Note: Descriptions are shown in the official language in which they were submitted.
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MASTICATION ARTICLES POSSESSING
MICROBE-INHIBITING PROPERTIES
Cross Reference to Related Applications
This application is a continuation in part of application S.N. 09/241,591,
filed February 2,
1999 and is a continuation in part of application S.N. 09/059,956, filed April
14, 1998 which
claims the benefit of U.S. patent application serial number 60/043,014, filed
April 15, 1997.
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates to a mastication article, principally for domestic
animals, and more
particularly to a mastication article having a microbe-inhibiting agent or
property that
substantially inhibits the proliferation of microbes on, within, or around the
mastication article.
The term "microbe" herein refers broadly td classes of bacteria, viruses,
germs, molds, mildew,
fungi, allergens, and other microorganisms. An article of the present
invention provides both
comfort and health benefits to both pets and people involved with the use of
such an article.
1~5 Description of the Related Art
Mastication articles are very popular with pets, and especially so with dogs.
There are
two basic types of mastication articles: digestible and non-digestible. The
prototypical digestible
type is "rawhide" or rawhide-derived; but starch- or seed-based or other
digestible materials may
be used as well. The non-digestible type is more variegated, and may include
alone or in part
components comprised of molded plastic, rope, textile fabrics, fiber-fill,
foam, as well as other
components.
Mastication articles can provide therapeutic as well as amusement value to the
pets that
chew on them. The mastication provides a degree of exercise and cleans and
massages the teeth
and gums of the pet; and, pets (especially dogs) seem to enjoy mastication on
things. In addition,
giving pets desirable articles on which to chew may preclude them from
mastication on other
things that may be harmful to them or would upset the pet's owner.
Mastication articles for pets tend to become messy and unsanitary as the pets
chew on
them. There is also a risk of microbial proliferation on or within the
mastication articles during
their storage. Both of these factors are especially problematic for digestible
mastication articles,
CA 02266839 1999-04-09
which provide ample nutritional resources for the abundant proliferation of
microbes. It is
therefore useful and valuable to provide sanitary mastication articles that
are resistant to the
proliferation of microbes and optionally to odors. Because pets chew
continually upon these
articles, and because pets can eventually digest these articles (even when
they are not intended
for digestion), toxicity considerations with regard to the microbe-inhibiting
treatment are
important.
Of the digestible type, rawhide is the most popular type of mastication
article. Ready-to-
use rawhide may be acquired commercially in a variety of forms and is
manufactured from
animal (preferably cattle) hides by methods known in the Art (see, e.g., U.S.
Patent
No. 5,114,704). The manufacturing process generally consists of several steps.
After the raw
hides are obtained, they are usually treated in a lime-based solution
(liming), the primary object
of which is to loosen the hair on the hide. To the solution may be added
ammonium salts,
sodium sulfide, or other additives. After the liming treatment, the hair is
removed from the hide,
either by hand or using a dehairing machine. In the next step, known as
"fleshing," tissue is
removed from the flesh side of the hide. This may be performed with a special
knife or with a
fleshing machine. It is then necessary to ensure that all of the lime is
removed from the hide.
Washing in water can remove much of the lime, but it is generally necessary to
use a more
aggressive treatment with acids or acid salts to remove the remainder.
After the hides are dehaired, fleshed, and cleaned, they may be cut into the
desired shapes
and manipulated. Drying may be done in ambient air or preferably in an oven at
elevated
temperatures (usually less than 150°C).
U.S. Patent No. 5,310,541 discloses a rawhide animal chew intended to inhibit
oral
pathogens from proliferating in a dog's mouth. The rawhide is treated with
enzymes that are
released into the dog's saliva upon mastication. Once in the dog's saliva,
these enzymes set off a
chain of reactions that attack oral pathogens present in the dog's mouth.
Thiocyanate and iodide
additives may optionally be added to enhance this effect.
U.S. Patent No. 5,476,069 discloses a molded rawhide mastication article, in
which
rawhide is ground into small pieces and then injection molded at high
temperature and pressure.
The addition of casein and gelatin before injection are said to facilitate
molding.
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U.S. Patent No. 4,419,372 discloses a simulated rawhide mastication article in
which a
mixture comprising an oil seed protein, a polyol plasticizes, lecithin, and
water are extruded into
a ribbon. The ribbon is then "sandblasted" (e.g., using ground walnet) to
impart a rawhide-like
texture to the surface. The material is then shaped or cut in a manner similar
to those of real
rawhides.
U.S. Patent No. 5,407,661 discloses a digestible mastication article for a pet
in which a
starch, a cellulosic fibrous material (e.g., corn cob fractions), a humectant,
a proteinacious binder
and a tarter-control oral care additive are mixed together and extruded in
such a manner that the
extrudate possesses an open, cellular structure.
U.S. Patent No. 5,419,283 discloses a molded mastication article for an animal
comprising a starch material and a biodegradable ethylene copolymer. Other
edible materials
can be added as plasticizers or as lubricants. These materials are mixed in
the presence of water
for subsequent injection molding into desired shapes (e.g., a bone).
Mastication articles of the non-digestible type are considerably more
variegated than
those of the digestible type. They may be comprised of solid molded plastic,
hollow molded
plastic, textile fabrics, rope-materials, synthetic or natural fiber-fill,
foams, etc. They generally
possess a texture and structure that combine to create a desirable "mouth-
feel" for the pet. This
feature is especially important if the article possesses no attractants (e.g.,
a meat scent).
U.S. Patent No. 4,557,219 discloses a molded polyurethane mastication article
for a pet in
which has been incorporated a surface-migrating flavoring extract.
U.S. Patent No. 5,477,815 discloses a mastication article for a dog comprising
a
composite rope, in which an inner core of the rope comprises brittle,
frangible, and non-water
absorbing threads (optionally with a flavoring extract), and the outer shell
comprises soft, pliable
cotton. The inner core is said to give the article a "crunchy" sound and
texture and to aid in the
dog's passing of the article if it should be eaten. It is said that the non-
water-absorbency of the
inner core material promotes faster drying of the outer water-absorbing cotton
material; and it
thereby inhibits bacterial growth in the cotton. U.S. Patent No. 5,467,741
discloses a similar
mastication article, but includes the incorporation of therapeutic dental
agents and/or breath-
freshening agents in the inner core.
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U.S. Patent No. 5,477,815 discloses a molded bone-shaped mastication article
that has
relatively sharp, conically-shaped spikes distributed over its surface. The
spikes are said to
remove tartar or plaque from the dog's teeth as the dog chews on the toy. The
mastication
articles is a rigid polymer, such as a rigid polyurethane or a rigid
polyamide. A meat scent or
flavor is optionally added to the article to increase its attractiveness to
dogs.
U.S. Patent No. 5,477,815 discloses a molded dog mastication article which is
constructed from a synthetic thermoplastic material (e.g., polyurethane) in
which an animal meal
(e.g., chicken meal, fish meal, etc.) has been incorporated prior the molding
process.
U.S. Patent No. 5,477,815 discloses a molded dog mastication article
comprising water
absorbing nylon in which at least a surface layer has been incorporated with
sugar.
Despite the desirability of effective microbe-inhibiting mastication articles
for pets, there
have been no practical solutions that would provide effective and continual
protection against
microbial proliferation in or on the articles. The only two disclosures which
even remotely relate
to microbe inhibition are the aforementioned U.S. Patent No. 5,477,815, which
only relates to
enhanced drying of a rope-based article to shorten the period of time it is
most susceptible to
microbial proliferation; and U.S. Patent No. 5,310,541, in which the rawhide
is a carrier for an
enzyme to be released into a dog's mouth. In the latter invention, the rawhide
is only a vehicle
for delivering a reaction-initiating enzyme into the dog's mouth. The enzyme,
which is inactive
with respect to microbes, reacts with the salivary solution in the dog's
mouth, ultimately
resulting in the temporary creation of ions in solution which attack oral
pathogens in the dog's
mouth; and these ions can exist only in the dog's saliva. The rawhide article
itself therefore
contains no species that will inhibit subsequent microbial proliferation in
and on the article (any
such species which are transferred to the article from the dog's saliva will
soon dry-up and thus
become ineffective).
Thus, there is a need in the art for mastication articles for pets, where the
proliferation of
microbes is prevented in and on the articles; where the microbe-inhibiting
properties of the
articles are continually active and durable; where these articles are
desirable and attractive to the
pets for which they are intended; and where these articles are safe for pets
and humans.
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SUMMARY OF THE INVENTION
According to the invention, mastication articles for pets have an effective of
amount of
microbe-inhibiting agent or property that is effective in limiting microbial
proliferation, and at
the same time is not present in quantity, concentration, or nature whereby the
articles may be
harmful to the pets or humans who come into contact with the articles. The
effective amount of
the microbe-inhibiting agent or property limits the spread of the microbe-
inhibiting chemicals or
agents within and about the article, and takes into consideration the patterns
of use and material
structure of the article. The microbe-inhibiting agent or property can be at
least one of a
microbe-cidal, microbe-starving, and microbe-impenetrable agent. In one
embodiment, a
digestible mastication article is selected from a group consisting of animal
skin, animal fat,
vegetable, a vegetable starch or some blend thereof. In another embodiment, a
non-digestible
mastication article comprises at least one material selected from a group
consisting of polymeric
resins or solutions, fibers or threads, textile materials, foams, or some
blend thereof.
