PROCESS FOR PRODUCING RIGID POLYURETHANE (PUR) AND POLYURETHANE/ POLYISOCYANURATE (PUR/PIR) FOAMS

Abstract

The invention relates to a process for producing rigid polyurethane (PUR) and polyurethane/polyisocyanurate (PUR/PIR) foams, comprising the steps of i) producing a reaction mixture containing the components A) an isocyanate-reactive component, B) a polyisocyanate component, and C) a blowing agent, and ii) applying the reaction mixture by using a system comprising at least one casting device. The casting device (100) having: a supply port (12) for feeding the reaction mixture (10), at least one discharge gap (13) extending in a transverse direction (Q) for the discharge of the reaction mixture (10), two gap-forming plates (14) arranged opposite one another, a gap space (15) extending between the gap-forming plates (14) above the discharge gap (13) in a height direction (H), wherein the reaction mixture can be introduced into the gap space (15), distributed over the length of the supply duct (16).

Claims

1. A process for producing polyurethane (PUR) and polyurethane/polyisocyanurate (PUR/PIR) rigid foams, comprising the steps of: i) producing a reaction mixture comprising the components: A) an isocyanate-reactive component comprising at least one polyol selected from the group consisting of polyether polyols, polyester polyols, polycarbonate polyols, polyether-polycarbonate polyols, and polyether ester polyols; B) a polyisocyanate component; and C) a blowing agent; and ii) applying the reaction mixture with a plant comprising at least one curtain coating apparatus, wherein the at least one curtain coating apparatus comprises: a feed connection for introducing the reaction mixture; at least one discharge slot extending in a transverse direction for discharging the reaction mixture; two opposing slot plates, wherein a slot space extends between the slot plates in a vertical direction above the discharge slot; and a feed channel connected to the feed connection which is formed between the slot plates and closes the slot space above the discharge slot in the vertical direction, wherein the feed channel has a channel cross section comprising a principal dimension greater than a width of the slot space so that the reaction mixture is introduceable into the slot space distributed over a length of the feed channel.

2. The process of claim 1, wherein the process is performed continuously.

3. The process of claim 1, wherein the channel cross section decreases with increasing distance from the feed connection.

4. The process of claim 1, wherein the at least one curtain coating apparatus is provided with a replaceable insert made of plastic, metal or another material which protects the inside of the slot plates of the curtain coating apparatus from contamination.

5. The process of claim 1, wherein over at least a partial width of an outerlayer, the plant comprises a plurality of curtain coating apparatuses, wherein the discharge slots of the curtain coating apparatuses extend in a common transverse direction or arcuately over the outerlayer.

6. The process of claim 1, wherein each individual curtain coating apparatus used in the plant or else the entire plant is configured such that the distance thereof from the lower outerlayer may be varied during application of the reaction mixture.

7. The process of claim 1, wherein in each case based on the total weight of the isocyanate-reactive component A), the isocyanate-reactive component A) comprises: a) 65% to 100% by weight of at least one of a base polyol component selected from the group consisting of polyester polyol, polyether polyol, polyether ester polyol, polycarbonate polyol, and polyether-polycarbonate polyol having a hydroxyl number in a range of 100 to 300 mg KOH/g and functionalities of 1.2 to 3.5; b) 0% to 25% by weight of long-chain polyether polyols having functionalities of 1.2 to 3.5 and a hydroxyl number in a range of 10 to 100 mg KOH/g; c) 0% to 10% by weight of low molecular weight isocyanate-reactive compounds having a molar mass M.sub.n of less than 400 g/mol; and d) 0% to 10% by weight of medium-chain polyether polyols having functionalities of 2 to 6 and a hydroxyl number in a range of 300 to 700 mg KOH/g.

8. The process of claim 1, wherein based on the total weight of the isocyanate-reactive component, the isocyanate-reactive component A) comprises: a) 65-100% by weight of at least one polyester polyol having a functionality of functionalities of 1.2 to 3.5, a hydroxyl number in a range of 100 to 300 mg KOH/g, and an acid number in a range of 0 to 5.0 mg KOH/g; and b) 0% to 10% by weight of a polyether polyol having a functionality of 1.8 to 3.5 and a hydroxyl number in a range of 10 to 100 mg KOH/g.

