 |
Description  |
|
|
DESCRIPTION
BACKGROUND OF THE INVENTION
This invention is in the field of asphalt compounds; more particularly, the
invention relates to a modified roofing asphalt formulation.
Two types of asphalt coated roofing materials are available; built up
roofs, and roofs made of roofing shingles. Built up roofing is the type
used on horizontal type roof structures which are typically commercial or
apartment type buildings. For the built up roofs, asphalt is heated to
400.degree.-450.degree. F., and then mopped on. The saturated asphalt felt
is then rolled over. The asphalt which acts both as an adhesive as well as
a water-proofing coating, is applied as the roof is being layed down.
Because the asphalt for built up roofing must retain adhesive properties,
it is less crosslinked or mildly oxidized compared to asphalt prepared for
roofing shingles. Roofing stone aggregate is spread over the entire built
up roof to provide weather resistance to the built up roof. Roofing stone
aggregate cann be stone or slag. Its purpose is to prevent ultraviolet
rays from degrading the roof coating. The stone allows walking over the
roof without disturbing the asphalt.
Roofing shingles are another type of roofing material coated with asphalt.
The asphalt is crosslinked or oxidized and is coated onto the roofing felt
in a manufacturing step. Generally, the asphalt is filled with stone dust.
The asphalt is heated to about 400.degree.-450.degree. F. and spread on
and pressed into the roofing felt. Roofing granules are then fed onto the
saturated asphalt felt and pressed in.
Roofing felt from a continuous roll is coated with the asphalt formulation
at about 400.degree. F. Roofing granules, a colored ceramic stone baked
onto stone granules, are pressed into the coating. The shingle color
becomes the color of the granules. This coated felt roll is cooled and the
shingles, with desired cut-outs, are continuously cut from the continuous
shingle roll. Typically, the roll is three feet wide and shingles are one
by three feet with cut-outs.
In recent years roofing felt material has been changed from cellulose to
glass fibers. The new glass fiber shingle is thinner and more flexible
than the old cellulose felt shingle. Therefore, the coating must have
better flexibility properties, particularly at cold temperatures. If this
is not the case, flexing at cold temperatures causes surface cracking in
the shingles. The cracks are failure sites and points for future leaks to
develop.
In addition to the change of material for the asphalt roofing felt, the
origin of asphalt supplies have changed in recent years, from domestic
crudes to Venezuela, Arabian or North Slope sources. These new changes
have made it necessary to re-evaluate the construction and composition of
roofing shingles and their components, particularly the asphalt coatings.
However, asphalts from various sources are commonly blended for
uniformity. There is, therefore, a need, in view of the changing
requirements of asphalt roofing shingles, to develop a roofing asphalt
formulation which can readily be substituted for existing asphalt
shingles, both in processing and application.
SUMMARY OF THE INVENTION
The present invention is an asphaltic composition which is useful as a
roofing asphalt formulation and method of making this formulation. The
composition includes about 39 to 99 percent by weight of oxidized asphalt
and between 1 and about 8 percent of oxidized polyethylene. It is
preferred to use between about 0 to 40 percent of the saturant, which can
be an unoxidized asphalt, to modify the viscosity of the formulation.
There can be a filled asphaltic composition comprising about 40 percent by
weight to about 99 percent by weight of the asphaltic composition and
about 1 percent by weight to about 60 percent by weight of filler, which
can be stone dust.
A preferred embodiment of the asphaltic composition of the present
invention which can be used as a roofing asphalt formulation, uses about
71 to 89 percent oxidized asphalt, about 1 to 4 percent oxidized
polyethylene, and about 10 to 25 percent saturant. A filled asphalt
formulation with about 40 to 50 percent by weight of the preferred roofing
asphalt formulation can be used with about 50 to 60 percent by weight
based on the total weight of the formulation, including the filler, of
ground stone dust filler or any other suitable filler. The preferred
oxidized polyethylene is a polyethylene having a molecular weight of
between 2,000 and 6,000, a softening point between 130.degree. C. and
150.degree. C., and a Brookfield viscosity between 5,000 and 30,000
centipoises at a temperature of 149.degree. C.
