Antifungal Gypsum Board

(12) United States Patent Toreki et al. US007473474B2 (10) Patent No.: US 7,473,474 B2 (45) Date of Patent: Jan. 6, 2009 (54) ANTIFUNGAL GYPSUM BOARD (75) Inventors: William Toreki, Gainesville, FL (US); Gerald Olderman, Bedford, MA (US); Gregory Staab, Ventura, CA (US) (73) Assignee: Quick-Med Technologies, Inc., Gainesville, FL (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. (21) Appl. No.: 10/546,850 (22) PCT Filed: Feb. 25, 2004 (86) PCT No.: PCT/US2004/005616 § 371 (OX1), (2), (4) Date: Aug. 24, 2005 (87) PCT Pub. No.: WO2004/076770 PCT Pub. Date: Sep. 10, 2004 (65) Prior Publication Data US 2006/0194072 A1 Aug. 31, 2006 Related U.S. Application Data (60) Provisional application No. 60/449,915, filed on Feb. 25, 2003. (51) Int. Cl. B32B 23/04 (2006.01) (52) U.S. Cl. .................. .. 428/536; 428/537.7; 514/255; 427/326 (58) Field of Classification Search ............... .. 428/536, 428/537.7; 514/255; 427/326 See application file for complete search history. (56) References Cited U.S. PATENT DOCUMENTS 3,778,476 A 12/1973 Rembaum et al. 3,898,336 A 8/1975 Rembaum et al. 3,945,842 A 3/1976 Green 4,027,020 A 5/1977 Green et al. 4,076,663 A * 2/1978 Masuda et al. ......... .. 525/54.31 4,379,890 A 4/1983 Konietzny et al. 4,970,211 A 11/1990 Fenyes et al. 5,049,383 A 9/1991 Huth etal. 5,051,124 A 9/1991 Pera 5,091,102 A 2/1992 Sheridan 5,432,000 A 7/1995 Young, Sr. et al. 5,658,915 A * 8/1997 Abe etal. ............ .. 514/252.11 5,700,742 A 12/1997 Payne 5,856,248 A 1/1999 Weinberg 6,126,931 A 10/2000 Sawan et al. 6,146,688 A 11/2000 Morgan et al. 6,803,420 B2 10/2004 Cleary et al. 7,045,673 B1 5/2006 Batich et al. 7,056,460 B2 * 6/2006 Englert ...................... .. 264/86 2002/0177828 A1 11/2002 Batich et al. 2003/0035981 A1* 2/2003 Capps ................. .. 514/252.11 2005/0003163 A1* 1/2005 Krishnan .................. .. 428/190 2005/0033251 A1 2/2005 Torekiet al. FOREIGN PATENT DOCUMENTS DE 147949 12/1979 EP 0493970 7/1992 GB 497958 A 12/1938 GB 818412 8/1959 GB 1461909 1/1977 GB 2300200 10/1996 GB 2408516 6/2005 JP 10-237763 9/1998 WO 98/21253 5/1998 WO 99/32157 7/1999 OTHER PUBLICATIONS Lee, Sang Beom; Koepsel, Richard R.; Morley, Scott W.; Matyjasezewski, Krzysztof; Sun, Yujie; Russell, Alan J.; “Perma- nent, Nonleaching Antibacterial Surfaces” 1. Synthesis by Atom Transfer Radial Polymerization, Biomacromolecules 2004, 5 pp. 877-882, 2004 American Chemical Society. (Continued) Primary Examiner—Leszek Kiliman (74) Attorney, Agent, or Firm—Gerry J. Elman; Elman Technology Law, P.C. (57) ABSTRACT A novel improved gypsum board having improved antifungal properties is disclosed. The board comprises a gypsum core, front and back paper facings and a polymeric antifungal agent effective at inhibiting fungal growth. A preferred polymeric antifungal agent is polyDADMAC or polyTMMC. In addi- tion to the polymeric antifungal agent, a non-polymeric anti- fungal agent, such as cetyl pyridinium chloride, sodium or zinc pyrithione, or both, may be included. The polymeric antifungal agent can be present in the gypsum core and/ or on one or both of the paper facings. In addition, the antifungal agent may be encapsulated in a material or ionically associ- ated with the polymeric antifungal agent, that releases the antifungal agent over time and/ or upon exposure to moisture. Also disclosed are methods for preparing the aforementioned improved antifungal gypsum board. 15 Claims, No Drawings US 7,473,474 B2 Page 2 OTHER PUBLICATIONS Abel, Tanya; Cohen, Jaimelee Iolani; Engel, Robert; Filshtinskaya, Maya; Melkonian, Alice; Melkonian, Karen; Preparation and inves- tigation of antibacterial carbohydrate-based surfaces, Carbohydrate Research 337 (2002) pp. 2495-2499. Onabe, Fumihiko; “Studies on Interfacial Properties of Polyelectrolyte-Cellulose Systems, I. Formation and Structure of Adsorbed Layers of Cationic Polyelectrolyte-(Poly-DMDAAC) on Cellulose Fibers”, Journal of Applied Polymer Science, vol. 22, 3495-3510 (1978) John Wiley & Sons, Inc. Wallace, Michele L., “Testing the Eflicacy of Polyhexamethylene Biguanide as anAntimicrobia1 Treatment for Cotton Fabric” AATCC Review, Nov. 2001, pp. 18-20. * cited by examiner US 7,473,474 B2 1 ANTIFUNGAL GYPSUM BOARD BACKGROUND OF THE INVENTION 1. Technical Field of the Invention The present invention relates generally to gypsum board and methods for making gypsum board. More specifically, the present invention relates to improved gypsum board pos- sessing antifungal properties and improved methods of mak- ing the same. 2. Description of Related Art Gypsum board, which is sold as wallboard and drywall, is a common building material used in various applications including interior walls, partitions and ceiling construction. Commercial gypsum board products are popular for a variety of reasons. They are durable, economical and fire-retardant. In addition, these boards provide excellent compressive- strength properties and a relatively low density. Finally, they are easily decorated and are therefore attractive as surfacing materials, especially for interior construction. One fundamental limitation of traditional gypsum board products is their susceptibility to moisture absorption in damp environments. To minimize this problem, gypsum board is normally used in interior construction where exposure to moisture is limited. Unfortunately, products used in interior construction sometimes encounter water due to seepage, leaky roofs or pipes, flooding, condensation, and the like, arising out of construction defects or other events unrelated to the manufacture of the gypsum board. Thus, a number of mechanisms result in the exposure of gypsum board products to moisture. Once exposed to moisture, traditional gypsum board products are susceptible to fungal growth. In patent publication number US2003/0035981 and US2003/0031898, there are disclosed antifungal gypsum boards in which monomeric antifungal agents are included in components of wallboard materials. Due to the monomeric nature of the antifungal agents, such as the preferred antifun- gal agents of those disclosures, cetyl pyridinium chloride, those patent publications discuss the inclusion of binders, retention aids, encapsulants and the like, for retaining the monomeric antifungal agents in association with the gypsum board components. The present invention provides an improved antifungal gypsum board by disclosing polymeric compounds which are antifungal and which therefore have enhanced antifungal efficacy and retention in the gypsum board components. We have also found that polymeric qua- ternary amines are significantly more antimicrobial than are monomeric quatemary amines. There