Adhesive Bonding Materials and Composite Lignocellulose Products Formed Using Same and Methods for Producing Composite Lignocellulose Products

Abstract

An adhesive bonding material can be provided. This adhesive bonding material comprises (a) an isocyanate polymer and/or (b) an amino resin, and (c) a plant oil modifier. The adhesive bonding system can be used in a method for producing a composite lignocellulosic product.

Description

BACKGROUND OF THE INVENTION

This invention relates to methods for the formation of composite lignocellulose products, to adhesive systems for producing same, and to the composite lignocellulose products formed thereby, particularly composite engineered lignocellulose products. More particularly, this invention relates to multi-layer integral, composite engineered lignocellulose products and to adhesive systems which reduce the cost of these products and which will also maintain, and in many instances enhance, the structural properties of the lignocellulose products.

Products such as fiberboard and particleboard have been found to be acceptable alternatives in most cases to lignocellulose products such as natural wood paneling, sheathing and decking lumber. Fiberboard and particleboard are produced from wood particles bonded together by an adhesive, the adhesive being selected according to the intended use of and the properties desired for the finished product. Often times, the adhesive is combined with other additives to impart additional properties to the lumber. Additives can include fire retardants, insect repellants, moisture resistants, fungus resistants and color dyes. A significant advantage of fiberboard and particleboard lumber products is that they have many of the properties of plywood, but can be made from lower grade wood species and waste from other wood product production. These products also can be formed into lumber in lengths and widths independent of size of the timber as harvested.

A major reason for the increased presence in the marketplace of the above-described product alternatives to natural solid wood lumber is that these materials exhibit properties like those of the equivalent natural solid wood lumber, especially the properties of retaining strength, durability, stability and finish under exposure to expected environmental and use conditions. A class of these alternative products are multilayer engineered lignocellulosic products, such as multi-layer oriented wood strand particleboards, particularly those with a layer-to-layer oriented strand pattern, such as OSB.

Oriented, multilayer wood strand boards are composed of several layers of thin wood strands. Wood strands are wood particles having a length, which is several times greater than their width. These strands are formed by slicing larger wood pieces of wood so that the fiber elements in the strands are substantially parallel to the strand length. The strands in each layer are positioned relative to each other with their length in substantial parallel orientation and extending in a direction approaching a line, which is parallel to one edge of the layer. The layers are positioned relative to each other with the oriented strands of adjacent layers perpendicular, forming a layer-to-layer cross-oriented strand pattern.

Aldehyde resins, such as PF resins, are the predominate adhesive for the production of composite wood products. PF resins are less costly than many alternatives (such as the isocyanates described below) but do have some serious limitations.

Isocyanates (in particular MDI polymers) have been known in the wood industry for many years. These materials can produce excellent results when used as adhesives for particulate products. They are, however, more expensive than PF resins.

Mixed resins are employed to a great extent in the present marketplace. MDI/phenol-formaldehyde, MDI/melamine-formaldehyde and MDI/urea-formaldehyde resins are known adhesives for composite wood products.

SUMMARY OF THE INVENTION

In one embodiment, the cost of producing composite lignocellulose products can be reduced through the use of a plant oil modifier in adhesive systems employed in the formation of these lignocellulosic products. In another embodiment, even though the adhesive systems include these plant oil modifiers the structural properties of the lignocellulosic products is maintained. In still a further embodiment, the utilization of these plant oil modifiers in the adhesive systems enhances the structural properties of the lignocellulosic products.

An adhesive bonding material can be provided for use in forming a lignocellulosic product. This adhesive bonding material comprises (a) an isocyanate polymer and/or (b) an amino resin, and (c) a plant oil modifier.

The amino resin can, in an embodiment, comprise an aldehyde resin. In one embodiment, the amino resin comprises urea formaldehyde resin. In another embodiment, the amino resin comprises melamine urea formaldehyde resin. In a further embodiment, the amino resin comprises melamine urea phenol formaldehyde resin.

