Information
-
Patent Grant
-
6730165
-
Patent Number
6,730,165
-
Date Filed
Monday, April 1, 200222 years ago
-
Date Issued
Tuesday, May 4, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Primeaux; Russel O.
- Kean, Miller, Hawthorne, D'Armond, McCowan & Jarman LLP
-
CPC
-
US Classifications
Field of Search
US
- 118 641
- 118 58
- 118 60
- 118 67
- 118 68
- 118 69
- 118 602
- 427 428
- 427 3741
-
International Classifications
-
Abstract
A device for impregnating a paper web with a molten polymer to produce a paper with improved resistance to oil and grease are provided. The device includes, as part of an on-machine process, an ordinary paper web composed of cellulose or synthetic fibers, a polymer applicator, a hot reel, and a winding reel. The web, which is created through a series of processes located upstream of the subject invention, first encounters the polymer applicator, which deposits a quantity of molten polymer onto the surface of the web. The web is next transferred to a hot reel, which maintains the temperature of the molten polymer above its melting point and thereby facilitates wicking of the molten polymer into the web. After the web passes the hot reel, it is wound onto a winding reel, where additional wicking occurs until the molten polymer cools to a temperature below its melting point. The invention further includes a method for impregnating a web of fibers and a polymer impregnated paper with improved resistance to oil and grease, produced by the described method.
Description
CROSS-REFERENCE TO RELATED APPLICATION
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates, generally, to the manufacturing of polymer impregnated specialty papers, and particularly to a method and device for impregnating a cellulose web with a molten polymer.
2. Description of Related Art
The growth of the fast food industry over the past several decades has been matched by an increase in the demand for paper products that are associated with fast food items, such as beverage cups, coffee filters, paper wrappers, and paper food containers. These paper products are fashioned from specially engineered papers (“specialty papers”), which are produced to suit both the commercial needs of fast food vendors as well as the domestic needs of families in their homes. Among these specialty papers, food wrappers comprise a generous portion of the food paper market.
Food wrappers are traditionally made from waxed paper, which may be imprinted with the name or logo of the vendor whose product is being sold. Waxed paper is commonly used to wrap various food items, including, among others, sandwiches, tacos, gyros, french fries, biscuits, onion rings, popcorn, and chicken tenders. Unfortunately, the ability of most waxed paper food wrappers to resist grease or oil is marginal at best, especially when the grease or oil is hot. In fact, if grease or oil, whether hot or cold, is allowed to remain in contact with food grade waxed paper for any substantial length of time, the grease or oil will penetrate the paper and come into contact with the hands, clothing, or surroundings of the user.
Therefore, there exists a need for an improved paper food wrapper that has improved resistance to oil and grease emanating from the food that is contained in the wrapper, while at the same time retaining flexibility and the ability to receive printed material on its surface. More importantly, the improved paper food wrapper needs to be inexpensive and easy to manufacture. In order to keep production costs at a minimum, the paper from which the improved food wrappers are generated should be manufactured as part of a continuous on-machine process, rather than a batch process, which consumes more time and resources.
Preferably, the device and process for making an improved food wrapper should be located at the end of a traditional paper manufacturing process as an additional and optional step in the specialty paper production process. The total process should flow as a single manufacturing operation without interruption from the time the paper web is formed from pulp fibers to the time the paper web encounters the finishing process that imparts superior oil and grease resistant qualities to the web. The process should not require the manufacturer to stop the machine before the paper web completes the finishing process. Moreover, the device should be quick and simple to operate, should eliminate unnecessary steps, and should not require the manufacturer to dedicate substantial time or resources to the production effort.
In the art of manufacturing specialty papers, a cellulose or synthetic paper web may be treated with various compounds to improve certain characteristics of the paper that is treated, including strength, durability, printability, and resistance to water, oil, grease, and ultraviolet radiation. One such compound that can be applied to paper is paraffin wax.
Waxed paper is produced in a number of ways, including the application of a paraffin film to a paper web using a mechanical roller. The paper produced by this particular method is a wax “coated” paper. The term “coated” is used to describe this process because the paraffin film is in contact with only one side of the paper web and the depth of penetration of the wax into the paper fibers is only superficial.
