EA046495B1 - COMPOSITE FIBER WITH AN "ISLANDS IN THE SEA" STRUCTURE - Google Patents

Description

Field of technology to which the invention relates

The present invention relates to a flat composite fiber with a sea island structure suitable for use when incorporated into a matrix material (eg, a thermoplastic resin molded article), and the use of such fibers, as well as a thermoplastic resin molded article including such composite fibers with a structure islands in the sea, and the method of obtaining it.

State of the art

A fiber-embedded resin molding containing, for example, a thermoplastic resin as a matrix material, in addition to the characteristics of the resin, exhibits advantages derived from the incorporated fibers, such as high tensile strength, thermal insulating ability, lightness, weather resistance and electrical insulating ability. Fiber-incorporating resin moldings can be used in a variety of applications such as building materials, automotive components, medical devices, and shock absorbers.

For example, Patent Document 1 (Japanese Patent Laid-Open Publication No. 2014-185265) discloses a method for generating bubbles by using a technique of dispersing a water-absorbing medium in a resin to form water bubbles. As described in Patent Document 1, when using water introduced into composite fibers with an island structure in the sea, the water can be mixed with a thermoplastic resin and then subjected to heating so that bubbles can be formed as the water evaporates during molding to form a molded product including small bubbles.

Prior art document

Patent document

Patent Document 1. Japanese Patent Publication No. 2014-185265.

The essence of the invention

In the method described in Patent Document 1, composite fibers containing the island component are uniformly dispersed in a thermoplastic resin.

In addition, due to the marine component exhibiting a melting point lower than that of the island component, the faster melting of the marine component than the island component upon heating makes it possible to disperse the island components. This makes it possible to obtain a molded thermoplastic resin product in which fine bubbles are uniformly dispersed.

However, in this method of dispersing sea island structure composite fibers, the sea island structure composite fibers are heated only through the thermoplastic resin by applying heat so that the sea island structure composite fibers in contact with the thermoplastic resin cannot be heated sufficiently, resulting in uneven heat dissipation into the sea island structure composite fibers and insufficient thermoplastic deformation of the sea island structure composite fibers. A composite fiber with an island structure in a sea exhibiting insufficient thermoplastic deformation inevitably contains a marine component characterized by insufficient thermoplastic deformation, such that the movement of the island component within the composite fiber is restrained by the marine component. When the island component is restrained by the sea component, the corresponding parts of the islands in the island component cannot move independently, resulting in uneven distribution of the island parts in the thermoplastic resin. In such a case, fiber characteristics such as improved tensile strength cannot be demonstrated in the thermoplastic resin molded article.

As discovered by the inventors as a result of intensive research conducted by the inventors of the present invention to solve this problem, specific sea island composite fibers dispersed in a matrix material make it possible to obtain improved heat dissipation by obtaining a cross-section of each island structure composite fiber in the sea with a predetermined aspect ratio, and thereby the marine component can have improved thermoplastic deformability by heating the matrix material for dispersing the island structure composite fibers in the sea such that the island structure composite fibers in the sea enable independent dispersion of the respective parts islands of the island component in the matrix material without containing the island component. Thus, the inventors of the present invention have made the present invention.

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That is, the present invention may include the following preferred aspects.

Aspect 1.

A sea island composite fiber (preferably a sea island composite flat staple fiber) containing an island component and a sea component having a melting point lower than that of the island component, wherein the fiber has an aspect ratio in the range of 2.0 to 5.0 (preferably 2.6 to 3.4) in fiber cross-section; and the sea component has a sea component thickness in the range of 0.2 to 2.0 μm (preferably 0.5 to 1.0 μm), the sea component thickness being defined as the distance between the outer periphery of the fiber and the island component closest to outer periphery on the minor axis of the fiber cross-section.

Aspect 2.

The sea island structure composite fiber according to aspect 1, wherein the island component comprises an ethylene vinyl alcohol copolymer (preferably an ethylene vinyl alcohol copolymer comprising ethylene with a proportion ranging from 25 to 70 mol %).

Aspect 3.

A composite fiber with an island structure in the sea, corresponding to aspects 1 or 2, where the marine component contains a polyolefin resin.

Aspect 4.

The sea island structure composite fiber according to any one of aspects 1 to 3, wherein the sea island structure composite fiber has a single fiber fineness of 50 dtex or less (preferably 20 dtex or less, and further preferably 15 dtex or less).

Aspect 5.

A sea island structure composite fiber corresponding to any one of the aspects 1 to 4, wherein the island component has an aspect ratio of 5.0 or less (preferably 4.0 or less, and more preferably 3.5 or less).

Aspect 6.

The sea island composite fiber according to aspect 5, wherein the aspect ratio for the island component has a CV value of 45% or less (preferably 35% or less, and more preferably 25% or less).

