WO1994025255A1 - Mousse de polyethylene gonfle avec du 1,1-difluoroethane et procede pour la fabriquer - Google Patents

Mousse de polyethylene gonfle avec du 1,1-difluoroethane et procede pour la fabriquer Download PDF

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Publication number
WO1994025255A1
WO1994025255A1 PCT/US1994/003309 US9403309W WO9425255A1 WO 1994025255 A1 WO1994025255 A1 WO 1994025255A1 US 9403309 W US9403309 W US 9403309W WO 9425255 A1 WO9425255 A1 WO 9425255A1
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WIPO (PCT)
Prior art keywords
blowing agent
foam structure
polymer material
foam
die
Prior art date
Application number
PCT/US1994/003309
Other languages
English (en)
Inventor
Martin H. Tusim
Chung P. Park
Bruce A. Malone
Original Assignee
The Dow Chemical Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/056,231 external-priority patent/US5411684A/en
Application filed by The Dow Chemical Company filed Critical The Dow Chemical Company
Priority to JP6524259A priority Critical patent/JPH08509763A/ja
Priority to KR1019950704753A priority patent/KR960701739A/ko
Publication of WO1994025255A1 publication Critical patent/WO1994025255A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • 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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
    • C08J9/149—Mixtures of blowing agents covered by more than one of the groups C08J9/141 - C08J9/143
    • 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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
    • 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
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment

Definitions

  • One aspect of this invention relates to an ethylene polymer foam structure having enhanced processability and physical properties and a process for making the foam structure
  • Isobutane has become a preferred blowing agent for making ethylene polymer foam structures because of its zero ozone depletion potential and relatively high degree of processability and foamability, which can result in end products having generally desirable physical properties
  • a drawback to using isobutane is that it is a volatile organic compound, which may cause environmental concern
  • Another drawback to using isobutane is the sometimes poor compressive recovery encountered in end product foam structures at certain critical times in the product life cycle
  • a means of reducing the volatile organic content of a blowing agent containing isobutane is to replace part ot the isobutane with a hydrofluorocarbon, which may not cause the same measure of environmental concern
  • a suitable hydrofluorocarbon is 1 , 1-d ⁇ fluoroethane (HFC- 152a)
  • Replacing isobutane with HFC- 152a can present processing and extrusion problems because of the relatively low solubility of HFC- 152a in melts of ethylene polymers
  • the processing and extrusion problems would be expected to take the form of a relatively narrow range or "window" of foaming temperatures or less than desirable physical properties in the end product
  • Undesirable physical properties can include poor skin quality, small cell size, high foam density, and small cross-section
  • Foam structures blown with a blowing agent comprised entirely of isobutane sometimes exhibit poor recovery after compression, which the foam structures are often subjected to during die cutting After compression and release from compression, foam structures blown entirely with isobutane recover a substantial proportion (that is, 88-95 percent by volume or thickness) of their initial volume prior to compression, but then shrink to some degree (that is, 3- 10 percent by volume or thickness) for an extended period of time before expanding and re-gaining a substantial proportion of the initial volume
  • This temporary shrinkage is a considerable problem for cushion packaging end users or customers because the shrinkage typically occurs while the foam structure is being used as cushion packaging The shrinkage results in an undesirable loose fit between the packaging material and the article or articles being packaged
  • an ethylene polymer foam structure comprising an ethylenic polymer material and a blowing agent
  • the ethylenic polymer material comprises greater than 50 percent by weight ethylenic monomeric units
  • the blowing agent comprises isobutane and 1 , 1 -difluoroethane (HFC- 152a)
  • HFC- 152a 1 , 1 -difluoroethane
  • an ethylenic polymer foam structure comprising a) heating an ethylenic polymer material to form a melt polymer material, b) incorporating into the melt polymer material at an elevated pressure a blowing agent to form a foamable gel, and c) expanding the foamable gel at a lower pressure to form a foam structure
  • the ethylenic polymer material and the blowing agent are as described above
  • Figure 1 is a view of a representational comparative plot of the general compressive recovery behavior of ethylene polymer foam structures blown with blowing agents of isobutane and ⁇ sobutane/HFC-152a
  • Foam structures are generally prepared by heating an olefin polymer material to form a plasticized or melt polymer material, incorporating therein a blowing agent to form a - foamable gel, and extruding the gel through a die to form the foam product
  • the polymer material Prior to mixing with the blowing agent, the polymer material is heated to a temperature at or above its glass transition temperature or melting point
  • the blowing agent may be incorporated or mixed into the melt polymer material by any means known in the art such as with an extruder, mixer, or blender
  • the blowing agent is mixed with the melt polymer material at an elevated pressure sufficient to prevent substantial expansion of the melt polymer material and to generally disperse the blowing agent homogeneously therein
  • a nucleator may be blended in the polymer melt or dry
  • the blowing agent of foam structures of this aspect of the present invention comprises isobutane and HFC-152a
  • the blowing agent preferably comprises 5 to 95, more preferably 1 5 to 85, and most preferably 25 to 75 weight percent isobutane based upon the total weight of the blowing agent
  • the blowing agent further preferably comprises 95 to 5, more preferably 85 to 15, and most preferably 75 to 25 weight percent of HFC-152a A most
  • 10 preferred blowing agent comprises entirely isobutane and HFC-152a
