FR2555994A1 - PROCESS FOR THE PRODUCTION OF HIGH MOLECULAR WEIGHT ACRYLAMIDE POLYMERS - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR THE PRODUCTION OF ACRYLAMIDE POLYMERS OF HIGH MOLECULAR WEIGHT. HIGH MOLECULAR WEIGHT ACRYLAMIDE HOMOPOLYMERS AND COPOLYMERS ARE PREPARED BY REVERSE EMULSION POLYMERIZATION OF ACRYLAMIDE IN THE PRESENCE OF ABOUT 50 TO ABOUT 250 PARTS PER MILLION (PPM) OF ERYTHORBIC ACID AND METALS OF ITS SALTS. THIS REACTION IS PROFITABLE WHATEVER THE LEVEL OF IMPURITIES IN THE MONOMERIC ACRYLAMIDE.

Description

The present invention relates to an improved process for the production of

  water-soluble high molecular weight monomeric acrylamide polymers and copolymers by inverse emulsion polymerization, in suspension or in solution, using extremely small quantities of erythorbic acid or its salts

of alkali metals.

  Acrylamide monomer is commercially available in the form of a crystalline solid or a 50% inhibited aqueous solution containing

  ppm CuSO4 to prevent polymerization. The acryl-

  solid monomeric amide also contains traces of various impurities formed from metal ions which inhibit the polymerization process and thus reduce the rate of polymerization, requiring

prolonged periods of reaction.

  This problem of inhibition is well known in the prior art; various compounds known as chelating agents have been used to eliminate interference from cupric or ferric ions in order to improve the efficiency of the acrylamide monomer polymerization system. Examples of agents

  chelators are compounds such as amino acids

  carboxylic acids, for example ethylenediamine

  tetra-acetic acid (EDTA) and diethylenetriamine

  penta-acetic acid (Versenex 80) and hydroxyl

  carboxylic acids, for example tartaric acid and citric acid. A disadvantage of these chelating agents is that they tend to produce a retarding effect themselves while counteracting the inhibition due to contamination by metal ions. In addition,

  these compounds are not effective at low concentrations

  which are used for erythorbic acid and its salts in the invention. The chelating agents mentioned above also have defined limits of toxicity and can not be used in

foodstuffs.

  Nothing that teaches the present invention has

  been found in the prior art.

  The present invention eliminates the problems of chelating agents of the prior art and its products can be used without restrictions as ant

food grade oxidants.

  The present invention is directed to a process for producing a polymer, comprising acrylamide reverse emulsion polymerization in the presence of about 50 to about 250 ppm of erythorbic acid and / or its

alkali metal salts.

  In the process of the present invention, compounds such as erythorbic acid, its alkali metal salts and riboflavin (vitamin B2) or mixtures thereof are used as novel additives for

  increase the polymerization rates. Poly-

  Acrylamides are used in cosmetics and in food products as thickeners, binders, emulsifiers and clarifiers for fruit juices. All the additives used in the practice of the present invention are well known food grade quality compounds and are commonly used in

  the food and beverage industry as anti-

  oxidants, etc. Using the antioxidants of the present invention, acrylamide polymers of various molecular weights are prepared by any of the commercially available inverse emulsion, suspension or solution polymerization processes. Depending on the desired molecular weight, one can use high or low

  temperatures according to the constraints of the chosen process.

  In the present invention, the polymerization rate can be high without sacrificing weight

  molecular weight of the polymer, thereby increasing the produc-

tivity.

  The present invention improves the predictability and compatibility of the polymerization rate and the molecular weight of the polymer when solid crystalline acrylamide is used and / or the 50% aqueous solution of available monomer is inhibited.

in the trade.

