MXPA96002523A - PROCESS FOR THE PREPARATION OF POLYMEROSVINILAROMATICOS CRISTALINOS WITH A STRUCTURAPREDOMINANTmente SINDIOTACT - Google Patents

Abstract

The present invention relates to a process for the preparation of crystalline vinylaromatic polymers with a predominantly syndiotactic structure, characterized in that it comprises the polymerization of vinylaromatic monomers, either alone or mixed with at least one of the copolymerizable ethylenically unsaturated monomers, in the presence of a catalytic system consisting essentially of: a) a titanium complex having the formula (I): Ti (OCONRR ') n in which R and R' are the same or different, represent an aliphatic radical of C1-C12 or an aromatic radical of C6-C20 wherein n is an integer equal to 3b4; b9 a cocatalyst selected from aluminoxane and a boron compound having the formula (II): BX1X2X3 or a salt thereof, wherein X1, X2 and X3 are the same or different, represent a perfluorinated hydrocarbon radical of C1-C

Description

PROCESS FOR THE PREPARATION OF CRYSTALLINE VINYLAROMATIC POLYMERS WITH A PREDOMINANTLY STRUCTURE SINDIOTACTICA DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of crystalline vinylaromatic polymers having a predominantly syndiotactic structure. More specifically, the present invention relates to a process for the preparation of crystalline polystyrene in which the polymer chains have a basically syndiotactic configuration. Polystyrene is a thermoplastic polymer obtained by the radical polymerization of styrene and is used in the production of molded articles, films, electrical materials, packaging materials, etc. It is an atactic polymer, amorphous, with excellent insulating properties and a reasonable thermal resistance. For many applications, however, it is preferable to use crystalline materials, with a high thermal resistance and resistance to solvents, characteristics in which atactic polystyrenes do not have. European Patent 210,615 describes a polystyrene having a structure characterized by a high degree of stereoregularity, in which the phenyl substituents are arranged in such a way that they give a syndiotactic polymer. This material does not have the above drawbacks of atactic polystyrene, since it is crystalline and consequently, once transformed, it can be subject to orientation processes, is almost completely insoluble in organic solvents and has a melting point within the range of 260- 280 ° C, giving a high thermal resistance, equal to or as high as thermoplastic condensation polymers (polyesters, polyamides, polyimides, etc.). The syndiotactic polystyrenes can be prepared according to that described in the literature, for example, European patent EP 272,584 or the patent of the U.S. 4,978,730, by the polymerization catalyzed by Ti, Zr, - V, Ni compounds in the presence of a cocatalyst represented by a methylaluminoxane (which is a mixture containing cyclic, linear or cage-shaped oligomers, containing the repeating unit -ALCH30-) or as described in the published European patent application 421,659, for the boron-containing fluorinated group derivatives. Examples of catalysts for the synthesis of the syndiotactic polystyrenes indicated in the literature are titanium halides (chloride, bromide, etc.), titanium alcoholates (methoxide, ethoxide, propoxide, isopropoxide, butoxide, etc.), carboxylated titanium, metallocenes (cyclopentadienyltrichloride titanium, cyclopentadienyl titanium dichloride, pentamethylcyclopentadienyltrichloride titanium, cyclopentadienylalcoxides titanium, cyclopentadienylalkyls titanium, pentamethylcyclopentadienylalkyls titanium, dicyclopentadienyldichloride titanium, dicyclopentadienylalcoxides titanium, etc. ), titanium alkyls (tetrabenzyl titanium, tetramethyl titanium, tetraethyl titanium, etc.) and the corresponding zirconium compounds. The Applicant has found that it is possible to synthesize the crystalline vinylaromatic polymers, and in particular the crystalline polystyrene, which has a predominantly syndiotactic configuration, using a new catalyst system which has never before been described in the literature. The catalysts of the present invention also have the property of giving polymers with high degrees of stereoregularity and with much higher molecular weight than the polymers obtained with the traditional catalysts. For example, it is possible to obtain polystyrene with a degree of stereoregularity of more than 99.5% and with an average molecular weight of more than 300,000 Mw, generally between 300/000 and 500,000. The present invention also relates to a process for the preparation of vinylaromatic polymers crystals with a predominantly syndiotactic structure which comprises the polymerization of vinylaromatic monomers, either alone or mixed with at least one of the ethylenically copolymerizable unsaturated monomers, in the presence of a catalyst system consisting essentially of: a) a titanium complex having the formula (I): Ti (OCONRR ') n (I) wherein R and R 'are the same or different, represent an aliphatic radical of C1-C12 ° an aromatic radical of g-C12 where n is an integer equal to 3 or 4; b) a cocatalyst selected from aluminoxane and a boron compound having the formula (II): or one of its salts, in which X-j_, X2 and X3 are the same or different, represent a perfluorinated hydrocarbon radical of C1-C20. The titanium catalyst having the general formula (I) is a known product, described in "Chemishe Berichte" 120, 955 (1987) or in "Journal of Chemical Society: Dalton Transactions ", 693 (1991) .These products can be prepared by reacting titanium tetrachloride or titanium trichloride with carbon dioxide and with an aromatic or aliphatic diamine.Non-limiting examples of titanium