CA1229448A - Preparation of lignocellulosic-isocyanate molded composition using a terpolymer of a functional polysiloxane-isocyanate-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 polyisccyanate binder systems are employed, the improvement being the provision of a functional polysiloxane-hydroxyl substituted mono-carboxylic acid or metal salt-isocyanate terpolymer as a release agent on the mold surface or surfaces to give multiple release. Optionally, organopolysiloxane fluids may be employed along with the terpolymer release agent as a diluent.

Description

PREPARATION OF I,IGMOCELLULOSIC-ISOCYA~ATE MULLED
COMPOSITIONS USING A TERPOL~MER OF A FU~J~TIO~
POLYSILOXANE-ISOCYANATE-CARBOX~LIC SUE OP. SALT
THEREOF AS RELEASE AGENT

BACKGROUND OF TOE 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 the preparation of particle or flake board with a pulse-Senate binder and the use of a terpolymer which is the no-action product of a functional polysiloxane, an isocyanate, and a hydroxyl substituted monocarboxylic acid or metal salt thereof as a release agent capable of providing an ease of release and 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 stability and mechanical strength; see, for example, US. Patents Nos.
3,428,592; 3,4~0,189; 3,557,263; 3,636,199; 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 tune base for the particle ode. h wooded phi or particle and isocyanate binder mixture i, then formed into a mat and molded with pressure and temperature to the desired size or shoe. water emulsion polyisocyan~te binder systems for use with lignocellulosis particles to prepare particle board are also Known. A reinitial disadvantage of the use of isocyanates in the preparation of particle 'Hoard is dye to their excellent adhesive properties. Thus, isocyanate systems, either the water emulsion or the straight polyisocyanate binders, stick tenaciously to the metal caulk plates which are employed to support the wood particles during transporting and the pressing or molding processes.
Such poor release of 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 platens or mat surface as described for example in U. S. Patent No. 4,110,397~ Other convent tonal release agents such as oils, waxes, polishes, silicones Ann polytetrafluoroethylene have been ~nsatis-factory as have the specialized urethane release agents including those used in structural foam applications.
Another method to overcome the sticking problem has been to overlay the isocyanate bound lignocellulosic particles with a veneer of wood as shown, for example, in US. Patent Nos. 3,39~,110; 4,197,219 and 3,919,017, or with the US I a release paper. These methods have the disadvartta~e of either adding more cost to the product or of not fully utilizing the sup wrier ox the isocyanate binder. Many of the release agent developed to date have to be applied during edgier composite production cycle in large quantities to be effective.

SUMMARY OF THE INVASION
The present invention provides for the preparation of lignocellulosic composite articles or sheets which comprises shaping in a mold or between mold surfaces a mixture of lignocellulosic particles and a polyisocyanate based binding agent, there being provided on the mold surface or surfaces a terpolymer of a functional polysiloxane, an isocyanate and a hydroxyl substituted monocarboxylic acid or metal salt thereof as a release agent, which release agent may also be admixed with an organopolysiloxane fluid as a delineate.
It is an object of the present invention to provide novel compositions which serve as release agents and provide for multiple release of the molded articles.
Another object it 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.

RETAILED Description I THE INVENTION
The present invention comprises a method or the preparation of lignocellulosic composite molded articles, particularly particle board, by hounding together wood chips or other lignocellulosic or organic material using heat and pressure with an organic polyp isocyanate employed as the binding agent and with tune application of a film of release agent by dipping, spraying or wiping of terpolymer formed by reacting a functional polysiloxane, an isocyanate and a hydroxyl substituted monocarboxylic acid or metal salt thereof to the mold surface or surfaces. A functional polyp selection hazing the formula (Chihuahuas I OOZE So oSi(CH3)3 wherein n is an integer ox from 5 to 30, m is an integer of from 1 to 20 and x is a group selected from -SHEA, SUE
-SHEA, -COO, -KIWI or I is reacted with a hydroxyl SHEA SHEA
substituted monocarboxylic acid or a hydroxyl substitute metal salt ox the monocarboxylic acid having the formula CH3-(CH2)~-COOz wherein hydrogen, Nay H, Cay Be, Cud, My, K or Fe which in turn is reacted with an isocyanate having the formula R-NCO wherein R is a group selected from CH3-CH2)y~ -C~2(CH2)Y~CO' Al, Al or Al Al NO
< I<

