TWI415889B - Polyolefin compositions having low hardness and low gloss - Google Patents

Abstract

A polyolefin composition comprising, in percent by weight: A. 20-35% of a propylene homopolymer or copolymer with up to 8% of comonomer (s); B. 65-80% of a copolymer of ethylene and (i) propylene or (ii) CH2 = CHR alpha-ole-fins, where R is a 2-8carbon alkyl radical, or(iii)a combination thereof, optionally with minor amounts of a diene, containing from 40 to less than 54% of ethylene; wherein the weight ratio B/XS, of the content B of copolymer component (B) to the fraction XS soluble in xylene at room temperature, both referred to the total weight of (A) + (B), is of 1.25 or less.

Description

Polyolefin composition having low hardness and low gloss

This invention relates to polyolefin compositions having low hardness and low gloss and methods of making same. It is well known to continuously polymerize propylene, optionally containing relatively small amounts of olefinic comon, and then the ethylene/propylene or ethylene/alpha-olefin mixture can be obtained with elastic properties while maintaining good thermoplastic properties (i.e., for use in thermoplastic polymers). The same technology can be converted into a polyolefin composition of the finished product.

For this purpose, a catalyst based on a titanium halide compound supported on magnesium chloride is used.

The important properties of polyolefins (eg, chemical inertia, mechanical properties, and non-toxicity), while increasing the practical importance of this type of composition, the results of the increased efforts in this technology to extend the use of these compositions to many different field.

In the European Patent Application No. 400333, an elastic plastic polyolefin composition obtained by continuous polymerization is described. Including: A) 10-60 parts by weight of crystalline polymer or copolymer of propylene; B) 10-40 parts by weight of ethylene-containing polymer fraction insoluble in xylene at room temperature; C) 30-60 Part by weight of ethylene/propylene/copolymer fraction which is soluble in xylene at room temperature and contains 40-60% by weight of ethylene.

The compositions are flexible and have important elastic properties, such as via low flexural modulus values (less than 700 MPa, but related to good tension settings). Typically greater than 200 MPa), but does not have particularly good hardness values and optical properties, especially with respect to gloss values, on the other hand, as a variety of uses such as: sheet extrusion, hot press forming, automotive outer lamination, blowing Gas forming, film, which preferably comprises a hardness of between 10 and 40 Shore measured on the extruded sheet, relating to a value of 200 MPa or lower flexural modulus, and to a hardness of Xiao ( Low value of Shore).

In another aspect, European Patent Application No. 472,946 shows that by reducing the ethylene content of the soluble fraction C in xylene, therefore, the ethylene content of the total ethylene/propylene elastomer copolymer fraction may be deflected. Improved balance of modulus and hardness. However, also in this case, the gloss value is too high, as shown in the examples.

Accordingly, there is a need for an elastic plastic polyolefin composition that is flexible (i.e., has a relatively low flexural modulus value), soft (i.e., has a relatively low hardness value), and also has a low gloss value.

In response to this need, the present invention provides a polyolefin composition comprising, by weight (all percentages by weight): A) 20-35%, preferably 23-33% of propylene homopolymer or propylene and Selected from ethylene and CH ₂ =CHR α-olefins, wherein R is a copolymer of one or more comonomers of a 2-8 carbon alkyl group, the copolymer contains up to 8% of a co-monomer, or a combination of polymers .

B) 65-80%, preferably 67-77% of ethylene with (i) propylene or (ii) CH ₂ =CHR α-olefin, wherein R is a 2-8 carbon alkyl group, or (iii) a combination thereof , if necessary, having a relatively small amount of diene, containing from at least 54%, preferably from 40 to 52% of ethylene; wherein the content of the copolymer component (B) is B at room temperature (about 25 ° C) The weight ratio of the fraction XS soluble in xylene is B/XS, both of which are 1.25 or less, preferably 1.20 or less, based on the total weight of (A) + (B), especially since 1.25 to 0.70, or from 1.20 to 0.70.

The total amount of copolymerized ethylene is preferably from 20 to 50% by weight, more preferably from 25 to 45% by weight, especially from 25 to 40% by weight.

