DE1619096B2 - PROCESS FOR PROPOLYMERIZING VINYL COMPOUNDS ON CELLULOSE FIBERS - Google Patents

Description

The invention relates to a process for the graft polymerization of vinyl monomers on cellulose fibers, those with the help of ionizing radiation and in the presence of catalytically active metal compounds is carried out.

Emulsion polymerization has hitherto been preferred in graft polymerization of vinyl compounds used because this method has a greater reaction speed than when using other methods, such as solution polymerization, can be achieved. In addition, owns the reaction system when using this technique is highly resistant to polymerization inhibitors, z. B. against oxygen. A serious disadvantage of this technique, however, is the fact that homopolymers form very easily, so that the degree of utilization is very low as a result.

For example, if a previously irradiated cellulose with a vinyl compound, e.g. B. ethyl acrylate is brought together in an emulsified system at 30 to 80 ⁰ C for the purpose of graft polymerization,

ίο then the effectiveness of the utilization of the Monomers usually less than 50% and a large amount of homopolymer is produced.

The formation of undesired homopolymer not only has a disadvantageous effect in that it reduces the degree of utilization of the monomeric reactant, but also leads to difficulties in separating the homopolymer from the desired end product.
The reasons for the formation of this homopolymer are probably the following:

If a cellulose is subjected to ionizing radiation in air, diperoxides and hydroxides are formed in the cellulose molecule. If this irradiated cellulose is then brought into contact with a vinyl monomer after the air has been removed and heated, the peroxy and hydroxy radicals formed from the peroxides initiate the graft polymerization.
The following equations serve to explain the mechanism in graft polymerization, in which PH denotes a cellulose molecule, while H denotes hydrogen. B means a monomer to be grafted on.

POO * > POOP

POOP
(POOH ■

PO "+ OP

PO '+ OH

POOH + P *

POBBB ... B

POBBB ... B + B ... BBBOH)

Accordingly, a homopolymer is formed in the form B ... BBBOH, caused by an OH radical, caused by the breakdown of one of the above mentioned peroxides.

To this prior art, from which it was known, cellulosic substrates such as cellulosic fibers by To refine grafting of vinyl monomers under the action of ionizing radiation, according to However, which has formed an undesirably large amount of homopolymer, belongs to the Belgian Patent specification 5 69 241 and the article by F. G ü 11-b a u e r et al. in "Österreichische Chemikerzeitung", 67 (1966), pp. 35 to 41. The invention is now the The object of the invention is a process for the graft polymerization of vinyl monomers onto cellulose fibers to make available, in which this undesirable formation of large amounts of homopolymer not entry. The theoretical explanations show that this either requires the formation of the OH radicals to control or to deactivate the resulting OH radicals. So it represents a big step forward if a suitable catalyst can be found that prevents the formation of OH radicals

in this way or the resulting radicals responsible for homopolymerization are deactivated.

Looking for such suitable catalysts to suppress homopolymer formation numerous scientists took part. So from the French patent 11 57 006 for Solution polymerization is a process known in which a small amount of oxygen in the Reaction system is dissolved. It is also used in Japanese Patent Application No. 11,984/61 of iron (II) or iron (III) ions for this purpose became known.

The inventors of the present application have looked for catalysts which OH radicals in the graft polymerization of cellulose, which has previously been irradiated in air, with a vinyl monomer Deactivate in an emulsion system, referring to the following theoretical Support considerations:

There are basically two ways to deactivate the "OH radicals:

(1) Deactivation by an electron donor, • according to the equation

OH + (electron donor) ->

OH- + '(electron donor),

being the newly formed radical of the electron donor should not act as a radical initiator;

(2) Deactivation by an electron acceptor, according to the equation

"OH + (electron acceptor)

OH

Gel turned out to be a jelly-like mass. It was cut into pieces and ^{washed several times with 200 cm 3 of} methanol each time by decanting in order to remove the acid contained. Subsequent to washing, the gel was dispersed in methanol, ³ to increase the concentration of alumina-silica (Al ₂ O ₃ + SiO ₂₎ to 1.2 x 10 ^-4 mol / cm. The ratio of alumina to silica in this catalyst mixture is 50:50. In this state, alumina has the activity as a catalyst for the intended purpose.

The catalyst mixtures contained in Table O with different ratios of aluminum oxide Silica, which also contains 100% aluminum oxide, was made in the same way manufactured.

