CA1229449A - Preparation of lignocellulosic-isocyanate molded compositions using a copolymer of a functional polysiloxane-carboxylic acid or salt thereof as release agent - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improvement is provided in the compression molding of lignocellulosic composite articles, such as particle or flake board, in which polyisocyanate binder systems are employed, the improvement being the provision of a copolymeric reaction product of a functional poly-siloxane and a monocarboxylic acid or metal salt thereof as release agent on the mold surfaces to give multiple release.
Optionally organopolysiloxane fluid may be employed along with the copolymer as a diluent.

Description

PREPARATION OF LIGNOCELLULOSIC ISOCYANATE lulled COMPOSITIONS USING A COPOLYMER OF A FUNCTIONAL POL~IL5XA.h7 AND A CARBOXYLIC ACID OR SALT THEREOF AS RELEASE AGENT

BACKGROUND OF THE INVENTION
The present invention relates to the compression molding of lignocellulosic materials into composite bodies, sheets and the like and more particularly to a method for preparation of particle board with a polyisocyanate binder and the use of a functional polysiloxane-monocarboxylic acid or metal salt copolymer as a release agent capable of pro-voiding multiple release from the forming mold surfaces.
The molding of lignocellulosic and lignocellulosic-containing fibers, particles or layers to form composite en-tides is known. Organic dip and polyisocyanates as useful binders for lignocellulose materials have been known for some time and give to particle board products increased stay ability and mechanical strength; see, for example, US. Pat-ens Nos. 3,428,592; 3,440,189; 3,557,263; 3,636,13~; 3,870, 665; 3,919,017 and 3,930,110. It is also known in the art that the isocyanate binders are mixed with the wood particles utilized as the base for the particle board. wood chip or particle and isocyanate binder mixture is then formed into a mat and molded with pressure and temperature to the . .

desired size or shape. Water emulsion pol~isoc~a~a~e binder systems for use with lignocellulo,ic particle, Jo prepare particle board are also known. A principal Dodd-vantage of two use ox isocyanates in the predation or particle board is due to their excellent adhesive properties. Thus, isocyanate systems, either the water emulsion or the straight polyisocyanate binders, stuck tenaciously to tune metal caulk plates which are employed to support the wood particles during transporting anc3 two pressing or molding processes. Such poor release o the molded particle board From the caulk or mold surface creates difficulty in the cleaning and automatic handling of the ; caulk. In order to prevent the sticking problem, external release agents have been developed and applied to the caulk plates or litanies or mat surface as described for example in U. I. Patent No. 4,110,3~7. Other conventional release agents such as oils, waxes, polishes, silicones and polyp tetra~luoroethylene have been unsatisfactory as have the specialized urethane release agent including those used in on structural foam applications. Another method to overcome the slicking problem has Zen to overlay the isocyanate bound lignocellulosic particles with a veneer of wood as shown, for example, in USE Patent Lucy. 3,390,110;
7,219 and yo-yo or with the use ox a release paper. These methods have the disadvantage of either adding more cost to the product or of not fully utilizing the superiority ox the isocyanate binder. Many of the release accents developed to date have to be applied during every composite produc~iorl suckle in large quantities to be on effective.

I
SUMMARY OF THE INVÆNTIO~1 The present invention provides for tune prepare-lion of lignocellulosic composite articles or skeets we an comprises shaping in a mold or bet~,J~en molt suracPs a mixture of lignocellulosic particles and a pol~isocyanate based binding agent, there being provided on the molt surface or surfaces a calmer of a functional polyp selection and a monocarboxylic acid or metal salt Thor as release agent which may also be admixed wit an organopol~-lo selection fluid as a delineate.
It is an object of the Rosen invention to provide novel compositions which serve as release agents and provide for multiple release of tune molded articles.
Another object is to provide release agents which are readily applied and adhere to the mold surfaces.
A further object is to provide release agents which need only be applied in small amounts.
These and other objects and advantages of this invention will become apparent from the description of the invention and from the claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a method or the preparation of lignocellulosic cotnposite molded articles, particularly particle board, by bonding together wood chits or other lignocellulosic or organic material using heat and pressure with an organic polyisocyanate employed as the binding agent and with the application of a film of release agent by dipping, spraying or wiping of a copolymer of a junctional polysiloxane and a monocarboxylic acid or metal I salt thereof to the mold surface or surfaces. A functional I

