Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2002-01-30
2004-11-23
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S150000, C522S153000, C522S154000, C522S155000, C522S158000, C522S159000, C522S165000, C522S160000, C264S494000, C264S496000
Reexamination Certificate
active
06822015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rubber composition for a medical treatment or a medicament, and a crosslinked product thereof, more specifically, a rubber composition used for an instrument for a medical treatment or medicament, or for a rubber stopper for a medicament or a rubber article for a medical treatment, in particular, comprising, as a predominant component, isobutylene copolymers capable of being readily subjected to a radiation treatment.
2. Description of the Prior Art
Use of rubbers in the fields of instruments or containers for medical treatments and medicaments has been started as natural rubbers from the olden time and gradually, synthetic rubbers have often been used. At the present time, thermoplastic elastomers or mixtures with synthetic resins have widely been used. As a test method of such a rubber composition article of this kind (which will hereinafter be referred to as “rubber article”), there are “48 Test Method of Rubber Stopper for Fluid Administration” and “49 Test Method of Plastic Container for Fluid Administration” according to Japanese Pharmacopoeia of 13th Revision, which will hereinafter be referred to as JP 13, in which the passing values are provided. Furthermore, in the field of rapidly advancing articles for medical treatments and for medicaments, it is the present situation that high quality materials and products have been required.
Since about 1950, isobutylene-isoprene copolymer rubbers (which will hereinafter be referred to as “IIR” sometimes), etc. have been recommended as a material suitable for sanitary rubber articles, but cross-linking of IIR is so difficult that a combination of a strong cross-linking agent and cross-linking aid is required. Such a combination is for example described in R. T. Vanderbilt, “RUBBER HANDBOOK”, “Vanderbilt” (published 1968), “Gosei Gomu Kako Gijutsu Zensho (Synthetic Rubber Working Technique Complete Book)”, Vol. 8, “Butyl Rubber”, Taiseisha, (published 1973), etc.
As to the cross-linking technique, there have been proposed a process for the production of adhesives by vulcanization of IIR at a low temperature (JP-A-60-130665), a method for cross-linking IIR in the coexistence of three materials of quinoid, organo peroxides and acryloyl monomer (JP-A-62-074934), cross-linking of IIR in the presence of organo peroxides and polyfunctional monomers having electron-withdrawing groups (JP-A-6-172547), etc.
As a rubber article in the field of requiring high sanitary property are known a rubber article comprising IIR compounded with a fine powder of ultrahigh molecular weight polyethylene (JP-A-60-144346), cross-linking of IIR by joint use of special organo peroxides and maleimides (JP-A-4-213347), etc.
On the other hand, it is apparent that use of butyl rubber most excellent in cleanness as well as gaseous permeability resistance is most suitable as a material of a rubber stopper for medicaments, needing a high sealing degree, for the rubber formulation.
As a method for the sterilization of containers for injections (according to Japanese Pharmacopoeia, a rubber stopper is also defined as a container) and for the sterilization of instruments for medical treatments, the ISO Guide Line or Japanese Pharmacopoeia describes that among a high pressure steam sterilization, gaseous sterilization with ethylene oxide and radiation sterilization, a high pressure steam sterilization is exclusively used for rubber stoppers for medicaments and gaseous sterilization and radiation sterilization are carried out for plastic instruments for medical treatments.
However, the gaseous sterilization method has been considered as a question as to the safety of residual gases in containers or instruments by FDA, etc. and in addition, items for controlling the sterilization step are considered difficult, because of difficulty in controlling or validating a gas concentration or gas temperature distribution, thus making hard identification of the sterilization integrity. Sterilization of a glass container for an injection, rubber stopper thereof or heat resistance plastic instrument for a medical treatment has ordinarily been carried out by a high pressure steam sterilization (autoclave sterilization) from the olden time, which has met a problem with respect to uniform controlling of the temperature in the autoclave and thus, has been subjected to improvement of the system.
For the production of a sterilized container for an injection agent or sterilized instrument for a medical treatment, a sterile test of a final product is an obligation and without passing this test, shipping of the product is impossible, which constitutes a large neck for improvement of the productivity in a production process for instruments for medical treatments. The sterile test requires two weeks until the test results are attained, during which a further step of charging a medicament as a subsequent process cannot be carried out, for example, in the case of a container for the sterile formulation.
FDA in USA has lately proposed the conception that it is equal to adaptability results in the sterile test to control the Parametric Release (shipping being dependent on the parameter administration), that is, the important Parameter for determining the precision of the process and to confirm and record the administrated state. Accordingly, as a first example, there is a sterilization operation utilizing a radiation and in the case of a product sterilized by this method, use and shipping of the product can be allowed by measurement and recording of the absorbed doses of materials sterilized such as containers for injections or instruments for medical treatments before the results of the sterile test. This conception is generally referred to as “Dosimetric Release” (shipping is allowed by dose measurement).
Various synthetic rubbers as raw materials are largely different in radiation resistance depending on their chemical structures, presence or absence of double bond or vinylidene type structure, cross-linking methods, presence or absence of quaternary carbon. EPM and EPDM (ethylene-propylene rubbers and ethylene-propylene terpolymer) having no double bond in the main chain have some problem on the vulcanization property as to working of the rubber, but are used as a material for rubber articles for medical treatments as disclosed by the present inventors in JP-A-62-176455.
On the other hand, the chemical structure of butyl rubber most suitable as a material of a rubber stopper for a medicament consists in having quaternary carbon in the main chain, isobutylene part, so that when applying a high energy such as radiation to the rubber molecule, polymer radicals are produced and the isobutylene part is cut off, resulting in oxidation deterioration. This chemical phenomenon is harder to occur in the case of chemically modified butyl rubber, such as by chlorine or bromine, but the tendency is not changed that it is inferior to any synthetic rubbers in radiation resistance.
The sterilization assurance level (SAL) of a rubber stopper for a medicament or an instrument for a medical treatment is ordinarily provided at 10
−6
and the radiation dose is often used at 25 kGy.
As a radiation, there are &agr;-rays (atomic nucleus of helium), &bgr;-rays (electron beam) and &ggr;-rays, and for the sterilization, there are used &bgr;-rays prepared by an accelerator and &ggr;-rays generated from
60
Co or
137
Cs. The electron beam has such a higher dose (several 10
4
times of &ggr;-rays) that the sterilization operation time is short, but only gives a small transmission because of being a particle beam. On the other hand, the &ggr;-rays (X-rays being the same) is a kind of electromagnetic waves and exhibits a large transmission capacity, but takes a longer operation time because of having a smaller dose than the electron beam.
In the case of sterilizing a rubber article by the large transmission &ggr;-rays, the radiation sterilization can be effected even if it is in the form of an article with a large apparent volume wrappe
Daikyo Seiko Ltd.
McClendon Sanza L.
Seidleck James J.
Wenderoth , Lind & Ponack, L.L.P.
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