is an ongoing need for gypsum board products that offer reduced susceptibility to fungal growth without com- promising their beneficial properties. In addition, there is an ongoing need for commercially viable manufacturing meth- ods for such products. The present invention solves these problems by using an improved antifungal agent that effec- tively inhibits fungal growth, is compatible with gypsum board materials, and can be incorporated into a cost-effective and commercially-viable manufacturing process. BRIEF SUMMARY OF PREFERRED EMBODIMENTS The preferred embodiments of the present invention include a novel gypsum board comprising an effective amount of an antifungal agent such that fungal growth on or in the board is inhibited. According to a preferred embodi- ment of the present invention, the antifungal agent is a poly- meric antifungal agent (PAA), alone or in combination with a 10 15 20 25 30 35 40 45 50 55 60 65 2 monomeric antifungal agent, such as cetyl pyridinium chlo- ride (CPC), a quatemary ammonium compound, or a pyrithione, such as sodium pyrithione, (SP), or another anionic antifungal compound which binds ionically to a cat- ionic PAA, and be thereby more effectively retained than if the pyrithione were simply mixed with or adsorbed to wall- board components. Preferably, the gypsum board comprises from about 0.01 to about 5 weight percent PAA and CPC or SP based on the dry weight of the gypsum in the board. More preferably, the gypsum board comprises between about 0.5 and about 1.0 weight percent PAA and CPC or SP based on the dry weight of the gypsum in the board. According to some preferred embodiments, the PAA and CPC or SP are encap- sulated in an encapsulator so that it is released over time and/or upon exposure to moisture. The preferred embodiments of the present invention also include methods of preparing the novel gypsum board described above. According to some preferred embodiments, PAA alone or PAA and CPC or SP are incorporated onto or into the gypsum core by premixing PAA with or without CPC or SP with the water, premixing the PAA with or without CPC or SP with the gypsum powder, admixing the PAA with or without CPC or SP with both the water and gypsum powder prior to or in the slurry mixer, and/or adding PAA with or without CPC or SP to a mixed gypsum slurry via a secondary or in-line mixer. According to other preferred embodiments, a PAA with or without CPC or SP solution is sprayed onto the front and/or back paper facings. According to other preferred embodiments, PAA with or without CPC or SP is incorporated into the front and/or back paper facings as they are manufactured. In another preferred embodiment the PAA is a polymeric quatemary amine. In another preferred embodiment, the PAA is covalently bonded to components of the gypsum, the front paper facing, the back paper facing or both. In another preferred embodiment, the PAA is a polymeric quatemary amine which binds an anionic antimicrobial agent, such as SP, thereby improving the retention of the SP in association with the wallboard. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention derives from the discovery that an improved effective antifungal agent exhibits compatibility with gypsum board without diminishing the qualities of the gypsum board. Preferably, the mechanical properties of the gypsum board such as density, break strengths, bond strength, core end and edge hardness, modulus of flexibility and the like are substantially unchanged by the addition of the anti- fungal agent. By substantially unchanged, a given mechanical property preferably remains within the parameters of govem- ing standards—e.g., ASTM standards. Consequently, the improved novel gypsum board product achieves the struc- tural, economic and other benefits of gypsum board while also offering significant resistance to fungal growth. The novel gypsum board product can be prepared according to methods that are cost-effective and commercially viable. The preferred embodiments of the present invention include a novel gypsum board comprised of a gypsum core, paper surfacing bonded to both sides of the core, and an antifungal agent. Any material suitable as a gypsum core is within the scope of the present invention. Therefore, without limiting the scope of the invention, the preferred embodi- ments comprise a gypsum core comprised of gypsum powder, water and optionally foam, pulp, starch and/or set controlling US 7,473,474 B2 3 agents. Typically, the gypsum core is sandwiched between two sheets that are commonly referred to as the front and back paper facings. The front paper facing is generally a light- colored, smoothly textured paper designed to face into the interior of the building. The back paper facing, in contrast, is typically a darker, less smoothly-textured paper designed not to be seen. Any material suitable as a front and/or back paper facing is within the scope of the present invention. Therefore, without limiting the scope of the invention, the preferred embodiments comprise front and back paper facings com- prised of a cellulosic material. The preferred embodiments of the present invention also employ an improved antifungal agent, as used herein mean- ing and including all agents, materials, and combinations thereof providing antimicrobial activity. Preferred antimicro- bial agents are those of the type and in an amount effective for inhibiting the growth and/or formation of microbes such as bacteria and/or fungi. Any known antifungal agent compat- ible with gypsum board composition and manufacturing pro- ces ses and providing the desired biocidal, antifungal, antimy- cogen, antibacterial, and/ or like activity in the gypsum board may be employed with the present invention. As will be readily apparent to one of skill in the art, a variety of antifun- gal agents are known including, for example, chlorhexidine, alexidine, cetyl pyridinium chloride, benzalkonium chloride, benzethonium chloride, cetalkonium chloride, cetrimide, cet- rimonium bromide, glycidyl trimethylammonium chloride, stearalkonium chloride, hexetidine, triclosan and triclocar- ban. The improved antifungal agent of this invention, how- ever, is a polymeric antifungal agent, comprising at least two monomeric units, and up to a thousand monomeric units, covalently linked to each other. The polymeric antifungal agent may be used alone or in combination with monomeric antifungal agents known in the art, such as quatemary ammo- nium compounds, including but not limited to the following compounds: Fluoride: Tetra-n-butylammonium Fluoride Tetraethylammonium Fluoride Chloride: Acetylcholine Chloride (3 -Acrylamidopropyl)trimethylammonium Chloride Benzalkonium