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
2000-03-07
2001-01-09
Szekely, Peter A. (Department: 1714)
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...
C524S270000, C524S764000, C524S773000, C525S054420, C526S216000, C526S238300
Reexamination Certificate
active
06172149
ABSTRACT:
This invention relates to novel rosin-fatty acid vinylic polymer compositions and the process for preparing them. In particular, the invention relates to novel rosin-fatty acid vinylic polymer compositions which exhibit properties that make them useful as surface sizing compositions for cellulosic materials.
BACKGROUND OF THE INVENTION
Sizing is a term used in the papermaking art to describe processes which reduce the water absorbency of cellulosic materials such as sheets of paper. This is commonly accomplished by precipitating a nearly fully saponified rosin soap or a free rosin dispersion on the cellulosic fibers with alum to form aluminum resinate. The aluminum resinate coats the exposed surface to give it a hydrophobic character, thereby rendering the surface resistant to wicking by water, inks, and other polar liquids.
Rosin sizes are normally water soluble alkali soaps or a colloidially stabilized dispersions of rosin. A variety of polymeric rosin resin sizes have been developed to address specific coating needs. However, certain rosins are highly prone to crystallization. Crystal formation in such rosins tend to occur during the production of the rosin size, during size storage, or after the size has been diluted to a low solids level.
The traditional process for producing a polymeric resin is well-known (see generally U.S. Pat. Nos. 4,839,413 and 5,216,064, which is hereby incorporated by reference). Commonly a solution polymerization reaction is employed wherein a styrenic monomer and acrylic acid is mixed with a hydrocarbon solvent, a polymerization initiator, and a chain transfer agent. Upon completion of the reaction, the solution is stripped of the solvent to yield the polymer composition.
However, major problems exist with the traditional methods of producing these polymeric resins. For example, these methods require the use of environmentally adverse hydrocarbon solvents. Moreover, as these solvents are not usable or desirable in water-based ink or overprint formulations, the solvents must be stripped from the resulting acrylic polymers (thereby causing a yield loss). This stripping step also adds expense to the process due to both the loss of yield and the energy consumed in performing the stripping. Also, these methods must utilize chain transfer agents to regulate the molecular weight of the resulting resin.
Therefore, an object of this invention is to solve these major problems by disclosing a method of producing rosin-fatty acid vinylic polymer compositions which exhibit properties that make them useful for formulating surface sizing compositions for cellulosic materials.
Another object of this invention is to disclose rosin-fatty acid vinylic polymer surface sizing compositions.
SUMMARY OF THE INVENTION
The objects of this invention are met by via a method that employs rosin and fatty acid to act as solvents in the polymerization reaction of the acrylic monomers, thereby producing rosin-fatty acid vinylic polymer compositions which exhibit properties that make them useful as surface sizing compositions for cellulosic materials. As this method does not require the use of hydrocarbon solvents, the need for solvent stripping is eliminated. Also, the polymerization reaction can be conducted at higher temperatures (i.e., up to boiling point of fatty acid) than traditional solution polymer methods, thereby allowing the practitioner to utilize smaller amounts of free radical initiators. Furthermore, the practitioner is able to regulate molecular weight without the use of chain transfer agents, thereby both reducing costs and avoiding the production of unpleasant odors associated with such agents. Moreover, the fatty acid and rosin can function as a reactive diluent to impart flexibility to the surface sizing compositions.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The rosin-fatty acid vinylic polymer surface sizing compositions are the products of the process of:
(A) reacting in an addition polymerization reaction:
(1) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(a) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of fatty acid, and
(b) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of rosin; and
(2) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(a) about 15.0% to about 45.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and combinations thereof,
(b) about 55.0% to about 85.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(c) about 0.5% to about 5.0% by total weight of the monomer mixture of a polymerization initiator,
(d) up to about 4.0% by total weight of the monomer mixture of a chain transfer agent, and
(e) up to about 30% by total weight of the monomer mixture of a hydrocarbon solvent, at a temperature in the range of about 135° C. to about 175° C. to produce a rosin-fatty vinylic polymer having a weight average molecular weight in the range of about 4,000 to about 12,000; and
(B) dispersing the rosin-fatty vinylic polymer in water; to produce the rosin-fatty acid vinylic polymer surface sizing composition.
Preferred rosin-fatty acid vinylic polymer surface sizing compositions are the products of the process of:
(A) reacting in an addition polymerization reaction:
(1) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(a) about 20.0% to about 50.0% by total weight of the fatty acid mixture of fatty acid, and
(b) about 50.0% to about 80.0% by total weight of the fatty acid mixture of rosin; and
(2) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(a) about 20.0% to about 25.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and combinations thereof,
(b) about 60.0% to about 70.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(c) about 1.0% to about 3.0% by total weight of the monomer mixture of a polymerization initiator,
(d) about 0.5% to about 2.0% by total weight of the monomer mixture of a chain transfer agent, and
(e) about 1.0% to about 4.0% by total weight of the monomer mixture of a hydrocarbon solvent, at a temperature in the range of about 135° C. to about 175° C. to produce a rosin-fatty vinylic polymer having a weight average molecular weight in the range of about 4,000 to about 12,000; and
(B) dispersing the rosin-fatty vinylic polymer in water; to produce the rosin-fatty acid vinylic polymer surface sizing composition.
The addition polymerization reaction used to produce the rosin-fatty acid vinylic polymer is a melt polymerization reaction in which no water is employed. Reaction temperatures suitable for use in the present method are within the range of about 135° C. to about 175° C.; with the preferred temperatures being in the range of about 140° C. to about 170° C.
The rosin and fatty acid function as solvents in the polymerization reaction of the acrylic monomers. Additionally, while a portion of the fatty acid and the rosin component remains unreacted, some of the fatty acid and rosin becomes graft polymerized onto the acrylic. The resulting rosin-fatty acid vinylic polymers have a weight average molecular weight in the range of about 4,000 to about 12,000; with the preferred molecular weights being in the range of about 5,000 to about 11,000. These rosin-fatty acid vinylic polymer compositions have characteristics which differ from the traditional melt blends of flake acrylic fatty acid rosin. For example, the low molecular weights of the rosin-fatty acid vinylic polymers enable the polymers to be neutralized at high solid levels while maintaining low viscosities. The low molecular weight coupled with the polymer
Adams Stanley C.
Shah Rajnikant
McDaniel Terry B.
Reece IV Daniel B.
Schmalz Richard L.
Szekely Peter A.
Westvaco Corporation
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