ITMI960363A1 - PROCEDURE FOR THE PREPARATION OF CRYSTALLINE VINYLAROMATIC POLYMERS WITH A PREDOMINANTLY SYNDIOTACTIC STRUCTURE - Google Patents

Abstract

Ribbon head for rapier textile loom in which a prefabricated ridge in any desired material and provided with a longitudinal series of anchoring holes is fixed orthogonally to a ribbon head, along the longitudinal axis thereof, by a thermoplastic material of molding that wraps most of the ridge and fits into the ridge and tape head holes. A method for the realization of such a construction is also described.

Description

The present invention relates to a process for the preparation of vinylaromatic crystalline polymers with a predominantly syndiotactic structure.

More particularly, the present invention relates to a process for the preparation of crystalline polystyrene in which the polymeric chains have an essentially syndotactic configuration, carried out in the presence of ultrasounds.

Polystyrene is a thermoplastic polymer obtained by radical polymerization of styrene and is used in the production of printed articles, films, electrical materials, packaging materials, etc. It is an atactic, amorphous polymer, with excellent insulating properties and moderate thermal resistance. However, for many applications it is preferred to have crystalline materials, with high thermal and solvent resistance, characteristics which atactic polystyrene does not possess.

European patent 210,615 describes a polystyrene having a structure characterized by a very high degree of sterearegularity, in which the phenyl substituents are arranged in such a way as to provide a synotactic polymer. This material does not have the aforementioned drawbacks of atactic polystyrene as it is crystalline and therefore, once transformed, can be subjected to orientation processes, is insoluble in almost all organic solvents and has a melting temperature in the 260-280 range. ° C, so that it has a high thermal resistance, comparable or superior to that of thermoplastic condensation polymers (polyesters, polyamides, polyimides, etc>.

The syndiotactic polystyrene can be prepared according to what is described in the literature, for example according to what is described in the European patent EP 272.504 or in the US patent 4.978.730, by polymerization catalyzed by compounds of Ti or Zr, in the presence of a cocatalyzer represented by methyl lailuminoxane (a mixture of cyclic and linear aligamers containing the repeating unit —AlCHoQ—) or, as described in published European patent application 421.659, by derivatives of boron containing fluorinated groups.

Examples of catalysts for the synthesis of syndiotactic polystyrene reported in the literature are titanium halides (chloride, bromide, etc.), titanium alkalates <methoxide, ethoxide, propoxide, isopropoxide, butoxide, etc.), titanium carboxylates, tnetallocenes (cìclapentadienyl titanium trichloride, cyclopentadienes 1 titanium dichloride, pentamethylcyclopentadienyl titanium trichloride, cìclapentadienyl titanium alkoxides, cyclopentadiene1 titanium alkyls, pentamethyl leyclopentadylenyl titanium dihydrogen 1 titanium dihydrogen alkyl, titanium dihydrogen 1 titanium alkyl titanium, titanium tetrameters, tetraethyl titanium, etc.) and the corresponding zirconium compounds.

For some applications of syndiotactic polystyrene, in particular to carry out the aforementioned orientation processes, it is particularly important to have preparation methods capable of giving polymers characterized by high molecular weights that allow to improve the quality of the product both for aspects of a process type, for example the elongational viscosity, which for aspects related to the product itself, for example the mechanical properties.

It has now been found by the Applicant that it is possible to synthesize crystalline vinylaromatic polymers, and in particular crystalline polystyrene, having a predominantly syndiotabtic configuration and high molecular weight by carrying out the polymerization of the corresponding monomers under ultrasound irradiation.

The application of ultrasound in polymer science is known and described, for example, in "Polymer News", Vol. 20 (1995), pages 138-1 * 3 or in "Trends in Polymer Science", Vol. S (199 *), pages 17 * -182. As far as polymerization is concerned, in the "Journal of the Chemical Society, Faraday Transact ions", Vol. * 6, 1950, page 996, the possibility of inducing root polymerization by ultrasound, for example of styrene, vinyl acetate or methyl methacrylate, is described , often citing a mechanism in which cavitation is an aid to reactivity and highlighting the importance of degradation processes, induced by the ultrasounds themselves, in order to increase reactivity. Aspects related to cavitation have also been mentioned in US patent 5.102.98 * relating to the polymerization of cyclic polycarbonate aligamers, operating by opening the same cycles.

