Gypsum board suitable for wet or humid areas

Abstract

Gypsum board having a core, said core having at least one side covered with a non-woven fabric; characterized in that the inner side of the non-woven fabric, which is in contact with the core of the gypsum board, has a surface roughness Ra of from 25 to 60 micrometers, preferably from 25 to 50 micrometers, advantageously from 25 to 40 micrometers.

Claims

1. A gypsum board comprising: a gypsum core, and a wet-laid non-woven fabric covering at least one side of the gypsum core; wherein the wet-laid nonwoven fabric has an inner side having a surface roughness Ra of from 25 to 60 micrometers in contact with the gypsum core.

2. The gypsum board according to claim 1, wherein the inner side of the non-woven fabric comprises an embossing pattern having said surface roughness.

3. The gypsum board according to claim 1, wherein the gypsum board contains water resistant agents in its core and/or in its non-woven fabric.

4. The gypsum board according to claim 1, wherein the non-woven fabric comprises fibers that are selected from the group consisting of cellulose fibers, inorganic or mineral fibers, synthetic polymeric fibers, and mixtures thereof.

5. The gypsum board according to claim 4, wherein the cellulose based fibers represent at least 25 wt % of the weight of the non-woven fabric.

6. The gypsum board according to claim 1, wherein an outer side of the non-woven fabric, which is in contact with the atmosphere, has a surface roughness Ra less of than 25 micrometers.

7. The gypsum board according to claim 1, wherein the non-woven fabric comprises at least one binder and/or at least one kind of mineral filler particles.

8. The gypsum board according to claim 7, wherein the at least one kind of mineral filler particles have a d50 from about 0.1 to about 10 μm.

9. The gypsum board according to claim 7, wherein the non-woven fabric comprises at least one binder and at least one kind of mineral filler particles, and wherein the weight ratio of binder:filler particles is from about 1:2 to about 8:1.

10. The gypsum board according to claim 1, wherein the non-woven fabric comprises at least two plies, an inner ply and an outer ply.

11. The gypsum board according to claim 10, wherein the inner ply is in contact with the core of said gypsum board and comprises a mixture of cellulose fibers, inorganic or mineral fibers and optionally organic fibers, and said outer ply comprises essentially cellulose fibers, and wherein said non-woven fabric further comprises at least a binder and at least mineral filler particles, said particles being distributed at least partially into said inner and/or outer ply.

12. The gypsum board according to claim 11, wherein the inner ply comprises, by weight based on the total weight of the fibers, from 25 to 60 wt % of cellulose fibers, from 25 to 60 wt % of glass fibers, and from 0 to 30 wt % of organic fibers.

13. The gypsum board according to claim 11, wherein based on the final weight of the non-woven fabric, the inner ply represents from about 30 to about 150 g/m.sup.2, the outer ply represents from about 10 to about 70 g/m.sup.2, and the binder and filler particles together represent from about 20 to about 150 g/m.sup.2.

14. The gypsum board according to claim 10, wherein the inner and/or outer plies are bonded with a hydrophobic binder.

15. The gypsum board according to claim 10, wherein the inner and/or outer plies further comprises a water-resistant agent.

16. The gypsum board according to claim 1, wherein the gypsum core comprises a water-resistant additive in an amount sufficient such that the core absorbs less than about 10% water when tested in accordance with ASTM method C-473 and/or in accordance with EN 520 method section 5.9.2.

17. A wet-laid non-woven fabric having an inner side having a surface roughness Ra of from 25 to 60 micrometers and configured for contact with a gypsum core.

18. The wet-laid non-woven fabric according to claim 17, wherein the inner side of the non-woven fabric comprises an embossing pattern having said surface roughness Ra of from 25 to 60 micrometers.

19. The wet-laid non-woven fabric according to claim 17, further comprising a water resistant additive.

20. The wet-laid non-woven fabric according to claim 17, wherein the non-woven fabric comprises cellulose-based fibers, and wherein the cellulose-based fibers comprise at least 25 wt % of the weight of the non-woven fabric.

21. The wet-laid non-woven fabric according to claim 17, wherein an outer side of the fabric, which is opposite the inner side, has a surface roughness Ra less than 25 micrometers.

22. The wet-laid non-woven fabric according to claim 17, wherein the fabric comprises mineral filler particles having a d50 from about 0.1 to about 10 μm.

