FR2510591A1 - COATING COMPOSITION RESISTANT TO ATMOSPHERIC AGENTS - Google Patents

Abstract

THE COATING COMPOSITION INCLUDES AN ACRYLONITRILE-TYPE POLYMER HAVING AN ACRYLONITRILE CONTENT OF 80 BY WEIGHT OR MORE AND CONSTITUTES SPHERICAL PARTICLES, SENSITIVELY SOLID, HAVING AN AVERAGE GRANULOMETRY OF 2 TO 200MICRONS IN 100MICRONS ADDED TO ONE POLYMICRONS, ONE POLYMICRON IS 5 TO 100MICRONS ADDED. BY WEIGHT RELATED TO 100 PARTS BY WEIGHT OF THE NON-VOLATILE MATERIAL OF THE SAID COMPOSITION AND IT FURTHER INCLUDES 0.01 TO 0.05 PART BY WEIGHT OF A BENZOTRIAZOL TYPE ULTRA-VIOLET RAY ABSORBER RELATIVE TO 100 PARTS OF WEIGHT OF NON-VOLATILE MATERIAL. THE ULTRA-VIOLET RAY ABSORBER MAY BE EITHER 2- (2-HYDROXY-4-N-OCTOXYPHENYL) BENZOTRIAZOLE OR 2- (2-HYDROXY-5-METHYL-PHENYL) BENZOTRIAZOLE.

Description

RESISTANT COATING COMPOSITION

WITH ATMOSPHERIC AGENTS

  The present invention relates to a coating composition which forms a coating layer of excellent resistance to atmospheric agents, on a shaped substrate such as a metal plate, plywood, plastic and concrete, when applied to those Various materials, including steel-coated plates have been coated for external use, the resistance of the coating layer to the atmospheric agents being in this case a problem. Vitality Most of the recently available coating layers have an organic resin base and an inorganic or organic pigment added to the resin. These layers are degraded under the influence of ultraviolet rays, hu dity, heat, ions and other environmental factors, alone or in combination As a result of this deterioration, the layers crack, become detached from the substrate, or appear to be encrusted. In particular, the colored layers,

  discolouration or serious alteration

  appearance cation, such as gloss or shine, due to fouling. Heretofore, various attempts have been made to improve the weather resistance of the coating layers, or they have been put into practical use. For example, it has already been proposed to use an atmospheric resistant resin which is excellent for atmospheric agents. coating layer forming resin component Because of their good durability, use has been made of a coating of the acrylic silicimide type comprising a silicone / acrylic resin modified with a silicon intermediate, a silicon / polyester coating comprising a silicon-type resin However, these coatings are expensive. In particular, the fluorinated-type coatings have a high resistance to atmospheric agents, but they are extremely expensive and create a problem. Economic factors commonly exert a considerable effect on the absorption of radii For this reason, pigment-free coatings are not reserved for outdoor use, although there are exceptions. In most cases, therefore, there are coatings containing pigments, preferably However, the effect of coatings with a high pigment content

  pigments on the absorption of ultraviolet rays is still

  unsatisfactory days To protect a substrate from rays

  ultraviolet and other methods, the addition of sub-

  However, the deposition of coating causes a problem in relation to the suitability for the implementation of the coating or the sedimentation of the coatings, such as iron oxide having a mica-like appearance.

pigments during storage.

  In addition, ultraviolet absorbers, oxidation stabilizers and the like have been added to the coatings to improve the weatherability of the coating layers. Sufficient resistance to atmospheric agents is not achieved even by the use of these additives. The applicant has already filed an application (application for

  Japanese Patent No. 54-12777) for an invention (designated as

  the invention of the prior art) in which one incorporates

  clothing a given range of a-rylonitrile polymer

  specific number (hereinafter referred to as PAN) 'to increase their

  matt effect, their resistance to atmospheric agents and

  The prior art coatings exhibit improvements in weatherability, due to some degree to the good weather resistance of the PAN itself. However, it has now been found that a greater amount of particles PAN does not offer any contribution

  appreciable to the increase in resistance to atmospheric agents.

eral.

  Following extensive studies, carried out to obtain

  Coatings which provide coating layers having excellent resistance to atmospheric agents, based on the invention of the prior art, the applicant

3 2 510591

  has now discovered that resistance to atmospheric agents

  In the presence of a small amount of ultraviolet absorbers, the effect produced by the presence of a small amount of ultraviolet absorbers becomes more difficult. pronounced in the presence of a

  larger amount of PAN particles.

