BRPI0620499A2 - polyolefinic compositions having low gloss - Google Patents

Abstract

POLYOLEFINIC COMPOSITIONS HAVING LOW GLOSS. The present invention describes a polyolefin composition comprising, in weight percentages: A) from 10 to 50% of a propylene copolymer with one or more comonomers (s) chosen from ethylene and CH-2 ~ = CHR <244> -olefins, wherein R is 2 to 8 carbon alkyl, which copolymer contains 1 to 8% comonomer (s); B) 50 to 90% of a mixture of copolymers (b ^ I ^) and (b ^ II ^), in which the copolymer (b ^ I ^) contains 18 to 40% ethylene, and the copolymer (b ^ II ^) contains from 55 to 85% ethylene, and the weight ratio of (b ^ I ^) / (b ^ II ^) is 0.2 to 2; in which composition the copolymeric component (b ^ I ^) is present in amounts of 15% or more with respect to the total weight of (A) + (B), the weight ratio C ~ 2 ~ ^ II ^ / C ~ 2 ~ ^ I ^ of the ethylene content (C ~ 2 ~ ^ II ^) in the copolymeric component (b ^ II ^) for the ethylene content (C ~ 2 ~ ^ I ^) in the copolymeric component (b ^ I ^) is 1.8 or more and the intrinsic viscosity [<sym>] of the fraction soluble in xylene (XS) at room temperature (about 25 <198> C), in relation to the total weight of (A) + (B), is 2 dL / g or more.

Description

Polyolefinic compositions having low gloss.

The present invention relates to low gloss flexible elastoplastic polyolefin compositions and the process for their preparation.

It is known that polyolefin compositions having elastic properties can be obtained while maintaining good thermoplastic behavior (ie, which can be made into finished products using the same techniques as thermoplastic polymers) by sequential propylene copolymerization, optionally containing minor amounts of olefin comonomers, and then mixtures of ethylene / propylene or ethylene / α-olefin.

Catalysts based on halogenated titanium compounds supported on magnesium chloride are generally used for this purpose.

Given the growing practical interest in this type of compositions due, among other things, to the valuable properties that are typical of polyolefins (such as chemical inertness, mechanical properties and non-toxicity), there is an increasing effort in the state of the art to extend the use. of said compositions to many different fields.

Published European Patent Application 400333 describes elastoplastic polyolefin compositions obtained by sequential polymerization comprising:

A) from 10 to 60 parts by weight of a crystalline polymer or propylene copolymer;

B) from 10 to 40 parts by weight of an ethylene-containing xylene-insoluble polymeric fraction at room temperature;

C) 30 to 60 parts by weight of a ethylene / propylene copolymer fraction.

Such compositions are flexible and have valuable elastic properties, as demonstrated by the low flexural modulus values (less than 700 MPa, and typically greater than 200 MPa) associated with good post-stretch permanent deformation values, but do not have particularly good optical characteristics. , in particular with regard to the gloss values which, on the other hand, for uses such as sheet extrusion, thermoforming, automotive skin layers, blow molding, films, should preferably be less than 40, measured in extruded sheets, associated with with flexural modulus values of 200 MPa or less, preferably 150 MPa or less.

Another important feature of the elastoplastic polyolefin compositions to be used in said applications is represented by the tensile properties, in particular the elongation at break, which should be as high as possible.

US Patent 4910262 and Japanese Patent Application JP published 162621/1983 describe elastoplastic polyolefin compositions containing two types of ethylene rich copolymers with different ethylene contents.

However, the specific component combinations described (in particular with reference to the description of the examples) do not provide a good balance of said properties.

Therefore, there is still a need for flexible elastoplastic polyolefin compositions (i.e., with relatively low flexural modulus values) but also having low gloss values and high elongation at break values.

In response to such needs, the present invention provides an elastoplastic polyolefin composition comprising, by weight percent (all percentages being by weight):

A) from 10 to 50%, preferably from 18 to 40%, more preferably from 20 to 40%, more preferably from 20 to 35%, of a propylene copolymer with one or more comonomer (s) chosen from ethylene and α- olefins CH2 = CHR where R is

an alkyl of 2 to 8 carbons which copolymer contains from 1 to 8%, preferably from 1 to 5% of comonomer, in particular from 1 to 4.5% when the only comonomer is ethylene;

