WO1994020568A1

WO1994020568A1 - Thermoplastic polyurethane-based foamed materials

Info

Publication number: WO1994020568A1
Application number: PCT/EP1994/000606
Authority: WO
Inventors: Joachim Fischer; Onno Graalmann; Dietrich Lausberg
Original assignee: Basf Aktiengesellschaft
Priority date: 1993-03-11
Filing date: 1994-03-02
Publication date: 1994-09-15
Also published as: DE4307648A1

Abstract

Foamed materials, in particular particulate foamed materials, based on thermoplastic polyurethanes are disclosed, as well as expandable, particulate, thermoplastic polyurethanes suitable in particular for producing shaped foamed material bodies.

Description

FOAMS BASED ON THERMOPLASTIC POLYURETHANE

description

The invention relates to foams based on thermoplastic polyurethanes and expandable, particulate, thermoplastic polyurethanes, which are particularly suitable for the production of foam moldings.

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

Polystyrene or polyolefins, such as polyethylene and polypropylene, are usually used as base polymers. They are used in many areas. Expanded polystyrene is e.g. used as an insulating material in construction or for the production of packaging, expanded polyolefins can be used, for example, as shock-absorbing foams in motor vehicle construction. Other uses are e.g. in Ullmann, op. cit.

Varying the base polymers can produce particle foams with very different properties.

However, it has not yet been possible to provide particle foams that combine high elasticity with good temperature behavior. This limits the use of the previously known products.

The object of the invention was to produce new foams, in particular particle foams, with good elasticity and temperature behavior.

The task was surprisingly achieved by foams made of thermoplastic polyurethanes (TPU).

The invention accordingly relates to foams, in particular particulate foams, based on thermoplastic polyurethanes and expandable, particulate, thermoplastic polyurethanes which are particularly suitable for the production of foam molded articles. According to the invention, all customary TPUs can be used, both those based on polyether and those based on polyester. The polymer chains can be branched, the branching is preferably carried out by allophanate bridges or the incorporation of polyfunctional alcohols.

The TPUs which can be used according to the invention correspond to the prior art and can be produced by reacting

a) organic and / or modified organic diisocyanates, with

b) polyhydroxyl compounds, preferably essentially linear polyhydroxyl compounds with molecular weights of 500 to 8000, in particular polyalkylene glycol polyadipates with 2 to 6 carbon atoms in the alkylene radical and molecular weights of 500 to 6000 or hydroxyl-containing polytetrahydrofuran with a molecular weight of 500 to 8000 and

c) Diols as chain extenders with molecular weights of 60 to 400, especially 1,4-butanediol

in the presence of

d) catalysts and optionally

e) aids and / or

f) additives

at elevated temperatures.

For 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 as examples: aliphatic diisocyanates such as 1,6-hexamethylene-diisocyanate, 1,5-2-methyl-pentamethylene-diisocyanate, 1,4-2-ethyl-butylene-diisocyanate or mixtures of at least two of the aliphatic mentioned Diisocyanates, cycloaliphatic diisocyanates such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, l-methyl-2,4- ^* and -2,6-cyclohexane diisocyanate and the corresponding isomer mixtures, 4,4'-, 2, 4'- and 2,2'-dicyclohexylmethane diisocyanate 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 diisocyanate, 4, 4 '-Diisocyanato-diphenylethane-1,2, mixtures of 4,4'-, 2, 4'- and 2,2'-diisocyanatodiphenylethane-1,2, advantageously those with a 4,4'-diisocyanatodiphenylethane-1,2 content of at least 95% by weight, 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, diisocyanate-1, 6, isophorone diisocyanate and 4,4'- and / or 2,4'-dicyclohexylmethane diisocyanate.

The organic diisocyanates can optionally be used in minor amounts, e.g. in amounts up to 3 mol%, preferably up to 1 mol%, based on the organic diisocyanate, can be replaced by a trifunctional or higher-functional polyisocyanate, the amount of which must however be limited so that 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 polyphenylpolymethylene polyisocyanates, so-called raw MDI, as well as liquid 4 modified with isocyanurate, urea, biuret, allophanate, urethane and / or carbodiimide groups 4, 4'- 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. called: monoamines such as Butyl, dibutyl, octyl, stearyl, N-methylstearylamine, pyrrolidone, piperidine and cyclohexylamine, and monoalcohols such as e.g. Butanol, amyl alcohol, 1-ethylhexanol, octanol, dodecanol, cyclohexanol and ethylene glycol monoethyl ether.

