METHOD FOR PRODUCING A LAMINATE OF WOOD AND CEMENTITIOUS COMPOSITIONS

Abstract

A method for producing a laminate, wherein a wooden element is provided, the wooden element is coated on the top side with a an adhesive that is applied in liquid form and includes at least one polymer that is liquid at room temperature and contains silane groups, at least one liquid epoxy resin and at least one amine hardener, the applied adhesive is covered with a layer of a liquid cementitious composition while still wet, and the liquid cementitious composition and the adhesive each cure. The method enables the durable joining of wooden elements and cementitious elements in an easy-to-implement, wet-on-wet method. The laminates obtained from the method are comparatively light, stable and robust and are especially suitable as sustainable components in above-ground construction.

Claims

1. A method of producing a laminate, wherein (i) a wood body is provided, (ii) the wood body is coated on its top face with an adhesive applied in liquid form, comprising at least one polymer containing silane groups which is liquid at room temperature, at least one liquid epoxy resin and at least one amine curing agent, (iii) the still-wet adhesive applied is overcoated with a liquid cementitious composition, and (iv) the liquid cementitious composition and the adhesive are each cured.

2. The method as claimed in claim 1, wherein the wood body in step (i) consists of hardwood or softwood, preferably beechwood or sprucewood, especially beechwood.

3. The method as claimed in claim 1, wherein the wood body has a thickness in the range from 10 to 300 mm.

4. The method as claimed in claim 1, wherein no primer is applied to the wood body before step (ii).

5. The method as claimed in claim 1, wherein the adhesive in step (ii) is applied in a layer thickness in the range from 0.1 to 10 mm.

6. The method as claimed in claim 1, wherein the wood body on application of the liquid cementitious composition in step (iii) has been provided with formwork elements on the outer sides, such that the liquid cementitious composition remains on the surface of the wood body after the application and cannot flow away.

7. The method as claimed in claim 1, wherein the liquid cementitious composition in step (iii) is applied in a layer thickness in the range from 10 to 300 mm.

8. The method as claimed in claim 1, wherein the curing in step (iv) is effected by standing at ambient temperature, optionally with protection of the cementitious composition on the surface against drying-out by means of a polymer film.

9. The method as claimed in claim 1, wherein the polymer containing silane groups has an average silicon content in the range from 0.3 to 2% by weight.

10. The method as claimed in claim 1, wherein the polymer containing silane groups has been obtained from the reaction of at least one polyether containing isocyanate groups and at least one amino-, mercapto- or hydroxysilane.

11. The method as claimed in claim 1, wherein the weight ratio between the polymer containing silane groups and the liquid epoxy resin in the adhesive is in the range from 20/80 to 70/30.

12. The method as claimed in claim 1, wherein the amine curing agent is selected from the group consisting of 1,5-diamino-2-methylpentane, 2,2 (4),4-trimethylhexamethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl) cyclohexane, 1,4-bis(aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 2 (4)-methyl-1,3-diaminocyclohexane, bis(4-aminocyclohexyl) methane, 2,5 (2,6)-bis(aminomethyl) bicyclo[2.2.1]heptane, 1,3-bis(aminomethyl)benzene, polyoxypropylenediamines and polyoxypropylenetriamines with average molecular weight M.sub.n in the range from 200 to 500 g/mol, bis(hexamethylene) triamine, triethylenetetramine, tetraethylenepentamine, N,N-bis(3-aminopropyl)ethylenediamine, N,N-dimethyldi (1,3-propylene)triamine, N-benzylethane-1,2-diamine, N-benzylpropane-1,2-diamine, N-benzyl-1,3-bis(aminomethyl)benzene, N-(2-phenylethyl)-1,3-bis(aminomethyl)benzene, the adduct of 1,5-diamino-2-methylpentane or propane-1,2-diamine with cresyl glycidyl ether, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 2,4,6-tris(dimethylaminomethyl) phenol and combinations of these amines.

