RU2731930C1 - Method of manufacturing shaped articles with base from foamed polymers - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: disclosed is a method of making a shaped article used as a bearing and self-supporting structures for door and window frames, transoms, other structures, requiring a combination of sufficient strength properties and low heat capacity. Profile article is made by moulding in mould in layer-by-layer, using denser foamed or non-foamable layer as product shell and foaming base from at least one layer or with combination of layers with different density, which provides required combination of strength and low heat capacity. Base material used is foamed polymer, composite materials or non-foaming polymer and composite materials in combination with bulk-forming additives - microspheres. Strength characteristics of the article are ensured by the presence of modifying components introduced into polymer media - nanoadditives, carbon microadditives, aluminosilicate microadditives providing strong bonds with conglomerates of polymer macromolecules, as well as treatment of polymer components with a high-frequency electromagnetic field immediately before their introduction into the mould. Processing of components with a microwave field increases the binding energy of monomers of the polymer composition during polymerisation, and promotes a much higher-quality distribution of micro- and nanoadditives in the volume of the medium, which significantly increases strength of the article, density distribution in mass, and significantly speeds up the polymerisation process, providing process efficiency and its industrial application. Protective layer is non-foaming polymer composition applied by spraying on inner surface of mould, any materials and decorating elements built into the mould before the polymer media forming the product base, or additionally applied on the surface.

EFFECT: article obtained from polymers using said method corresponds to environmental standards, has a long service life, is resistant to atmospheric effects, ultraviolet radiation.

5 cl, 3 dwg

Description

The present invention relates to the field of construction, in particular to the production of translucent enclosing structures - window frames, door leaves, profiles, elements for closing openings, fixed or movable covering elements, parts of rigidly fixed external frames associated with the installation of sashes and other building elements.

The currently widely used technologies for the manufacture of translucent enclosing structures based on wood or PVC with a metal internal reinforcement have a number of disadvantages, such as: fragility for wooden structures, a high level of thermal deformation for both technologies, a high degree of thermal conductivity in PVC profiles, the presence of harmful products such as natural decomposition of PVC and its thermal decomposition, low level of UV resistance. In addition to PVC and wood, windows and doors are also made of fiberglass by pultrusion, but despite a number of excellent properties compared to PVC and wood, they have a very high cost, as well as complex and expensive production technology and technological limitations associated with the peculiarity of production ...

Profiles consisting of metal, usually aluminum and its alloys, have an extremely high heat capacity and can only be used indoors or in mild climatic conditions. There are combined solutions that combine the use of various materials, such as aluminum-wood, aluminum-polyurethane foam, but all of them have the disadvantage of a different coefficient of thermal expansion of materials and a gradual destruction of the bond between materials with the accumulation of moisture in the internal cavities and deterioration of design and user properties.

From the general level of existing technologies, several methods are known for producing structures from polymeric foam used in construction, in particular in the form of enclosing structures, all technologies boil down to the fact that a relatively weak polymer layer in strength is reinforced by rigid plastic or metal linings. The author knows such methods of forming bodies of solid and translucent enclosing structures, such as external reinforcement with steel, aluminum profiles, and rigid types of plastics such as PVC. In all cases, there is a problem, which is difficult to solve today, between different composite materials with different coefficients of thermal expansion, poor adhesion, different levels of hygroscopicity and chemical incompatibility. Methods for solving the problem of excluding delamination are usually reduced to the introduction of intermediate layers with high plasticity and adhesion.

Under the profile products, in this application, products with a complex cross-sectional shape are accepted, the area of which is significantly less than the surface area of the product, taking into account its length. These are elements of frames and transoms of translucent enclosing structures - windows, doors with translucent inserts, other shaped products with self-supporting and bearing properties. The main engineering task in the construction of such shaped products is to ensure a high load, structural capacity at a low heat capacity. The profile must have strength in the body and along the surface, sufficient to ensure reliable fastening of fittings fasteners in it with a long service life under dynamic loads, the surface must be strong enough, protected from mechanical and thermal effects, ultraviolet radiation. The product as a whole must have a long service life without changing its mechanical and consumer properties.

