JPH0643660B2 - Non-woven fabric made of heat-bonded long fibers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a nonwoven fabric composed of heat-bonded long fibers.

(Prior Art) As a method for fixing fibers to each other in the production of a non-woven fabric, there are a method of interlacing 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 a soft and soft texture. In order to satisfy these required qualities as much as possible, a non-woven fabric production method 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, a method has been used in which fibers having a lower melting point than the fibers constituting the web are mixed as a binder into the web, the web is formed, and then the fibers are heat-treated and bonded. . 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 JP-B-61-10583 and JP-A-63-92722.

(Problems to be solved by the invention) The low melting point component of the conventionally used composite heat-bonding fiber for non-woven fabric is usually polyethylene, which is medium or high density polyethylene or linear low density polyethylene (hereinafter, LLDPE). It is called). A non-woven fabric made of a composite type heat-bonding fiber containing medium-density or high-density polyethylene as a low-melting point component has a defect that the texture is hard. Next, in the case of the above invention,
A non-woven fabric composed of a composite type heat-bonded fiber containing LLDPE, which is commercially available, obtained by copolymerizing α-olefins having 4 to 8 carbon atoms as a low-melting component, and can be expected to have a soft texture in terms of performance. However, since high-speed spinning is difficult, it is difficult to obtain a homogeneous nonwoven fabric by the spunbond method. In addition, the present inventors previously proposed, in Japanese Patent Laid-Open No. 63-92722, a nonwoven fabric composed of a composite fiber having LLDPE having a good spinnability as a sheath component and polyethylene terephthalate as a core component. Although the softness of the non-woven fabric is not impaired when the fabric weight is low, the texture is inevitably hard when the fabric weight is large, and there is a limit in softness. The object of the present invention is to
An object of the present invention is to provide a heat-bonded spunpond nonwoven fabric which has good spinnability and which is composed of a composite fiber containing a blended structure of LLDPE and polypropylene as a sheath component and polypropylene as a core component and having a soft texture.

(Means and Actions for Solving the Problems) The inventors of the present invention have arrived at the present invention as a result of intensive research to solve the above problems. That is, the present invention is
A fiber assembly that is a melt-spun composite fiber that is introduced into an air sacker and is blown onto a porous collector that is moved after being stretched and sent out by the action of an air jet. The fiber sheath component is a copolymer of ethylene and octene-1, which contains substantially 1 to 10% by weight of octene-1, has a density of 0.900 to 0.940 g / cm ³ , and has a melt index value of ASTM D-1238 ( 20-80g / 10 measured by method E)
The linear low density polyethylene with a heat of solution of 25 cal / g or more as measured by DSC and the melt flow rate value of ASTM
D-1238 (L) is a blended structure with polypropylene measured by the method of D-1238 (L) for 5 to 60 g / 10 min, the core component of the composite fiber is the polypropylene, and the single yarn fineness of the composite fiber is A heat-bonding continuous fiber having a denier of 5 denier or less, which is heat-welded at a temperature 15 to 30 ° C. lower than the melting point of the linear low-density polyethylene constituting a part of the sheath component of the conjugate fiber measured by DSC The heat-bonded long-fiber non-woven fabric is characterized in that the pressure contact area ratio of the non-woven fabric is 7 to 40%. Here, the press contact area ratio indicates the ratio of the press contact area to the sheet area.

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

The fiber in the present invention is suitable for a spun-pond nonwoven fabric, and if the single yarn fineness is thick, a good feeling cannot be obtained, and the fiber having a single yarn fineness of more than 5 denier is not intended.

The polypropylene used for the composite fiber must have a melt flow rate value of 5 to 60 g / 10 min as measured by the method of D-1238 (L). If the melt flow rate value (hereinafter simply referred to as MFR) exceeds 60 g / 10 minutes, it is difficult to obtain high-strength fibers, and a satisfactory nonwoven fabric cannot be obtained, and if the MFR is less than 5 g / 10 minutes, spinnability is increased. Is not good. In addition,
Lubricants, pigments, stabilizers and the like may be added to the polypropylene.

The composition ratio of the blend structure that is the sheath component of the composite fiber and the polypropylene that is the core component is 20 to 80% by weight of the blend structure.
On the other hand, polypropylene is preferably 20 to 20% by weight. If the blend structure is less than 20% by weight, the fiber strength will be high, but the adhesive strength will be weak and the texture will be coarse and hard, which is not preferable. On the other hand, when the blend structure exceeds 80% by weight, the fiber has high adhesive force and is soft in texture, but is not preferable because the strength becomes low.

