GB2233640A - Mineral composition - Google Patents

Abstract

A synthetically produced mineral composite is a cost effective substitute for naturally occurring materials such as marble, onyx and like materials. In the production process by the use of a stainless steel or likewise highly polished mould with adjustable lip, a thin section thickness of 2 mm can be produced. The mineral composite may have high optical brightness, reflectance or fluorescence and comprises a mineral powder, e.g. Irish marble dust, a pigment and a catalytically cured synthetic resinous binder.

Description

MINERAL COMPOSITION This invention relates to a mineral composition.

Particularly, but not exclusively, the invention relates to a mineral composite for use as a substitute for naturally occurring mineral materials such as marble, onyx and like materials valued for their aesthetic appearance. Another aspect of the invention relates to a mineral composite having high optical brightness, reflectance or fluorescence.

Marble and marble-like minerals have been valued since antiquity for their aesthetic appeal and have been use extensively through the ages not only in works of artistic sculpture but also in decorative facings for walls and floors and in the production of luxury articles for domestic use such as sanitary ware.

Marble occurs in numerous coloured forms, in addition to the common white form, many of which are believed to be extinct in nature or are, at least, very rare, almost acquiring the status of semi-precious stones. Although the term "marble" is normally associated with the pure white form, the term, as used herein, is intended to encompass material having a background of one principal colour with one or more colours or shade variations presented as veining or marbling therein. This definition encompasses, for example, the green marbled mineral onyx which, in strict geological terms is not related to marble.

According to the present invention there is provided a mineral composite comprising a moulded monolithic body having a pulverulent mineral base, a pigment for the mineral base and a catalytically cured synthetic resinous binder.

Preferably the binder is a polyester resin and it is further preferred that the mineral be marble dust, a material which is readily available from marble quarries and is currently of little or no commercial vaue or industrial utility.

The pigment may be an optical brightener, a colouring material, a fluorescent pigment or a light refelective material.

The present invention also provides a method of manufacturing a synthetic monolithic article comprising providing an appropriately shaped mould for the article, lining the mould with a gel coat, adding to the mould an amount of the mineral composition aforesaid including an appropriate catalyst for the resinous binder and allowing the composition to cure.

The pigment is preferably added to a mix of resin and base material in a mixer, the addition being follwed by only light or incomplete mixing of the pigment to avoid complete dispersion. Alternatively the mineral composition may be added to the mould in two or more batches, the said batches differing in their pigmentation, followed by partial intermixing of the batches so as to produce veining of the variously pigmented material thereby mimicing the veined or marbled appearance of natural minerals.

The pigment may be applied to the mineral base by spraying followed by drying.

In a preferred embodiment of the invention the mineral base material is crushed Irish marble.

In another embodiment the composition includes a light-reflecting or fluorescent pigment for application to highway or airport runway markers such as direction indicators, edge markers and lane markers.

It is preferred that the moulds used be of fibreglass construction but other materials, particularly those which present an unblemished surface finish, such as polished steel. However, the invention is not limited to the production of smooth surfaced articles, the surface texture being determined whooly by the surface texture of the mould.

The advantages of fibreglass moulds are that they are relatively simple to construct, using standard fibreglass fabrication techniques, present a good surface finish, be it smooth and shiny or textured in some way, are long lasting and easy to repair.

Stainless steel gives a good, durable surface for moulding of flat stocks anf sills. However, it is relatively expensive and damages such as deep dents and scratches are not easy to remove.

Synthetic sheet material, such as is sold under the Registered Trade Mark "Formica", is easy to use and is suitable for short production batches or special work but it is not particularly durable and tends to have only a semi-gloss surface which restricts its use.

Polymer concrete is a relatively recent commercial product which may be used as mould material. It is highly durable and thus is indicated for the construction of moulds for standard line articles which will be produced frequently and over long periods of time. Moulds made from this material tend to be very heavy.

The invention will now be described, by way of illustration, by the following description.

MOULD PREPARATION New fibreglass moulds should be post-cured and the surface primed before their first use. An application of several (for example, 6 to 8) coats of a good quality mould release agent such as Mirrorglaze MGH8 (Trade Mark) allowing time (30 minutes is sufficient) for each coat to dry before polishing and application of the next coat.

A thin coat of PVA (polyvinyl alcohol) may then be applied by spraying as a fine mist on to the mould surfaces, followed by a somewhat thicker second PVA coat. Since PVA is water soluble it can easily be removed from the moulded articles.

For the first two or three mouldings in a new mould it is preferable to coat the mould after each use with three successive coats of mould release agent (Mirrorglaze) and PVA. Subsequently a hand application of mould release agent is all that is required between mouldings.

APPLICATION OF THE GEL COAT A gel coat is applied to the mould before addition of the matrix mix. Freeman gel coat STYPOL 40-4901 is a clear water white high molecular weight N.P.G. isophthalic gel material. It is designed to be impact and atian resistant and to resist thermal shock.

It is recommended that those areas of the mould which are not to be coated with the gel coat be masked with tape, for example hinge and edge areas. The tape may be removed after application of the gel coat. Althogh the gel coat may be brushed on this is not recommended. Spraying at a 0 temperature of at least 20 C is the recommended method so that the gel coat performs as intended. Lower temperatures lead to inadequate atomisation of the spray, slow output, slow gel and cure, poor folw out and poor air release with the potential problem of porosity occurring.

THe recommended catalyst level for the gel coat is about 1.5 to 2.0% by weight of the gel coat resin.

To minimise porosity a layer thickness of 2-3 mil followed by layers of 5 mil to build up a total thickness of from 20 to 25 mils of wet thickness.

