FR2704550A1 - Process for the preparation of colored acrylate plastics having a metallic glossy surface - Google Patents

Abstract

The invention relates to a process for preparing objects made of plastic materials based on an acrylic and/or methacrylic resin and having a metallic shiny surface, process in which pearly pigments, having a particle size >= 5 mum, are introduced into acrylates or methacrylate monomers and/or customary polymerizable prepolymers, the polymerization is carried out until the end in forming polymerization chambers, then demoulding is carried out.

Description

The invention relates to a process for preparing in a reproducible manner

poly (meth) acrylate objects

containing a pearlescent pigment.

  The technique has already solved in a very satisfactory way the problem of

  color the plastics in the mass. For example

  in the acrylic glass sector, we have a whole range of dyes that allow us to color

  in the mass, in a homogeneous way, the acrylic glasses

  in almost every possible nuance.

  In certain applications, for example in the building industry, particularly in the field of tiles and objects for sanitary purposes, it has since become apparent

  a tendency to use elements that

  attempt a superficial differentiation by color,

  by making areas containing a dye - for example

  according to a statistical distribution - which give

  the eye an impression different from that of colora-

  basic training. As for materials currently

  available, and showing a differentiation of

  of this type, these are usually

ceramic base.

  DE-A 30 23 964 discloses a process for producing dye-containing areas in acrylic and methacrylic resins, in the vicinity of the surface, and during the polymerization of the monomers and prepolymers forming the resins, in polymerization chambers. formers, in which process dyes homogeneously distributed in a binder are initially applied in the form of a layer to the wall of the forming polymerization chamber, the binder being soluble or at least swell, in the liquid resin or in its precursors, and in that, after

  placement of the monomers and / or prepolymers with poly-

  merize, they are polymerized in a manner known per se.

  According to the publication DE-A 31 10 093, we obtain

  objects made of acrylic and methacrylic resins

  feeling the desired color differentiation, in form

  zones containing dyes, by preparing poly-

  pearls made from acrylic or methacrylic resins

  crylics, containing dyes having the color

  hated, then introducing the pearls containing a

  dye, thus prepared, or possibly mixtures

  of different types of pearls containing

  pigment pearls, in the precursors used in

  in the present state of the art to polymerize acrylic or methacrylic resins, for example

  in syrups, prepolymers and / or monomers usually

used.

  It is possible to obtain a pigmentary coloration parti-

  For example, inks of printing or varnish are used if pearlescent pigments are used, which are also called pigments with decorative effects. The pearlescent effect, which is a metallic gloss, is particularly

  appreciated in decorative applications.

  Pearlescent pigments can also be introduced into objects made of acrylic and methacrylic resins, for example in the sanitary field. The acrylic glass objects thus pigmented, having a pearlescent sheen uniform throughout the plate, can not however be manufactured in a manner reproducible in the

  usual conditions of polymerisation, which is

  feste by a still different aspect of the polymers containing the pearlescent pigment. In particular, in the acrylic glass surface, there are turbid zones (Bénard cells) of irregular structure, which

  give the objects a tormented appearance (Ullmann's Ency-

  clopedia of Industrial Chemistry, 5th ed. entirely

  revised, vol. A18, pp. 466-468; Spektrum der Wissen

  Schaft, September 1980, pp. 118-131), and further striated structures, appearing under the effect of a demixing during filling cavities (filling strips).

  The object of the invention is therefore to improve the conditions

  manufacture of pigmented articles based on acrylic and methacrylic resins, having a metallic glossy surface, during the coloring in the mass, by pearlescent pigments, acrylic and methacrylic resins, and their polymerization, so that the polymers colored and pigmented, having a shiny metal surface, can

  be made in a reproducible manner. To explain

  the formation of Benard cells on the surface of pigmented systems, convection currents can be used, caused mainly by differences in temperature and differences in density,

  only by variations in viscosity and therefore variations

  tions of surface tension. To avoid the

  Benard's lules, the

  temperature differences in systems of this type.

  As a result, the polymerization systems containing

  pigments are usually hardened at low temperatures

  ture, that is to say over long periods of polymerisation

  as a rule from 10 to 20 hours.

