RU2415162C2 - Shrinkable labels made from directed polystyrene film, containing fine rubber particles, low content of gel of rubber particles and block-copolymers - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of shrinkable polymer labels, particularly to preparation of a film composition. The composition contains (a) a high-impact polystyrene component (HIPS) with a block-copolymer grafted to the polystyrene, (b) 10-50 wt % general purpose polystyrene (GPPS) and (c) approximately 2-80 wt % styrene block-copolymer. Component (a) contains a grafted rubber component which is a styrene block-copolymer and a rubber-like diene with conjugated double bonds from 1 to 7 wt % of the weight of the HIPS; less than 10 wt % concentration of gel, defined by extraction of the methylethylketone/methanol mixture. The average particle size of the rubber is less than 1 mcm and 0.01 mcm or more. Approximately 40-90 vol % of the rubber particles have diametre approximately less than 0.4 mcm and approximately 10-60 vol % of the rubber particles have diametre of approximately 0.4-2.5 mcm. Most of the rubber particles have a nucleus-shell morphology and said particles are in concentration of 10-70 wt % of the total weight of the polymer composition, and 1-5 wt % of the rubber-like diene of the total weight of the polymer composition.

EFFECT: film made from said composition has ratio of directed length to non-directed length in the direction of the greatest drawing at least equal to 3:1 and enable increase in size by 20% in the direction of less stretching at 110°C.

10 cl, 3 tbl, 7 ex

Description

BACKGROUND

FIELD OF THE INVENTION

The present invention relates to a rubber-modified oriented polystyrene film that has a preferred orientation in the tensile direction, and to a shrink label film including such a polystyrene film, as well as to a composition used to make such films.

Description of the Related Art

Shrink labels are usually divided into two categories: roll-on shrink labels (ROSO) and sleeve-type labels; sleeve labels are also sometimes called circular labels. ROSO labels are sheets of film that are wound around a container. Sleeve labels have a hollow cylinder configuration and fit snugly to the container when placed around the container. The application of heat to the shrink label placed around the container causes the sticker to sit and fit snugly onto the container.

For a snug fit to the container, each type of label should sit preferably (i.e., more than in any other direction) around the circumference around the container. ROSO films are usually placed on the container in the longitudinal direction (MD) around the container around the circumference. Therefore, ROSO films predominantly shrink in the longitudinal direction (MD), due to the predominant orientation in the longitudinal direction (MDO). In contrast, sleeve labels are usually placed on the container in the transverse direction to the label (TD) covering the container around the circumference. Therefore, sleeve labels shrink predominantly in the transverse direction of the film (TD), due to the predominant orientation in the transverse direction (TDO).

While the use of ROSO labels offers performance benefits, it has historically been the case that the use of sleeve labels has provided an advantage in the degree of shrinkage around the container. Sleeve labels usually shrink up to 70 percent (%) around the circumference of the container. Sleeve labels, which are used either without an adhesive layer applied or with an adhesive layer carefully cured prior to application on the container, can tolerate large amounts of stress during shrinkage.

It has so historically developed that sleeve labels are characterized by a greater degree of shrinkage and therefore are more closely adhered to containers than ROSO labels. However, ROSO labels have a manufacturing advantage due to the fact that they are oriented in the longitudinal direction, that is, in the direction in which they move through the equipment used in the production process. Therefore, it is desirable to create an oriented film suitable for producing the ROSO label, which could shrink around the circumference of the container to a greater extent than the ROSO polypropylene labels, but preferably without breaking the adhesive of the label.

Polystyrene (PS) is a particularly suitable polymer for shrink labels. For example, films for shrink labels made of polypropylene (PP) usually shrink only about no more than 20% in any direction at temperatures below 120 ° C. To obtain an additional orientation, the crystalline nature of PP requires heating above the melting point of crystalline PP. In contrast, PS-based shrink labels, due to its amorphous nature, require only an increase in the glass transition temperature of the polymer (which is usually lower than the melting point of crystalline PP). Therefore, PS films can achieve a greater degree of shrinkage at lower processing temperatures than PP films.

In addition, PS retains higher surface energy after corona treatment (usually necessary in order to make the surface of the polymer film suitable for printing) for longer periods of time compared to PP. Therefore, in contrast to PP films, corona discharge processing of PS films can occur during their production, and not immediately before printing labels.

Unlike copolyester or polyvinyl chloride (PVC) films, the use of PS films makes it easier to recycle the bottle and label, as the lower density of the label material makes it easy to separate from bottles made from a material with a higher density (for example, polyester ) In addition, a lower PS density allows for additional advantages due to a higher film yield, or a higher area / pound or area / kg film ratio. The higher density of such label starting materials as copolyester or PVC films does not provide such advantages.

To increase label strength (e.g. tear resistance), a shrink label made of polystyrene films can include a high impact polystyrene component (HPS). However, rubber particles in a typical HIPS size range have an average particle size of more than one micrometer (see, for example, Patent Document US 6897260, Col. 4, pp. 26-27). Large rubber particles usually lower the brightness of the film for the label, which prevents its use for printing on the back side (printing the label on the side of the film that is in direct contact with the container) so that it can be read through the film, and also so that See the container or product through the label. Conventional HIPS also contains more than 7 percent rubber of the total mass of HIPS. High concentrations of rubber can impede the ability to print on the film, lower the brightness of the film, reduce dimensional stability and it is undesirable to increase the amount of gel in the finished film. However, in some cases, such as small-diameter bottles or narrow-necked bottles, the use of HIPS alone cannot provide sufficient strength to prevent cracking due to mechanical stress.

It is desirable to have an oriented PS film that is suitable for use as a shrink label. In addition, in order to achieve increased toughness without significant deterioration in printing performance or lowering the brightness of the film, it is desirable that the film contains high impact polystyrene, which contains finer rubber particles and lower rubber concentrations than typical HIPS. In addition, to further increase the impact strength of the film, it is desirable that the film contains transparent impact-resistant polystyrene, obtained on the basis of block copolymerization technology. In addition, it is still desirable that such a film can be used as a shrink label, which is characterized by shrinkability around the container, comparable to shrinkage achieved in the case of PVC or polyester.

SUMMARY OF THE INVENTION

The present invention improves the technology for producing a shrinkable label by creating an oriented polystyrene film suitable for use as a shrink label and containing HIPS with a rubber particle size and rubber concentration below the values typical for HIPS, as well as a block copolymer of polystyrene to increase the impact viscosity, shock resistance, or a combination thereof, and general polystyrene. The present invention makes it possible to create a rubber-modified polystyrene film and a shrink label including a film that unexpectedly has one or more of such properties as high brightness, corresponding stiffness in high-speed printing, for which preferred intervals of 1% secant module are indicated, as for MD, and for TD, from 90,000 to 300,000 lb / ⁱⁿ² (620 to 2070 MPa) and high usazhivaemost in the direction of orientation, which is characterized preferred degree intervals about usazhivaemosti 20 to 80% in the main direction of orientation, measured in the open air at 110 ° C for 10 minutes.

In a first aspect, the present invention is a polymer composition consisting of: (a) at least one component of high impact polystyrene (HIPS) comprising: (i) a block copolymer of styrene and a rubber-like diene with conjugated double bonds, where the copolymer is grafted onto polystyrene; (ii) optionally, two weight percent or more and 8 weight percent or less of a rubber homopolymer by weight of the component of the HIPS; (iii) the total content of rubber-like diene with conjugated double bonds from one mass percent or more to seven mass percent or less of the total mass of the component of the HIPS; (iv) a gel concentration of less than 10 wt.%, determined by extraction with a mixture of methyl ethyl ketone / methanol; (v) an average rubber particle size of less than 1.0 micrometer, and 0.01 micrometer or more; (vi) from about 40 to 90 volume percent of rubber particles with a diameter of about less than 0.4 microns, and from about 10 to 60 volume percent of rubber particles with a diameter of from about 0.4 to 2.5 microns; (vii) most rubber particles with core-shell morphology; (viii) and which is present at a concentration of at least about 10 weight percent and up to not more than 70 weight percent by weight of the polymers in the composition, and is one or more and five or less percent by weight of the weight of the rubbery diene relative to the total mass of the composition; and (b) at least one general purpose polystyrene with a weight average molecular weight of more than 200,000 grams per mole and 350,000 grams per mole or less, and which is present at a concentration of at least about 10 weight percent and not more than 50 weight percent of the weight of the polymers in the composition; and (c) at least one styrene block copolymer, which is present at a concentration of at least about 2 weight percent and up to about 80 weight percent of the weight of the polymers in the composition; (a), (b) and (c) comprise 100 percent by weight of the polymers in the polymer composition. This polymer composition is optionally mixed with additives known in the art, up to about 5 weight percent of the combined weight of the polymer composition and additives, to obtain a composition suitable for the production of films.

