GB2045305A - Reinforced Non-woven Webs - Google Patents

Abstract

The present invention provides a method and apparatus in which a plurality of fibers are dispersed in a water solution to form a fibrous slurry. A moving permeable screen 4, disposed in a hydroformer 1 having an inlet 3 for the fibrous slurry, is divided into a plurality of fiber collecting zones by a roller 7 defining an arcuate path. At least one reinforcement element or medium 13a, 13b is conducted by the roller to a position upon an initial fibrous layer collected on a first zone 5. The roller engages the moving screen and ensures that the reinforcement element or medium is properly positioned and disposed at the desired height within the web. A covering layer of fiber is deposited upon the initial layer and on the reinforcement element by injecting a fibrous slurry through separators 10. <IMAGE>

Description

SPECIFICATION Process and Device for the Production of a Non-Woven Fiber Fabric from a Suspension of Synthetic Fibers, especially Glass Fibers in Water Technical Field The present invention relates generally to the production of a nonwoven web. More particularly, the instant invention relates to a method and apparatus for making a reinforced non-woven web from synthetic fibers.

Background of the Invention It is well known to produce bonded fiber fabrics or thin non-woven webs from a suspension or a slurry of synthetic plastic fibers, especially glass fibers. Base fibers are usually dispersed in pure water or water having additives such as, e.g., binders, dyes or similar mixtures. The prior processes are provided with a head box or a hydroformer having an inlet for a fibrous slurry and a moving water-permeable wire screen over which the fibrous slurry flows. The wire screen is often arranged transversely across the hydroformer rising from the inlet of the hydroformer to the outlet of the hydroformer along the same direction as the flow of the fibrous slurry.As a result, the fibers are deposited on the surface of the wire screen while vacuum chambers, arranged beneath the wire screen, remove most of the water from the fibrous slurry thus forming a non-woven web of the fibers. After the web is formed on the moving screen, it is conveyed downstream from the hydroformer, removed from the moving screen and subsequently given further treatment as, e.g., a binder application, drying, finishing, smoothing or any similar treatment step whereby the web is made into a bonded fiber fleece or mat.

It is usually advantageous to use fibers longer than the base fibers because the longer fibers have a favouable effect upon the strength properties of the final product or mat. The prior processes suffer, however, from the disadvantage that fibers longer than the base fibers cannot readily be utilized. For example, fibers longer than 60 mm tend to flocculate or form clouds in an opening tank, pre-mixing tank, a main mixing tank usually located upstream of the hydroformer.

These longer fibers also form clouds in the hydroformer prior to deposition of the fibers on the moving screen. This disadvantageous flocculation can be reduced and longer fibers can be used if the fiber slurry is extremely diluted, i.e., the percentage by weight of the fibers is reduced in the fiber slurry. However, a dilution of the slurry results in the disadvantage that great amounts of water are brought into circulation in the hydroformer which must be removed from the pre-bonded fiber web or mat.

In order to impart the required strength to bonded non-woven webs using relatively short base fibers dispersed in an undiluted slurry, a reinforcing medium such as, for example, continuous reinforcement filaments or filament strands have been embedded in the longitudinal direction of the web. For example, in U.S. Patent No. 3,905,067 a plurality of depositing tubes are transversely disposed in a hydroformer for inserting reinforcing filaments in the web being formed. The tubes are immersed in the fibrous slurry fed to the moving wire of the hydroformer and produce turbulence in the slurry proximate the point where the wire exits from the hydroformer. A filament, drawn from a spool, may be conducted through each depositing tube and carried along with the flowing fibrous slurry.

Subsequently, the filament is conducted against the moving wire and embedded in the forming web.

Although this known method effectively embeds individual reinforcing filaments along adjacent parallel paths in the web, difficulties arise when it is desired to embed a great number of reinforcing filaments across the width of the web being produced, i.e., if it is desired to maintain a small distance between the filaments.

With an increase in the density distribution of the filaments, it becomes increasingly difficult and finally impossible to dispose a correspondingly larger number of depositing tubes in the hydroformer. While in practice it is desirable to space the filaments apart by 5 mm, there are presently difficulties in spacing the filaments with even greater spacing distances. It is possible to distribute the depositing tubes along an elongated moving wire so that the depositing tubes are disposed in several spaced rows along the machine direction of the hydroformer. However, the flow of the fiber slurry is usually obstructed through the hydroformer by the dense distribution of the depositing tubes.Depending upon the distribution of the several rows of the depositing tubes, the reinforcement filaments could also be embedded in several respectively different levels or depths within the forming non-woven web.

