Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-11-17
2003-01-21
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S432000, C524S433000, C524S457000, C524S458000, C524S461000, C524S533000, C524S609000, C524S535000, C524S547000
Reexamination Certificate
active
06509404
ABSTRACT:
TECHNICAL FIELD
This invention relates to ionomeric particulate compositions useful for modifying the rheology and functionality of a polymer matrix so as to render the matrix more useful in applications that require adhesive properties.
BACKGROUND
Suspension polymerization has been used to make polymer beads. For example, U.S. Pat. No. 4,833,179 (Young et al.) and U.S. Pat. No. 4,952,650 (Young et al.) describe methods of aqueous suspension polymerization to form pressure sensitive acrylate copolymer beads. The methods generally comprise making a monomer premix comprising acrylic acid esters of a non-tertiary alcohol, an acid monomer copolymerizable with the acrylic acid ester, a chain transfer agent, a free radical initiator, and a modifier moiety. The monomer premix is combined with a water phase, which contains a sufficient amount of suspending agent, to form a suspension. Polymerization occurs by mixing the premix phase with the water phase until the polymer beads are formed. The polymer beads may remain in the water prior to coating, during which time the beads are preferably storage-stable so as not to coalesce or agglomerate together. When coalescence is present, the beads tend to migrate towards one another and can form large masses. Coalescence of the beads hampers their handling and transportation and is undesirable.
U.S. Pat. No. 5,952,420 (Senkus et al.) discloses permeable, self-supporting, shaped structures that can be used in applications such as filters, masks, or respirators. The structure comprises a mass of active particulates (e.g., sorbents such as activated carbon, silica gel, or alumina granules) bonded together with pressure sensitive adhesive polymer particulates (also referred to as “PSA suspension beads”) distributed in the mass of active particulate. PSA suspension beads from about 10 to 100 micrometers can be prepared using a combination of surfactants and using, as another co-monomer, a styrene sulfonate salt, such as sodium salt, to control particle size in the suspension polymerization. PSA suspension beads from about 1 to 10 micrometer can be achieved by homogenizing the polymerization reaction mixture comprising (1) the styrene sulfonate salt and (2) an amount of surfactant above the critical micelle concentration to the water phase before suspension polymerization. See Column 9, lines 39-44 and lines 57-61. Senkus also discloses that the PSA polymer is essentially any polymer, copolymer, or blend of copolymer that has pressure sensitive adhesive properties. A related patent is U.S. Pat. No. 5,696,199 (Senkus et al.)
The polymeric particulate and beads discussed thus far typically use added chain transfer agents. Chain transfer refers to the termination of a growing polymer chain and the start of a new one thus controlling the molecular weight of the polymer. The process can be affected by use of a chain transfer agent, which, in many cases, is some species that has been added to the polymerization process to effect chain transfer (referred to as an “added chain transfer agent”). Chain transfer agents are used widely in polymerization processing to decrease the molecular weight of the polymer thereby imparting to the polymer one of the properties necessary for pressure sensitive tack. In suspension polymerization, chain transfer agents are typically added to the oil phase, which contains the monomers. When the monomers are acrylate esters of a non-tertiary alcohol having 1 to 14 carbon atoms, common chain transfer agents include mercaptans, alcohols, and carbon tetrabromide, with isooctyl thioglycolate being a preferred one. See U.S. Pat. No. 4,833,179, Column 4, lines 37-42. The beads discussed thus far typically possess room temperature tackiness and thus are well suited as a pressure sensitive adhesive.
To control the beads' particle size, surfactants in a certain amount, surfactants in combination with another comonomer, and homogenization techniques have been used. Homogenization, which generally refers to reducing a material to particles and dispersing the particles throughout a liquid, can be achieved by using the appropriate agitation. Typically, for laboratory size batches (i.e., on the order of a few liters), a Waring™ blender is used for homogenization. It is well known in the suspension polymerization art that agitation can be important to achieving the desired particle-size distribution in the final product.
While the foregoing methods of aqueous suspension polymerization and the resulting acrylate pressure sensitive adhesive beads have been proven useful, other suspension polymerization compositions are sought.
SUMMARY
This invention provides a novel ionomeric particulate composition where the particulate does not incorporate the use of an added chain transfer agent to control the molecular weight of the particulate. The resulting ionomeric particulates tend to have high molecular weight. The particulates can be formulated to have pressure sensitive tack or to have only minimal pressure sensitive tack, as desired. The particulates can act as a reinforcing agent when added to a polymer matrix. Also, in the present invention, ionomeric particulates' size can be controlled through the use of surfactants and polyacrylamides.
In brief summary, the ionomeric particulate composition of the invention comprises or consists essentially: at least one vinyl monomer; an acid monomer; a metal oxide; at least a first and a second surfactant, the first surfactant being a monomer surfactant; and a polyacrylamide.
The present invention provides ionomeric particulate compositions that can be dispersed into a polymer matrix to modify the rheology, functionality, and physical properties (e.g., cohesive strength, adhesion, toughness, elasticity, flexibility) of the polymer matrix so as to yield a useful organic particulate-filled adhesive. A key advantage of the present invention lies in the ability to tailor the ionomeric particulate so that when combined with a particular polymer matrix, the resulting organic particulate-filled adhesive exhibits the desired properties.
The ionomeric particulates can be used to modify any polymer matrix that is compatible with it to yield an organic particulate-filled adhesive useful for a variety of diverse applications. The adhesive can be formulated to have pressure sensitive adhesive properties by choosing the appropriate ionomeric particulate composition, polymer matrix, and various other components, such as plasticizers and tackifiers. For example, it has been discovered that the inventive ionomeric particulates are useful as part of a repulpable adhesive. Repulpability requires that the adhesive components be water-soluble or water dispersible. When the components are water dispersible, they are preferably of a sufficiently small particle size to pass through repulping equipment. The inventive ionomeric particulates are also useful as a part of an adhesive that is applied to mammalian skin to remove undesirable materials (e.g., comedomes, unwanted hair follicles, dirt, oil, debris, dead skin). These particular adhesives (repulpable and skin cleansing) are disclosed in Assignee's copending U.S. application Ser. No. 09/441,580, which is hereby incorporated by reference, the application being filed on the same day as this application.
As mentioned, the present invention provides an advantage to controlling the particulates' size through the use of surfactants and polyacrylamide and not relying on the more conventional method of homogenization. By relying on the surfactants and polyacrylamide, Applicants have discovered a robust system to control the particulates' by minimizing the need for homogenization during processing. Thus, during the manufacture of the ionomeric particulates, it is not necessary to monitor carefully the mixing of the monomer premix (often referred to as the “oil phase”) and the water phase to ensure a desired particulate size.
Another advantage of the present invention is the ability to make an ionomeric particulate that has little to no acid functional groups. Th
Engel Michael R.
Tseng Chi-Ming
Young Chung I.
3M Innovative Properties Co.
Egwim K C
Pribnow Scott R.
Wu David W.
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