Infrared reflecting vinyl polymer compositions

The invention relates to a vinyl polymer composition suitable for outdoor use in the sunlight. The heat buildup in articles made from the composition is lowered without changing the ultraviolet protection or the color of the articles. This is accomplished by employing in the composition a black infrared reflecting pigment, such as a mixture of Cr.sub.2 O.sub.3 and Fe.sub.2 O.sub.3, and other infrared reflecting pigments.

BACKGROUND OF THE INVENTION 
Polymeric materials, such as vinyl polymers, and products made therefrom, 
must exhibit resistance to degradation if they are to have any useful 
commercial value, particularly for outdoor use, such as in house siding, 
and the like. The degradation referred to can be a partial or total loss 
of structural integrity, a darkening or discoloration of the product, a 
loss of flexibility or resilience, loss of shape due to softening, or a 
combination of any of these phenomena. The various types of degradation, 
above referred to, are promoted or catalyzed by oxygen (air), heat, and 
light, particularly sunlight in the ultraviolet (UV), visible, and 
infrared (IR) ranges. 
In order to protect polymeric materials, it has been the practice 
heretofore to add various ingredients or stabilizers to the polymers, or 
compounds thereof, to prevent or inhibit degradation of finished articles 
made therefrom. These stabilizers work in diverse and complex ways, such 
that a compound that stabilizes against heat and oxygen degradation in a 
polymer or resin may not stabilize the same against light degradation, or 
vice versa. In many instances, to obtain optimum protection, a mixture of 
compounds, each specifically selected to afford maximum protection against 
a certain type of degradation, is often used. 
It is well known that light energy from the sun causes a temperature rise 
in articles exposed to the sun. This is a particularly bad problem in the 
case of vinyl house siding since it causes "oil canning" of the siding 
which is a surface distortion. Oil canning is caused by the fact that the 
center of the siding panel is longer than the butt and hanger and the 
longer center causes a wave in the panel. If the butt and hanger portions 
have shrunk, then the oil canning will be permanent. For example, the 
center of the panel, which is in the sun, will be hotter and therefore due 
to thermal expansion longer than the butt and hanger, which are shaded. To 
minimize the thermal expansion problem, colors must be chosen which do not 
absorb too much of the sun's energy and the materials chosen must not have 
too high a coefficient of linear expansion. 
Vinyl, and many other plastic materials, require ultraviolet absorbers for 
protection during weathering. These absorbers may be organic materials, 
titanium dioxide, carbon black, etc. However, by absorbing the ultraviolet 
light, the articles are heated by the ultraviolet and not much can be done 
to change this heating. Also, pigments which absorb or reflect in the 
visible light region are sometimes added to give color. However, these 
pigments absorb the visible light and heat the article by this absorbed 
light. To change the amount of light absorbed in the visible light region 
would change the color and, accordingly, nothing can be done to change the 
visible heat absorbed. 
It would be particularly desirable to have pigments, or other materials, 
which would reflect infrared energy and which would lower the heating of 
the article without changing the ultraviolet protection or the color 
thereof. It would be desirable to have a pigment, such as a black pigment, 
which reflects infrared light. Carbon black pigment has been proposed but, 
since it absorbs light in the ultraviolet, and infrared regions, it is 
particularly bad for causing heating of articles. 
In the "Encyclopedia of Polymer Science and Technology", (1971), Volume 10, 
page 165, it is stated that black iron oxides exhibit excellent 
light-fastness, good weathering resistance and fair to good heat 
resistance. Also, that brown iron oxides exhibit excellent light-fastness 
and good resistance to heat. However, there is no indication therein that 
the iron oxides are infrared reflecting, which is most desirable in vinyl 
compounds to reduce the heat buildup, and particularly in vinyl house 
siding which is exposed to the sun. 
SUMMARY OF THE INVENTION 
It has been found that, by the proper choice of pigments, which reflect 
infrared energy, the heating of the article, such as vinyl house siding, 
can be lowered without changing the ultraviolet protection or the color of 
the article. It has been further found that a black infrared reflecting 
pigment, such as a mixture of Cr.sub.2 O.sub.3 and Fe.sub.2 O.sub.3, which 
is weatherable, and other infrared reflecting pigments, when employed in 
vinyl polymer compounds, substantially reduce the heat buildup in articles 
made therefrom when exposed to the sun. It is important to have a black 
pigment which reflects infrared light since carbon black is particularly 
bad for causing heating of articles. 
