Modification polydimethylsiloxane rubber

 

(57) Abstract:

Describes how photochemical modification polydimethylsiloxane rubber irradiation with ultraviolet light with the introduction of the reagent, forming an active group, namely, that the irradiation with ultraviolet light is carried out in the presence of photoinitiator, which is used as carbonyl-containing organic compounds of a number of aromatic ketones and quinones, in the amount of 0.001 to 0.01 mol per 1 kg of rubber, at a temperature of 50-150oC for 30-90 min in an atmosphere of oxygen, as a reagent, forming an active group, use the oxygen and additionally carry out the substitution educated active groups by reacting with oxygen - or nitrogen-containing replacement reagent, which use compounds of the classes of amines, amino acids, hydrazines, alcohols and arteparon. The technical result is to obtain polydimethylsiloxane rubber with predetermined structure and properties. table 1.

The invention relates to methods of modifying polydimethylsiloxane rubber, not having in its composition of active groups, UV light and can be used in the active silicon-containing polymers, polymeric adsorbents, etc.

It is known that modification of polymers, including siloxane rubbers, by introducing into the composition of the macromolecule additional groups, is an effective method of its physico-chemical and biological properties, mechanical properties.

However, the absence of macromolecules polydimethylsiloxane polymers of active groups, makes it much harder for their modification. Available metal group is chemically inert and well withstand high temperatures. The number of terminal hydroxyl groups in the high molecular polydimethylsiloxanes the rubber very little in order to use them for modification of polymers. Therefore, the modification is carried out at the stage of synthesis by copolymerization dimethylsiloxane siloxane monomers with monomers that already have other substituents, which leads to significant costs.

Direct methods of inoculation ready purely polydimethylsiloxane polymers is very small. These include the direct modification polydimethylsiloxane polymers under the action of radiation.with. The USSR 176069, bull. Fig., 1965, 21), allowing the vaccine to islote.

Its disadvantages include the possibility of modifying only the low molecular polydimethylsiloxane polymers only some unsaturated compounds, the use of hazardous and require serious protection measures radiation.

Known photochemical oxidation polydimethylsiloxane polymers. However, in practice, the oxidation siloxane rubber has always been regarded as detrimental, leading to deterioration of the performance properties of polymers (Israeli, Y., etc. Photooxidation of polydimethylsiloxane oils. 3. Effect of dimethylene groups. Polym. Degrad. and Stab.,. 1993, V. 42, 3, R. 267-279; Kuzminsky A. S., Sedov centuries Chemical transformations of elastomers. M.: Chemistry, 1984, S. 160-177).

The closest technical solution is the modification polydimethylsiloxane rubber (patent US 2522053, published. 1950), which is that the modification is carried out by irradiation with UV light through the introduction of labile group, in which chlorine is used. When this occurs, the replacement of part of the hydrogen atoms of a metal of groups to chlorine.

The disadvantages of this method of modification is the difficulty of control of the chlorination process, because in the process of modification can be formed as a group CH2Cl, the Fort worth, their hydrolysis and others) cannot be meaningfully substituted for oxygen and nitrogen-containing substituents, consequently, in a further modification it is impossible to obtain polymers with predetermined structure and properties; partial degradation of the polymer siloxane bond as a result of selection during the reaction hydrogen chloride, resulting in complication of the further processing of the rubber due to the need for additional curing; possibility of application of the method only for low molecular weight polydimethylsiloxanes, because the process is carried out by passing chlorine gas through a layer of liquid polydimethylsiloxane and for its successful completion requires a good mixing of the mixture.

The objective of the proposed invention is to provide polydimethylsiloxane rubber with predetermined structure and properties by introducing into the molecule polydimethylsiloxane polymer oxygen - and nitrogen-containing groups from a wide range of replacement joints.

Objectives of the invention are also expanding class of modified rubbers and simplification of processing.

The task is solved by the fact that when carrying out the method sausage active group, features irradiation with ultraviolet light to hold in the presence of photoinitiator, which is used as carbonyl-containing organic compounds of a number of aromatic ketones and quinones, in the amount of 0.001 to 0.01 mol per 1 kg of rubber, at a temperature of 50-150oC for 30-90 min in an atmosphere of oxygen, as a reagent, forming an active group, it is proposed to use the oxygen and further substitution educated active groups by reacting with oxygen - or nitrogen-containing replacement reagent, which use compounds of the classes of amines, amino acids, hydrazines, alcohols and arteparon.

Data on the possibilities of practical application of oxidation for the modification of structure and properties polydimethylsiloxane rubbers are missing.

The proposed mechanism modification polydimethylsiloxane rubber includes the following stages:

- the absorption of carbonyl group of photoinitiator quantum of light, with its transition to the triplet-excited state (see figure 1 at the end of the description);

lead by the excited molecule photoinitiator of a hydrogen atom from the methyl group of the macromolecule polydymite castilnovo - for aromatic ketones) and subsequent recombination of macroradicals with the formation of crosslinking (see diagram 2 at the end of the description).

The products of photolysis of the initiator in the future participate in the secondary photochemical reactions:

photochemical oxidation links-CH2-CH2up-CH2-CO-. In figure 3 (at the end of the description) it is shown that oxygen is a reactant for the formation of an active carbonyl groups C=O in the macromolecule polydimethylsiloxane rubber. Mechanism (a) oxidation goes together with stitching. Mechanism (b) oxidizing agent is singlet oxygen, generated by energy transfer from the excited state of the initiator In.

