SE429136C - CURSOR COMPOSITION FOR CARBAMIDHARTS, PROCEDURES FOR PREPARING THE CURRENT COMPOSITION AND APPLICATION OF IT WITH MECHANICAL MIXING WITH CARBAMIDHARTS - Google Patents

Description

7819982 '4 10. 15. 20. 25. 30. thickening even when no hardener has been added, especially when it is subjected to temperature rises, which causes clogging problems in apparatus and pipelines. Clogging problems can also arise as a result of separating effects of fillers when they are included. These problems increase with the degree of mechanization, e.g. as apparatus is used not only for the mixture but also for dosing, transport and storage of components and adhesive mixture. An additional problem with equipment in connection with urea resins is the regular cleaning required to prevent curing in the equipment as urea resins easily form tough precipitates with water and thus make cleaning difficult, especially in hard-to-reach places. The cleaning liquid formed must also be disposed of in an environmentally sound manner, which makes it desirable to keep its volume as low as possible.

To date, mainly two types of hardeners for urea resins have been used in the preparation of adhesive mixtures, namely powdered harder and aqueous solutions of harder. Powder hardeners easily give rise to variations in volume weight during transport and risks with powder separation and lump formation under the influence of moisture, which makes handling and dosing difficult. With manual handling, particularly difficult hygienic problems arise due to dusting, and with mechanized mixing, special problems arise with dosing and transport. Liquid hardeners, on the other hand, have caused problems through the separation of fillers and problems with excessive water supply to the adhesive joint, which has severely limited the possibilities of use, both for manual and mechanized mixing. BACKGROUND OF THE INVENTION The present object of the present invention is to provide an improved hardener composition for urea resins which does not, or only to a small extent, give rise to the above-mentioned problems. In particular, the object of the invention is to provide a liquid hardener composition with expanded range of use and improved mixing properties, especially in connection with mechanization. mixed methods.

It is also an object of the invention to provide an efficient manufacturing process for such a hardener.

The invention also has for its object to offer a use of the hardener composition, in which the advantages of the composition are particularly well utilized.

These objects are achieved by the features specified in the claims.

According to the invention, a liquid, water-based hardener composition is formulated containing a high content of acid formers, fillers and texture sensors so that a high dry content and viscosity are obtained on the finished hardener composition. In this way, many benefits are gained. Because the hardener is liquid, the advantages of such hygienic problems are maintained with small hygienic problems, simple dosing, good pumpability and simplified mixing with powder hardeners. The high content of fillers fulfills several important functions. On the one hand, the filler in high concentration tends to stabilize its own presence in the resin component so that it becomes somewhat storage stable. The filler content also stabilizes the presence of other solid components in the composition. On the one hand, due to the high filler content, all or almost all of the filler requirement in the finished adhesive mixture can be added with the hardener, which eliminates or reduces the need for filler addition in the resin component.

A filler additive to the resin component always constitutes a small part of it and the risk of separation becomes large in the resin component for this and other reasons. In addition, it is not desirable to increase the viscosity of the resin component by means of fillers because a margin against viscosity increases_must be maintained at this. The viscosity of the resin increases both during storage at elevated temperature due to continued curing, and when the temperature drops, due to physical properties, and these changes are significantly greater in the resin component than in the hardener component.

Especially with mechanized mixing systems, margins must be maintained because the problems of hardening or separation become particularly troublesome in complicated equipment and because the requirements for good pumpability and homogeneity of the components are particularly pronounced here. A high content of active component and other salts means that a minimal amount of water is added to the finished mixture with the hardener component, which reduces the dilution and increases the usefulness to the level of powder hardener. The high content of salts is made possible in part by the low risk that any precipitated salts will be deposited, since the filler content as above also stabilizes solid material of this kind. A high content of consistency sensor further contributes to the stability of the hardener composition but also to a higher viscosity, which is desirable to correct the consistency in relation to the resin component, so that the mutual mixing properties are optimized throughout the viscosity range of the resin component. have. According to the invention, a particularly preferred texture sensor is polyvinyl alcohol, which shows good compatibility with the resin, good dispersing effect and good texture-giving properties through, among other things, a certain tacky effect. A problem with this texture sensor, however, is that it can polymerize or gel to an undesirable extent during manufacture.