The gel coat is then allowed to gel and cure for about 1 to 2 hours, dependent on temperature, although the application of gentle heat of 40 - S00C in a forced oven allows the time to be reduced to about 15 minutes.

However, it should be noted that excessive or uneven heating can cause pre-release of the gel coat.

FORMULATIONS 1. Non-translucent Marble Matrix Resin: STYPOL 40-5735 100 parts by weight Catalyst: M.E.K.P.(Medium Reactive) 1.0 part by weight Mineral Base: MICRODOL 40/200 (Coarse) 240 parts by weight MICRODOL 200 (Fine) 120 parts by weight The indications STYPOL, M.E.K.P and MICRODOL are Trade Marks. The STYPOL may be replaced by Grade 40-5746 to extend the pot-life of the composition from around 20 to about 40 minutes.

Alteration of the ratio of the coarse to fine particles allows adjustment of the viscosity of the mix.

2. Translucent Onyx Matrix Resin: STYPOL 40-5746 100 parts by weight Mineral Reynolds Aluminium Trihydrate RH34 180 parts by weight Catalyst: M.E.K.P. Medium Reactive 1.0 part by weight The above composition has a pot-life of about 40 minutes.

Reynolds Aluminium Trihydate RH34 is a Trade Mark.

The suppliers were whitfield and Sons, New castle under Lyme.

3. Non-translucent Marble Matrix Resin: ALPOLIT VUP 9203 100 parts by weight Catalyst: M.E.K.P. (Medium Reactive) 1.0 part by weight Mineral: MICRODOL 40/200 Coarse 240 parts by weight MICRODOL 200 Fine 120 parts by weight MIXING OF THE COMPOSITION Mixing may be carried out in a mechanical kneader such as a HOBART (Trade Mark) dough mixer. A pre-weighed quantity of resin (in accordance with the formaulations given above) is added to the bowl of the mixer followed by the appropriate amount of catalyst and mixed for one or two minutes only. The mineral material, and any required desired for colouring the background material, is then added and the mixture kneaded to ensure intimate admixture for five to ten minutes.

The next step is the introduction of the coloured veining. Either dry pigments or pigment dispersions may be used. Liquid pigments may also be used but care has to be taken to avoid the formation of soft spots in the mix.

The pigments are added to the mix and incompletely mixed so that the pigment is not consolidated into the mix but rather forms the characteristic veining of marble minerals.

After colouring the mix is ready for moulding. During introduction of the mix into a mould some additional attention may be given to the aesthetic appearance of the veining.

Introduction into the mould is preferably done by hand, random small aliquots of the mix are selected from the mixing bowl and added to the prepared mould. Hand mixing using a spatula ensures consolidation odf the mix in the mould.

Alternatively the prepared mix may be transferred in bulk to the mould but some care should be taken, for the sake of the appearance of the finished product, to ensure that the veining lines do not cross in an unnatural manner but resemble the linings and swirls of the natural mineral.

The mould is then closed and vibrated to consolidate the mix. Vibration for about three to five minutes is usually sufficient.

Certain hollow articles such as baths and bowls present particular difficulties which may be overcome by either of two methods: (i) Single Pour Method This is preferred for standard sized units. This requires the use of a "hat" section which forms the thickness of the bowl or bath section and has a lip which covers the whole of the mould, enabling it to be clamped so that the matrix does not flow out of the mould.

The veining process may be exactly the same as is described above with the veins being laid generally across the unit. Once the unit is veined the hat section, which has been pre-waxed, is clamped into position. The vibrator is then started and the remainder of the matric poured into a hole provided in the top of the hat. The unit is then vibrated for a further two to three minutes.

Upon setting of the mix it is advisable to remove the hat section as soon as possible and also to remove any gates in the mould to allow dissipation of heat arising from the exotheric reaction invloved in the curing of the resin.

(ii) Two Pour Method This procedure is indicated for custom-made articles. In this case the hat does not have a lip. The mould is veined and completely filled with veins over the whole bowl section in a thin layer. The matrix is then allowed just to gel and the hat is placed over the bowl and located by guides provided on the edge of the mould. The second pour is then made into a hole in the hat whilst vibrating the mould.

The second pour must be made as soon as possible after the first has begun to gel. If the second pour is delayed it may not consolidate with the first, resulting in the possiblity of cracking occurring along the interface with the first pour because of differential curing and shrinking times.

The synthetic marble of the present invention is a versatile material. Little capital investment is required and only a little experience is necessary to enable the production of aesthetically appealing veining. The synthetic material can mimic the beauty of the natural stone but is significantly more economic versatile and durable.

Claims (10)

1 A process for manufacturing imitation marble and the like, the composite comprising a moulded monolithic body having a pulverant mineral base, a pigment for the mineral base and a catalytically cured synthetic resinous binder.

2 A process, as claimed in Claim 1, in which the preferred base material is Irish Marble Dust.

3 A process, as claimed in Claim 1, in which the mould has an adjustable lip, so that thin sections and sections of varying thickness can be achieved.

4 A process, as claimed in Claim 1, where by the surface texture of the article is determined wholly or in part by the surface texture of the mould.

5 A process, as claimed in Claim 1, in which the highly polished mould results in the mineral composite having a high optical brightness.

6 A process, as claimed in Claim 1, which incorporates a light reflecting or fluorescent pigment.

7 A process, as claimed in Claim 1, which incorporate an optical brightner or colouring material.

8 A process, as claimed in Claim 1, where the pigments are added to the mix in such a way that the pigment is not consolidated into the mix and thus forms the characteristic veining of marble, onyx or similar materials.

9 A process, for manufacturing imitation marble, onyx and the like which is substantially as described herein.

10 A process, for manufacturing imitation marble, onyx and the like which is capable of fluorescence when manufactured according to the process hereinbefore described.