FR2615857A1 - Moulding made of stippled synthetic resin - Google Patents

Abstract

Fashioned moulding made of stippled or frosted synthetic resin made of a material comprising a thermoplastic resin and a stippling agent added to the resin. The stippling agent consists of transparent spherical particles all of which have a diameter of 3 to 100 mu m and are made of a crosslinked high polymer chosen from crosslinked polystyrene, crosslinked acrylate and crosslinked polyethylene. The proportion of stippling agent represents 0.5 to 45 % of the weight of the material.

Description

 The present invention relates to a synthetic resin molding and, more particularly, to a molding having a grainy or frosted appearance.

 Synthetic resin moldings have been widely used in various areas of the industry. They find a typical application as a container, for example for a cosmetic substance, on which it is particularly important to produce an attractive ornamental pattern. So far, various efforts have been made to give the container the appearance of a quality object, and it has been found to be effective in graining a surface of the molding so that the container has a velvety appearance. For certain containers such as vials, the wall must be transparent to allow customers to immediately identify the contents, and translucent containers with rough surfaces have also appeared on the market.

 Grained molds were commonly made by coating the molding with a paint containing a blasting agent. The coating is produced by spraying the paint onto the molding. However, this makes it necessary to mask certain parts of the molding such as the cap and thread so that they remain uncoated to avoid functional difficulties. Therefore, the coating has the disadvantages of poor manufacturing efficiency and increased costs.

 It is also known in the art to sand the surface of the molding with abrasive particles of desired particle size. The abrasive particles adhering to the surface must be blown out and the molding must then be rinsed and dried, resulting in increased cost and poor performance. In addition, the sanded surface is not only susceptible to damage, but also of unsatisfactory quality.

 We can realize on the. surface of the molding a grained layer by printing or stamping, if the molding is of simple shape. It is almost impossible to obtain such a layer over the entire surface of a complicated confi guration mixture. In addition, hot stamping tends, if applied to a large area of the molding, to annoyingly affect the surface part, causing cracking over a long period of service.

 All of the above prior techniques are intended to grind the pre-molded product. There are other known techniques which make it possible to grind a product simultaneously with its molding. According to one of these techniques, rough surfaces are provided on a molding matrix defining an imprint. In other words, the surfaces of the matrix defining the imprint are made rough by sandblasting, sparking, etc. Resin melt is introduced into the impression so that, after solidification, the surface of the molding takes on a grainy appearance corresponding to that of the impression surface made rough. However, this method requires strict regulation of the molding conditions in order to obtain a uniformly grained product. This is particularly so if the shape of the product to be molded is likely to cause a flache to appear on it. In addition, residual air present in the impression prevents part of the molten resin from coming into contact with the roughened matrix surfaces. If it is about. injection molding, the matrix must be given a configuration such that the product can be detached only from the matrix, failing which the grained surface having just been shaped. detached. The blow molding technique does not make it possible to shape a roughened surface because the # limited pressure applied to the parison is relatively low. In addition, a grainy surface shaped by a roughened matrix surface is susceptible to damage.

 A blasting agent has also been proposed to the thermoplastic resin before molding. The blasting agent must resist heat so as not to melt when the resin melts and the agents proposed so far are inorganic fillers such as powders of calcium carbonate, talc, zinc white and of silica and glass fibers These powders and fibers are of very small size, each crystal having a flat or acicular lamella shape and being only slightly dispersible in the receiving resin and hardly able to adhere thereto, which makes that it is difficult to mold a uniformly grained product. This is particularly so if the product has to be translucent, in which case the amount of addition filler is limited. In addition, the use of calcium carbonate powders involves the release of gas which rusts the molding matrix and burns the surface of the appliance. Rust can be avoided by making the matrix in stainless steel, but this increases the cost price. Glass fibers, if used as a blasting agent, wear out the cylinder of the molding machine and shorten its service life.

 The present invention relates in particular to a molding on a grained synthetic resin to be shaped by the latter process, and its originality lies in the choice of the blasting agent.

The invention therefore aims to provide a molding in grained synthetic resin
- endowed as desired with a uniformly grainy appearance thanks to the use of a peening agent which is well dispersible in the receiving resin and capable of adhering thereto
- which is likely to retain its grainy appearance almost permanently
- whose surface can be kept clean and pleasant to the touch
- which has the desired transparency
- that lton can manufacture with good yield and at low cost.

 According to one aspect of the invention, a molding is made of grained synthetic resin into a material comprising # a thermoplastic resin and a blasting agent added thereto. The blasting agent is composed of transparent spherical particles all having a diameter of 3 to 600 μm and produced from a high crosslinked polymer chosen from crosslinked pdlystyrene, crosslinked acrylate and crosslinked polyethylene. The proportion of addition of blasting agent ranges from 0.5 to 45% by weight of the material.

