IE41635B1 - Improvements in relating to bonding compositions - Google Patents

Abstract

Liquid adhesive compsn. for bonding surfaces of manufactured prods. and bonding together particles and fibres, consists of 5-95 esp. 20-80 wt.% polymer latex (1) and 95-5 esp. 80-20 wt.% aqs. soln. of a thermosetting resin (II). The compsn. has excellent adhesion, good resistance to water and cracking, good durability and is suitable for a wide range of applications. I is pref. a polychloroprene latex. II is pref. a urea/formaldehyde or melamine/formaldehyde resin.

Description

The present invention relates to liquid compositions containing an aqueous urea formaldehyde (UF) resin, melamine formaldehyde (MF) resin, or a mixture of the said resins.

Commercial cold-setting aqueous UF resins, cured with acids or acid-forming substances, have been used extensively as adhesives, for example for cellulosic and other porous materials, and for treating paper and textiles to impart thereto useful modified properties. However, they shrink excessively during curing and become very brittle and, as a result, exhibit little adhesion to smooth non-cellulosic surfaces, and if cast in thick masses they quickly undergo crazing (i.e. they quickly disintegrate by cracking, caused by the internal stresses which are set up during the curing process). To some extent, this crazing process can be reduced by the addition of filler, or by curing with formic acid, or by partial etherification of the resin with alcohols.

We have now found, however, that ordinary commercial water-soluble UF resins, for example AEROLITE 300 (Trade Mark of Ciba-Geigy Ltd)* in admixture with liquid polymer latex can be cured to give thick water-resistant masses which are much less susceptible to crazing and which exhibit excellent adhesion to surfaces for which UF resins by themselves are not suitable. These resin/latex mixtures have been tested and found to be useful, for example, as bonding agents, as water-resistant coatings for a variety of surfaces, and as binding agents for particulate and fibrous materials, such as glass fibres, asbestos, etc. Furthermore, these resin/latex mixtures, with or without added particulate or fibrous reinforcing materials, can be cast or hot-moulded to produce blocks, panels, tiles, which are extremely tough by comparison with conventional UF resin mouldings, and which do not subsequently disintegrate by cracking. This moulding can take place after partial drying and/or advancement of the cure of the resin.

* AEROLITE 300 is an aqueous urea formaldehyde resin prepared by condensing a mixture of urea and formaldehyde in a molar ratio of about 1.95:1, followed by concentration to a solids content of about 67% by weight. It has a viscosity of about 60 poise at 23°C. and a water tolerance of about 180%, Neoprene latex, for example, is alkaline (pH about 11 to 13) and precipitates upon acidification or in contact with various substances, for example ammonium or calcium salts. However, it is compatible with aqueous UF resin solutions, and we have found that stable liquid mixtures can be prepared containing from 5% to 95% (for example, from 20% to 80%) by weight of latex in admixture with 95% to 5% (for example, from 80% to 20%) by weight of UF resin solution. Such mixtures remain stable for several days at room temperature and then slowly gel, but this gelation can be further delayed by the addition to the mixture of conventional stabilizers. Such mixtures are useful when an alkaline (or, at least, neutral) composition is desired, and when rapid curing is neither particularly required nor desired, for example in the preparation, casting or application of cement and concrete mixtures. - 4 However, we have also found that such UF/latex mixtures can be acidified (eg with formic acid solution say a 10% solution in water of 85% w/w formic acid) to a point where the latex is still not precipitated and the mixtures are still liquid and homogeneous; however these acidified mixtures will now gel at room temperature, in times ranging from a few minutes, say 2 or 3 minutes, to something of the order of an hour, which makes them very suitable for casting as blocks, panels or tiles, for coating surfaces, for bonding similar or different surfaces together, and for binding particulate or fibrous materials.

The present invention accordingly provides a liquid bonding composition containing from 5% to 95% (for example, from 20% to 80%) by weight of a liquid polymer latex consisting of a neoprene, an acrylic polymer or copolymer, or a vinylidene chloride polymer or copolymer and from 95% to 5% (for example, from 80% to 20%) by weight of an aqueous urea formaldehyde (UF) resin, melamine formaldehyde (MF) resin, or a mixture of the said resins, the sum of the percentages of the liquid polymer latex and the aqueous resin totalling 100.

The invention also provides a derived composition containing a liquid composition as described in the immediately preceding paragraph, and a resin-curing catalyst in an amount insufficient to cause the latex to precipitate, so that the composition is still liquid and homogeneous.

