CS213344B2 - Method of making the polymerizable mixture of the methylethenylbenzene isomeres - Google Patents

Abstract

An ethyltoluene isomer mixture consisting essentially of from about 90 to about 99 weight percent of para-ethyltoluene, about 1 to about 10 weight percent of meta-ethyltoluene and 0 to about 0.1 weight percent of ortho-ethyltoluene, This isomer mixture is a valuable intermediate for the preparation of a vinyltoluene isomer mixture which in turn may be polymerized to polymers having unusual and advantageous proper-ties.

Description

The invention relates to a polymerizable mixture of isomeric methylvinylbenzenes and polymers obtained therefrom.

Styrene has been used for a long time in the production of polymers and polystyrene has found wide application for many purposes. Also alkylated styrenes such as o-methylstyrene are also of interest for certain purposes.

In the various applications styrenes substituted in the nucleus by an alkyl group have also been used. The monomer used was mainly the product referred to as vinyltoluene. Vinyltoluene is a product consisting mainly of a mixture consisting mainly of m- and p-methylstyrene (vinyltoluene) and obtained by catalytic dehydrogenation of a mixture of the corresponding m- and p-ethyltoluenes. The mixture of ethyltoluenes is obtained by fractional distillation from a mixture of o-, m- and p-ethyltoluene. The ratio of the m- and β-isomers in the monomer mixture is approximately 65:35. A suitable summary of the preparation and properties of the monomer mixture and the polymers produced therefrom is given in "Styrene: Its Polymers, Copolymers and Derivatives" Ed. R. H. Boundy, R. F. Boyer, ACS Monograph Series, 1952, Hafner Publishing Company, pp. 1232-1245.

Vinyltoluene is produced by dehydrogenation of ethyltoluene. Since the starting ethyltoluene feed is itself a mixture of isomers, the vinyltoluene product is also an isomeric mixture with approximately the same proportion of the individual isomers as the original ethyltoluene feed. Thus, if a different isomer distribution is to be achieved with vinyltoluene, the ethyltoluene isomer distribution must be adjusted accordingly.

Methods for making various mixtures of ethyltoluene isomers are known. In these mixtures, the p-isomer is usually present in an amount less than about 40% by weight, the m-isomer is usually present in larger amounts, and the o-isomer in smaller amounts. For example, U.S. Patent No. 2,763,702 discloses a mixture of ethyltoluene isomers, which is obtained by ethylating toluene with ethylene in the presence of a Friedel-Crafts catalyst such as aluminum chloride. This mixture contains isomeric monoethyltoluenes in a relative ratio of 8 to 30% of the o-isomer, 40 to 65% of the m-isomer and 20 to 40% of the β-isomer. U.S. Patent No. 2,773,862 also discloses the ethylation of toluene in the presence of aluminum chloride as a catalyst to form an isomeric mixture in which the m-isomer predominates, the β-isomer is present in a smaller amount and the o-isomer even less. A typical isomeric composition disclosed in this patent comprises 10 to 20% by weight of o-ethyltoluene, 25 to 30% by weight of p-ethyltoluene, and 55 to 60% by weight of m-ethyltoluene. U.S. Patent No. 2,920,119 relates to a conventional ethyltoluene isomer mixture obtained by ethylating toluene in the presence of a Friedel-Crafts catalyst. The mixture contains 72 why, the m-isomer, 20% of the β-isomer and 8% of the

-isomer. According to the method disclosed in this patent, the proportion of the β-isomer relative to the other isomers is likely to be increased by a combination of an alkylation, disproportionation, and isomerization step. The ethyltoluene isomer mixture obtained may contain about 20% of the o-isomer, 50% of the m-isomer and 30% of the β-isomer.

U.S. Pat. No. 3,720,725 discloses a reaction mixture comprising about 45% o-ethyltoluene, about 38% p-ethyltoluene, and about 3% m-ethyltoluene. This reaction mixture is obtained by alkylation of an aromatic hydrocarbon using a catalyst system comprising molybdenum halide, alkylaluminum dihalide and a proton donor.

