JPH0762310B2 - Anisotropic stretchable non-woven sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nonwoven sheet having anisotropic stretchability and shrinkability.

[Conventional technology]

There are two types of shrinkable films: a film that shrinks more in the uniaxial direction and a film that shrinks in the biaxial direction. As a film for wrapping an object to be packaged by utilizing the shrinkability of the film, a film that shrinks more in the uniaxial direction is generally used. This is because when a biaxially heat-shrinkable film is used as the shrinkable wrapping material, the film is made into a bag shape and then the object to be packed is put in the bag.
If it is not heat-shrinked, the object to be packaged may not be sufficiently covered, or if the object to be packaged has a three-dimensional structure, the bag-like film covered with the three-dimensional structure should be clipped at the required points. If it is not stopped, the film will not shrink evenly on the surface of the three-dimensional structure.
A film that shrinks heat in the axial direction has a problem that the shrinking process becomes complicated and the cost increases.

On the other hand, a film as a packaging material has low tear strength and tensile strength, and also has poor cushioning property against impact. Therefore,
When the protection of the article to be packaged is particularly important, it is desired to use a non-woven sheet having excellent physical properties. Even in that case, it is preferable that the packaging non-woven sheet has a property of shrinking more in the uniaxial direction as described above, that is, anisotropic heat shrinkability, since the packaging step can be performed very efficiently. However, non-woven sheets generally have a tendency to be heat-shrinked in biaxial directions, and more non-woven sheets have more heat shrinkage in uniaxial directions, that is, non-woven sheets having anisotropic heat-shrinkability have not yet appeared. Of course, by changing the fiber dispersion state during the manufacture of the non-woven sheet between the sheet flow direction (hereinafter referred to as the vertical direction) of the non-woven sheet and the direction perpendicular to the sheet flow direction (hereinafter referred to as the horizontal direction) during the manufacturing, the vertical direction The heat shrinkability can be changed depending on the horizontal direction. For example, a non-woven sheet having a heat shrinkage rate of about 10% in a specific direction can be made by using a single fiber having a heat shrinkability of about 20%, but in that case, the fiber must be extremely thin, As a result, physical properties such as strength are deteriorated, and a practical nonwoven sheet cannot be obtained.

[Problems to be solved by the invention]

An object of the present invention is to provide a non-woven sheet having anisotropic heat shrinkability and anisotropic stretchability by solving the problems of the conventionally known packaging sheet.

[Means for solving problems]

An object of the present invention is an aromatic polyester long-fiber non-woven sheet having a shrinkage ratio in a flow direction during production and a direction perpendicular to the flow direction, and having a partial thermocompression bonding portion. 120 ° C dry heat shrinkage in the lower direction is 2
0% or less, the difference between the shrinkage ratio and the shrinkage ratio in the direction of the higher shrinkage ratio is 20% or more at 120 ° C dry heat shrinkage ratio, and the 3% elongation stress in the stretching direction is 50 kg / cm ³ or more. Is achieved by an anisotropic stretchable non-woven sheet.

As a preferred production method for obtaining the anisotropic stretchable nonwoven sheet, the elongation at break is 80 to 300%, and the dry heat shrinkage at 120 ° C is 20%.
As described above, a web made of semi-stretched aromatic polyester long fibers having a birefringence of 0.01 or more is partially thermocompressed at a temperature of not less than the second-order transition point (Tg) of the polyester and not more than Tg + 50 ° C, and then one roll temperature A manufacturing method is characterized in that after partial thermocompression bonding is performed by a pair of rolls having a temperature difference of Tg + 50 ° C. or higher and a melting point of −60 ° C. or lower and the other roll temperature is Tg + 50 ° C. or lower, heat stretching is performed in the flow direction. it can.

Aromatic polyester in the nonwoven sheet of the present invention,
Tg is room temperature or more, a substantially amorphous semi-drawn yarn can be stably produced, and is a polyester that can be crystallized by heat treatment, such as polyethylene terephthalate, polybutylene terephthalate, and isophthalic acid and methyl terephthalic acid. It is a copolyester obtained by copolymerizing 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 or polycarbonate may be added to the polyester.

