U.S. patent application number 12/347844 was filed with the patent office on 2009-04-23 for gypsum board with a fluorine-containing antifungal agent.
This patent application is currently assigned to Quick-Med Technologies, Inc.. Invention is credited to Gerald Olderman, Gregory Staab, William Toreki.
Application Number | 20090104144 12/347844 |
Document ID | / |
Family ID | 32927594 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090104144 |
Kind Code |
A1 |
Toreki; William ; et
al. |
April 23, 2009 |
Gypsum board with a fluorine-containing antifungal agent
Abstract
A novel 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. The novel gypsum board further comprises a
non-polymeric antifungal agent comprising a fluorine-containing
quaternary ammonium compound. Preferred non-polymeric ammonium
compounds include Tetra-n-butylammonium fluoride and
Tetraethylammonium fluoride. The polymeric antifungal agent can be
present in the gypsum core and/or on one or both of the paper
facings. The non-polymeric antifungal agent may be encapsulated in
a material or ionically associated with the polymeric antifungal
agent to allow releases of the non-polymeric antifungal agent over
time and/or upon exposure to moisture. Methods for preparing the
aforementioned novel gypsum board are also disclosed.
Inventors: |
Toreki; William;
(Gainesville, FL) ; Olderman; Gerald; (Bedford,
MA) ; Staab; Gregory; (Westlake Village, CA) |
Correspondence
Address: |
ELMAN TECHNOLOGY LAW, P.C.
P. O. BOX 209
SWARTHMORE
PA
19081
US
|
Assignee: |
Quick-Med Technologies,
Inc.
Gainesville
FL
|
Family ID: |
32927594 |
Appl. No.: |
12/347844 |
Filed: |
December 31, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10546850 |
Aug 24, 2005 |
7473474 |
|
|
PCT/US04/05616 |
Feb 25, 2004 |
|
|
|
12347844 |
|
|
|
|
60449915 |
Feb 25, 2003 |
|
|
|
Current U.S.
Class: |
424/78.32 |
Current CPC
Class: |
B32B 13/08 20130101;
A01N 25/34 20130101; Y10T 428/31986 20150401; Y10T 428/31993
20150401; A01N 25/34 20130101; Y10T 428/31996 20150401; A01N 33/12
20130101; A01N 33/12 20130101; E04C 2/043 20130101; A01N 55/02
20130101; A01N 25/34 20130101; A01N 43/40 20130101; A01N 33/12
20130101; A01N 2300/00 20130101; A01N 37/12 20130101; A01N 2300/00
20130101 |
Class at
Publication: |
424/78.32 |
International
Class: |
A01N 33/02 20060101
A01N033/02; A01P 3/00 20060101 A01P003/00 |
Claims
1. An antifungal gypsum board comprising a polymeric antifungal
agent and a non-polymeric antifungal agent comprising a
fluorine-containing quaternary ammonium compound.
2. The antifungal gypsum board comprising a polymeric antifungal
agent and a non-polymeric antifungal agent of claim 1 wherein said
fluorine-containing quaternary ammonium compound is selected from
the group consisting of Tetra-n-butylammonium fluoride,
Tetraethylammonium fluoride,
3-(Trifluoromethyl)phenyltrimethylammonium bromide,
3-(Trifluoromethyl)-phenyltrimethylammonium iodide,
3-(Trifluoromethyl)phenyltrimethyl-ammonium hydroxide,
N-fluoro-N'-(chloromethyl)triethylenediamine
Bis(tetrafluoroborate), n-Hexadecyltrimethylammonium
hexafluorophosphate, n-Hexadecyltrimethylammonium
tetrafluoroborate, Tetra-n-butylammonium bifluoride,
Tetra-n-butylammonium difluoro-triphenylsilicate,
Tetra-n-butylammonium difluorotriphenylstannate,
Tetra-n-butylammonium dihydrogentrifluoride, Tetra-n-butyl ammonium
hexafluorophosphate, Tetra-n-butylammonium tetrafluoroborate,
Tetraethylammonium tetrafluoroborate, Tetraethylammonium
hexafluorophosphate, Tetramethylammonium tetrafluoroborate, and
Trifluoromethanesulfonic acid tetra-n-butylammonium salt.
3. The antifungal gypsum board of claim 2 wherein said polymeric
antifungal agent is selected from the group consisting of
polyDADMAC, polyTMMC, and quaternized polyvinyl pyridine
derivatives.
4. The antifungal gypsum board of claim 3 wherein said polymeric
antifungal agent is covalently bound by use of an initiator to a
component of the gypsum board, and whereby the non-polymeric
antifungal agent resists leaching.
5. The antifungal gypsum board of claim 4 wherein said polymeric
antifungal agent is polyDADMAC.
