DE10160375B4 - Polyurethanes and their use as exterior body parts - Google Patents

Abstract

Process for the production of polyurethanes by reacting a polyol component (A) with a polyisocyanate prepolymer (B), the polyol component (A1) polyetherols with an OH number of 10 to 100, (A2) crosslinking polyetherols with an OH number of 500 to 1000 and (A3) contains chain extenders based on amines and the polyisocyanate prepolymer (B) is produced by reacting (B1) a polyisocyanate with (B2) poly-THF.

Description

The invention relates to a process for the preparation of polyurethanes by reacting a polyol component (A) with a polyisocyanate prepolymer (B), wherein the polyol component contains a long-chain polyol (A1), a crosslinking polyol (A2) and a chain extender based on amines (A3) and the polyisocyanate prepolymer (B) is prepared by reacting a polyisocyanate (B1) with poly-THF (B2), and the use of the polyurethanes produced by this process as exterior body parts.

Components made of polyurethane (hereinafter referred to as PUR) are versatile materials and are used, inter alia, as exterior body parts, since they have, for example, a lower weight compared to conventional metal components. At these components, however, high demands are made, for example, in terms of stiffness, heat resistance, ease of processing and the optical surface finish. In particular, molded parts are desirable, which can be advantageously subjected to an online coating.

WO 00/50484 describes a polyurethane system based on a Polyisocyanatprepolymers and a polyol component containing an adduct based on butylene oxide, for the production of exterior body parts, which should occur as little as possible surface defects by the system according to the invention. The disclosed in this document polyurethane systems can be processed by the high-speed RIM process into moldings.

EP 601 383 describes integral polyurethane foams prepared from MDI prepolymer, polyether polyols having a functionality of at least 1.5, chain extenders, a linear alcohol having from 10 to 20 carbon atoms, water and catalysts wherein the MDI prepolymer is prepared by reacting the diisocyanate with polytetrahydrofuran. The polyurethanes can be used for auto parts, including for body parts.

The object of the present invention was to provide polyurethanes, in particular polyurethane molded parts, which have both an on-line paintable surface and good mechanical properties, such as high heat resistance, high modulus of elasticity and high rigidity.

Furthermore, polyurethanes are to be provided which enable a process-friendly process, for example with regard to long shot times.

Furthermore, it was an object of the present invention to provide a polyurethane system with the advantages mentioned above, which is also inexpensive to produce.

The objects of the present invention have been unexpectedly solved by a polyurethane prepared by reacting a balanced combination of long chain polyetherols (soft segments), crosslinker polyols, and amine-based chain extenders with suitable polyisocyanate prepolymers.

• (A1) Polyetherole mit einer OH-Zahl von 10 bis 100,
• (A2) Vernetzerpolyetherole mit einer OH-Zahl von 500 bis 1000 und
• (A3) Kettenverlängerungsmittel auf Basis von Aminen enthält und das Polyisocyanatprepolymer (B) hergestellt ist durch Umsetzung
• (B1) eines Polyisocyanats mit
• (B2) Poly-THF.

The invention therefore provides a process for the preparation of polyurethanes by reacting a polyol component (A) with a polyisocyanate prepolymer (B), wherein the polyol component

• (A1) polyetherols having an OH number of from 10 to 100,
• (A2) Vernetzerpolyetherole having an OH number of 500 to 1000 and
• (A3) Amine-based chain extender and the polyisocyanate prepolymer (B) is prepared by reaction
• (B1) a polyisocyanate with
• (B2) polyTHF.

The invention furthermore relates to polyurethanes obtainable by the processes described above and exterior body parts comprising the polyurethanes according to the invention.

The invention further relates to the use of the polyurethanes according to the invention for the production of exterior body parts and exterior body parts, containing the polyurethanes according to the invention.

The term "polyurethane" in the context of this invention comprises compounds obtainable by reaction of isocyanates with alcohols and / or amines, including polyureas.

