Polymeric blends

Polymer blends of at least one polar polymer are prepared by admixture with a poly(vinyl alcohol) and a (meth)acrylate copolymer also containing vinyl amide and/or unsaturated acid units. The ternary compositions have attractive processing and performance properties.

This invention relates to melt-processable thermoplastic combinations of 
polymers containing a high percentage of vinyl alcohol units blended with 
certain copolymers of alkyl methacrylates and/or acrylates with 
unsaturated organic acids, such as methacrylic acid, and/or vinyl amide 
structures, such as N-vinyl pyrrolidone group, which composites are then 
blended (or the three polymers simultaneously blended) with one or more 
polar polymers, such as polyesters, such as poly(ethylene terephthalate), 
poly(vinyl chloride), polyurethanes, such as thermoplastic polyurethanes, 
polyamides, polycarbonates, ethylene-vinyl alcohol co- and terpolymers, 
polyglutarimides, polymers and copolymers of methyl methacrylate, 
naturally occurring polymers such as starch, chitin, chitosan, lignin or 
cellulose and the like. Such blends may be processed by conventional 
plastics technology to form sheet, extruded or blown film, molded 
articles, and the like, which exhibit a useful balance of barrier and 
strength properties, such as good resistance to permeation of gases, low 
moisture absorptivity, and toughness/ modulus balance adequate for 
packaging uses. 
BACKGROUND OF THE INVENTION 
Of all the synthetic polymers considered as materials with useful gas 
permeation properties, such as resistance to passage of oxygen, carbon 
dioxide, water, and the like, poly(vinyl alcohol) (PVOH), which is a 
polymer made up of units of the structure 
##STR1## 
and generally prepared by the total or almost total hydrolysis of 
homopolymers of vinyl acetate or related vinyl esters, the starting 
polymer made up of units of the structure 
##STR2## 
where R is alkyl, that is, from one to eight carbon atoms, preferably 
methyl, ranks as the most impervious to the passage of small molecules. 
PVOH derives this property from the high cohesive energy density and 
polarity of the hydroxyl groups. The presence of the network of hydroxyl 
groups has the concomitant effect of rendering the polymer (PVOH) 
impermeable to gases, but sensitive to moisture. The strong intermolecular 
interaction resulting from the high polarity of the --OH functional group 
gives rise to a melting temperature in the vicinity of the degradation 
temperature of PVOH. Consequently, melting is accompanied by degradation. 
The degradation is so severe that PVOH by itself cannot either be melt 
extruded or injection molded. Co-polymers having a low mol percentage of 
ethylene, such as from about 5 to about 25 mol percent, are similar to 
poly(vinyl alcohol) in that they cannot be melt-processed into film 
without the aid of plasticizers. 
In U.S. patent application Ser. No. 07/781,715, filed Oct. 22, 1991, now 
U.S. Pat. No. 5,189,097 now also European Patent Application 91-311265, 
filed Dec. 4, 1991, which has some of the same inventors as the present 
application, are disclosed additive polymers useful in allowing melt 
processing of the poly(vinyl alcohol) materials discussed above without 
significant alteration of their physical and barrier properties. These 
additive polymers are copolymers of lower alkyl methacrylates or acrylates 
with a variety of nitrogenous monomers, especially those bearing amide 
groups, and most especially N-vinylpyrrolidone. Further is disclosed as 
more useful additives terpolymers containing lower alkyl methacrylates or 
acrylates, the same nitrogenous co-monomers, and copolymerized unsaturated 
carboxylic acids, such as methacrylic acid. It is further disclosed that 
these latter terpolymers form segmented copolymers on combining with the 
poly(vinyl alcohol) matrix polymers under certain processing conditions. 
In a patent application in the U.S., Ser. No. 872,478, filed on Apr. 23, 
1992, now abandoned also with some of the same inventors as the present 
application, is disclosed that copolymers of lower alkyl methacrylates 
and/or acrylates with unsaturated carboxylic acids, such as copolymers of 
methyl methacrylate with methacrylic acid, are also useful for the same 
purposes. It is further disclosed that the composites so formed may be 
segmented copolymers under certain processing conditions. 
What has been discovered in the present invention is that certain of these 
composites of poly(vinyl alcohol), or copolymers which contain at least 50 
mol % of 
##STR3## 
units, with lower alkyl methacrylate or acrylate copolymers with at least 
one of copolymerized acid or amide, especially cyclic amide, 
functionality, when melt-blended with structural polar polymers, produce 
blends of excellent physical, optical and barrier properties. 
