FR2530534A1 - Sheets for abrasion-resistant decorative laminates - Google Patents

Abstract

THE INVENTION RELATES TO ABRASION RESISTANT LAMINATES. IT REFERS TO A DECORATIVE LAMINATE WHICH INCLUDES, ON BACKING SHEETS, A DECORATIVE SHEET INCLUDING A 15 PAPER COATED WITH AN EXTREMELY THIN LAYER, 0.5 TO 7.6 MICRONS, OF ALUMINUM PARTICLES 19 BONDED BY MICROCRYSTALLINE CELLULOSE PARTICLES. SHAPED LAMINATES DO NOT REQUIRE AN EXTERNAL PROTECTIVE COATING. APPLICATION TO THE REALIZATION OF DECORATIVE LAMINATES VERY RESISTANT TO ABRASION.

Description

The present invention relates to laminates and

  more specifically, decorative laminates having a resistance

high abrasion rate.

  High pressure decorative laminates, by stacking and curing with heating and pressing, are usually produced from several layers of impregnated paper.

  various synthetic thermosetting resins Normal-

  the set comprises, from the bottom, several core sheets, from three to eight, made of phenolic resin-impregnated kraft paper, above which is placed a printed or patterned sheet impregnated with a melamine resin ; a covering layer is placed on the printed sheet

  and in the laminate it is almost transparent and

  re the protection of the sheet bearing the drawing.

  Soul leaves are usually formed of

  kraft paper with a strength of about 145 to 205 g / m 2.

  Before the stacking, the kraft paper is impregnated with a solution in water and alcohol of a phenol-formaldehyde resole resin, then it is dried and partially cured in an oven with hot air circulation and finally cut. The printed sheet is formed by a paper of

  high quality alpha cellulose, having a pigment charge

  80 to 205 g / m 2, the sheet having been impregnated with a solution in water and the alcohol of melamine formaldehyde resin, then dried and partially cured before final cutting into sheets The printed sheet, before impregnation by the resin, usually carries a decorative pattern formed by printing or a reproduction formed by photogravure of natural materials such as wood, marble, leather, etc. A cover sheet is almost invariably used when the printed or printed sheet has an impression on the surface, so that it is protected against abrasion wear. The cover sheet is formed by a quality alpha cellulose paper. high, having a strength of about 33 to 50 g / m, also impregnated with a melamine-formaldehyde resin, in the same way as the printed sheet, but the amount of resin used by

  unit of paper weight is increased Individual sheets-

  they are stacked as indicated above and, when using six impregnated core sheets, the finished laminate has a thickness of about 1.25 mm, but a different number of sheets can be used for the formation of

  thicker or thinner laminates.

  The stack of sheets indicated previously is arranged between polished steel plates and subjected to a temperature of about 110 to 170 ° C (for example 150 ° C) and a pressure of 5.5 to 1.10 10 7a (for example 7 106 Pa), during a

  sufficient time for laminate consolation and durability

  curing resins (eg about 25 min) The resin of the paper sheets can then flow, then harden and can

  consolidate the leaves which form a unitary mass

  called "high-pressure decorative laminate".

  In contrast, two laminate stacks are compressed back-to-back and separated by a release-molded sheet which allows subsequent separation of the laminates. In addition, a substantial portion of the stacks comprise a composite sheet formed of kraft paper and aluminum foil between the cladding sheet and the metal plate, the aluminum being turned on the side of the cladding so that the laminate

  is less glossy and has a slightly textured surface

  which is desirable in the case of certain products.

  At the end of the laminate forming operation, the backs of the laminates are sanded so that they can be glued to particleboard of the plywood or other substrates. The panels on the surface of which the laminate has been glued are then in the form of furniture, kitchen element coverings, table tops, storage accessories and other items for a wide variety of applications in a form commonly accepted for its qualities

  appearance, durability and economy -

  A number of variants of the above-mentioned general method are known, in particular operations intended to give special effects of appearance and texture.

  curing cycles are possible and, in fact, other systems

  Resin strips are sometimes used.

  Beside high-pressure decorative laminates

  mentioned earlier, a number of

  number of products formed at low pressure,

  low pressure laminates comprising either polyurethane resins or

  saturated esters either a melamine-formaldehyde resin One of the fastest competing materials in high pressure laminates in recent years is a product called

  low-pressure melamine board that is normally

  awarded a short cycle at 160-1750 C and at 1.25 106-

  1.6 10 Pa These low-pressure products have the advantage of

  to be normally less expensive, but they can not be called "high-pressure laminates" because

  this name, they must satisfy certain criteria

  are very narrowly defined by the National Electric Manufacturers Association, NEMA Lp 3-1975,

  laying down criteria concerning abrasive wear, the

  stain resistance, heat resistance, impact resistance, dimensional stability, etc. Although various

  other printed decorative coating materials, for example

  low-pressure laminates, some of the characteristics

  desirable characteristics, no products other than laminates

  high pressure currently available does not possess the total

of these properties.

