DE4309139A1 - Process for the production of powders and other small and ultra small particles - Google Patents

Abstract

The invention relates to a process for the production of powders from (A) crosslinked isocyanate-based plastics, optionally mixed with (B) thermoplastics, in which the isocyanate-based plastics (A) are polyurethane, polyurea and/or polyurethane-urea plastics, and where (A) and (B) are in a weight ratio of from 100 : 0 to 1 : 99, and where (A) has a mean functionality of >/= 2.5 in the soft segment, and whereby (A), without fillers, has a density of > 0.01, preferably from 0.01 to 1.0 g/cm<3>.

Description

The present invention relates to a novel method for producing Powders in which crosslinked polyurethanes, polyurethane polyureas, if appropriate Rigid polyurethane foam or flexible polyurethane foam is used.

The recycling of plastics has been very high in recent years Preserved importance. Also for cross-linked polyurethanes, such as z. B. in highly stressed bumpers are used, people have been looking for ways send them to material recycling. In this context are already Proposals have become known in which material reuse is networked Polyurethanes is detected by so-called extrusion, e.g. B. in DE 37 33 756, DE 38 09 524, DE 38 02 427, DE 38 22 331, DE 40 30 282, DE 40 30 282 and DE 40 39 020. This process has also been foamed Polyurethane systems, possibly in composite components with thermoplastics applied, compare e.g. B. DE 40 19 800. As binders can organic polyisocyanates, solvents and thermoplastics are used, see DE 38 40 167.

Although this work compared to the previously known prior art, the assumed that the thermosets could not be recycled, one great progress was the applicability of the methods described  limited in practice as much as for the production of large-area molded parts Large clamping forces that are usually not available (e.g. 10,000 tons Presses).

Further, not previously published proposals are based on the knowledge that even cross-linked polyurethanes, possibly with the addition of thermoplastics Have thermoplastics processed using thermoplastic machines, compare DE 41 02 999 and DE 41 20 693. In this context, special Polyurethane-polyurea systems for use in the reaction Injection molding technology (RIM technology for the production of polyurethane molded parts) developed, which is in a material reuse via thermoplastic machines processed; (DE 42 24 164). These methods are used in foamed Polyurethane systems, especially those with very low density, the disadvantage that there are blockages in the filling area of the thermoplastic processing machines and this leads to very low throughputs. Forced delivery units (Stuffing screws) are known to the person skilled in thermoplastic processing, However, the processing of such foamed plastics is considerably more expensive.

The person skilled in the art is also familiar with the possibility of very finely grinding polyurethanes and this regrind as a filler of thermoplastic materials in their Processing to incorporate. This method results in a strong one Property deterioration of the thermoplastic molded articles, so that these Method hardly contribute to the pressing problem of polyurethane recycling can.

According to another unpublished proposal, particularly fine powders are said to be used Are made available, which are then used in the recipes of polyurethane Have reactive systems used as fillers again, see DE 42 00 443. The route followed here about the use of rolling mills is apparatus complex; was therefore looking for an apparatus cheap and thus economic technical solution.

It was therefore the object of the present invention, a new method and to provide a device in which the above described Disadvantages of the prior art are avoided and the prior art moreover in an advantageous manner, particularly in economic terms, is enriched.

Surprisingly, it has now been found that foamed, chemically crosslinked polyurethanes with densities of more than 0.01 g / cm ³ can be ground to powder under the influence of shear forces and not too much heating of the material in a flat die press.

The following features are associated with the method according to the invention:

All foamed polyurethanes can be pulverized.
All foamed polyurethanes can be pulverized together in any combination.
All foamed polyurethanes can be pulverized together with any other material in any form of a, possibly even only partially, non-positive connection.
All foamed polyurethanes can be pulverized together in any form of a mixture or batch.

The present invention therefore relates to a process for the preparation of powders from (A) crosslinked isocyanate-based plastics, optionally in a mixture with (B) thermoplastic plastics, characterized in that the isocyanate-based plastics (A) are polyurethane or polyurea and / or polyurethane-urea plastics are used, where (A) and (B) are in a weight ratio of 100: 0 to 1:99, where (A) has an average functionality of 2.5 in the soft segment, where (A) without fillers has a density of <0.01, preferably 0.01 to 1.4 g / cm ³ and wherein (A) has been produced from

• a) organic polyisocyanates,
• b1) compounds with a molecular weight of 1800 to 12,000, which on average at least 3 compared to isocyanate groups have reactive groups,
• b2) optionally compounds with a molecular weight of 1800 to 12,000, which averages at least 2 compared Have isocyanate groups reactive groups,

possibly

• c) polyamines with at least two primary and / or secondary, aromatically bound amino groups in the molecular weight range 108 to 400

and if necessary

• d) optionally containing ether groups (cyclo) alkane polyols and / or (Cyclo) alkane polyamines in the molecular weight range 18 to 1799,

and possibly also with the use of

• e) the blowing, auxiliary and known from polyurethane chemistry Admixtures,

while maintaining an isocyanate index of 60 to 140 in one or Multi-stage process has been produced.

