KR20020022658A - Film with enhanced performance properties - Google Patents

Abstract

The present invention relates to tough hard films comprising a mixture comprising an alkenyl aromatic polymer and a substantially random interpolymer. The film is particularly suitable for use in applications requiring tough rigid films such as window envelope films or labels. The invention further relates to an article comprising such a film.

Description

Film with enhanced performance properties

Mixtures comprising alkenyl aromatic polymers such as polystyrene and α-olefins / hindered vinyl or vinylidene interpolymers such as ethylene-styrene copolymers are known in the art. Such mixtures have been proposed for several uses, including films and foams.

WO 95/32095 describes heat shrinkable films comprising an oriented film layer comprising a homogeneous α-olefin / vinyl aromatic copolymer. Further proposed is a laminate comprising a foam sheet and a film which can be adhered to such foam sheet and which can comprise a polystyrene homopolymer and a homogeneous α-olefin / vinyl aromatic copolymer.

U. S. Patent 5,460, 818 describes miscible mixtures of olefin polymers and monovinylidene aromatic polymers, and intumescent compositions comprising such polymer mixture compositions and swelling agents. The polymer mixture compositions described are substantially random inters comprising aliphatic α-olefin homopolymers or interpolymers (a), homopolymers or interpolymers of monovinylidene aromatic monomers (b) and aliphatic α-olefins and vinylidene aromatic monomers. Polymer (c).

WO 98/10014 relates to mixtures of α-olefin / hindered vinylidene monomer interpolymers and vinyl aromatic polymers and foams therefrom. Foams with general foam polystyrene and substantially random ethylene-styrene interpolymers and foam densities of about 40 to about 130 kg / m ³ are described in detail.

There is still a need for film structures with improved properties, particularly in areas where tough rigid films are desired. Particular preference is given to films which exhibit not only advantageous mechanical properties but also aesthetic appearance. It is an object of the present invention to provide a well balanced film in which performance contribution properties including high toughness, good hardness, wear resistance, crack resistance, high extreme elongation and good tear resistance are combined with excellent optical properties. These properties are required for films suitable for, for example, envelope window films, packaging films for window boxes, greeting card overlays and labels.

A window envelope is an envelope with one or more apertures that are any shape but typically rectangular. These hole (s) allow for identification of any information, such as name and address, which is printed over a limited area of the contents and sealed or sealed by a window composed of a transparent plastic film. Known window films typically consist of oriented polystyrene, optionally containing a low proportion of rubber reinforced polymers.

Typically, the label is attached or accompanied by a product for identification or to provide other information. For example, the label may be a component of a packaging material, such as a container, which component is not in contact with the contents of the packaging. Preferably, the label is printable. The label may, for example, have a protective function in terms of integrity with the product or packaging material.

Films for use as window films and labels require a high degree of hardness to be handled and converted well in high speed printing operations, in envelope production, in label production, and in end-use applications. In addition, these films require high surface gloss (eg appearance and printability), good tensile strength and toughness properties as well as good scratch and wear resistance.

It is an object of the present invention to provide a film that is well balanced between its performance characteristics to be particularly suitable for the above and related applications, in particular as window film or label.

Summary of the Invention

The present invention relates to a tough rigid film comprising a mixture comprising (at least) component (A) and component (B). Component (A) is present in an amount of about 45 to about 90 weight percent based on the total weight of components (A) and (B), and component (B) is the total of components (A) and (B) It is present in an amount of about 10 to about 55% by weight based on weight. Component (A) consists of one or more alkenyl aromatic polymers. Component (B) comprises about 50 to 74 mole percent ethylene and / or one or more α-olefin monomers (i), one or more vinyl or vinylidene aromatic monomers and / or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers (ii) 26 to about 50 mole percent, and other polymerizable ethylenically unsaturated monomer (s) (iii) from 0 to about 20 mole percent in polymerized form.

The mixture components and their ratios are selected to provide films with high hardness and toughness. The excellent hardness of the film is indicated by modulus of about 85,000 psi or more (1% secant modulus in the vertical direction). Toughness is indicated by high tensile toughness and ultimate elongation strength.

Further aspects of the invention relate to methods of making the films of the invention and the use of such films.

In another aspect, the present invention provides a window envelope having one or more window openings completely enclosed by a transparent plastic window formed from a film according to the present invention.

In addition, the present invention provides a label for a container made from a film according to the present invention.

The invention also provides an article comprising the film of the invention.

The present invention relates to tough hard films comprising a mixture of polymeric materials.

As used herein, the term “polymeric material” refers to a polymeric compound that can be obtained by polymerizing one or more monomers. The generic term “polymeric compound” or “polymer” includes the term homopolymers commonly used to refer to polymers made from only one monomer and the term interpolymer as described below.

As used herein, the term "comprising" refers to "including".

As used herein, the term “film” refers to thin articles including flakes, tapes and ribbons.

The term "multilayer film" as used herein refers to a film consisting of two, three, four, five, six, seven or more layers.

As used herein, the term “foamed film” refers to a single or multi-layered structure in which one layer of such structure is foamed and has a density of at least about 300 kg / m ³ and smaller than the unfoamed polymer.

The term "interpolymer" as used herein refers to a polymer prepared by polymerizing two or more monomers. Thus, the general term interpolymer includes the term copolymer, usually used to refer to polymers made from two different monomers, and polymers made from two or more different monomers, such as terpolymers.

As defined herein, the term "substantially random" in a substantially random interpolymer of component (B) means that the distribution of the monomers of the interpolymer is first-order or as described by Bernoulli statistical models or in the literature. It can be defined by a second-order Markian statistical model (see JC Randall, Polymer Sequence Determination, Carbon-13 NMR Method, Academic Press New York, 1977, pp. 71-78). One interpolymer contains no more than 15% of the total amount of vinyl aromatic monomer in a block of at least 3 units of vinyl aromatic monomer More preferably, the interpolymer is not characterized by high isotacticity or syndiotacticity. This is a backbone methylene and methine that represents a meso doublet sequence or racemic doublet sequence in a carbon-13 NMR spectrum of a substantially random interpolymer. It is meant that the peak area corresponding to carbon should not exceed 75% of the total peak area of the main chain methylene and methine carbons.