  Acrylamide is polymerized by free radicals in an inert atmosphere of N2 or CO2 gas

  at pH 3 to 8 using polymerization methods.

  reverse emulsion (microsuspension) or in solution. PH values above 9 cause hydrolysis while a pH below 2.5 causes crosslinking due to imide formation. The speed enhancing additives of the invention can be used in both polymerization systems since they are all water soluble. Polymerization in

  inverse emulsion represents a water-in-water type emulsion

  oil in which microscopic droplets of water and monomer are dispersed in a continuous oily phase, usually odorless mineral spirits

(WHO) or kerosene.

  The surfactant (or a mixture of surfactants) that is used in the inverse emulsion polymerization system must be soluble in the oil with a

  hydrophilic-lipophilic balance (EHL) included in

  range from 1 to 12, preferably from 4 to 6. Various types of water-in-oil emulsifiers are commercially available and include: sorbitan fatty acid esters, mono- and di-glycerides. fatty acids, substituted lanolins, esters of fatty acids

  polyoxyalkylenes, polyoxyethylene esters,

  sorbitol, esters of polyoxyethylene fatty acids

  sorbitan, various alkanolamides of oils and fatty acids, cholesterol and mixtures of apparent sterols, and polyoxyethylene alcohols. The amount of surfactant used can vary from 0.5 to 20.0 g per 100 g of oily phase, preferably from 2.5 to 15.0 g per 100 g of oily phase. The ratio of the aqueous phase to the oily phase is advantageously equal to about 1: 2; however, this ratio can generally be 1: 5 and even up to 2: 1. From the operating point of view, the most advantageous is to use

  a minimum amount of oily phase.

  The polymerization temperature for the inverse emulsion system should generally be in the range of about 20 to 80 ° C, preferably 25 to 60 ° C. The temperature range for the solution polymerization systems should generally be

  at 98 ° C. and preferably from 35 ° to 90 ° C.

  The monomer concentration for the solution polymerization system is generally between 1 and 40 parts by weight of monomer per 100 parts by weight of water, preferably between 5 and 20 parts by weight.

  of monomer per 100 parts by weight of water. No sur-

  filler is only used in the solution polymerization process. The concentration of the monomer for the inverse emulsion polymerization system is generally between 30 and 60 parts by weight of monomer per parts by weight of water, preferably between 45 and parts by weight of monomer per 100 parts by weight.

of water.

  The additives of the present invention can be used in the free radical polymerization of acrylamide and / or methacrylamide monomers alone or

  in combination with other suitable comonomers.

  A wide variety of methods are known in the art for generating free radicals, including water-soluble alkali metal salts such as

  peroxydisulphates of ammonium, sodium or potassium.

  A popular class of initiators, for the implementation

  of the present invention, comprises organic peroxides

  and azo initiators of free radicals

or their mixtures.

  The initiators used in the present invention may be organic peroxides and azo free radical initiators or any suitable mixture of these initiators. Concentration

  of the initiator for the polymerization process

  The inverse emulsion ratio is from about 0.005 to 5.0 parts.

  Page 5 was omitted at the time of the departure.

  Although riboflavin (vitamin B2) gave a higher rate of polymerization-than erythorbic acid and its alkali metal salts, the molecular weight of the polymer was significantly reduced. Although the preferred polymerization system for the present invention is reverse emulsion polymerization, solution and suspension polymerization systems

  also give results with the present invention.

  The concentration of the additive to promote the polymerization rate without adverse influence on the molecular weight in an inverse emulsion polymerization is in general from 50 to 2000, more preferably from 50 to 500 and in particular from 100 to 300 parts by weight.

  million parts by weight of monomer.

  These additive concentrations can also be used in a solution or suspension polymerization process to improve the polymerization rate without adverse influence on the weight.

molecular of the polymer.

