Patent GB-838413-A (GB)
Title: Modified synthetic condensation polymers and their production
IPC: C08J9/42
Filed: 1956-04-06
Abstract: Graft polymers, in which the substrate is a synthetic condensation polymer and the grafted structure at least in part contain free carboxyl groups or carboxylate salt groups and are derived from monomers containing reactive non-aromatic carbon-carbon unsaturation, are produced by irradiating the synthetic condensation polymer while it is in intimate contact with a modifier consisting of the corresponding unsaturated acid or an anhydride, half-acid ester or half-acid amide thereof or a derivative thereof that can be subsequently hydrolysed to the acid.  The acid grafted structures are preferably in the form of metal salts of the unsaturated carboxylic acids.  The modifier which may be dispersed, diffused or coated upon the polymer is preferably kept in an inert atmosphere or is enclosed by polyethylene film or aluminium foil or other material which is impervious to air and water while it is irradiated.  Additionally it may be in contact with a compound having protective or antioxidant effect with respect to the polymer or the modifier or both and during the irradiation the temperature is preferably kept between 0 DEG  and 75 DEG  C., if necessary by cooling.  The process is preferably carried out in the presence of calcium tungstate, zinc sulphide, metallic lead or other radiation transfer agents capable of absorbing radiation and re-emitting it in the form of the lower energy. Examples of radiation dosages are given.  The unsaturated acid or acid derivative is preferably of relatively low molecular weight, since it is desirable for maximum activation that the double bond is in close proximity to the carboxyl group.  Thus ethylenically unsaturated acids with up to 5 carbon atoms are preferred, though acids which have as many as 20 carbons in chain length may be used. Suitable acids are crotonic, furoic, acrylic, maleic, dichlormaleic, fumaric and itaconic acids.  The unsaturated acid may contain substituent groups which it may be desirable to attach to the polymer to confer other properties, such as static reduction or moisture repellance.  After the unsaturated acid has become attached to the substrate, a metal salt of the acid is formed by subjecting the irradiated composition or article to the action of a solution containing a basic metallic salt.  Any positively-charged metal ion from a basic-reacting salt can be attached to the grafted acid.  It is merely necessary that the anion of the said metal salt be a somewhat weaker acid than the grafted unsaturated acid. In general the greater this difference in acid strength, the greater is the amount of the metal ion taken up under constant conditions, e.g. irradiation dose, concentration and temperature. It is preferable that the dissociation constant of the anion acid be no greater than about one-thousandth of that for the unsaturated acid, or its first hydrogen in the case of a dibasic acid.  Synthetic condensation polymer can be formed by polymerization with elimination of small molecules such as HCl, H2O, NaCl, NH3.  Among such polymers may be mentioned polyamides, polyureas, polyurethanes, polyesters, polyethers, polysulphonamides and copolymers of such materials.  Of particular interest are the linear polyamides which are prepared from polymerizable monoamino-carboxylic acids or their amide-forming derivatives, or from suitable diamines and suitable dicarboxylic acids or amide-forming derivatives of these compounds, especially polyamides having at least one aliphatic -HCR- group in each repeating unit of the polymer molecule, -R- being -O-, hydrogen, halogen or other monovalent atom or radical.  The production of such polyamides is illustrated in Specification 461,236 and U.S.A. Specifications 2,071,250 and 2,130,948.  The modifiers may be incorporated in a polymer before shaping or they may be applied to the shaped articles, e.g. as solutions or in suitable cases as pure compounds, for example by spraying, calendering, immersion, padding or exposure to vapour condensations.  In suitable cases a solution of the melt may be applied to the surface of the shaped article and the solvents flashed-off before the irradiations.  If desired, excess liquid may be removed before irradiation by squeezing.  A particular advantage possessed by textile articles and films and other shaped articles comprising the graft copolymers of the invention, especially those in which the substrate is a polyamide, lies in their increased resistance to melting.  Other advantages include increased resistance to flash heat, higher zero strength temperature and a high unexpected degree of elasticity and deformability at high temperatures, for example about 185 DEG  C.; thus a polyamide fabric, after being treated, may be given a three-dimensional shape at high temperatures (e.g. by forming or embossing) without fusing of the individual filaments and without deleterious effect on the fabric hand, which shape is retained on cooling.  