  One of these properties that is very important in practice is the abrasion resistance A decorative laminate

  at high pressure can have sufficient resistance to abrasion

  for use in highly exposed areas.

  such as kitchen table tops, crate counters, etc. The standardized NEMA abrasion resistance test is that of the NEMA LD-301 standard. In this test, a sample of laminate is tightened onto a rotating disc on which pass two rubber wheels repelled by a mass and having on the surface strips of sandpaper calibrated When the surface of the laminate rotates under the

  wheels or grinding wheels, the abrasive action of the sandpaper provokes

  cutting the surface of the laminate, in the coating, jus-

  that the printed design which is then exposed and destroyed The criterion fixed for the laminates of class I of this norm is a destruction of 50% at the maximum of the design of the laminate after 400 cycles of rotation The passage to 50% is estimated by formation of the average number of cycles for which the drawing undergoes initial wear and the number of cycles for which the drawing is totally destroyed. When preparing a high pressure decorative laminate in a conventional manner, with a normal content of -35% resin on the printed sheet or drawing but without

  coating, the resistance to abrasion is only

  50 to 75 cycles When using melamine resins of special formula for the sheet forming the drawing, with a resin content of 50 to 55%, the abrasion resistance

  up to 150 to 200 cycles occasionally, without

  in the latter case, the laminates tend to have superficial cracking and furthermore their preparation is extremely difficult given the

  difficulty of uniform impregnation of the printed sheet.

  In addition, these sheets do not meet the criterion of 400

  cycles to a minimum, set by the NEMA standard.

  Nevertheless, it is desirable that a laminate * is produced without a coating sheet, but has the characteristics of a laminate-having such a coating,

  and in particular, it is desirable that the laminate

  In addition, it is desirable that the laminate not only withstands abrasion for 400 cycles, but also has an initial point of wear at least equal to the initial point of wear. a conventional high-pressure laminate having a coating,

  example of 175 to 200 cycles This characteristic is often

  in practice, the appearance of the laminate becomes

  fictitious-no when 50% of the drawing is destroyed but when.

  the percentage destroyed is much lower We know since

  many years of experience-that conventional laminates

  having a coating and the point of initial wear

  corresponds to 175 to 200 cycles, when they undergo a

  very hard, have a satisfactory appearance at least during the normal period before replacement, the replacement of most laminates used in the trade being decided for decoration reasons and not for the wear of the drawing As a result, a laminate having no no cover sheet must meet the same criteria, ie it must have a NEMA abrasion resistance of at least 400 cycles and an initial point of wear, during same test, of at least 175 to 200 cycles, although this latter criterion is not part of the standard, NEMA. Obtaining these characteristics without the use of a coating sheet is desirable for several reasons. The coating sheet significantly increases the cost of the raw materials for the manufacture of the laminates, firstly by the cost of the coating paper itself and that of the resin used for impregnating this paper, and on the other hand of losses in treatment and

handling of these materials.

  2 The coating sheet, since it imposes the provision of a thick intermediate layer

  between the printed sheet and the eyes of the observer.

  tor, significantly reduces the desired visual clarity of the drawing.

  The cellulose fibers used for the formation of the coating paper have a refractive index close to that of the hardened melamine-formaldehyde resin. The fibers are therefore

  almost invisible in the hardened laminate and allow observation of

  the printed design with very low attenuation.

  However, modern printing techniques make

  accurate reproductions of natural materials.

  and in particular various types of wood veneers.

  Since these printed reproductions look very similar to that of natural plating, even faint blur or jamming due to liner paper presents a visual disturbance and removes most of the visual effect.

Realism wanted by the user.

  3 In addition, the cladding sheet contributes to

  raising the scrap rate of laminate products formed.

  The dry and impregnated coating sheet tends to attract

  small particles of dirt as it creates static charges during drying The detection and removal of this dirt is difficult before lamination, and it causes the deterioration of stratified sheets that can not be reprocessed. the impregnated dried coating is fragile and its handling is difficult without breaking. The broken pieces can also be trapped on the surface of the coating and then give

  defects visible to the eye in the leaves.

  In addition, laminates with a coating sheet, especially those with a relatively glossy surface, tend to become matte very quickly when they are

  wear even when moderated by abrasion This characteristic

  is clearly unacceptable when

  laminates must be shiny.

  The problem of increasing resistance to

  the abrasion has been a long time in the considered field.

  Suggestions for solutions have been numerous and in fact some are used industrially Nevertheless, it has not yet been possible to produce a laminate not including

  coating sheet but having resistance to abrasion

  NEMA standard of at least 400 cycles and one

  initial wear in the same test of at least 175 to 200 cy-

  cles. It is known that small hard mineral particles dispersed in a coating paper or in mixtures

  of resins used for coating the unprocessed sheet

  As shown in US Pat. Nos. 3,135,643, 3,373,071 and 3,373,070, such techniques can increase the abrasion resistance of high pressure laminates. do not eliminate

  the coating sheet but only increase its resistance

  abrasion resistance or concern a variant of

  coating and associated resins.

  For example, the patent of the United States of America

  No. 3 123-515 describes the impregnation of the coating sheet.

  finely divided frit The cover sheet is used in a normal manner by arrangement on the sheet

printed, bearing the drawing.

  U.S. Patent No. 3,798,111 discloses another process employing small mineral particles, preferably alumina, incorporated into the diaper

  of the base paper during its manufacture and to the

  During the tests, it is noted that the laminates formed with this paper-printed and without a coating sheet have lower initial wear values.

  at 100 cycles, as low as 35 cycles in some cases.