Of particular importance for the industrial production of products is the reproducibility of shapes, the speed and complexity of production processes. The main disadvantage of the use of expandable polymers in serial industrial production is the low polymerization rate, especially for foamed polymers based on composite resins, and therefore requires a long residence time of the product in the mold to achieve stable geometric parameters.

The aim of the invention is to develop a method for the production of shaped products, including methods for increasing the strength of the material and methods for accelerating technological processes.

Foamed rigid closed-cell polymers obtained in the process of polymerization with the participation of a polymerization reaction combined with a chemical reaction accompanied by gas evolution were chosen as the main material of the profile product. The main available materials that meet the requirements of the method at the time of filing are rigid polyurethane, polyisocyanurate foam (PIR, PIR), epoxy resins with foaming reagents. These foams have a very low heat capacity and high stability of physical parameters during operation, do not emit harmful substances during natural decomposition. However, the structural strength of the starting material, as a rule, is insufficient for the production of load-bearing products from it, especially for polyurethane foams with low bulk density, and a number of solutions are used to increase the structural strength:

- external and internal mechanical reinforcement with mineral or polymer fibers, fiber, glass or basalt fibers, reinforcing mats, fabric and non-woven materials impregnated with non-expandable base material, or chemically compatible polymers;

- the use of internal reinforcement with fibromaterials - threads of mineral and synthetic origin, connecting the body of the profile with a uniform distribution in its mass. Such reinforcement makes it possible to increase the tensile and bending strength of products;

- the use of non-modifying reinforcing and volume-forming additives - fillers that do not affect or only slightly affect the intermolecular bonds of the main material of the profile, but change its physical properties - impact strength, heat capacity, fire resistance, chemical resistance and resistance to high-temperature exposure and ultraviolet radiation. These are mineral and synthetic microspheres that increase their volume along with an increase in impact strength and a decrease in heat capacity, talc and finely dispersed mineral fillers, flame retardants, dyes;

- the use of modifying additives that significantly affect the intermolecular bonds of the main material of the profile. These are micro and nanoadditives that have a fairly distributed active surface of the particles, participating in intermolecular bonds between conglomerates of polymer macromolecules and significantly changing the strength properties of the material.

The patent of the author of this application, DA Hristova, No. RU 2620486 C1 dated 11/30/2015, describes the effect of nanomaterials on the strength of the polymer matrix and their use for the manufacture of window and door structures from foamed polymers of sufficient strength. The author proposes as micro and nanomaterials carbon separated powders with small grains, within 5-50 nanometers, carbon nanofibers (CNFs) and nanotubes (multi-walled (MWNTs), thin (SDNTs) and single-walled (SWNTs), the length of which can be hundreds of nanometers , nanoplates based on organoclay, (MMT), having high relative surface area to volume, significant length and longitudinal strength, which allows you to bind more areas of polymer conglomerates;

Polymers modified and reinforced with non-modifying additives have significantly better strength properties, sufficient for their use as a base for load-bearing profiles. Particularly loaded areas subject to increased dynamic loads can be reinforced with external and internal reinforcement. The complex application of additives can bring the strength parameters of the product material to the parameters corresponding to dense wood species, while the foam polymer material favorably differs in lower heat capacity, high chemical and biological resistance, lack of hygroscopicity and a long service life without changing the physical and geometric parameters.

The only limitation on the use of foamed polymers in the production of complex-shaped structures is the low polymerization rate. If for polyurethane foam this parameter is not critical, since existing materials are capable of polymerizing within a few minutes, then for foam composites based on epoxy resins, the polymerization period of tens of minutes significantly limits the area of their industrial application.

From the general prior art, it is known that there is a method for accelerating the process of polymerization of polymeric materials, based on exposure of the polymerizable material to electromagnetic radiation of ultra-high frequency (microwave). Short-term exposure to a field, especially of a pulsed nature, causes polarization of the polymer dipoles and a significantly better distribution of agglomerates in the mass of the substance. The energy of interaction of electron pairs increases, the rate of the polymerization reaction multiplies. Along with the acceleration of the process, due to the more dense distribution of the reagents in the mass, the strength of the structure increases. The curing speed, for example, of ED20 epoxy resin is 2 minutes versus 20 minutes under the same temperature conditions. Moreover, its strength increases up to 4 times, heat resistance 1.6 times.

