DE1545126C3 - Gel-shaped polymers and processes for their production - Google Patents

Description

R ₃ R ₄

and or

It is known to convert monomers, oligomers or polymers by means of chemical processes via carbon-carbon bonds to network. It is also known that crosslinking occurs via radical intermediates and that ionizing radiation can generate radicals. Furthermore, from the Medical research known a measurement method in which the effect of ionizing radiation on the Crosslinking of polyethylene oxide is determined. , ο The nature of the substances involved was not examined.

The object of the invention is the production of polymeric substances, the crosslinking carbon-carbon bonds contained in the α-position to the oxygen of ether groups.

The substances according to the invention consist of gel-like Polymers composed of structural units of the general formulas linked to one another

^R 2

where the radicals R ₁ , R ₂ , R ₃ and R _{4 are} hydrogen atoms or where one of the radicals R ₁ and R ₂ and / or one of the radicals R ₃ and R _{4 is} a methyl radical, the other radicals are hydrogen atoms, and the end groups are identical or different, and are hydrogen atoms and / or methyl radicals, characterized in that they have been produced from an aqueous solution of polyethylene oxide and / or polypropylene oxide with respective molecular weights of 200 to 10 · 10 ⁶ by exposure to ionizing radiation.

2. A method for producing gel-like polymers according to claim 1, characterized in that an aqueous solution of polyethylene oxide and / or polypropylene oxide with respective molecular weights of 200 to 10 ■ 10 ^{6 is} exposed to ionizing radiation.

3. The method according to claim 2, characterized in that polyethylene oxide with a molecular weight of 1 ■ 10 ⁵ to 3 · 10 ^{6 is} used as the starting material.

4. The method according to claim 2 or 3, characterized in that an at least 2% aqueous Solution is irradiated.

5. The method according to any one of claims 2 to 4, characterized in that ionizing radiation with a dose of at least 5.2 · 10 ⁵ "rad" is used for irradiation.

25 c —c —o

H
H

I.
c - c - o-

R ₃ R ₄

and or

where the radicals R ₁ , R ₂ , R ₃ and R _{4 are} hydrogen atoms or where one of the radicals R ₁ and R ₂ and / or one of the radicals R ₃ and R _{4 is} a methyl radical, the other radicals are hydrogen atoms, and the end groups are identical or different, and hydrogen atoms and / or methyl radicals are and are characterized in that they have been produced from an aqueous solution of polyethylene oxide and / or polypropylene oxide with respective molecular weights of 200 to 10 · 10 ⁶ ionizing radiation.

Ionizing radiation whose dose is at least 5.2 · 10 ⁵ rad is particularly suitable.

In the context of the present invention, the term "ionizing radiation" is used on alpha- and

beta particles, x-rays and gamma rays, as well as electrons from Van de Graff and others

'' Applied high voltage accelerators.

Alpha and beta particles, which have a sufficiently high energy content to be removed from atoms or Detaching shell electrons from molecules causes a direct ionization of these atoms or molecules.

Gamma rays and X-rays are sufficient-

: the energy cause indirect ionization by adding they knock electrons out of atoms or molecules. These secondary electrons in turn can in turn have an ionizing effect on the type of beta particles.

: When interacting with ionizing radiation

hydrogen or hydroxyl radicals can be generated with water, which with certain organic

; niche connections can react. A general reaction is the detachment of a hydrogen atom by such radicals, where H ₂ O and

: a carbon radical can arise. Two of these ], Carbon radicals can create a new carbon

f form a carbon bond or carbon bond.

After the start of the irradiation, the starting solution generally shows an initial decrease in viscosity. As the irradiation progresses, the The viscosity of the solution rises above the initial value again, and with further irradiation the values according to the invention macromolecular, gel-like polymers formed.

The initial drop in viscosity is presumably due to initial degradation phenomena or to a crosslinking which changes the shape of the molecule while reducing the molecular volume. As the number of crosslinked molecules increases, the viscosity of the starting solution begins to increase.
As the irradiation continues, the number of carbon-carbon crosslinks increases and the starting solution is converted into an insoluble gel-like product. The structure of the macromolecular gel-like product consists of polymers of the starting materials that are cross-linked intra- and / or intermolecularly in the structure shown above. Water can be reversibly retained in the interstices of the resulting high molecular weight substance. In addition, the crosslinked structure can contain interwoven starting polymers which are not included in the crosslinking but are so interwoven with the crosslinked structure that they remain essentially insoluble.

The water can be removed from the structure by various methods, for example by Evaporation, whereby a tough, elastic material is obtained, which reversibly absorb water again can, and in such amounts that the initial absorption capacity of the from with continued Irradiation obtained gel-like material approximately equal. The delivery and admission of water through the polymer can be repeated as often as desired in a reversible manner.

