Abstrict Polymer-bound adsorbent beads are usable as a direct replacement
for conventional clay-bound beads in insulating glass unit manufacture
to eliminate the problem of dusting associated with conventional
beads. Polymer-bound beads provide good adsorption and superior
crush strength compared to clay-bound adsorbent beads previously
used in insulating glass units to desiccate the space between the
glass panes. The polymer-bound adsorbent beads may also be used
as a substitute for conventional desiccant beads in water adsorption
applications such as in bottle stoppers, sachets, blister packaging,
etc.
Claims What is claimed is:
1. An insulating unit comprising at least two panes of glass which
are fixed in a spaced relationship, at least one spacer member located
between said panes about the edges of said panes, said panes and
said spacer member(s) defining at least one closed interior space
in said unit, and at least one compartment located at the periphery
of said interior space(s), said compartments(s) being adapted to
contain adsorbent beads such that said adsorbent beads communicate
with said interior space(s) to provide an adsorbing function for
said interior space(s) while said beads are retained in and by said
compartment(s), wherein said compartment(s) contains adsorbent beads
and at least a portion of said adsorbent beads are polymer-bound
adsorbent beads comprising adsorbent compounded with a polymer binder.
2. The insulating glass unit of claim 1 wherein all of said adsorbent
beads are polymer-bound adsorbent beads.
3. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads comprise a molecular sieve adsorbent selected from
the group consisting of zeolite A, zeolite 3A, zeolite X, and mixtures
thereof.
4. The insulating glass unit of claim 1 wherein said polymer-bound
beads comprise a thermoplastic polymer resin binder.
5. The insulating glass unit of claim 1 wherein said polymer-bound
beads comprise an olefin polymer binder.
6. The insulating glass unit of claim 4 wherein said polymer-bound
beads comprise an olefin polymer binder.
7. The insulating glass unit of claim 5 wherein said olefin polymer
is selected from the group consisting of olefin resins, olefin waxes
and mixtures thereof.
8. The insulating glass unit of claim 7 wherein said olefin polymer
comprises a resin having a melt index of at least about 5.
9. The insulating glass unit of claim 8 wherein said olefin polymer
comprises a resin having a melt index of about 7 to 100.
10. The insulating glass unit of claim 7 wherein said olefin polymer
comprises a wax having a weight average molecular weight of at least
about 2000.
11. The insulating glass unit of claim 10 wherein said olefin polymer
comprises a wax having a weight average molecular weight of about
3000-5000.
12. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads contain at least about 10 wt. % molecular sieve
adsorbent.
13. The insulating glass unit of claim 12 wherein said polymer-bound
adsorbent beads contain about 30-80 wt. % molecular sieve adsorbent.
14. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads have an average particle size of at least about
0.1 mm.
15. The insulating glass unit of claim 14 wherein said polymer-bound
adsorbent beads have an average particle size of about 0.5-3.0 mm.
16. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads have an aspect ratio of about 2 or less.
17. The insulating glass unit of claim 16 wherein said polymer-bound
adsorbent beads have an aspect ratio of about 1.5 or less.
18. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads have a water adsorption capacity of at least 3 wt.
% at 50% relative humidity at room temperature.
19. The insulating glass unit of claim 18 wherein said polymer-bound
adsorbent beads have a water adsorption capacity of about 5-20 wt.
% at 50% relative humidity at room temperature.
20. The insulating glass unit of claim 1 wherein said polymer-bound
adsorbent beads have a compacted bulk density of at least 0.6 g/ml.
21. In a method of forming an insulating glass unit wherein said
method comprises filling at least one compartment with adsorbent
beads, said compartment(s) to be located at the periphery of an
interior space in said unit defined in part by at least two panes
of glass in said unit, said compartment(s) being adapted to contain
adsorbent beads such that said adsorbent beads communicate with
said interior space to provide an adsorbing function for said interior
space while said beads are retained in and by said compartment(s),
the improvement comprising filling said compartment(s) with adsorbent
beads wherein at least a portion of said adsorbent beads are polymer-bound
adsorbent beads comprising adsorbent compounded with a polymer binder.
