JP2769180B2 - Non-woven sheet with anisotropic heat shrink properties - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a nonwoven sheet having anisotropic heat shrink properties. More specifically, it is a nonwoven sheet excellent in elongation strength properties, especially excellent in initial modulus properties, and has anisotropic heat shrinkage properties, and is excellent in fuzz resistance properties and surface smoothness. It is used for shrink labels, wrapping tapes and the like.

(Prior Art) Conventionally, long-fiber nonwoven sheets have been used in various fields. For example, when used for a shrinkable label or the like that is wound around a container such as a glass bottle and heat-shrinked, the property of shrinking more in one axis direction, that is, having anisotropic heat shrinkage property, and a nonwoven sheet are sufficiently satisfied. At the same time, it is required that the nonwoven sheet has sufficient fuzz resistance and that the surface of the nonwoven sheet has sufficient smoothness when performing printing or the like.

Conventionally, in order to obtain a long-fiber nonwoven sheet having anisotropic heat shrinkage properties, there is a technique using undrawn fibers of an aromatic polyester. For example, JP-A-61-174463 discloses that the elongation at break is 100% or more. A nonwoven sheet is produced by partially thermocompressing a web made of polyester filament fibers having a heat shrinkage of 20% or more with an embossing roll or joining fibers together by mechanical entanglement with a needle punching machine. After relaxing heat treatment, a method of stretching while applying heat in a predetermined direction has been proposed. Also, JP-A-63-1274
No. 7, a method is proposed in which a web made of an unstretched aromatic polyester filament having a breaking elongation of 80 to 300% is partially thermocompression-bonded with an embossing roll, further partially thermocompression-bonded again, and then heated and stretched. ing.

(Problems to be Solved by the Invention) According to Japanese Patent Application Laid-Open No. 61-174463, when a nonwoven sheet is fuzzed, if the temperature of the partial thermocompression bonding of the web is low, the nonwoven sheet cannot be fuzzed. On the other hand, if the temperature for partial thermocompression bonding is increased to provide sufficient fuzzing, the nonwoven sheet shrinks during partial thermocompression bonding with an embossing roll, and the sheet width becomes narrow, or the spots are noticeably poor. There is a problem that a woven sheet is obtained, and in some cases, the web is fused to the embossing roll and wound around the roll.

On the other hand, in Japanese Patent Application Laid-Open No. 63-12747, after partial thermocompression is performed once at low temperature, partial thermocompression is performed again with a high-temperature embossing roll, and fuzzing is performed. However, the surface unevenness due to the embossing roll when partial thermocompression bonding is performed again remains, and the high level of surface smoothness intended by the present invention cannot be obtained.

On the other hand, when a long-fiber non-woven sheet is used in the field of wrapping tapes such as electric wire pressing, in addition to having sufficient tensile strength in the lapping direction and satisfying surface smoothness and fuzz resistance, it is particularly suitable for wrapping. In order to prevent the tape from entering the width, a sufficiently high initial modulus is required,
In the actual situation, the nonwoven sheet obtained by the conventional spunbonding method does not always have a sufficient initial modulus and has to cope with the increase in the basis weight of the nonwoven sheet.

The present inventors have conducted intensive studies to solve these problems, and as a result, have a relatively low crystallinity, molecular orientation and a low softening temperature, and from an aromatic polyester filament having a high elongation at break of single yarn. The present inventors have found that the above-mentioned problems can be solved by using a non-woven sheet made of the above-mentioned non-woven sheet and subjecting the sheet to appropriate processing.

The object of the present invention is that it is hard to fluff even by surface friction,
An object of the present invention is to provide a nonwoven sheet having a sufficiently satisfactory surface smoothness when performing printing and the like, having an excellent initial modulus, and having anisotropic heat shrinkage characteristics.

