U.S. patent application number 10/890351 was filed with the patent office on 2006-01-19 for fire resistant plastic pallet.
Invention is credited to Ismat A. Abu-Isa, Richard W. Marczewski.
Application Number | 20060011108 10/890351 |
Document ID | / |
Family ID | 35598095 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060011108 |
Kind Code |
A1 |
Abu-Isa; Ismat A. ; et
al. |
January 19, 2006 |
Fire resistant plastic pallet
Abstract
A fire resistant plastic pallet comprises greater than or equal
to 65 wt. % high density polyethylene; and a sufficient amount of
intumescence additive material to impart fire resistant properties
to the fire resistant plastic pallet such that the fire resistant
plastic pallet is capable of passing a fire test standard
consistent with UL 2335, wherein weight percents are based on a
total weight of the fire resistant plastic pallet.
Inventors: |
Abu-Isa; Ismat A.;
(Rochester Hills, MI) ; Marczewski; Richard W.;
(Dryden, MI) |
Correspondence
Address: |
Jimmy L. Funke;Delphi Technologies, Inc.
Legal Staff, Mail Code: 480-410-202
P.O. Box 5052
Troy
MI
48007-5052
US
|
Family ID: |
35598095 |
Appl. No.: |
10/890351 |
Filed: |
July 13, 2004 |
Current U.S.
Class: |
108/57.25 |
Current CPC
Class: |
B32B 27/18 20130101;
B65D 2519/00079 20130101; B65D 2519/00044 20130101; B65D 2519/00149
20130101; B65D 2519/00218 20130101; B65D 2519/00114 20130101; B65D
2519/0086 20130101; B65D 19/18 20130101; B65D 2519/00253 20130101;
B65D 2519/00184 20130101 |
Class at
Publication: |
108/057.25 |
International
Class: |
B65D 19/38 20060101
B65D019/38 |
Claims
1. A fire resistant plastic pallet, comprising: greater than or
equal to 65 wt. % high density polyethylene; and a sufficient
amount of intumescence additive material to impart fire resistant
properties to the fire resistant plastic pallet such that the fire
resistant plastic pallet is capable of passing a fire test standard
consistent with UL 2335, wherein weight percents are based on a
total weight of the fire resistant plastic pallet.
2. The fire resistant plastic pallet of claim 1, wherein the high
density polyethylene is present in an amount of 65 wt. % to about
80 wt. %.
3. The fire resistant plastic pallet of claim 1, wherein the
intumescence additive material is present in an amount of about 10
wt. % to about 35 wt. %.
4. The fire resistant plastic pallet of claim 3, wherein the
intumescence additive material is present in an amount of about 20
wt. % to about 35 wt. %.
5. The fire resistant plastic pallet of claim 1, wherein the
intumescence additive material is selected from the group
consisting of a gas-generating foaming agent, a char-forming agent,
a filler, and combinations comprising at least one of the foregoing
materials.
6. The fire resistant plastic pallet of claim 5, wherein the
gas-generating foaming agent is selected from the group consisting
of ammonium dihydrogen phosphate, ammonium polyphosphate, and
combinations comprising at least one of the foregoing
materials.
7. The fire resistant plastic pallet of claim 5, wherein the
gas-generating foaming agent is selected from the group consisting
of hydrated alumina, hydrated magnesia, melamine, and combinations
comprising at least one of the foregoing materials.
8. The fire resistant plastic pallet of claim 5, wherein the char
forming agent is selected from the group consisting of
monopentaerythritol, dipentaerythritol, and combinations comprising
at least one of the foregoing materials.
9. The fire resistant plastic pallet of claim 1, wherein the
intumescence additive material further comprises antimony oxide,
zinc borate, and combinations comprising at least one of the
foregoing materials.
10. The fire resistant plastic pallet of claim 1, wherein the fire
resistant plastic pallet is made of a fire resistant blend of the
high density polyethylene and the intumescence additive
material.
11. The fire resistant plastic pallet of claim 1, wherein the fire
resistant plastic pallet is a fire resistant laminate.
12. The fire resistant plastic pallet of claim 11, wherein the fire
resistant laminate comprises an intumescent plastic layer disposed
on a first side of a non-intumescent polymer layer.
13. The fire resistant plastic pallet of claim 12, wherein the fire
resistant laminate further comprises an adhesive layer disposed
between the intumescent plastic layer and the non-intumescent
polymer layer.
14. The fire resistant plastic pallet of claim 13, wherein the fire
resistant laminate further comprises a second intumescent plastic
layer disposed on a second side of the non-intumescent polymer
layer.
15. The fire resistant plastic pallet of claim 12, wherein the
non-intumescent layer has a thickness about 1.5 times to 2.5 times
a thickness of the intumescent plastic layer.
