JPH03294517A - Aromatic polyester fiber having high strength and high modulus of elasticity - Google Patents

Abstract

PURPOSE:To obtain the title fiber having a specific melting point and a specific tensile strength, having excellent spinnability free from foams in the interior and fluff on the surface, by spinning an anisotropic melt-forming aromatic polyester, heat-treating, heating and drawing. CONSTITUTION:An anisotropic melt-forming aromatic polyester (preferably one comprising repeating units shown by formula I and formula II and having >=40 deg.C difference between decomposition starting temperature and melting point) is spun, heat-treated in an insert atmosphere, coated with a mineral oil such as liquid paraffin, heated and drawn to give the objective fiber suitable for fiber-reinforced plastics, etc., having 8.7km/second sound speed in the direction of fiber axis, >=310 deg.C melting point, >=20g/d tensile strength and >=700g/d modulus of elasticity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to aromatic polyester fibers with high strength and high modulus. More specifically, the present invention relates to aromatic polyester fibers having high mechanical properties incomparable to conventionally known aromatic polyesters.

(Prior art) Conventionally, aromatic polyester exhibiting melt anisotropy forms a liquid crystal structure in a molten state, and when it is discharged from a hole in a nozzle, liquid crystal domains are aligned in the fiber axis direction due to stress (polymer molecular chains Second, it is known that a high elastic modulus can be achieved without going through a stretching process (for example, JP-A-54-77691).

It is known that high-strength, high-modulus fibers with improved toughness can be obtained by further proceeding with solid phase polymerization through heat treatment (for example, Japanese Patent Publication No. 5962630, Japanese Patent Application Laid-Open No. 60-239600).

However, fiber reinforced plastic (F RP')
Further improvements in performance are expected in various fields, and in terms of mechanical performance, it is still at a snail's pace.

In general, increasing the modulus of elasticity increases the rigidity of the constituent molecules, which tends to increase the melting point of the raw material polymer, but in the case of raw aromatic polyesters whose melting point is high, the decomposition temperature of the polymer itself tends to increase. When they get close to each other, air bubbles (defects) are generated inside the fiber during melt spinning, and this becomes a factor that destabilizes the spinning process, such as screw drop-off, making it difficult to industrially produce high-strength, high-modulus fibers.

In addition, the heat treatment system can be a heating roller, a contact type hollow heater,
A method is known in which the initial elastic modulus is improved by stretching using a non-contact hollow heater or the like (for example, JP-A-62-311668).

However, aromatic polyester fibers have poor stretchability,
There is a problem in that there are many yarn breakages due to the heating drawing, and only products with many abnormal yarns can be obtained. In particular, if fuzz is generated on the fiber surface, a uniform fiber structure cannot be obtained, causing a decrease in the sound velocity value.

In particular, this tendency becomes larger as the stretching ratio increases, which deviates from the gist of the present invention in terms of fiber performance.

In this way, the aromatic polyester exhibits substantially melting anisotropy, and the sound velocity in the fiber axis direction is 8.7 km/sec or more,
No fiber has been found that is satisfactory in terms of physical properties, such as a yarn melting point of 310° C. or higher, tensile strength of 20 g/d or higher, and elastic modulus of 700 g/d or higher.

(Problem to be Solved by the Invention) Aromatic polyester is produced by a universal manufacturing method called melt spinning, and its major feature is that it has extremely low hygroscopicity and water absorption. In particular, aromatic polyesters obtained from 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid have very good fiber-forming ability (spinnability), high strength, high elastic modulus, and heat resistance. It is an excellent high-performance fiber that has excellent properties such as durability and chemical resistance, and is well-balanced in terms of production and performance (Japanese Patent Application Laid-Open No. 77691/1983).

However, in the fields where these aromatic polyester fibers are used as fiber-reinforced plastics (FRP) and tension members in optical fibers, etc., they are used as high-modulus yarns with a uniform fiber surface and structure without fuzz, as mentioned above. Improvements are desired in this respect.

The present inventors have discovered the present invention through intensive research into high-performance fibers that have excellent spinnability, high tensile strength and elastic modulus, and are free from defects such as internal air bubbles and surface fuzz. It is.

Hereinafter, the present invention will be explained in further detail. (Means for Solving the Problems) An object of the present invention is to provide a fiber made of an aromatic polyester capable of forming a substantially anisotropic melt phase. The sound velocity in the fiber axis direction is 8.7+a/sec or higher, the melting point is 310℃ or higher, the tensile strength is 2h/d or higher, and the elastic modulus is 700g.
This can be achieved by using a high strength aromatic polyester fiber with a high modulus of elasticity of /d or more.

