KR20090033880A - Shrink label of oriented polystyrene film containing small rubber particles and low rubber particle gel content and block copolymer - Google Patents

Abstract

The present invention (a) a block copolymer grafted to polystyrene; A conjugated diene content of 1% by weight to 7% by weight based on the total weight of the HIPS component; Gel concentration of less than 10% by weight; Average rubber particle size of 1 to 0.01 μm or more; About 40 to about 90 volume% rubber particles less than about 0.4 μm in diameter, and about 10 to about 60 volume% rubber particles having diameters of about 0.4 and about 2.5 μm and rubber particles that are predominantly core / shell morphology; And from 1 to 5% rubber diene, based on the concentration of 10 to 70% by weight of the total polymer composition weight, and based on the total polymer composition weight; (b) a polymer composition comprising from 10 to 70% by weight of general purpose polystyrene and from about 2 to about 80% by weight of a styrene block copolymer component, based on the weight of the total polymer composition. In the preferably oriented film, the polymer composition comprises 95% by weight of the film and the remaining film or film composition weight is an additive. The shrink label is made of the film.

Description

Shrink labels of oriented polystyrene film containing small rubber particles and low rubber particle gel content and block copolymers

The present invention is directed to producing such films as well as oriented rubber-reinforced polystyrene films and shrink-label films comprising said polystyrene films, which are first oriented in the stretched direction. It relates to useful compositions.

Shrink labels generally fall into two categories: roll-on shrink-on (ROSO) labels and sleeve-type labels, sometimes referred to as tube labels. ROSO labels are film sheets that wrap around the container. The sleeve label is tubular and is mated around the container by being placed over the container and the container is wrapped by the tube. Heating the shrink label around the container causes the label to shrink and conform to the container.

In order to conform to the container, each type of label must first shrink (ie, to a greater extent than any other direction) in the direction of stretching around the container. ROSO films are generally placed on the vessel such that the machine direction (MD) of the film extends around the vessel. Thus, the ROSO film shrinks mainly in the machine direction (MD) of the film due to preferential machine direction orientation (MDO). In contrast, a sleeve label is typically placed on the container such that the transverse direction (TD) of the label extends around the container. Thus, the sleeve label shrinks mainly in the transverse direction (TD) of the film due to preferential transverse orientation (TDO).

While ROSO labels offer advantages in terms of manufacturing speed, sleeve labels have so far benefited in the degree of shrinkage around the container. Sleeve labels typically shrink below 70% around the container. Sleeve labels that have no adhesive joints or have excessively hardened adhesive joints before application to the container can withstand a greater degree of stress during shrinkage.

Sleeve labels have been better matched to contoured containers as compared to ROSO labels since they have a higher shrinkage rate. However, ROSO labels have the manufacturing advantage of being oriented in the machine direction, ie the direction in which they move through the device used during manufacture. Accordingly, it is desirable to identify an orientation film suitable for making ROSO labels that can shrink around the container to a greater extent than the current ROSO label (ie comparable to the sleeve label) without causing damage to the adhesive joint of the label.

Polystyrene (PS) is a particularly preferred polymer for shrink labels. For example, polypropylene (PP) shrink label films typically shrink only about 20% or less in any direction at temperatures below 120 ° C. The crystallinity of the PP requires heating above the melting point of the PP crystal to release further orientation. In contrast, PS-based shrink label films only need to exceed the glass transition temperature of the polymer (generally below the melting point of the PP crystal) due to its amorphous properties. Thus, the PS film can preferably provide greater shrinkage at lower processing temperatures than the PP film.

In addition, the PS retains higher surface energy for the elongated period compared to PP after corona treatment (needed to make the surface of the polymer film suitable for printing). Thus, unlike PP film, the corona treatment of the PS film can be done during manufacture rather than immediately before printing on the label.

Compared to copolyester and polyvinyl chloride (PVC) films, the use of PS films promotes bottle and label recyclability, which allows low density to easily separate labels from high density (eg, polyester) bottles. Because. In addition, lower PS densities advantageously provide higher film yield, or larger area per pound of film or kg. High density label stocks, such as copolyester or PVC film, do not provide similar advantages.

Polystyrene-based shrink label films often include a high impact polystyrene (HIPS) component to improve label toughness (eg, tear resistance). However, in the typical HIPS range, the average particle size of the rubber particles is greater than 1 μm (see, eg, US Pat. No. 6897260, step 4, lines 26-27). Large rubber particles reduce the transparency of the label film and tend to impede the use of the film for reverse side printing (printing on the side of the label film adjacent to the container to be readable through the film) and the observation of the container or product through the label. There is this. Conventional HIPS also contains more than 7% rubber based on the HIPS total weight. High concentrations of rubber can interfere with the printability of the film, reduce the transparency of the film, reduce dimensional stability, and undesirably increase the gel content in the final film. However, in some situations, such as small diameter bottles or bottlenecks, HIPS alone may not provide sufficient toughness to avoid the tendency to tear under stress.

Oriented PS films suitable for shrink label applications are preferred. It is also desirable for the film to contain high impact polystyrene of the type having smaller rubber particles and lower rubber concentrations than conventional HIPS to achieve film toughness without disturbing printability or transparency of the film. Further preferred are films that contain transparent impact resistant polystyrene based on block copolymer technology to further improve the toughness of the film. It is further highly desirable if such films can serve as shrink labels demonstrating shrink around the container compared to those achieved with PVC or polyester.

Brief summary of the invention

The present invention is suitable for use as shrink labels, and polystyrenes for improved toughness, impact resistance or combinations thereof, as well as oriented polystyrene based films containing HIPS with smaller rubber particles and lower rubber concentrations than conventional HIPS. The field of shrink-labels is developed by providing block copolymers, and general purpose polystyrene. The present invention is directed to rubber-reinforced polystyrene films, and surprisingly, 1% secant modulus of both MD and TD of high transparency, 90,000 to 300,000 lb / in ² (620 to 2070 MPa), as indicated by the preferred range. In the stretching direction as evidenced by a range of strength suitable for high speed printing, and a preferred shrink ratio of 20 to 80% in the primary stretching direction as measured for 10 minutes at 110 ° C. without air. Shrink labels comprising such films having one or more of high shrinkage rates can be provided.

In a first aspect, the invention is a polymer composition, the polymer composition

(a) at least one high impact polystyrene (HIPS) component,

  (i) a block copolymer of styrene and a rubbery conjugated diene (the copolymer is grafted to polystyrene);

  (ii) optionally at least 2 wt% and at most 8 wt% of a rubber homopolymer, based on the HIPS component weight;

  (iii) a total rubber conjugated diene content of at least 1% by weight and at most 7% by weight based on the total weight of the HIPS component;

  (iv) gel concentration of less than 10% by weight with methyl ethyl ketone / methanol extraction;

  (v) an average rubber particle size of at least 0.01 μm and less than 1.0 μm;

  (vi) about 40 to about 90 volume% of rubber particles having a diameter of less than about 0.4 μm, and about 10 to about 60 volume% of rubber particles having a diameter of about 0.4 and about 2.5 μm, and

  (vii) has rubber particles that are predominantly core / shell morphology,

  (viii) the at least one high impact polystyrene (HIPS) wherein the polymer in the composition is present at a concentration of at least about 10% by weight and at most about 70% by weight and comprises at least 1% and at most 5% by weight of the rubber diene relative to the total composition weight. ) ingredient;

(b) at least one general purpose polystyrene having a weight average molecular weight greater than 200,000 g / mole and 350,000 g / mole and present at a concentration of at least about 10% and at most about 50% by weight of the polymer in the composition, and

(c) at least one styrene block copolymer present at a concentration of at least about 2% to about 80% by weight of the polymer in the composition, wherein (a), (b) and (c) are 100% by weight of the polymer composition Occupies. The polymer composition is optionally mixed with about 5 weight percent of the combined weight of the polymer composition and the additive with additives belonging to the art, to produce a film composition that is a composition suitable for film production.

In a second aspect, the present invention is an oriented film consisting of 95 to 100% by weight of the polymer composition of the present invention and 0 to 5% by weight of additive, wherein the percentage is based on the combined weight of the polymer and the additive, and the film is preferred. Preferably in the primary stretched direction (typically MDO for ROSO or TDO for sleeve application) and greater than 4: 1, more preferably greater than 6: 1 The ratio in the more extended direction is larger than the ratio in the other direction.

