CA2342323A1

CA2342323A1 - Method for producing copolymers by radical polymerisation

Info

Publication number: CA2342323A1
Application number: CA002342323A
Authority: CA
Inventors: Maximilian Angel; Karin Neubecker
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1998-09-03
Filing date: 1999-08-25
Publication date: 2000-03-16
Also published as: WO2000014132A1; KR20010073092A; NO20011097D0; AU5740499A; NO20011097L; HUP0103892A2; DE19840268A1; EP1117712A1; JP2003524670A

Abstract

The invention relates to a method for producing copolymers by radical polymerisation of a) 5 to 95 wt. % of a monomer of formula (I), b) 95 to 5 wt.
% of a monomer of formula (II), wherein R1 and R2 represent H, C1-C3-alkyl, R3 = H, C1-c6-alkyl and n = 1 to 3 respectively and c) 0 to 40 wt. % of another fully or partially water-soluble monomer. The inventive method is characterised in that the polymerisation is carried out in an aqueous medium.

Description

METHOD FOR PRODUCING COPOLYMERS BY RADICAL POLYMERISATION
The present invention relates to a process for the preparation of copolymers by free radical polymerization of a) from 5 to 95~ by weight of a monomer of the formula I

H2C= C
~N-R2 to c= o b) from 95 to 5~ by weight of a monomer of the formula II
Ri H2C= C
~N~O (II) 20 ~ (CH2)n where in each case R1 and R2 are H or C1-C-.s-alkyl, R3 is H or C1-C6-alkyl and n is from 1 to 3, and c) from O.to 40a by weight of a further monomer which is 30 completely water-soluble or has limited water solubility, wherein the polymerization is carried out in an aqueous medium, and copolymers prepared by this process and their use as gas hydrate inhibitors.
w0 96/41785 discloses a process for inhibiting hydrate formation, i.e. a process by means of which the formation of gas hydrates in media which contain gas molecules and water' is prevented.

' 0050/49359 In this known process, the gas hydrate inhibitors used are copolymers which consist of N-methyl-N-vinylacetamide and an N-vinyllactam. The copolymers are prepared by free radical polymerization in benzene or in alcohols. However, these organic solvents present problems in the preparation and handling of the resulting copolymer solution. They must be removed in certain cases prior to use as gas hydrate inhibitors, which requires energy and time.
polymer 3ournal, 17, No. 1 (1985), 143-152 discloses that vinylpyrrolidone can be prepared by free radical polymerization in organic solvents or in H20, the polymers prepared in H20 being sensitive to oxidation.
It is an object of the present invention to avoid the abovementioned disadvantages during handling.
We have found that this object is achieved by carrying out the p°lYmerization in an aqueous medium.
The monomers of the formula I are preferably used in amounts of from 20 to 80~ by weight and the monomers'. of the formula II
preferably in amounts of from 80 to 20o try weight. In the formula I, Rz and R3 are each preferably methyl and R1 in both monomers I
and II is hydrogen. The preferred monomer of the formula I is N-methyl-N-vinylacetamide, and the preferred monomer of the formula II is vinylcaprolactam.
A comonomer which is completely water-soluble or has limited water solubility may be used as further copolymerizable comonomers c).
Preferably used comonomers c) are, for e~:ample, carboxylic acids and their esters, anhydrides, amides, nit:riles, vinyl esters or vinyl ethers. Particular examples are: acrylic acid, methacrylic acid, methyl acrylate, ethyl acry.late, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, l~ydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyisobutyl acrylate, hydroxyisobutyl methacrylate, monomethyl maleate, dimethyl maleate, monoethylene maleate, diethyl maleate, monoethyl maleate, diethylene maleate, maleimides, ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylamide, methacrylamide, N-dimethylacz:ylamide (sic], N-tert-butylacrylamide: [sic] N-isopropy7Lmethacrylamide, methacryloylpyrrolidine, acrylonitrile, rnethacrylonitrile, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, ' 0050/49359 diethylaminoethyl acrylate, diethylaminoethyl methacrylate and the salts of the last-mentioned monomers with carboxylic acids or mineral acids and the guaternized products. Examples of vinyl esters are vinyl acetate, vinyl propionate and vinyl esters of a synthetic fatty acid of 10 carbon atoms {versatic-10 acid) or of 9 carbon atoms (versatic-9 acid), both commercially available (e. g. from Shell). Examples of vinyl ethers are vinyl C1-C4-alkyl ethers, in particular vinyl isobutyl ether. Suitable as monomers are, in addition, acrylamidoglycolic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, sytrenesulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl met.hacrylate and acrylamidomethylpropanesulfonic acid and monomers containing phosphoric acid groups, such as vinyl phosphate, allyl phosphate and acrylamidomethylpropanephosphonic aci.d. It is of course also possible to use mixtures of said monomers,, for example mixtures of acrylates and vinyl acetate, mixtures of different acrylates, mixtures of acrylates and acrylamide or mixtures of acrylamide and hydroxyethyl acrylate.
Acrylamide and acrylates are particularly preferred.
The aqueous medium may consist exclusively of H20 or may be a mixture of H20 and alcohol, in particular CH30H or CZH50H.
The initiation is effected with water-soluble initiators in amounts of from 0.1 to 5, particularly preferably from 0.2 to 2, by weight, based on monomer.
Hydrogen peroxide is particularly preferred as water-soluble initiator, with simultaneous introduction of traces of Cu(II) salts into the reaction mixture comprising monomer and water.
The pH during the polymerization is from 4 to 9, particularly preferably from 6 to 8. The pH during the' (total) polymerization is controlled by adding aqueous acids anti alkalis. In general, the addition of an alkali is sufficient, an aqueous ammonia solution, e.g. 10~ strength, being particularly preferably used.
The K values of the polymers prepared according to the invention {determined according to Fikentscher, Cellulose Chemie, 13 {1932}, 58-64 and 71-74; 1~ strength aquE:ous solution, 20~C, K =
k-103) are from 10 to 100, preferably from 15 to 45. The molecular weights of the polymers (MW) are from 2000 to 800,000, preferably from 5000 to 100,000.