The second positive result of the effect of microwave radiation on the material is a significant improvement in the distribution in the mass of additives based on carbon materials - micro and nano additives. Possessing a high absorptive capacity, the particles accumulate energy and receive a charge, which leads to a more uniform distribution of them in the polymer body and, consequently, to a more even binding of polymer conglomerates. Treated by microwave radiation, the expandable polymer has strength properties that are several times higher than the properties of untreated polymer foam. An increase in the strength of the polymer material after treatment with a microwave field is due to a more acute crystallization phase and a more complete distribution of interacting oligomers participating in the reaction. The technology works equally efficiently both with compounds - epoxy resins, and with two-component polyurethane group materials, including polyisocyanurate foam (PIR). PIR forms a more durable environment than polyurethane foam due to a high-temperature reaction in which excess isocyanurate monomers bind, forming strong long alloy bonds. The effect of microwave radiation on the material immediately before the entry of its components into the reaction significantly accelerates the process of polymerization of both polyol-isocyanate groups and isocyanate-isocyanate groups.

As a result, the processing of the polymer by the microwave electromagnetic field immediately before introduction into the mold has a positive effect on three factors - acceleration of the polymerization reaction, enhancement of the strength properties of the foam directly and improvement of the distribution of micro and nano-additives based on carbon materials in the polymer mass, which significantly improves the strength characteristics of the product. ...

The essence of the method is the sequence of the following operations:

1. Preparation of the mold. The mold, made of a material that provides no or low adhesion to the polymeric materials used, is, if necessary, covered with a layer of a neutral separator. The method allows the use of a ready-made protective or decorating layer made in advance of polymer, polymer-composite materials, metals, ceramics, wood, glass, which is a solid contour layer or a partial insert into the product. Such a security element is placed in a mold and fixed in it by means of a vacuum or other holding system. Also, fasteners, fittings, external or built-in elements, stiffeners, profiles or decorating inserts, reinforcing mats, are introduced into the mold in advance.

2. Preparation of substances - reagents participating in the polymerization process with the introduction of non-modifying and modifying additives required by technical conditions. Metered components of the medium, which forms a certain layer of the product, are sequentially fed into the mixer. Mineral or polymer fibers, fiber, glass or basalt fibers, required according to technical conditions, are added to the component of the mixture and thoroughly mixed using mechanical and ultrasonic technologies. For the layer that forms the outer hard coating, a polymer composition without a foaming agent is used; for subsequent layers, the volume of foaming is determined either by the compositions of reagents for polyurethane foams, or by the volume of the added reagent - a foaming agent for composite resins. To regulate the plastic properties of the media, chemical reagents are used - plasticizers. When used as a base composition of a non-expandable polymer with bulk forming additives, such a composition is formed on the basis of one of the constituent components, followed by the addition of the second component immediately before being introduced into the mold. As a bulking agent in both foamable and non-foamable compositions, the method involves the use of aluminosilicate ash microspheres with a modified surface. The introduction of 15% ash microspheres not only increases the volume, but also reduces the cost up to 30%, the heat capacity, moisture absorption of the product up to 5 times, and increases its strength up to 2 times.

As a fire retardant, the method involves the use of composition 10/1 Intercalated graphite + melamine cyanurate in a mass volume up to 20% by weight of the base. This ratio of graphite to fire retardant achieves both the maximum compressive strength of the material in combination with optimal resistance to high temperatures. When exposed to high temperatures, intercalated graphite swells and blocks its further penetration into the depth of the material, and the flame retardant melamine cyanurate binds the easily destructible crust of expanded graphite, protecting it from destruction. In addition to the boost modifier property, i.e. a binder for the macromolecular structure of the polymer, the fire retardant composition makes the material self-extinguishing in the presence of a combustion source while maintaining its structural shape, which is important from the point of view of safety when used as load-bearing glazed elements.

3. Impact on the reagents of the electromagnetic field at the mixing stage by passing through the waveguide under pressure for a time period determined by the technical conditions. The power and time of exposure determines the rate of the crystallization and polymerization phases of the media. Depending on the materials used and the speed of reaction to the microwave action, separate processing by the microwave field of both components is used, followed by mixing directly in the sputtering unit. This scheme is relevant for materials with a high reaction rate.

