JPS6228220B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention mainly relates to a method for manufacturing a nonwoven fabric having a network structure with excellent bulk and drapability. In general, the mechanical properties of nonwoven fabrics are mainly controlled by the properties of the fibers, their aggregation mode, and the mutual bonding state of the fibers. A reticular fiber structure, which is different from a random assembly or an arrayed assembly (unidirectional assembly or intersection thereof) by methods, is easier to deform and recover from external forces, and is basically an assembly with excellent flexibility. He proposed a method for producing a nonwoven fabric exhibiting such a structure (reticular fiber web) in Japanese Patent Publications No. 49-3458, Japanese Patent Publication No. 6795-1982, Japanese Patent Publication No. 14346-1987, etc. Conventionally, the method proposed by the present inventors basically consists of overfeeding an arrayed fiber sheet in which fibers substantially arranged in the vertical direction are partially joined to each other in some way, and After being stretched in a direction to form a reticulated fiber web, it is pressed and fixed with heat fusion or adhesive. Although the nonwoven fabric obtained in this manner is flexible and easily deforms under stretching external forces due to its basic structure, it is unsatisfactory mainly in terms of bulkiness. As a result of repeated research aimed at improving this point, the present inventors were able to extremely easily impart bulky properties to the arrayed fiber sheet without impairing any of the characteristics of the spreading method, and moreover, it was possible to impart bulky properties to the fibers themselves. The present invention has been achieved by discovering a method that can improve many other value-added properties by easily controlling the state of bonding between fibers. That is, the present invention includes at least 10% by weight of thermoplastic synthetic fibers having latent heat crimpability or heat shrinkability.
The fibers in the fiber aggregate that are substantially arranged in the vertical direction intersect with each other at a minute angle, are partially intertwined, are partially bonded with an adhesive, or are partially self-bonded. Two or more aligned fiber sheets are laminated, and in an overfeed state, they are stretched in the width direction while holding both ends to form a reticulated fiber web, and then non-contact heat treatment is performed while holding both ends to increase the bulk. This is a method for producing a reticulated nonwoven fabric. The method of the present invention will be explained in detail below with reference to the accompanying drawings. The arrayed fiber sheet in the present invention refers to (a) a sheet-like single or multi-layered sheet in which aggregated fibers arranged substantially in the vertical direction intersect with each other at a minute angle, as shown in Figure 1-A; , or (b) a sheet-like single body or multilayer body in which aggregated fibers substantially arranged in the vertical direction are partially entangled with each other, as shown in Figure 1-B, or (c) Figure 1-B. A sheet-like single body or multilayer body in which aggregated fibers arranged substantially in the vertical direction are partially bonded with adhesive 1, as shown in FIG. A sheet-like material in which assembled fibers arranged in the vertical direction are partially self-bonded, for example,
A sheet-like structure having countless cracks in the vertical direction as described in Publication No. 3458, or the above-mentioned Japanese Patent Publication No. 52
A single or multilayer structure such as a self-bonded sheet-like material in which fibers are partially fused to each other as described in Publication No. 14346, or (a), (b), (c), and (d) above. Refers to a single or multi-layered sheet-like product in which two or more types of bonding methods such as the following are combined. As shown in FIG. 2, such an array sheet, for example, FIG. 1-C, has the basic property that when stretched in the width (horizontal) direction, it becomes a contracted network structure in the vertical direction. Therefore, if the overfeed of such an array sheet (the ratio of the feeding speed of the array sheet to the advancing speed of the spread web) is Of, and the average fiber orientation angle in the reticulated web is, then =
Sec ^-1 Of, and if Of = √2, then = 45°, and a web with excellent vertical and horizontal balance can be obtained. The method of the present invention is for easily and stably producing a nonwoven fabric mainly having excellent bulkiness and drapability from a reticulated web obtained by the above-described principle. By applying elasticity or shrinkage, it is possible to express a controlled bulkiness, and to fix the shape by heat setting or thermal adhesion while maintaining the assembled state. Hereinafter, the method of the present invention will be explained in more detail with reference to FIG. In FIG. 3, reference numeral 2 denotes an arrayed fiber sheet, which is substantially composed of thermoplastic synthetic fibers such as polyolefin, polyester, polyamide, etc. This may be made of the same type of fibers or may be a multilayer of different types of fibers (for example, an aligned fiber sheet made of a high melting point polymer and an aligned fiber sheet made of a low melting point polymer). In such an arrayed fiber sheet, in order to achieve the object of the present invention, at least 10% by weight of the constituent fibers must be
It is necessary that the fiber is a thermoplastic synthetic fiber that crimps or shrinks when heated. In other words, the front part or part (10% by weight or more) of the fibers constituting the arrayed fiber sheet has latent crimpability, such as composite fibers made of different polymers or anisotropically cooled fibers, which will develop crimp through heat treatment as described below. It needs to be a fiber or a heat-shrinkable fiber that easily shrinks by the heat treatment described below. Such an arrayed sheet 2 is fed at a speed of ₁ by a pair of feed rollers 3, ³¹ . Immediately after the feed rollers 3, ³¹ , a pair of spreading belts 5, each having needles 4 perpendicular to the belt or freely bendable chain, are installed as shown in Fig. 3, and move at _two speeds. There is. The aligned fiber sheet 2 fed from the feed roller is immediately connected to the needles 4 on both ends of the spreading belt 5.
The web 6 is fed so as to be penetrated and held by the web 6, and is gradually expanded in the width direction to form a web 6 having a net-like structure as shown in FIG. In this case, the above-mentioned overfeed Of is expressed as Of= ₁ / ₂ , and therefore the average fiber orientation angle θ is =Sec ^-1 _{( 1/2} ). When the net-like web thus gradually spread reaches a satisfactory state of spreading, it is pressed to a constant thickness by flat or embossed press rollers 7, ⁷¹ . The satisfactory spreading state here refers to the spreading state in which the mesh length of the reticulated web is maximized as shown in FIG. Although this varies depending on the properties of the array sheet, generally L ₂ /L ₁ (spreading magnification) in FIG. 3 is 5 to 20 times. If the stretching ratio is insufficient, the web will become flimsy and a nonwoven fabric with strong horizontal strength will not be obtained, and if the stretching ratio is too high, the web will tear at some point. still,
The press rollers 7, ⁷¹ are not necessarily required when the purpose is to manufacture a highly bulky nonwoven fabric. The reticulated web thus stretched to a satisfactory state of stretching is transferred to a non-contact heat treatment box 8 while its both ends are held by the stretching belt 5.
will be introduced in The heat source for this heat treatment box may be hot air, heated steam, infrared radiation, high frequency, microwave, etc., but in any case, non-contact heating is performed. As mentioned above, the main purpose of this non-contact heat treatment is to make the reticulated web bulky and dense by crimping and heat shrinking the fibers, and to fix the shape. This will be explained in detail by giving a typical example. First, as an arrayed fiber sheet, the