In addition, pigments are added to give the nonwoven sheet special properties.
Matting agents, antistatic agents, flame retardants, resins and the like may also be included.

The fibers constituting the non-woven sheet according to the present invention are 0.1 to 30.
It is denier. The fibers may have the same or different fineness.

Next, typical production examples of the nonwoven sheet having anisotropic stretchability of the present invention will be described in detail below.

A polyester continuous fiber web is formed by a known spunbond method. The breaking elongation of the single fiber is 80% to 30
It is necessary that the dry heat shrinkage at 0% and 120 ° C is 20% or more and the birefringence is 0.01 or more.

Using a pair of embossing rolls having a concavo-convex pattern on at least one surface of the web, a roll temperature of Tg or higher, Tg +
Partial thermocompression bonding is carried out under a linear pressure of 5 to 90 kg / cm ² at 50 ° C or lower to obtain a nonwoven sheet. The partial thermocompression bonding ratio is preferably 3 to 50%.

In this way, the non-woven sheet obtained by the first stage partial thermocompression bonding has a temperature difference such that one roll temperature is Tg + 50 ° C. or higher and the melting point is −60 ° C. or lower and the other roll temperature is Tg + 50 ° C. or lower. The second stage partial thermocompression bonding is performed in pairs. At that time, the embossing roll having a crimping area ratio of 3 to 40% and the crimping points distributed substantially evenly (preferably, the size of the crimping points is 0.1 to 5 mm ² , and the distance to the adjacent embossing pattern is 1 ~ 1
0 mm).

There are reasons for performing the above two steps separately. The thermocompression bonding in the first stage has the purpose of maintaining the shrinkage ratio and facilitating the handling of the sheet-like material, and at the same time, providing the entangled portions to give mechanical strength.

The second stage thermocompression bonding is performed in order to obtain the mechanical strength, abrasion resistance, and strength to withstand the subsequent heat drawing, which is the object of the present invention.

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

The aromatic polyester of the present invention can be easily stretched by heating it to a temperature of Tg or higher, and thus can be stretched by a nip roll, a clip tenter or the like in the same manner as the stretching of the film.

The anisotropic stretchable nonwoven sheet which is the object of the present invention can be obtained by stretching 1.2 to 3.5 times as the stretching ratio.

The nonwoven sheet of the present invention can be obtained by the above method. This is because when the semi-stretched polyester is heated and stretched, the orientation and crystallinity are improved and the shrinkability is reduced. Further, by stretching, the number of constituent fibers is increased in the stretching direction, so that the stretching stress in the stretching direction increases and the elongation decreases. That is, the 3% elongation stress in the heating and stretching direction is 50 kg / cm ² or more.

The nonwoven sheet of the present invention has shrinkability depending on the degree of heat drawing,
3% elongation stress changes. As the degree of stretching increases,
The shrinkage is reduced and the 3% elongation stress is increased.

In this way, a non-woven sheet having anisotropic heat-shrinkability, in which a large amount of heat shrinks in the uniaxial direction, and anisotropic stretchability is obtained, and exhibits excellent performance in the shrink-wrapping field, tapes and the like.

〔Example〕

Hereinafter, the anisotropic stretchable nonwoven sheet of the present invention will be described based on specific examples.

The definitions and measuring methods used in the present invention are shown below.

・ Unit weight: Take a test piece of 20 cm x 20 cm, weigh it, and convert it to unit weight.

・ Thickness: Measure at least 3 points using a diamond gauge (stylus 10 mmφ, weight 80 g), and express the average value.

