Note: Descriptions are shown in the official language in which they were submitted.
~06SZ83
This invention relates to the bonding of rod-shaped
fastener elements, such as nails or staples, and more particularly
to the bonding of such fasteners with specially formulated ad-
herent polyolefin copolymer, and is closely related to the inven
tion described and claimed in our copending Canadian application
No. 193,052, filed February 20, 1974.
Automatic nailers, especially those which are actuated
pneumatically, are a relatively new innovation in the building
industry. But they are finding wide acceptance and it is contem-
plated that the market will grow quite rapidly.
These automatic nailers require nails which are held to-
gether in a prearranged configuration so that they may be conven-
iently fed into the nailer itself and can be "processed" properly
; Within the nailer. The prearranged configuration in a specific
aspect is referred to as a nail stack. The concept is quite anal-
ogous to cartridges held in a belt which are fed into a heavy
caliber machine gun. Thus, by "processed" it is meant that the nails
in the stack have to move cleanly in the chamber and^into firing
position, The device used to feed the stack is a spring loaded
arrangement, (And, indeed, the inventive concept herein could be
; utilized for the purpose of adhering machine gun bullets, if so desir-
ed provided relatively heavy duty polyolefin based adhesives which
have been specially formulated to adhere to brass are used.)
Most nail stacks presently available utilize a hot-
melt adhesive which bridges the interstices between adjoining nails
in the stack. Paper strips are placed on one or even both sides ofthe stack. ~uch strips are required in order to increase the rigidit~
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of the nail stack but these strips also contribute towards improved
appearance.
Nail stacks prepared according to these techniques of the
art suffer from several major disadvantages. Some of these
include~
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1 (i) when exposed to low temperatures, which are
2 common to building activity which takes place
3 outside, the adhesives undergo brittle fail-
4 ures when dropped or during loading and cause
extensive stack breakage;
6 ~ii) the same adhesives will also tend to break
7 away from the nail during the firing process
8 with sufficient velocity to constitute a safe-
ty problem, to say nothing of the additional
clean-up problems;
11 (iii) very often a portion of paper strip, with an
l2 area exceeding that of the nail headg will be
caught by the nail and pinned underneath the
14 nail head, requiring additional manpower to
remove it prior to the finishing steps of
16 plastering, etc.
17 Thus, a potentially enormous and significant auto-
18 matic fastening industry is waiting poised at the threshold
19 of ma~or significance. Any improvements that can be effected
upon the unsolved disadvantages attendant upon the presently
21 available nail stack itself will accelerate that growth.
22 Furthermore, an additional related problem 1B in
23 the area of staples whlch are used elther in automatic dis-
24 pe~sers or hand-operated dispensers for a wide variety of
uses.
26 These are conventionally bonded together into a
27 fastener article having a plurality of rod elements rigidly
28 bonded to each other in an ad~acent planar, parallel rela-
29 tionship. Usually, in order to bondJ the wires are cleaned
in a solvent bath, dried, and exposed to an adhesive tank.
31 Conventionally, nitrocellulose is used as the ad-
32 hesive to bond the rod or wire elements of a staple fastener
article. This is not a particularly effective adhesive.
2 Moreover, it is applied from a solvent/nitrocellulose solu~
3 tion. The solvent is removed by passing the wires through a
4 series of electrical heaters (ovens) since the solvent is
not recovered (recycled) but vented to the atmosphere. This
6 presents a difficult problem of complying with increasingly
7 stringent solvent emission standards promulgated by various
8 governmental regulatory agencies. ~;
9 The invention comprises a fastener article of
manufacture, which is an assemblage of rod-shaped, fastener
11 elements suitable for use in automatic dispensing devices
l2 for dispensing fastener elements such as nails or staples.
13 These elements are held properly together in a prearranged
14 configuration by virtue of a specifically defined adhesive
polyolefinic composition.