  In addition, in a friction test to determine initial wear, these laminates trade to exhibit

  destruction of the design after only 3000 cycles of rubbing

  that is to say, after a number well below the

their necessary.

  Other patents are of some interest to the invention, for example U.S. Patents 3,445,327, 3,928,706 and 3,661,673.

  are less interesting, for example US patents

  United States of America Nos. 3,259,537, 3,157,518, 3,716,440,

3,946,137 and 3,318,760.

  The problems raised have not been solved until

  present, despite the considerable activity devoted to their

  solution in the field under consideration.

  The invention relates to a high-pressure decorative laminate which does not have a coating sheet but nevertheless meets the criteria of the NEMA abrasion resistance standard and has an initial wear point of at least

200 cycles in this same test.

  More specifically, the invention relates to the coating

  of a conventional printed paper or otherwise decorated by a drawing, using an ultrathin layer containing small mineral particles immobilized on the sheet of paper by a suitable binder, the printed sheet being

  then normally impregnated with a thermoset resin

  curable material, for example a melamine resin, the printed sheet being then used for the formation of

  decorative laminates without facing sheet.

  Other features and advantages of the invention

  will become more apparent from the following description,

  with reference to the accompanying drawing in which Figure 1 is a diagram showing the implementation of a method for preparing a printed layer according to the invention; Figure 2 is a schematic sectional view of an embodiment of printed sheet according to the invention; and Figure 3 is a schematic sectional view of a laminate

according to the invention.

  The invention relates to a novel composition

  containing small mineral particles, and which, when deposited without resin on a non-impregnated

  a drawing, gives surprising and unexpected properties,

  putting the use of paper for the preparation of

  decorative fabrics with no coating layer,

  the resulting laminates with a high resistance to

  In an advantageous embodiment, the composition

  coating comprises a mixture of small aluminum particles

  and a small amount of micro-cellulose particles

  crystalline, the whole being dispersed in a suspension

  Stable aqueous alumina particles, having a small

  so that they do not disturb the optical effects

  obtained in the final product, constitute a

  sistaxt to abrasion and micro-cellulose particles

  crystalline constitute an advantageous binder It should be noted that the binder must be compatible with the resin system used

  later in the process of forming the laminate, ha-

  usually a melamine resin, or, in the case of some -

  Low-pressure laminates, a resinous polyester-based system, and microcrystalline cellulose fills this function and stabilizes the small particles of alumina at the

  surface of the sheet that is printed.

  As shown in FIG. 1, in one embodiment

  Advantageously, a printed or non-impregnated printed paper of conventional type is coated at 12 with a mixture of hard mineral particles and a binder, preferably alumina particles and microcrystalline cellulose in the form of a stable aqueous suspension, and the coating is dried in

  14 at an elevated temperature, for example in a circulating oven.

  hot air, so that it remains a thin coating of which

253053-4

  the thickness is only 0.5 to 7.5 microns The paper

  result 16 (Figure 2) which is coated and resists abrasion

  The composition is then impregnated with melamine or polyester resin and is dried in a conventional manner and is thus ready for the laminate forming operation. In FIG. 2, reference numeral 15 denotes the non-impregnated base sheet of the printed sheet. , reference 17 designates the ink pattern formed by printing and reference 19 designates the particles of alumina A 1203 bound by the microcrystalline cellulose under

  form of a very thin coating that does not contain any resin.

  FIG. 3 indicates that the abrasion-resistant, resin-impregnated printed sheet 20 having an extremely thin abrasion-resistant coating 22 on its upper face is arranged for lamination 24 (FIG. in a conventional manner but without a coating sheet, on core sheets 26 The laminate is then hardened by heating and compression in a conventional manner A surprising feature of the extremely thin coating is that, despite its thinness, it gives the finished laminate a abrasion resistance that not only meets the criterion of the NEM 4 A standard of 400 cycles but also gives a point

  initial wear that exceeds 175 to 200 cycles.

  It is also amazing that this coating adheres

  on the surface of the printed paper when it is

  continued impregnated with melanin resin, without significant amounts of mineral particles passing into the impregnating solution or moving away from the surface of the paper Another outstanding feature of the coating is that it does not appear to prevent the penetration of the solution melamine-formaldehyde resin inside the paper, during the impregnation stage This penetration is essential because the printed sheet is in the opposite case low in resin in its central part and can then have a disintegration, after compression Another advantageous characteristic of the coating is that it does not diffuse or significantly attenuate the light, so that the appearance of the design

  finished laminate is very clean and well defined.

  Although the invention is not limited by any theory or other, it is believed that the features

  advantages of the invention are explained in the following manner.

  The microcrystalline cellulose particles exert

  cent of the very large external forces that bind to other polar substances, for example between cellulose

  and alumina Thus, an aqueous suspension of micro-cellulose

  Cralalline and alumina is stable and does not separate quickly

  sedimentation, although suspensions of alumina particles in the water are not stable.

  the suspension is deposited on the paper, the cellulose

  crystal apparently causes the binding of alumina particles to the surface fibers of the paper and to the

  of the pattern formed by the ink, so that

  alumina can not migrate below the surface.

