Polyolefin compositions and method and compositions for their preparation

A method for the nucleation of polyolefins containing residual polymerization catalyst by blending the polyolefins with at least one aliphatic dicarboxylic acid containing from about 4 to about 21 carbon atoms and at least one aliphatic monocarboxylic acid containing from about 8 to about 24 carbon atoms in a weight ratio between about 4:1 and about 1:4. Also a composition comprising at least one aliphatic dicarboxylic acid containing from about 4 to about 21 carbon atoms and at least one aliphatic monocarboxylic acid containing from about 8 to about 24 carbon atoms. The polyolefin product of the nucleation can be molded into shaped articles.

FIELD OF THE INVENTION 
The present invention relates to polyolefin compositions having improved 
transparency. It further relates to compositions capable of improving the 
transparency of polyolefins and to methods of incorporating said 
compositions into the often translucent polyolefins. An important aspect 
of the present invention is the nucleation of polyethylene, polypropylene, 
and copolymers and mixtures thereof with an aliphatic dicarboxylic acid 
containing from about 4 to about 21 carbon atoms and an aliphatic 
monocarboxylic acid containing from about 8 to about 24 carbon atoms. 
BACKGROUND OF THE INVENTION 
Olefin homopolymers and copolymers have become of commercial importance for 
the manufacturers of numerous shaped articles and other utilities. 
Unfortunately the olefin homopolymers and copolymers are often translucent 
due to the crystal structure of the polymer. Improvement in the clarity of 
the homopolymer and copolymer can be obtained by the use of nucleating 
agents which enhance nucleation rather than crystal growth during 
solidification of molten polymer. The use of nucleating agents causes the 
formation of smaller crystals and accordingly polyolefins having improved 
clarity and physical properties. In addition the nucleated polyolefins 
have higher crystallization temperatures. Consequently nucleating 
materials are of significant importance in improving the value of the 
polyolefins. 
The requirements for an effective nucleating agent are difficult to meet 
particularly since it must be effective at low concentrations. In order to 
function as an effective nucleating agent, the compound must be partially 
insoluble in the polyolefin. On the other hand in order to achieve 
clarity, the nucleating material must be transparent in the polyolefin at 
the concentration it is used as a nucleating agent. 
Among the other characteristics of a nucleating agent are good thermal 
stability and the substantial absence of odor, particularly at the melt 
processing temperatures of the polyolefin. Low melting points and good 
dispersibility are important in improving mixing of the nucleating 
compound into the molten polyolefin. 
An object of the present invention is a new nucleating agent for 
polyolefins. 
Another object of the present invention is a polyolefin having improved 
clarity. 
Still another object of the present invention is a shaped article from 
polyolefins which are substantially transparent. 
Also an object of the present invention is a method for improving the 
clarity of polyolefins. 
A particular object of the present invention is an improvement in the 
process for the preparation of polypropylene and polyethylene polymers and 
copolymers and mixtures thereof which are substantially transparent. 
Other objects will become apparent from the ensuing description. 
Many materials have been proposed for use as nucleating agents with some 
success. Among these disclosures are: 
U.S. Pat. No. 3,207,735 discloses the use of benzoic acid type compounds to 
improve the properties of polypropylene. 
U.S. Pat. No. 3,207,738 discloses the crystallization of polypropylene 
using aryl alkanoic acid type compounds. 
U.S. Pat. No. 3,268,499 discloses the crystallization of polymers such as 
polypropylene in the presence of lithium salts of carboxylic acids. 
U.S. Pat. No. 3,299,029 discloses the crystallization of polymers such as 
polypropylene in the presence of aluminum salts of carboxylic acids. 
U.S. Pat. No. 3,517,086 discloses aromatic sulfonic acids as nucleating 
agents. 
U.S. Pat. No. 4,704,421 discloses benzoic acid and adipic acid as 
nucleating agents for propylene polymers. 
U.S. Pat. No. 4,801,637 discloses the use of an alcoholic solution of an 
aromatic carboxylic acid as a nucleating agent for certain crystalline 
propylene homopolymers or copolymers. 