22. The insulating glass unit of claim 1 wherein the adsorbent
is inorganic desiccant.
23. The insulating glass unit of claim 22 wherein the adsorbent
comprises desiccant zeolite.
24. The method of claim 21 wherein the adsorbent is inorganic desiccant.
25. The method of claim 24 wherein the adsorbent comprises desiccant
zeolite.
Description BACKGROUND OF THE INVENTION
Multiple pane insulating glass (IG) units or windows have been
in use for many years. Over this time, many variations in window
design have been made. Most designs involve two or more panes of
glass which are held in a spaced relationship by a spacer which
is located between the panes at their edges. The spacer and panes
are typically fixed together by a sealant or other means. The spacer
and panes thereby define a closed interior space in the insulating
glass unit which is largely responsible for the insulating benefit
associated with the unit.
Typically, when the IG unit is sealed, some water vapor remains
in the resulting closed interior space. If no measures are taken,
this water vapor would condense on the panes when the unit is exposed
to typical service temperatures thereby causing fogging. A similar
effect may occur if materials used to construct the IG unit contain
volatile organic compounds which can pass to the interior space
of the unit. To prevent fogging, most IG unit designs provide a
means for adsorbing water vapor/chemical volatiles in the interior
space over the expected life of the IG unit.
In conventional designs, one or more compartments are located at
the periphery of the interior space either in the spacer itself
or adjacent to the spacer. The compartment(s) is adapted to contain
adsorbent materials (typically desiccants) in bead form in a manner
such that the adsorbent beads communicate with the interior space
to provide an adsorbing function for that space while the beads
are retained in and by the compartment(s). Thus, fogging is prevented.
The beads used for this type of application generally consist of
one or more types of molecular sieve bound by an inorganic binder
(typically clay). The beads are designed to be free-flowing. Thus,
they can easily be poured into the compartment to provide the desired
quantity of desiccant.
While this basic IG technology has been for many years, the conventional
clay-bound adsorbent beads present handling problems especially
for the window manufacturer. Specifically, clay-bound adsorbent
beads generally cause a large amount of dust. This dust is caused
in part by the fact that clays are powdery materials by nature and
also because the beads are susceptible to brittle crushing during
handling which causes disintegration of the beads into dust.
The dust problem has been considered to be largely inescapable.
The desire to avoid the problem has led to alternative designs which
avoid the use of beaded desiccants use of desiccated adhesive resins
which are adhered directly to the specially designed spacers and/or
by use of special spacer constructions whereby the spacer is formed
in part by a desiccated resin. These alternatives are expensive
both from the point of raw materials cost and from the point of
capital cost associated with the purchase of equipment needed to
implement the alternatives.
Thus, there is a need for a solution to the dusting problem which
still allows window manufacturers to use conventional IG unit designs
and manufacturing equipment while avoiding the dust problem associated
with conventional clay-bound beads.
There are similar needs for improved adsorbent beads to replace
conventional inorganic-bound adsorbent beads in other applications.
SUMMARY OF THE INVENTION
The invention provides a solution to the above problem by providing
polymer-bound adsorbent beads which are usable as a direct replacement
for conventional clay-bound beads in insulating glass unit manufacture.
In one aspect, the invention encompasses an insulating unit comprising
at least two panes of glass which are fixed in a spaced relationship,
at least one spacer member located between the panes about the edges
of the panes, the panes and the spacer member(s) defining at least
one closed interior space in the unit, and at least one compartment
located at the periphery of the interior space(s), the compartment(s)
being adapted to contain adsorbent beads such that the adsorbent
beads communicate with the interior space(s) to provide an adsorbing
function for the interior space(s) while the beads are retained
in and by the compartment(s), wherein the compartment(s) contains
adsorbent beads and at least a portion of the adsorbent beads are
polymer-bound adsorbent beads.