Furthermore, changing the reinforcing filament supply spools, necessitated either by a breakage in the filament being unwound from the spool or by a need to replace a spent spool, causes difficulties to arise in feeding the filament through the depositing tubes. Finally, the usage of a great number of filament supplying spools occupies space required for other devices needed to maintain or effect the flow of the fibrous slurry through the hydroformer as, for example, turbulence producers of a type disclosed by the published German Patent Application No.

1,913,012, mixers or the like.

In another known apparatus (German Patent No. 1,906,334), the hydroformer is designed as a manifolded hydroformer subdivided into several chambers along the machine direction. The subdivision is realized by means of a plurality of upper lips, i.e., metal plates disposed above the hydroformer whose surfaces are bent in the direction of the flow and extend across the width of the hydroformer. The lips serve as a guide for a plurality of reinforcing filaments or a similar reinforcing medium. In this known system, the reinforcing filaments are embedded upon a first layer of fibrous material of the non-woven fiber web that is formed within a first or an upstream chamber. A second chamber, placed downstream of the first chamber, is provided with a special influx of fibrous material which is deposited upon the first fibrous layer.

In practicing the method of German Patent No.

1,906,334, it was found that the individual filaments were not always precisely embedded in parallel paths within the fibrous layers. This is caused by the fact that the flow within the first chamber is deflected by the back of the wide metal plate forming an upper lip, causing the filaments to slide across the back surface of the lip. Furthermore, it is very difficult to position the lips adjacent the web closely proximate the moving screen in order to define the plurality of chambers without tearing the layer of fibers formed in the first chamber. Additionally, since the lower edge of each lip does not terminate superadjacent the fibrous layer being formed in each chamber a reinforcing filament, conducted under stress by the corresponding metal plate of each lip, is not deposited upon the surface of that layer of the forming web directly under the end of the lower edge of the lip.At best, the filament is initially deposited on a downstream portion of the layer being formed at a certain distance from the end of the lip. In a worse case, the reinforcing filaments are not properly embedded in the forming web and consequently may obstruct the formation of the next fibrous layer of the web which is intended to be used to cover the reinforcing filaments. The more the lip is shifted toward the moving wire or screen, used for collecting the fibers, for the purpose of eliminating the above described disadvantage the greater is the likelihood that the layer of the web being formed will be torn by the lip and the moving screen damaged. Deposits, known in the art as "hangers" or "soft lumps", form on the ends of the lips, i.e., filament accumulations which are torn loose from time to time by flow of fibrous slurry moving along the metal plates.

These deposits are usually observed as "clouds" in the resultant non-woven web. Furthermore, these deposits damage the forming web when the lip is positioned too closely to the moving screen of the hydroformer.

U.S. Patent No. 1,870,367 issued to Stone el al discloses the use of a driven roller which feeds reinforcing threads to the apron of a single, undivided hydroformer. A moving forming wire located downstream of the apron collects fiber from fibrous stock dispersed in the hydroformer.

The roller, which is completely immersed in the stock, is perforated and disturbs the flow of the stock material in the hydroformer as little as possible. However, such an arrangement does not realise advantages inherent in the multi-chamber system of German Patent No. 1,906,334 which has a special fiber feed or influx assigned for each chamber. The Stone el al method cannot ensure that the reinforcements are safely embedded by separately creating a base or an initial fibrous layer, depositing an intermediate layer of reinforcing filaments and then forming an upper layer of fiber.

Summary of the Invention It is an object of the present invention to provide an improved method and apparatus for making a non-woven fiber web reinforced with a great number of, preferably absolutely parallel, reinforcing elements. The reinforcing elements may be of different forms and types which are embedded in a non-woven bonded web which is free of "clouds".

According to one aspect of the invention there is provided a process for the production of a nonwoven web of fibers, comprising: dispersing a plurality of fibers in a water solution to form a fibrous slurry, conducting said fibrous slurry towards a permeable screen, dividing said screen into a plurality of fiber collecting zones using a moving guiding surface, said guiding surface defining an arcuate path; depositing fibers from said fibrous slurry in a first one of said zones, guiding at least one reinforcement element along a moving arcuate path of said guiding surface to a position within or on the fibers deposited in said first zone, said moving arcuate path having a motion which has the same direction as said screen, and depositing fibers upon said reinforcement element in a second one of said zones.

According to a second aspect of the invention there is provided an apparatus for the production of a non-woven web of fibers, comprising: a hydroformer having an inlet for a fibrous slurry, a movable permeable screen disposed in said hydroformer for collecting fibers from said slurry, means for supplying a reinforcement medium to said hydroformer, and at least one roller for dividing said screen into a plurality of fiber collecting zones, said roller engaging said screen and in use guiding said reinforcing medium to a position within or on fibers being collected in one of said zones.