According to the invention there is thus also provided a process for the preparation of a hardener composition according to the above, with polyvinyl alcohol as a consistency additive 10. 15. 20. 25. 30. 35. g7a1o9s2-4 additive, which comprises a solution of the polyvinyl alcohol in at least a part of the water content of the hardener composition, preferably at elevated temperature, addition of at least the main part of the salt content and filler content of the composition after dissolution of the polyvinyl alcohol at a lower temperature than the temperature of dissolution of the polyvinyl alcohol. By this approach, undesired precipitation is avoided and an otherwise simple and efficient production process for a composition according to the invention is obtained, by means of which the advantageous properties of the polyvinyl alcohol can be utilized.

According to the invention it is also proposed a preferred use of the invented composition in which use the hardener is mixed with a resin with a moderate dry content and with a relatively low viscosity. The given adaptation of dry content and viscosity to the properties of the hardener composition ensures a certain similarity between the components in physical terms, so that mixing is facilitated. In particular, the selected properties are designed to allow good, fast and easy mixing in mechanized systems by keeping the viscosity of the resin component low but effective mixing is also obtained in the upper part of the viscosity range of the resin component.

Particularly suitable is a use in which the components are mixed by atomization on a common collecting surface. A device for such mixing can be made simple, whereby the above-mentioned cleaning problems are reduced. The amount of cleaning liquid required is also reduced by the amount of glue retained in the device becoming very small, which also reduces the glue rejection and increases the possibilities of using fast gluing systems. The quick and easy mixing in this way is made possible by the good mixing properties between the components used according to the invention, at the same time as the 1810982-4 10. 15. 20. 25.

STAY. 55. rapid mixing procedure reduces the risk of dehydration of the concentrated hardener. DETAILED DESCRIPTION OF THE INVENTION As mentioned, the active curing component of urea resin hardener is an acid or an acid scavenger in the presence of formaldehyde-containing resins.

Suitable acid formers for a composition according to the invention are already known for the purpose, such as inorganic acids, organic acids or acid salts.

Suitable are organic acids, such as formic acid and maleic acid. Particularly preferred are ammonium salts of acids, e.g. inorganic, such as ammonium phosphates, ammonium rhodanide, ammonium sulphate and especially ammonium chloride, optionally supplemented with acids as above. The amount of acid formers contained in the composition should, as mentioned, be relatively high but limited by other soluble components in the water content of the composition. Of such components, an addition of formaldehyde absorbent, especially urea, is the most important in terms of quantity. Such an addition is made to absorb free formaldehyde in the finished mixture and to control the pot life. In other respects, smaller amounts of soluble salts may be included, which, however, do not appreciably affect the solubility of the active hardener substance or the formaldehyde absorbent. Together the soluble substances should constitute between 25 and 80% by weight of a saturated aqueous solution and at 20 ° C and preferably between 50 and 70% by weight of such a saturated aqueous solution. Since the total amount of urea in the composition may vary between 0 and 50% by weight, the amount of acid formers may vary between 1 and 25% by weight, but it is preferred that the amount of urea be kept between 10 and H0% by weight and that the amount of acid formers then be between 2 and 10 weight percent. The pH of the hardener varies with the buffer capacity but is suitably between 1 and 7 and preferably between 2 and 6.

Fillers should be included in the hardener for the reasons discussed above 10. 15. 20. 25. 30. 55- 7810982-4 reasons. Conventional fillers may be included but particularly suitable is kaolin and then preferably kaolin with an oil absorption number between 27 and UB and a surface layer area of between 5 and 10 m2 / g. To achieve the above advantages. The filler content must not be less than 10% by weight of the entire composition, but preferably exceeds 30% by weight for best stability. A filler content above 60% by weight easily causes problems with the viscosity and preferably the content should be less than 50% by weight.