Polymers that are capable of withstanding higher temperatures than paraffin have also been applied to a cellulose paper web using a method known as extrusion. In the extrusion method, a polymer is heated to a semi-solid state and then pushed through a die to form a semi-solid film, which is then fed into a nip where the film is pressed against a paper web. The features of the coated paper generated using this method are similar to those of wax coated paper, although the polymer coated paper may have better resistance to grease penetration.
While papers treated using the extrusion method may have certain advantages over wax coated papers, they still have inferior resistance to oil and grease due to the fact that the extruded material does not permeate throughout the paper, but adheres to only one side. Therefore, if the untreated side is exposed to grease or other liquid, the cellulose fibers will be weakened and the structural integrity of the paper product will be compromised. While extruded layers could be applied to both sides of a paper web, the process would be expensive and difficult to achieve at a commercial level. Moreover, introducing an additional layer would add unwanted weight, rigidity, and bulk to a paper product that is intended to be light, flexible and thin in order to conform to the shape of the food around which it is wrapped. Finally, even if the grease, oil, or other liquid contact the side of the paper containing the extruded material, the integrity of the extruded barrier may be compromised by the breaking of the film that commonly occurs when such paper is creased or folded.
The extrusion method is also inferior because it requires the use of sophisticated precision equipment. The material that is to be extruded must be heated to a temperature that is high enough to transform the material from a solid state to a pliable, semi-solid state. However, the temperature of the extruder should not be so high as to make the material a flowable liquid, which would be incapable of forming the film that is ultimately applied to the paper web. In addition, once the optimum temperature is achieved, the semi-solid material must be pushed through a die at a rate of speed sufficient to match the rate of speed at which the extruded film is pressed against the web. In practice, the extrusion method has proven difficult to implement in an on-machine process, where the web encounters the extruded film at a high rate of speed.
Another method of treating paper in order to improve grease resistance and durability is the impregnation method. In this method, a molten liquid compound is applied to a cellulose or synthetic web. The molten compound permeates the web and adheres to the individual cellulose or synthetic fibers. The paper produced by this method is superior to papers with wax film or extruded layers, which merely bond to the surface of the web and do not coat the fibers beneath the surface of the paper.
The impregnation method has been used exclusively in connection with the application of resinous compounds or aqueous polymeric dispersions (formed when a polymer is mixed with water). The disadvantage of using these resinous or aqueous compounds to impregnate a paper web is that each compound requires a subsequent processing step before the paper product may be stored on a winding reel. Resinous compounds must be allowed to cure over a period of time. The curing process may also involve the application of heat. After an aqueous polymeric dispersion is applied to a paper web, the product must undergo a drying period, in which the water must be evaporated away from the polymeric compound. This evaporation usually occurs in a drying step. Both of these secondary processing steps consume time and resources, and consequently reduce output volume and increase the price of the finished product.
What is needed is a polymer impregnation process and device for carrying out the process that overcome the shortfalls of the processes and devices that are currently known in the art.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a device for impregnating a cellulose paper web with a molten polymer.
Another object of the present invention is to provide a device for impregnating a cellulose paper web with a molten polymer that produces a polymer impregnated paper with superior resistance to grease.
Another object of the present invention is to provide a device for impregnating a cellulose paper web with a molten polymer that can be efficiently utilized as an on-machine process, rather than as a batch process.
Another object of the present invention is to provide a device for impregnating a cellulose paper web with a molten polymer that eliminates the need for a subsequent drying or curing step.
Another object of the present invention is to provide an on-machine method for impregnating a cellulose paper web with a molten polymer.
Another object of the present invention is to provide a polymer impregnated paper obtained by the method described hereinafter.
SUMMARY OF THE INVENTION
A device and method for impregnating a paper web with a molten polymer are provided. The device and method utilize a scientific phenomenon known as “wicking” to penetrate or “impregnate” a web of cellulose fibers with a polymer that has been heated to a molten state. Wicking, which is the process by which a liquid permeates a fibrous web and adheres to the individual fibers, can vary in degree, depending on the temperature, viscosity, and surface tension of the penetrating liquid. As a general rule, the longer the penetrating liquid remains above its melting point, the greater the degree of wicking that occurs. Once the liquid cools to a temperature below its melting point, the liquid begins to solidify and wicking ceases. Of course, some substances require curing or drying beyond the mere solidification of the substance, but these steps are unnecessary in the present invention.
