Amorphous propylene-ethylene copolymers
A low molecular weight copolymer is provided comprising propylene and ethylene, wherein the low molecular weight copolymer has a softening point in the range of 90 to 140° C., wherein the low molecular weight copolymer has a needle penetration that is equal to y, wherein y is defined by the following formula: y ≤−0.000000262249 x 6 +0.000172031278 x 5 −0.046669720165 x 4 +6.701746779438 x 3 −537.286013331959 x 2 +22,802.983472587 x −400,204.018086126 wherein x in the above formula is the softening point of the low molecular weight copolymer, and wherein the low molecular weight copolymer has a molecular weight polydispersity index of about 3 to about 25, a crystallinity of about 18% to about 30% measured by X-Ray diffraction, and a Brookfield viscosity in the range of about 1000 to about 4000 cp at 190° C. measured by ASTM D 3236. Adhesive compositions comprising the low molecular weight copolymer are also provided.
1. A low molecular weight copolymer comprising propylene and ethylene,
wherein said low molecular weight copolymer has a softening point in the range of 90 to 140° C.,
wherein said low molecular weight copolymer has a needle penetration that is equal to y,
wherein y is defined by the following formula:
y≤− 0.000000262249 x 6 +0.000172031278 x 5 −0.046669720165 x 4 +6.701746779438 x 3 −537.286013331959 x 2 +22,802.983472587 x− 400,204.018086126
wherein x in the above formula is the softening point of said low molecular weight copolymer,
wherein said low molecular weight copolymer has a molecular weight polydispersity index of about 3 to about 25, a crystallinity of about 18% to about 30% measured by X-Ray diffraction, and a Brookfield viscosity in the range of about 1000 to about 4000 cp at 190° C. measured by ASTM D 3236.
2. The low molecular weight copolymer of claim 1 wherein said copolymer has a crystallinity content of about 20% to about 30%.
3. The low molecular weight copolymer of claim 1 wherein said copolymer has a weight average molecular weight of 25,000 to 50,000.
4. The low molecular weight copolymer of claim 3 wherein said copolymer has a weight average molecular weight of 30,000 to 45,000.
5. The low molecular weight copolymer of claim 1 wherein said copolymer has a molecular weight polydispersity index of about 8 to about 23.
6. The low molecular weight copolymer of claim 5 wherein said copolymer has a molecular weight polydispersity index of about 6 to about 15.
7. The low molecular weight copolymer of claim 1 wherein said number average molecular weight ranges from about 1,000 to about 20,000.
8. The low molecular weight copolymer of claim 1 wherein said Brookfield viscosity ranges from about 1,500 to about 3,000.
9. The low molecular weight copolymer of claim 1 wherein the storage modulus (G′) at 25° C. of said low molecular weight copolymer ranges from about 1 MPa and 10 MPa.
10. The low molecular weight of claim 1 wherein the tensile strength of said low molecular weight copolymer ranges from about 2.5 MPa to about 4.5 MPa.
11. A low molecular weight copolymer comprising propylene and ethylene wherein said low molecular weight copolymer has a weight average molecular weight of about 25,000 to about 45,000, a number average molecular weight of about 1,000 to about 12,000, a z-average molecular weight of about 90,000 to about 140,000, a polydispersibility (Mw/Mn ratio) of about 3 to about 25, a crystallinity of about 20% to about 30%, and a Brookfield viscosity of 1,000 to 4,000 cp at 190° C.
12. A low molecular weight copolymer according to claim 11 wherein said low molecular weight copolymer has a storage modulus (G′) at 25° C. of 1 to 10 MPa; a crossover temperature (for G′ and G″) of 110 to 120° C. with an associated tan δ of 0.35 to 0.50; and a glass transition of −40 to −25° C.
13. An article comprising said low molecular weight copolymer of claim 1 .
14. An adhesive composition comprising said low molecular weight copolymer of claim 1 .
15. The adhesive composition of claim 14 , wherein said adhesive composition comprises in the range of 5 to 95 weight percent of said low molecular weight copolymer.
16. The adhesive composition of claim 14 , wherein said adhesive composition comprises in the range of 5 to 95 weight percent of at least one polymer.
17. The adhesive composition of claim 14 , wherein said adhesive composition comprises in the range of 0 to 70 weight percent of at least one tackifier.
18. The adhesive composition of claim 14 , wherein said needle penetration is in the range of 0.5 to 70 dmm.
19. The adhesive composition of claim 14 , wherein said adhesive composition applied at 100-145° C. has a peel strength in the range of 1 to 200 g/mm, and wherein said adhesive composition applied at 145-180° C. has a peel strength in the range of 1 to 250 g/mm.
20. The adhesive composition of claim 14 , wherein said adhesive composition has a loop tack in the range of 0.1 to 50 lbf.