  Acrylamide is the monomer used in the present invention; however, it may be polymerized together with isopropylacrylamide, acrolein, acrylic acid, acrylonitrile, butadiene, butyl methacrylate, diallylcyanamide, glycidyl acrylate, maleic anhydride, methacrylamide, methacrylic acid, methyl acrylate, styrene, unsaturated acyl gelatin, unsaturated alkyd compounds, vinyl acetate,

  vinyl ethers, vinyl ketones, vinyl

  pyridines, N-vinylpyrrolidone, sodium acrylate,

  beta-methacryloxyethyltrimethyl methylsulphate

  ammonium (MTMMS) and N, N-dimethylmethacrylate

  aminoethyl. With some of the above monomers, the amount of acrylamide used as a comonomer affects the water solubility of the copolymer. In addition, it is possible to prepare anionic, cationic or amphoteric polymers according to the choice of the comonomer used with the acrylamide.

Examples

  Definitions of the materials used in the examples

  Vitamin B2 - Riboflavin from Roche.

  Vitamin C - Ascorbic acid from Pfizer Inc.

  Niacin - Nicotinic acid from the firm Lonza.

  Vazo 64 - Azo-bis-isobutyronitrile

firm Dupont.

  Vazo 52 - 2,2'-azo-bis- (2,4-dimethylvalo)

nitrile) from Dupont.

  "Solid" monomeric acrylamide from two sources: 1) Aldrich Chemical Company, "Gold Label

  quality for 99%% electrophoresis.

  2) Fisher's reagent quality monomer.

  3) A 50% aqueous solution of monomeric acrylamide inhibited with about 25 ppm copper (Cu +)

Dow Chemicals.

  OMS - Odorless Mineral Essence, Shell Sol-71

Shell Oil co.

  Span 80 - sorbitan mono-oleate from firme ICI Americas, Inc. EA Erythorbic acid from Pfizer Inc. NaEA - Sodium Erythorbate from Pfizer Inc.

  Versenex 80 - pentaethylenetriamine

  acetic acid, a chelating agent from Dow Chemicals.

  Tridistilled water from Queen City Pure Water (Buffalo, N.Y.). Before use, this water was boiled and allowed to cool while purging with nitrogen. Until the moment of its use, it was

  kept under a nitrogen atmosphere.

  LUAZO 55 - 2-tert-butylazo-2-cyano-4-methoxy

  4-methylpentane of Lucidol Div. from PennwaltCorp.

  LUAZO 70 - 2-tert-butylazo-2-cyano-4-methyl

  pentane of the Lucidol Div. from Pennwalt Corp.

  LUPERSOL 223 - di (2-ethyl) peroxydicarbonate

  hexyl) of Lucidol Div. from Pennwalt Corp.

  LUPERSOL 256 - 2,5-dimethyl-2,5-di (2-ethyl)

  hexanoylperoxy) hexane from Lucidol Div. from Pennwalt Corp.

REFERENCE METHOD

  The formulation used for representative inverse emulsion polymerization using 50% aqueous inhibited acrylamide is as follows: Acrylamide aqueous solution inhibited with about 25 ppm CuSO4 (about% by weight aqueous acrylamide in H 2 O) 200 g of WHO Span 80 0.10 g of initiator (pure base) per 100 g of monomer (pure base) to 500 ppm of additive relative to the weight of

  monomer, especially 100 to 300 ppm. -

  The aqueous acrylamide was weighed at -0.05 g on a torsion scale and then set aside. WHO and Span 80 were weighed together at -0.1 g on a triple flail scale and then shaken for a few minutes to form

a homogeneous solution.

  The aqueous acrylamide and the OMS and Span 80 solution were poured into a stainless steel Waring blender which was then run at high speed for 3 minutes to form the emulsion. This

  emulsion was then poured into a pre-reactor

  heated with a nitrogen purge system, stirrer, thermometer and condenser. The heater was pre-set at the reaction temperature (normally 35 C) and thermostated at 0.1 C. The emulsion was

  then stirred, with nitrogen purge for one half

  hour before the addition of the initiator. The latter was weighed in a calibrated glass cup on a Mettler analytical balance at the accuracy of -0.0001 g, placed in a 10 ml beaker and dissolved in about 5 ml of acetone. The initiator solution in acetone was added to the stirring emulsion, the beaker was then rinsed with a further 5 ml

  of acetone and the stopwatch was triggered.