The device includes, as part of an on-machine process, an ordinary paper web composed of cellulose or synthetic fibers (along with any additives such as clays, dyes, fillers and other substances common in the art), a polymer applicator, a hot reel, and a winding reel. The web, which is created through a series of processes located upstream of the subject invention, first passes over the polymer applicator, where an applicator roller, part of which is immersed in a molten polymer bath, deposits a quantity of molten polymer onto the surface of the web. After the molten polymer has been applied by the polymer applicator, the web passes an optional distributing means, which evenly distributes the molten polymer onto the surface of the web and removes any excess polymer.
The web is next transferred to a hot reel, which is a metal drum heated to a temperature sufficient to maintain the molten polymer above its melting point. Because the polymer is maintained in liquid state while being applied to the web and during the time for which it is in contact with the hot reel, significant wicking of the polymer into the web occurs.
After the web passes the hot reel, it is transferred to a winding reel, where the paper web is wound and stored for further processing or shipment. For a period of time after the web is transferred to the winding reel, the polymer remains in a molten state and will continue to wick throughout the web. Once the polymer cools below its melting point, wicking will cease and the process is complete.
Depending on the temperatures of the various process components, the user can select the degree of wicking preferred. A higher temperature will maintain the temperature of the polymer above its melting point for a longer period of time and thereby produce a paper with fibers that are completely permeated and coated with polymer. A lower temperature will produce a paper with fibers that are minimally coated or superficially coated to a minimal depth.
An alternative embodiment of the invention includes replacing the hot reel with a cold reel or cold rolls to reduce the temperature of the molten polymer after application and to control the degree of wicking.
Another embodiment of the invention includes varying the respective velocities of the applicator roller and the web in order to increase or decrease the amount of polymer that is deposited on the web.
Another embodiment of the invention includes the addition of guide rollers to increase or decrease the amount of surface contact that the web has with the applicator roller and the hot reel.
Another embodiment of the invention includes a polymer applicator with a polymer recirculation means.
Another embodiment of the invention includes a polymer applicator that is capable of simultaneously depositing molten polymer onto both sides of the web.
An advantage of the present invention is that the device and process produce a polymer impregnated paper with superior resistance to oil and grease.
A further advantage of the present invention is that the web may be impregnated as part of an on-machine process, rather than a batch process.
A further advantage is that the invention eliminates the subsequent curing or drying steps required for resinous compounds or aqueous polymeric dispersions.
These and other objects, advantages, and features of this invention will be apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross-sectional view of a preferred embodiment of the polymer impregnation device and process.
FIG. 2
is a plan view of a preferred embodiment of the polymer impregnation device and process.
FIG. 3
is a perspective view of a preferred embodiment of the polymer impregnation device and process with the details of the polymer applicator assembly removed.
DETAILED DESCRIPTION OF THE INVENTION
With reference to
FIGS. 1
,
2
, and
3
, a preferred embodiment of the polymer impregnation device
1
will now be described. Device
1
includes as part of an on-machine process an ordinary paper web
10
composed of cellulose or synthetic fibers (including any additives, such as clays, dyes, fillers, and other substances common in the art), polymer applicator
15
, hot reel
23
, and winding reel
26
. Web
10
, which has a first side
30
and second side
31
, is created through a series of traditional paper manufacturing processes
55
located upstream of the subject invention. After web
10
has been generated, first guide roller
11
and second guide roller
13
, which are rotatably mounted on first guide roller axis
12
and second guide roller axis
14
, respectively, may be optionally used to guide web
10
with web velocity
34
to polymer applicator
15
.
Referring to
FIG. 1
, polymer applicator
15
comprises molten polymer
18
, polymer trough
19
, and applicator roller
16
. Molten polymer
18
is any synthetic, straight-chained, saturated hydrocarbon capable of being in molten form, but which exists in a solid state at room temperature (approximately 60-80 degrees Farenheit). In one preferred embodiment, web
10
is impregnated with molten C33, which is a paraffin-free polymer with a molecular chain length of 33 that is available commercially as Clariant Licolub XL 165 KB.
One of the advantages of using C33 and like materials is that the polymer, once applied, requires no further curing or drying step, unlike resinous compounds or aqueous polymeric dispersions. Resinous compounds are required to be cured using heat or other means. Similarly, with aqueous polymeric dispersions, the water in which the polymer is dissolved must be evaporated off of the web. Therefore, a process that uses either a resinous compound or an aqueous polymeric dispersion requires a subsequent curing or drying step after the polymer is applied to web
10
.