(Means for Solving the Problems) In the present invention, in a nonwoven sheet of long fibers made of an aromatic polyester, a web having a breaking elongation of a single fiber of more than 300% and 600 or less is used as the aromatic polyester, Partial thermocompression bonding at a temperature between the secondary transition point (Tg) and Tg + 20 ° C or lower, and further thermocompression bonding with a felt calender drum while suppressing surface area, the entanglement point between the surfaces of multiple single fibers in the nonwoven sheet The entangled points are fused and integrated with each other, then stretched, and the fused and entangled entangled points are irregularly joined in a tongue-like manner and are interspersed. The dry heat shrinkage differs in different directions, the surface is smooth, the direction of low dry heat shrinkage is 20% or less, and the low dry heat shrinkage and high dry heat shrinkage perpendicular to it The difference between the nonwoven fabric and the nonwoven fabric is 15% or more. 5% elongation stress at low bets of dry heat shrinkage direction is 5Kg / 5 cm
A non-woven fabric having anisotropic heat shrinkage characteristics of not less than width and having a dry heat shrinkage in a direction perpendicular to the width of not more than 0.2 kg / 5 cm width and a breaking elongation of not less than 130%. Sheet,
It is. The nonwoven sheet according to the present invention includes a step of partially thermocompression bonding a web composed of long fibers having a breaking elongation of an aromatic polyester of more than 300 and not more than 600% using an embossing roll; The subsequent non-woven sheet is heat-treated while the movement of the non-woven sheet is suppressed while restricting the movement due to the shrinkage of the fiber. Heating and stretching the woven sheet in the flow direction at the time of manufacturing the woven sheet.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1, 2 and 3 are micrographs showing the fiber shape of the nonwoven sheet of the present invention, and FIG.
2 is a magnification of 1,000 times, and FIG. 3 is a magnification of 100 times. FIG. 1 and FIG. 2 are photographs showing typical examples of entangled points having a tongue-like joint in the present invention. The surfaces of a plurality of single fibers in a nonwoven sheet are fused and integrated with each other. It shows that it has a tongue-shaped joint at the joint of the entangled points. FIG. 3 shows that the entangled points having a tongue-like joint in the present invention are scattered irregularly in the nonwoven sheet.

In the nonwoven sheet of the present invention, such entanglement points, in the average plane of the nonwoven sheet, within a square of 1 mm square,
Preferably there are at least three, preferably five.

FIG. 4 shows a web made of long fibers having relatively low crystallinity, molecular orientation and low softening temperature of a single fiber made of an aromatic polyester having a breaking elongation of more than 300% and 600% or less, and a pair of embossing rolls. When the nonwoven sheet when partially thermocompression-bonded at a relatively low temperature is used and viewed in the flow direction during manufacturing (hereinafter abbreviated as the vertical direction), a cross section cut in a direction perpendicular to the direction (hereinafter abbreviated as the horizontal direction) FIG. 3 is a view schematically showing the shape and bonding state of each fiber in FIG. However, in order to clearly show the configuration, this non-woven sheet is formed in a horizontal direction perpendicular to the vertical direction yarn (hereinafter abbreviated as vertical yarn) in the same plane as the vertical direction yarn (hereinafter abbreviated as vertical yarn). (Hereinafter abbreviated as weft thread)
In the figure, only the warp yarn is shown.

1 is a cross-section, 2 is a non-thermocompression part, and 3 is a partial thermocompression part. In the partial thermocompression bonding section 3, while each fiber substantially keeps the same cross-sectional shape as when the web is formed, most fibers are lightly joined to each other, while In the non-thermocompression bonding part 2, the apparent fiber density is low and bulky, and only the surfaces of some fibers are joined together. In the non-woven sheet at this stage,
There are also irregularities on the surface due to the embossing roll, and the fuzz resistance and surface smoothness aimed at by the present invention cannot be obtained.

FIG. 5 shows a non-woven sheet having the cross-sectional structure of FIG. 4 as an example, using a felt calender comprising a rotating drum and a rotating felt shown at 21 and 22 in FIG. At a relatively high temperature, a diagram schematically showing the shape and bonding state of each fiber in a cross section cut in the horizontal direction when viewed in the vertical direction of the nonwoven sheet when thermocompression-bonded in a planar manner at a relatively low temperature. is there. FIG. 5 shows a case in which the felt calender drum 6 has the felt 7 on a relatively flat surface on the surface having irregularities on the surface in FIG. 4, but the reverse is also possible. Reference numeral 2 'in the figure denotes a portion formed by heat treatment while suppressing the non-thermocompression bonding portion 2 in FIG. 2 ′, 2 was sandwiched between the felt calender drum 6 and the felt 7 and pressure and heat were applied, so that the bonding between the fiber surfaces increased compared to 2, especially the felt calender drum 6 side Near the surface, almost all of the fibers are sufficiently bonded to each other, the apparent fiber density is high, and the thickness is smaller than 2.