13. The method as claimed in claim 1, wherein the liquid cementitious composition contains at least one Portland cement, at least one mineral filler, water and optionally further additives.

14. A laminate obtained from the method as claimed in claim 1.

15. A component for building construction comprising the laminate as claimed in claim 14.

Description

[0155] FIG. 1 shows a laminate as just described for illustrative purposes. This comprises a wood layer (H), an adhesive layer (K), and a layer of a cementitious composition (Z).

[0156] The bottom side of the cuboid is preferably formed by the wood side, and the top side of the cuboid by the cementitious composition. The thickness of the wood layer is preferably equal to or greater than the thickness of the cementitious layer. FIG. 1 shows, by way of example, the thickness (D.sub.H) of the wood layer (H), the thickness (D.sub.K) of the adhesive layer (K), and the thickness (D.sub.Z) of the cementitious composition (Z).

[0157] The dimensions of the laminate are preferably such that the wood layer is capable of supporting the layer of the cementitious composition without being bent to a significant degree under its weight if there is no support, strengthening or reinforcement.

[0158] The laminate is stable and durable. It can especially be transported freely in space without permanent bending. It can be stacked and can come into contact with heat, moisture or UV light without suffering significant losses of stability.

[0159] The laminate may also be referred to as a board, beam, bar or sandwich element.

[0160] The invention further provides for the use of the laminate as a component in building construction, especially as roof element. The laminate is especially installed as a roof element such that the wood side forms the visible ceiling from the interior, and the side of the cementitious composition is directed toward the roof or an upper story.

[0161] The laminate from the method of the invention enables the installation of load-bearing wooden ceilings that are particularly sound- and heat-insulating and stable, require a lower level of hydraulic binder and admixtures and hence are particularly sustainable.

EXAMPLES

[0162] Working examples are adduced hereinafter, which are intended to further elucidate the invention described. The invention is of course not limited to these described working examples.

[0163] Standard climatic conditions (SCC) refer to a temperature of 231 C. and a relative air humidity of 505%.

[0164] The square-rod laminated beechwood used came from Fagus Suisse SA.

Production of the Adhesive:

Adhesive S1:

[0165] A first component was produced by mixing the following ingredients in the specified amounts (in parts by weight, PW) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) and storing the mixtures with exclusion of moisture: [0166] 61.6 PW of linear polymer containing silane groups with terminal trimethoxysilane groups, a polyether skeleton and a silicon content of 0.91% by weight, [0167] 1.7 PW of vinyltrimethoxysilane, [0168] 22.8 PW of 1,2-diaminocyclohexane (Dytek DCH-99, from Invista, AHEW 28.5 g/eq), [0169] 7.5 PW of polyoxypropylenediamine (Jeffamin D-400, from Huntsman, AHEW 115 g/eq), [0170] 2.65 PW of 3-aminopropyltrimethoxysilane (Silquest A-1110, from Momentive, AHEW 89.7 g/eq), [0171] 1.8 PW of diisodecyl phthalate (Palatinol 10-P, from BASF), [0172] 1.95 PW of catalysts and UV stabilizers.

[0173] Likewise produced was a second component, by mixing the following ingredients and storing the mixtures with exclusion of moisture: [0174] 66.4 PW of bisphenol A diglycidyl ether (Araldite GY 250, from Huntsman, EEW 187 g/eq), [0175] 22.1 PW of hexanediol diglycidyl ether (Araldite DY-H, from Huntsman, EEW 149 g/eq), [0176] 2.5 PW of emulsifier mixture, [0177] 1.4 PW of carbon black, [0178] 7.6 PW of fillers.

[0179] For the application, the two components were mixed in a mixing ratio of 0.6/1 in parts by weight of the first component relative to the second component, and processed by means of the centrifugal mixer or another suitable stirrer system to give a homogeneous liquid adhesive mixture, which was applied within 10 min.