The adhesive bonding material is comprised of, in one embodiment, up to about 50% by weight, in another embodiment up to about 45% by weight, in a further embodiment up to about 40% by weight, and in still a further embodiment up to about 35% by weight of the amino resin. The adhesive bonding material is comprised of, in one embodiment, from about 30% by weight, in another embodiment from about 35% by weight, in a further embodiment from about 40% by weight, in still a further embodiment from about 45% by weight, up to about 90% by weight, in another embodiment up to about 85% by weight, in a further embodiment up to about 80% by weight, and in still a further embodiment up to about 75% by weight of the isocyanate. The adhesive bonding material is comprised of, in one embodiment, up to about 30% by weight, in another embodiment up to about 25% by weight, in a further embodiment up to about 20% by weight, and in still a further embodiment up to about 15% by weight of the plant oil modifier. The amount of the adhesive bonding material in the treated lignocellulosic material comprises in one embodiment up to about 10% by weight, in another embodiment up to about 7% by weight, in a further embodiment up to about 3% by weight, and in still a further embodiment up to about 1.5% by weight.

Lignocellulosic material is bonded together with the adhesive bonding material to form the lignocellulosic product. The product comprises in one embodiment a plurality of layers of the lignocellulosic material. The lignocellulosic material in another embodiment comprises lignocellulosic particles. The lignocellulosic product in a further embodiment comprises oriented strand board

A method for producing a lignocellulosic product can also be provided. The method comprises providing lignocellulosic material. Then, the lignocellulosic material is treated with an adhesive bonding material comprising (a) an isocyanate polymer and (b) an amino resin, and (c) plant oil modifier. A mat is formed comprising the treated lignocellulosic material. The mat of lignocellulosic material is bonded together with the adhesive bonding material to form the lignocellulosic product.

DETAILED DESCRIPTION

The term “lignocellulosic product”, as used herein, can describe a number of lignocellulosic board products, preferably including multi-layer lignocellulosic board products. A primary example of such a lignocellulosic board product is particleboard or fiberboard. A primary example of such a multi-layer lignocellulosic board product is OSB.

The lignocellulosic products of this invention can be prepared by application of an adhesive bonding material to lignocellulosic material such as particles, chips or wafers, more specifically wood particles, wood chips and lignocellulosic fibers. The lignocellulosic material can also be formed into layers. Similarly, the method of the present invention and its attendant advantages can be achieved with respect to various forms of lignocellulosic starting material and is not limited to any particular form. The use of wood particles and wafers, for example, in the formation of a typical OSB product comprises the preferred environment for the method of the present invention.

Adhesive is typically blended with the above lignocellulosic materials using rotary blenders to achieve thorough mixing and dispensing of the adhesives. The adhesive bonding system of the present invention generally comprises an isocyanate polymer resin and an amino polymer resin, typically an aldehyde polymer resin, and a plant oil modifier. The polymers, which form the adhesive bonding system, are typically in liquid form so that they can be applied directly to a major surface of a layer of lignocellulosic material. The polymer resins can be combined together prior to their application or partially combined or can be individually added.

The amino resins can comprise thermosetting resins such as melamine-formaldehyde, urea-formaldehyde, melamine-urea-formaldehyde, melamine-urea-phenol formaldehyde, modified lignosulfonates, urea-furfural and condensed furfuryl alcohol resins.

The aldehydes reacted with the amino compounds can include any of the aldehydes heretofore employed in the formation of amino resins such as formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, and benzaldehyde. In general, the aldehydes employed have the formula R′CHO wherein R′ is a hydrogen or a hydrocarbon radical of 1 to 8 carbon atoms. The most preferred aldehyde is formaldehyde.

The isocyanate polymer may suitably be any organic isocyanate polymer compound containing at least 2 active isocyanate groups per molecule, or mixtures of such compounds. Generally, the isocyanate polymers employed in the method of this invention are those, which have an isocyanato group functionality of at least about two. Preferably, this functionality ranges from 2.3 to 3.5 with an isocyanate equivalent of 132 to 135. The isocyanato functionality can be determined from the percent available NCO groups and the average molecular weight of the isocyanate polymer composition. The percent available NCO groups can be determined by the procedures of ASTM test method D1638.

The isocyanate polymers which can be employed in the method of the present invention can be those that are typically employed in adhesive compositions, including typical aromatic, aliphatic and cycloaliphatic isocyanate polymers. Representative aromatic isocyanate polymers include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-methylene bis(phenyl isocyanate), 1,3-phenylene diisocyanate, triphenylmethane triisocyanate, 2,4,4′-triisocyanatodiphenyl ether, 2,4-bis(4-isocyanatobenzyl) phenylisocyanate and related polyaryl polyiscocyanates, 1,5-naphthalene diisocyanate and mixtures thereof. Representative aliphatic isocyanate polymers include bexamethylene diisocyanate, xylylene diisocyanate, and 1,12-dodecane diisocyanate and lysine ethyl ester diisocyanate. Representative cycloaliphatic isocyanate polymers include 4,4′-methylenebis(cyclohexyl isocyanate), 1,4-cyclohexylene diisocyanate, 1-methyl-2,4-cyclohexylene diisocyanate and 2,4-bis(4-isocyanatocyclhexylmethyl) cyclohexyl isocyanate.

