The finish of objects made of plastics, especially thermoplastics, is a subject that involves producers of raw materials, processors, designers, users etc., as it is decisive for the product's image and can influence, sometimes significantly, its commercial success.

Esthetic finishing of plastics objects is currently achieved using various systems, the most important of which are enumerated below. a) Bulk pigmentation. Color is imparted to the polymer matrix by means of pigments added to the material directly. b) Finishing with predecorated films. Color is obtained by inking/painting of films that are then thermoformed. The synthetic material is co-moulded on this shell and functions as a self-supporting substrate. c) Finishing with water-sensitive predecorated coating. The visible surface of the moulded object, with final material and form, is covered with a predecorated film using

hydrostatic pressure followed by a hot baking cycle. d) Painting. The object, in its final form, is finished using paint products that give the desired effect. The paints used have good hiding power and thus determine the color of the object.

In all these cases, the surface finish perceived by an observer is determined solely by the visible surface layer.

Moreover, in some cases, for example in case a), there are notable limitations connected with the rheological properties of the materials and with the production processes; for example, joint lines of the molten mass form during molding, giving rise to zones with different color, affecting the esthetic appearance. The smooth surfaces can then be damaged easily, especially by scratching.

In cases b) and c) the dimensions and the shape of the object represent important constraints for their use and in every case stylistic and economic limitations.

In the case of painting (case d) there are no limitations on shape and dimensions. The surface finish is imparted directly by the paint as a function of its composition, the pigments and the gloss. Therefore widely varying types of finish can be obtained. There are, however, certain limitations : -clear effects (both pastels and metallic or mica- like) reveal the defects on the object's surface, e. g. shrinkage cavities, ripples, streaks.

-opaque effects (with gloss values below 1.2), which are the most sought-after for decorative purposes, are critical as they are easily scratched.

-some materials, for example the polyolefins, require preparatory treatment of the surface and application of a primer whose function is to promote adhesion between the paint and the synthetic material.

Opaque finishes, with diffuse or partially direct reflection, and that are very pleasant to the touch, are of greater interest for design in the automotive sector, in interior design, design of domestic electrical appliances, etc.

The present invention relates to objects made of plastics with an opaque finish comprising a plastic substrate to which is applied a layer of enamel and optionally a layer of primer between the substrate and the enamel, characterized in that the coloration is present in the plastic substrate or in the layer of primer if present, and the enamel is transparent with opacity below 1.2 gloss, preferably below 0.8 gloss.

The term"plastic material"means thermosetting and thermoplastic synthetic resins, in particular thermoplastics such as polystyrene resins, polycarbonate, modified polycarbonate, polyolefins, polyurethanes, ABS plastics, acrylics, polyamides, polyvinyls etc. The materials mainly used are the polyolefins, polystyrenes, polyurethanes, and modified polycarbonate.

Transparent enamels, without fillers and pigments, with opacity below 1. 2 gloss, are known to persons skilled in the art and are available commercially.

Suitable enamels are for example acrylic, polyester, polyol and polyurethane enamels.

A particularly preferred enamel is the series 76 000 Trasparente Multisensoriale, available from Tego Becker, San Martino in Strada, Lodi, IT, which is a polyurethane enamel with gloss of 0.70.2.

Undercoat or primer means a paint adhesion promoter, and can be, for example, a modified acrylic or a polyurethane primer. The series 77 000 and 78 000 primers from Tego Becker, which are modified acrylic primers, are particularly preferred.

Application of the primer is optional and depends mainly on the type of plastic material of the substrate, which may have good paintability, as in the case of polystyrene, polyvinyl, polyurethane etc. resins, or poor paintability, as in the case of polyolefins. In the latter case, special preparation of the surface to be painted is required, for example by flame treatment, plasma treatment etc., and then application of an adhesion promoter (primer) between the synthetic material and the enamel.

The color is present in the plastic material (bulk pigmentation) or in the primer.

Fig. 1 shows the various alternatives that are possible as claimed in the invention: A) The substrate c), of plastic material, pigmented in the bulk, is covered on its outer surface with a layer of transparent enamel a) as claimed in the invention.

B) The substrate c), of plastic material, pigmented in the bulk, is covered with a layer of transparent primer b) and with a layer of transparent enamel a) as claimed in the invention.

C) The substrate c), of unpigmented plastic material, is covered with a layer of primer b) containing the color and with a layer of transparent enamel a) as claimed in the invention.

If a finish with a metallic or mica-like effect is desired, it is possible to add anisotropic fillers to the plastic material of the substrate or to the layer of primer if used. The coloring matter and the anisotropic fillers can be present simultaneously in the substrate or in the primer or alternatively the coloring matter can be present in the substrate and the anisotropic fillers in the primer.

The term"anisotropic fillers"means particles of metal for example of aluminium or of mica with which an anisotropic color rendering is obtained.