Other preferred features of the composition of the invention are: - equal to or less than 15% gloss value, more preferably equal to or less than 10%, especially equal to or less than 7%; - a Shore A value equal to or less than 90, More preferably equal to or less than 85; - Shore D value equal to or less than 35, especially from 35-15; - measured from 0.01 according to ASTM-D1238 condition L (230 ° C with a load of 2.16 gram) MFR value of -10g/10min, more preferably from 0.05-5g/10min; - 璩 璩 ASTM-D1238 condition L, the MFR value of the measured component (A) is equal to or higher than 2g/10min, more preferably equal to or Above 3g/10min; - flexural modulus equal to or less than 200MPa, preferably equal to or less than 120MPa; - stress at break: 4-15MPa; - elongation at break: above 550%; - when bent 1mm thick When the board is used, there is substantially no whitening (whitening). - the fraction (XS) soluble in xylene at room temperature is from 40 to 70% by weight, more preferably from 45 to 65% by weight, based on the total weight of (A) + (B) ). - the weight ratio of the fraction XS soluble in xylene at room temperature to the total ethylene content C ₂ , XS / C ₂ , both based on the total weight of (A) + (B) is 2.25 or less It is preferably 2.10 or less, especially from 2.25 to 1.6 or from 2.10 to 1.6. The ultimate viscosity [η] of the -XS fraction is less than 3 dl/g, especially from 2.9 to 1.5 dl/g. - The isotacticity index (II) of component A is equal to or greater than 90%, more preferably equal to or higher than 95%.

The polymerization process used to prepare the compositions of the present invention may be carried out in a continuous or batch manner, followed by well known techniques in the liquid phase, in the presence or absence of an inert diluent, or in the gas phase, or by mixing. Liquid-gas technology.

The polymerization time and temperature are not critical, each advantageously from 0.5 to 5 hours, and from 50 to 90 °C.

The propylene is polymerized to form component (A) which may be in ethylene or CH 2 =CHR α-olefin, wherein R is a 2-8 carbon alkyl group, for example, butene-1, pentene-1, 4-methylpentyl The presence of ene-1, hexene-1 and octene-1, or a combination thereof, is accomplished.

Copolymerization of ethylene with propylene or other alpha-olefins, examples of which have been shown above with respect to component (A), or a combination thereof to form component (B) can occur in the presence of a diene, which is conjugated or not For example, butadiene, 1,4-hexadiene, 1,5-hexadiene and ethylene-norborene-1.

When present, the typical amount of dienes is from 0.5 to 10% by weight relative to the weight of B.

In particular, the compositions can be prepared using a continuous polymerization process carried out in at least two stages, one or more stages for synthesizing component (A) and the other stages for synthesizing component (B). The polymerization in the subsequent stages occurs in the presence of the polymer obtained in the previous stages and the catalyst used. The molecular weight adjustment is accomplished using molecular weight regulators commonly used, such as hydrogen and ZnEt ₂ .

The high value of MFR can be obtained directly at the time of polymerization or via continuous degradation of the polymer (usually by chemical viscosity reduction).

The chemical viscosity reduction of the polymer is carried out in the presence of a free radical initiator, such as a peroxide. Examples of free radical initiators which can be used for this purpose are 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and dicumyl peroxide.

The viscosity reducing treatment is carried out using an appropriate amount of a free radical initiator and is preferably carried out in an inert atmosphere such as nitrogen. This method can be carried out using methods, apparatus, and operating conditions well known in the art. The value of the ultimate viscosity [η] of the previously defined XS fraction of the polymer composition of the present invention is reduced as an effect of the degradation method.

Particularly preferred is a polymer composition having a viscosity [η] of less than 3 dl/g, particularly from 2.9 to 1.5 dl/g, which comprises the same proportions of the same components (A) and (B) (i.e., each of the above components and ratios) The precursor composition was obtained by degradation, but the precursor composition had a viscosity [η] of an XS fraction of 3 dl/g or more.

However, a polymer composition having a viscosity [?] of 3 dl/g or more, particularly from XS fraction of 3-4 dl/g, is also within the scope of the present invention.

As already mentioned, the polymerization can be produced in the liquid phase, in the gas phase or in the liquid-gas phase.

For example, it is possible to prepare component (A) in a polymerization stage using liquid propylene as a diluent, and to prepare component (B) in the following copolymerization stage in the gas phase, except for partial degassing of propylene, without intermediate stage.

