AU6472199A

AU6472199A - Redox polymerization process

Info

Publication number: AU6472199A
Application number: AU64721/99A
Authority: AU
Inventors: Annemarieke Maltha; Andreas Petrus Van Swieten; Petrus Paulus Waanders
Original assignee: Akzo Nobel NV
Current assignee: Akzo Nobel NV
Priority date: 1998-10-12
Filing date: 1999-10-11
Publication date: 2000-05-01
Also published as: KR20010083906A; CN1326470A; EP1129113A1; PL347253A1; TR200101810T2; ZA200103009B; NO20011865D0; NO20011865L; CA2346993A1; JP2002527540A; WO2000022003A1

Description

SWO 00/22003 PCT/EP99/07769 REDOX POLYMERIZATION PROCESS The present invention relates to a process for emulsion polymerization, to the polymers obtainable by such a process, and to their uses. 5 The production of water based resins, for example by means of emulsion polymerization techniques, is carried out thermally with inorganic persulfates. A problem with thermal polymerization is the process time, which leads to a less than desirable reactor output. 10 An object of the present invention is to provide an alternative polymerization process which aims to improve the process time. The first aspect of the present invention provides a process according to claim 1. 15 Since the polymerization process according to the present invention provides a free radical initiator moiety by means of a redox reaction instead of by thermal decomposition, the polymerization can be carried out with a so-called "cold start", which involves the process time being reduced and the reactor output per unit 20 time being increased. A redox polymerization is known for tertiary butyl hydroperoxide "Trigonox A W70". The inventors have shown, however, that a redox polymerization utilizing other organic peroxides provides unexpectedly good results. 25 The inventors have shown that polymerization can start at a lower initial temperature, which means that because of the longer "heating-up" time necessary in thermal polymerization, the polymerization time can be reduced utilizing the process of the current invention. 30 The inventors have furthermore demonstrated that the process according to the present invention enables a polymer with a very low residual monomer level to be CONFIRMATION COPY WO 00/22003 PCT/EP99/07769 2 obtained, whilst, with respect to thermal polymerization, the amount of initiator used can be reduced. Good results have been achieved under the conditions as defined in claims 2-6. 5 The polymerization initiator is most preferably a substantially non-water-soluble initiator, such as defined in claim 7 or 8, since these non-water-soluble initiators yield an unexpectedly high efficiency in polymerization. 10 This higher efficiency results in shorter polymerization times and in polymer resins with improved properties. The higher efficiency of the organic peroxides is expressed by the low level of residual monomers and by the low molecular weights (Mw/Mn) of the polymers formed. 15 Furthermore, the conductivity of the resins initiated with the organic peroxide/redox system is lower than for corresponding resins that were initiated by persulfates. The reductor of the redox system preferably is chosen from the following group: 20 sodium formaldehyde sulfoxylate (SFS), sodium bisulfite, Ascorbic acid (vitamin C), aldehydes, for example glutaraldehyde, sodium metabisulfite, sodium dithionate, and sugars, wherein the reductor most preferably is sodium formaldehyde sulfoxide. 25 The polymerizable species preferably is chosen from the following group: acrylonitrile, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2 ethylhexyl acrylate, methoxyethyl acrylate, dimethyl aminoacrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearic 30 methacrylate, dimethyl aminomethacrylate, allyl methacrylate, 2-hydroxyethyl WO 00/22003 PCT/EP99/07769 3 acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylamide, methacrylamide, glycidyl acrylate, vinyl ester of versatic acid, styrene, para-methyl styrene, vinyl acetate, alpha-methyl styrene, wherein the polymerizable species most preferably comprises vinyl acetate 5 and/or the vinyl ester of versatic acid. Further preferred process conditions are detailed in claims 11-15. The polymerization is carried out in a conventional emulsion, for example in a o10 mixture of anionic and non-ionic surfactants such as Witconate (sodium alpha olefin sulfonate) and Syntopon (ethoxylated nonylphenol); however, other emulsifiers or mixtures are also possible. This emulsifier solution preferably is a mixture of nonionic and anionic emulsifiers 15is and most preferably is selected from the group consisting essentially of: - long-chain aliphatic carboxylates (ionic) - alkylbenzene sulfonates (ionic) - alkyl sulphates (ionic) - dialkylsulphosuccinate (ionic) 20 - ethoxylated alcohols (nonionic) - ethoxylated alkyl phenols (nonionic) - ethoxylated amine or amides (nonionic). A second aspect of the present invention provides a polymer obtainable 25 according to this process. The invention will now be further elucidated by way of the following examples. Examples 1-6 are comparative examples and Examples 7-12 are examples according to the present invention using a redox system. Examples 3, 4, 6, 8-12 30 were subjected to a temperature profile increasing from an initial temperature to a WO 00/22003 PCT/EP99/07769 4 final temperature, i.e. subjected to a so-called "cold-start", and Example 7 was carried out at constant temperature. Procedure of preparation 5 The polymerization in all the examples was carried out in a 0.25 L glass reactor with a stirrer under nitrogen. A seed was prepared first by adding 10% of the reactive components at polymerization temperature. The preparation of the seed was carried out as follows: 10 The reactor was filled with buffered (NaAc/HAc) emulsifier solution (Witconate/Syntopon), prepared with oxygen-free deionized water. At the polymerization temperature 10% of the pre-emulsion containing soaps (Witconate and Syntopon), monomers, and, in the case of the redox system according to the present invention, also reductor and catalyst, were added. In addition the solution is or pre-emulsion of the initiator was added to achieve control over the accurate dosing of the initiator. After a polymerization time of 30 minutes the remaining monomers, pre-emulsion, and initiator solution were dosed in 2.5 hours. In Examples 3, 4, 6, 8-12 the 20 temperature was increased to the final temperature in the same period, following a temperature profile. The final temperature was maintained for 1 hour. The composition of the buffered soap solution used was as follows: NaAC.3aq 0.25 g (sodium acetate) 2s HAc 0.11 g (acetic acid)

