DE4307648A1 - Foams based on thermoplastic polyurethanes as well as expandable, particulate, thermoplastic polyurethanes, particularly suitable for the production of foam molded articles - Google Patents

Description

The invention relates to foams based on thermo plastic polyurethanes and expandable, particulate, thermoplastic polyurethanes, especially for manufacturing of foam molded articles are suitable.

Foams, especially particle foams, have been around since long known and widely described in the literature, e.g. B. in Ullmann's "Encyclopady of Technical Chemistry", 4th edition, Volume 20, p. 416 ff.

The base polymers are usually polystyrene or polyols fine, such as polyethylene and polypropylene. Your commitment takes place in many areas. So expanded polystyrene z. B. as insulating material in construction or for the production of packaging used, expanded polyolefins can, for example, as shock-absorbing foams used in motor vehicle construction become. Other uses are e.g. B. in Ullmann, cited above.

Variations in the base polymers can result in particle foams with very different properties.

However, it has not yet been possible to use particle foams to provide a high elasticity with a good tem unite temperature behavior. This means the use of previously known products set limits.

The object of the invention was to insulate new foams special particle foams with good elasticity and temperature to produce temperature behavior.

Surprisingly, the task was solved by Foam from thermoplastic polyurethane (TPU).

The invention accordingly relates to foams, in particular particulate foams based on thermoplastic poly urethanes as well as expandable, particulate, thermoplastic Polyurethanes, especially for the production of foam Shaped bodies are suitable.  

According to the invention, all customary TPUs can be used both those based on polyether and those based on polyester Base. The polymer chains can be branched, the branching is preferably done by allophanate bridges or the incorporation of multifunctional alcohols.

The TPU that can be used according to the invention correspond to the state of the Technology and can be manufactured by implementing

• a) organic and / or modified organic diisocyanates, With
• b) polyhydroxyl compounds, preferably essentially line arene polyhydroxyl compounds with molecular weights of 500 to 8000, especially polyalkylene glycol polyadipates 2 to 6 carbon atoms in the alkylene radical and molecular weights of 500 to 6000 or hydroxyl-containing polytetrahydro furans with a molecular weight of 500 to 8000 and
• c) Diols as chain extenders with molecular weights from 60 to 400, especially 1,4-butanediol

in the presence of

• d) catalysts and optionally
• e) aids and / or
• f) additives

at elevated temperatures.

The structural components (a) to (d) and optionally (e) and / or (f) the following must be carried out:

• a) The organic diisocyanates (a) are preferably aliphatic, cycloaliphatic and aromatic diisocyanates. The following may be mentioned by way of example: aliphatic diisocyanates such as 1,6-hexamethylene-diisocyanate, 2-methyl-1-tamethylene-1,5-diisocyanate, 1,4-2-ethyl-butylene-diisocyanate or mixtures of at least two of the aliphatic mentioned Diisocyanates, cycloaliphatic diisocyanates such as isophonone diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and -2,6-cyclohexane diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4 '- and 2,2'-dicyclohexylmethane di isocyanate and the corresponding isomer mixtures and aromatic diisocyanates, such as 2,4-tolylene diisocyanate, mixtures of 2,4- and 2,6-tolylene diisocyanate, 4,4'- , 2,4′- and 2,2′-diphenylmethane diisocyanate, mixtures of 2,4′- and 4,4′-diphenylmethane diisocyanate, urethane-modified liquid 4,4′- and / or 2,4′-diphenylmethane diisocyanates, 4,4'-diiso-cyanato-diphenylethane-1,2, mixtures of 4,4'-, 2,4'- and 2,2'-diisocyanato-diphenylethane-1,2, advantageously those with a 4,4'- Diiso cyanato-diphenylethane-1,2-content of at least 95 wt .-%, and 1,5-naphthylene diisocyanate.
  Diphenylmethane diisocyanate isomer mixtures with a 4,4'-diphenylmethane diisocyanate content of greater than 96% by weight and in particular essentially pure 4,4'-diphenylmethane diisocyanate, hexamethylene diiso cyanate 1,6, are preferably used. Isophorone diisocyanate and 4,4'- and / or 2,4'-dicyclohexylmethane diisocyanate.
  The organic diisocyanates can optionally in subordinate amounts, for. B. in amounts up to 3 mol .-%, preferably up to 1 mol .-%, based on the organic diiso cyanate, to be replaced by a tri- or higher functional polyisocyanate, the amount of which must however be limited so that still thermoplastically processable polyurethanes can be obtained. A larger amount of such more than difunctional isocyanates is expediently compensated for by the use of less than difunctional compounds with reactive hydrogen atoms, so that chemical crosslinking of the polyurethane which is too extensive is avoided. Examples of more than difunctional isocyanates are mixtures of diphenylmethane diisocyanates and polyphenyl polymethylene polyisocyanates, so-called raw MDI, and also liquid 4,4 ′ modified with isocyanurate, urea, biuret, allophanate, urethane and / or carbodiimide groups. - And / or 2,4'-diphenylmethane diisocyanates.
  Suitable monofunctional compounds with a reactive hydrogen atom, which can also be used as molecular weight regulators, are e.g. B. called: monoamines such. B. butyl, dibutyl, octyl, stearyl, N-methylstearylamine, pyrrolidone, piperidine and cyclohexylamine, and monoalcohols such as. B. butanol, amyl alcohol, 1-ethylhexanol, octanol, dodecanol, cyclohexanol and ethylene glycol monoethyl ether.
• b) As higher molecular weight polyhydroxyl compounds (b) with molecular weights of 500 to 8000 are preferably polyetherols and especially polyesterols. However, other hydroxyl-containing polymers with ether or ester groups as bridge members are also suitable, for example polyacetals, such as polyoxymethylenes, and especially water-insoluble formals, e.g. B. polybutanediol formal and polyhexanediol formal, and polycarbonates, especially those made from diphenyl carbonate and hexanediol-1,6, produced by transesterification. The polyhydroxyl compounds must be at least predominantly linear and difunctional in the sense of the isocyanate reaction. The polyhydroxyl compounds mentioned can be used as individual components or in the form of mixtures.
  Suitable polyetherols can be prepared by known processes, for example by anionic polymerization with alkali hydroxides, such as sodium or potassium hydroxide or alkali alcoholates, such as sodium methylate, sodium or potassium ethylate or potassium isopropylate as catalysts and with the addition of at least one starter molecule, the 2 to 3, preferably 2 contains reactive hydrogen atoms bound, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate, etc. or bleaching earth as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical.
  Suitable alkylene oxides are preferably, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide and particularly preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately in succession or as mixtures. Examples of suitable starter molecules are: water, organic dicarboxylic acids, such as succinic acid, adipic acid and / or glutaric acid, alkanolamines, such as, for. B. ethanolamine, N-alkylalkanolamines, N-alkyl-dialkanolamines, such as. B. N-methyl and N-ethyl-di ethanolamine and preferably dihydric alcohols optionally containing ether bridges, such as. B. ethane diol, propanediol-1,2 and 1,3, butanediol-1,4, diethylene glycol, pentanediol-1,5, hexanediol-1,6, dipropylene glycol, 2-methylpentanediol-1,5 and 2-ethyl -butanediol-1,4. The starter molecules can be used individually or as mixtures.
  Polyetherols of 1,2-propylene oxide and ethylene oxide are frequently used in which more than 50%, preferably 60 to 80% of the OH groups are primary hydroxyl groups and in which at least part of the ethylene oxide is arranged as a terminal block. Such polyetherols can be obtained by e.g. B. to the starter molecule first the 1,2-propylene oxide and then the ethylene oxide polymerized or first copolymerized the entire 1,2-propylene oxide in a mixture with egg nem part of the ethylene oxide and then polymerized the rest of the ethylene oxide or stepwise first part of the Polymerized ethylene oxide, then all 1,2-propylene oxide and then the rest of the ethylene oxide onto the starter molecule.
  The hydroxyl-containing polymerization products of tetrahydrofuran are also particularly suitable.
  The essentially linear polyetherols have molecular weights of 500 to 8000, preferably 600 to 6000 and in particular 800 to 3500. They can be used both individually and in the form of mixtures with one another.
  Suitable polyesterols can be prepared, for example, from dicarboxylic acids having 2 to 12, preferably 4 to 6, carbon atoms and polyhydric alcohols. Examples of suitable dicarboxylic acids are: aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, cork acid, azelaic acid and sebacic acid and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acids can be used individually or as mixtures, e.g. B. in the form of a succinic, glutaric and adipic acid mixture can be used. For the preparation of the polyesterols it may be advantageous to use the corresponding dicarboxylic acid derivatives, such as dicarboxylic acid mono- and / or diesters having 1 to 4 carbon atoms in the alcohol radical, dicarboxylic acid anhydrides or dicarboxylic acid dichlorides instead of the dicarboxylic acids. Examples of polyhydric alcohols are glycols with 2 to 10, preferably 2 to 6 carbon atoms, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2,2- Dimethyl-1,3-propanediol, 1,3-propanediol and dipropylene glycol. Depending on the desired properties, the polyhydric alcohol can be used alone or, if necessary, in mixtures with one another.
  Also suitable are esters of carbonic acid with the diols mentioned, in particular those with 4 to 6 carbon atoms, such as 1,4-butanediol and / or 1,6-hexanediol, condensation products of ω-hydroxycarboxylic acids, for example ω-hydroxycaproic acid, and preferably polymerization products of Lactones, for example optionally substituted ω-caprolactones.
  Preferred polyesterols used are ethanediol polyadipate, 1,4-butanediol polyadipate, ethanediol-1,4-butane diol polyadipate, 1,6-hexanediol-neopentylglycol polyadipate, 1,6-hexanediol-1,4-butanediol polyadipate and polycaprolatone. The polyesterols have molecular weights from 500 to 6000, preferably from 800 to 3500.
• c) As a chain extender (c) with molecular weights of 60 to 400, preferably 60 to 300, preferably come ali phatic diols with 2 to 12 carbon atoms, preferably with 2, 4 or 6 carbon atoms, such as. B. ethanediol, hexane diol-1,6, diethylene glycol, dipropylene glycol and in particular 1,4-butanediol. However, diesters are also suitable of terephthalic acid with glycols with 2 to 4 carbon atoms, such as B. terephthalic acid bis-ethylene glycol or -butanediol-1,4 and hydroxyalkylene ether of hydroquinone, such as e.g. B. 1, 4-Di (β-hydroxyethyl) hydroquinone and polytetramethy Lenglycols with molecular weights from 162 to 378.
• d) Suitable catalysts, which in particular the reaction between the NCO groups of the diisocyanates (a) and the Accelerate hydroxyl groups of structural components (b) and (c) nigen, are the known according to the prior art and usual tertiary amines, such as. B. triethylamine, dimethyl cyclohexylamine, N-methylmorpholine, N, N'-dimethylpiperazine, Diazabicyclo- (2,2,2) octane and the like and in particular organic metal compounds such as titanium acid esters, iron ver bonds, tin compounds, e.g. B. tin diacetate, tin dioctoate, Tin dilaurate or tin dialkyl salts aliphatic carbon acids such as dibutyltin diacetate, dibutyltin dilaurate or the like liche. The catalysts are usually used in amounts of 0.001 to 0.1 parts by weight per 100 parts by weight of the mixture from polyhydroxyl compounds (b) and diols (c) used.