16 In the drawings:
Fig. l shows an enlarged view of a typical portion
18 of fastener elements, e.g. nails comprising the article of
19 manufacture of the invention;
Fig. 2 shows a cross-sectional view of the article
21 of Fig. l taken across 2-2;
22 Fig. 3 shows a fastener element of the invention
23 embedded in two pieces oE wood which it i6 ~oining together;
24 and
Fig. 4 is a photograph of an actual embodiment of
26 the invention.
27 It has been discovered and forms the substantial
28 conceptual basis of this invention, that a novel, unobvious
29 and highly useful fastener article of manufacture can be pre-
pared according to the invention. In essence, fastener art-
31 icles arranged and constructed in specific configurations
32 and held together with specifically defined bonding agents
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1 and technique~ comprise the subject matter of the invention.
2 In particular, the novel fastener articles of the
3 invention are a plurality of individual fastening elements,
4 e.g. nails, rods or staples especially adapted to be driven
s into a substrate material by automatic driving means such as ~-
6 pneumatic actuated automatic nailers.
7 These elements are firmly held in a specific and
8 prearranged structure and relationship to form the fastener
article by means of certain adhesive, binders comprising a
major portion of C2 to C8 polyolefin graft copolymers used
11 as tapeæ, film or powder. These latter are referred to gen-
l2 erally as adhesives.
13 When used herein the term copolymer is intended to -
include polymers with two or more monomers.
In one preferred aspect the binder, when used as a
l6 tape, comprises a ma~or portion of C2 C3 polyolefin copoly-
17 mer strip l mil to 40 mils, preferably 5 mils to 30 mils,
18 and most preferably 6 mils to 20 mils thick, having a width
19 suf~icient to cover from 5 to 75, preferably 20 to 60, and
most preferably 30 to 40% of the length of the fastener ele-
21 ments, e.g. nail shanks.
22 It ls mo~t deslrable and therefore preferred that
23 the tape covers both sides of the fastener article, e.g.
24 nail stack.
The polyolefin copolymer ls preferably grafted
26 rather than randomly copolymerized (but not limited to grafts)
27 with certaln reactlve compounds as described herein. The
28 adhesive co~ponent, e.g. graft, content will be from about
29 0.12 to 20, preferably l to lO and most preferably 2.0 to 8
weight percent of the total polymer.
31 Preferably this adhesive component of the composi-
32 tion, e.g. graft portion, will comprise the class of unsatu-
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rated mono- and di-carboxylic-containing acids (C3-Clo) with
preferably at least one olefinic unsaturation and will include
anhydrides, salts, esters, ethers, amides, nitriles, thiols,
thio acids, glycidyl, cyano, hydroxy, glycol, and other sub-
s~ituted derivatives from acids.
Preferred examples of such acids, anhydrides, andderivatives thereof include maleic acid, fumaric acid, himic acid,
itaconic acid, citraconic acid, acrylic acid, glycidyl acrylate,
methacrylic acid, glycidyl methacrylate, cyanoacrylate, hydroxy-
methacrylate, acrylic polyethers, acrylic anhydrides, sodiumacrylate~ calcium acrylate, magnesium acrylate. Substituted
styrenes, acrylonitrile, vinyl halides, acrylate esters, dimethyl
aminoethyl acrylate, vinyl pyridines, vinyl pyrrilidone, vinyl
ether copolymers, maleic anhydride-styrene copolym~rs, acrylamide,
strained ring diels-alder adducts such as ethylidenè norbornene
and the like are other unsaturated grafting monomers which can be
usefully employed.
Acrylic acid and glycidyl acrylate are especially preferred
species of monomeric grafting agent.
Although random copolymers and grafted copolymers can be
prepared utilizing any known techni~ue in the art, a particularly
preferred technique for preparing the preferred grafted copolymer
binders of the invention is that described in Italian Patent 953,632,
granted August 10, 1973 in the name of R.A. Steinkamp and T.J. Grail.
It will be recognized that a wide variety of pplyolefin
copolymer materials will be suitable so long as they will adhere well
to the individual fastener elements, e.g. rods, i.e. nails. Neverthe-
less, certain physical criteria defining especially preferred poly-
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olefins will be described. Such polyolefins will produce fastener
articles of outstanding commerical value.