[0180] In order to characterize the adhesive, the following tests were conducted: Mixed viscosity was measured 5 min after the two components had been mixed at a temperature of 20 C. with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1, cone tip-plate distance 0.05 mm) at a shear rate of 10 s.sup.1.

[0181] For the determination of pot life, an amount of 300 g of the freshly mixed adhesive was stirred in a 500 ml beaker with a spatula at intervals of 5 minutes until the adhesive had thickened to such an extent that it no longer had good workability. For determination of the mechanical properties, the mixed adhesive was poured onto a PTFE-coated film to give a film of thickness 2 mm and stored under standard climatic conditions. After one day, a number of dumbbell-shaped test specimens having a length of 75 mm with a bar length of 30 mm and a bar width of 4 mm were punched out of the film and stored under standard climatic conditions for a further 6 days. Subsequently, these, as described in DIN EN 53504, at a strain rate of 2 mm/min, tensile strength (breaking force), elongation at break, and modulus of elasticity at 0.05% to 0.25% elongation (MoE 0.25%) were determined.

[0182] Adhesive S1 had a mixed viscosity of 7.75 Pas, a pot life of 35 min, a tensile strength of 20 MPa, an elongation at break of 15% and a 0.25% modulus of elasticity of 779 MPa. It cured to give a nontacky, homogeneous, blister-free material with a silky mat surface and high tensile strength and impact resistance.

[0183] In adhesive S1, the weight ratio between the polymers containing silane groups and the bisphenol A diglycidyl ether is 35.7/64.3.

Production of Laminates:

Example 1

[0184] A number of laminates were produced under standard climatic conditions, in each case by positioning a 405030 mm wood body made of beechwood on a horizontal base such that an area of 4050 mm faced upward and the thickness was 30 mm. The surface was freed of dust by means of a brush. Subsequently, 3 g of the mixed adhesive S1 were applied to the clean surface and distributed uniformly by means of a spatula (corresponding to an application rate of 1.5 kg/m.sup.2).

[0185] The test specimen thus coated was then clamped into a formwork mold that seamlessly surrounded the outer sides of the wood body and projected above the surface of the wood body by 30 mm, so as to form a casting mold for the cementitious composition with a depth of 30 mm.

[0186] Subsequently, a freshly made-up mortar (SikaGrout-212N, from Sika Schweiz AG, made up with 2.9 l of water to 25 kg of dry mortar) was introduced into the casting mold in a layer thickness of 30 mm and hence onto the surface of the wood body coated with adhesive S1, with a wait time after the mixing of the adhesive and the pouring of the mortar of between 20 and 30 min. At the moment of application of the mortar, the adhesive had not yet formed a skin (when the adhesive was tapped with an LDPE pipette, it stuck to the pipette).

[0187] The test specimen thus produced was left under standard climatic conditions for 48 h and then the formwork mold was removed. The result was a 405060 mm laminate composed of beechwood of dimensions 405030 mm and cured mortar of dimensions 405030 mm, with firm bonding of wood and mortar via adhesive S1 over an area of 4050 mm.

[0188] A number of such test specimens were stored for 28 d under standard climatic conditions and then subjected to a compressive shear strength test. Compressive shear strength was determined in accordance with DIN EN 392 on the bonded 5040 mm shear area, at a testing speed of 1 mm/s.

[0189] Further test specimens of this kind were stored for 28 d under standard climatic conditions and then for 24 h at room temperature in water, and likewise subjected in the wet state to a compressive shear strength test as described above.

[0190] Example 1, after storage under standard climatic conditions for 28 d, showed a compressive shear strength of 3.9 MPa (average of 6 test specimens), with the fracture in each case in the mortar layer close to the adhesive.

[0191] After storage for 24 h in water, the wood layer was in each case distinctly swollen (increase in volume about 30%), but the test specimen was otherwise intact. The compressive shear strength of the wet specimens was 2.0 MPa (average of 6 test specimens), with the fracture in each case in the mortar layer close to the adhesive.

