JPH07207567A - Composite non-woven fabric, its preparation and apparatus for preparing it - Google Patents

Abstract

PURPOSE: To obtain a nonwoven suitable for medical or sanitary applications. CONSTITUTION: The combined nonwoven comprises at least two kinds of sheets that are a first sheet 2 made of thermobondable fibers and obtained by carding crimped fibers 5 and a second sheet 3 made of continuous filaments of a material to become thermobondable by extraction. The combined nonwoven has plural bonded points 4 passing vertically through two sheets in order to mutually adhere over a part of a contacting area while integrating fibers of two sheets 2 and 3. A method and an apparatus for producing these fibrous articles are also provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to composite non-woven fabrics for medical and hygiene use, the non-woven fabrics comprising at least two sheets joined together by welding points.
The invention also relates to a manufacturing method and a manufacturing apparatus specially designed for the production of this type of nonwoven fabric.

[0002]

Nonwoven fabrics are common parts of disposable diapers for infants, incontinence articles for adults, or hospital or medical articles, for example hygiene articles such as surgical clothing. When used as a diaper, non-woven fabrics are commonly used as dressings for absorbent mats made of cellulosic cotton, and non-woven fabrics are designed to contact the infant's skin.

Depending on the intended application, nonwovens need to have different qualities: soft feel; mechanical strength, especially tear resistance to both longitudinal and transverse directions; wettability, and It is hydrophilic or hydrophobic.

Nonwoven fabrics for such applications are generally composed of a single sheet of fibers or filaments. When the fibers are cut, the sheet is made by carding, while the filaments are continuous, spunbonded (s).
pin bonding).

In both cases, the raw material used is heat-meltable, preferably polypropylene, but polyethylene, polyester or other suitable heat-meltable substances can also be used. Polypropylene is preferred because of its cost, processability, skin adaptability and bacteriological grade, its inherent good mechanical properties, and incineration compatibility. Furthermore, it can be processed at lower temperatures than other raw materials, such as polyester, and therefore requires little energy for drawing and polishing operations.

In the production of nonwovens by carding, the web is first made by crimping and cutting, for example fibers made of polypropylene, but fibrous webs have a natural adhesiveness because the fibers are only slightly entangled. , So that multiple hot spots can be obtained, for example by hot calendering under pressure.
It is necessary to strengthen the web by deering.

The non-woven fabric thus produced by carding has a high degree of advantage due to the intertwined fibers in terms of woven feel, softness and bulkiness, in addition to good uniformity and good wetting. Shows sex. Symmetrically, its transverse mechanical strength is low, which results in tearing that occurs when used in the manufacture of sanitary articles such as napkins, sanitary napkins, or incontinence articles or medical garments.

In spunbond technology, pellets of hot melt material are converted directly by an extruder.
The extruded continuous filaments are adapted to aerodynamically form a sheet. The resulting sheet does not have sufficient adhesion and needs to be strengthened, especially by hot calendering under pressure, which results in a multi-point weld by localized melting of the filaments that adhere to each other.

For a given hot melt material, the operating conditions required for calendering a sheet of continuous filament are generally different from those used when calendering a sheet of carded fiber. It should be noted that this is done.

Nonwoven fabrics obtained by spunbonding exhibit good mechanical strength and good isotropy in both the longitudinal and transverse directions. However, it lacks flexibility and bulk and is relatively hard. Nevertheless, it may be preferred for certain applications, such as the use of nonwovens to form fecal obstructions in diapers or adult incontinence articles. Finally, the nonwoven is of irregular appearance due to the aerodynamic and random distribution of the filaments as they leave the extruder. The irregular appearance becomes even stronger when the speed at which the nonwoven is manufactured exceeds a certain threshold depending on the type of material used. Under these circumstances, the vortex phenomenon causes holes to form in the sheet prior to calendering.

Attempts have already been made to combine the above two types of advantages on the basis of making composite fiber products, one on the basis of fiber and the other on the other hand, having two sheets made of continuous filaments.

