Note: Descriptions are shown in the official language in which they were submitted.
35~
Docket D-1752
LQ~DING RESISI~NT OC~ED ABRASIVE
FIELD OF THE INVENTION
The present invention relates to those articles of manu-
facture known as coated abrasives, which consist of flexible
backings to which are adhered a plurality of abrasive grit -~
particles on at least one side. Coated abrasives are used
primarily for the shaping, dimensioning, or surface finish
alteration of other material objects kncwn generally as w~rk-
pieces. Small particles of material re~oved from the w~rk~
pieces and/or shed frQm the coated abrasives during working are
collectively called swarf. In many cases, the swzrf tends to
wholly or partially adhere to the surface of the coated
abrasive, eventually loading or clogging its abrasive surfaces
and rendering it unsuited for f~t~her use. This invention re-
lates particularly to coated abrasives which are specially
resistant to such failure by loading.
~ACKGRDUND OF THE INVENTION
A ccm~on c~mercial p~actice for the preparation of coated
abrasives which resist loading in the sanding of paints, primers,
wcod sealer coats, and a wide variety of other finishing com~osi-
tions used on wDrkpieces is essentially that described in U. S.Patent 2,768,886 to Tw~mbly. This patent describes the prepara-
tion of coated abrasives which have a final grit-side surface
coating of unfused metallic so~ps applied preferably from
dispersion of such soap in a volatile liquid. The application
~J~
35~
of this metallic soap is done as a separate coating step in
addition to the norm31 ma~ing and sizing coating steps which are
cusb3mlrily used for ach eving adherence of the ahrasive grits
to the backing. In some cases, it may be possible to prepare
products with adequate properties without using a sizing
adhesive. The need for an additional coating operation o~mpared
with most other coated abrasives i~oses labor and material
costs which it would obviously be advantageous to avoid.
Since the publication of the T~mbly patent, there have been
several other patents d;rected to other types or "third" coatings
(i.e., coatings in addition to the tw~ normal making and sizing
ones) which would achieve loading resistant coated abrasives.
Examples include polyvinylacetate as disclosed in Canadian Patent
931,767 to Greenwocd, polytetrafluoroethene and mixtures thereof
as disclosed in U. S. Patent 3,042,508 to Haigis, and mixtures of
thermosetting resins, elastomers, and me~llic soaps as dis-
closed in U. S. Patent 3,619,150 to Rinker et al.
U. S. Pat nt 3,043,673 to Klein et al. teaches the use of
oxy-containing compounds either in a third coat or in the conven-
tional sizing coat of a coated abrasive, together with anexceptionally high ratio of binder a & esive to grai~ as an
eff~ctive means for increasing the resistance of coated abrasives
to loading in the finishing of leather and similar materials.
The oxy compounds specified in this patent are all neutral
organic cQmpounds not expected to ionize in water solution. U. S.
Patent 3,089,763 to Gladstone teaches the use of polyoxyalkylene
ccmpounds in the size of coated abrasives, and one of the objects
stated is to reduce loading. However, the tea~ling of this
Gladstone patent is restricted to sizing compositions in which
the principal constituent is an amine catalyzed phenolic resin.
