JP3235868B2 - Core-sheath composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core-sheath conjugate fiber which has a high elastic modulus, hardly deteriorates in physical properties when absorbing moisture, and is suitable as a reinforcing fiber for various composite materials.

[0002]

2. Description of the Related Art In general, polyamides are widely used in fiber materials, general molding materials, structural materials, etc., utilizing their excellent properties.

[0003] Polyamide fibers such as nylon 6 and nylon 66 are generally used. These have a glass transition temperature of about 50 ° C, and suddenly in a temperature range exceeding the glass transition temperature. There is a disadvantage that the elastic modulus is reduced. In addition, these have a high water absorption speed,
Since the saturated water absorption is also high, there is a disadvantage that the mechanical strength and the rigidity at the time of moisture absorption are greatly reduced.

[0004] Therefore, for various material applications in which deterioration of physical properties in a high temperature region or under moisture absorption is a problem,
It was extremely difficult to use general polyamide fibers.

[0005] Nylon 12 and the like have low water absorption, but also have a low glass transition temperature.
In a high temperature region such as at least ℃, the elastic modulus is greatly reduced.

[0006] On the other hand, amorphous polyamide is excellent in mechanical strength, impact resistance, abrasion resistance, solvent resistance, dimensional stability, insulating properties, etc. as well as transparency, so that various types of mechanical parts, Although it is used for equipment parts and the like, it has been practically hardly used as a fiber, particularly as a multifilament, because of its poor melt drawability due to its amorphous nature.

[0007]

In view of the above, the present invention has a high elastic modulus which can be widely used in various material fields and the like, and is particularly suitable as a reinforcing fiber for various composite materials. An object of the present invention is to provide a core-in-sheath conjugate fiber that can be used for a fiber.

[0008]

The present invention has the following arrangement to solve the above-mentioned problems.

That is, according to the present invention, the polymer constituting the sheath component is a polymer having a water absorption of 1% or less when immersed in water at 23 ° C. for 24 hours, and the polymer constituting the core component at 60 ° C. Amorphous polyamide whose storage shear modulus G 'is larger than G' of the polymer constituting the sheath component.
A sheath-core composite fiber, which is a de.

The amorphous polyamide referred to in the present invention is different from a straight-chain aliphatic nylon such as nylon 6 or nylon 66 in that the crystallization of the polymer hardly occurs or the crystallization speed is extremely low. Point to.

The amorphous polyamide is also called a transparent polyamide (transparent nylon) and gives a transparent molded article under ordinary melt molding conditions, and the molded article is subjected to post-crystallization even during heat treatment and water absorption treatment. It is a polyamide that does not cause devitrification.

The term "amorphous" as used in the present invention indicates a heat of crystal fusion of 1 cal / g or more when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). What does not exist. In the present invention, “crystalline” means:
When measured at a heating rate of 10 ° C./min using a differential scanning calorimeter, it indicates a crystal heat of fusion of 1 cal / g or more.

Further, the “glass transition temperature” in the present invention
Can also be generally determined by a differential scanning calorimeter.

Since the amorphous polyamide has no crystalline phase, its thermal properties such as heat resistance are almost dominated by the glass transition temperature (Tg). Therefore, in order to satisfy the heat resistance required for practical use, the Tg of the amorphous polyamide must be high.

In the present invention, the amorphous polyamide that can be preferably used as the core component of the core-sheath conjugate fiber has a Tg in a dry state of 100 ° C. to 200 ° C.

Amorphous polyamide is practically used in a temperature range below Tg where the motion of the polymer chains is frozen, and therefore has a smaller linear expansion coefficient than crystalline polyamide and is excellent in dimensional stability. .

The heat distortion temperature (HDT) also corresponds to Tg.

As with the glass transition temperature, an important physical property required for the polymer constituting the fiber in practical use is the dynamic elastic modulus. The dynamic elastic modulus of the amorphous polyamide does not change much in the temperature range of Tg or lower, and sharply decreases from the vicinity of Tg, leading to plasticization and fluidization. This viscoelastic behavior is significantly different from crystalline polyamide.

The polymer which can be preferably used as the polymer constituting the core component of the core-sheath conjugate fiber of the present invention has a storage shear modulus G 'of 5 × 10 ⁹ dyne in a dry state in a temperature range from room temperature to 120 ° C. / Cm ² or more, and even in a relatively high temperature range of, for example, 80 to 100 ° C., the deterioration in physical properties is extremely small and stable.

The dry state in the present invention means that a sample is 1
It refers to a state of being vacuum-dried at 00 ° C. for 2 hours to 20 hours.