23. The wet-laid non-woven fabric according to claim 17, wherein the non-woven fabric comprises at least one binder and at least one kind of mineral filler particles, and wherein the weight ratio of binder:filler is from about 1:2 to about 8:1.

24. The wet-laid non-woven fabric according to claim 17, comprising at least two plies, an inner ply and an outer ply.

25. The wet-laid non-woven according to claim 24, wherein the outer ply is essentially made of cellulose based fibers and has a surface roughness Ra of less than 25 micrometers.

26. The wet-laid non-woven fabric according to claim 24, wherein the inner ply comprises a mixture of cellulose fibers, inorganic or mineral fibers and optionally organic fibers, and said outer ply comprises essentially cellulose fibers, and wherein said fabric further comprises at least a binder and at least mineral filler particles, said filler particles being distributed at least partially into said inner and/or outer ply.

27. The wet-laid non-woven according to claim 26, wherein the inner ply comprises, by weight based on the total weight of the fibers of the inner ply, from 25 to 60 wt % of cellulose fibers, from 25 to 60 wt % of glass fibers, and from 0 to 30 wt % of organic fibers.

28. The wet-laid non-woven according to claim 26, wherein the fibers and/or particles in the outer ply comprise about 0.5-20% by weight of the fibers in the inner ply, and wherein the fibers and/or particles in the outer ply are large enough that more than 90 percent of the particles and/or fibers are larger than the openings between the fibers in the inner ply.

29. The wet-laid non-woven according to claim 26, wherein, based on the final weight of the non-woven fabric, the inner ply represents from about 30 to about 150 g/m.sup.2, the outer ply represents from about 10 to about 70 g/m.sup.2, and the binder and filler particles together represent from about 20 to about 150 g/m.sup.2.

30. The wet-laid non-woven according to claim 24, wherein the inner and/or outer plies are bonded with a hydrophobic binder.

31. The wet-laid non-woven according to claim 24, wherein the inner and/or outer plies further comprise a water-resistant agent.

32. A process for manufacturing a gypsum board comprising: wet laying and simultaneously draining a suspension of fibers onto a screen assembly so as to produce a wet-laid non-woven fabric having a surface with roughness Ra of from 25 to 60 micrometers; optionally impregnating the wet-laid non-woven fabric with a solution containing at least a binder; drying the wet-laid non-woven fabric; and covering at least one side of a gypsum core with the wet-laid non-woven fabric such that the surface with said roughness is in contact with the gypsum core to form the gypsum board.

33. The process according to claim 32, wherein, in the process, the screen assembly comprises a first base screen and a second screen superimposed thereon.

Description

FIGURES

(1) FIG. 1 shows the Ra parameter vs the sample length of a rough surface.

(2) FIG. 2 is a schematic view of a method allowing the measurement the Ra parameter of a rough surface.

(3) FIG. 3 is a photo of the inner ply surface of the F1 nonwoven mat.

(4) FIG. 4 is a photo of the inner ply surface of the F2 nonwoven mat.

(5) FIG. 5 is a photo of the outer ply surface of the F1 nonwoven mat.

(6) FIG. 6 is a photo of the outer ply surface of the F2 nonwoven mat.

(7) FIGS. 7 and 8 represent schematically the equipment and the procedure of the peeling test.

EXAMPLES

(8) 1) Nonwoven Mats

(9) Two mats F1 and F2 (non woven fabrics) have been manufactured on an industrial papermaking line.

(10) Each mat comprises two plies (inner+outer).

(11) The inner ply comprises, in wt % based on the total weight of the fibers: 45% of cellulose fibers (length of about 2.5 to 5 mm, diameter of about 30 micrometers), 14% of polyester fibers (length of about 3 to 12 mm and diameter of about 12 to 13 micrometers), and 41% of glass fibers (length of about 6 to 12 mm and diameter of about 23 micrometers).

(12) The dry surface weight of the inner ply is about 73 g/m.sup.2.

(13) On the other hand, the outer ply comprises 100% cellulose fibers (length of about 2.5 to 5 mm, diameter of about 15 to 30 micrometers) The dry surface weight of the outer ply is about 26 g/m.sup.2.

(14) Both inner and outer plies are impregnated with a mixture comprising (in parts per weight of the impregnation mixture): 67 parts of a binder (self cross-linkable styrene acrylic polymer dispersion), 0.6 parts of a fongicide (iodine based organic dispersion) 1.5 part of a fluorocarbon water repellent (perfluoroacrylate copolymer dispersion) and optionally 27 parts of a filler.

