WO2005019293A1 - Thermoplastic polyurethane containing silane groups - Google Patents

Abstract

The invention relates to a thermoplastic polyurethane containing organosilicon groups, said groups being bonded to the thermoplastic polyurethane by means of two urea groups. According to the invention, no allophanate groups or urethane groups lie between the urea group(s) and the silane groups.

Description

Thermoplastic polyurethane containing silane groups

description

The invention relates to thermoplastic polyurethane, in particular fibers, cable sheathing and hoses, in particular compressed air hoses based on thermoplastic polyurethane, containing silicon-organic groups. Furthermore, the invention relates to processes for the production of modified with organic silicon compounds, i.e. Thermoplastic polyurethane containing silicon-organic groups and crosslinkable TPU, in particular fibers, cable sheaths and hoses, in particular compressed air hoses, and the corresponding products crosslinked via the silicon-organic groups, in particular siloxane groups.

Thermoplastic plastics are plastics that, when repeatedly heated and cooled in the temperature range typical for the material for processing and application, remain thermoplastic. Thermoplastic is understood to mean the property of a plastic to repeatedly soften in the heat in a temperature range typical for it and to harden on cooling and in the softened state to be capable of being repeatedly formed by molding, extrudate or molded part into semi-finished products or objects. Thermoplastic materials are widely used in technology and can be found in the form of fibers, sheets, foils, moldings, bottles, jackets, packaging, etc. Thermoplastic polyurethane (hereinafter referred to as TPU) is an elastomer that is used in many applications , e.g. Shoe applications, foils, fibers, ski boots, tubes. The advantage that the TPU offers due to the possibility of thermoplastic processability, however, is at the same time a disadvantage of these materials in view of the lower heat resistance compared to crosslinked polymers. It would therefore be desirable to combine the advantages of thermoplastic processing with those of the excellent heat resistance of cross-linked polymers.

In US 2002/0169255 and in S. Dassin et al in Polymer Engineering and Science, August 2002, Vol. 42, No. 8 is taught with a view to this goal of modifying a thermoplastic polyurethane with a silane, the silane being coupled to the polyurethane by means of a crosslinker. By hydrolysis of the silane, crosslinking of the originally thermoplastic polyurethane is subsequently achieved, for example after shaping. A disadvantage of this technical teaching is that a number of individual steps are required to obtain the networked TPU. Starting from the thermoplastic polyurethane, two reactions are necessary, first with the cross-linked and then with the silane. According to US 2002/0169255 the use of the Crosslinking agent, which binds the silane to the TPU, is required, since a direct use of the silane should lead to a degradation of the TPU.

The object of the present invention was to develop thermoplastic polyurethane, in particular fibers based on thermoplastic polyurethane, containing silicon-organic groups, which are accessible via a simple, fast and inexpensive production process, have excellent crosslinking properties and, in particular, are used as fibers have a very good level of properties when networked.

The term “silane” used in this document is to be understood as meaning organic silane compounds. Accordingly, the term “modified with silane” is understood to mean that the corresponding substance is modified with an organic silicon compound.

These objects were achieved in that silicon-organic groups are connected to the thermoplastic polyurethane via two urea groups and that no allophanate groups or urethane groups are present between the urea group or the silane groups.

This means that the connection with which the silane is introduced into the TPU is built directly into the polyurethane. In contrast to the teaching according to US 2002/0169255, it is not connected to the TPU indirectly, via a cross-linker, but is present in the TPU structure itself.

Another object was to provide an improved, simpler, faster and more economical process for producing crosslinkable TPU, especially processes for producing silane-modified, i.e. To develop thermoplastic polyurethane having organic silicon groups.

This object could be achieved in that the production of the thermoplastic polyurethane uses organic silicon compounds which have one or two, preferably two amino groups, particularly preferably one or two secondary amino groups.

