A continuous process to make and isolate methylal by - reacting a mixture M1 comprising formaldehyde and methanol with a ratio of the amount of substance of methanol to the amount of substance of formaldehyde in the mixture M1 of at least 3 mol/mol with an acid catalyst in a separate reactor A under at least partial formation of methylal and water, to form a mixture M2 comprising formaldehyde, methanol, methylal, and water, and feeding the mixture M2 to the side of the distillation column B to a feed point in a height corresponding to between 40 % and 70 % of the effective height of column B, said column B having a reaction zone C which is located between the feed point and the bottom of the said column B, in which reaction zone at least partial conversion to methylal occurs, - separating the said mixture M2 in a distillation column B into three distinct product streams, one being a distillate taken from the column head BH which is rich in methylal having a mass fraction of methylal of at least 80 %, one stream taken from the column bottom stream BB being almost pure water having a mass fraction of water of at least 95 %, and one stream taken from the side of the column B below the reaction zone which stream is rich in methanol having a mass fraction of methanol of at least 80 %, - optionally, feeding the product stream taken from the column head BH which consists almost exclusively of methylal having a mass fraction of methylal of at least 98 %, and further comprises a mass fraction of less than 10 % of methanol to the side of a rectifying column D which is operated with a pressure which is higher than the pressure in column B, where a stream comprising a mixture of methylal and methanol having a mass fraction of methylal of between 70 % and 95 % is recovered from the column top DH, and highly pure methylal is recovered as sump product stream from the bottom DB of the column D, in a purity in excess of 99.5 %. - reacting a mixture M1 comprising formaldehyde and methanol with a ratio of the amount of substance of methanol to the amount of substance of formaldehyde in the mixture M1 of at least 3 mol/mol with an acid catalyst in a separate reactor A under at least partial formation of methylal and water, to form a mixture M2 comprising formaldehyde, methanol, methylal, and water, and feeding the mixture M2 to the side of the distillation column B to a feed point in a height corresponding to between 40 % and 70 % of the effective height of column B, said column B having a reaction zone C which is located between the feed point and the bottom of the said column B, in which reaction zone at least partial conversion to methylal occurs, - separating the said mixture M2 in a distillation column B into three distinct product streams, one being a distillate taken from the column head BH which is rich in methylal having a mass fraction of methylal of at least 80 %, one stream taken from the column bottom stream BB being almost pure water having a mass fraction of water of at least 95 %, and one stream taken from the side of the column B below the reaction zone which stream is rich in methanol having a mass fraction of methanol of at least 80 %, - optionally, feeding the product stream taken from the column head BH which consists almost exclusively of methylal having a mass fraction of methylal of at least 98 %, and further comprises a mass fraction of less than 10 % of methanol to the side of a rectifying column D which is operated with a pressure which is higher than the pressure in column B, where a stream comprising a mixture of methylal and methanol having a mass fraction of methylal of between 70 % and 95 % is recovered from the column top DH, and highly pure methylal is recovered as sump product stream from the bottom DB of the column D, in a purity in excess of 99.5 %.