・ 120 ° C dry heat shrinkage (single fiber) Sample length L ₀ under load 0.1g / d, the load was removed, the sample was treated in 120 ° C dry heat for 5 minutes, and then measured again under the same load Let L be the length and obtain the dry heat shrinkage rate by the following formula (Non-woven sheet) Take a sample of 30 cm x 30 cm, and set its vertical direction,
Mark at 20 cm intervals in the horizontal direction, perform 120 ° C dry heat treatment for 5 minutes, and calculate the shrinkage ratio from the dimensional change before and after.

-Strength / elongation: Measured by Shimadzu Auto Graph DSS-2000 type universal tensile tester at a grasping length of 10 cm and a pulling speed of 20 cm / min.

・ Abrasion resistance: A vertical 20 cm × horizontal 3 cm test piece was rubbed 100 times with a friction tester type II (Gakushin type) under a load of 500 g, and then the appearance change of the test piece was checked against the following criteria. It was judged as the standard of wear resistance.

(Judgment Criteria) Class A: No fuzz at all.

Class B: Some fluff but not noticeable.

Class C: Conspicuous fuzz.

・ Breathability: Performed with a JIS-L-1079 Frajure tester.

・ Tear strength: (Bendurum method) 6.5 cm × 10 cm test pieces are taken in the vertical and horizontal directions, 3 or more in each direction, and measured vertically using an Elemerdorf type tester.
Expressed as an average value in each horizontal direction.

・ Cushioning: A glass plate with a thickness of 2 mm is placed on a concrete floor, a sample is placed on it, and a steel ball weighing 10 g is dropped from above, at which height the cushioning glass will break ( cm).

Birefringence (Δn); Δn is measured using a polarizing microscope Belex compensator under white light.

・ 3% elongation stress; grasped by Shimadzu's Auto Grap DSS-2000 type universal tensile tester at a length of 10 cm and a tensile speed of 20 cm / min.
The 3% elongation stress was measured, and the value was divided by the cross-sectional area of the sample.

Examples 1 to 3; Comparative Examples 4 and 5, using a rectangular spinneret having a hole diameter of 0.25 mm and 1000 holes, the discharge amount is 85
Polyethylene terephthalate with an intrinsic viscosity of 0.75 at 0 g / min was spun at a melting temperature of 290 ° C, and the distance from the spinneret to the air sucker for traction was 1000 mm, and the spun yarn was spun at a spinning speed.
A uniform web was collected by collecting on a wire net at 2600 m / min.

The above web (performance of the constituent fibers: fineness 3.3d, elongation at break
260%, Δn 0.03, single fiber heat shrinkage 62%, web weight 80g / c
m ² ) was subjected to partial thermocompression bonding using a pair of embossing rolls having an uneven pattern on one surface. In addition, the depth of the uneven shape is 0.6 m by using the embossing roll in which the rectangles having the thermocompression bonding area ratio of 12% and the fused area of 5 mm ² are arranged in a zigzag pattern.
Let m. Upper and lower roll surface temperature is 80 ℃, pressure is 20kg / cm
It was thermocompression bonded. (Hereinafter referred to as Sheet A) This Sheet A
Then, the upper part has a pitch of 2 mm, a diameter of 1 mm, a depth of 0.4 mm and an embossing roll having a pin-shaped pattern, and a surface having a smooth roll, at an upper roll temperature of 150 ° C. and a lower roll temperature of 90 ° C.,
Thermocompression bonding was carried out at a processing speed of 15 m / min, and immediately thereafter, the stretch ratio was changed to 1.6, 1.8, 2.0 in the flow direction by a nip roll to obtain the non-woven sheet (Examples 1, 2, 3) of the present invention.

As Comparative Example 4, the sheet A is not heat-stretched and thermocompression-bonded again.

As Comparative Example 5, a commercially available uniaxially shrinkable polyethylene film is shown.

