NO752616L - - Google Patents

Description

The invention relates to liquid binders which include

a thermosetting resin, especially urea formaldehyde (UF) resin, melamine formaldehyde (MF) resin, or a mixture of the aforementioned resins.

Commercial cold-curing liquid UF resins, cured with acids or acid-forming substances, have been widely

use as adhesives, for example for cellulose materials and

other porous materials, and for treating paper and textiles to give them useful modified properties. However, they shrink very much during curing and become very brittle and show as a

as a result of this little adhesion to smooth non-cellulose surfaces, and if they are cast in thick masses, they quickly undergo a so-called "crazing" (that is, they quickly dissolve by cracking, caused by the internal stresses that build up under the curing process). To a certain extent, this "crazing" process can be reduced by adding filler or by curing with formic acid or by partial etherification of the resin with alcohols.

It has now been found, however, that ordinary commercial water-soluble UF has r pik se r, . for example "AEROLITE 300", mixed with polymer latex can be cured so that you get thick, water-resistant masses which are much less prone to "crazing" and which exhibit excellent adhesion to surfaces for which the UF resins themselves are not suitable. These resin/latex mixtures have been investigated and found useful, for example, as binders, as water-resistant coatings for a wide range of surfaces and as binders for example glass fibers, asbestos, etc. -compounds, with or without added pairs of tickle or fiber reinforcing materials, cast hot or cold to produce blocks, panels, tiles, which are unusually tough compared to conventional UF resin castings. and which does not later crumble by cracking. This casting can take place after partial drying and/or promoting the hardening of the resin.

Neoprene latex, for example, is alkaline (pH approx. 11-13). and is filled in by acidification or in contact with various substances, ■for example ammonium or calcium salts. However, it is compatible with aqueous UF resin solutions, and it has been found that stable liquid mixtures can be prepared containing 5-95%,

(eg 20-80%) by weight of latex mixed with 95-5% (eg 80-20%) by weight of UF resin solution. Such mixtures remain stable for several days at room temperature and thus gel slowly, but this gelation can be delayed further by the addition to the mixture of conventional stabilizers. Such mixtures are useful when an alkaline (or at least neutral) binder sheet is desired, and if rapid curing is neither particularly desired nor required, for example in manufacture,

the pouring or application of cement and concrete mixing

However, it has also been found that such UF/latex mixtures can be acidified (for example with formic acid solution, for example a 10% solution in water of 35% formic acid by weight) to a point where the latex still does not precipitate and where the mixtures are still liquid and homogeneous. However, these acidified mixtures will now gel at room temperature, in periods of time varying from a few minutes, say 2 or 3 minutes, to a time in the neighborhood of an hour, making them very suitable for molding such as: panels, tiles or similar, for coating surfaces, for bonding similar or different surfaces, and for debonding particle or fiber materials. Accordingly, the invention provides a liquid binder composition comprising 5-95% (eg 20-80%) by weight of a polymer latex and 95-5% (eg 80-20%) by weight of an aqueous solution of eri thermosetting resin, especially urea formaldehyde (UF)-Sal^plMI> : fea^^^^åSSdéhyde (MF) -resin, or a mixture of the aforementioned resins. The invention also provides a liquid binder mixture as described in the preceding paragraph, which further contains a resin curing catalyst in an amount sufficient to cause the latex to precipitate, so that the product is still liquid and homogeneous.

The invention also provides methods for coating surfaces>bonding of objects having similar or different surfaces, debonding of particulate or fibrous materials, production of molded objects by preparing a mixture of a binder, with or without particle or fiber reinforcing naterial, and molding the mixture, all as described in the following, where the binder or binder is a mixture as described in each of the two previous paragraphs.

The resin curing catalyst is preferably an acid or acid-forming substance, especially formic acid. The polymer latex is preferably a neoprene, for example "NEOPRENE 400", but can be any other synthetic or natural polymer latex or an aqueous emulsion based on acrylic polymers.

It has also been shown that for certain purposes to be described in the following, the liquid binder mixtures according to the invention can be modified and improved by mixing with an alkali silicate, especially sodium silicate, in proportions of between 5 and 95%, (for example between 20 and 80%) by weight of silicate to between 95 and 5% (eg between 80 and 20%) by weight of the sum of the resin and latex. The number of possible variations with the three basic ingredients is considerable. As well as the proportions of the ingredients, different qualities of resin, silicate and types of latex can be used. It has been shown that wide variations regarding pot-life as well as debonding behavior can be achieved. Possible combinations are divided into four groups, which are shown in the following table.