U.S. Pat. No. 4,829,114 discloses a combination of carboxylic acids which 
contain at least three carbon atoms and an amine such as an ethoxylated 
amine as nucleating agents for polyolefins. 
SUMMARY OF THE INVENTION 
The method of the present invention provides for the effective nucleation 
of polyolefins containing residual polymerization catalyst by blending the 
polyolefin with an effective amount of a combination of at least one 
aliphatic dicarboxylic acid containing from about 4 carbon atoms to about 
21 carbon atoms and at least one aliphatic monocarboxylic acid containing 
from about 8 to about 24 carbon atoms wherein the weight ratio of the 
aliphatic dicarboxylic acid to the aliphatic monocarboxylic acid is 
between about 4:1 and about 1:4. The present invention further provides 
compositions comprising at least one aliphatic dicarboxylic acid 
containing from about 4 carbon atoms to about 21 carbon atoms and at least 
one monocarboxylic acid containing from about 8 to about 24 carbon atoms 
in a weight ratio of between about 4:1 and about 1:4. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides for polyolefins having improved clarity and 
higher crystallization temperatures. The polyolefins can be homopolymers 
and copolymers and mixtures thereof which under normal polymerization 
techniques vary from being translucent to opaque depending upon the 
polyolefin, the polymerization technique, the thickness of the film or 
shaped article made therefrom and other factors. Among the polyolefins of 
this description are ethylene and propylene homopolymers and copolymers. 
Polyethylene can be low density and high density polymeric material. 
Linear low density polyethylene is in general a copolymer of ethylene and 
up to about 10 weight percent of a second olefin, such as propylene, 
butene, hexane or octene. High density polyethylene is normally a 
homopolymer. 
Propylene polymers are also widely used and are useful in the present 
invention. They are prepared by well-known processes involving the use of 
various catalysts, particularly Ziegler-Natta type catalysts, which are 
highly active and stereospecific. The Ziegler type catalysts may be 
designated "metal alkyl-reducible metal halide type," and the Natta type 
catalysts "preformed metal subhalide type." This terminology is used, for 
example, in "Polyolefin Resin Processes" by Marshall Sittig, Gulf 
Publishing Company, Houston, Tex., 1961. These well known catalysts are 
the reaction products of halides, in order of preference chlorides and 
bromides, of transition metals from subgroups of groups 4 and 5 of the 
Mendeleeff Periodic Table, as illustrated on page 28 of Ephraim, 
"Inorganic Chemistry" 6th English Edition, i.e., of Ti, Zr, Hf, Th, V, Nb 
or Ta, with organo metallic reducing agents in which the metal is from 
groups 1, 2 or 3. Preferred reducing agents are organoaluminum compounds 
and particularly aluminum alkyls, including aluminum alkyl halides. The 
most effective catalysts for the production of isotactic polypropylene 
known to date are those prepared from certain forms of titanium 
tetrachloride supported on anhydrous magnesium halide, certain aluminum 
alkyls, and organic esters. 
In the current production of crystallizable alpha olefin polymers, the 
reaction mixture formed in the low pressure polymerization is treated to 
deactivate the catalyst. The resulting polymer almost invariably contains 
at least traces of the catalyst residue. Typically it may contain 10 to 
100 parts per million (p.p.m.) of each of the catalyst components, 
calculated as the corresponding metal. A carefully purified polymer may 
contain as little as 1 p.p.m. of each metal or less. In order for the 
additives of this invention to be fully effective the polymer should 
contain at least about 25 p.p.m. of the residue of at least one of the 
catalyst components, calculated as the corresponding metal. Often, these 
catalysts are comprised of an aluminum alkyl component and a titanium 
compound supported on magnesium dihalide as a second component. 
Homopolymers of propylene and copolymers of propylene with other 
1-olefins, such as ethylene and butene, and mixtures thereof can be used. 
Random copolymers of propylene and ethylene containing between about 1 and 
about 10 weight percent ethylene and mixtures of such random copolymers 
with a linear low density polyethylene are useful. 