6. The antifungal gypsum board of claim 4 wherein said polymeric
antifungal agent is polyDADMAC and wherein said non-polymeric
antifungal agent is selected from the group consisting of
Tetra-n-butylammonium fluoride, Tetraethylammonium fluoride,
N-Fluoro-N'-(chloromethyl)triethylene-diamine
bis(tetrafluoroborate), n-Hexadecyltrimethylammonium
tetrafluoroborate, Tetra-n-butylammonium tetrafluoroborate,
Tetraethylammonium tetrafluoroborate, and Tetramethylammonium
tetrafluoroborate.
7. The antifungal gypsum board of claim 6 wherein said
non-polymeric antifungal agent is Tetra-n-butylammonium fluoride or
Tetraethylammonium fluoride.
8. The antifungal gypsum board of claim 4, further comprising cetyl
pyridinium chloride (CPC) as an additional antifungal agent.
9. The antifungal gypsum board of claim 5, further comprising cetyl
pyridinium chloride (CPC) as an additional antifungal agent.
10. The antifungal gypsum board of claim 7, further comprising
cetyl pyridinium chloride (CPC) as an additional antifungal
agent.
11. An improved method for manufacturing an antifungal gypsum board
which comprises the steps: a. covalently bonding, by use of an
initiator and in the presence of a crosslinker, a polymeric
antifungal agent to the board or a component thereof, b. adding a
non-polymeric antifungal agent to the board or a component thereof,
wherein said non-polymeric antifungal agent is stabilized by the
polymeric antifungal gent, and whereby the non-polymeric antifungal
agent resists leaching.
12. The method of claim 11 further comprising encapsulating or
binding the non-polymeric antifungal agent such that the
non-polymeric antifungal agent is released over time, or upon
exposure to moisture, or both.
13. The method of claim 11 wherein the polymeric antifungal agent
is polyDADMAC and the non-polymeric antifungal agent is a
fluorine-containing quaternary ammonium compound.
14. The method of claim 13 wherein the non-polymeric antifungal
agent is Tetra-n-butylammonium fluoride or Tetraethylammonium
fluoride.
15. The method of claim 14 further comprising encapsulating or
binding the non-polymeric antifungal agent such that the
non-polymeric antifungal agent is released over time, upon exposure
to moisture, or both.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional application is a continuation of U.S.
patent application Ser. No. 10/546,850 issued as U.S. Pat. No.
7,473,474 on Jan. 6, 2009, which was a national stage filing of
PCT/US04/05616 filed Feb. 25, 2004 which claims priority to U.S.
Provisional Application No. 60/449,915 filed on Feb. 25, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field of the Invention
[0003] The present invention relates generally to gypsum board and
methods for making gypsum board. More specifically, the present
invention relates to improved gypsum board possessing antifungal
properties and improved methods of making the same.
[0004] 2. Description of Related Art
[0005] 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.
[0006] 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.
[0007] 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 antifungal 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 quaternary amines are
significantly more antimicrobial than are monomeric quaternary
amines.
[0008] There is an ongoing need for gypsum board products that
offer reduced susceptibility to fungal growth without compromising
their beneficial properties. In addition, there is an ongoing need
for commercially viable manufacturing methods for such products.
The present invention solves these problems by using an improved
antifungal agent that effectively inhibits fungal growth, is
compatible with gypsum board materials, and can be incorporated
into a cost-effective and commercially-viable manufacturing
process.
SUMMARY OF THE INVENTION
[0009] 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 embodiment of the present invention, the
antifungal agent is a polymeric antifungal agent (PAA), alone or in
combination with a monomeric antifungal agent, such as cetyl
pyridinium chloride (CPC), a quaternary ammonium compound, or a
pyrithione, such as sodium pyrithione, (SP), or another anionic
antifungal compound which binds ionically to a cationic PAA, and be
thereby more effectively retained than if the pyrithione were
simply mixed with or adsorbed to wallboard 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 encapsulated in an
encapsulator so that it is released over time and/or upon exposure
to moisture.
[0010] 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.
[0011] 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.
[0012] In another preferred embodiment the PAA is a polymeric
quaternary amine.
[0013] In another preferred embodiment, the PAA is covalently
bonded to components of the gypsum, the front paper facing, the
back paper facing or both.
[0014] In another preferred embodiment, the PAA is a polymeric
quaternary 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
[0015] 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 antifungal agent. By substantially
unchanged, a given mechanical property preferably remains within
the parameters of governing standards--e.g., ASTM standards.
Consequently, the improved novel gypsum board product achieves the
structural, 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.
[0016] 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 embodiments comprise a gypsum core
comprised of gypsum powder, water and optionally foam, pulp, starch
and/or set controlling 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 comprised of a cellulosic
material.