SUE -NO, Pal being hydrogen or an alkyd on group having from 1 to 6 carbon atoms and y is an integer of from 1 to I to form the terpol~mer release agent of the present invention. For essentially permanent I as or longer production use cycles the molt surface or surfaces with film applied may be 'netted to between 75C.
and 200C. for from 1 to 5 minutes before use.
The molded lignocellulosic composite such as, for example, particle board or Lowe board is generally prepared by spraying the particles Whitney the polyisocyanate binder as they are being mixed or agitated in suitable and conventional equipment such as a blender. Suitably, the polyisocyanate binder use levels, hosed on the weight of oven dried (0% moisture content) lignocellulosic material is from about 1.5 to 12 and preferably 2.5 to 5.5 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 coaxed lignocellulosic particles are formed into a loose mat or felt in the desired proportions onto a caulk plate of poll hod aluminum or steel which serves to carry tune "cake into the heated press to consolidate the wood particles into a board of desired thickness. Temperatures of the press are generally between about 143~ and 220C.
and pressures ox from about 100 to ~00 Sue Pressing times are from about 1 to in preferable 3 to 5 minutes. pressing times, temperature and pressures vary widely depending on the thickness ox the board produced thy desired density ox the board, the size of the lignocPllulosic particles used, and other factors well known in the art.
on The isocyanate binding agent will generally be I _ an organic polyisocyanate used alone jut may also ye in admixture with another type of binding agent, e.g. a synthetic resin glue, or in admixture with delineates Such as propylene carbonate. the isocyanate my be applied in liquid form as a solution in an inert solvent or in the form of an aqueous emulsion.
The polyisocyanate component which is used in the present invention in the binder system can ye any organic polyisocyanate and include aliphatic, alicyclic lo and aromatic polyisocyanates that contain at least two isocyanate groups per molecule. Such polyisocyanates include the diisocyanates and higher functionality isocyanates. Mixtures ox polyisocyanates may be used winch for example are the mixtures of dip and higher functional polyisocyanates produced by phosgenation of aniline-formaldehyde condensate or as described in US. Patent Nos. 3,962,302 and 3,~19,279. The organic polyisocyanates may be isocyanate-ended prepolymers made by reacting under standard known conditions, an excess of a polyisocyanate with polyol which on a polyisocyanate 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 diisocyanate, m- and p-phenylene diisocyanates or pa mixtures thereof, m- and p-diphenylene diisocyanates, polyethylene polyphenyl isocyanates, naphthalene-l, 5-diisocyanate, chlorophenylene diisocyanate, I -x~lene diisocyanate, triphenylmethane triisocyanate~ hex-ethylene diisocyanate, 3,3'-ditolylene-4,4-diisocyanate, battalion 1,4-diisocyanate, octylene-1,8-diisocyanate, 1,4-, 1,3- and 1,2-cyclohexylene diisocyanate 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 di~henylmethane diisocyanate 2,4' and 4,4' isomers including the 2,2' isomer and the higher functional polyisocyanate and polyethylene polyphenyl isocyana~e mixtures, which may contain from about 20 to 85 weight percent of the diphenylmethane diisocyanate isomers.
Typical of the preferred polyisocyanates are those sold commercially as "Rubinate-M" (~ubicon Chemicals, Ionic.
In general the organic polyisocyanates will have a molecular weight in the range between about 100 and 10,000.
The aqueous organic polyisocyanate or isocyanate-terminated pr~polymer emulsions are generally prepared by using any 20 of the technique known in the art for the preparation of aqueous emulsions or dispersions prior to use of the compositor as binder. In general the polyisocya~ate is dispersed in water in the presence of an emulsifying or surface active agent which may be any ox 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 4,2S7,995.
The lignocellulosic materials employed to prepare the molded compositions using polyisocyanate * Trade Mark 41~

