GB1592348A - Moulding compositions comprising cement clinker particles and a resin binder - Google Patents

Description

(54) MOULDING COMPOSITIONS COMPRISING CEMENT CLINKER PARTICLES AND A RESIN BINDER (71) I, KARL KRISTIAN KOBS KRYER, of Danish nationality, of Banegaadspladsen 4, DK-8100 Aarhus C, Denmark, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to moulding compositions which are useful in the production of moulded articles having excellent mechanical properties, in particular high mechanical strength.

In accordance with the present invention there is provided a moulding composition comprising, in admixture, a coarse aggregate comprising inorganic particles of cement clinker having a particle size in the range 250 to 5000 ,um and a binder therefore, wherein the binder comprises an intimate blend of an organic thermoplastic or thermosetting resin and finely divided filler, said filler comprising ground cement clinker having a particle size less than 250 ,um.

Also included are moulded articles formed from the above compositions by moulding under heat and pressure.

The particle size of the 'finely divided filler used in the binder can be varied to suit the use. Generally the particle size will be less than 250 Zm and preferably less than 150 jum. Cement clinker powders of ideal fineness characteristic, i.e. of a size distribution to permit dense packing, are preferred.

The preferred aggregate and finely divided filler is cement clinker particles which have been subjected to further heat treatment for the purpose of strengthening the crystalline and ceramic structure, and minimizing the hydraulic effect.

This further heat treatment can be provided preferably by renewed heating to at least 1000"C, particularly in a rotary kiln, after cooling the clinker to room temperature. The cement clinker may, for example be gradually heated to about 1050"C over a period of about two hours, after which the temperature is gradually lowered to about 500"C, followed by cooling the product to room temperature.

Alternatively, the heating period employed in the ordinary production of cement clinker may be extended by 30 minutes, for example, and/or the heating zone may be moved to a higher position in the kiln.

In these methods it is likewise possible to obtain wholly or partly crystallized and/or ceramized cement clinker particles although these' have a somewhat coarser crystal size and less strength than that attainable by cooling and re-heating.

A test of the cement clinker material before and after the aforesaid re-heating showed a crystallized product with relatively small crystals, and that the clinkers, which after the treatment owing to the crystallization are no longer'clinkers in the ordinary sense of this word, had obtained considerably improved crushing strength.

Normally, the strength of an aggregate is determined by the following standard test: A grain size fraction of 5-7 mm is clean-separated for 5 min. on a 5-mm screen, after which 500 g are weighed out and filled into a test cylinder. The sample is subjected to "a plunger provided with a 4-kg weight, whereupon there are applied 20 strokes with a 14-kg drop hammer at a 25-cm elevation.

The sample is now separated on 5-4-3-2-1 mm screens for 5 min., and the crushing number is calculated as indicated in the following example: +5 408g 81.6% +4 31- 6.2=3 18.4 (a+b+c+d+e) +3 17- 3.4=d 12.2 (A+b+c+d) +2 11- 2.2=c 8.8 (a+b+c) +1 11- 2.2=b 6.6 (a+b) -1 22- 4.4=a 4.4 (a) 500g 100.0% 50.4 Crushing number: 50 Test of cement clinkers: from room temperature Without heating after heating to 10500C 5 275 55.0 5 372 74.4 4 64 12.8 45.0% 4 39 7.8 25.6% 3 66 13.2 32.2- 3 37 7.4 17.8 2 29 5.8 19.0- 2 15 3.0 10.4 1 25 5.0 13.2- 1 13 2.6 7.4 1 41 8.2 8.2- -1 24 4.8 4.8 500 g 117.6% 500 g 66.0% Crushing number: 118 Crushing number: 66 The heat treatment thus resulted in almost halving the crushing number. It will be noted that the crushing strength increases with decreasing values of crushing number.

As the resin component of the binder can be used any organic resin. Examples of suitable resins are thermosetting resins or cold curing resins, such as epoxy resins, melamine resins, urea formaldehyde resins unsaturated polyesters, urethane resins and phenol formaldehyde resins, or thermoplastic resins, such as polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyacrylates, polystyrene, polyamides and polycarbonates.

The ratio between filler particles and the organic resin in the binder can be varied within wide limits. The proportion of resin should be kept as small as possible without reducing the desired mechanical properties. An amount of 5-20% resin, e.g. 10% resin, is suitable for most purposes. More resin can be used, for example 20-30% resin or 30-50% resin, if desired. Also, smaller amounts of resin can be used, for example 2-5% resin. Normally, this will reduce the mechanical strength and other properties of the final product. Generally preferred are amounts in the range 5-10% by weight.

