KR20010008911A - Polyolefin fiber and non-woven fabric, and preparation thereof - Google Patents

Abstract

PURPOSE: A polyolefin fiber for nonwoven fabric suitable for a high speed carding machine, capable of performing heat fusion at low temperatures and providing strength and softness after heat fusion and prepared from a polyolefin polymer containing a stabilizer and/or antioxidant, nonwoven fabrics and process for producing the same are provided, which have excellent workability and physical properties and make it possible to produce high quality nonwoven fabrics in high productivity. CONSTITUTION: The polyolefin fiber is obtained from polyolefin containing 0.03 to 2.0% by weight of a stabilizer and/or antioxidant and satisfies a melt index ratio of a polymer and fiber (Mlf/Mlp): 2.0 ≤ Mlf/Mlp ≤ 6.0 in which Mlp is 10 to 50 as a melt index of the polyolefin polymer and Mlf is more than 30 as a melt index of the polyolefin fiber wherein the polyolefin is isotactic polypropylene having a melt index of 10 to 50 and an isotactic index of 90 to 99%.

Description

Polyolefin fiber, nonwoven fabric and manufacturing method thereof {POLYOLEFIN FIBER AND NON-WOVEN FABRIC, AND PREPARATION THEREOF}

TECHNICAL FIELD The present invention relates to polyolefin fibers, and more particularly, to a polyolefin fiber, a nonwoven fabric, and a method of manufacturing the nonwoven fabric, which is suitable as a raw material for producing a nonwoven fabric, which is soft, has excellent strength, and provides excellent workability and physical properties during nonwoven fabric finishing.

In general, in preparing staple fibers from polyolefin polymers, a polymer is mixed with an amount of an additive or pigment and melt-extruded in a conventional commercial process to produce a fiber, and then the crimped fiber is melted and cut to a certain length. You will go through a series of processes.

A common process for preparing nonwoven fabrics with polyolefin staples is to prepare staples into a nonwoven web through a carding machine and thermally bond them.

In order to thermally bond the web, a pair of calendar rollers, a method of using ultrasonic waves, a method of using hot air, and the like are mainly used.

In particular, in the case of polypropylene fibers or staples, the fibers are arranged and entangled through an opening and carding process to form webs, which are thermally bonded by diamond or delta-shaped calender rolls. Non-woven fabrics made of non-woven fabrics that can be used for various industrial purposes, or by heating air in porous drums that reflux webs through carding processes by using hot air instead of calendar rolls. Is prepared.

Polypropylene nonwovens are used in disposable diapers, incontinence diapers, masks, sanitary nonwovens, medical nonwovens, and the like. Non-woven fabrics for this purpose do not require as much strength as woven fabrics, but require secondary processing and a degree of usability and, in the case of products directly touching the skin, should be soft and suitable for the safety of the skin.

The strength of the nonwoven fabric is different depending on the technology for producing the nonwoven fabric, and also depends on the physical properties of the fiber, which is a nonwoven fabric raw material.

Nonwovens producers are accelerating production speeds to improve productivity. As the speed of production increases, the fibers used in nonwovens also require better physical properties.

In order to meet this demand in the nonwovens industry, the inventors have invented a method capable of producing polyolefin fibers or staples suitable for them based on many years of research and development experience.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyolefin fiber for a nonwoven fabric which is suitable for a high speed carding machine and which is capable of heat fusion at low temperature and which provides excellent strength and softness after heat fusion.

Another object of the present invention is to provide a method for producing a polyolefin fiber for nonwoven fabric having the above characteristics.

It is also an object of the present invention to provide a nonwoven fabric made of polyolefin fibers for nonwovens of the above characteristics.

According to the present invention to achieve the above object is made from a polyolefin polymer containing a stabilizer and / or antioxidant of 0.03 to 2.0% by weight, characterized in that to satisfy the melt index change rate (MI _f / MI _p ) of the formula (1) Provided are non-woven polyolefin fibers:

2.0 ≤ MI _f / MI _p ≤ 6.0

Wherein MI _p is 10 to 50 as the melt index of the polyolefin polymer and MI _f is 30 or more as the melt index of the polyolefin fiber.

In addition, according to the present invention, 3 to 20% of the total molecular weight decomposition is carried out before spinning the polyolefin polymer containing 0.03 to 2.0% by weight of stabilizer and / or antioxidant and having a melt index (MI _p ) of 10 or more. The polyolefin fiber obtained by performing the remaining molecular weight decomposition of 97 to 80% has a melt index (MI _f ) of 30 or more but a melt index ratio (MI _f / MI _p ) of 2.0 to 6.0 or less. Provided are methods of making fibers.