The presence of larger amounts of the o-isomer in ethyltoluene is highly undesirable since, when dehydrogenated, the o-isomer tends to ring closure to produce indenes and indanes which adversely affect the properties of polymers made from the resulting vinyltoluene. Indenes and indanes are difficult to separate from the desired vinyltoluene. In the past, it has therefore been necessary to remove the o-isomer from the ethyltoluene feedstock prior to dehydrogenation by an expensive distillation technique.

It goes without saying that if ethyltoluene is available in which the o-isomer is absent from the beginning, or in which it is only present in trace amounts, this isomer would not need to be removed. Such products have hitherto not been available, but a process for producing an isomeric mixture of ethyltoluenes, which consists almost exclusively of the β-isomer, wherein the orthoisomer is absent or extremely low in the mixture has recently been described.

The present invention provides a process for the preparation of a polymerizable mixture of isomers of methylethenylbenzene containing up to 0.1% by weight of 1-methyl-2-ethenylbenzene, 1 to 10% by weight of 1-methyl-3-ethenylbenzene and 90 to 99% by weight of 1-methyl-4-ethenylbenzene. characterized in that a mixture of ethyltoluenes containing not more than 0.1% by weight of o-ethyltoluene, 1 to 10% by weight of m-ethyltoluene and 90 to 99% by weight of p-ethyltoluene is dehydrogenated.

In preferred mixtures, 1-methyl-4-ethenylbenzene is 97 to 99% by weight (and preferably 98 to 99% by weight), 1-methyl-2-ethenylbenzene is 0 to 0.1% by weight (less than 0.05% by weight), wherein 1-methyl-3-ethenylbenzene is the remainder of the ethenylbenzene product (preferably 1 to 3% by weight). However, the 1-methyl-4-ethenylbenzene content can be reduced to as much as 95% without negatively affecting the resulting polymers.

The isomeric mixture may contain impurities and randomly present substances in addition to methylethenylbenzenes. Usually these other substances do not constitute more than 1% by weight of the total mixture. These other substances enter the product during the production of methylethenylbenzene.

Total amount of ethenylbenzenes

Residue:

ethyltoluenes mesitylenes etc.

non-vinyl high-boilers

Distribution of ethenylbenzenes:

1-methyl-2-ethenylbenzene0.05 1-methyl-3-ethenylbenzene2,6 1-methyl-4-ethenylbenzene97,4

A mixture of isomeric methylethenylbenzenes can be obtained by catalytic dehydrogenation of a mixture of the corresponding ethyltoluenes. The dehydrogenation is conveniently carried out under the conditions generally used for dehydrogenating ethylbenzene to styrene. Thus, dehydrogenation is generally carried out in the gas phase at elevated temperature in the presence of a dehydrogenation catalyst. The pressure may be atmospheric or lower or higher than atmospheric pressure. Typically, atmospheric pressure is preferred for simplicity, but a non-reactive diluent may be present to reduce the ethyltoluene partial pressure so that dehydrogenation is actually performed under reduced pressure. This is important for achieving an appropriate balance. A suitable diluent is water in the form of steam and usually constitutes the bulk of the mixture. Usually, a ratio of 1: 1 to 5: 1 is preferred in the feed. Usually, a temperature of 500 to 750 degrees Celsius, preferably 600 to 650 ° C, is employed. A suitable hourly space velocity of the liquid phase is about 1.2 h * ¹ (for ethyltoluene) and is preferably operated at this rate. The degree of conversion is usually about 60% at a selectivity of about 94% to the 1-methyl-4-ethenylbenzene isomer. Conventional dehydrogenation type catalysts, which are generally composed of complex mixtures of oxides, are used as catalysts. A typical catalyst comprises ferric oxide, potassium carbonate, cerium oxide and molybdenum trioxide and has the following composition:

% by weight

Fe2O.3 55 to 61

K2CO3 · 25 and 25

Сб20з 4.6 to 5.6 (Ce)

MOO2 2.2 to 2.8

The ethyltoluene starting material is known.

