Poly vinyl acetate phthalate

The most commonly used polymers are cellulose acetate phthalate [9004-38-0] (CAP), poly(vinyl acetate phthalate) [34481-48-6] (PVAP), hydroxypropylmethyl-ceUulosephthalate [71138-97-1] (HPMCP), and polymethacrylates (111) (see Cellulose esters). Acrylate copolymers are also available (112). Eigure 11 shows the dissolution behavior of some commercially available enteric materials. Some manufacturers supply grades designed to dissolve at specific pH values with increments as small as 0.5 pH unit (113). 

In the past, the initial layers of coating (the sealing coat) were achieved by applying one or two coats of shellac. However, due to the variability between batches of this material, PVP-stabilized types of shellac or other polymeric materials, such as cellulose acetate phthalate (CAP) and poly(vinyl acetate phthalate) (PVAP), are now more popular. It should be appreciated that a fine balance must exist between minimizing the thickness of the sealing coat and providing an adequate moisture barrier. 

Hydroxypropyl methylcellulose phthalate (HPMCP) Poly(methacrylic acid-co-methyl methacrylate) Poly(vinyl acetate phthalate) (PVAP)... 

PVAc/Ph Poly(vinyl acetate)/phthalate C. E. Frosst Company... 

Although they lack commercial importance, many other poly(vinyl acetal)s have been synthesized. These include acetals made from vinyl acetate copolymerized with ethylene (43—46), propjiene (47), isobutjiene (47), acrylonitrile (48), acrolein (49), acrylates (50,47), aHyl ether (51), divinyl ether (52), maleates (53,54), vinyl chloride (55), diaHyl phthalate (56), and starch (graft copolymer) (47). 

Plasticizers. Plasticizers are materials that soften and flexibilize inherently rigid, and even britde polymers. Organic esters are widely used as plasticizers in polymers (97,98). These esters include the benzoats, phthalates, terephthalates, and trimeUitates, and aUphatic dibasic acid esters. Eor example, triethylene glycol bis(2-ethylbutyrate) [95-08-9] is a plasticizer for poly(vinyl butyral) [63148-65-2] which is used in laminated safety glass (see Vinyl POLYMERS, poly(vinyl acetals)). Di(2-ethyUiexyl)phthalate [117-81-7] (DOP) is a preeminent plasticizer. Variation of acid and/or alcohol component(s) modifies the efficacy of the resultant ester as a plasticizer. In phthalate plasticizers, molecular sizes of the alcohol moiety can be varied from methyl to tridecyl to control permanence, compatibiUty, and efficiency branched (eg, 2-ethylhexyl, isodecyl) for rapid absorption and fusion linear (C6—Cll) for low temperature flexibiUty and low volatility and aromatic (benzyl) for solvating. Terephthalates are recognized for their migration resistance, and trimeUitates for their low volatility in plasticizer appHcations. 

Vinyl polymers [polystyrene, PVC, polyethylene, polypropylene, poly(vinyl acetate), poly(vinyl alcohol), polyacrylonitrile] -1920 Packaging, tubing, household goods, records, carpets, toys, water based paint, adhesives, varnishes Phthalate esters, poly(vinyl alcohol) ... 

Table VII gives Tc values for solutions of PVC and poly (vinyl acetate) in a series of dialkyl phthalates (34).

As an example of the concentration dependence of viscoelastic properties in Fig. 16.11 the shear creep compliance of poly(vinyl acetate) is plotted vs. time for solutions of poly(vinyl acetate) in diethyl phthalate with indicated volume fractions of polymer, reduced to 40 °C with the aid of the time temperature superposition principle (Oyanagi and Ferry, 1966). From this figure it becomes clear that the curves are parallel. We may conclude that the various may be shifted over the time axis to one curve, e.g. to the curve for pure polymer. In general it appears that viscoelastic properties measured at various concentrations may be reduced to one single curve at one concentration with the aid of a time-concentration superposition principle, which resembles the time-temperature superposition principle (see, e.g. Ferry, General references, 1980, Chap. 17). The Doolittle equation reads for this reduction ... 