On the other hand, in the partial thermocompression bonding section 3 in FIG. 4, each fiber shrinks due to heating, and as a result, a part of the bonding between the light surfaces of the fibers is once dislodged, resulting in bulkiness and almost 2 ′. The fibers are formed to have the same thickness, and then almost the fibers near the surface on the side of the felt calender drum 6 receive more heat than the internal fibers as in 2 ', so that the surfaces are firmly joined to each other, and 3' Becomes Thus, the nonwoven sheet having the cross-sectional shape of FIG. 5 has a fairly high level of surface smoothness, and at least the felt calender drum side has a fairly high level of fuzz resistance.

Surprisingly, surprisingly, even after the subsequent heat stretching, the fuzz resistance of the surface smoothness is almost maintained, and the nonwoven sheet aimed at by the present invention is obtained.

FIG. 6 shows that the warp yarn 8 and the weft yarn 9 are fused and integrated firmly with each other at the surface of each fiber near the surface of the felt calender drum 6 in the nonwoven sheet shown in FIG. It is a schematic diagram which shows the state of the confounding point performed. The nonwoven sheet having this entangled point has a sufficiently satisfactory fuzz resistance, and by selecting an appropriate felt calender drum temperature and pressure, a high degree of stretchability and length can be maintained while maintaining the fuzz resistance. , And both have high heat shrinkage characteristics.

The non-woven sheet having the entangled point shown in FIG. 6 is stretched by heating in the vertical direction, so that it has high strength and high modulus in the vertical direction, and has low shrinkage in the vertical direction and high shrinkage in the horizontal direction. It is possible to obtain a nonwoven sheet having the characteristic of having an anisotropic heat shrinkage property and having a very small shrinkage stress in the transverse direction. That is, by stretching the nonwoven sheet having the entangled points shown in FIG. 6 in the vertical direction, most of the fibers in the nonwoven sheet are arranged in the vertical direction, and the fibers arranged in the vertical direction are: At the same time as the molecular orientation is increased by stretching, the degree of orientation and crystallinity also advances, so that the strength of the nonwoven sheet in the vertical direction, especially the initial modulus, is improved, and the nonwoven sheet has a reduced shrinkage in the vertical direction. On the other hand, since the fibers arranged in the horizontal direction are not drawn in the horizontal direction, unlike the fibers in the vertical direction, neither the molecular orientation nor the orientation crystallinity advances, and the shrinkage is as high as before the drawing. Is shown. However, since the number of fibers arranged in the horizontal direction decreases as the degree of stretching in the vertical direction advances and becomes extremely small, the shrinkage stress becomes extremely small despite the high contraction rate in the horizontal direction. ,
A nonwoven sheet having the above characteristics is obtained. In addition, even after the heat stretching, the fusion-bonded joint is hard to be detached, so that the nonwoven sheet is less fuzzy and the surface smoothness is maintained.

FIG. 7 is a cross-sectional view schematically showing the state of the entanglement points in the nonwoven sheet when the nonwoven sheet having the entanglement points in FIG. 6 is heated and stretched in the vertical direction. FIG. FIG. 7 is a view of FIG. 7 viewed from above. From FIGS. 7 and 8, the bonding interface 10 between the fused and integrated single fibers in FIG. 6 expands along with the drawing of the fiber 8 (vertical yarn), and is referred to in the present invention.
This shows that a tangled state having a tongue-shaped joint 11 is obtained.

The term "tongue-shaped bonding" as used in the present invention means that the bonded interface between the fused and integrated single fibers does not come off even if drawn, and extends together with the drawn yarn and spreads in a tongue shape. 9 to 11 show typical examples.