polysiloxan2 having tune formula If I I EYE
(Chihuahuas S So t OSi(CH~)3 wherein n is an integer of from 5 to 30, m is an integer of from 1 to I and X is a group selected from -KIWI, fH3 -C HUH, -c o n I, -COY or -OH
c~3 c~3 is reacted with a monocarboxylic acid or a metal salt of the monocarboxylic acid which has the formula C~3-(CH2)y~COOz wherein y is an integer of from 5 to 24 and z is selected from H, Nay H, Cay Be, Cud, My, K or Fe, to form the copolymer release agent of the present invention.
For essentially permanent release or longer production use cycles the mold surface or surfaces with film applied may be heated to between 75C. and 200~C. for from 1 to 5 minutes before use.
The molded lignocellulosic composite such as, for I example, particle board or Blake board is generally prepared by spraying the particles with the polyisocyanate binder as they are being mixed or agitated in suitable and conventional equipment such as a blender. Suitably, the olyisocyanate binder use levels, based on the weight of oven dried I moisture content) lignocellulosic material is from about 1.5 to 12 and preEorably 2.5 to 6.5 weight percent. Other materials such as fire retardants may also be added to the particles or sprayed with the binder during the blending or mixing step.
After forming a uniform mixture the coated lignocellulosic particles are formed into a loose mat or felt in the desired proportions onto a caulk plate o' polished aluminum or steel which serves to carry the "kiwi"
into the heated press to consolidate the wood par~icl3s into a board of desired thickness. Temperatures of tune press are generally between about 140 and 220C. and pressures of from about 10~ to 60~ psi. Pressing times are from about 1 to 10 preferable 3 to 5 minutes. Pressing times, temperatures and pressures vary widely depending on the thickness of the board produced, the desired density of the board, the size ox the lignocellulosic particles used, and other factors well known in the art.
The isocyanat2 binding agent will generally be an organic polyisocyanate used alone but may also be in admix-lure with another type of binding agent, e.g. a synthetic resin glue, or in admixture with delineates such as propylene carbonate. The isocyanate may be applied in liquid form, as a solution in an inert solvent or in the form of an aqueous emulsion.
I The polyisocyanate component which is used in the present invention in the binder system can be any organic ~olyisocyanate and include aliphatic, alicyclic and aromatic polyisocyanates that contain at least two isocyanate groups per molecule. Such polyisocyanates include the dozes-notes and higher functionality isocyanates. Mutters of polyisocyanates may be used which for example are the mixtures of dip and higher functional polyisocyanates produced by ~hosgenation of aniline-formaldehyde condensate or as described in US. Patent NQS~ 3,952,302 and 3,919,279.
on The organic polyisocyanates may be isocyanate-~nded propel-mere made by reacting under standard known conditions, an excess of a polyisocyanate with a polyol which on a polyp isocyanate to polyol basis may range from about 20 1 to 2:1 and include for example polyethylene glycol, polypropylene glycol, triethylene glossily, etc. as well as glycols or polyglycols partially esterified with carboxylic acids including polyester polyols and polyether polyols.
Illustrative of organic polyisocyanates which may be employed include for example, Tulane- and

2,6-diisocyanates or mixtures thereof, diphenylmethane diisocyanat m- and p-phenylene diisocyanates or mixtures thereof, m- and p-diphenylene diisocyanates, polyethylene p31yph~nyl isocyanates, naphthalene-l, 5-diisocyanate, ; chlorophenylene diisocyanate,c~c~ -zillion diisocyanate, triphenylmethane triisocyanate, hexamethylene diisocyanate,