The present invention relates to one or more alkenyl aromatic homopolymers or copolymers of alkenyl aromatic homopolymers and / or alkenyl aromatic monomers with at least one ethylenically unsaturated comonomer (other than ethylene or straight chain C ₃ -C ₁₂ α-olefins). Monomer) and a mixture comprising a copolymer of at least one substantially random interpolymer.

The alkenyl aromatic polymer material (component (A)) may further comprise a small amount of non-alkenyl aromatic polymer. The alkenyl aromatic polymer material may be one or more alkenyl aromatic homopolymers, one or more alkenyl aromatic copolymers, one or more mixtures of alkenyl aromatic homopolymers and copolymers, or mixtures of any of the foregoing nonalkenyl aromatic polymers. It can consist only of. Regardless of the composition, the alkenyl aromatic polymer material comprises at least 50%, preferably at least 70% by weight of alkenyl aromatic monomeric units. Most preferably, the alkenyl aromatic polymer materials all consist solely of alkenyl aromatic monomeric units.

Suitable alkenyl aromatic polymers are solely derived from alkenyl aromatic compounds such as styrene, α-methylstyrene, ethylstyrene, vinyl benzene, vinyl toluene, chlorostyrene, bromostyrene, tert-butyl styrene and all isomers of these compounds. Polymers and copolymers. Suitable polymers used as component (A) also include alkenyl aromatic polymers having a high syndiotactic configuration. Preferred alkenyl aromatic polymers are polystyrenes. Small amounts of monoethylenically unsaturated compounds such as C _2-6 alkyl acids and esters, ionomeric derivatives and C _4-6 dienes may be copolymerized with alkenyl aromatic compounds. Examples of copolymerizable compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl Methacrylate, vinyl acetate and butadiene.

Polystyrene for general use is the most preferred alkenyl aromatic polymer material suitable as component (A) as defined herein. The term "polystyrene for general use" is as defined in the literature. See Encyclopedia of Polymer Science and Engineering, Vol. 16, 1989, pages 62-71. Such polystyrenes are also referred to as crystalline polystyrenes or polystyrene homopolymers.

The monoalkenyl aromatic polymers can be suitably modified by rubber to improve their impact resistance. Examples of suitable rubbers are homopolymers of C _4-6 conjugated dienes, especially butadiene or isoprene; Interpolymers of at least one alkenyl aromatic monomer with at least one C _4-6 conjugated diene; Interpolymers of ethylene and propylene or ethylene, propylene and nonconjugated dienes, in particular 1,6-hexadiene or ethyledene norbornene; Homopolymers of C _4-6 alkyl acrylates; _{Interpolymers of} C _4-6 alkyl acrylates and interpolymerizable comonomers, especially alkenyl aromatic monomers or C _1-4 alkyl methacrylates. Also included are graft polymers in which the aforementioned rubbery polymers are grafted with alkenyl aromatic polymers. Preferred alkenyl aromatic polymers for use in all the aforementioned rubbery polymers are styrene. Most preferred rubbery polymers are polybutadiene or styrene / butadiene copolymers.

Impact resistant modified alkenyl aromatic polymers are well known in the art and commercially available.

Polymers suitable for use as component (A) also include alkenyl aromatic polymers having a high syndiotactic configuration.

Preferred alkenyl aromatic polymers for use as component (A) of the present invention include polystyrene, syndiotactic polystyrene, rubber modified impact resistant polystyrene, poly (vinyl-toluene), and poly (α-methylstyrene).

Substantially random interpolymers of component (B) as defined herein may comprise from about 50 to 74 mole percent of polymer units (i) derived from any one or more of ethylene and / or C _3-20 α-olefins Polymer units derived from vinyl or vinylidene aromatic monomers (a), one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers (b) or mixtures of one or more aromatic vinyl or vinylidene monomers (c) 26 To about 50 mole percent, and about 0 to about 20 mole percent of polymer units (iii) derived from one or more ethylenically unsaturated polymerizable monomers other than those derived from components (i) and (ii).

Suitable α-olefins are, for example, α-olefins having 3 to about 20 carbon atoms, preferably 3 to about 12 carbon atoms, more preferably 3 to about 8 carbon atoms. These α-olefins do not contain aromatic moieties.

Ethylene, propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1 or ethylene and one or more propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1 The combination of is particularly suitable.

Polymerizable ethylenically unsaturated monomer (s) include norbornene and C _1-10 alkyl or C _6-10 aryl substituted norbornene, with the interpolymers being illustrated being ethylene / styrene / norbornene.

Suitable vinyl or vinylidene aromatic monomers that can be used to prepare substantially random interpolymers are, for example, compounds of formula

In Formula 1 above,

R ¹ is selected from the group consisting of hydrogen and alkyl radicals having 1 to about 4 carbon atoms, preferably hydrogen or methyl,

Each R ² is independently selected from hydrogen and alkyl radicals having 1 to about 4 carbon atoms, preferably hydrogen or methyl,

Ar is a phenyl group or a phenyl group substituted with 1 to 5 substituents selected from halo, C _1-4 alkyl and C _1-4 haloalkyl,

n is a value from 0 to about 4, preferably 0 to 2, most preferably 0.

Illustrative vinyl aromatic monomers include styrene, vinyl toluene, α-methylstyrene, tert-butyl styrene, chlorostyrene, including all isomers of these compounds. Particularly suitable as such compounds include styrene and lower alkyl or halogen substituted derivatives thereof. Preferred monomers are styrene, α-methylstyrene, lower alkyl- (C ₁ -C ₄ ) or styrene derivatives substituted with phenyl rings (eg ortho-, meta- and para-methylstyrene), ring halogenated styrenes, para-vinyl Toluene or mixtures thereof. Most preferred aromatic vinyl monomer is styrene.

