JPH06158504A - Smooth polyolefinic three-dimensional netlike fiber nonwoven fabric and its production - Google Patents

Abstract

PURPOSE:To obtain smooth polyolefinic three-dimensional netlike fiber nonwoven fabric having specific characteristics as a printing substrate optimum for printing, etc., of heat transfer printing, etc., bar codes. CONSTITUTION:This smooth polyolefinic three-dimensional netlike fiber nonwoven fabric has 0.4-0.8 surface roughness (SMD value) measured with a KES(R) measuring instrument and the flatness regulated to <=2mm. Furthermore, this method for producing the nonwoven fabric is to further press a polyolefinic three-dimensional netlike fiber nonwoven fabric subjected to ordinary thermal joining from both sides with a flat metallic roll at 20-80 deg.C surface temperature under 30-100 kg/cm<2> linear pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent non-woven fabric for use as a printing substrate, and more particularly to a smooth polyolefin non-woven fabric most suitable for thermal transfer printing such as bar code printing and a method for producing the same.

[0002]

2. Description of the Related Art Printing technology on paper begins in letterpress printing, which was invented in the middle of the 15th century, and has entered the era of offset printing through gravure printing. The printing base material is paper or synthetic film made of stretched film. Paper, cloth, etc. are used. With regard to paper as a printing substrate, technological progress has been made in coated paper and art paper made of pulp, and satisfactory printability has been obtained, but the paper has drawbacks such as poor water resistance and insufficient tear strength. Can be a problem. As a printing substrate with improved water resistance, we have proposed synthetic paper consisting of polypropylene film, polyester film, etc. stretched containing an inorganic filler, but these synthetic papers have excellent water resistance but are unique to stretched films. Since the tear strength is small, it is easy to tear, and there is a problem in that it is torn from that portion particularly in applications such as business foams having punched holes, which is a problem.

In recent years, various non-woven fabrics having water resistance and large tear strength have been put on the market. Nonwoven fabrics, especially long-fiber non-woven fabrics produced by the spunbond method and polyolefin non-woven fabrics produced by the flash-spinning method, have high tear strength and are therefore being used for this purpose. However, since the fibers on the surface of the non-woven fabric made by the spunbond method or the non-woven fabric made by flash spinning have a constant diameter, the surface always has unevenness. Therefore, when these non-woven fabrics are used for printing, the influence of the unevenness due to the fibers cannot be eliminated, and ink unevenness due to the unevenness occurs at the time of thermal transfer printing such as a barcode, so that the printing cannot be performed properly. As a material for smoothing the surface of a polyolefin three-dimensional reticulated fiber nonwoven fabric, Japanese Unexamined Patent Publication No. 4-136249 discloses a nonwoven fabric sheet having a Bekk smoothness of 40 seconds or more and having a surface corona-treated surface. Such a smooth surface polyolefin three-dimensional reticulated fiber non-woven fabric is subjected to smoothing by applying heat and pressure, so that a partial strain is left inside the non-woven fabric. Unevenness will occur,
There is a problem that a flat surface cannot be obtained. Since such a product smoothed by heat is wound up with a certain width, there is also a problem that winding wrinkles occur due to macroscopic unevenness caused by partial distortion.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an excellent polyolefin non-woven fabric having good printability and ink acceptability at the time of thermal transfer printing such as a bar code. It is to provide the manufacturing method.

[0005]

As a result of various investigations in view of the above problems, the present inventors have found that the surface of a non-woven fabric is smoothed by a special method to give a specific surface roughness and flatness, thereby providing good printability. The present invention has been completed by finding out that the above can be obtained. That is, one aspect of the present invention is that the surface roughness (SMD value) measured by a KES measuring machine is 0.4 to 0.8.
And a flatness of 2 mm or less, which is a smooth polyolefin three-dimensional reticulated fiber nonwoven fabric, and another aspect of the present invention is a heat-bonded polyolefin three-dimensional reticulated fiber nonwoven fabric having a surface temperature of 20 to A method for producing a smooth polyolefin three-dimensional reticulated fiber non-woven fabric, characterized in that the linear pressure is further pressed from both sides with a flat metal roll at 80 ° C. at a pressure of 30 to 100 kg / cm.

The polyolefin nonwoven fabric used in the present invention is
A polyolefin nonwoven fabric having a three-dimensional network structure,
It can be produced by using a normal polyolefin flash spinning technique. That is, the polyolefin non-woven fabric used in the present invention is, for example, a polyolefin polymer dissolved in a solvent under high temperature and high pressure, then discharged into a low temperature and low pressure region, and at the same time, the solvent is flushed to form a three-dimensional, reticulated fibrillated polyolefin. It can also be manufactured by obtaining the above-mentioned polyolefin fiber, then depositing this fiber on a plate-like or mesh-like support, making it into a web, and thermally bonding it with an embossing roll or a calendar roll.

