DE2821342C2 - - Google Patents

Description

Thermoplastic elastomeric polymer blends consisting of polypropylene, Polyethylene and an ethylene-propylene polymer exist are out known from US-PS 39 57 919. This patent describes that the addition of a small amount of polyethylene to a polypropylene and an ethylene-propylene copolymer mixture existing the negative influence the crosslinking agent incorporated in the mixture, which increased in the Temperature during mixing can decompose and eliminate. The resulting crosslinked mixtures have a particularly low melt index, so that they almost can not be processed by injection molding.

From US-PS 39 19 358 is the production of mixtures from ethylene-propylene copolymers and polyethylene, wherein the crystallinity of the ethylene-propylene copolymer at least 10% and the Density of polyethylene is less than 0.94. This well processable However, polymer mixtures have less good mechanical properties. In particular let the resistance to high temperatures and the impact resistance to be desired at low temperature. Also the lasting one Deformation, rigidity and hardness are unsatisfactory. Furthermore is from US-PS 39 41 859 the preparation of mixtures of a Ethylene-propylene copolymer, polyethylene and an ethylene-vinyl acetate copolymer known. Also in this case, the crystallinity of the Ethylene-propylene copolymer is more than 10%. In both latter  It is noted in patents that ethylene-propylene copolymers with low crystallinity in mixtures with other polyolefins such as polyethylene can not lead to good properties.

It has now been found that thermoplastic elastomeric polymer mixtures, which consists of polypropylene, polyethylene and an ethylene-propylene polymer exist, can be processed very well and also have good mechanical properties.

According to the invention, these mixtures consist of:

• A. 30 to 75 parts of a crystalline, isotactic propylene homopolymer with a melt index between 1 and 25 dg / min (230 ° C, 2.16 kg) and
• B. 25 to 70 parts of a rubbery ethylene-propylene polymer a crystallinity of less than 10% by weight, an ethylene content of more as 58%, a tensile strength greater than 3.0 MPa and a Mooney viscosity (ML [1 + 4] 125 ° C) of a minimum of 30 and a maximum of 90, where
• C. maximum 15 parts of the propylene homopolymer and at least as many parts, as by half the numerical value of the melt index of the propylene homopolymer is given by just as many polyethylene parts with a Density between 0.91 and 0.98 g / cm³ be replaced.

The polymer mixtures according to the invention have a melt index, which is many times greater than the melt index of the US-PS 39 57 919 obtained mixtures, while the mechanical properties at least as good. The mixtures of the invention are suitable excellent for injection molding. The combination of their properties (very good processability, high impact strength at low temperature, Resistance to high temperatures, high rigidity) extremely low, while the cost price is relatively low.

Basically, one has according to the invention by the right one Choice of individual ingredients a mixture with a surprising and extremely attractive "package" of properties known.

Contrary to the current state of the art, one has for the Application of an ethylene-propylene polymer with inter alia lower Crystallinity decided. The resulting shortcomings with respect to z. B. the rigidity and the resistance to high temperatures could be compensated by using a propylene homopolymer. To the to fix the associated brittleness at low temperature became one small amount of polyethylene due to the melt index of the polypropylene added to the mixture. Furthermore, it was found that the ethylene-propylene polymer must meet a number of other requirements in order to mixture of the invention the desired favorable combination of properties  to rent.

The ethylene-propylene polymer used according to the invention preferably has an ethylene content of at least 61 wt .-%. As is known, increases with increasing Ethylene content and the tensile strength of ethylene-propylene polymers strong to. However, especially with an ethylene content of more than 77 wt .-%, the Crystallinity, which is unfavorable to a number of properties, such as permanent set and low temperature toughness, effect. The ethylene content is therefore preferably chosen below 77% by weight. and in particular below 75 wt .-%. Another advantage of this is the Improvement of the elongation at break. The best results are achieved when one chooses the ethylene content lower than 70 wt .-%. Ethylene-propylene polymers high molecular weight impart blends with other polyolefins generally better mechanical properties, but set at the same time the processability down. Very good properties are found when the ethylene-propylene copolymer has a maximum Mooney viscosity (as a measure of the molecular weight), which is determined by the melt index of the Propylene homopolymer is conditional. This maximum value for the Mooney viscosity follows from the equation

in the m.i. the Melt index of the polypropylene in dg / min, measured at 230 ° C. and 2.16 kg. The Mooney Viscosity (ML (1 + 4)) is measured at 125 ° C. The Mooney viscosity is preferably not higher than that of the equation

resulting value chosen because the processing properties in this case are optimal while the remaining good Properties are preserved. For explanation, a table is included, from which it is easy to read how big the maximum value of the Mooney viscosity at a certain melt index of the propylene polymer is preferred.  