[0017] The preferred embodiments of the present invention also
employ an improved antifungal agent, as used herein meaning and
including all agents, materials, and combinations thereof providing
antimicrobial activity. Preferred antimicrobial 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 compatible with gypsum board composition and
manufacturing processes and providing the desired biocidal,
antifungal, antimycogen, 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
antifungal agents are known including, for example, chlorhexidine,
alexidine, cetyl pyridinium chloride, benzalkonium chloride,
benzethonium chloride, cetalkonium chloride, cetrimide, cetrimonium
bromide, glycidyl trimethylammonium chloride, stearalkonium
chloride, hexetidine, triclosan and triclocarban. The improved
antifungal agent of this invention, however, 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 quaternary
ammonium compounds, including but not limited to the following
compounds:
Fluoride:
[0018] Tetra-n-butylammonium Fluoride [0019] Tetraethylammonium
Fluoride
Chloride:
[0019] [0020] Acetylcholine Chloride [0021]
(3-Acrylamidopropyl)trimethylammonium Chloride [0022] Benzalkonium
Chloride [0023] Benzethonium Chloride [0024] Benzoylcholine
Chloride [0025] Benzylcetyldimethylammonium Chloride [0026]
N-Benzylcinchonidinium Chloride [0027] N-Benzylcinchoninium
Chloride [0028] Benzyldimethylphenylammonium Chloride [0029]
Benzyldimethylstearylammonium Chloride [0030] N-Benzylquinidinium
Chloride [0031] N-Benzylquininium Chloride [0032]
Benzyltri-n-butylammonium Chloride [0033] Benzyltriethylammonium
Chloride [0034] Benzyltrimethylammonium Chloride [0035]
Carbamylcholine Chloride [0036] DL-Carnitine Hydrochloride [0037]
Chlorocholine Chloride [0038]
(3-Chloro-2-hydroxy-n-propyl)trimethylammonium Chloride [0039]
Choline Chloride [0040] n-Decyltrimethylammonium Chloride [0041]
Diallyldimethylammonium Chloride [0042]
Dichloromethylenedimethyliminium Chloride [0043]
Dimethyldistearylammonium Chloride [0044]
n-Dodecyltrimethylammonium Chloride [0045] Girard's Reagent T
[0046] n-Hexadecyltrimethylammonium Chloride [0047] Hexamethonium
Chloride [0048] Lauroylcholine Chloride [0049] Methacholine
Chloride [0050] Methacroylcholine Chloride [0051]
(2-Methoxyethoxymethyl)triethylammonium Chloride [0052]
beta-Methylcholine Chloride [0053] Methyltriethylammonium Chloride
[0054] Myristoylcholine Chloride [0055] n-Octyltrimethylammonium
Chloride [0056] Phenyltriethylammonium Chloride [0057]
Phenyltrimethylammonium Chloride [0058] Phosphocholine Chloride
Calcium Salt [0059] Phosphocholine Chloride Sodium Salt [0060]
Succinylcholine Chloride [0061] Tetra-n-amylammonium Chloride
[0062] Tetra-n-butylammonium Chloride [0063]
Tetradecyldimethylbenzylammonium Chloride [0064]
n-Tetradecyltrimethylammonium Chloride [0065] Tetraethylammonium
Chloride [0066] Tetramethylammonium Chloride [0067] Trimethyl
[2,3-(dioleyloxy)propyl]ammonium Chloride [0068]
Trimethylstearylammonium Chloride [0069] Trioctylmethylammonium
Chloride [0070] Tri-n-octylmethylammonium Chloride
Bromide:
[0070] [0071] Acetylcholine Bromide [0072] Benzoylcholine Bromide
[0073] Benzyltri-n-butylammonium Bromide [0074]
Benzyltriethylammonium Bromide [0075] Bromocholine Bromide [0076]
Cetyldimethylethylammonium Bromide [0077] Choline Bromide [0078]
Decamethonium Bromide [0079] n-Decyltrimethylammonium Bromide
[0080] Didecyldimethylammonium Bromide [0081]
Dilauryldimethylammonium Bromide [0082] Dimethyldimyristylammonium
Bromide [0083] Dimethyldioctylammonium Bromide [0084]
Dimethyldipalmitylammonium Bromide [0085] Dimethyldistearylammonium
Bromide n-Dodecyltrimethylammonium Bromide [0086]
(Ferrocenylmethyl)dodecyldimethylammonium Bromide [0087]
(Ferrocenylmethyl)trimethylammonium Bromide [0088]
n-Hexadecyltrimethylammonium Bromide [0089] Hexamethonium Bromide
[0090] Hexyldimethyloctylammonium Bromide [0091]
n-Hexyltrimethylammonium Bromide [0092] Methacholine Bromide [0093]
Neostigmine Bromide [0094] n-Octyltrimethylammonium Bromide [0095]
Phenyltrimethylammonium Bromide [0096] Stearyltrimethylammonium
Bromide [0097] Tetra-n-amylammonium Bromide [0098]
Tetra-n-butylammonium Bromide [0099] Tetra-n-decylammonium Bromide
[0100] n-Tetradecyltrimethylammonium Bromide [0101]
Tetraethylammonium Bromide [0102] Tetra-n-heptylammonium Bromide
[0103] Tetra-n-hexylammonium Bromide [0104] Tetramethylammonium
Bromide [0105] Tetra-n-octylammonium Bromide [0106]
Tetra-n-propylammonium Bromide [0107]
3-(Trifluoromethyl)phenyltrimethylammonium Bromide [0108]
Trimethylvinylammonium Bromide [0109] Valetharnate Bromide