  This characteristic may explain the good resistance to

  the abrasion given by such small amounts of alumina.

  Thus, the totality in practice of the particles of alumina

  surface where they give the best characteristics

  instead of dispersing below the surface where they

  relatively little to the initial wear resistance.

  As indicated above, the most advantageous composition of a suspension comprises a mixture of small particles of alumina and a smaller amount of particles.

  of microcrystalline cellulose, all the particles being

  in water The small mineral particles must be

  can be in sufficient quantity to obtain, in the pro-

  formed, the desired resistance to abrasion as indicated

  as before, and the binder must be in an amount sufficient for the mineral particles to remain in place on the surface of the printed sheet. It is generally found that satisfactory results are obtained with 5 to 10 parts by weight of microcrystalline cellulose for About 20 to 120 parts by weight of alumina; we can also use values outside this range, but without particular advantages and in addition, the problems of manipulation are -complicate.

  the amount of water in the suspension-is also fixed by

  practical considerations since, when the water is too small, the suspension is so thick that its application is difficult; similarly, when the water is too much, the suspension becomes so fluid that the maintenance of a regular thickness during the coating operation is difficult given the flow of the suspension Thus, a suspension holding about 2 , 0% by weight of microcrystalline cellulose and 24% by weight of alumina, relative to water, is stable, that is to say

  that alumina does not settle; however, when the quantities

  used exceed about 3.5% by weight of microcrystalline cellulose and 24% by weight of alumina relative to water, the suspension becomes thixotropic and its

application is difficult.

  The composition preferably also comprises one

  a quantity of a wetting agent, preferably a nonionic agent,

  The amount of wetting agent is not important.

  but only a very small amount is desirable and

  larger quantities do not have any advantages.

  When using a silane, it constitutes a tackifier which chemically binds the alumina particles to the melamine binder after impregnation and hardening and the initial wear resistance is better since the particles of alumina are chemically bonded to the melamine resin and not only mechanically, and they remain

  in place longer during abrasion wear.

  lane must be selected from a group compatible with the particular thermosetting resin used in the laminate in this regard, silanes having an amino group, for example gammaaminopropyltrimethoxysilane, are particularly effective with melamine resins. The amount of silane used should not be particularly important and in-fact an amount as low as 0.5% of the weight of the alumina effectively increases the abrasion resistance of the final laminate It seems that the maximum amount is of the order of 2% of the weight of alumina since higher amounts do not give much better results and increase

  simply the costâ raw materials.

  According to an important feature of the invention, the coating containing the microcrystalline cellulose as binder must be dried at elevated temperature before impregnation of the printed sheet with the melamine resin. Thus, the minimum drying temperature is about 820 C and it is advantageously between 115 and 1320 C. Among the mineral particles resistant to abrasion, alumina is the most advantageous material Silica,

  suggested in some patents as resistant material to

  brasion, gives results much lower than those which gives alumina, during the implementation according to the invention Other mineral materials of sufficient hardness, for example zirconium oxide, cerium oxide, diamond powder, etc.

  can be satisfying but either they are too expensive

  to be used in practice or they give

  an excessive color change in certain circumstances.

  We also tried glass beads but without success The car-

  Silicon bure which is also tried gives an excessive color change, although the abrasion resistance

be good.

  An important characteristic is the size of the alumina particles. Below a particle size of 20 microns, the abrasion resistance becomes poor and the most advantageous minimum particle size is of the order of 25 microns. maximum is

  limited by the surface roughness of the object and the disturbance

  The most advantageous maximum dimension for the alumina particles is of the order

50 microns.

  The nature of the binder of mineral particles is a very important feature of the invention Of all the materials tested, microcrystalline cellulose is by far the most satisfactory. The binder must not only maintain the mineral particles in position on the surface of the surface. printed sheet but must also be a suspending agent (if not, an additional suspending agent must be used) The particular property of microcrystalline cellulose is that it acts as a film-forming and binder-forming agent. in suspension but, unlike other agents, it is not water-soluble before or after suspension and it forms a very porous film allowing penetration of the thermosetting resin In addition, the binder must be compatible with the resin used in the laminate and the microcrystalline cellulose is compatible with both the melamine resin and with polyester resins Moreover, it must not diffuse or attenuate the light, at the thicknesses

  applied in the final laminate, and the micro-cellulose

crystalline gives satisfaction.

  Other binders that can be used and who

  give worse results than microcrystalline cellulose

  are various suspending binders such as anionic acrylic polymer, carboxymethylcellulose and the like, especially hydroxypropylcellulose,

  methylcellulose, polyvinyl alcohol, polyvinylpy-

  lidone, etc. However, as indicated above, cell

  microcrystalline lose is by far the most advantageous binder.

  Microcrystalline cellulose is a non

  fibrous cellulose, in which the walls of the

  lules of cellulose fibers have been broken into fragments whose length is between a few microns and a few tens of microns It is not a chemical derivative but a purified cellulose alpha Microcrystalline cellulose is available under the brand " Avicel "'with

  the preparation is described in the US Pat.