FIG. 16.11 Shear creep compliance of poly(vinyl acetate), M = 240 kg/mol, and four solutions in diethyl phthalate with indicated values of the polymer volume fraction, John Wiley Sons, Inc. 

Several polymers were found to fit all or most of the above criteria and were used to prepare the carrier films. Many polymers have been used for this purpose, viz., ethyl cellulose, poly(y-benzyl glutamate), poly(vinyl acetate), cellulose acetate phthalate, and the copolymer of methyl vinyl ether with maleic anhydride. In addition to the base polymers, plasticizers were often needed to impart a suitable degree of flexibility. Plasticizers, which are found to be compatible with polymeric materials include, acetylated monoglycerides, esters of phthalic acid such as dibutyl tartarate, etc. An excipient was usually incorporated into the matrix of the carrier films. The excipients used were water-soluble materials, which are capable of creating channels in the polymer matrix and facilitate diffusion of the drug. PEGs of different molecular weights were used for this purpose. 

Fig. 13. The Vogel parameters T and a as functions of for solutions of poly(vinyl acetate) in diethyl phthalate...

Fig. 16. lAygTj at constant temperature versus logq>2Z for solutions of poly (vinyl acetate) in diethyl phthalate, O, and cetyl alcohol, —O, at the theta temperature for dilute cetyl alcohol solutions. The straight lines have slopes 1.0 and 3.4. The independence of from may be noted... 

Fig. 17. Logi7 the viscosity corrected to constant friction factor versus logq> Z for poly(vinyl acetate) solutions in diethyl phthalate O, = 1 , gsj = 0.75 = 0.50 , gj = 0.25. The parameter C given by Eq. (2.30) ccsrrects the data at each ip to constant friction factor...

Data on poly (vinyl acetate) in diethyl phthalate 133, 160) also exhibit slopes 3.4 and 1.0 after correction by the factor l/ (7 — Tq), as shown in Fig. 21. Similarly, data on polystyrene in diethylbenzene 49) exhibit dependence on q>s > but do not extend into the region of unit slope. 

Nakayasc, H., and T. G Fox Molecular weight-temperature-concentration relationship for the viscosity of poly(vinyl acetate) and its dieth5rl phthalate solutions. Abstr. 137 th ACS, p. ll-I, Cleveland, Ohio (Apr. 1960). 

Poly(vinyl acetate) (PVAc), -[CH2-CH(OCOCH3) , is also prepared as an emulsion for adhesive applications, and is familiar to users as white glue. As mentioned already, the Tg of PVAc is above room temperature, which makes the polymer rigid and brittle at room temperature. For adhesive application, therefore, an external plasticizer, such as dibutyl phthalate, is added to lower the Tg below room temperature and to facilitate film formation from emulsions. 

Eighty to eighty-five percent of all plasticizers are used to produce plasticized PVC. The phthalates preferentially used to plasticize PVC also act as plasticizers with certain polyurethanes, polyester resins, and phenolic resins. Phosphate esters are good plasticizers for poly(vinyl acetate), poly(vinyl butyral), cellulose acetate, and phenolic resins. Sulfonamides are special plasticizers for melamine resins, unsaturated polyesters, phenolic resins, polyamides, and cellulose acetate. A total of about 500 different plasticizers are commercially available on the market. 

Polystyrene Poly(vinyl acetate) Poly(methyl methacrylate) Carnauba wax Dibutyl phthalate Dioctyl phthalate Fish oil Organo silane Organo titanate... 