Some of the applications include the addition of cement, or sand or clay as a filler, as described below:

The following are some examples of applications for binders used in connection with the invention: 1. Surface coating for wood, chipboard, expanded urea/formaldehyde, rigid synthetic sheet foam laminates, plasterboard, plaster articles. 2. Bonding of reinforcing skin, such as paper, glass, cloth, metal, or plates, panels, etc., which are made of the above materials. 3. Adhesive for bonding chipboard and adjacent materials (provided that at least one of the materials is sufficiently porous to allow moisture to escape). 4. Acid-resistant coatings for brick and stone. 5. Acid-resistant mortar clays containing sand, clay, gypsum, unburnt

gypsum or other fillers for jointing or sealing.

6. Casting of acid-resistant tiles containing sand, clay or

other reinforcing fillers; 7. Acid-resistant skin on concrete, especially for use in concrete silos. The concrete is coated first with the neutral binder mixture (as a primer) and then with the acidified binder mixture.

8. Coating on reinforced concrete pipelines.

9. Forming tubes or valéars using suitable conventional methods, for example by winding paper, felt stents, fibers or other reinforcing material that is impregnated with binders lb the landing, around paper sleeves or other temporary or permanent substrates, or by centrifugal spinning of the mixture on the inside of a mold, or by similar methods. The mixture can be filled and/or reinforced as indicated above.

10. Binding of vermiculite to blocks.

11. Insertion of bristles in brush production (a traditional ahyen deise for epoxy resins). 12. As a moisture-proofing material, for example in concrete floors, preferably with sand, clay or other reinforcing materials. 13. Belggg for paper, for the provision of wet strength paper

with high gloss.

14. Coating for cardboard, for example in the manufacture of inner soles for shoes.

15. As a binder in sandpaper.

16. Binder in gaskets.

17. As a binder in non-woven textiles, including treatment of asbestos fibers to prevent fine, short fibers from loosening. 18. Bonding of particulate materials, for example sand or coal dust for the production of casting cores, coal briquettes. 19. Sand-filled mortars for use as intumescent coatings.

20. Bonding of new concrete against old.

21. High-speed glue for wood on wood.

22. High speed adhesive for corrugated sheets, laminated paper,

laminated boards.

23. Improved concrete. Addition of a binder mixture i

according to the invention fills up the empty space and improves it

mechanical strength.

24. Bonding of concrete to steel—cement can be included in the binding medium lb la nd i nge n. 25. Improved plaster. Part or all of the slurry water can be replaced by a binder mixture according to the invention. This greatly increases the mechanical strength and gives gypsum products a weatherproof finish. 26. Laminated roofing material and adhesive boards for building purposes. 27. Concrete closing mechanisms and permanent bonding and other shaped profiles.

Since the liquid binder mixtures according to the invention will in most cases not be sold as they are, but assembled at the time they are to be used or shortly before, it should be understood that the invention also covers multipack binder mixtures where the components of the liquid binder mixtures are kept separately until they are to be used, after which the contents of the separate packs are mixed together.

EXAMPLE 1

The following recipes were prepared (in parts by weight):

Blocks cast into conical flasks of the above-mentioned liquid mixtures gave the following results: Control sample - cracks and fissures showed set after 3 days at

room temperature.

1. cracks appeared after about 5 days at room temperature. 2. very slight cracking appeared after 9 days at room temperature. 3. no cracking after 7 months at room temperature. 4. no cracking after 7 months at room temperature.

5. no cracking, but some shrinkage.

6. latex was precipitated from solution using formic acid, but the result was a solid block without cracks. Additional mix No. 7

The mix thus produced a firm, white, opaque crack-free, hard cast with a very high surface gloss.

EXAMPLE 2

Mix No. 4 was used as a coating that was brushed onto the surface of chipboard, molded plaster, hardboard and corrugated board, providing a hard, crack-free, water-resistant, shiny protective surface.

; EXAMPLE 3 •

This was used as a thick (| - 1 nim) surface coating on cast plasterboard, foamed polyurethane insulation board, chipboard UF board, and hard, waterproof, wear-resistant surfaces were obtained on these substrates.

EXAMPLE 4

This produced similar surface skins on the above-mentioned sub-; .. layers, but which were somewhat less wear-resistant.

The same mixture gave instead of casting thick blocks (7-10 mm thickness), hard, sharp-edged castings suitable for many purposes, for example as road reflector posts surface-coated with reflective glass beads.

EXAMPLE 5

Danne produced precise molded products with high water resistance and extreme hardness. Such 'cast' objects were coated on

o^neeoveEflater with mik» no. 4 (without filler) so that products with shiny surfaces were obtained, with improved surface hardness.

Alternatively, cast resin/gypsum products were ground and polished to produce products that resembled natural marble.

"'" EXAMPLE 6

Mixers no. 2, 3 and 4 have proven to be useful as adhesives - for example for attaching bristles to the metal fittings in brushes, but for such applications they can be coated with plaster as an

given above.

