LAMINATES

Abstract

A method of manufacturing a laminate comprises providing a binder impregnated core layer by impregnating at least one fibrous layer with an aqueous core binder solution having a viscosity in the range 75 cP to 500 cP at a temperature of 20° C. and a bake-out solid content in the range 40 wt % to 85 wt %, in which the aqueous core binder solution comprises (i) at least 25% by dry weight of a) reducing sugar reactant(s) and nitrogen-containing reactant(s) and/or b) curable reaction product(s) of reducing sugar reactant(s) and nitrogen-containing reactant(s); and (ii) between 5% and 15% by weight of a non-aqueous solvent based on the total weight of the aqueous binder solution; providing a semi-finished assembly by assembling the binder impregnated core layer with a surface layer; and applying heat and pressure to the semi-finished assembly to cure the binder in the binder impregnated core layer and secure the core layer and the surface layer together.

Claims

1. A method of manufacturing a laminate comprising providing a binder impregnated core layer by impregnating at least one fibrous core layer with an aqueous core binder solution having a viscosity in the range 10 cP to 500 cP at a temperature of 20° C. and a bake-out solid content in the range 40 wt % to 85 wt %, in which the aqueous core binder solution comprises (i) at least 25% by dry weight of: (a) reducing sugar reactant(s) and nitrogen-containing reactant(s) and/or (b) curable reaction product(s) of reducing sugar reactant(s) and nitrogen-containing reactant(s); and (ii) between 5% and 15% by weight of a non-aqueous solvent based on the total weight of the aqueous binder solution; providing a semi-finished assembly by assembling the binder impregnated core layer with a surface layer; and applying heat and pressure to the semi-finished assembly to cure the binder in the binder impregnated core layer and secure the core layer and the surface layer together.

2. The method of claim 1, wherein the aqueous binder solution comprises at least 25% by dry weight of reaction product(s) of (i) at least one nitrogen-containing reactant selected from the group consisting of a primary amine, a di-primary diamine, HMDA and combinations thereof and (ii) a reducing sugar reactant selected from the group consisting of dextrose, fructose, xylose, and mixtures thereof.

3. The method of claim 1, wherein the solvent comprises an alcohol.

4. The method of claim 1, wherein the solvent comprises methanol.

5. The method of claim 1, wherein the aqueous binder solution is substantially formaldehyde free.

6. The method of claim 1, wherein the at least one fibrous core layer comprises a cellulosic fibrous sheet, notably a kraft paper sheet.

7. The method of claim 1, wherein the aqueous core binder solution has a viscosity at 20° C. which is in the range 85 to 150 cP, preferably at least 90 cP to 120 cP.

8. The method of claim 1, wherein the aqueous core binder solution has a bake-out solid content in the range of 50 wt % to 70 wt %.

9. The method of claim 1, wherein the aqueous core binder solution is obtainable by combining: (i) carbohydrate reactant(s) present by dry weight in a quantity in the range 50% to 95%, preferably 60% to 80; (ii) nitrogen-containing reactant(s) present by dry weight in a quantity in the range 5% to 50%, preferably 10% to 40%; and (iii) water.

10. The method of claim 1, wherein the aqueous core binder solution comprises between 7% and 11% by weight of the non-aqueous solvent based on the total weight of the aqueous binder solution.

11. The method of claim 1, wherein during application of heat and pressure to the semi-finished assembly, at least part of the solvent is released, captured and collected.

12. The method of claim 1, wherein the surface layer in the semi-finished assembly is provided with a melamine formaldehyde binder.

13. The method of claim 1, wherein the laminate is selected from the group consisting of high pressure laminates (HPL), continuous pressure laminates (CPL), low pressure laminates (LPL) and compact laminates.

14. (canceled)

15. (canceled)

Description

[0053] The invention will be illustrated with reference to the non-limiting examples set out in Table 1.

TABLE-US-00001 TABLE 1 Average permeation time Viscosity Binder (seconds) (cP) Comparative Bakelite PF 1981 HD-RT 38.3 106.0 example Example aqueous core binder solutions Non- aqueous solvent (% weight carbohydrate nitrogen % of bake with reactant containing out solid respect to % by dry reactant in the the weight of the % by dry weight uncured uncured uncured of the uncured aqueous aqueous aqueous binder aqueous binder binder binder Example solution solution solution solution) 1 DMH 47% + HMDA (6%) 70% none 180.7 280.9 Fructose 47% 2 DMH 47% + HMDA (6%) 70% 5% 67.3 192.0 Fructose 47% methanol 3 DMH 47% + HMDA (6%) 70% 10% 17.3 132.0 Fructose 47% methanol 4 DMH 46% + HMDA (8%) 70% none 168.3 254.9 Fructose 46% 5 DMH 46% + HMDA (8%) 70% 5% 70.3 181.0 Fructose 46% methanol 6 DMH 46% + HMDA (8%) 70% 10% 16.3 134.0 Fructose 46% methanol 7 DMH 42.5% + HMDA (15%) 50% none 96.0 343.9 Fructose 42.5% 8 DMH 42.5% + HMDA (15%) 50% 5% 81.0 252.7 Fructose 42.5% methanol 9 DMH 42.5% + HMDA (15%) 50% 9% 36.0 182.2 Fructose 42.5% methanol 10  DMH 42.5% + HMDA (15%) 50% 10% 28.7 171.7 Fructose 42.5% methanol Key: DMH: dextrose monohydrate HMDA: hexamethylenediamine

[0054] The permeation time and viscosity of the binders of Examples 1-10 shown in Table 1 was assessed and compared against a comparative example of a phenol formaldehyde based binder which is not in accordance with the present invention using the following test protocol: [0055] Put a 2 cm depth of aqueous binder solution into 10 cm diameter flat bottomed glass beaker taking care to have a temperature of about 20° C. [0056] Put a 2 cm×2 cm square of kraft paper flat on the surface of the aqueous binder solution at the centre of the beaker taking care to always put the same paper surface side on aqueous binder solution surface (see carving direction of the paper) [0057] Measure the time with stop watch until by visual inspection at least about 95% of the surface area of the paper can be seen to have been penetrated by the binder solution.

[0058] Examples 3, 6, 9 and 10 in particular show an average permeation time (and thus an ability to impregnate laminate core material) which is comparable with, and indeed better than, the standard phenol formaldehyde resin of the comparative example.