Another embodiment of a mastication article includes a microbe-inhibiting
agent as a
particulate incorporated into the material comprising core particles over
which is coated with a
microbe-inhibiting active layer. The core particles are selected from the
group comprising zinc
oxide, titanium. barium sulfate and blends thereof. The active layer is
selected from a group
consisting of silver, copper oxide, zinc silicate and blends thereof. In a
further embodiment, the
active layer includes a barrier coating, whereby the rate of release of the
microbe-inhibiting agent
or property can be controlled. Also, the active layer can include a dispersion
coating, whereby
the core particles in the material are dispersed.
In another embodiment of the invention, the mastication article comprises
rope, wherein
the rope can be made of at least one material selected from a group, cotton,
sisal, hemp, jute,
henequen and blends thereof. Furthermore, the mastication article made from
rope can include a
core made of a hydrophobic material such as nylon.
In another embodiment of the invention, the mastication article is made of at
least one
material selected from the group including nylon, polyurethane, polyolefins
and blends thereof.
Such a mastication article can include a nutritive attracting agent within the
material. Such a
nutritive attracting agent is preferably selected from the group including
animal meal, meat
broth, dried meat, sugar and blends thereof.
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Further, according to the invention, a method for producing a mastication
article having a
tough, chew resistant material and defining a shape in the form of a small
article for enticing or
being retrieved by a domestic animal comprises the step of applying an
effective amount of a
microbe-inhibiting agent to the tough, chew resistant material. The microbe-
inhibiting agent can
be applied to the tough, chew resistant material by dissolving the agent in a
solution, which is
then applied to the tough, chew resistant material, either by soaking the
tough, chew resistant
material in the solution or spraying the solution onto the tough, chew
resistant material.
In one embodiment, the microbe-inhibiting agent is in particulate form and is
incorporated into core particles in the article. The core particles are
selected from a group
including zinc oxide, titanium oxide, barium sulfate and blends thereof. The
process can include
the additional step of incorporating the particles into a resin that is molded
into the tough, chew
resistant material. Alternatively, the particles can be incorporated into a
dope before spinning of
fibers that are incorporated into the tough, chew resistant material. In a
further embodiment, the
particles are incorporated into a spray for coating an outer surface of the
tough, chew resistant
material.
In another embodiment, the tough, chew resistant material is rawhide and the
step of
applying the microbe-inhibiting agent includes applying the microbe-inhibiting
agent to the
rawhide during cleaning of the rawhide. Alternatively, the microbe-inhibiting
agent can be
applied to the rawhide during liming of the rawhide.
In yet another embodiment, the microbe-inhibiting agent is incorporated into
the tough,
chew resistant material by applying a solution including the agent to the
material. In one
embodiment, the tough, chew resistant material is digestible and the microbe-
inhibiting agent is
added to the tough, chew resistant material when the material is in a molten
or substantially
liquid state, and the material is then molded to form the article. In a first
variation of this
process, the step of incorporating the microbe-inhibiting agent includes
applying the solution to
the tough, chew resistant material after the article has been formed. In
another variation, the
microbe-inhibiting agent is incorporated into the material by soaking the
tough, chew resistant
material in the solution after the article has been formed. For articles
including digestible
components, a first variation includes the anti-microbial agent is selected
from the group
consisting of triclosan, diiodomethyl p-tolylsulphone, tri-n-butyltin maleate
and chlorine
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dioxide. Commercial forms of the first three of these are available under the
trade names
Ultrafresh NM-100, UF-95, and DM-50, respectively). In another variation, the
agent is selected
from the group consisting of garlic and turmeric.
In any of the processes described above, a nutritive attracting agent
imparting a flavor or
smell to the mastication article can be incorporated into the tough, chew
resistant material.
Furthermore, for any of the processes set forth above, the microbe-inhibiting
agent can be
applied to the tough, chew resistant material at a temperature between 40 -
100° Celsius.
For a mastication article comprising cotton rope, a process according to the
invention
includes a step of applying moisture to the cotton rope as it is being formed,
and then spraying
the cotton rope with a solution including the microbe-inhibiting agent to
enhance the absorptive
properties of the cotton rope.
Where the process according to the invention includes forming the mastication
article of a
material including fibers, the application of the microbe-inhibiting agent can
be accomplished by
incorporating the agent into a doping agent for the fibers and then spinning
the fibers.
Where the process according to the invention includes molding the mastication
article,
the step of incorporating the microbe-inhibiting agent can include adding the
microbe-inhibiting
agent to a resin and then molding the resin into the mastication article.
In one embodiment, the tough, chew resistant material can be formed from a
latex
mixture that is molded into the tough, chew resistant material and the microbe-
inhibiting agent
can be added to the latex mixture before the molding step.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is perspective view of a first embodiment of a mastication article
according to the
invention;
FIG. 2 is perspective view of a second embodiment of a mastication article
according to
the invention;
FIG. 3 is a sectional view the mastication article of FIG. 2;
FIG. 4 is a perspective view of a third embodiment of a mastication article
according to
the invention; and
FIG. 5 is a sectional view of the mastication article of FIG. 4.
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DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1-5, several embodiments of a mastication article are
shown. In FIG.
1, a first embodiment of a mastication article 10 made of a tough chew-
resistant rawhide material
12 is shown. The rawhide material 12 includes a microbe-inhibiting agent
applied to or
incorporated therein, as will be discussed further below. A second embodiment
is a mastication
article 20 made of a rope material 22, as shown in FIG. 2. The rope material
22 preferably
comprises cotton, and is treated with a microbe-inhibiting agent as will be
described below. As
shown in FIG. 3, the mastication article 20 may include a core 24 comprising a
different
material, usually a hydrophobic material such as nylon. FIG. 4 shows another
embodiment of a
mastication article 30 made of a plastic material 32. The mastication article
30 may be hollow,
having a open center 34, as shown in FIG. 5, or solid (not shown), and is
treated with a microbe-
inhibiting agent during formation, as will be described below.
The term "microbe-inhibiting" in the present disclosure subsumes all
characteristics (and
the means for imparting these characteristics) which cause the mastication
articles to be
inhospitable to microbes. Distinctions can be made between three types of
microbe inhibition:
"Microbe-cidal" refers to a property whereby microbes are actively killed or
otherwise
rendered ineffective. If a microbe comes within a sufficiently close range
(direct contact, for
some materials; within a "zone of inhibition" for others ) of a microbe-cidal
material, it will be
killed or otherwise rendered ineffective. Microbe-cidal properties may be
imparted to materials
by a variety of means. A preferred means uses microbe-cidal agents during the
manufacturing
process of the materials and/or treats the materials with microbe-cidal
agents. A number of
preferred agents are disclosed below. For the microbe-cidal property to be
durable, it is often
preferred that the agents be bonded in some manner to the materials comprising
the pet article.
Such materials exhibit smaller zones of inhibition than materials containing
non- or weakly
bonded agents, but the microbe-cidal property with regard to microbes coming
directly into
contact with the material can be more durable. Using agents which are
insoluble or only
sparingly soluble in water can also be a key element for durability.
"Microbe-starving" refers to a property whereby microbes are controlled or
eliminated by
deprivation of sources of nutrition. A material is said possess microbe-
starving properties if
microbes in contact with the material have difficulty acquiring the resources
they need to
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survive. One can often provide or enhance a microbe-starving characteristic to
a material by
changing or altogether eliminating additives to the materials (e.g.,
plasticizers, fillers, or
processing aids). Since adhered dust or liquids can provide nutrition for
microbes, it is preferred
that the material be provided with anti-adhesion properties (e.g., anti-
static, low surface energy,
etc.).
"Microbe-impenetrable" refers to the property of a material or coating which
is
impenetrable whereby a microbe cannot pass through the material or coating. In
this case,
microbes may proliferate to some degree on a surface of the material, but such
proliferation will
be confined to the surface. Thus if an article is treated on its exterior by a
microbe-impenetrable
coating, microbes from the environment will not be able to pass into the
interior of the article,
will be limited in the degree to which they can proliferate, and can more
readily be removed by
washing. Appropriate placement of microbe-impenetrable materials is important
to their
effectiveness in providing the microbe-inhibiting property.
It is often efficacious to fight the battle against microbial proliferation on
several fronts.
Thus preferred microbe-inhibiting mastication articles for pets will often
possess combinations of
microbe-inhibiting behavior. For example, when a particular component of a
mastication article
is most susceptible to microbial attack, this component may be treated with
both a microbe-
impenetrable layer and a microbe-tidal agent, while the remainder of the
article is treated with
only the microbe-tidal agent. Further, an additive which serves as a resource
for microbial
growth may be important only for certain parts of the article. For example,
plasticizers often act
as an effective resource for microbial proliferation; and one can use the
plasticizes only where the
flexibility is needed, and then treat this area with an effective combination
of microbe-inhibiting
characteristics; and the remainder of the article, where the plasticizes was
not used, may be less
vigorously protected.
For durability, the microbe-inhibiting agents should not readily dissolve into
the fluids
with which they come into contact. This includes fluids associated with their
use (saliva, urine,
or other bodily fluids) as well as washing and cleaning fluids (the microbe-
inhibiting activity
should be durable to repeated home laundering). The insolubility may be an
intrinsic
characteristic of the agent-fluid combination, or it may be due to the fact
that the agents are well
bonded to the materials comprising the article. Both types are included in the
present invention.
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Although both water-durable and non-water-durable microbe-inhibiting
components can
be used with effectiveness in the present invention, if a non-water-durable
microbe-inhibiting
component is used, the exterior of the exposed material should desirably be
provided with water-
repellent or otherwise water-insulating qualities.