Moreover, the literature relating to the irradiation of polymers with ultrasound mainly reports examples of degradation. For example, in the "European Polymer Journal", Vol. 16 (1980), page 589, the reduction is reported! of molecular weight, with formation of radicals, following the irradiation of solutions of various polymers including atactic polystyrene. In any case, up to now the scientific literature has never described the possibility of obtaining significant improvements in polymerization processes catalyzed by arganometallic compounds and, in particular, in syndospecific polymerization processes of styrene.

Therefore, the object of the present invention is a process for the preparation of crystalline vinyl aromatic polymers with a predominantly syntactic structure which comprises polymers of the vinyl aromatic monomers, alone or in mixture with at least one other copolymerizable ethylenically unsaturated monomer, in the presence of a catalytic system comprising an organic complex of titanium or zirconium and characterized in that the polymerization occurs under the irradiation of ultrasounds.

More particularly, the object of the present invention is a process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure which then comprises imerizing the vinyl aromatic monamers, alone or in a mixture with at least one other copolymer ethylenically unsaturated monomer, in the presence of a catalytic system which includes:

a) a titanium or zirconium complex chosen from those of general formula:

AiMR IRGRD, ftiAEÌIRiRe (I)

where the groups Ri, Re, Rs and R *., equal to or different from each other, represent an alkyl alkyl radical (iso), <1ic isopalcassi, alkylamide alkyl Ci - This, an aryic radical C ", - C ± o or a halogen as chlorine while the groups Ai and Ao, the same or different from each other, represent a 1 ico cyclopentadiene binder, optionally substituted with C »-Cio alkyl radicals, or an indenyl binder; M represents a titanium or zirconium atom; And

b> a co-catalyst selected from an alkylumoxane and a boron compound of formula (II):

BXIXBXO <II)

or a salt thereof, in which X *, Xc and Χα, the same or different from each other, represent a C-Ceo fluorinated hydrocarbon radical;

characterized by the fact that the polymerization takes place under ultrasound irradiation with a frequency between 10 kHz and 50 MHz.

Compared to traditional polymerization processes, essentially based on the use of catalytic systems consisting of compounds (a) and (b>, with the projected process of the present invention one or more of the following advantages can be obtained; - increase in molecular weight of the polymer ;

- increase in the quantity of polymer formed; - improvements in the spherical configuration of the ραlintera.

The compounds of general formula (I) are products known in literature and described in the European patent B10.615 or in the US patent <*. 978.730.

Typical examples of complexes of the titanium or zirconium of formula (I), particularly suitable in the present invention are TiCl <*; Ti (CHeC ^ Hs) Ti (OCH3) *; Ti (OCt ^ Ha) Ti (DCsH ·?) «· | Ti (OÌ-C3H7) Ti (OC ^ Ti CNÌCHylo] ^; TU NÌCEHSIQÌU; TiCNÌCaHM sIU; TiCN <i-CaH- ^ a! U; TÌ [N (C * HV> B3 *; CpTiCl3; CpTi <OCHa <) > a CpTi (OCeHtj) sj CpTÌ <(> OC: BH-7> S; CpTi (Oi-CaH ^ Ja CpT i (QC ^ Ja; CpTi CN (CHa) a] 0; CpTi ENtCcHs) 3 CpTi CN (CnHv ) eia; CpTi CN <(> i-CaH · *) 3; CpTiCN <(> C «^^ <)> s <]> s Cp ~ TiCl3; Cp * Ti ÌDCHa> 3; Cp * Ti <GCsHs) = >; Cp ~ Ti (OC ^ H,> 3 Cp * Ti (Qi-CaH-y) 3; Cp * Ti (OC ^ H ^) Cp * TiCN (CHa) Q3a Cp ^ T ìCNCCJJHES) t; 3tj; Cp ~ TiENiCal ^) α33; Cp ~ TiCNii-Cal ^) EI13 Cp ^ TitNiC ^ H ^ l ^ ia; InTiCl3; InTiiOCH ^ Ja; InTiiOCeHsls InTi (CCsH · ^) ai InTi (0i “CSJ'I-T ·) 3j InTi <OC« .Hc) 3; InTiCN (CHra) e33; InTi CNtCeHy) d o; InTi HNiCsH · *) c3eS InTi CN (i-CaH ^) a] a; InTiCNICJ-1c) G2B; etc. and the corresponding zirconium derivatives.