16. A fire resistant plastic pallet, comprising: about 65 wt. % to
about 80 wt. % high density polyethylene; about 20 wt. % to about
35 wt. % intumescence additive material, wherein the intumescence
additive material comprises a gas-generating foaming agent, a
char-forming agent, and a filler; and wherein weight percents are
based on a total weight of the fire plastic resistant pallet.
17. The fire resistant plastic pallet of claim 16, wherein the
gas-generating foaming agent is selected from the group consisting
of ammonium dihydrogen phosphate, ammonium polyphosphate, and
combinations comprising at least one of the foregoing
materials.
18. The fire resistant plastic pallet of claim 16, wherein the
gas-generating foaming agent is selected from the group consisting
of hydrated alumina, hydrated magnesia, melamine, and combinations
comprising at least one of the foregoing materials.
19. The fire resistant plastic pallet of claim 16, wherein the char
forming agent is selected from the group consisting of
monopentaerythritol, dipentaerythritol, and combinations comprising
at least one of the foregoing materials.
20. The fire resistant plastic pallet of claim 16, wherein the
intumescence additive material further comprises antimony oxide,
zinc borate, and combinations comprising at least one of the
foregoing materials.
Description
BACKGROUND
[0001] Pallets are portable platforms used for handling, storing or
moving materials and heavy packages in, for example, warehouses or
during shipping. Traditionally, pallets have been made of wood,
which can harbor bacteria and other contaminants. As such, it has
been proposed to replace wood pallets with plastic pallets. Plastic
pallets are required to meet or exceed the fire resistance
standards set for wood pallets. The standards include requirements
that the material should have low heat release rate, low flame
spread rate, and should maintain strength during fire exposure.
[0002] A plastic that can be used in pallets is polyethylene,
because it is strong, has a high toughness, and is inexpensive.
Polyethylene, however, can melt, drip and burn when exposed to
fire. Dripping can contribute to the fast spread of fire. The heat
release rate during fire is also large for polyethylene.
Polyethylene itself will not be able to pass the UL 2335 fire test,
which is aimed at measuring fire resistance of stacked pallets.
[0003] There thus remains a need for fire resistant materials for
use in plastic pallets and other applications requiring fire
resistant plastics.
SUMMARY
[0004] Disclosed herein are fire resistant plastic pallets.
[0005] One embodiment of a fire resistant plastic pallet comprises
greater than or equal to 65 wt. % high density polyethylene; and a
sufficient amount of intumescence additive material to impart fire
resistant properties to the fire resistant plastic pallet such that
the fire resistant plastic pallet is capable of passing a fire test
standard consistent with UL 2335, wherein weight percents are based
on a total weight of the fire resistant plastic pallet.
[0006] On embodiment of a fire resistant pallet comprises about 65
wt. % to about 80 wt. % high density polyethylene; about 20 wt. %
to about 35 wt. % intumescence additive material, wherein the
intumescence additive material comprises a gas-generating foaming
agent, a char-forming agent, and a filler; and wherein weight
percents are based on a total weight of the fire resistant
pallet.
[0007] The above described and other features are exemplified by
the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Referring now to the figures, which are exemplary
embodiments, and wherein the like elements are numbered alike:
[0009] FIG. 1 is a cross-sectional view of an exemplary embodiment
of a fire resistant laminate comprising an intumescent plastic
layer and a non-intumescent polymer layer.
[0010] FIG. 2 is a cross-sectional view of an exemplary embodiment
of a fire resistant laminate comprising an intumescent plastic
layer, a non-intumescent polymer layer, and an adhesive layer.
[0011] FIG. 3 is a cross-sectional view of an exemplary embodiment
of a fire resistant laminate comprising a first intumescent plastic
layer, a non-intumescent polymer layer, and second intumescent
plastic layer.
[0012] FIG. 4 is a cross-sectional view of an exemplary embodiment
of a fire resistant laminate comprising a first intumescent plastic
layer, a first adhesive layer, a non-intumescent polymer layer, a
second adhesive layer, and a second intumescent plastic layer.
DETAILED DESCRIPTION
[0013] Fire resistant blends and fire resistant laminates are
disclosed herein for use as a fire resistant pallet. The blends may
employ an intumescent plastic or an intumescence additive(s) that
is blended with a non-intumescent polymer that is compatible with,
or can be made compatible with, the intumescent plastic or
intumescent material. By compatible, it is meant that the polymers
are miscible when blended or can be rendered miscible by the
addition of a compatibilizing agent. The laminates comprise a layer
comprising an intumescent plastic and an adjacent layer comprising
a non-intumescent polymer. As used herein, the term "intumescent
plastic" refers to a material that first expands and then chars
when exposed to fire to produce a heat resistant barrier that can
reduce the rate of heat transfer to nearby objects and also reduce
the spread of fires. Additionally, it is noted that the phrase
"sufficient to impart fire resistant properties" is used throughout
this disclosure to refer to fire resistant blends and fire
resistant laminates that are capable of passing a fire test
standard consistent with UL 2335 when the fire resistant blends and
fire resistant laminates are used to produce a pallet. It is noted
that a fire test standard for pallets included, but is not limited
to, those standards promulgated by the National Fire Protection
Association (NFPA), Underwriters Laboratories Inc. (UL) (e.g., UL
2335), Factory Mutual Research Company (FMRC), and National
Association of Fire Marshals. It is to be understood that the fire
resistant pallets disclosed herein are capable of passing a
comparable test to UL 2335 as set forth by various associates and
the like, which are similar to those described above.
