U.S. patent application number 15/681727 was filed with the patent office on 2017-11-30 for cross-linked polymers and their use in packaging films and injection molded articles.
The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to Steven C Pesek, Charles Anthony Smith.
Application Number | 20170342182 15/681727 |
Document ID | / |
Family ID | 49911839 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170342182 |
Kind Code |
A1 |
Pesek; Steven C ; et
al. |
November 30, 2017 |
CROSS-LINKED POLYMERS AND THEIR USE IN PACKAGING FILMS AND
INJECTION MOLDED ARTICLES
Abstract
Provided are novel cross-linked polymers and their use in
various materials, including packaging films and injection molded
articles. These polymers, which comprise certain
hydroxyl-containing crosslinking compounds, as well as optionally
adjuvants, show improved creep resistance when compared to
conventional ethylene acrylic or methacrylic acid copolymers and
their ionomers.
Inventors: |
Pesek; Steven C; (Orange,
TX) ; Smith; Charles Anthony; (Vienna, WV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Family ID: |
49911839 |
Appl. No.: |
15/681727 |
Filed: |
August 21, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14653890 |
Jun 19, 2015 |
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PCT/US13/76339 |
Dec 19, 2013 |
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15681727 |
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61739572 |
Dec 19, 2012 |
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61739557 |
Dec 19, 2012 |
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61739562 |
Dec 19, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 17/10036 20130101;
Y10T 428/31797 20150401; Y10T 428/31507 20150401; B32B 17/10743
20130101; Y10T 428/31913 20150401; B32B 17/10018 20130101; A63B
37/0003 20130101; C08L 2312/00 20130101; B32B 17/10697 20130101;
C09D 123/0876 20130101; Y10T 428/31699 20150401; Y10T 428/31663
20150401; C09D 123/0869 20130101; Y10T 428/31757 20150401; C08J
2333/02 20130101; C08J 2323/08 20130101; C08F 222/02 20130101; Y10T
428/31649 20150401; B32B 2307/558 20130101; Y10T 428/31935
20150401; C08L 2203/204 20130101; C08J 5/18 20130101; C08F 210/02
20130101; H01L 51/448 20130101; Y02E 10/549 20130101; C08F 2500/12
20130101; Y10T 428/31576 20150401; C08F 2500/26 20130101; C08F
220/06 20130101 |
International
Class: |
C08F 222/02 20060101
C08F222/02; C09D 123/08 20060101 C09D123/08; B32B 17/10 20060101
B32B017/10; C08J 5/18 20060101 C08J005/18; H01L 51/44 20060101
H01L051/44; A63B 37/00 20060101 A63B037/00 |
Claims
1. A polymer composition comprising an ethylene copolymer, said
ethylene copolymer comprising copolymerized units of ethylene,
about 5 to about 90 wt % of copolymerized units of a first
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 10 carbon
atoms; and optionally about 2 to about 40 wt % of copolymerized
units of a derivative of a second .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 10 carbon atoms; wherein the weight
percentages of the copolymerized units are based on the total
weight of the ethylene copolymer and the sum of the weight
percentages of the copolymerized units is 100 wt %; and wherein
optionally at least a portion of the carboxylic acid groups of the
copolymerized units of the .alpha.,.beta.-unsaturated carboxylic
acid units are neutralized to form carboxylate salts; a
hydroxyl-containing crosslinking agent; and a silane adjuvant.
2. A product of cross-linking the polymer composition of claim 1,
wherein at least a portion of the carboxylic acid groups or
carboxylate groups of two or more ethylene copolymers are reacted
with at least two of the hydroxyl groups of the hydroxyl-containing
crosslinking agent, so that the hydroxyl-containing crosslinking
agent forms a cross-link between two or more ethylene copolymer
molecules.
3. The polymer composition of claim 1, wherein about 5% to about
90% of the total content of the carboxylic acid groups present in
the ethylene copolymer have been neutralized to form carboxylate
groups having counterions.
4. The polymer composition of claim 1, wherein the ethylene
copolymer comprises about 10 wt % to about 30 wt % of copolymerized
units of the .alpha.,.beta.-ethylenically unsaturated carboxylic
acid.
5. The polymer composition of claim 4, wherein the
.alpha.,.beta.-ethylenically unsaturated carboxylic acid is
selected from the group consisting of acrylic acids, methacrylic
acids, and mixtures of two or more of an acrylic acid and a
methacrylic acid.
6. The polymer composition of claim 1, wherein the
hydroxyl-containing crosslinking agent comprises a diol.
7. The polymer composition of claim 6, wherein the
hydroxyl-containing crosslinking agent comprises
1,4-butanediol.
8. The polymer composition of claim 1, wherein the silane adjuvant
comprises a silanc is selected from the group consisting of
N-(2-aminoethyl-3-aminopropyl) trimethoxysilane, 3-glycidoxypropyl
trimethoxysilane, and combinations of
N-(2-aminoethyl-3-aminopropyl) trimethoxysilane and
3-glycidoxypropyl trimethoxysilane, and wherein the silane adjuvant
is present in amounts an amount of between about 0.025 and 2.0 wt
%, based on the total weight of the polymer composition.
9. A film comprising the composition of claim 1.
10. An injection molded article comprising the composition of claim
1.
11. A golf ball comprising the composition of claim 1.
12. The polymer composition of claim 1, exhibiting an elongation of
at least 10%, as determined by ASTM D2990-09.
13. The polymer composition of claim 3, wherein the counter ion is
sodium or zinc.
14. A package comprising the film of claim 9.
15. A film comprising the composition of claim 2.
16. An injection molded article comprising the composition of claim
2.
17. A golf ball comprising the composition of claim 2.
18. A film comprising the composition of claim 3.
19. An injection molded article comprising the composition of claim
3.
20. A golf ball comprising the composition of claim 3.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to novel cross-linked
polymers and their use in various materials, including packaging
films and injection molded articles. The herein-described polymers,
which comprise certain hydroxyl-containing crosslinking compounds,
as well as optionally adjuvants, show improved creep resistance and
exceptional stretch when compared to conventional ethylene acrylic
or methacrylic acid copolymers or ionomers thereof.
