CA1200336A

CA1200336A - Making composite articles

Info

Publication number: CA1200336A
Application number: CA000379884A
Authority: CA
Inventors: Steven G. Geye; Robert H. Leitheiser; Michael E. Londrigan
Original assignee: Qo Chemicals Inc
Current assignee: Penn Specialty Chemicals Inc
Priority date: 1980-09-22
Filing date: 1981-06-16
Publication date: 1986-02-04
Also published as: SE8103795L; DE3126800A1; JPS5763373A; AU7261281A; NZ197438A

Abstract

ABSTRACT
In the manufacture of composite articles such as wood particle board, a high hydroxymethyl furan-formaldehyde condensation product diluted with water is used as a binder.

Description

k336 This invention relates to the use of water-diluted resinous high hydroxymethyl furan-formaldehyde condensa-tion products.
Furan resins have been known to the ar-t for many years. Heretofore furan resins made by homopolymerization of furfuryl alcohol or copolymeriza-tion of furfuryl alcohol with formaldehyde have been characterized by -the presence of a variety of resinous componen-ts, including homologs of difurfurylmethane, difurfuryl ether, and furfuryl alcohol, in addition to polyfunctional species. This complex mix-ture has rendered the resins water insoluble requiring dilution with organic solvents such as furfural or furfuryl alcohol to reduce viscosi-ty and to increase application ease and efficiency. However, there are environmental problems associa-ted with the use of organic solvents~
The present invention is directed to the use of furan resins diluted with substantial amounts of water to acts as binders in the manufacture of composite articles. The furan resins diluted with water used in accordance with this in-vention are resinous high hydroxymethyl furan-formaldehyde condensation products. sy resinous high hydroxymethyl furan-formaldehyde condensation products is meant furan-formaldehyde condensa-tion products in which the majority (over 70%) of the molecular moieties are polyhydroxymethylat-ed, i.e. contain 2 or more hydroxymethyl substituents. Thesehigh hydroxymethyl furan-formaldehyde condensation products are in contrast to typical furfuryl alcohol-formaldehyde resins which contain less than 50% polyh~droxyme-thyl ter-minated structures and significant amounts (5 to 20%) of furan ring terminated compounds devoid of hydroxymethyl termination. A preferred product is a mixture ~ b~36 oE monomeric (20-40~) and polymeric (80-60%) 2,5~tbis-hydroxymethyl)furan. Furan compounds which can be polyhydroxy-methylated include compounds of the formula:

l~R

wherein R is selected from the group of H, or hydroxymethyl.
These resinous p~oducts have a viscosity, prior to dilution, in the range 5,000 to 100,000 centipoises Brookfield viscosity at 25 C., preferably in the range 7,500 centipoises to 25,000 centipoises.
The high hydroxymethyl furan-formaldehyde condensa-tion products can be produced in a number of ways, for example, by acidic polymeri2ation of 2,5-(bis-hydroxymethyl)furan and by the hydroxymethylation of furfuryl alcohol with formaldehyde using a weak acid such as, fox example, acetic acid, propionic acid, or formic acid at a pH above 4. A preferred method for producing such products comprises hydroxymethylation of a furan ring-termin~ted compound having the formula.
~3~
O R