The term "sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compound" means a polymerizable vinyl or vinylidene monomer of the formula:

In Formula 2 above,

A ¹ is a steric bulky aliphatic or alicyclic substituent having 20 or less carbon atoms,

R ¹ is selected from a radical group consisting of hydrogen and alkyl radicals having 1 to about 4 carbon atoms, preferably hydrogen or methyl,

R ² is each independently selected from a radical group consisting of hydrogen and alkyl radicals having 1 to about 4 carbon atoms, preferably hydrogen or methyl, or R ¹ and A ¹ together form a ring system.

Preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds are monomers in which one of the carbon atoms containing ethylenically unsaturated bonds is tertiary or quaternary substituted. Examples of such substituents include cyclic aliphatic groups such as cyclohexyl, cyclohexenyl and cyclooctenyl, or ring alkyl or aryl substituted derivatives thereof, tert-butyl or norbornyl. Most preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds are various isomeric vinyl ring substituted derivatives of cyclohexene and substituted cyclohexene, and 5-ethylidene-2-norbornene. 1,3- and 4-vinylcyclohexene are particularly suitable. For example, simple straight chain unbranched α-olefins containing 3 to about 20 carbon atoms, such as propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1, are steric It does not correspond to a hindered aliphatic or cycloaliphatic vinyl or vinylidene compound.

One method of preparing a substantially random interpolymer is James C., which is incorporated herein by reference in its entirety. James C. Stevens et al. EP-A 0,416,815 and Francis J. Polymerization in the presence of one or more metallocene or entrapped geometry catalysts in combination with various cocatalysts as described in US Pat. No. 5,703,187 to Francis J. Timmers. Preferred process conditions for this polymerization are atmospheric pressures to 3,000 atmospheres and temperatures of -30 ° C to 200 ° C. Performing polymerization and unreacted monomer removal at temperatures above the autopolymerization temperature of each monomer can result in the formation of significant amounts of homopolymer polymerization products from free radical polymerization.

Examples of methods for making substantially random interpolymers with suitable catalysts are EP-A 514,828 and U.S. Patent Nos. 5,055,438, 5,057,475, 5,096,867, 5,064,802, 5,132,380, 5,189,192, and 5,321,106, 5,347,024, 5,350,723, 5,374,696, 5,399,635, 5,470,993, 5,703,187 and 5,721,185, all of which are incorporated herein by reference.

Substantially random α-olefin / vinyl aromatic interpolymers may also be prepared by the process described in JP 07/278230 using compounds of the following formula (3).

In Formula 3 above,

Cp ¹ and Cp ² are each independently a cyclopentadienyl group, indenyl group, fluorenyl group or a substituent thereof,

R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group, or an aryloxy group,

m is a Group 4 metal, preferably Zr or Hf, most preferably Zr,

R ³ is an alkylene group or silandiyl group used to crosslink Cp ¹ and Cp ² .

Substantially random α-olefin / vinyl aromatic interpolymers can also be prepared by the methods described in the literature, which is incorporated herein by reference in its entirety. See WO 95/32095, John G. Bradfute et al. (WRGrace & Co. ); WO 94/00500, RBPannell (Exxon Chemical Patents, Inc.); And Plastics Technology , p. 25 (1992.9.).

Francis J. Two documents, Timmus et al., US patent application Ser. No. 08 / 708,869, filed Sep. 4, 1996 and at least one α-olefin / vinyl aromatic / vinyl aromatic / α-olefin quartet described in WO 98/09999. Substantially random interpolymers are also suitable. These interpolymers have an additional signal three times stronger than peak-to-peak noise in the carbon-13 NMR spectrum. These signals appear at 43.70 to 44.25 ppm and in the chemical shift range of 38.0 to 38.5 ppm. Specifically, main peaks are observed at 44.1, 43.9 and 38.2 ppm. Proton Test NMR experiments show that the signal in the chemical shift region 43.70 to 44.25 ppm is methine carbon and the signal in the region 38.0 to 38.5 ppm is methylene carbon.

These new signals may involve one or more α-olefin inserts, for example two head-to-tail vinyl aromatic monomer inserts that precede or follow the ethylene / styrene / styrene / ethylene quartet. The styrene monomer inserts of the quartet are exclusively formed only in a 1,2 (head-to-tail) fashion. Those skilled in the art will appreciate that for such quadrants involving vinyl aromatic monomers other than styrene and α-olefins other than ethylene, the ethylene / vinyl aromatic monomer / vinyl aromatic monomer / ethylene quartet is similar to the carbon-13 NMR peak. It will be appreciated that it represents slightly different chemical shifts.

These interpolymers can be prepared by carrying out polymerization at temperatures of about −30 ° C. to about 250 ° C., in the presence of a catalyst of Formula 4, optionally, but preferably in the presence of an activating promoter.

In Formula 4 above,

Cp are each independently a substituted cyclopentadienyl group π-bonded to M,

E is carbon or Si,

M is a Group 4 metal, preferably Zr or Hf, most preferably Zr,

Each R is independently hydrogen or hydrocarbyl, silahydrocarbyl or hydrocarbylsilyl having up to about 30 carbon atoms, preferably 1 to about 20, more preferably 1 to about 10 carbon atoms,

Each R ′ is independently hydrogen or halo or hydrocarbyl, hydrocarbyloxy, silahydrocarbyl or hydrocarbylsilyl having up to about 30, preferably 1 to about 20, more preferably 1 to about 10 carbon atoms or silicon atoms , The two R 'groups may together form C _1-10 hydrocarbyl substituted 1,3-butadiene,

M is 1 or 2.

