U.S. patent number 3,895,149 [Application Number 05/376,496] was granted by the patent office on 1975-07-15 for carpet backed with thixotropic polyurethane adhesive.
This patent grant is currently assigned to Atlantic Richfield Company. Invention is credited to Robert Koncos, Kenyon A. Riches, Robert H. Sheffler.
United States Patent |
3,895,149 |
Sheffler , et al. |
July 15, 1975 |
Carpet backed with thixotropic polyurethane adhesive
Abstract
A carpet backing is formed by applying a thixotropic
polyurethane adhesive composition as either a laminating adhesive,
a precoat adhesive or a unitary backing to the underside of the
primary fabric of tufted carpet. The thixotropic adhesive
composition, comprising a liquid, hydroxyl-terminated diene
polymer, a low molecular weight reinforcing polyol, an isocyanate,
a filler, and a catalyst, provides substantially complete bundle
wrap of each fiber tuft without penetration through the primary
fabric backing material to the top side or face of the carpet. The
thixotropic polyurethane adhesive composition is applied to the
underside of the primary fabric backing material in measured
quantity and cured by the application of heat with or without a
secondary fabric being applied prior to curing.
Inventors: |
Sheffler; Robert H.
(Harleysville, PA), Koncos; Robert (Moorestown, NJ),
Riches; Kenyon A. (Cherry Hill, NJ) |
Assignee: |
Atlantic Richfield Company
(Philadelphia, PA)
|
Family
ID: |
23485251 |
Appl.
No.: |
05/376,496 |
Filed: |
July 5, 1973 |
Current U.S.
Class: |
428/94;
428/97 |
Current CPC
Class: |
B32B
5/26 (20130101); D06M 15/564 (20130101); D06N
7/0071 (20130101); B32B 7/12 (20130101); C09J
175/14 (20130101); C08G 18/69 (20130101); B32B
2307/734 (20130101); B32B 2471/02 (20130101); Y10T
428/23993 (20150401); D06N 2203/068 (20130101); Y10T
428/23971 (20150401); D06N 2205/20 (20130101); D06N
2209/1628 (20130101) |
Current International
Class: |
C08G
18/69 (20060101); D06N 7/00 (20060101); D06M
15/37 (20060101); D06M 15/564 (20060101); C08G
18/00 (20060101); C09J 175/14 (20060101); D03d
027/00 (); D04h 011/00 () |
Field of
Search: |
;161/62-67,190
;260/37N,4TN ;156/72,435 ;117/161KP |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McCamish; Marion E.
Attorney, Agent or Firm: Reap; Coleman R.
Claims
What is claimed is:
1. Carpet including a primary backing material, tufted yarn
stitched through the primary fabric backing to provide a pile
surface on one side of the primary backing and a loop of yarn on
the underside of the primary backing and a layer of thixotropic
adhesive composition adhered to the underside of the primary
backing and the loop of yarn, said thixotropic composition having a
thixotropic ratio based on the viscosity at 1 rpm and at 20 rpm of
between 1.3:1 and 10:1, said composition comprising liquid,
hydroxyl-terminated diene polymer; high molecular weight polyol
having an average equivalent weight between about 500 and 2,200
present in an amount of about 0.1 to 5 times the equivalents of the
diene polymer; low molecular weight polyol having an equivalent
weight of between about 50 and about 300 present in an amount
between about 1.5 and about 8 times the equivalents of diene
polymer; isocyanate having a functionality of between 2 and 3
present in an amount to provide a NCO/OH equivalents ratio of
between 0.95:1 and 1.5:1; filler present in an amount between about
100 and about 600 parts per 100 parts by weight of diene polymer;
oil extending hydrocarbon liquid present in an amount of up to 200
parts per 100 parts by weight of diene polymer; water present in an
amount of about 1.0 to 8 parts per 100 parts by weight of diene
polymer; and catalyst for said composition present in an amount
between about 0.02 and about 4 parts per 100 parts by weight of the
diene polymer.
Description
FIELD OF THE INVENTION
The present invention relates to thixotropic adhesive compositions,
their application to carpets, and to the resulting carpet material.
More particularly, the present invention is directed to thixotropic
polyurethane adhesive compositions which can be advantageously
applied to carpets as a unitary backing, a precoat adhesive, or a
laminating adhesive, the application of such compositions and the
resulting carpet material.
BACKGROUND OF THE INVENTION
The tufting method which is now generally employed for the
manufacture of carpets comprises looping pile fibers of natural or
synthetic material through a relatively inexpensive woven or
non-woven textile base, known as the primary fabric backing
material. Short loops of the long pile fibers are pushed through
the primary fabric backing material such that one single continuous
length of fiber constituting a complete row of pile in the carpet
is formed. The elongated loops extending from the base (the top
side) of the primary fabric backing material can remain connected
or severed, depending on whether a loop pile or a cut pile carpet
is desired. The loops on the bottom side of the carpet are not cut.
These pile loops or tufts are not securely fastened in the tufting
process. Without additional anchorage these fibers or the tufts can
be pulled from the primary fabric or otherwise disarrayed.
Necessary anchorage is provided by applying an adhesive material in
liquid form to the underside of the carpet. The adhesive applied to
the underside of the carpet is accordingly of major importance to
the quality and performance of the carpet. It retains the pile
fibers or tufts in place, secures the individual fibers of the
yarn, prevents pilling of the yarn and controls dimensional
stability.