Iodide:
[0109] [0110] Acetylcholine Iodide [0111] Acetylthiocholine Iodide
[0112] Benzoylcholine Iodide [0113] Benzoylthiocholine Iodide
[0114] Benzyltriethylammonium Iodide [0115] n-Butylylcholine Iodide
[0116] n-Butyrylthiocholine Iodide [0117] Decamethonium Iodide
[0118] N,N-Dimethylmethyleneammonium Iodide [0119]
Ethyltrimethylammonium Iodide [0120] Ethyltri-n-propylammonium
Iodide [0121] (Ferrocenylmethyl)trimethylammonium Iodide [0122]
(2-Hydroxyethyl)triethylammonium Iodide [0123] beta-Methylcholine
Iodide [0124] O-.beta.-Naphthyloxycarbonylcholine Iodide [0125]
Phenyltriethylammonium Iodide [0126] Phenyltrimethylammonium Iodide
[0127] Tetra-n-amylammonium Iodide [0128] Tetra-n-butylammonium
Iodide [0129] Tetraethylammonium Iodide [0130]
Tetra-n-heptylammonium Iodide [0131] Tetra-n-hexylammonium Iodide
[0132] Tetramethylammonium Iodide [0133] Tetra-n-octylammonium
Iodide [0134] Tetra-n-propylammonium Iodide [0135]
3-(Trifluoromethyl)phenyltrimethylammonium Iodide
Hydroxide:
[0135] [0136] Benzyltriethylammonium Hydroxide [0137]
Benzyltrimethylammonium Hydroxide [0138] Choline [0139]
n-Hexadecyltrimethylammonium Hydroxide [0140]
Phenyltrimethylammonium Hydroxide [0141] Sphingomyelin [0142]
Tetra-n-butylammonium Hydroxide [0143] Tetra-n-decylammonium
Hydroxide [0144] Tetraethylammonium Hydroxide [0145]
Tetra-n-hexylammonium Hydroxide [0146] Tetramethylammonium
Hydroxide [0147] Tetra-n-octylammonium Hydroxide [0148]
Tetra-n-propylammonium Hydroxide [0149]
3-(Trifluoromethyl)phenyltrimethylammonium Hydroxide
Others:
[0149] [0150] Acetylcholine Perchlorate [0151]
Benzyltrimethylammonium Dichloroiodate [0152]
Benzyltrimethylammonium Tetrachloroiodate [0153]
Benzyltrimethylammonium Tribromide [0154] Betaine, Anhydrous [0155]
Betaine Hydrochloride [0156] Bis(tetra-n-butylammonium)Dichromate
[0157] Bis(tetra-n-butylammonium)Tetracyanodiphenoquinodimethanide
[0158] L-Carnitine [0159] 3-[(3-Cholamidopropyl)
dimethylammonio]-1-propanesulfonate [0160] Denatonium Benzoate
[0161] n-Dodecyldimethyl(3-sulfopropyl)ammonium Hydroxide, Inner
Salt [0162] N-Fluoro-N'-(chloromethyl)triethylenediamine
Bis(tetrafluoroborate) [0163] n-Hexadecyltrimethylammonium
Hexafluorophosphate [0164] n-Hexadecyltrimethylammonium Perchlorate
[0165] n-Hexadecyltrimethylammonium Tetrafluoroborate
(Methoxycarbonylsulfamoyl)triethylammonium Hydroxide, Inner Salt
[0166] Neostigmine Methyl Sulfate [0167]
n-Octadecyldimethyl(3-sulfopropyl)ammonium Hydroxide, Inner Salt
[0168] Phenyltrimethylammonium Tribromide [0169] Propionylcholine
p-Toluenesulfonate [0170] Tetra-n-butylammonium Azide [0171]
Tetra-n-butylammonium Bifluoride [0172] Tetra-n-butylammonium
Borohydride [0173] Tetra-n-butylammonium Bromodiiodide [0174]
Tetra-n-butylammonium Dibromoaurate [0175] Tetra-n-butylammonium
Dibromochloride [0176] Tetra-n-butylammonium Dibromoiodide [0177]
Tetra-n-butylammonium Dichloroaurate [0178] Tetra-n-butylammonium
Dichlorobromide [0179] Tetra-n-butylammonium
Difluorotriphenylsilicate [0180] Tetra-n-butylammonium
Difluorotriphenylstannate [0181] Tetra-n-butylammonium
Dihydrogentrifluoride [0182] Tetra-n-butylammonium Diiodoaurate
[0183] Tetra-n-butylammonium Hexafluorophosphate [0184]
Tetra-n-butylammonium Hydrogensulfate [for Ion-Pair Chromatography]
[0185] Tetra-n-butylammonium Hydrogensulfate [0186]
Tetra-n-butylammonium Perchlorate [0187] Tetra-n-butylammonium
Perrhenate [0188] Tetra-n-butylammonium Phosphate [0189]
Tetra-n-butylammonium Salicylate [0190] Tetra-n-butylammonium
Tetrafluoroborate [0191] Tetra-n-butylammonium Tetraphenylborate
[0192] Tetra-n-butylammonium Thiocyanate [0193]
Tetra-n-butylammonium Tribromide [0194] Tetra-n-butylammonium
Triiodide [0195] Tetraethylammonium Borohydride [0196]
Tetraethylammonium Perchlorate [0197] Tetraethylammonium
Tetrafluoroborate [0198] Tetraethylammonium p-Toluenesulfonate
[0199] Tetraethylammonium Trifluoromethanesulfonate [0200]
Tetramethylammonium Acetate [0201] Tetramethylammonium Borohydride
[0202] Tetramethylammonium Hexafluorophosphate [0203]
Tetramethylammonium Hydrogensulfate [0204] Tetramethylammonium
Perchlorate [0205] Tetramethylammonium Sulfate [0206]
Tetramethylammonium Tetrafluoroborate [0207] Tetramethylammonium
p-Toluenesulfonate [0208] Tetramethylammonium Triacetoxyborohydride
[0209] Tetra-n-propylammonium Perruthenate [0210]
Trifluoromethanesulfonic Acid Tetra-n-butylammonium Salt
[0211] The polymers may include polymers of any of the foregoing
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
diallyldimethylammonium chloride, (DADMAC), to form polyDADMAC,