B) from 50 to 90%, preferably from 60 to 82%, more preferably from 60 to 80%, more preferably from 65 to 80%, of a mixture of copolymers (b1) and (b "), both copolymers being copolymers of ethylene and (i) propylene or (ii) other α-olefin (s) CH 2 = CHR 1 wherein R is an alkyl radical of 2 to 8 carbon atoms, or (iii) a combination thereof, optionally with smaller amounts of a diene, wherein copolymer (b1) contains 18 to 40%, preferably 20 to 35% ethylene, and copolymer (b ") contains 55 to 85%, in particular 55 to 80%, preferably 65 to 85%, in particular 65 to 80% ethylene, and the weight ratio of (b ') / (b ") is 0.2 to 2, preferably 0.3 to 1.5; in which composition the copolymer component (b1) is present in amounts of 15% or more, preferably 20% or more, in particular 15 or 20 to 50%, relative to the total weight of (A) + (B), the weight ratio C2 "/ C2 'of the ethylene content (C2") in the copolymer component is rich (b ") for the ethylene (C2) content in the copolymer component (b1) is 1.8 or more, preferably 2 or more, more preferably 2.5 or more, in particular up to 4, and a The intrinsic viscosity [η] of the xylene-soluble fraction (XS) at room temperature (about 25 ° C) with respect to the total weight of (A) + (B) is 2 dL / g or more, more preferably 3 dL / g or more, in particular from 2 or 3 to 7 dL / g.

The total amount of copolymerized ethylene is preferably from 25 to 60 wt%, more preferably from 25 to 55 wt%, in particular from 25 to 50 wt%. The compositions typically have at least one melting peak determined by DSCl at a temperature greater than 120 ° C but equal to or less than 150 ° C, in particular 135 to 145 ° C.

Other preferred features of the compositions of the present invention are:

weight ratio (b ") / (A) greater than or equal to 1, more preferably greater than or equal to 1.1, more preferably greater than or equal to 1.2, the upper limit being more preferably up to 2;

gloss values less than or equal to 15%, more preferably less than or equal to 10%;

Shore D values less than or equal to 40, more preferably less than or equal to 35, in particular from 40 or 35 to 15;

- MFR values, measured according to ASTM-D 1238, condition L (230 ° C, with 2.16 kg load) from 0.01 to 10 g / 10 min, more preferably from 0.05 to 5 g / 10 min;

flexural modulus less than or equal to 200 MPa, more preferably less than or equal to 150 MPa;

- tensile strength at 5 to 22 MPa;

- elongation at break greater than 400%;

substantially no bleaching when bending a 1 mm plate;

the amount of xylene soluble fraction at room temperature (XS) of 40 to 70 wt%, more preferably 45 to 65 wt%, relative to the total weight of (A) + (B);

- weight ratio (B) / (XS) of the content (B) of the copolymer component (B) to the xylene-soluble fraction (XS) at room temperature (about 25 ° C), both (B and

XS) referring to the total weight of (A) + (B) 1 of 1.5 or less, more preferably 1.4 or less, in particular from 1.5 or 1.4 to 0.8;

- isotacticity index (II) of component (A) greater than or equal to 90%;

- molecular weight distribution in component (A), expressed as the Mw / Mn ratio as measured by GPC (Gel Permeation Chromatography), greater than or equal to 3,5, plus

preferably greater than or equal to 4 or 4.5, in particular 5 or more.

The above-mentioned GPC measure is preferably performed on 1,2,4-trichlorobenzene; in detail, samples are prepared at a concentration of 70 mg / 50 mL of stabilized 1,2,4-trichlorobenzene (250 μg / mL BHT - CAS Registry No. 128-38-0); the samples are then heated to 170 ° C for 2.5 hours to solubilize; measurements are taken on a Waters GPCV2000 equipment at 145 ° C at a flow rate of 1.0 mL / min. using the same stabilized solvent; Three Polymer Lab columns are used in series (Plgel, 20 μηι ALS mixed, 300 χ 7.5 mm). The polymerization process for preparing the compositions of the present invention may be carried out continuously or in batches, following known techniques, operating in liquid phase, in the presence or not of an inert diluent, or in gas phase, or with mixed liquid techniques. -gas.

Polymerization times and temperatures are not critical and are advantageously in the range of 0.5 to 5 hours, and 50 to 90 ° C, respectively.

The propylene polymerization to form component (A) is in the presence of ethylene or α-olefin (s) CH 2 = CHR where R is an alkyl of 2 to 8 carbon atoms, such as for example butene-1, pentene-1,4-methylpentene-1, hexene-1 and octeno-1, or combinations thereof.