In addition to catalysts, auxiliary components can also be used agents (e) and / or additives (f) are incorporated. Called Examples include lubricants, inhibitors, stabilizers against hydrolysis, light, heat or discoloration, flame retardants, Dyes, pigments, inorganic and / or organic fillers as well as nucleating agents.

The auxiliaries (e) and / or additives (f) can be found in the build-up components or in the reaction mixture position of the TPU. According to another procedure The auxiliary means (e) and / or additives (f) also mixed with the TPU and then fused. The latter method is used in particular for  Introduction of aluminum oxide, talc and / or silica gel as well optionally reinforcing fillers.

If applicable to the auxiliaries or additives that can be used following no further details can be given, the Technical literature, e.g. the monograph by J.H. Saunders and K.C. Fresh "High Polymers", Volume XVI, Polyurethane, Part 1 and 2 (Verlag Interscience Publishers 1962 and 1964), the art Stoff-Handbuch, volume 7, Polyurethane 1st and 2nd edition (Carl Hanser Verlag, 1966 and 1983) or DE-AS 29 01 774 become.

The structural components (a), (b) and (c) in the presence of catalysts (d) and optionally auxiliary means (e) and / or additives (f) in such quantities Reaction brought up the equivalence ratio of NCO groups the diisocyanates to the sum of the hydroxyl groups of components b) and (c) 0.80 to 1.20: 1, preferably 0.95 to 1.1: 1 and ins special is approximately 1: 1.

