DE4414773A1 - Processes for stabilising vinylic monomers against uncontrolled polymerisation, and protected surfaces - Google Patents

Abstract

Processes for stabilising vinylic monomers against uncontrolled polymerisation during preparation, transport and storage by addition of a polymerisation inhibitor are characterised in that the polymerisation inhibitor used is a fullerene, reaction products of a fullerene with a dienophile, or a mixture of fullerenes and/or reaction products of fullerenes with dienophiles, nucleophiles or halogens; surfaces, in particular metal surfaces, can be coated with the fullerene products, in particular by vapour deposition.

Description

The present invention relates to a method for stabilizing vinylic monomers against uncontrolled polymerization in Her positioning, transport and storage by adding a polymerization inhibitors. The invention further relates to preventive measures the growth of polymers on surfaces, especially those that come in contact with vinyl compounds. Finally, the concerns Invention also a special method for coating upper surfaces.

Vinylic monomers are used worldwide to make polymers, preferably by radical polymerization for a variety of Applications. Only thermoplastic are examples here Materials, dispersions for paints and coatings, detergents called additives and baby diapers.

Because vinyl monomers for spontaneous and uncontrolled polymerization tendency, which can lead to an explosive reaction Take precautions to prevent uncontrolled polymerization reactions in the production, storage and transport of vinyl Avoid monomers.

Not only explosive polymerization reactions are to be avoided, but also undesirable polymerization reactions, such as those in the  Purification of vinyl monomers, e.g. B. by distillation can occur.

After all, premature polymerization is also imperative in systems wishes to contain vinyl monomers; are only exemplary here Called pressure plates.

The stabilization of vinyl monomers against the above Reactions and effects by adding so-called polymerization Inhibitors are known per se, known polymerization inhibitors are Kerobit and phenothiazine, to name just two examples. The Stabili The effect of the known polymerization inhibitors is not, however always given to a sufficient extent.

The present invention was based on the object, a Ver drive to stabilize vinylic monomers through which vinyl monomers reliably prevent premature Polymerization can be protected.

This object is achieved in that as a poly merization inhibitor a fullerene, reaction products of a fullerene with a dienophile or a mixture of fullerenes and / or conversion products of fullerenes with dienophiles, nucleophiles or Halogens used.

Another object of the invention is the use of Above-mentioned fullerene products for coating in particular metallic surfaces and in a process for coating in particular metallic surfaces by vapor deposition one or more of the above fullerene products on the  surface concerned, as these items in the claims are defined.

Finally, the subject of the invention is a vessel or pipe arrangement as defined in the claims.

Fullerene C _60-70 as such and processes for its production are known _per se and, for. B. from Krätschmer et al. in Nature, Vol. 347, p. 357 (1990) or by Huffmann and Krätschmer in WO 92/04279.

In principle, all compounds are to be mentioned as vinyl monomers, which has a vinyl double bond of the general formula in the molecule

CH₂ = CH-R

have, where R is halogen or an organic radical can.

Examples include only styrene, acrylic acid and methacrylic acid as well their esters, vinyl esters of alkane carboxylic acids such as vinyl acetate, vinyl propionate etc., vinyl halides such as vinyl chloride and vinyl bromide, and Vinylacetonitrile mentioned as the most technically significant ones too Polystyrene, polyvinyl acetate or polyvinyl chloride or general Po ly (meth) acrylates are implemented. In addition, N-Vinylfor mamid and N-vinylpyrrolidone technically widespread products.

According to the process of the invention, the fullerene C _60-70 or its reaction products with dienophiles, nucleophiles or halogens (hereinafter referred to as fullerene inhibitor) is added to the monomer to be stabilized before uncontrolled polymerization occurs. This can take place during the production of the monomer itself or immediately before storage or transport.

In addition to fullerenes themselves, mixtures of different fullerenes can also be used and / or reaction products of fullerenes with dienophiles like them also used in Diels-Alder reactions, or implementation products with nucleophiles or halogens.

Corresponding compounds are known per se to the person skilled in the art, here are only exemplary maleic anhydride as dienophile and nucleophiles Thiols and amines, e.g. B. morpholine and 1,4-phenylenediamine and as Halogen called bromine or chlorine, with bromine being preferred.

The implementation of fullerene with these compounds takes place in all generally in a molar ratio of 1: 1 to 1:50, preferably 1: 1.5 to 1:10 and can be carried out in solution (e.g. in benzene) or in bulk. The temperatures used here are in general in the range from 20 ° C to 200 ° C and the reaction times in the range from 0.2 to 100 hours, preferably 2 to 30 hours.

