Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/14—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated alcohols, e.g. polyvinyl alcohol, or of their acetals or ketals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
  • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
  • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31551—Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31786—Of polyester [e.g., alkyd, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31826—Of natural rubber
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31931—Polyene monomer-containing
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31935—Ester, halide or nitrile of addition polymer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31938—Polymer of monoethylenically unsaturated hydrocarbon

Definitions

• This invention relates, in general, to blend compositions of an unmodified poly vinyl alcohol and a thermoplastic elastomer and thermoplastic film and fiber structures comprising these blend compositions. More specifically, this invention relates to substantially water-free films and fibers comprising unmodified polyvinyl alcohol and a thermoplastic elastomer.
• films and fibers are designed to be water-dispersible such that the product will partially or completely disperse in water, thereby allowing the product to be disposed of without dumping or incineration.
• These products may be placed in sewage systems or may be flushed down a conventional toilet.
• the films and fibers used in the products will typically use blend compositions that include a water-dispersible polymer such as polyethylene oxide or polyvinyl alcohol.
• PVOH Polyvinyl alcohol
• Modified PVOH is used in many different water-dispersible thermoformable articles, such as fibers, films and fabrics which maintain their integrity and strength when in use, but dissolve and disperse when placed in contact with water.
• Unmodified PVOH is used in industry for many different solution-based applications and is not generally considered to be thermoformable or melt-processable. Some such applications for unmodified PVOH include warp sizing in textiles, fabric finishing, adhesives, paper processing additives, and emulsifiers/dispersants.
• modified PVOH it is meant PVOH resin which has been chemically modified, including PVOH having another compound grafted thereto, or PVOH resin that has been mixed with one or more plasticizers. In each instance, these “modifications” have been needed to permit PVOH to be used in thermoformable articles.
• thermoformable articles To overcome the thermoplastic processing problems, chemically modified PVOH has been used.
• Some prior art teachings have used ethers of PVOH, ethoxylated PVOH or lacton-modified PVOH to produce thermoformable articles.
• PVOH polyvinyl alcohol
• plasticizers include water, ethylene glycol, glycerin and ethanolamine.
• films and fibers including modified PVOH or PVOH and a plasticizer may be limited in their utility. These films and fibers may be too stiff to be used for certain applications. Additionally, the texture of the films may not be soft enough for comfortable contact with the skin of an individual. Finally, these films and fibers may be too “noisy” such that bending or flexing of the film or fiber causes an audible sound that may be distracting to the user of the product.
• thermoplastically formed films and fibers that have enhanced softness and ductility and produce less noise when bent or flexed.
• the present invention desires to produce films and fibers including blend compositions having unmodified PVOH and a thermoplastic elastomer.
• Another desire of the present invention is to use unmodified PVOH and a thermoplastic elastomer in films and fibers without the use of a plasticizing agent.
• the present invention discloses the selection and use of commercially-available grades of PVOH for thermoplastic applications.
• “Thermoplastic” is defined, herein, as a resin which can be melted and easily extruded to form a desired article, i.e., the material is melt processable.
• These commercially-available grades of PVOH are combined with a thermoplastic elastomer to provide a blend composition useful in the production of films and fibers that have enhanced softness and ductility and produce less noise.
• PVOH is a commodity polymer, commonly used in solution-based applications. Since it is a commodity polymer, thermoplastic articles made using unmodified PVOH are generally less expensive than articles made using modified PVOH due to the additional process steps required to modify the PVOH. Also, unmodified PVOH is, in general, less expensive than other water-soluble polymers.
• PVOH has not been used for thermoplastic applications.
• some modification of the PVOH such as chemical grafting or addition of plasticizer, is necessary to achieve melt processability for PVOH.
• a window of thermoplastic processability has been discovered and defined for unmodified, commercially-available PVOH, according to: 1) the composition or % hydrolysis of the PVOH, 2) the molecular weight of the PVOH, 3) the solution viscosity of the PVOH, or 4) the melt viscosity of the PVOH.
• the selected grades of PVOH have demonstrated thermoplasticity, allowing for continuous, melt extrusion or conversion into thin films in a continuous, extrusion process.
• These grades of PVOH may be mixed with additional polymers, such as thermoplastic elastomers, to provide desired characteristics to the films and fibers, such as enhanced ductility, enhanced softness and lower noise generation.