Chloride Benzethonium Chloride Benzoylcholine Chloride Benzylcetyldimethylamrnonium Chloride N-Benzylcinchonidinium Chloride N-Benzylcinchoninium Chloride Benzyldimethylphenylammonium Chloride Benzyldimethylstearylamrnonium Chloride N-Benzylquinidinium Chloride N-Benzylquininium Chloride Benzyltri-n-butylammonium Chloride Benzyltriethylammonium Chloride Benzyltrimethylammonium Chloride Carbarnylcholine Chloride DL-Camitine Hydrochloride Chlorocholine Chloride (3-Chloro-2-hydroxy-n-propyl)trimethylammonium Chlo- ride Choline Chloride n-Decyltrimethylammonium Chloride Diallyldimethylammonium Chloride Dichloromethylenedimethyliminium Chloride Dimethyldistearylammonium Chloride n-Dodecyltrimethylammonium Chloride 10 15 20 25 30 35 40 45 50 55 60 65 4 Girard’s Reagent T n-Hexadecyltrimethylammonium Chloride Hexarnethonium Chloride Lauroylcholine Chloride Methacholine Chloride Methacroylcholine Chloride (2-Methoxyethoxymethyl)triethylammonium Chloride beta-Methylcholine Chloride Methyltriethylarnmonium Chloride Myristoylcholine Chloride n-Octyltrimethylammonium Chloride Phenyltriethylammonium Chloride Phenyltrimethylammonium Chloride Phosphocholine Chloride Calcium Salt Phosphocholine Chloride Sodium Salt Succinylcholine Chloride Tetra-n-amylamrnonium Chloride Tetra-n-butylammonium Chloride Tetradecyldimethylbenzylammonium Chloride n-Tetradecyltrimethylammonium Chloride Tetraethylammonium Chloride Tetrarnethylammonium Chloride Trimethyl[2,3-(dioleyloxy)propyl]ammonium Chloride Trimethylstearylammonium Chloride Trioctylmethylammonium Chloride Tri-n-octylmethylammonium Chloride Bromide: Acetylcholine Bromide Benzoylcholine Bromide Benzyltri-n-butylammonium Bromide Benzyltriethylammonium Bromide Bromocholine Bromide Cetyldimethylethylamrnonium Bromide Choline Bromide Decamethonium Bromide n-Decyltrimethylammonium Bromide Didecyldimethylamrnonium Bromide Dilauryldimethylamrnonium Bromide Dimethyldimyristylammonium Bromide Dimethyldioctylammonium Bromide Dimethyldipalmitylammonium Bromide Dimethyldistearylammonium Bromide n-Dodecyltrimethylammonium Bromide (Ferrocenylmethyl)dodecyldimethylammonium Bromide (Ferrocenylmethyl)trimethylammonium Bromide n-Hexadecyltrimethylammonium Bromide Hexarnethonium Bromide Hexyldimethyloctylammonium Bromide n-Hexyltrimethylammonium Bromide Methacholine Bromide Neostigmine Bromide n-Octyltrimethylammonium Bromide Phenyltrimethylammonium Bromide Stearyltrimethylammonium Bromide Tetra-n-amylamrnonium Bromide Tetra-n-butylammonium Bromide Tetra-n-decylammonium Bromide n-Tetradecyltrimethylammonium Bromide Tetraethylammonium Bromide Tetra-n-heptylammonium Bromide Tetra-n-hexylammonium Bromide Tetrarnethylammonium Bromide Tetra-n-octylamrnonium Bromide Tetra-n-propylammonium Bromide 3 -(Trifluoromethyl)phenyltrimethylammonium Bromide Trimethylvinylammonium Bromide US 7,473,474 B2 Valetharnate Bromide Iodide: Acetylcholine Iodide Acetylthiocholine Iodide Benzoylcholine Iodide Benzoylthiocholine Iodide Benzyltriethylammonium Iodide n-Butylylcholine Iodide n-Butyrylthiocholine Iodide Decamethonium Iodide N,N-Dimethylmethylenearnmonium Iodide Ethyltrimethylammonium Iodide Ethyltri-n-propylammomum Iodide (Ferrocenylmethyl)trimethylammonium Iodide (2-Hydroxyethyl)triethylammonium Iodide beta-Methylcholine Iodide 0- .beta. -Naphthyloxyc arb onyl choline Iodide Phenyltriethylammonium Iodide Phenyltrimethylammonium Iodide Tetra-n-amylammonium Iodide Tetra-n-butylammonium Iodide Tetraethylammonium Iodide Tetra-n-heptylamrnonium Iodide Tetra-n-hexylamrnonium Iodide Tetrarnethylammonium Iodide Tetra-n-octylammonium Iodide Tetra-n-propylammonium Iodide 3 -(Trifluoromethyl)phenyltrimethylammonium Iodide Hydroxide: Benzyltriethylammonium Hydroxide Benzyltrimethylammonium Hydroxide Choline n-Hexadecyltrimethylammonium Hydroxide Phenyltrimethylammonium Hydroxide Sphingomyelin Tetra-n-butylammonium Hydroxide Tetra-n-decylamrnonium Hydroxide Tetraethylammonium Hydroxide Tetra-n-hexylamrnonium Hydroxide Tetrarnethylammonium Hydroxide Tetra-n-octylammonium Hydroxide Tetra-n-propylammonium Hydroxide 3 -(Trifluoromethyl)phenyltrimethylammonium Hydroxide Others: Acetylcholine Perchlorate Benzyltrimethylammonium Dichloroiodate Benzyltrimethylammonium "etrachloroiodate Benzyltrimethylammonium "ribromide Betaine, Anhydrous Betaine Hydrochloride Bis(tetra-n-butylan1rnonium)Dichromate Bis(tetra-n-butylammonium)Tetracyanodiphenoquin- odimethanide L-Camitine 3 -[(3 -Cholamidopropyl)dimethylammonio] - l -propane- sulfonate Denatonium Benzoate n-Dodecyldimethyl(3-sulfopropyl)an1rnonium Hydroxide, Inner Salt N-Fluoro-N‘-(chloromethyl)triethylenediamine rafluoroborate) n-Hexadecyltrimethylammonium Hexafluorophosphate n-Hexadecyltrimethylammonium Perchlorate n-Hexadecyltrimethylammonium Tetrafluoroborate Bis(tet- 10 15 20 25 30 35 40 45 50 55 60 65 6 (Methoxycarbonylsulfamoyl)triethylammonium Hydroxide, Inner Salt Neostigmine Methyl Sulfate n-Octadecyldimethyl(3-sulfopropyl)ammonium Hydroxide, Inner Salt Phenyltrimethylammonium Tribromide Propionylcholine p-Toluenesulfonate Tetra-n-butylammonium Azide Tetra-n-butylammonium Bifluoride Tetra-n-butylammonium Borohydride Tetra-n-butylammonium Bromodiiodide Tetra-n-butylammonium Dibromoaurate Tetra-n-butylammonium Dibromochloride Tetra-n-butylammonium Dibromoiodide Tetra-n-butylammonium Dichloroaurate Tetra-n-butylammonium Dichlorobromide Tetra-n-butylammonium Difluorotriphenylsilicate Tetra-n-butylammonium Difluorotriphenylstannate Tetra-n-butylammonium Dihydrogentrifluoride Tetra-n-butylammonium Diiodoaurate Tetra-n-butylammonium Hexafluorophosphate Tetra-n-butylammonium Hydrogensulfate [for Ion-Pair Chromatography] Tetra-n-butylammonium Hydrogensulfate Tetra-n-butylammonium Perchlorate Tetra-n-butylammonium Perrhenate Tetra-n-butylammonium Phosphate Tetra-n-butylammonium Salicylate Tetra-n-butylammonium Tetrafluoroborate Tetra-n-butylammonium Tetraphenylborate Tetra-n-butylammonium Thiocyanate Tetra-n-butylammonium Tribromide Tetra-n-butylammonium Triiodide Tetraethylammonium Borohydride Tetraethylammonium Perchlorate Tetraethylammonium Tetrafluoroborate Tetraethylammonium p-Toluenesulfonate Tetraethylammonium Trifluoromethanesulfonate Tetrarnethylammonium Acetate Tetrarnethylammonium Borohydride Tetrarnethylammonium Hexafluorophosphate Tetrarnethylammonium Hydrogensulfate Tetrarnethylammonium Perchlorate Tetrarnethylammonium Sulfate Tetrarnethylammonium Tetrafluoroborate Tetrarnethylammonium p-Toluenesulfonate Tetrarnethylammonium Triacetoxyborohydride Tetra-n-propylammomum Perruthenate Trifluoromethanesulfonic Acid Tetra-n-butylammonium Salt The polymers may include polymers of any of the forego- ing monomers which are susceptible to polymerization. For example, in