Both components (A) and (B) are preferably produced by polymerization which is operated in the gas phase. The order in which the ingredients are prepared is not critical.

The reaction temperature in the polymerization stage for preparing component A and in the polymerization stage for preparing component (B) may be the same or different, and the reaction temperature for preparing component (A) is usually 40 to 90 ° C, preferably 50 -80 ° C, used to prepare component (B) is 40-70 ° C.

If carried out in a liquid monomer, the pressure in a single stage is a pressure which competes with the vapor pressure of liquid propylene at the operating temperature used and can be changed by the overpressure of the monomer and the use of hydrogen as a molecular weight regulator, and It may be altered by the vapor pressure of a small amount of inert diluent used in feeding the catalyst mixture.

If completed in the liquid phase, the indicated polymerization pressure may be from 5 to 30 atm. Based on the required ratio between components (A) and (B), the residence time relative to two or more stages is typically from 15 minutes to 8 hours.

The polymerization process is usually carried out in the presence of a stereospecific Ziegler-Natta catalyst supported on magnesium dihalide.

The stereospecific catalyst used in the polymerization comprises the product of the reaction between: 1) a solid component titanium-containing compound and an electron donor compound supported on magnesium dihalide (preferably chloride). Internal electron donor; 2) an alkyl aluminum compound (auxiliary catalyst) and, if desired, 3) An electron donor compound (external electron donor).

Preferably, the catalysts produce a homopolymer polypropylene having an index of isotacticity above 90%.

The solid catalyst component (1) contains a compound generally selected from the group consisting of ethers, ketones, lactones, and N, P, and/or S atoms, and monocarboxylic acid esters and dicarboxylic acid esters as electron donor compounds.

Catalysts having the above-described characteristics are well known in the patent literature, and are particularly advantageous in the catalysts described in U.S. Patent 4,398,054 and E.P. Patent 45,977.

Among the electron donor compounds, those which are particularly suitable are phthalates and succinates.

The appropriate succinate is represented by formula (I):

The R ₁ and R ₂ groups which are the same or different from each other are a C1-C20 linear or branched alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group or an alkylaryl group, optionally containing a hetero atom, the same or each other. Different R ₃ -R ₆ groups are hydrogen or C1-C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, aralkyl or alkaryl, optionally containing heteroatoms, and attached to the same The R ₃ -R ₆ groups on the carbon atom may be joined together to form a ring.

R ₁ and R _{2 are} preferably a C1-C8 alkyl group, a cycloalkyl group, an aryl group, an arylalkyl group or an alkylaryl group. Particularly preferred are those compounds wherein R ₁ and R ₂ are selected from the group consisting of a first alkyl group, particularly selected from a branched first alkyl group. Examples of suitable R ₁ and R ₂ are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl and 2-ethylhexyl. Particularly preferred are ethyl, isobutyl and neopentyl.

One of the preferred group compounds of the formula (I) is one wherein R _{3 -} R ₅ are hydrogen and R ₆ is a branched alkyl group having from 3 to 10 carbon atoms, a cycloalkyl group, an aryl group, an aralkyl group. Alkyl or alkaryl. Further preferred groups of compounds of the formula (I) are those wherein at least two of the radicals from R _{3 to} R ₆ are different from hydrogen and are selected from the group consisting of C 1 -C 20 linear or branched alkyl, alkenyl, cycloalkane A aryl group, an aryl group, an arylalkyl group or an alkylaryl group, optionally containing a hetero atom. Particularly preferred are those compounds in which two groups different from hydrogen are attached to the same carbon atom.

Further, a compound in which at least two groups different from hydrogen are also bonded to different carbon atoms, that is, R ₃ and R ₅ or R ₄ and R ₆ are particularly preferable. Other electron donors which are particularly suitable are the 1,3-diethers, as exemplified in the published EP patent applications EP-A-361 493 and 728 769.

As the auxiliary catalyst (2), a trialkyl aluminum compound such as triethyl aluminum, triisobutyl aluminum, and tri-n-butyl aluminum is preferably used.