[0014] It should further be noted that the terms "first," "second,"
and the like herein do not denote any order, quantity, or
importance, but rather are used to distinguish one element from
another, and the terms "a" and "an" herein do not denote a
limitation of quantity, but rather denote the presence of at least
one of the referenced item. Furthermore, all ranges disclosed
herein are inclusive and combinable (e.g., ranges of "up to about
25 weight percent (wt. %), with about 5 wt. % to about 20 wt. %
desired, and about 10 wt. % to about 15 wt. % more desired," is
inclusive of the endpoints and all intermediate values of the
ranges, e.g., "about 5 wt. % to about 25 wt. %, about 5 wt. % to
about 15 wt. %," etc.).
[0015] An intumescent plastic is a blend comprising a resin matrix,
a heat stabilizer for the resin matrix, and intumescence additives.
The intumescence additives include gas-generating foaming agents,
char-forming agents, fillers, and combinations comprising at least
one of the foregoing additives.
[0016] Preferably, the resin matrix of the intumescent plastic
comprises a polyethylene (e.g., high density polyethylene),
chlorinated polyethylene, and combinations comprising at least one
of the foregoing resins. For example, in an embodiment, the
polyethylene preferably is a high density polyethylene (HDPE)
having a density of about 0.940 to about 0.970 grams per cubic
centimeter (g/cm.sup.3). Generally, these HDPEs are available with
a number average molecular weight of about 10,000 atomic mass units
(amu) (usually waxes) to ultra high molecular weight HDPE
(UHMW-HDPE) of several million.
[0017] Different grades of high density polyethylene can be
employed depending on the application and the method of processing.
For example, high molecular weight/high melt viscosity grades are
used for blow molding applications. Low melt viscosity grades are
desirable for injection molding. Extrusion is generally performed
using intermediate melt viscosities. One measure of melt viscosity
is the melt flow index conducted per ASTM D1238 test procedure.
Melt index is the amount of molten resin, in grams, that flows
through a standard diameter capillary in a ten minutes period, when
the melt is heated to 190.degree. C. and is subjected to a load of
2,160 grams. It is noted that melt flow index is inversely related
to melt viscosity. Injection molding grades of polyethylene
preferably have a melt index of about 10 grams per 10 minutes to
about 50 grams per 10 minutes, where extrusion grades preferably
have a melt index of about 15 grams per 10 minutes to about 0.5
grams per 10 minutes. Furthermore, blow molding grades preferably
have a melt index of about 2 grams per 10 minutes to about 0.2
grams per 10 minutes, with a melt index of less than 0.2 grams per
10 minutes possibly obtained.
[0018] The chlorinated polyethylene (CPE) used as the resin matrix
of the intumescent plastic preferably comprises about 36 percent by
weight (wt. %) to about 42 wt. % chlorine, wherein weight percent
based on the total weight of the CPE. A suitable commercial example
of CPE is TYRIN.RTM. 3615P available from DuPont Dow Elastomers
Co., Midland, Mich., containing 36 wt. % chlorine based on the
total weight of the CPE. It is noted that the CPE can be combined
with HDPE at different ratios to produce moldable intumescent
thermoplastic elastomer grades with varying degrees of hardness.
CPE can also be formulated into an intumescent material without
HDPE through the addition of a small concentration of cross-linking
agents, as discussed in greater detail below. The intumescent
material formed can be highly elastomeric and can act as an
efficient noise and vibration isolator, especially if the material
is foamed during processing.
[0019] In other embodiments, HDPE may be mixed with CPE and/or
silicone rubber. An advantage of using silicone rubber is that
during burning, less smoke is evolved compared to materials that do
not include silicone rubber. In embodiments having no CPE, it is
noted that no chlorinated gaseous products may be produced as
burning products of the intumescent material.
[0020] In other embodiments, the resin matrix of the intumescent
plastic comprises a chlorinated polymer such as a chlorinated
polyethylene optionally mixed with polyvinyl chloride, high density
polyethylene, or a combination comprising at least one of the
foregoing components.
[0021] Furthermore, in various other embodiments, the resin matrix
of the intumescent plastic comprises a high density polyethylene
mixed with a chlorinated polyethylene and a silphenylene siloxane
elastomer. Suitable silphenylene siloxane elastomeric polymers
include those based on, for example,
1,4-phenylene-hexamethyltrisiloxanyl monomer or
1,4-phenylene-1,1,3,5,5-pentamethyl-3-vinyltrisiloxanyl monomer are
suitable provided that the polymers are of sufficient molecular
weight to provide the desired physical and intumescent properties
to the molded composition.
