CA1093724A - Acrylic wood filler - Google Patents

Abstract

R.I. C-1700 ACRYLIC WOOD FILLER The wood filler is prepared from essential ingredients including, on weight percent basis, 6-14% acrylic resin, 3-10% platy talc, 3-10% barytes filler, 3-12% clay filler, 40-65% calcium carbonate filler and 13-35% water.

Description

R.I, C~1700 This invention relates to an acrylic latex wood filler which provides exceptional performance on both soft and hard ~pecies of wood. It spreads easily when applied, resists shrinking on dr~iny an,1 has a natural wood color.
Dry film of the wood filler stains superbly, is highly water reslstant and is easy to sand. It takes nai]s, screws and can be cut, whittled, drilled and planed as well as shellacked~
varnished and paintedO It has excellent adheslon to wood, me~al, paint and wallboard and is non-toxic and non-flammabl~, as defined ~y the Federal Hazardous Substances Act, with no harmful vapors and, unlike solvent type wood fillers, it is easy to remove with water from hands and tools before it dries.
The best known wood iller on the market today is Plastic Wood which is based on wood flour and nitrocellulose 1~ a~d has many disadvantages when compared to the wood filler d~scribea ana claimed herein. Plastic Wood is flammable r ev~lves toxic vapors, is very hard to spread, does not stain properly and is more difficult ~o sand and cleanO
The wood filler described herein is prepared from the ~ollowin~ essential ingredients, given in parts by weight~for ~he preferred and broad ranges:

preferredbroad acrylic binding resin 8-11 6-14 platy talc 4-6 3-10

2~ barytes iller 4-~ 3-10 clay filler S-9 3-12 calcium carbonate filler50~56 40-65 water 17-28 13-35

3~

RoI~ C~1700 The acrylic resln is derived from an acrylic emulsion which can be prepared from resiliency imparting or so.~t monomers and hard monomers~ The soft monomers are represen-ted by the following structural formula:

S Rl O
~ ll 2 H2C = C - C - OR

where Rl is H or an alkyl group of 1 to 4 carbon atoms and R2 is a straight chain or branched chain alkyl radical containing rom 1 to about 14 carbon atoms. Examples of R2 include methyl, ethyl, propyl, n~butyl, 2~ethylhexyl, hexyl, heptyl, octyl, 2-methylbutyl, l~methylbutyl, 2-methylpentyl, n~hexylisobutyl, decyl, dodecyl, etc. To further define the preferred so-ft monomer, when Rl is H or a methyl alkyl radical, R2 should con-tain 2 to 14 carbon atoms; and when Rl is alkyl of 2 to 4 carbon atoms, alk~l radical R2 should contain from 6 to 14 carbon a$oms~
A soft monomer(s) can be combined with a hard monomer(s) in certain proportion to yield an emulsion with desired properties for use in formulating the wood filler described herein.
The hard monomer(s)l which can be used in the preparation of the acrylic emulsion, are represented by the formula Rl Q
I ll 3 2C = C - C--OR

where Rl is as defined in connection with the soft monomer, i.e~, is H or an alkyl ~roup of 1 ~o 4 carbon atoms, whereas R3 is pre~erably alkyl selected fxom methyl and alkyl groups ccntaining from about 13 to about 20 car~on atoms when R is H;

r--3~2~

R.X. C~1700 and R3 is preferably alkyl containin~ 1 to 5 or from 15 to 20 carbon atoms when Rl is methyl. Examples o~ hard monomers include methyl acrylate, ~in~l acetate, tetradecyl acrylate, pentadecyl acr~late, methyl methacrylate, ethyl methacrylate, t-butyl acrylate, butyl methacrylate and pentadecyl methacrylate.
The designation Tg stands for glass transition tem-perature of a polymer and is a conventional criterion of polymer hardness. For applications where exceptional flexibility is not necessary, as in this case, Tg of the polymer can be between 0 and 25C. Examples of Tg fo~ the more common homo-polymers are given below:

Homopolymer of: Tg C
ethyl acrylate ~ 23 n-octyl acrylate ~ -80 n-decyl methacrylate ~ 60 . .
2 ethylhexyl acrylate ~~~--- -70 n-butyl acrylate ---~ -56 octyl me~hacrylate -~ -20 n-~etradecyl methacrylat~ ------ -9 2D methyl acrylate --~ -- 9 N-tetradecyl acrylate -- ---------~ 20 : t-butyl acrylate ----~ 43 methyl methacrylate ---------------~----- 105 acrylic acid -- -----~-------~-------~--- 106 These and other monomers can be blended to give the desired Tg.
The acrylic resins used in preparing our wood filler are in the form of aqueous acrylic emulsions~ Preferred acrylic emulsions for our purpose are white in color wherein the particle size range is 0.18 to 0.20 of a micron in diameterO Although other Rhoplex(T) acrylic emulsions, sold ~y P~ohm and Haas~ are suitable, Rhoplex E-330 and ~hoplex ~C-34 acrylic emulsions in 1:1 ratio perform eminen~ly in the wood filler compositionO
Rhoplex E~330 acrylic emulsion has a non ionic charge~ percent 3~
R.I. C~1700 solids content of about 47~ pH o~ 9.5 to 10rOr a minimum film-forming temperature range of 10 to 12Cj T~ o~ the polymer is 6 to ~C and i~s clear film ul~imate Tukon hardness (K~IN) is less than 1 or a~out 0.5. I~hoplex E-330 acrylic emulsion is believed to have been prepared from the following monomers given in weight percent:

methyl methacrylate 70%
butyl acrylate 30%
i Rhoplex AC-34 acrylic emulsion has a particle size range of 0~10 to 0.11 of a micron in diameter, Tg of 7 to 9C, a minimum film forming temperatuxe of 9C and the same solids and p~I as Rhoplex ~-330 acrylic emulsion, i~e., solids of about 47~ and p~ of 9.~ to 10Ø Rhoplex AC-34 acrylic emulsion is ~elieved to have ~een prepared from the following monomers 1~ given in weight percent:

ethyl acrylate 66%
methyl methacrylate 33%
acrylic acid 1%

The acid which is used in the preparation o~ the emulsions aids in cross-linking and is selected from unsaturated mono or poly-carbGxylic acids, examples of which include sorbic, acrylic~
acr~loxy-acetic, cinnamic/ maleic, fumaric, crotonic, i-taconic~
etcO The alpha-beta unsa~urated monocarboxylic acids are pre-~erred; especially acrylic and methacrylic acids. On the basis of dry resin in the emulsions, amount o~ the acid can vary from about 0~2 to 5%~ pre~era~ly from 0.5 to 3%. A small amount of about 1 to 3% of a nitro~enous compound can also be used in the ~5- .

10~3'7Z~
R.I. C~1700 preparation o the acrylic emulsions. An example of such a nitrogenous compound is dimethylaminomethyl methacr~late which acts as a softening monomer and as a stabilizer. Other lower-alkylamino loweralkyl acrylates and methacry:Lates as well as other nitrogenous compounds, can be used as is known in the axt.
An essential ingredient in the acrylic wood filler described herein is platy talc, such as Emtal #500 talc sold by ; - Engelhard Minerals and Chemicals. This specific talc is a naturally occurring hydrous non~metallic magnesium silicate exhibiting high brightness and low abrasion. This talc is platy in character with no trace of any fibrous talc or ashestifo~m minerals. Platy talc is soft with low abrasion, has good lubricity with excellent sanding and troweling~ is low in soluble salts which results in good chemical and ~ater resistance, and has excellent dispersion in organic media. The use of platy talc results in wood fillers which are non-cracking, hava high solids conten~ and good spreadability. Composition of Emtal #500 talc is the following, in weight percent:

magnesium oxide (MgO) 30.8%
si:Licon dioxide (SiO2) 56~2%
calcium oxide (CaO~ 0.4%
aluminum oxide (A12O3) 0O5%

