Golf club shaft

1. A golf club shaft made of a fiber-reinforced epoxy resin material comprising a cured product of an epoxy resin composition and a reinforcing fiber,

wherein the epoxy resin composition comprises, as epoxy resin components,

a first epoxy resin component of at least one selected from the group consisting of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin and a novolac type epoxy resin; and

a second epoxy resin component of a tetraglycidyl type epoxy resin; and

wherein the cured product of the epoxy resin composition has a swelling ratio in a range from 20 mass % to 44 mass % in methyl ethyl ketone, and

the tetraglycidyl type epoxy resin content in the epoxy component ranges from 1 mass % to 19 mass %.

2. The golf club shaft according to claim 1 , wherein the content of the tetraglycidyl type epoxy resin in the epoxy resin components ranges from 5 mass % to 19 mass %.

3. The golf club shaft according to claim 1 , wherein the tetraglycidyl type epoxy resin is a glycidylamine type epoxy resin.

4. The golf club shaft according to claim 1 , wherein the epoxy resin composition further comprises a polyvinyl formal in an amount ranging from 2 parts by mass to 12 parts by mass with respect to 100 parts by mass of the epoxy resin components.

5. The golf club shaft according to claim 1 , wherein the epoxy resin composition comprises dicyandiamide as a curing agent and a urea derivative as a curing accelerator.

6. The golf club shaft according to claim 1 , wherein the epoxy resin components have an epoxy equivalent in a range from 200 g/eq to 400 g/eq.

7. The golf club shaft according to claim 1 , wherein the tetraglycidyl type epoxy resin includes at least one selected from the group consisting of tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenyl ether and tetraglycidyldiaminodiphenylsulfone.

8. The golf club shaft according to claim 1 , wherein the reinforcing fiber includes a carbon fiber.

9. The golf club shaft according to claim 1 , wherein the reinforcing fiber has a tensile elastic modulus in a range from 10 tf/mm 2 to 70 tf/mm 2 .

10. The golf club shaft according to claim 1 , wherein the swelling ratio of the cured product of the epoxy resin composition in methyl ethyl ketone is 25 mass % or more.

11. The golf club shaft according to claim 1 , wherein the swelling ratio of the cured product of the epoxy resin composition in methyl ethyl ketone is 38 mass % or less.

12. The golf club shaft according to claim 1 , wherein the epoxy resin composition comprises the bisphenol A type epoxy resin and the bisphenol F type epoxy resin as the first epoxy resin component.

13. The golf club shaft according to claim 12 , wherein a mass ratio (bisphenol A type epoxy resin/bisphenol F type epoxy resin) of the bisphenol A type epoxy resin to the bisphenol F type epoxy resin in the epoxy resin composition ranges from 0.3 to 3.0.

14. The golf club shaft according to claim 12 , wherein the epoxy resin composition further comprises the novolac type epoxy resin as the first epoxy resin component.

15. The golf club shaft according to claim 14 , wherein the bisphenol A type epoxy resin and the bisphenol F type epoxy resin are included in a difunctional epoxy resin, and

the difunctional epoxy resin content in the entire epoxy resin components ranges from 75 mass % to 98 mass %.

16. The golf club shaft according to claim 1 , wherein the epoxy resin composition comprises the novolac type epoxy resin as the first epoxy resin component.

17. The golf club shaft according to claim 16 , wherein the novolac type epoxy resin content in the entire epoxy resin components ranges from 2 mass % to 19 mass %.

18. The golf club shaft according to claim 16 , wherein the tetraglycidyl type epoxy resin and the novolac type epoxy resin total content in the entire epoxy resin components ranges from 4 mass % to 25 mass %.

19. A golf club shaft made of a fiber-reinforced epoxy resin material comprising a cured product of an epoxy resin composition and a reinforcing fiber,

wherein the epoxy resin composition comprises, as an epoxy resin component,

a bisphenol A type epoxy resin;

a bisphenol F type epoxy resin;

a novolac type epoxy resin; and

a tetraglycidyl type epoxy resin; and

wherein the cured product of the epoxy resin composition has a swelling ratio in a range from 20 mass % to 44 mass % in methyl ethyl ketone.

20. A golf club shaft made of a fiber-reinforced epoxy resin material comprising a cured product of an epoxy resin composition and a reinforcing fiber,

wherein the epoxy resin composition comprises, as an epoxy resin component,

a novolac type epoxy resin; and

a tetraglycidyl type epoxy resin; and

wherein the cured product of the epoxy resin composition has a swelling ratio in a range from 20 mass % to 44 mass % in methyl ethyl ketone, and

the tetraglycidyl type epoxy resin and the novolac type epoxy resin total content in the entire epoxy resin components ranges from 4 mass % to 25 mass %.