Next, the blending amount of polypropylene to the linear low-density polyethylene of the blend structure, which is the sheath component, is 2 to 25%.
It is preferably in the weight%. Thus, by blending a specific linear low-density polyethylene and polypropylene, it has excellent high-speed spinnability as known from JP-A-63-175113 and has the same polypropylene as the core polypropylene. By blending with the sheath component
The peeling phenomenon of the sheath component does not occur. In addition, the loss due to the ear cuts used in the nonwoven fabric manufacturing process can be reused as a blend structure of the sheath component. Therefore, the retention is improved as compared with the case where the core component is made of polyester.

If the blended amount of polypropylene in the blended structure is less than 2% by weight, no improvement in spinnability is observed. Also, 25
If the content exceeds 10% by weight, the physical properties of the non-woven fabric will be inferior because the thermal properties will be close to polypropylene. Furthermore, it is not preferable because the charge opening property after stretching is poor.

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. Also, LLD
When the density of PE 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 becomes difficult to obtain high strength fiber. .

Melt index value (hereinafter simply referred to as MI value)
20-80g / 10min LLD measured by ASTM D-1238 (E) method
The reason for limiting to PE is that if it exceeds this range, it becomes difficult to properly select the spinning conditions in the case of LLDPE, or the strength of the obtained fiber becomes low. In other words, LLDPE with an MI value of less than 20 g / 10 min cannot be easily spun at high speed unless the spinning temperature is set extremely high. It will be unfavorable. On the contrary, if the MI value exceeds 80 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, has poor spinnability at present, 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,
LLDPE with a heat of fusion of less than 25 cal / g needs to increase the air pressure of the air sucker. LLDP with a heat of solution of 25 cal / g or more
In the case of E, the air pressure can be lowered and the air pressure can be taken, and
It is possible to make finer denier.

The heat of fusion in the present invention is measured as follows. That is, using DSC-2C manufactured by Perkin Elmer, about 5 mg of a sample is sampled, the scanning speed is set to 20 ° C./min, and the DSC curve obtained by raising the temperature from room temperature is obtained according to the same device manual.

The fiber of the present invention can be obtained by using a conventionally known melt-spinning apparatus for conjugate fiber. As the melt spinning temperature, the spinning temperature of the blend structure is 200 to 265 ° C, preferably 220 to 240
On the other hand, the polypropylene spinning temperature is 230 to 270 ° C, preferably 240 to 260 ° 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 obtained non-woven fabric cannot be a homogeneous non-woven fabric due to 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, only non-uniform nonwoven fabric can be obtained due to yarn breakage due to nozzle surface soiling. For this reason, in order to eliminate the above-mentioned drawbacks, it is necessary to clean the nozzle surface at regular intervals and at a short pitch, which results in a large loss.

That is, in the present invention, the melt spinning temperatures of the blend structure and polypropylene are almost the same, so that the composite fiber after melt extrusion is cooled smoothly, and the strain on the yarn is less likely to remain. Therefore, the obtained conjugate fiber is uniform and the spinnability is good. In other words, it is only when LLDPE, which has good spinnability at high temperature, is selected and the spinning temperatures of both are brought close to each other to obtain a composite fiber with a low yarn breakage rate.

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. The disadvantage of large holes is that the weight is 1
In the case of a non-woven fabric having a low basis weight of 0 to 50 g / m ² , when it is pulled out from a roll in the processing step, it breaks or wrinkles or hangs occur at the defect points, resulting in a defect of the nonwoven fabric, resulting in poor appearance 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 in if holes are formed due to thread breakage. In addition, if the webs are overlapped with each other due to wrinkles or suspension during processing and the thickness of the woven fabric is too large, the piling is not performed smoothly and the needle sometimes breaks. Therefore, the operability and the appearance quality are deteriorated.

Therefore, in any case, the defect due to yarn breakage becomes the defect of the non-woven fabric as it is. Therefore, the defects caused by such yarn breakage must be cut at the time of shipment, resulting in short lengths of warp and poor yield.

Why the weight per unit area of the nonwoven fabric was 10 to 200 g / m ^2, when the nonwoven fabric weighing more than 200 g / m ² nonwoven fabric roughness becomes hard, and bulky undesirably. 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 7-40% due to the relationship between the texture and strength of the nonwoven fabric.
is necessary. 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. In addition, taking advantage of the soft texture of LLDPE for the non-woven web,
Heat pressure welding is performed to increase the strength of the non-woven fabric. As a pressure welding method, for example, an embossed heating roll or the like is used to bond the entangled filaments constituting the web by heat and pressure. This heat-bonding temperature affects the texture and strength of the non-woven fabric.
In the present invention, it is important to perform heat treatment by heat treatment at a temperature 15 to 30 ° C. lower than the melting point of LLDPE forming a part of the sheath component to thermally bond it. That is, when the surface temperature of the embossing heating roll is higher than the above temperature range, the heat treatment temperature affects the core component and the texture becomes hard.