The aromatic polyester capable of forming an anisotropic melt phase as used in the present invention is a polymer obtained mainly by aromatic diol, aromatic dicarphonic acid, aromatic hydroxycarboxylic acid, etc. It exhibits optical anisotropy (liquid crystallinity). Such characteristics can be easily recognized by heating a sample on a hot stage in a nitrogen atmosphere and observing the transmitted light.

Examples of the aromatic polyester compound forming the anisotropic melt phase used in the present invention include those consisting of a combination of repeating components shown below.

(where X and Y are H, CL Br or CH3 and Z is one row, 'ff-'') ) 〇 1 ■ −e−0−1・ −C←, −G−0−,
, Or-0←Particularly preferably, the following (1), (If
), [However, at least one hydrogen atom in the aromatic ring may be substituted with a substituent selected from the group of alkyl groups, alkoxyl groups, )\rogen atoms] (1) It is an aromatic polyester in which the sum of the units of (II) is 65% by weight or more of the constituent polymer, and the units of (n) are 5 to 50 mol% in the polymer component.

The aromatic polyester capable of forming an anisotropic melt phase used in the present invention may be mixed with other polymers in small amounts.

The decomposition start temperature (Td) referred to in the present invention is the start temperature of weight loss in the TG curve (thermogravimetric curve). Also, the melting point (
Tr) is the apex of the melting endothermic peak of the DSC curve.

Here, the difference (A
T) is less than 40°C (AT = Td - Ta < 40)
During the stay in the spinning machine, due to slight fluctuations in temperature,
Polymer decomposition occurs and screws, or yarn breaks, occur near the spinning nozzle. Even if no screws are formed, there are many bubbles in the fiber that are considered to be decomposed gas. As a result, the tensile strength decreases, which deviates from the gist of the present invention.

According to the research conducted by the present inventors, the high-strength, high-modulus aromatic polyester fiber of the present invention has the following characteristics: (1) polymer decomposition initiation temperature (Td) and melting point (Ta+
) difference (AT) is 40℃ or more (AT = Td - Tm
≧40) aromatic polyester is used as a raw material.

(2) Spinning at a spinning draft (defined below) of 30 or more and at a discharge rate and winding speed such that the single yarn fineness is 7 denier or less.

(3) The spun yarn is heat-treated in a combination of a heated inert atmosphere (for example, nitrogen gas) or an active atmosphere such as air.

(4) Mineral oil with smoothness and rich conjugation properties on the surface of the heat treatment system (
The melting temperature (T
1. ) directly below, preferably Tr, -t80°C or higher T1. −
10°C or less, yarn feed speed 1m/win or more 200
The film is heated and stretched at a speed of m/min or less.

I found out what you can get by doing this. Particularly characteristic of the present invention is that among the above four items, the difference (AT) between the decomposition start temperature (Td) and melting point (Tm) of the polymer in item (1) is 40°C or more (AT = Td - Tm≧ 40), spinning with a draft of 30 or higher as described in item (2), and applying a treatment agent as described in item (4) and drawing until it exhibits a special fiber structure, an integral combination of these. Only by this method can the high-strength, high-modulus aromatic polyester fiber of the present invention be obtained.

The sound velocity referred to in the present invention is the time it takes for a 10 KHz pulse wave to propagate in the fiber, and the aromatic polyester fiber of the present invention has substantially reduced molecular weight due to the high draft and stretching described in (1) and (4) above. It is thought that the sound velocity value is high because a fiber structure with fully extended chains is formed, there is no fluff on the fiber surface, and the molecules are highly oriented. (e.g. LW, Mo5eleyJ, ^pp1.Poly
m, Sci., 3.266 (1960)).

Next, a specific manufacturing example of the high-strength, high-modulus aromatic polyester fiber according to the present invention will be described.

First, the difference (AT) between the decomposition start temperature (Td) and the melting point (Tm) of pellets vacuum-dried at 140°C for 10 hours or more is 40
℃ or higher (AT = Td - Tm ≧ 40), the aromatic polyester is heated to a temperature of 10℃ or higher than the melting point (Tm), Tm +
The yarn is discharged from a nozzle at a temperature of 80° C. or lower and a shear rate of 103 sec-' or higher, and the yarn is taken up by a winder.

This winding speed (discharge linear velocity at the nozzle hole (vl)
), it is preferable to set it to a certain value or more. That is, the chain acid is represented by the spinning draft (
1) It becomes like the formula.

