TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The liquid phase (P1), is based on the molar amount of acrylic acid present in it, comprises at least 300 (preferably at least 400, especially at least 500, particularly at least 1000 or at least 1500) molar ppm of glyoxal. The liquid phase (P1) contains acrylic acid to an extent of at least 75 (preferably at least 80, especially at least 85, particularly at least 90, at least 95, at least 96, or at least 97) wt.%. The starting reaction gas mixture which, based on the molar amount of the 3C precursor compound present in it, comprises approximately 200 (preferably approximately 300, especially approximately 400, particularly approximately 500, approximately 750, approximately 1000 or approximately 1500) molar ppm of 2C compounds is used for the partial heterogeneously catalyzed gas phase oxidation of a 3C precursor compound. The starting reaction gas mixture comprises 3C precursor compound (4-20 vol.%); and water vapor approximately 1 (preferably greater than or equal to 2, especially greater than or equal to 3, particularly greater than or equal to 5 or approximately 7)%. The liquid phase (P1) has been obtained from the product gas mixture of the partial heterogeneously catalyzed gas phase oxidation by employing at least one noncrystallizative thermal separation process, where noncrystallizative thermal separation process involves at least one separation process from absorption, partial condensation, fractional condensation, rectification, stripping and desorption. The mother liquor which comprises enriched glyoxal and remains in the course of crystallization is recycled into at least one of the noncrystallizative thermal separation processes or a fractional condensation of the product gas mixture of the heterogeneously catalyzed gas phase oxidation. The crystallizative separation is undertaken by using suspension crystallization, where suspension crystals formed in the course of suspension crystallization and remaining mother liquor are separated from one another by using a wash column. The suspension crystals are washed in the wash column with the melt of acrylic acid crystals removed beforehand in the wash column. The process involves the following process steps: a) crystallizing acrylic acid out of the liquid phase (P1); b) separating the acrylic acid crystals from mother liquor which remains in the course of crystallization; c) at least partly melting the acrylic acid crystals removed in step b); d) at least partly recycling the molten acrylic acid crystals from step c) to step b) and/or step a). The liquid phase (P1), based on acrylic acid present in it, comprises water (0.2-30 wt.%). The liquid phase (P1) is obtained by transferring acrylic acid present and glyoxal present in the product gas mixture to an aqueous liquid phase, and removing at least a portion of the water from this liquid aqueous phase by azeotropic rectification, which leaves the liquid phase (P1). The liquid phase (P1) comprises the glyoxal in the form of monomeric glyoxal monohydrate and/or monomeric glyoxal dihydrate to an extent of more than 50 (preferably more than 70, especially more than 90) mol.%. The product gas mixture, based on the molar amount of acrylic acid present in it, comprises glyoxal (at least 200, preferably at least 400, especially at least 750) molar ppm. In the course of obtaining the liquid phase (P1), acrylic acid present in the product gas mixture is transferred to the condensed phase while residual gas remaining in gaseous form is recycled at least partly into the partial heterogeneously catalyzed gas phase oxidation of the 3C precursor compound. The process is followed by a process in which acrylic acid crystals are melted and free-radically polymerized into at least one polymer. Preferred Components: The 3C precursor compound is propylene, acrolein, propane or glycerol. EXAMPLE - No suitable example is given.