The roofing asphalt formulation of the present invention can be made by
adding oxidized asphalt to oxidized polyethylene, or by mixing an
unoxidized asphalt with unoxidized polyethylene and oxidizing the mixture
in a manner similar to oxidizing asphalt as known in the art.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a microphotograph of oxidized North Slope asphalt with no
additive.
FIG. 2 is a microphotograph of oxidized Mid-Continent asphalt with no
additive.
FIG. 3 is a microphotograph of oxidized North Slope asphalt with 5%
unoxidized polyethylene.
FIG. 4 is a microphotograph of oxidized Mid-Continent asphalt with 8%
Sample A oxidized polyethylene, 20% saturant and no aging.
FIG. 5 is a microphotograph of oxidized North Slope asphalt with 8% Sample
A oxidized polyethylene, 20% saturant and no aging.
FIG. 6 is a microphotograph of oxidized Mid-Continent asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and no aging.
FIG. 7 is a microphotograph of oxidized North Slope asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and no aging.
FIG. 8 is a microphotograph of oxidized Mid-Continent asphalt with 6% of
Sample F oxidized polyethylene, 20% saturant and no aging.
FIG. 9 is a microphotograph of oxidized North Slope asphalt with 6% of
Sample F oxidized polyethylene, 20% saturant and no aging.
FIG. 10 is a microphotograph of oxidized Mid-Continent asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and three days aging at
350.degree. F.
FIG. 11 is a microphotograph of oxidized North Slope asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and three days aging at
350.degree. F.
FIG. 12 is a microphotograph of oxidized Mid-Continent asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and aged seven days at
350.degree. F.
FIG. 13 is a microphotograph of oxidized North Slope asphalt with 3% of
Sample F oxidized polyethylene, 20% saturant and aged seven days at
350.degree. F.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention comprises an asphaltic formulation made of oxidized
asphalt, oxidized polyethylene, and optionally a saturant or asphalt
cut-back and filler. This composition is particularly useful as a roofing
asphalt formulation.
The addition of oxidized polyethylene to oxidized asphalt roof coating
increases the coating viscosity and hardness. A saturant such as
unoxidized asphalt can modify the viscosity of the roofing asphalt
formulation of the present invention. The roof coating viscosity can
thereby be modified to be equal to the typical viscosity of roofing
asphalt formulations without oxidized polyethylene. In this way the
roofing asphalt formulation of the present invention can be substituted
into existing processes for forming asphalt roof shingles, and the
shingles used in a manner in which they have been used in the past.
A roofing asphalt formulation of the present invention contains between
about 52 to 99 percent by weight oxidized asphalt and between about 1 to 8
percent by weight oxidized polyethylene. There can be 0 to 40 percent by
weight of saturant. Optionally, the roofing asphalt formulation of the
present invention can be filled so that the filled roofing asphalt
formulation comprises about 40 to about 99 percent by weight of the
roofing asphalt formulation and about 1 to 60 percent by weight of filler.
The filler increases resistance to weather, and decreases the cost of the
roofing asphalt formulation. A preferred filler used in roofing asphalt
formulations known in the art is stone dust. This filler can be used with
the present invention.
A preferred roofing asphalt formulation range has about 71 to 89 percent
oxidized asphalt, about 1 to 4 percent oxidized polyethylene and about 10
to 25 percent saturant. The preferred roofing asphalt can have 1 to 60
percent by weight of filler added to 40 to 99 percent by weight of the
roofing asphalt formulation resulting in a preferred filled roofing
asphalt formulation.
A particularly preferred formulation which has been successfully used is
one containing 77 percent oxidized asphalt, 3 percent oxidized
polyethylene and 20 percent saturant. A particularly preferred filled
formulation comprises 40 to 50 percent by weight of this preferred
formulation and further, 50 to 60 percent by weight of ground stone as
filler.
Roofing asphalt is manufactured from refined asphalt. This asphalt is
oxidized and crosslinked to give it better weather resistance. The
oxidization takes place by mixing the asphalt with air and heating to
between 350.degree. F. and 500.degree. F. with or without a catalyst. When
no catalyst is used, it takes between 4 to 6 hours to oxidize the asphalt.
