MXPA98004764A - Dispersions of polyhydroxycalanates in a - Google Patents

Abstract

This invention relates to an arrangement of polyhydroxyalkanoate (PHA) particles which improves the stability of the PHA and simplifies the process for making the dispersions, the invention relates to a composition of polyhydroxyalkanoate (PHA) particles in water and at least one water-soluble copolymer dispersant, wherein the dispersant contains a plurality of repeating units, wherein the units include at least one unit compatible with PHA and at least one hydrophilic unit, and the process for producing the composition; , the method comprises dissolving the PHA in a liquid of low water solubility, emulsifying the resulting solution in an aqueous solution of the dispersant and removing the liquid, the invention also relates to a process for making a PHA latex comprising producing a biomass. Containing PHA particles and cellular material without PHA (MCSP), solubilizing the MCSP, removing the MC Solubilized SP and suspend the PHS particles in an aqueous solution of disperse

Description

DISPERSIONS OF POLYHIDRQXIALCANOATOS IN WATER This invention relates to dispersions of pol hydroxy alkanoates (PHA) in water. In co-pending applications such as GB 9502522, filed on February 9, 1995, discloses networks of PHA crystal structure containing surfactant, generally of the conventional type consisting of an individual hydrophobic group having a single hydrophilic group at one of its ends or near the ends of the hydrophobic group. same. Such networks of crystal structure are of great practical utility, but could be conveniently improved in stability and convenience of preparation. According to the invention in this first aspect a dispersion of PHA particles in water is characterized by steric stabilization. The stabilization can be provided by the presence on the surface of such particles of at least one water soluble polymer dispersant. Copolymer dispersants are characterized in that they contain a plurality - at least 2 and commonly at least 10 and up to v. several hundred- repetition units, which include units of two types: A compatible with PHA; and Hydrophilic B. For example, type A units can be aliphatic hydrocarbon (for example as in addition polymers) or aromatic hydrocarbon or (in chain lengths sufficient to give insolubility in water in a corresponding polymer consisting of such units) polyoxyalkylene, especially polyalkyl, 2-propylene oxide or polyester of the types head to tail or head to head / tail to tail such as, for example, 1,2-hydroxystearic polcondensed acid or alkyd resin. Preferably, units of type A have substituents such as esterified carboxy groups or esterified or etherified hydroxy groups or both, since these have great compatibility with PHA. Below we describe particular examples of such substituents. The units of type B can be anionic, for example carboxylate, sulfate, sulfonate, phosphate or phosphonate; or cationic, for example ammonium, especially quaternary ammonium; or non-ionic, for example polyalkyl oxide or especially polyethylene oxide, or polyglycerol or sorbitan oxide or glucoside oxide. The dispersant may contain hydrophilic groups of more than one ionic grade chemical composition. Polyethylene oxide is very suitable, especially long 10 to 100 units of ethylene oxide, as is typical of conventional water soluble surfactants. The dispersant may contain a smaller proportion, for example below 20 mol percent, of falling units or in type A or type B. The balance of type A and type B units should be such to provide solubility in water, which is typically at least 1% w / w in water at 20 ° C. Preferably the type B units are a minority in moles, for example less than one third of the total units in the copolymer chain; correspondingly the water-soluble portion of the type B units, if it is polyethenoxy, must be sufficiently long. The HLB number (HLB means the degree of hydrophobic and co-lipophilic equilibrium) of the dispersant is adequate in the 10-15 scale. In general, the dispersant is preferably of the non-ionic emulsifier class, especially when the PHA particles are non-crystalline to the extent described below. The PHA is especially capable of a relatively high level of crystallinity, for example about 305%, especially 50-90%. Despite being so capable, it is preferably non-crystalline to the degree described below. Commonly it has units of the formula i: - 0 - CmH "- CO - where m is on the scale 1-13 and n is 2m or (except when m is one) 2m-l. commonly CmH "contains 2-5 carbon atoms in the polymer chain and the rest (if any) in a side chain. In very suitable polyesters m is 3 or 4, n is 2m and in particular there are units with m = 3 and m = 4 copolymers respectively imbedded together with a side chain Cx and C2 on the carbon near the oxygen. The particular polyesters they contain a preponderance of units m = 3, especially with at least 70 mol% of such units, the balance being units where m = 4. The molecular weight of the polymer is, for example, above 50000, in particular above 100000, up to 2 x 10β. The PHA of formula (1) containing only units m = 3 can be referred to as PHB, and PHA containing units m = 3 and m = 4 is copolymer polyhydroxy butyrate-co-valerate (PHBV). Preferably the PHBV contains 4-25% units m = 4. Since the intended PHA product can be a mixture of two or more PHAs that differ in the value of m, a corresponding mixture of suspensions can be used in the process of the invention. A particular example contains: (a) PHA consisting essentially of units of formula 1 in which 2-5 mol% of units have m = 4, the remainder m = 3; and (b) PHA consisting essentially of units of formula 1 in which 5-30 mol% of units have m = 4, the remainder m = 3. The proportions of the PHAs in such mixtures preferably give an average content rn = 4 on the scale 4-25 oi ?. The PHA may be the product of chemical synthesis but is more particularly the product of a microbiological process. In such a procedure the microorganism can formulate PHA during normal growth or can cause it by cultivation in the absence of one or more nutrients necessary for cell multiplication. The microorganism can be natural or mutated or it may have had the necessary genetic