Other typical physical properties of Emtal #500 talc are the following:

particle shape platy % on 200 mesh 0.01 3~

R.I. C~1700 ~ on 325 mesh 0.2 average particle size 9.0 microns P~ 9.3 - 9.
specific gravity 2.8 Another grade of Emta:L talc found to be suitable for our purpose includes Emtal #41 which is similar to Emtal ~500 except it is slightly denser and darker than Emtal ~500. Photo-volt brightness of Emtal #500 is 83~ as compared to 77~ for Emtal #41.
Fibrous or non-platy talcs such as Fibertal #2 and Fibertal ~6, were tried in the wood filler fo-mulations but produced undesirable results. Fibertal ~2, when substituted for Emtal #~00 resulted in a wood filler that - was excessively high in viscosity, difficult to manufacture and fill, and gave very poor spreading properties.
It also shrank more than the Emtal #~00 formulation and cracked slightly after drying. Fibertal ~6, when substitu-ted for Emtal #500, gave a more workable consistency but shrank and cracked more than the Fibertal #2 formulation.
Both Fibertals contain asbestos fibers which make them hazardous to health. It appears that the use of platy talc is mandatory to obtain a wood filler with excellent spreading properties and good viscosity stability for easy manufacture and filling. Due -to the presence of platy 2S talcs,the wood filler is resistant to sagging, shrinking and cracking during ana a~ter drying; and when dry, has excellent sandability.
Barytes is a heav~ ~iller being composed of about 9B~
barium sulfate and also contaîns 0.85~ silica, 0.009% ferric :

.

3~ ~J-~

R.I, C~1700 oxide and a maximum moisture of 0 25%. Its pH is 3.8 to

4.5 and oil absorption is 11. About 95% o~ bar~tes particles are less than 20 microns in diameter and 10% thereof have a particle size less than 1 mi.cron. The No. 1 Barytes s from Pfizer have been found to perform very well in the wood filler. The function of this filler is to allow ~or ~etter penetration of stain~
The clay filler is preferably ASP 400 aluminum silicate clay which can be obtained from Engelhard Minerals ~ Chemicals~ Its presence in the wood filler formulation facilitat~s sanding, reduces sagging, imparts proper pseudo-plasticity, makes it easier to accept stain probably for the reason that i~ has relatively large particle size, the average being at about 5 microns. About 90~ of this clay is smaller than 17 microns ana only 10~ is smaller than 1.6 microns. Its pH is 3.8 to 4.6 and oil absorption is 28 to 32.
The ~rincipal filler we use in the wood filler is calcium carbonate in~powder form of small particle size which is ~lended into the formulation to prvvide a crack-resistant ~D product which has good sandability. This filler also contributes to the proper consistency of the wood filler. The filler must have proper particl size since if it is too coarse, the spackle will be too fluid and it will settle out; and if too fine, the spackle will be difficult to spread and sand. The fillers pro-2~ mote proper consistency with high solids and texture of dry ~ilm which properties are related to non-shrinking, non-cracking and easy sanding features after drying. We prefer to use Chemcarb calclum carbonate which has a-mcan particle si2e of 12 microns, solubility in water of 0.06~, speci~ic gravity of 2.71, moisture i '7~
-R,I. C~1700 of 0.10% and p~ of 9.2 ~ 9.5. Its typical chemical composition is as ~ollows:

calcium carbonate 96.0%
magnesium carbonate (MgCO3) 3.0%
Silica (Si2) 0.50 alumina (A12 3) iron oxide (Fe2O3) 0.06%
mois~ure 0.10%

The mean particle size of the calcium carbonate filler lD herein is important to produce the wood illex with desired pro perties and should, in the preferred embodiment, be within the range o~ 11 to 13 microns although fillers with mean particle size o~ a~out 5 to 15 microns are suitable. Other gra~es o~ Chemcar~ ~iller which were found suLtable, although marginally in some cases, include Chemcarb ~44 which ~as a mean particle si~e of about 5 microns and Chemcarb which has a size of about 14 microns.
~nough water is added to the wood filler composition to o~tain a pasty consistency which translates into a viscosity ~0 ~hich should be in the range of about 120,000 to 250,000 and pxef~rably from 160,00Q to 180rO00 cps, Brookfield RVF with a ~7 spindle measured at 4 rpm and 25C. Its solids concentration should range within 75 to-Y0%, preferably about 82%.
~thex ingredlents are also adcled ~o th~ wood filler composi~ion including pigments~ pigmen-t dispersants, preservatives, ~ux~actants, deioamers, thlckeners, etc.
~r~paration procedure ~or the wood ~ er is quite ~traight forward. The ingredients are added to a blender and _g_ \

