DE1778126A1 - Process for the pressureless, continuous production of hard PVC foam sheets - Google Patents

Description

Process for the pressureless, continuous production of hard PVC foam sheets It is known that rigid polyvinyl chloride foams are discontinuous to produce under pressure by a mixture of polyvinyl chloride powder and propellant, optionally with the addition of solvent, under increased pressure in a form is preformed and then this shaped body above the softening point of the polyvinyl chloride is heated and decomposed due to the gas pressure during the blowing process Propellant is expanded.

It is also known to have unsupported soft polyvinyl chloride foam sheets produce, whereby on a polyvinyl chloride repellent carrier (paper), a Propellant-containing polyvinylchloride plastics are aurcoated and after gelation has taken place and expanding the foam sheet is released from the carrier. (This procedure is not applicable for the production of rigid polyvinyl chloride foams.) If the expansion of a carrierless, propellant-containing polyvinyl chloride film, via a melting roll mill, a calender or by means of a Breitschlltzdüse was produced via extruder, in a gelation channel, as from the coating technique known for the production of artificial leather, so it comes to strong distortions the film web. When the film expands, there is a simultaneous change in dimension in length, width and height, so that it is not possible to continuously one To obtain foam web that has a flat surface.

From the German Auslegeschrift 1 230 199 is still a four-stage Verrahren for the production of foam sheets from thermoplastics known: 1st stage: Production of a foaming agent-containing film by rolling through solvent dissolved or swollen thermoplastics.

2nd stage: Removal of the required solvents or swelling agents in one Drying chamber with hot air.

3rd stage: foaming of the film in a liquid bath at 70 to 120 ° C.

4th stage: Smoothing the foam sheet over heated rollers and subsequent drying.

This process can only be used with foamed plastic foils with foil thicknesses up to 1 mm can be produced; moreover, it is due to the implementation in 4 stages very expensive.

It has now been found that hard polyvinyl chloride foam webs can be produced continuously and without pressure by preforming a carrierless web of polyvinyl chloride, solid blowing agent, swelling agent and conventional additives and foaming the web in a heated liquid bath in an improved manner by using a 1 as swelling agent , 3-dioxolanone of the general formula in which R denotes hydrogen, the methyl, ethyl, propyl or iSO propyl radical, azodtcarbonnmtd as the solid propellant and glycerine or polyglycols of the general formula as the liquid bath in which R is hydrogen or the methyl radical and n is an integer from 1 to 16, or salt mixtures with a melting range between 130 and 1500C, preferably 140 and 1500C, are used and the foam sheets obtained are then passed through a water bath heated to 60 to 95C leads.

The method of the invention has over the closest prior art the technology (German Auslegeschrift 1 230 199) have the following advantages: The Manufacturing is much easier; only two stages were required: 1st stage: Production of the foaming agent-containing film using a calender or by means of a slot die About extruders.

The production of such films can be done on more conventional machines Kind of done.

2nd stage: foaming deg the film in a liquid bath at 170 up to 180 C. Here, the swelling agent used is simultaneously with the expansion removed by extraction. The outlay on equipment is lower.

It is not necessary to use the swelling agent before the expansion to remove.

In addition, foam sheets can be in thicknesses that are in a relative large area (from 0.2 to max. 10 mm) can be produced, with the structure can be set to open-cell or closed-cell. A subsequent smoothing by rolling is not necessary, as the foams are already in production have a closed, smooth surface.

It is also possible to carry out the expansion separately, since the Films can be stored and do not tend to stick when stored in rolls. Another The advantage lies in the fact that one does not have to rely on a specific one when producing the film Machine and its delivery rate is dependent.

Polymers with a K value below 70, especially in the range 55 to 60, has proven its worth. As suitable plasticizers have come from the series of Xthylencarbonate especially Xthyl-Xthylencarbonat and 1, 2-propylene carbonate has been tried and tested.

For the production of rigid polyvinyl chloride foams from 60 to 90 percent by weight of polyvinyl chloride and 40 to 10 percent by weight of ethylene carbonate a still free-flowing, non-pasty mixture is produced and passed through an extruder or over a rolling mill at temperatures below the decomposition point of the blowing agent processed into granules or a film. The film production can by means of an extruder via a slot die or via a calender below 1600C going on. The driving process can be carried out directly or separately, continuously in one Propellant bath can be carried out at 170 to 200 ° C. Can be used as propellant bath fluids Glycols, polydiols, glycerine and salt mixtures are used.

Among the glycols and polydiols, for example, ethylene glycol, Diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol or the corresponding polypropylene glycols can be used.

Those with molten salt areas between are suitable as molten salts 130 and 1500C, preferably 140 and 1500C, examples of which are: a mixture from 53 parts by weight of cold filtrate, 40 parts by weight of sodium nitrite and 7 parts by weight Sodium oil with a melting range of 140 to 150 C; or one Mixture of 53.6 parts by weight of potassium nitrate and 46.0 parts by weight of sodium nitrite with the melting range from 140 to 1500C.

The driving time depends on the thickness of the film, whereby a residence time of 1 to 10 minutes at 170 to 180 ° C. is completely sufficient.

Foam sheets with a uniform pore structure are created and a smooth surface.

The foaming takes place without pressure and at relatively low processing temperatures. For reaching a certain density, the residence time is at a given one The temperature in a propellant bath is significantly lower than in a Celier channel or heating furnace, because there is better heat transfer. Gelation and foaming proceed simultaneously.

The following table gives an overview of the mechanical values of foams, depending on the propellant content and the type of foaming.

