GB1567033A

GB1567033A - Amino-resin compositions

Info

Publication number: GB1567033A
Application number: GB2452376A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1977-09-14
Filing date: 1977-09-14
Publication date: 1980-05-08

Description

(54) AMINO-RLiSIN COMPOSITIONS (71) We, IMPERIAL CHEMI('AL INDUSTRIES LIMITED, Imperial Chemical house, Millbank, London SWII' 3JF a British Company do hereby declare the invention for which we pray that a patent may be grined lo us, and the method by which it is to be performed, to be particularly described in and by the following statement:: The present invention relates to amino-rcsin compositions in the form of free-flowing, finely-divided particles or powders, containing sufficicnt water to rcnder them workable but containing insufficient water lo CilUSt ciking or t'usion of the compositions under storage.

By the term "workable" we mcii' that the compositions are capable of being moulded at a temperature below lt)()0C using a pressure of < 1() ats. Such workable compositions may be shaped by processcs other than moulding; for example by casting, extruding, and may also be used as adhesives, coatings. additives for building materials and composites, and for similar or allied purposes as hereinafter described. The amino-rcsins of the compositions are preferably urea-formaldehyde, mclami ne-formaldehyde. or mixtures of these with each other or with phenol-formaldehyde.

Conventional aqueous solutions of amino-resins tend to crack upon being dried and cured. Conventional amino-resin moulding powders avoid this disadvantage by advancing the drying and curing of the resin, but on the other hand they require high pressures and temperatures to be moulded or otherwise used as workable compositions. These, and other, disadvantages are overcome by this invention by using free-flowing, finely-divided, particulate or powdered amino-resin compositions in accordance with the present invention.

The present invention provides an amino-resin composition comprising in combination: a) One or more amino-resins; b) At least one resin-modifier which prevents shrinkage and cracking of the resin upon curing thereof. Suitable resin-modifiers include. for example, sodium silicate (see British Patent 1515289); an addition polymer or copolymer latex (see British Patent 1522474); a precipitated amino-resin (see Australian Patent 497955); and/or a silica sol.

(c) Sufficient water to allow the composition to be moulded worked at a temperature below 100"C using a pressure below 10 ats., but insufficient to cause the composition to cake or fuse under storage. Optionally, the amino-resin compositions of the invention may include one or more of the following ingredients: (d) A particulate filler, such as sand, clay, plaster, or gypsum; (e) An acidic catalyst (preferably a solid), such as ammonium sulphate, citric acid, tartaric acid, or oxalic acid, or an anhydride such as phthalic anhydride. The catalyst should not be added until the compositions has the requisite water content; at an earlier stage in their preparation, the compositions may be in the form of liquids or slurries with a very much higher water content, and the catalyst should not be added during any such stage.The catalyst accelerates the curing of the final amino-resin product.

(f) At least one solid additive (e.g. a hydrate) which will liberate water upon heating preferably at below 100"C). During the moulding. casting, fusion, extrusion, or other processing of the amino-resin compositions of the invention, this water-liberating additive increases the free water-content of the compositions.

(g) Flame retardants, pigments, stabilizers, release agents and other conventional additives.

The compositions of the invention are workable free flowing powders and can be stored as such. However the workability, e.g. mouldability, can be improved by adding some additional water, as liquid water or steam, prior to use, and such addition is generally desirable. However, in some cases, where a water liberating additive is included in the composition, the need to add further water may be eliminated.

Some or all of the optional ingredients (with the exception of the catalyst) may be added during the preparation of the free-flowing, finely-divided particulate or powdery compositions from the essential ingredients (a), (b) and (c), but preferably they are added when the preparation of the compositions is complete (at which stage the catalyst may be added). Alternatively some or all of the optional ingredients, together with some additional liquid water or steam if necessary, can be added when the compositions are being prepared for use (e.g for moulding, casting, fusion, extrusion, etc).

The advantages of the amino-resin compositions of the present invention include the following: (1) They are free-flowing particles or powders which do not cake or fuse under storage.

(2) Products made from them do not shrink or crack after or during drying and curing which may be carried out at above 100"C).

(3) The products can be produced in the presence of small amounts of water; this, in turn means that drying and curing of the products require less time.