[0022] In yet another embodiment, the resin matrix of the
intumescent plastic comprises a recycled polyethylene and a
chlorinated polyethylene. Suitable resin matrixes include those
discussed in U.S. patent application Ser. No. 10/055,112 to Abu-Isa
and U.S. patent application Ser. No. 09/632,989 to Abu-Isa et al.
The recycled polyethylene may be obtained, for example, from scrap
generated during the manufacturing of plastic fuel tanks or from
regrind obtained from post consumer plastic fuel tanks, milk
bottles, garbage bags, or other plastic containers made of
polyethylene.
[0023] In addition to the resin matrixes discussed above, the
intumescent plastic comprises a heat stabilizer that is compatible
with HDPE and/or CPE. Preferably, the heat stabilizers include, for
example, thioesters such as distearylthiodipropionate (DSTDP) and a
butylated reaction product of p-cresol and dicyclopentadiene
(WINGSTAY L), which is a very effective hindered phenol
antioxidant, and combinations comprising at least one of the
foregoing heat stabilizers. It is noted that
distearylthiodipropionate is commercially available as DSDTP from
Witco Corporation, Greenwich, Conn., and the phenol is available as
WINGSTAY L from R.T. Vanderbilt, Norwalk, Conn. In addition to
these heat stabilizers, magnesium oxide may be employed to absorb
evolved HCl produced during aging of chlorinated polyethylene and
thus act as an effective dehydrochlorination stabilizer. Other heat
stabilizers include hydroquinone derivatives, organic phosphite
heat stabilizers such as tetraphenyl dipropylene glycol
diphosphate, and amine antioxidants, and combinations comprising at
least one of the foregoing heat stabilizers.
[0024] As briefly noted above, the intumescence additives of the
intumescent plastic include gas-generating foaming agents and
char-forming agents and combinations comprising at least one of the
foregoing additives. Gas-generating foaming agents are used in the
compositions to generate gases in order to foam the resin matrix
before it is consumed by fire. Two desirable gas-generating agents
are ammonium dihydrogen phosphate, NH.sub.4H.sub.2PO.sub.4,
ammonium polyphosphate (NH.sub.4PO.sub.3).sub.n, and combinations
comprising at least one of the foregoing agents, which emit ammonia
when heated. Hydrated alumina, hydrated magnesia, and combinations
comprising at least one of the foregoing agents are also desirable,
because they emit water vapor when heated. It is noted that the
ammonium dihydrogen phosphate can also form phosphoric acid, which
may act as a catalyst to encourage char formation from polyhydroxy
compounds. Preferably, the intumescent plastic comprises at least
one of ammonium dihydrogen phosphate and ammonium polyphosphate,
and at least one of hydrated alumina, hydrated magnesia and
melamine, or combinations comprising at least one of the foregoing
gas-generating foaming agents.
[0025] Char-forming agents for the intumescent plastic include
starch (e.g., corn starch) or other carbohydrates that form heavy
char when exposed to fire. Polyhydric alcohols such as trihydroxy
alcohols and tetrahydroxy alcohols, and combinations comprising at
least one of the foregoing alcohols, may also perform the same
function. Preferably, char forming agents are selected from the
group consisting of monopentaerythritol, dipentaerythritol, and
combinations thereof comprising at least one of the foregoing
char-formers. For example, a desirable char formation agent is a
blend of monopentaerythritol and dipentaerythritol, which is
commercially available as PERSTORP PE from Perstorp Compounds,
Inc., Florence, Mass.
[0026] Other optional ingredients may be added to the intumescent
plastic. A filler such as, for example, glass fibers, mica
particles, titanium oxide powder, and combinations comprising at
least one of the foregoing fillers, may be added to help strengthen
the composition and develop a strong structure of the material
after intumescing. Glass fiber reinforcing filler lead to increased
strength in the structure of the intumescent material after
burning. Other fillers that can also provide strength to the
residue are titanium dioxide, graphite, mica, and combinations
comprising at least one of the foregoing fillers. Antimony oxide
and/or zinc borate may also be added to impart fire retardancy to
the intumescent plastic and slow down the burning process. This
effect is helpful in decreasing heat release rate during fire and
increasing the char content.
[0027] The intumescent plastic can comprise a blend employing about
25 wt. % to about 60 wt. % of the resin matrix component, about 5
wt. % to about 15 wt. % of the heat stabilizer component, and about
25 wt. % to about 40 wt. % of the intumescence additives. For
example, an exemplary intumescent plastic composition is shown in
Table 1. It is noted that the weight percents illustrated in Table
1 are based on the total weight of the intumescent plastic.