[2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMMC), to
form polyTMMC, quaternized vinyl pyridine (VP) derivatives, to give
polyVP, or similar polymerizable quaternary amine monomers are
utilized to form suitable quaternary amine polymers. The polymer,
in one embodiment, is simply mixed with the gypsum core components.
The polymer, in another embodiment, 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
components of the gypsum core. For example, gypsum containing
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 convenient to
separately react the starch or cellulosic component with the
antimicrobial monomer and initiator under conditions which benefit
polymerization (heat, non-oxygenated atmosphere, high reaction
concentration of monomeric antifungals and polymerization
initiators). The starch or cellulosic component may be washed and
recovered following polymerization, if desired, or may be added
directly to the gypsum core in a concentration sufficient to
achieve the desired function 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
characteristics for the gypsum core. Such variations derived from
this disclosure are considered to come within the scope of
equivalents to the methodology disclosed herein. In one embodiment,
DADMAC monomers and an azo initiator are mixed with the cellulosic
component, heated, washed and the antifungal 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 polymer 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 benefits 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.
[0212] 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 quaternary 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, "Cyclopolymerization and Cyclocopolymerization",
published by Marcel Dekker, Inc., New York, Basel, Hong Kong, ISBN:
0-8247-8625-4, 1992.
[0213] Without limiting the scope of the present invention, certain
embodiments of the present invention may employ, in addition to the
polymeric antifungal agent, cetyl pyridinium chloride (CPC) as an
antifungal agent. The preferred embodiments are only exemplary.
References herein to antifungal agents in general and CPC in
particular are not intended to limit the scope of the
invention.
[0214] Cetyl pyridinium chloride--also known as CPC or n-hexadecyl
pyridinium chloride--is a cationic surfactant comprised 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 antifungal, antimycogen, and antibacterial chemical.
CPC is commonly available in a powder form as a monohydrate
manufactured by Zeeland/Cambrex and available from Johnson Matthey
Catalog Company Inc. of Ward Hill, Mass., among others.
[0215] 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. 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.
[0216] 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.
[0217] 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 polymeric antifungal agent equal to from about 0.5 to about 1.0
weight percent of the dry weight of the gypsum in the board.
[0218] The gypsum board production process typically commences with
the mining and transportation of gypsum rock. Once mined, the
gypsum rock is crushed and ground into a fine powder.
Alternatively, 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 preferred embodiments of the present invention
comprise mixing gypsum powder with water to form a gypsum slurry.
Optionally, one or more of foam, pulp, starch and/or
set-controlling agents may be added to the slurry.
[0219] The preferred embodiments of the present invention comprise
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 gypsum 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.
[0220] The preferred embodiments of the present invention also
comprise the addition of the antifungal agent during the gypsum
board manufacturing process. The antifungal agent may be added by
any method capable of incorporating effective quantities of such
agent into or onto the gypsum board product. 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.
[0221] The polymeric antifungal agent with or without monomeric
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, premixing 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 without 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 thickness, 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.
[0222] 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 manufacturing 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 spraying 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 components 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.