The present invention requires no such subsequent step. Once the polymer cools to a temperature below its melting point, the polymer is set on web
10
and the manufacturing process is at an end. In this respect, the present invention greatly enhances the efficiency of the specialty paper manufacturing process by conserving time and resources.
Molten polymer
18
is temporarily contained in polymer trough
19
with heating means
41
for maintaining the temperature of molten polymer
18
above its melting point. In
FIG. 1
, heating means
41
is shown as a steam jacket, which is a hollow cavity in the walls of polymer trough
19
adapted for receiving an envelope of steam. However, heating means
41
may also include a coil heater, electrical wraps, steam tracing, or other means suitable for maintaining molten polymer
18
above its melting point.
Polymer trough
19
may optionally be equipped with polymer recirculation means
32
, comprising overflow weir
42
for allowing molten polymer
18
to escape polymer trough
19
, polymer capture basin
44
, and return means
43
for returning molten polymer
18
from polymer capture basin
44
to polymer trough
19
. Polymer recirculation means
32
may also comprise heating means
41
in order to maintain the temperature of molten polymer
18
above its melting point. In a preferred embodiment, return means is a gravity downleg
51
that drains molten polymer
18
from polymer capture basin
44
into a day tank (not shown), and a submersible pump (also not shown) in the day tank that returns molten polymer
18
to polymer trough
19
through return hose
52
, as depicted in FIG.
2
. In this manner, polymer recirculation means
32
as described above helps maintain the purity of molten polymer
18
and reduces the amount of polymer that is wasted.
Applicator roller
16
is rotatably suspended between web
10
and molten polymer
18
on applicator roller axis
17
, which is further attached to applicator roller spindle
31
and mounting plate
30
. Applicator roller
16
has a tangential velocity
33
, which may be imparted by applicator roller motor
39
through belt
53
attached to pulley
54
. Tangential velocity
33
may be identical to or different from web velocity
34
. As will be more readily understood from the following paragraphs, the advantage of giving applicator roller
16
a tangential velocity
33
different from web velocity
34
is that the amount of molten polymer
18
deposited onto web
10
can be increased or decreased to suit the needs of the manufacturer.
Applicator roller
16
further comprises a polymer contact region
40
and a web contact region
29
. Polymer contact region
40
of applicator roller
16
is at least partially immersed in molten polymer
18
. Web contact region
29
is at least partially in contact with web
10
.
The surface area of web contact region
40
may be increased or decreased by changing the position of optional second guide roller
13
with respect to applicator roller
16
. For example, in the embodiment shown in
FIG. 1
, lowering second guide roller
13
with respect to applicator roller
16
will increase the angle at which web
10
approaches applicator roller
16
and thereby cause a greater portion of web
10
to be in contact with applicator roller
16
at a given time. By increasing or decreasing the surface area of web contact region
40
, the user can increase or decrease the amount of molten polymer
18
applied to web
10
, which ultimately affects the extent of wicking of molten polymer
18
into web
10
.
The amount of molten polymer
18
applied to web
10
can also be increased or decreased by increasing or decreasing the tension present in web
10
at applicator roller
16
. A higher degree of tension will cause more molten polymer
18
to be forced into web
10
, while a lesser degree of tension will cause web
10
to reject more molten polymer
18
.
The function of polymer applicator
15
can be readily understood from the following description. As applicator roller
16
rotates with tangential velocity
33
, the surface tension and adhesive qualities of molten polymer
18
permit molten polymer
18
to be transferred along the surface of applicator roller
16
from polymer contact region
40
to web contact region
29
. When molten polymer
18
on the surface of applicator roller
16
reaches web contact region
29
, a quantity of molten polymer
18
is deposited onto the surface of web
10
moving at web velocity
34
. Once molten polymer
18
contacts at least one of first side
30
or second side
31
of web
10
, molten polymer
18
begins to wick throughout web
10
and coat the cellulose or synthetic fibers.
