Tread enhancement additives
Provided herein are novel tire tread compositions. The tire tread compositions include a rubber, a terpene-based resin and at least one filler. The terpene-based resin comprises one terpene-based monomer such as α-pinene, referred to as a hompolymer, or combinations of several terpene-based monomers selected from α-pinene, β-pinene, δ-3 carene, β-phellandrene and pyrolysates of α-pinene, β-pinene, δ-3 carene, δ-2 carene, turpentine, and combinations thereof. The terpene-based resin is generally substantially free of limonene. The terpene-based resin has a softening point of about 80° C. to about 130° C., a number average molecular weight (M n ) ranging from about 500 g/mol to about 775 g/mol and a glass transition temperature (T g ) of from about 38° C. to about 81° C. The tire tread composition having the terpene-based resin shows improvements of tan δ at 0°, wet grip and rolling resistance as compared with the compositions without the terpene-based resin or comprising alpha methyl styrene resin.
1. A tire tread composition comprising:
(a) a rubber component selected from the group consisting of synthetic diene rubber and natural rubber;
(b) at least one filler in the amount of from about 5 to 250 phr; and
(c) a terpene-based resin comprising a terpene-based monomer selected from α-pinene, β-pinene, δ-3 carene, β-phellandrene and pyrolysates of α-pinene, β-pinene, δ-3 carene, δ-2 carene, turpentine, and combinations thereof;
wherein the terpene-based resin has
(i) a softening point of from about 80° C. to about 130° C.; (ii) a number average molecular weight (M n ) ranging from about 500 g/mol to about 775 g/mol; and (iii) a glass transition temperature (T g ) of from about 38° C. to about 81° C. ; and (iv) wherein the resin is substantially free of limonene.
2. The tire tread composition of claim 1 , wherein the terpene-based resin is an α-pinene homopolymer.
3. The tire tread composition of claim 2 , wherein the terpene-based resin comprises at least 99 wt. % of α-pinene based upon the total weight of the terpene-based resin.
4. The tire tread composition of claim 1 , wherein the terpene-based resin is a mixture of α-pinene and β-pinene, and wherein α-pinene is present in an amount of at least 80 wt. % based upon the total weight of the terpene-base resin.
5. The tire tread composition of claim 1 , wherein the terpene-based resin is a mixture of α-pinene and β-pinene present at a ratio ranging from 65:35 to 85:15.
6. The tire tread composition of claim 1 , wherein the terpene-based resin has a z-average molecular weight (M z ) ranging from about 1300 g/mol to about 1600 g/mol.
7. The tire tread composition of claim 1 , having a tan δ at 0° C. that is increased from about 135% to about 153% when compared to a composition without the resin.
8. The tire tread composition of claim 1 , having a rolling resistance improvement of at least 4% when compared with a composition with an Alpha Methyl Styrene resin.
9. The tire tread composition of claim 1 having an improvement of the wet grip/rolling resistance ration (WG*RR) of at least about 7.5%, when compared with a composition with Alpha Methyl Styrene.
10. A tire tread composition of claim 1 , wherein the terpene-based resin has a softening point of from about 60° C. to about 150° C., a weight average molecular weight of from about 800 g/mol to about 1100 g/mol, a z-average molecular weight of from about 1300 g/mol to about 1600 g/mol; and a glass transition temperature (T g ) of from about 38° C. to about 81° C.
11. The tire tread composition of claim 1 , wherein the terpene-based resin is present in the range of from about 1 to about 50 phr.
12. The tire tread composition of claim 1 , wherein component c) is an olefinically unsaturated non-acidic terpene compound.