In US Pat. No. 5,143,779, a card sheet made of bicomponent crimp fiber having an outer sheath made of polyethylene and an inner core made of polyester was preliminarily constructed of spunbonded polyethylene. Assembled in non-woven fabric. The product composed of the laminated card sheet and the spunbonded non-woven fabric is pressed at 129 ° C. for about 17 seconds against a rotating drum with a gap into which hot air is jetted. Due to the partial melting of the polyethylene that constitutes the sheath of the bicomponent fibers, the bicomponent fibers are also interconnected to some of the filaments of the spunbonded woven fabric on the surface which is contacted with the card sheet. The hot air connection makes it possible to maintain a considerable volume and bulk for the card sheet.

The two-sheet composite non-woven fabric described in document US Pat. No. 5,143,779 has a number of drawbacks. This requires the use of special bicomponent fibers and has two types of bonding, one for non-woven fabrics, especially spunbonded, and the other for air jet bonding.

Document US Pat. No. 4,041,203 relates to a two-sheet composite non-woven fabric, the first sheet being a prefabricated sheet of microfibers and the second a continuous filament drawn in a spunbond process. Is made of. Microfibers are made by the "melt-blow" process, which is of the same general type as spunbond, but with the action of high speed hot air for the purpose of breaking continuous filaments after being drawn. The fibers made in this way are collected on a grid or drum and form a unique sheet by the entanglement of the individual fibers and by thermal or self-bonding between the fibers. The fiber in question is straight and not crimped. Furthermore, it is not possible to control the fiber length. Although they are mostly discontinuous, it is known that they are generally longer than would be expected for a cut fiber.

This forms the first drawback, but also the second
There is also a drawback. According to this, the non-woven fabric uses two modes of bonding. This is firstly a characteristic bond to a prefabricated sheet of microfibres which makes it have the shape of a roll, and secondly a set constituted by a sheet of continuous filaments and a sheet pre-prepared with microfibres. Matching spot welding bonding.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composite non-woven fabric having at least two sheets for medical and hygiene articles, the literature being US Pat. No. 5,143,779 and US Pat. No. 4,041,203. It is to avoid the above-mentioned drawbacks with respect to the non-woven fabric of the book.

Another object of the present invention is a method of making the above-described composite fiber product for medical or hygiene articles, which has a soft fiber product feel and non-oriented mechanical strength and is made of at least two sheets. And to provide a manufacturing apparatus.

[0018]

[Means and Actions for Solving the Problems]
It is composed of a first sheet made of thin heat-fusible fiber and a second sheet of continuous fiber made of drawn heat-fusible material, the first sheet is a card sheet of crimp fiber, and the fiber product is Completely achieved by a composite non-woven fabric according to the invention characterized in that it comprises a plurality of weld points passing vertically through said two sheets for joining each of the sheets and for joining some of their contact surfaces to each other. It

The fiber product of the invention is thus made by means of crimped fibers and continuous filaments which are bonded to one another, ie both fibers are bonded to one another by means of a single bonding technique, namely Made by multi-point welding points. The fiber in question is a single fiber, for example polypropylene fiber.

The composite fiber product of the present invention has an excellent feel due to the crimp fibers emerging from the surface. It also has excellent mechanical properties both longitudinally and transversely due to the presence of a sheet of continuous filaments. Furthermore, the coating of card fibers gives the assembled composite nonwoven a uniform surface appearance. This appearance is maintained when a sheet of continuous filament is produced, especially when produced at speeds above the normal design limits of the production machine and when irregularities are encountered. This type of irregularity is not found in carded sheets.

The crimped fibers of the carded sheet are preferably between 1.5 and 6 dtex in weight and 35 to 60 m.
Polypropylene fibers cut to lengths in the range of m. These parameters ensure that the textile has a very good textile feel on the surface from which the carded fibers emerge.

The weld point is preferably about 1 of the total area of the nonwoven.
Indicates 7%. During the production of textiles having a single sheet of carded fibers, this proportion is about 18 to 21%, whereas for textiles having a single sheet of continuous filaments made by spunbond technology, this is about 13%. % To 16%. Current practice lies outside it, but about 17%
The selection ratio of 1 gives sufficiently satisfactory results to bond both fibers and filaments.