 According to another aspect of the invention, a molding is made of grained synthetic resin into a material comprising a transparent or translucent thermoplastic resin and a blasting agent added thereto.

The blasting agent is composed of transparent, heat-resistant spherical particles, all having a diameter of 3 to 600 μm and a refractive index of 1.3 to 2.7 measured with the spectral line D of sodium. The amount of blasting agent represents 0.5 to 30% of the weight of the material.

Other objects, characteristics and advantages of the invention will emerge from the detailed description given below of the invention with reference to the appended drawings, in which
FIG. 1A is a perspective view of a molding according to an exemplary embodiment of the invention
Figure 1B is a sectional view of detail on a larger scale
Figure 2 is a schematic elevational view of a molding according to another embodiment of the invention
Figure 3 is a view similar to Figure 2 showing another molding
Figure 4 is a sectional elevational view of a molding according to yet another embodiment of the invention
FIG. 5 is a perspective view of a molding according to another embodiment of the invention and
Figure 6 is an enlarged sectional view of the paroid 'a molding according to yet another embodiment of the invention.

 According to the invention, a molding is made of grained or frosted synthetic resin into a material comprising a thermoplastic resin and particles added thereto as a blasting agent. The thermoplastic resin added with graining particles is subjected to a molding treatment such as injection molding, extrusion molding or blow molding to manufacture the desired product, a typical example of which is a container for cosmetic substance which must have an attractive appearance.

 The graining particles must all be spherical and have a size of 3 to 600 μm. The uniform spherical shape promotes the dispersion of the particles in the receiving resin and ensures good adhesion of the particles to it. Particles with a uniform diameter of less than 3 µm are difficult to manufacture and only adhere poorly to the resin due to their small surface area. On the other hand, if the large particle size exceeds 600 -, the particles cannot disperse uniformly in the resin and the hardness of the latter becomes insufficient. In addition, the particles must be transparent so as not to undesirably color the product. Another requirement which the particles must meet is to resist heat: the particles must resist heat so as not to melt during molding of the thermoplastic resin.

 In one embodiment of the invention, any desired thermoplastic resin can be used as the receiving resin, typical examples being polyethylene, polypropylene, polystyrene, acrylonitrile-styrene (AS), ABS, polycarbonate, polyacetal , Nylon, polyethylene terephthalate (PET), polyvinyl chloride (PCV), ethylene-vinyl acetate copolymer (EVA), methyl methacrylate (MMA), methyl methacrylate-styrene copolymer, methyl methacrylate- copolymer styrene-butadiene and ethylene ethyl acrylate.

The graining particles are made of high cross-linked polymer chosen from cross-linked polystyrene, polyethylene and acryla. The particles in these crosslinked resins meet the above requirements, heat resistant up to over 3000C. They also have sufficient hardness and excellent chemical resistance and can be colored in any desired color. In addition, these particles have a sufficient refractive index to make the moldings mat.

 It is preferable to choose the combination of receptor resin and high crosslinked polymer according to the chemical affinities existing between them. For example, if polyethylene is chosen as the receiving resin, it is necessary to add particles of crosslinked polyethylene to it. It is however possible to add two or more kinds of particles to the chosen receptor resin. The proportion of addition of particles must represent 0.5 to 45% of the total weight of the material from which the products are molded. If the proportion of particles is less than 0.5% by weight, the resulting product is not sufficiently grainy. On the other hand, with a proportion exceeding 45% by weight, there is a risk that the particles do not disperse uniformly in the receiving resin and do not adhere intimately thereto. In addition, such an excessive proportion lowers the operating efficiency of the molding process, with a consequent increase in the cost price.

 In another embodiment of the invention, the receiving thermoplastic resin is transparent or at least translucent. In addition to meeting the other requirements above, the graining particles must have a high refractive index in order to be able to disperse the light enough to reveal the desired matte appearance. The materials which constitute the particles must be chosen. so that these have a refractive index of between 1.3 and 2.7 measured with the spectral line D of sodium (nD). Examples of preferred materials are glass, crosslinked polystyrene resin, crosslinked methyl methacrylate resin and crosslinked acrylate resin. Particles with a refractive index of less than nD = 1.3 cannot icify properly a product, while a refractive index greater than nD = 2.7 makes the transparency of the product disappear. The minimum proportion of addition of particles to the receiving resin is 0.1% of the total weight of the material, as according to the above embodiment.

However, the proportion of particles must not exceed 30% by weight so that the product remains transparent or translucent.

 The molding according to the invention can have a rough surface which contributes to giving the grainy appearance. In this case, the particles are mainly distributed in the surface part of the molding. Alternatively, the molding may have a smooth surface, most of the particles being dispersed in the interior of the wall of the molding. In order to distribute most of the particles in the surface part, one can proceed by blow molding or by extrusion molding. If it is desired to proceed by injection molding, it is preferable to set relatively low values at the pressure and at the speed of injection. On the other hand, injection molding with relatively high injection pressure and speed as well as casting molding are suitable for dispersing the particles within the inner wall part.

