DE10248877A1 - A process for preparation of integral foams based on polyisocyanate-polyaddition products with a propellant containing microhollow spheres useful for electronic equipment housings and coatings, automobile headrests and armrests - Google Patents

Abstract

A process for preparation of integral foams based on polyisocyanate-polyaddition products by reaction of (a) isocyates with (b) compounds reactive to isocyanates in the presence of (c) a propellant and optionally (d) catalysts and/or (e) adjuvants, where the propellant is 1-8 wt.% expandable, is filled with microhollow spheres and contains 0.1-0.3 wt.% water relative to the sum of the weights of b, c, and d is new. Independent claims are included for: (1) an integral foam based on polyisocyanate-polyaddition products obtainable as above; (2) housings and coatings for electronic equipment, skis, tubing rings, light connections, roof openings and dormer windows, cable sheaths, switch knobs, headrests, armrests, and beer barrel casings, (3) a process for preparation of automobile wheels and spoilers, and or shoe soles.

Description

The invention relates to methods for the production of integral foams, preferably soft, semi-hard or hard integral foams, particularly preferred soft integral foams based on polyisocyanate polyaddition products by reacting (a) isocyanates with (b) against isocyanates reactive compounds in the presence of (c) blowing agents and optionally (d) catalysts and / or (e) auxiliary substances. Furthermore concerns the invention integral foams, for example soft, semi-hard or hard integral foams, particularly preferably soft integral foams based on polyisocyanate polyadducts, preferred Automobile steering wheels, Spoilers and / or shoe soles, in particular automobile steering wheels available through the inventive method.

Integral foams based of polyisocyanate polyaddition products, for example polyurethanes is well known and diverse described. These integral foams have a cellular, foamed core and a compact skin.

US 5,260,343 describes the use of expandable, hydrocarbon-filled hollow microspheres in combination with water as a co-blowing agent for the production of flexible polyurethane integral foams. 0.5 percent by weight of water (based on polyol component) is used in each case.

The amount of expandable hollow microspheres can be between 1.5 and 15, preferably between 2.5 and 5.0 percent by weight can be varied. The thickness of the skin is so high low in water as a blowing agent.

WO 95/08590 describes the use of expandable, hollow hydrocarbons filled with hydrocarbons for the production of microcellular Structures that have an outer skin without cells. Here you can combinations of the aforementioned Expancel types can also be used. The use of co-blowing agents is not mentioned.

The task of the present Invention was based on the development of integral foams, the above an improved, i.e. especially thicker, more compact, more abrasion-resistant and have more stable skin. additionally the appearance of the skin should be improved. The process of making this improved integral foams based on polyisocyanate polyaddition products by reacting (a) isocyanates with (b) against isocyanates reactive compounds in the presence of (c) blowing agents and optionally (d) Catalysts and / or (e) excipients should be simple and get by without expensive security equipment.

These tasks could be done through a Process for the production of integral foams, preferably from soft, semi-hard or hard, particularly preferably soft integral foams based on polyisocyanate polyaddition products, in particular Polyurethanes, which may contain urea structures can, solved in which the blowing agent is between 1% by weight and 8% by weight expandable hollow microspheres filled with propellants and between 0.1 wt .-% and 0.3 wt .-% water, each based on the Sum of the weights of the (b) isocyanate-reactive compounds, the (c) blowing agents and optionally the (d) catalysts.

By adding small amounts of water results in an integral foam with a skin that the desired Has advantages, i.e. which is thicker, improved optics and a significantly improved abrasion resistance shows in comparison with a skin of integral foams, in which larger proportions of water, possibly in combination with expandable, with blowing agent filled Hollow microspheres are used.

A particular advantage when using it small amounts of water is in the ratio of the density of the component to determine the thickness of the skin. The foamed density is in use smaller amounts of water higher. This means that the polyurethane foam compression factor is in the component and thus the resulting internal pressure in the component is lower. This leads to, that the expandable hollow microspheres up to a larger diameter can expand because the expansion takes place against a smaller pressure. Result from this yourself at usual predetermined total density of the molded part, for example steering wheel, in particular improved mechanical properties and an improved Abrasion resistance due to the reduced density in the foamed core increases the thickness of the skin can be. usual Disadvantages of using water as a blowing agent Manufacture of integral foams occur, e.g. the small thickness the skin and its porosity are avoided according to the invention.