Copolymerization of ethylene and propylene or other α-olefin (s), examples of which are given above for component (A), or combinations thereof, to form components (b1) and (b ") may occur in presence of a diene, conjugated or not, such as butadiene, 1,4-hexadiene, 1,5-hexadiene and ethylidene norbornene-1.

Diene, when present, is typically in an amount of 0.5 to 10% by weight with respect to the weight of the component in question (namely, b 'or b ").

In particular, the compositions may be prepared with a sequential polymerization process performed at least three stages, one or more for the synthesis of component (A), the other for the synthesis of components (b1) and (b ") by least one separate stage being used for the preparation of each of (b1) and (b "). The polymerization in the subsequent stages occurs in the presence of the obtained polymer and the catalyst used in the preceding stage (s).

Molecular weight regulation is done using frequently used molecular weight regulators, eg hydrogen and ZnEt2. As already mentioned, polymerization can occur in liquid phase, gas phase, or liquid-gas phase.

For example, it is possible to prepare component (A) in a copolymerization stage using liquid propylene as a diluent, and components (b1) and (b ") in the following stages of gas phase copolymerization, without intermediate stages except for partial degassing. of propylene.

Preferably, all components (A), (b1) and (b ") are prepared by operating the gas phase copolymerization. The order in which the components are prepared is not critical.

The reaction temperature at the polymerization stage (s) for the preparation of component (A) and that for the preparation of components (b ') and (b ") may be the same or different, and is usually from 40 to 90 ° C, preferably from 50 to 80 ° C for the preparation of component (A) 1 and from 40 to 70 ° C for the preparation of components (b1) and (b ").

The single stage pressure, if executed in liquid monomer, is that which competes with the vapor pressure of liquid propylene at the operating temperature used, and is modified by overpressure of the monomer (s) and hydrogen used as regulator. molecular weight, and possibly by the vapor pressure of the small amount of diluent used to feed the catalytic mixture.

The polymerization pressure, if carried out in liquid phase, may indicatively be from 5 to 30 atm.

Residence times for the three or more stages depend on the desired ratio between components (A), (b1) and (b "), and are usually from 15 min to 8 hours.

Said polymerization processes are generally performed in the presence of stereospecific Ziegler-Natta catalysts supported on magnesium dihalets.

Said stereospecific catalysts used in polymerization comprise the reaction product between:

1) a solid component, comprising a titanium compound and an electron donor compound (internal electron donor) supported on magnesium dihalide (preferably chloride);

2) an alkyl aluminum compound (cocatalyst); and optionally

3) an electron donor compound (external electron donor).

Said catalysts are preferably capable of producing polypropylene homopolymer having an isotactic index greater than 90%.

Solid catalytic component (1) contains an electron donor compound generally chosen from ethers, ketones, lactones, compounds containing Ν, P and / or S atoms, and mono- and dicarboxylic acid esters.

Catalysts having the characteristics mentioned above are well known in the patent literature; Particularly advantageous are the catalysts described in US Patent 4,399,054 and European Patent 45977.

Among said electron donating compounds, phthalic acid esters and succinic acid esters are particularly suitable.

Suitable succinic acid esters are represented by formula (I): <formula> formula see original document page 7 </formula>

wherein the same or different R1 and R2 radicals are a straight or branched C1 -C20 alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms; the same or different radicals from R3 to R6 are hydrogen or a straight or branched C1 -C20 alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms, and R3 to R6 radicals which are attached to the same carbon atom can be linked together to form a cycle.

R 1 and R 2 are preferably C 1 -C 8 alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl groups. Particularly preferred are compounds wherein R1 and R2 are selected from primary alkyls, in particular branched primary alkyls. Examples of suitable R1 and R2 groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl and neopentyl.

One of the preferred groups of compounds described by formula (I) is that wherein R 3 to R 5 are hydrogen and R 6 is a branched alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl radical having from 3 to 10 carbon atoms. Another group of compounds of those of formula (I) is one wherein at least two radicals between R3 and R6 are different from hydrogen and are selected from C1-C20 straight or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl and alkylaryl groups optionally containing heteroatoms. Particularly preferred are compounds wherein the two different hydrogen radicals are attached to the same carbon atom.

Also, components in which at least two different hydrogen radicals are attached to different carbon atoms, ie R3 and R5 or R4 and R6, are particularly preferred.

Other particularly suitable electron donors are 1,3-diethers, as illustrated in published European patent applications EP-A-361 493 and 728769.