An electron donor compound (3) as an external electron donor can be used, (added to an alkyl aluminum compound) including an aromatic acid ester (for example, an alkyl benzoate) heterocyclic compound (for example, 2, 2, 6, 6- Tetramethyl acridine and 2,6-diisopropylacridine), and particularly an anthracene compound containing at least one Si-OR bond, wherein R is a hydrocarbyl group. The aforementioned 1,3-diether is also suitably used as an external donor. In the case where the internal donor is one of the 1,3-diethers, the external donor can be omitted.

The catalyst can be precontacted (prepolymerized) with a small amount of olefin to maintain the catalyst in suspension in a hydrocarbon solvent and polymerized at a temperature from room temperature to 60 ° C, thus producing a polymer amount of 0.5-3 times Media weight.

This operation can also be carried out in liquid monomers, in which case poly The amount of the compound is up to 1000 times the weight of the catalyst.

Other catalysts which can be used in the process according to the invention are metal-aromatic catalysts as described in USP 5,324,800 and EP-A-0129368; particularly advantageous are bridged bis-indenyl metal aromatics such as USP 5,145,819 and EP. -A-0 485823. A suitable class of suitable catalysts are the so-called constrained geometry catalysts such as: EP-A-0 416815 (Dow), EP-A-0 420436 (Exxon), EP-A-0 671404, EP-A-0 643066 and WO91/04257 and the like. The component (B) can be produced by using these metal aromatic compounds in particular.

The compositions of the present invention may also contain additives, fillers and pigments commonly used in olefin polymers, such as, for example, nucleating agents, extendable oils, mineral fillers, organic and inorganic pigments.

The polyolefin composition of the present invention is particularly useful in the range of sheet extrusion, blow molding, and hot press molding.

The utility and advantages of the present invention are disclosed in the following examples. The examples are merely illustrative of the indefinite and are not intended to limit the scope of the invention in any way.

The following analytical methods were used to indicate the properties of the polymer composition.

- Melt flow rate : ASTM-D 1238, Condition L (230 ° C, 2.16 Kg). - [η] ultimate viscosity : determined at 135 ° C in tetralin. - Ethylene content : IR spectroscopy. - Gloss : Method of ASTM D523 (1 mm extruded sheet). - Shaw A and D : ISO 868 (4 mm thick compression molded board). - Flexural modulus : ISO 178 (4 mm thick compression molded board). - Breaking stress : ISO 527 (1 mm extruded sheet). - Elongation at break : ISO 527 (1 mm extruded sheet).

Fractions of soluble and insoluble in xylene 2.5 g of polymer and 250 cm ³ of xylene were introduced into a glass flask equipped with a freezer and a magnetic stirrer. The temperature was raised to the boiling point of the solvent within 30 min. The clear solution thus obtained was kept under reflux and stirred for another 30 minutes. The closed flask was then kept in an ice and water bath for 30 minutes and also kept in a constant temperature water bath at 25 ° C for 30 minutes. The solid thus formed was filtered on a fast filter paper. 100 cm ^{3 of} the filtered liquid was poured into a previously weighed aluminum container, which was heated on a hot plate under a nitrogen flow to remove the solvent by evaporation. The vessel was then held in an oven at 80 ° C under vacuum until a constant weight was obtained. The weight % of the polymer soluble in xylene at room temperature is then calculated.

The weight % of the polymer insoluble in xylene at room temperature is taken into account as the isotactic index of the polymer. This value is substantially equivalent to the isocratic index determined by extraction with boiling n-heptane, which by definition constitutes the isotactic index of polypropylene.

Example 1 and Comparative Example 1

The solid catalyst component used for the polymerization is a highly stereospecific ruthenium-nanocatalyst component supported on magnesium chloride, containing about 2.2% by weight of titanium and diisobutyl phthalate as internal donors, similar to EP. The method described in Example 3 of the published patent application 395,083 is prepared.

Catalytic system and pre-polymerization The solid catalyst component was contacted with triethylaluminum (TEAL) and dicyclopentyldimethoxydecane (DCPMS) for 5 minutes at -5 ° C before being introduced into the polymerization reactor. At TEAL/DCPMS equal to or about 5 The weight ratio, and the TEAL/solid catalyst component weight ratio in this amount is equal to 5.

The catalyst system was then subjected to prepolymerization by maintaining it in suspension in liquid propylene at 25 ° C for about 30 minutes before introducing it into the first polymerization reactor.

polymerization The propylene copolymer component (A) produced by prepolymerizing the catalyst system, hydrogen (using a molecular weight regulator) and gaseous propylene and ethylene in a continuous and constant flow manner into the first gas phase polymerization reaction In the device.