a preferred embodiment, the polymer comprises a polymer comprising at least two and up to one thousand monomeric units of diallyldimethylamrnonium chloride, (DADMAC), to form polyDADMAC, [2-(methacryloyloxy) ethyl]trimethylammomum chloride (TMMC), to form polyT- MMC, quatermzed Vinyl pyridine (VP) deriVatiVes, to give polyVP, or similar polymerizable quaternary amine mono- mers are utilized to form suitable quatemary amine polymers. The polymer, in one embodiment, is simply mixed with the gypsum core components. The polymer, in another embodi- ment, is simply sprayed onto the exterior of the front, back or both paper surfacing. The polymer, in another embodiment, is mixed with the gypsum core components, and is sprayed onto the exterior of the front, back or both paper surfacing. In another embodiment, the polymer is bonded directly to com- ponents of the gypsum core. For example, gypsum containing US 7,473,474 B2 7 starch is susceptible to cerium initiated polymerization in which polymerization is initiated at carbons, hydroxyls or both of cellulosic substrates. In this embodiment, it is conve- nient to separately react the starch or cellulosic component with the antimicrobial monomer and initiator under condi- tions which benefit polymerization (heat, non-oxygenated atmosphere, high reaction concentration of monomeric anti- fungals and polymerization initiators). The starch or cellulo- sic component may be washed and recovered following poly- merization, if desired, or may be added directly to the gypsum core in a concentration sufiicient to achieve the desired func- tion of the starch or cellulosic material. Variations on this methodology, of course, may be derived from this disclosure as the need arises, for example, to achieve desired character- istics for the gypsum core. Such variations derived from this disclosure are considered to come within the scope of equiva- lents to the methodology disclosed herein. In one embodi- ment, DADMAC monomers and an azo initiator are mixed with the cellulosic component, heated, washed and the anti- fungal and antimicrobial starch or cellulosic material is then mixed with the gypsum component of the core at different ratios to achieve the physico-chemical characteristics desired, while also imparting an antimicrobially active poly- mer to the gypsum core. In this manner, any moisture and fungal spores, bacteria or the like that may penetrate to the gypsum core are denied an environment conducive to their growth. This is very beneficial to address such issues as mold induced illnesses in buildings with circulating air handling systems (so-called “sick building syndrome”). Similar ben- efits are achieved by including polyDADMAC in the gypsum core. In this case, we have found that gypsum mixed with water alone and then dried rehydrates much more quickly than gypsum mixed with polyDADMAC and then dried. In another embodiment, the polymer is covalently-bonded to fibers forming the paper surfacing of the gypsum, by cerium-catalyzed polymerization, or by the use of other free- radical initiators such as peroxides and azo compounds. Methods for polymerizing quatemary amine monomers are known in the art and are hereby incorporated by reference, for example, from PCT publication No. WO00033778; U.S. Pat. No. 4,076,663; see also George B. Butler, “Cyclopolymer- ization and Cyclocopolymerization”, published by Marcel Dekker, Inc., New York, Basel, Hong Kong, ISBN: 0-8247- 8625-4, 1992. Without limiting the scope of the present invention, certain embodiments of the present invention may employ, in addi- tion to the polymeric antifungal agent, cetyl pyridinium chlo- ride (CPC) as an antifungal agent. The preferred embodi- ments are only exemplary. References herein to antifungal agents in general and CPC i11 particular are not intended to limit the scope of the invention. Cetyl pyridinium chloride—also known as CPC or n-hexa- decyl pyridinium chloride—is a cationic surfactant com- prised of a hydrophilic quaternary ammonium moiety and a hydrophobic alkane moiety. CPC is commonly believed to possess biocidal activity due to its ability to bind readily to the negatively-charged cell walls of various microbes and to impact membrane integrity and function. It is a potent anti- fungal, antimycogen, and antibacterial chemical. CPC is commonly available in a powder form as a monohydrate manufactured by Zeeland/Carnbrex and available from Johnson Matthey Catalog Company Inc. of Ward Hill, Mass., among others. The preferred embodiments of the present invention employ an amount of PAA with or without CPC or other monomeric antifungal agents effective at inhibiting fungal, bacterial, and the like growth in or on the gypsum board. 10 15 20 25 30 35 40 45 50 55 60 65 8 Preferably, the amount of PAA with or without CPC in and/ or on the gypsum board is between about 0.01 and about 1.5 weight percent of the dry weight of the gypsum in the board. More preferably, the amount of PAA with or without CPC present in and/or on the gypsum board is between about 0.5 and about 1 .0 weight percent of the dry weight of the gypsum in the board. According to some preferred embodiments, the PAA with or without CPC is primarily present in the gypsum core. According to other preferred embodiments, the PAA with or without CPC is primarily located on one or both of the front and back paper facings, and more preferably on the outer surface of the front and back paper facings. According to yet other preferred embodiments, the PAA with or without CPC is primarily located in one or both of the front and back paper facings. The present invention includes a novel method for the production of gypsum board comprising the addition of PAA with or without other antifungal agents during gypsum board manufacturing. The PAA antifungal agent is added during manufacturing in an amount that yields an effective amount of the antifungal agent in and/ or on the board such that fungal, bacterial, and the like formation and/or growth in and/or on the board is inhibited. Preferably, the finished gypsum board product comprises an amount of polymeric antifungal agent equal to from about 0.01 to about 1 .5 weight percent of the dry weight of the gypsum in the board. More preferably, the finished gypsum board product comprises an amount of poly- meric antifungal agent equal to from about 0.5 to about 1.0 weight percent of the dry weight of the gypsum in the board. The gypsum board production process typically com- mences with the mining and transportation of gypsum rock. Once mined, the gypsum rock is crushed and ground into a fine powder. Altematively, gypsum powder can be created synthetically. This powder is then subjected