Copolymerization of beta-phellandrene with maleic anhydride, preferably in the presence of a free radical initiator such as AIBN, to form high molecular weight polymers (weight average molecular weight over 1,000) is disclosed. The polymerization may be conducted at a temperature up to about 190.degree. C., preferably in the range of about 40.degree. to 130.degree. C., preferably in the presence of a polar solvent.

BACKGROUND OF THE INVENTION 
This invention relates to terpene polymers and more particularly to high 
molecular weight beta-phellandrene-maleic anhydride copolymers. 
Turpentine, turpentine distillation cuts, and acid-isomerized turpentine 
are economical sources of ten-carbon olefins and di-olefins called 
terpenes. The electron-rich unsaturation present in terpenes makes them 
attractive coreactants with electron deficient olefins, e.g. maleic 
anhydride, in Diels-Alder and Ene reactions. An early exploitation of this 
chemistry was disclosed by Peterson in U.S. Pat. No. 1,993,031. Peterson 
reacted turpentine distillates, consisting of alpha-pinene, beta-pinene, 
dipentene and terpinolene with maleic anhydride at a temperature in the 
range of about 150.degree. to 200.degree. C. The products of these 
reactions are referred to as soft resins and are believed to have been 1:1 
and 1:2 terpene:maleic anhydride addition products which have molecular 
weights of 234 g/mol and 322 g/mol, respectively, and will be known 
hereinafter as "terpene maleic anhydride adducts." These low molecular 
weight adducts found early utility as components in alkyd resins because 
of their advantageous solubility behavior, the flexibility they provided 
in formulating alkyd resins, and their low cost. 
Alkyd resins based on terpene maleic anhydride adducts have been 
incorporated into coating and varnish formulations. However, because the 
terpene adducts are of low molecular weight and are less reactive toward 
chain-extending polyols than other alkylidene diacids, the derived 
coatings have relatively poor film strength, poor heat resistance, and 
elevated water sensitivity compared to coatings made from other polymers. 
If a method could be found whereby high molecular weight polymers formed 
between terpenes and maleic anhydride could be prepared, it is expected 
that inks, varnishes, paints and coatings based on these polymers would 
show improved properties. 
Attempts to increase the molecular weight of reaction products between 
terpenes and maleic anhydride are frustrated by the preference of most 
terpenes to undergo Ene and Diels-Alder reactions with maleic anhydride at 
elevated temperatures. The tendency of many terpenes to undergo 
isomerization in the presence of even a trace amount of acid further 
complicates the reaction chemistry of terpenes and maleic anhydride. 
Non-conjugated terpenes are frequently seen to isomerize to a conjugated 
form amenable to Diels-Alder reactions. 
In U.S. Pat. No. 4,046,748 and U.S. Pat. No. 4,107,420, Schluenze teaches 
that the addition of controlled amounts of iodine to a reaction mixture 
comprising maleic anhydride and non-conjugated monocyclic terpene(s) will 
increase the ratio of diadducts (two maleic anhydrides react with one 
terpene) to monoadducts (one maleic anhydride reacts with one terpene). In 
no case does Schluenze indicate that products with molecular weights 
higher than that of diadduct (332 g/mol) are formed under any of the 
reaction conditions disclosed. Apparently, the addition of iodine 
encourages various Ene and Diels-Alder reactions to occur, but not 
polymerization. 
Other descriptions of terpene maleic anhydride adductions and diadductions, 
derivatives of the (di)adducts, as well as uses for the (di)adducts and 
derivatives are disclosed in several patents and publications, including 
U.S. Pat. No. 3,043,789, U.S. Pat. No.4,055,576 and U.S. Pat. No. 
2,230,230. 
Polymers incorporating both maleic anhydride and terpenes have been 
prepared in the presence of reactive comonomers. In U.S. Pat. No. 
4,172,861 Li et al. disclose that materials with high softening 
temperatures can be formed from the mixture comprising styrene-butadiene 
rubber, styrene, beta-pinene, maleic anhydride, and a free-radical 
initiator. Li et al. indicate that limonene can be used in place of 
beta-pinene, but they neither indicate nor claim that useful materials can 
be formed under their reaction conditions in the absence of styrene and 
styrene-butadiene rubber. 
