DD149672A1 - METHOD OF NETWORKING VINYLAROMATIC POLYMERS - Google Patents

Abstract

The invention relates to a process for crosslinking vinylaromatic polymers, in particular polystyrene. The object of the invention was to develop an easily realizable process for the crosslinking of perlfoermigem polystyrene to obtain the spherical shape, the crosslinked products are optionally chemically modifiable in high yield.

Description

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VEB CHEMICAL COMPANY BITIERFJSLD Bitterfeld, 28. 4.

2069 WP О 08 F / 220 051

Process for crosslinking vinylaromatic polymers

Applicability of the invention

The invention relates to a process for the preparation of crosslinked vinylaromatic polymers.

Pre-charged vinylaromatic polymers, in particular crosslinked polystyrenes, can serve as starting materials for the synthesis of cation and anion exchangers as well as solid supports for peptide syntheses and types of catalysis resins. They can also be used as adsorber polymers and chromatography resins equipped with certain properties.

C characteristic of the known technical solutions

Vinyl aromatic polymers, especially polystyrenes, are soluble in esters, ketones, aromatic hydrocarbons and chlorohydrocarbons, thereby limiting their use. The crosslinking results in insolubility.

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The crosslinking of the vinylaromatics usually takes place by copolymerization with divinyl compounds. The system styrene-divinylbenzene has attained particular importance in this context, since it is technically accessible starting materials and it is possible to realize polymer-analogous reactions with high conversions on this system. Styrene-divinylbenzene copolymers have structural inhomogeneities due to the different reactivities of the monomers and the conditions of preparation used, which may be disadvantageous for the polar products produced by polymer-analogous reactions. This fact has led to numerous attempts to eliminate or mitigate the disadvantages mentioned. In this case, two directions of operation can be seen, one of which starts with divinylbenzene cross-linked polystyrene (DIS-AS 2 045 O96, DD-PS 125 824), while the other starts from polystyrene. Boi the networking of polystyrene can also tread two ways. On the one hand the pure cross-linking is described and on the other hand a cross-linking with simultaneous modification of the aromatic beads. DD-PS 126 74-1 and 126 738 describes the crosslinking of foam polystyrene with simultaneous sulfonation.

Similar methods describe the crosslinking of polystyrene with halogen-sulfur compounds or formaldehyde or formaldehyde-emitting substances with simultaneous sulfonation (DE-AS 1 079 326, 1025 145). Another method describes crosslinking with simultaneous chloromethylation or upstream chloromethylation and subsequent crosslinking by annealing (R. Hauptmann, dissertation MLU Hello, 1967). Processes of the same or similar objective are described in DE-AS 1 495 851, 1 495 792 and 1 495 768. These processes have the disadvantage that they are determined by the inevitable abr with ongoing chemical modification to a particular end product. However, it is more advantageous to achieve only crosslinking, since then the applicability of the crosslinked polymers is more extensive.

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Such a method is described in DD-PS 57 703. It is characterized in that polymers of styrene or styrene derivatives are reacted with aliphatic or aromatic dicarboxylic acid dichlorides, disulfochlorides or carbonic acid dichloride under Friedel-Orafts conditions. In the products thus obtained exchange-active groups can be introduced in a known manner. The difficulties and disadvantages of this method lie in the availability and manageability of the materials used, especially in a technical realization.

In DE-OS 2,206,914 a process for the crosslinking of polystyrene is described, which is characterized in that a part of the benzene nuclei of the polystyrene molecules is reacted with lionochlordimethyläther and then carried out a dehydrochlorination.

To maintain the bead shape of the polystyrene, it is proposed to carry out the reaction in a saturated aliphatic hydrocarbon. In this case, however, strict care must be taken that the initial concentration of monochlorodimethyl ether in the reaction mixture is kept equal to or less than 10% by volume, since it is easy to agglomerate the polystyrene beads, which is undesirable. The catalyst used, tin tetrachloride, iat Economically unfavorable and affects the post-crosslinking by this method only limited and provides products with some still considerable residual chlorine levels.

Object of the invention

The aim and object of the invention was to develop a process for the crosslinking of bead-shaped polystyrenes, which is easy to carry out and leads to products which are optionally chemically modifiable in high yield.

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Presentation of the 77th _T the invention

It has now been found that, according to the object of the invention, an easily practicable crosslinking process for polystyrene can be achieved by suspending polystyrene in sulfuric acid, adding the crosslinker before or after suspension, optionally with an inert medium, and adding the crosslinking reaction after a swelling phase of 0.5 to 3 hours with constant temperature control or with stepwise or continuous heating in the range of 20 to 100 ⁰ O performs.

