PROCESS FOR THE PRODUCTION OF POLYMERS VIA EMULSION POLYMERISATION

Abstract

The present invention relates to a process for the production of a polymer comprising the steps of: a) polymerisation of an emulsion comprising a reaction mixture to obtain a polymeric latex; and b) coagulating the polymeric latex by exposing the polymeric latex to one or more coagulant, and isolating the coagulated product to obtain a polymer; wherein the polymeric latex obtained under a) is stored prior to coagulation step b) for at most such a time that the polymeric latex contains 500 CFU/ml of pigment-producing organisms as determined in accordance with ASTM D 5465-93 (2012) when subjecting the polymeric latex to coagulation step b). Such process allows for the production of a polymer having a reduced discoloration. The polymers may have a desirable appearance such as an opaque, white appearance.

Claims

1. A process for the production of a polymer comprising the steps of: a) polymerisation of an emulsion or suspension comprising a reaction mixture to obtain a polymeric latex; and b) coagulating the polymeric latex by exposing the polymeric latex to one or more coagulant, and isolating the coagulated product to obtain a polymer; wherein the polymeric latex obtained under a) is stored prior to coagulation step b) for at most such a time that the polymeric latex contains 500 CFU/ml of pigment-producing organisms as determined in accordance with ASTM D 5465-93 (2012) when subjecting the polymeric latex to coagulation step b).

2. The process according to claim 1, wherein the reaction mixture comprises one or more reactants selected from styrene, acrylonitrile, butadiene, polybutadiene, butyl(meth)acrylate, poly(butyl acrylate), methyl(meth)acrylate, or combinations thereof.

3. The process according to claim 1, where the pigment-producing organisms are bacteria selected from the genera Bacillus, Microcossus, Serratia, Flavobacterium or Pseudomonas.

4. The process according to claim 1, wherein the pigment-producing organisms are bacteria selected from the species Bacillus Lentus, Bacillus Subtilis Serratia Marcencens, or Pseudomonas Pseudoalcaligenes.

5. The process according to claim 1, wherein the emulsion is an aqueous emulsion.

6. The process according to claim 1, wherein the emulsion comprises a quantity of emulsifying agent selected from: anionic emulsifiers selected from higher fatty alcohol sulphates, higher alkyl sulphonates, alkylaryl sulphonates, aryl sulphonates, the condensation products thereof with formaldehyde, salts of sulphosuccinic acid esters, and sulphated ethylene oxide adducts; and non-ionic emulsifiers selected from the reaction products of ethylene oxide, 2-ethyloxirane or methyloxirane with C.sub.10-C.sub.20 alkyl alcohol(s); C.sub.10-C.sub.20 alkyl acid(s); or C.sub.10-C.sub.20 alkyl amide(s); or a combination thereof.

7. The process according to claim 6, wherein: the C.sub.10-C.sub.20 alkyl alcohol(s) are selected from 1-decanol, 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-eicosanol; the C.sub.10-C.sub.20 alkyl acid(s) are selected from decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid or eicosanoic acid; and/or the C.sub.10-C.sub.20 alkyl amide(s) are selected from decanamide, dodecanamide, tetradecanamide, hexadecanamide, octadecanamide or eicosanamide.

8. The process according to claim 6, wherein the emulsifying agent is used in quantities of 0.1 wt %-10.0 wt % with regard to the total weight of the reaction mixture.

9. The process according to claim 1, wherein the reaction mixture further comprises a free radical initiator selected from: persulfate compounds including ammonium persulfate, potassium persulfate and sodium persulfate; peroxides including hydrogen peroxide, cumene hydroperoxide, t-butyl hydoperoxide, acetylperoxide, lauroyl peroxide, peracetic acid and perbenzoic acid; azo-compounds such as 2,2-azobisisobutyronitrile and 4,4-azobis(4-cyanovaleric acid); or combinations thereof.

10. The process according to claim 9, wherein the free radical initiator is used in quantities of 0.01-2.00 wt % with regard to the total weight of the reaction mixture.

11. The process according to claim 1, wherein the storage takes place in a storage tank, wherein the storage tank is cleaned prior to the introduction of the polymeric latex with a solution comprising 0.05-3 ppm chlorine.

12. The process according to claim 1, wherein the polymeric latex is exposed to ultraviolet radiation for at least a fraction of the time between the production of the latex and the coagulation.

13. The process according to claim 1, wherein a quantity of an antimicrobial agent is added to the polymeric latex obtained in step a) prior to storage.

14. The process according to claim 13, wherein the antimicrobial agent is selected from 1,2-benzisothiazolin-3-one, N-methyl-1,2-benzisothiazol-3(2H)one, 2-methyl-4-isothiazolin-3-one or combinations thereof, and wherein the antimicrobial agent is added to the polymeric latex in a quantity of 200-2000 ppm with regard to the total weight of the polymeric latex.

15. The process according to claim 1, wherein the reaction mixture comprises acrylonitrile and styrene, and/or wherein the reaction mixture comprises polybutadiene.