  • HFC- 152a could be used in a blowing agent with isobutane and maintain at least acceptable levels of certain desirable processing and physical properties in end product foam structures heretofore obtainable only with isobutane Preferably, desirable processing and physical properties are substantially maintained with the use of a HFC-
  • 20 152a/ ⁇ sobutane blowing agent need not offer advantageous performance in every property
  • Processing properties important in most conventional applications include foaming temperature range or window and cross-sectional size
  • Physical properties important in most conventional applications include skin quality, cell size, density, open-cell content, dimensional stability, and compressive recovery
  • Figure 1 is a representation of the general compressive recovery behavior sometimes exhibited by foam structures blown entirely with isobutane as well as the general
  • the present foam structure may be cross nked or non-cross nked, but is preferably substantially non-crosshnked or substantially free of crosslinking Substantially non- crosshnked is inclusive however, of the slight degree of crosslinking which may occur naturally without the use of crosslinking agents or radiation
  • the present foam structure has a density of 200 or less, more preferably 100 or less, and most preferably 10 to 70 kilograms per cubic meter according to ASTM D- 1622-88
  • the foam has an average cell size of 0 1 to 5 0 preferably 0 5 to 3 0, and most preferably from 0 2 to 1 8 millimeters according to ASTM D3576-77
  • the foam component of the present foam structure may be closed cell or open cell Open-cell content may vary from O to 100 percent according to ASTM D2856-A
  • the present foam is 50 percent or less open-cell and most preferably 20 percent or less according to ASTM D2856-A
  • the present foam may take the form of sheet, rods, tubes, planks, or coalesced- strand planks
  • Another aspect of the present invention relates to a low density, large cross- section olefmic polymer foam structure blown with a blowing agent having a large proportion of 1 ,1 -d ⁇ fluoroethane
  • a foam is useful in cushion packaging applications
  • HFC 152a has presented unique processing and extrusion problems because of its relatively low solubility in melts of olefin polymers
  • t ⁇ isre is an ⁇ ruded, unitary, closed-cell olefin polymer foam structure in plank form
  • the foam structure has a cross-section in one dimension of 2 or more inches (5 or more centimeters) and 18 or more inches (46 or more centimeters) in the other dimension
  • the olefin polymer material comprises greater than 50 percent by weight of olefin monomeric units
  • the olefin polymer material has a melt index of 3 5 grams/10 minutes or less
  • the foam structure has a blowing agent comprising 75 mole percent or more 1 , 1-d ⁇ fluoroethane (HFC- 152a) based upon the total moles of the blowing agent It was found surprising that HFC- 152a, which has relatively low solubility in olefin polymers, could be used to make olefin polymer foam structures of large cross-section and low density
  • the foam structure has a cross-section in one dimension of 2 or more inches and 18 or more inches in the other dimension
  • the process comprises the steps a) heating an olefin polymer material to form a melt polymer material, b) incorporating into the melt polymer material at an elevated pressure a blowing agent to form a foamable gel, c) cooling the foamable gel to an optimum foaming temperature, and d) extruding the foamable gel through a die to form the foam structure
  • it is extruded at a shear rate of 900/seconds (seconds ') or more
  • the olefin polymer material and the blowing agent are as described above -
  • a surprising aspect of the present invention was that it was possible to make an olefin polymer foam structure of large cross-section and low density It was not expected that HFC-152a, with its relatively low solubility and melts of olefin polymers, had adequate solubility to provide the measure of blowing or expansion necessary to make a foam structure of large cross-section and low density
  • melt index is measured according to ASTM D- 1238 at 190°C/2 16 kg
  • shear rate (6 X rale)/ (width X gap 2 ), where " rate" is the volumetric flow rate, "width” refers to the width of the opening of the die orifice, and "gap” refers to the height of the opening of the die orifice
  • a plank foam structure having a cross-section of 2 or more inches (5 or more centimeters) in one dimension and 18 or more inches (46 or more centimeters) in the other dimension can be made with an olefin polymer of a melt index of 3 5 grams/10 minutes or less at a shear rate of 900/seconds or more
  • a foam structure having a cross-section of 2 or more inches (5 or more centimeters) in one dimension and 48 or more inches ( 122 or more centimeters) in the other dimension can be made with an olefin polymer of a melt index of 0 6 grams/10 minutes or less at a shear rate of 400/seconds or more