In particular, suitable substituted cyclopentadienyl groups include groups of the formula

In Formula 5 above,

Each R is independently hydrogen or hydrocarbyl, silahydrocarbyl or hydrocarbylsilyl having up to about 30, preferably from 1 to about 20, more preferably from 1 to about 10 carbon atoms, or two R groups Form divalent derivatives of this group.

Preferably, each R is independently hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or silyl (including all suitable isomers thereof) or (optionally) these two R groups are bonded together To form a fused ring system such as indenyl, fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl or octahydrofluorenyl.

Particularly preferred catalysts are, for example, racemic- (dimethylsilandiyl) -bis- (2-methyl-4-phenylindenyl) zirconium dichloride, racemic- (dimethylsilandiyl) -bis- (2 -Methyl-4-phenylindenyl) zirconium 1,4-diphenyl-1,3-butadiene, racemic- (dimethylsilanediyl) -bis- (2-methyl-4-phenylindenyl) zirconium di-C _1-4 alkyl, racemic- (dimethylsilanediyl) -bis- (2-methyl-4-phenylindenyl) zirconium di-C _1-4 alkoxide, or any mixture thereof.

Further, the catalyst of the titanium-based trapped geometry, [N- (1,1-dimethylethyl) -1,1-dimethyl-1-[(1,2,3,4,5-η) -1, 5,6,7-tetrahydro-s-indacene-1 yl] silaneaminate (2-)-N] titanium dimethyl, (1-indenyl) (tert-butylamido) dimethylsilane titanium dimethyl, ((3-tert-butyl) (1,2,3,4,5-η) -1-indenyl) (tert-butylamido) dimethylsilane titanium dimethyl, and ((3-isopropyl) ( 1,2,3,4,5-η) -1-indenyl) (tert-butyl amido) dimethylsilane titanium dimethyl or mixtures thereof may also be used.

Further methods of preparing interpolymers for use in the present invention are described in the literature. A method using a catalyst system based on methylalumoxane (MAO) and cyclobutadienyltitanium trichloride (CpTiCl ₃ ) to prepare ethylene-styrene copolymers is reported in the literature. Longo and Grassi, Markromol. Chem., Volume 191, pages 2387 to 2396 (1990); And D'Anniello et al., Journal of Applied Polymer Science, Volume 58, pages 1701-1706 (1995). Copolymerization processes using MgCl ₂ / TiCl ₄ / NdCl ₃ / Al (iBu) ₃ catalysts to provide random copolymers of styrene and propylene have been reported in the literature. See Xu and Lin, Polymer Preprints, Am. Chem. Soc., Div. Polym. Chem., Volume 35, pages 686-687 (1994)]. Copolymerization of ethylene and styrene using TiCl ₄ / NdCl ₃ / MgCl ₂ / Al (Et) ₃ catalysts has been reported in the literature [Lu et al., Journal of Applied Polymer Science, Volume 53, pages 1453 to 1460 (1994). The effect of polymerization conditions on the copolymerization of styrene and ethylene using Me ₂ Si (Me ₄ Cp) (n-tert-butyl) TiCl ₂ / methylaluminoxane Ziegler-Natta catalyst is described in the literature. Sernetz and Mulhaupt, Macromol. Chem. Phys., Vol 197, pp. 1071-1083 (1997). Copolymers of ethylene and styrene produced by bridged metallocene catalysts are described in the literature. See Arai, Toshiaki and Suzuki, Polymer Preprints, Am. Chem. Soc., Div. Polym. Chem., Vol. 38, pags 349-350 (1997); And US Pat. No. 5,652,315 to Mitsui Toatsu Chemicals, Inc.]. Mitsui Petrochemical Industries LTd., US Pat. No. 5,244,996 to Mitsui Petrochemical Industries LTd. And also Mitsui Petrochemical Industries Limited As described in issued US Pat. No. 5,652,315 or as described in DE 197 11 339 A1 of Denki Kagaku Kogyo KK. All of the above described methods for preparing interpolymer components are incorporated herein by reference. In addition, even though the high isotacticity is not “substantially random,” random copolymers of ethylene and styrene as described in the literature can be used as component (B) in the films of the present invention. See Polymer Preprints Vol. 39, No. 1, March 3, 1998, Toru Aria et al.].

While producing substantially random interpolymers, some atactic vinyl aromatic homopolymers can be formed due to the homopolymerization of vinyl aromatic monomers at elevated temperatures. The pressure of the vinyl aromatic homopolymer is generally not fatal for the purposes of the present invention and is acceptable.

Most preferred substantially random interpolymers for use as component (B) are interpolymers of ethylene and styrene, and interpolymers of ethylene, styrene and one or more α-olefins having 3 to 8 carbon atoms.

Preferably, the substantially random interpolymer comprises up to about 70 mole percent of ethylene and / or one or more α-olefin monomers in copolymerized form. A preferred upper limit is about 60 mole percent ethylene and / or one or more α-olefin monomers.

Preferably, the substantially random interpolymer comprises at least about 30 mole percent of the one or more vinyl or vinylidene aromatic monomers and / or the one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers in copolymerized form. A preferred lower limit is about 40 mole percent of at least one vinyl or vinylidene aromatic monomer and / or at least one sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer.

The presence of other polymerizable ethylenically unsaturated monomer (s) is optional. Preferably component (B) does not contain such monomers.

The melt index (I ₂ ) according to ASTM D 1238 Procedure A, Condition E, is from about 0.01 to about 50 g / 10 minutes, preferably from about 0.01 to about 20 g / 10 minutes, more preferably from about 0.1 to about 7 g / 10 minutes. Most preferably about 0.3 to about 5 g / 10 minutes.

The density of the substantially random interpolymer is generally at least about 0.930 g / cm ³ , preferably from about 0.930 to about 1.045 g / cm ³ , more preferably from about 0.930 to about 1.040 g / cm ³ , most preferably About 0.930 to about 1.030 g / cm ³ . The molecular weight distribution, Mm / Mn, is generally about 1.5 to about 20, preferably about 1.8 to about 10, more preferably about 2 to about 5.

