JPH0641817A - Core-sheath conjugate fiber - Google Patents

Abstract

PURPOSE:To obtain core-sheath conjugate fiber, having a high elastic modulus widely usable in various fields of materials, etc., and suitably usable especially as reinforcing fiber for various composite materials. CONSTITUTION:The objective core-sheath conjugate fiber is composed of a polymer, constituting a sheath component and having <=1% water absorption coefficient when immersed in water at 23 deg.C for 24hr and a polymer, constituting a core component and having a higher storage shear elastic modulus G' at 60 deg.C than the G' of the polymer constituting the sheath component. This conjugate fiber has >=2g/d tensile strength, <=80% breaking elongation, >=15% shrinkage factor in boiling water and >=10% dry shrinkage factor when heat-treated at 140 deg.C for 30min as the whole fiber.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, polyamide is widely used as a fiber material, a general molding material, a structural material and the like by utilizing its excellent properties.

Polyamide fibers such as nylon 6 and nylon 66 are generally used, but they have a glass transition temperature of around 50 ° C., and in the temperature range above the glass transition temperature, they are abruptly increased. It has a drawback that the elastic modulus is lowered. Also, these have a high water absorption rate,
Since the saturated water absorption rate is also high, it also has a drawback that the mechanical strength and the rigidity decrease significantly when absorbing moisture.

Therefore, for various material applications in which the 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.

Nylon 12 and the like have low water absorption, but also have a low glass transition temperature.
In a high temperature range such as ℃ or more, the elastic modulus is greatly reduced.

On the other hand, amorphous polyamide is excellent in mechanical strength, impact resistance, abrasion resistance, solvent resistance, dimensional stability, insulation and the like as well as transparency, so that it is used in various mechanical parts and electrical components. Although it is used in equipment parts and the like, it has been practically rarely used as a fiber, particularly as a multifilament, due to its poor spinnability due to its amorphous nature.

[0007]

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

[0008]

The present invention has the following constitution in order to solve the above-mentioned problems.

That is, in the present invention, the polymer constituting the sheath component is a polymer having a water content of 1% or less when immersed in water at 23 ° C. for 24 hours, and the polymer constituting the core component at 60 ° C. The storage shear modulus G'is larger than that of the polymer constituting the sheath component, the tensile strength of the fiber as a whole is 2 g / d or more, and the elongation at break is 80% or less.
A core-sheath composite fiber having a boiling water shrinkage of 15% or more and a dry heat shrinkage of 10% or more when heat-treated at 140 ° C. for 30 minutes.

The amorphous polyamide referred to in the present invention is a polyamide which, unlike linear aliphatic nylon such as nylon 6 or nylon 66, causes almost no crystallization of the polymer or has an extremely low crystallization rate. Refers to.

Amorphous polyamide, which is also called transparent polyamide (transparent nylon), gives a transparent molded product under normal melt molding conditions, and the molded product is also subjected to post-crystallization even during heat treatment and water absorption treatment. A polyamide that does not cause devitrification.

The term "amorphous" as used in the present invention means a heat of fusion of crystals of 1 cal / g or more when measured with a differential scanning calorimeter (DSC) at a temperature rising rate of 10 ° C./min. I mean something that doesn't exist. Further, the term "crystallinity" as used in the present invention means
It refers to one that exhibits a heat of fusion of crystal of 1 cal / g or more when measured at a temperature rising rate of 10 ° C./min using a differential scanning calorimeter.

The "glass transition temperature" referred to in the present invention.
Can likewise be generally determined by a differential scanning calorimeter.

Since amorphous polyamide does not have a crystalline phase, its thermal properties such as heat resistance are almost governed by the glass transition temperature (Tg). Therefore, the Tg of the amorphous polyamide must be high in order to satisfy the heat resistance required in practical use.

In the present invention, the amorphous polyamide which 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 of Tg or lower where the movement of polymer chains is frozen, and therefore has a smaller coefficient of linear expansion than crystalline polyamide and is excellent in dimensional stability. .

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

Similar to the glass transition temperature, the important physical property required for the polymer constituting the fiber is the dynamic elastic modulus. The dynamic elastic modulus of the amorphous polyamide does not change much in the temperature range of Tg or less, and sharply decreases from the vicinity of the temperature exceeding Tg to plasticize and fluidize. A major difference from the crystalline polyamide is this viscoelastic behavior.

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

The term "dry state" as used in the present invention means that a sample is 1
It means a state of being vacuum dried at 00 ° C. for 2 hours or more and 20 hours or less.

Further, the behavior of the amorphous polyamide under moisture absorption is extremely specific among polyamide polymers which are considered to have a large property change due to moisture absorption.

Amorphous polyamide has a lower water absorption rate and a lower saturated water absorption than nylon 6 and nylon 66.
Therefore, the retention of mechanical strength, rigidity, and electrical properties of amorphous polyamide when moisture is absorbed is much better than that of absolutely dry nylon 6 and 66, and the amide group concentration is low and the moisture absorption is relatively high. Nylon 610, which is said to be less susceptible to
Is better than

The polymer which can be preferably used as the polymer constituting the core component of the core-sheath composite fiber of the present invention is a storage shear at room temperature to 100 ° C. in a water-absorbed state which is 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 the deterioration of physical properties under moisture absorption is small and stable.

