Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1999-08-17
2003-07-29
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S304400, C428S308800, C428S315500, C428S323000, C428S326000, C428S327000, C428S315700, C502S400000, C502S401000, C502S404000, C530S814000, C530S415000
Reexamination Certificate
active
06599620
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cellulosic particle body, a method of producing said particle body, a spherical type body which comprises crosslinked polymer particles interconnected with the aid of an organic binder comprising a non-crosslinked polymer, a method of producing said spherical type body, and an adsorbent for purification of body fluids which is capable of removing a target substance at a high speed in the therapy of hyperlipemia, autoimmune diseases and immunity-mediated diseases and the like.
BACKGROUND ART
A cellulosic particle body and a spherical type body comprising a crosslinked polymer particle are in broad use in a variety of fields, for example as a support for immobilization of microbial cells or enzymes, an adsorbent matrix for perfumes and pharmaceuticals, an adsorbent for purification of body fluids, a cosmetic additive, a chromatographic stationary phase material, etc. or, thorough introduction of a functional group, even as various ion exchangers.
Much research has been undertaken into the cellulosic particle body.
Japanese Kokai Publication Sho-63-90501 discloses a technology which comprises blending an anionic water-soluble compound with a mixture of viscose and a water-soluble macromolecular compound to prepare a dispersion of microfine particles, coagulating the dispersion under heating or with the aid of a coagulant, regenerating it with an acid, and removing the water-soluble macromolecular compound through a series of coagulation, regeneration and aqueous washing to provide a porous microfine cellulosic particle body with a mean particle diameter of not greater than 3×10
−4
m and a maximum pore volume within a pore volume range of 2×10
−8
to 8×10
−7
m, with the total pore volume of all the pores within said range being not less than 2.5×10
−5
m
3
/kg. The particle body provided by the above technology is such that the cellulosic particle body as such have fine pores.
Japanese Kokai Publication Sho-63-92602 discloses a technology which comprises blending viscose, calcium carbonate and a water-soluble anionic macromolecular compound to prepare a dispersion of finely divided particles of calcium carbonate-containing viscose, coagulating and neutralizing the dispersion, and decomposing calcium carbonate with an acid to provide a porous cellulosic particle body.
With those technologies, however, the cellulosic particle body obtained are relatively small in diameter, so that in certain applications such as a filler, an adsorbent, etc., it is difficult to carry out a large-scale treatment at a high flow rate and if a high-speed treatment is attempted, the cellulosic particle body tend to be destroyed. Moreover, when such a cellulosic particle body is used for the treatment of body fluids, plugging with blood corpuscles tend to take place.
Accordingly there has been a demand for development of a cellulosic particle body which would have sufficiently high mechanical strength, be compatible with treatment at high flow rates, exploit the pore structure of the cellulosic particle body providing for a large surface area, and be free from the trouble of plugging in the treatment of body fluids.
Meanwhile, in the field of body fluid treatment, a body fluid purification method is being practiced as a therapeutic technique comprising removal of a specific substance(s) from a body fluid, which comprises passing the body fluid through an adsorption device packed with an adsorbent immobilized a substance having an affinity for a target substance on a carrier to thereby adsorb and remove said substance. The method developed initially for this purpose comprised passing whole blood over active charcoal, particularly a coated charcoal particle to remove a target substance. With advances in plasma perfusion membranes, various adsorption devices for removing a target substance from separated plasma have been developed.
Generally speaking, in body fluid purification therapy, the treatment time is preferably as short as possible from the standpoint of the patient's quality of life. For reducing the treatment time, several approaches may be contemplated by using ingenuity in the aspect of operating conditions with the adsorbent material being held unchanged.
First, it may be contemplated to increase the flow rate of the body fluid in the extracorporeal circuit so as to increase the volume of the body fluid to be contacted with an adsorbent per unit time. However, it will adversely affect the patient's quality of life to excessively increase the flow rate of the body fluid withdrawn from the patient's body and circulated extracorporeally. The conventional flow rate of a body fluid for extracorporeal circulation is 0.833×10
−6
to 3.33×10
−6
m
3
/s (50 to 200 ml/min.). Thus, there is a limit to the flow rate of the body fluid which can be circulated extracorporeally.
It may also be contemplated to increase the capacity of the adsorption apparatus and thereby prolong the time of contact between the body fluid and the adsorbent. However, as the device capacity is increased, the volume of the body fluid existing outside the body during treatment is increased to adversely affect the patient's quality of life, with the result that the device capacity cannot be increased beyond a certain limit. The capacity of the conventional adsorption apparatus for purification of a body fluid is 50×10
−6
to 500×10
−6
m
3
(50 to 500 ml) at most.
Then it may also be contemplated to reduce the treatment time by increasing the static adsorptivity of the adsorption apparatus. The static adsorptivity means the saturated amount of adsorption. As a means for enhancing the static adsorptivity, it may be contemplated to enhance the static adsorptivity by increasing the amount of adsorption per unit adsorbent. The factors influencing the adsorption equilibrium relation are the substance having an affinity for the target substance and the contact area effective for adsorbing the target substance. However, said substance having an affinity for the target substance is restricted to a substance having a specific affinity for the particular target substance. Furthermore, it is restricted to a substance substantially not affecting the patient's physiology because the objective is the treatment of a body fluid. It may also be contemplated to increase the effective contact area but, as the minimum requirement, this contact area must have pores receptive to the target substance. Therefore, the maximum contact area of the porous body having such pores is limited by the diameter and number of pores. Thus, there is a limit to enhancing the static adsorptivity by improving the above-mentioned adsorption equilibrium relation.
As mentioned above, because of the restrictions associated with the body fluid purification technology, it has been found difficult to reduce the treatment time, with the amount of adsorption maintained, by improving the device capacity, the flow rate of a body fluid, and said static adsorptivity.
Lastly, it may be contemplated to reduce the treatment time by improving the dynamic adsorptivity of the adsorption apparatus. The dynamic adsorptivity means the magnitude of adsorption rate. As a means for improving the dynamic adsorptivity, it may be contemplated, for instance, to improve the dynamic adsorptivity by optimizing the particle diameter of the adsorbent and the intraparticle diffusion coefficient of the target substance.
Referring to the first approach, i.e. the method of reducing the particle diameter of the adsorbent and, hence, said diffusion distance to thereby improve the dynamic adsorptivity, reducing the particle diameter of the adsorbent results in a reduced diameter of the fluid flow passageway and an increased pressure loss so that the risk for plugging is increased. Therefore, in consideration of the safety of therapy, the particle diameter cannot be reduced too much. Actually, the particle diameter of the conventional adsorbent
Fujita Kouji
Okuyama Tsutomu
Takata Satoshi
Tanaka Kouichiro
Connolly Bove & Lodge & Hutz LLP
Kaneka Corporation
Morris Terrel
Vo Hai
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