In a third aspect, the present invention is a shrink label comprising the axially imbalanced oriented polymer film of the first aspect (ie, a film having a different amount of orientation in MD than TD), wherein the film is preferably single-sided or It is printed on both sides. The shrink label is preferably a ROSO or sleeve label, most preferably a sleeve label.

The film of the invention comprises a polymer composition comprising a HIPS component, a general purpose polystyrene (GPPS) and a styrene block copolymer component. The combination of the HIPS component, GPPS and styrene block copolymer component comprises 100% by weight of the polymer, ie the polymer composition, in the composition excluding the additive. The polymer composition preferably comprises at least 95% by weight, preferably at least 97% by weight, and may comprise 100% by weight of the film composition or the total weight of the film. If the polymer composition is less than 100% by weight of the film weight, the remainder up to 100% by weight consists of an additive comprising any additive that may be part of a commercially available or prepared HIPS component, GPPS and styrene block copolymer component. Additives include fillers, processing aids, slip agents or plasticizers, which belong to the art, and optionally include polymeric additives.

All percentages, preferred amounts, or measurements, ranges, and endpoints thereof are included herein, ie, "less than about 10" includes about 10. Thus, "greater than" is equivalent to "greater than or equal to" and therefore "less than" is equivalent to "less than or equal to". The "greater" number is equivalent to the "greater" number. Similarly, the number of "less than" is equivalent to the number of "less than". The numbers herein are not as precise as those described. Thus, "105" includes 104.5 and 105.49. In addition, every list includes a combination of two or more members of the list. All ranges of parameters described as "greater than", "greater than", "greater than or equal to" or similar expressions to "less than", "up to", "less than", "less than or equal to" or similar surfaces, respectively The preferred range is irrespective of the relative degree of preference indicated by the parameter of. Therefore, a range with advantageous lower limits in combination with the most preferred upper limits is preferred for the practice of the present invention. All amounts, ratios, ratios, and other measurements are by weight unless otherwise noted. The percentage of monomers in the polymer, unless otherwise stated, all percentages, unless stated otherwise, refer to% by weight based on the total composition according to the practice of the present invention. Unless otherwise described or otherwise recognized by one of ordinary skill in the art, the steps of the methods described herein are optionally performed in a different order than the order in which the steps are discussed herein. In addition, the steps are optionally performed separately, simultaneously or overlapping in time. For example, such steps in the art, such as heating and mixing, often overlap separately, simultaneously or partially in time. Unless stated otherwise, elements, materials, or steps that can cause undesired effects are considered to be substantially absent in the practice of the present invention when present in an amount or form that does not cause an unacceptable effect. do. In addition, the terms “unacceptable” and “unacceptable” mean that they are commercially useful, deviate from the range that may be useful in a given situation, or are outside of predetermined limits, which limits may apply to specific situations and applications. In various, predetermined, for example, can be determined by the specification. Those skilled in the art recognize that the acceptable limits vary by device, condition, application, and other variables, but can be determined without undue experimentation of each situation in which it may be applied. In some instances, diversification or deviation in one parameter is allowed to achieve another desirable ending.

The term "comprising" is synonymous with "comprising", "comprising" or "characterizing" and is not inclusive or limiting and does not exclude further unspecified ingredients, substances or steps. The term “consisting essentially of” means that, in addition to a particular element, material or step, an undescribed material or step may be present in an amount that does not have a substantial effect that is not acceptable to one or more basic and novel specifics of the subject. The term "consisting of" means that only the elements, materials or steps described are present. The term "comprising" includes "consisting of" and "consisting of".

The HIPS component is a styrene polymer containing a grafted rubber component. Grafting rubber components onto polystyrene tends to increase the toughness and mechanical strength of polystyrene. Bonding rubber to polystyrene through grafting has technical advantages over simple blending of polystyrene and rubber components. The bonded rubber generally provides a material with the same impact strength and higher modulus while having a lower rubber content than simply blended rubber. By blending the rubber component with the styrene polymer, the rubber component is typically grafted into the styrene polymer by dissolving the rubber in the styrene monomer prior to the polymerization of the styrene monomer. The styrene monomer is then polymerized to produce a polystyrene matrix containing the rubber grafted to the styrene polymer.

Polystyrene matrices usually have a sufficiently high weight average molecular weight (Mw) to give the composition the desired level of processability and mechanical properties, and Mw is usually at least 100,000 g / mol, preferably at least about 120,000 g / mol, more preferably Is at least about 130,000 g / mol, most preferably at least about 140,000 g / mol. Polystyrene has a Mw of usually about 260,000 g / mol or less, preferably about 250,000 g / mol or less, more preferably about 240,000 g / mol or less, and most preferably about 230,000 g / mol or less to provide sufficient processability. . The polystyrene matrix Mw is measured by gel permeation chromatography using polystyrene standards for calibration.

The rubber component is a copolymer of rubbery conjugated diene and styrene (rubber copolymer) or a mixture comprising both a rubber copolymer and a small amount of rubbery conjugated diene homopolymer (rubber homopolymer). The conjugated diene in both rubbers is usually 1,3-alkadiene, preferably butadiene, isoprene, or both butadiene and isoprene, most preferably butadiene. The conjugated diene copolymer rubber is preferably a styrene / butadiene (S / B) block copolymer. Polybutadiene is the preferred rubber homopolymer.

The rubber copolymer preferably has a Mw of at least 100,000 g / mol, preferably at least 150,000 g / mol, preferably at most 350,000 g / mol, preferably at most 300,000 g / mol, more preferably at 250,000 g / mol It is as follows. Mw is measured using triangular light scattering gel permeation chromatography.

The rubber copolymer also preferably has a solution viscosity of about 5 to about 100 cP (about 5 to about 100 mPa · s), preferably about 20 to about 80 cP (about 20 to about 80 mPa · s) and a cis content 20% or more, preferably 25% or more, more preferably about 30% or more, preferably 99% or less, preferably 55% or less, and more preferably 50% or less. Buna BL 6533 T brand rubber and other similar rubbers are preferred examples of rubber copolymers.

Including the rubber homopolymer with the rubber copolymer in preparing the HIPS component can increase the amount of elongation at break and contribute to the mechanical performance of the HIPS polymer. Suitable rubber homopolymers preferably have a secondary transition temperature of 0 ° C or below, preferably -20 ° C or below. Preferably, the rubber homopolymer has a solution viscosity of about 20 to about 250 cP (about 20 to about 250 mPa · s), more preferably about 80 to about 200 cP (about 80 to about 200 mPa · s). The rubber homopolymer preferably has a cis content of at least about 20%, preferably at least about 25%, more preferably at least about 30% and preferably at most about 99%, preferably at most 55%, more preferably Is 50% or less. Preferably, the rubber homopolymer has a Mw of at least 100,000 g / mol, more preferably at least 150,000 g / mol and preferably at most 600,000 g / mol, preferably at most 500,000 g / mol. Mw is determined by triangular light scattering gel permeation chromatography. An example of a suitable rubber homopolymer is the Diene ^™ 55 brand rubber (diene is a trade name of Firestone).

The rubber homopolymer, if present, is usually at least about 2% by weight, preferably at least about 4% by weight, more preferably at least about 6% by weight, most preferably based on the total rubber weight in the HIPS polymer And at least about 8% by weight. In order to avoid unnecessary low transparency or transparency, the rubber homopolymer content is preferably 25% by weight or less, preferably 20% by weight or less, more preferably 16% by weight or less, based on the total rubber weight Preferably it is 12 weight% or less.

The HIPS component has a total diene component content of the rubber component (i.e., content generated from the rubbery conjugated diene of both the rubber copolymer and the rubber homopolymer in the preparation of the HIPS component), based on the weight of the HIPS component, about 1% by weight. It is at least 1.5% by weight, more preferably at least 2% by weight, even more preferably at least 2.5% by weight, most preferably at least 3% by weight. Rubber concentrations below about 1% by weight fail to achieve the desired levels of mechanical strength and toughness. In order to provide the desired transparency, the rubber concentration is usually at most 7% by weight, preferably at most 6% by weight, more preferably at most 5% by weight, and even more preferably at 4, based on the total weight of the HIPS component. It is below weight%.

