DE1745005A1 - Process for the production of foils or sheets from copolymer foam - Google Patents

Description

Description

on the patent application of Imperial Chemical Industries Limited, London, S.W.1.,

concerning:

Process for the production of foils or sheets from copolymer foam

The priority of filing in Great Britain on October 28, 1966 is used

The invention relates to a method for the production of foils or plates from Gopolymer foam.

In the related British patent applications 18 329/65 and 2 281/66 of the applicant, a method is described that consists in being a mixture of styrene and maleic anhydride when the mixture is forced to move forward, it is copolymerized that this mixture before or during the polymerization or the copolymer formed therefrom, a blowing agent is added and that the resulting product is pressed through such a nozzle that it is formed into a sheet or sheet of copolymer foam. In the preferred process, the reaction is carried out in an extruder, since this makes it an expedient one Procedure is given. However, an extruder is a relatively expensive piece of equipment, and it is a goal of the invention to make the most economical use of the extruder. Another object of the invention is to improve the temperature control of the process during the polymerization in the extruder.

According to the invention, a method for the production of foils or sheets from copolymer foam is proposed, which consists in extruding a copolymeric mass and a blowing agent through a sheet-forming or sheet-forming nozzle, the copolymers being extruded characterized mass-2 ^ ago is found that a solution of the monomeric constituents ¹ share ^ is consisting formed from styrene and maleic anhydride in a is> liquid which is a solvent for the monomeric constituents and does not exert any inhibitory effect on the copolymerization, that the copolymerization is carried out and that at least part of the liquid is evaporated from the resulting coopolymer mass during the forced forward movement of the same in an extruder with a steam vent. BATH ORIGINAL

Liquids are preferably used which are either good solvents for the resulting copolymer, i.e. those that keep the whole copolymer in solution under the operating conditions, or the poor solvents for the represent the resulting copolymer, i.e. which precipitate essentially all of the copolymer from solution as it is formed. In the latter case it is essential that the copolymer remain in suspension. It is unfavorable if the copolymer is a has limited solubility in the liquid, since then the copolymer particles that are precipitated from the solution, tend to clump together making them sticky To form mass.

Examples of liquids that are good solvents for the copolymer include aliphatic ^, cycloaliphatic and aromatic ketones with up to 8 carbon atoms, such as acetone or methyl ethyl ketonate, and as examples of liquids which are poor solvents for the copolymer, one can Mention aromatic hydrocarbons such as benzene, toluene or one or more xylenes. The liquid can be a mixture of two or more solvents as long as the mixture is either a good or a very bad one Represents solvent for the copolymer in the sense mentioned above.

The boiling point of the liquid used according to the invention should preferably be below 20O ⁰ C so that the liquid can be easily removed from the extruder. The boiling point of the liquid should preferably also be at a value such that no excessively high pressures arise in a closed vessel that may be used under the temperature conditions of the process. This avoids the use of expensive pressure vessels. A very suitable liquid is methyl ethyl ketone, which boils at about 80 ° 0.

The polymerization can be carried out entirely in an extruder. In such a case, the control of the reaction is very easy because of the dilution achieved by the dissolving liquid. It is also possible to carry out the polymerization in another vessel or in other vessels outside the extruder until the reaction has progressed well or even if it is not preferred

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is accomplished. Such a vessel can be, for example, a use a simple container equipped with an agitator and cooling jacket or a number of such containers, the unpolymerized monomers in solution in the dissolving liquid to such a container or the first container of such a row. If neither the solvent or one of the monomers has a particularly low boiling point, you need these simple containers not to be designed to withstand pressures greater than substantially atmospheric pressure can. If a liquid is used that is a good solvent for the copolymer, the viscosity is of the mixture in reaction is far less than if no solvent is used, and if the Liquid is a very poor solvent for the copolymer, the resulting slurry is light to handle, so that in both cases the polymerization to a high degree of conversion in these simple and cheap reaction vessels can be carried out. The further the polymerization is carried out outside the extruder should be, the more solution liquid must be used to improve the viscosity of the solution or the Keep the concentration of the slurry within practical limits. If the implementation in such a vessel up to less than 100% is carried out, the resulting solution or slurry is transferred to an extruder in which the remaining monomers are polymerized. Experience has shown that a twin-screw extruder is used to carry out the polymerization most appropriate as it is in such a Extruder gives the reaction participants a steady forward movement along the cylinder, while there is a Single-screw extruder tends to backmix, i.e. the reactants move along the cylinder not completely uniform and there is a possibility that something unpolymerized at the exit of such an extruder Material is still present, while the depressions of the screw are for the most part covered with dormant polymer! Material are filled.