Plant oil modifier may in one embodiment be any of the edible oils including corn, soy, cottonseed, camelina, canola, palm, peanut, rapeseed, safflower, sunflower, castor, copra, radish, or rice bran oils, or combinations thereof. In another embodiment it may be drying oils such as linseed and tung oils. This plant oil modifier component of the above-described adhesive system in one embodiment maintains the structural properties of the lignocellulosic products, and in another embodiment improves the structural properties of the lignocellulosic products. The amount of plant oil modifier which may be employed in the subject adhesive bonding material is set forth above. In an embodiment herein, the plant oil modifier is soy oil. Soy oil is derived from soybeans which belong to the family Leguminosae.

Generally, when the adhesive composition is used in the method of the present invention within the ranges described above, one achieves a commercially attractive combination of desired board properties and economic advantages.

Typically the adhesive bonding composition is applied to the lignocellulosic material, formed into a mat, and subjected to heat and pressure to consolidate the mat. It should be appreciated that the adhesive composition can be applied to the lignocellulosic particles in any conventional means, such as spraying of the adhesive composition onto the lignocellulosic particles.

In one embodiment, lignocellulosic material is provided and a mat of this lignocellulosic material is then formed. The mat preferably comprises a plurality of layers of lignocellulosic material which produce a multi-layer product.

A lignocellulosic mat can be prepared by application of adhesive bonding material to lignocellulosic particles, chips or fibers, specifically wood particles, wood chips and lignocellulosic fibers, can be formed into layers. Also, instead of first forming a layer by bonding together lignocellulosic particles or the like, layers or sheets of lignocellulosic material, such as veneer layers or sheets or the like, can be provided and used to form the subject lignocellulosic mat. Mixtures of lignocellulosic particles may also be used. Typically, such materials are wood particles derived from wood and wood residues such as wood chips, wood fibers, shavings, veneers, wood wool, cork, bark, sawdust, and the like.

An adhesive bonding material is typically blended with the above lignocellulosic materials so that thorough mixing and dispensing of the adhesives is achieved. The adhesive bonding material of the present invention generally comprises the above described thermosetting resin such as an isocyanate polymer and an aldehyde polymer resin, and a plant oil modifier. The ingredients which form the adhesive bonding material are typically in liquid or powder form so that they can be applied directly to a surface of a layer of lignocellulosic material. The ingredients can be combined together prior to their application, or any two can be combined, or each can be applied separately.

The preferred formation of the layers of lignocellulosic material from lignocellulosic can involve the application of an adhesive bonding material to the lignocellulosic particles with subsequent application of heat and pressure to form the layers into its desired consolidated configuration. It should be appreciated that an adhesive bonding material can be applied to the lignocellulosic particles in any conventional manner, such as by spray coating of the adhesive bonding material onto the lignocellulosic particles.

A product formation press system is typically employed to form the lignocellulosic product. In one embodiment, the system comprises an upper platen and lower platen defining therewithin a product formation press work space. A screen caul can be located on upper surface of the lower platen. The screen caul supports a mat comprising lignocellulosic particles and an adhesive resin located on the mat during the heating and pressing thereof. The mat preferably comprises a plurality of layers of lignocellulosic material in which a multi-layer product is formed. The mat can be bonded together by the adhesive material, typically using heat and pressure in the product formation press system.

In a method for forming a lignocellulosic substrate having a multi-layer structure, a first layer of lignocellulosic particles and combined adhesive bonding material is generally laid down on a formation surface. This first layer is termed a “face mix” and forms a face of the finished product.

Then, a second layer of lignocellulosic particles and adhesive bonding material is deposited in one or more steps. This second layer is termed a “core mix” since it will form the core of the finished product.

Following this, a third layer of lignocellulosic particles and adhesive is laid down on top of the core mix of the second layer. This third layer is also a face mix and will form the opposite face of the finished product. The three layers which are deposited are termed the “mat.”

A pressing operation is carried out in order to form the desired product. During typical pressing operation, the mats are heated to an elevated temperature as they are being compressed. The exact conditions utilized in the pressing and heat curing of the mat can, of course, be easily selected by one skilled in the art depending, of course, upon the desired characteristics of the final product.