Without being bound by theory, lower rubber concentrations, such as up to 7% by weight, based on HIPS, are preferred to prevent excessive crosslinking of the rubber particles and to reduce the likelihood of gel formation. Some crosslinking in the rubber is desirable to maintain the integrity of the rubber during shear during manufacture, while excessive crosslinking can interfere with the deformation of the rubber particles during film orientation. The transparency and transparency of the film increases as the rubber particles deform into particles with higher aspect ratios. Less crosslinked rubber particles tend to deform and maintain their deformation form more easily than more crosslinked rubber particles, so less crosslinked particles are more easily adapted to transparent films. The limitation of the specific rubber concentration, in which crosslinking becomes undesirably excessive, is difficult because it depends on the specific processing conditions. However, based on HIPS weight, a rubber concentration of at least 12% by weight undesirably tends to cause excessive crosslinking.

Similarly, without being bound by theory, the films of the present invention seem to benefit from low gel formation as a result of low rubber concentrations. Gels are formed by excessive crosslinking of rubber aggregates that fail to shear into small particles during film production. Crosslinked gel aggregates can cause problems in film production, for example, by causing bubble bursts during the blowing film process. Gel aggregates also have a detrimental effect on film quality and appear as non-uniform defects in the film and cause depressions in the film wound over the aggregate particles. The depressions tend to interfere with ink introduction onto recessed points on the film surface during printing, causing problems.

The HIPS component also has a gel concentration of less than 10% by weight relative to the total HIPS component weight following methyl ethyl ketone / methanol extraction. Such low gel concentrations are desirable to maximize film clarity. To determine the gel concentration, methyl ethyl ketone / methanol extraction similar to the method of Unexamined Japanese Patent Application Publication No. P 2000-351860 A is performed. In essence, HIPS samples (sample weight is W1) are dissolved in methyl ethyl ketone / methanol mixed solvent (volume ratio 10: 1) at room temperature (about 23 ° C.). Insoluble fractions are separated by centrifugation. Insoluble fractions are isolated and dried. The weight of the isolated and dried insoluble fraction is W2. Gel concentration (% by weight) is 100 x W2 / W1.

The HIPS component has a volume average rubber particle size of less than 1 μm, preferably 0.5 μm or less, and generally 0.01 μm or more, preferably 0.1 μm or more, and more preferably 0.3 μm or more. This volume average rubber particle size is in contrast to conventional HIPS materials having an average rubber particle size of at least 1 μm (see, for example, US Pat. No. 6897260 B2, step 4, lines 22-34, incorporated herein by reference). . Small rubber particle sizes are preferred because they tend to produce higher transparency and lower haze than films with large rubber particles. However, rubber particles of less than 0.01 μm tend to contribute little to the durability of the composition despite their transparency and clarity.

The rubber particles in the HIPS component have a wide particle size distribution in which most of the particles are small and only a limited amount of particles are large. In particular, it is desirable to have a distribution in which the diameter of the particles of about 40 to about 90 volume percent is less than about 0.4 μm. Correspondingly, the diameter of the particles of about 10 to about 60 volume percent is about 0.4 to less than about 2.5 micrometers, preferably about 15 to 55 volume percent, more preferably about 20 to about 50 volume percent It is desirable to have a relatively large particle distribution of about 0.5 μm or more to about 2.5 μm or less. Preferably, for the above relatively large particles of the component, the specific amount of particles has a diameter of less than about 2 μm, more preferably about 1.5 μm or less, even more preferably about 1.2 μm or less, even more preferably It is about 1 micrometer or less.

Rubber particle size is a measure of rubber containing particles including all monovinylidene aromatic polymer occlusion in the rubber particles. Rubber particle size is measured by Beckham Coulter: LS230 light scattering instrument and software. Manufacturer's manual and literature [JOURNAL OF APPLIED POLYMER SCIENCE, VOL. 77 (2000), page 1165, "A Novel Application of Using a Commercial Fraunhofer Diffractometer to Size Particles Dispersed in a Solid Matrix" by Jun Gao and Chi Wu, provides a method for measuring rubber particle size using Beckham Coulter. Preferably, the optical model for calculating rubber particle size and distribution statistics using the instrument and software is as follows: (i) fluid refractive index 1.43, (ii) actual refractive index 1.57 and (iii) hypothetical sample Refractive index 0.01.

Most, preferably at least 70%, more preferably at least 80%, even more preferably at least 90% of the rubber particles in the HIPS component will have the core / shell particle form. Core / shell morphology means that the rubber particles have a thin outer shell and contain a single central closure of the matrix polymer. Particle morphologies of this type are commonly referred to as "single closed" or "capsule" forms. In contrast, the terms "entanglement" or "cell" morphology refer to "entanglement", "multiple closure", "labyrinth", "coil", "onion skin", or "conion skin" structures. It refers to various other rubber particle forms that are more complex, including. The percentage of rubber particles with a core / shell morphology is determined as a percentage from 500 particles on a transmission electron micrograph of the HIPS component.

In the HIPS component the core-shell particles are crosslinked to such an extent that they do not break under the shear field (ie, during the orientation process). Their thin walls will become much thinner (as a result of the high compatibility resulting from the presence of the copolymer rubber), but will remain intact to provide the necessary mechanical and tensile strength properties. Perhaps the oriented rubber morphology in film orientation is very close to the simultaneous continuous distribution of very thin rubber ribbons due to the small amount of multiple closed particles in the system (cell morphology). Very thin shell walls have better light transmittance than thick walls and are certainly superior to the presence of residual cells or multi-closed particles that do not distribute as very thin ribbons in orientation.

The HIPS component does not optionally contain or optionally contains other additives such as mineral oil or other plasticizers. Appropriate amounts of mineral oil can improve mechanical properties such as elongation at break. The HIPS component generally comprises at least about 0.4% by weight, preferably at least 0.6% by weight, more preferably at least 0.8% by weight, and even more preferably at least 1% by weight, based on the total weight of the HIPS component. Will contain. In order to obtain the desired transparency, the HIPS component is usually less than about 3% by weight, preferably 2.8% by weight or less, more preferably 2.6% by weight or less and most preferably 2.4% by weight, based on the total weight of the HIPS component. It will contain the following mineral oils:

Suitable materials for use as HIPS components are described in US Patent Publication No. 2006-0084761 (name of the invention: IMPROVED RUBBER MODIFIED MONOVINYLIDENE AROMATIC POLYMERS AND THEMOFORMED ARTICLES).

The HIPS component differs from standard bulk or solution polymerized HIPS in that the rubber particle size distribution is relatively wide and most of the rubber particles are core-shell morphologies. In contrast, conventional HIPS resins have a relatively narrow particle size distribution and tend to have predominantly or at least larger percentages of cell, multi-occluded particle structures.

The compositions and films of the present invention are preferably at least about 10% by weight, more preferably at least about 20% by weight, most preferably at least about 25% by weight, most preferably based on the total amount of polymer present. Preferably up to about 70%, more preferably up to about 65%, most preferably up to about 60% by weight of the HIPS component.

The total rubber content (based on the total diene content from the copolymers and homopolymers) resulting from the HIPS component in the films of the present invention is at least 1% by weight, preferably at least 3% by weight, based on the total film weight , 5% by weight or less.

The polymer composition of the film of the present invention contains crystalline polystyrene, also referred to as general purpose polystyrene (GPPS). GPPS for use in the present invention preferably has a Mw greater than 200,000 g / mol, preferably at least 280,000 g / mol, at most 350,000 g / mol, preferably at most 320,000 g / mol. Mw is determined according to gel permeation chromatography. GPPS preferably has a melt flow rate (MFR) of at least 1 g / 10 min, preferably at least 1.2 g / 10 min, preferably at most 3 g / 10 min, preferably at most 2 g / 10 min. MFR is measured according to ASTM method D1238. GPPS may or may not contain plasticizers such as mineral oils, ethylene or propylene glycol, phthalates or styrene oligomers. When present, the plasticizer is usually present at a concentration of up to 4% by weight, preferably up to 3% by weight, based on the GPPS weight. When present, plasticizers typically comprise at least 1% by weight of the GPPS weight. Examples of suitable GPPS include STYRON® 665 general purpose polystyrene (Styrone is a trademark of Dow Chemical Company), Styrone 663, Styrone 685D, Styrone 660 and Styrone 6856E. .

The compositions and films of the present invention, based on the total amount of polymer present, are preferably at least 10% by weight, more preferably at least about 20% by weight, most preferably at least about 35, and preferably about 50 Up to about 45%, more preferably up to about 45%, most preferably up to about 40% by weight of the GPPS component.

