Abstract: The present invention relates to a polysufone porous membrane having a high water flux, an excellent resistance to moist heat and an excellent repercolation characteristic, and which comprises a mixed polymer having polyarylsulfone and polyethersulfone at a ratio of from 9/1-1/9 (by weight), the membrane being a graded porous membrane forming a cross-linked polymer network wherein a number of micropores being interconnected from one surface to the other surface, and the membrane comprising two layers wherein one layer being a dense layer having a number of pores with pore sizes in the range of 0.01-1 &mgr;m and thereby having a separation function, and the other layer being a graded type supporting layer supporting said dense layer and having a pore size distribution wherein the pores existing therein and having sizes of 1-100 &mgr;m increase continuously from the dense layer side toward the other surface side, wherein the separation particle size is not larger than 0.

Abstract: Acrylic fiber comprising an acrylonitrile-based copolymer comprising 96.0 to 98.5% by weight of acrylonitrile units, 1.0 to 3.5% by weight of acrylamide units and 0.5% by weight or more of methacrylic acid units, the percentage by weight (A) of acrylamide units and the percentage by weight (M) of methacrylic acid units in the copolymer satisfying the following equations (I) and (II), and adsorbed iodine in an amount of 1% by weight or less based on the weight of the copolymer:X=0.21 to 0.23 (I)M+A.sup.x =1.82 to 2.18 (II)A copolymer having the above-mentioned composition is spun by a wet process, while adjusting the modulus in tension of coagulated fiber to approximately 2.0-3.0 g/d, wherein d means denier in terms of the weight of polymer in the coagulated fiber. There is provided acrylic fiber which permits production of carbon fiber with a high tensile strength and a high tensile modulus by pyrolysis for a shorter time.