Unfixed mixtures, for example no. 2, 3 and 4, can be used for bonding wood and other cellulosic material and also for a number of porous non-cellulosic materials under such conditions where there are large gaps between the parts to be joined, which must be filled with a non-s pr eck-forming (non-:crumbling) adhesive, or under such conditions where no pressure can be applied to the surfaces in order for them to be brought into reasonable contact.

EXAMPLE 7

(a) Other mixes used for casting and surface coating (non-cracking) included: (c) lOO UF + 10-50 parts "Scott Bader Latex" 13/002 with mapric acid- catalyst, so that molded products and coatings were obtained without cracks.

EXAMPLE 8

Mix no. 4 was mixed with the same weight of gypsum, and the combined mixture was impregnated in two layers of chopped string mat. (The weight per m of the glass mat was 300 g). The impregnated material was allowed to dry, with the top surface uncovered , for 16 hours at about 23° C. Two such laminates were then assembled and pressed under a pressure of 50 bar in a> hydraulic press and heated in this at 90° C> for 15 minutes. Rigid laminates with a smooth surface which containing 12% by weight of glass fiber was thus obtained.

EXAMPLE 9

(a) Equal parts of gypsum. and, mix no. 4 was used for the impregnation of three layers of fiberglass chopped strand mat (each with a density of 300 g/m ). That uncured laminate, coated with aluminum foil, was pressed in a hydraulic press using a pressure of 25 bar and heated in the press at 60°q for one minute. The edges of the casting were defined by a square mold with a metal sealing ring, thickness 3 mm. A shaped, but flexible, cast was removed from the Mold and cured overnight at 90°C to produce a rigid sheet. Mechanical sealing of the sheet showed a flexural modulus of 5.150 MNm -2 and a flexural strength of 55 MNm -2 and a flexural strength of 55 MNm . The glass fiber content was 9% by weight.

(b) This procedure was repeated with half the amount of plaster, but with four layers of fiberglass mat. The bending modulus was be--2 -2

rated at 4,200 MNm, and the bending strength was 79 MNm

(c) Other materials were produced using both three and four layers of fiberglass mat, with the following mixes:

In these cases, the materials were formed under low pressure (approx.: 1 bar) without an enclosing sealing ring, and were initially heated for 2 minutes at 70°c between sheets of aluminum foil. The foil was then removed, and the composite products heated for 16 hours at 90°C to substantially complete the curing. *■;•,: , . (d) ± another case, layers of fiberglass mat impregnated with equal parts by weight of gypsum and mix No. 4 were placed between sheets of aluminum foil in a mold with a 3 mm thick sealing ring, so that the initial thickness of the charge was 6 mm, and covered only approx. half of the area in the mold. The mixture was placed between the rollers in a hydraulic press, which had 60°C, and was held close to the rollers for half a minute before the press was closed. Casting was then carried out for one minute using a pressure of 25 bar. A flexible cast which corresponded to the shape in the mold and which had substantially uniform glass distribution was obtained.

This was then heated at 90°C for 16 hours. The glass content was 12% by weight.

EXAMPLE 10

The following materials were placed in a blade mixer:

These were mixed into a dough for approx. 10 minutes, with the formic acid in mix no. 4 being added in the last minute. The dough was removed and pressed between heated plates (70°C) for two minutes, followed by cold pressing at approx. 5 bar for 10 minutes. The cast sheet was post-cured at 90°C for 16 hours.

EXAMPLE 11

A tube was produced by impregnating glass fiber chopped strand mat with equal parts by weight of mix no. 4 and gypsum* This was wound in spiral form around a glass tube which itself had previously been wrapped with polyethylene terephthalate film. The coiled construction was smoothed and solidified, and the whole was heated in a drying cabinet for 15 minutes at 90°C. A flexible but self-supporting tube could then be removed from the sheath, the polyethylene terephthalate film was removed, and it was post-cured at 90°C for three hours. A rigid, impact-resistant tube was produced.

\

EXAMPLE 12

A mixture of like. quantities of mix No. 4 and gypsum were placed in a cylindrical mold and rotated about its longitudinal axis until the mixture gelled (about 45 minutes at 23°C). The fabricated tube was removed and allowed to dry at room temperature for 24 hours. This was wound in spiral form with impregnated glass fiber mat as indicated in the previous example, and then the whole was heated at 0°C for three hours so that a rigid, impermeable tube was obtained.

EXAMPLE 13

Mix No. 4 was cast in a mold with a 2 mm thick sealing ring between sheets of polytetrafluoroethylene-coated glass cloth, and the mold was held in this composite unit and heated for 3 minutes at 70°C by placing between hot metal plates. A flexible, compact material was removed; and was placed. in a drying cabinet at 60°C. After two hours, a sheet with good transparency was obtained. The casting was, and remained, free of cracks.