Without additional backing material applied to the adhesive
material on the undeside of the carpet, the carpet is said to have
a unitary backing. Carpets having a unitary backing are used
principally as commercial carpeting. If a sponge like material (or
foam) is applied after the adhesive material is applied, the
adhesive coating is referred to as a precoat composition. Uncured
foam material can be applied directly to the precoated carpet back
and cured in place, or it can be cured as a separate sheet and then
laminated to the back of the carpet by means of the precoat or use
of another adhesive. The precoat provides good tuft lock, while the
foam material, such as polyvinyl chloride or styrene butadiene
copolymer, serves as a cushion back for the carpet.
For the standard double back carpet, the adhesive layer is referred
to as a laminating adhesive. After the laminating adhesive is
applied to the underside of the primary fabric backing material of
a double back carpet, a further backing layer of secondary fabric
material, known as the scrim, is applied to the coated underside of
the carpet. The scrim serves to improve dimensional stability,
appearance of the carpet and also the enhance tuft lock, i.e., the
strength with which the fibers are retained in the primary fabric
backing. The laminating adhesive for double back carpets serves not
only to anchor the pile fabers or tufts, but also to adhere the
scrim to the carpet. Conventionally, in the process of making
double back tufted carpets the laminating adhesive is applied in
liquid form to the underside of the carpet and the scrim is applied
to the same side while the laminating adhesive is still wet and
uncured. The carpet is then passed through an oven to dry and cure
the laminating adhesive.
When reference is made herein to carpets, it will be understood
that any fabric like sheet material is contemplated, whether
tufted, woven, knitted, felted, cemented or otherwise, and that the
fabric can be a carpet, rug, mat, floor covering, floor tile, wall
covering or the like. The primary fabric is normally a material
such as jute, burlap or polypropylene. The scrim or secondary
fabric can consist of natural and/or synthetic materials, such as
jute, hessian, burlap, nylon, polypropylene and the like. The pile
fibers can also be natural or synthetic materials, such as wool,
polyacrylate, cellulose acetate, polyester, nylon,
polyacrylonitrile, polypropylene and the like, as well as mixtures
of such materials.
Styrene butadiene rubber latex or carboxylated styrene butadiene
rubber latex of the type commonly employed as a laminating adhesive
has several known disadvantages. Such adhesive requires a long cure
time at relatively high temperatures (e.g., 300.degree.F. for 8 to
10 minutes) and this means that large expensive curing ovens must
be employed. With certain heat sensitive fibers that require lower
curing temperatures, even longer curing times are necessary.
Carboxylated styrene-butadiene latex adhesive may have a strong
odor of ammonia associated with it and sometimes finished carpets
have a heavy and unpleasant odor of styrene. In addition,
carboxylated butadiene-styrene polymer adhesives can contain some
residual unsaturation which tends to cause unsatisfactory aging
characteristics, resulting in a loss of flexibility. In fact,
polymerization which occurs as a result of such residual
unsaturation has caused the backing of carpets and rugs to become
stiff after only a few years. Another disadvantage of carboxylated
styrene butadiene rubber latex adhesive is the required method of
application. In general a pan coater consisting of a latex pan, one
or two adjustable doctor or striker bars, one or two variable speed
coater rolls and one or two adjustable tension rolls are required
for the application of such adhesive. These require a fairly high
degree of operator skill and attention to achieve a proper degree
of penetration of adhesive into tufts. It is important that the
adhesive employed for carpets not migrate past the primary backing
fabric to the face or top side of the carpet since this migration
can cause the yarn to become stiff and render the final carpet
unacceptable. If the settings are not correct for the particular
type of yarn used rejects become quite high. Quality of the
finished carpet thus becomes highly dependent on operator skill and
conscientiousness and increased expenses are incurred from the fact
that several employees are required to operate the equipment.
Another disadvantage is the poor green strength of carboxylated
styrene butadiene rubber latex adhesive. If effective adhesion does
not occur until near the end of a curing cycle the chances of
delamination and product waste increase greatly. The advent of
certain synthetic materials in the carpet industry which permit a
carpet to be used both indoors and outdoors has given rise to
further problems in connection with the preparation or the
manufacture of carpeting. Polypropylene is a relatively cheap
material which in most respects is quite satisfactory for use as
the pile fiber, the primary fabric backing material, and the scrim,
or the secondary fabric substrate, or a carpet. However,
polypropylene presents an adhesion problem since latex compositions
normally employed in carpet manufacture do not adhere well to the
surface of polypropylene. Carpets prepared from polypropylene have
been subject to delamination of the scrim or secondary fabric
substrate. In order to overcome this problem attempts have been
made to employ multiple intervening adhesive layers, resulting in
increased production costs.
SUMMARY OF THE INVENTION
An object of the present invention is to provide improved adhesive
compositions which find particular application for rug and carpet
backing applications.
Another object of the present invention is to provide a
solvent-free polymer composition to avoid evaporation of water
and/or organic volatile materials into the atmmosphere while
curing.
A further object of the present invention is to provide improved
thixotropic polyurethane adhesive compositions which can be used as
carpet backing adhesive.
