Patent GB-477826-A (GB)
Title: Improvements in or relating to the production of porous or spony rubber or rubber-like masses
IPC: C08K5/07
Filed: 1936-04-06
Abstract: Polymerized aldehydes, e.g. paraldehyde and metaldehyde, with or without an unpolymerized aldehyde other than formaldehyde, e.g. acetaldehyde and propionaldehyde are produced by reagents such as an alcohol and an organic acid, e.g. ethylene glycol and glacial acetic acid, conditions being employed which are unfavourable to esterification.  In an example, 124 parts by weight of ethylene glycol and 60 parts of a glacial acetic acid are dissolved in 700 parts of distilled water at a temperature not higher than 10 DEG  C. and the solution is kept in the light for three days; a solution of 4 parts of potassium hydroxide in 15 parts of water and a solution of 50 parts of ammonia in 130 parts of water are then added, while stirring slowly and keeping the temperature at 12 DEG  C. or lower, to produce a pH of 9; after two days ,0001 part of rubidium or caesium carbonate in one part of water is added and the solution is allowed to stand for a further two days; there is then added one part of methyl alcohol.  The preparation contains a polymerized aldehyde formed by reaction between the ethylene glycol and the glacial acetic acid.ALSO:In processes for the production of porous, microporous, or solid rubber from latex, the latex is treated by the incorporation of a polymerized aldehyde, e.g. paraldehyde and metaldehyde, with or without an unpolymerized aldehyde other than formaldehyde, e.g. acetaldehyde and propionaldehyde.  The treatment modifies the albuminous layers surrounding the rubber particles so that their affinity to water is considerably reduced.  The dispersion becomes more viscous or creamy and can easily be beaten up into a foam. When heat is applied to the treated latex the water or serum falls away and is evaporated leaving a substantially dry reticulated structure of uncoagulated rubber which can be redispersed.  It can be broken up to form a rubber dust.  The mass may be coagulated by after treatment, e.g. prolonged heating, action of light, exposure to acids or acid fumes or by a long time interval, e.g. 100 hours.  The polymerized aldehyde, or the mixture of polymerized and unpolymerized aldehydes may be produced by reagents such as an alcohol and an organic acid, e.g. ethylene glycol and glacial acetic acid, conditions being employed which are unfavourable to esterification. In an example 124 parts by weight of ethylene glycol, and 60 parts of glacial acetic acid are dissolved in 700 parts of distilled water at a temperature not higher than 10 DEG  C. and the solution is kept in the light for three days; a solution of 4 parts of potassium hydroxide in 15 parts of water and a solution of 50 parts of ammonia in 130 parts of water, are then added, while stirring slowly and keeping the temperature at 12 DEG  C. or lower, to produce a pH of 9; after two days ,0001 parts of rubidium carbonate or caesium carbonate in 1 part of water is added and the solution is allowed to stand for a further two days; there is then added 1 part of methyl alcohol and the preparation, which contains a polymerized aldehyde formed by reaction between the ethylene glycol and the glacial acetic acid, is ready to be incorporated in a dispersion of rubber, e.g. "Revertex" (Registered Trade Mark).  The proportion added is from.  1 to 3 per cent based on the dry rubber content.  The dispersion is then stirred or whipped to a foam, dried and coagulated.  If the mass is not whipped or otherwise expanded, the rubber will possess when coagulated, a microporous structure. The dispersion may be foamed by an electrolytic method in which two or more electrodes, connected to a source of alternating current, e.g. of 50-100 cycles per sec., are arranged to revolve in the dispersion.  Other methods of frothing may be employed, e.g. carbon dioxide snow may be incorporated in the mix, or the mix may be injected into a cylinder, having two pistons the heads of which are perforated and contain curled hair or wire in the perforation.  Movement of one piston away from and towards the other draws the mix into the space between the pistons and then expels it as a foam.  Solid rubber may be formed by adding anti-foaming agents, the mass will then be microporous after evaporation of the water and will then shrink until it becomes solid.  A microporous mass having hollow spaces or cavities may be made by adding to the dispersion carbon black having a gas, e.g. benzine vapour, adsorbed thereon. The invention may be applied to the manufacture of a porous rubber backing for fabrics, e.g. rugs and carpets, and to the manufacture of ply fabrics having a microporous interlayer, suitable for shirt collars.  In an example, to a latex mix containing 130 parts of "Revertex" together with vulcanizing and compounding ingredients are added 15 parts of ethylene glycol, ,5 part of lanoline and ,5 part of a solution of 3 parts of paraldehyde, ,5 part of acetaldehyde and ,002 part of rubidium carbonate in 50 parts of water, together with a solution of 16 parts of egg albumen or 49 parts of water. This mix is applied to the fabrics and segregation of the water is caused to take place while the fabrics are still separate and in the piece.  The fabrics is then cut to the desired pattern, the treated sides are placed together and the compound fabric is pressed first with a cold iron and then in a hot press at about 100 lb. per sq. in at 140 DEG C., for a few seconds, after which it is vulcanized for 30 minutes at 120 DEG  C.