In dehydrogenation, the distribution of ethyltoluene isomers is also transferred to the dehydrogenated product, and therefore the product contains a high proportion of p-isorner (1-methyl-4-ethenylnylbenzene) either not present at all or only in trace amounts.

The process for producing the starting material consists of:

A typical isomeric mixture has the following composition as determined by gas chromatography:

% by weight

99.41

0.10

0.15

0.34

0.59

0.59 100.00 essentially in alkylation of toluene with ethylene in the presence of certain crystalline aluminosilicate zeolitic catalysts. The catalysts have a silica / alumina ratio of at least 12 and a C-index in the range of 1 to 12. In this process a mixture with an extremely high proportion of 1-methyl-4-ethylbenzene isomer is obtained, with only a small proportion of 1-methyl-3-ethylbenzene isomer and with a negligible amount of the 1-methyl-2-ethylbenzene isomer. The almost complete absence of 1-methyl-2-ethylisomer is very advantageous since, as mentioned, this isomer tends to form undesired byproducts in the dehydrogenation stage (indanes and indenes which adversely affect the properties of the resulting polymers and which cannot be easily separated from methylethenylbenzenes ).

The mixture of isomeric methylethylbenzenes may be prior to dehydrogenation. undergoing a distillation step to separate the various by-products, and after the dehydrogenation is complete, further distillation may be performed to separate the methylethenylbenzenes from their saturated precursors.

Since the proportion of 1-methyl-4-thenylbenzene in the mixture is so high, usually at least 95% by weight, the mixture can essentially be referred to as the para (1,4-) isomer.

Methylethenylbenzenových mixture of isomers can be polymerized either alone to polymers ¹ or together with copolymerizable monomers to copolymers. Polymerization conditions suitable for the polymerization of styrene are generally also suitable for the polymerization of a methylethenylbenzene mixture, whether the mixture is polymerized alone or together with other monomers. Thus, the polymerization can be carried out in block, solution, suspension or emulsion, similar to the polymerization of styrene. As polymerization catalysts, radical, anionic and cationic catalysts can be used. Suitable free-radical initiators are di-tertiary butyl peroxide, azobis (isobutyronitrile), di-benzoyl peroxide, tertiary butyl perbenzoate, dicumyl peroxide and potassium persulfate. The cationic catalysts are usually Lewis acid catalysts, for example aluminum chloride, boron trifluoride, boron trifluoride etherate complexes, titanium tetrachloride and the like.

The anionic catalysts are usually of the organometallic type and are, for example, trieths, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, butyl sodium, lithium naphthalene, phenyllithium, sodium lithium or cumyl sodium.

Polymers have useful and valuable properties that distinguish them from similar substances such as polystyrene.

The following examples serve to illustrate the invention. Example 1 describes a known process for preparing an ethyltoluene precursor. This process produces only a small amount of the β-isomer.

Example 1

1 g of aluminum chloride was added to 100 ml of toluene and ethylene was introduced at 80 DEG C. at a rate of 40 ml / min. After two hours the product of the composition given in Table 1 is obtained:

Table 1

Component % by weight benzene 0.20 toluene 71.90 ethylbenzene 0.17 xylenes p-xylene 0.15 m-xylene 0.06 o-xylene 0.04 ethyltoluenes p-ethyltoluene 6.43 m-ethyltoluene 14.37 o-ethyltoluene 3.24 higher hydrocarbons 1.45 other substances 1.99

The ratio of the p- / m- / o-isomer of ethyltoluene is 27/60/13.

Example 2

Preparation of the catalyst

A 5.3 g sample of the hydrogen form ZSM-5 having a crystal size of about 2 µm is steam treated at 515 ° C for 2 hours, at the rate of steam introduction.

8.8 ml of liquid water per hour. The temperature was then raised to 640 ° C and toluene was fed at 180 ml / h for 4 hours 15 minutes. The temperature is. The catalyst is purged with nitrogen and cooled. A precoking product is obtained.