The invention further provides methods of coating surfaces, bonding to one another articles having similar or dissimilar surfaces, binding particulate or fibrous materials, producing moulded articles by forming and casting a mixture, wherein the coating or bonding agent or the mixture comprises a composition as described in either of the two immediately preceding paragraphs.

The resin-curing catalyst is preferably an acid or acid-forming substance, in particular formic acid. The polymer latex is preferably a neoprene, for example NEOPRENE 400 (Trade Mark), but it may be an acrylic polymer or copolymer,or a vinylidene chloride polymer or copolymer, for example, as an aqueous emulsion thereof.

In Patent Specification No. 4-/4+4we have described and claimed a liquid composition containing two adhesive components, one of said components being an aqueous urea formaldehyde resin, melamine formaldehyde resin, or a mixture thereof, and the other of said components being an aqueous sodium silicate, the composition containing from 20% to 80% by weight of the first component and from 80% to 20% by weight of the second component, the sum of the percentages of the first and second components totalling 100%.

We have now further found that, for certain applications described hereinafter, the liquid compositions of the present invention, can be modified and improved by admixture with an alkali silicate, in particular sodium silicate, in proportions of between 20% and 80% by weight of silicate to between 80% and 20% by weight of the combined resin and latex. The number of variations possible with the three basic ingredients is considerable.

As well as the proportions of the ingredients, different grades of resin, silicate and types of latex can be used.

We have found that wide variations in pot-life, and bonding performance can be achieved. Possible combinations are classified into four groups, which are shown the following table. Some of the applications involve the addition of cement sand or clay as a filler, as hereinafter described: Uses Cement modifier; primer for steel cladding, with i or without cement being | added. Extensive applications as coatings, bondings. Good water resistance. Can use with fillers (but not with cement). Very cheap bonding system. Improved adhesion of latex. Cheaper systems than latex alone. 1 1 i Acid or Alkaline Alkaline/neutral Alkaline/neutral Ό β •ri Ή 0 u Preferably acid | Preferably acid Preferably acid Minor Component Latex Latex + silicate Latex Latex + silicate + X Ρ H U/F U/F + silicate Major * Component fcl ft ft ft DP Silicate X X 0) ni Λ rH »**» Ιβ Λ <·^ *·** CJ β «Μ* CQ More than 50% by weight of total in a two-component system. In a three-component system, the largest percentage by weight of the three components, but not necessarily larger than the combined percentage by weight of the two minor components. The functions of the components are set out below. All the materials are bonding agents, but the mixtures are better than the individual components.

Urea-formaldehyde resin Latex Acid Silicate May contain high polymer species which, when precipitated with silicates, impart rapid tack and cure.

Improves water resistance of silicate (if present) Imparts acid resistance Toughens system, thereby improving strength, adhesion and life of the bond.

Enables system to be used as a coating.

Accelerates and improves cure of U/F resin, but will precipitate silica or coagulate latex if used in excess.

Provides alkaline medium from which high polymer species precipitate.

Cheapens system.

Imparts high-temperature properties' The following are some examples of the uses to which the bonding compositions of the present invention can be put:1. Surface coatings for wood, wood particle board, expanded urea-formaldehyde, rigid synthetic plastics foam laminates, plasterboard, plaster articles. 2. Bonding reinforcing skins, such as paper, glass, cloth, metal, or boards, panels, etc., made from the above materials. - 8 3. Adhesive for bonding together wood, wood particle board, and like materials (provided at least one of the materials is sufficiently porous to allow moisture to escape). 4. Acid-proof coatings for brick and stone.

. Acid-proof mortars containing sand, clay, plaster, gypsum, or other fillers for jointing, sealing. 6. Moulding acid-proof tiles containing sand, clay, or other reinforcing fillers. 7. Acid-proof skins on concrete, particularly for use in concrete silos. The concrete is first coated with the neutral bonding composition (as a primer'), and thereafter with the acidified bonding composition. 8. Coatings on reinforced concrete pipes. 9. Forming pipes or rollers by suitable conventional methods, for example by winding paper, filaments, fibres, or other reinforcing material impregnated with the bonding composition around paper tubes or other temporary or permanent supports, or by centrifugally spinning the composition inside a mould. The composition may be filled and/or reinforced as suggested above.

. Bonding vermiculite into blocks. 11. Setting the bristles for brush manufacture (a traditional outlet for epoxy resins). 12. As a damp-proofing material, eg in concrete floors, preferably with sand, clay, or other reinforcing materials. 13. Coatings for paper, to give high gloss, wet strength papers. 14. Coatings for cardboard, eg in the manufacture of insoles for shoes.