It is a prim~ry object of this invention ~o provide coated
abrasives which are as resistant to loading as products with
metallic soap third coats but which do not require an actual
third coating. Other objects will be apparent from the descrip-
tion below.SU~M~RY C~ THE INVENTION
It has been found that loading resistance can be imparted to
otherwise conventional coated abrasives with size coats contain-
ing glue or arnino resins by the incorporation into the size of
small amounts of specific chemical ccmpounds and mixtures as
hereinafter described. These additives are total or partial
alkyl esters of phosphoric acid, amine salts of partial esters
of phosphoric acid, and qu~rternary ammonium salts with at least
one long alkyl or substituted long alkyl group. Typical
examples w~uld be the trietha~olarnine salt of mono- or di-
decylphosphate or stearamidopropyl-~~hydroxyethylar~onium
nitrate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the studies which led to this invention, use was made of
conventional coated abrasive bac~ings, maker adhesives, and
abrasive grits. The invention is applicable to any such prod-
ucts containing any such constituents, including the full range
of grit sizes of nornEll commercial practice, oomprising at least
those with numerical designations of size from 12 to 600 as
defined by the ANSI standard B74.18-1977. As is known to those
skilled in the art, suitable constituents include but are nct
limited to papers of weights varying from 50 to 300 gra~s per
square me-ter (gm/m2), suitably prepared (finished) cloth of a
wide variety of types, and vulcanized fiber. Grits can be
J~ ~ r- ~3
synthetic fused alumina, silicon carbide, garnet, zirconia
alumina, emery, flint, or o-ther ma-terials, and maker aclhesives
can be film-forming starches, animal hide glue, amino resins,
etc.
The aclditives inves-tigated which had detectable effec-t
in reducing loading when used in the size coat are lis-ted in
Table 1. These additives were most effective when used wi-th
amino resins such as urea-formaldehyde or melamine-formaldehyde.
Such amino resins could be mixed in up -to ec~ual parts by
weigh-t with phenol-formaldehyde resins, one amino resin could
be mixed with others, and any of -the resins or mixtures
could be filled with finely divided solids such as calcium
sulfate, walnut shell flour, or any of -the o-ther well-known
fillers used in -the manufacture of coated abrasives. Suitable
types of naturally derived glue can also be used as the size,
although the product performance with glue sizes will normally
not be as effective as with resin size, as is true in the
absence of the additives disclosed here.
S-till other conventionally known materials, such
as pigments or dyes, diluents for reducing viscosity, an-ti-
foam agents, etc. may be used -together with the addi-tives of
this invention when needed or desired. No adverse interactions
between such materials and -the additives of this inven-tion
have been noted. A particularly important class of conventional
components in amino resin adhesive formulations are the
oxyamines useful for craze resis-tance as -taught by Duke in
U.S. Paten-t 2,983,593. Use of adhesive compositions as
-taugh-t by Duke, in combination with -the additives of my
inven-tion, is preferred.
--4--
h\
5~:~
Table 1
ADDITIVES WHICH IMPROVE LOADING RESISTANCE OF AMINO RESIN
AND GLUE SIZINGADHESIVES FOR COATED ABRASIVES_
_
Trade Mark Name Chemical
of Additive Supplier Characterization* ~'
Group A
Zelec NE E. I. duPont Fatty alcohol phos-
phate, neutralized
Zelec NK E. I. duPont Fatty alcohol phos-
phate
Monafax L-10 Mona Industries Mixture of mono- and
di-phosphate esters
derived from ethyl-
ene oxide based sur-
factants
Monafax 786 Mona Industries Same as Monafax L-10
Group B
Emphos PS-400 Witco Chemical Complex organic phos-
phate esters
Monafax 785 Mona Industries Same as Monafax L-10
Monafax H-15 Mona Industries Same as Monafax L-10
Group C
Cyastat SN American Cyanamid) Stearamidopropyl-
Cyastat SP American Cyanamid) ~-hydroxyethyl-
dimethylammonium
salts, nitrate for
SN, dihydro~en phos-
phate for SP
E-1373 Calgon Corporation Mixture of Dimethyl-
diallylammonium
chloride and Methyl-
olacrylamide
.
*As specified by the supplier
0 ~J ~
It should be noted that some of the additives shown in
Table 1 are acidic and thus capable of catalyzing the cure of
amino resins. Hcwever, such a practice w~uld incur risk of
shortened pot life of the amino resin, ccmpared to use of the
catalysts taught by Duke. Thus it is usually preferable in
practicing my invention to neutralize the additive, if it is
acidic, with a suitable amine or ammorlium hydroxide before
adding it to an amino resin adhesive formulation. When this is
done, the resin adhesive with my additive can be ~ured with the
same time and temp~rature program as is useful for the same
resin without the additive. It is convenient to use one of
the oxyamunes taught by r~e to neutralize the additive of
my invention if needed.
