| CPC C08F 110/02 (2013.01) [D01D 5/06 (2013.01); D01F 6/04 (2013.01); D10B 2321/0211 (2013.01); D10B 2401/063 (2013.01); D10B 2505/00 (2013.01); H01M 50/417 (2021.01)] | 20 Claims |
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1. An ultrahigh-molecular-weight polyethylene powder
having a viscosity-average molecular weight (Mv) of 10×104 or higher and 1000×104 or lower,
having a difference of 3° C. or more between a swelling onset temperature and a dissolution onset temperature determined by the following method, and
having a rate of impregnation with liquid paraffin (rate of increase in weight) of 0.5% or more and 5.0% or less determined by the following method:
[method for measuring swelling onset temperature and dissolution onset temperature]
any one particle is collected while an ultrahigh-molecular-weight polyethylene powder having a major axis size and a minor axis size of 120 μm or larger and 130 μm or smaller is confirmed under an optical microscope; the collected one particle of the ultrahigh-molecular-weight polyethylene powder (hereinafter, also referred to as a “measurement particle”) is loaded onto a glass cover, and one drop of liquid paraffin is added to the measurement particle using a 2 ml dropper; then, another glass cover is placed thereon so as to sandwich the measurement particle; then, the glass covers with the measurement particle sandwiched therebetween are placed on a heat stage, and a process of heating the measurement particle from room temperature to 150° C. under heating conditions given below is observed under an optical microscope equipped with a camera; in the heating step, observation images of the measurement particle are taken every 6 seconds; after the completion of measurement, an equivalent circle diameter of the measurement particle is calculated from each observation image using image analysis software, and the swelling onset temperature and the dissolution onset temperature are determined as described below:
(heating conditions)
heating rate from room temperature to 35° C.: 5° C./min;
heating rate in a range from 35° C. to 80° C.: 8° C./min; and
heating rate in a range from 80° C. to 150° C.: 5° C./min;
[swelling onset temperature]
the equivalent circle diameter of the measurement particle is calculated from the observation image of the photographed measurement particle using image analysis software; the lowest temperature at which the equivalent circle diameter of the measurement particle is increased by 1% or more based on the equivalent circle diameter of the measurement particle at 80° C. in a temperature range of 80° C. or higher and 150° C. or lower is regarded as the swelling onset temperature; a mean from three such measurements is used as the final swelling onset temperature;
[dissolution onset temperature]
the equivalent circle diameter of the measurement particle is calculated from the observation image of the photographed measurement particle using image analysis software; the measurement temperature at which the equivalent circle diameter of the measurement particle exhibits the largest value is regarded as the dissolution onset temperature; a mean from three such measurements is used as the final dissolution onset temperature;
[method for calculating rate of impregnation with liquid paraffin (rate of increase in weight)]
10 g of the ultrahigh-molecular-weight polyethylene powder is mixed with 30 g of liquid paraffin to prepare a sample; the prepared sample is placed in a metal container, which is then covered with aluminum foil and left at 70° C. for 3 hours; next, the sample is dried under reduced pressure at 110° C./reduced pressure (−0.1 MPa G) for 5 hours; then, the sample is subjected three times to washing filtration operation using 10 g of hexane and then dried in air for 24 hours or longer, followed by the weight measurement of the ultrahigh-molecular-weight polyethylene powder; the rate of impregnation with liquid paraffin (LP) (rate of increase in weight) is calculated from the rate of increase in the weight of the ultrahigh-molecular-weight polyethylene powder impregnated with liquid paraffin (post-impregnation weight) from the original weight of the ultrahigh-molecular-weight polyethylene powder (pre-impregnation weight) according to the following expression:
Rate of impregnation with liquid paraffin (%)=(Post-impregnation weight−Pre-impregnation weight)/Pre-impregnation weight×100.
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