KR100350175B1 - Heat-sealed composite fiber, manufacturing method thereof and fused fabric or surface material produced therefrom - Google Patents

Abstract

The present invention relates to melt-adhesive composite fibers, nonwovens from composite fibers fused at intersections of fibers and surface materials for medical products such as sanitary napkins and paper diapers. The composite fiber contains a polypropylene as a first component and a polymer mainly composed of polyethylene that is continuously present on at least a portion of the fiber surface in the longitudinal direction of the fiber as the second component; The three-dimensional crimp is 4-16 / in, the filament denier is 1.0-2.0 and the apparent cut length is 20-40 mm. The composite fiber compresses a polymer comprising polypropylene and mainly polyethylene through a spinneret for spinning a composite fiber to form an unstretched composite filament having the above structure, and the unstretched composite filament at a temperature of 90 ° C. to 130 ° C. After drawing at a draw ratio of 0.60 to 0.85 times the maximum draw ratio, the drawn filaments are cooled to a temperature below the preheating temperature, the filaments are crimped, and the filaments are annealed at a temperature of 80 ° C or more and 120 ° C or less. It can manufacture.

Description

Heat-sealed composite fiber, method for manufacturing the same, and fused fabric or surface material produced therefrom

The present invention relates to a heat sealable composite fiber and a method for producing the same. In addition, the present invention includes a composite fiber, has a large recovery from strength and compression, has little nep (small fiber aggregate) formation, and is excellent in hand pliable, partially fused fabric. It is about. The present invention also relates to surface materials for medical products such as sanitary napkins and paper diapers comprising partially fused fabrics.

In recent years, the performance needed for nonwoven fabrics used in medical surface materials such as sanitary napkins and diapers has been developed and diversified. In particular, there has been a demand for such nonwoven fabrics to maintain high strength with as little weight as possible, to have large bulk recovery from compression, and to limit the number of NEPs (small fiber aggregates) as a fabric forming property and to have a soft hand feel.

In order to satisfy these requirements, the method for producing a bulky nonwoven fabric is that the heat-sealing composite fiber is a partially fused fiber and the Q value, preheating temperature, elongation ratio, crimp number and crimp elastic modulus of the first component in the production of the fiber It is proposed in Unexamined-Japanese-Patent No. 89-37505 which is specified.

However, the nonwoven fabric is still unsatisfactory as a surface material for medical products, in particular, the nonwoven fabric which is handed down in the above-mentioned Japanese Patent Laid-Open produces problems during the carding step, generates a large number of neps that are harmful to the fabric performance, and has a low bulk recovery rate and high strength. Small and poor hand feel. Therefore, there has been a strong demand for the development of nonwovens to solve the above problems.

As a result of research on the performance of the nonwoven fabric including the heat-sealing composite fiber and the manufacturing method of such a fabric, it has been found that the disadvantages of the prior art are solved as follows by the present invention.

The present invention comprises a first component comprising crystalline polypropylene and a second component comprising primarily polyethylene, a three-dimensional crimp of 4 to 16 / in, a filament denier of 1.0 to 2.0 and an apparent length of 20 to 40 mm A fused composite fiber is provided in which these components are arranged in a side-by-side relationship or in a seed-core relationship, with the second component at least part of the fiber surface in the longitudinal direction of the composite fiber. Exist in succession.

The composite fiber of the present invention

Spinning polymer components using spinnerets for parallel or seed-core composite fibers,

Stretching the thus obtained undrawn filament at a draw ratio of 0.60 to 0.85 times the maximum draw ratio at a temperature of 90 ° C. or more and 130 ° C. or less,

Cooling the stretched filament to a temperature lower than the preheating temperature and crimping the filament; and

The filament may be prepared by performing annealing at a temperature of 80 ° C. or more and 120 ° C. or less.

In addition, the present invention provides a partially fused fabric comprising at least 50% by weight of the above heat-sealed composite fiber or the fiber obtained according to the above-described method. In the fabric of the present invention, the intersections of the composite fibers are melted and bonded to each other through the second component of the composite fibers.

The present invention also provides a surface material for a medical product having a thickness of 1 mm or more and comprising the above-mentioned partially fused fabric.

In general, the crystalline polypropylene used as the first component in the composite fibers of the present invention means a crystalline polymer containing propylene polymerized as a main component, which is not only a propylene homopolymer but also propylene and ethylene, butene-1 or 4-methyl Copolymers with pentene are also included.