to a calcining process in which moisture is removed by heating. The novel gypsum board of the present invention may be prepared by any method capable of incorporating effective quantities of an agent having effective antifungal, antibacterial, and/ or like activity into or onto the gypsum board product. Therefore, without limiting the scope of the present invention, the pre- ferred embodiments of the present invention comprise mixing gypsum powder with water to form a gypsum slurry. Option- ally, one or more of foam, pulp, starch and/or set-controlling agents may be added to the slurry. The preferred embodiments of the present invention com- prise a gypsum board manufacturing process in which the slurry is deposited between two unwinding rolls of absorbent paper on a conveyor belt. Conveyor belts useful in gypsum board processing typically reach lengths of from about 200 to about 1000 feet. This belt may be operated at a speed of from about 50 to about 200 feet per minute and typically at about 110 feet per minute. This process results in a continuous sandwich of gypsum core between the two paper layers or facings. Thus, the forming gypsum board is cast as a sheet having a three-layer structure: a gypsum core having front and back paper facings. The sandwich then passes through a forming station that establishes the width and thickness of the gypsum board. As the gypsum board moves along the belt line, the slurry reverts to a solid gypsum matrix. As the gyp- sum core molds and hardens, it becomes firmly bonded to the outer paper layers. Once formed, the continuous board is cut to a desired length and passed through dryers to remove excess moisture. The preferred embodiments of the present invention also comprise the addition of the antifungal agent during the gyp- sum board manufacturing process. The antifungal agent may US 7,473,474 B2 9 be added by any method capable of incorporating effective quantities of such agent into or onto the gypsum board prod- uct. Therefore, without limiting the scope of the present invention, the preferred embodiments of the present invention comprise adding the antifungal agent into and/ or onto the gypsum core and/or by depositing the antifungal agent into and/ or onto the front and/ or back paper facings. The polymeric antifungal agent with or without mono- meric antifungal agents may be added to the gypsum slurry in any way capable of incorporating effective quantities of such agent into the gypsum core. Methods for adding PAA with or without CPC in solution form, powder form, or both during formation of the gypsum slurry include, but are not limited to, premixing PAA with or without CPC with the water, premix- ing the PAA with or without CPC with the gypsum powder, admixing the PAA with or without CPC with both the water and gypsum powder prior to or in the slurry mixer, or adding the PAA with or without CPC to a mixed gypsum slurry via a secondary or in-line mixer. In a preferred embodiment, dry PAA with or without CPC powder is added (via screw feeder) to dry gypsum powder prior to mixing with water to form the slurry. In another preferred embodiment, a PAA with or with- out CPC solution is co-metered with water to a slurry mixer and mixed with gypsum powder therein. The PAA with or without CPC solution preferably comprises from about 5 to about 20 weight percent PAA with or without CPC based on the total weight of the solution, provided however that the concentration and/ or addition rate of the PAA with or without CPC solution can be adjusted to match the manufacturing conditions (such as line speed, in linear feet per minute) and product specifications (such as desired concentration of PAA with or without CPC in the final board product, board thick- ness, etc.). The amount of PAA with or without CPC and addition rate thereof is adjusted to achieve an effective amount of PAA with or without CPC in the gypsum board for inhibiting fungal, bacterial, and the like formation and growth thereon, as discussed previously. In another preferred embodiment, the PAA with or without CPC solution is sprayed onto the front and/or back paper facings, which may occur at one or more points in the manu- facturing process. For example, the PAA with or without CPC solution can be sprayed onto the paper facings prior to or as they are unrolled to form the sheets, after the sheets have been formed, before and/or after drying the sheets, and/or after the sheets have been cut into boards. Furthermore, the PAA with or without CPC may be sprayed onto the inner surface, the outer surface, or both of the front and/or back paper facings. Preferably, the PAA with or without CPC solution for spray- ing comprises from about 5 to about 20 weight percent PAA with or without CPC based on the total weight of the solution. In another embodiment, the PAA with or without CPC may be added to one or both of the paper facings during manufacture of the paper facings. Adding PAA with or without CPC to the front and/or back paper facing (by either spraying or during manufacture of the paper) may be in addition to or as a substitute for adding PAA with or without CPC to the gypsum core of the board as described above. Thus, gypsum boards may have the following configurations: PAA with or without CPC treated core and untreated facings; untreated core and one or both PAA with or without CPC treated facings; PAA with or without CPC treated core and one or both PAA with or without CPC treated facings; PAA covalently linked to com- ponents of the core, with or without CPC admixed, with neither paper surface, one paper surface or both, either coated with PAA with or without CPC, or one or both paper surfaces covalently bonded with PAA with or without a coating of CPC. 10 15 20 25 30 35 40 45 50 55 60 65 10 Antifungal agents such as CPC frequently exhibit some toxicity to humans and animals. Consequently, minimizing human and animal exposure to CPC and other antifungal agents is desirable. Furthermore, the gypsum board should maintain its antifungal efiicacy over an extended period of time. The present invention provides a polymeric antifungal agent (the PAA) which significantly enhances the longevity and efiicacy of the antifungal agent, with or without mono- meric antifungals being present, such as the CPC. In addition, the gypsum board products may be specifically formulated to release an active antifungal agent slowly over time or upon becoming wet such that the antifungal properties and activity of the board are maintained at an effective level over time, in addition to the extended efiicacy of the PAA. The preferred embodiments also include methods for making same. For example, a time-release antifungal