Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1991-12-13
1995-03-14
Reddick, Judy M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524503, 524803, C08K 500
Patent
active
053978153
DESCRIPTION:
BRIEF SUMMARY
The object of this invention is the process for the production of an aqueous emulsion of polyvinyl alcohols (PVA) with different saponification number. This invention, more particularly, refers to the method of preparation of polyvinyl alcohol (PVA) intended to be utilized in polymerization for the industrial production of polyvinylchloride in aqueous suspension (PVC-S).
In the description of the following invention, the following parameters of evaluation and numeration of the characteristics of the products utilized and obtained are adopted:
saponification number (NS) that represents the milligrams of potassium hydroxide necessary for saponifying 1 g of the sample. For example, operating in the following order: 1 g. of sample is weighed, then the product is dissolved in 50 mL (cc) of water and 50 mL (cc) of methyl alcohol; 1 mL (cc) of alcoholic solution of phenolphthalein is added; 100 mL (cc) of solution of KOH N/10 are added and the product is reflux heated for 1 hour. The product is titrated with HCl N/10 and after that stoichiometric calculations of the milligrams of KOH utilized for saponifying the product are made.
Molecular weight of the polyvinylacetate (PVAc) expressed in K value of a PVAc that is determined by means of measuring the relative viscosity of a solution in acetone of the PVAc. The value of relative viscosity, by means of the table that reports the previously determined values, is transformed into K value. The method is the following: One gram of perfectly desiccated sample is weighed, then it is dissolved in 100 mL (cc) of acetone and with Ostwald Viscosimeter series 50, at 25.degree. C., the precipitation time of the solution is measured. The ratio of the precipitation times of the solution and of the pure acetone, furnishes the value of relative viscosity. It is known that for producing PVC-S with optimum morphological characteristics, in the formulations of polymerization of the vinyl chloride monomer (VCM), in aqueous suspension, a system of suspending agents based on polyvinyl alcohols with distinct characteristics of solubility and insolubility in water is utilized.
The PVAs with saponification number below 280 are soluble in water and are commonly called "primary suspending agents".
The PVAs with saponification number greater than 280 are partly insoluble in water and are empirically called "secondary suspending agents". In the production of the PVC-S, it is of great importance to utilize secondary suspending agents type PVA which are free from residues of methyl alcohol, methyl-acetate, ethyl alcohol, ethyl-acetate and preparations under the form of aqueous emulsion with microparticles of diameter less than 10 .mu.m, with NS greater than 280, preferably around 480.
Thanks to a perfect distribution, from the first instants of polymerization, of the microparticles of the secondary suspending agent in the reacting mass, the main characteristic of the PVC-S, namely distribution of the internal porosity in the granules of PVC-S, the apparent density, the quantity of granules totally or partly gelled commonly called "fish-eyes", the granulometric distribution, the thermic stability, the resistivity of volume, are notably improved.
EP-0123364 (STAMICARBON) discloses a method of production of the PVC-S that uses as suspending system an aqueous dispersion of polyvinyl alcohols; but this patent does not describe the technology of preparation of this aqueous dispersion.
In the patent IT-83315-A-86, a technology of hydrolysis of microparticles of PVAc, previously produced in aqueous emulsion, is claimed. The method indicated utilizes an aqueous solution of sodium hydroxide as basic catalyst of hydrolysis and the simultaneous removal of the salts, resulting from the hydrolysis, by means of the process of ultrafiltration.
But this method allows only the utilization of the technology of the direct saponification of the PVAc; the consequence is the production of PVAc without alternate distribution of the hydroxyl groups called in literature "RANDOM", obtainable only by acidic alcoholysis in
REFERENCES:
patent: 3049520 (1962-08-01), Gatta et al.
patent: 4189415 (1980-02-01), Eck et al.
patent: 4200708 (1980-04-01), McClain
patent: 4324878 (1982-04-01), Biaggi et al.
patent: 4401790 (1983-08-01), ter Jung et al.
patent: 4528315 (1985-07-01), Eck et al.
patent: 4923922 (1990-05-01), Carlin
Jaskiewicz Edmund M.
Reddick Judy M.
LandOfFree
Process for the production in watery emulsion of blends of polyv does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the production in watery emulsion of blends of polyv, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the production in watery emulsion of blends of polyv will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-714058