U.S. Pat. No. 2,383,399 to Lundquist discloses the preparation of 
terpolymers from a reaction mixture comprising maleic anhydride, 
terpene(s), and a third comonomer "capable of rapid and exothermic 
polymerization with maleic anhydride". This third comonomer is preferably 
styrene. The reaction of styrene, maleic anhydride and dipentene (racemic 
limonene) proceeds to give terpolymer in 75% yield, while the same 
reaction run in the absence of styrene leads to an unidentified polymer in 
a yield of 37%. The reaction of styrene, maleic anhydride and camphene 
proceeds to give terpolymer in 34% yield, while the same reaction run in 
the absence of styrene did not form polymer in a quantity sufficient for 
isolation. It is broadly claimed that all terpenes with the formula 
C.sub.10 H.sub.16 and having not more than two double bonds per molecule 
may be used in this terpolymerization. No claim is made for the 
preparation of copolymers between terpenes and maleic anhydride. 
German patent No. 1,694,829 serves as another example of the preparation of 
terpolymers containing terpenes, maleic anhydride and reactable 
termonomers. The formation of a polymer in the absence of a reactable 
termonomer is not indicated. 
Little success has heretofore been achieved in the preparation of high 
molecular weight polymers made solely from terpenes and maleic anhydride. 
One approach to preparing high molecular weight materials consisting 
solely of terpene and maleic anhydride has been to prepare a terpene 
homopolymer by methods well known in the art and in a subsequent operation 
attach maleic anhydride onto the preformed homopolymer, in some instances 
in the presence of an organic peroxide. Examples of this general approach 
can be found in disclosures made in U.S. Pat. No. 3,193,449, U.S. Pat. No. 
3,375,130, and U.S. Pat. No. 4,670,504. 
Such maleinated terpene homopolymers should be distinguished from the 
object of this invention, which, as will be described in more detail, is 
the copolymer formed between a terpene and maleic anhydride wherein both 
the terpene and maleic anhydride contribute to the backbone of the 
polymer. 
Direct copolymerizations of terpenes with maleic anhydride are almost 
without precedent. The free-radical induced copolymerization between 
limonene and maleic anhydride has been studied recently by Doiuchi et al. 
as described in European Polymer Journal Vol. 17, pp. 961-968, (1981). 
Although mostly interested in the mechanism of the copolymerization, they 
reported that their highest yield of copolymer occurred after 72 hours of 
reaction and was only 13%. A detailed study of the copolymer revealed that 
it was comprised of limonene and maleic anhydride in the molar ratio of 
1:2 and had a number average molecular weight of only 1300. W. J. Bailey, 
in Contemporary Topics in Polymer Chemistry, M. Shen, Ed., Vol. 3, p. 49, 
Plenum Press, N.Y. (1979) reports that beta-pinene will undergo an 
alternating copolymerization with maleic anhydride. Bailey makes no 
mention of the details and yields of this process and does not describe 
the formation of copolymers between maleic anhydride and any terpene other 
than beta-pinene. 
Successful copolymerization of a terpene and maleic anhydride in high yield 
to a resin of high melt point and high molecular weight evidently depends 
on the careful selection of the terpene isomer. Terpenes with cisoid 
conjugated double bonds, for example alpha-terpinene, will prefer to 
undergo rapid Diels-Alder adduction. Those with isolated double bonds may 
undergo limited copolymerization, as is seen, for example, with limonene, 
or are inert, as is the case with camphene, or isomerize under the 
reaction conditions, as occurs with terpinolene. 
SUMMARY OF THE INVENTION 
It is herein disclosed that a high yield preparation of a high weight 
average molecular weight copolymer between maleic anhydride and terpenes 
can be achieved when the terpene isomer is selected to have conjugated 
double bonds capable of copolymerizing rapidly with maleic anhydride yet 
incapable of adducting maleic anhydride via the Diels-Alder reaction. This 
is the case for para-mentha-1(7),2-diene, commonly known as 
beta-phellandrene. No other examples of polymeric materials being made 
from beta-phellandrene are known to the inventor. 
This invention therefore relates to polymers which comprise the reaction 
product of approximately equimolar quantities of beta-phellandrene and 
maleic anhydride, which polymers have a weight average molecular weight of 
at least about 1000. These polymers can be prepared in high yields, and 
their properties enable their use in various applications. This invention 
also relates to terpolymers, comprised mainly of beta-phellandrene and 
maleic anhydride and to methods for preparing the polymers of this 
invention. 
DETAILED DESCRIPTION OF THE INVENTION 
The terpene compound from which the copolymers of this invention are 
prepared is beta-phellandrene (i.e., para-mentha-1(7),2-diene), which is a 
conjugated diene having the structure 
##STR1## 
Turpentine is the major source of this terpene. Upon distillation of 
turpentine, that fraction boiling between 170.degree. and 176.degree. C. 
is rich in limonene and beta-phellandrene. Because their boiling points 
are similar, it is difficult to obtain beta-phellandrene free of limonene. 