Still a further object of the present invention is to provide low
cost adhesive compositions which have excellent adhesion with
respect to natural and synthetic materials and good resistance to
aging.
Yet another object of the present invention is to provide
thixotropic polyurethane compositions which can be used as unitary
backing, precoat adhesive or laminating adhesive for carpets.
Another object of the present invention is to provide improved
procedures for applying carpet backing adhesive compositions.
A still further object of the present invention is to provide
carpet material having good tuft lock and bundle wrap.
The thixotropic adhesive compositions provided in accordance with
the present invention comprise a mixture of a liquid
hydroxyl-terminated diene homopolymer or copolymer, a low molecular
weight polyol, an isocyanate, a filler, and catalyst. These
compositions have an initial Brookfield viscosity of between about
3,000 and about 100,000 centipoises at 5 rpm using a number 5
spindle. More especially, the adhesive compositions of the
invention comprise a mixture of a liquid hydroxyl-terminated diene
homopolymer or copolymer, a polyol having an equivalent weight of
between about 50 and about 300 present in an amount up to 5 times
the equivalents of diene polymer; a polyol having an equivalent
weight of between about 50 and about 300 present in an amount
between about 1.5 and about 8 times the equivalents of diene
polymer; an isocyanate material having a functionality of between 2
and 3 present in an amount to provide a NCO/OH equivalents ratio of
between 0.95:1 and 1.5:1; at least one filler present in an amount
of between about 40 and about 800 parts per 100 parts by weight of
diene polymer; an oil extending hydrocarbon liquid present in an
amount up to 200 parts per 100 parts by weight of the diene
polymer; water present in an amount up to 10 parts per 100 parts by
weight of the diene polymer; and at least one catalyst capable of
accelerating the cure time of the composition, present in an amount
between about 0.02 and about 4 parts per hundred parts by weight of
the diene polymer. The resulting composition has an initial
Brookfield viscosity at 5 rpm using a number 5 spindle of between
about 3,000 and about 100,000 and the ratio of the viscosity at 1
rpm and 20 rpm for the thixotropic composition is between about
1.3:1 and 10:1. Conventional additives such as oxidation
inhibitors, pot life inhibitors, stabilizers, pigments and the like
can be incorporated in the adhesive compositions for improved
characteristics.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polymeric materials combined with isocyanate to produce the
urethane adhesive compositions of the present invention are liquid,
hydroxyl-terminated diene homopolymers and copolymers. The polymers
possess predominantly primary, terminal hydroxyl groups of the
allylic type and have a hydroxyl content of between about 0.6 and
about 0.9 milliequivalents per gram and a viscosity at 30.degree.C.
of between about 30 and about 300 poises. The structure of the
polymers accounts for their high reactivity, especially with
aromatic diisocyanates. Oil extension, using low cost process oils,
provides formulation flexibility in controlling properties while
the liquid systems are uncured, such as viscosity pot life, gel
time and the like, as well as properties of the cured product,
including flexibility, cut growth, elongation and the like.
Hydroxyl terminated homopolymers and copolymers contemplated for
the present invention are disclosed in more detail in U.S. letters
Pat. Nos. 3,637,558, 3,674,743 and 3,714,110, which patent
disclosures are specifically incorporated by reference herein.
These patents disclose polymers which have an average of at least
2.1 and preferably between about 2.1 and about 2.5 predominantly
primary, terminal allylic hydroxyls per molecule and being an
addition polymer of 0 to 75 percent by weight of an
alpha-monoolefinically unsaturated monomer of 2 to 12 carbon atoms,
the balance consisting essentially of a 1,3-diene hydrocarbon of
about 4 to about 12 carbon atoms, said polymer having the majority
of its unsaturation in the main hydrocarbon chain and a number
average molecular weight of about 400 to about 25,000 as determined
by cryoscopic, ebullioscopic and osmometric methods.
As disclosed in the aforementioned patents, the dienes which can be
employed are unsubstituted, 2-substituted or 3,3-disubstituted
1,3-dienes of up to about 12 carbon atoms. The diene preferably has
up to six carbon atoms and the substituents in the 2- and/or
3-position can be hydrogen, alkyl, generally lower alkyl, e.g., of
one to four carbon atoms, aryl (substituted or unsubstituted),
halogen, nitro, nitrile, etc. Typical dienes which can be employed
are 1,3-butadiene, isoprene, chloroprene, 2-cyano-1,3-butadiene,
isoprene, chloroprene, 2-cyano-1,3-butadiene,
2,3-dimethyl-1,3-butadiene, etc.
Olefinically unsaturated monomers which can be incorporated into
the diene polymer products used in this invention include
alpha-mono olefinic materials of about two or three to 10 or 12
carbon atoms such as styrene, vinyl toluene, methyl methacrylate,
methylacrylate, acrylic esters, vinyl chloride, vinylidene
chloride, etc. Acrylonitrile, acrylic acid, vinylidene cyanide,
acrylamide, etc., provide low-molecular weight hydroxy-terminated
diene intermediate copolymers which have sites suitable for
cross-linking. As can be seen, the usable olefinic monomers can be
ethylenes, substituted with halogen, aromatic hydrocarbon, or even
cyano or carboxylcontaining radicals in some instances. The choice
and amount of mono olefinic monomer employed will often be
determined on the basis of properties desired. Generally the amount
of monoolefinic monomer in the polymer will be about 0-75 percent
by weight of the total addition polymer, preferably about 1 to 40
percent, or even about 10-40 percent.