The preparation of the polyisocyanate prepolymer used as components (B) is carried out in a manner known per se by reacting the polyisocyanate (B1), preferably at temperatures of about 80 ° C., with the polyTHF (B2) to form the polyisocyanate prepolymer. To exclude side reactions by atmospheric oxygen, the reaction vessel should be purged with an inert gas, preferably nitrogen.

The polyol-polyisocyanate ratio is chosen so that the NCO content of the prepolymer 10 to 25 wt .-%, preferably 15 to 23 wt .-%, is.

The component (B2) is preferably made of poly-THF. In a further embodiment it is possible that the component (B2) still contains proportions of conventional polyols, such as polyether polyols, or chain extenders, such as ethylene glycol, diethylene glycol or 1,4-butanediol. If the component (B2) in addition to poly-THF contains other ingredients, the proportion of poly-THF is at least 80 wt .-%, preferably at least 90 wt .-%, more preferably at least 95 wt .-%, based on the total weight the component (B2).

The poly-THF used in component (B2) generally has a number-average molecular weight of 500 to 10,000 g / mol, preferably from 1000 to 5000 g / mol, particularly preferably from 1500 to 3000 g / mol.

The polyisocyanates (B1) used to prepare the isocyanate prepolymers include the aliphatic, cycloaliphatic and aromatic isocyanates known in the art and any mixtures thereof. Examples are 4,4'-diphenylmethane diisocyanate containing mixtures of monomeric diphenylmethane diisocyanates and higher nuclear homologs of diphenylmethane diisocyanate (polymer-MDI), tetramethylene-diisocyanate, tetramethylene-diisocyanate-trimers, hexamethylene-diisocyanate, hexamethylene-diisocyanate-trimers, isophorone-diisocyanate-trimer, 4,4'-methylenebis (cyclohexyl) diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, and polyisocyanates having NCO groups of different reactivity, such as 2,4-tolylene diisocyanate (2,4-TDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), isophorone diisocyanate (IPDI), and 2,4'-methylenebis (cyclohexyl) diisocyanate.

As polyisocyanates, there are preferably used 4,4'-diphenylmethane diisocyanate, 1,3- and 1,4-phenylenediisocyanate, tolylene diisocyanate, isophorone diisocyanate (IPDI) and naphthylene diisocyanate (NDI). 4,4'-MDI is particularly preferably used.

In a preferred embodiment, the polyisocyanates used may contain proportions of up to about 20% by weight of carbodiimide, allophanate or uretonimine modified polyisocyanates. The polyisocyanates (B1) preferably contain carbodiimide and / or uretonimine groups.

In a particularly preferred embodiment, component (B1) used is 4,4'-MDI which contains 1 to 15% by weight, preferably 5 to 12% by weight, of carbodiimide groups and / or uretonimine groups.

It is also possible to use small amounts of polyphenylenepolymethylene polyisocyanate (crude MDI). The total amount of these high-functionality polyisocyanates should not exceed 5% by weight of the isocyanate used in order to avoid undesired crosslinking and thus a deterioration in the mechanical properties of the resulting foams.

• (A1) mindestens einem Polyetherol mit einer OH-Zahl von 10 bis 100, bevorzugt von 20 bis 80,
• (A2) mindestens einem Vernetzerpolyetherol mit einer OH-Zahl von 500 bis 1500, bevorzugt von 700 bis 1200, besonders bevorzugt von 800 bis 1000 und
• (A3) mindestens einem Kettenverlängerungsmittel auf Basis von Aminen.

For certain applications, it may be useful to use mixtures of 4,4'-MDI and other aromatic diisocyanates, such as 2,4- or 2,4'-diisocyanatodiphenylmethane. However, the proportion of these diisocyanates should not exceed 10% by weight. The polyol component (A component) used in the process according to the invention is generally composed of

• (A1) at least one polyetherol having an OH number of from 10 to 100, preferably from 20 to 80,
• (A2) at least one Vernetzerpolyetherol having an OH number of 500 to 1500, preferably from 700 to 1200, particularly preferably from 800 to 1000 and
• (A3) at least one chain extender based on amines.