  United States No. 3,275,580 "Avicel" cellulose RC 581 is a hygroscopic, white, odorless powder

  dispersed in water and contains about 11% carbon

  sodium xymethylcellulose forming a protective colloid Its particle size is such that less than 0.1% remains

  on a sieve with 0.25 mm orifices.

  Other features and advantages of the invention

  that are of particular importance are the following.

  (1) The mixture of alumina particles and cellulose

  lose microcrystalline is deposited from a suspension

  aqueous, and is not a filler of a resin solution.

  (2) The suspension is lined on an impregnated sheet

  awarded not impregnated and not on an impregnated sheet.

* (3) The coating is dried at high temperature

at least about 820 ° C.

  (4) The thickness of the coating is 0.5 to 5 microns

and not from 25 to 50 microns.

  (5) After applying the coating and drying, the sheet bearing the pattern is impregnated with the thermosetting resin, and this conventional impregnation of the printed sheet is carried out with conventional equipment and not by special coating and difficult adjustment of a thick suspension. (6) The extremely thin layer gives a resistance

  abrasion of a high value quite unexpected.

  The advantageous characteristics of the binding agent

  particles of alumina, all of them possessed by micro-cellulose.

  These binder constitutes a film-forming agent, it constitutes a binder of the mineral particles, it constitutes an agent for suspending these particles, it is not driven by the thermosetting resin during the subsequent impregnation, it is compatible with the resin

  subsequently applied thermosetting

  melamine or polyester, it is permeable to

  hardenable impregnation (microcrystalline cellulose actually forms a porous film), it resists the heat released during the formation of the laminate, and it does not scatter

  or does not attenuate the light in the laminate.

  Examples of implementation are now considered

  the work of the invention purely as an illustration.

EXAMPLE 1

  Microcrystalline cellulose (<Avicel "RC 581) is added to stirred water in a" Waring "mixer.

  2 to 3 minutes in the mixer, the cellulose is totally dissolved

  Then, with gentle stirring of the aluminum oxide ("Microgritl 'WCA), three drops of" Triton "X-100 (non-ionic detergent), which facilitates the wetting, are added. in the form of a coating on a non-impregnated sheet bearing a pattern,

  having a force of 106 g / m 2 and having an impression of over-

  face corresponding to the grain of the wood The dry coating

  then at 129 C for 3 min The paper then undergoes a

  turation in a normal way with a melamine-formaldehyde

  The resin content is 45 to 48% and the content of volatile materials is 5 to 6%. The laminate is then produced and compressed.

  in a typical cycle for general application, is it

  that is to say at about 150 ° C., 710 6 Pa, for about 25 minutes.

  Table I shows the compositions and results

  obtained during an abrasion test, for a coating

  with a thickness of 38 microns in the wet state,

  corresponding to a known layer 3.8 microns thick.

TABLE I

water (cm 3) "Avicel" RC 581

(quantity in g) -

Microgrit WCA

(quantity in g) -

  "Microgrit" WCA (particle size in microns) abrasion cycles, initial wear 25 design destruction,% to 500 cycles 100 In the table a powder of alumina is marked

2 3 4 5 6 7

250 250 250 250 250 250

6.5 7.5

7.5 7.5 7.5 7.5

30 30 60 60

40

9 30

100 400 475> 75

20 5

which precedes, "i

2 95 O

Microgrit "WCA de-

  lapping machine manufactured by Micro Abrasives Corporation, Westfield, Massachusetts, United States of America. The comparison of the tests shown in the table shows that microcrystalline cellulose alone is unsatisfactory (test No. 2), and that the use of alumina with a particle size of less than 20 microns does not give satisfactory results (test 6). note that the average particle size alumina "Microgrit" greater than 20 microns gives both satisfactory initial wear and satisfactory NEMA wear resistance. In addition, the obtained laminates have a sharper-looking appearance than the laminates conventional

  having coating sheets, and these laminates satisfying

  also do other NEMA durability tests.

EXAMPLE 2

  Four suspensions were prepared as described in Example 1, Test No. 3. Each was used for the formation of a 76 micron thick layer in the wet state on a non-impregnated paper of 106 g / m 2, and dry as described

  in example 1 so that the thickness of the coating is

  The dried paper is then impregnated with a melamine resin and placed in a stack of laminates as shown in FIG. 2. The production operation of the laminate is carried out as described in Example 1. The only difference between the four tests is the average particle size of alumina The results are as follows:

TABLE II

  Mean particle size, Destruction of drawing at 500 cycles

key microns

1%

<5%

20 20%

9 70%

EXAMPLE 3

  Example 2 is repeated for three trials in each

  case with particles of alumina having a particular dimension

  mean difference of 40 microns The only difference is the thickness of the wet coating The laminates are compared

  as described in Example 2 The results are as follows.

TABLE III

  Thickness of the wet coating Destruction of the drawing at 500 cycles

  cycles 76 p (7.6 to dry) 1% 51 p (5.1 p dry) 10% p (2.5 p dry) 30%

EXAMPLE 4

  The procedure of Example 1 is repeated, with one

  coating board of the printed sheet, having the

  following: 250 cm of water 7.5 g of microcrystalline cellulose g of alumina of average particle size equal to 40 microns, and

1 drop of "Triton" X-100.