For example, Zelec NE, which is neutral as supplied, could
be added directly to a conventional form~lation such as
Example III of the Duke patent, after all the other ingredients
listed there are mixed together. On the other hand, Zelec NK,
which is acidic, should first be neutralized, conveniently with
2~amino-2-methylpropanol, in a separate container, and the
neutralized mixture then added to such a conventional formula-
tion after all other ingredients had been added. All preceding
a~d subsequent stages of manufacture of the coated abrasive may
be carried out in a conventional manner.
The munimum amount of additive to give a useful loading
resistance effect was found to be that corresponding to a mass
of 0.74 grams per square meter. An amount more than 10% by
weight of the total sizing adhesive used is generally not
desirable, because of probable decrease in the heat-distortion
resistance of the sizing adhesive, with resultant danger of
reduction of grinding effectiveness. In general, the workable
range is fr3m 0.74 to 13.3 grams per square meter of additive,
and the preferred range is frcm 1.2 to 3.5 grams per square
meter. This can be conveniently achieved in most eas~s by using
the additive at a level of 3-5% by weight of the resin or glue
used.
The additives listed in Table 1 all mixed readily with
amino resins or glue suspensions to give liquid mixtures whieh
were uniform as far as could be noted visually, although in some
cases there was a hazy or miIky appearance to the mixture,
indieative of dispersion rather than true solution. There was
no direct evidence during processing of any tendency of the
adhesive mixtures containing the additives to develop inhcmc-
genei~ies under normal eonditions of coating, drying, or eure.
However, it is expected from the chemical nature of the prefer-
lS able additives, which contain oth ionie bonds and at least onelong organic chain in each mole~ule, that such additives may
effeetively reduee the surface tension of most liquid adhesives
into whieh they are mixed. If such reduction in surlace
tension aetually occurs, the well-known Gibbs equation for such
~0 surfaee active species predicts that the surface-aetive
e~ponent(s) will spontaneously distrib~lte themselves at
equilibrium so as to form a surfaee layer enriched in the
surface active ocmponent. This spontaneous coneentration of
additive in the surfaee layer may explain why the mlnlmum a~ount
of additive required to obtain a detectable increase in loading
resistanee was found to be related to the area of the coated
abrasive produet rather than ~o the volume of adhesive.
Size height levels for produets coated with sizes contain-
ing the additives taught herein should generally conform to
? r~
those for conventional pro~ucts which are not to receive an
a~ditional third coating. In any case, suitable levels can
easily be determined if necessary by those skilled in the art
of manufacturing coated abrasives.
Table 2 illustrates examplr?s of specific products pre-
Fal-ed according to the methods of this invention.
The group of the ~o~r additives listed in Table 1 as
Gr~up A all appeared to be approximately equal in their ability
to induce loading-resistance when added to amino resin sizes.
Products with these additives in the size coat were tested in
sanding of a wqde variety of painls, metal primers, enamelsl
lacquers, varnishes, etc. and found in general to have longer
useful lives than previous standard ccmmercial products made for
sanding such workpieces. (Such ca~nercial products norm lly
have a third coating containing primarily zinc stearate or some
other similar metallic soap.) The other additives sh~n in
Table 1 are listed in groups of decreasing effectiveness in
imparting loading-resistance to the size adhesives.