Fig. 2 shows various alternatives for obtaining a finish with a metallic effect: A) The substrate c) of plastic material, pigmented in the bulk and containing the anisotropic fillers, is covered on its outer surface with a layer of transparent enamel a). In this case the plastic material is responsible for the color and the type of finish. The transparent enamel determines the opacity and pleasantness to the touch.

B) The substrate c) of plastic material, pigmented in the bulk and containing the anisotropic fillers, is covered on its outer surface with a layer of primer b) which in its turn is covered with a layer of transparent enamel a). As in the preceding case, the plastic material is responsible for the color and type of finish.

The primer and the transparent enamel determine the opacity and pleasantness to the touch.

C) The pigment is added in the bulk to the plastic material that forms the substrate c) and the anisotropic fillers are added to the transparent primer b) which in its turn is

covered with a layer of transparent enamel a).

In this case the plastic material is responsible for the color, the primer determines the type of finish (metallic, mica- like) and the transparent enamel determines the opacity and pleasantness to the touch.

D) The pigment and the anisotropic fillers are both added to the primer b) that covers the substrate of plastic material c). The plastic material is without influence on the chromaic finish whereas the enamel a) determines as always the opacity and the pleasantness to the touch.

The invention also relates to the method for production of an object made of plastic material with opaque finish comprising the stages of: a) forming a substrate of plastic material; b) optionally applying a layer of primer to the surface of the synthetic material; c) applying a layer of enamel; characterized in that coloring matter is added in the bulk in the plastic material forming the substrate and/or in primer if present, and in that the enamel is transparent and has an opacity below 1.2 gloss.

Anisotropic fillers can be added if required, in bulk in the plastic material of the substrate or in the layer of primer.

It is possible to use all the conventional painting processes (by hand, electrostatic, etc.) without equipment modifications.

The thicknesses of the primer and of the enamel are within the usual ranges for the traditional products (from approx. 10 to approx. 80 Fm). These can

however be varied depending on the surface to be painted, which can be smooth, lightly embossed, heavily embossed etc., as well as the desired degree of pleasantness to the touch.

The plastic objects with opaque finish as claimed in the invention have particular visual and tactile qualities such that the finish can be described as "multisensorial". In particular said"multisensorial" finish has the following properties: -a very high opacity (gloss < 1.2) accompanied by high resistance to surface damage (antiscratch finish).

These properties are far superior to what is obtainable with the products currently in use; -a very high degree of pleasantness to the touch, superior to the standards currently achievable; -effect of transparency both with colors with isotropic and anisotropic effect. Such an effect of transparency is obtained with the existing methods, which use traditional paints, by means of a double cycle of painting that comprises application of a pigmented enamel and of a transparent enamel.

The painted object produced can be regarded as a "multimaterial"structure consisting of: -substrate of plastic material whose surface requires a finishing treatment; -primer (optional); -enamel.

In the objects obtained by the methods used at present, the final effect (visual and tactile properties) is due solely to the enamel whereas the plastic material and the primer have no influence in this respect.

The present invention, though substantially maintaining the same multimaterial structure of the

traditional products, has a finish or final esthetic appearance which results from a radically different contribution from the individual components of the structure. In fact this ensures that all the components of the structure participate directly and significantly in the final appearance of the object, no longer entrusting the esthetic properties to the enamel alone.

The color and type of finish are derived from the plastic material (bulk pigmentation) or from the primer. These therefore have a direct effect on the following properties of the finish: -hue (green, yellow, red, etc.) ; -saturation (amount of white, red present in the hue); -brightness (bright, dark, dull, etc.) ; -isotropy/anisotropy (pastel, metallic, mica- like, etc.).

The enamel always consists of a transparent product and has an effect on the following properties of the finish: -opacity; -tactile feel ; -resistance to scratching.

The transparent finishing enamel (without pigments and primers) therefore makes it possible to obtain painted objects with two typical and fundamental characteristics: -very high degree of pleasantness to the touch, superior to that obtainable with the existing enamels that are filled with pigments and colorants; -also very opaque surface finish (<1 gloss) though still accompanied by resistance to surface damage (scratchability) of a level far superior to the existing products.

Furthermore, the opacity obtainable with the inventionexerts a masking effect on the inherent defects of plastics and defects arising from the production processes, such as streaks, joint lines, ripples etc., which are not eliminated, and indeed are in some cases intensified, by traditional paint.

Consequently, in addition to esthetic improvement, production is simplified, in that there are fewer rejects and hence an economic advantage.

The transparent finishing enamel also imparts an appearance of"transparent"color, i. e. through the thickness of the transparent layer. This effect, which is of considerable interest in stylistic design, is achieved without any additional cost and can be varied as a function of the thickness of the enamel.