Description

[0075] The present invention will now be illustrated by the following non-limiting examples.

[0076] In a 3 l reaction vessel, an aqueous emulsified system comprising a fatty acid soap as emulsifier, prepared using demineralized water, was provided comprising 61 parts by weight of polybutadiene. The contents of the vessel were heated to 57 C. A first feed stream comprising 9 parts by weight of acrylonitrile, a second feed stream comprising 27 parts by weight of styrene, and a third feed stream comprising 0.45 parts by weight of cumene hydroperoxide as initiator were gradually added to the aqueous emulsified system over a period of 60 min. A fourth feed stream comprising 3 parts by weight of methyl methacrylate was added to the reaction vessel over a period of 5 min. A polymeric latex comprising ABS polymeric particles was obtained. The polymeric latex comprised 40.0 wt % of polymeric particles. The polymeric latex was cooled to 40 C.

[0077] The polymeric latex was transferred to a storage vessel and maintained in the storage vessel under the conditions as indicated in table I.

TABLE-US-00001 TABLE I storage conditions. In sample 1, the storage tank had been cleaned with chlorinated water, in samples 2-4 the storage tank had been cleaned with demineralised water. Sample 1 2 3 (C) 4 (C) Temperature ( C.) 40 40 40 40 Time (h) 15 15 PCT 48 Storage system Chlorinated Water Water Water cleaning water

[0078] Following the storage as described above, samples of the stored polymeric latices 1-4 were taken and subjected to microbial incubation for 4 days at 27 C. using a microbial testing kit (SANI Check B bacteria test kit, Biosan Lab). For each latex sample, a sampling paddle was immersed in the latex for 2-3 sec, then drained from excess fluid, and placed in a testing vial. The pigmented bacteria count was determined using the counting method of ASTM D5465-93. The results are presented in table II.

TABLE-US-00002 TABLE II quantity of pigmented bacteria in sample Sample 1 2 3 (C) 4 (C) CFU.sub.p/ml 100 100 1000 10000

[0079] Wherein CFU.sub.p/ml is the quantity of colony forming units of pigmented bacteria per ml of sample.

[0080] The polymeric latices obtained after storage as indicated above were subjected to an acid coagulation treatment of each sample of latex obtained after storage treatment, a sample of polymer was obtained accordingly.

[0081] In order to emulate the duration of the coagulation process as it takes place in large-scale production, where the coagulation itself takes a certain time, coagulation of the polymeric latices of each sample were performed for a portion of each latex sample at a time immediately after termination of the storage period (t.sub.0), and at 3 h, 6 h and 9 h after the termination of the storage period (t.sub.3, t.sub.6, and t.sub.9).

[0082] The polymer samples obtained from the above described coagulation were subjected to colour determination using a spectrophotometric colorimeter on a moulded polymer disk. The colorimetric coordinate a* was obtained. The yellowness index YI was determined according to ASTM E313 (2010). The obtained results are presented in table III.

[0083] For each polymer sample coagulated at to, the a* and YI are presented. For each polymer sample coagulated at t.sub.3, t.sub.6 and t.sub.9, the difference for a* and YI compared to the previous measurement are presented.

TABLE-US-00003 Sample 1 2 3 (C) 4 (C) a* 2.5 1.8 1.2 0.4 a*.sub.3-0 0.0 0.2 0.4 0.0 a*.sub.6-3 0.0 0.2 0.1 0.5 a*.sub.9-6 0.0 0.0 0.2 0.4 YI 27.4 28.4 30.3 32.1 YI.sub.3-0 0.0 0.1 0.1 YI.sub.6-3 0.1 0.0 0.4 YI.sub.9-6 0.0 0.0 0.2 The colour coordinate value a* and the YI are dimensionless. Wherein: a*.sub.3-0 is the difference between the a* colour coordinate determined on a sample of polymer coagulated at t.sub.3 and the a* colour coordinate determined on a sample of polymer coagulated at t.sub.0. a*.sub.6-3 is the difference between the a* colour coordinate determined on a sample of polymer coagulated at t.sub.6 and the a* colour coordinate determined on a sample of polymer coagulated at t.sub.3. a*.sub.9-6 is the difference between the a* colour coordinate determined on a sample of polymer coagulated at t.sub.9 and the a* colour coordinate determined on a sample of polymer coagulated at t.sub.6. YI.sub.3-0 is the difference between the yellowness index determined on a sample of polymer coagulated at t.sub.3 and the yellowness index determined on a sample of polymer coagulated at t.sub.0. YI.sub.6-3 is the difference between the yellowness index determined on a sample of polymer coagulated at t.sub.6 and the yellowness index determined on a sample of polymer coagulated at t.sub.3. YI.sub.9-6 is the difference between the yellowness index determined on a sample of polymer coagulated at t.sub.9 and the yellowness index determined on a sample of polymer coagulated at t.sub.6.

[0084] The above results clearly indicate that the samples having a low pigmented bacteria content, such as below 500 CFU/ml, show both a better yellowness index and a far less change of colour as represented by YI and a* as a dependent of the time to coagulation.