(15) The dry added weight due to the impregnation mixture is about 38 g/m.sup.2 when the mixture does not comprise any filler. However, it is about 56 g/m.sup.2 when the mixture does comprise a filler.

(16) The filler can either be calcium sulphate anhydrite or kaolin (the median particle diameter is such that D.sub.50 is from about 1 to about 5 micrometers).

(17) F1 is manufactured by a common wet-laid process.

(18) According to this process, mats are manufactured on an industrial papermaking line comprising a primary head box and a secondary head box wherein first and second dispersions of fibers are respectively prepared corresponding respectively to inner ply and outer ply of the mat. The first dispersion of fibers is wet laid on a screen comprising 32 warp yarns/cm having a diameter equal to 0.18 mm and 32 weft yarns/cm having a diameter equal to 0.22 mm, so as to form a web. Then the second suspension is wet layed on the top side of the web. The process consists in simultaneously draining water from the web to produce, on the bottom side of the web, the embossing pattern having a surface with the specific roughness. The web is then dried and impregnated by using a size press with the above mentioned mixture. The facer is finally dried.

(19) F2 differs from F1 in that a screen assembly comprising a first base screen and a second screen superimposed thereon is used instead of a single screen.

(20) In this embodiment: The first base screen comprises 32 weft yarns/cm and 32 warp yarns/cm, The second screen comprises 7 weft yarns/cm and 6.3 warp yarns/cm, The ratio of apertures per cm.sup.2 between the first and the second screen is equal to 23.2, The first base screen comprises weft yarns having a diameter equal to 0.18 mm, and warp yarns having a diameter equal to 0.22 mm, The second screen comprises weft yarns having a diameter equal to 0.7 mm, and warp yarns having a diameter equal to 0.75 mm.

(21) Two different mats, F1 and F2, have therefore been prepared. They have different inner and outer surface roughness as shown in table 1 below.

(22) 2) Surface Roughness Measurement

(23) As described above, the F1 and F2 mats comprise an inner ply and an outer ply, as well as an inner side and an outer side. These two sides are characterized by their inner surface roughness (inner side in contact with the gypsum core) and their outer surface roughness (outer side that is not in contact with the gypsum core).

(24) The surface roughness can be characterized by the roughness parameter Ra, which is the arithmetic mean of the absolute values of ordinates (x) along a fixed length (L) (FIG. 1) which defines the roughness profile. The Ra parameter is determined from at least 6 different roughness profiles within the working image, and correspond to the average of these at least 6 single Ra values. This Ra parameter is commonly used by the skilled man in the art in order to determinate the surface roughness of a substrate, especially in the paper and nonwoven industry, but also in other kind of materials industry (plastic, metals, etc).

(25) The Ra parameter is obtained as follows (FIG. 1):

(26) TABLE-US-00001 Ra Pa {close oversize brace} Arithmetical mean deviation Wa

(27) Arithmetical mean of the absolute ordinate values Z(x) within a sampling length

(28) $\mathrm{Ra},Pa,\mathrm{Wa}=\frac{1}{L}{\int }_0^L.Math.Z\left(x\right).Math.\mathrm{dx}$

(29) Roughness profiles of the mats were obtained through an optical measurement method based on enhanced white light vertical scanning interferometry. The principle of this optical based measurement method is the following (FIG. 2): A vertical scan white light interferometric microscopy tool is leading to the surface topography through a white light interferometry of 2 light beams. The first beam is reflected by a perfect flat mirror which forms the reference surface and the second is reflected by the sample which has a certain topography. The 2 beams interfere and form a figure consisting of alternate dark and bright fringes: the interferogram pattern. When the distances travelled by light from the sample surface and that of the mirror are identical, the light intensity on the detector is maximum. The two waves are then said to be in phase or at zerochromatic order. Conversely, when the 2 distances are becoming different, intensity oscillates for a short time and then decrease very quickly. The principle involves shifting the reference mirror and locating the greatest intensity during scanning.

(30) Experimental data have been collected on the TOPO3D instrument at the CTP (Centre Technique du Papier, Grenoble, France).

(31) The analyzed area of the mat corresponds to 3.5 mm by 3.5 mm.

(32) The Ra values of the F1 and F2 mats are listed in table 1.