. Bonding abrasive papers. 16. Bonding gaskets. 17. Binding non-woven fabrics, including the treatment of asbestos fibres to prevent detachment of fine short fibres. 18. Binding particulate materials, such as sand or coal dust to give foundry cores, coal briquettes. 19. Sand-filled mortars for use as intumescent coatings .

. Bonding new concrete to old. 21. High-speed wood-to-wood adhesives. 22. High-speed adhesives for corrugated boards, laminated papers, laminated boards. 23. Improved concrete. The addition of a bonding composition according to the invention fills up the voids and enhances mechanical strength. 24. Bonding concrete to steel - cement ean be included in the bonding composition.

. Improved plaster. Part or all of the slurrying water can be replaced by a bonding composition according to the invention. This greatly enhances mechanical strength and imparts a weatherproof finish to plaster products. 26. Laminated roofing and cladding sheets for building construction. 27. Concrete shuttering and permanent cladding and other formed profiles.

Since, in the majority of cases, the liquid bonding compositions of the invention will not be sold as such, but formulated at the time of or shortly before use, it is to be understood that the invention also covers multi-pack bonding compositions in which the components of the liquid bonding compositions are maintained separately until required, whereupon the contents of the separate packs are mixed together.

EXAMPLE 1 The following formulations were prepared:(in parts by weight) Control 1 2 3 4 5 6 Aerolite 300 100 100 100 100 loo 100 100 Neoprene 400* 0 5 10 20 25 100 200 10% Formic Acid solution 10 11.5 13 16 17.5 40 70 * Trade Mark of DuPont de Nemours.

Blocks cast in Petri dishes with the above liquid formulations gave the following results.

Control - fissures and cracks appeared in 3 days at room temperature. cracks appeared in approximately 5 days at room temperature. very slight cracking appeared after 9 days at room temperature. no cracking after 7 months at room temperature. no cracking after 7 months at room temperature. no cracking, but some shrinkage.

Latex was precipitated out of solution by the formic acid, eventually re Additional Mix No. 7 Aerolite 300 Dicrylan Latex 3793* % Formic Acid solution * Dicrylan Latex 3793 with a solids content but a solid non-cracked block suited. 100 parts by weight 25 II II II (Trade Mark of Ciba-Geigy Ltd) 17.5 II II is an acrylic copolymer latex of approximately 50% bv weight.

This mix produced a solid white opaque crack-free, hard casting, with very high surface gloss.

EXAMPLE 2 Mix No. 4 was used as a brush-on surface coating on woodparticle board, cast plaster, hardbdard, and corrugated paper board, and produced a hard crack-free water resistant glossy protective surface.

EXAMPLE 3 Mix No. 4 100 parts by weight Sand 100 This was used as a thick (¾ - 1mm) surface coating on cast plaster board, foamed polyurethane insulation board, wood particle board, and expanded UF board, to give hard, waterproof, abrasion-resistant surfaces to these substrates.

EXAMPLE 4 Mix No. 4 100 parts by weight Gypsum 1 100 This gave similar surface skins on the above substrates, but which were slightly less abrasion-resistant.

The same formulation when cast into thick blocks (7-l0mm thickness) gave hard sharp-edged castings suitable for many applications, eg road reflector studs surfaced with reflecting glass beads.

EXAMPLE 5 Mix No. 4 100 parts by weight Plaster 200 (hemihydrate) This produced accurate cast shapes, of high water resistance and extreme hardness. Such cast shapes were then coated on their surfaces with Mix No. 4 (without filler) to produce glossy-surfaced products with improved surface hardness.

Alternatively the cast resin/plaster shapes were ground and polished to give products resembling natural marble.

EXAMPLE 6 Mixes Nos. 2, 3 and 4 have been found useful as adhesives for example for bonding bristles into the metal ferrules of brushes, and for such applications may be extended with gypsum as described above.

Unfilled mixes, for example Nos. 2, 3 and 4, can be used for bonding wood and other cellulosic materials and also a range of porous non-cellulosic materials in conditions where large gaps exist between the members to be joined which must be filled with a non-cracking (non-disintegrating) adhesive, or in conditions where no pressure can be applied to the surfaces to bring them into reasonably close contact.

EXAMPLE 7 (a) Other mixes used for castings and- surface coatings (non-cracking) included: Aerolite 300 100 parts by weight Scott Bader Latex 33061* 15 % Formic Acid 10 (Transparent in 1mm layers) * (a vinylidene chloride copolymer latex with a solids content of approximately 55% by weight).