The TPU that can be used according to the invention can be produced after the extruder or preferably belt process by batch wise or continuous mixing of the components (a) to (d) and optionally (e) and / or (f), allow to react completely the reaction mixture in the extruder or on a carrier belt Temperatures of 60 to 250 ° C, preferably 70 to 150 ° C, and at final granulation of the TPU obtained. If necessary it should be expedient to obtain the TPU obtained before further processing at 80 to 120 ° C, preferably 100 to 110 ° C over a period annealing from 1 to 24 hours.

The foams according to the invention are produced in accordance with the known from the prior art and z. B. in Ullmanns "Encyclopedia of Technical Chemistry", 4th edition, volume 20, P. 416 ff., Described methods. Applied in particular become the impregnation or extrusion process.

A Mini is the starting product for the impregnation process granules with a particle weight of in particular 0.5 to 10 mg used. This is preferably obtained by using the TPU in a single or twin screw extruder with a downstream one processed granulator.

The extrusion is usually carried out at temperatures from 180 to 250 ° C, preferably 200 to 220 ° C. As granulators come in special strand, water ring, knife roller or underwater granulators for use.  

The use of single-screw extruders has proven to be cheap grasslands; the mini granules obtained here have a high Crystallite content and can become foams with special favorable mechanical properties can be processed.

The mini granulate obtained as described is with the blowing medium impregnated.

The blowing agents known in the prior art can be used as blowing agents means are used.

Examples include low-boiling halogenated, in particular special partially halogenated hydrocarbons, but preferably aliphatic hydrocarbons with 3 to 5 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane and / or Neopentane.

The use of inorganic blowing agents is also possible. Here Examples include carbon dioxide and nitrogen.

The blowing agents can be used individually or as a mixture.

The mini-granulate is impregnated with the blowing agent at increased pressure up to 10 MPa, especially up to 7.5 MPa.

The impregnation temperature is generally 100 up to 200 ° C, in particular 120 to 190 ° C, preferably 130 to 175 ° C.

Temperature and pressure depend heavily on the amount used Propellant.

To impregnate the mini-granulate, it is usually used together with the blowing agent, a suspension stabilizer, e.g. B. Calcium phosphate, magnesium carbonate or zinc carbonate, and one Dispersants, e.g. B. sodium dodecylbenzenesulfonate or sodium N-paraffin sulfonates, suspended in water and then in one Pressure vessel, which is conveniently equipped with a stirrer should be convicted.

The proportion of the blowing agent in the water is usually 5 to 50% by weight, based on the polymeric feedstock. After done Impregnation, the pressure vessel is relaxed, the granu lat foams.  

The foamed granulate particles are removed from the adhering ones Additives cleaned and dried. The drying is done purpose moderately with hot air.

The TPU particles usually have a medium after impregnation ren diameter between 1 mm and 20 mm and a bulk density of 30 g / l to 400 g / l, but preferably from 50 g / l to 200 g / l.

The foamed particles thus obtained can be molded are processed.

If necessary, a pressure loading can be carried out before the molded part is manufactured of the particles.

For this purpose, they are increased to a maximum of 1 MPa and at elevated pressure Temperatures, usually around 80 ° C, with an inert gas, mostly nitrogen, pressurized and 2 to 24 h under this condition stored.

For the production of molded parts, the pre-foamed, if necessary pressure-loaded TPU particles placed in a heatable mold and heated so far that the particles are welded together. The heating is usually done by adding something steam.

The molded part can then be removed. After demolding the molded part should be tempered to constant weight. The tempering should be carried out at temperatures from 20 to 120 ° C leads.

In the manufacture of the foams according to the invention The TPU is extruded together with the blowing agent extruded. The temperature should be between 180 ° C and 250 ° C lie.

As a blowing agent can be used in the description of the Impregnation process called substances, but also solid blowing agents agents that release gas when heated, such as azole carbonamide or p-Toluenesulfonic acid hydrazide can be used.

When exiting the extruder, the TPU foams up and can for example, can be formed into strands and plates.

It is also possible to granulate the foamed TPU and, to be processed into molded parts as described above.  

To produce the foams according to the invention, prinzi All TPUs in the usual hardness range are used.

Particularly good results, especially with regard to the elastic properties and the surface structure of the invention eats foams with a hardness in the range of Shore A85 to Shore A100 achieved. There are no essential ones here differences between polyether and polyester TPU.

Furthermore, it has surprisingly been found that TPU with a high crystallite content to foams with better mechanical Properties. The crystallite content in the used TPU can e.g. B. by using single screw extruders in the Extrusion of the TPU can be increased.

The foams according to the invention stand out in comparison to known particle foams based on other polymers improved mechanical properties.

