Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric
Reexamination Certificate
2000-02-22
2003-08-05
Morris, Terrel (Department: 1764)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
C210S500100, C442S327000
Reexamination Certificate
active
06602812
ABSTRACT:
TECHNICAL FIELD
This invention relates to a leukocyte-removing material composed mainly of a hydrophobic polyolefin and a process for producing a hydrophilized polyolefin material suitable as said leukocyte-removing-material.
BACKGROUND ART
In recent years, various adverse side effects due to contamination with leukocytes have been known in the field of blood transfusion. For preventing the side effects, leukocytes are removed by using a material such as highly hydrophilic polyester nonwoven fabric or cotton fabric. In the transfusion of a platelet product, a technique of coating the surface of a leukocyte-removing material with a hydrophilic polymer or the like is employed for suppressing the adhesion of platelets to the leukocyte-removing material.
On the other hand, improvements have been made in techniques for selectively removing leukocytes for curing autoimmune diseases such as systemic lupus erythematosus, malignant rheumatoid arthritis, multiple sclerosis, ulcerative colitis and Crohn disease, leukemia, cancer, etc., or for immunosuppression before transplantation.
Materials such as highly hydrophilic polyester nonwoven fabric, cotton fabric, etc. have been widely used as leukocyte-removing materials because of their high leukocyte-removing capability. From the viewpoint of compatibility at the time of contact with blood, an ester structure or an amide structure is generally given to a leukocyte-removing material in order to impart hydrophilicity to the blood contact surface of the material. Such leukocyte-removing materials, however, are thermally unstable in the excess of attachment of importance to hydrophilicity. Particularly when the materials are subjected to wet heat sterilization or the like, their hydrolysis or the like is liable to take place. Thus, they are not always satisfactory as materials for medical supplies.
JP-A-3-27317 discloses a leukocyte-removing material obtained by grafting a monomer onto polyester fiber having a pore major axis of 0.5 to 4 &mgr;m and a CWST (critical wet surface tension) of 55 to 80 dyne/cm, by means of a radiation. This material, however, is poor in thermal strength because the polyester fiber or the aforesaid monomer has ester linkages. Therefore, the grafted monomer is liable to be released by dissolution during wet heat sterilization.
On the other hand, polyolefins are materials having an excellent thermal stability and they can be said to be preferable as materials for medical supplies which should be sterilized by high energy, such as wet heat sterilization, because they retain their strength as the materials even after the sterilization. The polyolefins, however, have a CWST of approximately 25 dyne/cm-30 dyne/cm and hence it has been not suitable to utilize them as they are.
Therefore, JP-A-1-256971 discloses a leukocyte-removing material comprising polypropylene nonwoven fabric hydrophilized by plasma treatment. However, the plasma treatment can impart hydrophilicity to the material temporarily but the imparted hydrophilicity decreases with the lapse of time. Thus, the hydrophilicity cannot be stably retained for a long period of time. Such a leukocyte-removing material is used immediately after the hydrophilization in rare cases and hence should be kept hydrophilized for a certain period or permanently. Accordingly, the hydrophilization by the plasma treatment is not desirable. In addition, when the plasma treatment is carried out, a considerable amount of electric charge is produced for increasing the hydrophilicity, so that the possibility of complement activation and bradykinin production is increased. Thus, the material hydrophilized by the plasma treatment is not desirable as a material for treating blood.
In view of such problems, the present invention is intended to provide a leukocyte-removing material which is hardly decomposed even by wet heat sterilization and has a stable hydrophilicity, and to provide a material which can retain hydrophilicity permanently irrespective of the hydrophobicity of a raw material therefor, has good priming properties, and has an excellent ability to remove leukocytes selectively.
Furthermore, the present invention is intended to provide a process for producing a hydrophilized polyolefin which retains its hydrophilicity for a long period of time, without greatly changing characteristics of polyolefin.
DISCLOSURE OF THE INVENTION
The present inventors eanestly investigated in order to solve the problems described above, and consequently found that a leukocyte-removing material comprising a polyolefin and having a factor of hydrophilicity of less than 40% and not less than 30% is very effective. Moreover, the present inventors found that the above-mentioned leukocyte-removing material possesses greatly improved priming properties and is surprisingly stable to wet heat sterilization, whereby the present invention has been accomplished.
Thus, one aspect of the present invention is directed to a leukocyte-removing material composed substantially of a polyolefin and having a factor of hydrophilicity of less than 40% and not less than 30%.
Another aspect of the present invention is directed to a process for producing a hydrophilized polyolefin which comprises a step of irradiating substantially a polyolefin with a radiation in a dose of less than 300 kGy and not less than 15 kGy, and a step of heating said polyolefin at a temperature of lower than 125° C. and not lower than 75° C. after the irradiation with the radiation.
The term “leukocyte-removing material” used herein means a material for removing leukocytes from a leukocyte-containing fluid such as blood or a body fluid by a mechanism such as filtration or adsorption.
BEST MODE FOR CARRYING OUT THE INVENTION
In the leukocyte-removing material of the present invention, the term “composed substantially of a polyolefin” means that the leukocyte-removing material is composed essentially of a modified polyolefin obtained by imparting hydrophilicity to naturally hydrophobic polyolefin by modification. In detail, the term means that the leukocyte-removing material is composed of a product obtained by changing (modifying) a polyolefin itself, for example, by irradiation with a radiation without converting the polyolefin to another material.
Therefore, the leukocyte-removing material “composed substantially of a polyolefin” of the present invention does not include, for example, products obtained by grafting a hydrophilic monomer as another component onto a polyolefin, and products obtained by coating a polyolefin with a hydrophilic monomer as another component.
The leukocyte-removing material of the present invention may contain antioxidants and stabilizers, which are usually contained in polyolefins. In addition, the leukocyte-removing material of the present invention may contain a small amount of a hydrophobic polymer other than the polyolefin, for holding of the polyolefin.
The polyolefin refers to a polymer obtained by homopolymerization or copolymerization of one or more alkenes or alkynes. The polyolefin includes, for example, polyolefins obtained by homopolymerization, such as polyethylenes, polypropylenes, polybutylenes, etc., and polyolefins obtained by copolymerization, such as polypropylene-polyethylene copolymers, polybutylene-polypropylene copolymers, etc. From the viewpoint of thermal strength, the polypropylenes, polybutylenes, polyethylene-polypropylene copolymers, polyethylene-polybutylene copolymers, etc. are preferable. From the viewpoint of the controllability of the leukocyte-removing material, the polypropylenes, polypropylene-polyethylene copolymers, etc. are the most preferable.
The term “factor of hydrophilicity” used herein is defined as follow: there are prepared aqueous ethanol solutions having predetermined and stepwise varied weight ratios of ethanol to water, a droplet (volume: about 10&mgr;L) of each of the solutions is brought into contact with a leukocyte-removing material, starting from the lowest concentration, and a concentration of the aqueous ethanol solution at which said leukocyte-removing mater
Onodera Hirokazu
Yoshida Makoto
Asahi Medical Co., Ltd.
Morris Terrel
Wachtel Alexis
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