In a second aspect, the invention is an oriented film consisting of from 95 to 100 weight percent of the polymer composition of the invention and from 0 to 5 weight percent of additives, where percent is calculated from the combined weight of the polymers and additives; and where it is preferred that the film has a stretch ratio in the main stretch direction (typically MDO for ROSO or TDO for tubular applications) of more than 4: 1, more preferably 6: 1, and a stretch ratio in the direction of less stretch of 1.2: 1 or less, and where the degree of stretching in the direction that has received a large stretch is greater than the degree of stretching in the other direction.

In a third aspect, the present invention is a shrink label comprising an axially unbalanced oriented polymer film (i.e., a film having a degree of orientation in MD other than that in TD) of the first aspect, wherein it is preferred that the film has a print on one or both sides. Preferably, the shrink label is either a ROSO label or a sleeve label, most preferably a sleeve label.

DETAILED DESCRIPTION OF THE INVENTION

The films of the present invention include a polymer composition comprising an HIPS component, general purpose polystyrene (ONPS), a styrene block copolymer component. The combination of the HIPS component, ONPS and the styrene block copolymer component is 100 percent by weight (wt.%) By weight of the polymers in the composition, not counting the additives, i.e., by weight of the polymer composition. Preferably, the polymer composition is 95 wt.% Or more, preferably 97 wt.% Or more, and may include 100 wt.% Of the total weight of the film composition or film weight. When the polymer composition is less than 100 wt.% Of the film, the missing up to 100 wt.% Of the amount are additives, including any additives that may be part of the HIPS component, ONPS, and styrene block copolymer components supplied by the industry or specially synthesized . Additives include fillers known in the art, process improvers, friction reducing agents, or plasticizers, and optionally include polymer additives.

For the purposes of this application, all percentages, preferred amounts or measurements, ranges and their limiting values are inclusively different, that is, the expression “about less than 10” includes a value of about 10. Therefore, the expression “at least” is equivalent to the expression “greater than or is equal to "and therefore the expression" no more than "is equivalent to the expression" less than or equal to ". The expression for the numerical value "or more" is equivalent to the expression "at least" this numerical value. Similarly, the expression “or less” after a numeric value is equivalent to the expression “no more than” is a numeric value. Here, the numerical values have an accuracy not higher than that indicated. Therefore, the value "105" includes at least values from 104.5 to 105.49. In addition, all lists are inclusive-different for combinations of two or more elements of this list. All ranges from numerical parameters described as “at least”, “greater than”, “greater than or equal to” or similar, to numerical parameters described as “no more than”, “up to”, “less than”, “less than or equal to” or similar are preferred intervals, regardless of the relative degree of preference indicated for each parameter. Therefore, an interval that has a preferred lower limit combined with the most preferred upper limit is preferred for practicing this invention. All quantities, ratios, contents and other measured quantities are expressed by weight unless otherwise indicated. Unless otherwise indicated, all percentages refer to weight percentages of the total weight of the composition in accordance with an embodiment of the invention, excluding percentages of monomers in the polymer, and unless otherwise indicated, are weight percent. Unless otherwise indicated or it is obvious that otherwise is not possible for those skilled in the art, the steps of the method described herein are not necessarily carried out in a sequence different from the sequence in which the steps are discussed here. In addition, the steps are optionally carried out separately, simultaneously or with overlapping in time. For example, in the art, stages such as heating and mixing are often carried out separately, simultaneously or with partial overlap in time. Unless otherwise specified, when an element, material or stage capable of causing undesirable effects is present in such quantity or in such a form that they do not cause an undesirable effect to an unacceptable degree, they are considered practically absent in the practice of this invention. In addition, the terms “unacceptable” and “unacceptable” are used to indicate deviations from indicators that may be useful in industrial use, or useful in a given situation, or outside predefined limits that vary in specific situations and applications, and may be established by a preliminary definition, such as determining technical specifications. For specialists in this field, it is obvious that acceptable limits depend on the type of equipment, conditions, applications and other variables, and they can be determined without undue experimentation in each case of their use. In some cases, a change or deviation of one parameter may be acceptable when another goal is required.

The term “comprising” is synonymous with the term “comprising”, “comprising” or “intrinsic” and is inclusive-distinguishing or unlimited, and does not exclude additional, non-listed elements, materials or steps. The term "consisting essentially of" indicates that, in addition to the indicated elements, materials or steps, elements, unspecified materials or steps may be present in amounts that do not unacceptably perceptibly affect at least one basic and new feature of the subject matter. The term “consisting of” indicates that only the claimed elements, materials or steps are present. The term “comprising” includes the terms “consisting essentially of” and “consisting of”.

The HIPS component is a styrene polymer containing a grafted rubber component. The grafting of the rubber component on polystyrene can increase the toughness and mechanical strength of polystyrene. The bonding of rubber to polystyrene by grafting has technical advantages over simply mixing polystyrene with a rubber component. The addition of rubber usually allows a material with higher elasticity and equivalent impact strength to be obtained at a lower rubber content than with a simply mechanically mixed rubber. The rubber component is grafted onto the styrene polymer by combining the rubber component with styrene monomers, usually by dissolving the rubber in styrene monomers before polymerizing the styrene monomers. Polymerization of styrene monomers then leads to the formation of a matrix of polystyrene containing rubber grafted onto styrene polymers.

To ensure the required level of technological characteristics and mechanical properties, the polystyrene matrix in the composition usually has a sufficiently high weight average molecular weight (Mw), which usually is at least 100,000, preferably at least about 120,000, more preferably at least , about 130,000, and most preferably at least about 140,000 grams per mole (g / mol). In order to ensure appropriate process characteristics, polystyrene typically has an Mw that is less than or equal to about 260,000, preferably less than or equal to about 250,000, more preferably less than or equal to about 240,000 and most preferably less than or equal to about 230,000 g / mol. Polystyrene Mw matrices are measured by gel permeation chromatography using a polystyrene standard for calibration.

The rubber component is a copolymer of a rubber-like diene with conjugated double bonds and styrene (a copolymer of rubber) or a mixture comprising a copolymer of rubber and a small amount of a homopolymer of a rubber-like diene with conjugated double bonds (rubber homopolymer). The conjugated double bond diene in both rubbers is usually 1,3-alkadiene, preferably butadiene, isoprene or butadiene and isoprene, most preferably butadiene. Preferably, the copolymer of a rubber-like diene with conjugated double bonds is a styrene / butadiene (C / B) block copolymer. The desired rubber homopolymer is polybutadiene.

It is desirable that the rubber copolymer has an Mw of the order of 100,000 g / mol or more, preferably 150,000 g / mol or more, and preferably 350,000 g / mol or less, preferably 300,000 g / mol or less, more preferably 250,000 g / mol or less. Measure Mw using gel permeation chromatography at three light scattering angles.

In addition, it is desirable that the rubber copolymer has a solution viscosity in the range of about 5 to 100 centipoise (cP) (about 5 to 100 millipascal seconds (mPa · s)), preferably about 20 to 80 cP (about 20 up to 80 MPa · s); and a cis unit content of at least 20%, preferably at least 25%, and more preferably at least about 30%, and preferably 99% or less, preferably 55% or less, more preferably 50% or less. Examples of preferred rubber copolymers are rubber of the brand Buna BL 6533 T and other similar rubbers.

The inclusion of a rubber homopolymer with a rubber copolymer upon receipt of the HIPS component can help increase the mechanical characteristics of the HPS polymer as a result of an increase in tensile strength at break. It is desirable that suitable rubber homopolymers have a second-order transition temperature of the order of zero degrees Celsius (° C) or less, preferably −20 ° C or less. Preferably, the rubber homopolymer has a solution viscosity in the range of about 20 to 250 cP (about 20 to 250 mPa · s), more preferably about 80 cP to 200 cP (about 80 to 200 mPa · s). It is desirable that the rubber homopolymer has a cis unit content of at least about 20%, preferably at least about 25% or more, preferably at least about 30%, and preferably about 99% or less, preferably 55% or less, more preferably 50% or less. It is desirable that the rubber homopolymers have an Mw of the order of 100,000 g / mol or more, more preferably 150,000 g / mol or more, and preferably 600,000 g / mol or less, preferably 500,000 g / mol or less. Measure Mw using gel permeation chromatography at three light scattering angles. An example of a suitable rubber homopolymer is the rubber brand Diene (TM) 55 (Diene is a trademark of Firestone).

The rubber homopolymer, if present, typically comprises at least about 2 wt.%, Preferably at least about 4 wt.%, More preferably at least about 6 wt.%, And most preferably at least about 8 wt.% of the total mass of rubber in the HIPS polymer. To prevent too low transparency or brightness, it is desirable that the content of the rubber homopolymer is 25 wt.% Or less, preferably 20 wt.% Or less, more preferably 16 wt.% Or less, and most preferably 12 wt.% Or less than the total mass of rubber.