BACKGROUND OF THE INVENTION
[0002] Several patents, patent applications and publications are
cited in this description in order to more fully describe the state
of the art to which this invention pertains. The entire disclosure
of each of these patents, patent applications and publications is
incorporated by reference herein.
[0003] The use of polymers for packaging films, injection molded
articles, and other end-uses is well known in the art. Some films
are designed to be breathable, allow oxygen and/or moisture to pass
through, exhibit elastic properties, and protect the materials they
surround. See, for example, U.S. Pat. No. 7,438,940, U.S. Pat. No.
7,635,509, U.S. 2006/0094824, and U.S. 2010/0272898.
[0004] Polymeric materials can also be used for blown films (see,
for example, U.S. 2011/0028622) and for thermoforming (see, for
example, U.S. 2009/0099313 and U.S. Pat. No. 8,110,138).There is a
need for polymer materials for packaging end-uses that exhibit
exceptional elongation while maintaining mechanical integrity.
Moreover, there is a need for injection-molded articles that have
the exceptional clarity associated with ethylene acid copolymers
and ionomers combined with the improved mechanical properties
provided by cross-linking. Crosslinking occurs when chemical bonds
are formed between polymeric moieties that are present.
Crosslinking allows the formation of polymeric networks that can
enhance the overall strength of the material made from the
composition, and allow improved elongation, mechanical integrity,
and resistance to break.
[0005] Crosslinking by various methods is known. For example,
ethylene vinyl acetate (EVA) is often crosslinked with peroxides to
form sheets and encapsulants. However, unlike the crosslinking
accomplished by the present invention, the crosslinking of EVA with
peroxide can form gel and can lead to the degradation of the EVA.
See, for example, U.S. Pat. No. 6,093,757, issued Jul. 25, 2000 to
Pern.
[0006] It has been found, and is shown in the examples included
herein, that adding a hydroxyl-containing crosslinking agent to the
ionomers in the melt can act to cross-link the ionomer, thus making
the material more creep-resistant. While not wishing to be bound by
theory, it is believed that the hydroxyl-containing crosslinking
agent reacts with the carboxylate groups of the ionomers to form
esters, which then cross-link the ionomers. As shown in the
examples and figures included herein, the cross-linked ionomers
exhibit good tensile strength as well. Additionally, the materials
exhibit greater elongation with integrity when compared to sheets
or films without the hydroxyl-containing crosslinking agent
addition. The term "elongation with integrity", as used herein,
refers to the ability of a film to stretch by 10% or greater
without incurring any defects that would impair performance.
Non-limiting examples of such defects include breaking, stretching
and necking down to a thin fiber-like construction, and material
unable to support its own weight.
SUMMARY OF THE INVENTION
[0007] Provided herein is a polymer composition comprising an
ethylene copolymer, said ethylene copolymer comprising
copolymerized units of ethylene, about 5 to about 90 wt % of
copolymerized units of a first .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 10 carbon atoms; and optionally about 2
to about 40 wt % of copolymerized units of a derivative of a second
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 10 carbon
atoms. These weight percentages of the copolymerized units are
based on the total weight of the ethylene copolymer. Optionally, at
least a portion of the carboxylic acid groups of the copolymerized
units of the .alpha.,.beta.-unsaturated carboxylic acid units are
neutralized to form carboxylate salts. The acid copolymer
composition also includes a hydroxyl-containing crosslinking agent,
and may optionally include an adjuvant.
[0008] Further provided herein is a product of cross-linking the
acid copolymer composition described herein, wherein at least two
of the carboxylic acid groups of the ethylene copolymer are reacted
with two or more of the hydroxyl groups of the hydroxyl-containing
crosslinking agent, to form cross-links between two or more
ethylene copolymers
[0009] Further provided are packaging films, and injection-molded
articles comprising the polymer compositions described herein.
BRIEF DESCRIPTION OF THE FIGURES/DRAWINGS
[0010] FIG. 1 is a graphical representation of the tensile
elongation of a polymer composition of the invention compared to
that of a control material.
[0011] FIG. 2 is a differential scanning calorimetry (DSC) trace of
a polymer composition of the invention.
[0012] FIG. 3 is a differential scanning calorimetry (DSC) trace of
a control material.
[0013] FIG. 4 is a graphical representation of the laminate creep
resistance of several polymer compositions of the invention
compared to that of a control material.
[0014] FIG. 5 is a graphical representation of the viscosity shear
rate of a polymer composition of the invention compared to that of
a control material.
DETAILS OF THE INVENTION
[0015] The following definitions apply to the terms as used
throughout this specification, unless otherwise limited in specific
instances.
[0016] Moreover, unless otherwise defined, all technical and
scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. In case of conflict, the present specification,
including the definitions herein, will control.
[0017] Although methods and materials similar or equivalent to
those described herein can be used in the practice or testing of
the invention, suitable methods and materials are described
herein.
[0018] As used herein, the term "about" means that amounts, sizes,
formulations, parameters, and other quantities and characteristics
are not and need not be exact, but may be approximate and/or larger
or smaller, as desired, reflecting tolerances, conversion factors,
rounding off, measurement error and the like, and other factors
known to those of skill in the art. In general, an amount, size,
formulation, parameter or other quantity or characteristic is
"about" or "approximate" whether or not expressly stated to be
such.
[0019] The term "or", as used herein, is inclusive; more
specifically, the phrase "A or B" means "A, B, or both A and B".
Exclusive "or" is designated herein by terms such as "either A or
B" and "one of A or B", for example.
[0020] In addition, the ranges set forth herein include their
endpoints unless expressly stated otherwise in limited
circumstances. Further, when an amount, concentration, or other
value or parameter is given as a range, one or more preferred
ranges or a list of upper preferable values and lower preferable
values, this is to be understood as specifically disclosing all
ranges formed from any pair of any upper range limit or preferred
value and any lower range limit or preferred value, regardless of
whether such pairs are separately disclosed.