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1 Among these is the prerequisite that the tape be
2 made to have adequate toughness or flexural strength, e.g.
3 an ASTM D790 secant flexural modulus (p.s.i. x 105) of 1.8
4 to 0.5, preferably 1.5 to 0.5, and most preferably 1.20 to
o.6. The D790 test gives an indication o~ the flexibility
6 of the adhesive binders.
7 The preferred material will have an ASTM D256,
8 Izo~ ioom temperature impact strength in foot/pounds per
9 inch of notch of o.6 to DNB*, preferably 1.3 to DNB, and
most preferably 1.5 to DNB. Over the temperature range of
11 -40 to 150 F, preferably -20 to 130 F., and most prefera-
l2 bly -10 to 110 F. the unnotched Izod impact values range
13 from 6 to DNB. The D256 test indicates the resistance of
14 the binder material to shattering at low temperatures.
The other important criteria is the ASTM D638 ten-
l6 sile strength measured in psi, which is 6,ooo tolg500, pre-
17 ferably 4,000 to 1,700 and most preferably 3,000 to 1,800.
18 Furthermore, the adhesion values should be on the
19 order of at least 3 and can be up to 60, preferably at least
10 and can be up to 30, at least and most preferably 20
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21 pounds per squQrc inch, e.g. so that the grafted blnder ad-
. ~
22 heres to the fastener, i.e. nail, a~ is being nailed and
23 even after nailing. This is to ensure that no polymeric mat-
24 erial is forced off the surface of the nail. Thus the use
of the inventive article eliminates accumulations under and
26 extending beyond a nail head.
27 For nail stacks, a very crude and practical test
28 is to drop a nail stack fastener article of the invention,
29 such as that in Figure 4, with about 30-40 nails in itg from
a height of about four feet. The binder composition is con-
31 sidered to perform satisfactorily if no catastrophic break-
32 * DNB = Does Not Break
5~33
1 age occurs.
2 Furthermore, the polymeric tape material should -
3 not shatter and spray tape fragments as the individual fast-
4 ener elements of the fastener article are actually driven in-
to variouæ materials for fastening purposes.
6 SpecificallyJ in terms of nails, the nail itself
7 must penetrate the material to be nailed, carry the grafted
8 tape with it and at the same time the tape-to-nail adhesion
9 must be tenacious enough not to separate during the actual
automatic nailing step.
ll Not only are the fastener articles of manufacture
l2 of the invention possessed of outstanding utility for use in
13 automatic fastener dispensers, the invention also provides
~e~t~
14 an extremely important process advantage of grcat ease of
manufacturing the assembly of fastener elements comprising
16 the fastener articles~ than had been possible ~ the prior
17 art.
18 Thus, a erafted polyolefin tape meeting the physi-
~.
19 cal and other criteria set forth herein which is capable of
being strongly adhered to the surface of the nail or other
21 fastener element can be applied to fastener elements in at
22 least two extremely convenient ways.
23 One of these is that the nalls are assembled in
24 their prearranged configuration. The tape is placed on the
surface of the nails and the entire assembly is sub~ected to
2~ sufficient heat either by heating the nails or by placing
27 the assembly in an oven so that the tape is able to soften
28 and flow enough to adhere tenaciously to the surface of the
29 nail after solidification.
This also preferably permits some of the tape
31 material to flow into the interstices between the ad~acent
32 nails in the assembl~ Such flow contributes toward maximiz-
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1 ing the surface area of nail adhered to binder, e.g. tape.
2 The exact conditions will vary somewhat depending on the
3 particular fastener elements to which the tape is being fix-
4 ed and the exact composition of the tape.
Alternatively, the tape itself can be extruded
6 directly while the fastener elements are held in a jig or
7 other dévice in their prearranged configuration~ The soft,
8 extruded tape will be laid down over the fastener element,
9 e.g. nail surfaces, and will tenaciously adhere to these
surfaces upon cooling. The nails can be preheated to a pre-
11 determined temperature so that the extruded tape is not
I2 initially cooled too rapidly to develop proper adhesion.
