JP3107626B2 - Heat-bonded long-fiber nonwoven fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric made of heat-bonded filaments.

[0002]

2. Description of the Related Art In the production of non-woven fabrics, there are methods of fixing fibers to each other, such as a method by entanglement between fibers such as a needle punch method and a method using various adhesives as a binder.

[0003] Nonwoven fabrics such as disposable diapers and coated papers for sanitary absorbers, whose demand has been rapidly increasing in recent years, are required to have a soft and soft feel. In order to satisfy these required qualities as much as possible, a method of producing a nonwoven fabric mainly by a binder method has been adopted.

[0004] As a binder method, a method of adhering an adhesive solution to a web has been mainly employed, but there are problems such as the necessity of energy for removing the solvent of the adhesive solution and a poor working environment. . In order to solve these problems, a method has been proposed in which fibers having a lower melting point than the fibers constituting the web are mixed into the web as a binder, and after the web is formed, the fibers are bonded to each other by heat treatment.

For example, as a binder for a nonwoven fabric having a high strength and a good feel, Japanese Patent Publication No. Sho 1010583 discloses a composite fiber comprising a fiber-forming polymer having a different melting point as a composite component.

[0006]

The low-melting-point component of the conventional composite-type heat-bonding fiber for nonwoven fabric is usually polyethylene, and is low-, medium-, or high-density polyethylene. A nonwoven fabric made of a composite type heat-bonding fiber having a medium- or high-density polyethylene as a low-melting point component has a drawback that the feel is hard. On the other hand, nonwoven fabrics composed of composite adhesive fibers containing a commercially available linear low-density polyethylene having a low melting point component can be expected to have a soft feel, but since high-speed spinning is difficult, the spunbond method is not uniform. In addition, there is a problem that it is difficult to obtain a nonwoven fabric with high productivity.

The present inventors have previously proposed in Japanese Patent Application Laid-Open No. 02-139469 a nonwoven fabric comprising a composite fiber having a good low-spinning linear low-density polyethylene as a sheath component and polypropylene as a core component. did. Although the softness of this nonwoven fabric is not impaired, there is a limit in producing a nonwoven fabric having a low basis weight due to poor spreadability.

The present invention solves the above-mentioned problems, and is a nonwoven fabric comprising a composite fiber having good spinnability and spreadability, a blend structure of high-density polyethylene and polypropylene as a sheath component, and polypropylene as a core component. It is an object of the present invention to provide a heat-bonded long-fiber nonwoven fabric having a good formation even at a low basis weight.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention.

That is, the present invention relates to an aggregate sprayed on a porous collector that moves after being drawn and sent out by traction of air soccer with conjugate fiber melt-spun, wherein the sheath component is 0.945-0.965g density
/ Cm ³ using a blend structure of high density polyethylene (hereinafter, referred to as HDPE) and polypropylene,
Using the polypropylene as the core component, the melt flow rate value (hereinafter referred to as the MFR value) of the polypropylene is 5
７０70 g / 10 min. , Composed of heat-bonded filaments having a single-fiber fineness of 5 denier or less, and a melting point of the HDPE constituting a part of the sheath component of the composite fiber determined by DSC, which is 5 to 5 g
Heat-welded at a temperature lower by 25 ° C.
The present invention provides a heat-bonded long-fiber nonwoven fabric characterized by being 40%. The pressed area ratio is measured by the following measuring method. That is, using a small piece of non-woven fabric, an enlarged image was taken with a scanning electron microscope, and the ratio of the sum of the areas of the points pressed against the area of the minimum repeating unit was individually measured 10 times. The pressed area ratio of the nonwoven fabric was measured. HDPE has lubricants, pigments,
You may contain additives, such as a stabilizer and a flame retardant.

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

The reason why HDPE is used is that it is possible to obtain a nonwoven fabric which is excellent in charge opening property after drawing and has good formation. Next, the reason why the blend structure is used for the sheath component is that the yarn forming property is improved, and the loss due to ear cutting performed in the nonwoven fabric manufacturing process is reduced.

In the present invention, when the content of HDPE is 100% by weight, it is difficult to obtain a fine denier, the resulting fiber becomes hard and the feeling is not good. The HDPE density is 0.9
If it exceeds 65 g / cm ³ , the hand feels 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 opening property is poor, and the weight per unit area is low. It is difficult to obtain a nonwoven.

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

The Q value (weight average molecular weight / number average molecular weight), which is the main polymer component of the sheath, is preferably 3.5 or less. The Q value is the ratio between the weight average molecular weight and the number average molecular weight of the polymer 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 increases, the width of the molecular weight distribution increases, and the yarn cooling during melt spinning deteriorates, and the spinnability decreases. Therefore, the Q value is preferably 3.5 or less.