FIG. 10 shows an example in which the shape of the tongue-like joint (11 'in FIG. 10) is substantially symmetrical, and FIG. 9 shows that the shape is asymmetric because the yarns to be joined are not orthogonal. As an example, such an asymmetrical joint may be used. FIG. 11 shows a case in which the spread of the tongue-like joint is extremely small, and when viewed from directly above as shown in FIGS. 9 and 10, the tongue-like joints above and below the weft are difficult to see. FIG. 11 shows an example in which the upper joint is hidden behind the weft thread, as viewed from a position where the lower joint of the weft thread can be seen. Good.

In the present invention, the non-woven sheet is substantially free of a resin or the like for bonding the fibers in the non-woven sheet. By scattered irregularly in the seat,
It is possible to obtain a nonwoven sheet having extremely good fuzz resistance and having satisfactory tensile strength and elongation characteristics, surface smoothness and anisotropic heat shrinkage characteristics.

In the present invention, the direction in which the dry heat shrinkage is different from one direction in the nonwoven sheet in the direction perpendicular to the direction, and the direction in which the lower shrinkage is 20% or less, is specifically speaking. The stretching direction, that is, the direction in which the fibers are more arranged, and the direction in which the difference between the direction and the high shrinkage is 15% or more,
It means a direction perpendicular to the stretching direction.

The aromatic polyester in the nonwoven sheet of the present invention is a polyester containing a dibasic acid such as polyethylene terephthalate, polybutylene terephthalate and isophthalic acid and methyl terephthalic acid, and a dihydric alcohol such as ethylene glycol and propylene glycol as copolyesters. And so on. If necessary, a small amount of a different kind of polymer such as polyamide, polyolefin, or polycarbonate may be added to the polyester as long as the object of the present invention is not impaired.

The degree of polymerization of the aromatic polyester is not particularly limited as long as it is within a range for ordinary fiber formation.

Further, a small amount of pigment, matting agent, antistatic agent, flame retardant, resin, etc. may be added to the nonwoven sheet of the present invention within a range not to impair the purpose of the present invention.

In some cases, in order to impart a surface property, in a process after the nonwoven sheet after the partial thermocompression bonding is surface-suppressed and the surface is smoothed, the nonwoven sheet may be partially thermocompression bonded with an embossing roll. .

Next, a typical production example for obtaining the nonwoven sheet of the present invention will be described.

A web is formed by a so-called spunbond method in which a melt-spun long fiber made of an aromatic polyester is drawn by air soccer or the like and then dispersed and deposited on a collecting surface. Here, it is important that the spinning speed is 3,000 m / min or less, preferably 2,500 m / min or less, and the degree of stretching of the fibers constituting the web is reduced to lower the molecular orientation of the fibers. The elongation at break of the single fiber by 300%
Over 600%. Breaking elongation of single fiber is 3
Below 00%, Δη, a measure of the molecular orientation of the fiber, is 0.02
5 or more, the crystallinity also increases, and the softening temperature of the fiber is high. Therefore, after partially press-bonding a web made of this fiber using an embossing roll, the residual shrinkage ratio remains at least 20% in the vertical and horizontal directions, respectively. Insufficient bonding of the entangled points of the fibers in the nonwoven sheet when performing thermocompression bonding in a planar manner is not sufficient, and therefore, in the next drawing step, the bonding interface is detached and fluff is likely to occur. Results.

When the breaking elongation of a single yarn is 600% or more, the molecular orientation of the fiber is extremely low, the crystallinity is low, and the softening temperature of the fiber is extremely low. When partially press-bonded using a, non-woven sheet adhered to the embossing roll, the tensile strength of the obtained non-woven sheet after partial thermo-compression, low, poor handling properties when moving to the next step, or obtained When the non-woven sheet after the partial thermo-compression bonding is subjected to the thermo-compression bonding while the area is suppressed, the fibers are deteriorated, and only the non-woven sheet which is extremely fragile can be obtained.

Here, the fibers constituting the web are 0.5 to 30 denier, preferably 1 to 20 denier. The fibers may be mixed with fibers of the same or different fineness. or,
Fibers having an irregular cross section may be used.

Next, the process up to obtaining the nonwoven sheet as the object of the present invention will be described. First, the web is partially thermocompression-bonded using a pair of embossing rolls having an uneven pattern on at least one surface. The roll temperature is preferably not less than Tg + 20 ° C. at the time of the secondary transition (Tg) of the aromatic polyester.