The present invention also relates to those of the invention Process manufactured powder.

The polyurethane materials A) are produced in accordance with known methods Methods of polyurethane chemistry from the examples mentioned below Raw materials. For the production of such plastics or foams Suitable manufacturing methods are, for example, in the plastic manual "Polyurethane", 2nd edition, Carl-Hanser-Verlag Munich-Vienna (1983) described. These polyurethane materials A) are non-melting Polyurethanes, polyureas or polyurethane polyureas. The Starting materials can be used in one or more stages Be brought reaction, the implementation both in closed form as the free foaming of the starting materials A) also includes the known ones Polyurethane RIM materials, the polyurethane polyurea RIM materials, the known polyurethane soft and rigid foams, as well as the foams integral density distribution, as is known from the examples in a manner known per se mentioned starting materials can be obtained in closed forms.

Of course, here are the chemically cross-linked polyurethanes, Polyurethane ureas and polyureas produced by extrusion Materials can be used.

Suitable starting materials a) are any organic polyisocyanates, but preferably aromatic polyisocyanates. Consider, for example those mentioned in EP-B-00 81 701, column 3, line 30 to column 4, line 25 Links. Particular preference is given to component a) Polyisocyanate mixtures of the diphenylmethane series used as they are in themselves known way by phosgenation of aniline / formaldehyde condensates  are accessible and have a viscosity of 50 to 500 mPa · s at 23 ° C. The polyisocyanate mixtures are further particularly preferred as component a) based on toluene diisocyanate and the mixtures of both particularly preferred polyisocyanate mixtures.

Component b) is a compound with opposite Isocyanate groups reactive groups in the molecular weight range 1800 to 12,000, preferably 3,000 to 7,000, or mixtures thereof Compounds, component b) in the sense of the isocyanate addition reaction has a (medium) functionality above 2.2. Preferably, the average functionality of component b) at 2.2 to 3.0, in particular 2.5 to 3.0. Compounds which are particularly suitable as component b) are these Corresponding designs, polyether polyols or mixtures of polyether polyols as disclosed in DE-AS 26 22 951, column 6, line 65 to column 7, line 47 are, according to the invention also preferred those polyether polyols whose Hydroxyl groups at least 20%, preferably at least 40% from primary Hydroxyl groups exist. The examples disclosed in DE-AS 26 22 951, Hydroxyl group-containing polyesters, polythioethers, polyacetals, polycarbonates or polyester amides are in principle suitable as component b) according to the invention, if they correspond to the above statements, but compared to the Polyether polyols less preferred. Also those mentioned in DE-AS 26 22 951 modified by vinyl polymers polyether polyols or high molecular weight Polyhydroxy compounds containing polyadducts or polycondensates, which Above statements regarding functionality can correspond can advantageously be used as components b) or as part of component b).

The above statements are also suitable as the starting component b) corresponding polyetheramines or mixtures of polyetheramines, d. H. Polyether with groups which are reactive towards isocyanate groups and which at least become 10 equivalent%, preferably at least 20 equivalent% from primary and / or secondary, aromatic or aliphatic, preferably aromatic  bound amine groups and the rest of primary and / or secondary, Compose aliphatic bound hydroxyl groups. Suitable such Aminopolyethers are, for example, those in EP-B-00 81 701, column 4, lines 26 to Column 5, line 40, compounds mentioned. The amino groups in these Compounds can also be derivatized in a suitable form, e.g. B. as Ketimine groups.

Any component of course can also be used as component b) polyhydroxyl compounds exemplified with those exemplified Polyetheramines are used.

Component c), which may also be used, is aromatic polyamines of the in EP-B-00 81 701, column 5, line 58 to column 6, Line 34, of the type mentioned by way of example, wherein according to the invention also there as preferred diamines are preferred.