Maximum Mooney viscosity of the ethylene-propylene polymer as a function of the melt index of the polypropylene

The ethylene-propylene polymer used according to the invention also has a crystallinity of less than 10% by weight. It is preferably a amorphous ethylene-propylene copolymer used, d. H. a copolymer with a crystallinity of less than 4% by weight and in particular of less than 1% by weight. As a result, the compression set and the Toughness at low temperature greatly improved.

Furthermore, the rubbery ethylene-propylene polymer preferably has a tensile strength in unvulcanized state of more than 5.0 MPa. The Crystallization temperature of the polymer, recorded by means of "differential scanning calorimetry ", preferably above 0 ° C and in particular above 10 ° C.

The ethylene-propylene polymer can be used in an amount of at most 20% by weight. contain a polyunsaturated monomer. These multiply saturated Monomers are usually non-conjugated polyenes, especially dienes. They are usually used in amounts of at most 10 wt .-%. Examples for such monomers are dicyclopentadiene, alkylidenenorbornene, alkenylnorbornene, Alkadienes and cycloalkadienes. Preferably, dicyclopentadiene, Ethylidenenorbornene, norbornadiene, 1,5-hexadiene, 1,4-hexadiene and mixtures used these substances. The ethylene-propylene polymers used according to the invention  can be prepared in a conventional manner, for. B. under application in British Patents 10 14 873, 9 51 022 and 8 80 904 described method. For more details on this production will be refer to NL-OS 2 81 939.

The inventively used crystalline, isotactic propylene homopolymer has a melt index between 1 and 25 dg / min (230 ° C, 2.16 kg) and preferably between 1.5 and 20 dg / min (230 ° C, 2.16 kg). Particularly preferred is a melt index between 5 and 15 dg / min (230 ° C, 2.16 kg). This melt index determined in the present Invention the preferred maximum value of the Mooney viscosity of the ethylene-propylene polymer and the amount of polyethylene to be added. The Density of the propylene homopolymer used is preferably between 0.900 and 0.910 g / cc.

In NL-OS 2 81 939 describes that an ethylene-propylene copolymer with a specific propylene block copolymer can be mixed, which Mixture has very good mechanical properties. With the help of Mixtures according to the invention can exceed these properties become. Thus, the mixtures of the invention a better hardness, a better tensile strength and a better resistance to high temperatures than that in the mixture described in the aforementioned Netherlands patent application. Other Properties such as toughness remain at the same level. Further advantages are the better tear resistance and the lower thermal Loss. Of particular importance is the high melt index of the polypropylene used. Also the other mechanical properties are thereby improved. The same This causes low temperature brittleness, surprisingly completely eliminated, if you take a bigger part of the Polypropylene replaced by polyethylene, d. H. by a quantity of polyethylene, their numerical value at least half, but preferably at least ¾ of Melt index of the polypropylene is. It is very surprising that by application a polypropylene homopolymer in combination with the right one Amount of ethylene polymer obtained such greatly improved properties can be.

The polypropylene used in the present invention is in Basically isotactic and has a high crystallinity, preferably more than 50% by weight, measured by X-ray diffraction. It can be done using the  Well-known methods (see, for example, GB-PS 9 04 510) are produced, the mainly on the use of modified or unmodified Titanium chloride based z. B. is activated with an aluminum compound.

The third of the present invention to be included in the mixture Component is an ethylene polymer with a density between 0.91 and 0.98 g / cc, and preferably a melt index between 0.1 to 35 dg / min (190 ° C, 2.16 kg). Preferably, the density is greater than 0.94 g / cc and in particular greater than 0.96 g / cc, which means that no or only a small amount of comonomer was added to the polyethylene is, for. B. less than 0.5 wt .-%. The production of polyethylene can be done for example according to GB-PS 11 96 183.

For the thermoplastic elastomeric mixture according to the invention a composition of 50 to 70 parts of crystalline, isotactic propylene homopolymer and 30 to 50 parts of rubbery ethylene-propylene polymer prefers. When using a deficiency of ethylene-propylene polymer namely, the particular effects of the invention are best emphasized. The rigidity and high temperature properties are in this Case at a high level. The improvement in impact resistance at lower Temperature by means of the ethylene polymer is particularly pronounced, the Workability in this composition is very good, while also the other properties are optimal.

