SE448998B - PROCEDURE FOR PREPARING A MIXTURE OF POLYPROPENE, 1,2-POLYBUTADIA AND POLYETE - Google Patents

Description

448 998 have a good toughness and stiffness in a temperature range from -20 to + 130 ° C.

Platformed semi-finished products of this mixture shall be reshapable using vacuum technology. The highly fine cellular structure and smooth surface of foamed embodiments should in no way be inferior to those found in other known high-quality plastic materials.

To this end, the invention relates to a process of the kind mentioned in the introduction, in which the mixture used is added 10-50% by weight, based on the weight of the polypropylene, of low or high pressure polyethylene.

The mixture used in the proposed process consists predominantly of polyethylene and polypropylene, as well as a lower proportion of liquid 1,2-polybutadiene.

Surprisingly, it has new properties, which are outside the specific properties of the substances used. The new properties also do not show up in an intermediate area and have so far not been predictable.

The proposed method allows the production of structural parts with good thermal shape resistance. To determine the thermal resistance, according to Example 1, a foam has a gross density of 30 kg / m 2; produced. From this foam plastic a plate with a thickness of 10 mm was cut out and formed by means of a commercially available vacuum forming machine into a cylindrical cap with an outer diameter of 120 mm and a height of 60 mm. This hat was subjected to heat storage at ISÜÜC for 24 hours in an air flow oven, resulting in a diameter reduction of 3.3% and a height reduction of 4.89 ”. Comparable results were obtained using a foam with the same gross density of polypropylene.

In another experiment, the flattened plastic material of Example 1 was stored for a period of 24 hours at a temperature of 1500 in an air flow furnace. The shrinkage was about 1% in the longitudinal and transverse direction. The comparable pure polypropylene foam likewise showed a shrinkage of about 1% in the longitudinal and transverse directions.

Subsequently, in both cases the temperature was increased to lóüoC. Both the pure polypropylene foam and the proposed foam shrank sharply.

It can be seen from this that, despite the considerable content of the low-pressure polyethylene with a softening temperature of 130 DEG C., the thermoformability of the proposed plastic material is very similar to the thermoformability of the pure polypropylene.

Subsequently, the foam samples of Example 1 were subjected to a torsional oscillation test. Here it was found that a maximum of the attenuation decrement appeared at 4.1 Hz, TÖ = -40 ° C (Fig. 1). This cushioning maximum has neither the pure polypropylene foam material (Fig. 2) nor the pure low-pressure polyethylene (Fig. 3).

Such maximums of the damping decenter enable assessment of the properties of the materials at low temperatures. According to Fig. 1, the proposed plastic material has a transition temperature at -lt0 ° and is thus embrittled only below this temperature, while pure polypropylene foam material is already embrittled at a temperature of about + 7 ° C. To that extent, the proposed material is superior to the pure polypropylene foam material in the vicinity of the freezing point.

Figures 4 and 5 show the attenuation ratio of the different materials as a function of temperature. Curve A in Fig. 4 shows the attenuation ratio of a foam material body of the mixture according to Example 1, curve B in Fig. 1 shows the attenuation ratio of a comparison body with identical dimensions and the same gross density of pure polypropylene. The course of the two curves is almost identical. A sharp fall first occurs above a temperature of 1000 ° C.

In the comparative body of unfoamed low pressure polyethylene, a tendency comparable case occurs already at a temperature of IBOOC (Fig. 5).

When using low pressure polyethylene as an additive in the proposed mixture, the required amount of mesh (peroxide content and radiation dose) can be reduced by 10 to 20%, compared with an addition of high pressure polyethylene. Also from an economic point of view, the selection thus has a special significance.

The proposed process is also suitable for the production of net-forming, foamed polyolefin materials. These can preferably be further processed into load-bearing construction elements. They are distinguished in the temperature range between -40 and + 150 ° C for properties, which make them appear markedly superior to the known polyolefin materials.

