Title: Protective barrier coating composition
Abstract: The invention is directed to a protective barrier coating composition including a metal borate compound, a zinc compound, magnesium hydroxide, and a water based binder. The invention is also directed to a method of protecting building construction materials from termites and other insects, mold or mildew, and fire or water damage. The composition can be applied onto construction materials by a paint roller, spraying, or brushing, before, during, or after construction.
Patent Number: 6,881,247 Issued on 04/19/2005 to Batdorf
| Inventors:
|
Batdorf; Vernon Harland (Minneapolis, MN)
|
| Assignee:
|
Batdorf; Vernon H. (Mpls., MN)
|
| Appl. No.:
|
339426 |
| Filed:
|
January 9, 2003 |
| Current U.S. Class: |
106/15.05; 106/2; 106/18.13; 106/18.3; 252/601; 252/607; 424/641; 427/389.9; 427/393; 427/393.3; 427/39; 427/396; 427/397; 428/532; 428/537.1; 428/697; 428/703 |
| Intern'l Class: |
C09D 005//00; C09D 005//14; C09D 005//18 |
| Field of Search: |
106/2,15.05,18.13,18.3
252/601,607
424/641,389.9,393,393.3,394,396,397
428/532,537.1,697,703
|
References Cited [Referenced By]
U.S. Patent Documents
| 4762753 | Aug., 1988 | Perfetti | 428/450.
|
| 5549869 | Aug., 1996 | Iwakawa | 422/40.
|
| 5958463 | Sep., 1999 | Milne et al. | 424/660.
|
| 6094857 | Aug., 2000 | Kennedy et al. | 43/132.
|
| 6316016 | Nov., 2001 | Iwakawa | 424/409.
|
| 6319511 | Nov., 2001 | Van Voris et al. | 424/411.
|
| 6322803 | Nov., 2001 | Van Voris et al. | 424/406.
|
| 6370834 | Apr., 2002 | Nickell et al. | 52/741.
|
| 6453628 | Sep., 2002 | Traxler | 52/169.
|
| 2004/0043686 | Mar., 2004 | Batdorf | 442/123.
|
| 2004/0054058 | Mar., 2004 | Baldorf | 524/432.
|
| Foreign Patent Documents |
| 281226 | Sep., 1988 | EP.
| |
| 10-323807 | Dec., 1998 | JP.
| |
| 2000-191844 | Jul., 2000 | JP.
| |
Other References
Derwent Abstract No. 1998-175070, abstract of Japanese Patent Specification
No. 10-036591 (Feb. 1998).
|
Primary Examiner: Green; Anthony J.
Claims
I claim:
1. A protective barrier coating composition comprising a water based
binder, from about 5% to about 50% by weight of a metal borate compound,
zinc oxide, and magnesium hydroxide.
2. The protective barrier coating composition of claim 1, wherein the metal
borate compound comprises zinc borate, barium metaborate, magnesium
borate, calcium borate, potassium tetraborate or sodium borate.
3. The protective barrier coating composition of claim 1, wherein the water
based binder is selected from the group consisting of vinyl
acetate-ethylene emulsions, vinyl acrylic or acrylate-acrylenitrile
copolymer emulsions, styrene acrylic emulsions, styrene butadiene rubber
emulsions, acrylic homopolymer emulsions, ethylene-vinyl chloride
copolymer emulsions, vinyl acetate-vinyl chloride-ethylene terpolymer
emulsions, urethane-acrylic hybrid dispersions, polyvinyl acetate
emulsions, chloroprene emulsions, silicone resin dispersions, and
combinations thereof.
4. The protective barrier coating composition of claim 1, wherein the
composition exhibits a fungus resistance rating of no greater than 1 (one)
when measured according to test method ASTM D-5590.
5. The protective barrier coating composition of claim 4, wherein the
composition exhibits a flame spread about 6 inches (15cm) or less and a
burning rate of no greater than about 3.5 inches (9 cm) per minute when
measured according to the Fire Resistivity test method.
