JPH01111016A - Polyethylene composite fiber and production thereof - Google Patents

Abstract

PURPOSE:To obtain the above fiber which soft feel and high strength to be used for e.g. disposable diapers, by conjugate spinning with a blend of an ethylene copolymer of specific physical properties and crystalline polypropylene as the sheath component and polyethylene terephthalate as the core component under specified conditions. CONSTITUTION:(A) As the sheath component, a blend of (i) 99-50wt.% of a linear low-density polyethylene, a copolymer constituted of ethylene and octene-1, with the octene-1 content of 1-15wt.%, density of 0.900-0.940g/cm<3>, melt index determined by the procedure: ASTM D-1238(E) of 25-100g/10min, and heat of fusion of >=25cal/g and (ii) 1-50wt.% of a crystalline polypropylene with a melt flow rate determined by the procedure: ASTM D-1238(L) of <=20g/10min and (B) as the core component, polyethylene terephthalate are subjected to melt extrusion at spinning temperatures of 210-250 deg.C and 275-295 deg.C for the component A and the component B, respectively, followed by take-up at a speed of >=4,500m/min, thus obtaining the objective conjugate fiber.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a polyethylene composite fiber and a method for producing the same, and more specifically, it relates to the quality of yarn produced by a two-step method of spinning and drawing. The present invention relates to highly oriented undrawn fibers obtained by high-speed spinning of polyethylene composite fibers having performance similar to that of polyethylene composite fibers, and a method for producing the same.

(Prior art) After coating a part or all of the surface of a composite fiber with a low melting point component to give the fiber adhesiveness and forming a web, the adhesiveness is made apparent using a heating means, A method for producing composite fibers for nonwoven fabrics in which intertwined fibers are bonded is already known from Japanese Patent Publication No. 42-21318 and Japanese Patent Publication No. 43-1776. In addition, regarding non-woven fabrics made of composite fibers with good fiber performance and soft texture,
This method is known from Japanese Patent No. 10583. Note that polyethylene is widely used as a constituent polymer of these thermally adhesive composite fibers.

Low-density polyethylene is a type of polyethylene.

High-density polyethylene, LLDPE obtained by copolymerizing ethylene and octene-1, has already been used.

(Problems to be Solved by the Invention) However, in the case of low-density polyethylene (LDPR) and high-density polyethylene (IIDPE), the resulting nonwoven fabric has a hard texture and has the disadvantage that a soft feel cannot be obtained.

In order to compensate for this drawback, recently, Japanese Patent Application Laid-Open No. 60-20901
Linear low density polyethylene (hereinafter referred to as LLDPE) obtained by copolymerizing ethylene and octene-1 has been proposed as disclosed in Publication No. It has become widely used as a nonwoven fabric binder due to its soft texture and low melting point. The obtained nonwoven fabric had a soft texture, low basis weight, and high strength, but it was difficult to obtain fine denier yarn from the productivity point of view because it was difficult to increase the spinning speed. There were some difficult drawbacks.

An object of the present invention is to provide a composite fiber that has high-speed spinnability of 4,500 m/minute and can be manufactured into products at once without going through a drawing process.

(Means and effects for solving the problems) The present inventors have arrived at the present invention as a result of intensive research to improve the above-mentioned problems of the conventional LLDPH.

That is, 9 the present invention is a linear low-density copolymer of ethylene and octene-1, with an octene-1 content of 1 to 15
Weight%, density is 0.900-0.940g/cd, melt index is 25-100g/10 min as measured by STM Rho 1238 (E) method, heat of fusion is 25ca
Linear low density polyethylene consisting of l/g or more 99-50
Weight % and melt flow rate as per ASTM D-1238
A composite comprising a mixed polymer (abbreviated as Polymer A) consisting of 1 to 50% by weight of crystalline polypropylene smaller than 20g/lO measured by method (L) as a sheath component and polyethylene terephthalate (abbreviated as Polymer B) as a core component. A sheath component is a polyethylene composite fiber characterized by being a highly oriented undrawn yarn and a polymer A.

When performing melt spinning using Polymer B as a core component, melt extrusion was performed at a spinning temperature of Polymer A of 210 to 250°C and a spinning temperature of Polymer B of 275 to 295°C.

The gist of this invention is a method for producing polyethylene composite fibers, which is characterized by winding up at a winding speed of 4,500 m/min or more.

In the present invention, LLDPH, which is a component of polymer A,
It is important that the content of octene-1 is between 1 and 15% by weight. When the content of octene-1 is less than 1% by weight, the resulting composite fiber becomes hard, and when made into a product such as a nonwoven fabric, the texture becomes poor. Also.

