Process for producing short-chain end-group-functionalized macromolecules based on styrene

Abstract

End-group-functionalized oligomers with controlled degrees of functionality based on styrene are produced by reacting the monomer with a regulator by means of free-radical polymerization. At least some of the quantity of regulator is added according to a prescribed program so that at every juncture t the value of the quantitative fraction added up to said juncture does not fall short of the value of the respective conversion U(t) in the polymerization reaction at said juncture t by more than 5 percentage points and does not exceed said value U(t) by more than 5 percentage points.

Claims

1. A process for producing end-group-functionalized oligomers based on styrene by means of free-radical polymerization, starting from an amount of monomer comprising at least 90 mol % styrene, wherein the polymerization is started by self-initiation and is controlled by means of a difunctional regulator comprising the functional groups R.sub.F1 and R.sub.F2, where the group R.sub.F1 is an unsubstituted sulfanyl group and where the group R.sub.F2 of the regulator is selected from the group consisting of hydroxyl groups (OH), carboxyl groups (COOH), ester groups (COOR), primary amino groups (NH.sub.2), secondary amines (NHR), wherein the molar ratio of the total monomers used to the regulator is from 5:1 to 200:1 wherein the total amount of monomer is initially charged, the batch with the monomer comprises not more than 10% by weight of a solvent, up to 5% by weight of the total amount of regulator is added to the amount of monomer prior to the start of the reaction, the temperature of the amount of monomer is controlled such that the polymerization starts by self-initiation, and the further addition of regulator to the polymerization reaction is carried out continuously or in discrete steps, until a polymerization conversion of at least 85% is achieved, and in such a manner that at all times the following condition (I) is met:
C(t)0.05X.sub.reg(t)C(t)+0.05(I) wherein C(t)=polymerization conversion up to the time point t C(t)=n.sub.mon(t)/n.sub.mon,tot n.sub.mon(t)=total amount of reacted monomers in the course of the polymerization reaction up to the time point t n.sub.mon,tot=amount of all monomers used n.sub.mon,tot (amount converted) X.sub.reg(t)=fractional amount of regulator X.sub.reg(t)=R(t)/R.sub.B R(t)=total amount of regulator added up to the time point (t) R.sub.B=total amount of regulator.

2. The process as claimed in claim 1, wherein condition (I) is met up to a polymerization conversion of at least 90%.

3. The process as claimed in claim 1, wherein a still remaining, previously unadded amount of regulator is added continuously or periodically.

4. The process as claimed in claim 1, wherein the amount of monomer, in addition to styrene, comprises up to 10 mol % of other vinyl aromatic compounds.

5. The process as claimed in claim 1, wherein, apart from styrene and optionally other vinyl aromatic compounds, no further monomers are present in the amount of monomer.

6. The process as claimed in claim 1, wherein the polymerization is carried out at a temperature of at least 100 C.

7. The process as claimed in claim 1, wherein the polymerization is carried out free of solvent.

8. The process as claimed in claim 1, wherein the molar ratio of the total monomers used to the regulator is from 10:1 to 200:1.

9. The process as claimed in claim 1, wherein the regulator is selected from the group consisting of 2-aminoethanethiol, 2-mercaptoethanol, 3-mercaptopropionic acid, 2-mercaptopropionic acid and 2-mercaptoacetic acid, and combinations thereof.

10. The process as claimed in claim 1, wherein the number-average molecular weight of the resulting oligomers is in the range of 1000 g/mol to 20 000 g/mol.

11. The process as claimed in claim 1, wherein the polydispersity of the resulting polymers is not greater than 2.5.

12. The process as claimed in claim 1, wherein the polymerization product is purified by removing unreacted monomers and/or by-products from the polymerization product.

13. The process as claimed in claim 1, wherein in a subsequent process step, the oligomers obtained by the process of claim 1 are reacted with at least one compound Z having a functional group R.sub.F3 and an olefinic double bond to give a refunctionalized oligomer, wherein at least that part of the compound Z comprising the olefinic double bond is linked to the oligomers by reaction of the functional group R.sub.F2 with the functional group R.sub.F3.

14. The process as claimed in claim 13, wherein the reaction of the group R.sub.F2 with the functional group R.sub.F3 is a substitution reaction.

15. The process as claimed in claim 13 wherein the reaction of the group R.sub.F2 with the functional group R.sub.F3 is carried out at a temperature of at least 100 C.

16. The process as claimed in claim 13, wherein the polymerization and the reaction of the group R.sub.F2 with the functional group R.sub.F3 are carried out in the same reactor.

17. The process as claimed in claim 13, wherein the compound Z having the functional group R.sub.F3 and an olefinic double bond is selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, methacrylic esters, acrylic anhydride, methacrylic anhydride, glycidyl acrylate, glycidyl methacrylate, maleic anhydride, acryloyl chloride, methacryloyl chloride, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, 4-chloromethylstyrene, itaconic anhydride, 3,4-epoxycyclohexylmethyl acrylate, and epoxycyclohexylmethyl methacrylate.