Generally, polyethylene mainly used as the second component in the composite fibers of the present invention means polymers such as medium or low pressure polyethylene and high pressure polyethylene containing polymerized ethylene as the main component, which is a homopolymer of ethylene as well as propylene, butene Or copolymers with -1 or vinyl acetate (EVA). The melting point of the polyethylene is preferably at least 20 ° C lower than the melting point of the crystalline polypropylene as the first component.

The crystalline polypropylenes and polyethylenes described above may contain various additives, such as stabilizers, fillers and pigments generally used in polyolefin fibers, within the scope of which the object of the present invention is achieved.

The heat sealable composite fibers of the present invention are fibers extruded from spinnerets for parallel or seed-core composite fibers. The second component should be continuously present on at least a portion of the fiber surface in the longitudinal direction of the fiber and the second component should preferably occupy the fiber surface as broadly as possible. Since heat-sealed composite fibers produce crimps using the difference in elastic shrinkage of the two components, an eccentric seed-core structure as shown in FIG. 1 is preferable when the composite fiber is a seed-core structure, and a core The center of the component is preferably inclined 5 to 15% (based on the diameter of the seed-core composite fiber) with respect to the center of the seed component.

The composite fiber of the present invention can be obtained by a conventional method of spinning a parallel composite fiber or a seed-core type complex essential oil in which a second component is used as the seed component. There is no particular limitation on the ratio of the two components of the composite fiber, but the second component is preferably 40 to 70% by weight.

The heat sealable composite fiber of the present invention has a three-dimensional crimp. The composite fibers preferably do not produce crimps upon heat treatment for nonwoven fabric production, in other words, the composite fibers of the present invention preferably have no potential crimps. If the fibers are substantially free of potential crimps during heat treatment, shrinkage of the fibers due to the generation of crimps during heat treatment for nonwoven fabric production can be prevented.

The crimp number of the heat-sealing composite fiber of the present invention is usually 4 to 16 / in, preferably 6 to 14 / in. When the number of crimps is less than 4 / in, fibers may be wound in the cylinder of the carding machine. If the number of crimps exceeds 16 / in, the opening is poor, producing nep in the production of the nonwoven fabric.

The filament denier of the heat sealable composite fiber of the present invention should be 1.0 to 2.0. If denier is less than 1.0, the crimp may be too fine to produce a nep. If the denier exceeds 2.0, the hand feel is inflexible and the bulk recovery rate of the nonwoven fabric from compression tends to decrease.

The apparent cut length of the heat sealable composite fibers of the present invention is usually 20 to 40 mm, preferably 25 to 35 mm. If the length is less than 20 mm, the movement properties of the fibers in the carding machine are poor and the fibers can be wound around the work machine. If the length exceeds 40 mm, the fibers are noticeably entangled, creating a nep.

The ratio of the apparent cut length to the cut length of the heat sealable composite fiber of the present invention is preferably 50 to 70%. If the ratio is less than 50%, the movement characteristics of the fibers in the carding machine are poor, and the fibers are wound around the cylinder to form a nep. If the ratio exceeds 70%, the fibers are so entangled that the fibers are wound on a take-in roll and the carding step itself is impossible.

The method for producing a heat-sealed composite fiber of the present invention comprises the steps of spinning polymer components using spinnerets for parallel or seed-core composite fibers,

Stretching the thus obtained undrawn filament at a draw ratio of 0.60 to 0.85 times the maximum draw ratio at a temperature of 90 ° C. or more and 130 ° C. or less,

Cooling the stretched filament to a temperature lower than the preheating temperature and crimping the filament; and

Annealing the filament at a temperature of 80 ° C or more and 120 ° C or less.

In the spinning step, the first component comprising crystalline polypropylene and the second component comprising primarily polyethylene are extruded through spinnerets for parallel or seed-core composite fibers so that the second component is applied to at least a portion of the fiber surface. Generate filaments that exist in succession.

In the stretching step, the extruded unstretched filaments are preheated to the stretching temperature. If extending | stretching temperature is less than 90 degreeC, crimp becomes too fine. If the stretching temperature exceeds 130 ° C., the composite fibers are undesirably badly fused to each other through polyethylene.

If the draw ratio is less than 0.60 times the maximum draw ratio, the difference between the elastic recovery rates of the two components is small, and no crimp is produced. If the draw ratio exceeds 0.85 times the maximum draw ratio, the difference in the elastic recovery ratios of the two components becomes too large and the crimp cycle becomes small. As a result, not only the number of crimps is too large, but the apparent cut length of the fibers is undesirably too short. The maximum draw ratio refers to the draw ratio when the fluff starts to appear in the filament tow when the draw ratio is gradually increased.

