Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-01-11
2001-04-17
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S263000, C526S265000, C526S318000, C526S318440
Reexamination Certificate
active
06218490
ABSTRACT:
FIELD OF THE INVENTION
The area of the invention described here is that of crude petroleum oils and additives to improve the production conditions.
Crude oils may contain large fractions of paraffins, the exact quantity and nature of which are variable, depending on the producing field. At the temperature of the wells, the paraffins are liquid and dissolve in the crude oil. As the oil rises to the surface, its temperature becomes lower and the paraffins in it crystallize, forming a three-dimensional network of needles and flakes. This results in loss of fluidity which makes production, transportation, storage and even the treatment of these oils very difficult. Plugging of the pipelines and treatment apparatuses occurs frequently.
BACKGROUND OF THE INVENTION
Numerous methods have been proposed to solve this problem, such as mechanical scraping or heating of the walls. These methods are costly and cannot always be applied.
In order to improve the rheology of crude petroleum oils, SHELL did the pioneering work with FR 1,575,984: it teaches that macromolecular compounds of the “comb” type, constructed on the model of a principal hydrocarbon chain on which fairly long lateral hydrocarbon chains are grafted, that is, chains with at least 14 carbon atoms and at most 30 carbon atoms, can perturb the crystallization of heavy paraffins. This property is manifested well by macromolecules, which have an average molecular weight (number-average molecular weight M
n
, the definition of which is recalled here:
M
n
=&Sgr;
i
NiMi/&Sgr;
i
Ni,
where Mi are the molecular weights of the individual species Ni present in the polymer) is between 1000 and 1,000,000 and preferably between 4000 and 100,000. Thus, the utilization of additives was suggested, most frequently polymeric additives, the role of which is to retard or to modify the crystallization of paraffins and thus improve the flow properties of the oil and prevent agglomeration of the crystals formed on the walls.
Numerous studies then attempted to improve the efficacy of these first additives of polymeric nature, either by the synthesis or by the formulation, in order to adapt them to different types of crude oils encountered and to ameliorate successively the difficulties of synthesis and/or handling of the various generations of products, for example, among the most effective ones, C
18-30
acrylate copolymers, preferably mainly C
20-22
ones, with a heterocyclic monomer, notably vinylpyridine [U.S. Pat. Nos. 2,839,512 (1958) and FR 2,128,589 (1972) of SHELL]. The presence of polar units confers a dispersing character to the polymer, which permits avoidance of deposition of paraffins on the wall. Now, because of the higher reactivity of long-chain acrylates in comparison to the polar comonomers, incorporation of the latter is generally very difficult and the dispersing effect related to the rate of incorporation of the polar comonomer frequently remains very low.
In spite of these successive improvements, these additives cannot be applied universally to all crude oils, each one representing a particular case and presenting its own problems.
DESCRIPTION OF THE INVENTION
It was now found very unexpectedly that the performance of the paraffin inhibitors of the alkyl acrylate copolymer type or alkyl acrylate/vinylpyridine type can be improved considerably when a part of the monomer alkyl acrylate units participating in the polymer chains, represented by
in which R is H or CH
3
,
in which Ri remainder are linear saturated Ri-OH alcohol groups, the number of carbon atoms of which range from approximately 10 to approximately 50, and come from an acrylic cut having a special distribution of the alkyl chains, called distribution “U” for the purposes of the present patent. Distribution “U” is defined as the distribution of alkyl chains as a function of the length of the chains, here always with even number of carbon atoms, the envelope of which is very regular, the weight-average molecular weight M
w
being between 375 and 700, and the number-average molecular weight Mn being between 375 and 840, as well as their poly-dispersity factor M
w
/M
n
between 1.0 and 1.2 (M
w
is the weight-average molecular weight, the formula for calculating it being recalled here:
M
w
=&Sgr;
i
NiMi
2
/&Sgr;
i
NiMi,
where Mi are the molecular weights of individual species Ni present in the polymer).
FIG. 1
gives a representation of the distribution of the alcohols distributed according to a “U”-type distribution law with a mean molecular weight of 425 (in order to obtain such alcohols, see U.S. Pat. No. 4,426,329). The polymeric acrylates obtained by a single polymerization of monomers with a “U” distribution cannot be distinguished particularly from those that one obtains from arbitrary monomers, including here products usually available to the expert in the field and in which no particular distribution of the length of the attached chains is expected, in other words, the distribution of which is any distribution, but, in any case, it is not a “U” distribution. What is very astonishing and from which the Applicant derives all the advantageous consequences, is that a powerful synergism develops with regard to the inhibition of crystallization of paraffins in petroleum oils when the products of the “U” class and “non-U” class are distributed within the same polyacrylate or polyacrylate/vinylpyridine copolymer. As with all synergism in mixtures which can be highly variable in composition, the rules are very delicate to discern, but the guiding principles can be formulated, which will be most useful to the person in the field: The “U” components are centered on average lengths of the hanging chains i
u
in the copolymer which are longer than that of the i
nu
of the “non-U” component, and the weight of the total number of units with “U” chains in the copolymer is relatively low in comparison to the total number of “non-U” units. According to the invention, the term vinylpyridine includes 2-vinylpyridine, 4-vinylpyridine or the mixture of the two. The copolymers of the invention contain 1 to 10% of these.
In terms of structural description, one can say that alkyl acrylate copolymers or alkyl acrylate/vinylpyridine copolymers with a weight-average molecular weight between 5000 and 500,000, preferably between 40,000 and 350,000 form part of the invention, and that in these, with acrylate monomer units which participate in the polymer chain
in which R is H or CH
3
,
in which Ri are remainder saturated linear Ri-OH aliphatic alcohols where i represents the number of carbon atoms of these groups, extending between 10 and 50 carbon atoms, and following a distribution law which is the superposition of a “U” distribution law in which the i values are even numbers within the upper range of the interval of 24-50, the center value of which is i
u
, and a “non-U” distribution law in which the i values are odd or even, lying in the lower range of 10-22 of the interval and the centered value of which, i
nu
, is such that i
nu
<i
u
, the weight ratio of all the units
with Ri distributed according to the “U” law to the total number of units distributed according to the “non-U” law, ranges from 1:99 to 50:50, and preferably from 5:95 to 50:50.
The paraffin inhibitor formulations incorporating these copolymers as essential components eliminate the disadvantages cited above and permit the realization of a series of additives with a broad spectrum of utilization, having good solubility in crude oils, which have an effect both on the crystallization of paraffins as well as on the dispersion of crystals already formed. They retard the crystallization of paraffins, the distribution of which generally lies between C60 and C70, permitting lowering of the flow point and the viscosity of these oils and facilitating their transportation, storage and treatment. They are incorporated easily in crude oils of greatly diverse origins.
METHOD OF CARRYING OUT THE INVENTION
The copolymers according to the invention can be obtained according to a simple and not very restrict
Brunelli Jean-Francois
Fouquay Stephane
Cain Edward J.
CECA S.A.
Smith , Gambrell & Russell, LLP
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