Aspect 7.

A sea island structure composite fiber corresponding to any one of aspects 1 to 6, wherein the sea island structure composite fiber has a fiber length in the range of 0.5 to 30 mm (preferably 1.0 to 20 mm, more preferably from 1.5 to 10 mm, and, in addition, preferably from 2.7 to 3.3 mm).

Aspect 8.

The sea island structure composite fiber according to any one of aspects 1 to 7, wherein the sea island structure composite fiber comprises a sizing agent applied at a proportion ranging from 0.1 to 30 wt.% (more preferably from 0.1 up to 10 wt.%, and, in addition, preferably from 1.0 to 5.0 wt.%) based on the weight of the fiber.

Aspect 9.

A sea island structure composite fiber corresponding to any one of aspects 1 to 8, wherein the fiber has a shrinkability capable of shrinking 10% of the fiber length in the longitudinal direction of the fiber in 500 seconds or less when the fiber is heated at 160° C. with attachment mass of 0.14 mg/dtex to one end of the fiber.

Aspect 10.

Using the sea island structure composite fibers that are mentioned in any one of aspects 1 to 9 for molding, where the matrix material and the sea island structure composite fibers are mixed to form a mixture; and the mixture is heated at a temperature equal to or greater than the melting point of the sea component and less than the melting temperature of the island component of the island structure composite fibers in the sea.

Aspect 11.

A molded article comprising, at least in a portion of the molded article, the sea island structure composite fibers referred to in any one of aspects 1 to 9.

Aspect 12.

A method for producing a molded article, the method comprising mixing a matrix material and sea island structure composite fibers which are mentioned in any one of aspects 1 to 9 to form a mixture and heating the mixture at a temperature equal to or greater than the melting point marine component and lower than the melting point of the island component of composite fibers with an island structure in the sea, for molding a profile from the mixture.

The present invention covers any combination of at least two features, races

- 2 046495 covered in the claims and/or description of the invention and/or in the drawings. In particular, any combination of two or more claims shall be equally construed as being included within the scope of the present invention.

Effects of the invention

According to the present invention, a sea island structure flat composite fiber having excellent spinnability and thermoplastic deformability can be produced. Using such flat composite fibers with an island structure in the sea to obtain a molded article makes it possible to independently disperse the island component without being restrained by the sea component in a mixture of fibers and a matrix material, so as to obtain a molded article in which uneven distribution of the island component is suppressed.

Brief description of drawings

The present invention will be more clearly understood from the following description of preferred embodiments thereof when taken in conjunction with the accompanying drawings. However, the embodiments and drawings are presented for purposes of illustration and explanation only and should not be construed as limiting the scope of the present invention in any way, where such scope is to be defined in the accompanying claims. In the accompanying drawings, like reference designators are used to identify similar or corresponding parts throughout the several illustrations. The drawings are not necessarily shown to a consistent scale and are exaggerated for the purpose of illustrating the principle of the present invention. Among the figures:

fig. 1 is a typical schematic cross-sectional view of a sea island structure flat composite fiber used in the present invention, wherein the fiber is cut orthogonal to the longitudinal direction (ie, the direction of the fiber axis) of the fiber;

fig. 2 is a schematic cross-sectional view of a sea island structure flat composite fiber used in the present invention for the purpose of illustrating the thickness of the sea component, wherein the fiber is cut orthogonal to the longitudinal direction of the fiber.

Description of Embodiments

Hereinafter, embodiments of the present invention will be described in detail.

Flat composite fiber with island structure in the sea.

The sea island structure flat composite fiber of the present invention contains an island component and a sea component having a melting point lower than that of the island component. Such a sea island structure flat composite fiber can be stapled to an arbitrary fiber length to produce a sea island structure flat composite staple fiber.

Island component.

The resin used as the island component constituting the sea island structure flat composite fiber is not limited to a specific corresponding resin as long as it is a thermoplastic resin. Various fiber-forming thermoplastic polymers can be used, and examples of such thermoplastic polymers may include polyamide resins, polyester resins, polyolefin resins, acrylic resins and thermoplastic vinyl alcohol resins. Among them, thermoplastic vinyl alcohol resins (especially ethylene vinyl alcohol copolymers) are preferred for superior hydrophilicity. For example, if the molded product needs to demonstrate hydrophilicity for applications such as interior and exterior walls of a building, an ethylene vinyl alcohol copolymer may preferably be used.

Among them, the more preferable ethylene vinyl alcohol copolymer (melting point: 120 to 190°C) includes 25 to 70 mol% ethylene (preferably 30 to 60 mol%, and more preferably 35 to 55 mol%). There is a possibility that, during spinning, an ethylene vinyl alcohol copolymer having an ethylene content less than the lower limit value may undergo gelatinization, resulting in deterioration in spinnability. On the other hand, an ethylene vinyl alcohol copolymer having an ethylene content greater than the upper limit value is unlikely to exhibit hydrophilicity.