Specific hydroxyl-terminated homopolymers contemplated for the
present invention are those having the general formula:
HO--[(CH.sub.2 CH = CHCH.sub.2).sub..2 --(CH.sub.2 C (CH =
CH.sub.2)H).sub..2 --(CH.sub.2 CH = CHCH.sub.2).sub..6 ]--.sub.n
OH
where n = 44 to 65. Specific examples include resin R-45M having an
equivalent weight of 1330 and a hydroxyl content of 0.75
milliequivalents per gram; where n equals 44 to 60. Another example
is resin R-45HT having an equivalent weight of 1,180 and a hydroxyl
content of 0.85 milliequivalents per gram where n equals 57 to
65.
Specific hydroxyl-terminated copolymers contemplated for the
present invention are those having the general formula:
HO--[(CH.sub.2 CH = CHCH.sub.2).sub.a --
(C(X)HCH.sub.2).sub.b]--.sub.n OH
where a = 0.75, b = 0.25, n = 57 to 65, and X is the styrene
moiety. An example of such a styrene-butadiene copolymer is resin
CS-15 which has an equivalent weight of 1530, an iodine number of
335, and a hydroxyl content of 0.65 milliequivalents per gram.
The low molecular weight reinforcing polyols which can be employed
in the present invention in order to obtain improved tensile
strength, tear strength and adhesion are those polyols having an
equivalent weight of between about 50 and about 300 and preferably
those which have an average equivalent weight of between about 90
and about 250. The contemplated polyols, which can be di, tri or
tetra functional, should have an average functionality of between
2.0 and 2.5. In general, these polyols are employed in an amount
between about 1.5 and about 8 times the equivalents of liquid,
hydroxyl-terminated diene polymer utilized in connection with the
invention. Although bisisopropanol aniline is a preferred polyol
for the invention, other polyols which can be used include
bisisopropanol bisphenol A, 2-ethyl-1, 3-hexanediol, dipropylene
glycol, diethyleneglycol and bisisopropanol isophthalate.
Higher equivalent weight polyols, having an equivalent weight of
between about 500 and about 2200, can also be included in an amount
up to about 5 times the equivalents of diene polymer, preferably
between about 0.1 and about 5.0 times the equivalents of liquid,
hydroxyl-terminated diene polymer. For example, polypropylene
glycol can, if desired, be included in the fire retardant
polyurethane compositions.
Isocyanates which can be employed to form the polyurethane upon
reaction with the liquid, hydroxyl-terminated diene polymers
include tolyene diisocyanate (TDI), diphenyl methane 4,
4'-diisocyanate (MDI) and polymeric diisocyanates such as
polyphenylmethane polyisocyanate (PAPI). Other isocyanate materials
which can be used to produce urethane resin compositions of this
invention include any one of a number of materials containing two
or more isocyanate radicals, such as 1,5-naphthalene diisocyanate,
phenylene diisocyanates, trans-vinylene diisocyanate, hexamethylene
diisocyanate, octamethylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenyl diisocyanate, as well as related
aromatic and aliphatic isocyanates, which can also be substituted
with other organic or inorganic groups that do not adversely affect
the course of the urethane forming reaction. The isocyanate
material has a functionality of between 2 and 3 and is used in an
amount to provide a NCO/OH equivalents ratio of between about
0.95:1 and about 1.5:1 and preferably between about 1.0:1 and about
1.2:1.
A prepolymer can be employed as the isocyanate. An isocyanate
terminated prepolymer can be formed by adding an excess of
diisocyanate (e.g. tolylene diisocyanate) to the
hydroxyl-terminated diene homopolymer or copolymer.
Inorganic fillers are added in order to control viscosity and
prevent overpenetration into the carpet fibers. Among the fillers
which can incorporated into the adhesive compositions of this
invention include calcium carbonate, talc, clay, silica, zinc
oxide, feldspar, asbestos, carbon black and mixtures of these
fillers. In addition, fillers such as titanium dioxide, hydrated
alumina and barium sulfates can be employed. Generally, the amount
of filler utilized is between about 40 and about 800 parts per 100
parts by weight of the liquid, hydroxyl-terminated diene polymer
and preferably the amount of filler is between about 100 and about
600 parts per hundred parts by weight of hydroxyl-terminated diene
polymer. The fact that high filler levels can be employed means
that a significant economic advantage can be obtained using large
amounts of inexpensive filler in the formulation.
In order to keep the viscosity from becoming too high with the
filler loads utilized in connection with the invention up to about
200 and preferably up to about 100 parts of a hydrocarbon oil per
100 parts by weight of diene polymer are added. Preferably such
hydrocarbon oil is a naphthenic or aromatic oil which has a
viscosity at 100.degree. F. of between about 50 and about 2,500
Saybolt universal seconds and preferably between about 150 and
about 1,500 Saybolt seconds. Because of odor characteristics,
naphthenic oils are the preferred materials. Paraffinic oils can be
used, but occasionally a compatibilty problem occurs with such
oils. Since oil extension, which is desirable for lowering costs
and improving processibility, sometimes tends to be harmful to
certain physical properties, including adhesion and tuft lock,
higher molecular weight extenders can be used to replace part or
all of the oil employed. Examples of such extenders include
asphalt, vulcanized vegetable oils, factice and lower molecular
weight polystyrene.