Another important aspect is optimization of coloration, which can be achieved through bulk pigmentation of the plastic material or through pigmentation of the primer, as convenient. For finishes with isotropic rendering (for example pastels) and in the case of single colors (black, gray, dark blue etc.) with limited cost of the pigments, the most convenient solution is bulk coloration of the plastic material and then application of the primer, if required, and of the transparent enamel. When the color requires expensive pigments (for example bright red) it is possible to use the colored primer, reducing the amount of pigment and hence the cost to a minimum.

Furthermore, it is possible to obtain an equivalent colorimetric rendering with different surface patterns (for example smooth-embossed). This means that it is possible to produce, on the same object, zones with different surface finishes, with marked three-dimensional diversity of the embossing,

maintaining a uniform visual perception, eliminating the problem of color-matching or reducing it to a negligible level.

Finally, it is possible to alter the levels of opacity and pleasantness to the touch purely on the basis of the thickness of the transparent enamel. This makes it possible to obtain desired sensorial properties without resorting to altering the materials or the production process.

The plastic objects with opaque finish as claimed in the invention find particular interest in the automotive field, especially for interior trim.

To verify the validity of the performance offered by the invention, test specimens were prepared from two synthetic materials possessing different paintability: polypropylene (difficult paintability), polystyrene (easy paintability).

A series of tests was carried out on these test specimens to determine the validity of the invention.

Evaluation was based on the requirements of the car industry (painted components of interior trim) which are certainly the most stringent for these types of products.

Table 1 shows the assessments undertaken, the test methods employed and the results obtained.

TABLE 1 Comparison of quality index of sensorial and functional properties versus degree of opacity RIAL AND FUNCTIONAL PROPERTIES Dgr of pacity, gl. s- 17 ?' 3 R. , i, , . _ 1. i ; Resistance b 1 t f to surface c'. i )'') 1 [) 2) D 1 : gõ l 4 ; O S} 5} S I S "U 2jot45 S} = t S) S F"5 a t 1 1 a 1''r b' -1 t 1)-) t- ! i PleasanCness to the touch _. to2 131-i 5 1 erI r i 1 2 í 3 to t e tou zip, 2 isotropic C 1 2 2 J . 3 3 a , t"pl, 1 a t 1 ! 55oT !. 5S 'a* Jt i'i) FlM. th with b) 11 25 renderiaq d I 7'I 1 2 2 _-e t 2314j 5'-5 li 5 I S I a t- (I' 1 t tT 1 1 "t '-))'1) 1 Caving ]-----jiTj1 Fii. h ilthlb 2 TYPESd 1 rl" 1 A e'f 5 P 5 l 5 P $ 4 [4 H'4 TYPES OF FINISH QUALITY INDEX -Pieatation of lhetic matarial (bulk' _ gpg pignentatiool ... 2-AT THE LIMIT OF ACCEPTABILITY 2 AT THE LDMIT OF AC PTABILITY s-material with filler (polypropylene, talc)-- b = material without filler (ABS) FAIR -Painting -GOOD c = homogenizing (=iscratcb) EXCELLENT d-soft-feellng e = multisenaorial

It is clear from the results obtained that the invention,hasproperties such as to make it suitable even for applications for which very stringent conditions of use are envisaged.

With regard to resistance to surface damage, confirming what has already been said, a scratch resistance test (sclerometer test) was carried out on smooth test-pieces of polypropylene with multisensorial finish as claimed in the invention and with conventional bulk pigmentation. It was found that the test-pieces with multisensorial finish as claimed in the invention have far higher scratch resistance than the test-pieces obtained with conventional bulk pigmentation. Thus, the values of the pressure exerted by the tool that passes over the test-piece, for which permanent and visible damage starts to appear, are as follows: Multisensorial: scratching visible at pressure values above 1000 g.

Conventional bulk pigmentation: scratching visible with pressure values above 400 g.

These assessments demonstrate that painting as claimed in the invention imparts notable sensorial and functional properties.

In conclusion, painting as claimed in the present invention makes it possible to obtain types of finishes that cannot be achieved with the materials/processes in use at present. This can be seen by comparing the quality index, referring to the sensorial and functional properties, with the degree of opacity that can be achieved for the test-pieces obtained with multisensorial painting as claimed in the invention and the test-pieces obtained with traditional painting, as shown by the data in Table 1.

Multisensorial painting is the only solution that makes itpossible to obtain opacity below 1.2 gloss with still efficient scratch resistance, high degree of pleasantness to the touch, hiding of the surface defects of the substrate component, and a transparency effect of the chromatic properties.

Furthermore, multisensorial painting permits a priori"design"of the finish as a function of the following factors: -more suitable type of coloration -more convenient production cycle -cost of the pigments and of the anisotropic fillers The flexibility provided by the invention is thus translated into overall optimization of the painted end product, with effects on the costs of the materials and of the process even at the design stage.