JPS6312747A - Anisotropic extensible nonwoven sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonwoven sheet having anisotropy in extensibility and shrinkage.

[Conventional technology]

There are two types of shrinkable films: films that shrink more in the uniaxial direction and films that shrink more in the biaxial direction. Films that are heat-shrinkable more in one axis direction are generally used as films for packaging items by utilizing the shrinkability of the film. When using a biaxially heat-shrinkable film as a shrinkable packaging material, the film is shaped into a bag, and then the item to be packaged is placed inside the bag.
If the packaged item is not heat-shrinked, the packaged item may not be sufficiently covered, and if the packaged item is a three-dimensional structure, key points of the bag-shaped film placed over the three-dimensional structure may be temporarily held with clips, etc. If it is not stopped, there will be a problem that the film will not shrink evenly on the surface of the three-dimensional structure, and generally 2
Films that are heat-shrinkable in the axial direction have the problem that the shrinking process is complicated, leading to high costs.

On the other hand, films used as packaging materials have low tear strength and tensile strength, and also have low impact cushioning properties. Therefore,
When protection of the packaged object is particularly important, it is desired to use a nonwoven sheet that is excellent in these physical properties. In that case, it is preferable if the nonwoven packaging sheet has the property of shrinking more in one axis direction, that is, anisotropic heat shrinkability, as described above, since the packaging process can be carried out very efficiently. . However, nonwoven sheets generally have a tendency to thermally shrink in two axial directions, and a nonwoven sheet that thermally shrinks more in one axis, that is, has anisotropic thermal shrinkability, has not yet appeared. Of course, by changing the dispersion state of the fibers during manufacturing of the nonwoven sheet, the flow direction of the nonwoven sheet during manufacturing (hereinafter referred to as the vertical direction) and the direction perpendicular to the sheet flow direction (hereinafter referred to as the horizontal direction) are changed. It is possible to change the heat shrinkability in the horizontal and horizontal directions. For example, it is possible to make a nonwoven sheet that has a heat shrinkage rate of about 10% in a specific direction using single fibers that have a heat shrinkage rate of about 20%, but in that case, the fibers must be made extremely thin. As a result, physical properties such as strength deteriorate, making it impossible to obtain a practical nonwoven sheet.

[Problem that the invention seeks to solve]

An object of the present invention is to solve the problems of conventionally known packaging sheets and to provide a nonwoven sheet having anisotropic heat shrinkability and anisotropic extensibility.

[Means for solving problems]

The object of the present invention is to provide a nonwoven sheet made of aromatic polyester long fibers whose shrinkage rate differs in the machine direction during production and in a direction perpendicular to the machine direction, the nonwoven sheet having a shrinkage rate of 120% in the direction in which the shrinkage rate is lower. ℃ dry heat shrinkage rate is 20% or less, the difference between the shrinkage rate and the shrinkage rate in the direction of higher shrinkage rate is 120℃ dry heat shrinkage rate of 20% or more, and 3 in the direction of lower shrinkage rate.
% elongation stress is 50 kg, /co? This is achieved by an anisotropically extensible nonwoven sheet characterized by the above.

As a preferred manufacturing method for obtaining a nonwoven sheet having the above-mentioned anisotropically extensible nonwoven sheet, a web made of semi-stretched aromatic polyester long fibers having a breaking elongation of 80 to 300% is heated to a polyester secondary transition point (Tg ) or more, thermocompression bonded at a temperature of Tg + 50°C or less, then one side is Tg + 50°C or more,
A manufacturing method may be mentioned in which the other roll is thermally pressed again using a roll set at Tg+50° C. or lower, and then heated and stretched.

The aromatic polyester in the nonwoven sheet of the present invention is
When Tg is above room temperature, substantially amorphous semi-drawn yarn can be stably produced, and it is a polyester that can be crystallized by heat treatment. It is a copolymerized polyester containing a dibasic acid and a dihydric alcohol such as ethylene glycol or propylene glycol. Further, a small amount of a different polymer such as polyamide, polyolefin, polycarbonate, etc. may be added to the polyester.

Furthermore, pigments,
It may also contain matting agents, antistatic agents, flame retardants, resins, and the like.

The fibers constituting the nonwoven sheet in the present invention range from 0.1 to
It is 30 denier. The fibers may be a mixture of fibers of the same or different fineness.

Next, a typical manufacturing example of the nonwoven sheet having anisotropic extensibility of the present invention will be described in detail below.

A polyester long fiber web is formed using known spunbond methods. The elongation at break of the single fiber is 80%~
300%, the dry heat shrinkage rate at 105°C is 20% or more,
In addition, it is necessary that the birefringence index is 0.01 or more.