Another object of the invention is the manufacture of the above-described composite fiber product for medical or hygiene articles, which has a soft fiber product feel and a non-oriented mechanical strength and is made of at least two sheets. To provide a method and a manufacturing apparatus specifically designed for.

In this method, the following operations are performed.

Two heat-fusible, non-integrated sheets were produced simultaneously, the first sheet being a carding of fine crimp fibers and the second sheet being a spunbonding of continuous filaments, which were drawn. Are manufactured into sheets in an aerodynamic manner; two unmerged sheets are superposed; two sheets superposed in this manner are subjected to a single high temperature calendering operation under pressure at multiple welding points. Upon receipt, this causes the sheets to be simultaneously joined to join the two sheets over a portion of their contact area contact by the melting of the hot melt material which creates the crimp fiber and continuous filament weld points.

In contrast to the method described in the documents US Pat. No. 5,143,779 and US Pat. No. 4,041,203, the method of the invention is an in-line method, which as raw material is first fed to a carding device. It requires crimp fibers and then pellets of hot melt material for feeding to the drawing device. Since the two sheets are formed in-line at the same time, the two sheets are superposed on each other before the integration, and a single bond technique can be used to obtain an integrated body of an assembly composed of the two sheets of the superposition. it can. Furthermore, by using the joining technique with multiple welding points, the finished composite fiber product is especially made of continuous fiber with the feel of the fiber product of the carded first sheet and the second
The mechanical strength of the sheets makes it possible to maintain the inherent properties of each of the two sheets.

In order to obtain an effective joint by welding points,
It is important that the hot-melt material forming the fibers and filaments have a relatively uniform melting point. Unfortunately, for a given material, polypropylene, the melting temperature of cut, crimped fibers intended for carding differs from that of continuous filaments obtained by direct drawing. The temperature used during calendering is preferably determined such that it lies midway between the melting points of the crimp fibers and the continuous filaments.

Similarly, the calendering pressures used in the weld point bonding of conventional non-woven fabrics based on a single sheet are either made of crimped fiber where the sheet is carded or made of spunbonded continuous filaments. It makes a big difference depending on what you are doing. Illustratively, the carded sheet is 80 daN / cm and the continuous filament sheet is 30 daN / cm. In the process of the invention, the calender pressure is in particular 60 d.
It is determined to have an intermediate value that lies between aN / cm and 70 daN / cm.

That is, contrary to expectations, by selecting such an intermediate point which is a priori unsatisfactory for the fiber sheet and for the continuous filament sheet, it is satisfactory for the superposition of two sheets. You can get the result.

[0030]

The present invention has two superposed sheets,
It will be better understood by reading the following description of examples of composite nonwovens illustrated in the accompanying drawings.

As shown in FIG. 2, the non-woven fabric 1 of the present invention is a composite non-woven fabric for medical and hygiene articles, which has welding points 4
It is made of two superposed sheets 2 and 3 which are interconnected with each other. The first sheet 2 is made of a thin crimp fiber made of a heat fusible material, for example polypropylene.
Fiber grades are in the range of 1.5 dtex to 6 dtex, which are preferably cut to lengths of 35 mm to 60 mm. In one particular, but non-limiting example, the fibers are 2.5 dtex polyethylene fibers cut to 40 mm. These are 2
Dimensionally crimped fibers crimped into 13 corrugations per cm.

The sheet 2 of fibers 5 is made using carding techniques. For this purpose, the fibers are first oiled with a hydrophilic oil agent at a rate of about 0.40%. They have a strength of 18 cN / tex and a degree of elongational failure of 350%.

The second sheet 3 is made of continuous filaments obtained by the spunbond technique. In one particular example, each filament has a grade of 3.5 dtex, a strength of 20 cN / tex, and a breaking elongation of 400%.

Although the bond of the textile 1 is obtained at the welding point 4, there are three types of bonding, which are the bond between the fibers 5, the bond between the filaments 6 and the bond between the fibers 5 and 6. is there. These three types of adhesion are accomplished in a single operation as described below.