As a styrene polymer bead-like or granular polystyrene of all grain fractions and porous or foamy polystyrene, extruded polystyrene and a copolymer with acrylonitrile and other acrylate is einotzbar. In the case of the conversion to ion exchangers, it is practical to use an ICorn fraction which, in the end product, gives a particle size fraction between 0.3 and 1.2 at the diameter. The polystyrene can be synthesized by known suspension methods.

The sulfuric acid used is at the same time suspending agent and catalyst. This is a particular advantage of the method according to the invention. This eliminates the use of large amounts of solvent and conventional economically unfavorable Friedel-Crafts catalysts such as AlCl ^, ZnOl ₂ and SnOl ^. The sulfuric acid is used with a concentration greater than 00 % and in at least such an amount that a good stirrability is ensured. Sulfuric acid concentrations of 90 % and a weight ratio of polymer to sulfuric acid S 1: 4 are advantageous. To further increase the catalytic activity of the sulfuric acid, it is possible to add an oocatalyst. Suitable for this are, for example, cheap iron compounds.

As crosslinking agents are particularly Monochlordimethyläther, paraformaldehyde, trichloroacetaldehyde ·, xylylene dichloride and

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Dischwefeldichlorid and corresponding mixtures of these substances suitable.

The liquid crosslinking agents, which are also good swelling agents for polystyrene, are metered into the suspension and are taken up in a subsequent Sinquellphase of the polystyrene beads. It is possible to mix the crosslinking agents with a swelling or non-swelling polystyrene inerting agent. As swelling inert agents, halogenated hydrocarbons such as dichloroethane and methylene chloride are particularly suitable. Non-volatile inerting agents are mainly aliphatic hydrocarbons of various boiling ranges, for example, parex and white spirit. Lіг xylylene dichloride, it is advantageous to solve it in a swelling Inertmittel and dose. Ks is taken up with the swelling agent of the polymer. Paraformaldehyde is dissolved in dor sulfuric acid, the bildendo intermediate product is also absorbed by the polymer. The presence of swelling inert agent has a positive effect. The presence of the inerting agents is not absolutely necessary for the course of the crosslinking reaction. Their presence during crosslinking, however, exerts an influence on the structure of the end products. Thus, it is possible that in the presence of dichloroethane or Parex really macroporous Polystyrolpolymerisate be obtained.

A vue ererer advantage of the inventive method is that even in the synthesis of extremely highly crosslinked products with the swelling crosslinkers (i.lonochlordiinethyläther, trichloroacetaldehyde and / or Dischwefeldichlorid), if a dosage of large amounts of crosslinking component is necessary, there is no agglomeration the uncrosslinked or only slightly cross-linked products comes. It is also possible to use mixtures of different crosslinkers in the synthesis. This cross-linking reaction is characterized by a higher temperature and greater catalytic activity of sulfur.

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accelerated acid. The catalytic activity of the sulfuric acid depends on its concentration or on the addition of a cocatalyst. Sulfuric acid concentrations 2 * 95 % therefore already allow a constant temperature control in the range of 30 to 60 ⁰ C, while at lower concentrations, a stepwise or continuous heating to 100 ⁰ C is advantageous. Reaction time and reaction temperature can be varied within wide limits and depend on the objective of the crosslinking reaction.

The process according to the invention can be transferred with equally good success to crosslinked or already crosslinked styrene polymers for further post-crosslinking. However, it is an advantage of the method that prior crosslinking is not required.

The products obtained by the processes described can be chemically modified by known methods in high yield.

The following examples are intended to further illustrate the effect of the invention:

embodiments Example 1 :

A. In a boiling flask equipped with thermometer, reflux condenser and stirrer, stir 52 g of a pearl-shaped polystyrene (0.4 to 1.2 mm) in 200 ml of 90% sulfuric acid. To this suspension is over a period of ^1/2 hour, a mixture consisting of 35 ml of dichloroethane and 5 g Monochlordimethyläther, metered by means of a dropping funnel. Thereafter, zv / ecks complete swelling for 1 to 2 hours at room temperature. The reaction is then carried out at 60 ^° C. for 4 hours.

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In the following cases, the following amounts of monochlorodimethyl ether were added:

B. 35 ш1 dichloroethane / 10 g Monoch'lordimethyläther

C. 35% dichloroethane / 15 g monochlorodimethyl ether

D. 35% dichloroethane / 20 g of monochlorodimethyl ether

After completion of the reaction, it was carefully separated from the reaction mixture and the adherent solution was removed by washing with concentrated NaCl solution, methanol, and methanol.