A mixture comprising 62% limonene and 32% beta-phellandrene is a material 
of commerce, available from Union Camp Corporation as Unitene LP. 
Unexpectedly, a mixture of limonene and beta-phellandrene is conveniently 
and economically employed as the source of beta-phellandrene in forming 
the copolymers of this invention. Although limonene is capable of 
undergoing a free-radical initiated copolymerization with maleic 
anhydride, under the reaction conditions typically employed in the process 
of this invention a minimal amount of limonene-maleic anhydride copolymer 
forms. The limonene acts as a solvent, and feedstocks richer or poorer in 
limonene than the aforementioned Unitene LP can be employed equally well 
in the preparation of the copolymers of this invention. At the conclusion 
of the copolymerization, limonene can be removed along with any solvents 
used and recovered as a valuable co-product. 
The maleic anhydride employed in this invention is of standard commercial 
quality and is available from several chemical supply houses. 
In forming the copolymers of this invention, beta-phellandrene is contacted 
with maleic anhydride, preferably in the presence of an effective amount 
of at least one free radical polymerization initiator, to form 
unexpectedly high molecular weight copolymers. It is believed that the 
copolymer is formed through an alternating addition mechanism, with 
1,4-addition of maleic anhydride to the terpene. The structure therefore 
consists of a substantial number of 1:1 alternating units as schematically 
shown below: 
##STR2## 
Typically, substantially equal molar quantities of beta-phellandrene and 
maleic anhydride are utilized. Deviation from the use of equal molar 
quantities influences the rate of the copolymerization, the molecular 
weight of the copolymer, and the ease of copolymer isolation, but does not 
greatly affect the composition of the copolymer. Thus, when the polymers 
of this invention are described as comprising the reaction product of 
substantially equimolar quantities of beta-phellandrene and maleic 
anhydride, it is intended to describe the relative quantities of the 
monomers in the copolymer rather than the relative quantities of monomers 
which are contacted to prepare the copolymer. 
The polymers of this invention can further comprise one or more additional 
monomers capable of polymerizing with maleic anhydride. Such additional 
monomers preferably comprise not more than 50 mole % of the polymer, and 
the resulting polymers preferably comprise at least about 25 mole % 
beta-phellandrene and at least about 25 mole % maleic anhydride. Monomers 
capable of polymerizing with maleic anhydride are well known in the art 
and include, for example, styrene, acrylonitrile, and acrylic acid; 
terpenes capable of reacting with maleic anhydride such as beta-pinene and 
isoterpinolene; and abietic acids or esters thereof. 
An effective amount of the free radical polymerization initiator will 
generally range from about 0.01 to 2 weight percent, preferably about 0.1 
to 1 weight percent (based on total weight of monomeric starting 
materials). The preferred initiator is AIBN, i.e., 
2,2'-azobis(2-methylpropanenitrile). Other free radical initiators can be 
used including peroxides, e.g., benzoyl peroxide or dicumyl peroxide. 
Although the copolymerization can be conducted neat, it is preferable to 
conduct the copolymerization in the presence of a solvent, e.g., an 
aliphatic or aromatic hydrocarbon, or an ester or ether solvent. Most 
preferred solvents include toluene, ethyl acetate or tetrahydrofuran. To 
the extent the solvent dilutes the comonomers, the amount of solvent used 
will influence the rate of reaction. The amount of solvent can also 
influence the molecular weight of the product by functioning as a chain 
transfer agent. 
The temperature at which the copolymerization reaction is run is largely 
determined by the choice of free-radical initiator. Typically one selects 
a temperature such that the half-life of the initiator is about one hour. 
When AIBN is the initiator, a temperature of 70.degree. C. is conveniently 
employed, while copolymerizations initiated by dicumyl peroxide are 
typically run at 130.degree. C. Ordinarily the reaction temperature will 
be within the range from room temperature to about 190.degree. C., 
preferably about 40.degree. to 130.degree. C., and more preferably about 
60.degree. to 80.degree. C. 
The molecular weights of the copolymers of this invention are higher than 
ever previously reported for the product of a reaction solely between 
maleic anhydride and a terpene. Copolymers with a weight average molecular 
weight as measured by gel permeation chromatography of at least about 
1000, preferably at least about 5000, may be prepared according to this 
invention. Indeed, copolymers with a weight average molecular weight as 
high as 50,000 have been obtained in the absence of chain transfer and 
chain terminating agents. 
