High strength low density board for furniture industry

Details High strength low density board for furniture industry High strength low density board for furniture industry

1999-05-11

2001-07-31

Weisberger, Richard (Department: 1774)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S326000, C428S532000, C428S535000, C428S537700, C428S070000, C428S074000, C428S211100, C106S001150, C106S001150, C106S001150, C106S001150

Reexamination Certificate

active

06268042

ABSTRACT:

BACKGROUND ART
The present invention relates to fiber board panels for use in the furniture industry. More particularly, the present invention relates to a means by which fiber board panels can be made significantly stronger without significantly increasing their density. The present invention also relates to a novel mineral wool/lightweight aggregate material/cellulose fiber/binding agent composition, which can be used to manufacture high strength low density fiber board panels.
Fiber board panels are well known in the furniture industry, and are widely used as wall panels, office dividers, tackboards, chalkboards, and stoveboards, among other things. The stronger the panels are the better. At the same time, for ease of transport and installation, the less dense and lighter the panels are the better. Unfortunately, in traditional fiber board panels, strength and density have always seemed to be closely and directly related, which means that any attempt to increase the strength of a particular panel would necessarily result an increase in that panel's density, and therefore, weight.
Accordingly, it is an object of the present invention to produce an improved fiber board panel having high strength and low density, and which is suitable for use in the furniture industry.
It is another object of the present invention to provide an improved process for producing high strength low density fiber board panels which are suitable for use in the furniture industry.
DISCLOSURE OF INVENTION
The above objects are met or exceeded by the present fiber board panel and process for making same. The present fiber board panel includes a composition of mineral wool, a lightweight aggregate material, cellulosic fiber, a binding agent and gypsum. Surprisingly beneficial results were obtained by decreasing the mineral wool content, simultaneously increasing the cellulosic fiber content of conventional panels, and adding gypsum. Further modifications to the conventional recipe for fiber board panels may be made, including increasing the amount of lightweight aggregate material while decreasing the starch content.
An improved process for making the present high strength low density fiber board panel involves creating a dispersion of the above ingredients, in specific proportions by weight, and then causing the dispersion to flow onto a support mechanism for dewatering.
More specifically, a high strength low density fiber board panel is provided comprising mineral wool, a lightweight aggregate material, cellulosic fiber, a binding agent and gypsum, where the mineral wool comprises approximately 0% to approximately 33%, the lightweight aggregate material comprises approximately 25% to approximately 41%, the cellulosic fiber comprises approximately 20% to approximately 35%, the binding agent comprises approximately 5% to approximately 9%, and the gypsum comprises approximately 0% to approximately 23%, of a dry solids weight of the panel.
BEST MODE OF CARRYING OUT THE INVENTION
Fiber board panels are commonly used in the furniture industry, and are conventionally made through combining mineral wool, a lightweight aggregate material, cellulosic fiber, clay, and a binding agent, with water. More specifically, conventional fiber board panels typically contain the following ingredients in varying amounts: mineral wool, perlite, paper, starch, and optionally, clay.
Until now, the common belief has been that any increase in the strength of a fiber board panel would necessarily involve an increase in that panel's density, and therefore weight. Conversely, the belief has been that any decrease in a panel's density, and therefore weight, would necessarily involve a decrease in that panel's strength. Since, for use in the furniture industry, stronger panels are almost always preferred over weaker ones, while less dense, and therefore lighter, panels are preferred over those of higher density, this has proved to be a real problem.
The strength of a fiber board panel is typically referred to in terms of that panel's Modulus of Rupture (“MOR”). MOR refers to a panel's breaking point upon application of a specified amount of pressure, and is typically measured using the ASTM D-1037 static bending method, which is well-known in the art.
The high strength low density fiber board panels of the present invention were manufactured using the following ingredients: mineral wool, a lightweight aggregate material, cellulosic fiber, gypsum, and a binding agent. Surprisingly, it was found that by altering the amounts of the various ingredients panels having a significantly higher MOR could be produced without the expected significant increase in density, and conversely, that panels having a significantly lower density could be produced without the expected significant decrease in MOR.
A key ingredient in conventional fiber board panels is mineral wool. The presence of mineral wool provides bulk and strength to the panels, and helps render the panels relatively porous.
The conventional fiber board panels tested for purposes of the following examples contained approximately 42% to approximately 52% mineral wool. In the present invention, a mineral wool content ranging from approximately 0% to approximately 32.86% is contemplated. In the preferred embodiment, however, the mineral wool content is approximately 28%.
The next key ingredient in conventional fiber board panels is a lightweight aggregate material. Perlite is commonly used, due to its performance qualities and low cost. Perlite is a well known form of glassy rock, and generally contains 65-75% SiO
2
, 10-20% Al
2
O
3
, 2-5% H
2
O, and lesser amounts of soda, potash, and lime.
In preparing the perlite for use, the perlite is first ground to a size finer than minus 200 mesh. Once ground, the perlite is heated to a temperature of about 1500°-1800° F., and preferably to about 1750° F. The heating process is carried out in a perlite expander. First, the air is heated to approximately 1500° F. The finely ground perlite is then introduced into the heated air, which causes the perlite to expand. Once expanded, the perlite forms a light and fluffy material similar to pumice, and having a density of approximately 3.5-5 pcf. Perlite in this expanded form contributes significantly to the bulk, strength and porosity of the completed fiber board panels.
The density of expanded perlite varies according to the temperature to which the perlite is heated. Perlite heated to a temperature of about 1500°-1800° F. typically has a density of approximately 3.5-5 pcf. Heating the perlite to a lower temperature reduces the amount of expansion, resulting in perlite having a higher density. It is contemplated that perlite having a density up to approximately 20 pcf can be used in the present invention.
For purposes of the following examples, the conventional fiberboard panels tested contained between approximately 20% and approximately 25.4% perlite. In the present invention, a perlite content of approximately 25%-41% is contemplated.
The next key ingredient in conventional fiber board panels is cellulosic fiber. Paper fiber is very commonly used, and can be obtained from many sources, including hydropulp newsprint and scrap gypsum board panels, which would otherwise simply be thrown away.
As described in the examples below, conventional fiber board panels having a paper content of approximately 12% to approximately 28% were tested. The present invention contemplates a cellulosic fiber content of approximately 20% to approximately 35%. In the preferred embodiment, paper is the source of cellulosic fiber, at approximately 25% of the dry solids weight of the board panels.
The next key ingredient in conventional fiber board panels is a binding agent. Starch is very commonly used. Starch forms a viscous gel when dispersed in water and heated to approximately 180°-195° F. In the fiber board panel making process, the starch may be cooked prior to being added to the dispersion, or it may be added raw, in which case it will have an opportunity to be cooked during the panel dryin

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