  To use a speed-improving additive according to the invention, it has usually been incorporated before

  the addition of the initiator. It has been added, the most

  tagged directly to the inhibited aqueous monomeric acrylamide which was then stirred for 15 minutes before

  emulsification with the WHO solution and Span 80.

  The additives were weighed at 0.0001 g on a Mettler analytical balance. The solid additives, i.e., EA and NaEA, were weighed on enido crystal paper and the Versene: 80 liquid chelator was weighed into calibrated glass cups. Usually, they were then added without dilution to the 50% aqueous solution of inhibited acrylamide. However, if added on the contrary to the emulsion, the solid compound was first predissolved in a 10 ml glass beaker containing

about 5 ml of tridistilled water.

  The percentage of transformation was determined by taking samples of about 10 ml of the emulsion at certain times, using a syringe, weighing the syringe containing the sample, precipitating the polymer in water. acetone and weighing the syringe again

  empty. The polymer is filtered on filter paper prior to

  the percentage of conversion is determined gravimetrically after drying the polymer in a vacuum oven at 50 ° C for about 12 hours until

constant weight.

  The molecular weight of the polymer is directly proportional to the solution viscosity of the polymer,

  for a constant concentration of polymer and temperature

  constant ture. The polymer which was dried in a vacuum oven at 50 ° C for about 12 hours was then ground to a fine powder using a Micro-Mill (Model N 502 from Technilab Instruments) for about 3 minutes. 4.0 g of the polymer was mixed with 24 ml of methanol as a non-solvent to wet the polymer, before 198 ml of tridistilled water were rapidly added to the stirring vortex. If the solution becomes too viscous for the agitator, a tongue depressor is used to agitate the solution for about minutes. A N-spindle N RVF N-type Brookfield viscometer rotating at 4 rpm was used to measure the viscosity of this solution at 1.8% polymer at 25 ° C.

in mPa.s.

  The REFERENCE METHOD has been used in

  all examples, unless otherwise specified.

Example 1

  The initial concentration of the initiator for all the reactions of Table I was 0.1 g per g of monomer (pcm), taking into account the title. When EA acid was used, its concentration was 250 g per

  million grams of monomer (ppm).

T A B L E A U I

  Dre _. Percent Viscosity Initial Speed Initiator Initiator Initiate Adititf Brookfield reaction, polymerization transformation mPa.s (% / hour) LUAZO 55 control 6 hours 95 12,000 46 EA 3 hours 100 16,000 176 LUAZO 70 control 6 hours 82 17,000 35 EA 3 hours 100 24 500 178 LUPERSOL Witness 6 hours 88 20 000 41

223 .._

  EA 4 hours 100 18 500 172 Tpn Polymerisation temperature 350C

2555994.

Example 2

  In this example, the initiator, namely the product Lupersol 256, was used at an initial concentration of 0.1 g per 100 g of monomer, taking into account the title. The amount of erythorbic acid used was then varied to see how

  influenced reaction time and / or molecular weight.

  The results in Table II show that a certain amount of erythorbic acid is needed before the benefits of a longer reaction time and a similar or higher molecular weight of the polymer are achieved. When this amount is exceeded, that is to say from 250 to 500 ppm in this case, a low molecular weight polymer can be prepared at a

  improved polymerization speed.

TABLE II

  COncntration in EA Transformation Time, Viscosity parts per million reaction, h% Brokfield, mPa.s 0 (control) 6 95 14 500

50 6 76

6 89 _

250 4 100 20 000

500 2 100 3 000

  350C polymerization temperature

Example 3

  Monomeric acrylamide is commercially available in its solid form or as a 50% aqueous solution. The solution form contains about 25 ppm of cupric sulfate which acts as a polymerization inhibitor. The Dow Chemical Company supplies the monomer in the aqueous form and suggests the use of Versenex 80 so that the polymerization rate can

to be more efficient.

