Amino resin microcapsules. III. Release properties

Abstract

The release of microencapsulated active agents from amino resin microcapsules into water and air has been investigated with the example of methylparathion (0,O-dimethyl-O-p-nitrophenyl-thiophosphoric-ester). The release of the active agent has been proved to be strongly dependent on the conditions of capsule preparation. The release properties can also be influenced in a wide range by addition of salts during capsule preparation or by storage a t room temperature. The release in air shows similar results as in water. Under artificial light (Xenotest) after 30 h exposure a loss of active agent between 20 and 40% has been found. Aminoharz-Mikrokapseln. III. FreisetzungseigenschaftenDie Freisetzung von mikroverkapselten Wirkstoffen aus Aminoharz-Mikrokapseln in Wasser und Luft wurde am Beispiel von Methylparathion (0,O-Dimethyl-O-p-nitrophenyl-thiophosphorsaureester) untersucht. Die Freisetzungseigenschaften sind stark von den Herstellungsbedingungen der Kapseln abhangig und durch Salzzusatze wahrend der Herstellung sowie durch cine Lagerung bei Raumtemperatur zu verandern. Die Freisetzung des Wirkstoffs in Luft zeigt ahnliche Abhangigkeiten wie die in Wasser. Bci kunstlicher Belichtung (Xenotest) tritt nach 30 h ein Wirkstoffverlust von 20 bis 40% auf. MuEpokancyfibs u3 afiunog5opuafiadezudnog cMofibz. I I I . Ceoiicmsa sbzdefienua Ha IIpMMepe MeTMJIIIapaTHOHa (O,O-nMMeTMJI-O-n-HMTpO@eHMJI-3@IIpa THO@OC@OpHOfi KIICJIOTbI) MCCJIenyeTCJT BbI-,I(eJfeHAe 6~o j r o r a q e c~~ aKTMBHbIX BeWeCTB M 3 MHKpOKaIICyJI M 3 aMMHO@OpMaJIbnerHnHOfi CMOJIbI B Bone M H a B03-AyXe. CBOfiCTBa BbIneJIeHMR CMJIbHa 3aBMCRT OT yCJIOBMfi M3rOTOBJIeHHJT KaIICyJI EI H a HMX MOHCHO IIOBJIIIJTTb AO-6aBneHIIeM COJIefi BO BpeMJT II3rOTOBJIeHHJT, a TaKlKe XpaHeHHeM IIpI4 KOMHaTHOfi TeMIIepaType. BbIAeneHne IKTMB-HOrO BeueCTBa H a B03AyXe M B Bone MMeeT n o~o 6~b 1 e 3aBEICIIMOCTH. npM 0 6 n y q e~~n B Be3epOMeTpe Ha6JilOAaeTCJT OT 20 A0 40% aKTMBHOr0 BeIl(eCTBa IIOCJIe 30 YBCOB.

Amino resin microcapsules. II. Preparation and morphology

“…The estimation of the methylparathion diffusion from microcapsules into water was performed by UV spectroscopy a t 273 nm. The release into air was estimated by spectroscopy and by gravimetry [17]. investigations of the capsule formation showed the importance of water compatibility of the resins.…”

“…The rest of non-reacted resin remains dissolved in the aqueous microcapsule dispersion. These resin portions can be deposited later a t least partially onto the capsule walls during the after-treatment and storage, respectively [17]. From more detailed investigations of the resins could he derived t h a t obvioiisly reactive resin portions having tenside character are especially capahle of wall formation [IT].…”

“…The possibilities of influencing the release properties of microcapsules by additives, which have been added to the system during the capsule preparation and storage, respectively, will be discussed fully in a following publication [17]. Here, for instance, i t shall only be mentioned t h a t an addition of NaCl etc.…”

Amino resin microcapsules. II. Preparation and morphology

“…The estimation of the methylparathion diffusion from microcapsules into water was performed by UV spectroscopy a t 273 nm. The release into air was estimated by spectroscopy and by gravimetry [17]. investigations of the capsule formation showed the importance of water compatibility of the resins.…”

“…The rest of non-reacted resin remains dissolved in the aqueous microcapsule dispersion. These resin portions can be deposited later a t least partially onto the capsule walls during the after-treatment and storage, respectively [17]. From more detailed investigations of the resins could he derived t h a t obvioiisly reactive resin portions having tenside character are especially capahle of wall formation [IT].…”

