UV-photoinitiators

Although phosphine [7803-51-2] was discovered over 200 years ago ia 1783 by the French chemist Gingembre, derivatives of this toxic and pyrophoric gas were not manufactured on an industrial scale until the mid- to late 1970s. Commercial production was only possible after the development of practical, economic processes for phosphine manufacture which were patented in 1961 (1) and 1962 (2). This article describes both of these processes briefly but more focus is given to the preparation of a number of novel phosphine derivatives used in a wide variety of important commercial appHcations, for example, as flame retardants (qv), flotation collectors, biocides, solvent extraction reagents, phase-transfer catalysts, and uv photoinitiators. 

When free-radical initiation is used, cocatalysts, eg, phosphites (112), and uv photoinitiators such as acetophenone derivatives (113) can be used to increase the rate and conversion of the olefins to the desired mercaptans. 

In stereolithography the positions of polymerization x and y are controlled by a mirrored scanner which reflects the laser onto the surface of the to-be-polymerized monomer at a point x,y and the z dimension is determined by the position of the elevator, as shown in Figure 5. During the polymerization z, the depth to which reaction occurs, is held constant through the use of a UV photoinitiator that bleaches either not at all or very slowly, relative to the rate of polymerization. 

The reader may, perhaps, recognize 8 as being a derivative prepared from Rose Bengal which is first decarboxylated and then acetylated. We refer to 8 as RBAX. RBAX is a xanthone, analogous to the thioxanthones which are common commercial UV photoinitiators. The latter are used with typical... 

Based on the known photoreduction chemistry of Rose Bengal [275], one would anticipate that electron transfer would reduce the xanthene skeleton of RBAX and that the radical anion thence formed might decay by the elimination of an acetyl radical. Acetyl is totally analogous to benzoyl, the radical that initiates chains in the case of most Norrish type I UV photoinitiators, that is, benzoin ethers or acetophenone acetals. The putative scheme is shown in Scheme 7. 

Monoalkyl aminium radicals cannot be prepared from PTOC carbamates 29 due to an equilibrium in solution favoring 2-mercaptopyridine-Ar-oxide and an alkyl isocyanate [Eq.(ll)]. With Af-(monoalkyl)thiazole-2-thione carbamates, TTOC carbamates, the equilibrium lies far to the side of the carbamate 84, and these precursors can be prepared from an isocyanate and Ar-hydroxythiazole-2-thione [Eq. (12)]. Under UV photoinitiation in acidic media, TTOC carbamates are efficient precursors for monoalkyl aminium cation radicals (Scheme 26). Monoalkylaminium radical 85 ey-clizes as efficiently as its analogous dialkylaminium radical 66, and the resulting carbon radical 86 can be trapped by a variety of radicophiles (91JOC1309) to prepare substituted pyrrolidines. 

In contrast to some other procedures, the UV photoinitiated polymerization does not require elevated temperature for the reaction to be completed. Therefore, the mobile phase used for packing remains in both the outlet frit and the packing during polymerization of the inlet frit. Consequently, the conditioning time for the column prior to its use is shortened significantly. No bubble formation was observed while using packed capillary columns with photopolymer frits. 

Benzoic acid, 4-(dimethylamino)-, ethyl ester EINECS 233-634-3 Ethyl 4-dimethylaminobenzoate Parbenate Speedcure EDB. UV photoinitiator. Crystals mp= 63-65" d = 1.0610 insoluble in H2O, soluble in organic solvents. Aceto Corp. Lambson Ltd. 

State. Of course, this result does not preclude the involvement of an electronic excited state in the UV photoinitiated 1,3-hydrogen shift. 

These compounds were dissolved in dioxane in the presence of a UV photoinitiator and exposed to a medium pressure mercury lamp. The products were analyzed by GC/MS techniques(9). 

In this type of polymerization, it is important to study the parameters as initiator, monomer, stabilizer concentration, and the reaction time on the characteristics of the final micrcapsules. In this methodology, the inherent simplicity of the single-step process makes the procedure useful. Typical examples are alcohols, alcohol-ether, and alcohol-water mixtures. By UV photoinitiated dispersion polymerization, Wang et al. prepared a composite composed by stearic acid PCM in PMMA shell. 

Chem. Descrip. 2-Hydroxy-2-methylphenylpropan-1-one CAS 7473-98-5 EINECS/ELINCS 231-272-0 Uses UV photoinitiator in coatings, inks, adhesives AcetocureSI [Aceto]... 

Uses UV photoinitiator in coatings, inks, adhesives Properties Yel. clear oily liq. very faint odor insol. in water sp.gr. 1.07 (20 C) m.p, < 5 C b.p. 100-120 C (0.2 mm Hg) flash pt, > 110 C Toxicology LD50 (oral, rat) > 10,000 mg/kg irritating to eyes, skin, mucous membranes, upper respiratory tract may be harmful by inh., ing., skin absorp. TSCA listed Environmental Environmentally hazardous Hazardous Decomp. Prods. Emits toxic fumes of CO, CO2 under fire conditions... 

Uses UV photoinitiator in coatings, inks, adhesives Quantacure EPD [Aceto]... 

Uses UV photoinitiator for coatings, lacquers, printing inks, adhesives... 

Storage Store in cool, dry place keep tightly closed protect from light Uses UV photoinitiator for coatings, inks, adhesivesUV photoinitiator in coatings, inks, adhesives Trade Names Speedcure PDA... 

Uses UV photoinitiator for coatings, lacquers, printing inks, adhesives Manuf./Distrib. Aceto http //www.aceto.com Trade Name Synonyms Speedcure BEDB [Aceto http //www. aceto. com]... 

Uses Visible light and UV photoinitiator for UV curable systems, industrial adhesives, fingernail compositions, fiber optics, electronic components assembly... 

Magnesium fluoride UV photoinitiator, adhesives 2-Butoxyethyl-4-(dimethylamino) benzoate 2-(Dimethylamino) ethyl benzoate Ethyl 4-(dimethylamino) benzoate 2-Isopropyl thioxanthone 4-Isopropyl thioxanthone... 

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