agent may comprise an active antifungal agent combined with additional materials such as polymer binders or encapsulators to achieve the desired release profile of the active antifungal ingredient from the board over time or upon wetting. In a preferred embodiment, in addition to the presence of PAA, active antifungal agent such as CPC is included with an encapsulator such as JSMS Methocel hydroxypropyl methyl- cellulose, available from the Dow Chemical Company. Alter- natively, an active ingredient such as CPC may be physically adhered within the gypsum core (for example, encapsulated by calcium within the gypsum core) or on/in the paper facings such that the CPC is released upon wetting of the gypsum core and/or paper facings. Methods for encapsulating active mate- rials to achieve controlled release over time and/or upon wetting are well-known and any such methods and processes are within the scope of the present invention. For certain applications, the presence of the PAA is sufficient, however, and the incorporation of CPC or the like with or without binders is not necessary. To initiate polymerization of quatemary amine monomers, cerium ion is useful to target covalent linkage of the growing polymer chains to cellulosic substrates. In addition, Azo com- pounds such as AIBN (2,2'-azobisisobutyronitrile) are com- monly used as initiators for vinyl polymerizations, but are not generally thought of as catalysts for preparation of graft copolymers. We have found, however, that a water-soluble derivative of AIBN (2,2‘-Azobis[N-(2-carboxyethyl)-2-me- thylpropionamidine]tetrahydrate, or VA-057, available from Wako Specialty Chemicals) was a suitable initiator for the graft polymerization of quaternary vinyl monomers onto cel- lulosic substrates such as paper or onto starch substrates. AIBN, which is one of the most commonly used polymeriza- tion initiators, is not soluble in water; and thus carmot be used directly in aqueous solutions. AIBN is soluble in alcohols, however, and thus can possibly be used as an initiator for the graft polymerization of quatemary monomers onto cellulose since the monomers are also soluble in alcohols. It is also likely thatAIBN could be used in an emulsion system in order to achieve similar results. Other potentially useful Azo initia- tors include: (2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl) propane]dihydrochloride, or VA-041; 2,2'-Azobis{2-methyl- N-[ l ,1 -bis(hydroxymethyl)-2 -hydroxyethyl]propionarnide, or VA-080; 2,2‘-Azobis(2 -methylpropionamide)dihydro- chloride, or V-50; 2,2‘-Azobis(N-cyclohexyl-2-methylpropi- onamide), or Vam-l l l; l,l'-Azobis(cyclohexane-l -carboni- trile); all available from Wako Specialty Chemicals, Inc.; and numerous other similar compounds). Organic peroxides such as benzoyl peroxide (BPO) are also widely used as polymerization initiators. Just as in the case of AIBN (above), BPO is not water soluble, but it can possibly be used in alcoholic solution in order to graft qua- US 7,473,474 B2 11 ternary vinyl monomers onto cellulose. Otherpotentially use- ful peroxide initiators include: (dicumyl peroxide, t-butyl peroxide, methylethylketone peroxide, and a variety of other peroxides, peroxyketals, peroxydicarbonates, and hydroper- oxides). These and numerous other potentially useful cata- lysts are available from a variety of suppliers such as Lucidol- Penwalt, and Akzo. Combinations of two or n1ore of the initiators described above are also effective. These catalysts or initiators can also be used to form crosslinked cellulose-quatemary grafted materials. In a preferred embodiment, the gypsum board is formed by a process in which paper surfaces, either prior to or after application to the gypsum core, are sprayed with a combina- tion of reactive monomer and polymerization initiator. The polymerization mixture is typically aqueous, and is prefer- ably flash heated once in contact with the desired paper sur- face, (front, back or both, either with or without application of non-polymerizable antifungals, or previously polymerized antifungals, either before or after the flash heating step) to initiate polymerization. In this manner, the polymerization reaction can be initiated in a controlled fashion at the desired point in the gypsum board assembly process. If necessary, a glue, preferably a glue containing a fungicide, such as that disclosed in US Patent Publication 2003/0027889, is used to assist in adhering the paper to the gypsum core. No washing step is required, as any unpolymerized monomeric antifungal agent, such as DADMAC or TMMC, will have some poten- tially beneficial effect as a leachable antifungal. Should it be desirable, however, to remove these unreacted components, a brief rinse step following flash polymerization may be included. In this event, it may be preferable to treat the paper facing material prior to adhesion to the gypsum core. In connection with the paper component associated with wallboard, those skilled in the art will appreciate based on this disclosure that there are many methods of treating the paper to achieve the desired antimicrobial properties taught herein. According to one method, pulp is treated and used to make paper, optionally including blending with untreated pulp. Paper prepared in this manner was found to pass the ASTM method for mold growth. In another embodiment, the outer surface of the wallboard paper is treated before it is used in making the wallboard. Although the paper is treated on one side only, the paper can be used on both sides of the wallboard. The treated side is preferably oriented outward, away from the gypsum core. The antimicrobial polymer coating is non-uniform through- out the paper, and concentrated at the surface, thus the surface is more fungal resistant than the inside of the paper. A useful range of between 1 and 5 wt %, relative to the weight of the paper, may be utilized. In a further embodiment, a crosslinker is included to extend the degree of polymerization of the PAA. If the polymeriza- tion reaction is run under air, and without the crosslinker, the degree of polymerization can be low. During the course of polymerization, grafting of polymer occurs. Where a three- dimensional crosslinker is utilized, there is some network (gel) formation. This can result in the formation of a partial interpenetrating network (OPN), which further locks the polymer to the paper. The IPN can be formed between indi- vidual paper fibers, or within the pores of an individual fiber, or both. Without wishing to be limited to mechanism, although some of the IPN is possibly not covalently bonded, it is nevertheless “permanently” attached to the paper. It is anticipated that some