Substantially random interpolymers can be modified by typical grafting, hydrogenation, functionalization or other reactions well known to those skilled in the art. The polymer can be easily sulfonated or chlorinated according to techniques already established to provide functionalized derivatives. Substantially random interpolymers may also be modified by various chain extension or crosslinking processes, including but not limited to peroxide, silane, sulfur, radiation or azide based curing systems. A complete description of the various crosslinking techniques is described in US Pat. Nos. 5,869,591 and EP-A 778,852, which are incorporated herein by reference in their entirety. Dual curing systems using a combination of heat, humidification curing and radiation steps can be used effectively. For example, it may be desirable to use peroxide crosslinkers with silane crosslinkers, peroxide crosslinkers with radiation, or sulfur containing crosslinkers with silane coupling agents. Substantially random interpolymers can be prepared by incorporating a diene component as a third comonomer in their preparation and then crosslinking by the above-described method, for example by vulcanization through a vinyl group using sulfur as a crosslinking agent. It may also be modified by various crosslinking methods, including but not limited to additional methods including the step.

The above-mentioned substantially random interpolymers suitable as component (B) as defined herein are preferably thermoplastic, meaning that they can be molded or otherwise shaped and reworked at temperatures above the melting or softening point of the interpolymer. do.

Mixtures comprising polymeric materials for use in the present invention may be obtained according to methods known in the art, including but not limited to dry mixing in a screw extruder or Banbury mixer. Dry mixed pellets can be melt processed directly into the final solid state product.

Preference is given to mixtures in which component (A) is present in an amount of at least about 60% by weight, more preferably at least about 70% by weight. The upper limit with preferable component (A) is about 80 weight% or less. The preferred lower limit of component (B) in the mixture is at least about 20% by weight. The preferred upper limit of the content of component (B) in the mixture is about 40% by weight or less, more preferably about 30% by weight or less.

The thickness of the film according to the invention is less than about 350 μm, preferably less than about 300 μm, most preferably less than about 250 μm (10 mil).

Films according to the invention are, for example, antioxidants, light stabilizers, processing aids, plasticizers, pigments, fillers, suspending additives, anti-agglomerates, anti-coagulants, fixing agents, pressure-sensitive adhesives, foaming agents, nucleating agents, cleaning agents, It may include one or more additives, including but not limited to flame retardant additives.

The films provided herein have little or no free shrinkage at 90 ° C. This means that the film has a free shrinkage at 90 ° C. of less than about 20%, more preferably less than about 10%. The film of the present invention may be monolayer or multilayer. One or more layers of the film may be oriented or foamed. The multilayer film of the present invention may comprise one, two or more layers comprising a mixture as defined herein. Most preferably, the film according to the invention has a thickness of about 0.5 to about 10 mils. Preferably, the present invention relates to a tough rigid film comprising a mixture of polymeric materials consisting essentially of component (A) and component (B) as described herein. The film of the present invention can be printed thereon. Particular preference is given to films in which component (A) consists of one or more polystyrene (s) and component (B) consists of one or more substantially random ethylene-styrene interpolymer (s).

Films of the invention can be obtained according to methods known in the art. The films can be produced using foamed or cast film extrusion methods, including coextrusion and extrusion coating methods. One or more layers of the film can be expanded, for example, using conventional blowing agents to produce the foamed film. One or more films may be laminated to form a multilayer film. The film can be oriented (in addition) after foaming through a tenter frame, double bubble or foamed film technology.

In one embodiment, the film of the invention is an oriented film. As used herein, the term “orientation” refers to a process of stretching a heated polymer product to align molecular chains in the stretching direction (s). When extending | stretching is made in one direction, the said process is called uniaxial orientation, and the process at the time of extending | stretching making in two directions (two vertical directions) is called biaxial orientation. The orientation may be uniaxial or preferably biaxial. Orientation may be performed according to conventional methods such as "double bubble" film processes, cast or tentered film processes, or other techniques known in the art to orient.

Preferably, the oriented film according to the invention has a modulus (2% secant modulus in the vertical direction) of at least 150,000 psi (1034 MPa). Preferred oriented films comprise a mixture wherein component (A) is polystyrene and component (B) is an ethylene-styrene interpolymer. Preferably, component (A) is present in an amount of at least about 50 weight percent, less than about 80 weight percent, more preferably about 70 to 77 weight percent, most preferably about 70 to about 75 weight percent, (B) is present in an amount of at least about 20% by weight, less than about 50% by weight, more preferably 23 to about 30% by weight, most preferably 23 to about 25% by weight. Preferably, the substantially random ethylene-styrene interpolymer contains about 60 to about 75 weight percent of copolymerized styrene, preferably about 60 to about 70 weight percent. The melt index (condition E) is preferably from about 0.3 to about 5 g / 10 minutes.

The oriented film of the present invention is particularly suitable for use in window envelopes and related applications. For window envelopes and related applications, high modulus, good machinability and low haze are desirable properties. The oriented film according to the invention advantageously combines these properties. The oriented films provided herein are characterized by unusual changes or improvements in film performance, including toughness, modulus, and wear resistance. In addition, the optical properties of the inventive mixture films are improved compared to conventional rubber modified polystyrene films, in particular in terms of gloss (higher) and haze (lower). The film also improves the properties of maintaining the folded state as exhibited by the high stress relaxation properties. In addition, the tear property is advantageously affected. When the ethylene-styrene interpolymer resin is mixed with the crystalline syndiotactic polystyrene resin (component (A)) in the ratios described herein, a film is provided having excellent optical properties and exceptional elongation under suitable biaxial orientation conditions.

In another aspect, the present invention relates to a foamed film. Such films are particularly suitable for use as labels or for use in heat-foamable products.