  • the shear rates above are preferred shear rates for a given cross-section
  • the secondary blowing agent comprises 25 mole percent or less of the total weight of the blowing agent
  • Preferred secondary blowing agents include isobutane, n-butane, carbon dioxide, or mixtures of two or more of the foregoing A mixture of isobutane and carbon dioxide is especially preferred
  • the large cross-section foam structure has a density of 48 or less kilograms per cubic meter and most preferably from 24 to 44 kilograms per cubic meter according to ASTM D-3575
  • the foam has an average cell size of from 0 1 to 5 0 and preferably from 1 to 3 millimeters according to ASTM D3576-77
  • the large cross-section foam structure may be closed cell or open cell
  • the present foam is greater than 80 percent closed-cell according to ASTM D2856-A
  • Another aspect of the present invention relates to a process for making an extruded, coalesced strand olefin polymer foam structure of certain density with a blowing agent of 1 , -d ⁇ fluoroethane and any of isobutane, n-butane, and propane
  • a foam structure is useful in cushion packaging applications
  • HFC-152a has a relatively low solubility in melts of olefin polymers
  • the low solubility renders it very susceptible to variation in foaming temperature High foaming temperatures will cause excessive blowing agent loss; thus, the foaming temperature must be carefully maintained to prevent excessive blowing agent loss
  • an olefin polymer foam structure of a plurality of coalesced, extruded strands of a foamed olefin polymer composition of a density of 16 to 48 kilograms per cubic meter The process comprises a) heating a olefin polymer material to form a melt polymer material; b) incorporating into the melt polymer material at an elevated pressure a blowing agent to form a foamable gel; c) cooling the foamable gel to an optimum foaming temperature; and d) extruding the foamable gel through a die having a plurality of orifices therein (multi-orifice die) to form a plurality of coalesced extruded strands or profiles of the foamed olefin poly
  • Foam structures in coalesced strand form are formed by extrusion of the foamable gel through a multi-orif ice die
  • the orifices are arranged so that contact between adjacent streams of the foamable gel occurs during the foaming process and the contacting surfaces adhere to one another with sufficient adhesion to result in a unitary foam structure
  • the streams of foamable gel exiting the die take the form of strands or profiles, which desirably foam, coalesce, and adhere to one another to form the unitary structure
  • Foam strands or profiles will vary in cross-sectional shape or geometry according to the shape or geometry of the orifices in the multio ⁇ f ice die
  • the strands or profiles may be the same or different shape or geometry than the foam structure which they coalesce to form
  • the orifices may take on a circular shape or a noncircular shape though circular is preferred o Suitable noncircular shapes include X-shaped, cross- or star-shaped, or polygonal-shaped
  • the various orifices in the die may be spatially arranged in a desired configuration or array such as a sine wave, honeycomb, square saw tooth, or a triangular saw tooth wave pattern
  • the individual strands have a major dimension in cross-section, diameter in the case of circular strands, of between 0 5 and 10 millimeters and most preferably between 1 0 and 5 0 5 millimeters
  • the orifices in the multio ⁇ fice die preferably will be of shape or geometry and be spatially arranged such that there will be sufficient channel volume or clearance between the streams of molten extrudate exiting from the same for them to foam to form the strands or profiles without substantial distortion of the resulting unitary foam structure relative to the 0 geometry of the overall arrangement of the orifices
  • the streams of molten extrudate may foam to either partly or completely fill the open channel volume between the strands or profiles (open channel or closed channel)
  • Desirable olefin polymer materials may be employed to form foam structures of coalesced foam strands or profiles having a strand-to-strand tensile strength of at least 0 5 5 pounds force per inch length (lbf/ ⁇ n) (0 88 Newtons per centimeter (N/cm)) and preferably at least 2 0 Ibf/in (3 5 N/cm)
  • the average strand-to-strand tensile strength is defined as the average tensile strength required to pull apart any two, given adjacent strands within the foam structure
  • the blowing agent 0 comprises a first blowing agent of 20 to 90 mole percent 1,1-d ⁇ fluoroethane and from 80 to 10 mole percent of a second blowing agent selected from the group consisting of isobutane, n- butane, and propane based upon the total moles of the blowing agent
