EP2956499A1 - Bead polymer for producing pmi foams - Google Patents

Abstract

The invention relates to a foamable bead polymer consisting of (meth)acrylonitrile, (meth)acrylic acid, copolymerizable latent expanding agents and optionally (meth)acrylic acid esters, to the production of said polymer by means of suspension polymerization and to the use thereof for producing foams. Using a bead polymer of this type it is possible, for example, to carry out a simple in-mould foaming process to produce products directly in the form of the desired workpiece. These workpieces are particularly suitable for use as components in spacecraft, aircraft, water and land craft and for other construction elements.

Description

 Bead polymer for the production of PMI foams

Field of the invention

The invention relates to a foamable bead polymer consisting of (meth) acrylonitrile, (meth) acrylic acid, copolymerizable latent blowing agents and optionally

 (Meth) acrylic acid esters, its preparation via suspension polymerization and its use for the production of foams. With such a bead polymer, it is possible, for example, to carry out in-mold foaming in a simple manner and thus to produce products directly in the form of the desired workpiece. These

Workpieces are ideal as components in space, air, water and land vehicles and for other construction elements.

State of the art

Poly (meth) acrylimide foams based on (meth) acrylic acid, (meth) acrylonitrile and optionally (meth) acrylic acid esters are known for their high compressive strength and

 Temperature resistance. By default, these foams are produced by the polymerization of the corresponding monomers in the presence of blowing agent in the form of cast plates, which after polymerization by temperature treatment to

Foam boards are foamed. According to the prior art, these plates must be cut to form parts in a further process step. This process is naturally accompanied by a high yield loss.

In order to reduce this loss of material through the trimming, the WO

2012/013393 a method for in-mold foaming provided. Here, the cast plates are ground to a granulate before foaming. This granulate is then brought into a mold and foamed there to form. However, this process still has the disadvantage that the granulation in comparison to

Although cutting is easier, additional process steps are still required. Furthermore, the molded part produced by this method is mechanically less resilient compared to a shaped block cut from a block. This is due to the interfaces between the foam regions formed from individual granules. In order to improve the adhesion at the interfaces, in the international patent application with the application file PCT / EP2012 / 068885 an analogue with the aid of an adhesion promoter is described. In this way, although the mechanical properties can be improved. However, the level of a foam molded part made from a block does not reach them either.

DE 1817156 describes the preparation of a foamable molding compound, i.a. consisting of a polymer of (meth) acrylic acid and methacrylonitrile, which contains formamide or alkylformamide as blowing agent, as a suspension polymer or as a cast polymer to be granulated. In this case, with regard to the implementation of the suspension polymerization, it is only important that large diameters of at least 0.6 mm are achieved and preferably toxicologically harmful formamide is used as propellant.

However, suspension polymers according to DE 1817156 with a diameter between 0.6 and 1.0 mm are a disadvantage in the filling of very complex forms. It is shown that the polymerization would work independently of the distribution system and the monomer composition. This applies to inorganic as well as to organic parts, e.g. Polyvinyl alcohol, polyvinylpyrrolidone or copolymers of acrylic acid. That is not so. However, the high proportion of organic acids such as (meth) acrylic acid is already problematic in two respects. On the one hand, a large part of these monomers is present in the aqueous phase and is therefore not available for the polymerization. On the other hand, the formed acidic polymers lead to

 Interfacial effects that make stable performance of the suspension polymerization impossible.

The same applies to the propellants. The blowing agents described in DE 1817156 all have such a high water solubility that only a part of the

Suspension polymers is installed and the wastewater is loaded. However, this leads to several disadvantages. Thus, the amount of blowing agent to be used depends on the process control, in particular on the monomer composition, the ratio between monomer and water phase and the temperature at which the

Suspension polymerization is performed. This plays a major role in the later desired pore sizes in PMI foam. So only densities of over 120 kg / m ^{3 can be} shown. Furthermore, the wastewater would have to be cleaned consuming after the polymerization. DE 1817156 therefore proposes that propellant-free

Polymer is produced, which is swollen in a further step with blowing agent. However, this represents an additional process step. In principle, however, such suspension polymers would have a great advantage over granules for the foaming process. The smaller and more uniform particles would result in a more uniform foam. On the other hand one saves under

Using such a material a whole process step, for example the

Granulation.

