SE419956B - Method for performing insulation foaming, even of very large units, at a time after precise determination of the foam pressure - Google Patents

Abstract

Insulation foaming method according to the present invention involves a method which enables small or large units, constructed in a sandwich design or as flat units, to be foamed at the very same time, without layers being formed or sections which are different from each other. The method is characterised in that the density and the internal expanding pressure can be controlled and limited to the predetermined value, by using expansion samples, and that a certain overfilling of foam is permitted, which ensures that all cavities are filled up before the thread time of the foam occurs, which is the time when the outflow of foam is interrupted. The foaming method is also characterised in that it is system-related, by which is meant that changes in foam components, temperature, and the geometrical configuration of the product can be co-ordinated for each production scenario by performing an expansion test prior to the foaming. <IMAGE>

Description

10 1.5 20 25 30 35 40 7996856-8 2 moment, with guaranteed filling of the hâlnummen, limited foam pressure, homogeneous layer-free foam quality and a desired density.

For the manufacture of products, including polyurethane foam, is. man today referred. to, in principle, three different methods: _ a. Filling the breed closed form with a certain degree of overfilling. The shape must be strong enough, to be absorbed, the highest foam pressure, which may occur. b. -Sainmanfogliing of flat sandwich elements, made in a, mes- tadels, continuous process. K c. Stages, where cavities are gradually filled, surrounded by molds, which absorb the foam smoke. The procedure is repeated fermentation in the cavity, where röènyaa system addition takes place at the earliest at the stabilization phase. Some density variation and layering This method cannot be avoided.

Today, only large units are used in the manufacture of larger units methods b. and c. or a combination of these.

In order to achieve full clarity in the description of the invention, the following basic conditions are demonstrated.

Polyurethane foam is formed by mixing two. basic component in liquid form, formulated according to the manufacturer's recipe. At sam- the exothermic process is started, divided into a chemical reaction tion, which releases heat ooh polymerizes the plastic and a physical reaction where liquid boils to gas. The released heat accelerates the chemical reaction and the liquid formed in gaseous form propellant and rapidly transfer the liquid mixture to the various units of the unit straw. in Component A is an isocyanate, which has been given by various suppliers. ka product name.

Component B is a polyol, consisting of a system of components for process control and which gives the foam the desired properties per. Erz of the constituent components consists of a liquid y (Frigen 11) with a boiling point 23, a ° o, s k ariàfgas. in After a certain time, the so-called start time S, the exolaric reaction begins. simultaneous polymerization of the plastic and gasification of drivgesen begins.

At the so-called thread time T, the polymerization has progressed as follows. far, that the plastic begins to stick. ' At the stabilization time St, the plastic is so stable that the surface does not 10 15 20 25 50 55 40 5 7906850-8 longer is sticky. The plastic feels elastic. 1-VW., I ..

At the molding time F, such stability has been achieved that the plastic itself able to hold the propellant trapped in cavities, molds can be detached.

Only after several months are the conditions completely stable.

Different component systems are characterized by the suppliers with T and S, as well as the free-read density D, by which is meant the density of a sample, which is prepared without form.

The ratio between the density of the finished product and that free-read density is called degree of overfilling Ö.

For all systems, S, T and D are stated with tolerances of about 20% depending on a number of factors outside the manufacturer's role affects these values. ' Variation in the above characteristics is mainly affected by: - The properties of the components included in the system vary slightly between different deliveries.

~ The storage time affects the impact of the components on each other.

- The component temperature at the time of mixing affects.

- Different equipment for mixing gives different results.

- The same equipment gives different results at different dosages.

It is therefore recommended that a free reading test be performed at opportunity to change any production premise. The above variations can be said to be system-related To achieve a product of consistent quality, by which is meant minimum density variation, must be ensured that the shape as the foam is allowed to fill, in any case being filled before T. It- take achieved through a certain degree of overcrowding. The most important parameters the rs here are: I - Product geometry, surface size and thickness.

The molds temperature. ' - Components of the component system. The degree of overfilling can be said to be product-related. It is recommended that an appropriate degree of overfilling is determined by tests.

The method of the present invention has been developed with the goal of combining speed and quality according to method a. and with requirements pd molds required for method c, i.e. a low foam pressure against the mold surfaces.

As a basis for the procedure lingen attempts, intended to verify that certain simple laws apply with sufficient accuracy to a 10 1.5 20 25 50 35 40 'vs fl ssso-a 4 component system in the time interval S oohiT. verified is: _____________ v __ - The foam behaves, like a liquid. Currentsl can be considered, _, n som laminíir. The size resistance is proportional to the velocity square, i.e. inversely proportional to hydraulic diameters meters. Curves and section changes can be calculated set with equivalent cable length. Pig 3.

- The wall temperature of the space to be filled is inversely portionwise to the required degree of overfilling. Fig. 5.