In principle, 15 to 25% by weight of Expancel can also be used to produce integral foams in the desired density range. Disadvantages of such foams are, however, the high viscosity of the polyol component due to the high proportion of filler and the associated considerable disadvantages in process engineering and apparatus construction, and the high price of such formulations. In addition to the blowing agent combination according to the invention, halogenated or non-halogenated hydrocarbons, ketones or aldehydes can be used as blowing agents, for example tetrafluoroethane, 1,1,1,3,3-pentafluoropropane (245fa), 1,1,1,3,3-pentafluorobutane (365mfc), acetone, butanone, preferably hexane, n-pentane, 2-methylbutane and / or cyclopentane, particularly preferably n-pentane, 2-methylbutane and / or cyclopentane. This additional The blowing agent is preferably used in an amount between 0.1% by weight and 3% by weight, preferably between 0.1% by weight and 1.4% by weight, particularly preferably between 1.0% by weight and 1.4% by weight, based on the sum of the weights of the (b) isocyanate-reactive compounds, the (c) blowing agents and, if appropriate, the (d) catalysts.

Up to a weight proportion of 1.4 % Pentane, the polyol component has a flash point that has the A2 classification for flammable liquids Fulfills. This offers the advantage that during transportation and storage of the polyol component complex security measures, those when dealing with higher ones Concentrations of flammable propellants (A1 liquids) are necessary, can be dispensed with. The addition of these additional blowing agents, in particular of pentane, improves skin formation (thickness, abrasion, optics) and also the fluidity of the system in the component.

It is particularly preferred to use Blowing agent between 1 wt .-% and 8 wt .-% expandable, with blowing agents filled Hollow microspheres, between 0.1% and 0.2% water by weight and between 1.0 and 1.4% by weight of n-pentane, 2-methylbutane and / or cyclopentane a, each based on the sum of the weights of the (b) versus isocyanates reactive compounds, the (c) blowing agents and optionally the (d) catalysts. This means that some of the water can be 2-methylbutane and / or cyclopentane can be replaced.

Expandable hollow microspheres filled with propellant are generally known and commercially available. These hollow microspheres, which in the unexpanded state usually have a diameter of 2 μm to 150 μm, preferably 5 μm to 30 μm, usually contain a shell made generally of thermoplastic material, for example PVDC (acrylonitrile-polyvinylidene chloride copolymer) which is a physical blowing agent, for example hydrocarbons with 4, 5 or 6 carbon atoms, for example n-pentane, cyclopentane, isopentane, n-butane, isobutane. Suitable hollow microspheres are available, for example, under the brands Expancel ^® 091 DU, Expancel ^® 551 DU, Expancel ^® 820 DU, Expancel ^® 461 DU, Expancel ^® 051 DU from Akzo Nobel - Casco Products (Expancel). The way these hollow spheres function is based on the melting of the thermoplastic shell by the heat of reaction in the reaction of the isocyanates with the polyols and the increase in volume of the physical blowing agent. Further explanations of this hollow micro sphere are WO 95/08590, page 17, line 33 to page 25, line 5, and US 5,260,343 , Column 7, line 5 to line 22.

The integral foams of the invention, the a cellular, foamed Core and have a compact skin, preferably have a thickness the skin of at least 0.8 mm, preferably at least 1 mm, particularly preferably between 1 mm and 2 mm.

The total density of the integral foams, ie the density of the entire polyisocyanate polyaddition molded article with skin and foamed core, is preferably between 150 kg / m ³ and 800 kg / m ³ , particularly preferably between 300 kg / m ³ and 600 kg / m ³ , Well-known articles come into question as moldings, ie as products that can be produced with these integral foams, for example housings and covers for electronic devices, skis, curbs for skylights and skylights, cable guides and cable sleeves, window profiles, automobile steering wheels, gear knob, headrests, Armrests, cable sheathing, beer barrel sheathing, sheathed security elements, preferably automobile wheels, spoilers and / or shoe soles, in particular automobile steering wheels.

The production of the integral foams according to the invention can usually in such a way that the polyisocyanate polyadducts, preferably in one form, especially polyurethanes, which may have urea structures contain by reacting (a) isocyanates with (b) against isocyanates reactive compounds in the presence of (c) blowing agents and optionally (d) produces catalysts and / or (e) auxiliary substances. If steering wheels are manufactured that contain one or more carriers, they become Carrier usually placed in the mold, fixed and then with the polyurethane foam padded, wherein the foam adheres to the carrier or carriers after it has hardened.

For the production of integral foams the isocyanates (a) and the compounds reactive towards isocyanates (b) preferably implemented in amounts such that the equivalence ratio of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of components (b) 0.9: 1 to 1.2: 1, preferably 1.0: 1 to 1.1: 1 is.

The polyisocyanate polyaddition products are advantageously by the one-shot process or semi-prepolymer process with the help of high pressure or low pressure technology in open or closed, preferably closed molds, for example metallic molds. The inside walls of the Molding tools can preferably with a conventional one Release agents are provided. It has proven to be particularly advantageous proven to work according to the two-component process and the Build-up components (b), (c) and optionally (d) and / or (e) in to combine the component (A) and the organic as component (B) and / or modified organic polyisocyanates (a) or mixtures from the polyisocyanates mentioned and optionally blowing agents (c) to use.