As cocatalysts (2), trialkylaluminum compounds such as triethyl-AI, triisobutyl-AI and tri-n-butyl-AI may preferably be used.

Electron donating compounds (3) which may be used as external electron donors (added to the alkyl-AI compound) include aromatic acid esters (such as alkyl benzoates), heterocyclic compounds (such as 2,2,6,6). tetramethylpiperidine and 2,6-diisopropylpiperidine), and in particular silicon compounds containing at least one Si-OR bond (where R is a hydrocarbon radical). The aforementioned 1,3-diethers are also suitable for use as external donors. In case the internal donor is one of said 1,3-diethers, the external donor may be omitted.

Catalysts can be pre-contacted with small amounts of olefin (prepolymerization) by keeping the catalyst in suspension in a hydrocarbon solvent, and polymerizing at ambient temperatures up to 60 ° C, thereby producing a polymer amount of 0.5 to 3 times. the weight of the catalyst.

The operation may also occur in liquid monomer, in this case producing a polymer amount of up to 1000 times the weight of the catalyst.

Other catalysts that may be used in the process according to the present invention are metallocene type catalysts as described in US 5,324,800 and EP-A-O 129 368; Particularly advantageous are bridged bis-indenyl metallocenes, for example as described in U.S. Patent Nos. 5,145,819 and EP-AO 485,823. Another class of suitable catalysts are so-called restricted geometry catalysts, as described in EP-AO patents. 416,815 (Dow), EP-AO 420,436 (Exxon), EP-A-0 671 404, EP-A-0 643 066 and WO 91/04257. These metallocene compounds may be used in particular to produce components (bI) and (bII).

The compositions of the present invention may also contain additives, fillers and pigments frequently used for olefinic polymers, such as, for example, nucleating agents, extension oils, mineral fillers, organic and inorganic pigments.

The polyolefin compositions of the present invention find application particularly in the fields of sheet extrusion, blow molding and thermoforming, in particular, as previously mentioned, for uses such as automotive skin layers and films.

The practice and advantages of the present invention are described below in the following examples. These examples are illustrative only, and are not intended to limit the permitted scope of the present invention in any way.

The following analytical methods are used to characterize polymeric compositions. Melt flow rate: ASTM-D 1238, condition L. Intrinsic Viscosity fnl: determined in tetrahydronaphthalene at 135 ° C. Ethylene content: IR spectroscopy.

Gloss: Method ASTM D 523 (1 mm extruded sheet, measured at an angle of 60 °).

Shore AeD: ISO 868.

Flexural module: ISO 178 (4 mm thick compression molded plate).

Tensile strength: ISO 527 (1 mm extruded sheet).

Elongation at break: ISO 527 (1 mm extruded sheet).

Tear strength: ISO 6383.

Xylene-soluble and insoluble fractions: 2.5 g of polymer and 250 cm3 of xylene are introduced into a glass vial equipped with a refrigerator and a magnetic stirrer. The temperature is raised by 30 minutes to the boiling point of the solvent. The clear solution thus obtained is then refluxed and stirred for a further 30 minutes. The sealed vial is then kept for 30 minutes in an ice and water bath and a 25 ° C thermostatic water bath for 30 minutes as well. The solid thus formed is filtered on rapid filter paper. 100 cm @ 3 of the filtered liquid is poured into a pre-weighed aluminum container which is heated in a nitrogen flow hotplate to remove the solvent by evaporation. The vessel is then kept in an oven at 80 ° C under vacuum to constant weight. The weight percent of xylene soluble polymer at room temperature is then calculated.

The weight percent of xylene insoluble polymer at room temperature is considered to be the isotactic index of the polymer. This value substantially corresponds to the isotacticity index determined by boiling n-heptane extraction, which by definition constitutes the polypropylene isotacticity index.

Example 1 and Comparative Example 1

The solid catalyst component used in the polymerization is a highly stereospecific Ziegler-Natta magnesium chloride supported catalyst component containing about 2.2% by weight of titanium and diisobutyl phthalate as internal donor prepared in analogy to the method described in Example 3. of published European patent application 395083.

Catalytic system and prepolymerization treatment

Prior to introducing it into the polymerization reactors, the solid catalytic component described above is contacted at -5 ° C for 5 minutes with triethyl aluminum (TEAL) and dicyclopentyl dimethoxysilane (DCPMS) at a weight ratio of TEAL / DCPMS of about 5 ° C. and in an amount such that the weight ratio TEAL / solid catalyst component is 5.