- In products made from foam of different "ages" ferment. together, no stratification occurs, provided that the contact takes place in the time interval S and T. Fig. 4.

- A free reading test performed in a transparent tube gives in addition to the The site also provides information on when in time the fermentation should be stopped in terms of volume milling. .the remaining fermentation should be replaced by pressure rise, which derives from the general state of gases pv / l '= const. Pig 4.

As an exemplary embodiment, describe below a foaming procedure of a container construction.

Conditions: - A certain volume must be filled with foam of a certain density.

- Use foaming equipment with a certain capacity kg / sec. systems with the following data: start time s; 3o and 5 sec. wråatifl ll: 110 for 20 sec.

Freestand density D: approx. 30 kg / mš at current release content.

Container (1), fig. 1, is made with an outer jacket (2), which is equipped with corner reinforcements (3) and sockets (4), for lifting and inside with an inner jacket (5), and between these two. sheathes the polyurethane adhesive (6) injected according to the process.

The space between the jackets and (5) is divided into a number sections (7) with the bulkheads (8), Fig. 2, made as distance supports for mantelytolna and provided with openings adjacent to adjacent sections down to the places where the foam last reaches. At each section, llppta- get one or more needles (9) for injecting foam, which are supplied the sections via the nozzle (10) and the hose set (11) from the rinsing the unit (12). Around the container and inside it is located support molds, which absorb the skuxntryoket during the fermentation process and 10 15 20 30 55 40 7996850-8 symbolized here by the arrows (13).

The divided sections are limited in volume, so that within filling of the component system lasts longer than S, in this case oa 25 sec. In the part of the container where the foam reaches the last, make sure that openings to the adjacent section are in sufficient numbers and of sufficient size. Other leaks between the sections can be nas, but should have such a small hydraulic diameter that the foam leakage becomes slightly. The hydraulic diameter is determined.

In a tube with circular section and adjacent hydraulic diameters meters and a compensated length is made for the section change.

From a diagram, Fig. 5, which shows the result of a number of fermentation samples carried in a tube with three different diameters and three different temperatures, can be read to what extent the temperature conditions must be changed in order to achieve the correct density of the finished product. Possibly selected in this stage a different Frigenhalt of the system.

Through these tests, which are included in the design stage, related to the component system. Before the foaming process, electric After a production factor has changed, a fermentation is performed sample, according to Fig. 4, when the degree of overfilling Ö is determined. Within the section a, in the diagram, the space for foaming should be completely filled. b - a represents the safety margin for the foam to flow ma over to the next section or dropped. b indicates the ideal degree of filling. c indicates the fermentation, which should be prevented then in this part the density deviates and the cell walls are damaged.

As the propellant gas follows the general gas laws, the fermentation can in the section c is directly translated into mold pressure, since the temperature rise in this stage is not very large.

The determination now made is necessary to all cavities in the construction must be completed during the process and that the interior the pressure will not exceed the values for which the support molds are calculated.

Regardless of the product when skuning, requires one or a series refills, a sufficiently large outlet from this and the support mold must be occupied at the point where the foam last reaches. Fig. 5 schematically shows the process with respect to the leakage during foam filling ~ ning. This ensures that foam can flow out until the wire time T. 79oeaso-a 6 The outlet is closed at this time, whereby the mold pressure is determined. limited to a predetermined value.

The foamed unit is then allowed to stabilize to ancient times. The F or longer, whereby the molds can be loosened and disassembled.

Claims (1)

7906850-8 PATENT CLAIMS The present invention relates to an insulating foaming process which enables a continuous foam filling of small or large voids, by injecting a component system in liquid phase (polyurethane plastic) between two or more walls stiffened by support molds and which at this moment undergoes an exothermic reaction. , whereby a polymerization of the plastic and a gasification of the propellant included in the system is initiated, during which moment the injected plastic fills the cavities between the walls and flows out through occupied overfill holes, until these after a predetermined time interval or at the onset of the threading phase, is closed and the continued reaction and expansion takes place within the closed wall and mold structure, a continuous flow flow is maintained between the boundary walls. the foam is forced to fill the sub-section of the unit to which it has been added, at the same time as the foam is allowed to flow into the next sub-section of the unit through one or more openings. that foam, which flows over to adjacent sub-sections here meets foam added to this section, which is in the same liquid phase and is supplied to the unit within a maximized time. A foam from the sub-section last supplied to the unit is allowed to flow out of the unit through one or more occupied openings, which are closed after a predetermined time, determined in relation to the density of the finished vacuum and the maximum desired gas pressure during the reaction phase. The times and opening sizes for overflow of the foam are adapted to the amount of liquid injected and the threading time of the component system. The foam smoke against walls and support molds can be predetermined and minimized by determining the degree of overfilling in a free-reading test before foaming.