(33) TABLE-US-00002 TABLE 1 surface roughness of the F1 and F2 mats Ra value (micrometers) F1 mat F2 mat Inner surface 19.4 27.2 (FIG. 3) (FIG. 4) Outer surface  9.8 10.5 (FIG. 5) (FIG. 6)

(34) FIGS. 3-6 clearly show the roughness differences between the inner ply of the F1 and F2 mats. The roughness of the outer ply is similar since the second dispersion of fibers is applied in the same conditions on the inner ply of both F1 and F2. Applicant assume that the difference of roughness of the inner ply is due to the use of a double screen which not only confers a specific embossing pattern to the surface but also rearrange the fibers on the surface of the pattern.

(35) 3) Joint Tape: Preparation of Minibands

(36) Minibands have been prepared in a laboratory at 20° C.+/−3° C., and a relative humidity over 40%.

(37) Strips (50 mm wide and 297 mm long) of each nonwoven F1 and F2 mats are cut with a razor knife along the machine direction.

(38) A standard plasterboard (cellulose based cardboard) of 150 mm wide by 350 mm long is used as substrate for preparing the joint tape. Such suitable plasterboard includes PREGYPLAC BA13 available from LAFARGE

(39) Then, a 80 mm wide and 1 mm thick layer of joint compound is applied onto the plasterboard. This 1 mm thick layer is prepared with a blade and two 1 mm thick gauges.

(40) The mat strip is then laid down in the middle of the joint compound, the inner side of the mat being in contact with the joint compound. Going over the mat with the blade (on its 2 gauges) allows ensuring total and homogeneous contact between the mat and the joint compound.

(41) The resulting minibands are allowed to dry for 7 days into a 25° C. climate room with a relative humidity of 50%.

(42) The minibands are then directly tested (dry bonding strength), or conditioned (humid bonding test).

(43) As shown in table 2, two different joint compounds have been used.

(44) TABLE-US-00003 TABLE 2 C1 and C2 joint compound compositions Joint compound C1 C2 Commercial name Enduit WAB Enduit J1L Supplier LAFARGE SALSI Type Ready to use Powder Density  1.6 to 1.65 1.47 to 1.63 pH 8 to 9 6 to 8 Brookfield viscosity (cps) 400 000 to 500 000 400 000 to 500 000 Solid/Liquid ratio NA 2.2

(45) 4) Boards: Preparation of Miniboards

(46) Miniboards have been prepared in a laboratory at 20° C.+/−3° C. and a relative humidity over 40%.

(47) Strips (126 mm wide 176 mm long) of the nonwoven F1 and F2 mats are cut with a razor knife in the machine direction.

(48) The four edges of the inner side of the strips are then creased in order to obtain four sharp fold lines, 13 mm inside the strip.

(49) The four fold lines are therefore 100 mm apart along the cross direction, and 150 mm along the machine direction.

(50) The four corners of the fold lines are then stapled in order to give an open mould shape to the strip, the inner side of the strip facing the inside the mould.

(51) In the meantime, the gypsum core mixture is prepared as follows.

(52) The appropriate amount of water is poured into a plastic beaker, so as to get a fixed solid/liquid ratio of 1.67.

(53) Then, all the liquid additives are added in the beaker, and the mixture is homogenized under slight stirring.

(54) The hydratable calcium sulphate is then added into the beaker.

(55) The resulting slurry is allowed to rest for 2 minutes, and then the mixture is homogenized under mechanical mixing for 5 minutes at 200 rpm.

(56) After 5 min of stirring, the slurry is poured into the moulded nonwoven mat as described above.

(57) Excess of gypsum slurry is removed from the exceeded 13 mm height in order to leave a flat surface.

(58) The miniboard is then allowed to set at ambient conditions for 53 hours.

(59) Thereafter, the miniboard is dried at 70° C. in a ventilated oven for 6 hours.

(60) The resulting miniboard is then conditioned at 25° C. and 50% relative humidity for 24 hours before measuring the dry bonding strength.

(61) The different gypsum core compositions that have been tested are listed in Table 3.