In a preferred class of embodiments, microbe-inhibiting properties are
conferred upon
one or more of the materials comprising the pet article by treating the
material with or otherwise
incorporating into the material a microbe-inhibiting agent. This microbe-
inhibiting agent is a
chemical agent or particle that imparts to the material an effective microbe-
inhibiting property.
The microbe-inhibiting agents will often function primarily through a microbe-
cidal mechanism.
The microbe-inhibiting agents are typically chemicals, polymers, solutions
(solid or liquid), or
particulates (which may possess their own microbe-inhibiting activity or can
act as hosts for
other microbe-inhibiting agents). These microbe-inhibiting agents can exist in
a variety of forms
and be held in a variety of hosts before being incorporated into the
mastication article. For
example, they can be dissolved in a liquid; they can be incorporated in or
form a particulate
phase, either dry or suspended in a liquid; they can be included within a
plasticizer compound; or
they can be pre-incorporated into a material used in manufacturing the article
(e.g., one can
employ materials which already possess microbe-inhibiting properties).
Examples of chemical microbe-inhibiting agents for use in polymers may be
found in
Plastics Additives and Modifiers Handbook, pp. 338-350, J. Edenbaum, Ed.,
Chapman and Hall,
Great Britain, 1996, and herein incorporated by reference.
The microbe-inhibiting treatment can be carried out at different points during
the process
of manufacturing the article or its component materials. For example, one can
incorporate
microbe-inhibiting agents in fibers as they are being manufactured, which
microbe-inhibiting
fibers can be used as the filling of stuffed mastication articles or as the
fabric used as the external
covers of mastication articles. One can also manufacture a microbe-inhibiting
elastomeric-like
material for use in a component of the mastication article which is made of
(e.g., molded) plastic.
One can also treat (as by spraying or soaking) some or all of the materials
after they are partially
or completely manufactured (e.g., one can soak rawhide sheets or the rope
which will be later cut
and formed into rope-bones in a microbe-inhibiting treatment solution; or one
can treat the
external cover and/or the filling or some component of the filling of a
mastication articles before
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their final assembly). Alternatively or in addition, one can treat (as by
spraying or dipping) the
pet article when it is finished or nearly finished its manufacture. It is
often preferred to perform
soak treatments under elevated temperatures and/or pressures.
Microbe-inhibiting agents can be incorporated into the constituent materials)
of a
mastication article by admixing the agent or a carrier for the agent with the
raw ingredients to the
material (e.g., add a liquid containing the agent to the resin mix before
injection molding a
plastic article). In this case, the microbe-inhibiting agent is usually
dispersed relatively
uniformly throughout the final article.
In cases where surface attachment is desired, the use of adhesion promoters is
preferred,
particularly in conjunction with "raw" microbe-inhibiting agents, i.e., those
which do not need to
be in solution to work effectively.
In cases where a bonding agent is not used to adhere the microbe-cidal agent
to the
mastication article material, or where such bonding is not entirely effective,
it is often useful to
diminish the rate at which the active microbe-inhibiting agent becomes de-
activated. This
process can be done by inhibiting volatilization or adding stabilizers.
When the microbe-cidal agents are not bonded or are only weakly bonded to
materials
forming the mastication article, it is preferred to package the articles such
that the effective shelf
life of the antimicrobial character is enhanced. For example, when
volatilization of the
antimicrobial agent is a problem, the packaging material can be made
impervious to the anti-
microbial agent.
It is useful to have a microbe-inhibiting agent at the surface of the
mastication article, as
well as in the interior. The microbe-inhibiting agent at the surface can be
effective in inhibiting
the proliferation of microbes directly on the surface. If suitable microbe-
inhibiting agents are
present in the interior, they can migrate to the surface as the agent
initially at the surface becomes
displaced. This effectively constitutes a "time-release" of microbe-inhibiting
agent. In this
manner, the concentration of the agent can be maintained at a safe level, any
odors associated
with unduly high concentrations of the agent are avoided, and the period of
effective microbe-
inhibiting protection can be considerably prolonged.
The microbe-inhibiting agent can be applied in a liquid form (as dissolved in
a solvent)
and deposited on the surface of the mastication article material. By choosing
properly the liquid,
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material, environmental conditions (e.g., temperature, pressure) and
optionally any additives, the
agent can be made to penetrate the material; and a "time-release" system can
be obtained.
A "time-release" property may also be provided by incorporating the active
agent in a
separate material, optionally particulate, which releases the agent in a time-
controlled manner.
For example, one can saturate a particulate zeolitic material with a microbe-
inhibiting agent and
incorporate the zeolitic material into the pet article. Alternatively, one can
use a textile chosen
specifically for its time-release characteristics for a particular microbe-
inhibiting agent; and this
textile may be incorporated in the mastication article.
If some form of heat-assisted disinfection of the articles is desired, it is
important to use
material-agent systems which do not degrade in the disinfection environment
(e.g., washers,
microwave, thermal ovens, etc.). The softening or decomposition temperatures
of the polymers
and chemical agents used, for example, must be higher than the disinfection
temperature used.
Because the accumulation of undesired organic or inorganic matter may reduce
the
efficacy of microbe-inhibiting protection, the articles can be designed with
materials which
reduce the tendency for such accumulation. This can be accomplished by using
low surface
energy materials or applying a low surface energy coating; and/or by using
anti-static materials
or applying an anti-static coating. Non-hydrophilic materials (materials upon
which water
droplets form contact angles greater than about 30 degrees) are generally
preferred to prevent the
adhesion of such undesired matter.
Pets, especially dogs, often tear or otherwise damage or digest the
mastication articles
that they use. It is therefore important that the materials be non-toxic, non-
carcinogenic, and
effectively non-allergenic at the levels used in the articles. Some agents are
non-toxic even at
relatively high concentrations (e.g., triclosan, diiodomethyl p-tolylsulphone,
stabilized chlorine
dioxide); other agents are non-toxic at relatively low concentrations, but
become toxic at high
concentrations (e.g., many unbonded quaternary ammonium compounds). If a
mastication article
employs a time release property, one must ensure that the time-releasing
materials do not contain
concentrations of the agents which exceed those which can be safely eaten by
the animal of
interest. The pet should be able to eat the article without harm. Also, the
treated materials
should be non-skin-sensitizing, i.e., should not generally cause allergic or
other undesirable
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reactions on the skin or other membranes of the pet or people who effectively
come into contact
with the materials.
Preparation of Materials
Unless otherwise stated, concentrations given herein are weight percent.
Materials of the present invention can be made from natural animal products,
including
skin and fat-based materials, natural vegetable products, polymeric resins or
solutions, fibers or
threads, textile materials, foams, and other materials. At least some fraction
of the constituent
materials has microbe-inhibiting properties.
In preparing microbe-inhibiting synthetic materials derived from polymers, the
microbe-
inhibiting agents are preferably added to the precursor material (e.g., into
the resin mix for
molded plastics or into the melt or spin dope from which fibers are spun). For
natural materials,
the microbe-inhibiting agents are preferably either impregnated into the
materials via a spray or
soaking treatment. Microbe-inhibiting agents or carriers with such agents can
also be included in
an admixture of natural and/or synthetic materials that are to be transformed
into the finished
article.
Phenol derivatives, especially 2,4,4'-trichloro-2'-hydroxydiphenol (known as
Triclosan,
Irgasan, Microban, etc.) are attractive and are preferred. Methyl sulfones,
such as diiodomethyl-
p-tolylsulphone, are attractive and preferred. Organotins, especially tri-n-
butyltin maleate (as in
Ultra Fresh DM-50), are also attractive and preferred. Soak-treating in an
aqueous solution
containing stabilized chlorine dioxide is also preferred.
It is important to note that post-treatment methods involve importantly
different
considerations when one is using a "strongly-bonded" type of agent. In the
"diffusing" or "non-
strongly-bonded" case, one immerses or otherwise exposes the materials to a
solution containing
a particular concentration of the agent. Generally, the agent diffuses into
the material until its
concentration in the material is comparable to the concentration in the
solution, i.e., the treatment
level of the material is essentially proportional to the concentration of the
agent in solution; and
the agent concentration in the solution is the primary controlling variable.
In typical treatments,
the agent in solution is not appreciably depleted; and the amount of material
exposed to the
treatment solution is not carefully monitored and is not considered a primary
variable of the
treatment process.
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In the strongly-bonded case, however, the agent usually does not diffuse into
the material;
rather, it chemically reacts with the surface of the material. Here one
attempts to arrange
conditions such that most of the "reactable" agent present in the solution
reacts with and bonds to
the surface of the material being treated. Knowledge of the amount of material
being treated is
thus important in determining the treatment level; and the material amount,
along with the agent
concentration in solution, are considered controlling variables of the
treatment.
The term "amount of material," is intended to mean the "amount of readable
surface" of
the material. For porous materials which can take up the solvent in their
interiors (e.g., many
natural materials such as cotton or rawhide, fabrics, foams, etc.), the mass
of the material is often
used as an indicator of the readable surface area - i.e., one can specify an
agent level in solution
per unit weight of material being treated. For non-porous materials and/or
materials which do
not absorb the solvent being used (hard plastics, highly solvent-phobic
materials), more direct
knowledge of the reactable surface area is needed.