According to the present invention, there is provided a polyolefin nonwoven fabric which is produced from the above-described polyolefin fibers and has a THERMAL BONDING INDEX (hereinafter abbreviated as 'TBI') of 2.0 or more.

Hereinafter, the present invention will be described in more detail.

In preparing the fibers or staples of the invention, the polyolefin polymer used for spinning contains from 0.03 to 2.0% by weight of stabilizer or antioxidant.

In addition, the melt index (MI _p ) of the polyolefin polymer is preferably 10 to 50, more preferably 10 to 25. The molecular weight distribution of the polyolefin polymer preferably has a molecular weight distribution in the range of 3 to 7, more preferably 3.5 to 5.4. If the MI _p is less than 10, productivity is reduced by increasing the detention pressure during spinning, and high heat is required during melt spinning, which increases energy consumption and is not suitable for nonwoven fabrics requiring soft properties due to increased rigidity of fibers. . Therefore, it is preferable to use a polyolefin having a MI _p of 10 or more, but it cannot be used indefinitely high. If the MI _p exceeds 50, the strength of the fiber is unsuitable for nonwoven fabrics, and there are many cases of incomplete cooling in the cooling process after spinning, and in this case, incomplete cooling causes fusion with adjacent fibers. Sometimes.

_F MI / MI when _p is very small polyolefin polymer and MI _f / _p MI to manufacture a very large polyolefin staple observe the physical properties of the polyolefin fibers or staples according to the difference of the molecular weight distribution properties differences were not observed.

However, when MI _f / MI _p is less than 2.0, the value of TBI decreases after fabrication of the nonwoven fabric, and the nonwoven fabric has a hashing property. In manufacturing nonwoven fabric, it is possible to improve the strength or improve the TBI value by increasing the temperature of calenderol or increasing the thermal bonding area, but the hash properties remain. In addition, if MI _f / MI _p is greater than 6.0, the molecular weight decreases so much that the strength of the fiber decreases, the cooling effect after spinning in the deterioration decreases, and fusion between fibers occurs. When the manufacturing process, the fiber is broken a lot of fibers in the carding, carding process is adversely affected the process. In addition, heat sensitive portions are eluted to the surface of the calenderol to be thermally bonded, and the calenderol surface is likely to be dirty. Preferably MI _f / MI _p is 2.0 to 5.0, more preferably 2.2 to 3.5.

In the case of two-stage spinning, it is divided into spinning process that spins at high speed and stretching process that collects and bundles these fibers and stretches them again and gives crimping. There is little difference between the MI of the primary fiber produced in spinning and the MI of the fiber after the stretching process. Only about 10% of the difference can be caused by the type and amount of emulsion to be attached to the fiber to give functionality to the fiber and the error between the measurers.

In the present invention, the polyolefin polymer may include various copolymers. For example, polyethylene, such as low density polyethylene, high density polyethylene and straight chain low density polyethylene, including polyethylene prepared by copolymerizing ethylene with one or more C ₃ -C ₁₂ alphaolefins can be included. Polyolefin polymers also include polypropylenes such as isotactic polypropylene, atactic polypropylene, syndiotactic polypropylene. Polypropylene is suitable as the polyolefin, and isotactic polypropylene having an isotactic index of 90 to 99% is particularly preferable among polypropylene.

Hereinafter, a method for producing a polypropylene yarn having the structural features as described above will be described. It is to be understood that the manufacturing method described below is one example for implementing the present invention, and the present invention is not limited thereto.

First, the polyolefin polymer containing 0.03 to 2.0% by weight of stabilizer and / or antioxidant as an additive is melted and extruded. To 5 to 10%. Molecular weight decomposition in the melt extrusion step can be achieved by adjusting the temperature of the extruder, the pressure in the conveying pipe of the molten polyolefin, the residence time. Decomposition of the molecular chain is a natural phenomenon because it is under high temperature and pressure in the melting and extrusion process. However, if the molecular weight decomposition degree is lower than 3%, the viscosity in the spinneret becomes very high, and the pressure of the spinner will rise, making the spinning process very unstable. In addition, productivity is lowered and fiber quality is severely varied. If it is larger than 20%, many molecular chains are decomposed and it is impossible to maintain intrinsic strength. Too much decomposition occurs in the spinning process, resulting in a decrease in viscosity, inadequate molecular chains in orientation, and inability to maintain adequate pressure to spin. Therefore, it becomes a cause of productivity fall.