A consistency sensor must be included in the hardener composition to stabilize it. Known ones can be used, but polyvinyl alcohol is particularly preferred, especially those prepared by hydrolyzing polyvinyl acetate with a degree of hydrolysis in excess of 90 percent. Polyvinyl acetate not only contributes to the stability of the hardener but generally improves the viscosity properties without weakening the finished adhesive joint. The consistency sensor should be included in a content between 0.5 and 10% by weight, but it is preferred that the content is between 1.5 and 8% by weight.

The hardener composition is water-based, but the water content can to a lesser extent be replaced with solvents, e.g. alcohols. Otherwise, the composition may contain minor amounts of common additives such as antifoams, anti-mold agents, dyes, stabilizers, etc.

Within the given intervals for the different components of the hardener composition, different total dry contents and viscosity can be obtained for different selected materials. The dry matter content must, however, be regulated to between 35 and 85% by weight, preferably to between 60 and 83% by weight, calculated as remaining after one day in an air flow of 7000, ie. without significant loss of urea. The viscosity should be regulated to between 2000 and 12000 mPas (cP) and preferably to between 3000 and 1000 mPas at 2000. Preferably, the hardener composition is not appreciably thixotropic. With the conditions given above, the density of the composition becomes between about 1.25 and 7810982-4 10. 15. 20. 25. ÉO. 35- and 1.06.

Depending on the selected components, the hardener composition can be manufactured either by a simple mixing of the components regardless of the order or. a more planned manufacturing procedure may also be required. In general, the filler should be added after the other components have been added to the aqueous phase. Furthermore, salts and other water-soluble components should be added at a slightly elevated temperature to facilitate dissolution.

As indicated above, special measures should be taken in the manufacture of compositions containing polyvinyl alcohol. This component can easily polymerize, gel or otherwise cause problems. According to the invention, such a curing product is therefore prepared so that the polyvinyl alcohol is dissolved in water without the presence of any significant amount of acidifier or filler and that the acid former and filler are added only thereafter, the temperature at the addition of the acid former being kept below 5000 but preferably above 3000. The dissolution of the polyvinyl alcohol preferably takes place at a temperature above 50 ° C and preferably between 70 and 10000. It is then preferred that the temperature of the solution of polyvinyl alcohol before the addition of acid formers is lowered by adding a portion or the entire amount of urea, as such is included in the composition. It is further preferred that substantially the entire amount of filler is added after the addition and dissolution of the major part of the acid-formed additives. A possible final adjustment of the pH can be made after the filler addition.

Any antifoam is suitably added to the amount of water in which the polyvinyl alcohol is dissolved.

The hardener composition according to the invention is particularly suitable for use with a conventional urea resin with normal dry contents, but with a relatively low viscosity.

The dry content is thus suitably between S5 and 75% by weight and most preferably between 60 and 70% by weight. The viscosity at 20 ° C should then be between 500 and 20,000 mPas 10. 15. 20. 25. 30. 35. 781 0982-1: but is preferably between 800 and 8000 mPas. A good miscibility within the given viscosity ranges is obtained in that case even with the use of relatively simple mixing equipment and also in other respects the components work well. mechanized systems. Preferably only little or preferably no filler is included in the resin component. Otherwise, the urea resin may have conventional properties, such as a molar ratio of formaldehyde / urea between 1.3 and 2, more preferably between 1.5 and 1.8, a free formaldehyde content between 0.2 and 3% by weight and especially between 0, H and 0, 8% by weight, a pH between 7.5 and 9 and a density of about 1.3. The resin is preferably not thixotropic, especially not if it is to be mixed with the hardener by atomization on a common surface, as thixotropic properties can for worse admixture effects.