Using the invention it is possible to provide a method and apparatus for the production of a non-woven web of fibers in which a plurality of fibers are dispersed in a water solution to form a fibrous slurry. A moving permeable screen, disposed in a hydroformer having an inlet for the fibrous slurry is divided into a plurality of fiber collecting zones by a roller defining an arcuate path. At least one reinforcement element or medium is conducted by the roller to a position upon an initial fibrous layer collected in a first zone. The roller engages the moving screen and ensures that the reinforcement element or medium is properly positioned and disposed at the desired height within the web.

The invention is hereinafter described, by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 is a cross sectional, schematic view of one embodiment of apparatus according to the invention; Figure 2 is a view similar to Figure 1, but illustrating a further embodiment of apparatus according to the invention; Figure 3 is an enlarged view of a portion of apparatus like that of Figures 1 and 2; and Figure 4 is a view similar to Figures 1 and 2, but illustrating a third embodiment of apparatus according to the invention.

Referring to the drawings, Figure 1 generally represents a hydroformer in the form of a box or a receptacle 1 to which material in the form of a fibrous suspension or a slurry 2 is admitted through a conduit 3. A moving web forming wire or a screen 4, permeable to water, has an area which forms a bottom or a zone 5 in the hydroformer 1, known in the art as a "sheet or a web forming zone". The fibers contained in the suspension 2 are deposited upon the upper (as viewed in Figure 1 ) side of the moving wire 4 proximate the bottom 5 as a fiber layer with the water in the suspension being substantially removed by suction provided by a battery of suction boxes 6.

The hydroformer 1 is subdivided into two chambers 8 and 9 by a filament guiding surface or a roller 7 with the chamber 9 additionally being defined by means of a plurality of vertically positionable separators 10 disposed across the machine direction and shielded by a pair of adjustable retaining walls or skin plates 11 a, 1 b.

The skin plates 11 a, 1 b may be adjustable horizontally or vertically and aid in controlling fluid flow by which an additional means (e.g.

separators 10) may supply material to the hydroformer in the form of a water-fibersuspension.

A plurality of spools 1 2a and 1 2b are arranged in rows over the width of the hydroformer. A plurality of reinforcing filaments 1 3a, 1 3b are lead from the spools 1 2a and 1 2b and converge on the upstream (to the left as viewed) side of the chamber 9. The guiding roller 7 collects the filaments 1 3a, 1 3b and directs them upon an initially deposited fiber layer formed on the bottom 5 within the chamber 8. A covering layer of fiber is then deposited within the chamber 9 upon the initial layer and the filaments by injecting a fibrous slurry through the separators 10 whereby the position of the filaments 1 3a, 1 3b may be fixed within the non-woven fibrous body.The filaments 1 3a, 1 3b are embedded at a desirable position within the web being formed by supplying varying quantities and/or densities of fibrous material to the chamber 8 via the inlet 3, by vertically varying the position of the separators 10 and/or by supplying varying quantities and/or densities of fibrous material to the chamber via the separators 10. It will be understood that a non-woven fiber web may be formed in the invention using fibrous materials such as, e.g.

short and/or long fibers of different materials such as giass and plastic fibers, etc.

Figure 2 schematically illustrates a second embodiment in which a hyfroformer 14 may be provided with more than one chamber, e.g. three chambers 15, 16 and 17, each having a separate fibrous supply separator means 18, 19 and 20 dispersed across the width of the hydroformer respectively. Additionally, corresponding rollers 21 and 22 may be provided which divide the hydroformer 14 into the chambers 1 5, 1 6 and 1 7.

These rollers 21 and 22 guide a plurality of rows of reinforcements or filaments 24a, 24b and 25a, 25b, respectively, to positions (e.g. parallel positions) within the fibrous layers being formed in each of the chambers on a moving screen 23.

Consequently, a plurality of positions (e.g. two in the present case) may be defined for the filaments 24a, 24b and 25a, 25b which are embedded in two fibrous layers separated by an intermediate layer of fiber supplied by the supply means 19.

Figure 3 represents to, a scale enlarged relative to Figures 1 and 2, a second of apparatus according to the invention in which guiding rollers, separators and additional fiber supplying means are illustrated in greater detail. A roller 29, which rests on the forming wire of a hydroformer 26, separates the hydroformer into two chambers 26 and 27 and guides a plurality of reinforcing filaments 28 (which may be arranged in rows across the width of the hydroformer) to the moving fiber collecting wire of the hydroformer.