Suitable starting materials for the process according to the invention are those compounds which Contain ether bonds such as:

Copolymers of ethylene oxide and propylene oxide which each contain hydrogen, alkyl or alkyl-substituted end groups and in which the ethylene oxide polymer content in the copolymer is between 50 and 75%,
Polypropylene glycol, polyethylene glycol, ethylene polymers with molecular weights from 200 to 10 · 10 ⁶ and

Alkyl and dialkyl ethers of polyethylene glycol.

The infrared spectrum of the anhydrous polymers shows that the cross-links predominantly occur

ίο carbon atoms in α-position to the ether oxygen atoms have taken place. Shifts and intensities of corresponding bands also show that under the conditions preferably used, about every 1000th repeating unit of the starting polymer has been networked.

Particularly good results are obtained when the aqueous starting solutions are free from "radical scavengers" are. The term "radical scavenger" denotes those substances that deal with the reactive Reacting agent that is produced by the irradiation of water and / or substances that react with the organic radicals formed during this process react. Although very pure water that is preferred solvent for the starting solution, affects the presence of small amounts of "radical scavengers" the feasibility of the method according to the invention is not negative; the "radical scavengers" namely react at an early stage of irradiation and may be consumed, so that the desired crosslinking reaction can then proceed unhindered.

An example of a "radical scavenger" that can react with hydrogen atoms and / or organic radicals is molecular oxygen. According to the invention, however, the exclusion of oxygen is not necessary, since the oxygen is consumed after a short time and the crosslinking of the carbon radicals can proceed unhindered.
Obviously, the pH of the solution is not critical to the practice of the process of the invention, although the time required to form the gel-like material can be reduced considerably by using a starting solution having a pH of 7.0.

The temperature is obviously not critical for the feasibility of this process either, because the gel-like material in solutions with temperatures just above freezing point up to it is formed at the boiling point of the starting solution.

The amount of radiation absorbed, ie the dosage, is given in »rad«. One "rad" corresponds to an absorption energy of 100 ergs per gram of treated material.
The gel-like polymer of the present invention is useful as a humectant. The crosslinked, but still soluble substances are of the same use as the dissolved starting material and can also be used as an intermediate product for the production of the gel-like polymer.

When irradiating ethylene oxide polymers by the process according to the invention, preference is given to using polyethylene oxide with a molecular weight of 1 · 10 ⁵ to 3 · 10 ^b , an aqueous starting solution with at least 2.0 percent by weight

fts polyethylene oxide and irradiation of the starting solution with a total irradiation dose of at least 5.2 · K) ³ "rad" used to produce the gel-like material.

5 6

Table I contains a list of the results obtained when irradiating ethylene oxide polymers different molecular weights were obtained under different conditions.

Table I.

Molecular weight Concentrate,
Weight percent the atmosphere Type of
Irradiation Dosage in
wheel 10 ⁶ Weight percent
H ₂ O in the gel-like
material '-3.0 10 * 2.6 N ₂ roentgen 0.1 97.4 -3.0- 10 ⁶ 2.6 N ₂ roentgen 2.0 98 -3.0- 10 * 2.0 air gamma 1.6 98 -3.0 ■ 10 ⁶ 2.0 air gamma 6.3 brittle gel -3.0- 10 * 2.5 air gamma 1.9 96.5 -3.0 · 10 ⁶ 2.0 air gamma 0.5 97.7 -3.0 · 10 * 0.5 air roentgen 0.3 99 -3.0 · 10 ⁵ 3.0 air roentgen 1.0 98 -3.0 · 10 ⁵ 0.5 air roentgen 3.0 99 -3.0- 10 * 2.0 air e ~ 0.67 98

The gel-like material obtained by irradiating ethylene oxide polymers can under Dehydration can be dried. As it dries, the gel-like material gradually shrinks and goes if necessary in a tough, elastic material of light color. The anhydrous mass is in water and various organic liquids such as methanol, benzyl alcohol, formic acid, acrylic acid, Benzene, nitrobenzene, chlorobenzene, m-cresol, o-nitrotoluene, pyridine, morpholine, chloroform, 2-nitropropane and dioxane insoluble.

Table II contains the dosage and viscosity of a homogeneous aqueous solution which contained 0.2 percent by weight of polyethylene oxide with an approximate molecular weight of 3 · 10 ⁵ . The solution was irradiated with gamma rays in an atmosphere of air. After dilution of the irradiated sample of a concentration of 2.0 to 0.2 weight percent of the viscosity measurements were performed with a Hoeppler viscometer according to the falling ball method at 30 ⁰ C.

Table II

Dose in »rad« · 10 ⁴ Viscosity in centipoise 0.0 1.16 2.38 1.03 7.59 0.94 12.5 0.96 49.6 0.93 22.2 1.12 62.6 gel-like

To further illustrate the scope of the invention, a copolymer consisting of 75 weight percent Ethylene oxide and 25 percent by weight propylene oxide, in a homogeneous aqueous solution irradiated with gamma rays until a gel-like material was formed. The total dose was approximately 15.6 · 10 * "rad".

Claims (1)

Patent claims: 1. Gel-like polymers composed of structural units of the general types linked to one another Formulas c —c —ο C-O