To prepare a foamed film structures, the physical or chemical blowing agent using about 300kg / m ³ or more, preferably about 350kg / m ³ or more, and most preferably achieve about 400kg / m ³ or more of foam density. Typically, the foam density is less than about 1000 kg / m ³ , preferably less than about 950 kg / m ³ , most preferably less than 900 kg / m ³ . The bubble size of the macrobubble foam will be from about 0.01 to about 5.0 mm, preferably from about 0.02 to 2.0 mm, most preferably from 0.02 to about 1.8 mm according to ASTM D3576. The bubble size of the microbubble foam will be less than 0.1 mm. The foams may be continuous or independent foamed according to ASTM D2856.

Multilayer films of the invention comprising at least one foamed layer comprising a mixture comprising component (A) and component (B) as described herein are known in the art, for example, using coextrusion processes. It can be obtained according to the prepared method. Preference is given to two or three layer films having one or two surface layers and a foamed layer which is a core layer. The surface layer may or may not comprise a mixture of polymeric materials consisting essentially of component (A) and component (B) as described herein. A foamed layer comprising a mixture of component (A) and component (B) as described herein and one or two unfoamed layers made from component (A) as described herein, in particular from polystyrene The film containing is preferable. In a three layer structure, the foamed layer is preferably a core or intermediate layer.

Label films can be made from rolls that are cut in the printed width direction of a film having a label adhered to a container, such as a bottle, using conventional adhesives and glues known in the art. In addition, the films of the present invention may be printed or coated with a pressure sensitive adhesive that is laminated to release paper or film and applied to bottles, containers or other surfaces by conventional pressure sensitive techniques.

Preferred foamed films comprise a mixture of component (A) and component (B) wherein component (A) is polystyrene and component (B) is a substantially random ethylene-styrene interpolymer. Preferably, component (B) is present in an amount of about 25 to about 35 weight percent.

The bottle may be a glass bottle or a PET bottle. Labels that cover or adhere to the vial may also act as a protective action.

If the bottle is a PET bottle, the preferred label is a round wrapped label that tears at least about 8 g in the longitudinal direction and at least about 25 g in the transverse direction. The elongation of the foamed film according to the invention should be about 4 to about 5%.

Properties of polymers, mixtures and films useful for the purposes of the present invention can be measured by the following test procedures. This process is used in the examples.

Melt index (MI) is measured according to ASTM D-1238, Condition E (190 ° C., 2.16 kg).

The secant modulus , ultimate elongation and ultimate tensile strength are measured according to ASTM D-882-91.

Haze is measured according to ASTM D-1003.

Gloss is measured according to ASTM D-2457.

Styrene Analysis: The interpolymer or copolymer styrene content and atactic polystyrene content in the interpolymer of component (A) can be measured using proton nuclear magnetic resonance ( ¹ H-NMR). All proton NMR samples are prepared in 1,1,2,2-tetrachloroethane- ² D (TCE- ² D). The solution contains 1.6 to 3.2 weight percent polymer. Melt index (I ₂ ) is used as a measure for measuring sample concentration. Therefore, 40 mg of interpolymer is used when I ₂ is 2g / 10 minutes or more, 30 mg of interpolymer is used when I ₂ is 1.5 to 2g / 10 minutes, and 20 mg of interpolymer is used when I ₂ is less than 1.5 g / 10 minutes. Used. The interpolymer is weighed and placed directly into the 5 mm sample tube. 0.75 ml TCE- ² D aliquots are added by syringe and the tubes capped with a snug polyethylene cap. The sample is heated at 85 ° C. in a water bath to soften the interpolymer. For mixing, the capped sample is occasionally refluxed using a heat gun.

Proton NMR spectra were accumulated in Varian VXR 300 using a sample probe at 80 ° C. and based on residual protons of TCE- ² D at 5.99 ppm. The delay time is variable to about 1 second and data is collected three times in each sample. Interpolymer samples are analyzed using the following instrument conditions: Varian VXR-300, standard ¹ H; Sweep width, 5000Hz; Acquisition time, 3.002 sec; Pulse width, 8 μsec .; Frequency, 300 MHz; Delay, 1 second; Transient, 16.

Total analysis time per sample is about 10 minutes.

Initially, a polystyrene, a styryl Ron (STYRON ^TM) 680: obtains the ¹ H NMR spectrum of 1 second delay for the sample (manufactured by The Dow Chemical Company, Midland, Michigan, USA). Protons are "labeled" as shown in Formula 6: b, branch; α, alpha; o, ortho; m, meta; p, para.

The integral around the protons labeled in the formula is determined; 'A' represents PS. Integral A _7.1 (aromatic, about 7.1 ppm) is believed to be three ortho / para protons, while Integral A _6.6 (aromatic, _6.6 ppm) represents two meta protons. The two aliphatic protons labeled with resonate at 1.5 ppm and the single protons labeled with b at 1.9 ppm. The aliphatic region is integrated at about 0.8 to 2.5 ppm and is called A _al . The theoretical ratio of A _7.1 : A _6.6 : A _al is 3: 2: 3, or 1.5: 1: 1.5 and correlates closely with the observed ratio for the Styrone ^TM 680 sample over several delays of 1 second. . The ratio calculation used to check the integral and prove the peak assignment is performed by dividing the appropriate integral by Integral A _6.6 (ratio A _r is A _7.1 / A _6.6 ).

Area A _6.6 is assigned a value of one. The ratio Al is integral A _al / A _6.6 . All spectra collected have an (o + p): m: (α + b) predicted integration ratio of 1.5: 1: 1.5.0. The ratio of aromatic protons to aliphatic protons is 5 to 3. Aliphatic ratios of 2 to 1 are predicted based on the protons and b labeled with. This ratio is also observed when two aliphatic peaks are integrated separately.