Catalysts employed in connection with compositions of the present
invention in order to provide the necessary acceleration of cure
time include triethylene diamine (DABCO), various tin, lead and
zinc containing catalysts such as dibutyl tin dilaurate, nickel
acetyl acetonate, ferric acetyl acetonate, stannous octoate, cobalt
naphthenate and the like as well as combinations of such catalysts.
The amount of catalyst employed depends on the desired rate of cure
at the curing temperature. Generally, catalyst is used in an amount
varying between about 0.02 and about 4 parts per 100 parts by
weight of the liquid, hydroxyl-terminated diene polymer and
preferably is employed in an amount between about 0.1 and about 2.0
parts per 100 parts by weight of the diene polymer.
Water can also be added to the compositions to create a
polyurethane foam or sponge. Specifically, between 0 and about 10
parts of water per 100 parts by weight of the liquid, hydroxyl
terminated diene polymer can be incorporated in the composition.
Preferably, water is incorporated between about 1.0 and about 8
parts per hundred parts by weight of the diene polymer. Since the
isocyanate moiety is sensitive to water, the isocyanate should be
essentially isolated from water, air and the like before reaction.
In addition, the diene polymer and other reactants, and
particularly the fillers, which can contain variable amounts of
water, should be dried or degassed in a vacuum to remove moisture
before the reaction. The preferred procedure is to remove all the
moisture from the ingredients and then incorporate the desired
amount of water into the reaction mixture. By following this
procedure it is possible to know precisely how much water is in the
composition, and it is accordingly possible to obtain consistent
results for each formulation.
Generally when larger amounts of high molecular weight polyol are
used, amounts of the other ingredients used are at the upper end of
the ranges listed above. Conversely, when low amounts of high
molecular weight polyol are used, amounts of the other ingredients
are at the lower end of the ranges listed above. These various
amounts are adjusted to provide workable viscosities, desirable
cure times, and required fire retardancy, etc. for each specific
application.
Economically, it is often desirable to also incorporate various
inhibitors and other conventional additives in the adhesive
composition of the present invention. For example, oxidation
inhibitors can be added to improve aging characteristics. Such
inhibitors include alkylated phenol and aromatic amines.
Other substances, which can be added to the reaction mixture are
pigments, plasticizers, surfactants, stabilizers and the like.
Surfactants, for instance, can be added in order to increase the
penetration of the adhesive composition in the backing cloth or
primary fabric and around the pile so as to firmly bind the pile to
the backing cloth. Surfactants, such as various silicone materials,
serve to stabilize bubble formation. In some instances small
amounts of diluting agents, which decrease the viscosity of the
reaction mixture, can also be added to increase penetration.
Emulsifiers can be incorporated to disperse limited soluble
components. Dispersing aids can be incorporated to prevent filler
settlement. In addition, dehydrating agents such as molecular
sieves or zeolite materials, e.g., Linde 5A molecular sieve, can be
incorporated in order to regulate water content. Preferably these
materials are incorporated in the polyol blend, as hereinafter
defined.
Generally, all ingredients except the isocyanate are preblended.
This is commonly called the polyol blend. Conventional procedures
can be employed for mixing or blending the ingredients for the
polyol blend, including the use of double planetary arm mixers and
Cowles high speed mixers. The order of mixing can be varied to suit
the characteristics of the mixing equipment being used. The powder
material can be blended with a little liquid to obtain a good
dispersion and then the remainder of the liquid is added or liquid
can be blended and then the powder material is incorporated. Mixing
times will vary depending on the efficiency of the mixing equipment
and the type of filler used. The power material can be blended with
a little liquid to obtain a good dispersion and then the remainder
of the liquid is added or liquid can be blended and then the powder
material is incorporated. Mixing times will vary depending on the
efficiency of the mixing equipment and the type of filler used.
As previously indicated the isocyanate moiety is sensitive to water
and accordingly in the preferred practice moisture is initially
removed from the reactants. Alternatively, the reactants can be
mixed and then degassed, usually in a vacuum, to remove air bubbles
and moisture from the mixture. Following this procedure a mixture
can be degassed in a steam jacket kettle maintained under a vacuum
of 10 to 50 millimeters of mercury for a time period which can be
up to about 2 hours. Sometimes thin film evaporator type equipment
is used to remove moisture.
The viscosity of the resulting adhesive composition after the
isocyanate is added to the polyol blend is between about 3,000 and
about 100,000 centipoises and preferably between about 8,000 and
about 50,000 centipoises as measured using a Brookfield viscosity
device, Model RVT, operated at 5 rpm (revolutions per minute) using
a number 5 spindle. The viscosity measurement is made before
catalyst is added to the composition so as to eliminate the effects
of polymerization. The Brookfield viscometer and its operation are
described in "Development of Research Technique for Evaluating the
Low Temperature Fluidity of Automatic Transmission Fluids"
published by Coordinating Research Council, Inc., February 1963,
Appendix A. The thixotropic ratio for the adhesive composition
should be high enough that filler does not settle out of the
composition and also high enough to prevent overpenetration of the
carpet while being low enough to enable the adhesive composition to
be pumped, readily blended, and easily applied by doctoring
procedures conventional in the art. The thixotropic ratio
determined by viscosity measurements made at 1 and at 20
revolutions per minute is between about 1.3:1 and about 10:1 and
preferably between about 2:1 and about 8:1. Among the thixotropic
agents which can be incorporated to achieve the desired viscosity
and the aforementioned ratio are clays, such as kaolin; asbestos;
amines; and silica.