The polymerization process can be performed as a liquid or gas phase 
polymerization process. A slurry process uses a liquid hydrocarbon as a 
diluent and the polyolefin precipitates from the diluent as it is formed. 
Saturated hydrocarbons or liquid propylene can be used as the diluent. 
A gas phase process can also be used. In this type of process the monomer 
mixture is introduced into a stirred or fluidized bed of polyolefin 
particles. About 25 weight percent of the monomer is polymerized each pass 
through the reactor and the remaining monomer is recycled back into the 
reactor. This procedure serves to remove the heat of polymerization from 
the reactor. 
Various additives are often generally incorporated into the polyolefin. One 
such group of additives are antioxidants such as hindered phenols, 
phenolic phosphites, secondary arylamines and the like. These antioxidants 
are used in quantities between about 0.01 to about 1 weight percent of the 
polymer. Other additives such as colorants, antiblocking agents, 
antistatic agents and lubricants are commonly used. 
The method of the present invention results in improved clarity and higher 
crystallization temperatures for the aforedescribed polyolefins. It 
comprises melt blending into the polyolefin containing residual 
polymerization catalyst an effective amount of a combination of at least 
one aliphatic dicarboxylic acid containing from about 4 to about 21 carbon 
atoms and at least one aliphatic monocarboxylic acid containing from about 
8 to about 24 carbon atoms in a weight ratio between about 4:1 and about 
1:4, preferably about 1:1. The monocarboxylic acid and dicarboxylic acid 
can be added separately to the polyolefin or can be premixed prior to 
being blended with the polyolefin. 
The new compositions of the present invention useful for nucleating 
polyolefins comprise at least one aliphatic dicarboxylic acid containing 
from about 4 to about 21 carbon atoms and at least one aliphatic 
monocarboxylic acid containing from about 10 to about 24 carbon atoms in a 
weight ratio of between about 4:1 and 1:4, preferably 1:1. While the 
components in accordance with the present method can be blended separately 
with the polyolefin, it is preferred that the composition be preprepared 
by mixing the acids separately and then blending the compositions thus 
formed with the polyolefin. 
Various methods of blending the nucleating composition of the present 
invention into the polyolefin can be used. The nucleating acids can be 
melt blended into the polyolefin to form a masterbatch. This masterbatch 
can then be melt blended with additional polyolefin to obtain the desired 
concentration of the nucleating agents in the polyolefin. 
Variations of this procedure can be followed. For example the components of 
the present nucleating composition can be mixed in the same masterbatch or 
in separate masterbatches. The separate masterbatches can be blended into 
the polyolefin simultaneously or sequentially. 
Also the nucleating agents can be dissolved in solvent, such as isopropanol 
and the solution added to the polyolefin. After evaporation of the 
solvent, the resulting mixture can be melt blended to nucleate the 
polyolefin. 
The amount of nucleating agent used in the present method will depend upon 
various factors including but not limited to the identity and properties 
of the polyolefin; the specific identify of the nucleating agent; the 
temperature at which the method is performed, etc. In general a minimum of 
about 0.1 weight percent of the combined weight of aliphatic dicarboxylic 
acid and aliphatic monocarboxylic acid based on the weight of the 
polyolefin will suffice in nucleating the polyolefin. While higher amounts 
can be used, normally there is no significant improvement when there is 
used more than about 1 weight percent of the combined weight of aliphatic 
dicarboxylic acid and aliphatic monocarboxylic acid based on the weight of 
the polyolefin, although the use of higher amounts is within the scope of 
the present invention. 
Exemplary of aliphatic monocarboxylic acids useful in the present invention 
are oleic acid, stearic acid, behenic acid, myristic acid, pentadecanoic 
acid, palmitic acid, margaric acid, abietic acid, lauric acid, linoleic 
acid, ricinoleic acid, hydroxystearic acid, arachidic acid, eicosenoic 
acid, erucic acid, tetracosenoic acid, elaidic acid and mixtures thereof. 
It is of particular value in the present invention to use products of 
naturally occurring materials. Of particular use are products obtained by 
the hydrolysis of fats and oils, such as beef tallow, coconut oil, olive 
oil, palm oil, rapeseed oil, soybean oil and hydrogenated derivatives 
thereof. 
