DD217529A1 - METHOD FOR PRODUCING EXPANDABLE STYRENE POLYMERISES - Google Patents

Abstract

A process for the preparation of expandable styrene polymers obtained by suspension polymerization of styrene or monomer mixtures containing at least 70% styrene using at least two known oelloesic initiators of different decomposition rate, in the presence of brominated oligomers or polymers of butadiene or other auxiliaries, known suspension stabilizers and a special blowing agent are prepared, wherein the blowing agent is added in a separate process stage. The object of the invention is to produce such foamable polymers which have improved controllable processing properties, in particular with regard to dimensional stability and cooling time, and give foams having improved mechanical and physiological properties. This is achieved by adding the initiator at the lower rate of decomposition in at least two different portions at the beginning or in the course of the two stages of the process, the addition of the second portion together with a specific propellant and a small amount of crosslinking agent specifically tailored to a propellant component contained therein Monomers in the conversion range of 75 to 95% occurs.

Description

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Process for the preparation of expandable styrene polymers Field of application of the invention

The invention relates to an improved process for the preparation of expandable Styrenhomo- or copolymers obtained by suspension polymerization of styrene or monomer mixtures in the presence of initiators, using conventional additives such as processing aids, inorganic and / or organic suspension stabilizers, wherein the blowing agent is added in a second process stage.

Characteristic of the known technical solutions

It is known to produce foamable suspension homopolymers or copolymers of styrene in two process stages (DD-WP 129558, DD-WP 130482).

The polymerization of the styrene or styrene with comonomers is separated from the impregnation of the polystyrene beads with a blowing agent as the second stage of the process. As suspension stabilizers for the polymerization stage known inorganic and / or organic compounds are used (DE-AS 1161424, DE-AS 1072809, DE-AS 1151117, DE-OS 2056217).

In a conversion of more than 90% of the monomer (s), the resulting bead polymer is impregnated in suspension with a conventional blowing agent. The blowing agents used are known aliphatic or cycloaliphatic hydrocarbons which do not dissolve the polymer and have a boiling point below the softening point of the polymer.

In this process step, known inorganic or organic suspension stabilizers are also used.

The production of blocks and moldings from expandable styrenic homopolymers or copolymers and the technologies used are known (for example, BWA Keutgen in Encyclopaedia of Polymer Science and Technology, Interscience Publishers, New York 1969, KG FRISCH, JH SAUNDERS: Plastics Foams, Part 2, Marcel Dekker Inc. New York, 1973).

Of great importance for economical processing of expandable styrene polymers is then as short a cooling time as possible. This is understood to mean the time that must at least cool a molded article made of expandable styrene polymer in the form after completion of the vapor deposition, without causing any undue night rubbing, shrinkage or tearing of the molding.

It is already known to control the cooling time, for example by the addition of certain low-volatile organic halogen and possibly phosphorus-containing compounds (DE-AS 1256388, DE-OS 2542281, DE-OS 2706696).

However, the compounds proposed for this purpose are either relatively difficult to obtain and thus expensive, or they must be used in concentrations in the range of 0.05 to 0.5 wt .-%, based on the Styrenpoiymerisat, in order to reduce the cooling time a sufficiently large Effect to achieve. As a result, however, other properties of the expandable styrene polymers or of the foams produced therefrom are unfavorably influenced. The tendency to clumping and water absorption during pre-foaming is increased, the conveying and storage capacity of the prefoamed material are reduced, but the dimensional stability and the mechanical properties of the foams obtained after foaming are already clear by the addition of said cooling time-reducing compounds in the above-mentioned upper concentration ranges adversely affected.

Moreover, higher concentrations of halogen- and / or phosphorus-containing organic compounds, depending on the type of compound, are often either detrimental to health or, at least in their physiological activity, not always harmless.

It is also known to improve the mechanical properties of such foams and, to a certain extent, the processing behavior of the expandable styrene polymers by addition of low concentrations of divinylbenzene or other crosslinking substances or by increasing the molecular weight of the polymer (DE-AS 1100955).