  Two tests are carried out with wet thicknesses of 25 and 51 microns respectively. After formation of the laminate, abrasion resistance tests are carried out.

  do not indicate an initial destruction of the design for 500 cycles.

cles.

EXAMPLE 5

  The procedure of Example 4 is repeated with the same

  coating position, but containing 120 g of alumina of

  Average particle density equal to 30 microns Three tests are carried out with wet coatings of thickness 12.5, 25 and 38 microns. The abrasion resistance of the final laminate gives the following results, after 500 cycles.

TABLE IV

  12.5 p (1.3 p dry) destruction of the drawing 10% p (2.5 p dry) destruction of the drawing <1% 38 p (3.8 p dry) destruction of the drawing <1% The three laminates are very satisfying to all

  the other points of view The machinability is good, without formal

fragmentation.

  The physical properties of the third sample

  (prepared with a 2.5 micron coated paper) give the

  following results in a NEMA LD 3-1975 test after impregnation and compression

TABLE V

  wear resistance greater than 500 cycles stain resistance no effect moisture absorption 6.5% central swell 8.9% impact resistance (without backing) 91.5 cm thermal radiation (without backing) 1855 s water warm no effect hot wax no effect dimensional stability machine direction 0.24% cross direction 0.56%

  All these values are satisfactory or excellent.

EXAMPLE 6

  Example 4 is repeated in two tests with the same composition, but in the first test the alumina is replaced by 60 g of "Microgrit" SIC 400 (27 micron silicon carbide) and in the second test, replace the alumina

  with 60 g of "Microgrit" SIC 1000 (10 micron silicon carbide)

  crons) In each composition, coatings of 12.5, 25 and 38 microns are deposited.

  color "gray" given the color of the silicon carbide.

The results are as follows:

TABLE VI

  Coating Destruction of the drawing at 500 cycles

SIC 400 SIC 1000

  12.5 p (1.3 U dry) 20 85 p (2.5 p dry) 5 80 38 p (3.8 p dry) <5 70 It is noted that although the resistance to abrasion to be satisfactory, silicon carbide of 10 microns gives

  less good results than silicon carbide 27 microns.

  The color defect may be tolerated only for certain

print paper colors.

EXAMPLE 7

  Example 4 is repeated with three compositions, this time using, in place of the alumina particles, glass spheres (particle size less than 43 microns), 240 g of these glass spheres and 60 g of glass spheres. Cabosil "L-5 (mmicron sized silica aerosil), respectively Each composition is coated at a wet thickness of 12.5, 25 and 38 microns. The results are as follows:

TABLE VII

  TYPE Total wear on the appliance Taber * g glass 200 cycles 240 g glass 200 cycles g silica "Aerosil" <100 cycles The abrasion resistance test device described

  at the beginning of this memoir is an abrasion apparatus "Taber".

  None of these samples give resistance

satisfactory abrasion.

EXAMPLE 8

  The procedure of Example 4 is repeated, but the composition of a sample is changed by replacing the microcrystalline cellulos with 6 g of anionic acrylic polymer ("Rete: 420 from Hercules Powder Company"), and by replacing this

  same cellulose, in a second sample, with 9 g of carboxy-

  methylcellulose In both samples, the abbreviation test

  "Taber" indicates about 5% wear at 500 cycles, that is, a satisfactory value.

  anionic acrylic polymer gives a slight disturbance to the

  indicated that the use of this material is not

  satisfactory for some colors The laminate in which carboxymethylcellulose is used as a binder of alumina has poor resistance to boiling water and does not

  may not meet the NEMA criteria in this regard.

  This material can only be used in the form

  some lower quality low pressure laminates.

EXAMPLE 9

  The effect of silanes is investigated through the use of

  Next process 1 g of gamma-aminopropyltrimethoxy-

  silane with a solution of 10% water and 90% methanol,

  until dispersion, using a minimal amount of

  which is sufficient for the wetting of the alumina powder.

  The persion is then added to 100 g micron-sized micron-sized alumina (WCA 30) and the alumina is mixed with the solution until it is thoroughly wetted. The alumina is then dried. Example 4, but the coating was applied to the printed sheet at a thickness of 6.5 microns wet (0.65 micron dry). The resulting laminate was compared to those prepared in Example 4 (without silane), also applied at 6.5 micron wet thickness All laminates are compressed to mirror finish Resistance test results

  abrasion are shown in Table VIII.

2530534 =

TABLE VIII

  no silane silane initial wear (cycles) 300 525 final wear (cycles) 1075 1250 wear index 687 887

  It is noted that the silane improves the effectiveness of the coating.

resistant to abrasion.

EXAMPLE 10

  The effectiveness of the invention is determined for improving

  Improvement of the Characteristics of Low-Pressure Panels A slurry was prepared as described in Example 1 with 250 g of water, 6.5 g of microcrystalline cellulose, 30 g of 30 micron alumina and 2 drops of Triton. X-100 The slurry was coated as a 12.5 micron thick wet layer (1.3 micron dry) on a non-impregnated paper printed sheet and dried for 3 minutes at room temperature. 127 C The sheet is then impregnated and dried twice so that the impregnation is complete.

  impregnated on a panel of wood particles and compressed.

  at 1.4 Pa at 1500 ° C. for 6 minutes.

  prepares an identical low pressure laminate, without coating

  abrasion resistant on the upper side of the sheet

  The two samples were tested for resistance.