With a catalyst, the processing time is shortened to between 2 and 4
hours. A preferred catalyst is ferric chloride (FeCl.sub.3). Additionally,
the roofing asphalt formulation can contain filler. A common filler is 50
to 60 percent by weight of ground stone dust to reduce cost and improve
the weather resistance.
The asphalts used to make roofing asphalt formulations are characterized by
their geographic origin. As noted in the background, asphalt origins have
changed from domestic or Mid-Continent crudes to Venezuela, Arabian or
North Slope crude oil sources. The composition of the asphalts from the
various locations is different resulting in different properties. However,
asphalts from various locations are generally blended for uniformity.
The asphalt roofing formulation should have good low temperature flexural
properties. This is particularly important when using fiber-glass
shingles. In the present invention, it has been found that mixing oxidized
asphalt with oxidized polyethylene results in improved flexibility
properties.
Oxidized polyethylene which can be used in the formulations of the present
invention has a softening point of 100.degree. to 150.degree. C. as
measured by ASTM (E-28); a penetration hardness of about 10.0 dmm to about
0.1 dmm, preferably 9.0 dmm to 0.5 dmm or less as measured by ASTM (D-5);
a density of 0.90 to 1.00 grams per cubic centimeter as measured on the
ASTM (D-1505); a Brookfield viscosity at 149.degree. C. of 100 to about
40,000 cps; an acid number of about 10 to 35, preferably 15 to 30, based
on milligrams of KOH per gram; and a molecular weight of 1,000 to about
10,000, preferably 1,500 to 6,000. Typical oxidized polyethylene polymers
which can satisfactorily be used to making roofing asphalt formulations
are summarized in Table I:
TABLE I
______________________________________
Softening Point Hardness Viscosity-cps
.degree.C. .degree.F.
dmm 149.degree. C. (300.degree. F.)
Sample
(ASTM E-28) (ASTM D-5) (Brookfield)
______________________________________
A 104 219 5.5 157.5
B 107 225 2.5 132.5
C 100 212 9.0 122.5
D 110 230 1.5 190.0
E 111 232 1.2 190.0
F 138 280 <0.5 9,000
G 140 284 <0.5 30,000
______________________________________
A preferred oxidized polyethylene is Sample F, having a softening point of
138.degree. C.; a hardness of less than 0.5 dmm; a density of 0.99 grams
per cubic centimeter; a Brookfield viscosity at 149.degree. C. of between
about 8,000 and about 10,000 centipoises (cps) and an acid number of 28
with a molecular weight between 3,000 and 5,000.
Any suitable fillers known in the art can be used with the roofing asphalt
formulation. It is preferred to use ground stone, such as limestone or
trap rock. The ground stone is used in an amount of preferably 50 to 60
percent by weight of the total weight of the formulation. The stone is
ground to a particle size of about 180 microns or less.
The following examples and comparatives were conducted with Mid-Continent
(MC) and North Slope (NS) asphalts used as coatings and saturants.
Satisfactory performance was obtained using material from both sources.
Typical oxidized asphalt (coating) and saturant properties are summarized
in Table II.
TABLE II
______________________________________
Ball & Ring
Softening
Penetration Viscosity
Point (.degree.F.)
@ 77.degree. F. dmm
cps
______________________________________
MC Saturant
115 110 @ 250.degree. F.-648
MC Coating
243 14 @ 425.degree. F.-332
NS Saturant
101 306 @ 250.degree. F.-227
NS Coating
237 17 @ 425.degree. F.-337
______________________________________
The following examples illustrate two aspects of the present invention;
first to develop a roofing asphalt formulation which can satisfactorily be
applied to fiber-glass shingle mat and have satisfactory low temperature
flexibility properties; and secondly, this developed roofing asphalt
formulation should be readily substituted into existing roofing material
production processes. This first aspect was accomplished by adding
oxidized polyethylene to oxidize asphalt. The second aspect was
accomplished by modifying the formulation with saturant.
The cold temperature flexibility of roofing material containing an asphalt
formulation is related to the viscosity of the formulation; the lower the
viscosity, the more flexible the asphalt. Further, viscosity is also
considered important in processing the asphalt to make roofing material
without substantial changes to equipment and processes used with existing
material and asphalt composition.