The elasticity of the foams according to the invention is very high high. For example, the compressive stress is the same shape Part density significantly below the corresponding values of particles polyolefin-based foams.

But also with other mechanical properties such as abrasion strength and crack resistance are the inventive Foams clearly superior to conventional particle foams.

In addition, the particle foams according to the invention are distinguished due to good cold flexibility and high long-term use temperature ren out.

By introducing fillers, it is beyond that possible, the properties of the foams of the invention targeted improvement or modification.

So is the installation of glass fibers to improve the strength possible. The glass fibers can range from 20 to 30 wt .-%, based on the TPU, are added. The addition of the Glass fibers are expediently carried out during the melting process of the polymer in the extruder.

The foams of the invention can be easily thermo be recycled plastically.  

To do this, the foamed TPU using an extru extruded with a degassing device, the extru sion may be preceded by mechanical comminution can. You can then close them again in the manner described above Foams are processed.

The invention is illustrated by the following examples become:

example 1 Production of the foam particles

100 parts were placed in a pressure vessel with a volume of 2.5 l of the TPU specified in Table 1, which as granules with a Particle weight of about 2 mg was present, 260 parts by weight of water and the blowing agents and auxiliaries indicated in the table telteile entered with stirring, to the in Table 1 given temperature heated and maximum one hour on this Temperature maintained. After that, the contents of the pressure vessel discharged through a bottom valve and relaxed, the pressure in the boiler by repressing nitrogen or the one used Blowing agent was kept constant.

The foam particles were removed by washing with water from the start adhering remnants of aids are freed and dried at 20 ° C with air net.

The impregnation conditions and the blowing agents used Auxiliaries can be found in Table 2.

Example 2 Manufacture of molded parts

The foam particles produced according to Example 1 were under Pressure and compression filled in a preheated mold. This was alternately heated with steam from 4.5 to 7 bar.

Then the pressure in the mold was released, this with Cooled water or air, opened and removed the molded part.

After storing the molded parts up to constant weight in the circulating air The molded part density and the mechanics became a drying cabinet at 70 ° C the molded parts determined according to DIN 53 577.

The compressive stress of the molded parts was in each case with two molded parts determined with different molding density.  

The manufacturing parameters of the molded parts and the molded part characteristics values can be found in table 3.

The Shore hardness of the PU elastomers was determined according to DIN 53 505.

Claims (16)

1. Foams based on thermoplastic polyurethanes. 2. Foams according to claim 1, characterized in that the thermoplastic polyurethanes are polyester polyurethanes. 3. Foams according to claim 1, characterized in that the thermoplastic polyurethanes are polyether polyurethanes. 4. Foams according to one of claims 1 to 3, characterized characterized in that the thermoplastic polyurethanes Shore hardness from A 85 to A 100. 5. Foams according to one of claims 1 to 4, characterized characterized in that the polymer chains over allophanate bridges are branched. 6. Foams according to one of claims 1 to 4, characterized characterized in that the polymer chains have multifunctional Alcohols are branched. 7. Foams according to one of claims 1 to 6, characterized characterized in that they contain fillers. 8. Foams according to claim 7, characterized in that they Glass fibers included. 9. Expandable, particulate, blowing agent-containing thermo plastic polyurethanes. 10. Expandable, particulate, blowing agent-containing thermo Plastic polyurethanes according to claim 9, characterized net that the thermoplastic polyurethane polyester-poly are urethane. 11. Expandable, particulate, blowing agent-containing thermo Plastic polyurethanes according to claim 9, characterized net that the thermoplastic polyurethane polyether poly are urethane.   12. Expandable, particulate, blowing agent-containing thermo plastic polyurethanes according to one of claims 9 to 11, characterized in that the thermoplastic polyure thane have a Shore hardness of A85 to A100. 13. Expandable, particulate, blowing agent-containing thermo plastic polyurethanes according to one of claims 9 to 12, characterized in that the polymer chains via Allo phanate bridges are branched. 14. Expandable, particulate, blowing agent-containing thermo plastic polyurethanes according to one of claims 9 to 12, characterized in that the polymer chains have more functional alcohols are branched. 15. Expandable, particulate, blowing agent-containing thermo plastic polyurethanes according to one of claims 9 to 14, characterized in that they contain fillers. 16. Expandable, particulate, blowing agent-containing thermo Plastic polyurethane according to claim 15, characterized records that they contain glass fibers.