The composition ratio of the blend structure as the sheath component of the conjugate fiber and the polypropylene as the core component is preferably from 80 to 20% by weight of polypropylene to 20 to 80% by weight of the blend structure. When the blended structure is less than 20% by weight, the fiber strength is increased, but the adhesive strength is weakened, and the feeling becomes coarse and unpreferable. Conversely, if the blend structure is 80
When the content is more than 10% by weight, the fiber has a high adhesive strength and is soft in feeling, but the strength is low, which is not preferable.

Next, the HD of the blend structure, which is a sheath component,
It is preferable that the blend amount of polypropylene with respect to PE is 2 to 25% by weight. As described above, by blending the same polypropylene as the core component polypropylene with the sheath component, the core / sheath component peeling phenomenon does not occur.
Further, the loss due to the ear cutting performed in the nonwoven fabric manufacturing process can be used again as a blend structure of the sheath component. For this reason, the yield is improved as compared with those made of polyester or polyamide.

If the blend amount of the 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 nonwoven fabric are inferior because the thermal properties are close to those of polypropylene. Further, it is not preferable because the charge opening property after stretching is inferior.

The melt index value (hereinafter referred to as MI value) is measured by the method of ASTM D-1238 (E), and HDPE of 10 to 40 g / 10 minutes is preferable. That is, HDPE having an MI value of less than 10 g / 10 minutes cannot easily perform high-speed spinning unless the spinning temperature is extremely high, and the spinning at an extremely high temperature tends to cause stains on the nozzle surface. That would be undesirable. Conversely, the MI value is 4
If it exceeds 0 g / 10 minutes, it becomes difficult to appropriately select 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 has poor spinnability. In the spunbonding method, in which a continuous filament is drawn by air soccer and then a nonwoven fabric is directly produced, the heat of fusion is 35c in the case of fine denier.
HDPE of less than al / g needs to increase the air pressure of air soccer. When the heat of fusion is 35 cal / g or more, it can be taken off by lowering the air pressure, and the denier can be further reduced.

The heat of fusion in the present invention is measured as follows. In other words, DSCs manufactured by PerkinElmer
Using 2C, a sample of about 5 mg was taken, and the scanning speed was 2
The DSC curve obtained by setting the temperature to 0 ° C./min and raising the temperature from room temperature is determined in accordance with the same apparatus manual.

The fiber of the present invention can be obtained by using a conventionally known melt spinning apparatus for composite fibers. As the melt spinning temperature, the spinning temperature of the blend structure is 200 to 265 ° C.
Preferably it is 220-250 ° C, while the spinning temperature of the polypropylene is 210-270 ° C, preferably 220-26 ° C.
0 ° C. When the spinning temperature is outside the above range, the spinning condition becomes poor, and it becomes 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 air soccer. Further, the obtained nonwoven fabric does not become a homogeneous nonwoven fabric due to yarn breakage during spinning. On the other hand, when the spinning temperature is higher than the above temperature range, the nozzle surface is liable to be stained, and when operated for a long time, only a non-uniform nonwoven fabric is obtained due to thread breakage due to nozzle surface contamination. Therefore, in order to solve the above-mentioned drawbacks, it is necessary to clean the nozzle surface periodically and at a short pitch, so that the loss increases.

That is, in the present invention, since the melt spinning of both the blend structure and the polypropylene is performed at substantially the same temperature, the cooling of the conjugate fiber after the melt extrusion becomes smooth, and distortion to the yarn hardly remains. For this reason, the obtained nonwoven fabric fibers are uniform and the spinnability is good. That is,
By selecting HDPE having good spinnability at a high temperature and bringing the spinning temperatures of the two 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, a nonwoven fabric with spots or a nonwoven fabric with large holes is obtained. The disadvantage of the big hole 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 the sheet is pulled out from a roll, the sheet is broken or wrinkles or suspensions occur at the holes, resulting in poor appearance quality.

On the other hand, when a high-weight nonwoven fabric having a basis weight exceeding 50 g / m ² is used for a carpet base fabric, the pile cannot be driven if a hole is formed due to thread breakage. In addition, if the web is too overlapped due to wrinkling or hanging during processing and the thickness of the nonwoven fabric is too large, the piling is not performed smoothly, and the needle is sometimes broken. For this reason, the operability and the appearance quality deteriorate.

For these reasons, in any case, the defect caused by the yarn breakage becomes the defect of the nonwoven 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 nonwoven 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 undesirably coarse and bulky. If it is less than 10 g / m ² , the feel is soft but the strength is low and the practicality is poor.

In addition, the pressure contact area ratio when the web is heat-treated and the fibers are thermocompression-bonded to each other is required to be 4 to 40% from the relationship between the feeling and the strength of the nonwoven fabric. If it is less than 4%, the feeling is soft but the strength is insufficient. Conversely, if the pressed area ratio exceeds 40%, the strength increases, but it becomes a hard nonwoven fabric, which is not preferred in the present invention. Heat press welding is performed to increase the strength of the nonwoven fabric. The pressure welding method uses, for example, a hot embossing machine or an embossing machine having an ultrasonic welding mechanism to an engraving roll to bond a point portion of a web made of constituent fibers by heat and pressure. 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 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 feeling becomes hard, and the strength of the nonwoven fabric decreases.

On the other hand, when the surface temperature of the embossing heating roll is lower than the above range, the feeling of the nonwoven fabric is soft,
Insufficient adhesion between filaments results in lower strength. Next, a non-woven fabric sheet having a special feeling and a characteristic of the cross-sectional shape can be obtained by forming the cross-sectional shape of the fiber into a deformed or flat shape in addition to the circular cross-section.

The nonwoven fabric described above has a good opening property, has few defects even in a low basis weight, and has a good formation.

[0031]

[Function] Due to this constitution, the strength is high, the softness and texture are excellent, the yarn-making properties are good, and the charge opening property after drawing is also excellent. It is suitable,
On the other hand, nonwoven fabrics having a high basis weight can be applied to a wide range of uses such as articles, carpet base fabrics, and filters.

[0032]

The present invention will be described in more detail with reference to the following examples. The methods for measuring physical properties shown in the examples are as follows.

(1) Tensile strength of non-woven fabric According to the slip method described in JIS L-1096, a width of 3
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 materials show softness and have a slot width of 10 mm according to the handle ometer method described in JIS L-1096.
Was measured. Example 1 A density of 0.951 g / cm ³ and an MI value of ASTM D-
25 g / 10 min, measured by the method of 1238 (E), DS
HDPE having a heat of fusion of 40 cal / g, a Q value of 2.6 and a melting point of 130 ° C. as measured by C, and an MFR value of AS
30 g / 1 as measured by the method of TM D-1238 (L).
0 minutes polypropylene (PP) blend ratio (H
(DPE / PP) = 80/20% by weight as a sheath component, the polypropylene as a core component, four composite nozzles having 200 holes, and a spinning temperature of 240 ° C. for the blend structure. The spinning temperature of the polypropylene was set to 250 ° C., the composite ratio (ratio of weight and weight) of the blend structure and the polypropylene was set to 50:50, and the single hole discharge amount was 1.7.
The melt spinning was performed under the conditions of g / min.
The continuous multifilament was taken out using an air jet provided at a position of mm. Table 1 shows the performance of the obtained fibers.

[0035]

[Table 1]

Comparative Examples 1 to 3 As Comparative Example 1, the melt flow rate of polypropylene was 80 g as measured by the method of ASTM D-1238 (L).
A continuous multifilament was produced in the same manner as in Example 1 except that the product was used for 10 minutes.

Next, a continuous multifilament was manufactured in the same manner as in Example 1 except that the blend ratio of the sheath component polypropylene was 30% by weight in Comparative Example 2.

As Comparative Example 3, a continuous multifilament was produced in the same manner as in Example 1 except that the Q value of the sheath component HDPE was 3.9. As a result, as shown in Table 1, yarn breakage was large in Comparative Examples 1 to 3. Example 2 A multifilament obtained by using the air soccer of Example 1 was collected on a moving endless wire mesh and had a basis weight of 15%.
g / m ² , and a linear pressure of 30K is applied by a roll group including a metal embossing heating roll and a metal heating roll.
g / cm, pressure contact area ratio 15%, heat treatment temperature 105 ° C
From 125 ° C. to obtain a spunbonded nonwoven fabric. Table 2 shows the performance results of the obtained nonwoven fabric.

[0039]

[Table 2]

Comparative Example 4 Similarly, as Comparative Example 4, the heat treatment temperature was 100 ° C. and 130 ° C.
I also got one. Table 2 shows the performance results of the nonwoven fabric.

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

[0042]

The nonwoven fabric made of the heat-bonded filament according to the present invention has a low strength because of its high strength, excellent softness and texture, and good spinning properties, and also excellent charge opening properties after drawing. The basis weight nonwoven fabric is particularly suitable as a lining for disposable diapers, while the basis weight nonwoven fabric can be applied to a wide range of uses such as bags, carpet base fabrics, and filters.

Continuation of the front page (72) Inventor Yasuhiro Yonezawa 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Co., Ltd. Central Research Laboratory Co., Ltd. (56) References JP-A-3-59113 (JP, A) JP-A 5-186955 (JP, A) JP-A-1-111016 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D04H 1/00-18/00

Claims (1)

(57) [Claims] 1. An aggregate which is melt-spun and subjected to drawing and feeding actions by traction of air soccer and then sprayed onto a moving porous collector, wherein the sheath component has a density of 0.1%. a blend structure of high-density polyethylene and polypropylene are 945~0.965g / cm ^3, the polypropylene used in the core component, polyps
The propylene melt flow rate value is 5 to 70 g / 10
And a single-filament fineness of 5 denier or less, which is 5 to 2% higher than the melting point of the high-density polyethylene constituting a part of the sheath component of the composite fiber determined by DSC.
Heat-welded at a temperature lower by 5 ° C.
A heat-bonded long-fiber nonwoven fabric characterized by being 0%.