If the content of octene-1 exceeds 15% by weight, it will be difficult to spin the fiber and it will be difficult to obtain fibers with a fineness of 5 deniers or less.However, LDPE is particularly preferably a copolymer of ethylene and octene-1. but.

Other α-olefins such as butene-1, hexene-1, or a mixture of octene-1 and hexene-1 can also be used within the above-mentioned octene-1 content range.

Next, the density of LLDPH is 0.940g/c
If it exceeds d, the degree of crystallinity will increase and the texture of the obtained fiber will become hard (unfavorable).On the other hand, 0.900g/
If it is less than cd, it is difficult to obtain a high-performance fiber in terms of yarn quality performance.
940 g/cJ is preferred.

In the present invention, the above-mentioned LLDPE and polypropylene (hereinafter referred to as "polypropylene") are used.

It is called PP. ), but the flow characteristics of the blended state of both are particularly important for obtaining the composite fiber of the present invention at high speed, and the melt index (hereinafter referred to as MI value) of LLDPE is ASTMD- 1
238(E) and is required to be in the range of 25 to 100 g/10 minutes. MI value is 25g/10
If it is less than 1 minute, the deformation of the discharged yarn during melt spinning will not be smooth, and it will be susceptible to melt fracture, ballast effect, etc., and as a result, high-speed spinning will be difficult.

Furthermore, if the MI value exceeds 100 g/10 minutes, the viscosity will be too low and uneven fineness will occur in the warp direction, resulting in poor performance of the obtained fibers. Furthermore, if the melt viscosity with PP is too wide, the discharged yarn will break just below the spinneret, resulting in a serious drawback. Therefore, the MI of the above LLDPE
The required MI value is 25 to 100 g/10 minutes, and a more preferable MI value is 40 to 70 g/10 minutes.

The heat of fusion, which is a measure of the crystallinity of LLDPE, is 25c.
If it is less than al/g, the spinning properties are poor and high-speed spinning cannot be performed. Here, the heat of fusion was measured by the first-order method. Using a PerkinElmer product model 0SC-2C, sample 5+sg is taken and measured at a heating rate of 20° C./min, and the DSC curve obtained by raising the temperature from room temperature is determined according to the device manual.

Next, the PP to be blended with the LLDPE is isotactic polypropylene, and its melt flow rate (hereinafter referred to as MF value) conforms to ASTM D-12.
It is necessary that the amount is less than 20 g/10 minutes as measured by the method of 38(L). That is, if the MF value is 20 g/10 minutes or more, blending with LLDPE will not be smooth and a uniform structure will not be formed. This is because the polypropylene segments flow too much in the LLDPE component and are arranged linearly in the fiber axis direction, resulting in extremely high melt elasticity of the spun yarn, reducing yarn breakage during spinning. In order to achieve this, it is necessary to keep the spinning speed low.

Furthermore, the blend ratio of LLDPE and PP also affects the spinning properties. By adjusting the ratio of LLDPE and PP to 99-50% by weight and 1-50% by weight,
Blending of DPE and PP can be carried out smoothly, giving appropriate melt elasticity and improving silk-spinning properties compared to when LLDPE is used alone. When the amount of PPO in LLDPE is less than 1%, no improvement in silk-spinning properties is observed due to blending, and L
The spinning performance is the same as that of LDPE alone. On the other hand, if it exceeds 50% by weight, it becomes rich in PP, and it is difficult to improve the flow characteristics by blending, making it difficult to obtain thin fibers. Furthermore, when high-density polyethylene (HDPE) and low-density polyethylene (LIIPE) are substituted for the above LLDPE and blended with the above-mentioned polypropylene and their spinnability is examined, the spinability is inferior to that of LDPR at the above-mentioned blend ratio. . Regarding the blending mechanism of the present invention, inferring from the aspect of melt viscosity, polypropylene is located as an island component in the sea component of LLDPH with respect to the fiber cross section and axial direction, and it is the island component that affects the spinning property. If the size and melt viscosity of both components are too close,
The result is a fairly small island component.

Melt elasticity increases and has a negative impact on yarn reeling properties. Also.

If the melt viscosities of the two are too different, the island components will become too large, which will also have an adverse effect on the silk-spinning properties.

In addition, LLDPII! in Polymer A! Hygroscopic agents and lubricants to the extent that they do not inhibit spinnability of polypropylene or polypropylene.

Additives such as pigments, dyes, stabilizers, etc. may also be added.

Next, Polymer B as a core component constituting the composite fiber of the present invention
Polyethylene terephthalate has an intrinsic viscosity [η] of 0.5 to 1 when measured at 20°C in a mixed solvent of phenol:tetrachloroethane = 4:1 (volume ratio).
．． 20 is preferred.