Ethylation of toluene

The toluene is alkylated with ethylene in the presence of the above catalyst. The reaction conditions are as follows: temperature 300 ° C, mass hourly space velocity 7.4 h ^-1 , toluene to ethylene mole ratio in feed 5 and catalyst shift time of 1 h. The toluene conversion achieved is 4.1% % and ethylene 24.1%. The isomeric mixture of ethyltoluenes contains 93.15% by weight of the β-isomer and 6.85% by weight of the m-isomer.

Dehydrogenation of ethyltoluene

The mixture of ethyltoluene isomers is passed through a complex oxide dehydrogenation catalyst at a temperature of 620 to 640 ° C and at atmospheric pressure. As a diluent, water is present in a weight ratio water / ethyl toluene 3: 1 liquid hourly space velocity is 1.2 h phase ^'1. The degree of conversion at one pass is about 60% at a selectivity of 94% to the β-isomer.

The catalyst used is a Girdler G-64-C catalyst having the following composition:

% by weight

Fe2O3 55 to 61

K2CO3 1 5 to 5 25

Ce2, O3 4.6 to 5.6

MoO2 2.2 to 2.8

The isomer distribution in the dehydrogenated product is the same as in the ethyltoluene feedstock (p-isomer: m-isomer 93.15: 6.85, with the o-isomer substantially absent).

Example 3

Preparation of the catalyst

The zeolite ZSM-5 in the hydrogen form JHZSM-5) with a crystal size of 0.02 to 0.05 µm is mixed with 35% by weight of alumina as a binder and extruded from the mixture to produce cylindrical particles of 1.5 mm in size . A 10 g sample of this extrudate is soaked overnight at room temperature in a solution of 8 g of 85% phosphoric acid in 10 ml of water. The resulting product was filtered off, dried at 120 degrees Celsius for about 2 hours and calcined for an additional about 2 hours at 500 ° C. Ten grams of the phosphorous-impregnated extrudate are then soaked at room temperature overnight in a solution of 25 g of magnesium acetate tetrahydrate in 20 ml of water. The product is filtered off, dried at 120 ° C for about 2 hours and then calcined for about 2 hours in an oven at 500 ° C. The resulting product contains 4.18 wt% phosphorus and 7.41 wt% magnesium.

Ethylation of toluene

The toluene is alkylated with ethylene in the presence of the above catalyst. The reaction conditions and analysis results are shown in Table 2.

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Dehydrogenation of ethyltoluene

The ethyltoluene product is dehydrogenated under the conditions of Example 2 after preliminary distillation to remove the toluene starting material. Also, the dehydrogenated product is distilled to remove unreacted ethyltoluene.

The distribution of isomers in the dehydrogenated product (o-, m-, β-isomer) is always the same as the distribution in the starting ethyltoluene product.

Example 4

Preparation of a polymer from a mixture of methylethenylbenzene isomers

The mixture of methylethenylbenzene isomers used has the following composition:

Substance% by weight methylethenylbenzenes99,43 ethyltoluene0,53 xylenes, cumenes, mesitylenes0,01 high-boilers0,03

Methylethenylbenzene distribution: 1-methyl-2-ethenylbenzene- (1) 1-methyl-3-ethenylbenzene97,0 1-methyl-4-ethenylbenzene3,0

Note: (1) less than 0,05%.

The mixture [120 g] is dissolved in a solution of 46.75 g of toluene and 0.168 g of azobisphisobutyronitrile and poured into a dried bottle, which is then sealed by means of a connected ball valve. Dry nitrogen is bubbled through the mixture in the bottle through a septum and through an open ball valve for 10 minutes. Nitrogen exits through a short needle through the bulkhead at the top of the ball valve. Both needles are then removed, the ball valve is closed, and the bottle is placed in an oil bath where the temperature is maintained at 60 ° C for 96 hours and then at 90 ° C for 24 hours.