  Surprisingly, it has been discovered that objects can be produced in a reproducible manner.

  polymerised based on an acrylic resin and / or methacrylate

  crylic, having a very regular appearance and containing pearlescent pigments, if it is introduced into the polymerization mass, in the form of pigments, essentially

  those who do not have the usual amount of fines,

  that is to say particles of particle size

  less than 5 pm, and by using the polymer

  without delay, as quickly as possible, ie at significantly higher temperatures

  than usual, and therefore with polymerization times

  significantly shorter, but in a unique way

  form. The pearlescent pigments used in the invention have a particle size of 25 μm, preferably 5 to 50 μm, and

especially 5 to 30 μm.

  According to the invention, the polymerization is carried out

  at temperatures of 2 40 C, preferably

  its 40 to 60 C, especially between 40 and 50 C and especially 45 C, essentially without addition of substances slowing the gelling effect,

  that is, decreasing the rate of polymerization.

  If one chooses the initiator and the

  polymerization temperature, the duration of the polymerization

  For a layer thickness of 5 mm, this is 2.5 to 6 hours before reaching a conversion level of about 80% by weight. The final polymerization is

  made, for example, in an annealing oven, at temperatures of

between 100 and 120 C.

  The acrylic or methacrylic resins preferably used for the polymerization are the syrups usually usable for this purpose, that is to say

  prepolymer solutions in monomers.

  The invention relates to a method for manufacturing

  plastic objects made from acrylic resins

  and / or methacrylic, with a surface area

  metallic gloss, during the polymerisation,

  in itself, acrylic and / or methacrylic resins

  using polymerization chambers

  mantes, characterized in that nacreous pigments having a particle size of 25 μm are introduced into the monomers

  and / or conventional polymerizable prepolymers, the polymerization

  tion being implemented in the polymer chambers

  forming at temperatures of 40.degree. C., provided that the initiator and the polymerization temperature are chosen so that, for a layer thickness of 5 mm, the duration of the polymerization, until one arrives at a conversion rate of about 80%, ie from 2.5 to 6 hours, and that the demolding is carried out after the final polymerization, at a temperature of 100 to C. The pearlescent pigments used according to the invention to prepare poly (meth) acrylate articles and having a metal gloss surface, are white and colored nacreous pigments based on mica coated with metal oxides, such as for example titanium dioxide or

  iron oxide (III), in which the fraction

  particle size less than 5 μm, which is normally

  It is contained in the manufacture and has a particle size of from about 5 microns to about 50 microns.

  pm. The separation of the fine fraction, having a granular

  lometry <5 μm, can be achieved for example by sieving technical pearlescent pigments. The commercially available Iriodin brand is used as a pearlescent pigment. (R) On

  uses them in printing inks, coloring

  plastics in the mass and varnishes, for example automotive body varnishes. The color effects of these pigments appear under

  the effect of absorption of light and

  ference. The pearlescent pigments having a certain granulo-

  metry satisfy the conditions of interference and pre-

Feel iridescent colors.

  The ratio of pearlescent pigment to matrix polymers can vary within wide limits, depending on the desired effect. In general, the amount of pigments present in the overall plastic object is 0.1 to 10

  and preferably from 0.3 to 3% by weight.

  The introduction is advantageously carried out so as to guarantee, in the polymerization mass, the distribution of the pigmentary grains necessary for obtaining a uniform appearance, for example by

  thinning. The following steps, for example the introduc-

  syrup in the polymerization chambers

  mantes, and the next polymerization step, can then be implemented in a manner analogous to the methods of the current state of the art, and the same is true for demolding, etc. The manufacture of the polymer matrix, in which are incorporated the pearlescent pigments having a

  particle size> 5 μm, can be carried out following

  the indications of the state of the art.

