SU668615A3 - Method of obtaining foam-polyurethanes - Google Patents

Description

one

The invention relates to the production of polyurethane foams used as heat and sound insulating material in various industries.

A well-known and widely used foam fabrication technology is the one-stage foaming of liquid mixtures. Typical representatives of the so-called block foams obtained by this technology are polyurethane foams obtained from polyatomic alcohols with molecular weight of 250-7000 and with 2-6 hydroxyl groups or active hydrogen and organic isocyanates containing at least two free isocyanate groups, in the presence of surfactants, predominantly modified by an aliphatic side chain of silicone polymers and catalysts, it is advisable to use tertiary amines and / or coefficients eny using tin generated during the reaction of an isocyanate with carbon dioxide with water and / or another blowing agent, preferably trichlorofluoromethane. Under free foaming here

it should be understood that the surface of the reaction mixture during the foaming process can easily rise 1.

According to this technology it is possible to work both continuously and periodically. In a batch process, the reaction mixture is poured into an open form and this form is in the process of foaming.

filled with material. In continuously operating devices under a variable-motion mixing head, it is located moving at right angles to the line (direction)

variable motion conveyor belt, the first segment of which is set slightly obliquely. On the conveyor belt is mounted having a generally rectangular section and

moving together with the ribbon a cardboard box into which the reaction mixture during foaming on the first yVjacT path also flows under the force of gravity, while on the horizontal section of the path it moves along with the form.

Claims (2)