In a special embodiment, the weight is 20 g / m.
The textile product ² of ² is made of 9 g / m ² of fibers 5 and 11 g / m ² of filaments 6. It had a lateral tear strength of 9.5 N and a longitudinal tear strength of 28 N, a lateral tear extension of 95%, and a longitudinal tear extension of 65%.

The number of welding points is 20 / cm ^{2 to} 100 / c
It was m ² . In the special case mentioned above, this number is 30 / cm ^2.
Met.

The fiber product 1 of the present invention is manufactured by an apparatus of the type schematically shown in FIG. The device 7 has a conventional spunbonding line 8 and a conventional carding line 9. It also has a conveyor belt 10 for transporting the fiber sheet 2 coming from the carding line 9 onto the second sheet 3 of continuous fibers before calendering.

More specifically, the spunbonding line 8 has a drawing device 11 which is capable of producing fibers 6 in an aerodynamic manner, which fibers 6 are then placed on a fiber conveyor belt 12 for further calendering. Cylinders 13 and 14 are located at the exit of conveyor belt 12.

In the illustrated embodiment, the carding lines are Fiber conveyor belt 10 as seen in 1.
Are located on the floor above the spunbonding line 8 so as to be inclined rearward with respect to the moving direction of the continuous fiber sheet 3. The downstream of the fiber conveyor belt 10 ends immediately above the fiber conveyor belt 12, and with respect to the belts 12 and 10, the two sheets 2 and 3 are transferred in a superposed state so that they do not mutually deform at the downstream end of the fiber conveyor belt 12. Is moving. The construction 15 consists of two superposed but non-integrated sheets 2 and 3, which in turn pass between two calendering cylinders 13 and 14.

The lower cylinder 14 is smooth,
On the other hand, the upper cylinder 13 is provided with a plurality of relief points 1
It is patterned by 6.

In contrast to the calendering device disclosed in document US Pat. No. 4,041,203, the construction 15 is not rolled into a smooth cylinder, so that no pre-heating or post-heating occurs. Furthermore, the sheet of fiber 2
Faces a cylinder 13 having a relief point 16.

That is, during hot calendering operations under pressure, there is no unacceptable squeezing or compression of the fibers 5 at the points located between the points 16 in relief. In these respects, the fibers 5 emerge from the textile 1 and therefore give it a good appearance.

In a special device, 2 cylinders 13
The pressure between 68 and 14 is 68 daN / cm and the temperature of the cylinder is as follows: patterned upper cylinder 1
3 is 141 ° C; smooth lower cylinder is 142 ° C.

When the textile 1 must be highly hydrophilic, 0.35% when leaving the calendering stage.
Spray with the hydrophilic agent.

The textile product 1 is about 130 meters per minute (m /
Min) picked up in a roll on itself. These various rotary members are driven at a peripheral speed lower than the winding speed, but with respect to this peripheral speed, the sheets 2 and 3 and then the structure 15 are in a slightly tensioned state until they are wound. It is determined for each member so as to be maintained at. For example, winding is done at 130m / min,
Peripheral speed 122 of the calendering cylinders 13 and 14
m / min, while the fiber conveyor belt 10 is 102 m / min, the speed of the filament conveyor belt 12 is 117 m
/ Min. The transfer speed of the filament conveyor belt 12 for transferring the continuous filament sheet 3 is 1.1 to 1.2 times the speed of the fiber conveyor belt 10 for the carded fiber sheet 2.

The invention is not limited to the embodiments described above by way of non-limiting illustration. Especially textile products 1
Preferably has a weight of about 10 g / m ^{2 to} about 50 g / m ^2.
It can be changed within the range of ² . Furthermore, it is also possible to vary the distribution of weight between the two sheets 2 and 3. Finally, it is possible to combine by a similar method with a third sheet of cut and crimped fibers in a similar nonwoven so that a sheet of continuous filaments is sandwiched between sheets of carded fiber. This is accomplished by feeding a third sheet of carded fiber from the second carding line, but for the third sheet, see Figure. Feed from below structure 15 in the example shown in Example 1 just upstream of calendering cylinders 13 and 14.