When the roll temperature is Tg + 20 ° C or higher, the fibers constituting the web have a low softening temperature, so that when the web adheres to the roll and wraps around the roll, or when the web is partially thermocompressed, the fibers constituting the web are slightly At that time, in the thicker area, the fiber is hard to move and shrinks without moving much, so it becomes thicker.On the other hand, in the thinner area, the fiber moves more easily and becomes thinner. A very poor nonwoven sheet results. The roll linear pressure is 5-50kg / c
m is preferred. Here, the partial thermocompression ratio is 5 to 5
A 0% range is preferred. Further, the crimping depth is preferably 0.1 to 0.5 mm. The basis weight of the nonwoven sheet partially thermocompressed at this stage is preferably from 10 to 300 g / m ^2, but is not particularly limited.

The non-woven sheet obtained after the partial thermocompression bonding obtained in this manner is then subjected to a heat treatment while suppressing the area and controlling the movement of the fiber due to shrinkage or the like. The shrinkage of the nonwoven sheet at this stage is 20% or more, preferably in the vertical and horizontal directions, in order to obtain the anisotropic heat shrinkage property by lowering the shrinkage in the vertical direction in the next vertical stretching. It is better to leave 30% or more. As a preferred method, as shown in FIG. 12, a heat treatment is preferably performed through a heated felt calender drum 21. In that case, the drum temperature is Tg + 10 to Tg
+ 50 ° C, preferably Tg + 20 to Tg + 40 ° C. When the drum temperature is Tg + 50 ° C or higher, the fiber orientation of the non-woven sheet after partial thermocompression bonding is low due to low molecular orientation and crystallinity. Violently, cannot withstand drawing in the next step, or the constituent fibers are heated to a high temperature by a felt calender drum to promote crystallization, and the shrinkage of the nonwoven sheet is 20% or less in the vertical and horizontal directions Will decrease. If the drum temperature is Tg + 10 ° C or less, the nonwoven sheet after the partial thermocompression bonding is not sufficiently bonded at the intermingling points of the fibers in the nonwoven sheet when the thermocompression bonding is performed while the area is suppressed. It cannot control fluff. The surface pressure between the felt calender drum and the felt is preferably 10 to 200 g / cm ² .

In the present invention, to suppress the nonwoven sheet in a planar manner means that the nonwoven sheet is two-dimensionally controlled between the felt calender drum and the felt, or between a number of close tension rolls, or between hot rolls or calender rolls. It means to suppress it uniformly uniformly. In particular, it is preferably performed between the felt calender drum and the felt in order to reduce the spread of the non-woven sheet. In this way, by performing thermocompression bonding while suppressing the area, the unevenness of the surface due to partial thermocompression becomes smooth so that it is almost inconspicuous, and the entanglement points of the fibers in the nonwoven sheet are mutually The fibers are firmly fused and integrated with each other on the surfaces of the fibers and are irregularly scattered in the nonwoven sheet, and the fuzz resistance of the surface is improved.

Next, a pair of nip rolls (23, 25) in which at least one of the rolls is heated to a temperature equal to or higher than the secondary transition point (Tg) of the aromatic polyester, Then, stretching is performed in the vertical direction between the pair of nip rolls (24, 26).

The stretching ratio is preferably from 2 to 4 times, and thus, the fuzz resistance and surface smoothness, which are the objectives of the present invention, are good, and the tensile strength properties, especially the initial modulus properties are excellent, and the anisotropic heat A non-woven sheet having shrinkage characteristics can be obtained.

When using this nonwoven sheet as a shrink label,
The nonwoven sheet may be used as it is, or may be used by laminating it with a shrink film.

When this nonwoven sheet is used, for example, as a wrapping tape for holding down electric wires, since the initial modulus in the vertical direction is high, the width of the tape during wrapping is small, and shrinkage of 20% or less in the vertical direction. Because it has the property, by performing heat treatment as necessary, tightening of the winding occurs,
It has excellent morphological stability. In addition, since the contraction stress in the transverse direction is smaller than the surface frictional force between the tapes, there is almost no contraction in the width direction, and there is no problem in the lapping process.