In a preferred embodiment, tangential velocity
33
of applicator roller
16
is less than one half that of web velocity
34
, such that frictional resistance is generated between web
10
and applicator roller
16
in order to create a wiping effect. This wiping effect allows a greater amount of molten polymer
18
to be deposited onto web
10
, which is moving at a greater velocity than applicator roller
16
, than in the situation where web velocity
34
matches tangential velocity
33
. However, the present invention contemplates the scenario in which web velocity
34
equals tangential velocity
33
as well as the scenarios in which tangential velocity
33
is greater or lesser than web velocity
34
.
In an alternative embodiment, polymer applicator
15
can be modified to deposit molten polymer
18
onto both sides of web
10
. Those skilled in the art will realize that this double deposition can be achieved in a number of ways, including the addition of a second polymer trough and a second applicator roller suspended in a manner such that the second applicator roller deposits molten polymer
18
onto the side of web
10
that is opposite from applicator roller
16
and polymer trough
19
. Another way to accomplish a double deposition of molten polymer
18
would be to create a duplicate of polymer applicator
15
and position the duplicate polymer applicator in a manner such that the duplicate polymer applicator deposits molten polymer
18
on the opposite side of web
10
from that treated by polymer applicator
15
. This latter application method could be accomplished using a series of guide rollers after web
10
has passed polymer applicator
15
in order to reorient web
10
and position the untreated side of web
10
such that it is amenable to treatment by the duplicate polymer applicator.
After molten polymer
18
has been applied by polymer applicator
16
, web
10
passes optional distributing means
20
, which evenly distributes molten polymer
10
onto the surface of web
10
and removes any excess polymer. In the preferred embodiment as shown in
FIG. 1
, distributing means
20
is a doctoring blade. However, distributing means may also be an air knife, a plurality of scraping knives or any other means suitable for the removal of excess polymer.
After molten polymer
18
has been applied to web
10
and after molten polymer
18
has been evenly distributed by optional distributing means
20
, web
10
encounters hot reel
23
, which is rotatably mounted on axis
25
. Hot reel
23
is heated using hot reel heating means
50
to a temperature above the melting point of molten polymer
18
, so as to maintain molten polymer
18
above its melting point and thereby encourage wicking of molten polymer
18
into web
10
.
In the preferred embodiment shown in
FIGS. 1
,
2
, and
3
, hot reel
23
is a polished metal drum heated to a temperature above the melting point of molten polymer
18
. Hot reel heating means
50
is shown as a steam injection port for the introduction of steam into the cavity of hot reel
23
. A siphon (not shown) may also be located near the steam injection port to facilitate the removal of condensate from the interior walls of hot reel
23
, thereby preventing hot reel
23
from filling with water. Hot reel heating means
50
may also include adaptations to hot reel
23
to allow it to be heated by blowing hot air, filling with hot water, or any other means suitable for delivering heat to hot reel
23
.
If C33 is used with device
1
, then the temperature of hot reel
23
should be at least 160 degrees Fahrenheit and preferably 200 degrees Fahrenheit. If a polymer other than C33 is used with device
1
, then the temperature of hot reel
23
should be above the melting point of the polymer selected. As a general principle, the higher the temperature of hot reel
23
, the longer molten polymer
18
will remain in a molten state and the greater the extent of wicking of molten polymer
18
into web
10
. Therefore, by controlling the temperature of hot reel
23
, the degree of wicking can be increased or decreased.
The amount of wicking that occurs at hot reel
23
can be manipulated by raising or lowering the temperature of molten polymer
18
while molten polymer
18
is in polymer trough
19
. A higher temperature at polymer trough
19
will maintain the temperature of the polymer above its melting point for a longer period of time after application and thereby increase the amount of wicking that occurs upon contact with hot reel
23
. This embodiment with a higher temperature at polymer trough
19
produces a paper with cellulose or synthetic fibers that are more completely permeated with molten polymer
18
. A lower temperature at polymer trough
19
will result in the temperature of molten polymer
18
being closer to its melting point and thereby reduce the amount of wicking that occurs before web
10
encounters hot reel
23
. This embodiment with a lower temperature at polymer trough
19
will produce a paper with cellulose or synthetic fibers that are permeated to a minimal depth.
The amount of wicking that occurs at hot reel
23
can also be controlled by varying the amount of surface contact that web
10
has with hot reel
23
. The longer web
10
remains in contact with hot reel
23
, the longer molten polymer
18
remains above its melting point and the greater the amount of wicking of molten polymer
18
into web
10
.