However, this procedure often leads to an undesirable broadening of the Poiymerperispektrums well beyond the most favorable range between 0.6 to 2.5 mm bead diameter and thus to processing difficulties or separation into Perlfraktionen to increased attack less favorable processable or applicable sieve fractions. In addition, increasing the molecular weight of the styrenic polymers may require compaction or at least an uneconomical extension of the production cycle of the expandable styrene polymers.

In DD-PS 157418 we have described the production of foamable styrene homo- or copolymers, which can be processed by targeted modification of the edge zones of the propellant-containing perienes to foams with improved properties and thereby have improved processing behavior.

A disadvantage of this procedure, however, is that as blowing agents pentane mixtures are used which lead by their composition, for example when using Fiammschutzmittelkonzentrationen to unfavorable in certain areas influencing the processing properties and do not allow targeted control of the cooling times over the entire processing area.

Object of the invention

The object of the invention is to produce such foamable styrene polymers which can be processed economically into foams having a homogeneous fine-celled foam structure and improved mechanical and physiological properties and thereby have improved processing behavior, in particular with regard to dimensional stability, welding and cooling time.

Explanation of the essence of the invention The technical task

The invention is based on the object, a process for the preparation of expandable Styrenpoiymerisaten by suspension polymerization of styrene or monomer mixtures of at least 70 parts of styrene and at most 30 Teiien comonomers using at least two öllösiichen initiators of different disintegration rate and of special blowing agent mixtures, excipients and inorganic or organic Suspensionsstabisisatoren develop under standard reaction conditions, which allows to influence shape stability, welding and cooling time of the polymers targeted throughout the usual processing range.

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Features of the invention

The object is achieved in that after reaching 70 to 95% monomer conversion, 5 to 10% by mass of blowing agent mixture, 0.005 to 0.05% by mass of the initiator with the lower rate of decomposition as the second subset and 0.003 to 0.03% by mass. of a crosslinking monomer are added, wherein the blowing agent used is a mixture of the composition 12 to 18% by mass of hexanes, 16 to 28% by mass of i-pentanes, 50 to 63% by mass of n-pentane and 0.5 to 1.0% by mass % higher-boiling constituents is used and the fraction of η-paraffins must be at least 55% by mass in the blowing agent mixture and the molar ratio of η-hexane to crosslinking monomers is from 50 to 400.

As comonomers, for example, acrylonitrile, α-methylstyrene, methyl methacrylate and methacrylonitrile can be used alone or in admixture, which are polymerized according to the invention together with styrene.

The monomers or comonomers to be polymerized may also contain plasticizers, small amounts of dissolved elastomers, fillers, lubricants, dyes and processing aids.

As processing aids, known compounds e.g. from the group of the brominated oligomers or polymers of butadiene, such as hexabromocyclododecane and tetrabromocyclooctane or the a-methylstyrene or Haiogenalkanole example of the type of dibromobutenediol or brominated PB or SB rubber used.

Suitable crosslinking monomers are, for example, divinylbenzene, butanediol diacrylate, divinyl adipate, diallyl fumarate, methylenebisacrylamide, glycol divinyl ether, glycidyl acrylate, butadiene and 1,4-pentadiene. Preferably, two oil-soluble organic peroxidic initiators of differing disintegration rate are used, of which the lower disintegration initiator has a 10 hour half life, preferably in the range of 100 to 120 ° C, and the higher disintegration speed, half life in the 60 range has up to 80 ⁰ C.

According to the novel process, expandable styrenic homopolymers or copolymers are prepared, which have significant advantages over the known prior art.

The process is further illustrated by the following examples.

example 1

Become in a 4.5 l steel autoclave with impeller stirrer

1275 g of styrene

1200 g of deionized water

3.83g benzoyl peroxide (BPO)

0.383 g t-butyl perbenzoate (TBPB)

1.02g Hexabromocyclododecane (HBCD)

mixed with stirring.

This mixture is to monomer conversion of 91% at 90 ⁰ C polymerized at a stirrer speed of 580min ^"1, in which (at a conversion of 66% 12.5 ml of a 5% aqueous solution of 85% hydrolyzed polyvinyl acetate PVA solution ) are added to the suspension using a K-Werrt 62 according to Fikentscher.

