JPH05186951A - Hot melt bonded filament nonwoven fabric - Google Patents

Abstract

PURPOSE:To provide hot melt bonded filament nonwoven fabric having high strength, excellent softness, excellent hand touch, good fiber-formability and excellent electrostatic fiber-openability after drawn. CONSTITUTION:The objective hot melt bonded filament nonwoven fabric comprises a filament aggregate produced by spraying hot melt adhesive conjugate filaments on a moving porous catcher, the filaments being produced by melt-spinning and subsequently drawing by the suction of an air sucker. The conjugate filaments are produced from the blend of high density polyethylene having a density of 0.945-0.965g/cm<3> with polypropylene as the sheath component and the polypropylene as the core component and has a melt flow rate of 5-75g/10min and a single filament fineness of <=5 denier. The fabric is produced by heating and press-bonding the filament aggregate at a temperature lower 5-25 deg.C than the melting point (measured by DSC) of the high density polyethylene constituting a part of the sheath component of the conjugate filament and has a press-bonded area of 4-40%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonwoven fabric composed of heat-bonded long fibers.

[0002]

2. Description of the Related Art As a method for fixing fibers in a non-woven fabric, there is a method such as a needle punching method in which fibers are entangled with each other and a method using various adhesives as a binder.

[0003] 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 method of producing a nonwoven fabric by a binder method has been mainly adopted.

As a binder method, a method of adhering an adhesive solution to a 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 proposed in which fibers having a melting point lower than that of fibers constituting the web are mixed as a binder with the web to form the web, and then the fibers are heat-bonded to each other.

For example, as a binder for a non-woven fabric having high strength and good texture, Japanese Patent Publication No. 61-10583 discloses a composite fiber containing a fiber-forming polymer having different melting points as a composite component.

[0006]

The low melting point component of the conventionally used non-woven composite heat-bonded fibers is usually polyethylene, which is low density, medium density or high density polyethylene. 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 drawback that the texture is hard. On the other hand, a commercially available non-woven fabric composed of a composite type adhesive fiber containing a linear low-density polyethylene as a low melting point component can be expected to have a soft texture, but since it is difficult to perform high-speed spinning, a spun-bond method produces a homogeneous material. In addition, there is a problem that it is difficult to obtain a highly productive nonwoven fabric.

The inventors of the present invention have previously proposed, in Japanese Patent Application Laid-Open No. 02-139469, a non-woven fabric composed of a composite fiber containing a linear low-density polyethylene having good spinnability as a sheath component and polypropylene as a core component. did. Although the softness of this non-woven fabric is not impaired, it is inferior in openability, so there is a limit in producing a non-woven fabric with a low basis weight.

The present invention solves the above problems and is a non-woven fabric having good spinnability and openability, and a composite fiber having a blend structure of high-density polyethylene and polypropylene as a sheath component and polypropylene as a core component. Therefore, it is an object of the present invention to provide a heat-bonded long-fiber non-woven fabric having a good texture even in a low basis weight.

[0009]

The inventors of the present invention have reached the present invention as a result of intensive research to solve the above problems.

That is, the present invention relates to a melt-spun composite fiber which is sprayed onto a porous collector that is moved after being subjected to a stretching and feeding action by pulling air sucker and then moving to a sheath component. Density is 0.945 to 0.965g
/ Cm ³ high density polyethylene (hereinafter referred to as HDPE) and polypropylene blend structure,
Using the polypropylene as the core component, the melt flow rate value (hereinafter referred to as MFR value) of the composite fiber is 5 to 75.
g / 10 minutes, a single yarn fineness consisting of heat-bonded long fibers having a denier of 5 denier or less, and 5 to 25 ° C. from the melting point of the HDPE which constitutes a part of the sheath component of the composite fiber determined by DSC.
It is heat pressure welded at a low temperature and the pressure contact area ratio is 4-40%
The heat-bonded long-fiber non-woven fabric is characterized in that The pressure contact area ratio is measured by the following measuring method. That is, by using a small piece of non-woven fabric, magnified and photographed with a scanning electron microscope, the ratio of the total area of the point-pressed portion to the area of the minimum repeating unit is individually measured 10 times. The pressed area ratio of the non-woven fabric was measured. The HDPE may contain additives such as a lubricant, a pigment, a stabilizer and a flame retardant.