The copolymers of this invention have softening points (i.e., capillary 
melting point) of at least about 120.degree. C., more typically, greater 
than 170.degree. C., and are thermally stable to about 250.degree. C. A 
glass transition temperature in excess of 145.degree. C. has been observed 
for purified, high molecular weight copolymer. The product polymer 
generally contains 70% carbon and 9% hydrogen, as expected for a copolymer 
made from equal molar quantities of terpene and maleic anhydride. 
A reaction competitive to the desired copolymerization is frequently seen 
to occur. This is the adduction reaction between terpene and maleic 
anhydride to produce 1:1 and 1:2 terpene maleic anhydride adducts of 
molecular weight less than 400. Amounts of these adducts can be minimized 
by using lower temperatures, shorter reaction times, and/or a polar 
solvent, e.g., ethyl acetate. When undesirable terpene maleic anhydride 
adducts are present, pure polymer can be recovered from the product 
mixture through, for example, precipitation.

The invention will now be described in connection with the following 
examples wherein parts and percentages are by weight and temperatures are 
in degrees C. unless indicated. Molecular weights were measured by gel 
permeation chromatography using a refractive index detector, with 
retention times referenced to polystyrene of known molecular weight. The 
beta-phellandrene used in the following examples, unless otherwise 
indicated, was of 45% purity, with limonene constituting 50% of the feed. 
EXAMPLE 1 
A three-necked flask was fitted with a reflux condenser, mechanical 
stirrer, and addition funnel, and blanketed with a nitrogen atmosphere. 
The flask was charged with 45 g of terpene feedstock, 11.3 g maleic 
anhydride, 0.059 g AIBN, and 26.5 g butyl acetate. This mixture was heated 
to 75.degree. C. for 6.5 hours, during which time the copolymer 
precipitated from solution. At the conclusion of the reaction the 
copolymer was dissolved in tetrahydrofuran and reprecipitated by addition 
to pentane. A light-colored material was recovered in a yield of 17.2 g, 
which consisted of a mixture of 95% copolymer and 5% terpene-maleic 
anhydride adducts. This mixture had a glass transition temperature of 
145.degree. C. and the copolymer had a weight average molecular weight of 
75,000. For control reactions conducted in the absence of either terpene 
feedstock or maleic anhydride, no polymeric product was observed. An 
additional control reaction was conducted in which pure limonene was 
substituted for terpene feedstock with the result that only trace amounts 
of a low molecular weight polymer was formed. 
EXAMPLE 2 
The reaction apparatus of Example 1 was assembled and the flask charged 
with 30.4 g of terpene feedstock, 11.9 g of maleic anhydride, 20 g of 
para-xylene, and 0.0508 g AIBN. This mixture was heated with stirring to 
75.degree. C. for five hours, during which time the copolymer precipitated 
from solution. At the conclusion of the reaction the copolymer was 
dissolved in tetrahydrofuran and reprecipitated by addition to heptane. A 
light-colored material was recovered in a yield of 10.3 grams, which 
consisted of a mixture of 86% copolymer and 14% terpene maleic anhydride 
adducts. The copolymer of this mixture had a weight average molecular 
weight of 56,000. 
EXAMPLE 3 
The procedure of Example 2 was followed except that benzoyl peroxide, 0.032 
g, was used in place of AIBN and the reaction temperature was 115.degree. 
C. The product contained 11.8% adducts and had a weight average molecular 
weight of 58,300. 
EXAMPLE 4 
The procedure of Example 2 was followed except that dicumyl peroxide, 0.038 
g, was used in place of AIBN and the reaction temperature was 95.degree. 
C. The product contained 20.6% adducts, had a glass transition temperature 
of 70.degree. C. and a weight average molecular weight of 71,300. 
EXAMPLE 5 
The procedure of Example 1 was followed except that gamma-terpinene was 
used as solvent in place of butyl acetate. The product had a melting point 
of 136.degree. C., contained 1.6% adducts and had a weight average 
molecular weight of 11,800. 
Following the teachings herein, it can be seen that relatively high 
molecular weight copolymers of maleic anhydride and beta-phellandrene can 
be prepared under mild conditions. 
The copolymers of this invention have a reactive character due to the 
presence of the anhydride units and residual unsaturation in the chain. 
Both the anhydride units and the points of unsaturation are capable of 
undergoing reactions typical of such units in a polymer to effectively 
modify the character of the copolymer. Methods for achieving such 
reactions, for example partial or complete esterification of the anhydride 
functionality, are well known in the art. 
The following uses are among those in which the polymers prepared according 
to this invention may be applied: ink resins, scale inhibitors, epoxy 
curing agents, and components of coating compositions. Methods of 
employing polymers in the aforementioned uses are well known to those 
skilled in the art.