JP6871892B2 - Manufacturing method of core-sheath composite fiber and core-sheath composite fiber - Google Patents

Description

The present invention relates to a core-sheath composite fiber and a method for producing a core-sheath composite fiber.

The core-sheath composite fiber is a fiber having a composite structure composed of a thread-like core material and a sheath material that wraps the core material like a sheath. By combining the core material and the sheath material having different properties, a single core material is used. It exerts various effects that are difficult to achieve with structural fibers. Core-sheath composite fibers are used not only as materials for woven fabrics such as filters, but also in various fields such as reinforcing materials for synthetic resin parts.

Patent Document 1 describes a composite fiber composed of high-density polyethylene as a sheath component and polyester as a core component, in which the melting temperature of the sheath component is 110 to 180 ° C. and the melting temperature of the core component is 240 to 270. A ceiling material for an automobile is disclosed, which forms a three-dimensional porous network structure by melting the sheath component by high-temperature pressurization and fusing with the reinforcing fiber at ° C.

Japanese Patent No. 51986647

In such a core-sheath composite fiber, the core materials of the core-sheath composite fiber are fused to each other to form a cover, and the cover is fused to the outer skin of the target to improve the rigidity of the target. Can be used for. Since a cover made of core-sheath composite fiber has a large number of core materials passing through it, it can be expected to have higher rigidity than a cover made of a simple resin sheet. However, when the conventional core-sheath composite fiber is used for such reinforcement, the following problems occur.

If the melting points of the sheath material and the core material are close to each other, it is easy for the core material to be melted together when the sheath material is melted, and it becomes difficult to form the core-sheath composite fiber into a composite or a sheet. The invention of Patent Document 1 discloses the range of melting points of the sheath material and the core material, but does not disclose how much the temperature difference between the sheath material and the core material should be. The melting point difference calculated from the disclosed melting point range is 60 ° C. to 160 ° C., but even the maximum value of 160 ° C. is slightly insufficient for easily molding a composite or the like.

An even bigger problem is the decrease in strength of the core-sheath composite fiber due to the difference in melting points between the core material and the sheath material.
In order to realize a core-sheath composite fiber having high strength and excellent as a reinforcing material, it is necessary that the core material and the sheath material are firmly adhered to each other. However, if the melting point difference between the sheath material and the core material is increased in order to improve the moldability of the composite or the like, on the other hand, the core material and the sheath material are likely to be separated. Since the invention of Patent Document 1 does not deal with the decrease in strength due to the separation of the core and the sheath, it is considered that the strength is insufficient for use in the purpose of reinforcement.
In view of such a situation, it is an object of the present invention to provide a core-sheath composite fiber which is easy to form a composite or the like and has excellent strength.

In the core-sheath composite fiber of the present invention, the main component of the core material is polyamide, the main component of the sheath material is modified polyethylene to which an unsaturated functional group is added, and the melting point of the core material is the melting point of the sheath material. It is characterized by being 180 ° C or more higher than that.

According to the present invention, it is possible to provide a core-sheath composite fiber that can be easily formed into a composite or the like and has excellent strength.

It is a cross-sectional view of the core-sheath composite fiber sliced into round slices. It is a vertical cross-sectional view which cut the core-sheath composite fiber in the long side direction. It is the schematic of the apparatus used for the rigidity measurement experiment of a core-sheath composite fiber. It is the schematic of the composite composed of a plurality of core-sheath composite fibers. It is the schematic of the sheet composed of a plurality of core-sheath composite fibers. It is an enlarged view of the cross section of the sheet composed of a plurality of core-sheath composite fibers. It is a perspective view which shows the example which reinforces a fuel tank with a cover made of a core-sheath composite fiber. It is a figure which shows the arrangement of the cover in the stage before blow molding of a fuel tank. It is a figure which shows the blow molding of a fuel tank. It is a figure which shows the state which the sandwiching is completed in the blow molding of a fuel tank.

Next, the core-sheath structure yarn according to the embodiment of the present invention will be described.
The present invention is not limited to the following embodiments.