The starting components are usually mixed at a temperature of from 15 to 90 ° C., preferably from 20 to 60 ° C. and in particular from 25 to 45 ° C., and into the open or the closed one Forming tool introduced. The mold temperature is advantageously 20 to 110 ° C, preferably 30 to 60 ° C and in particular 35 to 50 ° C.

With a semi-prepolymer process prepolymers containing isocyanate groups are preferably used. The prepolymers preferably have isocyanate contents of 15 to 31 wt .-%, based on the total weight. These can follow generally known methods can be produced, for example by the implementation of a mixture that is an organic polyisocyanate (a) and at least one compound (b) against isocyanates is reactive, contains, the implementation being customary at temperatures from 80 to 160 ° C, preferably 90 to 150 ° C carried out becomes. A prepolymer containing isocyanate groups is to be produced a corresponding surplus is used for the production 1 compared to isocyanate groups the isocyanate-reactive groups used. The reaction is general finished after 15 to 200 min.

Suitable compounds for the production of the polyurethane foams or the coatings are the compounds known from polyurethane chemistry for this purpose, for which the following is carried out:
(Cyclo) aliphatic and / or in particular aromatic polyisocyanates, preferably diisocyanates, are used as isocyanates (a). Aromatic diisocyanates, preferably diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), are particularly suitable for producing the polyurethane foams according to the invention. The isocyanates can be used in the form of the pure compound or in modified form, for example in the form of uretdions, isocyanurates, uretonimines, carbodiimides, allophanates or biurets, preferably in the form of reaction products containing urethane and isocyanate groups, so-called isocyanate prepolymers. The preferably lightfast integral foams are preferably based on non-aromatic, (cyclo) aliphatic isocyanates, for example alkylene diisocyanates with 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecane diisocyanate, 2-ethyl-tetramethylene-1,4-diisocyanate, Methyl pentamethylene diisocyanate 1,5, tetramethylene diisocyanate 1,4 and preferably hexamethylene diisocyanate 1,6 and / or cycloaliphatic diisocyanates such as cyclohexane-1, 3- and -1,4-diisocyanate and any mixtures thereof Isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate), 2,4- and 2,6-hexahydrotoluylene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,2 ' - and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures.

As compounds reactive towards isocyanates (b), preferably those with at least two reactive hydrogen atoms, be convenient those with functionality from 2 to 8, preferably 2 to 6 and a molecular weight of 60 to 9000 g / mol used. proven have e.g. generally known polyether polyamines and / or preferably polyols with a molecular weight of 500 to 9000 g / mol selected from the group of polyether polyols, polyester polyols, polythioether polyols, hydroxyl-containing polyester amides, hydroxyl-containing Polyacetal and hydroxyl-containing aliphatic polycarbonates or mixtures of at least two of the polyols mentioned. Preferably Polyester polyols and / or polyether polyols are used.

For the production of low-fogging polyurethane foams the polyester polyols are expedient before use a distillation at temperatures from 140 to 280 ° C and below reduced pressure of 0.05 to 30 mbar, e.g. a thin film distillation, to separate volatile Subject to ingredients. The polyester polyols preferably have a functionality from 2 to 4, in particular 2 to 3 and a molecular weight of 500 up to 3000 g / mol, preferably 1200 to 3000 g / mol and in particular 1800 to 2500 g / mol. However, they are used in particular as polyols Polyether polyols which are produced by known processes can. The polyether polyols, preferably polyoxytetramethylene glycols, Polyoxypropylene and / or polyoxypropylene-polyoxyethylene-polyols, have an average functionality of preferably 2 to 3 and in particular 2 to 2.7 and molecular weights from 1800 to 9000 g / mol, preferably 2000 to 6500 g / mol and in particular 2400 to 5200 g / mol. Compounds (b) also include difunctional chain extension and / or 3 to 6 functional crosslinking agents with molecular weights less than 500 g / mol, preferably from 60 to 300 g / mol. In consideration come for example dialkylene glycols and aliphatic, cycloaliphatic and / or araliphatic diols with 2 to 14, preferably 4 to 10 Carbon atoms, e.g. Ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably 1,4-butanediol, 1,6-hexanediol and bis (2-hydroxyethyl) hydroquinone, Triols such as 1,2,4-, 1,3,5-trihydroxycyclohexane, glycerin and trimethylolpropane and low molecular weight hydroxyl group-containing polyalkylene oxides Based on ethylene and / or 1,2-propylene oxide and the aforementioned diols and / or Triplets as starter molecules, secondary aromatic diamines, primary aromatic diamines, 3,3'-di- and / or 3,3'-, 5,5'-tetraalkyl substituted Diaminodiphenylmethanes. The chain extenders mentioned and / or crosslinking agents individually or as mixtures of the same or different connection types be used. Provided chain extenders, crosslinking agents or mixtures thereof are used, these are conveniently used in amounts of 2 to 60% by weight, preferably 5 to 50% by weight and in particular 10 to 40 wt .-%, based on the weight of the component (b) used.