  • the second blowing agent comprises 20 to 50 mole percent based upon the total moles of the blowing agent
  • the second blowing agent functions to plasticize the foamable gel so that the gel may 5 be conveyed to the die at a lower temperature than possible without the second blowing agent
  • the first blowing agent, HFC- 152a has a relatively low level of solubility in the melt olefin polymer material; thus, foaming temperature must be carefully controlled to prevent excessive blowing agent loss upon extrusion through the die The foaming temperature is more difficult to control in a multi-orifice die compared to a conventional slit die because of the greater shear heating encountered
  • any of the second blowing agents may 5 plasticize the melt to the olefin polymer material to a degree sufficient so that the temperature of the foamable gel conveyed to the multio ⁇ fice die can be lowered enough to prevent excessive loss of HFC- 152a upon foaming without "freezing"
  • the second blowing agent may increase operable foaming temperature range or "foaming window" as referred to in the art o
  • Suitable foam structures in coalesced strand form have gross densities (that is bulk densities or densities of the closed-cell foam including interstitial channels or voids between strands or profiles), preferably varying from 0 2 to 3 pounds per cubic foot (pcf) (3 2 to 48 kilograms per cubic meter (kgm)) according to ASTM 1622-88
  • Most preferred foam structures have a density from 0 5 to 2 8 pcf (8 0 to 45 kgm)
  • Foam strands comprising coalesced strand structures having an average ceil size 0 of between 0 10 to 1 2 millimeters and preferably between 0 4 and 1 0 millimeters according to ASTM D3576-77
  • Suitable olefin polymer materials include olefinic homopol' ers and copolymers of olefinic compounds and copolyme ⁇ zable olefinically unsaturated comonomers
  • the olefinic polymer material may further include minor proportions of non-olefinic polymers
  • the olefinic polymer material may be comprised solely of one or more olefinic homopolymers, one or more olefinic copolymers, a blend of one or more of each of olefinic homopolymers and copolymers, or blends of any of the foregoing with a non-olefinic polymer Regardless of composition, the olefinic polymer material comprises greater than 50 and preferably greater than 70 weight percent of
  • Suitable olefinic copolymers may be comprised of olefinic monomeric units and minor amounts, preferably 20 percent or less by weight, of a monoethylenically unsaturated compounds copolymenzable therewith
  • Suitable comonomers include C _6 alkyl acids and esters, lonome ⁇ c derivatives, C 4 6 dienes, and C 3 9 olefins
  • suitable comonomers 5 include acrylic acid, itaconic acid, maleic acid, methacryhc acid, ethacryhc acid, methyl acrylate, methyl methacrylate, ethyl acrylate, vinyl acetate, carbon monoxide, maleic anhydride, acrylonit ⁇ le, propylene, isobutylene, and butadiene
  • blowing agents include inorganic agents, organic blowing agents and chemical 0 blowing agents
  • Suitable inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air, nitrogen, and helium
  • Organic blowing agents include aliphatic hydrocarbons having 1-9 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms
  • Aliphatic hydrocarbons include methane, ethane, n-pentane, isopentane, and neopentane
  • Aliphatic alcohols include 5 methanol, ethanol, n-propanol, and isopropanol
  • Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons Examples of fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride, 1 , 1
  • the amount of blowing agent incorporated into the polymer melt material to make a foam-forming polymer gel is from 0 2 to 5 0, preferably from 0 5 to 3 0, and most preferably from 1 0 to 2 50 moles per kilogram of polymer
  • Preferred foam structures exhibit excellent dimensional stability
  • Preferred foams structures recover 80 or more percent of initial volume within a month with initial volume being measured within 30 seconds after extrusion Volume may be determined by the cubic displacement test in water
  • a stability control agent to the foam structures of the present invention to enhance dimensional stabili ty
  • Suitable agents include any of those known in the art
  • Preferred agents include amides and esters of Cio 2 fatty acids
  • Most preferred agents include stearyl stearamide and glycerol monostearate
  • additives may be incorporated in the present foam structure such as inorganic fillers, pigments, antioxidants, acid scavengers, stability control agents, ultraviolet absorbers, flame retardants, processing aids, and extrusion aids
  • nucleating agent may be added in order to control the size of foam cells