Fig. 18 Activation energy of p-relaxation in (a) low-molecular weight glasses and (b) linear polymers vs the cohesion energy or cohesion energy of Kuhn statistical segment, respectively [86, 88,103]. (a) (1) Pentanol (2) isopropylbenzene (3) 5-methyl-3-heptanol (4) decalin (5) 1,1-diphenylpropane (6) diethyl phthalate (7) glycerol (8) 6>-terphenyl (9) hexamethyl disolox-ane (10) tetra-a-methylstyrene (11) pentastyrene. (b) (1) Polyethylene (2) polyisoprene (3) poly(dimethylsiloxane) (4) poly(diethylsiloxane) (5) poly(phenylene oxide) (6) poly(ethylene terephthalate) (7) polytetrafluoroethylene (8) polycarbonate (9) polyamide (10) polypropylene (11) polymethacrylate (12) poly(vinyl fluoride) (13) poly(vinyl acetate) (14) poly(vinyl chloride) (15) poly(vinyl alcohol) (16) poly(methyl methacrylate) (17) poly(diphenyl oxypheny-lene) (18) poly(butyl methacrylate) (19) polystyrene (20) polyacrylonitrile (21) poly(a-methylstyrene) (22) poly(cyclohexyl methacrylate) (23) polyimide I (24) polyimide II (25) poly(metaphenylene isophthalamide) (26) polyisobutylene...

As mentioned in the previous section, it is common practice to plasticize poly(vinyl acetate) intended for surface coatings by such materials as dibutyl phthalate, A limitation of external plasticizers of this kind is that they may eventually be lost by evaporation or by migration into the substrate, leaving an imperfect and brittle film. This limitation may be overcome by the use of copolymers and these are now widely used in surface coatings and other applications. Comonomers which may be employed for this purpose include alkyl (commonly 2-ethylhexyl) acrylates, fumarates and maleates. Typically, the copolymers contain 15—20% by weight of such comonomers. These... 

With increasing proportion of diluent, the monomeric friction coefficient fo is normally diminished, as evidenced by displacement of logarithmic plots of viscoelastic functions in the transition zone to higher frequencies or shorter times with relatively little change in shape. Examples are shown in Fig. 17-2 for the relaxation spectrum of poly( -bulyl methacrylate), and in Fig. 17-3 for the creep compliance of poly(vinyl acetate), both diluted to varying extents with diethyl phthalate. (In the latter figure, we focus attention now on the transition zone, where log J t) < -6.5 the other zones will be discussed later.) Introduction of diluent displaces the time scale by many orders of magnitude. Similar results were obtained in an ex-... 

Detailed studies of poly(vinyl acetate) in diethyl phthalate and cetyl alcohol and polystyrene in dibenzyl ether by Fox, Berry, and collaborators, in which the concentration dependence of fb was determined from temperature-dependence data, showed that i o/fo was proportional to (cA/) - over wide concentration ranges as would be specified by equation 27 with Me = At lower concentrations... 

Di-n-butyl phthalate Poly(vinyl acetate) (19), porosity enhancing in lithium cells (20), medical nail lacquers (21)... 

Vinyl resins - In the coatings industry, vinyl resins usually refer to either poly(vinyl chloride) (PVC) or poly(vinyl acetate) (PVAc) which is widely used in interior and exterior latex paints. Produced usually by emulsion polymerization, a PVAc homopolymer is too hard to allow its colloidal latex particles to coalesce well into a continuous film at ambient temperatures. Most PVAc emulsions used in the paint industry are copolymers with a plasticizing monomer such as dibutyl maleate, 2-ethyhexyl acrylate, n-butyl acrylate, dibutyl fumarate, isodecyl acrylate, or ethyl acrylate. By polymerizing under pressure, copolymers of vinyl acetate and ethylene are also produced for latex paints. External plasticizers such as dibutyl phthalate are used as well. All these methods not only soften the polymer to allow the latex particles to coalesce into a continuous film, but also impart the film flexiblity needed in exterior house paints. 

As mentioned in the previous section, improved film formation and film flexibility in poly(vinyl acetate) may be achieved by the addition of such materials as dibutyl phthalate. 

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