• additional polymers such as thermoplastic elastomers
• PVOH is generally produced by a two step process as shown in Scheme 1. Since vinyl alcohol is not a stable monomer, the polymerization of vinyl alcohol is not an option for making PVOH. Instead, the process utilizes a readily available monomer, vinyl acetate, as the starting point.
• the first step is the polymerization of vinyl acetate into polyvinyl acetate (PVA).
• the second step is the hydrolysis or alcoholysis of PVA into a copolymer of vinyl acetate and vinyl alcohol, or polyvinyl alcohol (PVOH).
• PVA polyvinyl acetate
• PVOH polyvinyl alcohol
• the degree of hydrolysis is controlled during the alcoholysis reaction and is independent of the control of the molecular weight of the PVOH formed. Fully hydrolyzed PVOH is obtained if alcoholysis is allowed to go to completion. The reaction is terminated by removing or neutralizing the sodium hydroxide catalyst used in the process. Typically, a small amount of water is added to the reaction vessel to promote the saponification reaction of PVA. The extent of hydrolysis is inversely proportional to the amount of water added.
• the alcoholysis can be carried out in a highly agitated slurry reactor. A fine precipitate forms as PVA, which is then converted to PVOH. The PVOH product is then washed with methanol and is filtered and dried to form a white, granular powder.
• the molecular weight of the PVOH is controlled by the polymerization condition of vinyl acetate.
• Many properties of PVOH depend on the degree of hydrolysis and the molecular weight. As the molecular weight increases, the solution viscosity, tensile strength, water resistance, adhesive strength, and solvent resistance increase. As molecular weight decreases, the flexibility, water solubility, and ease of solvation increase. As the degree of hydrolysis increases, the water resistance, tensile strength, block resistance, solvent resistance, and adhesion to polar substrates increase. As the degree of hydrolysis decreases, the water solubility, flexibility, water sensitivity and adhesion to hydrophobic substrates increase.
• PVOH Due to the strong dependence of PVOH on the molecular weight and degree of hydrolysis, PVOH is typically supplied in combination of these two parameters. PVOH is classified into 1) partially hydrolyzed (87.0 to 89.0% hydrolysis); 2) intermediately hydrolyzed (95.5 to 96.5% hydrolysis); 3) fully hydrolyzed (98.0 to 98.8% hydrolysis); and 4) super hydrolyzed (>99.3% hydrolysis). Within each category of PVOH, the resin is differentiated by solution viscosity, measured at 4% solution in water at 20° C. in centipoise. The viscosity is used as a molecular weight measure since solution viscosity is typically related to the molecular weight by the well known Mark-Houwink equation:
• a factor based on the rigidity of the polymer chains and is dependent on the polymer.
• melt viscosity of the PVOH grades could be used to determine which grades of PVOH were thermoplastic. In general, those grades having a melt viscosity less than about 1500 Pa ⁇ s at a shear rate of 500 s ⁇ 1 were determined to be melt processable.
• PVOH grades useful in this invention desirably have a solution viscosity of less than about 10 cp in a 4% water solution at 20° C. and a hydrolysis of less than about 90%.
• examples of commercially-available grades of PVOH useful in this invention are ELVANOL® 51-05 from DuPont (Wilmington, Del.), AIRVOL® 203 and 205 from Air Products and Chemical, Inc. (Allentown, Pa.), and GOHSENOL® KP-06 from Nippon Gohsei (Japan).
• PVOH is typically sold in powder or granule form, however pellets or other forms of resin can be used in this invention since the physical form of PVOH does not affect melt processability.
• thermoplastic grades may be better suited for the production of thermoplastic films while other grades may be more useful for the production of fibers.
• the exact grade to use will depend upon the item being made and the elastomer that is blended with the PVOH.
• the present invention uses these thermoplastic PVOH grades with an additional compound to form blend compositions. These blend compositions may then be formed into thermoplastic articles such as films and fiber.
• the additional compound is used to enhance the properties of the resulting films and fibers.
• a thermoplastic elastomer is used to help produce films that are softer, more ductile and less noisy than films comprising PVOH alone.
• thermoplastic PVOH grades and a thermoplastic elastomer may be extruded using most known extruding devices.