  • Preferred nucleating agents include inorganic substances such as calcium carbonate, talc, clay, titanium oxide, silica, barium sulfate, diatomaceous earth, and mixtures of citric acid and sodium bicarbonate
  • the amount of nucleating agent employed may range from 0 01 to 5 parts by weignt per hundre ⁇ parts oy weignt of a polymer resin Tne preferre ⁇ range is from 0 1 to 3 parts by weight
  • An ethylene polymer foam structure of the present invention was prepared with a blowing agent of HFC- 152a and isobutane Control foam structures prepared with a blowing agent of either 1 , 1 -dif luoroethane (HFC- 152a) or isobutane ( ⁇ C 4 ) were also prepared The present foam structure and the control structures were compared for processability and physical properties
  • the apparatus used was a 25 mm (1 inch) screw type extruder having additional zones for mixing and cooling at the end of usual sequential zones for feeding, metering, and mixing
  • An injection port for the blowing agent was provided between the metering and mixing zones
  • a die having a rectangular orifice was attached at the end of the cooling zone
  • the height of the orifice hereinafter called the die gap, was adjustable while its width was fixed at 3 68 mm (0 145 inch)
  • a granular low density polyethylene (LDPE) resin having a melt index (ASTM D- 1238 190°C/2 16 kgs) of 1 8 dg/min (decigrams/minute) and a density of 0 923 g/cmJ was pre- blended with a concentrate of glycerol monostearate (GMS) to yield an effective GMS level of 1 3 parts per hundred (pph) and a small amount (0 02 pph) of talcum powder to form a solid mixture
  • the solid mixture was fed to the extruder
  • the present structure and the control structures were compared for foamabihty, an indicator of processability, by measuring the range or "window" of foaming temperature
  • the foaming window was determined as follows Starting at the gel temperature where the foam rose and remained stabilized, a foam strand was saved at a critical die gap (a threshold die gap for pre-foaming) The gel temperature was then dropped one degree and another foam sample was taken The operation was repeated until there was an indication the cooling section was "froze off" The freeze-off (same as froze off) condition was indicated by deterioration of foam quality accompanied by a sharp increase of gel pressure entering into the cooling zone
  • the foaming temperature window was defined as the range of foaming temperature providing an open cell content in the foam no greater than a specified value ( 10 percent open cell for the examples herein) The optimum foaming temperature wherein minimum foam density was achieved varied between 107°C- 109°C for the three tests
  • the foam structures were aged for at least two weeks, and analyzed for cross- sectional size (area),
  • the present foam structure blown with the HFC- 152a/ ⁇ sobutane blowing agent was of good quality at a wide range of foaming temperatures Its foaming temperature window ( 13°C) was shown to be one degree wider than the control structure blown with isobutane alone (Test 1 2) and significantly greater than the control structure blown with HFC- 152a alone (Test 1 3)
  • the present foam structure was very comparable with the control structure blown with isobutane alone in foam cross-section, density, cell size, and skin quality, and clearly superior in those physical properties to those control structures blown with HFC-152a alone It was very surprising the desirable processing and physical properties of the foam structure blown with isobutane alone could be substantially maintained in the foam structure blown with one-half by mole isobutane and one-half by mole HFC- 152a in view of the much less desirable processing and physical properties of the foam structure blown with HFC-
  • An ethylene polymer foam structure of the present invention was prepared with a blowing agent of HFC- 152a and isobutane A control structure blown with HFC-152a alone was also prepared The foam structures were compared for processability and physical properties
  • the polymers used were a 74/26 by weight blend of a LDPE resin having 0 919 g/crr density and 0 22 dg/min melt index and another LDPE having 0 919 g/cm ⁇ density and 7 o dg/min melt index
  • the polyethylenes were pre-blended with a concentrate of stearyl stearamide to yield an effective stearamide level of 1 3 pph No nucleating agent was employed
  • the blowing agent was employed at a level of 1 3 mpk
  • the present foam structure blown with HFC-152a/ ⁇ sobutane had significantly better processing and physical properties than the control structure blown with only HFC- 152a
  • control structure had an undesirably small cell size even though no nucleating agent was 0 used
  • the control structure had an undesirably small cross-sectional size, relatively high open cell content (greater than 10 percent), and virtually no foaming window (zero)