In the applications noted above, it had been found that a polymeric 
composite comprising from about 40 to about 95 parts, of a first polymer 
containing at least 50 mol % of units, preferably at least 90 mol %, of 
the structure 
##STR4## 
and optionally units of the structure 
##STR5## 
where R is H or CH.sub.3, and from 5 to about 60 parts by weight of a 
second polymer containing at least about 70 parts of units derived from at 
least one lower alkyl methacrylate or acrylate, (lower alkyl meaning from 
1 to 4 carbon atoms such as methyl, ethyl, propyl, or butyl), preferably 
methyl methacrylate, and at least one of either up to about 25 parts of 
units derived from a vinyl or vinylidene monomer containing an amide 
group, preferably a cyclic anide group of units of the structure 
##STR6## 
where n is 2, 3, 4, or 5, preferably units derived from N-vinyl 
pyrrolidone, or up to about 25 parts of units derived from an unsaturated 
carboxylic acid or anhydride, preferably methacrylic acid, may be 
melt-processed, such as by extrusion, into useful objects such as sheet, 
film, and fiber. It had further been found that combination of the two 
polymers noted above by melt-mixing will form a segmented melt- 
processable polymer wherein the two polymers are chemically combined to 
form a graft copolymer. Lower levels, down to 2 parts, of the additive in 
the composite may be used when the additive polymer is free from amide 
functionality or when the composite contains poly(vinyl alcohol) which has 
been washed or has been neutralized with acid such as phosphoric acid to 
remove residual sodium acetate, as taught in U.S. Pat. No. 3,425,979. 
It is now been found that these composites may be blended, preferably in 
the melt, with polar polymers, to give a melt- processable blend which may 
be processed into useful sheet, film, or molded objects. In the sense that 
processing of the polar polymer is improved, these composites may be 
considered "processing aids". Polar polymers may be described as polymers 
which contain functionality other than carbon and hydrogen, and include 
poly(vinyl halides), such as poly(vinyl chloride) (PVC), poly (vinyl 
esters), such as poly(vinyl acetate), poly(meth)acrylic esters, 
polyglutarimides, polymers containing (meth)acrylonitrile, such as 
styrene/acrylonitrile copolymers or acrylonitrile/butadiene/styrene 
copolymers (ABS), polyesters, such as poly(alkylene terephthalates), 
polyamides, ethylene-vinyl alcohol co- and terpolymers, of less than 50 
mol % vinyl alcohol units, ethylene-carbon monoxide copolymers, 
polycarbonates, poly(alkylene oxides), such as poly (propylene oxide) or 
poly(ethylene oxide), phenoxy resins, such as those formed by the reaction 
of epichlorohydrin and a bisphenol, and the like. The invention further 
applies to polar polymers which are of natural origin or modified from 
polymers of natural origin, such as starch, lignin, chitin, chitosan, 
cellulose, or chemically modified cellulose, such as esters such as 
cellulose acetate, cellulose acetate-propionate, cellulose 
acetate-butyrate, or ethers such as methyl cellulose. Many of these 
polymers are extremely difficult to process, and may be described as 
melt-intractable. The ratio of polar polymers to the composites may be 
from about 10:95 to about 5:90, preferably for thermoplastic polar 
polymers from about 60:95 to about 5:40, and more preferably from about 
80:95 to about 5:20. Particularly useful polar polymers are aliphatic 
polyamides formed from lactams, such as polycaprolactam, 
polyundecanolactam, and polydodecanolactam, the polycarbonate formed from 
bisphenol A, poly(ethylene terephthalate), and elastomeric polyurethanes, 
such as those with polyether or polyester-polyol segments. 
DETAILED DESCRIPTION OF THE INVENTION 
Our invention is thus a polymeric blend comprising: 
(a) from about 80 to about 95 parts of at least one polar polymer selected 
from the group consisting of poly(vinyl chloride), a polycarbonate, a 
polyglutarimide, a polymer of methyl methacrylate, a polyamide, a 
polyester, or a polymer containing units derived from styrene and 
acrylonitrile; 
(b) from about 5 to about 20 parts of a polymeric composite of: 
i) from about 60 to about 95 parts by weight of a first polymer containing 
at least 50 mol % of units of the structure 
##STR7## 
ii) from about 5 to about 40 parts by weight of a second polymer 
containing at least about 70 parts of units derived from at least one of a 
lower alkyl (of from 1 to 4 carbon atoms such as methyl, ethyl, propyl, or 
butyl) methacrylate or acrylate, and at least one of either up to about 25 
parts of units derived from a vinyl or vinylidene monomer containing an 
amide group or up to about 25 parts of units derived from an unsaturated 
carboxylic acid or anhydride. 
