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Publication numberUS2460105 A
Publication typeGrant
Publication dateJan 25, 1949
Filing dateAug 21, 1943
Priority dateAug 21, 1943
Publication numberUS 2460105 A, US 2460105A, US-A-2460105, US2460105 A, US2460105A
InventorsMarion Richards Lawrence
Original AssigneeDu Pont
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Photopolymerization of vinylidene compounds with organic disulfides
US 2460105 A
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Description  (OCR text may contain errors)

Patented Jane 25, 1949 PHOTOPOLYMERIZATION OF VINYLIDENE COMPOUNDS WITH ORGANIC DISULFIDES Lawrence Marion Richards, Wilmington, Del.,

assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application August 21, 1943, Serial No. 499,555

Claims.

This invention relates to the photopolymerization of unsaturated organic compounds.

The polymerization of ethylenically unsaturated organic compounds under the influence of light is well known in the art. It is also well known that certain adjuvants are photopolymerization catalysts and have been employed in the photopolymerization of ethylenically unsaturated organic compounds but none of these have attained any degree of practical significance.

This invention has as an object the provision of a process for the photopolymerization of polymerizable organic compounds in the presence of new and improved photopolymerization catalysts. Other objects will appear hereinafter.

These objects are accomplished by the following invention which comprises irradiating, with light of wave lengths in the range from 2500 to 5000 Angstrom units, a composition comprising a photopolymerizable vinyl or vinylidene compound containing at least one CH2=C group activated by direct attachment to a different negative group, that is, halogen, k0, CN, -CEC-, O-, or aryl, and from 0.01 to 5.0% of an organic disulfide soluble in said vinyl or vinylidene compound and free from nitro, hydroxyl and primary amino groups on aromatic carbon, the irradiation being of suflicient intensity and employed for a time suificient to produce substantial polymerization.

In the preferred practice of this invention from 0.1 to 1.0% by weight of a diaryl disulflde, for example, diphenyl disulflde or a diaroyl disuliide, for example, dibenzoyl disulflde, is dissolved ina photopolymerizable vinyl or vinylidene compound, as above described. If desired, a mutual solvent can also be added to this solution. The solution is then placed in a vessel transparent to light of wavelengths from 2500 to 5000 Angstrom units. Borosilicate glass is a satisfactory transparent material for the construction of suitable containers for the polymerization reaction mixture. The air over the solution is displaced with nitrogen, and the vessel and contents are maintained at a temperature of from to 100 C. while exposed to a light source rich in ultraviolet light until a substantial degree of polymerization of the unsaturated compound has occurred.

The invention is further illustrated by the following examples in which parts are by weight.

styrene.

EXAMPLE 1 V under the same conditions for the same length of time but having no added agent contains only 7.5% of polymeric styrene. Likewise, a similar sample of styrene containing 1% by weight of benzoyl peroxide irradiated under the same conditions for the same length of time contains only 33% of polystyrene.

If pure styrene and styrene containing 1% dibenzoyl disulflde are heated under an atmosphere of nitrogen at C. for approximately 1'? hours in the absence of light, both samples contain approximately l'l% polystyrene, respectively.

EXAMPLE II Identical amounts of solutions of styrene each containing 1% by weight respectively of the disulfldes of Table I are placed in borosilicate glass tubes of the same size and shape. The air is displaced with nitrogen and the tube is closed. The borosilicate glass tubes containing the various solutions of disulfides in styrene are exposed to the radiation from a mercury lamp watt) at 80 C. and at a distance of 12 inches from the source of radiation. After 6 hours the radiation is stopped and the amount of polystyrene in each sample is determined. A sample of styrene containing no added agent is irradiated under the same conditions to serve as a control. In Table I below is shown the percent polymer formed in each one of the solutions tested and the comparative capacity of these disulfides to accelerate the formation of polystyrene is given under the heading Comparative rating." The relative amount of polymer formed by the use of dibenzoyl disulflde is arbitrarily designated as 1.0.

Tune I Phctopolymeriedtion of styrene at 80 C.