<Core sheath structure>
FIG. 1A shows a cross-sectional view of the core-sheath composite fiber 10 of the present embodiment cut into round slices, and FIG. 1B shows a vertical cross-sectional view of the core-sheath composite fiber 10 of the present embodiment cut in the long side direction.
The core-sheath composite fiber 10 of the present embodiment is composed of a core material 11 and a sheath material 12 that wraps the core material 11, and is manufactured by extrusion molding. Both the core material 11 and the sheath material 12 of the present embodiment have an outer diameter having a round cross section. The outer diameter of the core material is not limited to such a round cross section, and may be, for example, a modified cross section having a plurality of protrusions.

The ratio of the core material 11 to the sheath material 12 in the cross section vertically sliced in the length direction as shown in FIG. 1A is preferably 99: 1 to 1:99, and is 90:10 to 10:90. More preferably. Rigidity can be improved by increasing the proportion of the core material. On the other hand, the adhesiveness can be improved by increasing the proportion of the sheath material.

The core-sheath composite fiber 10 may have an eccentric structure, but it is desirable that the core material 11 is arranged substantially in the center of the sheath material 12 as shown in FIG. By arranging the core material 11 substantially in the center of the sheath material 12, the exposure of the core material 11 from the sheath material 12 is suppressed when the composite 100 (see FIG. 3) or the like is formed from the core sheath composite fiber 10. Can be done. By suppressing the exposure of the core material 11, the sheath materials 12 can be firmly bonded to each other, and the composite 100 or the like can be firmly formed.

<Rigidity of core-sheath composite fiber>
As an application of the core-sheath composite fiber 10, for example, reinforcement of a fuel tank of an automobile or the like can be considered. Polyethylene is often used for the outer skin of such a fuel tank or the like. Therefore, in order to improve the fusion property between the core-sheath composite fiber 10 and the outer skin, it is conceivable to include polyethylene in the sheath material 12.

However, polyethylene is generally a substance that is difficult to form a bond with other substances, and it is difficult to firmly bond the core material 11 and the sheath material 12 containing polyethylene. Therefore, when polyethylene is used for the core material 11, the rigidity of the core-sheath composite fiber 10 may decrease due to the separation of the core material 11 and the sheath material 12. In particular, when molding the composite 100 (see FIG. 3) from the core-sheath composite fiber 10, if the melting point difference between the core material 11 and the sheath material 12 is increased in order to facilitate the molding, the core material 11 and the sheath material 12 become The decrease in rigidity becomes more problematic because the separation is likely to occur. The molding of the composite 100 will be described later.

Therefore, the present researchers used modified polyethylene in which an unsaturated functional group was added to polyethylene for the sheath material 12, and formed a hydrogen bond between the functional group and the sheath material 12 to form a core material. An attempt was made to realize a core-sheath composite fiber 10 having a large melting point difference between 11 and the sheath material 12 and high rigidity.

FIG. 2 shows a schematic view of an apparatus used for a rigidity measurement experiment of the core-sheath composite fiber 10.
As an example, a core-sheath composite fiber 10 using polyamide as the core material 11 and maleic acid-modified polyethylene as the sheath material 12 is used. As a comparative example, a core-sheath composite fiber using polyamide for the core material 11 and polyethylene for the sheath material 12 is used.

The core-sheath composite fiber 10 is fixed on two rollers 2 as shown in FIG. 2, and a force of 0.5 N is applied from above to downward, that is, in the direction of the arrow in the figure, to form the core-sheath composite. The displacement due to the elongation generated in the fiber 10 is measured and compared.

As a result of the measurement, the displacement of the core-sheath composite fiber 10 of the comparative example was 2.140 mm. On the other hand, the displacement of the core-sheath composite fiber 10 of the example was 1.762 mm. By comparing the two, the core-sheath composite fiber 10 of the example in which the maleic acid-modified polyethylene was used for the sheath material 12 was more rigid than the core-sheath composite fiber 10 of the comparative example in which the non-modified polyethylene was used for the sheath material 12. Was found to improve by 17%.

As described above, the main component of the core material 11 of the core-sheath composite fiber 10 is polyamide, and the main component of the sheath material 12 is modified polyethylene. The main component of the core material 11 means that it is contained in an amount of 40% by mass or more with respect to the entire components of the core material 11. The main component of the sheath material 12 means that it is contained in an amount of 40% by mass or more based on the total components of the sheath material 12.