To apply the reactive ingredients to the carpet, the polyol blend
and the isocyanate are preferably accurately metered and mixed in a
multi-component mix-meter machine and continuously and immediately
fed by hose onto the underside of carpet (underside being up). If
desired, the catalyst, or water, or other components (including
fire retardant compound) can be fed into a multi-component mix
meter machine as separate accurately metered streams. To assure
better mixing a portion of the extender oil can be incorporated
with the isocyanate. Usually the ingredients are applied at a
temperature between room temperature and about 150.degree. F.
Preferably the temperature of application is between about
80.degree. and about 100.degree. F.
After the adhesive composition has been applied to the underside of
pile fiber or primary fabric substrate the adhesive composition is
then conventionally spread with a doctor blade. As the mixture
passes under the blade, the shearing action of the blade reduces
the viscosity so that the mixture can be forced down into and
around the tufts of yarn. After passing under the blade, the
original high viscosity is regained preventing undesirable
overpenetration. The amount of adhesive composition applied is
normally just sufficient to obtain adequate adhesion of the pile
fibers to the primary fabric substrate. Excess adhesive composition
is not only wasteful, but also can cause penetration of the primary
fabric, rendering yarn stiff and the final carpet unacceptable.
Typically, coating weights for carpets vary from about 12 to about
37 ounces per square yard. Preferably, however, the amount of
adhesive composition applied to the carpet ranges from about 20 to
about 30 ounces per square yard. In effect the lower limit with
respect to the amount applied is limited by the amount necessary to
adequately achieve the desired goal, whether it be that of a
laminating adhesive, precoat composition or unitary backing.
Curing time and temperature can be varied. Normally, curing is
accomplished at a temperature in the range between about
225.degree. and about 350.degree. F. and preferably in the range of
from about 275.degree. to about 325.degree. F. for a period of
about 0.3 to about 3 minutes. An oven or heated drum can be used
for curing.
Among the properties of a carpet which are directly affected by the
nature of the adhesive applied are tuft lock, anti-fray properties,
appearance and dimensional stability. Whereas closely woven carpets
of high pile density may have adequate tuft lock retention without
application of an adhesive, tufted carpets have virtually no tuft
retention in the absence of an adhesive. Anti-fray properties are
important with respect to the elimination of fraying of cut edges
of tufted carpets. To achieve complete anti-fray characteristics,
appreciable weight of adhesive coating is normally required. The
appearance of a carpet is judged by hand and visual appearance
after being laid. Certain adhesive compositions can provide a
better hand to a carpet by introducing a certain degree of
stiffness in the carpet. In addition, carpet stiffness also tends
to prevent buckling, imparts a high degree of resilience and
prevents slipping on a polished floor. Dimensional stability of a
carpet is obtained by locking the fibers together.
In addition to other requirements, the adhesive employed for
carpets must have long effectiveness and should have a high tensile
strength. In addition, the adhesive should not be degraded by water
or other common solvents which could be spilled on carpeting or
with which the carpet is likely to come in contact. Moreover, the
adhesive composition must be capable of application by simple
conventional techniques. Thus, in addition to good adhesion
characteristics, adhesive compositions must be judged by other
criteria.
Some of the important characteristics of adhesive compositions
utilized for carpet backing applications are T-peel, tuft lock and
pill test. T-peel is a value obtained when the secondary fabric
backing is pulled away from the primary fabric backing. This value
is determined using a Scott tester. Adhesion of the scrim or
secondary fabric backing to the primary fabric is referred to as
the "peel strength". This expression is used in its normal sense in
the carpet manufacturing industry to mean the force required to
peel apart a strip of two adhered components two inches wide which
have been aged 24 hours. It is measured by gripping components in
separate jaws of the Scott tensile tester and then moving the jaws
apart at a rate of two inches per minute. A value of between 6 and
15 pounds is normally obtained. Generally, the lighter the coating
weight, the lower the T-peel. Tuft lock is a determination of the
ability of the rug backing adhesive composition to hold fiber to
both the primary and secondary fabric backing material. Tuft lock
is determined by using a Scott tester to pull on one tuft of the
pile to measure the force required to pull the tuft away from the
primary and secondary fabric backing material. Normally, values for
styrene-butadiene rubber latex will vary from 6 to 15 pounds of
pull. At 20 to 30 pounds of pull, the yarns used in the carpet
industry usually break.
The pilling test is a determination of the ability of rug backing
composition to completely enclose individual fibers. Should the
fibers in the construction not be completely enclosed, mild rubbing
of the carpet produces loose strands of fibers which tend to form
into a small ball of fiber or a "pill."
The invention will be illustrated by the following examples, it
being understood that there is no intention to be necessarily
limited by any details thereof, since variations can be made within
the scope of the invention.
