Cellulose acetate phthalate plastic

Cellulose acetate phthalate (CAP) dissolves at pH higher than 6 and is soluble in ketones, ethers, esters, and alcohols. Permeation of water vapor and gastric fluids is a concern but can be overcome by adding other materials such as shellac. Plasticizers that are used with CAP include diethyl phthalate, triacetin, tributyl citrate, and acetylated monoglyceride. 

Crawford, R. R., and Esmerian, O. K. Effect of plasticizers on some physical properties of cellulose acetate phthalate films. J. Pharm. Sci. 60(2) 312—314, 1971. 

Cellulose acetate, Plasticized cellulose triacetate, Cellulose acetate methyl carbamate, Cellulose acetate Ethyl- carbamate, Cellulose acetate phthalate, Cellulose acetate succinate... 

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. 

Any plasticizers that are used with cellulose acetate phthalate to improve performance should be chosen on the basis of experimental evidence. The same plasticizer used in a different tablet base coating may not yield a satisfactory product. 

The cellulose acetate used commercially for acetate yam has an acetyl content of about 39.5 per cent and has a degree of polymerization of about 400. Material of this composition is soluble in acetone, and spinning dopes of about 25 per cent solids concentration can easily be prepared. Materials having a 39-41 per cent acetyl content can be made into plastics by compounding the cellulose acetate with plasticizers such as diethyl phthalate. Cellulose triacetate (43.0-44.8 per cent acetyl content) is finding increased commercial use. By coating from appropriate solvents, a film base of greatly improved phj ical properties has been produced. Triacetate yams are now in commercial production. 

Figure 11.5. Rockwell hardness of cellulose acetate samples plasticized with 24.9 wt% of diethyl phthalate at different moisture levels. [Data from Gamer D P DiSano M T, Polym. Mater. Sci. Eng., 75,2, 301-2, 1996.]...

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

Plasticised amorphous thermoplastics Certain plastics may be mixed with high-boiling low-volatility liquids to give products of lower T. The most important example occurs with p.v.c. which is often mixed with liquids such as di-iso-octyl phthalate, tritolyl phosphate or other diesters to bring the below room temperature. The resultant plasticised p.v.c. is flexible and to some degree quite rubbery. Other commonly plasticised materials are cellulose acetate and cellulose nitrate. 

Plasticizers are used in the polymer industry to improve flexibility, workability, and general handling properties. Dibutyl sebacate and phthalates, such as dibutyl phthalate, diethyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, and diphenyl-2-ethylhexyl phosphate, serve widely as plasticizers in vinylidene chloride copolymers, nitrocellulose-coated regenerated cellulose film, and cellulose acetate (Castle et ah, 1988a). In PVC, di(2-ethylhexyl)... 

In this technique, the material, say ethyl cellulose, is first plasticized and then a sleeve of a definite size and shape is extruded. This sleeve is applied to the grain by a special technique using ethyl cellulose cement which is prepared by dissolving ethyl cellulose in cellosolve-diethyl phthalate (1 1) mixture or ethyl lactate-butyl acetate (1 4) mixture. 

Phosphites. The phosphates, second only to phthalates in production volume, are favored for flame resistance and low volatility. Tricresyl phosphate (mixed meta and para isomers) is the most popular it is used in polyvinyl chloride and in nitrocellulose lacquers. Resins plasticized with tricresyl phosphate are deficient in low-temperature flexibility. Diphenyl cresyl phosphate and triphenyl phosphate are other examples, the former for polyvinyl chloride, the latter for cellulose acetate. Diphenyl-2-ethylhexylphosphate is preferred to tricresyl phosphate in polyvinyl chloride where its low toxicity and improved low-temperature flexibility are required. Tn(2-elliylliexyl)-phosphale is outstanding among phosphates used in polyvinyl chloride with respect to low-temperature flexibility in flame- and oil resistance, however, it is inferior to tricresyl phosphate. Tri(butoxvethyl)phosphate finds some use in synthetic rubber. 

Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate.26 In vinyls (plasticized), arylphos-phates are frequently used with phthalate plasticizers. Their principal applications are in wire and cable insulation, connectors, automotive interiors, vinyl moisture barriers, plastic greenhouses, furniture upholstery, and vinyl forms. Triarylphosphates are also used, on a large scale, as flame-retardant hydraulic fluids, lubricants, and lubricant additives. Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. Blends of triarylphosphates and pentabromodiphenyl oxide are extensively used as flame-retardant additives for flexible urethane foams. It has been also... 

PVF resins are generally compatible with phthalate, phosphate, adipate, and dibenzoate plasticizers, and with phenolic, melamine—formaldehyde, urea—formaldehyde, unsaturated polyester, epoxy, polyurethane, and cellulose acetate butylate resins. They are incompatible with polyamide, ethyl cellulose, and poly (vinyl chloride) resins (141). 

Cellulose acetate is incompatible with strongly acidic or alkaline substances. Cellulose acetate is compatible with the following plasticizers diethyl phthalate, polyethylene glycol, triacetin, and triethyl citrate. 

Dimethyl phthalate is used in pharmaceutical applications as a solvent and plasticizer for film-coatings such as hydroxypropyl methylcellulose, cellulose acetate and cellulose acetate-butyrate mixtures. ... 

Exchange between product and pack can occur in both directions, e.g. certain labelling materials such as heat sensitive and self-adhesive labels when in contact with plastic materials. Both the plastic and the adhesives may contain plasticisers or migratory constituents. Most cellulosics use phthalate, sebacate, phosphate-type plasticisers (e.g. methyl phthalate (DMP) may be used in cellulose acetate). Plasticisers may also be found in poly vinyl chloride/acetate copolymers, polyvinyl acetate and polyvinyl alcohol formulations, polymethyl methacrylate, nylon and certain thermosetting resins. 

The cellulose acetate most suitable for coatings have acetyl contents ranging from about 38 to 40% and a hydroxyl range between 3.0 and 4.0%. The lacquer-type cellulose acetates possess certain fundamental characteristics that have made them difficult to formulate as coatings, yet it is exactly these characteristics that make them valuable in certain areas of the protective coating field. The cellulose acetates are soluble only in very strong solvents (Table IV). They respond well to latent solvents, but they have very low tolerance for hydrocarbons. Compatibility with resins is poor, only a dozen or so commercially available resins are compatible. Only very active plasticizers like dimethyl phthalate, triacetin, or dimethoxyethy1 phthalate will remain in the film without exudation. 

The chief commercial uses of these substances are as solvents and as plasticizers of synthetic polymers such as polyvinyl chloride and cellulose acetate. Some of the lower aliphatic phthalates are used in the manufacture of varnishes, dopes, and insecticides. 

Dimethyl phthalate (DMP) also has high dissolving capacity for CN. It has good compatibility with cellulose esters and are used in celluloid made fi-om CN and plastic compounds or films made from other cellulosic polymers, cellulose acetate (CA), cellulose acetate-butyrate (CAB), cellulose acetate-propionate (CAP), and cellulose propionate (CP). It is light stable but highly volatile. Diethyl phthalate (DEP) possesses properties similar to DMP and is slightly less volatile. 

Monoisopropyl citrate, stearyl citrate, triethyl citrate (TEC), butyl and octyl maleates, and fumarates are other important plasticizers for the preparation of stable PC pastes and of low-temperature-resistant PVC products. Triethyl citrate and triethyl acetyldtrate are among the few plasticizers to have good solvency for cellulose acetate. In comparison with diethyl phthalate, with which they are in competition in this application, there are slight but not serious differences in volatility and water sensitivity. The interest in citrate esters is due to a favorable assessment of their physiological properties. They are intended for plastic components used for packaging of food products. 

---