H

2 0 30.3 g Witconate 0.38 g (soap) Syntopon 0.38 g (soap) WO 00/22003 PCT/EP99/07769 5 Example 1 Thermal system The temperature was kept at 700C during the polymerization. The composition of the used pre-emulsion was: Witconate 1.28 g Syntopon 1.28 g

H

2 0 34.43 g Vac (vinyl acetate) 52.5 g (monomer) VEOVA (vinyl ester of versatic acid) 22.5 g (monomer) 5 The initiator solution was composed of 4.18 mmoles ammonium/sodium or potassium persulfate in 25 g H 2 0. The total process time including the time needed for heating up the reactor contents to 700C before polymerization amounted to 5.5 hours. 10 Examples 2. 5. 7 The temperature was kept at 700C (Examples 2, 5) and 200C (Example 7), respectively. The composition of the used pre-emulsions was as follows: Witconate 1.28 g Syntopon 1.28 g

H

2 0 34.43 g Peroxide 1.04-4.18 mmoles as mentioned in the examples Vac (vinyl acetate) 52.5 g (monomer) VEOVA (vinyl ester of 22.5 g (monomer) versatic acid) 15is The reductor SFS (sodium formaldehyde sulfoxyde: 0.65 g) and the catalyst (FeSO 4 16.7 mg) were dissolved in 25 g H 2 0. The total process time was 4 hours.

WO 00/22003 PCT/EP99/07769 6 Examples 3. 4. 6. 8-12 The polymerization temperature was kept at 200C for the first 30 minutes to prepare a seed. The temperature was then increased by 20 0 C/hour to 700C following a temperature profile. 5 It is noted that other starting temperatures and temperature programmes can be used, either for initiating polymerization or for initiating and completing polymerization. o10 In all the examples the residual monomers were determined by gas chromatography (GC). The molecular weight of the prepared polymers was determined by gel permeation chromatography (GPC) with polystyrene for calibration. The conversion/solids content was determined by standard procedure. The viscosity was determined using a Brookfield digital viscometer. s15 The results are shown in Table 1. Examples 13-24 20 Procedure of preparation The polymerization in all examples was carried out in a 0.25 L glass reactor with a stirrer under nitrogen. A seed was prepared first by adding 10% of the reactive components at polymerization temperature. 2s The preparation of the seed was carried out as follows: The reactor was filled with the emulsifier solution (sodium lauryl sulfate in water) prepared with oxygen-free deionized water. At the starting polymerization temperature 10% of the pre-emulsion containing soap, monomers, and in the case of the redox system, also reductor and catalyst, were added. In addition the 30 solution or pre-emulsion of the initiator was added to achieve control over the .WO 00/22003 PCT/EP99/07769 7 accurate dosing of the initiator. After a polymerization time of 30 minutes the remaining monomers, pre-emulsion, and initiator solution were dosed in 2.5 hours. The temperature was increased to s the final temperature in the same period, following a temperature profile. The final temperature was maintained for 1 hour. The composition of the soap solution was as follows: 0.10 g sodium lauryl sulfate (emulsifier) 10 25.0 ml deionized water Pre-emulsion: 1.60 g sodium lauryl sulfate 30 ml deionized water 15is 70 g monomer mixture (butylacrylate / styrene / methacrylic acid = 6/4/0.1) including the initiator (1.04 meq), if not water-soluble. The reductor SFS (sodium formaldehyde sulfoxylate 0.16 g) and the catalyst (Fe"SO 4 2.8 mg) were dissolved in 10 ml water. 20 The molar ratio oxidator: reductor: Fe = 1: 1:0.01 The results are shown in Tables 2 and 3.