Stage 1-3 occur simultaneously during irradiation polydimethylsiloxane rubber UV light in the presence of photoinitiator and oxygen.

Subsequent chemical treatment of the oxidized polydimethylsiloxane rubber to replace the active carbonyl groups at various oxygen - and nitrogen-containing substituents is in interaction with the replacement reagent (see schemes 4 and 5 at the end of the description).

The degree of oxidation, and hence the content of the groups of deputies, took the initiator.

Substitution of carbonyl groups in oxidized polydimethylsiloxane polymers is output, close to quantitative.

The lower bound concentration photoinitiator due to the minimum necessary quantity to achieve the required concentration of carbonyl groups. With the increase of its concentration above the upper limit, the part of the initiator remains unspent.

Temperature in the range from 50 to 150oSelected to achieve compatibility of the used photoinitiators with polymer matrix. At lower temperatures there is a loss of the initiator of the polymer matrix in the form of the characteristic for each connection crystals, accompanied by a reduction in the rate of oxidation. Higher temperature increases the rate of oxidation, resulting in wasteful power consumption.

The selected exposure time due to the necessity to accumulate the required number of carbonyl groups. At low exposure times their number is small, at high - begins their photochemical decay.

As polydimethylsiloxane polymers used heat-resistant siloxane rubbers SKT: liquid SKT-A (average mo is popular weight 560 thousand .E.) without pre-treatment.

The method is as follows.

Example 1. To 20 g of a 15% solution of siloxane rubber SKT in toluene add a solution of 7.0 mg of 2-ethyl-anthraquinone in 1 ml of toluene. The mixture was thoroughly stirred. The concentration of 2-ethyl-anthraquinone is 0.001 mol per 1 kg of rubber. The mixture is applied to glass cell equipped with bumpers in one layer by drying for 3 h at room temperature. The amount of the applied mixture is 330 mg/cm2. After drying, the layer thickness of the dry polymer is 0.5 mm (with a precision of 5%). The dried samples exposed to the full light of the lamp, medium-pressure tank-1000, temperature-controlled cells, placed at a distance of 25 cm from the lamp in the presence of oxygen at a temperature of 100oWith over 90 minutes of Film of the oxidized polymer with a substrate placed in a 5% solution of 2,4-dinitrophenylhydrazine in 1,2-dimethoxyethane and heated at 100oC for 3 hours the Solution is poured, separated from the substrate film 4 times washed with hot suitable solvent and dried in one day at room temperature. The content of carbonyl and replacing them groups is determined using methods infer the target siloxane rubber SKT-And add toluene solution of 6.7 mg of 2-methyl-anthraquinone in 1 ml of toluene. The mixture was thoroughly stirred. The concentration of 2-methyl-anthraquinone is 0.01 mol per 1 kg of rubber. The mixture is applied on Metalocalypse cell, equipped with bumpers in one layer by drying for 3 h at room temperature. The amount of the applied mixture is 330 mg/cm2. After drying, the layer thickness of the dry polymer is 0.5 mm (with a precision of 5%). The dried samples exposed to the full light of the lamp, medium-pressure tank-1000 in temperature-controlled cells, placed at a distance of 25 cm from the lamp in the presence of oxygen at a temperature of 50oWith over 60 minutes of Film of oxidized polymer together with the substrate is placed in a 2% solution of paraphenylenediamine in toluene and heated at 100oC for 3 h in Toluene solution is drained and precipitated from it the rubber by addition of acetone. Released a modified rubber is separated from the solution and double distilled presidenial acetone from solutions in pure toluene. Cleaned the rubber is separated from the solution, washed with acetone and dried at room temperature during the day. The content of carbonyl and replacement of the group is determined using the methods of infrared, ultraviolet spectroscopy and chemical methods of analysis.

their quantitative content, temperature and time regimes of oxidation reagents and solvents used for replacement of the carbonyl groups of substitute groups and content of substitute groups.

The advantages of this modification polydimethylsiloxane rubbers are:

- the possibility of introducing in the composition of the macromolecule polydimethylsiloxane rubber large range of oxygen and nitrogen-containing groups, which allow you to obtain a modified rubber with a wide range of specified properties. The introduction of the polymers of amino acid groups may obtain biologically active polymers, amino - polymer ion-exchange polymers, nitroaniline groups of redox polymers, etc.;

- no degradation of the polymer, facilitating the isolation and purification of the obtained polymers, as well as their further processing;

- possibility of control over the modification process, because the oxidation with the formation of carbonyl groups is subject only to group-CH2-CH2- links. The content of the groups-CH2-CO - easily identified by electronic and infrared spectroscopy. Substitution of carbonyl groups on the other deputies proceeds with the output b is high permeability polydimethylsiloxane rubber allows oxidation in a heterogeneous environment without the use of a good mixing, and the substitution of carbonyl groups to other groups rather partial swelling of rubbers used in solvents. Thus, widen the range of modified rubbers.

The way photochemical modification polydimethylsiloxane rubber irradiation with ultraviolet light with the introduction of the reagent, forming an active group, wherein the irradiation with ultraviolet light is carried out in the presence of photoinitiator, which is used as carbonyl-containing organic compounds of a number of aromatic ketones and quinones, in the amount of 0.001 to 0.01 mol per 1 kg of rubber, at a temperature of 50-150oC for 30-90 min in an atmosphere of oxygen, as a reagent, forming an active group, use the oxygen and additionally carry out the substitution educated active groups by reacting with oxygen - or nitrogen-containing replacement reagent, which use compounds of the classes of amines, amino acids, hydrazines, alcohols and arteparon.

 

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