DETAILED DESCRIPTION 
The polymeric compositions of the present invention are comprised of a main 
vinyl polymer material and an infrared reflecting pigment. Also, the 
compositions may contain a plasticizer for the vinyl polymer. Thus, the 
vinyl polymer particles should be porous to allow for good penetration of 
the plasticizer therethrough. 
Vinyl polymer, or vinyl polymer material, as used herein, refers to 
homopolymers and copolymers of vinyl halides and vinylidene halides, such 
as vinyl chloride, vinyl bromide, vinylidene chloride, etc. The vinyl 
halides and vinylidene halides may be copolymerized with each other or 
each with one or more polymerizable olefinic monomers having at least one 
terminal CH.sub.2 =C< grouping. As examples of such olefinic monomers 
there may be mentioned the .alpha.,.beta. -olefinically unsaturated 
carboxylic acids, such as acrylic acid, methacrylic acid, ethacrylic acid, 
.alpha.-cyanoacrylic acid, and the like; esters of acrylic acid, such as 
methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, 
cyanoethyl acrylate, and the like; esters of methacrylic acid, such as 
methyl methacrylate, butyl methacrylate, and the like; nitriles, such as 
acrylonitrile, methacrylonitrile, and the like; acrylamides, such as 
methyl acrylamide, N-methylol acrylamide, N-butoxy methacrylamide, and the 
like; vinyl ethers, such as ethyl vinyl ether, chloroethyl vinyl ether, 
and the like; the vinyl ketones; styrene and styrene derivatives, such as 
-methyl styrene, vinyl toluene, chlorostyrene, and the like; vinyl 
naphthalene, allyl and vinyl chloroacetate, vinyl acetate, vinyl pyridine, 
methyl vinyl ketone; the diolefins, including butadiene, isoprene, 
chloroprene, and the like; and other polymerizable olefinic monomers of 
the types known to those skilled in the art. 
The present invention is particularly applicable to homopolymers and 
copolymers made by the polymerization of vinyl chloride or vinylidene 
chloride alone or in admixture with one or more polymerizable olefinic 
monomers copolymerizable therewith in amounts up to about 40% by weight, 
based on the weight of the monomer mixture. The most preferred vinyl 
polymer, or resin, is polyvinyl chloride (PVC) and the invention, for 
simplicity and convenience, will be described in connection therewith, it 
being understood that this is merely intended in an illustrative sense and 
not limitative. 
The vinyl polymer compositions of the present invention are useful in 
making any type article which will be exposed to sunlight, and 
particularly for prolonged periods of time. However, the vinyl polymer 
compositions are particularly useful in making vinyl house siding wherein 
weatherability is important and likewise, the reduction of heat buildup in 
the siding in order to prevent or substantially reduce surface distortion 
or oilcanning of the siding. The siding may be all one piece, or it may be 
an extruded composite of a substrate and a capstock thereover. When a 
composite is employed, the capstock will contain the infrared reflecting 
pigment. 
Irrespective of the article to be made, the proper vinyl chloride polymer 
should be employed. It is preferred, in most instances, to use PVC and 
particularly, in making house siding. In any event, the vinyl chloride 
polymer particles must have good porosity in order to efficiently absorb 
plasticizer. Solid nonporous polymers must be more highly swollen and 
require too high a concentration of plasticizer to produce acceptable 
products or articles. It has been found that vinyl chloride polymer 
particles containing from about 15% to about 50% by volume of pore space 
are satisfactory in making products suitable for use outdoors in the 
sunlight. Preferably, the polymer particles will contain from about 25% to 
about 35% by volume of pore space. 
The amount of plasticizer that is usually employed to give satisfactory 
results is in the range of about 10 parts to about 40 parts by weight 
based on the weight of 100 parts of vinyl chloride polymer. Preferably, 
however, the amount of plasticizer employed will be in the range of about 
20 parts to about 30 parts by weight, based on the weight of 100 parts of 
polymer. The amount of plasticizer employed in the present invention is 
well below the amounts usually employed in making plasticized vinyl 
polymers and, particularly, in making PVC plastisols for use in making 
films, etc., where flexibility is important. When amounts of plasticizer 
greater than 40 parts by weight per 100 parts by weight of vinyl chloride 
polymer are used, there is an adverse effect on the article or product 
resulting in lowering the impact retention thereof upon weathering. 
