Patent Description:
Fabric-feel resin molded articles having a cloth-like outer appearance (hereinafter, called fabric-feel molded articles) are used in a variety of fields for interior parts of vehicles such as automobiles and trains, interior materials of buildings such as houses and offices, furniture, interior goods, daily commodities, and others. As methods for forming fabric-feel molded articles, there have been conventionally a method by which short fibers are fixed to the surface of a resin molded article (see <CIT>) and a method by which a cloth pattern is formed by printing on the surface of a resin molded article (see <CIT>).

There has also been proposed a facing material with a textured concave-convex pattern on the surface of a base material for actualizing a more natural fabric design (see <CIT>). Further, there has been proposed a fabric-feel thermal barrier film material in which a resin layer is impregnated in and applied to both surfaces of fiber cloth for achieving surface characteristics of causing fewer ravels and abrasions while providing a fabric-specific outer appearance image by natural fibers (see <CIT>). In the thermal barrier film material described in <CIT>, core-in-sheath spun threads of yarn are used for at least one of warps and wefts constituting fiber cloth.

Core-in-sheath spun threads of yarn are also used in <CIT> to produce a woven fabric, a knitted fabric or a nonwoven fabric for use in a molded article, in <CIT> to produce a woven fabric, and in <CIT> to produce a nonwoven fabric. In <CIT>, the threads of yarn have a constitution as specified in the preamble of claim <NUM>.

However, the above-mentioned conventional fabric-feel molded articles have problems described below. The fabric-feel molded article described in <CIT> takes a lot of work with a complicated process of fixing short fibers to the surface of the molded article. The fabric-feel molded article described in <CIT> can be easily produced by laminating a cloth pattern-printed sheet on the base sheet, but it is difficult to provide the molded article by printing with gloss and texture of real cloth from when viewed from any direction.

Further, in the fabric-feel molded article described in <CIT>, a fiber-feel pattern is formed by finely engraving the surface of a sheet-like material. According to this method, however, it is not possible to provide the molded article with a fiber-specific gloss varying depending on the angle from which it is viewed, and it is difficult to imitate the texture of a real fiber material. In this regard, the fabric-feel molded article described in <CIT> is formed from fiber cloth and has an outer appearance close to real cloth. However, this fabric-feel molded article is inferior in processability due to yarn twisting and impregnation processes, and is also inferior in formability after molding the film material due to the use of twisted yarn and impregnated resin.

An object of the present invention is to provide a composite fiber from which a fabric-feel molded article having fiber texture can be obtained and a fabric-feel molded article using the composite fiber.

To solve the above-mentioned problems, the inventor of the present invention has found as a result of earnest experiments and examinations that forming woven cloth, knitted cloth, or braided cloth from a composite fiber with a specific optical characteristic and thermally molding the woven cloth, knitted cloth, or braided cloth would make it possible to obtain a fabric-feel molded article with texture closer to a real fiber, and has completed the present invention. In the present invention, the term "texture" means a visual impression from the color tone, pattern, gloss, and others of a fiber, and the phrase "having fiber texture" means that, in a fabric made of fiber of two vertical and horizontal axes, for example, the difference in brightness between warps and wefts resulting from the fiber's optical anisotropy can be visually recognized and, when the fabric is rotated <NUM>°, a light-and-dark change occurs between the warps and wefts as in the case of real cloth.

The composite fiber according to the present invention is a composite fiber as specified in claim <NUM>.

The composite fiber according to the present invention may have the features specified in claims <NUM> to <NUM>.

The molded article according to the present invention is a molded article as specified in claim <NUM>.

According to the present invention, the use of the composite fiber having the specific optical characteristic makes it possible to achieve a fabric-feel molded article with a fiber texture.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.

First, a composite fiber according to a first embodiment of the present invention will be described. <FIG> is a diagram schematically illustrating a cross-section structure example of the composite fiber according to the present embodiment, which is a cross-sectional view perpendicular to a longitudinal direction (drawing direction). As illustrated in <FIG>, the composite fiber <NUM> according to the present embodiment is a sea-island composite fiber in which a plurality of island components <NUM> is interspersed in a sea component <NUM> of which a cross section is perpendicular to the longitudinal direction, and the island components <NUM> are continuous in a length direction.

