaments were taken up at a speed of 1,000 MPM by the first godet roller and subsequently, at a speed of 3,400 MPM by the second godet roller. A heater plate maintained at a temperature of 1 10 i 5C was provided in between the two rollers. The individual filament was thereafter introduced through an ejector utilizing a highly pressured air flow and fibers of from 2 to 3 denier were obtained. Being entrained in this pressured air flow, the thusly obtained fibers were distributed in a webby form over a conveyer belt. At this moment, an aqueous solution of adhesive oiling agent was added to the fibrous mass for anti-static purposes. The conveyer belt moved so that the unit weight of the web should be 350 g/m and the web was processed through press rollers during movement of the belt. The width of the web was controlled at about 40 cm. Numerous lanceformed cutting needles having blades at their sharpened points (see FIG. 1A) were mounted on a porous board and the board was placed for several times in a pressure contact with the fibrous web for cutting purposes. Cutting was performed at a cutting density of in average from 5 to 10 times per 1 cm area. Pneumatic suction was effected from underneath the belt for dry- I ing the fibrous web. Subsequently, the fibrous web was subjected to needle punching at a density of 450 needles per 1 cm area. The needle punching could be performed very smoothly without any needle breakage and the obtained fibrous sheet was provided with desirable handling quality. The thickness of the obtained fibrous sheet under 5 g/cm load application was 4.36 mm. The apparent density of the fibrous mass calculated basing upon this value was 0.080 g/crn and the fibrous sheet in this condition was provided with appreciable resiliency. The loop strength of the fiber before cutting was 3.6 g/denier and the elongation thereof was 27 percent.
The obtained fibrous sheet was impregnated with 10 percent polyvinyl alcohol aqueous solution and dried. Removal of the sea component was performed by immersing the fibrous sheet in a benzene bath. After drying, the sheet was further impregnated with dimethylformamide solution of polyurethane, whose solidification was done in a water bath. Both surfaces of the obtained fibrous sheet were subjected to a buffing operation by sand paper and the property of the resulted fibrous sheet was as is shown in the following table.
COMPARATIVE EXAMPLE 1 In the process of the preceding example, the cutting operation was omitted and the fibrous web was directly subjected to the needle punching operation. When the punching density was increased up to 100 puncheslcm 13 needle breakage per 1 m area were caused. In order to examine the effect by the punching condition, the depth of the needle piercing was changed from 6 to 15 mm and it was confirmed that increase in the piercing depth dilutes the substantial punching effect. So, the needle piercing depth is preferably in a range from 8 to 12 mm. But this needle piercing depth tends to be accompanied with frequent needle breakage during the punching operation.
For the purpose of comparison with the result in the preceding example, the needle punching operation was carried out at a punching density of 450 punches/cm.
The resulted fibrous sheet was provided with tight superficial configuration but with relatively slackened internal configuration. Therefore, the product was provided with poor resilience against bending and application of bending operation to the product developed paper-like creases on its surface. The apparent density of the resultant fibrous sheet was 0.043 g/cm, which value apparently showed the relatively slackened internal configuration of the obtained product.
EXAMPLE 2 The islands-in-a-sea type fibers different in their composition from those used in Example 1 were used. That is, a blend of 95 percent by weight of polystyrene with percent by weight of polyethylene-glycol was used as the sea component forming material and polyethyleneterephthalate was used as the island components forming material. Sixty-five parts by weight of the former was amalgamated with 35 parts by weight of the latter in the islands-in-a-sea disposition and a fibrous sheet was manufactured in a manner similar to that in Example 1.
The loop strength of the fiber used was 1.2 g/denier. In the application of the needle punching, the needle piercing depth was changed as in case of the comparative example 1. Three needle breakages per 1 m surface area of the fibrous sheet were resulted at the needle piercing depth of 14 mm. However, increase of the piercing depth to 15 mm resulted only 1.3 needle breakages per that unit surface area.
kg/cm". However, after removal of the polystyrene component through immersion in a carbon tetrachloride bath, the felt was provided with'a strength of 7.36 kg/Cm From this result, it is supposed that the polystyrene component contributes less to the strength of the entire fibrous felt or that the polystyrene component rather functions to lower the strength of the entire fibrous felt.
