JPH0811864B2 - Nonwoven fabric made of heat-adhesive fiber and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a nonwoven fabric made of heat-bondable fibers and a method for producing the same.

(Prior Art) As a method of fixing fibers to each other in the production of a nonwoven fabric, there is a method of entanglement between fibers such as a needle punch method, and a method of using various adhesives as a binder. BACKGROUND ART Non-woven fabrics such as disposable diapers and coated papers for sanitary absorbents, which have been rapidly increasing in demand in recent years, are required to have various characteristics such as a soft texture and a light basis weight and a high tensile strength. In order to satisfy these required qualities as much as possible, a nonwoven fabric production system mainly using a binder method has been adopted. As the binder method, a method of adhering the adhesive solution to the web has been mainly adopted, but there are problems that energy is required to remove the solvent of the adhesive solution and the working environment is not good. In order to solve these problems, fibers having a lower melting point than the fibers that make up the web are mixed as binders in the web,
After the web is formed, a method of bonding the fibers by heat treatment has been used. As a binder for a non-woven fabric having high strength and good texture, a composite fiber including a fiber-forming polymer having a different melting point as a composite component has also been used. This is known in Japanese Patent Publication Nos. 61-10583 and 54-38214.

(Problems to be Solved by the Invention) The low melting point component of the conventionally used non-woven composite thermoadhesive fiber is usually polyethylene, and may be medium density or high density polyethylene or linear low density polyethylene (hereinafter , LLDPE). A non-woven fabric made of a composite type heat-adhesive fiber containing medium-density or high-density polyethylene as a low-melting point component has a drawback that the texture is hard. On the other hand, carbon number 4
A non-woven fabric made of a composite type heat-adhesive fiber containing LLDPE as a low melting point component, which is obtained by copolymerizing α-olefins of ~ 8 with a low melting point component, can be expected to have a soft texture in terms of performance, but high-speed spinning is difficult. Therefore, there is a problem that it is difficult to obtain a homogeneous nonwoven fabric with a small number of defects by the spun-pond method.

An object of the present invention is to provide a heat-bondable spun-pond nonwoven fabric composed of a composite fiber having good spinnability and having a small number of defects in the nonwoven fabric, including LLDPE as a sheath component and polyethylene terephthalate as a core component.

(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 5 ~ 45g / 10min, the heat of fusion is 25cal / g or more measured by DSC, the linear low density polyethylene is the sheath component, and polyethylene terephthalate is the core component. A composite fiber, wherein the aggregate of the fibers is a heat-bonded nonwoven fabric, and the number of defects in the nonwoven fabric is 0.01 pieces / kg or less per unit weight; A linear low-density copolymer of ethylene and octene-1, containing substantially 1-10% by weight of octene-1, a density of 0.900-0.940 g / cm ³ , and a melt index value of ASTM D-1238 (E). 5 to 45 measured by
g / 10 min, the heat of fusion measured by DSC is 25 cal / g or more linear low-density polyethylene as the sheath component, polyethylene terephthalate as the core component, and the sheath component and the core component respectively melt spinning temperature 220-280 ℃ And melt-extruding at 275 to 295 ° C., the filament is obtained by air sucking, and fibers having a single yarn fineness of 5 denier or less are deposited on a moving wire mesh belt to form a web. The gist of the present invention is a method for producing a non-woven fabric made of heat-adhesive fibers, which comprises heat-bonding by heat treatment at a temperature 15 to 30 ° C. lower than the melting point of the sheath component of the fibers. Here, the pressure contact area ratio in the present invention indicates the ratio of the pressure contact area to the sheet area. The larger the pressure contact area ratio, the higher the strength but the rougher the texture. Further, the number of defects indicates the number of thickness irregularities caused by holes, wrinkles, and breaks in the present invention.

The LLDPE may contain other α-olefins in the range of 15% or less by weight of octene-1. The LLDP
E may contain additives such as lubricants, pigments, stabilizers and flame retardants.

The fibers in the present invention are suitable for spunbonded nonwoven fabrics, and if the single-fiber fineness is large, good feeling cannot be obtained, and the fibers are not intended for fibers having a single-fiber fineness of more than 5 denier.

The polyethylene terephthalate used for the composite fiber preferably has an intrinsic viscosity in the range of 0.50 to 1.20 at 20 ° C. measured in a mixed solvent of phenol: tetrachloroethane = 1: 1. If the intrinsic viscosity is less than 0.50, it is difficult to obtain high-strength fibers, and a satisfactory nonwoven fabric cannot be obtained.
If it exceeds 1.20, the spinnability is poor. A lubricant, pigment, stabilizer, etc. may be added to the polyethylene terephthalate.