The preferred lignocellulosic substrate is an oriented, multilayer wood strand board which is composed of several layers of thin wood strands. Wood strands are wood particles having a length which is several times greater than their width. These strands are formed by slicing larger wood pieces so that the fiber elements in the strands are substantially parallel to the strand length. The strands in each layer are positioned relative to each other with their length in substantial parallel orientation and extending in a direction approaching a line which is parallel to one edge of the layer. The layers are positioned relative to each other with the oriented strands of adjacent layers perpendicular, forming a layer-to-layer cross-oriented strand pattern. Oriented, multilayer wood strand boards of the above-described type are described in detail in the following U.S. Patents: U.S. Pat. No. 3,164,511, U.S. Pat. No. 4,364,984, U.S. Pat. No. 5,435,976, U.S. Pat. No. 5,470,631, U.S. Pat. No. 5,525,394, and U.S. Pat. No. 5,718,786, all of which are incorporated herein by reference. For example, in oriented strand board (OSB) mills, green lignocellosic material is flaked, dried, and blended with resins and wax, formed into mats, which are typically multi-layer in structure, and then pressed in continuous or multi-opening presses at relative high temperature and pressure.

EXAMPLE 1

Southern Yellow pine wafers of nominal 4.6″ length, 0.028″ thickness and ¾″ width dimension were screened through ¼′″ and ⅜″ screens and dried to 5-6% moisture. The wafers were blended with resins and other ingredients as described below. A mat was formed such that 60% of the wafers were distributed evenly between top and bottom surfaces and oriented in the machine direction. Core wafers comprised 40% of the mat and were oriented in the cross-machine direction. Boards were pressed to 0.785″ at 430 degrees F. press temperature for 235 seconds plus about 35 sec. degassing. The target density out-of-press was 41 lbs/cu.ft. Boards were sanded 1-2 days later to 0.720″.

As Table 1 shows, at 25% substitution of the MDI by urea-formaldehyde in a plant oil modified formulation properties were achieved which were equivalent to unsubstituted MDI. At 50% substitution, these properties were sufficient to meet requirements for certain end uses such as for flooring. Properties including 24-hr swell and absorption, bending properties, and internal bond were determined using methods described in ASTM D-1037. Bond durability was assessed using a 3-cycle boil/cool exposure and also by 2-hr boil/dry conditioning method for internal bond.

TABLE 1
Partial Substitution of MDI by Urea-Formaldehyde Resin
	2.5% MDI	1.9% MDI	1.25% MDI
	No UF	0.6% UF	1.25% UF
	0.67% Soy Oil	0.47% Soy Oil	0.67% Soy Oil
Thickness swell, %	4.1	4.2	4.7
Edge swell, %	9.9	10.2	10.3
Water absorption, %	8.1	9.3	10.3
3-cycle boil swell, %	34	35	47
Internal bond, psi	114	129	99
Internal bond, 2-hr	12	9	0
boil, psi
MOR, psi	4896	5032	5076
MOE, psix10{circumflex over ( )}3	803	824	858

EXAMPLE 2

Boards were made as in Example 1 to compare performance with and without soy oil. Soy oil contributed to improved mechanical properties such as internal bond and bending strengths, as shown in Table 2. This is unexpected since soy oil is normally considered only an extender. In Table 2, the soy oil is added over and above the resin amounts, and shows better board properties. The soy oil not only contributes to improved properties, it also helps alleviate blender buildup that might otherwise occur when blending co-reactive resin components such as MDI and UF.

TABLE 2
Soy Oil w/1.9% MD I/0.6% UF Resin Blends
	Test #1	Test #2
	0.47% oil	No oil	0.47% oil	No oil
Thickness swell, %	4.2	4.8	4.7	5.0
Edge swell, %	10.2	11.0	10.3	10.2
Water absorption, %	9.3	9.8	9.1	9.6
3 cyc. Thick. swell %	35	42	40	42
IB, psi	129	104	101	89
2-hr boil, psi	9	8	5	5
MOR, psi	5032	4549	4581	4599
MOE, psi × 10{circumflex over ( )}3	824	801	826	752

EXAMPLE 3

Separate addition of MDI and UF was preferred over pre-mixing of these components as shown in Table 4 below. Separate addition also rectifies the issues of resin line and atomizer pluggage. These are major concerns with other combined resin systems such as mixed PF/MDI adhesive systems.