Application of needle punching operation to such a weak felt causes undesirable breakage of the componental fibers. In order to obviate such undesirable fiber breakages, punching needles having particular blades should be used in this case. Needle breakage during the punching operation can be obviated by merely lowering the strength of the componental fibers. In the process of the present invention, together with making the punching operation do the part of fiber cutting, the relative fiber strength is increased by removing the negative component after the completion of the fiber entanglement and the end product is formed of fibers of extremely fine nature. The end product can thusly be provided with uniformly interlaced and strengthened internal configuration.
EXAMPLE 3 The islands-in-a-sea type fibers were composed of parts by weight of a blend of percent by weight of polystyrene with 5 percent by weight of polyethyleneglycol and 35 parts by weight of nylon 6. The manufacturing process was basically the same with that employed the preceding example with the following exceptions.
Take-up speed of the first godet roller in MPM 500 Take-up speed of the first godet roller in MPM 1450 Temperature of the heater plate in C 1 l0 120 Width of the web on the conveyer belt in cm 35 Unit weight of the web in g/cm 458 Punching density in needles per 1 cm area 1,000
The needle punching could be practiced without any trouble. The loop strength of the fibers was 1.14 g/denier. The percent compression of the needle punched felt under 20 g/cm load application was 31, which fact proves that the felt was provided with high density.
The fibrous sheet now in a felt form was next impregnated with 15 percent polyvinylalcohol aqueous solution, softly squeezed by rollers and dried at C. Then, the fibrous sheet was washed in a trichroethylene bath for removal of polystyrene and was dried in a manner not to lower its bulky nature. The fibrous sheet was further impregnated with a solution of polyurethane in dimethylformamide and immersed in a water bath for coagulation. Thereafter, the fibrous sheet was immersed in a hot water bath for removal of polyvinylalcohol and dried. By the subsequent application of buffing, raising and rubbing, the fibrous sheet was converted into a deer skin-like fabric having remarkable softness, air permeability and durability against bending fatigue.
EXAMPLE 4 Instead of the material filament used in Example 3,
islands-in-a-sea type filaments composed of 50 parts by weight of polystyrene as the sea component and 50 parts by weight of polyethylene-terephthalate as the islands were used. The loop strength of the fiber was 1.5 g/denier. The fibrous sheet was manufactured from these filaments in a manner the same as that in Example 3 with no needle breakage during the needle punching operation. The final product was also provided with excellent qualities as in the case of the preceding examples.
COMPARATIVE EXAMPLE 2 Islands-in-a-sea type filaments were composed of 65 parts by weight of nylon 6 and 35 parts by weight of polyethyleneterephthalate and the manufacturing of the fibrous sheet was carried out in a manner similar to that employed in Example 3 with the only exception being that the extruded filaments were taken up at a speed of 500 MPM by the first godet roller and at a speed of 1,750 MPM by the second godet roller.
Omission of the cutting operation was accompanied with undesirable frequent needle breakage to such an extent that needle punching could not be practiced and the resultant fibrous sheet was provided with degraded functional properties. The loop strength of the fiber was 5.7 g/denier.
COMPARATIVE EXAMPLE 3 In the composition of the islands-in-a-sea type filament used in Example 3, nylon 6 was replaced by polypropylene and a fibrous sheet was manufactured in a similar manner with omission of the cutting operation. Frequent needle breakage during the needle punching operation together with the degraded quality of the end products resulted.
The loop strength of the fiber was 2.5 g/denier. The needle punching was accompanied with considerably frequent needle breakage and the needle punching could hardly be performed at a density over 300 punches/cm. The obtained non-woven fabric was provided with considerable bulkiness and the density thereof was 0.033 g/cm. Its strength was a mere 1.95 kg/cm EXAMPLE 5 The content ratio of nylon 6 in the islands-in-a-sea type filaments of Example 3 was changed variously and the loop strength of the resultant fibers was measured for the respective content ratio (percent by weight) as is shown inthe following table.
Sample Percent by weight Loop strength of the number of content ratio resultant fiber in of the island g/denier. component.
Webs are produced from the respective fibers in a manner the same with that employed in Example 1 and the obtained web of 30 cm. width and I in. length was subjected to a needle punching operation at a needle piercing depth of l2 mm. and a punching pitch of mm. using punching needles of 36 count without application of particular draft. The relationship obtained in between the selected punching density and the number of needle breakages per 1 m surface area of the felt was as is shown in FIG. 4. As is clearly seen from the result shown in the drawing, the number of the needle breakages increases suddenly at the loop strength of 1.5 g/denier. The larger is the frequency of the needle breakage, the lower is the quality of the end product. It was observed that, when the frequency of the needle breakage increases, there is a separation of the nylon 6 island components from the polystyrene sea component and the extremely fine nylon 6 fibers are exposed on the surface of the fiber without being cut. This proves the fact that the increase in the strength of the fiber makes the cutting by the needle punching more difficult.