The composition ratio of LLDPE which is the sheath component of the composite fiber and polyethylene terephthalate which is the core component is preferably 80 to 20% by weight of polyethylene terephthalate with respect to 20 to 80% by weight of LLDPE. If the LLDPE is less than 20% by weight, the adhesive strength will be weak even if the fiber strength is high, and the texture will be coarse and hard, and a desirable nonwoven fabric will not be obtained. On the contrary, when LLDPE exceeds 80% by weight, the non-woven fabric has a high fiber adhesive force and a soft feeling, but is not preferable because the strength is low.

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 is not 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 , it is difficult to obtain high strength fiber. Becomes

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 5g / 10 minutes cannot be easily spun at high speed unless the spinning temperature is extremely high.
Due to the relationship with the melt spinning temperature of polyethylene terephthalate, the nozzle surface is likely to become dirty during spinning at extremely high temperatures.
This is not preferable for operation. 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 for conjugate fiber. The spinning temperature of the LLDPE polymer is 220-280 ° C, preferably 230-270 ° C, while the spinning temperature of polyethylene terephthalate is 275-295 ° C, preferably 280-290 ° 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. That is, when the spinning temperature is lower than the above temperature range, it is difficult to increase the spinning speed, 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 regularly and at a short pitch for a short period of time, resulting in a large loss. This trend is LLDP
It appears more notably in the case of a composite fiber of E and polyethylene terephthalate. That is, in the present invention, the center value of the melt spinning temperature is 250 ° C. for LLDPE and 285 ° C. for polyethylene terephthalate, and the temperature difference during melt spinning of both is small, so that the composite fiber after melt extrusion can be cooled smoothly.・ Strain due to non-uniform cooling of the yarn is less likely to remain. For this reason, the obtained composite fiber is uniform and the spinnability is good. In other words, LLDP, which has good spinnability at high temperatures
Only when E is selected and the spinning temperatures of both are brought close to each other, a composite fiber with a low yarn breakage rate can be obtained.

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. In the case of a low-weight fabric with a basis weight of 10 to 50 g / m ² , a large hole has a defect that when it is pulled out from a roll in the processing step, it breaks or wrinkles or hangs occur at the defect point, resulting in a non-woven fabric defect. Poor quality.

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 pile cannot be driven if there are holes 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.

The basis weight of the non-woven fabric is preferably 10 to 200 g / m ² . If the weight of the non-woven fabric exceeds 200 g / m ² , the non-woven fabric becomes coarse and hard and bulky, which is not preferable. 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.

In addition, the pressure contact area ratio when heat-bonding the fibers by heat-treating the web is 7 to 40 because of the relationship between the texture and strength of the nonwoven fabric.
% Is preferred. 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 40%, the strength becomes high, but it becomes a hard nonwoven fabric, which is not preferable in the present invention. The nonwoven web is heat-welded to make use of the soft feel of LLDPE to increase the strength of the nonwoven. 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 thermal bonding temperature affects the texture and strength of the nonwoven fabric, and in the present invention, it is 15 to 3% higher than the melting point of LLDPE as the sheath component.
It is important to heat-treat at a low temperature of 0 ° C to bond them thermally. 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. Next, by making the cross-sectional shape of the fiber not only circular but also irregular or flat, it is possible to obtain a non-woven fabric sheet having a special texture and a feature of the cross-sectional shape.

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 method of measuring physical properties and the method of comprehensive evaluation of nonwoven fabrics 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 with a width of 30 mm and a length of 100 m.

(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 A camera (product name video measure, camera part type 3X2CA-ZLFXV, lens part type 23Y0111C (manufactured by Tateishi Electric Co., Ltd.)) with a built-in CCD (Charge Couple Device) type image sensor in the width direction of the nonwoven fabric. It is possible to continuously detect the light transmission intensity of the running non-woven fabric over the entire width of the non-woven fabric by using a plurality of non-woven fabrics during the production process. The above-mentioned camera was installed and the light transmission intensity was continuously measured over the entire width of the non-woven fabric.Defects were not determined by the basis weight of the non-woven fabric, but the voltage value (transmission intensity) of the photo sensor was adjusted to 1.5 V for the amount of light transmitted through the non-woven fabric. If the voltage value exceeds ± 30% of the adjusted value, it is counted as a defect, and the number of defects (unit / kg) per unit weight of the nonwoven fabric can be automatically displayed and recorded. It was measured.

(4) Comprehensive evaluation of non-woven fabric When the basis weight of the non-woven fabric is 15 g / m ² , the non-woven fabric having a tensile strength of 0.9 kg or more and a total hand value of 20 g or less was considered good.

Example 1 Containing 5% by weight of octene-1 and having a density of 0.937 g / m ³ , MI
The value is 25g / 10min, D measured by the method of ASTM D-1238 (E)
The heat of fusion obtained by SC measurement is 40 cal / g, and the melting point is 125 ℃.
LDPE is the sheath component, polyethylene terephthalate with an intrinsic viscosity of 0.70 (measured in a mixed solvent of phenol: tetrachloroethane = 1: 1 at 20 ° C) is the core component, and multiple compound nozzles with 200 holes are used. LLDPE melt spinning temperature 250 ℃, polyethylene terephthalate melt spinning temperature 290 ℃, single hole discharge rate 1.7 g / 10 min, LLDPE and polyethylene terephthalate composite ratio was 50:50 by weight and melt extruded.
A continuous multifilament was taken using an air soccer set at a position of 00 mm.