For ethylene / styrene interpolymers, the ¹ H-NMR spectrum using a 1 second delay time is defined such that the integration of the peaks at 7.1 ppm includes all aromatic protons of the copolymer as well as o and p protons of the polystyrene. Integral C _7.1 , C _6.6 and C _al as shown. Likewise, the integration of the aliphatic region C _al in the spectrum of the interpolymer includes aliphatic protons from both polystyrene and the interpolymer, and does not have an obvious baseline for analyzing signals from any polymer. Integral C _6.6 of the peak at _6.6 ppm is analyzed from other aromatic signals and is believed to be due only to polystyrene homopolymers (presumably meta-protons). [The peak assignment for atactic polystyrene at _6.6 ppm (Integral A _6.6 ) is based on a comparison with a reliable sample of styron ^TM 680.] This is only a very weak signal observed at very low levels of atactic polystyrene. Because of this is a reasonable estimate. Therefore, the phenyl proton of the copolymer should not contribute to this signal. With this estimation, Integral A _6.6 is the basis for quantitatively determining the content of polystyrene (atactic polystyrene).

The styrene incorporation is measured in the ethylene / styrene interpolymer sample using the following equations (1) to (6), and the mole percent of ethylene and styrene in the interpolymer is calculated using the following equations (7) and (8).

In the above equation,

s _c and e _c are the styrene and ethylene proton fractions, respectively, in the interpolymer,

S _c and E are the mole fractions of styrene monomer and ethylene monomer in the interpolymer, respectively.

The weight percentage of polystyrene in the interpolymer can be measured using Equation 9.

Total styrene content is also measured by a Fourier Transform Infrared Spectrometer (FTIR).

The following examples illustrate the invention but do not in any way limit the scope of the invention. In the examples the following abbreviations are used: PS stands for polystyrene, ESI stands for a substantially random ethylene-styrene interpolymer, MD stands for longitudinal direction, and CD stands for transverse direction.

Example 1-Oriented Film Including Polystyrene / Substantially Random Ethylene-Styrene Interpolymer Mixture

Polystyrene is Styrone ^™ 665 sold by The Dow Chemical Company.

ESI is obtained as follows: The interpolymer is prepared in a continuous loop reactor (36.8 gal, 140 L). The reactor had a residence time of about 25 minutes and operated with liquid filled at 475 psig (3,275 kPa). Feed the raw material and catalyst / catalyst stream. Solvent feed to the reactor is provided from two different sources. A fresh stream of toluene from the diaphragm pump is used while measuring the velocity to provide a blowdown flow to the reactor seal (20 lb / hour (9.1 kg / hour)). The recycle solvent is mixed with unrestricted styrene monomer on the intake of five parallel diaphragm pumps. These five pumps supply solvent and styrene to the reactor at 650 psig (4,583 kPa). The new styrene flow is measured with a flow meter and the total recycle solvent / styrene flow is measured with a separate flow meter. Ethylene is fed to the reactor at 687 psig (4,838 kPa). The ethylene stream is measured with a mass flow meter. A flow meter / regulator is used to supply hydrogen to the ethylene stream at the outlet of the ethylene control valve. The ethylene / hydrogen mixture is combined with the solvent / styrene stream at ambient temperature. The temperature of the entire feed stream introduced into the reactor loop is lowered to 2 ° C by an exchanger using -10 ° C glycol on the jackkit. Three catalyst components are prepared in three separate tanks: fresh solvent and concentrated catalyst / procatalyst premix are added and mixed into their respective process tanks and fed to the reactor via a variable diaphragm pump. The three component catalyst system introduces the reactor loop through the injector and the static mixer into the inlet of the twin screw pump. The feedstock stream is also fed to the reactor loop through the injector and static mixer downstream of the catalyst inlet rather than upstream of the biaxial pump intake.

The solution density is measured with a flow meter and then the polymerization deactivation is stopped by adding a catalyst deactivator (water mixed with solvent) to the reactor product line. A static mixer in the reactor product line disperses the catalyst deactivator and additives in the reactor effluent stream. This stream is then introduced to a heater after the reactor that provides additional energy for the solvent removal flash. This flash occurs as the effluent exits the heater after the reactor and the pressure drops from 475 psig (3,275 kPa) to 450 mmHg (60 kPa) of absolute pressure at the reactor pressure control valve. The plated polymer is then introduced to the first devolatilizer in the two heated oil jackjacked devolatilizers. Volatiles flashed from the first devolatilizer are condensed into a glycol jackkitted exchanger and passed through the inlet of the vacuum pump to the solvent and styrene / ethylene separation vessel. Ethylene is withdrawn from the top while solvent and styrene are removed from the bottom of this vessel as recycle solvent. The ethylene stream is measured with a mass flow meter. The ethylene conversion is measured by measuring the gas decomposed in the solvent / styrene stream while measuring the degassed ethylene. The polymer and residual solvent separated from the devolatilizer are pumped to the second devolatilizer using a gear pump. The second devolatilizer was operated at 5 mmHg (0.7 kPa) absolute pressure to flush out the residual solvent. The solvent is condensed in a glycol heat exchanger, pumped through another vacuum pump and discharged to a waste tank for disposal. The dried polymer (less than 1000 ppm total volatiles) is pumped and pelletized using a gear pump into a submerged pelletizer with six perforated dies, then rotary dried and collected in a 1000 lb (454 kg) box.

The aluminum catalyst component is commercially modified metalumoxane type 3A (MMMO-3A).

Boron promoter type 1 is tris (pentafluorophenyl) borane.

The titanium catalyst is (1H-cyclopenta [I] phenanthren-2-yl) dimethyl (tert-butylamido) -silanetitanium 1,4-diphenylbutadiene.

PS and ESI dry mix.

Films C, D, and F are prepared using a downward blown orientation process. The die diameter is 2 inches and the melting temperature is about 230 ° C. (linear speed 45 fpm (13.7 m / min)). The blowing ratio (the value obtained by dividing the circumference of the bubble-shaped film by the circumference of the die) is about 12. Film E is an oriented polystyrene window film DWF Clear LD commercially available from The Dow Chemical Company.