In another aspect, the invention comprises an improvement in the
method of manufacture of such insulating glass units wherein the
method comprises filling least one compartment with adsorbent beads,
the compartment(s) to be located at the periphery of an interior
space in the unit defined in part by at least two panes of glass
in the unit, the compartment(s) being adapted to contain adsorbent
beads such that the adsorbent beads communicate with the interior
space to provide an adsorbing function for the interior space while
the beads are retained in and by the compartment(s), and the improvement
comprising filling the compartment(s) with adsorbent beads wherein
at least a portion of the adsorbent beads are polymer-bound adsorbent
beads.
The polymer in the polymer-bound beads is preferably a thermoplastic
resin or a wax or a combination thereof.
The invention also encompasses the use of polymer-bound adsorbent
beads as a substitute for conventional desiccant beads in water
adsorption applications such as in bottle stoppers, sachets, blister
packaging, etc.
These and other aspects of the invention are described in detail
below.
DETAILED DESCRIPTION OF THE INVENTION
The invention encompasses providing polymer-bound adsorbent beads
which are usable as a direct replacement for conventional clay-bound
beads in insulating glass unit manufacture. The invention thus encompasses
improved insulating glass units containing such polymer-bound adsorbent
beads as well as improvements to methods for manufacturing insulating
glass units which involve the use of polymer-bound adsorbent beads.
The basic components of the polymer-bound beads of the invention
are a polymer binder component and an adsorbent component which
is bound by the polymer binder.
The polymer binder component may contain any of a variety of organic
polymers or combination of polymers. Preferably, the polymer binder
component comprises thermoplastic polymer(s). The polymer binder
component preferably comprises a thermoplastic resin or wax or combination
thereof. While the invention is not necessarily limited to any specific
polymer binder compositions, polyolefin resins and/or waxes are
preferred.
Preferred thermoplastic resins preferably have a melt flow index
of at least about 5 more preferably about 7-100 (ASTM D 1238-89
measured at 190.degree. C./2.16 kg or comparable conditions as specified).
In some instances, a thermoplastic resin having melt flow index
of less than 0.5 may be used at lower zeolite loadings (e.g. 10
to 30 wt. %) or in combination with waxes or higher melt flow index
resins. Alternatively, preferred thermoplastic resins have a weight
average molecular weight of about 1.times.10.sup.4 to 1.times.10.sup.8
more preferably about 5.times.10.sup.4 to 1.times.10.sup.7 most
preferably about 7.5.times.10.sup.4 to 2.times.10.sup.6. Waxes typically
have weight average molecular weights on the order of 1000 to 10000.
Preferred waxes have a weight average molecular weight of at least
about 2000 more preferably about 3000-5000. Preferably, the polymer
or combination of polymers is selected such that the mixture formed
in combination with the adsorbent component can be flowed or extruded
at a reasonable temperature (e.g. 50.degree.-450.degree. C., more
preferably 80.degree.-300.degree. C.) to form the desired beads.
The adsorbent component preferably includes conventional water-adsorbing
(desiccating) inorganic adsorbent such as zeolites, silica gels,
activated carbons, non-zeolite molecular sieves, etc. Zeolite desiccants
are generally preferred. Zeolite A, especially zeolite 3A is a most
preferred water-adsorbing material. If-desired, adsorbents designed
to adsorb low molecular weight organic compounds (e.g. zeolite 13X)
may be blended with the water-adsorbing material.
The polymer-bound adsorbents of the invention preferably contain
at least about 10 wt. % of the adsorbent component, more preferably
about 30-80 wt. %, most preferably about 40-75 wt. %. In some instances,
minor amounts of additional components may be included in the polymer-bound
adsorbents of the invention. For example, coloring agents, antistatic
agents, scents, lubricants, antioxidants, etc. may be included.
The beads of the invention can be made in a variety of sizes. Preferably,
the beads have a maximum dimension (particle size) of at least about
0.1 mm, more preferably at least about 0.5 mm. The upper limit on
the bead dimension is preferably about 15 mm. Beads which are useful
for conventional desiccation applications with typically have a
size of about 0.5-5 mm, more preferably 0.5-3 mm. The beads preferably
have an aspect ratio of about 2 or less, more preferably about 1.5
or less, most preferably about 1 to 1.2. The particle size is preferably
measured using an optical image analyzer (e.g. LECO 2001 Image Analyzer
from Leco Corp., Lakeview, Mich.), however other appropriate size
measurement techniques may also be used. The proper use of image
analyzer techniques for particle size measurement is well known
those skilled in the art.