In general, the amounts added are from 0.1 to 5000 ppm on the vinyl monomer, a sufficient stabilizing effect achieved; the required addition amount in individual cases depends of course to stabilize monomers.

The fullerene inhibitor is preferably used in amounts of 2 to 200 ppm used.  

In the following examples the stabilizing effect various polymerization inhibitors according to the so-called called isoperibolic calorimetry, which the specialist in Principle is known.

The vinyl monomer of interest is placed in a calorimeter together with the other recipe components (initiators, solvents and possibly auxiliary substances) and the inhibitor (kerobite, phenothiazine or fullerene C _60-70 ) and heated to a certain temperature.

With the beginning of the initiator decay, the radicals formed try To start polymerization.

With the start of polymerization, the heat of reaction released heats the Approach on.

From the period between the heating up of the batch and the beginning of the Polymerization (= inhibition time) allows the amount and, if known amount used, the effectiveness of the polymerization inhibitors determine.

According to the method preferred according to the invention, fullerene pro Products evaporated on metallic surfaces in particular. If those are brought into the corresponding systems, this constitutes a Measure represents the use of vinyl monomers in chemical plants and warehouses are reliably protected against premature polymerization.

Thermal evaporation of the fullerenes is particularly suitable for producing the layers according to the invention. The starting material in solid form is preferably introduced into an evaporator vessel and applied to the metal surface to be coated in a pressure range between 10 ^-6 bar and 10 mbar and a temperature range between 200 ° C and 500 ° C. The thickness of the applied layer is in particular in the range between 1 nm and 100 μm. It is possible according to the invention to pretreat the metal surface in order to improve the adhesiveness of the applied layer. The pretreatment can consist of a wet chemical treatment, a plasma treatment, a UV treatment, an ion bombardment treatment or a combination of these methods. The temperature of the substrate during the treatment can be kept between room temperature and 400 ° C.

example 1

Acrylic acid was added in an amount of 10 g with four times the amount of the inert solvent toluene, in which 2,2′-azobis-2,4- valeronitrile and the respective inhibitor were dissolved, mixed and in a plastic calorimeter reaction vessel is transferred and the Approach heated to 60 ° C.

The radical starter was activated by the temperature increase and formed radicals that started the acrylic acid polymerization.

This released heat of polymerization, which heated the reaction vessel.

The temperature change over time is plotted in FIG. 1 for a test without the addition of an inhibitor, a test with the addition of the inhibitor phenothiazine used hitherto and a test with the addition of C _60-70 fullerene. The longer inhibition time shows the significantly higher effectiveness of the C₆₀ fullerene at the same mass concentration. While one molecule of phenothiazine is able to trap 0.25 radicals, one molecule of C₆₀ fullerene can trap 3.5 radicals.

Example 2

Using the method described in Example 1, 1 part was 2-hydroxy ethyl acrylate, mixed with 0.5 mol% (based on the monomer) of Free radical generator 2,2'-azobis-2,4-valeronitrile, with 4 parts of a toluene Solution of the inhibitor to be examined added and polymerized.

2 shows the measured temperature profiles with the common inhibitor phenothiazine and with C _60-70 fullerene compared to a test without the addition of an inhibitor. While the addition of phenothiazine showed almost no inhibitory effect, C _60-70 fullerene is very effective as an inhibitor: from the measured duration of inhibition, it can be calculated that a molecule C _{60-70 captured} about 5.3 radicals.

Example 3

The polymerization of five very reactive monomers was examined in the presence of the inhibitors phenothiazine (PTZ, Thiodiphenylamine, C₁₂H₉NS) and Kerobit and in the presence of with the method described in Example 1. The results of the sub searches are summarized in the table (including the results nisse of Examples 1 and 2).  

Table 1

Effectiveness of inhibitors with fast monomers

Table 1 shows that C _{60-70 is} a more effective inhibitor for all monomers than the previously used inhibitors phenothiazine or kerobite BPD.

Example 4

The polymerization of acrylic acid in bulk was examined in the presence of the inhibitor used hitherto and in the presence of fullerene C _60-70 derivatives using the method described in Example 1.

Table 2

Efficacy of inhibitors in acrylic acid polymerization

As Table 2 shows, the fullerene derivatives are in acrylic acid polymerization more effective inhibitors than the previously used Phe nothiazine.