When [η] is less than 0.50, fibers with high strength cannot be obtained (
If <, [η] exceeds 1.2, spinnability is poor. In addition.

Additives such as pigments, stabilizers, lubricants, etc. may be added to Polymer B, and the fiber has a cross-sectional shape in which Polymer A coats Polymer B, with 20 to 80% by weight of Polymer A,
It is preferable that Polymer B has a composition ratio of 80 to 20% by weight. If Polymer A is less than 20% by weight, the strength of the fiber will be high, but the adhesive force will be weak and a favorable texture will not be obtained. ,vice versa.

If the content of Polymer A exceeds 80% by weight, the adhesion of the fibers will be strong and the texture will be good, but the strength will be weak, which is not preferable.

The fibers used in the present invention are composite fibers with a single filament fineness of 5 deniers or less, and thick fibers with a single filament fineness of more than 5 denier are difficult to obtain (preferably). do not have.

The polyethylene composite fiber of the present invention can be spun using a conventionally known composite melt spinning apparatus.

In the case of polymer A as a sheath component, at the spinning temperature.

LLDPI! An intermediate spinning temperature of 210 to 250°C is required, more preferably 220 to 250°C.
The temperature is 240°C. If it is lower than 210°C, fluidity during spinning will be insufficient, while if it exceeds 250°C, the LLDPE component will decompose, which is not preferable. Next, in the case of polymer B as the core component, the temperature is required to be 275 to 295°C. If it is less than 275°C, the fluidity during spinning will be insufficient, and if it exceeds 295°C, decomposition tends to occur, so it is not preferable.

In the present invention, the spinning speed is limited to 4,500 m/min or more because, in high-speed spinning of polyethylene terephthalate, the single yarn fineness is 5 denier or less and the spinning speed is 4,500 a+/min due to the relationship between the spinning speed and hot water shrinkage rate. If it is less than that, the orientation of the undrawn yarn is not sufficient, and as a result.

Although the hot water shrinkage rate increases, when the spinning speed exceeds 4,500 m/min, the orientation of the undrawn yarn progresses, the hot water shrinkage rate decreases rapidly, and fibers with stable yarn properties are obtained. be. That is, Δn of the undrawn yarn is 70×10−
``If it is more than that, the hot water shrinkage rate will decrease.

This is the fiber of the present invention.

Next, the cross-sectional shape of the conjugate fiber of the present invention is not limited to a circle, but may be an irregular type, and may be selected depending on the purpose. Although fibers having a cross section with a core-sheath structure are preferable, the fibers may have a so-called multi-core structure instead of having only one core component. however.

In order to take advantage of LLDPE's characteristics of softness, low melting point, and function as a binder in composite fibers, it is necessary that polymer A consisting of LLDPIE and polypropylene be present in the surface layer of the fibers. To obtain nonwoven fabrics using fibers.

Filaments or tows are produced using a melt-spinning device for composite spinning, cut into short fibers, mixed with other fibers depending on the purpose, passed through a card machine to create a web, and then used with calender rolls to create a web with a melting point lower than the melting point of LLDPH. Nonwoven fabrics can be manufactured by thermocompression bonding at high temperatures. In addition, depending on the application, considering productivity, nonwoven fabrics made by the spunbond method are preferable, and the manufacturing method involves sucking and opening the fibers coming out of a nozzle with a high-speed suction gun, and colliding them against a moving conveyor-like wire mesh. A method can be adopted in which a web is formed and then subjected to compression heat treatment using an embossing roll. In addition, the fibers for nonwoven fabrics are cut into short fibers and dispersed in water.

The polyethylene composite fiber of the present invention can also be used by conventional papermaking methods.

The fibers of the present invention are made of continuous filaments obtained by melt spinning, and can be spun at an unprecedented high speed. Furthermore, the fiber obtained in the present invention is composed of Polyethylene terephthalate as a core component and Polymer A consisting of LLDPE and polypropylene as a sheath component, and is satisfactory in terms of both strength and texture. In addition, in the case of the composite fiber of the present invention (1), the strength is LLDPE, polypropylene alone, the core component is polyethylene terephthalate, and the sheath component is LLDPE.
It has the advantage of being higher in strength than composite fibers made of LDPE.

As mentioned above, the fibers of the present invention can be used alone, or mixed with polyester, polyamide, polypropylene, polyethylene and other synthetic fibers, natural fibers such as cotton and wool, rayon, etc. Can be used as a binder for thermally bonding between.

(Example) Hereinafter, a specific example of the present invention will be explained with reference to Examples.

