RU2764438C1 - Water-dispersion adhesive system - Google Patents

Abstract

FIELD: chemical industry.SUBSTANCE: invention relates to the chemical industry, namely to adhesive compositions, specifically to water-dispersion adhesive systems with specified properties intended for gluing wood in the production of glued beams, window blocks, doors, wooden formwork, countertops, garden furniture, furniture panel. The water-dispersion adhesive system based on polymer-isocyanate emulsion (EPI) includes a polymer composition as an adhesive and a polyisocyanate hardener of the MDI type, while a multifunctional additive, the main component of which is an anion-active surfactant, is additionally introduced into the adhesive, main components of which are an aqueous polymer dispersion, a mineral filler.EFFECT: creation of a high-quality water-dispersion adhesive system that meets requirements of domestic regulatory documentation in the field of its application, suitable for use on standard equipment.3 cl, 9 dwg, 1 tbl

Description

The invention relates to the chemical industry, namely to adhesive compositions, specifically to water-dispersion adhesive systems with desired properties, designed for gluing wood in the production of glued beams, window blocks, doors, wooden formwork, countertops, garden furniture, furniture panels.

The bonding of solid wood parts is becoming increasingly important due to the increasing consumer demand for products made using such parts, such as glued laminated lumber.

The manufacture of glued laminated timber is a complex process that includes chemical, mechanical, and thermal processing of wood. The quality of the finished product will largely be determined by the quality of the wood used, as well as the right choice of glue.

Adhesives, depending on the strength, including long-term, and resistance are classified as I, II or III type. Classification of types of adhesives is carried out according to the resin component and the method of application

In the manufacture of KDK (glued wooden structures), the following types of adhesives are used:

Types I and II: Phenol-formaldehyde (FF) adhesives: Two-component adhesives based on phenol-formaldehyde resins cured with acid hardeners.

Phenolic-resorcinol-formaldehyde (FFR) adhesives: Two-component adhesives based on phenol-resorcinol-formaldehyde resins, cured with alkaline hardeners.

Aminoplastic adhesives (AP): Two-component adhesives consisting of resins based on aminoplastics (melamine-formaldehyde, urea-melamine-formaldehyde) and fillers (plasticizers), cured with acid hardeners. Use is carried out both with preliminary mixing of components, and separate application.

Disadvantages of adhesives: rather high price, low curing speed, high toxicity.

Phenol-formaldehyde glue gives a dark glue line, there is a risk of acid damage to wood fibers, some brands of glue require drying after application. Phenolic resins are mainly used for the production of hot-rolled water-resistant plywood, as well as for the impregnation of veneer in the production of baked plywood and wood-laminated plastics. The presence of a toxic component in urea-formaldehyde resins - free formaldehyde, significant shrinkage, poor gap filling and increased corrosion hazard of adhesives are also their main disadvantages. These shortcomings determine the area of application of the corresponding glued products - only in indoor or weather-protected conditions. Examples of phenol-formaldehyde adhesives are described in patents RU 2534549, RU 2447118, RU 2451708, US 4480055, CN 1974625, EP 1448741

Type III adhesives include one-component polyurethane adhesives, and adhesives based on polymer-isocyanate emulsion (EPI)

Polyurethane adhesives, for example RU 2726232, RU 2663779, US 6284836, SU 718472 are adhesives obtained by mixing components, one of which contains isocyanate groups, as well as one-component adhesives. In terms of performance, they are close to EPI systems, but there are a number of differences. Application requires special equipment.

Adhesives based on polymer-isocyanate emulsion (EPI). The use of adhesive EPI systems allows solving many environmental problems of finished adhesive structures, such as the absence of formaldehyde emission and other harmful volatile substances. Also, the advantages of adhesives of this type include a wide temperature range at which gluing is carried out, a short pressing time, and the possibility of gluing wood with a moisture content of up to 15%. The glue does not stain the wood. The resulting adhesive seam is stable under variable temperature and humidity effects.

A review of patent information at the moment did not show the existence of valid patents for adhesives of this type in the territory of the Russian Federation.

Adhesive EPI systems are a relatively new phenomenon on the Russian market. This technology came to Europe and then to Russia from Japan. In addition to Japanese JAS standards, European EN standards have been developed. In connection with the growing interest in this type of adhesives in the Russian Federation, GOSTs are also being developed based on the generalization and adaptation of the requirements of European and Japanese standards.

As mentioned above, EPI adhesives are free from many of the disadvantages of formaldehyde and polyurethane adhesives, they are environmentally friendly and safe. Currently, EPI systems are represented on the domestic market by most European manufacturers. Russian manufacturing companies are still represented in a fairly small number and are just beginning to enter the market. Therefore, the importance of improving and bringing domestic drugs to the level of European ones is extremely important.

