Building product

Abstract

A building product in the form of an internal lining board (10) made up of a mixture of hemp shiv (14) and a binder which may be clay based or lime based. The mixture is located between two layers (12) of lining paper (10).

Claims

1. A building product in the form of an internal lining board, the board being made up of a mixture of hemp shiv, binder, and cellulose adhesive, with a planar paper lining material provided on one or both outer faces of the board, wherein the building product thickness is between 12.5 and 50 mm.

2. The building product according to claim 1, wherein the binder comprises clay in the form of stoneware, fire clay, kaolinite, or bentonite, or comprises lime in the form of hydraulic lime and hydrated lime.

3. The building product according to claim 1, wherein the building product comprises a greater proportion of hemp shiv than clay.

4. The building product according to claim 1, wherein the binder comprises at least one of a naturally cementitious binder and sand.

5. The building product according to claim 1, wherein the building product comprises: hemp shiv 15-30% lime 40-60% cementitious binder 10-35% sand 20-30% methyl cellulose 0.5-2%.

6. The building product according to claim 1, wherein a cellulose solution is used to adhere the lining material to the board.

7. The building product according to claim 1, wherein the hemp shiv has a maximum particle size of substantially 5 mm.

8. The building product according to claim 1, wherein over 50% of the hemp shiv has a particle size of 1-4 mm.

9. The building product according to claim 1, wherein the hemp shiv comprises hemp fibres.

10. A building product in the form of an internal lining board, the board being made up of a mixture of hemp shiv, binder, and cellulose adhesive, with a planar paper lining material provided on one or both outer faces of the board, wherein the building product comprises: hemp shiv 15-30% lime 40-60% cementitious binder 10-35% sand 20-30% methyl cellulose 0.5-2%.

11. A building product in the form of an internal lining board, the board being made up of a mixture of hemp shiv, binder, and cellulose adhesive, with a planar paper lining material provided on one or both outer faces of the board, wherein the hemp shiv has a maximum particle size of substantially 5 mm.

12. A building product in the form of an internal lining board, the board being made up of a mixture of hemp shiv, binder, and cellulose adhesive, with a planar paper lining material provided on one or both outer faces of the board, wherein over 50% of the hemp shiv has a particle size of 1-4 mm.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a diagrammatic cross sectional view through a first building product according to the invention; and

(3) FIG. 2 is a diagrammatic cross sectional side view of the product of FIG. 1 in use.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a first building product according to the present invention in the form of a board 10 which is substantially 15 mm thick. The board 10 has inner and outer backing layers 12 of a breathable recycled lining paper 10 with a grade of 170 gsm. A mixture of hemp shiv 14 and binder in the form of clay 16 is located between the layers 12. A cellulose adhesive in the form of methyl cellulose is included in the mixture. As shown in FIG. 1, one layer 12 of the lining paper 10 may extend over the edge, and particularly a longer edge of a rectangular board of the board 10, and be overlapped by the other layer 12.

(5) FIG. 2 shows the board 10 of FIG. 1 being used as a lining on an internal wall face. The board is mounted by any suitable method such as fixing to wooden stud work on the inner side of a layer 18 of insulation which is provided on the internal side of an external brick wall 20. In times with a high humidity level such as may be produced by human activity such as cooking, cleaning or the presence of a number of people breathing, the board 10 has the ability to absorb the water vapour 22 into the capillaries inherent in the structure of the hemp shiv.

(6) When the levels of moisture in the building reduce, for instance when people leave the building or perhaps go to sleep, the board 10 releases the vapour 24 back into the internal environment. This regulates the relative humidity (RH) in the building, and reduces condensation and thus mould.

(7) The board 10 shown in FIGS. 1 and 2 may be formed as follows. Fire clay 16 is mixed with water and whisked into a slip at a mixture of approximately 50% water by volume. Methyl cellulose is then added. Dependent on the clay the slip may be sieved to remove any large sediments or sand.