At this time, a polyolefin nonwoven fabric having various physical properties can be obtained by changing the thermal bonding conditions, and the surface smoothness can be adjusted to some extent by adjusting the temperature, bonding pressure and bonding time of the embossing roll or calender roll. Can be done. Examples of the polyolefin include polyethylene and polypropylene, and polyethylene is preferable from the viewpoint of surface smoothness.

As the polyolefin non-woven fabric, a non-woven fabric made by a spunbond method or a melt blow method and a non-woven fabric made of polyolefin short fibers are known. Further, the nonwoven fabric obtained by the melt blow method is not practical because the constituent fibers have a fine diameter but the tear strength as a nonwoven fabric is small.

The basis weight of the smooth polyolefin three-dimensional reticulated fiber nonwoven fabric of the present invention is preferably 40 to 150 g / m ² .
When the basis weight of the non-woven fabric is less than 40 g / m ² , the dispersibility of the polyolefin three-dimensional reticulated fiber non-woven fabric may be poor, and there may be a case where a perforated spotted spot or an extremely low basis weight part is mixed. When the basis weight exceeds 150 g / m ² , the whole becomes thick, which is not preferable as a printing substrate.

In the present invention, the surface roughness means that measured by a KES surface tester. The KES surface tester is one of a series of testers designed for the purpose of measuring the texture of cloth, and is sold by Kato Tech Co., Ltd., for example. This surface tester (KES-FB4) has a built-in calculation circuit capable of measuring the geometrical roughness of the cloth surface, the coefficient of friction and its variation.

In the present invention, the surface roughness is a surface roughness (SMD value) measured by using a surface roughness detecting contact of a surface tester.
I will show you. In the present invention, the measurement of the surface roughness is
The process was repeated three times, and the total average was taken as the surface roughness of the nonwoven fabric. Usually, the surface roughness of the polyolefin three-dimensional reticulated fiber non-woven fabric which is just heat-bonded is about 1 to 1.5, which is larger than the surface roughness of the polyolefin three-dimensional reticulated fibrous non-woven fabric of the present invention. The surface roughness also serves as a measure of surface irregularities, and the larger this value, the larger the surface irregularities and the rougher the surface.

The surface roughness of the smooth polyolefin three-dimensional reticulated fiber of the present invention is required to be 0.4 to 0.8. If the surface roughness exceeds 0.8, the surface irregularities become severe, and the ink fixing at the time of printing a barcode or the like is unsatisfactory, which may cause blurring, which is not preferable. Surface roughness is 0.4
Even if it is less than that, it is preferable that there is little surface irregularity, but it is necessary to apply a large amount of heat and pressure at the time of manufacturing in order to reduce the surface roughness, which includes strain for that, and the flatness described below often deteriorates, which is preferable. Often not.

The smooth polyolefin three-dimensional reticulated fiber nonwoven fabric of the present invention is required to have not only surface roughness but also flatness of 2 mm or less. The flatness means the maximum value of the height at which a non-woven fabric cut into 1 m square is placed on a flat plate, and the end faces (four sides) thereof float above the flat plate. If it is a normal coated paper, it is 1 mm or less if there is no curl and the like, and it is very close to 0.
However, in the case of a polyolefin three-dimensional reticulated fiber nonwoven fabric, after the thermal bonding, the smoothing process is further performed, so that distortion is inevitably left inside, and when it is placed on a flat plate, the end face is lifted.

Flatness is what expresses the degree of this floating, and according to the manufacturing method of the present invention, the flatness can be suppressed to 2 mm or less. When the flatness exceeds 2 mm, internal distortion occurs, and there are disadvantages that the nonwoven fabric cannot be fed straight when printing a barcode or the like, and irregularities occur when rolled up, which is not preferable. Beck's smoothness was measured at the same time, but the Beck's smoothness was about 10 seconds for the unprocessed product and about 25 to 200 seconds for the nonwoven fabric of the present invention.

In the manufacturing method of the present invention, the surface temperature of the thermally bonded polyolefin three-dimensional reticulated fiber nonwoven fabric is 20 to 80 ° C.
A method for producing a smooth polyolefin three-dimensional reticulated fiber non-woven fabric, characterized by further pressing from both sides with a flat metal roll having a linear pressure of 30 to 100 kg / cm. The method for producing a smooth polyolefin three-dimensional reticulated fiber non-woven fabric of the present invention is generally characterized by further processing a bonded non-woven fabric having no problem in tensile strength and the like. Press from the top and bottom or left and right with a metal roll. Generally, it is often pressed from above and below. The flat metal roll means a smooth metal roll having no engraved surface, and the surface is preferably a mirror surface roll rather than satin finish. Particularly, a chrome-plated metal roll is preferable.