If at least part of the polymerization is carried out in an extruder, this extruder can be the one according to the invention used extruder with steam vent, which is designed in the area of the cylinder end such that volatile material such as that used in the present invention

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Liquid, can be withdrawn. Such vented extruders are known per se, see e.g. the British Applicant's patent 875 853. Another possibility consists in that the polymerization takes place either in a simple vessel with a stirrer or in an extruder is completed and the Mpolymerized material dissolved or suspended in the liquid in an extruder with steam exhaust. is passed in which the evaporation of the liquid is to be carried out. There is a single screw extruder is perfectly suitable as a vented extruder and cheaper than a twin screw extruder is preferred Carrying out part of the polymerization in an extruder of the twin-screw extruder for the polymerization reaction fully exploited and the polymerized product placed in a single-screw extruder with a steam vent to evaporate the liquid.

It was surprisingly found that with the present Arrangement, almost all of the solvent can be removed even when large amounts of liquid are used can.

The evaporation can be done in a single stage. But it becomes a large amount of liquid in a single step removed, the viscosity of the remaining contents of the extruder increases considerably and it becomes necessary to supply a large amount of heat to the system. In such cases, the evaporation is preferably carried out in several Stages. The amount of liquid evaporated at each stage can be adjusted by adjusting the temperature in the extruder with steam

can be precisely regulated - and by adjusting the pressure in the steam outlet. Thus, _e n along the extruder barrel to reach a gradual Viscositätserhöhung and a compensating increase in temperature. If the liquid is to be drawn off completely, the final vapor outlet can be under negative pressure. However, as discussed below, it is often convenient to leave a predetermined amount of liquid in the polymerized mixture which can then act as a blowing agent. This can be carried out expediently and precisely by regulating the pressure in the final steam vent.

The blowing agents which can be used in the process according to the invention are similar to those disclosed in the main application, i.e. a gaseous, liquid or solid propellant

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BATH ORIGINAL

be used with be L, that when heated to dLe temperature the film or plate forming nozzle develops a geis. In the case of a volatile liquid or gas, these must but the copolymer after evaporation of the solution liquid and shortly before the entry into the film- or plate-forming Abandon the nozzle. However, there is an exception the preferred JPaIl in which the invention is used Liquid is also used as a propellant and the Evaporation of the liquid is controlled in such a way that the remaining amount of the liquid is suitable as a propellant i.e., about 1 to 50 percent by weight of the copolymer. It it is nabüi'LLch also possible to evaporate the entire liquid and re-inject a predetermined amount thereof, but this li; t normally not necessary, well by that Adjustment of the pressure in the steam vent is very accurate Erz.ieibar is. In the case of solid propellants, these can be added at each stage of the reaction, i.e. they are added to the monomers before they have been dissolved in the solvent, the partially polymerized mixture at any time during the polymerization or the polymerizing mixture be added before or after the evaporation of the liquid. Of course, such solid propellants must be chosen, those under the temperature and pressure conditions before dtDi Do not spray from the film or plate forming nozzle been decomposed.

As described in the parent application, the monomer mixture consist of styrene and maleic anhydride alone, or at least one other monomer can be present, the resulting polymer replaces part of the styrene. The preferred other monomers that can be used include straight chain olefins having from 3 to 56 carbon atoms and aLphatiiiche vinyl ethers with 6 to 18 carbon atoms. The too polymericLorende mixture can also consist of styrene, maleic anhydride and a low modulus additive that is a "rubbery" polymer or copolymer, exist.

In order to be able to prepare the prepared according to the invention To increase copolymers, chain transfer agents, such as e.g. ALky! .mercaptane or carbon tebrachloride, the solution of monomeric components are added. By presence ^ its that kebben transmission mobbel in one concentration

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of 0.25 wt% or less becomes the reduced viscosity of the polymer obtained is reduced without the tensile strength of the foam sheets and plates being great is affected.

The catalysts described in the main application can possibly be mixed with an accelerator can also be used.

The same fillers and other additives, e.g. Plasticizers, heat stabilizers and ultraviolet stabilizers can be used in the same concentration at each stage of the according to the invention are added. For example, you can use the vessel with agitator, the possibly used polymerization extruder, the fully polymerized solution at the transition to the evaporation extruder or to the evaporation stage of the polymerization extruder. Should one or more additives not be inert during the polymerization reaction, these are added after the polymerization has taken place, if they would inhibit or otherwise affect the polymerization reaction.

The film or plate forming nozzle can include a slot nozzle, be an annular slot nozzle or a radial nozzle, in the latter two cases the emerging film ·; can be inflated into a bladder as described in the parent application.

The film or plate obtained in this way can in its thickness z. B, can be reduced by cutting, and the films or plates can be compressed, for example, between rollers under pressures of 0.7 to 7030 kg / cm.

The films or plates produced according to the invention have approximately the same properties as those produced according to the main application.

The invention is shown in the following purely by way of example with reference to FIG Embodiments explained in more detail. .