EXAMPLE I
A thixotropic adhesive composition was prepared by blending 100
parts by weight of a liquid, hydroxyl-terminated polybutadiene
(Resin R-45HT, manufactured by ARCO Chemical Company) having an
equivalent weight of 1180, a hydroxyl content of 0.85
milliequivalents per gram, and 0.05 weight percent moisture; with
24 parts by weight of bisisopropanol isophthalate having an
equivalent weight of 141 grams; 196 parts by weight of naphthenic
process oil (Acme S-60 oil, manufactured by Atlantic Richfield);
310 parts by weight of calcined kaolin (Glomax H. E., manufactured
by Georgia Kaolin Company); 0.02 parts by weight of dibutylin
dilaurate (T-12, manufactured by MeT Chemical Company); and 43.8
parts by weight of diphenyl methane 4,4'-diisocyanate (isonate
143-L, manufactured by Upjohn Company), having an equivalent weight
of 144 grams. This formulation can be used as an adhesive
composition for rug and carpet backing applications.
EXAMPLE II
A thixotropic adhesive composition was prepared by blending 100
parts by weight of R-45-HT resin (identified in Example I) with
17.7 parts by weight of bisisopropanol aniline (Isonol C-100,
manufactured by Upjohn Company) having an equivalent weight of 105
grams; 118 parts by weight of saturated naphthenic process oil
(Tufflo 6024 Oil, manufactured by Atlantic Richfield Company): 141
parts by weight of talc (Mistron Vapor, manufactured by United
Sierra); 94 parts by weight of dry ground fatty acid treated
calcium carbonate (Quincy-2-Electro, manufactured by Calcium
Carbonate Company); 0.25 parts by weight of dibutyltin dilaurate;
and 40.4 parts by weight of diphenyl methane 4,4' diisocyanate. The
resulting adhesive formulation gave good adhesion of jute backing
to carpet at a 15 ounce per square yard rate of application.
It was found that calcium carbonate (whiting) can be introduced at
higher levels than clay (Example I) or talc without causing
excessive viscosity increases and thus can be used to contribute to
lower cost. The use of higher levels of calcium carbonate does not
impart thixotropy and contributes little to reinforcement; hence a
balance between the filler and calcium carbonate loadings must be
achieved.
EXAMPLE III
An adhesive formulation was prepared by blending 100 parts by
weight of R-45HT resin (identified in Example I); 16.6 parts by
weight of bisisopropanol aniline; 100 parts by weight of a low
viscosity saturated naphthenic process oil (Tufflo 6004 Oil,
manufactured by Atlantic Richfield); 100 parts by weight of dry
ground calcium carbonate; 200 parts by weight of calcined kaolin;
1.06 parts by weight of water; 0.07 parts by weight of dibutyltin
dilaurate; and 70.8 parts by weight of diphenyl methane,
4,4'-diisocyanate.
The resulting adhesive composition had a NCO/OH ratio of 1.36. When
applied at an application rate of 28 ounces per square yard, tuft
lock equaled 12.7 pounds (average) and 15 pounds (maximum). In
addition, adhesion of the backing was excellent; jute was destroyed
when attempting to delaminate double backed carpet.
Addition of water to the formulation of this example prior to
isocyanate cure was found to be very beneficial for the following
reasons:
a. The thixotropy of the uncured mix was greatly increased,
presumably due to floculation of kaolin clay.
b. Tuft lock was increased. The same formulation without added
water and the equivalent amount of diisocyanate had a maximum tuft
lock of only 8.5 pounds. The water reaction contributes urea
linkages to the polymer which should provide additional
reinforcement.
c. Water reaction with isocyanate results in a chemical flow (foam
formation) which appears to be beneficial since it increases the
volume of the mix and allows lower application rates, provides
continued blow after application which helps prevent voids between
the carpet tufts, thereby resulting in more effective use of the
adhesive, particularly if the foam is crushed at the proper stage
of tackiness, and chemical blow brings the adhesive out of the
tufts into contact with the secondary backing thereby assuring good
adhesion of the latter to the carpet even if initial penetration of
the mix is excessive.
EXAMPLE IV
The following prepolymer precoat formulation was prepared and
applied to red nylon carpet. The formulation consisted of 100 parts
by weight of liquid, hydroxyl-terminated polybutadiene prepolymer
having 8.3 weight percent free NCO groups (R-45HT resin identified
in Example I reacted with tolylene diisocyanate); 13.5 parts by
weight of bisisopropanol aniline; 2.9 grams of bisisopropanol
bisphenol A; 100 grams of dry ground fatty acid treated calcium
carbonate; and 2.5 parts by weight of 5A molecular sieve; 0.10 part
by weight of dibutyltin dilaurate.
The resulting prepolymer composition had a NCO/OH ratio of 1.1 and
was cured for 30 minutes at 220.degree. F. It was applied to carpet
at 28 ounces per square yard. The resulting tuft lock was 20 pounds
while bundle wrap was 90 to 100.
EXAMPLE V
A prepolymer precoat formulation was prepared in the following
manner and applied to red nylon carpet. The formulation consisted
of 100 parts by weight of liquid, hydroxyl-terminated polybutadiene
prepolymer (identified in Example IV); 13.5 parts by weight of
bisisopropanol aniline; 11.6 grams of bisisopropanol bisphenol A;
100 grams of dry ground fatty acid treated calcium carbonate; 2.5
parts by weight of 5A molecular sieve; and 0.10 part by weight of
dibutyltin dilaurate.