r---~3'7~

R~I. C-1700 mixed until a smooth and a homogeneous dispersion is obtained, which may take about one hour. Extra precaution is applied to add thickener very slowly with agitation.
Surfaces to which the wood filler is applied should be clean, dry and free of grease, oil and loose particles. The surface and the wood filler should be at a te~perature of 40F
or warmerO Application of the wood filler should be generous and excess can be removed with a putty knife but some extra wood iller should remain to allow for f-ush sanding after drying~ For normal repairs, one application usually su~ices although for deeper er~cks, two or more applications are better ~han one heavy one. The wood ~iller must dry between applications. Shallow repairs can be sanded aiter 15 minutes of application but deep repairs require 1 to 8 hours. ~void high speed sanding. If a machine sander is used, use on-off~on-off action. Desired finish may be applied af-ter sanding~ 1 hour being allowed for drying of wa~er~based paint and overnight for oil-based paint, shellac or varnishO ~Stain should be applied within 1 hour aiter sanding~ Staining requires medium to coarse sanding for ~est result-s~ If fine-sanded, stain will need more time for penetration~ For true wood matchj test wood scrap to determine proper stain color and time for bo~h filler and wood. AEter finishing a job/ tools and hands can ~e washed with water ~efore the wood filler ~ries.
Preparation of the wood iller described herein will now be illustxated by showing exact amounts o~ ingredients used therefor~

~xa .
The followin~ constitute ingredients ~or prepar~ng --10~

7~4L

~.I, C-1700 a specific formulation for a wood filler described herein, in weight percent.
(1) water 6.79 (2~ bacteriocide (Merbac 35~ 0.15 t3) ~acteriocide and ~ungicide ~Proxel CRL) 0~05 ~4~ surfactant (~riton X-405) 0.51

(5) pigment dispersant (Tamol 850) 0.21

(6) anhydrous potasslum tripolyphosphate 0.50 t7) nonionic surfactant (Nopco NXZ~ 0.03 (8) 47% solids acrylic emulsion (~hoplex E-330) 10051 (9) 47% solids acrylic emulsion (Rhoplex AC-343 10.00 (10) platy talc (Emtal #500) 5.13 (11) barium sul~ate filler (No.l Barytes) 5.13 : (12) clay filler (ASP - 400 clay? 7.18 (13) calcium carbonate filler (Chemcarb 55~ 53.38 (14) thickener (Methocel E-4-M~ 0.31 (15) coloring materia1 (CB-262-A 45~ yellow oxide) 0.12 100, 00 Merbac 35 is sold by ~.erck and contains at least 90~ benzyl bromoacetate. It is miscible with many organic solvents but ls iI~miscible with water. When dispensed, it is extremely effective against a broad spectrum of micro~
organlsms which attack raw materials resulting in putrefaction, viscosity loss, and spollage of aqueous systems in storage and stored containers. ~roxel CRL, which 1s water-soluble, is soid by IC~ America, Inc, and contains 30~ 1, 2-benzisothiazolin~3-one and is a bacteriacide-~un~icide added for extra protection against microorganisms~ Triton