The description of DE 1817156 from the year 1969 was nevertheless not taken up again in the state of the art, although PMI foams are important materials. The technical problems were obviously too big. Only in JP 2005-364784 / EP 1964903A1 (Ejiri, Kureha Corp.) are thermally foamable

Microspheres described with a core-shell structure whose shell forms a copolymer which can form a polymethacrylimide structure and encapsulates a propellant in the interior of the shell. The copolymer which forms the shell is a copolymer of methacrylonitrile and methacrylic acid. The described foamable core shell

Microspheres are obtained by suspension polymerization and are proposed for use as additives. However, this relates to a fundamentally different field of technology and the teaching of JP2005-364784 is not suitable for suspension polymers for

Production of PMI foam workpieces to provide.

It was an object of the present invention to provide suspension polymers which are suitable for the in-mold foaming of poly (meth) acrylimide (PMI) for the production of PMI foam workpieces. They should do this

Suspension polymers can also be realized with diameters smaller than 0.6 mm.

In particular, the present invention has the object to produce polymer particles which are foamable and thereby lead to foams with high pressure resistance and temperature resistance. In this case, a method should be selected which bypasses the step of grinding polymer plates and provides foamable, particulate material in one step. In particular, the use of toxicologically questionable formamide derivatives should be dispensed with. In particular, it was an object of the present invention, corresponding

Make available suspension polymers that lead to a defined and uniform pore size of the foam material after in-mold foaming.

It was a particular object of the present invention to be able to provide in-mold foams based on suspension polymers having a density of less than 100 kg / m ³ .

Moreover, it was an object of the present invention to provide a method by means of which the production of lightweight crash elements

Plastic foam composite moldings, of molded parts and profile structures with foam core and a cover layer or more layers, of sheet-like

Plastic foam composite moldings, of integral components with force-introducing (inserts) or connecting or stiffening structures or the in-situ production of

Foam foils is possible.

Other non-explicitly stated objects underlying the present invention may be apparent from the description, the examples, or the claims.

solution

The objects are achieved by means of a new process for the preparation of suspension polymers and by a subsequent process for foaming these suspension polymers, as well as by the produced by the method

Supsensionspolymerisate itself.

In order to produce foamable, particulate material which can be processed in a mold to form pressure-resistant and temperature-resistant particle foam bodies, a copolymerization of (meth) acrylonitrile, (meth) acrylic acid and thermally labile (meth) acrylic acid esters in a suspension polymerization, if appropriate in the presence of further selected organic compounds such as alcohols. In addition, crosslinking components or other monomers copolymerizable with (meth) acrylonitrile can be incorporated into the polymer. In particular, the objects are achieved by a novel process for the preparation of suspension polymers for later foaming, wherein an organic distributor is used and the suspension polymerization is carried out at a temperature between 60 ° C and 100 ° C. The organic phase of the suspension polymerization contains between 30 and 70% by weight of (meth) acrylic acid, between 30 and 60% by weight of (meth) acrylonitrile, between 0.01 and 15% by weight of tert-butyl (meth) acrylate, isopropyl (meth ) acrylate and / or cyclohexyl (meth) acrylate and between 0.01 and 2% by weight of initiators. Furthermore, the organic phase may contain up to 10% by weight of crosslinker and up to 30% by weight of further alkyl (meth) acrylates and / or styrene. Suitable propellants here are copolymerizable (meth) acrylic esters, in particular tert-butyl (meth) acrylate, isopropyl (meth) acrylate and / or cyclohexyl (meth) acrylate, which can split off gaseous products on heating. In addition, based on the organic phase, 0.1 to 15% by weight of further blowing agents which are not copolymerized and which are contained atomically in the suspension particles after the polymerization can be added. These preferably have a significantly better solubility in the organic than in the aqueous phase. In particular, these optional additional blowing agents are alcohols, preferably C ₃ -C ₇ -alcohols and very particularly preferably n-propanol, isopropanol, n-butanol, tert-butanol, pentanols or hexanols. Less preferred are formic acid or blowing agent with amide structure, such as urea, monomethyl or Ν, Ν'-dimethylurea, formamide or monomethylformamide. An additional effect as blowing agent can be small amounts of water during the

Suspension polymerization in the polymer particles diffuse and remain there even after drying have.