6. The protective barrier coating composition of claim 4, wherein said
composition exhibits a measured termite survivorship of about 15% or less,
with substantially no visible signs of termite feeding damage when
measured by the Termite Feeding Damage Test Method.
7. The protective barrier coating composition of claim 1, wherein the metal
borate comprises zinc borate.
8. The protective barrier coating composition of claim 1, wherein the water
based binder includes at least one polymer, the content of the polymer
being from about 5% to about 40% by weight.
9. The protective barrier coating composition of claim 8, wherein the
content of the polymer is from about 6% to about 25% by weight.
10. The protective barrier coating composition of claim 1, comprising about
10% to about 30% by weight of a metal borate, about 15% to about 30% by
weight of magnesium hydroxide, and about 2% to about 30% by weight of zinc
Oxide.
11. The protective barrier coating composition of claim 1, wherein the
metal borate is calcium borate.
12. A method of protecting building construction material with a protective
barrier coating composition of claim 1, comprising applying the
composition onto at least one surface of the construction material.
13. The method of claim 12, wherein the construction materials comprise
wood, wood composites, gypsum wall board, cellulosic insulation, cement or
cement composites, concrete blocks, or ceiling tiles.
14. The method of claim 12, wherein the metal borate is zinc borate.
15. The method of claim 12, wherein the metal borate is calcium borate.
16. An article comprising a construction material and a layer of a
protective barrier coating composition of claim 1 that is coated on the
construction material.
Description
BACKGROUND
The invention is directed to a protective barrier coating composition that
protects buildings from the destructive effects of termites, or other wood
destroying insects, as well as mold or mildew, and water or fire damage.
Various methods have been used to protect buildings from being infested
with termites, and many more methods used to rid the buildings of termites
once infested. These protective methods are all very expensive, have a
limited effective life, and use hazardous chemicals to humans and animals.
To be effective, a chemical or physical barrier is necessary to eliminate
all possible points of entry, preventing any connection between the wood
and soil. This requires elaborate equipment and a complicated process
needed to be performed by a professional pest control service. Treatment
areas include the entire soil area to be covered by concrete, areas
adjacent to foundation walls, treatment of footings, back fill outside
foundation walls, inside walled areas where there is a crawl space, and
any other possible points of entry. The chemicals used are a hazard to
handle, and restricted to use by professional applicators. They will only
provide protection for about 5 years. This method drenches the soil with
liquid termiticide, which is not environmentally friendly. Baiting is
another method to control termites. Bait stations are installed
underground around the perimeter of the house every 10 to 20 feet and 2
feet out from the house. This method takes considerable time to eliminate
a colony of up to one year. It relies upon individual termites feeding on
the bait, and returning to the colony to pass the poison on to other
members, killing a portion of the exposed colony. Often termites are not
attracted to the bait, and can then seek out wood in the building to feed
on.
Another method used is to pretreat the wood with chemicals by using
pressure to impregnate the wood. Hazardous chemicals like CCA (chromated
copper arsenate) or ACZA (ammoniacol copper zinc arsenate) have been used
both against termites and fungal decay. Currently zinc borate is available
in some composite products, and disodium octaborate tetrahydrate is
popular for pretreatment of construction wood. These berates are
water-soluble, (zinc borate less so) and can be washed out of the wood
from rain on the construction site to some extent. The impregnation is
highly dependent upon the density or porosity of the wood or composite
material with dense areas obtaining insufficient protection. Pretreatment
by impregnation is also expensive adding about $3000 for a typical 2000
square feet house. Zinc borate is known as a smoke suppressant, but has
little effect upon lowering the fire spread or heat of combustion. Given
the small amount impregnated into the wood, even the smoke suppression is
minimal.
Lessor used methods of termite control include adding borates into a mulch
that is spread around a house. This is a very short-lived protection with
the borates being easily degraded in the soil, and washed away by rain.