“…The possibilities of influencing the release properties of microcapsules by additives, which have been added to the system during the capsule preparation and storage, respectively, will be discussed fully in a following publication [17]. Here, for instance, i t shall only be mentioned t h a t an addition of NaCl etc.…”

Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials

“…Using related methodology, chemistries including DCPD/ethylidene-norbornene [9], organic solvents [10,11], epoxy resins [12] and their cross-linkers such as amines [13,14], thiols [15] and glycidyl methacrylate [16] have been successfully encapsulated. Typical capsule shell materials include UF, melamine-UF (UMF) and melamine-formaldehyde (MF), which have proved promising for sequestration of various reactive ingredients [4,5,17,18].…”

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

“…One class of wall materials which is frequently used for microencapsulation are amino resins (especially resins of melamine and formaldehyde) which are low‐priced and easy to handle. For microcapsules based on amino resins an in situ encapsulation process, which is well described in literature,7–14 is used. In this process an emulsion or suspension of the core material, depending on whether a liquid or a solid material has to be encapsulated, is formed.…”

Amino resin microcapsules. II. Preparation and morphology

“…The estimation of the methylparathion diffusion from microcapsules into water was performed by UV spectroscopy a t 273 nm. The release into air was estimated by spectroscopy and by gravimetry [17]. investigations of the capsule formation showed the importance of water compatibility of the resins.…”

“…The rest of non-reacted resin remains dissolved in the aqueous microcapsule dispersion. These resin portions can be deposited later a t least partially onto the capsule walls during the after-treatment and storage, respectively [17]. From more detailed investigations of the resins could he derived t h a t obvioiisly reactive resin portions having tenside character are especially capahle of wall formation [IT].…”

“…The possibilities of influencing the release properties of microcapsules by additives, which have been added to the system during the capsule preparation and storage, respectively, will be discussed fully in a following publication [17]. Here, for instance, i t shall only be mentioned t h a t an addition of NaCl etc.…”

Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials

“…Using related methodology, chemistries including DCPD/ethylidene-norbornene [9], organic solvents [10,11], epoxy resins [12] and their cross-linkers such as amines [13,14], thiols [15] and glycidyl methacrylate [16] have been successfully encapsulated. Typical capsule shell materials include UF, melamine-UF (UMF) and melamine-formaldehyde (MF), which have proved promising for sequestration of various reactive ingredients [4,5,17,18].…”

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

“…One class of wall materials which is frequently used for microencapsulation are amino resins (especially resins of melamine and formaldehyde) which are low‐priced and easy to handle. For microcapsules based on amino resins an in situ encapsulation process, which is well described in literature,7–14 is used. In this process an emulsion or suspension of the core material, depending on whether a liquid or a solid material has to be encapsulated, is formed.…”

Amino resin microcapsules. II. Preparation and morphology

“…The estimation of the methylparathion diffusion from microcapsules into water was performed by UV spectroscopy a t 273 nm. The release into air was estimated by spectroscopy and by gravimetry [17]. investigations of the capsule formation showed the importance of water compatibility of the resins.…”

“…The rest of non-reacted resin remains dissolved in the aqueous microcapsule dispersion. These resin portions can be deposited later a t least partially onto the capsule walls during the after-treatment and storage, respectively [17]. From more detailed investigations of the resins could he derived t h a t obvioiisly reactive resin portions having tenside character are especially capahle of wall formation [IT].…”

“…The possibilities of influencing the release properties of microcapsules by additives, which have been added to the system during the capsule preparation and storage, respectively, will be discussed fully in a following publication [17]. Here, for instance, i t shall only be mentioned t h a t an addition of NaCl etc.…”

Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials

“…Using related methodology, chemistries including DCPD/ethylidene-norbornene [9], organic solvents [10,11], epoxy resins [12] and their cross-linkers such as amines [13,14], thiols [15] and glycidyl methacrylate [16] have been successfully encapsulated. Typical capsule shell materials include UF, melamine-UF (UMF) and melamine-formaldehyde (MF), which have proved promising for sequestration of various reactive ingredients [4,5,17,18].…”

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

“…One class of wall materials which is frequently used for microencapsulation are amino resins (especially resins of melamine and formaldehyde) which are low‐priced and easy to handle. For microcapsules based on amino resins an in situ encapsulation process, which is well described in literature,7–14 is used. In this process an emulsion or suspension of the core material, depending on whether a liquid or a solid material has to be encapsulated, is formed.…”