The mixing of the filler and the resin is carried out in such a way that the resin, usually in powder form, is ground into the interstices and the surface irregularities of the filler particles. Suitable mixing equipment for this purpose are ball mills and mixers having a similar grinding effect. Preferably the filler and resin are dry mixed by grinding in a ball mill. The mixing process may sometimes be facilitated by adding a solvent, or the resin may be introduced as a solution of the organic resin in a suitable solvent or as a suspension or emulsion in water. As the solvent can be used any conventional solvent for resins, Normally, the solvent evaporates during the mixing procedure.

If desired, it is possible to add also minor amounts of various additives or adjuvants to achieve desired effects or as fillers. Hence, silicon oxides or silicates may be added. For example, Aerosil (Registered Trade Mark) added to the binder in amounts of from 0.01 to 1 % by weight will result in increased fluidity, improved density and uniformity of the finished product.

Other additives suitable in small or moderate amounts are small glass spheres, short mineral fibres, for example of glass or rockwool, and pigments. Also, the products may be reinforced by metal threads or grating, glass 'fibre mats our woven cloth, cellulose' fibres, paper or the like. Pigmentation will produce various decorative effects. By mixing fractions of different colours it is also possible to obtain various marbled patterns. Particularly preferred are compositions in which the binder comprises a minor amount of fibrous filler in addition to the cement clinker powder and the resin.

The amount and particle size of the coarse aggregate particles to be mixed with the binder depend on the end use of the articles and the technology available for the forming process. For most purposes particle sizes from 250 to 1000 ,um are suitable. Even coarser particles can be used, however, for example 1-5 mm, especially whén articles of large dimensions are to be produced. The ratio of coarse particles to binder depends on the type of particles, the use and the desired properties of the product and may vary within wide limits. For example, 1 to 5 parts by weight of coarse particle to 1 part by weight of binder is generally suitable.

The composition of this invention may be compression moulded under heat and pressure or formed in any other desired manner to produce strong articles having extremely low resin content, based on the total mix. As the organic resin is by far the most expensive component of the mixture, very cheap products having satisfactory or excellent characteristics can be obtained.

The compositions of the invention can be formulated to obtain a large variety of properties of the end products. Thus, the formulation can be modified in order to obtain products having high mechanical strength, increased weather resistance, high porosity or non-porosity and different colour effects. A composition according to the present invention is illustrated in the following Example EXAMPLE Cement clinker produced in conventional manner by heating in a clinker kiln and cooling in a water bath are re-heated to 12000C in a rotary kiln for two hours and then slowly cooled to room temperature. These clinkers proved to have a higher degree of crystallization than normally. The clinkers are ground in a ball mill with steel balls for 10 minutes, after which there is added 6% by weight of phenolic resin, and grinding is continued for further 5 minutes.The grain size of the ground product is 0-300,um. The product is pressed into 6 mm thick panels by heating to 170or for 30 seconds.

WHAT I CLAIM IS: 1. A moulding composition comprising, in admixture, particles of a coarse aggregate and a binder therefor, wherein the coarse aggregate comprises particles of ground cement clinkers having a particle size in the range 250 to 5000 ,4m and wherein the binder comprises an intimate blend of an organic thermoplastic or thermosetting resin and a finely-divided filler, said filler likewise comprising particles of cement clinkers obtained by grinding but having a particle size less than 250,am.

2. A composition according to claim 1, wherein said aggregate particle size is in the range 250 to 1000 ,u,.

3. A composition according to any one of claims 1 or 2, wherein the finely divided filler particles have a maximum particle size not exceeding 150 im.

4. A composition according to any one of claims 1 to 3, wherein the weight ratio of said aggregate to said binder is from 1:1 to 5:1.

5. A composition according to any one of claims 1 to 4, wherein the organic resin constitutes from 5 to 10% by weight of the binder.

6. A composition according to any one of claims 1 to 5, wherein the coarse aggregate particles and/or the finely divided filler particles are particles of cement clinker which have been heat treated to strengthen the crystalline and ceramic structure thereof and to minimize the hydraylic effect.

7. A composition according to any one of the preceding claims, wherein the organic resin is a thermosetting resin.

8. A composition according to claim 7, wherein the thermosetting resin is a phenol formaldehyde resin.

9. A composition according to any one of the preceding claims, wherein the binder additionally contains a minor amount of a fibrous filler.