As component (A1), polyether polyols are used in the context of this invention. They are generally prepared by known processes, for example by anionic polymerization with alkali metal hydroxides or alkali metal alkoxides as catalysts and with the addition of at least one starter molecule containing 2 to 3 reactive hydrogen atoms bound, or by cationic polymerization with Lewis acids such as antimony pentachloride or borofluoride etherate one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical.

Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately in succession or as mixtures. Preference is given to mixtures of 1,2-propylene oxide and ethylene oxide, the ethylene oxide being used in amounts of 10 to 50% as endblock of ethylene oxide ("EO-cap"), so that the resulting polyols have more than 70% primary OH end groups ,

The polyether polyols (A1) generally have a nominal functionality of from 1.8 to 8, preferably from 2 to 5, more preferably from 2 to 4. In addition, they generally have a number average molecular weight of from 500 to 10,000, preferably from 1,000 to 8,000 , more preferably from 2,000 to 6,000.

Preferred starter molecules are water or dihydric to trihydric alcohols, such as ethylene glycol, 1,2-propanediol and 1,3-diol, diethylene glycol, dipropylene glycol, 1,4-butanediol, glycerol and Trimethylolpropane or 2- to 4-valent amines, such as ethylenediamine, into consideration.

As component (A2), crosslinker polyether polyols are used in the context of this invention. They can generally be prepared by the method described for component (A1). Crosslinker polyetherol is to be understood as meaning that component (A2) has a nominal functionality of greater than 2, preferably of at least 3, particularly preferably of 3 to 6.

The component (A3) used in this invention contains chain extenders based on amines. These are understood as meaning polyhydric amines or amino alcohols having molecular weights of less than 499 g / mol, preferably from 60 to 300 g / mol, particularly preferably from 60 to 200 g / mol. Suitable examples are ethylenediamine, N, N-dimethethylenediamine, toluenediamine, isophoronediamine, cysteamine, ethanolamine, N-methylethanolamine, propanolamine, isopropanolamine, 2- (butylamino) ethanol, 2- (cyclohexylamino) ethanol, 2-amino-1-butanol and Mixtures thereof.

Particularly preferred component (A3) Diethyltolyldiamin (DETDA), optionally in admixture with the above-mentioned chain extenders used.

In general, the polyol component (A) contains 10 to 70 wt .-%, preferably 15 to 50, particularly preferably 20 to 45 wt .-% of the polyetherol (A1), based on the total weight of the components (A1) to (A3).

In general, the polyol component (A) contains 1 to 40 wt .-% of the crosslinking polyol (A2), preferably 2 to 25 wt .-%, particularly preferably 5 to 20 wt .-%, based on the total weight of components (A1) to (A3).

In general, the polyol component (A) contains from 20 to 80% by weight, preferably from 25 to 60% by weight, particularly preferably from 30 to 55% by weight, of the chain extender based on amines (A3), based on the total weight of the components (A1) to (A3).

• A4) Polyetherol mit Aminendgruppen
• A5) Katalysatoren,
• A6) Treibmittel
• A7) Verstärkungsstoffe und
• A8) Zusatzstoffe

zugegeben werden.In a preferred embodiment, the reaction of the polyol component with the Polyisocyanatprepolymeren still one or more of the components

• A4) amine-terminated polyetherol
• A5) catalysts,
• A6) blowing agent
• A7) reinforcing materials and
• A8) additives

be added.

The components A4 to A5 may be added to the A or B component or separately. Preferably, they are added to the A component.