The HIPS component has a total content of the diene component from the rubber component (i.e., the content due to the presence of a rubber-like diene with conjugated double bonds, both as a rubber copolymer and a rubber homopolymer upon receipt of the HPS component) of about one wt.% Or more, preferably 1.5 wt.% Or more, more preferably 2 wt.% Or more, even more preferably 2.5 wt.% Or more, and most preferably 3 wt.% Or more by weight of the HIPS component. Rubber concentrations below about 1 wt.% Do not allow to obtain the required level of mechanical strength and toughness. To ensure the required transparency, the rubber concentration is usually 7 wt.% Or less, preferably 6 wt.% Or less, more preferably 5 wt.% Or less, even more preferably 4 wt.% Or less, based on the total weight of the HIPS component .

Without delving into the theory, it should be noted that to prevent a high degree of crosslinking in the rubber particles and reduce the likelihood of gel formation, lower rubber concentrations, such as 7 wt.% Or less by weight of the HSS, are desirable. Meanwhile, while some crosslinking in the rubber is desirable to maintain the integrity of the rubber during shear deformation during film production, a high degree of crosslinking may impede the ability of the rubber particles to deform during film orientation. The brightness and transparency of the film increases as the rubber particles are deformed into particles with higher size ratios. Particles of rubber with a lower degree of crosslinking tend to deform and more easily maintain a deformed shape than particles of rubber with a higher degree of crosslinking, which makes less crosslinked particles more suitable for bright and transparent films. It is difficult to determine the specific concentration of rubber at which the degree of crosslinking becomes undesirably high, since it depends on the specific processing conditions. Even rubber concentrations of 12 wt.% Or more by weight of the HIPS lead to an undesirable high degree of crosslinking.

Similarly, without delving into theory, the quality of the films of the present invention is likely to be positively affected by a lower degree of gelation as a result of a lower concentration of rubber. Gels are formed as a result of extensive crosslinking of rubber agglomerates, which are destroyed by shear into small particles during film production. Crosslinked agglomerate gels can cause problems in the production of the film, for example, rupture due to blowing during the production of the film by blown extrusion. Agglomerate gels also adversely affect the quality of the film, which manifests itself in the form of defects of inhomogeneity in the film and the appearance of sagging in the films wound over the agglomerate particles. The weights lead to problems when printing is applied to the film, since they prevent the application of ink on depressed portions of the film surface.

In addition, the HIPS component has a gel concentration determined by extraction with a mixture of methyl ethyl ketone / methanol, which is less than 10 wt.% Relative to the total weight of the HPS component. Such a low gel concentration is desirable to achieve maximum film brightness. The extraction with a mixture of methyl ethyl ketone / methanol is similar to the method for determining the concentration of the gel described in the patent document Unexamined Japanese Patent Application Kokai No. P2000-351860A. Namely: they dissolve the HIPS sample (sample weight equal to W1) in a mixed solvent methyl ethyl ketone / methanol (volume ratio 10: 1) at room temperature (about 23 ° C). The insoluble fraction is separated by centrifugation. The insoluble fraction is isolated and dried. The mass of the isolated and dried fractions of the insoluble fraction is W2. The gel concentration in wt.% Is equal to 100 x W2 / W1.

The HIPS component has a volumetric average rubber particle size of less than one micrometer (μm), preferably 0.5 μm or less, and usually 0.01 μm or more, preferably 0.1 μm or more, and more preferably 0.3 microns or more. This volumetric average rubber particle size is different from that for conventional HIPS materials that have an average rubber particle size of at least one micron (see, for example, US Pat. No. 6,897,260 B2, Col. 4, pp. 22-34; which illustrates the know-how and the content of which is given here by reference to it to the extent permitted by law). Small rubber particle sizes are desirable since they allow films with higher brightness and lower turbidity to be obtained than films with larger rubber particles. However, rubber particles of less than 0.01 μm, despite their transparency and brightness, do not allow the creation of wear-resistant compositions.

The rubber particles in the HIPS component have a wide particle size distribution when most of the particles are smaller and only a limited number of particles are larger. In particular, it is desirable to have a distribution in which from about 40 to 90 volume percent (vol.%) Of the particles have a diameter of about less than 0.4 microns. Accordingly, it is desirable to have a distribution of relatively large particles, in which about 10 to 60 vol.% Of the particles have a diameter of about greater than 0.4 μm, and about less than 2.5, preferably from about 15 to 55 vol.%, And more preferably, from about 20 to about 50 volume% of the particles have a diameter greater than or equal to about 0.5 microns, and less than or equal to about 2.5 microns. Preferably, for relatively large particles of this component, precisely defined percentages of particles have a diameter of about less than 2 microns, more preferably about 1.5 microns or less, even more preferably about 1.2 microns or less, even more preferably about 1 micron or less.

The particle size of the rubber is the size of the rubber-containing particles, including all occlusions of the monovinylidene aromatic polymer in the rubber particles. The rubber particle size was measured using an LS230 light scattering device and a Beckham Coulter software product. Manufacturer's Instructions and Publication (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) offer a measurement method particle size using a Beckham Coulter appliance. Preferably, using this instrument and software, the optical model for calculating the rubber particle size and distribution statistics is as follows: (i) the refractive index of the liquid is 1.43, (ii) the true refractive index of the sample is 1.57, and (iii) the apparent index the refraction of the sample is 0.01.

Most rubber particles, preferably 70% or more, more preferably 80% or more, more preferably 90% or more rubber particles in the HIPS component should have a core-shell particle morphology. Core-shell morphology means that rubber particles have a thin outer shell and contain a single, centered occlusion of the polymer matrix. This type of particle morphology is commonly referred to as a "single occlusion" morphology or "capsule" morphology. In contrast, morphology terms such as “weave” or “honeycomb” refer to other more complex morphologies of rubber particles, which include “entangled” structures, structures with “multiple occlusions”, structures like “labyrinth”, “spiral”, “ onion peel "or" concentric circle ". The percentage of rubber particles having a core-shell morphology is determined as a percentage of 500 particles from a snapshot of the HIPS component obtained using a transmission electron microscope.

Particles of the core-shell type in the HIPS component are crosslinked to such an extent that they are stretched, but not destroyed, under the action of shear fields (i.e., during the orientation process). Their thin walls (as a result of the high compatibility associated with the presence of rubber copolymers) become even thinner, but remain operational to provide the necessary mechanical and tensile strengths. Apparently, with film orientation, the oriented rubber morphology is very close to the joint continuous distribution of very thin rubber tapes, possibly as a result of the low number of multi-occlusion particles in the system (cellular morphology). Very thin shell walls have better light transmission than thicker walls, and are definitely better than honeycomb or multi-occlusal particles if they remain, which are not distributed as very thin ribbons during orientation.

The HIPS component does not necessarily contain or optionally contain 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 typically contains at least about 0.4 wt.%, Preferably 0.6 wt.% Or more, more preferably 0.8 wt.% Or more, and even more preferably 1 wt.% Or more mineral oil from the total mass of the component of the HIPS. In order to obtain the desired brightness, the HIPS component usually contains less than about 3 wt.%, Preferably 2.8 wt.% Or less, more preferably 2.6 wt.% Or less, and most preferably 2.4 wt. % or less of mineral oil from the total mass of the component of the HIPS.

A suitable material for use as a component of the HIPS is the material described in patent publication US 2006-0084761 “IMPROVED RUBBER MODIFIED MONOVINYLIDENE AROMATIC POLYMERS AND THERMOFORMED ARTICLES”.

The HIPS component is different from the standard HIPS obtained by polymerization in bulk or in a solution, since the particle size distribution of rubber is relatively wide and most rubber particles have a core-shell structure. In contrast, traditional HIPS resins typically have a relatively narrow particle size distribution and a predominantly or at least a larger percentage of particles with a honeycomb, multi-occlusion structure.

Preferably, the compositions and films of the present invention contain at least about 10, more preferably at least about 20, most preferably at least about 25, and preferably not more than about 70, more preferably not more than about 65, most preferably not more than about 60 weight percent of the total amount of polymer present in the HIPS component.

The total rubber content (based on the total content of the diene from the copolymer and homopolymer) due to the HIPS component in the films of the present invention is 1 wt.% Or more, preferably 3 wt.% Or more, and 5 wt.% Or less of the total weight films.

The polymer composition of this film contains crystalline polystyrene, also called general purpose polystyrene (ONPS). It is preferred that the ONPS for use in the present invention has an Mw of more than 200,000 g / mol, preferably 280,000 g / mol or more and 350,000 g / mol or less, preferably 320,000 g / mol or less. Measure Mw using gel permeation chromatography and a known standard. It is desirable that the ONPS has a melt flow rate (MFR) of one or more, preferably 1.2 grams per 10 minutes (g / 10 min) or more, and preferably 3 g / 10 min or less, preferably 2 g / 10 min or less. Measure the STR in accordance with ASTM standard D1238. ONPS may or may not contain plasticizers, such as mineral oil, ethylene glycol or propylene glycol, phthalates or styrene oligomers. Plasticizers, if used, are usually present at a concentration of 4 wt.% Or less, preferably 3 wt.% Or less, based on the weight of the ONPS. In case of use, the plasticizer is usually one wt.% Or more by weight of the ONPS. Examples of suitable ONPS include general purpose polystyrene grades STYRON (R) 665 (STYRON is a trademark of The Dow Chemical Company), STYRON 663, STYRON 685D, STYRON 660, and STYRON 6856E.

