JPS5950509B2 - Structural members of composite wood materials and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structural member made from a composite wood material consisting of wood flakes bonded together with a binder.

various types of structural members, e.g. utility poles, guardrails,
Fences and signal posts, construction beams, structural stacks, railroad ties, etc. are commonly made from solid wood.

Because of factors such as increased manufacturing costs, limited supply of trees of suitable species and/or sizes, and more economically efficient use for other purposes, these and other types of construction There is an increasing demand for suitable alternative materials from which parts can be made.

The use of wood residues and surplus wood of low commercial value for this purpose is highly desirable because of its widespread availability and low, more reasonable costs.

In order to be able to be used for the same purpose, the resulting structural member should have properties, especially strength, that match or exceed those of solid wood.

The wood particles are mixed with a suitable binder, for example a synthetic thermosetting resin, the mixture is formed into a mat, and then compressed between heated platens to harden the binder and form a densified form. It is known to make flat particleboard from ground wood by bonding wood particles together.

This type of method is described in U.S. Pat. No. 3.164.511 (Elm.
endorf), 3. , 391.233 (Polov
tseff) Oyobi 3.940.230 (Pott
er) is exemplified in the tail.

In this type of method, the wood particles are deposited so that they are oriented randomly with respect to each other or laterally oriented with respect to each other.

For example, E1mendorf patent 3.164.51
No. 1 discloses orienting wood grains or strands such that substantially any strand intersects at least one other at an average acute angle of about 40° or less.

Products with acceptable strength properties for typical uses of flat particleboard can be produced from methods in which the wood particles are oriented randomly or in the manner disclosed in the Elmendorf patent.

However, structural members manufactured in this manner that are 1 inch (2.54 cm) or thicker have poor strength properties,
In particular, its bending strength along the vertical axis is generally somewhat inferior to that of solid wood.

The main objective of the present invention is to provide a method for producing structural members from wood particles derived from low cost wood with strength properties comparable to or superior to that of solid wood.

Another object of the invention is to provide a high strength structural member made from a composite wood material composed of elongated wood flakes bonded together with a binder.

Another object of the invention is to provide a method of making a structural member that includes two or more elongate structural components, each structural component being formed from a composite wood material.

Yet another object of the invention is to provide an elongate structural member made from such a composite wood material, in which two or more elongate structural components are joined together at an angle to each other. .

Other objects, uses and advantages of the invention will become apparent from the following detailed description and accompanying drawings.

Structural members formed from composite wood materials whose strength is equal to or greater than Douglas fir or southern Pine include elongated wood flakes from a variety of species with a grain direction extending generally parallel to the longitudinal axis. and by orienting the flakes such that at least a majority of their longitudinal axes are generally parallel to a predetermined axis of the structural member.

In a preferred method of making elongated structural members, such as construction beams, railway sleepers, etc., the average length is about 0.0 mm.
5 to about 3.5 inches (about 1.27 to about 8.89 cm), with an average length to average width ratio of about 4:1 to about 10:
1 and has an average thickness of about 0.01 to about 0.605
Use wood flakes that are about 0.025 inches (about 0.025 cm to about 0.127 cm).

A suitable binder, such as a resinous particle board binder, is mixed with wood flakes and the resulting mixture or composition is formed into a loosely felted mat.
at least a majority of the wood flakes, preferably about 90
% or more are oriented such that their longitudinal axes are generally parallel to the longitudinal axis of the structural member to be formed from the mat.

Apply sufficient pressure to the mat, for example on a surface plate (heated,
In addition, the mat is compressed into a structural member of the desired thickness and the wood flakes are bonded together (alternatively at room temperature).

The resulting structural member typically weighs from about 38 to about 50 pounds per cubic foot, preferably from about 42 to about 45 pounds per cubic foot.
It has a density of approximately 0.72 g/cnr').

The resulting structural member preferably contains about 5 to 12% by weight of binder and optionally additives such as waxes for waterproofing and preservatives for protection against decaying fungi and insects.

Organic polyisocyanates are preferred binders as they provide high strength properties.

In one embodiment, by forming separate elongated structural components and joining two or more of them together at an angle to each other with a suitable adhesive, a beam, L.
It is formed into an elongated structural member having a shape such as a shaped bar or a miso-shaped bar.

FIG. 1 illustrates an elongated structural member 10 made from a composite wood material according to the present invention and having cross-sectional dimensions corresponding to a standard 2×4 lumber.

The structural member 10 is made of wood flakes 1, as will be described in detail hereinafter.
2 and a suitable [resin particleboard binder] as a solid, integral unit.