An alternating multilayer body of sheet-like nonwoven fiber structures (sheet-like structures having innumerable cracks in the longitudinal direction) X and Y produced by the method described in Japanese Patent No. 49-18508 is used. For example, X is 35% polystyrene, polyethylene
It is made of a blended polymer consisting of 65%, has a melting point of approximately 145°C, and a heat shrinkage rate of 35% at 120°C. On the other hand, Y
is made of 100% nylon-6, with a melting point of 195°C and a heat shrinkage rate of 10% at 150°C. In addition, due to the special irregularity effect of the fibers that make up this arrayed fiber sheet,
In the temperature range of 120-160℃, the number of crimp is 20~
High contractility of about 50C/cm is developed. When using such an arrayed fiber sheet, the spreading belt passing through the heat treatment box is set so that it gradually shrinks from the maximum spreading width L ₂ at the entrance to, for example, the minimum spreading width L ₃ =0.7L ₂ , and the spreading width L ₂ is It is variable. The temperature inside the box is set at 120°C at the entrance and gradually increases to a maximum of 160°C. When the reticulated web gripped at both ends is introduced into the heat treatment box set in this manner, it first shrinks gradually as the width of the spreading belt decreases due to the heat shrinkage of the X component.
The crimp of the X and Y components develops, and finally,
In the state _L3 , the X component melts and the fibers are partially fused together. Since the thus obtained nonwoven fabric 9 gradually heat-shrinked and crimped while both ends were held,
The thickness remains almost constant without increasing the thickness unnecessarily, and the structure has a three-dimensionally high-density bulky structure due to fine crimp and Y-component slack structure. The structure is stable and partially bonded at points. As in the above-mentioned example, when an aligned fiber sheet with multiple layers of X and Y2 components is used, a nonwoven fabric with less fuzz can be obtained by arranging the low melting point component X in the uppermost layer. In the present invention, by installing a flat or embossed press roller such as 10 in FIG. 3 at the rear of the heat treatment box or immediately after the heat treatment box, and pressing while the web is kept warm, the web can be formed into any desired thickness. A nonwoven fabric exhibiting a pattern can be produced extremely easily. In this case, since the fibers themselves are heated, there is no need to worry about heat transfer time as in commonly performed hot press processing, and delamination due to so-called insufficient heat transfer does not occur. In the case of the above example, the shrinkage rate of the web due to heat treatment was set to L ₂ - L ₃ /L ₂ ×100 = 70%, but this can be changed to any value depending on the type of fibers constituting the arrayed fiber sheet and the purpose. Just choose. In addition, when producing a nonwoven fabric using the method of the present invention, in order to balance the vertical and horizontal strength, in the case of shrinkage treatment, the overfeed rate Of should be Of>√2, and θ in Fig. 2 should be set to 45° or more. A reticular web with a high degree of lateral orientation should be formed. In the present invention, as a means to enhance the bulky effect by using different types of polymers, see FIGS. 4A, B,
Examples include those such as C, in which the aligned fiber sheet is constructed by mixing two or more different types of fibers having different thermal properties. FIG. 4A shows an arrayed fiber sheet in which two types of fibers having different thermal properties are spatially randomly arranged. For example, among a plurality of spinning machines, some are made of nylon and the rest are made of polyester, and they are collectively wound and made into a single tow. FIG. 4B shows the case of a fiber having a composite structure in which part or all of the individual fibers are composed of two types of polymers having different thermal properties. For example, a conjugate fiber of nylon and polyester shown in Japanese Patent Publication No. 52-28918 is assembled into a tow and then partially split. FIG. 4C shows a case where fibers having different thermal properties and different polymer compositions as well as fiber shapes are spatially randomly arranged. For example, the present inventors previously demonstrated in Japanese Patent Publication No. 49-18508 that numerous discontinuous cracks along one direction were obtained from a molten polymer of a thermoplastic resin (e.g., nylon, polypropylene, etc.) containing a foamable material. An example is a case in which a sheet-like structure having a polyester tow and a sheet-like structure obtained by opening polyester tow by the method disclosed in Japanese Patent Publication No. 10962/1982 are laminated as desired. Although several examples of the present invention have been shown above that can sufficiently exhibit the bulky effect, a sufficient bulky effect can also be expected to be achieved by combining A, B, and C in FIG. The reticulated nonwoven fabric produced by the method of the present invention is
Various materials for manufacturing non-woven fabrics, woven materials, packaging materials,
It can be used as an excellent material in many fields such as clothing, insulation materials, cushion materials, synthetic paper, electrical insulation materials, interior materials, vehicle materials, and agricultural materials.
In particular, because of its good bulk and drapability, it is ideal for high-grade filter materials, high-grade clothing materials, etc. Furthermore, the reticulated nonwoven fabric produced by the method of the present invention is also excellent in various impregnated base materials, coating base materials, etc., and its processing applications are not limited to these. These can be easily carried out by installing a general impregnating device or coating device either before or after the heat treatment box of the manufacturing method of the present invention. Further, when manufacturing according to the method of the present invention, various additives such as retardants, colorants, stabilizers, and absorbers may be added at the impregnation and coating treatment steps. The method of the present invention will be described in detail below with reference to Examples. Example 1 An example is shown in which an alternating multilayer body of sheet-like nonwoven fiber structures having numerous longitudinal cracks is used according to the method described in Japanese Patent Publication No. 49-18508 proposed by the present inventors. The X sheet component consists of a blended polymer consisting of 35% polystyrene and 65% polyethylene, and the Y sheet component consists of 100% nylon-6.
If the X and Y sheets are classified according to the classification shown in Figure 1, they will be classified as D.
become. These alternate composite layers have the sheet width shown in Figure 3.
L ₁ is 20cm and overfeed ratio (Of)
2.0, feed the rollers 3 and 3', and spread the belt 5.
With both ends held by pins 4, the web is stretched in the width direction to form a net-like web 6, and placed in a heat treatment box 8 after being lightly pre-pressed by a pair of rollers 7 and 7'. The temperature atmosphere inside this box is adjusted to a range of 120 to 160°C from the inlet to the outlet. Then, while keeping the heat insulated, it is finished to a thickness of 1.5 mm using finishing presses 10 and 10'. This reticulated nonwoven fabric has a number of crimp
The weight was 45C/cm, and the bulkiness and drape properties were good. Examples 2 to 7 Experiments were carried out in the same manner as in Example 1 by laminating fiber sheets arranged in the vertical direction that fit the classifications A to D in FIG. 1. The manufacturing method conditions and results of each example are summarized in Table 1. All examples had good bulkiness and drape.