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example 1

A solution of stabilizer-free styrene (1092 g) in methyl ethyl ketone (1060 ml) was a twin screw extruder in an hourly amount of 6 134 ml at the same time with a solution of maleic anhydride (980 g) in methyl ethyl ketone (1450 ml) in an hourly amount of 3 866 ml supplied. Ditertiary butyl peroxide (0.2% by weight based on the monomers) was used as the catalyst, and this was dissolved in the solution of maleic anhydride in methyl ethyl ketone. The screw rotated at a pot reference of 17 U / min and the extruder was maintained at a temperature of 15O ⁰ C. The residence time in the twin screw extruder was 14 minutes, during which time the polymerization was essentially completed. The solution of the resulting polymer was transferred to a single-screw extruder, in which the solution was partially evaporated by regulating the temperature and pressure in the steam vent. 5,707 ml / h of methyl ethyl ketone were evaporated off, so that 15% by weight of methyl ethyl ketone remained in the polymer, which was then extruded through an annular nozzle. The emerging polymer foamed because of the evaporation of the remaining methyl ethyl ketone. The film thus formed was inflated into a bubble and then passed through a pair of rollers, slit and spread out. Finally it was compressed between rollers, the film properties being approximately the same as those described in the main application. Example 2

Solutions according to Example 1 were made in a twin-screw extruder supplied, with the difference that the catalyst concentration was 0.1% by weight based on the monomers. the The speed of the screws, the reaction temperature and the residence time were also as in Example 1. The methyl ethyl ketone was completely withdrawn in the vaporization extruder, the screw of which rotated at 110 rpm. There were 864 g per hour Methyl ethyl ketone is injected into the polymer just before the nozzle. This acts as a propellant when it emerges from an annular nozzle, the film being treated further as in Example 1 became.

Example 3

A solution of maleic anhydride (1,768 g), methyl ethyl ketone (2,321 ml) and di-tertiary butyl peroxide (3.73 g) was simultaneously treated with styrene (1,969 g) in a twin-screw extruder

ORIGINAL

fed. The temperature in the inlet area was 111 ^e C and rose up to 147 ^e G bm along the extruder barrel. Exit end. The outlet end was followed by a 31175 * "& single-screw extruder with steam vent, in which 77 # of the methyl ethyl ketone originally present was drawn off, the remainder being left in the polymer to act as a blowing agent. A bubble with a 30.5 cm diameter made of polymer became - Foam blown from a conventional distribution ring nozzle with a diameter of 38.1 mm. The reduced viscosity of the foam product was 0.92 (measured in 1% strength solution in dimethylformamide).

Example 4

Styrene was fed to a twin screw extruder by a measuring pump, while a solution of ilaleic anhydride in methyl ethyl ketone was fed to the extruder by a second Hess pump, this solution being ditertiary Butyl peroxide (0.1% by weight based on the total monomers of styrene and maleic anhydride) and as a chain transfer agent Lauryl mereaptane (0.2% by weight based on the total monomers). The reactants were fed in a total hourly amount of 6 liters, wherein the styrene in an amount of 7 * 5 mol% more than the maleic anhydride was fed. The screw speed of the twin screw extruder was 12.5 rpm, and the temperature of the extruder was raised to about 150 ° C held. The polymerized material was fed into a single screw extruder fed, in which it partially evaporates and extruded to form a foam sheet as in Example 1 became. The reduced viscosity of the copolymer material was 0.52 (measured in 1% strength solution in dimethylformamide at 25 ° C) compared to a reduced viscosity of 0.70-1.00 in the absence of a chain transfer agent.

Example 5 and 6

The procedure according to Example 4 was carried out twice under the same Conditions repeated, with the difference that once n-octyl mercaptan us the other time n-butyl mercaptan (in each case 0.2% by weight based on the monomers) was used instead of lauryl mercaptan. The reduced viscosity the resulting polymers were 0.58 and 0.41, respectively.

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BATH ORIGINAL

Claims (3)

- 9 -patent claims 174bUUb 1. Process for the production of films or sheets from Oopolymer-foam by extruding a copolymer Mass and a propellant through a film or plate-forming nozzle, characterized in that the copolymeric mass is produced in that a solution of the monomeric constituents consists of Styrene and maleic anhydride are formed in a liquid which is a solvent for the monomers Represents constituents and does not have an inhibiting effect on the copolymerization that the copolymerization is carried out and that at least part of the liquid from the resulting copolymer mass in the forced Forward movement of the same is evaporated in an extruder with a steam vent. 2. The method according to claim 1, characterized in that the copolymerization in a different from the extruder simple, cooled vessel with a stirrer until the reaction has progressed well or is complete. 3. The method according to claim 1, characterized in that the final stage of the copolymerization is carried out in a twin screw extruder. l-o method according to one of the preceding claims, characterized characterized in that a chain transfer agent is added to the solution of the monomeric ingredients. / U- O Pt -1.VC H Y HR 2 0 9 8 1 UI 1 2 1 2