Polyvinyl alcohol manufacture

However, in a recent publication, Shirinyan, Mnatsalianov, et al. (20) find that differences between the rates of vinyl acetate emulsion polymerisation observed with samples of similar polyvinyl alcohols manufactured by the same process In three different factories could be attributed to a condensation product of acetaldehyde derived from hydrolysis of residual vinyl acetate this gave rise to a conjugated ketone type ultra-violet spectrum and could be extracted from the polyvinyl alcohol under suitable conditions. This could be the uncontrolled factor which appears to have confounded nmuiy of the experiments reported here. Even more recently the same laboratory ( ) has reported that there Is an optimum sequence length of hydroxyl groups in the polyvinyl cdcohol-acetate block copolymer for polymerisation rate and dispersion stability. 

Ethyne is the starting point for the manufacture of a wide range of chemicals, amongst which the most important are acrylonitrile, vinyl chloride, vinyl acetate, ethanal, ethanoic acid, tri- and perchloro-ethylene, neoprene and polyvinyl alcohol. Processes such as vinylation, ethinylation, carbonylation, oligomerization and Reppe processes offer the possibility of producing various organic chemicals cheaply. Used in oxy-acetylene welding. 

The linear arrangement of iodine atoms in the amylose inclusion compound has generated much interest right from the early days with respect to its spectroscopic and optical properties 138 -140). It has also been known for many years that polyvinyl alcohol (PVA) behaves similarly, and this was applied by Polaroid Corporation for the manufacture of polarising plastic using stretched sheets of iodine-stained polyvinyl alcohol170). 

Uses Manufacture of polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride-acetate resins used particularly in latex paint paper coatings adhesives textile finishing safety glass interlayers. 

Vinyl Acetate A monomer is a chemical building block used to manufacture a wide variety of polymers including polyvinyl acetate polyvinyl alcohol polyvinyl acetals ethylene vinyl acetate and ethylene vinyl alcohol. 

Polyvinyl alcohol is a vinyl polymer with a carbon-carbon backbone similar to other polymers such as polyethylene and polystyrene and is widely used as a water-soluble biodegradable polymer in the manufacture of delivery systems for fertilizers, pesticides and herbicides and is also used to manufacture containers and films. To date, only bacteria have been described as causing biodegradation of polyvinyl alcohols with some causing complete degradation of the polymer (see Shimao, 2001 for review). 

Most vinyl acetate is converted into polyvinyl acetate (PVA) which is used in the manufacture of dispersions for paints and binders and as a raw material for paints. It is also copolymerized with vinyl chloride and ethylene and to a lesser extent with acrylic esters. A substantial proportion of vinyl acetate is converted into polyvinyl alcohol by saponification or transesterification of polyvinyl acetate. The main applications for polyvinyl alcohol are either as raw material for adhesives or for fibres. It is also employed in textile finishing and paper glueing, and as a dispersion agent (protective colloid). The world production capacity of PVA was 4.35 Mt/a in 2005, of which 2.1 Mt were converted into polyvinyl alcohol. 

The effects of commercial grades of polyvinyl alcohol obtained from several manufacturers on the rate of polymerisation of vinyl acetate aqueous solutions and emulsions initiated by potassium persulphate at 60°C have been investigated. Increasing concentrations of polyvinyl alcohol in the same range tend to reduce the rate of polymerisation of the solutions but Increase the rate of polymerisation of emulsions. Considerable differences were noted between the effects of nominally simileir grades from different sources. Attempts to correlate the effect on the rate of polymerisation of vinyl acetate solutions with the acetyl content and molecular weight of the polyvinyl alcohol appear to have been confounded by an uncontrolled variable. A subsequent publication from the U.S.S.R. indicates that this may be the concentration of a by-product formed during the hydrolysis of the polyvinyl acetate. Other factors which may account for the effects are also discussed. 

Manufacture. The monomer of polyvinyl chloride is gas at room temperature and has a boiling point of -13.9°C. The monomer is manufactured in two ways (1) Acetylene and HCl gas are allowed to pass over active carbon and to react with each other at 150 200 C (2) chlorine gas is allov/-ed to react on ethylene to produce C H CI CEDC) at 200 350 C to produce vinyl chloride and HCl gas. These are separated by distillation. The monomer is then polymerized in a pressure vessel the mixture of water and liquid monomer is stirred violently. Benzoyl peroxide is used as a catalyzer and polyvinyl alcohol as a dispersion agent for the reaction. 

Summary Wacker Specialties succeeded in developing proprietary processes to manufacture silicone copolymers. The problems of combining silicone and vinyl polymers were overcome. So, for example, silicone-modified polyvinyl acetate, silicone-modified polyvinyl alcohol, and silicone-modified polyvinyl acetal were obtained on a laboratory or pilot plant scale. These products, having very interesting properties, could be advantageously used for various applications. 

Polyvinyl alcohol is manufactured indirectly by the hydrolysis of poly (vinyl... 

When making very dehcate materials it may be necessary to use a yam which is so fine that it would break down under the stresses imposed on it during manufacture. The strength, however, is sufficient once the fabric is made because of the mutual support of adjacent threads. In such cases it is customary to impart temporary strength to the yam by a process known as sizing. This consists of impregnating the thread with some easily removed substance such as starch or dextrine and, in the case of the more modern man-made fibres, with a synthetic product such as polyvinyl alcohol or polyacrylic acid. The size is usually removed before the article is dyed or bleached. Yarns are frequently referred to as warp or weft yarns. In a... 

Table Vll shows how the process used to manufacture lead azide, or the consequent product, significantly affects the quantity required to initiate a standard secondary explosive, RDX, in the stab-sensitive detonator (Figure la). Dextrinated lead azide has a lower output because it is less compressible and has more diluent namely, 8.5% dextrin compared to the 3.5% carboxymethyl cellulose (CMC) [34] in RD 1333, 2% polyvinyl alcohol in PVA lead azide, and no binder in Service lead azide (see Chapters 1 and 2). This situation is shown quantitatively in Table VII, which shows the minimum charge weights of each...

Polyvinyl alcohols (PVAl) are manufactured by saponification of vinyl acetate polymers (PVAc). Properties of PVC using PVAl as a protective colloid are influenced by the solution viscosity of the PVAl, i.e. the degree of polymerization of the PVAc and the degree of saponification. Polyvinyl alcohols of 75-90% hydrolysis are primary suspension agents for S-PVC, whereas polyvinyl alcohols of 25-40% hydrolysis are secondary suspension agents, which control the agglomeration of the primary particles. Partially hydrolyzed PVAc can be block or random polymers. 

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