The web is heated to a roll temperature of Tg or higher using a pair of embossing rolls having an uneven pattern on at least one surface.
A nonwoven sheet is obtained by partial thermocompression bonding at a temperature of g+50° C. or lower and a linear pressure of 5 to 90 kg/c++I. The partial thermocompression bonding ratio is preferably 3 to 50%.

On the other hand, a nonwoven sheet may be obtained by intertwining the fibers with each other using a mechanically intertwined needle punch.

The number of needle bunching is preferably 50 to 400 times/d. Incidentally, fused fibers may be mixed in the production of the nonwoven sheet.

The above-mentioned nonwoven sheet obtained by thermocompression bonding or needle punching in this way was heated to Tg+50 at one roll temperature.
℃ or higher, melting point -60℃ or lower, the other roll temperature is Tg+
Thermocompression bonding is performed using rolls with a temperature difference of 50°C or less.

In this case, the embossing roll has a crimping area ratio of 3 to 40%, the crimping points are substantially evenly distributed (preferably, the size of the crimping points is 0.1 to 5 mm, and the distance between adjacent embossed patterns is 0.1 to 5 mm. (1 to 10 mm).

There are reasons for doing the above two steps. The purpose of the first stage of thermocompression bonding is to maintain the shrinkage rate and facilitate handling of the sheet-like material, while providing partially intertwined portions and imparting mechanical strength. Therefore, other methods such as needle punch interlacing method, columnar flow method, etc. may be used to achieve this purpose.

The second stage of thermocompression bonding is carried out in order to obtain mechanical strength, abrasion resistance, and strength to withstand the subsequent heating and stretching, which are the objectives of the present invention.

Next, stretching is performed while being heated by hot rolls, hot air, or the like.

Since the aromatic polyester of the present invention can be easily stretched by heating it above Tg, it can be stretched between nip rolls, with a clip tenter, etc. in the same way as a film is stretched.

By stretching at a stretching ratio of 1.2 to 3.5 times, it is possible to obtain an anisotropically extensible nonwoven sheet, which is the object of the present invention.

The nonwoven sheet of the present invention can be obtained by the method described above. This is because when the semi-stretched polyester is heated and stretched, its orientation and crystallinity are improved and its shrinkability is reduced. In addition, by stretching, the arrangement of the constituent fibers increases in the stretching direction, so that the stretching stress in the stretching direction becomes thick (and the elongation decreases. In other words, the 3% stretching stress in the heating stretching direction is 50kg/cII! or more.

The nonwoven sheet of the present invention has shrinkability and
3% elongation stress changes. As the degree of stretching increases,
Contractibility decreases and elongation stress increases by 3%.

In this way, a nonwoven sheet having anisotropic heat shrinkability that causes a large amount of heat shrinkage in the uniaxial direction and anisotropic extensibility is obtained, and exhibits excellent performance in the field of shrink packaging, tapes, and the like.

[Examples] The anisotropically extensible nonwoven sheet of the present invention will be described below based on specific examples.

The definition and measurement method used in the present invention are shown below.

- Fabric weight: Take a 20cm x 2Qcm test piece, measure its weight, and convert it to fabric weight.

・Thickness: Dial gauge (gauge point 10mmφ1 weight 80
Measure at least three points using g) and express the average value.

・120℃ dry heat shrinkage rate (single fiber) Sample length Lo under 0.1g/d load,
After removing the load and processing in dry heat at 120°C for 5 minutes,
Again, let the sample length measured under the same load be L, and calculate the dry heat shrinkage rate using the following formula.Take a 30cm x 30c+p sample (nonwoven sheet), mark it at 20cm intervals in both the vertical and horizontal directions, and ℃ dry heat treatment for 5 minutes, and the shrinkage rate is calculated from the dimensional change before and after.

・Strong elongation; Shimadzu Auto Graph DSS-
Measurement was carried out using a 2000 model universal tensile tester at a grasping length of 10 cm and a tensile speed of 20 cm/min.

・Abrasion resistance: A test piece measuring 20 cm vertically x 3 cm horizontally was tested at a load of 500 g using a friction tester type ■ (Gakushin model).
After reciprocating friction, changes in the appearance of the test piece were judged based on the following criteria and used as a measure of wear resistance.

(Judgment basis) A grade: No fluff at all.

Grade 8: There is some fluff, but it is not noticeable.

Grade 0: Fluff is noticeable.

- Air permeability, conducted by Frazier type test W of J I 5-L-1079.