(Electron acceptor) Table O

The inventors first examined the second category catalysts. These include aluminum oxide sol and alumina-silica sol. They have activated sites for accepting electrons in their molecule, on which OH radicals are attached as ligands and deactivated.

According to the invention it has now been found that aluminum oxide sol and alumina-silica sol are very effective as a catalyst for this purpose.

The invention thus relates to a process for the graft polymerization of a vinyl monomer Cellulose fibers with the help of ionizing radiation and catalytic metal compounds that characterized in that the graft polymerization is carried out in an emulsified reaction system using an alumina sol and / or alumina-silica sol as a catalyst performs.

The use of these catalysts makes it possible according to the invention to use the monomers used to use almost completely and to obtain a graft copolymer which has such small amounts of Contains homopolymer so that subsequent work-up is unnecessary.

In general, any cellulose fibers are suitable for carrying out the process according to the invention, favorable results have been achieved with high-quality rayon, natural cotton and so-called "Polynosian rayon", d. H. Fibers made from regenerated cellulose with a low swelling value, high modulus of elasticity and high wet strength.

Any vinyl monomers are suitable as vinyl compounds, such as styrene, vinyl acetate and butyl acrylate.

The invention is illustrated by the following examples and experiments.

Manufacture of a catalyst
made of alumina-silica sol

16 cm ^{3 of} aluminum oxide sol were dissolved in 120 cm ^{3 of} water and then 8 cm ^{3 of} silica sol were added with continued stirring. A commercially available aluminum oxide sol was used which contained 10% aluminum oxide and a small amount of acetic acid as a stabilizer. A commercial product was used as the silica sol which contained 20% silica and a small proportion of a mineral acid as a stabilizer. The mixture of these two substances \ vurde heated to about 5O ⁰ C until the gel was precipitated. The resulting

description 20th AS-O (comparison test) relationship AS-IO Alumina: pebbles ²⁵ AS-20 acid AS-30 0: 100 AS-50 9.1: 90.9 AS-60 20:80 30 AS-70 33.3: 66.7 AS-100 50:50 58.9: 41.1 71.5: 28.5 100: 0

Concentration of 1.2 x 10 ~ ⁴ mol / l.

Using the alumina-silica sols produced in this way the following tests were carried out.

Attempt 1

A commercially available styrene was made with a 10% aqueous sodium hydroxide solution and water washed out until the complete removal of the polymerization inhibitor contained and then purified by distillation at a pressure of 40 mm Hg.

The volume of the sodium hydroxide solution used for washing out was twice that of the too treating styrene. The purified styrene was refrigerated until just prior to testing kept.

20 cm ^{3 of} the purified styrene were ^{mixed with 180 cm 3 of} water and 1 cm ^{3 of} an emulsifier, namely polyoxyethylene sorbitan monolaurate. A product with an HLB value of 16.7 was used as the emulsifier. The above-mentioned prepared alumina-silica sol was added to this emulsion in such an amount that the alumina concentration specified in Table 1 was obtained in the emulsion. The mixture was homogenized, the homogenizer rotating at a speed of 1000 to 2000 rpm.

To remove the oxygen, the emulsion was sprayed with 99.999% nitrogen for 25 minutes blow through. There was no undesirable foam formation.

Approximately 1 gram of polynosian rayon that has been moistened to a moisture content of 12.5% was placed in a polyethylene container

and rad irradiated in the presence of air at room temperature with a radiation dose of 3.05 x 10 ^s rad / sec up to a total dose of 3 × 10. ⁶ The electron radiation from a 2 MeV resonance electron beam generator from General Electric Co. was used for this purpose.

The prepared emulsion was then placed in an evacuated vessel together with the irradiated polynosian rayon. The vessel was located in a container which was thermostatically controlled at a temperature of 50 ⁰ C. The grafting reaction took place at this temperature.

The reason why a comparatively large amount of the emulsion is required to treat the rayon is that a large amount of heat is released during the grafting reaction.

After one hour, the rayon was removed, washed with water and benzene, and then washed with benzene using a Soxhlet extractor to remove any homopolymer formed. After the benzene extraction, the rayon was washed again with methanol and then dried ^{at a temperature of 80 ° C. for 24 hours.} After this treatment, the rayon turned out to be almost absolute

ίο dry. The graft ratio was determined by weighing des Reyons determined. The resulting homopolymer was recovered and weighed in the usual way.