catalysts having the general formula (I), which are particularly suitable for the present invention are: i OCON (CHS) g 33? i COCON (CH3) 2] 4; Ti C WITH CH2CH3) 233 * Ti OCON (CH2CH3) 2] 4; Ti OCON (CH2CH2CH3) 233? Ti C OCON CH2CH2CH3) 23? Ti [OCON (CH (CH3) 2> 233? TiC OCON (CH (CH3) 2) 23 ^? T C OCON C6H5) g 33 'Ti COCON (C6HS) 23' Ti C OCON (C6H4CH3) 3? Ti [OCON (C6H4CH3) 2 A * Ti [OCON (CH3) (CH2CH3) 337 Ti [OCON (CH3) (C? ^ CH,) 4 / Ti OCON CH3) (CH2CH2CH3 > 33 'TC OCON (CH3) ( CH2CH2CH3> 3 * Ti Ti COCON (CH3) (CH (CH3) 2) 33? Ti C OCON (CH3) (CH (CH3) 2) 3 ^; Ti [OCON (CH2CH3) (CH2CH2CH3) 33; T i [OCON (CH 2 CH 3) (CH 2 CH 2 CH 3)] 4; TÍ [OCON (CH2CH3) (CH (CH3) 233; Ti [OCON (CH2CH3) (CH (CH3) 2] 4 Ti [OCON (CH3) (C6H5)] 3; Ti [OCON (CH3) (C6Hj)] 4 Ti [OCON (CH3) (C6H4CH3)] 3 Ti [OCON (CH3) (C ^ CH,)] 4; Ti [OCON (CH2CH3) (^ Hg)] 3; TÍ [OCON (CH2CH3) (C6H5)] 4 The molar ratio between vinylaromatic monomer and titanium is not particularly critical but may vary between 1,000 and 100,000, preferably between 5,000 and 50,000. The aluminoxane cocatalyst consists essentially of mixtures of compounds having structures in the form of cyclic, linear cages. The linear structure has the general formula (III): while the cyclic structure has the general formula (IV): wherein m represents an integer between 1 and 40 and R1 is an alkyl radical of C-j ^ C ^, preferably of C - ^ - Cg; an aryl radical of Cg-C20, preferably Cg-C12; or an arylalkyl or C7-C20 alkylaryl radical, preferably of c7 ~ ci2; A C3-C20 cycloalkyl radical, preferably C5-C8; or a radical O-R ', in which R' represents an alkyl radical of C - ^ - Cg, preferably of C 1 -C 4; an aryl radical of Cg-C20, preferably Cg-C12; or a halogen atom, such as fluoro or bromo, with the proviso that not all radicals R-, are contemporaneously 0-R 'or halogens. The cage-shaped structures are described in Macromolecular Symposia, Vol. 97, 1995. The above cocatalysts, having the general formula (III) and (IV) are known in the literature and are described, for example, in the European Patent published 272,584 and 421,659 or in United States Patent 4,978,730. The cocatalyst having the general formula (II) or its salts, is known in the literature and is described in European patent applications 421,659 and 482,934. Preferred cocatalysts having the general formulas (II), (III) or (IV) are tris (pentafluorophenyl) boron or tetra (pentafluorophenyl) borate of organic cations such as carbon, ammonium, triphenylphosphonium, etc., and methylaluminoxane with a number average molecular weight between 400 and 2000 Mn. The cocatalyst is generally used in such amounts that the molar ratio of aluminum / titanium is between 50 and 2000 or the boron / titanium ratio is between 0.5 and 5. According to the process of the present invention, the catalytic system described previously can also comprising an aluminum alkyl in which the alkyl group contains from 1 to 6 carbon atoms, for example trimethylaluminum, triethylaluminum, triisobutylaluminum, etc., in such amounts that the molar ratio of aluminum / titanium alkyl is between 0 and 1,000. The term "vinylaromatic polymers" as used in the present invention and claims, basically means polymers of styrene and styrene derivatives and relative copolymers containing up to 20% by mole of another copolymerizable monomer selected from those having the general formula (V ): CH. CH - R * wherein R2 represents a hydrogen atom or an alkyl radical of C - ^ - Cg, an aromatic radical or C4-C12 cycloalkyl. The styrene derivatives comprise alkylstyrenes, in which the alkyl group contains from 1 to 4 carbon atoms, halogenated styrenes, alkoxystyrenes of carboxystyrenes, vinylnaphthalenes, such as alpha- or beta-vinylnaphthalene, vinyltetrahydronaphthalene such as 1, 2. , 3,4-tetrahydro-6-vinylnaphthalene, etc. Typical examples of substituted styrenes are p-methyl styrene, m-methylstyrene, alone or mixed with each of ethylstyrene, butyl styrene, p-tert-butyl styrene, dimethylstyrene, chloro-styrene, bromostyrene, fluorostyrene, chloromethylstyrene, methoxystyrene, acetoxymethylstyrene, etc. . The polymerization reaction can be carried out in bulk or in solvent. In the latter case, the solvent may consist of aliphatic or aromatic hydrocarbons or their mixtures and is used in such amounts in the volume ratio of the solvent / monomers which is between 0 and 100. The solvent is preferably toluene. More specifically, according to the general procedure used in this type of reaction, the above polymerization, vinylaromatic monomers are subject to direct treatment to eliminate catalytic poisons, such as phenolic stabilizers, water, phenylacetylene and consisting of a distillation, pass on columns containing activated molecular or activated alumina sludge or sieves, etc. The monomers and optionally, the solvent are charged to the reaction equipment together with the possible aluminum alkyl and the cocatalyst. After a time ranging from 5 seconds to 30 minutes, a solution of a titanium derivative having the general formula (I) is added. The reaction continues for a time ranging from 15 minutes to 20 hours at temperatures between 0 and 110 ° C. In the end, the obtained polymer is recovered by traditional methods. Some non-limiting illustrative examples are given in the following to provide a better understanding of the present invention and its modalities. Analysis of the procedure: The percentage of the syndiotactic polymer is determined by extracting the polymer with acetone or methyl ethyl ketone (MEK) at the boiling point for 10-20 hours. The degree of stereoregularity is determined by nuclear magnetic resonance spectroscopy of carbon 13 as described in U.S. Patent 4,680,353.