(Example) Hereinafter, an example of the nonwoven sheet of the present invention is shown, and a comparison of physical properties with a comparative example is also shown.

The definitions of the physical properties used in the examples and the measurement method thereof are as follows.

<Standard weight> A test piece of 20 cm × 20 cm is taken, weighed, and expressed in terms of weight per m ² .

<Dry heat shrinkage> Take a test piece 30cm x 30cm and set it in the vertical and horizontal directions.
Mark at 20 cm intervals, perform a dry heat treatment at 120 ° C. for 5 minutes, and calculate the shrinkage from the dimensional change before and after.

<Dry heat shrinkage stress> Sample is sandwiched between chucks using Toyo Baldwin's “Tensilon” STM-101 Universal Tensile Test Function and Orientec Tensilon high-temperature thermostat TKC-III 1-B, 120 ° C After performing the dry heat treatment for 5 minutes, the sample is cooled to room temperature with the sample held between the chucks, and the measurement is performed.

Specimen: 5cm width x 20cm length Between chucks, grasping length: 10cm <Stretching elongation and initial modulus (stress at 5% elongation)> Toyo Baldwin's "Tensilon" STM-101 type universal tensile tester ,Measure.

Specimen: 5 cm width x 20 cm length Between chucks, gripping length: 10 cm Peeling speed: 20 cm / min At this time, the conversion value of 100 g / m ² basis weight is also calculated.

<Elongation at break of single yarn> The tensile elongation is measured using a Tensileon TM-101 universal tensile tester manufactured by Toyo Baldwin.

Grasping length: 20mm, pulling speed: 20mm / min, <Abrasion resistance (indicating fuzz resistance)> A test piece of 20cm in length x 3cm in width is subjected to 100 with a load of 500gr using an abrasion tester type II (Gakushin type). After the reciprocating friction, the change in the appearance of the test piece is determined according to the following criteria, and is used as a measure of wear resistance.

Judgment criteria Class A: No fluff at all.

 Grade B: Some fluff, but not noticeable.

 Class C: Fluff is noticeable.

<Presence or absence of tongue-shaped confounding point> The confounding point is observed with an electron microscope to determine the presence or absence.

Examples 1-2, Comparative Examples 1-3 Using a rectangular spinneret having a hole diameter of 0.25 mm and a number of holes of 1,000, polyethylene terephthalate having an intrinsic viscosity of 0.75 at a discharge rate of 2,000 g / min was spun at a melting temperature of 290 ° C. The spinning yarn was collected on a wire net at a spinning speed of 1,700 m / min with a distance of 1,000 mm from the towed air soccer to take out a uniform web.

The above-mentioned web (performance of constituent fibers; fineness: 10.6 denier, elongation at break of single yarn: 370%, web basis weight: 50 g / m ² ) was subjected to partial thermocompression bonding using a pair of emboss rolls having an uneven pattern on one surface. Was. At this time, the unit area of the convex portion of the embossing roll was 2 mm ² , and the ratio of the pressure bonding area was 18%.
Partial thermocompression bonding was performed at a lower roll temperature of 75 ° C. and a roll linear pressure of 20 kg / cm. This non-woven sheet A is then heat-treated with a felt calender (drum diameter 1,500 mm, temperature 100 ° C., processing speed 10 m / min) shown in FIG. Immediately after, stretching was performed with a pair of nip rolls (heat roll temperature: 100 ° C.) while changing the magnification to 2.6, 2 and 3.1 times, to obtain the nonwoven sheets of the present invention (Examples 1 and 2).

As Comparative Example 1, a nonwoven sheet A was heat-treated with the above-described felt calender under the same conditions as described above, and stretched to 1.7 times with the pair of nip rolls.

As Comparative Example 2, a non-woven sheet A was heat-treated on the above-described felt calender under the same conditions as above, and was wound up without stretching.

As Comparative Example 3, after spinning under the same conditions as above, the basis weight was 20 g / m ^2.
The following shows a web obtained by subjecting the web to partial thermocompression bonding under the same conditions using the embossing roll, heat-treating under the same conditions using the felt calender, and winding without stretching.

