Rubber stopper for medical treatment

1. A rubber stopper for medical treatment, which is obtained by molding a resin composition containing

component (A): at least one of a block copolymer having at least two of a polymer block P containing a vinyl aromatic compound as the core and at least one of a polymer block Q containing a conjugated diene as the core and a hydrogenated block copolymer obtained by hydrogenating the block copolymer,

component (B): a hydrocarbon-based softening agent for rubbers, and

component (C): a polyolefin-based resin, wherein

containing amount of the component (C) in the resin composition is from 1 weight part to 45 weight parts based on 100 weight parts in total of from 5 weight parts to 95 weight parts of the component (A) and from 5 weight parts to 95 weight parts of the component (B), and

the resin composition has one or more peaks or one or more peak shoulders within each of the ranges of

(A-1) molecular weight: from 250,000 to 350,000;

(A-2) molecular weight: from 100,000 to 150,000;

(A-3) molecular weight: from 400,000 to 550,000 and

(A-4) molecular weight: from 150,000 to 250,000

on the styrene basis molecular weight by a gel permeation chromatography analysis.

2. A rubber stopper for medical treatment, which is obtained by molding a resin composition containing

component (A): at least one of a block copolymer having at least two of a polymer block P containing a vinyl aromatic compound as the core and at least one of a polymer block Q containing a conjugated diene as the core and a hydrogenated block copolymer obtained by hydrogenating the block copolymer,

component (B): a hydrocarbon-based softening agent for rubbers, and

component (C): a polyolefin-based resin, wherein

containing amount of the component (C) in the resin composition is from 1 weight part to 45 weight parts based on 100 weight parts in total of from 5 weight parts to 95 weight parts of the component (A) and from 5 weight parts to 95 weight parts of the component (B), and

the component (A) has one or more peaks or one or more peak shoulders within each of the ranges of

(A-1) molecular weight: from 250,000 to 350,000;

(A-2) molecular weight: from 100,000 to 150,000;

(A-3) molecular weight: from 400,000 to 550,000; and

(A-4) molecular weight: from 150,000 to 250,000

on the styrene basis molecular weight by a gel permeation chromatography analysis.

3. The rubber stopper for medical treatment as claimed in any one of claim 1 or 2 , wherein a peak signal intensity ratio of a peak presenting within the range of (A-1) and a peak presenting within the range of (A-2) obtained by peak separation, [A-1/A-2], is from 25/75 to 95/5.

4. The rubber stopper for medical treatment as claimed in claim 1 or 2 , wherein the component (A) contains 10% by weight or more of the polymer block P.

5. The rubber stopper for medical treatment as claimed in claim 1 or 2 , wherein the polymer block Q contains isoprene as the conjugated diene and 1,4-addition structure of isoprene in the microstructure of polymer block Q is from 60% by weight to 100% by weight.

6. The rubber stopper for medical treatment as claimed in claim 1 or 2 , wherein the component (B) contains one or more species selected from the group consisting of a paraffin-based oil, a naphthene-based oil and a carbon atom aromatic oil.

7. The rubber stopper for medical treatment as claimed in claim 1 or 2 , wherein the component (C) is a peroxide resoluble type polyolefin-based resin.

8. The rubber stopper for medical treatment as claimed in claim 1 or 2 , which is used for a plastic needle.

9. An infusion bag, which contains the rubber stopper for medical treatment as described in any one of claim 1 or 2 .