The method according to the invention is characterized in that the silane group can be introduced directly during the manufacturing process of the TPU. Complicated additional steps, such as the reaction of a finished TPU with isocyanates and the subsequent reaction of the isocyanate-modified TPU with silanes, as taught, for example, in US 2002/0169255, are not necessary. It was surprisingly found that the silane groups, which are integrated into the TPU during the manufacturing process, do not lead to cross-links in the further processing of the TPU before the actual shaping. This is surprising since the processing of the TPU, for example granulation under water, is optionally carried out in the presence of moisture, which can be followed by drying at elevated temperatures. These moist and warm conditions usually support the crosslinking reaction of the silanes, but this is only desired after the actual shaping, ie after extrusion, injection molding or spinning.

The crosslinkable thermoplastic polyurethane can preferably be prepared by reacting (a) isocyanates with (b) compounds which are reactive toward isocyanates and have a molecular weight between 500 and 10,000 and (c) chain extenders with a molecular weight of 50 to 499 and silane which preferably has two amino groups may have two secondary amino groups in the presence of (d) catalysts and / or (e) customary additives, the ratio of the sum of the isocyanate groups of component (a) to the sum of the isocyanate-reactive functions of components (b), (c ) and the amino groups of the silanes and optionally (d) and (e) is between 0.7: 1 and 1.3: 1. This preferred ratio thus describes the molar ratio of all isocyanate groups to the sum of all functions reactive towards isocants, i.e. reactive hydrogen atoms. This ratio is usually also referred to as a key figure, a ratio of 1: 1 corresponding to a key figure of 100. If the index is 100, an isocyanate group of component (a) has an active hydrogen atom, i.e. a function reactive towards isocyanates. With key figures above 100, there are more isocyanate groups than, for example, OH groups.

According to the invention, the silanes can thus already be incorporated during the TPU production process.

In this document, the term “organosilicon compounds” or “silanes” or “organosilicon groups” or “silane groups” refers to compounds, in particular generally known alkoxysilanes, for example di- or tri-methoxy and / or ethoxysilanes , understood, which preferably contain the following general structural unit: -Si (R) _3-x (OR) _x

with the following meaning for R and x:

R: alkyl radical or aryl radical, which can optionally be heteroatom-substituted, preferably alkyl radical with 1 to 10, preferably 1 to 6 carbon atoms, preferably methyl and / or ethyl, x: 1, 2 or 3, preferably 2 or 3, particularly preferably 3,

wherein the three alkyl radicals marked with R in the silane can be identical or different from one another, are preferably the same.

If the TPU is already prepared in the presence of the silane, the molar ratio of the polyols and chain extenders (b) and (c) to the silanes is preferably between 1: 0.01 and 1: 0.5.

Thermoplastic polyurethane means that it is preferably a thermoplastic elastomer based on polyurethane. A thermoplastic elastomer is an elastomer that, when repeatedly heated and cooled in the temperature range typical of the material for processing and application, remains thermoplastic. Thermoplastic is understood to mean the property of a plastic to repeatedly soften in the heat in a temperature range typical for it and to harden on cooling and in the softened state to be capable of being repeatedly formed by molding, extrudate or molded part into semi-finished products or objects.

Particularly suitable thermoplastic polyurethane are TPUs that have a Shore hardness of 50 A to 80 D. Also preferred are TPUs which have one, more or preferably all of the following properties:

TPUs with

- a modulus of elasticity from 10 MPa to 10,000 MPa measured according to DIN EN ISO 527-2 on a sample body of type A according to DIN EN ISO 3167 at a test speed of 1 mm / min. The modulus of elasticity is calculated from the initial slope of the stress-strain curve as a ratio of stress and strain. ■ a glass transition temperature T _g measured by DSC (at 10K / min) less than minus 10 ° C for types up to a maximum of 64 Shore D types up to less than minus 40 ° C for types minimum 85 Shore A types.

