DE1055814B - Process for the photopolymerization of one or more polymerizable unsaturated organic compounds - Google Patents

Description

GERMAN

The invention relates to a method for the photopolymerization of unsaturated organic compounds.

It has been found that the polymerization in an aqueous system triggered by exposure the light output can be increased considerably if the exposure is intermittent happens.

The process for polymerizing one or more polymerizable unsaturated organic Compounds is that an aqueous emulsion of this compound or compounds of an intermittent Exposure.

The exposure is preferably carried out at a low temperature and / or in the presence of a photosensitizer.

The monomer to be polymerized or the monomers to be copolymerized are in one aqueous medium with the aid of an emulsifier, such as soap, emulsified, and the emulsion is then exposed in any apparatus set up for intermittent exposure. For example, the emulsion can be circulated through an exposed chamber such that it is exposed to exposure for a desired time as it passes through the chamber. Or but the emulsion is poured into several transparent containers, which are preferably arranged in a circle and is intermittent by a lamp arranged in the center of the circle with a rotating reflector exposed.

In a further embodiment of the exposure device the exposure is done by a wandering beam of light that touches the surface of the emulsion brushed at the desired speed.

Whatever the type of exposure device, so> it is advisable to stir the emulsion so as to reduce the amount of emulsion irradiated to mix the main amount, since the emulsion are generally not very translucent and the Light rays therefore only have a low penetration depth.

The exposure can be by means of rays having a wavelength of about 2000 to 7000 Å, preferably but done with a wavelength of 2537 to 5500 Å. The light can come through any suitable Light source can be generated, for example by a tungsten wire lamp or a low-pressure mercury arc lamp, however, a high pressure mercury arc lamp with a quartz jacket is preferable.

Since the polymerization started by exposure is much more temperature-independent than a conventional polymerization the process of the present invention can be carried out at low temperature and nevertheless a polymer can be produced quickly.

Method of photopolymerization

one or more polymerizable

unsaturated organic compounds

Applicant:
Dunlop Rubber Company Limited, London

Representative: Dipl.-Ing. E. Rathmann, patent attorney,
Frankfurt / M., Neue Mainzer Str. 40-42

¹ S Claimed priority:

Great Britain June 5, 1956

Wilfrid Cooper,

Erdington, Birmingham, Warwickshire,
and Margaret Fielden, Sutton Coldfield, Warwickshire (UK),

have been named as inventors

The exposure can be carried out in the presence of a photosensitizer. Photosensitizers can be divided into two classes:

a) those that break down photolytically into free radicals, and

b) those that generate free radicals through an electron transfer reaction to produce. Examples of the first type are 1-chloroanthraquinone, azobis-isobutyronitrile, Diacetyl, benzil and benzoin, while examples of the second type are uranium dioxide and uranyl nitrate.

In the first case, the photosensitizer acts like a conventional initiator that is active during the polymerization used up. In the second case, however, it may be possible to recycle the reduced metal re-oxidize into a sensitizing form. In addition to the known types of photosensitizers others have been found suitable for use in intermittent exposure, in particular are effective in the polymerization of acrylates using a tungsten filament lamp. These are Anthraquinones N-bromosuccinimide, N-dichlorobenzenesulfonamide (Dichloramine B) and diazonium salts with

909 507/591

of the structure Ar N ₂ + · X-. Here, Ar means an aryi group. Diazotized sulfanilic acid may be mentioned as an example of a diazonium salt. When using short-wave light, e.g. B. from mercury arc lamps, iron salts can be used as photosensitizers.

In general, water-soluble photosensitizers are preferred when water-soluble monomers are used or micelle-forming soaps can be used, but are in the case of suspension polymerization Oil-soluble sensitizers more suitable. In another embodiment of the present invention Several photosensitizers are used, each of which is used within a certain portion of the time Light spectrum is absorbed and so a * 5 full recovery of the light energy is made possible. For example, a mixture of benzoin and uranyl nitrate can be used since benzoin is im Absorbed in the range between 2450 and 3700 Å and uranyl nitrate in the range between 3800 and 4800 Å.

A time of 0.005 to 0.5 seconds was found to be a suitable exposure period, while the Dark period should not be shorter than 0.2 seconds. In general, the ratio of exposure to Dark period must be less than 0.5.

In general, the process of the present invention can be applied to any organic compound with the group CH, = C = C applied will. Such compounds are, for example, vinyl esters, such as vinyl chloride and vinyl acetate, vinyl ketones, such as methyl vinyl ketone; Esters of acrylic acid and substituted acrylic acid, such as methyl acrylate, Ethyl acrylate and methyl methacrylate; Styrene, vinylidene halides such as vinylidene chloride; unsaturated Hydrocarbons, especially conjugated diolefins such as butadiene. Copolymers can according to of the present invention can also be produced if, for example, butadiene-styrene or Methyl acrylate, ethyl acrylate mixtures can be used.

The method according to the present invention is distinguished from the other conventional methods characterized in that high yields of polymers with high molecular weight within a short time be achieved. In addition, the cost of exposure as an initiator is much lower than for exposure the usual catalysts, and the product is relatively free from decomposition products of the catalyst system, compared to the usual polymerization processes.

example 1

Vinyl acetate was in an aqueous emulsion containing 30 weight percent monomer and 4 weight percent sulfonated methyl oleate, based on vinyl acetate, contains polymerized. As a photosensitizer was Uranyl nitrate is used in an amount of 0.5 percent by weight based on vinyl acetate.