13 Quenching a molten tape after a heat soak of a few minutes
14 on the fastener element develops maximum adhesion values,
but it is not necessary; less than maximum adhesion values
16 are perfectly adequate for the pu~poses of this invention.
17 Although polyolefin copolymer tapes as described
18 above are the preferred means for adhering fas~ener elements
19 together to form the fastener articles of the invention,
other techniques of utilizing the copolymer are available
21 and can be used to form novel fastener articles.
22 One approach which can be used is to coat the in-
23 divldual fastener elements with a thin partial or complete
24 coating of the adhesive polyolefinic copolymer. The coating
can be accomplished with solution, extrusion or powder tech-
26 nlques.
27 The coated elements are then placed into then pre-
28 arranged configuration proximi~ies by any convenient means
29 as described, such as a ~ig, subjected to sufficient he&t to
cause flow of the coating and cooled passively or actively
31 to obtain fastener articles.
32 The elements can also be placed in their pre-
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1 arranged configuration, coated with a polyolefin copolymer
2 powder either electrostatically or in a fluid bed, heated to
3 cause flow of the coating and cooled passively or actively
4 to obtain a fastener article.
Although the technique described in the paragraph
6 immediately above can be used for nail stack fastener arti- -
7 cles, it is especially preferred when the fastener article
8 i8 to be a planar configuration of staples for staple guns.
9 Although the articles and techniques of this in-
vention generically encompass both staple configurations and
11 nail stacks, there are enough differences in specifics to
l2 ~ustify discussion of a particular technique which is espe-
13 cially well adapted for forming staple fastener articles.
14 Staple fastener articles with good dispensing prop-
erties can most conveniently be prepared by first arranging
l6 a large number of staple elements in a touching, adjacent,
17 parallel, planar relationship. Subsequently, a film or
18 binder (as described herein) is placed over the staples.
19 Heat is applied either by heating in an oven, or
directly heating the staples sufficient to cause the film to
21 soften and flow. Upon cooling, the staples are held in the
22 prearranged configuration by the adhesive quality of the film.
23 Alternatively, the film can be melt-extruded
24 directly on the heated staples or other fastener element. A
tape can be used in the same manner.
26 It is also to be noted that for many fastening
27 applications the functional binder copolymer materlal used
28 on a fastener element will also adhere to the surface of the
29 materials it penetrates because of the interaction of the
binder's functional groups, e.g. carboxy with the functional
31 nature of the host material, i.e. wood, steel, etc. See
32 Figure 3.
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1 In the Figures, Fig. l shows partial fastener
2 article lO (nail stack) with Nails 12 and the adhesive - -
3 polyolefin tape 14 of the example bonded to the nails and
4 holding them in their prearranged configuration.
Fig. 2 is a cross-section view of Figure l taken~
6 across 2-2. -
7 Fig. 3 shows two pieces of wood held together by a
8 fastener element (nail) from the nail stack.
9 Fig. 4 is a photograph of a section of an actual
nail stack article according to a preferred embodiment of
11 this invention. Note that the nails are cliphead nails.
12 The especially preferred compositions used in the
13 articles of the invention will contain portions of plastic
14 and elastomer as set forth in TABLE I below.
TABLE I ~-
16 Ranges Plastic Elastomer
17 Isotactic polypropylene*, Ethylene, propylene,
18 or high density PE copolymer, or butyl or
l9 polyisobutylene, or -
other compatible elas-
21 tomers
22 General 30 to 90 wt. ~ 70 to lO wt.
23 Preferred 40 to 80 wt. ~ 60 to 20 wt.
24 Most Pre-
ferred 50 to 70 wt. ~ 30 to 50 wt. ~
26 * (including thermoplastic impact grades and block copoly-
27 mer impact grades.) that can be used without additional
28 additives.