• a thermoplastic film may be extruded at extrusion temperatures above the melting point of the PVOH/elastomer blend, it is preferred to use extrusion temperatures near the melting point as the resulting films and fibers are generally clearer, have fewer imperfections, are more ductile and stronger, and can be drawn into much thinner films.
• the films and fibers of the present invention can be extruded from unmodified PVOH/elastomer blends without the use of a plasticizer.
• plasticizers are known, including, for example, ethylene glycol, glycerines and ethanolamine.
• water is also known to be used as a plasticizer in the production of PVOH films and fibers.
• plasticizers, including water have several disadvantages when used in the production of films and fibers. In general, plasticizers, including water, will slowly diffuse out of a PVOH film or fiber causing the film or fiber to become lucid and brittle and therefore more likely to break or shatter.
• plasticizers, including water, added to PVOH may cause bubbling of the film during the extrusion process. This is especially true with water. Therefore, care must be taken prior to the blending with an elastomer and production of the film to ensure that the PVOH powder or pellets remain substantially water-free. This helps to ensure that the films and fibers produced are also substantially water-free.
• substantially water-free it is meant that the films and fibers produced using the unmodified PVOH/elastomer blends contain less than about 2.0 percent by weight of water. Desirably, the films and fibers contain less than about 1.0 percent by weight of water. More desirably, the films and fibers contain less than 0.5 percent by weight of water.
• thermoplastic elastomers There are three basic types of thermoplastic elastomers: 1) styrenic thermoplastic elastomers, 2) hard/polymer elastomer combinations, and 3) multi-block polymers with crystalline hard segments.
• the elastomer may be an A-B-A block polymer where “A” is a polystyrene and “B” is an elastomer segment.
• the elastomeric segments may be selected from polybutadiene, polyisoprene, poly(ethylene-butylene), and poly(ethylene-propylene).
• these polymers may be referred to as S-B-S, S-I-S, S-EB-S, and S-EP-S, respectively, where “S” refers to polystyrene, “B” refers to polybutadiene, “I” refers to polyisoprene, “EB” refers to poly (ethylene-butylene), and “EP” refers to poly (ethylene-propylene).
• Hard/polymer elastomer combinations include a hard thermoplastic polymer, such as polypropylene, in a fine dispersion within a matrix of an elastomer.
• the elastomer may be selected from ethylene-propylene-diene monomer (EPDM) or ethylene-propylene copolymer (EPR).
• EPDM ethylene-propylene-diene monomer
• EPR ethylene-propylene copolymer
• Other elastomers that may be used include nitrile, butyl, and natural rubbers.
• Multi-block polymers with crystalline hard segments generally include multi-block (A-B) n structures, wherein “A” is a crystalline thermoplastic, while “B” is a softer, elastomeric segment that is amorphous.
• hard segments include, but are not limited to, thermoplastic polyurethanes, thermoplastic polyesters, and thermoplastic polyamides.
• soft segments include, but are not limited to, polyesters.
• PVOH/elastomer blends have been discovered that may be directly extruded into a water-soluble, thin film without the need for any chemical modification of the PVOH or the addition of a plasticizer.
• the elimination of any chemical modification of the PVOH eliminates the labor intensive step of chemically modifying or grafting the PVOH.
• the elimination of a plasticizer admixed with the PVOH relieves the common problems involved with plasticizers as previously discussed.
• the water-soluble film of the present invention will keep its original properties and in-use performance unlike a PVOH/elastomer film containing a plasticizer which will become brittle over time.
• PVOH has a higher melting point than many other water-soluble polymer systems used for making water-dispersible, flushable articles, including, for example, polyethylene oxide-based materials.
• PVOH film can withstand heat from a hot-applied melt adhesive which may be used during product construction.
• PEO-based materials have limitations in this aspect due to the low melting temperature of the PEO of about 60 to 70° C. Therefore, the PVOH/elastomer films and fibers of the present invention have great usefulness in the production of water-dispersible, flushable products.
• the PVOH/elastomer blends, films and fibers of the present invention include a thermoplastic elastomer that enhances certain characteristics of the films and fibers when compared to films and fibers comprising only unmodified PVOH.
• the elastomer imparts improved softness and ductility to the film while reducing the amount of noise the film makes when manipulated.