soluble homopolymer is formed as well. Although the soluble homopolymer is not bound to the paper, it is only expected to represent a relatively small frac- 10 15 20 25 30 35 40 45 50 55 60 65 12 tion of the total polymer present. Accordingly, it will be appreciated from this disclosure that what is intended by PAA includes all combinations of grafted, IPN, and soluble poly- mer. A preferred polymer crosslinker is to be N,N'-methyl- enebisacrylamide, since it is highly water-soluble, and mis- cible with high DADMAC monomer concentrations. Other crosslinkers can be ethoxylated trimetholoylpropane triacry- late (SR9035, Sartomer Co.), polyethylene oxide diacrylate (SR344, Sartomer co.), or other di, tri, or polyfunctional monomers. Water-soluble crosslinkers are preferred, and crosslinkers completely soluble and miscible with the mono- mer solution are most preferred. Solvents such as alcohols can be used to compatibilize the monomer/crosslinker solu- tions if needed. In further embodiments according to this invention, formu- lations are utilized wherein soluble linear DADAMC homopolymer is added to the coating solution. This increases the viscosity of the solution, and provides a so-called “level- ing effect”, i.e. it produces smoother coatings. Naturally, the added polymer is not bonded to the paper, but it nonetheless serves an antimicrobial utility. The combination of mobile and bonded antimicrobial polymer is preferred in certain applications in that it combines fast action with prolonged eflicacy. We have discovered that the appearance of the treated paper can be improved by first wetting the paper surface with water. This allowed a higher amount of polymer to be applied uniformly, without mottling or discoloration of the paper. Prewetting was applied at a rate of approximately 1 to 3 grams water per square foot of paper. Curing of the paper (polymerization) may be carried out in a variety of formats. For example, in some applications according to this invention, curing was successfully carried out by radiant heating under a heat lamp, at a distance of approximately three inches for between 10 and 60 seconds, or by application of heat from heating metal plates, rollers, presses, or the like, set at appropriate temperatures, for between 10 and 30 seconds.A particularly useful method was to place two wet sheets of paper face-to-face, prior to heating with a heated metal surface. This prevented contact of the wet surface with the hot metal surface. Radiant heat, hot-presses or rollers, microwaves, and steam are all optional methods for curing of the polymer. Monomer solutions may be applied according to this invention by dipping, spraying, or roller application. The use of squeegees, doctor blades or air curtains are useful for controlling the coverage rate. Antimicrobial testing used in certain examples disclosed herein involves bacterial testing, or fungal testing. Bacterial challenge test is considerably more rapid and less costly than the ASTM mold growth test. It, nonetheless, serves as a convenient screening tool to determine general antimicrobial eflicacy. We have found that a high kill rate for bacteria in the tests performed as disclosed herein generally correlates with eflicacy in the mold/ fungus challenge. In a preferred embodiment according to this invention, the PAA is utilized as a complexing agent for monomeric ionic antifungal compounds. In one aspect of this embodiment of the invention, the PAA is utilized to “stabilize” an otherwise easily removed or diffusible antimicrobial, such as sodium pyrithione (SP). In the discussion which follows, SP is referred to specifically, both as a specific compound utilizable according to this invention, but also as an example of a class of ionic (whether anionic or cationic) antifungal compounds that may be bound by the polymeric antifungal agent (PAA), which itself may be polycationic, as where the polymer is a polyquatemary amine, or polyanionic. We have found that US 7,473,474 B2 13 pyrithione is significantly bound by polyquatemary amine PAA, and resists leaching much better than from untreated substrate. Two recent US patent applications discuss the use of sodium pyrithione in wallboard applications (US #2004/ 0005484 and US #2003.0234068, both of which are hereby incorporated by reference for this purpose). Both contain good general overviews of SP and related antifungal materi- als. It is noted that SP is very water soluble (i.e. >50 wt % aqueous solutions are possible). This makes it relatively easy to wash or leach the SP from the treated surface. Zinc pyrithione (ZP) may be used in place of or in addition to SP in wallboard applications. The solubility of zinc pyrithione is much less than SP (max. solubility in waster is 0.0015%). The average useful level of pyrithione in the gypsum slurry (as indicated in the 0005484 application) is about 250 ppm (:0.025%). It is unclear as to what level this represents at the surface of the paper; however, the discussion in that applica- tion indicates that the level in the paper facing would be similar. Since this level far exceeds the solubility of zinc pyrithione, it would be difiicult to achieve using the zinc salt. Apparently, this is the gist of the discussion in paragraph 17 of that application. Paragraph 19 describes the stabilization of SP by the calcium in the gypsum core. The wallboard accord- ing to the present invention achieves this function more effi- ciently than calcium, which itself is monomeric and poten- tially leacheable. Using a sufficiently high level of bonded polyquatemary amine as the PAA according to this invention, yields a dual mode of protection, assuming that only a small fraction of the quaternary amine sites are bonded to pyrithione (e.g. if 4% polyquat is utilized with 250 ppm SP, there is a vast excess of free polyquatemary amine sites). Even if all of the SP eventually migrates out of the panel (by contact with excessive moisture, for instance) the bonded polyquat continues to provide antimicrobial effect. In addi- tion, utilizing SP in combination with polyquatemary amine also allows much lower polyquat levels to be used, since the SP level is low, and only a comparable amount of polyquat is needed for stabilization. In this case, the antimicrobial con- tribution from the polyquat is reduced due to shielding by the bound SP. However, there is a cost savings from using less polyquat, and as SP is removed, the revealed polyquat sites continue to provide long-term antimicrobial efficacy. Accordingly, polyquat bonded to the paper stabilizes the sodium pyrithione and decreases the amount that can be washed off by a given amount of water. The SP is added to the wet