The beads preferably have a compacted bulk density of about 0.6
g/ml, more preferably about 0.65-0.80 g/ml. The compacted bulk density
refers to the density measured after the beads have been vibrated
or tapped to a constant volume. The compacted bulk density should
not be confused with a tamped bulk density wherein a compacting
force is directly applied to the particles. The beads of the invention
may be made in a very narrow size distribution. Where increased
bulk density is desired, it is possible to use beads which have
a broader size distribution or a multimodal (e.g. bimodal) particle
size distribution.
The beads of the invention are generally very low dusting or dustless.
Dusting is measured using a RM 61-03 smoke density monitor from
SICK Optic Electronic, Eden Prarie, Minn. The measurement procedure
involves placing a 100 ml sample of the beads into the bottom of
a chamber and dislodging the dust from the sample using a fan. The
light transmission through the air containing the dislodged dust
is then measured to indicate the amount of dust generated. The dusting
value is inversely proportional to the % of light transmission.
A range of 100%-82.2% transmission is broken down into a 320 point
scale with zero representing 100% transmission (i.e. a dustless
material). The reported value is based on the average of 5 readings.
The beads of the invention preferably have a dusting value of 30
or less, more preferably 10 or less, most preferably 0-5.
The polymer-bound adsorbents of the invention may be made with
a variety of adsorption capacities and adsorption rates. In general,
the adsorption capacity will increase with increasing adsorbent
content in the beads. The adsorption rate generally increases with
increasing adsorbent content and decreasing bead size. Preferably,
the beads have a water adsorption capacity of at least about 3 wt.
% measured at 50% relate room temperature, more preferably about
5-20 wt. %, most preferably about 6-15 wt. %.
The beads of the invention may be made by a variety of methods.
Preferably, the beads are formed by a process wherein the polymer
and absorbent are compounded while the polymer is in a molten state.
The resulting mixture is then formed into beads. The bead manufacturing
process is preferably characterized by the absence of solvent in
the polymer-adsorbent mixture throughout the bead forming process.
The compounding is preferably performed using a mixer followed
by an extruder (e.g. a single or twin screw extruder) or similar
mixing device. The compounded mixture is then preferably formed
into beads using device such as a centrifugal extruder or an underwater
pelletizer. Such devices are commonly known in the art for formation
of thermoplastic polymer pellets. These methods are generally characterized
by passing of the molten mixture through an orifice and chopping
or cutting the mixture as it is passed through the orifice. The
size and shape of the resulting beads can be controlled by selection
of the appropriate temperature, extrusion pressure, die orifice
size, cutting speed, etc. as is well known in the art of plastic
pellet formation. Preferably, the beads of the invention are formed
using an underwater pelletizer such as those sold by Gala Industries,
Inc. Examples of centrifugal extruders are disclosed in U.S. Pat.
Nos. 3358323; 3424832; 3483281; 4408972 and 4050874. See
also generally Modern Plastics Encyclopedia published by McGraw
Hill. The use of these particle forming techniques enables the formation
of precise particle sizes with tailored particle size distribution.
Where the extruder/pelletizer design and operating parameters are
adequately controlled, it is possible to produce very narrow particle
size distributions.
The beads of the invention may be used in any system where conventional
inorganic-bound adsorbent beads are used. The uses for conventional
adsorbent beads generally involve confining the beads in a specific
location and then contacting the confined beads with a fluid (gas
or liquid) to be treated. In some uses, the fluid to be treated
is actively circulated (e.g. via use of a pump or fan or heater)
through the confined beads. In other instances, the fluid is largely
static (e.g., the interior of a package or electronic device or
insulated glass window) and the species (typically water) to be
adsorbed migrates to the beads (e.g., by diffusion).