[0021] Moreover, where a range of numerical values is recited
herein, unless otherwise stated in specific circumstances, the
range is intended to include the endpoints thereof, and all
integers and fractions within the range. It is not intended that
the scope of the invention be limited to the specific values
recited when defining a range. Finally, when the term "about" is
used in describing a value or an end-point of a range, the
disclosure should be understood to include the specific value or
end-point referred to.
[0022] When materials, methods, or machinery are described herein
with the term "known to those of skill in the art", or a synonymous
word or phrase, the term signifies that materials, methods, and
machinery that are conventional at the time of filing the present
application are encompassed by this description. Also encompassed
are materials, methods, and machinery that are not presently
conventional, but that will have become recognized in the art as
suitable for a similar purpose.
[0023] As used herein, the terms "comprises," "comprising,"
"includes," "including," "containing," "characterized by," "has,"
"having" or any other synonym or variation thereof refer to a
non-exclusive inclusion. For example, a process, method, article,
or apparatus that is described as comprising a particular list of
elements is not necessarily limited to those particularly listed
elements but may further include other elements not expressly
listed or inherent to such process, method, article, or
apparatus.
[0024] The transitional phrase "consisting essentially of" limits
the scope of a claim to the specified materials or steps and those
that do not materially affect the basic and novel characteristic(s)
of the claimed invention. "A `consisting essentially of` claim
occupies a middle ground between closed claims that are written in
a `consisting of` format and fully open claims that are drafted in
a `comprising` format."
[0025] Where an invention or a portion thereof is described with an
open-ended term such as "comprising," it is to be understood that,
unless otherwise stated in specific circumstances, this description
also includes a description of the invention using the term
"consisting essentially of" as they are defined above.
[0026] The indefinite articles "a" and "an" are employed to
describe elements and components of the invention. The use of these
articles means that one or at least one of these elements or
components is present. Although these articles are conventionally
employed to signify that the modified noun is a singular noun, as
used herein the articles "a" and "an" also include the plural,
unless otherwise stated in specific instances. Similarly, the
definite article "the", as used herein, also signifies that the
modified noun may be singular or plural, again unless otherwise
stated in specific instances.
[0027] As used herein, the term "copolymer" refers to polymers
comprising copolymerized units or residues resulting from
copolymerization of two or more comonomers. In this connection, a
copolymer may be described herein with reference to its constituent
comonomers or to the amounts of its constituent comonomers, for
example "a copolymer comprising ethylene and 9 weight % of acrylic
acid", or a similar description. Such a description may be
considered informal in that it does not refer to the comonomers as
copolymerized units; in that it does not include a conventional
nomenclature for the copolymer, for example International Union of
Pure and Applied Chemistry (IUPAC) nomenclature; in that it does
not use product-by-process terminology; or for another reason. As
used herein, however, a description of a copolymer with reference
to its constituent comonomers or to the amounts of its constituent
to comonomers means that the copolymer contains copolymerized units
(in the specified amounts when specified) of the specified
comonomers. It follows as a corollary that a copolymer is not the
product of a reaction mixture containing given comonomers in given
amounts, unless expressly stated in limited circumstances to be
such. The term "acid copolymer" refers to a polymer comprising
copolymerized units of an .alpha.-olefin, an
.alpha.,.beta.-ethylenically unsaturated carboxylic acid, and
optionally other suitable comonomer(s), such as an
.alpha.,.beta.-ethylenically unsaturated carboxylic acid ester.
[0028] The term "(meth)acrylic", as used herein alone or in
combined form, such as "(meth)acrylate", refers to acrylic or
methacrylic, for example, "acrylic acid or methacrylic acid", or
"alkyl acrylate or alkyl methacrylate".
[0029] The term "ionomer" refers to a polymer that is produced by
partially or fully neutralizing an acid copolymer as described
above. More specifically, the ionomer comprises ionic groups that
are metal ion carboxylates, for example, alkali metal carboxylates,
alkaline earth metal carboxylates, transition metal carboxylates
and mixtures of such carboxylates. Such polymers are generally
produced by partially or fully neutralizing the carboxylic acid
groups of precursor or parent polymers that are acid copolymers, as
defined herein, for example by reaction with a base. An example of
an alkali metal ionomer as used herein is a sodium ionomer (or
sodium neutralized ionomer), for example a copolymer of ethylene
and methacrylic acid wherein all or a portion of the carboxylic
acid groups of the copolymerized methacrylic acid units are in the
form of sodium carboxylates.
[0030] The term "laminate", as used herein alone or in combined
form, such as "laminated" or "lamination" for example, refers to a
structure having at least two layers that are adhered or bonded
firmly to each other. The layers may be adhered to each other
directly or indirectly. "Directly" means that there is no
additional material, such as an interlayer or an adhesive layer,
between the two layers, and "indirectly" means that there is
additional material between the two layers. Layers or films can be
"laminated" together by heat and pressure, or can be co-extruded so
that the layers adhere to each other.
[0031] The materials, methods, and examples herein are illustrative
only and, except as specifically stated, are not intended to be
limiting.
[0032] Finally, all percentages, parts, ratios, and the like set
forth herein are by weight, unless otherwise stated in specific
instances. Provided herein is a polymer composition comprising an
ethylene copolymer, which in turn comprises copolymerized units of
ethylene, about 5 to about 90 wt % of copolymerized units,
preferably about 5 to about 30 wt % of copolymerized units, of a
first .alpha.,.beta.-unsaturated carboxylic acid having 3 to 10,
preferably 3 to 8, carbon atoms; and optionally about 2 to about 40
wt % or preferably from about 5 to 30 wt %, of copolymerized units
of a derivative of a second .alpha.,.beta.-unsaturated carboxylic
acid having 3 to 10, preferably 3 to 8, carbon atoms. The weight
percentages of the copolymerized units are based on the total
weight of the ethylene copolymer, and the sum of the weight
percentages of the copolymerized units is 100 wt %. Optionally at
least a portion of the carboxylic acid groups of the copolymerized
units of the .alpha.,.beta.-unsaturated carboxylic acid units are
neutralized to form carboxylate salts. The polymer composition
further comprises a hydroxyl-containing crosslinking agent; and,
optionally, also comprises an adjuvant.