Preferably, the compositions and films of the present invention contain at least 10, more preferably at least about 20, most preferably at least about 35, and preferably not more than about 50, more preferably not more than about 45, most preferably not more than about 40 weight percent of the component of the ONPS of the total amount of polymer present.

The third component of the composition is at least one styrene block copolymer. The term “styrene block copolymer or styrene block copolymer” means a polymer having at least one segment of a styrene monomer block in combination with at least one segment of a saturated or unsaturated rubber monomer, and more preferably not having a polymer block which is neither rubber nor styrene. Suitable styrene block copolymers having unsaturated rubber monomer fragments include, but are not limited to, styrene-butadiene (SB), styrene-isoprene (SI), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS) , α-methyl-styrene-butadiene-α-methylstyrene, α-methylstyrene-isoprene-α-methyl-styrene, and other similar block copolymers. As used herein, the term “styrene-butadiene block copolymer” includes SB, SBS, and higher amounts of styrene and butadiene blocks. Similarly, the term “styrene-isoprene block copolymer” is used to include polymers having at least one styrene block and one isoprene block. The structure of the styrene block copolymers used in the present invention may be linear or radial, and may be a diblock, triblock, or have more blocks. In some embodiments, it is desirable that the styrene block copolymers have at least four different blocks or a pair of two repeating blocks, for example repeating styrene / butadiene or styrene / ethylene-propylene blocks. Styrene block copolymers are well known to those skilled in the art and are commercially available from Dexco Polymers under the VECTOR trademark, KRATON Polymers under the KRATON trademark, Chevron Phillips Chemical Co. under the trademark SOLPRENE and K-Resin, and BASF Corp. under the trademark Styrolux. Styrene block copolymers are optionally used individually or in combinations of two or more block copolymers.

Preferably, the styrene portion of the block copolymer is a polymer or interpolymer of styrene or its analogues or homologues, including α-methylstyrene, and ring-substituted styrenes, in particular methylated in the ring styrene. Preferred styrene compounds are styrene and α-methylstyrene, with styrene being particularly preferred.

The rubber portion of the block copolymer is optionally either unsaturated or saturated. Block copolymers with unsaturated fragments of rubber monomer may include homopolymers of butadiene or isoprene, and copolymers of one or both of these two dienes with a small amount of styrene monomer. When the monomer used is butadiene, it is preferred that about 35 to 55 mole percent of the condensed butadiene moieties in the polymer butadiene block have a 1,2 configuration. When such a block is hydrogenated, the resulting product is a regular block copolymer of ethylene and 1-butene (EB), or resembles it. If isoprene is used as a conjugated diene, the resulting hydrogenated product is a regular block copolymer of ethylene and propylene (EP) or resembles it. Preferred block copolymers have unsaturated fragments of rubber monomer, more preferred include at least one segment of a styrene fragment and at least one segment of butadiene or isoprene, with SBS and SIS are most preferred. Among them, when a stretch irrigation line is used in the film production, block copolymers of styrene and butadiene are preferred, since in this case the film has a higher brightness and lower haze compared to SIS. However, in blown film processes, styrene-isoprene block copolymers are preferred because of their lower tendency to crosslink to form gels during production compared to SBS.

Among the styrene block copolymers, those having one property, preferably two, or more preferably all three properties of brightness, impact resistance and elastomeric nature, are preferred.

In the practice of the present invention, the elastomeric styrene block copolymers provide a more preferred toughness and lower stiffness than if these characteristics were obtained in the absence of the block copolymer. Preferably, the elastomeric character is manifested in the value of the elongation at break equal to at least about 200, preferably at least about 220, more preferably at least about 240, most preferably at least about 260 and preferably not more than about 2000, more preferably not more than about 1700, most preferably not more than about 1500 percent, measured using ASTM D-412 and / or D-882 techniques. In industrial production, most polymers of this type contain 10-80 wt.% Styrene. Within the specific type and morphology of the polymer, as the styrene content increases, the elastomeric properties of the block copolymer decrease.

It is desirable that the block copolymers have a melt flow rate (MFR) of at least about 2, preferably at least about 4 grams in 10 minutes (g / 10 min), and preferably not more than 20 g / 10 min, preferably not more than 30 g / 10 min. Measure the STR in accordance with ASTM standard D1238 condition G.

Preferred styrene block copolymers are extremely transparent (have high, that is, in preferred intervals, brightness), preferably having a brightness measured in accordance with ASTM D1746, corresponding to at least about 85%, preferably at least about 90% of visible light transmission. It is believed that such transparency is a consequence of the very small size of the domain, which is usually about 20 nm. In block copolymers, domain sizes are determined primarily by the molecular weights of the blocks.

It is preferable that the styrene block copolymers are also sufficiently impact resistant to increase the wear resistance when using films as compared to the wear resistance of films having a similar composition (component content) but not containing styrene block copolymers. The notched Izod impact strength is measured in accordance with ASTM D-256 and it is preferable that the measurements be carried out under the condition of no rupture when tested at 72 ° F or 23 ° C.

It is particularly preferred that the block copolymer of styrene and butadiene have a radial block configuration or in the form of a star with polybutadiene in the core and polystyrene at the ends of the rays. Such polymers are referred to herein as star-shaped block copolymers of styrene and butadiene, and they are know-how and commercially available from Chevron Phillips Chemical Co. under the trade name K-Resin. These polymers contain about 27% butadiene or more in the form of a star-shaped block and are often characterized by a bimodal molecular weight distribution of polystyrene. The inner segments of polybutadiene have approximately the same molecular weights, while the outer segments of polystyrene have different molecular weights. These features facilitate the adjustment of the thickness of the polybutadiene segment to obtain improved brightness. For high brightness, it is preferred that the thickness of the polybutadiene segment is about one tenth of the wavelength of the visible spectrum or less.

The styrene block copolymer component is used to improve toughness and reduce stiffness compared with these indicators for compositions containing other components, but without the block copolymer. However, the introduction of high amounts of the styrene-isoprene-styrene component can lead to a decrease in the brightness and transparency of the films. Preferably, the styrene copolymer is present in an amount of at least about 2 weight percent of the polymers in the film or composition, more preferably at least about 3, most preferably at least about 4, preferably not more than about 80 more preferably not more than about 75, most preferably not more than about 70 weight percent of the weight of the polymers in the film or the mass of the mixture (composition) used to make the film. In the ranges of these preferred amounts, when the block copolymer is a styrene-butadiene block copolymer, i.e. preferably SB or SBS, preferably, the amount is at least about 20, more preferably at least about 30, most preferably at least about 40, and preferably not more than about 80, more preferably not more than about 75, most preferably not more than about 70 weight percent of the total weight of the polymers in the film or composition. A content of styrene-butadiene block copolymer of more than about 80 weight percent leads to an undesirable decrease in 1% of the secant modulus and glass transition temperature, as a result of which film shrinkage may occur at low temperatures, for example below about 80 ° C. However, since SIS and SIS / SI at amounts of about 10 weight percent or more can lead to smokiness, lower contents of the styrene-isoprene block copolymer component are preferred. Preferably, the amount of styrene-isoprene block copolymer, when present, is at least about 1, more preferably at least about 2, most preferably at least about 3, and preferably not more than about 9, more preferably no more than about 8, most preferably no more than about 6 weight percent of the total weight of the polymers in the mixture or film. These amounts are preferred regardless of whether the SIS or SI block copolymers are used alone or together with other styrene block copolymers.

The films of the present invention have a preferred orientation in the direction in which they receive the greatest tension when forming or processing the film. The resulting film shrinks preferably in the direction in which the film was stretched to a greater extent during the manufacturing process. The longitudinal direction (MD) is the direction of movement of the film during or after extrusion or inflation of the film. The transverse direction (TD) is perpendicular to the longitudinal direction of movement of the film (MD). Shrinkage occurs preferably in the longitudinal direction orientation (MDO) if more tension is applied in MD than in TD, and in TDO if more tension is applied perpendicular to the longitudinal direction. Preferred TDO is the reason that the film of the present invention shrinks predominantly in TD with heat input, for example, in a sleeve label. Preferred MDOs result in greater shrinkage in the longitudinal direction than in TD commonly used for ROSO labels.