EXAMPLE 6 As in the usual case, polyethyleneterephthalate was melt spun into fibers and the produced fibers were, with drawing in between the godet rollers, taken up by the ejector for dispersion on the conveyer belt. The obtained fiber had a fineness of 2.3 denier and a loop strength of 4.2 g/denier. The webby mass of fibers on the conveyer belt was subjected to a thermal pressing at atemperature of 160C and, next, subjected to a cutting operation by the cutting blades such as shown in FIG. 1C planted in a board moving up and down. The density of this locational cutting was 7 punches/cm? The locationally cut web was further subjected to a subsequent needle punching operation at a punching density of 1200 punches/cm and a needle piercing depth of 10 mm. using punching needles of 40 count. The frequency of the needle breakage was 2.3 per 1 in surface area of the web.
The obtained felt was provided with a density of 0.152 g/cm, a unit weight of 386 g/cm and a strength of i7 kg/cm and was further provided with excellent resilience particularly suited for use as padsfor base material for carpets. When the web was subjected directly to the needle punching without application of the preliminary locational cutting, a punching density of 50 punches/cm was accompanied with up to 19 needle breakages per 1 m surface area, which frequency was too large to carry the punching operation further.
EXAMPLE 7 In Example 2, polystyrene was used as the sea component at a content ratio of 50 parts by weight and the loop strength of the fibers was 2.8 g/denier. A web composed of this fiber was subjected to a needle punching on a needle punching machine having needleshaped blades planted together with needles in the needle board. 10 in length of the web was processed through this needle punching simultaneously with cutting at a punching density of 700 punches/cm and only seven needle breakages resulted.
The obtained felt was heated within a dry atmosphere of C temperature for 10 minutes and was impregnated with 20 percent polyvinylalcohol aqueous solution of 50C temperature. Drying was performed at a temperature of C. After this drying, the imparted polyvinylalcohol was mostly contained within the superficial part of the felt and the inner part of the felt was provided with less of this substance. The thusly obtained felt was sliced at the middle thickness portion in the surface direction and the sliced felt was impregnated with 15 percent dimethylformamide solution of polyurethane. solidification of the polyurethane component was performed by perfectly washing the felt with hot water. Both surfaces of the sliced felt were subjected to a raising operation, thereby one of the raised surface was provided with numerous shortly raisedresilient fiber ends and the other of the raised surfaces was provided with raised fiber ends of soft touch. The obtained felt was provided with a particular softness together with a very natural leather like handling quality.
EXAMPLE 8 Seventy parts by weight of nylon 6 and 30 parts bybelt. The fineness of thusly obtained fibers were in a range from'0.6 to 4.0 denier and its average loop strength was 3.2 g/denier. A web of 320 g/m unit --weight was produced of these fibers and the web was subjected to a locational cutting operation at a punching density of 23 punches/cm using punching needles such as shown inFIG. 1A. In succession the 10- cationally cut felt was subjected to a needle punching operation at a punching density of 1,000 punches/cm using needles of 40 count and only 0.92 needle breakages/m resulted. The density of the obtained felt was 0.1 17 g/cm, which value shows that the obtained felt was provided with a dense internal configuration and enhanced resilience. When the locational cutting operation was .omitted, there resulted considerably =frequent needle breakages at a punching density of 350 punches/cm and the density of the felt was 0.033 g/cm", which-value apparently shows that the obtained felt was provided with undesirably slackened construction.
EXAMPLE 9 In Example 8, polystyrene was substituted for nylon :6. The fineness of the obtained fiber was in average 1.7
denier and the loop strength thereof was 0.78 g/denier. A web of 550 g/m unit weight was produced of these fibers. The obtained web was subjected to a needle punching at a punching density of 300 punches/cm and a needle piercing depth of 12 mm using needles of 32 count. Next, the punched felt was further subjected to an additional needle punching operation using punching needles of 40 count until the total needle punching density became 1200 punches/cm. Except for a few needle breakages at the initiating stage of the punching operation, the whole needle punching operation could be performed without any particular malfunctions. The obtained felt was provided with a density ofO. l 57 g/cm The felt was impregnated with 10 percent aqueous solution of polyvinylalcohol 4 and, after drying, was further immersed into a trichloroethylene bath. Next, the felt was further impregnated with dimethylformamide solution of polyurethane partly containing amino acid resin, solidified and dried. One hundred and fiftythree parts by weight of polyurethane was imparted to I00 parts by weight of fibrous component. The obtained fibrous felt had a strength of 51 kglcm an elongation of 141 percent a stress at percent elongation of 36 kg/cm and a very natural leather like soft handling quality.