With regard to different contents of acid formers, between 100 and H0 parts of hardener composition can be added to 100 parts of resin component, but with regard to also simple mixing procedure, it is preferred that between 100 and 25 parts of 100 parts of resin be added. The viscosity of the finished mixture at 2000 should exceed 500 mPas but less than 20000 mPas, but it is preferred that the viscosity be between 1000 and 5000 mPas.

It is preferred that the invention be applied in connection with mechanized mixing systems since the properties of the components are well adapted for this. Because the components are easily mixed with each other, it is preferred that mixing is used by comminuting the components on a common collecting vessel and in particular that the components are separately fed to a rotating disk surrounded by the common collecting surface. In order to make the best use of the post-mixing effects in such fast mixing systems, it is preferred that the components are not thixotropic. The resulting mixture is passed to a spreading means which may be of a conventional type and comprise, for example, spray nozzles, string spreaders, curtain spreaders or 78109824; 10. l5. 20. 25 .. 30. 55- 10 waltz. The latter is preferred. Mixing by atomization is a fast method that allows the use of fast-curing adhesive systems, e.g. with a pot life down to 10 minutes at 20 ° C. It is then also preferred that the adhesive mixture is led directly to the adhesive spreader, which is preferably of the roll type. Thus, it is preferred that for mixing the resin and hardener components, a device comprising a rotating disk, a collection surface surrounding the rotating disk and conduit means for conveying the resin and hardener component to the surface of the rotating disk is used. Suitably the conduit means are equipped with dosing means for regulating the resulting component quantities. It is preferred that the collecting surface is substantially funnel-shaped for collecting formed glue mixture. If heating or cooling of the adhesive mixture is desired, this is conveniently done via the collection surface. It is furthermore suitable that at least one roller is arranged for application of the adhesive mixture, preferably arranged directly below the funnel-shaped collecting surface. For simplest cleaning, the disc and / or collection surface can be designed or coated with hydrophobic material, such as polyethylene or polyethylene tetrafluoroethylene. It is preferred that the device be designed so that an air flow from the inlet of the components to the outlet of the mixture arises, whereby the mixture is improved, splashes are avoided and the formaldehyde emission is reduced.

The mixing device must thus in this case have openings at both inlet and outlet, the opening for the air flow at the outlet being suitably provided by the outlet being larger than that required for draining the mixture. A suction through the device can be provided e.g. by arranging wings or propellers on the rotating parts of the device, but is preferably achieved by the collecting surface at the rotating disc closing more slowly in the direction of the outlet than in the direction of the inlet. For good mixing, the peripheral hashing of the disc is in known applications, e.g. both at cold and 15. 20. 25. 35. 7810982-4 ll suitably above 0.5 m / s and preferably also above 2 m / s. Peripheral speeds above 30 m / s should be avoided as separation effects can easily occur. It is preferred that the disc and collecting surface are so designed in relation to each other that several atomization steps are obtained.

Conveniently, this is done by first comminuting material which is captured on the collecting surface flows down on a section of the disc with a larger diameter and again atomized on another part of the collecting surface.

The adhesive mixture can be used in hot pressing processes known for urea resin. However, it is preferred that the invention be applied in connection with hot pressing processes and then especially in connection with veneering, since the requirements for consistency and filler content in these contexts are particularly high, partly due to the risks of large glue penetration and glue adhesion.

Figure description The figure appendix shows a preferred embodiment of a plant for glue mixing according to the invention. Denoted by 1 is a disk which rotates about an axis 2. Hardener or resin component is fed to the upper side of the disk 1 through two conduits 3 and H. The components are ejected onto a collecting surface in the form of a static casing, generally designated with 5, which in this case is divided into an upper cylindrical part 6 and a lower conical part 7. The mixture flows to an outlet 8, located above a roller 9, which spreads an adhesive layer 10 on a joint surface 11. The actual mixing of the components is a two-step process in which the components are first ejected from the disc 1 towards a first collecting area 12 on the cylindrical part 6 of the housing 5. The vane has a ledge 13 with an enlarged diameter on which ledge the adhesive mixture from area 12 runs down. From the ledge 13, the mixture is atomized again by being ejected towards a second collecting area 1u on the conical part 7 of the housing 5, which area 1a has an enlarged diameter in relation to the collecting surface at area 12. By this design of disc and 7810982-1-r 10. 15. 20. 25. 30. 35- 012 collection area, a doubled atomization process is obtained in dnr by simple means. If desired, the rotating disk can of course be equipped with more ledges_for further fine distribution steps, but two steps have generally been found to be sufficient for the purpose. Example 1 A hardener composition was prepared as follows.