The sea component <NUM> is a binder (matrix) component for unifying the plurality of island components <NUM>, which is made of a thermoplastic resin (hereinafter, called first thermoplastic resin) and has a parallel light transmittance of <NUM>% or more. The "parallel light transmittance" here takes on a value obtained by measuring a sheet-like sample with a thickness of <NUM> ± <NUM> by a Haze meter.

As described later, when a fabric-feel molded article is formed using the composite fiber <NUM> in the present embodiment, the color tone and pattern of the fiber constituting a fabric design are represented by the island components <NUM>. However, when the parallel light transmittance of the sea component <NUM> is less than <NUM>%, the island components <NUM> become difficult to see and the color tone and pattern of the fiber constituting the fabric design in the molded article becomes unclear. The sea component <NUM> preferably has a parallel light transmittance of <NUM>% or more, which makes a texture of the molded article closer to real cloth.

Examples of the first thermoplastic resin constituting the sea component <NUM> include propylene copolymers (co-PP) such as an ethylene-propylene random copolymer and linear low-density polyethylene (LLDPE). However, the first thermoplastic resin is not limited to these examples but can be any thermoplastic resin with a parallel light transmittance of <NUM>% or more. The first thermoplastic resin may be a polymer alloy in which two or more kinds of polymers are mixed and may be mixed with various additives such as an antioxidant, neutralizer, light stabilizer, lubricant, and antistatic agent, and pigments for coloring as far as the foregoing range of the parallel light transmittance can be maintained.

The island components <NUM> are components that represent the color tone and pattern of the fiber in the fabric-feel molded article, which are made of a thermoplastic resin higher in melting point than the first thermoplastic resin (hereinafter, called second thermoplastic resin) and have a crystallinity of <NUM>% or more. When the melting point of the second thermoplastic resin constituting the island components <NUM> is equal to or less than the melting point of the first thermoplastic resin, the island components <NUM> will melt at the time of yarn spinning or drawing, so that the it is not possible to obtain the composite fiber <NUM> of a sea-island cross section structure in which the island components <NUM> are interspersed in the sea component <NUM>. The melting point of the second thermoplastic resin is preferably higher by <NUM> or more than the melting point of the first thermoplastic resin from the viewpoint of the ease of manufacturing the composite fiber <NUM> and the fabric-feel molded article.

In addition, when the fabric-feel molded article is formed using the composite fiber <NUM>, the color tone and pattern of the fiber are represented by the orientation of the crystalline resin constituting the island components <NUM>. Thus, when the oriented crystallization of the second thermoplastic resin constituting the island components <NUM> is insufficient, the difference in brightness between the warps and wefts becomes smaller to make the pattern of the fabric design hard to see. Specifically, when the crystallinity of the island components <NUM> is lower than <NUM>%, the difference in brightness between the warps and the wefts in the fabric-feel molded article becomes smaller to decrease the visibility of the color tone and pattern. Therefore, the crystallinity of the island components <NUM> is <NUM>% or more. In addition, the crystallinity of the island components <NUM> is preferably <NUM>% or more from the viewpoint of improving the texture of the formed fabric-feel molded article.

The crystallinity of the island components <NUM> can be measured by a differential scanning calorimeter (DSC). In general, in the case of measuring the melting point of a resin by using a DSC, the rate of temperature rise is set to <NUM>/minute. However, in the case of measuring the heat amount of fusion in an object having caused oriented crystallization such as a drawn object to determine a difference in crystallinity in fiber, a lower rate of temperature rise would advance the crystallization during the temperature rise so that the heat amount of fusion would be measured in a state different from the pre-measurement state. Accordingly, in the present invention, the crystallinity of the island components is prescribed as a value obtained by measurement at a rate of temperature rise of <NUM>/minute.

Examples of the second thermoplastic resin constituting the island components <NUM> include polypropylene (PP), polyethylene (PE), crystalline polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and nylons. However, the second thermoplastic resin is not limited to these examples but may be any thermoplastic resin that is higher in melting point than the first thermoplastic resin and has a crystallinity of the island components <NUM> of <NUM>% or more when being drawn into a composite fiber. The second thermoplastic resin may be a polymer alloy in which two or more kinds of polymers are blended, and may be mixed with various additives such as an antioxidant, neutralizer, light stabilizer, lubricant, and antistatic agent, and pigments for coloring as far as the second thermoplastic resin does not affect the effect of the present invention.