The object of the present invention is further illustrated by the following examples: Example 1 66.3 parts by weight of low pressure polypropylene (melt index 230 / 59/10 min 10) and 18.7 parts by weight of low pressure polyethylene (melt index 190 / 2.16 g / 10 min 11.6; p; = 0.927-0.929 g / cm 3 and 15 parts by weight of azodicarbonamide are mixed in a double snow compressor with 5.5 parts by weight of polybutadiene (molecular weight 3000, 1.2 content 90% by weight) The mass temperature of the mixture is maintained at 175-185 ° C. 448 998 the homogenized mixture of the extruder is formed with a wide slit nozzle into a web of material and is subsequently subjected to a mesh formation with electron beams in a surface dose of 7 Mrad.

The product crosslinked in this way is then transported on a sieve belt and foamed. The residence time in the oven is 8 minutes at a temperature of ZISOC. The formed foam plastic plate has a homogeneous cell structure and a density of 3D kg / mj.

The gel portion of the material is determined as follows in boiling xylene: 1 g of material is boiled for 5 minutes in 100 ml of xylene, filtered and washed three times with 50 ml of hot xylene each time. After 16 hours of drying the insoluble filtrate at 105 ° C, the gel content of the material used is determined by weighing the insoluble filtrate. The gel part constitutes 67%. The test results for the material are shown in Figures 1 and 4, the latter reference curve being curve A.

Example 2 85 parts by weight of low pressure polypropylene (melt index 230/5 g / 10 min = 10) and 15 parts by weight of azodicarbonamide are mixed in a double-screw extruder with 5.6 parts by weight of polybutadiene (molecular weight 3000, 1.2 content 9091 :). The mass temperature of the mixture is set at 175-85 ° C. The mixture homogenized in the extruder is formed with a wide slit nozzle into a web of material and crosslinked with electron beams with a surface dose of 8 Mrad. The crosslinked product is transported on a screen belt through an air oven and thereby foamed. The residence time is 8 minutes at a temperature of ZlSOC. The resulting foam web has a homogeneous cell structure and a density of 30 kg / m 3.

The test results for this foam are shown in Figures 2 and 4, in the latter diagram the curve B is the reference curve.

The differences between the bath products according to Example 1 and Example 2 are clear. The foam material according to the invention shows at -QÛOC a transition point, which is present neither for pure polypropylene (Fig. 1 nor for pure low-pressure polyethylene (Fig. 3).

This result is confirmed by the additional examples.

Example 3 74.3 parts by weight of polypropylene (melt index 230/5 g / 10 min = 10) and 20.7 parts by weight of low pressure polyethylene (melt index l90 / 2, 16 g / 10 min = 4.6; / I = 0.927-0.929 g / cm 2 ) and 5 parts by weight of azodicarbonamide are mixed in a double-axis extruder with 5.3% by weight of polybutadiene (molecular weight 3000; 1.2 content 90 wt.%) and further processed as in Example 1. 448 998 The resulting foam material has a gross density of 75 kg / m3.

The gel portion is 69%.

The logarithmic attenuation decrement according to DIN 53445 is shown in Fig. 6.

Example gel 4 95 parts by weight of polypropylene (melt index 230/5 g / 10 min = 10) and 5 parts by weight of azodicarbonamide are mixed in a double-axis extruder with 5.3% by weight of polybutadiene (molecular weight 3000; 1.2 content 90% by weight / fi) and further processed as in Example 2. The foam material obtained has a gross density of 80 kg / m3.

The gel part is 70%.

The logarithmic attenuation decrement according to DIN 53445 is shown in Fig. 7. '

Claims (1)

A process for the preparation of a polypropylene-containing, net-forming and optionally foamed mixture, in which polypropylene and 2-20%, by weight of polypropylene, of LZ-polybutadiene having a molecular weight of 3500-10000 and optionally a mesh formation and / or foaming agent is mixed at a temperature below the decomposition temperature of the meshing and foaming agent, respectively, and burned in the desired form and subsequently subjected to a treatment with high-energy radiation in a dose of 0.5-20 Mrad and / while heating in an oven for meshing and any foaming, characterized in that the mixture used is added to low or high pressure polyethylene in an amount of 10-50% by weight, based on the weight of polypropylene. IJ '