  NEMA abrasion resistance and obtained the following results

TABLE IX

  Resistant coating Uncoated abrasion initial wear 200 cycles NEMA abrasion 1050 cycles 150-200 cycles The results in Table IX show that the invention greatly increases the abrasion resistance of laminates

at low pressure.

EXAMPLE 11

  The procedure of Example 9 is repeated and the coatings are applied at a thickness of 38 microns wet (3.8 microns dry). Four attempts are made by varying the amount of silane, and the resulting laminate is subjected to for testing

  NEMA abrasion The initial wear is noted, the final results

listed in Table X.

PAINTINGS

  Amount of silane Initial wear, cycles g / 100 g of alumina

O 175

2,475

3,510

6,400

  These tests show that the effect of the silane does not increase significantly when the amount exceeds about 2% by weight relative to the weight of the alumina and in fact, the 6% silane test gives good results that the 2% test, although much better than a

not containing silane at all.

EXAMPLE 12

  The procedure of Example 9 is repeated in order to determine the initial finished wear resistance according to

  the temperature used for drying the coating applied

  That is, the sheet is coated with the composition of Example 4 at 13 to 16 g / m 2 (5 microns dry), but the composition contains a silane such as

  described with reference to Example 9 The coating is dried

  3 min for each sample, at various temperatures

  As indicated in Table XI After drying, the coated sheets are left so that they take the humidity equilibrium at room temperature, with a relative humidity of 50% at 210 ° C .; the leaves are then impregnated with conventional melamine-formaldehyde resin and then used for the formation of a laminate in a conventional manner, with

  a plate with a satin finish The results are as follows.

TABLE XI

  Oven temperature, 'C Initial wear, cycles

71,225

82,550

93,550

116,575

129,575

EXAMPLE 13

  A suspension of ingredients is prepared as described

  in Example 1, with 6.5 parts by weight of micro-cellulose

  crystalline "Avicel", 2 parts by weight of carboxymethyl

  cellulose, 30 parts of alumina of 30 microns and 250 parts

  in weight of water A trace of "Triton" X-100 is added.

  The resulting suspension was applied to a printed sheet using a "Meyer" rod coating machine at a rate of 9 g / m 2 (3.8 micron dry thickness). The printed paper was then impregnated a melamine-formaldehyde resin so that the resin content is 41.7%, and the drying is carried out and corresponds to a volatile matter content

  4.2% A laminate is then formed by compression of the

  coated printed staple, during a conventional laminating cycle

  cation, and using mirror-finish plates, so that

  the final laminate has a glossy surface.

  The laminate thus formed is compared to another conventionally formed mirror-finish laminate with a coating layer of 33 g / m 2, both laminates being subjected to a box slip test, as indicated in the following. The laminate according to the invention has wear

  325 cycles and a NEMA wear index of 1021 cycles.

  During the friction test of the boots that slip, the

  The comparative results obtained are as follows:

TABLE XII

SUPERFICIAL DEPOLISHING

  Cycles Laminate Coating Laminate formed with conventional coated sheet coated 1500 low no effect 3000 low no effect 6000 (more and more no bad effect) 12000 low 24000 wear very impor low wear aunt Destruction of drawing begins at 30000 cycles

  approximately for the two samples but it seems that the strati-

  classic fie presents a gradual frosting of the surface

  even for 1,500 friction cycles only and in fact, the

  Progressive polishing begins almost with the first few

  hundreds of cycles of friction In addition, the strat-

  The classic tified is completely frosted well before the destruction.

  initial drawing (30,000 cycles of friction).

  Compared to the known methods, the invention gives much higher results, so that it can be considered as a progress which revolutionizes the field of

  decorative laminates Given current knowledge-

  The invention relates to the first laminate having no coating sheet and capable of meeting the NEMA criteria for abrasion resistance of at least 400 cycles, and the initial wear criterion, in which

  the same test, of at least 175 to 200 cycles.

  Laminates in which the initial wear de-

  ends the acceptable length of the surface rather than the NEMA wear index, have many applications For example, supermarket checkout counters, food store counters, cafeteria tables and other surfaces. commercial establishments are exposed to the abrasive friction and sliding of unglazed crockery, canned goods, trays

  fiberglass, etc. If small parts of the drawing com

  begin to disappear after a relatively short period of use, especially irregularly, the surface is unacceptable to the owner and requires replacement

  When the surface wears out gradually and

  firstly over a long period, the wear time exceeds the normal replacement cycle for a change of decoration

which is about 3 to 5 years old.