(4) The compositions can be moulded at low pressures (e.g less than 10 ats.), and cast, fused, extruded, low-pressure-moulded at low temperatures (e.g 50"C to less than 100"C) without subsequent cracking during or after drying and curing.

The precise amount of water necessary to achieve workable free-flowing powders will depend upon the nature of the resins, resin-modifiers, fillers (if any) and the method of preparation. Typically, water-contents of 5 to 25coo by weight might be expected. Improved mouldability can be achieved by adding small amounts of water (as described above) in the moulding operation and/or by adding a hydrate which releases water when heated to a temperature below about 100"C.

Manufacture: (1) Free-flowing finely-divided particulate or powdered amino-resin compositions according to the invention can be prepared by first drying an aqueous solution of one or more amino-resins by conventional means (e.g spray-drying, drying in a ring-drier, drying in a drum-drier). To obtain a very finely-divided particulate or powdered composition, the dried amino-resin may then be ground. These steps may be carried out on the amino-resin alone or on the amino-resin in admixture with one or more of the other ingredients of the final composition (other than the catalyst); otherwise the said other ingredients may be admixed with the amino-resin after this drying stage.During this drying stage, the amino-resin may be dried only enough to ensure that the final composition contains the requisite amount of water, or it may be dried substantially completely, and the requisite amount of water may be added thereafter.

(2) Alternatively, all the ingredients (with the exception of the catalyst) may be mixed in an extruder. water being removed during the extrusion. and the product being subsequently ground finely. The catalyst may be added before or after the grinding step.

(3) The resin modifier, some water (if necessary) and an amino-resin (either spray-dried or in the form of a concentrated solution) are added to the particulate filler in a mixer, to produce a uniformly-coated filler. Further filler (in particular clay) may be added at the end of the operation to improve the free-flowing character of the composition. Specific additives, such as fumed silica, may also be added to the composition to achieve this object.

Other optional ingredients may be added to the composition before, during or after these steps.

(4) As an alternative to (3) above, all the essential ingredients (and, if desired, some or all of the optional ingredients, with the exception of the catalyst) may be added, in aqueous form, to the filler, in a fluidized drier.

Uses: (1) In composite articles, e.g sheets and pipes, with fibre-reinforcement if required, since the finely-divided, powdered amino-resin composition can be made to penetrate a fibrous structure before fusion. Alternatively, a "dough" can be made by warming the amino-resin composition and mixing it with a fibre, e.g chopped glass fibre strands. Extra water can be added at this stage.

As As a gap-filling adhesive.

2 As an additive to plaster for strengthening and water-proofing the plaster.

(4) As a coating for concrete, wood, plaster or the like.

Example 1 The following components were used to make moulding materials in accordance with the invention Ground Silica Sand, type HPF 2 from Nornef Minerals, mean particle size 60 microns. 100 part by weight used. 20 parts by weight of a latex of a vinyl acetate/ethylhexyl acrylate copolymer (ratio of monomers 80 : 20 respectively) containing 45% water. 80 parts by weight of a spray-dried urea formaldehyde resin (Aerolite 306 from Ciba-Geigy), approximate water content 6% by weight. 7 parts by weight of ammonium sulphate.

The sand filler was first blended with the latex, the latex being added slowly to the filler as it was stirred in a laboratory mixer. UF resin powder was then added slowly, and finally the ammonium sulphate catalyst was added. A free-flowing moulding powder was obtained, and was subsequently made finer by ball-milling to a particle size below 4251l.

It was found that this mixing procedure gave the best results; adding the resin to the sand, followed by the latex gave a poorer product, while adding the catalyst before the resin gave an infusible material. Mixing resin and latex before adding the filler did not result in a free-flowing powder system.

The moulding powder so obtained contained about 6.9% by weight water. It could be fused under a pressure of less than 1 atm. at 90 C to give a moulding of density 1.62 - 1.70 g cm -3. Final curing was done outside the mould by heating at 90"C for 24 hours. Curing proceeded without distortion and with a linear shrinkage of less than 1%. The flexural properties of a moulding was measured and found to be Flexural modulus 9900 MNm-2 Flexural strength 48 MNm-2 Example 2 As Example 1, but 75 parts by weight of Aerolite 306 and 5 parts by weight of melamine were used.