' wherein R is selected from the group of H or hydroxymethyl by ~0 contacting said compound with formaldehyde in the presence of a catalytic amount of an acid catalyst having a pKa value at 25 C~ between 3.0 and 5.0 inclusive under conditions which provide a reaction mixture having a room temperature acidic pH greater than or equal to 4.0, said contacting taking place between 50 C~ and 160 C., inclusive.
For use in accordance with this invention as binders in manufacturing composite articles, the high hydroxymethyl furan-formaldehyde condensation products are diluted with water in amounts up to about 50~ by weight. The amount of water to be used can be varied within this maximum to obtain working liquids having a desired viscosity for a particular application. The relationship of viscosity and water con-centration for an illustrative water-dilutable high hydroxy-methyl furan-formaldehyde resin is illustrated in the Figure of the drawing.
As can be seen from the drawing, the~ viscosity of the illustrative resin is decreased from an initial viscosity of about 18,000 centipoises to a viscosity of about 10.1 centipoises when diluted with water in an amount of 50~ by weight. Water dilution affords the significant advantage of permitting a formulator to formulate resin compositions with a latent catalyst which can be activated upon heating of the resin to cure the resin to a thermoset state.
Compositions used according to this invention comprise a high hydroxymethyl furan-formaldehyde condensa-tion product, water in an amount up to 50% by weight of theresin and a latent catalyst which, under the influence of elevated temperatures, cures the resin to a hardened thermoset condition. Any acid catalyst which does not cause curing of the water-diluted resin at ambient temperatures but which becomes active at slightly elevated temperatures to cure the resin can be used. However, strong acid catalyst~ which would adversely affect the manufactured article should be avoided.
~or example, when a composition in accordance with this inven-~ tion is used as a binder in the manufacture of particle boards, 25 3 strong acids such as sulfuric or hydrochloric acid should notbe used because of possible adverse effect on the finished particle board. Generally speaking, the latent heat activated catalysts employed to cure the compositions according to this invention are those acids or acid-producing compounds which do not trigger polymerization at ambient temperatures but which trigger polymerization at temperatures above about 200 ~.
such as, for example, maleic acid, oxalic acid, zinc chloride, ammonium lignosulfonate and the like.
The latent catalysts are senerally employed in catalytically effectiv~ amounts up to about 20~ by weight 33~i of the resin. Higher amounts of catalyst can be used, but higher amounts tend to be wasteful except when a catalyst such as ammonium lignosulfonate is employed as a-catalyst and extender. Temperatures on the order of 200 to 475 F. are generally suitable for curing the resin to a hard thermoset condition in periods of several minutes to 0.5 hour. If faster rates of cure are desired, the catalyst concentration and/or the curing temperatures can be increased.
As illustrative of the preparation of a resinous high hydroxymethyl furan-formaldehyde condensation product used accordin~ to this invention, the following example is set forth herein.

EXAMPLE
In a reaction vessel equipped or atmospheric reflux and for distillation under vacuum, paraformaldehyde and furfuryl alcohol are charged in a molar ratio of 1.25 paraformaldehyde/furfuryl alcohol. Acetic acid (4% by weight glacial, based on the weight of the furfuryl alcohol), water (10% by weight based on the weight of the other ingredients;
9% of the reaction mixture)'are also added to the reaction vessel. The charge is mixed and refluxed under atmospheric conditions for approximately 8 hours, at which time approxi-i mately 80~ of the furfuryl alcohol is converted. The reflux , temperature under atmospheric conditions stays at approxi-mately 108 C. During the course of the reaction, smallsamples are taken and viscosity is checked on a Brookfield viscometer. Initially the viscosity of the reaction mixture is approximately 18 centipoises and the reflux is allowed to continue until the Brookfield viscosity,reaches about 60 centipoises at 25 C. This typically takes about 8 hours.
The arrangement of the reaction vessel is then transferred to the vacuum distillation mode and the reaction mixture is distilled under vacuum until the bottoms tempera-ture of about 140 C. at 60 mm/Hg is observed. The viscosity ~3~