TABLE-US-00001 TABLE 1 Composition of Intumescent Plastics
Preferable Component Wt % Example, Wt % High density polyethylene
0-60 15-25 Chlorinated polyethylene 0-60 27-33 Chlorowax 0-15 5-10
Ammonium dihydrogen phosphate 0-15 7-15 Hydrated magnesium oxide
0-30 9-17 Hydrated aluminum oxide 0-30 9-17
Distearylthiopriopionate 0-5 0.5-5 Hindered phenol 0-5 0.5-5
Chopped glass fiber 0-20 2-20 Antimony oxide 0-10 2-5
Pentaerythritol, mono- and di- 3-10 3-5 Graphite 0-15 5-10
[0028] Other specific examples of exemplary intumescent plastic
compositions are shown in Table 2. In those examples, the
intumescent plastic comprises a resin matrix comprising recycled
polyethylene. It is noted that the weight percents illustrated in
Table 1 are based on the total weight of the intumescent plastic.
TABLE-US-00002 TABLE 2 Compositions Comprising Polyethylene Wt %
Composition Composition Composition Component 1 2 3 Recycled high
density 23 23 23 polyethylene Chlorinated polyethylene 30 30 30
Silicone 0 2 2 Chlorowax 7 5 5 Ammonium dihydrogen 8 7 7 phosphate
Hydrated magnesium oxide 2 16 16 Hydrated alumina 15 0 0
Distearylthiopriopionate 0.5 0.5 0.5 Hindered phenol 0.5 0.5 0.5
Chopped glass fibers 6 6 6 Antimony oxide 3 5 5 Titanium dioxide 0
2 2 Pentaerythritol 5 3 2.9 Dicumyl peroxide 0 0 0.05
Trimethylolpropane- 0 0 0.05 trimethylacrylate
[0029] Other specific examples of intumescent plastics are shown in
Table 3. TABLE-US-00003 TABLE 3 Other Intumescent Plastics Wt %
Compo- Compo- Compo- Compo- sition sition sition sition Component 4
5 6 7 High density polyethylene 10 5 5 0 Chlorinated polyethylene
45 50 50 38 Chlorowax 7 7 7 8 Ammonium dihydrogen 8 0 4 0 phosphate
Hydrated magnesium oxide 15 15 15 25 Distearylthiopriopionate 0.5
0.5 0.5 1 Hindered phenol 0.5 0.5 0.5 1 Antimony oxide 5 5 2 9
Pentarythritol, mono- 5 5 5 0 and di- Graphite 4 12 11 9 Chopped
Glass 0 0 0 9
[0030] The intumescent plastics can be mixed on a laboratory scale
by different methods including, for example, mixing on a two-roll
mill heated to about 65.degree. C. The polymeric resin or resins
and the stabilizers may be added to the rolls and shear mixed for
about five minutes. At that time suitable mixing may be visually
observed and the material may be banded on one of the rolls. The
actual temperature of the resin during mixing may approach about
150.degree. C. due to shearing of the mixture. The remaining
ingredients except filler may be added in a fine powder form and
mixed well with the resin. The filler may then be added and mixed
into the formulation for several minutes. The total mixing time of
each compound may be greater than or equal to 15 minutes.
[0031] In other embodiments, formulations may also be prepared by
mixing in a Brabender bowl, which is a small internal mixer, and in
a large Banbury internal mixer. For example, the Banbury cavity may
be preheated to about 93.degree. C. Then, a first batch of
ingredients is added to the bowl. These ingredients include (for
example) chlorinated polyethylene and high density polyethylene,
hydrated magnesium oxide, hydrated alumina, DSTDP, antimony oxide,
corn starch and chlorowax. The mixing speed of the bowl may then be
increased to, for example, about 120 revolutions per minute (rpm),
and the ingredients allowed to mix for about two to three minutes.
When using HDPE, the temperature of the mix may be permitted to
rise to about 120.degree. C. to about 140.degree. C. to melt the
polyethylene and incorporate it into the mixture. Following this
first mixing operation, a second batch of ingredients which may
include, for example, ammonium dihydrogen phosphate and glass may
be added to the bowl, with mixing continued for about three more
minutes or until the temperature reached about 160.degree. C.,
whichever first occurs. The mix may then be removed from the bowl
and dumped onto a mill to further mix and sheet out the
composition. The temperature of the mill may be about 132.degree.
C.
[0032] Another example of intumescent composition mixing that is
suitable involves a Brabender extruder. The temperatures of the
three extruder barrel zones and the die may be varied between about
150.degree. C. and about 175.degree. C. The screw speeds may be,
for example, about 50 rpm to about 100 rpm. Large scale batches may
be prepared using a twin screw Buss kneader. In addition, mixing of
the material may be conducted on plant scale using, for example,
about a 3.5 inch (about 8.9 centimeters) diameter Buss Kneader.