Suitable higher molecular weight polyhydroxyl compounds (b) with molecular weights of 500 to 8000 are preferably polyetherols and in particular 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 formal forms, for example polybutanediol formal and polyhexanediol-for al, and polycarbonates, in particular those made from diphenyl carbonate and hexanediol-1, 6, prepared 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, preferably 2 to 3 Contains 2 reactive hydrogen atoms bound, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate and others 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 e.g. Ethanolamine, N-alkylalkanolamines, N-alkyldialkanolamines, e.g. N-methyl and N-ethyl-di-ethanolamine and preferably divalent alcohols, optionally containing ether bridges, such as e.g. Ethanediol, 1,2-and 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, 2-methylpentanediol, 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, for example, by first polymerizing the 1,2-propylene oxide and then the ethylene oxide onto the starter molecule or first copolymerizing all of the 1,2-propylene oxide in a mixture with part of the ethylene oxide and the rest of the Ethylene oxide then polymerized or gradually polymerized first part of the 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, suberic 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. in the form of a mixture of succinic, glutaric and adipic acids. 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,

Pentanediol-1,5, hexanediol-1,6, decanediol-1,10, 2,2-dimethyl-propanediol-1,3, propanediol-1,3 and dipropylene glycol. Depending on the desired properties, the polyhydric alcohols can be used alone or, if appropriate, 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 polyadipates, 1,4-butanediol polyadipates, ethanediol-1,4-butanediol diol polyadipates, 1,6-hexanediol-neopentylglycol polyadipates, 1,6-hexanediol-1,4-butanediol -polyadipate and polycaprolatone. The polyesterols have molecular weights from 500 to 6000, preferably from 800 to 3500.

c) Suitable chain extenders (c) with molecular weights of 60 to 400, preferably 60 to 300, are preferably aliphatic diols having 2 to 12 carbon atoms, preferably having 2, 4 or 6 carbon atoms, such as e.g. Ethanediol, hexane-1,6-diol, diethylene glycol, dipropylene glycol and in particular 1,4-butanediol. However, diesters of terephthalic acid with glycols having 2 to 4 carbon atoms, such as Terephthalic acid-bis-ethylene glycol or

-butanediol-1,4 and hydroxyalkylene ethers of hydroquinone, e.g. 1,4-Di (β-hydroxyethyl) hydroquinone and polytetramethylene glycols with molecular weights from 162 to 378.

d) Suitable catalysts, which in particular accelerate the reaction between the NCO groups of the diisocyanates (a) and the hydroxyl groups of the structural components (b) and (c), are the conventional tertiary amines known and known in the art, such as e.g. Triethylamine, dimethylcyclohexylamine, 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 compounds, tin compounds, e.g. Tin diacetate, tin dioctoate tin dilaurate or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate or similar. The catalysts are usually used in amounts of 0.001 to 0.1 part by weight per 100 parts by weight of the mixture of polyhydroxyl compounds (b) and diols (c).

In addition to catalysts, auxiliaries (e) and / or additives (f) can also be incorporated into the structural components. Examples include lubricants, inhibitors, stabilizers against hydrolysis, light, heat or discoloration, flame retardants, dyes, pigments, inorganic and / or organic fillers and nucleating agents.

For this purpose, the auxiliaries (e) and / or additives (f) can be introduced into the structural components or into the reaction mixture for producing the TPU. According to another process variant, the auxiliaries (e) and / or additives (f can also be mixed with the TPU and then melted. The last-mentioned method is used in particular for Introducing aluminum oxide, talc and / or silica gel and, if necessary, reinforcing fillers.

If no further details are given below about the auxiliaries or additives that can be used, these can be found in the specialist literature, for example the monograph by J.H. Saunders and K.C. Fresh "High Polymers", volume XVI, polyurethanes, part 1 and 2 (publisher Interscience Publishers 1962 and 1964), the plastics manual, volume 7, polyurethane 1st and 2nd edition (Carl 0 Hanser Verlag, 1966 and 1983) or DE-AS 29 01 774.

To produce the TPU, the build-up components (a), (b) and (c) are reacted in the presence of catalysts (d) and optionally auxiliary agents (e) and / or additives (f) in amounts such that the Equivalence ratio of NCO groups of the diisocyanates to the sum of the hydroxyl groups of components b) and (c) is 0.80 to 1.20: 1, preferably 0.95 to 1.1: 1 and in particular approximately 1: 1. 0

The TPUs which can be used according to the invention can be produced by the extruder or, preferably, belt process, by batchwise or continuous mixing of the components (a) to (d) and, if appropriate, (e) and / or (f), allowing the reaction mixture to react in the extruder or on a carrier tape at temperatures from 60 to 250 ° C., preferably 70 to 150 ° C., and then granulating the TPU obtained. If appropriate, it may be expedient to anneal the TPU obtained at 80 to 120 ° C., preferably 100 to 110 ° C., for a period of 0 to 1 to 24 hours before further processing.

