Polyvinyl esters or ethers soluble or dispersible in aqueous liquids are manufactured by replacing, by ester or ether radicles containing acid or basic groups, exchangeable radicles or atoms of compounds containing a polyvinyl residue, or by replacing by or converting into acid or basic groups exchangeable or convertible radicles or atoms present in ester or ether radicles of esters or ethers of polyvinyl alcohol. The polyvinyl compounds may be prepared by wholly or partially esterifying or etherifying polyvinyl alcohol with acyl or other organic residues containing carboxyl or other acid or basic groups. For example the esterification may be effected with di- or polycarboxylic acids, sulphocarboxylic acids or aminocarboxylic acids of the aliphatic, aromatic or other series, such as citric acid, tartaric acid, malic acid, oxalic acid, succinic acid, maleic acid, benzene di- or poly-carboxylic acids, e.g. phthalic acid, sulphobenzenecarboxylic acids and aminobenzenecarboxylic acids. The esterification may be carried out by any known methods, e.g. by heating the polyvinyl alcohol with the acid or the anhydride or chloride thereof in the presence or absence of esterification catalysts such as acids, e.g. sulphuric acid, tertiary bases, e.g. pyridine, or zinc chloride, and in the presence or absence of solvents or diluents. In the case of di- or polycarboxylic acids the quantity of such acid employed relative to that of the polyvinyl alcohol should be such as to ensure that the product contains carboxyl or other acid or basic groups. The etherification may be effected with any suitable etherifying agents capable of introducing ether residues containing carboxyl or other acid or basic groups, such as organic halogen compounds containing carboxyl or sulphonic groups, e.g. halogen carboxylic p acids, e.g. chloracetic acid, or sulphonic or carboxylic acids of aralkyl halides, e.g. benzyl chloride-p-sulphonic acid. Etherification may be effected if desired in the presence of organic or inorganic bases with or without copper salts or other agents facilitating etherification, and in the presence or absence of solvents or diluents, e.g. water or organic liquids. The polyvinyl compounds may also be prepared by esterifying or etherifying with acyl or other organic residues containing acid or basic groups a polyvinyl alcohol partially esterified or etherified with residues not containing such groups. The production of the polyvinyl compounds may also be effected indirectly by subjecting a polyvinyl ester or ether containing in the ester or ether residues readily exchangeable atoms or groups to a treatment adapted to replace the said atoms or groups wholly or in part by acid or basic groups. For example, a halogen acyl derivative or halogen ether, e.g. polyvinyl chloracetate (obtainable by polymerizing vinyl chloracetate), may be prepared and treated with ammonia or substituted ammonias, e.g. alkyl, aralkyl or aryl amines, so as to replace the chlorine wholly or in part by amino or substituted amino groups, or with sulphites, e.g. sodium sulphite, to introduce sulphonic groups. Another indirect method of preparing compounds containing amino groups consists in acylating or etherifying polyvinyl alcohol with radicles containing nitro groups and reducing these to amino groups. Thus polyvinyl alcohol may be esterified with a nitro aromatic acid, e.g. o-, m- or p-nitrobenzoic acids or their chlorides, or etherified with a nitroaryl or nitroaralkyl residue, e.g. by using 2 : 4-dinitrochlorobenzene or nitrobenzyl chlorides, and the resulting nitro ester or ethers subsequently reduced. The polyvinyl compounds may also be produced from polyvinyl esters not containing acid or basic groups by partially hydrolysing them and esterifying or etherifying the partially hydrolysed product with radicles containing acid or basic groups. Alternatively, the polyvinyl ester may be treated so as to effect a direct replacement of some or all of the ester groups by ester or ether residues containing acid or basic groups. Thus a polyvinyl acetate may be subjected to the action of a di- or polycarboxylic acid, e.g. citric, tartaric or oxalic acid, in the presence or absence of esterification catalysts such as sulphuric or other acid or pyridine or other tertiary base, and in the presence or absence of diluents or of solvents for the polyvinyl ester or the acid or both, e.g. water, whereby some or all of the acetic acid residues are replaced by residues of the corresponding polycarboxylic acid. Compounds in which hydrogen atoms of the vinyl residue are replaced by other atoms or groups are manufactured by analogous methods. Thus a substituted polyvinyl alcohol may be esterified or etherified with residues containing acid or basic groups, or a polymerized substituted vinyl ester may be treated so as to replace acid residues by other acid residues containing carboxyl or other acid or basic groups. The products are valuable materials for sizing or impregnating fibrous materials, particularly textile yarns or other textile materials, being readily removable by washing or scouring in aqueous liquids. In examples: (1) polyvinyl acetate, obtained by polymerizing vinyl acetate, is refluxed with lactic, tartaric or citric acid; the product may be used for sizing textile yarn; (2) polyvinyl alcohol (obtainable by saponifying polymerized vinyl acetate) is reacted with sodium chloracetate in the presence of caustic soda solution; the product, with or without treatment with acid to neutralize excess alkali or liberate the free acid, and with or without removal of water-soluble salts by dialysis, may be used as a size; the sodium chloracetate may be replaced by the sodium salt of benzyl chloride-p-sulphonic acid; partially esterified products obtained according to this example may be further etherified or esterified with radicles which may or may not contain acid or basic groups; (3) polymerized b -chloropropylene is boiled with disodium tartrate solution; the product may be used for sizing or impregnating purposes, if desired after acidifying or diluting with water. Specifications 346,267 and 386,005 are referred to.ALSO:Polyvinyl esters and ethers (in which hydrogen atoms in the vinyl residue may be replaced by other atoms or groups) containing in the ester or ether radicles acid or basic groups are valuable materials for sizing fibrous materials, particularly textile yarns or other textile materials. The compounds are soluble or dispersible in water and are thus readily removable from the material by washing or scouring in aqueous solutions. Examples describe the use of: (1) the reaction product of polyvinyl acetate with lactic, citric or tartaric acid; (2) the reaction product of polyvinyl alcohol with sodium chloracetate or the sodium salt of benzyl chloride-p-sulphonic acid, if desired after treatment with acid, and if desired after removal of water-soluble salts by dialysis; (3) the reaction of product of polymerized b -chloropropylene with disodium tartrate, if desired after acidifying or diluting with water. Specifications 346,267 and 386,005 are referred to.