The preferred strongly-bonded agent for use in the present invention is 3-
trimethoxysilylpropyldimethyloctadecyl ammonium chloride (as in Dow Corning
5700).
For use in mastication articles that contain fabrics, microbe-inhibiting
fabrics can be
constructed by weaving, knitting, or otherwise forming the fabric from fibers
which possess the
desired microbe-inhibiting properties. Alternatively, the fabrics can be post
treated via spray-
treating or by using a padding system such as are common in the art of textile
finishing. For post
treatment, tri-n-butyltin maleate (as in Ultra Fresh) is a preferred diffusing
microbe-inhibiting
agent (at fabric pick-up about 0.1%-.5% by weight); and 3-
trimethoxysilylpropyldimethyloctadecyl ammonium chloride (as in Dow Corning
5700) is a
preferred strongly bonded microbe-inhibiting agent (at fabric pick-up about
0.08%-0.15% by
weight).
The preferred method for obtaining microbe-inhibiting foams is to include a
microbe-
inhibiting agent in the formulation of one of the foam precursors (i.e.,
before the material is
foamed). A preferred microbe-inhibiting foam is obtained by adding Ultra Fresh
DM-50 to the
polyurethane foam formulation before foaming (typically in amounts ranging
from 0.04% to
0.6% relative to the total weight of the formulation). Another preferred
method is to use Dow
Corning 5701 (a reactive silane quaternary ammonium compound, which works much
like Dow
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Corning 5700). This agent is also added into the polyurethane formulation
before foaming
(typically in amounts ranging from 0.1 % to 1.2% by weight relative to the
amount of polyol).
Another preferable microbe-inhibiting agent is known by the trade name,
Intercept. It is a
complex of polysubstituted imine salts and trialkyl phosphate esters with free
alkylated
phosphoric acid. It is relatively non-toxic; and it has been used as an
antimicrobial finish on
many building materials.
A further preferred type of microbe-inhibiting agent is typified by the
MicroFree brand of
particulates (available from DuPont). These particulates generally comprise a
core particle (zinc
oxide, titanium oxide, or barium sulfate) over which is coated a microbe-
inhibiting active layer
(silver, copper oxide, and/or zinc silicate). A barrier layer (to control the
rate of release of the
active component) and a dispersion coating (to facilitate dispersion of the
particles in host
materials) are included on top of the active layer. The particles range from
about 0.3~m to l~,m
in size. They can be incorporated into many resin systems for plastics
processing, into the dope
before fiber spinning, and into many coating systems for post-treatment. Good
microbe-
inhibiting efficacy can be imparted to various materials using these
particles; and the resulting
materials are generally non-toxic, very stable, and cost effective.
Other microbe-inhibiting agents may be used without departing from the spirit
of the
present invention.
Rawhide Mastication Articles
For rawhide mastication articles, microbe-inhibiting characteristics can be
imparted to the
rawhide by treating it with microbe-cidal agents as defined above during the
process of
manufacture. This treatment can be carried out during the liming or one of the
cleaning phases;
or an additional step can be added in which the hides are sprayed with or
soaked in a microbe-
cidal solution.
The rawhide can also be treated after it is essentially fully manufactured. In
its "hard"
form, it can be sprayed with a microbe-cidal solution (which can be allowed to
soak-in), or it can
be soaked in a microbe-cidal solution for a time sufficient for the microbe-
cidal agents to
infiltrate appreciably the rawhide. In the latter case, it will generally be
necessary to dry the
treated rawhide (in ambient air or in a furnace at elevated temperature).
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It is necessary to ensure that the processing temperature, either during or
after the
microbe-inhibiting treatment, is not excessively high so as to inactivate or
otherwise damage the
microbe-inhibiting properties of the article.
Because dogs often eat rawhide, toxicity considerations are important. A
preferred agent
for use with rawhide products is chlorine dioxide, which is safe for both
animal and human
consumption (e.g., it is used in mouthwashes, toothpaste, and as a drinking-
water additive). An
appropriate solution concentration is in the range of about 0.1-2% by weight.
Also preferred is diiodomethyl p-tolylsulphone. A commercially available form
is
available under the name Ultrafresh UF-95. It is generally desired to treat
the rawhide so that the
concentration of UF-95 is between 0.001 % and 2%, preferably between 0.05% and
0.8% by
weight. An alcohol, preferably ethanol, is the primary solvent of the
preferred treatment
solution. Acetone, in which the agent possesses a larger solubility than in
ethanol, can also be
used (provided the acetone does not persist substantially in the finished
articles). When treating
by soaking in such non-aqueous solutions, subsequent rinsing in an aqueous
solution is preferred.
Also preferred is tri-n-butyltin maleate. A commercially available form is
available under
the name Ultrafresh DM-50 . Water is the primary solvent for the preferred
treatment solution,
which contains between 0.005%-0.4%, preferably 0.008%-0.1 % by weight of the
DM-50 agent.
Also preferred is triclosan. It is generally desired to treat the rawhide so
that the
concentration of triclosan is between 0.01 % and 1.2%, preferably between
0.05% and 0.6% by
weight. An alcohol, preferably ethanol, is the primary solvent of the
preferred treatment
solution. When treating by soaking in a triclosan solution, subsequent rinsing
in an aqueous
solution is preferred.
It is generally preferred to treat the rawhide during its manufacture, i.e.,
before the final
drying step. In some cases, it is preferred to post-treat finished rawhide.
First, one must "open-
up" the rawhide structure. This is done by soaking the rawhide in water or
other suitable non-
toxic solvent (e.g., ethanol). The "opened" rawhide is then placed in the
desired treatment
solution for soaking. After sufficient time has elapsed for the rawhide to
absorb an efficacious
level of the microbe-inhibiting agent, it is removed from the treatment bath
and dried. If the
opening solvent and the treatment solvent are the same, one can combine the
two steps (i.e., the
treatment solution will serve also to open-up the rawhide).
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Adding an amount (typically 0.1-20% by weight) of a soluble or dispersible
polymer or
organic material to the treatment solution can assist in the retention of the
microbe-inhibiting
agent in the rawhide. For example, one can incorporate many cellulose ether
materials (e.g.,
methyl cellulose, hydroxyethyl cellulose, or carboxymethyl) or poly (vinyl
alcohol) in water-
s based solvents. Starches, agar, gelatin, casein, lard, etc. can also be
useful. Butyl cellulose,
among others, is soluble in ethanol, a preferred solvent for triclosan and
diiodomethyl p-
tolylsulphone. Preferred microbe-inhibiting agents to be used with retention-
assisting
ingredients are triclosan, diiodomethyl p-tolylsulphone, and Ultra Fresh DM-
50, and chlorine
dioxide. When retention aids are used in this manner, one must ensure that
both the retention aid
and the microbe-inhibiting agent are sufficiently soluble or dispersible in
the solvent.
According to one embodiment of the invention mastication articles such as
rawhide can
be molded. Molded rawhide articles are formed by initially cutting or
shredding conventional
rawhide into small pieces. This process is often facilitated by first soaking
the rawhide in a good
solvent, such as water. It is often preferred to boil the rawhide in water
before cutting it. The
small pieces should then be dried.
These dried small pieces can then be admixed with additives designed to give
the final
product an improved "mouth feel." Casein, agar, gelatin, sugary syrups (e.g.,
honey) are
examples; they are typically added in amounts less than about 10% by weight
based on the
weight of the final article.
The microbe-inhibiting agent is then added to this admixture. A preferred
agent is
triclosan, added in a quantity such that its concentration in the finished
product is between
0.001 % and 1 %, preferably between 0.004% and 0.1 % by weight. It is
frequently preferable to
dissolve the triclosan in a solvent before adding it to the mixture; the
preferred solvent is ethanol.
Diiodomethyl p-tolylsulphone, as in UF-95, is also preferred. It should be
added in a quantity
such that its concentration in the finished product is between 0.001 % and 2%,
preferably between
0.01 % and 0.8% by weight. It is sometimes preferable to dissolve the agent in
a solvent before
adding it to the mixture; the preferred solvent is either ethanol or acetone.
Ultrafresh DM-50 is
also preferred, added in a quantity such that its concentration in the
finished product is between
0.001 % and 1 %, preferably between 0.004% and 0.1 % by weight. It is
frequently preferred that
the DM-50 be carried in a solvent, preferably water.
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Chlorine dioxide dissolved in solvent is also preferred, added in a quantity
such that its
concentration in the finished product is between 0.0001 % and 0.5%, preferably
between 0.001
and 0.2% by weight.
The admixture is typically pre-heated to burn off a large part of the
remaining solvents.
The admixture is then fed into an injection molding machine under elevated
temperature and
pressure. It is desired that liquification occur. This generally requires
pressures in excess of 60
atm and temperatures in excess of 120° C. Pressures and temperatures in
the environs of 75 atm
and 145° C, respectively, are preferred. Desired shapes are then
molded.
Microbe-inhibiting molded rawhide can also be manufactured using other
techniques.
For example, one can obtain finely divided rawhide by boiling the rawhide;
cutting it into small
pieces; soaking the pieces in ethanol; drying the pieces in an oven; and
grinding the rawhide in a
coffee bean grinder. This finely divided rawhide can then be mixed with the
desired microbe-
inhibiting agent, a solvent, agar (or other degradable polymer), and optional
flavoring additives.
The mixture can be heated until it is quite thick, and then poured into a
mold. Subsequent
heating will further dry and congeal the product into a rawhide-based
mastication article.
Articles of this type, however, are generally much less tough than the
injection-molded type.