29 It will be noted that the preferred compositions
of the invention comprise a sizeable elastomeric component.
31 This plays an important role in the rheology of the adhesive
32 binder as well as the level of adhesion strength.
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1 The elastomer EPR or EPDM copolymers will contain
2 from 20 to 95~ preferably 40 to 80, and most preferably 50
3 to 80 weight percent of ethylene. Generally it is preferred
4 that they have a high crystalline component, e.g. high green
strength. The type and quantity of elastomer is not criti-
6 cal, so long as the final composition has the specified pro-
7 portions.
~..
8 Blends of ethylene polymers and propylene polymers
9 can also be used as the plastic component. They will com-
prise from 50 to 90 weigm percent polypropylene and 50 to
11 10 weight percent polyqthylene, preferably 50 to 85 weight
12 percent polypropylene and 15 to 50 weight percent polyethyl-
13 ene, and most preferably 60 to 75 weight percent polypropyl-
14 ene and 40 to 25 welght percent polyethylene. The polyethyl-
ene component can be either high density or low density.
16 The grafted or copolymer portion of these polymers
17 will preferably be acrylic acid or glycidyl acrylate and will
18 be present in quantities of 0.2 up to 20 welght percent as
19 described above. While the polymers can be grafted directly
to the desired level, it is often convenient to graft a poly-
21 mer to a relatively high level and then blend it with un-
22 grafted polymer to arrive at the particular desired level.
23 This i9 particularly u~e~ul when relatively low graft levels
24 are required.
Although the adhesive binder compositions de-
26 scrlbed hereln wlll adhere extremely well to all ferrous
27 metals and most nonferrous metals, special subgenus composi-
28 tions within the scope of the generally described binder com-
29 positions are necessary to achieve necessary adhesion to
copper and copper-containing alloys.
31 The binder composition that must be used to effect-
32 ively bond copper fastener elements or any other copper item
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1 or copper-containing alloy for that matter is as follows:
2 Generally, it has been found that blends of 60
3 to 97, preferably 80 to 95, and most preferably 85 to 90
4 weight percent of a low density polyethylene blended with
a balance of butyl rubber or polyisobutylene and ~hen
gra~ted with from abou~ 0.02 to 209 preferably O.l to lO,
7 and most preferably 0.2 to 8 weight p~rcent of acrylic ~-
8 acid or glycidyl acrylate will adhere well to copper or
9 copper alloy substrates. Glycidyl acrylate grafts to poly-
propylene containing a ~mall ethylene polymer component
1 are particularly outstanding for achieving maximum copper
l2 adhesion. --
13 In formulating the adhesive binders of the inven-
1~ tion, it was found that there was a delicate balance or
trade-off between full-contact of binder with fastener
l6 elements and melt-strength. The final composition must
17 be satisfactory in both regards.
8 Melt-strength is important since the binder will
19 often be applied under kinetic condition~, when it is
molten. And it must have the ability to han~g together
21 when being stre3sed and moved while molten.
22 On the other hand effectiveness of adhesion de-
23 pends on maximum contact of the binder with fastener ele-
24 ments. Therefore, the binder must flow to some extent while
molten to achieve best results.
26 A rough measure of these characteristics can be
27 obtained by measuring either melt index (MI) or melt flow
28 rate (MFR), which for the purposes of this discus~ion will
29 be con~idered interchangeable and will be referred to as
MFR.
31 Generally, the novel adhesive binder of the inven-
32 tion should have an MFR of about 1 to 30, preferably 5 to 20
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1 and most preferably 8 to 12.
2 When elastomer is blended into a given plastic,
3 the resulting MFR will tend to be lower than the MFR of the
4 starting plastic. Therefore, generally, a plastic is fab- -
ricated (by peroxide break-down for instance) with a higher
6 MFR than is desired in the final composition.
7 A wide variety of elastomers can be used for
8 blending with the plastic. These are largely amorphous
9 materials which provide additional flexibility to absorb the
shock of impact, particularly at low temperatures when the
11 plastic component approaches or exceeds its glass transition -
12 temperature.