Another method disclosed in U.S. Pat. No. 6,322,803 is to spray a structure
with a mixture of a quick setting liquid monomer and a pesticide, which
forms a bonded polyurethane coating upon curing. The disadvantages of this
method outweigh its value since it takes special expensive two component
spray equipment, and uses very hazardous isocyanate chemicals. These
monomers will very quickly react with any moisture on the wood surfaces
forming many carbon dioxide bubbles and pinholes in the film, leaving many
entry points for the termites. Urethanes are also very flammable, and give
off toxic gases in a fire.
U.S. Pat. No. 6,316,016 also describes a two component urethane system to
provide a foamed polyurethane barrier on various construction materials as
well as soil. Again, this method uses hazardous isocyanate chemicals as
well as flammable and hazardous solvents like Methyl Ethyl Ketone, and a
complicated, expensive, two component meter and mix spray equipment. The
pesticides used are also hazardous, such as tribulytin compounds,
chlordane, phenols, chromium, copper or arsenic compounds. This product is
also flammable, and would add considerably to the flame spread and heat
evolution in a fire.
U.S. Pat. No. 6,370,834 describes the use of manufactured plastic films or
sheets as a barrier, and incorporating a termiticide in the material such
as fipionil. The thermoplastic film or sheeting is selected from the group
of polyethylene, polypropylene, polyurethane and polystyrene, all of which
are very flammable. These materials are claimed to be useable as moisture
barriers, but for building external walls breathable materials must be
used to prevent condensate from forming within the wall cavity. Gaps or
openings in joints would be inevitable, allowing for points of termite
passage.
Therefore there remains the need for an effective, long term, simple, safe
and inexpensive means of protecting buildings from termites, and other
insect damage that is water resistive, while not contributing to the
flammability of the building.
SUMMARY
The inventor has discovered a synergistic combination of additives that
provides a single, economic and effective solution for imparting fire
resistivity, antimicrobial properties, water resistance, and termite or
other insect resistance to a protective barrier coating composition.
In one aspect the invention is directed to a protective barrier coating
composition comprising a metal borate compound, a zinc compound, magnesium
hydroxide, and a water based binder. In another aspect the invention is
directed to a method of protecting building construction materials from
termites and other insects, mold or mildew, and fire or water damage.
The composition features self-extinguishing and char forming with very
little heat, flame or smoke given off in a fire when applied to
construction materials, and maintains a char barrier on the surface
protecting substrates, e.g. wood from exposure to the flame, and thereby
reduces flame spread.
The composition inhibits growth of fungus, mold, mildew or bacteria on its
surface for the life of the coating.
The composition upon application provides a barrier against termites and
other insects such that they can not eat or break through to the
substrates, e.g. wood or other cellulosic based substrates.
The composition contains no hazardous solvents or other chemicals, provides
excellent adhesion to a variety of construction materials, and is not
adversely affected by water or weather. The composition can be easily
applied in a plant, shop or at the construction site by construction
workers. It can be applied onto the construction material by a paint
roller, spraying, caulking tube or brushing, before, during, or after
construction.
These and other features of the invention will be apparent from the
following description of the preferred embodiments thereof, and from the
claims.
DETAILED DESCRIPTION
The protective barrier coating composition includes a water based binder,
magnesium hydroxide, a metal borate, and a zinc compound. The composition
may also contain antimicrobial agents, or other paint additives such as
thickeners, surfactants, pigments, fillers, dispersants, freeze-thaw
stabilizers and coalesants. Preferably the composition contains neither
hazardous volatile components nor strong objective odors, and can be
applied by non-professionals.
Preferably the composition provides and maintains a barrier of char in a
fire, and inhibits flame spread.
The protective barrier coating composition when coated onto substrates,
e.g. wood exhibits resistance to termite feeding such that if termites do
attempt to feed on the coating, they find it not palatable or causes
mortality. The main component used in the coating composition that either
causes mortality or makes it not palatable is a metal borate compound.