Example 3 (Comparative) Adding an extra 5 parts by weight of water to the composition of Example 1 with the latex so that the overall water content was about 9.4% by weight, gave granules that were capable of being moulded, as in Example 1, without cracking or distorting, but the granules were tacky and not free flowing.

Example 4 (Comparative) Adding an extra 10 parts by weight of water to the composition of Example 1 with the latex gave a composition that was capable of being mixed with glass fibre reinforcement and moulded as a dough. However the composition containing additional water was a stickly paste and not a free flowing powder.

Example 5 As Example 1, but only 17.5 parts by weight of the latex were used, and this was added to the filler in the form of a fine spray as the material was mixed in a planetary mixer. After addition of the resin and catalyst, 4 parts by weight of fine talc were added. The mixture was further reduced by grinding to < 420y. The tapped bulk density of the moulding powder was 0.99 g cm-3. The material was moulded at the following pressures, and at 90"C, the densities recorded.

Pressure (Atm) Mean Density (g cm-3) 0.176 1.58 + 0.08 0.37 1.70 1 0.05 0.61 1.64 + 0.05 The material was also dry-blended with chopped glass fibre strands (length 20 mm) and compression moulded at 35 Atm pressure at 90"C. The glass fibre content was 10% by weight.

Example 6 As Example 1, except that 14 parts by weight of ground CaC12. 6H2O were added at the end of the mixing stage. The material was then compression-moulded at 90"C with glass fibre reinforcement. The purpose of the calcium chloride was to release further water during the moulding stage.

WHAT WE CLAIM IS: 1. An amino-resin composition in free flowing finely divided particulate form comprising, in combination, one or more amino-resins, at least one resin-modifier which prevents shrinkage and cracking of the resin upon curing thereof, and sufficient water to allow the composition to be moulded at a temperature below 100"C using a pressure below 10 atmospheres but insufficient to cause the composition to cake or fuse under storage.

2. An amino-resin composition as claimed in claim 1, wherein the amino-resin is urea-formaldehyde, melamine-formaldehyde or mixtures of these with each other or with phenol-form-aldehyde.

3. An amino-resin composition as claimed in claim 1 or claim 2, wherein the resin-modifier is sodium silicate; an addition polymer or copolymer latex; a precipitated amino-resin, and/or a silica sol.

4. An amino-resin composition as claimed in any one of claims 1 to 3, wherein the water comprises between 5% and 25% by weight of the total weight of the composition.

5. An amino-resin composition as claimed in any one of the preceding claims, also comprising a particulate filler.

6. An amino-resin composition as claimed in claim 5, wherein the particulate filler is sand, clay, plaster and/or gypsum.

7. An amino-resin composition as claimed in any one of the preceding claims, also comprising an acidic catalyst.

8. An amino-resin composition as claimed in claim 7, wherein the acidic catalyst is a solid.

9. An amino-resin composition as claimed in claim 7 or claim 8. wherein the acidic catalyst is ammonium sulphate, citric acid, tartaric acid, oxalic acid and/or phthalic anhydride.

10. An amino-resin as claimed in any one of the preceding claims, also comprising at least one solid additive which will liberate water upon heating.

11. An amino-resin composition as claimed in claim 10, wherein the solid additive liberates water upon heating at below 100"C.

12. An amino-resin composition as claimed in claim 10 or claim 11. wherein the said solid additive is a hydrate.

13. An amino-resin composition as claimed in claim 12, wherein the hydrate in CaC12 6H20.

14. An amino-resin composition according to claim 1 substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 6 As Example 1, except that 14 parts by weight of ground CaC12. 6H2O were added at the end of the mixing stage. The material was then compression-moulded at 90"C with glass fibre reinforcement. The purpose of the calcium chloride was to release further water during the moulding stage. WHAT WE CLAIM IS:

1. An amino-resin composition in free flowing finely divided particulate form comprising, in combination, one or more amino-resins, at least one resin-modifier which prevents shrinkage and cracking of the resin upon curing thereof, and sufficient water to allow the composition to be moulded at a temperature below 100"C using a pressure below 10 atmospheres but insufficient to cause the composition to cake or fuse under storage.