To demonstrate the inhibitory effect of the fullerene coating in the next example, the vinyl monomer of interest together with the other recipe components (initiators, solvents, etc.) and the with the fullerene coated surface in the reaction vessel of the Calorimeter introduced. In the opening of the reaction vessel  multi-pierced guide inserted. Through the middle hole a thermocouple in the middle of the reaction mixture. By a hose is run through a side hole to the bottom of the vessel through which the reaction approach for removing oxygen with stick fabric is fumigated. Is enough nitrogen passed through the batch the hose is pulled out of the neck and the Gas space of the reaction vessel is gassed with protective gas.

For the polymerization, the prepared reaction vessel is placed in the Ther immersed in mostaten liquid that the opening of the reaction vessel ßes above and the liquid level of the approach below the liquid level of the thermostat fluid. Since the thermostat on the the desired reaction temperature is preheated, the batch heats up, initiator decay begins or at sufficiently high temperatures radicals are formed from the monomers themselves, and the ones formed Radicals try to start the polymerization.

With the start of polymerization, the heat of reaction released heats the Approach on. The temperature rise is caused by the thermocouple in the reak tion vessel registered. Because the surrounding thermostat temperature is constant is held, heat flows out of the vessel. The temperature difference continues to rise as long as H. the temperature in the reaction vessel rises (if necessary up to and above the boiling point of monomers and / or Solvent), as the heat generation by the reaction is greater than the heat dissipation. If the heat production rate drops towards the end of the reaction, the temperature in the reaction vessel also drops.

From the period between the heating up of the batch and the beginning of the Polymerization (= inhibition time) can prevent the polymerization Determine the effect of the coated surface.  

Example 5

A stainless steel tube is placed in the reaction vessel of the isoperibolic calorimeter. Placed platelets, the vessel filled with monomers (acrylic acid or 2-hydroxyethyl acrylate) until the plate is covered with monomers and immersed in the thermostats. The thermostat is at a temperature preheated, which is a thermal polymerization of the respective monomers causes (acrylic acid 120 ° C, 2-hydroxyethyl acrylate 140 ° C). Detected is how the start of polymerization is delayed if one with fullerene C₆₀ coated stainless steel plate is introduced. For comparison is the time of start of polymerization with uncoated stainless steel plate Chen applied.

Table 3

Thermal polymerization delayed by a fullerene C₆₀ coating

Table 3 shows that the thermi chemical polymerization is either completely prevented (acrylic acid) or starts at least with a considerable delay (2-hydroxyethyl acrylate). An insult tion of product wetted parts in the column with fullerene C₆₀  therefore suitable the average operating time of the distillation column extend for monomers.

Claims (9)

1. A method for stabilizing vinyl monomers against uncontrolled polymerization during manufacture, transport and storage tion by adding a polymerization inhibitor, characterized in that a polymerization is a fullerene, reaction products of a fullerene with a dienophile or a mixture of fullerenes and / or Reaction products of fullerenes used with dienophiles, nucleophiles or halogens. 2. Use of fullerene C _60-70 , reaction products of a fullerene with a dienophile or a mixture of fullerenes and / or reaction products of fullerenes with dienophiles, nucleophiles or halogens as a polymerization inhibitor. 3. Use of fullerene products from the group of fullerenes C _60-70 , reaction products of a fullerene with a dienophile or a mixture of fullerenes and / or reaction products of fullerenes with dienophiles, nucleophiles or halogens for coating, in particular, metallic surfaces. 4. Use of fullerene products from the group of fullerene C _60-70 , reaction products of a fullerene with a dienophile or a mixture of fullerenes and / or reaction products of fullerenes with dienophiles, nucleophiles or halogens as a protective layer on a surface, in particular a metallic surface, the without this protective layer would come into contact with vinyl compounds, in particular with reaction mixtures containing vinyl monomers. 5. Use according to claim 4, characterized in that the Fullerene product as a protective layer on the inside of a container Polymerization reactor or its feed lines at the Polymerisa tion of vinyl monomers is used. 6. Use according to claim 4, characterized in that a device coated with the fullerene product part is manufactured. 7. A method for coating metallic surfaces, characterized in that a fullerene product from the group of Ful leren C _60-70 , reaction products of a fullerene with a dieno phil or a mixture of fullerenes and / or reaction products of fullerenes with dienophiles, nucleophiles or Haloge NEN evaporates and the generated steam is deposited on the metal surface to be coated. 8. The method according to claim 7, characterized in that vessels or pipes are steamed inside with the fullerene product. 9. vessel or tube arrangement with an inside, which is provided for the contact with reactive materials, in particular vinyl compounds, characterized in that at least a region of the inside with fullerene products from the group of fullerene C _60-70 , reaction products of a fullerene is coated with a dienophile or a mixture of fullerenes and / or reaction products of fullerenes with dienophiles, nucleophiles or halogens.