3,3'-ditolylene-4,4-diisocyanate, battalion 1,4-diisocyanate, octylene-1,8-diisocyanate, 1,4-, 1,3- and 1,2-cyclohexylene diisocvanate and in general the polyisocyanates disclosed in US. Patent No. 3,577,358, 3,012,008 and 3,097,191~ The preferred polyisocyanates are the diphenylmethane dozes-Nate 2,4' and 4,4' isomers including the 2,2' isomer and the higher functional polyisocyanate and polyethylene polyphenyl isocyanate mixtures, which may contain from about 20 to 85 weight percent of the diphenylmethane diisocyanate isomers. Typical of the preferred pulses-notes are those sold commercially as "Rubinate-M~ Rub icon Chemicals, Inc.). In general the organic polyisocyanates will have a molecular weight in the range between about 100 and 10,000. The aqueous organic p~lyisocyanate or * Trade Mark , isoc~anate-terminatQd prepolymQr emulsions art gerlerally prepared by using any ox the techniques Nina in the art for the preparation of aqueous emulsions or dispersions prior to use ox tune compositor as binder. In general tune polyisocyanate is dispersed in -water in the presence Or an emulsifying or surface active agent which may be an of the emulsifying agents also known in the art including anionic and non ionic agents. Preparation of the aqueous emulsions may be carried out as described in US. Patent Nos.
3,996,154; 4,143,014 and 4,257,995 The lignocellulosic materials employed to prepare the molded compositions using polyisocyan~te binders include wood chips, Good fibers, shavings, sawdust, wood wool, cork bark and the like products from the woodworking industry. Fibers, particles, etc. from owner natural products which are lignocellulosic such as straw, flax residues, dried weeds and grasses, nut shells, hulls from cereal crops such as rice and oats end the like may be used. In addition, thy lignoeellulosic materials may be mixed with inorganic flakes or fibrous material such as glass fibers or wool, mica and asbestos as well as with rubber and plastic materials in particulate form. The li~noeellulose may contain a moisture (water) content of up to us percent by weight but preferably contains between 4 and 12 percent by weight moisture.
The release agents of the present invention consisting of a copolymer of a junctional polysiloxane end a monocarboxylic acid or metal salt thereof are prepared by WriteNow at a temperature of from about 50C. to 150C.
preferably 90~C. to 110C., an excess of a ~ilanol terminated functional polysiloxane having tune formula (Chihuahuas ooze I t OSi(CH3J3 C~3 n : X m wherein n is an integer of from 5 to 30, m is an integer of from 1 to 20 and X is a group selected from f~3 -SHEA, -CHOW, -C0~H, -COY or -OH
SHEA SHEA
with a monocarboxylic acid or a metal salt of toe monkery-boxlike acid having the Formula C'd3-(CH2)~-COO~ wherein y is an integer of from 5 to 24 and z is a group selected from Hydrogen, pa, H, Cay Be, Cud, My, K or Fe. The acid or salt May also be hydroxy substituted such as for example 12 ~ydroxystearic acid. The reaction may be carried out in the presence of inert solvents such as the aromatic or aliphatic hydrocarbons, e.g. Tulane, zillion, Bunsen, Hutton, hexane, etc. 5 to 50% solids solutions may be prepared by the condensation process but are preferably prepared and applied as in to 20% solids solutions.
Typical monocarboxylic acids or metal salts which may be employed to prepare the copolymer are or example caprice Laurie, palmitic, Starkey, oleic, linoleic and the like as well as potassium owlet, calcium Stewart, iron Stewart, sodium palpitate, cadmium Stewart, magnesium decant, etc.
As indicated herein above organopolysiloxane fluids may be employed along with the copolymeric functional poly~iloxane-monocarboxylic acid or monkery-boxlike acid salt release agents as a delineate and are used on amounts of from 0 to 25 weight percent, preferably from 10 to 20 weight percent based on -the total copolymer-organopolysiloxane fluid mixture. The organopoly~iloxan~
fluids suitable for use in this invention are generally alkyl-terminated polysiloxane fluids having from 1 to 18 carbon atoms bonded to the silicon atom. Examples o.
suitable organopol~siloxane fluids are those having allele radicals such as methyl, ethyl, propel, bottle, hQxyl, octal, decal, dedecyl, tet-radecyl, hexadecyl, octadecyl and the like; aureole radicals such as phenol and naphthyl and mixtures thereof. Generally, it is preferred that the organopolysiloxane be free of termina~-hydroxyl groups;
however, a small number of terminal-hydroxyl groups will no materially affect the mold release composition. The organopoly~iloxane may have a minor proportion of molecules with only one hydroxyl group or there may be a small number of molecules present carrying in excess of two hydroxyl groups. However, as mentioned previously, it is preferred that the organopolysiloxane be substantially free of hydroxyl groups. In general, the polysiloxane fluids Shelley have a molecular weight of between about 3,000 and 90,000 which is equivalent to a viscosity of between about 50 and 100,000 centipoises, preferably from about 100 to 5,000 centipoises. Optiroum results have been obtained in the lower portion of these ranges such as from about zoo to 500 centipoises. In addition, it is possible to combine high and low viscosity fluids to form a fluid having the desired viscosity range.
The organopolysiloxane fluids used in accordance on Jo with this invention may be repre.s~ntPd by tile or Rosin Ooze- Oozier R L R R
wherein OR and R" which may no thy same or different represent organic groups having from 1 to 18 carbon atoms, preferably alkyd groups having from 1 to 4 carbon atoms, and has a value of from 80 to about 150,~00, The novel mold release agents of the instant invention whether the copolymeric release agent alone or the copolymer admixed with an organopolysiloxane fluid, may be employed in a liquid organic solvent which would prefer-ably be sufficiently volatile to vaporize during the apply-cation process. Preferred solvers include Tulane, x~lene, Bunyan, naphtha type solvents, higher C4 to C10 alcohols such as isobutanol and hydrocarbon solvents such as perchloroethylene.
the co~olymeric release agent of the present invention may be applied to the mold surfaces as a concern-treated or dilute solution, water emulsion or as a dispel-Zion. It it preferred that thy release agent composition be delved in a volatile organic solvent such as a mixture ox Tulane and isobutanol and then sprayed, wiped or brushed onto the mold surfaces in the -form of a thin illume this may best be obtained by rubbing the mold Ursa or traces with a swab saturated with a solution ox the release composition. However, when practical, the mold surfaces may be sprayed with the composition to Norm a I thin film thereon.