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 the texture is good.

(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, width 30mm, length 1
The maximum tensile strength was measured from a 00 mm test piece.

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

Example 1 Containing 5% by weight of octene-1 and having a density of 0.937 g / cm ³ , MI
Value of ASTM D-1238 (E) is 40g / 10min, heat of fusion obtained by DSC is 36cal / g, melting point is 125 ℃ LLDPE
A blend composed of polypropylene (PP) with a blending ratio (LLDPE / PP) = 80/20% by weight of 30 g / 10 min as measured by the method of ASTM D-1238 (L) with MFR as a sheath component. The structure has a sheath component, the polypropylene has a core component, and the number of holes is 20.
Using multiple compound nozzles of 0, the blending structure spinning temperature was 220 ° C, the polypropylene spinning temperature was 240 ° C, the blending ratio of polypropylene to the blending ratio was 50:50, and the single hole discharge rate was 1.7 g / Melt spinning was performed under the condition of minutes, and a continuous multifilament was taken using an air jet provided 200 cm below the nozzle. The performance of the obtained fiber is shown in Table 1.

Comparative Examples 1 and 2 As Comparative Example 1, the melt flow rate of polypropylene is
Other conditions were the same as in Example 1 except that 80 g / 10 min was used as measured by the method of ASTM D-1238 (L). A continuous multifilament was manufactured according to the above.

Next, in Comparative Example 2, a continuous multifilament was manufactured according to Example 1 except that the blend ratio of polypropylene as a sheath component was 30% by weight, which was more than 20% by weight.

As a result, as shown in Table 1, there were many yarn breakages in Comparative Examples 1 and 2.

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 was 15 g / m 2.
^{After 2} and 40 g / m ² of web, a linear pressure of 30 kg was applied by a roll group consisting of a metal embossing heating roll and a metal heating roll.
/ cm, pressing area ratio 15%, heat treatment temperature was changed from 95 ℃ to 110 ℃, and thermocompression bonding was performed to obtain spunpond nonwoven fabric. The performance results of the obtained non-woven fabric are shown in Table 2.

Comparative Example 3 Similarly, as Comparative Example 3, heat treatment temperatures of 90 ° C. and 115 ° C. were obtained. The performance results of the non-woven fabric are shown in Table 2.

Comparative Example 4 A polyethylene terephthalate having a blended structure of LLDPE and polypropylene used in Example 1 as a sheath component and an intrinsic viscosity of 0.70 (using a mixed solvent of phenol: tetrachloroethane = 1: 1, measured at 20 ° C.) was used as a core. As a component, filaments are collected according to Example 1. The filament was made into a web according to Example 2 to obtain a nonwoven fabric. The characteristics of the non-woven fabric are shown in Table 2. As is clear from Table 2, the heat treatment temperature is 15 to 30 ° C higher than the melting point of the sheath component.
It can be seen that a nonwoven fabric with good performance can be obtained in the low temperature range. Also, by changing the core component from polyethylene terephthalate to polypropylene, a soft texture can be obtained even if the weight of the nonwoven fabric is large.

(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, 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.

Claims (3)

[Claims] 1. A fiber assembly which is a melt-spun composite fiber which is introduced into an air sacker and is blown onto a porous collector which is moved after being subjected to a stretching and feeding action by the action of an air jet. And the sheath component of the composite fiber is a copolymer of ethylene and octene-1, which contains substantially 1 to 10% by weight of octene-1, the density is 0.900 to 0.940 g / cm ³ , and the melt index value is ASTM D-1238 (E) of 20 to 80 g / 10 min, heat of fusion measured by DSC of 25 cal / g
The linear low density polyethylene and the melt flow rate value above are 5 to 60 g / 10 measured by the method of ASTM D-1238 (L).
Is a blend structure with polypropylene, the core component of the composite fiber is the polypropylene, and the single fiber fineness of the composite fiber is a heat-bonding continuous fiber having a denier of 5 denier or less, D
15 to 30 from the melting point of the linear low-density polyethylene constituting a part of the sheath component of the conjugate fiber measured by SC
A heat-bonded long-fiber non-woven fabric, characterized in that the non-woven fabric is heat-pressed at a temperature lower by ℃, and the press-contact area ratio of the non-woven fabric is 7-40%. 2. The non-woven fabric comprising heat-bonded continuous fibers according to claim 1, wherein the composite ratio of the sheath component and the core component of the composite fiber constituting the non-woven fabric is 20-80: 80-20. 3. The heat-bonded long-fiber non-woven fabric according to claim 1, wherein the blend amount of polypropylene to the linear low-density polyethylene of the blend constituting the sheath component is 2 to 25% by weight.