According to the invention, the blowing agents shown at the outset are used as (c) blowing agents, wherein if necessary, additional, generally known blowing agents can also be used. The blowing agents according to the invention are preferably used exclusively.

Suitable catalysts, which in particular the reaction between the NCO groups of the diisocyanates (a) and Hydroxyl groups accelerate the structural component (b), are according to the state of the Technology known and usual tertiary Amines such as Triethylamine, dimethylcyclohexylamine, N-methylmorpholine, 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 Iron (III) acetylacetonate, tin compounds, e.g. Tin diacetate, tin dioctoate, tin dilaurate or the tin dialkyl salts aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate or the like. The catalysts are usually in amounts of 0.002 to 2 parts by weight per 100 parts by weight of polyhydroxy compound (b) used.

The implementation (s) may be carried out in the presence of (e) auxiliaries, such as fillers, cell regulators, surface-active Compounds, stabilizers, internal release agents, antioxidants, UV protection agents and / or dyes. The reactions are preferably carried out for the preparation of the polyisocyanate polyadducts in the presence of internal release agents, for example waxes, silicones, high-boiling petrochemical products, such as oils, unsaturated carboxylic acids 8 to 24 carbon atoms such as Oleic acid and its Implementation products with e.g. Metals or amines, metal salts of stearic acid, Alkyl and / or Alkylenbernsteinsäureester and / or half-esters or mixtures of at least two of the esters and / or half-term.

Examples

The examples described in Table 1 were processed with a laboratory mixer, the examples shown in Table 2 using a high-pressure machine. The free-foamed samples were produced with a total amount of polyurethane from 100 to 150 g. The test panels were produced in a mold heated to 45 ° C. (20 × 20 × 3 cm ³ ). The hardness of the plate was rated on a scale from 1 (soft) to 6 (very hard). The compression factor is the quotient of the density of the test plate and the density that has been exposed to foam. The thickness of the skin was determined by means of SEM images. The abrasion was determined according to Veslic (ISO 11 640) on a standard test plate with a grain (35 × 10 × 0.8 cm ³ ). The mold was heated to 45 ° C for the manufacture of the plate. The result of the abrasion test was evaluated on the basis of light microscopic images on a scale from 1 (no loss of the grain / no opening of the surface) to 6 (very strong loss of the grain / open surface).

Polyol A is a glycerin started Polypropylene-polyethylene oxide block copolymer with a molecular weight of 5400 g / mol and an OH number of 28 mg KOH / g.

The recipes given in Table 2 were also used to manufacture steering wheels using a high pressure machine.

Iso A is a mixture of 50% 4,4'-MDI and 50% 2,4'-MDI. Iso B is an isocyanate prepolymer made from 42% 4,4'-MDI, 50% polymer MDI and 8% of a propylene glycol-started polypropylene oxide homopolymer.
Cat 1: triethylenediamine in dipropylene glycol
Cat 2: Jeffcat ^® ZF22 from Huntsmann

Table 1

Table 2

Claims (7)

Process for the production of integral foams based on polyisocyanate polyadducts by reacting (a) isocyanates with (b) compounds reactive towards isocyanates in the presence of (c) blowing agents and optionally (d) catalysts and / or (e) auxiliaries, characterized that the blowing agent used is between 1% by weight and 8% by weight of expandable hollow microspheres filled with blowing agent and between 0.1% by weight and 0.3% by weight of water, in each case based on the sum of the weights of the (b) isocyanate-reactive compounds, the (c) blowing agents and optionally the (d) catalysts. Method according to claim 1, characterized in that additionally as a blowing agent between 0.1% by weight and 3% by weight of hexane, n-pentane, 2-methylbutane and / or Cyclopentane, based on the sum of the weights of the (b) versus isocyanates reactive compounds, the (c) blowing agents and optionally uses (d) catalysts. Method according to claim 1 for the production of integral foams with a thickness of Skin of at least 0.8 mm. A method according to claim 1 for the production of integral foams with a total density between 150 kg / m ³ and 800 kg / m3. Method according to claim 1 for the production of automobile steering wheels, spoilers and / or shoe soles. Integral foams based on polyisocyanate polyaddition products available by a method according to a of claims 1 to 5. casing and covers for electronic equipment, Skis, curbs for domelights and skylights, cable routing, Cable sleeves, window profiles, automobile steering wheels, gear knobs, headrests, armrests, Cable jackets, beer keg jackets, jacketed security elements, Spoilers and / or shoe soles available by a method according to a of claims 1 to 5.