According to the RCA vinyl record patent 1498409551006799538-03960790- the PVCa copolymer equals 96.2%. The remaining ingredients are varied in purpose and specified with reasons for each additive and its concentration. The heat stabilizer is described as follows:
One-and-six-tenths percent of an organotin salt (resin stabilizer) is included in the compound to neutralize the generation of hydrogen chloride gas (which is produced by partial decomposition of the polyvinyl chloride resin) when the compound is pressed into a record at the normal pressing temperature. The presence of hydrogen chloride gas creates blisters and voids under the record surface and in the record surface, which cause noise when the record is played.