The thermoplastic mixtures can be prepared in a known manner the usual equipment for plastics such as rollers, extruders, high-speed mixer and kneaders are made, wherein the plastic material at elevated temperature, especially at a temperature between 150 and 20 ° C, shear forces is suspended. For use on an industrial scale Kneaders and extruders in which mixing at temperatures of approx. 180 to 220 ° C takes place.

In the mixtures according to the invention all kinds of additives such as dyes, lubricants, fillers, antioxidants, UV stabilizers, flame retardants, zinc oxide and / or magnesium oxide, Fibers or combinations of fibrous and powdery substances without the specific properties are lost. In particular, soot and / or Oil is added to the mixture.

The polymer mixtures according to the invention can also be used with others Polymers such as styrene polymers, polyamides, polyvinyl chloride, polycarbonates, Block copolymers of styrene and butadiene, which may hydrogenated, chlorinated polyolefins, such as chlorinated polyethylene, and  Mixtures of these polymers are mixed. You can also improve the impact strength of other polymers are used. The invention Polymer mixtures can be used for many purposes because they are both soft and rubbery like stiff and impact resistant can. The mixtures are particularly suitable for the production of larger items, which are used outdoors, eg. For automobile bumpers.

The present thermoplastic Elastomers are extremely weather-resistant. This weather resistance can be further improved by that, especially if no Carbon black is used in the mixture UV stabilizers and / or zinc oxide, optionally next to a phenolic antioxidant. When UV stabilizer is preferably a combination of a so-called UV quencher, especially a disturbed amine, and a UV absorber, such as a benzotriazole and benzophenone compound.

Example 1

It is in a kneader, a series of ethylene-propylene polymer, Polypropylene and possibly polyethylene existing mixtures of in Table 1 prepared composition. An ethylene Propylene terpolymer rubber, referred to as EPDM I, used 64% ethylene, 30% propylene and 6% Äthylidennorbornen contains. The tensile strength in unvulcanized state is 6.5 MPa. The Mooney viscosity (ML [1 + 4] 125 ° C) is 52, and the crystallinity is below 0.25%. The propylene polymer referred to as PP I is a block copolymer of propylene with 7% ethylene, a density of 0.905 and a melt index (230 ° C, 2.16 kg) of 6.0 dg / min. The PP called propylene polymer is a propylene homopolymer having a density of 0.905 g / cc and a melt index of 5.2 dg / min (230 ° C, 2.16 kg). That in the table with PE I designated polyethylene has a density of 0.963 g / cm³ and a Melt index of 8 dg / min (190 ° C, 2.16 kg).

To carry out the experiments indicated in Table 1, the rubbery Ethylene-propylene polymer brought into the kneader. After 1 minute Kneading, the polypropylene and the polyethylene are added. To 4 minutes kneading (total time 5 minutes) is about 30 minutes without stamp printing kneaded; Thereafter, the kneading is continued until a temperature of 170 ° C is reached. From the mixtures are sprayed plates on the properties given in the table are checked.

The table also includes the characteristics of two commercial products.  

Table 1

The various properties are measured by the following standards:

melt index ASTM D-1238 (230 ° C, 5 kg) hardness ASTM D-2240 (reading after 3 sec.) tensile strenght NEN 5602, sample bar 2, elongation rate 15 cm / min Vicat temperature ASTM D-1525, load 1 kg Heatsagtest Sample tray 10 × 1 × 0.16 cm, heat load for 1 minute at 120 ° C Flat drop test after conditioning for 48 minutes, weight 5 kg, drop height 1 m, impact velocity 4.2 m / sec. The drop weight has a flat landing surface with a diameter of 1 cm. The sample plate, 1.6 mm thick, is supported by a 2 cm diameter ring. Tear strength DIN 53 515 Thermal fading DIN 53 497, heat load 24 hours at 90 ° C

The table shows that mixtures with PP homopolymer (Samples 2, 3, 4, 5) are significantly better resistant to high temperatures than the comparative sample  1 with PP copolymer. Resistance to high temperatures is also considerably better than the 2 comparable commercial products. For the favorable combination of low temperature toughness (high fracture energy, Tough break) and a good resistance to high temperatures Addition of PE essential. Samples 2, 3, 4 and 5 show that the PE content for sufficient toughness at low temperature must be at least as high as half the numerical value of the melt index of the PP homopolymer is given. Good resistance to High temperatures can also be achieved with a relatively high content of PP copolymer (Sample 6), in this case the toughness is lower Temperature but insufficient. Toughness at high temperature can be achieved by adding Although PE can be increased to an acceptable level, this has an impact However, so unfavorable to the resistance to high temperatures, that the mixtures ultimately did not improve compared to the commercial products (Sample 7).

