DE1495692B2 - PROCESS FOR THE POLYMERIZATION OF OPEN CHAIN N-VINYLAMIDES - Google Patents

Description

where R ₁ and R _{2 are} monovalent radicals of aliphatic hydrocarbons with 1 to 5 carbon atoms or hydrogen, alkynes per se or in a mixture with one another or with other free-radically polymerizable compounds in the presence of azo catalysts in aqueous solution or dispersion, characterized in that the catalysts are aliphatic azodinitriles and / or azodicarboxylic acids or their derivatives of the general formulas

a)

C-N = N-C

25th

R ₉ CN

CN R,

b)

C-N = N-C

R ₃ COOR ₄

COOR,

c)

C-N = N-C

CO-N

CO-N

R ₆

Azo-bis-isobutyronitrile known at 10 ³ Torr under nitrogen. This results in polymers with low molecular weights of a maximum of 2000.

The subject of patent 1151 940 is a method for the polymerization of open-chain N-vinylamides in aqueous solution or suspension with the Catalyst systems hydrogen peroxide / ammonia or hydrogen peroxide / amines.

There has now been a process for the polymerization of open-chain N-vinylamides of the general formula

O CH = CH ₂

R ₁ -CN

where R ₁ and R _{2 are} monovalent radicals of aliphatic hydrocarbons with 1 to 5 carbon atoms or hydrogen, alone or in a mixture with one another or with other free-radically polymerizable compounds in the presence of azo catalysts in aqueous solution or dispersion, in which then polymers with higher molecular weights can be obtained in good yields if aliphatic azodinitriles and / or azodicarboxylic acids or their derivatives of the general formulas are used as catalysts

From the thesis by G. Wel ze 1 (Freiburg 1960) is the polymerization of open-chain N-vinyl amides, namely N-vinylacetamide, at temperatures from 60 to 8O ⁰ C and in the presence of 0.1% of R ₁

C-N = N-C

35

40

45 R ₂ CN

CNR,

C-N = N-C

/ \
R ₃ COOR ₄

COOR ₄

R ₂

C-N = N-C

where R _{1 is} alkyl groups with 1 to 5 carbon atoms or the —CH ₂ —CH ₂ —COOH group, R ₂ , R _{3 are} alkyl groups with 1 to 5 carbon atoms and R ₄ , R ₅ , R _{6 are} alkyl groups with 1 to 5 carbon atoms or hydrogen atoms mean are used and the polymerization is optionally carried out together with a water-soluble organic solvent, at a pH value of not less than 6 between 60 and 140 ⁰ C or under UV irradiation between 0 and 14O ⁰ C.

60 CON

CON

R ₆

where R _{1 is} alkyl groups with 1 to 5 carbon atoms or the - CH ₂ - CH ₂ - COOH group, R ₂ , R _{3 are} alkyl groups with 1 to 5 carbon atoms and R ₄ , R ₅ , R _{6 are} alkyl groups with 1 to 5 carbon atoms or hydrogen atoms mean, are used and the polymerization, if appropriate together with a water-soluble organic solvent, is carried out at a pH of not below 6 between 60 and 140 ^° C. or with UV irradiation between 0 and 140 ^° C.

Working in an aqueous solution or dispersion enables the heat of polymerization to be dissipated well. In addition, very high mean Molecular weights of the polymers are obtained

with a very low residual monomer content (usually less than 1%). This method is z. B. clearly superior to bulk polymerization. By varying the reaction temperature and catalyst concentration a precise setting of a desired mean molecular size is easily possible. So products of are obtained at a relatively low temperature and a low catalyst concentration larger mean chain length, while relatively high temperatures and catalyst concentrations den Favor chain termination. These relationships can be seen from Example 2, Tables 1 and 2. Farther is a reduction in the molecular weight through the addition of regulators (e.g. alcohols, ketones, aldehydes) possible.

The preparation of the azo compounds used as catalysts can, for. B. be done according to Thiele and Heuser, Liebigs Annalen 290, 1 (1896), resp. after D ο x, J. Amer. Chem. Soc. 47, 1471 (1925).

As examples of the invention as polymerization compounds to be used are: α, ά - azo - isobutyric - dinitrile, a, a azo -isobuttersäure, a, a azo -isobuttersäure - dimethyl ester, a, a - azo - isobutyramide, azo - diethylacetonitrile and y, / - azo-bis-y-cyanopentanoic acid. In the latter case, R ₁ bears a carboxyl group. Of course, mixtures of the various aliphatic azo compounds can also be used as catalysts.

The catalysts mentioned are generally used in a concentration of 0.001 to 10 percent by weight, preferably 0.01 to 3 percent by weight, based on the monomer, used. As the aliphatic azo compounds in water are mostly insoluble, they are expediently first in the open-chain N-vinylamides to be polymerized dissolved at room temperature or slightly elevated temperature and in this form the aqueous Phase added. By mediating the monomer and the polymer, the solubility of the catalysts remains then obtained during the polymerization. Compounds with carboxyl groups, such as α, α'-Αζο-isobutyric acid and the ^, / - azo-bis-y-cyanopentanoic acid, can also be used as polymerization catalysts in the form of their water-soluble salts will.