(62) TABLE-US-00004 TABLE 3 B1-B3 gypsum core compositions Core compositions B1 B2 B3 Hemi-hydrate .sup.(a) 100% 99% 98.13%  Starch .sup.(b) —  1%   1% Silicone .sup.(c) — — 0.87% .sup.(a) CaSO.sub.4•½H.sub.2O .sup.(b) RediFILM 5400 from National Starch .sup.(c) Methylhydrogenopolysiloxane, MH1107 Fluid from Dow Corning

(63) 5) Bonding Tests

(64) This test consists in measuring the peeling strength necessary so as to delaminate from the gypsum core or the joint compound, a 50 mm wide strip of the nonwoven mat (nonwoven F1 or F2 in these examples). Furthermore, in order to ensure accuracy of the test, the peeling strength is measured at the steady speed of 100 mm/min, and perpendicularly to the surface.

(65) In the case of the miniboards, the 50 mm strip of nonwoven mat (nonwoven F1 or F2 in these examples) is cut along the machine direction, from the backside of the miniboard.

(66) In the case of miniboards, 5 to 10 mm of the nonwoven 50 mm strip is removed manually from the core at one of the two strip extremities. This free “tab” is then clamped in the upper jaws of a dynamometer. In the case of minibands, a 5 to 10 mm of nonwoven strip extremity is clamped in the upper jaws of a dynamometer in a similar way.

(67) The miniboard is then secured on a horizontal plate that can move horizontally at the same linear speed than the crosshead (100 mm/min).

(68) The peeling force is recorded by the dynamometer as a function of the crosshead position.

(69) The bonding strength represents the average of 3 measurements. It is expressed in grams.

(70) For the dry bonding test: prior to the testing, the samples have been conditioned for 24 hours into a climate room with a relative humidity of 50% and 25° C. The dry bonding test is carried out right after this 24 hour period.

(71) For the humid bonding test, prior to the testing, the samples have been conditioned for 24 hours into a climate room with a relative humidity adjusted to 90% and temperature of 30° C. The humid bonding test is carried out right after this 24 hour period.

(72) In addition to measuring the peeling force, the weight of the strip is weighted after being peeled off the gypsum board. It therefore allows comparing initial and final weights so as to calculate the overall weight difference. This typically corresponds to the amount of gypsum core or joint compound that is removed by the nonwoven mat.

(73) 6 Bonding Strength Results

(74) Joint Tape: Minibands

(75) TABLE-US-00005 TABLE 4 Bonding of the minibands to the joint compound Joint compound C1 C2 Nonwoven facer F1 F2 F1 F2 Dry bonding (g) 541 826 199 383 Humid bonding (g) 504 819 150 277 Weight uptake +3 +6 +3 +17 (g/m.sup.2) (dry)

(76) The dry and humid bonding strengths between the joint tape and the gypsum core is significantly improved when the F2 mat is used, regardless of the C1 or C2 joint compound.

(77) Additionally, without the willingness to be bind with theory, the weight uptake, in the case of the non woven facer F2, might be explained by the higher surface roughness.

(78) This certainly leads to a greater penetration of the joint compound within the fibrous structure.

(79) Miniboards

(80) TABLE-US-00006 TABLE 5 Bonding of the F1 and F2 non woven fabric to the gypsum core Core composition B1 B2 B3 Nonwoven facer F1 F2 F1 F2 F1 F2 Dry bonding (g) 20 275 480 714 214 408 Weight uptake 11 31 0 11 3 13 (g/m.sup.2) (dry)

(81) Regardless of the gypsum core composition of the example, the bonding with the nonwoven mat having a greater surface roughness (F2) is greater than with the nonwoven mat having a lower roughness.

(82) This trend is also confirmed when we look at the amount of gypsum that is removed by the nonwoven strip (weight uptake in the table). The nonwoven mat F2 (with the higher surface roughness) pull out a higher weight of gypsum per square meter, which may be due to a higher interpenetration of the gypsum slurry/core into the fibrous surface layer of the nonwoven.

(83) Plasterboards.

(84) The following plasterboards are manufactured.

(85) The line that is used for the manufacture is a standard line. The composition of the slurry of the core is a standard formulation for wet area boards and is the same composition as the composition of the core of the boards marketed by company SINIAT for the commercial product PREGYWAB, which is according to US 2006/0068186. The facer that is used for the manufacture of the plasterboards is facer F2.

(86) The boards thus obtained have been subjected to the following tests.