<Cp = cyclopentadienyl; In = indenile; Cp ^ pentamet i1-cic 1opentadienì le>.

The titanium or zirconium compounds of general formula (1) are added to the polymerization mixture in an amount such that the molar ratio of aromatic monomer / M (M = titanium or zirconium) is between 1,000 and EOO.ODO, preferably between 10,000 and 150,000.

The alkyl lumoxane cocatalyst essentially consists of mixtures of products having a linear or cyclic or cage structure. In the first case the structure is represented by the general formula (III>:

while in the second case from the general formula (IV)

in which m represents an integer between 1 and 40 and R 'a C1-Ceo alkyl radical, preferably C1-Co; a Cfi-Ccoo aryl radical, preferably C <a C ^ -Co arylalkyl or alkyl radical, preferably C7-C1H; or a Cs-Cso 1ic cycloalkyl radical, preferably C-s-Ce; or an O-R 'radical, wherein R' represents a C1-C0 alkyl radical, preferably C1-O .; a C ^ -Cco aryl radical, preferably C ^ -Cie »or a halogen atom, such as chlorine, fluorine or bromine, provided that not all the R1 radicals are at the same time 0-R 'or halogens. The cage structure is described in Molecular Symposium, Voi 97, 1995.

The aforementioned co-catalysts, of general formulas (III) and (IV), are known in the literature and described, for example, in published European patent applications 878.584 and 481.659 or in US patent 4.978.730.

Cocatalyst of general formula (Li), ie its salt, is known in the literature and is described in published European patent applications 481.659 and 488.934.

The preferred cocatalyst among those of general formulas (II), (III) or (IV) is methylailumoxane (MAO), a mixture of linear oligomers with an average m between 10 and 80 and cyclic oligomers with an average r between 10 and 20. Generally the co-catalyst is used in quantities such that the molar aluminum / M ratio is between 50 and 2,000 or such that the boron / M ratio is between 0.5 and 10.

The catalytic system used in the process object of the present invention can also comprise an organic compound of tin of general formula <V):

SnRcsfì ^ R? Rs <V) where the groups R0> Re ,, R7 and Ro, equal or different from each other, represent an alkyl or aryic radical (iso) Ci-CαQ-Compared to traditional catalytic systems, essentially based on compounds (a) and < b), the presence of the organic tin derivative determines increases in one or more of the following parameters:

- activity of the catalytic system;

- molecular weight of the observed tactical polystyrene;

- degree of stereoregularity of the polymer.

Preferred tin derivatives according to the present invention are 5n (Ct1⁄2) ""; Sn (COHEJ) <"; SniCgH? > * »Sn <(> i CaR? <)> <» Ϊ́ Sn (CÌ »H ^>) i»; SntC ^ I-ti; SniCH ^ Ce.Hcs), *; etc. These compounds are added to the polymerization mixture in an amount such that the Sn / M molar ratio is between 0.1 and 50.

According to the process object of the present invention, the catalytic system described above can optionally also comprise an alkyl aluminia in which the alkyl group contains from 1 to 6 carbon atoms, for example trimethyl aluminia, triethyl aluminum, triisobutyl aluminia, etc. in quantities such that the molar ratio of aluminum alkyl / M is between Ω and ODO.