Open-chain monomers are suitable as monomers for the polymerization by the process according to the invention N-vinyl amides with the following formula

CH = CH,

R ₁ -CON

as they are obtained by known methods (German Auslegeschrift 1088 479). R ₁ and R _{2 are} monovalent radicals of aliphatic hydrocarbons having 1 to 5 carbon atoms or hydrogen, and the radicals R ₁ and R _{2 can be} identical or different. The following compounds may be mentioned in detail, for example: N-vinyl-N-methylformamide, N-vinyl-N-methylacetamide, N-vinylpropionamide, N-vinyl-N-methylpropionamide, N-vinyl-N-ethylacetamide and N- Vinyl N-methylisobutyramide. The copolymerization components are free-radically polymerizable compounds such. B. vinyl ethers whose alkyl radicals contain 1 to 5 carbon atoms, also vinyl lactams such as vinylpyrrolidone or N-vinylcaprolactam, vinyl halides such as vinyl chloride, esters of vinyl alcohol with monobasic saturated aliphatic carboxylic acids having 1 to 18 carbon atoms, eg. B. vinyl acetate, vinyl propionate, vinyl butyrate and vinyl stearate. Derivatives of acrylic acid or methacrylic acid, e.g. B. esters of acrylic acid or methacrylic acid with aliphatic monohydric saturated alcohols having 1 to 8 carbon atoms and acrylic acid amide, methacrylic acid amide, acrylonitrile and methacrylonitrile. Maleic acid and its esters, the anhydride and the imides can also be used as copolymerization components.

The N-vinylamides are preferably in the form of a 5 to 60% strength aqueous solution or dispersion used. Larger dilutions and more concentrated solutions can also be suitable. at the N-vinylamides which are less soluble in water (e.g. N - vinyl - N - methylpropionamide, N - vinyl-N-ethylacetamide, N-vinyl-N-methylisobutyramide) can be used both in one phase and in a two-phase System to be polymerized. In the first case, the addition of a solubilizer, e.g. B. an organic water-soluble Solvent, such as methanol, ethanol, propanol or acetone, is necessary. As the polymeric N-vinylamides are much more soluble in water than the monomers, may disappear with initially two-phase Polymerization of the oil phase with increasing conversion.

The polymerization according to the process of the invention can be accelerated by irradiation with ultraviolet light. This embodiment is carried out at polymerization temperatures from 0 to 140 ⁰ C, preferably below 6O ⁰ C, applied. The reaction temperature depends on the decomposition temperature of the azo compound used as catalyst and can be between 60 and 140.degree. To increase the rate of polymerization and shorten the latency period, it is advantageous to carry out the polymerization in the absence of oxygen, e.g. B. under nitrogen, carbon dioxide or argon atmosphere. This is particularly advantageous at a temperature below 70 ° C.

Since the N-vinylamides easily hydrolyze in acidic solution to form acetaldehyde, the pH should be not be less than 6.

The process according to the invention is preferably carried out at atmospheric pressure.

The polymeric, open-chain N-vinylamides formed by the process according to the invention are in water and in various organic solvents (e.g. alcohols, halogenated hydrocarbons) soluble. The polymers can be removed from the solutions as colorless, win hard movies.

The polymers prepared according to the invention can be used for stripping vat dyes, as Thickeners and adhesives and can be used as hair setting agents.

In the following examples, all K and r \ _rei values relate to 1% solutions of the polymers in water at 25 ° C.

example 1

10 g of N-vinyl acetamide are dissolved in 10 g of water. 50 mg of α, α'-azobutyric acid dinitrile are added to this solution. It is then degassed, nitrogen is let in and 30 ml of O ₂ -free water are added. After adding 0.2 ml of ammonia (20%), the mixture is heated to 70 ° C. while stirring. The polymerisation soon starts and is noticeable through the evolution of heat and an increase in viscosity. The temperature is kept at 70 ^° C. for 22 hours, the water is then drawn off in vacuo and a colorless, clear, water-soluble polymer with a K value according to Fikentscher (cf. Cellulosechemie 13 [1932], 58) 107 and one is obtained in quantitative yield >? r "rvalue _V on 6.0.

Example 2

The following tables show the effect of the polymerization temperature (Table 1) and the catalyst concentration (Table 2) on the average chain length of the polymers. As an example, the Polymerization of N-vinyl-N-methylacetamide selected.

Table 1

Temperature, ⁰ C w-value K value 60
70
80 6.4
3.2
1.3 108.4
89.8
65.9

Table 2

α, α'-azo-iso-butter-
acid dinitrile conc. W value K value 0.25 weight
percent, related
on the mono
mere
0.5 weight
percent 4.4
3.2 98.4
89.8

15th

25th

30th

approach

18 g of N-vinyl-N-methylacetamide, 102 g of water, 90 mg of α, α'-azo-isobutyric acid dinitrile, nitrogen atmosphere.

40

45

approach

18 g of N-vinyl-N-methylacetamide, 102 g of water, temperature 70 ^° C., nitrogen atmosphere.