When reheated above about 185 DEG  C., the fabric returns substantially to its original shape.  Treated yarns may be elongated (drawn) at temperatures of 185 DEG  C. or above, whereby they acquire new tensile properties.  Alternatively, if a treated polyamide fibre is left free to retract when heated to temperatures of 185 DEG  C. or above, shrinkages of 50% or more are observed.  This property permits textured effects to be obtained when treated and untreated yarns are combined in the same fabric, or when the unsaturated acid or the metal ions are applied in a pattern (i.e. non-uniformly), or indeed when portions of the shaped substrate are shielded from the irradiation.  It has also been found that the elastic modulus (at 25 DEG  C.) of a polyamide treated in accordance with this invention is substantially increased, especially when the polyamide is held under tension during irradiation.  Specifications 543,466, 758,735 and 798,340 also are referred to.ALSO:Graft polymers, in which the substrate is a synthetic condensation polymer and the grafted structure at least in part contain free carboxyl groups or carboxylate salt groups and are derived from monomers containing reactive non-aromatic carbon-carbon unsaturation, are produced by irradiating the synthetic condensation polymer while it is in intimate contact with a modifier consisting of the corresponding unsaturated acid or an anhydride, half-acid ester or half-acid amide thereof or a derivative thereof that can be subsequently hydrolysed to the acid.  The acid grafted structures are preferably in the form of metal salts of the unsaturated carboxylic acids.  The modifier, which may be dispersed, diffused or coated upon the polymer is preferably kept in an inert atmosphere or is enclosed by polyethylene film or aluminium foil or other material which is impervious to air and water while it is irradiated.  Additionally it may be in contact with a compound having protective or antioxidant effect with respect to the polymer or the modifier or both and during the irradiation the temperature is preferably kept between 0 DEG  and 75 DEG  C., if necessary by cooling.  The process is preferably carried out in the presence of calcium tungstate, zinc sulphide, metallic lead or other radiation transfer agents capable of absorbing radiation and re-emitting it in the form of the lower energy. Examples of radiation dosages are given.  The unsaturated acid or acid derivative is preferably of relatively low molecular weight, since it is desirable for maximum activation that the double bond is in close proximity to the carboxyl group.  Thus ethylenically-unsaturated acids with up to 5 carbon atoms are preferred, though acids with as many as 20 carbons in chain length may be used.  Suitable acids are crotonic, furoic, acrylic, maleic, dichlormaleic, fumaric and itaconic acids.  The unsaturated acid may contain substituent groups which it may be desirable to attach to the polymer to confer other properties, such as static reduction or moisture repellance. After the unsaturated acid has become attached to the substrate, a metal salt of the acid is formed by subjecting the irradiated composition or article to the action of a solution containing a basic metallic salt.  Any positively-charged metal ion from a basic-reacting salt can be attached to the grafted acid.  It is merely necessary that the anion of the said metal salt be a somewhat weaker acid than the grafted unsaturated acid.  In general the greater this difference in acid strength, the greater is the amount of the metal ion taken up under constant conditions, e.g. irradiation dose, concentration and temperature.  It is preferable that the dissociation constant of the anion acid be no greater than about one thousandth of that for the unsaturated acid, or its first hydrogen in the case of a dibasic acid.  Synthetic condensation polymer can be formed by polymerization with elimination of small molecules such as HCl, H2O, NaCl, NH3.  Among such polymers may be mentioned polyamides, polyureas, polyurethanes, polyesters, polyethers, polysulphonamides and copolymers of such materials.  Of particular p  interest are the linear polyamides which are prepared from polymerizable monoamino-carboxylic acids or their amide-forming derivatives, or from suitable diamines and suitable dicarboxylic acids or amide-forming derivatives of these compounds, especially polyamides having at least one aliphatic -HCR- group in each repeating unit of the polymer molecule, -R- being -O-, hydrogen, halogen or other monovalent atom or radical.  The production of such polyamides is illustrated in Specification 461,236 and U.S.A. Specifications 2,071,250 and 2,130,948.  The modifiers may be incorporated in a polymer before shaping or they may be applied to the shaped articles, e.g. as solutions or in suitable cases as pure compounds, for example by spraying, calendering, immersion, padding or exposure to vapour condensations.  In suitable c