JPS6392722A - Heat-weldable fiber and nonwoven cloth made thereof - Google Patents

Abstract

PURPOSE:To provide a heat-weldable fiber consisting of a composite fiber produced by covering polyethylene terephthalate with a specific ethylene-octene-1 copolymer, having excellent spinnability and suitable for the production of a nonwoven cloth for disposable diaper or sanitary napkin. CONSTITUTION:The objective heat-weldable fiber has a single filament fineness of <=8 denier and composed of a polyethylene terephthalate covered with a straight-chain low-density copolymer containing 1-15wt% octene-1 and having a density of 0.90-0.940g/cm<3>, a melt index of 5-45g/10min measured in accordance with ASTM D-1238(E) and a heat of fusion of >=25cal/g measured by DSC.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a composite thermal adhesive fiber and a nonwoven fabric thereof.

(Prior Art) In the production of nonwoven fabrics, methods for adhering fibers to each other include a method of entangling fibers such as a needle punch method, and a method of using various adhesives as a binder. Nonwoven fabrics such as disposable diapers and covering paper for sanitary absorbent materials, for which demand has been increasing rapidly in recent years, require properties such as a soft texture that feels good on the skin, low basis weight, and high tensile strength. Ru. In order to satisfy these requirements as much as possible, a nonwoven fabric production method mainly using a binder method has been adopted. As the binder method, the method of attaching an adhesive solution to the web has mainly been used, but there are problems such as the need for energy to remove the solvent of the adhesive solution and the poor working environment. In order to solve these problems, a method has been used in which fibers with a melting point lower than those of the fibers constituting the web are mixed into the web as a binder, the web is formed, and the fibers are bonded together by heat treatment.

Composite fibers containing fiber-forming polymers with different melting points as composite components have also come to be used as binders for nonwoven fabrics that are strong and have good texture. Regarding this, the special public
It is publicly known in the publication No.-10583.

(Problems to be Solved by the Invention) In recent years, nonwoven fabrics have been required to have strong properties despite having a low basis weight as described above, and to have a texture that is soft to the touch. Composite heat-adhesive fibers are ideal for meeting these requirements.The low melting point components of conventionally used composite heat-adhesive fibers are generally For polyethylene, medium-density or high-density polyethylene or linear low-density polyethylene (hereinafter referred to as LLDPE) is used.However, composite thermal adhesive fibers containing medium-density or high-density polyethylene as a low melting point component The disadvantage is that the nonwoven fabric obtained using this method is hard and does not have a good feel.

In addition, nonwoven fabrics using composite heat-adhesive fibers containing commercially available LLDPE, which is obtained by copolymerizing α-olefins having 4 to 8 carbon atoms, as a low melting point component can be expected to have a soft texture, but the spinning speed There is a problem in that it is difficult to increase the yarn thickness and it is not possible to produce fine denier yarn with high productivity.

The present invention has good performance of fibers and nonwovens.

Another object of the present invention is to provide an ideal thermal bonding fiber with unprecedented good spinnability and a nonwoven fabric made of the thermal bonding fiber.

(Means and effects for solving the problems) The present inventor has arrived at the present invention as a result of intensive research aimed at improving the above-mentioned problems of conventional LLDPE.

That is, the present invention is a copolymer of ethylene and octene-1, which contains substantially 1 to 15% by weight of octene-1, has a density of 0.900 to 0.940 g/ctA, and has a melt index value of ASTM D- LLDPE whose heat of fusion is in the range of 5 to 45 g/10 minutes as measured by the method of 1238(E) and is 25 cal/g or more as measured by DSC.
but.

The gist of this invention is a nonwoven fabric made of thermal adhesive fibers and nuclear thermal adhesive fibers, which has a cross-sectional shape coated with polyethylene terephthalate (hereinafter referred to as PET) and has a single filament fineness of 8 denier or less.

The LLDPE may contain up to 15% by weight of the weight of octene-1 of other α-olefins. In addition, the LLDP
A moisture absorbent, lubricant, pigment, dye, stabilizer, flame retardant, etc. may be added to E.