As examples of suitable plasticizers for use in the present invention are 
the phthalic acid and isophthalic acid diesters of benzyl or phenyl 
radicals, or alkyl, alkoxyalkyl or cycloalkyl radicals containing from 1 
to 24 carbon atoms, and preferably 4 to 16 carbon atoms, such as, for 
example, diisooctyl isophthalate, butyl benzyl phthalate, diphenyl 
phthalate, dimethyl phthalate, diisobutyl phthalate, diisoamyl phthalate, 
diisohexyl phthalate, di-n-hexyl phthalate, di-(2-ethyl hexyl) phthalate, 
diisooctyl phthalate, di-n-octyl phthalate, butyl nonyl phthalate, butyl 
decyl phthalate, isooctyl isodecyl phthalate, n-octyl n-decyl phthalate, 
di(butoxyethyl) phthalate, dicyclohexyl phthalate, and the like. In 
addition, there are other plasticizers useful in the present invention, 
such as, for example, diisobutyl adipate, diisooctyl adipate, di-(2 ethyl 
hexyl) adipate, diisodecyl adipate, isooctyl isodecyl adipate, epoxidized 
soybean oil, di(2-ethyl hexyl) agelate, diisooctyl agelate, dibenzyl 
sebacate, dimethyl sebacate, dibutyl sebacate, di-(2-ethyl hexyl) 
sebacate, diisooctyl sebacate, and the like. Also suitable as plasticizers 
are the ricinoleates, such as, for example, diethylene glycol 
monorisinoleate, methyl recinoleate, and the like. Further, 
triorganophosphates may also be used, such as triphenyl phosphate, cresyl 
diphenyl phosphate, tributyl phosphate, and the like. The preferred 
plasticizers for use in the present invention are the liquid phthalate 
plasticizers, among which di-(2-ethyl hexyl) phthalate or diisodecyl 
phthalate are particularly good in producing the desired results. A 
mixture of plasticizers may also be employed, that is, two or more of the 
above type plasticizers, depending upon the particular vinyl chloride 
being used and the porosity thereof. 
Of course, the most important ingredients in the compositions of the 
present invention are the infrared reflecting pigments and, in particular, 
black infrared reflecting pigments. The most important infrared reflecting 
black pigment is O-1316 Black made by the Ferro Corporation of Cleveland, 
Ohio, which is a mixture of Cr.sub.2 O.sub.3 and Fe.sub.2 O.sub.3. By the 
use of such pigments, the heating of vinyl polymer articles, such as vinyl 
house siding, is lowered without changing the ultraviolet protection or 
the color thereof. 
In order to get variation in colors of the vinyl polymer articles, other 
infrared reflecting pigments are employed in combination with the black 
pigment. As examples of other infrared reflecting pigments there may be 
named phthalocyanine blue, meteor light brown #7229 (Mn-Zn-Al-Cr oxides), 
chromium oxide green, bright golden yellow (Ti-Sb-Cr oxides), chromathal 
brown 5R, phthalocyanine green, cobalt blue #1, titanium dioxide, etc. The 
black pigment should be used in the vinyl polymer compositions in the 
preferred range of about 0.25 part to about 15 parts by weight, more 
preferably from about 0.5 part to about 10 parts by weight, the black 
pigment should be used at an effective level, based on the weight of the 
vinyl polymer or polymers in the composition. The other infrared 
reflecting pigments will be varied in amounts, depending upon the desired 
color wanted in the finished article. However, it should again be pointed 
out that the use of carbon black pigment is to be avoided, since it 
absorbs light in the ultraviolet, visible and infrared and is particularly 
bad for causing heat buildup in vinyl polymer articles. This is very 
vividly shown in the specific examples that follow hereinafter. 
To further illustrate the present invention, the following specific 
examples are given, it being understood that this is merely intended in an 
illustrative and not a limitative sense. In the examples, all parts and 
percents are by weight unless otherwise indicated.

EXAMPLE I 
In this example, a series of 12 capstock runs and 2 rigid, unplasticized 
PVC runs were made, Capstock is the outer weatherable layer in coextended 
vinyl house siding and vinyl windows, etc. In the runs, carbon black was 
used as the control and compared to an infrared reflecting black pigment 
obtained from the Ferro Corporation of Cleveland, Ohio and referred to as 
" O- 1316 Black". The ingredients of each of the runs were mixed on a 
2-roll mill for 3 minutes at 340.degree. F. Each composition was preheated 
for 5 minutes at a temperature of 340.degree. to 350.degree. F. and then 
put in a press and formed into panels 6 in..times. 6 in..times. 0.45 in. 