Example 2

[0192] A number of laminates were produced under standard climatic conditions, in each case by positioning a 10206030 mm wood body made of beechwood on a horizontal base such that an area of 102060 mm faced upward and the thickness was 30 mm. The surface was freed of dust by means of a brush. Subsequently, the clean surface was coated with 1.5 kg/m.sup.2 of the mixed adhesive S1, and the test specimen was clamped in a formwork mold so as to result in a casting mold of depth 30 mm.

[0193] 30 min after the adhesive had been applied, a freshly made-up mortar (SikaGrout-212N, from Sika Schweiz AG, made up with 2.9 l of water to 25 kg of dry mortar) was introduced into the casting mold in a layer thickness of 30 mm and hence onto the surface of the wood body coated with adhesive S1.

[0194] The test specimens were left under standard climatic conditions for 48 h and then the formwork mold was removed. The result was a 10206060 mm laminate composed of beechwood of dimensions 10206030 mm and cured mortar of dimensions 10206030 mm, with firm bonding of wood and mortar via adhesive S1 over an area of 102060 mm.

[0195] A number of such test specimens were stored at 28 d under standard climatic conditions and then subjected to a 3-point bending test to DIN 512186 with a span width of 900 mm, an initial load of 5 N, and a testing speed of 5 mm/min. In order to determine the modulus of elasticity, such test specimens were subjected to an identical test, wherein the testing speed was 2 mm/min and the load range was 100 to 3200 N.

[0196] Example 2, in the 3-point bending test, showed a maximum force of 1.2 kN with a maximum deformation of 14 mm (average of 4 test specimens), with the fracture in each case in the mortar layer close to the adhesive. (By comparison, an uncoated beechwood specimen of dimensions 10206060 mm in the same test arrangement showed a maximum force of 1.8 kN with a maximum deformation of 28 mm.)

[0197] Example 2, in the 3-point bending test, showed a modulus of elasticity of 14.8 MPa (average of 5 test specimens). (By comparison, an uncoated beechwood specimen of dimensions 10206060 mm in the same test arrangement showed a modulus of elasticity of 13.4 MPa.)

Example 3

[0198] A number of laminates were produced under standard climatic conditions by positioning a beam of square-rod laminated wood of dimensions 5200320120 mm, made of glued square beechwood timbers (about 20004040 mm), on a horizontal base such that an area of 5200320 mm faced upward and the thickness was 120 mm. A formwork mold was mounted around the wooden beam, so as to result in a casting mold of depth 60 mm on the surface.

[0199] Subsequently, the surface of the wooden beam (=base of the casting mold) was freed of dust by blowing and coated with 1.5 kg/m.sup.2 of the mixed adhesive S1 by pouring and distributing by means of a spatula.

[0200] Then a reinforcement in the form of a construction steel mesh was placed onto the surface coated with the adhesive over its whole area, and the mesh came to rest at a height of 25 to 35 mm above the adhesive surface by means of spacers in the form of concrete blocks.

[0201] Subsequently, a freshly made-up self-compacting concrete (Sikacrete-16 SCC, from Sika Schweiz AG, made up with 2.2 l of water to 25 kg of dry mix) was poured into the casting mold to mold the concrete into the reinforcement. The wait time between the mixing of the adhesive and the pouring of the concrete was 20 to 30 min.

[0202] The arrangement thus produced was covered with a polymer film and left under standard climatic conditions for 48 h, and then the polymer film and the formwork were removed. The laminates thus obtained were stored under standard climatic conditions for a further 26 days and were then ready for use as roof element in building construction. They had dimensions of 5200320180 mm without distortions in length, width or height. In particular, they showed no shrinkage cracks and no warpage through shrinkage in the concrete layer, also called keying, nor any breaking of the concrete away from the wood surface after curing.