The behavior of an amorphous polyamide under moisture absorption is extremely specific among polyamide polymers which are considered to have a large change in properties due to moisture absorption.

Amorphous polyamide has a lower water absorption rate and a lower saturated water absorption rate than nylon 6 or nylon 66.
Therefore, the retention rate of the mechanical strength, rigidity, and electrical properties of the amorphous polyamide when absorbing moisture compared to when absolutely dry is significantly superior to that of nylon 6 or 66, and the amide group concentration is low and the moisture absorption is relatively low. Nylon 610, which is less susceptible to
Better than.

The polymer which can be preferably used as a polymer constituting the core component of the core-sheath conjugate fiber of the present invention is a storage shear from room temperature to 100 ° C. in a water-absorbed state immersed in boiling water at 90 ° C. or higher for 24 hours. Elastic modulus G '
Is 4 × 10 ⁹ dyne / cm ² or more, and a decrease in physical properties under moisture absorption is small and stable.

On the other hand, crystalline polyamides such as nylon 6 and nylon 66 are excellent in mechanical properties at room temperature and the like, and also excellent in spinnability during melt spinning, that is, excellent in fiber forming ability. Although widely used as clothing fibers, it has the above-mentioned drawbacks, and is therefore unsuitable for various materials and the like in which the deterioration of physical properties in a high-temperature region or under moisture absorption becomes a problem.

However, a low-water-absorbing crystalline polyamide typified by nylon 12 or another low-water-absorbing polymer is not combined with a single fiber but with a high-rigidity polymer such as an amorphous polyamide. When used together, they may compensate for each other's drawbacks and create new properties not found in both single fibers.

As a specific example of the present invention, an amorphous polyamide having a high elastic modulus is used as a core component of the core-sheath composite fiber.
By disposing a crystalline polyamide having a low water absorption to the sheath component, the spinnability in melt spinning of the amorphous polyamide is improved, and industrially stable production is enabled. It has succeeded in sufficiently exhibiting excellent physical properties under moisture absorption.

As for the polymer constituting the sheath component, 2
The water absorption when immersed in water at 3 ° C. for 24 hours is practically preferably 1% or less, and more preferably 0.7% or less.

Further, the fiber of the present invention can be suitably used as a reinforcing fiber for various composite materials, and the high crystallinity, which is used as a specific example of the sheath component constituting the present invention represented by nylon 12, is used. The reactive polyamide has a tan δ dispersion peak area of tan δ in dynamic viscoelasticity measurement larger than nylons 6 and 66 and is excellent in low-temperature impact characteristics. Therefore, the core-sheath composite fiber of the present invention, when used for various composite materials for the purpose of improving impact resistance, etc.,
Excellent characteristics can be exhibited. Moreover, because the adhesiveness between the core polymer and the sheath polymer is good, it maintains an extremely stable fiber structure even when it is arranged in a manufacturing process, a post-processing process, or another material. It is possible to exhibit physical properties stably.

In order to improve the impact resistance of the conjugate fiber while maintaining the excellent properties of the core component polymer at high temperatures, the storage shear modulus G ′ of the sheath component polymer is larger than that of the core component polymer G ′. Small is preferred, especially 8
The storage shear modulus G ′ of the sheath component polymer in the temperature range of 0 ° C. to 120 ° C. is preferably smaller than that of the core component polymer G ′, and the core component polymer maintains excellent properties under moisture absorption. In order to improve the impact resistance of the conjugate fiber, G ′ of the sheath component polymer having an arbitrary moisture content in the temperature range of 80 ° C. to 100 ° C. is 9%.
It is preferably smaller than G ′ of the core component polymer in a water-absorbed state after immersion treatment in boiling water at 0 ° C. or higher for 24 hours.

Specific examples of the polymer constituting the most preferable core component used in the present invention include an amorphous polyamide composed of the following three types of monomers.

Bis (3-methyl-4-aminocyclohexyl) methane isophthalate, that is, 4,4'-diamino-3,3'-dimethyldicyclohexylenemethane ω-laurolactam Specific examples of the polymer constituting the component include nylon 12 which is a crystalline polyamide produced by ring-opening polymerization of ω-laurolactam or polycondensation of 12-aminododecanoic acid.

With respect to the ratio of the core component polymer and the sheath component polymer constituting the present invention, excellent impact resistance is exhibited while maintaining the high temperature characteristics and the characteristics under moisture absorption of the core component polymer. For stable production, the cross-sectional area ratio of the core component polymer and the sheath component polymer in an arbitrary fiber cross section is preferably in the range of core / sheath = 30/70 to 95/5, and 50/50 to 90 / Particularly preferred is a range of 10.