The ethylene vinyl alcohol copolymer may have a saponification rate of, for example, 88% or more, preferably 95% or more, and more preferably 98% or more. The upper limit value of the saponification degree is not limited to a specific value and may be, for example, 99.8%.

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Marine component.

It is important that the polymer used as the marine component constituting the flat composite fiber with an island structure in the sea demonstrates a melting point lower than that of the polymer used as the island component. In the molding process in which the sea island structure flat composite fibers are dispersed in the matrix material, the sea component is melted faster than the island component, and the sea island structure composite fibers are characterized by an aspect ratio according to the definition below in the range 2.0 to 5.0 in its fiber cross-section so that heat is sufficiently dissipated into the marine component of the sea island structure composite fibers in the matrix. This increases the ability of the sea component to melt to reduce the bonding force of the sea component to the island component in the sea island composite fibers, resulting in uniform dispersion of the island component in the mixed fluid comprising the flat sea island composite fibers and the matrix material. Such a marine component is not limited to a specific corresponding component as long as it has a melting point lower than that of the island component and is capable of forming an island structure in the sea when spun. Examples of the marine component may include polyolefin resins, acrylic resins, polyamide resins and the like.

Among them, with regard to fiber dispersibility, a preferred corresponding component may comprise polyolefin resins. Examples of polyolefin resin may include: various types of polyethylene (low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), medium density polyethylene (MDPE) or high density polyethylene (HDPE); melting point: 95 to 150°C ); low-melting polypropylene (melting point: from 115 to 155°C); and ethylene-propylene block copolymer (melting point: 95 to 165°C).

With regard to improving thermoplastic deformability, the marine component may have a thermal conductivity (unit: 10 ^-4 cal/s-cm/°C-cm) of, for example, 3 or more, preferably 5 or more, and more preferably 7 or more, with In this case, thermal conductivity is measured in accordance with ASTM C177. The upper limit value of thermal conductivity is not limited to a specific value and may be, for example, 20 or less.

The melting point (Ms) of the marine component resin is only required to be less than the melting point (Mi) of the island component resin, and the difference (Mi-Ms) between these melting temperatures may preferably be in the range of 20 to 80°C, and more preferably from 30 to 60°C. The difference within a predetermined range makes it possible to improve the dispersibility of the island component while benefiting from the thermoplastic deformability of the marine component.

In the sea island structure flat composite fiber, the island component and the sea component may preferably be present at a weight ratio between the composite components of (island component)/(sea component)=10/90 to 90/10. There is a possibility that when the ratio between the components of the composite is unbalanced and the content of the island component is less than the lower limit value or greater than the upper limit value, the freshly spun fibers discharged from the spinning nozzle may be effectively bent, resulting in insufficient spinnability . The ratio between the island component and the marine component components of the composite may be more preferably in the range of 30/70 to 90/10, and further preferably 50/50 to 80/20.

The sea island structure flat composite fiber may contain a sizing agent applied to the surface of the fiber during spinning to improve the dispersibility of such fibers in the matrix material of the molded article. The type of sizing agent can be suitably selected depending on the type of matrix material mixed with the sea island structure flat composite fiber. Examples of the lubricant may include: animal oil, vegetable oil, synthetic lubricating oil, mineral oil, nonionic surfactant, anionic surfactant, cationic surfactant, amphoteric surfactant and other lubricants. The lubricant may be applied in an amount ranging from 0.1 to 30% by weight, more preferably from 0.1 to 10% by weight, and further preferably from 1.0 to 5.0% by weight, when calculated per fiber weight.

As long as the effect of the present invention is not deteriorated, the sea island structure flat composite fiber used in the present invention may optionally contain inorganic substances such as titanium dioxide, silica and barium oxide; carbon black; coloring agents such as dyes and pigments; additives such as antioxidants, UV absorbers and light stabilizers.

It is important that the sea island structure flat composite fiber of the present invention demonstrates high thermoplastic deformability. For example, heating a fiber at 160°C and attaching a predetermined mass (e.g.

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0.14 mg/dtex) to one end of the fiber, the fiber may exhibit a shrinkage capability that shrinks 10% of the fiber length in the longitudinal direction of the fiber, preferably in 500 seconds or less. When the fiber shrinks by 10% within the above range, the marine component can be effectively melted during the process of producing a molded article including flat composite fibers with an island structure in the sea, so that the island component can be independently dispersed in the mixture including flat composite fibers with island structure in the sea and matrix material. The range may more preferably be 400 seconds or less, further preferably 300 seconds or less, and further preferably 200 seconds or less.

