Copolymers containing an alpha-olefin and an alpha, beta-ethylenically unsaturated carboxylic acid plasticized with long-chain fatty acid

This invention relates to copolymers containing an alpha-olefin and alpha, beta-ethylenically unsaturated carboxylic acid plasticized with a selected long-chain fatty acid. In a preferred embodiment, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers and their respective salts, i.e. ionomers, are plasticized using a selected long-chain fatty acid. The plasticized copolymers so obtained are generally characterized by having higher melt index, lower glass transition temperature (TG), greater flexibility, lower stiffness, higher resiliency and easier processibility than the corresponding unplasticized copolymers.

BACKGROUND OF THE INVENTION 
1. Field of The Invention 
The plasticizer technology of today is a hybrid of art and science, 
formulated and derived from the discoveries by various primitive people. 
For example, Neat's-foot and sperm oil applied to leather were 
plasticizers utilized by early artisans. Similarly, the modern plasticizer 
industry evolved as a result of surface coatings. For example, when a 
resin used in a varnish left a film that was inelastic and too brittle it 
was modified with a drying oil or other material which would impart to it 
the requisite property of toughness by giving it the right amount of 
plasticity. The term "plasticizer" as used herein is a softner or 
substance which when incorporated in a material (usually a plastic or 
elastomer) increases its flexibility, workability or distensibility. 
A plasticizer may reduce the melt viscosity, lower the temperature of a 
second-order transition, or lower the elastic modulus of the material with 
which it is admixed. Second-order transition temperatures may be 
determined by plotting any temperature dependent property of a material, 
such as density or refractive index, against temperature. The transition 
temperature, which is believed to be identified with the onset of 
rotational freedom within the material's macromolecules, may be located 
and determined by a sharp change of curvature. Since plasticization lowers 
this temperature by reducing interchain barriers against rotation, it 
follows that a comparison of second-order transition temperatures on 
polymer plasticized compositions that are equivalent at room temperature 
affords a means of evaluating the temperature performance of plasticizers. 
2. Description of The Prior Art 
The plasticization of ethylene-acrylic acid copolymers is old and is 
described, for example, in U.S. Pat. No. 3,361,702 issued to Wartman et 
al., on Jan. 2, 1968, entitled Ethylene-Acrylic Acid Copolymers 
Plasticized With Polyols. In particular, glycols, glycerols and the like 
are described as suitable for use as melt index, stiffness, 
processability, glass transition temperature and resiliency improvers when 
added to ethylene-acrylic acid or ethylene methacrylic acid copolymers. As 
can readily be determined from the foregoing there is an ongoing search 
for new and superior plasticizers for various polymers and copolymers. 
Similarly, in U.S. Pat. No. 3,464,949, also issued to Wartman et al., on 
Sept. 2, 1969, entitled Ethylene-Acrylic Acid Copolymers Plasticized with 
Adducts of Alkylene Oxides and Amines, adducts of alkylene oxides and 
amines are used as plasticizers in said copolymers. 
SUMMARY OF THE INVENTION 
This invention relates to a composition of matter comprising a copolymer 
consisting essentially of an alpha-olefin of the formula: RCH .dbd. 
CH.sub.2, wherein R is a radical selected from the group of hydrogen and 
alkyl radicals having from about 1 to about 8 carbon atoms; and an alpha, 
beta-ethylenically unsaturated carboxylic acid, having from about 3 to 
about 8 carbon atoms, or the respective copolymer salts, said copolymer 
having a molecular weight of from about 20,000 to about 200,000, 
particularly copolymers of ethylene-acrylic acid, ethylene-methacrylic 
acid and their respective salts, plasticized with a long-chain fatty acid 
selected from either saturated or unsaturated fatty acids containing 9 to 
11 carbon atoms. 
DETAILED DESCRIPTION OF INVENTION 
The present invention resides in copolymers containing an alpha-olefin and 
an alpha, beta-ethylenically unsaturated carboxylic acid and their 
respective salts plasticized with a selected long-chain fatty acid, 
particularly copolymers of ethylene-acrylic acid and ethylene-methacrylic 
acid and their salts plasticized with selected long-chain fatty acids, as 
defined above, which impart certain desirable properties to said 
copolymers, such as higher melt index, greater flexibility, low stiffness, 
easier processability, higher resiliency and lower glass transition 
temperature (TG). The glass transition temperature as defined herein is 
the temperature at which an amorphous material, such as glass or a high 
polymer, changes from a brittle state to a plastic state. 