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

The reason why HDPE is used is that it is possible to obtain a nonwoven fabric which is excellent in charge opening property after stretching and has a good texture. Next, the reason why the blended structure is used for the sheath component is to improve the spinnability and to reduce the loss due to the ear cut performed in the nonwoven fabric manufacturing process.

In the present invention, when HDPE is 100% by weight, it is difficult to make fine denier, the obtained fiber becomes hard and the texture is not good. The density of HDPE is 0.9
If it exceeds 65 g / cm ³ , the texture is coarse and hard, and the weight of the fiber cannot be reduced. On the other hand, if it is less than 0.945 g / cm ³ , the slimy feeling increases, the spreadability is poor, and the weight is low. It is difficult to obtain a non-woven fabric.

The polypropylene used for the conjugate fiber in the present invention is required to have an MFR value in the range of 5 to 70 g / 10 minutes measured by the method of ASTM D-1238 (L). When the MFR value exceeds 70 g / 10 minutes, it is difficult to obtain a high-strength fiber and a satisfactory nonwoven fabric cannot be obtained, and when the MFR value is less than 5 g / 10, spinnability is poor.
A lubricant, pigment, stabilizer, etc. may be added to polypropylene.

The Q value (weight average molecular weight / number average molecular weight), which is the main polymer component of the sheath portion, is preferably 3.5 or less. The Q value is the ratio of the weight average molecular weight and the number average molecular weight of the polymer, which is determined by gel permeation chromatography, and the Q value indicates the width of the molecular weight distribution. It greatly affects the workability. When the Q value is large, the width of the molecular weight distribution is wide, and the yarn cooling during melt spinning is poor, and the spinnability is reduced. Therefore, the Q value is preferably 3.5 or less.

The composition ratio of the blend structure, which is the sheath component of the composite fiber, and the polypropylene, which is the core component, is preferably 80 to 20 wt% polypropylene to 20 to 80 wt% of the blend structure. 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 contrary, the blend structure is 80
When the content is more than 10% by weight, the fiber has a high adhesive force and is soft in terms of feeling, but the strength becomes low, which is not preferable.

Next, the HD of the blend structure which is the sheath component
The blending amount of polypropylene with respect to PE is preferably 2 to 25% by weight. Thus, by blending the same polypropylene as the core component with the sheath component, the phenomenon of peeling of the core / sheath component does not occur.
In addition, the loss due to the ear cut performed in the nonwoven fabric manufacturing process can be reused as the blend structure of the sheath component. Therefore, the yield is improved as compared with that made of polyester or polyamide.

If the blending amount of polypropylene in the blend structure is less than 2% by weight, no improvement in the spinnability is observed. On the other hand, if it exceeds 25% by weight, the physical properties of the non-woven fabric are poor because the thermal properties are close to those of polypropylene. Furthermore, it is not preferable because the charge opening property after stretching is poor.

The melt index value (hereinafter referred to as MI value) is measured by the method of ASTM D-1238 (E), and 10 to 40 g / 10 min of HDPE is preferable. In other words, HDPE with an MI value of less than 10 g / 10 minutes cannot be easily spun at high speed unless the spinning temperature is extremely high. Also, spinning at an extremely high temperature tends to cause stains on the nozzle surface. It will be unfavorable. Conversely, MI value is 4
If it exceeds 0 g / 10 minutes, it becomes difficult to properly select the spinning conditions, or the strength of the obtained fiber becomes low, which is not preferable.

HDPE having a heat of fusion of less than 35 cal / g does not have good spinnability. In the spunbond method in which a continuous filament is directly produced by drawing a continuous filament with air sucker, the heat of fusion is 35c when finely deniered.
HDPE of less than al / g requires a high air sucker air pressure. When the heat of fusion is 35 cal / g or more, the air pressure can be lowered and the heat can be taken out, and finer denier can be obtained.

The heat of fusion in the present invention is measured as follows. In other words, Perkin Elmer DSC
-2C is used to collect about 5 mg of sample and the scanning speed is set to 2
The DSC curve obtained by setting the temperature to 0 ° C./min and raising the temperature from room temperature is determined 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.
220-250 ° C, while polypropylene spinning temperature is 210-270 ° C, preferably 220-26 ° C.
It is 0 ° C. If the spinning temperature is out of 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 fibers, and it is necessary to increase the air pressure of the air sucker. Further, the obtained nonwoven fabric will not be a homogeneous nonwoven 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 a non-uniform nonwoven fabric is obtained due to yarn breakage due to nozzle surface soiling. Therefore, in order to eliminate the above-mentioned drawbacks, it is necessary to clean the nozzle surface regularly and at a short pitch, which results in a large loss.

