DE1206154B - Process for the production of foams - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C08f

German class: 39 b - 22/06

Number:
File number:
Registration date:
Display day:

1206154
F25007IVc / 39b
February 10, 1958
December 2, 1965

It is known to foam polyvinyl chloride plasticizer mixtures by giving them Substances are added which split off inert gases at the temperatures necessary for gelation and puff up the gelling mixture in the process. It has also been proposed to use polyvinyl chloride plasticizer pastes to saturate under pressure with inert gases, these mixtures saturated with gas by relaxation to foam and to gel the resulting foam by the action of heat.

It has now been found a process for the production of foams, in the pasty Mixtures of powdered polyvinyl chloride or copolymers of vinyl chloride and plasticizers mixed with gases or liquids gaseous at room temperature and these mixtures be foamed by relaxation and then gelled, which is characterized in that the pasty mixtures at room temperature under pressure with one or more liquefied Mixed gases are used. After leaving the mixing vessel, this mixture foams when relaxing to atmospheric pressure and can at this moment by the action of heat be gelled. In addition to pure polyvinyl chloride, copolymers can also be used in the process according to the invention are foamed with a predominant proportion of vinyl chloride, with the prerequisite that that paste-like mixtures can be produced from these copolymers with plasticizers.

The liquefied gases in the sense to be used according to the invention are primarily those as Blowing agent in the production of foams from polyvinyl chloride pastes already known fluorinated Chlorinated hydrocarbons in question. These have the advantage over other gases that they are incombustible and odorless and to be non-toxic. Difluorodichloromethane are particularly suitable, Difluoromonochloromethane, monofluorodichloromethane, monofluorotrichloromethane, tetrafluorodichloroethane as well as their mixtures. However, the inventive method is not limited to this Substances restricted. Also suitable as liquefied gases in the context of the invention are: propane, butane and monomeric vinyl chloride, either alone or as a mixture with one another and together with the above liquefied gases can be used. When choosing the gases, the requirement is to provide that they with the plasticizers used in each case for the preparation of the polyvinyl chloride paste are miscible. The proportion of the liquefied gas in the mixture should be around 2 to 8 percent by weight but can be - depending on the process used to manufacture foams

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning, Frankfurt / M ..

Named as inventor:

Dr. Georg Schulz, Kilchberg, Zurich (Switzerland);

Dipl.-Ing. Bernd Hoffmann,

Kelkheim (Taunus) -Hornau;

Dr. Helmut Becker, Frankfurt / M.

desired degree of foaming - also different amounts can be used.

The process can be carried out batchwise or continuously. In the discontinuous process, the necessary amount of the liquefied gas is pumped into a pressure-resistant stirred vessel containing the polyvinyl chloride plasticizer paste. After brief stirring, on a z. B. located at the bottom of the pressure vessel. Outlet the mixture, which foams immediately after relaxation, can be withdrawn.

In the continuous process, a mixing vessel is placed on one side with the polyvinyl chloride plasticizer paste while the finished mixture is removed from the other side. the The liquefied gas is expediently added via a metering pump, the delivery rate of which is accurate must be matched to the paste throughput so that the mixing ratio is always as uniform as possible is adhered to. The flow of the paste, which can also be fed in using a pump occurs, must be throttled so much at the outlet valve of the mixing vessel that the in this vessel The prevailing pressure is always slightly higher than the vapor pressure of the liquefied gas used in the in of the paste is the prevailing temperature. Otherwise, when it is added, partial evaporation would occur and thus premature foaming can occur.

The mixing vessel required in the method according to the invention can have any design features exhibit; for example, an extruder charged with the paste can be used which the addition of the liquefied gas takes place at the devices, which are usually used for degassing of plasticized materials used

509 740/446

I 206

will. A forced stirring of the mixture is not absolutely necessary, for example, too sufficient mixing of the paste with the liquefied paste by means of baffles in the mixing vessel Gas can be achieved.

