JPH10158971A - Nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonwoven fabric hardly generating the peeling between layers and the curling of a laminate, even when laminated to wet-made paper and subjected to a craping processing treatment, by partially integrally heat- pressing the web of specific sheath-core conjugate filaments. SOLUTION: This nonwoven fabric is obtained by melt-spinning an aromatic polyester such as polyethylene terephthalate as a core component and a polyolefin such as polyethylene containing 0.1-5wt.% of a hydrophilizing agent such as the mixture of a sodium 15C alkyl sulfonate with stearyl monoethanolamine as a sheath component into sheath-core conjugate filaments, cooling the spun filaments with cold wind, simultaneously taking off the filaments with an ejector, opening the taken filaments, collecting the opened filaments on a moving conveyer, and subsequently integrally heat-pressing the formed filament web without a grooved heat roll so as to partially adhere the sheath components to each other. The obtained nonwoven fabric has a bending resistance of <=50mm in the longitudinal direction, an area shrinkage rate of <=3% at 120 deg.C and a shrinkage rate of 0.5% in the latitudinal direction at 120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sanitary material, a food packaging material, which is excellent in lamination suitability with wet papermaking paper, and which can softly obtain a laminated nonwoven fabric (hereinafter sometimes referred to as a laminate). And a nonwoven fabric useful as a surgical sheet and the like.

[0002]

2. Description of the Related Art Spunbonded nonwoven fabrics made of continuous filaments have excellent mechanical properties such as tensile strength and tear strength, and the thermoplastic resin that is the raw material of the fibers is almost always hydrophobic. It is inferior in hydrophilicity and water absorption, but has the advantage of high strength retention when wet. On the other hand, paper obtained by wet papermaking from natural pulp is excellent in hydrophilicity and water absorption, but has drawbacks such as low tear strength and large decrease in wet strength. In view of the advantages and disadvantages of spunbond nonwoven fabrics and wet papermaking (papermaking), many attempts have been made to laminate them to provide a hydrophilic and water-absorbent nonwoven fabric with excellent strength.

[0003] For example, as disclosed in JP-A-1-111056 and JP-A-5-253160, there is a method of laminating a spunbonded nonwoven fabric layer and a papermaking layer and entangled them by a high-pressure water column flow. . According to these methods, a hydrophilic nonwoven fabric having excellent drape property and sufficient strength can be obtained. However, since water must be pressurized to a pressure of 50 kg / cm ² in the process of entanglement with a high-pressure water column flow, a large amount of water is required. Energy.

As a simplified method of laminating a spunbonded nonwoven fabric layer and a papermaking layer, a spunbonded nonwoven fabric layer made of a core-sheath type heat-fusible conjugate fiber is disclosed in Japanese Patent Application Laid-Open No. Hei 5-279997. There is a method of laminating with a papermaking layer in the papermaking process, drying and heat-bonding simultaneously. Further, as disclosed in Japanese Utility Model Laid-Open No. 3-106390, the spunbonded nonwoven fabric layer used in such a method has a polyolefin and a melting point of 30% from the melting point of the polyolefin.
There has been proposed a composite long-fiber nonwoven fabric made of a thermoplastic resin having a high melting point of not less than ° C.

However, in the method in which the spunbonded nonwoven fabric layer is laminated during the papermaking process and the papermaking layer is dried and heat-sealed at the same time, the resulting laminate has a hard texture and has a drapability lower than that of the high-pressure hydroentanglement method. It has the disadvantage of lacking. In order to improve the drapability of the laminate, a method of performing creping after heat fusion is considered.However, the heat fusion point between the spunbond nonwoven fabric layer made of the core-sheath type heat-fusible composite fiber and the papermaking layer is considered. There has been a problem that the laminate is peeled off by creping and the laminate is curled due to a difference in heat shrinkage characteristics between the two layers.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and has the advantage that even when a laminate formed by laminating a papermaking layer is subjected to finish processing such as creping, peeling and curling hardly occur. An object of the present invention is to provide a fibrous nonwoven fabric.

[0007]

According to the study of the present inventors, the object of the present invention is to form a core-sheath type composite continuous fiber having an aromatic polyester as a core component and a polyolefin as a sheath component. In the nonwoven fabric, the nonwoven fabric is thermocompression-bonded so that the sheath components are partially joined to each other, and the nonwoven fabric has a longitudinal softness of 50 mm or less and an area shrinkage at 120 ° C. of 3% or less. Nonwoven fabric characterized by the above. "

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric of the present invention is composed of a core-sheath type composite continuous fiber, and its core component is an aromatic polyester for imparting thermal dimensional stability to the nonwoven fabric. As the aromatic polyester, those having a fiber-forming ability with a melting point of 200 ° C. or higher, particularly those used as fibers, are preferably used. Specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or polyethylene naphthalate And a copolymerized polyester having a basic skeleton of In particular, polyesters in which ethylene terephthalate units account for at least 80 mol%, preferably at least 85 mol%, of all repeating units are most preferred. Examples of the acidic component that can be copolymerized include isophthalic acid, adipic acid, and sebacic acid. Examples of the glycol component include hexamethylene glycol, diethylene glycol, and triethylene glycol.

The polyolefin forming the sheath component of the core-sheath type long fiber preferably has a melting point of 140 ° C. or less in consideration of the heat fusibility when the obtained nonwoven fabric is laminated with the papermaking layer. Low-density polyethylene, medium-density polyethylene, used as film material
Examples thereof include high-density polyethylene, linear low-density polyethylene obtained by copolymerizing ethylene with an α-olefin having 4 to 8 carbon atoms, or acid-modified polyethylene. Examples of the acid-modified polyethylene include a copolymer of ethylene and an aliphatic monocarboxylic acid such as acrylic acid and methacrylic acid, and a copolymer of ethylene and an aliphatic dicarboxylic acid such as maleic acid and fumaric acid.

It is desirable that the polyolefin contains 0.1 to 5% by weight of a hydrophilizing agent. By doing so, the surface of the non-woven fabric constituent fibers is hydrophilized, so that when the non-woven fabric of the present invention and a papermaking layer containing pulp are formed into a laminate, the water absorption performance against moisture from the long-fiber non-woven fabric side is sufficient. Can be demonstrated. In addition, since the sheath component contains a hydrophilizing agent, blending between the composite filament and the pulp improves, and after laminating the composite filament nonwoven fabric on the papermaking layer containing a large amount of water during the papermaking process, drying is performed. When integrated, the adhesion between the two layers becomes stronger.

The hydrophilizing agents preferably used include alkane sulfonate metal salts, glycerin fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene fatty alcohol ethers, N, N-bis (hydroxyethyl) fatty amines, polyethylene glycol, Examples include condensates of fatty acids and ethanolamine, fatty acid amides, esters of higher fatty acids and aliphatic alcohols, and the like. Among them, metal salts of alkanesulfonates having an average of 5 to 25 carbon atoms account for 80% by weight or more of the total amount of the hydrophilizing agent, and the rest is glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene fatty alcohol ether, polyethylene glycol, A hydrophilizing agent comprising at least one selected from a condensate of a fatty acid and ethanolamine and a fatty acid amide is particularly preferred.

When the amount of the above-mentioned hydrophilizing agent contained in the polyolefin of the sheath component is less than 0.1% by weight, the effect of improving the hydrophilicity becomes insufficient. On the other hand, the amount of the hydrophilizing agent is 5% by weight.
If it exceeds, in the manufacturing process of long fiber nonwoven fabric,
There is a tendency for spinning breakage to occur easily.

The method for adding the above-mentioned hydrophilic agent to the polyolefin is not particularly limited, and a conventionally known method can be used. For example, a masterbatch is first produced by melt-mixing a hydrophilizing agent and a polyolefin, then mixed and melted with a polyolefin chip, and an inorganic substance such as magnesium stearate is added to the hydrophilizing agent to form a pellet. Examples include a method of chip-to-chip blending, and a method of directly melt-adding a hydrophilic agent in the process of melt-extruding a polyolefin.

The ratio of the core component to the sheath component in the composite continuous fiber of the present invention is in the range of 80:20 to 20:80, preferably 60:40 to 40:60, and the core is substantially circular or slightly round. And the core may or may not be eccentric in the cross section of the fiber.

The fineness of the composite filament is usually 0.5 to 5
de, preferably in the range of 1 to 3 de, and a nonwoven fabric is formed from the core-sheath type composite continuous fiber by, for example, a spunbonding method known per se.