Regarding the arrangement of the core and the sheath of the composite fiber,
Basically, it is preferable that the core is concentric. However, as long as the sheath is too thin and the portion where the core is exposed is not large, eccentricity or multi-core may be acceptable. Further, the cross-sectional shape of the entire conjugate fiber may be a deformed cross-section other than the round cross-section.

[0034] As a method for producing the core-sheath composite fiber of the present invention, first, the core component polymer and the sheath component polymer are separately melted and led to a spinning head, and the core-sheath structure is formed by a known method. And a general spinning method such as spinning from a spinneret after forming a composite stream.

The spun yarn is taken up at a predetermined speed after refueling and wound up into a package.

In order to widely use the core-sheath conjugate fiber of the present invention in various material fields, it is necessary that the multifilament having 3 or more, preferably 5 or more filaments can be flexibly passed through various post-processing steps. It is preferable in making it.
When used as a reinforcing fiber of various composite materials, a multifilament is preferable for sufficiently exhibiting the reinforcing effect.

In order to widely use the core-sheath conjugate fiber of the present invention in various material fields, the tensile strength is 1 g / d or more, preferably 1.5 g / d or more, and the boiling water shrinkage is 15%.
It is practically suitable that the dry heat shrinkage after dry heat treatment at 140 ° C. for 30 minutes is 10% or less, preferably 8% or less.

[0038]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

The physical properties in the examples are measured by the following methods.

(Storage Shear Modulus G 'in Dry State)
First, a test piece having a width of 12 mm, a thickness of 2 mm, and a length of 60 mm was prepared.
It was vacuum-dried at 00 ° C. for 3 hours, and measured by a dynamic viscoelasticity measuring apparatus, RDA-700, manufactured by Rheometrics Co., Ltd., at a substantial measurement sample length of 42 mm and a heating rate of 5 ° C./step.

(Storage Shear Modulus G 'in Water Absorbing State)
First, a 9 mm wide, 2 mm thick, 60 mm long test piece was
The test piece was immersed in boiling water at 4 ° C. for 24 hours, immediately immersed in water at room temperature until the test piece reached room temperature, and immediately before the measurement, the water adhering to the sample surface was wiped off, and the measurement was performed in the same manner as in the dry state.

[0042] (boiling water shrinkage percentage) initial length l was immersed for 30 minutes in boiling water yarns _0, the subsequent yarn length l _1,
It was measured under a load of 1/30 (g / d) and calculated by the following equation.

[0043]

(Equation 1)

[0044] The (dry heat shrinkage) yarns of the initial length l ₀ 140
℃ placed in the hot air dryer for 30 minutes, followed by the yarn length l ₁ was measured under a load of 1/30 (g / d), was calculated by the following equation.

[0045]

(Equation 2)

(Examples 1 to 6) Isophthalic acid and 4,4 '
TR55 (manufactured by EMS, glass transition temperature: 155), which is an amorphous polyamide comprising -diamino-3,3'-dimethyldicyclohexylenemethane and ω-laurolactam
C.) The polymer chips were vacuum-dried at 120 ° C. for 14 hours and then melted using a first extruder. On the other hand, nylon 12 (L2140, manufactured by Daicel Huls, glass transition temperature 41 ° C., 23) The water absorption when immersed in water at 24 ° C. for 24 hours is 0.25%.
After vacuum drying at 12 ° C. for 12 hours, the mixture was melted using a second extruder. Each of the melt streams is led to the spinning head, and a composite stream is formed using TR55 as a core component and nylon 12 as a sheath component so as to have a ratio of the core component and the sheath component as shown in Table 1, and then a hole diameter of 0. Using a spinneret provided with 24 3 mm circular spinnerets, each was spun at a spinning temperature shown in Table 1, and after lubrication, it was taken up at a spinning speed shown in Table 1 and wound up into a package.

The core / sheath component ratio in Table 1 means the cross-sectional area ratio of each core-sheath component polymer in the fiber cross section. In each of the examples, the denier of the conjugate fiber is 150 denier. The discharge rate of each component polymer was adjusted for each example to obtain a multifilament yarn of 150 denier / 24 filaments.

FIG. 1 shows the measurement results of the storage shear modulus G 'of the polymer constituting the core component of the conjugate fiber of this example in the dry state and the water-absorbing state.