7~

R.I. C-1700 X-405~ sold by Rohm and Haas, is octylphenoxy~pol~ethoxy ethanol nonionic surfactant containing 40 ethylene oxide units. I'amol 850, a sodium salt of glacial methacrylic acid sold by Rohm and Haas is a 30~ aqueous pigment S dispersant which is used to dispexse and stabilize pigments and extenders in aqueous systems. It is a low-foaming dispersant especially useful in systems involving dispersions in inorganic acids, such as titanium dioxide, and is efficient over a wide pH range in numerous latex system. Its pH is 9.0 to 10.5 (of a lO~ aqueous solution), freezing point of 0 to -10C, Brookfield viscosity (25C, ~2 spindle, 60 rpm) is 125 to 325 cps. Methocel E-4-M, sold hy Dow, is a hydroxypropyl meth~l cellulQse thickener~ Potassium tripolyphosphate is a pigment dispersant and wetting agent.
In preparing the wood :iller, ~l) was added with agitation to a ~lean, dry fibexglass bin which was followed ~y addi~ion of (2), -(3), (4~, (5~, (6), (7), (8~ and (9). Item ~6) was sprinkled-in. The dispersion was mixed 510wly for about 5 minutes and then, with continued agitation, items (10)~ (ll), ~121 and (13) were added with precautions taken to avoid lumping.
The agitator bow-tie blade was raised to just below the surface of the dispersion and ~ was sprinkled-in under medium agitation of the contents Item (15~ was added and slow agitation of the dispersion was continued for about one-hal~ hour or until it ~ecame smooth and homogeneous. A sample was removed for viscosity test, which can be adjustea with not more than about 0.75% of water~ The resulting wood filIer will have the ~ollowlng specificationsO

~12-~3'7~f!~k R.I. C-1700 viscosity at 4 RPM, 25C - 16,000 to 180,000 cps pH ~ about 9 solids - about 82%
color - light yellow It should be noted that the combination of about 1:1 of ~hoplex E~330 and Rhoplex AC-34 acrylic emulsions is used. A
wood filler needs more flexibility than Rhoplex E-330 can provide, it being relatively inflexible since methyl methacrylate has a T~ of +105C and butyl acrylate, a T~ of ~43C. ~hoplex AC-34 which apparently is prepared from 66~ ethyl acrylate, is relatively soft since Tg of ethyl acrylate lS -23C. Rhoplex AC-34 has specific adhesion to wood in addition to having higher flexibility than Rhoplex E-330, which has good properties for use on plaster and concrete but not on wood. When only Rhoplex E-330 was used, the resulting wood ~iller was too hard and no flexibility, which resulted in cracklng;~when only Rhoplex AC-34 was used, the wQod filler was too soft and could not be sandedO
Amount of the binder resin should be controlled since an excess thereof will affect the stainin~ property of the wood filler.
The fillers also have to be carefully selected. If the par~icle size of the fillers is too coarse, it will settle out, however; if the particle size is too small, penetration of the stain will be impeded. Fillers must be selected to achieve adequate acceptance o~ stain and to impart desirable sanding property and brl~f drying time.

.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Wood filler composition comprising 6 to 14%
acrylic resin on solids basis, 3 to 10% platy talc, 3 to 10 barytes filler, 3 to 12% clay filler, 40 to 65% calcium carbonate filler and 13 to 35% water.

2. Wood filler composition comprising 8 to 11 acrylic resin on solids basis, 4 to 6% platy talc, 4 to 6%
barytes filler, 5 to 9% clay filler, 50 to 56% calcium car-bonate filler and 17 to 28% water.

3. Composition of claim 2 wherein the resin has a Tg of about 0 C to 25 C, is in emulsion form and is prepared from ethyl acrylate, butyl acrylate, methyl methacry-late and an acid selected from acrylic and methacrylic acids.

4. Composition of claim 3 wherein the amount of ethyl acrylate exceeds 50% of the resin, and the amount of the acid is 0.5 to 3%.

5. Composition of claim 4 wherein the acryl resin is a combination in about 1:1 weight ratio of Rhoplex?
E-330 acrylic emulsion and Rhoplex? AC-34 acrylic emulsion.

6. Composition of claim 2 wherein the resin has a Tg of about 0 to 25°C, is in emulsion form and is prepared from ethyl acrylate in amount exceeding 50%, methyl methacrylate in amount of 25 to 35% and acrylic or methacrylic acid in amount of 0.5 to 3%.

7. Composition of claim 6 wherein the emulsion is selected from Rhoplex?E-330, Rhoplex?AC-34 and mixtures of these acrylic emulsions; average particle size of the platy talc is about 9; the barytes filler comprises in excess of about 95% barium sulfate with more than 90% thereof having particle size less than 20 microns; the clay filler is aluminum silicate having an average particle size of about 5 microns; and the calcium carbonate filler has a mean particle size of about 5 to 15; and viscosity of the composition is 16,000 to 18,000 cps .