In the nonwoven fabric of the present invention, it is necessary that the core-sheath composite long fiber having the aromatic polyester as the core and the polyolefin as the sheath is partially heat-welded, and the sheath components are joined to each other by heat fusion. is there. If the heat pressing is insufficient, the strength of the nonwoven fabric is reduced, and the strength of the laminate with a papermaking layer or the like is also insufficient, which is not preferable. The compression area ratio is preferably 5 to 15%, particularly preferably 8 to 12%.
%. An embossing roll is usually used for the partial thermocompression bonding, and its temperature is preferably set in a range from the melting point of the polyolefin sheath component to a temperature higher by 5 ° C. than the melting point. As described above, the nonwoven fabric of the present invention preferably employs a condition having a relatively low pressure bonding area ratio. However, when the pressure bonding temperature is lower than the above range, the surface of the nonwoven fabric is fluffed, and the adhesion when laminating with a papermaking layer or the like is preferred. Prone to worse. On the other hand, if the temperature of the embossing roll is too high, the texture of the obtained nonwoven fabric tends to be hard, and the softness tends to increase.

Further, the nonwoven fabric of the present invention has a softness in the longitudinal direction of the nonwoven fabric measured by a 45 ° cantilever method of 50 mm or less, preferably 20 to 45 mm, particularly preferably 25 to 45 mm.
It is important that it is 40 mm. Here, the nonwoven fabric longitudinal direction is the running direction of the nonwoven fabric in the long-fiber nonwoven fabric manufacturing process, and the width direction perpendicular to this is the horizontal direction. If the softness is greater than 50 mm, it is not preferable because, when the nonwoven fabric is laminated with the papermaking layer and then creped, partial peeling is likely to occur between the layers. The lower the softness of the nonwoven fabric, the better the ability to follow the creping process.However, to lower the softness of the nonwoven fabric, reduce the basis weight of the nonwoven fabric or lower the temperature of partial thermocompression bonding during the nonwoven fabric manufacturing process. Or, it is necessary to take a method such as reducing the pressure bonding area, all of these measures cause a decrease in the strength of the nonwoven fabric, and thus the strength of the laminate with the papermaking layer and the like is reduced, so that the rigidity is 20 mm or more, Preferably, it is more than 25 mm.

The nonwoven fabric of the present invention must have an area shrinkage at 120 ° C. of 3% or less. If the area shrinkage exceeds 3%, curling is likely to occur when forming a laminate with a papermaking layer or the like, which is not preferable. Further, the shrinkage in the lateral direction of the nonwoven fabric is preferably 0.5% or less.

The basis weight of the nonwoven fabric of the present invention is 10 to 30 g /
m ² , preferably in the range of 12 to 25 g / m ² is suitable. If the basis weight is smaller than this range, the strength of the nonwoven fabric will be insufficient, while if the basis weight exceeds this range, the hand tends to be hard.

The nonwoven fabric of the present invention described above can be obtained, for example, as follows. That is, a core-sheath composite long fiber having an aromatic polyester as a core component and a polyolefin as a sheath component is melt-spun, pulled by air soccer, opened, collected on a moving net, and the web is collected. Form. At this time, it is important to optimize the spinning and drawing conditions so that the degree of orientation of the aromatic polyester as the core component is within an appropriate range for the reasons described below. For example, when the aromatic polyester is polyethylene terephthalate, it is important that the birefringence (ΔN) of the core be in the range of 0.05 to 0.08. The spinning speed (drawing speed) for obtaining such a degree of orientation is 3500 to 4500 m / min. The obtained web is partially joined by thermocompression bonding with a heated embossing roll. Prior to this, it is important that the web is shrunk by heat treatment in a hot air atmosphere or the like. As a simple method, a method in which hot air is blown onto the web from above or below the net when the web is transported on the conveyor net is simple.
It is preferable that the web is temporarily fixed in advance with a hot roll having a groove at 70 to 100 ° C. so that the web is not disturbed when hot air is blown on the web. However, if the force of the temporary fixing is too large, the shrinkage treatment becomes insufficient, so that the contact pressure is desirably 5 kg / cm or less as a linear pressure. The temperature of the hot air is appropriately set according to the web transport speed and the nonwoven fabric weight.
A range from 150 to 180 ° C is suitable.