example 2

The mixtures listed in Table 2 are used in a laboratory kneader (Brabender Plastograph) at a kneading chamber temperature of 180 ° C and a kneading time made of 10 minutes. All components of the mixture become simultaneously brought into the kneading chamber. Subsequently, the mixtures are rolled and at 200 ° C pressed into plates. The components that make up the mixture are already described in Example 1, with the exception of PP III, a PP homopolymer with a melt index of 1.3 dg / min (230 ° C, 2.16 kg) and a density of 0.905 g / cm³. From Table 2 it is apparent that the samples 1-5 by a higher hardness, greater rigidity at room temperature, greater tear propagation resistance and distinguish higher tensile strength from Samples 6-7. From these facts it is apparent that mixtures with a PP homopolymer have better mechanical properties than mixtures with a PP copolymer.  

Table 2

The properties are measured according to the following standards or methods:

melt index ASTM D-1228 (190 ° C, 10 kg) hardness ASTM D-2240, read after 3 sec. Stiffness (G ') Torsion damping f = 0.2 H₂, 22 ° C Tear strength DIN 53 515 tensile strenght NEN 5602, sample bar 2, strain rate 30 cm / min

example 3

This example shows that the Mooney viscosity of the ethylene-propylene copolymer, for easy processing with the help of injection molding techniques to allow one by the melt index of the PP homopolymer conditional maximum value.

In a Brabender Plastograph 40 parts by weight of ethylene-propylene terpolymer (EPDM), 55 parts by weight of PP homopolymer and 5 parts by weight of low-pressure polyethylene are mechanically mixed together in the manner described in Example 2. In the 9 blends, both the Mooney viscosity of the EPDM and the melt index of the EPDM and the melt index of the PP homopolymer are varied. Three ethylene-propylene terpolymers having a Mooney viscosity (ML _W [1 + 4] 125 ° C.) of 39, 52 and 62 are each treated with three types of PP homopolymer having a melt index of 1.3, 5.2 and 30, respectively 9.5 dg / min (230 ° C, 2.16 kg). The melt indices of the mixtures are given in Table 3. For the mixtures investigated, the preferred maximum value of the Mooney viscosity of the EPDM, depending on the melt index of the PP homopolymer, is as follows:

From Table 3 it can be seen that the Mooney viscosity of the EPDM in the samples 6 and 9 is greater than the preferred maximum value. These samples have for a good processability too low melt index. The remaining samples have a sufficiently low Mooney plasticity, and consequently have the mixtures have such a melt index that good processability is guaranteed. Optimum processability is found in Samples 1, 2, 4 and 7 found. The processability of Samples 3 and 8 becomes critical applications not suffice.  

Table 3

example 4

The mixtures listed in Table 4 with a polypropylene homopolymer with a melt index of 9.5 dg / min (230 ° C, 2.16 kg) are similar to those in Example 1 described manner. The samples will however under other conditions, d. H. at higher temperature and lower pressure sprayed to plates. As a result, the test results are not entirely with those of the previous examples are comparable.

From Table 4 shows that even with a propylene homopolymer with a melt index of 9.5 dg / min (230 ° C, 2.16 kg) mixtures can be prepared, the have high toughness at low temperature. Well, it is required that the amount of PE be at least about 5% by weight, i. H. more than half the numerical value of the melt index of the PP homopolymer is specified.

Table 4

example 5

This example shows that the advantages described in the invention the addition of polyethylene by a too high polyethylene content To get picked up. In the kneader, the mixtures listed in Table 5 on prepared as described in Example 1. Samples 1, 2 and 3  are all easy to process, mixture 4 with 20 wt .-% PE has a high polyethylene content and has too low a melt index. Also the tensile strength is unsatisfactory.

Table 5

example 6

In this example it is shown that the density of the polyethylene also for the effectiveness of polyethylene as a means of improving the mechanical properties may be of importance. Become a kneader 40 parts of EPDM I, 55 parts of PP I and 5 parts of polyethylene mechanically on the in Example 1 mixed together.

The following PE types are used in the 5 mixtures:

The samples are used to determine their properties on those in Example 4 manner described splashed into plates. These properties are in Table 6 indicated.  