WO 00/22003 PCT/EP99/07769 8 E c (nL, c 0 L6( C6 C ' iC ' E c CD C) r.- 't (M m q co C1 o 000( 0000 0C 0 00000C It co r- LO N- C cu CN(0o o o 000- 0 6 0- M 06660c C 0 0 c0000 cr 0) 1, Tco' Cq C' o C 0 c,000 oCA A 0 AA 00 0 ~ ~ C Q) (U (1U 0 (0 C) C) CCD0C) 0 0 X X U~ ~ 000004 0) a CD>0 0 0 0 04 C 4(N( 0 C - 0 cc 2 00 0 0 0 NX CL CLNC~L a- CL CL~ WOO00/22003 PCT1EP99107769 C)C)LO V- O C o 1-1 c t 6 0000(D00 V O 0C) C LO 000000M C 0)00000 " U-)Loco m0co4 0 CC)C) m nct( E> 0 L0 r.- ) . . m>U) ~LL > - - 00 J0 000)U 0 :=I>> 0l U) 41 000 U rn. U) 0 C 0 EU) _0 a I00 0 CUa 0- 0 WO 00/22003 PCT/EP99/07769 10 00 0 N0 0 0 D0C 0 o ' a N 1r 0 C C 0- C Cf) 0 * ')C l C CO COCV C -o 0~ c CR 0. 00) -0 C) 'a ~LL - o 0> x co 14 )I I. .

CC 0 La oD com~ X~( 3 a 00 0- CC C)C 0 C C U) C I a) I->,2 __ CC0 FH~ co) 0 C: 0 C:H WO 00/22003 PCT/EP99/07769 11 Results As reference the emulsion copolymerization of vinylacetate and VeoVa with potassium persulfate at 70 0 C was used (thermal conditions). 5 The results show low residual monomer levels for the non-water-soluble organic peroxides (peroxyesters) under redox conditions. As the efficiency of the non-water-soluble peroxyesters such as Trigonox C was much higher than that of the water-soluble persulfates and hydroperoxides, the levels of addition 10 could be lowered to 20-40% of the original milli-equivalents of initiator used. Due to lower amounts of initiator and reductor, a higher value for pH and lower values for the conductivity were obtained. The prepared polymer had molecular weights (Mw/Mn) comparable with those of the reference copolymer of VeoVaNAc. 15 The peroxyesters such as Trigonox 21 gave a high conversion of monomers at ambient temperature. The invention is not limited to the above description; rather, the requested 20 rights are determined by the following claims.

Claims

1. A process for emulsion polymerization comprising the steps of reacting together a polymerization initiator, a reductor, and a polymerizable s species, with the proviso that the polymerization initiator is not a hydroperoxide, characterized in that the polymerization initiator and the reductor are reacted together to provide a free radical moiety of the initiator, whereupon this free radical moiety initiates polymerization of the polymerizable species, this step being carried out at an initial cold start o10 temperature, whereafter the temperature is increased to follow a temperature profile to a final preselected polymerization temperature.

2. Process according to claim 1 carried out at an initial temperature of up to 700C, for example carried out at an initial temperature of up to 500C and 15 preferably of up to 350C.

3. Process according to claim 1 or 2 carried out at an initial temperature lying in the range of +100 to 35 0 C, preferably in the range of 150 to 250C. 20

4. Process according to any one of the preceding claims wherein the initial temperature is maintained for a predetermined length of time, for example up to 2 hours, preferably up to 1 hour, most preferably up to half an hour.