~23~

Once the release composition ha, been Allah to the mold surfaces, it may be used immediate however, it is preferred that the coating be dried especially Lyon an organic solvent has been used. o'er referable, as indicated herein before the coated mold surfaces are heated to between about 7~ to 200C. for from 1 to 5 minutes to fill all pores and openings and to provide for an Essex-tidally permanent release or longer production use cycles.
The following examples are provided to illustrate 19 tune invention in accordance with the principles ox this invention, including examples of a comparative nature, but are not to be construed as limiting the invention in any way except as indicated by the appended claims.

580 grams of pine wood chips dried to a moisture content of 6 percent were placed in an open tumbler-mixer.
During tumbling 16 grams ox a diphenylmethane Assassinate-polyethylene polyphenylisocyanate (PMDI) mixture having a 46.5 percent diphenylmethane diisocyanate content as a binder was sprayed evenly onto the wood chips by an air pressurized system. 'two new aluminum caulk plates 12" x 12"
x 3/16" were wiped with a cloth saturated with a mixture of 10 parts ho weight of a so polymer of a sullenly (-SHEA) terminated polydimethyl selection, having a molecular weight of 28,00~ and 12 hydroxy Starkey acid and 90 parts by weight Tulane. The copolymer was prepared by charging 1 part by weight of the sullenly SHEA) terminated selection and 1 part by weigh 12-h~droxy Starkey acid into a 250 ml reaction Lucy. in 50~ by weight Tulane. the reaction was run for 4 hours at 95~r. in nitrogen with stirring. The reaction was cooled and dwelled wit Tulane_ Jo joy a 10 solids solution. The polyisocyanate coated wood clips err then preformed in a box 1~.5 inches square and 12 inches high which was supported by one of the release agent coated caulk plates and repressed to form a thick mat. The box was then taken out and the second coated caulk plate placed on top of the mat. The whole assembly was subjected to a temperature of 190C., pressed to stops at a thickness of 13mm and held for 4 minutes and the pressure released. The lignocellulosic (wood chip board) composite was easily released from the caulk plates. the board Mooney procedure as above was repeated six additional times using the same originally coated caulk plates with easy release of the composite.