The third component of the formulation is one or more styrene block copolymers. The term "styrene block copolymer or styrenic block copolymer" refers to a polymer having at least one block fragment of styrene monomer in combination with at least one saturated or unsaturated rubber monomer fragment, more preferably not having a block of polymer which is rubber or styrene. It means a polymer. Suitable styrene block copolymers having unsaturated rubber monomer units are, but are not limited to, styrene-butadiene (SB), styrene-isoprene (SI), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS) , α-methylstyrene-butadiene-α-methylstyrene, α-methylstyrene-isoprene-α-methylstyrene, and the like. The term “styrene butadiene block copolymer” as used herein includes SB, SBS, and a high number of blocks of styrene and butadiene. Similarly, the term "styrene isoprene block copolymer" includes polymers having at least one block styrene and one isoprene. The structure of the styrene block copolymers useful in the present invention may be linear or radial, and may be diblock, triblock or higher block. In some embodiments, the styrenic block copolymers preferably have four or more different blocks or two pairs of repeating blocks, such as a pair of repeating styrene / butadiene or styrene / ethylene propylene blocks. Styrene block copolymers are known in the art and are under the trade name vector (VECTOR) from Dexco polymers and under the trade name Kraton from KRATON polymers, Chevron Phillips Chemical Company Commercially under the trade name SOLPRENE from Phillips Chemical Co. and under the trade name Styrolux from K-Resin, and from BASF Corp. Styrene block copolymers are used alone or in combination of two or more.

The styrenic portion of the block copolymer is preferably a polymer or copolymer of styrene or α-methylstyrene, and analogs or homologues thereof including ring-substituted styrenes, in particular ring-methylated styrenes. Preferred styrene properties are styrene and α-methylstyrene, with styrene being particularly preferred.

The rubber part of the block copolymer is optionally unsaturated or saturated. Block copolymers with unsaturated rubber monomer units may include butadiene or isoprene homopolymers and copolymers of one or both of these two dienes with minor amounts of styrene monomers. When monomers are used in butadiene, it is preferred that about 35 to about 55 mole percent of the condensed butadiene units in the butadiene polymer block have a 1,2-coordination. When such blocks are hydrogenated, the product obtained is or is a common copolymer block of ethylene and 1-butene (EB). If the conjugated diene used is isoprene, the hydrogenated product obtained is or is similar to a typical copolymer block of ethylene and propylene (EP). Preferred block copolymers have unsaturated rubber monomer units, more preferably one or more fragments of styrene units and one or more fragments of butadiene or isoprene, with SBS and SIS being most preferred. Among them, styrene butadiene block copolymers have higher transparency and lower haze compared to SIS and are therefore preferred when cast tenter lines are used for film production. However, in the blown film process, styrene isoprene block copolymers are preferred because of the low tendency of gel-forming crosslinking during manufacture as compared to SBS.

Among the styrene block copolymers, it is preferred to have one, preferably two, or more preferably all three of transparency, impact resistance and elastic behavior.

Elastic styrene block copolymers are preferred in the practice of the present invention which provides toughness and lower stiffness than is obtained in the absence of block copolymers. The elastic behavior is advantageously at least about 200%, preferably at least about 220%, more preferably at least about 240%, most preferably at break at break measured according to ASTM D-412 and / or D-882 methods. Preferably at least about 260% and preferably at most about 2000%, more preferably at most about 1700%, most preferably at most about 1500%. Industrially, most polymers of this type contain from 10 to 80% by weight of styrene. Within certain types and morphologies of polymers, as the styrene content increases, the elastic properties of the block copolymers decrease.

The block copolymer preferably has a melt flow rate (MFR) of at least about 2 g / min, preferably at least about 4 g / 10 min and preferably at most 20 g / 10 min, preferably at most 30 g / 10 min. MFR is measured according to ASTM method D1238 Condition G.

Preferred styrene block copolymers have high transparency (high is a preferred range of transparency) and preferably have transparency corresponding to visible light transmittance of at least about 85%, preferably at least about 90%, measured according to ASTM D1746. This transparency is considered due to the very small domain size, which is typically on the order of 20 nm. In block copolymers, domain size is preferentially determined by block molecular weight.

The styrene block copolymer also preferably has sufficient impact resistance to add durability to the film application compared to the durability of the film having the same composition (ratio of components), except for the absence of the styrene block copolymer. Notched Izod Impact resistance is measured according to the ASTM D-256 method and preferably does not provide breaking conditions when tested at 72 ° F. or 23 ° C.

Particularly preferred styrene butadiene block copolymers have a radial or star block arrangement with polybutadiene at the core and polystyrene at the end of the arm. Such polymers are referred to herein as star styrene butadiene block copolymers, and belong to the art, and are commercially available under the tradename K-resin from Chevron Phillips Chemical Company. These polymers contain at least about 27% butadiene in star-block form and are often characterized by a bimodal molecular weight distribution of polystyrene. The inner polybutadiene fragments are approximately the same molecular weight, while the outer polystyrene fragments have different molecular weights. This feature facilitates control of the polybutadiene fragment thickness to obtain improved transparency. For high transparency, the polybutadiene fragment thickness is preferably about 1/10 of the wavelength of the visible light spectrum.

The styrene block copolymer component is useful for improving the toughness and lowering the stiffness of the composition having other components but no block copolymer. However, the introduction of large amounts of styrene-isoprene-styrene components may tend to blur the transparency and transparency of the film. The styrene block copolymer is preferably at least about 2% by weight, more preferably at least about 3% by weight, based on the amount of polymer in the film or blend (composition) used to make the film, Most preferably at least about 4% by weight, preferably at most about 80% by weight, more preferably at most about 75% by weight and most preferably at most about 70% by weight. Among these preferred amounts, when the block copolymer is a styrene-butadiene block copolymer, ie preferably SB or SBS, based on the total weight of the polymer in the film or composition, the amount is preferably about 20% by weight or more, More preferably at least about 30% by weight, most preferably at least about 40% by weight and preferably at most about 80% by weight, more preferably at most about 75% by weight and most preferably at most about 70% by weight. Styrene butadiene block copolymers of at least about 80% by weight undesirably tend to reduce the 1% secant modulus and glass transition temperature, and possibly the film shrinks at low temperatures, for example below about 80 ° C. However, in amounts greater than about 10% by weight, low proportions of styrene-isoprene block copolymer components are preferred because SIS and SIS / SI can cause haze. If present, the amount of styrene isoprene block copolymer is preferably at least about 1% by weight, more preferably at least about 2% by weight, most preferably about 3, based on the total weight of the polymer in the blend or film. By weight, and preferably about 9% by weight or less, more preferably about 8% by weight or less and most preferably about 6% by weight or less. These amounts are preferred when the SIS or SI block copolymers are used alone or in combination with other styrene block-copolymers.

The film of the present invention has an orientation that is preferentially oriented in the direction that receives most of the stretching from which the film is formed or processed. The film obtained shrinks preferentially in the direction in which the film is drawn more than it was produced. The machine direction MD depends on the direction of transport of the film during or after extrusion or blowing of the film. The transverse direction TD is perpendicular to the film transport direction MD. Shrinkage is perpendicular to the machine direction orientation (MDO) if stretching is applied to MD more than TD, and perpendicular to TDO if stretching is applied more transversely than machine direction. Preferred TDO causes initial shrinkage in the TD on the heat application in the film of the invention, for example in the sleeve label. Preferred MDOs cause greater shrinkage in the machine direction than the TDs typically used for ROSO labels.

Films of the invention advantageously have an MDO or TDO ratio of at least about 3: 1, preferably at least about 4: 1, more preferably at least about 5: 1, and even more preferably at least about 6: 1. Ratio of oriented length to unoriented length in the stretched MD or TD direction). Films typically have a TDO rate greater than the MDO rate to be useful for shrink tube label applications, and an MDO rate greater than the TDO rate to be useful for ROSO label films. Films with TDO for less than 3: 1 sleeve applications, or with MDO for ROSO applications, may have MDO or TDO, depending on the use, not sufficient orientation orientation (DO) to match the container in shrink label applications. Tend to have. Films typically have a DO ratio of 10: 1 or less, but the upper limit for the DO ratio is not clear. Films with a DO ratio of greater than 10: 1 are at risk of shrinking around the container in label applications such that the adhesive seam that holds the label around the container may weaken or drop.