[0047]

INDUSTRIAL APPLICABILITY A nonwoven fabric excellent in soft feel, mechanical strength, tear resistance, wettability, hydrophilicity, hydrophobicity and the like applied to medical or hygiene products can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus showing the present embodiment.

FIG. 2 is a partial schematic cross-sectional view through a welding point of a nonwoven fabric explaining the present invention.

[Explanation of Codes] 1 ... Nonwoven fabric 2 ... First sheet 3 ... Second sheet 4 ... Welding point 5 ... Fiber 6 ... Filament 7 ... Equipment 8 ... Spunbond line 9 ... Card line 10 ... Fiber conveyor belt 11 ... Pulling device 12 … Filament conveyor belt 13, 14… Calendering cylinder 15… 2 sheet assembly 16… Cylinder protruding point

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area A61F 13/15

Claims (10)

[Claims] 1. A first sheet (2) of fine heat fusible fibers.
And a second sheet (3) of continuous fibers of drawn heat-fusible material
In the composite non-woven fabric for medical or hygiene, the first sheet (2) is a carded sheet of crimped fibers (5), and the first and second sheets (2, 3) To integrate each of them and to connect them at a part of their contact surface.
2. A composite non-woven fabric for medical or hygiene use, which has a plurality of welding points (4) passing vertically through the sheet. 2. The crimped fibers (5) of the carded first sheet (2) are polypropylene fibers cut to a length in the range 35 mm to 60 mm with a weight in the range 1.5 dtex to 6 dtex. Claim 1 characterized by the above-mentioned.
The composite non-woven fabric described. 3. The composite non-woven fabric according to claim 1, wherein the total surface area of the weld points represents about 17% of the total surface area of the fiber product. 4. 20 to 10 per square centimeter
The composite non-woven fabric according to claim 1 or 2, characterized in that it has zero welding points (4). 5. A method for producing a non-woven fabric for medical or hygienic use, wherein the fibrous product has at least two sheets and has soft fiber feel and isotropic mechanical strength. Two non-coalesced sheets of material are produced at the same time, the first sheet (2) being made into carded thin crimp fibers (5) and the second sheet (3) being made into a sheet by drawing upper aerodynamics. Made, the two non-coalesced sheets are superposed, the superposed two sheets are subjected to a single high temperature calendering operation under pressure at multiple welding points (4), which results in crimp fibers and continuous fibers. Is melted at a multi-welding point of a hot-melt material made at a multi-welding point, and at the part of its contact surface, two sheets are joined and united at the same time, for medical or hygiene use The method of producing a composite non-woven fabric. 6. The method for producing a composite non-woven fabric according to claim 5, wherein the calendering temperature is determined so as to be between the respective melting temperatures of the crimp fiber and the continuous fiber. 7. The carded fiber and filament are made of polypropylene and have a calendering pressure of 60 daN /
7. The method for producing a composite non-woven fabric according to claim 6, which is in the range of cm to 70 daN / cm. 8. A device for producing a composite nonwoven fabric for medical and hygienic use, which has a soft fiber feel and isotropic mechanical strength, in which a fiber product is made of at least two sheets, and is used for extraction and aerodynamic drawing. A device (11),
A first conveyor belt (12), a spunbond line (8) having two calendering cylinders (13, 14), a carding line (9) mounted above the spunbond line, and further an upstream end At the exit of the carding line (9) and the downstream end is the first conveyor belt (1
2) just above the second conveyor belt (10), the second conveyor belt (10) being the first conveyor belt (1).
Of a composite non-woven fabric for medical or hygienic use, wherein the fiber product is made of at least two sheets and has a soft fiber feel and isotropic mechanical strength, characterized in that it is inclined rearward with respect to the carrying direction of 2). Manufacturing equipment. 9. Two calendar cylinders (13,
14) is a lower smooth cylinder (14) and a patterned upper cylinder (1) having a plurality of relief-like points (16).
9. The manufacturing apparatus according to claim 8, further comprising 3). 10. Manufacturing device according to claim 8, characterized in that the speed of movement of the first conveyor belt (12) is 1.1 to 1.2 times the speed of the second conveyor belt (10).