However, in the implementation of this method, it is only possible to preset the shape and size of the blocks in advance. The blocks in the horizontal plane with a periodic process of obtaining can be determined by the sizes of the forg with the continuous manufacturing process in the transverse direction, the distance between the side walls of the mold, and in the longitudinal direction the speed of movement of the conveyor and, accordingly, the removal of cutting elements from each other or their working cyc lom The height of blocks of a periodic process can be more or less precisely controlled by the amount poured into the form of the reaction mixture, and in a continuous process it can be related to the time specific amount of the reaction mixture introduced into the moving trough and / or modification of the reaction-kinematic parameters of the foaming system. In continuously operating devices, the height of the blocks can be modified while maintaining a constant amount of the reaction mixture per unit of time by varying the width of the mold or the speed of movement of the conveyor. The disadvantages associated with the deviation of the block size in height are aggravated by the fact that with the help of classical devices only blocks with a convex surface can be obtained. The resulting block blanks are subsequently processed by splitting or stripping a convex surface into plates or sheets of the desired thickness. Due to the deviation of dimensions and, accordingly, convex surfaces, when splitting, 16-18% of the foam goes to waste, and when it is removed, the convex surface is up to 32-40%, which significantly reduces the cost-effectiveness of the manufacturing process. The methods used to eliminate this drawback are based on the pattern that the formation of a convex surface with free foam substances is based on the viscous-elastic flow of materials known in the rheology: the surface of a block foamed into a cardboard mold can be treated with a good approximation picture of laminar flow enclosed in a form, rising up fluid This flow is due to the pressure differential that occurs between the pressure released from the reaction mixture of gases and ambient external pressure. When examining the acting particles of the expandable mixture of forces, it can be stated that the resultant force is caused, on the one hand, by the pressure difference between the lifting force and the opposing force of gravity and the force of friction, as well as by force air, on the other hand, determines the equilibrium state of the particles. In the process of foaming, the lift force acting on the particles is greater than the sum of the three downward forces, and the surface of the wall only ceases to rise, when the lift force and the forces opposing it are equal. In order to form a convex surface, it is decisive that the force of friction between the individual particles with each other is less than the force of friction between the wall of the skin or the wall of the form and the particles adjacent to it; Particles inside the block can therefore rise more quickly in the foaming process than particles in contact with the wall. Due to this so-called wall effect, on the one hand, the foam in the middle of the surface always rises up faster than it does along the walls, and on the other hand, the rise of the surface of the foam at the walls also ends faster. Since the gravitational force and air pressure are constant from the above mentioned forces, in previous experiments they were constantly trying to form the surface to compensate for the local dependence of the friction force by mechanical action or by mechanical means to reduce the edge effect. The closest to the technical essence of the invention is a known method for producing polyurethane foam by reacting in open form the isocyanate with a hydroxyl-containing compound in the presence of a catalyst, a blowing agent and an emulsifier. In order to form the surface, the local friction force is compensated by the use of a cardboard trough, both side walls of which are trapezoidally inclined towards each other, due to which the speed of raising the surface of the foam increases along the side walls 2. The disadvantage of this method of changing the surface of the foam is that it can can only be carried out using specially designed devices for this purpose, i.e. existing devices are not implemented. Further, it should be considered a drawback and the fact that only blocks with a smooth surface, i.e. blocks with a rectangular cross section, although the use of sections other than those mentioned above, and especially blocks with a circular cross section, is observed a constantly increasing demand. The aim of the invention is to obtain polyurethane foam of any section in any devices. This goal is achieved by the fact that when polyurethane foams are obtained by reacting, in open form, the isocyanate with a hydroxyl-containing compound in the presence of the ampli? Er. 5 of a foaming agent and an emulsifier, over the surface of the reaction mixture, perpendicular to the walls of the mold form a forced air flow causing a pressure drop of 0.03-0.15 kg / cm. A local pressure differential caused in this way can change the velocity of particles in the reaction mixture. mixture and thereby form the surface of the foam in a wide range of forms. Example 1. From toluylene diisocyanate (80:20 isomer ratio and polyether with TpexaTOMHbnvi alcohol with a molecular weight of 3,500 in the presence of tin octoate and dimethyl ethanolamine, soft polyurethane foam is obtained as a catalyst, while water is added as a foaming agent. Recipe (the ratio of components is taken up by weight); Toluene diisocyanate 38 Polyhydric alcohol 100 Water 3 Silicone emulsifier 0.75 Tin octoate 0.26 Dimethyl ethanol amine 0.30 Mixture of the indicated substances is mixed with a mixing head of a conventional blowing agent and fed in a cardboard box of a given cross section moving at a uniform speed, the mold is mounted along one side of the profile along the wall at a distance of 50 mm from both sides along one side of the profile. From the slots between the wall and the guide profile, air is sucked off a fan with a nominal capacity of 3000 m / h. Under the action of a local vacuum of 0.15 kg / s, a smooth foam surface is formed. Example 2. From toluylene diisocyanate (65:35 isomer ratio and polyether with triatomic alcohol from RnP molecules. weighing between 4200 and 5600 in the presence of tin octoate, bis- (2-dimethylaminoethyl) -ether and triethylenediamine, a soft polyurethane foam is obtained as a catalyst. Formulation (the ratio of components is taken in parts by weight): Toluene diisocyanate 34 Polyhydric alcohol 100 Water2.4 Trichlorofluoromethane8.0 Silicone emulsifier 0.40 Tin octoate 0.50 bis- (2-Dimethylaminoethyl) ether0 06 Triethylene diamine 0.06 A mixture of these substances is dosed with With the help of a mixing head of a conventional foaming agent, at a moving speed with a numbered speed, a cardboard mold of a given cross section, with one guide profile 2000 mm long each being mounted over the foam section of the mold along both sides. 15b In the gap between the surface of the foam and the guide profile, air is blown by means of a fan with a capacity of 3000 m / h. Increased pressure of 0.1 kgf / cm form a smooth surface of the foam. Example 3. From toluene diisocyanate (80:20 ratio of isomers) and ether with a trihydric alcohol with a molecular weight of from 3,500 to 4,000 in the presence of zinc octoate, dimethyl ethanolakine, a soft polyurethane foam is obtained as a catalyst, and water and trichloromethane serve as a foaming agent . Recipe (the ratio of the components is taken in parts by weight): Toluene diisocyanate 38 Polyhydric alcohol 100 Water3 Trichlorofluoromethane7.00 Silicone emulsifier 1.00 Tin octoate 0.30 Dimethyl ethanol amine 0.40 A mixture of these substances is dispensed with a mixing head of a conventional device for producing foam into the moving body with a foam device. the speed of the cardboard mold of a given cross section, while over one section of the foam of the mold along the wall on both sides, one profile is installed along a profi. 2000 mm long. Air is sucked out of the gaps between the surface of the foam and the guide profile using a fan with a nominal capacity of 3000. The resulting vacuum of 0.05 kgf / cm to form a sweat foam surface in the form of a semicircle, Example 4. From toluylene diisocyanate. (80:20 ratio of isomers) and polyether with a polyhydric alcohol with a molecular weight between 2800 and 3400 in the presence of N, N-dimethyldichexyxylamine and N-ethylmorpholine as a catalyst, a soft polyurethane foam is obtained, and mixed as a blowing agent water Recipe (the ratio of components is taken in parts by weight): Toluene diisocyanate 4.10 Polyhydric alcohol 100 Water 3.60 Silicone emulsifier 1.00 N, M-Dimethyl cyclohe. Slamin0, 30 B-Ethylmorpholi, n1.50 A mixture of the above substances is metered into a cardboard section moving at a constant speed using a mixing head of a conventional foaming device, while over the foam section of the mold along the wall at a distance of 50 mm from it on both sides, set on one 2000 ngtravlivuyu profile length. In the area between the wall and the guide profile with a fan. With a capacity of 3000 MV, BsuoT air is pumped out. The resulting vacuum of 0.03 kgf / cm forms the surface of the foam in the shape of a semicircle. The properties of polyurethane foams obtained according to examples 1-4 are shown below. Physical and mechanical properties Bulk density, kgf / m 25-40 Tensile strength for a minimum, kgf / cm 20.9 Tensile strength, minimum, kgf / cm 0.2 Degree minimum stretch% 120 Elasticity% 35-55 Residual strain, maximum% 10 Specificity of cage, cells / cm18 Thus, the advantage of the proposed method is that it can be used with any existing classical device with any molding tool by simple operations. The method is also suitable for producing blocks with a circular cross section; it also allows the density of the blocks to be adjusted. During the subsequent processing of the resulting block or semicircular profiles, the waste is reduced by 6–8% or 5–10%, respectively, in comparison with those obtained by known methods. Another advantage of the method is that the gases that are harmful to health and that are generated and released during the implementation of the method, such as carbon dioxide, trichlorofluoromethane and others, are diluted with forced circulating air and their concentrations are reduced. Claims method of producing polyurethane foams by reacting in an open form an isocyanate with a hydroxyl-containing compound in the presence of a catalyst, a foaming agent and an emulsifier, characterized in that, in order to obtain polyurethane foams of any cross section in any devices, a perpendicular bounding walls of the form create a forced flow over the surface of the reaction mixture air, causing a pressure drop of 0.03-0.15 kg / cm. Sources of information taken into account during the examination 1. US patent number 3509077, cl . 260-2.5, 1970. 2. The patent of Australia No. 428451, cl. 09.4-79, 1973.