FR2519991A1 - PROCESS FOR THE MANUFACTURE OF A MIXTURE CONTAINING POLYPROPYLENE - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR THE MANUFACTURE OF A CROSS-LINKED AND POSSIBLY EXPANDED MIXTURE CONTAINING POLYPROPYLENE, IN WHICH THE POLYPROPYLENE AND 2-20 OF 1,2-POLYBUTADIENE WITH A MOLECULAR WEIGHT OF 500-10000, ARE MIXED, WITH RESPECT TO THE WEIGHT OF THE POLYPROPYLENE, AND POSSIBLE A CROSS-LINKING AGENT, A FOAMING AGENT, OR THEIR MIXTURES, BELOW THE DECOMPOSITION TEMPERATURE OF THE CROSS-LINKING AGENT OR OF THE FOAMING AGENT AND THE DESIRED FORM IS THEN CARRIED OUT, THEN A HIGH ENERGY RADIATION TREATMENT AT A DOSE OF 0.5-20 MRAD OR HEATING IN AN OVEN, OR A COMBINATION OF THE TWO FOR CROSS-LINKING AND POSSIBLY FOR FOAMING. ACCORDING TO THE INVENTION, 10-50 BY WEIGHT OF LOW PRESSURE OR HIGH PRESSURE POLYETHYLENE IS ADDED TO THE MIXTURE USED, RELATING TO THE WEIGHT OF THE POLYPROPYLENE.

Description

The present invention relates to a method for

  manufacture of a reticulated and optionally expanded mixture

  polypropylene, in which polypropylene is mixed with 2-20% 1,2-polybutadiene of a molecular weight of 500-10000, relative to the weight of the polypropylene, and optionally a crosslinking agent, a foaming agent, or mixtures thereof, below the decomposition temperature of the crosslinking agent or foaming agent and is formed into the desired form, and then treated with high energy radiation at a dose of 0.50. -20 Mrad or furnace heating, or a combination of both,

  for crosslinking and optionally for foaming.

  Such a process is described in German patent DE-PS 28 39 733 It leads to products which have from the thermal point of view both the positive and negative properties of polypropylene. strong tendency to embrittlement at low temperatures

  gives rise especially to criticism.

  Japanese Patent Application Publication 49825/1972 relates to a process for the foaming of polyolefins having a

  0.3-40 parts by weight of a 1,4-polybutadiene rubber

  in a direct gasification process, therefore by physical means The content of 1,4-polybutadiene leads to the formation of small and stable pores, but causes a decrease in thermal stability at increasing temperatures and, in this

  detrimental effect on the thermal stability of the foam obtained

  DE-OS 29 37 528 relates to a foam based on a mixture of polypropylene, 1,2-polybutadiene, other thermoplastic resins, for example a copolymer ethylene-α-olefin, and a porogenic agent The foam is distinguished by a particularly high thermal stability and a uniform cell structure and a corresponding appearance But a vacuum forming

  only possible under certain conditions and at low temperatures.

  erosion in the freezing point region lead to a

strong weakening.

251 99 1

  The patent application of the Federal Republic

  Germany DE-AS 16 94 130 relates to a process for the manufacture of

  cation of a foam, in which a polyolefin, a 1,4-polybutadiene rubber and an organic peroxide are mixed, shaped and heated for subsequent crosslinking and foaming. These foams are very flexible and flexible. The low stiffness excludes use for the manufacture of self-supporting trim elements.

  The subject of the invention is a method for the manufacture of

  tion of a crosslinkable and optionally foamable mixture containing

  polypropylene, which allows the manufacture of structural elements

  high quality These must be distinguished, with good thermal stability corresponding to the properties of polypropylene

  in the freezing point region through the elimination of

  plete of the fragilisation known until now with the polypro-

  pylene and by good rigidity and good toughness in a temperature range of -20 to 130 C Semi-finished products in the form of plates of the mentioned mixture must be able to be shaped by the application of the vacuum technique The structure very thin cell and the smooth surface in the expanded embodiments should in no way be inferior to those

  other known high quality foams.

  According to the invention, it is proposed to solve this problem a process of the type mentioned at the beginning, in which 10-50% by weight of low pressure polyethylene is added to the mixture used.

  or high pressure, based on the weight of the polypropylene.

  The blend used in the proposed process consists essentially of polyethylene and polypropylene and a lower

  proportion of 1,2-polybutadiene liquid.