' 0050/49359 The novel copolymers can be used as gas hydrate inhibitors, as described in WO 96/41785. For this purpose, the polymers are added to the liquid systems, for example the mineral oil or natural gas mixtures, in the usual amounta which a person skilled in the art adapts to the respective conditions.
The polymers used according to the invention can be used together with other compositions for the purpose of gas hydrate inhibition. These other compositions may be other polymers, such l0 as hydroxyalkylcelluloses, polyvinylpyrrolidone or polyvinylcaprolactam, preferably in an amount of from 1 to 3.5%
by weight, based on the weight of the total liquid system, but also alcohols, such as methanol, ethanol or ethylene glycol, or water-soluble salts, preferably in an amount of from 10 to 30% by weight, based on the weight of the total liquid system.
Examples Preparation example Initially taken mixture: 1125.00 g of demineralized water 300.00 g of vinylcaprolactam 200.00 g of N-vinylmethylacetamide Feed 1: 8.30 g of hydrogen peroxide (30% strength) Feed 2: 0.50 g of copper(II) chloride (0.01% strength) Feed 3: xx g of ammonia water (5% strength) Feed 4: 0.50 g of copper(II) chloride (0.1% strength) Feed 5: 5.00 g of hydrogen peroxide (30% strength) Procedure The initially taken mixture is flushed with nitrogen and heated to an internal temperature of about 80~C.
At an internal temperature of about 78~C, feed 1 is added, followed by feed 2.
With feed 3, the pH is kept at 7.0 during the entire Polymerization time.
After a polymerization time of 3.5 hours,, feeds 4 and 5 are added.

After the addition of feeds 4 and 5, polymerization is continued for a further 4 hours at an internal temperature of about 80~C.
The experimental batch is then cooled to room temperature.
Characterization Solids content 30% by weight K value 34 (1% strength in water) pH 6 ° 0050/49359 ' 6 U

U

x x G o I 1 rlN
O

~'U

>~
uoo I 1 '~N
N

v o I I

M

U

x I I

M

o I I I

v ~o b a ~n x M f'~
~

N
x ., .I

dP

N
x x N
U

'b ~ b . v N
..

.
~ .~ ~

.w.D, I ~ C

..
' ~ G ~ ty ' U ow '~ ~ cd ''~
,N

. ~ N

a.~ a.~'~' ~ v 3 b ~ -~''t 3 r v c~''t'' r-I +~ U .-t U

z o I
In v~ .,~ ,-I n~

r, a a a o N .c r-Iv ~ ~.

V! rl v v (d .~ I 'rI
N ri ~ ~ GL ~-I z a ~ O O
O

!~ O U U

O U
E V H ~ a I DC ~

The "freezing point" was measured by the ball-stop method, analogously to the test method described in Example I of W095/32356.
This method relates to freezing points to be tested for water/THF
mixtures by adding various polymers (detection of hydrate formation), which are frozen in a concentration of 0.5o in a water/THF (8I/19~ by weight) mixture.
The following apparatuses and reagents are required for determining the freezing point of various polymer/(water/THF) mixtures:
- Water/THF mixture (81/19 by weight) - Julabo F 18 thermostat bath With water/ethylene glycol (5:I) refrigerant mixture - Multifix Constant stirrer - Holder for test tubes (5 ml) - Small stainless steel balls for better mixing in the test tube A 0.5~ strength solution of the polymer i~o be investigated in water/THF (81/19) is prepared. The test l:ube is 2/3 filled, provided with a small stainless steel ball, closed and fixed in the test tube holder. The measurement is started at a bath temperature of 4~C and a speed of 20 rpm and the temperature is decreased by 0.5~C per hour until the sample has frozen or the steel ball in the test tube no longer moves or the temperature of O~C has been reached. A blank test runs :>imultaneously with each measurement.

Claims

We claim:

1. A process for the preparation of copolymers by free radical polymerization of a) from 5 to 95% by weight of a monomer of the formula I
b) from 95 to 5% by weight of a monomer of the formula II
where in each case R1 and R2 are H or C1-C3-alkyl R3 is H or C1-C6-alkyl and n is from 1 to 3, and c) from 0 to 40% by weight of a further monomer which is completely water-soluble or has limited water solubility, wherein the polymerization is carried out in an aqueous medium.

2. A process as claimed in claim 1, wherein from 20 to 80% by weight of the monomer a) and from 80 to 20% by weight of the monomer b) are used.

3. A process as claimed in claim 1, wherein the monomer b) is vinylcaprolactam.

4. A process as claimed in claim 1, wherein R2 and R3 in the monomer a) are each methyl.

5. A process as claimed in claim 1, wherein R1 in the monomers a) and/or b) is hydrogen.

6. A process as claimed in claim 2, wherein the aqueous medium is water.

7. A process as claimed in claim 1, wherein a polymerization initiator system which contains H2O2 is used.

8. A copolymer prepared by a process as claimed in claim 1.

9. A copolymer as claimed in claim 8, which has terminal hydroxyl groups.

10. A copolymer as claimed in claim 8, which has a K value of from 10 to 100.

11. The use of a copolymer as claimed in claim 8 as a gas hydrate inhibitor.