By using the indicated blowing agents it is possible to surprise

To produce suspension polymers which have a much smaller diameter compared to the prior art. Dier prepared according to the invention

Suspension polymers preferably have a diameter between 0.1 and 1.0 mm. Particularly preferred and in particular over the prior art

Surprisingly, these suspension polymers have a diameter of between 0.2 and 0.8 mm, very particularly preferably between 0.4 and less than 0.6 mm, in particular less than 0.58 mm. The pores formed in the foaming of this suspension polymer preferably have a diameter between 10 and 500 μm, particularly preferably between 20 and 250 μm, and particularly preferably between 50 and 100 μm. In the suspension polymerization according to the invention, the monomers and optionally further organic compounds and crosslinking components are polymerized in the presence of a distributor and the initiator in water with stirring, wherein polymer particles, in which optionally other organic compounds, such as further blowing agents, are dissolved, are obtained , Salts may be dissolved in the water phase to reduce the solubility of the monomers and optional further blowing agents in the water phase. The distributor used for the suspension polymerization is preferably a poly (meth) acrylic acid.

A particular advantage of the present invention can be seen in the fact that the problems of the prior art discussed are circumvented by the use according to the invention of thermally labile (meth) acrylic esters as blowing agents. Surprisingly, it has been found that the blowing agent is incorporated as a monomer in a suspension polymerization in the polymer and thus an accurate adjustment of the blowing agent content over the monomer composition is possible. Thus, a targeted adjustment of the pore size is also possible for foamable polymers prepared by suspension polymerization. Furthermore, no second process step is required for loading the polymer with blowing agent.

The size of the particles can be adjusted within wide limits by the method according to the invention. The size can in particular by choice of the distributor used, the ratio of organic phase (especially monomers) to water phase, the

 Reaction temperature or especially the stirring speed can be adjusted. The variation of these process parameters is basically known to the person skilled in the art and can be optimized for the specific monomer mixture with only a few tests. The particle size per se has a direct influence on the distribution of the particles in a mold or the homogeneity of the foam during later foaming. Smaller particles can be distributed more evenly, while larger particles lead to a mechanically somewhat more stable foam material. The choice of particle size is therefore mainly application-dependent. Preferably, the particles produced by the method according to the invention have a size between 100 μηη and 5 mm, preferably between 500μηι and 3 mm.

The inventive method is particularly relevant for the production of

Poly (meth) acrylimide foams (PMI foams) which are obtainable by means of further process steps described below. The parenthetical notation should identify an optional feature. For example, (meth) acrylic means both acrylic and methacrylic and mixtures of both compounds.

The preparation of rigid poly (meth) acrylimide foams is known per se and disclosed, for example, in DE 1 817 156 (US Pat. No. 3,627,711), DE 27 26 259 (US Pat. No. 4,139,685) or DE 199 17 987.

As stated, the monomer mixtures used according to the invention may contain further monomers copolymerizable with (meth) acrylonitrile. These may be, for example, esters of acrylic or methacrylic acid, in particular with lower alcohols with C 1 -C ₄ radicals, styrene, maleic acid or its anhydride, itaconic acid or its anhydride, vinylpyrrolidone, vinyl chloride or vinylidene chloride, preferably alkyl (meth) acrylates and / or styrene. The proportion of comonomers which can not or only with difficulty be cyclized should not exceed 30% by weight, preferably 20% by weight and more preferably 10% by weight, based on the weight of the monomers.

As further monomers small quantities of crosslinking agents, such as. As allyl acrylate, allyl methacrylate, ethylene glycol diacrylate or dimethacrylate or polyvalent metal salts of acrylic or methacrylic acid, such as magnesium methacrylate can be advantageously used. The proportions of these crosslinkers are often, when used, in the range of 0.005 wt% to 10 wt%, preferably between 0.1 and 5 wt%, based on the total amount of polymerizable monomers. Furthermore, metal salt additives can be used as an option, in many cases

reduce smoke. These include, inter alia, the acrylates or methacrylates of the alkali or alkaline earth metals or zinc, zirconium or lead. Preferred are Na, K, Zn, and Mg (meth) acrylate. Quantities of 2 to 5% by weight of these monomers cause a significant reduction in the smoke gas density in the fire test according to FAR 25.853a. The suspension polymerization according to the invention is carried out with organic distributors. Poly (meth) acrylic acids, polyvinyl alcohols or poly (meth) acrylates having a high proportion of (meth) acrylic acid and / or others are preferred

(Meth) acrylates copolymerizable acids used. Optionally, these polymeric acids may be partially salted prior to use with a base such as ammonia, sodium or potassium hydroxide or amines. The polymerization initiators used are those which are customary per se for the polymerization of (meth) acrylates, for example azo compounds, such as azobiisobutyronitrile, and

Peroxides, such as dibenzoyl peroxide or dilauroyl peroxide, or others

Peroxide compounds, such as, for example, t-butyl peroctanoate or perketals, as well as optionally redox initiators (compare, for example, H. Rauch-Puntigam, Th. Völker, acrylic and methacrylic compounds, Springer, Heidelberg, 1967 or Kirk-Othmer,

Encyclopedia of Chemical Technology, Vol. 1, pp. 286 et seq., John Wiley & Sons, New York, 1978). The polymerization initiators are preferably used in amounts of from 0.01 to 0.3% by weight, based on the starting materials. The initiators can also be used as a mixture of different initiators.

