GB2125805A

GB2125805A - Oil-soluble polyacrylates

Info

Publication number: GB2125805A
Application number: GB08318983A
Authority: GB
Inventors: Ulrich Turck; Anton Capelle
Original assignee: Chemische Werke Huels AG
Current assignee: Huels AG
Priority date: 1982-07-14
Filing date: 1983-07-13
Publication date: 1984-03-14
Also published as: NL8302506A; GB8318983D0; GB2125805B; DE3226252A1; MY8600319A

Abstract

Oil-soluble polyacrylates useful as fluidity improvers for paraffin- containing crude oils are polymers having intrinsic viscosities of 4 to 80 [cm<3>. g<-1>] based on (C14- to C22-n-alkyl) (poly)oxyalkylene (meth)acrylates of the formula <IMAGE> in which R<1> and R<2>, independently of each other, are H or CH3, n is on average from 1 to 4, in particular 1.5 to 3.5, R<3> is an n-alkyl radical having on average from 14 to 22 carbon atoms and the structural units in brackets can be identical or different, optionally together with up to 15 mol% of maleic anhydride or up to 50 mol% of one or more acrylates of the formula <IMAGE> in which R<4> is H or CH3, R<5> is a C2- to C5-alkylene radical and R<6> and R<7>, independently of each other, are a C1- to C4-alkyl radical, the percentages being based on the mixture of monomers.

Description

SPECIFICATION A process for preparing oil-soluble polyacrylates, and their use in paraffin-containing crude oils Crude oils from different oil fields contain different amounts of qualitatively different long-chain paraffins (waxes). As the crude oil cools down these waxes can crystallise out and thereby impair the fluidity to a greater or lesser extent. The result can be very considerable problems in transporting and storing the crude oil.

An attempt is therefore made to improve the flow by adding to the crude oil in the warm state in which it is obtained at the oil well, i.e. in a state in which the paraffin is still dissolved in the crude oil, crystallisation inhibitors, which are also referred to as fluidity improvers. These generally are certain polymers. They effect a finely crystalline precipitation of the paraffin and hence a lowering of the pour point, which is the temperature at which the crude oil has a state of flow as defined by a standard method. Fluidity improvers are accordingly generally characterised by the amount by which they lower the pour point of a certain paraffin-containing crude oil.

The fluidity improvers should be as insensitive as possible to the kind of shear forces which arise during the transport of the crude oil.

It should furthermore be possible to adapt them to the particular application requirements which are the result of different oil provenances by a suitable choice of their structural parameters.

These requirements are largely met by the fluidity improvers proposed in German Offenlegungsschrift 2,926,474. They are certain polyacrylates derived from n-alkyl (meth)-acrylates having long-chain alkyl radicals. Particularly preferred fluidity improvers are copolymers of C16 - to C30-n-alkyl (meth)acrylates and certain dialkylaminoalkyl (meth)acrylates (containing 20 to 50 mol% of the second monomer, relatively to the monomer mixture on which the copolymer is based).

The properties of the prior art fluidity improvers described can be controlled, inter alia, by varying the number of C atoms of the n-alkyl radical in the n-alkyl (meth)acrylates, i.e. by choosing in a suitable manner the n-alkanols on which the acrylates are based. This way of controlling the application properties, however, is generally of limited practical use, since the industrial availability of n-alkanols differs and, moreover, can be subject to fluctuations. n-Alkanols having on average more than 22 C atoms are industrially not yet available.

The present invention seeks to remedy this defect and to place existing methods of preparing oil-solubie polyacrylates on a broader footing.

According to the present invention there is provided a process for preparing an oil-soluble polyacrylate having an intrinsic viscosity (I value measured in toluene at 25"C) of 4 to 80 [cm3 g-1], comprising polymerising one or more acrylates of the formula

in which R1 and R2, independently of each other, are H or CH3, n is on average from 1 to 4, in particular 1.5 to 3.5, R3isan alkyl radical having on averagefrom 14to 22 carbon atoms and the structural units in brackets can be identical or different, optionally together with up to 15 mol% of maleic anhydride or up to 50 mol% of one or more acrylates of the formula

in which R4 is H or CH3, R5 is a C2- to C5-alkylene radical and R6 and R7, independently of each other, are a C1to C4-alkyl radical, the percentages being based on the mixture of monomers, the polymerisation being carried in bulk, in solution in an inert organic solvent, or in an aqueous dispersion, in the presence of a free-radical polymerisation initiator and at a temperature of 60 to 1 20 C.

The products of the process are new.

