Soft elastomeric films
View Patent ↗Elastomeric films which are both soft and thermally, UV and oxidatively stable are provided. The films are composed of coupled, selectively hydrogenated block copolymers having a relatively high molecular weight and high vinyl content. In addition to the block copolymer other components may be present in formulated films such as other block copolymers, hydrocarbon resins, polyolefins, metallocene polyolefins, homopolystyrene or mineral oils. The softness of the films is determined by the stress at 100% tensile elongation where the films with suitable softness have a 100% stress of about 100 psi or less. While soft, the films also are strong with tensile strengths of 1000 psi or more and suitable hysteresis properties. The elastomeric films are useful as integral components of personal hygiene articles such as gloves, diapers, incontinence products, disposable swimwear and disposable undergarments.
1. A personal hygiene article comprising a soft elastomeric film consisting essentially of a coupled, selectively hydrogenated block copolymer having the general formula:
(A-B) n X
wherein
a. prior to hydrogenation the A block is a polymerized monoalkenyl arene hydrocarbon block having a molecular weight from 6000 to 7000;
b. prior to hydrogenation the B block is a polymerized conjugated diene hydrocarbon block having a vinyl content from 60 to 85% mol;
c. the total molecular weight of the block copolymer is from 180,000 to 400,000;
d. the monoalkenyl arene content of the block copolymer is from 9 to 16% wt;
e. X is the residue of a coupling agent and n is from 2 to 6; and
f. the block copolymer includes less than 10% of uncoupled A-B arms;
where the elastomeric film has a 100% stress of about 100 psi or less and a tensile strength of at least about 1000 psi.
2. The personal hygiene article of claim 1 wherein the total molecular weight of the block copolymer is from 200,000 to 300,000.
3. The personal hygiene article of claim 1 wherein the monoalkenyl arene content is from 10 to 14% wt.
4. The personal hygiene article of claim 1 wherein the monoalkenyl arene is styrene and the conjugated diene is butadiene.
5. The personal hygiene article of claim 4 wherein subsequent to hydrogenation greater than 95% mol of the conjugated diene units and less than 5% mol of the monoalkenyl arene units have been hydrogenated.
6. The personal hygiene article of claim 1 having a tensile elongation of at least 600%.
7. The personally hygiene article of claim 1 which is a glove, diaper, incontinence product, disposable swimwear or disposable undergarment.
8. A soft elastomeric film comprising two coupled, selectively hydrogenated block copolymers each having the general formula:
(A-B) n X
wherein the film comprises from 15 to 40 parts by weight of a first block copolymer having:
a. prior to hydrogenation the A block is a polymerized monoalkenyl arene hydrocarbon block having a molecular weight from 6000 to 7000;
b. prior to hydrogenation the B block is a polymerized conjugated diene hydrocarbon block having a vinyl content from 60 to 85% mol;
c. the total molecular weight of the block copolymer is from 180,000 to 400,000;
d. the monoalkenyl arene content of the block copolymer is from 9 to 16% wt;
e. X is the residue of a coupling agent and n is from 2 to 6; and
f. the block copolymer includes less than 10% of uncoupled A-B arms; and the film comprises from 60 to 85 parts by weight of a second block copolymer having:
g. prior to hydrogenation the A block is a polymerized monoalkenyl arene hydrocarbon block having a molecular weight from 5000 to 7000;
h. prior to hydrogenation the B block is a polymerized conjugated diene hydrocarbon block having a vinyl content from 60 to 85% mol;
i. the total molecular weight of the block copolymer is from 100,000 to 160,000;
j. the monoalkenyl arene content of the block copolymer is from 16% wt to 24% wt;
k. X is the residue of a coupling agent and n is from 2 to 6; and
l. the block copolymer includes less than 10% of uncoupled A-B arms; and
where the elastomeric film has a 100% stress of about 100 psi or less and a tensile strength of at least about 1000 psi.
9. The soft elastomeric film of claim 8 wherein the second block copolymer has a melt index of greater than or equal to 12 g/10 min according to ASTM D1238 at 230° C. and 2.16 kg weight.
10. A glove, diaper, incontinence product, disposable swimwear or disposable undergarment comprising the soft elastomeric film of claim 8 .
11. A soft elastomeric film comprising from 25 to 75 parts by weight of a coupled, selectively hydrogenated block copolymer having the general formula:
(A-B) n X
wherein
a. prior to hydrogenation the A block is a polymerized monoalkenyl arene hydrocarbon block having a molecular weight from 6000 to 7000;
b. prior to hydrogenation the B block is a polymerized conjugated diene hydrocarbon block having a vinyl content from 60 to 85% mol;
c. the total molecular weight of the block copolymer is from 180,000 to 400,000;
d. the monoalkenyl arene content of the block copolymer is from 9 to 16% wt;
e. X is the residue of a coupling agent and n is from 2 to 6; and
f. the block copolymer includes less than 10% of uncoupled A-B arms and from 75 to 25 parts by weight of a controlled distribution block copolymer having a general configuration A′-B′, A′-B′-A′, (A′-B′) n , (A′-B′-A′) n X, (A′-B′) n X or mixtures thereof, where n is an integer from 2 to about 30, and X is coupling agent residue wherein:
g. prior to hydrogenation each A′ block is a monoalkenyl arene polymer block and each B′ block is a controlled distribution copolymer block of at least one conjugated diene and at least one monoalkenyl arene;
h. subsequent to hydrogenation about 0-10% of the arene double bonds have been reduced, and at least about 90% of the conjugated diene double bonds have been reduced;
i. each A′ block has a number average molecular weight between about 3,000 and about 60,000 and each B′ block has a number average molecular weight between about 30,000 and about 300,000;
j. each B′ block comprises terminal regions adjacent to the A′ block that are rich in conjugated diene units and one or more regions not adjacent to the A′ blocks that are rich in mono alkenyl arene units;
k. the total amount of monoalkenyl arene in the hydrogenated block copolymer is about 20 percent weight to about 80 percent weight;
l. the weight percent of mono alkenyl arene in each B′ block is between about 10 percent and about 75 percent; and
m. the monoalkenyl arene blockiness in the B′ block is less than 40%;
where the elastomeric film has a 100% stress of about 100 psi or less and a tensile strength of at least about 1000 psi.
12. A glove, diaper, incontinence product, disposable swimwear or disposable undergarment comprising the soft elastomeric film of claim 11 .