  The main object of the invention is to provide a coating containing polymer particles which can provide a coating layer of excellent strength.

atmospheric agents.

  According to the invention, the aforementioned objective is

  achieved by the fact that a coating composition is proposed

  a high atmospheric resistance polymer comprising an acrylonitrile polymer having an acrylonitrile content of 80% by weight or more and consisting of spherical, substantially solid particles having an average particle size of 2 to 200 microns, said polymer being added in an amount of 5 to 100 parts by weight based on 100 parts by weight of the non-volatile matter of said composition, and which further comprises 0.01 to 0.05 parts by weight;

  the weight of an ultraviolet absorber of the benzotria-

  zole relative to 100 parts by weight of said non-material

  volatile. Other features and advantages of the invention

  will appear on reading the detailed description that will

  follow some examples of embodiment, given by way of indication but not limited to, with reference to the accompanying drawings, in which: Figure 1 is a schematic view, enlarged scale (of a section through a coating layer that can be

  obtained from the coating composition according to the invention.

  vention; FIG. 2 represents a perspective view, on a scale

the enlarged, PAN particles.

  In these figures, the numeral 1 is affected

to the PAN particles.

  The acrylonitrile-type polymer particle used

4 2510591

  according to the invention has an acrylonitrile content of

  % by weight or more, and consists of a granulo -

  average metric ranging from 2 to 200 microns The polymer itself is excellent in its resistance to atmospheric agents, and has good adhesion to the matrix of a coating layer In addition, said particles can be used of polymer in a larger amount, and disperse them uniformly throughout the coating composition. Since the PAN particle polymer preferably has the highest possible acrylonitrile content for weather resistance, an acrylonitrile content of at least 80% by weight must be present. This acrylonitrile polymer exhibits extremely good resistance to atmospheric agents as such, for the following possible reasons: As the nitrile group (-CEN) of acrylonitrile strongly attracts an electron, the -CH group adjacent to it is

  so strongly acidic that hydrogen in the alpha position is sus-

  able to undergo auto-oxidation, as will be understood from the following equation (I) (1) Hydroperoxide Formation Reaction

H H H

-CH 2 a CH I CH

2 C 2 CH 2 -C CH -

LEN C = -N LN LN

  (first stage of radical formation)

0 OOH H

-CH 2 CH 2

CEN C-N

  (hydroperoxide formation) However, the formed radical is then converted into a

  hydroperoxide which is brought to the close neighborhood of the group

  trile, because polyacrylonitrile has a syndiotactic structure

  than. The interaction of these groups produces the following stabilized structure (II)

00 H NOCE H

2 __ CH 'I

X 2 2 b ^ C ^ C-C_

  which has the effect of cutting the chain of auto-oxidation and a.

  to stop the further progression of the deterioration of the coating layer, thus contributing to the amn

  resistance to atmospheric agents.

  When the acrylonitrile polymer has an acrylonitrile content of the order of less than 80% by weight, it is nevertheless possible for the nitrile groups to be so spaced apart from one another in the aforementioned formula, which

  the radicals formed can not be properly trapped.

  This would then correspond to a lowering of the resistance

atmospheric agents.

  The acrylonitrile polymer mentioned above can be prepared in the manner described in Japanese Patent Applications Laid-open Nos. 52-8090, 52-40569, 52-107045, 54-18858, 54- 30281, etc. As described in Japanese Patent Application No. 52-8090 cited above

  for example, a monomer comprising a compound

  ethylenic saturate containing acrylonitrile as the main component and a sulfonic acid or a salt thereof combined with said component as a remaining part, to a polymerization in water, and an acid group is introduced

  sulphonic acid or its salt in the polymer thus formed, in

  thus providing an aqueous dispersion of polyamine droplets in which polymer particles are present in the molten state. The aqueous dispersion is then cooled.

  under agitation while preventing coagulation of

  polymer, so that an aqueous dispersion is obtained containing essentially spherical particles

  of PXN formed by the agglomeration of the polymer droplets.

  The aqueous dispersion thus obtained is dried by spray drying and is granulated directly in particular.

  PAN having the desired particle size distribution.

  It will be appreciated that all of the PAN polymers described in the above-mentioned patent applications can not be used as PAN polymers according to the invention. As a result, selective use of PAN polymers can be made except in those which include a monomer such as that viny or vinylidene chloride which are basically considered a

  poor resistance to atmospheric agents.