In addition to the initiators, it is possible to add regulators to adjust the molecular weight. Examples of such regulators are n-butyl mercaptan, n-dodecyl mercaptan, 2-mercaptoethanol or 2-ethylhexyl thioglycolate. In general, these regulators are used in amounts of from 0.01 to 5% by weight, preferably from 0.1 to 2% by weight and more preferably in amounts of from 0.2 to 1% by weight, based on the monomer mixture.

Furthermore, the suspension polymers may contain conventional additives. These include, but are not limited to, antistatics, antioxidants, mold release agents, dyes,

Flame retardants, fillers, adhesion promoters, light stabilizers and organic

Phosphorus compounds, such as phosphites or phosphonates, pigments, and plasticizers. Preferably, these additives have a reduced water solubility, so that they are present in the polymer particles after the polymerization. Alternatively, these can

Additives may also be added to the product at a later date. Such a time would be, for example, before drying or before filling in a mold for foaming. Mold release agents can for example also be presented on the surface of the mold.

In a process step following the suspension polymerization according to the invention, the polymer is filtered off after the suspension polymerization and preferably dried at a temperature of at most 100 ° C. This temperature limitation is preferred in order to prevent pre-foaming during drying. The exact depends

Drying temperature of the blowing agents used.

Subsequently, the dried suspension polymer is optionally tempered at a temperature between 1 10 and 130 ° C. Finally, the suspension polymer prepared is added as a solid in a mold and foamed in this form at a temperature between 150 and 250 ° C, preferably between 220 and 250 ° C. Optionally, this mold is rotated, shaken or rotated during foaming to ensure complete foaming thereof. For discharging the liberated propellant, the mold is preferably provided with one or more pressure compensations, for example in the form of openings or valves.

The foaming time is usually between 1 minute and 1.5 hours, preferably between 2 and 45 minutes and most preferably between 3 and 30 minutes. The foaming time depends mainly on the blowing agent used, the

 Foaming temperature and thus the desired density. Another influencing factor can be seen in the component thickness. After cooling, the Kunststoffschaumverbundkorper can be removed from the mold.

Surprisingly, it has been found that the process of foaming according to the invention prepared suspension polymers listed above composition in a mold to foam bodies, which are both pressure-resistant and temperature-resistant. In this case, the temperature resistance with materials of the prior art, which is

Foamed PMI sheets sawed or milled were comparable while the

Compressive strength surprisingly only slightly worse than that of these very expensive prepared bulk polymers.

In a variant of the present invention is before filling the

Suspension polymers a cover layer are inserted into the mold. Optionally, a release agent can be applied between the mold and cover layer to the

To facilitate removal of the Kunststoffschaumverbundkorpers. In this way, a molded plastic foam composite body is obtained. Corresponding process parameters and possible cover layer materials can be found in WO 2012/013393.

In addition to the described method are also foam molded articles, which by means of the method according to the invention or based on the invention

Suspension polymers are available, components of the present invention.

These likewise inventive foam moldings are characterized in that they have a density between 20 and 300 kg / m ³ , preferably between 30 and 200 kg / m ³ . Of foam moldings of the prior art, either cut from

Foam boards or larger granules were made, these products are distinguished by their microstructure. The foam materials according to the invention exhibit microscopically detectable, very uniform "interfaces" which image the original polymer particles, but surprisingly these "interfaces" have only a small influence on the mechanical properties, such as compressive strength.

Compared with foamed suspension polymers with only not

copolymerized blowing agents, especially formamide, as also described in the prior art, the foam materials of the invention differ by a more uniform and optionally smaller pore size and thus by significantly better mechanical properties.

The foam moldings of the invention have still further surprising advantages:

In the entire foam molding is a relatively homogeneous, almost 100% closed-cell foam structure and a uniform cell size distribution without significant preferential direction.