It is also useful to provide a spray bottle or the like containing microbe-
cidal solution
which the pet owner can apply periodically to the rawhide to refresh its
microbe-inhibiting
properties. In this case, an aqueous solution of chlorine dioxide (with
concentration about 0.08-
3%) is preferred. Ethanol solutions, used with sufficiently low frequency and
at sufficiently low
concentrations so as not to affect adversely the animal, are also useful for
this purpose. Other
"natural anti-microbials" can also be used.
Mastication Articles Containing a Digestible/Degradable Component
According to one embodiment of the invention, mastication articles made at
least in part
from materials containing a digestible/degradable component. Pets can derive
pleasure from
chewing them, and the pets can eventually digest them. Ideally, the articles
are sufficiently dense
and slow to absorb water that they retain their mechanical integrity and
"chewability" for a
significant period of time before they become very soft; and they exhibit a
significant element of
reversibility in characteristics upon drying.
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Such articles rarely comprise only starch, since pure starch tends to be
brittle and is
difficult to process. Starch is typically blended with other polymer materials
and/or with
materials that serve as plasticizers. Common polymer blending materials
include poly-ethylene-
acrylic acid or poly-ethylene-vinyl alcohol (see US 5,419,283, which is hereby
incorporated by
reference). Other common blending materials include polyethylene,
polypropylene, polystyrene,
polyvinyl chloride, polyurethanes, polyesters, polyamides, polyacrylates,
polyethers,
polyisoprene, rubbers, and polylactides. US 5,446,078, which is hereby
incorporated by
reference, describes the reactive blending of such materials with starch
materials.
Common plasticizers include sorbitol, glycerol, sucrose, and fructose. These
are typically
added in amounts ranging from 1 % to 20% by weight. Water can also serve to
some degree as a
plasticizer.
A shortcoming of prior mastication articles is that such digestible/degradable
articles are
extremely susceptible to the proliferation of microbes. This problem is
especially true of such
articles based on corn starch such as described in US Patent No. 5,419,283 and
available
commercially from Novamont under the mark Mater-Bi). In fact, a Mater-Bi
cornstarch-based
article purchased commercially and submerged in tap water for several days can
give rise to
dramatically visible proliferation of microbes.
Despite the fact that such articles have been on the market for years, no
solution has been
proposed to combat the problem of microbial proliferation in and on articles
constructed using
digestible polymers. It is therefore especially attractive to construct such
digestible articles such
that they will not support the growth of microbes.
Generally speaking, the anti-microbial agents) can be incorporated into the
materials)
which will comprise the digestible/degradable mastication article when the
material or blend of
materials are in a molten or substantially dissolved state, or they can be
incorporated into one or
more of the constituent raw materials at the time of forming of these raw
materials.
Alternatively, the anti-microbial agents) can be mechanically mixed with the
constituent raw
materials) before these materials are formed into the final article. In
addition, the anti-microbial
agents) can be included in a treatment solution to which the articles are
exposed or to which the
raw material is exposed prior to being used to form the articles. In this
latter case, it is preferred
to soak the articles in the treatment solution (rather than to spray or expose
to the vapor).
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A preferred method is to incorporate the anti-microbial agents) into one of
the polymeric
raw materials with which the starch is blended. This incorporation should
generally take place at
the time of compounding of the polymeric raw material. The concentration of
the anti-microbial
agents(s) in the polymeric raw material must be such that the ultimate
concentration in the
overall blend is as desired (i.e., the polymeric raw material must be
overloaded). Preferred
ultimate concentrations are given below.
One may use synthetic or natural microbe-inhibiting agents to provide the
desired
properties to these articles. Synthetic agents are generally preferred for
articles which are
intended primarily for purposes of mastication, although, especially since
these articles are often
at least in part consumed, natural agents can also be used. Natural agents are
generally preferred
for articles that are intended primarily or exclusively for purposes of
consumption by the animal.
A preferred synthetic agent is diiodomethyl p-tolylsulphone (see "Microbicides
for the
Protection of Materials," by Wilfried Paulus, 1993, Chapman & Hall, which is
hereby
incorporated by reference, for data on this and other biocidal/biostatic
agents). This agent
possesses a broad spectrum of anti-microbial activity, and it is most active
against fungi, yeasts,
and algae. This agent is especially preferred in applications where the
article may be partially or
wholly digested or in cases where the article is in contact with materials
which are to be digested.
This agent can cause yellowing in the final material, and if this is deemed as
unattractive, it may
be used in conjunction with color suppressants. The agent melts at about 157C.
It is relatively
insoluble in water (0.0001 g/1 at 25C). Acetone (350 g/1 at 25C) and ethanol
(20 g/1 at 25C) are
preferred solvents. The agent is generally stable in the pH range of 4-10. A
preferred form of
the agent is Ultrafresh UF-95, available from Thomas Research Associates. The
concentration of
OF 95 in the finished product should be between 0.001 % to 3 %, preferably
between 0.01 % and
1 %. Another preferred synthetic agent for incorporation into articles
possessing a digestible
component is Irgasan DP300 (triclosan). It should be used in a quantity such
that its average
concentration in the finished product is between 0.001 % and 1 %, preferably
between 0.004% and
0.1 % by weight. Ethyl alcohol is a preferred solvent for triclosan.
Ultrafresh NM-100 (available
from Thomas Research Associates) is another preferred form of triclosan, added
in a quantity
such that its concentration in the finished product is between 0.001 % and 2%,
preferably between
0.004% and 0.3% by weight.
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Triclosan melts at about 60°C, and decomposes at about 285°C.
The fact that triclosan
melts at 60°C facilitates the mixing of the triclosan with other raw
materials, especially when
such materials are in a powder form; and much flexibility in processing is
achieved in the large
window between melting and degradation.
Chlorine dioxide is also preferred, added in a quantity such that its
concentration in the
finished product is between 0.0001 % and 0.5%, preferably between 0.001 % and
0.2% by weight.
Water is a preferred solvent.
As noted earlier, in many cases, articles based on biodegradable materials,
especially
starch-based biodegradable materials, may be designed expressly as food items
(in contrast to
mastication articles that may be digestible or have a digestible component).
In this case, the need
for a microbe-inhibiting property is acute, since, in sharp contrast to human
foods, people do not
usually exercise the proper care to ensure that the articles are stored and
transported properly
before use. It is generally preferred in such cases to incorporate natural
anti-microbial agents or
food preservatives agents (or their oils) into mastication materials. These
anti-microbial agents
include garlic, turmeric, or other spices known to be inhospitable to
microbes. Common food
agents such as sugar and salt may be used to make the articles less
susceptible to microbial
proliferation. A variety of compatible preservatives and their properties are
described in
Disinfection, Sterilization, and Preservation, Edited by Seymour S. Block (Lea
& Feniger, 1991 ),
which is herein incorporated by reference.
It is preferred to comminute these natural microbe-inhibiting materials to
some degree
before incorporation into the base material. It is further preferred to
incorporate the natural anti-
microbial materials into the raw material and then use the raw material in the
usual manner to
produce the articles.
Alternatively, one can include the comminuted material with the mix of other
raw
materials before molding the articles (e.g., add to the hopper before
injection molding).
Treatment may also be carried out by soaking, optionally under high pressure,
the molded
articles in a solution or broth containing the natural microbe-inhibiting
materials.
In some cases (e.g., with garlic-based microbe-inhibiting agents), consumption
by the
animal can result in bothersome halitosis. If this is perceived as a problem,
it is preferred to treat
the natural microbe-inhibiting material in such a way as to derive an extract
or broth which
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possesses the desired microbe-inhibiting quality but does not cause halitosis.
Since many natural
anti-microbial materials are believed to possess therapeutic properties for
humans, there are
many known methods to produce such extracts (e.g., US Patent No. 5,391,390,
which is herein
incorporated by reference).
Natural anti-microbial agents are often perceived by people in a more
favorable light
because they are "natural." In addition, they can also be preferred because
they are frequently, at
least in part, water soluble. This property facilitates incorporation of these
materials into many
biodegradable materials, such as the starch-based materials, which possess a
significant degree of
solubility with respect to water (in contrast to triclosan or diiodomethyl p-
tolylsulphone, which
are not readily soluble in water). It is often preferable to use a
biodegradable material - microbe-
inhibiting agent combination which possess a common solvent).
Although articles constructed from many polymers containing a digestible
component,
such as those based on Mater-Bi, are in fact digestible, they may not provide
sufficient
enticement for the pet to chew on them. For this reason, it is preferred to
add enticing additives,
such as flavorings or scents, to the articles. For example, an amount of
catnip or catnip oil can
entice a cat to chew or otherwise be attracted to the article. Comminuted
catnip, for example,
can be added to the hopper with the raw materials.
Similarly, a fish scent or fish-flavored additive may encourage the cat to
chew on the
article. Meat scents or flavorings are particularly attractive for dogs.
It is further desirable to incorporate components into the chewing articles
which impart a
therapeutic quality. For example, various vitamins, minerals, breath-
freshening agents, and
therapeutic herbs can advantageously be incorporated into the articles. To
maintain the efficacy
of these agents, however, it is important to ensure that processing
temperatures subsequent to the
incorporation of the relevant agents do not exceed the degradation
temperatures of the active
component of the agents.
Collagen and/or gelatin derived materials are also very attractive for forming
degradable/digestible chewing articles. These may be used as the primary
ingredient in the
article or they can be blended with starch-based materials. The resulting
materials can be made
to possess microbe-inhibiting properties by methods described herein.