• thermoplastic elastomers include, but are not limited to, KRATON® polymers from Shell, such as Kraton D, a S-B-S or S-I-S polymer, and Kraton G, a S-EB-S or S-EP-S polymer, elastomeric polyurethanes, ethylene-octene copolymers, polyester polyurethane, natural rubber, nitrile rubber, butyl rubber, ethylene-propylene terpolymers, silicone rubber, polyurethane rubber, thermoplastic rubbers, elastomeric block copolymers, copolymers of polyethylene oxide and polybutylene terephthalate, polyamide-polyether block copolymers, styrenic block copolymers, elastomeric polypropylene, or mixtures thereof.
• KRATON® polymers from Shell, such as Kraton D, a S-B-S or S-I-S polymer, and Kraton G, a S-EB-S
• the amount of thermoplastic elastomer that may be used is in the amount of from about 1 to about 99% by weight of the PVOH/elastomer blend.
• the blend comprises from about 50 to about 90% by weight PVOH and from about 50 to about 10% thermoplastic elastomer. Even more desirably, the blend comprises from about 65 to about 80% by weight PVOH and from about 35 to about 20% thermoplastic elastomer.
• the relative amounts of PVOH to that of thermoplastic elastomers determine the water-responsiveness of the resulting PVOH/thermoplastic elastomer films.
• the resulting article is water-dispersible or water-disintegratable as defined by standard test methods.
• water-responsive includes articles that are water-dispersible, water-disintegratable and water-weakened. “Water-dispersible” is used herein to describe a 5 mil (0.005 of an inch) film that, under the water-responsiveness test described below, dissolves or breaks into pieces smaller than a 20 mesh screen.
• Water-disintegratable describes a 5 mil film that, under the water-responsiveness test, breaks into multiple pieces after two minutes with some of the pieces caught by a 20 mesh screen.
• Water-weakened describes a 5 mil film that, under the water-responsiveness test, remains intact, but loses rigidity and becomes drapable, i.e., will bend with an external force applied to the film when it is held by one corner at a substantially horizontal position.
• the degree of hydrolysis is 71-74%, it's viscosity in a 4% solution in water at 20° C. is 5 to 7 cp, as measured by Hoeppler falling ball method. It is supplied as a white granulate powder.
• the resin was fed to the Haake twin-screw extruder directly without pelletization.
• Example 2 the same PVOH resin used in Example 1 was tested to determine whether the film processing conditions could be improved.
• the extrusion temperature profile was modified. The barrel temperatures were set at 150, 185, 185 and 180° C. for zones 1, 2, 3 and 4 (die) respectively. The screw speed was maintained at 134 rpm. This lower die set temperature brought down the melt temperature to about 195 to 200° C. Surprisingly, as the melt temperature of the PVOH dropped, the film properties improved dramatically. At a melt temperature of about 195 to 200° C., the melt strength of PVOH improved greatly such that a PVOH film could be drawn down to less than 0.2 mil. In contrast to the hazy appearance of the PVOH made in Example 1, the PVOH film made in this example under the lower melt temperature had excellent clarity and was essentially free of film defects.
• the film made at a lower temperature had greater strength and softness.
• the tensile properties of the pellet-derived PVOH film were tested on a Sintech 1/D tensile tester available from MTS Systems Corp. (Machesny Park, Ill.).
• the PVOH film had a high melt strength such that the winding up of the film at high speed did not cause any tearing or breaking of the PVOH film.
• the peak stress of the film was over 60 MPa.
• the elongation-at-break of the PVOH was about 73%.
• the modulus of the film was also high, slightly over 1800 MPa.
• PVOH polystyrene resin
• Example 2 The same PVOH resin used in Example 1 was used for this example.
• PVOH is usually delivered from the manufacture in a powdered form. Since polymers in the pellet form are generally easier to work with, an experiment was devised to see if cast films created directly from PVOH powder had different tensile properties that those created from PVOH in the pellet form.
• PVOH pellets were made by extruding PVOH powder on a Werner & Pfleiderer (Ramsey, N.J.) ZSK-30 extruder at 20 lb/hr and 300 rpm.
• the ZSK-30 extruder has a pair of co-rotating screws arranged in parallel with the center-to-center distance between the shafts of the two screws at 26.2 mm.
• the nominal screw diameters are 30 mm.
• the actual outer diameters of the screws are 30 mm and the inner screw diameters are 21.3 mm.
• the thread depths are 4.7 mm.
• the length of the screws are 1328 mm and the total processing section length was 1338 mm.