The PET used in the present invention has an intrinsic viscosity (hereinafter referred to as [η]) measured in a mixed solvent of phenol:tetrachloroethane=1:1 at 20°C in the range of 0°50 to 1.20. preferable. If [η] is less than 0.50, fibers with high strength cannot be obtained.

When [η] exceeds 1.20, spinnability is poor. Note that pigments, stabilizers, lubricants, etc. may be added to the PET.

The heat-adhesive fiber in the present invention is a fiber having a cross-sectional shape in which LLDPE coats PET, and the LLDPE is coated with PET.
It is preferable that PET be composed of 80-80% by weight and 80-20% by weight. If LLDPE is less than 20% by weight,
Although the strength of the fibers can be increased, the adhesive strength becomes weaker and a desirable texture cannot be obtained. On the other hand, when LLDPE exceeds 80% by weight, the adhesion of the fibers becomes strong and the texture is good, but the strength becomes low, which is not preferable.

The fiber in the present invention refers to a coated fiber having a single filament fineness of 8 denier or less. In other words, the thermal bonding fiber of the present invention is used for nonwoven fabrics, fabrics, threads, cords, etc., and is particularly suitable for nonwoven fabrics that require softness. It is not intended for fibers exceeding 8 denier because it cannot be obtained.

In the present invention, if the content of octene-1 exceeds 15% by weight, there will be a limit to obtaining fine denier fibers;
If the amount is less than % by weight, the resulting fibers will become hard and have a poor feel.

In the present invention, if the density of LLDPE exceeds 0.940, it is not preferable because the weight of the fiber cannot be reduced. Moreover, when the density of LLDPE is less than 0.900, the strength of the obtained fiber becomes low.

Melt index value as per ASTM D-1238(E)
The reason for limiting LLDPE to 5 to 45 g/10 min measured by the method is that if LLDPE exceeding this range is used, it may be difficult to select spinning conditions appropriately, or the strength of the resulting fiber will not be high. It is from. In other words, LLDPE having a melt index value of less than 5 g/10 minutes has poor spinnability and cannot increase the spinning speed. Further, LLDPE having a melt index value exceeding 45 g/10 minutes is not preferable because the strength of the fiber is low.

LLDPE with a heat of fusion of less than 25 cal/g has poor spinnability, although the reason for this is currently unknown. L
LDPET: When spinning continuous filaments coated with PET, use LDPE with a heat of fusion of less than 25 cal/g.
When LLDPE is used, the spinning speed will not be high, but LLDPE with a heat of fusion of 25 cal/g or more can be spun at a high spinning speed, which has the advantage of increasing productivity and producing fine denier fibers. be.

In the present invention, the heat of fusion is determined by Perkin Elma (Perkin Elma).
- Eiller) D S C-2G was used, the sample collection amount was approximately 5 cm, and the scan rate was 20 cm.
．． It is determined from a DSC curve obtained by raising the temperature from room temperature according to the equipment manual under the conditions of 0° C./min.

The thermally adhesive fiber of the present invention can be produced using a conventionally known composite melt spinning apparatus. Spinning temperature is LLDPE
O side is 180~270℃, PET side is 280~295℃
It is ℃. The heat-adhesive fiber of the present invention is produced by taking continuous filaments obtained by melt spinning at a speed of 1500 m/min or more, and heating the undrawn yarn to around 100°C and drawing it several times to make a filament, or if necessary, stretching it. It is obtained by crimping and then cutting to an appropriate length to make staples.

The heat-adhesive fiber obtained by the present invention has a core made of PET but a sheath made of LLDPE, so the fibers can be easily heat-bonded without using an adhesive during the manufacturing process of nonwoven fabric, resulting in high strength. Become.

Since the polyethylene in the sheath comes into contact with the skin, the nonwoven fabric has a very soft texture.