9. The process of claim 16, wherein the catalyst component D) comprises an aminic catalyst D1) and a carboxylate D2), and the D2/D1 quantity ratio is between 0.1 and 80.

10. The process of claim 1, wherein a cream time of the reaction mixture is <5 seconds.

11. The process of claim 1, wherein a fiber time of the reaction mixture is <25 seconds.

12. The process of claim 1, wherein the blowing agent C) is a physical blowing agent comprising one or more compounds selected from the group consisting of hydrocarbons, halogenated ethers, and (per)fluorinated hydrocarbons.

13. The process of claim 1, wherein step ii) comprises applying a foaming mixture.

14. A PUR rigid foam or PUR/PIR rigid foam produced by the process of claim 1.

15. A composite element comprising one or two outerlayers and the PUR or PUR/PIR rigid foam of claim 14.

16. The process of claim 1, wherein the reaction mixture further comprises D) a catalyst component.

17. The process of claim 1, wherein the reaction mixture further comprises E) assistant and additive substances.

18. The process of claim 12, wherein the physical blowing agent comprises one or more compounds selected from the group consisting of pentane isomers and (hydro)fluorinated olefins.

19. The process of claim 9, wherein the D2/D1 quantity ratio is between 2 and 20.

Description

[0125] The figures show exemplary embodiments of the curtain coating apparatus employable in the process according to the invention and a plant containing this curtain coating apparatus.

[0126] FIG. 1 shows a general view of the plant comprising a curtain coating apparatus 100 and the feeding of outerlayers and also a double belt conveying plant 21.

[0127] FIG. 2 shows a perspective view of a slot plate 14 from the side which areally delimits the slot space,

[0128] FIG. 3 shows a cross sectional view of the curtain coating apparatus comprising two superposed slot plates to form the slot space between the slot plates,

[0129] FIG. 3a shows a developed embodiment of the discharge slot having slot lips formed thereupon

[0130] FIG. 4 shows a perspective view of the plant employed in the process according to the invention comprising an installed curtain coating apparatus for applying a foaming reaction mixture

[0131] FIG. 1 shows a schematic view of a plant for operating a process used for producing composite elements 1. The plant comprises a double belt conveying plant 21 which receives two outerlayers 11. A lower outerlayer 11 is unrolled from an outerlayer roll 20 and an upper outerlayer 11 is likewise unrolled from a further outerlayer roll 20. The two outerlayers 11 are introduced into the conveying plant 21 with a gap and a reaction mixture 10 is applied to the inner surface of the lower outerlayer 11 with a curtain coating apparatus 100. The curtain coating apparatus 100 is connected via a feed connection 12 to a mixing head 19 and at least the components polyol and isocyanate are introduced in the mixing head 19 in an appropriate mixing ratio represented by two arrows, wherein a possible air loading of the reaction mixture 10 may be provided but is not shown for the sake of simplicity.

[0132] The curtain coating apparatus 100 is positioned at a distance to the double belt conveying plant 21 such that over a foaming sector the reaction mixture undergoes sufficient foaming to ensure that foaming reaches the underside of the upper outerlayer 11 and as the thus-formed composite element 1 passes through the double belt conveying plant 21 the polyurethane foam core between the two outerlayers 11 can undergo curing. Once it has passed through the double belt conveying plant 21 the endless material of the composite element 1 may be separated into individual sandwich panels (not shown).

[0133] FIG. 2 shows an example of a slot plate 14, wherein the perspective view is chosen such that the slot space 15 is visible and wherein the opposed slot plate has been removed to show the flat slot space 15. The slot plate 14 shown has cutouts 23 for receiving securing means so that two slot plates 14 can be brought together to form the curtain coating apparatus 100 and to thus complete the slot space 15.

[0134] Shown by way of example is a feed connection 12 for supplying reaction mixture 10, wherein the feed connection 12 is in fluid communication with a feed channel 16 which has been incorporated into the slot plate 14. After an intermediate channel 24 for connection to the feed connection 12 the feed channel 16 branches to both sides of a transverse direction Q so that the feed channel 16 comprises two branches which extend laterally away from the feed connection 12.

[0135] A symmetrical configuration of the curtain coating apparatus is thus shown merely by way of example and said apparatus may alternatively also be formed asymmetrically on only one side of the feed connection 12 so that only one branch of the feed channel 16 connects to the feed connection 12.

[0136] The lower edge of the slot plate 14 forms a discharge slot 13 together with the further slot plate 14 (not shown). The discharge slot 13 extends in its length over the transverse direction Q between the two ends of the feed channel 16 and the feed channel 16 has a curvature such that it approaches the edge of the discharge slot 13 with increasing distance from the feed connection 12 and finally terminates therewith at its end. Thus the greater the distance from the feed connection 12, the smaller the height of the slot space 15 in the vertical direction H. The feed channel 16 itself has been incorporated into the slot plate 14 as a groove-like depression and has a channel cross section 17 which narrows as the distance from the feed connection 12 increases.

[0137] The changing channel cross section 17, the curvature in the feed channel 16 and thus the changing height in the vertical direction H of the slot space 15 are matched to one another such that the reaction mixture 10 experiences the same passthrough time through the curtain coating apparatus 100 over the entire length of the discharge slot 13 and the discharge velocity of the reaction mixture 10 from the discharge slot 13 is likewise identical over the length of the entire discharge slot 13.

[0138] FIG. 3 shows a cross sectional view through the curtain coating apparatus 100 with cross sectioned slot plates 14. Visible here is a slot space 15 which extends between the two slot plates 14 and extends in the vertical direction H from the feed channel 16 to the discharge slot 13 on the underside. The slot space 15 has a constant width B over its areal extent and the areal extent extends between the feed channel 16 and the discharge slot 13 in the vertical direction H and the transverse direction Q which is perpendicular to the vertical direction H.

[0139] FIG. 3a shows a modified embodiment of the discharge slot 13 having slot lips 26 formed thereupon, wherein the slot lips 26 protrude over the plate end of the slot plates 14 and form thin lip-like projections. This prevents reaction mixture from being able to collect in the outer region of the discharge slot 13 which in the case of larger accumulated amounts could disrupt the discharging of the reaction mixture at the outer surface of the slot plates 14.

[0140] FIG. 4 shows a perspective view of the plant used in the process according to the invention comprising a single curtain coating apparatus 100 for applying a foaming reaction mixture but showing only the application region of the reaction mixture 10 onto the lower outerlayer 11 that is relevant for the invention. The outerlayer is passed through underneath the curtain coating apparatus using the conveying rollers 33, provided with reaction mixture there and subsequently enters the double belt conveying plant 21 in the conveying direction T.

[0141] The opposite slot plate 14 facing the mixing head 19 is not shown in the figure in order to show the flat slot space 15. The slot plate 14 shown has cutouts 23 for receiving securing means so that two slot plates 14 can be brought together to form the curtain coating apparatus 100 and to thus complete the slot space 15.

[0142] Via the feed connection 12 the reaction mixture 10 is introduced through an intermediate channel 24 into the two symmetrical branches of the feed channel 16. In this case the feed channel has a circular cross section and has been incorporated into both slot plates symmetrically with a semicircular cross section in each case. The cross section of the feed channel is greatest in the region of the feed connection.

[0143] In the case of a circular cross section the ratio of the cross sectional area of the channel to the circumferencetypically referred to as hydraulic diameteris minimal, thus retarding blockage of the distributor channel at the channel end due to the wall adhesion of the reactive mixture and the decreasing velocity. Any other cross section shape, and in particular square cross sections, would be more disadvantageous in this respect.

[0144] To simplify manufacture and to facilitate cleaning the slot space 15 has been incorporated exclusively into the slot plate shown and has a constant width B over its entire areal extent between the feed channel above and the discharge slot 13 at the lower edge of the slot plate 14. The maximum height of the slot space is in the middle below the feed connection 12 and the intermediate channel 24. The discharge slot 13 extends over the transverse direction Q between both ends of the feed channel 16. The feed channel 16 has a curvature such that it approaches the edge of the discharge slot 13 with increasing distance from the feed connection 12 and finally terminates therewith at its end. At the end the feed channels 16 merge with the discharge slot in the exemplary embodiment. The cross section of the channels was made slightly larger than the width of the slot space in order to reduce the risk of blockage as a result of the chemical reaction of the mixture.

[0145] The changing cross section and the curvature in the feed channel 16 and thus the changing height in the vertical direction H of the slot space 15 were matched to one another such that the reaction mixture 10 experiences the same passthrough time through the curtain coating apparatus 100 over the entire length of the discharge slot 13 and the discharge velocity of the reaction mixture 10 from the discharge slot 13 is likewise identical over the length of the entire discharge slot 13.

[0146] As is shown in the exemplary embodiment depicted in FIG. 4 the curtain coating apparatus 100 is secured to a slide rail 34 via two lateral holders 28. The holders 28 allow for tilting of the nozzle around an axis parallel to the transverse direction Q. Tilting makes it possible to adjust the angle between the discharge film and the outerlayer 11 such that optimal flow conditions for the reaction mixture in the impact region are achieved. The slide rail 34 is displaceable on the crossmember 32 in the transverse direction Q in order to adapt the position of the discharge slot of the curtain coating apparatus to the position of the lower outerlayer 11. The distance to the crossmember and thus the distance of the discharge slot 13 of the curtain coating apparatus above the outerlayer may be chosen in the gravitational direction 9 via the two distance adjustment means 31 such that the reaction mixture is applied to the lower outerlayer in the desired manner and width. The two distance adjustment means 31 are movably mounted in the conveying direction T of the outerlayer on two lateral guide rails 29 which are secured to the plant table 30.

[0147] By displacement of the distance adjustment means 31 along the guide rails 29 the position of the curtain coating apparatus 100 in relation to the double belt conveying plant 21 can be chosen such that along the foaming sector shown in FIG. 1 the reaction mixture 10 reaches the underside of the upper outerlayer 11 in the desired manner as a result of the foaming.

EXAMPLES

Reactants:

[0148]

TABLE-US-00001 Polyol formulation Stepanpol PS-2352 Polyester from Stepan having an OHN of 240 mg KOH/g based on diethylene glycol and phthalic anhydride, functionality 2, acid number 1.0 Levagard PP Tris(2-chloropropyl) phosphate (Lanxess) Tegostab B 8421 Stabilizer comprising polydimethylsiloxane and polyoxyalkylene structural elements (Evonik) Water Desmorapid 1792 Preparation of 25% by weight potassium acetate and 75% by weight diethylene glycol (Covestro) Desmorapid 726b Dimethylcyclohexylamine (Covestro) Solstice LBA Trans-1-chloro-3,3,3-trifluoropropene (Honeywell) c-/i-pentane 30/70 Mixture of 30% by weight cyclopentane and 70% by weight isopentane, Julius Hoesch Duren GmbH & Co KG Isopentane 2-methylbutane (Julius Hoesch Dren GmbH & Co KG) Isocyanate Desmodur 44V70L Polymeric MDI having a viscosity of 600-750 mPas and an NCO content between 30.5% and 32% by weight

Determination of Properties:

[0149] Cream time: Time characterized by commencement of foaming of the reaction mixture (visual inspection)

[0150] Fiber time: The fiber time is determined by dipping a wooden stick into the polyurethane reaction mixture and withdrawing it again. It characterizes the time, measured from the time of mixing of the reaction components, from which the mixture starts to cure. This is the time at which it is first possible to draw out strings between the wooden stick and the reaction mixture.

Production and Evaluation of the Composite Elements:

[0151] Examples 1, 2 and 5 employed a double conveyor belt plant (DCB) having a conventional fixed application system (fixed rake applicator FPR 25.1-0 from Covestro, optimized for discharge amounts between 20 and 30 kg/min and a panel width of 1000 mm).

[0152] Inventive examples 3, 4 and 6 employed an inventive curtain coating apparatus according to FIG. 4 as the application apparatus. The length of the slot was 100 cm and the distance between the slot and the lower outerlayer was adjusted such that an optimal covering of the lower outerlayer was achieved.

[0153] Sandwich elements of 80 mm in thickness were produced by the double belt process with aluminum foil Aluminiumfolie HYDRO1200-N, lackiert, EP from Hydro Aluminium Rolled Products GmbH as outerlayers of 0.05 mm in thickness on both sides. The polyol formulation containing all components except for the isocyanate was mixed with the isocyanate in a linear mixing head at 140 bar. The reaction mixture was passed from the mixing head to the respective discharge apparatus via a connecting hose. The flowable starting material was supplied centrally (at 25 C. in examples 1-4 and at 23 C. in examples 5 and 6).

[0154] To evaluate the foam surface the outerlayer is removed and the surface of the panel is subjected to a visual examination. A + denotes that the foam contains no voids or bubbles and is homogeneous. A denotes that confluence zones in which the cells have a coarser structure are clearly apparent.

[0155] Adhesion was evaluated qualitatively by manual peeloff of the outerlayer. A score of 1 denotes a very good adhesion, 2+ an almost still very good adhesion etc., while virtually no adhesion is denoted by a score of 6.

[0156] Evaluation of fire characteristics (foam edge flaming) was carried out according to EN ISO 11925-2:2010 (German version).

[0157] Table 1 summarizes the employed amounts (in % by weight), parameters of the examples and evaluation of the composite elements produced.

TABLE-US-00002 TABLE 1 Example 1 2 3 4 5 6 Stepanpol PS-2352 23.44 23.39 23.44 23.39 22.39 22.39 Levagard PP 4.51 4.50 4.51 4.50 4.31 4.31 Tegostab B 8421 0.60 0.60 0.60 0.60 0.57 0.57 Water 0.36 0.36 0.36 0.36 0.34 0.34 Desmorapid 1792 0.81 0.96 0.81 0.96 0.78 0.78 Desmorapid 726b 0.21 0.30 0.21 0.30 0.20 0.20 Desmodur 44V70L 65.10 64.95 65.10 64.95 62.18 62.18 Solstice LBA 9.23 9.23 c-/i-pentane 30/70 4.96 4.95 4.96 4.95 Isocyanate index 313 313 313 313 313 313 Cream time s 6 3 5 3 5 5 Fiber time s 31 19 28 21 30 31 Foam edge flaming mm 148 147 103 Foam appearance + + + + top side Adhesion after 2+ 2+ 2+ 2 2+ 2+ 24 h top side Adhesion after 2 2 2 1 3 2 24 h bottom side Belt speed (actual) [m/min] 7.1 10.75 7.6 10.6 7.13 7.8 Total discharge [kg/min] 19.20 28.80 19.20 28.80 19.20 19.20 Air loading [Standard 1 1 3 3 1 3 liters/min]

TABLE-US-00003 List of reference symbols 100 Curtain coating apparatus 1 Composite element 10 Reaction mixture 11 Outerlayer 12 Feed connection 13 Discharge slot 14 Slot plate 15 Slot space 16 Feed channel 17 Channel cross section 19 Mixing head 20 Outerlayer roll 21 Double belt conveying plant 23 Cutout 24 Intermediate channel 26 Slot lip 28 Tilt angle adjustment means 29 Guide rail 30 Plant table 31 Distance adjustment means 32 Crossmember 33 Conveying rollers 34 Slide rail Q Transverse direction H Vertical direction B Width T Conveying direction g Gravitational direction