As component A4), polyetherols are used which have been prepared by a process as described above for component (A1), but these polyetherols have a primary or secondary amine end group by addition of a suitable amine for the polymerization reaction. Examples of preferably used components (A4) are those marketed by Huntsman Jeffamine ^®.

The component (A4) is usually used in an amount of 1 to 40, preferably 5 to 30 wt .-%, based on the total weight of the components (A1) to (A4).

As catalysts (A5) for the preparation of the polyurethanes, in particular compounds are used which greatly accelerate the reaction of the hydroxyl-containing compounds of components (A1) to (A4) with the polyisocyanate groups.

Tin (II) compounds such as tin diacetate or tin dioctoate or dialkyltin IV salts such as dibutyltin dilaurate etc. may be used, for example. The metal compounds are usually used in combination with strongly basic amines. Examples which may be mentioned are triethylamine, pentamethyldiethylenetriamine, tetramethyl-diaminoethyl ether, 1,2-dimethylimidazole or preferably triethylenediamine (Dabco).

As blowing agent (A6), generally known chemically or physically active compounds can be used for the production of foamed products. As the chemically acting blowing agent, water can preferably be used. Examples of physical blowing agents are inert (cyclo) aliphatic hydrocarbons having 4 to 8 carbon atoms which evaporate under the conditions of polyurethane formation. The amount of blowing agent used depends on the desired density of the foams. With particular preference, only water is used as blowing agent.

The reinforcing materials (A7) used may be fibers such as glass fibers, mineral fibers, natural fibers such as flax, jute or sisal, and / or synthetic fibers such as polyamide fibers, polyester fiber, carbon fibers or polyurethane fibers. It may also be particulate reinforcing agents such as mica, silica, quartz, bentonites, talc, Calcium carbonate, chalk, feldspar, wollastonite, kaolin or mica act. Likewise, mixtures of these are possible. Preferably wollastonite is used as the filler material.

The component (A7) is usually used in an amount of 0.1 to 90 wt .-%, preferably from 1 to 50, more preferably from 5 to 40 and particularly preferably from 10 to 30 wt .-%, based on the total weight of Components (A1) to (A8) used.

If appropriate, additives (A8) can also be incorporated into the reaction mixture for the production of the shaped bodies. Mention may be made, for example, of surface-active substances, foam stabilizers, cell regulators, external and internal release agents, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances.

To prepare the polyurethanes according to the invention, in particular polyurethane moldings according to the invention, the A and B components are reacted in amounts such that the equivalence ratio of NCO groups of the B component to the sum of the reactive hydrogen atoms of the A component is 1: 0, 8 to 1: 1.25, preferably 1: 0.9 to 11.15 amounts. A ratio of 1: 1 corresponds to an NCO index of 100.

Because of the low NCO content of the polyisocyanate prepolymers, the weight ratio of component (B) to component (A) is usually greater than 1.

The moldings are generally produced by the one-shot process with the aid of high-pressure technology in closed, suitably tempered molds. The molds are usually made of metal, for. As aluminum or steel. These procedures are described for example by Piechota and Röhr in "Integralschaumstoff", Carl Hanser Verlag, Munich, Vienna, 1975, or in the Plastics Handbook, Volume 7, Polyurethane, 2nd edition, 1983, pages 333ff.

The starting components are usually mixed at a temperature of 15 to 90 ° C, preferably 35-65 ° C and optionally introduced under elevated pressure in the closed mold. The mixing can be carried out mechanically by means of a stirrer or a stirring screw or under high pressure in the so-called countercurrent injection method. The mold temperature is suitably 20 to 90 ° C, preferably 40-80 ° C.

If appropriate, the polyurethanes according to the invention can also be prepared in a mold in which a film, for example a thermoplastic film or a metal film, has already been laid, so that the process according to the invention obtains composite elements composed of a film and a layer of the polyurethane according to the invention become.