The foams according to the invention are produced in accordance with the methods known from the prior art and e.g. described in Ullmanns "Encyklopadie der Technische Chemie *, 4th edition, volume 20, 5 p. 416 ff. The impregnation or the extrusion process are used in particular.

A mini granulate with a particle weight of in particular 0.5 to 10 mg 40 is used as the starting product for the impregnation process. This is preferably obtained by processing the TPU in a single- or twin-screw extruder with a downstream granulator.

The extrusion is usually carried out at temperatures from 180 to 45 250 ° C., preferably 200 to 220 ° C. In particular, strand, water ring, knife roller or underwater granulators are used as granulators. The use of single-screw extruders has proven to be favorable; The mini granules obtained in this way have a high crystallite content and can be processed into foams with particularly favorable mechanical properties.

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

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

Examples include low-boiling halogenated, in particular 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. Carbon dioxide and nitrogen are mentioned here as examples.

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

The mini-granulate is impregnated with the blowing agent at elevated pressure of up to 10 MPa, in particular up to 7.5 MPa.

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

Temperature and pressure strongly depend on the amount of blowing agent used.

To impregnate the mini-granulate, it is usually used together with the blowing agent, a suspension stabilizer, e.g. Calcium phosphate, magnesium carbonate or zinc carbonate, and a dispersant, e.g. Sodium dodecylbenzenesulfonate or sodium N-paraffin sulfonates, suspended in water and then transferred to a pressure vessel, which should expediently be equipped with a stirrer.

The proportion of the blowing agent in the water is usually 5 to 50% by weight, based on the polymeric starting material. After the impregnation has taken place, the pressure vessel is relaxed, the granules foaming. The foamed granulate particles are cleaned from the additives and dried. The drying is expediently carried out with hot air.

After impregnation, the TPU particles usually have an average diameter between 1 mm and 20 mm and a bulk density of 30 g / 1 to 400 g / 1, but preferably from 50 g / 1 to 200 g / 1.

The foamed particles thus obtained can be processed into moldings.

If necessary, the particles can be pressurized before the molded part is manufactured.

For this purpose, they are subjected to an inert gas, usually nitrogen, at elevated pressure up to a maximum of 1 MPa and elevated temperatures, usually from about 80 ° C., and stored under these conditions for 2 to 24 hours.

For the production of molded parts, the pre-expanded, possibly pressure-loaded TPU particles are placed in a heatable mold and heated to such an extent that the particles are welded together. The heating is usually carried out by applying water vapor.

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

When the foams according to the invention are produced by the extrusion process, the TPU is extruded together with the blowing agent. The temperature should be between 180 ° C and 250 ° C.

The blowing agents mentioned here can be the substances mentioned in the description of the impregnation process, but also solid blowing agents which release gas when heated, such as azole carbonamide or p-toluenesulfonic acid hydrazide.

As it emerges from the extruder, the TPU foams up and can, for example, be formed into strands and plates.

It is also possible to granulate the foamed TPU and, as described above, to process it into molded parts. To produce the foams according to the invention, it is possible in principle to use all TPUs in the used hard area.

Particularly good results, in particular with regard to the elastic properties and the surface structure of the foams according to the invention, are achieved with TPU with a hardness in the range from Shore A85 to Shore A100. There are no significant differences between polyether and polyester TPU.

Furthermore, it has surprisingly been found that TPUs with a high crystallite content lead to foams with better mechanical properties. The crystallite content in the TPU used can e.g. can be increased by using single screw extruders when extruding the TPU.

The foams according to the invention are distinguished by improved mechanical properties compared to known particle foams based on other polymers.

The elasticity of the foams according to the invention is very high. For example, the compressive stress with the same molded part density is significantly lower than the corresponding values of particle foams based on polyolefin.

However, the foams according to the invention are also clearly superior to conventional particle foams with other mechanical properties such as abrasion resistance and crack resistance.

In addition, the particle foams according to the invention are notable for good low-temperature flexibility and high long-term use temperatures.

By introducing fillers, it is also possible to specifically improve or modify the properties of the foams according to the invention.

This allows the installation of glass fibers to improve the strength. The glass fibers can be added in an amount of 20 to 30% by weight, based on the TPU. The glass fibers are expediently added during the melting of the polymer in the extruder.

The foams according to the invention can be thermoplastic recycled without problems. For this purpose, the foamed TPUs are extruded using an extruder with a degassing device, where the extrusion can optionally be preceded by mechanical comminution. Then they can be processed into foams again in the manner described above.