Spinning draft (DF) = vt/v.

DF≧30 (1) More preferably, it is desirable to set DF≧35. If this condition is exceeded, the desired high-strength, high-modulus fibers cannot be obtained in the post-treatment of the present invention due to insufficient molecular orientation.

The shear rate (te) referred to in the present invention refers to the nozzle radius r(c
a), polymer discharge amount per single hole is Q (am3/5e
e), it is calculated as follows.

Next, the spun yarn is heat treated in an inert atmosphere such as nitrogen, an active atmosphere containing oxygen such as air, or under reduced pressure.

Preferred temperature conditions are Ti-60°C to Tm+20°C (
Here, T@ is the melting point of the polymer mentioned above), and To+
A pattern in which the temperature is gradually increased from -40°C is more preferable. The processing time can range from several seconds to several tens of hours depending on the desired performance. Heat can be supplied by using a medium such as gas, by using radiation from a heating plate, infrared heater, etc.
There are methods such as contacting with a heat roller or plate, internal heating methods using high frequency, etc., but it is preferable to use a medium such as gas.

The heat-treated yarn thus obtained is subsequently hot-stretched. Various types of yarn stretching devices can be used, such as hollow heaters, heating plates, heating rollers, heating media (silicon oil), etc., but in order to obtain the high strength and high modulus aromatic polyester of the present invention, non-contact type It is preferable to use a hollow heater.

A heating plate, a heating roller, a heating medium, etc. are used to contact and heat the yarn, and in stretching immediately after melting, heat transfer is easy and phenomena such as melting that do not involve substantial polymer orientation may occur.

On the other hand, a hollow heater is a non-contact heating type and is most suitable for micro-stretching of several percent of aromatic polyester fibers that can form an anisotropic melt phase.

In addition, in order to prevent unraveling, yarn breakage, etc. that occur during stretching, 0.3 to 3.0% of oil (mineral oil) having substantially no hydrophilic groups may be applied to the fiber surface. preferable. Examples of the mineral oil include liquid paraffin specified in JIS K9003.

The stretching of the heat-treated yarn may be carried out in several stages, and a heat treatment step may be added at the final stage if necessary.

Although the final stretching ratio varies depending on the constituent units and constituent ratios (composition ratios) of the polymer, it is generally 5 to 90% of the cutting elongation of the heat treatment system at room temperature. Stretching should be carried out until the speed reaches 8.7 km/sea or more.

Hereinafter, the present invention will be explained more specifically with reference to Examples.
The present invention is not limited to these Examples.

[Example] Various physical property values in this example were measured by the following methods.

b) Decomposition start temperature (Td): 140°C using a differential thermal balance manufactured by Rigaku Denki Co., Ltd.
The pellets were vacuum dried for more than 10 hours at Io℃/sin.
C in the TG curve (thermogravimetric curve) measured under nitrogen atmosphere.
This is the temperature at which weight loss starts.

Melting point (To+) Using a PerkinElmer differential scanning calorimeter model DSC-2C, the pellet or fiber described above was heated at 10°C under a nitrogen atmosphere.
/win was measured from room temperature to 400'C, and the peak of the endothermic curve resulting from crystal melting was taken as the melting point.

c) Sound velocity (taste) Orientic pulse type direct reading elastic measuring instrument DD
Using V-5B type, sample length 20, 30, 40 and 50c
Measure the propagation time of a 1OKHz pulse wave in the fiber at m, and calculate the slope (km/
5ec) or the speed of sound.

2) Intrinsic viscosity (η1nh) Dissolve the sample in pentafluorophenol by 0.1% by weight (60 to 80°C), and place it in a constant temperature bath at 60°C using a Uherode capillary meter (e.g., ``Polymer Science'' edited by the Polymer Society of Japan). Experimental method”
Measured with Tokyo Kagaku Doujin P 179 (19H) Tokyo). The solvent flow time is 107 seconds.

e) Strength (DT) and elastic modulus (YM) According to J Is L 1013, the tensile strength at break and elongation and elastic modulus (initial tensile resistance ), and the average value of 5 points or more was adopted. Fineness (denier) was measured by gravimetric method.

F) Judgment of fuzz Fuzz is determined by the presence or absence of broken fibers that adhere to the rotating roller when the yarn is run under various conditions (drawing ratio, temperature) for 1 hour. I marked the item as ○.

Example A wholly aromatic polyester polymer containing the summer structural unit [1] and [I[] in a 73/27 molar ratio was synthesized.