About the foam process of the invention a very good shape is realized. Three-dimensional geometries with very small radii can be molded, but there is a very good impression of the three-dimensional geometry. - In the case of a composite molding with cover layers, there is a very good bond to the cover layers. The force required to detach the top layer (measuring method, standard: drum peel test according to DIN 53295), for example, is greater than the material typical peel moments of the foam materials. These are in the range of 10 to 80 Nmm / mm for a commercially available PMI foam (ROHACELL ^® ). the plastic composite molding has high bending and

 Torsion stiffness, high buckling loads and a very good buckling behavior.

The foam moldings obtainable by the process according to the invention or else the plastic foam composite moldings available as a variant are suitable, for example, as components in space, air, sea and land vehicles, without restricting these exemplary listings in any form due to their low weight and outstanding mechanical properties to understand. Examples

Examples 1 and 2 are carried out without crosslinker: Example 1 Aqueous phase: 500.0 g of water, 120.0 g of sodium sulfate and 7.4 g of Degapas 8105S; Mw: 580,000 g / mol; 13.5% solution in water

Degapas 8105S is a polyacrylic acid from the company Österreichische Chemiewerke

Organic phase: 1 14 g, methacrylic acid, 76 g methacrylonitrile, 10 g tert-butyl methacrylate, 0.9 g AIBN, 0.9 g dilauryl peroxide, 0.2 g tert-butyl per-2-ethylhexanoate

In a 1 L Schmizoreaktor porcelain blade, cooler and thermocouple, the water was introduced and the sodium sulfate dissolved therein at room temperature. The solution was heated to 75 ° C and the monomer phase (solution of the monomers and initiators) within 35 min with stirring (170U / min) was added dropwise. Subsequently, the mixture was stirred for a further 1.5 h at this temperature. Then, the distributor was added dropwise within 2 min. 4 h after the start of the reaction, an exotherm was detected. Thereafter, the mixture was stirred for a further 1 h at 90 ° C and then cooled to room temperature. There were 100 g of a 4% sodium percarbonate solution. dropwise. The batch was allowed to stand at RT overnight and the mother liquor was separated the next day over a metal sieve (450 μη.ΐ) The perl product was transferred to a porcelain suction chute and washed with water (2 l total) The product was finally allowed to stand for 20 h in a vacuum oven dried at 70 ° C.

Example 2 Aqueous phase: 706.50 g of water, 176.47 g of sodium sulfate, 42.52 g of Degapas 8105S, 13.5% solution in water

Organic phase: 159.26 g of methacrylic acid, 120.14 g of methacrylonitrile, 14.70 g of tert-butyl methacrylate, 1.28 g of AIBN, 1.28 g of dilauryl peroxide, 0.29 g of tert-butyl per-2-ethylhexanoate In a 1 L Schmizoreaktor with porcelain blade stirrer, condenser and thermocouple, the water was introduced and the sodium sulfate dissolved therein (about 75 ° C internal temperature). The ambient air in the reactor was displaced by means of dry ice. The stirring speed was 170 rpm. Then the organic phase was added dropwise within 30 min. After 2 h reaction time at about 77 ° C internal temperature, the distributor was added. 4 hours after

At the beginning of the reaction, a slight exotherm was observed. The mixture was stirred for 1 h at 89.5 ° C internal temperature. The thermocouple has been removed. After 1 h post-reaction time, the mixture was cooled to RT and filtered through a 450 μηη metal screen. The coarse fraction was disposed of (coagulum, caking), the rest washed with 71 parts water. The polymer was dried for several days at 70 ° C in a vacuum oven.

Yield:> 2 mm: 147.94 g (50.3% of the theoretical yield)

<2mm: 122.18g (41.5% of theoretical yield)

Example 3: Monomer mixture with allyl methacrylate as crosslinker Aqueous phase: 706.50 g of water, 176.47 g of sodium sulfate, 42.52 g of Degapas 8105S;

13.5% solution in water

Organic phase: 164.46 g of methacrylic acid, 124.23 g of methacrylonitrile, 5.74 g of tert-butyl methacrylate, 0.294 g of allyl methacrylate, 1.28 g of AIBN, 1.28 g of dilauryl peroxide, 0.29 g of tert-butyl per-2-ethylhexanoate In a 1 L Schmizoreaktor with porcelain blade stirrer, condenser and thermocouple, the water was introduced and the sodium sulfate dissolved therein (about 75 ° C internal temperature). The ambient air in the reactor was displaced by means of dry ice. The stirring speed was 170 rpm. Then the organic phase was added dropwise within 30 min. After 2 h of reaction time at about 77 ° C internal temperature, the distributor was added. After 4 h reaction time (exotherm 79, 9 ° C, bath temperature 79, 2 ° C), the reaction temperature was raised to 85 ° C internal temperature and the mixture was stirred for 1 h at this temperature.