As shown in Table 1, the nonwoven sheets of Examples 1, 2, and 3 have a small breaking elongation in the vertical direction and a large breaking elongation in the horizontal direction. Moreover, the 3% elongation stress in the vertical direction is large, and the 3% elongation stress in the lateral direction is small, that is, it is difficult to elongate in the longitudinal direction, easy to elongate in the lateral direction, and the 120 ° C dry heat shrinkage ratio in the longitudinal direction is small. This is an anisotropic heat-shrinkable non-woven sheet having a large dry heat shrinkage at 120 ° C and a difference in shrinkage between the vertical and horizontal directions of 20% or more. Furthermore, the tear strength is great,
Since the tensile strength is also large, it has been found that a tough non-woven sheet which is hard to break and which has abrasion resistance and air permeability can be obtained.

FIG. 1 shows the non-woven sheet of the present invention and the uniaxially shrinkable polyethylene film in comparison with each other at 120 ° C. dry heat shrinkage. From FIG. 1, it was found that the non-woven sheet of the present invention exhibits shrinkability similar to that of a uniaxial film.

Next, in Comparative Example 4, there is little difference between the vertical direction and the horizontal direction in all of the 3% elongation stress, the elongation at break, and the 120 ° C. dry heat shrinkability,
The anisotropy targeted by the present invention cannot be obtained.

Comparative Example 5 is a uniaxially shrinkable film, and the object of the present invention can be achieved with respect to the shrinkability, but the thickness is small, the cushioning property is poor, the air permeability is low, and the tear strength is extremely low. However, the object of the present invention cannot be achieved because it is easily broken.

[Effects of the Invention] The non-woven sheet according to the present invention is a novel non-woven sheet having both sides which have characteristics not possessed by the conventional non-woven sheet and characteristics possessed by the conventional non-woven sheet. It has excellent characteristics.

This is an anisotropic stretchable non-woven sheet that has different stretchability in the vertical and horizontal directions.

It is an anisotropic heat-shrinkable non-woven sheet with a difference of 20% or more in dry heat shrinkage at 120 ℃ in the vertical and horizontal directions.

Since it has a large thickness, it has better cushioning properties than a film.

Since it has a large tear strength, it has a toughness that is extremely difficult to tear as compared with a film.

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

As it is made of aromatic polyester fiber, it has excellent heat resistance and weather resistance.

Due to the above features, it has properties not possessed by films, and as shrink wrapping material, shrink wrapping is used as an unprecedented application field of packaging processing, especially in industrial materials, precision machine parts, glass, pottery, etc. It can be implemented efficiently.

Furthermore, since it is difficult to stretch to one side, adhesive tape,
It can be widely used in the field of tape such as wire holding tape.

[Brief description of drawings]

FIG. 1 is a graph showing shrinkage ratio characteristics of a nonwoven sheet and a polyethylene shrink film according to the present invention. Reference numerals a and a'represent the non-woven sheet of the present invention, and b and b'represent curves of the comparative film.

Claims (2)

[Claims] 1. An aromatic polyester long-fiber non-woven sheet having a shrinkage rate which differs between a flow direction during production and a direction perpendicular to the flow direction and which has a partial thermocompression bonding portion, wherein the shrinkage rate of the non-woven sheet is 120 ° C dry heat shrinkage in the lower direction is 20
% Or less, the difference between the shrinkage rate and the shrinkage rate in the direction of the higher shrinkage rate is 20% or more at 120 ° C dry heat shrinkage rate, and the 3% elongation stress in the stretching direction is 50 kg / cm ³ or more. An anisotropic stretchable non-woven sheet characterized by being present. 2. A web made of semi-stretched aromatic polyester continuous fibers having a breaking elongation of 80 to 300%, a dry heat shrinkage ratio of 120 ° C. of 20% or more, and a birefringence of 0.01 or more is subjected to a secondary transfer of polyester. Partial thermocompression bonding at a temperature above the point (Tg) and below Tg + 50 ° C,
Next, one roll temperature is Tg + 50 ° C. or higher, melting point −60 ° C. or lower, and the other roll temperature is Tg + 50 ° C. or lower, and partial thermocompression bonding is performed by a pair of rolls provided with a temperature difference, followed by heat stretching in the flow direction. A method for producing an anisotropic stretchable nonwoven sheet.