They were pressed for 5 minutes. The heat buildup in each case was 
measured by the procedure referred to in the article entitled 
"Understanding The Cooling and Sizing Requirements of Vinyl House Siding" 
by J. W. Summers and R. J. Brown, published May, 1979 in Soc. of Plastic 
Engrs., Technical Papers, Vol. XXV, p. 403. The formulations in each run 
and the heat buildup results are given in the following table. In the 
table, the odd-numbered runs, namely 1, 3, 5, 7, 9, 11 and 13, contain 
carbon black and the even-numbered runs 2, 4, 6, 8, 10, 12 and 14 contain 
the infrared reflective black pigment in amounts which given the same 
color match as with carbon black. In the table, all the figures are parts 
by weight based on 100 weight parts of PVC. 
TABLE I 
__________________________________________________________________________ 
RUN NO. 
1 2 3 4 5 6 
COLOR 
INGREDIENTS DARK BLUE 
DARK GREEN 
BEIGE 
__________________________________________________________________________ 
PVC (polyvinyl Chloride) 
100 100 100 100 100 100 
Tin Thioglycolate Type Stabilizer 
3 3 3 3 3 3 
Di-(2-Ethyl Hexyl) Phthalate 
25 25 25 25 25 25 
Lubricants 1.6 1.6 1.6 1.6 1.6 1.6 
Aluminum Silicate, Anhydrous 
10 10 10 10 10 10 
Titanium Dioxide 12.5 
12.5 
8 8 15 15 
Carbon Black 0.02 
-- 0.02 
-- 0.022 
-- 
Ferro Black (Cr.sub.2 O.sub.3 --Fe.sub.2 O.sub.3) 
-- 0.64 
-- 0.64 -- 0.7 
Pigments A 7.2 7.2 -- -- -- -- 
Pigments B -- -- 9.6 9.6 -- -- 
Pigments C -- -- -- -- 1.7 1.7 
Heat Buildup in .degree.C. 
30.degree. 
26.degree. 
31.degree. 
27.degree. 
27.degree. 
21.degree. 
__________________________________________________________________________ 
RUN NO. 
7 8 9 10 11 12 13 14 
COLOR 
INGREDIENTS TAN GRAY BROWN 
__________________________________________________________________________ 
PVC (polyvinyl Chloride) 
100 
100 
100 
100 
100 
100 
100 100 
Tin Thioglycolate Type Stabilizer 
3 3 3 3 3 3 2 2 
Di-(2-Ethyl Hexyl) Phthalate 
25 25 25 25 25 25 -- -- 
Lubricants 1.6 
1.6 
1.6 
1.6 
1.6 
1.6 
3.75 
3.75 
Aluminum Silicate, Anhydrous 
10 10 10 10 10 10 -- -- 
Titanium Dioxide 5 5 15 15 7 7 7 7 
Carbon Black 0.08 
-- 0.05 
-- 0.3 
-- .3 -- 
Ferro Black (Cr.sub.2 O.sub.3 --Fe.sub.2 O.sub.3) 
-- 2.56 
-- 1.54 
-- 9 -- 9 
Pigments D 9 9 -- -- -- -- 1.7 1.7 
Pigments E -- -- 9.6 
9.6 
1.7 
1.7 
1.5 1.5 
Processing Aid - Acrylic Type 
-- -- -- -- 1.7 
1.7 
-- -- 
Impact Modifier - Acrylic 
-- -- -- -- -- -- 6 6 
Heat Buildup in .degree.C. 
36.degree. 
27.degree. 
32.degree. 
22.degree. 
41.degree. 
28.degree. 
38.degree. 
27.degree. 
__________________________________________________________________________ 
As can be seen from the above data, heat buildup is lowered up to as much 
as 13.degree. C. when employing the infrared reflecting black pigment. 
This is a considerable improvement over the use of carbon black. 
The vinyl polymer compositions of the present invention are most useful in 
the manufacture of house siding and other building siding, shutters, roof 
vents, camper tops, and other like materials which are subjected to 
prolonged exposure to sunlight. Further, the present compositions 
substantially reduce "oil canning" in vinyl house siding. 
While the present invention has been described in terms of its specific 
embodiments, certain modifications and equivalents will be apparent to 
those skilled in the art and are intended to be included within the scope 
of the present invention, which is to be limited only by the scope of the 
appended claims.