Protective films and pressure sensitive adhesives
View Patent ↗Protective film in the form of a tape or sheet comprising a substrate layer and a pressure sensitive adhesive composition.
1. A protective film in the form of a tape or sheet comprising a substrate layer and a pressure sensitive adhesive composition, said pressure sensitive adhesive comprising:
(I) 100 parts by weight (pbw) of a block copolymer containing at least two poly(monovinyl aromatic hydrocarbon) blocks and at least one hydrogenated poly(conjugated) diene block,
(II) 0 to 200 pbw of a tackifying resin,
(III) 0 to 50 pbw of a polyolefin,
(IV) 0 to 100 pbw of a plasticizer, and
(V) 0 to 5 pbw of antioxidant,
wherein at least one of (II), (III), (IV) and (V) are present in said pressure sensitive adhesive composition; and wherein the block copolymer of said pressure sensitive adhesive composition
i. has a molecular structure according to the general formulae
S-EB-S(1) or (S-EB)nX(2),
wherein each S independently is a polymer block of predominantly styrene and EB is a hydrogenated polymer block of predominantly butadiene, n is an integer equal to or greater than 2, and X is the residue of a coupling agent,
ii. has a poly(styrene) content (PSC) from 17 to 24 wt %,
iii. has an apparent molecular weight of the poly(styrene) blocks (S) that is in the range of from 5,000 to 12,000,
iv. has an 1,2-addition degree (vinyl content) in the precursor poly(butadiene) block (EB) precursor is in the range of from 60 to 85 (mole/mole),
v. has a block EB that has a hydrogenation degree of at least 80%, and
vi. has an optional diblock S-EB content of at most 10 mole %, relative to the total block copolymer amount.
2. The protective film of claim 1 wherein the pressure adhesive composition comprises:
two poly(monovinyl aromatic hydrocarbon) blocks and at least one hydrogenated poly(conjugated diene) block;
(II) 10 to 200 pbw of a tackifying resin;
(III) 0 to 50 pbw of a polyolefin, wherein the polyolefin has a melt index of about 0.1-30 g/10 minutes (ASTM D-1238, Condition E at 190° C. at 2.16 kg load), and
(V) 0 to 5 pbw of antioxidant.
3. The protective film of claim 1 wherein the pressure adhesive composition comprises:
(I) 100 parts by weight (pbw) of a block copolymer containing at least two poly(mono vinyl aromatic hydrocarbon) blocks and at least one hydrogenated poly(conjugated diene) block,
(IV) 20 to 70 pbw of a plasticizer, and
(V) 0 to 5 pbw of antioxidant.
4. The protective film of claim 2 wherein the pressure sensitive adhesive composition shows a combination of high peel adhesion (i.e. PA 90 at 23° C. of at least 40 N/25 mm) and a melt flow rate of from 5 to 20 g/10 min. (measured according to ASTM D-1238, Condition E at 190° C. at 2.16 kg load).
5. The protective film of claim 2 wherein the tackifying resin has a softening point as determined by the Ring and Ball method (ASTM E-28) from 75 to 140° C.
6. The protective film of claim 2 wherein the plasticizer is selected from naphthenic oils and paraffinic oils.
7. The protective film of claim 2 wherein the poly(α-olefin) polymer is a poly(butene-)homopolymer or copolymer.
8. The protective film of claim 2 wherein the block copolymer(s) applied in the pressure adhesive composition have a polystyrene content from 19 to 21% and an 1,2-addition (vinyl) content in the midblock precursor from 65 to 75%.
9. A pressure sensitive adhesive composition to be used as a component of protective films, said pressure sensitive adhesive composition comprising:
(I) 100 parts by weight (pbw) of a block copolymer containing at least two poly(monovinyl aromatic hydrocarbon) blocks and at least one hydrogenated poly(conjugated) diene block,
(II) 0 to 200 pbw of a tackifying resin,
(III) 0 to 50 pbw of a polyolefin,
(IV) 0 to 100 pbw of a plasticizer, and
(V) 0 to 5 pbw of antioxidant,
wherein at least one of (II), (III), (IV) and (V) are present and wherein the block copolymer
i. has a molecular structure according to the general formulae
S-EB-S(1) or (S-EB)nX(2),
wherein each S independently is a polymer block of predominantly styrene and EB is a hydrogenated polymer block of predominantly butadiene, n is an integer equal to or greater than 2, and X is the residue of a coupling agent,
ii. has a poly(styrene) content (PSC) from 17 to 24 wt %,
iii. has an apparent molecular weight of the poly(styrene) blocks (S) that is in the range of from 5,000 to 12,000,
iv. has an 1,2-addition degree (vinyl content) in the precursor poly(butadiene) block (EB) precursor is in the range of from 60 to 85 (mole/mole),
v. has a block EB that has a hydrogenation degree of at least 80% and
vi. has an optional diblock S-EB content of at most 10 mole %, relative to the total block copolymer amount.
10. The pressure sensitive adhesive composition of claim 9 which shows a combination of high peel adhesion (i.e. PA 90 at 23° C. of at least 40 N/25 mm) and a melt flow rate of from 5 to 20 g/10 min. (measured according to ASTM 1238-D).
11. Shaped articles protected by the protective films according to claim 1 .