[0033] Suitable .alpha.-olefin comonomers may include, but are not
limited to, ethylene, propylene, 1-butene, 1-pentene, 1-hexene,
1-heptene, 3 methyl-1-butene, 4-methyl-1-pentene, and the like and
mixtures of two or more thereof. In one preferred copolymer, the
a-olefin is ethylene.
[0034] Suitable first .alpha.,.beta.-ethylenically unsaturated acid
comonomers may include, but are not limited to, carboxylic acids,
including acrylic acids, methacrylic acids, itaconic acids, maleic
acids, fumaric acids, and mixtures of two or more thereof.
[0035] In one preferred copolymer, the .alpha.,.beta.-ethylenically
unsaturated carboxylic acid is selected from acrylic acids,
methacrylic acids, and mixtures of two or more thereof. In another
preferred copolymer, the .alpha.,.beta.-ethylenically unsaturated
carboxylic acid is methacrylic acid.
[0036] The ethylene copolymers may further comprise copolymerized
units of one or more other comonomer(s), such as a second
.alpha.,.beta.-ethylenically unsaturated carboxylic acid having 2
to 10, or preferably 3 to 8 carbons, or derivatives thereof.
Suitable acid derivatives include acid anhydrides, amides, and
esters. Esters are preferred. Specific examples of preferred esters
of unsaturated carboxylic acids include, but are not limited to,
methyl acrylates, methyl methacrylates, ethyl acrylates, ethyl
methacrylates, propyl acrylates, propyl methacrylates, isopropyl
acrylates, isopropyl methacrylates, butyl acrylates, butyl
methacrylates, isobutyl acrylates, isobutyl methacrylates,
tert-butyl acrylates, tert-butyl methacrylates, octyl acrylates,
octyl methacrylates, undecyl acrylates, undecyl methacrylates,
octadecyl acrylates, octadecyl methacrylates, dodecyl acrylates,
dodecyl methacrylates, 2-ethylhexyl acrylates, 2-ethylhexyl
methacrylates, isobornyl acrylates, isobornyl methacrylates, lauryl
acrylates, lauryl methacrylates, 2-hydroxyethyl acrylates,
2-hydroxyethyl methacrylates, glycidyl acrylates, glycidyl
methacrylates, poly(ethylene glycol) acrylates, poly(ethylene
glycol)methacrylates, poly(ethylene glycol) methyl ether acrylates,
poly(ethylene glycol) methyl ether methacrylates, poly(ethylene
glycol) behenyl ether acrylates, poly(ethylene glycol) behenyl
ether methacrylates, poly(ethylene glycol) 4-nonylphenyl ether
acrylates, poly(ethylene glycol) 4-nonylphenyl ether methacrylates,
poly(ethylene glycol) phenyl ether acrylates, poly(ethylene glycol)
phenyl ether methacrylates, dimethyl maleates, diethyl maleates,
dibutyl maleates, dimethyl fumarates, diethyl fumarates, dibutyl
fumarates, dimethyl fumarates, vinyl acetates, vinyl propionates,
and mixtures of two or more thereof. In one preferred copolymer,
the suitable additional comonomers are selected from methyl
acrylates, methyl methacrylates, butyl acrylates, butyl
methacrylates, glycidyl methacrylates, vinyl acetates, and mixtures
of two or more thereof. In one preferred ethylene com polymer, the
first .alpha.,.beta.-ethylenically unsaturated carboxylic acid is
the same as the second .alpha.,.beta.-ethylenically unsaturated
carboxylic acid; in another preferred ethylene copolymer, however,
the first and the second .alpha.,.beta.-ethylenically unsaturated
carboxylic acids are different. In another preferred copolymer,
however, the precursor acid copolymer does not incorporate other
additional comonomers.
[0037] Suitable precursor acid copolymers have a melt flow rate
(MFR) of about 1 to about 4000 g/10 min, or about 1 to 1000 g/10
min, or about 20 to about 400 g/10 min, as determined in accordance
with ASTM method D1238-89 at 190.degree. C. and 2.16 kg.
[0038] Finally, suitable precursor acid copolymers may be
synthesized as described in U.S. Pat. Nos. 3,404,134; 5,028,674;
6,500,888; 6,518,365, or 8,399,096, for example. Some of these
methods are also described in detail in U.S. Pat. No. 8,334,033,
issued to Hausmann, et al.
[0039] To obtain the ionomers, the precursor acid copolymers are
partially neutralized by reaction with one or more bases. An
example of a suitable procedure for neutralizing the precursor acid
copolymers is described in U.S. Pat. Nos. 3,404,134 and 6,518,365.
After neutralization, about 1% to about 90%, or about 10% to about
60%, or about 20% to about 55%, of the hydrogen atoms of carboxylic
acid groups present in the precursor acid are replaced by other
cations. Stated alternatively, about 1% to about 90%, or about 10%
to about 60%, or about 20% to about 55%, of the total content of
the carboxylic acid groups present in the precursor acid copolymer
are neutralized. In another alternative expression, the acid groups
are neutralized to a level of about 1% to about 90%, or about 10%
to about 60%, or about 20% to about 55%, based on the total content
of carboxylic acid groups present in the precursor acid copolymers
as calculated or measured for the non-neutralized precursor acid
copolymers. The neutralization level can be tailored for the
specific end-use.
[0040] The ionomers comprise cations as counterions to the
carboxylate anions. Suitable cations include any positively charged
species that is stable under the conditions in which the ionomer
composition is synthesized, processed and used.
[0041] In some preferred ionomers, the cations used are metal
cations, which may be monovalent, divalent, trivalent, multivalent,
or mixtures thereof. Useful monovalent metal cations include but
are not limited to cations of sodium, potassium, lithium, silver,
mercury, copper, and the like, and mixtures thereof. Useful
divalent metal cations include but are not limited to cations of
beryllium, magnesium, calcium, strontium, barium, copper, cadmium,
mercury, tin, lead, iron, cobalt, nickel, zinc, and the like, and
mixtures thereof. Useful trivalent metal cations include but are
not limited to cations of aluminum, scandium, iron, yttrium, and
the like, and mixtures thereof. Useful multivalent metal cations
include but are not limited to cations of titanium, zirconium,
hafnium, vanadium, tantalum, tungsten, chromium, cerium, iron, and
the like, and mixtures thereof. It is noted that when the metal
cation is multivalent, complexing agents such as stearate, oleate,
salicylate, and phenolate radicals may be included, as described in
U.S. Pat. No. 3,404,134. In another preferred composition, the
metal cations used are monovalent or divalent metal cations.