Next, the degree of orientation of the core component and the heat shrinkage treatment will be described in detail. In order to reduce the heat shrinkage of the nonwoven fabric, heat treatment is required in the process of manufacturing the nonwoven fabric.However, since the nonwoven fabric of the present invention is composed of a core-sheath composite long fiber in which the sheath component is a polyolefin having a low melting point, Heat treatment cannot be performed to the extent that the sheath component is melted. Therefore, when the sheath component is, for example, polyethylene, the effective temperature for the fiber is at most about 100 to 130 ° C., and when the orientation degree of the aromatic polyester as the core component is too high, heat setting at such a low temperature is not possible. It becomes insufficient and the shrinkage of the nonwoven fabric cannot be sufficiently reduced. When the degree of orientation of the aromatic polyester is too low, the heat setting property is good, but the shrinkage of the fiber is large and the fiber after shrinkage is hard, so that the feeling of the nonwoven fabric is hard. To suppress the heat shrinkage while maintaining the softness of the nonwoven fabric, when the core is polyethylene terephthalate as described above, the birefringence ΔN is 0.05
The range of -0.08 is suitable. The nonwoven fabric thus obtained has an area shrinkage at 120 ° C. of 3% or less, and is suitable for forming a laminate with a papermaking layer or the like.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each evaluation item in an Example followed the following measuring method.

<Thermal and lateral thermal shrinkage of the nonwoven fabric> A sample of 25 cm x 25 cm was sampled from the nonwoven fabric,
According to the method of JIS L 1042, a mark indicating the length of 20 cm is provided at each of three places in the vertical and horizontal directions. This sample is heat-treated at 120 ° C. for 3 minutes in a thermostatic drier and cooled to room temperature, and then the lengths of three points, which are marked in advance, vertically and horizontally, are measured. The contraction rate is calculated by the following formula in each of the vertical and horizontal directions. Shrinkage (%) = (L ₀ −L ₁ ) / L ₀ × 100 where L ₀ is the total length (mm) of the three lines before the vertical or horizontal heat treatment, and L ₁ is after the vertical or horizontal heat treatment. Represents the total length (mm) of the three lines.

<Area shrinkage of nonwoven fabric> Measured by the same method as the heat shrinkage in the vertical and horizontal directions, and calculated by the following equation. Area shrinkage (%) = (S ₀ −S ₁ ) / S ₀ × 100 where S ₀ is the average length in the vertical direction (mm) before heat treatment × the average value in the horizontal direction (mm) before treatment, S ₁ represents the average length in the vertical direction after heat treatment (mm) × the average value in the horizontal direction after treatment (mm).

<Nonwoven fabric longitudinal rigidity> JIS L10
It is measured by a 45-degree cantilever method specified in 96.

<Curl of laminated nonwoven fabric> Visual judgment by 10 panelists. A 1 mx 1 m laminate sample is placed on a horizontal table, and the presence or absence of curling of the nonwoven fabric is determined. 10
When at least 8 of the persons recognized that there was curl, the result was ×, when at least eight of the persons recognized that there was no curl, the result was そ れ.
Displayed.

<Delamination of Laminate> A 1 m × 1 m laminate sample was examined, and a sample having partial delamination was indicated by x, and a sample having no delamination was indicated by ○. In addition,
The abbreviation MFR in the examples means the melt flow rate and was measured by the method described in JIS K6760.

Example 1 As a core component, polyethylene terephthalate (intrinsic viscosity = 0.6) was melted at 290 ° C. High-density polyethylene (MFR)
= 20) and melted at 240 ° C. Each of the polymers in the molten state was guided to a spinning apparatus, and a spinning temperature of 280 ° C. was obtained from a spinning head having 20 core-sheath composite spinnerets having 100 holes.
Was discharged. After discharging, while cooling by cooling air, 4000 m by 20 ejectors arranged under the base
/ Minute at the speed of opening. The opened yarn is
After being collected on a moving net conveyer to form a web, it was temporarily fixed with a 90 ° C. grooved heating roll. One more
After passing through a hot air atmosphere at 60 ° C. for 1 second, the web was thermocompression-bonded with an emboss calender at a temperature of 135 ° C. and a compression area ratio of 11% to obtain a long-fiber nonwoven fabric. The fiber constituting the nonwoven fabric has a thickness of 1.8 denier and a core / sheath ratio of 60.
/ 40. The basis weight of the nonwoven fabric was adjusted to 15 g / m ² (Example 1-1) and 20 g / m ² by adjusting the net conveyor speed.
² (Example 1-2) and 25 g / m ² (Example 1-3).