gypsum slurry, and allowed to migrate into the paper, where it is stabilized, or it is applied directly to the quat- treated paper. Altematively, or in addition, SP is mixed with DAMAC monomer prior to paper treatment. The quat-treated paper is also, optionally, or in addition, treated with SP sepa- rately, either before or after quat is applied to the paper. In yet a further option according to this invention, quat-treated starch is used to stabilize the SP in the gypsum core. Even if the quat is not bonded to the paper, it nonetheless stabilizes the SP to some extent. Since DADAMC homopolymer has a high molecular weight, it diffuses much more slowly than SP, thereby retarding diffusion away from the wallboard compo- nent of the SP bound to the homopolymer. In addition, the solubility of the quat:SP complex is expected to be less than that of either component alone. Having generally described the invention and methods of making and using this invention, certain specific examples are provided below which disclose specific methods for making antifungal gypsum board comprising polymeric antifungal agents. While these examples are provided to disclose the best mode and preferred embodiments, these examples should not 5 10 15 20 25 30 35 40 45 50 55 60 65 14 be construed as limiting on the scope of the present invention, which instead should be understood through reference to the appended claims. EXAMPLES Example 1 First and second sets of 0.5 inch thick sample gypsum boards comprising about 0.5 and about 1.0 weight percent CPC, respectively, based on the dry weight of the gypsum in the board are produced. The board manufacturing line is run at a speed of 255 linear feet per minute, and separate 5-minute trials are conducted for each set of sample boards. For each five minute trial, the total water in the gypsum slurry is 1 133 pounds per thousand square feet per minute of run time (lbs/ MSF/min), for a total of 5665 lbs and the total dry gypsum powder is 1300 lbs/MSF/min ofrun time, for a total of 6500 lbs. For the 0.5% PAA with or without CPC board, 0.005 .times.6500:32.5 lbs of PAA with or without CPC is added to the slurry as a 15 weight percent PAA with or without CPC solution, based on total weight of the solution. For the 1.0% PAA with or without CPC board, 0.01.times.6500:65.0 lbs of PAA with or without CPC is added to the slurry as a 15 weight percent PAA with or without CPC solution, based on total weight of the solution. A total of about 5000 square feet of each set of boards is pro- duced. Testing is expected to indicate that PAA with or without CPC-treated gypsum board effectively suppresses bacterial and fungal growth. It is currently believed that appropriately treated gypsum board will exhibit broad-based resistance to a wide variety of microbes. Example 2 In this example, polyDADMAC is formed by polymeriza- tion of DADMAC monomers in the presence of a polymer- ization initiator in an inert atmosphere, in the presence of a gypsum board component, selected from: the front or back paper facings, the pulp used to make the front and back paper facings, the starch included as a component of the gypsum core, or another component to which the nascent polymer becomes covalently bonded as it is formed. Appropriate poly- merization initiators are known, including various salts of cerium. Alternatively, an initiator such as a so-called “Azo” initiator, such as VA-057, V-50 and the like, available from Wako Pure Chemical Industries, is utilized. Other initiators, including but not limited to hydrogen peroxide, sodium per- sulfate (“SPS”), and the like are utilized to advantage accord- ing to this invention to initiate polymerization Example 3 In this example, polyDADMAC is formed by polymeriza- tion prior to contact of the polymer with a gypsum board component. An appropriate amount of polyDADMAC is then mixed with the gypsum core components or is sprayed onto the paper facing components of the gypsum board, either prior to or after the paper is affixed to the gypsum core. Example 4 In this example, polyDADMAC is formed by polymeriza- tion prior to contact of the polymer with a gypsum board component. An appropriate amount of polyDADMAC is then mixed with the gypsum core components and is sprayed onto US 7,473,474 B2 15 the paper facing components of the gypsum board, either prior to or after the paper is aflixed to the gypsum core. Example 5 In this example, polyDADMAC is formed by polymeriza- tion prior to contact of the polymer with a gypsum board component. An appropriate amount of polyDADMAC is then mixed with the gypsum core components and is sprayed onto the paper facing components of the gypsum board, either prior to or after the paper is aflixed to the gypsum core. In this example, a non-polymeric antifungal agent, such as cetyl pyridinium chloride, is also included in the gypsum core, the paper facings, or both, either with or without binders or reten- tion aids. Example 6 In this EXAMPLE, starch or cellulosic components of gypsum board, whether from the core or the paper facings, is reacted with antimicrobial monomer and initiator under con- ditions which benefit polymerization (heat, non-oxygenated atmosphere, high reaction concentration of monomeric anti- fungals and polymerization initiators). The starch or cellulo- sic component is washed and recovered following polymer- ization. Alternatively, that component is added directly to the gypsum core or paper facing material in a concentration suf- ficient to achieve the desired function of the starch or cellu- losic material. For this example, DADMAC monomer is reacted at a final concentration (v/v) of about 25-50%, while TMMC monomer is reacted at a final concentration of about 5-25%. An initiator is mixed with the starch or cellulosic component containing reactive monomer, heated, washed and the antifungal and antimicrobial starch or cellulosic material is then mixed with the gypsum component of the core or paper facing at different ratios to achieve the physico- chemical characteristics desired, while also imparting an antimicrobially active polymer to the gypsum core, paper facing or both In this marmer, any moisture and fungal spores, bacteria or the like that may penetrate to the gypsum core are denied an environment conducive to their growth. This is very beneficial to address such issues as mold induced illnesses in buildings with circulating air handling systems (so-called “sick building syndrome”). Example 7 In this EXAMPLE, 5 g of gypsum stucco was mixed with 2.5 g water (Sample A). In Sample B, 5 g of gypsum stucco was mixed with 2.5 g 1% aqueous polyDADMAC. The thus formed gypsum stucco material was allowed to dry into 2 cm>