Next, the cooling conditions after spinning are adjusted to perform molecular weight decomposition of the remainder (ie, 97 to 80%). The molecular weight decomposition in the cooling step is carried out by adjusting the temperature, atmosphere, cooling air temperature, speed and amount of the delayed cooling portion. The use of delayed cooling and cooling air is described in U.S. Pat. Described.

The present invention can be applied to both 1-step spinning and 2-step spinning, and is also applicable to the production of filaments of continuous fibers.

One-stage spinning is a method of producing staples by successive series of processes such as melting, spinning, stretching, crimping, heat setting, and cutting of raw materials, and two-stage spinning is melting, spinning, and cans in one step. It is a method of producing staples by drawing, crimping, heat setting and cutting in two stages.

An advantage of the method of producing staples in one-stage radiation of the two methods is that the productivity is high because the odd number of detention, which is a spinning equipment.

However, the single-stage spinning method has a limitation in speeding up the production speed because the equipment is connected in series. Therefore, the one-stage spinning method typically produces staples at low speeds in the range of 20 to 200 mpm.

In order to solve the shortcomings of the productivity limitations of the single-spinning method, the method of producing staples in two-stage spinning improves the spinning speed in the range of 500 to 3000 mpm to produce undrawn yarns whose orientation is not complete, which is the basic property of the fibers. .

The unstretched yarn has a low-strength and coarse shape because it has a shape as a fiber but is incomplete in orientation and not fully matured in crystallization. These undrawn yarns take the form of fibers in industrial and engineering aspects through the stretching process.

In order to process the undrawn yarn manufactured at high speed in the range of 500 to 3000 mpm at the same speed in the drawing process, that is, to produce in a single-stage spinning method, a very large and high speed facility is required.

In order to overcome this equipment imbalance, the two-stage spinning method draws and stretches dozens of bundles of spun fibers. In this case, the undrawn yarn is generally collected in a square can, and then 10 to 50 cans are collected again to form a very thick tow.

The work of collecting the cans to make a tow is called creeling.

The tow thus produced is stretched in one or two stages, and is imparted to a crimper consisting of a pair of upper and lower rolls to impart bulkiness and crimp to the stretched yarn to impart a variety of crimps.

In general, the thickness of the tow put into the crimper is preferably in the range of 50,000 to 100,000 denier / cm.

This two-stage spinning method improves productivity because the tow, which has collected dozens of unstretched yarns radiated in the stretching process, is collected again by several dozen bundles instead of slowing the stretching process.

Various additives, such as stabilizers, antioxidants, antacids, colorants, carboxylic acid metal salts, can be used for the polyolefin polymer.

In making fibers or staples in the present invention, additives such as stabilizers, antioxidants and the like are blended into the polymer in an amount of about 0.03 to 2.0% by weight. The present invention is not limited to the above examples, and additives described in European Patent No. 279,511 may be used, and various other methods are also possible.

The carboxylic acid metal salt may comprise at least one member selected from the group consisting of nickel salts of 2-ethylhexanoic acid, caprylic acid, decanoic acid and dodecanoic acid and 2-ethylhexanoate salts of Fe, Co, Ca and Ba. Can be.

In addition, the antacid and colorant may include a material such as calcium stearate used in the process for producing a polyolefin polymer material in a petrochemical plant.

In the production of nonwoven fabrics, the degree of machine direction and lateral arrangement of the fibers passing through the carding machine differs depending on the type of carding machine used and the machine arrangement. In other words, the machine direction strength and the transverse strength of nonwoven fabric are different according to the manufacturer of the carding machine. Even if the carding machine of the same manufacturer is used, there are differences in the properties due to the shape of the cloth, the material of the cloth and the presence or absence of random rolls. It can be seen that is generated. Nonwoven fabrics also vary in basis weight depending on the requirements of the post-processing.

The strength measurements of these nonwovens are simple and robust, and the units required vary uniquely from company to company. Therefore, it is not suitable to judge that the properties of nonwoven fabrics are improved by simple strength comparison because they can not be distinguished from each other.

However, even if there is a difference in the type of carding machine or the machine arrangement, it was found that comparing the adhesion index of the manufactured nonwoven fabric can compare the effect of the structure and the uniqueness of the fiber or staple on the nonwoven fabric.