The films of the present invention have an MDO or TDO ratio (ratio of oriented length to non-oriented length in the direction of greatest drawing, MD or TD, respectively), preferably at least about 3: 1, preferably at least about 4: 1, more preferably at least about 5: 1, even more preferably at least about 6: 1. Films typically have a TDO ratio greater than their MDO ratio so that they can be used when applying a shrink sleeve label, or an MDO ratio greater than the TDO ratio so that they can be used for ROSO labels. Films having TDO for sleeve application or MDO for ROSO application of less than 3: 1 have insufficient directional orientation (DO), or MDO, or TDO, depending on use, to fit snugly to the container when applying the shrink label. There is no clear upper limit for the DO ratio, although films typically have a DO ratio of 10: 1 or less. For films having a DO ratio of more than 10: 1, there is a possibility of such a degree of shrinkage around the container when applying the label that the adhesive bond holding the label around the bottle may weaken or cease to function.

The MDO ratio and TDO ratio are measured by using a 4-inch (10.16 cm) oriented film sample in both MD and TD (i.e. square samples). Place the sample in an air-heated oven at 120 ° C for 10 minutes and then measure the MD and TD sizes again. The ratio of the MD and TD measurements before and after heating corresponds to the MDO ratio and the TDO ratio, respectively.

It is desirable that the films of the present invention have shrinkage at 110 ° C, preferably at 100 ° C, at least about 20%, preferably at least about 30%, preferably at least about 40%, preferably at least about 50%, more preferably at least about 60%, most preferably at least about 70%, in the most elongated direction. Shrinkage below 20% may undesirably limit the tightness of the film to the contour of the container. Although the upper limit for the degree of targeted shrinkage is not known, it should be below 100%.

Desirably, the films exhibit oppositely directed shrinkage at 100 ° C, preferably at 110 ° C, at least about 5%, more preferably at least about 7, most preferably at least about 10 percent in the direction of smallest shrinkability. Films having shrinkability in the direction of less shrinkability of less than about 5% usually retain integrity during operation and crack when bent. Therefore, a certain amount of orientation and seating is desirable to improve film integrity. Extensive shrinkage in the direction of less stretching affects the performance of the film when applying the shrink label as a result of compression of the film and therefore distortion of the label in the other direction. Therefore, the films of the present invention usually have an orientation index in the direction of less tension not more than about 1.2: 1, preferably not more than about 1.15: 1, corresponding to shrinkage not more than about 20%, preferably not more than about 15% .

In addition, it is desirable that the films of the present invention are characterized by no more than about 10% increase in length (increase) in the direction opposite to the main direction of sitting, in the direction opposite to the main stretching, at 110 ° C, preferably at 100 ° C. (In the case of films that shrink by more than 20% or elongate by more than 10% in this direction at the indicated temperatures, problems arise when the film does not adhere to the container when shrink labels are applied due to distortion in this direction.) Shrink in accordance with ASTM standard method D-1204. In addition, it is desirable that the films of the present invention have a relatively low magnification in the direction of unintended stretching or the direction of less stretching in the test methods described in patent document USP 6897260 B2.

The presence of the HIPS component provides the films of the present invention with the desired high brightness and transparency while increasing the toughness of the film. Brightness and transparency are desirable properties of labels produced in the industry to provide a distinctive look for the product around which the label is located. High brightness and transparency are also desirable when printing the label "on the back", when the printed seal is located between the label and the container, and the consumer sees the printed print through the label. Typically, the films of the present invention upon receipt of them on industrial equipment, that is, equipment used for the industrial production of label films, have brightness values at a film thickness of 2.0 mils (50 μm) of at least about 10, preferably at least , about 15, preferably at least about 20, more preferably at least about 25, most preferably at least about 30. For specialists in this field it is obvious that thicker films have a lower brightness than more thin film of identical composition and manufactured by the same method. Measure the brightness in accordance with ASTM standard method D-1746.

Measurements of haze values also characterize the observed brightness of the film, with a low haze value corresponding to high brightness. The smokiness values for the films of the present invention may vary up to any possible value. However, one advantage of the present invention is the ability to produce oriented films with high brightness and low smoke. Typical haze values for the present films at a film thickness of 2.0 mils (50 μm) are not more than about 15, preferably not more than about 10, more preferably not more than about 6, most preferably not more than about 4. Measure smokiness in accordance with the standard method D-1003.

The styrene-based film preferably has a higher secant modulus than, for example, oriented polypropylene or oriented polyvinyl chloride films. An increase in the secant modulus of the film for the shrink label is desirable from the point of view of preventing possible stretching of the films during printing. As a result, the films of the present invention can move at higher print speeds without the risk of tearing the film or distortion, compared with a film with a lower secant module without the HIPS component. The films of the present invention have a one percent secant modulus in both MD and TD of at least about 90,000 psi (620 megapascals (MPa)), preferably at least about 100,000 psi (690 MPa), more preferably at least about 200,000 psi (1380 MPa). A one percent secant modulus was measured using ASTM D-882.

Similar to films with a high secant modulus, films with a high tensile stress at break, in particular in MD, are desirable from the point of view of the possibility of faster movement of the films and their higher tension in the printing process without stretching, compared to films with a lower tensile stress. It is desirable that the films of the present invention have a tensile stress at break of at least about 2000 psi (14 MPa), preferably at least about 2500 psi (17 MPa), more preferably at least about 3000 psi (21 MPa) and most preferably at least about 4000 psi (28 MPa). The tensile stress at break is measured in accordance with ASTM D-882.

Films with a high relative tensile strain at break are desirable from the point of view of the possibility of printing and moving the film in high-speed process equipment without delaminating the film. It is desirable that the films of the present invention have a relative tensile strain at break in both directions of the test of at least about 30 percent, preferably at least about 35 percent, more preferably at least about 40 percent and most preferably at least about 45 percent. The percent strain at break is measured in accordance with ASTM D-882. It is desirable that the films of the present invention have an impact strength measured in accordance with ASTM D-882 methods of at least about 2000 psi (14 MPa), preferably at least about 2500 psi (17 MPa), more preferably at least about 3000 psi (21 MPa), and most preferably at least about 4000 psi (28 MPa).

The films of the present invention typically have a thickness of at least about one mils (25 μm), preferably at least about 1.5 mils (38 μm), and usually no more than about 4 mils (100 μm), preferably not more than about 3 mils (76 microns). With a thickness of less than one mil (25 μm), it becomes difficult to cut the film during processing and transportation. Thicknesses greater than 4 mils (100 μm) are technically achievable, but usually economically unacceptable.

It is desirable that the films of the present invention have internal stresses caused by orientation (ORS) of 400 psi (2758 kPa) or less. ORS is a measure of the stress a film experiences during sitting while heating. Lowering the ORS values when sitting the film is desirable. Shrink films typically have at least one end glued to a container around which the film is applied. Labels with high ORS values can cause such tension in the glue line that holds the label around the container during sitting, which is enough to damage or break the glue line. Lowering the ORS values reduces the likelihood of damage or destruction during the sitting process of the seam line (film on film).

The films of the present invention are produced using any oriented film production methods, including a blown film method and stretch irrigation methods. Especially desirable are methods for producing a film by blown extrusion, for example, those described in US 6897260 and GB 862966 (the contents of which are incorporated herein by reference).

To prevent unwanted crosslinking, treatment temperatures and residence times must be minimized. Preferably, the melt temperatures are below 230 ° C, preferably below about 220 ° C, more preferably below about 210 ° C. The higher the melt processing temperature, the shorter the time the polymer can be at this temperature until unacceptable decomposition. For example, it is preferable that the effects of temperatures above about 230 ° C be limited to less than about 10 minutes, more preferably less than about 7 minutes, most preferably less than about 300 seconds.

One suitable method (“Method A”) for producing a film of the present invention is a method for producing a film by blown extrusion using the apparatus described in US Pat. from 170 ° C to 100 ° C; then the polymer melt is cooled to a temperature in the range from 130 ° C to 170 ° C, in order to increase the viscosity of the melt before extruding the polymer melt through a die for blowing a film in a gas atmosphere. The gas atmosphere is maintained at a temperature of at least 40 ° C below the temperature of the permissible deformation of each component (s) of the polymer composition (the HIPS component and, if present, the ONPS component and / or the styrene block copolymer component) in the polymer melt. The extrudable polymer melt is inflated in accordance with the method for producing a sleeve film disclosed in GB 862966.

Another possible blown film method (“Method B”) suitable for producing the film of the present invention uses two extruders connected in series (extruder 1 and extruder 2). Extruder 1 is a 24: 1 single screw extruder with a diameter of 2-1 / 2 inches (6.35 cm) with five zones in the cylinder of the extruder, the temperature in each of which is set from 155 ° C to 200 ° C, usually raising the temperature to the bottom of the extruder. Extruder 2 is a 32: 1 single screw extruder with a diameter of 3-1 / 2 inches (8.89 cm) with an insulated mixer screw and five zones in the extruder barrel, the temperature in each of which is usually set from 115 ° C to 175 ° C. The polymer tablets are introduced into the extruder 1 to plasticize the polymer and the polymer is pumped into the extruder 2 at a temperature of 200-260 ° C. The polymer is fed from the extruder 1 through a pumping line to the inlet of the extruder 2. Cool the polymer in the extruder 2 to a melt temperature (extrusion temperature), selected in the range of 150-190 ° C, to achieve stable bloating and to optimize the properties of internal stresses caused by orientation ( ORS) of the resulting film, to the desired value. The polymer is cooled by cooling the walls of the extruder 2. Extrude the polymer from the extruder 2 through a mouthpiece with an annular nozzle of 3.25 inches (8.3 cm) and then through an annular gap for supplying air with a diameter of 4.5 inches (11.4 cm) and blow or stretch the polymer into a sleeve with a diameter that is typically in the range of 9 inches (22.9 cm) to 24 inches (63.5 cm). The sleeve film blowing method described in GB 862966 is used.