- Tear strength: (Henschlam method) At least 3 test pieces each measuring 6.5 cm x 10 cm are taken in the vertical and horizontal directions, and measured using an Elemedorff type tester, and expressed as an average value in both the vertical and horizontal directions.

・Cushioning property: Place a 2 mm thick glass plate on the concrete floor, place the sample on top of it, and
When a ball is dropped from above, the height at which the glass below breaks is expressed as the height (cm).

- Birefringence (Δn): Δn is measured using a polarizing microscope and a helexcon insulator under white light.

・3% elongation stress; Auto Grap D manufactured by Shimabara Seisakusho
Grasp length IQcm using SS-2000 type universal tensile testing machine
, 3% elongation stress was measured at a tensile rate of 20 cm/min, and the value is expressed as the value divided by the cross-sectional area of the sample.

-11~3; Width 6V↓"(-knee"L hole diameter 0
．． Polyethylene terephthalate with an intrinsic viscosity of 0.75 was spun at a melting temperature of 290°C at a discharge rate of 1850 g/min using a rectangular spinneret with a diameter of 25 mm and 1000 holes, and the distance from the spinneret to the traction air server 7 car was 1000 mm. The spun yarn was collected on a wire mesh at a spinning speed of 2,600 m/min to obtain a uniform web.

The above web (performance of constituent fibers: fineness 3.3d, breaking elongation 260%, Δno, 03. Single fiber heat shrinkage rate 62%,
Web weight 80g/c++! Partial thermocompression bonding was performed using a pair of embossing rolls having an uneven pattern on one surface. The heat-compression bonding area ratio is 12%, and the fused area is 5 mm'' rectangles arranged in a staggered embossing roll using an embossing roll, and the depth of the uneven shape is Q, 5 mm.The upper and lower roll surface temperatures are , at 80°C and a pressure of 20 kg/cm.This sheet A (hereinafter referred to as sheet 8) was then bonded with a pitch of 2 mm at the top, a diameter of 1 mm, and a depth of 0.4 mm.
An embossing roll with a mm pin-like pattern and a roll with a smooth surface are thermocompressed at a processing speed of 15 m/min at an upper roll temperature of 150°C and a lower roll temperature of 90°C, and immediately after that, stretching is performed using a nip roll. Magnification 1.6, 1.8
, 2.0, the nonwoven sheet of the present invention (Example 1,
2, 3) were obtained.

As Comparative Example 4, sheet A was heat-pressed again without being heated and stretched.

Comparative Example 5 shows a commercially available uniaxially shrinkable polyethylene film.

As shown in Table 1, the nonwoven sheets of Examples 1, 2.3 have a small elongation at break in the longitudinal direction and a large elongation at break in the transverse direction. In addition, the 3% elongation stress in the vertical direction is large and the 3% elongation stress in the horizontal direction is small. It is an anisotropic heat-shrinkable nonwoven sheet having a large dry heat shrinkage rate at 120°C and a difference in shrinkage rate in the vertical direction and the horizontal direction of 20% or more. Furthermore, it has been found that a strong nonwoven sheet with high tear strength and high tensile strength, which is resistant to tearing, and has characteristics of wear resistance and air permeability can be obtained.

FIG. 1 shows a comparison of the dry heat shrinkability at 120° C. of the nonwoven sheet of the present invention and a uniaxially shrinkable polyethylene film.

From FIG. 1, the nonwoven sheet of the present invention resembles a uniaxial film.
It was found that it exhibits contractility.

Next, in Comparative Example 4, the difference in 3% elongation stress, elongation at break, and dry heat shrinkage at 120° C. in the vertical direction and the horizontal direction is small, and the anisotropy targeted by the present invention cannot be obtained.

Comparative Example 5 is a uniaxially shrinkable film, and although it can meet the purpose of the present invention in terms of shrinkability, it is small in thickness, has poor cushioning properties, and has poor breathability (and tear strength). The object of the present invention cannot be achieved because it is extremely small and easily torn.

Table 1 (Vertical/Horizontal) -1・["■ Using a rectangular spinneret with a hole diameter of 0.25 mm and 1000 holes, polyethylene terephthalate with an intrinsic viscosity of 0.75 was melted at a melting temperature of 290"C at a discharge rate of 1850 g/min. The distance from the spinneret to the traction air sucker was 1000 mm, and the spinning speed was 2000 m/m.
In was collected on a wire mesh and a uniform web was taken out. ”
A bipedal web (constituting fiber properties: fineness of 4.1 d, elongation at break of 3°10%, web basis weight of 100 g/m ) was needle punched and intertwined. The number of needle punches is 100 times/cn! , needle type No. 40 felting needle, depth of 12 mm. This sheet B (hereinafter referred to as sheet B) is subjected to relaxation heat treatment using a pin tenter. Relaxation contraction was performed by 20% in the vertical direction and 20% in the horizontal direction at an ambient temperature of 120° C. and a processing speed of 15 m/min.