It is an advantage of the present invention that the process according to the invention, preferably in the case of processing by the RIM process, in particular by the high-speed RIM process, is very easy to process. For example, they have an advantageously long shot time, d. H. the time during which the system components can be homogeneously introduced into the mold is guaranteed.

In general, in the method according to the invention the shot times are up to 2 seconds, preferably from 0.8 to 1.5 seconds. Conventional, known from the prior art systems, such as Bayflex ^® 190 or HH Spectrim ^® 390 and 400 typically have a shot time of less than 0.8 seconds.

Another advantage of the polyurethanes of the invention is their high heat resistance (HDT / B). The polyurethanes according to the invention generally have a heat resistance of 160 ° C, if fibers were used as reinforcing materials of usually 160 ° C parallel to the fiber and 140 ° C across the fiber. After annealing at 180 ° C for 30 minutes, a HDT / B value of 180/167 (paralle1 / cross) can be achieved.

Due to the high heat resistance, under certain conditions (component geometry and design), the annealing process can be saved in the case of offline painting, which is usually indispensable for the existence of, for example, climate change tests.

Furthermore, it is an advantage of the polyurethanes according to the invention that unexpectedly good mechanical properties are obtained. Thus, a tenacity of 10 to 80% can be achieved. Also, a bending modulus of preferably more than 2000 MPa, especially more than 2600 MPa is achieved.

The polyurethanes according to the invention can be used for the production of exterior body parts. In particular, they are for front and rear aprons and preferably for side skirts and fenders, but also door leaves or other large-scale exterior parts, such as roof modules, hoods and boot lid suitable.

The invention will be clarified by the following example:

example

The following A and B components were introduced into a mold and reacted by the known RIM method at an NCO index of 100. The shot time was 2 seconds and the demolding time 30 seconds. The mechanical properties of the resulting molded article were examined. All parts are by weight.

A component

• A1) 40 parts of polyetherol (OHZ 50, functionality 3)
• A2) 10 parts crosslinker polyol (OHZ 800, functionality 4)
• A3) 40 parts DEDTA
• A5) 3 parts catalyst (DABCO)
• A7) 20 parts wollastonite
• A8) 7 parts Zn-stearate based internal release agent

Component B

Polyisocyanate prepolymer with NCO content of 22%, obtained by reacting carbodiimisierten 4,4'-MDI with poly-THF 1500.

Mechanical properties:

• Bending modulus of elasticity: 2800 MPa
• Elongation: 60%
• HDT / B unannealed: 160/140 ° C (longitudinal / transverse to the fiber)
• HDT / B after 30 min. Annealing at 180 ° C: 180/165 ° C (longitudinal / transverse to the fiber).

Claims (7)

Process for the preparation of polyurethanes by reacting a polyol component (A) with a polyisocyanate prepolymer (B), wherein the polyol component (A1) polyetherols having an OH number of from 10 to 100, (A2) crosslinker polyetherols having an OH number of 500 to 1000 and (A3) Amine-based chain extender and the polyisocyanate prepolymer (B) is prepared by reaction (B1) a polyisocyanate with (B2) polyTHF. Process according to claim 1, characterized in that the polyisocyanate (B1) contains carbodiimide groups and / or uretonimine groups. Process according to claim 1 or 2, characterized in that the polyol component comprises 10 to 70% by weight of the polyetherol (A1), 1 to 40% by weight of the crosslinking polyol (A2) and 20 to 80% by weight of the chain extender based on of amines (A3) based on the total weight of components (A1) to (A3). Method according to one of claims 1 to 3, characterized in that the reaction additionally one or more of the components A4) amine-terminated polyetherol A5) catalysts, A6) blowing agent A7) reinforcing materials and A8) additives be added. Method according to one of claims 1 to 4, characterized in that the polyisocyanate (B1) comprises carbodiimide-containing 4,4'-MDI. Polyurethanes, obtainable by a process according to one of claims 1 to 4. Use of the polyurethanes according to claim 5 for the production of exterior body parts.