Production of flat composite fiber with island structure in the sea.

The sea island structure flat composite fiber can be produced using a known method using a known spin-drawing apparatus. For example, island component polymer pellets and marine component polymer pellets can be fed into separate melt extruders and melted to produce melts. Suitable melts can be combined in a spinneret to produce a composite fiber designed to form the desired fiber cross-section and discharged from the nozzle at the above ratio, i.e., (island component)/(marine component). Freshly spun fibers can typically be wound at speeds ranging from 500 to 4000 m/min. The number of island component parts (or number of islands) can be changed by the choice of the spinneret, and the composite fiber may include from 1 to 1000 islands, preferably from 2 to 600 islands, and more preferably from 4 to 200 islands, with regard to the dispersibility of the island component. The wound fibers can also be drawn (by dry heat drawing or moist heat drawing) as required.

Cross-sectional profile of a flat composite fiber with an island structure in the sea.

Fig. 1 is a schematic cross-sectional view showing one example of the cross-sectional profile of a sea island structure flat composite fiber used in the present invention in an orthogonal direction with respect to the fiber axis. In this example, the sea island structure flat composite fiber contains the island component A in the form of 16 flat profile pieces arranged uniformly in the sea component B throughout the fiber. What is important is that the sea island structure flat composite fiber exhibits as a single fiber a flat profile in its cross section orthogonal to the longitudinal direction of the fiber, or in other words, a substantially elliptical profile that is more elongated in one direction than the true one. circle and is characterized by an aspect ratio, which is the ratio between the major axis and the minor axis (major axis/minor axis) in the range of 2.0 to 5.0, more preferably 2.5 to 4.0, and further preferably from 2.6 to 3.4. The major axis and minor axis in the present invention correspond to the major axis and minor axis of a flat cross-sectional profile as shown in FIG. 1 respectively. The major axis is defined as the longest linear segment passing through the center of gravity in the plane cross-sectional profile of a single fiber. The minor axis is defined as the longest linear segment in a direction orthogonal to the major axis.

Sea island structure flat composite fibers enable efficient heat dissipation (heat transfer) when mixed with a melt spinning matrix material, compared with fibers having the same single fiber fineness but exhibiting an aspect ratio of 1, such that the heat can be sufficiently dispersed into flat composite fibers with an island structure in the sea (in particular, their marine component). As a result, the island component parts can be uniformly dispersed in the mixed fluid formed from the sea island structure flat composite fibers and the matrix material. In other words, due to each of the sea island structure flat composite fibers exhibiting a larger surface area than the true circle cross section fiber (i.e., aspect ratio 1), the flat fibers can more easily absorb heat supplied from the space outside the outer peripheral surfaces of the fibers, which facilitates the melting of the marine component in the mixture including the flat composite fibers with a sea island structure and the matrix material. Therefore, in the mixed fluid produced from the flat composite fibers with an island structure in the sea and the matrix material, the marine component releases the inner island component to independently disperse the island component of the composite fibers so as to prevent uneven distribution of the island component.

Fibers characterized by an excessively small aspect ratio may result in poor dispersion of the island component (potentially promoting uneven distribution) due to slow heat dissipation when the mixture is heated

- 5 046495 of fibers and matrix material, while fibers characterized by an excessively high aspect ratio may exhibit difficulty in spinning since freshly spun fibers discharged from the spinning nozzle may be more likely to induce rupture upon contact with the spinning nozzle.

The island component (in the form of part(s) of the island component or island(s)) may have an aspect ratio of, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.5 or less. The aspect ratio for the island component is determined in the same way as the aspect ratio for the composite fiber. The major axis is defined as the longest linear segment passing through the center of gravity in the plane cross-sectional profile of the island component. The minor axis is defined as the longest linear segment in a direction orthogonal to the major axis. It is possible that each portion of an island component having an excessively large aspect ratio will exhibit a larger surface area and thus tend to come into contact with other portion(s) of the island component such that the island components are more likely to become entangled, possibly leading to poor dispersion of the island components. The aspect ratio for the island component is not characterized by a specific lower limit value, and the specific lower limit value may be at least 1.

Further, in relation to the uniformity of the dispersible island component profile, the aspect ratio for the island component may be characterized by a CV value of preferably 45% or less, more preferably 35% or less, and further preferably 25% or less.

It is important that the marine component in the above-mentioned island-in-sea flat composite fiber exhibits a thickness of the marine component in the range of 0.2 to 2.0 µm, and preferably 0.5 to 1.0 µm, with the thickness of the sea composite being the shortest the distance (X) between the outer periphery of the fiber and the island component closest to the outer periphery on the minor axis of the cross section shown in FIG. 2. As used herein, the major axis is defined as the longest linear segment of the center of gravity line passing through the center of gravity in the cross-sectional profile of the fiber, and the minor axis is defined as the longest linear segment in the direction orthogonal to the major axis. When the thickness of the marine component is excessively small, the island component to be coated with the marine component is more likely to come into contact with the spinning nozzle such that the fibers can be effectively bent, resulting in insufficient spinnability. If the thickness of the marine component is excessively large, when the mixture of fibers and matrix material is heated, heat dissipation is slowed down.

