US3708365A

US3708365A - Production of continuous filament,non-woven webs

Info

Publication number: US3708365A
Application number: US00704543A
Authority: US
Inventors: G Barlow
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1967-02-17
Filing date: 1968-02-12
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02
Also published as: NL6802229A; BE710917A; FR1555103A; GB1156733A

Abstract

A method for the production of continuous filament, non-woven webs, comprising directing downwardly towards a moving receiving surface at least two curtains of continuous diverging filaments, in which the filaments are separated and substantially uniformly distributed across each curtain, influencing the direction of movement of the filaments of each curtain so that they cease to diverge and become substantially parallel in the vicinity of the receiving surface, the filamentary curtains being arranged in such a manner that neighboring edges of the filamentary curtains are in contact at the receiving surface, overfeeding the filamentary curtains onto the receiving surface to form a unitary non-woven web having a width dimension which is substantially equal to the sum of the widths of the webs which would be formed by the individual filamentary curtains and subjecting the unitary non-woven web to a heat bonding process to bond together the filaments.

Description

United States Patent US. Cl. 156-181 1 Claim ABSTRACT OF THE DISCLOSURE A method for the production of continuous filament, non-woven webs, comprising directing downwardly towards a moving receiving surface at least two curtains of continuous diverging filaments, in which the filaments are separated and substantially uniformly distributed across each curtain, influencing the direction of movement of the filaments of each curtain so that they cease to diverge and become substantially parallel in the vicinity of the receiving surface, the filamentary curtains being arranged in such a manner that neighbouring edges of the filamentary curtains are in contact at the receiving surface, overfeeding the filamentary curtains onto the receiving surface to form a unitary non-woven web having a width dimension which is substantially equal to the sum of the widths of the webs which would be formed by the individual filamentary curtains and subjecting the unitary non-woven web to a heat bonding process to bond together the filaments.

The present invention relates to the production of continuous filament, non-woven webs.

The width of a non-woven web is an important factor to be considered during its manufacture since the width of the web is to a large extent dictated by the nature of its intended end-use. However, the width to which a continuous filament, non-woven web can be made is limited by the design and dimenisons of the apparatus used to spray or lay the filaments into the form of a web.

Accordingly, in order to obtain wider webs, two or more webs may be joined together as, for example, by bonding or stitching, to produce a unitary web having the desired increased width. This procedure is only possible, however, when the intended end-use of the unitary web does not require the web to have continuous, uniform physical properties across its width, since the or each joint will exhibit different physical properties from the remainder of the unitary web.

Also, in order to obtain wider webs, use has been made of processes in which one or more sprays of continuous filaments are traversed across a moving receiving surface to build up a web having a width which is greater than would normally be produced if the sprays of continuous filaments were not traversed. In such processes, the filaments are usually forwarded to the receiving surface in the form of a diverging, conical spray, and as a result the web tends to have large marginal portions which taper, that is they decrease in thickness, towards the edges of the web. Excessive trimming of the marginal portions of the web is then needed to obtain a product having uniform thickness. The traverse movements of the or each filamentary spray causes long lengths of individual filaments to cover the surface of the web without intermingling with other filaments, such that after bonding of the filaments in the web the non-intermingled filament lengths may easily be torn away from the web surface. Further disadvantages of such processes are the restric- "ice tion of the web forwarding speed impose-d by the limitations of traversing the spraying apparatus at suitable frequencies, and the necessity for the design and control of the traversing pattern in order to achive thickness uniformity in the web.

According to the present invention, a method for the production of cotninuous filament, non-woven webs, comprises directing downwardly towards a moving receiving surface at least two diverging curtains of continuous filaments, in which the filaments are separated and substantially uniformly distributed across each curtain, influencing the direction of movement of the filaments of each curtain, so that they cease to diverge and become sub stantially parallel in the vicinity of the receiving surface, the filamentary curtains arranged in such a manner that neighbouring edges of the filamentary curtains are in contact at the receiving surface, and overfeeding the filamentary curtains onto the receiving surface to form a unitary non-woven web having a width dimension which is substantially equal to the sum of the widths of the webs which would be formed by the individual filamentary curtains.

By o verfeeding is meant that the speed at which the filaments travel towards the receiving surface is greater than the speed at which the web is taken away thereon.

The preferred contact occurs when the filaments in the neighbouring edges of the filamentary curtains are relatively positioned as are adjacent filaments in an individual curtain, so that they are laid down and intermingled on the receiving surface in a similar manner, with the result that the joining line of adjacent curtains is not visible in the web, and, after bonding thereof, is not detectable by tests for uniformity of thickness and tensile properties. However, a small amount of overlap between the edges of the filamentary curtains may be tolerated so long as this amount does not result in the web having objectional physical discontinuities therein.