As shown in Figure 4, wood flakes 12 (about 2
(illustrated at double size) is elongated and extends generally parallel to its longitudinal axis 16 in the direction of the grain (numerals 14
).

As shown in FIG. 1, at least a majority of the wood flakes 12 making up the structural member have their planes co-extensive, that is, generally parallel to each other, and their longitudinal axes 16 extend beyond the structural member 1. oriented generally parallel to the longitudinal axis 18 of the.

In other words, the grain direction of the wood particles oriented in this way is similar to that of a 2x4 natural wood,
extends generally parallel to the longitudinal axis 18 of the.

1 and 2 partially illustrate multi-piece structural members 20 and 40 made from composite wood materials according to the present invention.

The structural member 20 illustrated in FIG.
2.24 and 26 included.

Each structural component 22, 24 and 26 is formed from a mixture of wood flakes 12 and binder in the same general manner outlined above.

That is, at least a majority of the wood flakes 12 constituting each structural component have coextensive planes;
That is, they are oriented generally parallel to each other and such that their longitudinal axes 16 are generally parallel to the longitudinal axes 28, 30 and 32 of their respective structural members 22, 24 and 26.

The longitudinal edges 34 and 36 on either side of the middle component 24 are attached to components 22 and 26 with a suitable high strength adhesive 38, such as a resorcinol or isocyanate type adhesive or other adhesive suitable for bonding wood products. are combined by.

The structural member 40 illustrated in FIG. 3 has the shape of an L-bar and includes separate elongated, generally planar structural components 42 and 44, which are connected to the I-beam structural member 20.
The wood-binder mixture is molded and bonded together as described above.

■ As in the case of the components of a beam structure, at least the majority of the wood flakes 12 making up the structural components 42 and 44 have their planes coextensive, i.e. generally parallel to each other, and their It is oriented such that longitudinal axis 16 is generally parallel to longitudinal axes 46 and 48 of structural components 42 and 44.

Now, the method of the present invention will be explained in more detail.

The method broadly consists of pulverizing small logs, branches or rough pulp wood into flake-like particles, drying the wood flakes to a predetermined moisture content, sorting the dried flakes into predetermined sizes, and a predetermined amount of a suitable binder, and optionally a liquid wax composition;
Preservatives and other additives are combined with the dried, sized flakes, the resulting mixture or composition is formed into a loosely felted, layered mat (single layer or multilayer), and sufficient pressure is applied to ( (with or without heat) compressing the mat to the desired thickness of the structural member or component and bonding the wood flakes together.

The wood flakes used can be made from a variety of suitable hardwoods and softwoods.

Typical examples of suitable wood are poplar, kaete, errem,
These are balsam fir, pine, cedar, spruce, varieng, fir, birch, Douglas fir and mixtures thereof.

Wood has a property of directional strength, and the strength along the grain is much greater than the strength across the grain.

To maximize the strength of the resulting structural member, the wood flakes are manufactured with the grain direction generally parallel to the main longitudinal direction, and the flakes are kept coextensive with their planes during mat formation. oriented, i.e., generally parallel to each other, and such that at least a majority, preferably 90% or more, have a grain direction aligned with a predetermined axis of the structural member.

For elongated structural members used in applications requiring high load strengths along the longitudinal axis, such as structural members 10, 20 and 40 illustrated in FIGS. Align with direction.

Wood flakes can be produced by various techniques.

For example, a log with a pulp wood edge is a regular log flaker.
You can turn it into flakes in one operation.

Alternatively, the logs, whole log forming residue, can be cut into 0.5 to 3.5 inches (
Cut into small pieces of about 1.27 to 8.89 cm),
And these small ones are made into ordinary ring-shaped flakers.
can be made into flakes.

The wood is preferably peeled before flaking.

Log flakes are generally preferred because they allow for more precise control of length and thickness and are more uniform in width and shape.

Additionally, log flakes tend to be somewhat flattened, which can facilitate flake alignment during mat formation.

Log flakes generally produce less undesirable fines.

For best results, the wood flakes should have an average length of about 0.5 to about 3.5 inches (about 1.27 to about 8,8 inches).
9 cm), preferably about 1 to about 2 inches (about 2.54 to
approximately 5.08 cm), and the average thickness is approximately 0.0
1 to approximately 0.05 inch (approximately 0.025 to 0.127 cm)
), preferably about 0.015 to about 0.025 inches (about 0.038 to about 0.064 cm), most preferably about 0
．． It should be 0.02 inches (approximately 0.051 cm).

Flakes longer than about 3.5 inches tend to bend, which prevents proper alignment during mat formation, and flakes shorter than about 0.5 inches tend to bend. It is difficult to ensure alignment in the direction of the grain.