The polymerized mixture is removed from the bottle by dissolving at 90 ° C in added toluene. The volume of the final solution is about 400 ml. The polymer is precipitated by pouring the solution into about 1000 to 1500 ml of methanol in a Waring Blendor, adjusting the stirring rate to cut the polymer into pieces. The liquid was decanted and the polymer in the mixer was washed once with methanol. Solid poly-

The mer is filtered off and dried in a vacuum oven at 100 ° C for 48 hours. The polymer has the following characteristics: Molecular mass (viscosity molecular mass) 269 x ИР ³ (number average molecular mass) 589 x К-3З Translucent temperature Tg (° C) 111 Vicat temperature (° C) 119 Hot deflection (° C) 98 Melt flow index (Cond. G) í (g / 10 mm) 2.1 Density (g / cm ³ ) 1,008 Tensile strength (MPp) 41.7 Ductility (%) 3 Tensile modulus: using a test device Rheovibron (MPa) 2274 using a test device Instron (MPa) 2322 Impact strength ((/ cm) 0.11 Haze 4.4 Light transmittance (%) 89.7 Pentane absorption 41.0 Examples 4A, 4B, 4C

The polymer was prepared in the same manner as in Example 4 from similar monomer mixtures containing different proportions of the p-isomer (1-methyl-4-ethenylbenzene).

The properties of the polymers are given in the following table:

213344 11 12 Example IA 1B 1C P-isomer content (%) Molecular Weight: (Viscosity Molecular Weight- 89.3 95.5 99.7 company) (number average molecular 271 278 269 mass) - 168 177 Translucent temperature Tg (° C) 106 110 113 Vicat temperature (° C) 108 114 118 Hot deflection (° C) Melt Flow Index (Cond. G) 93 108 104 (g / 10 min) 3.0 2.4 2.3 Density (g / cm ³ ) 1,014 1,011 1,008 Tensile strength (MPa) 41.3 36.6 35.5 Ductility (%) Tensile modulus: using a tester 1.4 8 3 Rheovibron (MPa) using a test device 2494 2233 2439 Instron (MPa) 2123 2068 2281 Impact toughness (J / cm) 0.15 0.07 0.11 Haze 5.0 4.2 5.2 Light transmittance (%) 88.3 88.7 88.7 Pentane absorption 40.0 40.0 40.0

OBJECT OF THE INVENTION

Claims (3)

A process for the preparation of a polymerizable mixture of isomers of methylethenylbenzene containing not more than 0.1% by weight of 1-methyl-2-ethenylbenzene, 1 to 10% by weight of 1-methyl-3-ethenylbenzene and 90 to 99% by weight of 1-methyl-4-ethenylbenzene characterized in that a mixture of ethyltoluenes containing not more than 0.1% by weight of o-ethyltoluene, 1 to 10% by weight, m-ethyltoluene and 90 to 99% by weight of p-ethyltoluene is dehydrogenated. 2. The method of item 1 for producing a polymerizable mixture of isomers of methylethenylbenzene containing not more than 0.05% by weight of 1-methyl-2-ethenylbenzene, 1 to 5% by weight, 1-methyl-3-ethenylbenzene and 95 to 99% by weight 1-methyl- 4-Ethenylbenzene, characterized in that a mixture of ethyltoluenes containing not more than 0.05% by weight of o-ethyltoluene, 1 to 5% by weight of m-ethyltoluene and 95 to 99% by weight of p-ethyltoluene is dehydrogenated. 3. The method of item 2 for producing a polymerizable mixture of isomers of methylethenylbenzene containing not more than 0.05% by weight of 1-methyl-2-ethenylbenzene, 1 to 3% by weight of 1-methyl-3-ethenylbenzene and 97 to 99% by weight of 1-methyl -4-Ethenylbenzene, characterized in that a mixture of ethyltoluenes containing not more than 0.05% by weight of o-ethyltoluene, 1 to 3% by weight of m-ethyltoluene and 97 to 99% by weight of p-ethyltoluene is dehydrogenated.