  It surprisingly presents new

  properties which are beyond the specific properties of the substances used. The new properties are also not in an intermediate domain and, to that extent, they

  were not predictable so far.

  The proposed method allows the manufacture of structural parts having a good thermal stability when hot For the determination of thermal stability when hot, it is manufactured

  according to example 1 a foam having a density of 30 kg / m 3.

  A 10 mm thick plate is cut from this foam and a cylindrical bonnet having an outer diameter of 120 mm and a height of 60 mm is molded by means of a vacuum-forming machine. this hat for 24 h at a hot storage at 150 C in a circulating air oven, which leads to a decrease in the diameter of 3.37 and a decrease in the

  height of 4.8% Comparable results are obtained using

  a polypropylene foam of the same specific gravity.

  In another test, the corresponding plate-shaped foam according to Example 1 is stored for a period of

  24 h at a temperature of 150 C in a circulating air oven.

  The shrinkage is about 1% in the longitudinal direction and in

  cross direction Pure polypropylene foam compared

  In both cases, the temperature is also raised to 1600 ° C. Both the pure polypropylene foam and the proposed foam shrink strongly. hot form of the proposed foam,

  despite a notable low-pressure polyethylene content of one

  softening temperature of 1300 C, coincides widely with that

pure polypropylene.

  The invention will be better understood when reading

  the following description with reference to the accompanying drawings in the

what:

  Figure 1 represents the variations of decre-

  logarithmically the damping of the foam according to Example 1 in the torsion test according to DIN 53445, as a function of temperature;

  Figure 2 shows the variations of decre-

  damping-logarithmic of pure polypropylene foam as a function of temperature; FIG. 3 represents the log-decremental damping decrement of pure low-pressure polyethylene as a function of temperature;

  Figure 4 shows the damping behavior

  a piece of foam of the mixture according to the example (curve A) and a comparative piece made of pure polypropylene with the same dimensions and the same specific gravity (curve B); FIG. 5 represents the shear modulus of a comparative piece of low pressure polyethylhexene which is not expanded as a function of temperature; FIG. 6 represents the variations of the DIN log damping decrement of the mixture according to example 3 of the invention as a function of the temperature; and FIG. 7 shows the variations of the logarithmic damping decrement of the mixture of example 4 according to

of the temperature.

  Samples of the foam of Example 1 were then subjected to a torsional oscillation test according to the standard

  DIN 53 445 We see in this case that it appears a maximum of the decre-

  logarithmically for 4.1 Hz at T = -400 C (Figure 1) Neither pure polypropylene foam (Figure 2) nor low pressure polyethylene

  pure (Figure 3) do not have this maximum damping.

  These maxima of the damping decrement give

  indications on the behavior of materials at low temperatures.

  The proposed foam has, according to FIG.

  it does not break below this temperature; on the other hand, the pure polypropylene foam already breaks at a temperature of about 70 ° C. In this measurement, in the vicinity of the freezing point, the piece proposed is greater than that

made of pure polypropylene foam.

  Figures 4 and 5 show the behavior of

  amortization of the various parts according to the tempe-

  The curve A of FIG. 4 represents the amorphous behavior

  forming a piece of foam of the mixture of Example 1, the curve B that of a comparative piece of identical dimensions and the same density by pure polypropylene The appearance of the two curves is

  almost identical A strong fall appears above a tempera-

150 C.

  With a comparative piece of low-pressure polyethylene that has not expanded, a comparable potential drop appears

19,991

  already at a temperature of 130 C (Figure 5).

  In the case of the use of low pressure polyethylene as an additive to the proposed mixture, the necessary amount of crosslinking agent (peroxide content or radiation dose) can be reduced from 10 to 207, relative to an addition of high polyethylene. From the economic point of view, the choice

  is of this particular importance.

  The proposed process is also suitable for the manufacture of

  cation of cross-linked non-expanded polyolefin parts These can preferably be subsequently converted into self-supporting building elements. They are distinguished in the meantime

  temperatures of -40 to 150 C by properties that make them

  far superior to known polyolefin parts.

  The following examples illustrate the invention without

however, limit its scope.