However, it is believed that the magnesium hydroxide and other
antimicrobial agents used also contribute synergistically to this
protection against termites or other insects. The composition of examples
1 and 2 exhibited a measured termite survivorship of about 15% or less,
with substantially no visible signs of termite feeding damage when
measured by the Termite Feeding Damage test method.
Examples of useful metal borate compounds include barium metaborate
(Buckman Labs Inc.), zinc borates, calcium borate such as Cadycal.TM. from
Fort Cady Minerals, magnesium borate such as Charmax.TM. FRMB from R. J.
Marshall, and where water resistance is of less importance either sodium
or potassium borate. An example of sodium borate is Polybor.TM. from U.S.
Borax. An example of potassium borate is Potassium Tetraborate, also from
U.S. Borax. The metal borate content is preferably from about 5% to about
50% by weight, more preferably from about 10% to about 30% by weight, and
most preferably from about 15% to about 25% by weight, based on the total
weight of the composition. Examples of useful zinc borates include grades
ZB-112R.TM., ZB-237.TM., ZB-467.TM., and ZB-232.TM., from Great Lakes
Chemical Co., or Firebrake.RTM. ZB from U.S. Borax. The metal borates have
multiple functions in the composition, e.g. acting as a smoke suppressant,
flame retardant, termiticide and secondary antimicrobial agent.
Magnesium hydroxide is preferable used at about 10 to about 50% by weight,
more preferably from about 15 to about 35% by weight, and most preferably
from about 20 to about 30% by weight, based on the total weight of the
composition. A suitable source is MTH 100 from the Dow Chemical Co. The
magnesium hydroxide functions synergistically with zinc compounds to
promote char formation in a fire, and it absorbs considerable heat of
combustion being endothermic. The fire retardancy of magnesium hydroxide
and its synergism with zinc borate is shown in Table 1(examples 1,2, and
4) where the composition exhibits a flame spread of about 6.0 inches (15
cm) or less and a burning rate of no greater than about 3.5 inches (9 cm)
per minute when measured according to the Fire Resistivity test method. It
also functions as a primary antimicrobial by buffering the pH of the dried
coating at 8 to 10, thereby creating a hostile environment for
microorganisms, which typically need a pH in the range of 6 to 8. Metal
borates by themselves are not very effective for inhibiting growth over a
broad specimen of fungi strains, or against many bacteria. However, when
used along with magnesium hydroxide a synergism is obtained resulting in
broad and effective protection. It also makes the composition not
palatable for termites and other insects due to the high pH of magnesium
hydroxide, which disrupts the acidic digestion. Magnesium hydroxide has a
very low water solubility (about 9 ppm at 18 degrees C.), so it would not
be washed out of the coating. Although the water solubility of it is low,
magnesium hydroxide still can diffuse in sufficient amount to the surface
with moisture movement through the coating to maintain a surface
concentration of ions for inhibiting microbial growth, and warding off
insects.
Calcium hydroxide has been shown to be an effective antimicrobial agent
when used in coating, and such coatings were disclosed in U.S. Pat. Nos.
6,280,509 and 6,231,650. However, calcium hydroxide has a very high pH
(12.4) and water solubility (0.185 grams/100 grams water). The water-based
coatings described in these patents likewise has a final pH of over 12. At
that high pH, it will cause alkali burns and skin rashes for the
applicator from over-spray mist or inadvertent contact. The coating also
has been found to carbonate quickly from carbon dioxide in the air, and
loose its antimicrobial property after 1 to 6 months aging. In contrast,
coatings made with magnesium hydroxide have been shown to not form any
carbonate on their surface even after several years of service, and
thereby retain its antimicrobial and termite resistive properties.
Coatings made with the magnesium hydroxide have a much milder alkalinity
(less than 10.0 pH), and are only mildly irritating to the skin even on
overexposure.