4. Introduction or spraying of a mixture of reagents on the inner surface of the mold or on the previous layer at the stage of its expansion until the end of the polymerization stage. Compliance with the conditions of the cross phases of crystallization and polymerization ensures maximum intermedia adhesion and subsequent solidity of the product during sequential application of media with variable density parameters.

Particularly loaded sections of the product can be additionally reinforced with fabric and non-woven mats impregnated with a non-foaming polymer base material, laid out on the walls of the mold before the process of filling it begins. The time of the final polymerization of the impregnation of the mats is calculated so that it ends after filling the mold and approximately corresponds to the moment of the final polymerization of the surrounding medium. In this way, the mats are firmly integrated into the body of the product with the greatest possible inter-media adhesion.

Intermedium adhesion is also ensured by the natural pressure of expanding media in the closed space of the mold. The volume of the supplied media and the degree of expansion are calculated so that the pressure of the volume of expanding gases during foaming is moderate, does not affect the integrity of the geometry of the mold in the process of pneumatic impact and, subsequently, the strength and geometry of the product as a whole.

Depending on the technical conditions, the product can be made with the formation of an outer coating directly in the mold as a hard, non-foaming layer, with a repetition of the decorative texture applied to the walls of the mold, or using laminating inserts and films applied to the inner surface of the mold before filling it out.

Likewise, the external decorating and reinforcing coating can be applied to the finished product by glue or in any other way, which ensures reliable fixation. These can be decorative plastic and metal linings, fire-resistant and vandal-resistant coatings. Also, as a topcoat, depending on the design, you can use the following materials: paintwork materials (various enamels and varnishes), paint, gelcoat or laminating films. The surface of the product obtained by pressing has a high quality and completely repeats the texture of the coating of the mold. At this stage, only the processing of the product is required to remove the remnants of the separator - a substance applied to the surface of the mold to reliably separate the finished product from it. At the same time, the surface of the product is already a self-sufficient finishing coating, which provides a long product protection period and sufficient strength.

A significant acceleration of the polymerization process as a result of exposure to microwave frequencies makes it possible to significantly accelerate the production process of products, to achieve durability and uniformity of filling complex geometrical shapes with foamed media in the required proportions, which is difficult to achieve under normal polymerization conditions. For example, with the natural flow of foamed polymer from vertical sections of the mold, previously it was necessary to take measures for its constant or periodic rotation, which negatively affects the solidity of the medium during polymerization.

The rapid formation of layers, regardless of the position of the layer, makes it possible to consistently form a complex structure of layers with different density parameters, to form a reinforcing layer of high density (structural core) inside the product, which determines the structural strength and does not affect the heat capacity of the product.

The structure of the technological process of the method for manufacturing a shaped article with a foam polymer base is shown in FIG. 1, which schematically shows:

1 - preparation of reagents - components of a polymer or polymer-composite mixture;

2 - adding modifying and non-modifying additives to the components of the mixture;

3 - component mixing device;

4 - a waveguide and a device for pumping the mixture for adjusting the time of processing the microwave with an electromagnetic field;

5 - mold;

6 - an internal overlay in the mold, which forms an external decorative coating of the product;

7 - an external fastening element integrated into the product, fixed in a mold;

8 - sprayer of polymer composition (medium).

The stages of filling the mold with media of different densities are shown in FIG. 2, which schematically shows:

5 - mold;

8 - sprayer of the polymer composition (medium);

9 - layer of high-density polymer composition (medium) without foaming agent;

10 - layer of polymer composition (medium) with high density foaming;

11 - layer of polymer composition (medium) with low density foaming;

12 - layer of polymer composition (medium) with increased density foaming to form a structural core.

The process of forming layers in the process of volumetric expansion of the media is shown in FIG. 3, which is a diagram A, B, C. D, E, which schematically shows the cross section of the product profile, the sequence of the introduction of media and the stages of their expansion with the formation of layers with different density parameters:

5 - a mold, shown in section;

9 - layer of high-density polymer composition (medium) without foaming agent;

10 - layer of polymer composition (medium) with high density foaming;

11 - layer of polymer composition (medium) with low density foaming;

12 - layer of polymer composition (medium) with high density foaming;

13 - an increase in the volume of the medium from the moment it is applied to the moment the subsequent medium is applied to its surface.

Diagram A shows the stage of application of layer 9 with medium without foaming agent. The layer is not subject to volumetric expansion.

Diagram B shows the stage of application of the layer 10 with a high density, which, in combination with the outer layer 9, provides a high surface strength of the product, the load capacity when fastening the fittings, but at the same time has a relatively low heat capacity.

Diagram B shows an intermediate stage of volumetric expansion of layer 10, in which a low-density medium is applied to the surface of layer 10 - layer 11. The expansion of layer 10 continues along with the expansion of layer 11, there is an enhanced adhesion of chemically homogeneous media differing only in the volume of the foaming agent. At this stage, the polymerization process in media 9 and 10 is active, in medium 11 it is at its initial stage.

Diagram D shows the stage of introduction of the medium 12 of high density on the surface of the medium 11, which is in the stage of expansion together with the medium 10, in the medium 12 the process of foaming and polymerization begins.

Diagram E shows the final expansion phase of all expandable media with filling the mold with a slight overpressure to ensure a high degree of intermedia adhesion.

The result of the invention is a significant increase in the economic efficiency of the production of translucent enclosing structures - windows and doors, their structural elements, finishing materials, other building structures for both mass and individual purposes. It was possible to achieve a radical reduction in the weight of such structures, ensuring a reduction in the total load on the supporting structures of buildings. The technology made it possible to achieve the estimated operating time of products up to 50 years or more, to ensure the absence of emissions of harmful substances both during the natural decomposition of the substances used and in the case of thermal exposure. The fire safety of the structure has been significantly increased - composite materials using fiberglass or carbon fiber as reinforcement are highly resistant to open fire, solid polystyrene foam with the use of standard safe additives has self-extinguishing properties. The technology assumes an extremely low level of production wastes and recycling of residual materials, the safety of natural waste decomposition during standard disposal at solid waste landfills.

Technology advantages.

The claimed method has a clear advantage over the widely used technology for the production of PVC profile windows. Previously inaccessible high degree of product safety, durability, high mechanical characteristics, stability of the material used, low cost and high production variability make this technology promising both in industrial and small-scale production. When operating products at low temperatures, condensation is completely absent on their surface, the development of microorganisms and fungus is excluded. The products have an extremely high level of sound absorption.

Disadvantages of technology.

When organizing production, the modernization of existing facilities is required, and adequate ventilation is provided. The stage of polymerization of thermosetting polymers requires increased attention to ventilation and cleanliness of industrial premises. Microwave equipment has an increased level of danger of electromagnetic radiation, it is required to comply with measures for screening radiation and protecting service personnel.

Production test result.

This technology has been successfully tested at production facilities both in terms of obtaining single complex products, and in creating a technology for mass - in-line - production of structural elements for the subsequent formation of final products. The high speed of forming products in molds, low cost and high consumer properties have been confirmed, which makes it possible to consider the technology used in production to be in high demand on the market.

Claims (5)

1. A method of manufacturing a profile product with a base made of foamed polymers, characterized in that it comprises sequential formation of base layers in a mold, comprising at least one protective layer, at least one layer of a foamable polymer or polymer-composite material, while modification of polymer and polymer-composite materials can be performed by exposure to an electromagnetic field of ultrahigh frequency and nanoadditives. 2. A method of manufacturing a shaped product according to claim 1, characterized in that the protective layer can be made of a number of materials, such as polymer material, polymer-composite material, metal, ceramics, wood, glass, which is a solid contour layer, or partial insertion into the product. 3. A method for manufacturing a shaped product according to claim 1, characterized in that fasteners, fittings, external or built-in elements, stiffeners, profiles or decorating inserts, reinforcing mats are introduced into the mold before the layers are formed. 4. A method for manufacturing a shaped article according to claim 1, characterized in that the base of the article made of a foamed polymer or polymer-composite material can be formed from layers with different densities. 5. A method for manufacturing a shaped article according to claim 1, characterized in that polymer and polymer-composite materials can be modified by the inclusion of such additives as mineral or polymer fibers, fiber, glass, basalt fibers, fabrics, mats.

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