Similarly the aliphatic dicarboxylic acid useful in the present invention 
can be a single compound or a mixture of aliphatic dicarboxylic acids. 
Examples of aliphatic dicarboxylic acids useful in the present invention 
are adipic acid, sebacic acid, succinic acid, suberic acid, dodecanedioic 
acid and glutaric acid. 
The nucleated products of the present invention comprise an olefin polymer, 
particularly ethylene and propylene homopolymers and copolymers; residual 
polymerization catalyst; at least one aliphatic dicarboxylic acid 
containing from about 4 to about 21 carbon atoms and at least one 
aliphatic monocarboxylic acid containing from about 8 to about 24 carbon 
atoms. These polyolefin compositions have improved clarity and are often 
substantially transparent. 
Shaped articles according to this invention may be manufactured from the 
mixtures according to this invention by casting, compression molding or 
injection molding; films may be obtained by blowing or by extrusion; 
filament, bars, tapes and the like, may be obtained by extrusion. This 
invention is useful in all other processes involving melting of the 
polymer followed by solidification. 
A series of experiments were performed to determine the effectiveness of 
the present invention for nucleating polyolefins. The effectiveness of the 
materials was determined by measuring the haze of polypropylene blended 
with various nucleating materials. 
Haze values were determined by compressing a thin plaque (0.025 inches 
thick) molded at 220.degree. C. or injection molded at a thickness of 
0.050 inches. The haze value of the plaque was measured on a Pacific 
Scientific XL 211 Hazeguard System. Low haze values indicate high clarity. 
Also, where desired, crystallization temperatures were determined by the 
use of a Perkins-Elmer DSC-2 differential scanning calorimeter. In this 
test a polymer sample is heated to 200.degree. C. and held there for 5 
minutes. The sample is then cooled at a rate of 10.degree. C. per minute.

EXAMPLE 1 
The test nucleating compounds were blended with Quantum Chemical 8000GK 
polypropylene (399 grams) by shaking in a plastic bag for two minutes. 
Each of the mixtures was extruded through a twin screw extruder at 
210.degree. C. Then the extrusion was cooled in a water bath and 
pelletized. This procedure was repeated three time with each mixture and 
the haze determined with the following results: 
______________________________________ 
TEST COMPOSITION 
Amount Amount 
Diacid (Grams) Monoacid (Grams) 
HAZE 
______________________________________ 
-- -- 78 
Adipic 1 -- 81 
-- Hystrene.RTM. 7018 
1 76 
Adipic 1 Lauric 1 71 
Adipic 1 Stearic 1 72 
Adipic 1 Behenic 1 63 
Adipic 1 Oleic 1 63 
Adipic 1 Hystrene.RTM. 7018 
0.5 59 
Adipic 1 Hystrene.RTM. 7018 
1 64 
Adipic 0.5 Hystrene.RTM. 7018 
1.5 70 
Adipic 1 Hystrene.RTM. 7018 
2 68 
Adipic 1 Hystrene.RTM. 7018 
3 83 
Succinic 
1 -- 80 
Succinic 
1 Hystrene.RTM. 7018 
1 61 
Adipic 1 Elaidic 0.5 
Stearic 0.5 59 
______________________________________ 
Hystrene 7018 is a mixture of myristic acid (3%), pentadecanoic acid 
(0.5%), palmitic acid (29%), margaric acid (2%), stearic acid (65%) and 
oleic acid (0.5%) obtained by the hydrolysis of beef tallow, followed by 
hydrogenation. 
EXAMPLE 2 
The procedures of Example 1 were repeated using different diacids with the 
following results. 