(8) The slip is then mixed with fine hemp shiv 14 at a particle size of substantially less than 5 mm, with approximately one and a half times as much hemp shiv 14 by volume as clay 12. The hemp shiv 14 has a relatively narrow particle distribution, and percentages by mass are shown below of two examples which were filtered through an initial run of 2 mm and 1 mm sieves, with the above 2 mm portion processed again through 4 mm and 1 mm sieves. The particle size distributions are indicated below, along with the losses incurred during the sieving.

(9) Sample A

(10) TABLE-US-00001 Fraction Percentage by Mass 4 mm+ 1.47% 4 mm to 1 mm 62.2% 1 mm and lower 36.12% Losses 0.21%

(11) Sample B

(12) TABLE-US-00002 Fraction Percentage by Mass 4 mm+ 2.13% 4 mm to 1 mm 60.72 1 mm and lower 36.95% Losses 0.20%

(13) A formwork is provided, and an appropriate size piece 12 of recycled backing paper is laid in the formwork. The mixture of clay 16, water and hemp shiv which should be substantially homogenous by virtue of mixing, is poured into the formwork. The mix is evenly distributed across the formwork and pressed down gently. The paper lining on the bottom is over sized in its width by the depth of the board plus 30 mm, and 30 mm excess paper is therefore folded over the top surface of the board.

(14) A second similar piece 12 of paper with a methyl cellulose coating is placed on top of the mixture and then pressed or rolled down. The board 10 is turned over onto a metal drying tray and placed in a drying chamber at approximately 40 C. for 12 hours with constant air changes to take moisture away, to a moisture content in the range 10 to 15%.

(15) A building product in the form of an internal lining board is thus provided which can be used in a similar way to how plasterboard is used at present. Accordingly the product may also be used as partition walls, ceilings or otherwise.

(16) The board described above however has significant hygroscopic properties in absorbing water from the adjoining environment in humid conditions, and then emitting the water vapour when conditions are reduced. The board described above also has greater thermal insulation properties than plasterboard and is significantly lighter. Furthermore as a natural product the board or any off cuts can be composted and/or biodegraded.

(17) A second board is made with a lime based binder rather than a clay binder. This board is made from the following materials in the following constituents prior to drying.

(18) TABLE-US-00003 Hemp shiv 10.58% Lime 23.57% Cementitious binder 8.54% Sand 11.53% Water 45.26% Methyl Cellulose 0.51%

(19) The hemp shiv has a similar particular size as for the first board. The lime is a mixture of hydrated lime and naturally hydraulic lime.

(20) The cementitious binder is a natural binder but is a quick setting cement that sets and hardens quickly. It is produced exclusively by cooking argillaceous limestone at a moderate temperature of around 1000 to 1200 C., extracted from homongenous beds and subject to fine milling. It is composed mainly of tricalcium silicate, tricalcium silicate, dicalcium silicate, tricalcium aluminate and calcium ferroaluminate. Small quantities of lime, magnesia, sodium sulphate, potassium and calcium and traces of other elements may be present. Natural quick setting cement contains small quantities of insolubles in which free silica may possibly be found.

(21) This board may be formed in a generally similar manner to the above describe first building product.

(22) A methyl cellulose solution is again used to adhere the backing paper to the remainder of the materials. The methyl cellulose solution may contain between 0.5 and 2% methyl cellulose in water.

(23) There are thus described building products which provide for a number of advantageous features. The boards however can be relatively inexpensively made with conventional forming or rolling techniques. It is to be realised that the above described examples essentially relate to prototype samples, as opposed to a commercial product which could be made by appropriate manufacturing steps.

(24) It is to be realised that a wide range of other modifications may be made without departing from the scope of the invention. As indicated the product could be made by a different technique, and could for instance be formed by rolling the hemp shiv and binder mixture between two sheets of the backing paper on a conveyor between rollers to gauge the thickness.

(25) Different materials could be used, and a wide range of particularly different types of clay or mixtures of clay may be appropriate. Different backing papers or other backing materials may be used, which may have different permeable resistance factors, but these ideally should be in the range 5-15. A cellulose adhesive other than methyl cellulose could be used.

(26) Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.