^■ an impact strength according to Charpy according to DIN 53453 (DIN EN ISO 179) down to minus 60 ° C without break and a notched impact strength less than minus 40 ° C for types smaller than 95 Shore A types and less than minus 20 ° C for types up to a maximum of 60 Shore D types.

■ a density according to DIN 53479 or ISO 1183 between 1.05 and 1.30 g / cm ³ ■ a tensile strength greater than 40 MPa measured according to DIN 53504 or ISO 37 for non-plasticized TPU types

A tear resistance measured according to DIN 53515 or ISO 34 greater than 65 MPa for (non-plasticized) types less than 95 Shore A types and greater than 100 MPa for types greater than 50 Shore D.

■ an abrasion of less than 40 mm ³ measured according to DIN 53516 or ISO 4649

■ a compression set at 70 ° C measured according to DIN 53517 or ISO 815 between 30 and 70%.

The TPU exhibits these preferred properties in the uncrosslinked state, i.e. without cross-linking via the silane groups.

Processes for the production of thermoplastic polyurethanes, also referred to in this document as TPU, are generally known. In general, TPUs are reacted by reacting (a) isocyanates with (b) isocyanate-reactive compounds, usually with a molecular weight (M _w ) of 500 to 10,000, preferably 500 to 5000, particularly preferably 800 to 3000 and (c) chain extenders with a molecular weight of 50 to 499 optionally in the presence of (d) catalysts and / or (e) customary additives. As already mentioned at the beginning, the silanes are preferably additionally used according to the invention.

The starting components and processes for the production of the preferred polyurethanes are to be described below by way of example. The components (a), (b), (c) and, if appropriate, (d) and / or (e) which are normally used in the production of the polyurethanes are to be described by way of example below:

a) Generally known aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates can be used as organic isocyanates (a), for example tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2- Methyl-pentamethylene-diisocyanate-1, 5, 2-ethyl-butylene-diisocyanate-1,4, pentamethylene-diisocyanate-1, 5, butylene-diisocyanate-1, 4, 1-isocyanato-3,3,5-trimethyl- 5-isocyanato-methyl-cyclohexane (isophorone diisocyanate, IPDI), 1, 4- and / or 1, 3-bis (isocyanatomethyl) cyclohexane (HXDI), 1, 4-cyclohexane diisocyanate, 1-methyl-2,4 - and / or -2,6-cyclohexane-di-isocyanate and / or 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate, 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI), 1, 5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyl-diphenyl diisocyanate, 1, 2-diphenylethane diisocyanate and / or phenylene diisocyanate. 4,4 ^: -MDI is preferably used. b) The compounds (b) which are reactive toward isocyanates can be the generally known compounds which are reactive toward isocyanates, for example polyesterols, polyetherols and / or polycarbonate diols, which are usually also summarized under the term "polyols", with molecular weights between 500 and 8000 , preferably 600 to 6000, in particular 800 to less than 3000, and preferably an average functionality over isocyanates of 1.8 to 2.3, preferably 1.9 to 2.2, in particular 2. Polyether polyols are preferably used, for example those the basis of generally known starter substances and customary alkylene oxides, for example ethylene oxide, propylene oxide and / or butylene oxide, preferably polyetherols based on propylene oxide-1, 2 and ethylene oxide and in particular polyoxytetramethylene glycols. The polyetherols have the advantage that they have a higher hydrolysis stability than polyesterols. So-called low-unsaturated polyetherols can also be used as polyetherols. In the context of this invention, low-unsaturated polyols are understood in particular to mean polyether alcohols with an unsaturated compound content of less than 0.02 meg / g, preferably less than 0.01 meg / g.

Such polyether alcohols are usually produced by addition of alkylene oxides, in particular ethylene oxide, propylene oxide and mixtures thereof, onto the diols or triols described above in the presence of highly active catalysts. Such highly active catalysts are, for example, cesium hydroxide and multimetal cyanide catalysts, also referred to as DMC catalysts. A frequently used DMC catalyst is zinc hexacyanocobaltate. After the reaction, the DMC catalyst can be left in the polyether alcohol; it is usually removed, for example by sedimentation or filtration.