Preferred metal cations are sodium, lithium, magnesium, zinc,
potassium and mixtures thereof. In yet another preferred
composition, the cations of sodium, zinc and mixtures thereof are
more preferred.
[0042] The resulting neutralized ionomer will have a melt index, as
determined in accordance with ASTM method D1238-89 at 190.degree.
C. and 2.16 kg, that is lower than that of the corresponding
ethylene copolymer.
[0043] The acid copolymer composition also includes a
hydroxyl-containing crosslinking agent. As used herein, the term
"hydroxyl-containing crosslinking agent" refers to any molecule
that is miscible with the ethylene copolymer and that has two or
more hydroxyl groups. Generally, any hydroxyl-containing
crosslinking agent can be contemplated for use with the present
invention.
[0044] Combinations of two or more hydroxyl-containing crosslinking
agents may also be used. Examples of suitable hydroxyl-containing
crosslinking agents include, without limitation, dihydroxyl,
trihydroxyl and multihydroxyl compounds. Of note are glycols, such
as propylene glycol; sorbitol; glycerol; poly(alkylene glycols),
such as PEG600 and PEG2000; glycerol monstearate; and polyvinyl
alcohol. Preferred are diols, such as 1,4-butanediol,
1,3-propanediol and 1,6-hexanediol. 1,4-Butanediol is particularly
preferred.
[0045] The hydroxyl-containing crosslinking agent is included in
the acid copolymer composition in an amount of up to about 5 wt %,
preferably about 2 wt % or less or about 1.5 wt % or less, more
preferably about 1 wt % or less, 0.5 wt % or less, or 0.25 wt % or
less, or 0.1 wt %, based on total weight of the acid copolymer
composition.
[0046] Those of skill in the art are able to determine an
appropriate level of cross-linking based on the physical properties
that are desired in the cross-linked composition. For example,
higher levels of cross-linking are correlated with a higher flex
modulus, better high temperature adhesion, lower melt indices, and
better heat resistance. However, consideration should be made to
adjust the level of cross-linking so that the desired end use
performance is obtained. For example, a level of cross-linking may
be desirable at which the creep or displacement properties are
controlled or minimized at the expected stress level and
temperature range for said article. A level chosen by these
criteria allows for the ease of processing of the cross-linked
resin, through extrusion and any other secondary or forming/shaping
process.
[0047] Those of skill in the art are also aware that the time
required to obtain a desired level of cross-linking depends
directly on the concentration of carboxylic acid groups and
hydroxyl-containing groups. Likewise, the time required to obtain a
desired level of cross-linking can depend inversely on the
temperature at which the cross-linking reaction is carried out, and
also can depend inversely or in another negative logarithmic
relationship on the melt index of the polymer blend.
[0048] Cross-linking reactions can require heat, but the reaction
may also be carried out using catalysis, or by using a combination
of heat and catalysis. For example, esterification reactions are
known to be catalyzed by acid catalysts and by base catalysts.
[0049] While any hydroxyl-containing crosslinking agent compound
can be used for the purposes described herein, 1,4-butanediol has
been shown to have particularly good cross-linking capabilities.
Generally, amounts of 5% by weight of 1,4-butanediol can be added,
although preferably an amount of 2% or less, or more preferably an
amount of 1.5% or less, or more preferably about 1 wt % or less,
0.5 wt % or less, or 0.25 wt % or less, or 0.1 wt % or less is
used. All percentages are based on the total weight of the
composition.
[0050] The hydroxyl-containing crosslinking agent can be added to
the ionomer in any convenient manner. One particularly useful way
is to add the agent to the ionomer flake in the pre-mix chamber of
an extruder. Another way to introduce this agent is through an
injection port. As these materials are mixed, generally by tumbling
or dry-auger blending, before going into the extruder, the
cross-linking agent is incorporated into the polymer composition
and may react so that the cross-linking occurs in the ionomer as it
is extruded. Alternatively, the cross-linking reaction can take
place during melt mixing or extrusion of the melt.
[0051] The polymer composition described herein may optionally
comprise one or more adjuvants. The term adjuvant as used herein
refers to "additives that contribute to the effectiveness of the
primary ingredient" (The Condensed Chemical Dictionary, 10.sup.th
Ed., revised by Gessner G. Hawley, Van Nostrand Reinhold Co., New
York, N.Y., 1981). Without wishing to be held to theory, it is
believed that the adjuvants contribute to the effectiveness of the
crosslinking agent(s), for example, by enhancing the kinetics of
the acid or base catalysis. Examples of suitable adjuvants include
silanes. When silanes are used, they can be added in amounts of
between 0.025 and 0.1 weight percent (wt %). Non-limiting examples
of preferred silanes include N-(2-aminoethyl-3-aminopropyl)
trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, and
combinations thereof. Available from any convenient source, the
silane adjuvants can be added to the base resin in weight percent
amounts of 0.025, 0.25, 0.1, and 1.0, based on the total weight of
the polymer composition.
[0052] The adjuvant can be added at the same time and in the same
manner as the hydroxyl-containing crosslinking agent, or by any
other known method. In the case of extrusion processing, the
typical temperature range is generally between about 120.degree. C.
and 300.degree. C., depending on the melt point, melt viscosity and
specific equipment configuration. The reaction will be dependent on
the time and temperature parameters set forth and established
through the entire series of process steps. The degree of reaction
can be affected by the level of moisture within the resin, or any
added moisture. In general, increased levels of moisture decrease
the degree of reaction. Depending on the desired end result, this
may be an undesirable effect. Alternatively, moisture can
advantageously be used as a limiting means to reduce the extent of
the cross-linking. Catalysts may also be included, such as the
creation of either acid or base conditions to catalyze the
cross-linking. Alternatively, a specific catalyst, such as dibutyl
tin oxide or similar compound, could be employed.