In a tank with stirrer, 22 parts by weight of water, 0.1 part by weight of fatty acid ester and 3.5 parts by weight of polyvinyl alcohol were charged.

While stirring, the temperature was raised to 90 ° C and maintained until all the polyvinyl alcohol was dissolved¿ Then urea was added until the temperature dropped to 4090, to which 2ü parts by weight were added. After dissolving all the urea, 5.3 parts by weight of ammonium chloride were added and dissolved. Then another 6 parts by weight of urea were added and dissolved. Finally, 0.1 part by weight of anti-mold agent and 39 parts by weight of kaolin were added and stirred until a homogeneous and anhydrous mixture was obtained. The viscosity of the mixture was 5000 mPas at 20 ° C.

A urea resin composition in an amount of 500 parts by weight was prepared, which composition lacked fillers and had a dry content of about 65% by weight, a viscosity at 20 ° C of 1100 mPas, a water dilutability of 1: 5 and a free formaldehyde content of 0.6% by weight. . A mixing device according to the figures was prepared, which had a rotating disc with a ledge and with a minimum diameter of 02 mm and a maximum diameter of 120 mm and with a collecting surface surrounding the disc with a fit of about H mm. The hardener and resin components described above were pumped by means of metering pumps in a weight ratio of 20/100 in separate lines to the device where they were fed to the top of the disc. The disc was rotated at a speed of about 700 rpm and the adhesive mixture drained from the collection surface was added to a pair of rollers. With the rollers, an amount of adhesive of 150 g / m2 was spread on the board, after which a veneer layer was pressed in a press at 107 ° C for 3 minutes and with a press pressure between 6 and 7 kp / cm. The gluing result was satisfactory. 0

Claims (6)

10 15 20 “, 25 30 35 429 136 13 Patent claim Liquid hardener composition for admixture with liquid urea resin to form a sizing composition, characterized in that the hardener composition is aqueous and contains, expressed as a percentage by weight of the whole composition: 'acid or acid scavenger 1 - 25' filler 30 - 60 thickeners 0.5 - 10 ~ formaldehyde absorbent 0 - 50 and that the hardener composition has a dry content between 35 and 85% by weight and a viscosity at 20 ° C between 2000 and 12000 mPas. 2. A composition according to claim 1, characterized in that it contains, expressed as a percentage by weight of the whole composition: acid or acid scavenger 2 - 10 fillers 30 - 50 thickeners 1.5 - 8 formaldehyde absorbent 20 - 40 and that the hardener composition has a dry matter content between 60 and 83% by weight and a viscosity between 3000 and 10000 mPas. 3. A composition according to claim 2, characterized in that polyvinyl alcohol is included as a thickener. 4. A composition according to claim 3, characterized in that kaolin is included as filler. Use of an aqueous liquid hardener composition containing, expressed as 1% by weight of the whole composition: acid or acid scavenger 1 - 25 fillers 30 - 60 thickeners 0.5 - 10 formaldehyde absorbent 0 - 50 and having a dry matter content between 35 and 85 % by weight and a viscosity at 20 ° C between 2000 and 12000 mPas in the preparation of a sizing composition by mechanized liquid urea resin, by mixing with the two 429 136 H components being atomized on a common collecting surface from which the mixture is withdrawn. Use according to claim 5, when the atomization takes place by the components being separately fed to a rotating disc surrounded by the collecting surface.