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A wide variety of comminuted vegetable matter can also be used as a primary
ingredient
for mastication articles or as a component ingredient in a blend (e.g., with
starch, rawhide,
gelatin, etc.).
Rope-Based Mastication Articles
Cotton is a highly absorbent material and is particularly attractive for
constructing rope-
based mastication articles; but when cotton becomes wet with saliva, it tends
to dry relatively
slowly, which can lead to bacteria growth.
A "passive" approach includes limiting bacterial proliferation by limiting the
time for
which the material is exposed to moisture, such as by the inclusion of a
nonabsorbent core for a
cotton covered rope chew article. But the article will frequently still be
exposed to moisture for
periods sufficiently long for significant bacterial proliferation to occur.
The present invention discloses an "active" and complete approach in which
microbe-
cidal agents are incorporated into the article. In this way, the article is
directly protected against
the proliferation of a wide variety of bacteria, as well as other microbes,
regardless of factors
such as the specific environment or the way the dog uses the article.
A preferred process for treating cotton rope-based mastication articles for
pets, or for
treating rope-based mastication articles for pets in which cotton is a major
component, is to soak
the rope material in a solution containing Ultra Fresh DM-50. It is generally
desired to treat the
rope in an aqueous solution so that the content of the agent in the rope is
about 0.03%-1.2%,
preferably between 0.08% and 0.6% by weight.
Another preferred method for treating cotton rope-based mastication articles
for pets, or
for treating rope-based mastication articles for pets in which cotton is a
major component, is to
soak the rope in a solution containing diiodomethyl p-tolylsulphone. A
preferred form of the
agent is Ultrafresh UF-95, available from Thomas Research Associates. It is
generally desired to
treat the rope in an ethanol or acetone solution so that the final content of
the agent in the rope is
between 0.001 % to 3 %, preferably between 0.01 % and 1 %. Because this agent
can cause
yellowing in the final material, it may be desired to use color suppressants
(especially if one is
manufacturing a white rope).
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Another preferred method for treating cotton rope-based mastication articles
for pets, or
for treating rope-based mastication articles for pets in which cotton is a
major component, is to
soak the rope in a solution containing Dow Corning 5700 strongly bonded
microbe-inhibiting
agent. Preferably, the agent content is in the range of about 0.08%-0.15% by
weight.
Soak-treating in an aqueous solution containing stabilized chlorine dioxide
(concentration
range about 0.1-4%) is also preferred. Also preferred is triclosan. It is
generally desired to soak
the rope material in solution in which the concentration of triclosan is
between 0.01 % and 1.2%,
preferably between 0.05% and 0.6% by weight. An alcohol, preferably ethanol,
is the primary
solvent of the preferred treatment solution.
The soaking (or spraying) solution can optionally contain ingredients that
will impart a
desirable scent or flavor to the articles. These ingredients include meat
broth, meat meal, gravy,
etc.
It is generally preferred to that the treatment occur at an elevated
temperature, typically
between 40-100°Celsius. If a temperature higher than the boiling
temperature of the primary
solvent is used, however, increased pressured must be used. For example, the
articles can be
treated in an aqueous solution at temperatures exceeding 100°C if an
autoclave or pressure
cooker is used.
Adding an amount (typically 0.1-20% by weight) of a soluble or dispersable
polymer or
organic material to the treatment solution can assist in the retention of the
microbe-inhibiting
agent in the rope-material and is preferred. For example, one can incorporate
many cellulose
ether materials (e.g., methyl cellulose, hydroxyethyl cellulose, or
carboxymethyl) or poly (vinyl
alcohol) in water-based solvents. Starches, agar, gelatin, casein, lard, etc.
can also be useful.
Butyl cellulose is an example of a polymer which is soluble in ethanol, a
preferred solvent for
triclosan. Preferred microbe-inhibiting agents to be used with retention-
assisting ingredients are
triclosan, diiodomethyl p-tolylsulphone, Ultra Fresh DM-50, and chlorine
dioxide.
When using retention aids, the solvent, retention aid and the microbe-
inhibiting agent
should be selected so that both the retention aid and the microbe-inhibiting
agent are sufficiently
soluble or dispersable in the solvent.
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Many desired retention aids are easily digestible by microbes, and it is
therefore desirable
that the microbe-inhibiting agents are present in the retention aids at
concentrations sufficient to
inhibit the proliferation of microbes.
The rope material can also be disinfected or sanitized prior to its treatment
by soaking in
a disinfecting solution (e.g., ethanol), optionally at elevated temperature or
pressure. The rope
materials can also be sprayed with the treatment solutions.
After a soak or spray treatment, the rope material is dried. Air-drying and
oven drying
are preferred, as is drying in a vacuum oven, optionally at elevated
temperature.
Another preferred method for constructing a microbe-inhibiting cotton-rope-
based
mastication article is to spray with or otherwise expose the individual
filaments or threads to the
microbe-inhibiting agent (either in solution or carrier form) as the rope is
being formed. In order
to expand the threads and make them more open to the introduction of the
microbe-inhibiting
agents, it is preferable to expose the threads to moisture before the microbe-
inhibiting agents are
introduced. The microbe inhibiting agents may be introduced by spraying a
solution containing
the agent (solutions with concentrations similar to that of the soak-treatment
solutions can be
used) onto the filaments. The agents can be dissolved in solution or can be
part of a dispersion.
Other natural materials are useful in constructing rope-based mastication
articles for pets.
These include sisal, hemp, jute, henequen, and others. Ultra Fresh DM-50 ,
diiodomethyl p
tolylsulphone, Dow 5700, chlorine dioxide and triclosan are the preferred
agents for treating
these materials.
Rope-based mastication articles can be made from a variety of synthetic
materials as well.
They can be constructed, e.g., from fibers or threads composed of nylon, orlon
or other acrylics,
polyester, polypropylene, or other materials. For these materials, it is
preferred to incorporate
triclosan (e.g., Microban, Irgasan, Ultrafresh NM-100) or diiodomethyl p-
tolylsulphone (e.g.,
Ultrafresh UF-95) at the time of manufacture of the raw filaments. The agent
is preferably
incorporated into the melt or spin dope from which the filaments are drawn.
For triclosan, it is
preferred that the concentration in the finished filaments be between 0.01 %
and 1.8%, preferably
between 0.05% and 1 % by weight. For UF-95, it is preferred that the
concentration in the
finished filaments be between 0.001 % to 3 %, preferably between 0.01 % and 1
%.
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CA 02266839 1999-04-09
A rope can be combined with other functional features to create an improved
mastication
article. For example, holes can be punched through microbe-inhibiting rawhide
articles according
to the invention and a microbe-inhibiting rope according to the invention can
be threaded through
the holes. The rope can then be knotted at either end to secure the rawhide to
the rope.
Similarly, a microbe-inhibiting rope according to the invention can be
threaded through a fiber-
filled plush chew toy for a pet and triclosan microbe-inhibiting agent can be
incorporated in all
or part of the fiber in the plush chew toy.
Plastic Mastication Articles
Plastic-based mastication articles for pets are becoming increasingly popular.
Except in
some cases where degradable polymers are used, plastic-based mastication
articles are not
intended for digestion. Many non-digestible plastics possess a moderate
natural microbe-
starving quality - they provide little or no nutritive material for microbes
to digest or metabolize
and thereby thrive. Even with these articles, however, saliva and other fluids
or materials deposit
on the articles and provide nutrition for the proliferation of microbes. In
addition, many
plasticizers which are often used to increase flexibility in the final plastic
article or to facilitate
processing are readily digestible by microbes as described further below.
A greater source of nutrition in plastic-based mastication articles for pets
relates to the
methods by which the articles are made desirable to pets. Plastics are
generally not particularly
attractive to pets, especially those plastics that possess good natural
microbe-starving
characteristics. For this reason, animal meal, sugar, and similar attractive
elements have been
incorporated into such plastic-based mastication articles to make them more
attractive for pets.
Because these elements are also digestible by microbes, however, the natural
microbe-starving
characteristics which the articles may have possessed can become ineffectual.
According to one aspect of the invention, plastic-based mastication articles
possess
effective protection against the proliferation of microbes, even when
digestible elements intended
to make the articles more attractive for pets have been incorporated into the
articles.
Plastic mastication articles for pets are frequently made by molding (e.g.,
injection
molding, blow molding), or dipping processes known in the plastics fabrication
art.
Thermoplastic resins are typically used for injection molding and latex
solutions are typically
used for the dipping processes.
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CA 02266839 1999-04-09
For articles constructed by molding processes, it is preferred first to
incorporate the agent
in a concentrated form into a resin carrier. US 4,789,692, which is herein
incorporated by
reference, discloses numerous means for concentrating biocides in resin
carriers. The resin
carrier is then mixed or diluted in the appropriate ratio with the resins)
with which it will
comprise the final article, and the blend is processed, preferably by
injection molding, into the
desired shape. It is crucial to ensure that the resin mix is well-blended. The
mixing or dilution
factor is given by the ratio of the concentration of the agent in the
concentrate to the desired final
concentration in the article. For example, if the concentrated carrier
contained 2% of the agent,
and the desired final concentration was 0.2%, the mixing or dilution factor
would be
2%/0.2%=10, e.g., the final mix would contain 1 part in 10 of the concentrated
carrier.