Copolymers suitable for use in this invention preferably comprise an 
alpha-olefin having the general formula RCH .dbd. CH.sub.2, wherein R is a 
radical selected from the group of hydrogen and alkyl radicals having from 
about 1 to about 8 carbon atoms, preferably from about 1 to about 4 carbon 
atoms, the olefin content of said copolymer being at least about 50 mol 
percent based on the total weight of the copolymer, preferably from about 
50 to about 99.8 mol percent based on the total weight of the copolymer, 
and an alpha, beta-ethylenically unsaturated carboxylic acid having from 
about 3 to about 8 carbon atoms, preferably from about 3 to about 6 carbon 
atoms. 
Examples of suitable alpha-olefins preferably are selected from the group 
of ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, 
3-methylbutene-1, 4-methylbutene-1 and the like, especially ethylene. 
Examples of suitable alpha, beta-ethylenically unsaturated carboxylic acids 
include acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, 
maleic acid, fumaric acid and the like, especially acrylic acid and 
methacrylic acid. 
The copolymers useful in the practice of this invention can be prepared in 
a conventional manner by bulk, solution or dispersant polymerization 
methods using known catalysts. Thus, the copolymers utilized by this 
invention can be prepared from the corresponding monomers with a diluent 
such as water in a heterogeneous system, usually referred to as emulsion 
or suspension polymerization, or with a solvent such as toluene, benzene, 
hexane, cyclohexane, acetone, ethyl acetate, butyl acetate, ethylene 
dichloride, or methyl isobutyl ketone in a homogeneous system, normally 
referred to as solution polymerization. Solution polymerization in 
benzene, toluene or a solvent having similar chain transfer activity is 
the preferred method used in forming the copolymers disclosed herein, 
because this method and solvent produce an especially preferred copolymer 
characterized by a relatively high molecular weight. 
Copolymerization of the monomers disclosed herein readily takes place under 
the influence of heat, light and/or catalysts. Suitable catalysts include 
peroxide-type, free radical catalysts such as benzoyl peroxide, lauryl 
peroxide, or 5-butylhydroperoxide; and free radical catalysts such as 
.alpha., .alpha.'-azodiisobutyronitrile. The catalysts, when used, are 
employed in concentrations ranging from about a few hundreds percent to 
about two percent by weight of the monomers. The preferred concentration 
is from about 0.2 to about 1.0 percent by weight of the monomers. 
Copolymerization of the monomers disclosed herein takes place over a wide 
temperature range depending upon the particular monomers and catalysts 
utilized in the reaction. However, the copolymerization reaction is 
generally carried out at temperatures ranging from about 77.degree. F 
(25.degree. C) to about 302.degree. F (105.degree. C) when a catalyst such 
as .alpha., .alpha.'-azodiisobutyronitrile is used. The copolymerization 
reaction is preferably carried out in an inert atmosphere, for example, 
nitrogen or carbon dioxide to favor the formation of copolymers having 
relatively high viscosities and molecular weights. Normally, a reaction 
time of from about 3 to about 72 hours is sufficient to complete the 
copolymerization process. 
The copolymers disclosed herein have an average molecular weight of from 
about 20,000 to about 200,000, with a preferred molecular weight of from 
about 100,000 to about 200,000. The molecular weight of the copolymer can 
conveniently be determined using conventional techniques. 
Another method for preparing the copolymers herein is disclosed in U.S. 
Pat. No. 3,557,070 issued to Anspon et al., entitled Preparation of 
Ethylene Polymers. The reference teaches a process for preparing 
ethylene-acrylic or ethylene-methacrylic acid copolymers by thermal 
cracking. In particular, an ethylene-isopropyl ester of acrylic or 
methacrylic acid is thermally decomposed in an inert atmosphere to produce 
an ethylene-acrylic acid-anhydride or an ethylene-methacrylic 
acid-anhydride, followed by conversion of the anhydride in a second 
thermal reaction step to produce an ethylene-acrylic acid or 
ethylene-methacrylic acid polymer. The disclosure set-forth in U.S. Pat. 
No. 3,557,070 is incorporated herein by reference. 
The copolymers and their salts which are particularly suitable for use in 
the present invention, preferably are of high molecular weight which is 
defined by melt index, which is a measure of melt viscosity. The melt 
index of copolymers and their salts employed in this invention is 
preferably in the range of from about 0.1 to about 100 g/10 minutes, 
especially in the range of from about 0.5 to about 50 g/10 minutes. The 
method of obtaining the melt index of the copolymers herein is described 
in greater detail in ASTM:D-1238-57, the teaching of which is incorporated 
herein by reference. 