______________________________________ 
TEST COMPOSITION 
Amount Amount 
Diacid (Grams) Monoacid (Grams) 
HAZE 
______________________________________ 
-- -- 78 
-- Hystrene.RTM. 7018 
1 76 
Glutaric 
1 -- 72 
Glutaric 
1 Hystrene.RTM. 7018 
1 45 
Azelaic 1 -- 92 
Azelaic 1 Hystrene.RTM. 7018 
1 67 
Suberic 1 -- 73 
Suberic 1 Hystrene.RTM. 7018 
1 60 
Suberic 1 Oleic 1 67 
Suberic 1 Stearic 1 57 
Suberic 1 Behenic 1 60 
Sebacic 1 -- 70 
Sebacic 1 Hystrene.RTM. 7018 
1 66 
Sebacic 1 Stearic 1 62 
Sebacic 1 Behenic 1 57 
Dode- 1 -- 60 
cane- 
dioic 
Dode- 1 Stearic 1 58 
cane- 
dioic 
Dode- 1 Behenic 1 57 
cane- 
dioic 
Adipic 0.5 
Succinic 
0.5 Hystrene.RTM. 7018 
1 63 
Adipic 0.5 
Suberic 0.5 Hystrene.RTM. 7018 
1 71 
______________________________________ 
Example 3 compares the results of using the procedure of Example 1 and 
mixing two separate masterbatches. 
EXAMPLE 3 
A masterbatch of Quantum Chemical 8000 GK polypropylene (380 grams) and a 
mixture of Hystrenes.RTM. 7018 (10 grams) and adipic acid (10 grams) was 
melt blended in a twin-screw extruder and pelletized. A second masterbatch 
of the same polypropylene (390 grams) and adipic acid (10 grams) was also 
melt blended in a twin screw extruder and pelletized. An additional 
quantity of the polypropylene (360 grams) and the two masterbatches (40 
grams of each) were blended and extruded and pelletized three times for 
each sample. The final blends contained polypropylene (399 grams) and 
adipic acid (1 gram) and polypropylene (398 grams), adipic acid (1 gram) 
and Hystrene.RTM. 7018 (1 gram), respectively. Haze values of compression 
molded plaques of each sample were determined. These values were compared 
with haze values of samples prepared in accordance with Example 1, as 
follows: 
______________________________________ 
TEST COMPOSITION 
Test Composition 
Preparation Technique 
Adipic Acid 
Hystrene.RTM. 7018 
HAZE 
______________________________________ 
Example 3 1 gram -- 81 
Example 3 1 gram 1 gram 64 
Example 1 1 gram -- 60 
Example 1 1 gram 1 gram 48 
______________________________________ 
Example 4 demonstrates an alternative procedure for blending the nucleating 
compounds and polyolefin. 
EXAMPLE 4 
8000 GK polypropylene (399 grams) was blended with adipic acid (1 gram) and 
Hystrene.RTM. 7018 (1 gram) in a plastic bag for one minute. The mixture 
was extruded and pelletized a total of four times. A second polypropylene 
blend was prepared, with the adipic acid (1 gram) blended, extruded and 
pelletized with the polypropylene (399 grams) once, followed by blending 
with the Hystrenes.RTM. 7018 (1 gram) and being extruded and pelletized 
three times. A third polypropylene blend was prepared with the 
Hystrene.RTM. 7018 (1 gram) blended with the polypropylene (339 grams), 
extruded and pelletized once, followed by blending with the adipic acid (1 
gram), extruded and pelletized three times. The results of the tests of 
the samples are as follows: 
______________________________________ 
Crystallization 
First Additive 
Second Additive 
Temp (.degree.C.) 
Haze 
______________________________________ 
Components 124.degree. C. 
60 
added 
together 
Adipic Acid 
Hystrene.RTM. 7018 
124.degree. C. 
59 
Hystrene.RTM. 7018 
Adipic Acid 123.degree. C. 
48 
______________________________________ 
EXAMPLE 5 
Example 5 was performed with a polypropylene random copolymer prepared in a 
gas phase process by Eastman Kodak. This copolymer contained 3.2 weight 
percent ethylene as the comonomer and as residual polymerization catalyst, 
magnesium (14 ppm) and aluminum (58 ppm). Blends were made of 
polypropylene copolymer (397 grams). Irganox 1010 (0.8 grams), Irgafos 168 
(0.8 grams), sodium carbonate (0.4 grams) and nucleating test compound. 