MDO ratios and TDO ratios are measured using 4 inch (10.16 cm) oriented film samples (ie square samples) with both MD and TD. The sample is placed for 10 minutes at 120 ° C. in a heated air oven and then the MD and TD dimensions are measured again. The ratio of MD and TD dimensions before heating to after heating corresponds to the MDO ratio and TDO ratio, respectively.

The film of the invention is preferably at least about 20%, preferably at least about 30%, more preferably at least about 40%, and even more preferably at 110 ° C., preferably at 100 ° C. in the stretched direction. At least 50%, very more preferably at least about 60%, and most preferably at least about 70%. Shrinkage of less than 20% undesirably tends to limit the degree to which the film can be matched to the container contour. The upper limit of the extent of MD contraction is unknown but will be less than 100%.

Preferably, the film demonstrates at least about 5%, more preferably at least about 7% and most preferably at least about 10% shrinkage in the opposite direction in the minimum shrinkage direction at 100 ° C, preferably at 110 ° C. . Films that shrink in less than about 5% shrinkage direction tend to suffer poor preservation on management and disruption of the mixed phase. Thus, some orientation and shrinkage is desirable to improve film preservation. Excessive shrinkage in the less stretched direction interferes with the performance of the film in shrink label applications, which causes shrinkage of the film and thus distortion of the label in the other direction. Thus, the films of the present invention typically have an orientation ratio in less stretched directions of about 1.2: 1 or less, preferably about 1.15: 1 or less, which results in shrinkage of about 20% or less, preferably about 15% or less. Corresponds.

The films of the invention further demonstrate that at 110 ° C., preferably at 100 ° C., the length (growth) does not increase by more than about 10% in the direction opposite to the primary shrinkage direction in the opposite direction of primary stretching (direction at specific temperatures Shrinkage of at least 20% or growth of at least 10% tends to worsen the registration of the film to the container in the application of the shrink label due to the distortion in this direction). Shrinkage is measured according to ASTM method D-1204. Testing by the method according to US Pat. No. 6,897,260 B2 further demonstrates that the films of the present invention preferably grow relatively low in intentionally undrawn, or less stretched directions.

The presence of the HIPS component increases the toughness of the film while at the same time providing the film of the invention with desirable high transparency and transparency. Transparency and clarity are desired in the label industry to provide a clear view of the products that have labels around them. High clarity and transparency are also desirable for "reverse" printing of labels where there is a print between the label and the container and the consumer sees the print through the label. Typically, when produced by a commercial device, ie a device used for the manufacture of a commercial label film, the film of the present invention has a transparency value of at least about 10, preferably about 15, at a film thickness of 2.0 mils (50 μm). Or more, more preferably about 20 or more, even more preferably about 25 or more, even more preferably about 30 or more. One skilled in the art recognizes that thicker films will have less transparency than thick films of the same composition made in the same manner. Transparency is measured according to ASTM method D-1746.

Haze values also provide a measure of film clarity, with low haze corresponding to high clarity. The haze value of the film of the present invention may be in the range of any possible value. However, one advantage of the present invention is that it is possible to obtain an oriented film having high transparency and low haze. Typical film haze values of the films of the present invention at a film thickness of 2.0 mils (50 μm) are about 15 or less, preferably about 10 or less, more preferably about 6 or less and most preferably about 4 or less. Haze is measured according to ASTM method D-1003.

Styrenic films advantageously have a higher modulus modulus than, for example, oriented polypropylene or oriented polyvinyl chloride films. Increasing the secant modulus of the shrink label film is desirable to prevent the stretchability of the film during printing. As a result, the film of the present invention can proceed at a higher printing speed without the risk of film breakage or distortion as compared to the low-half modulus film without the HIPS component. Films of the present invention have a 1% secant modulus to both MD and TD of at least about 90,000 psi (620 MPa), preferably at least about 100,000 psi (690 MPa), more preferably at least about 200,000 psi (1,380 MPa). 1% secant modulus is measured by American Society for Testing and Materials (ASTM) Method D-882.

Similar to films with high shunt modulus, films with high tensile stresses, particularly upon breakage into MD, are preferred because they can proceed more quickly under higher tension without stretching in the printing process than films with low tensile stresses. Preferably, the films of the present invention have a tensile stress at break of at least about 2,000 psi (14 MPa), preferably at least about 2,500 psi (17 MPa), more preferably at least about 3000 psi (21 MPa), most preferably about 4,000 psi (28 MPa) or more. The tensile stress at break is measured according to ASTM D-882.

Films with high tensile strain at break preferably allow for printing and managing the film with a high speed processing apparatus without tearing the film. Preferably, the films of the present invention have a tensile strain at break of at least about 30%, preferably at least about 35%, more preferably at least about 40% and most preferably at least about 45% at break in both directions of the test. . The strain (%) at break is measured according to ASTM D-882. Preferably, the film of the present invention has a toughness of about 2,000 psi (14 MPa) or more, preferably about 2,500 psi (17 MPa) or more, and more preferably about 3000 psi (21 MPa) as measured according to the ASTM D-882 method. Or above, most preferably about 4,000 psi (28 MPa) or more.

Films of the invention generally have a thickness of at least about 1 mil (25 μm), preferably at least about 1.5 mils (38 μm) and generally at most about 4 mils (100 μm), preferably at most about 3 mils (76 μm) . At thicknesses below 1 mil (25 μm), the film undesirably tends to be difficult to cut during processing and handling. Thicknesses greater than 4 mils (100 μm) are technically achievable, but are generally economically undesirable.

The film of the present invention preferably has an orientation release stress (ORS) of 400 psi (2758 kPa) or less. ORS is a measure of the stress the film experiences during shrinkage upon heating. It is desirable to lower the ORS value in the shrink film. The shrink film generally has one or more ends attached to a container to which the film is applied. Labels with high ORS values may apply sufficient stress to the adhesive seam that holds the label around the container during shrinkage to damage or destroy the seam. Lowering the ORS value reduces the likelihood that the seam line (film on film) will be damaged or destroyed during shrinkage.

The film of the present invention is produced by any alignment film manufacturing means, including blown film process and cast-tentering process. Particular preference is given to blown film processes described in US Pat. No. 6,897,260 and UK Pat. No. 862,966, both of which are incorporated herein by reference.

To avoid unintentional crosslinking, process temperatures and residence times should be minimized. The melting temperature is preferably about 230 ° C. or less, preferably about 220 ° C. or less, more preferably about 210 ° C. or less. The higher the process melt temperature, the shorter the time the polymer can stay at an unacceptable temperature before decomposition. For example, exposure to temperatures above about 230 ° C. is preferably limited to less than about 10 minutes, more preferably less than about 7 minutes, and most preferably less than about 300 seconds.

One process suitable for making the films of the present invention (“Process A”) is a blown film process using an apparatus as described in US Pat. No. 6,897,260 or UK 862,966. The polymer pellets are fed into the apparatus and converted into molten polymers having a temperature of 170 ° C. to 100 ° C., then the molten polymer is cooled to a temperature of 130 ° C. to 170 ° C. to increase the melt viscosity, and then the molten polymer is passed through a blown film die. Extrude under a gas atmosphere. The gas atmosphere is maintained at a temperature of at least 40 ° C. below the heat distortion temperature of each of the polymer composition components (HIPS component and GPPS and / or styrene block copolymer component, if present) in the molten polymer. Blown molten polymer is blown according to the bubble process of British Patent 862,966.

Another possible blown film process ("Process B") suitable for making the films of the present invention employs two extruders (extruder 1 and extruder 2) in series. Extruder 1 is a 2.5 in. (6.35 cm) diameter, 24: 1 single screw extruder with five barrel zones, each set at a temperature of 155 ° C. to 200 ° C. (typically the temperature increases as it goes below the extruder). Extruder 2 is a 3.5: 1 (8.89 cm) diameter 32: 1 single screw with five barrel zones and barrier mixing screws, each having a temperature set point typically at temperatures of 115 ° C to 175 ° C. The polymer pellets are fed to extruder 1 to plasticize the polymer and the polymer is pumped to extruder 2 at a temperature of 200 to 260 ° C. The polymer runs from extruder 1 through a delivery line to the inlet of extruder 2. The polymer is cooled to a melt temperature (extrusion temperature) selected from 150 to 190 ° C. in Extruder 2 to obtain stable bubbles and to optimize the disorientation stress (ORS) properties of the resulting film to the desired values. The wall of extruder 2 is cooled to cool the polymer. The polymer is extruded from extruder 2 through a 3.25 inch (8.3 cm) annular die and then a 4.5 inch (11.4 cm) diameter air ring and blown into a bubble typically having a diameter of 9 inches (22.9 cm) to 24 inches (63.5 cm). Or inflate. The bubble blowing process of British Patent 862,966 is used.