binders include wood ants wood iris, sh~Jings, sawdust, wood wool, cork bark and the like prefects from the woodworking industry. iris, particles, etc. prom other natural products which are lignocellulosic sun us strati, flax residues, dried weeds and grasses, nut shells, hulls from cereal crops such as rice and oats and tune like may be used. In addition, the lignocellulosic materials may be mixed with inorganic flakes or Fibrous material suck as glass gibers or wool, mica and asbestos as well as with rubber and plastic materials in particulate form.
the lignocellulose may contain a moisture (water) content ox up to 25 percent by weight but prefer~ly contains between 4 and 12 percent by weight muzzler.
The release agents of the resent invention consisting of a terpolymer of a functional polysiloxane an isocyanate and a hydroxyl substituted monocarboxylic acid or metal salt thereon may be prepared by reacting, with or without an inert solvent such as aromatic or aliphatic hydrocarbons, e.g., Tulane, zillion, Bunyan, Hutton, hexane, to to control and maintain solution viscosity, at a temperature ox from about 5~C. to lSQC.
and preferably ~0C. to 110C. an excess of a sullenly terminated functional polvsiloxane having the formula Iffy ! IH3\

(C~1313SitOI i7toSi~OSi(CH3)3 jC~3 n X m wherein n is from 5 to 30, m is prom 1 to I and x is 1~3 a group selected prom -Clue, -foe, -COO, -fox or -OH, on C1~3 SHEA

with a hydroxyl substituted monocarooxylic acid or hydroxyl substituted metal salt of one monocar~oxylic acid having the formula CH3-(CH2)y~COOz -wherein y is an integer of from 5 to 24 and z is a group selected fro.
hydrogen, Nay H, Cay Be, Cud, My, K or Fe thus forming a copolymeric reaction product Russia is then reacted at a temperature of from about 50C. to 150C. preferably 90C. to 110C. with no more than a stoichiome~ric amount of an isocyanate having the formula RANCH wherein R
is a group selected from -CH2(CH2)yNCO~ Schick Al Al Al Al Al being hydrogen or an alkyd group having from l to 6 cartoon atoms and y is an integer of from 1 to 20 to form the terpolymer. The condensation reaction to form the terpolymer release agent may be considered completed when no free NO can be detected by known analytical methods such as Infer Red. The reaction with the isocyanates and copolymer reaction product may be carried out in the presence of from 0 to 50 weight percent inert aqueous free (dry) solvents containing no hyroxyl groups sun as the aromatic or aliphatic hydrocarbons, e.g. Tulane, zillion, Hutton, hexane etc. to maintain and control solution viscosity. 5 to 50% solids solutions may be prepared by the condensation process but are preferably prepared and applied as 10 to 20% solids solutions.
As indicated herein above organopolysiloxane fluid may be employed along with the terpolymer release agents as a delineate and are use in amounts of from 0 to 25 weight percent, preferably from lo to 20 weight percent selection fluid mixture. The organopol~silox~ne fly suitable for use in this invention are generally alp terminated polysiloxane fluids having from 1 to 18 carbon atoms bonded to the silicon atom. Examples of suitably organopolysiloxane fluids are those having alkali radicals such as methyl, ethyl, propel, bottle, Huxley, oxt~l, dozily, dedecyl, tetradecyl, hexadecyl, octadecyl and the like;
aureole radicals such as phenol and naphthyl and mixtures thereof. Generally, it is preferred that the organopoly-selection be free of terminal-hydroxyl groups; however, a small number of terminal-hydroxyl groups will not materially affect the mold release composition. The organopolysiloxane 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 hydrox~l groups. In general, the polysiloxane fluids should 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. Optimum results have been obtained in the lower portion of these ranges such as from about 200 to S00 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 with this invention may be represented by the formula R' r R' R' R-Si-¦ Ooze- I Ooze l l l l l I y wherein OR and R" which may be the same or different represent organic grouts having from 1 to I carbon atoms, preferably alkyd groups having prom 1 to 4 carbon atoms, and y has a value of from 80 to about 150,0~0.
The novel mold release agents of the instant invention, whether the polysiloxane-monocarboxylic acid or salt-isoc~anate terpolymer alone or the terpolymer admixed with an organopolysiloxane fluid, may be employed in a liquid organic solvent which would preferably be sufficiently volatile to vaporize during the application process. Preferred solvents include Tulane, zillion, Bunyan, naphtha type solvents, higher I to C10 alcohols such as isobutanol and hydrocarbon solvents such as perchloroethylene.
The functional polysiloxane-monocarboxylic acid or salt-isocyanate terpolymer release aunt may be applied to the mold surfaces as a concentrated or dilute solution or as a dispersion. It is preferred that the release agent composition be dissolved in a volatile organic solvent such as a mixture ox Tulane and isobutanol an then sprayed, wiped or brushed onto the mold surfaces in the form of a thin elm. This may best be obtained by rubbing the mold surface or surfaces with a swab saturated with a solution of the release composition. However, when practical, the mold surfaces may be sprayer with the I composition to form a thin film thereon.