The catalytic system is then subjected to polymerization by suspending it in liquid propylene at 25 ° C for about 30 minutes before introducing it into the first polymerization reactor.

Polymerization In a first gas phase polymerization reactor a propylene copolymer (component A) is produced by feeding in a continuous and constant flow the prepolymerized catalytic system, hydrogen (used as a molecular weight regulator) and propylene and ethylene in the gaseous state.

The polypropylene copolymer produced in the first reactor is discharged in a continuous stream and, after being purged from unreacted monomers, is introduced in a continuous stream into a second gas phase polymerization reactor, along with quantitatively constant flows of hydrogen, ethylene. and propylene in the gaseous state.

The polymer from the second reactor is discharged in a continuous stream and, after being purged from unreacted monomers, is introduced in a continuous stream into a third gas phase reactor, along with quantitatively constant flows of hydrogen, propylene and ethylene in the state. gaseous.

Propylene / ethylene copolymers (components b 'and b ") are thus produced in the second and third reactors. The polymerization conditions, reagent molar ratios and composition of the obtained copolymers are shown in Table 1.

The polymer particles leaving the third reactor are steam treated to remove reactive monomers and volatile substances, and then dried.

The polymer particles are mixed with the usual stabilizers in a Berstorff ZE 25 twin screw extruder (thread length / diameter ratio: 33) and are extruded under a nitrogen atmosphere under the following conditions:

Rotation Speed: 250 rpm;

Extruder output: 6 to 20 kg / hour

Melting temperature: 200 to 250 ° C

The characteristics relative to the polymeric compositions reported in Table 2 are obtained from the measurements made on the polymer thus extruded. For comparison purposes, Table 2 reports the properties of a polyolefin composition (Comparative Example 1C) prepared by sequential polymerization and comprising:

A) 31% by weight of a statistical propylene-ethylene copolymer containing about 3.5% by weight of ethylene;

B) 69% by weight of an ethylene propylene elastomeric copolymer containing about 27% by weight ethylene. TABLE 1

<table> table see original document page 11 </column> </row> <table>

Notes: C3 = propylene; C2 = ethylene; fraction = amount of polymer produced in the reactor in question; C2- (copolymer) content = ethylene content with respect to the copolymer prepared in the reactor in question.

TABLE 2

<table> table see original document page 11 </column> </row> <table> <table> table see original document page 12 </column> </row> <table>

Notes: X.S.I.V. = intrinsic viscosity of the xylene soluble fraction; MD = machine direction; TD = transverse direction.

Claims (7)

1. "Polyolefinic composition", characterized in that it comprises by weight percentages: A) from 10 to 50% of a propylene copolymer with one or more comonomer (s) chosen from ethylene and α-olefins CH2 = CHR in wherein R is an alkyl of 2 to 8 carbons which copolymer contains from 1 to 8% comonomer (s); B) from 50 to 90% of a mixture of copolymers (b1) and (b "), both copolymers being copolymers of ethylene and (i) propylene or (ii) other α-olefin (s) CH2 = CHR, wherein R is an alkyl radical of 2 to 8 carbon atoms, or (iii) a combination thereof, optionally with smaller amounts of a diene, wherein the copolymer (bI) contains from 18 to 40% ethylene, and the copolymer (b ") contains from 55 to 85% ethylene, and the weight ratio of (b ') / (b") is 0.2 to 2; in which composition the copolymer component (b1) is present in amounts of 15% or more with respect to the total weight of (A) + (B) 1 the weight ratio C2 "/ C2 'of the ethylene content (C2") in the copolymer component (b ") to the ethylene content (C2) in the copolymer component (b1) is 1.8 or more and the intrinsic viscosity [η] of the xylene soluble fraction (XS) at room temperature with respect to the total weight of (A) + (B) is 2 dL / g or more. "Composition" according to claim 1, characterized in that it has an MFR value of 0.01 to 10 g / 10 min. "Composition" according to Claim 1, characterized in that it has flexural modulus values less than or equal to 200 MPa. "Composition" according to Claim 1, characterized in that it has Shore D values less than or equal to 40. "Polymerization process" for preparing the polyolefinic composition according to claim 1, characterized in that it comprises at least three sequential stages, wherein components (A), (bI) and (bII) are prepared in stages. subsequently separated, operating at each stage except the first stage, in the presence of the formed polymer and catalyst used in the preceding step. 6. "Manufactured articles", characterized in that they comprise the polyolefin composition according to claim 1. "Articles" according to claim 6, characterized in that they are in the form of sheets, automotive skin layers, blow molded articles or films.