Furthermore, polybutadiene diols with a molar mass of 500-10000 g / mol, preferably 000-5000 g / mol, in particular 2000-3000 g / mol can be used. TPUs which have been produced using these polyols can be crosslinked by radiation after thermoplastic processing. This leads e.g. for better burning behavior.

Instead of a polyol, mixtures of different polyols can also be used.

c) The chain extenders (c) used are generally known aliphatic, aromatic lipatic, aromatic and / or cycloaliphatic compounds with a molecular weight of 50 to 499, preferably 2-functional compounds, for example diamines and / or alkanediols with 2 to 10 C atoms in the alkylene radical, in particular 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and / or Di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- and / or decaalkylene glycols with 3 to 8 carbon atoms, preferably corresponding oligo- and / or polypropylene glycols, whereby also mixtures of Chain extenders can be used.

Components a) to c) are particularly preferably difunctional

Connections, i.e. Diisocyanates (a), difunctional polyols, preferably polyetherols (b) and difunctional chain extenders, preferably diols.

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 tertiary amines known and customary in the prior art, such as e.g. Triethylamine, dimethylcyclohexylamine, N-methylimorpholine, N, N'-dimethylpiperazine, 2- (dimethylaminoethoxy) ethanol, diazabicyclo (2,2,2) octane and the like, and in particular organic metal compounds such as titanium acid esters, iron compounds such as e.g. Iron (III) acetylacetonate, 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 the like. The catalysts are usually used in amounts of 0.0001 to 0.1 part by weight per 100 parts by weight of polyhydroxy compound (b).

e) In addition to catalysts (d), customary auxiliaries and / or additives (e) can also be added to the structural components (a) to (c). Examples include blowing agents, surface-active substances, fillers, nucleating agents, lubricants and mold release agents, dyes and pigments, antioxidants, for example against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, flame retardants, reinforcing agents and plasticizers, metal deactivators. In a preferred embodiment, component (e) also includes hydrolysis stabilizers such as, for example, polymeric and low-molecular carbodiimides. The thermoplastic polyurethane particularly preferably contains melamine cyanurate in the materials according to the invention, which acts as a flame retardant. Melamine cyanurate is preferably used in an amount between 0.1 and 60% by weight, particularly preferably between 5 and 40% by weight, in particular between 15 and 25% by weight, in each case based on the total weight of the TPU. The thermoplastic polyurethane preferably contains triazole and / or triazole derivative and antioxidants in an amount of 0.1 to 5% by weight, based on the total weight of the thermoplastic polyurethane. Substances which inhibit or prevent undesired oxidative processes in the plastic to be protected are generally suitable as antioxidants. In general, antioxidants are commercially available. Examples of antioxidants tien are hindered phenols, aromatic amines, thiosynergists, organophosphorus compounds of trivalent phosphorus, and hindered amine light stabilizers. Examples of sterically hindered phenols can be found in Plastics Additive Handbook, 5th edition, H. Doubt, ed, Hanser Publishers, Munich, 2001 ([1]), _ p. 98-107 and pp. 116 - p. 121. Examples of aromatic amines can be found in [1] pp. 107-108. Examples of thiosynergists are given in [1], pp.104-105 and pp.112-113. Examples of phosphites can be found in [1], pp.109-112. Examples of hindered amine light stabilizers are given in [1], pp.123-136. Phenolic antioxidants are preferably suitable for use in the antioxidant mixture according to the invention. In a preferred embodiment, the antioxidants, in particular the phenolic antioxidants, have a molar mass of greater than 350 g / mol, particularly preferably of greater than 700 g / mol and a maximum molar mass of <10,000 g / mol, preferably <3000 g / mol. Furthermore, they preferably have a melting point of less than 180DC. Antioxidants which are amorphous or liquid are also preferably used. Mixtures of two or more antioxidants can also be used as component (i).