• This ZSK-30 extruder had 14 processing barrels which were numbered consecutively 1 to 14 from the feed barrel to the die. The first barrel was not heated, but cooled by water. Barrels 2 to 14 were divided into 7 zones. Barrels 2 and 3 comprised zone 1. Barrels 4 and 5 comprised zone 2. Barrels 6 and 7 comprised zone 3. Barrels 8 and 9 comprised zone 4. Barrels 10 and 11 comprised zone 5. Barrels 12 and 13 comprised zone 6.
• Barrel 14 (die) comprised zone 14.
• the extruded melt strands were cooled by air on a 15 foot conveyer belt equipped with fans, and then pelletized. As a rule of thumb, it was expected that the films from pellets would have lower tensile strength than the powder-derived films since the PVOH resin suffers from additional thermomechanical degradation during the extra pass through the extruder.
• the PVOH pellets made on the ZSK-30 twin-screw extruder had excellent cast film processability. Thin films were easily made from the pellets on the same Haake twin-screw film cast line used in Example 1. The barrel temperatures were set at 180, 190, 190 and 180° C. for zones 1, 2, 3 and 4 (die) respectively. The screw speed was maintained at 134 rpm. This film also crystallized very quickly. High quality water-soluble film was again made using the temperature profile set forth in Example 2.
• the peak stress of the pellet-derived film is nearly twice that of the powder-derived film, reaching a high value of 120 MPa versus a 60 MPa for the powder-derived film
• the modulus of the pellet-derived film was about 30% higher than the powder-derived film, reaching 2580 MPa, while the powder film had a modulus of 1800 MPa.
• the powder-derived film was a little more ductile giving slightly higher elongation-at-break. Due to the peak stress and its contribution to the film's overall tensile toughness as measured as the area under the tensile curve, the pellet-derived PVOH film had a 50% higher toughness than the powder-derived PVOH film.
• PVOH film produced from the PVOH pellets was determined to be stronger and tougher than powder-derived PVOH film. Unexpectedly, it showed an upgrade in tensile properties by subjecting the PVOH through more thermal processing. Typically, as a polymer is subjected to more thermomechanical stress, polymer degradation occurs which results in the loss of mechanical and other properties.
• Table 1 is a chart of solution viscosity versus percent hydrolysis according to vendor data, for the selected grades of PVOH. TABLE 1 Viscosity 4% solution, Manufacturer Trade Name % Hydrolysis 20° C. Nippon Gohsei KP-06 71-74 5-7 Air Products AIRVOL ® 125 99.3+ 26-30 AIRVOL ® 165 99.3+ 55-65 AIRVOL ® 107 98.0-98.8 5.4-6.5 AIRVOL ® 203 87.0-89.0 3-4 AIRVOL ® 205 87.0-89.0 5-6 AIRVOL ® 523 87.00-89.0 22-26 AIRVOL ® 540 87.0-89.0 40-50 DuPont ELVANOL ® 51-05 87.0-89.0 3-4 ELVANOL ® 52-22 87.0-89.0 22-26 ELVANOL ® 50-42 87.0-89.0 40-50
• Table 2 shows the average extrusion data for each of the thermoplastic grades of PVOH and two of the non-thermoplastic grades of PVOH, ELVANOL® 52-22 and AIRVOL® 523, before the die holes were plugged.
• TABLE 2 Feed Screw BARREL TEMPERATURE Zone 7 Melt Die Rate Speed 1 2 3 4 5 6 Temp Temp Pres Trade Name (lb/hr) (rpm) % Torque (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) (PSI) THERMOPLASTIC KP-06 20.00 301 39.00 179 181 180 180 180 180 180 192 203 270 AIRVOL ® 205 20.04 300 44.15 178 180 180 180 180 180 181 188 200 484 ELVANOL ® 51-05 19.79 300 41.75 178 180 181 180 180 180 180 180 192 203 446 AIRVOL ® 203 20.02 299 42.
• melt processable, thermoplastic grades had lower percent torque (at least 20% lower), melt temperature (at least 10° C. lower), and die pressure (over 65% lower), compared to the non-thermoplastic grades.
• melt temperature at least 10° C. lower
• die pressure over 65% lower
• Extruded pellets produced on the ZSK-30 extruder from each of the thermoplastic grades of PVOH were also converted into thin film on the Haake extruder, following the same procedure used for Example 3.