In this regard, hot reel
23
further comprises a hot reel contact region
24
, the surface area of which can be increased or decreased depending on the position of hot reel
23
relative to polymer applicator
15
and winding reel
26
. The surface area of hot reel contact region
24
can also be increased or decreased by the optional use of third guide roller
21
rotatably mounted on third guide roller axis
22
as depicted in
FIGS. 1
,
2
, and
3
. By changing the position of third guide roller
21
with respect to hot reel
23
, the surface area of hot reel contact region
24
can be increased or decreased.
After web
10
passes hot reel
23
, it is transferred to winding reel
26
, which is rotatably mounted on winding reel axis
45
and comprises winding core
27
and optional winding reel guides
28
. Web
10
winds about winding core
27
until winding reel
26
is full. During the time that web
10
is winding onto winding reel
26
, molten polymer
18
continues to wick into web
10
until the temperature of molten polymer
18
drops below its melting point. If the temperature of molten polymer
18
has not dropped below its melting point by the time winding reel
26
is full, winding reel
26
may be allowed to sit until the molten polymer
18
cools below its melting point and wicking has actually or substantially ceased.
In a preferred embodiment, winding reel axis
45
is journaled on rails
46
between forward rail stops
47
and retractable rail stops
48
. Once the storage capacity of winding reel
26
becomes exhausted, retractable rail stops
48
can be retracted and winding reel
26
can be rolled back against aft rail stops
49
to allow a second winding reel
26
to be positioned to receive web
10
from hot reel
23
. While winding reel
26
is being rolled back, winding reel axis
45
remains properly positioned between rails
46
due to winding reel guides
28
. Winding reel
26
resting against aft rail stops
49
can then be processed on another device, transported to storage, or loaded for shipping.
In an alternative embodiment of device
1
, hot reel
23
is replaced with a cold reel or multiple cold rolls to limit the extent of wicking of molten polymer
18
into web
10
. After molten polymer
18
has been applied by polymer applicator
15
and after wicking has commenced, web
10
encounters the cold reel (or cold rolls) with a temperature cooler than the melting point of molten polymer
18
. Contact with a cold surface(s) in this manner cools or solidifies molten polymer
18
and thereby either retards or ceases further wicking of molten polymer
18
into web
10
. The temperature of the cold reel or cold rolls can be varied in order to achieve the degree of wicking desired by user or required of the resultant paper product.
In the embodiment described above, the cold reel or cold rolls are cooled by a cooling means (not shown). Cooling means may include filling the cold reel with chilled air, chilled water, or any other means suitable for lowering the temperature of molten polymer
18
.
Another alternative embodiment of device
1
involves the optional use of cold air blowers (not shown) in place of or in conjunction with hot reel
23
(or cold reel or cold rolls in the alternative). In this manner, the application of cold air to web
10
will reduce the temperature of molten polymer
18
and thereby limit the degree of wicking.
The present invention also contemplates a method for making a polymer impregnated paper using the device described above. The method involves the steps of applying molten polymer
18
to at least one side of web
10
in a manner such that molten polymer
18
wicks into web
10
, rolling web
10
across hot reel
23
to maintain molten polymer
18
above its melting point, winding web
10
onto winding reel
26
, and allowing molten polymer
18
to further wick into web
10
while cooling to a temperature below its melting point.
In a preferred embodiment, molten polymer
18
is applied using polymer applicator
15
. The process includes the steps of containing molten polymer
18
in polymer trough
19
, providing applicator roller
16
with polymer contact region
40
and web contact region
29
, suspending applicator roller
16
in a manner such that polymer contact region
40
contacts molten polymer
18
contained in polymer trough
19
and web contact region
29
contacts web
10
, and rotating applicator roller
16
such that molten polymer
18
adheres to applicator roller
16
before being deposited onto web
10
so as to commence wicking.
The present invention also includes a polymer impregnated paper manufactured by the process described in the above paragraphs. The resultant paper has an improved and superior resistance to oil and grease due to the permeation of molten polymer
18
through the cellulose or synthetic fibers. The greater the depth of penetration of molten polymer
18
into web
10
, the greater the resistance that the polymer impregnated paper will have to the migration of grease or oil emanating from food contained within the paper. Additionally, the polymer can be selected so that a specific melting point can be achieved. This selectivity is not available with paraffin wax.