In addition to components a), b) and c) and, if appropriate, d) and e), chain regulators, usually with a molecular weight of 31 to 3000, can also be used. Such chain regulators are compounds that have only one isocyanate-reactive functional group, such as. B. monofunctional alcohols, monofunctional amines and / or monofunctional polyols. With such chain regulators, a flow behavior, in particular with TPUs, can be specifically set. Chain regulators can generally be used in an amount of 0 to 5, preferably 0.1 to 1 part by weight, based on 100 parts by weight of component b), and by definition fall under component (c).

All molecular weights mentioned in this document have the unit [g / mol].

To adjust the hardness of the TPUs, the build-up components (b) and (c) can be varied in relatively wide molar ratios. Molar ratios of component (b) to chain extenders (c) to be used in total from 10: 1 to 1:10, in particular from 1: 1 to 1: 4, have proven successful, the hardness of the TPU increasing with increasing content of (c).

The TPU can be produced continuously using the known processes, for example using reaction extruders or the belt process using one-shot or the prepolymer process, or batchwise using the known prepolymer process. In these processes, the components (a), (b), (c) and optionally (d) and / or (e) are mixed in succession or simultaneously with one another, the reaction commencing immediately. In the extruder process, the build-up components (a), (b), (c) and optionally (d) and / or (e) are introduced into the extruder individually or as a mixture, for example at temperatures from 100 to 280 ° C., preferably 140 to 250 ° C, and reacted. The TPU obtained is usually extruded, cooled and granulated. After the synthesis, the TPU can optionally be modified by assembly on an extruder. With this assembly, the TPU can be modified, for example, in terms of its melt index or its granulate shape in accordance with the requirements.

The processing of the TPUs produced according to the invention, which are usually in the form of granules or in powder form, into injection molding and extrusion articles, e.g. The desired foils, molded parts, rolls, fibers, cladding in automobiles, hoses, cable plugs, bellows, trailing cables, cable sheathing, seals, belts or damping elements are made using standard methods, such as Injection molding or extrusion. Such injection molding and extrusion articles can also be made from compounds containing the TPU according to the invention and at least one further thermoplastic, in particular a polyethylene, polypropylene, polyester, polyether, polystyrene, PVC, ABS, ASA, SAN, polyacrylonitrile, EVA, PBT, PET, polyoxy- methylene. In particular, the TPU produced according to the invention can be used to produce the articles shown at the beginning.

Preferably, the silane-modified thermoplastic polyurethane will be spun into fibers according to generally known processes and then the thermoplastic polyurethane will be crosslinked via the silane groups by means of moisture, optionally using a catalyst which accelerates the crosslinking. The crosslinking reactions above and through the silane groups are familiar to the person skilled in the art and are generally known. This crosslinking is usually carried out by moisture and can be carried out by heat or catalysts known for this purpose, e.g. Lewis acids, Lewis bases, Bronsted bases, Bronsted acids are accelerated. Acetic acid, organic metal compounds such as titanium acid esters, iron compounds such as e.g. Iron oil) acetylacetonate, 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 the like.

The product crosslinked via the silane groups preferably has the following properties: Vicat temperature (Vicat softening temperature, VST) according to DIN EN ISO 306 (10N / 120 K / h) greater than 145 ° C.

An important measure for the quality of an elastomer fiber is the heat resistance.

It has surprisingly been found that the heat resistance of the melt-spun fiber which has been crosslinked via silane groups has been significantly improved. For example, a fiber without silane crosslinking according to the invention shows an HDT (heat distortion temperature, measurement under a pretension of 0.04 mN / dtex; heating rate 10K / min; measuring range from -100 ° C. to 250 ° C.) of 120 ° C. The crosslinking by the silane groups increased the HDT to 173 ° C.