In another embodiment, a preferred method for producing films is a stretch-filling method (“Method C”). First, a film or sheet is cast, that is, a non-sagging film or sheet is molded from a melt fed by an extrusion system. The resin is extruded through a slit in the form of a flat sheet, with a thickness of about 0.3-2.5 mm, onto a cooled polished drum for irrigation at a temperature of from 30 to about 70 ° C to form a monolayer film. The speed of the irrigation drum is adjusted to obtain a film thickness of about 0.3 to 1 mm. This film or sheet is moved by means of rolls into a heated chamber containing a frame for stretching and orientation. The air in the chamber is heated to a temperature sufficient to heat the film or sheet to a temperature that allows stretching without breaking, depending on the film composition, from about 95 ° C to 150 ° C. The frame for stretching and orienting has two adjacent chain drives that diverge at a constant angle. The film is held onto the drives by means of film clips. The divergence of the chains causes the polymer to stretch as it moves along the chain drive and gives it the desired orientation. The degree of drawing is determined by the speed of the chain, the angle of divergence and the degree of orientation. To achieve the above tensile values and appropriate shrinkage, the degree of orientation is determined by the ratio of the width of the incoming film to the width of the film exiting the system. This gives the film a predominantly TD orientation. The film is then normalized, if necessary, and released as a finished product. In most cases, the edges of the film are cut, shredded, and reused, and the film is optionally rolled into a full-width roll or cut into pieces with a narrower width, which are optionally processed to improve printable properties, and then rolled up for further processing. If required, give the film longitudinal orientation in the previously described degree or by orienting it in the longitudinal direction with successively accelerating rolls at any stage when the film or sheet is sufficiently heated to stretch, for example, when the film or sheet is molded or before quick cooling, when heated for TD orientation; or at a separate stage.

The films of the present invention are effective for any application that requires shrinkage when heated. Films are particularly effective as shrink labels. To turn the film of the present invention into a shrink label of the present invention, cut the film to the desired width and corona discharge side of the film (in any order) and then print on the corona treated side of the film. The print may be on the "back" side of the film to create a print of the label on the back side. The reverse side of the film is adjacent to the container, and the printed print on the reverse side is visible through the film when the film is wrapped around the container when applying the shrink label. These stages are usually performed with continuous movement of the tape using any method used in the art.

Preferably, the films and labels of the present invention can also have perforations through the film or label. It is desirable that the perforations are generally located in that part of the film that is closer to the narrowest part or parts of the container around which the film is applied. Perforations allow gas to be released that could get between the label and the container, thereby ensuring a more snug fit between the label and the container. The films and labels of the present invention may contain perforations uniformly distributed over the surface of the film, or contain perforations specially located near the areas of the film (or label), preferably in the area that will align with the narrowest parts of the container around which the film (or label ) Punching of the films and labels of the present invention can be carried out at any time, however, in order to facilitate printing of the labels, it is desirable to perforate the films and labels after printing.

The objectives and advantages of the present invention are further illustrated by the following examples. The specific materials and their quantities, as well as other conditions and details described in these examples, should not be construed as limitations of this invention. Unless otherwise indicated, all percentages, parts, and ratios are calculated by weight. Examples of the invention are numbered numerically, while comparative examples, which are not examples of the invention, are numbered.

HIPS-X COMPONENT FOR EXAMPLES 1-4 AND COMPARATIVE SAMPLES B AND D

Further, in Examples 1-4 and Comparative Samples B and D, HIPS-X is used as a component of HIPS. Get HIPS-X, for example, in the following continuous process using three in series reactors with a stirrer. An injectable rubber solution is prepared by dissolving the rubber components shown in Table 1 in styrene with a rubber component ratio of 1 part Diene 55 to 15 parts Buna 6533 (i.e. 0.3 wt.% Diene 55 and 4.5 wt.% Buna 6533 of the total mass of the introduced rubber solution). Enter 2.5 wt.% Mineral oil (with a kinetic viscosity of 70 centistokes) and 7 wt.% Ethylbenzene with an injected rubber solution with the formation of a flow of incoming material, and wt.% Refer to the total mass flow of the incoming material. Add 0.1 wt.% Of the antioxidant Irganox 1076 to provide concentrations of about 1200 parts per million (ppm) in the finished product. Missing up to 100 wt.%. styrene is part of the feed. The flow of incoming material is fed into the first reactor at a speed of 750 grams per hour (g / h). The necessary content of the rubber mixture in the feed stream and the feed rate of styrene and rubber to the reactor are maintained to produce rubber-modified polystyrene (HPS-X) containing 4% by weight of butadiene.

Each of the three reactors has three zones with independent temperature control. Use the following temperature profile: 125, 130, 135, 143, 149, 153, 157, 165, 170 ° C. Stirred at 80 revolutions per minute (rpm) in the first reactor, 50 rpm in the second reactor and 25 rpm in the third reactor. Add 100 ppm molecular weight regulator (n-dodecyl mercaptan or NDM) to the second zone of the first reactor.

An extruder is used to remove volatile components to remove residual styrene and ethylbenzene diluent, and to crosslink the rubber. The temperature profile for the extruder with the removal of volatile components has 240 ° C at the beginning of the cylinder, in the middle zone of the cylinder and the last zone of the cylinder. The screw temperature is 220 ° C.

Use the following test methods (or the methods defined here above) to characterize the HIPS-X: Melt flow rate: ISO-133. Molecular weight distribution of the PS matrix: Gel permeation chromatography with calibration according to PS. Rubber Particle Size: Light scattering on a Beckman Coulter LS230 instrument using software. Yield Strength, Tensile, and Modules: ISO-527-2.

The concentration of the HIPS-X gel is determined by extraction with methyl ethyl ketone. For the analysis of HIPS-X, 0.25 grams of a sample of HIPS-X are dissolved in a mixture of methyl ethyl ketone / methanol (volume ratio 10: 1) by placing the sample and the mixture in a test tube with a known mass and shaken with a mixer for two hours at room temperature (23 ° C). The insoluble fraction is isolated by placing the tube in a high speed centrifuge and centrifuged at 19,500 rpm at 5 ° C for one hour. The excess liquid is decanted and the tubes are placed in a vacuum oven at 150 ° C for 45 minutes under a vacuum of 2-5 millimeters of mercury. Remove the tubes from the oven and cool to approximately 23 ° C. The tubes for determination are weighed, the known mass of the tube for determining the gel mass is subtracted. The mass of the gel is divided by 0.25 grams and multiplied by 100, resulting in a wt.% Of the gel content from the total mass of HIPS-X.

Table 1 Rubber diene copolymer conjugated Rubber homopolymer conjugated diene Property Buna BL 6533 T (trademark of Bayer) Diene 55
(trademark of Firestone) Styrene content (%) 40 0 Vinyl Content (%) 9 eleven Cis content (%) 38 38 Viscosity (Mooney viscosity ML1 + 4 100 ° C in pascal second) 45 70 The viscosity of the solution (5.43% in toluene)
millipascal second 40 170 Polymer structure AB block copolymer Usually linear

HIPS-X has a volumetric average rubber particle size of 0.35 μm, with 65% by volume of particles having a size of less than 0.4 μm, and 35% by volume of particles have a size of 0.4-2.5 μm. HIPS-X has a rubber concentration of 0.38% by weight of butadiene homopolymer and 5.6% by weight of styrene / butadiene copolymer, for a combined rubber concentration of 5.98% by weight of HIPS-X. HIPS-X has a gel concentration of about 8% by weight relative to the total weight of HIPS-X. HIPS-X contains 2 wt.% Of mineral oil, has an MFR of 7.0 g / 10 min, a Vic resistance of 101 ° C, a yield strength of 20 megapascals (MPa), an elongation at break of 25%, and a tensile modulus of 2480 MPa.

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

ONPS-1 is a general purpose polystyrene having a tensile modulus of greater than 400,000 psi (2750 MPa) and is commercially available from The Dow Chemical Company under the brand name STYRON (TM) 665 Polystyrene Resin.

Block copolymer-1 is a styrene-butadiene (SB) block copolymer having a diene content of more than 30 weight percent and a bending modulus of less than 200,000 (1380 MPa), and is commercially available from Chevron-Phillips Chemical Company under the trade called K-Resin (TM) KK3.8 styrene-butadiene-styrene resin.