The mixture was then cooled to room temperature and filtered through a 450μηι metal sieve, washed with about 7 L of water. The residue was transferred to a porcelain suction filter with paper filter and washed there again with about 2 L of water. After aspirating the bead product was transferred to a crystallizing and dried in a vacuum oven at 70 ° C. Yield:> 2mm: 1 1, 37g <2mm: 278.80g

Example 4: Monomer mixture with allyl methacrylate as crosslinker Aqueous phase: 706.50 g of water, 176.47 g of sodium sulfate, 42.52 g of Degapas 8105S;

13.5% solution in water

Organic phase: 163.94 g of methacrylic acid, 123.69 g of methacrylonitrile, 5.74 g of tert-butyl methacrylate, 0.735 g of allyl methacrylate, 1.28 g of AIBN, 1.28 g of dilauryl peroxide, 0.29 g of tert-butyl per-2-ethylhexanoate Procedure analogous to Example 3

Yield:> 2mm: 35.85 g

<2mm: 268.7g

Example 5: Monomer mixture with allyl methacrylate as crosslinker Aqueous phase: 706.50 g of water, 176.47 g of sodium sulfate, 42.52 g of Degapas 8105S;

13.5% solution in water

Organic phase: 163.61 g of methacrylic acid, 123.40 g of methacrylonitrile, 5.74 g of tert-butyl methacrylate, 1.47 g of allyl methacrylate, 1.28 g of AIBN, 1.28 g of dilauryl peroxide, 0.29 g of tert-butyl per-2 Ethylhexanoate Procedure analogous to Example 3 Example 6: Monomer mixture with ethylene glycol dimethacrylate as crosslinker

Water phase: 684.95 g of water, 175.38 g of sodium sulfate, 63.64 g of Degapas 8105S

Organic phase: 160.02 g of methacrylic acid, 120.86 g of methacrylonitrile, 14.80 g of tert-butyl methacrylate, 0.30 g of ethylene glycol dimethacrylate, 1.27 g of AIBN, 1.27 g of dilauryl peroxide, 0.30 g of tert-butyl per-2- ethylhexanoate

Procedure analogous to Example 3

The sodium sulfate and water were introduced and dissolved with stirring and nitrogen transfer. Then Degapas8105S was added and heated to 75 ° C. At 75 ° C, the monomer phase was added. The stirring speed was 300 U / min. In the next 4 h and 46 min. The internal temperature rose to 76, 7 ° C. After the temperature maximum, the internal temperature was raised to 85 ° C and allowed to react for 1 h. The mixture was then cooled to 20 ° C and washed through a metal filter with 10 L of deionized water. The bead polymer was about 3 days at 70 ° C in

Dryed vacuum oven. Batch size: 296 g; Yield: 21.1, 8 g (corresponds to 71, 55% of theory)

Example 7: Monomer mixture with ethylene glycol dimethacrylate as crosslinker

Aqueous phase: 684.95 g of water, 175.38 g of sodium sulfate, 63.64 g of Degapas 8105S;

13.5% solution in water Organic phase: 152.62 g of methacrylic acid, 120.86 g of methacrylonitrile, 22.20 g of tert.

Butyl methacrylate, 0.30 g ethylene glycol dimethacrylate, 1.27 g AIBN, 1.27 g dilauryl peroxide, 0.30 g tert-butyl per-2-ethylhexanoate

Procedure analogous to Example 6. The product was dried in a fluidized bed dryer. Example 8: Organic phase with ethylene glycol dimethacrylate as crosslinker and tert-butanol as additional blowing agent

Aqueous phase: 684.95 g of water, 175.38 g of sodium sulfate, 63.64 g of Degapas 8105S;

13.5% solution in water Organic phase: 152.62 g of methacrylic acid, 120.86 g of methacrylonitrile, 22.20 g of tert.

Butyl methacrylate, 0.30 g ethylene glycol dimethacrylate, 1.27 g AIBN, 1.27 g dilauryl peroxide, 0.30 g tert-butyl per-2-ethylhexanoate, 7.40 g tert-butanol

Procedure analogous to Example 6. The product was dried in a fluidized bed dryer.