The water based binder includes at least one polymer. Suitable water based
binders for the protective barrier coating composition include polyvinyl
acetate emulsions, terpolymers of vinyl acetate-vinyl chloride-ethylene
emulsions, flexible ethylene-vinyl chloride copolymer emulsions, styrene
butadiene rubber emulsions, vinyl acrylate or acrylic copolymer emulsions,
100% acrylic, styrene acrylic emulsions, chloroprene emulsions, silicone
resin dispersions, and combinations thereof. Examples of the water based
binders include Airflex.RTM. 500, 809, 728 or 4500 from Air Products,
Flexbond.RTM. 670,675,325 or 381 from Air Products, Styrofan.RTM. ND 565
or 422 from BASF, Neoprene 115 from Dow--DuPont, and PD 449, 124, 3823H
from H. B. Fuller Co. These and other polymer emulsions can be used as
long as they provide good wetting and adhesion to the construction
materials, have good binding properties for the inorganic components, good
film formation at application temperatures, and good water resistance for
the dried film. For a fire resistive composition that is
self-extinguishing, the polymer content from the water based binder needs
to be kept as low as possible in the dried film. It is preferred that the
polymer content be from about 5% to about 40% by weight, more preferred
from about 6% to about 30%, and most preferred from about 6% to about 25%
of the total dry weight. The composition may include other additives such
as dispersants, surfactants, thickeners, pigments, defoamers, biocides,
cross-linkers, plasticizers, coalescants, and adhesion promoters. The
choice of these additives is dependent upon the particular application
method, service requirements, manufacturing methods, and chosen
components, each used as chosen by one skilled in the art of formulating
paints, coatings, adhesives or sealants. Particularly beneficial
plasticizers are the liquid chlorinated paraffins, which can also act as
fire retardants. Useful plasticizers include Paroil.RTM. 1650, 53-NR,
58-NR, or 1160 from Dover Chemical Co. These are preferred to be used at
about 10 to about 100parts per 100 parts polymer, more preferred at about
15 to about 75 parts per 100 parts polymer, and most preferred at about 25
to about 50 parts per 100 parts of polymer.
The coating composition can be used on construction material surfaces
comprising wood, wood composites, gypsum wall board, cellulosic
insulation, cement or cement composites, concrete blocks, ceiling tiles,
or other synthetic materials normally known and understood by persons
skilled in the art who work in the construction industry. The coating has
been found to provide good barrier properties at a coverage rate of about
100 to about 600 square feet per gallon.
At higher coverage rates the film thickness becomes insufficient for good
fire protection of the substrate, and limited protection against termites,
and some molds. Higher coverage rates are obtainable with excellent
protection against molds and fungus if other antimicrobial agents are
added. Preferred antimicrobial agents include those of low water
solubility (<0.1% by weight) and low vapor pressure so substantially
non-volatile, and those that do not add any hazards to the product's use.
Examples of antimicrobials include Zinc Omadine.RTM. or IPBC-40 from Arch
Chemical, Amical.RTM. Flowable from Dow Chemical, and Rozone .TM.2000 from
Robin & Haas. These may be used typically at about 0.2% minimum to the
maximum allowed by the EPA.
The invention will now be described further by way of the following
examples. All percents stated in the Examples are by weight unless
indicated otherwise.
EXAMPLES
Test Procedures
Test procedures used in the examples include the following:
Termite Feeding Damage Test Method
Termites are exposed to wood blocks (7.5.times.9.times.2-cm, L:H:W) coated
with the protective barrier coating composition to be tested. The blocks
are placed in 15 cm diameter plastic Petri dishes lined with a sand and
vermiculite mixture to maintain sufficient moisture for termite survival.
A population of 650 termites is placed in each Petri dish for up to two
weeks. At the end of the test the number of termites still alive are
counted and the blocks visually examined for evidence of termite feeding
damage.