10. A moulded article comprising a composition according to any one of the preceding claims which has been compression moulded under heat and pressure.

11. A method of forming a composition according to any one of claims 1 to 12 which comprises grinding cement clinker particles in the presence of the organic resin to form said binder, and subsequently adding to the binder the coarse aggregate particles.

12. A method according to claim 11, wherein the cement clinker particles are dry ground with said resin in powder form.

13. A method according to claim 11 or 12, wherein the cement particles are ground

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

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. be reinforced by metal threads or grating, glass 'fibre mats our woven cloth, cellulose' fibres, paper or the like. Pigmentation will produce various decorative effects. By mixing fractions of different colours it is also possible to obtain various marbled patterns. Particularly preferred are compositions in which the binder comprises a minor amount of fibrous filler in addition to the cement clinker powder and the resin. The amount and particle size of the coarse aggregate particles to be mixed with the binder depend on the end use of the articles and the technology available for the forming process. For most purposes particle sizes from 250 to 1000 ,um are suitable. Even coarser particles can be used, however, for example 1-5 mm, especially whén articles of large dimensions are to be produced. The ratio of coarse particles to binder depends on the type of particles, the use and the desired properties of the product and may vary within wide limits. For example, 1 to 5 parts by weight of coarse particle to 1 part by weight of binder is generally suitable. The composition of this invention may be compression moulded under heat and pressure or formed in any other desired manner to produce strong articles having extremely low resin content, based on the total mix. As the organic resin is by far the most expensive component of the mixture, very cheap products having satisfactory or excellent characteristics can be obtained. The compositions of the invention can be formulated to obtain a large variety of properties of the end products. Thus, the formulation can be modified in order to obtain products having high mechanical strength, increased weather resistance, high porosity or non-porosity and different colour effects. A composition according to the present invention is illustrated in the following Example EXAMPLE Cement clinker produced in conventional manner by heating in a clinker kiln and cooling in a water bath are re-heated to 12000C in a rotary kiln for two hours and then slowly cooled to room temperature. These clinkers proved to have a higher degree of crystallization than normally. The clinkers are ground in a ball mill with steel balls for 10 minutes, after which there is added 6% by weight of phenolic resin, and grinding is continued for further 5 minutes.The grain size of the ground product is 0-300,um. The product is pressed into 6 mm thick panels by heating to 170or for 30 seconds. WHAT I CLAIM IS:

1. A moulding composition comprising, in admixture, particles of a coarse aggregate and a binder therefor, wherein the coarse aggregate comprises particles of ground cement clinkers having a particle size in the range 250 to 5000 ,4m and wherein the binder comprises an intimate blend of an organic thermoplastic or thermosetting resin and a finely-divided filler, said filler likewise comprising particles of cement clinkers obtained by grinding but having a particle size less than 250,am.

2. A composition according to claim 1, wherein said aggregate particle size is in the range 250 to 1000 ,u,.

3. A composition according to any one of claims 1 or 2, wherein the finely divided filler particles have a maximum particle size not exceeding 150 im.

4. A composition according to any one of claims 1 to 3, wherein the weight ratio of said aggregate to said binder is from 1:1 to 5:1.

5. A composition according to any one of claims 1 to 4, wherein the organic resin constitutes from 5 to 10% by weight of the binder.

6. A composition according to any one of claims 1 to 5, wherein the coarse aggregate particles and/or the finely divided filler particles are particles of cement clinker which have been heat treated to strengthen the crystalline and ceramic structure thereof and to minimize the hydraylic effect.

7. A composition according to any one of the preceding claims, wherein the organic resin is a thermosetting resin.

8. A composition according to claim 7, wherein the thermosetting resin is a phenol formaldehyde resin.

9. A composition according to any one of the preceding claims, wherein the binder additionally contains a minor amount of a fibrous filler.

10. A moulded article comprising a composition according to any one of the preceding claims which has been compression moulded under heat and pressure.

11. A method of forming a composition according to any one of claims 1 to 12 which comprises grinding cement clinker particles in the presence of the organic resin to form said binder, and subsequently adding to the binder the coarse aggregate particles.

12. A method according to claim 11, wherein the cement clinker particles are dry ground with said resin in powder form.

13. A method according to claim 11 or 12, wherein the cement particles are ground

with the organic resin to form said binder in a ball mill.