The products of the process according to the present invention differ significantly from those of the state of the art described. While the long-chain n-alkyl radical in the prior art products is bonded to a C atom in the main chain with an ester group or with two atoms in the longitudinal side chain axis, the products of the present invention have a non-paraffinic, hydrophilic group inserted between the ester group and the n-alkyl radical. This hydrophilic group contains on average 3 to 12 atoms in the longitudinal chain.

It would have been expected that the insertion of the non-paraffinic group would impair, or at least would not strengthen, the action of the n-alkyl radical, which, in the wider sense, is likely to be due to the principle of "like dissolves like", so that the effort would not be worthwhile. Surprisingly, however, the action of the n-alkyl radical is not only not impaired but is even strengthened, as is demonstrated by practical measurements of the pour point of paraffin-containing crude oils with the addition of the polyacrylates.

The process of the application, and its products, are also new compared with European Patent Publication 0,003,235 (see especially claims 1 and 3), because of the inventive choice made of the process parameters.

Preferred products according to the invention are obtained by copolymerising an acrylate or acrylate mixture of the formula I and 3 to 15 mol% of maleic anhydride or 5 to 50 mol% of an acrylate or acrylate mixture of the formula II, relative to the monomeric mixture. It is also preferred that, in the formula I, R3 be an alkyl radical having on average 16to 22 carbon atoms and that the remaining process parameters be adjusted in such a way that the I value of the products is 6 to 50 [cm3. g-1] The acrylates of the formula I can be obtained in two stages by known methods: 1) alkoxylation of n-alkanols of on average 14 to 22, preferably 16 to 22, carbon atoms with 1 to 4, preferably 1.5 to 3.5, mol of ethylene oxide and/or propylene oxide per mol of alkanol, and 2) esterification of the resulting alcohols with acrylic and/or methacrylic acid (analogously to the method described in German Offenlegungsschrift 2,926,474).

The n-alkanols can be of natural origin, i.e. they can have been obtained from vegetable or animal oils and fats (fatty alcohols). They can also be of synthetic origin, i.e. they can have been obtained by a Ziegler build-up reaction (namely by the ALFOL method, Ziegler alcohols also being referred to as alfols). (ALFOL is a Registered Trade Mark.) Species of either origin generally have an even number of C atoms.

Polyglycols which have formed in small amounts in reaction stage 1 are best largely separated out of the reaction mixture. Their removal prevents the formation, in reaction stage 2, of bifunctional acrylates, which could lead to partially cross-linked products in the process of the application.

Oil-soluble initiators, for example azo-bis-isobutyronitrile or benzoyl peroxide, are generally added at the start of the process of the invention. If the polymerisation is carried out in an aqueous dispersion, it is possible to use water-soluble initiators, in particular persulphates.

The polymerisation temperature is preferablywithinthe range from 80to 1000C.

The products of the process are obtained in the form of beads or powder particles or in a wax-like state or as viscous liquids. They are generally added to the crude oil at as early a stage as the lifting, in the form of a solution in organic solvents in which they are readily soluble.

The products can be tailored for use on the basis of what starting materials are industrially available.

For example, side chains having on average, in either case, a total of 30 carbon and oxygen atoms in the longitudinal chain extension but with different structures are obtained when the n-alkyl acrylates a) and b) respectively are used in the process after they have been obtained as follows: reaction of ethylene oxide with a) palmityl alcohol (molar ratio of 4:1) orb) behenyl alcohol (molar ratio of 2:1) as in reaction stage 1 and further reaction as in reaction stage 2.

The invention is illustrated by the following preparation and use Examples.

Alkoxylation of alkanols In a stirred autoclave, 1 mol of a synthetic fatty alcohol mixture having a C20- and C22 -n-alkanol content of more than 85% by weight was melted together with 0.5% by weight of sodium hydroxide and heated at 130"C for 30 minutes while the reaction system was flushed with dry nitrogen. The temperature was raised to 1700C. 2 mol of ethylene oxide were injected (2 to 3 bar) in the course of 15 minutes. Afterwards the heating at 170"C continued for a further 15 minutes. A small amount of polyethylene oxide present was separated out by extraction with an aqueous sodium chloride solution.

Esterification of alkoxylated alkanol 613 g (1.5 mol) of a mixture of alkoxyalkanols obtained above, 2 g of copper acetate, 140 g (1.9 mol) of acrylic acid and 10 g of toluene su Iphonic acid were dissolved in 890 g of toluene, and the solution was heated to the boil (120"C). 30 cm3 (1.65 mol) of water were taken off in the course of 41/2 hours by azeotropic distillation. When cooled down, the reaction mixture was washed twice with both water and NaHCO3 solution, was dried over sodium sulphate, and was stabilised with 70 mg of methylhydroquinone. The bulk of the solvent was separated off in a rotary evaporator to leave behind 688 g of a wax-like, slightly yellowish product (85% by weight of acrylate in the distillation residue).