Fire Resistivity Test Method
A smooth pine board about 11 inches (28 cm) by 31/2 inches (9 cm) by 3/4
inches (2 cm) is coated with the protective barrier coating composition
using a 3 inch (1.6 cm) wide draw down bar at the desired coverage rate,
using a wet film thickness gauge to measure its thickness. After at least
4 days dry time at ambient conditions it is marked with lines every inch
of length, starting with zero at one inch from the end, where the flame
will be placed directly under the zero mark. The coated board is mounted
at a 45.degree. inclined angle in a draft-free exhaust hood, with a
propane fueled Bunsen burner placed about 11/2 inches (4 cm) below the
board surface at the lower end, directly below the zero line, and adjusted
to have about a two inch (5 cm) flame. When placed under the board with
the coated side face down, the flame initially bends up to about the one
inch line. A stopwatch is used to record the maximum flame speed every 15
seconds through the first three minutes, and every 30 seconds for the last
two minutes of the five minute testing time. Results reported include the
maximum flame spread, the flame spread rate up to the maximum flame
spread, the char length, and if any after-glow or continued burning after
removal of the burner at five minutes. One may also note how much visible
smoke is developed, if any sparks, popping, or fall off occurs, or depth
of char into the surface.
Fungal Resistance Test Method
ASTM D-5590 is a test procedure for testing paints or coatings for
resistance to growth of various fungus on it surface. The method uses a
potato dextrose agar nutrient. The test specimens are set on the agar in
petri dishes and inoculated with a fungal culture of Aspergillus Niger
(ATCC 6275), Penicillium funiculosum ATCC 17797), and Aureobasidium
pullulans (ATCC 9348). The specimens are incubated at 28 degrees C. under
85% to 90% relative humidity for 4 weeks, and noted for visual growth.
Rating is 0 for none, 1 for a trace of growth (<10% over surface), 2
for light growth (10%-30%), 3 for moderate growth (30%-60%), and 4 for
heavy growth (60% to complete coverage).
EXAMPLES
Components 1 2 3 4
Water 29.2 28.2 31.3 29.2
Cellulosic Thickner .3 .2 .3 .3
Nonionic Surfactant .5 .5 .3 .5
Anionic Dispersant .8 -- .9 .8
Zinc Oxide 4.0 3.0 -- 4.0
Titanium Dioxide 2.0 2.0 -- 2.0
Magnesium Hydroxide 23.0 20.0 -- 23.0
Zinc Borate 18.0 15.0 10 --
Calcium Borate -- -- -- 18.0
Oil Based Defoamer .2 .3 .3 .2
Vinyl Acetate Ethylene 21.0 29.0 30.0 21.0
Emulsion (55% solids)
Silane Adhesion Promoter .2 -- -- .2
Urethane Thickener .8 .6 -- .8
Amical Flowable (40% solids) -- 1.2 -- --
Hydrated Alumina -- -- 26.0 --
Ethylene Glycol -- -- .9 --
Total 100 100 100 100
All four examples were made on a high shear cowles type lab mixer, with
components added in order listed. All were 3000-6000 cps in viscosity as
measured on a Brookfield Viscometer at 20 RPM at 75.degree. F. (24.degree.
C.). The pH was 9.0-9.5. Test results are shown in table 1.
TABLE 1
Example No.
Uncoated
1 2 3 4 Pine
ASTM D-5590 Rating -- -- -- -- 4
Uncoated
400 ft2/gal over oak veneer 0 0 3 1 --
600 ft2/gal over drywall paper -- 0 -- -- --
Fire Resistivity,
100-125 ft2/gal
a) Average burning rate, 2.4 2.8 -- 3.45 4.0
inches (cm)/minute (6) (7) -- (8.8) (10)
b) Maximum flame spread, 4.5 4.5 -- 6.0 7.0
inches (cm) (11.4) (11.4) -- (15) (17.8)
c) char length 4.0 4.0 -- 5.5 6.0
inches (cm) (10) (10) -- (14) (15)
Termite Feeding Damage
Average survivorship 2% 7% -- -- 100%
Feeding damage, visual none none -- -- major
*