In the crimping treatment, the stretched filament is cooled at a temperature lower than the stretching temperature, the filament is wound on a roll such as a take-up roll of a nip roll under tension conditions, and then the filament is relaxed to generate a crimp. Let's do it. When the crimping treatment is performed at a temperature exceeding the stretching temperature, crimping production is insufficient.

In the annealing step, the filaments produced by the crimping treatment are annealed at a temperature of 80 ° C. or more and 120 ° C. or less for 0.5 to 30 minutes. If the annealing temperature is lower than 80 ° C., latent crimping is undesirably produced in the step for producing the nonwoven fabric. If the annealing temperature is higher than 120 ° C., the resulting crimp is extended and the apparent cut length of the fiber is undesirably long due to the difference in elastic recovery of the two components.

The heat-sealing composite fiber of the present invention is mainly cut into a predetermined length, which is used as staple fiber in that it is easy to process into a nonwoven fabric.

The partially fused fabric of the present invention may comprise from 50% to 100% by weight of the above melt adhesive composite fiber. Partially fused nonwovens can be obtained by converting the heat-sealed composite fibers into nonwovens by conventional carding, air-laid or dry-pulp processes and then heat treating the nonwovens to partially fusion the fabric. . Partially fused monofilaments are fibers other than heat-sealed composite fibers and may be selected from polyester, polyamide, polypropylene, polyethylene or other synthetic fibers, natural fibers (such as cotton and wool), or recycled fibers (such as viscose rayon). It may include up to 50% by weight. In this step, the heat sealable composite fibers should be mixed with the fabric in an amount of at least 50% by weight. If the content of the heat-sealing composite fiber is less than 50% by weight, not only the fabric having a high nonwoven strength can be obtained because there are few cross points of the fiber, but also the bulk recovery rate of the fabric from the compression is high and the intended is high. It is not possible to obtain high fabrics.

As a method of partially fusing the heat-sealable composite fiber, a method of using a heated air dryer or a suction band dryer may be exemplified. By applying this method to the fabric, the intersections of the composite fibers are fused together by melting the second component to create the fabric. The fusion temperature is usually higher than the melting point of the second component but lower than the melting point of the first component, preferably 120 to 155 ° C. The fusion time is usually at least 5 seconds, for example when using a dryer.

The surface material for medical products of the present invention is manufactured using a partially fused nonwoven fabric, and is usually thicker than 1 mm. Surface materials are preferred when the bulk properties are greater than 1 mm and the elastic recovery from compression is particularly greater than 50%. If the thickness is less than 1 mm and the recovery rate is less than 50%, the hand feel of the flexible material cannot be obtained.

The thickness referred to herein means a thickness (mm) measured under a load of 2 gf / cm 2 after applying a load of 50 gf / cm 2 to the surface material for 24 hours, and resting for 1 hour without load to recover the thickness. The elastic recovery from compression means the difference between the thickness of the surface material measured after applying a 50 kgf / cm 2 load for 24 hours and the thickness (%) of the same surface material measured after restoring the thickness by standing for 1 hour without load. .

According to the present invention, it is possible to produce a heat-sealable composite fiber which is useful as a surface material for medical products due to its high bulk recovery rate, excellent formation characteristics, high strength, and flexible hand feel. In particular, the partially fused fabric of the present invention can be widely used in sanitary napkins and paper diapers.

Example

The present invention will be described in more detail with reference to examples. However, it should be understood that the present invention is not limited by these specific embodiments. The physical property value of an Example is measured by the following method.

Crimp Number:

Crimp number of heat-sealing composite fibers measured according to JIS L1015 (test method for chemical fiber staples) 7.12.1.

Filament Denier:

Filament denier of heat-sealable composite fibers measured according to JIS L1015 (test method for chemical fiber staples) 7.5.1-A.

Apparent cutting length:

The apparent cut length of the heat sealable composite fiber is a measure of the fiber length (mm) without stretching the staple crimp and without applying any other force to the staple. 30 measurements are taken to obtain an average value.

Bulk recovery rate:

The bulk recovery rate of the partially fused nonwoven fabric was measured by applying a 50 gf / cm 2 load to the fabric for 24 hours and then measuring the thickness (A) of the sample fabric and measuring the thickness (B) of the fabric under a load of 2 gf / cm 2 according to the following equation. Calculate the bulk recovery rate:

In evaluating the results, fabrics with a bulk recovery of at least 50% are considered acceptable and no other fabrics are considered acceptable. Acceptable fabrics are referred to as A and unacceptable fabrics are referred to as C.