The use of conventional inorganic-bound desiccant beads in insulating
glass units (windows) is illustrated by inter alia U.S. Pat. Nos.
4141186; 4520602; 4453855; 5253683; 5439716 and 5493821
the disclosures of which are incorporated herein by reference. Typically,
the insulating glass unit comprises at least two panes of glass
which are fixed in a spaced relationship, at least one spacer member
located between the panes about the edges of the panes, the panes
and the spacer member(s) defining at least one closed interior space
in the unit, and at least one compartment located at the periphery
of the interior space(s), the compartment(s) being adapted to contain
adsorbent beads such that the adsorbent beads communicate with the
interior space(s) to provide an adsorbing function for the interior
space(s) while the beads are retained in and by the compartment(s).
The polymer-bound adsorbent beads of the invention may be used as
all or part of the adsorbent beads contained in the spacer. Preferably
at least 50 wt. % of the adsorbent beads contained in the window
are the polymer-bound adsorbent beads of the invention.
The use of conventional inorganic-bound desiccant beads in refrigerant
drying for air conditioning/refrigeration is illustrated by inter
alia U.S. Pat. Nos. 4272264; 4436623; 4464261; 4619673;
5540348; and 5569316 the disclosures of which are incorporated
herein by reference. Typically, the conventional inorganic-bound
desiccant beads are placed in a canister and the refrigerant is
contacted with the conventional inorganic-bound desiccant beads
in the canister. The polymer-bound adsorbent beads of the invention
may be used as all or part of the adsorbent beads contained in the
canister. Preferably at least 50 wt. % of the adsorbent beads contained
in the canister are the polymer-bound adsorbent beads of the invention.
The use of conventional inorganic-bound desiccant beads in bottle
caps or stoppers, in sachets and in canisters is illustrated by
inter alia U.S. Pat. Nos. 3722188; 4957521; 5390475; and 4093105
the disclosures of which are incorporated herein by reference. In
bottle stoppers or bottle caps, the inorganic-bound desiccant beads
are typically placed in a compartment in the cap and are held in
place by a porous barrier which allows the desiccant beads to communicate
with the interior of the bottle. In sachets and canisters, the inorganic-bound
desiccant beads are typically placed in the sachet or canister which
is then closed to hold the beads in place. The sachet or canister
have one or more porous areas which allow the desiccant beads to
communicate with the space exterior to the sachet or canister where
the sachet or canister is located (e.g. the interior of a package
or an electronic device). The polymer-bound adsorbent beads of the
invention may be used as all or part of the adsorbent beads contained
in the sachet or canister. Preferably at least 50 wt. % of the adsorbent
beads contained in the sachet or canister are the polymer-bound
adsorbent beads of the invention.
The use of conventional inorganic-bound desiccant beads in blister
packaging is illustrated by inter alia U.S. Pat. Nos. 3211503;
3343897 and 4753352 the disclosures of which are incorporated
herein by reference. Typically, this use involves retaining one
or more conventional inorganic-bound desiccant beads in a compartment
of the package which communicates via a porous barrier or narrow
passage with the compartment(s) of the package to be desiccated.
The polymer-bound adsorbent beads of the invention may be used as
all or part of the adsorbent beads contained in the desiccant compartment.
Preferably at least 50 wt. % of the adsorbent beads contained in
the desiccant compartment are the polymer-bound adsorbent beads
of the invention.
The invention is further illustrated by the following examples.
The invention is not limited to the specific details of the examples.
EXAMPLE 1
50 parts by weight polyethylene wax (Epolene.RTM. N-14 from Eastman
Chemical) were combined with 45 parts by weight of 3A (Sylosiv.RTM.
A3 from Grace Davison) zeolite particles and 5 parts by weight of
zeolite 13X (Sylosiv.RTM. A10 from Grace Davison) at elevated temperature.
The resulting mixture was then fed to a centrifugal extruder and
the extruder was adjusted to yield beads having a particle size
of about 0.5-1.0 mm.