material introduced into it. Alternatively, the necessary genetic material can be housed by means of a eukaryote, to effect the microbiological process. The PHA produced by microbiology is (R) - stereospecific. Examples of suitable icrobiological methods are as follows: for formula 1 materials with m = 3; or m = in part 3, in part 4, EP-A-S9497 (Al ical genes eutrophus); for formula 1 materials with m = 3, E.U.A. 4101533 (A. eutrophus), EP-1-144017 (A. latus); for formula 1 material with m = 7-13; EP-A-0392687 (several Pseudomonas). The compatibility of the type A unit with the PHA when in the amorphous state appears to correspond to a solubility parameter closer to that of the PHA than that of conventional paraffin chain surfactants. The balance may also have substantial insolubility in water at 80 ° C. It is believed that in such dispersants the hydrophilic groups are thus by virtue of the interpenetration of polymeric molecules of water with polyethylene oxide chains, but this structure is 'melted' at the highest temperature. The particles can have a layer part of material such as surfactant agent other than the dispersant. The liquid phase may contain additional surfactant to that absorbed in the particles. It may contain hydrotropic compounds such as monomeric or water soluble oligomeric compounds, for example glycols and polyols. The invention provides methods for making the dispersion, in particular by any of: a) pouring PHA in liquid form with shear in a solution of the dispersant; b) dissolve PHA in a low water solubility liquid, emulsify the resulting solution in an aqueous solution of the dispersant and remove the liquid. This is especially convenient when the liquid is volatile, since it can then be removed by evaporation or diffusion; and c) making microbiological biomass containing PHA, solubilizing the material without PHA and applying the dispersant to the resulting PHA particles. In any of the above methods a dispersion of PHA in a conventional surfactant solution can be treated with the dispersant to replace the surfactant with the dispersant. In the dispersion the PHA particles are on average preferably low 30, especially low 20, especially low 1,% w / w crystalline. It seems that each individual particle is maximally or 0% crystalline: thus the percentage of crystallinity is the proportion by weight of maximum crystalline particles. It is thought that the effectiveness of the dispersant may be due to surface mixing or deeper mixing of such type A domains with non-crystalline PHA. The PHA particles are contacted with the dispersant at a temperature preferably above 5 ° C, for example 10-50 ° C. In the above procedures these levels of crystallinity apply to the particles the contact time with the dispersant. Thus for purposes (c) in particular the particles must be in virgin state without drying. In a particular dispersant are units having at least one hydrocarbon group bound to oxygen. Oxygen bonds can be ester or ether. Examples of esters are: (a) those of acrylic acids (as defined below), maleic, fumaric and itaconic, with alcohols and phenols C ^ j ^ ,; (b) those of allyl alcohol or notional vinyl alcohol with carboxylic acids C1_xß. Examples of ether groups are those of allyl alcohol or notional vinyl alcohol with alcohols and phenols Cx_ ß. such alcohols and carboxylic acids may be straight chain, branched or cyclic but, if substituted, do not include groups conferring water solubility to the polymer in the ratio used. Alcohols and carboxylic acids of esterification ? and esterification alcohols mentioned above, preferably each contain at least 2, preferably up to 9, carbon atoms. Another type of A units may be residues of, for example, one or more of ethylene, propylene, styrene, vinylidene halide, vinyl ether, vinyl acetate, vinyl carbonate, acrylic co (as defined below) nitrile or methyl ester and conjugated olefins. The term 'acrylic' herein is defined by means of the general formula: -CH 2 -C (R) ~ C = 0 0Ra where Rx is hydrogen, C ^^ - alkyl, (especially methyl), cycloalkyl, aryl, halogen or cyano and R_. is a hydrocarbon group C ^ j.,. The analogous definition of R applies to corresponding nitrile units, if any. In this second aspect the invention provides a method for making a PHA latex by means of the steps of: (a) producing a biomass containing PHA particles and cellular material without PHA (MCSP), (b) solubilizing the MCSP; (c) suspend the PHa particles in a solution aqueous of a dispersant as defined herein. Step (b) can be carried out by methods involving, for example, one or more of the following: (i) heat shock (ii) glycopeptide hydrolase solubilization (iii) protease solubilization of proteins (iv) sol ubi 1 ization of nucleic acids (v) action of surfactant on proteins (vi) oxidation by means of hypochlorite (vi i) oxidation by means of peroxide Methods (vi i) and (v) are preferred ), possibly following (i) and (ii) and (iv). If the dispersant is sufficiently soluble in water at the required operating temperature it can be used as the solubilizing surfactant in (v); otherwise a conventional surfactant can be used in the solution and subsequently replaced or supplemented by the dispersant. In its third aspect the invention provides a method for producing dry PHA suitable for solvent processing or melt processing, by means of the steps of: (A) producing a biomass of cells containing PHA in water; (b) solubilize and remove at 50% w / w of MCSP by one or more of the methods specified for step (b) anteri or; (c) stabilizing an aqueous dispersion of the resulting impure PHA by the dispersant defined herein; (d) concentrating the dispersion to v.gr. at least 200 g / l of PHA; (e) apply additional steps of solubilization and removal of MCSP to the dispersion so concentrated. Steps (d) and (e) can be carried out by separating a lump or pellet from PHA and redispersing it. The dispersion containing the dispersant, whether concentrated or not, can be used directly for purposes such as coating of water-sensitive materials such as paper or cardboard as described in the aforementioned co-pending application. Alternatively, it can be converted to solid PHA, possibly by steps or particle agglomeration at more than 80 ° C.

