Curable transparent rubber composition, a cured transparent rubber composition made thereof, and manufacturing process for the same

1. A solid curable, transparent, rubber composition that once cured has a haze of less than 30% and a total light transmission of more than 80%, both measured according to ASTM D1003-13, comprising:

Component (a): from 76 to 99.94 wt. % of a styrenic block copolymer having 2 or more poly(vinyl aromatic) blocks and at least one block of polymerized conjugated diene, wherein the styrenic block copolymer has a weight average molecular weight of 150,000 to 250,000, the poly(vinyl aromatic) blocks have a weight average molecular weight ranging from 9,000 to 15,000, and the content of poly(vinyl aromatic) blocks in the styrenic block copolymer ranges from 8 to 13 wt. %, based on the total styrenic block copolymer;

Components (b) and (c): from 0.05-8.0 wt. % of a combination of a curing agent and a co-agent, wherein the co-agent is present in an amount from greater than 0 to 7.95 wt. % and wherein the co-agent is any one or more selected from the group consisting of ethylene glycol methacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, and neophenylene glycol diacrylate, and

Component (d): from 0.01-20 wt. % of additives that do not influence the transparency,

wherein the amounts of components (a) through (d) are in percentages by weight of the total composition; and

wherein the co-agent (c) is used in a weight ratio (b) to (c) of 1:2-10.

2. The composition according to claim 1 , wherein component (b) is a peroxide.

3. The composition according to claim 2 , wherein the co-agent (c) is used in a weight ratio (b) to (c) of 1:3-7.

4. The composition according to claim 1 , that once cured has at least one of the following properties:

A Type A Durometer hardness (30 sec) of 25 or more, measured according to ASTM D2240; and

A Tear Strength of 10 N/mm or more, measured according to ASTM D624.

5. The composition according to claim 1 , wherein component (b) is 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 1,1-di(tert-butylperoxy)cyclohexane, or 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane.

6. An article based on the composition according to claim 1 .

7. A process for manufacturing a transparent, cured rubber composition from the composition according to claim 1 , wherein the process comprises the steps of:

mixing components (a), and (d) to obtain a mixture thereof;

adding a curing agent (b) and a co-agent (c); and

uniformly kneading the mixture and curing the same.

8. An article having a composition prepared by the process according to claim 7 .

9. The article according to claim 8 , wherein the article is selected from the group consisting of tubes, medical stoppers, catheters, dental dams and other medical applications, clothes and underclothes, rain gears, eyewear, masks, toys, damping materials, building materials, coating material for wiring, packaging materials, protective members for computers, computer peripherals, contraceptive devices, sex toys, artificial nipples, disposable diapers, stationery, containers, food trays, balls for sports, ball chairs, protection films, seals, and key covers.

10. A solid curable, transparent, rubber composition that once cured has a haze of less than 30% and a total light transmission of more than 80%, both measured according to ASTM D1003-13, comprising:

Component (a): from 76 to 99.94 wt. % of a styrenic block copolymer having a simple structure A-B-Y-(B-A)n wherein:

each A is independently a polymer block composed of at least 90 mole % of an alkenyl aromatic hydrocarbon;

the content of A by weight of the total weight of the polymer (PSC) is in the range of 8-13%;

Y is the remnant of a coupling agent having a functionality greater than 2;

the degree of branching (DoB) is n+1, wherein n is an integer from 2 to 5;

each B is independently a polymer block composed of at least 90 mole % of one or more conjugated dienes; and

the styrenic block copolymer has a coupling efficiency (CE) of at least 90%;

each A block independently has a weight average molecular weight (MW A) ranging from 9,000 to 15,000, and

each B Block independently has a weight average molecular weight (MW B) ranging from 75,000 to 150,000;

Components (b) and (c): from 0.05-8.0 wt. % of a combination of curing agent and co-agent, wherein the co-agent is present in an amount from greater than 0 to 7.95 wt % and wherein the co-agent is any one or more selected from the group consisting of ethylene glycol methacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, and neophenylene glycol diacrylate, and

Component (d): from 0.01-20 wt. % of additives that do not influence the transparency,

wherein the amounts of components (a) through (d) are in percentages by weight of the total composition; and

wherein the co-agent (c) is used in a weight ratio (b) to (c) of 1:2-10.

11. The composition according to claim 10 , wherein component (a) is a block copolymer the blocks A of which have weight average molecular weights between about 10,000 and about 12,000, and the blocks B thereof have weight average molecular weights between about 80,000 and about 120,000, and wherein the weight percentage of the A blocks in the block polymer is between 10% and 12% by weight.

12. The composition according to claim 10 , wherein

Component (b) is any one or more selected from the group consisting of is 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 1,1-di(tert-butylperoxy)cyclohexane, and 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane; and

Component (c) is any one or more selected from the group consisting of ethylene glycol methacrylate (EGDMA) and trimethylolpropane trimethacrylate (TMPTMA), wherein component (c) is used in a weight ratio (b) to (c) of 1:3-7.