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(12) United States Patent
Wright et al.
(io) Patent No.: (45) Date of Patent:
US 7,585,916 B2 *Sep. 8, 2009
(54) BLOCK COPOLYMER COMPOSITIONS
(75) Inventors: Kathryn J. Wright, Katy, TX (US);
Carl L. Willis, Houston, TX (US);
Tomomi Nishi, Tsukuba (JP); Norio
Masuko, Ami-machi (JP); Dale L.
Handlin, Jr., Houston, TX (US); Robert
C. Bening, Katy, TX (US)
(73) Assignee: Kraton Polymers US LLC, Houston, TX (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
This patent is subject to a terminal disclaimer.
(21) Appl.No.: 11/686,188
(22) Filed: Mar. 14, 2007
(65) Prior Publication Data
US 2008/0015306 Al Jan. 17, 2008
Related U.S. Application Data
(63) Continuation-in-part of application No. 11/388,909, filed on Mar. 24, 2006.
(51) Int. CI.
C08L 53/02 (2006.01)
(52) U.S. CI 525/98; 525/88; 525/89;
525/99; 525/242; 525/338; 524/505
(58) Field of Classification Search 525/88,
525/89, 98, 99, 242, 338; 524/505 See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
1
BLOCK COPOLYMER COMPOSITIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 11/388,909, filed Mar. 24, 2006.
5
FIELD OF THE INVENTION
This invention relates to novel compositions comprising (a) anionic block copolymers of mono alkenyl arenes and conjugated dienes where one of the blocks is a controlled io distribution copolymer of a conjugated diene and mono alkenyl arene having a specific arrangement of the monomers in the copolymer block, and (b) tailored softening modifiers have a particular structure that results in a surprising improvement in properties for the composition. 15
BACKGROUND OF THE INVENTION
The preparation of block copolymers is well known. In a representative synthetic method, an initiator compound is 20 used to start the polymerization of one monomer. The reaction is allowed to proceed until all of the monomer is consumed, resulting in a living homopolymer. To this living homopolymer is added a second monomer that is chemically different from the first. The living end of the first polymer 25 serves as the site for continued polymerization, thereby incorporating the second monomer as a distinct block into the linear polymer. The block copolymer so grown is living until terminated.
Termination converts the living end of the block copolymer 30 into a non-propagating species, thereby rendering the polymer non-reactive toward monomer or coupling agent. A polymer so terminated is commonly referred to as a diblock copolymer. If the polymer is not terminated the living block copolymers can be reacted with additional monomer to form 35 a sequential linear tri-block copolymer. Alternatively the living block copolymer can be contacted with multifunctional agents commonly referred to as coupling agents. Coupling two of the living ends together results in a linear triblock copolymer having twice the molecular weight of the starting, 40 living, diblock copolymer. Coupling more than two of the living diblock copolymer regions results in a radial block copolymer architecture having at least three arms.
One of the first patents on linear ABA block copolymers made with styrene and butadiene is U.S. Pat. No. 3,149,182. 45 These polymers in turn could be hydrogenated to form more stable block copolymers, such as those described in U.S. Pat. Nos. 3,595,942 and Re. 27,145. Various block copolymers and processes for making them have been proposed over the years. Recently, KRATON Polymers introduced a new class 50 of hydrogenated styrene/diene block copolymers that have a unique structure and a unique balance of properties. These polymers, known as controlled distribution block copolymers, have mono alkenyl arene end blocks and controlled distribution blocks of mono alkenyl arenes and conjugated 55 dienes. See US Published Patent Applications 2003/0176582 Al, 2003/0181585 Al, 2003/0176574 Al, 2003/0166776 Al and related patents and published applications around the world. Such block copolymers have found numerous uses in, e.g., personal hygiene applications, in compounding applica- 60 tions and for over molding applications.
While block copolymers are often used in compounded form, the presence of certain of the typical blending components can also have a detrimental impact on properties. Common blending components include plasticizing oils, tackify- 65 ing resins, polymers, oligomers, fillers, reinforcements and additives of all varieties. Oils are often added to such block
2
copolymers to increase softness and improve processability to the compound. However, such oils also typically reduce the strength and tear resistance of the compounds. What is needed now are new compounding materials that do not have such a dramatic negative effect on properties, while still imparting increased softness with improved processability.
Applicants have now discovered that, when certain low molecular weight anionic diene/vinyl aromatic oligomers or polymers are combined in a particular way with the controlled distribution block copolymers noted above, it is possible to obtain compounds having better strength and tear resistance than the analogous oiled compounds, and also experience significant improvements in manufacturing steps and economies as well as improved properties such as increased softness without a significant reduction in processability. In addition, such compositions have lower volatility at equivalent hardness, resulting in improved organoleptics, reduced fogging and reduced extractables.
SUMMARY OF THE INVENTION
The particular compositions of the present invention are "in-situ compositions", since the low molecular weight tailored softening modifier (which improves flow and softness) is made and/or finished "in-situ", along with the controlled distribution block copolymer. This "in-situ" recovery is essential since recovery of the tailored modifier as a neat material from the solvent in which it is manufactured is very difficult and problematic. At room temperature, softening modifiers have physical properties that are intermediate between free flowing solids and pourable liquids. They are difficult to handle as neat materials. For this reason, it is desirable to recover (finish) them from the manufacturing solvent as a blend with the base block copolymer that they have been designed to modify. The blend can thus be recovered as an easy to handle solid.
The tailored softening modifier/base polymer blend may be prepared before recovery from the manufacturing solvent by 1) combining separate process streams containing the individual components—modifier and base block copolymer or 2) preparing them in the same process stream. The two approaches have different advantages. When the two components are polymerized separately and the solvent blend is prepared by mixing prior to finishing, there are few constraints on the chemistry that may be used to make the softening modifier or the base polymer. The manufacturing chemistry and associated technologies can be rather simple and robust. The softening modifier might be prepared by a conventional anionic polymerization technique—1) initiation using a metal alkyl such as a lithium alkyl, 2) propagation by addition of the appropriate monomer(s), and 3) termination of the living chain end by addition of a stoichiometric amount of a protic reagent such as an alcohol. Alternatively, a polymerization chain transfer agent, such as a secondary amine, might be used to allow the preparation of more than one tailored softening modifier molecule per molecule of polymerization initiator. In this embodiment, the base block copolymer is prepared in a separate process step and can be made using any of the known processes for the synthesis of a block copolymer. Another approach may be to take the controlled distribution block copolymer and redissolve it in an appropriate solvent, and then combine it with a solution of the tailored softening modifier, and finish the two together.
Accordingly, the present invention broadly comprises a novel block copolymer composition comprising:
(a) 100 parts by weight of a solid hydrogenated controlled distribution block copolymer having the general con
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