EXAMPLE A crude PHA latex was produced by the following steps: 1 growth of Alicaligenes eutrophus on glucose substrate in an aqueous medium containing nitrogen and phosphate sources and other common nutrients and trace elements to phosphate depletion; 2 accumulation of 76.6: 23.4 mol percent of PHBV feeding more glucose and also sodium propionate and a trace of phosphate until the speed of accumulation becomes slow; 3 heat shock at 150 ° C; 4 treat with proteolytic enzyme to effect the solubilization of MCSP. The crude latex was further treated in the following manner: (a) The crude latex samples containing 134.3 g / kg solids (90% PHA) and 38.6 g of solubles were formulated as follows: A No more addition; B 0.5% w / w of dispersant CG6. which is an acrylic / water-propylene glycol copolymer formulation containing 32% w / w of active agent of approximatively HLB number 11-12, available from Imperial Chemical Industries PLC with the name HYPERMER (RTM) CG6. C, D, E 0.99%, 3.0% and 4.97% w / w of dispersant A respectively. (These percentages are calculated in the PHA). Each sample is subjected to centrifugation at 4300 rpm for 30 minutes. The supernatant was discarded and the pellet was resuspended in deionized water. The particle size distribution of the resulting suspension was then measured. Then samples that did not flocculate were subjected to centrifugation and resuspended to Determine if the dispersant was washed of solids. The particle size distribution of the samples that did not flocculate are shown in table 1.

TABLE 1 Even 0.5% addition of the dispersant had an important effect on the redispersity of the centrifuge pellet. The lowest dose that prevented flocculation completely was 3%. When centrifuged and resuspended a second time, both 3% and %% pellets flocculated. This is explained as follows: when resuspended for the first time the solubles become diluted 10 to 20 times, reducing the dispersant concentration between 0.15 and 0.5%. The particle sizes obtained after the second centrifugation are similar to those of 0.5% addition to the original material. This suggests that the dispersant would need "coating" after each centrifugal wash, or that the resuspension should be carried out in dispersing solution at 0.5% w / w adequately. (b) Raw latex samples containing 368 g / Kg of solids, initially the viscosity of 8 to 15 mpas was formulated with 3% w / w of various surfactants and dispersants and was tested in a Bohlin rheometer system. 25 ° C, slimming speed 1460 sec-a- during period of up to 1 hour. Their viscosities were observed to increase sharply at times as shown in table 2.

TABLE 2 It is evident that most of the surfactants cause an increase in viscosity in a much shorter time than in its absence; but that the dispersants stabilize the viscosity. (c) A sample of the crude latex was digested with hydrogen peroxide and Synperonic A20 surfactant (TTM) (C13 alkyl 20 mols ethylene oxide, 19 g / 1), at 80 ° C for 10 hours and allowed to cool. The crystallinity of a test sample was evaluated by centrifugation with 40% w / v Nycodenz (RTM) at 15,000 rpm for 15 minutes. No crystalline fraction was observed. Three additional samples were centrifuged without Nycodenz and an attempt was made to resuspend the resulting solid pellets in water. The results are shown in table 3.