The principle of obtaining an adhesive composition is based on the production of a high-quality polyisocyanate emulsion, where the polymer composition acts as an emulsifier (and an additional film former in the formation of the adhesive seam).

For all two-component adhesives, the problem of phase separation / obtaining a high-quality stable mixture of components is relevant. The process of improving the miscibility characteristics can be carried out both by chemical modification of the components or optimization of mixing modes, and by introducing surfactants. Each of the possible methods has disadvantages associated with a decrease in the shelf life of components, the migration of surfactants, and the use of complex mixing equipment.

Known composition of glue for wood (RU 2618224, C08G 18/40). The invention relates to a compound for the production of glue, to a composition for the preparation of glue and to a method for producing the same, as well as to a lignocellulosic material obtained using said compound or composition. This connection consists of two components. The first component is derived from at least one isocyanate and at least one amino resin. Said amino resin is a condensation product of an aldehyde with a compound selected from urea, melamine and mixtures thereof. The second component includes at least one polyether containing at least one ethylene oxide unit and at least one hydroxyl group capable of reacting with isocyanate. This composition has a significantly increased miscibility relative to adhesives of this group. The solution of the problem in this case was carried out by creating hybrid adhesive systems (the introduction of polyether into the system).

Currently, most Russian enterprises use EPI (EPI) systems of foreign production (AkzoNobel, Dynea, Kiilto, Jowat, etc.). The ratio of polymer and polyisocyanate components in most cases corresponds to 100:15

Known adhesive systems company AkzoNobel (Netherlands) represented by a wide range of adhesives and hardeners. Adhesives differ from each other in the initial viscosity in the range from 2000 to 17000 mPa * s, and the finished adhesive mixtures in the conditional working pot life in the range from 40 to 120 minutes. Conforms to the JAS 523 standard. Other manufacturers produce several, more often one brand of adhesive and the corresponding hardener.

Glue systems Dynea (Norway/Germany) produce - BINDAN-EPI - a two-component adhesive based on an emulsion polymer and an isocyanate hardener. BINDAN-EPI complies with the requirements of the Japanese standard JISK 6806. The pot life of the mixture is 60 minutes (at 20°C), the adhesive viscosity is from 5000 to 7000 mPa*s.

Domestic EPI-adhesives are also known, for example, from Himtekh-N N-glue Viar-D4.1 LLC, which meets the requirements of GOST 24700-99, GOST 15613-1-84 for adhesives of increased water resistance, GOST 17005-82, GOST 11047-90, EN 204 (class D4), ONORMB3013 (for window timber) and JAS 234 (for load-bearing structures).

As a prototype, we take two-component adhesives from European manufacturers (for example, DyneaHolzleimeGmbH (Germany), AkzoNobel (Sweden), Klebchemie (Germany), Japanese Oshika, AICA), in which the hardener is selected from the MDI-type polyisocyanates on the market. (https://lesprominform.ru/jarticles.html?id=3409), Art. M. Tarasenko, Adhesives in the production of DCC, J. LesPromInform, No. 8(98), 2013

The first adhesive component (adhesive) is a composition based on polyvinyl acetate, copolymers of vinyl acetate with acrylate, styrene, ethylene or copolymers of acrylic acid esters. The composition may include a mineral filler in an amount of up to 40% by weight.

The second component of the adhesive is Methylene Diphenyl Diisocyanate (MDI), which is a yellow to brown liquid.

After mixing, the components of the system enter into a chemical reaction with each other: the isocyanate groups of the hardener react with the functional groups of the polymers in the adhesive and with water to form a complex polymer containing, among other things, polyurea and polyurethane fragments of the polymer chain.

The disadvantage is the insufficient uniformity of the application of glue during gluing and insufficient quality emulsification.

The technical result of the invention is to improve the quality of the emulsification of the water-dispersion adhesive system and ensure the uniformity of its application to the bonded material.

The objective of the invention is to create a high-quality water-dispersion adhesive system that meets the requirements of domestic regulatory documentation in the field of its application, suitable for use on standard equipment.

The problem is solved by the fact that in the well-known adhesive system, represented by a two-component adhesive based on a polymer-isocyanate emulsion (EPI), where the polymer composition (adhesive) - liquid and the polyisocyanate hardener of the MDI type - liquid act as components of the system, a polyfunctional additive is introduced, and also selected the optimal composition of the remaining components of the adhesive, which determines the properties of the adhesive and makes it suitable for use on most typical equipment.

The main substances in the composition of the adhesive are water, mineral filler, polymer dispersion. The system is distinguished by the introduction of a multifunctional additive, the main component of which is an anionic surfactant, in the following ratio of components, wt.h:

Polymer-isocyanate emulsion (EPI) 100 wt. hours, of which:

Aqueous polymer dispersion - 30-60 wt. h.

Mineral filler - 0-40 wt. h

Polyfunctional additive - 0.5-5 wt. h.

Technological additives (other) < 1 wt. h., and

Hardener MDI - 15 wt. h.

As an aqueous dispersion of the polymer, both polyvinyl acetate dispersions and dispersions of vinyl acetate copolymers can be used, the latter showing comparatively better results when testing finished adhesive systems in terms of the strength of the adhesive line.

As a mineral additive, it is preferable to use finely dispersed carbonate fillers. The use of such additives helps to reduce the shrinkage of the glue line, filling the uneven gouging.

A multifunctional additive, the main component of which is an anionic surfactant, affects many of the functional features of the adhesive, in addition to facilitating the mixing of the components, it improves the wetting of the substrate (works as a filling regulator), the systemic fluidity of the adhesive, and facilitates the process of application to contaminated hydrophobic substances (including resins) surfaces.

When mixing EPI-glue components that differ from each other in density and viscosity, the homogenization of the mixture may be unsatisfactory, and the required uniformity and dispersion of the emulsion is not achieved. In addition, resinous and other substances contained in wood can make it difficult to apply glue to the surface, preventing uniform wetting. All these factors lead to a decrease in the strength of the adhesive joint or non-gluing. In addition, taking into account the fact that during the curing of the adhesive there is a chemical process in which all components of the system interact, the additive should provide stability and help control the main technological parameters: the gelatinization time of the mixture (conditional working pot life), the viscosity of the mixture during application, etc. .P.

Other functional additives include biocide, defoamer, and dispersant additives.

The hardener is a polyisocyanate of the MDI type, which is the safest of the entire range of polyisocyanates, since it is almost non-volatile and partially polymerized.

Thus, the novelty lies in the selection of types of polymer dispersion, mineral filler, their quantitative ratio in the composition of the adhesive, as well as the selection of technological additives, including additives that provide optimal homogenization of the mixture components to obtain a high-quality emulsion, and also determine the quality of applying the mixture to the glued surfaces.

The choice of values for the physical and mechanical properties of the adhesive, as well as its activity, which determines its performance characteristics (viscosity of the mixture, "conditional working pot life", fluidity, etc.), was carried out on the basis of an analysis of currently available products on the market and taking into account the wishes of consumers . The established physical and mechanical properties of the adhesive meet the requirements of most industries.

The curing of the adhesive occurs due to a chemical reaction between the adhesive and the hardener, as well as with the wood due to the moisture contained in it, which further strengthens the adhesive bond.

The adhesive may only be used within its "working viability", as a chemical process takes place in its volume. During the reaction, the viscosity of the mixture increases and its volume increases due to the release of carbon dioxide and foaming. The process of gelatinization of the mixture quite well reflects the kinetics of the curing process and its dynamics is important for understanding the processes that occur in the mixture of isocyanate and emulsifying agent. The gelatinization time of the mixture for most systems is about 40 minutes (i.e. the glue sets quite quickly). Several factors influence the gelatinization time: the introduction of a polyfunctional additive in an amount of 0.5-1% by weight of the adhesive does not significantly affect the viscosity of the adhesive itself, but significantly affects the viscosity of the mixture.

The viscosity of the mixture is an important technological parameter, on which the convenience of applying the mixture depends, and in the case of a machine method, the very possibility of application. When mixing the components, the viscosity of the mixture increases. When the viscosity of the mixture reaches 25,000 mPa*s, the mixture is considered unsuitable for further use, since the reaction process has already passed.

The "conditional working pot life" of the system is the period of time in which the viscosity of the mixture is less than 25,000 mPa * s. For convenience of work, this indicator should not be less than 10 minutes, but it should not exceed 1-2 hours to save time during which KDK (glued wooden structures) are kept under load. During pressing, the adhesive should "grab" sufficiently. It should be noted that wood moisture above 15% slows down the curing process of the adhesive. The maximum difference in humidity between two adjacent glued lamellas in the production of glued laminated timber should be no more than 4%.

The use of a water-dispersion adhesive system is carried out as follows:

The preparation of the adhesive is carried out by mixing its components in the specified proportion: for 100 mass parts of the adhesive - 13-15 mass parts of the polyisocyanate hardener. Mixing is carried out immediately before using the adhesive, since the viability of the mixture is limited. The mixing process can be carried out both manually and with the help of mechanical devices, including as part of automated glue application plants.

Glue application is carried out using manual glue applicators or automatic application lines. Glue is applied to one of the surfaces to be glued. When gluing hardwoods, double-sided application is possible. The consumption of the adhesive mixture is from 200 to 300 g/m ² depending on the type of application equipment.

Bonding must be carried out during the "pot life" of the adhesive mixture. A full set of strength properties of the adhesive joint is achieved in 7-10 days.

The conducted studies made it possible to reveal the regularities of the influence of both the universal additive and the general ratio of components, which in the future will expand the range of EPI-adhesives to provide all the necessary technological parameters used in different types of industries.

Examples:

For a better understanding of the invention, the examples are illustrated by the following illustrations, where:

Fig. 1 - Graph of the dynamics of the increase in the viscosity of the adhesive system, depending on the content of the additive;

Fig. 2 - The surface of the wood before applying the adhesive layer;

Fig. 3 - Adhesive layer of the EPI-system of the basic recipe;

Fig. 4 - The surface of the wood before applying the adhesive layer;

Fig. 5 - Adhesive layer of EPI-system Umacoll 552/024;

Fig. 6 - Fragment of the KDK (glued wooden structure) after testing to determine the indicator of the total delamination of the glue line;

Fig. 7 - The surface of the wood after opening the glue joints;

Fig. 8 - Change in the volume of the adhesive mixture over time

Fig. 9 - Penetration of the adhesive mixture through wood defects (knot).

In the accompanying illustrations, examples of the applied adhesive layer of the base recipe (figs. 2 and 3) and Umacoll 552/024 (figs. 4 and 5). It is clear that the adhesive system Umacoll 552/024, containing a multifunctional additive, provides a much more uniform application. In addition, it provides penetration into knots, preventing them from falling out, and fills the glue line completely, including irregularities and minor surface defects, ensures high-quality gluing of resinous areas.

In FIG. 6 shows a fragment of the FTC after testing to determine the overall delamination of the adhesive joint. The wood after the test, which consists in impregnating the sample with water under excess pressure and subsequent drying, noticeably undergoes cracking, while the strength of the glue line is comparable to the strength of the wood itself. It should be noted that the areas of the glue line adjacent directly to the resinous surfaces remained intact, which indicates a high quality of gluing.

In FIG. 7 shows the adhesive seams of this sample after opening (split). Most of the destruction goes through the material (wood), despite its very high resin content.

The dynamics of the increase in the viscosity of the adhesive system with an additive in the amount of 0.7% (Umacoll 552/024) and without additive (basic recipe) is shown in Fig. one.

It is noticeable that the adhesive system made using a multifunctional additive has a shorter curing time.

In FIG. 8 shows how, over time, the volume of the adhesive mixture increases as a result of the reaction proceeding with the release of carbon dioxide.

In FIG. 9 shows that the glue applied to the surface of the wood in the knot area penetrates into the pores, passing under pressure even through. Properties of the glue line: first of all, the strength of the glue joint is evaluated after exposure to various factors: lower temperatures. The results of tests carried out both in our laboratory conditions and at production sites and in third-party laboratories are presented in table 1.

This product received a certificate of conformity GOST R

Thus, a two-pack composition for gluing solid wood in the production of glued laminated timber and other wood products is claimed. In order to obtain a product of a higher quality that meets the requirements of European standards and domestic GOSTs, a special additive was selected to ensure the best combination of adhesive components (high-quality emulsification) and uniform application of the adhesive mixture to the material being glued, even in the case of tarred wood, and as a result, obtaining high-strength and uniform glue line.

The implementation of the invention solves all the tasks set by the authors.

Claims (6)

1. A water-dispersion adhesive system based on a polymer-isocyanate emulsion, including a polymer composition as an adhesive and a polyisocyanate hardener of the MDI type, characterized in that the adhesive, the main components of which are an aqueous polymer dispersion, a mineral filler, is additionally introduced a polyfunctional additive, the main a component of which is an anionic surfactant, with the following ratio of components, parts by weight: Polymer-isocyanate emulsion one hundred among them: Aqueous polymer dispersion 30-60 mineral filler 0-40 Multifunctional additive, the main component which is an anionic surfactant, 0.5-5 Technological additives (other) <1 Hardener MDI 15 2. Water-dispersion adhesive system according to claim 1, characterized in that both polyvinyl acetate dispersions and dispersions of vinyl acetate copolymers are used as an aqueous polymer dispersion. 3. Water-dispersion adhesive system according to claim 1, characterized in that other technological additives include biocide, defoamer, and dispersant additives.

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