 The description of the invention will be continued below with reference to examples of implementation, which are, however, devoid of any limiting character.

EXAMPLE 1
A molding material was prepared by adding 20% by weight of crosslinked polyethylene particles of substantially uniform size from 200 tim to 80% by weight of polyethylene resin. The material was brought into an injection molding machine which heated it to melt and injected the molten resin, in which the particles were dispersed, in an imprint defined in a matrix to shape a product as shown in Figure 1. The product shown by way of example is a cap 10 for a container of the bottle type (not shown). In FIG. 1B, the particles of crosslinked polyethylene, designated by the reference 14, are dispersed in the receiving polyethylene 12. It was observed that the cap 10 was uniformly roughened on the surface.

EXAMPLE 2
5% by weight of crosslinked acrylate particles with a substantially uniform size of 50 rm to 95% by weight of highly resilient polystyrene resin were added to form a molding material which was brought to a blow molding0 The resulting molding was a powder container 20 as shown in Figure 2, uniformly roughened on the surface. The entire surface of container 20 was covered with fine spherical projections, uniform, formed by the particles, and experiments revealed that these projections reduce the frictional resistance exerted between the neck 22 and the cap 24 to facilitate the installation and the removal of the latter0
EXAMPLE 3
25% by weight of crosslinked Epolystyrene particles with a substantially uniform diameter of 15 mm were added to 75% by weight of polypropylene resin. The material was then subjected to an injection molding to form a cap 30 for lipstick container 32 as shown in Figure 3. It was observed that the cap 30 was uniformly roughened on the surface. In addition, it was found that a peripheral rib 34 of the cap 30 could only fit into a groove 36 of the container 32 and come out. Apparently, the reason is the same as that explained in Example 2.

EXAMPLE 4
To 91.6% by weight of ABS resin was added 8.0% by weight of crosslinked polystyrene particles with a substantially uniform diameter of 11 µm and 0.40 by weight of carbon black and as a coloring agent. We made a make-up box out of the material by injection molding. The product, of black color, was uniformly grained. The current black moldings have the disadvantage that the traces of abrasion and / or scratches made on their surface during l use of the product are much more visible than on other color casts. However, in the example according to the invention, the particles provided with greater hardness prevented the surface of the make-up box from being scratched.

EXAMPLE 5
A container for cosmetic substance of the lamella type was molded comprising three thin plates hinged on each other so that each of them could pivot relative to the others. Each plate was molded from a material comprising 90% by weight of resin
ABS containing a desired coloring agent, 7% by weight of crosslinked polystyrene particles all having a diameter of 11 μm and 3% by weight of crosslinked acrylate particles 200 μm in diameter. The resulting molding (plate) was uniformly grained, which was estimated to be mainly due to the polystyrene particles. Experiments have shown that each plate can be very simply rotated relative to the others, this being mainly due, it is believed , to the presence. acrylate particles. In addition, each plate was only slightly warped.

EXAMPLE 6
5% by weight of cross-linked polystyrene particles with a diameter of 11 µm was added to 15% by weight of transparent AS resin, and the material was subjected to injection molding to form a container of the type bottle 40-as shown in Figure 4. The container 40 had a wall thickness of 7.5 mm. The particles, indicated at 44 in the figure, were uniformly dispersed in the receiving resin 42 and the container 40 had an appearance similar to that of frosted glass.

EXAMPLE 7
A container similar to that according to Example 6, but with a wall thickness of 3.7 mm, was injection molded from a material composed of 90% by weight of transparent AS resin and 10% by weight of particles of crosslinked polystyrene 11 μm in size. The container had substantially the same appearance as that according to example 6.

EXAMPLE 8
In this example, the molding is a closure for a container of the vial type, the closure comprising an inner cap and an outer cap. The inner cap was made of a colored resin. The outer cap was molded from a material composed of 87 by weight.

of transparent MMA resin, 5% by weight of crosslinked polystyrene particles with a size of 6.0 jun and 8% by weight of crosslinked acrylate particles with a diameter of 100 rm. The outer cap fitted over the inner cap and the whole offered a very original appearance. The color of the inner cap was perceived through the grained outer cap, some of the light being reflected by the larger acrylate particles.