[0033] In an embodiment, the intumescent plastic may be used to
form fire resistant blends, wherein the fire resistant blend is a
blend of the intumescent plastic and a non-intumescent polymer that
is compatible with, or can be made compatible with, the intumescent
plastic. If the non-intumescent polymer is not compatible with the
intumescent plastic, a compatibilizing agent may be employed. As
used herein, the term "compatibilizing agent" refers to those
polyfunctional compounds that interact with either the intumescent
plastic, the non-intumescent polymer, or both. This interaction may
be chemical (e.g. grafting) or physical (e.g. affecting the surface
characteristics of the dispersed phases).
[0034] Suitable non-intumescent polymers include, for example,
polyethylene, polypropylene, nylon,
acrylonitrile-butadiene-styrene, polyphenylene oxide, and
combinations comprising at least one of the foregoing plastics.
[0035] Suitable polyethylene includes high density (HDPE, density
greater than or equal to 0.941 g/cm.sup.3), medium density (MDPE,
density from 0.926 to 0.940 g/cm.sup.3), low density (LDPE, density
from about 0.910 to about 0.925 g/cm.sup.3) and linear low density
polyethylene (LLDPE, density from about 0.910 to about 0.925
g/cm.sup.3). Furthermore, suitable polyethylenes include
polyethylene homopolymers or copolymers of ethylene and
C.sub.3-C.sub.10 alpha-olefin monomers. When copolymers are used,
the ethylene content can be about 90 mol percent to about 100 mol
percent, with the balance being made up of the C.sub.3-C.sub.10
alpha olefin.
[0036] Propylene polymers may be obtained by polymerizing monomers
mainly composed of propylene. Examples of polypropylenes include a
propylene homopolymer obtained by homo-polymerization of propylene,
a propylene-ethylene random copolymer obtained by copolymerization
of propylene and ethylene, a propylene-.alpha.-olefin random
copolymer obtained by copolymerization of propylene and an
.alpha.-olefin having 4 to 12 carbon atoms, and the like, and
combinations comprising at least one of the foregoing polymers.
[0037] Suitable polyamides or nylons include nylon-4,6, nylon-6,6,
nylon-6,10, nylon-6,9, nylon-6,12, nylon-6, nylon-11, nylon-12, 6T
through 12T, 6I through 12I, and the like, and blends and
copolymers and combinations comprising at least one of the
foregoing polyamides.
[0038] Acrylonitrile-butadiene-styrene (ABS) graft copolymers
contain two or more polymeric parts of different compositions,
which are bonded chemically. The graft copolymer is preferably
prepared by first polymerizing a conjugated diene, such as
butadiene or another conjugated diene, with a monomer
copolymerizable therewith, such as styrene, to provide a polymeric
backbone. After formation of the polymeric backbone, at least one
grafting monomer, and preferably two, are polymerized in the
presence of the polymer backbone to obtain the graft copolymer.
[0039] The polyphenylene oxide polymers can comprising a plurality
of aryloxy repeating units. Both homopolymer and copolymer
polyphenylene oxides are suitable for use in the present
disclosure. Suitable homopolymers are those containing, for
example, 2,6-dimethyl-1,4-phenylene oxide units. Suitable
copolymers include random copolymers containing such units in
combination with, for example, 2,3,6-trimethyl-1,4-phenylene oxide
units. Poly-(2,6-dimethyl-1,4-phenylene oxide) is an example of a
suitable polyphenylene oxide.
[0040] If a compatibilizer is used, it can be, for example,
copolymers, in particular block copolymers, of styrene with
butadiene and, if desired, acrylonitrile. They can be copolymers of
ethylene and propylene, and may contain a third monomer component,
for example butadiene. Chlorinated polyethylene or ethylene-vinyl
acetate copolymers are also suitable as compatibilizers, naturally
depending on the particular composition of the recyclate. Other
suitable compatibilizers contain, in particular, polar groups, e.g.
maleic anhydride-styrene copolymers or graft polymers containing
acrylic acid groups, maleic anhydride groups or glycidyl groups.
The compatibilizers can be a combination comprising at least one of
the foregoing compatibilizers.
[0041] The fire resistant blend can be mixed by any suitable mixing
method. Such methods include solution blending or melt mixing in
single or twin screw type extruders, mixing bowl, roll, kneader, or
similar mixing device that can apply a shear to the components.
[0042] In an embodiment, the fire resistant blend may employ an
amount of intumescent plastic or intumescent material sufficient to
impart fire resistant properties to the fire resistant blend. For
example, the fire resistant blend may employ about 20 wt. % to
about 80 wt. % of the intumescent plastic, preferably about 20 wt.
% to about 60 wt. %, and more preferably about 20 wt. % to about 40
wt. % based on the total weight of the fire resistant blend. The
fire resistant blend may employ about 20 wt. % to about 80 wt. % of
the non-intumescent polymer, preferably about 40 wt. % to about 80
wt. %, and more preferably about 60 wt. % to about 80 wt. % based
on the total weight of the fire resistant blend. The
compatibilizer, when used, may be employed in an amount less than
or equal to 5 wt. %, preferably about 1 wt. % to about 5 wt. %, and
more preferably about 1 wt. % to about 2 wt. % based on the total
weight of the fire resistant blend. In this embodiment, the
intumescent plastic may act as a carrier such that intumescence
additives may readily be blended with the non-intumescent polymer
to form the fire resistant blend.