[0053] The present invention also includes a product of the
cross-linking the polymer composition as described above, so that
at least a portion of the carboxylic acid groups of one or more
ethylene copolymer molecules are reacted with at least two hydroxyl
groups of the hydroxyl-containing crosslinking agent, thereby
forming cross-links between or within the ethylene copolymer
molecules. In one embodiment, at least a portion of the carboxylic
acid groups of two or more ethylene copolymer molecules are reacted
with at least two hydroxyl groups of the hydroxyl-containing
crosslinking agent, thereby forming cross-links between the
ethylene copolymer molecules.
[0054] Without wishing to be held to theory, it is hypothesized
that during the extrusion process, the crosslinking agent and
optionally, the adjuvant compound will react with the resin to form
a low-density level of crosslinks in at least an intermolecular
fashion. The crosslinking agent can react with carboxylic acid
groups thus forming an ester-bond, and can additionally react via
trans-esterification with existing or thus-formed ester-bonds. This
reactivity can be controlled via selection of the crosslinking
agent and specific resin composition containing reactive functional
groups. One skilled in the art can utilize conventional
understanding of relative reactivity and dependencies on adjacent
chemical groups/atoms, steric hindrance, and other
molecular/structural effects. Again without wishing to be held to
theory, it is hypothesized that the adjuvant compound enhances the
crosslink density by forming or by promoting the formation of
ester-bonds. Additionally, the choice of other pendant functional
groups within silane adjuvants may enable other reactions to occur.
For example, amino-groups could form an amide bond and epoxy groups
can react with hydroxyl groups to form additional hydroxyl
side-groups. Alternatively, epoxy groups may initiate various other
reactions via a free-radical pathway.
[0055] The resulting cross-linked polymer composition may have a
MFR of 25 g/10 min or less, or about of 20 g/10 min or less, or
about 10 g/10 min or less, or about 5 g/10 min or less, or about
0.7 to about 5 g/10 min, as determined in accordance with ASTM
method D1238-89 at 190.degree. C. and 2.16 kg.
[0056] The polymer composition described herein may further contain
other additives known within the art. The additives include, but
are not limited to, processing aids, flow enhancing additives,
lubricants, pigments, dyes, flame retardants, impact modifiers,
nucleating agents, anti-blocking agents such as silica, thermal
stabilizers, UV absorbers, UV stabilizers, dispersants,
surfactants, chelating agents, coupling agents, reinforcement
additives, such as glass fiber, fillers and the like. General
information about suitable additives, suitable levels of the
additives in the ionomeric polymers, and methods of incorporating
the additives into the ionomeric polymers may be found in reference
texts such as, for example, the Kirk Othmer Encyclopedia, the
Modern Plastics Encyclopedia, McGraw-Hill (New York, 1995) or the
Wiley Encyclopedia of Packaging Technology, 2d edition, A. L. Brody
and K. S. Marsh, Eds., Wiley-Interscience (Hoboken, 1997). Four
types of additives are of note for use in the ionomeric polymers,
specifically thermal stabilizers, UV absorbers, hindered amine
light stabilizers (HALS), and silane coupling agents. Further
information about these four types of additives, such as preferred
examples and suitable levels in ionomeric polymers, may be found in
the reference texts cited above and in U.S. Pat. No. 7,641,965, for
example.
[0057] The present invention also includes the use of the
aforementioned novel polymer compositions in end-uses including
packaging films and sheets, and injection molded/thermoformed
articles. Accordingly, provided herein are sheets and films
comprising or made from the polymer composition. Further provided
are sheets and films comprising or made from a product of
crosslinking the polymer composition.
[0058] The difference between a film and a sheet is the thickness;
however, there is no set industry standard as to when a film
becomes a sheet. As used herein, the term "film" refers to a
structure having a thickness of about 20 mils (0.50 mm) or less,
and the term "sheet" refers to a structure having a thickness of
greater than about 20 mils (0.50 mm). Nevertheless, when the
polymer compositions are in sheet form, they can be of any useful
thickness. For example, when used as packaging films, these polymer
compositions can have a thickness between about 0.4 mil and about
20 mils (about 10 to about 500 micrometers), and preferably between
about 0.9 and about 6 mils (about 25 to about 150 micrometers). The
packaging films can comprise more than one layer.
[0059] Sheets comprising the polymer compositions may be formed by
any suitable method, including without limitation dipcoating,
solution casting, compression molding, injection molding,
lamination, melt extrusion casting, blown film, extrusion coating,
tandem extrusion coating, or by a combination of two or more of
these methods. Preferably, the sheets are formed by an extrusion
method, such as melt extrusion casting, melt coextrusion casting,
melt extrusion coating, or tandem melt extrusion coating
processes.
[0060] In another embodiment, the article is a film or sheet, which
may be prepared by any convention process, such as, dipcoating,
solution casting, lamination, melt extrusion, blown film, extrusion
coating, tandem extrusion coating, or by any other procedures that
are known to those of skill in the art. In certain embodiment, the
films or sheets are formed by melt extrusion, melt coextrusion,
melt extrusion coating, blown film process, or tandem melt
extrusion coating process.
[0061] Alternatively, the article comprising the polymer
composition disclosed herein is a molded article, which may be
prepared by any conventional molding process, such as, compression
molding, injection molding, extrusion molding, blow molding,
injection blow molding, injection stretch blow molding, extrusion
blow molding and the like. Articles may also be formed by
combinations of two or more of these processes, such as for example
when a core formed by compression molding is overmolded by
injection molding.
[0062] Information about these fabrication methods may be found in
reference texts such as, for example, the Kirk Othmer Encyclopedia,
the Modern Plastics Encyclopedia, McGraw-Hill (New York, 1995) or
the Wiley Encyclopedia of Packaging Technology, 2d edition, A. L.
Brody and K. S. Marsh, Eds., Wiley-Interscience (Hoboken,
1997).