[Table] The abbreviations in the table above represent the following, respectively. Pst Polystyrene PE Polyethylene PP Polypropylene NY-6 Nylon 6 PET Polyethylene terephthalate

[Brief explanation of the drawing]

FIG. 1 is a classification diagram of fiber aggregates arranged in the vertical direction used in the present invention, and FIG.
It is a figure which extended the said fiber aggregate of a figure in the width direction. FIG. 3 is a perspective view showing an example of the method of the present invention. FIG. 4 schematically represents a cross-sectional view of a nonwoven fabric according to an example of the method of the present invention.

Claims (1)

[Scope of Claims] 1. A fiber aggregate containing at least 10% by weight of thermoplastic synthetic fibers having latent heat crimpability or heat shrinkability and arranged substantially in the vertical direction, in which the fibers are arranged at a slight angle to each other. intersect with each other, or are partially intertwined, or partially joined with adhesive,
Alternatively, two or more partially self-bonded aligned fiber sheets are laminated, and in an overfeed state,
A method for producing a reticulated nonwoven fabric, which comprises forming a reticulated fiber web by stretching it in the width direction while gripping both ends, and then increasing the bulk by non-contact heat treatment while gripping both ends. 2. The method according to claim 1, in which flat or embossed pressing is performed before non-contact heat treatment. 3. Claim 1, in which after non-contact heat treatment, flat or embossed pressing is performed in a heat-retaining state.
Method as described in section. 4. The method according to claim 1, wherein the arranged fiber sheet is composed of the same type of fibers. 5. The method according to claim 1, wherein the aligned fiber sheet is constituted by a mixed assembly of two or more types of different types of fibers having different thermal properties. 6. The method according to claim 1, wherein at least some of the fibers constituting the arrayed fiber sheet are conjugate fibers of different types of polymers.