In all experiments, the polymerization is carried out by adding ammonia at a pH of 8 to 9 executed. With polymerization times of 8 to 20 hours, the conversions are 97 to 99.5%, Der The low residual monomer content enables the aqueous polymer solutions to be used for many purposes without removing the residual monomer.

Example 3

22.5 g N-vinyl-N-methylacetamide polymerized in a mixture of 63 g ethanol and 63 g water with 112 mg α, α'-azo-isobutyric acid dinitrile at 70 ⁰ C in N ₂ atmosphere, one obtains a polymer with an iC value of 45. Without the addition of ethanol (126 g of water), on the other hand, a product with a K value of 90 is obtained. Z B. aldehydes such as n-butyraldehyde. Here, 0.25 g is sufficient to obtain a K value of 48 under similar polymerization conditions.

Example 4

25 g each of N-vinyl-N-methylpropionamide, N-vinyl-N-ethyl-propionamide and N-vinyl-N-methylisobutyramide are dissolved in 75 ml of water in the absence of oxygen with 250 mg of α, α'-azobutyric acid dinitrile polymerized with stirring at 7O ⁰ C and pH. 8 A second phase is initially formed, which in the case of N-vinyl-N-methylpropionamide, however, disappears completely in the course of the polymerization (8 hours). In the case of N-vinyl-N-ethylpropionamide and N-vinyl-N-methyl-isobutyramide, on the other hand, a latex-like dispersion of the polymers is formed, which only slowly turns into a clear solution on cooling. The following K values are obtained with yields of about 95%: poly-N-vinyl-N-methylpropionamide 52, poly-N-vinyl-N-ethylpropionamide 34 and poly-N-vinyl-N-methylisobutyramide 42.

What is interesting about these polymers is the negative temperature coefficient of solubility in water. Thus, all of the polymers mentioned in Example 4 are clearly soluble at room temperature, but fall when increased the temperature under cloudiness. The temperature of the onset of turbidity is of the type of the polymer. It amounts to z. B. with 25% aqueous solutions in the case of poly-N-vinyl-N-ethylpropionamide ~ 45 ° C, for poly-N-vinyl-N-methylisobutyramide ~ 39 ° C and for poly-N-vinyl-N-methylpropionamide ~ 84 ° C.

Example 5

12.5 g of N-vinyl-N-methylacetamide are copolymerized with 12.5 g of N-vinylpyrrolidone at 70 ° C. in 75 g of water. Catalyst: 250 mg of α, α'-azo-isobutyric acid dinitrile, N ₂ atmosphere, 7 hours polymerization time. A copolymer with a K value of 82 is obtained in very good yield.

Example 6

In the copolymerization of N-vinyl-N-methylacetamide with vinyl acetate in water and α, α'-azo-isobutyric acid dinitrile As a catalyst, up to about 18% vinyl acetate can be built into the polymer in such a way that that there is complete solubility throughout the polymerization (temperature 70 ° C., 2% α, α'-Αζο-isobutyric acid dinitrile). If you try to polymerize more vinyl acetate, the batch remains cloudy during the polymerization and the polymer is at the end of the polymerization only soluble in a cloudy manner, even in the cold. During the interpolymerization of N-vinyl-N-methylacetamide is preferably used at a pH value> 6 in a solution buffered with Na acetate worked under nitrogen.

Example 7

If 100 g of N-vinyl-N-methylacetamide and 200 mg of α, α'-azoisobutyric acid dinitrile in 900 ml of H ₂ O are stirred for 24 hours at 30 ° C. in the absence of oxygen, no polymerization occurs.

If UV light is radiated in with an Hg vapor lamp at the same temperature, then the

Approach as a result of the polymerization of N-vinyl-N-methylacetamide soon more viscous. One obtains in almost quantitative yield after 24 hours of polymerization UV radiation a polymer with a K value of 104.

Example 8

166 mg of y.y'-azo-bis-y-cyanopentanoic acid are dissolved in 100 ml of water (degassed and _{saturated with N 2} ) after adding 0.5 ml of ammonia (25%) and 33.3 g of N- Vinyl-N-methylacetamide added. The mixture is heated to 75 ° C. with stirring and a _{blanket of N 2.} After a polymerization time of 22 hours, a colorless, highly viscous solution of a is obtained

Polymer with a K value of 87.2. The conversion is over 99%.

Example 9

21 ml of N-vinyl-N-methylacetamide are dissolved in 50 ml of water with 200 mg ^, / - azo-bis-y-can-pentanoic acid and 2 ml of ammonia (25%) are added. 8.8 ml of methyl acrylate are then slowly added dropwise at 76.degree. After 4 hours, the polymerization is terminated and the water and the monomer residues evaporated in vacuo. The yield is 18 g (~ 65%), the value 0.64 (1% in dimethylformamide at 25 ° C). Saponification number 320 mg KOH / g substance.

309518/513

Claims (1)

Claim: Process for the polymerization of open-chain N-vinylamides of the general formula Il, R ₁ -CN CH = CH,