<Material of core-sheath composite fiber>
The melting point difference between the core material 11 and the sheath material 12 is 170 ° C. or higher, preferably 180 ° C. or higher.
If the melting point difference is 170 ° C. or higher, the failure of melting the core material 11 when melting the sheath material 12 is unlikely to occur, and the composite 100 (see FIG. 3) or the like is formed from the core-sheath composite fiber 10. Becomes easier. The molding of the composite 100 will be described later.
Therefore, the polyamide as the main component of the core material 11 and the modified polyester as the main component of the sheath material 12 are selected in a combination such that the melting point difference between the two is 170 ° C. or more.

Details of each of the components of the core material and the sheath material will be described below.
(Core material)
The polyamide, which is the main component of the core material 11 of the present embodiment, is not particularly limited as long as it has a melting point difference of 170 ° C. or more from the modified polyethylene, which is the main component of the sheath material 12, but is used as a reinforcing material. From the viewpoint, it is preferable to have high rigidity. As the polyamide, for example, polyamide 6, polyamide 12, polyamide 66 and the like can be used.

(Sheath material)
The modified polyethylene, which is the main component of the sheath material 12 of the present embodiment, can be melted in blow molding of a fuel tank or the like to be fused, and has a melting point difference from the polyamide, which is the main component of the core material 11. Is not particularly limited as long as it has a melting point of 170 ° C. or higher and can form a hydrogen bond with the polyamide.

Examples of the method for obtaining modified polyethylene include graft modification. This is a method of imparting an unsaturated functional group to a carbon radical generated by cleaving a carbon-hydrogen bond of polyethylene. Carbon radicals can be generated by irradiation with electron beams or ionizing radiation, or by using radical generators such as organic and inorganic peroxides.
The functional group used for the modification can be selected from a carboxyl group, an amino group, a hydroxyl group, a silanol group and the like. Among these functional groups, a hydroxyl group is preferable, and a carboxyl group is more preferable.

The structural unit containing the functional group includes, for example, a structure derived from a compound such as an unsaturated carboxylic acid or a derivative thereof, a hydroxyl group-containing ethylenically unsaturated compound, an amino group-containing ethylenically unsaturated compound, or a vinyl group-containing organic silicon compound. The unit is mentioned. Among these structural units, a hydroxyl group-containing ethylenically unsaturated compound is preferable, and an unsaturated carboxylic acid or a derivative thereof is more preferable.
Examples of the unsaturated carboxylic acid or a derivative thereof include an unsaturated compound having one or more carboxylic acid groups, an ester of a compound having a carboxylic acid group and an alkyl alcohol, and an unsaturated compound having one or more anhydrous carboxylic acid groups. it can.

Examples of unsaturated carboxylic acids include acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and nadic acid [trademark] (endosys-bicyclo [2.2.1] hept -5-ene-2,3-dicarboxylic acid) and the like.
Examples of the unsaturated carboxylic acid derivative include maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate.

These unsaturated carboxylic acids and / or their derivatives can be used alone or in combination of two or more, with acrylic acid being preferred and maleic anhydride having high reactivity. More preferable in terms of points.

<Composite molding>
FIG. 3 shows a schematic view of a composite 100 composed of a plurality of core-sheath composite fibers 10.
FIG. 3 As shown in the upper figure of FIG. 3, a plurality of core-sheath composite fibers 10 are arranged side by side to form a bundle, and the sheath material 12 is melted by heating and then molded by cold pressing to form a polygonal cross section as shown in the lower figure of FIG. It can be a composite 100 having.
When the core-sheath composite fiber 10 is processed into the composite 100 in this way, it is easier to process the core-sheath composite fiber 10 into a sheet 101 (see FIG. 4A) than the core-sheath composite fiber 10 remains.

The heating method is not particularly limited, and IR (infrared) heater, hot air heating, hot plate heating, and the like can be considered. Among them, an IR heater and hot air heating are preferable because they are inexpensive and simple.

Although IR heaters and hot air heating are inexpensive, temperature differences are likely to occur due to differences in distance from the heat source, making temperature control difficult. However, in the case of the core-sheath composite fiber 10 of the present embodiment, the melting point difference between the core material 11 and the sheath material 12 is 170 ° C. or more. Even if the temperature of the material 12 becomes higher than necessary, the core material 11 is difficult to melt. Therefore, the core-sheath composite fiber 10 of the present invention can easily form the composite 100 by using an inexpensive IR heater or hot air heating at a low cost without requiring precise temperature control.