Examples 1-2. Comparative Examples 1-2 Linear low density polyethylene (LLDPE) (octene-
15% by weight, density "0.935g/cd, MI
Value (melt index) 43g/10min, heat of fusion 36
cal/g) and isotactic polypropylene (PP)
(Density 0.905g/cd, MF value (melt flow rate) 15g/10min) Weight ratio 90:10
Polymer A blended in the proportion of is the sheath component, [η] = 0
．． Using a melt spinning device for composite spinning, using Polymer B consisting of polyethylene terephthalate No. 69 as a core component, spinning Polymer A at a ratio of core/sheath = 50:50 (weight ratio) at 230° C. and spinning Polymer B. Temperature 285℃,
Spinneret 0.4inφ×24 holes, discharge amount 2. A composite fiber was produced under the conditions of 1 min/hole and a spinning speed of 5800 m/min. (Example 1) Table 1 shows the yarn properties of the obtained fibers.

Table 1 Next, the core-sheath composite ratio of Example 1 was 2:1. Spinning speed 55
Polyethylene composite fibers were produced in the same manner as in Example 1 except that the speed was changed to 00 m/min.

The results are shown in Table 1.

Next, LLDPE, which is a component of polymer A in Example 1,
Composite fibers made of each single polymer were produced using polyethylene terephthalate (Polymer B) as a sheath component and a core component, respectively. A polyethylene composite fiber was produced using a spinning speed of 3600 m/min and all other conditions as in Example 1. The yarn quality performance results of the obtained composite fibers are shown in Table 1.

(Comparative Example 1) Next, the undrawn yarn obtained in Comparative Example 1 was stretched at a stretching temperature of 90°C, a hot plate temperature of 105°C, and a stretching ratio of 1.5 times to obtain a drawn yarn. Table 1 shows the yarn quality performance obtained.

(Comparative Example 2) As is clear from the table, the composite fiber of Example 1.2 of the present invention has good yarn quality performance comparable to drawn yarn simply by high-speed spinning without incorporating a drawing process. A composite fiber was obtained. On the other hand, in the case of the composite fiber of Comparative Example 1, the spinning speed did not increase, and in terms of yarn quality performance, the fiber had a high hot water shrinkage rate and high elongation. In the case of the drawn yarn of Comparative Example 2.

It was excellent in terms of yarn quality performance, but the number of steps increased.

It had the disadvantage of high cost due to low manufacturing speed.

(Effects of the Invention) The polyethylene composite fiber of the present invention has a soft texture and is excellent in strength, so it is ideal for the inner part of disposable diapers. Further, according to the method of the present invention, products can be manufactured all at once using a high-speed spinning method, and.

It is extremely economical due to its high production rate, and is also excellent in terms of yarn quality performance, so it is widely used in fields such as nonwoven fabrics, woven fabrics, and knitted fabrics that require thermal bonding.

Patent applicant: Unitika Co., Ltd.

Claims (4)

[Claims] (1) A linear low-density copolymer of ethylene and octene-1, with an octene-1 content of 1 to 15% by weight, a density of 0.900 to 0.940 g/cm^3, and a melt index of ASTM D- Linear low-density polyethylene with a heat of fusion of 25 to 100 g/10 minutes as measured by the method of 1238 (E) and 99 to 50% by weight of 25 cal/g or more and a melt flow rate of 25 to 100 g/10 minutes according to the method of ASTM D-1238 (L). It is a composite fiber whose sheath component is a mixed polymer (abbreviated as Polymer A) consisting of 1 to 50% by weight of crystalline polypropylene that is less than 20 g/10 min when measured at A polyethylene composite fiber characterized in that the fiber is a highly oriented undrawn yarn. (2) The polyethylene composite fiber according to claim 1, wherein the single fiber fineness of the composite fiber is 5 denier or less. (3) The polyethylene composite fiber according to claim 1, wherein the composite fiber has a composite ratio of polymer A and polymer B of 20 to 80% by weight: 80 to 20% by weight. (4) A linear low-density copolymer of ethylene and octene-1, with an octene-1 content of 1 to 15% by weight, a density of 0.900 to 0.940 g/cm^3, and a melt index of ASTM D- 1238 (E) method, it is 25 to 100 g/10 minutes, and the heat of fusion is 25 cal/10 minutes.
linear low-density polyethylene consisting of 99 to 50% by weight and a mel flow rate of ASTM D-1238 (L)
Melt spinning is performed using a mixed polymer (abbreviated as Polymer A) consisting of 1 to 50% by weight of crystalline polypropylene (abbreviated as Polymer A) as a sheath component and polyethylene terephthalate (abbreviated as Polymer B) as a core component as measured by the method of During this process, the spinning temperature of Polymer A was set at 210 to 250°C.
A method for producing polyethylene composite fibers, which comprises melt-extruding Polymer B at a spinning temperature of 275 to 295°C and winding it up at a take-off speed of 4500 m/min or more.