• NG KP-06 appeared to show the best film processability, in terms of clarity, melt strength, and uniformity (with no visible gels).
• ELVANOL® 51-05 produced a very thin film (down to less than 0.2 mil) with excellent clarity.
• ELVANOL® 51-05 was not as “clean” as the KP-06 as shown by a few visible gels in the film AIRVOL® 203 and 205 produced very thin films (drawn down to about 0.5 mil) with less clarity than NG KP-06 or ELVANOL® 51-05.
• the Air Products resins were even less “clean” with several gels in the film
• the gels in the film for AIRVOL® grades made it more difficult to draw down to less than 0.5 mil, because of splitting due to gels.
• non-thermoplastic grades of PVOH in either powder or extruded pellet form, could not be converted into film on the Haake extruder following the same procedure used for Example 3. No thin film could be produced for any of the non-melt processable grades. Severe discoloration and die pressure were observed. For some grades, totally black sheets of thick rigid plastic were produced. After several minutes, the thin slit in the film die plugged and no thin film could be collected.
• thermoplastic grades of PVOH powder had an average M w ranging from 8,750 g/mole to 46,500 g/mole and M w /M n ranging from 1.71 to 2.05.
• the extruded pellets had an average M w ranging from 10,850 g/mole to 52,400 g/mole and M w /M n ranging from 1.63 to 1.88.
• the non-thermoplastic grades of PVOH however, had significantly higher M w at 148,300 and 143,400 and higher M w /M n at 2.40 and 2.57.
• the commercial grade PVOH resins were tested to determine whether or not the melt viscosity of the PVOH could be used to determine whether that particular resin was melt processable.
• the NG KP-06 resin, along with several of the AIRVOL® and ELVANOL® resins were used.
• the apparent melt viscosity of the thermoplastic and non-thermoplastic grades of PVOH were significantly different.
• Table 4 shows the apparent melt viscosity at a shear rate of 500 s ⁇ 1 for PVOH powder and pellets produced on the ZSK-30 extruder.
• Unmodified PVOH with a melt viscosity greater than about 1500 Pa ⁇ s was not melt processable and grades with a melt viscosity less than 1500 Pa ⁇ s were melt processable.
• grades having a solution viscosity less than 10 cp are melt processable while grades having a solution viscosity greater than 20 cp are not, leaving the range from 10-20 cp uncertain.
• melt viscosity it is possible to determine the exact range of melt processability using melt viscosity. Those grades having a melt viscosity less than about 1500 Pa ⁇ s are melt processable while grades having a melt viscosity greater than about 1500 Pa ⁇ s are not melt processable.
• a blend of 65% by weight of DuPont ELVANOL® 51-05 polyvinyl alcohol resin powder and 35% by weight of a KRATON® thermoplastic elastomer, G-1659x (a tri-block copolymer of S-EB-S, polystyrene-co-ethylene-butylene-co-styrene with a glass transition temperature of the rubber block of ⁇ 42° C.) was fed to a counter-rotating twin-screw extruder TW-100 (manufactured by Haake, Paramus, N.J.) at a rate of 5 pounds per hour (lb/hr).
• the extruder had a screw length of 300 mm.
• a 4′′ die for film casting purpose (manufactured by Haake) was used to make cast film from the blend.
• Each conical screw had a diameter of 30 mm at the feed port and a diamtere of 20 mm at the die.
• the extruder had four heating zones which were set at 170° C., 180° C., 180° C. and 175° C., respectively.
• the screw speed was 70 rpm.
• the screw speed and the the film wind-up speed were adjusted to obtain a thin film of uniform thickness and substantially free from film defects.
• a translucent, soft film was formed.
• blends including unmodified PVOH and a thermoplastic elastomer may be used in the absence of any chemical modification or grafting of the PVOH, or without the addition of any plasticizing agent or water to produce quality thermoplastic film and fibers comprising a blend of the PVOH and the thermoplastic elastomer.
• the use of an unmodified PVOH in these blends avoids the additional process steps associated with chemical modification or grafting of the PVOH and the problems associated with the use of plasticizers with the PVOH.

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• 2000
  • 2000-08-01 US US09/629,678 patent/US7012116B1/en not_active Expired - Lifetime
• 2002
  • 2002-05-06 US US10/140,785 patent/US20030040574A1/en not_active Abandoned

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