The emulsion was exposed to light using a high-pressure mercury arc lamp at various time intervals, each followed by a dark period, in such a way that the amount of light irradiated was 5 · 10 ¹⁵ quanta / sec / ml.

The results are given in the following table; the abbreviations have the following Meaning:

/ = ° / o of the exposure time.
B = exposure period in seconds.
D = dark period in seconds.
P = ° / o rate of polymerization / min.
W = efficiency Pll ■ 100.

/ B. D. BID P. W. 3.1 0.0062 0.194 0.32 0.298 9.5 18.7 0.0062 0.027 0.230 1.31 7.01 25.6 0.0062 0.018 0.344 1.27 5.07 3.1 0.0124 0.388 0.032 0.235 7.5 12.5 0.25 0.175 0.143 0.71 5.68 6.7 0.0406 0.562 0.72 0.33 5.25 25.0 0.05 0.15 0.333 1.39 5.56 12.6 0.075 0.520 0.143 0.83 6.64 12.5 0.175 0.225 0.143 0.78 6.24 250 0.175 0.525 0.333 1.14 4.56 37.5 0.175 0.292 0.600 1.61 4.29 50.0 0.175 0.175 1.0 1.96 3.92 12.5 0.35 2.45 0.143 0.64 4.92 100 continually - - ■ 3.45 3.45

From the table it can be clearly seen that with intermittent exposure the light energy with a higher efficiency is used than with continuous exposure.

Example 2

Vinyl acetate was in an aqueous emulsion containing 50 weight percent monomer and 5 weight percent Gum arabic, based on the monomer, contained as an emulsifier, polymerized. As a photosensitizer 1 percent by weight of azo-bisisobutyronitrile, based on the monomer, was added.

The emulsion was exposed to a tungsten filament lamp for 0.01 seconds each time. The exposure period was followed by a 0.32 second dark period. The total amount of light irradiated was 3 · 10 ⁴ quanta / sec / ml. It was a polymerization rate of 11.4% / hour. achieved. The efficiency was P · ΙΟ ¹⁴ = 3.8%, with P % degree of polymerization / hour. and A is the amount of irradiated light in quanta / sec / ml.

A similar sensitized emulsion was prepared as described above and continuously exposed to light using a high pressure mercury arc lamp; the total amount of light irradiated was 7 · 10 ¹⁵ quanta / sec / ml. A polymerization rate of 105% per hour was achieved; the efficiency was calculated using the above formula to be 1.5. the

Results show that the light utilization is greater with intermittent exposure than with continuously.

Example 3

Vinyl acetate was in an aqueous emulsion containing 40 weight percent monomer and 4 weight percent sulfonated methyl oleate, based on the monomer, contained as an emulsifier, polymerized. as Photosensitizer was 1 percent by weight azo-bisisobutyronitrile, based on the monomer.

The emulsion was produced intermittently using a tungsten filament lamp as described in Example 2 exposed. It was 9.5% polymerization rate / hour. achieved. The efficiency is calculated according to the formula in Example 2 to 3.2. Compared to polymerization using continuous exposure (Example 2) results in a higher efficiency with intermittent exposure.

Example 4

Vinyl acetate was obtained by means of intermittent exposure under the same conditions as in Example 2 polymerized, but 1 percent by weight of p-bromophenacyl bromide, based on the monomer. The rate of polymerization was 6.1% / hour. and the efficiency was 2.0. Here, too, is the efficiency achieved according to the formula in Example 2 higher with intermittent exposure than with continuous exposure.

Example 5

A monomer emulsion was prepared by mixing 70 parts by weight of butadiene, 30 parts by weight of styrene, 0.17 parts by weight of tert-dodecyl mercaptan and 5 parts by weight of potassium oleate as an emulsifier and 180 parts by weight of water. the The emulsion thus obtained was photosensitized by adding 1 percent by weight of uranyl nitrate.

The interpolymerization of the monomers was carried out by intermittent exposure, as in Example 2 described, brought about. The rate of polymerization was 21.0% / hour. and the efficiency 7.0.

The same emulsion was prepared as described above and continuously exposed to light using a tungsten filament lamp. The total amount of light irradiated was 6 · 10 ¹⁴ quanta / sec / ml.

The rate of polymerization was 14.6% / hour and the efficiency was 2.4.

This also shows that the amount of light irradiated is better with intermittent exposure than is used continuously.

Claims (5)

Patent claims: 1. Process for the photopolymerization of one or more polymerizable unsaturated organic Compounds, characterized in that an aqueous emulsion of the compound or the compounds of intermittent exposure using light of a wavelength of about 2000 to 7000 Å, the ratio of the exposure period to the dark period is less than 0.5. 2. The method according to claim 1, characterized in that that the exposure of the aqueous emulsion is carried out in the presence of a photosensitizer will. 3. The method according to claim 1 and 2, characterized in that the exposure period 0.005 lasts up to 0.5 seconds and the dark period is not shorter than 0.2 seconds. 4. The method according to claim 2 and 3, characterized in that the photosensitizer at Exposure photolytically breaks down into free radicals. 5. The method according to claim 2 and 3, characterized in that the photosensitizer at Exposure to free radicals generated by electron transfer reaction. Considered publications:
Transactions Faraday Society, 49, pp. 1096-1104 (1953). © 909 507091 4.59