TABLE 3
Methods of Addition of MDI, UF, and Soy Oil Components
	1.9% MDI/0.6% UF	1.5% MDI/1.0% UF
	Combined	Separate*	Combined	Separate*
Thickness swell, %	5.5	5.1	6.1	5.0
Edge swell, %	12.0	11.8	14.7	11.7
Water absorption, %	11.8	11.4	13.3	11.1
3 cyc. Thick. swell %	58.9	47.2	64.1	51.7
Internal bond, psi	67	86	65	90
Internal bond, 2-hr	0	4	0	0
boil, psi
MOR, psi	4061	4904	4605	4487
MOE, psiX10{circumflex over ( )}3	722	781	766	790
*Soy Oil addition was split between MDI and UF; in all other tests, soy oil was pre-blended with MDI only

EXAMPLE 4

Table 4 depicts board properties of OSB which employs various melamine-urea based resins in the adhesive system. MUF and MUPF showed equivalent swell properties to UF, and were superior to UF in bond durability as reflected by the 2-hr boiled IB.

TABLE 4
Melamine Alternatives to UF
	75%	75%
	MDI/	MDI/	75%
	25%	25%	MDI/
	UF	MUPF	25%
	0.47% soy	0.67%	MUF
	oil	soy oil	0.67% soy oil
Thickness swell, %	4.2	4.6	4.7
Edge swell, %	10.2	10.2	11.0
Water absorption, %	9.3	8.9	9.0
3 cyc. Boil. swell 1%	35.2	34.5	38.7
Internal bond, psi	129	118	110
Internal bond, 2-hr boil, psi	9	18	10
MOR, psi	5032	4029	4356
MOE, psiX10{circumflex over ( )}3	824	413	738

Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. I claim all modifications and variation coming within the spirit and scope of the following claims.

Claims

1. A method for producing a lignocellulosic product comprising:

providing lignocellulosic material;

treating said lignocellulosic material with an adhesive bonding material comprising (a) an isocyanate polymer and/or (b) an amino resin, and (c) plant oil modifier;

forming a mat comprising said treated lignocellulosic material; and

bonding together said mat of lignocellulosic material with said adhesive bonding material to form said lignocellulosic product.

2. The method of claim 1, wherein said plant oil modifier comprises soy oil

3. The method of claim 1, wherein said mat comprises a plurality of layers of said treated lignocellulosic material.

4. The method of claim 1, wherein said lignocellulosic material comprises oriented strand board resin.

5. The method of claim 1, wherein said amino resin comprises an aldehyde resin.

6. The method of claim 1, wherein said amino resin comprises urea formaldehyde resin.

7. The method of claim 1, wherein said amino resin comprises at least one of melamine urea formaldehyde resin and melamine urea phenol formaldehyde resin.

8. The method of claim 1, wherein said adhesive bonding material comprises up to about 50% by weight of said amino resin.

9. The method of claim 1, wherein said adhesive bonding material comprises from about 30% up to about 80% by weight of said isocyanate polymer.

10. The method of claim 1, wherein said adhesive bonding material comprises up to about 30% plant oil modifier

11. A lignocellulosic product comprising:

lignocellulosic material; and

an adhesive bonding material comprising (a) an isocyanate polymer and/or (b) an amino resin, and (c) a plant oil modifier,

said lignocellulosic material bonded together with said first adhesive bonding material to form said lignocellulosic product.

12. The product of claim 11, wherein said plant oil modifier comprises soy oil

13. The product of claim 11, which comprises a plurality of layers of said lignocellulosic material.

14. The product of claim 11, wherein said lignocellulosic material comprises oriented strand board.

15. The product of claim 11, wherein said amino resin comprises an aldehyde resin.

16. The product of claim 11, wherein said amino resin comprises urea formaldehyde resin.

17. The product of claim 11, wherein said amino resin comprises at least one of melamine urea formaldehyde resin and melamine urea phenol formaldehyde resin.

18. The product of claim 11, wherein said adhesive bonding material comprises up to about 50% by weight of said amino resin.

19. The product of claim 11, wherein said adhesive bonding material comprises from about 30% up to about 80% by weight of said isocyanate polymer.

20. The product of claim 11, wherein said adhesive bonding material comprises up to about 30% plant oil modifier.

21. An adhesive bonding material comprising (a) an isocyanate polymer and/or (b) an amino resin, and (c) a plant oil modifier.