Characteristics of Oriented PS / ESI Films (C, D, and F) and DWF Clear LD (MD) film F C D E ^* ESI copolymer styrene content (% by weight) 60 70 70 - MI 0.5 1.0 1.0 - PS / ESI ratio (% by weight) 75/25 75/25 50/50 100/0 Film thickness (㎛) 30.5 30.5 38 33 Ultimate elongation (%) 75 41 57 26 Ultimate Tensile Force (MPa) 53.1 53.8 45.5 82.7 Toughness (J / cc) 18.3 18.6 21.4 17.9 2% secant modulus (MPa) 1724 1724 1344 2758 Initial haze (%) 7.9 6 13 5 Gloss at 60 ° 114 130 84 150 Number of scratch lines 27 32 invisible > 150 Haze rate of change (%) 0.0 8.5 1.7 82.0 ^* Not an embodiment of the present invention.

In Sample C, the combination of high gloss and high transparency (low haze), high modulus, high tensile strength and toughness are obtained compared to conventional polystyrene homopolymer film Sample E. Sample D exhibits the effect of increasing ESI concentration above the most desirable value with decreasing gloss, tensile strength and hardness. Sample F has the effect of lowering the styrene content of the ESI material with lower gloss and higher haze. Samples D and F result in an unusual combination of high toughness, high modulus, high tensile strength and good optical properties, but are not as good as the most preferred Film C.

Scratch resistance is very important for window film applications. The scratch resistance of films C, D and F is tested with reference to film E as a reference. In the test, the haze value of each film is measured and recorded. The film is then moved relative to the LF Smith 527 bronze drum under a vacuum of 10 in Hg to scratch the film. The haze value of each film is then measured and recorded again. The degree of scratch on the film is then measured by calculating the change in haze value measured for each film before and after scratching. If the change in the optical haze of the film due to scratching is smaller than that of the larger film under the same conditions, the scratch resistance of the film is considered to be greater.

Films C, D and F appear to be greatly improved over film E. PS / ESI films appear to have little whitening and haze increase due to wear as is commonly found in clear LDs.

Example 2 Tough Rigid Foamed Films Prepared from PS / ESI Mixtures

A blown film coextrusion process is used to produce a polystyrene-based foam core surrounded by two surface layers of unfoamed polystyrene. The foam cores are made without ESI resin and with varying ESI content. No ESI is added to the surface layer. ESI was prepared as described in Example 1 with a copolymer styrene content of 69% by weight and a MI of 4.6. Polystyrene is Krasten 144 (manufactured by Kaucuk Corp .; Mw: 260,000; Mn: 104,000; MI: 6-8 g / 10 min; mineral oil 1.5-2%). Dry mix PS and ESI. The total thickness or gauge of the foamed film is 130 μm ± 20 μm.

Foamed film properties Foamed film Longitudinal tear (g) Transverse tear (g) 20 ° gloss 2% secant modulus, landscape (MPa) 0% by weight ESI (control) 8 25 20.1 850 10 wt% ESI 8 42 27.4 674 20 wt% ESI 8 40 38.4 660 30 wt% ESI 8 56 46.4 658

Films made from PS / ESI mixtures are tough hard films with improved tear characteristics and gloss.

Example 3 Tough Hard Films Prepared from PS / ESI Mixtures

Films are prepared as described in Table 3 using commercially available polystyrene resins, Styrone ^™ 665 commercially available from The Dow Chemical Company and ESI materials having a copolymer styrene content of 60.6, 67.5 and 71.3 wt%, respectively.

As can be seen from the data, higher copolymer styrene content improves gloss, increases modulus, improves tensile strength and improves toughness, and the most preferred styrene content is in the range of 67-72% styrene.

Films are prepared as described in Table 4 from anhydrous mixtures of ESI and polystyrene (Styrone ^™ 678, available from The Dow Chemical Company), with increased polystyrene content.

Extrusion Parameters 1.25 in (3.2 cm) Killion extruder with 3 in (7.6 cm) blown film die Melt Temperature (℉) 446 447 447 Axial speed (rpm) 50 49.7 49.8 Screw Amp 13 12 12 Nip Roll Speed (m / min) 7.7 6.5 9.1 Lay flat width (cm) 23 24 24

From Table 5, even low values (10%) of ESI affect tensile elongation and toughness, while high values (40%) maintain high gloss and hardness as indicated by 45 degree gloss and 1% secant modulus. It can be seen that the toughness and tensile elongation are improved.

Claims (13)

Component (A) consisting of one or more alkenyl aromatic polymers, and from about 50 to 74 mole percent of ethylene and / or one or more α-olefin monomers (i), one or more vinyl or vinylidene aromatic monomers and / or one or more sterically hindered At least one substantially substantially polymerized form comprising from 26 to about 50 mole percent of an aliphatic or cycloaliphatic vinyl or vinylidene monomer (ii), and from 0 to about 20 mole percent of other polymerizable ethylenically unsaturated monomer (s) (iii). Component (B) consisting of a random interpolymer, wherein component (A) is present in an amount of 45 to about 90 weight percent based on the total weight of components (A) and (B), Tough hard film comprising a mixture wherein B) is present in an amount of from 10 to 55% by weight, based on the total weight of components (A) and (B). The film of claim 1, which is a single layer film. The film of claim 1 which is a multilayer film. The film according to any one of claims 1 to 3, which is an oriented film. The film of claim 1, wherein the at least one layer is a foam layer. The film according to any one of claims 1 to 5, wherein component (A) is polystyrene. The film of claim 1, wherein component (B) is a substantially random ethylene-styrene interpolymer. The film of claim 1, wherein the film is a printed film. A window envelope having one or more window openings completely enclosed with a transparent plastic window patch formed of a film according to claim 1. Label made from a film according to claim 1. The film of claim 4, wherein the longitudinal 2% secant modulus is at least 150,000 psi (1034 MPa). The film of claim 1, wherein the longitudinal 1% secant modulus is at least 85,000 psi (586 MPa). An article comprising the film of claim 1.