EXAMPLE 2
50 parts by weight low density polyethylene resin (PE1017 from
Chevron Chemical) having a melt index of 7 were combined with 45
parts by weight of 3A (Sylosiv.RTM. A3 from Grace Davison) zeolite
particles and 5 parts by weight of zeolite 13X (Sylosiv.RTM. A10
from Grace Davison) in a twin screw co-rotating extruder. The resulting
mixture was then fed to an underwater pelletizer which was adjusted
to yield beads having a particle size of about 2-3 mm.
EXAMPLE 3
17.5 parts by weight low density polyethylene resin (PE1017 from
Chevron Chemical) having a melt index of 7 and 17.5 parts by weight
polyethylene wax (Epolene.RTM. N-14 from Eastman Chemical) were
combined with 58.5 parts by weight of 3A (Sylosiv.RTM. A3 from Grace
Davison) zeolite particles and 6.5 parts by weight of zeolite 13X
(Sylosiv.RTM. A10 from Grace Davison) in a twin screw co-rotating
extruder. The resulting mixture was then fed to an underwater pelletizer
which was adjusted to yield beads having a particle size of about
2-3 mm.
The resulting beads had a water adsorption capacity of about 13
wt. % when exposed to 50% relative humidity at room temperature.
EXAMPLE 4
12.5 parts by weight low density polyethylene resin (PE1017 from
Chevron Chemical) having a melt index of 7 and 12.5 parts by weight
polyethylene wax (Epolene.RTM. N-14 from Eastman Chemical) were
combined with 67.5 parts by weight of 3A (Sylosiv.RTM. A3 from Grace
Davison) zeolite particles and 7.5 parts by weight of zeolite 13X
(Sylosiv.RTM. A10 from Grace Davison) in a twin screw co-rotating
extruder. The resulting mixture was then fed to an underwater pelletizer
which was adjusted to yield beads having a particle size of about
2-3 mm.
The resulting beads had a water adsorption capacity of about 15
wt. % when exposed to 50% relative humidity at room temperature.
EXAMPLE 5
20.8 parts by weight polyethylene wax (Epolene.RTM. N-14 from Eastman
Chemical) were combined with 64.4 parts by weight of 3A (Sylosiv.RTM.
A3 from Grace Davison) zeolite particles to form an initial mixture.
The resulting mixture was then combined with 14.8 parts by weight
low density polyethylene resin (PE1017 from Chevron Chemical) having
a melt index of 7 in a twin screw co-rotating extruder. The resulting
mixture was then fed to an underwater pelletizer which was adjusted
to yield beads having a particle size of about 2-3 mm.
The beads had a compacted bulk density of about 0.78 g/ml and water
adsorption capacity in excess of 7.3 wt. % when exposed to 50% relative
humidity at room temperature. The beads had a dusting value of 1.
EXAMPLE 6
Three portions of the beads produced in example 5 were used as
a feed for another underwater pelletizer having a finer die orifice
sizes. This resulted in three samples of beads having particle size
0.25-0.45 mm, 0.5-0.75 mm and 0.8-1.0 mm respectively. The beads
respectively had water adsorption capacity of 6.96 wt. %, 8.09 wt.
% and 8.33 wt. % when exposed to 50% relative humidity at room temperature.
The beads respectively had compacted bulk density of about 0.70
g/ml, 0.68 g/ml and 0.68 g/ml. All three samples had a dusting value
of zero.
EXAMPLE 7
24 parts by weight polyolefin resin (PE-2075 from Rexene Corp.)
having a melt index of 70 were combined with 68 parts by weight
of 3A (Sylosiv.RTM. A3 from Grace Davison) zeolite particles and
8 parts by weight of zeolite 13X (Sylosiv.RTM. A10 from Grace Davison)
in a twin screw co-rotating extruder. The resulting mixture was
then fed to an underwater pelletizer which was adjusted to yield
beads having a particle size of about 2-3 mm. The resulting beads
had a water adsorption capacity in excess of 13.6 wt. % when exposed
to 50% relative humidity at room temperature. |