EXAMPLES 1-3
Table III below summarizes a comparison of viscosity at various aging
conditions, between Comp. 1-3 of MC oxidized asphalt, and Examples 1-3 of
MC oxidized asphalt containing 3% by weight of Sample F oxidized
polyethylene, and 20% MC saturant as described in Table I.
TABLE III
______________________________________
Aging
Temp Viscosity cps @ 300.degree. F.
.degree.F. 0 Days 3 Days @ 350.degree. F.
7 Days @ 350.degree. F.
______________________________________
Comp. 1
300 64,000 >100,000 >100,000
Ex. 1 300 77,000 51,000 68,500
Comp. 2
350 4,000 5,500 8,000
Ex. 2 350 3,350 2,350 3,100
Comp. 3
400 640 740 910
Ex. 3 400 910 400 485
______________________________________
EXAMPLES 4-6
Table IV below summarizes a comparison of viscosity at various aging
conditions, between Comp. 4-6 of NS oxidized asphalt, and Examples 4-6 of
NS oxidized asphalt containing 3% by weight of Sample F oxidized
polyethylene, and 20% NS saturant as described in Table I.
TABLE IV
______________________________________
Aging
Temp Viscosity cps @ 300.degree. F.
.degree.F. 0 Days 3 Days @ 350.degree. F.
7 Days @ 350.degree.0 F.
______________________________________
Comp. 4
300 53,000 >100,000 >100,000
Ex. 4 300 40,000 32,000 36,250
Comp. 5
350 4,100 6,000 7,100
Ex. 5 350 2,350 1,900 2,225
Comp. 6
400 660 810 885
Ex. 6 400 385 350 400
______________________________________
Tables III and IV show that not only does the formulation of the present
invention provide a substitutable roofing asphalt formulation, but that
the roofing asphalt formulation of the present invention has better
properties in retaining its viscosity based on accelerated heat aging
test. Specifically, Tables III and IV show that the viscosities of
Mid-Continent and North Slope asphalt formulations of the present
invention were approximately maintained at 300.degree. F., 350.degree. F.
and 400.degree. F. In all cases the viscosity of asphalt without the
oxidized polyethylene increased significantly.
The seven day accelerated aging test of the asphalt coating at 350.degree.
F. shows that the viscosity of the Example, modified asphalts did not
increase whereas the viscosity of the Comparatives showed considerable
increase in both asphalts from Mid-Continent and North Slope sources. This
indicates that the asphalt formulation of the present invention, will have
improved low-temperature properties including flexibility. Similar
viscosities at 0 days aging indicate that the Example formulations can be
used to produce fiber-glass shingles with the same equipment used to
produce roofing shingles made of cellulose felt.
Microphotographs at 425X magnification illustrating the compatibility of
materials in the formulation of the present invention are discussed in the
examples and comparatives below.
COMPARATIVES 7 AND 8
FIGS. 1 and 2 are microphotographs of NS and MC oxidized asphalt
respectively. These two materials contain no additives and are unaged. In
both cases there is a homogeneous dispersion.
COMPARATIVE 9
FIG. 3 is a microphotograph of NS oxidized asphalt with 5% by weight of
unoxidized polyethylene. Polyethylene is compatible with asphalt prior to
oxidization, but is incompatible when blended to oxidized asphalt. The
microphotograph of FIG. 3 shows the colloidal structure of the oxidized
asphalt is destroyed and a light oil face separates from the darker
colloidal mask. Once the colloidal structure of the asphalt is destroyed,
the coating cracks, and does not weather properly.
EXAMPLES 7, 8
FIG. 4 (Example 7) and FIG. 5 (Example 8), respectively, show: a blend of
MC oxidized asphalt, 8% of Sample A oxidized polyethylene and 20% of MC
saturant; and a blend of NS oxidized asphalt, 8% of Sample A oxidized
polyethylene and 20% of NS saturant. There was no aging and the blend in
both examples remained homogeneous as shown in FIGS. 4 and 5.
EXAMPLES 9-16
Examples 9-16, which follow, illustrate the compatibility of NS and MC
oxidized asphalt at various levels and conditions. The results are
summarized in Table V below, which also references the corresponding
Figures which are microphotographs at 425X magnification of the
corresponding Example sample. FIGS. 1 and 2 are referred to for
comparison.