It has been discovered that the plasticizers of the present invention are 
suitable for use to plasticize the ionomers (salts) of the above-described 
copolymers. The ionic copolymers are obtained by the reaction of the 
copolymer with an ionizable metal compound which is well known and 
referred to as neutralization. As such, the ionomers which are suitable 
for use in the invention are those in which at least 5 percent by weight, 
preferably from about 20 to about 100 percent by weight of the acid groups 
have been neutralized. Metal ions which are suitable for neutralizing the 
copolymers of the present invention are selected from monovalent, divalent 
and trivalent metals of Groups I, II, III, IV-A, and VIII of the Periodic 
Table of Elements. Specific examples of suitable monovalent metal ions are 
selected from Na.sup.+, K.sup.+, Li.sup.+, Cs.sup.+, Rb.sup.+, Hg.sup.+, 
and Cu.sup.+. Examples of suitable divalent ions include Be.sup.+2, 
Mg.sup.+2, Ca.sup.+2, Sr.sup.+2, Ba.sup.+2, Cu.sup.+2, Cd.sup. +2, 
Hg.sup.+2, Sn.sup.+2, Pb.sup.+2, Fe.sup.+2, Co.sup.+2, Ni.sup.+2, and 
Zn.sup.+2. Trivalent metal ions suitable for use herein are selected from 
the group of Al.sup.+3, Sc.sup.+3, Fe.sup.+3, Y.sup.+3. 
The preferred metals suitable for neutralizing the copolymers used herein 
are the alkali metals of Group I, particularly cations such as Sodium, 
Lithium, Potassium, and alkaline earth metals of Group II, in particular, 
cations such as Calcium, Magnesium, and Zinc. It should be noted that more 
than one metal ion may be incorporated into the copolymer in certain 
applications. 
A convient method of preparing the ionomers herein is disclosed in U.S. 
Pat. No. 3,437,718, issued to Rees, entitled Polymer Blends. In 
particular, the metal compound is added to an alpha-olefin/alpha, 
beta-ethylenically unsaturated carboxylic acid and the mixture is milled 
at a temperature of from about 140.degree. to about 180.degree. C for 
about 15 minutes or until the reaction proceeds to completion. The 
disclosure of U.S. Pat. No. 3,437,718 is incorporated herein by reference. 
Another method of preparing the alkali metal salts of copolymers herein is 
disclosed in U.S. Pat. No. 3,970,626, issued to Hurst et al., on July 20, 
1976; the disclosure of which is incorporated herein by reference. In 
particular, the reference teaches a hydrolysis process for preparing 
aqueous copolymer salt emulsions of alpha-olefin, alpha, 
beta-ethylenically unsaturated carboxylic acids by suspending a particular 
alpha-olefin, alpha beta-ethylenically unsaturated carboxylic acid ester 
interpolymer in water having an alkali metal dissolved therein and heating 
said mixture to a temperature of at least 180.degree. C under autogenous 
pressure for a period of time sufficient to enable the alkali metal to 
react with a sufficient portion of the ester groups of the copolymer to 
render said copolymer emulsifiable in the aqueous alkali medium. 
Examples of long chain fatty acids useful as plasticizers herein include 
saturated fatty acids selected from nonanoic acid (pelargonic acid) 
decanoic acid and undecanoic acid and unsaturated fatty acids selected 
from nonenoic acid, decenoic acid and 10-undecenoic acid. The amount of 
long-chain fatty acids that can be used varies over a wide range, but, in 
general can range from about 5 to about 50 weight percent based on the 
weight of the copolymer, preferably from about 20 to about 40 weight 
percent, based on the weight of the copolymer. 
The plasticizers of this invention can be dispersed in the copolymer by any 
of the conventional methods and processes known in the art for dispersing 
conventional plasticizers. These methods and processes include dry 
blending, milling, kneading, Brabender mixing, plasticizing extrusion and 
the like. The method of dispersing the plasticizer in the copolymer is not 
critical and will depend to some extent on the copolymer and plasticizer 
used. 
The temperature behavior of plasticized copolymers is a very important 
characteristic, because modern day applications, especially the military, 
may require not only that plastics made from plasticized copolymers be 
equally suitable for use in the Artic or in the Tropics; and additionally 
such copolymers utilized in aircraft may in a matter of minutes pass from 
high summer temperatures on the ground to subzero temperatures high in the 
air. Thus a highly desirable plasticized copolymer should possess uniform 
performance over a broad range of temperatures. 