Each blend was extruded three times and compression molded samples were 
tested for haze, with the following results: 
______________________________________ 
TEST COMPOSITION 
Amount 
Diacid Amount (gr) 
Monoacid (gr) HAZE 
______________________________________ 
-- -- 68 
-- Hystrene.RTM. 7018 
1 67 
Adipic 0.5 Hystrene.RTM. 7018 
0.5 43 
Adipic 1 -- 43 
Adipic 1 Hystrene.RTM. 7018 
1 38 
Adipic 1 Hystrene.RTM. 7018 
2 40 
Suberic 1 -- 40 
Suberic 1 Hystrene.RTM. 7018 
1 38 
Sebacic 1 Hystrene.RTM. 7018 
1 39 
Adipic 1 Elaidic 1 43 
Adipic 1 Abietic 1 42 
Succinic 
1 Hystrene.RTM. 7018 
1 47 
______________________________________ 
IRGANOX is a trademark for an antioxidant for polyolefins comprising 
hindered phenol compounds. IRGAFOS is a trademark for a stabilizer 
containing a phosphorus compound. 
EXAMPLE 6 
Example 6 was performed for comparative purposes with de-ashed 
polypropylene prepared by Eastman Kodak not containing more than a trace 
of polymerization catalyst residues. Tenite 424 polypropylene contained 
calcium (29 ppm), magnesium (2 ppm) and aluminum (2 ppm). Pellets were 
blended with the test nucleating compounds by shaking in a plastic bag for 
1 minute. Each mixture was extruded at 200.degree. C. through a twin-screw 
extruder three times. Compression molded plaques were prepared from each 
sample and haze values were determined for each sample with the following 
results: 
______________________________________ 
TEST COMPOSITION 
Amount 
Diacid Amount (gr) 
Monoacid (gr) HAZE 
______________________________________ 
-- -- 72 
-- Hystrene.RTM. 70I8 
1 70 
Adipic 1 -- 85 
Adipic 1 Hystrene.RTM. 70I8 
1 97 
Suberic 1 -- 74 
Suberic 1 Hystrene.RTM. 7018 
1 78 
Sebacic 1 -- 74 
Sebacic 1 Hystrene.RTM. 7018 
1 73 
______________________________________ 
Example 6 demonstrates the need for residual catalyst in order to obtain 
improved clarity with the present nucleating compounds. 
EXAMPLE 7 
Blends using the procedure of Example 6 were prepared from Union Carbide 
G-7049 linear low density polyethylene containing magnesium (i ppm) and 
aluminum (52 ppm) prepared in a gas phase polymerization process. Each 
blend was extruded three times. Compression molded plaques were prepared. 
Haze values were determined for the plaques. Crystallization temperatures 
of the blends were also measured. The results were as follows: 
______________________________________ 
TEST COMPOSITION 
Amount Amount Crystalline 
Diacid 
(gr) Monoacid (gr) Temp. (.degree.C.) 
HAZE 
______________________________________ 
-- -- 106 77 
Adipic 
1 -- 109 48 
Adipic 
1 Hystrene.RTM. 
1 109 60 
7018 
______________________________________ 
As can be seen from the foregoing experimental test results, the method of 
the present invention results in polyolefin compositions having improved 
clarity and higher crystallization temperatures. These results were 
obtained from a variety of polyolefin compositions provided they contained 
sufficient residual polymerization catalyst. This amount will vary 
depending upon the identity of the catalyst, the polyolefin and the 
nucleating agent. In general, levels of residual polymerization catalyst 
as low as 25 parts per million, or lower, can be sufficient. 
The examples demonstrate that various polyolefin compositions can be 
effectively nucleated in accordance with the present invention. Also 
demonstrated is that various procedures for blending the polyolefin and 
nucleating agent can be used without altering the effectiveness of the 
method. Also the examples establish that the use of the mono- and diacids 
in accordance with this invention results in product having improved 
clarity over that obtained using only the monoacid or diacid as a 
nucleating agent. 
It should be understood that embodiments of the present invention have been 
described are merely illustrative of a few of the applications of the 
principles of the present invention. Numerous modifications may be made by 
those skilled in the art without departing from the spirit and scope of 
the invention.