Single fiber fineness.

The single fiber fineness of the sea island structure flat composite fiber used in the present invention may suitably be set and typically may be 50 dtex or less, preferably 20 dtex or less, and further preferably 15 dtex or less. If the fineness is too high, the heat dissipation slows down when the mixture of fibers and matrix material is heated. The fineness of a single fiber does not have a specific lower limit and can typically be 0.01 dtex or more, and preferably 4 dtex or more. Single fiber fineness is measured in accordance with JIS L 1013:2010 8.3.1, method A.

Flat composite staple fiber with island structure in the sea.

By mixing the sea island structure flat composite fibers with the matrix material, the fibers can be processed into staple fibers each having a short fiber length to obtain the sea island structure flat composite staple fibers of the present invention. Such sea island structure flat composite staple fiber may preferably have a fiber length in the range of 0.5 to 30 mm, more preferably 1.0 to 20 mm, further preferably 1.5 to 10 mm, and more preferably from 2.7 to 3.3 mm. It may be difficult to disperse fibers having excessively long fiber lengths in the matrix material. Fibers that are characterized by excessively short fiber lengths may exhibit difficulties in the forming of staples in a technical sense, as well as increased production costs.

Matrix material.

The matrix material for forming the molded article used in the present invention is not limited to a particular suitable material. Examples of such material may include: polyolefin resins such as polyethylene resins (low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear chain low density polyethylene (L-LDPE)), ethylene copolymer -a-olefin, polypro

- 6 046495 pylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-ethylene-1-butene random copolymer, propylene-4-methyl-1-pentene random copolymer and polybutene; thermoplastic polyvinyl alcohol resins such as ethylene vinyl alcohol copolymer; vinyl resins such as polyvinyl chloride and ethylene-vinyl acetate copolymer, acrylic resins such as methacrylic resin, ethylene-acrylic ester copolymer; thermoplastic elastomers such as polyurethane elastomer; rubbers such as polyisoprene, polybutadiene, styrene butadiene rubber, ethylene propylene diene rubber and acrylic rubber. Among them, when used as a marine component of a polyolefin resin, preferred corresponding resins with respect to dispersibility may include thermoplastic elastomers such as polyurethane elastomer and rubbers such as polyisoprene, polybutadiene, styrene butadiene rubber, ethylene propylene diene rubber and acrylic rubber.

Production of molded products.

Flat composite fibers with an island structure in the sea are mixed with the matrix material in dispersed form or mixed with the matrix material while softening the matrix material to obtain a mixture. The mixture is then formed into a desired molded article using a conventional molding method such as extrusion molding and injection molding. The matrix material is formed at a temperature equal to or greater than the melting point of the marine component and less than the melting point of the island component. The molded article includes flat composite fibers with a sea island structure in at least a portion thereof. In other words, the molded article contains a matrix material and an island component of flat composite fibers with an island structure in the sea, at least in part thereof. The marine component may be melted by heating to integrate with the matrix material.

Adding composite fibers to a molded product.

The molded article includes composite fibers added at a proportion preferably ranging from 0.1 to 20 wt%, more preferably from 0.2 to 10 wt%, and further preferably from 0.5 to 5 wt%. If the addition of fibers is insufficient, the molded article may not sufficiently exhibit the effects derived from the inclusion of flat composite fibers with an island structure in the sea, such as high tensile strength, thermal insulation ability and lightness. If fibers are added excessively, the molded article as a molded article may exhibit insufficient performance characteristics such as brittleness and poor formability.

Examples

Hereinafter, the present invention will be described more specifically by referring to examples. However, these examples should not be taken as limiting the scope of the present invention in any way. Composite fibers were produced, measured and evaluated in various aspects as follows.

Examples 1-8.

(1) Production of flat composite fibers with island structure in the sea.

Melt extrusion extruders were fed with ethylene vinyl alcohol copolymer (EVOH, available from Kuraray Co., Ltd.; ethylene content: 44% (mol), saponification rate: 99%, melting point: 165°C) and polyethylene ( HDPE; melting point: 125°C, thermal conductivity: 11 to 12.4 (10 ^-4 cal/s-cm/°C-cm)) to obtain appropriate melts. Melts were discharged from the spinning nozzle to produce a flat sea island composite fiber (having a flat profile in the cross section of a single spinning nozzle opening) to spin fibers that contained EVOH as the island component and HDPE as the sea component (at a spinning temperature of 260° WITH). The design of the spinning nozzle was changed for each of the examples in order to produce flat composite fibers with an island structure in the sea with the number of islands, the ratio between the components of the composite, the fineness of a single fiber, the aspect ratio in the cross section, the aspect ratio for the island component in the cross section and its the CV value and the thickness of the marine component, as indicated in Table. 1.