Example 2 A high-density polyethylene (MFR) containing 2.0% by weight of a hydrophilizing agent consisting of 80% by weight of an alkylsulfonic acid sodium salt having an average carbon number of 15 and 20% by weight of stearyl monoethanolamide = 2
The basis weight was set to 2 by the same method as in Example 1 except that 0) was used as a sheath.
A non-woven fabric of 0 g / m ² was obtained.

Example 3 A hydrophilizing agent consisting of 90% by weight of an alkylsulfonic acid sodium salt having an average carbon number of 15 and 10% by weight of ethylenebisstearylamide was used.
High-density polyethylene containing 0% by weight (MFR = 20)
20 g of basis weight in the same manner as in Example 1 except that
/ M ² was obtained.

Comparative Example 1 Polyethylene terephthalate (intrinsic viscosity = 0.6) was melted at 290 ° C. as a core component. High-density polyethylene (MFR)
= 20) and melted at 240 ° C. Each of the polymers in the molten state was guided to a spinning apparatus, and a spinning temperature of 280 ° C. was obtained from a spinning head having 20 core-sheath composite spinnerets having 100 holes.
Was discharged. After discharging, while cooling with cooling air, 5000m by 20 ejectors arranged under the base
/ Minute at the speed of opening. The opened yarn is
After being collected on a moving net conveyor and formed into a web, it was temporarily fixed with a 90 ° C. grooved heating roll. Further, the web was subjected to thermocompression bonding using an emboss calender having a compression area of 15% and a temperature of 120 ° C. without heat treatment in a hot air atmosphere to obtain a long-fiber nonwoven fabric. The thickness of the fibers constituting the nonwoven fabric was 3.0 denier, and the core / sheath ratio was 60/40. The basis weight of the nonwoven fabric is adjusted by adjusting the net conveyor speed.
g / m ² (Comparative Example 1-1), 20 g / m ² (Comparative Example 1-
The level was set to 2).

Comparative Example ² A nonwoven fabric having a basis weight of 20 g / m ² was obtained in the same manner as in Example 1 except that the take-up speed by an ejector was 5000 m / min. The composite fiber constituting the nonwoven fabric was 1.5 denier.

[Comparative Example 3] Crimping area ratio 25%, temperature 13
A long-fiber nonwoven fabric was obtained in the same manner as in Example 2 except that an embossed calender at 0 ° C. was used. Nonwoven fabric weight is 20
g / m ² .

The properties of the long-fiber nonwoven fabrics of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1. In addition, a papermaking layer composed of 70% by weight of wood pulp, 30% by weight of short fibers having a denier of 2 denier and a fiber length of 5 mm, composed of core polypropylene / sheath polyethylene, and the above-mentioned long-fiber nonwoven fabric are laminated in the papermaking process. After drying with a Yankee dryer at 140 ° C., 5% creping was performed, and the curl and delamination of the obtained laminate were examined. Table 2 shows the results.
Shown in

[0035]

[Table 1]

[0036]

[Table 2]

As is evident from Tables 1 and 2, long-fiber nonwoven fabrics having a high degree of softness and softness are exfoliated when subjected to creping after being formed into a laminate with a papermaking layer, and have a function as a laminate. Does not work. When the long-fiber nonwoven fabric has a large heat shrinkage, curling occurs when the laminate is formed with the papermaking layer. Such a laminate not only has poor processing characteristics when laminating a polyethylene film or the like later, but also significantly impairs the appearance of the obtained product.

[0038]

The nonwoven fabric of the present invention can be maintained in a good laminated state even if it is laminated with, for example, wet papermaking and creped, so that it is extremely useful for sanitary materials, packaging materials, surgical sheets and the like. is there.

Claims (4)

[Claims] 1. A non-woven fabric composed of a core-sheath type composite continuous fiber having an aromatic polyester as a core component and a polyolefin as a sheath component, wherein the non-woven fabric is subjected to thermocompression bonding so that the sheath component is partially joined to each other. A nonwoven fabric, characterized in that the nonwoven fabric has a longitudinal softness of 50 mm or less and an area shrinkage at 120 ° C. of 3% or less. 2. A polyolefin containing 0.1% of a hydrophilizing agent.
The nonwoven fabric according to claim 1, which is contained in an amount of from 5 to 5% by weight. 3. The nonwoven fabric according to claim 1, wherein the shrinkage in the transverse direction at 120 ° C. of the nonwoven fabric is 0.5% or less. 4. The nonwoven fabric according to claim 1, wherein the aromatic polyester is polyethylene terephthalate, and the polyolefin is polyethylene.