The procedure of Example 1 was repeated except that the aluminum caulk plates wiped with the 28,000 mow wt.
sullenly terminated polydimethyl selection hydroxy Starkey acid copolymer release agent were heated at 176C. for 3 minutes prior to use. Seven repeated cycles ox hoard proper-anion and release at 190~C. were recorded.
E _ POLES 3 to 8_ Various copolymers ox sullenly terminated polyp dim ethyl selection, molecular weight 28,00Q, with a moo-carhoxylic acid or metal salt thereof were prepared by charging 1 part by weight of the sullenly and 1 part by weight of toe acid or metal salt into a reaction flask with $0% by weight Tulane. Roy reaction was run for four hours at ~5C in nitrogen with stirring and then cooled and diluted with Tulane to provide pa 10~ solids solution. Thy procedure of ~,xam~le 1 was repeated to Produce par~iclG
Burr using the release agents an giving the release cycles as indicated below.

CopolymerRelease C~C1DS
Example No Release Agent at 190C_ _ 3 Silanol(-CH2O~) terminated Polydime-thyl Selection and Calcium Stewart 5

4 Silanol(-C~l2O~) terminated Polydimethyl Selection and Iron Stewart Carbinol(-COH) terminated Polydimethyl Selection and Potassium Owlet 6 6 Carboxy(-COOH) terminated Polydimethyl Selection and l2-Hydroxy Starkey Acid 7 7 .Silanol(-C}~2OH) terminated Polydimethyl Selection and Caprice (decanoic) Acid S Silanol(-CH2OH) terminated Polydimethyl Selection and Palmitic (hexadecanoic) acid 7 SAMPLE 9_ the procedure ox Example 2 was repeated employing I of the copolymer of Example 1 mixed with 15% polyp selection fluid and diluted to a 10g solids solution with Tulane. Six repeated cycles of particle board preparation and release at 1~C. were recorded.

The procedure ox Example 2 was repeater employing an on 20 mixture of the copolymer of example and ply-: methyl selection fluid diluted to lo in 3 5~:5n mixture of Tulane and isobutanol. Six release cycles were recorder at 190C.

Exemplify Al oNrno 1, Example ] was repeated except that no releas~agent was applied to tune caulk plates. The prows lingo-cellulosic composite could not be released even after cooling down.

F.xam~les 1 an 2 were repeated except that the caulk slates in three composite preparations wore wipe with a 15% solution of zinc Stewart, aluminum Stewart and lithium Stewart in isohutanol. Only one cycle of release was recorded with each when hot ~190C.)

Claims (11)

1. The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:
   
   l. A copolymeric polysiloxane composition, useful as a release agent for lignocellulosic composite molded ar-ticles containing an organic polyisocyanate based binder, comprising the copolymeric reaction product of a functional polysiloxane having the formula:
   
   wherein n is an integer of from 5 to 30, m is an integer of from 1 to 20 and X is a group selected from -CH2OH, , -COOH, or -OH and a monocarboxylic acid having the formula CH3-(CH2)y-COOH, or a metal salt thereof, wherein y is an integer of from 5 to 24 and wherein the (CH2)y group may have one or more of the hydrogen atoms substituted by hydroxy or the (CH2)y group may be interrupted therein by a -CH=CH- group.
2. 2. The composition according to claim 1 wherein the functional polysiloxane is -CH2OH terminated.
3. 3. The composition according to claim 1 wherein the functional polysiloxane is terminated.
4. 4. The composition according to claim 1, 2 or 3 wherein the functional polysiloxane is -COOH terminated.
5. 5. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid of the copolymer is a 12-hydroxy stearic acid.
6. 6. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid of the copolymer is palmitic acid.
7. 7. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid of the copolymer is stearic acid.
8. 8. The composition according to claim 1, 2 or 3 wherein the metal salt is a sodium, lithium, calcium, bar-ium, cadmium, magnesium, potassium or iron salt.
9. 9. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid salt is calcium stearate.
10. 10. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid salt is iron stearate.
11. 11. The composition according to claim 1, 2 or 3 wherein the monocarboxylic acid salt is potassium oleate.