Thus, it can be seen that the unit concept of the adhesion index (TBI) is very appropriate in order to accurately determine the influence of the unique properties of the fibers or staples in the nonwoven fabric. TBI is described in detail in pages 40/1 to 40/10 of a paper on polypropylene fibers and textiles presented at the Forth International conference at The Plastics and Rubber Institute. In fact, in the present invention, it was found that it is most preferable to introduce TBI in order to be able to make a comparative comparison of the evaluation of the nonwoven fabric by the intrinsic properties of fibers or staples.

Therefore, in the present invention, the TBI presented by PRI was introduced as an evaluation item of the nonwoven fabric.

In the present invention, the physical properties of the fibers and staples and the adhesion index and physical properties of the nonwoven fabric were measured using the following analysis method.

※ Denier measurement of fibers and staples: Vibroskop [Lens

zing)].

※ Measurement of the elongation of fibers and staples: It was measured according to ASTM D 638 using an Instron (Universal Testing Instrument).

※ Melt index measurement: It was measured according to ASTM D 1238 using MODEL MP 993 of Timinius Olsen.

※ Measurement of adhesion index of nonwoven fabric: It was measured by the method of Equation 2 below.

Adhesion index = (MD × CD) ^1/2 × (20 / basis weight)

MD: Machine direction strength of nonwoven fabric (㎏ / 50㎜)

CD: Lateral strength of nonwoven fabric (㎏ / 50㎜)

Basis weight: weight of nonwoven fabric (g / ㎡)

※ Measurement of properties of nonwoven fabric: A sample having a width of 50 mm and a length of 140 mm was measured at a tensile speed of 100 mm / min using an Instron.

Specific features and advantages of the present invention will be described with reference to the following examples. However, the following examples do not limit the present invention as a preferred embodiment for the implementation of the present invention.

<Example>

An additive containing 0.09% by weight of an antioxidant and a stabilizer, and melt spinning the isotactic polypropylene polymer having a MI as shown in Table 1 below, but the temperature of the extruder is 250 to adjust the degree of molecular chain decomposition before detention. The heating from the extruder to the detention after adjusting to 290 ° C. was adjusted in the range of 285 to 310 ° C. using the fruit. For comparison of the raw material and the pre-mold melt, the sample was collected by bypass to obtain a sample while minimizing the pressure drop just before the inlet of the gear pump to quantitatively supply to the detention. The spinning speed was 1500 m / min, and the fineness of the primary fiber was 2.4 denier fibers. The primary fibers thus prepared were collected to draw a bundle and stretched at a draw ratio of 1.5 times in the stretching process to give a crimp in the crimper, and cut them to 38 mm to prepare staple fibers. The number of crimps of the staple was 6.5 piece / cm.

Thus prepared staples were applied to each manufacturer of the carding machine to produce a nonwoven fabric.

Raw material MI _p Before custody MI _bs Staples MI _f MI _f / MI _p MI _f -MI _p Primary decomposition rate (%) Secondary decomposition ratio (%) Crimp Count Example One 16.1 18.2 45.0 2.8 28.9 7.3 92.7 6.5 2 16.1 19.0 44.8 2.8 28.7 10.1 89.9 6.2 3 12.2 16.2 42.0 3.4 29.8 13.4 86.6 6.4 4 12.2 15.0 36.5 3.0 24.3 11.5 88.5 6.5 5 12.2 13.0 25.6 2.1 13.4 6.0 94.0 6.7 6 11.0 13.0 38.0 3.5 27.0 7.4 92.6 6.2 7 11.0 13.5 33.0 3.0 22.0 11.4 88.6 6.4 Comparative example One 12.2 12.9 21.0 1.7 8.8 8.0 92.0 6.8 2 12.2 12.4 21.0 1.7 8.6 2.3 87.7 6.4 3 12.2 16.2 21.0 1.7 4.8 45.5 54.5 6.4 4 12.2 16.0 79.3 6.5 63.3 5.6 94.4 6.9 5 8.0 11.0 28.0 3.5 20.0 15.0 85.0 6.4 6 52.0 60.0 98.0 1.9 46.0 17.4 82.6 6.5

Carding Strength (Kg / 5cm) TBI Remarks Softness Carding machine Carding Speed (m / min) Basis weight (g / ㎡) MD CD Example One THIBEAU 180 21.0 5.3 1.4 2.6 5 2 SPINNBAU 100 19.0 5.2 1.2 2.6 4 3 SPINNBAU 100 19.5 4.9 0.9 2.2 5 4 HERGETH 100 17.8 5.2 1.5 3.1 4 5 HERGETH 95 20.1 4.9 1.8 3.0 5 6 HERGETH 95 22.1 4.9 1.5 2.5 4 7 HERGETH 95 20.3 4.5 1.6 2.6 4 Comparative example One SPINNBAU 100 20.2 3.2 0.9 1.7 crustiness One 2 HERGETH 150 21.0 3.5 0.8 1.6 TBI degradation 3 3 SPINNBAU 150 20.3 3.4 0.9 1.7 TBI degradation One 4 SPINNBAU 160 20.4 3.5 1.0 1.8 TBI degradation 2 5 SPINNBAU 100 19.8 3.8 0.9 1.9 crustiness 2 6 SPINNBAU 90 19.5 3.8 0.9 1.9 Hard to process NEP 3

Bonding area = 22%,

Top roll type: Diamond type, Bottom roll type: Smooth type

Upper calendar roll temperature = 147 ° C, lower calendar roll temperature = 147 ° C,

Calender roll pressure = 95kg / cm,

Softness = ratings of a person's senses

As can be seen from Tables 1 and 2, the polypropylene fiber according to the present invention has properties suitable for high-speed production of nonwoven fabrics, and the nonwoven fabrics produced have the advantages of being soft to the touch. It becomes possible to manufacture a nonwoven fabric.

Claims (12)

It is prepared from a polyolefin polymer containing from 0.03 to 2.0% by weight of stabilizer and / or antioxidant and the melt index ratio (MI _f / MI _p ) of the polymer and fiber is 2.0 ≦ MI _f / MI _p ≦ 6.0 where MI _p is 10 to 50 as the melt index of the polyolefin polymer, MI _f is 30 or more as the melt index of the polyolefin fibers.) Polyolefin fibers for nonwoven fabrics, characterized in that. The polyolefin fiber for nonwoven fabrics according to claim 1, wherein MI _f / MI _p is 2.0 or more and 5.0 or less. The polyolefin fiber for nonwoven fabric according to claim 2, wherein MI _f / MI _p is 2.2 or more and 3.5 or less. The polyolefin fiber for nonwoven fabric according to claim 1, wherein the polyolefin used for spinning is isotactic polypropylene. The polyolefin fiber for nonwoven fabric according to claim 4, wherein the isotactic polypropylene has a melt index of 10 to 50 and an isotactic index of 90 to 99%. 3 to 20% of the total molecular weight decomposition is carried out before spinning the polyolefin polymer containing 0.03 to 2.0% by weight of stabilizer or antioxidant with a melt index (MI _p ) of 10 or more, and the remaining molecular weight of 97 to 80% after spinning A method for producing a polyolefin fiber for a nonwoven fabric, characterized in that the polyolefin fiber obtained by performing the decomposition has a melt index (MI _f ) of 30 or more but a melt index ratio (MI _f / MI _p ) of 2.0 or more and 6.0 or less. The method for producing a polyolefin fiber for nonwoven fabric according to claim 6, wherein the melt index is adjusted so that MI _f / MI _p is 2.0 or more and 5.0 or less. The method for producing a polyolefin fiber for nonwoven fabric according to claim 7, wherein the melt index is adjusted so that MI _f / MI _p is 2.2 or more and 3.5 or less. The method for producing a polyolefin fiber for nonwoven fabric according to claim 6, wherein the polyolefin used for spinning is isotactic polypropylene. 10. The method of claim 9, wherein the polypropylene has a melt index of 10 to 50 and an isotactic index of 90 to 99%. It is prepared from a polyolefin polymer containing from 0.03 to 2.0% by weight of stabilizer and / or antioxidant and the melt index ratio (MI _f / MI _p ) of the polymer and fiber is 2.0 ≦ MI _f / MI _p ≦ 6.0 where MI _p is A polyolefin nonwoven fabric having a TBI of 2.0 or more, wherein the polyolefin polymer has a melt index of 10 to 50 and MI _f is 30 or more as the melt index of the polyolefin fiber. 12. The polyolefin nonwoven fabric of claim 11 wherein the polyolefin polymer is an isotactic polypropylene having a melt index of 10 to 50 and an isotactic index of 90 to 99%.