The following results were obtained:

variant crosslinker Quellungcgrad Rest chi orv / ert Cl-CH ₂ -O-CH ₂ (G) (s / e) ^x) (Wt .-%) A 5 0.2 B 10 2.4 0.7 O 15 0.96 1.3 D 20 0.42 3.2

^J weight ratio of toluene swollen crosslinked polystyrene to dry wetted polystyrene

Example 2:

200 ml of 90% strength sulfuric acid are placed in a boiling flask with thermometer, reflux condenser and stirrer and 52 g of beaded polystyrene (0.4-1.2 mm) are stirred in advance. A mixture consisting of 35 ml of dichloroethane and 40 g Monochlordimethyläther is metered over a period of about У2 hour. For complete swelling, it is pre-swollen for 2 hours at room temperature. Thereafter, the reaction is carried out at the following temperature control each ^half hour at 40, 50, 60,

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⁰ C and 2 hours at 80 ⁰ C. After cooling the batch is carefully separated from the reaction mixture and washed with methanol.

The analysis yields the following results:

Vernetzermenge degree of swelling residual chlorine specific Cl-CH ₂ -O-GII ₃ surface

(б) (e / ε) (wt%) (m ² / g)

40 1.66 4.1 7.30

Example 3:

A. In a flask equipped with the same equipment as in Examples 1 and 2, 200 ml of 90% strength aqueous hydrochloric acid are added and 2 g of paraformaldehyde are stirred. After 1/2 hour, 52 g of perlförraiges polystyrene of the same quality as in Example 1 are suspended, metered for the purpose of swelling 35 lіі dichloroethane and 2.5 g FeCl ^ added. The mixture is then stirred for 2 hours at room temperature. Thereafter, the crosslinking reaction is carried out according to the following temperature control: 1 hour at 40 ⁰ C, 2 hours at 50 and 1 hour at 60 ⁰ C After cooling the mixture is carefully separated from the reaction mixture and washed with methanol.

For the same reaction, the following amounts of paraformaldehyde were used in the experiments and the following results were obtained:

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variant crosslinker swelling (S) (G / g) paraformaldehyde A 2 10 В 4 3.0 0 8th 1.5 D 16 1.5

Example 4:

200 ml of 90% strength sulfuric acid are placed in a flask having the same equipment as in Examples 1 and 2, and 52 g of polystyrene of the same quality as in Example 1 are stirred. 10 g of xylylene dichloride, dissolved in 35 ml of dichloroethane, are added dropwise, 2.5 G FeCl. added and stirred for 2 hours at room temperature. The reaction is carried out according to the following temperature control: 1 hour 60 ⁰ C, 1 hour 70 ⁰ C, 2 hours GO ⁰ C and V'2 hour 85 ⁰ C. It is separated after cooling from the reaction mixture and washed with methanol. The product shows a degree of 4.78.

Example 5:

In the same reaction vessel, as in Examples 1 to 4, 200 ml of approximately 100% sulfuric acid are introduced and stirred 52 g of the same polystyrene, 17.5 g of chloral (trichloroacetaldehyde) added, and as a cocatalyst 2.5 g of PeClIo entered. After stirring for 2 hours at room temperature, the reaction is carried out at 45 ^° C. for 4 hours. After separating the reaction mixture is washed with methanol and analyzed. The non-extractable product has a degree of swelling of 1.78.

Example 6:

After the same experimental conditions, as in Example 5, 37 g Dischwefeldichlorid are added dropwise, stirred for 2 hours at room temperature and then at 40 ⁰ C to

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Reaction brought. The washed and analyzed product has a degree of swelling of 1.67 for the non-extractable part.

Claims (5)

-41- 2069 Inventory claim 1. A process for crosslinking vinylaromatic polymers, in particular polymers and copolymers based on styrene, characterized in that the polymer is suspended in sulfuric acid, which optionally contains iron compounds as cocatalyst, the crosslinker before or after suspension, optionally mixed with an inert medium, is added and the crosslinking reaction after a swelling phase of 0.5 to 3 hours with constant temperature control or with stepwise or continuous heating in the range of 20 to 100 C is performed. 2. The method according to item 1, characterized in that the sulfuric acid is used with a concentration greater than 80 % and in at least such! Close! That a good stirrability is ensured. 3. Procedure according to point. 1 and 2, characterized in that the polyvinyl aromatic swelling or non-swelling, resistant to sulfuric acid, organic substances are used as the inert. - 12 - 2069 4. The method of item 1 to 3 », characterized in that are used as crosslinking substances individually or in a mixture Monochlordimethyläther, paraformaldehyde, trichloroacetaldehyde, xylylene dichloride and Dischwefeldichlorid. 5 · Method according to item 1 to 4, characterized in that the iron compounds iron chloride, iron sulfate, iron oxide and mixtures thereof are added in solid or dissolved form as cocatalyst to sulfuric acid. She / E