Comparative Examples 4 to 5 Using a rectangular spinneret having a hole diameter of 0.25 mm and a number of holes of 1,000, spinning polyethylene terephthalate having an intrinsic viscosity of 0.75 at a discharge rate of 1,000 g / min at a melting temperature of 290 ° C., from the spinneret to the towed air soccer At a spinning speed of 4,800 m / min, and a uniform web was taken out.

The above web (performance of constituent fibers: fineness: 1.9 denier, single yarn breaking elongation: 70%, web basis weight: 20,50 g / m ² ) Using the same embossing roll as shown in Examples 1-2, the upper and lower roll temperature was set to 230 Partial thermocompression bonding was performed at 20 ° C. and a roll linear pressure of 20 kg / cm to obtain nonwoven sheets of Comparative Examples 4 and 5, respectively.

Table 1 shows the physical property values of the nonwoven sheets of Examples 1 and 2 and Comparative Examples 1 to 5 described above.

As shown in Table 1, the nonwoven sheets of Examples 1 and 2 may be nonwoven sheets having an anisotropic heat shrinkage property that is excellent in fuzz resistance, tensile strength in at least one direction, and initial modulus. understood.

Next, in each of Comparative Examples 1 to 3, the molecular orientation of the constituent fibers was determined because the stretching ratio of the hot stretching was too low or the heating stretching was not performed after the heat treatment while the area was suppressed by a felt calender. , Low tensile strength in both the vertical direction and the horizontal direction, and does not have favorable anisotropic heat shrinkage properties, and thus cannot be a nonwoven sheet aimed at by the present invention.

Next, Comparative Examples 4 and 5 are nonwoven sheets obtained by the conventional spun-pound method and hardly shrink, and thus are not used for shrink labels. When used for wrapping tape,
Because the initial modulus is low, you have to use it by increasing the basis weight.

Examples 3-4, Comparative Examples 6-7 Polyethylene terephthalate having an intrinsic viscosity of 0.75 at a discharge rate of 2,000 g / min and a melting temperature of 290 ° C. was spun using a rectangular spinneret having a pore size of 0.25 mm and 1,000 holes. or the distance to the traction air sucker as 1,000mm, by adjusting the traction of air sucker to obtain several basis weight 50 g / m ² of web of filaments having a variety of single yarn elongation at break, example Under the same conditions as in Examples 1 and 2, partial thermocompression with an embossing roll and thermocompression with a felt calender were performed while suppressing the surface area, and a good stretching ratio was selected in the vertical direction according to each sample. Stretching was performed in the same manner as in Examples 1 and 2 to obtain various nonwoven sheets. Table 2 shows the results. Examples 3 and 4 show the effect of the present invention.

Example 5, Comparative Examples 8 to 9 The nonwoven sheet A obtained in Examples 1 and 2 was subjected to a heat treatment by changing the temperature conditions using a felt calender shown in FIG. In the same manner as in 2, stretching was performed in the vertical direction at a magnification of 3.0 times to obtain various nonwoven sheets. Table 3 shows the results. Example 5 shows the effect of the present invention.

Examples 6 to 7, Comparative Example 10 Using a rectangular spinneret having a hole diameter of 0.25 mm and a number of holes of 1.000, polyethylene terephthalate having an intrinsic viscosity of 0.75 and a discharge rate of 850 g / min was spun at a melting temperature of 290 ° C., and pulled from the spinneret. With the distance to the air soccer set at 1,000 mm, the spun yarn was collected on a wire mesh at a spinning speed of 1,800 m / min to take out a uniform web.

Under the same conditions as in Examples 1 and 2, the above web (performance of constituent fibers: 4.3 denier fineness, elongation at break of single yarn 335%, web basis weight 50 g / m ² ) was subjected to partial thermocompression bonding using embossing rolls. In addition, the felt calender shown in Fig. 12 (drum diameter 1,500 mm, temperature 95 ° C, processing speed 10 m / min)
Immediately after that, stretching was performed with a pair of nip rolls (hot roll temperature: 95 ° C.) and the magnification was changed to 1.7, 2.5, and 3.0 times, and Comparative Example 10 and the nonwoven sheet of the present invention (Example 6-7) were obtained. Table 4 shows the results. Examples 6 and 7 show the effects of the present invention.