That is, in the present invention, since melt spinning of both the blend structure and polypropylene is performed at substantially the same temperature, the composite fiber after melt extrusion is smoothly cooled, and the strain on the yarn is unlikely to remain. Therefore, the obtained non-woven fiber is uniform and the spinnability is good. That is,
Only when HDPE, which has good spinnability at high temperature, 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 spunbonded nonwoven fabric of the present invention, if yarn breakage occurs during spinning, the nonwoven fabric will have a mottled spot or a large hole. The drawback of large holes is
In the case of a low basis weight nonwoven fabric having a basis weight of 10 to 50 g / m ² ,
In the processing step, when pulled out from the roll shape, it breaks or wrinkles or hangs at the hole, resulting in poor appearance quality.

On the other hand, when a high basis weight non-woven fabric having a basis weight of more than 50 g / m ² is used as the carpet base fabric, the pile cannot be driven in if holes are formed due to yarn breakage. Further, if the webs are overly overlapped due to wrinkles or suspension during processing and the thickness of the non-woven fabric is excessively increased, the piling is not performed smoothly and the needle sometimes breaks. Therefore, the operability and the appearance quality are deteriorated.

For these reasons, in any case, the defect due to the yarn breakage becomes the defect of the non-woven fabric as it is. Therefore, since the defects caused by the yarn breakage of the spinning need to be cut at the time of shipping, a short length reaction occurs and the yield is deteriorated.

The basis weight of the non-woven fabric is 10 to 200 g / m ²
The reason is that if the weight of the nonwoven fabric exceeds 200 g / m ² , the nonwoven 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.

Further, the pressure contact area ratio when heat-bonding the fibers by heat-treating the web needs to be 4 to 40% in view of the texture and strength of the nonwoven fabric. If it is less than 4%, 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 a hard nonwoven fabric is formed, which is not preferable in the present invention. Heat pressing is performed to increase the strength of the non-woven fabric. As a pressure welding method, for example, a hot embossing machine or an embossing machine having an ultrasonic welding mechanism on an engraving roll is used to bond the point portions of the web made of the constituent fibers by heat and pressure. This thermal bonding temperature affects the feel and strength of the nonwoven fabric, and in the present invention, it is important to perform thermal bonding at a temperature 5 to 25 ° C. lower than the melting point of HDPE which is the main component of the sheath component. 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, the feel becomes hard and the strength of the nonwoven fabric becomes low.

On the other hand, when the surface temperature of the embossing heating roll is lower than the above range, the texture of the nonwoven fabric is soft,
Inadequate adhesion between filaments results in low strength. Next, the cross-sectional shape of the fiber is not only circular but also irregular or flat, so that a non-woven sheet having a special texture and a characteristic of the cross-sectional shape can be obtained.

The above-mentioned non-woven fabric is excellent in openability, has few defects even in low basis weight, and has good texture.

[0031]

With this structure, since the strength is high, the softness and the feel of the texture are excellent, the yarn-forming property is good, and the electrostatic fiber opening property after stretching is also excellent, the non-woven fabric having a low basis weight is particularly suitable as a lining for a disposable diaper. Suitable one,
On the other hand, the non-woven fabric having a high basis weight can be applied to a wide range of applications such as products, carpet base fabrics and filters.

[0032]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, the measuring method of the physical-property value shown in the Example is as follows.

(1) Tensile strength of nonwoven fabric Width 3 according to the slip method described in JIS L-1096.
The maximum tensile strength was measured from a test piece having a length of 0 mm and a length of 100 mm.