[0223] 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
efficacy over an extended period of time. The present invention
provides a polymeric antifungal agent (the PAA) which significantly
enhances the longevity and efficacy of the antifungal agent, with
or without monomeric 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 efficacy 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.
[0224] In a preferred embodiment, in addition to the presence of
PAA, active antifungal agent such as CPC is included with an
encapsulator such as J5MS Methocel hydroxypropyl methylcellulose,
available from the Dow Chemical Company. Alternatively, 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 materials 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.
[0225] To initiate polymerization of quaternary amine monomers,
cerium ion is useful to target covalent linkage of the growing
polymer chains to cellulosic substrates. In addition, Azo compounds
such as AIBN (2,2'-azobisisobutyronitrile) are commonly 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-methylpropionamidine]tetrahydrate,
or VA-057, available from Wako Specialty Chemicals) was a suitable
initiator for the graft polymerization of quaternary vinyl monomers
onto cellulosic substrates such as paper or onto starch substrates.
AIBN, which is one of the most commonly used polymerization
initiators, is not soluble in water; and thus cannot 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 quaternary monomers onto cellulose since
the monomers are also soluble in alcohols. It is also likely that
AIBN could be used in an emulsion system in order to achieve
similar results. Other potentially useful Azo initiators include:
(2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl)propane]
dihydrochloride, or VA-041;
2,2'-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]pro-
-pionamide, or VA-080; 2,2'-Azobis(2-methylpropionamide)
dihydrochloride, or V-50;
2,2'-Azobis(N-cyclohexyl-2-methylpropionamide), or Vam-111;
1,1'-Azobis(cyclohexane-1-carbonitrile); all available from Wako
Specialty Chemicals, Inc.; and numerous other similar
compounds).
[0226] 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 quaternary vinyl monomers
onto cellulose. Other potentially useful peroxide initiators
include: (dicumyl peroxide, t-butyl peroxide, methylethylketone
peroxide, and a variety of other peroxides, peroxyketals,
peroxydicarbonates, and hydroperoxides). These and numerous other
potentially useful catalysts are available from a variety of
suppliers such as Lucidol-Penwalt, and Akzo.
[0227] Combinations of two or more of the initiators described
above are also effective. These catalysts or initiators can also be
used to form crosslinked cellulose-quaternary grafted
materials.
[0228] 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 combination of
reactive monomer and polymerization initiator. The polymerization
mixture is typically aqueous, and is preferably flash heated once
in contact with the desired paper surface, (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 potentially 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.
[0229] 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.
[0230] 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.
[0231] In a further embodiment, a crosslinker is included to extend
the degree of polymerization of the PAA. If the polymerization
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 individual 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 fraction 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 polymer. A preferred polymer
crosslinker is to be N,N'-methylenebisacrylamide, since it is
highly water-soluble, and miscible with high DADMAC monomer
concentrations. Other crosslinkers can be ethoxylated
trimetholoylpropane triacrylate (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 monomer solution are most preferred. Solvents such as alcohols
can be used to compatibilize the monomer/crosslinker solutions if
needed.
[0232] In further embodiments according to this invention,
formulations 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 "leveling 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 efficacy.
[0233] 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.
[0234] 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.
[0235] 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.
[0236] 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 efficacy. We have
found that a high kill rate for bacteria in the tests performed as
disclosed herein generally correlates with efficacy in the
mold/fungus challenge.
[0237] 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 polyquaternary amine, or polyanionic. We
have found that pyrithione is significantly bound by polyquaternary
amine PAA, and resists leaching much better than from untreated
substrate.
[0238] 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 materials. 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 application
indicates that the level in the paper facing would be similar.
Since this level far exceeds the solubility of zinc pyrithione, it
would be difficult 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 according to the present invention
achieves this function more efficiently than calcium, which itself
is monomeric and potentially leacheable. Using a sufficiently high
level of bonded polyquaternary 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 polyquaternary 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 addition, utilizing SP in
combination with polyquaternary 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 contribution 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.
[0239] 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.
Alternatively, 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 separately, 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
component 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.
[0240] 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 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
[0241] 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 1133 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 of run 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
produced.
[0242] 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
[0243] In this example, polyDADMAC is formed by polymerization of
DADMAC monomers in the presence of a polymerization 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 polymerization 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 persulfate
("SPS"), and the like are utilized to advantage according to this
invention to initiate polymerization
Example 3
[0244] In this example, polyDADMAC is formed by polymerization
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
[0245] In this example, polyDADMAC is formed by polymerization
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 affixed to the
gypsum core.
Example 5
[0246] In this example, polyDADMAC is formed by polymerization
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 affixed 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
retention aids.
Example 6
[0247] 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 conditions which benefit
polymerization (heat, non-oxygenated atmosphere, high reaction
concentration of monomeric antifungals and polymerization
initiators). The starch or cellulosic component is washed and
recovered following polymerization. Alternatively, that component
is added directly to the gypsum core or paper facing material in a
concentration sufficient to achieve the desired function of the
starch or cellulosic 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 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").