Identical amounts of the vinyl and vinylidene compounds of Table 11 below both in the pure state and containing in solution 1% or the disuliides shown were placed in borosilicate glass tubes 01' the same size and shape, the air was replaced with nitrogen, the tubes were closed, and were irradiated at 25 C. with the light from a mercury lamp (100 watt) placed 12 inches from the tubes. After a suitable period irradiation was stopped, and the percent polymer obtained was determined both for the sample containing the added disulflde and the samples containing no added agent. The results are given in the following table.

Tm: H

for 20 hours. The lens produced in this way is advantageous for use in systems subject to severe shock which would shatter inorganic glass lenses.

The photopolymerizable compounds with which this invention is concerned are the photopolymerizable vinyl and vinylidene compounds containing at least one CHa=C group activated by attachment to a diii'erent negative group, that is, halogen, C=O, -CN, C.=.C-, or aryl. These include vinyl esters, e.g., vinyl acetate, vinyl propionate; vinyl halides, e.g.. vinyl chloride; vinyl ketones. e.g., methyl vinyl ketone; vinyl ethers, e.g.,. vinyl ethyl ether; vinyl cyanides, e.g., acrylonitrile and methacrylonitrile; esters oi acrylic acid, e.g., methyl acrylate and ethylene dlacrylate; styrene; and vinylethinyl carbanols,

vinylidene compounds which can be used are esters of methacrylic acid, e.g., methyl methacrylate, allyl methacrylate, and ethylene dimethacrylate; vinylidene halides, e.g., vinylidene chloride, and esters of alpha-substituted acrylic acids, e.g., methyl alpha chloracrylate. Oi these compounds those having a vinyl or vinylidene group attached to an aromatic ring, and in particular styrene, are preferred since the organic disul des are most efl'ectlve in bringing about satisfactory rate of photopolymerization and in the production of colorless products adapted to Photopolymerization of selected vinyl and vinylidene compounds in the presence of organic disulfides at 25 6'.

Methyl Dimethyl t 3255? sense:

Polymer in P0 ymor in Polymer in ymer in cent Pol 7! hrs. 23 his. 75 hm 8 hrs, in 22 a 1 None con 1) 0 0 0 I Diben zcyl uliide 21 5 78 is m I Dl-gira-tolyl disulilde 74 42 77 4 N, '-dipentamethylene thiuram disulnde. 7 29 0 N, N'-dimethyl thiuram disulilde 7 Other vinyl and vinylidene compounds likewise show a marked acceleration in their rate of photopolymerization in the presence of an organic disuli'ide. For example, at C. under the influence of ultraviolet light acrylonitrile containing 1% by weight of dibenzoyl disuli'lde is converted in 2 hours to a solid white polymer, while a control sample containing no added agent is unchanged. Similarly, under these conditions allyl methacrylate containing 1% dibenzoyl disulflde is converted to a solid polymer in 7.5 hours in comparison with an unchanged control sample. Vinyl isobutyrate, methyl acrylate, and n-octyl methacrylate likewise show a marked increase in the rate or photopolymerization in the presence of 1 by weight of dibenzoyl disulflde over a control sample of these compounds similarly irradiated.

EXAMPLEIV Pure monomeric styrene containing 0.5% dibenzoyl disulflde and 0.1% benzoyl peroxide by weight is heated at 90C. for 15 hours to produce a viscous syrup. This syrup is placed in a cell consisting of a glass lens blank and a sheet of plate glass separated by a gasket or rubber tubing coated with polyvinyl alcohol. The syrup is further polymerized to a precisely shaped optical lens by irradiating the syrup in the cell at 75-90 C. with a mercury lamp at a distance of 10 inches and mixed disuli'ldes containing radicals selected from any of the above classes. Of these disulfldes, best results are obtained with the diaryl disulfides and the diaroyl disulfldes. In general from 0.01 5% by weight of the disulilde based on the vinyl or vinylidene compound can be used although it is preferred to use amounts from 0.1 to 1.0%. The disulfides must be soluble in the vinyl or vinylidene compound with which they are used. They must also be free from nitro, hydroxyl and primary amino groups on aromatic carbon.