  As monomers for

  to implement the process according to the invention, the mono-

  for preparing plastic resins by polymerization in a mold. Here we think primarily of materials intended for objects molded in

  the following applications: technical, health

  and household goods, that is to say, that of

  plastics which are characterized by their insolubility in the usual solvents, and by good mechanical properties. In theory, the process

  may use compounds with double bonds

  polymerizable sounds. By way of example, mention may be made of esters of acrylic and methacrylic acid, in particular methyl methacrylate monomer, and

  other copolymerizable monomers, such as, for example,

  only styrene, vinyl acetate, etc. Matrix polymers, based on methyl methacrylate, can still contain, for example, from 0 to

  about 45% by weight of other comonomers.

  Other esters of methacrylic acid or acrylic acid, such as, for example

  methyl acrylate, butyl acrylate,

  methyl chloroacrylate, ethyl methacrylate; and furthermore optionally substituted amides of acrylic or methacrylic acid, such as acrylamide and

  methacrylamide, methylolmethacrylamide and methyl-

  lolacrylamide. It is also necessary to mention acrylonitrile, styrene and its derivatives, such as α-methylstyrene, vinyl esters of carboxylic acids, such as vinyl acetate, etc. It is particularly appropriate to mention the presence of crosslinkable monomers such as

  ethylene dimethacrylate, 1,4-dimethacrylate

  butanediol, triglycol trimethacrylate,

  trimethylolpropane methacrylate or the allyl compounds

  such as, for example, allyl methacrylate,

  triallyl cyanurate or triallyl isocyanurate.

  The polymerization can be carried out in a manner known per se, using experience

  acquired in the art (see H. Rauch-Puntigam and Th.

  VOlker in "Acryl- und Methacrylverbindungen", Springer-Verlag 1967, and J. Brandrup - E. H. Immergut,

  Polymer-Handbook, 2nd ed., Wiley-Interscience (1975)).

  Corresponding techniques are already described in

DE N 639 095.

  It is possible to use, for example, peroxides or azo compounds, in the usual amounts, as an initiator for the polymerization of double bonds.

  polymers, such as, for example, acrylic monomers

  polymers, styrene and its derivatives, the esters of

  vinyls. To act on the molecular mass, one

  can use the already known regulators, by

  Usualities. Examples that may be mentioned include organic compounds of sulfur. We know that he is

  possible to adjust, through the concentration

  initiator and / or regulator, the degree of

  polymerization and thus the molecular weight of the

  resin that will form. This is how we will generally use, during the polymerization of

  acrylic resins, from 0.01 to 1.0% by weight of an amorphous

  ceur. The added amount of the regulator is generally between 0.01 and 0.5% by weight and preferably

  between 0.05 and 0.2% by weight. In general, the molecular mass

  weight average (Mw) of the matrix polymer is

  between 2 x 105 and 5 x 106 daltons. In most

  In some cases, the matrix polymer is slightly

  culé. The Vicat softening temperature (according to DIN 53 46, process B) is generally> 100 C.

  Moreover, the polymerisation masses can still con-

  hold adjuvants known per se such as UV absorbers, plasticizers, thermal stabilizers, antioxidants, flame retardants, etc. On the technical scale, it will be possible to use, for example as described below, the preparation of acrylic resins containing pearlescent pigments: a syrupy prepolymer is prepared (with a value indicative of 20% for the conversion rate), in which a suitable initiator, for example an azo initiator, is advantageously stirred advantageously, essentially an initiator having a relatively low half-life period, and optionally crosslinking agents uniformly

  distributed. If it is a question of coloring in the mass the poly-

  matrix mother itself, is added, before distributing until homogeneity, the dye (s) in a suitable form, for example in the form of a paste

  colored, which has been prepared with a (soluble) polymer.

  The mixture thus obtained represents the basic mixture.

  The pearlescent pigments are added to the basic mixture.

  particle size> 5 μm, so that they can be

  shot in the mass, preferably with stirring; then, advantageously, it is stirred again for a short time

  time, and fill the polymerization chamber

  mantis. The thickness of the layer then depends on the use

  the molded object. For articles intended to be used in construction, and particularly in the sanitary field, the thickness of the layer should generally not exceed 10 mm. We can give as

  indicative value a thickness of 5 mm.