Example 7
[0248] 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.times.1 cm.times.0.5 cm chunks.
Exposure of Samples A and B by immersion in water revealed that
Sample A was water saturated within 2 minutes, while sample B was
only about half-saturated after 20 minutes (by visual inspection of
cross-sectioned chunks of Samples A and B. Accordingly, we conclude
that gypsum core treated in this manner with polyDADMAC has
unexpected property of increased water resistance.
Example 8
[0249] In this example, polyDADMAC is formed by polymerization
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 affixed to the
gypsum core.
Example 9
[0250] 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 retention
aids.
Example 10
[0251] In this example, 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 combination of reactive monomer and
polymerization initiator. The polymerization mixture is, and is
flash heated once in contact with the desired paper surface,
(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. The final concentration of polyDADMAC
formed on the thus treated surfaces is about 0.5 to 1.5% of the
total mass of paper. Of this, approximately 10% to 99% of the
DADMAC is converted to polyDADMAC which is covalently linked to the
paper and does not leach. The polymerization reaction is initiated
in a controlled fashion at the desired point in the gypsum board
assembly process. In one variation, a glue containing a fungicide
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, remains as a leachable antifungal. Nonetheless, in
a variation, unreacted components are removed by a brief rinse step
following flash polymerization.
Example 11
[0252] A solution containing 50 mL of DADAMC monomer (65 wt %
solution, Aldrich Chemical Co.), 0.75 grams of sodium persulfate
(Acros Chemical) dissolved in 10 mL water, 10 grams of 40%
polyDADMAC solution in water (AF6545, Axchem, Inc), and 30 mL
distilled water was prepared. Sheets of wallboard facing paper
measuring 6''.times.6'' were cut. Each sample weighed approximately
5.4 grams. The paper sheets were wiped with a damp sponge to
moisten the surface. The amount of water applied was between 0.0
and 0.6 grams per sheet. Immediately after moistening, the monomer
solution was applied using a foam rubber paint roller. Excess
monomer solution was applied, and then leveled using a silicone
rubber squeegee and light hand pressure. The samples were then
weighed again to determine the amount of monomer solution applied,
which was between 0.1 and 0.5 grams per sheet. The samples were
then immediately cured by placing them on an aluminum pan three
inches under a red 250 watt incandescent reflector bulb (Heat
Ray--Westinghouse). Samples were moved under the bulb for between
10 and 60 seconds to ensure even heating and to prevent hot spots
or charring. The coated samples were tested for uniformity and
durability of coverage by soaking 1''.times.1'' cut squares in 0.5%
bromthymol blue (BTB) solution for 10 seconds, followed by rinsing
under running tap water for ten seconds. Samples were then placed
into 1 liter of water containing a small amount of ammonia, and
evaluated periodically over the course of several hours. Samples
prepared as described in this paragraph exhibited a distinct and
uniform blue coloration, which persisted for at least six hours or
more, even with continuous stirring. Untreated paper was colorless
after the initial rinsing. Samples treated in the same manner,
except without the use of crosslinker exhibited a distinct blue
color; however, this color faded more quickly after soaking in
ammonia solution. Samples prepared without using the prewetting
step showed less uniformity of color.
[0253] Samples of wallboard paper treated in the above manner were
tested according to a modified AATCC 100 method: Samples were cut
into 3/4''-1'' squares and autoclaved for 20 min., then
subsequently immersed into saline solution (PBS) until saturated.
After saturation wallboard samples were inoculated with 100
microliters of 10.sup.-2 dilution (.about.3.times.10.sup.6 CFU) of
overnight culture (S. Aureus). Inoculated samples were then
incubated for 18 hours at 37 C and 95% RH. After incubation samples
were placed in 50 ml tubes containing 15 ml saline solution (PBS)
and shaken vigorously. After removing samples from tubes sample
elutes were diluted and plated for population count. The content of
the polymeric antimicrobial coating was determined from the weight
of coating solution applied. Samples containing 0%, 1.2%, 2.0%, and
4.0% polymer were tested. The results are presented below, and
indicate that the coated paper has good antimicrobial efficacy:
TABLE-U.S. Pat. No. 00001 S. Aureus Sample (CFU) Wallboard paper
3.times. 10.sup.1 W-7 (2.0%) 1.times. 10.sup.11.times. 10.sup.1
Wallboard paper 1.times. 10.sup.1 W-10 (1.4%)<2.times.
10.sup.0<2.times. 10.sup.0 Wallboard paper<2.times. 10.sup.0
W-11 (4.0%)<2.times. 10.sup.0<2.times. 10.sup.0 Wallboard
paper 1.4.times. 10.sup.4 (untreated, as received) 1.2.times.