Aerolite 300 100 parts by weight Scott Bader Latex 33061 15 Η „ (1 Ti02 20 (1 II tt 20% Formic Acid 10 (white, opaque) (c) (i) 100 parts by weight UF + 10 parts by weight Scott Bader Latex 13/002* (ii) 100 parts by weight UP + 20 parts by weight Scott Bader Latex 13/002 * (iii) 100 parts by weight UP + 50 parts by weight Scott Bader Latex 13/002* ) ) ? in each case with 14 . parts by weight of 10% ( formic acid for every . 100 parts by weight of j the mixture. ) ) to give non-crack castings and coatings.

* Scott Bader Latex 13/002 is an acrylic copolymer latex with a solids content of approximately 55% by weight.

EXAMPLE 8 Mix No. 4 was mixed with an equal amount by weight of gypsum, and the combined mixture was impregnated into two layers of chopped strand mat. (The weight/m of the glass mat was 300g). The impregnated material was allowed to dry, with the top surface uncovered, for 16 hours at about 23°C. Two such laminates were then put together and pressed under a pressure of 50 bars in a hydraulic press and heated therein at 90°C for 15 minutes. Rigid, smooth-faced laminates containing 12% by weight of glass fibre were thus obtained.

EXAMPLE 9 (a) Equal parts of gypsum and Mix No. 4 were used to impregnate three layers of glass fibre chopped strand mat 2 (each of density 300g/m ). The uncured laminate, faced with sheets of aluminium foil, was pressed in a hydraulic press, using a pressure of 25 bars, and heated therein at 60°C for one minute. The edges of the moulding were defined by a square metal gasket mould of thickness 3mm.

A shaped, but flexible, moulding was removed from the mould and cured overnight at 90°C to give a rigid sheet.

Mechanical testing of the sheet revealed a flexural -2 modulus of 5,150 MNm and a flexural strength of 55 MNm _2 and a flexural strength of 55 MNm . The glass fibre content was 9% by weight. (b) This procedure was repeated with half the amount of gypsum, but with four layers of glass fibre mat. The _2 flexural modulus was determined at 4.200 MNm , and the _2 flexural strength as 79 MNm (c) Other materials were prepared, using three and four layers of glass fibre mat, with the following mixtures.

Mix No. 4 100 parts by weight Fine Sand 200 II II II Mix No. 4 100 II II II Kaolin 25 II II It Mix No. 4 100 II ll II Kaolin 50 II II It Fine Sand 50 II II II Mix No. 4 100 II It II Bentonite 25 π π it Fine sand 100 It II n In these instances, the materials were shaped under low pressures (about 1 bar) without a restraining gasket. and were initially heated for 2 minutes at 70°C between sheets of aluminium foil. The foil was then removed, and the composites heated for 16 hours at 90°C to substantially complete the cure. (d) In another instance, layers of glass fibre mat impregnated with equal amounts of gypsum and Mix No. 4 were placed between sheets of aluminium foil in a 3mm thick gasket mould, so that the initial thickness of the charge was 6mm, and covered only about half the area of the mould. The mixture was placed between the platens of a hydraulic press, which were at 60°C, and held close to the platens for % minute before closing the press. Moulding was then carried out for 1 minute, using a pressure of 25 bars. A flexible moulding conforming to the shape of the mould and of 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 charged to a blade mixer. 100 parts Mix No. 4 by weight 50 parts Kaolin 100 parts Pine Sand parts by weight 1 chopped glass fibre strands.

These were mixed into a dough for about ten minutes, 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 about 5 bars for ten minutes. The moulded sheet was post-cured at 90°C for 16 hours.

EXAMPLE 11 A pipe was prepared by impregnating glass fibre chopped strain mat with equal amounts of Mix No. 4 and gypsum. This was helically wound around a glass tube previously itself wrapped with poly(ethylene terephthalate) film. The wound structure was smoothed and consolidated, and the assembly heated in an oven for 15 minutes at 90°C. A flexible but self-supporting pipe could then be removed from the tube, the poly(ethylene terephthalate) film removed, and post-cured at 90° C for three hours. A rigid, impact-resistant pipe was produced.

EXAMPLE 12 A mixture of equal amounts of Mix No. 4 and gypsum was placed in a cylindrical mould and rotated about its longitudinal axis until the mixture gelled (about 45 minutes at 23°C). The tube produced was removed, and allowed to dry at room temperature for 24 hours. This was helically wound with impregnated glass fibre mat as in the previous example, and then the whole heated at 90°C for three hours to give a rigid, impervious pipe.

EXAMPLE 13 Mix No. 4 was cast into a 2mm thick gasket mould between sheets of poly(tetrafluorethylene) coated glass cloth, and the casting held in this assembly heated for 3 minutes at 70°C by placing it between hot metal plates.