Block copolymer-2 is a styrene-isoprene-styrene / styrene-isoprene (SIS / SI) block copolymer having a styrene content of about 15 weight percent and shore hardness 24 (ASTM D-2240), and is commercially available from Dexco Polymers LP under the trade name VECTOR (TM) 4114A Styrene-Isoprene-Styrene / Styrene-Isoprene SIS / SI Styrenic Block-Copolymer.

Block copolymer-3 is a styrene-isoprene-styrene (SIS) block copolymer having a styrene content of about 18 weight percent and a shore hardness of 39, and is commercially available from Dexco Polymers LP under the trade name VECTOR (R) 4111A Styrene- Isoprene-Styrene (SIS) Styrenic Block-Copolymer.

Block copolymer-4 is a thermoplastic styrene-butadiene block copolymer having a styrene content of 70 to 80 weight percent and a tensile modulus of 120,000 psi (825 MPa), and is commercially available from BASF Corporation under the trade name Styrolux (TM) 3G55 Q420 styrene-butadiene-styrene Block-Copolymer.

METHODS FOR EXAMPLES 1-4 AND FOR COMPARATIVE SAMPLES B-D

In each of the following examples, each component shown in Table 2 is in granular form and loaded into a drum mixer, where the components are mixed for about 2 minutes to form a mixture. Additives are not added, but it is known that some of the commercial polymers used may contain additives.

The mixture is placed in each of 3 extruders with a diameter of one inch (2.54 cm) and with a length to diameter ratio (L / D) of 24: 1. The mixture is heated to a temperature of 390 ° F (198 ° C) using heaters that are integral with the extruders. This temperature is maintained until the film is watered through a die with a slit of 10 inches (25.4 cm) wide and 0.040 inches (0.10 cm) thick onto a polished water / glycerin-mixed water polishing drum at 130 ° F (54 ° C) with the formation in each case of a monolayer film. The speed of the irrigation drum is adjusted so as to obtain the film thickness given in each example or for each sample.

The film of examples and samples was cut into 4 ”squares (10.16 cm) and stretched using a TM Long Film Stretching Machine, manufactured by the industry from TM Long Co., Inc of Somerville, NJ. The stretching machine has a sample holder with with several clamps on the sides for each of the four sides of the sample. Hot air is blown from below into the sample, which hangs in the air due to the clamps. Below the sample holder is a deflecting device to deflect hot air blowing directly onto the sample. There is no property, hot air blows onto the sample.Each example of a film or sample is heated at the air temperature indicated in Table 2 for one minute with the deflector turned on and off for the time periods specified in Table 2. Then the sample or example is stretched at 0.4 inch / second (1.0 cm / sec) until the film is stretched 4 times from its original size in the transverse direction of extrusion, and stretching in the longitudinal direction is completely limited by clamping on the sides .

In the examples and comparative samples, in order to prevent rupture of the samples, clamps on the sides change the air temperature. The selected air temperature is selected using a dial gauge on the machine and maintained by the machine. To prevent rupture of the sample during stretching, the length of the on and off time of the deflecting device is selected, since it affects the temperature change of the sample.

Examples (Ex.) 1-4 and comparative samples (S.O.) B-D

table 2
Mass contents of components and film thickness Sample or Sample Number Project 1 Project 4 S.O. AT Project 2 Project 3 S.O. FROM S.O. D HIPS-X thirty fifty 65 twenty 60 thirty ONPS-1 thirty 40 35 twenty 35 Block copolymer-1 40 Block copolymer-2 10 Block copolymer-3 5 Block copolymer-4 one hundred 70 Thickness 10
mil
(0.25 nm) fifteen
mil
(0.38 nm) fifteen
mil
(0.38 nm) fifteen
mil
(0.38 nm) fifteen
mil
(0.38 nm) fifteen
mil
(0.38 nm) fifteen
mil
(0.38 nm) Stretching at air temperature 125 ° C 130 ° C 135 ° C 125 ° C 135 ° C 115 ° C 130 ° C Deflector on time in seconds thirty thirty thirty thirty thirty fifteen fifteen Deflector shutdown time in seconds thirty thirty thirty 45 thirty fifteen fifteen

All percentages are mass percent of the polymers present, with the exception of additives, except for those additives that may be found in industrial products.

Comparative samples are not examples of the present invention.

Table 3 shows the properties of the films for examples 1-4 and comparative samples B-D. The following test methods are used to characterize the films of the present invention. Smoke is measured in accordance with ASTM Method D-1003. Measure the brightness in accordance with the methods of ASTM standard method D-1746. Tensile stress and stress, impact strength and secant modulus are measured in accordance with ASTM Method D-882. Orientation induced stresses (ORS) are measured in accordance with ASTM Method D-2838. Outdoor shrinkage is measured in accordance with ASTM Method D-1204.

Examples 1-4 illustrate the many compositions within the scope of the invention and show that their properties are suitable for the manufacture of shrink labels. Example 4 also shows that the use of excess ICU can lead to more smokiness than may be desirable for some shrink labels. Comparative sample B shows that the absence of a styrene block copolymer leads to a decrease in the impact toughness MD below that which is suitable for shrink labels, since it is observed that these labels peel off easily along an unstretched direction. Comparative Sample C shows that labels without HIPS-X have low moduli and it is observed that these labels made using such a formulation will have an undesirably low stiffness. Comparative example D shows that a label without ONPS has a greater smokiness than is desirable for shrink labels.

A comparison of comparative sample C and comparative sample D shows that the addition of HIPS-X to the block copolymer leads to higher stiffness, as indicated by a higher one percent secant modulus.

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

1. The film composition, comprising from 0 to 5 weight percent of additives and from 95 to 100 weight percent of the polymer composition, consisting mainly of:

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

(i) a block copolymer of styrene and a rubbery diene with conjugated double bonds, where the copolymer is grafted to polystyrene;

(ii) optionally, two weight percent or more and 8 weight percent or less of a homopolymer of a rubber-like diene with conjugated double bonds of the total mass of rubber in the HIPS component;

(iii) the total content of the diene component from the rubber component is one weight percent or more and seven weight percent or less of the total mass of the HIPS component;

(iv) less than 10 wt.% the concentration of the gel, determined by extraction with a mixture of methyl ethyl ketone / methanol;

(v) an average rubber particle size of less than 1.0 micrometer and 0.01 micrometer or more;

(vi) from about 40 to 90 volume percent of rubber particles with diameters of less than about 0.4 microns and from about 10 to 60 volume percent of rubber particles with diameters of from about 0.4 and 2.5 microns;

(vii) most rubber particles with core-shell morphology;

(viii) which is present at a concentration of at least about 10 weight percent and up to no more than about 70 weight percent of the polymers in the composition and is one or more and five or less percent by weight of the rubbery diene relative to the total weight of the composition;

(b) at least one general purpose polystyrene having a weight average molecular weight of more than 200,000 grams per mole and 350,000 grams per mole or less, and which is present at a concentration of at least about 10 weight percent and not more than about 50 weight percent of the polymers in the composition; and

(c) at least one styrene block copolymer having a relative elongation at break of at least about 200 and a melt flow rate determined in accordance with ASTM D1238, Condition G of at least about 2 g / 10 min, and which is present at a concentration of at least about 2 weight percent and up to no more than about 80 weight percent of the polymers in the composition;

where the total combination of (a), (b) and (c) is 100 wt.% the polymer composition.

2. The composition of Embodiment 1, wherein the styrene block copolymer has a brightness measured in accordance with ASTM D1746 corresponding to at least about 85%, preferably at least about 90% of the transmittance of visible light.

3. The composition of embodiment 1 or 2, wherein one or more of the HIPS, ONPS, styrene block copolymer is selected and used in amounts effective to achieve at least one, preferably at least 2, preferably at least 3, most preferably at least 4, preferably at least 5, more preferably at least 6, most preferably at least 7, of the following characteristics, when the composition is used to make a film having a thickness preferably defined in the method specified for measuring properties, as an option, with a thickness intended for use, preferably from about 25 or 38 microns to 76, 100 or 110 microns, more preferably an elongated thickness of 64, 65, 89, 90, 100, 104, 105, 109 or 110 microns, most preferably an elongated thickness of 50 microns:

(a) a brightness corresponding to a brightness of 50 μm of a film of at least about any of 10, 15, 20, 25, or 30, measured in accordance with ASTM D-1746;

(b) a haze corresponding to a haze of a 50 μm film, less than any of about 15, 10, 6, or 4, measured in accordance with ASTM D-1003;

(c) 1% secant modulus in MD, TD, or more preferably in both directions of at least any of about 620 MPa, 680 MPa, or 1380 MPa, measured in accordance with ASTM D-882;

(d) the relative tensile strain at break in MD, TD, or, more preferably, in both directions, at least any of about 30, 35, 40 or 45 percent, measured in accordance with the methods of ASTM D-882;

(e) tensile stress at break in MD, TD, or, more preferably in both directions, at least any of about 14, 17, 21, or 28 MPa, measured in accordance with ASTM D-882;

(f) impact strength in MD, TD, or, more preferably in both directions, at least any of about 14, 17, 21, or 28 MPa, measured in accordance with ASTM D-882;

(g) internal stresses caused by orientation of less than 2758 kPa, measured in accordance with ASTM D-2838.