(87) Binding

(88) The peeling test aims at measuring the load necessary to pull off the liners from the core over 50 mm length The equipment comprises the following, the general description being given in FIG. 7: Grip+bucket+glass balls ({acute over (Ø)} 2 mm)+feeding system for glass balls with automatic stop at failure or trial end. Support for the sample Scale accurate to 0.1 g Climate room: 23° C. 50% RH and 30° C. 90% RH Cutter

(89) The procedure is the following: Cut 6 specimens 300×300 mm (12×12 in) across the sampled board as shown on drawing (far from any edge): 3 for ambient peeling test (23° C. 50% RH) and 3 for humid peeling (24 hours at 30° C. 90% RH)
2 modes of conditioning are used: Ambient mode: 24 hours at 23° C. 50% RH or by default in lab room at 23° C. if no humidity control Humid conditions: 24 hours in ventilated humid cabinet at 30° C. 90% RH. In order to achieve a consistent moistening of the board, the number of specimens is limited: for instance: maximum of 30 specimens placed on trays in a 190 L cabinet.
The installment procedure is the following (see the FIG. 8): In the central part of the board and along the machine direction, trace 2 parallel lines at 50 mm centres. Cut the liner along these lines. Peel off a liner strip of 50 mm wide on a 50 mm distance, and at the 2 ends of the specimen. Using a cutter, initiate the facer peeling cautiously over the 50 mm (2 in) Put the sample on the support, face to be tested downward Clip the grip and the bucket on the strip and make sure the clip and bucket are perfectly centred and aligned. Start to fill in the bucket with the balls until getting a delamination over 50 mm (2 in). The load rate should be about 1 kg/min. The feeding system is automatically stopped when the liner tears, peels off, or delaminate over 50 mm. Record the total weight: grip+bucket+glass beads, and the mode of failure Repeat the test on the other end of the specimen, then return the specimen and carry out 2 other tests on the opposite side
The humid peeling procedure is the following: Weigh the specimen before and after conditioning in order to determine the moisture regain Remove the specimens one by one from the humid chamber and test them immediately. Alternatively, remove them three by three, but place them in a closed plastic bag just after weighing. Cut the liner along the 2 lines and initiate the peeling after weighing the specimen Start peeling test on face side first, than on back side. The testing time of each side should be less than 4 minutes for each side in order to avoid superficial drying

(90) The results are expressed as follows: For ambient and humid conditioning: Record the load necessary to remove the facer along 50 mm (2 in) on each specimen Calculate the mean value for the board (on the basis of 6 measurements) Note the mode of failure: loss of bonding core-facer, or decohesion in the facer, or tearing of the facer, and mention the test conditions for each result (dry or wet conditions) If not measurable because bonding too high, indicate it. For humid peeling Record the moisture regain after 24 hours conditioning

(91) The Cobb 2H and the immersion tests are according to the standard EN520; said standard is followed unless specified otherwise.

(92) The following results have been obtained on two industrial runs. The value given is the result of averaging 8 different measures. For the peeling, results are so good that most specimen are not measurable (delamination at start).

(93) TABLE-US-00007 Cobb Immer- 2H Peeling Peeling Peeling Peeling sion (face/ ambient ambient humid humid Run Weight 2H back) face back face back 1 10.98 2.12 67/62 2652 2606 1853 1848 2 10.89 2.37 73/63 2404 2618 1870 1903

(94) Compared to existing boards, especially the boards manufactured according to US 2006/0068186, the boards of the invention exhibit a marked improvement in bonding.

(95) A further test is carried out with a core composition (facer F2 not changed) that differs as far as the stucco is concerned. In the runs 1 and 2, the stucco has the following PSD:PSD (wt) after splitting in water, the d10 is from 1 to 2 μm, the d50 is from 10 to 20 μm and the d90 is from 35 to 50 μm. 100% of the particles fit into pores less than 60 μm and about 90% or more of stucco particles fit into pores less than 40 μm.

(96) In run 3, the stucco has the following PSD:

(97) PSD (wt) after splitting in water, the d10 is from 1 to 2 μm, the d50 is from 20 to 35 μm and the d90 is from 50 to 85 μm. About 90% or less of the particles fit into pores less than 60 μm and about 70% of stucco particles fit into pores less than 40 μm

(98) The results are below. Again for the peeling, results are so good that most specimen are not measurable (delamination at start).

(99) TABLE-US-00008 Peeling ambient Peeling humid Run Face/back Face/back 3 2000-2500 1700-2100

(100) Thus, the change of the supply of stucco has little influence of the result for the peeling, which is advantageous for industrial production.