Comparative Example 1 contains 5% by weight of octene-1, has a density of 0.937 g / m ³ , and a melt index value of ASTM D-1238.
A multifilament was taken in the same manner as in Example 1 by using LLDPE having a heat of fusion of 20 cal / g and a melting point of 125 ° C., which was measured by the method (E) at 25 g / 10 minutes, and was measured by DSC. .

The results obtained are shown in Table 1. When the LLDPE of Example 1 was used, the spinning speed was higher than that when the LLDPE of Comparative Example 1 was used, and a fine single yarn was obtained. In addition, the air pressure of the air sucker can be lowered, and the strength and elongation characteristics of yarn quality were excellent.

Example 2 The multifilament obtained by using the air sucker of Example 1 was collected on a moving endless wire mesh and the basis weight 15
After making a web of g / m ^2, a linear pressure of 30 kg / cm, with a roll group consisting of a metal embossing heating roll and a metal heating roll.
A spunbonded non-woven fabric was obtained by heat treatment with a pressing area ratio of 15% and a heat treatment temperature varied from 95 ° C to 110 ° C.

Similarly, as Comparative Example 2, those having the temperatures of 90 ° C. and 115 ° C. were obtained.

The properties of the resulting nonwoven fabric are shown in Table 2. As is clear from Table 2, the number of defects in the obtained non-woven fabric is small, and it can be seen that the non-woven fabric with good performance can be obtained in the temperature range where the heat treatment temperature is 15 to 30 ° C lower than the melting point of the sheath component.

Example 3 LLDPE and polyethylene terephthalate of Example 1 were used, and spinning was performed in the same manner as in Example 1 except that the composite ratio of LLDPE and polyethylene terephthalate was set to 60:40 by weight, and the single yarn fineness was 3.0 denier and strength. A multifilament having 3.0 g / d and an elongation of 60.0% was obtained, and a spunpond nonwoven fabric was obtained in the same manner as in Example 2. Similarly, as Comparative Example 3, heat treatment temperatures of 90 ° C. and 115 ° C. were obtained.

The characteristics of the obtained nonwoven fabric are shown in Table 3. As is clear from Table 3, the number of defects of the obtained non-woven fabric is small, and it can be seen that a non-woven fabric with good performance can be obtained when the heat treatment is conducted at a temperature 15 to 30 ° C lower than the melting point of the sheath component.

(Effects of the Invention) Since the nonwoven fabric made of the heat-bonded continuous fiber according to the present invention has high strength and is excellent in 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.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location D04H 3/16 (72) Inventor Yoshiki Miyahara 23 Uji Kozakura, Uji city, Kyoto unitika stock company center In the laboratory (56) Reference JP-A-1-6161 (JP, A) JP-A-59-9255 (JP, A) JP-A-57-25460 (JP, A) JP-B-54-38214 (JP, B2) ) Japanese Patent Publication Sho 61-10583 (JP, B2)

Claims (4)

[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
It is 5 to 45 g / 10 minutes measured by the method of ASTM D-1238 (E), and the heat of fusion measured by DSC is 25 cal / g or more as a sheath component of linear low density polyethylene and polyethylene terephthalate as the core. A composite fiber as a component, which is a non-woven fabric in which an aggregate of the fibers is heat-sealed, and the number of defects of the non-woven fabric is 0.01 piece / kg or less per unit weight Non-woven fabric. 2. The single yarn fineness of the composite fiber constituting the non-woven fabric is 5.
A non-woven fabric made of the heat-adhesive fiber according to claim 1, which has a denier or less. 3. A linear low density polyethylene having a composition ratio of linear low density polyethylene 20 to 80 which is a sheath component of a composite fiber constituting a non-woven fabric and a polyethylene terephthalate which is a core component.
The nonwoven fabric comprising the heat-adhesive fiber according to claim 1, which is 80 to 20% by weight of polyethylene terephthalate with respect to% by weight. 4. 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
It is 5 to 45 g / 10 minutes measured by the method of ASTM D-1238 (E), and the heat of fusion measured by DSC is 25 cal / g or more as a sheath component of linear low density polyethylene and polyethylene terephthalate as the core. As a component, a sheath component and a core component are melt-extruded at a melt-spinning temperature of 220 to 280 ° C. and 275 to 295 ° C., respectively, and a fiber having a single yarn fineness of 5 denier or less is obtained by taking up the filament by air sucker. Production of a non-woven fabric composed of heat-adhesive fibers characterized by being deposited on a moving wire mesh belt to form a web, heat-treated at a temperature 15 to 30 ° C. lower than the melting point of the sheath component of the composite fiber, and thermally bonded Method.