There are, of course, other alternate embodiments that are obvious from the foregoing descriptions of the invention, which are intended to be included within the scope of the invention, as defined by the following claims.
Claims
- 1. A device for impregnating a web of fibers, including cellulose or synthetic fibers and any additives thereto, said web having a first side, and a second side, said device comprising:(1) a polymer applicator, said polymer applicator being in contact with said first side, said polymer applicator further comprising: (a) a molten polymer which is substantially non-resinous and non-aqueous, said polymer existing in a solid state at room temperature; (b) an applicator roller for depositing said molten polymer onto said web, said applicator roller being capable of having a tangential velocity; (c) a polymer trough, said polymer trough disposed below said applicator roller and capable of maintaining said molten polymer above said melting point; (2) a hot reel for maintaining said molten polymer above its melting point after application of said molten polymer onto said web, said hot reel being in contact with at least one of said first side or said second side; and (3) a winding reel, said winding reel being positioned to receive said web from said hot reel and store said web while said molten polymer cools on said web to a temperature below said melting point.
- 2. The device for impregnating a web of fibers described in claim 1, said device further comprising a distributing means for evenly distributing said molten polymer on said web and for removing excess molten polymer, said distributing means being located between said applicator roller and said hot reel.
- 3. The device of claim 2, wherein said distributing means is selected from the group consisting of a doctoring blade, an air knife, or a plurality of scraping knives.
- 4. The device for impregnating a web of fibers as described in claim 1, wherein said polymer trough further comprises a polymer recirculation means.
- 5. The device for impregnating a web of fibers as described in claim 1, wherein said polymer applicator further comprises a second applicator roller, said second applicator roller being disposed in a manner such that said second applicator roller contacts said second side of said web and applies said molten polymer to said second side of said web while said applicator roller applies said molten polymer to said first side of said web.
- 6. The device for impregnating a web of fibers as described in claim 1, wherein it is capable of moving said web at a velocity greater than said tangential velocity of said applicator roller.
- 7. The device for impregnating a web of fibers as described in claim 1, wherein said web is one received from a traditional paper manufacturing process and is capable of flowing uninterrupted to said device from said traditional paper manufacturing process.
- 8. A device for impregnating a web of fibers, including cellulose or synthetic fibers and any additives thereto, said web having a first side, and a second side, said device comprising:(1) a polymer applicator, said polymer applicator being in contact with said first side or said second side, said polymer applicator further comprising: (a) a molten polymer which is substantially non-resinous and non-aqueous, said polymer being a solid state at room temperature; (b) an applicator roller for depositing said molten polymer onto said web, said applicator roller being capable of having a tangential velocity; (c) a polymer trough, said polymer trough disposed below said applicator roller and capable of maintaining said molten polymer above said melting point; (2) a cooling means for cooling said molten polymer thereby being capable of limiting any wicking of said molten polymer when said device is in use, said cooling means being in contact with at least one of said first side or said second side; and (3) a winding reel, said winding reel being positioned to receive said web from said cooling means.
- 9. The device for impregnating a web of fibers as described in claim 8, wherein said cooling means is selected from the group consisting of a cold reel, cold rolls, and cold air blowers.
- 10. A method for impregnating a web of fibers, including cellulose or synthetic fibers and any additives thereto, said web having a first side and a second side and a web velocity, said method comprising the steps of:(1) applying a molten polymer to said first side of said web, which polymer is substantially non-resinous and non-aqueous and which polymer is a solid at about room temperature; (2) rolling said web across a hot reel such that said molten polymer remains in the molten state such that said molten polymer at least partially penetrates said web and wicking of said molten polymer into said web occurs; (3) winding said at least partially penetrated web onto a winding reel; and (4) allowing said molten polymer to cool to below its melting point and to further wick into said web while cooling.
- 11. The method for impregnating a web of fibers described in claim 10, step 1 of which further comprises the steps of:(1) containing said molten polymer in a polymer trough; (2) providing an applicator roller, said applicator roller having a polymer contact region, a web contact region, and a tangential velocity; (3) suspending said applicator roller in a manner such that said polymer contact region contacts said molten polymer contained in said polymer trough and said web contact region contacts said web; and (4) rotating said applicator roller such that said molten polymer adheres to said applicator roller before being deposited onto said web.