On the other hand, crystalline polyamides typified by nylon 6 and nylon 66 are excellent in mechanical properties at room temperature, and are also excellent in spinnability during melt spinning, that is, fiber forming ability. Although it is widely used as a fiber for clothing, it has the drawbacks as described above, and is therefore unsuitable for various material applications in which physical properties decrease in a high temperature range or under moisture absorption.

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

As a specific example of the present invention, an amorphous polyamide having a high elastic modulus is used as the core component of the core-sheath composite fiber.
By arranging a crystalline polyamide with a low water absorption rate in the sheath component, the spinnability in the melt spinning of the amorphous polyamide is improved, and industrial stable production is made possible. The present invention succeeds in promoting the orientation of molecular chains and sufficiently exerting the extremely excellent physical properties of the amorphous polyamide in the high temperature region and under the moisture absorption.

Regarding the polymer constituting the sheath component, 2
The water absorption rate when immersed in water at 3 ° C. for 24 hours is 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 is a high crystal used as a specific example of the sheath component constituting the present invention represented by nylon 12. The characteristic polyamide has a larger γ-dispersion peak area of tan δ in dynamic viscoelasticity measurement than nylon 6 and 66, and is excellent in low-temperature impact properties. Therefore, the core-sheath composite fiber of the present invention, when used in various composite materials, for the purpose of improving impact resistance,
Excellent characteristics can be demonstrated. Moreover, since the adhesion between the core polymer and the sheath polymer is good, the fiber structure maintains an extremely stable fiber structure even during the manufacturing process, the post-processing process, or when it is placed in another material. It is possible to exhibit physical properties stably.

In order to improve the impact resistance of the composite fiber while maintaining the excellent properties of the core component polymer at high temperature, the storage shear modulus G'of the sheath component polymer is higher than that of the core component polymer G '. It is preferably small, and 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 G ′ of the core component polymer, while maintaining excellent properties of the core component polymer under moisture absorption. In order to improve the impact resistance of the composite 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 being immersed in boiling water at 0 ° C or higher for 24 hours.

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

Isophthalic acid bis (3-methyl-4-aminocyclohexyl) methane, ie, 4,4'-diamino-3,3'-dimethyldicyclohexylenemethane ω-laurolactam Also, the most preferred sheath for use in the present invention. Specific examples of the polymer that constitutes 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 of the core component polymer under moisture absorption, and further, by the melt spinning. For stable production, the cross-sectional area ratio of the core component polymer to the sheath component polymer in an arbitrary fiber cross section is preferably in the range of core / sheath = 30/70 to 95/5, 50/50 to 90 / The range of 10 is particularly preferable.

Regarding the arrangement of the core and the sheath of the composite fiber,
Basically, they are preferably concentric, but unless the sheath portion is too thin to expose a large portion of the core portion, eccentricity or multiple cores may be used. The cross-sectional shape of the composite fiber as a whole may be a deformed cross section other than the round cross section.

As the 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, introduced into the spinning head, and then the core-sheath structure is formed by a commonly known method. It is possible to employ a general spin-drawing method in which a composite flow is formed so as to obtain a non-drawn yarn by spinning from a spinneret, and then a drawing heat setting process is passed.

A further feature of the present invention is that the unstretched yarn once obtained is further stretched and heat set to promote orientation of the polymer chains and has a dense structure, that is, a relatively high strength, which is a core-sheath composite. To get the fiber.

In order to widely use the core-sheath composite fiber of the present invention in various fields of materials and the like, it is necessary that the number of filaments is 3 or more, preferably 5 or more. It is preferable to do this.
When used as a reinforcing fiber for various composite materials, a multifilament is preferable for sufficiently exhibiting its reinforcing effect.

In order to use the core-sheath composite fiber of the present invention in various fields of materials and the like, the tensile strength is 2 g / d or more, preferably 2.5 g / d or more, and the boiling water shrinkage is 15% or more.
10% dry heat shrinkage when dry heat treated at 140 ℃ for 30 minutes
It is practically preferable that it is not less than 15%, preferably not less than 15%.

[0038]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Each physical property value in the examples is measured by the following method.

(Storage shear modulus G'in dry state)
A test piece having a width of 12 mm, a thickness of 2 mm, and a length of 60 mm is first vacuum-dried at 100 ° C. for 3 hours, and a dynamic viscoelasticity measuring device, RDA-700, manufactured by Rheometrics Co., is used to measure a real sample length of 42 mm and temperature rise It was measured at a speed of 5 ° C./step.

(Shear storage elastic modulus G'in water absorption state)
A test piece having a width of 12 mm, a thickness of 2 mm and a length of 60 mm is first immersed in boiling water at 94 ° C. for 24 hours, then immediately immersed in room temperature water until the test piece reaches room temperature, and immediately before measurement. The water adhering to the surface was wiped off and the measurement was performed in the same manner as in the dry state.