Flakes thinner than about 0.01 inch (about 0.025 cm) require excessive amounts of binder to obtain a proper bond, and flakes thicker than about 0.05 inch (about 0.127 cm) require relatively It is rigid and requires excessive compression to obtain the desired tight contact between the flakes.

In any given batch, portions of flakes may be shorter than 0.5 inches (1,27 cm) and portions may be longer than 3.5 inches (8,89 cm), but the overall average The length must be within the above range.

The same holds true for flake thickness.

To facilitate proper alignment, the flakes should have a length several times their width, preferably from about 4 to about 10 times.

Using this limit as a guide, the average width of the flakes generally ranges from about 0.1 to about 0.5 inches (about 0.254 to about 1
．． 27 cm).

Although the size of the flakes can be adjusted to a large extent during the flake manufacturing operation, undesirable particles, both too small and too large, are removed so that the average length, thickness, and width of the flakes are within the desired range. Some classification is usually necessary to ensure that

Flakes from somewhat green wood can contain up to 90% moisture.

The moisture content of the mat must be substantially low for compaction operations.

Additionally, wood flakes tend to stick together prior to compounding, complicating sorting and handling.

Therefore, the flakes are preferably dried in a conventional dryer prior to sorting to achieve the desired moisture content for the compounding process.

Drying the flakes to a moisture content depends primarily on the particular compounder used, and this moisture content is usually on the order of no more than about 3 to about 20 percent by weight, based on the dry weight of the flakes.

If desired, the flakes can be partially dried before sorting and then dried to the desired moisture content for post-sorting formulation.

This two-step drying is useful when a substantial amount of improperly sized flakes must be removed during sorting, and thus when complete drying is not required, flakes produced from green wood can be Total energy requirements for drying can be reduced.

A known amount of dried, sorted flakes is introduced into a common compounding machine in which they are tumbled or stirred while a predetermined amount of binder and, if necessary, waxes, preservatives and other additions are added. Add the agent to the flakes.

Suitable bonding agents include those used in the manufacture of particle board and similar pressed textile products, and other chemical bonding systems.

Resin particle board binders are currently preferred.

Representative examples of suitable binders are: thermosetting resins such as phenol-formaldehyde, resorcinol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, urea-furfural and condensed furfuryl alcohol resins, and Organic polyisocyanates, alone or in combination with urea or melamine-formaldehyde, including those that cure at room temperature.

Particularly suitable polyisocyanates are those containing at least two active isocyanate groups per molecule, for example schifermethane diisocyanate, m- and p-phenylene diisocyanate, chlorophenylene diisocyanate, toluene di and triisocyanate, triphenylmethane triisocyanate. , diphenyl ether-2,4°4'-triisocyanate, polyphenol polyisocyanate, especially diphenyl-methane-
4,4'-diisocyanate.

The particular bonding agent used depends primarily on the intended use of the structural member.

For example, structural members made using urea-formaldehyde resins are sufficiently moisture resistant for many applications where exposure to moisture is minimal, but cannot withstand long-term outdoor exposure.

Phenol-formaldehyde and melamine-formaldehyde resins provide structural members with the durability required for long-term exterior use.

Polyisocyanates, even in lower amounts, provide comparable weather resistance and greater strength to phenol-formaldehyde and melamine-formaldehyde resins.

Polyisocyanates cure in about the same or less time than urea-formaldehyde resins.

However, polyisocyanates are more expensive and
And because it tends to stick to metal parts, it may require the use of a mold release agent.

These factors are balanced against each other when choosing the particular binding agent to use.

The amount of binder added to the flakes during the compounding process depends primarily on the particular binder used, the size, moisture content and type of wood flakes, and the desired properties of the resulting structural member.

Generally, the amount of binder added to the flakes is from about 5% to about 12%, preferably from about 6% to about 10% by weight solids, based on the dry weight of the flakes.

The binder can be mixed with the flakes in dry or liquid form.

To maximize flake coverage, the binder is preferably applied by spraying drops of binder in liquid form onto the flakes as they are being tumbled or mixed in the compounder.

The moisture resistance of the structural component can be improved by spraying an emulsion of liquid wax onto the flakes during the compounding process.

The amount of wax added is generally from about 0.5% to about 5% by weight solids based on the dry weight of the flakes.

When using structural components for long-term external applications, preservatives are added to protect the wood against attack by decaying fungi and insects.
Add to wood flakes during or before the compounding process.

Any preservative compatible with the adhesive can be used.

Typical examples are pentachlorophenol, creosote, chromated copper asenate, ammoniated copper asenate, and the like.