(2) Melting point measurement.

The melting point of the obtained fibers of each sample (sample amount: from 3 to 8 mg) was measured using a Thermo plus TG 8120 differential thermogravimetric analyzer, manufactured by Rigaku Corporation, at a temperature increase rate of 5°C/min in the measured temperature range from 35 to 200° WITH.

(3) Measuring aspect ratios.

The resulting fibers of each sample were stapled using a rotary cutter and the fiber cross-sections for the staple fibers were observed on an enlarged scale using an optical microscope. Using the optical microscope's measurement function, each of the 10 fibers was measured along the major axis and minor axis of the fiber to calculate

- 7 046495 defining the relationship between the major axis and the minor axis (ie major axis/minor axis) as an aspect ratio. The average value of aspect ratios for 10 fibers was used. With regard to the aspect ratio for island parts, one of the above-mentioned fiber cross sections was randomly selected and all island parts in the fiber were measured at that fiber cross section to calculate the average value of the measurement results. As should be noted, in the case of 200 or less island parts in a selected fiber, all island parts may be measured, and in the case of more than 200 island parts in a selected fiber, a randomly selected 200 island parts may be measured. .

(4) Marine component thickness measurement.

The resulting fibers of each sample were directly stapled using a rotary cutter. The fiber cross-section of each staple fiber was observed using an electron microscope (JCM-6000Plus, manufactured by JEOL Ltd.) to determine the distance from the outer periphery of the sea island composite fiber at the cutting section to the island component closest to the periphery of the fiber on the minor axis. . Measurements were taken at 5 cutting points to calculate the average value of the measurement results.

(5) Assessment of spinning ability.

Spinning ability was assessed according to the following criteria:

excellent: less than 1 fiber break per hour during continuous spinning for 1 hour;

good: 1 to less than 3 fiber breaks per hour during continuous spinning for 1 hour and unsatisfactory: 3 or more fiber breaks per hour during continuous spinning for 1 hour.

In table 1 shows the results.

(6) Evaluation of thermoplastic deformation.

As a sample from the obtained fibers from each of the Examples and Comparative Examples, a bundle of 500 filaments having a length of 10 cm was prepared. The sample was suspended such that one end of the sample was held in a clamp and a mass (0.14 mg) was attached to the other end of the sample /dtex). After this, the sample was fixed on a scaled plate. In this state, the sample was placed in a dryer set to 160°C to observe the shrinkage of the island structure composite fibers in the sea in the longitudinal direction from the front side of the dryer. The time required for the fiber length to shrink by 1 cm (10%) was measured. In table 1 shows the results.

(7) Evaluation of the variation of elastic modulus of molded products.

The composite fibers obtained in each of the Examples and Comparative Examples were stapled to a fiber length of 3 mm. Staple fibers and the same HDPE resin as the corresponding resin used as the marine component of the composite fibers were mixed under stirring with a mass ratio of 98:2 to obtain a mixture. The mixture was heated at 160° C. to form 5 pieces of resin molding samples, each having a size of 50 mm by 50 mm by 3 mm. Using a precision universal tester AG-5000B manufactured by Shimadzu Corporation, the elastic modulus of each resin molding was measured. The variation of elastic moduli measured for 5 pieces of samples was calculated as the CV value and the variation of elastic moduli was evaluated according to the following criteria:

excellent: elastic moduli had a CV value of less than 10%;

good: elastic moduli were characterized by a CV value of exactly or more than 10% and less than 15%; and unsatisfactory: elastic moduli were characterized by a CV value of exactly or more than 15%.

Comparative example 1.

The same ethylene vinyl alcohol copolymer and polyethylene as the corresponding materials in Example 1 were used as the island component and the marine component, respectively. Melts of ethylene vinyl alcohol-polyethylene copolymer were discharged from the spinning nozzle to produce the sea island composite fiber (having a circular profile in the cross section of the single opening of the spinning nozzle) to produce the sea island composite fibers shown in Table 1. 1.

Comparative example 2.

The same ethylene vinyl alcohol copolymer and polyethylene as the corresponding materials in Example 1 were used as the island component and the marine component, respectively. Sea island structure composite fibers were spun using a nozzle designed to spin fibers each having a cross-sectional aspect ratio of 1.5 and a sea component thickness of 0.8 µm, as shown in Table 1. 1.

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Comparative example 3.