  In essence, the PAN particles thus obtained are

  a solid, transparent and uniform structure and their

  The particles have sufficient negative charges and are thus very stably dispersed in a coating composition. This allows the PAN particles to be present in a larger amount.

  in the composition of coatings.

  In addition, the PAN particles have a low specific gravity compared to ordinary mineral fillers, and are difficult to deposit in the coating composition, thus ensuring good storage and drying properties.

  ability to implement or workability of the coating.

  The proper particle size of PAN particles is

  closely related to the thickness of the coating layer.

  As can be understood from FIG. 1, the protective effect of the PAN particles on the matrix of the coating layer is even greater than the amount of PAN particles present on the surface of the coating layer. is large However, when the particle size of the PAN particles exceeds twice the thickness of the coating layer, said particles have a poor adhesion to the matrix of the coating layer,

  so that separation of the layer from a substrate can

  occur as a result of different tensions and friction occurring during treatment

  have an average particle size of at least 2 microns,

  all the particles are virtually embedded in the coating layer, since it is commonly 5 microns or more thick As a result, no protective effect is obtained As in most cases the coating layers have a thickness 2-300 microns, the average particle size of the PAN particles is preferably between

  2 and 200 microns in view of the fact that a granulometric distribution

  Current cue is close to the normal logarithmic distribution. Fig. 2 shows PAN particles having unetell

  grain size, which are present in the coating layer

  ment. The amount of PAN particles in the coating composition ranges from 5 to 100 parts by weight relative to

  to 100 parts by weight of the non-volatile matter of the com-

  coating position to which no UV absorber has heretofore been added (hereinafter also referred to as the radiation absorber-free composition

  ultraviolet) When the content of PAN particles is

  less than 5 parts by weight, no appreciable effect on the improvements in atmospheric resistance occurs, since said particles are spaced apart from each other by too great a distance. However, the presence of PAN particles in large quantities contributes at

  to improve the resistance to atmospheric agents

  if one does not apply a small amount of absorbency

  For this purpose, a small amount of the ultraviolet absorber is added to the coating medium having a content of at least 1% by weight of PAN particles in accordance with the invention. absorber on resistance to atmospheric agents

  pronounced as the amount of PAN particles increases

  However, the incorporation of PAN particles in too large amounts leads to a lowering of the processability of the coated substrate because of their hardness. As a result, the PAN particle content is preferably equal.

  at most 100 parts by weight, and ranges from 10 to 60 parts

  by weight for common applications for

  properties and performance of the coatings and

coating layers -

  Ultraviolet absorbers may include

  those based on the benzophenone type, the type.

  benzotriazole, phenyl salicylate type and the like.

  When PAN particles are used in accordance with

  invention, an absorber of ultraviolet rays of the ben-

  zotriazole is however more preferable.

  The amount of the ultraviolet absorber used

  range from 0.01 to 0.05 parts by weight

  parts by weight of the non-volatile matter of the

  In an amount of less than 0.01 parts by weight, the absorber does not absorb an ultraviolet absorber.

  produces no pronounced effect on improvements in

  the atmospheric agents of the coating layer in combination with the PAN particles while, in an amount greater than 0.05 parts by weight, no

  particular effect and the cost is made high.

  In the prior art, 0.1 to 0.5 part by weight of the radiation absorber was added to the coating compositions.

  In contrast, according to the invention, the present invention

  The presence of PAN particles allows the absorber to be used

  in a much smaller amount.

  In accordance with the invention, a minor amount of the ultraviolet absorber contributes greatly to improvements in the weatherability of the coating layers in cooperation with

  PAN for the following reasons, although not confirmed.

  As shown in FIGS. 1 and 2, the major proportion of the coating layer according to the invention is occupied by the PAN particles. As mentioned above, the PAN particles themselves have a good resistance to atmospheric agents. , and the major portion of the coating layer surrounded by said particles

  has a good resistance to atmospheric agents

  In addition, when ultraviolet light is

  come on the relatively small portion of the coating layer that is not surrounded by PAN particles, the base resin and the pigment of the coating layer

  are excited under the influence of ultraviolet rays

  radicals, which are then partially trapped by the nitrile groups of the adjacent PAN particles, and stabilized according to the mechanism already mentioned above.