Once the release composition nay teen Apple to the mold surfaces, it may be used immediately.
however, it is preferred that the coating be dried especially when an organic solvent has been used. -lore preferably, as indicated hereinbe~ore the coated mold surfaces are heated to between about 75 to 200C. for from 1 to 5 minutes to fill all pores and openings and to provide for an essentially permanent release or longer production use cycles.
The following examples are provided to illustrate the invention in accordance with the principles of this invention, including examples ox 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 diphenyl-methane diisocyanate-polyme~hylene polyphenylisocyanate (PMDI) mixture having a 46.S 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 terpolymer release agent mixture of 10 parts by weight of a polymerization reaction product of a sullenly (-SHEA) terminated polydimetnyl selection, having a molecular weight ox 28,000, 12-hydroxy Starkey acid, and a diphenylmethane diisocyan~te-polymethylene polyPhenyl isocyanate (PMDI) mixture having a 46.5~
diphenylmethane diisocyanate content and 90 parts by weight Tulane. the terpolymer Teas prepared by charging 50 grams of silanol(-CH2OH) terminated polydimethyl siloxane(MW 2~,000) and 6 grams 12-hydroxy Starkey acid into a 250ml reaction flask in 50% by weight Tulane.
The reaction was run for 3 1/2 hours at 90C. in nitrogen with steady stirring. The reaction was cooled and .23 grams of diphenylmethane diisocyanate-pol~ymethylene polyphenyl isocyanate (PMDI) having 46.5~ diphenylmet'n~n~
diisocyanate was charged into the reaction flask. The complete mixture of materials was reacted for 4 additional hours at 100C. in nitrogen under steady stirring at which time no tree NO could be detected by infer red analysis.
Tulane was added to make a solution of 10% 501 its. Tune polyisocyanate coated wood chips were then preformed in a box 10.5 inches square and 12 inches high which was supported by one of the terpolymer 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 ox the mat. Thy whole assembly way subjected to a temperature of 190C.~ pressed to stops at a thickness of 13mm and Hoyle for 4 minute and the pressure released.
The lignocellulosic (wood chip board) composite was easily released from the caulk plates r The board making procedure as above way repeated four additional times using the same originally coated caulk plates with easy release ox the composite.

he procedure ox Example 1 was repeated except that the aluminum caulk plots wiped with the sullenly terminated poly~imethyl selection hyrax Starkey acid-I

isocyanate terpolymer release agent mixture was ~atedat l76C. for 3 minutes prior to use. Six repeated cycles ox board reparation and release a l30C. were recorded.
EXAMPLES 3 to _ Various terpolymers of sullenly terminated pol~dimethyl selections, molecular weight 28,0~0, -with a monocarboxylic acid or metal salt thereof were Prepared by reacting l part by weight of toe sullenly and l part by weight of the acid or metal salt in a 250 ml reaction lo flask with 50~ by weight Tulane. The siloxane-acid reaction was run for four hours at ~5C. in nitrogen with stirring, cooled and then reacted with l part by weight of di~henylmethane diisocyanate-polymethylene polyisocyanate (PMDI) hazing 46.5% diphenyl methane diisocyanate which reaction was run for 4 hours at 100C.
in nitrogen with stirring until no free NO could be detected by infer red analysis. ~oluene was added to provide a lo solids solution. The procedure of Example 1 was repute to Produce particle hoar using the release agents and giving the release cycles as indicated below.

Terpolymer Release Cycles E ample No. Release Agent at 190C.