<Sheet molding>
FIG. 4A shows a schematic view of a sheet 101 composed of a plurality of core-sheath composite fibers 10, and FIG. 4B shows an enlarged view of a cross section of the sheet 101.
A sheet 101 can be obtained as shown in FIG. 4A by arranging a plurality of core-sheath composite fibers 10 or composite 100 and melting and fusing the sheath materials 12 to each other by heating. As shown in FIG. 4B, in the cross section of the sheet 101, a plurality of core materials are arranged in the melted and fused modified polyethylene, and the strength is higher than that of a simple resin sheet.

Such a sheet 101 can be easily processed into a cover 102 that is in close contact with the outer skin of a fuel tank or the like, rather than the core-sheath composite fiber 10 as it is. Generally, a fuel tank or the like has a complicated shape, and in order to create a cover 102 that has the same shape as the outside of the fuel tank or the like and can be closely attached to the cover 102, high workability is important. ..

<Fusion of fuel tank and cover>
FIG. 5 is a perspective view showing an example in which the fuel tank is reinforced with a cover made of core-sheath composite fiber 10.
The fuel tank is composed of a tank body T and two covers 102. In FIG. 5, the tank body T and the cover 102 are separated, but in reality, the tank body T and the upper and lower covers 102 are fused in the following steps.

6 to 8 show a schematic view of an apparatus for performing blow molding.
First, as shown in FIG. 6, the air suction device starts sucking air from the suction hole 44 prior to the arrangement of the cover 102 (dashed line arrow). After that, the preformed cover 102 is arranged inside the mold 42. The cover 102 has the same shape as the outer shape of the tank body T to be molded, and is in a state of being fitted to the mold 42.

Next, as shown in FIG. 7, the melted parison P is discharged from the die 41, for example, in a tubular shape. Along with this discharge, the parison P from which the left and right molds 42 are discharged is sandwiched. Further, at the same time as this sandwiching, compressed air is supplied to the inside of the parison P via the air pin 43 (solid arrow), and blow molding is performed. As a result, the parison P expands, and the expanded parison P is pressed against the cover 102 (see FIG. 8).

When the parison P and the cover 102 come into contact with each other, the heat of the parison P melts the portion of the cover 102 in contact with the parison P. As a result, the tank body T (Parison P) and the cover 102 are fused. The temperature of the parison P is preferably 160 ° C. to 190 ° C., more preferably 180 ° C. to 190 ° C.

10 Core-sheath composite fiber 11 Core material 12 Sheath material 100 Composite 101 Sheet 102 Cover 2 Roller 41 Die 42 Mold 43 Air pin 44 Suction hole (hole drilled in mold, fixing mechanism)
P parison (thermoplastic resin typified by polyethylene)
T tank body

Claims (6)

The main component of the core material is polyamide,
The main component of the sheath material is modified polyethylene with unsaturated functional groups.
A core-sheath composite fiber characterized in that the melting point of the core material is 180 ° C. or more higher than the melting point of the sheath material. The main component of the core material is polyamide,
The main component of the sheath material is modified polyethylene with unsaturated functional groups.
A composite of core-sheath composite fibers in which the melting point of the core material is 180 ° C. or higher higher than the melting point of the sheath material.
The core material has a circular cross section and includes a plurality of core materials.
A composite characterized in that the overall cross-sectional shape is polygonal. The core-sheath composite fiber according to claim 1, wherein the core-sheath composite fiber is used in a fuel tank. The composite according to claim 2, wherein the composite is used for a fuel tank. It is characterized by including a step of configuring the core material containing polyamide as a main component so that the melting point of the core material containing an unsaturated functional group is 180 ° C. or more higher than the melting point of a sheath material containing modified polyethylene as a main component. A method for producing a core-sheath composite fiber. The core-sheath composite fiber is formed by configuring the core material containing polyamide as the main component so that the melting point of the core material containing unsaturated functional groups is 180 ° C. or more higher than the melting point of the sheath material containing modified polyethylene as the main component. Process and
A method for producing a composite , which comprises a step of extruding a bundle of the core-sheath composite fibers in which the sheath material is melted by a cold press to form a composite having a polygonal cross section.

Images