In this specification and in the claims bel~w, the ter~n
"organyl" is used to include any chemical group which could be
formed by the breaking of one valence b~nd in an organic
cc~pound. Thus organyl includes the groups normally designaterl
as alkyl, alkenyl alkynyl, aryl such as phenyl, and oombina-
tions of and substitutions on the other simple groups, as well
as a wide variety of others. The term "long organyl" refers to
an oryanyl group which ccmprises at least eight OE bon atcms
bonded linearly to each other. The linear bonding may include
double or triple as well as single carbon-carkon bon~s. The
term "layer" in the description of a body of adhesive material
L~
Table 2
SPECIFIC EXPMPT,E~ OF LC~DIMG RESISI~NT CCA~ED ABR~SrVES
Mbker Abrasive Grits _ _ Sizing Adhesive
Adhesive Grit To ~ Main ~~~ Addl~1ve ~
Backin~ ~ Type Size ~ Gm~m _YE~ Name*
Bl Ml 15 Gl 360 44 30 Sl Zelec NE 1.2
Bl Ml 15 G2 320 44 30 Sl ~bnafax L-10 1.2
Bl MQ 19 G3 220 77 62 Sl Zelec NE 2.5
Bl M2 12 G4 220 40 30 Sl Zelec NK 1.2
B2 Ml 22 G2 lB0 98 62 Sl ~nafax 785 2.5
Bl Ma 22 G5 180 53 30 S2 ~bnafax 786 1.2
B3 M3 118 G6 80 129 133 S2 Cyastat SN 5.3
Bl Ma 26 Gl 120 138 77 S3 Emphos PS-400 3.1
B4 Ml 56 Gl 220 115 81 Sl E~1373 3.3
~ . . . , .. ,... :
*As listed in Table 1.
Symbol Keys
Gm/m indicates dried grams of item indic~Ated Fer squ3re meter of coated
abrasive.
Bac ~ : Bl is 68 gm/m Kraft paper (S-tyle 28729 frGm Kim~exly-Clar~ 2
ls slightly heavier Kraft paper (Style 54729 from Kim~exly-Clark); B3 is 130
p3und basis weight (220 gm/mZ) N cylinder paper frcm James River; B4 is cotton
jeans cloth finish 207CC from Norton Co.
Mbkers: Ma is 82 millipoise animal glue; M2 is Ucar 131 latex from Union
Carhide; M3 ls urea-form21dehyde resin GPX~J1-6 frcm Georgia-Pacific.
Abrasi~ Gritso Gl is type SWPL alumina fr3m Trei~acher USA, Inc.; G~ is
type FRPL alumina fron Treibach~rj G3 is type 57 Alluxh~m fr~m ~orbon Co.;
Gg is garnet from Barton Mines; G5 is silicon ~-~rbide from Norb~n COo; G6 is
a mixh~re of type ~7 Alund~n and NZ Alundum fmm Norton Co. ~n a v~l~ne ratio
o~ 6:4~
Sizer A~hesives: Sl ls urea-formaldehyde resin type Beetle 7238-20 fmm
~id; S2 is urea-formaldehyde resin type ~PX~ 6 fran Georgia-
Pacific; S3 is a mixture of Beetle 7238-20 and Fihenolic resin 2535 .frc~m
Varc~ Chernical Co~ in eqLlal proportions by ~ght.
5 CD
-1~
is to be eonsidered to include any substantially continuous
kody of material of substantially uniform ccmposition, with a
projected area covering substantially all of the area of an
abrasive kacking. Because of the presenee of abrasive grit
partieles in a eoated abrasive, the layers of adhesive used in
the construction thereof are expected to have very irregular
outer surfaees rather than the smooth parallel surfaces normally
suggested by the w~rd layer in ordinary usage. An an example,
the ~aker and sizer adhesive eoats noted abo~e in the brief
deseription of the normal manufacturing proeess for a coated
abrasive would constitute layers in the finished product, as
would any separate eoat of metallie soap intended to eonfer
loading resistance. It should be f~rther rDted that substantial
uniformity of ccmposition of an adhesive layer is intended to
inelude any natural surface enrichment of a surface active
material ineorporated into the adhesive layer when it is
applied in liquid form. Also, ~ubstantial continuity of an
adhesive is not violated by the presenee of normal flex cracks
in a eoated abrasive.
I elaim:
