Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
  • B29C44/30—Expanding the moulding material between endless belts or rollers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
  • C08J2375/04—Polyurethanes

Definitions

• the present invention relates to a process and to a low- 5. output plant for the continuous production of polyurethane slab-stock foams.
• EP-A-0 645 226 proposes the use of C0 2 or liquid carbon dioxide as blowing agent, in order to froth the polyurethane mixture as it is delivered and distributed on the moving substrate, in combination with post-expansion
• viscosity of the frothed mixture substantially eliminates the aforementioned underrunning phenomenon, in practice such a plant has proved to be less suited for low-output applications which use conventional chemical systems based on toluene diisocyanate (TDI), in accordance with the
• the main object of the present invention is to provide a 10. process and a plant for the continuous production of open- cell polyurethane slab-stock foam, able to overcome the drawbacks resulting from the use of conventional TDI-based chemical systems and plants, so that it is possible to operate with low-output, with a plant of small sizes, by 15. means of which a conveyor path having a steeply inclined initial surface may be used, while avoiding the underrunning phenomenon of the mixture in respect to the expanding foam.
• Another object of the invention is to provide for a process 20. and a plant as referred above, by which at the same time it is possible to maintain a wide range of variability for density and hardness values of the foams produced, while using suitable quantities of formulation water allowing high reactivity and avoiding process difficulties normally 25. occurring with conventional process and plants.
• an object of the present invention is to overcome the abovementioned drawbacks by providing a small sized plant of a new constructional design for continuous MDI- based slab-stock foam production, which is distinguishing over the traditional designs.
• a further object of the present invention is to provide a plant of the kind referred to, for the continuous slab- stock production, which offers clear advantages over single block or batch foaming machines, as wall over conventional plants, requiring a simple and quick installation in a
• Another object of the invention is to provide a plant for the continuous slab-stock foam production, as referred to above, having a compact design for minimum space consumption, which ensure high quality engineering, minimum transport costs and high quality foam.
• first isocyanate-based chemical component and a second chemical component containing active terminal hydrogen atoms such as a polyol, to react with the isocyanate component, are mixed in metered quantities and in which the resulting mixture is frothed and foamed by using in
• reaction product thereof for example an MDI prepolymer; and in that the resulting mixture comprises a quantity of carbon dioxide within 1 to 10%, preferably within 1.5 to 5% in respect to the second chemical component, and a metered quantity of formulation water for post-expansion until to
• a plant has been provided for the continuous production of MDI-based polyurethane slab-stock foams, in such a way as to considerably reduce the lengthwise dimensions of the plant itself, by providing a mixer and a frothing device, a fall-
• the plant for the continuous production of polyurethane slab-stock foam according to the invention may be differently constructed, depending on the specific requirements of the user, without departing from modular
• design and the arrangement according to the invention Preferably may be housed and transported inside ISO standard containers which thus constitute an integral frame part of the plant itself.
• the container for the conveyor and the control unit may comprise a framework
• ⁇ Fig. 1 is a general diagram of the plant
• ⁇ Fig. 2 is a graph comparing the characteristics of an MDI system according to the invention, with a conventional TDI system
• module containing the control unit and the conveyor with the associated devices;
• Fig. 4 is a top view of the module shown in Figure 3;
• FIG. 5 is a view from the right-hand end of the module according to Figure 3;
• FIG. 10 is top view of the second module comprising the metering pumps and storage tanks, inside a second container;
• _ Fig. 7 is a diagram of plant.
• the plant substantially comprises a lay-down device 10 for delivering an MDI-based, polyurethane mixture, which is frothed and distributed on a moving substrate 11, for example a web of
• paper which is continuously unwound from a bobbin 11' in a per se known manner and moved along a fall-plate 12 which is downwardly slanted towards a horizontal conveyor 13.
• a second web of paper 14, or plastic film covers the upper surface of the polyurethane foam 15, while additional web
• LI in Figure 1 denotes the length of the fall-plate 12 or an initial inclined conveyor, while L2 denotes the total length of the plant, as far as the cutting zone 16 of the slab-stocks .
• an MDI-based chemical system is used: this term is understood as referring to any chemical
• the foaming agent m turn consists in the combination of carbon dioxide, C0 2 , able to cause an intensive frothing of
• the polyurethane mixture, and formulation water may be pre-mixed into one of the two chemical components, preferably in the polyol, either m liquid or gas form; the resulting mixture is supplied and distributed on the moving substrate 11 by means of a
• frothing and delivery device 10 so as to avoid violent or rapid evaporation of the C0 2 m the polyurethane mixture, allowing m th s way gradual frothing of the mixture along the fall-plate 12, followed by a foaming phase involving post-expansion of the frothed mixture caused by the
• Figure 1 illustrates the basic concept of the plant which operates in accordance with the process
• the plant m Figure 1 has been designed for a relatively low production output and very small overall dimensions, in relation to its specific use with a polyurethane mixture based on MDI formulation in accordance with the principles of the invention.
• a plant according to the invention may have the dimensions and operational parameters indicated below:
• the graph represented by the broken lines PI, 25. P2, P3 and P4 shows the variability range of the percentages of water (H 2 0%) and carbon dioxide (C0 2 %) which can be obtained in a traditional TDI-based formulation.
• the density of the foam is regulated by the total expansion index, consisting of a numerical value which represents the theoretical expansion of the foam due to the combined effect of the water and the
• C0 2 as foaming agents, expressed as water equivalent in percentage parts, compared to the polyol, taken as 100.
• the hardness of the foam is regulated by varying the proportions of water and C0 2 , keeping the total expansion index at a constant value for a same density; in
• hard foams are obtained by increasing the percentage of water and reducing C0, while soft foams are obtained by reducing the water and increasing the percentage of C0 2 .
• points PI and P4 relate to foams with high densities and varying hardness as a result of the reduced percentage of C0 and the varying formulation water content.
• the points P2 and P3 relate to foams with an average density and varying hardness as a result of
• an MDI- based chemical system is used in order to obtain a wide range of variability m the density of the foam produced, using a substantially constant quantity of C0 2 , greater 5. than 1%, for the preliminary frothing stage, and varying consequently the percentage or quantity of water necessary for post-expansion, until a predetermined value of the total expansion index is obtained, depending on the required foam density.
• Table I relates to the case of a mixture with 4% of C0 2 , for a foam density ranging between 14 kg/m and 40 kg/m 3 ; however, by modifying the quantity of water, the density of the foam which can be obtained could also be greater or 5. less than that indicated.
• the first column shows the foam density values expressed in kg/m
• the second column shows the total expansion index values, at the various densities, expressed in percentage of water
• the third column shows
• Table II is similar to the preceding one, but relates to a 20. C0 2 content of 5%, while maintaining the same MDI formulation.
• Figures 3 to 7 show various views of the first module of a plant, according to the invention: the plant, as usual, comprises a mixer for delivering a polyurethane mixture, a 25. conveyor, a slab-stock cutting device and a process control unit. More precisely, as shown, this first module comprises an open-end container 17, of the standard type, for example an ISO 40 container having a length of about 12 metres; the container 17 consists, for example, of a peripheral framework comprising a series of uprights 18 connected at the top and the bottom sides by longitudinal beams 19, and by cross beams 19' , to provide a strong frame structure for the entire container.
• the standard type for example an ISO 40 container having a length of about 12 metres
• the container 17 consists, for example, of a peripheral framework comprising a series of uprights 18 connected at the top and the bottom sides by longitudinal beams 19, and by cross beams 19' , to provide a strong frame structure for the entire container.
• the container On both sides the container is moreover provided with closing panels 23 to define an open-end or tunnel-like chamber; the panels 23 are removably fixed to the framework so as to allow access by an operator and inspection of the plant at any point along the same container.
• a footboard 24 for an operator At one end of the container 17 there is arranged a footboard 24 for an operator, and a control unit 25 for the entire production process.
• a conveyor 13 extends longitudinally inside the container 17, from a downwardly slanted plane 12, also referred to as
• rollers 21 and 22 are also provided for attaching rollers 21 and 22 for unwinding and respectively for winding-up webs of paper or plastic films sliding inside and along the side walls 20, to contact the foam advancing on the conveyor 13.
• the winding- up rollers 22 are operated by a suitable geared motor 22'.
• a moving substrate in the form of a paper sheet or plastic film 11, slides along the fall-plate 12 and the conveyor 13, being unwound from a bobbin 11' outside the front end of the container 17; the paper web or plastic film 11 which is unwound from the bobbin 11' passes and is guided, for
• a mixing head 10' of conventional type for the polyurethane components is pending from a support bracket 26 fixed to a mounting plate 26' fastened at the top wall of the 15. container 17; the mixing head 10' is connected to a frothing device 10, for delivering a pre-expanded or frothed mixture at the upper end of the fall-plate 12.
• Reference 28 in Figures 1 and 2 denotes moreover two suction fans fixed to respective mounting plates at the top 20. wall of the container 17, in the vicinity of the fall-plate 12 and at the midway point of the conveyor 13, for sucking up air and gases inside the said container.
• Figure 6 of the drawings shows the second module for housing some of the storing tanks for the chemical 25 . component and metering pumps, which forms part of the plant according to the invention.
• a smaller container of standard dimensions for example an ISO 20 container, is used, said container being shown diagrammatically by the dot-dash line 30 in Figure 6.
• the container 30, like the container 17, also comprises a framework formed by beams, uprights and by side closing panels suitably provided with connection fittings for the pipeworks and wiring which for the 5. connection to the various equipment of the plant.
• this second module comprises the tanks 32, 33 and 34 for storing chemicals or activators, including the tank 31 for the formulation water necessary for chemical expansion of the 10. polyurethane mixture, with respective metering pumps 31' , 32' , 33' and 34' pre-assembled with the respective control valves 36, 37, 38 and 39 and pipeworks.
• the container 30 also comprises a pump 40 and a respective control valve 41 for the circulation of one of the
• polyurethane components for example the MDI-based component contained in a storage tank 43 ( Figure 7) outside the container 30; the container 30 also comprises two additional metering pumps 44 and 45 with respective control valves 46 and 47 for the circulation of a second and
• a third chemical component of the polyurethane mixture for example a first and a second polyol, each stored in a respective tank 48 and 49.
• reference 50 in Figure 5 denotes a fourth metering pump inside the container 30, with a respective control 25.
• valve 51 for supplying a blowing agent, for example C0 2 , stored into a tank 52 which can be located outside or in a special space accessible inside one of the two containers 17 or 30.
• the general circuit diagram of the plant is shown m Figure 7 of the drawings, where the same reference numbers have been used to denote corresponding parts of the other figures.
• reference number 53 5 denotes a pressure air source for supplying nucleating air directly to the mixing head 10' .
• the invention substantially resides in a modular plant for the continuous production of polyurethane slab-stock foam by using an MDI-based
• polyurethane mixture according to which the plant consists of two operative modular units preassembled m housing and transportation containers of standard sizes and in which the two plant modules, together with all the operationally necessary equipment, may be tested directly at the factory
• foam blocks in which a polyurethane mixture is intensively frothed by using a relatively large quantity of C0 2 ,to obviate the underrunning phenomenon and in which the C02 percentage may remain substantially constant at a predetermined value, varying solely the quantity of

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Applications Claiming Priority (5)

Publications (1)

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Family Applications (1)

Country Status (3)

Family Cites Families (7)

• 1997
  • 1997-11-24 EP EP97953694A patent/EP0942819A2/de not_active Withdrawn
  • 1997-11-24 WO PCT/EP1997/006555 patent/WO1998023429A2/en not_active Ceased
• 1999
  • 1999-05-26 NO NO992533A patent/NO992533L/no not_active Application Discontinuation

Non-Patent Citations (1)

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