  As a result, ultraviolet light is absorbed in the

  sorbeur, and useful for the stabilization of the coating layer Thus, there is a considerable difference between the

  stabilization of the coating layer obtained by means of

  and that obtained by the sole use of the benzotriazole type ultraviolet absorber, which can be explained in accordance with the following possible mechanism, although not confirmed. The ultraviolet absorber has in its chemical structure a hydroxyl group and a carboxyl group or a nitrogen atom, which are intended to be combined mutually by means of a hydrogen bond. Reason: for which the nitrogen-containing ben triazole type ultraviolet absorber has a negative This pronounced effect in the context of the invention probably lies in the fact that the combinations by hydrogen are also between the nitrile groups of the PAN particles, forming part of the invention, and the hydroxyl groups of the absorber of which the The strength of the bond is similar in magnitude to that of the hydrogen bonding between the hydroxyl groups and the nitrogen atoms. These combinations by hydrogen are in addition to hydrogen combinations present in the absorber,

  thus increasing the density of combinations by hydro-

  As a result, the energy of the ultraviolet rays is efficiently absorbed, and radiates readily under heat energy. The synergistic effect produced by The combination of PAN particles with the benzotriazole ultraviolet light absorber thus considerably reduces

  the amount of absorber used.

  The ultraviolet absorber of the benzotrial type

  The zole used may include 2- (2 'hydroxyl-4'-n-octoxy)

  phenyl) benzotriazole, 2- (2'-hydroxy-5'-methyl-phenyl) benzo

triazole, and the like.

  From the above discussion, it will be understood that the greater the amount of PAN particles, the better the effect of a small amount of ultraviolet absorber on improvements in atmospheric resistance. it is understood that the subject of the pre

  cited is independent of the value of the invention.

  According to the invention, no particular limitation is imposed on the other constituents and solvents requ for the formation of the coating layers.

2510591

  base forming the coating layers can be based on the polyester type, the silicon type, the fluorine type, the acryl type, and others, and can be supplemented with various inorganic or organic pigments. As a solvent, it is possible to use a solvent organic or water In general, all sub-

  stanzas or solvents which are now used as substan-

  These coatings or coatings, and stabilize a mixture of PAN particles or the ultraviolet absorber with another substance, can be used in accordance with the invention. making use of a variety of commonly available coating or coating substances

  and by adding the ultraviolet absorber and

  specific PAN particles so that the defined conditions

  according to the invention are satisfied.

  The PAN particles are mixed with a vehicle or

  coating material in the conventional manner, namely by

  direct mixing or mixing, or by dispersing them beforehand in a coating diluent, this operation being followed by

agitation.

  The invention can provide various types of coating or coating compositions, including, for example, solvent, non-solvent, aqueous, soil, oily, synthetic resin, transparent coating compositions. , opaque, of the type to be dried at normal temperature

and the type to cook.

  The following examples illustrate the invention in more detail without limiting it in its scope and spirit. Examples 1-10, plus Comparative Examples 1-21 450 parts by weight of acrylonitrile, 40 parts by weight of methyl acrylate, 16 parts by weight of sodium p-styrene sulfonate and 1181 parts by weight of water are introduced in a 2-liter autoclave, to which an initiator agent was added, the di-tert-butyl peroxide in an amount of 0.5% by weight relative to the total monomers. The autoclave was then closed to carry out polymerization with stirring at room temperature. 1500 C for 23 minutes After the end of the reaction,

  the autoclave is cooled down by lowering its temperature in the vicinity.

  swimming at 900 C with continual stirring, and

  The product polymer is then autoclaved.

  PAN obtained by spray drying into spherical PAN particles having a granular

average lometre of 15 microns.

  Blue-enamel, polyester-based, solvent-type coating compositions are prepared which are entirely

  free from PAN particles and ultraviolet absorbers

  violet and having a non-volatile content of 50% by weight to these coating compositions, respective additions

  0, 10, 30, 50, 70, 100 and 120 parts by weight of parti-

  PAN calculated on 100 parts by weight of

  the non-volatile material, and to an ultraviolet absorber

  benzotriazole type violets, or an ultraviolet absorber of another type, in the amount (in parts by weight) specified in Table I and calculated in relation to parts by weight of the nonvolatile material. By stirring the particles are uniformly dispersed. of PAN and the absorber in the coating compositions by respectively obtaining

  the coating compositions of Examples 1-lf and examples

comparative plots N 01-21.