[0063] In one alternative, the article comprising the polymer
composition disclosed herein is an injection molded article having
a minimum thickness (i.e, the thickness at the smallest dimension
of the article) of at least about 1 mm. Or, the injection molded
article may have a thickness of about 1 mm to 100 mm, or 2 mm to
100 mm, or 3 to about 100 mm, or about 3 to about 50 mm, or about 5
to about 35 mm.
[0064] In yet another alternative, the article is an injection
molded article in the form of a multi-layer structure (such as an
over-molded article), wherein at least one layer of the multi-layer
structure comprises or consists essentially of the ionomer
composition disclosed above and that layer has a minimum thickness
of at least about 1 mm. Preferably, the at least one layer of the
multi-layer article has a thickness of about 1 to about 100 mm, or
2 mm to 100 mm, or 3 to about 100 mm, or about 3 to about 50 mm, or
about 5 to about 35 mm.
[0065] In yet another alternative, the article is an injection
molded article in the form of a sheet, a container (e.g., a bottle
or a bowl), a cap or stopper (e.g. for a container), a tray, a
medical device or instrument (e.g., an automated or portable
defibrillator unit), a handle, a knob, a push button, a decorative
article, a panel, a console box, or a footwear component (e.g., a
heel counter, a toe puff, or a sole).
[0066] In yet another alternative, the article is an injection
molded intermediate article for use in further shaping processes.
For example, the article may be a pre-form or a parison suitable
for use in a blow molding process to form a container (e.g., a
cosmetic container). The injection molded intermediate article may
be in the form of a multi-layer structure such as the one described
above, and it may therefore produce a container having a
multi-layer wall structure.
[0067] In yet another alternative the article is an injection
molded article in the form of a golf ball or a sub-part of a golf
ball, for example a core or a mantle of a golf ball.
[0068] Injection molding is a well-known molding process. When the
article disclosed herein is in the form of an injection molded
article, it may be produced by any suitable injection molding
process. Suitable injection molding processes include, for example,
co-injection molding and over-molding (also referred to as two-shot
or multi-shot molding processes).
[0069] When the injection molded article is produced by an
over-molding process, the polymer composition may be used as the
substrate material, the over-mold material or both. In certain
articles, when an over-molding process is used, the polymer
composition disclosed herein may be over-molded on a glass or metal
container. Or the polymer compositions may be over-molded on any
other articles (such as house items, medical devices or
instruments, electronic devices, automobile parts, architectural
structures, sporting goods, and etc.) to form a soft touch and/or
protective overcoating. When the over-mold material comprises the
polymer composition described herein, the melt index of the polymer
composition is preferably from 0.75 up to about 25 g/10 min, as
determined in accordance with ASTM D1238 at 190.degree. C. and 2.16
kg.
[0070] In fabrication processes that incorporate a form of blow
molding, such as, for example, injection blow molding, injection
stretch blow molding and extrusion blow molding, the polymer
composition preferably comprises an ionomer having zinc cations.
Also preferably, the precursor acid copolymer preferably has a melt
index of about 10 to about 100 g/10 min, or about 10 to 70 g/10
min, as determined in accordance with ASTM D1238 at 190.degree. C.
and 2.16 kg. In addition, the zinc ionomer preferably has a melt
index of from about 0.1 to about 2.0 g/10 min, as determined in
accordance with ASTM D1238 at 190.degree. C. and 2.16 kg.
[0071] The polymer composition may be molded at a melt temperature
of about 120.degree. C. to about 250.degree. C., or about
130.degree. C. to about 210.degree. C. In general, slow to moderate
fill rates with pressures of about 69 to about 110 MPa may be used.
The mold temperatures may be in the range of about 5.degree. C. to
about 50.degree. C. Based on the polymer composition and the
process type that is to be used, one skilled in the art would be
able to determine the proper molding conditions required to produce
a particular type of article.
[0072] One preferred injection molded article is a golf ball. For
example, without limitation, injection molding conditions may
include temperatures, pressures and cycle times as indicated in
Table A.
TABLE-US-00001 TABLE A Temperature Injection Pressure Cycle Times
(.degree. C.) (mPa) (sec) Melt 160-260 Packing 25-180 Filling and
Packing 40-90 Mold 10-30 Hold 5-15 Hold 15-30 Front/Back Cooling
Time 50-100 Screw Retraction 5-50
The compositions described herein may be used with any type of ball
construction. It may be used in the core, cover, or one or more
intermediate layers of a golf ball. Suitable golf ball
constructions, including one-piece golf balls, two-piece golf
balls, three-piece golf balls and multi-piece golf balls, are
described in U.S. Pat. No.8,044,136, filed on Oct. 30, 2008, as
well as U.S. Pat. No. 8,202,925, and in the references cited
therein, both issued to de Garavilla.
[0073] The following examples are provided to describe the
invention in further detail. These examples, which set forth a
preferred mode presently contemplated for carrying out the
invention, are intended to illustrate and not to limit the
invention.
EXAMPLES
Materials and Methods
[0074] "Resin A" was an ionomer of an ethylene acid copolymer
comprising copolymerized repeat units of ethylene and about 21.7 wt
% of copolymerized repeat units of methacrylic acid. Resin A was
neutralized to a level of about 26% with a base having sodium
cations as counterions. The melt index of the Resin A base resin
was about 24 g/10 min, and that of Resin A was about 1.8 g/10 min.
The polymers and additives were blended and extruded using a 28-mm
twin-screw compounding extruder manufactured by Werner-Pfleiderer
Corp. of Tamm, Germany. The extruded was equipped with a 6-mm
single hole die and the melt strand was passed through a water bath
for cooling and then cut into pellets using a Conair cutter.
[0075] 1,4-Butanediol was obtained from the Aldrich Chemical
Company, Inc., (Cat. No. B8, 480-7, 99% purity) and added to the
base resin in amounts of 1.0, 1.5 and 2.0 wt %. When the adjuvants
were used, they were added in amounts of between 0.025 and 0.1 wt
%. The examples included below used N-(2-aminoethyl-3-aminopropyl)
trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, and
combinations thereof, and were added to the base resin in amounts
of 0.025, 0.25 and 0.1 wt %. The formed strand-cut pellets
containing the blended polymer, hydroxyl-containing crosslinking
agent, and optionally adjuvant, were dried and compression molded
into plaques. Specimens were then punched out of the plaques and
used for conducting tensile measurements.