(Effect of the Invention) The nonwoven sheet of the present invention has the following excellent features.

It is a non-woven sheet that is extremely binderless and has extremely excellent fuzz resistance.

The nonwoven sheet has an anisotropic heat shrinkage property in which the lower shrinkage in at least one direction is 20% or less and the difference between the lower shrinkage and the high shrinkage in the perpendicular direction is 15% or more.

It is a nonwoven sheet having a high tensile strength in the vertical direction, especially a high initial modulus.

In the horizontal direction, in the free state where no load is applied,
It is a non-woven sheet that shrinks considerably but has very low shrink strength.

Since it is a binderless material, it is a non-woven sheet that has no restrictions on uses that dislike foreign substances such as food and medicine.

Due to the above characteristics, it can be widely used for various shrink labels, various wrapping tapes and the like.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are micrographs showing the shape of the fiber at the entanglement point having a tongue-like joint in the nonwoven sheet of the present invention. The photographic magnification of FIG. 1 is 500 times, and FIG. The photo magnification is 1,000 times. FIG. 3 is a micrograph showing the shape of the fiber on the surface of the nonwoven sheet of the present invention, and the magnification is 100 times. 4 and 5 are diagrams schematically showing a cross section of a nonwoven sheet as an intermediate product when producing the nonwoven sheet of the present invention. 7 and 8 are a cross-sectional view and a top view, respectively, schematically showing a state of an interlaced point having a tongue-like junction according to the present invention. FIG. 6 is a plan view of FIG. 7 and FIG. FIG. 9 is a view schematically showing the state of the entanglement point at the same place as in FIGS. 7 and 8 before the nonwoven sheet having the indicated entanglement point is stretched. FIG. 9, FIG. 10, and FIG. 11 are schematic views showing typical examples of the tongue-shaped joining according to the present invention. FIG. 12 shows an apparatus 1 for producing the nonwoven sheet of the present invention.
It is a front view showing an example. 1: Intermediate product (partially thermo-compressed sheet), 1 ': Intermediate product (1 sheet constrained in area and thermo-compressed) 2: Non-thermo-compressed part, 2': 1 constrained in area, 3: a portion corresponding to 2 in 1 in the thermocompression-bonded sheet; 3: a thermocompression-bonded portion, 3 ': 1 in a sheet corresponding to 3 in 1 in a thermocompression-bonded sheet; 4: a nonwoven sheet 5: Fibers whose surfaces are joined together, 6: Huet calender drum, 7: Felt, 8,
8 ', 8 ": warp yarn, 9,9', 9": weft yarn, 10,10 ': bonding interface, 11,11': tongue-like bonding, 12: spin block, 13:
Spinneret, 14: cold air chamber, 15: air circulation, 1
6: pneumatic chamber, 17: filament group, 18: web, 19: emboss roll, 20: flat roll, 21: felt calender drum, 22: felt, 23, 24: rubber nip roll, 25:
Metal heating roll, 26: metal roll, 27: take-up roll, 28: suction drum, 29: conveyor net.

Claims (1)

(57) [Claims] 1. A nonwoven sheet of a long fiber made of an aromatic polyester, wherein a web having a breaking elongation of a single fiber of more than 300% and not more than 600% is used as the aromatic polyester, and a secondary transition point (Tg) As described above, partial thermocompression bonding is performed at Tg + 20 ° C or less, and further thermocompression bonding is performed by a felt calender drum while the surface is suppressed, and the entanglement points of the surfaces of a plurality of single fibers in the nonwoven sheet are fused and integrated with each other. Then, after being stretched, the fusion-integrated entangled points are irregularly joined in a tongue-like manner and scattered, and the dry heat shrinkage differs in one direction in the nonwoven sheet and in a direction perpendicular thereto. And the surface is smooth and the direction of low dry heat shrinkage is 20% or less, and the difference between the low dry heat shrinkage and the high dry heat shrinkage in the direction perpendicular thereto is 15% or more. And in the direction of low dry heat shrinkage of the nonwoven sheet. Stress at 5% elongation is 5kg / 5cm
Not less than 0.2 Kg / 5 cm in width and a breaking elongation of not less than 130% in a direction perpendicular thereto. Woven sheet.