In the composite fiber <NUM> of the present example, the component ratio between the sea component <NUM> and the island components <NUM> (sea component/island components) is <NUM>/<NUM> to <NUM>/<NUM> in volume. The proportion of the island components <NUM> in the composite fiber <NUM> is <NUM> to <NUM> volume%. When the proportion of the island components <NUM> in the composite fiber <NUM> is smaller than <NUM> volume%, the thickness of the sea component <NUM> from the surface of the composite fiber <NUM> will increase and the color tone and pattern of fiber represented by the island components <NUM> will become hard to view. On the other hand, when the proportion of the island components <NUM> in the composite fiber <NUM> exceeds <NUM> volume%, the sea component <NUM> as a binder component will become lacking, which will make it difficult to form the composite fiber <NUM> into a molded article such as a sheet by heat processing.

Next, a method for manufacturing the composite fiber <NUM> according to the present embodiment will be described. <FIG> is a diagram schematically illustrating a cross-section structure example of undrawn yarn used for the composite fiber <NUM> illustrated in <FIG>. The composite fiber <NUM> in the present embodiment can be formed using core-in-sheath undrawn yarn with a cross section structure as illustrated in <FIG>, for example. In that case, a sheath part <NUM> of the undrawn yarn constitutes the sea component <NUM> of the composite fiber <NUM> and a core part <NUM> of the same constitutes the island components <NUM>. Thus, the sheath part <NUM> is formed from the first thermoplastic resin, and the core part <NUM> is formed from the second thermoplastic resin.

About <NUM> to <NUM> threads of undrawn yarn of the core-in-sheath structure are bound together, then are drawn and unified while being heated at a temperature that is equal to or higher than the melting point of the resin constituting the sheath part <NUM> (the first thermoplastic resin) to equal to or lower than the melting point of the resin constituting the core part <NUM> (the second thermoplastic resin). This makes it possible to obtain the composite fiber <NUM> in which the plurality of island components <NUM> is interspersed in the sea component <NUM>. The method for manufacturing the composite fiber <NUM> in the present embodiment is not limited to the foregoing method but the drawing process and the unifying process may be separately performed, for example.

As described above in detail, the composite fiber in the present embodiment has the sea-island cross section perpendicular to the longitudinal direction, and the parallel light transmittance of the sea component is <NUM>% or more, the crystallinity of the island components is <NUM>% or more, and the proportion of the island components is <NUM> to <NUM> volume%, thereby improving the visibility of the color tone and pattern in the fabric-feel molded article. The use of the composite fiber in the present embodiment makes it possible to achieve the fabric-feel molded article with a fiber texture.

Next, a molded article according to a second embodiment of the present invention will be described. The molded article in the present embodiment is a fabric-feel molded article that is formed by thermally molding woven cloth, knitted cloth, or braided cloth in which threads of yarn are arranged in two or more directions. In the woven cloth, knitted cloth, and braided cloth used in the molded article of the present embodiment, the composite fiber <NUM> of the first embodiment is used for two or more axes.

The "woven cloth", "knitted cloth", and "braided cloth" used in the molded article of the present embodiment is a fabric formed by combining threads of yarn of two or more axes, and among the constitutional threads of the raw yarn, threads of yarns of two or more axes cross each other at an angle. For example, plain-woven cloth, twill-woven cloth, satin-woven cloth, and others formed from treads of yarn in two or more axes fall under the category of woven cloth, and tri-axial braided cloth and the like fall under the category of braided cloth. There is no particular limitation on the methods for producing the woven cloth, knitted cloth, and braided cloth but the woven cloth, knitted cloth, and braided cloth can be produced by any publicly known methods.

The molded article in the present embodiment is manufactured by thermally molding the woven cloth, knitted cloth, or braided cloth using the composite fiber <NUM> in the first embodiment for two or more axes. There is no particular limitation on the method for thermal molding but any method can be selected as appropriate according to the purpose or shape of the molded article, such as a thermal press molding method or a molding method using non-contact heating including infrared heating. At that time, the heating temperature is preferably higher than the melting point of the sea component <NUM> (the first thermoplastic resin) and lower than the melting point of the island components <NUM> (the second thermoplastic resin) from the viewpoint of improving the moldability and the visibility of color tone and pattern. Accordingly, in the composite fiber <NUM>, only the sea component <NUM> melts and the island components <NUM> remain in the non-melted state. As a result, the difference in brightness between the warps and wefts represented by the island components <NUM> provides the molded article with a texture close to a real fiber material.

There is no particular limitation on the shape of the molded article in the present embodiment but the molded article can have any of various shapes such as sheet shape, substantially box shape, and curved shape.

As described above in detail, the molded article in the present embodiment is formed by thermally molding woven cloth, knitted cloth, or braided cloth formed from the composite fiber in the first embodiment, which makes it possible to obtain the fabric-feel molded article in which the color tone and pattern are close to real cloth and the fiber texture is reproduced.

Advantageous effects of the present invention will be specifically described with reference to examples and comparative examples. Sheet-like molded articles (hereinafter, simply called sheets) of the examples and the comparative examples were produced by methods described below and were evaluated for texture.

Two hundred forty threads of undrawn yarn of core-in-sheath structure were bound together to produce a composite fiber of sea-island structure that had island components made of a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) and having a degree of crystallinity of <NUM>%) and a sea component made of a PE (UZ4051 with a melting point of <NUM> produced by Prime Polymer Co. ) and having a parallel light transmittance of <NUM>% and in which the volume ratio of the sea component to the island components was <NUM>/<NUM>.

The composite fiber was woven to obtain plain-woven cloth and the cloth was thermally molded to obtain the sheet of the example <NUM>. The thermal molding was performed such that the woven cloth was sandwiched between iron plates to which fluorine resin sheets were stuck, set in a thermal press machine having been heated to <NUM>, heated at <NUM> for one minute to melt the sea component, and pressurized for one minute at <NUM> MPa while remaining heated at <NUM>. The thermally molded sheet was cooled to <NUM> or less in the pressurized state by water-cooling the thermal press machine, and was taken out of the thermal press machine.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a resin in which a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) was mixed with <NUM> mass% of a red pigment (PPM(F) <NUM> red produced by Tokyo Printing Ink Mfg Co. ) and the sea component was formed from a PE (SP1071C with a melting point of <NUM> produced by Prime Polymer Co. In the composite fiber, the crystallinity of the island components was <NUM>%, and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a resin in which a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) was mixed with <NUM> mass% of a black pigment (TPM 9BB019 produced by Tokyo Printing Ink Mfg Co. In the composite fiber, the crystallinity of a resin forming the island components was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a resin in which a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) was blended with a homo-PP (S135 with a melting point of <NUM> produced by Prime Polymer Co. ) and the sea component was formed from a co-PP (Y2045GP with a melting point of <NUM> produced by Prime Polymer Co. In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) and the sea component was formed from a PE (SP1071C with a melting point of <NUM> produced by Prime Polymer Co. In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain tri-axial braided cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a PET (NEH2050 with a melting point of <NUM> produced by Unitika Ltd. ) and the sea component was formed from a co-PP (WFW4 with a melting point of <NUM> produced by Japan Polypropylene Corporation). In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) and the sea component was formed from a HDPE (S6932 with a melting point of <NUM> produced by Keiyo Polyethylene Co. In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a resin in which a homo-PP (Y2000GV with a melting point of <NUM> produced by Prime Polymer Co. ) was mixed with <NUM> mass% of a black pigment (TPM 9BB019 produced by Tokyo Printing Ink Mfg Co. ) and the sea component was formed from a resin in which a PE (SP1071C with a melting point of <NUM> produced by Prime Polymer Co. ) was mixed with a black pigment (EPE-K522432 produced by K. Since this composite fiber was lower in draw ratio than the composite fiber used in the example <NUM>, the crystallinity of the island components including the black pigment was <NUM>% and the parallel light transmittance of the sea component including the black pigment was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet in comparative example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the island components were formed from a PET (NEH2050 with a melting point of <NUM> produced by Unitika Ltd. ) and the sea component was formed from a resin in which a co-PP (WFW4 with a melting point of <NUM> produced by Japan Polypropylene Corporation) was mixed with <NUM> mass% of a white pigment (TPM 1BB111 WHITE MF AL produced by Tokyo Printing Ink Mfg Co. In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component including the white pigment was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of comparative example <NUM>.

A composite fiber was produced by the same method and under the same conditions as those of the example <NUM>, except that the draw ratio was decreased in the drawing step. In the composite fiber, the crystallinity of the island components was <NUM>% and the parallel light transmittance of the sea component was <NUM>%. The composite fiber was woven to obtain plain-woven cloth, and the cloth was thermally molded by the same method and under the same conditions as those of the example <NUM> to obtain the sheet of comparative example <NUM>.

The "crystallinity" and the "parallel light transmittance" of the thermoplastic resins used in the examples <NUM> to <NUM> and the comparative examples <NUM> to <NUM> were measured by the following methods.

The crystallinity of the island components was measured by a differential scanning calorimeter (DSC). Specifically, <NUM> of raw yarn sample (composite fiber) was set in the DSC, heated at a rate of temperature rise of <NUM>/minute to melt at a temperature of <NUM>. Then, the sample was cooled at a rate of temperature drop of <NUM>/minute, and was left at a temperature of <NUM> in an isothermal condition for five minutes. This sample was heated again to <NUM> at a rate of <NUM>/minute.

Then, an area (J) of a melting peak of the island components was measured and divided by mass (g) of the island components to determine heat amount of fusion (J/g). Then, the crystallinity of the island components was determined by the following equation <NUM> from the heat amount of fusion at the first time of temperature rise (ΔHm), the heat amount of fusion at the second time of temperature rise (ΔHc), and the heat amount of fusion of perfect crystal (ΔHm0).

Resin (raw material pellets) forming the sea component was uniformly arranged on an iron plate with a fluorine resin sheet stuck, and surrounded by an iron frame with a thickness of <NUM>. Another iron plate with a fluorine resin sheet stuck was placed on the resin. In this state, the iron plates were set into a thermal press machine having been heated to a temperature equal to or higher than the melting point of the sample to be measured, then heated for one minute to melt the resin, and then pressurized for one minute at <NUM> MPa while being further heated. Then, the sample was taken out of the thermal press machine and put into water together with the iron plates for rapid cooling. By the foregoing process, a resin sheet with a thickness of <NUM> ± <NUM> was produced. This resin sheet for measurement was used to measure the parallel light transmittance by a Haze meter (NDH-<NUM>, a light source halogen lamp produced by Nippon Denshoku Industries Co.

Next, the glossiness, color tone, and pattern of the sheets in the examples and comparative examples produced by the methods described above were measured by the following methods.

The composite fibers used in the examples and the comparative examples were arranged on a flat plate in parallel to one another without a gap. The overlaps between the composite fibers would not cause a problem and thus were left intact. The composite fibers arranged in substantially parallel were pressurized while being heated at a temperature at which only the sea component was melted, thereby to obtain sheet-like molded articles in which the island components were arranged in one axis. Then, the glossinesses of the sheet-like molded articles were measured in the longitudinal direction and the width direction by using a glossmeter (a light source tungsten bulb produced by Suga Test Instruments Co.

The sheets of the examples and the comparative examples were placed under electric light of <NUM> lux and were visually observed by a panel of five examiners who judged whether it was possible to identify the pattern generated by a difference in light and dark between fibers with different axes (a difference in brightness between warps and wefts) and the color tone of the fibers. As a result, the sheets judged as identifiable by all the (five) examiners were given the symbol ∘, the sheets judged as identifiable by three or four examiners were given the symbol △, and the sheets judged as identifiable by two or less examiners were given the symbol ×.

Table <NUM> shows the foregoing results as follows:
<IMG>.

As shown in Table <NUM>, in the sheets of the comparative example <NUM> and the comparative example <NUM> in which the parallel light transmittance of the sea component was less than <NUM>%, the fiber pattern was visible but the color tone was hard to see. In addition, in the sheet of the comparative example <NUM> in which the parallel light transmittance of the sea component was <NUM>% or more but the crystallinity of the island components was less than <NUM>%, the difference in brightness between the warps and wefts was small and the visibility of the fiber pattern and color tone was inferior.

Claim 1:
A composite fiber (<NUM>) of a sea-island structure in which, in a sea component (<NUM>) of which a cross section vertical to a longitudinal direction is made of a first thermoplastic resin, a plurality of island components (<NUM>) made of a second thermoplastic resin higher in melting point than the first thermoplastic resin is interspersed, wherein
the island components (<NUM>) have a crystallinity of <NUM>% or more as measured by a differential scanning calorimeter at a rate of temperature rise of <NUM>/min, and
the volume ratio of the island components (<NUM>) is <NUM> to <NUM>%,
characterized in that
the sea component (<NUM>) has a parallel light transmittance of <NUM>% or more as obtained by measuring a sheet-like sample of the first thermoplastic resin with a thickness of <NUM> ± <NUM> by a Haze meter.