The invention further comprises a polymeric blend comprising: 
(a) from about 10 to about 95 parts of at least one polar polymer; 
(b) from about 5 to about 90 parts of a polymeric composite of: 
i) from about 40 to about 95 parts by weight of a first polymer containing 
at least 50 mol % of units of the structure 
##STR8## 
ii) from about 5 to about 60 parts by weight of a second polymer 
containing at least 70 parts of units derived from a lower alkyl (of from 
1 to 4 carbon atoms such as methyl, ethyl, propyl, or butyl) methacrylate 
acrylate, and at least one of either up to about 25 parts of units derived 
from a vinyl or vinylidene monomer containing an amide group or up to 
about 25 parts of units derived from an unsaturated carboxylic acid or 
anhydride, wherein the polar polymer is a natural and melt-intractable 
polymer, such as starch, chitin, chitosan, lignin or cellulose. Again, the 
components (a), (b)(i), and (b)(ii) may be combined essentially 
simultaneously. 
The invention further comprises a polymeric blend comprising: 
(a) from about 25 to about 95 parts of at least one polar polymer; 
(b) from about 5 to about 75 parts of a polymeric composite of: 
i) from about 40 to about 95 parts by weight of a first polymer containing 
at least 50 mol % of units of the structure 
##STR9## 
ii) from about 5 to about 60 parts by weight of a second polymer 
containing at least about 70 parts of units derived from at least one of a 
lower alkyl (of from 1 to 4 carbon atoms such as methyl, ethyl, propyl, or 
butyl) methacrylate or acrylate, and at least one of either up to about 25 
parts of units derived from a vinyl or vinylidene monomer containing an 
amide group or up to about 25 parts of units derived from an unsaturated 
carboxylic acid or anhydride, wherein the polar polymer is a polyurethane, 
such as an elastomeric polyurethane, a phenoxy resin, an ethylene/carbon 
monoxide copolymer, a modified cellulosic, such as a cellulose ester, or a 
poly(alkylene oxide). 
The invention further comprises all such above-described blends wherein the 
polymeric composite comprises: 
(a) from about 60 to about 95 parts by weight of a first polymer containing 
at least 50 mole % of units of the structure; 
##STR10## 
ii) from about 5 to about 40 parts by weight of a second polymer 
containing at least about 75 parts of units derived from methyl 
methacrylate, and at least one of either up to about 25 parts of units 
derived from N-vinyl pyrrolidone or up to about 25 parts of units derived 
from methacrylic acid. 
Such blends may be in the form of an extruded film, extruded sheet, 
extruded fiber, or injection-molded article. Such blends may be prepared 
by methods wherein components (a), (b)(i), and (b)(ii) are combined 
essentially simultaneously 
In the claims and description, the parts of polar polymer and of composite 
total 100 parts, and other materials may be present as long as the polar 
polymer and composite are within the specified ratios. Similarly, the 
parts by weight of the vinyl alcohol polymer and the acrylic co- or 
terpolymer in the composite total 100 parts, and other materials may be 
present as long as the vinyl alcohol and acrylic polymers are within the 
specified ratios. 
The composite may contain a blend of high and low molecular weight vinyl 
alcohol polymers. The composite may further contain glycerol or other 
plasticizer in small amounts. The composite may further contain impact 
modifiers known to the art, such as multistage polymers based on a 
poly(acrylate) first stage or a polybutadiene first stage and a 
methacrylate or styrene second stage, which may be present as a shell or 
in separate domains within the core. Either stage may contain 
acid-functional groups. 
The blends may be prepared by dry-blending the components and 
melt-processing in an extruder or thermal mixer to form pellets, which are 
then re-processed into the desired object, or the dry blend may be 
directly melt-processed into the final article. The blend may contain more 
than one polar polymer. The blend may further contain pigments, dyes, 
thermal stabilizers, antioxidants, lubricants, fillers, and the like. The 
blend may further be prepared by admixing the additive polymer in emulsion 
form, when an emulsion polymerization is a feasible way to prepare the 
additive polymer, with the poly(vinyl alcohol) in solid form, and then 
processing directly with water removal such as by extrusion in a vented 
extruder, or by drying the powder blend under vacuum, and then blending 
with the matrix polymer. The blend may further be prepared by admixing the 
additive polymer in emulsion form, when such is feasible to prepare the 
additive polymer, with the poly(vinyl alcohol) and the matrix polymer in 
solid form, and then processing directly with water removal such as by 
extrusion in a vented extruder, or by drying the powder blend under 
vacuum, to form the blend. 
The blend may further be prepared by admixing the additive polymer in 
emulsion form, when an emulsion polymerization is a feasible way to 
prepare the additive polymer, with the poly(vinyl alcohol) in solid form, 
and then processing directly with water removal such as by extrusion in a 
vented extruder, or by drying the powder blend under vacuum, and then 
blending with the matrix polymer. The blend may further be prepared by 
admixing the additive polymer in emulsion form, when such is feasible to 
prepare the additive polymer, with the poly(vinyl alcohol) and the matrix 
polymer in solid form, and then processing directly with water removal 
such as by extrusion in a vented extruder, or by drying the powder blend 
under vacuum, to form the blend. 
