JPH0811865B2 - Polyolefin non-woven fabric and method for producing the same - Google Patents

Description

The present invention relates to a polyolefin-based nonwoven fabric and a method for producing the same.

(Prior Art) Conventionally, low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been used to obtain polyethylene fibers, but recently, they have been recently disclosed in JP-A-60-209010 and US Pat. No. 4,644,045. As disclosed in the publication, a linear low density polyethylene (hereinafter, LLDPE) obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms such as octene-1.
Say. ) Has come to be used in the production of polyethylene fibers.

Further, in recent years, there has been a strong tendency to increase the speed of spinning for the purpose of streamlining the manufacturing process in order to obtain a nonwoven fabric by the spunpond method or when obtaining a yarn of multifilament. However, the LLDP of Japanese Patent Laid-Open No. 60-209010, in which the density and melt index (hereinafter referred to as MI value) are made constant
In E, the spinnability required for high-speed spinning was still unsatisfactory. In other words, in the spun-pond method in which a continuous filament is drawn by suction of air (hereinafter referred to as air sucker) and then a non-woven fabric is directly produced on the collecting surface, the LLDPE has a drawback that it is difficult to obtain a thin denier fiber. It was In order to solve such a problem, a method for producing a spun-pond nonwoven fabric has recently been disclosed in US Pat. No. 4,644,045.
This is the crystallinity of LLDPE, cone die melt flow value,
A method for producing a spunbonded non-woven fabric by melt-spinning at a melt extrusion temperature of 185 to 215 ° C using a linear low density polyolefin polymer with a limited ratio of the natural logarithm of the die swell and the melt index, etc. The purpose is to obtain. However, in the above method, since the melt extrusion temperature is low, the take-up tension during spinning is high, and when the spinning speed is high, the yarn breaks frequently and the defects of the non-woven fabric increase, so that only low-quality non-woven fabric can be obtained. Had a problem. An object of the present invention is to provide a spunpond nonwoven fabric made of LLDPE which has good spinnability and has a small number of defects in the nonwoven fabric.

(Means and Actions for Solving Problems) The inventors of the present invention have reached the present invention as a result of intensive research to solve the above problems of the conventional LLDPE. That is, the present invention is a linear low-density copolymer of ethylene and octene-1, containing substantially 1 to 10% by weight of octene-1, having a density of 0.900 to 0.940 g / cm ³ , and a melt index value of ASTM D-1238 (E) is a fiber consisting of linear low density polyethylene having a melting heat of 25 cal / g or more as measured by DSC of 5 to 45 g / 10 minutes, and the aggregate of the fibers is A heat-bonded non-woven fabric having a number of defects of 0.01 / kg or less per unit weight, a weight per unit area of 10 to 100 g / m ² , a pressing area ratio of 7 to 20% and a total hand value of 4 to A non-woven fabric of 300 g and a linear low density copolymer of ethylene and octene-1 containing substantially 1-10% by weight of octene-1,
Density 0.900 to 0.940 g / cm ³ , melt index value ASTM
D-1238 (E) of 5 to 45g / 10 minutes, and the heat of fusion measured by DSC is 25cal / g or more of linear low density polyethylene melted at spinning temperature 220-280 ℃. Extruded, the filament is taken up by air sucker, and fibers having a single yarn fineness of 5 denier or less are deposited on a moving wire mesh belt to form a web, which is 15 to 30 ° C lower than the melting point of the fiber. The gist is a method for producing a non-woven fabric, which is characterized by heat treatment at a temperature and thermal bonding.

Here, the pressing area ratio in the present invention is the ratio of the pressed area to the total sheet area, and the number of defects is the number of holes, wrinkles, and wrinkles in the nonwoven sheet caused by yarn breakage during spinning.
The number of thickness irregularities caused by bending is shown.

In the present invention, if the content of octene-1 exceeds 10% by weight, it is difficult to make it into fine denier, while if it is less than 1% by weight, the obtained fiber becomes hard and the texture becomes good. When the density of LLDPE exceeds 0.940 g / cm ³ , the texture is coarse and hard and the weight of the fiber cannot be reduced. On the other hand, when it is less than 0.900 g / cm ³ , high strength fiber can be obtained. It will be difficult.

The MI value was measured by the method of ASTM D-1238 (E), and was measured as 5-45.
The reason for limiting to LLDPE of g / 10 min is that LLD is beyond this range.
This is because in the case of PE, it is difficult to properly select the spinning conditions, or the strength of the obtained fiber becomes low.
In other words, LLDPE with an MI value of less than 5 g / 10 min cannot be easily spun at high speed unless the spinning temperature is raised. Spinning at high temperature is likely to cause contamination of the nozzle surface, which is not preferable for operation. Become. On the other hand, if the MI value exceeds 45 g / 10 minutes, the strength of the obtained fiber becomes low, which is not preferable.