The roller is supported by one or more arms 30 which are attached to a framework or a chassis 31. A filament guiding roller 33 is also supported on the framework 31 by one or more arms 32 allowing the roller 33 to adjust the tension imposed on the filaments 28 and prevent the filaments 28 from sliding laterally across the hydroformer 26. Optionally, a plurality of separated roller plates or grooves 33a (arranged across the width of the hydroformer) may be used to stretch and prevent a group of filaments from sliding laterally across the hydroformer 26. A material separator 34, arranged across the width of the hydroformer, for the chamber 26 is provided with a separating head 35.The head 35 is provided with a plurality of lateral openings or slots 36a, 36b for directing a variable influx of additional fibrous slurry onto the initial fibrous layer of the forming web. As can be clearly seen, the only openings in the head 35 are the lateral openings 36a, 36b which avoid the creation of any turbulence in the downward direction, as viewed in Fig. 3. The quantity of slurry emanating from the slots 36a, 36b may be adjusted by means of valves (not shown). By a careful selection of the slurry influx using the slurry flow control valves, a controllable quantity of fiber may be deposited (e.g., across the width of the hydroformer) upon an initial fibrous layer. A pair of retaining walls or baffle plates 37 and 38 reduce turbulence in the flow of the influx of fiber slurry from the slots 36a and 36b.

The level of the fiber slurry in a hydroformer in the invention is usually denoted in the figures by an inverted triangular symbol. The slurry level in the hydroformer, denoted in Fig. 3 as 39, is adjusted so that it is as low as possible upstream of the first separating and guiding roller 29 in the first chamber 26. On the other hand, the slurry level is higher than the level 39 in the chamber 27 outside the baffle plates 37 and 38 and substantially higher within the space defined between the baffle plates, as shown at 40. The level of the slurry within the space defined between the baffle plates may be controlled by the quantity of fibrous slurry injected by the separator 34 or by horizontally or vertically varying the position of the baffle plates.A precisely predetermined embedding of the filament 28 in the fiber body can be obtained using the present apparatus, i.e., the filaments 28 can be embedded within a web so that they do not rise above the surface of the fibers being deposited upon the moving screen within the hydroformer. An end roller, designated by 41, is disposed outside of the hydroformer 26 to aid in properly conveying the newly formed reinforced web. Since the roller 29 is urged against the moving wire, it is rotated by the moving wire, ensuring that the roller 29 rotates at the same speed as the fibrous layer being formed on the moving wire. The roller 29 is thus appropriately supported to avoid placing fiber deposits, e.g.

clots or abnormally strong accumulations of fiber on the forming fiber layer.

Fig. 3 also clearly illustrates that the present combination, i.e., a roller 29 which separates the chambers and conducts the filaments and a guide roller 33, allows the looping angle on the roller 29 to be kept small.

In another alternative embodiment of an apparatus according to the invention, Fig. 4 illustrates an apparatus capable of imparting a swirl to a reinforcement to be embedded in a nonwoven web. In Fig. 4, a row of filaments 46, drawn from a number of spools 45, are conducted in a wedge-like fashion between an upper and lower filament 43, 44, respectively. The filaments 43, 44 and 45 converge between the chambers, separated as before, at a filament guiding roller 42. Each filament 46 runs to a swirl imparting device, e.g., one or more nozzles 47, into which transversely flowing air is supplied by means of a connection or connections 48.The filaments 46 are given a greater feeding speed by the nozzles 47 than the feeding speed of the filaments 43 and 44 whereby the filaments 46 are deposited in a loop or curl-shaped fashion onto the forming fiber layer. The wedge-like converging motion of these reinforcing filaments readily takes place, allowing the filaments to be readily deposited upon a first layer of fiber produced in a first chamber defined upstream of the roller 42. The relative position of the filaments 43 and 44 perform a kind of holding function, i.e., they tend to confine the area within which the swirl reinforcement 46 may be embedded within the forming web. The nozzles 47 can also be reciprocated thereby enhancing the distribution and/or the formation of the swirls in the filaments 46.Additionally swirl reinforcements as well as the other reinforcing filaments can be selectively deposited within the forming fiber web, i.e., only within positions where reinforcements are necessary. The holding or constraining function of the filaments 43, 44 can also be used to aid in bringing a non-woven veil or light weight mat, or a bonded fiber, such as sliver to the forming web. A loom or a warping means could consequently be substituted for the spools 45. Instead of a non-woven mat, it is possible to slowly embed a scrim material using the strength increasing filaments 43 and 44.