Table 6

From Table 6 shows that when using polyethylene with a density better than 0.94 g / cc. The best combinations Properties are found at a density greater than 0.96 g / cc.

example 7

In the manner described in Example 2 are in Brabender Plastographen Mixtures of 40 parts by weight of ethylene-propylene terpolymer, 55 parts by weight Propylene homopolymer and 5 parts by weight of polyethylene produced. Subsequently The mixtures are rolled and pressed at 200 ° C to plates. There are 4 mixtures made. In 3 mixtures become "greenstrength" EPDM types used. For the properties of the mixtures, see Table 7.

The table shows that the mixture does not contain greenstrength EPDM (Sample 1) differ from mixtures with greenstrength EPDM (Samples 2, 3 and 4) distinguished by a lower hardness, tear propagation resistance and tensile strength.  To fully exploit the advantages described in the present invention Thus, the application of a "greenstrength" EPDM is required. Height Ethylene contents lead to low elongation at break (sample 3).

Table 7

Claims (18)

1. Thermoplastic elastomeric polymer mixture of polypropylene, ethylene-propylene polymer and polyethylene, characterized by a content of:

• A. 30 to 75 parts of a crystalline, isotactic propylene homopolymer having a melt index between 1 and 25 dg / min (230 ° C, 2.16 kg) and
• B. 25 to 70 parts of a rubbery ethylene-propylene polymer having a crystallinity of less than 10 wt .-%, an ethylene content of more than 58 wt .-%, a tensile strength of more than 3.0 MPa and a Mooney viscosity (ML [1 + 4] 125 ° C) as a measure of the molecular weight, which is at least 30 and at most 90, wherein
• C. a maximum of 15 parts of the propylene homopolymer and at least as many parts as indicated by half the numerical value of the melt index of the propylene homopolymer are replaced by as many polyethylene parts having a density between 0.91 and 0.98 g / cm³ ,

2. Mixture according to claim 1, characterized in that the maximum Mooney viscosity of the rubbery ethylene-propylene polymer from the equation where mi is the melt index of the propylene polymer used. 3. Mixture according to claim 2, characterized in that the maximum Mooney viscosity from the equation results. 4. Mixture according to claims 1 to 3, characterized in that the content of
A: 50 to 70 parts of propylene homopolymer and
B: 30 to 50 parts of ethylene-propylene polymer
is. 5. Mixture according to Claims 1 to 4, characterized that the minimum number of propylene homopolymer parts, the are replaced by polyethylene, ¾ of the numerical value of the melt index of the propylene polymer. 6. Mixture according to Claims 1 to 5, characterized that the rubbery ethylene-propylene polymer a Has ethylene content of at least 61% by weight. 7. Mixture according to claim 6, characterized in that the rubbery ethylene-propylene polymer maximum 77% by weight, preferably not more than 75% by weight and in particular not more than 70% by weight Contains ethylene. 8. Mixture according to Claims 1 to 7, characterized that the rubbery ethylene-propylene copolymer a Crystallinity of at most 4 wt .-% and in particular of maximum 1 wt .-% has. 9. mixture according to claims 1 to 8, characterized that the rubbery ethylene-propylene polymer has a tensile strength of more than 5.0 MPa. 10. Mixture according to claims 1 to 9, characterized that the ethylene-propylene polymer in an amount of maximum 20 wt .-% and in particular of at most 10 wt .-% a multiple contains unsaturated monomer. 11. Mixture according to claim 10, characterized in that the polyunsaturated monomers from the group dicyclopentadiene, Ethylidenenorbornene, 1,4-hexadiene, 1,5-hexadiene and norbornadiene is selected. 12. Mixture according to Claims 1 to 11, characterized the crystalline propylene homopolymer has a melt index between 1.5 and 20 dg / min (230 ° C, 2.16 kg) and preferably between 5 and 15 dg / min (230 ° C, 2.16 kg).   13. Mixture according to claims 1 to 12, characterized that the propylene homopolymer has a density between 0.900 and 0.910 g / cm³ has. 14. Mixture according to claims 1 to 13, characterized that the density of the polyethylene is more than 0.94 g / cm³. 15. Mixture according to Claims 1 to 14, characterized that the density of the polyethylene is more than 0.96 g / cm³. 16. Mixture according to claims 1 to 15, characterized that the polyethylene has a melt index between 0.1 and 35 dg / min (190 ° C, 2.16 kg) and preferably between 1 and 25 dg / min (190 ° C, 2.16 kg). 17. Mixture according to claims 1 to 16, characterized the polyethylene contains a maximum of 0.5% by weight of comonomer. 18. Use of the mixtures according to claims 1 to 17 for Production of objects.