After completion of the first process stage are 76,5g blowing agent A at a temperature of 90 ⁰ C, 0,255g 0,255g TBPB and divinylbenzene is added (technical) common to the suspension.

The reaction mixture is subjected to the second process stage at a temperature of 120 ° C and a pressure of 0.6 to 0.7 MPa, wherein after 30 minutes, the addition of a further 50 ml of ¹ PVA solution. After 3 hours, the impregnation is completed.

The reactor contents are cooled down to room temperature and subjected to work-up.

Table 1 contains the propellant composition.

This gives a foamable polystyrene with narrow particle size distribution and good performance properties (Table 2).

Example 2

In a 40 l steel autoclave with impeller stirrer, 17.0% H ₂ O 15.5 kg of styrene 46.5 g of BPO

4.65 g of TBPB

7.75 g of HBCD

mixed with stirring.

This mixture is polymerized at a stirrer speed of 135min- ¹ at 88 to 90 ⁰ C to a conversion of monomers of 63%, it 230mi of an aqueous PVA solution are added analogously to Example 1 and the polymerization continued until the conversion of 93.1% ,

Then, 700 ml of the aqueous PVA solution, 1 750 ml of propellant B containing 4.65 g of TBPB and 3.1 g of divinylbenzene dissolved are added.

The process step of the impregnation then proceeds over 4 h at 115 ³ C and a pressure of 0.6 to 0.7 MPa. The parameters obtained are summarized in Table 2.

Example 3

In a lO-m ^ -Email / ekessei with impeller stirrer and baffle 3900 kg of desalinated water 4295 kg of styrene

13 kg BPO 0.860 kg TBPB 2 kg HBCD

20kg Tricalcim phosphate 0.500kg Caicium carbonate 0.085kg Alkylbenzenesulfonate (C ₁₂ -C ₁₈ ) mixed with stirring.

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The mixture is polymerized at 88 ⁰ C in the course of about 6h and at a stirrer speed of 88min ~ - to a monomer conversion of 94.2% and then cooled to 45 ⁰ C.

The suspension is then forced into a 10 m ³ steel autoclave with impeller stirrer and 500% propellant A 43OgTBPB 860g divinylbenzene 140IPVA solution added 5%.

The reaction mixture is impregnated at 120 ° C in the course of 4h at an adjusting pressure of about 0.7 MPa.

The parameters obtained contain the table

Example 4

The process step of the polymerization proceeds in accordance with Example 3, with the difference that 430 g of TBPB and 600 g of DVB are added to the suspension during the cooling phase at 60 ° C.

The suspension is then pressed into a 10 m ³ steel autoclave, 500 l of blowing agent B are added and the impregnation according to Example 3 is completed.

Example 5 In a 40 l steel autoclave with impeller stirrer, 17.01% deionized water 5500 g styrene 46.5 g BPO 3.75 g TBPB 7.75 g HBCD are mixed with stirring.

This mixture is polymerized at a stirrer speed of 135min " ¹ at 88 to 90 ⁰ C to a conversion of 65%, then 230ml of an aqueous 5% PVA solution are added and the polymerization continued until the conversion 94.5%.

Then, to the suspension are added 700 ml of the aqueous PVA solution and 1750 ml of blowing agent C containing 3.75 g of TBPB and 3.5 g of divinylbenzene.

The reaction mixture is impregnated in the course of 4 h at 118 ° C and an adjusting pressure of 0.65 MPa. The parameters obtained contain the table

Example 6

In an enamelled 10 m ³ reactor with impeller and baffle, 3900 kg of desalinated water 4296 kg styrene 13 kg BPO 0.7 kg TBPB 6 kg HBCD

25 kg Tricaiciumphosphat 0.1 kg Dodecylbenzensulfonat mixed with stirring.

This mixture is polymerized in the course of 5.5 h at 89 ° C and a stirrer speed of 88min " ¹ to the monomer conversion of 93.2% and then cooled to 50 ° C.