The thermal transition temperatures (Tm = melting point, Tg = glass transition temperature) are determined by differential scanning calorimetry. The molecular weights of the polymers obtained are determined by Gel Permeation Chromatography in 1, 2, 4-trichlorobenzene at 135 ° C.

EXAMPLE 1 ml of styrene, purified by a passage over a basic alumina column and 1.2 ml of a 1.57 M toluene solution of methylaluminoxane are introduced into a glue test tube under an inert atmosphere. 2.26 ml of a toluene solution of 0.00275 M of titanium tris (diisopropylcarbamate) are introduced after 5 minutes. The reaction was carried out for 5 hours at 60 ° C. At the end the mixture was suspended in 200 ml of methanol, which contains 2 ml of concentrated HCl and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 2.24 g of syndiotactic polystyrene were obtained (yield of 12.3%). Insoluble fraction in methyl ethyl ketone (MEK): 76.4% 13 C NMR analysis showed that the polymer has a percentage of 99.5% of the syndiotactic pairs.

Thermal properties: Tm = 261 ° C; Tg = 94 ° C. Average molecular weight weight Mw: 417,000. Average number of molecular weight Mn: 205,000.

EXAMPLE 2 ml of styrene, purified by a passage over a basic alumina column and 0.8 ml of a 1.57 M toluene solution of methylaluminoxane are introduced into a glue test tube under an inert atmosphere. 2.26 ml of a toluene solution of 0.00275 M of titanium tris (diisopropylcarbamate) are introduced after 5 minutes. The reaction was carried out for 5 hours at 60 ° C. At the end the mixture was suspended in 200 ml of methanol, which contains 2 ml of concentrated HCl and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 1.02 g of syndiotactic polystyrene (5.6% yield) were obtained. , Fraction insoluble in methyl ethyl ketone (MEK): 62.5% 13-C NMR analysis showed that the polymer has a 99.6% percentage of the syndiotactic pairs. Thermal properties: Tm = 264 ° C; Tg = 95 ° C. Average weight of molecular weight Mw: 423,000. Average number of molecular weight Mn: 184,000.

EXAMPLE 3 ml of styrene, purified by a passage over a basic alumina column and 2.4 ml of a 1.57 M toluene solution of methylaluminoxane are introduced into a glue test tube under an inert atmosphere. 5.75 ml of a toluene solution of 0.00217 M of titanium tris (diisopropylcarbamate) are introduced after 5 minutes. The reaction was carried out for 5 hours at 60 ° C.