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

5. The composition according to any one of embodiments 1-4, wherein the amount (a) of the HIPS is at least about any value of 10, 20, or 25 wt.%, And not more than about any value of 60, 65, or 70 wt.%, (B) ONPS is at least about any value of 10, 20 or 35 wt.%, And not more than about any value of 40, 45 or 50 wt.%, Or (c) component the styrene block copolymer is at least about 2, 3 or 4 wt.%, and not more than about 70, 75 or 80 wt.% of the total weight of the polymer components (a), (b) and (c) or any combination of them.

6. The composition according to any one of embodiments 1-5, wherein the styrene block copolymer is at least one styrene butadiene block copolymer and is present in an amount of at least about 20, 30, or 40 wt. %, or not more than about 70, 75 or 80 wt.% of the total mass (a), (b) and (c).

7. The composition according to any one of embodiments 1-6, wherein the styrene block copolymer is at least one styrene-isoprene block copolymer and is present in an amount of at least about 2, 3, or 4 wt. %, or not more than about 6, 8 or 9 wt.% of the total mass (a), (b) and (c).

8. The composition according to any one of embodiments 1-7, wherein the rubbery diene with conjugated double bonds in the copolymer (a) is butadiene.

9. The composition according to any one of embodiments 1-8, wherein 90 percent or more of the rubber particles have a particle size of less than 0.4 micrometers, and less than 100 percent of the rubber particles have a particle size of 2.5 micrometers or less.

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

11. The film of embodiment 10, which exhibits a size increase of less than 10% in the direction of less stretching after 5 minutes in an air-heated oven at 110 degrees Celsius.

12. The film according to any one of embodiments 10-11, wherein the polymer composition comprises at least 95% by weight of the oriented film, and up to 100 percent is not selected from additives; and where the film has a directional orientation in the direction of extension of at least about 3: 1.

13. A film according to any one of embodiments 10-12, which has a one percent cut-off module in the longitudinal direction (MD) and transverse direction (TD) in accordance with Method 882 of the American Society for Testing Materials of at least about 250,000 psi. (1724 megapascals).

14. The film according to any one of embodiments 10-13, having a thickness of preferably from about 25 or 38 microns to 76, 100 or 110 microns, more preferably any thickness of 64, 65, 89, 90, 100, 104, 105, 109 , or 110 microns, most preferably a thickness of 50 microns.

15. The film according to any one of embodiments 10-14 at any thickness specified in the embodiment, having at least one, preferably at least 2, better at least 3, best at least , 4, preferably at least 5, more preferably at least 6, most preferably at least 7 of the characteristics indicated in embodiment 3.

16. The film according to any one of embodiments 10-15, which has one or both of (a) a relationship oriented to an unoriented length in the direction of greatest tension, at least about 3: 1, 4: 1, 5: 1, or 6 : 1 or (b) the ratio of the oriented to the non-oriented length in a direction perpendicular to the direction of greatest stretching (also known as the direction of least stretching), at least from about 1.05: 1, 1.07: 1 or 1.10: 1, and up to not more than 1.2: 1 or 1.15: 1.

17. A film according to any one of embodiments 10-16, which has one or both shrinkability values from (a) shrinkability in the direction of greatest tension, at least about 20, 30, 40, 50, 60, or 70 percent; or (b) shrinkage in the direction of least stretch from any of 5, 7, or 10 percent to any of 15 or 20 percent.

18. The film according to any one of embodiments 10-17, further comprising perforations.

19. A shrink label comprising an oriented polymer film according to any one of embodiments 10-18, which preferably has a print on one or both sides.

Claims (10)

1. The film composition for the production of shrink labels, including from 0 to 5 wt.% Additives and from 95 to 100 wt.% Polymer composition, consisting mainly of:
(a) at least one component of high impact polystyrene (HIPS), including:
(i) a grafted rubber component, which is a block copolymer of styrene and a rubber-like diene with conjugated double bonds;
(ii) an optionally grafted rubber component representing 2 wt.% or more and 8 wt.% or less homopolymer of a rubber-like diene with conjugated double bonds from the total mass of the grafted rubber component in the HIPS component;
(iii) the total content of the diene component from the grafted rubber component (s) is 1 wt.% or more and 7 wt.% or less of the total mass of the HIPS component;
(iv) less than 10 wt.% the concentration of the gel determined by extraction with a mixture of methyl ethyl ketone / methanol;
(v) an average rubber particle size of less than 1.0 and 0.01 microns or more;
(vi) from about 40 to 90 vol.% of rubber particles with diameters of less than about 0.4 microns and from about 10 to 60 vol.% of rubber particles with diameters of from about 0.4 to 2.5 microns;
(vii) a plurality of rubber particles with core-shell morphology;
(viii) which is present at a concentration of at least about 10 wt.% and up to no more than about 70 wt.% of the polymers in the composition and is one or more and five or less% by weight of the rubbery diene relative to the total weight composition;
(b) at least one general purpose polystyrene (ONPS) having a weight average molecular weight of more than 200,000 g per mole and 350,000 g per mole or less, and which is present at a concentration of at least about 10% by weight , and up to no more than about 50 wt.% of the polymers in the composition; and
(c) at least one styrene block copolymer, preferably having a relative elongation at break of at least about 200% and a melt flow rate determined in accordance with ASTM D1238, Condition G of at least about 2 g / 10 min, and which is present at a concentration of at least about 2 wt.%, and up to no more than about 80 wt.% of the polymers in the composition; where the total combination of (a), (b) and (c) is 100 wt.% the polymer composition. 2. The composition according to claim 1, in which the styrene block copolymer has a brightness measured in accordance with ASTM D1746, corresponding to at least about 85% of the transmittance of visible light. 3. The composition according to claim 1, in which the component of high impact polystyrene has a volumetric average rubber particle size of 0.5 μm or less, and 0.01 μm or more. 4. The composition according to claim 1, wherein the amount of the styrene block copolymer component is at least about 3% by weight of the polymer composition. 5. The composition according to claim 1, in which the block copolymer of styrene is at least one block copolymer of styrene and butadiene, and it is present in an amount of at least about 20 wt.% Of the total weight of the polymer composition. 6. The composition according to claim 1, in which the block copolymer of styrene is at least one block copolymer of styrene and isoprene, and it is present in an amount of from 2 to 9 wt.% Of the total weight of the polymer composition. 7. The composition according to claim 1, in which the rubbery diene with conjugated double bonds in the copolymer (a) is butadiene. 8. The composition according to claim 1, in which 90% or more of the rubber particles have a particle size of less than 0.4 μm, and the amount of rubber particles lacking up to 100% has a particle size of 2.5 μm or less. 9. The composition according to claim 1, in which one or more of the HIPS, ONPS, block copolymer of styrene is selected and used in amounts effective to achieve at least 3 of the following characteristics when the composition is used to make a film having a thickness defined in the procedure provided for measuring the property, or, if thickness is not specified, with a thickness of 100 μm:
(a) a brightness corresponding to a brightness of 50 μm of a film of at least about any of 10, 15, 20, 25, or 30, measured in accordance with ASTM D-1746;
(b) a haze corresponding to a haze of a 50 μm film, less than any of about 15, 10, 6 or 4, measured in accordance with ASTM D-1003;
(c) 1% secant modulus in MD, TD, or more preferably in both directions of at least any of about 620 MPa, 680 MPa, or 1380 MPa, measured in accordance with ASTM D-882;
(d) the relative tensile strain at break in MD, TD, or, more preferably, in both directions, at least any of about 30, 35, 40, or 45%, measured in accordance with ASTM D-882;
(e) tensile stress at break in MD, TD, or, more preferably in both directions, at least any of about 14, 17, 21, or 28 MPa, measured in accordance with ASTM D-882;
(f) impact strength in MD, TD, or, more preferably in both directions, at least any of about 14, 17, 21, or 28 MPa, measured in accordance with ASTM D-882; or
(g) internal stresses caused by orientation of less than 2758 kPa, measured in accordance with ASTM D-2838. 10. A film that can be used for the production of shrink labels, containing the composition according to any one of claims 1 to 9, and the specified film has a ratio of oriented length to non-oriented length in the direction of greatest drawing, mainly at least about 3: 1, and demonstrates an increase in size of at least 20% in the direction of less stretching at 110 ° C, has a ratio of oriented length to non-oriented length of at least about 1.2: 1 and shrinkability at 110 ° C, at least around 5%.