Diiodomethyl p-tolylsulphone is a preferred agent. It is preferred to
incorporate UF-95
into the concentrated resin fraction such that the concentration in the final
article is between
0.001 % to 3%, preferably between 0.01 % and 1 %. The preferred concentration
of UF-95 in the
concentrated resin depends on the polymer or polymers comprising the resin,
but is generally
between .5% and 15%, preferably between 1% and 9%.
Preferred plastic materials for the articles according to the invention, alone
or in
combination, are nylon and polyurethane, although many other types of
plastics, e.g.,
polyolefins, are suitable as well. It is generally preferred to use
thermoplastics.
Another preferred microbe-inhibiting agent is 2,4,4'-trichloro-2'-
hydroxydiphenol
(triclosan). The microbe-inhibiting resin fraction is added to the base
material resin in an amount
such that the concentration of the agent in the final product is between 0.001
% and 1.5%,
preferably between 0.004% and 0.7% by weight. The preferred concentration of
triclosan in the
concentrated resin depends on the polymer or polymers comprising the resin,
but is generally
between .5% and 15%, preferably between 1% and 9%.
Another preferred agent is a form of triclosan commercially available as Ultra
Fresh NM-
100. It is added such that its concentration in the final article is between
0.001 % and 1.5%,
preferably between 0.004% and 0.7% by weight.
In latex processing, the microbe-inhibiting agent is in powder or liquid form
or suitably
and is incorporated into a solid or liquid carrier that is preferably added to
the latex mixture
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before molding. Preferred microbe-inhibiting agents are triclosan,
diiodomethyl p-tolylsulphone,
tri-n-butylin maleate, and chlorine dioxide.
2,4,4'-trichloro-2'-hydroxydiphenol can also be obtained in a crystalline
powder form
(e.g., from TRInternational, Inc.), and the powder can be added to the article
forming
composition. For example, the powder can be added directly to the latex
mixture. It can also be
incorporated directly into the molten form of many thermoplastics. In the
latter case, however,
appropriate mixing should be carried out to ensure homogeneity.
Other desirable ingredients, such as meat broths, ground-up dried meat
products, etc., can
be added to the plastic-based mastication articles to impart a desirable
flavor or scent. The
addition of such ingredients can, however, negate the natural microbe-starving
quality of these
base polymer materials. Unfortunately, ingredients which are likely to make
the make the article
more attractive to pets are generally of a digestible nature (meat-based
products, sugars, etc.),
and are therefore likely to provide nutrition for the proliferation of
microbes. This fundamental
trade-off is circumvented by the invention. According to the invention,
plastics-based
mastication articles with such flavoring ingredients include a microbe-
inhibiting agent in the
resin mix or the precursor solution of the base plastic material. The
preferred concentrations and
related considerations given above apply.
A preferred method for constructing plastics-based mastication articles with
such
flavoring ingredients is to pre-treat the flavoring ingredients themselves
with microbe-inhibiting
agents. These pre-treatments can be done alone or in combination with adding
microbe-
inhibiting agent to the base plastic material.
If one is incorporating a solid or solid-like flavoring ingredient into a
resin or melt
mixture, it is preferred to soak the flavoring ingredients in a solution
containing one or more
microbe-inhibiting agents before incorporating the ingredients intro the resin
or melt mixture.
The ingredients should be dried before incorporation into the resin or melt
mixture.
A preferred agent for use in treating the flavoring ingredients is chlorine
dioxide, which is
safe for both animal and human consumption. An appropriate solution
concentration is in the
range of about 0.1-2% by weight.
Also preferred is diiodomethyl p-tolylsulphone. The treatment solution has a
concentration between 0.01 % and 5%, preferably between 0.05% and 2% by
weight. Ethanol or
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acetone are preferred candidates for the primary solvent of the treatment
solution. When treating
by soaking in a diiodomethyl p-tolylsulphone solution, subsequent rinsing in
an aqueous solution
is preferred.
Also preferred is Ultrafresh DM-50. Water is the primary solvent for the
preferred
treatment solution, which contains between 0.005%-0.4%, preferably 0.008%-0.1
% by weight, of
the DM-50 agent.
Also preferred is triclosan. The treatment solution has a concentration
between 0.01
and 1.2%, preferably between 0.05% and 0.6% by weight. An alcohol, preferably
ethanol, is the
primary solvent of the preferred treatment solution. When treating by soaking
in a triclosan
solution, subsequent rinsing in an aqueous solution is preferred.
If one is incorporating a flavoring agent by soaking the article in a solution
containing
that agent (and possibly at elevated temperature and/or pressure), it is
preferred to incorporate a
preferred microbe-inhibiting agent in the treatment solution. A preferred
agent in this case is
chlorine dioxide, preferably in the range of about 0.1-2% by weight.
The microbe-starving quality of some synthetic polymers is often
unintentionally
destroyed by processing with a plasticizes which contains nutritive elements
which can support
microbial proliferation. The plasticizers used in processing many polymers are
digestible and/or
degradable by microbes. If a plasticizes is to be used in processing materials
used for
constructing a mastication article for a pet, it is preferred to choose a
plasticizes that does not
diminish the natural microbe-starving and/or microbe-impenetrable property of
the polymer.
Plasticizers that are particularly resistant to fungal growth include: Abietic
acid; hydrog. methyl
abietate; tri-n-butyl aconitate; triethyl aconitate; di-(2-ethylhexyl)adipate;
di-(2-
ethylhexyl)acetate; ethyl-o-benzyl benzoate; chlorinated diphenyls;
chlorinated paraffins; tri-n-
butyl citrate; triethyl citrate; 2-nitro-2 methyl-1,3-propanediol diacetate;
dimethyl phthalate; di-
n-propyl phthalate; diisopropyl phthalate; dibutyl phthalate; diisobutyl
phthalate; diisodecyl
phthalate; dihexyl phthalate; dicapryl phthalate; di-(2 ethylhexel) phthalate;
di-(2 ethylhexyl)
phthalate; dicyclohexyl phthalate; dicyclohexyl phthalate; and dibenzyl
phthalate.
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Other Types of Plastic Articles
Plastics articles to be used for purposes other than as mastication articles
for pets can be
made with a microbe-inhibiting agent according to the invention. Particularly
desirable are
feeding bowls, litter boxes, and scoopers (e.g., for food, feces, used
litter). It is preferred first to
incorporate the microbe inhibiting agent in a concentrated form into a resin
carrier. US-A
4,789,692, which is herein incorporated by reference, discloses numerous
techniques for
concentrating biocides in resin carriers. The resin carrier is then mixed or
diluted in an
appropriate ratio with the resins) which will be used in the final article,
and the blend is
processed, preferably by injection molding, into the desired shape. The mixing
or dilution factor
is given by the ratio of the concentration by weight of the microbe-inhibiting
agent in the resin
carrier to the desired final concentration by weight in the article. For
example, if the
concentrated carrier contained 2% of the microbe-inhibiting agent by weight,
and the desired
final concentration was 0.2% by weight, the mixing or dilution factor would be
2%/0.2%=10,
e.g., the final mix would contain 1 part in 10 of the concentrated carrier.
For bowls or other food-contacting products, diiodomethyl p-tolylsulphone is
the
preferred microbe-inhibiting agent. It is specifically preferred to
incorporate UF-95 into the
concentrated resin fraction such that the concentration in the final article
is between 0.001 % to
3 %, preferably between 0.01 % and 0.1 %. The preferred concentration of UF-95
in the
concentrated resin depends on the polymer or polymers comprising the resin,
but is generally
between .5% and 15%, preferably between 1% and 9%.
The primary material comprising the bowl is preferably polypropylene,
polyethylene,
although many thermoplastic polymers are adequate.
Triclosan is also preferred for bowls in cases where anti-mildew and anti-mold
properties
are not essential. Using triclosan, it is preferred to incorporate the agent
into a resin concentrate
which is then blended with other resin to produce the final article via
injection molding. It is
preferred to incorporate UF-95 into the concentrated resin fraction such that
the concentration in
the final article is between 0.001 % to 3 %, preferably between 0.01 % and 1
%. The preferred
concentration of triclosan in the concentrated resin depends on the polymer or
polymers
comprising the resin, but is generally between .5% and 15%, preferably between
1 % and 9%.
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For litter boxes and scoopers which will contact feces or other bodily waste,
tri-n-butylin
maleate is the preferred microbe-inhibiting agent. A commercial form,
Ultrafresh DM-50, is
specifically preferred. It is preferred to incorporate DM-50 into the
concentrated resin fraction
such that the concentration in the final article is between 0.005% to 4% by
weiight, preferably
between 0.04% and 2%. The preferred concentration of DM-50 in the concentrated
resin
depends on the polymer or polymers in the resin blend, but is generally
between .5% and 15%,
preferably between 1 % and 9% by weight.
Diiodomethyl p-tolylsulphone is also a preferred microbe-inhibiting agent. It
is
preferred to incorporate UF-95 into the concentrated resin fraction such that
the concentration in
the final article is between 0.005% to 4%, preferably between 0.05% and 2%. By
weight The
preferred concentration of UF-95 in the concentrated resin depends on the
polymer or polymers
comprising the resin, but is generally between .5% and 15%, preferably between
1 % and 9% by
weight.
Combs and other grooming aids can similarly be manufactured according to the
invention.
Mastication Articles with Porosity
It is sometimes desirable, especially for animals that do not have powerful
jaws (such as
small dogs, cats, and rodents), to have a substantial porosity in the
mastication articles according
to the invention. In such cases, the articles can be made porous with well-
known foaming
techniques as disclosed, for example, in US Patent No. 5,360,830, which is
herein incorporated
by reference.