The propylene copolymer produced in the first reactor is discharged in a continuous flow and flushed with unreacted monomers, and introduced into the second gas phase polymerization in a continuous flow manner together with quantitative constant flow of hydrogen, gaseous ethylene and propylene. In the reactor.

The propylene/ethylene copolymer, component (B), is produced in the second reactor. The polymerization conditions, the molar ratio of the reactants, and the composition of the obtained polymer are shown in Table 1.

The polymer particles present in the second reactor are subjected to steam treatment to remove reactive monomers and volatile materials, and then dried.

The polymer particles were mixed with a usual stabilizer in a twin-screw extruder Berstorff ZE25 (screw length/diameter ratio: 33) and extruded in a nitrogen atmosphere under the following conditions: - Rotation rate: 250 rpm. - Extruder output: 6-20kg/hour. - Melt temperature: 200-250 °C.

The properties listed in Table 2 related to the composition of the polymer are so extruded The measurement carried out on the polymer is obtained.

Also the polymer of the composition thus obtained was 0.02% by weight of Luperox ^TM 101 (2,5- dimethyl-2,5-bis (t-butyl peroxide when present) hexane, twin-screw extruder after Werner58 Extrusion/granulation in the press. Extrusion is carried out in a nitrogen atmosphere under the following conditions: - Rotation rate: 200 rpm - Extruder output: 1.50 kg/hour - Melt temperature: about 240 ° C

The properties of the polymer thus obtained are listed in Table 3.

For comparison purposes, Tables 2 and 3 also list the properties of the polyolefin composition prepared by continuous polymerization, (Comparative Example 1C), and include: A) 31% by weight of a random copolymer of propylene and ethylene, inclusive About 3.5% by weight of ethylene; B) 69% by weight of an elastomeric copolymer of propylene and ethylene containing about 27% by weight of ethylene.

Claims (11)

A polyolefin composition comprising, by weight %: (A) 20-35% of a propylene homopolymer or propylene and an ethylene and CH ₂ =CHR alpha-olefin selected from the group consisting of 2-8 carbon alkyl A copolymer of one or more comonomers containing up to 8% co-monomer or a combination of such polymers. (B) 65-80% of ethylene with (i) propylene or (ii) CH ₂ =CHR α-olefin, wherein R is 2-8 carbon alkyl or (iii) a combination thereof, if desired a smaller amount of diene, containing from 40 to less than 54% of ethylene; wherein the content B of the copolymer component (B) is a weight ratio B/XS of the fraction XS soluble in xylene at room temperature (two All are based on the total weight of (A) + (B) and are 1.25 or less. The polyolefin composition of claim 1, wherein the fraction XS soluble in xylene at room temperature has a weight ratio XS/C2 to the total ethylene content C2 (both are (A) + (B The total weight is based on 2.25 or less. The polyolefin composition of claim 1, wherein the ultimate viscosity [η] of the XS fraction measured in tetralin at 135 ° C is less than 3 dl / g. The polyolefin composition according to claim 3 of the patent application is a polyolefin composition obtained by degrading a precursor composition comprising the same components (A) and (B) in the same ratio, but the precursor composition The material has a viscosity [η] of an XS fraction of 3 dl/g or more. A polyolefin composition as claimed in claim 1 which has an MFR value of from 0.01 to 10 g/10 min as measured according to ASTM-D 1238, Condition L. . The polyolefin composition of claim 1, which has a flexural modulus value equal to or less than 120 MPa. A composition of a polyolefin according to claim 1 which has a Shore A value equal to or less than 90. A polymerization process for preparing a polyolefin composition as in claim 1 of the patent application, comprising at least two successive stages, wherein components (A) and (B) are prepared in separate successive stages, except for the first stage In addition, each stage operates in the presence of the polymer formed in the previous stage and the catalyst used. A manufactured article comprising a polyolefin composition as in claim 1 of the patent application. Articles manufactured according to claim 9 of the patent application are prepared by extrusion or injection molding. Articles manufactured in the scope of claims 9 and 10 are in the form of sheets, films or automotive parts.