  Each of the compositions thus obtained is subjected to baking on a standard phosphated zinc plate, having a thickness of 0.35 mm, after having coated said plate with an epoxy-type coating as a first layer or base layer, on a thickness of about 50 microns by calendering Then, the coating thus cooked, is subjected to a calar

  to a thickness of about 15 microns.

  With a weatherometer (a device for measuring resistance to atmospheric agents) of the carbon-arc type

  emitting a light reproducing the sunlight, one pro-

  gives an accelerated atmospheric resistance test for 2000 hours to determine the color difference of the coated plates (with the color analyzer, manufactured and marketed under the name Color Analyzer Type 307 by Hitachi, Ltd) and the gloss retention of said coated plates (expressed by the degree of

  reflection from a mirror to 60) The results are presented

Table 1.

  From Table 1, it can be seen that coating or coating compositions containing both PAN particles and an ultraviolet absorber exhibit excellent weatherability, whereas an ultraviolet absorber and containing the PAN particles do not show

  no significant improvement in resistance to atmospheric agents

  compared to compositions free of PAN particles. It is also found that the application of a greater amount of ultraviolet absorbers alone, makes little contribution to improvements in atmospheric resistance. ultraviolet rays are effective in an amount of 0.01 to 0.05

  part by weight but 0.1 part by weight of the absorber does not

  there is no increase in resistance to atmospheric agents

  In addition, it is found that an absorber other than the

  Benzotriazole type sorbent does not result in a significant increase in resistance to atmospheric agents, and that

  When using the ultraviolet absorber, the

  resistance to atmospheric agents is even better than

  the amount of PAN particles is large When the quantity of

  The amount of PAN added is 120 parts by weight based on 100 parts by weight of the non-volatile material, the resulting coating layer is hard and its processability

is mediocre.

  Examples 11-19 and Comparative Examples 22-25 As described in the examples above,

  uniformly disperses the same PAN particles and an absorbent

  ultraviolet light, ie 2- (2'-hydroxy-4'-n-

  octoxyphenyl) benzotriazole, to obtain compositions of

  clear coating of the silicon-polyester type applied by

  with a non-volatile content of 50% in

  weight, so as to prepare the coating compositions

shown in Table 2.

  Using a clear coating of the polyester as the first layer, calendering is carried out on a plate

13 2510591

TABLE 1

  EXAMPLE PAN Difference Absorber Retention Example (parts in UV rays of comparative color weight): 1 (parts in (AE) shine no _ __ids) '11 _ _) _ Ex compar 1 O 20 6.8 50.0 Ex compared 2 O UV 1 0.3 5.0 57.0 Ex Compar 3 10 O 4.8 58.5 Example 1 10 U Vi 0.01 2.9 71.5 Ex Compar 4 10 UV 2 30.01 4.5 59.3 EXAMPLE 2 U V 0.05 2.5 72.5 Ex Comparative 5 10 UV 2 0.05 4.5 61.3 Ex Compared 6 10 U Vi 0.1 2.5 73.0 Example 3 U Vi 0.01 2, 4 73.8 Ex compare 7 30 UV 2 0.01 4.5 63.8 Example 4 Uvi 0.05 2.3 75.2 Ex compare 8 30 UV 2 0.05 4, 4 66.0 Ex compared 9 30 O 4.5 62.0

_

  Example 5 50 U Vi 10.01 2.4 78.6 Ex Compar 10 50 UV 2 0.01 4.3 66.8 Example 6 50 Uvi 0.05 4.2 80.4 Ex Compared 11 50 UV 2 0, 05 4.2 60.9 Ex compare 12 50 UVI 0.1 2.2 82.0 Example 7 70 Uvi 0.01 2.0 83.5 Ex compare 13 70 UV 2 0.01 4.2 67.0 Example 8 70 Uvi 0.05 2.0 '83.7 Ex Compared 14 70 UV2 0.05 4.1 67.2 Ex Compared 15 70 O 4.0 63.5 Example 9 100 UVI 1 0.01 1.7 85 EXAMPLE 10 100 U V 0.05 1.5 86, 0 Ex Comparative 17 100 UV 2 0.05 4.1 68.4 EX Compared 18 100 UVI 0.1 1.4 86.5 Ex compare 19 100 O 3.8 64.4 Ex compare 20 120 O 3.5 65.1 Ex compare 21 120 Uvi 0.1 1.4 86.6 1: The parties by weight are given relative to 100 parts by weight of the non-volatile matter of the PAN-free coating composition and ultraviolet absorber (this also applies

to the following tables).