A flexible, opaque material was removed, and was placed in an oven at 60°C. After two hours a sheet of good transparency was obtained. The casting was, and remained, free of cracks.

EXAMPLE 14 Aerolite 300 was acidified by 10% by weight of a 10% formic acid solution, and the resin impregnated into glass fibre chopped strand mat. The impregnated mat was gelled by heating at 70° C for 3 minutes between PTPE coated glass cloth and hot metal plates, as described in the previous example. The gelled mat was heated at 60°C overnight, and then overnight at 90°C. Upon examination, the resin in the finished mat was observed to be cracked.

A mat prepared in the same way from Mix No. 4 was found to be free of cracks.

EXAMPLE 15 The following mixtures were prepared.

A. 100 parts Control Resin (Aerolite 300 + 10% of a 10% formic acid solution) 1/3 parts kaolin 133 1/3 parts Fine sand B. 100 parts Mix No. 4 1/3 parts kaolin 133 1/3 parts Fine Sand Both A and B were impregnated into glass fibre chopped strand mat and lightly pressed between hot plates at 70°C for 3 minutes, as described in previous examples, to provide sheets which were then cured at 9o°C for 15 hours.

Strips of each sample were immersed in water at 80°C, 60° C and 40°C, for 120 hours. The samples were removed, wiped dry, and weighed. They were then allowed to dry overnight at room temperature then dried at 60°C overnight, and finally reweighed. The overall change in the thickness of each sample was also determined. The results were as follows.

At 80°C Change in weight after immersion A - 8.1% B - 0.75% Change in weight after immersion and drying A - 21.7% B - 15% Change in thickness after immersion and drying A - 8.2% B - 3.5% At 60°C Change in weight after immersion A + 0.4% B + 3.6% Change in weight 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 Change in weight after immersion A + 4.8% B + 6.1% Change in weight after immersion and drying A - 4.6% B - 4.3% Change in thickness after immersion and drying A - 8.1% B - 2.5% It was also observed that the surfaces of samples of material A were loose and powdery, this being worst for samples immersed in water at'80°C. The surfaces of samples of material B prepared according to the invention were significantly more coherent, and unlike those of material A, were not subject to loss of material from the surface by light abrasion. Material B thus exhibited a significantly better resistance to water attack than sample A.

Claims (12)

1. CLAIMS:1. A liquid composition containing from 5% to 95% by weight of a liquid polymer latex consisting of a neoprene, an acrylic polymer or copolymer, or a vinylidene chloride polymer or copolymer, and from 95% to 5% by weight of an aqueous urea formaldehyde resin, melamine formaldehyde resin, or a mixture thereof, the sum of the percentages of the liquid polymer latex and the aqueous resin totalling 100.

2. A derived composition containing a composition as claimed in claim 1, and a resin curing catalyst in an amount insufficient to cause the latex to precipitate, so that the composition is still liquid and homogeneous.

3. A derived composition as claimed in claim 2, wherein the catalyst is an acid.

4. A derived composition as claimed in claim 3, wherein the acid is formic acid.

5. A derived composition as claimed in any of claims 2-4, additionally containing an alkali metal silicate.

6. A derived composition as claimed in claim 5, wherein the alkali metal silicate is sodium silicate.

7. A derived composition as claimed in either of claims 5 and 6, when dependent on claim 1, containing between 20% and 80% by weight of the alkali metal silicate and between 80% and 20% by weight of the composition of claim 1, the sum of the percentages of the silicate and Of the composition of claim 1 totalling 100.

8. A method of coating surfaces, which comprises applying thereto a liquid composition as claimed in claim 1 or a derived composition as claimed in any one of claims 2-7.

9. A method of bonding to one another articles having similar or dissimilar surfaces, which comprises applying to at least one of the surfaces a liquid composition as claimed in claim 1 or a derived composition 5 as claimed in any one of claims 2 to 7, and thereafter pressing the surfaces together.

10. A method of bonding to one another articles having similar or dissimilar surfaces, which comprises applying to one surface at least one component of a 10 liquid composition as claimed in claim 1, or a derived composition as claimed in any one of claims 2 to 7, and applying to the other surface the other component(s) of the composition, and thereafter pressing the surfaces together.

11. 15 11. A method of binding particulate or fibrous materials, which comprises applying thereto a liquid composition as claimed in claim 1, or a derived composition as claimed in any one of claims 2 to 7, and forming the material into any desired shape.

12. 20 12. A method of producing moulded articles, which comprises forming a liquid composition as claimed in claim 1, or a derived composition as claimed in any one of claims 2 to 7, and casting the composition in a mould.