LLDPE, which has a heat of fusion of less than 25 cal / g, is currently unknown for its spinnability, although the reason is unknown. In the spun pond method of directly producing a non-woven fabric after stretching a continuous filament by air sucker, in the case of fine denier,
For LLDPE with a heat of fusion of less than 25 cal / g, it is necessary to increase the air pressure of the air sucker. In the case of LLDPE with a heat of fusion of 25 cal / g or more, the air pressure can be lowered to be taken up, and finer denier can be obtained.

The heat of fusion in the present invention is measured as follows. In other words, Perkin-Elme
r) Using DSC-2C, sample about 5 mg, and scan speed (s
can be obtained by raising the temperature from room temperature to 20 ° C / min.
Obtain the DSC curve according to the device manual.

The fiber of the present invention can be obtained by using a conventionally known melt spinning apparatus. Spinning temperature of LLDPE polymer 220-280 ℃,
It is preferably 230 to 270 ° C. If the spinning temperature is outside the above range, the spinning condition will be poor and it will be difficult to obtain a satisfactory nonwoven fabric. In other words, it is difficult to increase the spinning speed when the spinning temperature is lower than the above temperature range.
It is difficult to obtain fine denier fiber, and it is necessary to increase the air pressure of the air sucker. In addition, the resulting non-woven fabric has many defects due to frequent yarn breakage during spinning.

On the contrary, when the spinning temperature is higher than the above temperature range, the nozzle surface is easily soiled, and when operating for a long time, a non-woven fabric with many defects is obtained due to yarn breakage due to soiling of the nozzle surface. Therefore, in order to prevent this, it is necessary to clean the nozzle surface periodically and at a short pitch for a short period of time, resulting in a large loss.

In the production of the spunpond nonwoven fabric of the present invention, if yarn breakage occurs during spinning, the fabric will always have a non-uniform weight or a large hole. A disadvantage of the large hole, if a weight per unit area of the low basis weight nonwoven 10 to 30 g / m ^2, in the process step, when withdrawn from a roll, appearance quality becomes wrinkled or hanging occurs nonwoven disadvantages or drawbacks portion breaks Becomes worse.

On the other hand, when a high basis weight non-woven fabric with a basis weight of 50 g / m ² or more is used as the carpet base fabric, the pipe cannot be driven if the hole is opened due to thread breakage. In addition, if the webs overlap too much due to wrinkles or suspension during processing and the thickness of the non-woven fabric increases too much, piling may not be performed smoothly and the needle may occasionally break. For this reason, the operability and the appearance quality deteriorate.

Therefore, in any case, the defect due to yarn breakage becomes the defect of the non-woven fabric as it is. Therefore, such a defect caused by the yarn breakage of the spinning needs to be cut at the time of shipping, so that a short length is formed and the yield is deteriorated.

Reason why the weight per unit area of the nonwoven fabric with 10 to 100 g / m ^2, the nonwoven fabric weight 100 g / m ² by weight, the nonwoven fabric is rough and hard to be wind if it is not preferred. On the other hand, if it is less than 10 g / m ² , the texture is soft, but the strength is low and the practicality is poor. The reason why the total hand value is limited to 4 to 300 g is that the strength is insufficient in the case of a non-woven fabric of less than 4 g. On the other hand, if it exceeds 300 g, the texture becomes coarse and hard, which is not preferable.

When the web is heat-treated and the fibers are thermocompression-bonded to each other, the pressure contact area ratio needs to be 7 to 20% in consideration of the texture and strength of the nonwoven fabric. If it is less than 7%, the texture is soft, but the strength is insufficient. On the contrary, when the pressure contact area ratio exceeds 20%, the strength becomes high, but it becomes a hard nonwoven fabric, which is not preferable in the present invention. In addition, the non-woven web is heat-welded to enhance the strength of the non-woven fabric by taking advantage of the soft texture of LLDPE. In the pressure welding method, for example, an entangled filament constituting the web is bonded by heat and pressure using an embossing heating roll or the like. This heat-bonding temperature affects the feel and strength of the nonwoven fabric, and in the present invention, it is important to heat-bond at a temperature 15 to 30 ° C. lower than the melting point of LLDPE for heat-bonding. That is, when the surface temperature of the embossing heating roll is higher than the above temperature range, the strength of the nonwoven fabric increases, but the hand becomes hard, which is not preferable.
On the other hand, when the surface temperature of the embossing heating roll is lower than the above range, the texture of the non-woven fabric is soft, but the adhesion between filaments is insufficient and the strength is low.

The fiber in the present invention is intended to provide a non-woven fabric suitable for a coated paper such as a disposable diaper, and if the single yarn fineness exceeds 5 denier, the texture becomes coarse and hard, which is not preferable. Next, by making the cross section of the fiber hollow or flat in addition to the circular cross section, it is possible to obtain a non-woven sheet having a special texture and a sheet having a special cross section. That is, the non-woven fabric made of hollow fibers is excellent in bulkiness, lightweight feeling and heat retention effect, and the non-woven fabric made of flat yarns is much more soft feeling.