By use of the term "composite" in the specifications and claims, there is 
meant no restriction that the poly(vinyl alcohol) component and the 
acrylic copolymer additive component must be blended together prior to 
admixture with the polar polymer. Indeed, one particular aspect of the 
invention could be described equally well as a polymeric blend comprising: 
(a) from about 25 to about 95 parts of at least one polar polymer; 
b) from about 2 to about 71.25 parts of a first polymer containing at least 
50 mol % of units of the structure 
##STR11## 
c) from about 0.25 to about 45 parts by weight of a second polymer 
containing at least about 70 parts of units derived from a lower alkyl 
methacrylate or acrylate, and at least one of either up to about 25 parts 
of units derived from a vinyl or vinylidene monomer containing an amide 
group or up to about 25 parts of units derived from an unsaturated 
carboxylic acid or anhydride. 
Thus, the invention is meant to describe those blends where the three 
components are combined together all at one time, i.e.., essentially 
simultaneously, as well as when the second (additive) polymer and the 
first polymer containing poly(vinyl alcohol) are combined first and then 
blended with the matrix polymer. 
The resulting objects may be especially useful in packaging, such as film, 
sheet, bottles, etc., where improved barrier properties are desirable, 
since the invention offers a way to combine poly(vinyl alcohol), with 
outstanding barrier properties, into polar polymers by an economically 
attractive means. Such uses may include bottles for beverages, film 
packaging for food, and the like. The blends may also be useful in a 
variety of molded or thermoformed objects, where a combination of improved 
modulus and good processing is required. Such objects include toys, 
electrical equipment housing, and the like. 
Melt blends of polyamides with the polymeric composites described herein 
may be fabricated into film, film tubes, toys, gears, packing, shafts, 
curtain sliders, door rollers, household containers, and the like. Blends 
of the composites with a compatible, flexible elastomeric material may be 
used as compositions for contact with water and a rigid substrates, as for 
example in improved wiper blades. 
The composite (or the two separate components of the composite) may be 
blended with polymers which are environmentally degradable, such as 
polylactates and other biologically derived polyesters, or polyamides or 
polyesters chemically modified with hydrolyzable, oxidizable, or 
photolytically unstable units or photosensitizing additives., such as 
benzophenone. Such polymers may include polycaprolactam modified by 
copolymerization with caprolactone, oxalate esters, or glycolides. Such 
polymers, especially when in monofilament, thin rod, or net form, will in 
the environment tend to develop a higher level of exposed surface upon 
leaching of the poly(vinyl alcohol) and thus degrade more rapidly to lower 
molecular weight, more brittle, less form-retaining polymers upon longer 
exposure to the environment, such as sun, rain, lake or sea water, compost 
piles, trash piles, garbage dumps, and the like. 
Blends of the composite with a water-soluble or water- dispersible 
polyester may be useful as powdered sizing aids for textiles, which may be 
removed at the appropriate time by washing. 
The composite in combination with polar polymers, with or without 
water-soluble electrolytes, may be processed into sheet from which, with 
appropriate extraction techniques, the electrolytes and/or the poly(vinyl 
alcohol) may be removed to leave a porous plastics sheet, useful, inter 
alia, in separations technology. Extracted fibers with a porous structure 
may also be prepared. 
The composites may be blended with ethylene-vinyl alcohol copolymers and 
melt-processed as adhesive resin compositions or as tie layers with 
improved barrier properties for composite multi- layer bottles or 
packaging. 
The blends, where the polar polymer may readily form fibers, may be 
processed by melt-extrusion techniques into fibers of high water 
absorption. The blends may also be extruded and fibrillated into fibers 
for uses, such as non-woven bonded materials, with high water absorption. 
Such fibers or other extrudates may be useful, especially those prepared 
with an environmentally degradable polyamide, as netting, monofilaments, 
components of diaper backings, ground covers, and the like. 
In the following examples, which describe the physical and mechanical 
properties of numerous blends formed from combining the melt processable 
PVOH/Acrylic co- and terpolymer composites with polar polymers such as 
polycaprolactam, the following abbreviations are used: "Nylon" for 
polyamides in general, Nylon 6 for polycaprolactam, PVOH for the one or 
more specific polymers of the Example with greater than 50 mol % of units 
of vinyl alcohol, "Acrylic polymer" for the one or more particular 
copolymers of an alkyl methacrylate with a vinyllactam and/or a 
copolymerizable acid.