The term "vinylam inatic polymers" as used in the present description and in the claims essentially means the polymers of styrene and derivatives of styrene and the related copolymers containing -up to SO3⁄4 in moles of another copolymerizable monomer selected from those of general formula V> s

CH «= CH - R" (V)

wherein R "represents a hydrogen atom or an alkyl radical Cj— or a cycloalkyl radical C <.- Cia -The derivatives of styrene include the alkyl styrenes, in which the alkyl group contains from 1 to ** carbon atoms, halogenated styrenes, C-C * "- alkoxy styrenes, carboxy styrenes, wines Naphthalenes, such as alpha- or beta-vinyl naphthalene, vinyl tetrahydro naphthalene such as 1, 2,3, *" - tetrahydro-6-wines 1 naphthalene , etc . Typical examples of substituted styrenes are p-methylstyrene, m-methylstyrene, alone or in a mixture of laro, ethylstyrene, butylstyrene, p-thi-butylstyrene, dimethylstyrene, chlorostyrene, bromostyrene, fluorostyrene, chloromethylstyrene, methylstyrene , acetoxy methylstyrene, etc.

The polymerization reaction can be carried out in bulk or in solvent. In this second case, the solvent can consist of aliphatic or aromatic hydrocarbons or their mixtures and is used in quantities such that the solvent / monomer volume ratio is between □ and 10. Preferred solvent is toluene.

More specifically, according to the general procedure adopted for this type of reaction, before polymerization the vinyl aromatic manomers are subjected to treatments aimed at eliminating catalytic poisons, such as phenal stabilizers, water, phenyl acetylenes, and consisting in distillation, passage on columns containing activated molecular sieves or activated alumina, etc. The monomers and, optionally, the solvent are loaded into the reaction apparatus together with the possible aluminum alenyl and the cocatalyst. Then, after a time varying between 5 seconds and 30 minutes, the titanium or zirconium complex and any organic derivative of tin are added, preferably in the form of a solution. The reaction proceeds for times ranging from 15 minutes to 10 hours at temperatures between 0 and 100 ° C, preferably between 40 and 90 ° C. At the end, the obtained polymer is recovered according to traditional methods.

The reaction medium, during the polymerization, is subjected to irradiation with ultrasounds having a frequency between 10 kHz and 50 MHz, preferably between 25 kHz and 1 MHz. It being understood that the power and the possible focusing depend on the type of reactor. polymerization adopted, the energy flow transmitted to the reaction medium is comprised between 0.01 and 100 W / cm °, preferably between 0.1 and 10 W / cm. Furthermore, the transmitted sound wave is not stationary but pulsed, with a frequency between 1 and 10,000 Hz, preferably between 10 and 1,000 Hz.

In order to better understand the present invention and to put it into practice, some illustrative but not limiting examples are given below.

Analysis procedures:

The percentage of syndiotactic polymer is determined by extracting the polymer with acetone or methyl ethyl ketone (MEK) at boiling for 10-SO hours.

- The degree of stereoregularity is determined by nuclear magnetic resonance spectroscopy of carbon 13 as described in US patent 4,680,353.

- The molecular weights of the polymers obtained were determined by Gel Permeation Chromatography in trichlorobenzene at 135 ° C.

- The melting point (Tm> and the melt crystallization temperature (Tee) of the polymer were determined by differential scanning calorimetry. The Tm is relative to the second rise (scanning rate of 20 ° C / min) and the Tee at the first downward scan (scan speed of 10 ° C / min).

COMPARATIVE EXAMPLE 1

SO ml of styrene (0.175 moles) purified by passage on a basic alumina column and 1 ml of a 1.57 M solution in toluene of methyllailuminoxane (1.88 10 <-3 > moles). After 5 minutes 0.5 ml of a 0.01S5 M solution in toluene of (cyclopentddiyl) titanium trichloride <6.25 10- * moles were introduced.

The reaction was carried out for 2 hours at 60 ° C. At the end, the mixture was suspended in 200 ml of methanol containing 2 ml of concentrated HCl and filtered.

The solid was suspended again in methanol, filtered and dried under vacuum.

4.18 g of product were attenuated (yield 31.6 * /.).

- Insoluble fraction in MEK: 89%

· - Degree of stereoregularity: 97.8 * /.

- Weight average molecular weight: 93,000

Tm: 256 <®> C

Tee: 221 <®> C.