In those that may also be used as further structural components d) Polyols and / or polyamines are any non-aromatic Compounds with at least two isocyanate reactive Groups in the molecular weight range 18 to 1799, preferably 18 and 62 to 500, in particular 18 and 62 to 400. Also suitable are, for example polyhydric alcohols as described in EP-B-00 81 701, column 9, lines 32 to 50, are disclosed. Also suitable are, for example, ether groups containing aliphatic polyamines, for example terminal primary Polypropylene oxides of the abovementioned having amino groups Molecular weight range. Cycloaliphatic rings are also suitable containing polyols such as 1,4-di-hydroxycyclohexane or 1,4-bis hydroxy-methyl-cyclohexane and polyamines such as 1,4-cyclohexane diamine, isophoronediamine, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-amino cyclohexyl) methane. Water is also an option.  

It is an essential point that in the production of polyisocyanate Polyaddition products component b) in such an amount arrives that the proportion by weight of component b), based on the weight of the Components a) to d) at least 5% by weight, preferably at least 10% by weight is, the total proportion of components c) and (or d) is accordingly preferably below 20% by weight, in particular below 8% by weight, based on the Weight of component b). Often the polyisocyanate Polyaddition products A) around pure polyurethane foams, in their manufacture no compounds with amino groups reactive towards isocyanate groups can also be used.

If the polyisocyanate polyadducts A) are foams known blowing agents e), optionally used in addition to other auxiliaries and additives e). In Both chemical and physical blowing agents or also inert gases dissolved in the starting components. Suitable blowing agents are for example in EP-B-00 81 701, column 8, line 31 to line 51, or in the "Plastic manual" cited there described as such. Preferred blowing agent is Water.

If the polyisocyanate polyadducts A) are massive Materials that have a density of more than 0.4 to 0.6 gr / ccm will be At most, propellants are used in very small quantities to a certain extent microporous structure or to maintain the processability of the To facilitate reaction mixtures.

The preparation of the polyisocyanate polyadducts A) can also be found below Use of fillers and / or reinforcing materials e), which, if in general, in amounts of up to 80% by weight, in particular from 20 to 60% by weight, based on the total weight of all starting components a) to e) can be.  

Suitable fillers and / or reinforcing materials are, for example, barium sulfate, Diatomaceous earth, sludge chalk, mica or in particular glass fibers, LC fibers, Glass flakes, glass balls, metal or carbon fibers. Very fine can also be advantageous Polymer powder, especially polyurethane powder made from ground soft or Rigid foam and PUR-RIM powder can be used.

Further auxiliaries and additives e) that may be used are for example the usual catalysts for the polyisocyanate Polyaddition reactions, surface-active additives, cell regulators, pigments, Dyes, flame retardants, stabilizers, plasticizers or fungist or bacteriostatic substances, such as those described in EP-B-00 81 701, Column 6, line 40 to column 9, line 31 are described by way of example.

Component B) is a thermoplastic, for example polyolefins such as polypropylene or polyethylene, Copolymers of propylene with other olefinically unsaturated monomers, impact modified polyolefins such as mixtures of polypropylene and Ethylene / propylene / diene copolymers, polyacrylates such as Polymethyl methacrylates, polystyrenes, styrene / acrylonitrile copolymers, Polycarbonates, linear, thermoplastic polyurethanes, polyesters such as polyethylene or polybutylene terephthalate, vinyl chloride polymers and copolymers such as Polyvinyl chloride or PVC-ABS polymers. Polypropylene, Copolymers of propylene with other olefinically unsaturated monomers, linear thermoplastic polyurethanes, plasticized polyvinyl chloride or PVC / ABS blend used.

The use is also possible, but less preferred in the present case of polyimides, polysulfones, polyether sulfones, aromatic polyacrylates, Polybenzthiazoles, aliphatic and / or aromatic polyamides, Polyether ketones, polyphenylene sulfides.  

Component B) can consist of individual plastics of this type or also any physical mixtures, for example as heterogeneous or homogeneous Polymer system, in the form of blends or polymer alloys reach.

Component B) can also contain auxiliaries and additives, in particular fillers and Reinforcing materials of the type mentioned in amounts of up to 80% by weight contain the weight of component B).

The method is preferably developed on a feed Flat die press carried out; such machines are for example from Kahl-Maschinenbau, Reinbeck, FRG, available. Run on these machines several small rollers in a circle on a horizontal perforated disc; the drive the rolling is done by a central shaft. There is also the option of small rollers over sprockets on the die level and sprockets on the To drive the axes of the small rollers via the central shaft, so that the rollers rotate under friction with the perforated disc on the perforated discs. For it is essential that the ratio of hole diameter and Hole length of a hole in the flat die has a value of 7.5, preferably 5 falls below.