  The product Lupersol 256 was the initiator used in all the reactions of Table III, where its initial concentration was 0.1 g per 100 g of

  monomer, taking into account the title.

  In this example, Versene X80 was compared in its recommended range of concentrations with erythorbic acid at the usual concentration of 250 ppm. The results in Table II show that EA acid behaves quite well by reducing the overall reaction time to achieve a 100% conversion rate while producing a polymer.

high molecular weight.

T A B L E A U III

Concentration V Initial speed

  of additive Transformation Time, Additive Viscosity of Additive to Reaction Parts, Brookfield, polymerization per million h (% / h) Control - 6 95 14 500 47

-_, ,, _ ,, ......

Versenex.

2000 5 0 0

Versenex

500 6 0 0

EA 250 4,100 20,000 174

  Polymerization temperature: 35 C rhi tn Ln AN 0'o

Example 4

  The results in Table IV are based on reactions in which the Lupersol 256 initiator was used at a concentration of 0.1 g per 100 g of monomer, taking into account the titer. When additives were used, they were evaluated at a concentration

  250 g per million monomer (ppm).

  The advantageous additives which have given

  Virtually identical results are erythoric acid

  bique and its alkali metal salt. Vitamin B2 has

  faster to reach a trans-

  100% formation but the molecular weight of the polymer was dramatically reduced. In addition, the vitamin

B2 is quite expensive.

  Therefore, EA acid and its NaEA salt both produce a significant increase in the rate of polymerization, a reduction in reaction time to achieve a 100% conversion rate, while giving a high molecular weight polymer compared to witness, as indicated

  the corresponding values of Brookfield viscosity.

T A B L E A U IV

  W.,.,, .. .. ....... _..................

  Transformation Time, Viscosity Initial Speed Brookfield Additive, polymerization reaction, h mPa.s (% / h) Control 6 95 14 500 47

E .. A ... ,

EA 4 100 20 000 174

NaEA 4 100 21 000 174

  . ,,,, ...... DTD: Vitam B2 3 100 2 500 136 Polymerization temperature: 35 C rN vn tn o

Claims (9)

  1. Process for the preparation of a polymer or a copolymer, characterized in that it consists in carrying out the polymerization in inverse aqueous emulsion of acrylamide in the presence of at least one surfactant, at least one radical initiator from 50 to about 250 parts per million parts of a representative of the group comprising erythorbic acid,   alkali metals of erythorbic acid, or mixtures thereof.   2. Process according to claim 1, characterized in that the alkali metal salt of the acid   erythorbic is sodium erythorbate.   3. Process according to claim 1, characterized in that the inverse aqueous emulsion polymerization is a water-in-oil emulsion polymerization in which the water constitutes the dispersed phase and the oil constitutes the continuous phase.   4. Process according to claim 3, characterized in that the ratio of the aqueous phase to the oily phase is in the range of about 1: 1 at about 1: 5.   5. Process according to claim 1, characterized in that the surfactant of which there is at least one representative is soluble in the oil and has a hydrophilic: lipophilic balance within the range of about 1 to 12.   6. A process according to claim 5, characterized in that the surfactant of which there is at least one representative is present in an amount of from about 0.5 to about 20.0 parts by weight per 100 parts by weight. weight of the oily phase.   7. Process according to claim 1, characterized in that the polymerization temperature   is in the range of about 20 to about 80 C.   8. Process according to claim 1, characterized in that the concentration of acrylamide is in the range of about 30 to 60 parts by weight   of monomer per 100 parts by weight of water.   The process according to claim 1, characterized in that the free radical initiator of which there is at least one representative is present in the medium being polymerized in the range of about 0.005 to about 5.0 parts. by weight for parts by weight of monomer.