The resulting prepolymer formulation had a NCO/OH ratio of 1.1 and
was cured 30 minutes at a temperature of 220.degree. F. It was
applied to tufted nylon carpet at 28 ounces per square yard. The
carpet had a tuft lock of 20 pounds and a bundle wrap of 75.
EXAMPLE VI
A prepolymer adhesive precoat formulation was prepared in the
following manner. 100 parts by weight of liquid,
hydroxyl-terminated polybutadiene polymer (identified in Example
IV) was mixed with 18 parts by weight of bisisopropanol aniline;
0.10 part by weight of dibutyltin dilaurate; 2 grams of silicone
(GE SF 1156 surfactant); and 1 gram of water.
The resulting formulation had a NCO/OH ratio of 1.1. After being
applied to blue nylon carpet the formulation was treated for 30
minutes at a temperature of 220.degree. F. The coating was applied
at 32 ounces per square yard. The resulting tuft lock was 15 pounds
and a bundle wrap of 90 was obtained.
EXAMPLE VII
A prepolymer adhesive precoat formulation was prepared by adding
100 parts by weight of liquid, hydroxyl-terminated polybutadiene
prepolymer (identified in Example IV); 4.3 parts by weight of
bisisopropanol aniline; 34.8 grams of bisisopropanol bisphenol A;
200 grams of dry ground fatty acid treated calcium carbonate; 2.5
grams of 5A molecular sieve; and 0.10 part by weight of dibutyltin
dilaurate.
The resulting prepolymer composition, having an NCO/OH ratio of
1.1, was applied to blue nylon carpet and heated for 30 minutes at
a temperature of 220.degree. F. The coating was applied at 28
ounces per square yard. A tuft lock measurement of 18 pounds and an
average bundle wrap of 97 were obtained.
EXAMPLE VIII
A prepolymer adhesive precoat formulation was prepared by adding
100 parts by weight of liquid, hydroxyl-terminated polybutadiene
prepolymer (identified in Example IV); 4.3 parts by weight of
bisisopropanol aniline; 34.8 grams of bisisopropanol bisphenol A;
100 grams of dry ground fatty acid treated calcium carbonate; 2
grams of silicone (GE SF 1156 surfactant); 1 gram of water; 2.5
grams of 5A molecular sieve; and 0.10 part by weight of dibutyltin
dilaurate.
The resulting prepolymer composition, having an NCO/OH ratio of
1.1, was applied to blue nylon carpet and heated for 30 minutes at
a temperature of 220.degree. F. The coating was applied at 28
ounces per square yard. A tuft lock measurement of 14 pounds and an
average bundle wrap of 90 were obtained.
The compositions of the foregoing examples had a viscosity between
about 3,000 and about 100,000 centipoises as measured using a
Brookfield Viscosity Device, Model RVT, operated at 5 rpm using a
number 5 spindle. The thixotropic ratio of said compositions,
determined by viscosity measurements made at 1 and at 20 rpm, was
between about 1.3:1 and about 10:1.
From the foregoing it will be seen that this invention is well
adapted to obtain all of the ends and objects hereinabove set
forth, together with other advantages which are obvious or inherent
in the system. Characteristics of formulations prepared in
accordance with the present invention include a 12 to 20 pound tuft
lock; 75 to 100 percent bundle wrap; a backing destroying bond
(i.e., the secondary fabric backing is torn upon attempted
delamination); a good hand which is soft to firm without causing
"boardiness"; a viscosity low enough to allow pumping, mixing and
ease of application but high enough to prevent rapid uncontrolled
penetration into the fibers (i.e., a thixotropic formulation); and
rapid curing.
The thixotropic polyurethane adhesive compositions of the present
invention have several advantages over the carboxylated styrene
butadiene rubber latex adhesives which have been used for so many
years. First the "cure" of carboxylated latex adhesive is primarily
a drying cycle which cannot be catalyzed in order to shorten the
time. In contrast, the thixotropic adhesive compositions of the
present invention cure through reaction with diisocyanate which can
be catalyzed to any desired degree. Moreover, the cure, if
sufficiently catalyzed, will take place rapidly at lower
temperatures (e.g., 200.degree. F.) Rapid cure increases production
and greatly decreases capital investment since smaller curing ovens
are required. Fuel requirements are also greatly reduced. The
thixotropic adhesive compositions of the present invention also
have the advantage of having a higher early green strength which
thereby reduces the chances of accidental delamination. Application
of the thixotropic adhesive compositions of the present invention
is also simpler than application of carboxylated latex adhesives.
The composition of the invention can be discharged onto a carpet
continuously by means of a hose or nozzle and the resulting
adhesive adjusted using a conventional doctor blade to give the
desired rate of application and degree of penetration. Another
advantage is the fact that smaller and simpler equipment can be
used with the thixotropic adhesive compositions of the present
invention and this means a reduction in capital investment and
required operators, thus reducing production costs.
Obviously, many modifications and variations of the invention as
hereinbefore set forth can be made without departing from the
spirit and scope thereof.
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