  2: UV 1 denotes 2- (2'-hydroxy-5'-methylphenyl) benzotriazole.

  3: UV 2 is 2,2'-dihydroxy-4-methoxybenzophenone.

  of 0.3 mm thick stainless steel, degreased with

  an alkali, to form on said plate a coating layer

  with a thickness of about 5 microns (calculated on the

basis of the dry matter).

  Then, each of the coating compositions obtained as mentioned above is applied to the shell to form a coating layer which is baked on said layer to form a layer of a thickness of 15. microns calculated on the basis of the material

  In this way, the stainless steel plates are obtained.

coated dable.

  With the plates thus obtained, the atmospheric resistance accelerated test is carried out on a carbon-arc-type dew-cycle weathermeter measuring apparatus for 1000 hours.

  in the same way as in Examples 1-10.

  visually the production of fouling.

  For comparative purposes, a similar test is

  with stainless steel plates coated with coating compositions that are not within the scope of

  The invention is also visually determined fouling.

  The results are shown in Table 2.

TABLE 2

  EXAMPLE PAN Cracking Absorber Retention Example (parts in UV rays of comparative weight) (parts in gloss n weight) Ex Compar 22 0 OX 9, 5 Example 11 10 0.01 O 70.0 Example 12 10 0.05 O 72 EXAMPLE 13 0.01 73.0 EXAMPLE 14 0.05 O 76.2 Ex Comparative 24 30 OO 35.6 Example 15 50 0.01 80.0 Example 16 50 0 , 05 O 83,1 Ex compar 25 50 O 40,3 ENCRASSAGE :: not determined 0 determined, slightly determined X determined, considerably According to table 2, it can be seen that the composition, which contains PAN particles, but does not contain any

  absorber of ultraviolet rays, is liable to become

  ser and demonstrates a sign of lowering of gloss retention, while the presence of a small amount of ab-

  ultraviolet ray sorter leads to the recovery layer

  garment improved resistance to atmospheric agents.

  Examples 17 and 18 plus comparative example 26

  As described in Examples 1-10,

  Persian uniformly PAN particles similar to those

  used by the said examples, with the difference that their

  the particle size is 170 microns, and an ultraviolet absorber, namely 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, to obtain blue emulsion coating compositions having an acrylic system of solvent, having a residual content of 50% by weight after heating, and a coating layer density of 1.4, obtaining the coating compositions as shown in FIG.

table 3.

  Subsequently, two 30 x 30 cm 2 concrete slabs are subsequently brushed with the aid of a composition which is dried by air and obtained layers of coating having

  a thickness of 150 microns.

For a year, the exterior of the cement slabs were tested for color change and cracking for comparison purposes. Similar tests were also performed with an absorber-free coating composition.

  ultraviolet rays The results are presented in the table

Bleau 3.

TABLE 3

  Example PAN Shearing Change Absorber Example (parts in UV rays of comparative weight) (parts in coloring no weight) Example 17 30 0.05 None None Example 18 50 0.05 None None Ex Compared 26 50 O Production Of considerable fine crumbs are formed all over the face From Table 3 it is found that the PAN particles serve to increase the resistance of the layers to the agents

  atmospheres, in the presence of the ultraviolet absorber

  purple, but the coating layer undergoes considerable discoloration and cracking in the absence of

ultraviolet rays.

  The coating or coating compositions according to the invention provide coating layers having a greatly improved resistance to atmospheric agents, are

  little costly to prepare, and have a great industrial interest.

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Claims (3)

  1 Coating or coating composition, characteristic   in that it comprises a polymer of the acrylic type   nitrile having an acrylonitrile content of 80% by weight or more and consisting of substantially solid spherical particles having an average particle size of 2 to 200 microns, said polymer being added in an amount of 5 to 100 parts by weight, based on 100 parts by weight of the non-volatile matter of said composition and further comprising   0.01 to 0.05 parts by weight of an ultraviolet absorber   violets of the benzotriazole type compared to 100 parts in   weight of said non-volatile material.   Coating composition according to Claim 1, characterized in that the benzotriazole ultraviolet light absorber used is 2- (2'-hydroxy-4'-n-octoxyphenyl) benzotriazole. 3 coating composition according to claim 1, characterized in that the ultraviolet absorber   of the benzotriazole type used is 2- (2'-hydroxy-5'-methyl) phenyl) benzotriazole.