A convenient method of producing a curtain of continuous filaments is that .described in copending (US. Ser. No. 605,351), wherein a bundle of continuous filaments is formed into a substantially uniform ribbon of filaments by passing the bundle through a gas-operated banding device and the ribbon of filaments is passed through a gas-operated spreading device and issues therefrom as a diverging curtain of filaments. For the purpose of the present invention, this prior method is at least duplicated by arranging at least two sets of the curtainproducirrg apparatus in side-by-side arrangement.

One method of achieving the parallel arrangement of the filaments in the viciinty of the receiving surface is to position the gas-operated spreading devices at a height above the receiving surface suflicient to ensure that the effect of the exhaust gases from the spreading devices is so diminished that the gravitational forces on the filaments becomes the dominant influence. Another method involves the use of suitably positioned deflector plates which serve to redirect the exhaust gases from the spreading devices to impinge on the diverging filaments whereby they become substantially parallel under the influence of the redirected exhaust gases.

A preferred embodiment of the invention will now be described by way of example:

Two separate bundles of thermoplastic, synthetic, continuous filaments, each bundle containing 112 filaments,

were formed into two ribbons, each of inch width,

The spreading devices, which provided sufiicient tension on the filamentary ribbons to remove them from the rolls, also spread the filaments into two side-by-side filamentary curtains and forwarded the diverging curtains, initially entrained in high velocity air issuing from the spreading devices, towards an air-permeable conveyor surface having a width of 14 inches and moving at 15 feet per minute. The arcuate slot of each spreading device had a radius of 9 /2 inches, a gap of 0.012 inch, and was supplied With air under a pressure of 8 pounds per square inch. The distance from the slot of each spreading device to the conveyor surface was 26 inches. The filaments were forwarded from each spreading device at a speed of 4000 feet per minute and were overfed onto the conveyor surface.

It was found that, while the filaments issuing from each spreading device were formed into a diverging filamentary curtain in which the filaments were separated and substantially uniformly distributed across the curtain, the filaments of the curtain ceased to diverge as they approached the conveyor surface and became less influenced by the high velocity air issuing from the spreading device. As a result the filaments became substantially parallel due to the action of gravity.

The spreading devices were adjusted so that the centre of each filamentary curtain was positioned at a point 2% inches from, and on the appropriate side of, the longitudinal axis or centre line of the conveyor surface. The filamentary curtains were then adjusted, each to an effective width of /2 inches, so as to merge the neighbouring edges of the curtains on the centre line of the conveyor and form a non-Woven web having an effective width of 11 inches.

The web was then passed through a hot calendering process to bond the filaments, whereafter no visible joining line of the curtains forming the web could be detected. Subsequent tests for thickness uniformity and tensile properties also failed to detect the joining line.

Making non-woven webs according to the method of the invention has the advantages over the known processes in that no undue limitation in the web forwarding speed on the conveyor surface is imposed and less trimming of the web is required since the tapering marginal portions 4 of the web are not present to the extent of those found in traversed-filament webs.

What I claim is:

1. A method for the production of continuous filament, non-woven webs, comprising directing downwardly towards a moving receiving surface at least two curtains of continuous diverging filaments, in which the filaments are separated and substantially uniformly distributed across each curtain, influencing the direction of movement of the filaments of each curtain so that they cease to diverge and become substantially parallel in the viciinty of the receiving surface, the filamentary curtains being arranged in such a manner that neighbouring edges of the filamentary curtains are in contact at the receiving surface, overfeeding the filamentary curtains onto the receiving surface to form a unitary non-woven web having a width dimension which is substantially equal to the sum of the widths of the webs which would be formed by the individual filamentary curtains and subjecting the unitary non-woven web to a heat bonding process to bond together the filaments.

References Cited UNITED STATES PATENTS 2,413,551 12/1946 Englund 156----167 2,736,676 2/1956 Frickert 156167 3,288,582 11/1966 Wong et al. 156---167 3,341,394 9/1967 Kinney 156-167 3,436,797 4/ 1969 Graf et a1. 156167 3,442,751 5/1969 Langlois 156167 2,900,700 8/1959 Frickert 156181 2,577,214 12/1951 Slayter 156181 FOREIGN PATENTS 1,246,398 12/1959 France 156-167 787,872 6/1968 Canada 156-166 470,675 9/1937 Great Britain 156 166 BENJAMIN R. PADGE'IT, Primary Examiner B. H. HUNT, Assistant Examiner US. Cl. X.R.