The nonwoven fabric of the present invention is made by conventional wet papermaking methods and carding methods. In that case, the blend of fibers in the nonwoven fabric may consist of 100% of the thermal adhesive fiber of the present invention, and may also include polyester, polyamide, polypropylene,
The thermoadhesive fiber of the present invention acts as a binder in polyethylene, other synthetic fibers, natural fibers such as cotton and wool, and nonwoven fabrics such as rayon. In that case, 15% of the heat bonding fiber of the present invention is added to act as a binder.
It is necessary to include the above.

When the nonwoven fabric of the heat-adhesive fibers of the present invention is produced by a wet papermaking method, the fibers have a fiber length of about 5 mm, and it is preferable that the fibers have less crimp and are straight. A suitable fiber concentration in the slurry is 1-2%. Additives such as adhesives such as polyacrylamide are sometimes added to the slurry liquid.

In the carding method, the thermally bonded fiber of the present invention must have a fiber length of approximately 51 mm and must be crimped. Naturally, it is also necessary that the fibers be coated with an oil suitable for carding.

In both the wet papermaking method and the carding method, heat treatment must be performed using a calendar, hot plate, or chamber in order to thermally fuse the heat-adhesive fibers of the present invention.

Temperature control at this time is important, and the set temperature and set time (speed) differ depending on the equipment used. However, the permissible range of the set temperature must be controlled within ±3°C.

(Example) The present invention will be specifically described below with reference to Examples.

The method of measuring the tensile strength, compression stiffness (softness), and basis weight of the short fiber nonwoven fabrics shown in the examples is shown below.

■Tensile strength JIS L-1096 strip method, medium 30
m1. The maximum tensile strength of a test piece with a length of 100 dragons was measured.

■Compression bending resistance (softness) A test piece of 5QmmX Loolm was taken and this test piece was made into a cylindrical shape with a height of 50m+* and a circumference of 100mm.

A cylindrical test piece was crushed on a flat plate type load cell, and the maximum load at that time was measured.

■Eyes (size) According to JIS P-8142.

Example 1 Contains 5% by weight of octene-1 and has a density of 0.937g/
d, melt index value is ASTM D-1238 (
The sheath component is LLDPE, which has a heat of fusion of 25 g/10 minutes as measured by method E) and 28 cal/g as measured by DSC, and is heated at 20°C in a mixed solvent of phenol:tetrachloroethane = 1:1. Intrinsic viscosity obtained by measurement [η)
= 0.70 PET as the core component, using a composite nozzle with 200 holes, LLDPE melting temperature 250 ° C., PET
Melting temperature 290℃, single hole discharge rate 2.081 minutes, LLD
A composite of PE and PET was melt-extruded at a weight ratio of 50:50, and a multifilament was obtained.

As Comparative Example 1, 5% by weight of octene-1 was contained.

Density is 0.937 g/cri, melt index value is 25 as measured by ASTM D-1238 (P:) method.
g/10 minutes.

Spinning was performed in the same manner as in Example 1 using LLDPE having a heat of fusion of 20 cal/H as measured by DSC.

When LLDPE of Example 1 was used, Comparative Example 1(l)
Compared to when using LLDPE, it was possible to increase the spinning speed and wind up the undrawn yarn.

The spinning speed of Example 1 and Comparative Example 1 was 2000 m, respectively.
/min and 960 m/min. Further, the obtained composite undrawn yarn was heated to 100°C and stretched.5. The drawn yarn was crimped in a stuffing box and then cut into fibers with a length of 51 mm to obtain a stable product. In Example 1, a single yarn fineness of 2.6 denier was obtained at a drawing ratio of 3.5 times, whereas in the undrawn yarn of Comparative Example 1, when the drawing ratio was increased to make the single yarn fineness finer, the composite component Peeling occurred during the drawing process, and the drawing ratio was limited to 4.2 times, and the minimum single yarn fineness reached was 4.5 denier. Table 1 shows the measurement results of the physical properties of the staples of Example 1 and Comparative Example 1.

Example 2 The stable single yarn fineness of 2.6 denier obtained in Example 1 was fed to a carding machine to form a web with a basis weight of Log/rd, and then heated at 145°C for 15 seconds using a hot air suction heat treatment machine. It was processed to make a nonwoven fabric. The performance of the obtained nonwoven fabric was excellent, and it was a very good nonwoven fabric with a soft texture. The basis weight of the nonwoven fabric is 10.0g/m,
Tensile strength is 1.0kg/3cm, compression stiffness is 12.0
It was g.