Mixing the paste with the liquefied gas, ie mixing two liquids, has the advantage over the known methods in which the paste is saturated with a gaseous substance that a relatively small mixing vessel is sufficient here. In the previous methods, however, it is necessary to achieve the fastest possible equilibrium that a large surface area of the paste is created, for which relatively large gassing vessels are required. Another advantage of the method according to the invention is that the necessary pressure can be kept relatively low. In the known processes, on the other hand, a relatively high gas pressure must be used in order to set the absorption equilibrium as quickly as possible. So z. B. worked according to the method of the US Pat. No. 2,666,036 with a gas pressure of 7 to 56 kg / cm ² , vessels being used which must withstand a pressure of at least 70 kg / cm ^2. Since the vapor pressure of the liquefied gases or their mixtures is so low or can be kept so low by suitable mixing ratios that it ^{does not exceed 3 to 7 kg / cm 2} , no high pressure is necessary to produce the mixture from the paste and the liquefied gas is, the compressive strength of the vessels can be kept significantly lower in the method according to the invention.

Furthermore, the inventive method has the advantage that for mixing with the liquefied Gas pastes with a relatively low plasticizer content and thus with a high consistency are also used can be, while in the previously known methods to achieve a large surface area of the Pastes required a relatively low consistency, narrowing the practical mixing range.

Example 1

A paste of 60 parts by weight of powdered polyvinyl chloride and 40 parts by weight of dioctyl phthalate is made by an extruder that has a very low pitch and / or core progression in and short behind the filling zone has, promoted, with so much throttled at the nozzle that at one approximately in the center of the extruder housing, a pressure of about 5 to 6 atmospheres is measured. At this point, liquefied difluorodichloromethane is injected through a second nozzle with the aid of a piston metering pump in an amount of about 3 to 5 percent by weight, based on the paste. By conveying the mixture from the point where the liquefied gas is pumped in to the nozzle the liquefied difluorodichloromethane is mixed with the plasticizer of the paste. When the Mixture from the nozzle foams up strongly within a relatively short time and is in this state gelled by the action of heat.

Example 2

The procedure is as described in Example 1, but instead of the extruder, the mixing vessel is used a vertical cylindrical container is used, the inside with some deflection or baffle plates is equipped. The paste and the liquefied gas are fed in at the lower end of the container, while the nozzle and the throttle device to build up the necessary Overpressure on the upper face.

Example 3

The procedure is as in Example 1 or 2, but instead of liquefied difluorodichloromethane a liquefied mixture of 50 percent by weight difluorodichloromethane and 50 percent by weight monofluorotrichloromethane used. Because of the lower vapor pressure of the mixture of liquefied gases, the back pressure of the paste can be kept lower in this example. The one emerging from the nozzle Mixture foams up a little more slowly than after the procedure according to example 1 or 2.

Example4

It is carried out according to Example 1 or 2, but a paste is used from 40 parts by weight, Polyvinyl chloride, 60 parts by weight of tricresyl phosphate and 2 parts by weight of highly disperse silica. the Paste is mixed with 3 percent by weight of the liquefied gas mixture according to Example 3.

Example 5

The procedure is as in Example 1 or 2, but a paste is used from 60 parts by weight of one Copolymer of 95% vinyl chloride and 5% vinyl acetate and 40 parts by weight of acetyl tributyl citrate. This paste is mixed with 5 parts by weight of liquefied tetrafluorodichloroethane.

Claims (1)

Claim: Process for the production of foams, in which pasty mixtures of powdery Polyvinyl chloride or copolymers of vinyl chloride and plasticizers with gases or gaseous at room temperature Liquids mixed and these mixtures foamed by relaxation and then be gelled, characterized in that the pasty mixtures at room temperature applied under pressure mixed with one or more liquefied gases. Considered publications:
Austrian Patent No. 185 991;
U.S. Patent Nos. 2,515,250, 2,666,036. 509 740/446 11.65 © Bundesdruckerei Berlin