In addition to the characteristics of the above-mentioned cross-sectional shape, in the melt-spinning of hollow fibers by LLDPE, there is a close relationship with the above-mentioned melt-spinning temperature. The effect of the polymer melt elasticity is less likely to occur, and the number of yarn breakages during drawing by air sucker is extremely small, and it is possible to obtain a spun-pond nonwoven fabric having a finer denier.

In the case of hollow fibers, the number of hollow portions is not limited to one, and it does not matter if the hollow portions are hollow. The hollowness is preferably 3 to 50%, which is 50%.
If it exceeds%, the silkiness deteriorates, and fibrillation occurs in the obtained theater. On the other hand, if it is less than 3%, it is difficult to achieve the effect of weight saving and heat retention of the fibers, which is a characteristic of hollow fibers.

In the case of flat yarn, the flatness is preferably 1.5 to 4.0, and when it exceeds 4.0, the spinnability is deteriorated and the strength of the obtained yarn is lowered. On the other hand, if it is less than 1.5, no difference in softness is recognized as compared with the normal circular cross section, and the characteristics due to the flat yarn are less likely to appear.

The hollow degree in the present invention by observing the cross section of the filament under a microscope, measuring the diameter d of the outer diameter D and a hollow portion d ² / D
Calculate using the formula of ² x 100 (%). If there are n hollow holes inside the equipment (d ₁ ² + ... dn ² )
Calculate using the formula / D ² × 100 (%). When the filament is a hollow fiber with a modified cross section, the fiber cross section A and the hollow cross section a are calculated using the image processing system of Luzex II manufactured by Nireco Co., and calculated using the formula (a / A) × 100 (%) .

Oblateness is obtained by observing the cross section of the filament with a microscope, measuring the major axis length (L) and the minor axis length (l) of the elliptical shape, and using the formula L / l.

As described in detail above, the nonwoven fabric of the present invention has few defects and has good feeling.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.

The methods for measuring the physical properties shown in the examples are as follows.

(1) Tensile strength of nonwoven fabric According to the strip method described in JIS L-1096, the maximum tensile strength was measured from a test piece having a width of 30 mm and a length of 100 mm.

(2) Total hand of non-woven fabric This shows softness and was measured with a slot width of 10 mm in accordance with the handle odometer method described in JIS L-1096.

(3) Number of defects Camera with built-in CCD (Charge Couple Device) type image sensor (product name video measure, camera part type 3X2CA-ZLFV, lens part type 23Y 0111C, Tateishi Electric K.
Multiple K. products) are used in the width direction of the non-woven fabric so that the light transmission intensity of the non-woven fabric during running in the production process can be continuously detected with respect to the non-woven fabric width. That is, a certain amount of light was emitted from one side of the running nonwoven fabric, and the above-mentioned camera was installed on the opposite side to continuously measure the light transmission intensity over the entire width of the nonwoven fabric. Judgment of defects does not depend on the basis weight of the non-woven fabric, but the voltage value (transmission intensity) of the photo sensor regarding the amount of light transmitted through the non-woven fabric
Is adjusted to 1.5 V, and when the voltage value exceeds ± 30% of the adjusted value, it is counted as a defect and the number of defects per unit weight of nonwoven fabric (pieces / kg) is automatically displayed. And measured so that it can be recorded.

Example 1 Containing 5% by weight of octene-1 and having a density of 0.937 g / cm ³ , M
I value is 25g / 10min when measured by ASTM method D-1238 (E),
The heat of fusion obtained by DSC measurement is 40 cal / g and the melting point is 125 ° C.
LLDPE with multiple nozzles of 0.20 mm x 64 holes, 1.5 g
/ Min / ・ Hole discharge is carried out in the spinning temperature range of 230-270 ℃, and the continuous multifilament is caught on the moving endless wire mesh using the air sucker installed 200 mm below the nozzle. After gathering to make a web with a basis weight of 10 g / m ^2, a linear pressure of 30 kg / cm, a pressure contact area ratio of 12%, and a roll group consisting of a metal embossing heating roll and a metal heating roll.
Heat treatment was performed at a heat treatment temperature of 105 ° C. to obtain a spunpond nonwoven fabric. The results are shown in Table 1.

Comparative Example 1 As Comparative Example 1, a nonwoven fabric was prepared in the same manner as in Example 1 except that the spinning temperature was 200 ° C. As a result, as is clear from the table, Comparative Example 1 has more defects than Example 1, and the result of the melt spinning temperature is clear.