EXAMPLE 9
The lid 52 of the make-up box 50 was molded which had two differently colored parts 54 and 56, as shown in FIG. 5. The material of the part 54 comprised 92% by weight of AS resin containing 0.009% by weight of violet anthraquinone and 0.005% by weight of anthraquinone blue, and 8% by weight of crosslinked polystyrene particles having 6.0 µm in diameter. The material of part 56, which formed a part with part 54, comprising 96% by weight of translucent AS resin containing 0.002% - of titanium oxide and 0.00003% by weight of anthraquinone violet, as well as 4 in weight of glass particles 60 mm in diameter. Part 54 was blue and had an appearance similar to that of frosted glass, while part 56 reflected more light. In combination, these two parts made the whole box 50 very attractive and managed to give it. the look of a quality item. The glass particles used in part 56 should preferably have a refractive index of about 2.0 over nD.

EXAMPLE 10
To 75% by weight of PET resin were added 15 by weight of crosslinked acrylate particles having a diameter of 15 µm and 10% by weight of glass particles having 100 µm in diameter to obtain a material from which shaped a bottle-type container by blow molding. Part of a wall 60 of the container is shown in Figure 6. The glass particles 64 were distributed in. the surface and prevented the wall surface from becoming smooth, with the presence of small depressions near the particles. This last point was due to the inexpansible nature of the glass particles. Small crosslinked acrylate particles 66, on the other hand, were dispersed within the interior to give the wall the appearance of frosted glass.

 As will be understood from the above description, a molding according to the invention can be uniformly peened because the peening particles are uniformly dispersed. The receiving resin can be colored to obtain a grained molding of any desired color, and the degree of graining can be adjusted according to the proportion and the refractive index of the particles.

Thus, one can obtain a new and original ornamentation of the moldings. In addition, the hardness of the molding is more or less increased by the grit particles, which can serve to protect the surface of the molding from scratching. The spherical shape of the particles appearing on the surface reduces the frictional resistance of the product, which is particularly advantageous in the case where the product is called upon to engage over or inside other parts. Spherical particles can also be used to keep the mold surface clean and to help remove stains. In addition, the grained molding according to the invention can easily undergo a hot stamping or printing treatment intended to include any desired ornamentation.

 Although the present invention has been described with regard to its preferred embodiments and examples, many modifications and variations may be made to these without departing from the scope of the invention.

Claims (10)

 1. Molding in grained synthetic resin shaped into a material comprising a thermoplastic resin and a blasting agent added to the resin, this blasting agent being composed of transparent spherical particles all having a diameter of 3 to 600 μm and formed from a top crosslinked polymer chosen from crosslinked polystyrene, crosslinked acrylate and crosslinked polyethylene, and one blasting agent representing 0.5 to 45% by weight of the material.  2. Molding according to claim 1, characterized in that said thermoplastic resin is chosen from polyethylene, polypropylene, polystyrene, acrylonitrile-styrene, # acrylonitrile-butadiene-styrene, polycarbonate, polyacetal, Nylon, polyethylene terephthalate, polyvinyl chloride, ethylene-vinyl acetate copolymer, methyl methacrylate, methyl methacrylate-styrene copolymer, methyl methacrylate-styrene-butadiene copolymer and ethylene ethyl acrylate .  3. Molding according to claim 2, characterized in that the thermoplastic resin is transparent or translucent.  40 Molding according to claim 3, characterized in that said particles have a refractive index of 1.3 to 2.7 measured with the spectral line D-of sodium.  5. Molding according to claim 4, characterized in that the peening agent represents 0.5 to 30% of the weight of the material.  6. Molding according to claim 1, characterized in that the material also comprises a coloring agent.  7. Molding according to claim 1, characterized in that the molding is a container shaped by injection molding, extrusion molding, blow molding or casting molding.  8 Grained synthetic resin molding shapes into a material comprising a transparent or translucent thermoplastic resin and a blasting agent added to the resin, this blasting agent being composed of transparent and heat-resistant spherical particles all having a diameter of 3 to 600 rmî all these particles having a refractive index of 1.3 and 2.7 measured with the spectral line D of sodium and the blasting agent representing 0.5 to 30% of the weight of the material.  9. Molding according to claim 8, characterized in that said thermoplastic resin is chosen from polyethylene, polypropylene, polystyrene, acrylonitrile-styrene, acrylonitrile-butadiene-styrene, polycarbonate, polyactal, nylon, polyethylene terephthalate, polyvinyl chloride, ethylene-vinyl acetate copolymer, methyl methacrylate, methyl methacrylate-styrene copolymer, methyl methacrylate-styrene-butadiene copolymer and ethylene ethyl acrylate.  10. Molding according to claim 8, characterized in that said particles are made of a material chosen from glass and high crosslinked polymers.  11. Molding according to claim 10, characterized in that the high crosslinked polymer is chosen from crosslinked polystyrene and crosslinked acrylate.  12. Molding according to claim 8, characterized in that the material also comprises a coloring agent.  130 Molding according to claim 8, characterized in that the molding is a container shaped by injection molding, extrusion molding, blow molding or casting molding.