EXAMPLE 14

"Aerolite" 300 was acidified with 10% by weight of the 10% formic acid solution, and resin beads impregnated into fiberglass chopped string mass. The laminate was gelled by heating at 70°C for 3 minutes between PTFE-coated glass cloth and hot metal plates, as described in the previous example. The laminate was heated at 60°C overnight and then overnight at 90°C. Upon inspection, the resin in the laminate was found to be cracked. A laminate prepared in the same way from mix No. 4 was found to be free of cracks.

EXAMPLE 15

The following mixtures were prepared: .

Both A and B were impregnated in fiberglass chopped string mat and lightly pressed between hot plates at 70°C for 3 minutes, as described in the previous examples, so that sheets were obtained which were then cured at 90°C for 15 hours.

Strips of each sample were immersed in water at 80°C, 60°C o / and 40°C, for 120 hours. The testicles were removed, dried and weighed. They were allowed to dry the hat over at room temperature and were then dried at 66°C overnight and finally dried again. The total change in thickness for each sample was also determined. Resul-

the toes were as follows:

At 8Q°C

Weight change after immersion

A 8.1%

B. 0.75% Weight change after immersion and drying

A - 21.7% •;. ■•'

B - 15%'

Change in thickness'after immersion and drying A — :'8@3* *•

B 3.5% .-■

At oQ°C

Weight change after immersion

A + 0.4%

B 3.6%

Weight change after immersion and drying

A 12%

B * - 8.8% Change in thickness after immersion and drying

A - 4.7%

B - 3.6%

At 40°C

Weight change after immersion

A., 4.8% B + 6.1%

Weight change after immersion and drying

A 4.6%

B 4.3%

Change in thickness after immersion and drying

A. 8.1% '..'.v-, .

B 2.5%

It was also observed that the surfaces of samples of material A were loose and powdery, and this was worst for samples that "were immersed in water at 80°C. The surfaces of samples of material

■'. B produced according to the invention was decidedly more coherent and, unlike the samples of material A, they were not exposed to loss of material from the surface by light rubbing./''Material B up-; thus showed decidedly better resistance to water attack than sample A.

Claims (19)

1.. Liquid binder mixture, characterized in that it comprises 5-95% by weight of a polymer latex and 95-5% by weight of an aqueous solution-moulding resin. 2. B interior agent mixture as stated in claim 1, c a r a k-t e , characterized in that it comprises 20-80% by weight of the latex and 80-20% by weight of the resin solution. 3. Mixture as specified in claim 1 or 2, characterized by having <p> ixene eru rea/ fbraaldehyde resin, melamine/- formaldehyde resin or a mixture thereof.. 4. Mixture as stated in any of the preceding claims, characterized in that the polymer latex is a synthetic or natural latex or an aqueous emulsion based on acrylic polymers. 5. Mixture as stated in claim 4, characterized in that the polymer latex is a neoprene..' 6. Mixture as set forth in any of the preceding claims, characterized in that it also contains a resin curing catalyst in one quantity which is insufficient to to precipitate the latex, so that the mixture is still liquid and homogeneous. Mixture as stated in claim 6, characterized in that the catalyst is an acid. 8. Mixture as stated in claim 7, characterized in that the acid is formic acid. 9. Mixture as set forth in any of the preceding claims, characterized in that it also contains a alkali silicate. 10. Mixture as specified in claim 10, characterized in that the alkali silicate is sodium silicate. 11. Mixture as stated in claim 9 or 10, characterized in that it contains between 5 and 95% by weight of silicate and between 95 and 5% by weight of the combined resin solution and latex.. 12. Mixture as stated in claim 11, characterized in that it contains between 20 and 80% by weight silicate and between 80 and 20% by weight of the combined resin solution and latex. 13. Liquid binder mixture, essentially as described here. 14. Liquid multipack binder mixture as set forth in any one of the preceding claims, characterized in that it comprises a plurality of packages each containing at least one component of the mixture for the purpose of keeping said components separate until they are to be broken. , 15. Process for coating surfaces, car act t e-r^i s e r t by applying to them a liquid mixture as specified in any of the preceding claims. 16. Method for joining together objects that have the same or different surfaces, characterized by applying to at least one of the surfaces" a liquid binder mixture as set forth in any of claims 1-14, and then pressing the surfaces together. 17. Method for joining together objects with similar or different surfaces, characterized by applying to one surface at least one of a liquid binder mixture, as specified in any of claims 1-14, and applying to the other surface the component or components in the mixture, after which the surfaces are pressed together. 18. Process for debonding particle-shaped or fibrous materials, characterized by applying these a liquid binder mixture as set forth in any of claims 1-14, and forming the material into any desired shape. 19. Procedure for the production of cast objects, characterized by making a liquid binder mixture as set forth in any of claims 1-14, with or without particulate or fibrous reinforcing material, and casting in a mold.