Claims (11)

  1 Decorative sheet for use in the preparation of large decorative laminates   resistance to abrasion, characterized in that it   takes a decorative paper sheet substrate and an abrasion-resistant ultra-thin coating on the decorative substrate, said ultra-thin abrasion-resistant coating comprising (1) a hardness resistant hard mineral material; abrasion formed of fine particles   in a high enough concentration to produce a   abrasion-resistant layer without interfering with visibility; and (2) a binder for the mineral material compatible with a thermosetting resin for lamination, selected from a melamine formaldehyde resin and a polyester resin, the binder being present in an amount sufficient to bind and stabilizing the abrasion resistant material on the surface of the decorative paper sheet. -2 decorative sheet according to claim 1, characterized in that the binder is mainly formed   of microcrystalline cellulose, the mineral   as the abrasion is preferably alumina and / or silica. 3 Decorative sheet according to claim 1, characterized in that it is impregnated with melamine resin, the abrasion resistant mineral material is -alumina and / or silica and the binder is mainly   formed of microcrystalline cellulose, the ultra-fine   a thin film having a thickness of 0.5 to 5.8 micrometers, the coating comprising 5 to 10 parts by weight of microcrystalline cellulose for about 20 to 150 parts by weight of mineral substance, this coating preferably further comprising 0.5 to 2 , 0% by weight of a silane on the basis of weight of mineral substance.   4 Abrasion resistant decorative laminate, meeting NEMA abrasion resistance standards and also capable of withstanding 175-200 initial wear cycles in the same test, characterized in that it comprises a backing layer to which is laminated a decorative sheet of resin impregnated coating   thermoset for laminating, having a coating of   The ultra-thin, abrasion-resistant coating on its upper surface is ultra-thin, abrasion-resistant coating consisting of a mixture of (1) a hard mineral material which is abrasion-resistant to fine particles. a high concentration sufficient to ensure the abrasion resistance without hindering the visibility and (2) a stabilizing binder for said mineral substance, the thermoset resin completely impregnating the decorative coating sheet, the binder not impeding visibility and ultra-thin abrasion-resistant coating forming the top layer of the laminate.   Decorative laminate according to claim 4, characterized in that the thermoset resin is a melamine-formaldehyde resin, the binder is mainly formed of microcrystalline cellulose and the abrasion-resistant mineral particles are formed of alumina and / or silica.   Laminate according to claim 4, characterized   in that the ultra-thin layer resistant to abrasion   sion is applied directly to the decorative sheet and   has a thickness of 0.5 to 5.1 micrometers.   7 High pressure decorative laminate next   claim 4, characterized in that the support   takes several sheets of paper impregnated with a phenolic material and the decorative sheet comprises a sheet of paper impregnated with melamine resin, the particles   resistant to abrasion being formed of aluminum particles   the binder is formed of microcrystalline cellulose, the abrasion-resistant coating comprises about 5 to 10 parts by weight of microcrystalline cellulose for about 20 to 120 parts by weight of alumina, the thickness of said coating being about 0 , 5 to 5.08 micrometers, the alumina preferably being bonded to the melamine resin by a silane.   8 Laminate according to claim 5, characterized   in that the inorganic substance resistant to abrasion   is alumina and this alumina is chemically bound   melamine resin with a silane.   9 decorative sheet according to claim 1, characterized in that the ultra-thin layer has a   maximum thickness of 7.6 micrometers.   Laminate according to claim 4,   in that the ultra-thin layer resistant to abrasion   sion has a thickness not exceeding 7.6 micrometers.   11 Decorative sheet according to claim 1, characterized in that it is impregnated with a thermosetting resin suitable for lamination, the binder   preferably consisting of a mixture of micro-cellulose   crystalline and carboxymethylcellulose.   Decorative sheet according to Claim 1, characterized in that the amount by weight of binder in the abrasion-resistant coating does not exceed   the quantity by weight of mineral substance that it contains.   Laminate according to claim 4, characterized   characterized in that the amount by weight of binder in the abrasion-resistant coating is not greater than the amount by weight of the mineral contained therein,   the binder being in the form of a mixture.   14 Decorative sheet for use in the production of large decorative laminates   resistance to abrasion, characterized in that it comprises   takes a substrate formed of a sheet of decorative paper and   an ultra-thin coating resistant to abrasion   on top of the decorative paper, this ultra-thin   abrasion-resistant thin having a thickness of the order of 0.5 to 7.6 micrometers and being formed of a mixture (1)   of a hard mineral material resistant to abrasion   small particles of sufficient diameter to form an abrasion-resistant layer, without interfering with visibility, and (2) a binder for said mineral substance, wherein the binder is present in an amount sufficient to bind -and stabilizing the abrasion-resistant mineral material to the paper sheet to provide abrasion resistance without the need for a cover sheet, the coating being impregnated with a laminating resin selected from a melamine-formaldehyde resin and a polyester resin. Decorative sheet for use in the production of large decorative laminates   abrasion resistance, for which a thermosetting resin   curable laminating material, selected between a melamine formaldehyde resin and a polyester resin, is used, characterized in that it comprises a sheet of non-impregnated substrate paper with a laminating resin having an ultrathin coating resistant to abrasive material having a thickness in the range of 0.5 to 7.6 microns and consisting of a mixture (1) of an abrasion-resistant hard mineral material formed of small diameter particles in an amount sufficient to form a layer abrasion resistant without disturbing the   visibility and (2) a binder for the said mineral substance   wherein said binder is present in a smaller amount than the inorganic substance but sufficient to bind and stabilize the abrasion-resistant mineral on the paper sheet, the decorative sheet carrying said coating being impregnated with said resin of stratification -