of the bottoms is then measured and the distillation is con-tinued, if necessary, to provide a viscosity of 10,000 centi-poises + ~,000 centipoises.
During the course of this distillation, acetic -~ acid, water, formaldehyde and unreacted furfuryl alcohol are removed overhead.
The resultin~ 10,000 centipoise viscosity product, upon analysis, shows 2% furfuryl alcohol, 1% formaldehyde and 1% water remaining in the product. This distillation residue product is referred to herein as BHMF Resin. ~pon addition of 10% water to this product, a viscosity of 350 centipoises is achieved and on addition of 30% water a viscosity of 30 centipoises is achie~ed.
One embodiment of the present invention relates to the use of high hydroxymethyl furan-formaldehyde condensation products diluted with water as a binder in the manufacture of particle boardO As is known in the art, wood particle boards are prepared by compression of woody particles such as sawdust, bark, shavings and chips into rigid sheets. Urea-formaldehyde resins and phenol-formaldehyde resins are commonly used as binders in the manufacture of the particle boards. Various methods of formin~ the boards and incorporatin~ the binder with the matrix-forming particles are known in the art. Both ~ the urea~formaldehyde and phenol-formaldehyde resins can be diluted with water to form low viscosity solutions having viscosities of less than 500 centipoises (Brookfield viscosity at 25 C.) and preferably about 100 centipoises capable of being sprayed uniformly onto the wood particles. The phenol-formaldehyde resins exhibit better moisture resistant properties and are thus preferred for use in forming board products which in use will be exposed to moisture, such as in exterior building applications. A major objection ko the use of ~he urea~
formaldehyde and phenol-formaldehyde resins, in addition to their cost, is khe tendency of the resins to emit objectionable water and air pollutants such as formaldehyde and phenol during fabrication and under use conditions. ~eretofore the use of furan-formaldehyde resins as binders in the manufacture of partiele board has not been generally feasible because to obtain a low viscosity, sprayable binder solution it was necessary to employ solvents such as furfuryl alcohol or urfuralO These organic solvents entail certain fire and toxic hazards and also tend to impregnate or soak into the board, adversely affectiny the overall strength of the particle board.
Thus, in accordance with our invention, an appropriate high hydroxymethyl furan-formaldehyde condensation product is diluted with water to produce a low viscosity liquid, the viscosity being less than 500 centipoises (Brookfield viscosity at 25 C.), and used as a binder in the manufacture of partiele board. By the use of the high hydroxymethyl furan~formaldehyde condensation products diluted with water, the problems associated with use of organie solvents in the manufacture of particle board are eliminated. The use of water-diluted high hydroxy-methyl furan-formaldehyde condensation products as binders in the manufacture of composite articles has general applicability.
The water-diluted condensation products can be used as binders in the manufacture of pressure molded medium or high density eomposite articles such as partiele board, wafer board, ~ oriented fiber board, matboard, hardboard, pressboarcl, fiber-. glass board, ete. and in the manu~aeture of low density non-molded composite artieles sueh as aeoustieal tile and thermal insulating mats or boards. Various methods of manufacturing the pressure molded high density composite articles and non molded low density composites are known in the art using as matrix-forming materials a resinous binder and glass fiber, woody particles sueh as sawdust, bark, shavings and chips as well as other fibrous lignocellulosic materials such as straw~
bagasse, corn stalks, cork and the like. The binder composi-tions of this invention can be used in accordance with the known manufacturing procedures.

For purposes of illustrating this invention, high hydroxymethyl furan-formaldehyde condensation products diluted with water were used as a binder in the manufactuxe of wood _ particle boards. The boards were manufactured by spraying 5 binder solutions on wood particles (Pallman flaker chips~ in a 4 foot diameter by 2 foot deep rotating drum. An air atomi-zation gun having a nozzle insertable into the drum was used to spray the liquid binder on the wood particles. Spraying of the binder solutions on the chips was done over a period of about 2 minutes to insure uniform distribu~ion o the binder on the wood particles while they were being rotated.
After application of the binder, the wood particles were removed from the rotating drum and formed into a mat. The mat was then pressed at a pressure of 600 psig between metal caul platens at a temperature of about 350 F. for about 7 minutes at which time the pressure was gradually released.
This temperature was sufficient to cure the binders into a rigid thermoset condition. Resin and wood quantities were calculated so as to give a l/2 inch nominal thickness wood particle board with a density of 0.7 and a resin solids content o 7~. Binder formulations and board properties are shown in the following Table Io .
3~j o O a~
-dP ~ I I r~1 ~ a~ u~ o In o ~i ~ ~) ~, 3 ~, O ~ '~ U~ ~ ~ ~ C;~ ~ O O

rl O ~ r~ D N ~1 ~1 O Q~ c~ n ~ N
~I N N N N N ~1 N ~ _ ~Do ~1 X I N ~ ~0 Q
~g O ~ O
_ ~ ~ ~ t, ~l ~ O ~ ~ U ) r~ ~ O r~ ~
h r ~n ~ ~ o~ ~ ~ o ~ o o r ~ ~
H o Q~ ~-1 ~1 ~I r-l ~1 ~ r L~, H ~ r rl 11 J ~ ~

h O

~ ~ - u~

~q 2 ~ r~

~2~ 3~

Ammonium lignosulfonate, a low cost by-product from the paper industry, can be used as a catalyst for cuxing the high hydroxymethyl furan-formaldehyde water-diluted condensa-tion products and it also serves as an extender therefor.
S Wood particle boards were prepared by the general procedure described above with varying amounts of ammonium lignosulfonate incorporated with the resin. The binder compositions and board properties are shown in Table II.