[0043] In other embodiments, a fire resistant blend may be made by
blending a sufficient amount of intumescence additives directly
with the non-intumescent polymer to impart fire resistant
properties to the fire resistant blend. In other words, an
intumescent plastic is not formed as a precursor. Rather, the
intumescence additives are blended with the non-intumescent polymer
in a manner as described above for making the intumescent plastic.
In this embodiment, the non-intumescent polymer acts as the resin
matrix for the fire resistant blend.
[0044] In all of the embodiments of the fire resistant blend, the
fire resistant blend employs about 10 wt. % to about 35 wt. %
intumescence additives, with about 20 wt. % to about 35 wt. %
preferred, wherein the weight percents are based on a total weight
of the fire resistant blend. The balance of the fire resistant
blend comprises a resin matrix material, e.g., high-density
polyethylene, and optionally a heat stabilizer. It is further noted
that the weight percents disclosed above in relation to the
intumescent plastic, e.g., in Tables 1-3, can readily be adjusted
such that the weight percents are based on a total weight of the
fire resistant blend.
[0045] Preferably, the fire resistant blend employs greater than or
equal to 65 wt. % high density polyethylene, with about 65 wt. % to
about 80 wt. % preferred; and intumescent additives in an amount
sufficient to impart fire resistant properties to the fire
resistant blend, wherein weight percents are based on a total
weight of the fire resistant blend.
[0046] The fire resistant blend can be molded into a fire resistant
pallet by injection molding, extrusion, compression molding, vacuum
forming, blow molding, and the like.
[0047] In another embodiment, a fire resistant laminate is
disclosed, wherein the fire resistant laminate comprises layer(s)
of intumescent plastic and layer(s) of non-intumescent polymer,
wherein the intumescent plastic is present in an amount sufficient
to impart fire resistant properties to the fire resistant blend. It
is noted that the fire resistant laminate employs the same amount
of intumescent material and non-intumescent polymer as disclosed
above for the fire resistant blends. For example, the fire
resistant laminate comprises about 20 wt. % to about 80 wt. %
intumescent plastic and about 20 wt. % to about 80 wt. %
non-intumescent polymer, wherein the weight percents are based on a
total weight of the fire resistant laminate. In other words, the
fire resistant laminate may comprise about 10 wt. % to about 35 wt.
% intumescence additives, with about 20 wt. % to about 35 wt. %
preferred, wherein the weight percents are based on a total weight
of the fire resistant laminate.
[0048] Furthermore, it is noted that the fire resistant laminate
preferably comprises greater than or equal to 65 wt. % high density
polyethylene, with about 65 wt. % to about 80 wt. % preferred; and
intumescent additives in an amount sufficient to impart fire
resistant properties to the fire resistant blend, wherein weight
percents are based on a total weight of the fire resistant
laminate. It is further noted that the weight percents disclosed
above in relation to the intumescent plastic, e.g., in Tables 1-3,
can readily be adjusted such that the weight percents are based on
a total weight of the fire resistant laminate.
[0049] The thickness of each layer in the fire resistant laminate
may vary with the desired application. For example, a fire
resistant laminate for use in a pallet may comprise an intumescent
plastic layer having a thickness of about 1 millimeter (mm) to
about 6 mm, with a thickness of about 1 mm to about 4 mm more
preferred. The non-intumescent polymer preferably has a thickness
of about 1.5 to 2.5 times that of the intumescent plastic layer.
Furthermore, it is noted that the thickness of the plastic layer
may vary based on various design criteria, e.g., the load
requirement in service. In various embodiments, the plastic layer
preferably has a thickness of about 4 mm to about 15 mm, with a
thickness of about 4 mm to about 10 mm more preferred.
[0050] An exemplary laminate generally designated 10 is illustrated
in FIG. 1. The laminate 10 comprises an intumescent plastic layer
12 and a non-intumescent polymer layer 14 disposed in physical
communication with the intumescent plastic layer 12. It is noted
that the intumescent plastic and the non-intumescent polymer
comprise those materials discussed above.
[0051] The laminate may further comprise an adhesive layer in
physical communication with the intumescent plastic layer and the
non-intumescent polymer layer. Suitable adhesives, include, for
example, epoxy-based adhesives, urethane-based adhesives,
acrylic-based adhesives, polyvinyl acetate/urethane adhesives,
polychloroprene contact adhesives, and the like and combinations
comprising at least one of the foregoing adhesives. For example, a
laminate generally designated 100 is illustrated in FIG. 2. The
laminate 100 comprises an adhesive layer 116 disposed between an
intumescent plastic layer 112 and a non-intumescent polymer layer
114.