At the end the mixture was suspended in 200 ml of methanol, which contains 2 ml of concentrated HCl and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 1.72 g of syndiotactic polystyrene (9.5% yield) were obtained. Insoluble fraction in methyl ethyl ketone (MEK): 81.6% 13-C NMR analysis showed that the polymer has a percentage of 99.5% of the syndiotactic pairs. Thermal properties: Tm = 267 ° C; Tg = 98 ° C. Average molecular weight weight Mw: 308,000. Average number of molecular weight Mn: 153,000.

EXAMPLE 4 20 ml of styrene are introduced, purified by a passage over a column of basic alumina and 1. 2 ml of a 1.57 M toluene solution of methylaluminoxane in a glue test tube under an inert atmosphere. After 3.0 minutes 3.0 ml of a toluene solution of 0.00211 M of titanium tetrakis (diisopropylcarbamate) are introduced. The reaction was carried out for 5 hours at 60 ° C.

At the end the mixture was suspended in 200 ml of methanol, which contains 2 ml of concentrated HCl and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 3.02 g of syndiotactic polystyrene were obtained (16.5% yield). Insoluble fraction in methyl ethyl ketone (MEK): 71.5% 13 C-NMR analysis showed that the polymer has a 99.5% percentage of the syndiotactic pairs. Thermal properties: Tm = 265 ° C; Tg = 96 ° C. Average weight of molecular weight Mw: 383,000. Average number of molecular weight Mn: 192,000.

EXAMPLE 5 694 ml of styrene, purified by passage over a basic alumina column, was charged into a one liter reactor under an inert atmosphere. Styrene was maintained at 60 ° C and 41.7 ml of a 1.57 M toluene solution of methylaluminoxane and 125 ml were added. of titanium tetrakis (diisopropylcarbamate) dissolved in 20 ml of toluene. The reaction was carried out for 5 hours at 60 ° C.

At the end the mixture was suspended in 1 liter of ethanol, which contains 8 ml of concentrated HCl and filtered. The solid was suspended again in ethanol, filtered and dried under vacuum. 94.3 g of syndiotactic polystyrene were obtained (yield of 14.9%). Insoluble fraction in methyl ethyl ketone (MEK): 84.8% 13-C NMR analysis showed that the polymer has a 99.6% percentage of the syndiotactic pairs. Thermal properties: Tm = 267 ° C; Tg = 99 ° C. Average weight of molecular weight Mw: 348,000. Average number of molecular weight Mn: 155,000.

COMPARATIVE EXAMPLE Under analogous experimental conditions as those in Examples 1 and 4, polymerization was carried out using cyclopentadienyl titanium trichloride. 5.98 g (32.9% yield) of the syndiotactic polystyrene were obtained. Insoluble fraction in methyl ethyl ketone (MEK): 87.0% 13 C-NMR analysis showed that the polymer has a percentage of 98.1% of the syndiotactic pairs. Thermal properties: Tm = 252 ° C; Tg = 97 ° C. Average weight of molecular weight Mw: 105,000. Average number of molecular weight Mn: 44,000.

Having described the invention as above, property is claimed as contained in the following:

Claims (8)

1. A process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure, characterized in that it comprises the polymerization of vinylaromatic monomers, either alone or mixed with at least one of the copolymerizable ethylenically unsaturated monomers, in the presence of a catalyst system consisting essentially of from: a) a titanium complex that has the formula (I): Ti (OCONRR ') n (I) wherein R and R 'are the same or different, represent an aliphatic radical of C1-C12 or an aromatic radical of Cg-C20 where n is an integer equal to 3 or 4; b) a cocatalyst selected from aluminoxane and a boron compound having the formula (II): BX1X2X3 (II) or one of its salts, in which X- ^ X2 and X3 are the same or different, represent a perfluorinated hydrocarbon radical

2. The process according to claim 1, characterized in that the molar ratio between the vinylaromatic monomer and titanium is ejtre 1,000 and 100,000.

3. The process according to claim 1 or 2, characterized in that the cocatalyst is used in such quantities that the aluminum / titanium molar ratio is between 50 and 2000 or the boron / titanium ratio is between 0.5 and 5.

4. The process according to any of the previous claims, characterized in that the catalytic system comprises an aluminum alkyl, in which the alkyl group contains from 1 to 6 carbon atoms.

5. The process according to claim 4, characterized in that the aluminum / titanium alkyl molar ratio is between 0 and 1,000.

6. The process according to any of the previous claims, characterized in that the polymerization reaction is carried out in bulk or in a solvent.

7. The process according to claim 6, characterized in that the solvent is used in such amounts that the ratio in the volume of the solvent / monomers is between 0 and 100.

8. The process according to any of the previous claims, characterized in that the polymerization is carried out at temperatures between 0 and 110 ° C.