  • the present structure exhibited substantially better performance in most of these properties
  • Ethylene polymer foam structures of the present invention were prepared with a 5 blowing agent of varying proportions of HFC- 152a and isobutane Control foam structures were prepared with blowing agents of either HFC-152a or isobutane alone.
  • HFC- 152a/ ⁇ sobutane mixed blowing agent provided the present foam structures with better compressive recovery than one blown with isobutane alone
  • the apparatus used was a 3 50 inch (8 9 cm) screw-type extruder having 0 substantially the same configuration as the extruder of Example 1
  • the apparatus was equipped with a gap-adjustable slit die with 2 25 inch (5 72 cm) width at the end of the cooling zone
  • the polymer used was a 75/25 blend by weight of a granular LDPE resin having
  • Foam structures of 39-42 mm thickness and 203-213 mm width formed at a fixed die gap of 0 13 inch were recovered Two specimens of 254-280 mm length from each test were examined for dimensional stability by periodically measuring the dimensions of the foams o Compressi e recovery tests were conducted upon foam structures aged at ambient temperature (72°F) for specific periods of time Foam structures were compressed to 80 percent of original thickness at 0 5 inches/minute rate, and allowed to recover During recovery, thickness was monitored periodically
  • the present foam structures exhibited greater compressive recovery 5 than the control structure blown with isobutane alone
  • the greater compressive recovery allows retention of foam structure dimensions after die cutting Example 4
  • Olefin polymer foam structures of large dimensions in plank form were blown with HFC- 152a according to the process of the present invention
  • the olefin resins employed 0 were polyethylene homopolymers
  • blowing agent comprised HFC- 152a
  • Additives were 1 3 pph stearyl stearamide as a stabilty control agent and Hydrocerol CF-20 (Boerhinger 5 Ingelheim) as a nucleating agent, 0 03 pph of Irganox 1010 (Ciba-Geigy) as an anti-oxidant
  • the foamable gel of the polymer melt and the blowing agent was extruded through the dies at various shear rates Shear rate varied by adjusting the size of the dies and extrusion throughput rates
  • the size of the dies was varied to form foams of various cross-sections
  • the size (area) of the die was varied by adjusting the die gap 0
  • the surface (skin) quality of the foam structure was examined for quality Good foam structures exhibited relatively smooth, matte-like surfaces Fair foam structures exhibited matte-like surfaces with some bumps and surface irregularities Poor foam structures exhibited rough surfaces, some grooving or crevices, and larger irregularities Acceptable foam structures had fair or good surface quality Results are seen in Table 4 5
  • An ethylene polymer foam structure in coalesced strand form was made according to the process of the present invention with a blowing agent of 75 pph HFC-152a and 25 pph isobutane
  • the apparatus comprised an extruder and a multi-orifice die in series
  • the die had 224 0 064 inch ( 1 62 millimeters (mm)) orifices therein
  • the polymer used was a blend of low density polyethylenes having an average melt index of 15 according to ASTM D 1238 ( 190 o C 2 16 kg)
  • Additives used were glycerol monostearate (GMS) at 1 pph as a stability control agent and Hydrocerol CF-70 (Boehringer Ingelheim) at 0 3 pph as a nucleating agent
  • GMS glycerol monostearate
  • Hydrocerol CF-70 Hydrocerol CF-70
  • the blowing agent was injected into and homogeneously dispersed within the o flowable melt at an elevated temperature to form a foamable gel
  • the foamable gel was cooled to an optimum foaming temperature, and conveyed through the die to form the foam structure
  • the foaming temperature was 108 5 ⁇ C
  • the foam structure stabilized to a desirable density of 1 95 pcf (31 2 kgm)
  • the structure formed without collapsing The foaming temperature was sufficiently low to prevent 5 excessive loss of blowing agent, and, thus, collapse Comparative Example 5
  • An ethylene polymer foam structure in coalesced strand form was made 5 according to the present invention with a blowing agent of HFC-152a and propane
  • Example 5 A smaller-scale version of the apparatus of Example 5 was used except the multi- o ⁇ fice die had 13 0 060 inch ( 1 52 mm) holes therein
  • the procedure used was substantially the same as in Example 5 except the polymer and additives were fed at a rate of 20 Ibs/hr (9 1 kg/hr), and the blowing agent was composed of 4 pph HFC-152a and 4 pph propane 0
  • the foam structure stabilized to a desirable density of 2 00 pcf (32 0 kgm)
  • the foaming temperature was sufficiently low to prevent excessive loss of blowing agent, and, thus, collapse