The following examples are intended to illustrate the invention:

example 1

Production of the foam particles

100 parts of the TPU shown in Table 1, which were in the form of granules with a particle weight of approx. 2 mg, 260 parts by weight of water and the propellant and auxiliary parts indicated in the table were introduced into an autoclave with stirring, to which in Table 1 heated temperature and held at this temperature for a maximum of one hour. The contents of the pressure vessel were then discharged and released through a bottom valve, the pressure in the boiler being kept constant by repressing nitrogen or the blowing agent used. The foam particles were freed from adhering auxiliary residues by washing with water and dried at 20 ° C. with air.

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

Example 2 Production of the molded parts

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

The pressure in the mold was then released, this was cooled with water or air, opened and the molded part was removed.

After the molded parts had been stored to constant weight in a forced-air drying cabinet at 70 ° C., the molded part density and the mechanics of the molded parts were determined in accordance with DIN 53 577.

The compressive stress of the molded parts was determined with two molded parts with different molded part densities. The production parameters of the molded parts and the molded part parameters can be found in Table 3.

The Shore hardness of the PU elastomers was determined in accordance with DIN 53 505.

Table 1

TMP - trimethylolpropane, *) +0.05 mol TMP

Table 2

Production of the foam particles

TPU no. according to blowing agent [parts by weight] tricalcium sodium dodecyl temperature time Table 1 phosphate benzoyl sulfonate bulk density n-butane co ₂ [parts by weight] [parts by weight] [° C] [min] [g / i]

1 20 - 6.8 0.13 152 92 115

2 20 - 6.8 0.13 152 92 100

2 - 10 6.8 0.13 152 92 140

3 20 - 6.8 0.13 150 91 100

4 20 - 6.8 0.13 149.5 90 95

5 20 - 6.8 0.13 159.5 95 90

5 - 10 6.8 0.13 158 94 180

6 20 - 6.8 0.13 161 96 85

7 20 - 6.8 0.13 175 104 165

8 20 - 6.8 0.13 150 91 110

9 20 - 6.8 0.13 157 94 95

10 20 - 6.8 0.13 157 94 95

11 20 - 6.8 0.13 160.5 96 80

12 20 - 6.8 0.13 152 92 80

13 20 - 6.8 0.13 150 91 80

14 20 - 6.8 0.13 167 99 55

15 20 - 6.8 0.13 165 98 100

Table 3

Manufacture of molded parts

Molding manufacture of molded part characteristics PU according to Schütt¬ compression pressure Beda p- molded part water pressure at table 1 density level time tightness *) (molded part density)

[g / i] [bar] [sec] [g / i] [wt%] [N / mm ² ] ([g / 1])

2 100 2 -3 5 -7 10-30 200-300 1- 9 0.38 (250) 0.51 (300)

3 100 2.2-3 4.5-7 15-40 220-300 1-10

4 95 1.4-3.2 4.5-7 10-40 130-300 1- 9 0.24 (150) 0.39 (230)

5 90 2.2-3.3 5 -7 10-35 200-300 1-10 0.41 (230) 0.56 (300)

9 95 2.1-3.2 5 -7 10-40 200-320 1-10 0.40 (250) 0.54 (300)

11 80 2.4-3.5 5 -7 10-40 190-280 1-10 0.44 (230) 0.60 (280)

13 80 2.3-3.5 5 -7 10-40 180-280 1-10 0.38 (230) 0.52 (280)

*) before tempering

Claims

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 in that the thermoplastic polyurethanes have a Shore hardness of A 85 to A 100.

5. Foams according to one of claims 1 to 4, characterized in that the polymer chains are branched via allophanate bridges.

6. Foams according to one of claims 1 to 4, characterized in that the polymer chains are branched via polyfunctional alcohols.

7. Foams according to one of claims 1 to 6, characterized in that they contain fillers.

8. Foams according to claim 7, characterized in that they contain glass fibers.

9. Expandable, particulate, blowing agent-containing thermoplastic polyurethanes.

10. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to claim 9, characterized in that the thermoplastic polyurethane is polyester-polyurethane.

11. Expandable, particulate, blowing agent-containing thermoplastic polyurethanes according to claim 9, characterized in that the thermoplastic polyurethanes are polyether-polyurethane.

12. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to one of claims 9 to 11, characterized in that the thermoplastic polyurethane have a Shore hardness of A85 to A100.

13. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to one of claims 9 to 12, characterized in that the polymer chains are branched via Allo¬ phanate bridges.

14. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to one of claims 9 to 12, characterized in that the polymer chains are branched over polyfunctional alcohols.

15. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to one of claims 9 to 14, characterized in that they contain fillers.

16. Expandable, particulate, blowing agent-containing thermoplastic polyurethane according to claim 15, characterized gekenn¬ characterized in that they contain glass fibers.