The small rollers shear the material to be processed together with the Flat die and then press it through the holes, this can be the material be compressed. It is sheared on the walls of the hole and the generated friction of the material against each other and on the bore walls a - in this case undesirable - temperature increase of the material. This The temperature can be increased in a simple manner via the thickness of the flat die or about the diameter and the exact shape of the holes in the flat die can be set.  

The flat die should have a certain thickness so that it can withstand the pressure of the Press rolls can withstand; for the reason mentioned above, the Flat die, however, should not be too thick for the powder in the following Compression process not to heat too much and again to a compact To sinter material. It is important to ensure that the procedural Heating of the materials values of 140 ° C for soft foam and 170 ° C for RIM Materials.

Of course, the flat die can also be tempered separately; is preferred however, the flat die is cooled. An effective cooling method is that used coolant with the regrind directly into the flat die press to enter; a preferred coolant is water. Foam materials are preferably soaked in the coolant in the flat die press entered.

The exact mode of operation of this flat die press in is exemplary Maschinenmarkt Würzburg 32 (1989) page 2 ff and 37 (1989) page 4 ff.

The powders according to the invention have a high bulk density of approximately 0.3 to 0.5 g / cm ³ , are free-flowing and are therefore well suited for economical further processing.

The powder produced in this way is suitable as a starting material for a wide variety of products Recycling techniques:

• - Powder made of polyurethane, polyurea and polyurethane-polyurea Materials can be fed to conventional thermoplastic processing and can be done relatively easily with conventional Process thermoplastics together and dazzle them.  
• - Polyurethanes are in this powder form in chemolytic processes such. B. glycolysis, aminolysis and hydrolysis can be used advantageously.
  The powder form is also advantageous for extrusion. This is especially true if coated RIM components are used as the starting material.
• - Polyurethanes are only in powder form with the Regrind technique, i.e. with incorporation as fillers in polyurethane reaction mixtures usable at all.
• - The powder thus produced can be used for thermoplastic Treatment methods can be used advantageously.

example 1 Production of a powder from foamed polyisocyanate polyaddition product

Production: component a)
60 parts by weight of a trifunctional polyether, molecular weight 6000, produced by adding a total of 87% PO and 13% EO to TMP,
40 parts by weight of a filled polyether, molecular weight 6000, produced by blockwise addition of 68.75% PO, 14.58% EO and 16.66% TDI-hydrazine polyaddition product on TMP,
3.8 parts by weight of water,
0.05 part by weight of catalyst 1,
0.25 part by weight of catalyst 2,
0.45 part by weight of catalyst 3,
0.4 part by weight of crosslinking diethanolamine
1.0 part by weight of a stabilizer based on polysiloxane-polyether block copolymer
are mixed together and stirred until homogeneous.

Production: component b)
TDI 80/20 and PMDI are mixed homogeneously in a ratio of 70:30.

Production of polyisocyanate polyaddition product A)
105.95 parts by weight of component a) are combined with 48.5 parts by weight of component b) and homogenized for 5 s with a laboratory stirrer (diameter of the stirring blade approx. 5 cm) to 4200 rpm. Immediately afterwards, the reaction mixture is placed in a mold preheated to 55 ° C. and separated with a wax-based release agent and the mold is closed. After 10 minutes of mold life, the foamed polyisocyanate polyaddition product can be removed from the mold.

The demolded molded article is available on a commercially available cutting mill e.g. B. from Pallmann, D-6660 Zweibrücken, model PS-4-5, in about 6 mm Pre-shredded flakes and then placed in the flat die press. The Flat die press, manufacturer Kahl, Reinbeck, model 14-175 was with one 20 mm thick die. The die had 200 holes in diameter 5 mm. The flat die press was operated at a speed of 100 rpm.

Flakes of this material were at a throughput of 6.5 kg / h and one Product discharge temperature of 120 ° C processed into a powder. The middle Particle size of this powder, measured as a 50% value of the residue curve Sieve analysis, is 140 µm.

Example 2 Production of a powder from solid polyisocyanate polyaddition product

The following are mixed:

• - 67.40 parts of a polyether of OH number 35, obtained by block Addition of first 87% by weight of propylene oxide and then 13% by weight Ethylene oxide on trimethylolpropane  
• 24 parts of a mixture of 65 parts of 1-methyl-3,5-diethyl-2,4- diamino-benzene and 35 parts of 1-methyl-3,5-diethyl-2,6-diamino-benzene
• - 2 parts of a polyricinoleic acid ester with an acid number <5
• - 4.7 parts of a 2: 1: 1 mixture of detda, zinc stearate and bis- (3- dimethylaminopropyl) amine
• - 0.7 parts of Dabco 33 LV, an amine catalyst from Air Products
• - 0.1 parts of UL 28, a tin catalyst from Witco
• 0.1 parts of B 8404, a siloxane stabilizer from Goldschmidt AG.