(2) Total hand of non-woven fabric These show softness, and the slot width is 10 mm in accordance with the handle odometer method described in JIS L-1096.
It was measured at. Example 1 D-having a density of 0.951 g / cm ³ and an MI value of ASTM
25g / 10 minutes, DS measured by the method of 1238 (E)
The heat of fusion obtained by measurement with C is 40 cal / g, the Q value is 2.6, the melting point is HDPE with 130 ° C., and the MFR value is AS.
30 g / 1 as measured by the method of TM D-1238 (L)
The blend ratio (H
DPE / PP) = 80/20% by weight as a sheath component, the polypropylene as a core component, four composite nozzles with 200 holes, and a spinning temperature of the blend structure of 240 ° C. The spinning temperature of polypropylene was 250 ° C., the composite ratio of the blend structure and polypropylene (heavy ratio) was 50:50, and the single hole discharge rate was 1.7.
Melt spinning under the condition of g / min, 1200
A continuous multifilament was pulled using an air jet provided at the position of mm. The performance of the obtained fiber is shown in Table 1.

[0035]

[Table 1]

Comparative Examples 1 to 3 As Comparative Example 1, the melt flow rate of polypropylene was 80 g measured by the method of ASTM D-1238 (L).
A continuous multifilament was manufactured in accordance with Example 1 except that / 10 minutes was used.

Next, in Comparative Example 2, a continuous multifilament was manufactured according to Example 1 except that the blending ratio of the sheath component polypropylene was 30% by weight.

As Comparative Example 3, a continuous multifilament was manufactured in accordance with Example 1 except that the HDPE of the sheath component had a Q value of 3.9. As a result, as shown in Table 1, in Comparative Examples 1 to 3, there were many yarn breakages. 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 30K is applied by a roll group composed of a metal embossing heating roll and a metal heating roll.
g / cm, pressing area ratio 15%, heat treatment temperature 105 ℃
To 125 ° C. to obtain a spunbonded nonwoven fabric. The performance results of the obtained nonwoven fabric are shown in Table 2.

[0039]

[Table 2]

Comparative Example 4 Similarly as Comparative Example 4, the heat treatment temperatures were 100 ° C. and 130 ° C.
I also got one. The performance results of the non-woven fabric are shown in Table 2.

As is clear from Table 2, a nonwoven fabric with good performance can be obtained in the temperature range in which the heat treatment temperature is lower by 5 to 25 ° C. than the melting point of the sheath component. Comparative Example 5 Density of 0.936 g / cm ³ and MI value of ASTM D-
38g / 10min, DS by the method of 1238 (E)
A linear low-density polyethylene having a heat of fusion of 40 cal / g and a melting point of 124 ° C. measured by C and an MFR value of A
30 g / measured by the method of D-1238 (L) of STM
10 minutes polypropylene (PP) and both blend ratio (linear low density polyethylene / polypropylene) = 8
The blend structure composed of 0/20% by weight was used as a sheath component, the polypropylene was used as a core component, four composite nozzles having 200 holes were used, and the spinning temperature of the blend structure was 2
40 ° C., the polypropylene spinning temperature was 250 ° C., the composite ratio (weight ratio) of the blend structure and polypropylene was 50:50, melt spinning was performed under the conditions of single hole discharge rate of 1.7 g / min, and a nozzle An air jet provided at a position of 1200 cm below was used to obtain a spunbonded nonwoven fabric having a basis weight of 15 g / m ² . The obtained non-woven fabric was a non-woven fabric lacking in openability and poor in texture.

[0042]

EFFECT OF THE INVENTION The non-woven fabric comprising the heat-bonded long fibers according to the present invention has high strength, excellent softness and feeling to the touch, good spinnability, and excellent charge spreadability after stretching. The non-woven fabric having a unit weight becomes particularly suitable as a lining for a disposable diaper, while the non-woven fabric having a high unit weight is applicable to a wide range of applications such as bags, carpet base fabrics and filters.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuhiro Yonezawa 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A melt-spun composite fiber, which is sprayed onto a porous collector that moves after being subjected to a stretching and feeding action by traction of air sucker and then moved, and has a density of 0. A blend structure of high density polyethylene and polypropylene of 945 to 0.965 g / cm ³ is used, the polypropylene is used as the core component, the melt flow rate value of the composite fiber is 5 to 75 g / 10 minutes, and the single yarn fineness is Made of heat-bonded long fibers of 5 denier or less, DSC
Characterized in that it is heat-pressed at a temperature 5 to 25 ° C. lower than the melting point of the high-density polyethylene constituting a part of the sheath component of the composite fiber, which is obtained by measurement with the pressure-contact area ratio of 4 to 40%. Heat bonded long-fiber non-woven fabric.