Comparative Example 2 Containing 5% by weight of octene-1 and having a density of 0.937 g / cm ³ MI
The value is 25g / 10min, D measured by the method of ASTM D-1238 (E)
Heat of fusion obtained by SC measurement is 20 cal / g, melting point is 125 ℃ L
Using LDPE, the multifilament was taken out in the same manner as in Example 1 to prepare a spunpond nonwoven fabric. As is clear from Table 2, the spinning speed cannot be increased unless the air pressure of the air sucker is increased, and accordingly, only a low-quality nonwoven fabric having a very large number of defects is obtained.

Example 2 Containing 5% by weight of octene-1 and having a density of 0.937 g / cm ³ MI
The value is 25g / 10min, D measured by the method of ASTM D-1238 (E)
LLDPE with a heat of fusion of 40 cal / g measured by SC was set at a spinning temperature of 230 ° C, the discharge shape was () type, and a spinneret with 64 holes was used, and the discharge rate was 1.5 g / min · hole and the take-up speed. 7,000m
The hollow fiber was spun at a rate of 1 / min to form a web on the moving wire mesh, and then the spunpond nonwoven fabric was produced in the same manner as in Example 1. The results are shown in Table 3.

Comparative Example 3 A nonwoven fabric was prepared in the same manner as in Example 2 except that the spinning temperature was 210 ° C. The results are shown in Table 3. As is clear from the table, the low road speed did not increase, and the number of defects in the non-woven fabric was large.

Example 3 Containing 5% by weight of octene-1 and having a density of 0.937 g / cm ³ , M
Nozzle for flat yarn 0.6 mm (slit length) x 0.10 mm (slit width) x 64 with LLDPE having an I value of 25 g / 10 minutes and a heat of fusion of 40 cal / g
After melt-extruding at a spinning temperature of 230 ° C with a discharge rate of 1.5 g / min · hole using multiple nozzles for holes, flat yarn was produced at a take-up speed of 7000 m / min using an air sucker. A web was formed on the moving wire mesh, and a spunpond nonwoven fabric was manufactured in the same manner as in Example 1. The results are shown in Table 4.

Comparative Example 4 A nonwoven fabric was produced in the same manner as in Example 3 except that the spinning temperature was changed to 210 ° C. As a result, as shown in Table 4, only a non-woven fabric having a large number of defects was obtained.

(Effects of the Invention) Since the nonwoven fabric made of the heat-bonded long fibers according to the present invention is strong and high and has excellent softness and texture, the nonwoven fabric having a low basis weight is particularly suitable as a lining for disposable diapers. On the other hand, the non-woven fabric with a high basis weight can be applied to a wide range of applications such as bags, carpet base fabrics and filters.

Front page continuation (72) Inventor Shunichi Kiriyama 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Institute (72) Inventor Yasunobu Mishima 23 Uji Kozakura, Uji City Kyoto Prefecture Unitika Central Company Central Research Institute (56 ) References JP-A-60-209010 (JP, A) JP-A-60-194113 (JP, A)

Claims (5)

[Claims] 1. A linear low-density copolymer of ethylene and octene-1, containing substantially 1 to 10% by weight of octene-1, a density of 0.900 to 0.940 g / cm ³ , and a melt index value of
Fiber made of linear low-density polyethylene with a heat of fusion of 25 cal / g or more as measured by DSC, measured by the method of ASTM D-1238 (E). The body is a heat-fused nonwoven fabric, and the number of defects in the nonwoven fabric is 0.01 pieces / kg or less per unit weight, the weight per unit area is 10 to 100 g / m ² , the pressing area ratio is 7 to 20%, and the total hand value is Non-woven fabric that is 4-300g. 2. The non-woven fabric according to claim 1, wherein the fibers constituting the non-woven fabric have a single yarn fineness of 5 denier or less. 3. The single yarn fineness of the fibers constituting the non-woven fabric is 5 denier or less, the cross section of the fibers is hollow, and the hollowness is 3
The non-woven fabric according to claim 1, which is -50%. 4. The single yarn fineness of the fibers constituting the non-woven fabric is 5 denier or less, the fiber cross section is flat, and the flatness is 1.
The non-woven fabric according to claim 1, which is 5 to 4.0. 5. A linear low density copolymer of ethylene and octene-1 containing substantially 1 to 10% by weight of octene-1, a density of 0.900 to 0.940 g / cm ³ , and a melt index value of
5 to 45g / 10min measured by ASTM method D-1238 (E), linear low density polyethylene with heat of fusion measured by DSC of 25cal / g or more at spinning temperature 220-280 ℃ Melt extrusion is carried out, and fibers having a fineness of 5 denier or less obtained by picking up the filaments with an air sucker are deposited on a moving wire mesh belt to form a web, and the temperature is 15 to 30 ° C. from the melting point of the fibers.
A method for producing a non-woven fabric, characterized by heat-treating at a low temperature and thermally adhering.