The following examples illustrate specific embodiments of the invention:
Example 1
A treatment bath was prepared as follows: A chlorine dioxide starting solution
comprising 2% by weight chlorine dioxide and 0.085% by weight sodium carbonate
was
obtained (from 3R Marketing Associates). 100 ml of this solution was mixed
with 400m1 of
water. The solution was heated to 90C. Four grams of agar was then added to
this solution.
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Rawhide was acquired commercially in strip form. A strip with dimensions
approximately 6cm x 6cm, and about 1.6mm thick was cut using a knife.
The rawhide strip was placed in the treatment bath, which was then covered.
The strip
was treated in the bath, with occasional stirring, for 2 hours.
The strip was removed from the bath and air dried.
Example 2
A first treatment bath is prepared using 800 ml of water as the treatment
solution.
A second treatment bath was prepared as follows: A mixture of 1 gm of
triclosan
crystalline powder (obtained from TRInternational, Inc.) was mixed with 200m1
of grain alcohol
(95% ethanol by volume); and the mixture was stirred.
A third treatment bath is prepared using 800 ml of water maintained at
80°C.
Rawhide was acquired commercially in strip form. A strip with dimensions
approximately 6cm x 6cm, and about 1.6mm thick was cut using a knife.
The rawhide strip was placed in the first treatment bath, which was then
covered. The
bath with the strip was allowed to sit at room temperature for eight hours
The rawhide strip was then removed from the first treatment bath and placed
into the
second treatment bath, which was then covered. The bath with the strip was
maintained, with
occasional stirring, at room temperature for four hours.
The rawhide strip was then removed from the second treatment bath and placed
into the
third treatment bath, which was then covered. The third treatment bath with
the strip was
allowed to sit at 80° C for four hours.
The strip was removed from the bath and air dried.
Example 3
A first treatment bath is prepared using 800m1 of a 0.9% saline solution (0.9%
by weight
Sodium Chloride Irngation, USP, from Baxter Healthcare Corporation).
A second treatment bath was prepared as follows: A mixture of 0.3gm of
triclosan
crystalline powder (obtained from TRInternational, Inc.) was mixed with 200m1
of grain alcohol
(95% ethanol by volume); and the mixture was stirred.
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CA 02266839 1999-04-09
Rawhide was acquired commercially in strip form. A strip with dimensions
approximately 6cm x 6cm, and about 1.6mm thick was cut using a knife.
The rawhide strip was placed in the first treatment bath at room temperature
and then
covered for six hours. The rawhide strip was then removed from the first
treatment bath and
rinsed with water. It was then placed into the second treatment bath, which
was then covered,
and soaked at room temperature for three hours. The strip was then removed
from the bath,
rinsed generously with water and air dried.
Example 4
A treatment bath was prepared as follows: A mixture of 0.7 gm of triclosan
crystalline
powder (obtained from TRInternational, Inc.) was mixed with 100m1 of grain
alcohol (95%
ethanol by volume); and the mixture was stirred. 100 ml of water was added to
the mixture,
causing the solution to take on a white, milky appearance.
Rawhide was acquired commercially in strip form. A strip with dimensions
approximately 6cm x 6cm, and about 1.6mm thick was cut using a knife.
The rawhide strip was placed in the treatment bath, which was then covered,
and soaked
at room temperature for eight hours. The strip was then removed from the bath
and air dried.
Example 5
A first treatment bath is prepared by adding two ounces of sugar to 800 ml of
water, and
stirring and heating until the sugar dissolves. The bath is then placed on a
hotplate and
maintained at 60° C.
A second treatment bath was prepared as follows: A solution of 0.3% by weight
Ultra
Fresh DM-50 in water (Thomas Research Associates) is covered and heated at
35° C.
Rawhide was acquired commercially in strip form. A strip with dimensions
approximately 6cm x 6cm, and about 1.6mm thick was cut using a knife.
The rawhide strip was placed in the first treatment bath, which was then
covered. The
bath with the strip was allowed to sit at 60° C for 3 hours.
The rawhide strip was removed from the first treatment bath, rinsed
generously, and
placed into the second treatment bath, which was then covered. The bath with
the strip was
allowed to sit at 35° C for four hours.
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CA 02266839 1999-04-09
The strip was removed from the bath and dried in an oven for 1 hour at
85° C.
Example 6
An 8" length piece is cut from a roll of cotton rope. An aqueous treatment
solution is
prepared containing 0.2% by weight Ultra Fresh DM-50 (Thomas Research
Associates). The
solution is kept covered and maintained at room temperature. The cut rope is
placed into the
treatment solution, weighted down with a U-shaped piece of glass. The rope
piece is periodically
agitated in the treatment solution. After 2 hours, the rope is removed from
the treatment solution
and dried in a vacuum oven at 60° C.
Example 7
An 10" length piece is cut from a roll of cotton rope. A treatment solution is
prepared
comprising an ethanol solvent with 0.2% by weight triclosan (obtained from
TRInternational,
Inc.) and 1 % by weight butyl cellulose. The solution is heated to 40°
C and kept covered. The
cut rope is rope is placed into the treatment solution and is periodically
agitated. After 1.2 hours,
the rope is removed from the treatment solution and hung from a clothesline
for 40 minutes. The
rope is then dried in a vacuum oven at 80° C.
Example 8
An 8" length piece is cut from a roll of cotton rope. A knot is tied at either
end to give
the rope the appearance roughly of a bone. An aqueous treatment solution is
prepared as follows:
300m1 of a chlorine dioxide starting solution comprising 2% by weight chlorine
dioxide and
0.085% by weight sodium carbonate (from 3R Marketing Associates) was mixed
with 700m1 of
water. The solution is maintained at 80° C. 20gm of beef flavor
bouillon (Herbox, from Hormel
Foods) is added to the solution, which is stirred until the bouillon is
dissolved. The solution is
kept covered and maintained at 80° C. The cut rope is rope is placed
into the treatment solution
and weighted down with a U-shaped piece of glass. The rope piece is
periodically agitated in the
treatment solution. After 2 hours, the rope is removed from the treatment
solution and dried in a
vacuum oven at 60° C.
Example 9
An 8" length piece is cut from a roll of cotton rope. A knot is tied at either
end to give
the rope the appearance roughly of a bone. An aqueous treatment solution is
prepared as follows:
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CA 02266839 1999-04-09
300m1 of a chlorine dioxide starting solution comprising 2% by weight chlorine
dioxide and
0.085% by weight sodium carbonate (from 3R Marketing Associates) is mixed with
700m1 of
water. The solution is heated to and maintained at 95° C. lOgm of agar
is stirred into the
solution. The cut rope is rope is placed into the treatment solution and
weighted down with a U-
shaped piece of glass. The rope piece is periodically agitated in the
treatment solution. After 2
hours, the rope is removed from the treatment solution and dried in a vacuum
oven at 60° C.
Example 10
98 gm of dry starch are mixed 38 gm of maleated ethylene-propylene copolymer.
This
mixture is then blended with 4 gm of a carrier resin comprising 7% Ultrafresh
UF-95 in ethylene
vinyl acetate. This mixture is then mixed in an internal hot mixer for 12
minutes at 185° C. The
resulting material can be used as raw material for molding a mastication
article.
Example 11
9.8 kg of dry starch are mixed with 3.8 kg of maleated ethylene-propylene
copolymer.
This material is mixed in an internal hot mixer for 12 minutes at 185°
C. The resulting material
is then extruded into pellet form. The resulting pellets are blended with
400gm of a carrier resin
pellets comprising 6% Ultrafresh UF-95 in ethylene vinyl acetate. Care is
taken to ensure that
the sizes of the pellets are comparable. The blend is placed in the hopper of
an injection molding
machine and is used for injecting molding a bone-shaped chewing article for a
dog.
Example 12
Ultrafresh UF-95 is incorporated at a concentration 2% by weight into an
ethylene vinyl
acetate carrier resin which is processed to be in pellet form. 20 gm of this
material is mixed with
110 gm of a dry starch powder and 80 grams of polypropylene. This mixture is
then mixed in an
internal hot mixer for 12 minutes at 185° C. The resulting material can
be used as raw material
for molding a mastication article.
Example 13
14 kg polypropylene pellets are blended with 400gm of a carrier resin pellets
comprising
3% Ultrafresh UF-95 in ethylene vinyl acetate. Care is taken to ensure that
the sizes of the
pellets are comparable. The blend is placed in the hopper of an injection
molding machine and is
used for injecting molding a feeding bowl for a dog.
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CA 02266839 1999-04-09
Example 14
Polypropylene resin in pellet form and ethylene vinyl acetate in pellet form
containing
6% Ultrafresh UF-95 are separately fed into the feeders of a dual-feed
injection molding machine
at a proportion of 40 parts polypropylene to 1 part ethylene vinyl acetate.
The material is
injection molded into the shape of a feeding bowl for dogs.
Example 14
Polypropylene resin in pellet form and polypropylene resin in pellet form
containing 3%
triclosan by weight are separately fed into the feeders of a dual-feed
injection molding machine
at a proportion of 35 parts polypropylene to 1 part treated polypropylene by
weight. The
material is injection molded into the shape of a bone shaped mastication
article.
Reasonable variation and modification are possible within the forgoing
disclosure and
drawings without departing from the spirit of the invention which is defined
in the appended
claims.
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