Copolymerisation of acrylate Example 1 50 g of the distillation residue obtained above were admixed with 1.0 g of (3-(N,N-diethylamino)ethyl acrylate (molar ratio of the first monomer to the second monomer: 16:1), and the mixture was heated to 90"C. 50 mg of azo-bis-isobutyronitrile were then added. The reaction was complete after 41/2 hours. The product obtained had a yellowish colour and a wax-like consistency. The I value of the copolymer was 6 [cm3 .g 1], Example 2 Example 1 was repeated, except that only 35 mg of the initiator given there was used. I value: 11 [cm3.

g j.

Example 3 50 g of the distillation residue obtained above were heated to 90"C. 0.57 g of maleic anhydride (molar ratio of 16:1) was added, followed by 50 mg of azo-bis-isobutyronitrile once a temperature of 90"C had become re-established. The temperature briefly rose to 96"C. The reaction was completed at 900C in the course of 4 hours. The product obtained had a yellowish colour and a wax-like consistency.I value: 6 [cm3. g-1] Example 4 Example 3 was repeated, except that the reaction was carried out at 75"C. I value: 49 [cm3. g-1] Determination ofpourpoint An hydrous Arensheide crude oil (density: 0.87 g/cm3; viscosity: 41.3 mm2. s- at 20"C; paraffin content 5.1% by weight) was admixed in the concentrations specified in the table below with the products obtained in the examples. The pour points were determined as follows: the crude oil mixture was heated to 10400 and was then shock-cooled to -20"C. The cooling crystallised out the paraffins contained in the sample. The sample was then heated to 46"C and had its "true" maximum pour point determined in accordance with ASTM D 97 B, Section 6f.

TABLE Determination of pour points (in C) Concentration of the fluidity improvers of Example the invention in the crude oil mixture (in ppm) 0 25 50 75 1 24 18 9 -6 2 24 -5 - - 3 24 9 -6 -12 4 24 3 -

Claims

1. A process for preparing an oil-soluble polyacrylate having an intrinsic viscosity (I value measured in toluene at 25"C) of 4 to 80 [cm3. g-1], comprising polymerising one or more acrylates of the formula

in which R' and R2, independently of each other, are H or OH3, n is on average from 1 to 4, in particular 1.5 to 3.5, R3 is an n-alkyl radical having on average from 14to 22 carbon atoms and the structural units in brackets can be identical or different, optionally together with up to 15 mol% of maleic anhydride or up to 50 mol% of one or more acrylates of the formula

in which R4 is H or CH3, R5 is a 02- to C5-aikylene radical and R6 and R7, independently of each other, are a Ci- to C4-alkyl radical, the percentages being based on the mixture of monomers, the polymerisation being carried in bulk, in solution in an inert organic solvent, or in an aqueous dispersion, in the presence of a free-radical polymerisation initiator and at a temperature of 60 to 120"C.

2. A process according to claim 1, wherein from 3 to 15 mol% of maleic anhydride and/or from 5 to 50 mol% of one or more acrylates of the formula Il are polymerised, based on the mixture of monomers.

3. A process according to claim 1 or 2, wherein in the formula I, R3 is an n-alkyl radical having on average from 16to 22 carbon atoms.

4. A process for preparing an oil-soluble polyacrylate carried out substantially as described in any of the foregoing Examples 1 to 4.

5. An oil-soluble polyacrylate having an I value of 4 to 80 [cm3. g-1] when prepared by a process according to any of claims 1 to 4.

6. An oil-soluble polyacrylate having an I value of 4 to 80 [cm3. g-1] and being a polymer of one or more acrylates of formula I defined in claim 1 or 3 with or without up to 15 mol% of maleic anhydride and/or up to 50 mole% of one or more acrylates of formula ll defined in claim 1, the percentages being based on total monomer.

7. An oil-soluble polyacrylate according to claim 5 or6 having an I value of 6 to 50 [cm3 .g-'].

8. The use of an oil-soluble polyacrylate according to claim 5, 6 or 7 as an additive (fluidity improver) which lowers the pour point and improves flow properties, in a paraffin-containing crude oil.

9. A paraffin-containing crude oil containing 10 to 1,000 ppm of an oil-soluble polyacrylate according to claim 5,6 or7.

10. A crude oil according to claim 9, wherein the content of the oil-soluble polyacrylate is 20 to 300 ppm.