The same ethylene vinyl alcohol copolymer and polyethylene as the corresponding materials in Example 1 were used as the island component and the marine component, respectively. Spinning was carried out using a nozzle designed for spinning fibers each having a cross-sectional aspect ratio of 6.0 and a marine component thickness of 0.5 µm, as shown in Table 1. 1. However, composite fibers with an island structure in the sea could not be obtained.

Comparative example 4.

The same ethylene vinyl alcohol copolymer and polyethylene as the corresponding materials in Example 1 were used as the island component and the marine component, respectively. Spinning was carried out using a nozzle designed to spin fibers each having a cross-sectional aspect ratio of 3.0 and a marine component thickness of 0.1 µm, as shown in Table 1. 1. However, composite fibers with an island structure in the sea could not be obtained.

Comparative example 5.

The same ethylene vinyl alcohol copolymer and polyethylene as the corresponding materials in Example 1 were used as the island component and the marine component, respectively. Sea island structure composite fibers were spun using a nozzle designed to spin fibers each having a cross-sectional aspect ratio of 3.0 and a sea component thickness of 3.0 µm, as shown in Table 1. 1.

Table 1

Island component Marine component Ratio between the components of the composite (mass ratio) Single die fineness (dtex) Aspect ratio in cross section (major axis/minor axis) Aspect ratio for the island component (major axis/minor axis) CV value of the aspect ratio for the island component (%) Marine component thickness (µm) Spinability Thermoplastic deformation bath (sec) Variations in modulus of elasticity and formability of other products Smol a Melting temperature (°C) Number of “acute WWII” Smol a Melting temperature (°C) "Islands"/ "sea" Etc. 1 EVO N 165 16 HDP E 125 60/40 5 h,o 3.2 20 0.6 Excellent BOTTOM 224 Perfect Etc . 2 EVO N 165 16 HDP E 125 60/40 5 2.0 2.3 18 0.6 Excellent BOTTOM 280 Perfect Etc. 3 EVO N 165 16 HDP E 125 60/40 5 4.0 3.5 34 0.7 Excellent BOTTOM 131 Perfect Etc. 4 EVO N 165 16 HDP E 125 60/40 5 5.0 4.2 42 0.6 Excellent BOTTOM 123 Perfect Etc. 5 EVO N 165 16 HDP E 125 60/40 5 h,o 3.4 26 o, s Fine 205 Perfect Etc. 6 EVO N 165 16 HDP E 125 60/40 5 h,o 2.9 15 1.5 Excellent BOTTOM 362 Fine Etc. 7 EVO N 165 16 HDP E 125 60/40 10 h,o 3.4 20 0.8 Excellent BOTTOM 315 Fine Etc. 8 EVO N 165 16 HDP E 125 60/40 20 h,o 3.2 21 0.6 Excellent BOTTOM 433 Fine Wed. etc. 1 EVO N 165 16 HDP E 125 60/40 5 1.0 1.3 10 Excellent BOTTOM >600 Unsatisfactory Wed. etc. 2 EVO N 165 16 HDP E 125 60/40 5 1.5 1.9 13 0.8 Excellent BOTTOM >600 Unsatisfactory Wed. etc. 3 EVO N 165 16 HDP E 125 60/40 5 6.0 0.5 Unsatisfactory creator Wed. etc. 4 EVO N 165 16 HDP E 125 60/40 5 h,o 0.1 Unsatisfactory creator Wed. etc. 5 EVO N 165 16 HDP E 125 60/40 5 h,o 2.6 15 h,o Excellent BOTTOM >600 Unsatisfactory

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In each of Examples 1 to 8, the composite fiber with a sea island structure contains an island component and a sea component having a melting point lower than that of the island component, and the fiber has an aspect ratio (major axis/minor axis) in the range of 2 .0 to 5.0 in the fiber cross-section and a marine component thickness ranging from 0.2 to 2.0 μm in the fiber cross-section, and thus the fibers in Examples 1 to 8 exhibit excellent spinnability and thermoplastic deformability . Therefore, it is believed that the use of the sea island composite fibers of Examples 1 to 8 makes it possible to produce molded articles in which the independent dispersion of island components in a matrix material including the flat sea island composite fibers can be facilitated. In fact, due to the dispersibility of the island components, the molded articles of Examples 1 to 8 exhibited less variation in elastic modulus than the molded articles of Comparative Examples 1 to 2 and 5.