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

On décrit un procédé pour fabriquer des structures en mousse de polyoléfine gonflé avec du 1,1-difluoroéthane (HFC-152a). Une structure de mousse est constituée par du polyéthylène gonflé par un mélange d'isobutane et de 1,1-difluoroéthane. Une autre structure de mousse avec une section transversale de 2 pouces ou davantage (5 centimètres ou davantage) selon une dimension et 18 pouces ou davantage (46 centimètres ou davantage) dans une autre dimension est obtenu avec un mélange gonflant contenant 75 pour cent (en moles) ou davantage de HFC-152a. Une autre structure de mousse est sous forme de caron extrudé coalescé ayant une densité de 16 à 48 kilogrammes par mètre cube et elle est obtenue par gonflage avec un premier agent gonflant constitué par 20 à 90 pour cent (en moles) de 1,1-difluoroéthane et 80 à 10 pour cent (en moles) d'un second agent gonflant choisi parmi l'isobutane, le n-butane et le propane.
PCT/US1994/003309 1993-04-30 1994-03-25 Mousse de polyethylene gonfle avec du 1,1-difluoroethane et procede pour la fabriquer WO1994025255A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP6524259A JPH08509763A (ja) 1993-04-30 1994-03-25 １，１−ジフルオロエタンで発泡したエチレンポリマーフォームおよびそれを製造する方法
KR1019950704753A KR960701739A (ko) 1993-04-30 1994-03-25 1, 1-디플루오로에탄으로 발포시킨 에틸렌 중합체 발포체 및 이의 제조방법(Ethylene polymer foams blown with 1,1-difluoroethane and method of making same)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US5623093A 1993-04-30 1993-04-30
US08/056,231 1993-04-30
US08/056,231 US5411684A (en) 1993-04-30 1993-04-30 Process for making large cross-section olefinic polymer foam structure blown with 1, 1-difluoroethane
US08/056,230 1993-04-30
US9083393A 1993-07-12 1993-07-12
US08/090,833 1993-07-12

Publications (1)

Publication Number Publication Date
WO1994025255A1 true WO1994025255A1 (fr) 1994-11-10

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PCT/US1994/003309 WO1994025255A1 (fr) 1993-04-30 1994-03-25 Mousse de polyethylene gonfle avec du 1,1-difluoroethane et procede pour la fabriquer

Country Status (3)

Country Link
JP (1) JPH08509763A (fr)
KR (1) KR960701739A (fr)
WO (1) WO1994025255A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7350482B2 (ja) * 2018-12-18 2023-09-26 株式会社カネカ 無架橋ポリエチレン系樹脂押出発泡ボードおよびその製造方法

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US4983677A (en) * 1988-04-15 1991-01-08 Minnesota Mining And Manufacturing Company Extrudable thermoplastic hydrocarbon polymer composition
US5015693A (en) * 1988-04-15 1991-05-14 Minnesota Mining And Manufacturing Company Extrudable thermoplastic hydrocarbon polymer composition

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4215202A (en) * 1979-02-22 1980-07-29 The Dow Chemical Company Soft ethylenic polymer blend foams
US4370378A (en) * 1979-03-15 1983-01-25 The Dow Chemical Company Low density, extruded ethylenic polymer foams
US4317888A (en) * 1980-04-28 1982-03-02 Asahi-Dow Limited Process for manufacturing an olefin resin foam
US4323528A (en) * 1980-08-07 1982-04-06 Valcour Imprinted Papers, Inc. Method and apparatus for making large size, low density, elongated thermoplastic cellular bodies
US4387169A (en) * 1981-10-01 1983-06-07 The Dow Chemical Co. Low density, extruded ethylenic polymer foams
US4528300A (en) * 1984-01-31 1985-07-09 The Dow Chemical Company Process for producing dimensionally stable polyolefin foams using environmentally acceptable blowing agent systems
US4640933A (en) * 1985-12-24 1987-02-03 The Dow Chemical Company Expandable polyolefin compositions and preparation process utilizing isobutane blowing agent
US4640933B1 (en) * 1985-12-24 1996-09-10 Dow Chemical Co Expandable polyolefin compositions and preparation process utilizing isobutane blowing agent
US4983677A (en) * 1988-04-15 1991-01-08 Minnesota Mining And Manufacturing Company Extrudable thermoplastic hydrocarbon polymer composition
US5015693A (en) * 1988-04-15 1991-05-14 Minnesota Mining And Manufacturing Company Extrudable thermoplastic hydrocarbon polymer composition

Also Published As

Publication number Publication date
JPH08509763A (ja) 1996-10-15
KR960701739A (ko) 1996-03-28

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