When changing from sheet B (hereinafter referred to as sheet C) to sheet C, the dimensional changes are as follows. The vertical direction is from 100cm to 80cm, and the horizontal direction is from 100cm to 80cm.
It becomes m.

Further, the sheet C was heated between an embossing roll whose upper part had a pin-like pattern with a pitch of 2 mm, a diameter of 1 mm, and a depth of 0.4 mm, and a roll with a smooth surface, at a temperature of 130°C with the upper roll A.
Thermocompression bonding was carried out at a lower roll temperature of 85° C. and a processing speed of 15 m/1 lIin, and immediately after that, the stretching ratio was set to 1.
3 and 1.5, the nonwoven sheet of the present invention (Example 6.
7) was obtained.

As Comparative Example 8, the Sea 1-B was used.

As shown in Table 2, the nonwoven sheets of Examples 6 and 7 had a dry heat shrinkage rate of 120°C in the vertical direction of 30% or more, a dry heat shrinkage rate of 120°C in the horizontal direction of 10% or less, and , it has anisotropic heat shrinkability with a difference in horizontal shrinkage of 20% or more. In addition, these are non-woven sheets with a 3% elongation stress in the vertical direction of 50 kg/
cn1 or more, 3% elongation stress in the horizontal direction is 30 kg /
co! Below, the elongation at break in the vertical direction is small at 30% or less, and the elongation at break in the horizontal direction is large at 100% or more, so it is difficult to stretch in the vertical direction and easy to stretch in the horizontal direction.
It is a nonwoven sheet with anisotropic extensibility. Furthermore, it is a nonwoven sheet with high tear strength and excellent toughness, cushioning properties, etc.

Table 2 (Vertical/Horizontal) On the other hand, Comparative Example 8 shows approximately the same values for both shrinkage and extensibility in the vertical and horizontal directions, and is not a nonwoven sheet that satisfies the purpose of the present invention.

〔Effect of the invention〕

The nonwoven sheet according to the present invention is a novel nonwoven sheet that has both characteristics that are not present in conventional nonwoven sheets and characteristics that conventional nonwoven sheets have, and has the following excellent characteristics. .

■It is an anisotropically stretchable nonwoven sheet with different ease of stretching in the vertical and horizontal directions.

■It is an anisotropic heat-shrinkable nonwoven sheet with a difference of 20% or more in dry heat shrinkage at 120°C in the vertical and horizontal directions.

■Because it is thicker, it has better cushioning properties than film.

■Due to its high tear strength, it is extremely tough and difficult to tear compared to film.

■Since it is a non-woven sheet, it has breathability.

■As it is made of aromatic polyester fiber, it has heat resistance of 1I
Excellent weatherability.

Because of the above characteristics, it has performance that film does not have, and it is used as a shrink wrapping material in unconventional packaging processing fields, especially in the fields of industrial materials, precision machine parts, glass, ceramics, etc. Efficient (can be implemented)

Furthermore, due to its characteristic of being difficult to stretch in one direction, adhesive tape,
It can also be widely used in tape fields such as wire holding tape.

[Brief explanation of drawings]

FIG. 1 is a graph showing shrinkage characteristics of a nonwoven sheet and a polyethylene shrink film according to the present invention. a and a' are the curves of the nonwoven sheet of the present invention, and b and b' are the curves of the film of the comparative example, respectively.

Claims (2)

[Claims] 1. A nonwoven sheet made of aromatic polyester long fibers whose shrinkage rate differs in the flow direction during production and in a direction perpendicular to the flow direction, the shrinkage rate of the nonwoven sheet being 1 in the direction in which the shrinkage rate is lower.
The dry heat shrinkage rate at 20℃ is 20% or less, and the difference between that shrinkage rate and the shrinkage rate in the direction of the higher shrinkage rate is 2 at 120℃ dry heat shrinkage rate.
0% or more, and a 3% elongation stress in the direction of low shrinkage rate is 50 kg/cm^2 or more. 2. A web made of semi-stretched aromatic polyester long fibers with a breaking elongation of 80 to 300% is thermocompression bonded at a temperature above the secondary transition point (Tg) of polyester and below Tg + 50°C, and then one side is bonded to Tg + 50°C. Above, the other side is Tg+50℃
A method for producing an anisotropically extensible nonwoven sheet, which comprises heat-stretching the sheet after thermocompression bonding is carried out again using rolls set as follows.