+C 0← ... [I] The physical properties of this polymer are r) 1nh=6. Ode/g Td = 400°C Ta = 281''C,', ΔT = 119°C. After drying this polymer in a dryer at 140°C for 10 hours, it was extruded from a single-screw vented extruder and sanded. (
The fibers were passed through a filter consisting of a layer of stainless steel powder and fine metal wires and spun at 320°C. The nozzle has a hole diameter of 0.
125a+mφ, the number of holes is 300g, the discharge amount per single hole is 0.0057cm'/sec, and the shear rate is 3. OX
It was wound up at 10'5 ec-' and a spinning speed of 90 Qm/a+in.

At this time, the performance of the spun yarn obtained with D F = 32.4 is as follows: Yarn denier (DR) = over 1498 dr
Degree (DT') = 12.3g/d elongation
degree (DE) = 2.43% elastic modulus (YM) = 592g/d melting
The temperature (Tm) was 280°C. This spinning yarn was wound around a perforated aluminum bobbin and heated at 260°C for 1 hour at 27°C.
Heat treatment was performed from 0°C to 280°C for 5 hours and from 280°C to 285°C for 10 hours. The performance of the obtained heat treatment system was as follows: D R-H18dr DT = 26.8 g/d D E = 4.4% Y M = 588 g/d T m = 325°C. After attaching 1iif amount of processing agent (liquid paraffin) to this heat treatment system, the heat treatment system was heated to 34% of the cutting elongation (stretching rate 1 .5%) for continuous stretching treatment.

The properties of the obtained threads are shown in Table 1.

Example 2 For the purpose of two-stage drawing of the drawn yarn obtained in Example 1-2,
When drawn using a hollow heater controlled at 20° C., the drawn yarn could be drawn to 60% of its elongation at break, resulting in the performance shown in Table 1.

Comparative example 1 In Example 1, the discharge amount per single hole o, oos.

Cll13/sec, shear rate 2.6x 10 sec
'-', it was wound at a spinning speed of 600a/11in. The spinning draft at this time was 24.5, and the obtained spun yarn was heat-treated under the same conditions as in Example 1-2, and then continuously at 40% of the cutting elongation of the drawn yarn using a hollow heater at 300°C. Stretched. Table 1 shows the performance of the obtained yarn.

Comparative Example 2 In Example 1, stretching was carried out under the same conditions without adhering the processing agent to the heat treatment system, but fluffing and the like occurred frequently.

Table 1 shows the performance of the obtained drawn yarn.

The following margin Example 3 The following structural unit is [r]/[■ko/[111]/[■
] = 60/8/16/16 mole% ratio of wholly aromatic polyester polymers were prepared.

The properties of this polymer were 771nh = 5.2d12/g Td = 400°C Tm = 331°C ΔT - 61°C, and this polymer was prepared in the same manner as in Example 1 except that the nozzle temperature for spinning was 355°C. The obtained spun yarn was spun at 280°C for 1 hour, then from 280°C to 330°C for 5 hours.
Heat treatment was performed from 330°C to 335°C for 10 hours. The performance of the obtained heat treatment system was as follows: D R-1503dr DT = 264 g/d DE = 3.7% Y M = 695 g/d T m = 348°C Sound velocity: 8.48 kta/sec.

This heat-treated yarn was coated with a treatment agent in the same manner as in Example 1, and was continuously stretched using a device consisting of a hollow heater heated to various temperatures shown in Table 2.

Table 2 shows the performance of the obtained drawn yarn.

Comparative Example 3 In Example 3, the composition was [I]/[■ko/[I[[]
/[IV] = 60/ 2/ 19/ 19 mol%
A fully aromatic polyester polymer with a ratio of

The properties of this polymer were 771nh = 4.9d12/g Td = 400°C Tm = 378°C 61222°C, and this polymer was spun in the same manner as in Example 1 except that the spinning nozzle temperature was 390°C. Although the obtained F2-spun yarn was brittle and had many bubbles in the fiber, it was heat-treated and hot-stretched in the same manner as in Example 1. Table 2 shows the performance of the obtained drawn yarn.

Margin below

Claims (1)

[Claims] (1) A fiber made of aromatic polyester capable of forming a substantially anisotropic melt phase, the fiber has a sound velocity in the fiber axis direction of 8.7 km/sec or higher, a melting point of 310°C or higher, and a tensile strength of 20 g/sec or higher. d or more and has an elastic modulus of 700g
/d or more aromatic polyester fiber.