Similar experiments were carried out with different mixing ratios of aluminum oxide to silicic acid carried out. The results of these tests are given in Table 1.

Table 1 concentration • 100 concentration A. B. C. D. E. catalyst Al ₂ O ₃ + SiO ₂ mol / 1 of the sol in the Weight of Weight of Weight of Graft percentage Utilization Alumina emulsion _B. BA (1-0.125) emulsion Reyons in front of the Reyons after Styrene homo- sentence degree of / ■
Styrene \ · Silicic Acid Scl B-A (1-0.125) + C (mol / 1) grafting the graft polymers (%) 4.0 · ΙΟ " ³ Tatelle 2 (0.00) (s) (G) (S) (%) 4.2 2.1 · ΙΟ " ³ catalyst 1.3 · ΙΟ " ⁵ 1.0330 1.2235 7.360 35.5 5.1 AS-O 2.1 · ΙΟ " ³ Alumina 2.3 · 10- * 0.9997 1.5560 8,959 55.0 16.2 AS-IO 2.1 · ΙΟ " ³ Silica sol 8.7 10- * 1.0962 1.7415 4.068 81.9 13.9 AS-20 2.1 · ΙΟ- ³ 2.1 · ΙΟ- ³ 1.01822 1.8325 5,852 106.1 33.8 AS-30 2.1 · ΙΟ- ³ 9.0 ΙΟ- ³ 1.0127 1.9615 2.108 122 71.5 AS-50 2.1 · ΙΟ " ³ AS-100 1 5.3 ΙΟ- ⁸ 0.9834 1.5810 0.2880 84.0 59.8 AS-70 - 2 1.7 x 10- ⁵ 1.0243 1.4700 0.385 64.0 27.7 AS-100 A: At 12.5% moisture content. 3 2.3 · 10- * 1.0545 1.3440 1.075 43.6 No catalyst B: When dry. 4th 8.8 10- * C: in the dry state. 5 2.1 · ΙΟ " ³ B-A (1-0.125) 6th 9.0 ΙΟ- ³ A (1-0.125) AS-70 1 2 3 4th 5 E. 6th A. B. C. D. Utilization Weight of Weight of Weight of Graft percentage degree of Reyons in front of the Reyons after Styrene homo- sentence Styrene grafting the graft polymers (%) Cg) (G) (G) (%) 27.7 1.0545 1.3440 1.075 43.6 45.5 - 1.0983 1.3702 0.502 52.4 50.6 1.0179 1.4117 0.507 58.5 59.5 0.9987 1.4270 0.376 63.2 59.8 1.0243 1.4700 0.385 64.0 60.4 1.0098 1.4231 0.352- 61.0 35.0 1.0213 1.3353 0.818 49.3 54.2 1.0115 1.3910 0.426 56.9 65.5 1.1003 1.6891 0.332 80.0 70.8 1.0053 1.5748 0.287 79.1 71.5 0.9834 1.5810 0.288 84.0 70.9 0.9959 1.6152 0.305 85.2

The results of Experiment 1 show that the aluminum oxide sol and the alumina-silica sol are equally effective, but mixtures from aluminum oxide and silica in proportions over 50:50, especially 70:30, than am proven to be most effective.

Attempt 2

With the brines, which are designated in Table 1 with AS-100 and AS-70, tests were carried out to determine the influence of the catalyst concentration in the emulsion of the styrene monomer. The experimental conditions were completely the same as in Experiment 1. The result is shown in Table 2.

Table 2 shows that the effective range of catalyst concentration is from 10 ^-3 mol / liter to 5 x 10 -3 mol / liter and that the most favorable concentration is about 10 ^-3 mol / liter.

Attempt 3

Using an aluminum oxide-silica sol, mixing ratio 70:30 (AS-70 in Table O), an experiment analogous to Experiment 1 was carried out, but with polynosic rayon and a vinyl acetate monomer. The vinyl acetate was purified in the same way as in Experiment 1 and an emulsion was prepared ^{therefrom in an amount of 250 cm 3.} The emulsion contained:

5% vinyl acetate,. .. _ ..

0.8% of a commercially available polyoxyethylene alkylphenol ether, the HLB of which is 15.
The aluminum oxide / silica sol AS-70 (Table O) was added to the emulsion so that an aluminum oxide / silica concentration as shown in Table 3 was established in the emulsion.