  The polymerization is generally carried out at high temperature, for example between 40 and 60 ° C. and in particular between 40 and 50 ° C.

  indicative value about 45 C. The duration of polymerisation

  The conversion, for a conversion rate of about 80 C by weight, is between 2.5 and 6 hours, preferably between 3 and 6 hours, for a layer thickness of 5 mm. An indicative duration may be considered

about 4 hours.

  Then advantageously still proceeds to an annealing, for example at 100120 C for a period of time from 3 to

  8 hours and average of about 5 hours.

  The invention will be better understood with regard to the examples

  ples below which show that, if one puts into practice

  the measures according to the invention, such as granulometry,

  indicated for the pearlescent pigment to be used, as well as the control of the polymerization, poly (meth) acrylate articles containing a pearlescent pigment are obtained,

  with a metallic luster and a very uni-

form. Examples

Example 1

  Comparative Example: Reaction mass: 1000 parts of the methyl methacrylate prepolymer (viscosity about 1000 cP) parts of a pearlescent pigment having a particle size of 0.01 to 15 μm (Iriodin (R) 9111 WR, from Merck)

  0.004 part of a mixture of anthraquinone dyes

solubles.

  1 part 2,2'-azobis- (2,4-dimethylvaleronitrile)

  The reaction mass is intimately mixed

  tionally, it is introduced into a silicate glass chamber with a spacer bead 5 mm thick, and polymerized in a water bath at C. The final polymerization is carried out in an oven of

annealed at 115 C.

Example, 2

  The procedure is as in Example 1, but the polymer

  in a water bath at 45 C.

Example 3

  The procedure is as in Example 1, but with 15

  parts of the pearlescent pigment with a granular

  Metric from 5 to 20 pm (Iriodin (R) 9119 WR from the company

Merck).

Example 4

  The procedure is as in Example 2, but with 15

  parts of the pearlescent pigment with a granular

Metric 5 to 20 pm.

  Results: Ex. A B Aspect 1 510 0.01 - 15 pm Very turbid (Benard cells) and filling strips. 2 220 0.01 - 15 pm Moderately irregular, and only weak bands

filling.

  3 510 5.00 - 20 pm Moderately irregular, and only weak bands

filling.

  4,220 5.00 - 20 pm Very consistent appearance.

  A: Duration of the polymerization in a water bath, in minutes B: Granulometric distribution of the pearlescent pigment

Claims (7)

claims   1. Process for making articles of matter   plastics based on acrylic resins and / or methacrylate   with a metallic glossy surface, during the polymerization, common in itself, resins   acrylic and / or methacrylic   forming polymers, characterized in that   pearlescent pigments having a particle size   25 microns in customary monomers and / or polymerizable prepolymers, the polymerization being carried out in the forming polymerization chambers at temperatures of 240.degree. C., provided that the initiator and the polymerization temperature are selected so that for a layer thickness of 5 mm, the duration of the polymerization, until a conversion rate of about 80% is reached, ie 2.5 to 6 hours, and that the demolding is performed after polymerization   final, at a temperature of 100 to 120 C.   2. Method according to claim 1, characterized in that the conditions are chosen so that the resin   acrylic and / or methacrylic acid has a molecular weight   average weight (Mw) of 2 x 105 to 5 x 106 dal-   tones or is weakly cross-linked, and presents a   Vicat softening temperature (according to DIN 53 460, method B)> 100 C.   3. Process according to claims 1 and 2, characterized   in that the quantity of pearlescent pigment in   the overall plastic object is 0.1 to 10 and preferably 0.3 to 3% by weight.   4. Process according to claims 1 to 3,   in that the pearlescent pigments have a particle size   from 5 to 50 and preferably from 5 to 30 μm.   5. Process according to claims 1 to 4,   characterized in that the acrylic and / or methacrylic resin   contains still other suitable dyes.   6. Process for preparing articles of matter   plastics based on acrylic resin and / or methacrylate   and having a metallic glossy surface, characterized in that a thermal transformation of the objects prepared by the process according to the Claims 1 to 5.   7. Objects made of plastics based on acrylic and / or methacrylic resin with a surface having a metallic gloss, characterized in that they are   prepared by processes according to claims 1 to 6.