At this time, the surface temperature of the metal roll is 20 to 8
It needs to be 0 ° C. If the temperature is lower than 20 ° C, cooling is required, and there is a drawback that equipment specifications become large.
When the temperature exceeds ° C, the surface roughness is satisfactory, but the flatness is lacking and the end faces are wavy. Further, heating is preferably performed on only one side. When heating both sides, the flatness may deteriorate, so it is preferable to heat from one side as much as possible.

The linear pressure of the metal roll pressed from both sides is 30.
~ 100 Kg / cm is required. The linear pressure of the metal roll is usually the oil pressure (Kg) that supports the metal roll, and the roll width (c
Represents the apparent value divided by m). In the manufacturing method of the present invention, the surface temperature of the metal roll is 20 to 80 ° C., and the linear pressure is 30.
It is necessary to satisfy ~ 100 Kg / cm at the same time.
If it exceeds this range, the flatness of the obtained polyolefin three-dimensional reticulated fiber non-woven fabric deteriorates, the surface becomes wavy in appearance, and the ink adhesiveness deteriorates in the printing of barcodes or the like, which is not preferable.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples. Prior to the description of the examples, a method for measuring various physical properties of the smooth polyolefin three-dimensional reticulated fiber nonwoven fabric of the present invention will be described. Surface Roughness A base material is prepared as a sample having a size of 20 cm × 20 cm. The testing machine is Kato Tech's product name KES
-Use the FB4 surface tester (with automatic calculation function). Set the sample to the tester with a load of 400g and set to 10g.
Contact the sample for surface roughness detection with the load applied to the sample and start the device. The background of the sample is measured three times, and the average thereof is used as the surface roughness (SMD value).

Flatness: A non-woven fabric cut into 1 m square is placed on a flat plate, and the end face (four sides) of the non-woven fabric represents the maximum value of the height above the flat plate. Beck's smoothness According to the Beck's smoothness test method specified by JIS P8119. The unit of measurement is expressed in seconds, and the larger this value is, the smoother the surface is.

Printability A thermal transfer type BC-8 model manufactured by Autonics was used as a printing machine, and it was visually judged whether or not printing was actually carried out, and it was judged whether it was good, good, bad, or bad.
Graded.

[0021]

[Example 1, Comparative Example 1] A polyethylene nonwoven fabric (Luxar, trade name, manufactured by Asahi Chemical Industry Co., Ltd.) in which a web made of polyethylene three-dimensional reticulated fibers is heat-bonded has a basis weight of 60 g / m ² .
The thickness was about 0.18 mm and the surface roughness was 1.2. This non-woven fabric was smoothed under the following conditions using a calender machine consisting of two metal rolls plated with chrome at the top and bottom. The surface temperature of the upper metal roll was set to 60 ° C., and the pressure of the hydraulic pump for lifting the roll was adjusted to a linear pressure of 80 Kg / cm. The lower metal roll was unheated for the experiment. The above polyethylene nonwoven fabric was passed through this metal roll at a speed of 3 m / min (Example 1). As Comparative Example 1, the surface temperature of the metal roll was 110 ° C. and the linear pressure was 80.
Smoothing was performed at Kg / cm.

In Example 1, the surface roughness was 0.7 and the flatness was also less than 1 mm. When a barcode was printed on this nonwoven fabric, a clear and good printed product was obtained. On the other hand, Comparative Example 1 has a partial shrinkage and a surface roughness of 0.9.
The flatness was 6 mm. As a matter of course, when the barcode was printed, partial blurring occurred.

[0023]

[Examples 2 to 4 and Comparative Examples 2 to 4] The same chrome-plated metal as in Example 1 was prepared using a polyethylene non-woven fabric having the same basis weight of 60 g / m ² (Luxar, trade name, manufactured by Asahi Kasei Corporation). Smoothing was performed using a roll while changing the surface temperature and the linear pressure. Table 1 shows the results of evaluating the physical properties and printability of the obtained nonwoven fabric.

[0024]

[Table 1]

[0025]

EFFECT OF THE INVENTION According to the production method of the present invention, a smooth polyolefin three-dimensional reticulated fiber nonwoven fabric having specific values of surface roughness and flatness is obtained, and the obtained nonwoven fabric is most suitable for thermal transfer printing such as barcode printing. It is a non-woven fabric for a printing substrate having good ink fixing property.

Claims (2)

[Claims] 1. A smooth polyolefin three-dimensional reticulated nonwoven fabric having a surface roughness of 0.4 to 0.8 and a flatness of 2 mm or less measured by a KES measuring machine. 2. A smooth polyolefin tertiary characterized in that the heat-bonded polyolefin three-dimensional reticulated fiber nonwoven fabric is further pressed from both sides at a linear pressure of 30 to 100 kg / cm with a flat metal roll having a surface temperature of 20 to 80 ° C. Method for producing original reticulated fiber nonwoven fabric.