Again, about 1 g of polynosic rayon with a moisture content of 12.5% was ^{exposed to electron irradiation with a total dose of 1 × 10 6} rad and brought into contact with the prepared emulsion in an evacuated vessel. The result is shown in Table 3.

Table 3 A. B. C. D. E. catalyst Weight of
Reyons in front of the
grafting Weight of
Reyons after the
grafting Weight of
formed vinyl
acetate homo-
polymers Graft Percentage Utilization
degree of styrene Alumina silica
Sol content Cg) (S) (G) (%) (%) 1.1115 1.8778 0.210 91.5 81 4.8 · 10- * 1.1263 1.7856 0.160 79.7 83 9.8 x 10- ⁴ 1.1526 1.7638 0.010 73.5 99 2.4 × 10 ^-3 1.0271 1.9675 1.06 117.0 23 No catalyst

Attempt 4

An experiment analogous to experiment 1 was carried out, but this time using a gamma ray source with the isotope cobalt-60.

A styrene emulsion with the same composition as has already been described in connection with Experiment 1, with a content of 2.4 · 10 ^-3 mol / l aluminum oxide-silica sol in a mixing ratio of 60:40 (AS-60 in Table O) was prepared accordingly. In contrast to Experiment 1, commercially available polyoxyethylene stearate with an HLB of 16.7 was used as the emulsifier.

Polynosic rayon, the moisture content of which was adjusted to a value of 11.0%, was placed in a polyethylene container and exposed to radiation from the cobalt-60 gamma ray source. The amount of radiation was 1 · 10 ⁶ r / hour. and the total dose 3 · 10 ⁶ r. The result is shown in Table 4.

Table 4

catalyst
Sol

salary

Weight of
Reyons before grafting

(G)

Weight of
polynosian
Reyons after
the graft

Weight of
educated
Acrylate homopolymer

(S)

Graft Percentage

Utilization of the
Styrene

AS-60

No catalyst

2.4 × 10 ^-3

1.0035
1.1045

1.5144
1.6750

0.123
1.905

69.8
70.5

75
28

Attempt 5

In the same way as in Experiment 1, using a catalyst made of aluminum oxide

10

Silicic acid in a mixing ratio of 60:40 on natural Cotton and high-strength rayon fibers grafted on. The test conditions and the results can be found in Table 5.

Table 5 catalyst salary A. B. C. D. E. fiber Fiber weight
before the
graft Fiber weight
after
grafting Weight of
educated
Styrene homo-
polymers Graft percentage
sentence Utilization
degree of
Styrene 5.4 x 10 (S) (S) (S) (X) (%) AS-60
no catalysis
sator 5.3 · ΙΟ " ⁴ 1.0423
1.0049 1.5610
1.4902 0.101
1.611 58.0
56.7 85
25th cotton AS-60
no catalysis
sator 1.1002
0.9763 1.4945
1.2437 0.131
1,335 49.0
39.9 79
21 High strength
Reyon

Trial 6

Butyl acrylate was grafted onto polynosic rayon in a technical pilot plant. the Butyl acrylate emulsion was prepared using the following materials:

Purified butyl acrylate 551

Polyoxyethylene sorbitan monolaurate 51

Prepared Alumina Silica

acid sol (AS-65) 41

Pure water 10361

Total 11001

The alumina-silica sol AS-65 was prepared as described above. The actual ratio of alumina to silica was 65.8: 34.2, and it contained 1 × 10 ^-4 mol / cm ³ alumina-silica. The content of alumina-silica in the prepared emulsion was 4 x 10 ^-4 mol / l. Oxygen was removed by bubbling nitrogen through it for 30 minutes at a rate of 10-20 l / min.

15 kg of polynosic rayon, the moisture level of which had been adjusted to a value of 11.0%, was divided into 30 parts and each part was placed in a small container. About 1 g of this rayon was accurately weighed. All of the Reycn was irradiated in air using the electron beam generator already used in Experiments 1, 2, 3 and 5 up to a total dose of 1.0 Mrad. After the irradiation, the individual portions were placed on supported dishes in a number of 2 or 3 parts per dish in a reaction vessel with a volume of 1 m ³ . The air in the main space of the vessel was completely replaced with pure nitrogen by evacuating and filling with nitrogen three times. After 1.5 hours had elapsed, the batch was removed, the rayon was removed from the reaction mixture and dried and weighed in accordance with the experiments mentioned above. The result is shown in Table 6.