Comparisons based on copolymers containing equal volume or weight 
percentages of plasticizers are not dependable because of the great 
differences in plasticizing effectiveness among the various compounds. One 
convenient method of comparing plasticized compounds involves plotting 
second-order transition temperatures which are determined by plotting any 
temperature-dependent property of the specimen, such as density or 
refractive index against temperature. The transition temperature which is 
believed to be identified with the onset of rotational freedom within the 
copolymer macromolecules, is located by a sharp change of curvature. Since 
plasticizers lower this temperature by reducing inter-chain barriers 
against rotation, a comparison of second-order transition temperatures on 
copolymer-plasticizer compositions that are equivalent at room temperature 
affords a means of evaluating the temperature performance of plasticizers. 
The plasticized copolymers of the present invention have a second-order 
transition temperature below about 0.degree. C. The second-order 
transition temperature herein is conviently defined as the copolymer glass 
transition temperature (TG), as determined using a model #900 DuPont 
Differential Scanning Caloremeter. 
It should be noted that the plasticized copolymers suitable for use herein 
are especially suitable to bind safety glass, thus it is critical that the 
plasticized copolymer be substantially clear and free of discoloration 
which would render it opaque. Another critical feature of suitable 
plasticizers is the vapor pressure. Unfortunately, the use of lower chain 
fatty acids (i.e. 8 carbon atoms and lower) as plasticizers for 
alpha-olefin and alpha, beta-ethylenically unsaturated carboxylic acid 
copolymers are not acceptable because their vapor pressures are too high 
and would cause them to boil out during copolymer processing and impart a 
bad odor to the finished product. Thus plasticizers suitable for use are 
required to have a vapor pressure of less than 1 mm of Hg at 100.degree. 
C. 
It should additionally be noted that lauric acid (C.sub.12 -fatty acid) 
caproic acid (C.sub.6 -fatty acid) and octanoic acid (C.sub.8 -fatty acid) 
render alpha-olefin/alpha, beta-ethylenically unsaturated carboxylic acid 
copolymers either brittle, opaque or foul smelling when used as 
plasticizers, because it has been determined, that only the C.sub.9 to 
C.sub.11 saturated or unsaturated fatty acids work as plasticizers for the 
copolymers herein, when used in the context of a safety glass binder.

The following examples serve to demonstrate the best mode of how to 
practice the invention herein and should not be construed as a limitation 
thereof. 
EXAMPLE I 
A safety glass binder was prepared by mixing 30 grams of an 
ethylene-acrylic acid copolymer containing 6 mol percent acrylic acid and 
having a melt index of 0.5 g/10 min., with 10 grams of 10-undecenoic acid 
in a Brabender mixer at 190.degree. C for 10 minutes. The finished product 
was removed and compression molded into 0.030 inch thick sheets. The 
plasticizer was substantially compatible with the copolymer with minimum 
surface bleeding and the finished product did not have a discernable odor. 
The plasticized copolymer was clear, had a melt index of 17.5 g/10 min. 
and a glass transition temperature of less than -10.degree. C. 
Substantially the same results are obtained when an ethylene-methacrylic 
acid copolymer is substituted for the ethylene-acrylic acid copolymer 
above and when undecanoic acid is substituted for the 10-undecenoic acid 
above. This example is typical of those fatty acids which fall within the 
scope of the discovery herein. 
EXAMPLE II 
Twenty-Four grams of an ethylene-acrylic acid copolymer containing 6 mol 
percent acrylic acid and having a melt index of 0.5 g/10 min. were mixed 
with 16 grams of 10-undecenoic acid in a Brabender mixer at 190.degree. C. 
for 10 minutes. The finished product was substantially compatible with the 
copolymer with only slight surface bleeding and did not have a discernable 
odor. The compound was substantially clear and had a melt index of 100 
g/10 min. and a glass transition temperature of less than -40.degree. C. 
Substantially the same results are obtained when ethylene-methacrylic acid 
is substituted for the ethylene-acrylic acid copolymer above. This example 
is typical of those fatty acids which fall within the scope of the 
discovery herein. 
EXAMPLE III 
Thirty grams of an ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid and having a melt index of 0.5 g/10 min. were mixed with 10 
grams of hexanoic acid (caproic acid) in a Brabender mixer at 190.degree. 