EXAMPLE 2

The procedure of example 1 was substantially repeated, but subjecting the sample to irradiation with ultrasound at the frequency of 50 kHz, having an effective energy flow of the order of 0.5 W / cm <8> and pulsed with a frequency of 50 Hz. The yield was 30.4%.

- Insoluble fraction in MEK: 80%

- Degree of stereoregularity: 98.6%

- Weight average molecular weight: 156,000

Tm: 256 <®> C

Tee: S10 ° C.

EXAMPLE 3

The procedure of example 2 was substantially repeated, but subjecting the sample to irradiation with ultrasound at the frequency of 250 kHz, having an effective energy flow of the order of 0.2 W / cm and pulsed with a frequency of 600 Hz. yield was 40%.

- Fraction insoluble in (ΊΕΚ: 91%

- Degree of stereoregularity: 98.0%

Weight average molecular weight: 141,000

Claims (3)

CLAIMS 1> Process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure which then comprises imerising the vinyl aromatic monomers, either alone or in a mixture with at least one other capable ethylenically unsaturated monomer, in the presence of a catalytic system comprising an organic complex of titanium or zirconium is characterized by the fact that the polymerization occurs under ultrasonic irradiation. 2) Process according to claim 1 which then comprises imerising the vinyl aromatic monomers, alone or in admixture with at least one other copolymerizable ethylenically unsaturated monamer, in the presence of a catalytic system which comprises: a) a complex of titanium or zirconium selected from those of general formula: MR1R2R3R4, A MR1R2R3, A1A2MR1R2 (I) where the groups Ri, Ra, Ra and R4, the same or different from each other, represent an <iso) alkyl, <iso) alkoxy radical, C 1 -Cio alkylamide, an aryic radical C ^ -Cio or a halogen such as chlorine while the groups Ai and A20, equal to each other, represent a cyclapentadienyl ligand, optionally substituted with C, -CiD alkyl radicals, or an indenyl ligand; fi represents a titanium or zirconium atom b> a cocatalyst selected between an alkylumoxane and a boron compound of formula (II): BXiX ^ Xo (II> or a salt thereof, in which Xi, Xa and X3f equal or different from each other, represent a C * --CE> 0 fluorinated hydrocarbon radical; characterized by the fact that the polymerization takes place under the irradiation of ultrasounds with frequency between 10 kHz and 50 MHz. 3) Process according to claim 1 or 2, in which the vinylaromatic monomer / M molar ratio is comprised between 1,000 and 200,000. a) Process according to claim 1, 2 or 3, wherein the cocatalyst is used in quantities such that the molar aluminum / M ratio is between 50 and 2000 or such that the boron / M ratio is between 0.5 and 10 . 5) Process according to any one of the preceding claims, in which the catalytic system comprises an organic compound of the tin of general formula (V): SnRijR ^ R- ^ Rfj (V) wherein the groups Re, R *, R-7 and RQ, the same or different from each other, represent a radical <iso) alkyl or aryl C1 ~ Ci0. Hi Process according to claim 5, wherein the molar ratio Sn / M is comprised between Q, 1 and 50. 7. Process according to any one of the preceding claims, wherein the catalytic system comprises an aluminum alkyl in which the alkyl group contains from 1 to 2 carbon atoms. 8) Process according to claim 7, wherein the molar ratio of aluminum alkyl / M is comprised between 0 and 800. 9) Process according to any one of the preceding claims, in which the polymerization reaction is carried out in bulk or in solvent. 10. Process according to claim 9, wherein the solvent is used in quantities such that the solvent / monomer volume ratio is between 0 and 10. 11) Process according to any one of the preceding claims, in which the polymerization is carried out at temperatures between 0 and 100 ° C. 15) Process according to any one of the preceding claims, in which the reaction medium, during the polymerization, is subjected to irradiation with ultrasounds having a frequency comprised between SS kHz and 1 MHz. 13. Process according to any one of the preceding claims, in which the energy flow transmitted to the reaction medium, by means of the irradiation with ultrasounds, is comprised between 0.01 and 100 W / cm <B>. 1 **) Process according to any of the preceding claims, in which the transmitted sound wave is pulsed with a frequency between 1 and 10,000 Hz.