18. The process as claimed in claim 13, wherein the resulting refunctionalized oligomers have on average 0.95 to 1.05 olefinic double bonds introduced by the compound Z.

19. A refunctionalized oligomer obtained by the process of claim 13.

Description

EXAMPLES

(1) The invention will be illustrated in detail below by means of examples. In addition to the test methods already described above, the following methods are used:

(2) Methods

(3) Molar mass determination was carried out by means of gel permeation chromatography using THF (HPLC Grade, non-stabilizedBiosolve cat. No. 202220602) as eluent, at room temperature and at a flow rate of 1 ml/min. The GPC system consists of a pump from FLOW, Modell Intelligent Pump AL-12, a sampling device from Schambeck SFD, Modell S5200, and a column combination from MZ Analysentechnik GmbH. A degasser from Schambeck of the type Gastorr BG 12 is connected upstream of the pump. The column combination consists of a precolumn of porosity 100 and also three main columns having porosities of 10 000, 1000 and 100 and including a styrene-divinylbenzene copolymer (type Gel Sd plus). The detectors were a Waters 486 Turnable Absorbance Detector and a Schambeck SFD RI 2000 Differential Refractometer, which are connected in series. Polystyrene standards in the range of 575 to 3 114 000 g/mol were used for calibration. Toluene is added to the samples as internal standard.

(4) 300 MHz .sup.1H-NMR spectroscopic measurements were recorded using a Bruker Advance DRX 300 NMR spectrometer at room temperature.

Example 1

(5) Starting Compounds and Amounts

(6) TABLE-US-00001 Monomer Regulator Styrene 2-Mercaptoethanol Amount 200 g 3 g (1.92 mol) (0.038 mol) Molar ratio 50 1

(7) Styrene and 2-mercaptoethanol are used in a molar ratio of 50:1. 200 g of styrene and 3 mol % of regulator are initially charged in a 500 ml laboratory reactor and the reactor is inertized with nitrogen. The reaction mixture is heated to an internal temperature of 145 C. up to reflux of the monomer and maintained at this temperature throughout the entire reaction. The styrene conversion is checked throughout the whole reaction. 2-Mercaptoethanol is added continuously, wherein the percentage total molar amount of regulator added does not deviate by more than 5% of the percentage total molar conversion of the monomer. The polymerization is conducted until monomer conversion reaches 97%.

(8) A prepolymer is obtained having a molar mass of M.sub.n=5030 g/mol where M.sub.w/M.sub.n=1.7. The functionality is 1.04.

Example 2

(9) Starting Compounds and Amounts

(10) TABLE-US-00002 Monomer Regulator Styrene 2-Mercaptoethanol Amount 200 g 0.75 g (1.92 mol) (0.0096 mol) Molar ratio 200 1

(11) The procedure is conducted analogously to Example 1. The amounts used are 200 g of styrene and 0.75 g of 2-mercaptoethanol.

(12) A prepolymer is obtained having a molar mass of Mn=19 960 g/mol where Mw/Mn=2.48. The functionality is 1.18.

Example 3

(13) The prepolymer prepared from Example 1 is dissolved in 500 g of ethyl acetate and heated to 75 C. The solution is then treated with 10 g of isocyanatoethyl methacrylate and stirred for 24 hours. The polymer is then precipitated in 5 L of methanol, filtered off and dried under vacuum. A refunctionalized oligomer is obtained, namely a polymerizable polystyrene macromonomer having a methacrylic end group.

Example 4 (Comparative Example)

(14) As described in JP 1064705A, a laboratory reactor was equipped with two dropping funnels, reflux condenser and anchor stirrer. As precharge, 500 parts of styrene and 300 parts of methyl isobutyl ketone (MIBK) were filled into the reactor. A further 500 parts of styrene were filled in one dropping funnel (dropping funnel 1) and 12.5 parts of AIBN, 21.2 parts of mercaptopropionic acid and a further 250 parts of MIBK in the other dropping funnel (dropping funnel 2). After inertizing with nitrogen, the solution was heated in the reactor to 90 C. The contents of dropping funnel 1 were added dropwise over 4 hours and the contents of dropping funnel 2 were added dropwise over 10 hours into the reactor. After a further 2 hours, the reaction was terminated by cooling to room temperature.

(15) The conversion of styrene was 88%. The resulting polymer had a molar mass of M.sub.n=8 300 g/mol with M.sub.w/M.sub.n=2.8. The functionality is only 0.7.

(16) Comparison of Examples 1 and 4 shows that the oligomer produced by the process according to the invention at comparable molar mass has a distinctly low dispersity and a much improved functionality close to 1.

(17) Example 2 in comparison with Example 1 shows the effect of a change to the ratio of the starting monomer to regulator. If a lower ratio of monomer to regulator is used, oligomers are obtained of greater molar mass at higher dispersity.