5. Process according to any one of the preceding claims wherein the 25 temperature is increased subsequent to the initial temperature maintenance period to follow a temperature profile to a final polymerization temperature, preferably up to a final polymerization temperature of at the most 900C, and wherein the final polymerization temperature preferably lies in the range of 50-800C and most preferably is . WO 00/22003 PCT/EP99/07769 13 700C or less.

6. Process according to claim 5 wherein the initial temperature is increased incrementally per pre-selected time period, preferably by about 200C per 5 hour.

7. Process according to claim 6 wherein the initiator is selected from the group consisting essentially of: diisobutanoyl peroxide, cumyl peroxyneodecanoate, 2,4,4-trimethylpentyl-2-peroxyneodecanoate, tert 10 amyl peroxyneodecanoate, bis(4-tert-butylcyclohexyl)peroxydicarbonate, bis(-ethylhexyl)peroxydicarbonate, tert-butyl peroxyneodecanoate, dibutyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxy dicarbonate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, bis(3,5,5 trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5" i5 bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-amyl peroxy-2 ethylhexanoate, dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxydiethylacetate, 1,4-bis(tert-butylperoxycarbo)cyclohexane, tert-butyl peroxyisobutanoate, 1,1-bis(tert-butylperoxy)-3,3,5 trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, tert-butyl 20 peroxy-3,5-trimethylhexanoate, 2,2-bis(tert-butylperoxy)butane, tert butylperoxy isopropyl carbonate, tert-butylperoxy 2-ethylhexyl carbonate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, dicumyl peroxide, bis(tert-butylperoxyisopropyl)benzene, 2,5-bis(tert butylperoxy)-2,5-dimethylhexane, tert-butyl cumyl peroxide, 2,5-bis(tert 2s butylperoxy)-2,5-dimethyl-3-hexyne, and di-tert-butyl peroxide.

8. Process according to claim 7 wherein the initiator is substantially non water-soluble and is selected from the group consisting essentially of: - alifatic and aromatic peroxyesters, preferably tert-butyl peroxy-2- WO 00/22003 PCT/EP99/07769 14 ethylhexanoate (Trigonox 21), tert-amyl peroxy-2-ethylhexanoate, tert butyl peroxybenzoate (Trigonox C), tert-amyl peroxybenzoate, tert-butyl peroxyacetate, tert-butyl peroxy-3,5-trimethylhexanoate, tert-butyl peroxyisobutanoate, tert-butyl peroxydiethylacetate, tert-butyl s peroxypivalate; - peroxycarbonates, preferably tert-butyl peroxyisopropyl carbonate (Trigonox BPIC), and tert-butyl peroxy-2-ethyl hexyl carbonate Trigonox 117). o10

9. Process according to any one of the preceding claims wherein the reductor is chosen from the group consisting essentially of: sodium formaldehyde sulfoxylate (SFS), sodium bisulfite, Ascorbic acid (vitamin C), aldehydes, for example glutaraldehyde, sodium metabisulfite, sodium dithionate, and sugars. s15

10. Process according to any one of the preceding claims wherein the polymerizable species is selected from the group consisting essentially of: acrylonitrile, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2 ethylhexyl acrylate, methoxyethyl acrylate, dimethyl aminoacrylate, 20 methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearic methacrylate, dimethyl aminomethacrylate, allyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2 hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylamide, 2s methacrylamide, glycidyl acrylate, vinyl ester of versatic acid, styrene, para methyl styrene, vinyl acetate, alpha-methyl styrene.

11. Process according to any one of the preceding claims carried out in the presence of a catalyst, said catalyst preferably being a water-soluble salt . WO 00/22003 PCT/EP99/07769 15 derived from a transition metal, and most preferably being selected from the group consisting essentially of Fe 2 +, Co 3+ , Cu+, and Ce 3 +.

12. Process according to any one of the preceding claims wherein the initiator s and the reductor are provided in the following ratios 10:1 to 1:5, preferably 4:1 to 1:2.

13. Process according to any one of the preceding claims wherein the ratio of catalyst: oxidator is about 0-0.1 on a molar basis. 10

14. A polymer obtainable according to the process of any one of the preceding claims.

15. Polymer according to claim 14 having one or more of the following 15 characteristics: - a conductivity lower than about 5, - a low residual monomer level, - a particle size of less than about 220 nm, preferably less than 200 nm. 20

16. Use of a polymer according to claims 14 and/or 15 in coatings and/or adhesives.