3 ,Silanol(-CH2OH) terminated Polydimethyl Selection and 12-Hydroxy Calcium Stewart 4 with PMDI

4 Sullenly (-SHEA) terminated Polydimethyl Selection and 12-Hydroxy Iron turret 5 with PMOI
Cardinal (-COIN) terminated Polydim2thyl Selection and

2-Hydroxy Potassium Owlet 6 with PMDI

Terpol~mer Release I 5 Example Jo. Release Agent at lgOC, 6 Car boxy (-COO) terminated Polydimethyl Selection and 12-~ydroxy Static Acid 7 with PMDI

7 Sullenly (-C~20H) terminated Polydimethyl Selection with 2-~y~roxy Caprice (decanoic) Acid and phenylisocyanate 5 8 Sullenly (-~H20H) terminated Pol~dimethyl Selection with 12-~ydroxy Palmitic (hexadecanoic) and hexamethylene diisocyanate The procedure of Example 2 was repeated employing 85% of the terpolymer of example 1 mixed with 15~ polysiloxane fluid and diluted to a 10% solids solution with Tulane. Six repeated cycles of particle board preparation and release at 190C. were recorded.
EXAMPLE lo The procedure of Example 2 was repeated employing an ~0:20 mixture of the terpolymer of Example 5 an polydimethyl selection fluid diluted to 10% in a 50:50 mixture of Tulane and isobutanol. five repeated suckle ox particle board preparation and release at 190C. were recorded.
EXAMPLE if CONTROL
I__ Example l was repeated except that no release agent way applied to the caulk plates. The pressed lingo-cellulosic composite could not be released even after cooling down.

Examples 1 and were repeated except that the on caulk plate in three composite preparations were wipe with a 15% solution of zinc Stewart, aluminum st~arag~
and lithium Stewart in isobutanol, Only on cycle of release was recorded with each when hot (19~C,).

Claims (12)

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

1. A terpolymeric polysiloxane composition, useful as a release agent for lignocellulosic composite molded ar-ticles containing an organic polyisocyanate based binder, which comprises the terpolymeric reaction product of a func-tional 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, with a monocarboxylic acid of the formula CH3-(CH2)y-COOH, or a metal salt thereof, wherein y is an in-teger of from 5 to 24 and wherein the (CH2)y group may be sub-stituted by hydroxyl, reacted with an isocyanate having the formula R-NCO wherein R is a group selected from CH3-(CH2)y,-;

-CH2-(CH2)y,-NCO; wherein R1 is hydrogen or an alkyl group having from 1 to 6 carbon atoms and y' is an integer of from 1 to 20.

2. The composition according to claim 1 wherein the metal salt is a sodium, potassium, lithium, cadmium, cal-cium, barium, magnesium or iron salt.

3. The composition according to claim 1 wherein the functional polysiloxane is -CH2OH terminated.

4. The composition according to claim 1 wherein the functional polysiloxane is terminated.

5. The composition according to claim 1 wherein the functional polysiloxane is -COOH terminated.

6. The composition according to claim 1, 3 or 4 wherein the hydroxyl substituted monocarboxylic acid of the terpolymer is 12-hydroxy stearic acid.

7. The composition according to claim 1, 3 or 4 wherein the isocyanate of the terpolymer is a polymethylene polyphenyl polyisocyanate containing from 20 to 85 percent by weight of diphenylmethane diisocyanate.

8. The composition according to claim 1, 3 or wherein the isocyanate of the terpolymer is hexamethylene diisocyanate.

9. The composition according to claim 1, 3 or 4 wherein the isocyanate of the terpolymer is phenylisocyanate.

10. The composition according to claim 1, 3 or wherein the isocyanate of the terpolymer contains from 20 to 85 percent by weight of diphenylmethane 2,4'-diisocyanate.

11. The composition according to claim 1, 3 or 4 wherein the isocyanate of the terpolymer contains from 20 to 85 percent by weight of diphenylmethane 4,4'-diisocyanate.

12. The composition according to claim 1, 3 or 4 wherein the isocyanate of the terpolymer contains from 20 to 85 percent by weight of diphenylmethane 2,2'-diisocyanate.