FIG. 2 shows an example of comparison between G ′ of the polymer constituting the core component and G ′ of the polymer constituting the sheath component of the composite fiber of the present embodiment in a dry state.

[0050]

[Table 1]

[0051]

According to the present invention, there is provided a fiber having a high modulus of elasticity up to a high-temperature region and a small decrease in physical properties at the time of moisture absorption. Can be suitably used for various material applications in which is a problem.

Further, since the fiber of the present invention can be made into a multifilament, post-processing such as knitting or the like, which has been conventionally difficult, becomes extremely easy, and fiber structures having various forms can be easily formed. can get. Therefore, it can be widely applied to various industrial fields utilizing the properties of the fiber structure in addition to the excellent properties of the constituent polymer itself.

Further, the core-sheath composite fiber of the present invention can be used very preferably as a reinforcing fiber for various composite materials, particularly, a carbon fiber composite material using an epoxy resin as a matrix. This has the effect of improving impact resistance without lowering the modulus of elasticity of the composite material.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a measurement result of storage shear modulus G ′ of a polymer constituting a core component of a core-sheath conjugate fiber of the present invention. A: storage shear modulus in dry state B: storage shear modulus in water absorption state (after immersion in boiling water at 94 ° C. for 24 hours)

FIG. 2 shows a storage shear modulus G ′ (A) of a polymer constituting a core component of the core-sheath conjugate fiber of the present invention in a dry state.
FIG. 5 is a diagram showing an example in which G ′ (C) of the polymer constituting the sheath component of the composite fiber of the present invention is compared with G ′ (C).

────────────────────────────────────────────────── ─── Continued on the front page Examiner Yoko Nakajima (56) References JP-A-62-244330 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D01F 8/00-8 / 18

Claims (9)

(57) [Claims] The polymer constituting the sheath component is a polymer having a water absorption of 1% or less when immersed in water at 23 ° C. for 24 hours, and the storage shear modulus of the polymer constituting the core component at 60 ° C. A core-sheath conjugate fiber, wherein G 'is an amorphous polyamide larger than G' of the polymer constituting the sheath component. 2. The core-sheath conjugate fiber according to claim 1, wherein the polymer constituting the sheath component is a crystalline polyamide having a water absorption of 1% or less when immersed in water at 23 ° C. for 24 hours. 3. The core-sheath conjugate fiber according to claim 1, wherein the polymer constituting the core component is a polymer having a glass transition temperature in the range of 100 ° C. to 200 ° C. 4. A polymer constituting the core component, storage shear modulus at the temperature range of 120 ° C. from room temperature in a dry state G 'is 5 × 10 ⁹ dyne / cm ² or more polymers according to claim 1 to 3 The core-sheath conjugate fiber according to any one of the above. 5. The polymer constituting the core component is a polymer having a storage shear modulus G ′ of 5 × 10 ⁹ dyne / cm ² or more in a dry state in a temperature range from room temperature to 120 ° C. and at 80 ° C. In a temperature range from to 120 ° C., G ′ of the polymer constituting the sheath component is changed to G ′ of the core component polymer.
The sheath-core composite fiber according to any one of claims 1 to 3 , which is smaller than the core-sheath composite fiber. 6. A water-absorbing state in which a polymer constituting a core component is immersed in boiling water at 90 ° C. or higher for 24 hours.
The core-sheath conjugate fiber according to any one of claims 1 to 5 , wherein the core-sheath conjugate fiber is a polymer having a storage shear modulus G 'in a temperature range from room temperature to 100 ° C of 4 × 10 ⁹ dyne / cm ² or more. 7. A water-absorbing state in which a polymer constituting a core component is immersed in boiling water at 90 ° C. or higher for 24 hours.
A polymer having a storage shear modulus G ′ of 4 × 10 ⁹ dyne / cm ² or more in a temperature range from room temperature to 100 ° C., and a polymer constituting a sheath component in a temperature range from 80 ° C. to 100 ° C. The core-sheath conjugate fiber according to any one of claims 1 to 5 , wherein ′ is smaller than G ′ of the core component polymer. 8. The cross-sectional area ratio of a core component polymer and a sheath component polymer in an arbitrary fiber cross section is core / sheath = 30 / 70-9.
The core-sheath conjugate fiber according to any one of claims 1 to 7 , which is in a range of 5/5. 9. Tensile strength 1 g / d or more, 15% boiling water shrinkage of not more than, according to any one of claims 1 to 8 dry heat shrinkage rate of 10% or less when heat-treated at 140 ° C. 30 minutes Core-sheath conjugate fiber.