13 Generally, the elastomers are selected because of
14 convenience in blending with the plastics, particularly when
only extruder mixing is available. A1SOJ the saturated
16 elastomers, or low unsaturated elastomers (ERR, EPDM) are
17 usually preferred over the highly unsaturated elastomers,
18 e-g natural rubber, polybutylene, etc.
19 The invention is further illustrated by the follow-
ing examples.
21 Example l
22 In a preferred~embodiment, the fastener article of
23 Fig. 4 comprising a plurality of nails held in a flexible,
24 pre-arranged configuration was prepared by the ~ollowing
technique.
26 The nails were placed in a ~ig in the prearranged
27 configuration. A strip of grafted polyolefin tape 3/8"
28 wide, 6 mils thick, consisting of 60 weight percent high
29 molecular weight isotactic polypropylene having an MF~ of
between 1-22 and 40 weight percent ethylene-propylene elast-
31 omer (EMD-492, obtained from Exxon Chemical Co. U.S.A.),
32 both of which were grafted with 4 weight percent of acrylic
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1 acid, to result in a grafted adhesive composition having an
2 MFR of - 10, was used to hold the nails in the proper confie-
3 uration. The polyolefin tape had a ASTM D638 tensile strength
4 of 2000 psi ft/lb/in of Notch, a ASTM D790 secant ~lexural
modulus of 75,000 psi and a notched Izod ASTM D256 room tem-
6 perature impact of 1.7 ft/lbs/inch.
7 The tape was placed over the nails which were in
8 the same configuration as illustrated in Fig. 1. The nails
9 with the tape on top were heated to a temperature of 425 F. -
for a time of 3 minutes. Simultaneo~sly an identical tape
11 was applied to the opposite side of the nail configuration
l2 utilizing the same adhesion process conditions.
13 The resulting article was allowed to cool to room
14 temperature. Adhesion of the tape to the nails was tested.
Adhesion strengths of 15-30 lbs/in width were measured.
l6 The resulting nail stack article9 after passing
17 the drop test, was tested in a pneumatic automatic n~iler
18 manufactured by the Paslode Division of Signode Corporation.
19 The test results indicated that the nails performed ext~emely
well in the pneumatic nailer. The results were far superior
21 to those obtained using nail stacks bonded together with con-
22 ventional adhesive techniques.
23 Example 2
24 The technique of Example 1 is repeated, except that
the nails are replaced with glass-fiber reinforced thermo-
26 plastic rods which are to be used as fastening elements.
27 Example 3
28 Example 1 is repeated except that the steel nails
29 are replaced with aluminum rods which are to be used as fas-
tening elements.
31 Example 4
32 Example 1 is repeated except that the steel nalls
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1 are replaced with copper wires and the tape is low density
2 ethylene polymer containing 10 wt. % of butyl rubber, the
3 total compoæition grafted with 3 wt. ~ of acrylic acid.
4 Example 5
A staple article according to the invention is pre-
6 pared by arranging wire staple elements in an adjacent,
7 touching, planar relationship. The elements while heated to
8 a temperature exceeding that of the binder are covered with
9 a thin film (about 3 mils) of the binder of Example 1.
Example 6
11 Example 5 is repeated except that the elements are
l2 covered with a fine powder prepared from~the binder of
13 Example 1.
14 It is to be noted that the specific embodiments
described above are for nail-stack fastener articles in
l6 which clip-head nails are the fastener elements.
17 Other types of nails can also be used in nail-
18 stacks with suitable adjustments for the particular type o~
19 nail. For instance drywall nails have a full-head as opposed
to the half-head of a clip-head nail. ThereforeJ they, of
21 necessity, are pIaced further apart in the stack.
22 Preferably, when tapes are used for dry-wall nail
23 stacks, they are notched, marked J or indented ln the approxi-
24 mate middle of the span between each nail. This is so that
the tape breaks in such a manner that each nail carries with
26 it no more than ite share of the tape binder.
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