Properties, Synthesis and Spinning of Liquid Crystal Polymer PBO Fibers

(1 School of Materials and Metallurgy, Northeastern University, Shenyang 110004; 2 School of Applied Chemistry, Shenyang Institute of Chemical Technology, Shenyang 110142; 3 Dalian Research and Design Institute of Chemical Industry, Dalian 116023) High-performance fiber. The PBO fiber properties, synthesis and spinning were studied in more detail. The synthesis methods of 4,6-diamino-1,3-benzenediol hydrochloride and PBO fiber were described in detail, and various methods were also described. Compare it.

Cui Tianfang: born in 1969, female, associate professor and doctoral student, engaged in functional polymer materials and fine chemical research E-mail: cuitianfangsyict.edu. In recent years, with the continuous development of national defense industry, aerospace industry, cutting-edge science and technology and civil industry With the rapid progress in molecular design and process technology, new types of high-strength, high-modulus, and high-temperature resistant fibers emerge in an endless stream. PBO fiber (poly(p-phenylene benzobis(Doxazole)) is a lyotropic liquid crystal heterocyclic polymer, which is a new generation of ultra-high performance fiber following Kevlar fiber, and it is also the best organic fiber with comprehensive performance.

1.1 PBO fiber mechanical properties PBO fiber has excellent mechanical properties, its tensile strength, tensile modulus is about twice that of para-aramid composites, its modulus is considered to be the limit of linear polymer Modulus; PBO composite material impact energy absorption is about twice that of para-aramid composite; its modulus is 2 times that of Kevlar fiber, PBO fiber strength not only exceeds that of steel fiber, but also above carbon fiber; PBO The creep resistance, wear resistance and bending fatigue resistance of the fiber are superior to para-aramid.

Table 1 Comparison of properties of PBO fibers with other fibers Fiber Strength Modulus Elongation Density Moisture Absorption Heat Resistance Wire Carbon Fiber A High-Strength Polyethylene Polybenzimidazole Polyester Fiber 1.2 Heat Resistance and Flame Resistance The limiting oxygen index of PBO fibers (LOI) is 68, heating does not melt, decomposition temperature in the air is 650C, CO, H2S and other toxic gases produced during combustion are particularly low, and the best heat resistance and flame retardancy in organic fiber. W. 1.3 Chemical stability resistance PBO fiber is stable in organic solvents, bleaching powders, and alkalis, and its strength is almost constant. However, PBO fiber uses acid as the spinning solvent, and its acid resistance is not high, and the strength of the fiber decreases with time at room temperature and in an acidic environment.

1.4 Insufficiency of PBO fiber The porosity of PBO fiber affects the fiber density. When MSA is used as a solvent, there are many pores, and when PPA is used as a solvent, the pores are very few. Therefore, the structure of PBO fiber is not only related to the solidification rate, but also related to the spinning solvent.

Poor light resistance, adhesiveness, and poor dyeability PBO fibers have poor lightfastness. Exposure to UV light to wide wavelength visible light areas can cause a decrease in strength. Use in outdoor applications requires coating protection; poor adhesion to resin substrates, limiting The application of PBO fiber in advanced composite materials; PBO fiber molecules are very rigid and dense, the dye is difficult to diffuse into the fiber interior, difficult dyeing.

2 Synthesis of Monomer 4,6-Diamino-1,3-benzenediol Hydrochloride The synthesis of diamino-1,3-benzenediol hydrochloride was mainly performed by Dow Chemical Industry Co., USA and Nissan Chemical, Japan. Industrial companies' patents represent 1. According to the raw materials are mainly divided into: 1,3-dichlorobenzene, trichlorobenzene, resorcinol 3 routes.

2.1 Benzene trichloride method In 1980, Lysenko of Dow Chemical Company synthesized 4,6-diamino-1,3-benzenediol hydrochloride from benzene trichloride. The specific synthesis route is as follows: 11 Industrialization in China It also has a very good prospect of industrialization. The disadvantage is that trichlorinated benzene is highly toxic and easily contaminates the environment. The normal 1,3-dichlorobenzene line is as follows: The advantage of this reaction is that the nitration reaction is performed at a lower temperature, which can effectively reduce the formation of by-products. Since the by-product 1,3-dibenzyloxy-2,4-dinitrobenzene remains completely in the reaction solution, it is easily separated from the main product, 1,3-dibenzyloxy-4,6-dinitrobenzene. Therefore, 2,4-dinitro-1,3-dichlorobenzene, a byproduct of the 1,3-dichlorobenzene nitration reaction, has little effect on the subsequent reaction.

2.3 Synthesis of 4,6-diamino-1,3-benzenedioxime hydrochloride from benzoquinone as raw material (1) Resorcinol acetylation and nitration method This method is an early traditional synthesis method, and the technique is relatively simple. Specific synthetic route The disadvantage of this reaction is that the nitration reaction can proceed at the 2, 4 and 6 positions simultaneously, and the nitration product containing the 2-nitro group is liable to cause explosion. The various by-products produced need to be recrystallized to separate and purify, resulting in a high cost, low yield, and unsuitable for industrialization.

(2) Resorcinol Sulfonation Chlorination In 1994, Nader invented the synthesis method. The use of halogen atoms to protect the 2-position prevents the formation of by-products of nitrification. The specific synthesis route is as follows: This method effectively avoids 2 The formation of by-products, nitration of high-purity 2-chloro-4,6-dinitro-1,3-benzenediol, and finally hydrogenation reduction of 4,6-diamino-1,3-benzenediol hydrochloride The disadvantage is the introduction of toxic halogen-containing compounds.

In 2000, Kumamoto Hiroshi invented this synthesis method. The specific synthetic route is as follows: Resorcinol is used as a raw material, and halogenated benzene with high toxicity is not needed. The biggest advantage is that the formation of 2-nitrification by-products can be suppressed and high purity can be obtained. 4,6-Diamino-1,3-benzenediol hydrochloride.

Resorcinol acetylation and oximation were carried out using resorcinol as the raw material through the diacetylation, deuteration, Beckmann rearrangement, and rehydrolysis processes in the 4,6-position.

This method avoids the production of nitro-substituted compounds and aniline with high carcinogenicity, and avoids the strong corrosion caused by HC1 produced in the catalytic hydrogenation process. The process is simple, the cost is low, and the total yield is about 72.2%. 2.4 Aniline Method In 1993, Morgan of Dow Chemical Company proposed a new and highly industrialized synthetic route: The biggest advantage of this method is that it does not use toxic halides. Aniline can be recycled and its product purity is high.

Synthesis of 3PBO Polymers PBOs can be polymerized in a variety of ways: using terephthaloyl dichloride or terephthalic acid with diamino-1,3-benzenediol hydrochloride to produce soluble o-phenylhydroxy polyamides and further dehydration Cyclization gives PBO. The PBO obtained by this method is insoluble and infusible and can not form a liquid crystal solution for spinning; it uses 4,6-diamino-1,3-benzenediol hydrochloride and terephthalonitrile or PBO can be obtained by melt polycondensation of diphenylphthalate; however, PBO fibers are most commonly obtained by polycondensation of polyphosphoric acid (PPA) or polyphosphoric acid and methanesulfonic acid (PPA/MSA) systems. Solution polymerization can The conversion of homogeneous polymerization to liquid crystal polymerization is achieved.

3.1 Terephthalic acid method In 1981, Wolfe et al. first reported the synthesis of PBO, which is composed of monomeric 4,6-diamino-1,3-benzenediol hydrochloride and terephthalic acid in polyphosphoric acid (PPA). ) Polycondensation of polyphosphoric acid and methane sulfonic acid (PPA/MSA) solution. First remove HC1 to increase the activity of 4,6-diamino-1,3-benzenediol, and then add hydrazine 25 to control the final concentration of P205 in PPA. In the 120210C program, the reaction temperature rises to form a liquid crystal phase during the reaction. A high molecular weight polymer is obtained.