[0076] These bars were index marked, weight added (where noted),
then loaded and placed into an oven. Periodically, the oven was
cooled, samples were removed and the "permanent" amount of
elongation was measured. The samples were then placed back into the
oven for additional exposure time, and the temperature was
increased as noted.
EXAMPLES
Comparative Example A and Example 1
[0077] As described above, polymers were obtained, prepared and
extruded to produce test specimens in the form of tensile strips.
The tensile creep was measured according to ASTM D2990-09. The
strips were then hung in an oven with a weight (82 g) attached to
the bottom. As shown in Table 1 and FIG. 1, the tensile strip of
Comparative Example A, achieved an elongation of less than 400%
before mechanical integrity was lost. The strip of Example 1
continued to elongate to at least 1400% over a period of greater
than 500 hours, without a loss of mechanical integrity.
[0078] DSC traces were obtained according to ASTM D3418-08, using a
Model DSC 821 differential scanning calorimeter available from
Mettler Toledo, Inc., of Columbus, Ohio. The results are shown in
FIGS. 2 and 3.
Comparative Example B and Examples 2-7
[0079] As described above, additives were added to Resin A
(Comparative Example B) in the weight percent amounts indicated
below in Table 2, and dog-bone plaques were formed. These plaques
were die-cut using a punch and conformed to ASTM D638-10, Type
V.
[0080] The tensile creep was measured according to ASTM D2990-09.
Two indelible marks 10 mm apart were put onto each plaque. The
plaques were then suspended in an oven at the temperatures
indicated in Table 3, below, and heated for the times indicated. No
weight was applied to the bottom of the plaques. Table 3 shows the
amount of elongation measured for each sample. These data show that
the addition of 1,4-butanediol, N-(2-aminoethyl-3-aminopropyl)
trimethoxysilane, and 3-glycidoxypropyl trimethoxysilane positively
enhanced the tensile creep properties of the control Resin A (C.E.
B). This is also shown in FIG. 4.
TABLE-US-00002 TABLE 2 Resin Additives Compounded into Resin,
weight percent N-(2-aminoethyl-3- Resin aminopropyl)
3-Glycidoxypropyl Identification 1,4-Butanediol trimethoxysilane
trimethoxysilane Resin `A`, 0 0 0 Comp. Ex. B Resin `B` 1 0 0 Resin
`C` 0 0.025 0.025 Resin `D` 1 0.025 0.025 Resin `E` 0.05 0 0.1
Resin `F` 0.05 0 0.25 Resin `G` 0.1 0 0.25 Resin `H` 0.25 0 0
Comparative Example C and Example 8
[0081] The rheology of both the control Resin A (Comparative
Example C) and Resin H (Example 8, Resin A+0.25 wt %
1,4-butanediol) were measured. An Bohlin Instruments RH7 Advanced
Capillary Rheometer, available from Bohlin Instruments of East
Brunswick, N.J., was used to measure melt viscosity at 190.degree.
C., 210.degree. C., and 230.degree. C. and at various shear rates
as shown in FIG. 5. The data show that there was only a modest
change (increase) in melt viscosity at these shear rates and
temperatures. Therefore, cross-linked compositions are expected to
be readily and easily processible by conventional melt processing
methods (e.g., extrusion, blown-film, injection molding, etc.).
[0082] Additionally, die swell was measured for both Comparative
Example C and Example 8. The measurement represents how much larger
in diameter a strand swells as it came out of the rheometer at a
given shear stress/flow rate/temperature. Comparative Example C had
a die swell of 41%, and Example 8 had a die swell of 73%, which was
an indication that the molecular weight distribution has been
broadened and most likely some higher molecular weight material had
been created in the latter.
[0083] As shown in Table 4, melt draw and tension were measured for
both Comparative Example C and Example 8 on a Bohlin Instruments
RH7 Advanced Capillary Rheometer at 190.degree. C. and a crosshead
speed of 2.26 mm/min. The haul-off die had a diameter of 2 mm, a
length of 20 mm, and a 180 degree (flat) entry angle. The following
data shows the maximum haul-off speed (M/min) and haul-off force
(N) at maximum haul-off speed for Comparative Example C and Example
8:
TABLE-US-00003 TABLE 4 Max Haul-off Haul-off Resin Speed (M/min)
Force (N) Comp. Ex. C 300 0.07 Comp. Ex. C 281 0.07 Comp. Ex. C 247
0.06 Comp. Ex. C 179 0.07 Comp. Ex. C 243 0.07 Comp. Ex. C 243 0.07
Comp. Ex. C 281 0.06 Comp. Ex. C 242 0.06 Comp. Ex. C 282 0.06
Comp. Ex. C 282 0.06 Average 258 0.065 Example 8 <25 0.16
Example 8 <25 0.24 Example 8 <25 0.23 Example 8 <25 0.22
Example 8 <25 0.17 Example 8 <25 0.24 Example 8 <25 0.31
Example 8 <25 0.30 Average <25 0.234
[0084] As can be seen in the data above, the melt tension for
Example 8 was much higher than that of the Comparative Example C,
although the maximum haul-off speed was reduced. Additionally, the
melt tension at 10-25 meters/min for Comparative Example C was
about 0.06 Newtons, and thus was fairly independent of draw speed.
Also, the melt tension of Comparative Example C was much lower than
the melt tension of Example 8, which was measured at 0.234
Newtons.
[0085] In summary, these Examples demonstrate that the
cross-linking system described herein modifies the rheology,
including the creep properties, of the acid copolymer resins and of
their ionomers. The extrusion melt pressure and extruder torque
necessary to process these compositions were not substantially
affected by the crosslinking, however.
[0086] While certain of the preferred embodiments of this invention
have been described and specifically exemplified above, it is not
intended that the invention be limited to such embodiments. Various
modifications may be made without departing from the scope and
spirit of the invention, as set forth in the following claims.
* * * * *