The present invention recognizes that if reinforcing filaments are freely conducted through the water dispersion or fiber slurry in the hydroformer, i.e., are not conducted by a depositing tube, their exposure to the danger of being shifted or immersed in the flow controlled by a guiding surface may be reduced if the path through which they are guided is relatively short.

Additionally, the time that a filament dwells on a guiding surface of the present invention is reduced because a rotating guiding element is provided which separates the hydroformer into a first and second chamber. Simultaneously, the guiding element moves in the direction of the flow of the slurry through the hydroformer and forces the filaments to move in a loop. The separated chambers and the filament guiding or leading elements are designed to ensure that a safe separation in the different chambers may be effected. Damaging of the formed layer or layers and the formation of fiber deposits such as, e.g., hangers, may also be prevented in the present invention.

At times it is desirable to make a voluminous or a thick non-woven fiber web by means of additional embedded filaments which do not serve as reinforcing filaments. Consequently, the addition of these additional filaments must not be placed in a contiguous parallel relationship, but should be deposited sinuously and/or loopingly (in "swirls") in addition to the reinforcing filaments. A general increase in tensile strength and stiffness can be imparted to a bonded non-woven fiber web without making the web dependent on the direction that the filaments are embedded within it. Loop-shaped reinforcements, e.g. swirl reinforcements, embedded in the marginal areas of a web largely increase the resistance of a reinforced web to a starting and to a continuing tear.It should also be mentioned that a swirlreinforced web of the present invention enjoys an excellent nail-holding strength or nail-pull resistance. This is required when the reinforced bonded fiber web is used for roll roofing, built-up roofing (BUR), or shingles which are attached to a roof by nails.

Stiffening of a shingle using a swirl reinforced web, as above, aids in enhancing the handleability of the shingles and the blow-off resistance or wind resistance of an installed shingle. For an increase in the nail and/or tear resistance of a reinforced web, it is often sufficient that the additional reinforcements are applied in strips where it is expected that the resultant product will experience stress in use.

The method and apparatus described above and illustrated eliminates heretofore occurring uncertainties regarding the predetermined height and lateral positioning of the reinforcing filaments which are embedded in the form of loops or swirls within the non-woven fiber web. The filaments which constrain the positioning of the additional reinforcements (mats, scrim, swirls or the like) serve the function of holders during the embedding process, i.e. establish the swirls, for example within the web at predetermined heights as well as predetermined lateral distances across the web.

Claims (10)

Claims

1. A process for the production of a non-woven web of fibers, comprising: dispersing a plurality of fibers in a water solution to form a fibrous slurry, conducting said fibrous slurry towards a permeable screen, dividing said screen into a plurality of fiber collecting zones using a moving guiding surface, said guiding surface defining an arcuate path; depositing fibers from said fibrous slurry in a first one of said zones, guiding at least one reinforcement element along a moving arcuate path of said guiding surface to a position within or on the fibers deposited in said first zone, said moving arcuate path having a motion which has the said direction as said screen, and depositing fibers upon said reinforcement element in a second one of said zones.

2. A process according to Claim 1 comprising moving said guiding surface by said screen.

3. A process according to Claim 1, wherein at least two rows of reinforcement elements are supplied to said guiding surface at different angles, said guiding surface sinuously positioning said reinforcement elements in said first zone of fibers.

4. An apparatus for the production of a nonwoven web of fibers, comprising: a hydroformer having an inlet for a fibrous slurry, a movable permeable screen disposed in said hydroformer for collecting fibers from said slurry, means for supplying a reinforcement medium to said hydroformer, and at least one roller for dividing said screen into a plurality of fiber collecting zones, said roller engaging said screen and in use guiding said reinforcing medium to a position within or on fibers being collected in one of said zones.

5. Apparatus according to Claim 4, comprising means for supplying fibers to a second zone downstream of said one zone, said second zone being defined by at least one baffle wall juxtaposed between said roller and said fiber supply means.

6. Apparatus according to Claim 4 or Claim 5, comprising means for varying the level of fibrous slurry in each of said zones.

7. Apparatus according to any of Claims 4 to 6, comprising means for supplying a plurality of reinforcement medium to said hydroformer and means for supplying one of said reinforcement medium at a rate which is greater than the rate of supply of the other reinforcement medium.

8. A process for the production of a non-woven web of fibers, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. An apparatus for the production of a nonwoven web of fibers, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

10. A non-woven web of fibers whenever produced by a process according to any of Claims 1 to 3 or 8 or in an apparatus according to any one of Claims 4 to 7 or 9.