Strength of Nonwovens:

The strength of the partially fused nonwoven fabric is measured according to JIS L1085 (test for nonwoven wick fabrics), in which a 5 cm wide sample fabric is stretched under conditions of a grip distance of 10 cm and an elongation of 30 ± 2 cm / min. And the strength of the vertical direction (CD) of the fabric direction. In evaluating the results, fabrics with an MD strength of at least 2,500 g / 5 cm are considered acceptable and fabrics less than 2,500 g / 5 cm are not considered acceptable; Fabrics with a CD strength of at least 500 g / 5 cm are considered acceptable and fabrics less than 500 g / 5 cm are not considered acceptable. Allowed fabrics are referred to as A and unacceptable fabrics are referred to as C.

Nep:

The number of Nep of the partially fused nonwoven fabric is measured by counting the number of Nep in 1 m 2 of the sample fabric, and is expressed as Nep number / m 2. In the evaluation, partially fused nonwoven fabrics having one or more nep numbers are considered acceptable and those with two or more nep numbers are not permitted. Acceptable fabrics are referred to as A and unacceptable fabrics are referred to as C.

Touch of the hand:

The hand feel of the partially fused nonwoven fabric is measured by sensory testing by five participants. If all participants determine that the sample fabric is flexible, the fabric is considered "good"; If three or more of the participants determine that the sample fabric is flexible, the fabric is considered "good"; If three or more participants determine that the sample fabric is inflexible, the fabric is considered “poor”. A good fabric is referred to as A, a good fabric is referred to as B, and a poor fabric is referred to as C.

Fabric Shrinkage:

The shrinkage rate of the partially fused nonwoven fabric is measured by cutting a 25 cm 2 sample fabric, heating the fabric at 145 ° C. for 5 minutes without load, measuring the shrinkage in the fabric direction at three points, and calculating the average value. . In the evaluation, fabrics with a shrinkage of 10% or more are considered to be unacceptable. Acceptable fabrics are referred to as A and unacceptable fabrics are referred to as C.

Examples 1-4 and Comparative Examples 1-9

Each of the heat-sealed composite fiber staples shown in Table 1 is made of polypropylene as a first component and polyethylene as a second component through a spinneret for seed-core or parallel composite fibers having 350 orifices 0.6 mm in diameter. It is obtained by forming a filament, stretching the filament under the conditions shown in Table 1, and then stapling the drawn filament. Table 1 shows the physical properties of the fibers thus obtained.

Each of the heat-sealable composite fiber staples thus obtained was formed into a web having a basis weight of 20 to 30 g / m 2 with a carding machine, and the web was sucked for 5 seconds at a predetermined temperature of 135 to 140 ° C. Heat treatment to obtain a nonwoven fabric in which the intersection points of the fibers are fused together. The properties of the fabric are shown in Table 2. In Example 4 and Comparative Example 9 of Table 2, the staples of Example 1 and Comparative Example 3 are used.

Figure 1 shows a cross-sectional view of the composite fiber of the present invention.

Claims (4)

A first component comprising crystalline polypropylene and a second component comprising primarily polyethylene, wherein the components are arranged in a side-by-side or sheath-core relationship; Heat-sealable composite fibers having components present continuously on at least a portion of the fiber surface in the longitudinal direction of the fibers, three-dimensional crimps of 4 to 16 / in, filament deniers of 1.0 to 2.0, and apparent cut lengths of 20 to 40 mm. . Spinning polymer components using spinnerets for parallel or seed-core composite fibers, Stretching the thus obtained undrawn filament at a draw ratio of 0.60 to 0.85 times the maximum draw ratio at a temperature of 90 ° C. or more and 130 ° C. or less, Cooling the stretched filament to a temperature below the preheating temperature and crimping the filament; and Annealing the filament at a temperature of 80 ° C or more and 120 ° C or less, the method of producing a heat-sealed composite fiber according to claim 1. The intersection of the composite fibers is melted and bonded to each other through the second component of the composite fiber, and contains at least 50% by weight of the heat-sealed composite fiber according to claim 1 or the heat-sealed composite fiber obtained by the method according to claim 2. Partially fused non-woven fabric. The surface material for medical goods containing the partially fused nonwoven fabric of Claim 3 whose thickness is 1 mm or more.