Another advantage of the crosslinking of melt-spun elastomer fibers according to the invention is the improved resistance to conventional spinning preparations. While melt-spun fibers without crosslinking according to the invention in contact with spin finishes are attacked even at low temperatures (<120 ° C.) and in some cases completely destroyed, crosslinked fibers according to the invention show almost no damage even at temperatures above 190 ° C.

The thermoplastically processable polyurethane elastomers according to the invention can be used for extrusion, injection molding, calendar articles and for powder slush processes.

comparison sample

900 g of a linear polytetrahydrofuran diol with an OH number of 113.6 mg KOH / g were reacted at 95 ° C. with 187 g 1,4-butanediol, 4 and 747 g of 4,4′-diphenylmethane diisocyanate heated to 50 ° C. with constant stirring , The NCO / OH ratio of the reactants is 1.0: 1.0. When the reaction mixture reached a temperature of 110 ° C, it was poured onto a hot table. The solidified elastomer material was then crushed after an intermediate storage period of 12 hours at 80 ° C. and processed into test specimens by means of injection molding. These test specimens were stored at 80 ° C. for 48 hours with the addition of catalytic amounts of acetic acid and were then soluble in dimethylformamide.

example

882 g of a linear polytetrahydrofuran diol with an OH number of 113.6 mg KOH / g were at 95 ° C. with 181 g butanediol-1,4,18 g N- (beta-aminoethyl) -gamma-aminopropyl trimethoxysilanes and 747 g of 4,4'-diphenylmethane diisocyanate heated to 50 ° C. are reacted with constant stirring. The NCO / OH ratio of the reactants was 1.0: 1.0. When the reaction mixture reached a temperature of 110 ° C, it was poured onto a hot table. The solidified elastomer material was then crushed after an intermediate storage period of 12 hours at 80 ° C and processed into test specimens by means of injection molding. These test specimens were stored at 80 ° C. in water with the addition of catalytic amounts of acetic acid and were then insoluble in dimethyiformamide.

Characteristic values of both materials are compared in the following table.

Claims

claims 1. Thermoplastic polyurethane containing silicon-organic groups, characterized in that silicon-organic groups are connected to the thermoplastic polyurethane via two urea groups and that there are no allophanate groups or urethane groups between the urea group or groups and the silane groups. 2. A process for the preparation of thermoplastic polyurethane modified with organic silicon compounds, characterized in that organic organic compounds (“silane”) which have two amino groups are used in the production of the thermoplastic polyurethane. 3. The method according to claim 2, characterized in that the thermoplastic polyurethane is prepared by reacting (a) isocyanates with (b) isocyanate-reactive compounds with a molecular weight between 500 and 10,000 and (c) chain extenders with a molecular weight of 50 to 499 and silane which has one or two secondary amino groups, the ratio of the sum of the isocyanate groups of component (a) to the sum of the isocyanate-reactive functions of components (b), (c) and the secondary amino groups of the silanes being between 0, 7: 1 and 1.3: 1. 4. The method according to claim 2, characterized in that the thermoplastic polyurethane modified with organic silicon compounds is spun into fibers and then the thermoplastic polyurethane is crosslinked via the silane groups by means of moisture. 5. The method according to claim 4, characterized in that Lewis acid, Lewis bases, Bronsted bases, Bronsted acids are used as the catalyst for the cross-linking with moisture. 6. Thermoplastic polyurethane obtainable by a process according to one of claims 2 to 5. 7. fiber based on thermoplastic polyurethane obtainable according to one of claims 2 to 5. 8. Cable sheaths based on thermoplastic polyurethane obtained loan according to one of claims 2 to 5. Use of the thermoplastically processable polyurethane elastomers obtainable by a process according to one of claims 2 to 5 for extrusion, injection molding, calendar articles and for powder slush processes.