EXAMPLE 1

  66.3 parts by weight of low-pressure polypropylene (melt index 230/5 g / 10 min) and 18.7 parts by weight of low-pressure polyethylene (melt index 190/2) are mixed in a twin-screw extruder. 16 g / 10 min = 4.6;> = O, 927-0.929 gm 3 and 15 parts by weight of azodicarbonamide with 5.6 parts by weight of polybutadiene (molecular weight 3,000, content of 1.2 90% by weight). weight) During mixing the temperature of the mass is adjusted to -185 ° C. The homogenized mixture in the extruder is formed into a ribbon by means of a wide slit nozzle and then crosslinked by

  electronic radiation at a superficial dose of 7 Mrad.

  The cross-linked product thus obtained is transported on an endless sieve through a circulating air oven and thus

  expanded The oven residence time is 8 min at a temperature of

  The foam plate has a uniform cell structure and a density of 30 kg / m 3. The gel content of the product is determined in boiling xylene as follows: 1 g of product is boiled for 5 min. 100 ml of xylene is filtered and washed three times each with 50 ml of hot xylene. After drying the insoluble residue at 105 ° C. for 16 hours, the gel content of the product is determined.

  used by weighing the insoluble residue.

The gel content is 67%.

  The results of the foam test are

  shown in Figures 1 and 4; in this last graph, the reference curve is curve A.

EXAMPLE 2

  Two screw 85 parts by weight of low-pressure polypropylene (melt index 230/5 g / 10 min = 10) and 15 parts by weight of azodicarbonamide with 5.6 parts by weight of polybutadiene (molecular weight) are mixed in an extruder b. 3000, content of 1.2 = 90%) The temperature of the mass is adjusted during mixing b 175-185 ° C. The homogenized mixture in the extruder is formed into a ribbon by means of a wide, crosslinked nozzle.

  electronic radiation at a superficial dose of 8 Mrad.

  The crosslinked product is transported on an endless sieve through an air circulating oven and thus foamed. The residence time is 8 minutes at a temperature of 215 ° C. The foam tape obtained has a uniform cell structure and a density

of 30 kg / m 3.

  The results of the test of this foam are represented

  shown in Figures 2 and 4; in this last diagram, the reference curve is curve B. We can see the different of the two products

  Examples 1 and 2 The foam according to the process of the present invention

  a transitional point that exists neither with the poly-

  pure propylene (Figure 2), or with pure low pressure polyethylene (Figure 3)

  This result is confirmed in the other examples.

EXAMPLE 3

  74.3 parts by weight of polypropylene (melt index 230/5 g / 10 min = 10) and 7 parts by weight of low-pressure polyethylene (melt index / 2.16 g / m) are mixed in a twin-screw extruder. 10 min 4.6, P = 0.927-0.929 g / cm 3) and 5 parts by weight

  asodicarbonamide with 5.3% by weight of polybutadiene (molecular weight

  3,000; 1.2 content = 90% by weight) and is subsequently treated

as in Example 1.

  The foam obtained has a density of 75 g / m

The gel content is 69%.

  The logarithmic decrement of damping according to

  DIN 53445 is shown in Figure 6.

EXAMPLE 4

  95 parts by weight of polypropylene (melt index 230/5 g / 10 min 10) are mixed in a twin-screw extruder.

  and 5 parts by weight of azodicarbonamide with 5.3% by weight of poly-

  butadiene (molecular weight 3000, content 1.2 90% by weight) and

  then treated as in Example 2.

  The foam obtained has a density of 80 kg / m 3

The gel content is 70%.

  The logarithmic decrement of damping according to

  DIN 53445 is shown in Figure 7.

  It is understood that the invention is not limited to

  preferred embodiments described above as illustrative

  and that the person skilled in the art may make various modifications and changes thereto without departing from the framework and the spirit.

of the invention.

Claims (1)

CLAIM   Process for the production of a cross-linked and optionally expanded polypropylene-containing mixture in which polypropylene and 2-20% 1,2-polybutadiene of a molecular weight of 500-10000 are blended, based on the weight of the polypropylene and optionally a crosslinking agent, a foaming agent, or mixtures thereof, below the decomposition temperature of the crosslinking agent or the foaming agent and is formed into the desired form, followed by treatment with high energy radiation at a dose of 0.5-20 Mrad or heating in an oven, or a combination of both, for crosslinking and optionally for foaming, characterized in that 10-50 % by weight of polyethylene at low pressure or high pressure, relative to the weight of the polypropylene.