The source of radiation is limited only to those providing wave lengths in the range of 2500-5000 Angstrom units. and preferably in tlie wave length region of 2800 to 4000 Angstrom units. Sources of radiation that are commercially available include mercury lamps and arcs. carbon arcs, and hydrogen discharge tubes. Sunlight can also be used as a. source oi light containing the desired wave lengths. Tungsten tensity also ilnd utility as light sources.

The photopolymerization can be carried out at temperatures of from to 150 C. but in practice the range from 25 to 100 C. is the most useful. Methyl methacrylate operates best at around 25 C. whereas styrene requires a temperature of from 60 to 80 C. for a sui'flciently rapid polymerization cycle.

The vessel in which the polymerization is conducted must be transparent to light of the desirable wave lengths when the reaction is conducted so that the light passes through the sides of the container. It is also possible to place the source 01' light directly over the surface of the monomer in a container or within the reaction mixture itself.

The exclusion of oxygen from the photopolymerization systems of this invention has been found advantageous and in carrying out the photopolymerlzation, steps are usually taken to replace the air by an inert gas, for example, nitrogen.

Photopolymerizations in accordance with this process can be carried out in solution, emulsion, or in granular systems. In the preferred process, however, the photopoiymerizable monomer contains in addition to the disulfide at most only limited quantities oi a mutual solvent.

In some cases, however, it may be desirable to add an organic peroxide catalyst, for example, benzoyl peroxide, lauroyl peroxide, or diethyl peroxide to the Photopolymerization mixture containing the disulflde since the monomer/disulflde/peroxide combination may be heated to give viscous casting syrups which when poured into a transparent mold polymerize rapidly upon exposure to light to give a precisely shaped object.

This invention is applicable not only to the photopolymerizable vinyl and vinylidene compounds above described but also to mixtures thereof and to mixtures of other unsaturated materials photopolymerizable in the presence of the compounds of this invention.

The products oi this invention are useful as molding powders, adhesives, coating and impregnating agents, transparent resinous enclosures, safety glass inter-layers, etc. In addition, when photopolymerization of the compositions is carried out within a mold, useful optical articles such as lenses, prisms, diffraction gratings, etc. can be obtained. These are less brittle than the inorganic glasses and require no expensive and laborious grinding procedure. They also have the added advantage of being considerably lighter in weight than the inorganic glasses. The term "vinylidene compound" in the claims is inclusive 01' "vinyl compound, 1. e. a vinylidene compound having one of the free valences of the vinylidene radical satisfied by hydrogen.

The above description and examples are intended to be illustrative only, and no unnecessary limitations should be understood therefrom.

What is claimed is:

i. A process for preparing polymers which comprises irradiating, with light of wave length in the lamps oi suiiicient inrange or from 2500 to 5000 Angstroms, a composition comprising a photopolymerizable vinylidene compound having one CH2=C group and that activated by direct attachment to a diflerent negative group, said group being selected from the class consisting of halogen, C=O, -C::N, CEC, O, and aryl, and from 0.01 to 5%, based on the photopolymerizable compound, 01' an organic disulflde tree from nitro, hydroxyl and primary amino groups on aromatic carbon, the irradiation being of suflicient intensity and employed for a time suflicient to produce substantial polymerization.

2. A process for preparing polymers of styrene which comprises irradiating, with light of wave length in the range of from 2500 to 5000 Angstrom units, a mixture of monomeric styrene with from 0.01 to 5.0%, based on the styrene, 01 dibenzoyl disulflde, the irradiation being of sumcient intensity and employed for a time sufllcient to produce substantial polymerization.

3. A process for preparing polymers which comprises irradiating, with light of wave length in the range of from 2500 to 5000 Angstrom units, a mixture 01' a compound having the vinyl group attached to an aryl radical with from 0.01 to 5.0%, based on the vinyl aryl compound, of an organic disulfide, the irradiation being of suflicient intensity and employed for a time suilicient to produce substantial polymerization.