[0052] In another embodiment, illustrated in FIG. 3, a laminate
generally designated 200 comprises a first intumescent plastic
layer 212, a second intumescent plastic layer 218, and a
non-intumescent polymer layer 214 disposed between and in physical
communication with the first and second intumescent plastic layers
(212, 218). Optionally, as noted above, an adhesive layer(s) may be
disposed between the intumescent each intumescent plastic layer and
the non-intumescent polymer layer.
[0053] For example, a laminated generally designated 300 comprises
a first intumescent plastic layer 312, a first adhesive layer 316,
a non-intumescent polymer layer 314, a second adhesive layer 320,
and a second intumescent plastic layer 318. More particularly, a
first adhesive layer 316 is disposed between and in physical
communication with first intumescent plastic layer 312 and
non-intumescent polymer layer 314. Similarly, second adhesive layer
320 is disposed between and in physical communication with second
intumescent plastic layer 318 and non-intumescent polymer layer
314.
[0054] It is noted that the various laminates disclosed herein may
be formed as a part by, for example, co-extrusion (FIG. 2), by
stacking sheets of intumescent plastic and non-intumescent polymer
and molding the sheets to form a fire resistant laminate, e.g., a
pallet. Suitable molding methods include, for example, injection
molding, compression molding, vacuum forming, blow molding, and the
like. During the molding process, the sheets develop adhesion and
form a laminate. Optionally, an adhesive layer can be disposed
between the intumescent plastic sheet and the non-intumescent
polymer sheet prior to molding, as discussed above.
[0055] The fire resistant laminates and blends can be manufactured
into fire resistant pallets. The laminates are also useful for
shipping containers, school bus seats, car flooring, bulkheads,
wheel wall covers, floor tile or wall tile doors, file cabinets,
safes, and other applications requiring fire resistant materials.
In the case of shipping pallets, a new standard for flammability of
shipping pallets is under consideration by the National Fire
Protection Agency. The test will be based on Underwriters
Laboratory test UL 2335. The test consists of burning a stack of
six 12 foot (about 3.7 meters) by 12 foot (about 3.7 meters)
pallets located under a sprinkler ceiling. Criteria for evaluation
include: stack stability (e.g., for 30 minutes) during the test;
time for the fire to extend to the end of the array (e.g., more
than 7 minutes); number of activated sprinklers (e.g., less than
14); and the maximum average temperature of a steel beam over the
fire (e.g., less than 537.degree. C.).
EXAMPLE
[0056] A pallet made of a blend of 25 wt. % intumescent plastic
described above with 75 wt. % high density polyethylene, wherein
weight percents are based on the total weight of the blend, was
tested per UL 2335 idle pallet storage fire test. The results are
discussed below. It is noted that the pallets passed the
flammability test and showed excellent performance.
[0057] During the test only four sprinklers were engaged, when a
total of six sprinklers were allowed. The steel beam over the fire
reached a temperature of 175.degree. F. (about 79.degree. C.), when
the temperature of about 200.degree. F. (about 93.degree. C.) was
allowed. The temperature of the outside wall of the pallet reached
a temperature of about 150.degree. F. (about 66.degree. C.), when a
temperature of about 600.degree. F. (about 316.degree. C.) was
allowed. After 30 minutes, the fire was extinguished. Minimal fire
involvement was observed around the four gasoline soaked torches
employed that were employed in the test. Most of the pallets looked
like new.
[0058] Pallets made of polymers containing traditional fire
retardants (e.g., halogens, phosphates, borates, and the like) are
expected to fail the test because they are unable to resist large
fires for long exposure times. It is expected that for such
compositions, a high rate of heat release and failure to maintain
stack stability will result. Furthermore, flaming melt dripping may
also observed for many of those polymers. In other words, flaming
melt dripping is another source of failure, since this phenomenon
can lead to flame spread to neighboring materials In contrast to
compositions comprising traditional fire retardants, intumescent
fire resistant plastics are formulated to withstand intense fire
situations for longer periods of time. The fire retardancy activity
of the intumescent plastics slows down the heat release rate. In
addition, they foam when exposed to fire or high temperature
conditions to improve thermal insulation. Also, under fire
conditions they develop a char on the surface of the part and
improve resistance to burning. Intumescent plastics do not
significantly melt or burn through when exposed to fire and thus
can provide a fire shield.
[0059] The plastic blends and laminates disclosed herein are useful
in applications where fire resistant properties are desirable. The
blends and laminates are particularly useful in shipping pallet
applications and have improved fire resistance as compared to other
plastic pallets. In particular, pallets comprising the fire
resistant blends and laminates are expected to pass the National
Fire Protection Agency fire resistance standard. In addition, the
disclosed fire resistant pallets are expected to be significantly
less expensive than those made from polyphenylene oxide and other
specialty plastics.
[0060] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
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