- 12. The method for impregnating a web of fibers described in claim 10, wherein said method further comprises the steps of receiving said web from a traditional paper manufacturing process and treating said web immediately thereafter using said method.
- 13. The method for impregnating a web of fibers described in claim 11, wherein said method further comprises the steps of receiving said web from a traditional paper manufacturing process and treating said web immediately thereafter using said method.
- 14. The method for impregnating a web of fibers described in claim 10, said method further comprising the step of distributing said molten polymer on said web and removing excess molten polymer from said web with a distributing means, said distributing means being located between said applicator roller and said hot reel.
- 15. The method for impregnating a web of fibers described in claim 11, said method further comprising the step of distributing said molten polymer on said web and removing excess molten polymer from said web with a distributing means, said distributing means being located between said applicator roller and said hot reel.
- 16. The method of claim 14, wherein said distributing means is selected from the group consisting of a doctoring blade, an air knife, or a plurality of scraping knives.
- 17. The method of claim 15, wherein said distributing means is selected from the group consisting of a doctoring blade, an air knife, or a plurality of scraping knives.
- 18. The method for impregnating a web of fibers as described in claim 11, wherein said polymer trough further comprises a polymer recirculation means.
- 19. The method for impregnating a web of fibers as described in claim 11, wherein step (2) of said method further comprises the steps of providing a second applicator roller, said second applicator roller being disposed in a manner such that said second applicator roller contacts said second side of said web, and applying said molten polymer to said second side of said web while said applicator roller applies said molten polymer to said first side of said web.
- 20. The method for impregnating a web of cellulose fibers as described in claim 11, wherein said web velocity differs from said tangential velocity of said applicator roller.
- 21. A method for impregnating a web of fibers, including cellulose or synthetic fibers and any additive thereto, said web having a first side and a second side and a web velocity, said method comprising the steps of:(1) applying a molten polymer to said first side or said second side of said web such that said molten polymer at least partially penetrates said web, which polymer is substantially non-resinous and non-aqueous and which is a solid at about room temperature; (2) exposing said web to a cooling means such that said molten polymer is cooled before substantial wicking of said polymer occurs; and (3) winding said web onto a winding reel.
- 22. The method for impregnating a web of fibers described in claim 21, step 1 of which further comprises the steps of:(1) containing said molten polymer in a polymer trough; (2) providing an applicator roller, said applicator roller having a polymer contact region a web contract region, and a tangential velocity; (3) suspending said applicator roller in a manner such that said polymer contact region contacts said molten polymer contained in said polymer trough and said web contact regions contacts said web; and (4) rotating said applicator roller such that said molten polymer adheres to said applicator roller before being deposited onto said web.
- 23. The method for impregnating a web of fibers described in claim 21, wherein said cooling means is selected from the group consisting of a cold reel, cold rolls, or cold air blowers.
- 24. A polymer impregnated paper produced by a method for impregnating a web of fibers, including cellulose or synthetic fibers and any additives thereto, said web having a first side and a second side and a web velocity, said method comprising the steps of:(1) applying a molten polymer to said first side of said web, which molten polymer is substantially non-resinous and non-aqueous and which is a solid at about room temperature; (2) rolling said web across a hot reel such that said molten polymer remains in the molten state such that said molten polymer at least partially penetrates said web and wicking of said molten polymer into said web occurs (3) winding said at least partially penetrated web onto a winding reel; and (4) allowing said molten polymer to cool to below its melting point and to further wick into said web while cooling; wherein said fibers of said polymer impregnated paper are permeated by said molten polymer and, as a result, said polymer impregnated paper has improved resistance to oil and grease.
- 25. The polymer impregnated paper of claim 24 produced by the method described therein, step 1 of which further comprises the steps of:(1) containing said molten polymer in a polymer trough; (2) providing an applicator roller, said applicator roller having a polymer contact region, a web contact region, and a tangential velocity; (3) suspending said applicator roller in a manner such that said polymer contact region contacts said molten polymer contained in said polymer trough and said web contact region contacts said web; and (4) rotating said applicator roller such that said molten polymer adheres to said applicator roller before being deposited onto said web; wherein said fibers of said polymer impregnated paper are permeated by said molten polymer and, as a result, said polymer impregnated paper has improved resistance to oil and grease.
US Referenced Citations (17)