Example 9: Organic phase with ethylene glycol dimethacrylate as crosslinker and tert-butanol as additional blowing agent

Aqueous phase: 684.95 g of water, 175.38 g of sodium sulfate, 63.64 g of Degapas 8105S;

13.5% solution in water Organic phase: 152.62 g of methacrylic acid, 120.86 g of methacrylonitrile, 22.20 g of tert.

Butyl methacrylate, 0.30 g ethylene glycol dimethacrylate, 1.27 g AIBN, 1.27 g dilauryl peroxide, 0.30 g tert-butyl per-2-ethylhexanoate, 14.80 g tert-butanol

Procedure analogous to Example 6. The product was dried in a fluidized bed dryer.

Comparative Examples

Comparative Example 1 Suspension Polymerization with an Inorganic ("Pickering") Distributor and Without Crosslinker

Aqueous phase: 480 g sodium sulphate solution, 35% in water Distributor: 13 g aluminum hydroxide, very pure Organic phase: 45.9 g of methacrylic acid, 56.1 g of methacrylonitrile, 18.0 g of methyl methacrylate, 0.6 g of AIBN, 0.6 g of dilauryl peroxide, 0.30 g of tert-butyl per-2-ethylhexanoate, 14.80 g of tert butanol

In a Schmizoreaktor 168 g of sodium sulfate were suspended at room temperature in 312 g of water and dissolved at 90 ° C. The solution was allowed to stand at room temperature overnight. Then, the aluminum hydroxide was added with stirring. The

 Stirring speed was increased to 600 rpm. The organic phase was then added and the mixture heated to 81 ° C outside temperature. From one

Outside temperature of 81 ° C, the time was counted as the reaction time. After 3 h reaction time, the batch began to coagulate, separating the phases defying agitation. The monomer phase is not fully polymerized at this time. The reaction was stopped.

Comparative Example 2:

Apparatus: 1 L Schmizoreaktor with stirring; Cooler; Nitrogen inlet and thermostat, as well as thermocouple

Aqueous phase: 425 g sodium sulfate solution, 35% in water

Distributor: 9.74 g aluminum sulfate hydrate = 8.12% solids based on the organic phase

Precipitation: 39.84 g of soda solution (10%) = 3.32% of solids based on the monomers, 9.74 g of sodium C ₅ -paraffin sulfonate solution (1%, which corresponds to 1% based on the aluminum sulfate hydrate), 9.74 g of polyethylene glycol (molecular weight 5000-6000) (1%, equivalent to 1% based on aluminum sulfate hydrate) pH after precipitation of the aluminum hydroxide: 5.00 -5.50

Organic phase: 56.1 g methacrylonitrile, 45.9 g methacrylic acid, 18.00 g

Methyl methacrylate, 0.60 g dilauryl peroxide (corresponds to 0.5% based on the organic phase), 0.60 g AIBN (corresponds to 0.5% based on the organic phase)

Reaction of the aluminum hydroxide to the sulfate after polymerization

Ratio of water: monomers = 4: 1 Execution:

To the 35% sodium sulfate solution prepared on the previous day (dissolved at 80 ° C, then cooled to RT), the alusulfate were added and the mixture was stirred at 40 ° C. The sulfate dissolved. Then the hydroxide was added by means of Sodalsg. like and added the auxiliary distributor. Subsequently, the initiated Monomerlsg. added and the emulsion at 81 ° C outside temp. heated. The mixture was stirred at 600 rpm for the entire time. After 3 hours, the batch coagulated. After 5 h, the reaction was stopped and the mixture discarded.

Comparative Example 3 (with urea):

Aqueous phase: 120.0 g sodium sulfate, 480.4 g water Distributor: 29.6 g Degapas 8105S; 13.5% solution in water

Organic phase: 80.0 g methacrylonitrile, 120.0 g methacrylic acid, 20.0 g urea, 0.90 g dilauryl peroxide, 0.90 g AIBN

Execution:

In a 1 L Schmizo with porcelain blade stirrer, condenser and thermocouple, the water was introduced with the degas gas and the sodium sulfate was dissolved therein at room temperature. A short time later, a coherent precipitate formed but was redissolved as the mixture was heated to 75 ° C internal temperature. At 1 0 rpm

 Stirring rate, the organic phase was added dropwise at 75 ° C internal temperature within 30 min. The reactor was previously rendered inert with dry ice. 9 min after

At the beginning of the reaction, the mixture became cloudy. 4 h after the start of the reaction was a

Polymer exotherm observed. After 11 hours, the mixture was cooled to room temperature and allowed to stand overnight. The next day was the mixture

(consisting mainly of suspension polymers with a diameter of about 0.5 mm) sucked through a porcelain suction filter and washed five times with about 400 g of water. The bead product with some coagulum was dried in a desiccator for about 15 h at room temperature and over silica gel in vacuo. Yield: coagulum: 21 g (9.5%); Pearl product sieved over 1, 4mm metal mesh: 189.3g (86.0%)

Comparative Example 4

Same amounts as in Comparative Example 3 but with the addition of the distributor after

Initial polymerization of the monomer phase.

