The present invention relates to polymers which have pH-depending solubility characteristics in aqueous solutions, whereby the polymers are copolymers between (a) methylmethacrylate (b) at least a monomer of the formula III ##STR1## wherein R.sup.3 is an alkyl group having 4 to 18 carbon atoms and R.sup.4 is hydrogen or methyl; and (c) a monomer of the formula I ##STR2## wherein R is hydrogen or methyl, n is an integer of from 1 to 4, and X is .dbd.CH.sub.2 or .dbd.O; and/or a monomer of the formula II ##STR3## wherein R is hydrogen or methyl, R.sup.1 and R.sup.2 are each hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, t-butyl or n-butyl, and m is an integer of from 1 to 4, as well as a process for their preparation, and a product in the form of particles which have been coated with such a polymer, whereby the product is protected against dissolution at pH above 5, but shall be dissolved at pH below 4, the product preferably being one which is administered to ruminants in order to obtain rumen-by-pass.
Disclosed is a process for producing a composition for ruminants, which is characterized in that a nucleus containing a physiologically active substance is coated with a coating material prepared by suspending in water (i) an emulsion comprising water and at least one hydrophobic substance hardly soluble in water and (ii) a slurry containing at least one polymer soluble in water of pH 5.0 or below and insoluble in water of pH over 5.0 In the process, an aqueous suspension is used for coating instead of a meterial dissolved in an organic solvent.
A composition for coating a biologically active substance which is stable in a medium in which the pH is greater than or equal to 5 and which permits the release of the active substance in a medium in which the pH is less than or equal to 3.5, comprises a film-forming, water-insoluble binder which possesses controlled hydrophilicity and is optionally slightly sensitive to pH variations, and a substance which is sensitive to pH variations (e.g. an inorganic filler, simple aminated substance, basic polymer or copolymer, chitosan). Pellets for feeding to ruminants consist of a core containing the biologically active substance, e.g. methionine or lysine, coated with this substance.
Coating materials for pharmaceutical dosage forms contain, besides the conventional liquid or solid additives for pharmaceutical coatings, a binder comprising a synthetic polymer, prepared by emulsion polymerization, having 5 to 100% by weight of units derived from monomers of the formula ##STR1## wherein R.sub.1 is a hydrogen atom or a lower alkyl group, R.sub.2 is an alkylene or aralkylene group having at least 3 carbon atoms in the chain between the amino nitrogen and the ester oxygen atom of which at least one is tertiary or quaternary, and R.sub.3 and R.sub.4 are lower alkyl radicals or together with the amino-nitrogen atom form a heteroaliphatic ring, and, optionally, additional comonomer units.
An animal feed additive comprises a composite of a relatively insoluble binder, a particulate soluble material and an active material. The particulate material is such that it is readily soluble under a particular range of pH conditions, e.g. under said conditions. Dissolution of the particulate material renders the binder water permeable thus permitting release of the active material.
A post-rumen effective composition for oral administration to ruminants containing a bioactive substance molecularly dispersed with a basic polymer. The bioactive substance is miscible with the polymer and may be a vitamin, antibiotic, peptide or anti-inflammatory agent. The basic polymer contains from about 1 percent to about 25 percent by weight of nitrogen and is resistant to a pH of greater than about 5 and soluble or swellable at a pH of less than about 3.5.