In another embodiment, the preferred method of making the film is the cast tentering method (“Method C”). First the film or sheet is cast, ie the film or sheet supporting itself is formed from the melt fed by the extrusion system. The resin is extruded through a slit as a flat sheet (on a cold, soft cast roll, at a temperature of about 0.3 to 2.5 mm, at a temperature of about 30 to about 70 ° C.) to form a monolayer film. The cast roll speed is adjusted to make the film thickness from about 0.3 to about 1 mm thick. The film or sheet is carried out by a roller into a heated chamber containing a tenter frame. The air in the chamber is heated at a temperature at which the film or sheet depends on the composition of the film, from about 95 ° C. to about 150 ° C. to be sufficient to allow extension without tearing. The tenter frame has two side by side endless chains that are split at an angle. The film is held on the chain by a film clip. The cracking of the chain moves along the chain to extend the polymer and impart the desired orientation. Elongation is determined by chain speed, degree of splitting and degree of orientation. The degree of orientation is lifted or determined by the ratio of the width of the film to the amount of extension and the width of the film leaving the system to achieve the corresponding shrinkage described above. This is first given to the TD orientation. The film is then annealed and, if desired, released. In most instances, the film is torn, grounded, and circulated, and the film is optionally cracked to a full or higher width, which is optionally treated to improve printability, and then rolled onto a roll for further processing. It is wound. If desired, the machine direction orientation is continuous at any stage when the film or sheet is sufficiently heated to extend, for example, when sufficiently heated to the TD orientation or before the film or sheet is formed and quenched in a separate stage. It is imparted by the fastener roller to the extent described above by the machine direction orientation.

The films of the present invention have utility in any application that benefits from heat triggered shrinkage. The film is particularly useful as a shrink label. In order to convert the film of the present invention to the shrink label of the present invention, the film is cut to the desired width, the side of the film (in any order) is corona treated, and then printed on the corona treated side of the film. The print may be on the opposite side of the film to produce the opposite side printing label. If there is a film around the container in a shrink label application, the opposite side of the film contacts the container and the print on the opposite side is seen through the film. These steps are usually carried out in a continuous web process by any method useful in the art.

Films and labels of the present invention may also advantageously have a perforation through the film or label. The perforation is most preferably located in the film portion adjacent to the narrowest portion or portions of the container to which the film is applied. The perforation releases the gas trapped between the label and the container, allowing the label to fit more tightly into the container. Films and labels of the present invention may contain perforations distributed evenly across the surface of the film, or may be specific to the area of the film (or label) that will conform to the narrowest portion of the container where the film (or label) will be placed around. May comprise adjacent perforations. Although the perforations of the films and labels of the present invention can be perforated at any time, the films and labels are preferably perforated after printing to facilitate printing of the labels.

The objects and advantages of the invention are further illustrated by the following examples. Certain materials and amounts thereof as well as other conditions and details described in these examples are not used to limit the present invention. Unless stated otherwise, all percentages, parts and ratios are by weight. Examples of the present invention are numbered, while comparative samples that are not embodiments of the present invention are designated alphabetically.

HIPS-X Component for Examples 1-3 and Comparative Samples A, B, and C

Examples 1 to 3 and Comparative Samples A, B, and C below used HIPS-X as the HIPS component. For example, HIPS-X was produced in the following continuous process using three continuously stirred reactors. The rubber component of Table 1 was dissolved in styrene at a ratio of 1 part to diene 55 or 15 parts to 6533 rubber component (i.e., 0.3% by weight of diene 55 and 4.5% by weight of buena 6533, based on the total rubber feed solution weight). To prepare a rubber feed solution. 2.5 wt% mineral oil (70 cSt viscosity) and 7 wt% of ethylbenzene were incorporated into the rubber feed solution to form a feed stream having a wt% relative to the total feed stream weight. 0.1 wt% antioxidant Irganox 1076 was added to provide a level of about 1200 ppm in the final product. 100% by weight was settled with styrene, the remainder of the feed. The feed stream was fed to the first reactor at a rate of 750 g / h. The rubber blend content in the feed stream and the reactor feed rate of styrene and rubber were targeted to produce a rubber modified polystyrene product (HIPS-X) containing 4% by weight butadiene.

Each of the three reactors had three zones that were independently temperature controlled. The following temperature profiles were used: 125 ° C, 130 ° C, 135 ° C, 143 ° C, 149 ° C, 153 ° C, 157 ° C, 165 ° C, 170 ° C. Stirred at 80 RPM per minute in the first reactor, 50 RPM in the second reactor and 25 RPM in the third reactor. 100 ppm of chain transfer agent (n-dodecyl mercaptan or nDM) was added to the second zone of the first reactor.

A volatile removal extruder was used to release the residual styrene and ethylbenzene diluent and crosslink the rubber. The temperature profile for the volatile removal extruder was 240 ° C. at the beginning of the barrel, the middle region of the barrel and the final region of the barrel. Screw temperature was 220 ° C.

The following test methods (or the methods defined herein above) were used to characterize HIPS-X: Melt Flow Rate: ISO-133, PS Matrix Molecular Weight Distribution: PS Calibration Gel Permeation Chromatography, Rubber Particle Size: from Beckham Coulter Scattering using LS230 instruments and software. Tensile Yield, Elongation and Modulus: ISO-527-2.

Gel concentration of HIPS-X was measured by methyl ethyl ketone extraction. For the analysis of HIPS-X, the samples and mixtures were placed in tubes of known weight and stirred on an armed stirrer at room temperature (23 ° C.) for 2 hours, so that 0.25 g of HIPS-X sample was mixed with a methyl ethyl ketone / methanol mixture ( Dissolved in volume ratio 10: 1). The insoluble fraction was isolated by placing the tube into a high speed centrifuge and rotating at 19500 revolutions per minute at 5 ° C. for 1 hour. The excess liquid was decanted and the tube was placed in a vacuum oven at 150 ° C. for 45 minutes under vacuum of 2-5 ml of mercury. The tube was removed from the oven and cooled to about 23 ° C. The gel weight was determined by weighing the tube and subtracting the known tube weight. The gel weight was divided by 0.25 g and multiplied by 100 to give the gel content (% by weight) relative to the total HIPS-X weight.

Conjugated diene copolymer rubber Conjugated diene homopolymer rubber characteristic Buna BL 6533 T (trade name of Bayer) Dien 55 (trade name of Firestone) Styrene Content (%) 40 0 Vinyl content (%) 9 11 Sheath Content (%) 38 38 Viscosity (Mooney Viscosity MLl + 4 100 ° C) (Pas) 45 70 Solution Viscosity (5.43% in Toluene) (mPas) 40 170 Polymer structure AB block copolymer Generally linear

HIPS-X had a volume average rubber particle size of 0.35 μm, wherein 65 volume% of the particles were less than 0.4 μm in size and 35 volume% of the particles were 0.4 to 2.5 μm in size. HIPS-X had a rubber concentration of butadiene homopolymer of 0.38% by weight and a rubber concentration of styrene / butadiene copolymer for a combined rubber concentration of 5.98% by weight based on HIPS-X weight. HIPS-X had a gel concentration of about 8% by weight relative to the total HIPS-X weight. HIPS-X contains 2% by weight mineral oil, MFR is 7.0g / 10min, Vicat temperature is 101 ° C, tensile yield is 20MPa, elongation at break is 25%, tensile modulus is 2480MPa It was.

The following materials are those used in addition to HIPS-X in the examples of this invention and in some comparative samples:

GPPS-I is a general purpose polystyrene having a tensile modulus of at least 400,000 psi (2750 MPa) and commercially available from Dow Kye Company under the tradename STYRON ™ 665 polystyrene resin.

Block-1 has a diene content of at least 30% by weight, a luminance modulus of less than 200,000 (1380 MPa), and a styrene-commercially available under the tradename K-Resin KK 3.8 styrene-butadiene-styrene from Chevron Phillips Kcal Company Butadiene (SB) block copolymer.

-2 is a block styrene content of about 15% by weight, SHORE A hardness of 24, and (ASTM D-2240), trade name from the index copolymer LP commercially Vector ^TM 4114A styrene-isoprene-styrene / styrene-isoprene SIS / SI styrene Styrene-isoprene-styrene / styrene-isoprene (SIS / SI) block copolymers available under the block copolymers.