TABLE V
______________________________________
Ex. 9 10 11 12 13 14 15 16
______________________________________
% NS Asphalt 77 74 77 77
% MC Asphalt
77 74 77 77
% Sample F
3 3 6 6 3 3 3 3
% NS Saturant 20 20 20 20
% MC Saturant
20 20 20 20
Figure 6 7 8 9 10 11 12 13
Days
Aged @
350.degree. F.
0 0 0 0 3 3 7 7
______________________________________
FIGS. 6 and 7 show homogeneous blends of oxidized Mid-Continent and North
Slope asphalt containing 3% of Sample F oxidized polyethylene, 20%
saturant and no aging.
FIG. 8 shows a blend of oxidized Mid-Continent asphalt, 6% Sample F
oxidized polyethylene, 20% saturant and no aging. The dispersion was
slightly worse than in FIG. 2 but the blend is stable and homogeneous.
FIG. 9 shows a blend of oxidized North Slope asphalt, 6% Sample F oxidized
polyethylene, 20% saturant and no aging. The dispersion appears to be
flocculent and upset. At 6% of Sample F, the Mid-Continent asphalt was
more homogeneous and is preferred.
FIG. 10 shows a homogeneous blend of oxidized Mid-Continent asphalt
containing 3% of Sample F oxidized polyethylene, 20% saturant and aging
for three days at 350.degree. F. There are some coarse particles present
which do not appear to be oxidized polyethylene.
FIG. 11 shows a homogeneous blend of oxidized North Slope asphalt,
containing 3% of Sample F oxidized polyethylene, 20% saturant and aging
for three days at 350.degree. F.
FIG. 12 shows a homogeneous blend of oxidized Mid-Continent asphalt
containing 3% of Sample F oxidized polyethylene, 20% saturant and aging
for seven days at 350.degree. F.
FIG. 13 shows a blend of oxidized North Slope asphalt containing 3% of
Sample F oxidized polyethylene, 20% saturant and aging for seven days at
350.degree. F. The blend is homogeneous with occasional crystals of what
is apparently oxidized polyethylene.
Therefore, the oxidized polyethylene used in the formulation of the present
invention achieves compatibility with the oxidized asphalt and results in
an asphalt formulation having superior aging properties as well as low
temperature flexibility. Additionally, modified asphalt can be used in
existing roof shingle production facilities and processes.
The formulation of the roofing asphalt of the present invention can be made
by one of two methods. In the first method unoxidized asphalt is mixed
with unoxidized polyethylene. The mixture is heated to about 400.degree.
F. to 500.degree. F. for about 4 to 6 hours. While it is being heated, air
is blown through the mixture. The asphalt becomes crosslinked and oxidized
and the polyethylene becomes oxidized. Alternatively, and preferably the
asphalt may be oxidized and/or crosslinked to any degree and then the
unoxidized polyethylene added. The oxidation process is then continued
thereby controlling the oxidation of each component while insuring a
uniform and compatible mixture. Under these oxidation conditions, saturant
may or may not be needed to control or adjust the viscosity of the blend.
The oxidized mixture of asphalt and polyethylene form a compatible
colloidal mixture. The viscosity of this mixture can be modified by the
addition of saturant when air is no longer being blown through the
mixture.
A catalyst can be used during the step of heating and blowing air through
the mixture. The mixture can then be heated between 350.degree. F. and
500.degree. F. for 2 to 4 hours and achieve the same result as if a
catalyst is not used. A preferred catalyst is ferric chloride
(FeCl.sub.3), although any catalyst known in the art which is used to
oxidize asphalt can be used.
In an alternative and preferred method, oxidized asphalt can be added and
mixed directly with oxidized polyethylene. Saturant can be added to the
mixture to modify it to the desired viscosity. In this way, a satisfactory
formulation is also obtained. The formulations in the above Examples were
prepared according to this method.
Modifications, changes, and improvements to the preferred forms of the
invention herein disclosed, described and illustrated may occur to those
skilled in the art who come to understand the principles and precepts
thereof. Accordingly, the scope of the patent to be issued hereon should
not be limited to the particular embodiments of the inventions set forth
herein, but rather should be limited by the advance of which the invention
has promoted the art.
* * * * *
|
|
 |
|
 |
Description |
|