TABLE 3 It is evident that it is possible to resuspend amorphous latex particles if the CG6 dispersant is present, even at 0.5% w / v, when the centrifugation conditions are not too severe. Optimization is likely to lead to intermediate conditions between the second and third in Table 4, possibly (see Table 1) at a higher CG6 concentration.

EXAMPLE 2 A PHA latex was prepared by the following steps: 1 crystalline PHVB powder (76.6: 23.4 mole) was dissolved in chloroform to give a 5% w / w solution. 2 The solution was eluted in an aqueous solution (1% w / v) of Sarkosyl (RTM) (N-lauryl Isarcosinate sodium). 3 The chloroform was stirred under a stream of nitrogen leaving a latex solid amorphous particles with an average diameter of 0.56 μm. The latex was concentrated at 6% w / v solids and released from excess Sarkosyl by means of diafiltration. It was then concentrated to 40% w / v solids by means of evaporation. The cutting capacity of samples 2A (without CG6) and 2B (with 5% w / v of CG6 in the PHVB) was tested in a Bohlin rheometer system at 21 ° C, 3000 rpm: Flocculation times were: 2A: 500 sec 2B: about 3600 sec. It is evident that the dispersant is as effective for latex by means of emulsification as it is for virgin latex.

Claims (18)

NOVELTY OF THE INVENTION CLAIMS

1. A composition comprising polydihydroxyalkanoate particles in water and at least one water-soluble copolymer dispersant in an amount suitable for dispersing the particles, wherein the dispersant contains a plurality of repeating units, wherein the units include minus one unit compatible with the hydroxyalkanoate pol and at least one hydrophilic unit, wherein the unit compatible with the polyhydroxyalkanoate is an aliphatic hydrocarbon, aromatic hydrocarbon or polyoxyalkylene, and wherein the hydrophilic unit is anionic, cationic or non-ionic. 2. The composition according to claim 1, further characterized in that the polyhydroxyalkanoate consists of repeating units of: - O - CmH "- CO - where m is on the scale 1-13 and n is 2m or 2m-

2.

3. The composition according to claim 1, further characterized in that the polyhydroxyalkanoate is polyhydroxybutyrate-co-valerate.

4. The composition according to claim 1, further characterized in that the polyhydroxyalkanoate is produced microbiologically.

5. The composition according to the rei indication 1, further characterized in that the unit compatible with pol ihydroxyalkanoate comprises a group of hydrocarbon bonded to oxygen.

6. The composition according to the rei indication 1, further characterized because the hydrophilic group is non-ionic.

7. The composition according to the rei indication 1, further characterized because the dispersant is a polypropylene oxide.

8. The composition according to claim 1, further characterized in that the dispersant is an acrylic graft copolymer.

9. A process for making the composition according to claim 1, comprising pouring polyhydroxyalkanoate in liquid form with shear in a solution of the dispersant.

10. A process for making the composition according to claim 1, comprising: dissolving polyhydroxy alkanoate in a liquid of low solubility in water to produce a solution; and ulsifying the solution in an aqueous solution of the dispersant; and remove the liquid from said solvent.

11. The process according to the indication 10, further characterized in that the liquid of said solvent is volatile. .0

12. - A process for making a polyhydroxy alkanoate latex comprising: producing a biomass containing particles of polyhydroxyalkanoate and cellular material without polyhydroxyalkanoate (MCSP); solubilize the MCSP; remove the solubilized MCSP 1 lifted; and suspending the polyhydroxyalkanoate particles in an aqueous solution of a dispersant to produce a dispersion, wherein the dispersant contains a plurality of repeating units, wherein the units include at least one unit compatible with polyhydroxyalkanoate and at least a hydrophilic unit, wherein the polyhydroxyalkanoate compatible unit is an aliphatic hydrocarbon, aromatic hydrocarbon or polyoxyalkylene, and wherein the hydrophilic unit is anionic, cationic or non-ionic.

13. The process according to claim 12, further comprising: concentrating the dispersion to at least 200 g / L of polyhydroxyalkanoate; and repeating said solubilization and said removal.

14. The process according to claim 12, further characterized in that the polydihydroxyalkanoate compatible unit comprises a hydrocarbon group attached to oxygen.

15. The process according to claim 12, further characterized in that the hydrophilic group is nonionic. 16.- The procedure in accordance with the claim 12, further characterized in that the dispersant is a polypropylene oxide. 17. The process according to claim 12, further characterized in that the dispersant is a mere copolymer of acrylic graft. 18. The process according to claim 12, further characterized in that said solubilization is carried out by: heat shock, solubilization of glycopeptide hydrolase, protein protease solubilization, acid solubilization nucleic acids, action of surfactant on proteins, oxidation by means of hypochlorite, or oxidation by means of peroxide.