Comparative Example 1, characterized by an aspect ratio of 1.0 in the fiber cross-section (circular cross-section), deteriorated heat dissipation throughout the fiber, resulting in poor thermoplastic deformability and large variation in the elastic moduli of the molded articles, similar to the characteristics demonstrated for ordinary fibers. Comparative Example 2 had an aspect ratio of 1.5 in the fiber cross-section and was thus not sufficiently flat as in the case of Comparative Example 1, resulting in slow heat dissipation throughout the fiber, poor thermoplastic deformability, and unfavorable variation in the elastic moduli of the molded products. In particular, Comparative Examples 1 and 2 exhibited poor thermoplastic deformability compared to Examples 7 and 8 despite Comparative Examples 1 and 2 exhibiting lower fineness than Examples 7 and 8.

On the other hand, Comparative Example 3 had an aspect ratio of 6.0 in the fiber cross section and was thus very flat. Therefore, frequent fiber breakage occurred such that it was impossible to obtain fibers. The cause of fiber breakage is believed to be due to contact between the spinning nozzle and the island components of the freshly spun fibers discharged from the spinning nozzle. Comparative Example 4 had a marine component thickness of 0.1 µm and was even thinner than Example 5 such that Comparative Example 4 had reduced spinnability and had difficulty in continuous winding. Comparative Example 5 had a marine component thickness of 3.0 μm and was even thicker than Example 6 such that Comparative Example 5 had good spinnability but exhibited poor thermoplastic deformability and large variation in the elastic moduli of the molded articles.

Comparative Examples 1 to 2 and 5 were characterized by unsatisfactory thermoplastic deformability and large variations in the elastic modulus of the molded products. Therefore, it is believed that using the sea island composite fibers of Comparative Examples 1 to 2 and 5 to produce a molded article results in uneven distribution in the molded product due to the retention of portions of the island component in the sea island composite fibers by the marine component.

Industrial applicability

The sea island structure composite fibers of the present invention are characterized by excellent thermoplastic deformability when melt processed into a mixture of fibers and matrix material such that the resulting molded article is expected to contain island component portions dispersed without causing unevenness, and sufficiently demonstrate the characteristics of the included composite fibers (such as hydrophilicity, high tensile strength, thermal insulating ability, lightness, weather resistance and electrical insulating ability). Such a resin molded product can suitably be used for applications that require the above-mentioned characteristics, such as building materials, automotive components, medical devices and shock absorbers.

While the present invention has been described in connection with preferred embodiments by way of example, those skilled in the relevant art will appreciate that various changes, additions and substitutions may be made without departing from the scope of the invention as disclosed in the claims.

Positional designations

A - island component;

B - marine component;

X is the thickness of the marine component.

Claims (12)

1. A composite fiber with an island structure in the sea, containing an island component and a marine component characterized by a melting point lower than that of the island component, where the fiber has an aspect ratio ranging from 2.0 to 5.0 in the cross section of the fiber and the marine component has a sea component thickness in the range of 0.2 to 2.0 μm, which is provided by a combination die, the sea component thickness being defined as the distance between the outer periphery of the fiber and the island component closest to the outer periphery on the minor axis of the fiber cross-section. 2. The fiber according to claim 1, wherein the island component contains an ethylene vinyl alcohol copolymer. 3. The fiber according to claim 1 or 2, wherein the marine component comprises a polyolefin resin. 4. The fiber according to any one of claims 1 to 3, wherein the sea island composite fiber has a single fiber fineness of 50 dtex or less. 5. The fiber according to any one of claims 1 to 4, wherein the island component has an aspect ratio of 5.0 or less. 6. The fiber of claim 5, wherein the aspect ratio for the island component has variations calculated as a CV value of 45% or less. 7. The fiber according to any one of claims 1 to 6, wherein the sea island structure composite fiber has a fiber length in the range of 0.5 to 30 mm. 8. The fiber according to any one of claims 1 to 7, wherein the composite fiber with an island structure in the sea contains a sizing agent applied at a proportion ranging from 0.1 to 30 wt.% based on the weight of the fiber. 9. The fiber according to any one of claims 1 to 8, wherein the fiber has a shrinkability capable of shrinking 10% of the fiber length in the longitudinal direction of the fiber in 500 seconds or less when the fiber is heated at 160°C with an attachment mass of 0.14 mg/dtex to one end of the fiber. 10. Using the sea island structure composite fibers according to any one of claims 1 to 9 for molding, wherein the matrix material and the sea island structure composite fibers are mixed to form a mixture; and the mixture is heated at a temperature equal to or greater than the melting point of the sea component and less than the melting point of the island component of the sea island structure composite fibers to form the mixture into a profile. 11. A molded article comprising, at least in part of the molded article, composite fibers with a sea island structure according to any one of claims 1 to 9. 12. A method for producing a molded product, the method comprising mixing a matrix material and composite fibers with an island structure in the sea according to any one of claims. 1 - 9 to obtain a mixture and heating the mixture at a temperature equal to or greater than the melting point of the sea component and less than the melting point of the island component of the composite fibers with an island structure in the sea to form the mixture into a profile.