Block-3 has a styrene content of about 18% by weight, has a SHORE A hardness of 39, and is commercially available from Dexco Polymer LP under the tradename vector ^R 4111A styrene-isoprene-styrene (SIS) styrene block copolymer. Isoprene-styrene (SIS) block copolymer.

Block -4 is 70 to 80% by weight styrene content, the tensile modulus 120,000psi (825MPa), and from BASF Corporation, commercially available under the trade name ^TM polystyrene lux 3G55 Q420 styrene-butadiene-thermoplastic, available under the styrene block copolymer styrene- Butadiene block copolymer.

Methods of Examples 1-3 and Comparative Samples A-D

In each of the examples below, each of the ingredients listed in Table 2 is in the form of pellets which are mixed into a tumble blender where the ingredients are mixed for about 2 minutes to form a mixture. Although no additives have been added, it is recognized that some of the commercial polymers used may contain commercially available additives.

The mixture is placed in an extruder with a length of diameter (L / D) ratio of 24: 1 each of three 1 inch (2.54 cm) diameters. The mixture is heated at a temperature of 390 ° F. (198 ° C.) with a heater essential to the extractor. This temperature is cast at a temperature of 130 ° F. (54 ° C.) on a water / glycol cooled smooth cast roll through a die with a film 10 in. (25.4 cm) in width slit and a 0.040 in. (0.10 cm) gap. In the example, it is maintained until forming a monolayer film. The cast roll speed is adjusted to result in the thickness of the film listed in each example or sample.

The film examples and samples were then cut into 4 "(10.16 cm) squares and purchased from T. M. Long Film Stretching Machine (commercially available from TM Long Co., Inc of Somerville, NJ). The film stretcher has a sample holder with several corner clamps for each of the four corners of the sample.Hot air is blown from underneath the springs dispersed in the air by the clamp. Under the sample holder to divert the hot air by blowing in. In the absence of the diverter, the hot air is blown onto the sample Each film example or sample is 1 minute into the diverter in and out for the periods described in Table 2. Is heated at the air temperatures indicated in Table 2. The sample or example is then taken at four times its original size in the transverse direction of the extrusion. Shin and is stretched at 0.4in / sec (1.0cm / s) the speed until no extension in the machine direction by an edge clamp.

In the examples and comparative examples, the air temperature is varied to avoid tearing the sample by the edge clamp. The selected air temperature is selected by the dial indicator on the machine and maintained by the machine. The length of time of the internal or external converter is chosen to avoid tearing the sample during extension because it affects the temperature change of the sample.

Examples (Ex) 1-3 and Comparative Samples (C.S.) A-D

All percentages are weight percent of polymer excluding additives, except those that may be in the commercially obtained product obtained.

^* Comparative Sample is not an embodiment of the present invention.

Table 3 describes the film properties of Examples 1-3 and Comparative Samples A-D. The use of the following test method is characterized by the film throughout this disclosure. Haze is measured according to the ASTM method D-1003 method. Transparency is measured according to ASTM Method D-1746. Tensile stress and strain, toughness and secant modulus are measured according to ASTM method D-882. Orientation release stress (ORS) is measured according to ASTM method D-2838. Air free shrinkage is measured according to ASTM Method D-1204.

^* While not certain, it is contemplated that the relative high haze and lack of clarity of the sample may be due, at least in part, to one or more additives of Block-2 received.

^** The transparency obtained using this laboratory apparatus is lower than expected in the same composition prepared in commercially available apparatus. The data is considered to indicate that Examples 1, 2, and 3 would fall within the preferred range when manufactured on a commercially purchased device.

Examples 1-3 illustrate various formulations within the scope of the present invention and show their properties suitable for the manufacture of shrink labels. Comparative Sample A causes more haze than is desirable in the shrink label due to excessive use of SIS. Comparative Sample B causes lower MD toughness than is available for shrink labels due to the absence of styrene block copolymers, since the shrink labels will be observed to easily break along unextended directions. Comparative Sample C describes a label without a low coefficient of HIPS-X, which label was prepared in a formulation where undesirably low toughness was observed. Comparative sample D illustrates a label without GPPS with a haze greater than that desired for the shrink label.

Comparison of Comparative Sample C and Comparative Sample D shows that the addition of HIPS-X to the block copolymer results in higher toughness as indicated by the higher 1% secant modulus.

Preferred embodiments of the invention include, but are not limited to, the following:

1. 0 to 5% by weight of additives and

A film composition comprising 95 to 100% by weight of a polymer composition consisting essentially of the following components,

The polymer composition

(a) at least one high impact polystyrene (HIPS) component,

   (i) a block copolymer of styrene and a rubbery conjugated diene (the copolymer is grafted to polystyrene);

   (ii) optionally from 2% to 8% by weight of a rubbery conjugated diene homopolymer, based on the total rubber weight in the HIPS component;

   (iii) total diene-component from 1% to 7% by weight of the rubber component, based on the total weight of the HIPS component;

   (iv) gel concentration of less than 10% by weight with methyl ethyl ketone / methanol extraction;

   (v) an average rubber particle size of at least 0.01 μm and less than 1.0 μm;

   (vi) about 40 to about 90 volume% of rubber particles having a diameter of less than about 0.4 μm, and about 10 to about 60 volume% of rubber particles having a diameter of about 0.4 to about 2.5 μm, and

   (vii) has rubber particles that are predominantly core / shell morphology,

   (viii) the at least one high impact polystyrene (HIPS) wherein the polymer in the composition is present at a concentration of at least about 10% by weight and at most about 70% by weight and comprises at least 1% and at most 5% by weight of the rubber diene relative to the total composition weight. ) ingredient;

(b) at least one general purpose polystyrene having a weight average molecular weight greater than 200,000 g / mol and no greater than 350,000 g / mol and present at a concentration of at least about 10% to about 50% by weight of the polymer in the composition, and

(c) the elongation at break at break is advantageously at least about 200, the melt flow rate measured by the method of ASTM D1238, condition G of at least about 2 g / 10 minutes, at least about 2% by weight to about 80% by weight of the polymer in the composition A film composition composed of one or more styrene block copolymers present in the following concentrations, wherein the combination of (a), (b) and (c) comprises 100% by weight of the polymer composition.

2. The composition of embodiment 1 wherein the styrene block copolymer corresponds to a visible light transmittance of at least about 85%, preferably at least about 90%, as measured by the ASTM D1746 method.

3. The composition of embodiment 1 or 2, wherein the composition is preferably used to prepare a film having a thickness devised in a method specified for measuring properties, or alternatively preferably from about 25 or 38 μm to about 76 μm, Stretched thickness of 100 μm or 110 μm, more preferably 64 μm, 65 μm, 89 μm, 90 μm, 100 μm, 104 μm, 105 μm, 109 μm or 110 μm, most preferably 50 μm If intended to be used in thickness, one or more HIPS, GPPS, styrene block copolymers are selected and at least one of the following, advantageously at least two, more advantageously at least three, most advantageously four A composition used in an amount effective to achieve at least, preferably at least 5, more preferably at least 6, and most preferably at least 7.

(a) a transparency corresponding to the transparency of a 50 μm film, the transparency being at least one of 10, 15, 20, 25 or 30, measured according to the ASTM D-1746 method;

(b) a haze corresponding to the haze of a 50 μm film, wherein the haze is at least one of 15, 10, 6 or 4, measured according to the ASTM D-1003 method;

(c) 1% secant modulus of any one or more of 620 MPa, 680 MPa or 1380 MPa, MD, TD, or, more preferably, both measured according to the ASTM D-882 method;

(d) tensile strain at break of any one or more of 30, 35, 40, or 45%, MD, TD, or both, measured according to the ASTM D-882 method;

(e) tensile stress at break of any one or more of 14, 17, 21 or 28 MPa, MD, TD, or, more preferably both, measured according to ASTM D-882 method;

(f) toughness of MD, TD, or, more preferably both, of at least one of 14, 17, 21 or 28 MPa, measured according to ASTM D-882 method or

(g) Orientation peel stress of less than 2758 kPa, measured according to ASTM D-2838 method.

4. The composition according to any one of embodiments 1 to 3, wherein the high impact polystyrene component has a volume average rubber particle size of 0.01 µm or more and 0.5 µm or less.