Effective amounts of preservatives, up to about 5% by weight, can be added to wood flakes without appreciable reduction in the structural strength of the resulting structural member, i.e., no loss of strength occurs when treated with the same preservative. It turned out that it was almost the same as the wood of the dripping wood.

Other additives, such as colorants, flame retardants, can also be added to the flakes during or before the compounding process.

Binder, wax and other additives separately and in order
Alternatively, they can be added in combined form.

The moistening mixture or composition of flakes, binders, waxes, preservatives, etc. from the compounding process is formed into a loose felted, single layer or multilayer mat, which is then compressed, as illustrated in FIG. For the assembly of either a solid, unitary structural member, such as structural member 10, or a multi-piece structural member, such as the components for structural members 20 and 40 illustrated in FIGS. 2 and 3. Make it an ingredient.

Generally, the moisture content of the composition after completion of formulation, including the inherent moisture content of the flakes and the moisture added during formulation of the binder wax and other additives, will be from about 5% to about 25% by weight;
Preferably it should be from about 10 to about 20% by weight.

Generally, high moisture content within these ranges can be used for polyisocyanate binders.

The composition is formed into a generally flat, loosely felted, single layer or multilayer mat by suitable equipment;
This mat is placed in a suitable press, which compresses it to consolidate the wood flakes into a structural member of the desired size and cross-section.

For example, the composition can be deposited from one or more hoppers spaced above a plate-like carriage supported on an endless belt or conveyor in the direction of travel.

When forming multilayer mats, multiple hoppers are used, each hopper having a dispensing or forming head extending across the width of the carriage, each head dispensing a separate layer of the composition as the carriage moves beneath it. Continuously deposited.

To produce a structural member with the desired strength properties, the mat should have a substantially uniform thickness and the flakes should be aligned with the aforementioned orientation during mat formation.

The thickness of Pine 1 can be adjusted primarily by properly metering the flow of composition from the forming head.

The flakes are located between the laterally spaced baffle system or the forming head and the carriage, and the composition is deposited onto the carriage or onto a previously deposited layer of composition. The elongated flakes can then be aligned using any other suitable means arranged to guide them in the desired orientation.

The thickness of the mat is 1, the size and shape of the wood flakes,
It will vary depending on such factors as the particular technique used to form the mat, the desired thickness and density of the structural members or components, and the compaction pressure used.

The thickness of the mat is typically about 5 to 6 times the final thickness of the structural member or component.

For example, it has a thickness of 1 inch (2,54 cm) and a density of approximately 40 lbs/cubic foo (0,64 g/cm3)
For structural components that are
It would be 6 inches (approximately 12.7-15.2 cm).

The mat is approximately 25-30 inches (approximately 63.5-76, 2c
m) For thicker mats, the mat usually has to be pre-compacted with rollers or the like to partially reduce the thickness before it is introduced into the compactor.

The temperature, pressure and time of compaction will depend on the thickness and desired density of the structural member or component, the size and type of wood flakes,
It will vary widely depending on the moisture content of the flakes and the type of binder.

The compaction temperature used is one that is sufficient to at least partially cure the binder and drive water from the mat without charring the wood within a reasonable period of time.

Generally, from ambient temperature (room temperature curable binder) to about 45
Compression temperatures ranging up to 0°F (about 234°C) can be used.

Temperatures above 450°F (234°C) can char the wood flakes.

Compression temperatures of about 250 to about 375°F (about 121 to about 191°C) are generally preferred for catalyzed polyisocyophyl binders, and about 350 to about 425°F.
(about 177°C to about 218°C) is generally phenol-
Preferred for formaldehyde resins.

The pressure should be sufficient to compress the wood into intimate contact with each other without crushing the wood flakes to the point of breaking the fibers so much that they reduce structural integrity.

The pressure is typically about 325 to about 500 psi (about 22.8 to about 35.2 kg/cm2).

The compression time is sufficient to at least partially cure the binder to the point that the structural member or component has sufficient integrity for handling.

Compression cycles typically range from about 2 to about 20 minutes, but longer times can be used when using pressure cure binders or when more complete curing of thermoset binders is desired. .

Although different species of solid wood typically exhibit widely varying strength properties, the properties of structural members made in accordance with the present invention are substantially the same for a wide range of high and low strength species.

Thus, species not previously considered useful for structural products can be used without sacrificing strength properties.