[0042] The (boiling water shrinkage percentage) yarn of initial length 1 ₀ was immersed for 30 minutes in boiling water, the subsequent yarn length 1 _1,
It was measured under a load of 1/30 (g / d) and calculated from the following formula.

[0043]

[Equation 1]

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

[0045]

[Equation 2]

(Examples 1 to 9) Isophthalic acid and 4,4 '
TR55 (manufactured by EMS; glass transition temperature 155) which is an amorphous polyamide composed of -diamino-3,3'-dimethyldicyclohexylenemethane and ω-laurolactam.
(° C.) The polymer chips were vacuum dried at 120 ° C. for 14 hours and then melted using the first extruder, while nylon 12 (manufactured by Daicel Hüls, L2140, glass transition temperature 41 ° C., 23 The water absorption rate after immersion in water at ℃ for 24 hours is 0.25%)
After vacuum drying at 12 ° C. for 12 hours, it was melted using a second extruder. Each melt stream was guided to the spinning head, and TR55 was used as the core component, and nylon 12 was used as the sheath component to form a composite flow having the ratio of the core component and the sheath component as shown in Table 1, and then the pore size was adjusted to 0. Using a spinneret provided with 24 3 mm circular spinnerets, each was spun at the spinning temperature shown in Table 1, and after oiling, it was drawn at the spinning speed shown in Table 1 and wound into a package.

The core / sheath component ratio in Table 1 means the cross-sectional area ratio of the core / sheath component polymers in the fiber cross section, and the denier of the composite fiber in each example is 150 denier. The discharge amount of each component polymer was adjusted for each example to obtain a multifilament undrawn yarn of 150 denier / 24 filament.

The maximum breaking ratio when the undrawn yarn was drawn at 80 ° C. is shown in Table 1. These undrawn yarns at 80 ° C
At 130 ° C.
Pass through the hot plate set to to heat set, and
The drawn yarn was wound at a speed of m / min. Table 1 also shows the stability when passing through the twisting step and the physical properties of the obtained drawn yarn.

[0049]

[Table 1]

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

An example in which G'of the polymer constituting the core component and G'of the polymer constituting the sheath component of the composite fiber of this example in a dry state are compared is shown in FIG.

[0052]

According to the present invention, there is provided a fiber having a high elastic modulus even in a high temperature region and having little deterioration in physical properties when absorbing moisture. It can be suitably used for various material applications in which

Further, since the fiber of the present invention can be made into a multifilament, post-processing such as weaving and weaving, which has been difficult in the past, is extremely easy, and a fiber structure having various forms can be easily obtained. can get. Therefore, in addition to the excellent properties of the constituent polymer itself, the properties of the fibrous structure can be utilized for wide application in various industrial fields.

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

[Brief description of 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 composite 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 composite fiber of the present invention in a dry state.
It is a figure which shows the example which compared with G '(C) of the polymer which comprises the sheath component of the conjugate fiber of this invention.

Claims (9)

[Claims] 1. A polymer constituting a sheath component is a polymer having a water absorption rate of 1% or less when immersed in water at 23 ° C. for 24 hours, and a storage shear modulus G of the polymer constituting the core component at 60 ° C. ′ Is larger than G ′ of the polymer constituting the sheath component, and the tensile strength of the entire fiber is 2 g /
A core-sheath composite fiber characterized by having d or more, breaking elongation of 80% or less, boiling water shrinkage of 15% or more, and dry heat shrinkage of 10% or more when heat-treated at 140 ° C. for 30 minutes. 2. The core-sheath composite fiber according to claim 1, wherein the polymer constituting the sheath component is a crystalline polyamide having a water absorption rate of 1% or less when immersed in water at 23 ° C. for 24 hours. 3. The core-sheath composite fiber according to claim 1, wherein the polymer constituting the core component is an amorphous polyamide. 4. The core-sheath composite 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. 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 temperature range from room temperature to 120 ° C. in a dry state. The core-sheath composite fiber according to any one of 1. 6. 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 temperature range of room temperature to 120 ° C. in a dry state, and 80 ° C. In the temperature range from
The core-sheath composite fiber according to any one of claims 1 to 4, wherein G'of the polymer constituting the sheath component is smaller than G'of the core component polymer. 7. A polymer constituting a core component in a water-absorbed state 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 6, which is a polymer having a storage shear elastic modulus G'in the temperature range of room temperature to 100 ° C of 4 x 10 ⁹ dyne / cm ² or more. 8. A polymer constituting a core component in a water-absorbed state 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 the temperature range of room temperature to 100 ° C., and G of the polymer constituting the sheath component in the temperature range of 80 ° C. to 100 ° C. 7. The core-sheath composite fiber according to claim 1, wherein'is smaller than G'of the core component polymer. 9. The cross-sectional area ratio of the core component polymer and the sheath component polymer in an arbitrary fiber cross section is core / sheath = 30 / 70-9.
The core-sheath composite fiber according to any one of claims 1 to 8, which is in a range of 5/5.