The foaming was carried out as follows: A. in glycerol B. in triethylene glycol C. in a 15 m long gelation channel A B C A B C propellant content in% 0.25 0.25 0.25 2 2 2 Expansion: Temp. 0C 170 170 170 170 170 170 Time min. 5 5 10 2 2 10 Density g / cm3 0.200 0.548 0.940 0.190 0.202 0.535 Pore volume: open Cells% 86.7 10.7 2.5 81.0 29.5 61.9 closed ° 0 50.2 30.4 5.4 56.1 0 Furthermore is it possible to use the spec. Weight of the foam sheets due to an aftertreatment can be reduced by 50% in a vacuum oven. Foams are obtained with Volume weights that are less than 100 kg / m3.

For example, a foam sheet produced according to Example 2 is used with a density of 0.180 g / cm3 stored for 1 h at 85 ° C at 740 mm Torr and under Cooled vacuum, it is expedient to lower the temperature to 45 ° C. The foam sheet obtained now has a density of 0.09 g / cm3, accordingly a density of 90 kg / m3.

Example 1 A mixture of 80 parts of emulsion polyvinyl chloride, K value 60 20 parts 1,2-propylene carbonate 3 parts DOP 2 parts ZnO, active 1 part a mixture of 87.5 percent by weight basic lead stearate and 12.5 percent by weight Lead carbonate 2 parts azodicarbonamide 10 parts Omya chalk BSH is made at room temperature mixed in a powder mixer for about 10 - 15 minutes, then this powder mixture is mixed Plasticized in a mixing mill at 100 - 110 ° C and then on one 4-roll calender extended at a temperature of 155 ° C to form a film with a thickness of 0.5-0.8 mm. The not yet expanded film has a density of 1.3 - 1.4 g / cm3. In the following Expansion in a triethylene glycol bath at 1720C and an operating speed from 0.3 m / min = 3 'blowing time, the film stretches in the longitudinal direction by approx. 75%, in the transverse direction by approx. 80% and in the thickness by approx. 90%. The foam sheet obtained has a density of 0.16 g / cm3 and a tensile strength of approx. 20 kg / cm2. The cell structure consists of approx. 67% open and 21 ffi closed cells.

Example 2 Preparations are carried out using a mixing mill and granulating plant granules of the following composition: 80 parts of suspension polyvinyl chloride, K value 55 20 parts 1,2-propylene carbonate 3 parts DOP 2 parts Zn 0, active 1 part of a Mixture of 87.5 percent by weight basic lead stearate and 12.5 percent by weight Lead carbonate 2 parts azodicarbonamide An extruder is used by means of a slot die at a temperature of the DUse of 1200C a film with a Made of 1 mm thick. This film is then placed in a propellant bath system raised in triethylene glycol at 180C. At a working speed of 1.0 m / min. = 3 'driving time you get a foam sheet with a uniform Pore structure.

The density is 0.2 g / cm3 and the proportion of closed cells is 80%.

Example 3 80 parts of suspension polyvinyl chloride, K value 55 20 parts 1,2-propylene carbonate 1 part ZnO, active 0.8 stearic acid 2 parts azodicarbonamide A film was produced from the above recipe at 110 ° C. using a rolling mill. The expansion was at 1760C to 1790C in triethylene glycol at 1.0 m / min. performed. The foam obtained had a density of 0.159 g / cm3; cells were 84.4 % closed and 4.2% open cells determined. The foams produced in this way with a density of 170 to 200 kg / m3 resulted in the determination of the coefficient of thermal conductivity, in a measuring range from 20 to 600C, values from 0.043 to 0.049 (kcal / m. h. ° C).

Example 4 80 parts of suspension polyvinyl chloride, K value 58, 20 parts 1,2-propylene carbonate 3 parts DOP 2 parts ZnO, active 0.875 lead stearate 0.125 "lead carbonate 2 parts of azodicarbonamide are made from the recipe at 110 ° C over a roller mill Films made. The gelation and expansion takes place at 1800C. The dwell time is 1 minute.

The adhering salt is removed with water and the foam is added Dried at 70 to 80 ° C.

A foam with a density of 0.25 g / cm3 is obtained.

Example 5 80 parts of suspension polyvinyl chloride, K value 58, 20 parts Ethyl ethylene carbonate 3 parts DOP 2 parts ZnO, active 0.875 lead stearate 0.125 "lead carbonate 10 parts of TiO2 2 parts of azodicarbonamide 0 From the recipe given, 110 C foils are produced in a rolling mill. The gelation and expansion takes place at 1800C. The residence time is 1 minute.

The adhering salt is removed with water and the foam is added Dried at 70 to 800C.

A foam with a density of 0.30 g / cm3 is obtained.

The foams produced according to the invention can be used e.g. for anti-drumming and insulation in car body construction, for the production of deep-drawn articles, by lamination with other foils or veneer for the production of decorative panels, as a carrier or for stiffening in the production of floor coverings, primarily as sheet goods on a textile basis, in thin versions as a replacement for cardboard and Paper.

The waste, processed into chippings, can be used to loosen the soil find use in horticulture.

Claims (1)

A process for the continuous pressureless production of hard polyvinyl chloride foam webs by preforming a carrierless web of polyvinyl chloride, solid blowing agent, swelling agent and customary additives and foaming the web in a heated liquid bath, characterized in that the swelling agent is a 1,3-dioxolanone of the general formula in which R denotes hydrogen, the methyl, ethyl, propyl or isopropyl radical, azodicarbonamide as the solid propellant and glycerol or polyglycols of the general formula as the liquid bath in which II is hydrogen or the methyl radical and n is an integer from 1 to 16, or salt mixtures with a melting range between 130 and 150 ° C, preferably 140 and 150 ° C, and the foam sheets obtained by a heated to 60 to 95 ° C Water bath leads.