10.sup.4 Control 1.4.times. 10.sup.4
Example 12
[0254] This example demonstrates the production of antimicrobial
wallboard paper using wood pulp grafted with a quaternary ammonium
polymer. Brown wood pulp produced from recycled corrugated
cardboard was used in this experiment. The wood pulp was mixed with
a solution of DADMAC monomer, SPS initiator, and water, and then
heated to effect graft polymerization. The treated wood pulp was
thoroughly rinsed to remove any soluble polymer. The graft level
was approximately 10 wt % based on the observed weight gain. The
treated wood pulp was subjected to the BTB dye test described
above, and was found to give a persistent, uniform, dark blue
color. Hand sheets of paper, approximately 12'' square were made
using a lab-scale screen type papermaking process. Paper was made
using 100% treated wood pulp, as well as 75/25, 50/50, and 25/75
blends with untreated pulp. The finished paper had good mechanical
and physical properties, and was similar to paper made form 100%
untreated pulp. The BTB dye test applied to the papers showed a
blue color intensity proportional to the amount of treated pulp in
the composition. The treated paper was subjected to antimicrobial
testing as described above, and was found to have good
antimicrobial properties. In addition, samples of paper made from
100% wood pulp were sent to a commercial testing laboratory for
evaluation of mold and mildew resistance according to ASTM method
#D3273. The results demonstrate a high antifungal activity for the
paper prepared from wood pulp grafted with quaternary ammonium
polymer.
Example 13
[0255] This example demonstrates the stabilization of pyrithione by
a cationic cellulose surface. A nonwoven rayon gauze material
(SofWick, a commercially available rayon gauze material
manufactured by Johnson & Johnson) was graft polymerized with
diallyldimethylammonium chloride (DADAMC) to 10 weight %
poly(DADMAC), to form the cationic cellulose surface. Each gauze
substrate treated in this manner measured approximately 40 square
inches. One gram samples of cationic cellulose prepared in this
manner (sample K), and untreated SofWick (sample L) were each
soaked overnight in 25 ml of 0.5% SP solution. Samples were removed
and squeezed to remove excess liquid. Samples were then washed in
25 mL of distilled water for one hour with agitation, and then
squeezed to remove excess liquid. Each sample was subjected to four
sequential extractions using 25 mL of distilled water for one hour
at room temperature with agitation. Samples were squeezed to remove
excess solution between extraction cycles. A fifth extraction was
performed using pH 7.4 phosphate buffered saline (PBS). Saline is
expected to remove a greater amount of pyrithione due to ion
exchange. The extract solutions were tested for antimicrobial
activity by placing single 20 microliter drops of the solutions at
marked locations on an agar culture plate spread with
.about.3.times.10.sup.3 CFU (continuous lawn) of S. aureus
bacteria. Plates were incubated overnight at 37.degree. C., and the
diameter of the "zone of inhibition", or "ZOI" was measured. The
size of this zone corresponds to the antibacterial activity (and
therefore the antifungal activity) of the extract solutions.
Results are listed below: TABLE-US-00002 Cationic Cellulose
SofWick: ZOI Extraction # ZOI diameter (mm) diameter (mm) 1 12 0 2
11 0 3 14 0 4 12 0 5 (saline) 27 0
[0256] SP control solutions exhibited the following ZOI (0.1% SP:
26 mm; 0.01% SP: 12 mm). This example clearly shows the binding and
stabilization of SP by the cationic cellulose substrate. Sodium
pyrithione was completely removed from untreated rayon after a
single washing; however, a significant amount of SP remained on the
cationic cellulose sample, even after washing four times in a
25.times. excess of water. The large increase in activity after the
final extraction in saline shows that a considerable amount of SP
remained bonded to the cationic cellulose after the first four
extractions in distilled water, and also confirms the lack of any
initial SP binding to the untreated cellulose. It is expected that
SP bound to cationic wallboard paper (cellulose) as substrate
behaves in the same manner as shown in this example.
[0257] While the preferred embodiments of the invention have been
shown and described, modifications thereof can be made by one
skilled in the art without departing from the spirit and teachings
of the invention. The embodiments described herein are exemplary
only, and are not intended to be limiting. Many variations and
modifications of the invention disclosed herein are possible and
are within the scope of the invention.
[0258] Accordingly, the scope of protection is not limited by the
description set out above, but is only limited by the claims which
follow, that scope including all equivalents of the subject matter
of the claims. Each and every claim is incorporated into the
specification as an embodiment of the present invention. Thus the
claims are a further description and are an addition to the
preferred embodiments of the present invention. The discussion of a
reference in the Description of Related Art is not an admission
that it is prior art to the present invention, especially any
reference that may have a publication date after the priority date
of this application. The disclosures of all patents, patent
applications and publications cited herein are hereby incorporated
herein by reference, to the extent that they provide exemplary,
procedural or other details supplementary to those set forth
herein.
* * * * *