Table 6 Share no. Weight of
Reyons in front of the
grafting Weight of
Reyon after the
grafting Graft percentage
sentence Average peel (S) (S) (%) 1
2
3 0.9036
0.9391
0.8537 1.2049
1.6448
1.4356 (33.3)
75.1
68.2 68.1 (at the bottom)
1 4th
5 0.9318
0.8662 1.5568
1.4032 67.1
62.0 2 6th
7th
8th 0.8784
0.9427
0.9147 1.4768
1.4446
1.5155 68.1
53.2
65.7 62.2 3 9
10 0.9122
0.9029 1.4794
1.5496 62.2
71.6 4th

11th 16 19 096 Graft percentage
sentence Average 6 (continued) (%) Tabel Share no. 67.1
55.9
68.5 65.2 peel Weight of
Reyons in front of the
grafting Weight of
Reyons after the
grafting 70.5
69.3 11th
12th
13th (S) <g> 58.9
61.2
74.0 66.7 5 14th
15th 0.8710
0.8893
0.8737 1.4558
1.3867
1.4720 71.9
67.4 6th 16
17th
18th 0.8741
0.8795 1.4903
1.4892 65.2
61.4
69.4 66.4 7th 19th
20th 0.8762
0.8819
0.9252 1.3927
1.4220
1.6095 71.0
65.0 8th 21
22nd
23 0.9645
0.8914 1.6577
1.4922 60.0
67.2
64.1 9 24
25th 0.8589
0.9373
0.9158 1.4189
1.5128
1.5517 51.1
50.0 58.5 10 26th
27
28 0.9084
0.8839 1.5538
1.4584 11th (top) 29
12 30 0.8866
0.8663
0.9106 1.4182
1.4478
1.4940 0.8757
0.9092 1.3234
1.3637

The following data can be derived from Table 6:

Average grafting

gradin% 64.5%

Total amount of

Homopolymer 2.87 kg

Total amount of grafted
Butyl acrylate (corresponding to

64.5% of 15 kg) 9.7 kg

Utilization 77.2%

Standard deviation in the grafting percentage less than 7%

It has been observed that, according to the invention, the formation of the undesired homopolymer actually occurs reduced to a minimum and maintained a practically reasonable rate of response will. It is known that this type of graft polymerization is carried out by ionizing radiation is accelerated.

It is therefore understood that any ionizing radiation in the method according to the present invention Invention can be used. As for the radiation dose, it is also known that at least about 1 Mrad is required to generate enough radicals which one guarantee practically reasonable reaction speed. An exposure dose of over 5 Mrad however, it results in deterioration of the irradiated fiber. The range will be from 1 to 3 Mrad considered sufficient and safe.

All experiments described above were carried out at a temperature of 50 ^0C. It is known that at temperatures below 30 ⁰ C, the reaction rate of this type of reaction is low, whereas there is a risk at temperatures above 70 ° C, that once formed, initiating radicals are easily deactivated and accordingly, the reaction is also slowed down. A vacuum operation of the reaction system is neither necessary nor recommended. The reaction can be carried out either under a neutral gas atmosphere or in vacuo. In the latter case, the main room atmosphere consists of vaporized monomer to be grafted on.

Instead of the nitrogen used in the last experiment 6 in the reaction vessel, no further use any other inert gas in the reaction system.

As for the emulsification of the reaction system, the selection of suitable surfactants can be made Meet substances by any professional. Nonionic surfactants are compatible with the Reaction system compatible.

In the experiments described above, there were Polynosian rayon, high strength rayon and natural cotton as cellulose materials and styrene, vinyl acetate and butyl acrylate as vinyl monomers to use. It is readily apparent to those skilled in the art that the method according to the present invention Invention can apply to cellulosic fibers and vinyl monomers in general.

Claims (2)

Patent claims: 1. A method for the graft polymerization of a vinyl monomer onto cellulose fibers with the aid of a ionizing radiation and catalytic metal compounds, characterized in that one can use the graft polymerization in an emulsified reaction system an aluminum oxide sol and / or aluminum oxide silica sol as a catalyst performs. 2. The method according to claim 1, characterized in that the catalyst is in the emulsified reaction system in an amount of 10 ~ ⁴ to 5 · I ³ mol / l, based on the emulsion.