4. A process for preparing polymers which comprises irradiating, with light of wave length in the range 2500-5000 Angstrom units, a mixture of a photopolymerizable vinylidene compound having but one ethylenic double bond and that attached to a carbon in turn attached to a different negative group, said group being selected from the class consisting of halogen, C=O, -CEN, CEc-, -O and aryl, with from 0.01 to 5.0%, based on the photopolymerizable compound, of an organic disulfide, the irradiation being of sumcient intensity and employed for a, time sufflcient to produce substantial polymerization.

5. Process for preparing polymers which comprises irradiating, with light of wave length in the range 2500-5000 Angstrom units, a mixture of a vinyl aryl compound and from 0.01 to 5%, based on the vinyl aryl compound, of a diaroyl disulflde, the irradiation being of sufllcient intensity and employed for a time suflicient to produce substantial polymerization.

6. Process for preparing polymers which comprises irradiating, with light of wave length in the range 2500-5000 Angstrom units, a mixture of a vinyl aryl compound and from 0.01 to 5%, based on the vinyl aryl compound, of a diaryl disulflde, the irradiation being of sufficient intensity and employed for a time suflicient to produce substantial polymerization.

7. A process for preparing styrene polymers which comprises irradiating a mixture of styrene and from 0.01 to 5% based on the styrene, of a diaroyl disulflde with light of wave length of 2500-5000 Angstrom units, the irradiation being of sufllcient intensity and employed for a time sufficient to produce substantial polymerization.

8. A process for preparing styrene polymers which comprises irradiating a mixture of styrene and from 0.01 to 5%, based on the styrene, of a diary] disulflde with light of wave length of 2500-5000 Angstrom units, the irradiation being of suflicient intensity and employed for a time suiiicient to produce substantial polymerization.

9. A process for preparing polymers oi styrene which comprises irradiating, with light of wave length in the range 01 tram 2600-5000 Angstrom units, a mixture of monomeric styrene with from 0.01 to 0.0%. based on the styrene. o1 di-parstolyl disuiiide, the irradiation being or sumcient intensity and employed lo:- a time suiiicient to produce substantial polymerisation.

10. A process for preparing polymers of styrene which comprises irradiating with light in the ultraviolet range. a mixture of monomeric styrene, with from .196 to 5.0%, based on the weight of styrene, of dibenzoyl clisulnde, the irradiation being of sumcient intensity and employed for a time sufllcient to produce substantial polymerization.

LAWRENCE MARION RICHARDS.

The following references are of record in the tile 01 this patent:

UNITED STATES PATENTS OTHER C38 Chemical Action of Ultraviolet Boys," 1941, pages 131 to 134 sud-406 to 412, Ellis and Wells. Reinhold Publishing Corp., 330 W. 42d Bt., New York. N. Y.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1721034 *Nov 8, 1926Jul 16, 1929Ostromislensky IwanPolymer of vinyl chloride and process of making the same
US1950438 *Feb 28, 1931Mar 13, 1934Du PontPolymerized halogenated hydrocarbons and process for producing same
US1950439 *May 6, 1931Mar 13, 1934Du PontHalogenated butadiene polymer and process for producing same
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2738319 *Dec 5, 1952Mar 13, 1956Monsanto ChemicalsMetal mercaptides as photosensitizers in photopolymerization
US2769777 *Jan 4, 1954Nov 6, 1956Monsanto ChemicalsInitiation of photopolymerization
US2861933 *Jul 1, 1953Nov 25, 1958Monsanto ChemicalsPhotopolymerization
US5230982 *Nov 19, 1991Jul 27, 1993The Mead CorporationHeterocyclic disulfides for crosslinking
Classifications
U.S. Classification522/54, 522/24, 522/50, 522/188, 522/173, 522/178, 522/182, 522/177
International ClassificationC08F2/46
Cooperative ClassificationC08F2/46
European ClassificationC08F2/46