100 parts of this polyol formulation are mixed with 45.6 parts of ground glass fiber MF 7901 (Bayer AG) mixed (corresponds to a final glass content of 22.5% by weight).

100 parts of this polyol / glass mixture are mixed with 40 parts of a polyisocyanate according to the principle of reaction injection molding technology using a closed plate shape processed into a plate-shaped body. When Polyisocyanate was a reaction product of 4,4'-diisocyanato-diphenylmethane used with tripropylene glycol with an NCO content of 24.5%.

The plate-shaped molded body is sawn into palm-sized pieces and z. B. on a granulator, available e.g. B. at Pallmann, D-6660 Zweibrücken, model PS-4-5, granulated with a sieve insert of 3 mm.

This granulate with a grain size of approx. 2 mm to 3 mm, is in one Flat die press, Hersfeller from Kahl, Reinbeck, Germany, model 14-175 at one Throughput of 4 kg / h and a product discharge temperature of 100 ° C in one Powder processed (for layout of the flat die, see example 1). To cool the  Ground material was 100 g of water on 1 kg of the ground material Given flat bed die press. The average particle size of this powder, measured as a 50% value of the residue curve of a sieve analysis is 220 µm.

Claims (15)

1. A process for the preparation of powders from (A) crosslinked isocyanate-based plastics, optionally in a mixture with (B) thermoplastic plastics, characterized in that as isocyanate-based plastics (A) polyurethane, polyurea and / or polyurethane / Urea plastics are used, where (A) and (B) are in a weight ratio of 100: 0 to 1:99, where (A) has an average functionality of 2.5 in the soft segment, where (A) without fillers has a density of <0.01, preferably 0.01 to 1.0 g / cm ³ and wherein (A) has been produced from

• a) organic polyisocyanates,
• b1) compounds with a molecular weight of 1800 to 12,000, which on average have at least 3 groups which are reactive toward isocyanate groups,
• b2) optionally compounds with a molecular weight of 1800 to 12,000, which on average have at least 2 groups which are reactive toward isocyanate groups,

possibly

• c) polyamines with at least two primary and / or secondary, aromatically bound amino groups in the molecular weight range from 180 to 400

and if necessary

• d) ether groups (cyclo) alkane polyols and / or (cyclo) alkane polyamines of the molecular weight range 18 to 1799,

and possibly also with the use of

• e) auxiliaries and additives known per se from polyurethane chemistry,

while maintaining an isocyanate index of 60 to 140 in one or Multi-stage process has been produced. 2. The method according to claim 1, characterized in that the Powder production is carried out in a flat die press the rotating rollers press the material through a perforated disc, and the ratio of hole length to hole diameter the holes of the perforated disc have a value of 7.5, preferably 5 differs. 3. The method according to claim 1 or 2, characterized in that the Powder production at temperatures in the range from 10 ° C to 150 ° C, preferably at temperatures in the range from 20 ° C to 130 ° C and particularly preferably at temperatures in the range from 30 ° C. to 110 ° C. is made. 4. The method according to any one of claims 1 to 3, characterized in that the regrind by additional coolant added to the regrind is cooled. 5. The method according to any one of claims 1 to 4, characterized in that the powder production with residence times of the material in the  Bores of the flat die press in the range from 0.1 second to 10 Minutes, preferably in the range from 0.1 second to 10 minutes, preferably in the range from 0.1 second to 60 seconds and particularly preferably in the range of 0.2 seconds to 30 seconds becomes. 6. The method according to any one of claims 1 to 5, characterized in that (A) is a rigid polyurethane foam. 7. The method according to any one of claims 1 to 5, characterized in that that (A) is a flexible polyurethane foam. 8. The method according to any one of claims 1 to 5, characterized in that (A) is an integral polyurethane foam. 9. The method according to any one of claims 1 to 5, characterized in that (A) a polyurethane, a polyurethane / polyurea and / or Polyurea RIM material is. 10. The method according to any one of claims 1 to 9, characterized in that as thermoplastics B) polypropylene, copolymers of propylene with other olefinically unsaturated monomers, linear thermoplastic polyurethane, plasticized polyvinyl chloride or PVC / ABS blends are used. 11. The method according to any one of claims 1 to 10, characterized in that that when processing 100 parts of the mixtures of A) and B) 0 to 80 parts of fillers and reinforcing materials C) can also be used.