During cooling, 500 l of Propellant C containing 650 g of TBPB and 1100 g of divinylbenzene are added. The process step of the impregnation is carried out according to Example 4.

Example 7

In a 40 l steel autoclave with impeller stirrer, 17.0) desalted water 15.5 kg of styrene 46.5 g of BPO 4,6SgTBPB 7,75 g of tetrabromocyclooctane are mixed with stirring.

This mixture is polymerized at a stirrer speed of 135 min " ¹ at 88 to 9O ⁰ C to a conversion of 62%, then 230 ml of a 5% aqueous PVA solution are added and the polymerization to the conversion of 93% · continued ,

Subsequently, the suspension is again the 700 ml of PVA solution and 1 750ml propellant D and 4.35g TBPB and 3.1 g of divinylbenzene fed and the reaction mixture in the course of 4h at a temperature of 120 ⁰ C and a pressure of 0.69 MPa impregnated , The parameters obtained contain the table

Table 1: Driving agent composition

A B C D

<c ₄ 0.8 0.2 0.4 1.1 i-pentane 22.3 19.7 32.1 26.9 n-pentane 57.6 57.0 29.3 26.2 i-hexane 9.3 11.8 15.9 21.7 n-hexane 9.2 10.4 20.2 22.4 SC ₇ 0.8 0.9 2.1 1.7

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Table 2

Parameter examples

C value [mm] (average

Grain size d. EPS) 1.3 1.2 1.3 1.4 1.2 1.2 1.4

F value (grain distribution width between 5 and 95%) K value according to Fikentscher residual monomer content [%] foaming after 3 min

6 min

9 min

Foaming agglomeration {%] cooling time d. Test specimen (ZyI 30 cm φ 10 cm height) [min] Welding d. Test specimen (% broken beads) Shrinkage of specimen Density of specimen [g / cm ³ ] Flexural strength jkp / cm ² ] Compressive strength [kp / cm ² ]

at 10% compression 2.0 2.1 2.2 2.2 1.2 1.5 1.8

1.7 1.75 1.85 2.0 2.2 2.0 2.1 56 56 57 53 58 56 58 0.06 0.10 0.07 0.08 0.2 0.3 0.2 13.4 13.8 13.5 13.8 12.8 12.5 14.0 11.4 12.2 12.0 12.3 12.0 10.4 12.8 9.9 11.0 10.5 10.9 11.2 9.3 11.4 0 0.6 0.7 0 1.7 2.0 2.8 8.5 12.0 11.5 11.0 12.5 7.5 21.0 95 90 95 95 65 35 60 none none none none light light none 18 19 18 19 18 18 19 1.9 2.1 1.9 2.0 1.5 1.2 1.8

Claims (1)

-5- 254 953 4 Invention claim: A process for the preparation of expandable Styrenhomo- or copolymers obtained by suspension polymerization of styrene or monomer mixtures of at least 70 parts of styrene and at most 30 parts of comonomers, for example acrylonitrile, α-methylstyrene, methyl methacrylate and methacrylonitrile using at least two oil-soluble initiators of different decomposition rate, and of blowing agents and auxiliary materials such as brominated oligomers or polymers of butadiene and / or other known Hüfsstoffe and known inorganic suspension stabilizers such as tricalcium phosphate, calcium pyrophosphate, partially hydrolyzed polyvinyl acetate, and optionally a surface-active compound at Realetionstemperaturen in the range 85-145 ⁰ C are erhatten, wherein the Propellant is added in a second process stage and the addition of the initiator with the lower decomposition rate in at least two different parts at the beginning or in the course of both process stages, characterized in that after reaching SO to 95Ma monomer conversion, 5 to 10Ma propellant mixture, 0.005 to 0.05Ma% of the initiator with the lower Zerfailsgeschwindigkeit as the second subset and 0.003 to 0.03M% hexanes, 16 to 28M% i-pentanes, 50 to 63M% n-pentane, and 0.5 to 1.0M% higher boiling components, and the proportion of η paraffins must be at least 55Ma% in the blowing agent mixture and the molar ratio of n-hexane to crosslinking monomers is 50 to 400.