5. The process according to any one of embodiments 1 to 4, based on the total weight of the polymer components (a), (b) and (c) or any combination thereof

(a) the amount of HIPS is about 10%, 20%, or 25% or more, about 60%, 65% or 70% or less, or

(b) the amount of GPPS is about 10%, 20%, or 35% or more, about 40%, 45% or 50% or less, or

(c) A composition wherein the amount of styrene block copolymer component is at least about 2%, 3%, or 4% by weight, about 70%, 75% or 80% by weight.

6. The method of any one of embodiments 1 to 5, wherein the styrene block copolymer is one or more styrene butadiene block copolymers and based on the total weight of (a), (b) and (c), about 20, 30 Or in an amount of at least 40 wt% or up to 70 wt%, 75 wt% or 80 wt%.

7. The method of any one of embodiments 1 to 6, wherein the styrene block copolymer is one or more styrene isoprene block copolymers and based on the total weight of (a), (b) and (c), about 2% by weight , At least 3%, at least 4%, or at most about 6%, 8%, or 9% by weight.

8. The composition of any one of embodiments 1 to 7 wherein the rubbery conjugated diene in the copolymer of (a) is butadiene.

9. The composition of any of embodiments 1-8, wherein at least 90% of the rubber particles have a particle size of less than 0.4 μm, and up to 100% of the remaining rubber particles have a particle size of 2.5 μm or less.

10. A film comprising the composition according to any one of embodiments 1 to 9.

11. The film of embodiment 10, wherein the film shows less than 10% growth in the less stretched direction after 5 minutes in an air oven heated to 110 ° C.

12. The method of embodiment 10 or 11, wherein the polymer composition comprises at least 95% by weight of the orientation film weight, the remainder to 100% by weight is selected from additives, and the film has a directional orientation in the stretched direction of at least about 3: 1. film.

13. The method of any of embodiments 10-12, wherein the film has a machine direction (MD) and transverse (TD) 1% secant modulus per ASTM Society 882 method 882 of about 250,000 psi (1,724 MPa) Film.

14. The method of any one of embodiments 10 to 13, preferably about 25 μm or 38 μm to about 76 μm, 100 μm or 110 μm thick, more preferably 64 μm, 65 μm, 89 μm, 90 μm Film having a thickness of 100 μm, 104 μm, 105 μm, 109 μm or 110 μm, most preferably 50 μm.

15. The method of any one of embodiments 10 to 14, wherein any thickness specified in the embodiment is at least one, advantageously at least two, advantageously at least three, most advantageously of the properties specified in embodiment 3 A film having four or more, preferably five or more, more preferably six or more, most preferably seven or more.

16. The method of any one of aspects 10 to 15, wherein

(a) the ratio of the orientation length to the unoriented length in the most extending direction of at least about 3: 1, 4: 1, 5: 1 or 6: 1 or

(b) one or both of the ratio of the orientation length to the unoriented length in the vertical direction to a further extending direction of about 1.05: 1, 1.07: 1 or 1.10: 1 or more and about 1.2: 1 or 1.15: 1 or less. Having a film.

17. The method according to any one of embodiments 10 to 16 wherein the film is

(a) at least about 20, 30, 40, 50, 60 or 70% shrinkage in the extending direction or

(b) a film having one or both of 5, 7 or 10% to 15 or 20% shrinkage with less prolonged echo.

18. The film of any one of embodiments 10 to 17 further comprising perforation.

19. A shrink label comprising the oriented polymer film according to any one of embodiments 10 to 18, wherein the film is preferably printed on one or both sides.

Claims (16)

0-5 wt% of additives and A film composition comprising 95 to 100% by weight of a polymer composition consisting essentially of the following components, The polymer composition (a) at least one high impact polystyrene (HIPS) component,   (i) a block copolymer of styrene and a rubbery conjugated diene (the copolymer is grafted to polystyrene);   (ii) optionally at least 2% and at most 8% by weight of a rubbery conjugated diene homopolymer, based on the total rubber weight in the HIPS component;   (iii) total diene-component from 1% to 7% by weight of the rubber component, based on the total weight of the HIPS component;   (iv) gel concentration of less than 10% by weight with methyl ethyl ketone / methanol extraction;   (v) an average rubber particle size of at least 0.01 μm and less than 1.0 μm;   (vi) about 40 to about 90 volume% of rubber particles having a diameter of less than about 0.4 μm, and about 10 to about 60 volume% of rubber particles having a diameter of about 0.4 to about 2.5 μm, and   (vii) has rubber particles predominantly core / shell morphology,   (viii) said at least one high impact polystyrene in which the polymer in the composition is present at a concentration of at least about 10% by weight and at most about 70% by weight and accounts for at least 1% and at most 5% by weight of the rubber diene compared to the total composition weight; (HIPS) component; (b) at least one general purpose polystyrene having a weight average molecular weight greater than 200,000 g / mol and no greater than 350,000 g / mol and present at a concentration of at least about 10% to about 50% by weight of the polymer in the composition, and (c) the tensile elongation at break is advantageously at least about 200, the melt flow rate as measured in the course of ASTM D1238, condition G is at least about 2 g / 10 minutes and at least about 2% by weight to about 80% by weight of the polymer in the composition A film composition composed of one or more styrene block copolymers present in the following concentrations, wherein the combination of (a), (b) and (c) comprises 100% by weight of the polymer composition. The composition of claim 1 wherein the styrene block copolymer has a transparency as measured by ASTM D1746 corresponding to at least about 85% visible light transmittance. The composition according to claim 1, wherein the high-impact polystyrene component has a volume average rubber particle size of 0.01 µm or more and 0.5 µm or less. The composition of claim 1, wherein the amount of styrene block copolymer component is at least about 3% by weight, based on the weight of the polymer composition. The composition of claim 1, wherein the styrene block copolymer is at least one styrene butadiene block copolymer and is present in an amount of at least about 20% by weight, based on the total weight of the polymer composition. The composition of claim 1, wherein the styrene block copolymer is one or more styrene isoprene block copolymers and present in an amount of from 2 to 9 weight percent based on the total weight of the polymer composition. The composition of claim 1 wherein the rubbery conjugated diene in the copolymer of component (a) is butadiene. The composition of claim 1, wherein at least 90% of the rubber particles have a particle size of less than 0.4 μm, and up to 100% of the remaining rubber particles have a particle size of 2.5 μm or less. The at least one HIPS, GPPS, styrene block copolymer of claim 1, wherein the composition is used to prepare a film having a thickness devised in a method specified for measuring properties, or when the thickness is not specified to 100 μm. Is selected and used in an amount effective to achieve at least three of the following. (a) a transparency corresponding to the transparency of a 50 μm film, the transparency being at least one of 10, 15, 20, 25 or 30, measured according to the ASTM D-1746 method; (b) haze of a 50 μm film, wherein the haze is any one or more of 15, 10, 6 or 4, measured according to ASTM D-1003 method; c) 1% secant modulus of any one or more of 620 MPa, 680 MPa or 1380 MPa, MD, TD, or more preferably both, measured according to ASTM D-882 method; (d) tensile strain at break of any one or more of 30, 35, 40, or 45%, MD, TD, or both, measured according to the ASTM D-882 method; (e) tensile stress at break of any one or more of 14, 17, 21 or 28 MPa, MD, TD, or, more preferably both, measured according to ASTM D-882 method; (f) toughness of MD, TD, or, more preferably both, of at least one of 14, 17, 21 or 28 MPa, measured according to ASTM D-882 method or (g) Orientation peel stress of less than 2758 kPa measured according to ASTM D-2838 method. 10. A film comprising the composition of claim 1. The film of claim 10, wherein the film grows less than 10% in the less stretched direction after 5 minutes in an air oven heated at 110 ° C. 12. The film of claim 10, wherein the polymer composition comprises 95% by weight of the oriented film, the remainder being selected from additives up to 100% by weight, and the film is oriented in a direction in which the film is stretched at least about 3: 1. The film of claim 10, wherein the film has a machine direction (MD) and transverse (TD) 1% split modulus per American Society for Testing and Materials (ASTM) Method 882 of at least about 250,000 lb / in ² (1,724 MPa). The film of claim 10, wherein the film shrinks at least about 50% in the most stretched direction and shrinks by 5-20% in the least stretched direction. The film of claim 10, wherein the film further comprises perforation. A shrink label comprising an oriented polymer film according to claim 10, wherein the film is printed on one or both sides.