The water was placed in a 1 L Schmizoreraktor porcelain blade, cooler and thermocouple and the sodium sulfate dissolved therein at room temperature. In the

 Production of the organic phase, the urea dissolved with slight heating in the organic phase. At 170 rpm stirring rate, the organic phase was added dropwise at 75 ° C internal temperature within 35 min. The reactor was previously rendered inert with dry ice. Then, the mixture was stirred at this temperature at 170 rpm for 1.5 hours. The mixture became cloudy and small "droplets" were visible, then the distributor was added dropwise within 2 min, 4 h after the beginning of the reaction an exotherm was observed, then the mixture was stirred for 4 h at this temperature The mixture was allowed to stand for 4 days, then 100 g of a 4% sodium percarbonate solution was added dropwise, the mixture was allowed to foam slightly, and the reaction was allowed to stand overnight at RT and the next day through a metal sieve (450 μη.ΐ) Mother liquor separated. The

Pearl product was transferred to a porcelain suction chute and washed with water (2 l total). The product was then dried for a total of 20 h in a vacuum oven at 70 ° C. Yield: 190.4 g (86.3% of theory)

Foaming of the bead polymers:

The foaming of the bead polymers was carried out in a heated press under the conditions listed in the table. The compressive strengths of the resulting foaming bodies (determined at 3% deformation) are shown in the table.

The foamed products of the examples according to the invention showed a very uniform structure and high compressive strength - even at low densities.

On the other hand, the foaming of the suspension polymers of Comparative Examples 3 and 4 led to unstable, very heterogeneous products of relatively high density. This means that only a very low foaming has taken place. These materials were not pressure resistant and were discarded.

Claims

claims

1 . Process for the preparation of suspension polymers for later

 Foaming, characterized in that an organic distributor is used as distributor, that the suspension polymerization is carried out at a temperature between 60 ° C and 100 ° C and that the organic phase of the

 Suspension polymerization between 30 and 70% by weight of (meth) acrylic acid, between 30 and 60% by weight of (meth) acrylonitrile, between 0 and 10% by weight of crosslinker, between 0.01 and 15% by weight of tert-butyl (meth) acrylate, isopropyl (meth) acrylate and / or cyclohexyl (meth) acrylate as a copolymerizable blowing agent, between 0 and 30% by weight of further alkyl (meth) acrylates and / or styrene, and between 0.01 and 2% by weight of initiators.

2. The method according to claim 1, characterized in that the mixture for

Suspension polymerization, based on the organic phase, in addition 0.1 to 15% by weight of a C ₃ -C ₇ alcohol is added as a second blowing agent.

3. The method according to claim 1, characterized in that it is in the

 Distributor is a poly (meth) acrylic acid.

4. The method according to claim 1, characterized in that the polymer is filtered off after suspension polymerization and dried at a temperature of at most 100 ° C.

5. The method according to claim 4, characterized in that the dried

 Suspension polymer is annealed at a temperature between 1 10 and 130 ° C.

6. The method according to claim 4, characterized in that the

Suspension polymer has a diameter between 0.2 and less than 0.6 mm.

7. A process for producing a foam molding, characterized in that a suspension polymer prepared according to any one of claims 1 to 6 is added as a solid in a mold and is foamed in this form at a temperature between 150 and 250 ° C.

8. A method for producing a foam molding according to claim 7, characterized in that the mold is rotated during shaking, shaken or rotated.

9. foam molding, characterized in that it is obtainable by means of a method according to one of claims 6 or 7.

10. foam molding according to claim 8, characterized in that the

Foam molding has a density between 20 and 300 kg / m ³ .

1 1. Foamed article according to claim 9, characterized in that the

Foam molding has a density between 30 and 200 kg / m ³ .

12. foam molding according to any one of claims 9 to 1 1, characterized

 characterized in that the foam molding has a pore diameter between 20 and 250 μηη.

13. Use of a foam molding according to any one of claims 9 to 12 as a component in space, air, sea and land vehicles.