Example 3 40% by weight of the staple with a single yarn fineness of 2.6 denier obtained in Example 1, PET staple (3, Od.

Cut length 51mm, strength 4.5g/d, elongation 40.0%
.

Crimping rate: 20 pieces/25m, i ¥1 shrinkage rate: 12.0% 2 Elastic crimp rate: 70, θ%, residual crimp rate: 12. O%) 60% by weight
Mix it.

It was fed to a carding machine, turned into a web with a basis weight of 10 g/rrr, and then heated at 145° C. for 15 seconds using a hot air suction type heat treatment machine to obtain a nonwoven fabric. The obtained nonwoven fabric had a very good soft texture. The basis weight of the nonwoven fabric is 10.0g/rd, and the tensile strength is 0.50kg/rd.
3 cm, and compression stiffness was 5.0 g.

Example 4 Contains 5% by weight of octene-1 and has a density of 0.937g/
d, D-12 with melt index value ASTM
LLDP with a heat of fusion of 25 g/10 minutes as measured by the method of 38(E) and 28 cal/g as measured by DSC.
E is the sheath component, phenol: tetrachloroethane = 1
: The core component was PET with an intrinsic viscosity [η) of 0.70 measured at 20°C in a mixed solvent of 1, and the number of pores was 200.
Using a composite nozzle, the melting temperature of LLDPE was 250℃,
PET melting temperature 290℃, single hole discharge rate 1.6g/min,
Composite ratio of LLDPE and PET is 50:50 by weight
Melt extrusion at a speed of 2000 m/min.

The multifilament was heated to 100° C. to a stretching ratio of 3.5 times, and the multifilament was taken out. = The single yarn fineness of the multifilament is 2.1 denier, the strength is 3.6 g/d, and the elongation is 5
It was 2.4%. 5m of Iris multifilament in wet condition using EC cutter without crimping
The fibers were cut into lengths of m and immediately made into a slurry with a fiber concentration of 1%. This was made into paper using a circular wire paper machine and heat treated for 5 seconds in a Yankee dryer at 140°C to complete heat fusion with polyethylene.

The finished nonwoven fabric had a basis weight of 20.3 g/rd, tensile strength of 1.10 kg/3 cm, and compression stiffness of 7.0 g. The nonwoven fabric had an undeniably hard feel compared to the dry method, but on the contrary, it had excellent uniformity in appearance and was soft with a slimy feel.

(Effects of the Invention) The heat-adhesive fibers obtained in the present invention can be made into nonwoven fabrics with excellent softness and texture, and are especially suitable for uses such as the lining of disposable diapers. Furthermore, even in fields that do not utilize thermal adhesive properties, polyethylene has excellent resistance to radiation, so it can be used in medical clothing and the like because it can withstand washing using radiation.

Claims (2)

[Claims] (1) A copolymer of ethylene and octene-1, containing substantially 1 to 15% by weight of octene-1 and having a density of 0.
900-0.940g/cm^3, melt index value is 5 when measured by ASTM D-1238(E) method.
~45g/10min, and the heat of fusion is 2 as measured by DSC.
Linear low density polyethylene having a content of 5 cal/g or more,
1. A thermally adhesive fiber having a cross-sectional shape coated with polyethylene terephthalate and having a single filament fineness of 8 denier or less. (2) A copolymer of ethylene and octene-1, containing substantially 1 to 15% by weight of octene-1 and having a density of 0.
900-0.940g/cm^3, melt index value is 5 when measured by ASTM D-1238(E) method.
~45g/10min, and the heat of fusion is 2 as measured by DSC.
Linear low density polyethylene having a content of 5 cal/g or more,
A nonwoven fabric characterized by being made of heat-adhesive fibers having a cross-sectional shape coated with polyethylene terephthalate and having a single filament fineness of 8 denier or less.