The concentration of the polymer and the final mass fraction of P205 are the key to the synthesis of high molecular weight PBO fibers. Due to the low solubility of P2S in the system, it should be added in batches during the reaction process, and the final P205 mass fraction between 82.5% and 84% should be controlled by adding P2Os to ensure that the polyphosphoric acid is not hydrolyzed. Since the solubility of terephthalic acid (TA) in polyphosphoric acid is extremely low, TA needs to be micro-treated to increase its solubility.

3.2 Terephthaloyl method In 1988, Sybert et al. proposed the terephthaloyl chloride method to use terephthaloyl chloride (TPC) instead of terephthalic acid (TA). Jin Junhong of Donghua University in China also studied this method.

In addition, SoYH replaces TA polycondensation with poly-p-phthalic anhydride to increase the activity of polycondensation to obtain a polymer with an intrinsic viscosity of 2829 dL/g, and also designs 4,6-diaminos for the problems associated with the polymerization of TA and TC1. - Polycondensation of 1,3-benzenediol with 1,4-(trimethyl)benzene solution. The 1,4-bis(trichloromethyl)benzene does not need to be micronized or water, and the polycondensation process does not generate small molecules, so the polymerization process does not need to add 3.3 mesophase polymerization in methanesulfonic acid as a solvent and polycondensation agent. Adding 45% of 45% P205 to 4,6-diamino-1,3-benzenediol and terephthaloyl chloride, the reaction time is shortened from 100 h to 10 h, and the yield is high. The practical application of the trimethylsilylation method was invented by Yoshiohnai of Tokyo Technical Research Center. It first synthesized N,N,N-tetrakis(trimethylsilanyl)-4,6-diamino-. The 1,3-benzenediol intermediate is reacted with terephthaloyl chloride in UC under NMP, and then cyclized at 250C to remove the silane to give PBO. This method is characterized by the dissolution of the prepolymer in NMP. Into the desired shape of the product after heating cyclization into insoluble PBO. 3.5 parabens method of methyl paraben as raw materials, mixed acid reaction at room temperature intermediates, and then reacted under alkaline conditions, Coarse crystals are neutralized with acid to obtain 4-hydroxy-3-aminobenzoic acid salt, and self-condensed in stannous tin solution The hydrochloride salt of 4-hydroxybenzoic acid is condensed in a polyphosphoric acid medium with dimethylacetamide solvent to give a high molecular weight PBO. The specific synthetic route is as follows: This method avoids the process of removing HC1 gas in the traditional method, and the polymerization time is shortened to 21 h; the equivalence ratio polymerization of the two monomers, DAR and TA, is ensured, and the inhibition due to the excessive presence of DAR is avoided; the polymerization process is further improved. It is simple, fast, and has a relatively high molecular weight PBO fiber.

4 PBO fiber spinning PBO is usually used PPA solvent spinning dry spinning process liquid crystal spinning.

The spinning dope consisting of 10% 20% PBO and PPA was extruded through a spinneret at 9018C (diameter of the spinneret hole was 0.0130.2mm), passed through a 5mm25cm gas layer and entered the water or 5 conclusions of the PBO fiber. The use can be divided into two categories, namely the application of heat resistance and the application of mechanical property enhancement materials. The heat-resistant material is most suitable for use as a heat-resistant cushioning material, heat-resistant workwear, and heat-resistant filter material for aluminum alloys and glass and other manufacturing processes. The application of mechanical property-improving materials has a wide range of applications. It is used for reinforcing materials and concrete for rubber products. A variety of sportswear and active sports equipment such as reinforcing materials, racing suits and pilot suits; composites made of PBO fiber can be widely used in aviation and aerospace fields. The excellent physical and chemical properties of PBO fiber make it the best industrial new material and high-performance fiber in the 21st century, and its appearance will bring about a revolution in new organic fibers.