In the practical utilization of the method of the present invention, it is also desirable to use polymer blend filaments which are obtained by blend spinning at least two component polymers. In this case, it is desirable that, in the internal configuration of the filaments, at least one of the components should elongate more than 1 cm. along the length of the filament.
Although the above-described fibrous sheet composed of the islands-in-a-sea type filamentary fibers provides many advantages over the conventional fibrous sheets such as artificial leather or non-woven fabrics, it is still inferior in its internal configuration, dimensional stability and easiness in its processability when compared with the natural collagen fibers. This inferiority of the islands-in-a-sea type filamentary fibers can be improved by application of a pertinent thermal treatment to the webby mass after the entanglement of the fibers in the mass. In this thermal treatment, the internally entangled webby fibrous mass is subjected to a thermal application at temperatures higher than the drawing temperature of the fibers or higher than the crystallization or compactness temperature, temperature of the island component forming material for a period longer than the drawing time. In this connection, it is especially desirable to form the webby mass from the fibers containing the island components in an imperfectly crystallized state. Then, by the application of the above-described thermal treatment, the crystallization of the island components is well promoted, thereby the fibers shrink in the internal configuration of the webby mass for enhancing the compactness of the entangled fibrous configuration of the webby mass.
What we claim is:
1. An improved method of manufacturing a nonwoven fibrous sheet comprising, in a sequential combination, forming a fibrous webby mass from a plurality of continuous filamentary fibers and thereafter repeatedly penetrating said mass with a multiplicity of small spaced cutting instruments comprising needles having cutting blade-formed points to effect locational cutting operations at random locations to sever individual fibers of said mass into random lengths, and subjecting the resulting fibrous webby mass of random length fibers to a needling operation three dimensionally to entangle said random length fibers with one another.
2. An improved method claimed in claim 1, wherein said random locational cutting is carried out by pressing said webby fibrous mass by'a porous board and piercing blade-pointed cutting instruments into said mass through holes of said porous board.
3. An improved method claimed in claim 1, wherein said random locational cutting is performed in combination with a needle punching operation.
. 4. An improved method claimed in claim 1, wherein said fibrous webby mass is made up of fibers having a loop strength in a range from 0.2 to 1.5 g/denier.
5. An improved method claimed in claim 1, wherein said fibrous webby mass is made up of polymer blend filaments.
6. An improved method claimed in claim I, wherein I a plurality of said fibrous webby masses are superposed 8. An improved method claimed in claim 1, wherein said continuous filamentary fibers are deposited on a conveyor belt under pneumatic suction force.
9. An improved method of manufacturing a non woven fibrous sheet comprising, in a sequential combination, forming a fibrous webby mass from a plurality of islands-in-a-sea type continuous filamentary fibers, repeatedly penetrating said mass with a multiplicity of small spaced cutting instruments comprising needles having cutting blade-formed points to effect locational cutting operations at random locations to sever individual fibers of said mass into random lengths, subjecting the resulting fibrous webby mass of random length fibers to a needle punching operation three dimensionally to entangle said random length fibers with one another, and thereafter removing the sea component of said islands-in-a-sea type filamentary fibers.
10. An improved method claimed in claim 9, wherein said islands-in-a-sea type filamentary fiber is composed of island components of from 0.001 to 0.5 denier fineness and sea component having a loop strength of 1.5 g/d or smaller in a single filament form.
11. An improved method claimed in claim 9, wherein said islands-in-a-sea fiber contains discontinuous fine island components of at least l cm length embraced by sea component having a loop strength of 1.5 g/d or smaller in a single filament form. 7
12. An improved method claimed in claim 9, wherein said needle punched webby mass is impregnated with a water soluble polymeric substance, said sea component is removed from said mass by'a solvent thereof, said mass is further impregnated with an elastic polymeric substance and said water soluble polymeric substance is removed from said mass simultaneously with or after coagulation of said elastic polymeric substance.
13. An improved method claimed in claim 9, wherein a plurality of said fibrous webby masses are superposed and are subjected to said locational cutting and needling operations while superposed.