JPH0450333B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> The present invention relates to a method for producing a polymer composite with excellent mechanical properties from a solution containing a polyazole as a reinforcing polymer and a flexible polymer as a matrix. <Background Art> Fiber-reinforced plastics have been regarded as important as composite materials for load-bearing structures because of their dramatically improved physical properties, and various materials have been developed and put into practical use. The production of such composite materials requires a process of arranging reinforcing fibers manufactured separately in one direction, and a process of impregnating the plastic to be further reinforced as a matrix polymer, and this process is carried out in an autoclave. requires complicated step-by-step operations such as On the other hand, the strength and durability of composite materials are
It greatly depends on the state of the interface between the reinforcing fiber and the matrix polymer. The interface between the two is a macroscopic interface because the fiber itself is a macroscopic object, and defects existing there propagate macroscopically and lead to destruction of the composite material. In order to solve this drawback, instead of the fibrous reinforcing material that can only be dispersed in a macroscopic form, we used a highly modulus reinforcing polymer that can be dispersed in a microscopic molecular form, and combined it with a matrix polymer. By dissolving both in a common solvent and mixing them in a microscopic molecular form, and solidifying and molding this, the reinforcing component and the reinforced component are dispersed and mixed in an extremely microscopic state, and are oriented. Producing polymer composites has been considered. Conventionally, the reinforcing fibers used in composite materials are more likely to fibrillate as they become organic fibers with higher modulus, but by making them into polymer composites like the one described above, they have a high modulus and are less likely to fibrillate. It is thought that things can be obtained from this, and research has been carried out toward this end. By the way, in order to improve the mechanical properties of these polymer composites, it is necessary to further add a reinforcing polymer to the primary molded product of the polymer composite (for example, a tape, film, or fibrous molded product). If necessary, the matrix polymer also needs to be highly oriented. If both polymers are sufficiently oriented, the modulus will be a value expressed by the sum of the ratios of each component of the expected value for each polymer component alone, but in reality, the orientation is insufficient. Therefore, the current value is lower than this value. The present inventors have discovered that currently, organic polymer fibers include:
The results of intensive studies on achieving high modulus in a system using a polyazole polymer such as poly-p-phenylenebenzobisoxazole, which provides the highest tensile modulus, as a reinforcing polymer and a flexible polymer as a matrix polymer. , the present invention has been achieved. That is, in the present invention, a polymer solution mainly containing a reinforcing polymer (A) consisting of a polyazole having a substantially rod-shaped skeleton and a matrix polymer (B) having fusibility is introduced into a gas through a die or orifice. In a method for producing a polymer composite consisting of extrusion, then introduction into a coagulation bath, and continuous withdrawal, the temperature range in which the polymer solution exhibits optical isotropy and the optical quasi-anisotropy are determined. The temperature of the die or orifice is maintained within a temperature range in which the polymer solution exhibits optical isotropy, and the temperature of the gas and/or coagulation bath is Production of a polymer composite characterized in that the polymer solution is maintained within a temperature range exhibiting optical quasi-anisotropy, and the reinforcing polymer (A) has an intrinsic viscosity of 15 or less. It is the law. As the reinforcing polymer (A) used in the present invention,
The following formula [However, in the formula, X is -S-, -O- or

[Formula], and the bonds (a) and (b) are bonds that further form an azole ring or a hydrocarbon ring, or a hydrogen atom is bonded to one of them and the other is a bond. It is. ] Substantially rod-like polyazoles having an azole skeleton represented by the following are mentioned, and specifically, there are polymers described in U.S. Pat. No. 4,207,407, among which poly-p-phenylenebenzobisthiazole , poly-p-phenylene benzoxazole, poly-p-phenylene benzobisimidazole, and other polyazoles. The molecular weight of the reinforcing polymer (A) is usually such that the intrinsic viscosity, which is a guideline for molecular weight, is 1 or more, preferably 1.5 or more,
Particularly preferably 2 or more. On the other hand, it is not preferable that the intrinsic viscosity is too high, and if the intrinsic viscosity is 20, a good product cannot be obtained. In order to achieve the effects of the present invention, the reinforcing polymer should have an intrinsic viscosity of 15 or less, preferably 12 or less, particularly preferably 10 or less. Matrix polymer used in the present invention
(B) is dissolved in the same solvent as the reinforcing polymer (A), and includes nylon 6, nylon 66, nylon 610,
Aliphatic polyamides such as nylon 12 and nylon 11;
Semi-aromatic polyamides such as polyhexamethylene isophthalamide; Aromatic polyamides such as polymetaphenylene isophthalamide; Flexible aromatic polyamides into which flexible groups such as ether groups have been introduced; Polyester; Polycarbonate; Polyvinyl acetate; Polysulfon; Examples include polyether sulfone; polyetherimide; polyether ketone; polyphenylene sulfide, and the like. The common solvent may be any solvent that can dissolve the constituent polymers, and examples thereof include acidic solvents such as concentrated sulfuric acid, methanesulfonic acid, chlorosulfonic acid, polyphosphoric acid, trifluoroacetic acid, and phosphoric acid. These may be mixed and used. Further, in order to suppress hydrolysis of the dissolved polymer, an additive may be mixed in to reduce the amount of water in the solvent as much as possible. For example, addition of fuming sulfuric acid, chlorosulfonic acid, etc. may be mentioned. The stock solution for forming a polymer composite is a polymer solution in which a reinforcing polymer and a matrix polymer are dissolved in the above-mentioned common solvent. A region of solution exhibiting quasi-anisotropy is required. The temperature range showing optical isotropy and the temperature range showing optical quasi-anisotropy vary depending on the type of polymer, degree of polymerization, component ratio, and concentration, but are determined by the following measurement method. be able to. That is, a predetermined polymer solution is prepared, spread thinly on a slide glass, and placed so that the thickness of the polymer solution is 0.1 mm, and is covered with a slide. The sample thus prepared is placed under observation using a polarizing microscope with crossed Nicols. First, the temperature of the sample is lowered to below room temperature (20°C) to bring the polymer composite solution on the slide glass into a state where it exhibits optical anisotropy. Using a melting point measuring device (YANAGIMOTO Co., Ltd.),
When the temperature of the sample is gradually increased (5° C./min.) while observing it with a polarizing microscope, it is observed that the field of view becomes dark at a certain temperature and changes to an optically isotropic state. The temperature at this time is called the transition temperature. After confirming that it has become isotropic, the polymer solution on the slide glass is rapidly cooled from this temperature to a predetermined temperature, for example, 20°C. The cooling method is achieved by placing the film on a material with good thermal conductivity, such as copper or silver, which has been cooled to the above temperature without adding any shear. When this sample is observed using a polarizing microscope with crossed Nicols, the time it takes for optical anisotropy to appear varies greatly depending on the conditions of the polymer solution preparation method. In this case, the higher the transition temperature of the system, the shorter the time until optical anisotropy appears. Therefore, when applying rapid cooling as described above, if the time from the start of cooling to the appearance of optical anisotropy continues for 30 seconds or more, this temperature is within the optical quasi-anisotropy temperature range. be. In the method of the present invention, once the types, molecular weights, solvent systems, and component ratios and concentrations of the reinforcing polymers and matrix polymers are determined, optical isotropy and optical quasi-anisotropy are determined according to the above measurement method. The temperature range showing the anisotropy is measured, and the temperature of the die or orifice is kept in the optically isotropic temperature range, and the temperature of the gas and/or coagulation bath is kept in the optically quasi-anisotropic temperature range. According to the method, a polymer solution is extruded through a die or orifice, guided through a gas into a coagulation bath, and continuously withdrawn to produce films or fibers in a semi-dry and semi-wet manner. At this time, the polymer solution extruded from the die or orifice is rapidly cooled in a gas and/or coagulation bath and rapidly reaches a temperature at which it exhibits optical quasi-anisotropy. The conditions for forming a rod-shaped aggregate are now in place. On the other hand, when the temperature of the gas and/or coagulation liquid is in the optically anisotropic temperature range (the time is less than 30 seconds), the molded product obtained has poor stretchability and does not exhibit good mechanical properties. In addition, if a reinforcing polymer (A) with an intrinsic viscosity of 15 or less, especially one with an intrinsic viscosity of 12 or less, is used, extremely small rod-shaped aggregates of the reinforcing polymer (A) are likely to be formed. The mechanical properties are surprisingly improved, probably because the reinforcing polymer (A) is easily oriented quickly in the matrix polymer during the subsequent stretching operation. On the other hand, if the temperatures of the gas and coagulation liquid are in the optically isotropic temperature range, the mechanical properties of the final molded product, especially the absolute value of the modulus, will be inferior to those obtained by the method of the present invention. Another way to form rod-shaped micro aggregates of reinforcing polymers is to change optical isotropy to optical anisotropy at a constant temperature by appropriately selecting the polymer concentration of the polymer composite solution. It is known that reinforcing polymers are aggregated into rod shapes in the region of transition, but the reason for this method is not clear, perhaps because the conditions for forming microscopic aggregates of reinforcing polymers are extremely narrow, but the present invention Comparatively, better molded products cannot be obtained. As a coagulating liquid for coagulating the polymer solution, a system in which an insoluble solvent is mixed with the solvent used,
Examples include sulfuric acid aqueous solution, methanesulfonic acid aqueous solution, and the like. The temperature of the coagulation liquid must be maintained at a temperature at which the polymer composite solution exhibits optical quasi-anisotropy. In general, it is preferable to set the temperature difference between the holding temperature of the slit die or orifice and the temperature of the coagulation bath to be large in order to obtain a molded product with high orientation and high modulus in the subsequent stretching operation. The ratio of reinforcing polymer (A) and matrix polymer (B) used in the present invention is 5 to 45% A/A+B.
It is good that it is within the range of . When the reinforcing polymer (A) is less than 5%, the reinforcing effect is small, and when it exceeds 45%, the orientation of the reinforcing polymer (A) is reduced and the characteristics of the present invention cannot be expressed. The intrinsic viscosity used in the present invention is 100
% sulfuric acid, methanesulfonic acid or chlorosulfonic acid with a concentration of reinforcing polymer (A) of 0.2g/100c.c.
ηinh was determined by a conventional method at 30°C after dissolving so that When the reinforcing polymer (A) dissolves in any of the above solvents, the lowest value among them is taken as the intrinsic viscosity of the reinforcing polymer (A). The effects of the present invention will be shown below with examples,
Percentages in the examples are given on a weight basis unless otherwise specified. Mechanical properties of fibers and films were measured using a sample length of 2 cm at an elongation rate of 100% per minute. Examples 1-2, Comparative Examples 1-3 As the reinforcing polymer (A), poly-p-phenylenebenzobisthiazole (abbreviated as PPBT) was polymerized according to a conventional method, and the intrinsic viscosity in methanesulfonic acid solvent was I got the 3.0 one. The matrix polymer (B) was prepared by adding 3.4′-diaminodiphenyl ether (50 mol%) and paraphenylene diamine (50 mol%) to N-methylpyrrolidone at a concentration of 6% in a dry nitrogen atmosphere. After cooling to 5°C, terephthalic acid dichloride powder (100 mol%) was immediately added to the solution with vigorous stirring, and the mixture was heated to 1°C at 35°C.
A polymerization reaction was carried out for a period of time, and the resultant was precipitated and neutralized with water. Hereinafter, this polymer will be abbreviated as PPOT-50.
ηinh of PPOT-50 was 3.6 in sulfuric acid solvent.
PPBT and PPOT-50 were dissolved in methanesulfonic acid at a component ratio of 25/75 to prepare polymers with total polymer concentrations of 4, 5, 6, 7, and 8%.
The temperature at which the polymer composite solution transitions from anisotropy to isotropy (phase transition temperature) was as shown in Table 1. After heating the polymer solution to 96°C, which is higher than the transition temperature,
It was placed on a silver plate at 20°C to cool it, and then the time required for anisotropy to appear was measured. The appearance times were as shown in Table 1. The polymer solution was placed in a syringe-shaped container and extruded at a temperature of 80° C. through an orifice with a diameter of 0.25 mm at a linear velocity of 5 m/min. Air layer (temperature 25℃, distance 18cm)
After passing through, it was led to an ice water coagulation solution. The somewhat stretched undrawn yarn after coagulation was thoroughly washed, neutralized with aqueous ammonia, and then wound onto a bobbin. After stretching in warm water at 60°C, the film was air-dried, further dried in an oven at 200°C, and then hot-stretched in electric furnaces at 350°C and 450°C. The mechanical performance of the hot drawn yarn is as shown in Table 1, clearly demonstrating the effects of the present invention.

[Table] Examples 3 to 5 and Comparative Examples 4 to 5 Using PPBT and PPOT-50 used in Example 1,
PPBT and PPOT-50 were dissolved in methanesulfonic acid at a component ratio of 30/70 to prepare polymers with total polymer concentrations of 4, 5, 6, 7, and 8%. If there is a transition in the anisotropy of the polymer solution, change the temperature and the temperature after heating the polymer solution to 90°C.
It was placed on a silver plate at 20°C to cool it, and then the time for anisotropy to appear was measured. The results were as shown in Table 2. Spinning and drawing were carried out in the same manner as in Example 1, and the mechanical properties were evaluated. As shown in Table 2, those that met the conditions of the present invention exhibited good mechanical properties.

[Table] Example 6, Comparative Example 5 As a reinforcing polymer, PPBT was polymerized according to the method of Example 1 to obtain one with ηinh of 7.3. this
The ratio of PPBT to the matrix polymer PPOT-50 obtained in Example 1 was 25/75, and the mixture was dissolved in methanesulfonic acid so that the total polymer concentration was 6%. The transition temperature of the polymer solution was 62°C, and when it was rapidly cooled to 20°C, the time for anisotropy to appear was 60 seconds or more, indicating quasi-anisotropy. The polymer solution was extruded through a slit die of 10 mm x 0.1 mm, stretched with hot water,
Thickness (μm)/
Modulus (GPa) / Elongation (%) / Strength (GPa)
= 51/82/3.5/1.1 was obtained. On the other hand, a film with a total polymer concentration of 4% does not exhibit a quasi-anisotropic state, and a film formed from an isotropic solution has a thickness (μm)/modulus (GPa)/elongation (%)/strength (GPa). )=52/
53/2.6/0.8, which was not good. Comparative Example 7 PPBT as a reinforcing polymer was polymerized according to the method of Example 1, and a polymer having ηinh=21 was obtained. A solution with a polymer concentration of 3.5% was prepared at a ratio of PPBT-PPOT-50 = 25/75. Phase transition temperature is 82℃
, and the anisotropy appearance time after cooling to 20°C was approximately 20 seconds, exhibiting quasi-anisotropy. A polymer composite fiber was obtained by discharging from an orifice (temperature: 90°C), hot water stretching, and hot stretching. Fiber performance is diameter (μm) / modulus (GPa) / elongation (%) / strength (GPa) = 41 / 65 /
2.3/1.1, which was inferior to PPBT with small ηinh.

Claims (1)

[Claims] 1 A polymer solution mainly containing a reinforcing polymer (A) consisting of a polyazole having a substantially rod-shaped skeleton and a matrix polymer (B) having fusibility is extruded into a gas through a die or orifice, and then solidified. In a method for producing a polymer composite, which involves introducing the polymer solution into a bath and then continuously taking it out, the temperature range in which the polymer solution exhibits optical isotropy and the temperature range in which it exhibits optical quasi-anisotropy is determined. and
The temperature of the die or orifice is maintained within a temperature range in which the polymer solution exhibits optical isotropy, and the temperature of the gas and/or coagulation bath is maintained such that the polymer solution exhibits optical quasi-anisotropy. and the reinforcing polymer
A method for producing a polymer composite characterized in that (A) has an intrinsic viscosity of 15 or less.