Also, the strength properties of composite wood materials are more uniform than solid wood because there are no knots or grain inconsistencies that are normally present in solid wood.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of a solid monolithic member made in accordance with the present invention. FIG. 2 is a partial perspective view of a three-piece structural member made in accordance with the present invention and having a ■beam shape. FIG. 3 is a partial perspective view of a two-piece member in the form of an L-bar made in accordance with the present invention. FIG. 4 is an enlarged top plan view of typical wood flakes used in making structural members according to the present invention. 10... Elongated structural member, 12... Wood flakes, 14... Wood grain direction, 16. 18
．． 28. 30, 32. 46. 48...
- Vertical axis, 20, 40...Multi-piece structural member, 22.
24. 26. 42. 44... Structural component, 34, 36... Vertical edge, 38...
··glue.

Claims (1)

Claims: 1(a) Provide elongated wood flakes having a grain direction extending generally parallel to a longitudinal axis, provided that the average length of the flakes is between 0.5 and 3.5 inches (1, 27-8.8
9 cm), and the ratio of average length to average width is 4:1 ~
10:1, and the average thickness is 0.01-0.0
5 inches (0.025-0.127 cm); (b) the binder is mixed with the wood flakes; (C)
forming a layered mat from the resulting mixture, orienting at least a majority of the wood flakes so that their longitudinal axes are generally parallel to the axis of the structural member to be formed from the mat; and (d) 1. A method of manufacturing a structural member of composite wood material having a shaft, the method comprising the step of applying sufficient pressure to bond the wood flakes together and form a structural member. 2. The method of claim 1, wherein at least 90% of the wood flakes are oriented in the described manner. 3 Wood flakes have an average length of 1 to 2 inches (2,5
4-5.08 cm). 4 Wood flakes are 0.015 to 0.025 inches (0
.038 to 0.064 cm). 5 The average width of wood flakes is 0.1 to 0.5 inches (0.1 to 0.5 inches).
, 254 to 1.27 cm). 6 The amount of binder mixed with the wood flakes during step (b) is 5% as solids based on the dry weight of the wood flakes.
12. The method of claim 1, wherein the amount is 12% by weight. 7. The method of claim 6, wherein the binder comprises an organic polyisocyanate having at least two active isocyanate groups per molecule. 8(a) Provide elongated wood flakes with a grain direction extending generally parallel to the longitudinal axis, provided that the flakes have an average length of 0.5 to 3.5 inches (1.27 to 8.8 inches).
9 cm), and the ratio of average length to average width is 4:1 ~
10:1, and the average thickness is 0.01-0.0
(b) mix the binder with the wood flakes; (C) form a layered mat of the resulting mixture for each component;
orienting at least a majority of the wood flakes so that the longitudinal axis of the wood flakes is generally parallel to the longitudinal axis of the component to be formed from the mat; (e) bonding the components together to form a structural member;
A method for producing an elongated structural member of composite wood material having at least two elongated structural components joined at an angle to each other, the method comprising the steps of: 9 Consisting of elongated wood flakes bound together with a binder, the wood flakes having a grain direction running generally parallel to the longitudinal axis and having an average length of 0.5 to 3.5 inches (
1,27 to 8.89 cm), an average length to average width ratio of 4:1 to 10:1, and an average thickness of 0.01 to 0.05 inch (0,025 ~0.127c
m) and at least predominantly oriented such that the longitudinal axis is generally parallel to the axis of the structural member. . 10. A structural member according to claim 9, wherein at least 90% of the wood flakes are oriented in the described manner. 11 Wood flakes have an average length of 1 to 2 inches (2,
10. The structural member according to claim 9, wherein the structural member has a diameter of 54 to 5.08 cm. 12 Wood flakes have an average length of 0.015 to 0.0
10. The structural member of claim 9 which is 25 inches (0.038-0.064 cm). 13 The average width of wood flakes is 0.1 to 0.5 inches (
0,254-1.27 cm) Claim No. 9
Structural members as described in Section. 14 As a solid based on the dry weight of wood flakes,
Claim 9 containing 5-12% by weight of binder
Structural members as described in Section. 15. The structural member of claim 14, wherein the binder comprises an organic polyisocyanate having at least two active isocyanate groups per molecule. 16 comprising at least two elongated structural components bonded together at an angle to each other, each of the structural components consisting of elongated wood flakes bonded together with a bonding agent, the wood flakes comprising: having a grain direction generally parallel to the longitudinal axis and an average length of 0.5 to 3
．． 5 inches (1,27 to 8.89 cm), with an average length to average width ratio of 4:1 to 10:1, and an average thickness of 0.01 to 0.05 inches ( 0,025～
0.127 cm) and is at least predominantly oriented such that its longitudinal axis is generally parallel to the longitudinal axis of the structural component. 17. A structural member according to claim 16, wherein at least 90% of the wood flakes are oriented in the described manner.