r?~ 6 ~ o2 n ~ V ~ ~ ~( ~
O ~ O

O ~D ~ ~D ~
~ O ~

H ¦ ~ ~ o r-- ~ ~ :' ~ . ~ ~

._ r~ o o u~ o ~Z O ~ ~ --i N

O O 11~ 0 .
33~

Utilizing the same general procedure as described for manufacturing wood particle boards referred to in Table I, a number of wood particle boards were manufactured using _ various binder formulations. The binder formulations and 5: board properties are shown in Table III.

TABLE III

2 hour Water Boil Wet Mbdulus Mbdulus Mbdulus Internal of of of Board BinderBond Rupture Elasticity R~pture Number Formulation (psi) (psi) (psi) x 106 (psi) 1 140.7 gm BHMF Resin 130 1840 .26 668 86.6 sm Water 10 gm 50/50 Furfural/
Maleic ~ lydride 2 129 gm B~MF Resin 147 1965 .28 710 19.7 gm Amm~nium Lignosulfonate 51.6 sm Water

3 115 gm BHMF Resin 86 1343 .22 256 1.16 gm Pmmonium 1 Li~nosulfonate l 4 97.5 gm Urea 2 Formaldehyde Resin 100 1889 .27 Dissolved 97.5 gm BHMF Resin 33.8 gm Water 30 5150 gm Urea 2 Formaldehyde Resin 97 1710 .24 Dissolved 75 gm B~MF Resin 20 ym Water 1 50% water solution of Pnn~ium lign~sulfonate 35 sold ccmmercially as Orzan A
~rea-forn~ldehyde resin sold by Borden Chnical Co.
as Caseo~Resin 12-4039A (67% solids~

Q33~

~ 12 -In accordance with another embodiment of the invention, water-diluted hiyh hydroxymethyl furan-formal-dehyde condensation products are employed as a binder for glass fibers to form insulation ba-tting. As illus-tra-tive of this embodimentr the BHMF Resin was diluted with 30% water -to provide a solu-tion viscosi-ty of 40 centipoises. To this solution was added 5 parts per hundred resin of 50%
aqueous zinc chloride and the solution was spray applied -to glass fibers. After spraying, ~he glass fiber BHMF Resin matrix was placed in an oven at 212 F. and heated for about 0.5 hour. During heating, water of solution was removed and the resin cured acting as a binder for the glass fibers. Cure was demonstrated by the rigid insoluble na-ture of the resins. The pickup of tl~e resin binder is shown in the following Table IV.

TABLF IV
Tria _ Trial 2 Trial ~_ Wt. glass before spray (grams11.3 16.6 19.
20 Wt. glass after cure (grams) 29.3 22.2 70.2 Percent resin binder pickup 159.3 33.7 261.9

Claims

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. In a method for manufacturing a composite art-icle wherein a resinous binder is applied to matrix-form-ing particles and then cured to a thermoset condition, the improvement which consists in employing as a binder a high hydroxymethyl furan-formaldehyde condensation product di-luted with water.

2. The improvement in accordance with claim 1 wherein there is employed a high hydroxymethyl furan-formaldehyde condensation product diluted with water in an amount up to about 50% by weight.

3. The improvement in accordance with claim 1 wherein the composite article is a pressure molded high density composite article.

4. The improvement in accordance with claim 1 wherein the composite article is a non-molded low density composite article.

5. The improvement in accordance with claim 1 wherein the composite article is a wood particle board.

6. The improvement in accordance with claim 1 wherein the composite article is a fiberglass board.

7. The improvement in accordance with claim 1 wherein the composite article is an acoustical tile.

8. The improvement in accordance with claim 1 wherein the composite article is a thermal insulating mat.

9. A composition for use as a binder in the man-ufacture of composite articles comprising a high hydroxy-methyl furan-formaldehyde condensation product, water and a latent catalyst which under elevated temperatures but not at ambient temperatures is activated to cause curing of the condensation product to a rigid thermoset condition.

10. A composition in accordance with claim 9 wherein the latent catalyst is ammonium lignosulfonate.