C. for 10 minutes. The product was removed and compression molded into 
0.030 inch thick sheets. The compound was not very compatible with the 
copolymer, there was excessive liquid present, a large amount of surface 
bleeding and the product gave off a very offensive odor. This example is 
representative of those fatty acids which do not plasticize 
alpha-olefin/alpha, beta-ethylenically unsaturated carboxylic acid 
copolymers. 
EXAMPLE IV 
Thirty grams of an ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid and having a melt index of 0.5 g/10 min. were mixed with 10 
grams of dodecanoic acid (lauric acid) in a Brabender mixer at 190.degree. 
C. for 10 minutes. The product was removed and compression molded into 
0.030 inch thick sheets. The lauric acid produced a gel when mixed with 
the above copolymer, there was no evidence of surface bleeding or an 
offensive odor. The finished product, however, was brittle and opaque, 
rendering it not suitable for use as a safety glass binder. This example 
demonstrates that lauric acid is not suitable for use as a plasticizer for 
the above copolymer in the context of a safety glass binder. 
EXAMPLE V 
Thirty grams of an ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid and having a melt index of 0.5 g/10 min. were mixed with 10 
grams of decanoic acid (capric acid) and allowed to stand overnight. The 
finished product was compression molded into a 0.030 inch sheet. The 
capric acid was compatible with the copolymer with no discernable surface 
bleeding. However, a moderate odor was present, the compound was 
substantially clear and had a melt index of 13.4 g/10 min., and the glass 
transition temperature was 0.degree. C. Decenoic acid can be substituted 
for the decanoic acid above with substantially the same results. 
EXAMPLE VI 
Thirty grams of an ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid and having a melt index of 0.5 g/10 min., were mixed with 10 
grams of 10-undecenoic acid and allowed to stand overnight. The finished 
product was compression molded into a 0.030 inch sheet. The undecanoic 
acid was substantially compatible with the copolymer and did not have any 
surface bleeding and substantially no offensive odor was evident. The 
finished composition was substantially clear and had a melt index of 17.5 
g/10 min., and a glass transition temperature of less than -10.degree. C. 
Substantially the same results are obtained when ethylene-methacrylic acid 
is substituted for the ethylene-acrylic acid copolymer. This example is 
typical of those fatty acids which fall within the scope of the discovery 
herein. 
EXAMPLE VII 
Thirty grams of an ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid and having a melt index of 0.5 g/10 min were mixed with 10 
grams of nonanoic acid (pelargonic acid) and allowed to stand overnight. 
The finished product was compression molded into a 0.030 inch sheet. The 
nonanoic acid (pelargonic acid) was substantially compatible with the 
copolymer, there was indication of very slight surface bleeding, and only 
a moderate odor was present. The finished product was substantially clear, 
had a melt index of 15 g/10 min. and a glass transition temperature of 
about -40.degree. C. When ethylene-methacrylic acid is substituted for the 
ethylene-acrylic acid above, substantially the same results occur. 
Nonenoic acid can be substituted for the pelargonic acid above with 
substantially the same results. This example is typical of those fatty 
acids which fall within the scope of the discovery herein. 
The data obtained from analyzing the plasticized copolymers of Examples I 
to VII are set forth in greater detail in Table I below. 
Table I 
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Surface Melt 
Example 
Compatibility 
Bleeding 
Odor Stiffness.sup.(1) (PSI) 
Optics.sup.(2) 
Index (q/10 min).sup.(3) 
Tg(.degree. C).sup.(4) 
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Control.sup.(5) 
-- -- -- 12,000 6 0.5 +40 
I good none none To low to measure 
4 17.5 -10 
II good slight 
none To low to measure 
4 100 -40 
III excessive liquid 
large 
offensive 
-- -- -- -- 
IV gel none none brittle opaque 
150 +40 
V good none moderate 
To low to measure 
5 13.4 0 
VI good none none To low to measure 
4 17.5 -10 
VII good slight 
moderate 
To low to measure 
6 15 -40 
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.sup.(1) ASTM D-882-56T 
.sup.(2) Blue haze based on scale of polyvinyl butryal = 1 and a 20% 
ethylene-methyl acrylate copolymer = 10 
.sup.(3) ASTM D-1238-62T 
.sup.(4) Glass transition temperature as determined by a model #900 DuPon 
Differential Scanning Caloremeter. 
.sup.(5) An ethylene-acrylic acid copolymer containing 6 mol percent 
acrylic acid. 
Obviously, many modifications and variations of the invention, as herein 
above set forth, can be made without departing from the spirit and scope 
thereof, and therefore only such limitations should be imposed as are 
indicated in the appended claims.